927 research outputs found

    Fate of topological states in incommensurate generalized Aubry-Andr\'e models

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    We study one-dimensional optical lattices described by generalized Aubry-Andr\'e models that include both commensurate and incommensurate modulations of the hopping amplitude. This brings together two interesting features of this class of systems: Anderson localization and the existence of topological edge states. We follow changes of the single-particle energy spectrum induced by variations of the system parameters, with focus on the survival of topological states in the localized regime.Comment: 5 pages, 5 figure

    Ground-states of spin-1 bosons in asymmetric double-wells

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    In this work we investigate the different states of a system of spin-1 bosons in two potential wells connected by tunneling, with spin-dependent interaction. The model utilizes the well-known Bose-Hubbard Hamiltonian, adding a local interaction term that depends on the modulus of the total spin in a well, favoring a high- or low-spin state for different signs of the coupling constant. We employ the concept of fidelity to detect critical values of parameters for which the ground state undergoes significant changes. The nature of the states is investigated through evaluation of average occupation numbers in the wells and of spin correlations. A more detailed analysis is done for a two-particle system, but a discussion of the three-particle case and some results for larger numbers are also presented.Comment: 7 pages, 10 figure

    Finite-size effects in Anderson localization of one-dimensional Bose-Einstein condensates

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    We investigate the disorder-induced localization transition in Bose-Einstein condensates for the Anderson and Aubry-Andre models in the non-interacting limit using exact diagonalization. We show that, in addition to the standard superfluid fraction, other tools such as the entanglement and fidelity can provide clear signatures of the transition. Interestingly, the fidelity exhibits good sensitivity even for small lattices. Effects of the system size on these quantities are analyzed in detail, including the determination of a finite-size-scaling law for the critical disorder strength in the case of the Anderson model.Comment: 15 pages, 7 figure

    A STUDY ON MASTERING ENGLISH PASSIVE VOICE IN SIMPLE PRESENT, SIMPLE PAST AND SIMPLE FUTURE TENSES BY THE GRADE 12TH STUDENTS OF ESCOLA SECUNDARIA PUBLICA NOBEL DA PAZ, DILI TIMOR-LESTE IN ACADEMIC YEAR 2020

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    This study is entitled “A study on Mastering English Passive Voice (simple present, simple past and simple future tense) by the Grade 12 Students of Escola Secundária Pública Nobel da Paz, Dili Timor-Leste in the School Year 2020”. The aim of this study is to find out whether or not the grade 12 students master English passive voice as well as to know their mastery level. The population of this study is all the grade 12 students that consisted of four classes and only 30 students who were selected randomly as the sample or respondents. The instrument used for the data collection is a questionnaire in which it comprisis 30 numbers of questions. The methods used in this research are qualitative and quantitative approaches

    Effects of band filling in the Anderson-Falicov-Kimball model

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    In this work, we study the Anderson-Falicov-Kimball model within the dynamical mean field theory for the Bethe lattice, restricting our analysis to the nonmagnetic case. The one-particle density of states is obtained by both arithmetic and geometric averages over disorder, since only the latter can detect localization in the absence of an energy gap. Varying the strengths of Coulomb interaction and disorder at zero temperature, we construct phase diagrams for this model, where we distinguish spectral regions with localized states, with extended states, or with a correlation-induced gap. With this, we identify metal-insulator transitions driven by correlation and disorder, as well as the competition between these effects. This is done for various band fillings, since our main interest here is to study how the variation of the electron density affects the phase diagrams previously obtained for half-filling. The picture revealed by the density of states is further checked by evaluating the static and dynamic conductivities, including temperature effects

    Portuguese crypto-Jews: The genetic heritage of a complex history

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    The first documents mentioning Jewish people in Iberia are from the Visigothic period. It was also in this period that the first documented anti-Judaic persecution took place. Other episodes of persecution would happen again and again during the long troubled history of the Jewish people in Iberia and culminated with the Decrees of Expulsion and the establishment of the Inquisition: some Jews converted to Catholicism while others resisted and were forcedly baptized, becoming the first Iberian Crypto-Jews. In the 18th century the official discrimination and persecution carried out by the Inquisition ended and several Jewish communities emerged in Portugal. From a populational genetics point of view, the worldwide Diaspora of contemporary Jewish communities has been intensely studied. Nevertheless, very little information is available concerning Sephardic and Iberian Crypto-Jewish descendants. Data from the Iberian Peninsula, the original geographic source of Sephardic Jews, is limited to two populations in Portugal, Belmonte, and Bragança district, and the Chueta community from Mallorca. Belmonte was the first Jewish community studied for uniparental markers. The construction of a reference model for the history of the Portuguese Jewish communities, in which the genetic and classical historical data interplay dynamically, is still ongoing. Recently an enlarged sample covering a wide region in the Northeast Portugal was undertaken, allowing the genetic profiling of male and female lineages. A Jewish specific shared female lineage (HV0b) was detected between the community of Belmonte and Bragança. In contrast to what was previously described as a hallmark of the Portuguese Jews, an unexpectedly high polymorphism of lineages was found in Bragança, showing a surprising resistance to the erosion of genetic diversity typical of small-sized isolate populations, as well as signs of admixture with the Portuguese host population

    Tendências Seculares na Mortalidade por Doenças Cerebrovasculares em Portugal: 1902-2012

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    Introduction: Cerebrovascular diseases (CVD) are one of the main causes of death in Portugal. Research on the epidemiologic history might help to understand the phenomenon and guide intervention strategies. Objectives: (1) Describe historic trends in mortality. (2) Estimate the impact of demographic variations on the registered number of cases. Methods: (1) We calculated rates, specific and standardized, for deaths registered as CVD (ICD-10: I60-I69, G45; ICD8/9: 430-438; ICD-6/7: 330-334) by sex (1902-2012) and by sex and age groups (1913-2012). We used Join point analysis to identify statistically significant changes in standardized death rates, and multivariate regression models, Poisson and negative binomial, controlling for demographic dynamics and time trend, from 1913 to 2012. (2) We calculated the contribution of demographic variations using the application RiskDiff. (3) We evaluated if changes in coding rules might have been a source of bias. Data source: National Institute of Statistics. Results: (1) We gathered the longest and most discriminated mortality series from CVD in Portugal with data since the beginning of nationwide collection. Mortality increases exponentially with age and is higher in men. (2) We observed significant variations in age-standardized time trends (1913-1933: APC 2.0%; 1933-1955: APC -0.9%; 1955-1974: 2.9%; 1974- 1996: -2.4%; 1996-2012: -6.5%). (3) Population ageing exerted a significant pressure to increase the number of deaths, particularly in the second half of the twentieth century. However, this effect was counterweighted by protective factors. Conclusion: CVD mortality in Portugal is particularly expressive when compared to other European countries, although significant gains have been observed in the last decades. Population ageing combined with a transition between the morbid and mortality dimensions changed the public health paradigm.Introdução: As doenças cerebrovasculares (DCV) são uma das principais causas de morte em Portugal. O estudo da história epidemiológica deste fenómeno contribui para a sua compreensão e ajuda a orientar estratégias de intervenção. Objetivos: (1) Descrever tendências históricas na mortalidade. (2) Estimar o impacto das variações demográficas no número de casos registado. Métodos: (1) Calculámos taxas, específicas e padronizadas, para as mortes registadas como resultantes de DCV (CID-10: I60-I69, G45; ICD-8/9: 430-438; ICD-6/7: 330-334) por sexo (1902-2012) e por sexo e grupos etários (1913- 2012). Utilizámos Joinpoint-analysis para identificar variações estatisticamente significativas na tendência temporal e modelos multivariados de regressão, Poisson e binomial negativo, controlando dinâmicas demográficas e tendências temporais, constrangidos à população exposta, de 1913 a 2012. (2) Aferimos o peso relativo de variações demográficas recorrendo à aplicação RiskDiff. (3) Avaliámos se as interrupções na continuidade das séries definidas por alterações nos critérios de codificação da causa de morte podem ter constituído factores confundentes. Fontes dos dados: Instituto Nacional de Estatística. Resultados: (1) Elencámos a mais longa e discriminada série de mortalidade por DCV em Portugal com dados desde que há registo com abrangência nacional. A mortalidade aumenta exponencialmente com a idade e é superior nos homens. (2) Observámos variações significativas na direcção e amplitude da tendência temporal das taxas padronizadas (1913-1933: APC 2,0%; 1933-1955: APC -0,9%; 1955-1974: 2,9%; 1974-1996: -2,4%; 1996-2012: -6,5%). (3) O envelhecimento demográfico exerceu uma pressão significativa para o aumento no número de casos particularmente na segunda metade do século XX. No entanto este efeito foi neutralizado por factores protectores. Conclusão: Em Portugal a DCV é particularmente expressiva quando comparada com outros países da Europa embora se tenham observado ganhos significativos nas últimas décadas. O envelhecimento demográfico combinado com uma eventual transição relativa entre as dimensões morbil e de mortalidade proporcionaram uma mudança no paradigma de saúde pública.info:eu-repo/semantics/publishedVersio

    Simple and highly discriminatory microsatellite-based multiplex PCR for Aspergillus fumigatus strain typing

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    AbstractThe answers to important questions concerning Aspergillus fumigatus pathogenicity, transmissions routes and efficacy of treatments require highly discriminating and reproducible genotyping methods. The present study was aimed at improving microsatellite methodology for A. fumigatus typing by reducing the task of strain identification to a single multiplex reaction and by selecting highly accurate short tandem repeat polymorphisms. A set of eight primer pairs was used for the genotype determination of 116 clinical isolates of A. fumigatus obtained from three healthcare centres. A new, automated and highly discriminatory typing method is described for A. fumigatus strains. The optimized multiplex PCR was successfully performed with all tested clinical strains and showed a discriminatory power of 0.9997 among presumably unrelated isolates. The comparison of groups of strains from different health centres showed that 99.6% of the genotypic variation was present within groups. Strains with the same genotype were isolated from the same patient, sometimes recovered more than 1 year later. A few cases of patients at the same clinic unit carrying strains of identical genotype strongly suggested colonization by A. fumigatus during their hospitalization. Specific measures must therefore be taken in order to prevent and restrict such incidents
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