Search

Using data from the Galactic Arecibo L-band Feed Array Continuum Transit Survey (GALFACTS), we report the discovery of two previously unidentified, very compressed, thin, and straight polarized filaments approximately centred at Galactic coordinates, $(l,b)=(182.5^\circ,-4.0^\circ)$, which we call G182.5--4.0. Using data from the Isaac Newton Telescope Galactic Plane Survey (IGAPS), we also find straight, long, and extremely thin H$\alpha$ filaments coincident with the radio emission. These filaments are positioned in projection at the edge of the Orion-Eridanus superbubble and we find evidence indicating that the filaments align with the coherent magnetic field of the outer Galaxy. We find a lower limit on the total radio flux at 1.4~GHz to be $0.7\pm0.3$~Jy with an average linearly polarized fraction of $40\substack{+30 \\ -20}\%$. We consider various scenarios that could explain the origin of these filaments, including a shell-type supernova remnant (SNR), a bow shock nebula associated with a pulsar, or relic fragments from one or more supernova explosions in the adjacent superbubble, with a hybrid scenario being most likely. This may represent an example of a new class of objects that is neither an SNR nor a bow shock. The highly compressed nature of these filaments and their alignment with Galactic plane suggests a scenario where this object formed in a magnetic field that was compressed by the expanding Orion-Eridanus superbubble, suggesting that the object is related to this superbubble and implying a distance of $\sim$400~pc., Comment: 17 pages, 9 figures, accepted to Astrophysical Journal

Understanding how the Galactic magnetic field threads the multi-phase interstellar medium (ISM) remains a considerable challenge, as different magnetic field tracers probe dissimilar phases and field components. We search for evidence of a common magnetic field shared between the ionized and neutral ISM by comparing 1.4 GHz radio continuum polarization and HI line emission from the Galactic Arecibo L-Band Feed Array Continuum Transit Survey (GALFACTS) and Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey, respectively. We compute the polarization gradient of the continuum emission and search for associations with diffuse/translucent HI structures. The polarization gradient is sensitive to changes in the integrated product of the thermal electron density and line-of-sight field strength ($B_\parallel$) in warm ionized gas, while narrow HI structures highlight the plane-of-sky field orientation in cold neutral gas. We identified one region in the high-Galactic latitude Arecibo sky, G216+26 centered on $(\ell,b)\sim(216\deg,+26\deg)$, containing filaments in the polarization gradient that are aligned with narrow HI structures roughly parallel to the Galactic plane. We present a comparison of multi-phase observations and magnetic field tracers of this region, demonstrating that the warm ionized and cold neutral media are connected likely via a common magnetic field. We quantify the physical properties of a polarization gradient filament associated with H$\alpha$ emission, measuring a line-of-sight field strength $B_\parallel=6{\pm}4 \mu$G and a plasma beta $\beta=2.1^{+3.1}_{-2.1}$. We discuss the lack of widespread multi-phase magnetic field alignments and consider whether this region is associated with a short-timescale or physically rare phenomenon. This work highlights the utility of multi-tracer analyses for understanding the magnetized ISM., Comment: 30 pages, 17 figures, minor edits to reflect published version

Using the Global Magneto-Ionic Medium Survey (GMIMS) Low-Band South (LBS) southern sky polarization survey, covering 300 to 480 MHz at 81 arcmin resolution, we reveal the brightest region in the Southern polarized sky at these frequencies. The region, G150-50, covers nearly 20deg$^2$, near (l,b)~(150 deg,-50 deg). Using GMIMS-LBS and complementary data at higher frequencies (~0.6--30 GHz), we apply Faraday tomography and Stokes QU-fitting techniques. We find that the magnetic field associated with G150-50 is both coherent and primarily in the plane of the sky, and indications that the region is associated with Radio Loop II. The Faraday depth spectra across G150-50 are broad and contain a large-scale spatial gradient. We model the magnetic field in the region as an expanding shell, and we can reproduce both the observed Faraday rotation and the synchrotron emission in the GMIMS-LBS band. Using QU-fitting, we find that the Faraday spectra are produced by several Faraday dispersive sources along the line-of-sight. Alternatively, polarization horizon effects that we cannot model are adding complexity to the high-frequency polarized spectra. The magnetic field structure of Loop II dominates a large fraction of the sky, and studies of the large-scale polarized sky will need to account for this object. Studies of G150-50 with high angular resolution could mitigate polarization horizon effects, and clarify the nature of G150-50., Comment: 25 pages, 14 figures. Accepted for publication in MNRAS

Understanding how the Galactic magnetic field threads the multi-phase interstellar medium (ISM) remains a considerable challenge, as different magnetic field tracers probe dissimilar phases and field components. We search for evidence of a common magnetic field shared between the ionized and neutral ISM by comparing 1.4 GHz radio continuum polarization and HI line emission from the Galactic Arecibo L-Band Feed Array Continuum Transit Survey (GALFACTS) and Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey, respectively. We compute the polarization gradient of the continuum emission and search for associations with diffuse/translucent HI structures. The polarization gradient is sensitive to changes in the integrated product of the thermal electron density and line-of-sight field strength ($B_\parallel$) in warm ionized gas, while narrow HI structures highlight the plane-of-sky field orientation in cold neutral gas. We identified one region in the high-Galactic latitude Arecibo sky, G216+26 centered on $(\ell,b)\sim(216\deg,+26\deg)$, containing filaments in the polarization gradient that are aligned with narrow HI structures roughly parallel to the Galactic plane. We present a comparison of multi-phase observations and magnetic field tracers of this region, demonstrating that the warm ionized and cold neutral media are connected likely via a common magnetic field. We quantify the physical properties of a polarization gradient filament associated with H$\alpha$ emission, measuring a line-of-sight field strength $B_\parallel=6{\pm}4 \mu$G and a plasma beta $\beta=2.1^{+3.1}_{-2.1}$. We discuss the lack of widespread multi-phase magnetic field alignments and consider whether this region is associated with a short-timescale or physically rare phenomenon. This work highlights the utility of multi-tracer analyses for understanding the magnetized ISM., Comment: 30 pages, 17 figures, minor edits to reflect published version

Using the Global Magneto-Ionic Medium Survey (GMIMS) Low-Band South (LBS) southern sky polarization survey, covering 300 to 480 MHz at 81 arcmin resolution, we reveal the brightest region in the Southern polarized sky at these frequencies. The region, G150-50, covers nearly 20deg$^2$, near (l,b)~(150 deg,-50 deg). Using GMIMS-LBS and complementary data at higher frequencies (~0.6--30 GHz), we apply Faraday tomography and Stokes QU-fitting techniques. We find that the magnetic field associated with G150-50 is both coherent and primarily in the plane of the sky, and indications that the region is associated with Radio Loop II. The Faraday depth spectra across G150-50 are broad and contain a large-scale spatial gradient. We model the magnetic field in the region as an expanding shell, and we can reproduce both the observed Faraday rotation and the synchrotron emission in the GMIMS-LBS band. Using QU-fitting, we find that the Faraday spectra are produced by several Faraday dispersive sources along the line-of-sight. Alternatively, polarization horizon effects that we cannot model are adding complexity to the high-frequency polarized spectra. The magnetic field structure of Loop II dominates a large fraction of the sky, and studies of the large-scale polarized sky will need to account for this object. Studies of G150-50 with high angular resolution could mitigate polarization horizon effects, and clarify the nature of G150-50., Comment: 25 pages, 14 figures. Accepted for publication in MNRAS

We report the results of an HCO+ (3-2) and N2D+ (3-2) molecular line survey performed toward 91 dense cores in the Perseus molecular cloud using the James Clerk Maxwell Telescope, to identify the fraction of starless and protostellar cores with systematic radial motions. We quantify the HCO+ asymmetry using a dimensionless asymmetry parameter $\delta_v$, and identify 20 cores with significant blue or red line asymmetries in optically-thick emission indicative of collapsing or expanding motions, respectively. We separately fit the HCO+ profiles with an analytic collapse model and determine contraction (expansion) speeds toward 22 cores. Comparing the $\delta_v$ and collapse model results, we find that $\delta_v$ is a good tracer of core contraction if the optically-thin emission is aligned with the model-derived systemic velocity. The contraction speeds range from subsonic (0.03 km/s) to supersonic (0.4 km/s), where the supersonic contraction speeds may trace global rather than local core contraction. Most cores have contraction speeds significantly less than their free-fall speeds. Only 7 of 28 starless cores have spectra well-fit by the collapse model, which more than doubles (15 of 28) for protostellar cores. Starless cores with masses greater than the Jeans mass (M/M$_J$ > 1) are somewhat more likely to show contraction motions. We find no trend of optically-thin non-thermal line width with M/M$_J$, suggesting that any undetected contraction motions are small and subsonic. Most starless cores in Perseus are either not in a state of collapse or expansion, or are in a very early stage of collapse., Comment: Accepted to ApJ, 18 pages, 12 figures, 4 tables

We report the results of an HCO+ (3-2) and N2D+ (3-2) molecular line survey performed toward 91 dense cores in the Perseus molecular cloud using the James Clerk Maxwell Telescope, to identify the fraction of starless and protostellar cores with systematic radial motions. We quantify the HCO+ asymmetry using a dimensionless asymmetry parameter $\delta_v$, and identify 20 cores with significant blue or red line asymmetries in optically-thick emission indicative of collapsing or expanding motions, respectively. We separately fit the HCO+ profiles with an analytic collapse model and determine contraction (expansion) speeds toward 22 cores. Comparing the $\delta_v$ and collapse model results, we find that $\delta_v$ is a good tracer of core contraction if the optically-thin emission is aligned with the model-derived systemic velocity. The contraction speeds range from subsonic (0.03 km/s) to supersonic (0.4 km/s), where the supersonic contraction speeds may trace global rather than local core contraction. Most cores have contraction speeds significantly less than their free-fall speeds. Only 7 of 28 starless cores have spectra well-fit by the collapse model, which more than doubles (15 of 28) for protostellar cores. Starless cores with masses greater than the Jeans mass (M/M$_J$ > 1) are somewhat more likely to show contraction motions. We find no trend of optically-thin non-thermal line width with M/M$_J$, suggesting that any undetected contraction motions are small and subsonic. Most starless cores in Perseus are either not in a state of collapse or expansion, or are in a very early stage of collapse., Comment: Accepted to ApJ, 18 pages, 12 figures, 4 tables

The distribution of platinum-group elements (PGE) in the Main Sulfide Zone of the Great Dyke of Zimbabwe, in the arsenide ores of Vammala and Kylmäkoski mines in Finland, and in the chromite-Ni arsenide ores from the Ronda and Beni Bousera massifs (Spain and Morocco) has been studied by means of different optical and microanalytical techniques. The results show a bimodal distribution of PGE in the ores from the Great Dyke and the Vammala and Kylmäkoski mines where Pd, Pt and, to lesser extent, Rh occur both as discrete platinum-group minerals and in solid solution in sulfides, arsenides and sulfarsenides. In the ores from Ronda and Beni Bousera, platinum-group elements occur only in solid solution in arsenides and sulfarsenides. Trace electron probe (EPMA) and micro-PIXE analyses of Pd in sulfides, arsenides and sulfarsenides produce comparable results at concentration levels well above their limit of detection (LOD). These are 27–29thinspppm by EMPA and 2.5–7thinspppm by micro-PIXE. Whereas trace EPMA on arsenides and sulfarsenides measure Pt concentrations above 33–35thinspppm, the proximity of the Pt L lines and the As Kagr line severely degrade de detection limit for Pt in micro-PIXE analyses, increasing the LOD up to 440thinspppm. The rest of PGE were randomly detected by both methods at concentrations close to their LOD.

Climate change due to greenhouse gas emissions is predicted to raise the mean global temperature by 1.0-3.5°C in the next 50-100 years. The direct and indirect effects of this potential increase in temperature on terrestrial ecosystems and ecosystem processes are likely to be complex and highly varied in time and space. The Global Change and Terrestrial Ecosystems core project of the International Geosphere-Biosphere Programme has recently launched a Network of Ecosystem Warming Studies, the goals of which are to integrate and foster research on ecosystem-level effects of rising temperature. In this paper, we use meta-analysis to synthesize data on the response of soil respiration, net N mineralization, and aboveground plant productivity to experimental ecosystem warming at 32 research sites representing four broadly defined biomes, including high (latitude or altitude) tundra, low tundra, grassland, and forest. Warming methods included electrical heat-resistance ground cables, greenhouses, vented and unvented field chambers, overhead infrared lamps, and passive night-time warming. Although results from individual sites showed considerable variation in response to warming, results from the meta-analysis showed that, across all sites and years, 2-9 years of experimental warming in the range 0.3-6.0°C significantly increased soil respiration rates by 20% (with a 95% confidence interval of 18-22%), net N mineralization rates by 46% (with a 95% confidence interval of 30-64%), and plant productivity by 19% (with a 95% confidence interval of 15-23%). The response of soil respiration to warming was generally larger in forested ecosystems compared to low tundra and grassland ecosystems, and the response of plant productivity was generally larger in low tundra ecosystems than in forest and grassland ecosystems. With the exception of aboveground plant productivity, which showed a greater positive response to warming in colder ecosystems, the magnitude of the response of th

Climate change due to greenhouse gas emissions is predicted to raise the mean global temperature by 1.0-3.5°C in the next 50-100 years. The direct and indirect effects of this potential increase in temperature on terrestrial ecosystems and ecosystem processes are likely to be complex and highly varied in time and space. The Global Change and Terrestrial Ecosystems core project of the International Geosphere-Biosphere Programme has recently launched a Network of Ecosystem Warming Studies, the goals of which are to integrate and foster research on ecosystem-level effects of rising temperature. In this paper, we use meta-analysis to synthesize data on the response of soil respiration, net N mineralization, and aboveground plant productivity to experimental ecosystem warming at 32 research sites representing four broadly defined biomes, including high (latitude or altitude) tundra, low tundra, grassland, and forest. Warming methods included electrical heat-resistance ground cables, greenhouses, vented and unvented field chambers, overhead infrared lamps, and passive night-time warming. Although results from individual sites showed considerable variation in response to warming, results from the meta-analysis showed that, across all sites and years, 2-9 years of experimental warming in the range 0.3-6.0°C significantly increased soil respiration rates by 20% (with a 95% confidence interval of 18-22%), net N mineralization rates by 46% (with a 95% confidence interval of 30-64%), and plant productivity by 19% (with a 95% confidence interval of 15-23%). The response of soil respiration to warming was generally larger in forested ecosystems compared to low tundra and grassland ecosystems, and the response of plant productivity was generally larger in low tundra ecosystems than in forest and grassland ecosystems. With the exception of aboveground plant productivity, which showed a greater positive response to warming in colder ecosystems, the magnitude of the response of th

The objective of the first experiment reported below was to measure the cognitive demands associated with transitioning across Advanced Traveler Information System (ATIS) functions. This required the development of both objective and subjective indices of driver behavior and cognition. To accomplish this, a small number of pre-drive trip scenarios that invoke appropriate transitions across ATIS functions were developed. Driving performance under more representative conditions was investigated in experiment 2 using a driving simulator. This study investigated several issues on the influence of an ATIS on driving behavior. The questions asked were: 1. How does a moving map display of the current vehicle location influence driving performance? 2. How do ATIS control inputs influence driving performance? Should they be allocated to pre-drive? Is it too much to expect the driver to do while in transit? 3. Do ATIS messages affect drivers' reactions to roadway events? 4. Does message potency affect drivers' reactions to roadway events? Overall, the two experiments reported here suggest that in-vehicle ATIS devices can be learned, understood, and successfully used by drivers for both pre-drive trip planning tasks and on-road driving conditions. ATIS devices have the potential to improve driver compliance to regulatory information, as compared with standard roadside signs. While concurrent visual and auditory ATIS alert messages may be beneficial, the visual ATIS messages alone are significantly better than roadside signage alone. While cognitive demands associated with ATIS transitions and ATIS complexity should continue to be a concern, these demands can be addressed by selecting ATIS functions with clear benefits to the driving task.

The objective of the first experiment reported below was to measure the cognitive demands associated with transitioning across Advanced Traveler Information System (ATIS) functions. This required the development of both objective and subjective indices of driver behavior and cognition. To accomplish this, a small number of pre-drive trip scenarios that invoke appropriate transitions across ATIS functions were developed. Driving performance under more representative conditions was investigated in experiment 2 using a driving simulator. This study investigated several issues on the influence of an ATIS on driving behavior. The questions asked were: 1. How does a moving map display of the current vehicle location influence driving performance? 2. How do ATIS control inputs influence driving performance? Should they be allocated to pre-drive? Is it too much to expect the driver to do while in transit? 3. Do ATIS messages affect drivers' reactions to roadway events? 4. Does message potency affect drivers' reactions to roadway events? Overall, the two experiments reported here suggest that in-vehicle ATIS devices can be learned, understood, and successfully used by drivers for both pre-drive trip planning tasks and on-road driving conditions. ATIS devices have the potential to improve driver compliance to regulatory information, as compared with standard roadside signs. While concurrent visual and auditory ATIS alert messages may be beneficial, the visual ATIS messages alone are significantly better than roadside signage alone. While cognitive demands associated with ATIS transitions and ATIS complexity should continue to be a concern, these demands can be addressed by selecting ATIS functions with clear benefits to the driving task.

The objective of the first experiment reported below was to measure the cognitive demands associated with transitioning across Advanced Traveler Information System (ATIS) functions. This required the development of both objective and subjective indices of driver behavior and cognition. To accomplish this, a small number of pre-drive trip scenarios that invoke appropriate transitions across ATIS functions were developed. Driving performance under more representative conditions was investigated in experiment 2 using a driving simulator. This study investigated several issues on the influence of an ATIS on driving behavior. The questions asked were: 1. How does a moving map display of the current vehicle location influence driving performance? 2. How do ATIS control inputs influence driving performance? Should they be allocated to pre-drive? Is it too much to expect the driver to do while in transit? 3. Do ATIS messages affect drivers' reactions to roadway events? 4. Does message potency affect drivers' reactions to roadway events? Overall, the two experiments reported here suggest that in-vehicle ATIS devices can be learned, understood, and successfully used by drivers for both pre-drive trip planning tasks and on-road driving conditions. ATIS devices have the potential to improve driver compliance to regulatory information, as compared with standard roadside signs. While concurrent visual and auditory ATIS alert messages may be beneficial, the visual ATIS messages alone are significantly better than roadside signage alone. While cognitive demands associated with ATIS transitions and ATIS complexity should continue to be a concern, these demands can be addressed by selecting ATIS functions with clear benefits to the driving task.

Yeast autonomously replicating sequences (ARSs) were originally identified as segments of DNA that permitted autonomous replication of colinear DNA as plasmids in yeast (Struhl et al., 1979). Direct evidence that ARSs function as origins of replication on plasmids, and more important, that a subset of ARSs function as origins of replication in the chromosome, comes from 2-D gel analysis of replication intermediates (Brewer and Fangman, 1987; Huberman et al., 1987, 1988). ARS1, the ARS with which we have been working for many years, is an active origin within the chromosome. Sequence comparisons between the 20 or so different ARSs that have been identified and the effect of mutations on plasmid stability have revealed two underlying similarities: A high A/T content compared to chromosomal DNA and the presence of a conserved core consensus sequence: 5’ (A/T)TTTA(T/C)(A/G)TTT(A/T(T/C/G) 3’ (see Campbell and Newlon, 1991 for review). Point mutations, small deletions and small substitutions abolish ARS function. Many ARSs contain multiple close matches to this sequence, though spacing and orientation varies. The core consensus sequence is a potential initiator protein binding site. DNase I footprinting patterns of the chromosomal copy of ARS1 showed that the core might be protected from digestion (Lohr and Torchia, 1988).

This report describes the System Optical Quality (SOQ) code structure and the input to the code required for analyzing High Power Laser Optical Systems. The SOQ code provides the designer with a physical optics model of the system. The code traces the beam from its point of origin in the resonator through the optical train into the far field. This report is divided into three parts. Part 1 describes the general structure of the SOQ code and establishes a correlation between the usual optical elements encountered in the optical train/gas dynamic laser resonator and the appropriate SOQ models. Part 2 acquaints the user with the individual SOQ subroutines and their analytical formulations as manifested in Fortran within the SOQ framework. It also delineates the input required to exercise the subroutines, familiarizes the user with the operation of the SOQ model, and contains working input modules which carry the user through the usual calculations of the SOQ code from input generation to loaded cavity calculations. Part 3 contains Appendices describing SOQ updates. (Author), Includes update dated Jun 80. See also Part 3, AD-A103 286.

This report describes the System Optical Quality (SOQ) code structure and the input to the code required for analyzing High Power Laser Optical Systems. The SOQ code provides the designer with a physical optics model of the system. The code traces the beam from its point of origin in the resonator through the optical train into the far field. This Part contains Appendices describing SOQ updates., Includes update dated Jun 80. See also Part 1, AD-A103 284.

This report describes the System Optical Quality (SOQ) code structure and the input to the code required for analyzing High Power Laser Optical Systems. The SOQ code provides the designer with a physical optics model of the system. The code traces the beam from its point of origin in the resonator through the optical train into the far field. This report is divided into three parts. Part 1 describes the general structure of the SOQ code and establishes a correlation between the usual optical elements encountered in the optical train/gas dynamic laser resonator and the appropriate SOQ models. Part 2 acquaints the user with the individual SOQ subroutines and their analytical formulations as manifested in Fortran within the SOQ framework. It also delineates the input required to exercise the subroutines, familiarizes the user with the operation of the SOQ model, and contains working input modules which carry the user through the usual calculations of the SOQ code from input generation to loaded cavity calculations. Part 3 contains Appendices describing SOQ updates. (Author), See also Part 2, AD-A103 285. Includes update dated Jun 80.

DNAs that contain specific yeast chromosomal sequences called ARSs transform Saccharomyces cerevisiae at high frequency and can replicate extrachromosomally as plasmids when introduced into S. cerevisiae by transformation. To determine the boundaries of the minimal sequences required for autonomous replication in S. cerevisiae, we have carried out in vitro mutagenesis of the first chromosomal ARS described, ARS1. Rather than identifying a distinct and continuous segment that mediates the ARS+ phenotype, we find three different functional domains within ARS1. We define domain A as the 11-base-pair (bp) sequence that is also found at most other ARS regions. It is necessary but not sufficient for high-frequency transformation. Domain B, which cannot mediate high-frequency transformation, or replicate by itself, is required for efficient, stable replication of plasmids containing domain A. Domain B, as we define it, is continuous with domain A in ARS1, but insertions of 4 bp between the two do not affect replication. The extent of domain B has an upper limit of 109 bp and a lower limit of 46 bp in size. There is no obvious sequence homology between domain B of ARS1 and any other ARS sequence. Finally, domain C is defined on the basis of our deletions as at least 200 bp flanking domain A on the opposite side from domain B and is also required for the stability of domain A in S. cerevisiae. The effect of deletions of domain C can be observed only in the absence of domain B, at least by the assays used in the current study, and the significance of this finding is discussed.

DNAs that contain specific yeast chromosomal sequences called ARSs transform Saccharomyces cerevisiae at high frequency and can replicate extrachromosomally as plasmids when introduced into S. cerevisiae by transformation. To determine the boundaries of the minimal sequences required for autonomous replication in S. cerevisiae, we have carried out in vitro mutagenesis of the first chromosomal ARS described, ARS1. Rather than identifying a distinct and continuous segment that mediates the ARS+ phenotype, we find three different functional domains within ARS1. We define domain A as the 11-base-pair (bp) sequence that is also found at most other ARS regions. It is necessary but not sufficient for high-frequency transformation. Domain B, which cannot mediate high-frequency transformation, or replicate by itself, is required for efficient, stable replication of plasmids containing domain A. Domain B, as we define it, is continuous with domain A in ARS1, but insertions of 4 bp between the two do not affect replication. The extent of domain B has an upper limit of 109 bp and a lower limit of 46 bp in size. There is no obvious sequence homology between domain B of ARS1 and any other ARS sequence. Finally, domain C is defined on the basis of our deletions as at least 200 bp flanking domain A on the opposite side from domain B and is also required for the stability of domain A in S. cerevisiae. The effect of deletions of domain C can be observed only in the absence of domain B, at least by the assays used in the current study, and the significance of this finding is discussed.