4,369 research outputs found
pp Elastic Scattering at LHC in a Nucleon-Structure Model
We predict pp elastic differential cross sections at LHC at c.m. energy 14
TeV and momentum transfer range |t| = 0 - 10 GeV*2 in a nucleon-structure
model. In this model, the nucleon has an outer cloud of quark-antiquark
condensed ground state, an inner shell of topological baryonic charge (r ~
0.44F) probed by the vector meson omega, and a central quark-bag (r ~ 0.2F)
containing valence quarks. We also predict elastic differential cross section
in the Coulomb-hadronic interference region. Large |t| elastic scattering in
this model arises from valence quark-quark scattering, which is taken to be due
to the hard-pomeron (BFKL pomeron with next to leading order corrections). We
present results of taking into account multiple hard-pomeron exchanges, i.e.
unitarity corrections. Finally, we compare our prediction of pp elastic
differential cross section at LHC with the predictions of various other models.
Precise measurement of pp elastic differential cross section at LHC by the
TOTEM group in the |t| region 0 - 5 GeV*2 will be able to distinguish between
these models.Comment: To be published in the Proceedings of the 12th International
Conference on Elastic and Diffractive Scattering, DESY, Hamburg. Presented by
M. M. Islam, May 200
Socio-technical paths and crossings in business development
In this paper an evolutionary model of business development is proposed, which links cooperationbetween organizations and their exchanges to path dependence and crossings.While the concept of path dependence restricts action to the exploitation of the existing path, theconcept of crossings emphasizes that within existing structures there are opportunities to take an otherpath. In a case study, over a period of twelve years the business development of a firm and itsevolving network relations are described. To find out if a firm can change is taken path, the conceptsof path dependence and crossings are explored along the cycle of development
Statistical analysis for thermometric sensors test program final report
Statistical models for regression analysis of thermometric sensor
Simulations of the last interglacial and the subsequent glacial inception with the Planet Simulator
International audienceThe Planet Simulator was used to perform equilibrium simulations of the Eemian interglacial at 125 kyBP and the glacial inception at 115 kyBP. Additionally, an accelerated transient simulation of that interval was performed. During this period the changes of Earth's orbital parameters led to a reduction of summer insolation in the northern latitudes. The model has been run in different configurations in order to evaluate the influence of the individual sub-models. The strongest reaction on the insolation change was observed when the atmosphere was coupled with all available sub-systems: a mixed-layer ocean and a sea-ice model as well as a vegetation model. In the simulations representing the interglacial, the near-surface temperature in northern latitudes is higher compared to the preindustrial reference run and almost no perennial snow cover occurs. In the run for the glacial inception, wide areas in mid and high northern latitudes show negative temperature anomalies and wide areas are covered by snow or ice. The transient simulation shows that snow volume starts to increase after summer insolation has fallen below a critical value. The main reason for the beginning glaciation is the locally reduced (summer) temperature as a consequence of reduced summer insolation. Therefore, a larger fraction of precipitation falls as snow and less snow can melt. That mechanism is amplified by the snow-albedo-feedback
Magnetic interaction of Co ions near the {10\bar{1}0} ZnO surface
Co-doped ZnO is the prototypical dilute magnetic oxide showing many of the
characteristics of ferromagnetism. The microscopic origin of the long range
order however remains elusive, since the conventional mechanisms for the
magnetic interaction, such as super-exchange and double exchange, fail either
at the fundamental or at a quantitative level. Intriguingly, there is a growing
evidence that defects both in point-like or extended form play a fundamental
role in driving the magnetic order. Here we explore one of such possibilities
by performing {\it ab initio} density functional theory calculations for the
magnetic interaction of Co ions at or near a ZnO \{100\} surface. We
find that extended surface states can hybridize with the -levels of Co and
efficiently mediate the magnetic order, although such a mechanism is effective
only for ions placed in the first few atomic planes near the surface. We also
find that the magnetic anisotropy changes at the surface from an hard-axis
easy-plane to an easy axis, with an associated increase of its magnitude. We
then conclude that clusters with high densities of surfacial Co ions may
display blocking temperatures much higher than in the bulk
Smooth tail index estimation
Both parametric distribution functions appearing in extreme value theory -
the generalized extreme value distribution and the generalized Pareto
distribution - have log-concave densities if the extreme value index gamma is
in [-1,0]. Replacing the order statistics in tail index estimators by their
corresponding quantiles from the distribution function that is based on the
estimated log-concave density leads to novel smooth quantile and tail index
estimators. These new estimators aim at estimating the tail index especially in
small samples. Acting as a smoother of the empirical distribution function, the
log-concave distribution function estimator reduces estimation variability to a
much greater extent than it introduces bias. As a consequence, Monte Carlo
simulations demonstrate that the smoothed version of the estimators are well
superior to their non-smoothed counterparts, in terms of mean squared error.Comment: 17 pages, 5 figures. Slightly changed Pickand's estimator, added some
more introduction and discussio
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