Modeling and manufacturability assessment of bistable quantum-dot cells

We have investigated the behavior of bistable cells made up of four quantum dots and occupied by two electrons, in the presence of realistic confinement potentials produced by depletion gates on top of a GaAs/AlGaAs heterostructure. Such a cell represents the basic building block for logic architectures based on the concept of quantum cellular automata (QCA) and of ground state computation, which have been proposed as an alternative to traditional transistor-based logic circuits. We have focused on the robustness of the operation of such cells with respect to asymmetries derived from fabrication tolerances. We have developed a two-dimensional model for the calculation of the electron density in a driven cell in response to the polarization state of a driver cell. Our method is based on the one-shot configuration-interaction technique, adapted from molecular chemistry. From the results of our simulations, we conclude that an implementation of QCA logic based on simple ¿hole arrays¿ is not feasible, because of the extreme sensitivity to fabrication tolerances. As an alternative, we propose cells defined by multiple gates, where geometrical asymmetries can be compensated for by adjusting the bias voltages. Even though not immediately applicable to the implementation of logic gates and not suitable for large scale integration, the proposed cell layout should allow an experimental demonstration of a chain of QCA cells.

Metàfores en venda : La metàfora conceptual en la publicitat televisiva en català

Aquest treball pretén ampliar els estudis relacionats amb la lingüística cognitiva en la llengua catalana, en aquest cas en el camp d'experiència de la publicitat televisiva, i complementar els existents sobre el llenguatge publicitari i la comunicació dels mitjans audiovisuals.

Association of car ownership and physical activity across the spectrum of human development : Modeling the Epidemiologic Transition Study (METS).

BACKGROUND: Variations in physical activity (PA) across nations may be driven by socioeconomic position. As national incomes increase, car ownership becomes within reach of more individuals. This report characterizes associations between car ownership and PA in African-origin populations across 5 sites at different levels of economic development and with different transportation infrastructures: US, Seychelles, Jamaica, South Africa, and Ghana. METHODS: Twenty-five hundred adults, ages 25-45, were enrolled in the study. A total of 2,101 subjects had valid accelerometer-based PA measures (reported as average daily duration of moderate to vigorous PA, MVPA) and complete socioeconomic information. Our primary exposure of interest was whether the household owned a car. We adjusted for socioeconomic position using household income and ownership of common goods. RESULTS: Overall, PA levels did not vary largely between sites, with highest levels in South Africa, lowest in the US. Across all sites, greater PA was consistently associated with male gender, fewer years of education, manual occupations, lower income, and owning fewer material goods. We found heterogeneity across sites in car ownership: after adjustment for confounders, car owners in the US had 24.3 fewer minutes of MVPA compared to non-car owners in the US (20.7 vs. 45.1 minutes/day of MVPA); in the non-US sites, car-owners had an average of 9.7 fewer minutes of MVPA than non-car owners (24.9 vs. 34.6 minutes/day of MVPA). CONCLUSIONS: PA levels are similar across all study sites except Jamaica, despite very different levels of socioeconomic development. Not owning a car in the US is associated with especially high levels of MVPA. As car ownership becomes prevalent in the developing world, strategies to promote alternative forms of active transit may become important.

Characterizing the vulnerability of frequent emergency department users by applying a conceptual framework: a controlled, cross-sectional study.

BACKGROUND: Frequent emergency department (ED) users meet several of the criteria of vulnerability, but this needs to be further examined taking into consideration all vulnerability's different dimensions. This study aimed to characterize frequent ED users and to define risk factors of frequent ED use within a universal health care coverage system, applying a conceptual framework of vulnerability. METHODS: A controlled, cross-sectional study comparing frequent ED users to a control group of non-frequent users was conducted at the Lausanne University Hospital, Switzerland. Frequent users were defined as patients with five or more visits to the ED in the previous 12 months. The two groups were compared using validated scales for each one of the five dimensions of an innovative conceptual framework: socio-demographic characteristics; somatic, mental, and risk-behavior indicators; and use of health care services. Independent t-tests, Wilcoxon rank-sum tests, Pearson's Chi-squared test and Fisher's exact test were used for the comparison. To examine the -related to vulnerability- risk factors for being a frequent ED user, univariate and multivariate logistic regression models were used. RESULTS: We compared 226 frequent users and 173 controls. Frequent users had more vulnerabilities in all five dimensions of the conceptual framework. They were younger, and more often immigrants from low/middle-income countries or unemployed, had more somatic and psychiatric comorbidities, were more often tobacco users, and had more primary care physician (PCP) visits. The most significant frequent ED use risk factors were a history of more than three hospital admissions in the previous 12 months (adj OR:23.2, 95%CI = 9.1-59.2), the absence of a PCP (adj OR:8.4, 95%CI = 2.1-32.7), living less than 5 km from an ED (adj OR:4.4, 95%CI = 2.1-9.0), and household income lower than USD 2,800/month (adj OR:4.3, 95%CI = 2.0-9.2). CONCLUSIONS: Frequent ED users within a universal health coverage system form a highly vulnerable population, when taking into account all five dimensions of a conceptual framework of vulnerability. The predictive factors identified could be useful in the early detection of future frequent users, in order to address their specific needs and decrease vulnerability, a key priority for health care policy makers. Application of the conceptual framework in future research is warranted.

Discrete distributions when modeling the disability severity score of motor victims

Many European states apply score systems to evaluate the disability severity of non-fatal motor victims under the law of third-party liability. The score is a non-negative integer with an upper bound at 100 that increases with severity. It may be automatically converted into financial terms and thus also reflects the compensation cost for disability. In this paper, discrete regression models are applied to analyze the factors that influence the disability severity score of victims. Standard and zero-altered regression models are compared from two perspectives: an interpretation of the data generating process and the level of statistical fit. The results have implications for traffic safety policy decisions aimed at reducing accident severity. An application using data from Spain is provided.

Marco teórico y conceptual para la definición y evaluación de competencias del profesional de enfermería en el ámbito hospitalario. Parte I

El objetivo de este artículo es presentar el marco teórico y conceptual empleado en el desarrollo del proyecto COM VA© de definición y evaluación de competencias asistenciales y de gestión asistencial del profesional de enfermería en el ámbito hospitalario. El marco teórico recoge principalmente los trabajos de la Dra. Benner y de los profesores Dreyfus en relación con el modelo de adquisición de competencia que define 5 niveles de pericia, de aprendiz a experto. El marco conceptual explora los significados y las interrelaciones de los términos competencia, expertez, pericia, experiencia e inteligencia, entre otros. El artículo incluye también una revisión sobre los principales aspectos relacionados con los instrumentos y los métodos de evaluación de competencias.

La vida quotidiana : exploració d'un marc conceptual i d'una proposta d'indicadors

L'interès per la vida quotidiana ha crescut de manera paral•lela a la necessitat d'augmentar el coneixement racional sobre la realitat social. I, més específicament, si hem de fer cas al que diuen algunes especialistes, aquest interès neix, lligat a la clarificació del que s'entén per benestar. Tal com aquest breu estudi exploratori posa de manifest, la complexitat comença en la polisèmia que acompanya el concepte de vida quotidiana, afavoridora de no poques confusions. I, continua amb una de les dificultats més greus amb les que pot ensopegar el coneixement científic. L'interès per clarificar conceptualment la vida quotidiana, en aquesta ocasió, com en tantes d'altres, ha sorgit de la necessitat de conèixer millor per actuar de manera més acurada. Els objectius de l'informe han estat deutors d'aquesta orientació. En concret, han perseguit una doble fita. En primer lloc, han anat dirigits a aconseguir la clarificació i racionalització de la polisèmia conceptual esmentada. En segon lloc, els objectius de l'informe s'han dirigit a obtenir informació sobre els indicadors socials més adients per fer visible l'abast de la vida quotidiana. Això ha suposat la revisió d'una sèrie de bases de dades existents. L'interès d'aquesta revisió és la possibilitat de reconèixer l'existència d'una sèrie de dades objectives, resultatd'enquestes o d'altres tipus de recollida de dades. Els resultats d'aquesta part de l'informe es presenten, de manera ordenada, mostrant les característiques de les bases de dades revisades. I senyalant la informació que, a parer nostre,resulta més pertinent per a ser reutilitzada com a indicadors objectius capaços de mostrar l'àmbit i abast de la vida quotidiana. Aquesta informació es completa amb una sèrie de consideracions sobre aquest tipus d'indicadors socials i la conveniència d'utilitzar els indicadors de tipus subjectiu. I sobre laconveniència de dibuixar una prova pilot sobre uns possibles itineraris de vida quotidiana.

The internal wave field in Sau reservoir : Observation and modeling of a third vertical mode

Water withdrawal from Mediterranean reservoirs in summer is usually very high. Because of this, stratification is often continuous and far from the typical two-layered structure, favoring the excitation of higher vertical modes. The analysis of wind, temperature, and current data from Sau reservoir (Spain) shows that the third vertical mode of the internal seiche (baroclinic mode) dominated the internal wave field at the beginning of September 2003. We used a continuous stratification two-dimensional model to calculate the period and velocity distribution of the various modes of the internal seiche, and we calculated that the period of the third vertical mode is ;24 h, which coincides with the period of the dominating winds. As a result of the resonance between the third mode and the wind, the other oscillation modes were not excited during this period

Developing a conceptual framework to analyse professionalisation in sport federations

Existing research on sport organisations is imprecise in the use of the concept 'professionalisation'. Furthermore, we do not know if analytical concepts of professionalisation correspond with the understanding in practice. This study explores the perceptions of practitioners and proposes a framework to analyse professionalisation in national sport federations. Expert interviews were conducted with six key people from Swiss national sport federations and then analysed these for characteristics of professionalisation using a hermeneutic approach. The characteristics were divided into three areas: (1) changed management philosophy, (2) functional differentiation and specialisation, and (3) application of management tools. However, professionalisation is primarily perceived to be a matter of 'professional' attitude that transforms into federation culture. The practitioners disclose an ambivalent view of professionalisation, e.g. business-like culture vs. voluntarism, for-profit vs. non-profit orientation, autonomy vs. control. A framework is developed that synthesises analytical concepts and practitioners' perceptions to support future comprehensive research into causes, forms and consequences of professionalisation in national sport federations.

Conceptual Interpretation of LOM and its Mapping to Common Sense Ontologies

Peer-reviewed

A conceptual model for grid learning services automatic composition

Peer-reviewed

Fischer-Tropsch Slurry Bubble Column Reactor Modeling

The literature part of the work reviews overall Fischer-Tropsch process, Fischer-Tropsch reactors and catalysts. Fundamentals of Fischer-Tropsch modeling are also presented. The emphasis is on the reactor unit. Comparison of the reactors and the catalysts is carried out to choose the suitable reactor setup for the modeling work. The effects of the operation conditions are also investigated. Slurry bubble column reactor model operating with cobalt catalyst is developed by taking into account the mass transfer of the reacting components (CO and H2) and the consumption of the reactants in the liquid phase. The effect of hydrostatic pressure and the change in total mole flow rate in gas phase are taken into account in calculation of the solubilities. The hydrodynamics, reaction kinetics and product composition are determined according to literature. The cooling system and furthermore the required heat transfer area and number of cooling tubes are also determined. The model is implemented in Matlab software. Commercial scale reactor setup is modeled and the behavior of the model is investigated. The possible inaccuraries are evaluated and the suggestions for the future work are presented. The model is also integrated to Aspen Plus process simulation software, which enables the usage of the model in more extensive Fischer-Tropsch process simulations. Commercial scale reactor of diameter of 7 m and height of 30 m was modeled. The capacity of the reactor was calculated to be about 9 800 barrels/day with CO conversion of 75 %. The behavior of the model was realistic and results were in the right range. The highest uncertainty to model was estimated to be caused by the determination of the kinetic rate.