Vibrational Excitations in Weakly Coupled Single-Molecule Junctions: A Computational Analysis

In bulk systems, molecules are routinely identified by their vibrational spectrum using Raman or infrared spectroscopy. In recent years, vibrational excitation lines have been observed in low-temperature conductance measurements on single molecule junctions and they can provide a similar means of identification. We present a method to efficiently calculate these excitation lines in weakly coupled, gateable single-molecule junctions, using a combination of ab initio density functional theory and rate equations. Our method takes transitions from excited to excited vibrational state into account by evaluating the Franck-Condon factors for an arbitrary number of vibrational quanta, and is therefore able to predict qualitatively different behaviour from calculations limited to transitions from ground state to excited vibrational state. We find that the vibrational spectrum is sensitive to the molecular contact geometry and the charge state, and that it is generally necessary to take more than one vibrational quantum into account. Quantitative comparison to previously reported measurements on pi-conjugated molecules reveals that our method is able to characterize the vibrational excitations and can be used to identify single molecules in a junction. The method is computationally feasible on commodity hardware.Comment: 9 pages, 7 figure

Is ultra-violet radiation the main force shaping molecular evolution of varicella-zoster virus?

<p>Abstract</p> <p>Background</p> <p>Varicella (chickenpox) exhibits a characteristic epidemiological pattern which is associated with climate. In general, primary infections in tropical regions are comparatively less frequent among children than in temperate regions. This peculiarity regarding varicella-zoster virus (VZV) infection among certain age groups in tropical regions results in increased susceptibility during adulthood in these regions. Moreover, this disease shows a cyclic behavior in which the number of cases increases significantly during winter and spring. This observation further supports the participation of environmental factors in global epidemiology of chickenpox. However, the underlying mechanisms responsible for this distinctive disease behavior are not understood completely. In a recent publication, Philip S. Rice has put forward an interesting hypothesis suggesting that ultra-violet (UV) radiation is the major environmental factor driving the molecular evolution of VZV.</p> <p>Discussion</p> <p>While we welcomed the attempt to explain the mechanisms controlling VZV transmission and distribution, we argue that Rice's hypothesis takes lightly the circulation of the so called "temperate VZV genotypes" in tropical regions and, to certain degree, overlooks the predominance of such lineages in certain non-temperate areas. Here, we further discuss and present new information about the overwhelming dominance of temperate VZV genotypes in Mexico regardless of geographical location and climate.</p> <p>Summary</p> <p>UV radiation does not satisfactorily explain the distribution of VZV genotypes in different tropical and temperate regions of Mexico. Additionally, the cyclic behavior of varicella does not shown significant differences between regions with different climates in the country. More studies should be conducted to identify the factors directly involved in viral spreading. A better understanding of the modes of transmissions exploited by VZV and their effect on viral fitness is likely to facilitate the implementation of preventive measures for disease control.</p

Artificial neural network applied in the analysis of health-related quality of life of adolescents / Rede neural artificial aplicada na análise da qualidade de vida de adolescentes

Objetivo: construir um modelo que explique a qualidade de vida em adolescentes escolares a partir do instrumento KIDSCREEN-27 por meio da criação de uma rede neural artificial. Método: estudo transversal e analítico com 635 adolescentes utilizando-se o KIDSCREEN-27. Foi desenvolvida uma rede neural artificial com quatro camadas para avaliar a variável qualidade de vida por meio da média das respostas. Para as três primeiras camadas de neurônios foi utilizada função logística como função de transferência e para a ativação foi utilizada função linear. Resultados: a rede neural alcançou acurácia de 98,96% e quando comparadas as dimensões do KIDSCREEN-27 com sexo e prática de atividades físicas todas apresentaram associação estatística significativa, exceto as dimensões suporte social e grupo de pares e ambiente escolar. Conclusão: os resultados podem ter importantes consequências para a identificação de adolescentes em risco e o direcionamento de políticas públicas de saúde.

Artificial neural network applied in the analysis of health-related quality of life of adolescents / Rede neural artificial aplicada na análise da qualidade de vida de adolescentes

Objective: to build a model that explains the quality of life in school adolescents from the KIDSCREEN-27 instrument through the creation of an artificial neural network. Method: cross-sectional and analytical study with 635 adolescents using KIDSCREEN-27. An artificial neural network with four layers was developed to evaluate the variable quality of life by means of the mean responses. For the first three layers of neurons, logistic function was used as transfer function and linear function was used for activation. Results: the neural network reached accuracy of 98.96% and when compared the dimensions of kidscreen-27 with sex and practice of physical activities all presented significant statistical association, except the dimensions social support and peer group and school environment. Conclusion: the results may have important consequences for the identification of adolescents at risk and the direction of public health policies.Objetivo: construir un modelo que explique la calidad de vida en adolescentes escolares a partir del instrumento KIDSCREEN-27 a través de la creación de una red neuronal artificial. Método: estudio transversal y analítico con 635 adolescentes utilizando KIDSCREEN-27. Se desarrolló una red neuronal artificial con cuatro capas para evaluar la variable calidad de vida mediante las respuestas medias. Para las tres primeras capas de neuronas, la función logística se utilizó como función de transferencia y la función lineal se utilizó para la activación. Resultados: la red neuronal alcanzó una precisión del 98,96% y cuando se compararon las dimensiones de kidscreen-27 con el sexo y la práctica de actividades físicas todos presentaron una asociación estadística significativa, excepto las dimensiones de apoyo social y grupo de pares y entorno escolar. Conclusión: los resultados pueden tener consecuencias importantes para la identificación de adolescentes en riesgo y la orientación de las políticas de salud.Objetivo: construir um modelo que explique a qualidade de vida em adolescentes escolares a partir do instrumento KIDSCREEN-27 por meio da criação de uma rede neural artificial. Método: estudo transversal e analítico com 635 adolescentes utilizando-se o KIDSCREEN-27. Foi desenvolvida uma rede neural artificial com quatro camadas para avaliar a variável qualidade de vida por meio da média das respostas. Para as três primeiras camadas de neurônios foi utilizada função logística como função de transferência e para a ativação foi utilizada função linear. Resultados: a rede neural alcançou acurácia de 98,96% e quando comparadas as dimensões do KIDSCREEN-27 com sexo e prática de atividades físicas todas apresentaram associação estatística significativa, exceto as dimensões suporte social e grupo de pares e ambiente escolar. Conclusão: os resultados podem ter importantes consequências para a identificação de adolescentes em risco e o direcionamento de políticas públicas de saúde.

History of Spinal Neurosurgery and Spine Societies

info:eu-repo/semantics/publishedVersio

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

Combined search for the quarks of a sequential fourth generation

Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO

Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV

A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 inverse picobarns collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

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