116 results on '"Freundt, A."'
Search Results
2. CCAT: characterizing the Fabry-Pérot interferometer mirrors and mount for the epoch of reionization spectrometer
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Zmuidzinas, Jonas, Gao, Jian-Rong, Zou, Bugao, Bond, J. Richard, Butler, Victoria, Freundt, Rodrigo, Huber, Zachary B., Niemack, Michael D., Nikola, Thomas, Stacey, Gordon J., and Vavagiakis, Eve M.
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- 2024
- Full Text
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3. CCAT: nonlinear effects in 280 GHz aluminum kinetic inductance detectors
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Zmuidzinas, Jonas, Gao, Jian-Rong, Duell, Cody J., Austermann, Jason, Burgoyne, James R., Chapman, Scott C., Choi, Steve K., Crites, Abigail T., Freundt, Rodrigo G., Huber, Anthony I., Huber, Zachary B., Hubmayr, Johannes, Keller, Ben, Lin, Lawrence T., Middleton, Alicia M., Murphy, Colin C., Niemack, Michael D., Nikola, Thomas, Patel, Darshan, Sinclair, Adrian K., Smith, Ema, Stacey, Gordon J., Vaskuri, Anna, Vavagiakis, Eve M., Vissers, Michael, Walker, Samantha, and Wheeler, Jordan
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- 2024
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4. CCAT: a status update on the EoR-Spec instrument module for Prime-Cam
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Zmuidzinas, Jonas, Gao, Jian-Rong, Freundt, Rodrigo, Li, Yaqiong, Henke, Doug, Austermann, Jason, Burgoyne, James R., Chapman, Scott, Choi, Steve K., Duell, Cody J., Huber, Zach, Niemack, Michael, Nikola, Thomas, Lin, Lawrence, Riechers, Dominik A., Stacey, Gordon, Vaskuri, Anna K., Vavagiakis, Eve M., Wheeler, Jordan, and Zou, Bugao
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- 2024
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5. A phenotypic screening platform for identifying chemical modulators of astrocyte reactivity
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Clayton, Benjamin L. L., Kristell, James D., Allan, Kevin C., Cohn, Erin F., Karl, Molly, Jerome, Andrew D., Garrison, Eric, Maeno-Hikichi, Yuka, Sturno, Annalise M., Kerr, Alexis, Shick, H. Elizabeth, Sepeda, Jesse A., Freundt, Eric C., Sas, Andrew R., Segal, Benjamin M., Miller, Robert H., and Tesar, Paul J.
- Abstract
Disease, injury and aging induce pathological reactive astrocyte states that contribute to neurodegeneration. Modulating reactive astrocytes therefore represent an attractive therapeutic strategy. Here we describe the development of an astrocyte phenotypic screening platform for identifying chemical modulators of astrocyte reactivity. Leveraging this platform for chemical screening, we identify histone deacetylase 3 (HDAC3) inhibitors as effective suppressors of pathological astrocyte reactivity. We demonstrate that HDAC3 inhibition reduces molecular and functional characteristics of reactive astrocytes in vitro. Transcriptional and chromatin mapping studies show that HDAC3 inhibition disarms pathological astrocyte gene expression and function while promoting the expression of genes associated with beneficial astrocytes. Administration of RGFP966, a small molecule HDAC3 inhibitor, blocks reactive astrocyte formation and promotes neuroprotection in vivo in mice. Collectively, these results establish a platform for discovering modulators of reactive astrocyte states, inform the mechanisms that control astrocyte reactivity and demonstrate the therapeutic benefits of modulating astrocyte reactivity for neurodegenerative diseases.
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- 2024
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6. Hematopoietic Stimulation During Impella 5.5 Support to Avoid Transfusions in a Jehovah’s Witness
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Devich, Robert, Neuendorff, Nina Rosa, Frazier, Oscar Howard, Eisen, Howard J., Dowling, Robert, and Freundt, Miriam
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The population presenting with cardiogenic shock is heterogenous. Anemia is common in advanced heart failure and associated with poor outcomes. Microaxial flow pumps may cause ongoing blood trauma and worsen anemia. Treatment with recombinant erythropoietin, iron, vitamin B, and folate is recommended before cardiac surgery to reduce perioperative transfusion requirements but no data exist on the feasibility and safety during support with microaxial flow pumps. This novel strategy was born out of necessity to support a Jehovah’s Witness who opposes blood transfusion but required mechanical circulatory support. We present its efficacy over the duration of 19 days of Impella 5.5 support where hemoglobin level remained stable, and platelet count significantly improved despite a brief episode of gastrointestinal bleeding. No thromboembolic complications occurred. We anticipate this strategy could help not only Jehovah’s Witnesses, but also patients awaiting cardiac transplantation since transfusions stimulate development of antibodies which may preclude or postpone finding a suitable donor organ. Furthermore, it may minimize or prevent perioperative needs for transfusions for patients being bridged to durable left ventricular assist devices.
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- 2023
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7. Global Citizenship in Comparative Perspective: Youth Perceptions of Global Rights, Responsibilities and Efficacy Across Five Continents.
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Gerodimos, Roman, Balbin, Cecilia, Chan, Connie, Freundt-Thurne, Ursula, Gutiérrez Atala, Fernando José, Nyaole-Kowuor, Rosemary, and Melki, Jad
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WORLD citizenship ,MEDIA literacy ,POLITICAL science ,DEVELOPING countries ,YOUNG adults ,COSMOPOLITANISM - Abstract
The quest for a global polity has faced many criticisms and barriers, yet it continues to have strong moral, historical, political, and practical foundations. In this exploratory study, we present a rationale and conceptualization of global citizenship as a response to contemporary global challenges. The study is premised on a need for a robust comparative understanding of youth values, civic attitudes, and perceptions of globalization to identify similarities and differences across cultures. The article makes a case for global empirical research exploring youth perceptions of globalization and modes of citizenship and participation. We first present a conceptualization of global citizenship, drawing on an interdisciplinary body of literature on globalization, cosmopolitanism, political theory, media literacy and civic engagement. We then survey students (n=1,214 students) from 10 countries (Argentina, Chile, Hong Kong/China, Colombia, Greece, Kenya, Lebanon, Peru, the UK, and the US) about the extent to which they are personally affected by globalization and other specific global issues. The findings reveal several patterns, including a divide between participants in Western liberal democracies, who feel more removed from globalization and express less global efficacy and civic responsibility, and those in the Global South, who demonstrate greater levels of engagement, responsibility and efficacy. In addition, only a small group was identified as super-globalized, a term we gave for those who scored high across all indicators of global citizenship. [ABSTRACT FROM AUTHOR]
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- 2022
8. Extending Noble Gas Solubilities in Water to Higher Temperatures for Environmental Application.
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Schwenk, Cornelis, Freundt, Florian, Aeschbach, Werner, and Boehrer, Bertram
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- 2022
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9. CCAT: Prime-Cam optics overview and status update
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Zmuidzinas, Jonas, Gao, Jian-Rong, Huber, Zachary B., Lin, Lawrence T., Vavagiakis, Eve M., Freundt, Rodrigo G., Butler, Victoria, Chapman, Scott C., Choi, Steve K., Crites, Abigail T., Duell, Cody J., Gallardo, Patricio A., Huber, Anthony I., Keller, Ben, Middleton, Alicia, Niemack, Michael D., Nikola, Thomas, Orlowski-Scherer, John, Smith, Ema, Stacey, Gordon, Walker, Samantha, and Zou, Bugao
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- 2024
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10. Künstliche Intelligenz und Simulation in der Pränatalmedizin – was wir von Maschinen lernen können
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Steinhard, J., Freundt, P., Janzing, P., Popov, V., Menkhaus, R., and Ross, L.
- Abstract
Zielsetzung: Ziel der Arbeit war es, einen Überblick über derzeit verfügbare Anwendungen künstlicher Intelligenz (KI) und Simulationstechniken in der Pränatalmedizin mit dem Schwerpunkt auf eine mögliche Verbesserung der Aus- und Weiterbildung zu geben. Methoden: Es werden in der Pränatalmedizin existierende KI-Anwendungen sowie Simulatoren anhand von Beispielen und Studien vorgestellt. Schlussfolgerung: KI-Anwendungen werden zunehmend in den klinischen Alltag eingebunden und können zukünftig auch für die Aus- und Weiterbildung interessant werden. Strukturiertes simulationsbasiertes Ultraschalltraining sollte in ein Ausbildungscurriculum integriert werden.
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- 2022
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11. CCAT-prime: the design and characterization of the silicon mirrors for the Fabry-Perot interferometer in the Epoch of reionization spectrometer
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Zmuidzinas, Jonas, Gao, Jian-Rong, Zou, Bugao, Choi, Steve K., Cothard, Nicholas F., Freundt, Rodrigo, Huber, Zachary B., Li, Yaqiong, Niemack, Michael D., Nikola, Thomas, Riechers, Dominik A., Rossi, Kayla M., Stacey, Gordon J., and Vavagiakis, Eve M.
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- 2022
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12. CCAT-prime: the epoch reionization spectrometer for primce-cam on FYST
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Zmuidzinas, Jonas, Gao, Jian-Rong, Nikola, Thomas, Choi, Steve K., Duell, Cody J., Freundt, Rodrigo G., Huber, Zachary B., Li, Yaqiong, Malavalli, Kshama, Niemack, Mike, Rossi, Kayla M., Stacey, Gordon J., Vavagiakis, Eve M., Zou, Bugao, Cothard, Nicholas F., Austermann, Jason, Wheeler, Jordan D., Gao, Jiansong, Vissers, Michael R., Hubmayr, Johannes, Beall, James, and Ullom, Joel
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- 2022
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13. CCAT-prime: the optical design for the Epoch of reionization spectrometer
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Zmuidzinas, Jonas, Gao, Jian-Rong, Huber, Zachary B., Choi, Steve K., Duell, Cody J., Freundt, Rodrigo G., Gallardo, Patricio A., Keller, Ben, Li, Yaqiong, Lin, Lawrence T., Niemack, Michael D., Nikola, Thomas, Reichers, Dominik A., Stacey, Gordon, Vavagiakis, Eve M., and Zou, Bugao
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- 2022
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14. Extending Noble Gas Solubilities in Water to Higher Temperatures for Environmental Application
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Schwenk, Cornelis, Freundt, Florian, Aeschbach, Werner, and Boehrer, Bertram
- Abstract
Noble gas concentrations in natural waters are widely used to determine ambient temperature conditions during the last intensive contact with the atmosphere (equilibration). Such applications require accurate solubility functions, which so far are available only for the common environmental temperature range between (0 and 35) °C. Nonetheless, environmental scenarios that generate higher surface-water temperatures (such as volcanism) exist. Previous solubility measurements beyond ∼35 °C are sparse or outdated and were determined through equilibration of water with pure noble gases. This can potentially render them not suitable for environmental applications where equilibration with atmospheric air is considered. We therefore conducted new measurements for the solubilities of helium, neon, argon, krypton, and xenon in deionized water equilibrated with atmospheric air at ∼1 bar for temperatures ranging from (25 to 80) °C. These measurements were combined with data from the literature that were obtained in a similar manner and fitted with a commonly used function to determine new noble gas solubility functions valid from (0 to 80) °C. We estimate relative standard uncertainties with a 0.99 level of confidence between 0.015 and 0.030 for the new functions, which are thus suitable for the investigation of environmental high-temperature equilibration scenarios. For temperatures beyond 35 °C, the new functions deviate significantly from previous studies.
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- 2022
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15. Stille Hypoxie bei COVID-19: Eine Fallserie
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Fuehner, Thomas, Renger, Isabelle, Welte, Tobias, Freundt, Tobias, and Gottlieb, Jens
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Hintergrund:Die Coronavirus-Pandemie 2019 (COVID-19) ist eine anhaltende globale Krise, die die weltweiten Gesundheitssysteme herausfordert. Bei vielen Patienten besteht ein Missverhältnis zwischen schwerer Hypoxämie und wenigen Anzeichen von Atemnot (d.h. stille Hypoxämie). Dieses besondere klinische Bild wird häufig angeführt, aber die Daten sind begrenzt. Hauptteil:Die vorliegende Studie beschreibt das Empfinden von Dyspnoe, das mithilfe der BORG-Skala über einen Zeitraum von 4 Wochen bei Lungenpatienten ermittelt wurde, die in die Notaufnahme aufgenommen und dann in die Lungenabteilung des Siloah-Krankenhauses in Hannover verlegt wurden. Vom 1. Oktober bis zum 1. November 2020 wurden 82 Patienten mit Hypoxämie, definiert mit einem Sauerstoffbedarf zum Erreichen einer Sauerstoffsättigung (SpO
2 ) ≥92%, eingeschlossen. Bei 45/82 (55%) Patienten wurde bei der Aufnahme durch PCR SARS-CoV-2 nachgewiesen. Bei den Nicht-COVID-Patienten war die Exazerbation der COPD die Hauptdiagnose (15/37, 41%). Alle Probanden bewerteten ihre wahrgenommene Dyspnoe anhand der modifizierten Borg-CR10-Skala. Die Patienten in der Nicht-COVID-Gruppe litten mehr unter Dyspnoe auf der modifizierten Borg-CR10-Skala (Median 1, IQR: 0–2 vs. Median 5, IQR: 3–6, p< 0,001). In der multivariaten Analyse war eine «stille Hypoxämie», definiert durch die Dyspnoe-Borg-CR10-Skala ≥5, unabhängig von COVID-19 und dem Vorhandensein einer schweren Hypokapnie mit einer Odds Ratio von 0,221 (95%-Konfidenzintervall 0,054, 0,907, p0,036) verbunden. Schlussfolgerungen:Bei Lungenpatienten mit akuter Hypoxämie, die mit einem Sauerstoffbedarf definiert wurden, leiden COVID-19-Patienten im Vergleich zu Nicht-COVID-Patienten weniger unter Dyspnoe. «Stille» Hypoxämie trat bei COVID-19-Patienten häufiger auf.- Published
- 2022
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16. Graded cleavage of elastic titin in living mouse hearts reveals the role of titin stiffness for cardiac contractility
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Freundt, Johanna K., Unger, Andreas, Loescher, Christine M., Holtmeier, Richard, Hille, Susanne, Müller, Oliver J., and Linke, Wolfgang A.
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- 2024
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17. Stable germination behavior but partly changing seed–seed interactions along a steep rainfall gradient.
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Metz, Johannes, Freundt, Hanna, and Jeltsch, Florian
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GERMINATION ,RAINFALL ,BRACHYPODIUM ,DORMANCY in plants ,SEEDS - Abstract
Germination marks a critical transition in plant life that is prone to high mortality. Strong selection pressure is therefore expected to finely tune it to environmental conditions. Our study on the common Mediterranean grass Brachypodium hybridum assessed whether germination behavior changes systematically along a steep natural rainfall gradient ranging from harsh desert to rather mild mesic-Mediterranean conditions. We specifically tested hypotheses that germination behavior confers greater risk-spreading in populations from drier, unpredictable environments, and that seeds from wetter populations are better competitors. In 14 populations (spanning 114–954 mm annual rainfall) we assessed three alternative key parameters of germination in a greenhouse experiment: between-year dormancy, days to emergence within a season, and temporal spread. Addition of neighbor seeds accounted for competition as another crucial environmental factor. In six of the 14 populations, we also compared seeds originating from corresponding north (more mesic) and south (more arid) exposed hill slopes to test whether germination patterns along the large-scale rainfall gradient are paralleled at this smaller scale. B. hybridum exhibited generally high germination fractions and rapid emergence with very little temporal spread, indicating overall little risk-spreading germination. Surprisingly, none of the three parameters changed systematically with increasing aridity, neither at large scale along the rainfall gradient nor at small scale between north and south exposures. Neighbor seeds, however, mildly suppressed germination. Germination of neighbor seeds, in turn, was more strongly suppressed by B. hybridum seeds from drier populations, and this effect was stronger for forb than for grass neighbor species. Our results provide strong evidence that increased risk-spreading germination is not a universal, essential strategy to persist in increasingly dry, unpredictable environments. They also highlight that competition with neighbors occurs even at the earliest plant life stage. Since neighbor effects were species-specific, competition among seeds can affect community composition at later plant stages. [ABSTRACT FROM AUTHOR]
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- 2018
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18. CARC2: Novel use of newer intravascular ambulatory left ventricular assist devices as a bridging strategy for cardiogenic shock
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Mahesh, Balakrishnan, Devich, Robert, Freundt, Miriam, Lavanga, Elizabeth, Dowling, Robert, and Soleimani, Behzad
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- 2023
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19. P61: Novel use of newer intravascular ambulatory systemic ventricular assist devices as a bridging strategy for cardiogenic shock with pulmonary hypertension in patients with complex congenital cardiac conditions
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Mahesh, Balakrishnan, Myers, John, Bradley, Elisa, Freundt, Miriam, Dowling, Robert, and Soleimani, Behzad
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- 2023
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20. Abstract 9457: Primary Cardiac Allograft Dysfunction Caused by Pretransplantation Amiodarone Therapy
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Freundt, Miriam, Eisen, Howard J, Mahesh, Balakrishnan, Dowling, Robert D, Brehm, Christoph, and Soleimani, Behzad
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Background:Primary graft dysfunction (PGD) is devastating. Amiodarone therapy prior to cardiac transplantation (TxP) is common but has recently been reported as potential cause of PGD.Case:66-year-old male with non-ischemic cardiomyopathy, severely reduced LVEF with LVAD, recurrent VT on amiodarone for 6 months presented with ICD shocks. Amiodarone was increased due to VT storm in the setting of Rhinovirus infection. Infusions with amiodarone and lidocaine were started but repeat IV boli of lidocaine and amiodarone were needed. VT-ablation was not feasible due to multiple morphologies. He underwent TxP with an ideal organ from a 28 yo donor. Paragonix SherpaPak was used for transport. Pre-explanation EF was 70% with serologies positive for EBV (+/+), Strongyloides (+/-), negative for Toxoplasmosis (-/-), CMV (-/-). Donor heart was arrested with appropriate cardioplegia and no distention occurred. Total ischemic time was 3 hours 10 minutes, warm ischemic time 40 minutes, crossclamp time in recipient 2 hours 2 minutes with total cardiopulmonary bypass time 2 hours 58 minutes. Coming off bypass both ventricles appeared markedly dilated with severely reduced function and due to high doses of inotropic and vasopressor support veno-arterial ECMO was placed. The chest was left open and during postoperative course in the intensive care unit pressor and inotropes could slowly weaned. Induction therapy was administered with ATG, Solumedrol and mycophenolate mofetil. Strongyloides infection was treated with four doses of Ivermectin. On postoperative day LVEF recovered to 40-45% with moderately reduced RV function and patient was successfully decannulated from VA ECMO with chest closure. Endomyocardial biopsies showed no signs of rejection throughout. After prolonged ICU and rehab stay patient has now recovered to independent life.Conclusion:Amiodarone associated PGD may be underreported and increasing awareness of this etiology may warrant early empiric discontinuation of the medication if transplantation remains a therapeutic option in the future.
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- 2022
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21. Abstract 334: Cardiogenic Shock In Heart Transplant Candidates - Improved Outcome With Impella 5.5
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Freundt, Miriam, Devich, Robert, Mahesh, Balakrishnan, Eisen, Howard J, Soleimani, Behzad, and Dowling, Robert D
- Abstract
Background:Heart transplant (HTX) candidates often develop cardiogenic shock (CS) and require mechanical circulatory support (MCS). UNOS criteria prioritize temporary MCS over durable left ventricular assist devices (LVADs). Extracorporeal membrane oxygenation (ECMO) or intra-aortic balloon pump are associated with poor outcome. In early 2020, we transitioned to using axillary Impella 5.5 in CS patients with both isolated LV or biventricular failure as bridge to HTX. This reports our two-year experience.Methods:We performed a retrospective single center chart review. 19 patients treated with Impella 5.5 as bridge to HTX were identified. UNOS criteria were used to classify CS. If inotropes and diuresis failed to resolve CS, Impella 5.5 was placed via a 10 mm graft sewn to the axillary artery. Key endpoints were survival to transplant without disabling stroke, 30-day and 1-year post-HTX survival.Results:Mean age 55 yrs, 89% male, mean Impella support 19 days (2 - 71, total 369). 58% biventricular failure with at least moderate right ventricular dysfunction (RVD). RVD was managed medically, no RV assist device or ECMO was needed. Transient elevation (>40 mg/dl) of free plasma hemoglobin occurred in 42% but resolved with device repositioning and/or fluids. No renal replacement therapy was required. No serious infectious, vascular or bleeding complication occurred. There was no device malfunction, one pump was replaced due to an exposed wire after 22 days of support. 100% of patients were able to ambulate prior to HTX. Overall survival was 100%. 89% patients were successfully bridged to HTX without major morbidity. Two cases received durable LVAD. One developed non-disabling ischemic stroke on day 16 of Impella support. One elected LVAD as destination therapy after 71 days of support. Stroke free survival during Impella support was 95%. There were no disabling strokes. Post-transplant 30-day survival was 100% (n=17). 1-year post-HTX survival data was 100% (n=10).Conclusion:Impella 5.5 successfully restores hemodynamics in CS in HTX eligible patients with both isolated LV and biventricular failure. RVD in this situation can be managed medically. With this strategy, patients are able to ambulate prior to HTX and survival after HTX exceeds national average.
- Published
- 2022
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22. Unterbauten.
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Mehlhorn, Gerhard and Freundt, Ursula
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- 2007
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23. Lagerung.
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Mehlhorn, Gerhard and Freundt, Ursula
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- 2007
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24. Volcanogenic Tsunamis in Lakes: Examples from Nicaragua and General Implications.
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Satake, Kenji, Okal, Emile A., Borrero, José C., Freundt, Armin, Strauch, Wilfried, Kutterolf, Steffen, and Schmincke, Hans-Ulrich
- Abstract
This paper emphasizes the fact that tsunamis can occur in continental lakes and focuses on tsunami triggering by processes related to volcanic eruptions and instability of volcanic edifices. The two large lakes of Nicaragua, Lake Managua and Lake Nicaragua, host a section of the Central American Volcanic Arc including several active volcanoes. One case of a tsunami in Lake Managua triggered by an explosive volcanic eruption is documented in the geologic record. However, a number of events occurred in the past at both lakes which were probably tsunamigenic. These include massive intrusion of pyroclastic flows from Apoyo volcano as well as of flank-collapse avalanches from Mombacho volcano into Lake Nicaragua. Maar-forming phreatomagmatic eruptions, which repeatedly occurred in Lake Managua, are highly explosive phenomena able to create hugh water waves as was observed elsewhere. The shallow water depth of the Nicaraguan lakes is discussed as the major limiting factor of tsunami amplitude and propagation speed. The very low-profile shores facilitate substantial in-land flooding even of relatively small waves. Implications for conceiving a possible warning system are also discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2007
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25. Multi-Axes Micro Gripper for the Handling and Alignment of Flexible Micro Parts.
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Ratchev, Svetan, Brecher, Christian, Peschke, Christian, Freundt, Martin, and Lange, Sven
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Optical micro parts, such as glass fibres, require handling and alignment accuracies down to the sub micrometer range. Addressing this task, one aim of the Fraunhofer IPT is the development of new concepts of active gripper systems. In this context a highly integrated, adaptive, rugged and economical gripper system particularly for accurate handling and alignment of flexible micro parts down to the sub-micron level has been developed. This gripper system can be used on conventional robot systems for carrying out micro-assembly operations. The robot system does the pre-positioning, the tolerances necessary for the micro-assembly are subsequently realized directly at the tip of the gripper with the gripper integrated multi-axes system. Positioning systems that achieve the required positioning increments in the sub micron range are already existent. However, the problem of such systems is that they are normally highly sensitive against mechanical impact and extremely cost intensive. In this paper the development of a highly robust gripper-integrable axes system and its integration in a novel gripper design with a multi-axis adjustment system is presented. [ABSTRACT FROM AUTHOR]
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- 2006
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26. Preclinical study on combined chemo- and nonviral gene therapy for sensitization of melanoma using a human TNF-alpha expressing MIDGE DNA vector.
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Kobelt, Dennis, Aumann, Jutta, Schmidt, Manuel, Wittig, Burghardt, Fichtner, Iduna, Behrens, Diana, Lemm, Margit, Freundt, Greta, Schlag, Peter M., and Walther, Wolfgang
- Abstract
Nonviral gene therapy represents a realistic option for clinical application in cancer treatment. This preclinical study demonstrates the advantage of using the small‐size MIDGE® DNA vector for improved transgene expression and therapeutic application. This is caused by significant increase in transcription efficiency, but not by increased intracellular vector copy numbers or gene transfer efficiency. We used the MIDGE‐hTNF‐alpha vector for high‐level expression of hTNF‐alpha in vitro and in vivo for a combined gene therapy and vindesine treatment in human melanoma models. The MIDGE vector mediated high‐level hTNF‐alpha expression leads to sensitization of melanoma cells towards vindesine. The increased efficacy of this combination is mediated by remarkable acceleration and increase of initiator caspase 8 and 9 and effector caspase 3 and 7 activation. In the therapeutic approach, the nonviral intratumoral in vivo jet‐injection gene transfer of MIDGE‐hTNF‐alpha in combination with vindesine causes melanoma growth inhibition in association with increased apoptosis in A375 cell line or patient derived human melanoma xenotransplant (PDX) models. This study represents a proof‐of‐concept for an anticipated phase I clinical gene therapy trial, in which the MIDGE‐hTNF‐alpha vector will be used for efficient combined chemo‐ and nonviral gene therapy of malignant melanoma. Highlights: The minimalistic MIDGE‐vector improves transcription compared to plasmid vectors.This vector achieved high‐level hTNF‐alpha expression for melanoma sensitization.This sensitization is mediated by accelerated and increased caspase activation.Nonviral in vivo MIDGE‐vector gene transfer leads to efficient TNF‐expression.Combined gene‐ and chemotherapy improves melanoma growth inhibition in vivo. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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27. CCAT-prime: design of the Mod-Cam receiver and 280 GHz MKID instrument module
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Zmuidzinas, Jonas, Gao, Jian-Rong, Vavagiakis, Eve M., Duell, Cody J., Austermann, Jason, Beall, James, Bhandarkar, Tanay, Chapman, Scott C., Choi, Steve K., Coppi, Gabriele, Dicker, Simon, Devlin, Mark, Freundt, Rodrigo G., Gao, Jiansong, Groppi, Christopher, Herter, Terry L., Huber, Zachary B., Hubmayr, Johannes, Johnstone, Doug, Keller, Ben, Kofman, Anna M., Li, Yaqiong, Mauskopf, Philip, McMahon, Jeff, Moore, Jenna, Murphy, Colin C., Niemack, Michael D., Nikola, Thomas, Orlowski-Scherer, John, Rossi, Kayla M., Sinclair, Adrian K., Stacey, Gordon J., Ullom, Joel, Vissers, Michael, Wheeler, Jordan, Xu, Zhilei, Zhu, Ningfeng, and Zou, Bugao
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- 2022
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28. Contenidos de la actividad expresivo motriz en los programas de las carreras de pedagogía en Educación Física, en Chile.
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Freundt, Alda Reyno
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BODY movement ,BODY language ,PHYSICAL education ,PHYSICAL training & conditioning ,PHYSICAL fitness ,PHYSICAL education teachers ,EDUCATIONAL programs ,LITERACY programs - Abstract
Copyright of Cultura, Ciencia y Deporte is the property of Cultura, Ciencia y Deporte and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2010
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29. Investigation of the Substrate/Epitaxial Interface of Si/Si1-xGexLayers Grown by LPCVD
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Loo, R., Vescan, L., Dieker, C., Freundt, D., Hartmann, A., Mück, A., Loo, R., Vescan, L., Dieker, C., Freundt, D., Hartmann, A., and Mück, A.
- Abstract
The paper reports a study of the quality of the substrate/epilayer interface. Before growing the Si or Si/Si1-xGexstructures by low pressure chemical vapour deposition, Si(100) substrates were cleaned by a modified RCA-cleaning and just before epitaxy different ex-situ and in-situ processes were applied to remove the oxide layer grown on the wafer substrates in the last step of the RCA-cleaning. The effect of interfacial contamination on electrical and optical properties were studied. By a wet-chemical removal of the oxide layer an interfacial oxygen level of 1.3x1013atoms/cm2is found, while a thermal removal leads to an interfacial oxygen level below 6x1012atoms/cm2. In both cases carbon levels of (1-2)x1014atoms/cm2have been detected. By electrochemical capacitance-voltage profiling it was found that these contaminations are connected with electrically active donors. According to our investigations, electrochemical capacitance-voltage profiling is suitable to give a quick indication on the quality of the substrate/epitaxial interface. In addition, the removal of the oxide layer was investigated by high resolution electron energy loss spectroscopy on cleaned Si-surfaces.
- Published
- 1995
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30. Emergence in a complex network with two types of directed edges – A numerical investigation.
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Freundt, Stefan
- Abstract
[Display omitted] • In a dynamic network we are looking for structures. • If the number and density of edges exceeds a threshold, structures are formed. • If the number and/or density falls below a threshold, the structures disappear. I have considered the "electron-positron pair annihilation" and have come to the conclusion that while the current models and associated mathematics are very useful, some essential questions remain unanswered. To give direction to an alternative, I pose the following question and answer it by way of example. What may a model look like containing objects with the following properties: 1. The objects consist of components. 2. The environment comprises the same components. 3. There are conditions under which objects are formed and then remain stable. Accordingly, the objects have at least one property that, with time, does not change or changes only insignificantly. 4. There are conditions under which the objects are destroyed or dissolved. 5. The objects are dynamic, i.e., at any time, they are formed by different components. To answer the above question, I create a network of nodes and two types of directed edges. The edges give properties to the nodes and, at the same time, want to move to nodes with certain properties. Thus, the edges have a target. Since the targets of the edge types contradict each other, the edges always keep moving. What one type of edges creates is destroyed by the other type of edges and vice versa. The network thus has an internal dynamic. If the average node degree exceeds the threshold of approx. 11, simple objects are formed. The objects are the more stable, • the higher the average node degree. • the more nodes and edges the network has. If edges are now randomly deleted from the network so that the average node degree falls below 11, the objects disappear again. If someone looks at the objects at different times, they are formed by different edges again and again. The article presents a simple and well-defined model for emergent behavior. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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31. Tumor de células esteroideas de ovario: Reporte de un caso.
- Author
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LUQUE CUBA, Edith Jacqueline, GARCIA RAMOS, Freddy, RECHKEMMER PRIETO, Adolfo, SOLIS VILLANUEVA, José, ROSAS VARGAS, Luz, CASTILLO SAYAN, Oscar, RODRIGUEZ LAY, Elba, CORN EJO ARENAS, María del Pilar, FIGUEROA DIAZ, Victor, NEIRA ARIZMENDIZ, Luis, CALDERON TICONA, Jorge, MANRIQUE HURTADO, Helard, and FREUNDT ESPINOSA, Joscemin
- Abstract
The suggestive clinical characteristics of hyperandrogenism are very common problems in women and have been related with excessive androgen production from ovaries, suprarenal glands or both. The most common identifiable cause of androgen excess is the polycystic ovary syndrome. The virilizing tumors are rare. We report the case of a postmenopausal women with virilizing signs and a left anexial mass. Testosterone 4.3ng/mL (0.2-0.95); DHEAS 56ug/dL (35-430); androstenedione: 10ng/ml (0.4-2.7); Cortisol 16ug/dL. Testosterone post dexamethasone suppression test 3.5ng/mL. Ovarian steroid cell tumors secrete great quantities of testosterone or androstenedione and differ from Leydig cell tumors in that they lack crystals of Reinke. Usually, they are benign, but 20% of malignancy has been reported. They can produce different substances. The election treatment is oophorectomy. As in our patient, the androgens levels are normalized after surgery. [ABSTRACT FROM AUTHOR]
- Published
- 2005
32. Do Tax-Benefit Packages Treat Families in the Same Manner When Unemployment Strikes?
- Author
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Freundt, Anders, Straubinger, Simon Grundt, and Kvist, Jon
- Abstract
Social protection against unemployment is on the European agenda because of the economic crisis. Since European family patterns have changed over the last three decades, the social protection for unemployment may be very different during this economic crisis from what it was previously. In particular the combination of more diverse families and high unemployment raises the general question of how today's systems of social protection cater for different types of families and income groups. Based on a micro-simulation analysis, this article examines how, and to what extent, packages of social security provide support for various types of unemployed families at different income levels. The comparison is between four countries representing different welfare state models and dominant family types. Using the OECD Tax-Benefit model, the article surveys the disposable income and provides a breakdown of benefits for different family types facing unemployment. It takes into account housing costs and childcare costs, and the benefits related to them. The analysis shows that unemployed families experience different levels of support depending not only on the country they live in, but also on their income level and family type. Often differences between families at different income levels within countries are larger than differences between families at the same income level between countries. The analysis illustrates how important it is to look beyond unemployment insurance and include family related benefits to understand the support provided to families faced with unemployment.
- Published
- 2013
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33. Measurement Validity in Comparative Welfare State Research: The Case of Measuring Welfare State Generosity
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Kvist, Jon, Straubinger, Simon Grundt, and Freundt, Anders
- Abstract
Examining the generosity of welfare states and individual benefit schemes is a classical task in comparative welfare state studies. Three types of welfare states can be discerned based, in part, on their level of benefit generosity. Although significant advances have been made in the development of measures of welfare state generosity, this progress has not been without its challenges and limitations. In this article, the authors examine two sets of limitations related to measurement validity in comparative welfare state research: securing content validation and ensuring comparability across time and place. Through the use of illustrative examples to compare the situation of the unemployed in five European countries across several income levels and two family types, we demonstrate that, by profiling and stacking public benefits using the OECD Tax-Benefit micro-simulation model, we are able to carry out a more informed analysis of the redistributive strategies of the welfare state.
- Published
- 2013
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34. Durability Testing of a Short SOFC Stack under Direct Internal Steam Reforming of Methane
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Fu, Qingxi, Freundt, Pierre, Bomhard, Jakob, and Hauler, Felix
- Abstract
One 5-cell SOFC stack has been tested under both hydrogen and direct internal steam reforming of methane for a total duration of 3200 hours. Electrochemical impedance spectroscopy has been used to monitor the evolution of internal resistances of all repeating units in the stack. It has been found that repeating units in the stack degraded two times faster under direct internal steam reforming of methane (6.7 - 14.4%/kh voltage degradation) than under H2 (2.3 - 4.0%/kh). In combination with impedance results, this indicates deterioration of the anode as the main cause of degradation for operation under CH4/H2O. The degradation process is at least partially reversible when changing the gas from CH4 to H2.
- Published
- 2013
35. Entrance of hot pyroclastic flows into the sea: experimental observations
- Author
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Freundt, Armin
- Abstract
The entrance of hot pyroclastic flows into water has been observed in a series of experiments in which shooting granular flows of hot ignimbrite ash (≤403 °C), of bulk density near that of water, run down a smooth chute and enter a water-filled tank at an angle of 26°. Flows of relatively cool ash (<150 °C) impulsively displace some volume of near-shore water upon impact, generating a water wave that rapidly travels away from shore. The granular flow material then separates into two portions. (1) A fine-ash surge cloud is formed where the granular flow hits water and rapidly travels down-tank over the water. (2) The main portion of material penetrates the surface and mixes with the water, creating a turbulent mixing zone resembling a hydraulic jump, which advances downstream as long as the pyroclastic flow is maintained. Most pumice floats to the surface, lithics and coarse ash fall out onto the floor, but ash that remains in suspension forms a turbidity current that travels down the floor of the tank. With increasing ash temperature, an increasing fraction of incoming material is initially transported along the water surface; almost all material takes this path at temperatures >250 °C. Mixing across the water surface over some distance from shore generates steam explosions forming fountains of wet and dry ash and convectively rising fine-ash plumes. Steam explosions increase in strength and lateral extent towards higher ash temperatures and mass fluxes. The explosions generate water waves that remain driven by massive fountain fallout across some distance from shore. The ash fountains feed pyroclastic surges, which advance down tank over water at high speeds. Underwater plumes of sediment falling from the ash fountains and surges drop coarse load onto the floor whereas the finer load forms a turbidity current. High temperature and poor size sorting of pyroclastic flows are key parameters that determine the processes of interaction with water and the associated hazards. Poor sorting allows for the formation of ash-cloud surges moving over water, even from cool flows. High temperatures cause littoral explosions and facilitate extensive mass transport over water. All flows generate tsunami waves by different mechanisms.
- Published
- 2003
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36. On the voluntary provision of public goods under risk
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Freundt, Jana and Lange, Andreas
- Abstract
•Provide experimental evidence on how risks in different dimensions of the return from a public good impact investments decisions.•Identify a particularly strong effect of the risk in the public component of the return.•Demonstrate that the correlation between private and public returns is crucial when risks in both dimensions exist.•Provide insights into behavioral motivations of pro-social behavior.
- Published
- 2021
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37. Formation of high-grade ignimbrites Part II. A pyroclastic suspension current model with implications also for low-grade ignimbrites
- Author
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Freundt, Armin
- Abstract
Abstract: Analogue experiments in part I led to the conclusion that pyroclastic flows depositing very high-grade ignimbrite move as dilute suspension currents. In the thermo–fluid–dynamical model developed, the degree of cooling of expanded turbulent pyroclastic flows dynamically evolves in response to entrainment of air and mass loss to sedimentation. Initial conditions of the currents are derived from column-collapse modeling for magmas with an initial H
2 O content of 1–3 wt.% erupting through circular vents and caldera ring-fissures. The flows spread either longitudinally or radially from source up to a runout distance that increases with higher mass flux but decreases with higher gas content, temperature, bottom slope and coarser initial grain size. Progressive dilution by entrainment and sedimentation causes pyroclastic currents to transform into buoyant ash plumes at the runout distance. The ash plumes reach stratospheric heights and distribute 30–80% of the erupted material as widespread co-ignimbrite ash. Pyroclastic suspension currents with initial mass fluxes of 107 -1012 kg/s can spread for tens of kilometers with only limited cooling, although they move as supercritical, strongly entraining currents for the eruption conditions considered here. With increasing eruption mass flux, cooling during passage through the fountain diminishes while cooling during flow transport increases. The net effect is that eruption temperature exerts the prime control on emplacement temperature. Pyroclastic suspension currents can form welded ignimbrite across their entire extent if eruption temperature is To >1.3. Tmw , the minimum welding temperature. High eruption rates, a large fraction of fine ash, and a ring-fissure vent favor the formation of extensive high-grade ignimbrite. For very hot eruptions producing sticky, partially molten pyroclasts, analysis of particle aggregation systematics shows that factors favoring longer runout also favor more efficient aggregation, which reduces runout. As a result, very high-grade ignimbrites cannot spread more than a few tens of kilometers from their source. In cooler pyroclastic currents, particles do not aggregate, and the sedimentation process may involve re-entrainment of particles, which potentially leads to more extensive cooling and longer runout; such effects, however, are only significant when net erosion of substrate occurs. Model results can be employed to estimate mass flux and duration of ignimbrite eruptions from measured ignimbrite masses and aspect ratios. The model also provides an alternative explanation of the observed decrease in H/Lratios with ignimbrite mass.- Published
- 1999
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38. Blood acetaldehyde in alcoholized rats and humans during inhalation of carbon disulphide vapor
- Author
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Freundt, K. J., Lieberwirth, K., Netz, H., and Pöhlmann, E.
- Abstract
Exposure of rats to 20 ppm CS
2 (the current MAC in various countries) for 8 h was followed by i.p. administration of 2 g/kg ethanol (blood level: 3-1‰) and another up to 4-h exposure to the same concentration of CS2 . During the second exposure the acetaldehyde concentration increased significantly, the rise representing one third of the control values. Inhalation of 400 ppm CS2 for the same period, or 8-h exposures at 400 ppm CS2 on 5 consecutive days produced only a slight additional increase in acetaldehyde. The increased appearance of acetaldehyde in blood is considered to be due to inhibition of aldehyde dehydrogenase by CS2 . This conclusion was derived from the significant lag in the clearance rate of acetaldehyde given i.v. (1 mmol/kg) after exposure at 400 ppm CS2 /8 h, involving an increase of the excretion half-life of acetaldehyde (1 min, 45 s in the controls) to 2 min, 24 s. The finding thus obtained could be reproduced in man (adult males). At a blood alcohol concentration of approximately 0.75‰, maintained at this level for 8 h, the blood acetaldehyde concentration was found to be approximately 6 × 10-3 ‰; it rose significantly by about 50% during simultaneous 8-h exposure of the test subjects to a nonfluctuating, analytically defined concentration of 20 ppm CS2 . When increasing the dose Of CS2 to 40 ppm and 80 ppm for 8 h, only a slight additional increase was noted. Administration of ethanol (ca. 0./5‰) for 8 h, instituted at 16 h after 8-h inhalation of 20 ppm CS2 , produced a rise in blood acetaldehyde to slightly more than twice the control value. An approximately identical quantitative effect was observed after exposure to 20 ppm on 5 consecutive days at the same time of the day (8.00 a.m. - 4.00 p.m.). Under the conditions employed, there was no evidence of any subjective or objective signs of alcohol intolerance in terms of an “antabuse syndrome” in the experiments. Inhalation of CS2 vapor failed to exert a significant effect on the pharmacokinetic behavior of ethanol in with a blood alcohol content up to 0.8%., contact with CS2 is not likely to give rise to a CS2 -alcohol reaction, provided the concentrations of CS2 encountered in the work environment are within the range of the MAC.- Published
- 1976
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39. Highly spatially resolved electron energy‐loss spectroscopy in the bandgap regime of GaN
- Author
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Bangert, U., Harvey, A. J., Freundt, D., and Keyse, R.
- Abstract
The possibilities of obtaining information about interband scattering processes in the bandgap regime of GaN from electron energy‐loss spectra, taken in a dedicated scanning transmission electron microscope (STEM), are investigated. With the help of precise simulations of the zero‐loss peak it is feasable to process, extract and analyse data in the extreme low‐loss regime of a few electronvolts. The accuracy of the results is restricted predominantly by instrumental broadening functions. By modelling these accurately, it is possible to eliminate the effects of the tail of the zero‐loss peak and to extract the low‐loss spectrum together with the correct value for the bandgap of GaN. Furthermore, differences in the shapes of the low‐loss spectra can be revealed, depending on the microstructural features, probed at different beam locations.
- Published
- 1997
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40. The entrainment of high-viscosity magma into low-viscosity magma in eruption conduits
- Author
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Freundt, Armin and Tait, Stephen R.
- Abstract
We report experiments on the flow of two fluids of contrasting viscosity through a pipe in which low-viscosity fluid occupies the center of the pipe. The volume flux of the low-viscosity fluid in the pipe increased during an experiment but did not reach 100% in most cases. The transition from high- to low-viscosity-dominated outflow involved a drop in pressure gradient and an increase in flow rate due to reduced viscous resistance in the pipe. Initially, the central flow was thin and parallel-sided, but as its diameter increased the flow became unstable. A sequence of instabilities was observed during the course of each experiment, both in time and as a function of height in the pipe. In the most commonly observed instability the central flow adopted a helical geometry. The transition from parallel-sided to unstable flow first appeared at the top of the pipe and propagated downwards against the flow. Axisymmetric instabilities originating at the pipe entrance were also observed. All forms of instability exhibited entrainment of viscous fluid into the faster moving central flow. Entrainment was extensive early in the existence of the central flow, but later on the volume flux of lower-viscosity fluid in the central flow rose more rapidly than the rate of entrainment and the proportion of lower-viscosity fluid increased with time. These compositional changes determined the viscosity of the central flow which was found to control its diameter and velocity. In banded pumice deposits, silicic pumice without mafic component is commonly erupted alongside banded pumice blocks. We infer that banded pumice may correspond to the central flow in our experiments, i. e., that viscous magma has been incorporated into less viscous melt, and that pure acid pumice is derived from the outer flow. Changes in eruption style may be caused by variations in pressure gradient and flow rate due to changes in the viscosity of the melt in the conduit. Varied mafic/silicic proportions and degree of mixing in magmatic associations are controlled by the bulk volume erupted, discharge rate, initial temperature difference and aspect ratio of the conduit.
- Published
- 1986
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41. Emplacement of small-volume pyroclastic flows at Laacher See (East-Eifel, Germany)
- Author
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Freundt, A. and Schmincke, H. -U.
- Abstract
We distinguish three eruptive units of pyroclastic flows (T1, T2, and T3; T for trass) within the late Quaternary Laacher See tephra sequence. These units differ in the chemical/mineralogical composition of the essential pyroclasts ranging from highly differentiated phonolite in T1 to mafic phonolite in T3. T1 and T2 flows were generated during Plinian phases, and T3 flows during a late Vulcanian phase. The volume of the pyroclastic flow deposits is about 0.6 km
3 . The lateral extent of the flows from the source vent decreases from > 10 km (T1) to < 4.5 km (T3). In the narrow valleys north of Laacher See, the total thickness of the deposits exceeds 60 m.- Published
- 1986
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42. Disposition of exposed antigens on the faces of isolated Mycoplasma gallisepticum membranes
- Author
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Vinther, O and Freundt, E A
- Abstract
The transverse disposition of exposed protein antigens on the two faces of isolated Mycoplasma gallisepticum membranes have been investigated by using indirect immunoferritin labeling to accomplish visualization of the antigens at the ultrastructural level. Comparison between the labeling patterns obtained with unabsorbed specific mycoplasma antiserum and antiserum from which antibodies directed against outer side determinants had been removed revealed that the majority of protein antigens were the same on the opposed membrance faces or at least displayed extensive interside cross-reactivity. The relatively scarce tagging of isolated Acholeplasma laidlawii membranes, contrary to membranes on intact organisms observed in this investigation, precluded conclusions regarding the disposition of membrane antigens of this species. The advantages and limitations of the employed method in disposition studies and the factors influencing the transverse distribution of membrane proteins in mycoplasmas are discussed.
- Published
- 1980
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43. Flagellation and swimming motility of Thermoplasma acidophilum
- Author
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Black, F T, Freundt, E A, Vinther, O, and Christiansen
- Abstract
Electron microscopy of thin sections of Thermoplasma acidophilum confirmed previous observations of the absence of a typical cell wall in this organism. Negatively stained specimens revealed the almost consistent occurrence in both strains examined of monotrichously arranged flagella, about 9 micrometer long, which describe a sinuous curve with a wavelength of 1.5 to 2.0 micrometer and an amplitude of 0.33 to 0.59 micrometer. Motility of T. acidophilum could be demonstrated microscopically by microcinematography and macroscopically. The theoretical implications of the demonstration of functioning flagella in a wall-defective organism are discussed in the light of current theories of the mechanism of flagellar motility and from a taxonomic point of view.
- Published
- 1979
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44. Total Body Water Measured by 18O Dilution and Bioelectrical Impedance in Well and Malnourished Children
- Author
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FJELD, CARLA R., FREUNDT-THURNE, JAIME, and SCHOELLER, DALE A.
- Abstract
Total body water (TBW) is an indicator of fat-free mass and thus of nutritional status but cannot be measured readily in children in developing countries who are at greatest risk of becoming malnourished. We therefore developed equations to predict 18O TBW from bioelectrical impedance (Z), wt, and ht in well and malnourished infants and children whom we considered characteristic of children evaluated in nutritional surveillances in Peru. Children 3 to 30 mo of age, whose wt were 3.4 to 14.4 kg, which was —2.8 to 1 SD wt-for-ht, were randomly assigned to group I (n30) to develop equations to predict TBW or to group II («14) to cross-validate the predictive equations. Mean TBW measured by 180 dilution was 4.8 ± 1.2 kg in group I, and 5.6 ± 1.7 kg in group II. TBW ranged from 57 to 78 of body wt (65 ± 6) in group I and from 56 to 80 (64 ± 6) in group II, indicating no statistically significant differences in body composition. The following equation was developed and cross-validated TBW, kg0.48 0.68 ht2Z; standard error estimate0.36; r0.98). A slight improvement was achieved by the addition of body wt (TBW, kg0.76 0.18 ht2Z 0.39 wt; standard error estimate0.23; r0.99).
- Published
- 1990
45. Total Body Water Measured by 18O Dilution and Bioelectrical Impedance in Well and Malnourished Children
- Author
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Fjeld, Carla R, Freundt-Thurne, Jaime, and Schoeller, Dale A
- Abstract
ABSTRACT: Total body water (TBW) is an indicator of fat-free mass and thus of nutritional status but cannot be measured readily in children in developing countries who are at greatest risk of becoming malnourished. We therefore developed equations to predict 18O TBW from bioelectrical impedance (Z), wt, and ht in well and malnourished infants and children whom we considered characteristic of children evaluated in nutritional surveillances in Peru. Children 3 to 30 mo of age, whose wt were 3.4 to 14.4 kg, which was —2.8 to +1 SD wt-for-ht, were randomly assigned to group I (n = 30) to develop equations to predict TBW or to group II (n = 14) to cross-validate the predictive equations. Mean TBW measured by 18O dilution was 4.8 ± 1.2 kg in group I, and 5.6 ± 1.7 kg in group II. TBW ranged from 57 to 78% of body wt (65 ± 6%) in group I and from 56 to 80% (64 ± 6%) in group II, indicating no statistically significant differences in body composition. The following equation was developed and cross-validated: TBW, kg = 0.48 + 0.68 ht2/Z; standard error estimate = 0.36; r = 0.98). A slight improvement was achieved by the addition of body wt (TBW, kg = 0.76 + 0.18 ht2/Z + 0.39 wt; standard error estimate = 0.23; r = 0.99).
- Published
- 1990
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46. The formation of high-grade ignimbrites, I: Experiments on high- and low-concentration transport systems containing sticky particles
- Author
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Freundt, Armin
- Abstract
Abstract: High-grade ignimbrites are thought to be deposited by pyroclastic flows at temperatures exceeding minimum welding temperature or even solidus temperature. Corresponding pyroclastic-flow particles range from plastic to partially liquid and are able to aggregate or coalesce. This contrasts with particles in pyroclastic flows producing unwelded ignimbrite, which are capable of elastic grain interactions. The low aspect ratio and great areal extent of high-grade ignimbrites requires transport in a particulate state either by (a) high-concentration mass flow facilitated by fluidizing gas reducing internal friction, or by (b) expanded turbulent flow of low but downward increasing concentration. This paper presents experiments designed to investigate the effects of plastic to liquid particles on these two contrasting transport mechanisms. Gas fluidization experiments using polyethyleneglycole (PEG) powders heated above minimum sintering (T
ms ) and melting (Tm ) temperatures cover a wide range of fluidization velocities (Umf >Ua >0.6·Ut ) but are always in the bubbly fluidization regime similar to fluidized ignimbrite ash, where particle volume concentration outside the bubbles is high (≈10–1 ). When the powders reach a critical temperature Tm ≥T≥Tms , defluidization by catastrophic particle aggregation immediately commences in both stationary and laterally moving fluidized beds as well as in experiments using mixtures of high- and low-Tm (≥30 wt.%) PEG powders, when T≥Tms of the lower-Tm powder. This indicates that extended particulate transport at T≥Tms is not possible at such high particle concentrations. In the turbulent flow experiments, liquid sprays of molten PEG or water, vertically injected into a high-Re (>104 ) horizontal air flow, form a low-concentration (10–5 to 10–4 ) turbulent suspension current. Proximal formation of partially coalesced aggregates, which settle faster than individual particles, causes the measured downstream decay of sedimentation rate to be steeper than predicted by theory of single solid-particle sedimentation from turbulent suspensions. As particles become finer downstream and coalescence efficiency decreases in response to cooling, more distally formed aggregates become too small and rare to modify sedimentation-rate decay from that of suspension flows containing solid particles. The key difference between the two transport systems is particle concentration, C. Since particle collision rate Rcoll ∝C2 , collision rates in fluidized beds are so high that all particles immediately aggregate when coalescence efficiency (1≥Ecoal ≥0) is larger than 10-3 . Low-concentration suspensions, on the other hand, require much higher values of Ecoal for significant aggregation to occur. Dilute pyroclastic flows will have higher particle volume fractions (≈10–3 ) than the experimental currents, but then viscous pyroclasts should have lower coalescence efficiencies than PEG droplets. Experimental results thus support an expanded turbulent transport mechanism of pyroclastic flows generating extensive high-grade ignimbrite sheets.- Published
- 1998
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47. Effect of acute exposure to carbon bisulfide vapour upon some components of the hepatic-microsomal enzyme system in rats
- Author
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Freundt, K. J., Schauenburg, K.-J., and Eichhorn, P.
- Abstract
Adult female rats were exposed for 8 h to graded carbon-disulfide (CS
2 ) concentrations between 20 and 400 ppm. It was found that the lipid content of the hepatic microsomal fraction rose significantly due to an increase in phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, phosphatidylserine, sphingomyeline, lysophosphatidylcholine, cholesterol, triglycerides, diglycerides, and free fatty acids. The alterations occurred quickly and were completely reversible after exposure. Since the microsomal cytochrome P-450 content, as well as the activity of the microsomal NADPH cytochrome c-reductase, remained within the normal range following identical CS2 exposures, it is assumed that the alteration in the lipid pattern of the endoplasmic reticulum is a causal factor in inhibition of the microsomal-oxidative drug metabolism, induced by identical inhalatory CS2 doses. It is suggested that the altered lipid pattern impairs the microsomal membranes, thus affecting electron transport and resulting in a dysfunction of the oxidation chain. A slight elevation of the microsomal total protein was observed in relation both to a rise of the microsomal RNA content and an enhanced incorporation of [2,4 -3 H]-L-phenylalanine into the liver microsomes after identical CS2 exposures. It is considered that this finding might represent an unspecific stimulatory reaction.- Published
- 1974
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48. Eruption and emplacement of a basaltic welded ignimbrite during caldera formation on Gran Canaria
- Author
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Freundt, A. and Schmincke, H. -U.
- Abstract
The 14.1 Ma old composite ignimbrite cooling unit P1 (45 km
3 ) on Gran Canaria comprises a lower mixed rhyolite-trachyte tuff, a central rhyolite-basalt mixed tuff, and a slightly rhyolite-contaminated basaltic tuff at the top. The basaltic tuff is compositionally zoned with (a) an upward change in basalt composition to higher MgO content (4.3–5.2 wt.%), (b) variably admixed rhyolite or trachyte (commonly <5 wt.%), and (c) an upward increasing abundance of basaltic and plutonic lithic fragments and cognate cumulate fragments. The basaltic tuff is divided into three structural units: (I) the welded basaltic ignimbrite, which forms the thickest part (c. 95 vol.%) and is the main subject of the present paper; (II) poorly consolidated massive, bomb- and block-rich beds interpreted as phreatomagmatic pyroclastic flow deposits; and (III) various facies of reworked basaltic tuff. Tuff unit I is a basaltic ignimbrite rather than a lava flow because of the absence of top and bottom breccias, radial sheet-like distribution around the central Tejeda caldera, thickening in valleys but also covering higher ground, and local erosion of the underlying P1 ash. A gradual transition from dense rock in the interior to ash at the top of the basaltic ignimbrite reflects a decrease in welding; the shape of the welding profile is typical for emplacement temperatures well above the minimum welding temperature. A similar transition occurs at the base where the ignimbrite was emplaced on cold ground in distal sections. In proximal sections the base is dense where it was emplaced on hot felsic P1 tuff. The intensity of welding, especially at the base, and the presence of spherical particles and of mantled and composite particles formed by accretion and coalescence in a viscous state imply that the flow was a suspension of hot magma droplets. The flow most likely had to be density stratified and highly turbulent to prevent massive coalescence and collapse. Model calculations suggest eruption through low pyroclastic fountains (<1000 m high) with limited cooling during eruption and turbulent flow from an initial temperature of 1160°C. The large volume of 26 km3 of erupted basalt compared with only 16 km3 of the evolved P1 magmas, and the extremely high discharge rates inferred from model calculations are unusual for a basaltic eruption. It is suggested that the basaltic magma was erupted and emplaced in a fashion commonly only attributed to felsic magmas because it utilized the felsic P1 magma chamber and its ring-fissure conduits. Evolution of the entire P1 eruption was controlled by withdrawal dynamics involving magmas differing in viscosity by more than four orders of magnitude. The basaltic eruption phase was initially driven by buoyancy of the basaltic magma at chamber depth and continued degassing of felsic magma, but most of the large volume of basalt magma was driven out of the reservoir by subsidence of a c. 10 km diameter roof block, which followed a decrease in magma chamber pressure during low viscosity basaltic outflow.- Published
- 1995
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49. Lithic-enriched segregation bodies in pyroclastic flow deposits of Laacher See Volcano (East Eifel, Germany)
- Author
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Freundt, Armin and Schmincke, Hans-Ulrich
- Abstract
Small-volume (ca. 0.6 km3) pyroclastic flow deposits at Laacher See contain lithic breccias and two types of ground layers that differ significantly in their structure and composition from the main body of flow units. Lithic breccia bodies, up to 3.5 m thick, containing up to 85 weight% lithic blocks, occur locally at various distances from the vent. The deposition of these breccias was apparently governed by the strong influence of paleomorphology on the dynamics of the pyroclastic flows. The breccias were deposited at three main changes in bottom gradient along the path of the pyroclastic flows. The accumulation of large lithics is explained: (a) by compression of flows on the rising bottom close to the vent; (b) by thinning of flows accelerating over a steep incline; (c) by deceleration of the pre-concentrated lower part of flows in hydraulic jumps; and (d) possibly by a stationary vortex at the inner bend of a valley curvature.
- Published
- 1985
- Full Text
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50. Legumin antibodies recognize polypeptides in coated vesicles isolated from developing pea cotyledons
- Author
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Robinson, D. G., Balusek, K., and Freundt, H.
- Abstract
Summary A highly enriched coated vesicle fraction has been isolated from cotyledons of developing pea seeds. This, and coated vesicles isolated from bovine brain as well as from bean leaves were subjected to SDS-PAGE followed by Western blotting with legumin antibodies. A distinct cross reaction with two polypeptides at around 60 kDa was seen, but only with the coated vesicles isolated from peas. Since legumin is synthesized as a 60 kDa precursor, but occurs as 40 and 20 kDa polypeptides in the protein body, we interpret our results as giving support to the idea that reserve proteins, like lysosomal proteins, are transported via coated vesicles.
- Published
- 1989
- Full Text
- View/download PDF
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