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Aachen, Germany

RWTH Aachen University is a research university of technology located in Aachen, North Rhine-Westphalia, Germany. With over 40,000 students enrolled in 130 study programs, it is the largest technical university in Germany. The institution maintains close links to industry and accounts for the highest amount of third-party funds of all German universities in both absolute and relative terms per faculty member.In 2007, RWTH Aachen was chosen by DFG as one of nine German Universities of Excellence for its future concept RWTH 2020: Meeting Global Challenges and additionally won funding for one graduate school and three clusters of excellence. In 2012, RWTH Aachen was selected again as a University of Excellence and altogether financially endowed for one graduate school and two clusters of excellence. RWTH Aachen is one of only six German universities to retain this status from the previous funding period of 2007 - 2012.RWTH Aachen is a founding member of IDEA League, a strategic alliance of five leading universities of technology in Europe. The university is also a member of TU9, DFG and the Top Industrial Managers for Europe network. Wikipedia.


Dynamic recrystallization (DRX) is widely used in industrial hot working processes to control the microstructure and properties of the workpiece and to keep the forming forces low. For the analysis and design of metal forming processes powerful simulation methods, must notably the Finite Element (FE) method, have been developed. Various models are available that consider the coupled evolution of microstructure and flow stress during hot deformation processes. Some of these models have been implemented into FE codes and are widely available now. However, for the implementation of flow stress models incorporating DRX into an FE formulation, special smoothness requirements exist that are not automatically fulfilled by the available flow stress models. This work reviews some conditions that a flow stress model incorporating DRX has to fulfill in order to be consistently embedded into an FE code for large plastic deformation. A specific Sellars-type model is analyzed for consistency with these conditions. It is shown that the use of a classical JMAK equation for the DRX kinetics within these models is problematic for Avrami exponents smaller than or equal to 3, for which the flow stress model is not sufficiently smooth. DRX kinetics based on the work of Cahn are proposed to remedy the differentiability issues. © (2013) Trans Tech Publications, Switzerland. Source


Huckelhoven R.,TU Munich | Panstruga R.,RWTH Aachen | Panstruga R.,Max Planck Institute for Plant Breeding Research
Current Opinion in Plant Biology | Year: 2011

Powdery mildew fungi represent a paradigm for obligate biotrophic parasites, which only propagate in long-lasting intimate interactions with living host cells. These highly specialized phytopathogens induce re-organization of host cell architecture and physiology for their own demands. This probably includes the corruption of basal host cellular functions for successful fungal pathogenesis. Recent studies revealed secretory processes by both interaction partners as key incidents of the combat at the plant-fungus interface. The analysis of cellular events during plant-powdery mildew interactions may not only lead to a better understanding of plant pathological features, but may also foster novel discoveries in the area of plant cell biology. © 2011 Elsevier Ltd. Source


Vinogradova O.I.,RWTH Aachen | Belyaev A.V.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Journal of Physics Condensed Matter | Year: 2011

We discuss how the wettability and roughness of a solid impacts its hydrodynamic properties. We see in particular that hydrophobic slippage can be dramatically affected by the presence of roughness. Owing to the development of refined methods for setting very well controlled micro-or nanotextures on a solid, these effects are being exploited to induce novel hydrodynamic properties, such as giant interfacial slip, superfluidity, mixing and low hydrodynamic drag, that could not be achieved without roughness. © 2011 IOP Publishing Ltd. Source


Dewald U.,Karlsruhe Institute of Technology | Fromhold-Eisebith M.,RWTH Aachen
Environmental Innovation and Societal Transitions | Year: 2015

This paper proposes that spatial dynamics of new environmental technologies can be better understood when positioned in a multi-scalar theoretical framework based on innovation system approaches. We combine territorial innovation system concepts with a technological innovation systems (TIS) perspective. The investigation of photovoltaic (PV) technology in Germany indicates that the relevance of different scales and actor constellations shifts in the course of a 'maturing' innovation system. First, the convergence of regional and institutional subsystems forms a temporary window of opportunity for a robust TIS formation within a national framing. Second, consolidation according to basic patterns of the underlying national innovation system takes place. This is illustrated by the robust performance of German mechanical PV equipment suppliers within a globalized PV value chain. The empirical findings allow for drafting a theoretical framework that offers a generalized view on this shifting spatial context pattern of an emerging environmental technology. © 2015 Elsevier B.V. All rights reserved. Source


Bindel J.R.,RWTH Aachen
Nature Physics | Year: 2016

As the Rashba effect is an electrically tunable spin–orbit interaction, it could form the basis for a multitude of applications, such as spin filters, spin transistors and quantum computing using Majorana states in nanowires. Moreover, this interaction can determine the spin dephasing and antilocalization phenomena in two dimensions. However, the real space pattern of the Rashba parameter, which critically influences spin transistors using the spin-helix state and the otherwise forbidden electron backscattering in topologically protected channels, is difficult to probe. Here, we map this pattern down to nanometre length scales by measuring the spin splitting of the lowest Landau level using scanning tunnelling spectroscopy. We reveal strong fluctuations correlated with the local electrostatic potential for an InSb inversion layer with a large Rashba coefficient (∼1 eV Å). This type of Rashba field mapping enables a more comprehensive understanding of its fluctuations, which might be decisive towards robust semiconductor-based spintronic devices. © 2016 Nature Publishing Group Source


Czakon M.,RWTH Aachen | Mitov A.,CERN
Journal of High Energy Physics | Year: 2013

We compute the next-to-next-to-leading order QCD correction to the total inclusive top pair production cross-section in the reaction qg→ tt+X. We find moderate O (1%) correction to central values at both Tevatron and LHC. The scale variation of the cross-section remains unchanged at the Tevatron and is significantly reduced at the LHC. We find that recently introduced approximation based on the high-energy limit of the top pair cross-section significantly deviates from the exact result. The results derived in the present work are included in version 1.4 of the program Top++. Work towards computing the reaction gg→ tt+X is ongoing. © 2013 SISSA. Source


Gamenara D.,University of the Republic of Uruguay | Dominguez De Maria P.,RWTH Aachen
Organic and Biomolecular Chemistry | Year: 2014

Adding value to organic synthesis. Novel imine reductases enable the enantioselective reduction of imines to afford optically active amines. Likewise, novel bioinspired artificial metalloenzymes can perform the same reaction as well. Emerging proof-of-concepts are herein discussed. © 2014 The Royal Society of Chemistry. Source


Dual P- and E-selectin-targeted microbubbles (MBs) have previously been used for ultrasonography (US) of acute inflammatory bowel disease in mice. In the study by Wang and colleagues, such dual-targeted MBs were evaluated in pigs. After induction of ileitis by means of 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)/ethanol installation, early inflammation, as well as mild and severe disease stages, could be distinguished. The molecularly targeted US method was characterized by high reproducibility and matched with histologic findings. This work is considered an important intermediate step in translating molecularly targeted US of inflammation from preclinical toward clinical application. Copyright © 2015 Radiological Society of North America. Source


Chenadec V.L.,Stanford University | Pitsch H.,Stanford University | Pitsch H.,RWTH Aachen
Journal of Computational Physics | Year: 2013

This paper presents a novel methodology for interface capturing in two-phase flows by combining a Lagrangian-Eulerian Volume-of-Fluid approach with a Level Set method. While the Volume-of-Fluid transport relies on a robust and accurate polyhedral library, any high-order Level Set transport may be used. The method is shown to be less restrictive in terms of CFL conditions than split Volume-of-Fluid methods. Various geometric integration schemes are proposed and tested. For linear velocity fields, mass error is shown to vanish, and to be third order otherwise. The method is validated on 2D and 3D test cases. Conservation properties are shown to be excellent, while geometrical accuracy remains satisfactory even for complex flows such as the primary breakup of a liquid jet. © 2012 Elsevier Inc. Source


Floege J.,RWTH Aachen
American Journal of Kidney Diseases | Year: 2011

Immunoglobulin A (IgA) nephropathy is the most common glomerulonephritis worldwide. For example, in Japan, full-blown IgA nephropathy has been detected in ∼1.5% of all allograft kidneys at the time of transplant. Genetic and environmental modifiers, as well as generic progression factors (eg, hypertension), must have a major role in determining who will become clinically overt and who will experience progression. In patients with clinically overt IgA nephropathy and/or progressive disease, it now is relatively well established that the pathogenesis involves 6 major steps: (1) Increased occurrence of IgA1 with poor galactosylation in the circulation. This might relate to the migration of mucosal B cells to bone marrow, where they produce "correct" poorly galactosylated IgA. Modulation of mucosal immunity may offer new therapeutic options. (2) Generation of IgG antibodies against poorly galactosylated IgA1. This could lay the foundation for immunosuppression, whereas detection of such IgG autoantibodies may accommodate the noninvasive monitoring of IgA nephropathy. (3) Mesangial deposition and/or formation of IgG-IgA1 or IgA1-IgA1 complexes. (4) Activation of mesangial IgA receptors and/or complement; both lend themselves to therapeutic interference. (5) Mesangial cell damage and activation of secondary pathways, such as overproduction of platelet-derived growth factor, which can be targeted specifically. (6) Activation of pathomechanisms that are not specific for IgA nephropathy and that drive glomerulosclerosis and tubulointerstitial fibrosis. Although at present our therapeutic armamentarium is still limited largely to supportive care and immunosuppression in some instances, these new insights can be expected to yield novel, perhaps individualized, therapeutic options in primary and recurrent IgA nephropathy. © 2011 National Kidney Foundation, Inc. All rights reserved. Source


Hille B.,RWTH Aachen
Progress in molecular biology and translational science | Year: 2014

G-protein-coupled receptors mediate responses to external stimuli in various cell types. We are interested in the modulation of KCNQ2/3 potassium channels by the Gq-coupled M1 muscarinic (acetylcholine) receptor (M1R). Here, we describe development of a mathematical model that incorporates all known steps along the M1R signaling cascade and accurately reproduces the macroscopic behavior we observe when KCNQ2/3 currents are inhibited following M1R activation. Gq protein-coupled receptors of the plasma membrane activate phospholipase C (PLC) which cleaves the minor plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) into the second messengers diacylgycerol and inositol 1,4,5-trisphosphate, leading to calcium release, protein kinase C (PKC) activation, and PI(4,5)P2 depletion. Combining optical and electrical techniques with knowledge of relative abundance of each signaling component has allowed us to develop a kinetic model and determine that (i) M1R activation and M1R/Gβ interaction are fast; (ii) Gαq/Gβ separation and Gαq/PLC interaction have intermediate time constants; (iii) the amount of activated PLC limits the rate of KCNQ2/3 suppression; (iv) weak PLC activation can elicit robust calcium signals without net PI(4,5)P2 depletion or KCNQ2/3 channel inhibition; and (v) depletion of PI(4,5)P2, and not calcium/CaM or PKC-mediated phosphorylation, closes KCNQ2/3 potassium channels, thereby increasing neuronal excitability. © 2014 Elsevier Inc. All rights reserved. Source


Jantzen B.,RWTH Aachen
Journal of High Energy Physics | Year: 2011

The "expansion by regions" is a method of asymptotic expansion developed by Beneke and Smirnov in 1997. It expands the integrand according to the scaling prescriptions of a set of regions and integrates all expanded terms over the whole integration domain. This method has been applied successfully to many complicated loop integrals, but a general proof for its correctness has still been missing. This paper shows how the expansion by regions manages to reproduce the exact result correctly in an expanded form and clarifies the conditions on the choice and completeness of the considered regions. A generalized expression for the full result is presented that involves additional overlap contributions. These extra pieces normally yield scaleless integrals which are consistently set to zero, but they may be needed depending on the choice of the regularization scheme. While the main proofs and formulae are presented in a general and concise form, a large portion of the paper is filled with simple, pedagogical one-loop examples which illustrate the peculiarities of the expansion by regions, explain its application and show how to evaluate contributions within this method. © SISSA 2011. Source


Feldmeyer D.,Julich Research Center | Feldmeyer D.,RWTH Aachen
Frontiers in Neuroanatomy | Year: 2012

Neocortical areas are believed to be organized into vertical modules, the cortical columns, and the horizontal layers 1-6. In the somatosensory barrel cortex these columns are defined by the readily discernible barrel structure in layer 4. Information processing in the neocortex occurs along vertical and horizontal axes, thereby linking individual barrel-related columns via axons running through the different cortical layers of the barrel cortex. Long-range signaling occurs within the neocortical layers but also through axons projecting through the white matter to other neocortical areas and subcortical brain regions. Because of the ease of identification of barrel-related columns, the rodent barrel cortex has become a prototypical system to study the interactions between different neuronal connections within a sensory cortical area and between this area and other cortical as well subcortical regions. Such interactions will be discussed specifically for the feed-forward and feedback loops between the somatosensory and the somatomotor cortices as well as the different thalamic nuclei. In addition, recent advances concerning the morphological characteristics of excitatory neurons and their impact on the synaptic connectivity patterns and signaling properties of neuronal microcircuits in the whisker-related somatosensory cortex will be reviewed. In this context, their relationship between the structural properties of barrel-related columns and their function as a module in vertical synaptic signaling in the whisker-related cortical areas will be discussed. © 2012 Feldmeyer. Source


Wahl T.B.,Max Planck Institute of Quantum Optics | Tu H.-H.,Max Planck Institute of Quantum Optics | Schuch N.,RWTH Aachen | Cirac J.I.,Max Planck Institute of Quantum Optics
Physical Review Letters | Year: 2013

We show that projected entangled-pair states (PEPS) in two spatial dimensions can describe chiral topological states by explicitly constructing a family of such states with a nontrivial Chern number. They are ground states of two different kinds of free-fermion Hamiltonians: (i) local and gapless; (ii) gapped, but with hopping amplitudes that decay according to a power law. We derive general conditions on topological free-fermionic projected entangled-pair states that show that they cannot correspond to exact ground states of gapped, local parent Hamiltonians and provide numerical evidence demonstrating that they can nevertheless approximate well the physical properties of topological insulators with local Hamiltonians at arbitrary temperatures. © 2013 American Physical Society. Source


Kirschmer M.,RWTH Aachen | Voight J.,University of Vermont
SIAM Journal on Computing | Year: 2010

We provide algorithms to count and enumerate representatives of the (right) ideal classes of an Eichler order in a quaternion algebra defined over a number field. We analyze the run time of these algorithms and consider several related problems, including the computation of two-sided ideal classes, isomorphism classes of orders, connectin g ideals for orders, and ideal principalization. We conclude by giving the complete list of definite Eichler orders with class number at most 2. © 2010 Society for Industrial and Applied Mathematics. Source


Le Chenadec V.,Stanford University | Pitsch H.,Stanford University | Pitsch H.,RWTH Aachen
Journal of Computational Physics | Year: 2013

This paper presents a novel approach for solving the conservative form of the incompressible two-phase Navier-Stokes equations. In order to overcome the numerical instability induced by the potentially large density ratio encountered across the interface, the proposed method includes a Volume-of-Fluid type integration of the convective momentum transport, a monotonicity preserving momentum rescaling, and a consistent and conservative Ghost Fluid projection that includes surface tension effects. The numerical dissipation inherent in the Volume-of-Fluid treatment of the convective transport is localized in the interface vicinity, enabling the use of a kinetic energy conserving discretization away from the singularity. Two- and three-dimensional tests are presented, and the solutions shown to remain accurate at arbitrary density ratios. The proposed method is then successfully used to perform the detailed simulation of a round water jet emerging in quiescent air, therefore suggesting the applicability of the proposed algorithm to the computation of realistic turbulent atomization. © 2013 Elsevier Inc. Source


Momber A.W.,RWTH Aachen
Rock Mechanics and Rock Engineering | Year: 2013

The erosion of schist due to impinging quartz and glass particles is investigated. The experimental set-up used to perform the erosion tests is briefly described. The erosion process is characterized by two failure modes, namely intercrystalline fracture and lateral cracking. The power exponent for particle velocity effects is 2.44. The schist shows the features of plastic deformation, and a model proposed by Ruff and Wiederhorn (Erosion. Academic Press, New York, pp 69-126, 1979) can be applied to the erosion process. The formation of glassy microfibers is noted, and it is attributed to localized heating due to the particle impact process. © 2012 Springer-Verlag. Source


Rana A.,University of Victoria | Torrilhon M.,RWTH Aachen | Struchtrup H.,University of Victoria
Journal of Computational Physics | Year: 2013

In this work we present a finite difference scheme to compute steady state solutions of the regularized 13 moment (R13) equations of rarefied gas dynamics. The scheme allows fast solutions for 2D and 3D boundary value problems (BVPs) with velocity slip and temperature jump boundary conditions. The scheme is applied to the lid driven cavity problem for Knudsen numbers up to 0.7. The results compare well with those obtained from more costly solvers for rarefied gas dynamics, such as the Integro Moment Method (IMM) and the Direct Simulation Monte Carlo (DSMC) method. The R13 equations yield better results than the classical Navier-Stokes-Fourier equations for this boundary value problem, since they give an approximate description of Knudsen boundary layers at moderate Knudsen numbers. The R13 based numerical solutions are computationally economical and may be considered as a reliable alternative mathematical model for complex industrial problems at moderate Knudsen numbers. © 2012 Elsevier Inc. Source


Canetti L.,Ecole Polytechnique Federale de Lausanne | Drewes M.,TU Munich | Drewes M.,RWTH Aachen | Shaposhnikov M.,Ecole Polytechnique Federale de Lausanne
Physical Review Letters | Year: 2013

We demonstrate for the first time that three sterile neutrinos alone can simultaneously explain neutrino oscillations, the observed dark matter, and the baryon asymmetry of the Universe without new physics above the Fermi scale. The key new point of our analysis is leptogenesis after sphaleron freeze-out, which leads to resonant dark matter production, evading thus the constraints on sterile neutrino dark matter from structure formation and x-ray searches. We identify the range of sterile neutrino properties that is consistent with all known constraints. We find a domain of parameters where the new particles can be found with present day experimental techniques, using upgrades to existing experimental facilities. © 2013 American Physical Society. Source


Dreiner H.,University of Bonn | Kramer M.,RWTH Aachen | Tattersall J.,University of Bonn
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

If supersymmetry (SUSY) has a compressed spectrum the current limits from the LHC can be drastically reduced. We take possible "worst case" scenarios where combinations of the top squark, squark and gluino masses are degenerate with the mass of the lightest SUSY particle. To accurately derive limits in the model, care must be taken when describing QCD radiation and we examine this in detail. Lower mass bounds are then produced by considering all the 7 TeV hadronic SUSY and monojet searches. The evolution of the limits as the mass splitting is varied is also presented. © 2013 American Physical Society. Source


Zador J.,Sandia National Laboratories | Taatjes C.A.,Sandia National Laboratories | Fernandes R.X.,RWTH Aachen
Progress in Energy and Combustion Science | Year: 2011

Advanced low-temperature combustion concepts that rely on compression ignition have placed new technological demands on the modeling of low-temperature oxidation in general and particularly on fuel effects in autoignition. Furthermore, the increasing use of alternative and non-traditional fuels presents new challenges for combustion modeling and demands accurate rate coefficients and branching fractions for a wider range of reactants. New experimental techniques, as well as modern variants on venerable methods, have recently been employed to investigate the fundamental reactions underlying autoignition in great detail. At the same time, improvements in theoretical kinetics and quantum chemistry have made theory an indispensible partner in reaction kinetics, particularly for complex reaction systems like the alkyl + O2 reactions. This review concentrates on recent developments in the study of elementary reaction kinetics in relation to the modeling and prediction of low-temperature combustion and autoignition, with specific focus placed on the emerging understanding of the critical alkylperoxy and hydroperoxyalkyl reactions. We especially highlight the power of cooperative theoretical and experimental efforts in establishing a rigorous mechanistic understanding of these fundamental reactions. © 2010 Elsevier Ltd. All rights reserved. Source


Busch A.,Royal Dutch Shell | Gensterblum Y.,RWTH Aachen
International Journal of Coal Geology | Year: 2011

This article reviews the state of research on sorption of gases (CO2, CH4) and water on coal for primary recovery of coalbed methane (CBM), secondary recovery by an enhancement with carbon dioxide injection (CO2-ECBM), and for permanent storage of CO2 in coal seams.Especially in the last decade a large amount of data has been published characterizing coals from various coal basins world-wide for their gas sorption capacity. This research was either related to commercial CBM production or to the usage of coal seams as a permanent sink for anthropogenic CO2 emissions. Presently, producing methane from coal beds is an attractive option and operations are under way or planned in many coal basins around the globe. Gas-in-place determinations using canister desorption tests and CH4 isotherms are performed routinely and have provided large datasets for correlating gas transport and sorption properties with coal characteristic parameters.Publicly funded research projects have produced large datasets on the interaction of CO2 with coals. The determination of sorption isotherms, sorption capacities and rates has meanwhile become a standard approach.In this study we discuss and compare the manometric, volumetric and gravimetric methods for recording sorption isotherms and provide an uncertainty analysis. Using published datasets and theoretical considerations, water sorption is discussed in detail as an important mechanisms controlling gas sorption on coal. Most sorption isotherms are still recorded for dry coals, which usually do not represent in-seam conditions, and water present in the coal has a significant control on CBM gas contents and CO2 storage potential. This section is followed by considerations of the interdependence of sorption capacity and coal properties like coal rank, maceral composition or ash content. For assessment of the most suitable coal rank for CO2 storage data on the CO2/CH4 sorption ratio data have been collected and compared with coal rank.Finally, we discuss sorption rates and gas diffusion in the coal matrix as well as the different unipore or bidisperse models used for describing these processes.This review does not include information on low-pressure sorption measurements (BET approach) to characterize pore sizes or pore volume since this would be a review of its own. We also do not consider sorption of gas mixtures since the data base is still limited and measurement techniques are associated with large uncertainties. © 2011 Elsevier B.V. Source


Luchow A.,RWTH Aachen
Wiley Interdisciplinary Reviews: Computational Molecular Science | Year: 2011

Simulations of complex systems have seen rapid progress over the last decade not only due to the continuous acceleration of computer resources but also due to improvements of methods and algorithms. Simulations complement experiments and model calculations in the effort to get insight into complex systems such as materials, complex liquids, or complicated molecules. As such, computer simulations are a strongly interdisciplinary field where chemistry meets physics, biology, and material science. Most simulations are based on classical physics because the interaction between atoms or even larger entities can be modeled accurately with classical mechanics for most problems as long as no chemical reactions are involved. If the interaction between atoms in a molecule or between molecules is to be calculated, for instance, to obtain parameters for modeling the interactions in classical simulations, classical physics has to be abandoned because these interactions involve the electron distributions which require a quantum mechanical description. © 2011 John Wiley & Sons, Ltd. Source


Garbrecht B.,TU Munich | Garbrecht B.,RWTH Aachen
Nuclear Physics B | Year: 2013

It is shown that the mixing of lepton doublets of the Standard Model can yield sizable contributions to the lepton asymmetry, that is generated through the decays of right-handed neutrinos at finite temperature in the early Universe. When calculating the flavour-mixing correlations, we account for the effects of Yukawa as well as of gauge interactions. We compare the freeze-out asymmetry from lepton-doublet mixing to the standard contributions from the mixing and direct decays of right-handed neutrinos. The asymmetry from lepton mixing is considerably large when the mass ratio between the right-handed neutrinos is of order of a few, while it becomes Maxwell-suppressed for larger hierarchies. For an intermediate range between the case of degenerate right-handed neutrinos (resonant leptogenesis) and the hierarchical case, lepton mixing can yield the main contribution to the lepton asymmetry. © 2012 Elsevier B.V. Source


Clemens B.,RWTH Aachen
Restorative neurology and neuroscience | Year: 2013

Behavioural studies of attention training after brain damage have shown that only training procedures specifically related to the impaired attention function lead to significant improvements in the respective attention domain when using psychometric tests addressing these functions. The main objective of this fMRI study was to investigate specific as well as common neural correlates of alertness and focused attention and to assess the degree of neural overlap for two different tasks of the same attention function. To investigate how different attention functions are processed, we tested 32 healthy participants using fMRI. Each participant was randomly assigned to the alertness (n = 16) or the focused attention (n = 16) group, where participants underwent two different attention tasks, one being a diagnostic computerized test procedure and the other being a computer-game like training procedure. The present results show similar activation patterns when assessing the same attention function with two different tasks. Activation overlap for test and training tasks of the same attention function was more clear-cut than the activation overlap for two different attention functions. Clinically validated diagnostic test paradigms and computer game-like training paradigms for both alertness and focused attention activated common brain systems processing the respective attention function. These findings may help to explain the beneficial effect of specifically designed attentional training procedures and the validity of related psychometric tests in detecting specific changes in performance after training of the same attention functions. Source


Khatab K.,RWTH Aachen
American Journal of Tropical Medicine and Hygiene | Year: 2010

Major progress has been made over the last 30 years in reducing the prevalence of malnutrition amongst children less than 5 years of age in developing countries. However, approximately 27% of children under the age of 5 in these countries are still malnourished. This work focuses on the childhood malnutrition in one of the biggest developing countries, Egypt. This study examined the association between bio-demographic and socioeconomic determinants and the malnutrition problem in children less than 5 years of age using the 2003 Demographic and Health survey data for Egypt. In the first step, we use separate geoadditive Gaussian models with the continuous response variables stunting (height-for-age), underweight (weight-for-age), and wasting (weight-for-height) as indicators of nutritional status in our case study. In a second step, based on the results of the first step, we apply the geoadditive Gaussian latent variable model for continuous indicators in which the 3 measurements of the malnutrition status of children are assumed as indicators for the latent variable "nutritional status". Copyright © 2010 by The American Society of Tropical Medicine and Hygiene. Source


Cariprazine (RGH-188), which is being codeveloped by Gedeon Richter Ltd, Forest Laboratories Inc and Mitsubishi Tanabe Pharma Corp, is a novel putative antipsychotic drug that exerts partial agonism at dopamine D2/D 3 receptors, with preferential binding to D3 receptors, and partial agonism at serotonin 5-HT1A receptors. Its activity at D2/D3 receptors may be lower than that of the prototype partial agonist aripiprazole. The antipsychotic activity of cariprazine was demonstrated in animal models, and data also suggest that the propensity for extrapyramidal side effects is low and that the drug may have procognitive properties. Cariprazine is rapidly absorbed, with high oral bioavailability and a long plasma elimination t1/2. Cariprazine is in phase III clinical trials in patients with schizophrenia and in patients with bipolar disorder. Data from phase II trials in patients with schizophrenia and bipolar mania indicate that the drug has antipsychotic and antimanic properties that are superior to placebo. With its unique receptor affinity profile, cariprazine may represent a potential enrichment of the therapeutic armamentarium for schizophrenia and affective disorders. Its activity against the cognitive deficits associated with schizophrenia has to be carefully investigated. © Thomson Reuters (Scientific) Ltd. Source


Peuckmann V.,RWTH Aachen
Cochrane database of systematic reviews (Online) | Year: 2010

In healthy individuals, fatigue is a protective response to physical or mental stress, often relieved by rest. By contrast, in palliative care patients fatigue can be severely debilitating, thereby impacting daily activity and quality of life, often with rest not counteracting fatigue. Fatigue frequently occurs in patients with advanced disease and modalities treating cancer often contribute or cause fatigue. Further complicating issues are its multidimensionality, subjective nature, and lack of a consensus definition of fatigue. Pathophysiology is not fully understood and evidence-based treatment approaches are needed. The objective was to determine efficacy of pharmacological treatments on non-specific fatigue in palliative care. The focus was on patients at an advanced stage of disease, including cancer and other chronic diseases associated with fatigue, aiming to relieve fatigue. Studies aiming at curative treatment (e.g. surgical intervention for early breast cancer) were not included. We searched EMBASE; Psych Lit, CENTRAL and MEDLINE to June 2009. We considered randomised controlled trials (RCTs) concerning adult palliative care with focus on pharmacological treatment of fatigue. The primary outcome had to be non-specific fatigue (or related terms such as asthenia). Results were screened and included if they met the selection criteria. If two or more studies were identified that investigated a specific drug in a population with the same disease, meta-analysis was conducted. In addition, comparison of type of drug investigated in a specific population as well as comparison of frequent adverse effects of fatigue treatment was done by creating overview tables. More than 2000 publications were screened, and 22 met inclusion criteria. In total, data from 11 drugs and 1632 participants were analysed. Studies investigating amantadine, pemoline, and modafinil in participants with Multiple Sclerosis (MS)-associated fatigue and methylphenidate in patients suffering from advanced cancer and fatigue could be used for meta-analysis. Amantadine in MS and methylphenidate in cancer patients showed a superior effect. Most studies had low participant numbers and were heterogenous. Based on limited evidence, we cannot recommend a specific drug for treatment of fatigue in palliative care patients. Surprisingly, corticosteroids have not been a research focus for fatigue treatment, although these drugs are frequently used. Recent fatigue research seems to focus on modafinil, which may be beneficial although there is no evidence currently. Amantadine and methylphenidate should be further examined. Consensus regarding fatigue assessment in advanced disease is needed. Source


Gradel E.,RWTH Aachen
Theoretical Computer Science | Year: 2013

Logics of dependence and independence have semantics that, unlike Tarski semantics, are not based on single assignments (mapping variables to elements of a structure) but on sets of assignments. Sets of assignments are called teams and the semantics is called team semantics. We design model-checking games for logics with team semantics in a general and systematic way. The construction works for any extension of first-order logic by atomic formulae on teams, as long as certain natural conditions are observed which are satisfied by all team properties considered so far in the literature, including dependence, independence, constancy, inclusion, and exclusion. The second-order features of team semantics are reflected by the notion of a consistent winning strategy which is also a second-order notion in the sense that it depends not on single plays but on the space of all plays that are compatible with the strategy. Beyond the application to logics with team semantics, we isolate an abstract, purely combinatorial definition of such games, which may be viewed as second-order reachability games, and study their algorithmic properties. A number of examples are provided that show how logics with team semantics express familiar combinatorial problems in a somewhat unexpected way. Based on our games, we provide a complexity analysis of logics with team semantics. © 2013 Elsevier B.V. All rights reserved. Source


Mazumder P.,University of Michigan | Kang S.M.,University of California at Santa Cruz | Waser R.,RWTH Aachen
Proceedings of the IEEE | Year: 2012

Some important aspects of memristor technology, which include theory, device engineering, circuit modeling, digital and analog systems, and neuromorphic systems, are discussed. A new era in research on resistive switching started in the late 1990s, initiated independently by Asamitsu et al. using manganites, Kozicki et al. studying AgYGeSe systems, and Beck et al. investigating titanates and zirconates. A conceptual extension of digital memory is digital logic, and memristors have been proposed and demonstrated for different digital logic applications. An experimental demonstration of chaos with analog components used to build the memristor is presented in . An image encryption application using piecewise linear memristors is also presented. Querlioz et al. showed that memristors utilized in neuromorphic configuration for unsupervised learning can tolerate device variation. Source


Blumlein J.,German Electron Synchrotron | Hasselhuhn A.,German Electron Synchrotron | Klein S.,RWTH Aachen | Schneider C.,Johannes Kepler University
Nuclear Physics B | Year: 2013

The O(α s 3n fT F 2CA,F) terms to the massive gluonic operator matrix elements are calculated for general values of the Mellin variable N using a new summation technique. These twist-2 matrix elements occur as transition functions in the variable flavor number scheme at NNLO. The calculation uses sum-representations in generalized hypergeometric series turning into harmonic sums. The analytic continuation to complex values of N is provided. © 2012 Elsevier B.V. Source


The emergency medical service (EMS) should work according to criteria of evidence-based medicine. In Germany the EMS of each state is under the control of at least one medical supervisor known as emergency medical directors (EMD) and most states have several different EMDs responsible for one or more provinces of the state. The German Medical Association advises these supervisors to specify the pharmacological resources in store for use in physician powered EMSs. This study examines the pharmacological resources in EMSs which is provided by the EMDs in Germany. Furthermore, a comparison of the inventory analysis of stored drugs was carried out with the requirements according to guidelines for selected tracer diagnoses. In the period of May 2008 to January 2009 a total of 148 EMDs were contacted and asked to supply drug storage lists for emergency physician-staffed rescue vehicles in their respective jurisdiction. The addresses of all EMDs who could be identified by the federal office of the National Association of Emergency Medical Director, Germany were used over the period. The evaluation was conducted anonymously. The tracer diagnoses "cardiopulmonary resuscitation", "acute coronary syndrome", "status generalized tonic-clonic seizure," "severe asthma attack", "acute exacerbation of chronic obstructive pulmonary disease", "supraventricular tachycardia", "severe brain trauma" and "acute heart failure with signs of hypoperfusion" were selected. Current and established guidelines have been identified with the homepage of the Scientific Medical Societies in Germany and supported by the leading European and International guidelines. The corresponding lists were returned by 95 different emergency service areas (response rate 64.2%). With a total of 39 groups of substances 142 different drugs could be identified, an average of 54±9.6 and median 55 (range 31-77). Listed are agents giving the provision in percent, for which the comparison with guidelines for tracer diagnoses could show deficits: sodium bicarbonate 75.8%, calcium 50.5%, magnesium 45.3%, noradrenaline 65.3%, adenosine 58.9%, dobutamine 57.9%, lorazepam iv 13.7%, salbutamol 41.1%, ipratropium bromide 13.7% (the last two as liquid preparations for inhalation). With a frequency of about 30-80%, depending on the respective tracer diagnosis, no medical emergency treatment according to the highest level of evidence is possible. Due to recent treatment recommendations provision with sodium bicarbonate, calcium, magnesium, noradrenaline, adenosine, lorazepam iv, dobutamine and as well with ipratropium bromide and salbutamol (both as liquid preparations for inhalation) should be improved. For the future, a federal uniform minimum standard due to evidence-based principles is desirable. Source


Helicobacter species are important pathogens and previous studies in mice suggested a link between colonization by Helicobacter hepaticus (H. hepaticus) and hepatocellular carcinoma (HCC). This study aimed at corroborating this potential link in human patients. We used a sensitive and specific Helicobacter ssp PCR assay to screen stool samples from a collective of patients with viral-induced HCC (hepatitis B or hepatitis C) and a control group for presence of Helicobacter ssp DNA. Although retrieving DNA of H. pylori and H. canadensis from stool samples of non-HCC patients, we found no evidence indicating the presence of H. hepaticus in HCC-patients with chronic hepatitis B or hepatitis C. Interestingly we found H. canadensis in a stool sample of a patient presenting with diarrhea. Taken together, our data argue against a pathogenic role of H. hepaticus in viral-induced HCC. Yet, our results do not exclude a role of H. hepaticus in those HCC cases caused by other carcinogens, such as aflatoxin. Moreover, we speculate that H. canadensis might be a novel gastrointestinal pathogen. Source


Liu T.,Dalian University of Technology | Liu T.,RWTH Aachen | Wang Y.,Beijing University of Chemical Technology
Automatica | Year: 2012

For industrial nonlinear batch processes that can be practically divided into a series of piecewise affine operating regions, a two-dimensional (2D) closed-loop iterative learning control (ILC) method is proposed for robust tracking of the set-point profile against cycle-to-cycle process uncertainties and load disturbances. Both state feedback and output feedback are considered for the control design, together with the process input and output constraints for implementation. Based on a 2D system description for the batch operation, a few synthetic performance and robust control objectives are proposed for developing the 2D ILC schemes, in combination with the 2D Lyapunov-Krasovskii functions that can guarantee monotonic state energy (or output error) decrease in both the time (during a cycle) and batch (from cycle to cycle) directions. Both the polyhedral and norm-bounded descriptions of process uncertainties are considered to derive the corresponding linear matrix inequality (LMI) conditions for the closed-loop ILC system robust stability. An important merit of these LMI conditions is that there are adjustable convergence indices prescribed for both the time and batch directions, and an adjustable robust control performance level for the closed-loop system. By specifying/optimizing these adjustable parameters to solve these LMI conditions, the 2D ILC controller can be explicitly derived for implementation. The application to a highly nonlinear continuous stirred tank reactor (CSTR) is shown to illustrate the effectiveness and merits of the proposed ILC method. © 2012 Elsevier Ltd. All rights reserved. Source


Cordes S.E.,RWTH Aachen
CIRP Journal of Manufacturing Science and Technology | Year: 2012

Stainless steels are widely used in several industrial sectors, such as engine production, medical and chemical industry. Their high strength, low thermal conductivity, high ductility and high tendency towards work hardening are the main factors for their poor machinability. In order to improve the cutting tools performance, they are often coated. γ-Al 2O 3 seems to be one promising candidate as coating material for machining difficult-to-machine materials. The performance, wear mechanism and thermal stability in turning, milling and drilling operations of austenitic steels with coated cemented carbide cutting tools (coating system (Ti,Al)N/γ-Al 2O 3) were investigated. The thermal stability was analysed with TEM/STEM. © 2011 CIRP. Source


Feijs K.L.,RWTH Aachen
Nature reviews. Molecular cell biology | Year: 2013

ADP-ribosylation of proteins was first described in the early 1960's, and today the function and regulation of poly(ADP-ribosyl)ation (PARylation) is partially understood. By contrast, little is known about intracellular mono(ADP-ribosyl)ation (MARylation) by ADP-ribosyl transferase (ART) enzymes, such as ARTD10. Recent findings indicate that MARylation regulates signalling and transcription by modifying key components in these processes. Emerging evidence also suggests that specific macrodomain-containing proteins, including ARTD8, macroD1, macroD2 and C6orf130, which are distinct from those affecting PARylation, interact with MARylation on target proteins to 'read' and 'erase' this modification. Thus, studying macrodomain-containing proteins is key to understanding the function and regulation of MARylation. Source


Rebound effect studies of road vehicle travel focus mostly on increases in distance traveled after increases in energy efficiency. Average journeying speed also increases with energy efficiency, but rebound studies avoid quantifying speed-related rebound effects. This may underestimate rebound effects by around 60%. This study offers a first attempt to show how increases in speed and acceleration contribute to rebound effects, and how these can be quantified. Its empirical data is dynamometer test results for a plug-in electric car and an internal combustion engine (ICE) pick-up van with automatic transmission, each on the WLTP and NEDC drive cycles, representing driving styles from today and 1975 respectively. Rebound effects are estimated by comparing the WLTP and NEDC results, using typical 1975 energy efficiencies for the NEDC. The electric car shows a 20.5% speed rebound effect, and a mathematical development sets out how speed rebound effects can be included in traditional rebound effect analyses. Results for the ICE-vehicle do not allow a direct rebound effect estimate due to wasteful engine revving on the NEDC and wrong gear ratios for sedate travel. However, this can be seen as a form of 'transformational' rebound effect, where vehicle design locks drivers into fast driving styles. © 2016 Elsevier Ltd. Source


Liang Y.-C.,Agency for Science, Technology and Research Singapore | Chen K.-C.,National Taiwan University | Li G.Y.,Georgia Institute of Technology | Mahonen P.,RWTH Aachen
IEEE Transactions on Vehicular Technology | Year: 2011

Cognitive radio (CR) is the enabling technology for supporting dynamic spectrum access: the policy that addresses the spectrum scarcity problem that is encountered in many countries. Thus, CR is widely regarded as one of the most promising technologies for future wireless communications. To make radios and wireless networks truly cognitive, however, is by no means a simple task, and it requires collaborative effort from various research communities, including communications theory, networking engineering, signal processing, game theory, software-hardware joint design, and reconfigurable antenna and radio-frequency design. In this paper, we provide a systematic overview on CR networking and communications by looking at the key functions of the physical (PHY), medium access control (MAC), and network layers involved in a CR design and how these layers are crossly related. In particular, for the PHY layer, we will address signal processing techniques for spectrum sensing, cooperative spectrum sensing, and transceiver design for cognitive spectrum access. For the MAC layer, we review sensing scheduling schemes, sensing-access tradeoff design, spectrum-aware access MAC, and CR MAC protocols. In the network layer, cognitive radio network (CRN) tomography, spectrum-aware routing, and quality-of-service (QoS) control will be addressed. Emerging CRNs that are actively developed by various standardization committees and spectrum-sharing economics will also be reviewed. Finally, we point out several open questions and challenges that are related to the CRN design. © 2010 IEEE. Source


Struchtrup H.,University of Victoria | Torrilhon M.,RWTH Aachen
Physics of Fluids | Year: 2013

The regularized 13 moment equations of rarefied gas dynamics are derived for a monatomic hard sphere gas in the linear regime. The equations are based on an extended Grad-type moment system, which is systematically reduced by means of the Order of Magnitude Method [H. Struchtrup, "Stable transport equations for rarefied gases at high orders in the Knudsen number," Phys. Fluids16(11), 3921-3934 (2004)]10.1063/1.1782751. Chapman-Enskog expansion of the final equations yields the linear Burnett and super-Burnett equations. While the Burnett coefficients agree with literature values, this seems to be the first time that super-Burnett coefficients are computed for a hard sphere gas. As a first test of the equations the dispersion and damping of sound waves is considered. © 2013 AIP Publishing LLC. Source


Roscher M.A.,RWTH Aachen | Assfalg J.,BMW AG | Bohlen O.S.,BMW AG
IEEE Transactions on Vehicular Technology | Year: 2011

Lithium ion (Li-ion) batteries exhibit high power and energy densities, as well as high-cycle-lifetime capabilities. Li-ion cells based on LiFePO 4 cathodes are promising alternatives to predominant metal oxide technologies, particularly for applications with high power and cycle lifetime requirements. This paper includes investigations on high-power LiFePO 4 cells' cycle lifetime. Therefore, 3000 full charge-discharge cycles are applied to the cells with high constant current rates. Through reference testing, increasing battery impedance and a fading capacity are identified as a consequence of battery aging. Capacity fade proceeds in a way that cells' open-circuit voltages (OCVs) change only in the range of high state-of-charge (SOC). A model-based method that can detect the decreasingly utilizable capacity is outlined. The proposed method considers the changing OCV characteristics and enables the determination of capacity loss without complete charge and discharge being necessary during battery operation. By the evaluation of capacity loss information, an accelerated battery aging or even possible battery damage caused by overcharge can be avoided during battery charging scenarios. © 2010 IEEE. Source


Kumbaroglu G.,Bogazici University | Madlener R.,RWTH Aachen
Energy and Buildings | Year: 2012

In this study, a techno-economic evaluation method for the energy retrofit of buildings is introduced, geared toward finding the economically optimal set of retrofit measures. Split incentives of building owners and users are considered explicitly in a conventional (static) evaluation to identify the investment alternatives maximizing the net present value (NPV). Energy price uncertainty for various distributional assumptions of the stochastic variables is addressed through Monte Carlo simulation. Results from the simulation are used to compute probabilities and expected NPVs. Based on this, a sequential (dynamic) evaluation method is developed, featuring a real options investment appraisal. The real options approach is introduced as an advancement in the practice of economic evaluation of building retrofit investment options. The new method is applied to an office building in Germany, illustrating its performance. The case study results indicate that energy price changes significantly affect the profitability of retrofit investments, and that high price volatility creates a substantial value of waiting, making it more rational to postpone the investment. © 2012 Elsevier B.V. All rights reserved. Source


Nebe G.,RWTH Aachen
Finite Fields and their Applications | Year: 2012

Let C be an extremal self-dual binary code of length 72 and gεAut(C) be an automorphism of order 2. We show that C is a free F 2«g» module and use this to exclude certain subgroups of order 8 of Aut(C). We also show that Aut(C) does not contain an element of order 10. Combining these results with the ones obtained in earlier papers we find that the order of Aut(C) is either 5 or divides 24. If 8 divides the order of Aut(C) then its Sylow 2-subgroup is either D 8 or Z 2×Z 2×Z 2. © 2011 Elsevier Inc. All rights reserved. Source


Sullivan G.J.,Microsoft | Ohm J.-R.,RWTH Aachen | Han W.-J.,Gachon University | Wiegand T.,Fraunhofer Institute for Telecommunications, Heinrich-Hertz-Institut | Wiegand T.,TU Berlin
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2012

High Efficiency Video Coding (HEVC) is currently being prepared as the newest video coding standard of the ITU-T Video Coding Experts Group and the ISO/IEC Moving Picture Experts Group. The main goal of the HEVC standardization effort is to enable significantly improved compression performance relative to existing standards-in the range of 50% bit-rate reduction for equal perceptual video quality. This paper provides an overview of the technical features and characteristics of the HEVC standard. © 1991-2012 IEEE. Source


Strzelecki P.,University of Warsaw | von der Mosel H.,RWTH Aachen
Physics Reports | Year: 2013

Motivated by the suggestions of Gonzalez and Maddocks, and Banavar et al. to use geometrically defined curvature energies to model self-avoidance phenomena for strands and sheets we give a self-contained account, aimed at non-experts, on the state of art of the mathematics behind these energies. The basic building block, serving as a multipoint potential, is the circumradius of three points on a curve. The energies we study are defined as averages of negative powers of that radius over all possible triples of points along the curve (or via a mixture of averaging and maximization). For a suitable range of exponents, above the scale invariant case, we establish self-avoidance and regularizing effects and discuss various applications in geometric knot theory, as well as generalizations to surfaces and higher-dimensional submanifolds. © 2013 Elsevier B.V. Source


Hebecker A.,University of Heidelberg | Knochel A.K.,University of Heidelberg | Knochel A.K.,RWTH Aachen | Weigand T.,University of Heidelberg
Nuclear Physics B | Year: 2013

The Higgs quartic coupling λ has now been indirectly measured at the electroweak scale. Assuming no new low-scale physics, its running is known and, together with gauge and Yukawa couplings, it is a crucial new piece of information constraining UV completions of the Standard Model. In particular, supersymmetry broken at an intermediate or high energy scale with tanβ = 1 (i.e. λ = 0) is consistent with present data and has an independent theoretical appeal. We analyze the possible string-theoretic motivations for tanβ = 1 (including both the shift-symmetry and the more economical variant of a Z2 symmetry) in a Higgs sector realized on either 6- or 7-branes. We identify specific geometries where λ≃0 may arise naturally and specify the geometrical problems which need to be solved to determine its precise value in the generic case. We then analyze the radiative corrections to λ. Finally we show that, in contrast to naive expectations, λ<0 at the SUSY breaking scale is also possible. Specifically, string theory may produce an MSSM plus chiral singlet at a very high scale, which immediately breaks to a non-SUSY Standard Model with λ<0. This classically unstable theory then becomes metastable through running towards the IR. © 2013 Elsevier B.V. Source


Misiorny M.,Julich Research Center | Misiorny M.,Adam Mickiewicz University | Hell M.,Julich Research Center | Wegewijs M.R.,Julich Research Center | Wegewijs M.R.,RWTH Aachen
Nature Physics | Year: 2013

Superparamagnetism of magnetic adatoms and molecules-preferential alignment of their spins along an easy axis-is a useful effect for nanoscale applications as it prevents undesired spin reversal. The underlying magnetic anisotropy barrier-a quadrupolar energy splitting-originates from spin-orbit interaction and can nowadays be probed by electronic transport measurements. Here we predict that in a much broader class of systems, quantum dots with spins larger than 1/2, superparamagnetism can arise without spin-orbit interaction: by attaching them to ferromagnets, a quadrupolar spintronic exchange field is generated locally. It is observable by means of conductance measurements and leads to enhanced spin filtering even in a state with zero average spin. Analogously to the spintronic dipolar exchange field, giving rise to a local spin torque, the effect is susceptible to electric control and increases with tunnel coupling as well as with spin polarization. © 2013 Macmillan Publishers Limited. Source


Berkholz C.,RWTH Aachen
Logical Methods in Computer Science | Year: 2013

The existential k-pebble game characterizes the expressive power of the existential-positive k-variable fragment of first-order logic on finite structures. The winner of the existential k-pebble game on two given finite structures can be determined in time O(n2k) by dynamic programming on the graph of game configurations. We show that there is no O(n(k-3)/12)-time algorithm that decides which player can win the existential k-pebble game on two given structures. This lower bound is unconditional and does not rely on any complexity-theoretic assumptions. Establishing strong k-consistency is a well-known heuristic for solving the constraint satisfaction problem (CSP). By the game characterization of Kolaitis and Vardi [14] our result implies that there is no O(n(k-3)/12)-time algorithm that decides if strong k-consistency can be established for a given CSP-instance. © Christoph Berkholz. Source


Achtnicht M.,Center for European Economic Research | Madlener R.,RWTH Aachen
Energy Policy | Year: 2014

In this paper, we identify key drivers and barriers for the adoption of building energy retrofits in Germany, which is promoted by public policy as an important measure to address the future challenges of climate change and energy security. We analyze data from a 2009 survey of more than 400 owner-occupiers of single-family detached, semidetached, and row houses in Germany, that was conducted as a computer-assisted personal interview (CAPI). In the survey, respondents were asked directly for reasons for and against retrofitting their homes, but also faced a choice experiment involving different energy retrofit measures. Overall, we find that house owners who are able to afford it financially, for whom it is profitable, and for whom there is a favorable opportunity are more likely to undertake energy retrofit activities. The latter point seems to be of particular importance in explaining the persistent low retrofit rate in Germany. Our results suggest that professional energy advice could stimulate the demand for building energy retrofits. © 2014 Elsevier Ltd. Source


May G.,RWTH Aachen
Communications in Computational Physics | Year: 2011

In this short note we present a derivation of the Spectral Difference Scheme from a Discontinuous Galerkin (DG) discretization of a nonlinear conservation law. This allows interpretation of the Spectral Difference Scheme as a particular discretization under the quadrature-free nodal DG paradigm. Moreover, it enables identification of the key differences between the Spectral Difference Scheme and standard nodal DG schemes. © 2011 Global-Science Press. Source


Garbrecht B.,RWTH Aachen
Nuclear Physics B | Year: 2011

For standard leptogenesis from the decay of singlet right-handed neutrinos, we derive source terms for the lepton asymmetry that are present in a finite density background but absent in the vacuum. These arise from cuts through the vertex correction to the decay asymmetry, where in the loop either the Higgs boson and the right-handed neutrino or the left-handed lepton and the right-handed neutrino are simultaneously on-shell. We evaluate the source terms numerically and use them to calculate the lepton asymmetry for illustrative points in parameter space, where we consider only two right-handed neutrinos for simplicity. Compared to calculations where only the standard cut through the propagators of left-handed lepton and Higgs boson is included, sizable corrections arise when the masses of the right-handed neutrinos are of the same order, but the new sources are found to be most relevant when the decaying right-handed neutrino is heavier than the one in the loop. In that situation, they can yield the dominant contribution to the lepton asymmetry. © 2011 Elsevier B.V. Source


Felderhof B.U.,RWTH Aachen
Physics of Fluids | Year: 2011

The efficiency of ferrohydrodynamic pumping of a ferrofluid through a planar duct by means of a running magnetic plane wave is studied to second order in the amplitude of the exciting current density. The rate of dissipation in the fluid is calculated from the first order magnetic field and magnetization. It turns out that the efficiency, defined as the ratio of net flow velocity to power input, is comparable in magnitude to that for Stokes peristaltic pumping. The theory for electrohydrodynamic pumping of a polar liquid by means of a running electric plane wave is shown to be nearly identical. © 2011 American Institute of Physics. Source


Ferrohydrodynamic pumping of a ferrofluid through a circular tube by means of a running magnetic wave is studied in the framework of magnetostatics. The theory for electrohydrodynamic pumping of a polar liquid by means of a running electric wave is shown to be nearly identical. For given fluid parameters, the net flow rate can be optimized by suitable choice of wavenumber and frequency of the running wave. © 2011 American Institute of Physics. Source


Ferrohydrodynamic pumping of a ferrofluid through a planar duct by means of a running magnetic wave is studied to second order in the amplitude of the exciting current density. The theory for electrohydrodynamic pumping of a polar liquid by means of a running electric wave is shown to be nearly identical. For the given fluid parameters, the net flow rate can be optimized by suitable choice of wavenumber and frequency of the running wave. © 2011 American Institute of Physics. Source


Using the recently introduced Stripper approach to double-real radiation, we evaluate the total cross sections for the main partonic channels of the next-to-next-to-leading order contributions to top quark pair production in hadronic collisions: gg→tt gg, gg→tt qq, qq →tt gg, qq →tt q'q ', q'≠ q. The results are given as Laurent expansions in ∈, the parameter of dimensional regularization, at a number of m/ECM values spreading the entire variation range, with m the mass of the top quark and ECM the center-of-mass energy. We describe the details of our implementation and demonstrate its main properties: pointwise convergence and efficiency. We also prove the cancellation of leading divergences after inclusion of the double-virtual and real-virtual contributions. On a more technical note, we extended the double-soft current formulae to the case of massive partons. © 2011 Elsevier B.V. Source


Herpertz-Dahlmann B.,RWTH Aachen
PPmP Psychotherapie Psychosomatik Medizinische Psychologie | Year: 2015

Adolescent anorexia nervosa often takes a chronic and disabling course associated with reduced health-related quality of life in adulthood. The aim of this short review is to introduce new aspects on the somatic and psychotherapeutic treatment of AN, such as nutritional rehabilitation, prophylaxis of osteoporosis as well as new findings on the effect of treatment settings and new psychotherapeutic methods. © Georg Thieme Verlag KG Stuttgart New York. Source


Floege J.,RWTH Aachen
Journal of Nephrology | Year: 2015

Magnesium fulfils important roles in multiple physiological processes. Accordingly, a tight regulation of magnesium homeostasis is essential. Dysregulated magnesium serum levels, in particular hypomagnesaemia, are common in patients with chronic kidney disease (CKD) and have been associated with poor clinical outcomes. In cell culture studies as well as in clinical situations magnesium levels were associated with vascular calcification, cardiovascular disease and altered bone-mineral metabolism. Magnesium has also been linked to diseases such as metabolic syndrome, diabetes, hypertension, fatigue and depression, all of which are common in CKD. The present review summarizes and discusses the latest clinical data on the impact of magnesium and possible effects of higher levels on the health status of patients with CKD, including an outlook on the use of magnesium-based phosphate-binding agents in this context. © 2014, The Author(s). Source


Pandolfo M.,Free University of Colombia | Hausmann L.,RWTH Aachen
Journal of Neurochemistry | Year: 2013

Friedreich's ataxia (FRDA) is a neurological disease related to a deficiency of the protein frataxin involved in iron-sulfur (Fe-S) cluster biogenesis. This leads to an increased cellular iron uptake accumulating in mitochondria, and a subsequently disturbed iron homeostasis. The detailed mechanism of iron regulation of frataxin expression is yet unknown. Deferiprone, an iron chelator that may cross the blood-brain barrier, was shown to shuttle iron between subcellular compartments. It could also transfer iron from iron-overloaded cells to extracellular apotransferrin and pre-erythroid cells for heme synthesis. Here, clinical studies on Deferiprone are reviewed in the context of alternative agents such as desferoxamine, with specific regard to its mechanistic and clinical implications. © 2013 International Society for Neurochemistry. Source


Evenepoel P.,University Hospitals Leuven | D'Haese P.,University of Antwerp | Brandenburg V.,RWTH Aachen
Kidney International | Year: 2015

For more than a decade, the Wnt-β-catenin pathway has been the focus of intense basic and clinical research in the bone field because of its importance in skeletal development and maintenance of bone mass. Wnt activation increases bone formation and decreases bone resorption. The Wnt-β-catenin signaling pathway is tightly regulated by several inhibitors, among which Dickkopf-related protein 1 (DKK1) and sclerostin have been most comprehensively studied. Mounting evidence indicates that a disturbed Wnt-β-catenin signaling is also implicated in the pathogenesis of the chronic kidney disease-associated bone and mineral disorder (CKD-MBD) and affects its various components. DKK1 and sclerostin, more specifically, may be involved in the intense cross-talk between the kidneys, vasculature, and bone. Studies exploring clinical correlates of circulating sclerostin and DKK1 levels so far yielded conflicting results. Biological variability and analytical issues account at least partly for this inconsistency. Antibodies neutralizing Wnt inhibitors may be an appealing strategy to prevent or treat CKD-MBD. Caution is however warranted as sclerostin not only opposes mineralization in the bone but possibly also in the vasculature. Additional studies are required to define determinants of Wnt inhibitors in CKD and to evaluate the efficacy and safety of recently introduced pharmaceuticals targeting these inhibitors. © 2015 International Society of Nephrology. Source


Herpertz-Dahlmann B.,RWTH Aachen
Child and Adolescent Psychiatric Clinics of North America | Year: 2015

The prevalence of eating disorders among adolescents continues to increase. The starvation process itself is often associated with severe alterations of central and peripheral metabolism, affecting overall health during this vulnerable period. This article aims to convey basic knowledge on these frequent and disabling disorders, and to review new developments in classification issues resulting from the transition to DSM-5. A detailed description is given of the symptomatology of each eating disorder that typically manifests during adolescence. New data on epidemiology, and expanding knowledge on associated medical and psychiatric comorbidities and their often long-lasting sequelae in later life, are provided. © 2015 Elsevier Inc.. Source


Kirn T.,RWTH Aachen
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

The Alpha Magnetic Spectrometer (AMS-02) is a general purpose high energy particle detector which was successfully deployed on the International Space Station (ISS) on 19 May 2011 to conduct a unique long duration mission of fundamental physics research in space. The main goals of the AMS-02 experiment include antimatter and dark matter search and cosmic ray physics in the energy range from few GeV up to 2 TeV. The indirect search for dark matter candidates requires precise e+-spectroscopy with a suppression of the dominant proton background by six orders of magnitude. In AMS-02 it will be achieved with a combination of an electromagnetic calorimeter and a transition radiation detector. ©2012 Elsevier B.V. All rights reserved. Source


Bernreuther W.,RWTH Aachen | Si Z.-G.,Shandong University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

A number of top-spin observables are computed within the Standard Model (SM), at next-to-leading order in the strong and weak gauge couplings for hadronic top-quark anti-quark (.tt-) production and decay at the LHC for center-of-mass energies 7 and 8 TeV. For dileptonic final states we consider the azimuthal angle correlation, the helicity correlation, and the opening angle distribution; for lepton plus jets final states we determine distributions and asymmetries that trace a longitudinal and transverse polarization, respectively, of the t and t- samples. The QCD-induced transverse polarization of the top quarks leads to an asymmetry of about 8% that should be detectable with existing data. In addition, we investigate the effects of a non-zero chromo-magnetic and chromo-electric dipole moment of the top quark on these and other top-spin observables and associated asymmetries. These observables allow to disentangle the contributions from the real and imaginary parts of these moments. © 2013 Elsevier B.V. Source


Drewes M.,RWTH Aachen | Drewes M.,TU Munich | Mendizabal S.,Goethe University Frankfurt | Weniger C.,Max Planck Institute for Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We show from first principles the emergence of classical Boltzmann equations from relativistic nonequilibrium quantum field theory as described by the Kadanoff-Baym equations. Our method applies to a generic quantum field, coupled to a collection of background fields and sources, in a homogeneous and isotropic spacetime. The analysis is based on analytical solutions to the full Kadanoff-Baym equations, using the WKB approximation. This is in contrast to previous derivations of kinetic equations that rely on similar physical assumptions, but obtain approximate equations of motion from a gradient expansion in momentum space. We show that the system follows a generalized Boltzmann equation whenever the WKB approximation holds. The generalized Boltzmann equation, which includes off-shell transport, is valid far from equilibrium and in a time dependent background, such as the expanding universe. © 2012 Elsevier B.V. Source


Schlich B.,RWTH Aachen
Transactions on Embedded Computing Systems | Year: 2010

The interest of industries in model checking software for microcontrollers is increasing. However, there are currently no appropriate tools that can be applied by embedded systems developers for the direct verification of software for microcontrollers without the need for manual modeling. This article describes a new approach to model checking software for microcontrollers, which verifies the assembly code of the software. The state space is built using a tailored simulator, which abstracts from time, handles nondeterminism, and creates an overapproximation of the behavior shown by the real microcontroller. Within this simulator, we apply abstraction techniques to tackle the state-explosion problem. In our approach, we combine different formal methods, namely, model checking, static analysis, and abstract interpretation. We also combine explicit and symbolic model checking techniques. This article presents a case study using several programs to demonstrate the efficiency of the applied abstraction techniques and to show the applicability of this approach. © 2010 ACM. Source


Berge S.,Johannes Gutenberg University Mainz | Bernreuther W.,RWTH Aachen | Spiesberger H.,Johannes Gutenberg University Mainz
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We investigate the prospects of determining the CP nature of the 126 GeV neutral spin-0 (Higgs) boson h, discovered at the LHC, at a future linear e+e- collider (ILC). We consider the production of h by the Higgsstrahlung process e+e-→Z+h and its subsequent decays to τ leptons, h→τ-τ+. We investigate how precisely a possible pseudoscalar component of h can be detected by the measurement of a suitably defined angular distribution, if all major decay modes of the τ lepton are used. From our numerical simulations, we estimate the expected precision to the scalar-pseudoscalar mixing angle φ, including estimates of the background and of measurement uncertainties, to be δφ≃2.8° for Higgs-boson production at a center-of-mass energy of 250 GeV and for a collider with integrated luminosity of 1 ab-1. © 2013 Elsevier B.V. Source


Rosenbaum M.A.,RWTH Aachen | Franks A.E.,La Trobe University
Applied Microbiology and Biotechnology | Year: 2014

Over the past decade, microbial electrochemical technologies, originally developed from an interesting physiological phenomenon, have evolved from a rush of initiatives for sustainable bioelectricity generation to a multitude of specialized applications in very different areas. Genetic engineering of microbial biocatalysts for target bioelectrochemical applications like biosensing or bioremediation, as well as the discovery of entirely new bioelectrochemical processes such as microbial electrosynthesis of commodity chemicals, open up completely new possibilities. Where stands this technology today? And what are the general and specific challenges it faces not only scientifically but also for transition into commercial applications? This review intends to summarize the recent advances and provides a perspective on future developments. © 2013 Springer-Verlag Berlin Heidelberg. Source


Dominguez de Maria P.,RWTH Aachen
Journal of Chemical Technology and Biotechnology | Year: 2014

Recent years have witnessed the use of different ionic liquids for biomass processing, either at the level of lignocellulose pre-treatment, to fractionate biomass in its main components, separating hemicellulose and lignin from cellulose, or directly in cellulose decrystallization by dissolving it in the ionic liquid and subsequent precipitation by adding anti-solvents. Yet, most of the ILs employed in these strategies (e.g. imidazolium-based solvents) are (still) expensive for such applications, and provide discussable ecological footprints. In an attempt to combine the highly useful generated knowledge with novel neoteric solvents with improved properties, economics, availability and ecology, several new trends have appeared in these areas during recent years. They comprise the use of switchable ILs, based on strong organic bases and CO2, the application of distillable ILs, as well as the use of bio-based and low-cost ILs and deep-eutectic-solvents (DES), e.g. choline chloride-based derivatives. Apart from other emerging uses, for all these solvents some preliminary applications in biomass processing involving pretreatments, cellulose dissolution and other applications have been successfully reported. This Minireview contextualizes these recent trends and discusses them with emphasis on future use of them in biorefineries and biomass valorization. © 2013 Society of Chemical Industry. Source


Felderhof B.U.,RWTH Aachen
Physics of Fluids | Year: 2010

Swimming at low Reynolds number of a cylindrical body due to wavelike surface displacement is studied for the situation where the fluid is confined to a circular tube. The body has infinite length and swims in the direction of the tube axis. The swimming speed and dissipation are calculated to second order in the surface displacement for four different strokes. Both speed and dissipation are affected significantly by the confinement. For a helical stroke the body achieves both a translational and a rotational swimming velocity. © 2010 American Institute of Physics. Source


Czakon M.,RWTH Aachen
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

A general subtraction scheme, STRIPPER (SecToR Improved Phase sPacE for real Radiation), is derived for the evaluation of next-to-next-to-leading order (NNLO) QCD contributions from double-real radiation to processes with at least two particles in the final state at leading order. The result is a Laurent expansion in the parameter of dimensional regularization, the coefficients of which should be evaluated by numerical Monte Carlo integration. The two main ideas are a two-level decomposition of the phase space, the second one factorizing the singular limits of amplitudes, and a suitable parameterization of the kinematics allowing for derivation of subtraction and integrated subtraction terms from eikonal factors and splitting functions without non-trivial analytic integration. © 2010 Elsevier B.V. Source


The combination of the advantageous properties of molecular and solid catalysts is considered the "Holy Grail" in catalysis research. Great potential is provided by nanoporous polymers. Chemically well-defined moieties in combination with a high stability render these materials suitable as catalyst supports for liquid-phase and even aqueous-phase catalytic processes, especially regarding the transition from fossil resources to renewable resources. In this Minireview, recent developments are summarized, covering the three main approaches: solid metal-free organocatalysts, immobilized molecular catalyst species, and supported metal nanoparticles and clusters. Their potential is evaluated and the question as to whether nanoporous polymers can bridge the gap between homogeneous and heterogeneous catalysis is critically discussed. Poring over polymers: Nanoporous polymers pose great potential for the future development of catalytic processes. They unite the advantages of homogeneous and heterogeneous processing by providing solid organocatalysts, immobilized molecular metal species, and stabilized metal nanoparticles and clusters. Recent developments in these three main areas are summarized. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Roscher M.A.,Imk Automotive GmbH | Bohlen O.S.,BMW AG | Sauer D.U.,RWTH Aachen
IEEE Transactions on Energy Conversion | Year: 2011

Lithium-ion (Li-ion) batteries are nowadays the best tradeoff between performance, cost, and lifetime to store electric power and energy effectively. The reliable determination of the batteries instantaneous power capability and energy content is mandatory for many mobile high-energy and power-consuming applications. Herein, the battery impedance and state of charge (SOC) are the relevant values. In energy storage systems, these values are to be considered for each battery cell individually, due to arising limitations caused by cell-specific variations. Simple algorithms to determine the battery systems impedance and SOC are presented including parameter and state-estimation techniques. Furthermore, methods are derived making the impedance and SOC determination possible for a large number of particular cells in a battery system. The applicability of the demonstrated algorithms for battery control unit implementation is proved incorporating data achieved from load scenarios applied to a cell stack Li-ion battery module. Cell impedance and SOC variations could be detected precisely. Moreover, a combination of impedance and SOC spread was identified during typical battery operation. © 2011 IEEE. Source


Rotering N.,RWTH Aachen | Ilic M.,Carnegie Mellon University | Ilic M.,Technical University of Delft
IEEE Transactions on Power Systems | Year: 2011

Plug-in hybrid electric vehicles are a midterm solution to reduce the transportation sector's dependency on oil. However, if implemented in a large scale without control, peak load increases significantly and the grid may be overloaded. Two algorithms to address this problem are proposed and analyzed. Both are based on a forecast of future electricity prices and use dynamic programming to find the economically optimal solution for the vehicle owner. The first optimizes the charging time and energy flows. It reduces daily electricity cost substantially without increasing battery degradation. The latter also takes into account vehicle to grid support as a means of generating additional profits by participating in ancillary service markets. Constraints caused by vehicle utilization as well as technical limitations are taken into account. An analysis, based on data of the California independent system operator, indicates that smart charge timing reduces daily electricity costs for driving from $0.43 to $0.2. Provision of regulating power substantially improves plug-in hybrid electric vehicle economics and the daily profits amount to $1.71, including the cost of driving. © 2011 IEEE. Source


The Integrated Energy and Climate Protection Program of the German government includes the political target of doubling the share of combined heat and power generation (CHP) in Germany from currently about 13% to 25% by 2020. In order to reach this goal, a new CHP law was enacted to improve the framework conditions for CHP generation. In this paper, we aim at identifying which CHP technologies are most likely to be installed in the near future to reach the CHP target stipulated by the German government. In our model, we apply Mean-Variance Portfolio (MVP) theory to consider return- and risk-related aspects of various CHP technologies. The analysis pays tribute to specific characteristics of CHP generation, such as promotion via guaranteed feed-in tariffs, additional revenues from heat sales, specific operational features, and specifics concerning the allocation of CO 2 allowances. The investigation is based on four generic standard CHP technologies currently available on a commercial basis: large coal-fired CHP plants, combined-cycle gas turbines (CCGT-CHP), engine-CHP and micro-turbine CHP. As selection criteria for the portfolio performance we take, independently from each other, the net present value (NPV) of investment in CHP and the expected annual portfolio return, and compare the results obtained from both approaches. Irrespective of the chosen selection criteria, the analysis shows that CCGT-CHP and engine-CHP are the most attractive CHP technologies from a return perspective. A diversification of the portfolio with other kinds of CHP technologies can contribute to stabilizing portfolio returns. In view of the results obtained we conclude for the further development of CHP generation in Germany that a large portion of additional new CHP capacity will probably be built in the industrial sector. © 2011 Elsevier Ltd. Source


Petrochemical-free commodities: Recent developments in the biosynthetic production of different hydrocarbons by engineered microorganisms offer further examples of how white biotechnology can provide chemicals and biofuels in a sustainable manner by coupling natural cycles or de novo-designed metabolic routes with industrial interests. Non-edible and cheap lignocellulosic residues are a renewable feedstock to secure the sustainability of the process. © 2011 Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim. Source


Horn P.,RWTH Aachen
Methods in molecular biology (Clifton, N.J.) | Year: 2011

Human mesenchymal stromal cells (MSC) raise high hopes for tissue engineering and therapeutic -applications. So far, it is not possible to isolate pure fractions from bone marrow and therefore MSC cell preparations notoriously represent heterogeneous mixtures of different cell types. The composition of -subpopulations can already be affected by the initial steps of cell preparation. Usually, isolation of MSC involves density fractionation to separate the mononuclear cells (MNCs) from erythrocytes and -granulocytes. However, this method is difficult to standardize especially under GMP conditions. Here, we describe an alternative approach for isolation of human MSC based on red blood cell (RBC) lysis with ammonium chloride. This results in a slightly higher number of fibroblastic colony forming units (CFU-F), whereas morphological analysis of the CFU-F reveals the same heterogeneous composition of MSC cultures indicating that the proportion of subpopulations is not affected by RBC lysis. Immunophenotype (CD73+, CD90+, CD105+, CD31-, CD34-, CD45-), adipogenic, and osteogenic differentiation potential of MSC were also similar with both methods. In conclusion, RBC lysis comprises an efficient method for the isolation of human MSC from bone marrow aspirate. This technique is faster and can be standardized more easily for clinical application of MSC. Source


Belyaev A.V.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry | Vinogradova O.I.,RWTH Aachen
Journal of Fluid Mechanics | Year: 2010

A super-hydrophobic array of grooves containing trapped gas (stripes) has the potential to greatly reduce drag and enhance mixing phenomena in microfluidic devices. Recent work has focused on idealized cases of stick-perfect slip stripes. Here, we analyse the experimentally more relevant situation of a pressure-driven flow past striped slip-stick surfaces with arbitrary local slip at the gas sectors. We derive approximate formulas for maximal (longitudinal) and minimal (transverse) directional effective slip lengths that are in a good agreement with the exact numerical solution for any surface slip fraction. By representing eigenvalues of the slip length tensor, we obtain the effective slip for any orientation of stripes with respect to the mean flow. Our results imply that flow past stripes is controlled by the ratio of the local slip length to texture size. In the case of a large (compared to the texture period) slip at the gas areas, surface anisotropy leads to a tensorial effective slip, by attaining the values predicted earlier for a perfect local slip. Both effective slip lengths and anisotropy of the flow decrease when local slip becomes of the order of texture period. In the case of a small slip, we predict simple surface-averaged isotropic flows (independent of orientation). © 2010 Cambridge University Press. Source


Weber C.,Ludwig Maximilians University of Munich | Weber C.,Maastricht University | Noels H.,RWTH Aachen
Nature Medicine | Year: 2011

Coronary artery disease (CAD) arising from atherosclerosis is a leading cause of death and morbidity worldwide. The underlying pathogenesis involves an imbalanced lipid metabolism and a maladaptive immune response entailing a chronic inflammation of the arterial wall. The disturbed equilibrium of lipid accumulation, immune responses and their clearance is shaped by leukocyte trafficking and homeostasis governed by chemokines and their receptors. New pro-and anti-inflammatory pathways linking lipid and inflammation biology have been discovered, and genetic profiling studies have unveiled variations involved in human CAD. The growing understanding of the inflammatory processes and mediators has uncovered an intriguing diversity of targetable mechanisms that can be exploited to complement lipid-lowering therapies. Here we aim to systematically survey recently identified molecular mechanisms, translational developments and clinical strategies for targeting lipid-related inflammation in atherosclerosis and CAD. © 2011 Nature America, Inc. All rights reserved. Source


Abele E.,TU Darmstadt | Altintas Y.,University of British Columbia | Brecher C.,RWTH Aachen
CIRP Annals - Manufacturing Technology | Year: 2010

This paper presents the state-of-the-art in machine tool main spindle units with focus on motorized spindle units for high speed and high performance cutting. Detailed information is given about the main components of spindle units regarding historical development, recent challenges and future trends. An overview of recent research projects in spindle development is given. Advanced methods of modeling the thermal and dynamical behavior of spindle units are shown in overview with specific results. Furthermore concepts for sensor and actuator integration are presented which all focus on increasing productivity and reliability. © 2010 CIRP. Source


Witzens J.,RWTH Aachen | Hochberg M.,University of Washington
Optics Express | Year: 2011

We theoretically investigate a novel scheme to detect target molecule induced, or suppressed, aggregation of nanoparticles. High-Q optical resonators are used to both optically trap gold nanoparticle clusters and to detect their presence via a shift in the resonance wavelength. The well depth of the optical trap is chosen to be relatively low compared to the thermal energy of the nanoparticles, so that trapping of single nanoparticles is marginal and results in a comparatively small wavelength shift. Aggregation of functionalized gold nanoparticles is mediated or suppressed via binding to a target molecule. The well depth for the resulting nanoparticle clusters scales much more favorably relative to Brownian motion, resulting in large nanoparticle concentration enhancements in the evanescent field region of the resonator. We predict a target molecule sensitivity in the tens of fM range. In order to predict the resonator response, a complete theory of time resolved nanoparticle cluster trapping dynamics is derived. In particular, the formalism of Kramers' escape time is adapted to 2D (silicon wire) and 3D (ring resonator) optical traps. ©2011 Optical Society of America. Source


Gugat M.,Lehrstuhl 2 fur Angewandte Mathematik | Herty M.,RWTH Aachen
ESAIM - Control, Optimisation and Calculus of Variations | Year: 2011

We consider the flow of gas through pipelines controlled by a compressor station. Under a subsonic flow assumption we prove the existence of classical solutions for a given finite time interval. The existence result is used to construct Riemannian feedback laws and to prove a stabilization result for a coupled system of gas pipes with a compressor station. We introduce a Lyapunov function and prove exponential decay with respect to the L2-norm. © 2009 EDP Sciences, SMAI. Source


Rampf C.,RWTH Aachen
Journal of Cosmology and Astroparticle Physics | Year: 2012

We derive a recursion relation in the framework of Lagrangian perturbation theory, appropriate for studying the inhomogeneities of the large scale structure of the universe. We use the fact that the perturbative expansion of the matter density contrast is in one-to-one correspondence with standard perturbation theory (SPT) at any order. This correspondence has been recently shown to be valid up to fourth order for a non-relativistic, irrotational and dust-like component. Assuming it to be valid at arbitrary (higher) order, we express the Lagrangian displacement field in terms of the perturbative kernels of SPT, which are itself given by their own and well-known recursion relation. We argue that the Lagrangian solution always contains more non-linear information in comparison with the SPT solution, (mainly) if the non-perturbative density contrast is restored after the displacement field is obtained. © 2012 IOP Publishing Ltd and Sissa Medialab srl. Source


Dual-specificity tyrosine phosphorylation-regulated kinases (DYRKs) constitute an evolutionarily conserved family of protein kinases with key roles in the control of cell proliferation and differentiation. Members of the DYRK family phosphorylate many substrates, including critical regulators of the cell cycle. A recent report revealed that human DYRK2 acts as a negative regulator of G1/S transition by phosphorylating c-Jun and c-Myc, thereby inducing ubiquitination-mediated degradation. Other DYRKs also function as cell cycle regulators by modulating the turnover of their target proteins. DYRK1B can induce reversible cell arrest in a quiescent G0 state by targeting cyclin D1 for proteasomal degradation and stabilizing p27Kip1. The DYRK2 ortholog of C. elegans, MBK-2, triggers the proteasomal destruction of oocyte proteins after meiosis to allow the mitotic divisions in embryo development. This review summarizes the accumulating results that provide evidence for a general role of DYRKs in the regulation of protein stability. © 2012 Landes Bioscience. Source


Kesselheim T.,RWTH Aachen
Proceedings of the Annual ACM Symposium on Principles of Distributed Computing | Year: 2012

We consider protocols that serve communication requests arising over time in a wireless network that is subject to interference. Unlike previous approaches, we take the geometry of the network and power control into account, both allowing to increase the network's performance significantly. We introduce a stochastic and an adversarial model to bound the packet injection. Although taken as the primary motivation, this approach is not only suitable for models based on the signal-to-interference-plus-noise ratio (SINR). It also covers virtually all other common interference models, for example the multiple-access channel, the protocol model, the radio-network model, and distance-2 matching. Packet-routing networks allowing each edge or each node to transmit or receive one packet at a time can be modeled as well. Starting from an algorithm for the respective scheduling problem with static transmission requests, we build distributed stable protocols. This is more involved than in previous, similar approaches because the algorithms we consider do not necessarily scale linearly when scaling the input instance. We can guarantee a throughput that is as large as the one of the original static algorithm. In particular, for SINR models the competitive ratios of the protocol in comparison to optimal ones in the respective model are between constant and O(log 2 m) for a network of size m. © 2012 ACM. Source


Bissels U.,Miltenyi Biotec GmbH | Bosio A.,Miltenyi Biotec GmbH | Wagner W.,RWTH Aachen
Haematologica | Year: 2012

Hematopoiesis is regulated by microRNAs (miRNAs). These small regulatory RNAs are master regulators of developmental processes that modulate expression of several target genes post-transcriptionally. Various miRNAs are up-regulated at specific stages during hematopoietic development and the functional relevance of miRNAs has been proven at many different stages of lineage specification. Knockout of specific miRNAs can produce dramatic phenotypes leading to severe hematopoietic defects. Furthermore, several studies demonstrated that specific miRNAs are differentially expressed in hematopoietic stem cells. However, the emerging picture is extremely complex due to differences between species, cell type dependent variation in miRNA expression and differential expression of diverse target genes that are involved in various regulatory networks. There is also evidence that miRNAs play a role in cellular aging or in the inter-cellular crosstalk between hematopoietic cells and their microenvi-ronment. The field is rapidly evolving due to new profiling tools and deep sequencing technology. The expression pro-files of miRNAs are of diagnostic relevance for classification of different diseases. Recent reports on the generation of induced pluripotent stem cells with miRNAs have fuelled the hope that specific miRNAs and culture conditions facilitate directed differentiation or culture expansion of the hematopoietic stem cell pool. This review summarizes our current knowledge about miRNA expression in hematopoi-etic stem and progenitor cells, and their role in the hematopoietic stem cell niche. © 2012 Ferrata Storti Foundation. Source


Mohnke O.,RWTH Aachen | Hughes B.,Celle Technology Center
Water Resources Research | Year: 2014

Nuclear magnetic resonance (NMR) relaxometry is a geophysical method widely used in borehole and laboratory applications to nondestructively infer transport and storage properties of rocks and soils as it is directly sensitive to the water/oil content and pore sizes. However, for inferring pore sizes, NMR relaxometry data need to be calibrated with respect to a surface interaction parameter, surface relaxivity, which depends on the type and mineral constituents of the investigated rock. This study introduces an inexpensive and quick alternative to the classical calibration methods, e.g., mercury injection, pulsed field gradient (PFG) NMR, or grain size analysis, which allows for jointly estimating NMR surface relaxivity and pore size distributions using NMR relaxometry data from partially desaturated rocks. Hereby, NMR relaxation experiments are performed on the fully saturated sample and on a sample partially drained at a known differential pressure. Based on these data, the (capillary) pore radius distribution and surface relaxivity are derived by joint optimization of the Brownstein-Tarr and the Young-Laplace equation assuming parallel capillaries. Moreover, the resulting pore size distributions can be used to predict water retention curves. This inverse modeling approach - tested and validated using NMR relaxometry data measured on synthetic porous borosilicate samples with known petrophysical properties (i.e., permeability, porosity, inner surfaces, pore size distributions) - yields consistent and reproducible estimates of surface relaxivity and pore radii distributions. Also, subsequently calculated water retention curves generally correlate well with measured water retention curves. Key Points NMR surface relaxivity and pore sizes are jointly calibrated and estimated Inverse modeling using simple pore bundle models was tested and validated Water retention curves were predicted © 2014. American Geophysical Union. All Rights Reserved. Source


Kasah T.,RWTH Aachen
International Journal of Life Cycle Assessment | Year: 2014

Purpose: The environmental aspects of paper as a consumer good have been extensively studied. However, the paper machine has been mostly neglected in the literature. The purpose of this article is to present a LCA case study that explicitly focuses on the system of a newsprint paper machine and its environmental impacts and not on the system of the consumer good paper. The relevance of the paper machine as capital equipment is analyzed, and conclusions for the environmental improvement of paper machines are drawn based on identified hotspots. The article hereby answers the more general research questions of whether capital equipment has rightly been neglected in other studies regarding pulp and paper and which impact categories are important for analyzing the environmental burdens of a paper machine. Methods: The study has been executed in collaboration with Voith Paper, an original equipment manufacturer. Hence, in distinction to literature-based studies, primary data on the paper machine was available resulting in a high overall data quality. Based on the ISO 14040 (2006) and 14044 (2006) standards, this article pursues a cradle-to-grave approach for the paper machine. It assesses the environmental impacts in the impact categories defined by the ReCiPe impact assessment methodology. Different types of energy generation are examined in a scenario analysis with combined heat and power generation (CHP) as the baseline case. For interpretation, a normalization and a sectoral analysis are performed. Results and discussion: The normalized results indicate fossil resource depletion and global warming as the most important impact categories. Global warming impacts are highly dependent on the energy processes and result to 432.7 kg CO2e per production of 1 t of paper for CHP and to 701.7 kg CO2e for EU25 grid mix. The sectoral analysis shows that the machinery's operations/use phase is clearly dominating most impact categories due to its long lifetime. An exception is the metal depletion, for which the materials and manufacturing processes are most important. Conclusions: These findings prove that for most categories, the operations/use phase of the paper machine is the most important life cycle stage. In systems focusing on the consumer good paper, it is therefore sufficient to model the operation of the paper machine, whereas the manufacturing, transport, and end-of-life processes regarding the paper machine equipment can be neglected, unless metal depletion is important to the study. © 2013 Springer-Verlag Berlin Heidelberg. Source


Van Aerde K.I.,Julich Research Center | Van Aerde K.I.,Royal Netherlands Academy of Arts and science | Feldmeyer D.,Julich Research Center | Feldmeyer D.,RWTH Aachen | Feldmeyer D.,Julich Aachen Research Alliance
Cerebral Cortex | Year: 2015

The medial prefrontal cortex (mPFC) has been implicated in cognitive and executive processes including decision making, working memory and behavioral flexibility. Cortical processing depends on the interaction between distinct neuronal cell types in different cortical layers. To better understand cortical processing in the rat mPFC, we studied the diversity of pyramidal neurons using in vitro whole-cell patch clamp recordings and biocytin staining of neurons, followed by morphological analysis. Using unsupervised cluster analysis for the objective grouping of neurons, we identified more than 10 different pyramidal subtypes spread across the different cortical layers. Layer 2 pyramidal neurons possessed a unique morphology with wide apical dendritic field spans and a narrow basal field span. Layer 3 contained the only subtype that showed a burst of action potentials upon current injection. Layer 5 pyramidal neurons showed the largest voltage sags. Finally, pyramidal neurons in layer 6 (L6) showed a great variety in their morphology with 39% of L6 neurons possessing tall apical dendrites that extend into layer 1. Future experiments on the functional role of the mPFC should take into account the great diversity of pyramidal neurons. © 2013 The Author. Source


Asmolov E.S.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry | Vinogradova O.I.,RWTH Aachen
Journal of Fluid Mechanics | Year: 2012

In many applications it is advantageous to construct effective slip boundary conditions, which could fully characterize flow over patterned surfaces. Here we focus on laminar shear flows over smooth anisotropic surfaces with arbitrary scalar slip b(y), varying in only one direction. We derive general expressions for eigenvalues of the effective slip-length tensor, and show that the transverse component is equal to half of the longitudinal one, with a two times larger local slip, 2b(y). A remarkable corollary of this relation is that the flow along any direction of the one-dimensional surface can be easily determined, once the longitudinal component of the effective slip tensor is found from the known spatially non-uniform scalar slip. © 2012 Cambridge University Press. Source


Reich S.,RWTH Aachen | Schierz O.,University of Leipzig
Clinical Oral Investigations | Year: 2013

Objectives: The objective of this prospective clinical study was to evaluate the performance of chair-side generated crowns after 48 months. Materials and methods: Forty-one posterior full contour crowns made of a machinable lithium disilicate ceramic (e.max CAD LT) were inserted in 34 patients applying a chair-side CAD/CAM technique. One crown per patient was randomly selected for evaluation at baseline, after 6, 12, 24, 36, and 48 months according to modified US Public Health Service criteria. Results: After a mean observation time of 51 months (min, 48 months; max, 56 months; SD ± 2.3 months), 29 crowns were available for re-examination. Within the observation period, one failure occurred due to a crown fracture after 2.8 years. Four abutment teeth revealed signs of biological complications: Two abutment changed sensibility perception from positive to negative within the first 13 month. Two abutment teeth showed secondary caries below the crown margin, one after the 24, and another after the 48 month recall. Both abutments received cervical adhesive composite fillings. The failure-free rate was 96.3 % after 4 years according to Kaplan-Meier (CI: upper bound, 4.4 years; lower bound, 4.7 years). Conclusions: Due to the fact that the secondary caries was not caused as a result of an inaccuracy of the crown margins and the endodontic complications were in a normal range, the clinical performance of the crowns was completely satisfying. Clinical relevance: The chair-side application of lithium disilicate crowns can be recommended. © 2012 Springer-Verlag Berlin Heidelberg. Source


Aeolian sediments are an important archive for palaeoclimate reconstructions on the Tibetan Plateau. The accumulation of aeolian sediments and the formation of palaeosols are used as a proxy for dry and wet phases, respectively. During the last decade the number of OSL (optically stimulated luminescence) ages of aeolian sediments has been rapidly increasing. This study summarises the results from more than 300 individual OSL ages. Despite the widespread occurrence of aeolian sediments on the Tibetan Plateau nearly all OSL samples are located on the northeastern and the southern part. In most regions the strongest accumulation occurred during the late Glacial and in the early Holocene. This coincides with the strengthening of the Asian summer monsoon on the Tibetan Plateau and wetter climate conditions after the relatively dry glacial times. The development of a sufficient vegetation cover, acting as a sediment trap, seems to be an important requirement for the preservation of aeolian archives. Short dry periods like the Younger Dryas led to a more enhanced aeolian accumulation without destruction of previously formed archives in some regions. The formation of palaeosols occurred mainly during the wet early and mid-Holocene, but the number of ages is relatively small. In contrast, a second phase of aeolian accumulation during the late Holocene was related to the weakening of the Asian summer monsoon and drier climate conditions. This indicates that the reaction of aeolian accumulation on the Tibetan Plateau depends on the previous climate state. A comparison between the OSL ages from aeolian sands and loess deposits yields a different timing of deposition of these two sediment types. While the sand deposits in different basins resemble wet and dry phases, loess deposits show no common signal between the analysed areas. This indicates an influence of local factors, such as varying source areas and erosive processes on the slopes. In general, the aeolian archives in the high mountain environment are governed by numerous factors besides the climatic influence. © 2015 Elsevier B.V. Source


Schippers J.H.M.,RWTH Aachen
Current Opinion in Plant Biology | Year: 2015

Plant senescence is a natural phenomenon known for the appearance of beautiful autumn colors and the ripening of cereals in the field. Senescence is a controlled process that plants utilize to remobilize nutrients from source leaves to developing tissues. While during the past decades, molecular components underlying the onset of senescence have been intensively studied, knowledge remains scarce on the age-dependent mechanisms that control the onset of senescence. Recent advances have uncovered transcriptional networks regulating the competence to senesce. Here, gene regulatory networks acting as internal timing mechanisms for the onset of senescence are highlighted, illustrating that early and late leaf developmental phases are highly connected. © 2015 Elsevier Ltd. Source


Kesselheim T.,RWTH Aachen
Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms | Year: 2011

In modern wireless networks devices are able to set the power for each transmission carried out. Experimental but also theoretical results indicate that such power control can improve the network capacity significantly. We study this problem in the physical interference model using SINR constraints. In the SINR capacity maximization problem, we are given n pairs of senders and receivers, located in a metric space (usually a so-called fading metric). The algorithm shall select a subset of these pairs and choose a power level for each of them with the objective of maximizing the number of simultaneous communications. This is, the selected pairs have to satisfy the SINR constraints with respect to the chosen powers. We present the first algorithm achieving a constant-factor approximation in fading metrics. The best previous results depend on further network parameters such as the ratio of the maximum and the minimum distance between a sender and its receiver. Expressed only in terms of n, they are (trivial) Ω (n) approximations. Our algorithm still achieves an O(log n) approximation if we only assume to have a general metric space rather than a fading metric. Furthermore, existing approaches work well together with the algorithm allowing it to be used in single-hop and multi-hop scheduling scenarios. Here, we also get polylogn approximations. Source


Klusemann B.,RWTH Aachen | Klusemann B.,42 Technology | Yalcinkaya T.,European Commission
International Journal of Plasticity | Year: 2013

Abstract A gradient crystal plasticity model in the framework of continuum thermodynamics and rate variational formulation is presented for the description of plastic deformation patterning in a system with non-convex energetic hardening. The paper focuses on the extension of the 1D deformation patterning analysis of Yalcinkaya et al. (2011) to 2D for monotonic loading histories. Solution algorithm is based on the simultaneous solution of displacement and plastic slip fields, which have been considered as primary variables. The incorporation of non-convexity in the plastic slip potential in the Landau-Devonshire form makes the framework dual to phase field modeling approaches with a strong coupling between the deformation and the plastic slip fields. In the phase field modeling approaches the coupling is rather weak, i.e. fields do not have to be coupled as in the current approach based on the decomposition of the total strain. The numerical examples illustrate the intrinsic formation of (laminate type) microstructures and their evolution under mechanical loading together with the macroscopic hardening-softening-stress plateau response. The effect of different number of slip systems, loading rates and boundary conditions are investigated in detail. © 2013 Elsevier Ltd. Source


Salge T.O.,RWTH Aachen
Journal of Product Innovation Management | Year: 2013

Given the growing popularity of the open innovation model, it is increasingly common to source knowledge for new product ideas from a wide range of actors located outside of organizational boundaries. Such open search strategies, however, might not always be superior to their closed counterparts. Indeed, widening the scope of knowledge sourcing at the ideation stage typically comes at a price given the substantial monetary and nonmonetary costs often incurred in the process of identifying, assimilating, and utilizing external knowledge inputs. Considering both the benefits and costs of search openness, the authors develop a project-level contingency model of open innovation. This model suggests that search openness is curvilinearly (taking an inverted U-shape) related to new product creativity and success. They hence assume that too little as well as too much search openness at the ideation stage will be detrimental to new product outcomes. Moreover, they argue that the effectiveness of open search strategies is contingent upon the new product development (NPD) project type (typological contingency), the NPD project leader (managerial contingency), and the NPD project environment (contextual contingency). To test these propositions empirically, multi-informant data from 62 NPD projects initiated in the English National Health Service (NHS) were collected. The econometric analyses conducted provide considerable support for a curvilinear relationship between search openness and NPD outcomes as well as for the hypothesized contingency effects. More specifically, they reveal that explorative NPD projects have more to gain from search openness at the ideation stage than their exploitative counterparts. Moreover, the project-level payoff from search openness tends to be greater, when the project leader has substantial prior innovation and management experience, and when the immediate work environment actively supports creative endeavors. These findings are valuable for NPD practice, as they demonstrate that effective knowledge sourcing has much to contribute to NPD success. In particular, pursuing an open search strategy might not always be the best choice. Rather, each NPD project is in need of a carefully tailored search strategy, effective leadership, and a supportive climate, if the full value of external knowledge sourcing is to be captured. © 2013 Product Development & Management Association. Source


Polotsky A.A.,RAS Institute of Macromolecular Compounds | Plamper F.A.,RWTH Aachen | Borisov O.V.,CNRS Institute of Analytical Sciences
Macromolecules | Year: 2013

We present a theory of a conformational collapse-to-swelling transition that occurs in aqueous dispersions of multiresponsive (pH- and thermoresponsive) microgels upon variation of ionic strength, temperature, or pH. Our theory is based on osmotic balance arguments and explicitly accounts for ionization equilibrium inside microgel partices. The theory predicts complex patterns in the dependence of the microgel particle dimensions on the control parameters: An increase in temperature leads to worsening of the solvent quality for the gel forming LCST-polymers and to concomitant decrease in the dimensions of the gel particles. This collapse of the gel particles provoked by an increase in temperature occurs either smoothly (at high or low ionic strength), or may exhibit a jump-wise character at intermediate ionic strength. The theory further predicts that the degree of swelling of microgel particles varies nonmonotonously and exhibits a maximum as a function of salt concentration at a pH close to the pK. This nonmonotonous variation of the particle dimensions occurs continuously at temperatures below or slightly above LCST (good or marginal poor solvent strength conditions, respectively), whereas at higher temperatures the jump-wise swelling of the gel particles is followed by either continuous or jump-wise collapse induced by progressive increase in the salt concentration. A decrease/increase in pH leads to deswelling of the weak polyacid/polybase gel particles, which occurs smoothly at temperatures below LCST, but may exhibit a discontinuity above LCST. These theoretical predictions can be used for design of smart stimuli-responsive microgels. © 2013 American Chemical Society. Source


Keim W.,RWTH Aachen
Angewandte Chemie - International Edition | Year: 2013

Luck, talent, and hard work: Currently, over a million tons of α-olefins are manufactured per annum using the Shell Higher Olefin Process (SHOP). The discovery of the process was the result of correct model conceptions and lucky coincidence. W. Keim, one of the main participants in the development of SHOP, gives a personal account of the events. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Krewinkel R.,RWTH Aachen
International Journal of Heat and Mass Transfer | Year: 2013

Effusion-cooling is the next logical step in gas turbine blade cooling. Research on this topic has been done since the early 1950s, but manufacturing and modelling difficulties have prevented its commercial application so far. Still, there is a multitude of scientific publications about most aspects of this technology. Here, an overview over the publications most relevant for engineering uses is provided, with a focus on its application to gas turbine blades. The topics addressed here include the basic geometric and aerodynamic parameters known from film-cooling, but also the thermal conductivity of the base material, simplified approaches for modelling effusion-cooling and finally the application to blades, which incorporates the combination of impingement- and effusion-cooling as well as influences from operation. © 2013 Elsevier Ltd. All rights reserved. Source


Shabtai N.R.,RWTH Aachen
Journal of the Acoustical Society of America | Year: 2015

Microphone arrays usually combine multiple input signals into one output signal, such that spatial information on the sound sources is not included in the output signal. Since spatial information on the sound sources may increase the intelligibility of a speech signal that is perceived by a human listener, recent works aim to include this spatial information in the output of the microphone array by utilizing binaural cues preservation. More current works apply binaural sound reproduction (BSR) using spherical microphone arrays by incorporating the head related transfer functions (HRTFs) in the weight function of a conventional maximum-directivity beamformer. However, the HRTFs may affect the optimality of beamformers that were already designed to provide a maximal directivity without the HRTFs. This work presents a more general mathematical framework than previously presented for the incorporation of HRTFs in the weight function, which allows the optimization of the weight function using an averaged maximum-directivity criterion under the condition that the HRTFs are already incorporated. It is shown that the proposed optimized BSR beamformer achieves higher directivity index. © 2015 Acoustical Society of America. Source


Findeisen H.M.,RWTH Aachen
Current atherosclerosis reports | Year: 2013

Epigenetics involve heritable and acquired changes in gene transcription that occur independently of the DNA sequence. Epigenetic mechanisms constitute a hierarchic upper-level of transcriptional control through complex modifications of chromosomal components and nuclear structures. These modifications include, for example, DNA methylation or post-translational modifications of core histones; they are mediated by various chromatin-modifying enzymes; and ultimately they define the accessibility of a transcriptional complex to its target DNA. Integrating epigenetic mechanisms into the pathophysiologic concept of complex and multifactorial diseases such as atherosclerosis may significantly enhance our understanding of related mechanisms and provide promising therapeutic approaches. Although still in its infancy, intriguing scientific progress has begun to elucidate the role of epigenetic mechanisms in vascular biology, particularly in the control of smooth muscle cell phenotypes. In this review, we will summarize epigenetic pathways in smooth muscle cells, focusing on mechanisms involved in the regulation of vascular remodeling. Source


Sauer R.A.,RWTH Aachen
Journal of Adhesion Science and Technology | Year: 2010

A computational contact formulation is presented that is suitable for simulating contact interaction problems at very small length scales. The contact model is based on the coarse-graining of the intermolecular forces between neighboring bodies, like van der Waals attraction, into an effective continuum contact description. The model is cast into a nonlinear 3D finite element implementation that is capable of integrating the challenges encountered in the modeling of adhesive systems. The contact model is then applied to the dynamic modeling and simulation of the adhesion and deformation of a gecko seta based on a 3D multiscale approach. The approach spans six orders of magnitude and combines three distinct modeling levels, that describe the effective adhesion behavior at the seta scale, the spatula scale and the molecular scale. The rate-dependent pull-off behavior of adhering setae and spatulae is computed and it is shown that the model is successful in capturing pull-off forces that have been observed experimentally. © 2010 VSP. Source


Antonova E.,University of Kiel | Christian Nather,University of Kiel | Kogerler P.,RWTH Aachen | Bensch W.,University of Kiel
Angewandte Chemie - International Edition | Year: 2011

New docking sites: Sb-N bonds formed under hydrothermal conditions enable the attachment of primary and secondary organic amines (see structures, C gray, N blue) to antimonato polyoxovanadate cluster anions (polyhedral representations; O red, Sb yellow), whose charge can be compensated by protonated amines. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Dimensions of cylindrical domains and microphase separation behavior in thin films of polystyrene-b-polybutadiene diblock copolymer (SB) are analyzed under fine variation of the surface fields, polymer-polymer interactions, film thickness, and the symmetry of the wetting conditions. In thermally and in solvent annealed films the dimensions of the closest to the substrate cylinders are smaller than both in thicker films and in bulk due to the confinement effect. The related excess of the stretching energy favors a transition to nonbulk perforated lamella morphology in a narrow window of the film thickness, solvent concentration, and annealing temperature. The discussion of the apparent stability/instability of thin film morphologies includes the analysis of molecular architecture, interfacial tensions, and possible influence of dynamic effects. © 2012 American Chemical Society. Source


Hempel M.,RWTH Aachen | Nezich D.,Massachusetts Institute of Technology | Kong J.,Massachusetts Institute of Technology | Hofmann M.,National Cheng Kung University
Nano Letters | Year: 2012

Here we report on the fabrication and characterization of a novel type of strain gauge based on percolative networks of 2D materials. The high sensitivity of the percolative carrier transport to strain induced morphology changes was exploited in strain sensors that can be produced from a wide variety of materials. Highly reliable and sensitive graphene-based thin film strain gauges were produced from solution processed graphene flakes by spray deposition. Control of the gauge sensitivity could be exerted through deposition-induced changes to the film morphology. This exceptional property was explained through modeling of the strain induced changes to the flake-flake overlap for different percolation networks. The ability to directly deposit strain gauges on complex-shaped and transparent surfaces was presented. The demonstrated scalable fabrication, superior sensitivity over conventional sensors, and unique properties of the described strain gauges have the potential to improve existing technology and open up new fields of applications for strain sensors. © 2012 American Chemical Society. Source


Bonsma P.,RWTH Aachen
Leibniz International Proceedings in Informatics, LIPIcs | Year: 2012

A rerouting sequence is a sequence of shortest st-paths such that consecutive paths differ in one vertex. We study the Shortest Path Rerouting Problem, which asks, given two shortest st-paths P and Q in a graph G, whether a rerouting sequence exists from P to Q. This problem is PSPACE-hard in general, but we show that it can be solved in polynomial time if G is planar. To this end, we introduce a dynamic programming method for reconfiguration problems. © Paul Bonsma. Source


Bonnes L.,University of Stuttgart | Wessel S.,University of Stuttgart | Wessel S.,RWTH Aachen
Physical Review Letters | Year: 2011

We examine the equilibrium properties of lattice bosons with attractive on-site interactions in the presence of a three-body hard-core constraint that stabilizes the system against collapse and gives rise to a dimer superfluid phase. Employing quantum Monte Carlo simulations, the ground state phase diagram of this system on the square lattice is analyzed. In particular, we study the quantum phase transition between the atomic and dimer superfluid regime and analyze the nature of the superfluid-insulator transitions. Evidence is provided for the existence of a tricritical point along the saturation transition line, where the transition changes from being first order to a continuous transition of the dilute Bose gas of holes. The Berzinskii-Kosterlitz-Thouless transition from the dimer superfluid to the normal fluid is found to be consistent with an anomalous stiffness jump, as expected from the unbinding of half-vortices. © 2011 American Physical Society. Source


Klinge U.,RWTH Aachen | Klosterhalfen B.,Institute for Pathology
Hernia | Year: 2012

Background It is an undisputable fact that meshes have become standard for repair of abdominal wall hernias. Whereas in the late eighties there were only a couple of different devices available, today we have to choose among some hundreds, with lots of minor and major variations in polymer and structure. As most of the minor variations may not lead to significant change in clinical outcome and may be regarded as less relevant, we should focus on major differences. Eventually, this is used to structure the world of mesh by forming groups of textile devices with distinct biological response. Many experimental and some clinical studies have underlined the outstanding importance of porosity, which fortunately, in contrast to other biomechanical quanlities, is widely unaffected by the anisotropy of meshes. Methods In accordance with the major manufacturers of meshes, a classification of meshes was derived from a huge pool of textile data based briefly on the following: (1) large pores, (2) small pores, (3) additional features, (4) no pores, (5) 3D structure and (6) biological origin. At 1,000 explanted meshes the value of this classification was evaluated by group-specific assessment of inflammatory and connective tissue reaction. Results Application of this classification to common products has proved feasable, and each of the six different classes includes devices that in clinical trials failed to show relevant differences in patients' outcome when comparing products within the same group. Furthermore, histological analysis confirmed significant differences in tissue reactions between but not within the different classes. Conclusions Classifying implants according to a similar response enables grouping patients into comparable cohorts despite implantation of different devices. Furthermore, it enables the examination of the impact of mesh classes for the various indications even from heterogenous data of registries. Finally and not the least, any grouping supports the surgeon to select the best device to meet the individual need and to tailor patients therapy. © The Author(s) 2012. Source


Weiskirchen R.,RWTH Aachen
Frontiers in Bioscience | Year: 2011

CCN proteins are small secreted cysteine-rich proteins containing up to four individual structural modules including an insulin-like growth factor binding domain, a von Willebrand Factor type C motif, a thrombospondin type I module and a carboxyl-terminal cystine knot. Actually, there is a large body of evidence suggesting that members of the CCN protein family encompass an expansive repertoire of functions in crucial areas including control of development, cell fate, angiogenesis, tumorigenesis, osteogenesis, cell adhesion, mitogenesis, migration, chemotaxis, and cell survival. Moreover, this family is supposed to modulate signalling of integrins, transforming growth factor-betas, bone morphogenetic proteins, vascular endothelial growth factor, Notch and factors that mediate signals via the canonical Wingless-type MMTV integration site family. However, several of these properties are not substantiated by experimental data but were deduced from proteins sharing one or more of the structural modules with these proteins. In this review, the actual knowledge of biological activities and molecular involvement of CCN proteins in maintenance of liver health and in initiation and progression of hepatic diseases is summarized and discussed. Source


Belyaev A.V.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry | Vinogradova O.I.,RWTH Aachen
Physical Review Letters | Year: 2011

We give a general theoretical description of electro-osmotic flow at striped superhydrophobic surfaces in a thin double layer limit, and derive a relation between the electro-osmotic mobility and hydrodynamic slip-length tensors. Our analysis demonstrates that electro-osmotic flow shows a very rich behavior controlled by slip length and charge at the gas sectors. In the case of an uncharged liquid-gas interface, the flow is the same or inhibited relative to the flow in a homogeneous channel with a zero interfacial slip. By contrast, it can be amplified by several orders of magnitude provided slip regions are uniformly charged. When gas and solid regions are oppositely charged, we predict a flow reversal, which suggests the possibility of a huge electro-osmotic slip even for electroneutral surfaces. On the basis of these observations we suggest strategies for practical microfluidic devices. © 2011 American Physical Society. Source


Kom C.H.,University of Cambridge | Kulesza A.,RWTH Aachen | Stirling W.J.,University of Cambridge
Physical Review Letters | Year: 2011

We argue that the recent LHCb observation of J/ψ-pair production indicates a significant contribution from double parton scattering, in addition to the standard single parton scattering component. We propose a method to measure the double parton scattering at LHCb using leptonic final states from the decay of two prompt J/ψ mesons. © 2011 American Physical Society. Source


Galvin R.,RWTH Aachen
Building Research and Information | Year: 2014

Germany is frequently seen as a leader in thermal retrofit policy, with stringent mandatory standards for insulation, windows and boilers. However, the annual rate and average depth of thermal retrofits are considerably lower than expected. One of the main policy planks for promoting thermal upgrades is the claim that thermal retrofitting, to federal standards, is always economically viable, i.e. it always pays back, through fuel savings, over the technical lifetime of the upgrade measures. Policy discourse therefore tends to blame homeowners for complacency or ignorance in failing to see the financial opportunity offered by retrofitting. However, a five-year in-depth study of the policy, buildings and occupants finds this policy is out of step with both the buildings and the majority of their owners. The policy's claimed economic viability of retrofits fails to account for the real nature of the buildings and overstates the savings. The negative effect of misplaced claims of economic viability is considerable. Many thoughtful homeowners are deterred. It is argued that policy needs to change: more nuanced upgrade measures are needed that suit specific buildings and occupants; top-end retrofits can be promoted where appropriate and affordable, but for reasons other than economic gain. © 2014 Taylor & Francis. Source


The extended Navier-Stokes equations describing the steady-state hydrodynamics of a viscous fluid with spinning particles are solved for flow through a planar duct. The flow caused by an applied torque density in the transverse direction and linear in the transverse coordinate is compared with the flow caused by a uniform applied force density in the longitudinal direction. In both cases the flow velocity is of Poiseuille type plus a correction. In the first case the flow velocity is caused by the conveyor belt effect of spinning particles. The corrections to the Poiseuille flow pattern in the two cases differ only by a proportionality factor. The spin rate profiles in the two cases are also proportional. © 2012 American Institute of Physics. Source


Garbrecht B.,RWTH Aachen | Garny M.,TU Munich
Annals of Physics | Year: 2012

We derive solutions to the Schwinger-Dyson equations on the Closed-Time-Path for a scalar field in the limit where backreaction is neglected. In Wigner space, the two-point Wightman functions have the curious property that the equilibrium component has a finite width, while the out-of equilibrium component has zero width. This feature is confirmed in a numerical simulation for scalar field theory with quartic interactions. When substituting these solutions into the collision term, we observe that an expansion including terms of all orders in gradients leads to an effective finite-width. Besides, we observe no breakdown of perturbation theory, that is sometimes associated with pinch singularities. The effective width is identical with the width of the equilibrium component. Therefore, reconciliation between the zero-width behaviour and the usual notion in kinetic theory, that the out-of-equilibrium contributions have a finite width as well, is achieved. This result may also be viewed as a generalisation of the fluctuation-dissipation relation to out-of-equilibrium systems with negligible backreaction. © 2011 Elsevier Inc. Source


Schmeink A.,RWTH Aachen
European Transactions on Telecommunications | Year: 2011

A fair allocation of scarce resources is crucial in systems where multiple entities compete for the same goods. General interference-limited communication systems with rate adaption are investigated in this paper and the problem of fair resource allocation is addressed by two different approaches. First, a non game theoretic fairness approach is applied to the system model. Then bargaining theory is exploited to derive a game theoretic fairness concept. To compensate the information transmission necessary in the bargaining game, so-called incentive parameters are introduced. The solution of the thereby obtained local problem coincides with the Nash bargaining solution of the global problem if the incentive parameters are properly chosen. Numerical results show the advantage of the game theoretical modelling with respect to fairness and efficiency. Copyright © 2011 John Wiley & Sons, Ltd. Source


Sauer R.A.,RWTH Aachen
International Journal for Numerical Methods in Engineering | Year: 2011

During peeling of a soft elastic strip from a substrate, strong adhesional forces act locally inside the peeling zone. It is shown here that when a standard contact finite element (FE) formulation is used to compute the peeling process, a large mesh refinement is required since the numerical solution procedure becomes unstable otherwise. To improve this situation, several different efficient enrichment strategies are presented that provide stable solution algorithms for comparably coarse meshes. The enrichment is based on the introduction of additional unknowns inside the contact elements discretizing the slave surface. These are chosen in order to improve the approximation of the peeling forces, while keeping the overall number of degrees of freedom low. If needed, these additional unknowns can be condensed out locally. The enrichment formulation is developed for both 2D and 3D nonlinear FE formulations. The new enrichment technique is applied to the peeling computation of a gecko spatula. The proposed enriched contact element formulations are also investigated in sliding computations. Copyright © 2011 John Wiley & Sons, Ltd. Source


Veeck J.,Maastricht University | Dahl E.,RWTH Aachen
Biochimica et Biophysica Acta - Reviews on Cancer | Year: 2012

Aberrant activation of the Wnt signaling pathway is a major trait of many human cancers. Due to its vast implications in tumorigenesis and progression, the Wnt pathway has attracted considerable attention at several molecular levels, also with respect to developing novel cancer therapeutics. Indeed, research in Wnt biology has recently provided numerous clues, and evidence is accumulating that the secreted Wnt antagonist Dickkopf-related protein 3 (Dkk-3) and its regulators may constitute interesting therapeutic targets in the most important human cancers. Based on the currently available literature, we here review the knowledge on the biological role of Dkk-3 as an antagonist of the Wnt signaling pathway, the involvement of Dkk-3 in several stages of tumor development, the genetic and epigenetic mechanisms disrupting DKK3 gene function in cancerous cells, and the potential clinical value of Dkk-3 expression/. DKK3 promoter methylation as a biomarker and molecular target in cancer diseases. In conclusion, Dkk-3 rapidly emerges as a key player in human cancer with auspicious tumor suppressive capacities, most of all affecting apoptosis and proliferation. Its gene expression is frequently downregulated by promoter methylation in almost any solid and hematological tumor entity. Clinically, evidence is accumulating of Dkk-3 being both a potential tumor biomarker and effective anti-cancer agent. Although further research is needed, re-establishing Dkk-3 expression in cancer cells holds promise as novel targeted molecular tumor therapy. © 2011 Elsevier B.V. Source


Arnold S.,RWTH Aachen
Advances in Experimental Medicine and Biology | Year: 2012

A hallmark of neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, and stroke is a malfunction of mitochondria including cytochrome c oxidase (COX), the terminal enzyme complex of the respiratory chain. COX is ascribed a key role based on mainly two regulatory mechanisms. These are the expression of isoforms and the binding of specific allosteric factors to nucleus - encoded subunits. These characteristics represent a unique feature of COX compared with the other respiratory chain complexes. Additional regulatory mechanisms, such as posttranslational modification, substrate availability, and allosteric feedback inhibition by products of the COX reaction, control the enzyme activity in a complex way. In many tissues and cell types, COX represents the rate-limiting enzyme of the respiratory chain which further emphasizes the impact of the regulation of COX as a central site for regulating energy metabolism and oxidative stress. Two of the best-analyzed regulatory mechanisms of COX to date are the allosteric feedback inhibition of the enzyme by its indirect product ATP and the expression of COX subunit IV isoforms. This ATP feedback inhibition of COX requires the expression of COX isoform IV-1. At high ATP/ADP ratios, ADP is exchanged for ATP at the matrix side of COX IV-1 leading to an inhibition of COX activity, thus enabling COX to sense the energy level and to adjust ATP synthesis to energy demand. However, under hypoxic, toxic, and degenerative conditions, COX isoform IV-2 expression is up-regulated and exchanged for COX IV-1 in the enzyme complex. This COX IV isoform switch causes an abolition of the allosteric ATP feedback inhibition of COX and consequently the loss of sensing the energy level. Thus, COX activity is increased leading to higher levels of ATP in neural cells independently of the cellular energy level. Concomitantly, ROS production is increased. Thus, under pathological conditions, neural cells are provided with ATP to meet the energy demand, but at the expense of elevated oxidative stress. This mechanism explains the functional relevance of COX subunit IV isoform expression for cellular energy sensing, ATP production, and oxidative stress levels. This, in turn, affects neural cell function, signaling, and -survival. Thus, COX is a crucial factor in etiology, progression, and prevalence of numerous human neurodegenerative diseases and represents an important target for developing diagnostic and therapeutic tools against those diseases. © 2012 Springer Science+Business Media, LLC. Source


Thumann G.,RWTH Aachen
Current Genomics | Year: 2012

Retinal degenerations encompass a large number of diseases in which the retina and associated retinal pigment epithelial (RPE) cells progressively degenerate leading to severe visual disorders or blindness. Retinal degenerations can be divided into two groups, a group in which the defect has been linked to a specific gene and a second group that has a complex etiology that includes environmental and genetic influences. The first group encompasses a number of relatively rare diseases with the most prevalent being Retinitis pigmentosa that affects approximately 1 million individuals worldwide. Attempts have been made to correct the defective gene by transfecting the appropriate cells with the wild-type gene and while these attempts have been successful in animal models, human gene therapy for these inherited retinal degenerations has only begun recently and the results are promising. To the second group belong glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy (DR). These retinal degenerations have a genetic component since they occur more often in families with affected probands but they are also linked to environmental factors, specifically elevated intraocular pressure, age and high blood sugar levels respectively. The economic and medical impact of these three diseases can be assessed by the number of individuals affected; AMD affects over 30 million, DR over 40 million and glaucoma over 65 million individuals worldwide. The basic defect in these diseases appears to be the relative lack of a neurogenic environment; the neovascularization that often accompanies these diseases has suggested that a decrease in pigment epithelium-derived factor (PEDF), at least in part, may be responsible for the neurodegeneration since PEDF is not only an effective neurogenic and neuroprotective agent but also a potent inhibitor of neovascularization. In the last few years inhibitors of vascularization, especially antibodies against vascular endothelial cell growth factors (VEGF), have been used to prevent the neovascularization that accompanies AMD and DR resulting in the amelioration of vision in a significant number of patients. In animal models it has been shown that transfection of RPE cells with the gene for PEDF and other growth factors can prevent or slow degeneration. A limited number of studies in humans have also shown that transfection of RPE cells in vivo with the gene for PEDF is effective in preventing degeneration and restore vision. Most of these studies have used virally mediated gene delivery with all its accompanying side effects and have not been widely used. New techniques using non-viral protocols that allow efficient delivery and permanent integration of the transgene into the host cell genome offer novel opportunities for effective treatment of retinal degenerations. © 2012 Bentham Science Publishers. Source


Chattopadhyay A.,RWTH Aachen
User Modeling and User-Adapted Interaction | Year: 2013

For a design to survive unforeseen physical effects like aging, temperature variation, and/or emergence of new application standards, adaptability needs to be supported. Adaptability, in its complete strength, is present in reconfigurable processors, which makes it an important IP in modern System-on-Chips (SoCs). Reconfigurable processors have risen to prominence as a dominant computing platform across embedded, general-purpose, and high-performance application domains during the last decade. Significant advances have been made in many areas such as, identifying the advantages of reconfigurable platforms, their modeling, implementation flow and finally towards early commercial acceptance. This paper reviews these progresses from various perspectives with particular emphasis on fundamental challenges and their solutions. Empowered with the analysis of past, the future research roadmap is proposed. © 2013 Anupam Chattopadhyay. Source


Hristodorov D.,RWTH Aachen
Immunology and Cell Biology | Year: 2016

Classical immunotoxins compromise a binding component (for example, a ligand, antibody or fragment thereof) and a cytotoxic component, usually derived from bacteria or plants (for example, Pseudomonas exotoxin A or ricin). Despite successful testing in vitro, the clinical development of immunotoxins has been hampered by immunogenicity and unsatisfactory safety profiles. Therefore, research has focused on fully human pro-apoptotic components suitable for the development of cytolytic fusion proteins (CFP). We recently reported that human microtubule-associated protein tau (MAP) can induce apoptosis when delivered to rapidly proliferating cancer cells. Here, we describe a new fully human CFP called H22(scFv)-MAP, which specifically targets CD64+ cells. We show that H22(scFv)-MAP can efficiently kill proliferating HL-60 pro-monocytic cells in vitro. In addition, the human CFP specifically eliminates polarized M1 macrophages in a transgenic mouse model of cutaneous chronic inflammation. Because M1 macrophages promote the pathogenesis of many chronic inflammatory diseases, targeting this cell population with H22(scFv)-MAP could help to treat diseases such as atopic dermatitis, rheumatoid arthritis and inflammatory bowel disease.Immunology and Cell Biology advance online publication, 23 February 2016; doi:10.1038/icb.2016.4. © 2016 Australasian Society for Immunology Inc. Source


Chekhovich E.A.,University of Sheffield | Makhonin M.N.,University of Sheffield | Tartakovskii A.I.,University of Sheffield | Yacoby A.,Harvard University | And 4 more authors.
Nature Materials | Year: 2013

The interaction of an electronic spin with its nuclear environment, an issue known as the central spin problem, has been the subject of considerable attention due to its relevance for spin-based quantum computation using semiconductor quantum dots. Independent control of the nuclear spin bath using nuclear magnetic resonance techniques and dynamic nuclear polarization using the central spin itself offer unique possibilities for manipulating the nuclear bath with significant consequences for the coherence and controlled manipulation of the central spin. Here we review some of the recent optical and transport experiments that have explored this central spin problem using semiconductor quantum dots. We focus on the interaction between 104-106 nuclear spins and a spin of a single electron or valence-band hole. We also review the experimental techniques as well as the key theoretical ideas and the implications for quantum information science. © 2013 Macmillan Publishers Limited. All rights reserved. Source


We study the crossover between thermodynamic Casimir forces arising from long-range fluctuations due to Goldstone modes and those arising from critical fluctuations. Both types of forces exist in the low-temperature phase of O(n)-symmetric systems for n>1 in a d-dimensional Lâ̂¥d- 1×L slab geometry with a finite aspect ratio ρ=L/L â̂¥. Our finite-size renormalization-group treatment for periodic boundary conditions describes the entire crossover from the Goldstone regime with a nonvanishing constant tail of the finite-size scaling function far below Tc up to the region far above Tc including the critical regime with a minimum of the scaling function slightly below Tc. Our analytic result for ρâ‰1 agrees well with Monte Carlo data for the three-dimensional XY model. A quantitative prediction is given for the crossover of systems in the Heisenberg universality class. © 2013 American Physical Society. Source


Shababi M.,University of Missouri | Lorson C.L.,University of Missouri | Rudnik-Schoneborn S.S.,RWTH Aachen
Journal of Anatomy | Year: 2014

Spinal muscular atrophy (SMA) is an autosomal recessive disorder that is the leading genetic cause of infantile death. SMA is characterized by loss of motor neurons in the ventral horn of the spinal cord, leading to weakness and muscle atrophy. SMA occurs as a result of homozygous deletion or mutations in Survival Motor Neuron-1 (SMN1). Loss of SMN1 leads to a dramatic reduction in SMN protein, which is essential for motor neuron survival. SMA disease severity ranges from extremely severe to a relatively mild adult onset form of proximal muscle atrophy. Severe SMA patients typically die mostly within months or a few years as a consequence of respiratory insufficiency and bulbar paralysis. SMA is widely known as a motor neuron disease; however, there are numerous clinical reports indicating the involvement of additional peripheral organs contributing to the complete picture of the disease in severe cases. In this review, we have compiled clinical and experimental reports that demonstrate the association between the loss of SMN and peripheral organ deficiency and malfunction. Whether defective peripheral organs are a consequence of neuronal damage/muscle atrophy or a direct result of SMN loss will be discussed. © 2013 Anatomical Society. Source


Hoefer M.,RWTH Aachen
Algorithmica (New York) | Year: 2011

We consider a general class of non-cooperative buy-at-bulk cost sharing games, in which k players make investments to purchase a set of resources. Each resource has a certain cost and must bought to be available to the players. Each player has a certain constraint on the number and types of resources that she needs to have available, and she can specify payments to make a resource available to her. She strives to fulfill her constraint with the smallest investment possible. Our model includes a natural economy of scale: for a subset of players capacity must be installed at the resources, and the cost increase for a resource r is composed of a fixed price c(r) and a global concave capacity function g. This cost can be shared arbitrarily between players. We consider the existence and total cost of pure-strategy exact and approximate Nash equilibria. In general, prices of anarchy and stability depend heavily on the economy of scale and are Θ(k/g(k)). For non-linear functions g pure Nash equilibria might not exist, and deciding their existence is {NP} -hard. For subclasses of games corresponding to covering problems, primal-dual methods can be applied to derive cheap and stable approximate Nash equilibria in polynomial time. In addition, for singleton games optimal Nash equilibria exist. In this case expensive exact as well as cheap approximate Nash equilibria can be computed in polynomial time. Most of these results can be extended to games based on facility location problems. © 2009 Springer Science+Business Media, LLC. Source


Gerlach H.,Ecole Polytechnique Federale de Lausanne | von der Mosel H.,RWTH Aachen
Archive for Rational Mechanics and Analysis | Year: 2011

We consider the variational problem of finding the longest closed curves of given minimal thickness on the unit sphere. After establishing the existence of solutions for any given thickness between 0 and 1, we explicitly construct for each given thickness n: sinπ (2n),nN, exactly (N) solutions, where is Euler's totient function from number theory. Then we prove that these solutions are unique, and also provide a complete characterisation of sphere filling curves on the unit sphere; that is of those curves whose spherical tubular neighbourhood completely covers the surface area of the unit sphere exactly once. All of these results carry over to open curves as well, as indicated in the last section. © 2011 Springer-Verlag. Source


Mesenchymal stem cells change dramatically during culture expansion. Long-term culture has been suspected to evoke oncogenic transformation: overall, the genome appears to be relatively stable throughout culture but transient clonal aneuploidies have been observed. Oncogenic transformation does not necessarily entail growth advantage in vitro and, therefore, the available methods - such as karyotypic analysis or genomic profiling - cannot exclude this risk. On the other hand, long-term culture is associated with specific senescence-associated DNA methylation (SA-DNAm) changes, particularly in developmental genes. SA-DNAm changes are highly reproducible and can be used to monitor the state of senescence for quality control. Notably, neither telomere attrition nor SA-DNAm changes occur in pluripotent stem cells, which can evade the 'Hayflick limit'. Long-term culture of mesenchymal stem cells seems to involve a tightly regulated epigenetic program. These epigenetic modifications may counteract dominant clones, which are more prone to transformation. © 2012 BioMed Central Ltd. Source


Kull H.-J.,RWTH Aachen
New Journal of Physics | Year: 2012

The quantum Wigner function of an electron scattered by an ion in a strong laser field is considered in the framework of a one-dimensional scattering model with a soft-core Coulomb potential. The Wigner function contains much more information on the scattering process than the projected probability distributions in position and momentum space considered previously. The formation of the above-threshold ionization (ATI) energy spectrum, including ATI peaks, modulations and transients, can be easily explained by using the interference of phase-space trajectories. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Source


Concern has recently intensified regarding increases in the consumption of energy services that often follow energy efficiency improvements, a phenomenon widely called the 'rebound effect'. However, while some economists have precisely defined this as a metric, much discussion in academic and policy literature is imprecise, leading to confusion and miscommunication. This is especially so regarding direct 'rebound effects' in thermal retrofits of existing homes. This study surveys common usages of the term 'rebound effect' in domestic heating, identifying three main metrics, which employ different mathematical forms and therefore give different results, but are often lumped together. It defines these as the 'classic' rebound effect; the 'energy savings deficit', and the 'energy performance gap'. It then applies these to an empirical case study of three recently retrofitted 30-apartment buildings in Germany. It finds that each metric gives different results for identical situations, ranging from 2.0% to 29.9% for one building, 15.7% to 56.8% for the second, and 43.7% to 272.9% for the third. This may be one reason so-called 'rebound effect' results from various studies are so disparate. Nevertheless, specific uses are identified for each of the three metrics, provided their precise definitions are made clear. © 2013 Elsevier B.V. All rights reserved. Source


Schwarze M.,TU Braunschweig | Reese S.,RWTH Aachen
International Journal for Numerical Methods in Engineering | Year: 2011

In this paper we address the extension of a recently proposed reduced integration eight-node solid-shell finite element to large deformations. The element requires only one integration point within the shell plane and at least two integration points over the thickness. The possibility to choose arbitrarily many Gauss points over the shell thickness enables a realistic and efficient modeling of the non-linear material behavior. Only one enhanced degree-of-freedom is needed to avoid volumetric and Poisson thickness locking. One key point of the formulation is the Taylor expansion of the inverse Jacobian matrix with respect to the element center leading to a very accurate modeling of arbitrary element shapes. The transverse shear and curvature thickness locking are cured by means of the assumed natural strain concept. Further crucial points are the Taylor expansion of the compatible cartesian strain with respect to the center of the element as well as the Taylor expansion of the second Piola-Kirchhoff stress tensor with respect to the normal through the center of the element. © 2010 John Wiley & Sons, Ltd. Source


Mastalerz M.,University of Ulm | Oppel I.M.,RWTH Aachen
Angewandte Chemie - International Edition | Year: 2012

Small molecule, large surface area: A rigid triptycene derivative self-assembles by hydrogen bonds to a porous crystal with one-dimensional channels of about 14 Å diameter. Solvents in the channels can be removed to generate an extrinsic porous material with a specific BET surface area of 2796 m 2g -1. Furthermore, gases can be selectively adsorbed within the pores at 1 bar. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Van Helden J.,MVZ Dr. Stein und Kollegen | Weiskirchen R.,RWTH Aachen
Clinical Chemistry and Laboratory Medicine | Year: 2015

Background: Previous studies have shown that the measurement of vitamin D and its derivatives, especially its active metabolite 1α, 25-dihydroxy-vitamin D [1,25(OH)2D], is highly complex and prone to analytical error. We have evaluated a new immunological method for detecting and quantifying of 1,25(OH)2D. This assay is fully automated, sensitive and uses a specific recombinant fusion protein for capturing of 1,25(OH)2D. The assay was originally developed by DiaSorin for the immunoassay analyzer LIAISON XL. Methods: Performance data of this assay were determined including intra- and inter-assay precision, recovery, linearity, and limit of detection of the DiaSorin 1,25(OH)2D immunoassay on the LIAISON XL analyzer. Respective data were compared from two different liquid chromatography tandem mass spectrometry (LC-MS/MS) assays and a common radioimmunoassay (RIA) using clinical samples taken from patients suffering from vitamin D deficiency, chronic renal failure, biliary atresia, hyperparathyroidism, vitamin D-dependent rickets or sarcoidosis, as well as from pregnant women and high-level athletes. Results: The performance evaluation of 1,25(OH)2D resulted in an intra-assay and total imprecision correlation variant between 1.4% and 5.2% and 3.8%-7.1% with the new immunoassay and 3.5%-5.8% or 3.8%-7.5% with the LC-MS/MS method, respectively. Limits of detection and quantification of the immunoassay were 0.7 ng/L and 5.0 ng/L for the LIAISON XL immunoassay and 1.8 ng/L and 5.4 ng/L for the LC-MS/MS assay, respectively. Pearson's coefficients of correlation were 0.998 and 0.952 for method comparison to different established LC-MS/MS methods. Linear regression according to Passing and Bablok showed larger deviations to the RIA (slopes 0.64-0.97, coefficients of correlation 0.822-0.823). Conclusions: The DiaSorin LIAISON XL 1,25(OH)2D immunoassay appears to have improved comparability to LC-MS/MS with low imprecision and limits of detection. The assay time of 65 min, the small sample volume required (75 μL) and the throughput of 90 tests/hour without manually handling time for extraction and purification procedures is superior to the LC-MS/MS method. © 2015 by De Gruyter. Source


Monitoring of radiochemotherapy (RCX) in patients with glioblastoma is difficult because unspecific alterations in magnetic resonance imaging with contrast enhancement can mimic tumor progression. Changes in tumor to brain ratios (TBRs) in positron emission tomography (PET) using O-(2-18fluoroethyl)-l-tyrosine (18F-FET) after RCX with temozolomide of patients with glioblastoma have been shown to be valuable parameters to predict survival. The kinetic behavior of 18F-FET in the tumors is another promising parameter to analyze tumor metabolism. In this study, we investigated the predictive value of dynamic 18F-FET PET during RCX of glioblastoma. Time-activity curves (TACs) of 18F-FET uptake of 25 patients with glioblastoma were evaluated after surgery (FET-1), early (7-10 days) after completion of RCX (FET-2), and 6 to 8 weeks later (FET-3). Changes in the time to peak (TTP) and the slope of the TAC (10-50 minutes postinjection) were analyzed and related to survival. Changes in kinetic parameters of 18F-FET uptake after RCX showed no relationship with survival time. In contrast, the high predictive value of changes of TBR to predict survival was confirmed. We conclude that dynamic 18F-FET PET does not provide additional prognostic information during RCX. Static 18F-FET PET imaging (20-40 minutes postinjection) appears to be sufficient for this purpose and reduces costs. Source


OBJECTIVE: The aim of this study was to systematically investigate the course of magnetic resonance (MR) signal intensity (SI) changes that occur in noncirrhotic livers after irreversible electroporation (IRE) of liver metastases. METHODS: This study is an institutional review board–approved prospective longitudinal follow-up study on 27 patients with 37 liver metastases who underwent computed tomography–guided percutaneous IRE and a standardized follow-up protocol by serial hepatic MR imaging studies that consisted of a gadobutrol-enhanced dynamic series, axial T2-weighted (T2w) turbo spin echo, and diffusion-weighted imaging (b = 0/50/800), acquired before, within 2, and at 24 hours after IRE; at 1, 2, 4, 6, 8, and 12 weeks after IRE; and every 3 months thereafter for a follow-up of at least 12 months. RESULTS: The ablated target lesion remained visible within the ablation zone in 23 (62%) of 37 of cases for a mean time of 21 ± 20 weeks (median, 12 weeks). The ablation zone appeared homogeneously hyperintense on T2w turbo spin echo images on the day of IRE in 37 of 37 cases. By 24 hours after IRE, the ablation zone inverted its SI in 35 of 37 cases to intermediately hypointense, with a rim of T2w bright SI that exhibited arterial phase enhancement; this persisted for 7 ± 5 weeks (median, 4 weeks). The rim resolved in 35 (95%) of 37 cases within 3 months. The ablation zone increased slightly over the first 48 hours, then shrank progressively. Complete healing of the ablation zone was observed in 57% (21/37) after an average of 14 ± 15 (median, 8 weeks).Average apparent diffusion coefficient values of the ablation zone decreased from 0.74 ± 0.36 × 10 mm/s pre-IRE to 0.63 ± 0.27 × 10 mm/s within the first 24 hours (P < 0.05), followed by a progressive normalization to 0.91 ± 0.30 × 10 mm/s at 2 months. CONCLUSIONS: Knowledge of the broad spectrum of MR imaging findings after IRE is important to avoid diagnostic errors in the follow-up of patients after IRE.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Source


Conrath U.,RWTH Aachen
Trends in Plant Science | Year: 2011

Plants can be primed for more rapid and robust activation of defence to biotic or abiotic stress. Priming follows perception of molecular patterns of microbes or plants, recognition of pathogen-derived effectors or colonisation by beneficial microbes. However the process can also be induced by treatment with some natural or synthetic compounds and wounding. The primed mobilization of defence is often associated with development of immunity and stress tolerance. Although the phenomenon has been known for decades, the molecular basis of priming is poorly understood. Here, I summarize recent progress made in unravelling molecular aspects of defence priming that is the accumulation of dormant mitogen-activated protein kinases, chromatin modifications and alterations of primary metabolism. © 2011 Elsevier Ltd. Source


Buttelmann D.,University of Erfurt | Bohm R.,University of Erfurt | Bohm R.,RWTH Aachen
Psychological Science | Year: 2014

Humans demonstrate a clear bias toward members of their own group over members of other groups in a variety of ways. It has been argued that the motivation underlying this in-group bias in adults may be favoritism toward one's own group (in-group love), derogation of the out-group (out-group hate), or both. Although some studies have demonstrated in-group bias among children and infants, nothing is known about the underlying motivations of this bias. Using a novel game, we found that in-group love is already present in children of preschool age and can motivate in-group-biased behavior across childhood. In contrast, out-group hate develops only after a child's sixth birthday and is a sufficient motivation for in-group-biased behavior from school age onward. These results help to better identify the motivation that underlies in-group-biased behavior in children. © The Author(s) 2014. Source


Sorda G.,RWTH Aachen | Banse M.,Johann Heinrich Von Thunen Institute | Kemfert C.,German Institute for Economic Research
Energy Policy | Year: 2010

In the last decade biofuel production has been driven by governmental policies. This article reviews the national strategy plans of the world's leading producers. Particular attention is dedicated to blending targets, support schemes and feedstock use. Individual country profiles are grouped by continent and include North America (Canada and the US), South America (Argentina, Brazil, and Colombia), Europe (the European Union, France, and Germany), Asia (China, India, Indonesia, Malaysia, and Thailand) and Australia. © 2010 Elsevier Ltd. Source


Pagani M.,Polytechnic of Milan | Reese S.,RWTH Aachen | Perego U.,Polytechnic of Milan
Computer Methods in Applied Mechanics and Engineering | Year: 2014

Solid-shell formulations based on reduced integration with hourglass stabilization have several advantages. Among these are the smaller number of Gauss points and the direct modelling of the thickness stretch, a feature which is usually not present in standard degenerated shell elements. The latter issue is especially important for applications where contact is involved, e.g. for almost all relevant systems in production technology. Obviously this makes solid-shell formulations very attractive for their use in industrial design. A major disadvantage in the context of explicit analyses is, however, the fact that the critical time step is determined by the thickness of the solid-shell element which is usually smaller than the smallest in-plane dimension. Therefore, four-node shells (where the critical time step is determined by the in-plane dimensions) are still often preferred for explicit analysis. In the present paper we suggest several techniques to overcome this difficulty, also in the case of problems dominated by nonlinearities such as finite deformations, elastoplasticity and contact. Reference is made to an 8-node hexahedron solid-shell element recently proposed by Schwarze and Reese (2011) [32] in an implicit context. First of all, the time steps in explicit analyses are so small that it may be not necessary to update the hourglass stabilization and the implicit computation of the internal element degrees-of-freedom in every time step. Performing the update in only every hundredth step or computing an explicit rather than implicit update can reduce the computational effort up to about 50%. Another important issue is selective mass scaling which means to modify the mass matrix in such a way that the speed of sound in thickness direction is reduced. This enables the choice of a larger time step. The CPU effort can be finally noticeably decreased without changing the structural response significantly. This makes the presently used solid-shell formulation competitive to four-node shells, also for explicit analysis. © 2013 Elsevier B.V. Source


Schlieper G.,RWTH Aachen
Kidney International | Year: 2014

Cardiovascular calcifications are associated with an increased cardiovascular risk. Different regions of the arterial tree show a variable susceptibility to cardiovascular calcification. O'Neill and Adams investigated breast arteries with vascular calcification in chronic kidney disease patients. They found no evidence for osteogenic transdifferentiation or apoptosis of vascular smooth muscle cells in these arteries, suggesting that the pathogenesis of medial calcification differs between arterial regions. © 2013 International Society of Nephrology. Source


Sauter T.,RWTH Aachen | Venema V.,University of Bonn
Journal of Climate | Year: 2011

The paper presents an approach for conditional airmass classification based on local precipitation rate distributions. The method seeks, within the potential region, three-dimensional atmospheric predictor domains with high impact on the local-scale phenomena. These predictor domains are derived by an algorithm consisting of a clustering method, namely, self-organizing maps, and a nonlinear optimization method, simulated annealing. The findings show that the resulting spatial structures can be attributed to well-known atmospheric processes. Since the optimized predictor domains probably contain relevant information for precipitation generation, these grid points may also be potential inputs for nonlinear downscaling methods. Based on this assumption, the potential of these optimized large-scale predictors for downscaling has been investigated by applying an artificial neural network as a nonparametric statistical downscaling model. Compared to preset local predictors, using the optimized predictors improves the accuracy of the downscaled time series, particularly in summer and autumn. However, optimizing predictors by a conditional classification does not guarantee that a predictor increases the explained variance of the downscaling model. To study the contribution of each predictor to the output variance, either individually or by interactions with other parameters, the sources of uncertainty have been estimated by global sensitivity analysis, which provides model-free sensitivity measures. It is shown that predictor interactions play an important part in the modeling process and should be taken into account in the predictor screening. © 2011 American Meteorological Society. Source


Eurich D.,Visceral and Transplantation Surgery | Eurich D.,RWTH Aachen
Transplantation | Year: 2012

Background: The development of liver graft disease is partially determined by individual genetic background. Interleukin 28B (IL28B) is strongly suspected to be involved in susceptibility for hepatitis C virus (HCV) infection, inflammation, and antiviral treatment response before and after liver transplantation (LT). Currently, the role of IL28B polymorphism (rs12979860) in the development of hepatocellular carcinoma (HCC) is unclear, and only limited data are available on the course of HCV recurrence. Methods: One hundred sixty-seven HCV-positive patients after LT were genotyped for IL28B (C→T; rs12979860). Sixty-one patients with histologically confirmed HCC in the explanted liver were compared with 106 patients without HCC regarding IL28B genotypes. Among patients with HCC, IL28B genotypes were correlated with tumor histology and pretransplant α-fetoprotein (AFP) levels. Furthermore, the role of IL28B polymorphism was evaluated regarding interferon-based treatment success and fibrosis progression after LT. Results: The prevalence of HCC in explanted livers was significantly higher among patients with TT genotype, suggesting a protective role of the C allele in HCC development (P=0.041). Median AFP level was closely to significance higher in the presence of T allele (P=0.052). Significant differences in IL28B genotype distribution were detected between AFP-negative and AFP-positive HCCs (<15 μg/L vs. >15 μg/L; P=0.008). Although no impact could be observed regarding acute cellular rejection (P=0.940), T allele was significantly associated with antiviral therapy failure (P=0.028) and faster development of advanced fibrosis (P=0.017) after LT. Conclusion: IL28B polymorphism seems to be involved in the development of HCV-induced HCC and in the course of HCV recurrence after LT. T allele may be regarded as a genetic risk factor for HCV-related carcinogenesis, posttransplant fibrosis progression, and antiviral therapy failure. Copyright © 2012 by Lippincott Williams & Wilkins. Source


Schemionek M.,RWTH Aachen
Leukemia | Year: 2015

Chronic myeloid leukemia (CML) is driven by malignant stem cells that can persist despite therapy. We have identified Metastasis suppressor 1 (Mtss1/MIM) to be downregulated in hematopoietic stem and progenitor cells from leukemic transgenic SCLtTA/Bcr-Abl mice and in patients with CML at diagnosis, and Mtss1 was restored when patients achieved complete remission. Forced expression of Mtss1 decreased clonogenic capacity and motility of murine myeloid progenitor cells and reduced tumor growth. Viral transduction of Mtss1 into lineage-depleted SCLtTA/Bcr-Abl bone marrow cells decreased leukemic cell burden in recipients, and leukemogenesis was reduced upon injection of Mtss1-overexpressing murine myeloid 32D cells. Tyrosine kinase inhibitor (TKI) therapy and reversion of Bcr-Abl expression increased Mtss1 expression but failed to restore it to control levels. CML patient samples revealed higher DNA methylation of specific Mtss1 promoter CpG sites that contain binding sites for Kaiso and Rest transcription factors. In summary, we identified a novel tumor suppressor in CML stem cells that is downregulated by both Bcr-Abl kinase-dependent and -independent mechanisms. Restored Mtss1 expression markedly inhibits primitive leukemic cell biology in vivo, providing a therapeutic rationale for the Bcr-Abl-Mtss1 axis to target TKI-resistant CML stem cells in patients.Leukemia advance online publication, 19 January 2016; doi:10.1038/leu.2015.329. © 2015 Macmillan Publishers Limited Source


Fliescher S.,RWTH Aachen
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2012

AERA - the Auger Engineering Radio Array - is currently being set up at the southern site of the Pierre Auger Observatory. AERA will explore the potential of the radio-detection technique to cosmic ray induced air showers with respect to the next generation of large-scale surface detectors. As AERA is co-located with the low-energy enhancements of the Pierre Auger Observatory, the observation of air showers in coincidence with the Auger surface and fluorescence detector will allow to study the radio emission processes in detail and to calibrate the radio signal. Finally, the combined reconstruction of shower parameters with three independent techniques promises new insights into the nature of cosmic rays in the transition region from 10 17 to 10 19 eV. Besides the detection of coherent radiation in the MHz frequency range, the setups AMBER - Air-shower Microwave Bremsstrahlung Experimental Radiometer - and MIDAS - MIcrowave Detection of Air Showers - prepare to check the possibility to detect air showers due the emission of molecular bremsstrahlung in the GHz range at the Auger site. This article presents the status of the radio-detection setups and discusses their physics potential as well as experimental challenges. Special focus is laid on the first stage of AERA which is the startup to the construction of a 20 km 2 radio array. © 2010 Elsevier B.V. Source


Seeger O.,RWTH Aachen
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2012

The Pierre Auger Observatory constitutes the largest detector for measurements of ultra-high-energy cosmic rays (UHECRs) through extended air showers. Radio signals originating from the shower development have been detected with suitable antennas in the 50 MHz regime. The Auger engineering radio array (AERA) is being established to exploit the radio technique at these high energies. The favoured antenna for the first stage of AERA is a logarithmic periodic dipole antenna (LPDA) especially designed to suit the demands of cosmic-ray detection at the Auger site. This antenna is characterized by ultra-broadband sensitivity in the frequency range from 30 to 80 MHz and allows polarization-sensitive measurements of radio signals from all incoming directions. Our characterization of this LPDA includes careful evaluation of the frequency range obtained by combining wire-based dipoles, stability and weather testing, quality assurance in the mass production process, and a benchmark measurement of the sensitivity obtained with the time dependence of the galactic radio background. For the final setup, a fully calibrated radio-detection system including antennas, filters and low-noise amplifiers is required. We present our approach for this calibration in simulations and measurements. © 2010 Elsevier B.V. Source


The 'passive house' (PH) is a specific, pan-nationally recognised building standard designed to consume 15 kilowatt-hours of space heating energy per square metre of living area per year (kWh/m2a), significantly less than most countries' current standard for a conventional house (CH). Most PHs cost some 5-15% more to build than a CH of equivalent size and layout. Investor-households therefore often enquire as to whether building a PH is economically viable: will the extra cost pay back in the long-run through fuel savings? A number of studies have offered cost-benefit analyses to address this, usually based on modelled heating consumption figures and prescriptive approaches to setting values for unknowable variables such as future fuel price rises and the investor's discount rate. This study offers a novel 'reality-based, subjectivist' approach. It uses empirically derived (i.e. real rather than modelled) consumption figures for PHs and CHs, and allows flexibility in setting fuel price increase and discount rates according to investor-households' subjective judgments. Drawing on a wide range of data from peer-reviewed and non-peer-reviewed studies, it presents sample results in terms of years to amortisation against PH-CH consumption differences, and offers an 11-point decision-making process for would-be investor-households. © 2014 Elsevier B.V. Source


Konschelle F.,RWTH Aachen
European Physical Journal B | Year: 2014

Quasi-classical theory of superconductivity provides a powerful and yet simple description of the superconductivity phenomenology. In particular, the Eilenberger and Usadel equations provide a neat simplification of the description of the superconducting state in the presence of disorder and electromagnetic interaction. However, the modern aspects of superconductivity require a correct description of the spin interaction as well. Here, we generalize the transport equations of superconductivity in order to take into account space-time dependent electromagnetic and spin interactions on equal footing. Using a gauge-covariant Wigner transformation for the Green-Gor'kov correlation functions, we establish the correspondence between the Dyson-Gor'kov equation and the quasi-classical transport equation in the time-dependent phase-space. We give the expressions for the gauge-covariant current and charge densities (quasi-particle, electric and spin) in the transport formulation. The generalized Eilenberger and Usadel limits of the transport equation are given, too. This study is devoted to the formal derivation of the equations of motion in the electromagnetic plus spin plus particle-hole space. The studies of some specific systems are postponed to future works. © 2014 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source


Sellge G.,RWTH Aachen | Kufer T.A.,University of Hohenheim
Seminars in Immunology | Year: 2015

Recognition of bacterial pathogens by the mammalian host relies on the induction of early innate immune responses initiated by the activation of pattern-recognition receptors (PRRs) upon sensing of their cognate microbe-associated-patterns (MAMPs). Successful pathogens have evolved to intercept PRR activation and signaling at multiple steps. The molecular dissection of the underlying mechanisms revealed many of the basic mechanisms used by the immune system. Here we provide an overview of the different strategies used by bacterial pathogens and commensals to subvert and reprogram PPR-mediated innate immune responses. A particular attention is given to recent discoveries highlighting novel molecular details of the host inflammatory response in mammalian cells and current advances in our understanding of the interaction of commensals with PRR-mediated responses. © 2015 Elsevier Ltd. Source


The local magnetic structures around substitutional 3d transition metal impurities at cation sites in zinc blende structures of III-V (GaN, GaAs) and II-VI (ZnTe) semiconductors are investigated by using a spin-polarized density functional theory. We find that Cr-, Co-, Cu-doped GaN, Cr-, Mn-doped GaAs and Cr-, Fe-, Ni-doped ZnTe are half metallic with 100% spin polarization. The magnetic moments due to these 3d transition metal (TM) ions are delocalized quite significantly on the surrounding ions of host semiconductors. These doped TM ions have long range interactions mediated through the induced magnetic moments in anions and cations of host semiconductors. For low impurity concentrations Mn in GaAs also has zero magnetic moment state due to Jahn-Teller structural distortions. Based upon half metallic character and delocalization of magnetic moments in the anions and cations of host semiconductors these above mentioned 3d TM-doped GaN, GaAs and ZnTe seem to be good candidates for spintronic applications. © 2009 Elsevier B.V. All rights reserved. Source


The band diagram, deformation potential and photoelastic tensor of silicon are calculated self-consistently under uniaxial and shear strain by solving for the electronic wavefunctions with a finite-difference method. Many-body effects are accounted for by the local density approximation. In order to accommodate the large number of grid points required due to the diverging electrostatic potential near the atomic nuclei in an all-electron calculation, a non-uniform meshing is adopted. Internal displacements are taken into account by adding an additional coordinate transform to the method of Bir and Pikus. Good consistency of the calculated deformation potential and photoelastic coefficients is obtained with prior experimental and theoretical results, validating the numerical methods. Furthermore, it is shown that a slight correction of the multiplicative coefficient of the Xα approximation for conduction bands results in good agreement with experiment for both the direct and indirect bandgaps. © 2014 The Author. Published by Elsevier B.V. Source


There is growing evidence that chronic inflammatory processes are involved in triggering the sequence from chronic liver injury to liver fibrosis, ultimately leading to liver cancer. In the last years this process has been recapitulated in a growing number of different mouse models. However, it has remained unclear whether and how these mouse models reflect the clinical reality of human hepatocellular carcinoma (HCC). Research with animal models but also human liver specimens has indicated that the NF-κB signaling pathway might withhold a crucial function in the mediation of chronic hepatic inflammation and the transition to HCC in humans. However, previous studies led to divergent and partly conflicting results with regards to the functional role of NF-κB in hepatocarcinogenesis. Here, we discuss a new genetic mouse model for HCC, the liver-specific TAK1 knockout mouse, which lacks the NF-κB activating kinase TAK1 specifically in parenchymal liver cells. Molecular findings in this mouse model and their possible significance for chemopreventive strategies against HCC are compared to other murine HCC models. Source


Czakon M.,RWTH Aachen | Mitov A.,CERN
Computer Physics Communications | Year: 2014

We present the program Top++ for the numerical evaluation of the total inclusive cross-section for producing top quark pairs at hadron colliders. The program calculates the cross-section in (a) fixed order approach with exact next-to-next-to leading order (NNLO) accuracy and (b) by including soft-gluon resummation for the hadronic cross-section in Mellin space with full next-to-next-to-leading logarithmic (NNLL) accuracy. The program offers the user significant flexibility through the large number (29) of available options. Top++ is written in C++. It has a very simple to use interface that is intuitive and directly reflects the physics. The running of the program requires no programming experience from the user. © 2014 Elsevier B.V. All rights reserved. Source


Schmidt M.J.,RWTH Aachen | Schmidt M.J.,University of Basel
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

A bosonic field theory is derived for the tunable edge magnetism at graphene zigzag edges. The derivation starts from an effective fermionic theory for the interacting graphene edge states, derived previously from a two-dimensional Hubbard model for graphene. The essential feature of this effective model, which gives rise to the weak edge magnetism, is the momentum-dependent nonlocal electron-electron interaction. It is shown that this momentum dependence may be treated by an extension of the bosonization technique and leads to interactions of the bosonic fields. These interactions are reminiscent of a φ4 field theory. Focusing on the regime close to the quantum phase transition between the ferromagnetic and the paramagnetic Luttinger liquid, a semiclassical interpretation of the interacting bosonic theory is given. Furthermore, it is argued that the universal critical behavior at the quantum phase transition between the paramagnetic and the ferromagnetic Luttinger liquid is governed by a small number of terms in this theory, which are accessible by quantum Monte Carlo methods. © 2012 American Physical Society. Source


Mottaghy D.,Geophysica Beratungsgesellschaft GmbH | Dijkshoorn L.,RWTH Aachen
Renewable Energy | Year: 2012

We present an effective finite difference formulation for implementing and modeling multiple borehole heat exchangers (BHE) in the general 3-D coupled heat and flow transport code SHEMAT. The BHE with arbitrary length can be either coaxial or double U-shaped. It is particularly suitable for modeling deep BHEs which contain varying pipe diameters and materials. Usually, in numerical simulations, a fine discretization of the BHE assemblage is required, due to the large geometric aspect ratios involved. This yields large models and long simulation times. The approach avoids this problem by considering heat transport between fluid and the soil through pipes and grout via thermal resistances. Therefore, the simulation time can be significantly reduced. The coupling with SHEMAT is realized by introducing an effective heat generation. Due to this connection, it is possible to consider heterogeneous geological models, as well as the influence of groundwater flow. This is particularly interesting when studying the long term behavior of a single BHE or a BHE field. Heating and cooling loads can enter the model with an arbitrary interval, e.g. from hourly to monthly values. When dealing with large BHE fields, computing times can be further significantly reduced by focusing on the temperature field around the BHEs, without explicitly modeling inlet and outlet temperatures. This allows to determine the possible migration of cold and warm plumes due to groundwater flow, which is of particular importance in urban areas with a high BHE installation density.The model is validated against the existing BHE modeling codes EWS and EED. A comparison with monitoring data from a deep BHE in Switzerland shows a good agreement. Synthetic examples demonstrate the field of application of this model. © 2012 Elsevier Ltd. Source


Combustion instability events in lean premixed combustion systems can cause spatio-temporal variations in unburnt mixture fuel/air ratio. This provides a driving mechanism for heat-release oscillations when they interact with the flame. Several Reduced Order Modelling (ROM) approaches to predict the characteristics of these oscillations have been developed in the past. The present paper compares results for flame describing function characteristics determined from a ROM approach based on the level-set method, with corresponding results from detailed, fully compressible reacting flow computations for the same two dimensional slot flame configuration. The comparison between these results is seen to be sensitive to small geometric differences in the shape of the nominally steady flame used in the two computations. When the results are corrected to account for these differences, describing function magnitudes are well predicted for frequencies lesser than and greater than a lower and upper cutoff respectively due to amplification of flame surface wrinkling by the convective Darrieus-Landau (DL) instability. However, good agreement in describing function phase predictions is seen as the ROM captures the transit time of wrinkles through the flame correctly. Also, good agreement is seen for both magnitude and phase of the flame response, for large forcing amplitudes, at frequencies where the DL instability has a minimal influence. Thus, the present ROM can predict flame response as long as the DL instability, caused by gas expansion at the flame front, does not significantly alter flame front perturbation amplitudes as they traverse the flame. © 2012 The Combustion Institute. Source


Mellado J.P.,RWTH Aachen | Mellado J.P.,Max Planck Institute for Meteorology
Journal of Fluid Mechanics | Year: 2010

Direct numerical simulations of the turbulent temporally evolving cloud-top mixing layer are used to investigate the role of evaporative cooling by isobaric mixing locally at the stratocumulus top. It is shown that the system develops a horizontal layered structure whose evolution is determined by molecular transport. A relatively thin inversion with a constant thickness h = k/we is formed on top and travels upwards at a mean velocity w e 0.1(|bs|c2)1/3, where is the mixture-fraction diffusivity, bs < 0 is the buoyancy anomaly at saturation conditions s and c is the cross-over mixture fraction defining the interval of buoyancy reversing mixtures. A turbulent convection layer develops below and continuously broadens into the cloud (the lower saturated fluid). This turbulent layer approaches a self-preserving state that is characterized by the convection scales constructed from a constant reference buoyancy flux B s = |bs|we/Xs. Right underneath the inversion base, a transition or buffer zone is defined based on a strong local conversion of vertical to horizontal motion that leads to a cellular pattern and sheet-like plumes, as observed in cloud measurements and reported in other free-convection problems. The fluctuating saturation surface (instantaneous cloud top) is contained inside this intermediate region. Results show that the inversion is not broken due to the turbulent convection generated by the evaporative cooling, and the upward mean entrainment velocity we is negligibly small compared to the convection velocity scale w* of the turbulent layer and the corresponding growth rate into the cloud. © 2010 Cambridge University Press. Source


Dominguez F.,CSIC - Institute of Materials Science | Hassler F.,RWTH Aachen | Platero G.,CSIC - Institute of Materials Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We analyze the current-biased Shapiro experiment in a Josephson junction formed by two one-dimensional nanowires featuring Majorana fermions. Ideally, these junctions are predicted to have an unconventional 4π-periodic Josephson effect and thus only Shapiro steps at even multiples of the driving frequency. Taking additionally into account the overlap between the Majorana fermions, due to the finite length of the wire, renders the Josephson junction conventional for any dc experiments. We show that probing the current-phase relation in a current-biased setup dynamically decouples the Majorana fermions. We find that, besides the even integer Shapiro steps, there are additional steps at odd and fractional values. However, different from the voltage-biased case, the even steps dominate for a wide range of parameters even in the case of multiple modes, thus giving a clear experimental signature of the presence of Majorana fermions. © 2012 American Physical Society. Source


Schaefer P.,RWTH Aachen
Journal of Turbulence | Year: 2012

Geometrical features of turbulent flows are analyzed by studying the curvature field of streamlines based on the instantaneous fluctuating velocity field of four different direct numerical simulations (DNS) at Taylor-based Reynolds numbers in the range Reλ = 50-300. Among the flows are two decaying homogeneous isotropic flows, one isotropic forced flow and the other homogeneous shear flow. Two different measures of curvature are extracted, the first one is the geometrical curvature of streamlines based on Frenet's formulas, and the second one is the Gaussian curvature describing the divergence of streamlines. The two curvature fields are found to be related to each other by the divergence of the directional tensor of streamlines, which is also related to the total acceleration along streamlines. The latter identity allows the identification of the convective term in the Navier-Stokes equations, as the term determining the curvature- related geometrical features of streamlines. Based on the random sweeping hypothesis, a scaling of the standard deviation of the two curvatures of streamlines in turbulent flows with the inverse of the Taylor microscale is obtained. The curvature fields are in a first step analyzed via their probability density functions (pdfs) of the fluctuating fields (including their sign), and a normalization with the standard deviation yields a good collapse of the curves for different Reynolds numbers and flow types. Both, the positive and negative tails of the pdf display a pronounced algebraic tail with a decay exponent of -4. To analyze the curvatures as geometrical features of streamlines, the pdf of their absolute values normalized with their respective mean values are examined, and the curves are found to collapse well for the different Reynolds numbers. All pdfs again display an algebraic tail for large values of the curvature with a scaling exponent of -4. This result is theoretically explained based on the expression for the Gaussian curvature, and turns out to be related to the regions in the flow close to stagnation points where streamlines get strongly diverted. It turns out that at the origin the pdf of the Gaussian curvature is dominated by regions where the gradient of the absolute value in streamline direction us vanishes. = 0, However, it defines an isosurface in which all local extreme points of the field of the absolute value of the velocity u as well as those of the turbulent kinetic energy k lie. As stagnation points are absolute minima of the kinetic energy field, these points too lie in the isosurface. The topology of the isosurface is analyzed in the vicinity of stagnation points, and it is found that independent of the type of stagnation point, the isosurface is locally always a degenerated quadric surface of cone type, a conjecture that is verified based on the comparison of the analytical expansion and the DNS data. © 2012 Taylor & Francis. Source


Karrasch C.,University of California at Berkeley | Karrasch C.,Lawrence Berkeley National Laboratory | Schuricht D.,RWTH Aachen
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We investigate the dynamics following sudden quenches across quantum critical points belonging to different universality classes. Specifically, we use matrix product state methods to study the quantum Ising chain in the presence of two additional terms which break integrability. We find that in all models the rate function for the return probability to the initial state becomes a nonanalytic function of time in the thermodynamic limit. This so-called "dynamical phase transition" was first observed in a recent work by Heyl, Polkovnikov, and Kehrein for the exactly-solvable quantum Ising chain, which can be mapped to free fermions. Our results for "interacting theories" indicate that nonanalytic dynamics is a generic feature of sudden quenches across quantum critical points. We discuss potential connections to the dynamics of the order parameter. © 2013 American Physical Society. Source


Villa L.,RWTH Aachen
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association | Year: 2011

Renoprotective actions of angiotensin receptor blockers are not well established in normotensive, low-grade proteinuric glomerular diseases. We examined the effect of low-dose telmisartan (LT) and high-dose telmisartan (HT) versus conventional antihypertensive therapy in the rat anti-Thy1.1 model of glomerulonephritis. Rats were randomized on Day 4 after disease induction to no treatment (CT, control), LT or HT or hydrochlorothiazide + hydralazine (HCT + H). All rats remained normotensive: HT and HCT + H reduced blood pressure by 15-20%. LT, HT and HCT + H reduced glomerular endothelial cell proliferation and glomerular and interstitial matrix deposition on Day 14. Only HT reduced podocyte damage and tubular cell dedifferentiation on Day 9 and mesangial cell activation on Day 14. By gene expression analysis arrays, we identified discs-large homolog 1 and angiopoietin-like 4 as potential mediators of the HT effects. In addition, we identified several pathways possibly related to the pleiotropic effects of HT, including growth factor signalling, mammalian target of rapamycin signalling, protein ubiquitination, the Wnt-beta catenin pathway and hypoxia signaling. In summary, treatment with HT, initiated after the induction of disease, ameliorates glomerular and tubulointerstitial damage. We provide the first comprehensive insight into the mechanisms underlying the renoprotective effect of high-dose angiotensin II receptor blockers (ARBs). Our study lays the basis for future investigations on novel pathways affected by ARBs in renal disease. Source


Schneider M.W.,University of Ulm | Oppel I.M.,RWTH Aachen | Griffin A.,Agilent Technologies | Mastalerz M.,University of Ulm
Angewandte Chemie - International Edition | Year: 2013

Interior decorating: A post-synthetic method allows porous organic cage compounds to be prepared with functionalized interior cavities. The approach produces modified cage compounds in quantitative yield and opens the possibility of preparing organic alloys with different functionality. The solution-based technique shows the advantage of solubility, an inherent property of porous materials derived from discrete organic molecules. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Westner G.,E.ON Energy Projects GmbH | Madlener R.,RWTH Aachen
Energy Economics | Year: 2012

In this paper, we apply a spread-based real options approach to analyze the decision-making problem of an investor who has the choice between an irreversible investment in a condensing power plant without heat utilization and a plant with combined heat-and-power (CHP) generation. Our investigation focuses on large-scale fossil-fueled generation technologies and is based on a stochastic model that uses copula functions to provide the input parameters of the real options model. We define the aggregated annual spread as assessment criteria for our investigation since it contains all relevant volatile input parameters that have an impact on the evaluation of investment decisions. We show that the specific characteristics of CHP plants, such as additional revenues from heat sales, promotion schemes, specific operational features, and a beneficial allocation of CO 2 allowances, have a significant impact on the option value and therefore on the optimal timing for investment. For the two fossil-fueled CHP technologies investigated (combined-cycle gas turbine and steam turbine), we conclude from our analysis that a high share of CHP generation reduces the risk exposure for the investor. The maximal possible CHP generation depends significantly on the local heat demand in the surroundings of the power plant. Considering this, the size of the heat sink available could gain more relevance in the future selection process of sites for new large-scale fossil power plants. © 2011 Elsevier B.V. Source


Noone C.J.,Massachusetts Institute of Technology | Torrilhon M.,RWTH Aachen | Mitsos A.,Massachusetts Institute of Technology
Solar Energy | Year: 2012

In this article, a new model and a biomimetic pattern for heliostat field layout optimization are introduced. The model, described and validated herein, includes a detailed calculation of the annual average optical efficiency accounting for cosine losses, shading and blocking, aberration and atmospheric attenuation. The model is based on a discretization of the heliostats and can be viewed as ray tracing with a carefully selected distribution of rays. The prototype implementation is sufficiently fast to allow for field optimization. Parameters are introduced for the radially staggered layout and are optimized with the objective of maximizing the annual insolation weighted heliostat field efficiency. In addition, inspired by the spirals of the phyllotaxis disc pattern, a new biomimetic placement heuristic is described and evaluated, which generates layouts of both higher insolation-weighted efficiency and higher ground coverage than radially staggered designs. Specifically, this new heuristic is shown to improve the existing PS10 field by 0.36% points in efficiency while simultaneously reducing the land area by 15.8%. Moreover, the new pattern achieves a better trade-off between land area usage and efficiency, i.e., it can reduce the area requirement significantly for any desired efficiency. Finally, the improvement in area becomes more pronounced with an increased number of heliostats, when maximal efficiency is the objective. While minimizing the levelized cost of energy (LCOE) is typically a more practical objective, results of the case study presented show that it is possible to both reduce the land area (i.e. footprint) of the plant and number of heliostats for fixed energy collected. By reducing the capital cost of the plant at no additional costs, the effect is a reduction in LCOE. © 2011 Elsevier Ltd. Source


Schmid H.,RWTH Aachen
Biomechanics and modeling in mechanobiology | Year: 2010

Recent experimental and computational studies have shown that transmurally heterogeneous material properties through the arterial wall are critical to understanding the heterogeneous expressions of constituent degrading molecules. Given that expression of such molecules is thought to be intimately linked to local magnitudes of stress, modelling the transmural stress distribution is critical to understanding arterial adaption during disease. The aim of this study was to develop an arterial growth and remodelling framework that can incorporate both transmurally heterogeneous constituent distributions and residual stresses, into a 3-D finite element model. As an illustrative example, we model the development of a fusiform aneurysm and investigate the effects of elastinous and collagenous heterogeneities on the stress distribution during evolution. It is observed that the adaptive processes of growth and remodelling exhibit transmural variations. For physiological heterogeneous constituent distributions, a stress peak appears in the media towards the intima, and a stress plateau occurs towards the adventitia. These features can be primarily attributed to the underlying heterogeneity of elastinous constituents. During arterial adaption, the collagen strain is regulated to remain in its homoeostatic level; consequently, the partial stress of collagen has less influence on the total stress than the elastin. However, following significant elastin degradation, collagen plays the dominant role for the transmural stress profile and a marked stress peak occurs towards the adventitia. We conclude that to improve our understanding of the arterial adaption and the aetiology of arterial disease, there is a need to: quantify transmural constituent distributions during histopathological examinations, understand and model the role of the evolving transmural stress distribution. Source


This study attempts to examine the competing hypotheses, whether planation surfaces separated by scarp zones arise from differences in lithology and structure or are directly linked with episodic uplift and long periods of tectonic quiescence, as is supposed in conventional geomorphic concepts. In these concepts, variations in lithology and structure and climatic changes do not divert the general course of landscape development. Multivariate statistical analysis of morphometric parameters indicates a strong association between lithology and scarp-zone terrain types. The variability within petrographically homogeneous areas is determined by structures such as fractures that are exploited more easily by streams, whilst on granitoid rocks in particular, differences in terrain types appear to result from a combination of differences in fracture density and the differing susceptibility of the rock to chemical weathering in moist and dry environments. These factors promoted the development of scarps and knickpoints that became structurally/lithologically controlled base levels and act as barriers for the continuous transmission of base-level changes caused by tectonic uplift or by sea-level lowering. Accordingly, the surface sequence of the study area is likely to be entirely of denudational origin and may be virtually unrelated to episodic changes in base level. Numerical process-response modelling indicates that in lithologically/structurally variable terrains, an initial perturbation may induce diverging landscape-developmental trends. Local adjustments of denudation and river downcutting rates on structurally/lithologically controlled base levels and the differing coupling strength of landscape elements to base-level changes may obscure both the direct links between the number and magnitude of perturbations and the distinction between continuous and intermittent vertical displacements. This implies that the vertical separation between planation surfaces does not necessarily indicate episodic vertical tectonic displacement or sea-level change. According to the complex array of factors influencing the development of planation surface sequences, evolutionary models relying on a synchronous continent-wide formation of planation surfaces appear to be untenable in lithologically and structurally variable basement regions. © 2009 Elsevier B.V. All rights reserved. Source


Selig P.,RWTH Aachen
Angewandte Chemie - International Edition | Year: 2013

Lewis acid and oxidation catalysis are merged in the reaction discussed here, which provides access to diversely substituted N-hydroxycarbamates (see scheme). This reaction highlights the potential of nitrosoformates as electrophilic amination reagents as well as the benefits of aerobic oxidation for the formation of highly reactive species. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Trautwein C.,RWTH Aachen | Friedman S.L.,Mount Sinai School of Medicine | Schuppan D.,University Hospital Freiburg | Schuppan D.,Beth Israel Deaconess Medical Center | Pinzani M.,University College London
Journal of Hepatology | Year: 2015

Understanding the molecular mechanisms underlying liver fibrogenesis is fundamentally relevant to developing new treatments that are independent of the underlying etiology. The increasing success of antiviral treatments in blocking or reversing the fibrogenic progression of chronic liver disease has unearthed vital information about the natural history of fibrosis regression, and has established important principles and targets for antifibrotic drugs. Although antifibrotic activity has been demonstrated for many compounds in vitro and in animal models, none has been thoroughly validated in the clinic or commercialized as a therapy for fibrosis. In addition, it is likely that combination therapies that affect two or more key pathogenic targets and/or pathways will be needed. To accelerate the preclinical development of these combination therapies, reliable single target validation is necessary, followed by the rational selection and systematic testing of combination approaches. Improved noninvasive tools for the assessment of fibrosis content, fibrogenesis and fibrolysis must accompany in vivo validation in experimental fibrosis models, and especially in clinical trials. The rapidly changing landscape of clinical trial design for liver disease is recognized by regulatory agencies in the United States (FDA) and Western Europe (EMA), who are working together with the broad range of stakeholders to standardize approaches to testing antifibrotic drugs in cohorts of patients with chronic liver diseases. Source


The resistance of six geomaterials (rocks and cementitious composites) against the impingement of quartz particles at velocities between vP=40 and 140m/s is investigated. Erosion models developed for brittle, elastic-plastic responding materials cannot characterize the response of geomaterials over the entire particle impingement velocity range. An integral approach ER=K1ERP+K2ERL is introduced, which considers plastic and elastic-plastic material removal modes. The constants K1 and K2 balance the amount of either mode. For K1=0, the elastic-plastic erosion models are valid; but they cannot deliver realistic results for K1>0. For K2=0, erosion models for plastically responding materials are valid. The transition between the erosion modes can be determined by a transition ratio KIc 12/4/HM 23/4. A target material parameter function, that considers effects of particle impingement velocity variations, is derived in order to improve the predictability of damages to geomaterials with different response characteristics. © 2014 Elsevier B.V. Source


Grottke O.,RWTH Aachen
Current Opinion in Critical Care | Year: 2012

PURPOSE OF REVIEW: Trauma-induced coagulopathy is a frequent complication in severely injured patients. To correct coagulopathy and restore haemostasis, these patients have traditionally been treated with fresh frozen plasma, but in the last decade, there has been a shift from empirical therapy to targeted therapy with coagulation factor concentrates and other haemostatic agents. This review highlights emerging therapeutic options and controversial topics. RECENT FINDINGS: Early administration of the antifibrinolytic medication tranexamic acid was shown in the multicentre CRASH-2 trial to be an effective and inexpensive means of decreasing blood loss. Numerous retrospective and experimental studies have shown that the use of coagulation factor concentrates decreases blood loss and may be useful in reducing the need for transfusion of allogeneic blood products. In particular, early use of fibrinogen concentrate and thrombin generators has a positive impact on haemostasis. However, the use of prothrombin complex concentrate to correct trauma-induced coagulopathy has also been associated with a potential risk of serious adverse events. SUMMARY: Current evidence in trauma resuscitation indicates a potential role for coagulation factor concentrates and other haemostatic agents in correcting trauma-induced coagulopathy. Despite a shift towards such transfusion strategy, there remains a shortage of data to support this approach. Copyright © 2012 Lippincott Williams & Wilkins. Source


Schmidt M.J.,RWTH Aachen | Rainis D.,University of Basel | Loss D.,University of Basel
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We propose and study a realistic model for the decoherence of topological qubits, based on Majorana fermions in one-dimensional topological superconductors. The source of decoherence is the fluctuating charge on a capacitively coupled gate, modeled by noninteracting electrons. In this context, we clarify the role of quantum fluctuations and thermal fluctuations and find that quantum fluctuations do not lead to decoherence, while thermal fluctuations do. We explicitly calculate decay times due to thermal noise and give conditions for the gap size in the topological superconductor and the gate temperature. Based on this result, we provide simple rules for gate geometries and materials optimized for reducing the negative effect of thermal charge fluctuations on the gate. © 2012 American Physical Society. Source


DNase-seq allows nucleotide-level identification of transcription factor binding sites on the basis of a computational search of footprint-like DNase I cleavage patterns on the DNA. Frequently in high-throughput methods, experimental artifacts such as DNase I cleavage bias affect the computational analysis of DNase-seq experiments. Here we performed a comprehensive and systematic study on the performance of computational footprinting methods. We evaluated ten footprinting methods in a panel of DNase-seq experiments for their ability to recover cell-specific transcription factor binding sites. We show that three methods—HINT, DNase2TF and PIQ—consistently outperformed the other evaluated methods and that correcting the DNase-seq signal for experimental artifacts significantly improved the accuracy of computational footprints. We also propose a score that can be used to detect footprints arising from transcription factors with potentially short residence times. © 2016 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved. Source


Lammers T.,University Utrecht | Lammers T.,German Cancer Research Center | Lammers T.,RWTH Aachen
Advanced Drug Delivery Reviews | Year: 2010

Copolymers based on N-(2-hydroxypropyl)methacrylamide (HPMA) are prototypic and well-characterized polymeric drug carriers that have been broadly implemented in the delivery of anticancer agents. HPMA copolymers circulate for prolonged periods of time, and by means of the Enhanced Permeability and Retention (EPR) effect, they localize to tumors both effectively and selectively. Because of their beneficial biodistribution, and because of the fact that they are able to improve the balance between the efficacy and the toxicity of chemotherapy, it is reasonable to assume that HPMA copolymers combine well with other treatment modalities. In the present review, efforts in this regard are summarized, and HPMA copolymers are shown to be able to beneficially interact with surgery, with radiotherapy, with hyperthermia, with photodynamic therapy, with chemotherapy and with each other. Together, the insights provided and the evidence obtained strongly suggest that HPMA copolymer-based nanomedicine formulations hold significant potential for improving the efficacy of combined modality anticancer therapy. © 2009 Elsevier B.V. All rights reserved. Source


Barrales Mora L.A.,RWTH Aachen
Mathematics and Computers in Simulation | Year: 2010

A vertex model for the simulation of grain growth and grain boundary migration is developed and its implementation is explained in detail. The utilization of the model is also exemplified with different setups. In particular, the model was used to study the evolution of magnetically affected grain growth in samples with randomly oriented grains and the effect of the finite mobility of the boundary junctions on boundary migration. These examples emphasize the versatility of the model and illustrate its ample scope. The results of the simulations showed that a magnetic field can effectively affect the evolution of the grain growth kinetics and texture independently of the initial texture since the magnetic field will cause grains, with particular orientations, to have an advantage for their growth. As consequence, the sample will become strongly textured during grain growth. Theoretical considerations for the grain boundary migration with a finite mobility of the triple junctions were also reproduced and confirmed by means of computer simulation. The simulation results showed a very good agreement with the theoretical expectations. © 2009 IMACS. Source


Bodlaender H.L.,University Utrecht | Koster A.M.C.A.,RWTH Aachen
Information and Computation | Year: 2010

For more and more applications, it is important to be able to compute the treewidth of a given graph and to find tree decompositions of small width reasonably fast. This paper gives an overview of several upper bound heuristics that have been proposed and tested for the problem of determining the treewidth of a graph and finding tree decompositions. Each of the heuristics produces tree decompositions whose width may be larger than the optimal width. However, experiments show that in many cases, the heuristics give tree decompositions whose width is close to the exact treewidth of the input graphs. © 2009 Elsevier Inc. All rights reserved. Source


Steffensen S.,RWTH Aachen | Ulbrich M.,TU Munich
SIAM Journal on Optimization | Year: 2010

We present a new relaxation scheme for mathematical programs with equilibrium constraints (MPEC), where the complementarity constraints are replaced by a reformulation that is exact for the complementarity conditions corresponding to sufficiently nondegenerate complementarity components and relaxes only the remaining complementarity conditions. A positive parameter determines to what extent the complementarity conditions are relaxed. The relaxation scheme is such that a strongly stationary solution of the MPEC is also a solution of the relaxed problem if the relaxation parameter is chosen sufficiently small. We discuss the properties of the resulting parameterized nonlinear programs and compare stationary points and solutions. We further prove that a limit point of a sequence of stationary points of a sequence of relaxed problems is Clarke-stationary if it satisfies a so-called MPEC-constant rank constraint qualification, and it is Mordukhovich-stationary if it satisfies the MPEC-linear independence constraint qualification and the stationary points satisfy a second order sufficient condition. From this relaxation scheme, a numerical approach is derived that is applied to a comprehensive test set. The numerical results show that the approach combines good efficiency with high robustness. © 2010 Society for Industrial and Applied Mathematics. Source


Adams A.,RWTH Aachen
TrAC - Trends in Analytical Chemistry | Year: 2016

Nuclear magnetic resonance (NMR) is today one of the most important analytical tools for the detailed characterization of solid polymers at various length and time scales. Such information is key for establishing proper structure-property relationships required for the rational design of polymers for particular applications. Several microscopic properties can be probed without chemical resolution, thereby enabling the investigator to retrieve this information by using static measurements at magnetic fields of lower strength and homogeneity. Thus, this current paper discusses methods currently available in compact low-field NMR for the analysis of polymers in the solid state and compares these methods in terms of similarities and differences in implementation and function for NMR sensors with different magnetic-field homogeneities. The high potential of low-field NMR is demonstrated with the help of selected applications from fundamental and applied research. © 2016 Elsevier B.V. Source


Mitsos A.,RWTH Aachen
Journal of Global Optimization | Year: 2010

An algorithm for the global optimization of nonlinear bilevel mixed-integer programs is presented, based on a recent proposal for continuous bilevel programs by Mitsos et al. (J Glob Optim 42(4):475-513, 2008). The algorithm relies on a convergent lower bound and an optional upper bound. No branching is required or performed. The lower bound is obtained by solving a mixed-integer nonlinear program, containing the constraints of the lower-level and upper-level programs; its convergence is achieved by also including a parametric upper bound to the optimal solution function of the lower-level program. This lower-level parametric upper bound is based on Slater-points of the lower-level program and subsets of the upper-level host sets for which this point remains lower-level feasible. Under suitable assumptions the KKT necessary conditions of the lower-level program can be used to tighten the lower bounding problem. The optional upper bound to the optimal solution of the bilevel program is obtained by solving an augmented upper-level problem for fixed upper-level variables. A convergence proof is given along with illustrative examples. An implementation is described and applied to a test set comprising original and literature problems. The main complication relative to the continuous case is the construction of the parametric upper bound to the lower-level optimal objective value, in particular due to the presence of upper-level integer variables. This challenge is resolved by performing interval analysis over the convex hull of the upper-level integer variables. © Springer Science+Business Media, LLC. 2009. Source


Momber A.W.,RWTH Aachen
International Journal of Impact Engineering | Year: 2016

The subject of the investigation is the response of geo-materials, namely rocks and cementitious composites, to the impact of liquid drops at very high velocities. A single drop impact jet apparatus is utilized for the simulation of drop impacts with a velocity of 885 m/s. The response of six materials (igneous, sedimentary and metamorphic rocks; concretes) with defined mechanical parameters is investigated. The removed volume is measured, and it is related to material parameters, namely uniaxial compressive strength, splitting tensile strength, Young's modulus, mode-I fracture toughness, and elastic strain energy density. The highest correlation exists between removed volume and fracture toughness. SEM inspections revealed a variation of brittle failure features, but barely any signs of plastic response. Threshold criteria are derived, which indicate that hard and brittle rocks respond entirely elastically to the impact in the investigated loading case. A brittle material resistance function is derived, which combines fracture toughness, Young's modulus and density. The results of this study can be used to approximate the resistance of geo-material against high-speed liquid impact, when brittle fracture dominates the material removal process. © 2015 Elsevier Ltd. Source


Momber A.W.,RWTH Aachen
Rock Mechanics and Rock Engineering | Year: 2016

A procedure for the estimation of distribution parameters of a Weibull distribution model K1 = f(KIc 12/4/σC 23/4) for solid particle erosion, as recently suggested in Rock Mech Rock Eng, doi: 10.1007/s00603-014-0658-x, 2014, is derived. The procedure is based on examinations of elastic–plastically responding rocks (rhyolite, granite) and plastically responding rocks (limestone, schist). The types of response are quantified through SEM inspections of eroded surfaces. Quantitative numbers for the distribution parameter K1 are calculated for 30 rock materials, which cover a wide range of mechanical properties. The ranking according to the parameter K1 is related to qualitative rock classification schemes. A modified proposal for the erosion of schist due to solid particle impingement at normal incidence is introduced. © 2015, Springer-Verlag Wien. Source


Felderhof B.U.,RWTH Aachen
Journal of Fluid Mechanics | Year: 2010

The flow of a viscous compressible fluid in a circular tube generated by a sudden impulse at a point on the axis is studied on the basis of the linearized Navier-Stokes equations. A no-slip boundary condition is assumed to hold on the wall of the tube. Owing to the finite velocity of sound the flow behaviour differs qualitatively from that of an incompressible fluid. The flow velocity and the pressure disturbance at any fixed point different from the source point vanish at short time and decay at long times with a t-3/2 power law. Copyright © 2010 Cambridge University Press. Source


Vonderschen K.,Karolinska Institutet | Wagner H.,RWTH Aachen
Trends in Neurosciences | Year: 2014

Interaural time differences (ITDs) represent an important cue in sound localization and auditory scene analysis. To assess this cue the auditory system internally delays binaural inputs to compensate for the outer delay, before neurons in the brainstem detect the coincident arrival of the inputs from the two ears. Different origins of internal delays have been controversially discussed and have given rise to conflicting interpretations of the ITD representation ensuing from coincidence detection. Yet, recent findings indicate that ITD representations undergo substantial transformations or remodeling after the detection step. Here we treat the detection step separately from remodeling, and explain why a similar representation of ITD across species may exist in the forebrain despite differences in detection and representation in the midbrain. © 2014 Elsevier Ltd. Source


Weis S.,RWTH Aachen | Hausmann M.,Durham University
Neuroscientist | Year: 2010

Functional cerebral asymmetries (FCAs), which constitute a basic principle of human brain organization, are supposedly generated by interhemispheric inhibition of the dominant on the nondominant hemisphere. It has repeatedly been shown that FCAs are sex specific: While they are relatively stable in men, they change during the menstrual cycle in women, indicating that sex hormones might play an important role in modulating functional brain organization and brain asymmetries in particular. Modern brain imaging techniques like functional magnetic resonance imaging (fMRI) allow for the noninvasive study of the mechanisms underlying changing FCAs. Imaging data show that in women the inhibitory influence of the dominant on the nondominant hemisphere is reduced with rising levels of sex hormones in the course of the menstrual cycle. Apart from modulating interhemispheric inhibition, sex hormones also seem to change functional organization within hemispheres. These results reveal a powerful neuromodulatory action of sex hormones on the dynamics of functional brain organization in the female brain. They may further contribute to the ongoing discussion of sex differences in brain function in that they help explain the dynamic part of functional brain organization in which the female differs from the male brain. © 2010 The Author(s). Source


Bevilacqua G.,National Institute of Nuclear Physics, Italy | Worek M.,RWTH Aachen
Journal of High Energy Physics | Year: 2014

Triggered by ongoing experimental analyses, we report on a study of the cross section ratio σ (pp → tt̄bb̄)/ σ (pp →tt̄ jj) at the next-to-leading order in QCD, focusing on both present and future collider energies: √s = 7, 8, 13 TeV. In particular, we provide a comparison between our predictions and the currently available CMS data for the 8 TeV run. We further analyse the kinematics and scale uncertainties of the two processes for a single set of parton distribution functions, with the goal of assessing possible correlations that might help to reduce the theoretical error of the ratio and thus enhance the predictive power of this observable. We argue that the different jet kinematics makes the t t ̄ b b ̄ and t t ̄ jj processes uncorrelated in several observables, and show that the scale uncertainty is not significantly reduced when taking the ratio of the cross sections. © 2014 The Author(s). Source


Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine that exerts protective effects during myocardial ischemia/reperfusion injury. We hypothesized that elevated MIF levels in the early postoperative time course might be inversely associated with postoperative organ dysfunction as assessed by the simplified acute physiology score (SAPS) II and sequential organ failure assessment (SOFA) score in patients after cardiac surgery. A total of 52 cardiac surgical patients (mean age [± SD] 67 ± 10 years; EuroScore: 7) were enrolled in this monocenter, prospective observational study. Serum levels of MIF and clinical data were obtained after induction of anesthesia, at admission to the intensive care unit (ICU), 4 h after admission and at the first and second postoperative day. To characterize the magnitude of MIF release, we compared blood levels of samples from cardiac surgical patients with those obtained from healthy volunteers. We assessed patient outcomes using the SAPS II at postoperative d 1 and SOFA score for the first 3 d of the eventual ICU stay. Compared to healthy volunteers, patients had already exhibited elevated MIF levels prior to surgery (64 ± 50 versus 13 ± 17 ng/mL; p < 0.05). At admission to the ICU, MIF levels reached peak values (107 ± 95 ng/mL; p < 0.01 versus baseline) that decreased throughout the observation period and had already reached preoperative values 4 h later. Postoperative MIF values were inversely correlated with SAPS II and SOFA scores during the early postoperative stay. Moreover, MIF values on postoperative d 1 were related to the calculated cardiac power index (r = 0.420, p < 0.05). Elevated postoperative MIF levels are inversely correlated with organ dysfunction in patients after cardiac surgery. Source


Felderhof B.U.,RWTH Aachen
Physical Review Letters | Year: 2014

A Comment on the Letter by F. Kümmel, Phys. Rev. Lett. 110, 198302 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.198302. The authors of the Letter offer a Reply. © 2014 American Physical Society. Source


A common strategy to reduce energy consumption and CO2 emissions is retrofitting residential buildings to high thermal standards. But households in retrofitted homes often consume more space heating energy than expected, thus frustrating climate and energy goals. Most interventions to mitigate this focus on energy-inefficient 'behaviours', and assume that identifying the causes of these behaviours can deliver interventions that change consumption patterns and habits across large groups of consumers. A detailed investigation of sensor data from 60 retrofitted apartments served as a testing ground for an alternative or supplementary approach: targeting 'behavers' rather than 'behaviours'. Consumption patterns supported the division of households into 'light', 'medium' and 'heavy' consumers, each showing a normally distributed picture of consumption. Heavy consumers (23% of households) consumed 52% of the space heating energy, medium consumers (57% of households) consumed 45% and light consumers (20% of households) consumed 3%. Among both heavy and medium cohorts the data indicates very stable patterns of consumption across time, deeply entwined with routines and with the physical fabric of the indoor environment, and therefore very difficult to change. Since the heavy cohort is a small minority of households that consumes around half the total energy, it could be cost-effective to target this group specifically rather than aim interventions at consumers in general. Other datasets of low energy homes suggest that a similar heuristic could be appropriate. © 2013 Elsevier B.V. All rights reserved. Source


Gibalov V.I.,Moscow State University | Pietsch G.J.,RWTH Aachen
Plasma Sources Science and Technology | Year: 2012

Based on experimental results, numerical investigations of dielectric barrier discharges (DBDs) have been performed in three basic configurations: in the volume, coplanar and surface discharge arrangements. It is shown that the DBD dynamics is the same in all arrangements and it is determined by the development of a few principal constituents, i.e. cathode- and anode-directed streamers, discharge channel, cathode layer and surface charges. It is found that the anode- and cathode-directed streamers appear with a highly conductive channel in between. The interaction of the streamers with conductive and dielectric surfaces determines the filamentary or homogeneous appearance of the discharge and its properties. The cathode-directed streamer is a self-sustaining phenomenon, which moves in a gas gap or along an electrode driven by a positive loop-back between photoemission and electron multiplication. The anode-directed streamer plays a subsidiary role. Depending on the kind of gas (electronegative or electropositive) and/or the degree of development of the cathode-directed streamer, the field strength in the conductive channels changes significantly. When the cathode-directed streamer touches the electrode surface, a cathode layer appears with parameters close to those of normal glow discharges. In volume discharge arrangements the movement of the streamers results in the appearance of Lichtenberg figures on dielectric surfaces. © 2012 IOP Publishing Ltd. Source


Blank L.M.,RWTH Aachen
Current Opinion in Biotechnology | Year: 2012

Phosphate is the element that arguably fulfills the most diverse cellular functions, including structure, energy and information storage, and energy and information transfer. While the phosphate inventory of a cell can be rapidly quantified by ever improving analytical techniques, the (dynamic) interplay of the molecules and the thereof resulting functions cannot easily be resolved. While the earlier is interesting to assess the minimum phosphate amount required for life, the latter is important to design engineering strategies for efficient phosphate use. Future developments in 'phosphate biotechnology' will use in depth understanding of the intertwined functions phosphate has in a cell. Finally, contributing technologies enable us to shift from a mineral phosphate-based economy to an economy that has a sustainable phosphate cycle. Strategies based on (engineered) microbes that potentially can contribute to this cycle are summarized. © 2012 Elsevier Ltd. Source


Amsberg G.K.-V.,University of Hamburg | Koschmieder S.,RWTH Aachen
OncoTargets and Therapy | Year: 2013

Bosutinib (SKI-606) is an orally available, once-daily, dual Src and Abl kinase inhibitor with promising clinical potential in first-, second-, and third-line treatment of chronic myeloid leukemia (CML). Bosutinib effectively inhibits wild-type BCR-ABL and most imatinib-resistant BCR-ABL mutations except for V299L and T315I. Low hematologic toxicity is a remarkable characteristic of this novel second-generation tyrosine kinase inhibitor, and this has been ascribed to its minimal activity against the platelet-derived growth factor receptor and KIT. Low-grade, typically self-limiting diarrhea, which usually appears within the first few weeks after treatment initiation, represents the predominant toxicity of bosutinib. Other treatment-associated adverse events are mostly mild to moderate. Bosutinib has been approved by the US Food and Drug Administration for the treatment of chronic, accelerated, or blast phase Philadelphia chromosome-positive CML in adult patients with resistance or intolerance to prior therapy. This review summarizes the main properties of bosutinib and the currently available data on its clinical potential in the treatment of CML. © 2013 Keller-von Amsberg and Koschmieder, publisher and licensee Dove Medical Press Ltd. Source


Junge T.,RWTH Aachen
Journal of environmental science and health. Part. B, Pesticides, food contaminants, and agricultural wastes | Year: 2011

Recently, we reported on soil fate of SDZ residues amended with pig manure treated with 1C-labeled sulfadiazine 1C-SDZ). The first objective of the present study was to determine whether this strategy can be substituted by application of 1C-SDZ to soil. The second objective was to characterize non-extractable SDZ residues by fractionation, size exclusion chromatography (SEC) and solid state 13C-NMR. The fate of 1C-SDZ was examined for 28 d, using two soils with and without amendment of pig manure. Mineralization of 1C-SDZ was low; extractable residues decreased to 7-30%. Compared to the previous study, results were similar. 1C-SDZ derived bound radioactivity was found in HCl-washings, fulvic, humic acids and humin. According to SEC, one bound 1C portion (70%) co-eluted with fulvic acids (above 910 g mol1); the other consisted of adsorbed/entrapped 1C-SDZ. The 13C-SDZ study was performed for 30 d; humic acids were examined by 13C-NMR. A signal (100-150 ppm) was referred to 13C-SDZ. SEC and 13C-NMR demonstrated rapid integration of SDZ into humics. Source


The lower bound shakedown analysis is a most convenient tool to determine the load bearing capacity of engineering structures subjected to thermo-mechanical loadings. In order to achieve realistic results, limited nonlinear kinematical hardening needs to be taken into account. Although there exist different formulations incorporating limited kinematical hardening in the literature, it is still not conclusively clarified, whether or not these are applicable to generally-nonlinear hardening laws as well. Thus, the aim of this paper is to propose a method to determine the shakedown limit loads accounting for limited, generally-nonlinear kinematical hardening, and to close the discussion about the effect of the nonlinearity of the hardening law. The proposed method is based on an extension of the statical shakedown theorem by Melan using a two-surface model, which captures both incremental collapse and alternating plasticity. Furthermore, it is implemented into an interior-point algorithm, which is tailored to shakedown analysis and thus capable of handling large-scale problems. The algorithm allows for an arbitrary number of thermo-mechanical loadings. To illustrate the method's potential, numerical results are shown for several examples from the field of power plant engineering. © 2012 Elsevier Ltd. All rights reserved. Source


Mause S.F.,Institute for Molecular Cardiovascular Research | Mause S.F.,RWTH Aachen | Weber C.,Institute for Molecular Cardiovascular Research
Circulation Research | Year: 2010

Microparticles represent a heterogeneous population of vesicles with a diameter of 100 to 1000 nm that are released by budding of the plasma membrane and express antigens specific of their parental cells. Although microparticle formation represents a physiological phenomenon, a multitude of pathologies are associated with a considerable increase in circulating microparticles, including inflammatory and autoimmune diseases, atherosclerosis, and malignancies. Microparticles display an broad spectrum of bioactive substances and receptors on their surface and harbor a concentrated set of cytokines, signaling proteins, mRNA, and microRNA. Recent studies provided evidence for the concept of microparticles as veritable vectors for the intercellular exchange of biological signals and information. Indeed, microparticles may transfer part of their components and content to selected target cells, thus mediating cell activation, phenotypic modification, and reprogramming of cell function. Because microparticles readily circulate in the vasculature, they may serve as shuttle modules and signaling transducers not only in their local environment but also at remarkable distance from their site of origin. Altogether, this transcellular delivery system may extend the confines of the limited transcriptome and proteome of recipient cells and establishes a communication network in which specific properties and information among cells can be efficiently shared. At least in same cases, the sequential steps of the transfer process underlie complex regulatory mechanisms, including selective sorting (" packaging") of microparticle components and content, specificity of interactions with target cells determined by surface receptors, and ultimately finely tuned and signal-dependent release and delivery of microparticle content. © 2010 American Heart Association. All rights reserved. Source


Poilblanc D.,CNRS Laboratory for Theoretical Physics | Schuch N.,RWTH Aachen
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

Gapped Z2 spin liquids have been proposed as candidates for the ground state of the S=1/2 quantum antiferromagnet on the kagome lattice. We extend the use of projected entangled pair states to construct (on the cylinder) resonating valence bond (RVB) states including both nearest-neighbor and next-nearest-neighbor singlet bonds. Our ansatz - dubbed "simplex spin liquid" - allows for an asymmetry between the two types of triangles (of order 2%-3% in the energy density after optimization) leading to the breaking of inversion symmetry. We show that the topological Z2 structure is still preserved and, by considering the presence or the absence of spinon and vison lines along an infinite cylinder, we explicitly construct four orthogonal RVB minimally entangled states. The spinon and vison coherence lengths are extracted from a finite size scaling with regard to the cylinder perimeter of the energy splittings of the four sectors and are found to be of the order of the lattice spacing. The entanglement spectrum of a partitioned (infinite) cylinder is found to be gapless, suggesting the occurrence, on a cylinder with real open boundaries, of gapless edge modes formally similar to Luttinger liquid (nonchiral) spin and charge modes. When inversion symmetry is spontaneously broken, the RVB spin liquid exhibits an extra Ising degeneracy, which might have been observed in recent exact diagonalization studies. © 2013 American Physical Society. Source


The morning portion of the near-surface diurnal temperature cycle is analyzed in combination with heat-flux and vertical temperature-gradient data. During summer, mean diurnal cycles of temperature rates-of-change show periods that can be related to defined points of the morning transition (MT). The start of the MT is clearly marked with a temperature discontinuity, apparent even on individual days, while the end of the transition is apparent only when using averages over many days. The findings concerning the timing of the MT using temperature cycle analysis correspond well with studies using heat-flux measurements. Mean diurnal cycles of temperature rates-of-change for stations in different urban and valley positions show differences that can partly be explained by apparent effects of the surroundings. For the valley situation, the timing differences and their relation to station position in the valley are generally plausible, while urban effects on the diurnal cycle are apparent but less distinct, which may be due to the small number of stations used. The results indicate that warming already begins before heat-flux crossover, which is the current definition of the beginning of the MT. This definition should be extended to include the phase between the temperature rate-of-change crossover and heat-flux crossover, which represents the early part of the MT before warming reaches instrument level. © 2013 Springer Science+Business Media Dordrecht. Source


Elberfeld M.,RWTH Aachen | Kawarabayashi K.-I.,Japan National Institute of Information and Communications Technology
Proceedings of the Annual ACM Symposium on Theory of Computing | Year: 2014

Graph embeddings of bounded Euler genus (that means, embeddings with bounded orientable or nonorientable genus) help to design time-efficient algorithms for many graph problems. Since linear-time algorithms are known to compute embeddings of any bounded Euler genus, one can always assume to work with embedded graphs and, thus, obtain fast algorithms for many problems on any class of graphs of bounded Euler genus. Problems on graphs of bounded Euler genus are also important from the perspective of finding space-efficient algorithms, mostly focusing on problems related to finding paths and matchings in graphs. So far, known space-bounded approaches needed the severe assumption that an embedding is given as part of the input since no space-efficient embedding procedure for nonplanar graphs was known. The present work sidesteps this assumption and shows that embeddings of any bounded Euler genus can be computed in deterministic logarithmic space (logspace); allowing to generalize results on the space complexity of path and matching problems from embedded graphs to graphs of bounded Euler genus. The techniques developed for the embedding procedure also allow to compute canonical representations and, thus, solve the isomorphism problem for graphs of bounded Euler genus in logspace. © 2014 ACM. Source


Wiemuth D.,RWTH Aachen
Channels (Austin, Tex.) | Year: 2013

Bile acid-sensitive ion channel (BASIC) is a member of the DEG/ENaC gene family of unknown function. Rat BASIC (rBASIC) is inactive at rest. We have recently shown that cholangiocytes, the epithelial cells lining the bile ducts, are the main site of BASIC expression in the liver and identified bile acids, in particular hyo- and chenodeoxycholic acid, as agonists of rBASIC. Moreover, it seems that extracellular divalent cations stabilize the resting state of rBASIC, because removal of extracellular divalent cations opens the channel. In this addendum, we demonstrate that removal of extracellular divalent cations potentiates the activation of rBASIC by bile acids, suggesting an allosteric mechanism. Furthermore, we show that rBASIC is strongly activated by the anticholestatic bile acid ursodeoxycholic acid (UDCA), suggesting that BASIC might mediate part of the therapeutic effects of UDCA. Source


Vasina E.M.,RWTH Aachen
Cell death & disease | Year: 2011

Platelets shed microparticles not only upon activation, but also upon ageing by an apoptosis-like process (apoptosis-induced platelet microparticles, PM(ap)). While the activation-induced microparticles have widely been studied, not much is known about the (patho)physiological consequences of PM(ap) formation. Flow cytometry and scanning electron microscopy demonstrated that PM(ap) display activated integrins and interact to form microparticle aggregates. PM(ap) were chemotactic for monocytic cells, bound to these cells, an furthermore stimulated cell adhesion and spreading on a fibronectin surface. After prolonged incubation, PM(ap) promoted cell differentiation, but inhibited proliferation. Monocyte membrane receptor analysis revealed increased expression levels of CD11b (integrin α(M)β(2)), CD14 and CD31 (platelet endothelial cell adhesion molecule-1), and the chemokine receptors CCR5 and CXCR4, but not of CCR2. This indicated that PM(ap) polarized the cells into resident M2 monocytes. Cells treated with PM(ap) actively consumed oxidized low-density lipoprotein (oxLDL), and released matrix metalloproteinases and hydrogen peroxide. Further confirmation for the differentiation towards resident professional phagocytes came from the finding that PM(ap) stimulated the expression of the (ox)LDL receptors, CD36 and CD68, and the production of proinflammatory and immunomodulating cytokines by monocytes. In conclusion, interaction of PM(ap) with monocytic cells has an immunomodulating potential. The apoptotic microparticles polarize the cells into a resident M2 subset, and induce differentiation to resident professional phagocytes. Source


Felderhof B.U.,RWTH Aachen
European Journal of Mechanics, B/Fluids | Year: 2012

It is shown that for a body which is swimming at low Reynolds number and is spherical at some time of its motion the mean surface flow velocity and the mean surface rotational flow velocity in the laboratory frame vanish at that time. The instantaneous translational and rotational swimming velocities are the opposite of the mean surface flow velocity and the mean surface rotational flow velocity in the rest frame. The swimming velocities are calculated for an example of spherical squirming motion. In the example, the translational swimming velocity oscillates in time about a steady value and the rotational swimming velocity is steady. © 2011 Elsevier Masson SAS. All rights reserved. Source


Felderhof B.U.,RWTH Aachen
European Journal of Mechanics, B/Fluids | Year: 2012

Two planar sheets are considered which swim parallel in a viscous incompressible fluid in the limit of low Reynolds number by means of transverse plane wave displacement. The swimming velocities and the rate of dissipation depend on the phase difference between the plane waves. It is shown that for equal amplitudes of the waves the speed and efficiency are minimal for in-phase swimming and maximal for out-of-phase swimming. © 2011 Elsevier Masson SAS. All rights reserved. Source


The loss of fluid momentum due to friction at one or two planar walls bounding a viscous compressible fluid is studied as a function of time for the situation where the flow is due to a sudden impulse applied at a selected point in initially quiescent fluid. The no-slip condition is assumed to hold at the walls, and the initial impulse is assumed to be sufficiently small, so that the linearized Navier-Stokes equations may be used. When the initial impulse is directed parallel to the walls the time-dependent total fluid momentum is independent of compressibility and volume viscosity. For initial impulse directed perpendicular to the walls an echoing effect, corresponding to sound bouncing between the two walls, is observed. © 2010 American Institute of Physics. Source


Belyaev A.V.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry | Vinogradova O.I.,RWTH Aachen
Soft Matter | Year: 2010

Patterned surfaces with large effective slip lengths, such as super-hydrophobic surfaces containing trapped gas bubbles, have the potential to reduce hydrodynamic drag. Based on lubrication theory, we analyze an approach of a hydrophilic disk to such a surface. The drag force is predicted analytically and formulated in terms of a correction function to the Reynolds equation, which is shown to be the harmonic mean of corrections expressed through effective slip lengths in the two principal (fastest and slowest) orthogonal directions. The reduction of drag is especially pronounced for a thin (compared to texture characteristic length) gap. It is not really sensitive to the pattern geometry, but depends strongly on the fraction of the gas phase and local slip length at the gas area. © 2011 The Royal Society of Chemistry. Source


Recently an enriched contact finite element formulation has been developed that substantially increases the accuracy of contact computations while keeping the additional numerical effort at a minimum reported by Sauer (Int J Numer Meth Eng, 87: 593-616, 2011). Two enrich-ment strategies were proposed, one based on local p-refinement using Lagrange interpolation and one based on Hermite interpolation that produces C 1-smoothness on the contact surface. Both classes, which were initially considered for the frictionless Signorini problem, are extended here to friction and contact between deformable bodies. For this, a symmetric contact formulation is used that allows the unbiased treatment of both contact partners. This paper also proposes a post-processing scheme for contact quantities like the contact pressure. The scheme, which provides a more accurate representation than the raw data, is based on an averaging procedure that is inspired by mortar formulations. The properties of the enrichment strategies and the corresponding post-processing scheme are illustrated by several numerical examples considering sliding and peeling contact in the presence of large deformations. © 2012 Springer-Verlag Berlin Heidelberg. Source


Dornisch W.,University of Kaiserslautern | Klinkel S.,University of Kaiserslautern | Klinkel S.,RWTH Aachen | Simeon B.,University of Kaiserslautern
Computer Methods in Applied Mechanics and Engineering | Year: 2013

An isogeometric Reissner-Mindlin shell derived from the continuum theory is presented. The geometry is described by NURBS surfaces. The kinematic description of the employed shell theory requires the interpolation of the director vector and of a local basis system. Hence, the definition of nodal basis systems at the control points is necessary for the proposed formulation. The control points are in general not located on the shell reference surface and thus, several choices for the nodal values are possible. The proposed new method uses the higher continuity of the geometrical description to calculate nodal basis system and director vectors which lead to geometrical exact interpolated values thereof. Thus, the initial director vector coincides with the normal vector even for the coarsest mesh. In addition to that a more accurate interpolation of the current director and its variation is proposed. Instead of the interpolation of nodal director vectors the new approach interpolates nodal rotations. Account is taken for the discrepancy between interpolated basis systems and the individual nodal basis systems with an additional transformation. The exact evaluation of the initial director vector along with the interpolation of the nodal rotations lead to a shell formulation which yields precise results even for coarse meshes. The convergence behavior is shown to be correct for k-refinement allowing the use of coarse meshes with high orders of NURBS basis functions. This is potentially advantageous for applications with high numerical effort per integration point. The geometrically nonlinear formulation accounts for large rotations. The consistent tangent matrix is derived. Various standard benchmark examples show the superior accuracy of the presented shell formulation. A new benchmark designed to test the convergence behavior for free form surfaces is presented. Despite the higher numerical effort per integration point the improved accuracy yields considerable savings in computation cost for a predefined error bound. © 2012 Elsevier B.V. Source


Ohm J.-R.,RWTH Aachen | Sullivan G.J.,Microsoft
IEEE Signal Processing Magazine | Year: 2013

High Efficiency Video Coding (HEVC) is a new video compression standard developed jointly by ITU-T Video Coding Experts Group (VCEG) and ISO/IEC Moving Pictures Expert Group (MPEG) through their Joint Collaborative Team on Video Coding (JCT-VC). HEVC has been designed to address essentially all existing applications of previous standards and to particularly focus on two key issues, increased video resolution and the increased use of parallel processing architectures. The video coding layer of HEVC employs essentially the same hybrid approach used in all video compression standards since H.261. Coding and decoding of nonzero coefficients is performed by grouping them into 4 × 4 coefficient groups and scanning the coefficients in each group using a scanning order that is usually diagonal, but changes to horizontal or vertical in the case of small TBs (8 × 8 and smaller) that are coded using certain directional modes of intrapicture prediction. Source


Bernreuther W.,RWTH Aachen | Uwer P.,Humboldt University of Berlin
Nuclear and Particle Physics Proceedings | Year: 2015

Results are reviewed which were obtained within the project Top-quark physics at colliders. These include QCD and weak-interaction corrections to hadronic tt- production, determinations of the the top-quark mass, predictions of the tt- charge asymmetry and tt- spin correlations, NLO QCD corrections to hadronic tt-+1-jet production, and partial results for hadronic t-channel single-top production at NNLO QCD. In addition, some methodical developments made in this project are outlined, which are relevant for NLO and NNLO QCD calculations. © 2015 Elsevier B.V.. Source


Torrilhon M.,RWTH Aachen
Communications in Computational Physics | Year: 2015

The accuracy of moment equations as approximations of kinetic gas theory is studied for four different boundary value problems. The kinetic setting is given by the BGK equation linearized around a globally constant Maxwellian using one space dimension and a three-dimensional velocity space. The boundary value problems include Couette and Poiseuille flow as well as heat conduction between walls and heat conduction based on a locally varying heating source. The polynomial expansion of the distribution function allows for different moment theories of which two popular families are investigated in detail. Furthermore, optimal approximations for a given number of variables are studied empirically. The paper focuses on approximations with relatively low number of variables which allows to draw conclusions in particular about specific moment theories like the regularized 13-moment equations. Copyright © Global-Science Press 2015. Source


Ruppert A.M.,Technical University of Lodz | Weinberg K.,Medical University of Lodz | Palkovits R.,RWTH Aachen | Palkovits R.,Max-Planck-Institut fur Kohlenforschung
Angewandte Chemie - International Edition | Year: 2012

In view of the diminishing oil resources and the ongoing climate change, the use of efficient and environmentally benign technologies for the utilization of renewable resources has become indispensible. Therein, hydrogenolysis reactions offer a promising possibility for future biorefinery concepts. These reactions result in the cleavage of C-C and C-O bonds by hydrogen and allow direct access to valuable platform chemicals already integrated in today's value chains. Thus, hydrogenolysis bears the potential to bridge currently available technologies and future biomass-based refinery concepts. This Review highlights past and present developments in this field, with special emphasis on the direct utilization of cellulosic feedstocks. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Tacke F.,RWTH Aachen
Liver international : official journal of the International Association for the Study of the Liver | Year: 2011

Chemokines are chemotactic mediators that are implicated in liver diseases. In viral hepatitis and primary biliary cirrhosis, a predominant chemokine receptor expressed in the liver is CXCR3, suggesting that its specific ligands are important in the progression of chronic liver diseases across different aetiologies. We analysed the serum concentrations of the CXCR3 ligands, CXCL9 (monokine induced by interferon-γ), CXCL10 (interferon-γ-inducible protein 10) and CXCL11 (interferon-inducible T cell α chemo-attractant) in healthy controls (n=53), subjects with histologically determined liver fibrosis (n=109) and patients with different stages of cirrhosis (n=153) of various disease aetiologies. Chemokine concentrations were determined by cytometric bead assay or ELISA respectively. Serum concentrations of all three chemokines were significantly increased in patients with chronic liver diseases compared with healthy controls (P<0.001). In the biopsied fibrosis cohort, CXCL9 and CXCL10 were positively associated with the severity of liver fibrosis (histology and serum markers), while CXCL11 was not. In cirrhotic patients, CXCL9 was increased in early Child-Pugh stages, while CXCL11 was elevated only in Child B and C patients and CXCL10 across all stages. Notably, CXCR3 chemokines were also associated with the development of clinical complications of cirrhosis, especially portal hypertension. All chemokines significantly correlated with serum levels of the hepatoprotective cytokines interleukin (IL)-6 and IL-10, suggesting their involvement in a counter-regulatory response during the progression of liver disease, shedding new light on their involvement in the pathophysiology of chronic liver diseases. CXCR3 chemokines are differentially expressed during chronic liver diseases across different disease stages and aetiologies. Their association with portal hypertension and hepatoprotective cytokines implies biological functions beyond immune cell recruitment, thereby provoking new diagnostic and therapeutic concepts. © 2011 John Wiley & Sons A/S. Source


Czakon M.,RWTH Aachen
Nuclear and Particle Physics Proceedings | Year: 2015

We review the recent progress in the determination of top-quark pair production cross sections at hadron colliders, in particular the Tevatron and the LHC. We discuss the theoretical developments, which lead to the determination of next-to-next-to-leading (NNLO) corrections to this process. Furthermore, we describe some applications which follow from a comparison of theory predictions with data, e.g. the determination of the top-quark pole mass, constraints on the gluon distribution function and bounds on light top squarks. Finally, we present the most recent analysis of the Tevatron forward-backward asymmetry, where we demonstrate agreement between the Standard Model and the measurement. © 2015 Elsevier B.V. Source


Busch A.,Royal Dutch Shell | Amann-Hildenbrand A.,RWTH Aachen
Marine and Petroleum Geology | Year: 2013

This study provides a compilation, evaluation and correlation of published petrophysical datasets determined for 233 rock samples (165 mudrocks, 27 sandstone, 25 carbonate, 11 anhydrite and 5 marlstone datasets). With predominant focus on mudrocks a review of the methods used for determination of capillary breakthrough and snap-off pressures is given. Additionally, based on more recent data, previously published empirical correlations are critically investigated.Knowledge about these two critical pressures is important for both, the prediction of the capillary sealing capacity of natural gas reservoirs or CO2 storage sites, but also for production estimates from tight gas or shale gas plays.Capillary pressure experiments, when performed on low-permeability core plugs, are difficult and time consuming. Laboratory measurements on core plugs under in-situ conditions are mostly performed using nitrogen, but also with methane and carbon dioxide. Therefore, mercury injection porosimetry (MIP) measurements are preferably used in the industry to determine an equivalent value for the capillary breakthrough pressure. These measurements have the advantage to be quick and cheap and only require cuttings or trim samples.When evaluating the database in detail we find that (1) MIP data plot well with the drainage breakthrough pressures determined on sample plugs, while the conversion of the system Hg/air to gas/brine (e.g. CH4, CO2) using interfacial and wettability data does not provide a uniform match, potentially caused by different wettability characteristics; (2) brine permeability versus capillary breakthrough pressure determined on sample plugs shows a good match and could provide a first estimate of Pc-values since permeability is easier to determine than capillary breakthrough pressures. For imbibition snap-off pressures a good correlation was found for CH4 measured on sample plugs only; (3) porosity shows a fairly good correlation with permeability for sandstone only, and with plug-derived capillary breakthrough pressures for sandstones, carbonates and evaporates. No such correlations exist for mudrocks; (4) air and brine-derived permeabilities show an excellent correlation and (5) from the data used we do not infer any direct correlations between specific surface area (SSA), mineralogy or organic carbon content with permeability or capillary pressure. However we were able to better predict permeabilities using a more sophisticated model that relies on a combination of these parameters. © 2013 Elsevier Ltd. Source


Walther A.,RWTH Aachen | Muller A.H.E.,Johannes Gutenberg University Mainz
Chemical Reviews | Year: 2013

Some of the advancements in the field of non-centrosymmetric Janus particles (JP) along with the synthesis, self-assembly behavior, physical properties, and applications, are discussed. Researchers focus on describing biological, biobased, and bioinspired JPs, access routes based on classical organic synthesis, along with macromolecular engineering and self-assembly of polymers, symmetry breaking at interfaces, selective growth of second compartments, and symmetry-breaking in confined volumes. The researchers also discuss related techniques using the break-up or patterning of side-by-side flown liquids, and miscellaneous techniques. They inform that significant progress has been made in diversifying synthetic strategies for the preparation of JPs over a period of time with the aim to include diverse functionalities, target inorganic or organic hybrid materials, along with finding ways toward a scale-up. Source


The sine law is a simple geometrical model for incremental sheet metal forming (ISF). It is based on the assumption that the deformation is a projection of the undeformed sheet onto the surface of the final part. The sine law provides approximations of sheet thinning for shear spinning and ISF at negligible computational cost, but as a plane strain model it can be applied only when plane strain deformation prevails. In this paper, a new model for the process kinematics of ISF is presented that is more general than the sine law. The model treats ISF as an evolution of a surface from the undeformed sheet to the final shape. It computes trajectories of surface points based on idealized intermediate shapes, assuming that the deformation between intermediate shapes proceeds by displacements along the surface normal of the current shape. For 2D and axisymmetrical problems, an analytical solution of the model is developed, which is useful for visualizing and discussing the kinematics of ISF. In order to use the new model with arbitrary parts, it was cast into a computer program that calculates membrane strains and the sheet thickness on a triangular mesh. For a benchmark shape, the model is compared to the sine law and experimental results. It is shown that the new model yields better thickness estimates than the sine law, especially in non-flat part areas where strains parallel to the direction of tool motion are significant. © 2010 Elsevier B.V. Source


Zilles K.,Heinrich Heine University Dusseldorf | Zilles K.,Julich Research Center | Amunts K.,Julich Research Center | Amunts K.,RWTH Aachen
Science | Year: 2012

Are there unifying principles behind the structural complexity of the cerebral cortex? Source


Felderhof B.U.,RWTH Aachen
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The momentum relaxation of a relativistic Brownian particle immersed in a fluid is studied on the basis of the Fokker-Planck equation for the relativistic Ornstein-Uhlenbeck process. An analytical expression is derived for the short-time relaxation rate. The relaxation spectrum has both discrete and continuum components. It is shown that the Fokker-Planck equation under consideration is closely related to the Schrödinger equation for the hydrogen atom. Hence it follows that there is an infinite number of discrete states. The momentum autocorrelation function is calculated numerically for a strongly relativistic particle. © 2012 American Physical Society. Source


Felderhof B.U.,RWTH Aachen
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The hydrodynamic force on a particle oscillating in a viscous fluid near a wall with partial-slip boundary condition is studied on the basis of the linearized Navier-Stokes equations. Both incompressible and compressible fluids are considered. It is assumed that the slip length characterizing the partial-slip boundary condition depends on frequency. The consequences of this assumption for the spectrum of Brownian motion near a wall are investigated and compared with a recent experiment. © 2012 American Physical Society. Source


Jahnen-Dechent W.,RWTH Aachen | Ketteler M.,Klinikum Coburg
CKJ: Clinical Kidney Journal | Year: 2012

As a cofactor in numerous enzymatic reactions, magnesium fulfils various intracellular physiological functions. Thus, imbalance in magnesium status - primarily hypomagnesaemia as it is seen more often than hypermagnesaemia - might result in unwanted neuromuscular, cardiac or nervous disorders. Measuring total serum magnesium is a feasible and affordable way to monitor changes in magnesium status, although it does not necessarily reflect total body magnesium content. The following review focuses on the natural occurrence of magnesium and its physiological function. The absorption and excretion of magnesium as well as hypo- and hypermagnesaemia will be addressed. © The Author 2012. Source


Korden S.,RWTH Aachen
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

In this article we replace the semiheuristic derivation of the Rosenfeld functional of hard convex particles with the systematic calculation of Mayer clusters. It is shown that each cluster integral further decomposes into diagrams of intersection patterns that we classify by their loop number. This extends the virial expansion of the free energy by an expansion in the loop order, with the Rosenfeld functional as its leading contribution. Rosenfeld's weight functions then follow from the derivation of the intersection probability by generalizing the equation of Blaschke, Santalo, and Chern. It is found that the 0-loop order can be derived exactly and reproduces the Rosenfeld functional. We further discuss the influence of particle dimensions, topologies, and geometries on the mathematical structure of the calculation. © 2012 American Physical Society. Source


Zhang G.,University of Heidelberg | Presly O.,Agilent Technologies | White F.,Agilent Technologies | Oppel I.M.,RWTH Aachen | Mastalerz M.,University of Heidelberg
Angewandte Chemie - International Edition | Year: 2014

Discrete interlocked three-dimensional structures are synthetic targets that are sometimes difficult to obtain with "classical" synthetic approaches, and dynamic covalent chemistry has been shown to be a useful method to form such interlocked structures as thermodynamically stable products. Although interlocked and defined hollow structures are found in nature, for example, in some viruses, similar structures have rarely been synthesized on a molecular level. Shape-persistent interlocked organic cage compounds with dimensions in the nanometer regime are now accessible in high yields during crystallization through the formation of 96covalent bonds. The interlocked molecules form an unprecedented porous material with intrinsic and extrinsic pores both in the micropore and mesopore regime. Two is better than one: During the crystallization of a giant shape-persistent organic cage compound, a dimeric catenated structure is formed by a 96-fold condensation reaction of 40molecular subunits. The crystals of the molecular catenane contain one intrinsic mesopore (2.0nm) and one extrinsic micropore (1.3nm). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Kuhl C.K.,RWTH Aachen
Investigative Radiology | Year: 2015

Compared with other fields of medicine, there is hardly an area that has seen such fast development as the world of breast cancer. Indeed, the way we treat breast cancer has changed fundamentally over the past decades. Breast imaging has always been an integral part of this change, and it undergoes constant adjustment to new ways of thinking. This relates not only to the technical tools we use for diagnosing breast cancer but also to the way diagnostic information is used to guide treatment. There is a constant change of concepts for and attitudes toward breast cancer, and a constant flux of new ideas, new treatment approaches, and new insights into the molecular and biological behavior of this disease. Clinical breast radiologists and even more so, clinician scientists, interested in breast imaging need to keep abreast with this rapidly changing world. Diagnostic or treatment approaches that are considered useful today may be abandoned tomorrow. Approaches that seem irrelevant or far too extravagant today may prove clinically useful and adequate next year. Radiologists must constantly question what they do, and align their clinical aims and research objectives with the changing needs of contemporary breast oncology. Moreover, knowledge about the past helps better understand present debates and controversies. Accordingly, in this article, we provide an overview on the evolution of breast imaging and breast cancer treatment, describe current areas of research, and offer an outlook regarding the years to come. © 2015 Wolters Kluwer Health, Inc. Source


Zhang G.,University of Heidelberg | Presly O.,Agilent Technologies | White F.,Agilent Technologies | Oppel I.M.,RWTH Aachen | Mastalerz M.,University of Heidelberg
Angewandte Chemie - International Edition | Year: 2014

Recently, porous organic cage crystals have become a real alternative to extended framework materials with high specific surface areas in the desolvated state. Although major progress in this area has been made, the resulting porous compounds are restricted to the microporous regime, owing to the relatively small molecular sizes of the cages, or the collapse of larger structures upon desolvation. Herein, we present the synthesis of a shape-persistent cage compound by the reversible formation of 24 boronic ester units of 12 triptycene tetraol molecules and 8 triboronic acid molecules. The cage compound bears a cavity of a minimum inner diameter of 2.6 nm and a maximum inner diameter of 3.1 nm, as determined by single-crystal X-ray analysis. The porous molecular crystals could be activated for gas sorption by removing enclathrated solvent molecules, resulting in a mesoporous material with a very high specific surface area of 3758 m2 g-1 and a pore diameter of 2.3 nm, as measured by nitrogen gas sorption. Big boronic ester cages: A shape-persistent cuboctahedron can be almost quantitatively formed by a 48-fold one-pot condensation of 12 molecules of a triptycene tetrol with 8 molecules of triboronic acid. The desolvated crystalline material of this cage has a specific surface area of 3758 m2 g-1 and a maximum pore size of 2.3 nm, thus making it mesoporous by the IUPAC definition. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Kesselheim T.,RWTH Aachen
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

We consider scheduling problems in wireless networks with respect to flexible data rates. That is, more or less data can be transmitted per time depending on the signal quality, which is determined by the signal-to- interference-plus-noise ratio (SINR). Each wireless link has a utility function mapping SINR values to the respective data rates. We have to decide which transmissions are performed simultaneously and (depending on the problem variant) also which transmission powers are used. In the capacity-maximization problem, one strives to maximize the overall network throughput, i.e., the summed utility of all links. For arbitrary utility functions (not necessarily continuous ones), we present an O(logn)-approximation when having n communication requests. This algorithm is built on a constant-factor approximation for the special case of the respective problem where utility functions only consist of a single step. In other words, each link has an individual threshold and we aim at maximizing the number of links whose threshold is satisfied. On the way, this improves the result in [Kesselheim, SODA 2011] by not only extending it to individual thresholds but also showing a constant approximation factor independent of assumptions on the underlying metric space or the network parameters. In addition, we consider the latency-minimization problem. Here, each link has a demand, e.g., representing an amount of data. We have to compute a schedule of shortest possible length such that for each link the demand is fulfilled, that is, the overall summed utility (or data transferred) is at least as large as its demand. Based on the capacity-maximization algorithm, we show an O(log 2 n)-approximation for this problem. © 2012 Springer-Verlag. Source


Domcke V.,National Institute of Nuclear Physics, Italy | Heisig J.,RWTH Aachen
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Despite its importance for modeling the homogeneous hot early Universe very little is experimentally known about the magnitude of the reheating temperature, leaving an uncertainty of remarkable 18 orders of magnitude. In this paper we consider a general class of polynomial inflaton potentials up to fourth order. Employing a Monte Carlo scan and imposing theoretical and experimental constraints we derive a robust lower limit on the energy scale at the end of inflation, Vend1/4>3×1015 GeV for sizable tensor modes, r≥10-3. If the reheating phase is perturbative and matter dominated, this translates into a lower bound on the reheating temperature, yielding Trh>3×108(7×102) GeV for gravitational inflaton decay through a generic dimension five (six) operator. © 2015 American Physical Society. Source


Gulder T.,RWTH Aachen | Baran P.S.,Scripps Research Institute
Natural Product Reports | Year: 2012

Covering: up to 2011 Cyclophane natural products comprise an intriguing class of structurally diverse compounds. As inherent for all cyclic compounds regardless of their origin, macrocyclization is naturally the most decisive step, which defines the overall efficiency of the synthetic pathway. Especially in small cyclophane molecules, this key step constitutes an even greater challenge. Due to the strain imparted by the macrocyclic system, free rotation of the benzene ring(s) is often restricted depending on both the constitution of the tether and the aromatic portions. Not surprisingly, the synthesis of natural cyclophanes with their often outstanding pharmaceutical activities and the inherent issues associated with their preparation has attracted much attention among the synthetic community. In particular, it stimulated the development of new strategies for the ring-closing step, as often otherwise well established and robust reactions fail to perform effectively. In this review, we describe the challenges synthetic chemists are facing during the synthesis of this small, but structurally and biologically fascinating class of natural products, concentrating on the representatives exhibiting configurational stability. The main focus will be on the different concepts for the installation of the macrocyclic system, in most cases the central problem in assembling these extremely rigid molecules. This journal is © The Royal Society of Chemistry 2012. Source


Aqueous 3Y-TZP inks with solid contents of 22 and 27 vol% were used for fabricating three-dimensional ceramic components by the direct ink-jet printing process (DIP). The DIP fabrication was realized using a thermal ink-jet (TIJ) printing system. Despite the different physical properties of the inks, both inks were successfully ejected and deposited. To define the optimum window of the ink properties required for a stable printing operation, both ceramic inks as well as a typical TIJ ink were characterized in terms of particle size distribution, zeta potential, viscosity, surface tension, and the inverse Ohnesorge number (Oh-1). Moreover, single drops of all inks were deposited and analyzed by scanning electron microscopy (SEM) to examine the form and integrity of the ejected drops. Demonstration objects (a base with curved channels and a sample molar tooth) were DIP fabricated using both of the ceramic inks. These objects show the potentials of the DIP process for ceramics manufacturing particularly by using TIJ printing systems. © 2013 The American Ceramic Society. Source


Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low, but also to control the microstructure and final properties of the workpiece. According to Poliak and Jonas, the onset of DRX can be detected from an inflection point in the strain hardening rate as a function of flow stress. Various models are available that predict the evolution of flow stress from incipient plastic flow to steady-state deformation in the presence of DRX, but their consistency with the criterion of Poliak and Jonas has not been investigated. This work analyzes the conditions that a flow stress model incorporating DRX has to fulfill to be consistent with the criterion of Poliak and Jonas. As the most important inconsistency, it is found that a model might suffer from insufficient differentiability at the critical point. For all models that use a classical JMAK equation for the DRX kinetics, it is shown that the Avrami exponent must exceed a value of 3. If the Avrami exponent is at most 3, a kink may develop in the strain hardening rate, and the second derivative criterion is violated. For DRX kinetics based on nucleation and growth rates that are functions of time, criteria are derived that ensure consistency with the criterion of Poliak and Jonas. DRX kinetics that are consistent with the second derivative criterion are put forward, drawing upon kinetics proposed by Cahn for transformations that originate at grain boundaries. Finally, a minimal model that is consistent with the second derivative criterion is formulated. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source


Heidenreich A.,RWTH Aachen | Bastian P.J.,Klinikum Golzheim | Bellmunt J.,University of the Sea | Bolla M.,C.H.U. Grenoble | And 7 more authors.
European Urology | Year: 2014

Context The most recent summary of the European Association of Urology (EAU) guidelines on prostate cancer (PCa) was published in 2011. Objective To present a summary of the 2013 version of the EAU guidelines on screening, diagnosis, and local treatment with curative intent of clinically organ-confined PCa. Evidence acquisition A literature review of the new data emerging from 2011 to 2013 has been performed by the EAU PCa guideline group. The guidelines have been updated, and levels of evidence and grades of recommendation have been added to the text based on a systematic review of the literature, which included a search of online databases and bibliographic reviews. Evidence synthesis A full version of the guidelines is available at the EAU office or online (www.uroweb.org). Current evidence is insufficient to warrant widespread population-based screening by prostate-specific antigen (PSA) for PCa. Systematic prostate biopsies under ultrasound guidance and local anesthesia are the preferred diagnostic method. Active surveillance represents a viable option in men with low-risk PCa and a long life expectancy. A biopsy progression indicates the need for active intervention, whereas the role of PSA doubling time is controversial. In men with locally advanced PCa for whom local therapy is not mandatory, watchful waiting (WW) is a treatment alternative to androgen-deprivation therapy (ADT), with equivalent oncologic efficacy. Active treatment is recommended mostly for patients with localized disease and a long life expectancy, with radical prostatectomy (RP) shown to be superior to WW in prospective randomized trials. Nerve-sparing RP is the approach of choice in organ-confined disease, while neoadjuvant ADT provides no improvement in outcome variables. Radiation therapy should be performed with ≥74 Gy in low-risk PCa and 78 Gy in intermediate- or high-risk PCa. For locally advanced disease, adjuvant ADT for 3 yr results in superior rates for disease-specific and overall survival and is the treatment of choice. Follow-up after local therapy is largely based on PSA and a disease-specific history, with imaging indicated only when symptoms occur. Conclusions Knowledge in the field of PCa is rapidly changing. These EAU guidelines on PCa summarize the most recent findings and put them into clinical practice. Patient summary A summary is presented of the 2013 EAU guidelines on screening, diagnosis, and local treatment with curative intent of clinically organ-confined prostate cancer (PCa). Screening continues to be done on an individual basis, in consultation with a physician. Diagnosis is by prostate biopsy. Active surveillance is an option in low-risk PCa and watchful waiting is an alternative to androgen-deprivation therapy in locally advanced PCa not requiring immediate local treatment. Radical prostatectomy is the only surgical option. Radiation therapy can be external or delivered by way of prostate implants. Treatment follow-up is based on the PSA level. © 2013 European Association of Urology. Published by Elsevier B.V. All rights