754 research outputs found
Self-discharge characteristics of spacecraft nickel-cadmium cells at elevated temperatures
The effects of heat generation were determined in NiCd cells during high temperature storage on open circuits. The testing was designed to determine the extent to which thermal stability is a valid concern, at temperature of exposure (externally effected) between 40 and 120 C
Nickel hydrogen low Earth orbit test program update and status
The current status of nickel-hydrogen (NiH2) testing ongong at NWSC, Crane In, and The Aerospace Corporation, El Segundo, Ca are described. The objective of this testing is to develop a database for NiH2 battery use in Low Earth Orbit (LEO) and support applications in Medium Altitude Orbit (MAO). Individual pressure vessel-type cells are being tested. A minimum of 200 cells (3.5 in diameter and 4.5 in diameter) are included in the test, from four U.S. vendors. As of this date (Nov. 18, 1986) approximately 60 cells have completed preliminary testing (acceptance, characterization, and environmental testing) and have gone into life cycling
HIV in the Heartland: Experiences of Living with HIV in Urban and Rural Areas of the Midwest
Scholarly research on HIV/AIDS and stigma has largely demonstrated a different experience for people living with HIV and AIDS (PLWHA) who inhabit urban and rural areas. Largely missing from this scholarship are experiences in low prevalence areas. Low prevalence areas typically have fewer resources, social networks, and HIV infection and prevalence is less common. In this paper, we examine the challenges PLWHAs in rural and urban areas of the Midwest face and how these individuals manage, respond, and combat HIV/AIDS related stigmas in their communities. This paper utilizes interview data to understand the lived experiences of 18 persons living with HIV and AIDS. This paper reveals that respondents in rural areas are likely to be geographically dispersed, struggle with accessing healthcare services, believe their communities are less tolerant, and are less likely to disclose their positive status or seek out social support. Respondents who lived in urban areas were more likely to disclose their positive status, have access to AIDS service organizations and social support, and to participate in advocacy in the “HIV Community.” Our study demonstrates how social and community context are agentic players in shaping life chances, decisions, and behavior of the PLWHAs we interviewed
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Strategic plan for infrastructure optimization
This document represents Fluor Daniel Hanford`s and DynCorp`s Tri-Cities Strategic Plan for Fiscal Years 1998--2002, the road map that will guide them into the next century and their sixth year of providing safe and cost effective infrastructure services and support to the Department of Energy (DOE) and the Hanford Site. The Plan responds directly to the issues raised in the FDH/DOE Critical Self Assessment specifically: (1) a strategy in place to give DOE the management (systems) and physical infrastructure for the future; (2) dealing with the barriers that exist to making change; and (3) a plan to right-size the infrastructure and services, and reduce the cost of providing services. The Plan incorporates initiatives from several studies conducted in Fiscal Year 1997 to include: the Systems Functional Analysis, 200 Area Water Commercial Practices Plan, $ million Originated Cost Budget Achievement Plan, the 1OO Area Vacate Plan, the Railroad Shutdown Plan, as well as recommendations from the recently completed Review of Hanford Electrical Utility. These and other initiatives identified over the next five years will result in significant improvements in efficiency, allowing a greater portion of the infrastructure budget to be applied to Site cleanup. The Plan outlines a planning and management process that defines infrastructure services and structure by linking site technical base line data and customer requirements to work scope and resources. The Plan also provides a vision of where Site infrastructure is going and specific initiatives to get there
X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
AGN are known to have complex X-ray spectra that depend on both the
properties of the accreting SMBH (e.g. mass, accretion rate) and the
distribution of obscuring material in its vicinity ("torus"). Often however,
simple and even unphysical models are adopted to represent the X-ray spectra of
AGN. In the case of blank field surveys in particular, this should have an
impact on e.g. the determination of the AGN luminosity function, the inferred
accretion history of the Universe and also on our understanding of the relation
between AGN and their host galaxies. We develop a Bayesian framework for model
comparison and parameter estimation of X-ray spectra. We take into account
uncertainties associated with X-ray data and photometric redshifts. We also
demonstrate how Bayesian model comparison can be used to select among ten
different physically motivated X-ray spectral models the one that provides a
better representation of the observations. Despite the use of low-count
spectra, our methodology is able to draw strong inferences on the geometry of
the torus. For a sample of 350 AGN in the 4 Ms Chandra Deep Field South field,
our analysis identifies four components needed to represent the diversity of
the observed X-ray spectra: (abridged). Simpler models are ruled out with
decisive evidence in favour of a geometrically extended structure with
significant Compton scattering. Regarding the geometry of the obscurer, there
is strong evidence against both a completely closed or entirely open toroidal
geometry, in favour of an intermediate case. The additional Compton reflection
required by data over that predicted by toroidal geometry models, may be a sign
of a density gradient in the torus or reflection off the accretion disk.
Finally, we release a catalogue with estimated parameters such as the accretion
luminosity in the 2-10 keV band and the column density, , of the
obscurer.Comment: 28 pages, 18 figures, catalogue available from
https://www.mpe.mpg.de/~jbuchner/agn_torus/analysis/cdfs4Ms_cat/, software
available from https://github.com/JohannesBuchner/BX
Bose-Einstein condensate collapse: a comparison between theory and experiment
We solve the Gross-Pitaevskii equation numerically for the collapse induced
by a switch from positive to negative scattering lengths. We compare our
results with experiments performed at JILA with Bose-Einstein condensates of
Rb-85, in which the scattering length was controlled using a Feshbach
resonance. Building on previous theoretical work we identify quantitative
differences between the predictions of mean-field theory and the results of the
experiments. Besides the previously reported difference between the predicted
and observed critical atom number for collapse, we also find that the predicted
collapse times systematically exceed those observed experimentally. Quantum
field effects, such as fragmentation, that might account for these
discrepancies are discussed.Comment: 4 pages, 2 figure
Nuclear quadrupole resonances in compact vapor cells: the crossover from the NMR to the NQR interaction regimes
We present the first experimental study that maps the transformation of
nuclear quadrupole resonances from the pure nuclear quadrupole regime to the
quadrupole-perturbed Zeeman regime. The transformation presents an interesting
quantum-mechanical problem, since the quantization axis changes from being
aligned along the axis of the electric-field gradient tensor to being aligned
along the magnetic field. We achieve large nuclear quadrupole shifts for I =
3/2 131-Xe by using a 1 mm^3 cubic cell with walls of different materials. When
the magnetic and quadrupolar interactions are of comparable size, perturbation
theory is not suitable for calculating the transition energies. Rather than use
perturbation theory, we compare our data to theoretical calculations using a
Liouvillian approach and find excellent agreement.Comment: 4 pages, 4 figure
ATP-sensitive potassium channel (K(ATP )channel) expression in the normal canine pancreas and in canine insulinomas
BACKGROUND: Pancreatic beta cells express ATP-sensitive potassium (K(ATP)) channels that are needed for normal insulin secretion and are targets for drugs that modulate insulin secretion. The K(ATP )channel is composed of two subunits: a sulfonylurea receptor (SUR 1) and an inward rectifying potassium channel (Kir(6.2)). K(ATP )channel activity is influenced by the metabolic state of the cell and initiates the ionic events that precede insulin exocytosis. Although drugs that target the K(ATP )channel have the expected effects on insulin secretion in dogs, little is known about molecular aspects of this potassium channel. To learn more about canine beta cell K(ATP )channels, we studied K(ATP )channel expression by the normal canine pancreas and by insulin-secreting tumors of dogs. RESULTS: Pancreatic tissue from normal dogs and tumor tissue from three dogs with histologically-confirmed insulinomas was examined for expression of K(ATP )channel subunits (SUR1 and Kir(6.2)) using RT-PCR. Normal canine pancreas expressed SUR1 and Kir(6.2 )subunits of the K(ATP )channel. The partial nucleotide sequences for SUR1 and Kir(6.2 )obtained from the normal pancreas showed a high degree of homology to published sequences for other mammalian species. SUR1 and Kir(6.2 )expression was observed in each of the three canine insulinomas examined. Comparison of short sequences from insulinomas with those obtained from normal pancreas did not reveal any mutations in either SUR1 or Kir(6.2 )in any of the insulinomas. CONCLUSION: Canine pancreatic K(ATP )channels have the same subunit composition as those found in the endocrine pancreases of humans, rats, and mice, suggesting that the canine channel is regulated in a similar fashion as in other species. SUR1 and Kir(6.2 )expression was found in the three insulinomas examined indicating that unregulated insulin secretion by these tumors does not result from failure to express one or both K(ATP )channel subunits
Stability of fermionic Feshbach molecules in a Bose-Fermi mixture
In the wake of successful experiments in Fermi condensates, experimental
attention is broadening to study resonant interactions in degenerate Bose-Fermi
mixtures. Here we consider the properties and stability of the fermionic
molecules that can be created in such a mixture near a Feshbach resonance (FR).
To do this, we consider the two-body scattering matrix in the many-body
environment, and assess its complex poles. The stability properties of these
molecules strongly depend on their centre-of-mass motion, because they must
satisfy Fermi statistics. At low centre-of-mass momenta the molecules are more
stable than in the absence of the environment (due to Pauli-blocking effects),
while at high centre-of-mass momenta nontrivial many body effects render them
somewhat less stable
Characterization of AGN and their hosts in the Extended Groth Strip: a multiwavelength analysis
We have employed a reliable technique of classification of Active Galactic
Nuclei (AGN) based on the fit of well-sampled spectral energy distributions
(SEDs) with a complete set of AGN and starburst galaxy templates. We have
compiled ultraviolet, optical, and infrared data for a sample of 116 AGN
originally selected for their X-ray and mid-infrared emissions (96 with single
detections and 20 with double optical counterparts). This is the most complete
compilation of multiwavelength data for such a big sample of AGN in the
Extended Groth Strip (EGS). Through these SEDs, we are able to obtain highly
reliable photometric redshifts and to distinguish between pure and
host-dominated AGN. For the objects with unique detection we find that they can
be separated into five main groups, namely: Starburst-dominated AGN (24 % of
the sample), Starburst-contaminated AGN (7 %), Type-1 AGN (21 %), Type-2 AGN
(24 %), and Normal galaxy hosting AGN (24 %). We find these groups concentrated
at different redshifts: Type-2 AGN and Normal galaxy hosting AGN are
concentrated at low redshifts, whereas Starburst-dominated AGN and Type-1 AGN
show a larger span. Correlations between hard/soft X-ray and ultraviolet,
optical and infrared luminosities, respectively, are reported for the first
time for such a sample of AGN spanning a wide range of redshifts. For the 20
objects with double detection the percentage of Starburst-dominated AGN
increases up to 48%.Comment: 38 pages, 8 figures, 5 tables. Accepted by A
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