4,479 research outputs found
The Blueshift Of Civ Broad Emission Line In Qsos
For the sample from Ge et al. of 87 low- Palomar--Green (PG) quasi-stellar
objects (QSOs) and 130 high- QSOs () with \hb-based single-epoch
supermassive black hole (SMBH) masses, we performed a uniform decomposition of
the \civ\ 1549 broad-line profile. Based on the rest frame defined by
the \oiii 5007 narrow emission line, a medium-strong positive
correlation is found between the \civ\ blueshift and the luminosity at 5100\AA\
or the Eddington ratio \leddR. A medium-strong negative relationship is found
between the \civ\ blueshift and \civ\ equivalent width. These results support
the postulation where the radiation pressure may be the driver of \civ\
blueshift. There is a medium strong correlation between the mass ratio of
\civ-based to \hb-based \mbh and the \civ\ blueshift, which indicates that
the bias for \civ-based \mbh is affected by the \civ\ profile.Comment: 18 pages, 8 figures, Accepted for publication in A
Fermionic Zero Mode and String Creation between D4-Branes at Angles
We study the creation of a fundamental string between D4-branes at angles in
string theory. It is shown that part of the one-loop potential of
open string changes its sign due to the change of fermionic zero-mode vacua
when the branes cross each other. As a result the effective potential is
independent of the angles when supersymmetry is partially unbroken, and leads
to a consistent picture that a fundamental string is created in the process. We
also discuss the s-rule in the configuration. The same result is obtained from
the one-loop potential for the orthogonal D4-branes with non-zero field
strength. The result is also confirmed from the tension obtained by deforming
the Chern-Simons term on one D4-brane, which is induced by another tilted
D4-brane.Comment: 10 pages, Late
State-resolved rotational cross sections and thermal rate coefficients for ortho-/para-H2+HD at low temperatures and HD+HD elastic scattering
Results for quantum mechanical calculations of the integral cross sections
and corresponding thermal rate coefficients for para-/ortho-H2+HD collisions
are presented. Because of significant astrophysical interest in regard to the
cooling of primodial gas the low temperature limit of para-/ortho-H2+HD is
investigated. Sharp resonances in the rotational state-resolved cross sections
have been calculated at low energies. These resonances are important and
significantly contribute to the corresponding rotational state-resolved thermal
rate coefficients, particularly at low temperatures, that is less than K. Additionally in this work, the cross sections for the elastic HD+HD
collision have also been calculated. We obtained quite satisfactory agreement
with the results of other theoretical works and experiments.Comment: 16 pages, 5 figures, additional results include
Population Synthesis of Hot Subdwarfs: A Parameter Study
Binaries that contain a hot subdwarf (sdB) star and a main sequence companion
may have interacted in the past. This binary population has historically helped
determine our understanding of binary stellar evolution. We have computed a
grid of binary population synthesis models using different assumptions about
the minimum core mass for helium ignition, the envelope binding energy, the
common envelope ejection efficiency, the amount of mass and angular momentum
lost during stable mass transfer, and the criteria for stable mass transfer on
the red giant branch and in the Hertzsprung gap. These parameters separately
and together can significantly change the entire predicted population of sdBs.
Nonetheless, several different parameter sets can reproduce the observed
subpopulation of sdB + white dwarf and sdB + M dwarf binaries, which has been
used to constrain these parameters in previous studies. The period distribution
of sdB + early F dwarf binaries offers a better test of different mass transfer
scenarios for stars that fill their Roche lobes on the red giant branch.Comment: 21 pages, 15 figures, accepted for publication in Ap
Cryo-EM model of the bullet-shaped vesicular stomatitis virus.
Vesicular stomatitis virus (VSV) is a bullet-shaped rhabdovirus and a model system of negative-strand RNA viruses. Through direct visualization by means of cryo-electron microscopy, we show that each virion contains two nested, left-handed helices: an outer helix of matrix protein M and an inner helix of nucleoprotein N and RNA. M has a hub domain with four contact sites that link to neighboring M and N subunits, providing rigidity by clamping adjacent turns of the nucleocapsid. Side-by-side interactions between neighboring N subunits are critical for the nucleocapsid to form a bullet shape, and structure-based mutagenesis results support this description. Together, our data suggest a mechanism of VSV assembly in which the nucleocapsid spirals from the tip to become the helical trunk, both subsequently framed and rigidified by the M layer
In an in vitro model of human tuberculosis, monocyte-microglial networks regulate matrix metalloproteinase-1 and -3 gene expression and secretion via a p38 mitogen activated protein kinase-dependent pathway.
BACKGROUND: Tuberculosis (TB) of the central nervous system (CNS) is characterized by extensive tissue inflammation, driven by molecules that cleave extracellular matrix such as matrix metalloproteinase (MMP)-1 and MMP-3. However, relatively little is known about the regulation of these MMPs in the CNS. METHODS: Using a cellular model of CNS TB, we stimulated a human microglial cell line (CHME3) with conditioned medium from Mycobacterium tuberculosis-infected primary human monocytes (CoMTb). MMP-1 and MMP-3 secretion was detected using ELISAs confirmed with casein zymography or western blotting. Key results of a phospho-array profile that detects a wide range of kinase activity were confirmed with phospho-Western blotting. Chemical inhibition (SB203580) of microglial cells allowed investigation of expression and secretion of MMP-1 and MMP-3. Finally we used promoter reporter assays employing full length and MMP-3 promoter deletion constructs. Student's t-test was used for comparison of continuous variables and multiple intervention experiments were compared by one-way ANOVA with Tukey's correction for multiple pairwise comparisons. RESULTS: CoMTb up-regulated microglial MMP-1 and MMP-3 secretion in a dose- and time-dependent manner. The phospho-array profiling showed that the major increase in kinase activity due to CoMTb stimulation was in p38 mitogen activated protein kinase (MAPK), principally the α and γ subunits. p38 phosphorylation was detected at 15 minutes, with a second peak of activity at 120 minutes. High basal extracellular signal-regulated kinase activity was further increased by CoMTb. Secretion and expression of MMP-1 and MMP-3 were both p38 dependent. CoMTb stimulation of full length and MMP-3 promoter deletion constructs demonstrated up-regulation of activity in the wild type but a suppression site between -2183 and -1612 bp. CONCLUSIONS: Monocyte-microglial network-dependent MMP-1 and MMP-3 gene expression and secretion are dependent upon p38 MAPK in tuberculosis. p38 is therefore a potential target for adjuvant therapy in CNS TB
Active faulting controls bedform development on a deep-water fan
Tectonically controlled topography influences deep-water sedimentary systems. Using 3-D seismic reflection data from the Levant Basin, eastern Mediterranean Sea, we investigate the spatial and temporal evolution of bedforms on a deep-water fan cut by an active normal fault. In the footwall, the fan comprises cyclic steps and antidunes along its axial and external portions, respectively, which we interpret to result from the spatial variation in flow velocity due to the loss of confinement at the canyon mouth. Conversely, in the hanging wall, the seafloor is nearly featureless at seismic scale. Numerical modeling of turbidity currents shows that the fault triggers a hydraulic jump that suppresses the flow velocity downstream, which thus explains the lack of visible bedforms basinward. This study shows that the topography generated by active normal faulting controls the downslope evolution of turbidity currents and the associated bedforms and that seafloor geomorphology can be used to evince syn-tectonic deposition
The benefits of neighborhood racial diversity: Neighborhood factors and its association with increased physical activity in ACS patients
Regular physical activity reduces the risk of adverse events after an acute coronary syndrome (ACS) [1]. Physical activity level is influenced by neighborhood factors such as racial diversity in the general population [2] and [3], but the impact of neighborhood factors on physical activity after an ACS is unknown. We therefore prospectively evaluated the relationship of post-ACS physical activity assessed by continuous activity monitors with neighborhood characteristics, including ethnic density, income, female headed households, and racial diversity, in patients enrolled in the Prescription Use, Lifestyle, and Stress Evaluation (PULSE) Study.
We included 107 patients enrolled in the PULSE study from February 1, 2009 to June 30, who were monitored with an Actical® (Philips Respironics, Inc., Bend, Oregon) accelerometer device during the first 45 days following discharge from their ACS. For this analysis, physical activity level was operationalized as the mean maximum 6 min of activity during the day (M6m), which has previously been employed in studies of patients with chronic heart failure to summarize the patients' peak activity level [4] and [5]. Because the trajectory of physical activity is expected to change after hospital discharge, we calculated the M6m measure at 7, 14, 21, and 28 days post-discharge
Thermal Field Theory and Infinite Statistics
We construct a quantum thermal field theory for scalar particles in the case
of infinite statistics. The extension is provided by working out the Fock space
realization of a "quantum algebra", and by identifying the hamiltonian as the
energy operator. We examine the perturbative behavior of this theory and in
particular the possible extension of the KLN theorem, and argue that it appears
as a stable structure in a quantum field theory context.Comment: 25 pp, INLN 92/16, ENSLAPP-A-372/9
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