263 research outputs found
Semiclassical Theory of Coulomb Blockade Peak Heights in Chaotic Quantum Dots
We develop a semiclassical theory of Coulomb blockade peak heights in chaotic
quantum dots. Using Berry's conjecture, we calculate the peak height
distributions and the correlation functions. We demonstrate that the
corrections to the corresponding results of the standard statistical theory are
non-universal and can be expressed in terms of the classical periodic orbits of
the dot that are well coupled to the leads. The main effect is an oscillatory
dependence of the peak heights on any parameter which is varied; it is
substantial for both symmetric and asymmetric lead placement. Surprisingly,
these dynamical effects do not influence the full distribution of peak heights,
but are clearly seen in the correlation function or power spectrum. For
non-zero temperature, the correlation function obtained theoretically is in
good agreement with that measured experimentally.Comment: 5 color eps figure
Thrips species (Insecta: Thysanoptera) associated with flowers in a restinga fragment in northeastern Brazil
Classification of the Mediterranean lowland to submontane pine forest vegetation
Vegetation SurveyAim: Vegetation types of Mediterranean thermophilous pine forests dominated by
Pinus brutia, Pinus halepensis, Pinus pinaster and Pinus pinea were studied in various
areas. However, a comprehensive formal vegetation classification of these forests
based on a detailed data analysis has never been developed. Our aim is to provide
the first broad-scale classification of these pine forests based on a large data set of
vegetation plots.
Location: Southern Europe, North Africa, Levant, Anatolia, Crimea and the Caucasus.
Methods: We prepared a data set of European and Mediterranean pine forest vegetation
plots. We selected 7,277 plots dominated by the cold-sensitive Mediterranean
pine species Pinus brutia, Pinus halepensis, Pinus pinaster and Pinus pinea. We classified
these plots using TWINSPAN, interpreted the ecologically and biogeographically
homogeneous TWINSPAN clusters as alliances, and developed an expert system for
automatic vegetation classification at the class, order and alliance levels.
Results: We described Pinetea halepensis as a new class for the Mediterranean lowland
to submontane pine forests, included in the existing Pinetalia halepensis order,
and distinguished 12 alliances of native thermophilous pine forests, including four
newly described and three informal groups merging supposedly native stands and
old-established plantations. The main gradients in species composition reflect elevational
vegetation belts and the west–east, and partly north–south, biogeographical
differences. Both temperature and precipitation seasonality co-vary with these
gradients.
Conclusions: We provide the first formal classification at the order and alliance levels
for all the Mediterranean thermophilous pine forests based on vegetation-plot data.
This classification includes traditional syntaxa, which have been critically revised,
and a new class and four new alliances. We also outline a methodological workflow that might be useful for other vegetation classification syntheses. The expert system,
which is jointly based on pine dominance and species composition, is a tool for applying
this classification in research and nature conservation survey, monitoring and
managementinfo:eu-repo/semantics/publishedVersio
Characterization of typical and atypical enteropathogenic Escherichia coli (EPEC) strains of the classical O55 serogroup by RAPD analysis
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Projeto RiskBenefit4EU - uma estratégia para a avaliação de risco-benefício de alimentos em Portugal
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Membrana amniótica e pericárdio canino como curativos biológicos na preparação do leito receptor para enxertia cutânea autógena
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