Quasienergy spectrum and tunneling current in ac-driven triple quantum dot shuttles

The dynamics of electrons in ac driven double quantum dots have been extensively analyzed by means of Floquet theory. In these systems, coherent destruction of tunneling has been shown to occur for certain ac field parameters. In the present work we analyze, by means of Floquet theory, the electron dynamics of a triple quantum dot in series attached to electric contacts, where the central dot position oscillates. In particular, we analyze the quasienergy spectrum of this ac driven nanoelectromechanical system, as a function of the intensity and frequency of the ac field and of external dc voltages. For strong driving fields, we derive, by means of perturbation theory, analytical expressions for the quasienergies of the driven oscillator system. From this analysis we discuss the conditions for coherent destruction of tunneling (CDT) to occur as a function of detuning and field parameters. For zero detuning, and from the invariance of the Floquet Hamiltonian under a generalized parity transformation, we find analytical expressions describing the symmetry properties of the Fourier components of the Floquet states under such transformation. By using these expressions, we show that in the vicinity of the CDT condition, the quasienergy spectrum exhibits exact crossings which can be characterized by the parity properties of the corresponding eigenvectors

Análisis de la contaminación ambiental producida por el plasma frío de baja presión en la limpieza de láminas metálicas

La presente investigación aborda un análisis del nivel de contaminación producido por los gases generados de monóxido de carbono (CO), dióxido de carbono (CO2) y los hidrocarburos (HC) en la limpieza de láminas metálicas de acero inoxidable AISI/SAE 304 aplicando plasma frío de oxígeno a baja presión para la remoción de los aceites ISO 32, ISO 68 e ISO 220, con diferentes parámetros de control del generador de acuerdo con el aceite lubricante removido de la superficie de la lámina metálica de acero inoxidable. La experimentación se realizó en un primer proceso con una descarga aplicada directamente a la superficie de la lámina impregnada con el aceite colocando con un volumen de 0,1 ml y en un segundo proceso donde la lámina con el aceite impregnado fue sumergida en un desengrasante para aceites y grasas con la finalidad de realizar una limpieza previa a la aplicación del plasma frío a baja presión en la superficie. Para el análisis de los resultados en el nivel de gases generados por cada aceite se aplica un análisis estadístico para determinar si existe una diferencia significativa en el nivel de los gases generados en las dos etapas.//level of contamination produced by gases generated from carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) in the cleaning of metallic sheets of stainless steel AISI / SAE 304 when applying low pressure cold oxygen plasma for the removal of oils ISO 32, ISO 68 and ISO 220, with different generator control parameters according to the lubricating oil removed from the surface of the stainless steel sheet metal. The experimentation was carried out in a first phase in which a discharge was applied directly to the surface of the sheet contaminated with a volume of 0.1 ml of oil, and in a second phase in which the sheet with the oil was immersed in an oil degreaser to perform a pre-cleaning prior to the application of lowpressure cold plasma on the surface. For the analysis of the results in the level of gases generated by each oil, an statistical analysis is applied to determine if there is a significant difference in the level of the gases generated between the two phases

Harbouring public good mutants within a pathogen population can increase both fitness and virulence

Existing theory, empirical, clinical and field research all predict that reducing the virulence of individuals within a pathogen population will reduce the overall virulence, rendering disease less severe. Here, we show that this seemingly successful disease management strategy can fail with devastating consequences for infected hosts. We deploy cooperation theory and a novel synthetic system involving the rice blast fungus Magnaporthe oryzae. In vivo infections of rice demonstrate that M. oryzae virulence is enhanced, quite paradoxically, when a public good mutant is present in a population of high-virulence pathogens. We reason that during infection, the fungus engages in multiple cooperative acts to exploit host resources. We establish a multi-trait cooperation model which suggests that the observed failure of the virulence reduction strategy is caused by the interference between different social traits. Multi-trait cooperative interactions are widespread, so we caution against the indiscriminant application of anti-virulence therapy as a disease-management strategy

Finding Single Copy Genes Out of Sequenced Genomes for Multilocus Phylogenetics in Non-Model Fungi

Historically, fungal multigene phylogenies have been reconstructed based on a small number of commonly used genes. The availability of complete fungal genomes has given rise to a new wave of model organisms that provide large number of genes potentially useful for building robust gene genealogies. Unfortunately, cross-utilization of these resources to study phylogenetic relationships in the vast majority of non-model fungi (i.e. “orphan” species) remains an unexamined question. To address this problem, we developed a method coupled with a program named “PHYLORPH” (PHYLogenetic markers for ORPHans). The method screens fungal genomic databases (107 fungal genomes fully sequenced) for single copy genes that might be easily transferable and well suited for studies at low taxonomic levels (for example, in species complexes) in non-model fungal species. To maximize the chance to target genes with informative regions, PHYLORPH displays a graphical evaluation system based on the estimation of nucleotide divergence relative to substitution type. The usefulness of this approach was tested by developing markers in four non-model groups of fungal pathogens. For each pathogen considered, 7 to 40% of the 10–15 best candidate genes proposed by PHYLORPH yielded sequencing success. Levels of polymorphism of these genes were compared with those obtained for some genes traditionally used to build fungal phylogenies (e.g. nuclear rDNA, β-tubulin, γ-actin, Elongation factor EF-1α). These genes were ranked among the best-performing ones and resolved accurately taxa relationships in each of the four non-model groups of fungi considered. We envision that PHYLORPH will constitute a useful tool for obtaining new and accurate phylogenetic markers to resolve relationships between closely related non-model fungal species

Evidence for maintenance of sex determinants but not of sexual stages in red yeasts, a group of early diverged basidiomycetes

<p>Abstract</p> <p>Background</p> <p>The red yeasts are an early diverged group of basidiomycetes comprising sexual and asexual species. Sexuality is based on two compatible mating types and sexual identity is determined by <it>MAT </it>loci that encode homeodomain transcription factors, peptide pheromones and their receptors. The objective of the present study was to investigate the presence and integrity of <it>MAT </it>genes throughout the phylogenetic diversity of red yeasts belonging to the order Sporidiobolales.</p> <p>Results</p> <p>We surveyed 18 sexual heterothallic and self-fertile species and 16 asexual species. Functional pheromone receptor homologues (<it>STE3.A1 </it>and <it>STE3.A2</it>) were found in multiple isolates of most of the sexual and asexual species. For each of the two mating types, sequence comparisons with whole-genome data indicated that synteny tended to be conserved along the pheromone receptor region. For the homeodomain transcription factor, likelihood methods suggested that diversifying selection acting on the self/non-self recognition region promotes diversity in sexual species, while rapid evolution seems to be due to relaxed selection in asexual strains.</p> <p>Conclusions</p> <p>The majority of both sexual and asexual species of red yeasts have functional pheromone receptors and homeodomain homologues. This and the frequent existence of asexual strains within sexual species, makes the separation between sexual and asexual species imprecise. Events of loss of sexuality seem to be recent and frequent, but not uniformly distributed within the Sporidiobolales. Loss of sex could promote speciation by fostering the emergence of asexual lineages from an ancestral sexual stock, but does not seem to contribute to the generation of exclusively asexual lineages that persist for a long time.</p

Children’s and Adolescents’ Happiness Conceptualizations at School and their Link with Autonomy, Competence, and Relatedness

Previous research on children’s and adolescents’happiness either focused on their conceptualisations or the link between self-reported happiness with different outcomes. However, very few studies have connected both approaches to better understand children’s and adolescents’ happiness. To address this gap, we used a mixed-method approach, to investigate if the conceptualizations of happiness at school of 744 British children and adolescents could signal differences in autonomy, competence, and relatedness. An initial coding of the responses showed thirteen conceptualizations (i.e., positive feelings, harmony/balance, leisure, friends, getting good grades, non-violence, moral actions, purpose, autonomy, competence, teachers, emotional support, and learning). Log-linear models showed that some of the conceptualizations differed across both age groups and gender. Latent class analysis showed that happiness conceptualizations could be classified in five different groups. Interestingly, whereas for children there were no differences; for adolescents, there were differences between classes in their levels of autonomy and relatedness. The implications of these findings for promoting students' well-being at school are discussed

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Deleterious effects of recombination and possible nonrecombinatorial advantages of sex in a fungal model

Why sexual reproduction is so prevalent in nature remains a major question in evolutionary biology. Most of the proposed advantages of sex rely on the benefits obtained from recombination. However, it is still unclear whether the conditions under which these recombinatorial benefits would be sufficient to maintain sex in the short term are met in nature. Our study addresses a largely overlooked hypothesis, proposing that sex could be maintained in the short term by advantages due to functions linked with sex, but not related to recombination. These advantages would be so essential that sex could not be lost in the short term. Here, we used the fungus Aspergillus nidulans to experimentally test predictions of this hypothesis. Specifically, we were interested in (i) the short-term deleterious effects of recombination, (ii) possible nonrecombinatorial advantages of sex particularly through the elimination of mutations and (iii) the outcrossing rate under choice conditions in a haploid fungus able to reproduce by both outcrossing and haploid selfing. Our results were consistent with our hypotheses: we found that (i) recombination can be strongly deleterious in the short term, (ii) sexual reproduction between individuals derived from the same clonal lineage provided nonrecombinatorial advantages, likely through a selection arena mechanism, and (iii) under choice conditions, outcrossing occurs in a homothallic species, although at low rate