Monte Carlo Simulation of the Director Field of a Nematic Liquid Crystal with Three Elastic Coefficients

In this article, a Monte Carlo simulation is presented, which generates the equilibrium director field of a nematic liquid crystal under the influence of an external field and fixed boundary conditions. The liquid crystal is characterized by a set of directors on a spatially fixed lattice. The simulation is based on an expression for the Frank free energy with three elastic coefficients. The chosen discretisation conserves the nematic symmetry, which means n and - n are equivalent. The results for several Frederiks geometries with homogeneous and spatially modulated external fields are shown, as well as an investigation of a capillary with homeotropic boundary conditions. Further we compare our method with the Lebwohl-Lasher model and introduce an extension of the latter which distinguishes between splay-, twist-and bend-configurations.DFG, SFB 335, Anisotrope Fluid

Indium-Gallium Segregation in CuInx_{x}Ga1−x_{1-x}Se2_2: An ab initio based Monte Carlo Study

Thin-film solar cells with CuIn$_x$Ga$_{1-x}$Se$_2$ (CIGS) absorber are still far below their efficiency limit, although lab cells reach already 19.9%. One important aspect is the homogeneity of the alloy. Large-scale simulations combining Monte Carlo and density functional calculations show that two phases coexist in thermal equilibrium below room temperature. Only at higher temperatures, CIGS becomes more and more a homogeneous alloy. A larger degree of inhomogeneity for Ga-rich CIGS persists over a wide temperature range, which may contribute to the low observed efficiency of Ga-rich CIGS solar cells

A General Model of Mobile Environments: Simulation Support for Strategic Management Decisions

Since the ability of Workforce Management Systems to handle mobility induced challenges of mobile environments like data-communication cut-offs, reduced network bandwidth, and security concerns improved recently, the optimization efforts of mobile enterprises increasingly focus on the organizational setup of their mobile environment. This includes issues like, e.g., the dimension and staffing of regional subdivisions, qualification balance of the workforce, and resource allocation strategies. While this multitude of possible adjustment parameters for optimization prevents from the analytical prediction of organizational change efforts, simulation is a promising approach to analyze mobile environments and their change. In this work we present a formal model representing a generalization of mobile environments. This model can be utilized to examine the cost situation and performance of both real mobile enterprises and projected future development scenarios of such enterprises. The model is developed using colored petri nets (CPN) and the software suite CPN Tools. We show that our model is capable of predicting the outcomes of organizational change projects by the utilization of simulation and present a validation of our model based on real-world data of a German gas and power supply

Konfigurierbare Sicherheit für Java Laufzeitumgebungen

Bei der Entwicklung von Java-Applikationen stehen Entwicklern eine Reihe von Mechanismen zur Verfügung, unsichere Kommunikationskan¨ale mit Verschlüsselung abzusichern. Diese Techniken sind dann in der Regel tief im Programmcode verwoben. Für Sicherheitsadministratoren ist die Verwaltung dieser Programme dann oft nicht einfach. Die Ergebnisse dieser Arbeit ermöglichen es, die von Anwendungen genutzten Sicherheitsdienste unabhängig von der Software-Entwicklung erst zum Zeitpunkt der Installation hinzuzufügen und zu konfigurieren. Dadurch wird die Anwendungsentwicklung von Sicherheitsaspekten befreit, was eine Verringerung von Aufwand und möglichen Fehlerquellen verspricht. Sicherheitsmerkmale können so auch nachträglich zu Anwendungen hinzugefügt werden, wobei die Benutzung und die Parametrisierung sämtlicher Sicherheitsdienste für jede Installation individuell festgelegt werden können. Das Java-Sicherheitsmodell wird so erweitert, dass nicht nur die Zugriffskontrolle, sondern auch weitere Sicherheitsmechanismen in einer Sicherheitspolitik definiert werden können und nicht bei der Entwicklung von Anwendungen vorgegeben werden müssen. Beispielsweise kann für Dateien oder Netzverbindungen neben den Zugriffsberechtigungen auch eine Verschlüsselung oder Integritätsprüfung konfiguriert werden. Dazu wurde eine Bibliothek von Klassen entwickelt, die in Verbindung mit einer für diese Zwecke weiterentwickelten Java Virtual Machine eingesetzt werden kann und die erforderliche Funktionalität bietet. Dabei wurden einerseits existierende Sicherheitsdienste eingebunden, andererseits aber auch neue Funktionalität zu dieser Bibliothek hinzugefügt

Phase-field-crystal models for condensed matter dynamics on atomic length and diffusive time scales: an overview

Here we review the basic concepts and applications of the phase-field-crystal (PFC) method, which is one of the latest simulation methodologies in materials science for problems, where atomic- and microscales are tightly coupled. The PFC method operates on atomic length and diffusive time scales, and thus constitutes a computationally efficient alternative to molecular simulation methods. Its intense development in materials science started fairly recently following the work by Elder et al. [Phys. Rev. Lett. 88 (2002), p. 245701]. Since these initial studies, dynamical density functional theory and thermodynamic concepts have been linked to the PFC approach to serve as further theoretical fundamentals for the latter. In this review, we summarize these methodological development steps as well as the most important applications of the PFC method with a special focus on the interaction of development steps taken in hard and soft matter physics, respectively. Doing so, we hope to present today’s state of the art in PFC modelling as well as the potential, which might still arise from this method in physics and materials science in the nearby future

Aging is associated with positive responding to neutral information but reduced recovery from negative information

Studies on aging and emotion suggest an increase in reported positive affect, a processing bias of positive over negative information, as well as increasingly adaptive regulation in response to negative events with advancing age. These findings imply that older individuals evaluate information differently, resulting in lowered reactivity to, and/or faster recovery from, negative information, while maintaining more positive responding to positive information. We examined this hypothesis in an ongoing study on Midlife in the US (MIDUS II) where emotional reactivity and recovery were assessed in a large number of respondents (N = 159) from a wide age range (36–84 years). We recorded eye-blink startle magnitudes and corrugator activity during and after the presentation of positive, neutral and negative pictures. The most robust age effect was found in response to neutral stimuli, where increasing age is associated with a decreased corrugator and eyeblink startle response to neutral stimuli. These data suggest that an age-related positivity effect does not essentially alter the response to emotion-laden information, but is reflected in a more positive interpretation of affectively ambiguous information. Furthermore, older women showed reduced corrugator recovery from negative pictures relative to the younger women and men, suggesting that an age-related prioritization of well-being is not necessarily reflected in adaptive regulation of negative affect

Phase-field-crystal models for condensed matter dynamics on atomic length and diffusive time scales: an overview

Here, we review the basic concepts and applications of the phase-field-crystal (PFC) method, which is one of the latest simulation methodologies in materials science for problems, where atomic- and microscales are tightly coupled. The PFC method operates on atomic length and diffusive time scales, and thus constitutes a computationally efficient alternative to molecular simulation methods. Its intense development in materials science started fairly recently following the work by Elder et al. [Phys. Rev. Lett. 88 (2002), p. 245701]. Since these initial studies, dynamical density functional theory and thermodynamic concepts have been linked to the PFC approach to serve as further theoretical fundaments for the latter. In this review, we summarize these methodological development steps as well as the most important applications of the PFC method with a special focus on the interaction of development steps taken in hard and soft matter physics, respectively. Doing so, we hope to present today's state of the art in PFC modelling as well as the potential, which might still arise from this method in physics and materials science in the nearby future.Comment: 95 pages, 48 figure

Haploidentical hematopoietic stem cell transplantation as individual treatment option in pediatric patients with very high-risk sarcomas

Background Prognosis of children with primary disseminated or metastatic relapsed sarcomas remains dismal despite intensification of conventional therapies including high-dose chemotherapy. Since haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is effective in the treatment of hematological malignancies by mediating a graft versus leukemia effect, we evaluated this approach in pediatric sarcomas as well. Methods Patients with bone Ewing sarcoma or soft tissue sarcoma who received haplo-HSCT as part of clinical trials using CD3+ or TCRα/β+ and CD19+ depletion respectively were evaluated regarding feasibility of treatment and survival. Results We identified 15 patients with primary disseminated disease and 14 with metastatic relapse who were transplanted from a haploidentical donor to improve prognosis. Three-year event-free survival (EFS) was 18,1% and predominantly determined by disease relapse. Survival depended on response to pre-transplant therapy (3y-EFS of patients in complete or very good partial response: 36,4%). However, no patient with metastatic relapse could be rescued. Conclusion Haplo-HSCT for consolidation after conventional therapy seems to be of interest for some, but not for the majority of patients with high-risk pediatric sarcomas. Evaluation of its future use as basis for subsequent humoral or cellular immunotherapies is necessary