1,991 research outputs found
In-situ materials processing systems and bioregenerative life support systems interrelationships
The synergy and linkages between bioregenerative life support systems and the materials produced by in-situ materials processing systems was investigated. Such systems produce a broad spectrum of byproducts such as oxygen, hydrogen, processed soil material, ceramics, refractory, and other materials. Some of these materials may be utilized by bioregenerative systems either directly or with minor modifications. The main focus of this project was to investigate how these materials can be utilized to assist a bioregenerative life support system. Clearly the need to provide a sustainable bioregenerative life support system for long term human habitation of space is significant
The history of the Forty-Fifth Division news
Thesis (M.A.)--University of Oklahoma, 1968.Includes bibliographical references (leaves 83-84
A Sub-Damped Ly Absorber with Unusual Abundances: Evidence of Gas Recycling in a Low-Redshift Galaxy Group
Using Hubble Space Telescope/Space Telescope Imaging Spectrograph G140M
spectroscopy, we investigate an absorption-line system at =0.07489 in the
spectrum of the quasi-stellar object PG 1543+489 (=0.401). The
sightline passes within kpc of an edge-on disk galaxy at a
similar redshift, but the galaxy belongs to a group with four other galaxies
within kpc. We detect H I [log (H I/) = 19.120.04]
as well as N I, Mg II, Si II, and Si III, from which we measure a gas-phase
abundance of [N/H] = . Photoionization models indicate that the
nitrogen-to-silicon relative abundance is solar, yet magnesium is underabundant
by a factor of 2. We also report spatially resolved emission-line
spectroscopy of the nearby galaxy, and we extract its rotation curve. The
galaxy's metallicity is higher than [N/H] in the absorber,
and interestingly, the absorber velocities suggest that the gas at 66
kpc is corotating with the galaxy's stellar disk, possibly with an inflow
component. These characteristics could indicate that this sub-damped Ly
absorber system arises in a "cold-accretion" flow. However, the absorber
abundance patterns are peculiar. We hypothesize that the gas was ejected from
its galaxy of origin (or perhaps is a result of tidal debris from interactions
between the group galaxies) with a solar nitrogen abundance, but that
subsequently mixed with (and was diluted by) gas in the circumgalactic medium
(CGM) or group. If the gas is bound to the nearby galaxy, this system may be an
example of the gas "recycling" predicted by theoretical galaxy simulations. Our
hypothesis is testable with future observations.Comment: 16 pages (in print): The Astrophysical Journal, vol 872, 12
Asymmetric Chemical Synthesis of (R)- and (S)-Citramalate in High Enantiomeric Purity
Both enantiomers of dimethyl 2-acety1citramalate have been
asymmetrically synthesized in over 96% enantiomeric excess and
good overall chemical yield (500/0)from 2-keto-1,3-oxathianes 1a,
and 1b
Chemical probes for methyl lysine reader domains
The primary intent of a chemical probe is to establish the relationship between a molecular target, usually a protein whose function is modulated by the probe, and the biological consequences of that modulation. In order to fulfill this purpose, a chemical probe must be profiled for selectivity, mechanism of action, and cellular activity, as the cell is the minimal system in which âbiologyâ can be explored. This review provides a brief overview of progress toward chemical probes for methyl lysine reader domains with a focus on recent progress targeting chromodomains
Observations of the Gas Reservoir around a Star Forming Galaxy in the Early Universe
We present a high signal-to-noise spectrum of a bright galaxy at z = 4.9 in
14 h of integration on VLT FORS2. This galaxy is extremely bright, i_850 =
23.10 +/- 0.01, and is strongly-lensed by the foreground massive galaxy cluster
Abell 1689 (z=0.18). Stellar continuum is seen longward of the Ly-alpha
emission line at ~7100 \AA, while intergalactic H I produces strong absorption
shortward of Ly-alpha. Two transmission spikes at ~6800 Angstroms (A) and ~7040
A are also visible, along with other structures at shorter wavelengths.
Although fainter than a QSO, the absence of a strong central ultraviolet flux
source in this star forming galaxy enables a measurement of the H I flux
transmission in the intergalactic medium (IGM) in the vicinity of a high
redshift object. We find that the effective H I optical depth of the IGM is
remarkably high within a large 14 Mpc (physical) region surrounding the galaxy
compared to that seen towards QSOs at similar redshifts. Evidently, this
high-redshift galaxy is located in a region of space where the amount of H I is
much larger than that seen at similar epochs in the diffuse IGM. We argue that
observations of high-redshift galaxies like this one provide unique insights on
the nascent stages of baryonic large-scale structures that evolve into the
filamentary cosmic web of galaxies and clusters of galaxies observed in the
present universe.Comment: Accepted for publication in ApJL (corrected typos
A search for solar neutrons on a long duration balloon flight
The EOSCOR 3 detector, designed to measure the flux of solar neutrons, was flown on a long duration RACOON balloon flight from Australia during Jan. through Feb, 1983. The Circum-global flight lasted 22 days. No major solar activity occurred during the flight and thus only an upper limit to the solar flare neutrons flux is given. The atmospheric neutron response is compared with that obtained on earlier flights from Palestine, Texas
Peptide Technologies in the Development of Chemical Tools for ChromatinâAssociated Machinery
Discerning a mechanistic understanding of the causeâandâeffect relationships between chromatin postâtranslational modifications (PTMs) and DNA accessibility for replication, transcription, and repair is an elusive goal being pursued using molecular and cellular biology, biochemistry, and more recently chemical inhibition. Chemical intervention of the chromatinâassociated complexes that regulate PTM maintenance and chromatin structure faces numerous challenges due to the broad surfaceâgroove interactions between many of these proteins and histones; yet, the increasing interest in understanding chromatinâmodifying complexes suggests tractable lead compounds will be critical for elucidating the mechanisms of chromatin dysregulation in disease states and validating the druggability of these domains. Peptides and peptidomimetics afford several advantages to efficient inhibitor development including a rational starting point, modular assembly, and retention of secondary structure. Numerous peptide technologies have been employed in the chromatin field to characterize substrate interactions, evaluate ligand selectivity, and optimize potent peptidomimetic inhibitors. We describe the progress and advantages of these efforts, and provide a perspective on their implications for future chemical probe and drug discovery efforts. Drug Dev Res 78 : 300â312, 2017. © 2017 Wiley Periodicals, Inc
Path integral evaluation of Dbrane amplitudes
We extend Polchinski's evaluation of the measure for the one-loop closed
string path integral to open string tree amplitudes with boundaries and
crosscaps embedded in Dbranes. We explain how the nonabelian limit of
near-coincident Dbranes emerges in the path integral formalism. We give a
careful path integral derivation of the cylinder amplitude including the
modulus dependence of the volume of the conformal Killing group.Comment: Extended version replacing hep-th/9903184, includes discussion of
nonabelian limit, Latex, 10 page
Targeting Chromatin Readers
Modulation of gene expression through epigenetic signaling has recently emerged as a novel approach in treating human disease. Specifically, chromatin reader proteins, which mediate proteinâprotein interactions via binding to modified lysine residues, are gaining traction as potential therapeutic targets. Herein, we review recent efforts to understand and modulate the activity of chromatin reader proteins with small-molecule ligands
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