Impacts of Climate Change on European Critical Infrastructures: The Case of the Power Sector

23 p.

As formas de transmissão do HIV/AIDS determinando representações: um estudo de enfermagem entre adolescentes soropositivo

Este estudo objetivou analisar e comparar a incorporação psicossocial do HIV/AIDS entre adolescentes soropositivos considerando os diferentes meios de transmissão: vertical e sexual. Trata-se de um estudo de natureza descritiva, com abordagem qualitativa, fundamentado na teoria das representações sociais, na perspectiva da Psicologia Social. Foram estudados 30 adolescentes soropositivos atendidos em um Hospital Universitário do Rio de Janeiro. Foi utilizada como técnica de coleta de dados entrevistas semi-estruturadas e dois instrumentos de coleta: um questionário de caracterização dos sujeitos e um roteiro temático que guiou as entrevistas. As entrevistas foram gravadas e os conteúdos transcritos e analisados conforme a técnica de análise de conteúdo temática. O resultado evidenciou que o significado do HIV/AIDS para os sujeitos, numa análise geral, é marcado predominantemente por sentimentos negativos como medo e sofrimento. Imagens comuns aos dois grupos foram da morte e destruição, assim como o preconceito foi um importante conteúdo representacional. Ao comparar os dois grupos percebe-se que os elementos mais presentes na representação de adolescentes contaminados por relação sexual são sofrimento e o medo, com uma dimensão imagética associada à morte. O uso do preservativo também é outro conteúdo representacional marcante nos discursos deste grupo. A sexualidade está incorporada na representação relacionada às dificuldades com a mesma pós descoberta do vírus. Já os adolescentes contaminados por transmissão vertical tiveram como elementos mais presentes a aceitação e conformação da doença. O tratamento torna-se um importante conteúdo da representação para este grupo, relacionando-o ao cuidado à saúde e a imunodeficiência. Conclui-se, então, que a escolha do estudo das representações sociais e das técnicas de análise utilizadas foram pertinentes, pois permitiram identificar os principais elementos constituintes da representação social do HIV/AIDS, comparando as diferenças representacionais nos dois grupos de adolescentes estudados. Estes resultados servirão para reflexão crítica de profissionais de saúde , tanto na contribuição para repensar estratégias de educação em saúde para prevenção de DST/AIDS, quanto no posicionamento diante de adolescentes soropositivos.

Radio frequency studies of surface resistance and critical magnetic field of type I and type II superconductors

The surface resistance and the critical magnetic field of lead electroplated on copper were studied at 205 MHz in a half-wave coaxial resonator. The observed surface resistance at a low field level below 4.2°K could be well described by the BCS surface resistance with the addition of a temperature independent residual resistance. The available experimental data suggest that the major fraction of the residual resistance in the present experiment was due to the presence of an oxide layer on the surface. At higher magnetic field levels the surface resistance was found to be enhanced due to surface imperfections.

The attainable rf critical magnetic field between 2.2°K and T_c of lead was found to be limited not by the thermodynamic critical field but rather by the superheating field predicted by the one-dimensional Ginzburg-Landau theory. The observed rf critical field was very close to the expected superheating field, particularly in the higher reduced temperature range, but showed somewhat stronger temperature dependence than the expected superheating field in the lower reduced temperature range.

The rf critical magnetic field was also studied at 90 MHz for pure tin and indium, and for a series of SnIn and InBi alloys spanning both type I and type II superconductivity. The samples were spherical with typical diameters of 1-2 mm and a helical resonator was used to generate the rf magnetic field in the measurement. The results of pure samples of tin and indium showed that a vortex-like nucleation of the normal phase was responsible for the superconducting-to-normal phase transition in the rf field at temperatures up to about 0.98-0.99 T_c' where the ideal superheating limit was being reached. The results of the alloy samples showed that the attainable rf critical fields near T_c were well described by the superheating field predicted by the one-dimensional GL theory in both the type I and type II regimes. The measurement was also made at 300 MHz resulting in no significant change in the rf critical field. Thus it was inferred that the nucleation time of the normal phase, once the critical field was reached, was small compared with the rf period in this frequency range.

Temporary ponds in the UK; a critical biodiversity resource for freshwater plants and animals

The importance of ponds for biodiversity in Britain has been demonstrated by a number of studies. However, most of the research and interest has been directed at permanent waterbodies, and temporary ponds have been largely neglected. In this article the author present some preliminary findings from a project which aims to fill some of the many gaps in our knowledge of temporary ponds in Britain. The project, which runs for three years until the end of 2001, aims specifically to investigate the ecology of temporary ponds in England and Wales by describing (i) their wetland plant and macroinvertebrate communities, (ii) their physico-chemical characteristics, and (iii) their value as a biodiversity resource. The article focuses on the assessment of temporary ponds as a biodiversity resource and briefly considers aspects of species richness, rarity and distinctiveness. Where possible, temporary ponds are compared with other waterbody types, mainly permanent ponds from the National Pond Survey (NPS), to give the results a broader context.

Interpretações de linguagens artísticas em Gerd Bornheim

Este estudo propõe uma leitura histórico-cultural das interpretações de Gerd Bornheim (1929-2002), destacando a temática da linguagem, sobretudo das linguagens artísticas. A partir dessas expressões, as colocações críticas de Bornheim a respeito da estética e filosofia da arte apresentam um panorama dos questionamentos. Nesse sentido, são notáveis em seus trabalhos as reflexões sobre o teatro e a música. A linguagem teatral permite o acesso às outras atividades artísticas (poesia, música, artes plásticas, cinema) de forma livre e aberta. A linguagem musical, em consonância com a teatral, corrobora a pesquisa de Bornheim, que observou o processo criativo, a comunicação, o papel da interpretação (advento da crítica) e as rupturas nas poéticas contemporâneas. Tal itinerário sublinha a pesquisa que Bornheim realizou na França nas décadas de 1950 e 1960-70. O estímulo dessa atmosfera, marcada pelo diálogo entre filosofia, ciências sociais, psicologia, psicanálise, história, antropologia, linguística, comunicação, teatro e música foi decisivo para ele. Esses pontos são importantes para a apreensão do tema da linguagem e sua ambiência histórica, na qual Bornheim revela outras perspectivas de pesquisa. O pano de fundo é a crise da metafísica e os novos parâmetros para se pensar a dialética, a teoria e a prática. O diagnóstico de tal crise estende-se também à estética. Por conseguinte, o entendimento das ideias de Bornheim conduz aos temas da diferença e alteridade na contemporaneidade. Com isso, persegue-se um percurso temático que aborda: a linguagem e o problema da comunicação a partir da ligação das interpretações de Bornheim com as de Sartre e Merleau-Ponty. Além disso, o surgimento da crítica e os questionamentos da normatividade ética e estética levam à discussão das motivações coincidentes entre artes e ciências. Por fim, a linguagem musical enfatiza ainda o processo de transformação da subjetividade, que propicia uma percepção mais ampla das expressões artísticas e culturais.

Microwave dynamics of quasiparticles and critical fields in superconducting films

The microwave response of the superconducting state in equilibrium and non-equilibrium configurations was examined experimentally and analytically. Thin film superconductors were mostly studied in order to explore spatial effects. The response parameter measured was the surface impedance.

For small microwave intensity the surface impedance at 10 GHz was measured for a variety of samples (mostly Sn) over a wide range of sample thickness and temperature. A detailed analysis based on the BCS theory was developed for calculating the surface impedance for general thickness and other experimental parameters. Experiment and theory agreed with each other to within the experimental accuracy. Thus it was established that the samples, thin films as well as bulk, were well characterised at low microwave powers (near equilibrium).

Thin films were perturbed by a small dc supercurrent and the effect on the superconducting order parameter and the quasiparticle response determined by measuring changes in the surface resistance (still at low microwave intensity and independent of it) due to the induced current. The use of fully superconducting resonators enabled the measurement of very small changes in the surface resistance (< 10^-9 Ω/sq.). These experiments yield information regarding the dynamics of the order parameter and quasiparticle systems. For all the films studied the results could be described at temperatures near T_c by the thermodynamic depression of the order parameter due to the static current leading to a quadratic increase of the surface resistance with current.

For the thinnest films the low temperature results were surprising in that the surface resistance decreased with increasing current. An explanation is proposed according to which this decrease occurs due to an additional high frequency quasiparticle current caused by the combined presence of both static and high frequency fields. For frequencies larger than the inverse of the quasiparticle relaxation time this additional current is out of phase (by π) with the microwave electric field and is observed as a decrease of surface resistance. Calculations agree quantitatively with experimental results. This is the first observation and explanation of this non-equilibrium quasiparticle effect.

For thicker films of Sn, the low temperature surface resistance was found to increase with applied static current. It is proposed that due to the spatial non-uniformity of the induced current distribution across the thicker films, the above purely temporal analysis of the local quasiparticle response needs to be generalised to include space and time non-equilibrium effects.

The nonlinear interaction of microwaves arid superconducting films was also examined in a third set of experiments. The surface impedance of thin films was measured as a function of the incident microwave magnetic field. The experiments exploit the ability to measure the absorbed microwave power and applied microwave magnetic field absolutely. It was found that the applied surface microwave field could not be raised above a certain threshold level at which the absorption increased abruptly. This critical field level represents a dynamic critical field and was found to be associated with the penetration of the app1ied field into the film at values well below the thermodynamic critical field for the configuration of a field applied to one side of the film. The penetration occurs despite the thermal stability of the film which was unequivocally demonstrated by experiment. A new mechanism for such penetration via the formation of a vortex-antivortex pair is proposed. The experimental results for the thinnest films agreed with the calculated values of this pair generation field. The observations of increased transmission at the critical field level and suppression of the process by a metallic ground plane further support the proposed model.

1. Ultrasonic studies of binary liquid structure in the critical region. Theory and experiment for the 2,6-lutidine/water system. 2. Hartree-Fock calculations of electric polarizabilities of some simple atoms and molecules, and their practicality. 3. Calculation of vibrational transition probabilities in collinear atom-diatom and diatom-diatom collisions with Lennard-Jones interaction

Part 1. Many interesting visual and mechanical phenomena occur in the critical region of fluids, both for the gas-liquid and liquid-liquid transitions. The precise thermodynamic and transport behavior here has some broad consequences for the molecular theory of liquids. Previous studies in this laboratory on a liquid-liquid critical mixture via ultrasonics supported a basically classical analysis of fluid behavior by M. Fixman (e. g., the free energy is assumed analytic in intensive variables in the thermodynamics)--at least when the fluid is not too close to critical. A breakdown in classical concepts is evidenced close to critical, in some well-defined ways. We have studied herein a liquid-liquid critical system of complementary nature (possessing a lower critical mixing or consolute temperature) to all previous mixtures, to look for new qualitative critical behavior. We did not find such new behavior in the ultrasonic absorption ascribable to the critical fluctuations, but we did find extra absorption due to chemical processes (yet these are related to the mixing behavior generating the lower consolute point). We rederived, corrected, and extended Fixman's analysis to interpret our experimental results in these more complex circumstances. The entire account of theory and experiment is prefaced by an extensive introduction recounting the general status of liquid state theory. The introduction provides a context for our present work, and also points out problems deserving attention. Interest in these problems was stimulated by this work but also by work in Part 3.

Part 2. Among variational theories of electronic structure, the Hartree-Fock theory has proved particularly valuable for a practical understanding of such properties as chemical binding, electric multipole moments, and X-ray scattering intensity. It also provides the most tractable method of calculating first-order properties under external or internal one-electron perturbations, either developed explicitly in orders of perturbation theory or in the fully self-consistent method. The accuracy and consistency of first-order properties are poorer than those of zero-order properties, but this is most often due to the use of explicit approximations in solving the perturbed equations, or to inadequacy of the variational basis in size or composition. We have calculated the electric polarizabilities of H₂, He, Li, Be, LiH, and N₂ by Hartree-Fock theory, using exact perturbation theory or the fully self-consistent method, as dictated by convenience. By careful studies on total basis set composition, we obtained good approximations to limiting Hartree-Fock values of polarizabilities with bases of reasonable size. The values for all species, and for each direction in the molecular cases, are within 8% of experiment, or of best theoretical values in the absence of the former. Our results support the use of unadorned Hartree-Pock theory for static polarizabilities needed in interpreting electron-molecule scattering data, collision-induced light scattering experiments, and other phenomena involving experimentally inaccessible polarizabilities.

Part 3. Numerical integration of the close-coupled scattering equations has been carried out to obtain vibrational transition probabilities for some models of the electronically adiabatic H₂-H₂ collision. All the models use a Lennard-Jones interaction potential between nearest atoms in the collision partners. We have analyzed the results for some insight into the vibrational excitation process in its dependence on the energy of collision, the nature of the vibrational binding potential, and other factors. We conclude also that replacement of earlier, simpler models of the interaction potential by the Lennard-Jones form adds very little realism for all the complication it introduces. A brief introduction precedes the presentation of our work and places it in the context of attempts to understand the collisional activation process in chemical reactions as well as some other chemical dynamics.