920 resultados para FOCK REPRESENTATIONS


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In Seychelles, cardiovascular diseases (CVD), notably stroke, ischemic heart disease and hypertensive heart disease has become the largest contributor of deaths (40%) in the entire population. CVD also results in a large burden of disability and also has subsequent social and economic impact. The Unit for Prevention and Control of Cardiovascular Diseases (UPCCD) provides leadership, expertise and capacity at national level for the surveillance, prevention and control of cardiovascular diseases through education, programs and input into policy.

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The tonotopic representations within the primary auditory cortex (PAC) have been successfully mapped with ultra-high field fMRI. Here, we compared the reliability of this tonotopic mapping paradigm at 7 T with 1.5 mm spatial resolution with maps acquired at 3 T with the same stimulation paradigm, but with spatial resolutions of 1.8 and 2.4 mm. For all subjects, the mirror-symmetric gradients within PAC were highly similar at 7 T and 3 T and across renderings at different spatial resolutions; albeit with lower percent signal changes at 3 T. In contrast, the frequency maps outside PAC tended to suffer from a reduced BOLD contrast-to-noise ratio at 3 T for a 1.8 mm voxel size, while robust at 2.4 mm and at 1.5 mm at 7 T. Overall, our results showed the robustness of the phase-encoding paradigm used here to map tonotopic representations across scanners.

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The CaMir is a questionnaire aimed at measuring attachment cognitions. It is based on subjects' evaluations of past and present attachment experiences and family functioning. It is a widely used tool both in research and in clinical settings. The aim of this study was to develop a short version of CaMir in Spanish (CaMir-R) and to obtain evidence about its validity and reliability in a sample of 676 adolescents (364 female and 312 male) belonging to different groups (clinical, maltreated, and community samples) with an age range between 13 and 19 years (M = 15.62, SD = 1.49). We examined its internal structure, convergent, and decision validity, the relationship between its dimensions and psychopathological symptoms, as well as its internal consistency and temporal stability. The CaMir-R included 7 factors whose internal consistency indexes ranged between 0.60 and 0.85. With the exception of the «Parental Permissiveness» dimension, which did not show good reliability, the results suggest that the CaMir-R provides a valid and reliable assessment of attachment representations and of the conception of family functioning.

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Different spatial representations are not stored as a single multipurpose map in the brain. Right brain-damaged patients can show a distortion, a compression of peripersonal and extrapersonal space. Here we report the case of a patient with a right insulo-thalamic disconnection without spatial neglect. The patient, compared with 10 healthy control subjects, showed a constant and reliable increase of her peripersonal and extrapersonal egocentric space representations - that we named spatial hyperschematia - yet left her allocentric space representations intact. This striking dissociation shows that our interactions with the surrounding world are represented and processed modularly in the human brain, depending on their frame of reference.

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In the framework of social representation, this research explores how the concept of cleanness does not refer solely to individual hygienic praxes and thoughts, but it is also linked to social and cultural aspects. In this way, the definitions of what is dirty and what is clean, what is pure and what is impure, are linked to social discrimination attitudes, based for example on the fear for contamination. Our general hypothesis is that the representations of dirt/cleanness and purity/impurity define ideas and praxes linked to personal hygiene, but refer also to the way people interact with the world and the others. Hence, we hypothesize that the representations of dirt/cleanness and purity/impurity are linked to values and political and religious orientations. A questionnaire with closed-answer questions and a free association task were distributed to 450 subjects. Results show how, in effects, the concepts of dirt/cleanness, purity/ impurity skip from their daily praxis connotations and assume a symbolic function for discriminating between individuals and social groups.

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VEsquisse (1895) ainsi que le chapitre VII de L'interprétation du rêve (1900) de Freud offrent un modèle psychologique - sous-jacent à toute la psychanalyse élaborée par la suite - qui présente des analogies frap¬pantes avec les conceptions aristotéliciennes sur la psyché, principalement développées dans le De l'âme et les Petits traités d'histoire naturelle. Ceci peut se comprendre entre autres par le fait que les seuls cours uni¬versitaires de psychologie et de philosophie que Freud fréquenta, parallèlement à ses études de médecine, furent ceux du théologien, psychologue et philosophe Franz Brentano, grand spécialiste d'Aristote, dont l'impact de l'enseignement sur le jeune Freud est aujourd'hui mieux connu grâce à son échange épistolaire, au début de ses études, avec son ancien ami de gymnase Eduard Silberstein. En effet, plus d'un élément du paradigme psychologique aristotélicien, qui chez cet auteur s'ancre dans la biologie, semblent trouver écho chez Freud : ainsi, la génération de diverses sortes de représentation au sein de l'appareil psychique par l'investissement des traces mnésiques, chez Freud, fait penser à la production ât phantâsmata dans l'âme, par le travail de la phantasîa sur les mouvements résiduels de la perception sensorielle, chez Aristote. De là, ce sont autant le fonctionnement mnésique, que l'explication des phénomènes du rêve et de l'hallucination, que la compréhension du désir dans sa capacité de mettre en mouvement le vivant animé (c'est-à-dire un être doté d'une âme) qui vont représenter les points d'articulation de cette comparaison. -- The Project for a Scientific Psychology (1895) as well as Chapter VII of Freud's Interpretation of Dreams (1900) offer a psychological model - underlying the entire psychoanalysis developed hereafter - which is strikingly similar to Aristotelian conceptions of the psyche in On the Soul and Little Physical Treatises. One explanation may be that the only lectures in psychology and philosophy that Freud attended at university, alongside lectures in medicine, were given by the theologist, psychologist, and philosopher Franz Brentano, who had a deep knowledge of Aristotle. Because of young Freud's correspondence with his high school friend Eduard Silberstein at the beginning of his studies, the influence of Brentano's teachings on Freud is now better known. Indeed, much of the Aristotelian psychological paradigm - rooted in biology - seems to echo in Freud's writings. Thus, the production of various sorts of representations within the psychic apparatus by means of the investment in memory traces in Freud's model evokes the phantâsmata generated in the soul by the action of phantasîa on the residual movements of the sensory perception in Aristotle's psychology. From there, this comparison will hinge as much on the operation of memory as on the explanation of the phenomena of dreams and hallucinations, as on the understanding of desire in its ability to set the animated living being (i.e. a being with a soul) in motion.

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Deduction allows us to draw consequences from previous knowledge. Deductive reasoning can be applied to several types of problem, for example, conditional, syllogistic, and relational. It has been assumed that the same cognitive operations underlie solutions to them all; however, this hypothesis remains to be tested empirically. We used event-related fMRI, in the same group of subjects, to compare reasoning-related activity associated with conditional and syllogistic deductive problems. Furthermore, we assessed reasoning-related activity for the two main stages of deduction, namely encoding of premises and their integration. Encoding syllogistic premises for reasoning was associated with activation of BA 44/45 more than encoding them for literal recall. During integration, left fronto-lateral cortex (BA 44/45, 6) and basal ganglia activated with both conditional and syllogistic reasoning. Besides that, integration of syllogistic problems additionally was associated with activation of left parietal (BA 7) and left ventro-lateral frontal cortex (BA 47). This difference suggests a dissociation between conditional and syllogistic reasoning at the integration stage. Our finding indicates that the integration of conditional and syllogistic reasoning is carried out by means of different, but partly overlapping, sets of anatomical regions and by inference, cognitive processes. The involvement of BA 44/45 during both encoding (syllogisms) and premise integration (syllogisms and conditionals) suggests a central role in deductive reasoning for syntactic manipulations and formal/linguistic representations.

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A select-divide-and-conquer variational method to approximate configuration interaction (CI) is presented. Given an orthonormal set made up of occupied orbitals (Hartree-Fock or similar) and suitable correlation orbitals (natural or localized orbitals), a large N-electron target space S is split into subspaces S0,S1,S2,...,SR. S0, of dimension d0, contains all configurations K with attributes (energy contributions, etc.) above thresholds T0={T0egy, T0etc.}; the CI coefficients in S0 remain always free to vary. S1 accommodates KS with attributes above T1≤T0. An eigenproblem of dimension d0+d1 for S0+S 1 is solved first, after which the last d1 rows and columns are contracted into a single row and column, thus freezing the last d1 CI coefficients hereinafter. The process is repeated with successive Sj(j≥2) chosen so that corresponding CI matrices fit random access memory (RAM). Davidson's eigensolver is used R times. The final energy eigenvalue (lowest or excited one) is always above the corresponding exact eigenvalue in S. Threshold values {Tj;j=0, 1, 2,...,R} regulate accuracy; for large-dimensional S, high accuracy requires S 0+S1 to be solved outside RAM. From there on, however, usually a few Davidson iterations in RAM are needed for each step, so that Hamiltonian matrix-element evaluation becomes rate determining. One μhartree accuracy is achieved for an eigenproblem of order 24 × 106, involving 1.2 × 1012 nonzero matrix elements, and 8.4×109 Slater determinants

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Restricted Hartree-Fock 6-31G calculations of electrical and mechanical anharmonicity contributions to the longitudinal vibrational second hyperpolarizability have been carried out for eight homologous series of conjugated oligomers - polyacetylene, polyyne, polydiacetylene, polybutatriene, polycumulene, polysilane, polymethineimine, and polypyrrole. To draw conclusions about the limiting infinite polymer behavior, chains containing up to 12 heavy atoms along the conjugated backbone were considered. In general, the vibrational hyperpolarizabilities are substantial in comparison with their static electronic counterparts for the dc-Kerr and degenerate four-wave mixing processes (as well as for static fields) but not for electric field-induced second harmonic generation or third harmonic generation. Anharmonicity terms due to nuclear relaxation are important for the dc-Kerr effect (and for the static hyperpolarizability) in the σ-conjugated polymer, polysilane, as well as the nonplanar π systems polymethineimine and polypyrrole. Restricting polypyrrole to be planar, as it is in the crystal phase, causes these anharmonic terms to become negligible. When the same restriction is applied to polymethineimine the effect is reduced but remains quantitatively significant due to the first-order contribution. We conclude that anharmonicity associated with nuclear relaxation can be ignored, for semiquantitative purposes, in planar π-conjugated polymers. The role of zero-point vibrational averaging remains to be evaluated

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The contributions of the correlated and uncorrelated components of the electron-pair density to atomic and molecular intracule I(r) and extracule E(R) densities and its Laplacian functions ∇2I(r) and ∇2E(R) are analyzed at the Hartree-Fock (HF) and configuration interaction (CI) levels of theory. The topologies of the uncorrelated components of these functions can be rationalized in terms of the corresponding one-electron densities. In contrast, by analyzing the correlated components of I(r) and E(R), namely, IC(r) and EC(R), the effect of electron Fermi and Coulomb correlation can be assessed at the HF and CI levels of theory. Moreover, the contribution of Coulomb correlation can be isolated by means of difference maps between IC(r) and EC(R) distributions calculated at the two levels of theory. As application examples, the He, Ne, and Ar atomic series, the C2-2, N2, O2+2 molecular series, and the C2H4 molecule have been investigated. For these atoms and molecules, it is found that Fermi correlation accounts for the main characteristics of IC(r) and EC(R), with Coulomb correlation increasing slightly the locality of these functions at the CI level of theory. Furthermore, IC(r), EC(R), and the associated Laplacian functions, reveal the short-ranged nature and high isotropy of Fermi and Coulomb correlation in atoms and molecules

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A topological analysis of intracule and extracule densities and their Laplacians computed within the Hartree-Fock approximation is presented. The analysis of the density distributions reveals that among all possible electron-electron interactions in atoms and between atoms in molecules only very few are located rigorously as local maxima. In contrast, they are clearly identified as local minima in the topology of Laplacian maps. The conceptually different interpretation of intracule and extracule maps is also discussed in detail. An application example to the C2H2, C2H4, and C2H6 series of molecules is presented

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An analytical set of field-induced coordinates is defined and is used to show that the vibrational degrees of freedom required to completely describe nuclear relaxation polarizabilities and hyperpolarizabilities is reduced from 3N-6 to a relatively small number. As this number does not depend upon the size of the molecule, the process provides computational advantages. A method is provided to separate anharmonic contributions from harmonic contributions as well as effective mechanical from electrical anharmonicity. The procedures are illustrated by Hartree-Fock calculations, indicating that anharmonicity can be very important

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Electrical property derivative expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any molecule) makes an important contribution to the static second vibrational hyperpolarizability of CF4 and SF6. A comparison between calculated and experimental values for the difference between the (anisotropic) Kerr effect and electric field induced second-harmonic generation shows that, at the Hartree-Fock level, the nuclear relaxation/infinite frequency approximation gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small

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A comparision of the local effects of the basis set superposition error (BSSE) on the electron densities and energy components of three representative H-bonded complexes was carried out. The electron densities were obtained with Hartee-Fock and density functional theory versions of the chemical Hamiltonian approach (CHA) methodology. It was shown that the effects of the BSSE were common for all complexes studied. The electron density difference maps and the chemical energy component analysis (CECA) analysis confirmed that the local effects of the BSSE were different when diffuse functions were present in the calculations

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Geometries, vibrational frequencies, and interaction energies of the CNH⋯O3 and HCCH⋯O3 complexes are calculated in a counterpoise-corrected (CP-corrected) potential-energy surface (PES) that corrects for the basis set superposition error (BSSE). Ab initio calculations are performed at the Hartree-Fock (HF) and second-order Møller-Plesset (MP2) levels, using the 6-31G(d,p) and D95++(d,p) basis sets. Interaction energies are presented including corrections for zero-point vibrational energy (ZPVE) and thermal correction to enthalpy at 298 K. The CP-corrected and conventional PES are compared; the unconnected PES obtained using the larger basis set including diffuse functions exhibits a double well shape, whereas use of the 6-31G(d,p) basis set leads to a flat single-well profile. The CP-corrected PES has always a multiple-well shape. In particular, it is shown that the CP-corrected PES using the smaller basis set is qualitatively analogous to that obtained with the larger basis sets, so the CP method becomes useful to correctly describe large systems, where the use of small basis sets may be necessary