Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius

We have carried out optical-absorption and reflectance measurements at room temperature in single crystals of AWO4 tungstates (A = Ba, Ca, Cd, Cu, Pb, Sr, and Zn). From the experimental results their band-gap energy has been determined to be 5.26 eV (BaWO4), 5.08 eV (SrWO4), 4.94 eV (CaWO4), 4.15 eV (CdWO4), 3.9-4.4 eV (ZnWO4), 3.8-4.2 eV (PbWO4), and 2.3 eV (CuWO4). The results are discussed in terms of the electronic structure of the studied tungstates. It has been found that those compounds where only the s electron states of the A2+ cation hybridize with the O 2p and W 5d states (e.g BaWO4) have larger band-gap energies than those where also p, d, and f states of the A2+ cation contribute to the top of the valence band and the bottom of the conduction band (e.g. PbWO4). The results are of importance in view of the large discrepancies existent in prevoiusly published data.Comment: 16 pages, 3 figures, 1 tabl

Counterfactual thinking in everyday life situations: Temporal order effects and social norms.

Razonamiento contrafáctico en situaciones de la vida diaria: Efectos de
 orden temporales y normas sociales. El razonamiento contrafáctico es la
 comparación de una situación fáctica con una alternativa simulada. Cuando
 las personas imaginan cómo las cosas podrían haber sido diferentes, tienden
 a deshacer mentalmente el último suceso de una secuencia de
 acontecimientos independientes previos a un resultado. Se presentan dos
 experimentos que examinan este fenómeno que ha sido denominado el
 efecto de orden temporal. El primer experimento, con 132 participantes,
 examinó el efecto de variar el número de eventos de la vida diaria en el
 efecto de orden temporal. Los resultados muestran que en situaciones
 cotidianas, es necesario un número suficiente de sucesos para que efecto se
 produzca. El segundo experimento, con 177 participantes, examinó una
 posible relación entre el efecto de orden temporal con un efecto diferente: la
 tendencia a cambiar eventos controlables que son excepcionales respecto a
 las normas interpersonales de conducta. Los resultados muestran que la
 posición en una secuencia temporal de sucesos independientes afecta a la
 facilidad para cambiar esos eventos excepcionales. Los resultados se
 discuten en términos de normas sociales

Dual-function injectable angiogenic biomaterial for the repair of brain tissue following stroke.

Stroke is the primary cause of disability due to the brain's limited ability to regenerate damaged tissue. After stroke, an increased inflammatory and immune response coupled with severely limited angiogenesis and neuronal growth results in a stroke cavity devoid of normal brain tissue. In the adult, therapeutic angiogenic materials have been used to repair ischaemic tissues through the formation of vascular networks. However, whether a therapeutic angiogenic material can regenerate brain tissue and promote neural repair is poorly understood. Here we show that the delivery of an engineered immune-modulating angiogenic biomaterial directly to the stroke cavity promotes tissue formation de novo, and results in axonal networks along thee generated blood vessels. This regenerated tissue produces functional recovery through the established axonal networks. Thus, this biomaterials approach generates a vascularized network of regenerated functional neuronal connections within previously dead tissue and lays the groundwork for the use of angiogenic materials to repair other neurologically diseased tissues

Impact of nitrogen fertilization on guinea grass (Panicum maximum, Jacq) in the humid premountain forest in the Department of Tolima.

P?ginas 17-21El objetivo del trabajo de investigaci?n fue evaluar la respuesta de diferentes dosis (0, 100, 150 y 300 kg/ha) de nitr?geno en la producci?n de pasto guinea (Panicum maximum, Jacq). Los resultados servir?n para establecer una recomendaci?n t?cnico-econ?mica viable de fertilizaci?n para la producci?n de esta gram?nea bajo condiciones de bosque h?medo sub-andino. El dise?o experimental utilizado fue bloques completos al azar con las cuatro dosis de nitr?geno mencionadas. Se aplic? 246 y 60 kg ha/a?o de CaCO3 y K2 O, respectivamente para correcci?n del pH. La producci?n y el porcentaje de materia seca en el forraje fueron medidos en los tres cortes realizados a intervalos de 28 d?as. Los cortes presentaron efecto significativo (P<0,01) en la producci?n y porcentaje de materia seca. La mayor producci?n de materia seca se encontr? en el corte dos (56 d?as) con 0,23 kg/m2 y el m?ximo porcentaje de MS se encontr? en el corte tres (84 d?as) con 21,4%; mientras que la fertilizaci?n de 300 kg N/ha/a?o present? el mayor rendimiento productivo de la gram?nea. La mayor rentabilidad financiera fue encontrada en el testigo (0 kg N/ha/a?o).ABSTRACT. The goal of this study was to evaluate different levels of nitrogen fertilization (0, 100, 150 and 300 kg/ha/year) on the production of Guinea grass (Panicum maximum). The results should support a viable technical-economical recommendation of fertilization for the production of this grass under sub-Andean humid forest conditions. An experimental design of randomized blocks was used, with four treatments of nitrogen fertilization. It was also applied to all plots 246 and 60 kg/ha/yearof CaCO3 and K2O as pH corrective inputs. The production and percentage of dry mater were evaluated in all three cuttings, which were carried out every 28 days. The cutting presented a significant effect (P<0.01) in the production and percentage of dry matter. The highest dry matter production was found in the second cutting (56 days) with 0.23 kg/m2; and the highest dry matter percentage was found in the third cutting (84 days) with 21%; whereas, the fertilization with 300kg N/ha/year showed the highest grass productivity. The greatest financial profitability was found in the control treatment (0 kg N/ha/year)

Finitely fibered Rosenthal compacta and trees

We study some topological properties of trees with the interval topology. In particular, we characterize trees which admit a 2-fibered compactification and we present two examples of trees whose one-point compactifications are Rosenthal compact with certain renorming properties of their spaces of continuous functions.Comment: Small changes, mainly in the introduction and in final remark

Thin shell morphology in the circumstellar medium of massive binaries

We investigate the morphology of the collision front between the stellar winds of binary components in two long-period binary systems, one consisting of a hydrogen rich Wolf-Rayet star (WNL) and an O-star and the other of a Luminous Blue Variable (LBV) and an O-star. Specifically, we follow the development and evolution of instabilities that form in such a shell, if it is sufficiently compressed, due to both the wind interaction and the orbital motion. We use MPI-AMRVAC to time-integrate the equations of hydrodynamics, combined with optically thin radiative cooling, on an adaptive mesh 3D grid. Using parameters for generic binary systems, we simulate the interaction between the winds of the two stars. The WNL+O star binary shows a typical example of an adiabatic wind collision. The resulting shell is thick and smooth, showing no instabilities. On the other hand, the shell created by the collision of the O star wind with the LBV wind, combined with the orbital motion of the binary components, is susceptible to thin shell instabilities, which create a highly structured morphology. We identify the nature of the instabilities as both linear and non-linear thin-shell instabilities, with distinct differences between the leading and the trailing parts of the collision front. We also find that for binaries containing a star with a (relatively) slow wind, the global shape of the shell is determined more by the slow wind velocity and the orbital motion of the binary, than the ram pressure balance between the two winds. The interaction between massive binary winds needs further parametric exploration, to identify the role and dynamical importance of multiple instabilities at the collision front, as shown here for an LBV+O star system.Comment: 10 pages, 13 figures. Accepted for publication in A&

High-pressure study of substrate material ScAlMgO4

We report on the structural properties of ScAlMgO4 studied under quasi-hydrostatic pressure using synchrotron high-pressure x-ray diffraction up to 40 GPa. We also report on single-crystal studies of ScAlMgO4 performed at 300 K and 100 K. We found that the low-pressure phase remains stable up to 24 GPa. At 28 GPa, we detected a reversible phase transformation. The high-pressure phase is assigned to a monoclinic distortion of the low-pressure phase. No additional phase transition is observed up to 40 GPa. In addition, the equation of state, compressibility tensor, and thermal expansion coefficients of ScAlMgO4 are determined. The bulk modulus of ScAlMgO4 is found to be 143(8) GPa, with a strong compressibility anisotropy. For the trigonal low-pressure phase, the compressibility along the c-axis is twice than perpendicular one. A perfect lattice match with ZnO is retained under pressure in the pressure range of stability of wurtzite ZnO.Comment: 22 pages, 5 figures, 4 tables, 24 reference