Author: "Michael R. Bell" - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"Michael R. Bell"' showing total 43 results

Start Over Author "Michael R. Bell"

43 results on '"Michael R. Bell"'

1. Establishing a Health Information Technology for the Vaccination of National Institutes of Health Staff

Author: Jon Walter McKeeby, Christopher M. Siwy, Jordan Southers, Derek A. Newcomer, Samantha Hughes, Jeffery M. Sano, Jharana J. Patel, Falguni Kanthan, Marilyn Farinre, Megan Morgan Brose, Rebecca V. Anderson, Judy Chan, Heike Bailin, Michael R. Bell, John S. McLamb, Stephen Novak, Dennis J. House, Mary J. Sparks, Michael Nansel, Seth D. Carlson, Yenshei Liu, Cory Stephens, Erin Tsui, Patricia S. Coffey, and Jessica McCormick-Ell
Subjects: Health, Toxicology and Mutagenesis, Public Health, Environmental and Occupational Health, Management, Monitoring, Policy and Law, Biotechnology
Published: 2022

2. Genetically encoded multivalent liquid glycan array displayed on M13 bacteriophage

Author: Susmita Sarkar, Amira Khalil, Todd L. Lowary, Chang-Chun Ling, Michael R. Bell, Revathi Reddy, Daniel Ferrer Vinals, Shaurya Seth, Ping Zhang, Nicholas J. Bennett, James C. Paulson, Mirat Sojitra, Emily Rodrigues, Matthew S. Macauley, Ruixiang Blake Zheng, Jasmine Maghera, Xiaochao Xue, Corwin M. Nycholat, Eric J. Carpenter, Ratmir Derda, and Justin J. Bailey
Subjects: chemistry.chemical_classification, 0303 health sciences, Glycan, M13 bacteriophage, biology, Chemistry, Glycoconjugate, viruses, 030302 biochemistry & molecular biology, CD22, Cell Biology, biology.organism_classification, DNA sequencing, In vitro, Deep sequencing, carbohydrates (lipids), 03 medical and health sciences, chemistry.chemical_compound, Biochemistry, biology.protein, Molecular Biology, DNA, 030304 developmental biology
Abstract: The central dogma of biology does not allow for the study of glycans using DNA sequencing. We report a liquid glycan array (LiGA) platform comprising a library of DNA 'barcoded' M13 virions that display 30-1,500 copies of glycans per phage. A LiGA is synthesized by acylation of the phage pVIII protein with a dibenzocyclooctyne, followed by ligation of azido-modified glycans. Pulldown of the LiGA with lectins followed by deep sequencing of the barcodes in the bound phage decodes the optimal structure and density of the recognized glycans. The LiGA is target agnostic and can measure the glycan-binding profile of lectins, such as CD22, on cells in vitro and immune cells in a live mouse. From a mixture of multivalent glycan probes, LiGAs identify the glycoconjugates with optimal avidity necessary for binding to lectins on living cells in vitro and in vivo.
Published: 2021

3. Genetically encoded multivalent liquid glycan array displayed on M13 bacteriophage

Author: Mirat Sojitra, Susmita Sarkar, Jasmine Maghera, Edward N. Schmidt, Emily Rodrigues, Eric J. Carpenter, Shaurya Seth, Daniel F. Vinals, Nicholas J. Bennett, Revathi Reddy, Amira Khalil, Xiaochao Xue, Michael R. Bell, Ruixiang B. Zheng, Ping Zhang, Corwin Nycholat, Justin J. Bailey, Chang‐Chun Ling, Todd L. Lowary, James C. Paulson, Matthew S. Macauley, and Ratmir Derda
Subjects: Genetics, Molecular Biology, Biochemistry, Biotechnology
Published: 2022

4. One-Pot Regioselective Diacylation of Pyranoside 1,2

Author: Taeok, Kim, Michael R, Bell, V Narasimharao, Thota, and Todd L, Lowary
Subjects: Acylation, Alcohols, Hydrolysis, Carboxylic Acids, Esters
Abstract: A one-pot strategy for functionalizing pyranoside 1,2
Published: 2022

5. Genetically Encoded, Multivalent Liquid Glycan Array (LiGA)

Author: Nicholas J. Bennett, Mirat Sojitra, Ping Zhang, Susmita Sarkar, Chang-Chun Ling, Revathi Reddy, Corwin M. Nycholat, Michael R. Bell, Daniel Ferrer Vinals, Eric J. Carpenter, Emily Rodrigues, Ratmir Derda, Jasmine Maghera, Xiaochao Xue, Matthew S. Macauley, Ruixiang Blake Zheng, James C. Paulson, Shaurya Seth, Amira Khalil, and Todd L. Lowary
Subjects: chemistry.chemical_classification, 0303 health sciences, Glycan, biology, Glycoconjugate, CD22, 010402 general chemistry, 01 natural sciences, DNA sequencing, Deep sequencing, In vitro, 3. Good health, 0104 chemical sciences, carbohydrates (lipids), 03 medical and health sciences, chemistry.chemical_compound, chemistry, Biochemistry, biology.protein, LIGA, DNA, 030304 developmental biology
Abstract: The Central Dogma of Biology does not allow for the study of glycans using DNA sequencing. We report a “Liquid Glycan Array” (LiGA) platform comprising a library of DNA ‘barcoded’ M13 virions that display 30-1500 copies of glycans per phage. A LiGA is synthesized by acylation of phage pVIII protein with a dibenzocyclooctyne, followed by ligation of azido-modified glycans. Pulldown of the LiGA with lectins followed by deep sequencing of the barcodes in the bound phage decodes the optimal structure and density of the recognized glycans. The LiGA is target agnostic and can measure the glycan-binding profile of lectins such as CD22 on cells in vitro and immune cells in a live mouse. From a mixture of multivalent glycan probes, LiGAs identifies the glycoconjugates with optimal avidity necessary for binding to lectins on living cells in vitro and in vivo; measurements that cannot be performed with canonical glass slide-based glycan arrays.DedicationThe paper is dedicated to Laura L. Kiessling on the occasion of her 60th birthday.
Published: 2020
Full Text: View/download PDF

6. The ABHIDE (Army Behavioral Health Integrated Data Environment): A suicide registry

Author: John V. Wills, Michael R. Bell, Amy Millikan Bell, Elizabeth Corrigan, M. Shayne Gallaway, J. Christopher Weir, Anita Spiess, and Eren Youmans Watkins
Subjects: medicine.medical_specialty, Suicide attempt, business.industry, Public health, Human factors and ergonomics, Poison control, medicine.disease, Suicide prevention, Occupational safety and health, 030227 psychiatry, 03 medical and health sciences, Military personnel, 0302 clinical medicine, medicine, 030212 general & internal medicine, Medical emergency, medicine.symptom, business, Suicidal ideation, General Psychology, Social Sciences (miscellaneous)
Abstract: The Army Behavioral Health Integrated Data Environment (ABHIDE) is a suicide registry containing extensive data on U.S. Army Soldiers with suicidal behavior. Development of the ABHIDE began in 2009 in response to the doubling of the Army suicide rate from 2004 to 2008. It now consists of 28 administrative data sets from 11 organizations throughout the Departments of the Army and Defense. Data include personnel variables, military characteristics, medical claims, criminal histories, characteristics of the suicidal events, and stressors. Through the ABHIDE, the U.S. Army is better able to answer requests for information, inform public health practice, and develop suicide prevention programs.
Published: 2015

7. A mixed methods epidemiological investigation of preventable deaths among U.S. Army soldiers assigned to a rehabilitative warrior transition unit

Author: Michael Shayne Gallaway, Kelly L. Forys-Donahue, Michael R. Bell, Dabbs Cr, David S. Fink, Joseph A Pecko, Christine Lagana-Riordan, Bender Aa, Amy M. Millikan, Schmissrauter Sc, Coombs Ma, Rattigan Mr, and Perales R
Subjects: Adult, Male, Suicide Prevention, medicine.medical_specialty, Adolescent, Poison control, Rehabilitation Centers, Risk Assessment, Suicide prevention, Occupational safety and health, Social support, Surveys and Questionnaires, Injury prevention, Humans, Medicine, Risk factor, Psychiatry, Retrospective Studies, business.industry, Mental Disorders, Rehabilitation, Public Health, Environmental and Occupational Health, Human factors and ergonomics, Focus Groups, Middle Aged, United States, Death, Epidemiologic Studies, Suicide, Military Personnel, Case-Control Studies, Female, Drug Overdose, business, Risk assessment
Abstract: BACKGROUND: The prevalence of medical risk factors for suicide (e.g., mental disorders, severe disability, social disruption) may be higher among WTs compared to traditional Army units. Likewise, the extent to which traditional factors that protect soldiers from developing serious mental disorders (e.g., social support, unit cohesion, leadership) are present among soldiers assigned to the WTU is unclear. OBJECTIVES: An epidemiological consultation (EPICON) was conducted in 2010 to assess potential causes for a perceived high rate of suicides and preventable deaths in U.S. Army Warrior Transition Units (WTUs) and to identify potential improvements to the system of care. METHODS OF STUDY: The EPICON focused on: (1) risk factors for suicide/preventable deaths; (2) chronic pain management; (3) utilization of and access to WTU medical and behavioral health (BH) services; and (4) the impact of the WTU environment on mission focus and warrior disposition. BH history was examined for soldiers who died by suicide or preventable death while assigned to the WTU (index cases) and a representative comparison group of non-index case soldiers. Surveys and focus groups were conducted at four WTUs with Warriors in Transition (WTs) and key support staff. RESULTS: The use of psychotropic and/or CNS depressant medications, prevalence of BH diagnoses and substance use disorders, polypharmacy, alcohol use, and a high cumulative number of stressors were identified as important risk factors for preventable deaths in the WTC. Areas of potential improvement to the system of care included addressing negative perceptions of the WTU environment, lack of social support, barriers to accessing BH services and issues related to coordination of care. CONCLUSIONS: There was no one single risk factor found to be associated with an increased likelihood of preventable deaths within the WTU. The unique design and operation of the WTUs as environments focused on treatment and rehabilitation provide both benefits and challenges to recovery and risk mitigation. Language: en
Published: 2015

8. Combat Exposure Factors Associated With the Likelihood of Behavioral and Psychiatric Issues

Author: Michael R. Bell, Michael Shayne Gallaway, Mary M. Mitchell, Joseph A Pecko, David S. Fink, Amy M. Millikan, and Kelly L. Forys-Donahue
Subjects: medicine.medical_specialty, Intervention (counseling), medicine, Combat exposure, Passive Exposure, Psychiatry, Psychology, General Psychology, Social Sciences (miscellaneous), Structural equation modeling
Abstract: The objective was to evaluate correlated combat exposure factors among active-duty combat veterans deployed to Afghanistan and then determine how these factors are associated with behavioral and psychiatric issues postdeployment. Active-duty soldiers from one brigade combat team (N = 1,739) were surveyed to assess their most recent combat exposures and behavioral outcomes. Combat exposures were factor analyzed and included in a larger structural equation model. Three factors emerged from the analysis: some combat exposures (e.g., “active exposure”) are protective of screening positive for post-traumatic stress, while others (“passive exposure” and “exposure invoking emotion”) are predictive of screening positive for post-traumatic stress. These varying relationships should be considered during implementation of intervention and treatment of redeploying soldiers.
Published: 2014

9. Combat Exposure, Unit Cohesion, and Demographic Characteristics of Soldiers Reporting Posttraumatic Growth

Author: Michael R. Bell, Mary M. Mitchell, Amy M. Millikan, and M. Shayne Gallaway
Subjects: medicine.medical_specialty, Social Psychology, Posttraumatic growth, business.industry, education, Human factors and ergonomics, Poison control, Suicide prevention, Occupational safety and health, Psychiatry and Mental health, Social support, Injury prevention, medicine, Pshychiatric Mental Health, Psychiatry, business, Psychosocial, Social Sciences (miscellaneous)
Abstract: Posttraumatic growth (PTG) refers to the positive cognitive, spiritual, emotional, and social changes that can occur after a traumatic experience. The current study uses data from 1,663 soldiers who participated in a voluntary survey 6 months after redeployment. The purpose of this study was to predict posttraumatic growth from combat exposure, unit cohesion, and demographic characteristics. We found that greater combat exposure and stronger unit cohesion were associated with more PTG. Being married, a minority, and a junior enlisted soldier were also predictive of greater PTG. Our study defines a group of soldiers with low PTG who are at risk for adverse psychosocial problems. Our results suggest that unit cohesion could be targeted and strengthened to improve PTG.
Published: 2013

10. The Association Between U.S. Army Enlistment Waivers and Subsequent Behavioral and Social Health Outcomes and Attrition From Service

Author: Michael R. Bell, Christine Lagana-Riordan, Charles E. Meyer, Amy M. Millikan, M. Shayne Gallaway, and David S. Fink
Subjects: Adult, Male, medicine.medical_specialty, education, Population, Military medicine, Young Adult, Misconduct, Risk Factors, Surveys and Questionnaires, medicine, Humans, Attrition, Social determinants of health, Psychiatry, health care economics and organizations, Retrospective Studies, Psychiatric Status Rating Scales, education.field_of_study, business.industry, Incidence, Mental Disorders, Public health, Public Health, Environmental and Occupational Health, General Medicine, medicine.disease, United States, humanities, Test (assessment), Substance abuse, Military Personnel, Female, business
Abstract: Soldiers granted enlistment waivers for medical concerns, misconduct, or positive alcohol/drug tests may or may not be associated with an increased likelihood of negative behavioral outcomes. Soldiers in the population examined (n = 8,943) who were granted enlistment waivers from 2003 to 2008 were significantly more likely to subsequently be screened for alcohol/substance abuse, test positive for illicit substances, or receive an Army separation for behavioral misconduct. These associations were highest among Soldiers granted waivers for nonlawful alcohol/drug violations. Soldiers granted waivers for felony offenses and serious nontraffic violations were significantly less likely to separate from the Army compared with Soldiers not granted enlistment waivers.
Published: 2013

11. Synchronous X-ray and Radio Mode Switches: A Rapid Global Transformation of the Pulsar Magnetosphere

Author: Y. Tang, Anna M. M. Scaife, Steve Rawlings, Aris Karastergiou, Michael W. Wise, Harvey Butcher, B. Ciardi, S. Duscha, V. N. Pandey, Gianni Bernardi, John McKean, Charlotte Sobey, Emanuela Orrú, Chiara Ferrari, M. Kuniyoshi, H. Munk, Marcus Brüggen, Michael Kramer, Cyril Tasse, J. W. Broderick, E. de Geus, Ashish Asgekar, Jason W. T. Hessels, F. de Gasperin, Matthias Hoeft, George Heald, L. Kuiper, A. P. Schoenmakers, P. Maat, R. H. van de Brink, Sera Markoff, Dipanjan Mitra, Philip Best, G. Wright, Ralph A. M. J. Wijers, J. de Plaa, Heino Falcke, V. I. Kondratiev, Rahul Basu, A. Noutsos, T. Coenen, Benjamin Stappers, Michel Tagger, Frank Breitling, Giulia Macario, Rob Fender, Rene C. Vermeulen, Michael R. Bell, F. Batejat, A. Alexov, Marco Iacobelli, H. Paas, Sarod Yatawatta, Patrick Weltevrede, Tim Hassall, R. J. van Weeren, W. Reich, M. Pilia, Laura Birzan, W. Hermsen, Evan Keane, Aleksandar Shulevski, Mark J. Bentum, M. Serylak, Martin Bell, Annalisa Bonafede, J. van Leeuwen, A. Horneffer, Jochen Eislöffel, Maaijke Mevius, H. J. A. Röttgering, A. G. Polatidis, R. Morganti, I. M. Avruch, S. ter Veen, A. W. Gunst, Olaf Wucknitz, Matthias Steinmetz, M. Pandey-Pommier, K. Zagkouris, J. Sluman, Roberto Pizzo, Jean-Mathias Grießmeier, G. Kuper, Philippe Zarka, Joanna M. Rankin, M. A. Garrett, James Miller-Jones, Wilfred Frieswijk, Hermsen, W., Hessels, J.W.T., Kuiper, L., Van Leeuwen, J., Mitra, D., De Plaa, J., Rankin, J.M., Stappers, B.W., Wright, G.A.E., Basu, R., Alexov, A., Coenen, T., Grießmeier, J.-M., Hassall, T.E., Karastergiou, A., Keane, E., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Noutsos, A., Serylak, M., Pilia, M., Sobey, C., Weltevrede, P., Zagkouris, K., Asgekar, A., Avruch, I.M., Batejat, F., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Duscha, S., Eislöffel, J., Falcke, H., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., De Gasperin, F., De Geus, E., Gunst, A.W., Heald, G., Hoeft, M., Horneffer, A., Iacobelli, M., Kuper, G., Maat, P., Macario, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Morganti, R., Munk, H., Orrú, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Rawlings, S., Reich, W., Röttgering, H., Scaife, A.M.M., Schoenmakers, A., Shulevski, A., Sluman, J., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van De Brink, R.H., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., SRON Netherlands Institute for Space Research (SRON), University of Amsterdam [Amsterdam] (UvA), National Centre for Radio Astrophysics [Pune] (NCRA), Tata Institute for Fundamental Research (TIFR), University of Vermont [Burlington], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Astronomy Centre, University of Sussex, Space Telescope Science Institute (STSci), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Oxford Astrophysics, University of Oxford, Centre for Astrophysics and Supercomputing, Swinburne University of Technology [Melbourne], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Kapteyn Astronomical Institute, Astronomy, Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Electromagnetic field, POLARIZATION, Electromagnetic spectrum, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Magnetosphere, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, EMPIRICAL-THEORY, 01 natural sciences, Binary pulsar, Pulsar, Millisecond pulsar, 0103 physical sciences, 010306 general physics, XMM-NEWTON OBSERVATIONS, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, DRIFTING SUBPULSES, Multidisciplinary, B0943+10, Polarization (waves), GAMMA-RAY, [SDU]Sciences of the Universe [physics], 13. Climate action, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, RADIATION, EMISSION, Astrophysics - High Energy Astrophysical Phenomena, PHOTON IMAGING CAMERA, POWERED PULSARS, Radio wave
Abstract: Pulsars emit low-frequency radio waves through to high-energy gamma-rays that are generated anywhere from the surface out to the edges of the magnetosphere. Detecting correlated mode changes in the multi-wavelength emission is therefore key to understanding the physical relationship between these emission sites. Through simultaneous observations, we have detected synchronous switching in the radio and X-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio 'bright' mode, the X-rays show only an un-pulsed, non-thermal component. Conversely, when the pulsar is in a radio 'quiet' mode, the X-ray luminosity more than doubles and a 100%-pulsed thermal component is observed along with the non-thermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories., Paper published in Science including supplementary material
Published: 2013

12. Interaction of Combat Exposure and Unit Cohesion in Predicting Suicide-Related Ideation Among Post-Deployment Soldiers

Author: Amy M. Millikan, Mary M. Mitchell, Michael Shayne Gallaway, and Michael R. Bell
Subjects: Public Health, Environmental and Occupational Health, Protective factor, Human factors and ergonomics, Poison control, medicine.disease, Suicide prevention, Occupational safety and health, Psychiatry and Mental health, Clinical Psychology, Distress, Military personnel, Injury prevention, medicine, Medical emergency, Psychology, Clinical psychology
Abstract: Suicide is one of the leading causes of death among U.S. Army soldiers. Suicide-related ideation, which is associated with suicide attempts and suicide, can cause considerable distress. In a sample of 1,663 recently redeployed soldiers, we used factor analysis and structural equation modeling to test the associations between combat exposure, unit cohesion, and their interaction in predicting suicide-related ideation. We found that combat exposure was a significant risk factor for suicide-related ideation, while unit cohesion was a significant protective factor. The significant interaction between the two factors indicated that soldiers who experienced greater combat exposure but also had higher levels of unit cohesion had relatively lower levels of suicide-related ideation. In addition, those who had higher levels of combat exposure and lower unit cohesion were most at risk for suicide-related ideation. Our findings indicate the importance of unit cohesion in protecting soldiers from suicide-related ideation and suggest a higher risk group of soldiers who should be targeted for interventions.
Published: 2012

13. Factors Associated With Physical Aggression Among US Army Soldiers

Author: David S. Fink, Michael Shayne Gallaway, Amy M. Millikan, and Michael R. Bell
Subjects: Conflict tactics scale, education.field_of_study, medicine.medical_specialty, Aggression, Population, Human factors and ergonomics, Poison control, Suicide prevention, Arts and Humanities (miscellaneous), Injury prevention, Developmental and Educational Psychology, medicine, Anxiety, medicine.symptom, education, Psychology, Psychiatry, General Psychology
Abstract: There are a growing number of studies that have approximated levels of aggression and associated outcomes among combat veterans returning from Iraq and Afghanistan using brief screening assessments. However, further research to evaluate the relative role of combat exposures and overt physical behaviors is required to further elucidate potential associations between military service, combat deployment, and overt physical aggression. The purpose of the current study was to assess the prevalence of self-reported physical aggression in a sample of US Army soldiers using an adaptation of the Revised Conflict Tactics Scale (CTS2), and examine factors associated with higher levels of aggression. A population-based cross-sectional study was conducted at a single US Army Installation within a sample of active duty US Army soldiers (n = 6,128) from two large units. Anonymous surveys were collected 6 months following deployment to measure overt aggressive behaviors, posttraumatic stress disorder, anxiety, depression, traumatic brain injury, and misuse of alcohol. There were a relatively higher number of minor and severe physical overt aggressive actions reported among soldiers who previously deployed, notably highest among deployed soldiers reporting the highest levels of combat intensity. Soldiers screening positive for the misuse of alcohol were also significantly more likely to report relatively higher levels of physical aggression. This study quantified overt aggressive behaviors and associated factors, showing increasing combat exposures may result in increased physical aggression. Clinicians treating service members returning from combat may consider assessing relative levels of combat.
Published: 2012

14. Combat Stressors Predicting Perceived Stress Among Previously Deployed Soldiers

Author: Amy M. Millikan, Michael R. Bell, M. Shayne Gallaway, and Mary M. Mitchell
Subjects: medicine.medical_specialty, Social support, Stress (linguistics), Stressor, medicine, Experimental and Cognitive Psychology, Psychiatry, Psychology, Mental health, General Psychology, Social Sciences (miscellaneous), Clinical psychology
Abstract: While combat exposures are considered principle stressors in developing mental health problems, research suggests social support can reduce this risk. Using data from 1,592 previously deployed sold...
Published: 2011

15. Prevalence and risk factors associated with suicides of Army soldiers 2001–2009

Author: Michael R. Bell, Sandra A. Black, M. Shayne Gallaway, and Elspeth Cameron Ritchie
Subjects: business.industry, education, Advertising, Experimental and Cognitive Psychology, Suicide rates, behavioral disciplines and activities, humanities, parasitic diseases, Medicine, business, General Psychology, Social Sciences (miscellaneous), Demography
Abstract: Prevalence and risk factors associated with soldiers' suicides 2001–2009 (N = 874) were examined. Army suicide rates increased from 9 per 100,000 in 2001 to 22 per 100,000 in 2009. Soldier suicides...
Published: 2011

16. Female Soldiers and Post-Traumatic Stress Disorder

Author: Elspeth Cameron Ritchie, Sharon McBride, M. Shayne Gallaway, Michael R. Bell, Jeffrey L. Thomas, Paul D. Bliese, and Michael Carino
Subjects: business.industry, Traumatic stress, Medicine, business, Clinical psychology
Published: 2015

17. Breastfeeding in the Military: Part I. Information and Resources Provided to Service Women

Author: Michael R. Bell and Elspeth Cameron Ritchie
Subjects: Gerontology, Service (business), Medical education, business.industry, media_common.quotation_subject, Public Health, Environmental and Occupational Health, MEDLINE, Breastfeeding, Legislature, General Medicine, Health care, Medicine, Quality (business), Duration (project management), business, Breast feeding, media_common
Abstract: Increasing the incidence and duration of breastfeeding is a major goal in Healthy People 2010. Little is known about the progress that the Department of Defense (DoD) health care system, TRICARE, has made toward reaching that goal. This study is the first of a two-part series that reviews DoD/TRICARE support for breastfeeding and discusses policy issues related to breastfeeding. Methods used include searches of MEDLINE, DoD/TRICARE documents, legislative and policy websites, and the Internet. A survey of DoD hospitals was also conducted. Based on the search results and survey, TRICARE may not be meeting the goals of Healthy People 2010. There is minimal policy guidance regarding breastfeeding. Programs are in place at most hospitals, but the quality and content varies greatly. After mothers return to work, support is meager. DOD/TRICARE may need to establish written policy guidelines and devote additional resources to adequately support breastfeeding.
Published: 2003

18. Breastfeeding in the Military: Part II. Resource and Policy Considerations

Author: Elspeth Cameron Ritchie and Michael R. Bell
Subjects: Gerontology, Active duty, Resource (project management), Nursing, business.industry, Health care, Public Health, Environmental and Occupational Health, Breastfeeding, Medicine, General Medicine, Duration (project management), Return to work, business
Abstract: Breastfeeding is widely acknowledged as the ideal form of nutrition for infants. Because of this, increasing the incidence and duration of breastfeeding is a major goal in Healthy People 2010. Part I of this series illustrated that the Department of Defense and its health care system, TRICARE, may not be meeting that goal, particularly after active duty mothers return to work. This study outlines the resources that would be required to optimally support breastfeeding after active duty mothers return to work. Selected policy implications of supporting breastfeeding are discussed, and recommendations for policy on breastfeeding are presented.
Published: 2003

19. Comparison of algorithms for determination of rotation measure and Faraday structure I. 1100 - 1400 MHz

Author: T. O'Brien, Anna M. M. Scaife, Justin D. Bray, M. Wolleben, Takuya Akahori, Keitaro Takahashi, Lawrence Rudnick, R. Stepanov, J. M. Stil, Michael R. Bell, Kohei Kumazaki, Jamie Farnes, Craig S. Anderson, Xiaohui Sun, S. Ideguchi, Shane O'Sullivan, and R. J. van Weeren
Subjects: Physics, Point spread function, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Bandwidth (signal processing), FOS: Physical sciences, Astronomy and Astrophysics, law.invention, Narrow bandwidth, Wavelet, Compressed sensing, Space and Planetary Science, law, Figure of merit, Faraday cage, Astrophysics - Instrumentation and Methods for Astrophysics, Algorithm, Instrumentation and Methods for Astrophysics (astro-ph.IM), Test data, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: (abridged) We run a Faraday structure determination data challenge to benchmark the currently available algorithms including Faraday synthesis (previously called RM synthesis in the literature), wavelet, compressive sampling and $QU$-fitting. The frequency set is similar to POSSUM/GALFACTS with a 300 MHz bandwidth from 1.1 to 1.4 GHz. We define three figures of merit motivated by the underlying science: a) an average RM weighted by polarized intensity, RMwtd, b) the separation $\Delta\phi$ of two Faraday components and c) the reduced chi-squared. Based on the current test data of signal to noise ratio of about 32, we find that: (1) When only one Faraday thin component is present, most methods perform as expected, with occasional failures where two components are incorrectly found; (2) For two Faraday thin components, QU-fitting routines perform the best, with errors close to the theoretical ones for RMwtd, but with significantly higher errors for $\Delta\phi$. All other methods including standard Faraday synthesis frequently identify only one component when $\Delta\phi$ is below or near the width of the Faraday point spread function; (3) No methods, as currently implemented, work well for Faraday thick components due to the narrow bandwidth; (4) There exist combinations of two Faraday components which produce a large range of acceptable fits and hence large uncertainties in the derived single RMs; in these cases, different RMs lead to the same Q, U behavior, so no method can recover a unique input model., Comment: 15 pages, 8 figures, 5 tables, accepted by AJ. Some figures have been degraded, for a full resolution version, see http://physics.usyd.edu.au/~xhsun/datachallengeI.pdf
Published: 2014
Full Text: View/download PDF

20. Studying Galactic interstellar turbulence through fluctuations in synchrotron emission First LOFAR Galactic foreground detection

Author: Torsten A. Enßlin, I. van Bemmel, A. W. Gunst, H. Junklewitz, Wilfred Frieswijk, J. W. Broderick, Martin Bell, C. Vogt, Rainer Beck, M. Iacobelli, Cathy Horellou, E. de Geus, Vibor Jelić, Y. Tang, Sarod Yatawatta, Anna M. M. Scaife, Aris Karastergiou, R. J. van Weeren, Krzysztof T. Chyzy, J. Sluman, Michael W. Wise, Gianni Bernardi, Harvey Butcher, G. Mann, Jörg R. Hörandel, George Heald, J. van Leeuwen, D. D. Mulcahy, A. Horneffer, V. I. Kondratiev, M. Pandey-Pommier, Roberto Pizzo, Charlotte Sobey, Emanuela Orrú, Marcus Brüggen, W. Jurusik, Michel Tagger, C. Toribio, W. N. Brouw, R. Vermeulen, S. Duscha, F. de Gasperin, Jean-Mathias Griessmeier, I. M. Avruch, Heino Falcke, Gerard H. Kuper, John McKean, R. J. Dettmar, C. Tasse, Tim Hassall, Rosita Paladino, Ashish Asgekar, Anton Zensus, Michael R. Bell, Laura Birzan, J. P. Hamaker, H. J. A. Röttgering, Oleg Smirnov, Chiara Ferrari, Olaf Wucknitz, John Conway, W. Reich, Dominik J. Schwarz, Luitje Koopmans, P. Zarka, Matthias Hoeft, Carlos Sotomayor-Beltran, F. Breitling, D. Engels, H. Munk, Richard Fallows, A. Alexov, Philip Best, M. A. Garrett, C. Vocks, Jochen Eislöffel, Marijke Haverkorn, Annalisa Bonafede, B. Ciardi, M. Kuniyoshi, Matthias Steinmetz, Jason W. T. Hessels, Giulia Macario, Ben Stappers, A. G. Polatidis, Mark J. Bentum, Michael Kramer, James M. Anderson, Astronomy, Kapteyn Astronomical Institute, Iacobelli, M., Haverkorn, M., Orrú, E., Pizzo, R.F., Anderson, J., Beck, R., Bell, M.R., Bonafede, A., Chyzy, K., Dettmar, R.-J., Enßlin, T.A., Heald, G., Horellou, C., Horneffer, A., Jurusik, W., Junklewitz, H., Kuniyoshi, M., Mulcahy, D.D., Paladino, R., Reich, W., Scaife, A., Sobey, C., Sotomayor-Beltran, C., Alexov, A., Asgekar, A., Avruch, I.M., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Hörandel, J., Jelic, V., Karastergiou, A., Kondratiev, V.I., Koopmans, L.V.E., Kramer, M., Kuper, G., Van Leeuwen, J., MacArio, G., Mann, G., McKean, J.P., Munk, H., Pandey-Pommier, M., Polatidis, A.G., Röttgering, H., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B.W., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Vogt, C., Van Weeren, R.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: ISM: general, ISM: magnetic fields, ISM: structure, radio continuum: general, radio continuum: ISM, techniques: interferometric, POLARIZATION, Astronomy, Continuum (design consultancy), Astrophysics, 01 natural sciences, Power law, GHZ, EWI-24132, 010303 astronomy & astrophysics, Physics, general [ISM], MAGNETIC-FIELD, Magnetic field, interferometric [techniques], METIS-302576, WIDE-FIELD, interferometric, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Galactic coordinate system, general [radio continuum], ANGULAR POWER SPECTRUM, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, ISM [radio continuum], IR-89497, Astrophysics::Cosmology and Extragalactic Astrophysics, ISM: magnetic field, radio continuum: ISM techniques, 0103 physical sciences, Radio continuum: ISM, ALGORITHM, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, magnetic fields [ISM], Spectral density, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, W-PROJECTION, Galaxy, radiation mechanisms: non-thermal / galaxies: active / galaxies: individual: M 87 / galaxies: clusters: individual: Virgo / galaxies: jets / radio continuum: galaxies, GALAXY, 350 MHZ, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Techniques: interferometric, RADIO-EMISSION
Abstract: The characteristic outer scale of turbulence and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters. We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l,b) (137.0,+7.0) at 80"x70" resolution in the range [146,174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations . We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum of the foreground synchrotron fluctuations displays a power law behaviour for scales between 100 and 8 arcmin with a slope of (-1.84+/-0.19). We find an upper limit of about 20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence of the Galactic synchrotron foreground, finding a range of plausible values of 10-20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates., Comment: 13 pages, 11 figures, accepted for publication in A&A
Published: 2013

21. Risk factors associated with suicide in current and former US military personnel

Author: Besa Smith, Teresa M. Powell, Cynthia A. LeardMann, Tomoko I. Hooper, Charles W. Hoge, Mark Ghamsary, Edward J. Boyko, Michael R. Bell, Tyler C. Smith, and Gary D. Gackstetter
Subjects: Adult, Male, medicine.medical_specialty, Time Factors, Population, Poison control, National Death Index, Suicide prevention, Stress Disorders, Post-Traumatic, Young Adult, Sex Factors, Risk Factors, Cause of Death, medicine, Humans, Prospective Studies, Registries, Psychiatry, education, Iraq War, 2003-2011, Depression (differential diagnoses), Aged, education.field_of_study, Afghan Campaign 2001, business.industry, Data Collection, Incidence, Mental Disorders, General Medicine, Middle Aged, United States, Suicide, Millennium Cohort Study (United States), Mental Health, Military Personnel, Attributable risk, Female, business, Military deployment, Demography
Abstract: Beginning in 2005, the incidence of suicide deaths in the US military began to sharply increase. Unique stressors, such as combat deployments, have been assumed to underlie the increasing incidence. Previous military suicide studies, however, have relied on case series and cross-sectional investigations and have not linked data during service with postservice periods.To prospectively identify and quantify risk factors associated with suicide in current and former US military personnel including demographic, military, mental health, behavioral, and deployment characteristics.Prospective longitudinal study with accrual and assessment of participants in 2001, 2004, and 2007. Questionnaire data were linked with the National Death Index and the Department of Defense Medical Mortality Registry through December 31, 2008. Participants were current and former US military personnel from all service branches, including active and Reserve/National Guard, who were included in the Millennium Cohort Study (N = 151,560).Death by suicide captured by the National Death Index and the Department of Defense Medical Mortality Registry.Through the end of 2008, findings were 83 suicides in 707,493 person-years of follow-up (11.73/100,000 person-years [95% CI, 9.21-14.26]). In Cox models adjusted for age and sex, factors significantly associated with increased risk of suicide included male sex, depression, manic-depressive disorder, heavy or binge drinking, and alcohol-related problems. None of the deployment-related factors (combat experience, cumulative days deployed, or number of deployments) were associated with increased suicide risk in any of the models. In multivariable Cox models, individuals with increased risk for suicide were men (hazard ratio [HR], 2.14; 95% CI, 1.17-3.92; P = .01; attributable risk [AR], 3.5 cases/10,000 persons), and those with depression (HR, 1.96; 95% CI, 1.05-3.64; P = .03; AR, 6.9/10,000 persons), manic-depressive disorder (HR, 4.35; 95% CI, 1.56-12.09; P = .005; AR, 35.6/10,000 persons), or alcohol-related problems (HR, 2.56; 95% CI, 1.56-4.18; P.001; AR, 7.7/10,000 persons). A nested, matched case-control analysis using 20:1 control participants per case confirmed these findings.In this sample of current and former military personnel observed July 1, 2001-December 31, 2008, suicide risk was independently associated with male sex and mental disorders but not with military-specific variables. These findings may inform approaches to mitigating suicide risk in this population.
Published: 2013

22. The association between combat exposure and negative behavioral and psychiatric conditions

Author: Michael Shayne Gallaway, Michael R. Bell, David S. Fink, Mary M. Mitchell, and Amy M. Millikan
Subjects: Adult, Male, medicine.medical_specialty, Time Factors, Poison control, Logistic regression, Suicide prevention, Occupational safety and health, Surveys and Questionnaires, parasitic diseases, Injury prevention, medicine, Humans, Psychiatry, Association (psychology), Psychiatric Status Rating Scales, Combat Disorders, Aggression, business.industry, Mental Disorders, Human factors and ergonomics, United States, Psychiatry and Mental health, Alcoholism, Military Personnel, Spouse Abuse, Female, Crime, medicine.symptom, business
Abstract: This study evaluated the association between cumulative combat exposures and negative behavioral and psychiatric conditions. A total of 6128 active-duty soldiers completed a survey approximately 6 months after their unit's most recent combat deployment. The soldiers self-reported combat exposures and behavioral and psychiatric conditions. Multivariable logistic regression was used to assess the association between cumulative combat exposures and behavioral and psychiatric outcomes. In comparison with the referent group of soldiers not previously deployed, the soldiers categorized as having the highest cumulative combat exposures were significantly associated with self-reporting a history of behavioral and psychiatric diagnoses, problematic alcohol misuse, aggression, criminal behavior, and physical altercations with a significant other. The magnitude and the consistency of the association among the soldiers with the highest number of combat exposures suggest that the number of cumulative combat deployment exposures is an important consideration for identifying and treating high-risk soldiers and units returning from combat. Language: en
Published: 2013

23. Calibrating high-precision Faraday rotation measurements for LOFAR and the next generation of low-frequency radio telescopes

Author: Olaf Wucknitz, J. Kohler, D. D. Mulcahy, Aris Karastergiou, M. Iacobelli, Wilfred Frieswijk, Michael W. Wise, Gianni Bernardi, Philip Best, Gerard H. Kuper, V. I. Kondratiev, M. Pandey-Pommier, Y. Tang, Tim Hassall, Sarod Yatawatta, P. Maat, R. J. van Weeren, Evan Keane, George Heald, Frank Breitling, A. Noutsos, S. Duscha, H. Munk, R. C. Vermeulen, W. N. Brouw, J. Eisloeffel, John McKean, Stefan J. Wijnholds, T. Grit, Heino Falcke, J. Sluman, Roberto Pizzo, C. Tasse, Jean-Mathias Griessmeier, Rob Fender, I. M. Avruch, G. de Bruyn, Carlos Sotomayor-Beltran, Sera Markoff, M. Brueggen, Ralph A. M. J. Wijers, B. Ciardi, E. Juette, S. ter Veen, A. W. Gunst, Chiara Ferrari, M. Kuniyoshi, J. W. Broderick, Giulia Macario, Matthias Hoeft, A. Horneffer, M. Pilia, Michel Tagger, Jason W. T. Hessels, F. de Gasperin, Annalisa Bonafede, Richard Fallows, A. Alexov, Luitje Koopmans, Martin Bell, M. A. Garrett, Rainer Beck, M. Serylak, Michael Kramer, P. Zarka, Huub Roettgering, J. van Leeuwen, James M. Anderson, R. J. Dettmar, Mark J. Bentum, Ben Stappers, A. G. Polatidis, Laura Birzan, Ashish Asgekar, Charlotte Sobey, Emanuela Orrú, Michael R. Bell, A. van Duin, H. Paas, W. Reich, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), University of Amsterdam [Amsterdam] (UvA), Netherlands Institute for Radio Astronomy (ASTRON), SRON Netherlands Institute for Space Research (SRON), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Institute of Mathematical and Physical Sciences, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Oxford Astrophysics, University of Oxford [Oxford], Centre for Astrophysics and Supercomputing, Swinburne University of Technology [Melbourne], Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Astronomy, Kapteyn Astronomical Institute, High Energy Astrophys. & Astropart. Phys (API, FNWI), Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Sotomayor-Beltran, C., Sobey, C., Hessels, J.W.T., De Bruyn, G., Noutsos, A., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Beck, R., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Ciardi, B., De Gasperin, F., Dettmar, R.-J., Van Duin, A., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Keane, E., Kohler, J., Kramer, M., Kondratiev, V.I., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., MacArio, G., Markoff, S., McKean, J.P., Mulcahy, D.D., Munk, H., Orru, E., Paas, H., Pandey-Pommier, M., Pilia, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Serylak, M., Sluman, J., Stappers, B.W., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van Weeren, R.J., Wijers, R.A.M.J., Wijnholds, S.J., Wise, M.W., Wucknitz, O., Yatawatta, S., and Zarka, P.
Subjects: 010504 meteorology & atmospheric sciences, Astronomy, VLA, Polarimetry, FOS: Physical sciences, IR-89498, Astrophysics::Cosmology and Extragalactic Astrophysics, Rotation, 01 natural sciences, law.invention, Radio telescope, PULSAR ROTATION, symbols.namesake, MHZ, Pulsar, DISPERSION, law, 0103 physical sciences, Faraday effect, DEPOLARIZATION, Faraday cage, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, EWI-24501, polarization, Astrophysics::Instrumentation and Methods for Astrophysics, METIS-302716, Astronomy and Astrophysics, GALACTIC MAGNETIC-FIELD, LOFAR, Astronomy and Astrophysic, GALAXY, techniques: polarimetric, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, symbols, ARRAY, Ionosphere, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: International audience; Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achieving the full potential of these measurements requires accurate removal of the time-variable ionospheric Faraday rotation contribution. We present ionFR, a code that calculates the amount of ionospheric Faraday rotation for a specific epoch, geographic location, and line-of-sight. ionFR uses a number of publicly available, GPS-derived total electron content maps and the most recent release of the International Geomagnetic Reference Field. We describe applications of this code for the calibration of radio polarimetric observations, and demonstrate the high accuracy of its modeled ionospheric Faraday rotations using LOFAR pulsar observations. These show that we can accurately determine some of the highest-precision pulsar rotation measures ever achieved. Precision rotation measures can be used to monitor rotation measure variations - either intrinsic or due to the changing line-of-sight through the interstellar medium. This calibration is particularly important for nearby sources, where the ionosphere can contribute a significant fraction of the observed rotation measure. We also discuss planned improvements to ionFR, as well as the importance of ionospheric Faraday rotation calibration for the emerging generation of low-frequency radio telescopes, such as the SKA and its pathfinders.
Published: 2013

24. NIFTY - Numerical Information Field Theory - a versatile Python library for signal inference

Author: Torsten A. Enßlin, Martin Reinecke, Niels Oppermann, Michael R. Bell, Maksim Greiner, H. Junklewitz, Marco Selig, and Carlos Pachajoa
Subjects: FOS: Computer and information sciences, Theoretical computer science, Discretization, Information field, Computer Science - Information Theory, Inference, FOS: Physical sciences, Astrophysics, Statistics - Computation, symbols.namesake, Instrumentation and Methods for Astrophysics (astro-ph.IM), Computation (stat.CO), Mathematical Physics, computer.programming_language, Physics, Information Theory (cs.IT), Wiener filter, Astronomy and Astrophysics, Probability and statistics, Mathematical Physics (math-ph), Python (programming language), Grid, Software package, Space and Planetary Science, Physics - Data Analysis, Statistics and Probability, symbols, Computer Science - Mathematical Software, Astrophysics - Instrumentation and Methods for Astrophysics, computer, Mathematical Software (cs.MS), Data Analysis, Statistics and Probability (physics.data-an)
Abstract: NIFTY, "Numerical Information Field Theory", is a software package designed to enable the development of signal inference algorithms that operate regardless of the underlying spatial grid and its resolution. Its object-oriented framework is written in Python, although it accesses libraries written in Cython, C++, and C for efficiency. NIFTY offers a toolkit that abstracts discretized representations of continuous spaces, fields in these spaces, and operators acting on fields into classes. Thereby, the correct normalization of operations on fields is taken care of automatically without concerning the user. This allows for an abstract formulation and programming of inference algorithms, including those derived within information field theory. Thus, NIFTY permits its user to rapidly prototype algorithms in 1D, and then apply the developed code in higher-dimensional settings of real world problems. The set of spaces on which NIFTY operates comprises point sets, n-dimensional regular grids, spherical spaces, their harmonic counterparts, and product spaces constructed as combinations of those. The functionality and diversity of the package is demonstrated by a Wiener filter code example that successfully runs without modification regardless of the space on which the inference problem is defined., 9 pages, 3 tables, 4 figures, accepted by Astronomy & Astrophysics; refereed version, 1 figure added, results unchanged
Published: 2013

25. Initial deep LOFAR observations of Epoch of Reionization windows: I. The North Celestial Pole

Author: M. A. Garrett, Vibor Jelić, Michel Tagger, B. Ciardi, Aris Karastergiou, Harish Vedantham, Marco Iacobelli, Michael W. Wise, Gianni Bernardi, Garrelt Mellema, F. Breitling, F. B. Abdalla, Panagiotis Labropoulos, H. Paas, R. J. van Weeren, Richard Fallows, Léon V. E. Koopmans, M. Kuniyoshi, Michiel A. Brentjens, W. N. Brouw, R. Nijboer, E. Juette, Emanuela Orru, Olaf Wucknitz, V. Veligatla, Gottfried Mann, Ben Stappers, John McKean, M. Mevius, A. G. Polatidis, J. M. Anderson, A. Alexov, Gerard H. Kuper, J. D. Mol, S. ter Veen, Annalisa Bonafede, R. Pizzo, A. W. Gunst, T. E. Hassall, M. Pandey-Pommier, Ph. Zarka, Joop Schaye, Geraint Harker, Michael Kramer, J. Sluman, P. Maat, Jason W. T. Hessels, M. J. Norden, H. J. A. Röttgering, A. R. Offringa, Philip Best, V. I. Kondratiev, Heino Falcke, V. N. Pandey, Chiara Ferrari, J. Noordam, S. Duscha, E. de Geus, John Conway, R. Vermeulen, Sarod Yatawatta, S. Kazemi, Matthias Hoeft, S. Daiboo, F. Batejat, Michael R. Bell, Wolfgang Reich, Saleem Zaroubi, J. M. Griessmeier, R. H. van de Brink, Rajat M. Thomas, Cyril Tasse, Y. Tang, J. W. Broderick, Emma Chapman, Mark J. Bentum, Stefan J. Wijnholds, J. van Leeuwen, Joel N. Bregman, H. Munk, Marcus Brüggen, F. de Gasperin, W. Frieswijk, I. M. Avruch, Oleg Smirnov, Matthias Steinmetz, Martin Bell, O. Martinez Rubi, de Antonius Bruyn, Netherlands Institute for Radio Astronomy (ASTRON), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Department of process and energy, Delft University of Technology (TU Delft), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Center for Astrophysics and Space Astronomy [Boulder] (CASA), University of Colorado [Boulder], Stockholm Observatory Department of Astronomy, Stockholm University, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Génétique Diversité et Ecophysiologie des Céréales (GDEC), Institut National de la Recherche Agronomique (INRA)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Max-Planck-Institut für Radioastronomie (MPIFR), Radboud university [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Thüringer Landessternwarte Tautenburg (TLS), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], University of Amsterdam [Amsterdam] (UvA), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Center for Information Technology CIT, Université de Groningen, Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de la Recherche Agronomique (INRA), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Yatawatta, S., De Bruyn, A.G., Brentjens, M.A., Labropoulos, P., Pandey, V.N., Kazemi, S., Zaroubi, S., Koopmans, L.V.E., Offringa, A.R., Jelić, V., Martinez Rubi, O., Veligatla, V., Wijnholds, S.J., Brouw, W.N., Bernardi, G., Ciardi, B., Daiboo, S., Harker, G., Mellema, G., Schaye, J., Thomas, R., Vedantham, H., Chapman, E., Abdalla, F.B., Alexov, A., Anderson, J., Avruch, I.M., Batejat, F., Bell, M.E., Bell, M.R., Bentum, M., Best, P., Bonafede, A., Bregman, J., Breitling, F., Van De Brink, R.H., Broderick, J.W., Brüggen, M., Conway, J., De Gasperin, F., De Geus, E., Duscha, S., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Griessmeier, J.M., Gunst, A.W., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., Mann, G., McKean, J.P., Mevius, M., Mol, J.D., Munk, H., Nijboer, R., Noordam, J.E., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Sluman, J., Smirnov, O., Stappers, B., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van Weeren, R.J., Wise, M., Wucknitz, O., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astronomy, first stars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, Instrumentation: interferometer, METIS-302720, Celestial pole, first stars -instrumentation: interferometers -techniques: interferometric -methods: data analysis, 0103 physical sciences, dark ages, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Reionization, Physics, reionization, instrumentation: interferometers, techniques: interferometric, methods: data analysis, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, IR-89500, Instrumentation: interferometers – Techniques: interferometric – Cosmology: observations, Astrophysics::Instrumentation and Methods for Astrophysics, EWI-24509, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Redshift, Galaxy, diffuse radiation, Dark ages, reionization, first star, Orders of magnitude (time), Space and Planetary Science, Instrumentation: interferometers, Techniques: interferometric, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Ionosphere, Astrophysics - Instrumentation and Methods for Astrophysics, Noise (radio), Methods: data analysi, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP., 19 pages, 24 figures. Draft version with low resolution images. Accepted on 08/01/2013 Astronomy & Astrophysics. Abstract abridged. Version with high resolution images: http://www.astro.rug.nl/~yatawatta/ncp_eor.pdf
Published: 2013

26. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author: Jochen Eislöffel, Maaijke Mevius, R. J. van Weeren, Ralph A. M. J. Wijers, A. G. Polatidis, D. McKay-Bukowski, Chiara Ferrari, John Conway, Wilfred Frieswijk, Y. Tang, Glenn J. White, Robert Braun, Michael R. Bell, J. Sluman, W. A. van Cappellen, V. N. Pandey, Richard Fallows, Raffaella Morganti, H. J. A. Röttgering, Philip Best, M. A. Garrett, T. Grit, Charlotte Sobey, Emanuela Orrú, I. M. Avruch, P. Maat, M. J. Norden, Rainer Beck, D. D. Mulcahy, Michel Tagger, Annalisa Bonafede, James Miller-Jones, Aris Karastergiou, Sarod Yatawatta, J.-M. Grießmeier, J. B. R. Oonk, H. Paas, B. Ciardi, C. Tasse, Michael W. Wise, Heino Falcke, Gianni Bernardi, Ashish Asgekar, M. Kuniyoshi, Oleg Smirnov, Matthias Steinmetz, J. Kohler, Marco Iacobelli, E. Juette, John McKean, H. Munk, Marcus Brüggen, Harvey Butcher, G. Kuper, J. M. Anderson, V. I. Kondratiev, Christian Vocks, T. E. Hassall, M. Pandey-Pommier, Casey J. Law, F. Breitling, M. de Vos, A. W. Gunst, S. Duscha, Neal Jackson, Olaf Wucknitz, Sera Markoff, A. de Jong, Laura Birzan, Giulia Macario, A. Schoenmakers, Wolfgang Reich, Huib Intema, J. W. Broderick, J. D. Mol, E. de Geus, Jason W. T. Hessels, R. Pizzo, P. Zarka, George Heald, Mark J. Bentum, W. N. Brouw, Gottfried Mann, R. Vermeulen, Matthias Hoeft, F. Batejat, Bart Scheers, I. van Bemmel, Martin Bell, F. de Gasperin, J. van Leeuwen, R. H. van de Brink, Netherlands Institute for Radio Astronomy (ASTRON), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], SLAC National Accelerator Laboratory (SLAC), Stanford University, Jodrell Bank Cent. for Astrophysics, University of Manchester [Manchester], Max-Planck-Institut für Radioastronomie (MPIFR), SRON Netherlands Institute for Space Research (SRON), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Southampton, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jacobs University [Bremen], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Institute of Mathematical and Physical Sciences, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Jodrell Bank Centre for Astrophysics, University of Amsterdam [Amsterdam] (UvA), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Rhodes University, Grahamstown, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Harvard University-Smithsonian Institution, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Asgekar, A., Oonk, J.B.R., Yatawatta, S., Van Weeren, R.J., McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, M.R., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Braun, R., Breitling, F., Van De Brink, R.H., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Van Cappellen, W., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., De Jong, A., De Vos, M., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C., Van Leeuwen, J., Maat, P., MacArio, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevius, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scheers, B., Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Astronomy, and Kapteyn Astronomical Institute
Subjects: Astronomy, chemistry.chemical_element, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, ISM: individual objects: Cassiopeia A, IR-89496, Astronomy & Astrophysics, Low frequency, ISM: individual objects: Cas siopeia A, 01 natural sciences, ISM: clouds, Spectral line, CARBON, MHZ, ISM: cloud, 0103 physical sciences, EWI-24495, Spectral resolution, Supernova remnant, 010303 astronomy & astrophysics, Helium, Radio lines: ISM, Astrophysics::Galaxy Astrophysics, Line (formation), Physics, radio lines : ISM, 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, REGIONS, Astrophysics - Astrophysics of Galaxies, METIS-302711, Cassiopeia A, chemistry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ISM: clouds / radio lines: ISM / ISM: individual objects: Cassiopeia A, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: Cassiopeia A was observed using the Low-Band Antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon-alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of > 5 from two independent LOFAR datasets. The derived line velocities (v_LSR ~ -50 km/s) and integrated optical depths (~ 13 s^-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR dataset and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 %) integrated optical depths, indicating that there is small-scale angular structure on the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 x 10^-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band., Accepted for publication in A&A Letters; 5 pages, 4 colour figures
Published: 2013

27. The brightness and spatial distributions of terrestrial radio sources

Author: W. N. Brouw, D. A. Rafferty, Oleg Smirnov, John McKean, Harvey Butcher, M. A. Garrett, M. Pandey-Pommier, Geraint Harker, Stefan J. Wijnholds, H. J. A. Röttgering, Marco Iacobelli, Jean-Mathias Grießmeier, Ashish Asgekar, Michael R. Bell, R. J. van Weeren, Abhik Ghosh, S. Duscha, Olaf Wucknitz, Christian Vocks, G. Kuper, Saleem Zaroubi, W. Reich, Frank Breitling, P. Maat, M. J. Norden, Ilian T. Iliev, I. M. Avruch, B. Ciardi, C. Tasse, Rene C. Vermeulen, Giulia Macario, Wilfred Frieswijk, V. I. Kondratiev, Chiara Ferrari, Rainer Beck, Laura Birzan, Y. Tang, Anna M. M. Scaife, Charlotte Sobey, S. ter Veen, A. Horneffer, M. Kuniyoshi, Emanuela Orrú, A. Alexov, Jochen Eislöffel, H. Paas, Luitje Koopmans, M. de Vos, E. Juette, Wouter Klijn, Michel Tagger, H. Meulman, A. G. Polatidis, F. B. Abdalla, J. van Leeuwen, J. Sluman, F. de Gasperin, A. R. Offringa, Roberto Pizzo, Richard Fallows, A. G. de Bruyn, Tim Hassall, R. van Nieuwpoort, Martin Bell, Mark J. Bentum, C. Toribio, J. W. Broderick, E. de Geus, M. Loose, Philippe Zarka, Philip Best, Marcus Brüggen, Gottfried Mann, J. M. Anderson, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Garrelt Mellema, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Netherlands Institute for Radio Astronomy ( ASTRON ), University College of London [London] (UCL), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, University of Sussex, Center for Astrophysics and Space Astronomy [Boulder] (CASA), University of Colorado [Boulder], AlbaNova University Center, Stockholm University, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Space Telescope Science Institute (STSci), Max-Planck-Institut für Radioastronomie (MPIFR), SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Leibniz-Institut für Astrophysik Potsdam (AIP), School of Physics and Astronomy [Southampton], University of Southampton, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], University of Amsterdam [Amsterdam] (UvA), Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Physics-Electronics, Rhodes University, Grahamstown, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Harvard University-Smithsonian Institution, Universiteit Leiden, Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Rhodes University, Kapteyn Astronomical Institute, Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Brightness, IR-89516, Astronomy, radio continuum: general, 02 engineering and technology, Astrophysics, PROPAGATION, Interference (wave propagation), 01 natural sciences, Cosmology, 0202 electrical engineering, electronic engineering, information engineering, EWI-24493, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Physics, INTERFERENCE MITIGATION, Astrophysics::Instrumentation and Methods for Astrophysics, ASTRONOMY, Physics - Atmospheric and Oceanic Physics, techniques: interferometric, Dark Ages, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, reionization, methods: observational, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, atmospheric effects, Cosmology and Nongalactic Astrophysics (astro-ph.CO), [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], first stars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, reionisation, 0103 physical sciences, dark ages, reionization, first stars, Visibility, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), EPOCH, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], atmospheric effects – instrumentation: interferometers – methods: observational – techniques: interferometric – radio continuum: general – dark ages, 020206 networking & telecommunications, Astronomy and Astrophysics, LOFAR, Redshift, METIS-302710, Space and Planetary Science, Atmospheric and Oceanic Physics (physics.ao-ph), TELESCOPES
Abstract: Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obstruct the detection of the weak astronomical signals of interest. This issue is especially important for Epoch of Reionisation (EoR) projects that try to detect the faint redshifted HI signals from the time of the earliest structures in the Universe. We explore the RFI situation at 30-163 MHz by studying brightness histograms of visibility data observed with LOFAR, similar to radio-source-count analyses that are used in cosmology. An empirical RFI distribution model is derived that allows the simulation of RFI in radio observations. The brightness histograms show an RFI distribution that follows a power-law distribution with an estimated exponent around -1.5. With several assumptions, this can be explained with a uniform distribution of terrestrial radio sources whose radiation follows existing propagation models. Extrapolation of the power law implies that the current LOFAR EoR observations should be severely RFI limited if the strength of RFI sources remains strong after time integration. This is in contrast with actual observations, which almost reach the thermal noise and are thought not to be limited by RFI. Therefore, we conclude that it is unlikely that there are undetected RFI sources that will become visible in long observations. Consequently, there is no indication that RFI will prevent an EoR detection with LOFAR., Accepted for publication in MNRAS
Published: 2013

28. The LOFAR radio environment

Author: R.-J. Dettmar, Steve Rawlings, Vibor Jelić, Benedetta Ciardi, Ben Stappers, Aris Karastergiou, Y. Tang, R. Pizzo, V. N. Pandey, A. Alexov, Michael W. Wise, Gianni Bernardi, J. Eisloeffel, J. Sluman, W. A. van Cappellen, Panagiotis Labropoulos, Garrelt Mellema, A. Schoenmakers, M. Mevius, John Conway, P. Maat, M. P. van Haarlem, Rainer Beck, G. van Diepen, M. J. Norden, Heino Falcke, A. W. Gunst, Sarod Yatawatta, R. Nijboer, V. Veligatla, Joop Schaye, J. M. Anderson, D. A. Rafferty, S. Daiboo, M. Kuniyoshi, Michael R. Bell, A. G. Polatidis, A. van Duin, H. Paas, Harish Vedantham, A. G. de Bruyn, V. I. Kondratiev, H. Meulman, A. van Ardenne, Harvey Butcher, J. D. Mol, Laura Birzan, M. Pandey, Michel Tagger, Michiel A. Brentjens, M. Gerbers, Jason W. T. Hessels, George Heald, Matthias Steinmetz, Rob Fender, Marcus Brüggen, Annalisa Bonafede, Gottfried Mann, Mark J. Bentum, Saleem Zaroubi, J. Noordam, Charlotte Sobey, John McKean, John D. Swinbank, Olaf Wucknitz, Gerard H. Kuper, Stefan J. Wijnholds, O. Martinez-Ruby, Léon V. E. Koopmans, Ph. Zarka, Philip Best, Ashish Asgekar, Y. Koopman, R. Vermeulen, A. R. Offringa, R. J. van Weeren, Matthias Hoeft, A. Horneffer, Huub Röttgering, M. Avruch, T. E. Hassall, Martin Bell, J. M. Griessmeier, Geraint Harker, M. de Vos, Ralph A. M. J. Wijers, Christian Vocks, W. Frieswijk, Wolfgang Reich, Oleg Smirnov, Cyril Tasse, J. W. Broderick, F. Breitling, S. Kazemi, J. van Leeuwen, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Netherlands Institute for Radio Astronomy (ASTRON), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Department of process and energy, Delft University of Technology (TU Delft), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Radboud university [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Thüringer Landessternwarte Tautenburg (TLS), Oxford Astrophysics, University of Oxford [Oxford], Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), Center for Information Technology CIT, Université de Groningen, Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Rhodes University, Grahamstown, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Department of Reproduction and Development, Erasmus University Rotterdam, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Offringa, A.R., De Bruyn, A.G., Zaroubi, S., Van Diepen, G., Martinez-Ruby, O., Labropoulos, P., Brentjens, M.A., Ciardi, B., Daiboo, S., Harker, G., Jelić, V., Kazemi, S., Koopmans, L.V.E., Mellema, G., Pandey, V.N., Pizzo, R.F., Schaye, J., Vedantham, H., Veligatla, V., Wijnholds, S.J., Yatawatta, S., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, M., Beck, R., Bell, M., Bell, M.R., Bentum, M., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H., Conway, J., De Vos, M., Dettmar, R.J., Eisloeffel, J., Falcke, H., Fender, R., Frieswijk, W., Gerbers, M., Griessmeier, J.M., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J., Hoeft, M., Horneffer, A., Karastergiou, A., Kondratiev, V., Koopman, Y., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McKean, J., Meulman, H., Mevius, M., Mol, J.D., Nijboer, R., Noordam, J., Norden, M., Paas, H., Pandey, M., Pizzo, R., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., Röttgering, H.J.A., Schoenmakers, A.P., Sluman, J., Smirnov, O., Sobey, C., Stappers, B., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Van Ardenne, A., Van Cappellen, W., Van Duin, A.P., Van Haarlem, M., Van Leeuwen, J., Van Weeren, R.J., Vermeulen, R., Vocks, C., Wijers, R.A.M.J., Wise, M., Wucknitz, O., UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Anton de Kom University of Suriname, Rhodes University, SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), university Rotterdam, Astronomy, Kapteyn Astronomical Institute, Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Astronomy, instrumentation: interferometers, methods: data analysis, techniques: interferometric, telescopes, radio continuum: general, FOS: Physical sciences, RFI, 02 engineering and technology, Interference (wave propagation), 01 natural sciences, EWI-22636, Instrumentation: interferometer, Radio continuum: general, REMOVAL, Instrumentation: interferometers - Methods: data analysis - Techniques: interferometric - Telescopes - Radio continuum: general, 0103 physical sciences, Broadband, 0202 electrical engineering, electronic engineering, information engineering, Range (statistics), 010303 astronomy & astrophysics, IR-82457, Instrumentation and Methods for Astrophysics (astro-ph.IM), Telescope, FILTERING TECHNIQUES, Remote sensing, Significant difference, INTERFERENCE MITIGATION, Linearity, ASTRONOMY, 020206 networking & telecommunications, Astronomy and Astrophysics, Time resolution, LOFAR, Astronomy and Astrophysic, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Techniques: interferometric, TELESCOPES, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Environmental science, Astrophysics - Instrumentation and Methods for Astrophysics, METIS-293223, Radio astronomy, Methods: data analysi
Abstract: Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz / 1 s resolution. Results: We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linearly when decreasing the data frequency resolution. Conclusions: Currently, by using an automated RFI detection strategy, the LOFAR radio environment poses no perceivable problems for sensitive observing. It remains to be seen if this is still true for very deep observations that integrate over tens of nights, but the situation looks promising. Reasons for the low impact of RFI are the high spectral and time resolution of LOFAR; accurate detection methods; strong filters and high receiver linearity; and the proximity of the antennas to the ground. We discuss some strategies that can be used once low-level RFI starts to become apparent. It is important that the frequency range of LOFAR remains free of broadband interference, such as DAB stations and windmills., Comment: Accepted for publication in A&A. 15 figures, 16 pages
Published: 2013

29. RESOLVE: A new algorithm for aperture synthesis imaging of extended emission in radio astronomy

Author: H. Junklewitz, Marco Selig, Torsten A. Enßlin, and Michael R. Bell
Subjects: Point spread function, Physics, Spatial correlation, Aperture synthesis, media_common.quotation_subject, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Weighting, Space and Planetary Science, Sky brightness, Sky, 0103 physical sciences, Surface brightness, Astrophysics - Instrumentation and Methods for Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Algorithm, Instrumentation and Methods for Astrophysics (astro-ph.IM), Radio astronomy, media_common
Abstract: We present RESOLVE, a new algorithm for radio aperture synthesis imaging of extended and diffuse emission in total intensity. The algorithm is derived using Bayesian statistical inference techniques, estimating the surface brightness in the sky assuming a priori log-normal statistics. RESOLVE not only estimates the measured sky brightness in total intensity, but also its spatial correlation structure, which is used to guide the algorithm to an optimal reconstruction of extended and diffuse sources. For a radio interferometer, it succeeds in deconvolving the effects of the instrumental point spread function during this process. Additionally, RESOLVE provides a map with an uncertainty estimate of the reconstructed surface brightness. Furthermore, with RESOLVE we introduce a new, optimal visibility weighting scheme that can be viewed as an extension to robust weighting. In tests using simulated observations, the algorithm shows improved performance against two standard imaging approaches for extended sources, Multiscale-CLEAN and the Maximum Entropy Method., Comment: 22 pages, 8 figures, submitted to Astronomy & Astrophysics
Published: 2013
Full Text: View/download PDF

30. Improved CLEAN reconstructions for rotation measure synthesis with maximum likelihood estimation

Author: Michael R. Bell, Alexandra Crai, Niels Oppermann, and Torsten A. Enßlin
Subjects: Discretization, Point source, Computer science, Maximum likelihood, media_common.quotation_subject, FOS: Physical sciences, Astronomy and Astrophysics, Measure (mathematics), Space and Planetary Science, Sky, Deconvolution, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Algorithm, Rotation (mathematics), media_common
Abstract: The CLEAN deconvolution algorithm has well-known limitations due to the restriction of locating point source model components on a discretized grid. In this letter we demonstrate that these limitations are even more pronounced when applying CLEAN in the case of Rotation Measure (RM) synthesis imaging. We suggest a modification that uses Maximum Likelihood estimation to adjust the CLEAN-derived sky model. We demonstrate through the use of mock one-dimensional RM synthesis observations that this technique shows significant improvement over standard CLEAN and gives results that are independent of the chosen image pixelization. We suggest using this simple modification to CLEAN in upcoming polarization sensitive sky surveys., 5 pages, 4 figures, submitted to A&A
Published: 2012

31. Wide-band simultaneous observations of pulsars: disentangling dispersion measure and profile variations

Author: P. Maat, Benjamin Stappers, Heino Falcke, Charlotte Sobey, Emanuela Orrú, Jason W. T. Hessels, E. Rol, L. Bähren, H. Meulman, Joris P. W. Verbiest, C. Tasse, A. Alexov, Matthias Hoeft, M. A. Garrett, Sarod Yatawatta, James Miller-Jones, Evan Keane, Michael Kramer, S. ter Veen, J. Masters, A. W. Gunst, Casey J. Law, Jochen Eislöffel, B. Scheers, Maaijke Mevius, T. E. Hassall, J. W. Broderick, R. C. Vermeulen, B. Ciardi, Martin Bell, John McKean, Luitje Koopmans, J. E. Noordam, Gerard H. Kuper, Annalisa Bonafede, Harvey Butcher, Sera Markoff, M. P. van Haarlem, E. J. Daw, Rudy Wijnands, M. Kuniyoshi, V. I. Kondratiev, M. Pandey-Pommier, A. Noutsos, K. Zagkouris, Michael R. Bell, H. Paas, J. Sluman, Michiel A. Brentjens, Ashish Asgekar, Roberto Pizzo, Marcus Brüggen, C. G. M. Sterks, W. Reich, R. A. Osten, Albert-Jan Boonstra, Michel Tagger, Stephane Corbel, A. G. Polatidis, P.G. Jonker, M. Gerbers, Stefan J. Wijnholds, J. van Leeuwen, H. Spreeuw, A. de Jong, Matthias Steinmetz, R. J. van Weeren, P. Zarka, K. Lazaridis, George Heald, Mark J. Bentum, G. M. Loose, W. N. Brouw, Patrick Weltevrede, V. S. Dhillon, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, M. Serylak, Rob Fender, Ralph A. M. J. Wijers, H. J. A. Röttgering, H. A. Holties, Y. Tang, Anna M. M. Scaife, Olaf Wucknitz, H. Munk, John D. Swinbank, Jean-Mathias Griessmeier, Vishambhar Pandey, Philip Best, Pim Schellart, T. Coenen, Kenneth C. Anderson, Kapteyn Astronomical Institute, Astronomy, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Oxford Astrophysics, University of Oxford [Oxford], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Southampton, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), University of Sheffield [Sheffield], Thüringer Landessternwarte Tautenburg (TLS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Space Telescope Science Institute (STSci), School of Physics and Astronomy [Southampton], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Jacobs University [Bremen], Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], National Radio Astronomy Observatory (NRAO), Applied Stochastics (IMAPP), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Center for Information Technology CIT, Université de Groningen, Netherlands Foundation for Scientific Research. Joeri van Leeuwen and ThijsCoenen are supported by the Netherlands Research School for Astronomy (GrantNOVA3-NW3-2.3.1), European Project: 224838,EC:FP7:PEOPLE,FP7-PEOPLE-2007-4-3-IRG,PULSARS WITH LOFAR(2008), European Project: 236394,EC:FP7:PEOPLE,FP7-PEOPLE-IEF-2008,PULSAR SURVEY(2010), Hassall, T.E., Stappers, B.W., Hessels, J.W.T., Kramer, M., Alexov, A., Anderson, K., Coenen, T., Karastergiou, A., Keane, E.F., Kondratiev, V.I., Lazaridis, K., Van Leeuwen, J., Noutsos, A., Serylak, M., Sobey, C., Verbiest, J.P.W., Weltevrede, P., Zagkouris, K., Fender, R., Wijers, R.A.M.J., Bähren, L., Bell, M.E., Broderick, J.W., Corbel, S., Daw, E.J., Dhillon, V.S., Eislöffel, J., Falcke, H., Grießmeier, J.-M., Jonker, P., Law, C., Markoff, S., Miller-Jones, J.C.A., Osten, R., Rol, E., Scaife, A.M.M., Scheers, B., Schellart, P., Spreeuw, H., Swinbank, J., Ter Veen, S., Wise, M.W., Wijnands, R., Wucknitz, O., Zarka, P., Asgekar, A., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Boonstra, A.J., Brentjens, M., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Garrett, M.A., Gerbers, M., Gunst, A.W., Van Haarlem, M.P., Heald, G., Hoeft, M., Holties, H., De Jong, A., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., Loose, G.M., Maat, P., Masters, J., McKean, J.P., Meulman, H., Mevius, M., Munk, H., Noordam, J.E., Orrú, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A., Reich, W., Röttgering, H., Sluman, J., Steinmetz, M., Sterks, C.G.M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Van Weeren, R.J., Wijnholds, S.J., Yatawatta, S., University of Oxford, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Harvard University-Smithsonian Institution, Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Rhodes University, SKA South Africa, and Ska South Africa
Subjects: 010504 meteorology & atmospheric sciences, Astronomy, Magnetosphere, Astrophysics, magnetic fields, 01 natural sciences, law.invention, law, Dispersion (optics), 010303 astronomy & astrophysics, Telescope, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], Astrophysics::Instrumentation and Methods for Astrophysics, SPECTRAL BEHAVIOR, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, ARRIVAL-TIME DELAY, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, SUPERDISPERSION DELAY, EMPIRICAL-THEORY, Pulsar, pulsars: general, 0103 physical sciences, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, ISM: general, METIS-287956, Gravitational wave, Astronomy and Astrophysics, telescopes, LOFAR, Astronomy and Astrophysic, EWI-22107, Pulse (physics), PULSES, Interstellar medium, PSR 0809&74, FREQUENCY-DEPENDENCE, Magnetic field, Space and Planetary Science, [SDU]Sciences of the Universe [physics], RADIO-EMISSION, IR-80985, REFRACTION, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], INTERSTELLAR SCATTERING
Abstract: Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR (at 40-190 MHz), the 76-m Lovell Telescope (at 1400 MHz) and the Effelsberg 100-m Telescope (at 8000 MHz) to test the accuracy of the dispersion law over a broad frequency range. In this paper we present the results of these observations which show that the dispersion law is accurate to better than 1 part in 100000 across our observing band. We use this fact to constrain some of the properties of the ISM along the line-of-sight and use the lack of any aberration or retardation effects to determine upper limits on emission heights in the pulsar magnetosphere. We also discuss the effect of pulse profile evolution on our observations, and the implications that it could have for precision pulsar timing projects such as the detection of gravitational waves with pulsar timing arrays., 20 Pages, 14 Figures, Accepted for publication in Astronomy & Astrophysics
Published: 2012

32. An epidemiologic investigation of homicides at Fort Carson, Colorado: summary of findings

Author: Michael G. Sweda, Maureen T. Lagana, Anthony L. Cox, Michael R. Bell, Amy M. Millikan, and M. Shayne Gallaway
Subjects: medicine.medical_specialty, Colorado, Poison control, Health Promotion, Suicide prevention, Occupational safety and health, Cohort Studies, Risk Factors, Environmental health, Surveys and Questionnaires, Interview, Psychological, medicine, Cluster Analysis, Humans, Social determinants of health, Military Medicine, Retrospective Studies, business.industry, Public health, Public Health, Environmental and Occupational Health, General Medicine, Focus Groups, Focus group, Aggression, Health promotion, Military Personnel, Family medicine, business, Homicide, Cohort study
Abstract: In response to an apparent clustering of homicides at Fort Carson, Colorado, the U.S. Army Public Health Command (formerly the U.S. Army Center for Health Promotion and Preventive Medicine) Behavioral and Social Health Outcomes Program conducted a multidisciplinary epidemiologic consultation to identify factors contributing to violent behavior among soldiers at Fort Carson. This article summarizes the findings of the epidemiologic consultation report as provided to the Secretary of the Army and the Fort Carson Senior Mission Commander and released in its entirety publicly July 2009 and elaborates on the mixed-methods analytic approach used to study a complex behavioral issue at the community level. To aid in answering the key study questions, six study arms were designed and carried out: (1) index case analysis, (2) confinee interviews, (3) analysis of installation-level trends, (4) retrospective cohort analysis, (5) soldier focus groups and interviews, and (6) aggression risk factors survey. Although not conclusive, the findings suggest a combination of individual, unit, and environmental factors converged to increase the risk of violent behaviors, which made clustering of negative outcomes more likely.
Published: 2012

33. Reconstruction of Gaussian and log-normal fields with spectral smoothness

Author: Michael R. Bell, Marco Selig, Torsten A. Enßlin, and Niels Oppermann
Subjects: FOS: Computer and information sciences, Mathematical optimization, Random field, Gaussian, Spectral density, FOS: Physical sciences, Reconstruction algorithm, Methodology (stat.ME), symbols.namesake, Gaussian noise, Physics - Data Analysis, Statistics and Probability, Log-normal distribution, Maximum a posteriori estimation, symbols, Statistical physics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Statistics - Methodology, Data Analysis, Statistics and Probability (physics.data-an), Mathematics, Ansatz
Abstract: We develop a method to infer log-normal random fields from measurement data affected by Gaussian noise. The log-normal model is well suited to describe strictly positive signals with fluctuations whose amplitude varies over several orders of magnitude. We use the formalism of minimum Gibbs free energy to derive an algorithm that uses the signal's correlation structure to regularize the reconstruction. The correlation structure, described by the signal's power spectrum, is thereby reconstructed from the same data set. We show that the minimization of the Gibbs free energy, corresponding to a Gaussian approximation to the posterior marginalized over the power spectrum, is equivalent to the empirical Bayes ansatz, in which the power spectrum is fixed to its maximum a posteriori value. We further introduce a prior for the power spectrum that enforces spectral smoothness. The appropriateness of this prior in different scenarios is discussed and its effects on the reconstruction's results are demonstrated. We validate the performance of our reconstruction algorithm in a series of one- and two-dimensional test cases with varying degrees of non-linearity and different noise levels., Comment: 18 pages, 12 figures
Published: 2012
Full Text: View/download PDF

34. Faraday synthesis: The synergy of aperture and rotation measure synthesis

Author: Michael R. Bell and Torsten A. Enßlin
Subjects: Computer science, Dynamic range, Aperture, business.industry, Measure (physics), ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, FOS: Physical sciences, Astronomy and Astrophysics, law.invention, Interferometry, Signal-to-noise ratio, Optics, Space and Planetary Science, law, Deconvolution, Faraday cage, business, Astrophysics - Instrumentation and Methods for Astrophysics, Rotation (mathematics), Image resolution, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract: We introduce a new technique for imaging the polarized radio sky using interferometric data. The new approach, which we call Faraday synthesis, combines aperture and rotation measure synthesis imaging and deconvolution into a single algorithm. This has several inherent advantages over the traditional two-step technique, including improved sky plane resolution, fidelity, and dynamic range. In addition, the direct visibility- to Faraday-space imaging approach is a more sound foundation on which to build more sophisticated deconvolution or inference algorithms. For testing purposes, we have implemented a basic Faraday synthesis imaging software package including a three-dimensional CLEAN deconvolution algorithm. We compare the results of this new technique to those of the traditional approach using mock data. We find many artifacts in the images made using the traditional approach that are not present in the Faraday synthesis results. In all, we achieve a higher spatial resolution, an improvement in dynamic range of about 20%, and a more accurate reconstruction of low signal to noise source fluxes when using the Faraday synthesis technique., 11 pages, 5 figures, submitted to A&A
Published: 2011

35. The association between deployment-related posttraumatic growth among U.S. Army soldiers and negative behavioral health conditions

Author: M. Shayne Gallaway, Michael R. Bell, and Amy M. Millikan
Subjects: Male, medicine.medical_specialty, Warfare, Demographics, media_common.quotation_subject, Human Development, Arts and Humanities (miscellaneous), parasitic diseases, medicine, Humans, Psychiatry, Association (psychology), Suicidal ideation, Iraq War, 2003-2011, media_common, Combat Disorders, Posttraumatic growth, Mental Disorders, U s army, Resilience, Psychological, United States, Clinical Psychology, Mental Health, Military Personnel, Software deployment, Multivariate Analysis, Female, Psychological resilience, medicine.symptom, Psychology, Clinical psychology
Abstract: Objectives: This study assessed posttraumatic growth (PTG) in a sample of U.S. Army Soldiers using the Post-Traumatic Growth Inventory (PTGI), and the relationship between PTG and negative behavioral health (BH) conditions. Design: A sample of Soldiers with prior combat deployment experience (n = 1,834) completed an anonymous survey including demographics, the PTGI, and negative BH conditions. Results: Among previously deployed Soldiers, those reporting the highest number of combat experiences also reported significantly higher overall PTG. A significant inverse relationship was observed between PTG and recent suicidal ideation, whereby Soldiers reporting recent suicidal ideation reported significantly lower overall PTG. Conclusions: This study quantified PTG resulting from deployment and demonstrated the degree to which combat experiences might result in PTG. © 2011 Wiley Periodicals, Inc. J Clin Psychol 67:1–10, 2011.
Published: 2011

36. Factors associated with physical aggression among US Army soldiers

Author: Michael Shayne, Gallaway, David S, Fink, Amy M, Millikan, and Michael R, Bell
Subjects: Adult, Aggression, Male, Cross-Sectional Studies, Military Personnel, Surveys and Questionnaires, Humans, Female, United States
Abstract: There are a growing number of studies that have approximated levels of aggression and associated outcomes among combat veterans returning from Iraq and Afghanistan using brief screening assessments. However, further research to evaluate the relative role of combat exposures and overt physical behaviors is required to further elucidate potential associations between military service, combat deployment, and overt physical aggression. The purpose of the current study was to assess the prevalence of self-reported physical aggression in a sample of US Army soldiers using an adaptation of the Revised Conflict Tactics Scale (CTS2), and examine factors associated with higher levels of aggression. A population-based cross-sectional study was conducted at a single US Army Installation within a sample of active duty US Army soldiers (n = 6,128) from two large units. Anonymous surveys were collected 6 months following deployment to measure overt aggressive behaviors, posttraumatic stress disorder, anxiety, depression, traumatic brain injury, and misuse of alcohol. There were a relatively higher number of minor and severe physical overt aggressive actions reported among soldiers who previously deployed, notably highest among deployed soldiers reporting the highest levels of combat intensity. Soldiers screening positive for the misuse of alcohol were also significantly more likely to report relatively higher levels of physical aggression. This study quantified overt aggressive behaviors and associated factors, showing increasing combat exposures may result in increased physical aggression. Clinicians treating service members returning from combat may consider assessing relative levels of combat.
Published: 2011

37. Structure and Magnetic Fields in the Precessing Jet System SS433 III. Evolution of the Intrinsic Brightness of the Jets from a Deep Multi-Epoch VLA Campaign

Author: Michael R. Bell, John F. C. Wardle, and David H. Roberts
Subjects: Brightness, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, symbols.namesake, Intrinsic brightness, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Line (formation), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Spectral index, Jet (fluid), 010308 nuclear & particles physics, Balmer series, Astronomy and Astrophysics, Magnetic field, Projection (relational algebra), Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, symbols, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present a sequence of five deep observations of SS433 made over the summer of 2007 using the VLA in the A configuration at 5 and 8 GHz. In this paper we study the brightness profiles of the jets and their time evolution. We also examine the spectral index distribution in the source. We find (as previously reported from the analysis of a single earlier image) that the profiles of the east and west jets are remarkably similar if projection and Doppler beaming are taken into account. The sequence of five images allows us to disentangle the evolution of brightness of individual pieces of jet from the variations of jet power originating at the core. We find that the brightness of each piece of the jet fades as an exponential function of age (or distance from the core), exp(-tau/tau'), where tau is the age at emission and tau' = 55.9 +- 1.7 days. This evolutionary model describes both the east and west jets equally well. There is also significant variation (by a factor of at least five) in jet power with birth epoch, with the east and west jets varying in synchrony. The lack of deceleration between the scale of the optical Balmer line emission (10^15 cm) and that of the radio emission (10^17 cm) requires that the jet material is much denser than its surroundings. We find that the density ratio must exceed 300:1., Comment: 26 pages, 13 Figures, Accepted for publication in the Astrophysical Journal
Published: 2011
Full Text: View/download PDF

38. LOFAR: Recent Imaging Results and Future Prospects

Author: Carlos Sotomayor, John Conway, Giulia Macario, David Rafferty, Rainer Beck, Huub Röttgering, Joris E. van Zwieten, Roberto Pizzo, Emanuela Orrú, Cyril Tasse, Francesco de Gasperin, Chiara Ferrari, Annalisa Bonafede, Sebastiaan van der Tol, Reinout J. van Weeren, A. Horneffer, A. R. Offringa, John McKean, Marijke Haverkorn, James M. Anderson, Laura Birzan, Anna M. M. Scaife, Neal Jackson, Olaf Wucknitz, H. Miraghaei, Michael R. Bell, Monica Trasatti, Ilse van Bemmel, George Heald, Aleksandar Shulevski, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Heald, George, Bell, Michael R., Horneffer, Andrea, Offringa, A.R., Pizzo, Roberto, van der Tol, Sebastiaan, van Weeren, Reinout J., van Zwieten, Joris E., Anderson, James M., Beck, Rainer, van Bemmel, Ilse, Bîrzan, Laura, Bonafede, Annalisa, Conway, John, Ferrari, Chiara, De Gasperin, Francesco, Haverkorn, Marijke, Jackson, Neal, Macario, Giulia, McKean, John, Miraghaei, Halime, Orrù, Emanuela, Rafferty, David, Röttgering, Huub, Scaife, Anna, Shulevski, Aleksandar, Sotomayor, Carlo, Tasse, Cyril, Trasatti, Monica, Wucknitz, Olaf, and Kapteyn Astronomical Institute
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astronomy, FOS: Physical sciences, Image processing, 02 engineering and technology, Astrophysics, 01 natural sciences, law.invention, Telescope, Radio continuum: general, Software, law, 020204 information systems, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, CALIBRATION, Physics, RADIO, business.industry, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Instrumentation: interferometers, Space and Planetary Science, Systems engineering, Instrumentation: interferometers - Radio continuum: general, business, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The Low Frequency Array (LOFAR) is under construction in the Netherlands and in several surrounding European countries. In this contribution, we describe the layout and design of the telescope, with a particular emphasis on the imaging characteristics of the array when used in its "standard imaging" mode. After briefly reviewing the calibration and imaging software used for LOFAR image processing, we show some recent results from the ongoing imaging commissioning efforts. We conclude by summarizing future prospects for the use of LOFAR in observing the little-explored low frequency Universe., Accepted for publication in special issue of Journal of Astrophysics and Astronomy: conference proceedings of "Diffuse Relativistic Plasmas" conference, Bangalore, 1-4 March 2011
Published: 2011

39. Structure and Magnetic Fields in the Precessing Jet System SS 433 II. Intrinsic Brightness of the Jets

Author: Michael R. Bell, Phoebe R. Upton Sanderbeck, Matthew R. Mallory, Valerie V. Marchenko, David H. Roberts, and John F. C. Wardle
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Very large array, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Power law, Magnetic field, Exponential function, symbols.namesake, Intrinsic brightness, Space and Planetary Science, 0103 physical sciences, symbols, High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Doppler effect
Abstract: Deep Very Large Array imaging of the binary X-ray source SS 433, sometimes classified as a microquasar, has been used to study the intrinsic brightness distribution and evolution of its radio jets. The intrinsic brightness of the jets as a function of age at emission of the jet material tau is recovered by removal of the Doppler boosting and projection effects. We find that intrinsically the two jets are remarkably similar when compared for equal tau, and that they are best described by Doppler boosting of the form D^{2+alpha}, as expected for continuous jets. The intrinsic brightnesses of the jets as functions of age behave in complex ways. In the age range 60 < tau < 150 days, the jet decays are best represented by exponential functions of tau, but linear or power law functions are not statistically excluded. This is followed by a region out to tau ~ 250 days during which the intrinsic brightness is essentially constant. At later times the jet decay can be fit roughly as exponential or power law functions of tau., 30 Pages, 11 Figures, Submitted to ApJ
Published: 2010

40. Breastfeeding in the military: Part II. Resource and policy considerations

Author: Michael R, Bell and Elspeth Cameron, Ritchie
Subjects: Breast Feeding, Military Personnel, Health Policy, Health Resources, Humans, Female, United States
Abstract: Breastfeeding is widely acknowledged as the ideal form of nutrition for infants. Because of this, increasing the incidence and duration of breastfeeding is a major goal in Healthy People 2010. Part I of this series illustrated that the Department of Defense and its health care system, TRICARE, may not be meeting that goal, particularly after active duty mothers return to work. This study outlines the resources that would be required to optimally support breastfeeding after active duty mothers return to work. Selected policy implications of supporting breastfeeding are discussed, and recommendations for policy on breastfeeding are presented.
Published: 2003

41. Breastfeeding in the military: Part I. Information and resources provided to service women

Author: Michael R, Bell and Elspeth Cameron, Ritchie
Subjects: Breast Feeding, Military Personnel, Health Policy, Health Resources, Humans, Female, Health Education
Abstract: Increasing the incidence and duration of breastfeeding is a major goal in Healthy People 2010. Little is known about the progress that the Department of Defense (DoD) health care system, TRICARE, has made toward reaching that goal. This study is the first of a two-part series that reviews DoD/TRICARE support for breastfeeding and discusses policy issues related to breastfeeding. Methods used include searches of MEDLINE, DoD/TRICARE documents, legislative and policy websites, and the Internet. A survey of DoD hospitals was also conducted. Based on the search results and survey, TRICARE may not be meeting the goals of Healthy People 2010. There is minimal policy guidance regarding breastfeeding. Programs are in place at most hospitals, but the quality and content varies greatly. After mothers return to work, support is meager. DOD/TRICARE may need to establish written policy guidelines and devote additional resources to adequately support breastfeeding.
Published: 2003

42. An improved map of the Galactic Faraday sky

Author: Bryan Gaensler, Uli Klein, Timothy Robishaw, C. L. Van Eck, A. R. Taylor, Lisa Harvey-Smith, Shude Mao, Annalisa Bonafede, A. Tanna, George Heald, Ilana Feain, Michael R. Bell, Subhashis Roy, G. Robbers, J. Stevens, Naomi McClure-Griffiths, Melanie Johnston-Hollitt, Niels Oppermann, A. Hammond, Torsten A. Enßlin, Dominic Schnitzeler, C. Sunstrum, Luke Pratley, Carlos Sotomayor-Beltran, H. Junklewitz, Tracy Clarke, J. M. Stil, Shane O'Sullivan, Jo-Anne Brown, Phil Kronberg, Robert Braun, Oppermann, N., Junklewitz, H., Robbers, G., Bell, M.R., Enßlin, T.A., Bonafede, A., Braun, R., Brown, J.C., Clarke, T.E., Feain, I.J., Gaensler, B.M., Hammond, A., Harvey-Smith, L., Heald, G., Johnston-Hollitt, M., Klein, U., Kronberg, P.P., Mao, S.A., McClure-Griffiths, N.M., O'Sullivan, S.P., Pratley, L., Robishaw, T., Roy, S., Schnitzeler, D.H.F.M., Sotomayor-Beltran, C., Stevens, J., Stil, J.M., Sunstrum, C., Tanna, A., Taylor, A.R., and Van Eck, C.L.
Subjects: Offset (computer science), media_common.quotation_subject, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Power law, law.invention, ISM: magnetic field, symbols.namesake, Galaxies: magnetic field, law, Faraday effect, Radio continuum: ISM, Faraday cage, Galaxy: structure, Astrophysics::Galaxy Astrophysics, Multiple, media_common, Physics, Isotropy, Techniques: polarimetric, Spectral density, Astronomy and Astrophysics, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Space and Planetary Science, Sky, Astrophysics of Galaxies (astro-ph.GA), symbols, Methods: data analysi
Abstract: We aim to summarize the current state of knowledge regarding Galactic Faraday rotation in an all-sky map of the Galactic Faraday depth. For this we have assembled the most extensive catalog of Faraday rotation data of compact extragalactic polarized radio sources to date. In the map making procedure we use a recently developed algorithm that reconstructs the map and the power spectrum of a statistically isotropic and homogeneous field while taking into account uncertainties in the noise statistics. This procedure is able to identify some rotation angles that are offset by an integer multiple of pi. The resulting map can be seen as an improved version of earlier such maps and is made publicly available, along with a map of its uncertainty. For the angular power spectrum we find a power law behavior with a power law index of -2.14 for a Faraday sky where an overall variance profile as a function of Galactic latitude has been removed, in agreement with earlier work. We show that this is in accordance with a 3D Fourier power spectrum P(k) proportional to k^-2.14 of the underlying field n_e times B_r under simplifying geometrical and statistical assumptions., 16 pages, 11 figures. Update in one data catalog. All results are available at http://www.mpa-garching.mpg.de/ift/faraday/
Published: 2012

43. Faraday caustics

Author: Torsten A. Enßlin, Michael R. Bell, and H. Junklewitz
Subjects: Physics, Line-of-sight, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Dissipation, Polarization (waves), Astrophysics - Astrophysics of Galaxies, Geomagnetic reversal, Magnetic field, law.invention, Computational physics, Space and Planetary Science, law, Astrophysics of Galaxies (astro-ph.GA), Gravitational singularity, Astrophysics - Instrumentation and Methods for Astrophysics, Faraday cage, Instrumentation and Methods for Astrophysics (astro-ph.IM), Taylor microscale
Abstract: We describe singularities in the distribution of polarized intensity as a function of Faraday depth (i.e. the Faraday spectrum) caused by line-of-sight (LOS) magnetic field reversals. We call these features Faraday caustics because of their similarity to optical caustics. They appear as sharply peaked and asymmetric profiles in the Faraday spectrum, that have a tail that extends to one side. The direction in which the tail extends depends on the way in which the LOS magnetic field reversal occurs (either changing from oncoming to retreating or vice versa). We describe how Faraday caustics will form three-dimensional surfaces that relate to boundaries between regions where the LOS magnetic field has opposite polarity. We present examples from simulations of the predicted polarized synchrotron emission from the Milky Way. We derive either the probability or luminosity distribution of Faraday caustics produced in a Gaussian magnetic field distribution as a function of their strength, F, and find that for strong Faraday caustics P(F)\proptoF^{-3} . If fully resolved, this distribution is also shown to depend on the Taylor microscale, which relates to the largest scale over which dissipation is important in a turbulent flow., Comment: 14 pages, 9 figures, Accepted for publication in Astronomy & Astrophysics
Published: 2011

Catalog

Books, media, physical & digital resources

See catalog results

Searchworks

Select search scope, currently: Articles Catalog books, media & more in Jio Institute collections Articles journal articles & other e-resources

Search

Search Constraints

Refine your results

Search Limiters

Topic

Publication Year Range

Language

Journal

Database

Publisher

43 results on '"Michael R. Bell"'

Search Results

Catalog

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources