668 resultados para Bethe ansatz


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In Anlehnung an Begriffe wie Web 2.0, an dem sich Internet-Nutzer mit unterschiedlichen Aktivitäten beteiligen können, und Enterprise 2.0 wird das Konzept der „Wartung 2.0“ entwickelt. Bei diesem Ansatz steht die Einbeziehung von Nutzergemeinschaften zur Verbesserung des Webauftritts und insbesondere von B2C-Systemen im Vordergrund. Wartung 2.0 ist eine Komponente des Web Engineerings und damit auch ein Element des von Lutz J. Heinrich vertretenen Konzepts des Information Engineerings

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Die meisten Bevölkerungsumfragen in der Schweiz beruhen auf Stichproben, die aus dem Telefonregister gezogen werden. Da solche Stichproben bezüglich der Abdeckung der Grundgesamtheit als problematisch anzusehen sind, diskutiere ich hier ein alternatives, von Fritschi et al. (1976) entwickeltes Stichprobenverfahren, bei dem in einem ersten Schritt Gemeinden ausgewählt und dann die Adressen der Zielpersonen über die Einwohnerregister bestimmt werden. Das Verfahren ist dabei so angelegt, dass die Stichprobe ähnlich wie bei einer einfachen Klumpenstichprobe auf eine relativ geringe Anzahl Gemeinden verdichtet wird, die Stichprobe aber trotzdem eine möglichst hohe statistische Effizienz beibehält. Eine Analyse der theoretischen Eigenschaften des Berner Stichprobenplans zeigt, dass das ursprüngliche Verfahren zu leicht verzerrten Stichproben führt. Eine korrigierende Modifikation des Verfahrens wird vorgeschlagen. Zudem wird ein alternativer Ansatz mit verbesserten Eigenschaften, die ex ante geteilte Stichprobe, vorgestellt. Mit Hilfe einer Simulationsstudie werden sodann die Vorzüge des Berner Stichprobenplans gegenüber einer einfachen Klumpenstichprobe illustriert.

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A hybrid protein, tPA/GFP, consisting of rat tissue plasminogen activator (tPA) and green fluorescent protein (GFP) was expressed in PC12 cells and used to study the distribution, secretory behavior, and dynamics of secretory granules containing tPA in living cells with a neuronal phenotype. High-resolution images demonstrate that tPA/GFP has a growth cone-biased distribution in differentiated cells and that tPA/GFP is transported in granules of the regulated secretory pathway that colocalize with granules containing secretogranin II. Time-lapse images of secretion reveal that secretagogues induce substantial loss of cellular tPA/GFP fluorescence, most importantly from growth cones. Time-lapse images of the axonal transport of granules containing tPA/GFP reveal a surprising complexity to granule dynamics. Some granules undergo canonical fast axonal transport; others move somewhat more slowly, especially in highly fluorescent neurites. Most strikingly, granules traffic bidirectionally along neurites to an extent that depends on granule accumulation, and individual granules can reverse their direction of motion. The retrograde component of this bidirectional transport may help to maintain cellular homeostasis by transporting excess tPA/GFP back toward the cell body. The results presented here provide a novel view of the axonal transport of secretory granules. In addition, the results suggest that tPA is targeted for regulated secretion from growth cones of differentiated cells, strategically positioning tPA to degrade extracellular barriers or to activate other barrier-degrading proteases during axonal elongation.

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Translocation of nucleotide sugars across the membrane of the Golgi apparatus is a prerequisite for the synthesis of complex carbohydrate structures. While specific transport systems for different nucleotide sugars have been identified biochemically in isolated microsomes and Golgi vesicles, none of these transport proteins has been characterized at the molecular level. Chinese hamster ovary (CHO) mutants of the complementation group Lec2 exhibit a strong reduction in sialylation of glycoproteins and glycolipids due to a defect in the CMP-sialic acid transport system. By complementation cloning in the mutant 6B2, belonging to the Lec2 complementation group, we were able to isolate a cDNA encoding the putative murine Golgi CMP-sialic acid transporter. The cloned cDNA encodes a highly hydrophobic, multiple membrane spanning protein of 36.4 kDa, with structural similarity to the recently cloned ammonium transporters. Transfection of a hemagglutinin-tagged fusion protein into the mutant 6B2 led to Golgi localization of the hemagglutinin epitope. Our results, together with the observation that the cloned gene shares structural similarities to other recently cloned transporter proteins, strongly suggest that the isolated cDNA encodes the CMP-sialic acid transporter.

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We describe Janus, a massively parallel FPGA-based computer optimized for the simulation of spin glasses, theoretical models for the behavior of glassy materials. FPGAs (as compared to GPUs or many-core processors) provide a complementary approach to massively parallel computing. In particular, our model problem is formulated in terms of binary variables, and floating-point operations can be (almost) completely avoided. The FPGA architecture allows us to run many independent threads with almost no latencies in memory access, thus updating up to 1024 spins per cycle. We describe Janus in detail and we summarize the physics results obtained in four years of operation of this machine; we discuss two types of physics applications: long simulations on very large systems (which try to mimic and provide understanding about the experimental non equilibrium dynamics), and low-temperature equilibrium simulations using an artificial parallel tempering dynamics. The time scale of our non-equilibrium simulations spans eleven orders of magnitude (from picoseconds to a tenth of a second). On the other hand, our equilibrium simulations are unprecedented both because of the low temperatures reached and for the large systems that we have brought to equilibrium. A finite-time scaling ansatz emerges from the detailed comparison of the two sets of simulations. Janus has made it possible to perform spin glass simulations that would take several decades on more conventional architectures. The paper ends with an assessment of the potential of possible future versions of the Janus architecture, based on state-of-the-art technology.

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We numerically study the aging properties of the dynamical heterogeneities in the Ising spin glass. We find that a phase transition takes place during the aging process. Statics-dynamics correspondence implies that systems of finite size in equilibrium have static heterogeneities that obey finite-size scaling, thus signaling an analogous phase transition in the thermodynamical limit. We compute the critical exponents and the transition point in the equilibrium setting, and use them to show that aging in dynamic heterogeneities can be described by a finite-time scaling ansatz, with potential implications for experimental work.

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We present a mean field model for spin glasses with a natural notion of distance built in, namely, the Edwards-Anderson model on the diluted D-dimensional unit hypercube in the limit of large D. We show that finite D effects are strongly dependent on the connectivity, being much smaller for a fixed coordination number. We solve the nontrivial problem of generating these lattices. Afterward, we numerically study the nonequilibrium dynamics of the mean field spin glass. Our three main findings are the following: i the dynamics is ruled by an infinite number of time sectors, ii the aging dynamics consists of the growth of coherent domains with a nonvanishing surface-volume ratio, and iii the propagator in Fourier space follows the p4 law. We study as well the finite D effects in the nonequilibrium dynamics, finding that a naive finite size scaling ansatz works surprisingly well.

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A microcanonical finite-size ansatz in terms of quantities measurable in a finite lattice allows extending phenomenological renormalization the so-called quotients method to the microcanonical ensemble. The ansatz is tested numerically in two models where the canonical specific heat diverges at criticality, thus implying Fisher renormalization of the critical exponents: the three-dimensional ferromagnetic Ising model and the two-dimensional four-state Potts model (where large logarithmic corrections are known to occur in the canonical ensemble). A recently proposed microcanonical cluster method allows simulating systems as large as L = 1024 Potts or L= 128 (Ising). The quotients method provides accurate determinations of the anomalous dimension, η, and of the (Fisher-renormalized) thermal ν exponent. While in the Ising model the numerical agreement with our theoretical expectations is very good, in the Potts case, we need to carefully incorporate logarithmic corrections to the microcanonical ansatz in order to rationalize our data.

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The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials V(ϕ) = λ|ϕ|^n /n. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained c_eff^ 2  = ω = (n − 2)/(n + 2) with ω the effective equation of state. We also obtain the first order correction in k^ 2/ω_eff^ 2 , when the wavenumber k of the perturbations is much smaller than the background oscillation frequency, ω_eff. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the natural ansatz for δϕ; and for sub-Hubble modes, exploiting Floquet’s theorem.

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We report absolute experimental integral cross sections (ICSs) for electron impact excitation of bands of electronic-states in furfural, for incident electron energies in the range 20-250 eV. Wherever possible, those results are compared to corresponding excitation cross sections in the structurally similar species furan, as previously reported by da Costa et al. [Phys. Rev. A 85, 062706 (2012)] and Regeta and Allan [Phys. Rev. A 91, 012707 (2015)]. Generally, very good agreement is found. In addition, ICSs calculated with our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arise due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section for electron-furfural scattering. Where possible, those calculated IAM-SCAR+I ICS results are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, but only for the band I and band II excited electronic states, we also present results from our Schwinger multichannel method with pseudopotentials calculations. Those results are found to be in good qualitative accord with the present experimental ICSs. Finally, with a view to assembling a complete cross section data base for furfural, some binary-encounter-Bethe-level total ionization cross sections for this collision system are presented. (C) 2016 AIP Publishing LLC.

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Die wesentliche Aufgabe des Controllings besteht darin, dem Management aufbereitete Informationen zur Verfügung zu stellen. Die zu verarbeitenden Informationen liegen allerdings nicht immer in der gewünschten Genauigkeit vor. Trotz dieser Unschärfe muss eine Beschreibung stattfinden, um eine Entscheidungsfindung zu realsieren. Eine Möglichkeit ist der hier vorgestellte wissensbasierte Ansatz der Fuzzy Logic. Anhand von drei Controllinginstrumenten wird in der vorliegenden Arbeit das Anwendungspotential der Fuzzy Logic im Controlling bewertet.

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Trotz der steigenden Bedeutung von familienexternen Nachfolgeregelungen wie MBO und MBI bestehen hinsichtlich dieser Nachfolgeoptionen noch große Forschungslücken. Obwohl die Informationsökonomie einen viel versprechenden Ansatz darstellt, um ein fundierteres Verständnis zu erlangen, ist sie in diesem Kontext noch zu wenig angewandt worden. Dies wäre jedoch vor allem in Bezug auf einen MBI sinnvoll, da dort die deutlichsten Informationsasymmetrien zwischen Übergeber und Nachfolger auftreten können. In diesem Beitrag bedienen wir uns daher der Informationsökonomie und analysieren die verschiedenen Informationsasymmetrien bei einem MBI im Detail. Außerdem zeigen wir verschiedene Möglichkeiten auf, wie die entsprechenden Asymmetrien überwunden werden können. Damit leisten wir einen wertvollen Beitrag zu Wissenschaft und Praxis.

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Bibliographical foot-notes.

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Vol. 3, Index.

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"LA-UR-76-1844."