University of Valencia
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Opening the Hysteresis Loop in Ferromagnetic Fe3GeTe2 Nanosheets Through Functionalization with TCNQ Molecules
No full textFerromagnetic metal Fe3GeTe2 (FGT), whose structure exhibits weak van-der-Waals interactions between 5-atom thick layers, was subjected to liquid-phase exfoliation (LPE) in N-methyl pyrrolidone (NMP) to yield a suspension of nanosheets that were separated into several fractions by successive centrifugation at different speeds. Electron microscopy confirmed successful exfoliation of bulk FGT to nanosheets as thin as 6 nm. The ferromagnetic ordering temperature for the nanosheets gradually decreased with the increase in the centrifugation speed used to isolate the 2D material. These nanosheets were resuspended in NMP and treated with an organic acceptor, 7,7,8,8-tetracyano-quinodimethane (TCNQ), which led to precipitation of FGT-TCNQ composite. The formation of the composite material is accompanied by charge transfer from the FGT nanosheets to TCNQ molecules, generating TCNQ⋅− radical anions, as revealed by experimental vibrational spectra and supported by first principles calculations. Remarkably, a substantial increase in magnetic anisotropy was observed, as manifested by the increase in the coercive field from nearly zero in bulk FGT to 1.0 kOe in the exfoliated nanosheets and then to 5.4 kOe in the FGT-TCNQ composite. The dramatic increase in coercivity of the composite suggests that functionalization with redox-active molecules provides an appealing pathway to enhancing magnetic properties of 2D materials
Survival and growth of embryo axes of temperate trees after two decades of cryo-storage
No full textLiquid nitrogen (LN) storage is recommended for conserving plants with seeds for which standard seed banking is not feasible, but there are few empirical reports confirming its long-term effectiveness. In this study we evaluated in vitro viability and ex vitro growth of embryo axes of a species that is short-lived in seed bank conditions (Juglans nigra) and two recalcitrant seeded species (Aesculus hippocastanum and A. glabra) that were stored 11-23 years in LN. Viability of J. nigra axes did not decrease significantly after 23 years and produced normal-appearing plantlets. Similarly, viability of A. hippocastanum axes did not decrease after 23 years. However, A. glabra axes showed a significant decline in viability after 23 years, from 80% when freshly harvested to 33%. These results demonstrate that LN storage can preserve embryo axes of J. nigra and Aesculus sp. for over two decades, providing a workable conservation tool for these and similar species
Interplay between spin crossover and proton migration along short strong hydrogen bonds
No full textThe iron(II) salt [Fe(bpp)2](isonicNO)2·HisonicNO·5H2O (1) (bpp = 2,6-bis(pyrazol-3-yl)pyridine; isonicNO = isonicotinate N-oxide anion) undergoes a partial spin crossover (SCO) with symmetry breaking at T1 = 167 K to a mixed-spin phase (50% high-spin (HS), 50% low-spin (LS)) that is metastable below T2 = 116 K. Annealing the compound at lower temperatures results in a 100% LS phase that differs from the initial HS phase in the formation of a hydrogen bond (HB) between two water molecules (O4W and O5W) of crystallisation. Neutron crystallography experiments have also evidenced a proton displacement inside a short strong hydrogen bond (SSHB) between two isonicNO anions. Both phenomena can also be detected in the mixed-spin phase. 1 undergoes a light-induced excited-state spin trapping (LIESST) of the 100% HS phase, with breaking of the O4W/O5W HB and the onset of proton static disorder in the SSHB, indicating the presence of a light-induced activation energy barrier for proton motion. This excited state shows a stepped relaxation at T1(LIESST) = 68 K and T2(LIESST) = 76 K. Photocrystallography measurements after the first relaxation step reveal a single Fe site with an intermediate geometry, resulting from the random distribution of the HS and LS sites throughout the lattic
Thermal phenotypic plasticity of pre-and post-copulatory male harm buffers sexual conflict in wild Drosophila melanogaster
No full textStrong sexual selection frequently leads to sexual conflict and ensuing male harm, whereby males increase their reproductive success at the expense of harming females. Male harm is a widespread evolutionary phenomenon with a strong bearing on population viability. Thus, understanding how it unfolds in the wild is a current priority. Here, we sampled a wild Drosophila melanogaster population and studied male harm across the normal range of temperatures under which it reproduces optimally in nature by comparing female lifetime reproductive success and underlying male harm mechanisms under monogamy (i.e. low male competition/harm) vs. polyandry (i.e. high male competition/harm). While females had equal lifetime reproductive success across temperatures under monogamy, polyandry resulted in a maximum decrease of female fitness at 24°C (35%), reducing its impact at both 20°C (22%), and 28°C (10%). Furthermore, female fitness components and pre- (i.e. harassment) and post- copulatory (i.e. ejaculate toxicity) mechanisms of male harm were asymmetrically affected by temperature. At 20°C, male harassment of females was reduced, and polyandry accelerated female actuarial aging. In contrast, the effect of mating on female receptivity (a component of ejaculate toxicity) was affected at 28°C, where the mating costs for females decreased and polyandry mostly resulted in accelerated reproductive aging. We thus show that, across a natural thermal range, sexual conflict processes and their effects on female fitness components are plastic and complex. As a result, the net effect of male harm on overall population viability is likely to be lower than previously surmised. We discuss how such plasticity may affect selection, adaptation and, ultimately, evolutionary rescue under a warming climate
Synthesis and characterization of nanostructured tetrahedrite and its composite with dielectric inclusions
No full textThe nanostructured Cu-Sb-S materials have been synthesized by a low-cost and versatile polyol technique in a triethylene glycol medium at different temperatures (Ts = 473-533 K). The content of tetrahedrite (Cu12Sb4S13), skinnerite (Cu3SbS3), famatinite (Cu3SbS4), and chalcostibite (CuSbS2) phases was quantitatively determined via the Rietveld refinement of X-ray diffraction (XRD) patterns which showed that Cu-Sb-S pellets densified from powders synthesized at 493 K possess the highest content of tetrahedrite (i.e., ∼96.6 vol%) with small amount of skinnerite (i.e., ∼3.4 vol%). The inclusion of dielectric polyvinylpyrrolidone (PVP) up to 2.5 wt.% to tetrahedrite phase induced the alteration of structural (unit cell parameter a and volume Vunit) and microstructural (sizes of coherent scattering domains L, levels of microdeformations lε, microstresses lσ, and density of dislocations dρ) parameters. The change in the microstructure of Cu12Sb4S13-PVP composites caused the decrease of electronic thermal conductivity κe by 3 times. The increase of Seebeck coefficient (S) resulted in a power factor (PF) of (100-180) μV/K at (300-473) K for Cu12Sb4S13-PVP composite. The presented approach proves the effectiveness of the tuning thermoelectric characteristics of tetrahedrite via admixing with dielectric inclusions
Singularidad y experiencia común
No full text¿A qué se debe ese interés creciente en centrar el eje de lo político en la figura del espectador? Ante la consumación de la 'sociedad del espectáculo', anticipada por Guy Debord, y consolidada en los modelos de la 'sociedad de figurantes', teorizada por Nicolás Bourriaud, o incluso en la 'sociedad de la performance', descrita Rick Allsopp y J. McKenzie, la pregunta es: ¿Qué entendemos por participación en un contexto marcado por el descrédito de lo político? ¿Cuáles son las estrategias participativas que se implementan desde la creación escénica actualmente? La participación, entendida como 'actividad' del espectador, es cuestionada desde propuestas que cancelan las dicotomías sobre las que, tradicionalmente, se ha asentado la idea de acción entorno al espectador, multiplicando las posibilidades de experimentación con los dispositivos, las poéticas y la politicidad en el campo de las artes escénicas. La problematización del concepto de público, en tanto que entidad unitaria y más allá de su deconstrucción en función de género, etnia, etc., pone en primer plano la necesidad de obras aptas para una traducción singular, en las que el espectador co-crea el sentido y a su vez es co-creado como ser singular en esa operación. Multiplicidad de traducciones, de singularidades, en un encuentro potencial que abre el campo a la experiencia común y a la bella práctica del pensar-sentir algo por primera vez
La regulación de los precios de la vivienda en España
No full textLa posibilidad de acceder a una vivienda digna y adecuada no es una realidad para toda la población española. Desde hace ya algunos años nos encontramos en un contexto de crisis habitacional especialmente caracterizado por fuertes aumentos en los precios de los contratos de compraventa y en las rentas de los alquileres como consecuencia del hecho que la demanda de vivienda ha crecido más que la oferta por distintos motivos (presiones demográficas y económicas, un mayor atractivo de la inversión en esta para dedicarla a alquiler, etc.), que no han venido aparejados de aumentos correlativos en los ingresos de los hogares y que han supuesto una intensificación de las dificultades en el acceso a la vivienda residencial así como un significativo incremento del gasto en alquiler en la cesta del consumo de las familias. Pese a que esta es una situación compartida en numerosos países de nuestro entorno comparado, la severidad de la crisis habitacional es especialmente manifiesta en España, donde se ha visto agravada por el hecho de que las políticas de vivienda desarrolladas durante las últimas décadas se han revelado especialmente inconsistentes e insuficientes. Estas circunstancias han supuesto, recientemente, una profundización en el debate sobre la necesidad de reforzar las políticas públicas en materia de vivienda, de acuerdo con lo previsto por los arts. 47 y 148.1.3.ª de la Constitución Española (CE) y en la línea de la interpretación que del derecho a la vivienda han realizado distintas instituciones y tribunales internaciona¬les4. Como consecuencia de esta discusión, se han sucedido distintas normas, especialmente en el contexto autonómico5, pero también en el estatal -esencialmente, la Ley 12/2023, de 24 de mayo, por el derecho a la vivienda (LDV), la primera ley estatal reguladora del derecho a la vivienda desde la aprobación de la CE- que, si bien hasta la fecha no han conllevado cambios sustanciales en relación con la resolución de dicha crisis, sí que han tratado de dar más efectividad jurídica a este derecho. A estos avances cabe sumar la mayor sensibilidad hacia el derecho de la vivienda que se observa en las sentencias del Tribunal Constitucional más recientes, más en línea con los pronunciamientos de los tribunales internacionales, que ha afianzado estas políticas. En este contexto, las políticas de limitación del precio de los contratos de arrendamiento de vivienda han resurgido, tanto en el ámbito estatal como en el autonómico, siguiendo modelos ensayados en países de nuestro entorno comparado, por el atractivo que sus efectos inmediatos producen frente a los escasos costes que suponen, en principio, para la hacienda pública. El interés por el estudio de estas experiencias normativas justifica el presente artículo, que analizará, después de hacer una breve referencia a los conflictos que subyacen a este tipo de medidas, las políticas de control de precios ensayadas en nuestro ordenamiento jurídico en relación con la compra y con el alquiler de viviendas. El trabajo seguirá con un examen de los límites normativos que encuadra tanto la actuación del legislador como la de las Administraciones públicas en esta materia y finalizará con una breve valoración de los mecanismos de control de precios estudiados
Approximate Lax-Wendroff discontinuous Galerkin methods for hyperbolic conservation laws
No full textThe Lax-Wendroff time discretization is an alternative method to the popular total variation diminishing Runge-Kutta time discretization of discontinuous Galerkin schemes for the numerical solution of hyperbolic conservation laws. The resulting fully discrete schemes are known as LWDG and RKDG methods, respectively. Although LWDG methods are in general more compact and efficient than RKDG methods of comparable order of accuracy, the formulation of LWDG methods involves the successive computation of exact flux derivatives. This procedure allows one to construct schemes of arbitrary formal order of accuracy in space and time. A new approximation procedure avoids the computation of exact flux derivatives. The resulting approximate LWDG schemes, addressed as ALWDG schemes, are easier to implement than their original LWDG versions. In particular, the formulation of the time discretization of the ALWDG approach does not depend on the flux being used. Numerical results for the scalar and system cases in one and two space dimensions indicate that ALWDG methods are more efficient in terms of error reduction per CPU time than LWDG methods of the same order of accuracy. Moreover, increasing the order of accuracy leads to substantial reductions of numerical error and gains in efficiency for solutions that vary smoothly
Heuristics for the constrained incremental graph drawing problem
No full textVisualization of information is a relevant topic in Computer Science, where graphs have become a standard representation model, and graph drawing is now a well-established area. Within this context, edge crossing minimization is a widely studied problem given its importance in obtaining readable representations of graphs. In this paper, we focus on the so-called incremental graph drawing problem, in which we try to preserve the user's mental map when obtaining successive drawings of the same graph. In particular, we minimize the number of edge crossings while satisfying some constraints required to preserve the position of vertices with respect to previous drawings. We propose heuristic methods to obtain high-quality solutions to this optimization problem in the short computational times required for graph drawing applications. We also propose a mathematical programming formulation and obtain the optimal solution for small and medium instances. Our extensive experimentation shows the merit of our proposal with respect to both optimal solutions obtained with CPLEX and heuristic solutions obtained with LocalSolver, a well-known black-box solver in combinatorial optimization
Clinical impact of multidrug-resistant bacteria in older hospitalized patients with community-acquired urinary tract infection
No full textIntroduction Previous studies have described some risk factors for multidrug-resistant (MDR) bacteria in urinary tract infection (UTI). However, the clinical impact of MDR bacteria on older hospitalized patients with community-acquired UTI has not been broadly analyzed. We conducted a study in older adults with community-acquired UTI in order to identify risk factors for MDR bacteria and to know their clinical impact. Methods Cohort prospective observational study of patients of 65 years or older, consecutively admitted to a university hospital, diagnosed with community-acquired UTI. We compared epidemiological and clinical variables and outcomes, from UTI due to MDR and non-MDR bacteria. Independent risk factors for MDR bacteria were analyzed using logistic regression. Results 348 patients were included, 41.4% of them with UTI due to MDR bacteria. Median age was 81 years. Hospital mortality was 8.6%, with no difference between the MDR and non-MDR bacteria groups. Median length of stay was 5 [4-8] days, with a longer stay in the MDR group (6 [4-8] vs. 5 [4-7] days, p = 0.029). Inadequate empirical antimicrobial therapy (IEAT) was 23.3%, with statistically significant differences between groups (33.3% vs. 16.2%, p < 0.001). Healthcare-associated UTI variables, in particular previous antimicrobial therapy and residence in a nursing home, were found to be independent risk factors for MDR bacteria. Conclusions The clinical impact of MDR bacteria was moderate. MDR bacteria cases had higher IEAT and longer hospital stay, although mortality was not higher. Previous antimicrobial therapy and residence in a nursing home were independent risk factors for MDR bacteria