8,133 research outputs found

    The magnetic structure of the Jahn-Teller System LaTiO3

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    We investigate the effect of the experimentally observed Jahn-Teller distortion of the oxygen octahedra in LaTiO3 on the magnetic exchange. We present a localized model for the effective hopping between nearest-neighbor Ti ions and the intra-site Coulomb interactions, based on a non-degenerate orbital ground state due to the static crystal field. The latter corresponds to an orbital order which recently has been confirmed experimentally. Using perturbation theory we calculate, in addition to the Heisenberg coupling, antisymmetric and symmetric anisotropy terms of the superexchange spin Hamiltonian which are caused by the spin-orbit interaction. Employing our superexchange Hamiltonian, we deduce the magnetic order at low temperatures which is found to be in good agreement with experiment.Comment: 21 pages, 6 figure

    T=0 Phase Diagram of the Double-Exchange Model

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    We present the T=0 phase diagram of the double-exchange model (ferromagnetic Kondo lattice model) for all values of the carrier concentration nn and Hund's couplng JJ, within dynamical mean field theory. We find that depending on the values of nn and JJ, the ground state is either a ferromagnet, a commensurate antiferromagnet or some other incommensurate phase with intermediate wave vectors . The antiferromagnetic phase is separated by first order phase boundaries and wide regimes of phase separation. The transition from the ferromagnetic phase to an incommensurate phase is second order.Comment: 4 pages, 5 figures. The analysis now includes incommensurate phases with arbitrary wave vectors. Correspondingly, the figures have been change

    Characterization of novel elongated Parvulin isoforms that are ubiquitously expressed in human tissues and originate from alternative transcription initiation

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    BACKGROUND: The peptidyl prolyl cis/trans isomerase (PPIase) Parvulin (Par14/PIN4) is highly conserved in all metazoans and is assumed to play a role in cell cycle progression and chromatin remodeling. It is predominantly localized to the nucleus and binds to chromosomal DNA as well as bent oligonucleotides in vitro. RESULTS: In this study we confirm by RT-PCR the existence of a longer Parvulin isoform expressed in all tissues examined so far. This isoform contains a 5' extension including a 75 bp extended open reading frame with two coupled SNPs leading to amino acid substitutions Q16R and R18S. About 1% of all Parvulin mRNAs include the novel extension as quantified by real-time PCR. The human Parvulin promoter is TATA-less and situated in a CpG island typical for house keeping genes. Thus, different Parvulin mRNAs seem to arise by alternative transcription initiation. N-terminally extended Parvulin is protected from rapid proteinaseK degradation. In HeLa and HepG2 cell lysates two protein species of about 17 and 28 KDa are detected by an antibody against an epitope within the N-terminal extension. These two bands are also recognized by an antibody towards the PPIase domain of Parvulin. The longer Parvulin protein is encoded by the human genome but absent from rodent, bovine and non-mammalian genomes. CONCLUSION: Due to its molecular weight of 16.6 KDa we denote the novel Parvulin isoform as Par17 following the E. coli Par10 and human Par14 nomenclature. The N-terminal elongation of Par17-QR and Par17-RS suggests these isoforms to perform divergent functions within the eukaryotic cell than the well characterized Par14

    European clinical guidelines for Tourette syndrome and other tic disorders:summary statement

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    In 2011 a working group of the European Society for the Study of Tourette syndrome (ESSTS) developed the first European Guidelines for Tourette syndrome (TS) published in the ECAP journal. After a decade ESSTS now presents updated guidelines, divided into four sections: Part I: assessment, Part II: psychological interventions, Part III: pharmacological treatment and Part IV: deep brain stimulation (DBS). In this paper, we summarise new developments described in the guidelines with respect to assessment and treatment of tics. Further, summary findings from a recent survey conducted amongst TS experts on these same topics are presented, as well as the first European patient representative statement on research. Finally, an updated decision tree is introduced providing a practical algorithm for the treatment of patients with TS. Interestingly, in the last decade there has been a significant shift in assessment and treatment of tics, with more emphasis on non-pharmacological treatments

    Atrial fibrillation impairs the diagnostic performance of cardiac natriuretic peptides in dyspneic patients. results from the BACH Study (Biomarkers in ACute Heart Failure)

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    Objectives: The purpose of this study was to assess the impact of atrial fibrillation (AF) on the performance of mid-region amino terminal pro-atrial natriuretic peptide (MR-proANP) in comparison with the B-type peptides (BNP and NT-proBNP) for diagnosis of acute heart failure (HF) in dyspneic patients. Background: The effects of AF on the diagnostic and prognostic performance of MR-proANP in comparison with the B type natriuretic peptides have not been previously reported. Methods: A total of 1,445 patients attending the emergency department with acute dyspnea had measurements taken of MR-proANP, BNP, and NT-proBNP values on enrollment to the BACH trial and were grouped according to presence or absence of AF and HF. Results: AF was present in 242 patients. Plasma concentrations of all three peptides were lowest in those with neither AF nor HF and AF without HF was associated with markedly increased levels (p < 0.00001). HF with or without AF was associated with a significant further increment (p < 0.00001 for all three markers). Areas under receiver operator characteristic curves (AUCs) for discrimination of acute HF were similar and powerful for all peptides without AF (0.893 to 0.912; all p < 0.001) with substantial and similar reductions (0.701 to 0.757) in the presence of AF. All 3 peptides were independently prognostic but there was no interaction between any peptide and AF for prediction of all-cause mortality. Conclusions: AF is associated with increased plasma natriuretic peptide (MR-proANP, BNP and NT-proBNP) levels in the absence of HF. The diagnostic performance of all three peptides is impaired by AF. This warrants consideration of adjusted peptide thresholds for diagnostic use in AF and mandates the continued search for markers free of confounding by AF

    Near optimal configurations in mean field disordered systems

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    We present a general technique to compute how the energy of a configuration varies as a function of its overlap with the ground state in the case of optimization problems. Our approach is based on a generalization of the cavity method to a system interacting with its ground state. With this technique we study the random matching problem as well as the mean field diluted spin glass. As a byproduct of this approach we calculate the de Almeida-Thouless transition line of the spin glass on a fixed connectivity random graph.Comment: 13 pages, 7 figure
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