1,411 research outputs found
Swift Observations of X-ray supernovae
We present a result of X-ray supernovae (SNe) survey using the Swift
satellite public archive. An automatic searching program was designed to search
X-ray SNe among all of the Swift archival observations between November 2004
and February 2011. Using the C++ program, 24 X-ray detectable supernovae have
been found in the archive and 3 of them were newly-discovered in X-rays which
are SN 1986L, SN 2003lx, and SN 2007od. In addition, SN 2003lx is a Type Ia
supernova which may be the second X-ray detectable Type Ia after SN 2005ke
(Immler et al. 2006). Calibrated data of luminous type Ib/c supernovae was
consistent to the X-ray emission model done by Chevalier & Fransson (1994).
Statistics about the luminosities and hardness ratio have been done to purpose
of getting the X-ray emission features of the X-ray supernovae. The results
from this work help investigating the X-ray evolution of SNe and developing
similar X-ray SNe surveys in various X-rays missions
Phase resolved PLIF and chemiluminescence for measuring combustion dynamics
Transient behavior of combustion systems has long been a subject of both fundamental and practical concerns. Extreme cases of very rapid changes include the ignition of reacting mixtures and detonation. At the other extreme is a wide range of quasi-steady changes of behavior, for example adjustments of the operating point of a combustion chamber. Between the limiting cases of 'infinitely fast' and 'infinitesimally slow' lie important fundamental problems of time-dependent behavior and a wide array
of practical applications. Among the latter are combustion instabilities and their active control, a primary motivation for the work reported in this paper. Owing to the
complicated chemistry, chemical kinetics and flow dynamics of actual combustion systems, numerical simulations of their behavior remains in a relatively primitive state.
Even as that situation continually improves, it is an essential part of the field that methods of measuring true dynamical behavior be developed to provide results having both fine spatial resolution and accuracy in time. This paper is a progress report of recent research
carried out in the Jet Propulsion Center of the California Institute of Technology
Unsteady flow around a Rectangular Cylinder
This paper describes an investigation into the unsteady flow behaviour around a rectangular cylinder using particle image velocimetry (PIV). Instantaneous and average velocity fields were obtained from PIV images. Analysis of the structures observed in the instantaneous velocity fields reveals the presence of small scale (Kelvin-Helmholtz) vortex structures in the shear layer that separates at the leading edge of the rectangular cylinder, and evidence of von Karman vortex shedding was observed in the wake region
The Discovery of an X-ray/UV Stellar Flare from the Late-K/Early-M Dwarf LMC 335
We report the discovery of an X-ray/UV stellar flare from the source LMC 335,
captured by XMM-Newton in the field of the Large Magellanic Cloud. The flare
event was recorded continuously in X-ray for its first 10 hours from the
precursor to the late decay phases. The observed fluxes increased by more than
two orders of magnitude at its peak in X-ray and at least one in the UV as
compared to quiescence. The peak 0.1-7.0 keV X-ray flux is derived from the
two-temperature APEC model to be ~(8.4 +/- 0.6) x 10^-12 erg cm-2 s-1.
Combining astrometric information from multiple X-ray observations in the
quiescent and flare states, we identify the NIR counterpart of LMC 335 as the
2MASS source J05414534-6921512. The NIR color relations and spectroscopic
parallax characterize the source as a Galactic K7-M4 dwarf at a foreground
distance of (100 - 264) pc, implying a total energy output of the entire event
of ~(0.4 - 2.9) x 10^35 erg. This report comprises detailed analyses of this
late-K / early-M dwarf flare event that has the longest time coverage yet
reported in the literature. The flare decay can be modeled with two exponential
components with timescales of ~28 min and ~4 hours, with a single component
decay firmly ruled out. The X-ray spectra during flare can be described by two
components, a dominant high temperature component of ~40-60MK and a low
temperature component of ~10MK, with a flare loop length of about 1.1-1.3
stellar radius.Comment: 35 pages, 6 figures, 5 tables, accepted for publication in Ap
Digital Image Processing of Electron Micrographs: The PIC System II
The PIC system, an integrated package of Fortran programs and subroutines designed to run on the Digital Equipment Corporation VAX family of computers, has been developed for analysis of electron micrographs with emphasis on the particular requirements for structural analysis of biological macromolecules. The substantially improved VAX version of PIC reported here has been developed from an earlier PDP-11 version which was, in turn, developed from a set of IBM 370 programs called MDPP. PIC now encompasses over 150 commands or processing operations that afford a comprehensive range of image processing operations including image restoration, enhancement, Fourier analysis, correlation averaging, and multivariate statistical analysis including clustering and classification. In particular, we describe our software for correction of imperfect lattices, as well as programs for correlation alignment and averaging of single particle images
Air pollution and mortality: Effect modification by personal characteristics and specific cause of death in a case-only study
Short-term effects of air pollution on mortality have been well documented in the literature worldwide. Less is known about which subpopulations are more vulnerable to air pollution. We conducted a case-only study in Hong Kong to examine the potential effect modification by personal characteristics and specific causes of death. Individual information of 402,184 deaths of non-external causes and daily mean concentrations of air pollution were collected from 2001 to 2011. For a 10 μg/m3 increase of pollution concentration, people aged ≥∇65 years (compared with younger ages) had a 0.9–1.8% additional increase in mortality related to PM, NO2, and SO2. People dying from cardiorespiratory diseases (compared with other non-external causes) had a 1.6–2.3% additional increase in PM and NO2 related mortality. Other subgroups that were particularly susceptible were females and those economically inactive. Lower socioeconomic status and causes of cardiorespiratory diseases would increase the likelihood of death associated with air pollution.postprin
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