3,328 research outputs found
Observing the Earth as an exoplanet with LOUPE, the Lunar Observatory for Unresolved Polarimetry of Earth
The detections of small, rocky exoplanets have surged in recent years and
will likely continue to do so. To know whether a rocky exoplanet is habitable,
we have to characterise its atmosphere and surface. A promising
characterisation method for rocky exoplanets is direct detection using
spectropolarimetry. This method will be based on single pixel signals, because
spatially resolving exoplanets is impossible with current and near-future
instruments. Well-tested retrieval algorithms are essential to interpret these
single pixel signals in terms of atmospheric composition, cloud and surface
coverage. Observations of Earth itself provide the obvious benchmark data for
testing such algorithms. The observations should provide signals that are
integrated over the Earth's disk, that capture day and night variations, and
all phase angles. The Moon is a unique platform from where the Earth can be
observed as an exoplanet, undisturbed, all of the time. Here, we present LOUPE,
the Lunar Observatory for Unresolved Polarimetry of Earth, a small and robust
spectropolarimeter to observe our Earth as an exoplanet.Comment: 14 pages, 3 figures, submitted in special Issue of Planetary and
Space Science on Scientific Preparations for Lunar Exploratio
Filament rigidity and connectivity tune the deformation modes of active biopolymer networks
Molecular motors embedded within collections of actin and microtubule filaments underlie the dynamics of cytoskeletal assemblies. Understanding the physics of such motor-filament materials is critical to developing a physical model of the cytoskeleton and designing biomimetic active materials. Here, we demonstrate through experiments and simulations that the rigidity and connectivity of filaments in active biopolymer networks regulates the anisotropy and the length scale of the underlying deformations, yielding materials with variable contractility. We find that semiflexible filaments can be compressed and bent by motor stresses, yielding materials that undergo predominantly biaxial deformations. By contrast, rigid filament bundles slide without bending under motor stress, yielding materials that undergo predominantly uniaxial deformations. Networks dominated by biaxial deformations are robustly contractile over a wide range of connectivities, while networks dominated by uniaxial deformations can be tuned from extensile to contractile through cross-linking. These results identify physical parameters that control the forces generated within motor-filament arrays and provide insight into the self-organization and mechanics of cytoskeletal assemblies
Compound-specific stable isotope analysis of nitrogen-containing intact polar lipids
RATIONALE: Compound-specific isotope analysis (CSIA) of nitrogen in amino acids has proven a valuable tool in manyfields (e.g. ecology). Several intact polar lipids (IPLs) also contain nitrogen, and their nitrogen isotope ratios have thepotential to elucidate food-web interactions or metabolic pathways. Here we have developed novel methodology forthe determination of d15N values of nitrogen-containing headgroups of IPLs using gas chromatography coupled withisotope-ratio mass spectrometry. METHODS: Intact polar lipids with nitrogen-containing headgroups were hydrolyzed and the resulting compoundswere derivatized by (1) acetylation with pivaloyl chloride for compounds with amine and hydroxyl groups or(2) esterification using acidified 2-propanol followed by acetylation with pivaloyl chloride for compounds withboth carboxyl and amine groups. The d15N values of the derivatives were subsequently determined using gaschromatography/combustion/isotope-ratio mass spectrometry. RESULTS: Intact polar lipids with ethanolamine and amino acid headgroups, such as phosphatidylethanolamine andphosphatidylserine, were successfully released from the IPLs and derivatized. Using commercially available purecompounds it was established that d15N values of ethanolamine and glycine were not statistically different from theoffline-determined values. Application of the technique to microbial cultures and a microbial mat showed that themethod works well for the release and derivatization of the headgroup of phosphatidylethanolamine, a common IPLin bacteria. CONCLUSIONS: A method to enable CSIA of nitrogen of selected IPLs has been developed. The method is suitable formeasuring natural stable nitrogen isotope ratios in microbial lipids, in particular phosphatidylethanolamine, and will beespecially useful for tracing the fate of nitrogen in deliberate tracer experiments. Copyright © 2015 JohnWiley & Sons, Ltd
End-of-life decisions and involvement of Physical and Rehabilitation Medicine Physicians in Europe
Objective: As Physical and Rehabilitation Medicine physicians are experts in functional prognoses of disabling health conditions, the aim of this study was to gain insight into their involvement in end-of-life decisions in patients with neurological or terminal diseases in European countries. Design: Exploratory cross-sectional survey. Subjects: Delegates of the Union of European Medical Specialists, Physical and Rehabilitation Medicine Section. Methods: In July 2020, a self-constructed survey was sent to 82 delegates from 38 European countries, who were asked to answer from the point of view of their country. Topics included the legal status of end-of-life decisions and the involvement of Physical and Rehabilitation Medicine physicians in these decisions. Results: Between July 2020 and December 2020, 32 delegates from 28 countries completed the survey (response rate country level of 74%). If legal frameworks allow for these specific end-of-life decisions, involvement of Physical and Rehabilitation Medicine physicians was reported in 2 of 3 countries in euthanasia cases, 10 of 17 countries in non-treatment decision cases, and 13 of 16 countries in cases of intensified symptom management by the administration of drugs using potentially life-shortening doses. Conclusion: Estimated involvement of Physical and Rehabilitation Medicine physicians in end-of-life decisions varied between European countries, even when legal frameworks allow for these decisions.</p
End-of-life decisions and involvement of Physical and Rehabilitation Medicine Physicians in Europe
Objective: As Physical and Rehabilitation Medicine physicians are experts in functional prognoses of disabling health conditions, the aim of this study was to gain insight into their involvement in end-of-life decisions in patients with neurological or terminal diseases in European countries. Design: Exploratory cross-sectional survey. Subjects: Delegates of the Union of European Medical Specialists, Physical and Rehabilitation Medicine Section. Methods: In July 2020, a self-constructed survey was sent to 82 delegates from 38 European countries, who were asked to answer from the point of view of their country. Topics included the legal status of end-of-life decisions and the involvement of Physical and Rehabilitation Medicine physicians in these decisions. Results: Between July 2020 and December 2020, 32 delegates from 28 countries completed the survey (response rate country level of 74%). If legal frameworks allow for these specific end-of-life decisions, involvement of Physical and Rehabilitation Medicine physicians was reported in 2 of 3 countries in euthanasia cases, 10 of 17 countries in non-treatment decision cases, and 13 of 16 countries in cases of intensified symptom management by the administration of drugs using potentially life-shortening doses. Conclusion: Estimated involvement of Physical and Rehabilitation Medicine physicians in end-of-life decisions varied between European countries, even when legal frameworks allow for these decisions.</p
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