Hamiltonian formulation of nonAbelian noncommutative gauge theories

We implement the Hamiltonian treatment of a nonAbelian noncommutative gauge theory, considering with some detail the algebraic structure of the noncommutative symmetry group. The first class constraints and Hamiltonian are obtained and their algebra derived, as well as the form of the gauge invariance they impose on the first order action.Comment: enlarged version, 7 pages, RevTe

Thermodynamics of quantum crystalline membranes

We investigate the thermodynamic properties and the lattice stability of two-dimensional crystalline membranes, such as graphene and related compounds, in the low temperature quantum regime $T\rightarrow0$. A key role is played by the anharmonic coupling between in-plane and out-of plane lattice modes that, in the quantum limit, has very different consequences than in the classical regime. The role of retardation, namely of the frequency dependence, in the effective anharmonic interactions turns out to be crucial in the quantum regime. We identify a crossover temperature, $T^{*}$, between classical and quantum regimes, which is $\sim 70 - 90$ K for graphene. Below $T^{*}$, the heat capacity and thermal expansion coefficient decrease as power laws with decreasing temperature, tending to zero for $T\rightarrow0$ as required by the third law of thermodynamics.Comment: 13 pages, 1 figur

Reply to 'Comment on "Thermodynamics of quantum crystalline membranes"'

In this note, we reply to the comment made by E.I.Kats and V.V.Lebedev [arXiv:1407.4298] on our recent work "Thermodynamics of quantum crystalline membranes" [Phys. Rev. B 89, 224307 (2014)]. Kats and Lebedev question the validity of the calculation presented in our work, in particular on the use of a Debye momentum as a ultra-violet regulator for the theory. We address and counter argue the criticisms made by Kats and Lebedev to our work.Comment: 5 pages, 4 figure

The Hamiltonian BRST quantization of a noncommutative nonabelian gauge theory and its Seiberg-Witten map

We consider the Hamiltonian BRST quantization of a noncommutative non abelian gauge theory. The Seiberg-Witten map of all phase-space variables, including multipliers, ghosts and their momenta, is given in first order in the noncommutative parameter $\theta$. We show that there exists a complete consistence between the gauge structures of the original and of the mapped theories, derived in a canonical way, once we appropriately choose the map solutions.Comment: 10 pages, Latex. Address adde

Influência da quantidade de fibras e de cinzas volantes, para diferentes idades, no comportamento em flexão do betão reforçado com fibras de aço

Recentemente foram propostas recomendações no sentido de normalizar os procedimentos associados ao ensaio de flexão que permite determinar a capacidade de absorção de energia do Betão Reforçado com Fibras de Aço (BRFA), tendo sido sugerida a utilização de parâmetros para simular o comportamento à tracção deste compósito fendilhado, nas verificações aos estados limites de utilização e últimos. Neste trabalho descrevem-se os ensaios efectuados, apresentam-se e discutem-se os resultados obtidos, principalmente a influência, na resistência equivalente em flexão, da percentagem de fibras, da quantidade de cinzas volantes e da idade do compósito.Fundação para a Ciência e a Tecnologia (FCT) - POCTI, “POCTI/34793/99 - Cost competitive steel fibre reinforced concrete for industrial pavements

Evolutionary dynamics of the human pseudoautosomal regions

Recombination between the X and Y human sex chromosomes is limited to the two pseudoautosomal regions (PARs) that present quite distinct evolutionary origins. Despite the crucial importance for male meiosis, genetic diversity patterns and evolutionary dynamics of these regions are poorly understood. In the present study, we analyzed and compared the genetic diversity of the PAR regions using publicly available genomic sequences encompassing both PAR1 and PAR2. Comparisons were performed through allele diversities, linkage disequilibrium status and recombination frequencies within and between X and Y chromosomes. In agreement with previous studies, we confirmed the role of PAR1 as a male-specific recombination hotspot, but also observed similar characteristic patterns of diversity in both regions although male recombination occurs at PAR2 to a much lower extent (at least one recombination event at PAR1 and in ˜1% in normal male meioses at PAR2). Furthermore, we demonstrate that both PARs harbor significantly different allele frequencies between X and Y chromosomes, which could support that recombination is not sufficient to homogenize the pseudoautosomal gene pool or is counterbalanced by other evolutionary forces. Nevertheless, the observed patterns of diversity are not entirely explainable by sexually antagonistic selection. A better understanding of such processes requires new data from intergenerational transmission studies of PARs, which would be decisive on the elucidation of PARs evolution and their role in male-driven heterosomal aneuploidies.This work was supported by: - FEDER - Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 - Operacional Programme for Competitiveness and Internationalization (POCI), Portugal 2020. - Fundação para a Ciência e a Tecnologia, in the framework of the Project POCI-01–0145-FEDER-007274 to i3S. - Fundação para a Ciência e a Tecnologia, in the PhD fellowship SFRH/BD/ 135612/2018 to B.M. - Ministerio de Ciencia, Innovación y Universidades, in the Grant “Ramón y Cajal” RYC-2015-18241 to M.A. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Eficácia de fibras discretas de aço no reforço à flexão de elementos de betão

Com base em ensaios experimentais efectuados segundo a mais recente proposta da RILEM, foi avaliada a eficácia, no reforço à flexão, proporcionada pela adição de fibras de aço ao betão. O número e a distribuição das fibras na secção de fractura dos provetes foram determinados, por forma a ser possível justificar os resultados obtidos. Utilizando um modelo numérico que simula o comportamento não linear dos materiais intervenientes, o reforço introduzido por fibras discretas foi comparado com o reforço obtido por uma armadura convencional (fictícia) de área igual à das fibras existentes na secção de fractura, por forma a estimar, de forma indirecta, a influência do comprimento, orientação e aderência das fibras.Fundação para a Ciência e a Tecnologia (FCT) - “Cost competitive steel fibre reinforced concrete for industrial pavements”, com referência POCTI/34793/9

Exploring the outcomes of digital marketing on historic sites' visitor behaviour

Purpose – Digital communication and social media have an increasing importance in society and in tourism boosting. This study aims to analyse the role of digital marketing in the destination image and visitor loyalty of historic sites. Design/methodology/approach – Using a mixed-method approach combining survey data from 318 respondents and three in-depth interviews. Using structural equations modelling results reveals experience, satisfaction, image and loyalty are concepts to be considered by the destinations’ digital marketing promotion, as well as the increasing use of digital marketing by tourists, in the sense that tourists are increasing the habit of checking the opinion of others before scheduling their trip and gives them more importance, and a growing importance is given by tourists to the web/social networks of places they intend to visit. Findings – This study contributes to the theory on tourism digital marketing which can be transposed to organizations management in order to encourage discussion on the processes of capture, retention and loyalty of target audiences. Research limitations/implications – To enhance the importance of digital marketing in the process of the tourist development of the city, it is fundamental to define a clear strategy for attracting and responding to the greatest demand from cultural tourists who are increasingly interested in actively participating in learning experiences. Practical implications – The results show that digital communication and social media have an increasing importance in society and in tourism boosting and economy recovery. Social implications – The paper presents digital marketing as a possible factor in tourism development and social inclusion, advancing practical measures aimed at social justice through a fairer distribution of tourism revenues and the defence of historic centre residents’ way (i.e. Barcelos’), and quality of life. Originality/value – The authors suggest the development of a strategic digital marketing plan applied to the development and promotion of tourism in the city of Barcelos (Portugal), to complement the research presented here, thus contributing with a more practical perspective of the subject under study.info:eu-repo/semantics/acceptedVersio

A pipeline to assess disease-associated haplotypes in repeat expansion disorders: The example of MJD/SCA3 locus

At least 40 human diseases are associated with repeat expansions; yet, the mutational origin and instability mechanisms remain unknown for most of them. Previously, genetic epidemiology and predisposing backgrounds for the instability of some expanding loci have been studied in different populations through the analysis of diversity flanking the respective pathogenic repeats. Here, we aimed at developing a pipeline to assess disease-associated haplotypes at oligonucleotide repeat loci, combining analysis of single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs). Machado-Joseph disease (MJD/SCA3), the most frequent dominant ataxia worldwide, was used as an example of a detailed procedure. Thus, to identify genetic backgrounds that segregate with expanded/mutated alleles in MJD, we selected a set of 26 SNPs and 7 STRs flanking the causative CAG repeat. Key criteria and steps for this selection are described, and included (1) haplotype blocks minimizing the occurrence of recombination (for SNPs); and (2) match scores to increase potential for polymorphic information content of repetitive sequences found in Tandem Repeats Finder (for STRs). To directly assess SNP haplotypes in phase with MJD expansions, we optimized a strategy with preferential amplification of normal over expanded alleles, in addition to SNP allele-specific amplifications; this allowed the identification of disease-associated SNP haplotypes, even when only the proband is available in a given family. To infer STR haplotypes, we optimized a multiplex PCR, including 7 STRs plus the MJD_CAG repeat, followed by analysis of segregation or the use of the PHASE software. This protocol is a ready-to-use tool to assess MJD haplotypes in different populations. The pipeline designed can be used to assess disease-associated haplotypes in other repeat-expansion diseases. This should be of great utility to study (1) genetic epidemiology (population-of-origin, age and spreading routes of mutations) and (2) mechanisms responsible for de novo expansions, in these neurological diseases; (3) to detect predisposing haplotypes and (4) phenotype modifiers; (5) to help solving cases of apparent homoallelism (two same-size normal alleles) in diagnosis; and (6) to identify the best targets for the development of allele-specific therapies in ethnically diverse patient populations.This work was financed by FEDER-Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020-Operacional Program for Competitiveness and Internationalization (POCI), Portugal 2020, and by Portuguese funds through FCT-Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Inovação in the framework of the project “Institute for Research and Innovation in Health Sciences” (POCI-01-0145-FEDER-007274). SM is funded by FCT (IF/00930/2013). This article is a result of the project NORTE-01-0145-FEDER-000008, supported by Norte Portugal Regional Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF)

On Coulomb drag in double layer systems

We argue, for a wide class of systems including graphene, that in the low temperature, high density, large separation and strong screening limits the drag resistivity behaves as d^{-4}, where d is the separation between the two layers. The results are independent of the energy dispersion relation, the dependence on momentum of the transport time, and the wave function structure factors. We discuss how a correct treatment of the electron-electron interactions in an inhomogeneous dielectric background changes the theoretical analysis of the experimental drag results of Ref. [1]. We find that a quantitative understanding of the available experimental data [1] for drag in graphene is lacking.Comment: http://iopscience.iop.org/0953-8984/24/33/335602