Thermodynamics of the classical spin-ice model with nearest neighbour interactions using the Wang-Landau algorithm

In this article we study the classical nearest-neighbour spin-ice model (nnSI) by means of Monte Carlo simulations, using the Wang-Landau algorithm. The nnSI describes several of the salient features of the spin-ice materials. Despite its simplicity it exhibits a remarkably rich behaviour. The model has been studied using a variety of techniques, thus it serves as an ideal benchmark to test the capabilities of the Wang Landau algorithm in magnetically frustrated systems. We study in detail the residual entropy of the nnSI and, by introducing an applied magnetic field in two different crystallographic directions ([111] and [100],) we explore the physics of the kagome-ice phase, the transition to full polarisation, and the three dimensional Kasteleyn transition. In the latter case, we discuss how additional constraints can be added to the Hamiltonian, by taking into account a selective choice of states in the partition function and, then, show how this choice leads to the realization of the ideal Kasteleyn transition in the system.Comment: 9 pages, 9 figure

La traducción de textos científicos inglés><español

71 p.La experiencia que origina este trabajo se inscribe en el marco de las asignaturas Traducción Técnica y Traducción Científica, de la carrera Traductorado de Inglés en la Facultad de Lenguas de la Universidad Nacional de Córdoba. Hasta el año 2007, el enfoque de la enseñanza de la traducción en este contexto fue eminentemente temático, es decir, se intentaba cubrir los temas y la terminología pertenecientes a los distintos campos de la ciencia y la tecnología, como si fuera posible abarcar todo ese universo en un año académico. Es a partir de entonces que se introdujeron cambios sustanciales estructurados en torno a un enfoque textual que hoy se centra fuertemente en el análisis de los géneros técnicos y científicos. La idea subyacente es preparar al futuro traductor para que enfrente cualquier campo temático a través del conocimiento de estrategias de traducción acotadas a cada género textual. Otra de las modificaciones metodológicas que se derivan del nuevo enfoque es la enseñanza de la documentación y la terminología mediante recursos en línea y herramientas de traducción asistida por computadora en aras de que el estudiante desarrolle su competencia instrumental en cada una de las fases del proceso traductológico. Es por eso que presentamos por un lado, nuestra fundamentación teórica para los cambios producidos y por el otro, textos-ejemplos que van a ser de suma utilidad para la elaboración de estrategias en la resolución de problemas. Las demás pautas de trabajo en el desarrollo de la asignatura Traducción Científica están alineadas con este enfoque constructivista: el entorno colaborativo, el uso de software libre, el énfasis en el encargo de traducción, el perfil de un traductor egresado autónomo y con las herramientas digitales necesarias para llevar a cabo su actividad laboral con eficiencia

Spectral properties of a short-range impurity in a quantum dot

The spectral properties of the quantum mechanical system consisting of a quantum dot with a short-range attractive impurity inside the dot are investigated in the zero-range limit. The Green function of the system is obtained in an explicit form. In the case of a spherically symmetric quantum dot, the dependence of the spectrum on the impurity position and the strength of the impurity potential is analyzed in detail. It is proven that the confinement potential of the dot can be recovered from the spectroscopy data. The consequences of the hidden symmetry breaking by the impurity are considered. The effect of the positional disorder is studied.Comment: 30 pages, 6 figures, Late

Boundary conditions and the residual entropy of ice systems

We would like to acknowledge financial support from CONICET (Argentina) and from ANPCYT (Argentina) via Grant No. PICT-2013-2004.In this work we address the classical statistical mechanical problem of calculating the residual entropy of ice models. The numerical work found in the literature is usually based on extrapolating to infinite-size results obtained for finite-size systems with periodic boundary conditions. In this work we investigate how boundary conditions affect the calculation of the residual entropy for square, cubic, and hexagonal lattices using periodic, antiperiodic, and open boundary conditions. We show that periodic boundary conditions lead to noticeable oscillations in the entropy as a function of lattice size, and we calculate in open finite systems the contribution to the entropy from the open boundary. For our calculations we introduce a variation on multicanonical simulation methods that directly calculate the number of states in the ground state without the need of a Hamiltonian.Publisher PDFPeer reviewe

Characterizations of k-commutative equalities for some outer generalized inverses

[EN] In this paper, we present necessary and sufficient conditions for the k-commutative equality , where X is an outer generalized inverse of the square matrix A. Also, we give new representations for core EP, DMP, and CMP inverses of square matrices as outer inverses with prescribed null space and range. In addition, we characterize the core EP inverse as the solution of a new system of matrix equations.D. E. Ferreyra F. E. Levis Partially supported by a Consejo Nacional de Investigaciones Científicas y Técnicas CONICET s Posdoctoral Research Fellowship, UNRC [grant number PPI 18/C472] and CONICET [grant number PIP 112-201501-00433CO], respectively. N. Thome Partially supported by Secretaría de Estado de Investigación, Desarrollo e Innovación Ministerio de Economía, Industria y Competitividad of Spain [grant number DGI MTM2013-43678-P and Grant Red de Excelen- cia PMTM2017-90682-REDT]. D. E. Ferreyra and N. Thome Partially supported Universidad Nacional de La Pampa (UNLPam), Facultad de Ingeniería [grant Resol. No 155/14].Ferreyra, DE.; Levis, F.; Thome, N. (2018). Characterizations of k-commutative equalities for some outer generalized inverses. Linear and Multilinear Algebra. 1-16. https://doi.org/10.1080/03081087.2018.1500994S116Baksalary, O. M., & Trenkler, G. (2010). Core inverse of matrices. Linear and Multilinear Algebra, 58(6), 681-697. doi:10.1080/03081080902778222Manjunatha Prasad, K., & Mohana, K. S. (2013). Core–EP inverse. Linear and Multilinear Algebra, 62(6), 792-802. doi:10.1080/03081087.2013.791690Malik, S. B., & Thome, N. (2014). On a new generalized inverse for matrices of an arbitrary index. Applied Mathematics and Computation, 226, 575-580. doi:10.1016/j.amc.2013.10.060Mehdipour, M., & Salemi, A. (2017). On a new generalized inverse of matrices. Linear and Multilinear Algebra, 66(5), 1046-1053. doi:10.1080/03081087.2017.1336200Malik, S. B., Rueda, L., & Thome, N. (2016). The class ofm-EPandm-normal matrices. Linear and Multilinear Algebra, 64(11), 2119-2132. doi:10.1080/03081087.2016.1139037Wang, H. (2016). Core-EP decomposition and its applications. Linear Algebra and its Applications, 508, 289-300. doi:10.1016/j.laa.2016.08.008Wang H, Chen J. Weak group inverse. Available from: http://arxiv.org/abs/1704.08403v1Wei, Y. (1998). A characterization and representation of the generalized inverse A(2)T,S and its applications. Linear Algebra and its Applications, 280(2-3), 87-96. doi:10.1016/s0024-3795(98)00008-1Rakić, D. S., Dinčić, N. Č., & Djordjević, D. S. (2014). Core inverse and core partial order of Hilbert space operators. Applied Mathematics and Computation, 244, 283-302. doi:10.1016/j.amc.2014.06.112Stanimirović, P. S., Katsikis, V. N., & Ma, H. (2016). Representations and properties of theW-Weighted Drazin inverse. Linear and Multilinear Algebra, 65(6), 1080-1096. doi:10.1080/03081087.2016.1228810Ferreyra, D. E., Levis, F. E., & Thome, N. (2017). Revisiting the core EP inverse and its extension to rectangular matrices. Quaestiones Mathematicae, 41(2), 265-281. doi:10.2989/16073606.2017.1377779Deng, C. Y., & Du, H. K. (2009). REPRESENTATIONS OF THE MOORE-PENROSE INVERSE OF 2×2 BLOCK OPERATOR VALUED MATRICES. Journal of the Korean Mathematical Society, 46(6), 1139-1150. doi:10.4134/jkms.2009.46.6.1139Wang, H., & Liu, X. (2014). Characterizations of the core inverse and the core partial ordering. Linear and Multilinear Algebra, 63(9), 1829-1836. doi:10.1080/03081087.2014.97570

Cryptic genetic structure in an Argentinian population of Anastrepha fraterculus (Diptera: Tephritidae) evidenced by SSR markers and quantitative traits

In some regions of Argentina and Brazil, the South American fruit fly Anastrepha fraterculus (Wied.) (Diptera: Tephritidae) causes significant damage to crops. An efficient integrated management program requires knowledge of pest population dynamics, dispersion patterns, sexual and oviposition behaviour, and adaptive landscape. The present study combined simple sequence repeat (SSR) molecular markers and morphometric datasets in order to analyse the population structure and infer the oviposition resource use strategy of the females. Infested guava fruits were collected from nine wild trees in Tucumán, Argentina, and a total of 140 adult A. fraterculus were recovered. These were then measured for six morphometric traits and 89 of them were genotyped for eight SSR loci. Genetic variability estimates were high (expected heterozygosity = 0.71, allelic richness = 12.5), with 8 to 20 alleles per locus. According to Wright's F-statistics estimates, the highest proportion (83%) of genetic variation occurred within individuals while variance between and within fruits were similar (≈ 8.5%). Analysis of the cryptic genetic structure based on SSR using different approaches, namely discriminant analysis of principal components (DAPC) and sparse non-negative matrix factorization (SNMF), yielded results consistent with the occurrence of two clusters with virtually no admixture. Average kinship between individuals which had emerged from the same fruit (0.07) was lower than that expected for full-sib families. Univariate and multivariate analyses of phenotypic data showed 54-66% of variance among individuals within fruits and 34-46% among fruits. The comparison between phenotypic (PST) and molecular (FST) differentiation identified wing width and length as possible target of positive selection. The average kinship and high genetic variation within fruits, together with the highly significant genetic differentiation among fruits, supports the hypothesis that each fruit was colonised by about three ovipositing females. The results also indicate that females were able to disperse widely from the emergence site before mating and starting oviposition activity.Instituto de GenéticaFil: Rodriguez, Angeles I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Ferreyra, Laura Ines. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Lanzavecchia, Silvia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética. Laboratorio de Genética de Insectos de Importancia Económica; ArgentinaFil: Gomez Cendra, Paula V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vilardi, Juan Cesar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Field-tuned order by disorder in frustrated Ising magnets with antiferromagnetic interactions

We demonstrate the appearance of thermal order by disorder in Ising pyrochlores with staggered antiferromagnetic order frustrated by an applied magnetic field. We use a mean-field cluster variational method, a low-temperature expansion, and Monte Carlo simulations to characterize the order-by-disorder transition. By direct evaluation of the density of states, we quantitatively show how a symmetry-broken state is selected by thermal excitations. We discuss the relevance of our results to experiments in 2D and 3D samples and evaluate how anomalous finite-size effects could be exploited to detect this phenomenon experimentally in two-dimensional artificial systems, or in antiferromagnetic all-in-all-out pyrochlores like Nd2Hf2O7 or Nd2Zr2O7, for the first time.Publisher PDFPeer reviewe

Epidemiologia da gastrenterite viral aguda em crianças hospitalizadas na cidade de Córdoba, Argentina: uma percepção ao impacto da doença

Information concerning the disease burden of viral gastroenteritis has important implications for the use and monitoring the impact of public health policies. The present study, carried out in Córdoba city, Argentina, documents the epidemiology of severe viral diarrhea as well as the burden of viral gastrointestinal disease in the hospital children admission. A total of 133 stools were collected from hospitalized children (Town Childhood Hospital) suffering from acute diarrhea and studied for the presence of Group A rotavirus, astrovirus and adenovirus 40/41 by enzyme-immuno assay, between November 1997 and October 1998. Enteric viruses accounted for 42.1% of the total diarrheal cases analyzed. Group A rotaviruses, astroviruses, adenoviruses 40/41 and mixed infections were found in 35.3, 4.5, 1.5, and 0.8% studied specimens respectively. We estimated that 1 in 27 children in the 0-35 month-old cohort/range would be annually hospitalized for a viral gastroenteritis illness. The major impact on viral diarrhea lies on rotaviral infection, accouting for 84.0% of the viral diarrheal cases analyzed and for approximately one third of severe diarrheas requiring hospital admission in Córdoba City, Argentina.Dados a respeito do impacto das gastrenterites virais têm implicações importantes para o monitoraramento do impacto das políticas de saúde pública. O presente estudo, feito na cidade de Córdoba, Argentina, documenta a epidemiologia da diarréia viral severa como também o impacto que a mesma representa na admissão hospitalar de crianças. Pesquisou-se a presença de Rotavírus grupo A, Astrovírus e Adenovírus 40/41 por ensaio imuno-enzimático em 133 amostras de fezes obtidas durante o período de novembro de 1997 a outubro de 1998, de crianças hospitalizadas por diarréia aguda. Os virus entéricos constituíram 42,1% do total de casos de diarréia analisados. Encontraram-se Rotavírus Grupo A, Astrovírus, Adenovírus 40/41 e infecções mistas em 35,3; 4,5; 1,5 e 0,8% das amostrras estudadas, respectivamente. Observamos que uma de cada 27 crianças entre 0-35 meses de idade seria hospitalizada por ano devido a uma gastrenterite viral. O principal impacto da diarréia viral é representado pela infecção por Rotavírus, correspondendo a 84,0% dos casos analisados e cerca de um terço das diarréias graves que precisam hospitalização em Córdoba, Argentina

Determination of the mating system of tucumã palm using microsatellite markers.

A palmeira Astrocaryum aculeatum produz frutos comestíveis, utilizados na alimentação por populações indígenas, tradicionais e urbanas. Esta espécie é incipientemente domesticada e pouco estudada apesar de sua importância econômica para pequenos produtores e extrativistas. Estudos do sistema reprodutivo são necessários para conservação e uso dos recursos genéticos da espécie. O objetivo foi estimar parâmetros do sistema reprodutivo do tucumã-do-Amazonas usando marcadores microssatélites

Optimización preliminar del peletizado de sorgo lignocelulósico para generación de gas de síntesis

La generación de energía en Argentina está sustentada principalmente por combustibles fósiles. Se vienen realizando diversas acciones para generar una transición hacia una generación distribuida, sostenible y amigable con el entorno. Distintos programas de financiamiento fomentan la instalación de pequeñas plantas de generación de energía térmica con biomasa. El crecimiento de esta tecnología depende en gran medida de la capacidad de generar combustibles con buena capacidad térmica, así como de la disponibilidad y aprovechamiento de los recursos. En Argentina, existen zonas de baja producción agrícola, que resultan aptas para el desarrollo de sorgo lignocelulósico. La posibilidad de almacenar y disponer del sorgo como combustible, requiere de un proceso de acondicionamiento que involucra picado, secado y peletizado. El objetivo de este trabajo fue optimizar el proceso de acondicionamiento, así como evaluar la reducción de energía en el proceso de secado en una instalación piloto. El proceso de extrusión requirió la modificación mecánica de la extrusora a fin de ajustar los huelgos al material procesado. Las muestras de sorgo presentaron dificultades para el acondicionamiento, empastando tanto la extrusora como la peletizadora, mientras que las muestras híbridas fluyeron mejor y se obtuvieron pélets con buenas características mecánicas, aptos para el almacenamiento y gasificación