Broken-symmetry magnetic phases in two-dimensional triangulene crystals

We provide a comprehensive theory of magnetic phases in two-dimensional triangulene crystals, using both Hubbard model and density functional theory (DFT) calculations. We consider centrosymmetric and non-centrosymmetric triangulene crystals. In all cases, DFT and mean-field Hubbard model predict the emergence of broken-symmetry antiferromagnetic (ferrimagnetic) phases for the centrosymmetric (non-centrosymmetric) crystals. This includes the special case of the [4,4]triangulene crystal, whose non-interacting energy bands feature a gap with flat valence and conduction bands. We show how the lack of contrast between the local density of states of these bands, recently measured via scanning tunneling spectroscopy, is a natural consequence of a broken-symmetry N\'eel state that blocks intermolecular hybridization. Using random phase approximation, we also compute the spin wave spectrum of these crystals, including the recently synthesized [4,4]triangulene crystal. The results are in excellent agreement with the predictions of a Heisenberg spin model derived from multi-configuration calculations for the unit cell. We conclude that experimental results are compatible with an antiferromagnetically ordered phase where each triangulene retains the spin predicted for the isolated species

Aprendizajes sobre la virtualización de las clases en Posgrados

A fines del 2019 la Secretaría de Posgrado implementó un nuevo sistema de identidad visual. El mismo fue resultado de un intenso trabajo que incluyó sondeos con alumnos/as de Posgrados, graduados/as de la Facultad e intercambios con docentes. En ese marco, se utilizó un modelo (Brand Key) para definir los diferenciales y el posicionamiento de la Facultad en referencia a la enseñanza en este nivel. De allí fue que surgió la esencia de la marca “Posgrados Económicas UNLP”: el compromiso por el aprendizaje.Hoy, solo seis meses después, esa esencia se verifica nítidamente en el valioso trabajo de todos/as los/as docentes del área y de nuestro equipo de acompañamiento administrativo, técnico y pedagógico, frente a la virtualización de las clases. De igual manera, en el esfuerzo y compromiso de nuestros/as alumnos/as.La conducción de la Facultad entendió, desde el comienzo, que la pandemia del COVID-19 supone una situación compleja, dinámica e incierta. En este contexto hay solo una certeza: la educación (como el mundo) no volverá a ser igual que antes.La mayoría de los/as especialistas coinciden en que la emergencia sanitaria, más que producir cambios, aceleró procesos que ya se venían observando. Hablamos de la transformación digital, la desglobalización, la economía contactless, los negocios digitales, la educación virtual, la telemedicina, entre otros; pero también, por ejemplo, de la democratización del conocimiento: hoy disponible de manera gratuita

Preparation and characterization of 33-S samples for 33-S(n,alpha)30-Si cross-section measurements at the n_TOF facility at CERN

Thin 33S samples for the study of the 33S(n,a)30Si cross-section at the n_TOF facility at CERN were made by thermal evaporation of 33S powder onto a dedicated substrate made of kapton covered with thin layers of copper, chromium and titanium. This method has provided for the first time bare sulfur samples a few centimeters in diameter. The samples have shown an excellent adherence with no mass loss after few years and no sublimation in vacuum at room temperature. The determination of the mass thickness of 33S has been performed by means of Rutherford backscattering spectrometry. The samples have been successfully tested under neutron irradiation.Ministerio de Economía y Competitividad de España-FPA2013-47327- C2-1-R, FPA2014-53290-C2-2-P, FPA2016-77689-C2-1-RJunta de Andalucía-P11-FQM-8229Ministerio de Economía y Empresa de España (Fondos FEDER)-FIS2015-69941-C2-1-PAECC (Asociación Española Contra el Cáncer)-PS16163811POR

Combined kinetic and DFT studies on the stabilization of the pyramidal form of H3PO2 at the heterometal site of [Mo3M’S4(H2O)10]4+ clusters (M’= Pd, Ni)

Kinetic and DFT studies have been carried out on the reaction of the [Mo3M’S4(H2O)10]4+ clusters (M’= Pd, Ni) with H3PO2 to form the [Mo3M’(pyr-H3PO2)S4(H2O)9]4+ complexes, in which the rare pyramidal form of H3PO2 is stabilized by coordination to the M’ site of the clusters. The reaction proceeds with biphasic kinetics, both steps showing a first order dependence with respect to H3PO2. These results are interpreted in terms of a mechanism that involves an initial substitution step in which one tetrahedral H3PO2 molecule coordinates to M’ through the oxygen atom of the P=O bond, followed by a second step that consists in tautomerization of coordinated H3PO2 assisted by a second H3PO2 molecule. DFT studies have been carried out to obtain information on the details of both kinetic steps, the major finding being that the role of the additional H3PO2 molecule in the second step consists in catalysing a hydrogen shift from phosphorus to oxygen in O-coordinated H3PO2, which is made possible by its capability of accepting a proton from P-H to form H4PO2 + and then transfer it to the oxygen. DFT studies have been also carried out on the reaction at the Mo centres to understand the reasons that make these metal centres ineffective for promoting tautomerizatio

Aproximación a la discapacidad en una población de la cultura de El Argar

A new research fi eld is being developed on disability in Archaeology and Physical Anthropology, which is investigated in this article in the context of the Argaric Culture. More than 200 skeletons, coming from sites in Granada province (Castellón Alto, Fuente Amarga, Cuesta del Negro, Terrera del Reloj and Cerro de la Encina), were studied, fi nding four with signs of physical impairment: one male and one female who must both have used a walking aid, and two males with shoulder dislocations. All four individuals were buried according to Argaric Culture rituals, beneath their dwellings, indicating that they were not socially rejected. Nevertheless, further insight into disability in this culture is hampered by the limited biological and archaeological data available.La discapacidad, entendida como la consideración de una persona con invalidez por parte de su comunidad, constituye un nuevo campo de investigación en Ar queología y Antropología Física. Aquí se investiga este concepto en el marco de la cultura de El Argar. Se han estudiado más de 200 esqueletos procedentes de yacimientos de la provincia de Granada (Castellón Alto, Fuente Amarga, Cuesta del Negro, Terrera del Reloj y Cerro de la Encina) entre los cuales cuatro muestran señales de invalidez: un hombre y una mujer que debieron haber requerido ayuda para caminar y dos varones con luxaciones de hombro. Los cuatro individuos fueron enterrados según los rituales de la cultura argárica, bajo sus propias viviendas, lo que indica que no fueron rechazados socialmente. Sin embargo, no se puede profundizar sobre la concepción de la discapacidad en esta cultura puesto que los datos arqueológicos y biológicos son muy limitados

EPD and Spark Plasma Sintering of bimodal alumina/titania concentrated suspensions

Alumina-aluminium titanate (A-AT) composites and laminates have been recently investigated because they can provide improved flaw tolerance and toughness associated to a microcracking mechanism. A-AT composites have been produced by slip casting and reaction sintering of submicron sized alumina and titania powders. This work deals with the preparation of thick self-sustained A-AT films from mixtures of submicron sized alumina and nanosized titania powders and further sintering by conventional and non-conventional (spark plasma sintering, SPS) methods. Suspensions were prepared in water to high solid loadings, up to 50 vol.%. Self-sustained films were obtained by aqueous electrophoretic deposition (EPD) using graphite substrates under constant current density conditions. The evolution of mass per unit area with current density and deposition time was recorded. The films were characterized in the green state and after sintering at different temperatures (1300-1400) degrees C. Fully dense A-AT reaction sintered materials were obtained at low temperature by SPSThis study has been supported by the Spanish Ministry of Science and Innovation MAT2009-14369-C02-01 and MAT2009-14144-C03-02. A. Borrell, acknowledges the Spanish Ministry of Science and Innovation for her Juan de la Cierva contract (JCI-2011-10498) and the Generalitat Valenciana for the BEST/2012/302 grant and the financial support for ACOMP/2012/166.Borrell Tomás, MA.; Salvador Moya, MD.; Rocha, VG.; Fernández, A.; Molina, T.; Moreno, R. (2013). EPD and Spark Plasma Sintering of bimodal alumina/titania concentrated suspensions. Journal of Alloys and Compounds. 577:195-202. https://doi.org/10.1016/j.jallcom.2013.04.175S19520257

Factor de impacto de revistas: ¿amenaza u oportunidad?

Este artículo contiene un resumen de las críticas a la utilización del factor de impacto (FI) como indicador de calidad de las publicaciones y de producción de investigadores. Tales críticas alcanzan a los autores que intentan publicar en revistas con FI, argumentando que así renuncian a la propia identidad, primando su currículum sobre la utilidad de su investigación. En oposición a esas críticas se afirma que unos criterios de evaluación exigentes sirven de estímulo para la internacionalización del sistema científico. Existe consenso en la comunidad académica sobre las imperfecciones del FI y su aceptación como recurso válido y necesario para la evaluación científica, como también en que el debate identitario contribuye poco a resolver la invisibilidad internacional de la investigación de enfermería en español. Se esbozan propuestas que apuestan por aprovechar las fortalezas para incrementar y visibilizar dicha investigación, desarrollar estrategias para incluir y mantener a las revistas en español en el Journal Citation Reports (JCR), fomentar la formación y cooperación interdisciplinar, promover la publicación de investigaciones desarrolladas en los programas de posgrado, y reclamar la apuesta editorial por la indexación de sus revistas en el JCR. Se concluye que, aunque difícil, es posible aumentar la visibilidad de la producción científica de enfermería en español

Authentication of tequilas using pattern recognition and supervised classification

[Abstract] Sales of reputed, Mexican tequila grown substantially in last years and, therefore, counterfeiting is increasing steadily. Hence, methodologies intended to characterize and authenticate commercial beverages are a real need. They require a combination of analytical characterization and chemometric tools. This work reports concisely on the former and focus on the chemometric tools employed so far in connection with them. Further, a practical case study presents the classification capabilities of nine supervised classification methods to differentiate white, rested, aged and extra-aged tequilas. The largest set of certified tequilas employed so far was considered. In general, non linear methods performed best than linear ones (accuracy higher than 94% in both training and validation). The case study demonstrates that it is possible to develop fast, cheap, easy to implement and reliable analytical methodologies to authenticate and classify samples of tequilas.Xunta de Galicia; GRC2013-047Ministerio de Industria, Energía y Competitividad; FJCI-2015-2607

Recent results in nuclear astrophysics at the n_TOF facility at CERN

The neutron time of flight (n_TOF) facility at CERN is a spallation source characterized by a white neutron spectrum. The innovative features of the facility, in the two experimental areas, (20 m and 185 m), allow for an accurate determination of the neutron cross section for radioactive samples or for isotopes with small neutron capture cross section, of interest for Nuclear Astrophysics. The recent results obtained at n_TOF facility are presented