127 research outputs found
Chandra view of Kes 79: a nearly isothermal SNR with rich spatial structure
A 30 ks \chandra ACIS-I observation of Kes 79 reveals rich spatial
structures, including many filaments, three partial shells, a loop and a
``protrusion''. Most of them have corresponding radio features. Regardless of
the different results from two non-equilibrium ionization (NEI) codes,
temperatures of different parts of the remnant are all around 0.7 keV, which is
surprisingly constant for a remnant with such rich structure. If thermal
conduction is responsible for smoothing the temperature gradient, a lower limit
on the thermal conductivity of 1/10 of the Spitzer value can be derived.
Thus, thermal conduction may play an important role in the evolution of at
least some SNRs. No spectral signature of the ejecta is found, which suggests
the ejecta material has been well mixed with the ambient medium. From the
morphology and the spectral properties, we suggest the bright inner shell is a
wind-driven shell (WDS) overtaken by the blast wave (the outer shell) and
estimate the age of the remnant to be 6 kyr for the assumed dynamics.
Projection is also required to explain the complicated morphology of Kes 79.Comment: 12 pages, 6 figures (3 in color), ApJ, in press, April 20, 200
Sub-Cycle Optical Response Caused by Dressed State with Phase-Locked Wavefunctions
The coherent interaction of light with matter imprints the phase information
of the light field on the wavefunction of the photon-dressed electronic state.
Driving electric field, together with a stable phase that is associated with
the optical probe pulses, enables the role of the dressed state in the optical
response to be investigated. We observed optical absorption strengths modulated
on a sub-cycle timescale in a GaAs quantum well in the presence of a
multi-cycle terahertz driving pulse using a near-infrared probe pulse. The
measurements were in good agreement with the analytical formula that accounts
for the optical susceptibilities caused by the dressed state of excitons, which
indicates that the output probe intensity was coherently reshaped by the
excitonic sideband emissions
The X-ray CCD camera of the MAXI Experiment on the ISS/JEM
MAXI, Monitor of All-sky X-ray Image, is the X-ray observatory on the
Japanese experimental module (JEM) Exposed Facility (EF) on the International
Space Station (ISS). MAXI is a slit scanning camera which consists of two kinds
of X-ray detectors: one is a one-dimensional position-sensitive proportional
counter with a total area of , the Gas Slit Camera (GSC), and
the other is an X-ray CCD array with a total area , the
Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular
dimension of 1 while the SSC subtends a field of view
with an angular dimension of 1 times a little less than 180. In
the course of one station orbit, MAXI can scan almost the entire sky with a
precision of 1 and with an X-ray energy range of 0.5-30 keV. We have
developed the engineering model of CCD chips and the analogue electronics for
the SSC. The energy resolution of EM CCD for Mn K has a full-width at
half maximum of 182 eV. Readout noise is 11 e^- rms.Comment: 10 pages, 4 figures Accepted for Nuclear Instruments and Method in
Physics Researc
Enhanced abundances in three large-diameter mixed-morphology supernova remnants
We present an X-ray study of three mixed-morphology supernova remnants
(SNRs), HB 21, CTB 1 and HB 3, using archival ASCA and ROSAT data. These data
are complemented by archival Chandra X-ray Observatory data for CTB 1 and
XMM-Newton X-ray Observatory data for HB 3. The spectra from HB 21 and HB 3 are
well-described with a single-temperature thermal plasma in ionization
equilibrium, while a two-temperature thermal plasma is found in CTB 1. We found
enhanced abundances in all three SNRs. The elemental abundance of Mg is clearly
enhanced in CTB 1, while HB 21 has enhanced abundances of Si and S. The
situation is not so clear in HB 3 -- the plasma in this SNR either has
significantly enhanced abundances of O, Ne and Mg, or it has marginally
enhanced abundances of Mg and under-abundant Fe. We discuss the plausibility of
mixed-morphology SNR models for the three SNRs and the presence of enhanced
abundances. We revise a list of MM SNRs and their properties, compare the three
SNRs studied here with other members of this class, and discuss the presence of
enhanced elemental abundances in MM SNRs. We also report the ASCA detection of
a compact source in the southern part of HB 3. The source spectrum is
consistent with a power law with a photon index of ~2.7, and an unabsorbed
X-ray flux of ~10^{-12} erg/cm^2/s in the 0.5--10.0 keV band. The column
density towards this source differs from that towards the SNR, and it is
therefore unlikely they are related.Comment: 26 pages, 15 figures, revised version (minor changes), accepted for
publication in ApJ (10 Aug 2006
J-shaped relationship between waist circumference and subsequent risk for Type 2 diabetes: An 8-year follow-up of relatively lean Japanese individuals
金沢大学医薬保健研究域医学系金沢医科大学健康増進予防医学(公衆衛生学)Aims This study investigated the relationship between waist circumference and the subsequent incidence of Type 2 diabetes and the association with insulin resistance and pancreatic B-cell function in relatively lean Japanese individuals. Methods The study participants were 3992 employees (2533 men and 1459 women, aged 35-55 years) of a metal-products factory in Japan. The incidence of diabetes was determined in annual medical examinations during an 8-year follow-up. We calculated age- and sex-adjusted hazard ratios (HRs) according to the sex-specific quintile of waist circumference at baseline. Differences in baseline insulin resistance [homeostatis model assessment (HOMA)-IR] and pancreatic B-cell function (HOMA-B) were compared between participants who developed diabetes and those who did not. Results During the follow-up, 218 participants developed diabetes. Age- and sex-adjusted HRs across the quintiles of waist circumference were 1.78, 1.00 (reference), 1.59, 3.11 and 3.30, respectively (P for trend, < 0.0001). The HR for the lowest quintile was significantly higher than that for the second quintile. Among participants with waist circumference of the lowest quintile, HOMA-B was lower in those who developed diabetes than in those who did not [33.1 (24.1-45.0) vs. 54.3 (37.9-74.6) median (interquartile range), P < 0.0001], but HOMA-IR did not differ between these groups. Conclusions There was a J-shaped relationship between waist circumference and subsequent risk for Type 2 diabetes in relatively lean Japanese individuals; lower pancreatic B-cell function may also increase the risk of diabetes in very lean Japanese people. © 2009 Diabetes UK
Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te doped GaAs single crystals
We have performed voltage dependent imaging and spatially resolved
spectroscopy on the (110) surface of Te doped GaAs single crystals with a low
temperature scanning tunneling microscope (STM). A large fraction of the
observed defects are identified as Te dopant atoms which can be observed down
to the fifth subsurface layer. For negative sample voltages, the dopant atoms
are surrounded by Friedel charge density oscillations. Spatially resolved
spectroscopy above the dopant atoms and above defect free areas of the GaAs
(110) surface reveals the presence of conductance peaks inside the
semiconductor band gap. The appearance of the peaks can be linked to charges
residing on states which are localized within the tunnel junction area. We show
that these localized states can be present on the doped GaAs surface as well as
at the STM tip apex.Comment: 8 pages, 8 figures, accepted for publication in PR
Investigation of the urinary sodium-to-potassium ratio target level based on the recommended dietary intake goals for the Japanese population: The INTERMAP Japan
Growing epidemiological evidence has shown an association of the urinary sodium (Na) to potassium (K) ratio (Na/K ratio) with blood pressure and cardiovascular diseases. However, no clear cutoff level has been defined. We investigated the cutoff level of the urinary Na/K ratio under different dietary guidelines for Japanese individuals, especially that endorsed by the 2020 revised Japanese Dietary Reference Intakes (DRIs). A population of 1145 Japanese men and women aged 40 to 59 years from the INTERMAP study was examined. Using high-quality standardized data, the averages of two 24 h urinary collections and four 24 h dietary recalls were used to calculate the 24 h urinary and dietary Na/K ratios, respectively. Associations between the urinary and dietary Na/K ratios were tested by sex- and age-adjusted partial correlation. The optimal urinary Na/K ratio cutoff level was determined by receiver operating characteristic (ROC) curves and sex-specific cross tables for recommended dietary K and salt. Overall, the average molar ratio of 24 h urinary Na/K was 4.3. We found moderate correlations (P < 0.001) of the 24 h urinary Na/K ratio with 24 h urinary Na and K excretion (r = 0.52, r = −0.49, respectively) and the dietary Na/K ratio (r = 0.53). ROC curves showed that a 24 h urinary Na/K ratio of approximately 2 predicted Na and K intake that meets the dietary goals of the Japanese DRIs. The range of urinary Na/K ratios meeting the dietary goals of the Japanese DRIs for both Na and K was 1.6‒2.2 for men and 1.7‒1.9 for women. Accomplishing a urinary Na/K ratio of 2 would be desirable to achieve the DRIs dietary goals for both Na and K simultaneously in middle-aged Japanese men and women accustomed to Japanese dietary habits. This observational study is registered at www.clinicaltrials.gov as NCT00005271
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