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Horsley R.,University of Edinburgh | Nakamura Y.,University of Regensburg | Nakamura Y.,University of Tsukuba | Pleiter D.,German Electron Synchrotron | And 8 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

By determining the quark momentum fractions of the octet baryons from Nf=2+1 lattice simulations, we are able to predict the degree of charge symmetry violation in the parton distribution functions of the nucleon. This is of importance, not only as a probe of our understanding of the nonperturbative structure of the proton, but also because such a violation constrains the accuracy of global fits to parton distribution functions and hence the accuracy with which, for example, cross sections at the LHC can be predicted. A violation of charge symmetry may also be critical in cases where symmetries are used to guide the search for physics beyond the standard model. © 2011 American Physical Society.

Ehrig H.,TU Berlin | Golas U.,Konrad Zuse Zentrum fur Informationstechnik | Habel A.,University of Oldenburg | Lambers L.,University of Potsdam | Orejas F.,Polytechnic University of Catalonia
Fundamenta Informaticae | Year: 2012

Graph transformation systems have been studied extensively and applied to several areas of computer science like formal language theory, the modeling of databases, concurrent or distributed systems, and visual, logical, and functional programming. In most kinds of applications it is necessary to have the possibility of restricting the applicability of rules. This is usually done by means of application conditions. In this paper, we continue the work of extending the fundamental theory of graph transformation to the case where rules may use arbitrary (nested) application conditions. More precisely, we generalize the Embedding theorem, and we study how local confluence can be checked in this context. In particular, we define a new notion of critical pair which allows us to formulate and prove a Local Confluence Theorem for the general case of rules with nested application conditions. All our results are presented, not for a specific class of graphs, but for any arbitrary ℳ-adhesive category, which means that our results apply to most kinds of graphical structures. We demonstrate our theory on the modeling of an elevator control by a typed graph transformation system with positive and negative application conditions. © 2012 IOS Press.

Plattner A.,ETH Zurich | Maurer H.R.,ETH Zurich | Vorloeper J.,Ruhr West University of Applied Sciences | Blome M.,Konrad Zuse Zentrum fur Informationstechnik
Geophysical Journal International | Year: 2012

We present a novel adaptive model parametrization strategy for the 3-D electrical resistivity tomography problem and demonstrate its capabilities with a series of numerical examples. In contrast to traditional parametrization schemes, which are based on fixed disjoint blocks, we discretize the subsurface in terms of Haar wavelets and adaptively adjust the parametrization as the iterative inversion proceeds. This results in a favourable balance of cell sizes and parameter reliability, that is, in regions where the data constrain the subsurface properties well, our parametrization strategy leads to a fine grid, whereas poorly resolved areas are represented only by a few large blocks. This is documented with eigenvalue analyses and by computing model resolution matrices. During the initial iteration steps, only a few model parameters are involved, which reduces the risk that the regularization dominates the inversion. The algorithm also automatically accounts for non-linear effects caused by pronounced conductivity contrasts. Inside conductive features a finer grid is generated than inside more resistive structures. The automated parameter adaptation is computationally efficient, because the coarsening and refinement subroutines have a nearly linear numerical complexity with respect to the number of model parameters. Because our approach is not tightly coupled to electrical resistivity tomography, it should be straightforward to adapt it to other data types. © 2012 The Author Geophysical Journal International © 2012 RAS.

Yan H.-D.,TU Braunschweig | Lemmens P.,TU Braunschweig | Ahrens J.,TU Braunschweig | Broring M.,TU Braunschweig | And 6 more authors.
Wuli Xuebao/Acta Physica Sinica | Year: 2012

Au nanowire arrays with high aspect ratios are prepared in anode aluminum oxide templates by electrochemical deposition. The obtained structures are investigated by scanning Auger microscopy. Surface plasmon resonances of Au nanowire arrays induce a transverse mode (T mode) and a longitudinal mode (L mode) in the optical absorption, which indicates the strong anisotropy of the Au nanowires. The L mode intensity is related to the angle and polarization of the incident light. The L mode position shows a shift with the increase of aspect ratio of the nanowires. The plasmon coupling between Au nanowires is compared with the H-aggregation of organic chromophores. The blue shift of the L mode in the arrays compared with a single nanowire is induced by multi-coupling of the electromagnetic field between neighbouring nanowires. A finite element method is used to simulate the electric field distributions of a single Au nanowire and an array of plasmonically coupled wires. © 2012 Chinese Physical Society.

Fasting C.,Free University of Berlin | Schalley C.A.,Free University of Berlin | Weber M.,Konrad Zuse Zentrum fur Informationstechnik | Seitz O.,Humboldt University of Berlin | And 6 more authors.
Angewandte Chemie - International Edition | Year: 2012

Multivalent interactions can be applied universally for a targeted strengthening of an interaction between different interfaces or molecules. The binding partners form cooperative, multiple receptor-ligand interactions that are based on individually weak, noncovalent bonds and are thus generally reversible. Hence, multi- and polyvalent interactions play a decisive role in biological systems for recognition, adhesion, and signal processes. The scientific and practical realization of this principle will be demonstrated by the development of simple artificial and theoretical models, from natural systems to functional, application-oriented systems. In a systematic review of scaffold architectures, the underlying effects and control options will be demonstrated, and suggestions will be given for designing effective multivalent binding systems, as well as for polyvalent therapeutics. Unified strength: Multivalent structures function in a number of biological systems to generate a strong but reversible interaction between two objects. The chemical realization of this natural principle with organized multiple interactions enables, for example, the development of multivalent drugs for an effective inhibition of viral cell attachment. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kramer T.,Konrad Zuse Zentrum fur Informationstechnik | Kramer T.,Harvard University | Noack M.,Konrad Zuse Zentrum fur Informationstechnik
Astrophysical Journal Letters | Year: 2016

The Rosetta probe around comet 67P/Churyumov-Gerasimenko (67P) reveals an anisotropic dust distribution of the inner coma with jet-like structures. The physical processes leading to jet formation are under debate, with most models for cometary activity focusing on localized emission sources, such as cliffs or terraced regions. Here we suggest, by correlating high-resolution simulations of the dust environment around 67P with observations, that the anisotropy and the background dust density of 67P originate from dust released across the entire sunlit surface of the nucleus rather than from few isolated sources. We trace back trajectories from coma regions with high local dust density in space to the non-spherical nucleus and identify two mechanisms of jet formation: areas with local concavity in either two dimensions or only one. Pits and craters are examples of the first case; the neck region of the bi-lobed nucleus of 67P is an example of the latter case. The conjunction of multiple sources, in addition to dust released from all other sunlit areas, results in a high correlation coefficient (∼0.8) of the predictions with observations during a complete diurnal rotation period of 67P. © 2016. The American Astronomical Society. All rights reserved.

Kramer T.,Konrad Zuse Zentrum fur Informationstechnik | Kramer T.,Harvard University | Noack M.,Konrad Zuse Zentrum fur Informationstechnik
Astrophysical Journal Letters | Year: 2015

Dust transport and deposition behind larger boulders on the comet 67P/Churyumov-Gerasimenko (67P/C-G) have been observed by the Rosetta mission. We present a mechanism for dust-transport vectors based on a homogeneous surface activity model incorporating in detail the topography of 67P/C-G. The combination of gravitation, gas drag, and Coriolis force leads to specific dust transfer pathways, which for higher dust velocities fuel the near-nucleus coma. By distributing dust sources homogeneously across the whole cometary surface, we derive a global dust-transport map of 67P/C-G. The transport vectors are in agreement with the reported wind-tail directions in the Philae descent area. © 2015. The American Astronomical Society. All rights reserved.

Lamas-Rodriguez J.,University of Santiago de Compostela | Heras D.B.,University of Santiago de Compostela | Arguello F.,University of Santiago de Compostela | Kainmueller D.,Konrad Zuse Zentrum fur Informationstechnik | And 2 more authors.
Journal of Real-Time Image Processing | Year: 2013

The level-set method, a technique for the computation of evolving interfaces, is a solution commonly used to segment images and volumes in medical applications. GPUs have become a commodity hardware with hundreds of cores that can execute thousands of threads in parallel, and they are nowadays ideal platforms to execute computational intensive tasks, such as the 3D level-set-based segmentation, in real time. In this paper, we propose two GPU implementations of the level-set-based segmentation method called Fast Two-Cycle. Our proposals perform computations in independent domains called tiles and modify the structure of the original algorithm to better exploit the features of the GPU. The implementations were tested with real images of brain vessels and a synthetic MRI image of the brain. Results show that they execute faster than a CPU-sequential implementation of the same method, without any significant loss of the segmentation quality and without requiring distributed parallel computer infrastructures. © 2013 Springer-Verlag Berlin Heidelberg.

Fugenschuh A.,Konrad Zuse Zentrum fur Informationstechnik | Gausemeier P.,TU Berlin | Seliger G.,TU Berlin | Severengiz S.,TU Berlin
Lecture Notes in Business Information Processing | Year: 2010

Scenario technique is a tool to reveal the knowledge of an expert group about possible and consistent scenarios of the future. The current use of this technique suffers from an inflexibility of the available software. To overcome this shortage, the core part of this solver, i.e. the scenario generation phase, has to be re-implemented. It is demonstrated that this problem can be formulated as an integer linear programming problem. To find all feasible solutions the solver SCIP was adapted. The solutions are then clustered and these clusters are verbally described. The approach is demonstrated by using data from the research project remanufacturing oriented production equipment development, in which scenarios for sustainable value creation were identified and described. © 2010 Springer-Verlag.

PubMed | Konrad Zuse Zentrum fur Informationstechnik
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2012

Multivalent ligand-receptor systems often show an enhancement in binding compared to the constituent monovalent systems. This cooperativity effect is often attributed to the favorable spatial preorganisation of the ligands by the connecting spacer that leads to a reduction of entropy loss at ligand binding. A different factor that has been proposed to contribute to the cooperativity effect is rebinding: As soon as a single ligand-receptor complex dissociates, the presence of another ligand on coat-tails will increase the probability of another binding event, which in turn will drive the system to a state where all ligands are bound. In this article, we derive a first quantitative description of the rebinding effect. In order to model the inherent memory effect of a spacer-connected system, we pursue a mathematical approach based on Markov state models and conformation dynamics. The theoretical investigations are illustrated by studying different prototypic ligand-receptor systems.

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