2,267 research outputs found
Remote sensing of Pacific hurricane and radiometric measurements from foam and slicks
There are no author-identified significant results in this report
Acute Cheese Consumption Reduces Sodium Induced Cutaneous Microvascular Dysfunction by Decreasing Oxidative Stress
Please refer to the pdf version of the abstract located adjacent to the title
Ram pressure stripping of the multiphase ISM in the Virgo cluster spiral galaxy NGC 4438
Ram pressure stripping of the multiphase ISM is studied in the perturbed
Virgo cluster spiral galaxy NGC 4438. This galaxy underwent a tidal interaction
~100 Myr ago and is now strongly affected by ram pressure stripping. Deep VLA
radio continuum observations at 6 and 20 cm are presented. We detect prominent
extraplanar emission to the west of the galactic center, which extends twice as
far as the other tracers of extraplanar material. The spectral index of the
extraplanar emission does not steepen with increasing distance from the galaxy.
This implies in situ re-acceleration of relativistic electrons. The comparison
with multiwavelength observations shows that the magnetic field and the warm
ionized interstellar medium traced by Halpha emission are closely linked. The
kinematics of the northern extraplanar Halpha emission, which is ascribed to
star formation, follow those of the extraplanar CO emission. In the western and
southern extraplanar regions, the Halpha measured velocities are greater than
those of the CO lines. We suggest that the ionized gas of this region is
excited by ram pressure. The spatial and velocity offsets are consistent with a
scenario where the diffuse ionized gas is more efficiently pushed by ram
pressure stripping than the neutral gas. We suggest that the recently found
radio-deficient regions compared to 24 mum emission are due to this difference
in stripping efficiency.Comment: 8 pages, 6 figures, A&A, accepted for publicatio
HCN(1-0) enhancement in the bar of NGC 2903
We have mapped the \hcn emission from two spiral galaxies, NGC2903 and
NGC3504 to study the gas properties in the bars. The HCN(1-0) emission is
detected in the center and along the bar of NGC2903. The line ratio
HCN(1-0)/CO(1-0) ranges from 0.07 to 0.12 with the lowest value in the center.
The enhancement of HCN(1-0) emission along the bar indicates a higher fraction
of dense molecular gas in the bar than at the center. The mass of dense
molecular gas in the center (2.2x 10^7 Msun) is about 6 times lower than that
in the bar (1.2x 10^8 Msun). The total star formation rate (SFR) is estimated
to be 1.4 Msun/yr, where the SFR at the center is 1.9 times higher than that in
the bar. The time scale of consumption of the dense molecular gas in the center
is about 3x 10^7 yr which is much shorter than that in the bar of about 2 to 10
x 10^8 yr. The dynamical time scale of inflow of the gas from the bar to the
center is shorter than the consumption time scale in the bar, which suggests
that the star formation (SF) activity at the center is not deprived of fuel. In
the bar, the fraction of dense molecular gas mass relative to the total
molecular gas mass is twice as high along the leading edge than along the
central axis of the bar. The \hcn emission has a large velocity dispersion in
the bar, which can be attributed partially to the streaming motions indicative
of shocks along the bar. In NGC3504, the HCN(2-0) emission is detected only at
the center. The fraction of dense molecular gas mass in the center is about
15%. Comparison of the SFR with the predictions from numerical simulations
suggest that NGC2903 harbors a young type B bar with a strong inflow of gas
toward the center whereas NGC3504 has an older bar and has already passed the
phase of inflow of gas toward the center.Comment: Acceoted for publication in A&A, 12 figure
Topological Orthoalgebras
We define topological orthoalgebras (TOAs) and study their properties. While
every topological orthomodular lattice is a TOA, the lattice of projections of
a Hilbert space is an example of a lattice-ordered TOA that is not a toplogical
lattice. On the other hand, we show that every compact Boolean TOA is a
topological Boolean algebra. We also show that a compact TOA in which 0 is an
isolated point is atomic and of finite height. We identify and study a
particularly tractable class of TOAs, which we call {\em stably ordered}: those
in which the upper-set generated by an open set is open. This includes all
topological OMLs, and also the projection lattices of Hilbert spaces. Finally,
we obtain a topological version of the Foulis-Randall representation theory for
stably ordered TOAsComment: 16 pp, LaTex. Minor changes and corrections in sections 1; more
substantial corrections in section
Atomic and Molecular Gas Components in Spiral Galaxies of the Virgo Cluster
Based on two models, we investigate the molecular-to-atomic gas ratio in
Virgo cluster galaxies in comparison with field galaxies. We show that the
enhanced metallicity for cluster members and the ram pressure stripping of
atomic gas from the disk periphery cannot fully explain the observed gas
component ratios. The additional environmental factors affecting the
interstellar medium and leading to an increase in the molecular gas fraction
should be taken into account for cluster galaxies.Comment: 11 pages, 4 figure
Epstein-Barr virus-specific methylation of human genes in gastric cancer cells
<p>Abstract</p> <p>Background</p> <p>Epstein-Barr Virus (EBV) is found in 10% of all gastric adenocarcinomas but its role in tumor development and maintenance remains unclear. The objective of this study was to examine EBV-mediated dysregulation of cellular factors implicated in gastric carcinogenesis.</p> <p>Methods</p> <p>Gene expression patterns were examined in EBV-negative and EBV-positive AGS gastric epithelial cells using a low density microarray, reverse transcription PCR, histochemical stains, and methylation-specific DNA sequencing. Expression of PTGS2 (COX2) was measured in AGS cells and in primary gastric adenocarcinoma tissues.</p> <p>Results</p> <p>In array studies, nearly half of the 96 human genes tested, representing 15 different cancer-related signal transduction pathways, were dysregulated after EBV infection. Reverse transcription PCR confirmed significant impact on factors having diverse functions such as cell cycle regulation (<it>IGFBP3</it>, <it>CDKN2A, CCND1, HSP70, ID2, ID4)</it>, DNA repair <it>(BRCA1, TFF1</it>), cell adhesion (<it>ICAM1</it>), inflammation (<it>COX2</it>), and angiogenesis (<it>HIF1A</it>). Demethylation using 5-aza-2'-deoxycytidine reversed the EBV-mediated dysregulation for all 11 genes listed here. For some promoter sequences, CpG island methylation and demethylation occurred in an EBV-specific pattern as shown by bisulfite DNA sequencing. Immunohistochemistry was less sensitive than was western blot for detecting downregulation of COX2 upon EBV infection. Virus-related dysregulation of COX2 levels <it>in vitro </it>was not recapitulated <it>in vivo </it>among naturally infected gastric cancer tissues.</p> <p>Conclusions</p> <p>EBV alters human gene expression in ways that could contribute to the unique pathobiology of virus-associated cancer. Furthermore, the frequency and reversability of methylation-related transcriptional alterations suggest that demethylating agents have therapeutic potential for managing EBV-related carcinoma.</p
The Central Region of Barred Galaxies: Molecular Environment, Starbursts, and Secular Evolution
Despite compelling evidence that stellar bars drive gas into the inner 1--2
kpc or circumnuclear (CN) region of galaxies, there are few large, high
resolution studies of the CN molecular gas and star formation (SF). We study a
sample of local barred non-starbursts and starbursts with high-resolution CO,
optical, Ha, RC, Br-gamma, and HST data, and find the following. (1) The inner
kpc of bars differs markedly the outer disk and hosts molecular gas surface
densities Sigma-gas-m of 500-3500 Msun pc-2, gas mass fractions of 10--30 %,
and epicyclic frequencies of several 100--1000 km s-1 kpc-1.Consequently,
gravitational instabilities can only set in at high gas densities and grow on a
short timescale (few Myr). This high density, short timescale, `burst' mode may
explain why powerful starbursts tend to be in the CN region of galaxies. (2) We
suggest that the variety in CO morphologies is due to different stages of
bar-driven inflow. At late stages, most of the CN gas is inside the outer inner
Lindblad resonance (OILR), and has predominantly circular motions. Across the
sample, we find bar pattern speeds with upper limits of 43 to 115 km s-1 kpc-1
and OILR radii of > 500 pc. (3) Barred starbursts and non-starbursts have CN
SFRs of 3--11 and 0.1--2 Msun yr-1, despite similar CN gas mass. Sigma-gas-m in
the starbursts is larger (1000--3500 Msun pc-2) and close to the Toomre
critical density over a large region. (4) Molecular gas makes up 10%--30% of
the CN dynamical mass (6--30 x 10^9 Msun).In the starbursts, it fuels CN SFRs
of 3--11 Msun yr-1, building young, massive, high V/sigma components. We
present evidence for such a pseudo-bulge in NGC 3351. Implications for secular
evolution along the Hubble sequence are discussed.Comment: Accepted by the Astrophysical Journal. Paper length reduced to fit
within APJ page limits. Version of paper with high resolution figures is at
http://www.as.utexas.edu/~sj/papers/ms-hires-sj05a.ps.g
Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array
We apply two methods to estimate the 21~cm bispectrum from data taken within
the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA).
Using data acquired with the Phase II compact array allows a direct bispectrum
estimate to be undertaken on the multiple redundantly-spaced triangles of
antenna tiles, as well as an estimate based on data gridded to the -plane.
The direct and gridded bispectrum estimators are applied to 21 hours of
high-band (167--197~MHz; =6.2--7.5) data from the 2016 and 2017 observing
seasons. Analytic predictions for the bispectrum bias and variance for point
source foregrounds are derived. We compare the output of these approaches, the
foreground contribution to the signal, and future prospects for measuring the
bispectra with redundant and non-redundant arrays. We find that some triangle
configurations yield bispectrum estimates that are consistent with the expected
noise level after 10 hours, while equilateral configurations are strongly
foreground-dominated. Careful choice of triangle configurations may be made to
reduce foreground bias that hinders power spectrum estimators, and the 21~cm
bispectrum may be accessible in less time than the 21~cm power spectrum for
some wave modes, with detections in hundreds of hours.Comment: 19 pages, 10 figures, accepted for publication in PAS
The SKA Particle Array Prototype: The First Particle Detector at the Murchison Radio-astronomy Observatory
We report on the design, deployment, and first results from a scintillation
detector deployed at the Murchison Radio-astronomy Observatory (MRO). The
detector is a prototype for a larger array -- the Square Kilometre Array
Particle Array (SKAPA) -- planned to allow the radio-detection of cosmic rays
with the Murchison Widefield Array and the low-frequency component of the
Square Kilometre Array. The prototype design has been driven by stringent
limits on radio emissions at the MRO, and to ensure survivability in a desert
environment. Using data taken from Nov.\ 2018 to Feb.\ 2019, we characterize
the detector response while accounting for the effects of temperature
fluctuations, and calibrate the sensitivity of the prototype detector to
through-going muons. This verifies the feasibility of cosmic ray detection at
the MRO. We then estimate the required parameters of a planned array of eight
such detectors to be used to trigger radio observations by the Murchison
Widefield Array.Comment: 17 pages, 14 figures, 3 table
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