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Search Results: 1 - 10 of 223870 matches for " R. Siems "
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Low temperature phase diagram and critical behaviour of the four-state chiral clock model
M. Pleimling,B. Neubert,R. Siems
Physics , 1998, DOI: 10.1088/0305-4470/31/21/006
Abstract: The low temperature behaviour of the four-state chiral clock ($CC_4$) model is reexamined using a systematic low temperature series expansion of the free energy. Previously obtained results for the low temperature phases are corrected and the low temperature phase diagram is derived. In addition, the phase transition from the modulated region to the high temperature paraphase is shown to belong to the universality class of the 3d-XY model.
Professores da Educa o Especial: as rela es com a diferen a em quest o
Maria Edith Romano Siems
Revista Educa??o Especial , 2009,
Abstract: Este artigo discute a forma como professores que atuam na educa o de pessoas com deficiência, os chamados professores da Educa o Especial, estabelecem rela es com a diferen a. Toma como referencial teórico-metodológico a perspectiva histórico-cultural, fundada em Bakhtin e sua teoria enunciativa da linguagem e Vygotsky com a teoria da constru o social do conhecimento. Com base nesses autores se orienta n o só as análises dos dados coletados, mas também a própria metodologia de pesquisa, desenvolvida através de entrevistas coletivas, entendendo que a presen a do pesquisador em campo pode constituir-se também em espa o de reflex o e reorienta o de procedimentos. Ao longo das entrevistas realizadas com um grupo de sete professores atuantes na rede pública de ensino do Estado de Roraima, aspectos das histórias de vida pessoal, acadêmica e profissional, constituidores da identidade profissional destas professoras, destacaram-se em seus discursos, apontando os meios como essas se relacionam com a diferen a. S o professoras que assumem posturas que variam entre a perspectiva de corre o do “defeito”; da compreens o deste como elemento a ser social e culturalmente incorporado e a da conscientiza o, que toma o Múltiplo como elemento de enriquecimento da coletividade. Palavras-chave: Educa o Especial. Diferen a. Identidade.
Networks, Dialogue or One-Way Traffic? An Empirical Analysis of Cross-Citations Between Ten of Europe’s Highest Courts
Martin Gelter,Mathias Siems
Utrecht Law Review , 2012,
Abstract: Today judges are said to 'see each other not only as servants and representatives of a particular polity, but also as fellow professionals in an endeavour that transcends national borders' (A.M. Slaughter). This statement was made in the context of transnational litigation but it may also reflect a more general trend. Interaction may take place in various forms. There is some direct transnational cooperation between judges, but it can also be seen as a form of influence when a particular court is frequently cited by its foreign counterparts. In this article, which is part of a wider research project, we present our findings on cross-citations between ten of Europe's highest courts. We considered 636,172 decisions and found 1,430 cross-citations between 2000 and 2007. The first section of the article summarises the data considered and the search methodology used. The next two sections present different ways of visualising these data: on the one hand three types of bar charts, and on the other hand two network presentations of the cross-citations between the ten courts. Subsequently, we examine the relationship between incoming and outgoing citations, in particular whether some of our countries may be regarded as 'the core' and the others as 'the periphery'.
Models for the description of uniaxially modulated materials
Boris Neubert,Michel Pleimling,Rolf Siems
Physics , 1997,
Abstract: Models which allow an explicit application to structurally modulated substances are reviewed within the frame of a symmetry-based approach starting from discrete lattice theory. Focus is set on models formulated in terms of local variables assigned to discrete crystallographic units (unit cells or parts of them). Especially considered are symmetry-based pseudo spin models. Methods are discussed which permit the handling of the statistical mechanics of such models, the translation of model calculation results to a form allowing the prediction of experimental data, and the theoretical determination of point defect influences.
Derivation of symmetry-based pseudo spin models for modulated materials
Boris Neubert,Michel Pleimling,Rolf Siems
Physics , 1997,
Abstract: A general concept for the derivation of symmetry-based pseudo spin Hamiltonians is described. It systematically bridges the gap between the atomistic basis and various pseudo spin models presented in literature. It thus allows the application of the multitude of analytical and numerical procedures derived for the statistical mechanics treatment of the latter to the description of structurally modulated crystals and furnishes a general frame for reviewing these models from a common point of view.
Transitions between Phases with Equal Wave Numbers in a Double Ising Spin Model. Application to Betaine Calcium Chloride Dihydrate
Boris Neubert,Michel Pleimling,Rolf Siems
Physics , 1998, DOI: 10.1088/0953-8984/10/31/007
Abstract: A Double Ising Spin model for uniaxially structurally modulated materials exhibits as a special feature phase transitions between phases with equal wave numbers but different pseudo spin configurations. The character of these `internal' transitions is investigated in mean field approximation, with the mean field transfer matrix method, and in Monte Carlo simulations. The structural changes at the transitions are characterized by different strengths of harmonics in a Fourier analysis of the spatial modulation. A dielectric anomaly in the phase diagram of betaine calcium chloride dihydrate (BCCD) and seemingly contradictory structure analyses are explained.
Plants traditionally used against malaria: phytochemical and pharmacological investigation of Momordica foetida
Froelich, Sonja;Onegi, Bernadina;Kakooko, Adrian;Siems, Karsten;Schubert, Carola;Jenett-Siems, Kristina;
Revista Brasileira de Farmacognosia , 2007, DOI: 10.1590/S0102-695X2007000100002
Abstract: leaves from momordica foetida traditionally used to treat symptoms of malaria in parts of east africa were studied for in vitro antimalarial activity. using an [3h] hypoxanthine-incorporation assay the antiplasmodial activity of hydrophilic and lipophilic extracts against the chloroquine-sensitive strain pow and the multiresistant clone dd2 of plasmodium falciparum was determined. the petrol ether/ethyl acetate extract showed significant activity with ic50 values of 7.3 μg/ml (pow) and 13.0 μg/ml (dd2). cytotoxicity was estimated on two human cell lines hepg2 and ecv-304 and a selectivity index (si) was calculated, ranging between 12 and 15. phytochemical analysis led to the isolation of a number of phenolic glycosides, e.g. eriodictyol-, 5,7,4?-trihydroxyflavanone-, kaempferol- and 5,7-dihydroxychromone-7-o-b-d-glucopyranoside, not previously known from m. foetida. in order to prove one possible mode of action the influence of the crude extracts as well as the isolated compounds on the heme degradation with chloroquine as reference compound was evaluated. the ethyl acetate extract showed about 88% inhibition of heme degradation, quite similar to chloroquine (84 %), and also eriodictyol-7-o-b-d-glucopyranoside (2) inhibited heme degradation by 86 %.
Phenylethanoid glycosides from Stachytarpheta cayennensis (Rich.) Vahl, Verbenaceae, a traditional antimalarial medicinal plant
Froelich, Sonja;Gupta, Mahabir P.;Siems, Karsten;Jenett-Siems, Kristina;
Revista Brasileira de Farmacognosia , 2008, DOI: 10.1590/S0102-695X2008000400003
Abstract: the boiled juice of stachytarpheta cayennensis, verbenaceae, whole plant material is used ethnomedicinally in different countries of latin-america to treat symptoms of malaria. in the ethyl acetate extract, five phenylethanoid glycosides could be identified. three of these phenylethanoid glycosides, leucosceptoside a, martynoside and jionoside d were detected for the first time in the genus stachytarpheta.
High-Protein Diet in Lactation Leads to a Sudden Infant Death-Like Syndrome in Mice
Thomas Walther,Nils Dietrich,Martina Langhammer,Marzena Kucia,Harald Hammon,Ulla Renne,Wolf-Eberhard Siems,Cornelia C. Metges
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0017443
Abstract: It is well accepted that reduced foetal growth and development resulting from maternal malnutrition are associated with a number of chronic conditions in later life. On the other hand such generation-transcending effects of over-nutrition and of high-protein consumption in pregnancy and lactation, a proven fact in all developed societies, are widely unknown. Thus, we intended to describe the generation-transcending effects of a high-protein diet, covering most relevant topics of human life like embryonic mortality, infant death, and physical health in later life.
Genetic Deficiency in Neprilysin or Its Pharmacological Inhibition Initiate Excessive Stress-Induced Alcohol Consumption in Mice
Bj?rn Maul, Matthias Becker, Florian Gembardt, Axel Becker, Heinz-Peter Schultheiss, Wolf-Eberhard Siems, Thomas Walther
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050187
Abstract: Both acquired and inherited genetic factors contribute to excessive alcohol consumption and the corresponding development of addiction. Here we show that the genetic deficiency in neprilysin [NEP] did not change the kinetics of alcohol degradation but led to an increase in alcohol intake in mice in a 2-bottle-free-choice paradigm after one single stress stimulus (intruder). A repetition of such stress led to an irreversible elevated alcohol consumption. This phenomenon could be also observed in wild-type mice receiving an orally active NEP inhibitor. We therefore elucidated the stress behavior in NEP-deficient mice. In an Elevated Plus Maze, NEP knockouts crossed more often the area between the arms, implicating a significant stronger stress response. Furthermore, such animals showed a decreased locomotor activity under intense light in a locomotor activity test, identifying such mice to be more responsive in aversive situations than their wild-type controls. Since the reduction in NEP activity itself does not lead to significant signs of an altered alcohol preference in mice but requires an environmental stimulus, our findings build a bridge between stress components and genetic factors in the development of alcoholism. Therefore, targeting NEP activity might be a very attractive approach for the treatment of alcohol abuse in a society with increasing social and financial stress.
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