Ising-nematic order in the bilinear-biquadratic model for the iron pnictides

Motivated by the recent inelastic neutron scattering (INS) measurements in the iron pnictides which show a strong anisotropy of spin excitations in directions perpendicular and parallel to the ordering wave-vector even above the magnetic transition temperature $T_N$, we study the frustrated Heisenberg model with a biquadratic spin-spin exchange interaction. Using the Dyson-Maleev (DM) representation, which proves appropriate for all temperature regimes, we find that the spin-spin dynamical structure factors are in excellent agreement with experiment, exhibiting breaking of the $C_4$ symmetry even into the paramagnetic region $T_N<T<T_{\sigma}$ which we refer to as the Ising-nematic phase. In addition to the Heisenberg spin interaction, we include the biquadratic coupling $K (\mathbf{S}_i\cdot \mathbf{S}_j)^2$ and study its effect on the dynamical temperature range $T_{\sigma}-T_N$ of the Ising-nematic phase. We find that this range reduces dramatically when even small values of the interlayer exchange $J_c$ and biquadratic coupling $K$ are included. To supplement our analysis, we benchmark the results obtained using the DM method against those from different non-linear spin-wave theories, including the recently developed generalized spin-wave theory (GSWT), and find good qualitative agreement among the different theoretical approaches as well as experiment for both the spin-wave dispersions and the dynamical structure factors

Unified Spin Model for Magnetic Excitations in Iron Chalcogenides

Recent inelastic neutron scattering (INS) measurements on FeSe and Fe(Te$_{1-x}$Se$_x$), have sparked intense debate over the nature of the ground state in these materials. Here we propose an effective bilinear-biquadratic spin model which is shown to consistently describe the evolution of low-energy spin excitations in FeSe, both under applied pressure and upon Se/Te substitution. The phase diagram, studied using a combination of variational mean-field, flavor-wave calculations, and density-matrix renormalization group (DMRG), exhibits a sequence of transitions between the columnar antiferromagnet common to the iron pnictides, the non-magnetic ferroquadrupolar phase attributed to FeSe, and the double-stripe antiferromagnetic order known to exist in Fe$_{1+y}$Te. The calculated spin structure factor in these phases mimics closely that observed with INS in the Fe(Te$_{1-x}$Se$_x$), series. In addition to the experimentally established phases, the possibility of incommensurate magnetic order is also predicted.Comment: 9 pages, 10 figures in the main text; plus 5 pages of supplementary material

Hacia una justicia victimal

[ES] Dedicatoria y reflexión realizada con razón del Encuentro Internacional en homenaje de Antonio Beristain Ipiña.[EU] Bilera Internazionala izanda eta, Antonio Beristain Ipiñarekiko omenaldia

Hacia una justicia victimal

[ES] Dedicatoria y reflexión realizada con razón del Encuentro Internacional en homenaje de Antonio Beristain Ipiña.[EU] Bilera Internazionala izanda eta, Antonio Beristain Ipiñarekiko omenaldia

Incidencia de pacientes COVID19 en la Clínica Santo Domingo de enero a agosto del 2022

Objetivo: Determinar la incidencia de pacientes covid19 en la clínica Santo Domingo de enero a agosto del 2022. Metodología: Esta investigación fue básica, diseño no experimental y descriptivo, de naturaleza cuantitativa, tipo transversal y retrospectivo. En esta investigación se recolectaron los datos de ingreso de pacientes positivos para coronavirus que ingresaron al área de tomografía en la clínica Santo Domingo, recolectando información estadística de incidencias en la región Junín, con una población muestral de 119 pacientes; la información se tomó según los informes radiológicos redactados por el especialista médico radiólogo en la clasificación internacional CoRads para coronavirus. Resultados: Ingresaron 119 pacientes al área de tomografía de la Clínica Santo Domingo de enero a agosto del 2022; se halló con diagnóstico CoRads3 o mayor al 18.4% (22), Se halló pacientes con diagnóstico menor a CoRads3 81.5% (97), el 53.8% (64) de los pacientes fueron masculinos y el 46.2% (55) femeninas. Conclusiones: Se halló 119 pacientes covid19, en el área de tomografía de la clínica Santo Domingo de enero a agosto del 2022. Se encontró la incidencia de pacientes covid19 según la clasificación, con clasificación CoRads mayor o igual a 3 en 18.4% (22). Se encontró la incidencia de pacientes covid19 según la clasificación, con clasificación CoRads menor a 3 en 81.5% (97). Se determinó la distribución de los pacientes de acuerdo al género de los pacientes covid19, hubo mayor incidencia de pacientes masculinos con 53.8% (64), pacientes femeninas 46.2% (55)

Repercusiones sociales y ambientales de la soja transgénica en la alimentación industrial del ganado

El 50% del pienso que se utilizan en la industria ganadera contiene soja (Glycine max), en su mayoría transgénica, la soja Roundup Ready® de Monsanto. En EE.UU, el cultivo de soja RR ha aumentado 15 veces el uso del glifosato, herbicida que destruye los organismos primarios de los ecosistemas, amenazando la supervivencia de las cadenas tróficas. En Argentina, el cultivo de soja RR ha pasado de 800.000 hectáreas a 13 millones en los últimos siete años, deforestando bosques y sabanas, y utilizando tierras dedicadas a pastos o cultivos alimentarios; reduciendo así la biodiversidad y la producción de alimentos para la población argentina. La intensificación del modelo productivo ganadero en España genera degradación medioambiental y pobreza en otros territorios. La soberanía alimentaria plantear modelos de producción más locales y respetuosos con el medioambiente y con las personas.Fifty per cent of intensive animal feeding contains soybean (Glycine max), mainly genetically modified Roundup Ready® soybean from Monsanto. In USA, RR soybean growing has increased 15 times the use of glifosate, herbicide that destroys primary organisms in ecosystems, threatening survival of trophic chains. In Argentina, soybean growing has increased from 800.000 to 13.000.000 hectares during the last seven years, deforesting rainforest and savannas, and using soil formerly employed for pastures and human food production; reducing biodiversity and food production for Argentinean people. The intensification of livestock productive model in Spain causes environmental degradation and poverty in other countries. Food sovereignty proposes other productive models, more local and respectful with environment and people

Insights into the Nature of the Active Sites of Pt-WOx/Al2O3 Catalysts for Glycerol Hydrogenolysis into 1,3-Propanediol

The chemo-selective hydrogenolysis of secondary hydroxyls is an important reaction for the production of biomass-derived α,ω-diols. This is the case for 1,3-propanediol production from glycerol. Supported Pt-WOx materials are effective catalysts for this transformation, and their activity is often related to the tungsten surface density and Brönsted acidity, although there are discrepancies in this regard. In this work, a series of Pt-WOx/γ-Al2O3 catalysts were prepared by modifying the pH of the solutions used in the active metal impregnation step. The activity–structure relationships, together with the results from the addition of in situ titrants, i.e., 2,6-di-tert-butyl-pyridine or pyridine, helped in elucidating the nature of the bifunctional active sites for the selective production of 1,3-propanediol.This work was supported by the University of the Basque Country (UPV/EHU), European Union, through the European Regional Development Fund (ERDF) (Spanish MICIN Project: RTI2018-094918-BC43), and the Basque Government (IT993-16). Clara Jarauta Cordoba acknowledges financial support from the Spanish Government (BES-2014-069165 and EEBB-I-18-13018)

Characterization of the genetic resource of Criollo goats and their socio-economic role in Cochabamba, Bolivia.

The present study is based on data registered between January 1999 and March 2000 in the province of Mizque, Cochabamba Department, Bolivia. A series of traits were studied in a total of 1078 Criollo goats on 16 farms. The socio-economical setting was investigated applying participant observation, group conversations, and informal as well as structured interviews in 46 households of goat keepers. Criollo goats gave birth throughout the year with peaks in June and March. The average weight at parturition was 26.9 kg, the number of kids per litter was 1.2, and the mortality rate of kids up to 3 months old was 11.2 %. Weights at birth and at 120 days of age were 2.2 and 9.2 kg, respectively. During the dry and rainy seasons, milk production amounted to 235 g/d and 444 ml/d on average, respectively. The majority of farms (16 out of 42) cultivated 1 to 2 ha with potato, maize, and other crops. Animal husbandry formed an integral part of the farming systems. Various species of animals were kept with goats and sheep being the most numerous. The interviewed families stated that the main reasons for keeping goats were the production of dung, milk and meat as well as the traditional functions of goats in their culture. The main problems indicated were: a shortage of forage; diseases; and predators

Effect of atomic substitution on the sodium manganese ferrite thermochemical cycle for hydrogen production

This work presents the effect of atomic substitution on the MnFe2O4-Na2CO3 thermochemical cycle for H-2 production. The non-oxidative decarbonation/carbonation reaction of the MnFe2O4-Na2CO3 mixture is investigated as the starting reference. Repeated cycling results in a 30% loss of reversibility due to an overall reduction of the reactive interfaces. The substitution of Na2CO3 for Li2CO3 decreases the decarbonation onset temperature by about 100 degrees C, but almost no reversibility is observed during the cycles due to the irreversible Li+ intercalation. The effect of partial Mn substitution for Ca, Ni, and Zn is presented. The 5% Zn mixture shows the best decarbonation/carbonation reversibility and is tested for H-2 production together with MnFe2O4-Na2CO3. The reference mixture produces more H-2 during the first cycle (asymptotic to 1.1 vs. 0.7 mmol/g), but its production drastically drops by two orders of magnitude upon cycling and becomes negligible after 5 cycles. By contrast, the Zn-doped mixture exhibits a stable H-2 production of 0.22 mmol/g with no decreasing trend observed from cycle 2 to cycle 5. As result, in the fifth cycle, the Zn-doped mixture produces 23 times more H-2 than MnFe2O4-Na2CO3. Thermogravimetry and X-ray diffraction confirm that doping with Zn significantly improves the regeneration of the reactants.Acknowledgment This Project is funded by the Department of Economic Devel-opment, Sustainability and Environment of the Basque Govern-ment (CICe 2019-KK-2019/00097-and H2BASQUE-KK-2021/00054) . The authors express their sincere gratitude to Cristina Luengo and Mikel Intxaurtieta for their technical support