Synthesis, characterization and benzylation activity of nanocrystalline chromia loaded sulfated titania prepared via sol–gel route

Chromia loaded sulfated titania has been synthesized via sol–gel route with different chromia loadings. These catalysts are characterized using conventional techniques such as XRD analysis, FTIR analysis, surface area and pore volume measurements, EDX, SEM and UV–Vis diffuse reflectance spectral analysis. Acidity is measured using spectrophotometric monitoring of adsorption of perylene, thermogravimetric desorption of 2,6-dimethylpyridine and temperature programmed desorption of ammonia. Activity studies are done in the liquid phase. It has been concluded that Lewis acid sites are responsible for the benzylation of arenes with benzyl chloride.

Influence of residual cations (Na+, K+ and Mg2+) in the alkylation activity of benzene with 1-octene over rare earth metal ion exchanged FAU–Y zeolite

The effect of residual cations in rare earth metal modified faujasite–Y zeolite has been monitored using magic angle spinning NMR spectral analysis and catalytic activity studies. The second metal ions being used are Na+, K+ and Mg+. From a comparison of the spectra of different samples, it is concluded that potassium and magnesium exchange causes a greater downfield shift in the 29Si NMR peaks. Also, lanthanum exchanged samples show migration behavior from large cages to small cages, which causes the redistribution of second counter cations. It is also observed that Mg2+ causes the most effective migration of lanthanum ions due to its greater charge. The prepared systems were effectively employed for the alkylation of benzene with 1-octene in the vapor phase. From the deactivation studies it is observed that the as-exchanged zeolites possess better stability towards reaction condition over the pure HFAU zeolite.

Vanadia supported on ceria: Characterization and activity in liquid-phase oxidation of ethylbenzene

Vanadia/ceria catalysts (2–10 wt% of V2O5) were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution. Structural characterization was done with energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), BET surface area measurements, FT-IR spectroscopy and nuclear magnetic spectral analysis (51V MASNMR). XRD and 51V MASNMR results show highly dispersed vanadia species at lower loadings and the formation of CeVO4 phase at higher V2O5 loading. The catalytic activity of catalysts was conducted in liquid phase oxidation of ethylbenzene with H2O2 as oxidant. The oxidation activity is increased with loading up to 8 wt% V2O5 and then decreased with further increase in V2O5 content to 10 wt%. Different vanadia species evidenced by various techniques were found to be selective towards ethylbenzene oxidation. The CeVO4 formation associated with increased concentration of vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone.

Techniques for Enhancing Wind Energy Generation - A CFD Based Multibody Dynamics Approach in Horizontal Axis Wind Turbines

Wind energy has emerged as a major sustainable source of energy.The efficiency of wind power generation by wind mills has improved a lot during the last three decades.There is still further scope for maximising the conversion of wind energy into mechanical energy.In this context,the wind turbine rotor dynamics has great significance.The present work aims at a comprehensive study of the Horizontal Axis Wind Turbine (HAWT) aerodynamics by numerically solving the fluid dynamic equations with the help of a finite-volume Navier-Stokes CFD solver.As a more general goal,the study aims at providing the capabilities of modern numerical techniques for the complex fluid dynamic problems of HAWT.The main purpose is hence to maximize the physics of power extraction by wind turbines.This research demonstrates the potential of an incompressible Navier-Stokes CFD method for the aerodynamic power performance analysis of horizontal axis wind turbine.The National Renewable Energy Laboratory USA-NREL (Technical Report NREL/Cp-500-28589) had carried out an experimental work aimed at the real time performance prediction of horizontal axis wind turbine.In addition to a comparison between the results reported by NREL made and CFD simulations,comparisons are made for the local flow angle at several stations ahead of the wind turbine blades.The comparison has shown that fairly good predictions can be made for pressure distribution and torque.Subsequently, the wind-field effects on the blade aerodynamics,as well as the blade/tower interaction,were investigated.The selected case corresponded to a 12.5 m/s up-wind HAWT at zero degree of yaw angle and a rotational speed of 25 rpm.The results obtained suggest that the present can cope well with the flows encountered around wind turbines.The areodynamic performance of the turbine and the flow details near and off the turbine blades and tower can be analysed using theses results.The aerodynamic performance of airfoils differs from one another.The performance mainly depends on co-efficient of performnace,co-efficient of lift,co-efficient of drag, velocity of fluid and angle of attack.This study shows that the velocity is not constant for all angles of attack of different airfoils.The performance parameters are calculated analytically and are compared with the standardized performance tests.For different angles of ,the velocity stall is determined for the better performance of a system with respect to velocity.The research addresses the effect of surface roughness factor on the blade surface at various sections.The numerical results were found to be in agreement with the experimental data.A relative advantage of the theoretical aerofoil design method is that it allows many different concepts to be explored economically.Such efforts are generally impractical in wind tunnels because of time and money constraints.Thus, the need for a theoretical aerofoil design method is threefold:first for the design of aerofoil that fall outside the range of applicability of existing calalogs:second,for the design of aerofoil that more exactly match the requirements of the intended application:and third,for the economic exploration of many aerofoil concepts.From the results obtained for the different aerofoils,the velocity is not constant for all angles of attack.The results obtained for the aerofoil mainly depend on angle of attack and velocity.The vortex generator technique was meticulously studies with the formulation of the specification for the right angle shaped vortex generators-VG.The results were validated in accordance with the primary analysis phase.The results were found to be in good agreement with the power curve.The introduction of correct size VGs at appropriate locations over the blades of the selected HAWT was found to increase the power generation by about 4%

Investigations on some amino acid based single crystals for nonlinear optical applications and amino acid capped nanocrystals

Organic crystals possess extremely large optical nonlinearity compared to inorganic crystals. Also organic compounds have the amenability for synthesis and scope for introducing desirable characteristics by inclusions. A wide variety of organic materials having electron donor and acceptor groups, generate high order of nonlinearity. In the present work, a new nonlinear optical crystal, L-citrulline oxalate (LCO) based on the aminoacid L-citrulline was grown using slow evaporation technique. Structural characterization was carried out by single crystal XRD. It crystallizes in the noncentrosymmetric, orthorhombic structure with space group P21 P21 P21. Functional groups present in the sample were identified by Fourier transform infra red (FTIR) and FT-Raman spectral analysis. On studying the FTIR and Raman spectra of the precursors L-citrulline and oxalic acid, used for growing L-citrulline oxalate crystal, it is found that the significant peaks of the precursors are present in the spectra of the L-citrulline oxalate crystal . This observation along with the presence of NH3 + group in the spectra of L-citrulline oxalate, confirms the formation of the charge transfer complex

FT-IR and FT-Raman study of Nasicon type phosphates, ASnFe(PO4)3 [A=Na2, Ca, Cd]

FT-Raman and FT-IR spectra of ASnFe(PO4)3 [A=Na2, Ca, Cd] were recorded and analyzed. The bands were assigned in terms of the vibrational group frequencies of SnO6 octahedral and PO4 tetrahedral. The spectral analysis shows that the symmetry of corner shared octahedral (SnO6) and the tetrahedral (PO4) are lowered from their free ion symmetry state. The presence of Fe3+ ions disrupts the S–N–O–S–N chain in the structure. This causes distortion of SnO6 and PO4 in the structure of all the compounds. Also it is seen that there are two distinct PO4 tetrahedra of different P–O bond lengths. One of these tetrahedra is linearly distorted in all the title compounds. The PO4 frequencies and bond lengths are calculated theoretically and are in agreement with the experimental values. The presence of PO4 polyanion in the structure can reduce the redox energy and hence reduce the metal oxygen covalency strength in the structure

Efecto de la glicemia materna en la monitoría electrónica fetal

Introducción: Después del ingreso de la monitoría fetal electrónica como estudio de bienestar fetal, se ha considerado por décadas que un aporte de carbohidratos a la gestante antes de la realización de la monitoría fetal influye en el reporte pero existen estudios que consideran que los niveles de glicemia materna no afecta la variabilidad de la monitoría fetal. Metodología: Se realizó un estudio de corte transversal, para evaluar el efecto de la glicemia materna en la monitoría fetal electrónica comparando los valores de glicemia materna con su resultado, según la categorización del ACOG. Las principales variables fueron las horas de ayuno, valores de glicemia, variabilidad de la monitoría fetal y presencia de aceleraciones. Resultados: Se incluyeron un total de 60 pacientes, que ingresaron al servicio de obstetricia y ginecología del Hospital Universitario Mayor Méderi en el periodo de estudio. No se encontraron diferencias estadísticamente significativas entre los resultados de monitoría fetal y los valores de glicemia materna. Ninguna paciente presentó monitoría categoría III (según categorización de la ACOG). Discusión Se requieren estudios analíticos más amplios para evaluar el papel de la glicemia en el resultado de la monitoría, pero el presente estudio sugiere que no existe relación entre la glicemia materna y el resultado de la monitoría fetal electrónica en la categorización del Colegio Americano De Ginecología Y Obstetricia (ACOG).

Relación de los factores laborales e individuales con la carga mental de los trabajadores de una institución minera (2014)

Objetivo: Establecer la relación de los factores laborales e individuales con la carga mental en los trabajadores del área de contratación y titulación minera y los de seguimiento y control en una institución minera durante el año 2014. Materiales y métodos: Estudio de corte transversal en 298 trabajadores que trabajan en una Institución Minera, en la ciudad de Bogotá. La identificación de los factores laborales e individuales relacionados con la carga mental se hizo mediante la aplicación de un cuestionario autodiligenciado utilizando la guía de Estimación de la carga mental de trabajo: método NASA TLX, en el cual se realizó análisis de medidas de tendencia central y se indagó relación a través de la prueba Chi cuadrado de Pearson, usando nivel de significación del 5%, con el programa SPSS 20. Resultados: La población predominante era de género masculino, donde la mayoría de los trabajadores fueron ingenieros pertenecientes al área de seguimiento y control, se evidenció asociación estadísticamente significativa entre la profesión con la percepción de exigencia física (p ≤ 0,001), de igual modo entre área de trabajo con la percepción de exigencia mental (p ≤ 0,001), en la cual se establece que la carga mental y el factor profesional (técnicos) y el factor laboral (área de seguimiento y control), son determinantes para la aparición de fatiga fisiológica y cognitiva, ya que en estos se evidencia mayor exigencia física en los trabajadores técnicos con un 81,40% y en los trabajadores del área de seguimiento y control con un 99,04%. Conclusión: Se encontró una alta exigencia mental, temporal y esfuerzo en los trabajadores y una relación significativa entre la profesión con la percepción de exigencia física, predominando en los técnicos, seguidos de abogados e ingenieros y entre el área de trabajo con la percepción de exigencia mental, siendo mayor en el área de seguimiento y control.

Hipotensión arterial y variabilidad de la frecuencia cardiaca en pacientes embarazadas llevadas a cesarea bajo anestesia raquídea

INTRODUCCION La hipotensión arterial por anestesia raquídea en embarazadas llevadas a cesárea es frecuente y deletérea para la madre y el feto, sin que a la fecha exista una herramienta clínicamente útil para predecirla. La variabilidad de la frecuencia cardiaca es una medida que estima la actividad del sistema nervioso autónomo y algunos estudio iniciales indican una posible utilidad como herramienta predictiva de hipotensión arterial en esta población. METODOLOGIA Se realizó un estudio observacional descriptivo para examinar el comportamiento de la variabilidad de la frecuencia cardiaca, medida como razón de Baja frecuencia/Alta frecuencia, con un punto de corte de 2.5 tomada con un reloj POLAR RS800CX, en una población de pacientes con embarazo a término llevadas a cesárea, en un hospital de tercer nivel en Bogotá- Colombia entre Febrero y Abril del 2015. RESULTADOS El estudio incluyó 82 pacientes. Se determinó que la razón Baja frecuencia/Alta frecuencia mayor a 2,5 era poco frecuente en nuestra población (15.85%), y su asociación no fue significativa. DISCUSION El presente estudio demostró que la asociación entre la presencia de hipotensión y un índice Baja frecuencia/Alta frecuencia con punto de corte de 2.5 no es significativo para nuestra población de mujeres con embarazo a término llevadas a cesárea con anestesia espinal. Según los resultados se sugieres un punto de corte de 1.6 como punto de partida para la realización de nuevos estudios que permitan validar este valor.

Análisis financiero de la empresa E.M.E. Estructuras Metálicas S.A. y el sector metalmecánico

El presente trabajo de grado se basa en el estudio y análisis financiero de la empresa E.M.E. Estructuras Metálicas S.A., ubicada en la ciudad de Manizales, Caldas, éste tomará como referencia los últimos cuatro años de funcionamiento operativo de la empresa y se realizará una comparación en el comportamiento de los mismos. El trabajo busca identificar las fortalezas y las debilidades que presentó el desarrollo de las actividades de la empresa, a su vez se realizará un breve análisis del sector metalmecánico, al cual pertenece la empresa, para sentar bases comparativas que permitan fortalecer el análisis. El análisis financiero se realizará basado en el método tradicional utilizando indicadores como solvencia, liquidez, actividad, y rentabilidad de la empresa, a este se le sumará el análisis moderno el cual incluye indicadores de creación y/o destrucción de valor por parte de la empresa junto con su flujo de efectivo y su demás componentes. Al final se realizará una descripción de los diferentes sistemas de costos que se utilizan generalmente en las empresas y se identificará el más acorde con la empresa. Finalmente, se identificarán los principales problemas que presenta la empresa los cuales llevaran las respectivas recomendaciones de mejora que el autor definirá de acuerdo a los resultados obtenidos después del análisis.

Diferencias intergrupales en el sistema de metas personales, satisfacción y rendimiento en adolescentes.

Integrar diferentes unidades de análisis para el estudio de la personalidad y considerar estas unidades en su predicción de la satisfacción y el rendimiento en adolescentes. 296 estudiantes de ESO de entre 15 y 18 años. 162 son mujeres y 134 varones. Las aplicaciones de las pruebas se realizan en horario de tutorías dentro del Plan Acción Tutorial (PAT). Se les explica a los alumnos que participan en la investigación sobre 'metas que se proponen realizar en un futuro' y que las pruebas que se administran les pueden ayudar en el futuro para la toma de decisiones. Las aplicaciones de las pruebas se realizan en dos sesiones de evaluación. En la primera, se aplican las pruebas de personalidad y satisfacción. En la segunda se evalúan metas personales. El rendimiento académico se operativiza por la puntuación del adolescente en su curso académico. Todos los alumnos participan voluntariamente en la investigación. Escala de objetivos o metas personales, escala de satisfacción por áreas vitales (ESAV), Inventario de personalidad para adolescentes de Millón (MAPI), estilos básicos de personalidad, escalas de correlatos comportamentales. Para el análisis de los datos, se utilizan programas estadísticos SPSS, SPAD, LISREL VIII y para el cálculo del tamaño del efecto el Statistical Power Computer Analysis. Las técnicas de análisis de datos se centran en Análisis de Correspondencia Múltiple (ACM), análisis de conglomerados K means, Análisis de varianza y diferencias entre coeficientes de correlación. Los resultados indican que los adolescentes que se plantean metas relacionadas con las tareas vitales a desarrollar en un futuro próximo manifiestan mayores niveles de satisfacción. Además, las diferencias en los estilos de personalidad, permiten entender el sistema de metas personales en cuatro grupos de adolescentes. La consideración de los estilos de personalidad y las metas personales permiten entender la adaptación de los adolescentes a su entorno considerando la satisfacción autopercibida y el rendimiento académico.

Evaluating the Potential Impact of a Gas Pipeline on Whimbrel Breeding Habitat in the Outer Mackenzie Delta, Northwest Territories

We used ground surveys to identify breeding habitat for Whimbrel (Numenius phaeopus) in the outer Mackenzie Delta, Northwest Territories, and to test the value of high-resolution IKONOS imagery for mapping additional breeding habitat in the Delta. During ground surveys, we found Whimbrel nests (n = 28) in extensive areas of wet-sedge low-centered polygon (LCP) habitat on two islands in the Delta (Taglu and Fish islands) in 2006 and 2007. Supervised classification using spectral analysis of IKONOS imagery successfully identified additional areas of wet-sedge habitat in the region. However, ground surveys to test this classification found that many areas of wet-sedge habitat had dense shrubs, no standing water, and/or lacked polygon structure and did not support breeding Whimbrel. Visual examination of the IKONOS imagery was necessary to determine which areas exhibited LCP structure. Much lower densities of nesting Whimbrel were also found in upland habitats near wetlands. We used habitat maps developed from a combination of methods, to perform scenario analyses to estimate the potential effects of the Mackenzie Gas Project on Whimbrel habitat. Assuming effective complete habitat loss within 20 m, 50 m, or 250 m of any infrastructure or pipeline, the currently proposed pipeline development would result in loss of 8%, 12%, or 30% of existing Whimbrel habitat. If subsidence were to occur, most Whimbrel habitat could become unsuitable. If the facility is developed, follow-up surveys will be required to test these models.

Equatorial waves in the lower stratosphere. I: A novel detection method

Wavenumber-frequency spectral analysis and linear wave theory are combined in a novel method to quantitatively estimate equatorial wave activity in the tropical lower stratosphere. The method requires temperature and velocity observations that are regularly spaced in latitude, longitude and time; it is therefore applied to the ECMWF 15-year re-analysis dataset (ERA-15). Signals consistent with idealized Kelvin and Rossby-gravity waves are found at wavenumbers and frequencies in agreement with previous studies. When averaged over 1981-93, the Kelvin wave explains approximately 1 K-2 of temperature variance on the equator at 100 hPa, while the Rossby-gravity wave explains approximately 1 m(2)s(-2) of meridional wind variance. Some inertio-gravity wave and equatorial Rossby wave signals are also found; however the resolution of ERA-15 is not sufficient for the method to provide an accurate climatology of waves with high meridional structure.

Boundary value problems for the N-wave interaction equations

We consider boundary value problems for the N-wave interaction equations in one and two space dimensions, posed for x [greater-or-equal, slanted] 0 and x,y [greater-or-equal, slanted] 0, respectively. Following the recent work of Fokas, we develop an inverse scattering formalism to solve these problems by considering the simultaneous spectral analysis of the two ordinary differential equations in the associated Lax pair. The solution of the boundary value problems is obtained through the solution of a local Riemann–Hilbert problem in the one-dimensional case, and a nonlocal Riemann–Hilbert problem in the two-dimensional case.

Baroclinic stationary waves in aquaplanet models

An aquaplanet model is used to study the nature of the highly persistent low-frequency waves that have been observed in models forced by zonally symmetric boundary conditions. Using the Hayashi spectral analysis of the extratropical waves, the authors find that a quasi-stationary wave 5 belongs to a wave packet obeying a well-defined dispersion relation with eastward group velocity. The components of the dispersion relation with k ≥ 5 baroclinically convert eddy available potential energy into eddy kinetic energy, whereas those with k < 5 are baroclinically neutral. In agreement with Green’s model of baroclinic instability, wave 5 is weakly unstable, and the inverse energy cascade, which had been previously proposed as a main forcing for this type of wave, only acts as a positive feedback on its predominantly baroclinic energetics. The quasi-stationary wave is reinforced by a phase lock to an analogous pattern in the tropical convection, which provides further amplification to the wave. It is also found that the Pedlosky bounds on the phase speed of unstable waves provide guidance in explaining the latitudinal structure of the energy conversion, which is shown to be more enhanced where the zonal westerly surface wind is weaker. The wave’s energy is then trapped in the waveguide created by the upper tropospheric jet stream. In agreement with Green’s theory, as the equator-to-pole SST difference is reduced, the stationary marginally stable component shifts toward higher wavenumbers, while wave 5 becomes neutral and westward propagating. Some properties of the aquaplanet quasi-stationary waves are found to be in interesting agreement with a low frequency wave observed by Salby during December–February in the Southern Hemisphere so that this perspective on low frequency variability, apart from its value in terms of basic geophysical fluid dynamics, might be of specific interest for studying the earth’s atmosphere.