1,223 research outputs found

    Absence of singular superconducting fluctuation corrections to thermal conductivity

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    We evaluate the superconducting fluctuation corrections to thermal conductivity in the normal state which diverge as T approaches T_c. We find zero total contribution for one, two and three-dimensional superconductors for arbitrary impurity concentration. The method used is diagrammatic many-body theory, and all contributions -- Aslamazov-Larkin (AL), Maki-Thompson (MT), and density-of-states (DOS) -- are considered. The AL contribution is convergent, whilst the divergences of the DOS and MT diagrams exactly cancel.Comment: 4 pages text; 2 figure

    Moduli-Space Dynamics of Noncommutative Abelian Sigma-Model Solitons

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    In the noncommutative (Moyal) plane, we relate exact U(1) sigma-model solitons to generic scalar-field solitons for an infinitely stiff potential. The static k-lump moduli space C^k/S_k features a natural K"ahler metric induced from an embedding Grassmannian. The moduli-space dynamics is blind against adding a WZW-like term to the sigma-model action and thus also applies to the integrable U(1) Ward model. For the latter's two-soliton motion we compare the exact field configurations with their supposed moduli-space approximations. Surprisingly, the two do not match, which questions the adiabatic method for noncommutative solitons.Comment: 1+15 pages, 2 figures; v2: reference added, to appear in JHE

    Spain - The right to be forgotten. The right to privacy and the initiative facing the new challenges of the information society

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    This article aims to show the current situation surrounding the right to privacy in the Spanish legal system. First of all, we look at the regulations governing the right to privacy and at the characteristics of the Spanish protection of privacy. In the second part of the paper, we consider the current regulations on personal data protection as the grounds for new ways of protecting privacy. Finally, the paper shows how two new rights have emerged from the legal discourse on privacy and, overall, from the regulation of the protection of personal data: informative self-determination and the right to be forgotten. This study focuses on the latter, due to the prominent role of Spanish judges in shaping the incipient right to be forgotten via inter-action with the European Court of Justice in 2014

    Multiplicities, fluctuations and QCD: Interplay between soft and hard physics?

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    Multiplicity fluctuations are studied both globaly (in terms of high-order moments) and locally (in terms of small phase-space intervals). The ratio of cumulant factorial to factorial moments of the charged-particle multiplicity distribution shows a quasi-oscillatory behaviour similar to that predicted by the NNLLA of perturbative QCD. However, an analysis of the sub-jet multiplicity distribution at perturbative scales shows that these oscillations cannot be related to the NNLLA prediction. We investigate how it is possible to reproduce the oscillations within the framework of Monte-Carlo models. Furthermore, local multiplicity fluctuations in angular phase-space intervals are compared with Monte-Carlo models and with first-order QCD predictions. While JETSET reproduces the experimental data very well, the predictions of the Double Leading Log Approximations and estimates obtained in Modified Leading Log Approximations deviate significantly from the data.Comment: 11 pages, 11 eps figures, Presented at the XXVII Symposium on Multiparticle Dynamics, September 8-12, 1997 Frascati-Rome, Ital

    Rheological Chaos in a Scalar Shear-Thickening Model

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    We study a simple scalar constitutive equation for a shear-thickening material at zero Reynolds number, in which the shear stress \sigma is driven at a constant shear rate \dot\gamma and relaxes by two parallel decay processes: a nonlinear decay at a nonmonotonic rate R(\sigma_1) and a linear decay at rate \lambda\sigma_2. Here \sigma_{1,2}(t) = \tau_{1,2}^{-1}\int_0^t\sigma(t')\exp[-(t-t')/\tau_{1,2}] {\rm d}t' are two retarded stresses. For suitable parameters, the steady state flow curve is monotonic but unstable; this arises when \tau_2>\tau_1 and 0>R'(\sigma)>-\lambda so that monotonicity is restored only through the strongly retarded term (which might model a slow evolution of material structure under stress). Within the unstable region we find a period-doubling sequence leading to chaos. Instability, but not chaos, persists even for the case \tau_1\to 0. A similar generic mechanism might also arise in shear thinning systems and in some banded flows.Comment: Reference added; typos corrected. To appear in PRE Rap. Com

    Exponential distribution of long heart beat intervals during atrial fibrillation and their relevance for white noise behaviour in power spectrum

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    The statistical properties of heart beat intervals of 130 long-term surface electrocardiogram recordings during atrial fibrillation (AF) are investigated. We find that the distribution of interbeat intervals exhibits a characteristic exponential tail, which is absent during sinus rhythm, as tested in a corresponding control study with 72 healthy persons. The rate of the exponential decay lies in the range 3-12 Hz and shows diurnal variations. It equals, up to statistical uncertainties, the level of the previously uncovered white noise part in the power spectrum, which is also characteristic for AF. The overall statistical features can be described by decomposing the intervals into two statistically independent times, where the first one is associated with a correlated process with 1/f noise characteristics, while the second one belongs to an uncorrelated process and is responsible for the exponential tail. It is suggested to use the rate of the exponential decay as a further parameter for a better classification of AF and for the medical diagnosis. The relevance of the findings with respect to a general understanding of AF is pointed out

    Bekalking en toevoegen van nutriënten; evaluatie van de effecten op het bosecosysteem; een veldonderzoek naar vegetatie, humus en bodemfauna

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    Dit rapport doet verslag van een deelonderzoek uit de Evaluatie van effectgerichte maatregelen in multifunctionele bossen 2004-2005 en is gericht op de effecten van de maatregelen bemesting en bekalking in bossen als overbruggingsmaatregel in het ka-der van het Overlevingsplan Bos en Natuur (OBN). In dit rapport worden de effecten besproken van de uitgevoerde maatregelen bekalking en mineralengiften (`bemesting¿) op de vegetatie, het humusprofiel en de bodemfauna in een veldonderzoek. Bemesting en bekalking leiden beide tot een significante (sterke) toename van het aantal planten-soorten en tot hogere indicatiewaarden voor vocht, zuur en stikstof. Ook is een duide-lijk toename zichtbaar van de verjonging van struiken en ¿ alleen bij bemesting - ook van loofbomen. Bekalking en bemesting hebben beide effect op de dikte van de ver-schillende humuslagen. Beide maatregelen leiden dus tot een snellere omzetting van strooisel en tot accumulatie van humus bovenin de Hr-laag. De aard van de humusla-gen is niet veranderd. De maatregelen bemesting en bekalking verschillen sterk van elkaar in het effect dat ze hebben op de bodemfauna. Bemesting laat enkele jaren na uitvoering geen aantoonbare veranderingen zien ten opzichte van de onbemeste situa-tie. Bekalking heeft enkele jaren na uitvoering van de maatregel wèl geleid tot aan-toonbare veranderingen in de bodemfauna. Het is mogelijk dat de veranderingen in de bodemfauna die na bekalking zijn opgetreden slechts tijdelijk zijn

    Spin battery operated by ferromagnetic resonance

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    Precessing ferromagnets are predicted to inject a spin current into adjacent conductors via Ohmic contacts, irrespective of a conductance mismatch with, for example, doped semiconductors. This opens the way to create a pure spin source spin battery by the ferromagnetic resonance. We estimate the spin current and spin bias for different material combinations.Comment: The estimate for the magnitude of the spin bias is improved. We find that it is feasible to get a measurable signal of the order of the microwave frequency already for moderate rf intensitie

    A probabilistic model for gene content evolution with duplication, loss, and horizontal transfer

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    We introduce a Markov model for the evolution of a gene family along a phylogeny. The model includes parameters for the rates of horizontal gene transfer, gene duplication, and gene loss, in addition to branch lengths in the phylogeny. The likelihood for the changes in the size of a gene family across different organisms can be calculated in O(N+hM^2) time and O(N+M^2) space, where N is the number of organisms, hh is the height of the phylogeny, and M is the sum of family sizes. We apply the model to the evolution of gene content in Preoteobacteria using the gene families in the COG (Clusters of Orthologous Groups) database
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