Dans la thèse nous traitons les propriétés magnétiques, orbitales et de transport des super-réseaux (LaMnO3) 2N (SrMnO3) N et des couches minces de LaxMnO3-d déposées par épitaxie à jet moléculaire (MBE) sur des substrats SrTiO3. Ces super-réseaux représentent un nouveau genre d'hétérostructure, récemment très étudié, composée par un nombre entier de mailles, où des effets de reconstruction électronique aux interfaces sont prévus. Dans la première partie du travail de thèse, des techniques de lithographie optique et des différentes techniques de dépôt sont utilisées afin d'effectuer des mesures de transport avec courant perpendiculaire à la surface des échantillons (CPP) et sous l'effet de champ électrique. La technique CPP peut donner de l'information supplémentaire sur les interfaces par rapport aux mesures de transport traditionnelles. L'effet de champ a été largement étudié dans des systèmes de manganite, puisque il représente une méthode pour changer la densité de porteurs, et afin de fabriquer des dispositifs à effet de champ avec des oxydes. On rapporte les résultats de l'optimisation de telles techniques, ainsi que l'optimisation des matériaux utilisés en tant qu'électrode de base, isolateur de flanc ou de barrière et électrode supérieure. Dans la deuxième partie de la thèse, les deux systèmes sont étudiés par des techniques traditionnelles (transport, aimantation par SQUID) et par des techniques d'absorption et d'émission de rayon X par rayonnement de synchrotron. Des informations précieuses sur le ferromagnétisme, l'antiferromagnétisme et l'ordre orbital sont obtenues.

The thesis focuses on the qualitative analysis of a general class of SEIRS models in periodic and non-periodic environments. The classical SEIRS model, with standard incidence function, is, first of all, extended to incorporate multiple infectious stages. Using Lyapunov function theory and LaSalle's Invariance Principle, the disease-free equilibrium (DFE) of the resulting SEIⁿRS model is shown to be globally-asymptotically stable whenever the associated reproduction number is less than unity. Furthermore, this model has a unique endemic equilibrium point (EEP), which is shown (using a non-linear Lyapunov function of Goh-Volterra type) to be globally-asymptotically stable for a special case. The SEIⁿRS model is further extended to incorporate arbitrary number of latent stages. A notable feature of the resulting SE^mIⁿRS model is that it uses gamma distribution assumptions for the average waiting times in the latent (m) and infectious (n) stages. Like in the case of the SEIⁿRS model, the SE^mIⁿRS model also has a globally-asymptotically stable DFE when its associated reproduction threshold is less than unity, and it has a unique EEP (which is globally-stable for a special case) when the threshold exceeds unity. The SE^mIⁿRS model is further extended to incorporate the effect of periodicity on the disease transmission dynamics. The resulting non-autonomous SE^mIⁿRS model is shown to have a globally-stable disease-free solution when the associated reproduction ratio is less than unity. Furthermore, the non-autonomous model has at least one positive (non-trivial) periodic solution when the reproduction ratio exceeds unity. It is shown (using persistence theory) that, for the non-autonomous model, the disease will always persist in the population whenever the reproduction ratio is greater than unity. One of the main mathematical contributions of this thesis is that it shows that adding multiple latent and infectious stages, gamma distribution assumptions (for the average waiting times in these stages) and periodicity to the classical SEIRS model (with standard incidence) does not alter the main qualitative dynamics (pertaining to the persistence or elimination of the disease from the population) of the SEIRS model.

The thesis focuses on the qualitative analysis of a general class of SEIRS models in periodic and non-periodic environments. The classical SEIRS model, with standard incidence function, is, first of all, extended to incorporate multiple infectious stages. Using Lyapunov function theory and LaSalle's Invariance Principle, the disease-free equilibrium (DFE) of the resulting SEIⁿRS model is shown to be globally-asymptotically stable whenever the associated reproduction number is less than unity. Furthermore, this model has a unique endemic equilibrium point (EEP), which is shown (using a non-linear Lyapunov function of Goh-Volterra type) to be globally-asymptotically stable for a special case. The SEIⁿRS model is further extended to incorporate arbitrary number of latent stages. A notable feature of the resulting SE^mIⁿRS model is that it uses gamma distribution assumptions for the average waiting times in the latent (m) and infectious (n) stages. Like in the case of the SEIⁿRS model, the SE^mIⁿRS model also has a globally-asymptotically stable DFE when its associated reproduction threshold is less than unity, and it has a unique EEP (which is globally-stable for a special case) when the threshold exceeds unity. The SE^mIⁿRS model is further extended to incorporate the effect of periodicity on the disease transmission dynamics. The resulting non-autonomous SE^mIⁿRS model is shown to have a globally-stable disease-free solution when the associated reproduction ratio is less than unity. Furthermore, the non-autonomous model has at least one positive (non-trivial) periodic solution when the reproduction ratio exceeds unity. It is shown (using persistence theory) that, for the non-autonomous model, the disease will always persist in the population whenever the reproduction ratio is greater than unity. One of the main mathematical contributions of this thesis is that it shows that adding multiple latent and infectious stages, gamma distribution assumptions (for the average waiting times in these stages) and periodicity to the classical SEIRS model (with standard incidence) does not alter the main qualitative dynamics (pertaining to the persistence or elimination of the disease from the population) of the SEIRS model.

科学研究費補助金 研究種目:一般研究(B)→基盤研究(B) 課題番号:07458091 研究代表者:庄司 多津男 研究期間:1995-1996年度

We investigate the manifestation of strong electronic correlations in the quasiparticle interference (QPI), arising from the scattering of conduction electrons from defects and impurities in an otherwise translationally-invariant host. The QPI may be measured experimentally as the Fourier transform of the spatial modulations in the host surface density of states that result, which are mapped using a scanning tunnelling microscope. We calculate the QPI for a range of physically relevant models, demonstrating the effect of strong local electronic correlations arising in systems of magnetic impurities adsorbed on the surface of non-interacting host systems. In the first instance the effect of these magnetic impurities is modelled via the single Anderson impurity model, treated via numerical renormalization group (NRG) calculations. The scattering of conduction electrons, and hence the QPI, demonstrate an array of characteristic signatures of the many-body state formed by the impurity, for example due to the Kondo effect. The effect of multiple impurities on the QPI is also investigated, with a numerically-exact treatment of the system of two Anderson impurities via state-of-the-art NRG calculations. Inter-impurity interactions are found to result in additional scattering channels and additional features in the QPI. The QPI is then investigated for the layered transition metal oxide Sr2RuO4, for which strong interactions in the host conduction electrons give rise to an unconventional triplet superconducting state at T_c ∼ 1.5K. The detailed mechanism for this superconductivity is still unknown, but electron-electron or electron-phonon interactions are believed to play a central role. We simulate the QPI in Sr₂RuO₄, employing an effective parametrized model consisting of three conduction bands derived from the Ru 4d t2g orbitals that takes into account spin orbit coupling and the anisotropy of the Ru t2g orbitals. Signatures of such interactions in the normal state are investigated by comparing these model calculations to experimental results. We also calculate the QPI in the superconducting state, and propose how experimental measurements may provide direct evidence of the anisotropy and symmetry of the superconducting gap, and thus offer insight into the pairing mechanism and the superconducting state.

While the free electron model can often be surprisingly successful in describing properties of solids, there are plenty of materials in which interactions between electrons are too significant to be neglected. These strongly correlated systems sometimes exhibit rather unexpected, unusual and useful phenomena, understanding of which is one of the aims of condensed matter physics. Heat capacity measurements of paramagnetic YFe$_{2}$Ge$_{2}$ give a Sommerfeld coefficient of about 100 mJ mol$^{−1}$ K$^{−2}$, which is about an order of magnitude higher than the value predicted by band structure calculations. This suggests the existence of strong electronic correlations in the compound, potentially due to proximity to an antiferromagnetic quantum critical point (QCP). Existence of the latter is also indicated by the non-Fermi liquid T$^{3/2}$ behaviour of the low temperature resistivity. Below 1.8 K a superconducting phase develops in the material, making it a rare case of a non-pnictide and non-chalcogenide iron based superconductor with the 1-2-2 structure. This thesis describes growth and study of a new generation of high quality YFe$_{2}$Ge$_{2}$ samples with residual resistance ratios reaching 200. Measurements of resistivity, heat capacity and magnetic susceptibility confirm the intrinsic and bulk character of the superconductivity, which is also argued to be of an unconventional nature. In order to test the hypothesis of the nearby QCP, resistance measurements under high pressure of up to 35 kbar have been conducted. Pressure dependence of the critical temperature of the superconductivity has been found to be rather weak. μSR measurements have been performed, but provided limited information due to sample inhomogeneity resulting in a broad distribution of the critical temperature. While the superconductivity is the result of an effective attraction between electrons, under different circumstances the electronic properties of a system can instead be dictated by the Coulomb repulsion. This is the case for another transition metal based compound NiS$_{2}$, which is a Mott insulator. Applying hydrostatic pressure of about 30 kbar brings the material across the Mott metal-insulator transition (MIT) into the metallic phase. We have used the tunnel diode oscillator (TDO) technique to measure quantum oscillations in the metallised state of NiS$_{2}$, making it possible to track the evolution of the principal Fermi surface and the associated effective mass as a function of pressure. New results are presented which access a wider pressure range than previous studies and provide strong evidence that the effective carrier mass diverges close to the Mott MIT, as expected within the Brinkman-Rice scenario and predicted in dynamical mean field theory calculations. Quantum oscillations have been measured at pressures as close to the insulating phase as 33 kbar and as high as 97 kbar. In addition to providing a valuable insight into the mechanism of the Mott MIT, this study has also demonstrated the potential of the TDO technique for studying materials at high pressures.

Submitted by ELIAS ELY GOMES VITÓRIO (eliasvitorio@yahoo.com.br) on 2015-06-08T16:32:42Z No. of bitstreams: 1 Tese Elias -EBAPE_FGV_05_06_2015 Submeter.pdf: 1669985 bytes, checksum: f6e0908b2cae43a30b8a218b9071970e (MD5) / Approved for entry into archive by ÁUREA CORRÊA DA FONSECA CORRÊA DA FONSECA (aurea.fonseca@fgv.br) on 2015-06-09T14:04:13Z (GMT) No. of bitstreams: 1 Tese Elias -EBAPE_FGV_05_06_2015 Submeter.pdf: 1669985 bytes, checksum: f6e0908b2cae43a30b8a218b9071970e (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2015-06-11T12:52:53Z (GMT) No. of bitstreams: 1 Tese Elias -EBAPE_FGV_05_06_2015 Submeter.pdf: 1669985 bytes, checksum: f6e0908b2cae43a30b8a218b9071970e (MD5) / Made available in DSpace on 2015-06-11T12:53:25Z (GMT). No. of bitstreams: 1 Tese Elias -EBAPE_FGV_05_06_2015 Submeter.pdf: 1669985 bytes, checksum: f6e0908b2cae43a30b8a218b9071970e (MD5) Previous issue date: 2015-05-05 / Despite the Brazil rely on free public distribution model of drugs, representing progress compared to most developing countries, the overall scenario presents problems of many orders. The public supply is flawed and inefficient, with poorly motivated professionals. This condictions results in losses arising from deviations, poor condition of inadequate storage and distribution processes. The use of private distribuition through Programa Farmácia Popular do Brasil, to the government's point of view, promotes capillary in attendance, increasing social welfare and reduces costs by using staff. From the point of view of society, increases the drug access to the population. Thus, the program has represented an efficient solution for the distribution of medicines in the country. However, from a business point of view, the results of the use of private mesh for the free distribution of medicines are still less described. This study aims to assess the impacts related to the accreditation in the federal program in independent pharmacy chains and private drugstores free distribution of medicines to the population. It addresses a multifunctional matter, and consist of one program analysis that is part of the federal government guidelines and be an unprecedented nature theme with focus on the business environment. From a business point of view, the service to the distribution of free drug program in compliance with the federal government program may represent a business leverage factor to bring potential customers to the establishment. However, it is necessary adaptations occurring in cash flow management to support the possible delays in the transfer of government and meet the supply of medicines to the growing demands. So drugstores inserted in the pharmaceutical retail sector in developing cities acquire competitive advantage and provide greater value to their customers. The free distribuition project implies generalized net benefits. For the population, the direct and effective access. For the private sector, market expansion and the stability of demand. For the government, the replacement of a strategy that converges to the economic, social and political friction. / Esta tese teve por objetivo identificar os principais fatores de motivação de pessoas que trabalham em organizações públicas fortemente hierarquizadas, como as do Exército Brasileiro, preenchendo uma lacuna de conhecimento existente em pesquisas acadêmicas sobre o tema. Diferentes trabalhadores possuem diferentes fatores de motivação, fatores estes que liberam a motivação que está dentro dessas pessoas.Estudou-se dezoito teorias sobre motivação dentre as mais citadas no meio acadêmico. Estas teorias permitiram estruturar um roteiro de entrevistas que foi aplicado em trinta e três militares do Exército Brasileiro.Estas entrevistas foram submetidas à análise de conteúdo, o que permitiu a identificação dos principais fatores de motivação desses profissionais.Concluiu-se que os principais fatores de motivação das pessoas que trabalham em organizações fortemente hierarquizadas, em ordem de importância, são: 1) valorização, 2) fazer o que se gosta, 3) exemplo do chefe, 4) importância do que se faz, 5) realização, 6) confiança e 7) justiça. Os três primeiros fatores formam um primeiro grupo e os outros quatro fatores formam um segundo grupo. Essa divisão se fez necessária porque os fatores do primeiro grupo se revelaram muito mais fortes que os fatores do segundo grupo, havendo necessidade de destacá-los. Confirmou-se, também, que as teorias de motivação são perfeitamente aplicáveis às organizações públicas fortemente hierarquizadas e que estas teorias produzem alguns fatores de motivação específicos à realidade organizacionaldessas instituições. Após a análise do conteúdo das entrevistas, à luz das teorias de motivação, concluiu-se que há uma necessidade psicológica muito forte nas pessoas: a necessidadede se sentir valorizada. A motivação no contexto organizacional normalmente depende do relacionamento entre o gestor de pessoas, ou o líder e os seus liderados. A ação do líder é fundamental para despertar a motivação que já está dentro das pessoas. O foco das atenções do líder deve estar voltado para os liderados e não para si mesmo.Porque quando os liderados são fortes, o líder é forte e a organização obtém resultados surpreendentes. Por fim, conclui-se que a motivação das pessoas, nas organizações públicas fortemente hierarquizadas, como o Exército Brasileiro, é liberada quando a organização procura aplicar os sete principais fatores de motivação de pessoas revelados nesta tese.E acima de tudo, quando o líder cria condições para a satisfação da principal necessidade das pessoas: se sentir valorizadas.

Submitted by ANA KARLA PEREIRA RODRIGUES (anakarla_@hotmail.com) on 2017-08-22T16:03:10Z No. of bitstreams: 1 arquivototal.pdf: 1039820 bytes, checksum: 2e99f469c22f0b9c57e0059499fc3b27 (MD5) / Made available in DSpace on 2017-08-22T16:03:10Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1039820 bytes, checksum: 2e99f469c22f0b9c57e0059499fc3b27 (MD5) Previous issue date: 2017-02-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The goal of our work is to study the class of the Cohen strongly summing operators. Initially, we present basic results from Functional Analysis that are necessary for the development of the text and then we deal with sequence spaces which will be used to de ne and study the classes of operators involved in this work, as necessarily the class of the absolutely summing operators. We also study the sequence space of the Cohen- Khalil strongly (q; p)-summable sequences and the sequence space of the Cohen strongly p-summable sequences, as a particular instance of the former. From this, we de ne the class of the Cohen strongly p-summing operators and the class of the Cohen-Khalil strongly (s; r; p)-summing operators which, under certain conditions, are equivalent. We conclude with a study, from the viewpoint of the operator ideal theory, using the abstract environment created by G. Botelho and J. R. Campos, in order to show that p and Dp are Banach ideals and the relations dual p = Dp and Ddual p = p are valid, where p and p are conjugate indexes. / objetivo de nosso trabalho e estudar a classe dos operadores Cohen fortemente p- somantes. Inicialmente, apresentamos resultados b asicos de An alise Funcional necess arios ao desenvolvimento do texto e, em seguida, tratamos dos espa cos de sequ^encias que ser~ao usados na de ni c~ao e estudo das classes de operadores envolvidas no trabalho, como necessariamente a classe dos operadores absolutamente somantes. Apresentamos tamb em o espa co das sequ^encias Cohen-Khalil fortemente (q; p)-som aveis e o espa co das sequ^encias Cohen fortemente p-som aveis, como caso particular do primeiro. A partir disto, de - nimos a classe dos operadores Cohen fortemente p-somantes e a classe dos operadores Cohen-Khalil fortemente (s; r; p)-somantes que, sob certas condi c~oes, s~ao equivalentes. Conclu mos com um estudo, sob o ponto de vista da teoria dos ideais de operadores, usando o ambiente abstrato criado por G. Botelho e J. R. Campos, para mostrar que p e Dp s~ao ideais de Banach e valem as rela c~oes dual p = Dp e Ddual p = p, onde p e p s~ao ndices conjugados.

L'utilisation de systèmes légers non linéaires permet de réaliser le contrôle vibratoire de structures subissant des oscillations non acceptables en termes de confort pour l'usager ou de sécurité de l'ouvrage. L'étude des puits d'énergie non linéaires, ou « Nonlinear Energy Sinks » (NES), a notamment fait l'objet de nombreuses recherches depuis le début des années 2000. Sa non-linéarité lui confère des capacités de pompage énergétique large bande, c'est-à-dire pour un large intervalle de fréquences de sollicitation, ce qui représente un avantage significatif en comparaison des absorbeurs comme l'amortisseur à masse accordée. Le but de ce manuscrit est d'étudier le couplage de chaîne d'oscillateurs non linéaires à des systèmes dynamiques linéaires soumis à des sollicitations harmoniques et d'analyser d'une part le comportement global du système, et d'autre part les potentialités de contrôle passif de telles chaînes. Une méthodologie analytique générale est présentée, puis appliquée à des exemples où des absorbeurs à non-linéarités cubiques à un, puis à N degrés de liberté sont attachés à un oscillateur linéaire. Une variation de cette méthodologie adoptant une vision continue de la chaîne est ensuite proposée. Enfin, un dispositif expérimental étudie le comportement d'un modèle réduit de bâtiment à un étage couplé à une chaîne de huit oscillateurs non linéaires. / Nonlinear light oscillators can be used for performing vibratory passive control of structures undergoing unacceptable oscillations in terms of comfort and safety. The study of Nonlinear Energy Sinks (NES) has been especially subject to an important research effort since the beginning of the 2000s. Its essential nonlinearity enables it to achieve large-band energy pumping, which is a significant advantage in comparison with classical Tuned Mass Dampers. In this manuscript, nonlinear chains of oscillators coupled to linear systems under harmonic excitation are studied. The main goal is to understand the behavior of the whole system and find evidence of passive control abilities of such chains. First of all, a general analytical methodology is presented and applied to examples where single and multi-degree-of-freedom absorbers with cubic nonlinearities are linked to a linear oscillator. A modification of this approach by considering the chain in the form of a continuous approximation is then proposed. Finally, an experimental device composed of a single storey reduced-scale building coupled to a chain of eight nonlinear oscillators is investigated.

Made available in DSpace on 2014-12-17T15:15:03Z (GMT). No. of bitstreams: 1 CarlenePSF_DISSERT.pdf: 1687677 bytes, checksum: 1148ebf1be9615049fa1952b3098a785 (MD5) Previous issue date: 2013-10-18 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The aim of this work is to derive theWard Identity for the low energy effective theory of a fermionic system in the presence of a hyperbolic Fermi surface coupled with a U(1) gauge field in 2+1 dimensions. These identities are important because they establish requirements for the theory to be gauge invariant. We will see that the identity associated Ward Identity (WI) of the model is not preserved at 1-loop order. This feature signalizes the presence of a quantum anomaly. In other words, a classical symmetry is broken dynamically by quantum fluctuations. Furthermore, we are considering that the system is close to a Quantum Phase Transitions and in vicinity of a Quantum Critical Point the fermionic excitations near the Fermi surface, decay through a Landau damping mechanism. All this ingredients need to be take explicitly to account and this leads us to calculate the vertex corrections as well as self energies effects, which in this way lead to one particle propagators which have a non-trivial frequency dependence / Nesse trabalho derivamos e checamos a Identidade de Ward (IW) para uma teoria efetiva de baixas energias de um sistema fermi?nico acoplado a um campo de gauge U(1), em 2+1 dimens?es, na presen?a de uma superf?cie de Fermi parab?lica. As identitades deWard s?o muito importantes pois, estabelecem requisitos para que a teoria efetiva seja invariante de gauge. Veremos que a IW n?o ? preservada em ordem de 1-loop. Isto caracteriza a presen?a de uma an?malia qu?ntica. Assim, uma simetria cl?ssica ? destruida dinamicamente por flutua??es qu?nticas. O nosso sistema f?sico se encontra na vizinhan?a de um Ponto Cr?tico Qu?ntico. Portanto, as excita??es fermi?nicas, que se situam pr?ximo a superf?cie de Fermi, decaem com o tempo, produzindo assim um amortecimento de Landau. Todos esses ingredientes de um regime de forte acoplamento devem ser levados em conta. E em fun??o disso calcularemos as corre??es de v?rtice e os efeitos das auto-energias, que dessa forma fazem com que os propagadores de uma part?cula da teoria dependam da frequ?ncia de uma forma n?o-trivial