2,069 research outputs found
High-resolution Elemental Mapping of the Lunar Surface
New instruments and missions are being proposed to study the lunar surface as a result of the resurgence of interest in returning to the Moon. One instrument recently proposed is similar in concept to the x-ray fluorescence detectors flown on Apollo, but utilizes fluorescence from the L- and M-shells rather than the K-shell. This soft X-Ray Flourescence Imager (XRFI) is discussed
Deployment of convalescent plasma for the prevention and treatment of COVID-19
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease 2019 (COVID-19), has spurred a global health crisis. To date, there are no proven options for prophylaxis for those who have been exposed to SARS-CoV-2, nor therapy for those who develop COVID-19. Immune (i.e., convalescent ) plasma refers to plasma that is collected from individuals following resolution of infection and development of antibodies. Passive antibody administration through transfusion of convalescent plasma may offer the only short-term strategy for conferring immediate immunity to susceptible individuals. There are numerous examples in which convalescent plasma has been used successfully as postexposure prophylaxis and/or treatment of infectious diseases, including other outbreaks of coronaviruses (e.g., SARS-1, Middle East respiratory syndrome [MERS]). Convalescent plasma has also been used in the COVID-19 pandemic; limited data from China suggest clinical benefit, including radiological resolution, reduction in viral loads, and improved survival. Globally, blood centers have robust infrastructure for undertaking collections and constructing inventories of convalescent plasma to meet the growing demand. Nonetheless, there are nuanced challenges, both regulatory and logistical, spanning donor eligibility, donor recruitment, collections, and transfusion itself. Data from rigorously controlled clinical trials of convalescent plasma are also few, underscoring the need to evaluate its use objectively for a range of indications (e.g., prevention vs. treatment) and patient populations (e.g., age, comorbid disease). We provide an overview of convalescent plasma, including evidence of benefit, regulatory considerations, logistical work flow, and proposed clinical trials, as scale-up is brought underway to mobilize this critical resource
Guidance on the use of convalescent plasma to treat immunocompromised patients with coronavirus disease 2019
Coronavirus disease 2019 (COVID-19) convalescent plasma (CCP) is a safe and effective treatment for COVID-19 in immunocompromised (IC) patients. IC patients have a higher risk of persistent infection, severe disease, and death from COVID-19. Despite the continued clinical use of CCP to treat IC patients, the optimal dose, frequency/schedule, and duration of CCP treatment has yet to be determined, and related best practices guidelines are lacking. A group of individuals with expertise spanning infectious diseases, virology and transfusion medicine was assembled to render an expert opinion statement pertaining to the use of CCP for IC patients. For optimal effect, CCP should be recently and locally collected to match circulating variant. CCP should be considered for the treatment of IC patients with acute and protracted COVID-19; dosage depends on clinical setting (acute vs protracted COVID-19). CCP containing high-titer severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies, retains activity against circulating SARS-CoV-2 variants, which have otherwise rendered monoclonal antibodies ineffective
Difference in Brain Densities Between Chronic Alcoholic and Normal Control Patients.
The densities of the brains of 11 chronic alcoholics were compared with those of 11 age-matched normal control subjects. Densities were determined from the density numbers generated by computerized tomography at three levels of the brain-the highest level of the lateral ventricles and the next two higher levels-with adjustments made to control for possible artifacts in the data. The advantage of the dominant hemisphere over the nondominant hemisphere was lessened in alcoholic
Orbital Instabilities in a Triaxial Cusp Potential
This paper constructs an analytic form for a triaxial potential that
describes the dynamics of a wide variety of astrophysical systems, including
the inner portions of dark matter halos, the central regions of galactic
bulges, and young embedded star clusters. Specifically, this potential results
from a density profile of the form , where the radial
coordinate is generalized to triaxial form so that . Using the resulting analytic form of the potential, and the
corresponding force laws, we construct orbit solutions and show that a robust
orbit instability exists in these systems. For orbits initially confined to any
of the three principal planes, the motion in the perpendicular direction can be
unstable. We discuss the range of parameter space for which these orbits are
unstable, find the growth rates and saturation levels of the instability, and
develop a set of analytic model equations that elucidate the essential physics
of the instability mechanism. This orbit instability has a large number of
astrophysical implications and applications, including understanding the
formation of dark matter halos, the structure of galactic bulges, the survival
of tidal streams, and the early evolution of embedded star clusters.Comment: 50 pages, accepted for publication in Ap
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Limits on the Emission From Fe VIII-XII in the Hot Local Interstellar Medium.
The majority of the emitted power from an optically thin million degree plasma (such as the one thought to produce the soft xray background) originates in the EUV band at wavelengths longer than 170 degrees A. Lines from Fe VIII - Fe XII dominate the emission in this wavelength region. This paper describes work in progress on the analysis of three years of data from the ALEXIS mission in search of this flux
The ROTSE detection of early optical light from GRB 990123
An overview is given of the Robotic Optical Transient Search Experiment, a ground-based observational astronomy project intended to detect visible radiation from gamma-ray bursts. The major result of the project was the detection of an early bright optical transient from a GRB. (AIP) © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87569/2/82_1.pd
Dark solitons in atomic Bose-Einstein condensates: from theory to experiments
This review paper presents an overview of the theoretical and experimental
progress on the study of matter-wave dark solitons in atomic Bose-Einstein
condensates. Upon introducing the general framework, we discuss the statics and
dynamics of single and multiple matter-wave dark solitons in the quasi
one-dimensional setting, in higher-dimensional settings, as well as in the
dimensionality crossover regime. Special attention is paid to the connection
between theoretical results, obtained by various analytical approaches, and
relevant experimental observations.Comment: 82 pages, 13 figures. To appear in J. Phys. A: Math. Theor
Nonlinear Waves in Bose-Einstein Condensates: Physical Relevance and Mathematical Techniques
The aim of the present review is to introduce the reader to some of the
physical notions and of the mathematical methods that are relevant to the study
of nonlinear waves in Bose-Einstein Condensates (BECs). Upon introducing the
general framework, we discuss the prototypical models that are relevant to this
setting for different dimensions and different potentials confining the atoms.
We analyze some of the model properties and explore their typical wave
solutions (plane wave solutions, bright, dark, gap solitons, as well as
vortices). We then offer a collection of mathematical methods that can be used
to understand the existence, stability and dynamics of nonlinear waves in such
BECs, either directly or starting from different types of limits (e.g., the
linear or the nonlinear limit, or the discrete limit of the corresponding
equation). Finally, we consider some special topics involving more recent
developments, and experimental setups in which there is still considerable need
for developing mathematical as well as computational tools.Comment: 69 pages, 10 figures, to appear in Nonlinearity, 2008. V2: new
references added, fixed typo
From Euler's play with infinite series to the anomalous magnetic moment
During a first St. Petersburg period Leonhard Euler, in his early twenties,
became interested in the Basel problem: summing the series of inverse squares
(posed by Pietro Mengoli in mid 17th century). In the words of Andre Weil
(1989) "as with most questions that ever attracted his attention, he never
abandoned it". Euler introduced on the way the alternating "phi-series", the
better converging companion of the zeta function, the first example of a
polylogarithm at a root of unity. He realized - empirically! - that odd zeta
values appear to be new (transcendental?) numbers. It is amazing to see how, a
quarter of a millennium later, the numbers Euler played with, "however
repugnant" this game might have seemed to his contemporary lovers of the
"higher kind of calculus", reappeared in the analytic calculation of the
anomalous magnetic moment of the electron, the most precisely calculated and
measured physical quantity. Mathematicians, inspired by ideas of Grothendieck,
are reviving the dream of Galois of uncovering a group structure in the ring of
periods (that includes the multiple zeta values) - applied to the study of
Feynman amplitudes.Comment: v.2: minor corrections, references adde
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