Low-angle X-ray diffraction patterns from a variety of myelinated nerves

Low-angle X-ray diffraction patterns from a variety of myelinated nerves are described. Different kinds of patterns are obtained from peripheral nerve and central nervous system myelin. The intensity variation between the first five diffraction orders is the same for each variety of peripheral nerve myelin, and similarly, an intensity variation exists which is the same for each variety of central nervous system myelin. However, the intensity variation for myelinated nerves from fish is different from peripheral nerve and central nervous system myelin. New diffraction orders higher than five for both peripheral nerve and central nervous system myelin have been recorded.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32982/1/0000366.pd

A low-angle X-ray diffraction study of the swelling behavior of peripheral nerve myelin

The swelling behavior of peripheral nerve myelin has been studied by recording low-angle X-ray diffraction patterns of nerve after various chemical treatments. Peripheral myelin swells in distilled water, hypotonic Ringer's solution and sucrose solutions. The resulting low-angle pattern is called a swollen pattern (by comparison, the normal pattern is obtained from live nerve). The swelling of myelin is reversed by a reimmersion of the nerve in salt solutions and the resulting low-angle pattern is called a subnormal pattern. A relationship between these three kinds of patterns is given in terms of the width of the membrane pair. The forces between the adjacent membrane pairs in swollen myelin are likely to be long-range attractive Van der Waals' and long-range electrical repulsive forces. However, an equilibrium between the attrative and repulsive forces has not been observed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32983/1/0000367.pd

AMTD: Update of Engineering Specifications Derived from Science Requirements for Future UVOIR Space Telescopes

The Advance Mirror Technology Development (AMTD) project is in Phase 2 of a multiyear effort, initiated in FY12, to mature by at least a half TRL step six critical technologies required to enable 4 meter or larger UVOIR space telescope primary mirror assemblies for both general astrophysics and ultra-high contrast observations of exoplanets. AMTD uses a science-driven systems engineering approach. We mature technologies required to enable the highest priority science AND provide a high-performance low-cost low-risk system. To give the science community options, we are pursuing multiple technology paths. A key task is deriving engineering specifications for advanced normal-incidence monolithic and segmented mirror systems needed to enable both general astrophysics and ultra-high contrast observations of exoplanets missions as a function of potential launch vehicles and their mass and volume constraints. A key finding of this effort is that the science requires an 8 meter or larger aperture telescop

Compellingly high SARS-CoV-2 susceptibility of Golden Syrian hamsters suggests multiple zoonotic infections of pet hamsters during the COVID-19 pandemic

Golden Syrian hamsters (Mesocricetus auratus) are used as a research model for severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). Millions of Golden Syrian hamsters are also kept as pets in close contact to humans. To determine the minimum infective dose (MID) for assessing the zoonotic transmission risk, and to define the optimal infection dose for experimental studies, we orotracheally inoculated hamsters with SARS-CoV-2 doses from 1 * 105 to 1 * 10-4 tissue culture infectious dose 50 (TCID50). Body weight and virus shedding were monitored daily. 1 * 10-3 TCID50 was defined as the MID, and this was still sufficient to induce virus shedding at levels up to 102.75 TCID50/ml, equaling the estimated MID for humans. Virological and histological data revealed 1 * 102 TCID50 as the optimal dose for experimental infections. This compelling high susceptibility leading to productive infections in Golden Syrian hamsters must be considered as a potential source of SARS-CoV-2 infection for humans that come into close contact with pet hamsters

Solid-state NMR evidence for inequivalent GvpA subunits in gas vesicles

Gas vesicles are organelles that provide buoyancy to the aquatic microorganisms that harbor them. The gas vesicle shell consists almost exclusively of the hydrophobic 70-residue gas vesicle protein A, arranged in an ordered array. Solid-state NMR spectra of intact collapsed gas vesicles from the cyanobacterium Anabaena flos-aquae show duplication of certain gas vesicle protein A resonances, indicating that specific sites experience at least two different local environments. Interpretation of these results in terms of an asymmetric dimer repeat unit can reconcile otherwise conflicting features of the primary, secondary, tertiary, and quaternary structures of the gas vesicle protein. In particular, the asymmetric dimer can explain how the hydrogen bonds in the β-sheet portion of the molecule can be oriented optimally for strength while promoting stabilizing aromatic and electrostatic side-chain interactions among highly conserved residues and creating a large hydrophobic surface suitable for preventing water condensation inside the vesicle.National Institutes of Health (U.S.) (Grant EB002175)National Institutes of Health (U.S.) (Grant EB003151)National Institutes of Health (U.S.) (Grant EB002026

Wide Field Infrared Survey Telescope (WFIRST) Observatory Overview

NASA's Wide Field Infrared Survey Telescope (WFIRST) is being designed to deliver unprecedented capability in dark energy and exoplanet science, and to host a technology demonstration coronagraph for exoplanet imaging and spectroscopy. The observatory design has matured since 2013; we present a comprehensive description of the observatory configuration as refined during the WFIRST Phase-A study. The observatory is based on an existing, repurposed 2.4 meter space telescope coupled with a 288 megapixel near-infrared (0.6 to 2 microns) HgCdTe focal plane array with multiple imaging and spectrographic modes. Together they deliver a 0.28 square degree field of view, which is approximately 100 times larger than the Hubble Space Telescope, and a sensitivity that enables rapid science surveys. In addition, the coronagraph technology demonstration will prove the feasibility of new techniques for exoplanet discovery, imaging, and spectral analysis. A composite truss structure meters both instruments to the telescope assembly, and the instruments and the spacecraft are flight serviceable. We present configuration changes since 2013 that improved interfaces, improved testability, and reduced technical risk. We provide an overview of our Integrated Modeling results, performed at an unprecedented level for a phase-A study, to illustrate performance margins with respect to static wavefront error, jitter, and thermal drift

Global wealth disparities drive adherence to COVID-safe pathways in head and neck cancer surgery

Peer reviewe