Application of [Lambda] to the fourth perturbation theory in calculating the equation of state of rare gas solids and fcc metals

We have calculated the thermodynamic properties of monatomic fcc crystals from the high temperature limit of the Helmholtz free energy. This equation of state included the static and vibrational energy components. The latter contribution was calculated to order A4 of perturbation theory, for a range of crystal volumes, in which a nearest neighbour central force model was used. We have calculated the lattice constant, the coefficient of volume expansion, the specific heat at constant volume and at constant pressure, the adiabatic and the isothermal bulk modulus, and the Gruneisen parameter, for two of the rare gas solids, Xe and Kr, and for the fcc metals Cu, Ag, Au, Al, and Pb. The LennardJones and the Morse potential were each used to represent the atomic interactions for the rare gas solids, and only the Morse potential was used for the fcc metals. The thermodynamic properties obtained from the A4 equation of state with the Lennard-Jones potential, seem to be in reasonable agreement with experiment for temperatures up to about threequarters of the melting temperature. However, for the higher temperatures, the results are less than satisfactory. For Xe and Kr, the thermodynamic properties calculated from the A2 equation of state with the Morse potential, are qualitatively similar to the A 2 results obtained with the Lennard-Jones potential, however, the properties obtained from the A4 equation of state are in good agreement with experiment, since the contribution from the A4 terms seem to be small. The lattice contribution to the thermal properties of the fcc metals was calculated from the A4 equation of state, and these results produced a slight improvement over the properties calculated from the A2 equation of state. In order to compare the calculated specific heats and bulk moduli results with experiment~ the electronic contribution to thermal properties was taken into account~ by using the free electron model. We found that the results varied significantly with the value chosen for the number of free electrons per atom.

Oxygenation-sensitive cardiovascular magnetic resonance imaging (OS-CMR) : potential confounding factors in use of OS-CMR

La résonance magnétique cardiovasculaire sensible à l'oxygénation (OS-CMR) est devenue une modalité d'imagerie diagnostique pour la surveillance de changements dans l'oxygénation du myocarde. Cette technique offre un grand potentiel en tant qu'outil diagnostic primaire pour les maladies cardiovasculaires, en particulier la détection non-invasive d'ischémie. Par contre, il existe plusieurs facteurs potentiellement confondants de cette technique, quelques-uns d'ordre méthodologique comme les paramètres de séquençage et d'autres de nature physiologiques qui sont peut compris. En raison des effets causés par le contenu tissulaire d'eau, l'état d'hydratation peut avoir un impact sur l'intensité du signal. Ceci est un des aspects physiologiques en particulier dont nous voulions quantifier l'effet confondant par la manipulation de l'état d'hydratation chez des humains et l'observation des changements de l'intensité du signal dans des images OS-CMR. Méthodes: In vitro: Du sang artériel et veineux de huit porcs a été utilisé pour évaluer la dilution en série du sang et son effet correspondant sur l'intensité du signal de la séquence OS. In vivo: Vingt-deux volontaires en santé ont subi OS-CMR. Les concentrations d'hémoglobine (Hb) ont été mesurées au niveau de base et immédiatement après une l'infusion cristalloïde rapide de 1000 mL de solution Lactate Ringer's (LRS). Les images OS-CMR ont été prises dans une vue mid-ventriculaire court axe. L'intensité du signal myocardique a été mesurée durant une rétention respiratoire volontaire maximale, suite à une période d'hyperventilation de 60 secondes. Les changements dans l'intensité du signal entre le début et la fin de la rétention de la respiration ont été exprimés relativement au niveau de base (% de changement). Résultats: L'infusion a résulté en une diminution significative de l'Hb mesurée (142.5±3.3 vs. 128.8±3.3 g/L; p<0.001), alors que l'IS a augmenté de 3.2±1.2% entre les images du niveau de base en normo- et hypervolémie (p<0.05). L'IS d'hyperventilation ainsi que les changements d'IS induits par l'apnée ont été attenués après hémodilution (p<0.05). L'évaluation quantitative T2* a démontré une corrélation négative entre le temps de T2* et la concentration d'hémoglobine (r=-0.46, p<0.005). Conclusions: Il existe plusieurs éléments confondants de la technique OS-CMR qui requièrent de l'attention et de l'optimisation pour une future implémentation clinique à grande échelle. Le statut d'hydratation en particulier pourrait être un élément confondant dans l'imagerie OS-CMR. L'hypervolémie mène à une augmentation en IS au niveau de base et atténue la réponse IS durant des manoeuvres de respiration vasoactives. Cette atténuation de l'intensité du signal devrait être tenue en compte et corrigée dans l'évaluation clinique d'images OS-CMR.

Extent and limitations of density functional theory in describing magnetic systems

The performance of density-functional theory to solve the exact, nonrelativistic, many-electron problem for magnetic systems has been explored in a new implementation imposing space and spin symmetry constraints, as in ab initio wave function theory. Calculations on selected systems representative of organic diradicals, molecular magnets and antiferromagnetic solids carried out with and without these constraints lead to contradictory results, which provide numerical illustration on this usually obviated problem. It is concluded that the present exchange-correlation functionals provide reasonable numerical results although for the wrong physical reasons, thus evidencing the need for continued search for more accurate expressions.

Semantic Web In Use

Presentation given as part of the EPrints/dotAC training day on 26 Mar 2010.

Foundation Year RTS Part 3 Handin Front Sheet - no longer in use

No longer current Front Sheet for handin to be completed by student

Professional English in use : ICT. Intermediate to advanced.

Recurso para estudiantes con nivel medio o avanzado en inglés que cuenta con cuarenta unidades en la tecnología de las comunicaciones de información. Incluye sistemas informáticos, procesamiento de textos, hojas de cálculo y bases de datos, aplicaciones multimedia, correo electrónico, diseño web y seguridad de Internet, también tiene temas referentes a los teléfonos móviles y a la video conferencia. Hay unidades que explican la formación de palabras y funciones del lenguaje característico utilizado en el mundo de las TIC y como utilizarlo. Diseñado principalmente como una referencia de autoaprendizaje y libro de prácticas, también puede utilizarse para complementar el trabajo de aula.

English grammar in use : a self-study reference and practice book for intermediate students of Enlighs.

Libro orientado al auto-estudio para alumnos de nivel intermedio de inglés. Está estructurado en ciento cuarenta y cinco lecciones, cada una sobre un tema determinado de gramática inglesa, con su explicación y ejemplos en la página izquierda y ejercicios para practicar en la página derecha. Al final del libro hay una sección con las soluciones, siete apéndices sobre verbos regulares e irregulares, formas verbales para el presente y pasado, formas verbales para el futuro, verbos modales, contracciones, ortografía e inglés americano, un apartado con ejercicios adicionales que concentran varios temas de gramática en un mismo ejercicio, y una guía de estudio para ayudar a decidir qué temas repasar. Incluye un cd-rom con más ejercicios y mil setecientas preguntas de examen.

Testing prospect theory in students’ performance

Resumen basado en el de la publicación.

Contemporary organizational theory in the management of construction projects

The level of insolvencies in the construction industry is high, when compared to other industry sectors. Given the management expertise and experience that is available to the construction industry, it seems strange that, according to the literature, the major causes of failure are lack of financial control and poor management. This indicates that with a good cash flow management, companies could be kept operating and financially healthy. It is possible to prevent failure. Although there are financial models that can be used to predict failure, they are based on company accounts, which have been shown to be an unreliable source of data. There are models available for cash flow management and forecasting and these could be used as a starting point for managers in rethinking their cash flow management practices. The research reported here has reached the stage of formulating researchable questions for an in-depth study including issues such as how contractors manage their cash flow, how payment practices can be managed without damaging others in the supply chain and the relationships between companies" financial structures and the payment regimes to which they are subjected.

Parcel theory in three dimensions and the calculation of SCAPE

Slantwise convective available potential energy (SCAPE) is a measure of the degree to which the atmosphere is unstable to conditional symmetric instability (CSI). It has, until now, been defined by parcel theory in which the atmosphere is assumed to be nonevolving and balanced, that is, two-dimensional. When applying this two-dimensional theory to three-dimensional evolving flows, these assumptions can be interpreted as an implicit assumption that a timescale separation exists between a relatively rapid timescale for slantwise ascent and a slower timescale for the development of the system. An approximate extension of parcel theory to three dimensions is derived and it is shown that calculations of SCAPE based on the assumption of relatively rapid slantwise ascent can be qualitatively in error. For a case study example of a developing extratropical cyclone, SCAPE calculated along trajectories determined without assuming the existence of the timescale separation show large SCAPE values for parcels ascending from the warm sector and along the warm front. These parcels ascend into the cloud head within which there is some evidence consistent with the release of CSI from observational and model cross sections. This region of high SCAPE was not found for calculations along the relatively rapidly ascending trajectories determined by assuming the existence of the timescale separation.