Structure and spectroscopy of doped helium clusters using quantum Monte Carlo techniques

We present a comparative study of the rotational characteristics of various molecule-doped 4He clusters using quantum Monte Carlo techniques. The theoretical conclusions obtained from both zero and finite temperature Monte Carlo studies confirm the presence of two different dynamical regimes that correlate with the magnitude of the rotational constant of the molecule, i.e., fast or slow rotors. For a slow rotor, the effective rotational constant for the molecule inside the helium droplet can be determined by a microscopic two-fluid model in which helium densities computed by path integral Monte Carlo are used as input, as well as by direct computation of excited energy levels. For a faster rotor, the conditions for application of the two-fluid model for dynamical analysis are usually not fulfilled and the direct determination of excitation energies is then mandatory. Quantitative studies for three molecules are summarized, showing in each case excellent agreement with experimental results

Compact strain-sensitive flexible photonic crystals for sensors

A promising fabrication route to produce absorbing flexible photonic crystals is presented, which exploits self-assembly during the shear processing of multi-shelled polymer spheres. When absorbing material is incorporated in the interstitial space surrounding high-refractive-index spheres, a dramatic enhancement in the transmission edge on the short-wavelength side of the band gap is observed. This effect originates from the shifting optical field spatial distribution as the incident wavelength is tuned around the band gap, and results in a contrast up to 100 times better than similar but nonabsorbing photonic crystals. An order-of-magnitude improvement in strain sensitivity is shown, suggesting the use of these thin films in photonic sensors

Blueshift and intramolecular tunneling of NH[sub 3] umbrella mode in [sup 4]He[sub n] clusters

International audienceWe present diffusion Monte Carlo calculations of the ground and first excited vibrational states of NH(3) (4)He(n) for n< or =40. We use the potential energy surface developed by one of us [M. P. Hodges and R. J. Wheatley, J. Chem. Phys. 114, 8836 (2001)], which includes the umbrella mode coordinate of NH(3). Using quantum Monte Carlo calculations of excited states, we show that this potential is able to reproduce qualitatively the experimentally observed effects of the helium environment, namely, a blueshift of the umbrella mode frequency and a reduction of the tunneling splittings in ground and first excited vibrational states of the molecule. These basic features are found to result regardless of whether dynamical approximations or exact calculations are employed

Primordial non-Gaussianities in the intergalactic medium

We present results from the first high-resolution hydrodynamical simulations of non-Gaussian cosmological models. We focus on the statistical properties of the transmitted Lyman-\u3b1 flux in the high-redshift intergalactic medium. Imprints of non-Gaussianity are present and are larger at high redshifts. Differences larger than 20 per cent at z > 3 in the flux probability distribution function for high-transmissivity regions (voids) are expected for values of the non-linearity parameter fNL = +/-100 when compared to a standard \u39b cold dark matter cosmology with fNL = 0. We also investigate the one-dimensional flux bispectrum: at the largest scales (corresponding to tens of Mpc), we expect deviations in the flux bispectrum up to 20 per cent at z ~ 4 (for fNL = +/-100), significantly larger than deviations of ~3 per cent in the flux power spectrum. We briefly discuss possible systematic errors that can contaminate the signal. Although challenging, a detection of non-Gaussianities in the interesting regime of scales and redshifts probed by the Lyman-\u3b1 forest could be possible with future data sets

Discriminating Minimal SUGRA and Minimal Gauge Mediation Models at the Early LHC

Among various supersymmetric (SUSY) standard models, the gravity mediation model with a neutralino LSP and the gauge mediation model with a very light gravitino are attractive from the cosmological view point. These models have different scales of SUSY breaking and their underlying physics in high energy is quite different. However, if the sparticles' decay into the gravitino is prompt in the latter case, their collider signatures can be similar: multiple jets and missing transverse momentum. In this paper, we study the discrimination between these models in minimal cases at the LHC based on the method using the significance variables in several different modes and show the discrimination is possible at a very early stage after the discovery.Comment: 29 pages, 3 figures, captions improved, typos corrected, appendix added, version published in JHE

Determining the Mass for a Light Gravitino

Gauge mediated supersymmetry breaking scenarios with an ultra-light gravitino of mass m_{3/2}=1-10 eV are very interesting, since there is no cosmological gravitino problem. We propose a new experimental determination of the gravitino mass for such an ultra-light gravitino, by measuring a branching ratio of two decay modes of sleptons.Comment: 9 pages, 12 figure

Avaliação do efeito do dossel vegetativo na estimativa da perda do solo em área de vinhedos usando SIG.

O presente trabalho avaliou o efeito do dossel vegetativo de vinhedos para estimativa da perda superficial de solos. Este estudo integra técnicas de Sensoriamento Remoto e Sistema de Informações Geográficas (SIG) para quantificar e mapear a erosão do solo na região da Denominação de Origem (DO) Vale dos Vinhedos - Brasil. A aplicação da Equação Universal de Perda de Solos (EUPS) considerou fatores como tipo de solo, declividade, erosividade e uso da terra. Os produtos cartográficos gerados foram confirmados por observações em campo. A perda superficial de solo média em vinhedos com dossel vegetativo foi de 388,33 kg/ha/ano, já a perda superficial de solo média em vinhedos que não possuíam o dossel vegetativo foi de 935,67 kg/ha/ano. Comparativamente os cruzamentos realizados evidenciaram pouca diferença entre as classes, sendo a principal diferença observada entre a classe de 0 a 1 t/ha/ano. Em vinhedos com dossel vegetativo, esta classe apresentou perda de solo de 82 % da área de estudo, já para o método que não considerou o dossel vegetativo do vinhedo, esta classe apresentou 75 % da área de estudo, indicando diferença de 7 %, evidenciando uma perda de solo maior no período de dormência do vinhedo. A diferença entre os resultados dos modelos é ressaltada quando se analisa a classe com maior perda de solo, pois no cruzamento que desconsidera o dossel vegetativo do vinhedo houve um aumento de 4,92 km², representando 11 % da área de estudo. Esta avaliação demonstra que a diferença da condução dos vinhedos e o dossel vegetativo infl uenciam na perda superfi cial de solo. Sendo assim, os resultados podem contribuir para o monitoramento de processos erosivos laminares e para medidas de conservação e planejamento ambiental em áreas onde se desenvolve a vitivinicultura. Palavra-chave: Geoprocessamento, Vitivinicultura, EUPS, Uso da Terra. The present study evaluated the eff ect of the vegetative canopy of vineyards to estimate the soil loss. This study integrates Remote Sensing and Geographic Information System (GIS) techniques to quantify and map soil erosion in the Denomination of Origin (DO) Vale dos Vinhedos region, Brazil. The application Universal Equation of Soil Loss (USLE) considered factors such as soil type, slope, erosivity and land use. The cartographic products generated were confi rmed by fi eld observations. The average soil surface loss in vineyards with vegetative canopy was 388.33 kg/ha/ year, while the average soil loss in vineyards that did not have the vegetative canopy was 935.67 kg/ha/year. Comparatively the crosses showed little diff erence between the classes, being the main diff erence observed between the class from 0 to 1 t/ha/year. In the case of vineyards with vegetative canopy, this class had a soil loss of 82% of the study area. For the method that did not consider the vegetative canopy of the vineyard, this class presented 75% of the study area, indicating a diff erence of 7%, evidencing a loss of greater soil in the period of dormancy of the vineyard. The diff erence between the results of the models is highlighted when the class with the highest soil loss is analyzed, since at the intersection that disregarded the vegetative canopy of the vineyard there was an increase of 4.92 km², representing 11% of the study area. This evaluation demonstrates that the diff erence in vineyard conduction and the vegetative canopy infl uence soil loss. Thus, the results can contribute to the monitoring of erosive laminar processes and to environmental conservation and planning measures in areas where wine growing is developed. Keywords: GIS, USLE, Winegrowing, Land Use

Estudo da erosão superficial do solo por meio de SIG na região da denominação de origem Vale dos Vinhedos (Brasil).

O presente trabalho investigou a perda superfi cial de solos na região da denominação de origem Vale dos Vinhedos, RS, Brasil, associando aos condicionantes que influenciam na vulnerabilidade dos solos, tendo como base modelos matemáticos e ferramentas de Geoprocessamento. A aplicação da Equação Universal de Perda de Solos (EUPS) foi realizada em Sistema de Informações Geográfi cas (SIG) com o uso integrado de dados meteorológicos, de declividade, geológicos, pedológicos, de uso e cobertura da terra e obtidos em campo. Os resultados indicaram que os processos erosivos mais intensos estão associados com a falta de cobertura vegetal em maiores declividades, esses aliados ao manejo inadequado. As áreas com Cambissolo foram as que registraram os maiores valores de perda de solos. A perda superfi cial de solo média para a região é de 935,67 kg/ha/ano. Os baixos valores de perda superfi cial de solo estão relacionados a pouca existência de solo exposto e a maior parte da área ser ocupada por culturas permanentes e vegetação nativa. O mapa de vulnerabilidade à perda de solo e a base de dados em SIG gerada, com alta resolução espacial, podem contribuir para o monitoramento da qualidade ambiental e elaboração de planos de recuperação e conservação da área de estudo Palavras-chave: Perda Superfi cial de Solo; Cobertura Vegetal; Geoprocessamento. This work was investigated the soil loss in de Designation of Origin Vale dos Vinhedos, region, Brazil, associating the conditions that infl uence the vulnerability of soil, based on mathematical models and geoprocessing techniques. The Universal Soil Loss Equation (USLE) was applied to identify susceptible areas with Geographical Information System (GIS) and using interaction amongst meteorological, slope, geological, soil, land use data and local observation. The most critical areas, in relation to the soil loss were associated to high slopes, Cambisol areas and inadequate land use practices and management. The soil loss average for the region is 935.67 kg/ha/year. The areas with relatively low values of soil loss are related mainly by the occurrence of permanent cropland and native vegetation areas. The map of soil loss vulnerability and GIS database with high spatial resolution, can contribute to the monitoring of environmental quality and development planning conservation measures in study area. Keywords: Soil Loss; Geoprocessing; Vegetal CoverTítulo em Inglês: Surface soil loss study by gis in designation of origin Vale dos vinhedos (Brazil) region