Phonon spectra and thermodynamic properties of rare gas solids based on empirical and semi-empirical (ab initio) two-body potentials : a comparative study /

We study the phonon dispersion, cohesive and thermal properties of raxe gas solids Ne, Ar, Kr, and Xe, using a variety of potentials obtained from different approaches; such as, fitting to crystal properties, purely ab initio calculations for molecules and dimers or ab initio calculations for solid crystalline phase, a combination of ab initio calculations and fitting to either gas phase data or sohd state properties. We explore whether potentials derived with a certain approaxih have any obvious benefit over the others in reproducing the solid state properties. In particular, we study phonon dispersion, isothermal ajid adiabatic bulk moduli, thermal expansion, and elastic (shear) constants as a function of temperatiue. Anharmonic effects on thermal expansion, specific heat, and bulk moduli have been studied using A^ perturbation theory in the high temperature limit using the neaxest-neighbor central force (nncf) model as developed by Shukla and MacDonald [4]. In our study, we find that potentials based on fitting to the crystal properties have some advantage, particularly for Kr and Xe, in terms of reproducing the thermodynamic properties over an extended range of temperatiures, but agreement with the phonon frequencies with the measured values is not guaranteed. For the lighter element Ne, the LJ potential which is based on fitting to the gas phase data produces best results for the thermodynamic properties; however, the Eggenberger potential for Ne, where the potential is based on combining ab initio quantum chemical calculations and molecular dynamics simulations, produces results that have better agreement with the measured dispersion, and elastic (shear) values. For At, the Morse-type potential, which is based on M0ller-Plesset perturbation theory to fourth order (MP4) ab initio calculations, yields the best results for the thermodynamic properties, elastic (shear) constants, and the phonon dispersion curves.

Perturbing the impulse activity of a single identified neuron augments the formation of long-term memory in a molluscan semi-intact preparation /

The aim of this study was to investigate the neural correlates of operant conditioning in a semi-intact preparation of the pond snail, Lymnaea stagnalis. Lymnaea learns, via operant conditioning, to reduce its aerial respiratory behaviour in response to an aversive tactile stimulus to its open pneumostome. This thesis demonstrates the successful conditioning of na'ive semiintact preparations to show learning in the dish. Furthermore, these conditioned preparations show long-term memory that persists for at least 18 hours. As the neurons that generate this behaviour have been previously identified I can, for the first time, monitor neural activity during both learning and long-term memory consolidation in the same preparation. In particular, I record from the respiratory neuron Right Pedal Dorsal 1 (RPeD 1) which is part of the respiratory central pattern generator. In this study, I demonstrate that preventing RPeDl impulse activity between training sessions reduces the number of sessions needed to produce long-term memory in the present semi-intact preparation.

Some electrical properties of semi-conductor crystals / |nPhyu Phyu Khin. -- 260 St. Catharines, Ont. : [s. n.],

SiC and AtB 12 have been prepared and their resistivities and Hall voltages measured. The resistivities and Hall voltages were measured by the Van der Pauw's method, using spring loaded tungsten contacts. In this method, the major requirement is to have samples of plane parallel surfaces of arbitrary shape with four small contacts at the circumference. Similar measurements were made with a number of SiC crystals obtained from the Norton Research Corporation (Canada)-Ltd., Carolina Aluminum Co., Exolon Co. and Carborundum Co. It was found that resistivity, carrier concentration and mobility of ions depend on the type of impurity. AtB 12 was prepared from the melt containing At and B in the ratio of 4:1. They formed amber-colour pseudo tetragonal crystals. As the crystals obtained were small for electrical measurements, hot pressed lumps have been used to measure their resistivity.

Comportamiento de genotipos contrastantes de sorgo (Sorghum bicolor(L.) Moench), bajo dos métodos de siembra y cuatro densidades de población y viabilidad económica de la siembra al voleo

Tesis (Maestría en Ciencias Especialista en Producción Agrícola) UANL

Evaluación genética, reproductiva y económica de los métodos de apareamiento en ganado bovino productor de carne

Tesis (Maestría en Ciencias Especialidad en Producción Animal) UANL

Determinación por métodos histoquímico enzimáticos del tiempo de aparición de las células de Langerhans en la epidermis del ratón albino (Mus musculus cepa C-D1)

Tesis (Maestría en Ciencias con Especialidad en Morfología) UANL

Estudio comparativo de los métodos más utilizados para la evaluación del impacto ambiental.

Tesis (Maestría en Ciencias con Especialidad en Ingeniería Ambiental) UANL

Desarrollo de un sistema para control de calidad de métodos análistas en un laboratorio de investigación

Tesis (Maestría en Ciencias con Especialidad en Química Análitica) UANL

Análisis comparativo de métodos de reclutamiento y selección de personal

Tesis (Maestría en Ciecias de la Administración con Especialidaden Relaciones Industriales) UANL

Descarte : objetivos, criterios y métodos

Tesis (Maestría en Bibliotecología) UANL

Determinación de los mecanismos de filtración mediante métodos geólogo-geofísicos en la presa El Cuchillo-Solidaridad, China, Nuevo León, México

Tesis (Maestría en Ciencias Geológicas) UANL

Análisis de riesgo ambiental : métodos, criterios de seleccióny una aplicación en el almacenamiento y manejo de cloro industrial

Tesis (Maestría en Ciencias de Especialidad en Ingeniería Ambiental) UANL

Tres métodos para el análisis estructural de silos de concreto reforzado

Tesis (Maestría en Ciencias con Especialidad en Ingeniería Estructural) UANL

Comparación de métodos de laboreo del suelo en sistemas de rotación con maíz (Zea mays L.) y Sorgo (Sorghum bicolor M.) y su efecto sobre el rendimiento de grano, en Padilla, Tamaulipas

Tesis (Maestría en Ciencias Especialista en Producción Agrícola) UANL