281 research outputs found
PREIS-E. Erweiterung der PREIS um die wahrgenommene soziale Norm und die wahrgenommene Verhaltenskontrolle
No full textDie Items sind zur Ergänzung der Professionsunabhängigen
Einstellungsskala zum inklusiven Schulsystem (PREIS, Lüke, & Grosche, 2017).</p
Strong Coupling Superconductivity in the Vicinity of the Structural Quantum Critical Point in (CaxSr1-x)3Rh4Sn13
No full textThe family of the superconducting quasiskutterudites (CaxSr1?x)3Rh4Sn13 features a structural quantum critical point at xc=0.9, around which a dome-shaped variation of the superconducting transition temperature Tc is found. Using specific heat, we probe the normal and the superconducting states of the entire series straddling the quantum critical point. Our analysis indicates a significant lowering of the effective Debye temperature on approaching xc, which we interpret as a result of phonon softening accompanying the structural instability. Furthermore, a remarkably large enhancement of 2?/kBTc and ?C/?Tc beyond the Bardeen-Cooper-Schrieffer values is found in the vicinity of the structural quantum critical point. The phase diagram of (CaxSr1?x)3Rh4Sn13 thus provides a model system to study the interplay between structural quantum criticality and strong electron-phonon coupling superconductivity
Path integrals for potential problems with -function perturbation
No full textThe author presents several examples of potential problems with a δ-function perturbation by means of path integrals. The idea is to sum a perturbation series expansion resulting in an energy-dependent Green function G(E). The energy levels E of the perturbed problem are determined by the equation (one-dimensional case) iG(a, a; E)=/ gamma where G is the Green function of the unperturbed problem, gamma is the strength of the δ potential and a its location in R. In D-dimensional radial problems with a spherically shaped delta function located at r=a this equation changes into iGl(a, a; E)=/a , where l denotes the angular momentum number
Estudo das interações entre o escoamento de uma emulsão e a sonda de um espectrofotômetro baseada em simulações numéricas.
No full textIn the present work, the flow behavior of an oil-in-water emulsion around and inside the measurement chamber of an in-line optical sensor probe is studied. The emulsion consists of a metalworking fluid, with oil droplets diameter ranging from 100 nanometers to 100 micrometers. The design of the UV-Vis light spectrometer probe is in accordance with the concept proposed in the research project named EPM (Emulsion Process Monitor in Metalworking Processes), carried out within the scope of the BRAGECRIM program between the University of São Paulo and the University of Bremen. This study is based on the numerical simulation of the interactions between the emulsion and the measurement system using computational fluid dynamic techniques, and is aimed at evaluating the effects of the probe geometry, its position relative to the flow field, and fluid properties on the expected spectrometer readings. Such effects are correlated with changes in droplet concentration and or droplet size segregation inside the measurement chamber of the optical probe, which can cause changes in the scattered light intensity readings. Segregation effects due to flow disturbances around the probe can be neglected under normal measurement conditions, with the probe facing the slit area inlet against the flow stream. Based on the simulation results, even if the probe is misplaced, the effect on the measurements is still insignificant. In-situ measurements carried out in a laboratory set up installed in the injection tube of a drilling machine support the simulation results, since no segregation effect related to the measurement system was observed. In addition to the study, the possibility of bacteria attachment on the internal glass walls of the probe was evaluated and it was found that when the flow velocity is large enough to produce a wall shear stress of about 3-5 Pa the bacterial contamination may be avoided. Changes in the probe geometry are proposed in order to attain an isokinetic condition for the flow around and inside the probe, resulting in a higher wall shear stress for lower inlet flow velocities. An additional study was performed using a tracking particle model to understand the relevance of the individual particles behavior under different flow conditions. The results do not indicate any significant effect on the measurements inside the probe, although additional studies should be carried out in this topic by considering a population balance model for the oil droplets.O presente trabalho tem como objetivo o estudo do comportamento do escoamento de uma emulsão do tipo óleo - em água que flui no interior de câmara/duto de medição e que tem como obstáculo em seu caminho uma sonda de um sensor óptico, sensor óptico este que deve avaliar em tempo real a estabilidade da emulsão onde está inserido. A emulsão é constituída por um fluido de corte para usinagem, com gotículas de óleo de diâmetro variando de 100 nanômetros para 100 micrometros. A sonda utilizada junto ao espectrômetro de luz UV- Vis está de acordo com o conceito proposto no projeto de pesquisa chamado EPM (Emulsion Process Monitor in Metalworking Fluid), realizado no âmbito do programa BRAGECRIM entre a Universidade de São Paulo e a Universidade de Bremen. Este estudo baseia-se na simulação numérica das interações entre a emulsão e o sistema de medição proposto, utilizando técnicas de Fluido Dinâmica Computacional (CFD), e tem por objetivo avaliar os efeitos da geometria da sonda, a sua posição em relação ao campo do escoamento, e propriedades do fluido, em especial as propriedades a serem medidas pelo espectrômetro. Tais efeitos estão correlacionadas com alterações na concentração de gotas e a segregação ou o tamanho das gotas dentro da câmara de medição da sonda óptica, o que pode causar mudanças nas leituras de intensidade de luz difusa. Efeitos de segregação devido a perturbações do escoamento em torno da sonda podem ser negligenciados, em condições normais de medição, com a sonda voltada para frente e sua área de entrada contra a corrente do escoamento. Com base nos resultados de simulação, mesmo que a sonda seja deslocada, o efeito sobre as medições ainda é insignificante. Medições foram efetuadas em laboratório e também foram realizadas medições in-situ utilizando um adaptador de medição acoplado diretamente no tubo de injeção de fluido de corte da máquina de perfuração, estes testes foram feitos para de validar os resultados obtidos por simulação, uma vez que não se observou qualquer efeito de segregação relacionada com o sistema de medição. Além disso, foi acrescentada ao estudo, a possibilidade de fixação de bactérias nas paredes de vidro internas da sonda e verificou-se que quando a velocidade de escoamento é suficientemente grande para produzir uma tensão de cisalhamento de cerca de 3-5 Pa a fixação de bacteriana pode ser evitado. Aproveitando os resultados do estudo para prevenção de contaminação por bactéria, mudanças na geometria da sonda foram propostas a fim de atingir uma condição isocinética para o escoamento ao redor e dentro da sonda, resultando em uma maior tensão de cisalhamento para baixas velocidades de fluxo de entrada. Por fim um estudo adicional foi realizado utilizando um modelo de rastreamento de partículas para compreender a relevância do comportamento individual de cada partícula no escoamento da emulsão. Os resultados não indicam qualquer efeito significativo sobre as medições no interior da sonda, embora estudos adicionais devem ser realizados neste tópico, considerando um modelo de balanço populacional para as gotículas de óleo
Synthesis of value-added material from coal combustion co-product: characterization and application in aqueous effluent remediation
No full textO presente projeto se insere na sugestão encontrada no \"Roadmap tecnológico para a produção e uso limpo do carvão mineral nacional: 2012 a 2035\" quanto às ações necessárias para que seja estabelecido um ambiente favorável ao maior uso do carvão mineral no Brasil. Isso se dá no que tange ao desenvolvimento de tecnologia considerada prioritária para o setor da geração termelétrica, a saber: aproveitamento de coprodutos da combustão de carvão (PCC). Neste contexto, o projeto envolveu o desenvolvimento de processos capazes de sintetizar material de valor agregado a partir de PCC, como fonte alternativa de silício e alumínio. O material escolhido, proveniente da queima do carvão foi o resíduo de dessulfurização de gases de exaustão, e os nanomateriais sintetizados são considerados produtos de alto valor agregado por possibilitar inúmeras aplicações. O presente trabalho foi dividido em duas etapas; a primeira etapa tratou da síntese e caracterização dos nanomateriais obtidos a partir de diferentes condições da reação de ativação alcalina buscando aperfeiçoar o processo de síntese. Os resíduos de dessulfurização foram coletados de três localidades diferentes, que no início do projeto representavam todas as localidades onde a tecnologia de dessulfurização já estava sendo aplicada na geração de energia elétrica a partir do carvão. Quanto a caracterização dos resíduos, embora existam diferenças envolvidas nos processos que originam as amostras gerando muitas vezes materiais com formas cristalinas diferentes, foram encontrados em todas as amostras os elementos cálcio, alumínio e sílicio. As amostras das três localidades de amostragem foram submetidas ao processo de ativação hidrotérmica alcalina formando principalmente materiais zeolíticos (Sodalitas), tobermoritas e outros compostos do tipo hidrotalcitas. A segunda etapa do trabalho foi direcionada ao uso dos materiais no tratamento de água contaminada com césio, com este objetivo o resíduo de dessulfurização que indicou maior presença de tobermoritas e hidrotalcitas foi selecionado para otimização do processo de síntese hidrotérmica por duas etapas incluindo fusão previa do resíduo. E o material com os melhores resultados de acordo com os materiais cristalinos obtidos foi testado quanto a sua capacidade de remoção de íons de césio em solução, assim como sua seletividade em relação ao sódio presente em certos meios como, por exemplo, na água do mar, em soluções salinas sintéticas e também em uma amostra de água marinha. A capacidade de adsorção do Cs+ sobre o material adsorvente foi de 1949 μmol g-1, indicando que o adsorvente sintetizado pertence ao grupo de materiais com alta capacidade de adsorção de césio quando comparado com outros materiais estudados na literatura, além de apresentar seletividade para o íon de césio em relação à água do mar. Por fim entende-se que o material tem grande potencial para aplicações em remediações em acidentes como o de Fukushima, onde césio radioativo foi liberado na água do mar. Especialmente devido ao material como o resíduo de dessulfurização ser produzido em larga escala e não possuir aplicação na indústria sendo destinado a aterros onde pode se tronar passivo ambiental.The present work is part of the suggestion found in the \"Technology Roadmap for the Clean Production and Use of National Coal: 2012 to 2035\" regarding the actions required to establish a favourable environment for the greater use of coal in Brazil. This concerns the development of technology considered a priority for the thermoelectric generation sector, namely: Use of Coal Combustion Co-products (CCP). In this context, the project involved the development of processes capable of synthesising value-added material from CCP as an alternative source of silicon and aluminium. The material chosen from the burning of coal was the waste gas desulphurization residue, and the synthesised nanomaterials are considered high value-added products because they allow numerous applications. The present work was divided into two stages; The first stage dealt with the synthesis and characterisation of nanomaterials obtained from different conditions of the alkaline activation reaction aiming to improve the synthesis process. Desulphurization residues were collected from three different locations, which at the beginning of the project represented all locations where desulphurization technology was already being applied to coal-fired power generation. Regarding the characterisation of the residues, although there are differences involved in the processes that originate the samples, often generating materials with different crystalline forms, the elements calcium, aluminium and silicon were found in all samples. Samples from the three sampling sites were subjected to the alkaline hydrothermal activation process forming mainly zeolite (Sodalite), tobermorite and other hydrotalcite type materials. The second stage of the work was directed to the use of materials in the treatment of cesium-contaminated water. For this purpose, the desulphurization residue that indicated a higher presence of tobermorites and hydrotalcites was selected for the optimisation of the hydrothermal synthesis process by two steps including previous fusion of the product residue. And the material with the best results according to the crystalline materials obtained was tested for its ability to remove cesium ions in solution, as well as its selectivity to sodium present in certain media, such as seawater, in synthetic saline solutions and also in a sample of marine water. The adsorption capacity of Cs+ on the adsorbent material was 1949 μmol g-1, indicating that the synthesised adsorbent belongs to the group of materials with high cesium adsorption capacity when compared to other materials studied in the literature, besides presenting cesium ion selectivity in relation to seawater and presented selectivity for the Cs ion over seawater. In conclusion, we understand that the material has an interesting potential for accident remediation applications such as Fukushima, where radioactive cesium was released into seawater mainly as the material such as desulphurization residue is produced on a large scale and has no industrial application without landfill where an environmental liability can be traced
The Risk of Childhood Leukaemia in the Vicinity of Nuclear Installations: a review
No full textSince the early years of the peaceful use of atomic energy there has been a debate on possible adverse health effects due the radioactive discharges from the reactors. While this discussion was focussed on infant mortality in the 1960s (1), it is since the 1980s mainly based on findings of increased numbers of leukaemia cases. In 1984 there was the famous report on a ten-fold increase in leukaemia mortality among young people close to the Sellafield reprocessing plant (2). Further local excesses were reported such as from the second British reprocessing plant Dounreay in Scotland (3) and from the German nuclear power station Kruemmel (4, 5). Each of these reports led to a number of further investigations to find possible explanations. Partly based on these investigations, the hypothesis of population mixing as a cause of an increased leukaemia risk was developed by Kinlen (6).
Next to these local studies, larger multi-site studies were launched in several countries, e.g. UK, France and Germany. The population under study were mostly children at ages below 15 years. The multi-site studies revealed no elevated leukaemia risk among all children (see (7)). Still, some studies showed that there might be an elevated risk for the youngest age group (0-4 years) in the closest vicinity of the sites (about up to 5 km).
All the multi-site studies were ecological studies which compared the mortality or incidence rates in certain areas around the nuclear sites. Until recently and except one study conducted in relation to the excess cases found near the Sellafield site (8), there were no case-control studies or cohort studies looking into a relationship between living close to a nuclear site and the risk of leukaemia among children. Early 2008, a case-control study from Germany, which looked at 16 nuclear sites with overall 22 power stations, reported a trend for an increasing leukaemia risk among 0-4 years old children with decreasing distance of place of residence to the sites (9). This trend could be detected even when not taking the cases near the Kruemmel site into consideration. Within the 5-km circle around the sites, the leukaemia risk was roughly twofold increased.
As already mentioned, taking all internationally available ecological studies together, there is no hint for an increased leukaemia risk in the vicinity of nuclear installations for all children below the age of 15 (7). Thus, an elevated risk amongst the 0-4 years old would imply a lower risk amongst the 5-14 years old. That is exactly what can be seen based on German data (10). A recent re-analysis of extended data from Great Britain, which was first reported by COMARE (11), showed no increased risk for all children, but a higher risk for 0-4 years old than for those being 5-14 years of age. This risk was although not statistically significant highest within the 5-km-circle (12). For France, no elevated risks were found close to nuclear installations (13). Still, the values for the relative risks though lower than expected are higher amongst the 0-4 years old than they are for the other children.
A highly speculative assumption is that a yet undefined agent causes by gene-environment interaction an earlier onset of the disease close to the sites amongst vulnerable children (14). If so, this would explain the absence of additional cases among children of all ages.
Based on current knowledge on radiation risk, the radiation exposure to the public has to be considered as being too low by a factor of at least 1,000 to explain the observed effect described in the German study (9). But is has to be kept in mind that little is known about radiation effects from antenatal exposures or those during infancy on the leukaemia risk for ages up to 4 years.
References
1. L. A. Sagan, The infant mortality controversy. Bulletin of the Atomic Scientists 25, 26-28 (1969).
2. D. Black, Investigation of the possible increased incidence of cancer in West Cumbria. Report of the Independent Advisory Group. HMSO, London, 1984.
3. S. Darby and R. Doll, Fallout, radiation doses near Dounreay, and childhood leukaemia. BMJ 294, 603-606 (1987).
4. B. Grosche, D. Lackland, L. Mohr, J. Dunbar, J. Nicholas, W. Burkart and D. Hoel, Leukaemia in the vicinity of two tritium-releasing nuclear facilities: a comparison of the Kruemmel Site, Germany, and the Savannah River Site, South Carolina, USA. J Radiol Prot 19, 243-252. (1999).
5. W. Hoffmann, H. Dieckmann and I. Schmitz-Feuerhake, A cluster of childhood leukemia near a nuclear reactor in northern Germany. Arch Environ Health 52, 275-280. (1997).
6. L. J. Kinlen, F. O'Brien, K. Clarke, A. Balkwill and F. Matthews, Rural population mixing and childhood leukaemia: effects of the North Sea oil industry in Scotland, including the area near Dounreay nuclear site. BMJ 306, 743-748. (1993).
7. D. Laurier, B. Grosche and P. Hall, Risk of childhood leukaemia in the vicinity of nuclear installations-- findings and recent controversies. Acta Oncol 41, 14-24 (2002).
8. M. J. Gardner, M. P. Snee, A. J. Hall, C. A. Powell, S. Downes and J. D. Terrell, Results of case-control study of leukaemia and lymphoma among young people near Sellafield nuclear plant in West Cumbria. BMJ 300, 423-429. (1990).
9. P. Kaatsch, C. Spix, R. Schulze-Rath, S. Schmiedel and M. Blettner, Leukaemia in young children living in the vicinity of German nuclear power plants. Int J Cancer 122, 721-726 (2008).
10. U. Kaletsch, R. Meinert, A. Miesner, M. Hoisl, P. Kaatsch and J. Michaelis, Epidemiologische Studien zum Auftreten von Leukämieerkrankungen bei Kindern in Deutschland. BMU, Bonn, 1997.
11. COMARE, Tenth Report: The incidence of childhood cancer around nuclear installation in Great Britain. p. 46. HPA, 2005.
12. J. Bithell, Childhood Leukemia near British nuclear installations: methodological issues and recent results. In ICNIRP/WHO/BfS International Workshop on Risk Factors for Childhood Leukemia, Berlin, 2008.
13. M. L. White-Koning, D. Hemon, D. Laurier, M. Tirmarche, E. Jougla, A. Goubin and J. Clavel, Incidence of childhood leukaemia in the vicinity of nuclear sites in France, 1990-1998. Br J Cancer 91, 916-922 (2004).
14. D. Sinnett, N. N'Diaye, P. St-Onge and J. Healy, La leucémie de lenfant : Une maladie génétique!. Med Sci (Paris) 23, 968-974 (2007)
Separation of variables in path integrals and path integral solution of two potentials on the Poincare upper half-plane
No full textThe author discusses how to separate variables in path integrals. It is assumed that a one-dimensional problem with potential V(x) has an exact solution with energy levels Elambda and wavefunctions Psi lambda . In order to perform the separation of variables, a time transformation is performed back and forth in the path integral which allows one to insert the path integral solution corresponding to the potential V(x). The author illustrates the method by discussing some specific potential problems on the Poincare upper half-plane
Path integrals for two- and three-dimensional -function perturbations
No full textThe incorporation of two- and three-dimensional Δ-function perturbations into the path integral formalism is discussed. Contrary to the one-dimensional case, a regularization prescription is needed due to the divergence of the Green function corresponding to a potential V, G(v) (x,y;E) (x, y ϵ ℝ2, ℝ3) for x→y. The known procedure to define proper self-adjoint extensions for Hamiltonians with point-interactions can be exploited to define the incorporation of δ-function perturbations in the path integral. Several examples illustrate the formalism
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