2,4,5-Tris(pyridin-4-yl)-4,5-dihydro-1,3-oxazole

In the title compound, C18H14N4O, the mol­ecules are disordered about a crystallographic twofold axis, leading to 50:50 disorder of the O- and N-atom sites within the oxazole ring. As a consequence, symmetry-related oxazole C—N and C—O bonds are averaged. The oxazole ring makes a dihedral angle of 6.920 (1)° with the pyridyl ring in the 2-position and 60.960 (2)° with the pyridyl rings in the 4- and 5-positions

Dichloridobis(methanol-κO)[cis-(±)-2,4,5-tris­(pyridin-2-yl)-2-imidazoline-κ3 N 2,N 3,N 4]ytterbium(III) chloride

In the crystal structure of the title complex, [YbCl2(C18H15N5)(CH3OH)2]Cl, the pseudo-penta­gonal–bipyramidal coordination geometry of the YbIII cation is composed of three N atoms from one cis-(±)-2,4,5-tris­(pyridin-2-yl)imidazoline (HL) ligand, two O atoms from two methanol mol­ecules and two Cl− anions. Chains are formed along [010] through N—H⋯Cl, O—H⋯Cl and O—H⋯N hydrogen bonds

3-Amino­pyridin-1-ium 3-carb­oxy­benzo­ate

In the title organic salt, C5H7N2 +·C8H5O4 −, the carb­oxy­lic group is nearly coplanar with the benzene ring [dihedral angle 1.9 (4)°] whereas the carboxyl­ate group is twisted relative to the benzene ring by 13.6 (4)°. In the crystal, N-H⋯O and O—H⋯O hydrogen bonds connect the components into a three-dimensional framework consisting of stacks of alternating pairs of anions and cations exhibiting π–π stacking inter­actions with centroid–centroid distances in the range 3.676 (2)–3.711 (1) Å. The π–π stacks extend along [110] and [-110]

Modulation of argon pressure as an option to control transmittance and resistivity of ZnO:Al films deposited by DC magnetron sputtering: on the dark yellow films at 10^-7 Torr base pressures

In a previous paper, we reported that thin films of ZnO:Al [aluminum-zinc oxide (AZO)] deposited after achieving a very low base pressure [from 4.0×10-7 Torr (5.6×10-5 Pa) to 5.7×10-7 Torr (7.6×10-5 Pa)] result dark yellow in color and are resistive. These are undesirable characteristics for the application of AZO thin films as front electrodes in solar cells. However, given the increasingly tendency in the acquisition of equipment that allow us to reach excellent vacuum levels, it is necessary to find the deposition conditions that lead to an improving of transmittance without greatly impacting the electrical properties of materials deposited after achieving these levels of vacuum. In this way, the present work is focused on AZO thin films deposited after achieving a very low base pressure value: 4.2×10-7 Torr (5.6×10-5 Pa). For this, we studied the effect of the variation of the oxygen volume percent in the argon/oxygen mixture (by maintaining the deposition pressure constant) and the effect of deposition pressure with only argon gas on the main properties of AZO thin films. The depositions were done at room temperature on glass substrates by direct-current magnetron sputtering with a power of 120 W (corresponding to a power density of 2.63 W/cm2). As results, we found that the variation of deposition pressure with only argon gas is a good option for the control of optical and electrical properties, since the addition of oxygen, although improves transmittance, greatly impacts on the electrical properties. Furthermore, an interesting correlation was found between the optical and electrical properties and the chemical composition of the AZO films, the latter depending on the argon pressure (for this, a careful X-ray photoelectron spectroscopy analysis was performed). Also, the inverse relationship between crystallinity and deposition rate was confirmed, in which deposition rate inversely depends on argon pressure

Determinación de la transmisibilidad hidráulica en un acuífero costero mediante estimación óptima de la relación Qe-T usando el filtro de Kalman

Background: The knowledge on the management of water as a vital resource to develop agriculture allows having greater effectiveness in its use. Goals: The agricultural activity in the lower part of the Sinaloa Riverdepends on the fresh water of the regional dams and the aquifer. Methods: The use of groundwater represents approximately 15% of the total water used. In the presence of prolonged periods of drought, new wells are drilled without the use of an appropriate guide for farmers on the location of aquifer areas with a greater hydraulic transmissivity with the purpose of exploiting them more rationally. The National Water Commission has registered more than 680 wells on both banks of the Sinaloa River. Results: The information of 205 of these pumping wells for agricultural or domestic use and the specific capacity information was analyzed. Then, 79 out of 205 wells have pumping tests. It is then determined that the objective of this research work was to find the relationship between the specific capacity (Qe) and hydraulic transmissivity (T) data of the study area using the Thiem formula, considering a fixed value of the radius of influence. This hypothetical consideration and the heterogeneities of the aquifer environment add to the T-Qe relationship an additional component, it is determined that it has a normal behavior. Using the Kalman filter it is possible to eliminate or reduce such a component, thus improving the determination of the T-Qe relation of an R-value of 0.95 (without filter) to 0.97 (with filter), for a linear and exponential relationship. Conclusions: The application of a T-Qe estimate allows characterizing the aquifer area, with this procedure a map was obtained on the distribution of T, which will serve as a guide for future exploitations of groundwater in the study area.Antecedentes: El conocimiento sobre el manejo del agua como recurso indispensable para desarrollar la agricultura permite tener mayor efectividad en su uso. Objetivos: La actividad agrícola en la parte baja del río Sinaloa depende del agua dulce de las presas regionales y del acuífero. Métodos: El uso del agua subterránea, representa aproximadamente el 15% del agua total usada. Ante la aparición de periodos de sequía prolongados, se perforan nuevos pozos sin el uso de una guía apropiada que oriente a los agricultores sobre la ubicación de las zonas acuíferas que tienen una mayor transmisividad hidráulica con el propósito de explotarlos de manera más racional. Resultados: La Comisión Nacional del agua tiene registrados más de 680 pozos en ambas márgenes del Río Sinaloa. Se analizó la información de 205 de estos pozos de bombeo para uso agrícola o doméstico y la información de capacidad específica. De este número, 79 pozos tienen pruebas de bombeo. Se determina entonces que el objetivo de este trabajo de investigación fue encontrar la relación entre los datos de capacidad especifica (Qe) y transmisividad hidráulica (T) de la zona de estudio usando la fórmula de Thiem, considerando un valor fijo del radio de influencia. Conclusiones: Esta consideración hipotética y las heterogeneidades del medio acuífero suman a la relación T Qe una componente adicional, se determina que tiene un comportamiento normal. Mediante el filtro de Kalman es posible eliminar o reducir tal componente, mejorando así la determinación de la relación T-Qe de un valor r de 0.95 (sin filtro) a 0.97 (con filtro), para una relación lineal y exponencial. La aplicación de una estimación T-Qe permite caracterizar la zona acuífera, con este procedimiento se obtuvo un mapa sobre ladistribución de T, que servirá de guía para futuras explotaciones del agua subterránea en la zona de estudio

Resilience factors and coping as predictors of academic performance of the students in private universities

Predecir el rendimiento académico en estudiantes universitarios peruanos es una garantía para cumplir las exigencias de licenciamiento y acreditación. Se realiza un diseño transversal, comparativo y explicativo para establecer los factores de resiliencia y afrontamiento que predicen el rendimiento académico, en dos muestras probabilísticas estratificadas de universidades privadas de Lima. El RESI-, CAE, Smilkstein, CP-LS y estimadores DWLS, GLS, demostraron que el modelo predictivo de resiliencia y promedio ponderado tienen efecto en la percepción de rendimiento académico y un efecto mínimo en el promedio ponderado. Ambos factores predicen de manera directa, indirecta y relacional el rendimiento académico. Destacan los factores confianza en sí mismo, capacidad social, estrategias de autofocalización emocional abierta, exposición emocional abierta y apoyo familiar social como predictores relevantes en expectativa de logro, aprendizaje percibido y satisfacción global. El funcionamiento familiar, es un predictor indirecto a través de la resiliencia del rendimiento académico. Factores de afrontamiento activo, predicen mejor la percepción del rendimiento que factores de protección y riesgo. Muestras homogéneas grandes con valor psicométrico pueden mejorar los modelos predictivos, identificar perfiles, diseñar estudios causales, desarrollar programas de aprendizaje de talento y estrategias activas que mejorarían la calidad del aprendizaje universitario.Predicting academic performance in Peruvian university students is a guarantee to meet licensing and accreditation requirements. A transversal, comparative and explanatory (predictive) design was used to establish the resilience and coping factors that predict academic performance, in two stratified probabilistic samples from private universities in Lima. The RESI-, CAE, Smilkstein, CP-LS and DWLS estimators, GLS, showed that the predictive model of resilience and weighted average have an effect on the perception of academic performance and a minimal effect on the weighted average. Both factors predict academic performance directly, indirectly and relationally. The self-confidence factor, social capacity, open emotional self-targeting strategies, open emotional exposure and social family support are highlighted as relevant predictors in expectation of achievement, perceived learning and overall satisfaction. Family functioning is an indirect predictor through the resilience of academic performance. Factors of active coping better predict the perception of performance than protection and risk factors. Large homogeneous samples with psychometric value can improve predictive models, identify profiles, design causal studies, develop talent learning programs and active strategies that would improve the quality of university learnin

Environmental effects of ozone depletion, UV radiation and interactions with climate change : UNEP Environmental Effects Assessment Panel, update 2017

Peer reviewe

Effect of dietary protein level and commercial feeds on growth and feeding of juvenile common snook, Centropomus undecimalis (Bloch, 1792)

Preliminary results of the effects of different dietary protein levels and commercial feeds on growth and feeding of juvenile common snook, Centropomus undecimalis (Bloch, 1792), were obtained under controlled laboratory conditions in two experiments. In the first experiment (60 days), juveniles (initially 2.9 g) maintained at 26.6degreesC were fed one of four isocaloric experimental diets containing different protein levels (diet A = 28.8%, diet B = 40.4%, diet C = 53.4%, and diet D = 65.8%). Shrimp-, soybean-, and fish-meal were used as protein sources. Best growth, specific growth rate, and feed conversion ratio were obtained with diets B, C, and D. There Were no significant differences (P > 0.05) among these three treatments. Protein efficiency ratio decreased as the level of dietary protein increased and was highest for fish fed diet A. In the second experiment (65 days), the effects of three different commercial pellets (for tilapia, catfish, and trout) and diet C were determined on snook (initially 22.7 g) at 29.1degreesC. There was no significant difference in fish weight gain between diet C and trout pellets. Significantly higher (P < 0.05) weight gain was achieved with diet C and trout pellets compared with that of fish fed the tilapia and catfish pellets. Specific growth rate and feed conversion ratio were best with diet C, and significant differences among all treatments were obtained. Protein efficiency ratio for fish fed diet C and trout and tilapia feeds was not significantly different. The results confirm the snook's ability to feed on pellets, its capability to adapt to dry feeds, the potential of commercial feeds for raising snook, and its relatively high dietary protein requirement