207 research outputs found
Diffuse X-ray emission in spiral galaxies
We compare the soft diffuse X-ray emission from Chandra images of 12 nearby
intermediate inclination spiral galaxies to the morphology seen in Halpha,
molecular gas, and mid-infrared emission. We find that diffuse X-ray emission
is often located along spiral arms in the outer parts of spiral galaxies but
tends to be distributed in a rounder morphology in the center. The X-ray
morphology in the spiral arms matches that seen in the mid-infrared or Halpha
and so implies that the X-ray emission is associated with recent active star
formation. We see no strong evidence for X-ray emission trailing the location
of high mass star formation in spiral arms. However, population synthesis
models predict a high mechanical energy output rate from supernovae for a time
period that is about 10 times longer than the lifetime of massive ionizing
stars, conflicting with the narrow appearance of the arms in X-rays. The
fraction of supernova energy that goes into heating the ISM must depend on
environment and is probably higher near sites of active star formation. The
X-ray estimated emission measures suggest that the volume filling factors and
scale heights are high in the galaxy centers but low in the outer parts of
these galaxies. The differences between the X-ray properties and morphology in
the centers and outer parts of these galaxies suggest that galactic fountains
operate in outer galaxy disks but that winds are primarily driven from galaxy
centers.Comment: 28 pages, 4 figures, to be submitted to Ap
Explicit solution for vibrating bar with viscous boundaries and internal damper
We investigate longitudinal vibrations of a bar subjected to viscous boundary
conditions at each end, and an internal damper at an arbitrary point along the
bar's length. The system is described by four independent parameters and
exhibits a variety of behaviors including rigid motion, super
stability/instability and zero damping. The solution is obtained by applying
the Laplace transform to the equation of motion and computing the Green's
function of the transformed problem. This leads to an unconventional
eigenvalue-like problem with the spectral variable in the boundary conditions.
The eigenmodes of the problem are necessarily complex-valued and are not
orthogonal in the usual inner product. Nonetheless, in generic cases we obtain
an explicit eigenmode expansion for the response of the bar to initial
conditions and external force. For some special values of parameters the system
of eigenmodes may become incomplete, or no non-trivial eigenmodes may exist at
all. We thoroughly analyze physical and mathematical reasons for this behavior
and explicitly identify the corresponding parameter values. In particular, when
no eigenmodes exist, we obtain closed form solutions. Theoretical analysis is
complemented by numerical simulations, and analytic solutions are compared to
computations using finite elements.Comment: 29 pages, 6 figure
Direct CP Violation in Hadronic B Decays
There are different approaches for the hadronic B decay calculations,
recently. In this paper, we upgrade three of them, namely factorization, QCD
factorization and the perturbative QCD approach based on factorization,
by using new parameters and full wave functions.
Although they get similar results for many of the branching ratios, the
direct CP asymmetries predicted by them are different, which can be tested by
recent experimental measurements of B factories.Comment: 11 pages, 3 figures, revtex4, Talk given at the Workshop on the
Frontiers of Theoretical Physics and Cross-Disciplinary, NSFC, Beijing, March
200
Effect of Fasciola gigantica excretory secretory antigen on rat hematological indices
The present study was undertaken to investigate the effect of Fasciola gigantica excretory secretory antigen (Fg-ESA) on rat hematological indices. Fg-ESA was prepared by keeping thoroughly washed 40 F. gigantica flukes in 100 ml phosphate buffer saline (PBS) for 2 h at 37℃, and centrifuging the supernatant at 12,000 g at 4℃ for 30 min. The protein content of Fg-ESA was adjusted to 1.8 mg/ml. The rats were randomly divided into two groups of six rats each. Rats in group A received 0.5 ml of Fg-ESA intraperitoneally (i.p.) for 7 days, whereas control rats in group B received 0.5 ml of PBS i.p. for 7 days. Hemograms of both groups were studied initially and on days 0, 2, 4, 14 and 21 after the final injection of Fg-ESA or PBS. Progressive and significant (p < 0.01) declines in the values of hemoglobin, hematocrit, and total erythrocyte count were observed without significant (p > 0.05) changes in the values of mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, or mean corpuscular volume in group A. Thus, we conclude that Fg-ESA induces normocytic normochromic anemia in rats
The Supernova Relic Neutrino Background
An upper bound to the supernova relic neutrino background from all past Type
II supernovae is obtained using observations of the Universal metal enrichment
history. We show that an unambiguous detection of these relic neutrinos by the
Super-Kamiokande detector is unlikely. We also analyze the event rate in the
Sudbury Neutrino Observatory (where coincident neutrons from anti-nu_e + D -->
n + n + e+ might enhance background rejection), and arrive at the same
conclusion. If the relic neutrino flux should be observed to exceed our upper
bound and if the observations of the metal enrichment history (for z<1) are not
in considerable error, then either the Type II supernova rate does not track
the metal enrichment history or some mechanism may be responsible for
transforming anti-nu_{mu,tau} --> anti-nu_e.Comment: Matches version accepted for publication in Phys. Rev.
Hematopoietic growth factor inducible neurokinin-1 (Gpnmb/Osteoactivin) is a biomarker of progressive renal injury across species
We sought to find a urinary biomarker for chronic kidney disease and tested hematopoietic growth factor inducible neurokinin-1 (HGFIN, also known as Gpnmb/Osteoactivin) as it was found to be a kidney injury biomarker in microarray studies. Here, we studied whether HGFIN is a marker of kidney disease progression. Its increase in kidney disease was confirmed by real-time PCR after 5/6 nephrectomy, in streptozotocin-induced diabetes, and in patients with chronic kidney disease. In the remnant kidney, HGFIN mRNA increased over time reflecting lesion chronicity. HGFIN was identified in the infarct portion of the remnant kidney in infiltrating hematopoietic interstitial cells, and in distal nephron tubules of the viable remnant kidney expressed de novo with increasing time. In vitro, it localized to cytoplasmic vesicles and cell membranes. Epithelial cells lining distal tubules and sloughed luminal tubule cells of patients expressed HGFIN protein. The urine HGFIN-to-creatinine ratio increased over time after 5/6 nephrectomy; increased in patients with proteinuric and polycystic kidney disease; and remained detectable in urine after prolonged freezer storage. The urine HGFIN-to-creatinine ratio compared favorably with the urine neutrophil gelatinase-associated lipocalin (NGAL)-to-creatinine ratio (both measured by commercial enzyme-linked immunosorbent assays (ELISAs)), and correlated strongly with proteinuria, but weakly with estimated glomerular filtration rate and serum creatinine. Thus, HGFIN may be a biomarker of progressive kidney disease
Stochastic Behavior of Effective Field Theories Across Threshold
We explore how the existence of a field with a heavy mass influences the low
energy dynamics of a quantum field with a light mass by expounding the
stochastic characters of their interactions which take on the form of
fluctuations in the number of (heavy field) particles created at the threshold,
and dissipation in the dynamics of the light fields, arising from the
backreaction of produced heavy particles. We claim that the stochastic nature
of effective field theories is intrinsic, in that dissipation and fluctuations
are present both above and below the threshold. Stochasticity builds up
exponentially quickly as the heavy threshold is approached from below, becoming
dominant once the threshold is crossed. But it also exists below the threshold
and is in principle detectable, albeit strongly suppressed at low energies. The
results derived here can be used to give a quantitative definition of the
`effectiveness' of a theory in terms of the relative weight of the
deterministic versus the stochastic behavior at different energy scales.Comment: 32 pages, Latex, no figure
Event extraction of bacteria biotopes: a knowledge-intensive NLP-based approach
International audienceBackground: Bacteria biotopes cover a wide range of diverse habitats including animal and plant hosts, natural, medical and industrial environments. The high volume of publications in the microbiology domain provides a rich source of up-to-date information on bacteria biotopes. This information, as found in scientific articles, is expressed in natural language and is rarely available in a structured format, such as a database. This information is of great importance for fundamental research and microbiology applications (e.g., medicine, agronomy, food, bioenergy). The automatic extraction of this information from texts will provide a great benefit to the field
Comparison of the protein-coding genomes of three deep-sea, sulfur-oxidising bacteria: “Candidatus Ruthia magnifica”, “Candidatus Vesicomyosocius okutanii” and Thiomicrospira crunogena
Abstract Objective “ Candidatus Ruthia magnifica”, “Candidatus Vesicomyosocius okutanii” and Thiomicrospira crunogena are all sulfur-oxidising bacteria found in deep-sea vent environments. Recent research suggests that the two symbiotic organisms, “Candidatus R. magnifica” and “Candidatus V. okutanii”, may share common ancestry with the autonomously living species T. crunogena. We used comparative genomics to examine the genome-wide protein-coding content of all three species to explore their similarities. In particular, we used the OrthoMCL algorithm to sort proteins into groups of putative orthologs on the basis of sequence similarity. Results The OrthoMCL inflation parameter was tuned using biological criteria. Using the tuned value, OrthoMCL delimited 1070 protein groups. 63.5% of these groups contained one protein from each species. Two groups contained duplicate protein copies from all three species. 123 groups were unique to T. crunogena and ten groups included multiple copies of T. crunogena proteins but only single copies from the other species. “Candidatus R. magnifica” had one unique group, and had multiple copies in one group where the other species had a single copy. There were no groups unique to “Candidatus V. okutanii”, and no groups in which there were multiple “Candidatus V. okutanii” proteins but only single proteins from the other species. Results align with previous suggestions that all three species share a common ancestor. However this is not definitive evidence to make taxonomic conclusions and the possibility of horizontal gene transfer was not investigated. Methodologically, the tuning of the OrthoMCL inflation parameter using biological criteria provides further methods to refine the OrthoMCL procedure
Curcumin activates the p38MPAK-HSP25 pathway in vitro but fails to attenuate diabetic nephropathy in DBA2J mice despite urinary clearance documented by HPLC
<p>Abstract</p> <p>Background</p> <p>Curcumin has anti-inflammatory, anti-oxidant, and anti-proliferative properties, and depending upon the experimental circumstances, may be pro- or anti-apoptotic. Many of these biological actions could ameliorate diabetic nephropathy.</p> <p>Methods/Design</p> <p>Mouse podocytes, cultured in basal or high glucose conditions, underwent acute exposure to curcumin. Western blots for p38-MAPK, COX-2 and cleaved caspase-3; isoelectric focusing for HSP25 phosphorylation; and DNase I assays for F- to G- actin cleavage were performed for <it>in vitro </it>analyses. <it>In vivo </it>studies examined the effects of dietary curcumin on the development of diabetic nephropathy in streptozotocin (Stz)-induced diabetes in DBA2J mice. Urinary albumin to creatinine ratios were obtained, high performance liquid chromatography was performed for urinary curcuminoid measurements, and Western blots for p38-MAPK and total HSP25 were performed.</p> <p>Results</p> <p>Curcumin enhanced the phosphorylation of both p38MAPK and downstream HSP25; inhibited COX-2; induced a trend towards attenuation of F- to G-actin cleavage; and dramatically inhibited the activation of caspase-3 in <it>vitro</it>. In curcumin-treated DBA2J mice with Stz-diabetes, HPLC measurements confirmed the presence of urinary curcuminoid. Nevertheless, dietary provision of curcumin either before or after the induction of diabetes failed to attenuate albuminuria.</p> <p>Conclusions</p> <p>Apart from species, strain, early differences in glycemic control, and/or dosing effects, the failure to modulate albuminuria may have been due to a decrement in renal HSP25 or stimulation of the 12/15 lipoxygenase pathway in DBA2J mice fed curcumin. In addition, these studies suggest that timed urine collections may be useful for monitoring curcumin dosing and renal pharmacodynamic effects.</p
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