Dynamical Mean-Field Theory and Its Applications to Real Materials

Dynamical mean-field theory (DMFT) is a non-perturbative technique for the investigation of correlated electron systems. Its combination with the local density approximation (LDA) has recently led to a material-specific computational scheme for the ab initio investigation of correlated electron materials. The set-up of this approach and its application to materials such as (Sr,Ca)VO_3, V_2O_3, and Cerium is discussed. The calculated spectra are compared with the spectroscopically measured electronic excitation spectra. The surprising similarity between the spectra of the single-impurity Anderson model and of correlated bulk materials is also addressed.Comment: 20 pages, 9 figures, invited paper for the JPSJ Special Issue "Kondo Effect - 40 Years after the Discovery"; final version, references adde

The Kondo Resonance in Electron Spectroscopy

The Kondo resonance is the spectral manifestation of the Kondo properties of the impurity Anderson model, and also plays a central role in the dynamical mean-field theory (DMFT) for correlated electron lattice systems. This article presents an overview of electron spectroscopy studies of the resonance for the 4f electrons of cerium compounds, and for the 3d electrons of V_2O_3, including beginning efforts at using angle resolved photoemission to determine the k-dependence of the resonance. The overview includes the comparison and analysis of spectroscopy data with theoretical spectra as calculated for the impurity model and as obtained by DMFT, and the Kondo volume collapse calculation of the cerium alpha-gamma phase transition boundary, with its spectroscopic underpinnings.Comment: 32 pages, 11 figures, 151 references; paper for special issue of J. Phys. Soc. Jpn. on "Kondo Effect--40 Years after the Discovery

On the relationship between individual and population health

The relationship between individual and population health is partially built on the broad dichotomization of medicine into clinical medicine and public health. Potential drawbacks of current views include seeing both individual and population health as absolute and independent concepts. I will argue that the relationship between individual and population health is largely relative and dynamic. Their interrelated dynamism derives from a causally defined life course perspective on health determination starting from an individual’s conception through growth, development and participation in the collective till death, all seen within the context of an adaptive society. Indeed, it will become clear that neither individual nor population health is identifiable or even definable without informative contextualization within the other. For instance, a person’s health cannot be seen in isolation but must be placed in the rich contextual web such as the socioeconomic circumstances and other health determinants of where they were conceived, born, bred, and how they shaped and were shaped by their environment and communities, especially given the prevailing population health exposures over their lifetime. We cannot discuss the “what” and “how much” of individual and population health until we know the cumulative trajectories of both, using appropriate causal language

Molecular medicine and concepts of disease: the ethical value of a conceptual analysis of emerging biomedical technologies

Although it is now generally acknowledged that new biomedical technologies often produce new definitions and sometimes even new concepts of disease, this observation is rarely used in research that anticipates potential ethical issues in emerging technologies. This article argues that it is useful to start with an analysis of implied concepts of disease when anticipating ethical issues of biomedical technologies. It shows, moreover, that it is possible to do so at an early stage, i.e. when a technology is only just emerging. The specific case analysed here is that of ‘molecular medicine’. This group of emerging technologies combines a ‘cascade model’ of disease processes with a ‘personal pattern’ model of bodily functioning. Whereas the ethical implications of the first are partly familiar from earlier—albeit controversial—forms of preventive and predictive medicine, those of the second are quite novel and potentially far-reaching

RELATIONSHIP BETWEEN HISTOPATHOLOGICAL LESIONS AND MAGNETIC RESONANCE IMAGING (MRI) IN DISEASES OF THE FOOT OF THE HORSE

Le nombre croissant d’études histopathologiques portant sur les tissus du pied a permis d’expliquer et de valider les variations des signaux obtenus par l’imagerie de résonance magnétique (IRM) dans la pratique équine clinique. En particulier, l’IRM a permis d’élucider les différents grades des anomalies histologiques et peut-être aussi les différentes étapes de la progression de la dégénérescence du tendon fléchisseur profond et de l’os naviculaire. Cependant, des travaux supplémentaires sont nécessaires pour continuer d’améliorer nos connaissances sur les différentes causes de boiterie du pied et leur pathogénie.Le nombre croissant d'études histopathologiques portant sur les tissus du pied a permis d'expliquer et de valider les variations des signaux obtenus par l'imagerie de résonance magnétique (IRM) dans la pratique équine clinique. En particulier, l'IRM a permis d'élucider les différents grades des anomalies histologiques et peut-être aussi les différentes étapes de la progression de la dégénérescence du tendon fléchisseur profond et de l'os naviculaire. Cependant, des travaux supplémentaires sont nécessaires pour continuer d'améliorer nos connaissances sur les différentes causes de boiterie du pied et leur pathogénie

Lightness Constancy: Shades are compensated in perception, scattering light not

Luminance of three-dimensional achromatic objects under given illumination depends on remittance of the material, shading and scattering light (mutual illumination of opposed surfaces). We studied perception of lightness of six flat surfaces, three exposed to direct illumination, three in the shade in opposite position, thus allowing mutual illumination of neighboring pairs. Six achromatic cardboards forming a logarithmic scale of remittance (step factor = 1.2) were used. Direct illumination increased the luminance of the cardboards by a factor of two with respect to those in the shade. The luminance sequence of the cardboards varied with their positions in light and shade. Altogether there are 720 permutations of the sequence of the six cardboards. For any of the 720 permutations selected for the experiments, the subjects tried to report the lightness sequence correctly in spite of the different luminance sequences. The difference between the empirical lightness sequence reported by the subjects and the physically measured sequence according to remittance was taken as the measure of lightness constancy. We used Kendall´s rank correlation coefficient τ, which is τR=1 if the two above sequences are identical. We also calculated τL from the empirical and the luminance sequences. If the subjects were unable to perceive the lightness, they would report the luminance sequence with τL=1 and τRτL (with exception of control experiments in which the sequence according to lightness and luminance happened to be the same physically, yielding τR=τL=1 correctly). Thus, lightness constancy of three-dimensional objects under asymmetric illumination as reported since more than 100 years (summary e.g. in A. L. Gilchrist: Lightness, Brightness, and Transparency, 1994) has been confirmed quantitatively with our novel method. In addition, a quantitative result concerning mutual illumination can be derived from our data. Mutual illumination of cardboards can change the luminance sequence as a consequence of neighborhood. From a light cardboard under direct illumination more light is scattered to and reflected by its dark neighbor in the shaded position, than from the same cardboards in exchanged position. We calculated the degree of lightness constancy separately for those cases, in which the luminance sequence was not changed by mutual illumination, and those were the difference with the lightness sequence was increased and decreased. Separate calculations of these groups revealed that the effect of local scattering light makes it more difficult to detect the correct lightness. Mutual illuminations increasing the difficulty resulted in less constancy (τR smaller), whereas mutual illumination resulting in greater similarity of the lightness and luminance sequences (thus reducing the difficulty) yielded better constancy (τR greater). The effect of light scattered locally at three-dimensional objects is not taken into account in the process leading to lightness constancy of perception