984 research outputs found
XANES calculation with an efficient ``Non Muffin-Tin'' method: Application to the angular dependence of the AlK-edge in corundum
No full textWe present a reciprocal-space ``non mufin-tin'' scheme for calculating X-ray Absorption Near-Edge Structure (XANES). The method uses pseudopotentials and reconstructs all electron wave functions within the Projector Augmented Wave framework. The method incorporates a recursive method to compute absorption cross section as a continued fraction. The continued fraction formulation of absorption is advantageous in that it permits the treatment of core-hole-electron interaction through large supercells ( hundreds of atoms). This opens new fields of applications like surfaces, molecules, small aggregates or amorphous materials, for which large supercells are required. The method is applied to the natural linear dichroism at the Al K-edge in corundum (alpha-Al2O3). Details about the convergence process of the calculation are given. The influence of the core-hole effects is emphasized and comparison with ``muffin-tin'' multiple scattering calculation is made
Analysis of Mathieu Equation Stable Solutions in the First Zone of Stability
No full textAbstractThe paper presents the results of a homogeneous Mathieu equation studies. Mathieu equation solutions are oscillations, modulated in amplitude and frequency. In the computational experiments we found dependences of the given oscillations on the ratio of the coefficients. These dependences are shown in graphs that can be used for an approximate estimation of the Mathieu equation solutions without integration
Pensar las escalas para pensar las luchas: Autor: Mathieu UHEL
No full textA través de un título sugerente, “pensar las escalas para pensar las luchas”, Mathieu Uhel entreteje la construcción teórico-crítica del concepto escala, generada por la geografía radical anglosajona de finales del siglo XX, con la necesidad/utilidad práctica de la escala para concienciar las luchas sociales. El artículo cumple un doble propósito: por un lado, delinear los elementos de lectura sobre el concepto escala; y, con ello, promover la atención de esta problemática en las luchas contemporáneas. En un primer apartado, Uhel ubica las discusiones académicas en torno a la escala, como herramienta metodológica útil para comprender la complejidad de las sociedades capitalistas; en el segundo apartado, el autor avanza la exposición en torno al contexto de la dimensión escalar del imperialismo capitalista; finalmente, el autor se centra en el rol de la actividad política a escala nacional en la tensa relación entre las imposiciones del capital y la lucha social.Por meio de um título sugestivo, “pensando escalas para pensar lutas”, Mathieu Uhel entrelaça a construção teórico-crítica do conceito de escala, gerado pela geografia radical anglo-saxônica do final do século XX, com a necessidade / utilidade prática escala para aumentar a consciência das lutas sociais. O artigo tem um duplo propósito: por um lado, delinear os elementos de leitura sobre o conceito de escala; e, com isso, promover atenção a esse problema nas lutas contemporâneas. Na primeira seção, Uhel localiza as discussões acadêmicas em torno da escala, como uma ferramenta metodológica útil para compreender a complexidade das sociedades capitalistas; na segunda seção, o autor avança a exposição em torno do contexto da dimensão escalar do imperialismo capitalista; por fim, o autor enfoca o papel da atividade política em escala nacional na tensa relação entre as imposições do capital e a luta social.Mathieu Uhel\u27s suggestive title, “Thinking about scales to think about struggles”, he interweaves the theoretical-critical construction of concept scale, generated by radical Anglo-Saxon geography in the late 20th century, with it´s practical utility to social struggles. The article serves two purposes: on the one hand, Uhel locates academic discussion around scale; and, with this, he promotes attention to this problem in contemporary struggles. In the first section, Uhel locates academic discussions around scale, as a useful methodological tool to understand the complexity of capitalist societies; in the second section, the author advances the argument around the context of the scalar dimension of capitalist imperialism; finally, the author focuses on the role of political activity on a national scale in the tense relationship between the impositions of capital and the social movement
Mathieu Ichou, Les Enfants d’immigrés à l’école
No full textIt is common to hear in the fields of educational and immigration sociology that on average, the children of immigrants do not perform as well in school as children of native-born parents. Mathieu Ichou offers an innovative sociological analysis on a topic that is heavily exploited by political and media discourse, and subject to much scientific controversy. The author takes distance from the homogenized vision of a “second generation” of students who have totally failed academically, and rep..
Quelques mécanismes non conventionnels de l'effet Hall anormal
No full textThis thesis is divided in three distinct parts. In the first andsecond parts, we speak about unconventional mechanisms of theAnomalous Hall Effect (AHE). The first part gives a short review ofthe conventional and unconventional mechanisms of the AHE (chapter~1).chapter~2 is devoted to geometrical phases. The second part of this thesis answer to some questions about the AHE.The third chapter treats the role of impurities in intrinsic mechanismof the AHE. By calculating of the off-diagonal conductivity in thelinear response theory for a model of 2DEG in presence of spin-orbitcoupling, we obtained two contributions related to the diffusion ofelectrons by impurities of defaults but independent of theconcentration of impurities. The second one is the Karplus andLuttinger term, which depends on the topology of the energy band. Inthe chapter~4, we propose an experimental setup based on 2DEG inpresence of inhomogeneous magnetic field created by magneticnanostructure. In this system, the Hall conductivity has discontinuousvariations related to the topology of the magnetic field, which can bemodified by applying an additional constant magnetic field. In thechapter~5, we study the spin chirality mechanism of the AHE on thekagome lattice and discuss the results of recent experiments on the pyrochlore compound NdMoO. The last part of this thesis is devoted to electron dynamic ininhomogeneous magnetic field. The chapters~6 and~7 give a introductionof electrons dynamic in two dimensional periodic magnetic field. Thelast chapter is a study of electron dynamic in 2D periodic magneticfield. We find that it exists persistent currents related tolocalization of electrons around the regions where the magnetic fieldis canceling.Ce manuscrit est divisé en trois parties distinctes. les deuxpremières parties sont axées sur l'étude de quelques mécanismesintrinsèques de l'effet Hall anormal. Nous montrons notamment que ladiffusion des porteurs de charge par des impuretés ou des défautsdonne une contribution intrinsèque non négligeable à l'effet Hallanormal. Nous proposons ensuite une expérience, basée sur un réseau denanocylindres magnétiques, placé au dessus d'un gaz d'électronsbidimensionnel, dans laquelle les contributions intrinsèques del'effet Hall anormal sont clairement identifiables et contrôlables.Enfin, nous abordons le problème du mécanisme de chiralité de spinproposé pour expliquer l'effet Hall dans le composé pyrochloreNdMoO. En utilisant un modèle de gaz sur réseau ainsiqu'une configuration magnétique non colinéaire (chirale), nousmontrons que la conductivité transverse a une dépendance complexe parrapport à la chiralité de spin.La dernière partie de ce manuscrit est dédiée à l'étude de quelquespropriétés des gaz d'électrons soumis à un champ magnétiqueinhomogène. Après un bref rappel sur la dynamique d'électron enprésence d'un gradient de champ magnétique constant, nous abordons leproblème d'un champ magnétique périodique spatialement. En calculantquelques états de Bloch aux points de haute symétrie, nous montrons qu'ilexiste des états pour lesquels les électrons sont localisés auvoisinage des lignes de champ nul. Le calcul des courants deprobabilité montre que ces états sont porteurs de courants permanentsdont l'origine est liée aux inhomogénéités du champ magnétique auvoisinages des lignes de champ nul
L'impatto dell'attività tintoria sull'ambiente. Firenze alla fine del Medioevo
No full textThe author aims to examine and categorize the range of dyeings materials used in the Florentine wool and silk textile industries in the late Middle Ages, focusing mainly on those produced within the regional space in order to evaluate the impact of the Florentine dyeing activity on the natural environment and the productive landscape of the Tuscan countryside. In particular, the author establishes a line of demarcation between cultivated and uncultivated resources in order to verify which constitutes an indication of the level of industrial development of medieval textile production. This further focuses on how the transition from the exploitation of wild resources to the exploitation of cultivated resources could reflect a greater degree of economic integration between the countryside and the city and contribute to the formation of a regional economic space
Mathieu de Fossey: su visión del mundo indígena mexicano
No full textThroughout these pages the author shows how Mathieu de Fossey perceived that it was not easy to make indigenous communities fit within the mould of the nation-state which, being based on the liberal and egualitarian ideology, was against the recognition of special regimes, such as those that created a peculiar status for the native population of the American territory during the period of Spanish colonial domination
Mathieu de Fossey: su visión del mundo indígena mexicano
No full textÀ travers ces pages, l’auteur montre comment Mathieu de Fossey avait perçu la difficulté d’insérer le monde des communautés indigènes dans le moule d’un État national qui, accroché à une idéologie libérale égalitaire, refusait d’établir des régimes spéciaux comparables à ceux qui, durant la domination espagnole, avaient reconnu un statut particulier aux populations natives du continent américain.A través de estas páginas se muestra cómo Mathieu de Fossey percibió el difícil acoplamiento del mundo de las comunidades indígenas en el molde de un Estado nacional que, por estar sustentado en la ideología liberal igualitaria, era contrario al reconocimiento de regímenes especiales como los que, durante la dominación española, habían establecido un status peculiar para los aborígenes del territorio americano.Throughout these pages the author shows how Mathieu de Fossey perceived that it was not easy to make indigenous communities fit within the mould of the nation-state which, being based on the liberal and egualitarian ideology, was against the recognition of special regimes, such as those that created a peculiar status for the native population of the American territory during the period of Spanish colonial domination
Investigation of documents persistency on the Web
No full text@inproceedings{CI-Lancieri-2004-2, author = {Lancieri, Luigi and Lecouvey, Mathieu and Glasse, Veronique}, title = {Investigation of documents persistency on the Web}, booktitle = {International conference E-Society 2004 (ES2004), IADIS}, year = {2004}, address = {Spain} }International audienc
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