Comparison of Calculations for the Hubbard model obtained with Quantum-Monte-Carlo, exact and stochastic Diagonalization

In this paper we compare numerical results for the ground state of the Hubbard model obtained by Quantum-Monte-Carlo simulations with results from exact and stochastic diagonalizations. We find good agreement for the ground state energy and superconducting correlations for both, the repulsive and attractive Hubbard model. Special emphasis lies on the superconducting correlations in the repulsive Hubbard model, where the small magnitude of the values obtained by Monte-Carlo simulations gives rise to the question, whether these results might be caused by fluctuations or systematic errors of the method. Although we notice that the Quantum-Monte-Carlo method has convergence problems for large interactions, coinciding with a minus sign problem, we confirm the results of the diagonalization techniques for small and moderate interaction strengths. Additionally we investigate the numerical stability and the convergence of the Quantum-Monte-Carlo method in the attractive case, to study the influence of the minus sign problem on convergence. Also here in the absence of a minus sign problem we encounter convergence problems for strong interactions.Comment: 24 pages, 9 figure

Archaeological Analysis of an Early Mississippian Frontier Structure in Southwestern Virginia

Ely Mound (44LE12) is a significant prehistoric frontier site located in Lee County, Virginia. Frontier sites are important in understanding processes of cultural hybridity and the formation of social hierarchies. Through an analysis of artifacts recovered from a household structure during a 2019 excavation, this research explores Ely’s function on the Mississippian cultural frontier, and discusses its relationship to the Carter Robinson site located within the county (44LE10). Finally, I conclude that the occupants of Ely Mound were a local people engaging with select Mississipian cultural practices and suggest that this site could be an example of Mississippianization

Critical Current in the High-T_c Glass model

The high-T_c glass model can be combined with the repulsive tt'--Hubbard model as microscopic description of the striped domains found in the high-T_c materials. In this picture the finite Hubbard clusters are the origin of the d-wave pairing. In this paper we show, that the glass model can also explain the critical currents usually observed in the high-T_c materials. We use two different approaches to calculate the critical current densities of the high-T_c glass model. Both lead to a strongly anisotropic critical current. Finally we give an explanation, why we expect nonetheless a nearly perfect isotropic critical current in the high-T_c superconductors.Comment: 8 pages with 5 eps-figures, LaTeX using RevTeX, accepted by Int.J.Mod.Phys.

The Role of Cognition in Oral & Written Transmission as Demonstrated in Ritual Chant

This thesis examines the role of cognition in oral and written transmission. It looks at areas of music history where cognition is already used as a reference, including the development of notation, trends and changes in oral transmission, and performance practice. The thesis examines three different case studies on ritual chant in order to demonstrate how the cognitive process can be used to explain the ways learning, retention, and transmission work in oral and written transmission. The first case study is on the chant practices originating in Jerusalem. It discusses the intervallic relationships and music patterns involved in retention of chant, using pitch hierarchy and grouping structure. The second case study is on the Ethiopian Christian chant tradition. It illustrates how shared cognitive processes between oral and written traditions can help explain the ways oral and written traditions work together in preserving ritual. The last case study is on African and Afro-Cuban rituals derived from a common ancestor. It explores sound symbolism and the phonetics of language in chant, and how they work to maintain a stable ritual tradition. The study concludes that cognition plays a greater role in studying oral and written transmission than has been recognized heretofore in historical scholarship

Parallelization of the exact diagonalization of the t-t'-Hubbard model

We present a new parallel algorithm for the exact diagonalization of the $t-t'$-Hubbard model with the Lanczos-method. By invoking a new scheme of labeling the states we were able to obtain a speedup of up to four on 16 nodes of an IBM SP2 for the calculation of the ground state energy and an almost linear speedup for the calculation of the correlation functions. Using this algorithm we performed an extensive study of the influence of the next-nearest hopping parameter $t'$ in the $t-t'$-Hubbard model on ground state energy and the superconducting correlation functions for both attractive and repulsive interaction.Comment: 18 Pages, 1 table, 8 figures, Latex uses revtex, submitted to Comp. Phys. Com

Glass Model, Hubbard Model and High-Temperature Superconductivity

In this paper we revisit the glass model describing the macroscopic behavior of the High-Temperature superconductors. We link the glass model at the microscopic level to the striped phase phenomenon, recently discussed widely. The size of the striped phase domains is consistent with earlier predictions of the glass model when it was introduced for High-Temperature Superconductivity in 1987. In an additional step we use the Hubbard model to describe the microscopic mechanism for d-wave pairing within these finite size stripes. We discuss the implications for superconducting correlations of Hubbard model, which are much higher for stripes than for squares, for finite size scaling, and for the new view of the glass model picture.Comment: 7 pages, 7 figures (included), LaTex using Revtex, accepted by Int. J. Mod. Phys.

Material in Skulptur, Plastik und Objektkunst in Österreich zwischen 1945 und heute

Die vorliegende Diplomarbeit widmet sich dem Thema des Materials in der Skulptur, der Plastik sowie der Objektkunst in Österreich und behandelt den Zeitraum zwischen 1945 und der Gegenwart. Die unterschiedlichen Materialien, ihre Möglichkeiten der Verwendung sowie ihre Stellung im Kontext der Kunst werden untersucht, nachdem die Möglichkeiten der Materialwahl der dreidimensionalen Kunst gerade in den letzten Jahrzehnten maßgeblich erweitert wurden. Anhand von konkreten Künstlerbeispielen, wird das Material, seine verschiedenartige Anwendung und die daraus resultierenden Ausdrucksmöglichkeiten in der österreichischen Skulptur, Plastik und Objektkunst untersucht. Die Konzentration auf ausgewählte Positionen österreichischer Kunst ab 1945 hilft hierbei eine Eingrenzung der vielfältigen Themen durchzuführen. Der erste Teil der Arbeit behandelt die theoretische Auseinandersetzung mit dem Material und seiner Ästhetik. In der Folge wird der Versuch unternommen die Entwicklung, die das Material im chronologischen Verlauf der Kunstgeschichte genommen hat, in Form eines groben Überblickes nach zu zeichnen. Eine spezifische Auswahl von Positionen österreichischer Künstler und Künstlerinnen seit 1945, soll den unterschiedlichen Zu- und Umgang mit dem Material in der dreidimensionalen Kunst zunächst auf einer regionalen Ebene aufzeigen. Satz gelöscht In diesem Zusammenhang bildet das Werk von Fritz Wotruba den Ausgangspunkt für die bildhauerische Entwicklung nach 1945. Das Material in der Skulptur, Plastik und Objektkunst nach 1945 umfasst ein weites Spektrum an Möglichkeiten, wozu neben dem traditionellen Material Stein auch Abfallmaterial, die neuesten synthetisch entwickelten Kunststoffe – Plexiglas, Schaumstoff, Polyester – sowie Pappmaché, Gips, Mullbinden, Staub und vieles mehr zählen. Entscheidend für die Veränderung des Materialgebrauchs ist der zunehmend konzeptuelle Ansatz in der Kunst seit Anfang der 1960er Jahre. So wurde das Material etwa bei Valie Export, Franz West, später bei Erwin Wurm sowie Gelitin, um den menschlichen Körper als autonomen künstlerischen Werkstoff erweitert, der zum Ergänzer bzw. Vollender der Skulptur wurde und in weiterer Folge auch um die technischen Medien der Fotografie, des Films und des Videos, die selbst zur Skulptur wurden. Abschließend werden die österreichischen Künstlerpositionen in Form eines Vergleiches in einen internationalen Kontext gestellt, um die spezifischen Veränderungen im Umgang mit dem Material auch über die Grenzen Österreichs hinaus, hinsichtlich der Materialauswahl und Materialbehandlung zu kontextualisieren

THE INFLUENCE OF OXYTOCIN ON THE PRODUCTION OF PROSTAGLANDINS IN VITRO AND IN VIVO

Peer Reviewe

Simulation of the HIV-1 Vpu transmembrane domain as a pentameric bundle

AbstractThe transmembrane domain of oligomeric protein Vpu encoded by HIV-1 has been studied by means of a molecular dynamics simulation. A pentameric bundle of unconstrained helices (residues 6–28 of Vpu) with a water filled pore was initially assembled in a membrane mimetic octane/water system. This system was simulated, using the CHARMm19 and OPLS united atom force fields with no constraints at a temperature of 300 K and a pressure of 1 atm. For these forcefields and the initial conditions tested, the oligomeric bundle expelled most of the pore water molecules. The resulting bundle and residual waters adopt a conical structural motif with some resemblance to a potassium channel

Action Recognition in Video Recordings from Gynecologic Laparoscopy

Action recognition is a prerequisite for many applications in laparoscopic video analysis including but not limited to surgical training, operation room planning, follow-up surgery preparation, post-operative surgical assessment, and surgical outcome estimation. However, automatic action recognition in laparoscopic surgeries involves numerous challenges such as (I) cross-action and intra-action duration variation, (II) relevant content distortion due to smoke, blood accumulation, fast camera motions, organ movements, object occlusion, and (III) surgical scene variations due to different illuminations and viewpoints. Besides, action annotations in laparoscopy surgeries are limited and expensive due to requiring expert knowledge. In this study, we design and evaluate a CNN-RNN architecture as well as a customized training-inference framework to deal with the mentioned challenges in laparoscopic surgery action recognition. Using stacked recurrent layers, our proposed network takes advantage of inter-frame dependencies to negate the negative effect of content distortion and variation in action recognition. Furthermore, our proposed frame sampling strategy effectively manages the duration variations in surgical actions to enable action recognition with high temporal resolution. Our extensive experiments confirm the superiority of our proposed method in action recognition compared to static CNNs