Path Integral Description of a Semiclassical Su-Schrieffer-Heeger Model

The electron motion along a chain is described by a continuum version of the Su-Schrieffer-Heeger Hamiltonian in which phonon fields and electronic coordinates are mapped onto the time scale. The path integral formalism allows us to derive the non local source action for the particle interacting with the oscillators bath. The method can be applied for any value of the {\it e-ph} coupling. The path integral dependence on the model parameters has been analysed by computing the partition function and some thermodynamical properties from $T= 1K$ up to room temperature. A peculiar upturn in the low temperature {\it heat capacity over temperature} ratio (pointing to a glassy like behavior) has been ascribed to the time dependent electronic hopping along the chain

Análise da repetibilidade em alguns descritores morfológicos para soja

Estudos envolvendo descritores adicionais têm sido de importância para o melhoramento genético de soja. Por isso, neste trabalho, objetivou-se estimar o coeficiente de repetibilidade do comprimento do hipocótilo, do epicótilo, do internódio entre o nó das folhas unifolioladas e da primeira folha trifoliolada, do pecíolo e da raque da primeira folha trifoliolada e determinar o número mínimo de avaliações necessário para predizer o valor real dos genótipos. O trabalho foi desenvolvido na Universidade Federal de Viçosa, analisando-se 85 genótipos de soja em quatro experimentos, no delineamento inteiramente casualizado. A partir das estimativas dos coeficientes de repetibilidade e de determinação obtidos pelos métodos - da análise de variância, dos componentes principais e da análise estrutural -, foram calculados os números de avaliações necessárias. Concluiu-se que os comprimentos do hipocótilo, do epicótilo e do internódio requereram menor quantidade de medição em comparação com os comprimentos do pecíolo e da raque, para o mesmo nível de confiabilidade; e com 15 medições obteve-se 85% de confiabilidade para comprimento do hipocótilo pelos métodos ANOVA e AE(correl) e 90% para CP(correl) e CP(cov); 90% de confiabilidade para comprimento do epicótilo e do internódio pelos métodos ANOVA, CP(correl), CP(cov) e AE(correl); 80% de confiabilidade para comprimento da raque da primeira folha trifoliolada pelos métodos ANOVA, CP(correl), CP(cov) e AE(correl); e, para o comprimento do pecíolo da primeira folha trifoliolada, seriam necessárias 21 medições para confiabilidade de 80% pelos métodos ANOVA e AE(correl) e de 85% pelos CP(correl) e CP(cov).Studies involving additional descriptors has been important for soybean genetic improvement, so this study aimed to estimate the repeatability the length coefficient of hypocotyl, epicotyl, the internode between the unifoliated leaf nodes and the first trifoliate leaf, from the petiole and from the rachis of the first trifoliate leaf stage and determine the minimum number of evaluations needed to predict the real value of the genotypes. The study was conducted at the Universidade Federal de Viçosa, analyzing 85 soybean genotypes in four experiments in a completely randomized design. The numbers of necessary evaluations were calculated from the estimates of repeatability and coefficient of determination obtained by the methods of analysis of variance of the principal component and by the structural analysis. It was concluded that the lengths of the hypocotyl, epicotyl and the internode required fewer measurements compared with the length of the petiole and rachis to the same level of reliability, and with 15 measurements 85% of reliability was obtained for hypocotyl length by ANOVA and AE(correl) methods and 90% by CP(correl) and CP(cov) methods; 90% reliability was obtained for epicotyl and internode length by ANOVA, CP(correl), CP(cov) and AE(correl) method; 80% reliability was obtained for rachis length by ANOVA, CP(correl), CP(cov) and AE(correl) methods; and for petiole length, 21 measurements were needed for reliability by ANOVA and AE(correl) methods and 85% for CP(correl) and CP(cov) methods

Genomic analysis of two phlebotomine sand fly vectors of Leishmania from the New and Old World.

Phlebotomine sand flies are of global significance as important vectors of human disease, transmitting bacterial, viral, and protozoan pathogens, including the kinetoplastid parasites of the genus Leishmania, the causative agents of devastating diseases collectively termed leishmaniasis. More than 40 pathogenic Leishmania species are transmitted to humans by approximately 35 sand fly species in 98 countries with hundreds of millions of people at risk around the world. No approved efficacious vaccine exists for leishmaniasis and available therapeutic drugs are either toxic and/or expensive, or the parasites are becoming resistant to the more recently developed drugs. Therefore, sand fly and/or reservoir control are currently the most effective strategies to break transmission. To better understand the biology of sand flies, including the mechanisms involved in their vectorial capacity, insecticide resistance, and population structures we sequenced the genomes of two geographically widespread and important sand fly vector species: Phlebotomus papatasi, a vector of Leishmania parasites that cause cutaneous leishmaniasis, (distributed in Europe, the Middle East and North Africa) and Lutzomyia longipalpis, a vector of Leishmania parasites that cause visceral leishmaniasis (distributed across Central and South America). We categorized and curated genes involved in processes important to their roles as disease vectors, including chemosensation, blood feeding, circadian rhythm, immunity, and detoxification, as well as mobile genetic elements. We also defined gene orthology and observed micro-synteny among the genomes. Finally, we present the genetic diversity and population structure of these species in their respective geographical areas. These genomes will be a foundation on which to base future efforts to prevent vector-borne transmission of Leishmania parasites

The Physics of Star Cluster Formation and Evolution

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe