5,829 research outputs found
The EXOSAT medium-energy slew survey catalog
We present a catalog of X-ray sources observed during slew maneuvers by the
Medium Energy Detector Array onboard the EXOSAT Observatory. The EXOSAT Medium
Energy slew-survey catalog (EXMS) provides a unique record of the 1--8 keV
X-ray sky between 1983 and 1986. 98% of the sky was observed, with 85%
receiving an exposure of >60 s. 1210 sources were detected. By comparing these
source positions with other catalogs, identifications are given for 992
detections (82% of the sample). These identifications consist of 250 distinct
objects, including 95 different X-ray binary systems, and 14 different AGN. A
further 58 detections have multiple candidates, while 160 detections remain
unidentified. Collimator transmission corrected 1-8 keV count rates are given
for the identified sources, together with raw count rates for the other
detections. The construction of the EXMS and the checks performed to ensure the
validity of the derived source properties are discussed. A publically available
version of this catalog is maintained on the EXOSAT database and archive system
(telnet://[email protected]).Comment: 52 pages. 22 Figures. To be published in A&AS. For more information,
see http://astro.estec.esa.nl/SA-general/Projects/Exosat/exmsintro.htm
Search for periodicities near 59 s in the COS-B gamma-ray data of 2CG195+04 (Geminga)
The COS-B data relating to five observations in the general direction of Geminga, spanning 6.7 years, were searched for pulsation near 59 s. The SAS-2 indication is not confirmed. An indication of a 59 s pulsation in the gamma ray emission from 2CG195+04 (Geminga) was reported. Early analysis of COS-B data supported the result while later improved statistics did not confirm it. Subsequently, detection of a 59 s pulsation in the emission from the direction of Geminga at ultra high gamma and X-rays was reported. Geminga was identified with the X-ray source 1E0630+128. The final COS-B data on Geminga which was observed five times for a total of 214 days are reported
Variational Density Matrix Method for Warm Condensed Matter and Application to Dense Hydrogen
A new variational principle for optimizing thermal density matrices is
introduced. As a first application, the variational many body density matrix is
written as a determinant of one body density matrices, which are approximated
by Gaussians with the mean, width and amplitude as variational parameters. The
method is illustrated for the particle in an external field problem, the
hydrogen molecule and dense hydrogen where the molecular, the dissociated and
the plasma regime are described. Structural and thermodynamic properties
(energy, equation of state and shock Hugoniot) are presented.Comment: 26 pages, 13 figures. submitted to Phys. Rev. E, October 199
Threaded-nail Fasteners - Research and Standardization Needs
Threaded nail fasteners are commonly used in agricultural and commercial post-frame structures, yet there has been insufficient research to fully understand the effect of threads on withdrawal and lateral load resistance. The objective of this article is to review technical information on threaded nail fasteners and to identify problems facing manufacturers, designers, and users of threaded nail fasteners for engineering applications. Recommendations are given concerning research and standardization needs
How do liquids confined at the nanoscale influence adhesion?
Liquids play an important role in adhesion and sliding friction. They behave
as lubricants in human bodies especially in the joints. However, in many
biological attachment systems they acts like adhesives, e.g. facilitating
insects to move on ceilings or vertical walls. Here we use molecular dynamics
to study how liquids confined at the nanoscale influence the adhesion between
solid bodies with smooth and rough surfaces. We show that a monolayer of liquid
may strongly affect the adhesion.Comment: 5 pages, 9 color figures. Some figures are in Postscript Level 3
format. Minimal changes with respect to the previous version. Added doi and
reference to the published article also inside the pape
Patient and researcher perspectives on facilitating patient and public involvement in rheumatology research
No abstract available
Why do some CEOs become celebrities while others don’t?
Celebrity benefits chief executives personally: increased pay, more opportunities to join boards, and protection from dismissal. But their firms do not enjoy similarly positive outcomes. These CEOs often demonstrate higher levels of complacency, risk-taking, and hubris. But what leads them to attain celebrity in the first place? Jeffrey B. Lovelace, Jonathan N. Bundy, Tim Pollock, and Donald Hambrick write that a CEO’s personal attributes, a firm’s non-conforming actions, and a CEO’s use of self-promotion tactics play important roles in attracting high levels of positive media attention — with implications for individuals, firms, and society
Cyg X-3: Not seen in high-energy gamma rays by COS-B
COS-B had Cyg X-3 within its field of view during 7 observation periods between 1975 and 1982 for in total approximately 300 days. In the skymaps (70 meV E 5000 meV) of the Cyg-X region produced for each of these observations and in the summed map, a broad complex structure is visible in the region 72 deg approximately less than 1 approximately less than 85 deg, approximately less than 5 deg. No resolved source structure is visible at the position of Cyg X-3, but a weak signal from Cyg X-3 could be hidden in the structured gamma-ray background. Therefore, the data has been searched for a 4.8 h timing signature, as well as for a source signal in the sky map in addition to the diffuse background structure as estimated from tracers of atomic and molecular gas
Lowering of the Kinetic Energy in Interacting Quantum Systems
Interactions never lower the ground state kinetic energy of a quantum system.
However, at nonzero temperature, where the system occupies a thermal
distribution of states, interactions can reduce the kinetic energy below the
noninteracting value. This can be demonstrated from a first order weak coupling
expansion. Simulations (both variational and restricted path integral Monte
Carlo) of the electron gas model and dense hydrogen confirm this and show that
in contrast to the ground state case, at nonzero temperature the population of
low momentum states can be increased relative to the free Fermi distribution.
This effect is not seen in simulations of liquid He-3.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett., June, 200
Sequential motif profile of natural visibility graphs
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