Exchange interaction effects in the thermodynamic properties of quantum dots

We study electron-electron interaction effects in the thermodynamic properties of quantum-dot systems. We obtain the direct and exchange contributions to the specific heat C_v in the self-consistent Hartree-Fock approximation at finite temperatures. An exchange-induced phase transition is observed and the transition temperature is shown to be inversely proportional to the size of the system. The exchange contribution to C_v dominates over the direct and kinetic contributions in the intermediate regime of interaction strength (r_s ~ 1). Furthermore, the electron-electron interaction modifies both the amplitude and the period of magnetic field induced oscillations in C_v.Comment: 4 pages, 4 figures; To appear in Phys. Rev.

Toward a simulation approach for alkene ring-closing metathesis : scope and limitations of a model for RCM

A published model for revealing solvent effects on the ring-closing metathesis (RCM) reaction of di-Et diallylmalonate 7 has been evaluated over a wider range of conditions, to assess its suitability for new applications. Unfortunately, the model is too flexible and the published rate consts. do not agree with exptl. studies in the literature. However, by fixing the values of important rate consts. and restricting the concn. ranges studied, useful conclusions can be drawn about the relative rates of RCM of different substrates, precatalyst concn. can be simulated accurately and the effect of precatalyst loading can be anticipated. Progress has also been made toward applying the model to precatalyst evaluation, but further modifications to the model are necessary to achieve much broader aims

Análise espacial da mortalidade neonatal no Vale do Paraíba, 1999 a 2001

OBJETIVO: Analisar os padrões de distribuição espacial da mortalidade neonatal. MÉTODOS: Estudo ecológico e exploratório, utilizando técnicas de análise espacial dos dados de mortalidade neonatal no Vale do Paraíba paulista, nos anos 1999-2001. A análise estatística espacial utilizou uma base de dados georreferenciados de 35 municípios e rotinas de estatística espacial. Os dados de mortalidade foram obtidos na Secretaria de Estado da Saúde de São Paulo. As variáveis estudadas foram os coeficientes de mortalidade neonatal precoce, tardia e total, e o Índice de Desenvolvimento Humano relativos ao ano de 2000. Para avaliação da dependência espacial foram utilizados os coeficientes de autocorrelação de Moran global e o Índice de Moran local e analisadas as correlações entre as variáveis. RESULTADOS: Foram registrados 111.574 nascidos vivos, com 1.149 óbitos no período neonatal precoce (10,29/1.000 nascidos vivos), 285 no neonatal tardio (2,55/1.000 nascidos vivos) totalizando 1.434 óbitos no período neonatal (12,85/1.000 nascidos vivos). Os coeficientes de Moran (global) mostraram significância estatística (pOBJECTIVE: To assess the spatial distribution of neonatal mortality. METHODS: An ecological and exploratory study using a spatial distribution of mortality data approach was carried out in the Paraiba Valley, Southeastern Brazil, from 1999-2001. Spatial analysis was conducted in a georeference database for 35 cities in the region and routines of spatial statistics. Mortality data were obtained from the State of São Paulo Health Department. The following variables were analyzed in this study: early, late and total neonatal mortality rates; and Human Development Index (HDI) values per city in 2000. Spatial dependency was measured using global Moran's Coefficients and local Moran's Index. A correlation analysis between variables was also conducted. RESULTS: There were 111,574 newborns with 1,149 deaths in the early neonatal period (10.29/1,000 newborns), 285 in the late neonatal period (2.5/1,000 newborns) totalizing 1,434 neonatal deaths (12.85/1,000 newborns). Estimated global Moran's coefficients showed statistical significance (

Anomalous magnetic field dependence of the thermodynamic transition line in the isotropic superconductor (K,Ba)Bi03

Thermodynamic (specific heat, reversible magnetization, tunneling spectroscopy) and transport measurements have been performed on high quality (K,Ba)BiO$_3$ single crystals. The temperature dependence of the magnetic field $H_{Cp}$ corresponding to the onset of the specific heat anomaly presents a clear positive curvature. $H_{Cp}$ is significantly smaller than the field $H_\Delta$ for which the superconducting gap vanishes but is closely related to the irreversibility line deduced from transport data. Moreover, the temperature dependence of the reversible magnetization present a strong deviation from the Ginzburg--Landau theory emphasazing the peculiar nature of the superconducting transition in this material.Comment: 4 pages, 4 figures, 28 reference

Integração de métodos multicritério na busca da sustentabilidade agrícola para a produção de tomates no município de São José de Ubá-RJ.

Este estudo discute alternativas para os sistemas produtivos da terra no plantio de tomates em São José de Ubá-RJ e as relações de trabalho passíveis de serem colocadas em pratica de forma a promover uma agricultura sustentavel na região, priorizando os aspectos economicos, ambientais e culturais do problema. A introdução da questão cultural aumenta a complexidade da questão, sendo necessário o uso de uma metodologia capaz de lidar com toda a subjetividade envolvida nesse processo de tomada de decisão. O estudo visa contribuir para a conquista de um processo sustentavel na região, estabelecendo um processo de tomada de decisão pautado nas opinioes do agricultor, respeitando principalmente as questões culturais do problema. As características do ambiente de tomada de decisão indicaram o uso de uma combinação de métodos de apoio a decisão multicritério - MACBETH e VIP Analysis - para a seleção da melhor alternativa capaz de possibilitar o alcance dos objetivos propostos

Evidence for the h_b(1P) meson in the decay Upsilon(3S) --> pi0 h_b(1P)

Using a sample of 122 million Upsilon(3S) events recorded with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we search for the $h_b(1P)$ spin-singlet partner of the P-wave chi_{bJ}(1P) states in the sequential decay Upsilon(3S) --> pi0 h_b(1P), h_b(1P) --> gamma eta_b(1S). We observe an excess of events above background in the distribution of the recoil mass against the pi0 at mass 9902 +/- 4(stat.) +/- 2(syst.) MeV/c^2. The width of the observed signal is consistent with experimental resolution, and its significance is 3.1sigma, including systematic uncertainties. We obtain the value (4.3 +/- 1.1(stat.) +/- 0.9(syst.)) x 10^{-4} for the product branching fraction BF(Upsilon(3S)-->pi0 h_b) x BF(h_b-->gamma eta_b).Comment: 8 pages, 4 postscript figures, submitted to Phys. Rev. D (Rapid Communications

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Search for anomalous t t-bar production in the highly-boosted all-hadronic final state

A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version includes a minor typo correction that will be submitted as an erratu

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV

The production of b jets in association with a Z/gamma* boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector. The inclusive cross section for Z/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.55) (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by PYTHIA.Comment: Submitted to the Journal of High Energy Physic