1,329 research outputs found
Mise en ligne des IEP du groupe des chambres à bulles (hydrogène)
Nous nous proposons de décrire très brièvement le système de mise en ligne employé par le Groupe des Chambres à Bulles de Strasbourg. Cette opération a été décidée dans le but d'améliorer de façon sensible le rendement et de parfaire le système de mesures, sans toutefois augmenter notablement les frais de fonctionnement. Les « IEP » ont été connectés à un ordinateur IBM 1800 de 16 000 mots de mémoire. Cette mise en ligne est actuellement opérationnelle pour trois IEP. Le système, relativement complexe, permet l'instauration d'un dialogue assez élaboré entre l'ordinateur et les opérateurs de mesure, en utilisant des informations contenues sur des « cartes de scanning » . Des précautions particulières ont été prises afin que toute panne sur un canal (appareils de mesures, interface, périphériques de l'ordinateur) n'arrête pas le fonctionnement des autres appareils, et afin qu'en aucun cas une panne n'entraîne des pertes de mesures. Les premiers résultats d'exploitation montrent que la capacité de mesure du groupe a été sensiblement multipliée par deux
Modeling DNA Structure, Elasticity and Deformations at the Base-pair Level
We present a generic model for DNA at the base-pair level. We use a variant
of the Gay-Berne potential to represent the stacking energy between neighboring
base-pairs. The sugar-phosphate backbones are taken into account by semi-rigid
harmonic springs with a non-zero spring length. The competition of these two
interactions and the introduction of a simple geometrical constraint leads to a
stacked right-handed B-DNA-like conformation. The mapping of the presented
model to the Marko-Siggia and the Stack-of-Plates model enables us to optimize
the free model parameters so as to reproduce the experimentally known
observables such as persistence lengths, mean and mean squared base-pair step
parameters. For the optimized model parameters we measured the critical force
where the transition from B- to S-DNA occurs to be approximately . We
observe an overstretched S-DNA conformation with highly inclined bases that
partially preserves the stacking of successive base-pairs.Comment: 15 pages, 25 figures. submitted to PR
Validity domain and limitation of non-retarded Green's tensor for electromagnetic scattering at surfaces
Hard diffractive quarkonium hadroproduction at high energies
We present a study of heavy quarkonium production in hard diffractive process
by the Pomeron exchange for Tevatron and LHC energies. The numerical results
are computed using recent experimental determination of the diffractive parton
density functions in Pomeron and are corrected by unitarity corrections through
gap survival probability factor. We give predictions for single as well as
central diffractive ratios. These processes are sensitive to the gluon content
of the Pomeron at small Bjorken-x and may be particularly useful in studying
the small-x physics. They may also be a good place to test the different
available mechanisms for quarkonium production at hadron colliders.Comment: 7 pages, 3 figures, 1 table. Final version to be published in
European Physical Journal
Documento de consenso sobre el tratamiento antimicrobiano de las infecciones bacterianas odontogénicas
Las infecciones de la cavidad bucal son un problema de salud pública frecuente y motivo constante de prescripción
antibiótica; el 10% de los antibióticos se emplean para tratar este problema. Sin embargo, hasta la fecha son
pocos los estudios realizados para determinar su incidencia. Asímismo, su relación con ciertas enfermedades sistémicas
(cardiacas, endocrinas, etc...) confiere a estas patologías una importancia vital. A pesar de la reconocida
frecuencia e importancia de las infecciones odontogénicas, llama la atención la actual dispersión de criterio en
varios aspectos referentes a su clasificación, terminología y recomendaciones terapéuticas. El objetivo principal
de este documento, realizado con el consenso de especialistas en microbiología y odontología, es establecer unas
recomendaciones útiles para todos los profesionales implicados en el manejo clínico de estas patologías. Recibe
especial atención el aumento de la prevalencia de resistencias bacterianas observado durante los últimos años y,
en concreto, la proliferación de cepas productoras de betalactamasas. Otro factor causal importante de la aparición
de resistencias es la falta de cumplimiento terapéutico, en especial en lo que respecta a la dosis y a la duración
del tratamiento. Así pues, estas patologías constituyen un problema complejo cuyo abordaje requiere la instauración
de antimicrobianos de amplio espectro, con adecuados parámetros farmacocinéticos, con buena tolerancia
y una posología cómoda que permita que el paciente reciba la dosis adecuada durante el tiempo necesario.
Amoxicilina/ácido clavulánico a dosis altas (2000mg/ 125mg) ha demostrado buenos resultados y capacidad
para superar resistencias. Otros agentes como metronidazol y clindamicina, seguidos de claritromicina y azitromicina
han demostrado también ser activos frente a la mayoría de los microorganismos responsables de las infecciones
odontogé[email protected]
Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV
A search for pair-production of supersymmetric particles under the assumption
that R-parity is violated via a dominant LQDbar coupling has been performed
using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV.
The observed candidate events in the data are in agreement with the Standard
Model expectation. This result is translated into lower limits on the masses of
charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for
m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81
GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the
95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging
We present a measurement of the top quark pair () production cross
section () in collisions at TeV
using 230 pb of data collected by the D0 experiment at the Fermilab
Tevatron Collider. We select events with one charged lepton (electron or muon),
missing transverse energy, and jets in the final state. We employ
lifetime-based b-jet identification techniques to further enhance the
purity of the selected sample. For a top quark mass of 175 GeV, we
measure pb, in
agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let
Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV
We present a study of events with Z bosons and jets produced at the Fermilab
Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV.
The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding
to the integrated luminosity of 0.4 fb-1 collected using the D0 detector.
Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross
section have been measured for n = 1 to 4 jet events. Our measurements are
found to be in good agreement with a next-to-leading order QCD calculation and
with a tree-level QCD prediction with parton shower simulation and
hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
- …