Ecdiesteroides II. Propiedades geométricas y electrónicas: una aproximación QSAR para determinar el potencial de actividad biológica

Se hace un análisis molecular a nivel semiempírico de los ecdiesteroides, uno de los grupos hormonales más importantes del reino animal. Actualmente, se han descrito mas de 120 compuestos naturales pertenecientes a esta familia, los cuales están involucrados en los procesos de metamorfosis, desarrollo, reproducción y activación metabólica de los procesos vitales de los invertebrados (esp. Artrópodos) y además, pueden ser antagónicos de los brasinoesteroides en plantas, donde actúan como agentes protectores contra insectos fitófagos. En esta comunicación, se describen los estudios preliminares mecanocuánticos y estructurales, de 21 ecdiesteroides naturales diferentes (a partir de la ecdisona y sus modificaciones) y la relación estructuraactividad biológica, así como los principales parámetros y descriptores que potencian la acción ecdiesteroide y las interacciones con el receptor (distancia O3-O22; O22HOMO 3; áng. 2,3,4; áng. 8,9,10; distancia C2-C3; O3 Mayor contribuyente a HOMO-3; Carga de C16) . Se detalla el proceso analítico hasta la obtención de una ecuación que describe el comportamiento de las relaciones estructura-actividad para una serie de dichos compuestos a partir de las variables determinadas a partir de cuya resolución se diferencian significativamente los grupos de moléculas con actividad biológica diferente a partir de la estructura base. Y = 15 071,3 + 66,506 (O22 HOMO 3) 10,166 (O3 HOMO-3) + 34,278 (distancia O3-O22) +172,698 3 (distancia C2-C3) 24, 306 (áng. C2,3,4) +127, 276 (áng. C8,9,10) 611,975 (qC16)

Characterization of source rocks and groundwater radioactivity at the Chihuahua valley

As part of a scientific research project about alpha radioactivity in groundwater for human consumption at the Chihuahua City, the charac-terization of rock sources of radioactivity around de Chihuahua valley was developed. The radioactivity of groundwater and sediments wasdetermined, too. The radioactivity of uranium- and thorium- series isotopes contained in rocks was obtained by high resolution gamma-rayspectroscopy. Some representative values are 50 Bq/kg for the mean value of Bi-214 activity, and 121.5 Bq/kg for the highest value at Westof the city. The activity of sediments, extracted during wells perforation, was determined using a NaI(Tl) detector. A non-reported beforeuranium ore was localized at the San Marcos range formation. Its outcrops are inside the Chihuahua-Sacramento valley basin and its activ-ity characterization was performed. Unusually high specific uranium activities, determined by alpha spectrometry, were obtained in water,plants, sediments and fish extracted at locations close to outcrops of uranium minerals. The activity of water of the San Marcos dam reached7.7 Bq/L. The activity of fish, trapped at San Marcos dam, is 0.99 Bq/kg. Conclusions about the contamination of groundwater at North ofChihuahua City were obtained.Como parte de un proyecto cient ́ıfico sobre actividad alfa en agua subterr ́anea de consumo humano en la ciudad de Chihuahua, se hadesarrollado la caracterizaci ́on de las rocas fuentes de la radiactividad en el valle de Chihuahua. Se determin ́o tambi ́en la actividad de muestrasde agua subterr ́anea y de sedimentos. La actividad de los is ́otopos de las series radiactivas en las rocas se obtuvo usando espectroscop ́ıagamma de alta resoluci ́on. Algunos valores representativos son 50 Bq/kg para el valor medio de la actividad del Bi-214 y 121.5 Bq/kg para elvalor m ́as alto al oeste de la ciudad. La actividad de los sedimentos extra ́ıdos durante la perforaci ́on de pozos para agua potable, se determin ́ousando un detector de NaI(Tl). En la formaci ́on monta ̃nosa de San Marcos se localiz ́o un dep ́osito de uranio no publicado. Sus afloramientosse encuentran dentro de la cuenca del valle Chihuahua-Sacramento y se realiz ́o la caracterizaci ́on de su radiactividad. Se determinaronactividades por espectrometr ́ıa alfa de agua, plantas, sedimentos y peces extra ́ıdos en emplazamientos cercanos a los afloramientos deminerales de uranio. La actividad del agua en la presa de san Marcos lleg ́o a 7.7 Bq/L. La actividad de pescados de la misma presa alcanza0.99 Bq/kg. Se obtuvieron conclusiones sobre la contaminaci ́on del agua subterr ́anea al norte de la ciudad de Chihuahua

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

The biogeography of the Amazonian tree flora

We describe the geographical variation in tree species composition across Amazonian forests and show how environmental conditions are associated with species turnover. Our analyses are based on 2023 forest inventory plots (1 ha) that provide abundance data for a total of 5188 tree species. Withinplot species composition reflected both local environmental conditions (especially soil nutrients and hydrology) and geographical regions. A broader-scale view of species turnover was obtained by interpolating the relative tree species abundances over Amazonia into 47,441 0.1-degree grid cells. Two main dimensions of spatial change in tree species composition were identified. The first was a gradient between western Amazonia at the Andean forelands (with young geology and relatively nutrient-rich soils) and central–eastern Amazonia associated with the Guiana and Brazilian Shields (with more ancient geology and poor soils). The second gradient was between the wet forests of the northwest and the drier forests in southern Amazonia. Isolines linking cells of similar composition crossed major Amazonian rivers, suggesting that tree species distributions are not limited by rivers. Even though some areas of relatively sharp species turnover were identified, mostly the tree species composition changed gradually over large extents, which does not support delimiting clear discrete biogeographic regions within Amazonia

Mapping density, diversity and species-richness of the Amazon tree flora

Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

Mapping density, diversity and species-richness of the Amazon tree flora

Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

Mapping density, diversity and species-richness of the Amazon tree flora

Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

Chihuahua, Tierra de Cristales 2014, Año Internacional de la Cristalografía

Se presenta la definición de cristal, su diferencia respecto del vidrio, y la historia del descubrimiento de la difracción de rayos X, cuyo centenario ha motivado la declaración del año 2014 como Año Internacional de la Cristalografía. Se muestran los experimentos de Max von Laue, así como de William H. y William L. Bragg y se explican mediante la analogía con la difracción de la luz visible. Se exhiben las estructuras cristalinas de numerosos materiales importantes para el ser humano, su evolución y su desarrollo. Se exponen qué son los monocristales y los policristales, así como las diferentes estructuras cristalinas del carbono. Se explica cómo el progreso de la cristalografía, junto con la mecánica cuántica, han conducido a la tecnología moderna de la computación y las comunicaciones, comenzando desde el diodo semiconductor y el transistor hasta los modernos microprocesadores. Se describen la ferroelectricidad y la superconductividad y sus aplicaciones. Por último, se divulgan ejemplos del desarrollo moderno de la nanotecnología. Se explica cómo un monocristal nace y crece a partir de un nanocristal, para terminar con la demostración de que Chihuahua es Tierra de Cristales por la presencia de la Cueva de los Cristales Gigantes en Naica. Abstract It is presented the definition of a crystal, the differences with glass, and the history of the discovery of the X-ray diffraction, whose centenary has led to the declaration of 2014 as the International Year of Crystallography. The experiments of Max von Laue, as well as of William H. and William L. Bragg are described and explained using an analogy with the diffraction of visible light. The crystal structures of several important materials for human kind, their evolution and development are exhibited. The questions of what are single crystals and what are polycrystals are answered, as well as the different crystal structures of carbon atoms can form. The process of how Crystallography, along with quantum mechanics have led to the modern technology of computing and communications is detailed starting from semiconductor diodes and transistors up to the advent of modern microprocessors. The ferroelectric and superconductor materials are described, and their applications. Finally, examples of modern development due to nanotechnology are disclosed. The explanation of how a single crystal is born and grows from a nanocrystal is provided, finishing with the demonstration that Chihuahua is a land of crystals because of the presence of the Giant Crystals Cave at Naica. Keywords: Naica, crystallography, crystal structure, selenite

Application of the alpha spectrometry for the study of core sediment extracted in the San Marcos dam in Chihuahua

4 páginas, 4 figuras, 3 tablas.-- PACS: 91.67.Pq; 91.67.Qr; 91.67.Ty.[EN]: The determination of the specific activities of 210Po and isotopic uranium by alpha spectrometry was performed in a sediment core from San Marcos Dam. The objective of this work was to analyze the vertical distribution of isotopic uranium and 210Po and the behavior of these radionuclides along sediment core collected from the San Marcos Dam. Sample was divided into 11 sections, in which 210Po and Isotopic Uranium were determined using liquid-liquid extraction with tributyl phosphate (TBP). Furthermore, it was made a comparison between the TBP technique and the technique of extraction chromatography using UTEVA resins for uranium. The results of specific activities for 210Po show a trend to decrease along the core, whereas the uranium isotopic does not show a pointed trend. The results of isotopic ratios between the 234U and 238U show that they are close to secular equilibrium in each of the core sections. The comparison between the two uranium extraction techniques indicates that chemical yield is better using the UTEVA technique than TBP extraction.[ES]: La determinación de las actividades específicas de 210Po y uranio isotópico mediante espectrometría alfa fue realizada en un núcleo de sedimento de la Presa San Marcos. El objetivo de este trabajo fue analizar la distribución vertical de uranio isotópico y de 210Po así como el comportamiento de estos radionúclidos a lo largo del núcleo de sedimento recolectado en la presa San Marcos. La muestra fue dividida en 11 secciones. Para la determinación de 210Po y de uranio isotópico en cada una de las secciones se utilizó la técnica de extracción líquido-líquido con tributil fosfato (TBP). También se realizó una comparación entre la técnica del TBP y la técnica de cromatografía de extracción con resinas UTEVA para el uranio isotópico. Los resultados de las actividades específicas para 210Po muestran una tendencia decreciente a lo largo del núcleo, mientras que para uranio isotópico muestran una tendencia no monótona. Los resultados de las relaciones isotópicas entre el 234U y el 238U muestran estar cerca del equilibrio secular en cada una de las secciones del núcleo. La comparación entre las dos técnicas de extracción de uranio indica que se tiene un mayor rendimiento químico mediante empleando la técnica de UTEVA.Peer reviewe

The Global and Local Symmetries of Nanostructured Ferroelectric Relaxor 0.94(Bi0.5Na0.5)TiO3 0.06BaTiO3

Paper presented at the International Workshop on Relaxor Ferroelectrics (IWRF-2013) that took place in Ioffe Institute (St. Petersburg, Russia) during 1-6th July 2013.Novel submicrometer-grained 0.94(Bi0.5Na0.5)TiO3 ¿ 0.06 BaTiO3 ceramic, prepared from nanopowder by a combination of hot-pressing and recrystallization, is investigated by high-resolution synchrotron x-ray diffraction and x-ray absorption near-edge spectroscopy (XANES). The simplest and best-fitting Rietveld refinement of the performed wide-Q diffraction experiment corresponds to a three-phase system formed by a ferroelectric rhombohedral R3c phase, a globally cubic P-3mm phase and a small amount of nanosized (~12 nm) quasi-cubic phase. The globally cubic phase and the nanosized one built up a complex, nanostructured, configuration that accounts for the reported dielectric relaxor behavior. XANES reveals that the departures from centro-symmetry at the unit cell scale for the precursor powder and for the sintered ceramic are practically the same