3,015 research outputs found
Comparison between S. T. radar and in situ balloon measurements
A campaign for simultaneous in situ and remote observation of both troposphere and stratosphere took place near Aire-sur-l'Adour (in southeastern France) on May 4, 1984. The aim of this campaign was a better understanding of the physics of radar echoes. The backscattered signal obtained with a stratosphere-troposphere radar both at the vertical and 15 deg. off vertical is compared with the velocity and temperature measurements made in the same region (about 10 km north of the radar site) by balloon-borne ionic anenometers and temperature sensors. In situ measurements clearly indicate that the temperature fluctuations are not always consistent with the standard turbulent theory. Nevertheless, the assumptions generally made (isotropy and turbulent field in k) and the classical formulation so derived for radar reflectivity are able to reproduce the shape of the radar return power profiles in oblique directions. Another significant result is the confirmation of the role played by the atmospheric stratification in the vertical echo power. It is important to develop these simultaneous in situ and remote experiments for a better description of the dynamical and thermal structure of the atmosphere and for a better understanding of the mechanisms governing clear-air radar reflectivity
Multi-locus barcoding confirms the occurrence of Elegant Tern in Western Europe
We are very grateful to the following people who helped in various ways with sample collection: JĂ©rome Fuchs and Eric Pasquet (National Museum of Natural History, Paris), Sharon M. Birks (Burke Museum of Naturel History of Seattle), Charlotte Francesiaz, Benjamin Vollot and Gilles Balança (Sandwich Tern, France), Charles Collins (Elegant Tern, USA), Arnaud Lenoble (Royal Tern, Guadeloupe), Lorien Pichegru (Crested Tern, South Africa), Abdulmaula Hamza (Lesser Crested Tern, Libya) and Clive Barlow (The Gambia). Marcio Efe and Eli Bridge helped with genotyping and shared unpublished sequences. We thank Juan Antonio GĂłmez for advice and Miguel ChardĂ and Francisco Javier GarcĂa-Gans for field assistance in Valencia (Spain). Mathias Grandpierre (SociĂ©tĂ© pour lâEtude et lâAmĂ©nagement de la Nature dans le Sud-Ouest) helped with fieldwork at the Banc dâArguin (France). All the experiments comply with the current laws of the country in which they were performed.Peer reviewedPostprin
Heavy quark(onium) at LHC: the statistical hadronization case
We discuss the production of charmonium in nuclear collisions within the
framework of the statistical hadronization model. We demonstrate that the model
reproduces very well the availble data at RHIC. We provide predictions for the
LHC energy where, dependently on the charm production cross section, a
dramatically different behaviour of charmonium production as a function of
centrality might be expected. We discuss also the case in elementary
collisions, where clearly the statistical model does not reproduce the
measurements.Comment: 8 pages, 5 figures; proceeding of SQM09, Buzios, Brazil, to be
published in J. Phys.
Kaon production at subthreshold and threshold energies
We summarize what we have learnt about the kaon production in nucleus-nucleus
collisions in the last decade. We will address three questions: a) Is the
production sensitive to the nuclear equation of state? b) How can it happen
that at the same excess energy the same number of and are produced
in heavy ion collisions although the elementary cross section in pp collisions
differs by orders of magnitudes? and c) Why kaons don't flow?Comment: 5 pages, 4 figures, contribution to Strange Quark Matter 200
Effects of momentum conservation on the analysis of anisotropic flow
We present a general method for taking into account correlations due to
momentum conservation in the analysis of anisotropic flow, either by using the
two-particle correlation method or the standard flow vector method. In the
latter, the correlation between the particle and the flow vector is either
corrected through a redefinition (shift) of the flow vector, or subtracted
explicitly from the observed flow coefficient. In addition, momentum
conservation contributes to the reaction plane resolution. Momentum
conservation mostly affects the first harmonic in azimuthal distributions,
i.e., directed flow. It also modifies higher harmonics, for instance elliptic
flow, when they are measured with respect to a first harmonic event plane such
as one determined with the standard transverse momentum method. Our method is
illustrated by application to NA49 data on pion directed flow.Comment: RevTeX 4, 10 pages, 1 eps figure. Version accepted for publication in
Phys Rev
Intersubband decay of 1-D exciton resonances in carbon nanotubes
We have studied intersubband decay of E22 excitons in semiconducting carbon
nanotubes experimentally and theoretically. Photoluminescence excitation line
widths of semiconducting nanotubes with chiral indicess (n, m) can be mapped
onto a connectivity grid with curves of constant (n-m) and (2n+m). Moreover,
the global behavior of E22 linewidths is best characterized by a strong
increase with energy irrespective of their (n-m) mod(3)= \pm 1 family
affiliation. Solution of the Bethe-Salpeter equations shows that the E22
linewidths are dominated by phonon assisted coupling to higher momentum states
of the E11 and E12 exciton bands. The calculations also suggest that the
branching ratio for decay into exciton bands vs free carrier bands,
respectively is about 10:1.Comment: 4 pages, 4 figure
Differential directed flow in Au+Au collisions
We present experimental data on directed flow in semi-central Au+Au
collisions at incident energies from 90 to 400 A MeV. For the first time for
this energy domain, the data are presented in a transverse momentum
differential way. We study the first order Fourier coefficient v1 for different
particle species and establish a gradual change of its patterns as a function
of incident energy and for different regions in rapidity.Comment: 5 pages, Latex, 5 eps figures, accepted for publication in Phys. Rev.
C (Rapid Communications). Data files available at
http://www-linux.gsi.de/~andronic/fopi/v1.htm
Temperature distribution in selective laser-tissue interaction
Selective photothermal interaction using dye enhancement has proven to be effective in minimizing surrounding tissue damage and delivering energy to target tissue. During laser irradiation, the process of photon absorption and thermal energy diffusion in the target tissue and its surrounding tissue are crucial. Such information allows the selection of proper operating parameters such as dye concentrations, laser power, and exposure time for optimal therapeutic effect. Combining the Monte Carlo method for energy absorption and the finite difference method for heat diffusion, the temperature distributions in target tissue and surrounding tissue in dye enhanced laser photothermal interaction are obtained. Different tissue configurations and dye enhancement are used in the simulation, and different incident beam sizes are also used to determine optimum beam sizes for various tissue configurations. Our results show that the algorithm developed in this study could predict the thermal outcome of laser irradiation. Our simulation indicates that with appropriate absorption enhancement of the target tissue, the temperature in the target tissue and in the surrounding tissue can be effectively controlled. This method can be used for optimization of lesion treatment using laser photothermal interactions. It may also provide guidance for laser immunotherapy in cancer treatment, since the immunological responses are believed to be related to tissue temperature changes
Directed flow in Au+Au, Xe+CsI and Ni+Ni collisions and the nuclear equation of state
We present new experimental data on directed flow in collisions of Au+Au,
Xe+CsI and Ni+Ni at incident energies from 90 to 400A MeV. We study the
centrality and system dependence of integral and differential directed flow for
particles selected according to charge. All the features of the experimental
data are compared with Isospin Quantum Molecular Dynamics (IQMD) model
calculations in an attempt to extract information about the nuclear matter
equation of state (EoS). We show that the combination of rapidity and
transverse momentum analysis of directed flow allow to disentangle various
parametrizations in the model. At 400A MeV, a soft EoS with momentum dependent
interactions is best suited to explain the experimental data in Au+Au and
Xe+CsI, but in case of Ni+Ni the model underpredicts flow for any EoS. At 90A
MeV incident beam energy, none of the IQMD parametrizations studied here is
able to consistently explain the experimental data.Comment: RevTeX, 20 pages, 30 eps figures, accepted for publication in Phys.
Rev. C. Data files available at http://www.gsi.de/~fopiwww/pub
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