MECHANISTIC STUDY OF A RUTHENIUM HYDRIDE COMPLEX OF TYPE [RuH(CO)(N-N)(PR3)2]+ AS CATALYST PRECURSOR FOR THE HYDROFORMYLATION REACTION OF 1-HEXENE

Indexación: Web of Science; Scopus; Scielo.The catalytic activity of systems of type [RuH(CO)(N-N)(PR3)(2)](+) was evaluated in the hydroformylation reaction of 1-hexene. The observed activity is explained through a reaction mechanism on the basis of the quantum theory. The mechanism included total energy calculations for each of the intermediaries of the elemental steps considered in the catalytic cycle. The deactivation of the catalyst precursors takes place via dissociation of the polypyridine ligand and the subsequent formation of thermodynamically stable species, such as RuH(CO)(3)(PPh3)(2) and RuH3(CO)(PPh3)(2), which interrupt the catalytic cycle. In addition, the theoretical study allows to explain the observed regioselectivity which is defined in two steps: (a) the hydride migration reaction with an anti-Markovnikov orientation to produce the alkyl-linear-complex (3.1a), which is more stable by 19.4 kJ/mol than the Markovnikov orientation (alkyl-branched-complex) (3.1b); (b) the carbon monoxide insertion step generates the carbonyl alkyl-linear specie (4.1a) which is more stable by 9.5 kJ/mol than the alternative species (4.1b), determining the preferred formation of heptanal in the hydroformylation of 1-hexene. Palabras clavehttp://ref.scielo.org/db4yc

Influencia de las Relaciones Interpersonales en los resultados deportivos de los equipos de Voleibol y Baloncesto masculinos y femeninos y Fútbol de la UNAN CUR Matagalpa en el año 2005

Este trabajo estuvo dirigido al estudio de las relaciones interpersonales de los equipos del Basketball, Volleyball, masculino y femenino, como también al equipo de Football masculino de UNAN CUR MATAGALPA, durante el año 2005 y la influencia de esta en los resultados deportivos. Este estudio permitió conocer a través de los test aplicados a los 55 atletas, el nivel de sus relaciones dentro del conjunto deportivo donde se denota la influencia positiva de estas relaciones dentro de los resultados competitivos. La investigación se aplico desde el inicio del proceso de entrenamiento y la composición de estos equipos en su proceso de preparación con vista a participar en las distintas competencias universitarias. Los test estuvieron conformados con contenidos relativos a la composición de los equipos, características de las edades, elementos de juego, y de convivencia social. Los resultados muestran entre los integrantes de los equipos que los atletas se destacan ante el colectivo tanto en los diferentes momentos de competencia como de la vida social. También a través del test sociométrico y del test de liderazgo se pudo llegar a la conclusión de que son los líderes democráticos con características universales apoyados con altos por cientos de popularidad por los atletas. Todos estos por sus grados de experiencias dentro y fuera del juego. No existe ningún componente del grupo rechazado sino que las características son de aislados que no representan ningún grado de conflictos dentro de las relaciones interpersonales de los equipo

Nickel oxide-based heterostructures with large band offsets

We present research results on the electronic transport in heterostructures based on p-type nickel oxide (NiO) with the n-type oxide semiconductors zinc oxide (ZnO) and cadmium oxide (CdO). NiO is a desirable candidate for application in (opto-)electronic devices. However, because of its small electron affinity, heterojunctions with most n-type oxide semiconductors exhibit conduction and valence band offsets at the heterointerface in excess of 1 eV. ZnO/NiO junctions exhibit a so called type-II band alignment, making electron-hole recombination the only process by which a current can vertically flow through the structure. These heterojunctions are nevertheless shown to be of practical use in efficient optoelectronic devices, as exemplified here by our UV-converting transparent solar cells. These devices, although exhibiting high conversion efficiencies, suffer from two light-activated recombination channels connected to the type-II interface, one of which we identify and analyse in more detail here. Furthermore, CdO/NiO contacts were studied - a heterostructure with even larger band offsets such that a type-III band alignment is achieved. This situation theoretically enables the development of a 2-dimensional electronic system consisting of topologically protected states. We present experiments demonstrating that the CdO/NiO heterostructure indeed hosts a conductive layer absent in both materials when studied separately

Crucial aspects of the initial mass function (I): The statistical correlation between the total mass of an ensemble of stars and its most massive star

Our understanding of stellar systems depends on the adopted interpretation of the IMF, phi(m). Unfortunately, there is not a common interpretation of the IMF, which leads to different methodologies and diverging analysis of observational data.We study the correlation between the most massive star that a cluster would host, mmax, and its total mass into stars, M, as an example where different views of the IMF lead to different results. We assume that the IMF is a probability distribution function and analyze the mmax-M correlation within this context. We also examine the meaning of the equation used to derive a theoretical M-char_mmax relationship, N x int[Char_mmax-mup] phi(m) dm = 1 with N the total number of stars in the system, according to different interpretations of the IMF. We find that only a probabilistic interpretation of the IMF, where stellar masses are identically independent distributed random variables, provides a self-consistent result. Neither M nor N, can be used as IMF scaling factors. In addition, Char_mmax is a characteristic maximum stellar mass in the cluster, but not the actual maximum stellar mass. A -Char_mmax correlation is a natural result of a probabilistic interpretation of the IMF; however, the distribution of observational data in the N (or M)-cmmax plane includes a dependence on the distribution of the total number of stars, N (and M), in the system, Phi(N), which is not usually taken into consideration. We conclude that a random sampling IMF is not in contradiction to a possible mmax-M physical law. However, such a law cannot be obtained from IMF algebraic manipulation or included analytically in the IMF functional form. The possible physical information that would be obtained from the N (or M)-mmax correlation is closely linked with the Phi(M) and Phi(N) distributions; hence it depends on the star formation process and the assumed.Comment: Accepted by A&A; 16 pages, 10 figure

Crucial aspects of the initial mass function (II): The inference of total quantities from partial information on a cluster

In a probabilistic framework of the interpretation of the initial mass function (IMF), the IMF cannot be arbitrarily normalized to the total mass, M, or number of stars, N, of the system. Hence, the inference of M and N when partial information about the studied system is available must be revised. (i.e., the contribution to the total quantity cannot be obtained by simple algebraic manipulations of the IMF). We study how to include constraints in the IMF to make inferences about different quantities characterizing stellar systems. It is expected that including any particular piece of information about a system would constrain the range of possible solutions. However, different pieces of information might be irrelevant depending on the quantity to be inferred. In this work we want to characterize the relevance of the priors in the possible inferences. Assuming that the IMF is a probability distribution function, we derive the sampling distributions of M and N of the system constrained to different types of information available. We show that the value of M that would be inferred must be described as a probability distribution Phi[M; m_a, N_a, Phi(N)] that depends on the completeness limit of the data, m_a, the number of stars observed down to this limit, N_a, and the prior hypothesis made on the distribution of the total number of stars in clusters, Phi(N).Comment: Accepted by A&A; 9 page

La rentabilidad en la empresa Cervecería San Juan S.A.A., periodo 2017 - 2019

El presente informe de investigación tiene como objetivo analizar la situación de la rentabilidad en la empresa Cervecería San Juan S.A.A., periodo 2017-2019. El enfoque de la investigación es cuantitativo debido a que el trabajo de investigación se fundamenta en lo descriptivo y de diseño no experimental, la población y la muestra corresponden a los estados financieros de la empresa, el análisis e instrumento de recolección de datos es la guía de análisis documentario, todo dato es realizado en el programa de Microsoft Excel. De tal forma que los resultados presentan la rentabilidad de los años 2017,2018 y 2019, de acuerdo al contexto del estudio. La recolección de datos fue utilizada de la información validada por la Superintendencia del Mercado de Valores donde proporciona los estados financieros de la empresa, que permitió conocer la situación actual de la entidad y poder emplear estrategias de gestión para mejorar la rentabilidad empresarial. Finalmente, se concluye la investigación con un crecimiento continúo debido a una ganancia neta apropiada, en relación con su nivel de capital estable. Se recomienda que para próximas investigaciones se amplíen el número de los periodos a investigar, seguidamente anexos y tablas de comparación de los tres periodos

Positron annihilation spectroscopy for the determination of thickness and defect profile in thin semiconductor layers

We present a method, based on positron annihilation spectroscopy, to obtain information on the defect depth profile of layers grown over high-quality substrates. We have applied the method to the case of ZnO layers grown on sapphire, but the method can be very easily generalized to other heterostructures (homostructures) where the positron mean diffusion length is small enough. Applying the method to the ratio of W and S parameters obtained from Doppler broadening measurements, W∕S plots, it is possible to determine the thickness of the layer and the defect profile in the layer, when mainly one defect trapping positron is contributing to positron trapping at the measurement temperature. Indeed, the quality of such characterization is very important for potential technological applications of the layer.Peer reviewe

Morphology and optical properties of ordered GaN and InGaN nanocolumns grown on non-polar and semipolar orientations

Relacionado con línea de investigación del GDS del ISO