Porous carbonaceous materials simultaneously dispersing N, Fe and Co as bifunctional catalysts for the ORR and OER: electrochemical performance in a prototype of a Zn-air battery.

Infiltration of the mesoporous structure of SBA-15 silica as a hard template with phenanthroline complexes of Fe3+ and Co2+ allowed the simultaneous dispersion of nitrogen, iron and cobalt species on the surface of the obtained carbonaceous CMK-3 silica replica, with potential as bifunctional heterogeneous catalysts for the cathodic oxygen reduction and evolution reactions (ORR and OER). The textural properties and mesopore structure depended on the composition of the material. The carbonaceous FeCoNCMK-3 (1/1), obtained with an Fe/Co molar ratio of 1/1, exhibited an ordered cylindrical mesoporous structure with a high mesopore volume, a rather homogeneous composition in terms of total and surface concentrations of iron and cobalt, and a balanced presence of pyridinic-, pyrrolic- and graphitic-N species. FeCoNCMK-3 (1/1) could improve the ORR kinetics by adsorption and reduction of O2 through the 4-electron mechanism with a current density of -17.37 mA cm-2, Eonset of 1.13 V vs. RHE and E1/2 of 0.75 V when compared to metal-free, monometallic or bimetallic electrocatalysts with a higher amount of cobalt than that of iron. In addition, FeCoNCMK-3 (1/1) exhibited activity for the OER, presenting lower values of Eonset (1.52 V), Ej10 (1.78 V) and the Tafel slope (76.3 mV dec-1) with respect to other catalysts. When evaluated as a cathode in a prototype of a Zn-air battery, FeCoNCMK-3 (1/1) exhibited a high open circuit voltage of 1.41 V, a peak power density of 66.84 mW cm-2, a large specific capacity of 818.88 mA h gZn-1, and cycling for 20 h but with deactivation upon cycling.

Bird extirpations and community dynamics in an Andean cloud forest over 100 years of land-use change.

Long-term studies to understand biodiversity changes remain scarce-especially so for tropical mountains. We examined changes from 1911 to 2016 in the bird community of the cloud forest of San Antonio, a mountain ridge in the Colombian Andes. We evaluated the effects of past land-use change and assessed species vulnerability to climate disruption. Forest cover decreased from 95% to 50% by 1959, and 33 forest species were extirpated. From 1959 to 1990, forest cover remained stable, and an additional 15 species were lost-a total of 29% of the forest bird community. Thereafter, forest cover increased by 26% and 17 species recolonized the area. The main cause of extirpations was the loss of connections to adjacent forests. Of the 31 (19%) extirpated birds, 25 have ranges peripheral to San Antonio, mostly in the lowlands. Most still occurred regionally, but broken forest connections limited their recolonization. Other causes of extirpation were hunting, wildlife trade, and water diversion. Bird community changes included a shift from predominantly common species to rare species; forest generalists replaced forest specialists that require old growth, and functional groups, such as large-body frugivores and nectarivores, declined disproportionally. All water-dependent birds were extirpated. Of the remaining 122 forest species, 19 are vulnerable to climate disruption, 10 have declined in abundance, and 4 are threatened. Our results show unequivocal species losses and changes in community structure and abundance at the local scale. We found species were extirpated after habitat loss and fragmentation, but forest recovery stopped extirpations and helped species repopulate. Land-use changes increased species vulnerability to climate change, and we suggest reversing landscape transformation may restore biodiversity and improve resistance to future threats.

Extirpaciones de Aves y las Dinámicas Comunitarias en un Bosque Nuboso Andino durante más de Cien Años de Cambios de Uso de Suelo Resumen Los estudios a largo plazo para entender cambios en la biodiversidad todavía son escasos - especialmente en las montañas tropicales. Examinamos los cambios en la comunidad de aves del bosque de San Antonio en los Andes colombianos, desde 1911 hasta 2016. Evaluamos los efectos pasados del cambio en el uso del suelo y analizamos la vulnerabilidad de las especies ante la disrupción climática. La cobertura del bosque disminuyó del 95% al 50% para el año 1959, y 33 especies de bosque fueron extirpadas. Desde 1959 y hasta 1990, la cobertura permaneció estable y se perdieron 15 especies más - un total del 29% de la comunidad de aves de bosque. A partir de ahí la cobertura del bosque incrementó en un 26% y 17 especies recolonizaron el área. La principal causa de las extirpaciones fue la pérdida de conectividad con los bosques adyacentes. De las 31 (19%) especies de aves extirpadas, 25 especies tienen una distribución periférica a San Antonio, principalmente en las tierras bajas. La mayoría de las especies aún tenían presencia regional, pero las conexiones rotas entre los bosques limitaron su recolonización. Otras causas de las extirpaciones fueron la caza, el mercado de fauna y el desvío de cursos de agua. Los cambios en la comunidad de aves incluyeron una transición de especies predominantemente comunes a especies raras; las especies generalistas de bosque reemplazaron a las especies especialistas que requieren bosques maduros y los grupos funcionales, como los grandes frugívoros y nectarívoros, declinaron desproporcionadamente. Todas las aves dependientes del agua fueron extirpadas. De las 122 especies que permanecen en el bosque, 19 son vulnerables a la disrupción climática, diez han disminuido en abundancia y cuatro se encuentran amenazadas. Nuestros resultados muestran una pérdida inequívoca de especies y cambios en la estructura y abundancia de la comunidad de aves a escala local. En general, encontramos que las especies fueron extirpadas después de la pérdida y fragmentación del hábitat, pero la recuperación del bosque detuvo las extirpaciones y ayudó a las especies a recolonizar. Los cambios en el uso de suelo incrementaron la vulnerabilidad de las especies ante el cambio climático, por lo que sugerimos que revertir la transformación del paisaje podría restaurar la biodiversidad y aumentar la resistencia a futuras amenazas.

Biogeographic regions and events of isolation and diversification of the endemic biota of the tropical Andes.

Understanding the spatial and temporal evolution of biota in the tropical Andes is a major challenge, given the region's topographic complexity and high beta diversity. We used a network approach to find biogeographic regions (bioregions) based on high-resolution species distribution models for 151 endemic bird taxa. Then, we used dated molecular phylogenies of 14 genera to reconstruct the area history through a sequence of allopatric speciation processes. We identified 15 biogeographical regions and found 26 events of isolation and diversification within their boundaries that are independently confirmed with disjunct distributions of sister taxa. Furthermore, these events are spatially congruent with six geographical barriers related to warm and/or dry river valleys, discontinuities in elevation, and high peaks separating fauna from different range slopes. The most important barrier is the Marañon River Valley, which limits the boundaries of four bioregions and is congruent with eight phylogenetic distribution breaks, separating the Central and Northern Andes, where the most bioregions are found. We also show that many bioregions have diffuse and overlapping structures, with contact and transition zones that challenge previous conceptions of biogeographical regions as spatially simple in structure. This study found evidence that the drivers of our identified bioregions were processes of Andean uplift and mountain dispersal facilitated by temperature oscillations of the Pleistocene. Therefore, Andean bioregions were not formed from one simple biogeographical event in a certain time frame, but from a combination of vicariance and dispersal events, which occurred in different time periods.

CuO/CeO2 catalysts for glycerol selective conversion to lactic acid.

Ceria supported copper oxide catalysts were produced by a deposition-precipitation method, at a high copper loading (up to >25 wt%). These materials demonstrated excellent properties for glycerol selective conversion to lactic acid, with a conversion reaching up to 87% with a selectivity to lactic acid of 74% (8 h reaction, 220 °C, under N2 pressure). These catalysts also exhibited high stability upon 5 successive reaction cycles. The formation of a crystalline CuO phase was demonstrated in the nanocomposites at a high Cu loading, with elongated shaped particles formed on the cerium oxide surface. Such particles were however, not observed at low Cu loadings. XPS analysis revealed that Cu(ii) was the main Cu species on the fresh catalyst, and that this species was reduced to Cu(i) during the reaction. Complementary characterization over the spent catalyst clearly showed the morphological modifications of the CuO phase, however, did not impact significantly either glycerol conversion or selectivity to lactic acid upon recycling. For instance, apparently, the catalytic activity of CuO largely depends on the Cu(ii) species.

Adsorption of Uranium over NH2-Functionalized Ordered Silica in Aqueous Solutions.

The aim of this work was to obtain an in-depth understanding of the U(VI) adsorption mechanism over amino-functionalized mesoporous silica SBA-15 and highlights its high efficiency in aqueous media for U(VI) removal and preconcentration. The samples were synthesized and functionalized by both grafting and co-condensation methods, using different alkyl-substituted amine groups and were characterized using X-ray diffraction, N2 physisorption, Fourier transform infrared spectroscopy, and elemental C-H-N-S analyses. The properties for U(VI) adsorption were evaluated under discontinuous conditions, with the determination of the effect of several parameters (initial pH, contact time, initial U(VI) concentration, functionalization method, and organic moiety composition). U(VI) adsorption over grafted materials reached equilibrium at around 30 min, with a maximum adsorption capacity of 573 mgU·gads-1 for the most efficient material at its optimal adsorption pH (equal to 6) at 20 °C. Functionalized materials by grafting exhibit better adsorption capacities than co-condensed samples because of higher function surface density and function availability. U(VI) adsorption mechanisms were also studied by measuring the electrophoretic mobilities of the particles, aqueous U(VI) speciation, in situ attenuated total reflection infrared and Raman spectroscopies, and transmission electron microscopy analysis. U(VI) adsorption occurred through the formation of an inner sphere complex. The localization of adsorbed U(VI) has also been determined inside of the mesopores, with the formation of several particles on the nanometer scale, in the size of U-hydroxy phases. Besides, the study of the reusability of amino-functionalized SBA-15 by applying adsorption-desorption cycles was also conducted. The adsorption capacity of the material remains stable for at least four adsorption-desorption cycles without any noticeable capacity decrease.

Poliformismo del gen de la enzima convertidora de la angiotensina I, e hipertensión arterial en poblaciones negras del Estado Miranda / Polymorphism of the angiotensin I converting enzyme gene hypertension arterial black population of the Miranda State

El polimorfismo Inserción/Deleción I/D de la Enzima Convertidora de la Angiotensina-I (ECA-I) ha sido implicado en Hipertensión Arterial (HTA) y en otras enfermedades cardiovasculares. La controversia en algunos estudios de asociación ha sugerido que las diferencias étnicas deben ser consideradas. Determinar la asociación entre el polimorfismo I/D con HTA y/o Actividad de la ECA-I en un grupo étnico bien definido. Los pacientes (n=44) del presente estudio fueron tomados de las poblaciones negras de Ganga, Tacariguita y Guatirito del Estado Miranda. Estas poblaciones presentan una contribución génica negra del 76-79 por ciento. Se dividieron en dos grupos (n=21) PAS mayor e igual 140 mmHg/PAD mayor e igual 90 mmHg, y Control (n=23) PAS menor e igual 130 mmHg/PAD menor e igual 80 mmHg. El polimorfismo I/D fue determinado por PCR a partir del ADN leucocitario. Los genotipos DD fueron reamplificados con Dimetilsulfoxido 5 por ciento para evidenciar el enmascaramiento del genotipo ID. La actividad de la ECA-I fue determinada por espectrofotometría. No hubo diferencia estadísticamente significativa en las frecuencias de los genotipos y los alelos entre ambos grupos (p=0.942 y p=0.692 respectivamente). La actividad de la ECA-I fue similar entre los genotipos en cada grupo. Los resultados del presente estudio no lograron demostrar ninguna-asociación entre el polimorfismo I/D del gen de la ECA-I, la actividad de la ECA-I e HTA