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O ajudante de acção directa na medida de rendimento social de inserção: um estudo de caso

Ribeiro, Ana Cláudia Dias
Fonte: Instituto Superior de Ciências Sociais e Políticas Publicador: Instituto Superior de Ciências Sociais e Políticas
Tipo: Dissertação de Mestrado
Publicado em 26/03/2010 Português
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Dissertação de Mestrado em Política Social; A prevenção de situações de pobreza e exclusão bem como a promoção da autonomia e integração pessoal, social e comunitária constituem o objectivo primordial da Medida de Política Social de Rendimento Social de Inserção. Este trabalho avalia o papel do Ajudante de Acção Directa na execução da Medida acima referida nos protocolos de acompanhamento de indivíduos e famílias estabelecidos entre o Instituto da Segurança Social e Instituições do Distrito de Setúbal, ao nível do seu desempenho profissional, enquanto interventor social integrado em equipas multidisciplinares, na relação com o Gestor de Caso e na relação com o sistema cliente. Para a sua concretização, recolhemos dados por via da observação e da aplicação de inquéritos por questionário aplicados a 73 Ajudantes de Acção Directa e 43 Gestores de Caso, e por entrevista realizada a 34 Ajudantes de Acção Directa. Foi possível identificar o grau de adequabilidade entre o descritivo funcional e a prática verificada, bem como elencar as potencialidades, constrangimentos e formas de superação dos mesmos referentes ao Ajudante de Acção Directa na execução da Medida RSI. Percebemos que este interventor social representa uma figura de proximidade determinante na prossecução dos objectivos e metodologias de intervenção definidas para esta Medida; The prevention of poverty situations...

A Century of Gestalt Psychology in Visual Perception I. Perceptual Grouping and Figure-Ground Organization

Wagemans, Johan; Elder, James H.; Kubovy, Michael; Palmer, Stephen E.; Peterson, Mary A.; Singh, Manish; von der Heydt, Rüdiger
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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In 1912, Max Wertheimer published his paper on phi motion, widely recognized as the start of Gestalt psychology. Because of its continued relevance in modern psychology, this centennial anniversary is an excellent opportunity to take stock of what Gestalt psychology has offered and how it has changed since its inception. We first introduce the key findings and ideas in the Berlin school of Gestalt psychology, and then briefly sketch its development, rise, and fall. Next, we discuss its empirical and conceptual problems, and indicate how they are addressed in contemporary research on perceptual grouping and figure-ground organization. In particular, we review the principles of grouping, both classical (e.g., proximity, similarity, common fate, good continuation, closure, symmetry, parallelism) and new (e.g., synchrony, common region, element and uniform connectedness), and their role in contour integration and completion. We then review classic and new image-based principles of figure-ground organization, how it is influenced by past experience and attention, and how it relates to shape and depth perception. After an integrated review of the neural mechanisms involved in contour grouping, border-ownership, and figure-ground perception...

Comment on "Anomalous proximity effect in underdoped YBa_2Cu_3O_{6+x} Josephson junctions"

Quintanilla, J.; Capelle, K.; Oliveira, L. N.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/01/2003 Português
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In recent photodoping experiments Decca et al. [PRL 85, 3708 (2000)] have observed an unusually long-ranged proximity effect between the superconducting and insulating phases of YBCO. Here we critically examine the claim in that reference that such long range is anomalous. We show that, once the novel nature of the experiments has been properly accounted for, the conventional theory of the proximity effect predicts comparably long ranges.; Comment: RevTeX4, 1 page, 1 figure. Accepted by Phys. Rev. Lett

Coulomb Blockade of Proximity Effect at Large Conductance

Ostrovsky, P. M.; Skvortsov, M. A.; Feigel'man, M. V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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We consider the proximity effect in a normal dot coupled to a bulk superconducting reservoir by the tunnel contact with large normal conductance. Coulomb interaction in the dot suppresses the proximity minigap induced in the normal part of the system. We find exact expressions for the thermodynamic and tunneling minigaps as functions of the junction's capacitance. The tunneling minigap interpolates between its proximity-induced value in the regime of weak Coulomb interaction to the Coulomb gap in the regime of strong interaction. In the intermediate case a non-universal two-step structure of the tunneling density of states is predicted. The charge quantization in the dot is also studied.; Comment: 4 pages (RevTeX), 3 figures. Version 2: minor corrections, a figure and two references added

Lateral Casimir Force between Two Sinusoidally Corrugated Eccentric Cylinders Using Proximity Force Approximation

Setare, M. R.; Seyedzahedi, A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/02/2014 Português
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This paper is devoted to the presentation of the lateral Casimir force between two sinusoidally corrugated eccentric cylinders. Despite that applying scattering matrix method explains the problem exactly, procedure of applying this method is somehow complicated specially at nonzero temperature. Using the proximity force approximation (PFA) helps to achieve the lateral Casimir force in a truly explicit manner. We assume the cylinders to be slightly eccentric with similar radiuses and separations much smaller than corrugations' wave length for the validity of PFA. For such short distances the effect of finite conductivity would be non negligible. In addition to the effect of finite conductivity, we investigate thermal corrections of the lateral Casimir force to reduce the inaccuracy of the result obtained by PFA. Assuming the Casimir force density between two parallel plates, the normal Casimir force between two cylinders is obtained. With the aid of additive summation of the Casimir energy between cylinders without corrugation, we obtain the lateral Casimir force between corrugated cylinders.; Comment: 12 pages, 1 figure

Theory of the proximity effect in junctions with unconventional superconductors

Tanaka, Y.; Golubov, A. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We present a general theory of the proximity effect in junctions between diffusive normal metals (DN) and unconventional superconductors in the framework of the quasiclassical Green's function formalism. Various possible symmetry classes in a superconductor are considered which are consistent with the Pauli principle: even-frequency spin-singlet even-parity (ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity (OSO) state. For each of the above four cases symmetry and spectral properties of the induced pair amplitude in the DN are determined. It is shown that the pair amplitude in a DN belongs respectively to an ESE, OTE, OTE and ESE pairing state.; Comment: 5 pages with one figure

Interband proximity effect and nodes of superconducting gap in Sr2RuO4

Zhitomirsky, M. E.; Rice, T. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/02/2001 Português
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The power-law temperature dependences of the specific heat, the nuclear relaxation rate, and the thermal conductivity suggest the presence of line nodes in the superconducting gap of Sr2RuO4. These recent experimental observations contradict the scenario of a nodeless (k_x+ik_y)-type superconducting order parameter. We propose that interaction of superconducting order parameters on different sheets of the Fermi surface is a key to understanding the above discrepancy. A full gap exists in the active band, which drives the superconducting instability, while line nodes develop in passive bands by interband proximity effect.; Comment: 4 pages, 1 figure

Application of the proximity force approximation to gravitational and Yukawa-type forces

Decca, R. S.; Fischbach, E.; Klimchitskaya, G. L.; Krause, D. E.; López, D.; Mostepanenko, V. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/03/2009 Português
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We apply the proximity force approximation, which is widely used for the calculation of the Casimir force between bodies with nonplanar boundary surfaces, to gravitational and Yukawa-type interactions. It is shown that for the gravitational force in a sphere-plate configuration the general formulation of the proximity force approximation is well applicable. For a Yukawa-type interaction we demonstrate the validity of both the general formulation of the proximity force approximation, and a simple mapping between the sphere-plate and plate-plate configurations. The claims to the contrary in some recent literature are thus incorrect. Our results justify the constraints on the parameters of non-Newtonian gravity previously obtained from the indirect dynamic measurements of the Casimir pressure.; Comment: 13 pages, 1 figure

Casimir forces beyond the proximity approximation

Bimonte, G.; Emig, T.; Jaffe, R. L.; Kardar, M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/10/2011 Português
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The proximity force approximation (PFA) relates the interaction between closely spaced, smoothly curved objects to the force between parallel plates. Precision experiments on Casimir forces necessitate, and spur research on, corrections to the PFA. We use a derivative expansion for gently curved surfaces to derive the leading curvature modifications to the PFA. Our methods apply to any homogeneous and isotropic materials; here we present results for Dirichlet and Neumann boundary conditions and for perfect conductors. A Pad\'e extrapolation constrained by a multipole expansion at large distance and our improved expansion at short distances, provides an accurate expression for the sphere-plate Casimir force at all separations.; Comment: 4 pages, 1 figure

Proximity fingerprint of s+- superconductivity

Koshelev, A. E.; Stanev, V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We suggest a straightforward and unambiguous test to identify possible opposite signs of superconducting order parameter in different bands proposed for iron-based superconductors (s+- state). We consider proximity effect in a weakly coupled sandwich composed of a s+- superconductor and thin layer of s-wave superconductor. In such system the s-wave order parameter is coupled differently with different s+- gaps and it typically aligns with one of these gaps. This forces the other s+- gap to be anti-aligned with the s-wave gap. In such situation the aligned band induces a peak in the s-wave density of states (DoS), while the anti-aligned band induces a dip. Observation of such contact-induced negative feature in the s-wave DoS would provide a definite proof for s+- superconductivity.; Comment: 4 pages, one figure

Driven superconducting proximity effect in interacting quantum dots

Moghaddam, Ali G.; Governale, Michele; König, Jürgen
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We present a theory of non-equilibrium superconducting proximity effect in an interacting quantum dot induced by a time-dependent tunnel coupling between dot and a superconducting lead. The proximity effect, that is established when the driving frequency fulfills a gate-voltage-dependent resonance condition, can be probed through the tunneling current into a weakly-coupled normal lead. Furthermore, we propose to generate and manipulate coherent superpositions of quantum-dot states with electron numbers differing by two, by applying pulsed oscillatory variations to the couplings between dot and superconductors.; Comment: 6 pages, 5 figures, paper substantially extended: new section, new figure, new references introduced

Strongly far proximity and hyperspace topology

Peters, J. F.; Guadagni, C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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This article introduces strongly far proximity, which is associated with Lodato proximity $\delta$. A main result in this paper is the introduction of a hit-and-miss topology on $\mbox{CL}(X)$, the hyperspace of nonempty closed subsets of $X$, based on the strongly far proximity.; Comment: 6 pages, 1 figure

Proximity Effect in Gold Coated $YBa_2Ca_3O_{7-\delta}$ Films Studied by Scanning Tunneling Spectroscopy

Sharoni, Amos; Asulin, Itay; Koren, Gad; Millo, Oded
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/07/2003 Português
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Scanning tunneling spectroscopy on gold layers over-coating \textit{c}-axis $YBa_2Ca_3O_{7-\delta}$ (YBCO) films reveals proximity induced gap structures. The gap size reduced exponentially with distance from \textit{a}-axis facets, indicating that the proximity effect is primarily due to the (100) YBCO facets. The penetration depth of superconductivity into the gold is $\sim 30$ nm, in good agreement with estimations for the dirty limit. The extrapolated gap at the interface is $\sim 15$ meV, consistent with recent point-contact experiments. The proximity-induced order parameter appears to have predominant \textit{s}-wave symmetry.; Comment: 4 revtex pages, 3 figure

Singlet-triplet conversion and the long-range proximity effect in superconductor-ferromagnet structures with generic spin dependent fields

Bergeret, F. S.; Tokatly, I.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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The long-range proximity effect in superconductor/ferromagnet (S/F) hybrid nano-structures is observed if singlet Cooper pairs from the superconductor are converted into triplet pairs which can diffuse into the fer- romagnet over large distances. It is commonly believed that this happens only in the presence of magnetic inhomogeneities. We show that there are other sources of the long-range triplet component (LRTC) of the con- densate and establish general conditions for their occurrence. As a prototypical example we consider first a system where the exchange field and spin-orbit coupling can be treated as time and space components of an effective SU(2) potential. We derive a SU(2) covariant diffusive equation for the condensate and demonstrate that an effective SU(2) electric field is responsible for the long-range proximity effect. Finally, we extend our analysis to a generic ferromagnet and establish a universal condition for the LRTC. Our results open a new avenue in the search for such correlations in S/F structures and make a hitherto unknown connection between the LRTC and Yang-Mills electrostatics.; Comment: 5 pages; 1 Figure; updated file with new references

Dual proximity effect near superconductor-insulator transition

Kwon, Hyok-Jon
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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We show that quantum vortex-loop proliferation may be one possible explanation of the super-long-range proximity effect observed in an insulating underdoped cuprate, using the dual theory of quantum vortices. As a test of this scenario, we propose that a dual proximity effect experiment can confirm the superfluid motion of the quantum vortices in the vortex-proliferated insulator and can measure the divergent correlation lengths near the superconductor-insulator transition.; Comment: 4 pages, 1 eps figure; revised presentation

Calculation of cluster decays half-lives for nuclei between 56 < Zp < 120 by using temperature dependent proximity model

Zanganeh, Vahid
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/08/2014 Português
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Cluster decays half-lives of elements with proton numbers between 56 < Zp < 120 are calculated by applying temperature dependent proximity potential approach. for showing the influence of temperature on cluster decays, we compared the results among temperature dependent and inde-pendent case with experimental values. The obtained results of the present investigation reveal that we have more accurate results for temperature dependent proximity potential in comparison to ignoring one. In the present work, we find that results provided with temperature dependent prox-imity model are reasonable estimates for cluster decays half-lives and provide reliable predictions for other super heavies cluster decays.; Comment: 15 pages, 1 figure

Thermal screening at finite chemical potential on a topological surface and its interplay with proximity-induced ferromagnetism

Nogueira, Flavio S.; Eremin, Ilya
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Motivated by recent experiments on EuS/Bi$_2$Se$_3$ heterostructures, we study the temperature dependent screening effects on the surface of a three-dimensional topological insulator proximate to a ferromagnetically ordered system. In general, we find that besides the chemical potential and temperature, the screening energy scale also depends on the proximity-induced electronic gap in an essential way. In particular, at zero temperature the screening energy vanishes if the chemical potential is smaller than the proximity-induced electronic gap. We show that at finite temperature, $T$, and/or chemical potential, $\mu$, the Chern-Simons (topological) mass, which is generated by quantum fluctuations arising from the proximity-effect, can be calculated analytically in the insulating regime. In this case the topological mass yields the Hall conductivity associated to edge states. We show that when the chemical potential is inside the gap the topological mass remains nearly quantized at finite temperature.; Comment: 5 pages, 1 figure; v3: extended version; improved discussion of the Hall conductivity at finite temperature

Proximity effects in the superconductor / heavy fermion bilayer system Nb / CeCu_6

Otop, A.; Hendrikx, R. W. A.; Hesselberth, M. B. S.; Ciuhu, C.; Lodder, A.; Aarts, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/03/2003 Português
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We have investigated the proximity effect between a superconductor (Nb) and a 'Heavy Fermion' system (CeCu_6) by measuring critical temperatures $T_c$ and parallel critical fields H_{c2}^{\parallel}(T) of Nb films with varying thickness deposited on 75 nm thick films of CeCu_6, and comparing the results with the behavior of similar films deposited on the normal metal Cu. For Nb on CeCu_6 we find a strong decrease of T_c with decreasing Nb thickness and a finite critical thickness of the order of 10 nm. Also, dimensional crossovers in H_{c2}^{\parallel}(T) are completely absent, in strong contrast with Nb/Cu. Analysis of the data by a proximity effect model based on the Takahashi-Tachiki theory shows that the data can be explained by taking into account both the high effective mass (or low electronic diffusion constant), {\it and} the large density of states at the Fermi energy which characterize the Heavy Fermion metal.; Comment: 7 pages, 2 figure. Manuscript has been submitted to a refereed journal

Andreev Reflection and Proximity effect

Pannetier, B.; Courtois, H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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The Andreev Reflection is the key mechanism for the superconducting proximity effect. It provides phase correlations in a system of non-interacting electrons at mesoscopic scales, i.e. over distances much larger than the microscopic lengths : Fermi wavelength and elastic electron mean free path. This field of research has attracted an increasing interest in the recent years in part because of the tremendous development of nanofabrication technologies, and also because of the richness of the involved quantum effects. In this paper we review some recently achieved advances. We also discuss new open questions, in particular non-equilibrium effects and proximity effect in systems with ferromagnetic elements.; Comment: 17 pages, no figure, to appear in J. of Low Temp. Phys., proceeding of the LT satellite conference "Electron Transport in Mesoscopic Systems", reference list corrected

Spin-dependent Proximity Effects in d-wave Superconductor/Half-metal Heterostructures

Yoshida, Nobukatsu; Fogelstrom, Mikael
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/11/2005 Português
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We report on mutual proximity effects in d-wave superconductor/half-metal heterostructures which correspond to systems composed of high-Tc cuprates and manganite materials. In our study, proximity effects are induced by the interplay of two separate interface effects: spin-mixing (or rotation) surface scattering and spin-flip scattering. The surface spin-mixing scattering introduces spin-triplet pairing correlations in superconducting side; as a result, Andreev bound states are formed at energies within the superconducting gap. The spin-flip scattering introduces not only long range equal-spin pairing amplitudes in the half-metal, but also an exotic magnetic proximity effect extending into the superconductor.; Comment: 2 pages, 1 figure, submitted to 24th International Conference on Low Temperature Physics