5,186 research outputs found
The Interplanetary Network Supplement to the BeppoSAX Gamma-Ray Burst Catalogs
Between 1996 July and 2002 April, one or more spacecraft of the
interplanetary network detected 787 cosmic gamma-ray bursts that were also
detected by the Gamma-Ray Burst Monitor and/or Wide-Field X-Ray Camera
experiments aboard the BeppoSAX spacecraft. During this period, the network
consisted of up to six spacecraft, and using triangulation, the localizations
of 475 bursts were obtained. We present the localization data for these events.Comment: 89 pages, 3 figures. Submitted to the Astrophysical Journal
Supplement Serie
A pertubative approach to the Kondo effect in magnetic atoms on nonmagnetic substrates
Recent experimental advances in scanning tunneling microscopy make the
measurement of the conductance spectra of isolated and magnetically coupled
atoms on nonmagnetic substrates possible. Notably these spectra are
characterized by a competition between the Kondo effect and spin-flip inelastic
electron tunneling. In particular they include Kondo resonances and a
logarithmic enhancement of the conductance at voltages corresponding to
magnetic excitations, two features that cannot be captured by second order
perturbation theory in the electron-spin coupling. We have now derived a third
order analytic expression for the electron-spin self-energy, which can be
readily used in combination with the non-equilibrium Green's function scheme
for electron transport at finite bias. We demonstrate that our method is
capable of quantitative description the competition between Kondo resonances
and spin-flip inelastic electron tunneling at a computational cost
significantly lower than that of other approaches. The examples of Co and Fe on
CuN are discussed in detail
De-blending Deep Herschel Surveys: A Multi-wavelength Approach
Cosmological surveys in the far infrared are known to suffer from confusion.
The Bayesian de-blending tool, XID+, currently provides one of the best ways to
de-confuse deep Herschel SPIRE images, using a flat flux density prior. This
work is to demonstrate that existing multi-wavelength data sets can be
exploited to improve XID+ by providing an informed prior, resulting in more
accurate and precise extracted flux densities. Photometric data for galaxies in
the COSMOS field were used to constrain spectral energy distributions (SEDs)
using the fitting tool CIGALE. These SEDs were used to create Gaussian prior
estimates in the SPIRE bands for XID+. The multi-wavelength photometry and the
extracted SPIRE flux densities were run through CIGALE again to allow us to
compare the performance of the two priors. Inferred ALMA flux densities
(F), at 870m and 1250m, from the best fitting SEDs from the
second CIGALE run were compared with measured ALMA flux densities (F) as an
independent performance validation. Similar validations were conducted with the
SED modelling and fitting tool MAGPHYS and modified black body functions to
test for model dependency. We demonstrate a clear improvement in agreement
between the flux densities extracted with XID+ and existing data at other
wavelengths when using the new informed Gaussian prior over the original
uninformed prior. The residuals between F and F were calculated. For
the Gaussian prior, these residuals, expressed as a multiple of the ALMA error
(), have a smaller standard deviation, 7.95 for the Gaussian
prior compared to 12.21 for the flat prior, reduced mean, 1.83
compared to 3.44, and have reduced skew to positive values, 7.97
compared to 11.50. These results were determined to not be significantly model
dependent. This results in statistically more reliable SPIRE flux densities.Comment: 8 pages, 7 figures, 3 tables. Accepted for publication in A&
Selective ALDH3A1 Inhibition by Benzimidazole Analogues Increase Mafosfamide Sensitivity in Cancer Cells
Aldehyde dehydrogenase enzymes irreversibly
oxidize aldehydes generated
from metabolism of amino acids, fatty acids, food, smoke, additives,
and xenobiotic drugs. Cyclophosphamide is one such xenobiotic used
in cancer therapies. Upon activation, cyclophosphamide forms an intermediate,
aldophosphamide, which can be detoxified to carboxyphosphamide by
aldehyde dehydrogenases (ALDH), especially ALDH1A1 and ALDH3A1. Consequently,
selective inhibition of ALDH3A1 could increase chemosensitivity toward
cyclophosphamide in ALDH3A1 expressing tumors. Here, we report detailed
kinetics and structural characterization of a highly selective submicromolar
inhibitor of ALDH3A1, 1-[(4-fluorophenyl)sulfonyl]-2-methyl-1H-benzimidazole (CB7, IC50 of 0.2
μM). CB7 does not inhibit ALDH1A1, ALDH1A2, ALDH1A3,
ALDH1B1, or ALDH2 activity. Structural, kinetics, and mutagenesis
studies show that CB7 binds to the aldehyde binding pocket
of ALDH3A1. ALDH3A1-expressing lung adenocarcinoma and glioblastoma
cell lines are sensitized toward mafosfamide (MF) treatment in the
presence analogues of CB7, whereas primary lung fibroblasts
lacking ALDH3A1 expression, are not
The second Konus-Wind catalog of short gamma-ray bursts
In this catalog, we present the results of a systematic study of 295 short
gamma-ray bursts (GRBs) detected by Konus-Wind (KW) from 1994 to 2010. From the
temporal and spectral analyses of the sample, we provide the burst durations,
the spectral lags, the results of spectral fits with three model functions, the
total energy fluences and the peak energy fluxes of the bursts. We discuss
evidence found for an additional power-law spectral component and the presence
of extended emission in a fraction of the KW short GRBs. Finally, we consider
the results obtained in the context of the Type I (merger-origin) / Type II
(collapsar-origin) classifications.Comment: Accepted to the Astrophysical Journal Supplement Series (7 Figures, 8
Tables
X-Ray Light Curves of Gamma-ray Bursts Detected with the All-Sky Monitor on RXTE
We present X-ray light curves (1.5-12 keV) for fifteen gamma-ray bursts
(GRBs) detected by the All-Sky Monitor on the Rossi X-ray Timing Explorer. We
compare these soft X-ray light curves with count rate histories obtained by the
high-energy (>12 keV) experiments BATSE, Konus-Wind, the BeppoSAX Gamma-Ray
Burst Monitor, and the burst monitor on Ulysses. We discuss these light curves
within the context of a simple relativistic fireball and synchrotron shock
paradigm, and we address the possibility of having observed the transition
between a GRB and its afterglow. The light curves show diverse morphologies,
with striking differences between energy bands. In several bursts, intervals of
significant emission are evident in the ASM energy range with little or no
corresponding emission apparent in the high-energy light curves. For example,
the final peak of GRB 970815 as recorded by the ASM is only detected in the
softest BATSE energy bands. We also study the duration of bursts as a function
of energy. Simple, singly-peaked bursts seem consistent with the E^{-0.5} power
law expected from an origin in synchrotron radiation, but durations of bursts
that exhibit complex temporal structure are not consistent with this
prediction. Bursts such as GRB 970828 that show many short spikes of emission
at high energies last significantly longer at low energies than the synchrotron
cooling law would predict.Comment: 15 pages with 20 figures and 2 tables. In emulateapj format. Accepted
by ApJ
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