33,842 research outputs found
Rotating Leaks in the Stadium Billiard
The open stadium billiard has a survival probability, , that depends on
the rate of escape of particles through the leak. It is known that the decay of
is exponential early in time while for long times the decay follows a
power law. In this work we investigate an open stadium billiard in which the
leak is free to rotate around the boundary of the stadium at a constant
velocity, . It is found that is very sensitive to . For
certain values is purely exponential while for other values the
power law behaviour at long times persists. We identify three ranges of
values corresponding to three different responses of . It is
shown that these variations in are due to the interaction of the moving
leak with Marginally Unstable Periodic Orbits (MUPOs)
TagF-mediated repression of bacterial type VI secretion systems involves a direct interaction with the cytoplasmic protein Fha
The bacterial type VI secretion system (T6SS) delivers effectors into eukaryotic host cells or toxins into bacterial competitor for survival and fitness. The T6SS is positively regulated by the threonine phosphorylation pathway (TPP) and negatively by the T6SS-accessory protein TagF. Here, we studied the mechanisms underlying TagF-mediated T6SS repression in two distinct bacterial pathogens, Agrobacterium tumefaciens and Pseudomonas aeruginosa. We found that in A. tumefaciens, T6SS toxin secretion and T6SS-dependent antibacterial activity are suppressed by a two-domain chimeric protein consisting of TagF and PppA, a putative phosphatase. Remarkably, this TagF domain is sufficient to post-translationally repress the T6SS, and this inhibition is independent of TPP. This repression requires interaction with a cytoplasmic protein, Fha, critical for activating T6SS assembly. In P. aeruginosa, PppA and TagF are two distinct proteins that repress T6SS in a TPP-dependent and -independent pathways, respectively. P. aeruginosa TagF interacts with Fha1, suggesting that formation of this complex represents a conserved TagF-mediated regulatory mechanism. Using TagF variants with substitutions of conserved amino acid residues at predicted protein-protein interaction interfaces, we uncovered evidence that the TagF-Fha interaction is critical for TagF-mediated T6SS repression in both bacteria. TagF inhibits T6SS without affecting T6SS protein abundance in A. tumefaciens, but TagF overexpression reduces the protein levels of all analyzed T6SS components in P. aeruginosa. Our results indicate that TagF interacts with Fha, which in turn could impact different stages of T6SS assembly in different bacteria, possibly reflecting an evolutionary divergence in T6SS control
Collider Inclusive Jet Data and the Gluon Distribution
Inclusive jet production data are important for constraining the gluon
distribution in the global QCD analysis of parton distribution functions. With
the addition of recent CDF and D0 Run II jet data, we study a number of issues
that play a role in determining the up-to-date gluon distribution and its
uncertainty, and produce a new set of parton distributions that make use of
that data. We present in detail the general procedures used to study the
compatibility between new data sets and the previous body of data used in a
global fit. We introduce a new method in which the Hessian matrix for
uncertainties is ``rediagonalized'' to obtain eigenvector sets that
conveniently characterize the uncertainty of a particular observable.Comment: Published versio
New Production Mechanism of Neutral Higgs Bosons with Right scalar tau neutrino as the LSP
Motived by the neutrino oscillation data, we consider the lightest tau
sneutrino (which is mostly the right tau sneutrino) to be
the lightest supersymmetric particle (LSP) in the framework of the minimal
supersymmetric Standard Model. Both the standard and the non-standard trilinear
scalar coupling terms are included for the right tau sneutrino interactions.
The decay branching ratio of
can become so large that the production rate of the lightest neutral Higgs
boson () can be largely enhanced at electron or hadron colliders, either
from the direct production of or from the decay of
charginos, neutralinos, sleptons, and the cascade decay of squarks and gluinos,
etc. Furthermore, because of the small LSP annihilation rate, can be a good candidate for cold dark matter.Comment: 11 pages, RevTex, 3 eps figures. We clarify the theoretical framework
of this study, with a note added in the end, and correct an equation, with
updated figure
Fluctuations of Entropy Production in Partially Masked Electric Circuits: Theoretical Analysis
In this work we perform theoretical analysis about a coupled RC circuit with
constant driven currents. Starting from stochastic differential equations,
where voltages are subject to thermal noises, we derive time-correlation
functions, steady-state distributions and transition probabilities of the
system. The validity of the fluctuation theorem (FT) is examined for scenarios
with complete and incomplete descriptions.Comment: 4 pages, 1 figur
Examining the Effectiveness of Relationship Marketing Strategies on Medical Tourism
Medical tourism is one of the fastest-growing industries in the world as many patients are looking to access healthcare services that are not available to them in their home countries. Many hospitals and healthcare centers are now offering numerous products and services in order to fully reap the benefits from it. However, little research which examines the effects of relationship marketing on the medical tourism exists. Hence, the aims of this study are to: (1) examine the relationship between the relationship marketing strategies and the medical tourism industry; and (2) help medical tourism operators to identify some of the key issues that exist within the industry. In-depth interviews were conducted with ten senior Taiwanese tour guides who had extensive experience in dealing with the medical tourism industry. The results indicate that relationship marketing was one of the crucial factors which had an impact on the willingness of tour guides to make necessary travel arrangements for medical tourists. The environment of health examination center, the ability of its doctors to diagnose a patient’s condition, and the professional image of its doctors could also affect the effectiveness of the relationship marketing on medical tourism as well as the efforts in arranging a follow-up visit to the health examination center. The findings can provide senior executives of health examination centers and travel agencies with a more realistic insight in dealing with issues and challenges arising from the medical tourism
Chemical Abundances For Evolved Stars In M5: Lithium Through Thorium
We present analysis of high-resolution spectra of a sample of stars in the globular cluster M5 (NGC 5904). The sample includes stars from the red giant branch (RGB; seven stars), the red horizontal branch (two stars), and the asymptotic giant branch (AGB; eight stars), with effective temperatures ranging from 4000 K to 6100 K. Spectra were obtained with the HIRES spectrometer on the Keck I telescope, with a wavelength coverage from 3700 angstrom to 7950 angstrom for the HB and AGB sample, and 5300 angstrom to 7600 angstrom for the majority of the RGB sample. We find offsets of some abundance ratios between the AGB and the RGB branches. However, these discrepancies appear to be due to analysis effects, and indicate that caution must be exerted when directly comparing abundance ratios between different evolutionary branches. We find the expected signatures of pollution from material enriched in the products of the hot hydrogen burning cycles such as the CNO, Ne-Na, and Mg-Al cycles, but no significant differences within these signatures among the three stellar evolutionary branches especially when considering the analysis offsets. We are also able to measure an assortment of neutron-capture element abundances, from Sr to Th, in the cluster. We find that the neutron-capture signature for all stars is the same, and shows a predominately r-process origin. However, we also see evidence of a small but consistent extra s-process signature that is not tied to the light-element variations, pointing to a pre-enrichment of this material in the protocluster gas.National Science Foundation AST-0802292NSF AST-0406988, AST-0607770, AST-0607482DFGW. M. Keck FoundationAstronom
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