Der Fachverband der Historiker und sein historischer Ort.: Dimensionen einer vergleichenden Verbandsgeschichte

The history of the German Historical Association is to evaluate and to write appropriate only in comparison with other scientific associations and academic cultures. This issue is dedicated to this transdisciplinary comparison of scientific associations and presents essays on the development of the German Sociological Association (Deutsche Gesellschaft für Soziologie), the German Association of German Studies (Deutscher Germanistenverband) and the American Studies Association

The proteome of the heterocyst cell wall in Anabaena sp. PCC 7120

Anabaena sp. PCC 7120 is a filamentous cyanobacterium that serves as a model to analyze prokaryotic cell differentiation, evolutionary development of plastids, and the regulation of nitrogen fixation. The cell wall is the cellular structure in contact with the surrounding medium. To understand the dynamics of the cell wall proteome during cell differentiation, the cell wall from Anabaena heterocysts was enriched and analyzed. In line with the recently proposed continuity of the outer membrane along the Anabaena filament, most of the proteins identified in the heterocyst cell-wall fraction are also present in the cell wall of vegetative cells, even though the lipid content of both membranes is different

Investigating communication networks contextually: Qualitative network analysis as cross-media research

This article introduces the approach of contextualised communication network analysis as a qualitative procedure for researching communicative relationships realised through the media. It combines qualitative interviews on media appropriation, egocentric network maps, and media diaries. Through the triangulation of these methods of data collection, it is possible to gain a differentiated insight into the specific meanings, structures and processes of communication networks across a variety of media. The approach is illustrated using a recent study dealing with the mediatisation of community building among young people. In this context, the qualitative communication network analysis has been applied to distinguish “localists” from “centrists”, “multilocalists”, and “pluralists”. These different “horizons of mediatised communitisation” are connected to distinct communication networks. Since this involves today a variety of different media, the contextual analysis of communication networks necessarily has to imply a cross-media perspective

A supersymmetric multicritical point in a model of lattice fermions

We study a model of spinless fermions with infinite nearest-neighbor repulsion on the square ladder which has microscopic supersymmetry. It has been conjectured that in the continuum the model is described by the superconformal minimal model with central charge c=3/2. Thus far it has not been possible to confirm this conjecture due to strong finite-size corrections in numerical data. We trace the origin of these corrections to the presence of unusual marginal operators that break Lorentz invariance, but preserve part of the supersymmetry. By relying mostly on entanglement entropy calculations with the density-matrix renormalization group, we are able to reduce finite-size effects significantly. This allows us to unambiguously determine the continuum theory of the model. We also study perturbations of the model and establish that the supersymmetric model is a multicritical point. Our work underlines the power of entanglement entropy as a probe of the phases of quantum many-body systems.Comment: 16 pages, 8 figure

Identification and characterization of Ca2+-activated K+ channels in granulosa cells of the human ovary

<p>Abstract</p> <p>Background</p> <p>Granulosa cells (GCs) represent a major endocrine compartment of the ovary producing sex steroid hormones. Recently, we identified in human GCs a Ca²⁺-activated K⁺channel (K_Ca) of big conductance (BK_Ca), which is involved in steroidogenesis. This channel is activated by intraovarian signalling molecules (e.g. acetylcholine) via raised intracellular Ca²⁺levels. In this study, we aimed at characterizing 1. expression and functions of K_Cachannels (including BK_Cabeta-subunits), and 2. biophysical properties of BK_Cachannels.</p> <p>Methods</p> <p>GCs were obtained from in vitro-fertilization patients and cultured. Expression of mRNA was determined by standard RT-PCR and protein expression in human ovarian slices was detected by immunohistochemistry. Progesterone production was measured in cell culture supernatants using ELISAs. Single channels were recorded in the inside-out configuration of the patch-clamp technique.</p> <p>Results</p> <p>We identified two K_Catypes in human GCs, the intermediate- (IK) and the small-conductance K_Ca(SK). Their functionality was concluded from attenuation of human chorionic gonadotropin-stimulated progesterone production by K_Cablockers (TRAM-34, apamin). Functional IK channels were also demonstrated by electrophysiological recording of single K_Cachannels with distinctive features. Both, IK and BK_Cachannels were found to be simultaneously active in individual GCs. In agreement with functional data, we identified mRNAs encoding IK, SK1, SK2 and SK3 in human GCs and proteins of IK and SK2 in corresponding human ovarian cells. Molecular characterization of the BK_Cachannel revealed the presence of mRNAs encoding several BK_Cabeta-subunits (beta2, beta3, beta4) in human GCs. The multitude of beta-subunits detected might contribute to variations in Ca²⁺dependence of individual BK_Cachannels which we observed in electrophysiological recordings.</p> <p>Conclusion</p> <p>Functional and molecular studies indicate the presence of active IK and SK channels in human GCs. Considering the already described BK_Ca, they express all three K_Catypes known. We suggest that the plurality and co-expression of different K_Cachannels and BK_Cabeta-subunits might allow differentiated responses to Ca²⁺signals over a wide range caused by various intraovarian signalling molecules (e.g. acetylcholine, ATP, dopamine). The knowledge of ovarian K_Cachannel properties and functions should help to understand the link between endocrine and paracrine/autocrine control in the human ovary.</p

Rotationally adiabatic pair interactions of para- and ortho-hydrogen with the halogen molecules F2, Cl2, and Br2

The present work is concerned with the weak interactions between hydrogen and halogen molecules, i.e., the interactions of pairs H2–X2 with X = F, Cl, Br, which are dominated by dispersion and quadrupole-quadrupole forces. The global minimum of the four-dimensional (4D) coupled cluster with singles and doubles and perturbative triples (CCSD(T)) pair potentials is always a T shaped structure where H2 acts as the hat of the T, with well depths (D e ) of 1.3, 2.4, and 3.1 kJ/mol for F2, Cl2, and Br2, respectively. MP2/AVQZ results, in reasonable agreement with CCSD(T) results extrapolated to the basis set limit, are used for detailed scans of the potentials. Due to the large difference in the rotational constants of the monomers, in the adiabatic approximation, one can solve the rotational Schrödinger equation for H2 in the potential of the X2 molecule. This yields effective two-dimensional rotationally adiabatic potential energy surfaces where pH2 and oH2 are point-like particles. These potentials for the H2–X2 complexes have global and local minima for effective linear and T-shaped complexes, respectively, which are separated by 0.4-1.0 kJ/mol, where oH2 binds stronger than pH2 to X2, due to higher alignment to minima structures of the 4D-pair potential. Further, we provide fits of an analytical function to the rotationally adiabatic potentials

Formal verification of cryptographic security proofs

Verifying cryptographic security proofs manually is inherently tedious and error-prone. The game-playing technique for cryptographic proofs advocates a modular proof design where cryptographic programs called games are transformed stepwise such that each step can be analyzed individually. This code-based approach has rendered the formal verification of such proofs using mechanized tools feasible. In the first part of this dissertation we present Verypto: a framework to formally verify game-based cryptographic security proofs in a machine-assisted manner. Verypto has been implemented in the Isabelle proof assistant and provides a formal language to specify the constructs occurring in typical cryptographic games, including probabilistic behavior, the usage of oracles, and polynomial-time programs. We have verified the correctness of several game transformations and demonstrate their applicability by verifying that the composition of 1-1 one-way functions is one-way and by verifying the IND-CPA security of the ElGamal encryption scheme. In a related project Barthe et al. developed the EasyCrypt toolset, which employs techniques from automated program verification to validate game transformations. In the second part of this dissertation we use EasyCrypt to verify the security of the Merkle-Damgård construction - a general design principle underlying many hash functions. In particular we verify its collision resistance and prove that it is indifferentiable from a random oracle.Kryptographische Sicherheitsbeweise manuell zu überprüfen ist mühsam und fehleranfällig. Spielbasierte Beweistechniken ermöglichen einen modularen Beweisaufbau, wobei kryptographische Programme - sog. Spiele - schrittweise so modifiziert werden, dass jeder Schritt einzeln überprüfbar ist. Dieser code-basierte Ansatz erlaubt die computergestützte Verifikation solcher Beweise. Im ersten Teil dieser Dissertation präsentieren wir Verypto: ein System zur computergestützten formalen Verifikation spielbasierter kryptographischer Sicherheitsbeweise. Auf Grundlage des Theorembeweisers Isabelle entwickelt, bietet Verypto eine formale Sprache, mit der sich kryptographische Eigenheiten wie probabilistisches Verhalten, Orakelzugriffe und polynomielle Laufzeit ausdrücken lassen. Wir beweisen die Korrektheit verschiedener Spieltransformationen und belegen deren Anwendbarkeit durch die Verifikation von Beispielen: Wir zeigen, dass Kompositionen von 1-1 Einwegfunktionen auch einweg sind und dass die ElGamal Verschlüsselung IND-CPA sicher ist. In einem ähnlichen Projekt entwickelten Barthe et al. das EasyCrypt System, welches Spieltransformationen mit Methoden der Programmanalyse validiert. Im zweiten Teil dieser Dissertation verwenden wir EasyCrypt und verifizieren die Sicherheit der Merkle-Damgård Konstruktion - ein Designprinzip, das vielen Hashfunktionen zugrunde liegt. Wir zeigen die Kollisionsresistenz der Konstruktion und verifizieren, dass sie sich wie ein Zufallsorakel verhält

Identification of SAR Detected Targets on Sea in Near Real Time Applications for Maritime Surveillance

Remote sensing technologies are widely used in maritime surveillance applications. Nowadays, spaceborne Synthetic Aperture Radar (SAR) systems provide outstanding capabilities for target detection at sea for large areas independently from the weather conditions. The generated value added target detection product is composed by complementary information from the Automatic Identification System (AIS). Resulting information layers provides a more reliable picture on the maritime situation awareness. This paper describes the approach of SAR-AIS data fusion and its visualization means developed for Near Real Time (NRT) Applications for Maritime Situational Awareness by the Maritime Security Lab at the Ground Station in Neustrelitz, part DLR’s German Remote Sensing Data Center (DFD). Presented implementation is based on combination of many open source geospatial libraries and frameworks (e.g., GDAL/OGR, Geoserver, PostgresSQL) and shows their effectiveness in the context of complex automated data processing in the frame of NRT requirements