58,446 research outputs found
Empirical Parameterization of Nucleon-Nucleon Elastic Scattering Amplitude at High Beam Momenta for Glauber Calculations and Monte Carlo Simulations
A parameterization of the nucleon-nucleon elastic scattering amplitude is
needed for future experiments with nucleon and nuclear beams in the beam
momentum range of 2 -- 50 GeV/c/nucleon. There are many parameterizations of
the amplitude at 25--50 GeV/c, and at 5 GeV/c. Our
paper is aimed to cover the range between 5 -- 50 GeV/c.
The amplitude is used in Glauber calculations of various cross sections and
Monte Carlo simulations of nucleon-nucleon scatterings. Usually, the
differential nucleon-nucleon elastic scattering cross sections are described by
an exponential expression. Corresponding experimental data on interactions
at 0.005 (GeV/c) and 0.125 (GeV/c) have been fit. We
propose formulae to approximate the beam momentum dependence of these
parameters in the momentum range considered. The same was done for
interactions at 0.5 (GeV/c). Expressions for the momentum
dependence of the total and elastic cross sections, and the ratio of real to
imaginary parts of the amplitude at zero momentum transfer are also given for
and collisions. These results are sufficient for a first
approximation of the Glauber calculations. For more exact calculations we fit
the data at 0.005 (GeV/c) without restrictions on the maximum value
of using an expression based on two coherent exponential. The parameters
of the fits are found for the beam momentum range 2 -- 50 GeV/c.Comment: 14 pages, 10 figure
SDF1 Gene Variation Is Associated with Circulating SDF1 alpha Level and Endothelial Progenitor Cell Number-The Bruneck Study
BACKGROUND: Stromal cell-derived factor-1 (SDF1) and its receptor CXC chemokine receptor 4 (CXCR4) play a critical role in progenitor cell homing, mobilization and differentiation. It would be interesting to assess the predictive value of SDF-1alpha level for EPC number, and to ascertain whether there is a relationship between SDF1 gene variation, plasma SDF-1alpha level, and the number and function of circulating EPCs. We also tested whether EPC number and function was related to CXCR4 gene variation.
METHODOLOGY AND PRINCIPAL FINDINGS: We genotyped a cohort of individuals who participated in the Bruneck Study for single nucleotide polymorphisms (SNPs) in the SDF1 and CXCR4 genes, and measured blood SDF1alpha level as well as EPC number and function. SDF1alpha levels were correlated with age, gender, alcohol consumption, circulating reticulocyte numbers, and concentrations of matrix metalloproteinase-9, C-reactive protein, cystatin C, fibrinogen and homocytein. In blood samples taken in 2005, EPC number was inversely associated with SDF1alpha level (p<0.001). EPC number in 2005 was also inversely associated with SDF1alpha level in 2000 (p = 0.009), suggesting a predictive value of plasma SDF1alpha level for EPC number. There was an association between the SDF1 gene rs2297630 SNP A/A genotype, increased SDF1alpha level (p = 0.002) and lower EPC number (p = 0.006).
CONCLUSIONS: Our data indicate that a SDF1 gene variation (rs2297630) has an influence on SDF1alpha level and circulating EPC number, and that plasma SDF1alpha level is a predictor of EPC number
Web service management system for bioinformatics research: a case study.
In this paper, we present a case study of the design and development of a Web Service management system for bioinformatics research. The described system is a prototype that provides a complete solution to manage the entire life cycle of Web services in bioinformatics domain, which include semantic service description, service discovery, service selection, service composition, service execution, and service result presentation. A challenging issue we encountered is to provide the system capability to assist users to select the "right" service based on not only functionality but also properties such as reliability, performance, and analysis quality. As a solution, we used both bioinformatics and service ontology to provide these two types of service descriptions. A service selection algorithm based on skyline query algorithm is proposed to provide users with a short list of candidates of the \best" service. The evaluation results demonstrate the eciency and
scalability of the service selection algorithm. Finally, the important lessons we learned are summarized and remaining challenging issues are discussed as possible future research directions
Schottky barrier and contact resistance of InSb nanowire field effect transistors
Understanding of the electrical contact properties of semiconductor nanowire
(NW) field effect transistors (FETs) plays a crucial role in employing
semiconducting NWs as building blocks for future nanoelectronic devices and in
the study of fundamental physics problems. Here, we report on a study of the
contact properties of Ti/Au, a widely used contact metal combination, to
individual InSb NWs via both two-probe and four-probe transport measurements.
We show that a Schottky barrier of height is
present at the metal-InSb NW interfaces and its effective height is gate
tunable. The contact resistance () in the InSb NWFETs is also
analyzed by magnetotransport measurements at low temperatures. It is found that
at on-state exhibits a pronounced magnetic field dependent
feature, namely it is increased strongly with increasing magnetic field after
an onset field . A qualitative picture that takes into account
magnetic depopulation of subbands in the NWs is provided to explain the
observation. Our results provide a solid experimental evidence for the presence
of a Schottky barrier at Ti/Au-InSb NW interfaces and can be used as a basis
for design and fabrication of novel InSb NW based nanoelectronic devices and
quantum devices.Comment: 12 pages, 4 figure
A Bjorken sum rule for semileptonic decays to ground and excited charmed baryon states
We derive a Bjorken sum rule for semileptonic decays to ground and
low-lying negative-parity excited charmed baryon states, in the heavy quark
limit. We discuss the restriction from this sum rule on form factors and
compare it with some models.Comment: 10 pages, RevTex, no figure, Alberta Thy--26--9
Morphological characterization of shocked porous material
Morphological measures are introduced to probe the complex procedure of shock
wave reaction on porous material. They characterize the geometry and topology
of the pixelized map of a state variable like the temperature. Relevance of
them to thermodynamical properties of material is revealed and various
experimental conditions are simulated. Numerical results indicate that, the
shock wave reaction results in a complicated sequence of compressions and
rarefactions in porous material. The increasing rate of the total fractional
white area roughly gives the velocity of a compressive-wave-series.
When a velocity is mentioned, the corresponding threshold contour-level of
the state variable, like the temperature, should also be stated. When the
threshold contour-level increases, becomes smaller. The area increases
parabolically with time during the initial period. The curve goes
back to be linear in the following three cases: (i) when the porosity
approaches 1, (ii) when the initial shock becomes stronger, (iii) when the
contour-level approaches the minimum value of the state variable. The area with
high-temperature may continue to increase even after the early
compressive-waves have arrived at the downstream free surface and some
rarefactive-waves have come back into the target body. In the case of energetic
material ... (see the full text)Comment: 3 figures in JPG forma
Hyperon polarization in e^-p --> e^-HK with polarized electron beams
We apply the picture proposed in a recent Letter for transverse hyperon
polarization in unpolarized hadron-hadron collisions to the exclusive process
e^-p --> e^-HK such as e^-p-->e^-\Lambda K^+, e^-p --> e^-\Sigma^+ K^0, or
e^-p--> e^-\Sigma^0 K^+, or the similar process e^-p\to e^-n\pi^+ with
longitudinally polarized electron beams. We present the predictions for the
longitudinal polarizations of the hyperons or neutron in these reactions, which
can be used as further tests of the picture.Comment: 15 pages, 2 figures. submitted to Phys. Rev.
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