80 research outputs found
Solar Effects on Global Climate Due to Cosmic Rays and Solar Energetic Particles
Although the work reported here does not directly connect solar variability with global climate change, this research establishes a plausible quantitative causative link between observed solar activity and apparently correlated variations in terrestrial climate parameters. Specifically, we have demonstrated that ion-mediated nucleation of atmospheric particles is a likely, and likely widespread, phenomenon that relates solar variability to changes in the microphysical properties of clouds. To investigate this relationship, we have constructed and applied a new model describing the formation and evolution of ionic clusters under a range of atmospheric conditions throughout the lower atmosphere. The activation of large ionic clusters into cloud nuclei is predicted to be favorable in the upper troposphere and mesosphere, and possibly in the lower stratosphere. The model developed under this grant needs to be extended to include additional cluster families, and should be incorporated into microphysical models to further test the cause-and-effect linkages that may ultimately explain key aspects of the connections between solar variability and climate
Parent formulation at the Lagrangian level
The recently proposed first-order parent formalism at the level of equations
of motion is specialized to the case of Lagrangian systems. It is shown that
for diffeomorphism-invariant theories the parent formulation takes the form of
an AKSZ-type sigma model. The proposed formulation can be also seen as a
Lagrangian version of the BV-BRST extension of the Vasiliev unfolded approach.
We also discuss its possible interpretation as a multidimensional
generalization of the Hamiltonian BFV--BRST formalism. The general construction
is illustrated by examples of (parametrized) mechanics, relativistic particle,
Yang--Mills theory, and gravity.Comment: 26 pages, discussion of the truncation extended, typos corrected,
references adde
Changing Places and Partners: Associations of Neighborhood Conditions With Sexual Network Turnover Among African American Adults Relocated From Public Housing
Neighborhood conditions and sexual network turnover have been associated with the acquisition of HIV and other sexually transmitted infections (STIs). However, few studies investigate the influence of neighborhood conditions on sexual network turnover. This longitudinal study used data collected across 7 visits from a predominantly substance-misusing cohort of 172 African American adults relocated from public housing in Atlanta, Georgia, to determine whether post-relocation changes in exposure to neighborhood conditions influence sexual network stability, the number of new partners joining sexual networks, and the number of partners leaving sexual networks over time. At each visit, participant and sexual network characteristics were captured via survey, and administrative data were analyzed to describe the census tracts where participants lived. Multilevel models were used to longitudinally assess the relationships of tract-level characteristics to sexual network dynamics over time. On average, participants relocated to neighborhoods that were less economically deprived and violent, and had lower alcohol outlet densities. Post-relocation reductions in exposure to alcohol outlet density were associated with fewer new partners joining sexual networks. Reduced perceived community violence was associated with more sexual partners leaving sexual networks. These associations were marginally significant. No post-relocation changes in place characteristics were significantly associated with overall sexual network stability. Neighborhood social context may influence sexual network turnover. To increase understanding of the social–ecological determinants of HIV/STIs, a new line of research should investigate the combined influence of neighborhood conditions and sexual network dynamics on HIV/STI transmission over time
Escuela de ayudantes alumnos: arte y parte del ayudante alumno como tutor de pares
La preocupación por cómo y para qué enseñar y aprender se muestra como una constante a lo largo del tiempo; ello invita a plantear alternativas innovadoras. Las experiencias en Escuelas de Ayudantes resultan alentadoras en capacitación docente; inserción en equipos docentes; mejoramiento en la formación de grado; integración transversal y vertical; reflexión crítica; apropiación de conocimientos; etc. Dentro del contexto de las “prácticas de docencia compartida”, precisamente le cabe a los alumnos compartir los procesos de aprendizaje entre ellos y los docentes. Objetivo: implementar un sistema de Tutorías de Pares en Histología en las dimensiones pedagógica y disciplinar. Participan del trabajo: docentes, no docente, asesora pedagógica y alumnos. Se preveen actividades áulicas y de Formación y Capacitación Pedagógica y Científica. Se aspira a estimular el pensamiento reflexivo entre el contenido teórico y la práctica profesional; generar un espacio de discusión y formulación de propuestas orientadas al mejoramiento del aprendizaje, propiciar el desarrollo de habilidades; capacitar al aspirante en actividades de docencia; ofrecer un ámbito para el desarrollo de actividades de investigación propiamente dichas y como saber científico aplicado a la docencia de grado; fomentar la habilidad para desempeñar tareas en equipo; favorecer la formación de recursos humanos desde el grado; abordar la problemática de deserción estudiantil. PIIMEG SECyTUNRC( 2011-2012).Eje temático 2: Los cambios e innovaciones en los procesos de formación
a - Alternativas didácticas y experiencias de renovación de la enseñanzaFacultad de Ciencias Agrarias y Forestale
Electric and magnetic charges in N=2 conformal supergravity theories
General Lagrangians are constructed for N=2 conformal supergravity theories
in four space-time dimensions involving gauge groups with abelian and/or
non-abelian electric and magnetic charges. The charges are encoded in the gauge
group embedding tensor. The scalar potential induced by the gauge interactions
is quadratic in this tensor, and, when the embedding tensor is treated as a
spurionic quantity, it is formally covariant with respect to electric/magnetic
duality. This work establishes a general framework for studying any deformation
induced by gauge interactions of matter-coupled N=2 supergravity theories. As
an application, full and residual supersymmetry realizations in maximally
symmetric space-times are reviewed. Furthermore, a general classification is
presented of supersymmetric solutions in
space-times. As it turns out, these solutions allow either eight or four
supersymmetries. With four supersymmetries, the spinorial parameters are
Killing spinors of that are constant on , so that they
carry no spin, while the bosonic background is rotationally invariant.Comment: 49 pages, typos correcte
ATLAS pixel detector electronics and sensors
The silicon pixel tracking system for the ATLAS experiment at the Large Hadron Collider is described and the performance requirements are summarized. Detailed descriptions of the pixel detector electronics and the silicon sensors are given. The design, fabrication, assembly and performance of the pixel detector modules are presented. Data obtained from test beams as well as studies using cosmic rays are also discussed
Measurement of dsigma/DM Forward-Backward Charge Asymmetry for High Mass Drell-Yan e+e- Pairs from p-pbar Collisions at sqrt(s)=1.8 TeV
We report on a measurement of the mass dependence of the forward-backward
charge asymmetry, A_FB, and production cross section dsigma/dM for e+e- pairs
with mass M_ee>40 GeV/c2. The data sample consists of 108 pb-1 of p-pbar
collisions at sqrt(s)=1.8 TeV taken by the Collider Detector at Fermilab during
1992-1995. The measured asymmetry and dsigma/dM are compared with the
predictions of the Standard Model and a model with an extra Z' gauge boson.Comment: 7 pages submitted to Phys. Rev. Lett. 1 figure, 2 Table
Search for Higgs Bosons Decaying into b anti-b and Produced in Association with a Vector Boson in Proton-Antiproton Collisions at 1.8 TeV
We present a new search for production, where is a scalar
Higgs boson decaying into with branching ratio , and is a
boson decaying into , , or .
This search is then combined with previous searches for where is a
boson or a hadronically decaying . The data sample consists of
pb of collisions at TeV
accumulated by the Collider Detector at Fermilab. Observing no evidence of a
signal, we set 95% Bayesian credibility level upper limits on
. For masses of 90, 110 and 130
GeV/, the limits are 7.8, 7.2, and 6.6 pb respectively.Comment: 6 pages, 3 figures, to be submiited to PR
Search for light resonances decaying to boosted quark pairs and produced in association with a photon or a jet in proton–proton collisions at √s=13 TeV with the ATLAS detector
This Letter presents a search for new light resonances decaying to pairs of quarks and produced in association with a high-pT photon or jet. The dataset consists of proton–proton collisions with an integrated luminosity of 36.1 fb−1at a centre-of-mass energy of √s=13TeV recorded by the ATLAS detector at the Large Hadron Collider. Resonance candidates are identified as massive large-radius jets with substructure consistent with a particle decaying into a quark pair. The mass spectrum of the candidates is examined for local excesses above background. No evidence of a new resonance is observed in the data, which are used to exclude the production of a lepto-phobic axial-vector Z boson
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