2,394 research outputs found
The examination of the validity of the Divisia price index for the almost ideal demand system model: Some Monte Carlo results
In this paper, we have investigated about the validity of an exact price index suggested by Feenstra and Reindorf (2000) in the almost ideal demand (AID) system model. This index can express by the use of the Divisia index with the weighted shares, and it has been evaluated using data on the expenditure shares and prices at two data points. Our Monte Carlo experiments show that the Divisia index does not perform so suitable estimates in any design. And then we find that the Divisia index would yield the poor estimates against the AID price index.Demand system AID model Divisia price index
Observations of the post shock break-out emission of SN 2011dh with XMM-Newton
After the occurrence of the type cIIb SN 2011dh in the nearby spiral galaxy M
51 numerous observations were performed with different telescopes in various
bands ranging from radio to gamma-rays. We analysed the XMM-Newton and Swift
observations taken 3 to 30 days after the SN explosion to study the X-ray
spectrum of SN 2011dh. We extracted spectra from the XMM-Newton observations,
which took place ~7 and 11 days after the SN. In addition, we created
integrated Swift/XRT spectra of 3 to 10 days and 11 to 30 days. The spectra are
well fitted with a power-law spectrum absorbed with Galactic foreground
absorption. In addition, we find a harder spectral component in the first
XMM-Newton spectrum taken at t ~ 7 d. This component is also detected in the
first Swift spectrum of t = 3 - 10 d. While the persistent power-law component
can be explained as inverse Compton emission from radio synchrotron emitting
electrons, the harder component is most likely bremsstrahlung emission from the
shocked stellar wind. Therefore, the harder X-ray emission that fades away
after t ~ 10 d can be interpreted as emission from the shocked circumstellar
wind of SN 2011dh.Comment: Accepted for publication as a Research Note in Astronomy and
Astrophysic
Moments in a Movement: APEN 2002 Annual Report
Community organizing is our central strategy to achieve environmental, social and economic justice. Our two local San Francisco Bay Area projects are the 8-year old Laotian Organizing Project (LOP) in Richmond, which also houses the Asian Youth Advocates program for young women, and the year-old Power in Asians Organizing (PAO) working with the pan-Asian immigrant community in Oakland. This report includes case studies and reflections on the work APEN does
3D Hydrodynamic Simulations of the Galactic Supernova Remnant CTB 109
Using detailed 3D hydrodynamic simulations we study the nature of the
Galactic supernova remnant (SNR) CTB 109 (G109.1-1.0), which is well-known for
its semicircular shape and a bright diffuse X-ray emission feature inside the
SNR. Our model has been designed to explain the observed morphology, with a
special emphasis on the bright emission feature inside the SNR. Moreover, we
determine the age of the remnant and compare our findings with X-ray
observations. With CTB 109 we test a new method of detailed numerical
simulations of diffuse young objects, using realistic initial conditions
derived directly from observations. We performed numerical 3D simulations with
the RAMSES code. The initial density structure has been directly taken from
CO emission data, adding an additional dense cloud, which, when it is
shocked, causes the bright emission feature. From parameter studies we obtained
the position for an elliptical
cloud with based on the preshock density
from Chandra data and a maximum diameter of 4.54 pc, whose encounter with the
supernova (SN) shock wave generates the bright X-ray emission inside the SNR.
The calculated age of the remnant is about 11,000 yr according to our
simulations. In addition, we can also determine the most probable site of the
SN explosion. Hydrodynamic simulations can reproduce the morphology and the
observed size of the SNR CTB 109 remarkably well. Moreover, the simulations
show that it is very plausible that the bright X-ray emission inside the SNR is
the result of an elliptical dense cloud shocked by the SN explosion wave. We
show that numerical simulations using observational data for an initial model
can produce meaningful results.Comment: 9 pages, 6 figures, accepted for publication in A&
ROSAT HRI catalogue of X-ray sources in the LMC region
All 543 pointed observations of the ROSAT High Resolution Imager (HRI) with
exposure times higher than 50 sec in a field of 10 deg x 10 deg covering the
Large Magellanic Cloud (LMC) were analyzed. A catalogue was produced containing
397 X-ray sources with their properties measured by the HRI. The list was
cross-correlated with the ROSAT Position Sensitive Propotional Counter (PSPC)
source catalogue presented by Haberl & Pietsch (1999), the SIMBAD data base,
and the TYCHO catalogue. 138 HRI sources are contained in the PSPC catalogue.
The spatial resolution of the HRI was higher than that of the PSPC and the
source position could be determined with errors mostly smaller than 15 arcsec
which are dominated by systematic attitude errors. 94 HRI sources were
identified with known objects based on their positional coincidence and X-ray
properties. The catalogue contains 39 foreground stars, 24 supernova remnants
(SNRs), five supersoft sources (SSSs), nine X-ray binaries (XBs), and nine AGN
well known from literature. Another eight sources were identified with known
candidates for these source classes. Additional 21 HRI sources are suggested in
the present work as candidates for SNR, X-ray binary in the LMC, or background
AGN because of their extent, hardness ratios, X-ray to optical flux ratio, or
flux variability.Comment: 22 pages, 8 figures, 4 table
Design Principles of Pancreatic Islets: Glucose-dependent Coordination of Hormone Pulses
Pancreatic islets are functional units involved in glucose homeostasis. The
multicellular system comprises three main cell types; and
cells reciprocally decrease and increase blood glucose by producing insulin and
glucagon pulses, while the role of cells is less clear. Although their
spatial organization and the paracrine/autocrine interactions between them have
been extensively studied, the functional implications of the design principles
are still lacking. In this study, we formulated a mathematical model that
integrates the pulsatility of hormone secretion and the interactions and
organization of islet cells and examined the effects of different cellular
compositions and organizations in mouse and human islets. A common feature of
both species was that islet cells produced synchronous hormone pulses under
low- and high- glucose conditions, while they produced asynchronous hormone
pulses under normal glucose conditions. However, the synchronous coordination
of insulin and glucagon pulses at low glucose was more pronounced in human
islets that had more cells. When cells were selectively
removed to mimic diabetic conditions, the anti-synchronicity of insulin and
glucagon pulses was deteriorated at high glucose, but it could be partially
recovered when the re-aggregation of remaining cells was considered. Finally,
the third cell type, cells, which introduced additional complexity in
the multicellular system, prevented the excessive synchronization of hormone
pulses. Our computational study suggests that controllable synchronization is a
design principle of pancreatic islets.Comment: 24 pages, 7 figure
Evidence for Recombining Plasma in the Supernova Remnant G346.6-0.2
We present the Suzaku results of the supernova remnant (SNR) G346.6-0.2. The
X-ray emission has a center-filled morphology with the size of 6' x 8' within
the radio shell. Neither an ionization equilibrium nor non-equilibrium
(ionizing) plasma can reproduce the spectra remaining shoulder-like residuals
in the 2-4 keV band. These structures are possibly due to recombination of free
electrons to the K-shell of He-like Si and S. The X-ray spectra are well fitted
with a plasma model in a recombination dominant phase. We propose that the
plasma was in nearly full ionized state at high temperature of 5 keV, then the
plasma changed to a recombining phase due to selective cooling of electrons to
lower temperature of 0.3 keV. G346.6-0.2 would be in an epoch of the
recombining phase.Comment: Accepted for publication in PAS
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