TY  - THES
A1  - Lang, Thomas C.
T1  - Quantum Monte Carlo methods and strongly correlated electrons on honeycomb structures
T1  - Quanten Monte Carlo Methoden und stark korrelierte Elektronen auf hexagonalen Strukturen
N2  - In this thesis we apply recently developed, as well as sophisticated quantum Monte Carlo methods to numerically investigate models of strongly correlated electron systems on honeycomb structures. The latter are of particular interest owing to their unique properties when simulating electrons on them, like the relativistic dispersion, strong quantum fluctuations and their resistance against instabilities. This work covers several projects including the advancement of the weak-coupling continuous time quantum Monte Carlo and its application to zero temperature and phonons, quantum phase transitions of valence bond solids in spin-1/2 Heisenberg systems using projector quantum Monte Carlo in the valence bond basis, and the magnetic field induced transition to a canted antiferromagnet of the Hubbard model on the honeycomb lattice. The emphasis lies on two projects investigating the phase diagram of the SU(2) and the SU(N)-symmetric Hubbard model on the hexagonal lattice. At sufficiently low temperatures, condensed-matter systems tend to develop order. An exception are quantum spin-liquids, where fluctuations prevent a transition to an ordered state down to the lowest temperatures. Previously elusive in experimentally relevant microscopic two-dimensional models, we show by means of large-scale quantum Monte Carlo simulations of the SU(2) Hubbard model on the honeycomb lattice, that a quantum spin-liquid emerges between the state described by massless Dirac fermions and an antiferromagnetically ordered Mott insulator. This unexpected quantum-disordered state is found to be a short-range resonating valence bond liquid, akin to the one proposed for high temperature superconductors. Inspired by the rich phase diagrams of SU(N) models we study the SU(N)-symmetric Hubbard Heisenberg quantum antiferromagnet on the honeycomb lattice to investigate the reliability of 1/N corrections to large-N results by means of numerically exact QMC simulations. We study the melting of phases as correlations increase with decreasing N and determine whether the quantum spin liquid found in the SU(2) Hubbard model at intermediate coupling is a specific feature, or also exists in the unconstrained t-J model and higher symmetries.
N2  - Wir untersuchen mit Hilfe von neu entwickelten sowie technisch ausgereiften Quanten-Monte-Carlo Methoden Modelle stark korrelierter Elektronen auf hexagonalen Gittern. Letztere zeichnen sich durch die einzigartigen Eigenschaften der auf ihnen simulierten Elektronen aus, wie zum Beispiel deren relativistische Dispersionsrelation, die starken Quantenfluktuationen und deren Beständigkeit gegenüber Instabilitäten. Diese Arbeit umfasst mehrere Projekte, einschließlich der Erweiterung des weak-coupling continuous time Quanten-Monte-Carlo Verfahrens und dessen Anwendung auf Phononen-Systeme und den Null-Temperatur Grundzustand, der Studie eines Quanten-Phasenübergangs in einem Kristall mit dominanter Valenzbindung in einem Spin-1/2 Heisenberg model mit vier-Spin Wechselwirkung, und der Untersuchung eines gekippten Antiferromagneten im Hubbard Model, induziert durch ein externes Magnetfeld. Die Schwerpunkte dieser Arbeit liegen bei zwei Studien der Phasendiagramme des SU(2) und SU(N)-symmetrischen Hubbard Models auf dem hexagonalen Gitter. Bei niedrigen Temperaturen haben Elektronen in Festkörpern die Tendenz, Ordnung zu entwickeln. Eine Ausnahme sind Quanten Spinflüssigkeiten, in denen Fluktuationen Ordnung selbst bei niedrigsten Temperaturen verhindern. Bislang war es nahezu unmöglich, diese in experimentell realistischen mikroskopischen Modellen zu finden und zu simulieren. In aufwändigen Quanten-Monte-Carlo Simulationen des SU(2) Hubbard Models konnten wir das Auftreten einer solchen Quanten Spinflüssigkeit zeigen, welche die Phasen der masselosen Dirac-Fermionen und eines antiferromagnetischem Isolators trennt. Dieser unerwartete, ungeordnete Quantenzustand weist kurzreichweitige Korrleationen ähnlich einer Resonanz-Valenzbond-Flüssigkeit auf, welche in Zusammenhang mit Hochtemperatur-Spuraleitung steht. Motiviert durch die reichhaltigen Phasendiagramme von SU(N)-symmetrischen Modellen, untersuchen wir mit Hilfe von Quanten-Monte Carlo-Simulationen den SU(N)-Hubbard-Heisenberg-Antiferromagneten auf dem hexagonalen Gitter in Bezug auf die Verlässlichkeit von 1/N Korrekturen von Molekularfeldnäherungen. Wir untersuchen das Schmelzen von Phasen als Funktion von abnehmendem N und bestimmen, ob die im SU(2)-Hubbard-Model gefundene Quanten-Spinflüssigkeit eine spezielle Eigenschaft dieses Modells ist, oder ob diese auch im erweiterten t-J Modell bei höheren Symmetrien gefunden werden kann.
KW  - Monte-Carlo-Simulation
KW  - Niederdimensionaler Festkörper
KW  - Hexagonaler Kristall
KW  - Elektronenstruktur
KW  - Starke Kopplung
KW  - Monte Carlo
KW  - Markov-Ketten-Monte-Carlo-Verfahren
KW  - Theoretische Physik
KW  - Niederdimensionaler Festkörper
KW  - Festkörpertheorie
KW  - Quantum Monte Carlo
KW  - Condensed matter theory
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-53506
ER  - 
TY  - JOUR
A1  - Weber, Heike
A1  - Scholz, Claus Jürgen
A1  - Domschke, Katharina
A1  - Baumann, Christian
A1  - Klauke, Benedikt
A1  - Jacob, Christian P.
A1  - Maier, Wolfgang
A1  - Fritze, Jürgen
A1  - Bandelow, Borwin
A1  - Zwanzger, Peter Michael
A1  - Lang, Thomas
A1  - Fehm, Lydia
A1  - Ströhle, Andreas
A1  - Hamm, Alfons
A1  - Gerlach, Alexander L.
A1  - Alpers, Georg W.
A1  - Kircher, Tilo
A1  - Wittchen, Hans-Ulrich
A1  - Arolt, Volker
A1  - Pauli, Paul
A1  - Deckert, Jürgen
A1  - Reif, Andreas
T1  - Gender Differences in Associations of Glutamate Decarboxylase 1 Gene (GAD1) Variants with Panic Disorder
N2  - Background: Panic disorder is common (5% prevalence) and females are twice as likely to be affected as males. The heritable component of panic disorder is estimated at 48%. Glutamic acid dehydrogenase GAD1, the key enzyme for the synthesis of the inhibitory and anxiolytic neurotransmitter GABA, is supposed to influence various mental disorders, including mood and anxiety disorders. In a recent association study in depression, which is highly comorbid with panic disorder, GAD1 risk allele associations were restricted to females. Methodology/Principal Findings: Nineteen single nucleotide polymorphisms (SNPs) tagging the common variation in GAD1 were genotyped in two independent gender and age matched case-control samples (discovery sample n = 478; replication sample n = 584). Thirteen SNPs passed quality control and were examined for gender-specific enrichment of risk alleles associated with panic disorder by using logistic regression including a genotype6gender interaction term. The latter was found to be nominally significant for four SNPs (rs1978340, rs3762555, rs3749034, rs2241165) in the discovery sample; of note, the respective minor/risk alleles were associated with panic disorder only in females. These findings were not confirmed in the replication sample; however, the genotype6gender interaction of rs3749034 remained significant in the combined sample. Furthermore, this polymorphism showed a nominally significant association with the Agoraphobic Cognitions Questionnaire sum score. Conclusions/Significance: The present study represents the first systematic evaluation of gender-specific enrichment of risk alleles of the common SNP variation in the panic disorder candidate gene GAD1. Our tentative results provide a possible explanation for the higher susceptibility of females to panic disorder.
KW  - Medizin
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-75830
ER  - 
TY  - THES
A1  - Lang, Thomas
T1  - Vergleich der rheologischen Qualität von Erythrozytenkonzentraten, gewonnen durch herkömmliche Vollblutspende oder Multikomponentenspende und Einfluß der Entnahmeverfahren auf ausgewählte rheologische Laborparameter und in-vivo-Mikrozirkulation des Spenders
T1  - Comparison of the rheological quality of red cell concentrates extracted from conventional whole blood donation or multicomponent apheresis and examination of the influence of the extraction method on selected rheological laboratory parameters and in-vivo microcirculation of the donor
N2  - 20 Probanden nahmen im prospektiven Paarvergleich im Abstand von mindestens 8 Wochen im cross-over-Verfahren an je einer Vollblutspende (VBS) und einer maschinellen Multikomponentenspende (MKS) teil. Die erzeugten leukozyten-depletierten Erythrozytenkonzentrate beider Gruppen wurden mittels CPD-50 antikoaguliert und über einen Zeitraum von 63 Tagen in PAGGS-Mannitol gelagert. Beurteilt wurden zum einen rheologische in-vitro-Parameter bei Spendern und Blutkonserven in zweiwöchentlichen Abständen: oszillierende Kapillarviskosimetrie, Erythrozytenaggregometrie und Filtrometrie. Zudem kam bei den Maschinenspendern die neue Methode der Laser-Doppler-Anemometrie zur Ermittlung der kapillären in-vivo-Blutflußgeschwindigkeit in Einzelkapillaren zur Anwendung. Konkordant kam es in beiden Gruppen zum Ansteigen der viskösen Viskosität der Erythrozytenkonzentrate mit überproportionalem Anstieg nach 7 Wochen Lagerung. Die elastische Viskosität stieg ebenfalls in beiden Gruppen an, hier wurden in der Gruppe der Vollblutspender bereits zu Beginn deutlich höhere Werte gemessen, welche in der Vergleichsgruppe erst nach 49 Tagen erreicht wurden. Bei den Blutspendern konnten 24 Stunden nach Spende Veränderungen von visköser und elastischer Viskosität gezeigt werden, welche stark mit Erythrozytenanzahl, Hämoglobin und Hämatokrit korrelierten. Bei konstanten Werten der dynamischen Erythrozytenaggregation zeigte die statische Erythrozytenaggregation bei den Vollblutspenden nach drei Wochen eine Zunahme, in der MKS-Gruppe imponierte ein biphasisches Verhalten mit initialer Abnahme der Lichttransmission. Unabhängig vom Spendeverfahren, trat eine deutliche Abnahme der Filtrierbarkeit der Produkte in beiden Gruppen in den letzten beiden Lagerungswochen auf. Eindrucksvoll war die Reduktion der Filterokklusionsrate auf unter 40 % des Ausgangswertes durch Leukozytenfiltration vor der Lagerung. Bereits 1 Stunde nach der Spende konnten filtrometrische Veränderungen bei den Spendern gezeigt werden, das Signifikanzniveau wurde hier nur knapp verfehlt. Die Bestimmung der kapillären Blutflußgeschwindigkeit zeigte eine Stunde nach Spende eine deutliche Abnahme auf 81 % des Ausgangswertes (p=0,064) in der Gruppe der Maschinenspender. Dies wird als Ausdruck einer diskreten Kreislaufbelastung durch das Aphereseverfahren gewertet.
N2  - 20 test persons took part in the prospective pair-comparison at intervals of at least eight weeks in the cross-over method, consisting of one whole blood donation and one automated cytapheresis. The produced leukocyte-depleted red blood cell concentrates of both groups were anticoagulated via CPD-50 and stored in PAGGS-Mannitol for a period of 63 days. Rheological in-vitro parameters of the donors and the products were evaluated at intervals of two weeks: oscillating capillary viscosimetry, erythrocyte aggregometry and filtrometry. Furthermore the new method of laser-Doppler anemometry was implemented with the cytapheresis group in order to determine the capillary in-vivo blood flow velocity in single-capillaries. In both groups the viscous viscosity of the red blood cell concentrates increased by a disproportionately rise after seven weeks in storage. The elastic viscosity also increased in both groups. Notably higher values were gauged in the cytapheresis group already at the beginning, which were reached by the comparison group only after 49 days. 24 hours after the donation alterations of viscous and elastic viscosity of the donors’ blood could be observed, highly correlating with number of erythrocytes, hemoglobin and hematocrit. With the values of the dynamic erythrocyte aggregation remaining constant the static erythrocyte aggregation of whole blood donors showed an increase after three weeks. Within the automated cytapheresis group a biphasic behaviour with initial decrease of light transmission was noticeable. Independent of the donation method a significant decrease of the products’ filterability could be noted in both groups during the last two weeks in storage. The reduction of the clogging rate to below 40 % of the initial value by means of leukocyte filtration before putting the samples into storage was quite impressive. Filtrometric alterations within the donor groups could be verified only one hour after the donation. The level of significance was not reached here. In the automated cytapheresis group the capillary blood flow velocity showed a significant decrease to 81 % of its initial value (p=0,064) one hour after the donation. This is seen as the expression of a discrete strain on the donor’s circulation caused by the apheresis.
KW  - Blut
KW  - Erythrozyten
KW  - Rheologie
KW  - Apherese
KW  - Qualität
KW  - blood
KW  - erythrocyte
KW  - rheology
KW  - cytapheresis
KW  - quality
Y1  - 2002
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-6055
ER  - 
TY  - JOUR
A1  - Rayner, Christopher
A1  - Coleman, Jonathan R. I.
A1  - Purves, Kirstin L.
A1  - Hodsoll, John
A1  - Goldsmith, Kimberley
A1  - Alpers, Georg W.
A1  - Andersson, Evelyn
A1  - Arolt, Volker
A1  - Boberg, Julia
A1  - Bögels, Susan
A1  - Creswell, Cathy
A1  - Cooper, Peter
A1  - Curtis, Charles
A1  - Deckert, Jürgen
A1  - Domschke, Katharina
A1  - El Alaoui, Samir
A1  - Fehm, Lydia
A1  - Fydrich, Thomas
A1  - Gerlach, Alexander L.
A1  - Grocholewski, Anja
A1  - Hahlweg, Kurt
A1  - Hamm, Alfons
A1  - Hedman, Erik
A1  - Heiervang, Einar R.
A1  - Hudson, Jennifer L.
A1  - Jöhren, Peter
A1  - Keers, Robert
A1  - Kircher, Tilo
A1  - Lang, Thomas
A1  - Lavebratt, Catharina
A1  - Lee, Sang-hyuck
A1  - Lester, Kathryn J.
A1  - Lindefors, Nils
A1  - Margraf, Jürgen
A1  - Nauta, Maaike
A1  - Pané-Farré, Christiane A.
A1  - Pauli, Paul
A1  - Rapee, Ronald M.
A1  - Reif, Andreas
A1  - Rief, Winfried
A1  - Roberts, Susanna
A1  - Schalling, Martin
A1  - Schneider, Silvia
A1  - Silverman, Wendy K.
A1  - Ströhle, Andreas
A1  - Teismann, Tobias
A1  - Thastum, Mikael
A1  - Wannemüller, Andre
A1  - Weber, Heike
A1  - Wittchen, Hans-Ulrich
A1  - Wolf, Christiane
A1  - Rück, Christian
A1  - Breen, Gerome
A1  - Eley, Thalia C.
T1  - A genome-wide association meta-analysis of prognostic outcomes following cognitive behavioural therapy in individuals with anxiety and depressive disorders
JF  - Translational Psychiatry
N2  - Major depressive disorder and the anxiety disorders are highly prevalent, disabling and moderately heritable. Depression and anxiety are also highly comorbid and have a strong genetic correlation (r(g) approximate to 1). Cognitive behavioural therapy is a leading evidence-based treatment but has variable outcomes. Currently, there are no strong predictors of outcome. Therapygenetics research aims to identify genetic predictors of prognosis following therapy. We performed genome-wide association meta-analyses of symptoms following cognitive behavioural therapy in adults with anxiety disorders (n = 972), adults with major depressive disorder (n = 832) and children with anxiety disorders (n = 920; meta-analysis n = 2724). We (h(SNP)(2)) and polygenic scoring was used to examine genetic associations between therapy outcomes and psychopathology, personality and estimated the variance in therapy outcomes that could be explained by common genetic variants learning. No single nucleotide polymorphisms were strongly associated with treatment outcomes. No significant estimate of h(SNP)(2) could be obtained, suggesting the heritability of therapy outcome is smaller than our analysis was powered to detect. Polygenic scoring failed to detect genetic overlap between therapy outcome and psychopathology, personality or learning. This study is the largest therapygenetics study to date. Results are consistent with previous, similarly powered genome-wide association studies of complex traits.
KW  - Human behaviour
KW  - Personalized medicine
KW  - Prognostic markers
KW  - Psychiatric disorders
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225048
VL  - 9
IS  - 150
ER  - 
TY  - JOUR
A1  - Gottschalk, Michael G.
A1  - Richter, Jan
A1  - Ziegler, Christiane
A1  - Schiele, Miriam A.
A1  - Mann, Julia
A1  - Geiger, Maximilian J.
A1  - Schartner, Christoph
A1  - Homola, György A.
A1  - Alpers, Georg W.
A1  - Büchel, Christian
A1  - Fehm, Lydia
A1  - Fydrich, Thomas
A1  - Gerlach, Alexander L.
A1  - Gloster, Andrew T.
A1  - Helbig-Lang, Sylvia
A1  - Kalisch, Raffael
A1  - Kircher, Tilo
A1  - Lang, Thomas
A1  - Lonsdorf, Tina B.
A1  - Pané-Farré, Christiane A.
A1  - Ströhle, Andreas
A1  - Weber, Heike
A1  - Zwanzger, Peter
A1  - Arolt, Volker
A1  - Romanos, Marcel
A1  - Wittchen, Hans-Ulrich
A1  - Hamm, Alfons
A1  - Pauli, Paul
A1  - Reif, Andreas
A1  - Deckert, Jürgen
A1  - Neufang, Susanne
A1  - Höfler, Michael
A1  - Domschke, Katharina
T1  - Orexin in the anxiety spectrum: association of a HCRTR1 polymorphism with panic disorder/agoraphobia, CBT treatment response and fear-related intermediate phenotypes
JF  - Translational Psychiatry
N2  - Preclinical studies point to a pivotal role of the orexin 1 (OX1) receptor in arousal and fear learning and therefore suggest the HCRTR1 gene as a prime candidate in panic disorder (PD) with/without agoraphobia (AG), PD/AG treatment response, and PD/AG-related intermediate phenotypes. Here, a multilevel approach was applied to test the non-synonymous HCRTR1 C/T Ile408Val gene variant (rs2271933) for association with PD/AG in two independent case-control samples (total n = 613 cases, 1839 healthy subjects), as an outcome predictor of a six-weeks exposure-based cognitive behavioral therapy (CBT) in PD/AG patients (n = 189), as well as with respect to agoraphobic cognitions (ACQ) (n = 483 patients, n = 2382 healthy subjects), fMRI alerting network activation in healthy subjects (n = 94), and a behavioral avoidance task in PD/AG pre- and post-CBT (n = 271). The HCRTR1 rs2271933 T allele was associated with PD/AG in both samples independently, and in their meta-analysis (p = 4.2 × 10−7), particularly in the female subsample (p = 9.8 × 10−9). T allele carriers displayed a significantly poorer CBT outcome (e.g., Hamilton anxiety rating scale: p = 7.5 × 10−4). The T allele count was linked to higher ACQ sores in PD/AG and healthy subjects, decreased inferior frontal gyrus and increased locus coeruleus activation in the alerting network. Finally, the T allele count was associated with increased pre-CBT exposure avoidance and autonomic arousal as well as decreased post-CBT improvement. In sum, the present results provide converging evidence for an involvement of HCRTR1 gene variation in the etiology of PD/AG and PD/AG-related traits as well as treatment response to CBT, supporting future therapeutic approaches targeting the orexin-related arousal system.
KW  - human behaviour
KW  - molecular neuroscience
KW  - personalized medicine
KW  - predictive markers
KW  - psychiatric disorders
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227479
VL  - 9
ER  -