bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurological disorders in complex humanitarian emergencies and natural disasters
Authors: Mateen Farrah J. 
Published: September 2010

AbstractComplex humanitarian emergencies include the relatively acute, severe, and overwhelming health consequences of armed conflict, food scarcity, mass displacement, and political strife. Neurological manifestations of complex humanitarian emergencies are important and underappreciated consequences of emergencies in populations worldwide. This review critically assesses the existing knowledge of the range of neurological disorders that accompany complex humanitarian emergencies and natural disasters in both the acute phase of crisis and the “long shadow” that follows. Ann Neurol 2010;68:282–294
JC virus persistence following progressive multifocal leukoencephalopathy in multiple sclerosis patients treated with natalizumab
Authors: Ryschkewitsch Caroline F. , Jensen Peter N. , Monaco Maria Chiara , Major Eugene O. 
Published: September 2010

AbstractJC virus (JCV) DNA in the cerebrospinal fluid (CSF) provides the laboratory confirmatory diagnosis of progressive multifocal leukoencephalopathy (PML) in patients whose clinical symptoms and magnetic resonance imaging findings are consistent with PML.The Laboratory of Molecular Medicine and Neuroscience (LMMN), National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), made the confirmatory laboratory diagnosis in 35 multiple sclerosis (MS) patients treated with natalizumab. Thirteen patients had 3 or more CSF samples taken from weeks to months following PML diagnosis. Seven of the 13 patients demonstrated persistence of JCV DNA in the CSF even though all patients experienced immune reconstitution inflammatory syndrome (IRIS), 11 patients had plasma exchange, and 2 had immunoabsorption. Specific anti‐JCV antibody was measured in plasma/sera samples from 25 of the 35 patients. Most of the samples showed moderate to high or rising antibody levels from the time of PML diagnosis. However, plasma from 1 patient at or near the time of PML diagnosis had a titer considered seronegative and 2 other plasma samples from patients had titers considered at baseline for seropositivity. In several PML cases, viral persistence and neurological deficits have continued for several years, indicating that once initiated, JCV infection may not entirely clear, even with IRIS. Ann Neurol 2010;68:384–391
Natalizumab dosage suspension: Are we helping or hurting?
Authors: West Timothy W. , Cree Bruce A.C. 
Published: September 2010

AbstractThe risk of developing progressive multifocal leukoencephalopathy increases with the duration of treatment with natalizumab. Planned dosage interruptions have been proposed as a means of decreasing cumulative risk. The clinical consequences of dosage interruption were evaluated in a single center cohort of natalizumab‐treated patients. Medical records were reviewed for 84 patients identified with multiple sclerosis who received 12 or more infusions of natalizumab at an academic multiple sclerosis center. Eighty‐one percent (68/84) underwent a dosage interruption, and 19% (16/84) had no interruption in natalizumab treatment. Of those with a treatment interruption, 27.9% (19/68) experienced a clinical relapse within 6 months of the suspension, whereas none of the patients with ongoing treatment experienced a flare during months 12 to 18 of treatment (p = 0.017, Fisher exact test). Survival analysis showed that Kaplan‐Meier curves comparing dosage interruption to ongoing treatment diverged (p = 0.025). Median time from treatment interruption to relapse onset was 3 months. No clinical predictors associated with an increased risk of developing flares during dosage interruption were identified. Among the 19 patients who had a flare, 7 had severe flares, with a mean number of 16 Gad+ lesions on brain magnetic resonance imaging (range, 6–40). Their median Expanded Disability Status Scale at natalizumab interruption was 3.0 and increased to 6.0 during the flare (p = 0.0008). Natalizumab dosage interruption is associated with clinical flares and return of radiographic inflammatory disease activity. Some of these flares can be clinically severe, with a high number of contrast‐enhanced lesions, suggesting a possible rebound of disease activity. Ann Neurol 2010;68:395–399
Broadband study of the scattering of ultrasound by polystyrene‐latex‐in‐water suspensions
Authors: Kaatze U. , Trachimow C. , Pottel R. , Brai M. 
Published: September 2010

AbstractUltrasonic absorption spectra have been measured between 0.1 and 2000 MHz of aqueous suspensions of polystyrene latex globules. Samples of different diameter (60 to 100 nm) and different concentration of the polystyrene latex particles (volume fraction between 0.05 and 0.38) have been studied. The broadband spectra exhibit a Debye‐type relaxation term in the frequency range around some MHz and a contribution with special characteristics at higher frequencies. The former term is assumed to be due to counterion effects in the surface layer of the globules. No special attention is payed to this effect. The latter contribution is attributed to scattering and mode conversion mechanisms. An approximate explicit and an exact formulation of the theoretical description of the sound wave attenuation by the scattering process are discussed. The explicit formulation enables valuable insights into the mode conversion mechanisms but does not allow for a complete representation of the measured spectra. Application of the exact version leads to the conclusion that in the frequency range under consideration monopole and quadrupole oscillations of the polystyrene latex globules are the dominant cause of ultrasonic wave attenuation. It is found that even at the elevated concentrations used effects of multiple scattering are of minor importance here.
Impurity spin dynamics and quantum coherence in mesoscopic rings
Authors: Schwab P. , Eckern U. 
Published: September 2010

AbstractWe investigate the effects of impurity spin dynamics on quantum coherence in mesoscopic metallic rings. Spin relaxation induces temporal current fluctuations which are closely related to persistent currents in such systems. The persistent current is suppressed in the presence of magnetic impurities. We discuss spin‐polarisation effects, spin‐glass ordering, and the Kondo effect which are shown to restore the current even in the presence of magnetic scattering.
On the Yang‐Mills effective action with instanton gauge field
Authors: Tinebra F. 
Published: September 2010

AbstractThe calculation of the determinant for the second order covariant derivative operator is analyzed in the space R4 and for Yang‐Mills instanton field configurations. The problems inherent to the ultraviolet ζ‐function renormalization method and infrared divergencies of this operator are reviewed. A method for estimating the asymptotic coefficients of its determinant has been discussed and the failure of the general conformal invariance induced by any regularization technique has also been considered. A particular solution valid for a Yang‐Mills multi instanton configuration, valuable in order to get the non conformally invariant piece of the general solution, is the main result obtained here. We give it as an integral equation, namely in a semi‐explicit form.
Combinatorial computation of Clebsch‐Gordan coefficients
Authors: Schertler Klaus , Thoma Markus H. 
Published: September 2010

AbstractThe addition of angular momenta can be reduced to elementary coupling processes of spin‐‐particles. In this way, a method is developed which allows for a non‐recursive, simultaneous computation of all Clebsch‐Gordan coefficients concerning the addition of two angular momenta. The relevant equations can be interpreted easily, analogously to simple probabilistic considerations. They provide an improved understanding of the addition of angular momenta as well as a practicable evaluation of Clebsch‐Gordan coefficients in an easier way than within the well‐known methods.
Spin‐charge fluctuations in itinerant helical magnets
Authors: Brenig Wolfram 
Published: September 2010

AbstractUsing a generalized random phase approach quantum fluctuations beyond the helical mean‐field states of the Hubbard model off half filling are discussed. The collective mode spectrum is shown to exhibit spin‐charge mixing and is found to be strongly renormalized by coupling to low‐energy incoherent particle‐hole excitations. Results for the collective mode dispersion which displays a significant anisotropy are presented for selected helical phases. Moreover phase space regions of ‘missing’ modes are identified with a finite wave length instability of the helical states suggesting novel inhomogeneous phases of the doped Hubbard model.P.A.C.S. : 71.27.+a, 75.30.Fv, 75.40.Gb
Properties of the t‐J model in the dynamical mean field theory: One‐particle properties in the antiferromagnetic phase
Authors: Obermeier Thomas , Pruschke Thomas , Keller Joachim 
Published: September 2010

AbstractWe study the one‐particle properties of the t‐J model within the framework of Vollhardt's dynamical mean field theory. By introducing an AB‐sublattice structure we explicitly allow for a broken symmetry for the spin degrees of freedom and are thus able to calculate the one‐particle spectral function in the antiferromagnetic phase. We observe surprisingly rich structures in the one‐particle density of states for T < T N at finite doping up to 15%. These structures can be related to the well known results for one single hole in the Néel background. We are thus able to establish the relevance of this at a first sight academic limit to physical properties of the t‐J model with a finite density of holes in the thermodynamical limit.
Ferromagnetism in the Hubbard model on the square lattice: Improved instability criterion for the Nagaoka state
Authors: Wurth P. , Uhrig G. , Müller‐Hartmann E. 
Published: September 2010

AbstractThe instability of the fully polarized ferromagnetic state (Nagaoka state) with respect to single spin flips is re‐examined for the Hubbard model on the square lattice with a large family of variational wave functions which include correlation effects of the majority spins in the vicinity of the flipped spin. We find a critical hole density of δcr = 0.251 for U = ∞ and a critical coupling of Ucr = 77.7t. Both values improve previous variational results considerably.
Spin waves and static susceptibility in the weakly doped t‐J model
Authors: Vojta Matthias , Becker Klaus W. 
Published: September 2010

AbstractWe investigate the spin dynamics in weakly doped high‐temperature superconductors. The system is described by the two‐dimensional t‐J model. Our focus is on the interaction between mobile holes and spin waves. The calculations are based on a recently introduced cumulant method for computing the ground state energy of correlated electronic systems. Contrary to previous works using dynamical quantities like correlation functions or spectral densities our approach contains a static view to the system. This new method treats spin and hole dynamics on the same basis and allows for the calculation of static and dynamical quantities. We present results for spin‐wave energies and transverse static susceptibilities for small hole concentrations and various values of t/J. We find a strong renor‐malization of the spin‐wave energies due to the spin‐hole interaction. In agreement with neutron scattering experiments the spin‐wave velocity vanishes at a critical hole density of a few percent which is equivalent to the instability of the antiferromagnetic order.
Coulomb interactions in Al doped FeSi at low temperatures
Authors: Friemelt K. , Ditusa J. F. , Bucher E. , Aeppli G. 
Published: September 2010

AbstractA metal‐insulator transition is observed in Al doped FeSi. For samples in the metallic region, a T1/2 contribution to the low temperature conductivity is found. An analysis based on the Coulomb interaction model in disordered systems is presented to explain this behavior. It is shown that the sum of Coulomb interactions and localization theories yields the best description of the results.
High resolution neutron scattering study of low‐energy magnetic excitations in Nd2‐xCexCuO4
Authors: Loewenhaupt M. , Metz A. , Pyka N. M. , Paul D. McK. , Martin J. , Duijn V. H. M. , Franse J. J. M. , Mutka H. , Schmidt W. 
Published: September 2010

AbstractThe low‐energy magnetic excitations (ħω ≤ 2 meV) of polycrystalline samples of Nd2‐xCexCuO4 with x = 0, 0.1 and 0.15 have been measured with high resolution inelastic neutron scattering using time‐of‐flight technique at temperatures below 0.3 K. All observed scattering originates from transitions within the ground state doublet of Nd3+. For Nd2CuO4 the response is inelastic, and shows at least three different modes, of which one is almost dispersionless. For x = 0.1 the excitation spectrum shifts towards lower energies, but the main features of the undoped compound are still visible, whereas for x = 0.15 the response is mainly quasi‐elastic but remains localised in Q‐space around the first magnetic Bragg point (0.5 0.5 1). A comparison with data obtained on a triple‐axis‐spectrometer on single crystals with x = 0.0 and x = 0.15 reveals that the response of the doped sample in the [0 0 1] direction is still inelastic.
Disorder in ballistic systems: A numerical analysis
Authors: Altland Alexander , Loosen Roland 
Published: September 2010

AbstractWe present a numerical analysis of the single particle energy spectra of ballistic condensed matter systems and compare with recent theoretical results. We show that the presence even of weak disorder induces full chaoticity on time scales larger than the elastic disorder scattering time. To disentangle the effect of boundary, respectively disorder scattering on the spectral statistics, different types of correlation functions are introduced and discussed.
Striped phase in the cuprates as a semiclassical phenomenon
Authors: Zaanen Jan , Oleś Andrzej M. 
Published: September 2010

AbstractThe striped phase, a novel type of electron solid, has been observed recently in a number of doped Mott‐Hubbard insulators (including cuprates). This solid consists of a parallel array of charged‐domain walls, bound states of carriers and Néel walls in the antiferromagnetic spin system. The existence of these states has been predicted well in advance of their experimental observation on the basis of semiclassical (‘Hartree‐Fock’) theory. Nevertheless, it is not at all clear whether semiclassics yields a correct explanation. In this paper we will focus especially on the variety of striped phases realized in the cuprates, characterized by a domain wall filling of half a hole per domain wall unit cell. We will unfold the reasons why semiclassics, as applied to simple Hubbard models, favours strongly a filling of one hole per domain wall unit cell, as is for instance the case in the nickelates. Nevertheless, the occurrence of half‐filled walls as semiclassical ground states cannot be excluded on general grounds. It might be that Hubbard models do not incorporate the microscopic situation correctly. Instead, we derive a qualitative criterion: in order to acquire a special stability on the semiclassical level, the half‐filled domain walls should be characterized by a quadrupling of the period along the walls, involving a modulation in the longitudinal spin‐ and/or charge channel.64.60. ‐ i, 71.27. + a, 74.72. ‐ h, 75.10. ‐ b
Influence of boundary conditions on the ordering of elastic dipoles
Authors: Schotte Klaus‐Dieter , Topalis Panagiotis , Schotte Ursula 
Published: September 2010

AbstractWe consider elastic dipoles in several two‐dimensional geometries. Using Cauchy integral techniques and the image method, the state of elastic equilibrium under different boundary conditions can be determined. The results are used to find the ground state of systems of anisotropic dipoles via the simulated annealing method. Only in the case of fixed boundaries the ordering depends on the boundary condition.
Quasiclassical approach to impurity effect on magnetooscillations in 2D metals
Authors: Mirlin A. D. , Altshuler E. , Wölfle P. 
Published: September 2010

AbstractWe develop a quasiclassical method based on the path integral formalism, to study the influence of disorder on magnetooscillations of the density of states and conductivity. The treatment is appropriate for electron systems in the presence of a random potential with large correlation length or a random magnetic field, which are characteristic features of various 2D electronic systems presently studied in experiment. In particular, we study the system of composite fermions in the fractional quantum Hall effect device, which are coupled to the Chem‐Simons field and subject to a long‐range random potential.
Anomalous peak effect in heavy‐fermion, intermediate‐valence and A15 superconductors: Evidence for a Fulde‐Ferrell‐Larkin‐Ovchinnikov state?
Authors: Gegenwart P. , Deppe M. , Köppen M. , Kromer F. , Lang M. , Modler R. , Weiden M. , Geibel C. , Steglich F. , Fukase T. , Toyota N. 
Published: September 2010

AbstractAn experimental study based upon magnetic and dilatometric measurements is presented for the clean high‐κ superconductors UPd2Al3, CeRu2 and V3Si. All three compounds show an enhanced spin susceptibility. Their superconducting state is strongly Pauli limited, and an anomalous peak effect is observed at T<(0.8‐0.9)Tc, slightly below Hc2(T). This phenomenon appears to be qualitatively consistent with a first‐order transition between weak and collective pinning, caused by the formation of a staggered order parameter in a generalized Fulde‐Ferrell‐Larkin‐Ovchinnikov phase (M. Tachiki et al., Z. Phys. B, in press).
D‐wave superconductivity: New paradigm?
Authors: Maki Kazumi , Won Hyekyung 
Published: September 2010

AbstractAs the 10th anniversary of the discovery of high Tc cuprate superconductors by Bednorz and Müller is approaching, a simple picture of high Tc cuprates based on d‐wave superconductivity is emerging. Here we shall describe the effect of impurity scattering and compare with experiments on Zn‐substituted LSCO and YBCO. We shall discuss some characteristics of the vortex state in d‐wave superconductor. In a magnetic field parallel to the c axis a square vortex lattice tilted by 45° from the a axis is stable, which have been seen experimentally though elongated in the b direction in monocrystals of YBCO.
Electronic structure calculations and strong correlations: A model study
Authors: Runge Erich , Zwicknagl Gertrud 
Published: September 2010

AbstractMetals with strong correlations are a major challenge for realistic electronic structure calculations. The complexity of the systems under consideration precludes a direct fully microscopic treatment by means of the theoretical and computational methods available at present. The present paper analyzes the applicability and restrictions of common approximation schemes by comparing their predictions for a model pertinent to heavy fermion metals to the exact solution. The criteria chosen for the assessment are the density distribution in the ground state as well as the energy scale for low‐lying excitations.
Towards an incremental expansion of strong correlation effects in solids
Authors: Stoll Hermann 
Published: September 2010

AbstractA scheme based on local correlation‐energy increments, which has been applied successfully to the investigation of dynamical correlation effects in semiconductors and ionic crystals, is extended here to include non‐dynamical (static) electron correlation as well. It is shown how to use abinitio multi‐configuration self‐consistent‐field and multi‐reference configuration‐interaction calculations for this purpose, and test applications are reported for potential curves of molecules at the dissociation limit.
Two Anderson impurities in the framework of the non‐crossing approximation: Spectral functions and spin correlations
Authors: Schiller A. , Zevin V. 
Published: September 2010

AbstractUsing a novel slave boson mapping, which was recently proposed by us for two Anderson impurities embedded in a metal, we present here spectral functions for all pseudoparticles involved in the mapping. These were numerically calculated in the framework of the Non‐Crossing Approximation for different temperatures and inter‐impurity distances, both for the degenerate (Nf = 6) and nondegenerate (Nf = 2) models. For the nondegenerate case, temperature dependencies of the partial occupancies and the spin‐spin correlation function suggest that an antiferromagnetic (AFM)‐like ground state is formed at suitable inter‐impurity separation. By contrast, Kondo quenching of the impurity moments takes place for the isotropic Nf = 6 case even when a direct AFM interaction is introduced in order to amplify the indirect (inherent) one. Numerical calculations are in agreement with our previous prediction [Phys. Rev. B 47, 14,297 (1993)] that no AFM‐like ground state can appear for two isotropic degenerate impurities.
Microcanonical thermodynamics of first order phase transitions studied in the potts model
Authors: Gross D. H. E. , Ecker A. , Zhang X. Z. 
Published: September 2010

AbstractPhase transitions of first and second order can easily be distinguished in small systems in the microcanonical ensemble. Configurations of phase coexistence, which are suppressed in the conventional canonical formulation, carry important information about the main characteristics of first order phase transitions like the transition temperature, the latent heat, and the interphase surface tension. The characteristic backbending of the microcanonical caloric equation of state T(E) (not to be confused with the well known Van der Waals loops in ordinary thermodynamics or mean field approximations) leading to a negative specific heat is intimately linked to the interphase surface entropy.
Single ion description of photoemission spectra of metallic cerium systems
Authors: Hüfner S. 
Published: September 2010

AbstractThe conflicting evidence presented for and against the single ion description of photoemission data of metallic cerium compounds is analysed. It can be shown that for low TK materials the single ion description of photoemission spectra (in the cluster or Anderson‐Hamiltonian approximation) of metallic cerium compounds is valid. However, some of the thermal effects seen in the photoemission spectra are caused either by the temperature dependence of the Fermi function or by coupling to phonons.
Heavy fermions and superconductivity in doped cuprates
Authors: Tornow Sabine , Zevin Vilen , Zwicknagl Gertrud 
Published: September 2010

AbstractWe present a Fermi liquid description for the low‐energy excitations in rare earth cuprates Nd2‐xCexCuO4. The strongly renormalized heavy quasiparticles which appear in the doped samples originate from the coherent decoupling of rare earth spins and correlated conduction electrons. The correlations among the conduction electrons are simulated by assuming a spin density wave ground state. We discuss results for the thermodynamic properties in the insulating, normal metallic and superconducting phases which are in fair agreement with experimental data. In addition, the model predicts interesting behaviour for the superconducting state of samples with low transition temperature Tc which may help to assess the validity of the underlying assumptions.
The Anderson transition in conjugated polymers
Authors: Markoš P. , Evangelou S. N. 
Published: September 2010

AbstractWe study the electronic transport properties of mutually connected wires with loops in a “spaghetti”—like morphology by transfer matrix scaling methods. We obtain the conductance of the system and show the existence of an Anderson metal‐insulator transition. Our results are discussed in connection with recent experiments in conjugated polymers.