Latest documents http://publikationen.stub.uni-frankfurt.de/index/index/ Wed, 21 Dec 2011 04:27:02 +0000 Wed, 21 Dec 2011 04:27:02 +0000 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23684 The research performed in the DeepThought project (http://www.project-deepthought.net) aims at demonstrating the potential of deep linguistic processing if added to existing shallow methods that ensure robustness. Classical information retrieval is extended by high precision concept indexing and relation detection. We use this approach to demonstrate the feasibility of three ambitious applications, one of which is a tool for creativity support in document production and collective brainstorming. This application is described in detail in this paper. Common to all three applications, and the basis for their development is a platform for integrated linguistic processing. This platform is based on a generic software architecture that combines multiple NLP components and on robust minimal recursive semantics (RMRS) as a uniform representation language. Hans Uszkoreit; Ulrich Callmeier; Andreas Eisele; Ulrich Schäfer; Melanie Siegel conferenceobject http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23684 Wed, 21 Dec 2011 04:27:02 +0000 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23654 The research performed in the DeepThought project aims at demonstrating the potential of deep linguistic processing if combined with shallow methods for robustness. Classical information retrieval is extended by high precision concept indexing and relation detection. On the basis of this approach, the feasibility of three ambitious applications will be demonstrated, namely: precise information extraction for business intelligence; email response management for customer relationship management; creativity support for document production and collective brainstorming. Common to these applications, and the basis for their development is the XML-based, RMRS-enabled core architecture framework that will be described in detail in this paper. The framework is not limited to the applications envisaged in the DeepThought project, but can also be employed e.g. to generate and make use of XML standoff annotation of documents and linguistic corpora, and in general for a wide range of NLP-based applications and research purposes. Ulrich Callmeier; Andreas Eisele; Ulrich Schäfer; Melanie Siegel conferenceobject http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/23654 Tue, 20 Dec 2011 02:50:29 +0000 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/22566 Background: Hypoxia inducible factor (HIF)-1 is the key transcriptional factor involved in the adaptation process of cells and organisms to hypoxia. Recent findings suggest that HIF-1 plays also a crucial role in inflammatory and infectious diseases. Methodology/Principal Findings: Using patient skin biopsies, cell culture and murine infection models, HIF-1 activation was determined by immunohistochemistry, immunoblotting and reporter gene assays and was linked to cellular oxygen consumption. The course of a S. aureus peritonitis was determined upon pharmacological HIF-1 inhibition. Activation of HIF-1 was detectable (i) in all ex vivo in biopsies of patients suffering from skin infections, (ii) in vitro using cell culture infection models and (iii) in vivo using murine intravenous and peritoneal S. aureus infection models. HIF-1 activation by human pathogens was induced by oxygen-dependent mechanisms. Small colony variants (SCVs) of S. aureus known to cause chronic infections did not result in cellular hypoxia nor in HIF-1 activation. Pharmaceutical inhibition of HIF-1 activation resulted in increased survival rates of mice suffering from a S. aureus peritonitis. Conclusions/Significance: Activation of HIF-1 is a general phenomenon in infections with human pathogenic bacteria, viruses, fungi and protozoa. HIF-1-regulated pathways might be an attractive target to modulate the course of life-threatening infections. Nadine Werth; Christiane Beerlage; Christian Rosenberger; Amir Sadegh Yazdi; Markus Edelmann; Amro Amr; Wanja Bernhardt; Christof von Eiff; Karsten Becker; Andrea Schäfer; Andreas Peschel; Volkhard A. J. Kempf article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/22566 Thu, 01 Sep 2011 16:05:31 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/6631 Mitochondrien sind die Kraftwerke unserer Zellen. In ihnen findet die Zellatmung statt, die unseren Körper mit lebenswichtiger Energie versorgt. Zusätzlich teilen sich die Zellorganellen und verschmelzen wieder miteinander im Minutentakt. Was aber passiert, wenn Teile dieses dynamischen Geflechts Defekte aufweisen? Die Antwort dazu könnte ein Protein sein, das auf zwei verschiedene Weisen in die Mitochondrien-Membranen eingebaut wird. Liegt keine kurze Form des Proteins vor, ist das ein Hinweis dafür, dass die Organellen defekt sind. Die Mitochondrien verbrennen die mit der Nahrung zugeführten Kohlenhydrate und Fette unter Verbrauch von Sauerstoff zu Kohlendioxid und Wasser. Bei diesem Vorgang, der Zellatmung, wird über eine Reihe von Proteinkomplexen ein elektrochemisches Potenzial aufgebaut, das zur Produktion des Energieträgers ATP (Adenosintriphosphat) genutzt wird. ATP kann aus den Mitochondrien abtransportiert werden und steht somit als eine Art Treibstoff für alle Stoffwechselprozesse zur Verfügung. Die Arbeit der Mitochondrien ist der Hauptgrund für unseren täglichen Sauerstoffbedarf. Außerdem tragen die Nano-Kraftwerke der Zelle dazu bei, unsere Körpertemperatur auf 37 °C aufrechtzuerhalten. Aufgrund dieser zentralen Funktionen ist es nicht verwunderlich, dass eine Reihe von Krankheiten beim Menschen durch den Funktionsverlust von Mitochondrien verursacht oder beeinflusst wird. Das sind in erster Linie neurologische oder muskuläre Erkrankungen, aber auch Diabetes, Fettleibigkeit, verschiedene Formen von Krebs und Alterungsprozesse. Folglich ist es von immenser Bedeutung zu verstehen, wie Mitochondrien funktionieren, wie sie ihre Funktionalität aufrechterhalten und gegebenenfalls repariert oder entsorgt werden können. Dem können wir am Wissenschaftsstandort Frankfurt hervorragend nachgehen, da sich einige international ausgewiesene Forschungsgruppen in den Fachbereichen Medizin, Biologie, Chemie und am Max-Planck-Institut für Biophysik mit verschiedenen Aspekten der mitochondrialen Biologie befassen. In zahlreichen interdisziplinären Kooperationen wird so versucht, dieses komplexe System besser zu verstehen. Anja Schäfer; Andreas Reichert article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/6631 Thu, 25 Jun 2009 08:59:17 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/17202 Adolph Gysenhard; Andreas Schäfer book http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/17202 Wed, 12 Sep 2007 10:20:29 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2379 An alternative theoretical description of axial electron channeling in the multi-GeV region has been developed. We solve a kinetic equation to evaluate an electron distribution function in axially oriented single crystals. Based on the single-string model, the required matrix elements for radiation and scattering by lattice vibrations are calculated employing solutions of the Dirac equation in cylindrical coordinates. Results obtained for 150-GeV electrons propagating along the 〈110〉 axis of germanium are in good agreement with experimental observations. Jürgen Augustin; Andreas Schäfer; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2379 Fri, 14 Jul 2006 10:41:26 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2376 We have investigated the channeling process of charged particles in a bent crystal. Invoking simple assumptions we derive a criterion, which determines whether channeling occurs or not. We obtain the same criterion using the Dirac equation. It is shown that the centrifugal force acting on the particle in the bent crystal significantly alters the effective transverse potential. The cases of axial and planar channeling are considered. The channeling probability and the dechanneling probability due to tunneling of the particle under the barrier in the effective transverse potential are estimated. These probabilities depend on the specific scaling parameter characterizing the process. Using the quasiclassical theory of synchrotron radiation we have calculated the contribution to the radiation spectrum, which arises due to the curvature of the channel. This contribution becomes significant to TeV electrons or positrons. Some practical consequences of our results are briefly discussed. Andrey V. Solov'yov; Andreas Schäfer; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2376 Fri, 14 Jul 2006 10:28:15 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2385 We discuss the prospects for parity-nonconservation experiments with highly charged heavy ions. Energy levels and parity mixing for heavy ions with 2–5 electrons are calculated. We investigate two-photon transitions and the possibility of observing interference effects between weak-matrix elements and Stark matrix elements for periodic electric field configurations. M. Maul; Andreas Schäfer; Walter Greiner; Paul Indelicato article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2385 Fri, 14 Jul 2006 10:17:31 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2406 The electron-positron pairs observed in heavy-ion collisions at Gesellschaft für Schwerionen-forschung Darmstadt mbH have been interpreted as the decay products of yet unknown particles with masses around 1.8 MeV. The negative results of resonant Bhabha scattering experiments, however, do not support such an interpretation. Therefore we focus on a more complex decay scenario, where the e+e- lines result from a two-collision process. We discuss the induced decay of a metastable 1++ state into e+e- pairs. For most realizations of a 1++ state such a decay in leading order can only take place in the Coulomb field of a target atom. This fact has the attractive consequence that for such a state the Bhabha bounds are no longer valid. However, the absolute value of the e+e- production cross section turns out to be unacceptably small. E. Stein; J. Reinhardt; Andreas Schäfer; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2406 Wed, 12 Jul 2006 10:14:06 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2405 We investigate the possibility that high-energy photons are channeled, when passing through an oriented single crystal, due to Delbrück scattering. For this purpose the exact electron propagator for the single-string model is constructed. Starting from a separation of variables, we solve the Dirac equation for a cylindrical electrostatic potential. The propagator for such external fields is constructed from solutions of the radial Dirac equation. This propagator is applied to a calculation of the S matrix for Delbrück scattering. We specify the conditions under which photon channeling takes place. Unfortunately these conditions are only matched for a very small fraction of those photons being produced by channeled electrons. J. Klenner; Jürgen Augustin; Andreas Schäfer; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2405 Wed, 12 Jul 2006 10:02:26 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2413 The Gottfried sum-rule violation reported by the New Muon Collaboration was interpreted as an indication for a flavor asymmetry of the sea quark in the nucleon. We investigate the alternative possibility that isospin symmetry between the proton and the neutron is breaking. We examine systematically the consequences of this possibility for several processes, namely, neutrino deep inelastic scattering, the charged pion Drell-Yan process, the proton Drell-Yan process, and semi-inclusive deep inelastic scattering, and conclude that a decision between the two alternative explanations is possible. Bo-Qiang Ma; Andreas Schäfer; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2413 Tue, 11 Jul 2006 10:45:36 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2429 Parity mixing of electron states should be extremely strong for heliumlike uranium. We calculate its size and discuss whether it could be determined experimentally. We analyze one specific scheme for such an experiment. The required laser intensities for two-photon spectroscopy of the 23P0–2 1S0level splitting is of the order of 1017 W/cm2. A determination of parity mixing would require at least 1021 W/cm2. Andreas Schäfer; G. Soff; P. Indelicato; B. Müller; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2429 Fri, 07 Jul 2006 15:13:42 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2436 We evaluate the Delbrück scattering amplitude to all orders of the interaction with the external field of a nucleus employing nonperturbative electron Green's functions. The results are given analytically in form of a multipole expansion. Alexander Scherdin; Andreas Schäfer; Walter Greiner; Gerhard Soff article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2436 Fri, 07 Jul 2006 12:04:09 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2462 We discuss the possibility that the line structure observed in the spectrum of the positrons produced in heavy ion collisions is due to the decay of a new neutral elementary particle. We argue that this can be ruled out unless one is willing to accept fine tuning of parameters, or to assume the dominance of nonlinear effects. J. Reinhardt; Andreas Schäfer; B. Müller; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2462 Mon, 03 Jul 2006 10:25:33 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2473 A new spontaneous-symmetry-breaking mechanism is formulated for SU(3), which is used to describe the formation of bags around quarks. The Higgs field is replaced by the scalar product of two colored fermion fields. This model gives mass only to one gluon (equivalent to Aμ8) when spontaneously broken. The consequences of this scheme are discussed, and it is argued that it can explain several puzzling high-energy heavy-ion experiments. Andreas Schäfer; B. Müller; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2473 Fri, 30 Jun 2006 13:13:38 +0200