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The Freie Universität Berlin is a renowned research university located in Berlin and one of the most prominent universities in Germany. It is internationally known for its research in the humanities and social science, as well as in the field of natural and life science. Founded in West Berlin during the early Cold War period and born out of the increasingly Communist-controlled Humboldt University, its name refers to West Berlin's status as part of the free world, as opposed to the Soviet-occupied "unfree" areas surrounding the city.Freie Universität Berlin was one of nine German universities to win in the German Universities Excellence Initiative, a national competition for universities organized by the German federal government. Winning a distinction for five doctoral programs, three interdisciplinary research clusters and its overall institutional strategy as an "International Network University", Freie Universität Berlin is one of the most successful universities in the initiative. Wikipedia.


Gorenflo R.,Free University of Berlin | Mainardi F.,University of Bologna
European Physical Journal: Special Topics | Year: 2011

The uncoupled Continuous Time Random Walk (CTRW) in one space-dimension and under power law regime is splitted into three distinct random walks: (rw1), a random walk along the line of natural time, happening in operational time; (w2), a random walk along the line of space, happening in operational time; (rw3), the inversion of (rw1), namely a random walk along the line of operational time, happening in natural time. Via the general integral equation of CTRW and appropriate rescaling, the transition to the diffusion limit is carried out for each of these three random walks. Combining the limits of (rw1) and (rw2) we get the method of parametric subordination for generating particle paths, whereas combination of (rw2) and (rw3) yields the subordination integral for the sojourn probability density in space - time fractional diffusion. © 2011 EDP Sciences and Springer. Source


Farag Ali A.,Benha University | Tawfik A.,Cairo University | Tawfik A.,Free University of Berlin
Advances in High Energy Physics | Year: 2013

A recent theory about the origin of the gravity suggests that the gravity is originally an entropic force. In this work, we discuss the effects of generalized uncertainty principle (GUP) which is proposed by some approaches to quantum gravity such as string theory, black hole physics, and doubly special relativity theories (DSR), on the area law of the entropy. This leads to a area -type correction to the area law of entropy which implies that the number of bits N is modified. Therefore, we obtain a modified Newton's law of gravitation. Surprisingly, this modification agrees with different sign with the prediction of Randall-Sundrum II model which contains one uncompactified extra dimension. Furthermore, such modification may have observable consequences at length scales much larger than the Planck scale. © 2013 Ahmed Farag Ali and A. Tawfik. Source


Grosu C.,Free University of Berlin
Electronic Journal of Combinatorics | Year: 2016

More than a century after its proposal, the Towers of Hanoi puzzle with 4 pegs was solved by Thierry Bousch in a breakthrough paper in 2014. The general problem with p pegs is still open, with the best lower bound on the minimum number of moves due to Chen and Shen. We use some of Bousch’s new ideas to obtain an asymptotic improvement on this bound for all p ≥ 5. © 2016, Australian National University. All rights reserved. Source


Specht J.,Free University of Berlin | Luhmann B.M.,University of Illinois at Chicago | Geiser C.,Utah State University
Journal of Personality and Social Psychology | Year: 2014

Consistency and change in personality were analyzed by examining personality types across adulthood and old age using data from 2 nationally representative panel studies from Germany (N = 14,718; 16-82 years) and Australia (N = 8,315; 15-79 years). In both samples, the Big Five personality traits were measured twice across a period of 4 years. Latent profile analyses and latent profile transition analyses revealed 4 main findings: First, solutions with 3 (in the German sample) or 4 (in the Australian sample) personality types were found to be most interpretable. Second, measurement invariance tests revealed that these personality types were consistent across all age groups but differed slightly between men and women. Third, age was related to the number of individuals classified within each personality type. Namely, there were more resilients and fewer undercontrollers in older compared with younger age groups. Fourth, there was strong consistency of personality type membership across a period of 4 years in both genders and most age cohorts. Comparatively less consistency across time was found for undercontrollers and individuals in old age. Taken together, these findings show that in the 2 nations studied here, personality types were highly consistent across gender, age, and time. © 2014 American Psychological Association. Source


Aptroot A.,ABL Herbarium | Sipman H.J.M.,Free University of Berlin | Caceres M.E.D.S.,Federal University of Sergipe
Lichenologist | Year: 2013

Abstract Twenty-three species of Pyrenula from Latin America are treated here. Several species show characters that were not previously reported in the genus and are rare or new to lichenized fungi, viz. yellow, orange or red (KOH+ green) oil inspersion in the hymenium, yellow oil in young ascospores or longitudinal ridges on the ascospore wall. Two taxonomically significant types of over-mature spores are illustrated. The following new species are described: Pyrenula aggregataspistea Aptroot & M. Cáceres, P. aurantioinspersa Aptroot & Sipman, P. cornutispora Aptroot & M. Cáceres, P. flavoinspersa Aptroot & Sipman, P. guyanensis Sipman & Aptroot, P. infraleucotrypa Aptroot & M. Cáceres, P. inframamillana Aptroot & M. Cáceres, P. infrastroidea Aptroot & Sipman, P. maritima Sipman & Aptroot, P. mattickiana Sipman & Aptroot, P. minoides Aptroot & Sipman, P. monospora Aptroot & Sipman, P. paraminarum Aptroot & M. Cáceres, P. perfecta Aptroot & Sipman, P. plicata Sipman & Aptroot, P. rubroinspersa Aptroot & Sipman, P. rubronitidula Aptroot & M. Cáceres, P. rubrostigma Aptroot & M. Cáceres, P. tetraspora Aptroot & Sipman, P. triangularis Aptroot & Sipman, P. viridipyrgilla Aptroot & M. Cáceres. Pyrenula seminuda (Müll. Arg.) Sipman & Aptroot is a new combination. Copyright © British Lichen Society 2013. Source


Bonthuis D.J.,University of Oxford | Netz R.R.,Free University of Berlin
Journal of Physical Chemistry B | Year: 2013

Standard continuum theory fails to predict several key experimental results of electrostatic and electrokinetic measurements at aqueous electrolyte interfaces. In order to extend the continuum theory to include the effects of molecular solvent structure, we generalize the equations for electrokinetic transport to incorporate a space dependent dielectric profile, viscosity profile, and non-electrostatic interaction potential. All necessary profiles are extracted from atomistic molecular dynamics (MD) simulations. We show that the MD results for the ion-specific distribution of counterions at charged hydrophilic and hydrophobic interfaces are accurately reproduced using the dielectric profile of pure water and a non-electrostatic repulsion in an extended Poisson-Boltzmann equation. The distributions of Na+ at both surface types and Cl- at hydrophilic surfaces can be modeled using linear dielectric response theory, whereas for Cl- at hydrophobic surfaces it is necessary to apply nonlinear response theory. The extended Poisson-Boltzmann equation reproduces the experimental values of the double-layer capacitance for many different carbon-based surfaces. In conjunction with a generalized hydrodynamic theory that accounts for a space dependent viscosity, the model captures the experimentally observed saturation of the electrokinetic mobility as a function of the bare surface charge density and the so-called anomalous double-layer conductivity. The two-scale approach employed here - MD simulations and continuum theory - constitutes a successful modeling scheme, providing basic insight into the molecular origins of the static and kinetic properties of charged surfaces, and allowing quantitative modeling at low computational cost. © 2013 American Chemical Society. Source


von Raab-Straube E.,Free University of Berlin
Willdenowia | Year: 2011

Investigation of type material of Chinese taxa of Saussurea revealed that the names S. erubescens, S. globosa, S. hypsipeta and S. polycolea var. acutisquama are frequently misapplied in the literature. As a consequence, S. acutisquama is described here as a species new to science, S. obvallata var. gymnocephala is lectotypified and raised to specific rank as S. gymnocephala, S. sorocephala var. glabrata is lectotypified and raised to specific rank as S. inversa and the concept of S. erubescens is amended. All four species are described and illustrated. S. nigrescens var. acutisquama, S. hypsipeta and S. quercifolia var. major are lectotypified. Earlier neotypifications of S. hypsipeta and S. paxiana are superseded by the rediscovery of original material. © 2011 BGBM Berlin-Dahlem. Source


Niemann-Pick Type C disease is characterized by disrupted lipid trafficking within the late endosomal (LE)/lysosomal (Lys) cellular compartments. Cholesterol transport within the LE/Lys is believed to take place via a concerted hand-off mechanism in which a small (131aa) soluble cholesterol binding protein, NPC2, transfers cholesterol to the N-terminal domain (NTD) of a larger (1278aa) membrane-bound protein, NPC1(NTD). The transfer is thought to occur through the formation of a stable intermediate complex NPC1(NTD)-NPC2, in which the sterol apertures of the two proteins align to allow passage of the cholesterol molecule. In the working model of the NPC1(NTD)-NPC2 complex, the sterol apertures are aligned, but the binding pockets are bent with respect to one another. In order for cholesterol to slide from one binding pocket to the other, a conformational change must occur in the proteins, in the ligand, or in both. Here, we investigate the possibility that the ligand undergoes a conformational change, or isomerization, to accommodate the bent transfer pathway. To understand what structural factors influence the isomerization rate, we calculate the energy barrier to cholesterol isomerization in both the NPC1(NTD) and NPC2 binding pockets. Here, we use a combined quantum mechanical/molecular mechanical (QM/MM) energy function to calculate the isomerization barrier within the native NPC1(NTD) and NPC2 binding pockets before protein-protein docking as well as in the binding pockets of the NPC1(NTD)-NPC2 complex after docking has occurred. The results indicate that cholesterol isomerization in the NPC2 binding pocket is energetically favorable, both before and after formation of the NPC1(NTD)-NPC2 complex. The NPC1(NTD) binding pocket is energetically unfavorable to conformational rearrangement of the hydrophobic ligand because it contains more water molecules near the ligand tail and amino acids with polar side chains. For three NPC1(NTD) mutants investigated, L175Q/L176Q, L175A/L176A, and E191A/Y192A, the isomerization barriers were all found to be higher than the barrier calculated in the NPC2 binding pocket. Our results indicate that cholesterol isomerization in the NPC2 binding pocket, either before or after docking, may ensure an efficient transfer of cholesterol to NPC1(NTD). © 2014 American Chemical Society. Source


Caruso T.,Free University of Berlin | Taormina M.,University of Siena | Migliorini M.,University of Siena
Journal of Animal Ecology | Year: 2012

1. Ecologists are debating the relative role of deterministic and stochastic determinants of community structure. Although the high diversity and strong spatial structure of soil animal assemblages could provide ecologists with an ideal ecological scenario, surprisingly little information is available on these assemblages. 2. We studied species-rich soil oribatid mite assemblages from a Mediterranean beech forest and a grassland. We applied multivariate regression approaches and analysed spatial autocorrelation at multiple spatial scales using Moran's eigenvectors. Results were used to partition community variance in terms of the amount of variation uniquely accounted for by environmental correlates (e.g. organic matter) and geographical position. Estimated neutral diversity and immigration parameters were also applied to a soil animal group for the first time to simulate patterns of community dissimilarity expected under neutrality, thereby testing neutral predictions. 3. After accounting for spatial autocorrelation, the correlation between community structure and key environmental parameters disappeared: about 40% of community variation consisted of spatial patterns independent of measured environmental variables such as organic matter. Environmentally independent spatial patterns encompassed the entire range of scales accounted for by the sampling design (from tens of cm to 100m). This spatial variation could be due to either unmeasured but spatially structured variables or stochastic drift mediated by dispersal. Observed levels of community dissimilarity were significantly different from those predicted by neutral models. 4. Oribatid mite assemblages are dominated by processes involving both deterministic and stochastic components and operating at multiple scales. Spatial patterns independent of the measured environmental variables are a prominent feature of the targeted assemblages, but patterns of community dissimilarity do not match neutral predictions. This suggests that either niche-mediated competition or environmental filtering or both are contributing to the core structure of the community. This study indicates new lines of investigation for understanding the mechanisms that determine the signature of the deterministic component of animal community assembly. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society. Source


Nill B.,University of Georgia | Ziegler G.M.,Free University of Berlin
Mathematics of Operations Research | Year: 2011

We show that up to unimodular equivalence in each dimension there are only finitely many lattice polytopes without interior lattice points that do not admit a lattice projection onto a lower-dimensional lattice polytope without interior lattice points. This was conjectured by Treutlein [Treutlein, J. 2008. 3-Dimensional lattice polytopes without interior lattice points. September 10, http://arXiv.org/abs/0809.1787.] As an immediate corollary, we get a short proof of a recent result of Averkov, Wagner, and Weismantel [Averkov, G., C. Wagner, R. Weismantel. 2010. Maximal lattice-free polyhedra: Finiteness and an explicit description in dimension three. Math. Oper. Res. Forthcoming.], namely, the finiteness of the number of maximal lattice polytopes without interior lattice points. Moreover, we show that, in dimension four and higher, some of these finitely many polytopes are not maximal as convex bodies without interior lattice points. © 2011 INFORMS. Source


Kirmaci M.,Adnan Menderes University | Kurschner H.,Free University of Berlin
Nova Hedwigia | Year: 2013

Four species, S. contortum, S. fallax, S. magellanicum and S. rubellum are recorded for the first time from Southwest Asia respectively Turkey, increasing the total known number of species to 22 (resp. 21 from Turkey). Five species (S. capillifolium, S. girgensohnii, S. inundatum, S. teres, S. warnstorfii) are re-collected after more than 100 resp. 40 years. In addition, first hints to the occurence of Oxycocco-Sphagnetea communities (e.g., Sphagnetalia magellanici) in Turkey are given. © 2013 J. Cramer in Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany. Source


Jaeger P.A.,Free University of Berlin | Jaeger P.A.,Stanford University | Wyss-Coray T.,Stanford University | Wyss-Coray T.,Geriatric Research Education and Clinical Center
Archives of Neurology | Year: 2010

Beclin 1 is a protein involved in the regulation of autophagy and has been shown to be reduced in patients with Alzheimer disease. This review summarizes the current research data that link disturbances in autophagy, a cellular degradation and maintenance pathway, to the development of Alzheimer disease and related neurodegenerative diseases. It also provides a brief overview of the existing pharmacological interventions available to modulate autophagy activity in mammalian cells. ©2010 American Medical Association. All rights reserved. Source


Padrol A.,Free University of Berlin
Discrete and Computational Geometry | Year: 2013

In this paper we present a new technique to construct neighborly polytopes, and use it to prove a lower bound of (formula presented) for the number of combinatorial types of vertex-labeled neighborly polytopes in even dimension d with r+d+1 vertices. This improves current bounds on the number of combinatorial types of polytopes. The previous best lower bounds for the number of neighborly polytopes were found by Shemer in 1982 using a technique called the Sewing Construction. We provide a new simple proof that sewing works, and generalize it to oriented matroids in two ways: to Extended Sewing and to Gale Sewing. Our lower bound is obtained by estimating the number of polytopes that can be constructed via Gale Sewing. Combining both new techniques, we are also able to construct many non-realizable neighborly oriented matroids. © 2013 Springer Science+Business Media New York. Source


Horenko I.,Free University of Berlin
Journal of the Atmospheric Sciences | Year: 2010

A numerical framework for data-based identification of nonstationary linear factor models is presented. The approach is based on the extension of the recently developed method for identification of persistent dynamical phases in multidimensional time series, permitting the identification of discontinuous temporal changes in underlying model parameters. The finite element method (FEM) discretization of the resulting variational functional is applied to reduce the dimensionality of the resulting problem and to construct the numerical iterative algorithm. The presented method results in the sparse sequential linear minimization problem with linear constrains. The performance of the framework is demonstrated for the following two application examples: (i) in the context of subgrid-scale parameterization for the Lorenz model with external forcing and (ii) in an analysis of climate impact factors acting on the blocking events in the upper troposphere. The importance of accounting for the nonstationarity issue is demonstrated in the second application example: modeling the 40-yr ECMWF Re-Analysis (ERA-40) geopotential time series via a single best stochastic model with time-independent coefficients leads to the conclusion that all of the considered external factors are found to be statistically insignificant, whereas considering the nonstationary model (which is demonstrated to be more appropriate in the sense of information theory) identified by the methodology presented in the paper results in identification of statistically significant external impact factor influences. © 2010 American Meteorological Society. Source


Kummerow J.,Free University of Berlin
Geophysics | Year: 2010

A procedure to locate seismic events uses the value of the crosscorrelation coefficient between waveforms of different events. First, an empirical relation between spatial event separation and maximum crosscorrelation coefficient is established for a subset of a priori located reference events. Then this relation is used to determine the hypocenters of an increasing number of events by a grid-search strategy. Measured arrival-time differences between S- and P-waves also constrain the location. Although the reference events are located by a standard method using the arrival-time measurements at three or more receivers, the correlation-based location requires only one receiver. The method has been applied to microseismic data recorded at a single borehole sensor during the 2004/05 injection experiment at the Continental Deep Drilling Site (KTB) in Germany. With the approach, significantly more weak seismic events were located, compared to the number of events recorded by a near-surface receiver array and by inversion of arrival times. The proposed location method is particularly well suited to locate small-magnitude earthquakes within dense event clouds when too few arrival-time observations for part of the events are available and standard location methods fail. These conditions are frequently met in the case of microseismic monitoring of geothermal or enhanced oil recovery experiments. © 2010 Society of Exploration Geophysicists. Source


Heiber I.,Bielefeld University | Cai W.,Free University of Berlin | Baier M.,Bielefeld University
Molecular Plant | Year: 2014

All genes encoding chloroplast antioxidant enzymes are nuclear-encoded and posttranscriptionally targeted to chloroplasts. The transcript levels of most of them decreased upon sucrose feeding like the transcript levels of many genes encoding components of the photosynthetic electron transport chain. However, the transcript abundance of stromal ascorbate peroxidase (s-APX; At4g08390) increased. Due to mild sugar application conditions, the plants kept the phosphorylation status of the ADP+ATP pool and the redox states of the NADPH+NADP+ and the ascorbate pools under control, which excludes them as signals in s-APX regulation. Correlation with ascorbate pool size regulation and comparison of transcript abundance regulation in the starch-biosynthetic mutant adg1, the ascorbate biosynthesis mutant vtc1, and the abscisic acid (ABA) biosynthetic mutant aba2 showed a link between sugar induction of s-APX and ascorbate biosynthesis. © 2013 The Author. Source


Schuz N.,University of Tasmania | Schuz B.,University of Tasmania | Eid M.,Free University of Berlin
Health Psychology | Year: 2013

Objective: Health promotion often faces the problem that populations with high behavioral risk profiles respond defensively to health promotion messages by negating risk or reactant behavior. self-affirmation theory proposes that defensive reactions are an attempt of the self-system to maintain integrity. in this article, we examine whether a self-affirmation manipulation can mitigate defensive responses to personalized visual risk feedback in the skin cancer prevention context (ultraviolet [uv] photography), and whether the effects pertain to individuals with high behavioral risk status (high personal relevance of tanning). method: we conducted a full-factorial randomized controlled trial (n 292; age 11-71) following a 2 2 design (uv photo yes/no, self-affirmation yes/no). follow-up period was 2 weeks. subsequent tanning behavior, sun avoidance intentions, and risk perception. results: a multivariate analysis of variance (manova) revealed a three-way interaction between risk feedback, the self-affirmation manipulation, and risk status for the three outcome measures. follow-up analyses of variance (anovas) indicated that high-risk individuals receiving only the risk feedback intervention reacted defensively and reported higher exposure. a self-affirmation manipulation mitigates this reactance effect both on the level of cognitions and behavior. conclusion: self-affirmation has influential implications not only for social psychology but also for health prevention measures. the findings support the effectiveness of self-affirmation in reducing reactant and defensive reactions to personalized visual risk feedback. interactions with health risk status indicate that self-affirmation might increase the effectiveness of health promotion messages in high-risk populations. © 2013 American Psychological Association. Source


Mattes D.,Free University of Berlin
Anthropology and Medicine | Year: 2012

The experiences and practices of antiretroviral drug consumers in Tanzania are shaped by economic scarcity, limited state-provided social welfare, and fragile kinship-based solidarity. Embedding antiretroviral therapy (ART) in patients local moral worlds brings further existential dimensions to the fore that articulate closely with the priority the treatment acquires in their lives. An exemplary case study of a middle-aged HIV-positive man suggests that dignity, social recognition, and belonging may be of central interest and temporarily overshadow patients concern for mere survival. A stronger focus on patients moral concerns contributes to a better understanding of the complex dynamics that prevent HIV-positive people from becoming the pharmaceutical selves that are promoted during treatment enrolment. Moreover, it is indispensable to account for the lived experiences of patients struggling with what too readily has been termed a chronic disease. © 2012 Taylor & Francis. Source


Carota F.,Medical Research Council Cognition and Brain science Unit | Moseley R.,Medical Research Council Cognition and Brain science Unit | Pulvermuller F.,Medical Research Council Cognition and Brain science Unit | Pulvermuller F.,Free University of Berlin
Journal of Cognitive Neuroscience | Year: 2012

Word meaning processing in the brain involves ventrolateral temporal cortex, but a semantic contribution of the dorsal stream, especially frontocentral sensorimotor areas, has been controversial. We here examine brain activation during passive reading of object-related nouns from different semantic categories, notably animal, food, and tool words, matched for a range of psycholinguistic features. Results show ventral stream activation in temporal cortex along with category-specific activation patterns in both ventral and dorsal streams, including sensorimotor systems and adjacent pFC. Precentral activation reflected action-related semantic features of the word categories. Cortical regions implicated in mouth and face movements were sparked by food words, and hand area activation was seen for tool words, consistent with the actions implicated by the objects the words are used to speak about. Furthermore, tool words specifically activated the right cerebellum, and food words activated the left orbito-frontal and fusiform areas. We discuss our results in the context of category-specific semantic deficits in the processing of words and concepts, along with previous neuroimaging research, and conclude that specific dorsal and ventral areas in frontocentral and temporal cortex index visual and affective-emotional semantic attributes of object-related nouns and action-related affordances of their referent objects. © 2012 Massachusetts Institute of Technology. Source


Gaquerel E.,Max Planck Institute for Chemical Ecology | Steppuhn A.,Free University of Berlin | Baldwin I.T.,Max Planck Institute for Chemical Ecology
New Phytologist | Year: 2012

Nicotiana attenuata α-DIOXYGENASE1 (α-DOX1) is an oxylipin-forming gene elicited during herbivory by fatty acid amino acid conjugates (FACs) contained in oral secretions of Manduca sexta. To understand the roles of Naα-DOX1 and its major product, 2-hydroxylinolenic acid (2-hydroxylinolenic acid), in N. attenuata's anti-herbivore defenses, we used a transgenic line specifically silenced in Naα-DOX1 expression (ir-α-dox1) and monitored 2-HOT production in M. sexta-damaged tissues and its role in influencing the production of direct defense compounds and resistance to this insect. Attack by M. sexta larvae amplified 2-HOT formation at the feeding sites; a reaction probably facilitated by Naα-DOX1's high pH optimum which allows 2-HOT formation to occur in the more alkaline conditions at the feeding sites or potentially in the insect mouth parts after the leaf tissue is ingested. Manduca sexta larvae performed better on ir-α-dox1 plants than on wild-type (WT) plants as a result of attenuated herbivory-specific JA and 2-HOT bursts as well as JA-inducible well-established defenses (nicotine, caffeoylputrescine and trypsin proteinase inhibitors). Repeated applications of 2-HOT to wounds before insect feeding partly amplified JA-controlled defenses and restored the resistance of ir-α-dox1 plants. We conclude that 2-HOT, produced by attack-activated α-DOX1 activity, participates in defense activation during insect feeding. © 2012 New Phytologist Trust. Source


Mobarak M.,Free University of Berlin | Pelster A.,University of Kaiserslautern
Laser Physics Letters | Year: 2013

We analyze theoretically the emergence of different superfluid phases of spin-1 bosons in a three-dimensional cubic optical lattice by generalizing the recently developed Ginzburg-Landau theory for the Bose-Hubbard model to a spinor Bose gas. In particular at zero temperature, our theory distinguishes within its validity range between various superfluid phases for an anti-ferromagnetic interaction with an external magnetic field. In addition, we determine that the superfluid-Mott insulator phase transition is of second order and that the transitions between the respective superfluid phases with anti-ferromagnetic interaction can be both of first and second order. © 2013 Astro Ltd. Source


Lanzer P.,Hospitals and Clinics Bitterfeld Wolfen | Prechelt L.,Free University of Berlin
Catheterization and Cardiovascular Interventions | Year: 2011

Objectives: Accelerate and improve the training and learning process of operators performing percutaneous coronary interventions (PCI). Background: Operator cognitive, in particular decision-making skills and technical skills are a major factor for the success of coronary interventions. Currently, cognitive skills are commonly developed by three methods: (1) Cognitive learning of rules for which statistical evidence is available. This is very incomprehensive and isolates cognitive learning from skill acquisition. (2) Informal tutoring received from experienced operators, and (3) personal experience by trial-and-error are both very slow. Methods: We propose in this concept article a conceptual framework to elicit, capture, and transfer expert PCI skills to complement the current approach. This includes the development of an in-depth understanding of the nature of PCI skills, terminology, and nomenclature needed to streamline communication, propensity of reproducible performance assessment, and in particular an explication of intervention planning and intra-intervention decision-making. We illustrate the impact of improved decision-making by simulation results based on a stochastic model of intervention risk. Results: We identify several key concepts that form the basis of this conceptual framework, in particular different risk types and the notions of strategy, interventional module, and tactic. Conclusions: The increasing complexity of cases have brought PCI to the point where the decision-making skills of master operators need to be made explicit to make them systematically learnable such that the skills of beginner and intermediate operators can be improved much faster than is currently possible. © 2010 Wiley-Liss, Inc. Source


Tawfik A.,Cairo University | Tawfik A.,Free University of Berlin
Advances in High Energy Physics | Year: 2013

We calculate the first six nonnormalized moments of particle multiplicity within the framework of the hadron resonance gas model. In terms of the lower order moments and corresponding correlation functions, general expressions of higher order moments are derived. Thermal evolution of the first four normalized moments and their products (ratios) are studied at different chemical potentials, so that it is possible to evaluate them at chemical freeze-out curve. It is found that a nonmonotonic behaviour reflecting the dynamical fluctuation and strong correlation of particles starts to appear from the normalized third order moment. We introduce novel conditions for describing the chemical freeze-out curve. Although the hadron resonance gas model does not contain any information on the criticality related to the chiral dynamics and singularity in the physical observables, we are able to find out the location of the QCD critical endpoint at 350 MeV and temperature T 162 MeV. © 2013 A. Tawfik. Source


Domenech C.,Free University of Berlin | Wehr T.,Mission Research
IEEE Transactions on Geoscience and Remote Sensing | Year: 2011

The Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) mission responds to the need to improve the understanding of the interactions between cloud, aerosol, and radiation processes. The fundamental mission objective is to constrain retrievals of cloud and aerosol properties such that their impact on top-of-atmosphere (TOA) radiative fluxes can be determined with an accuracy of 10 W · m -2. However, TOA fluxes cannot be measured instantaneously from a satellite. For the EarthCARE mission, fluxes will be estimated from the observed solar and thermal radiances measured by the Broadband Radiometer (BBR). This paper describes an approach to obtain shortwave (SW) fluxes from BBR radiance measurements. The retrieval algorithms are developed relying on the angular distribution models (ADMs) employed by Clouds and the Earth's Radiant Energy System (CERES) instrument. The solar radiance-to-flux conversion for the BBR is performed by simulating the Terra CERES ADMs using a backpropagation artificial neural network (ANN) technique. The ANN performance is optimized by testing different architectures, namely, feedforward, cascade forward, and a customized-forward network. A large data set of CERES measurements used to resemble the forthcoming BBR acquisitions has been collected. The CERES BBR-like database is sorted by their surface type, sky conditions, and scene type and then stratified by four input variables (solar zenith angle and BBR SW radiances) to construct three different training data sets. Then, the neural networks are analyzed, and the adequate ADM classification scheme is selected. The results of the BBR ANN-based ADMs show SW flux retrievals compliant with the CERES flux estimates. © 2011 IEEE. Source


Kreutzmann H.,Free University of Berlin
Journal of Mountain Science | Year: 2011

Water management in general and in the Indus Basin in particular is concerned with the energy-efficient transportation of hydrologically exploitable resources from the upper zone to climatically favourable areas where irrigation helps to supersede arid conditions for the cultivation of crops and watering of meadows. In other words: Human intervention sets the stage for the allocation of water from a wider catchment area in a smaller habitat where this resource is deficient. Emphasis on mountain irrigation practices is counteracted with developments in the forelands where different frame conditions prevail and peculiar development problems occur. In dealing with the importance of water from the mountain regions three dimensions have to be evaluated: 1) natural factors and their validity for the environmental frame conditions and technological adaptation processes; 2) social factors and their impact on culture, economy and equitability; 3) institutional factors and their importance for sustainable growth and for the implementation of development projects. In the study of decentralized irrigation systems in high mountain regions of the Indus Basin a systems theoretical approach values the complexity of interrelationships between different systems elements. Human activities in arid mountain regions are restricted by limiting ecological factors and are characterized by certain utilization and adaptive strategies. © 2011 Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg. Source


Buchin K.,TU Eindhoven | Mulzer W.,Free University of Berlin
Journal of the ACM | Year: 2011

We present several results about Delaunay triangulations (DTs) and convex hulls in transdichotomous and hereditary settings: (i) the DT of a planar point set can be computed in expected time O(sort(n)) on a word RAM, where sort(n) is the time to sort n numbers. We assume that the word RAM supports the shuffle operation in constant time; (ii) if we know the ordering of a planar point set in x-and in y-direction, its DT can be found by a randomized algebraic computation tree of expected linear depth; (iii) given a universe U of points in the plane, we construct a data structure D for Delaunay queries :for any P ⊆ U, D can find the DT of P in expected time O(| P| log log |U |); (iv) given a universe U of points in 3-space in general convex position, there is a data structure D for convex hull queries :for any P ⊆ U, D can find the convex hull of P in expected time O(|P|(loglog |U|)2); (v) given a convex polytope in 3-space with n vertices which are colored with x ≥ 2 colors, we can split it into the convex hulls of the individual color classes in expected time O(n(log log n)2). The results (i)-(iii) generalize to higher dimensions, where the expected running time now also depends on the complexity of the resulting DT. We need a wide range of techniques. Most prominently, we describe a reduction from DTs to nearest-neighbor graphs that relies on a new variant of randomized incremental constructions using dependent sampling. © 2011 ACM. Source


Rillich J.,Free University of Berlin | Stevenson P.A.,University of Leipzig
Hormones and Behavior | Year: 2014

Social defeat, i.e. losing an agonistic dispute with a conspecific, is followed by a period of suppressed aggressiveness in many animal species, and is generally regarded as a major stressor, which may play a role in psychiatric disorders such as depression and post-traumatic stress disorder. Despite numerous animal models, the mechanisms underlying loser depression and subsequent recovery are largely unknown. This study on crickets is the first to show that a neuromodulator, dopamine (DA), is necessary for recovery of aggression after social defeat. Crickets avoid any conspecific male just after defeat, but regain their aggressiveness over 3. h. This recovery was prohibited after depleting nervous stores of DA and octopamine (OA, the invertebrate analogue of noradrenaline) with α-methyl-tyrosine (AMT). Loser recovery was also prohibited by the insect DA-receptor (DAR) antagonist fluphenazine, but not the OA-receptor (OAR) blocker epinastine, or yohimbine, which blocks receptors for OA's precursor tyramine. Conversely, aggression was restored prematurely in both untreated and amine depleted losers given either chlordimeform (CDM), a tissue permeable OAR-agonist, or the DA-metabolite homovanillyl alcohol (HVA), a component of the honeybee queen mandibular pheromone. As in honeybees, HVA acts in crickets as a DAR-agonist since its aggression promoting effect on losers was selectively blocked by the DAR-antagonist, but not by the OAR-antagonist. Conversely, CDM's aggression promoting effect was selectively blocked by the OAR-antagonist, but not the DAR-antagonist. Hence, only DA is necessary for recovery of aggressiveness after social defeat, although OA can promote loser aggression independently to enable experience dependent adaptive responses. © 2014 Elsevier Inc. Source


Kleinert H.,Free University of Berlin | Xue S.-S.,ICRANeT Piazzale della Repubblica | Xue S.-S.,University of Rome La Sapienza
Annals of Physics | Year: 2013

Using semiclassical WKB-methods, we calculate the rate of electron-positron pair-production from the vacuum in the presence of two external fields, a strong (space- or time-dependent) classical field and a monochromatic electromagnetic wave. We discuss the possible medium effects on the rate in the presence of thermal electrons, bosons, and neutral plasma of electrons and protons at a given temperature and chemical potential. Using our rate formula, we calculate the rate enhancement due to a laser beam, and discuss the possibility that a significant enhancement may appear in a plasma of electrons and protons with self-focusing properties. © 2013 Elsevier Inc. Source


Tawfik A.,Cairo University | Tawfik A.,Free University of Berlin
Journal of Physics G: Nuclear and Particle Physics | Year: 2013

The event-by-event dynamical fluctuations in kaon-proton and proton-pion ratios have been studied as a function of the center-of-mass energies of nucleon- nucleon collisions √s. Based on the changing phase space volume which apparently is the consequence of the phase transition(s) from hadrons to a quark-gluon plasma at large √s, the single-particle distribution function f is assumed to bemodified.Varying f and the phase space volume are implemented in the grand-canonical ensemble, especially at √s > 17 GeV, so that the hadron resonance gas model, when taking into account the experimental acceptance A and the quark phase space occupation factor, turns out to be able to reproduce the dynamical fluctuations in (K+ + K-)/(p + p) and (p + p)/(p+ + p- ) ratios over the entire range of √s. It seems that the applied thermodynamic statistics could come up with a new modification to the Tsallis statistics. Both non-extensivity and changing the phase space are suggested and utilized in the present work. © 2013 IOP Publishing Ltd. Source


Hartmann C.,Free University of Berlin
Mathematical and Computer Modelling of Dynamical Systems | Year: 2011

We study balanced model reduction of partially observed stochastic differential equations of Langevin type. Upon balancing, the Langevin equation turns into a singularly perturbed system of equations with slow and fast degrees of freedom. We prove that in the limit of vanishing small Hankel singular values (i.e. for infinite scale separation between fast and slow variables), its solution converges to the solution of a reduced-order Langevin equation. The approach is illustrated with several numerical examples, and we discuss the relation to model reduction of deterministic control systems having an underlying Hamiltonian structure. © 2011 Taylor & Francis. Source


Fiolhais M.C.N.,University of Coimbra | Kleinert H.,Free University of Berlin
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

The tricritical point, which separates first and second order phase transitions in three-dimensional superconductors, is studied in the four-dimensional Coleman-Weinberg model, and the similarities as well as the differences with respect to the three-dimensional result are exhibited. The position of the tricritical point in the Coleman-Weinberg model is derived and found to be in agreement with the Thomas-Fermi approximation in the three-dimensional Ginzburg-Landau theory. From this we deduce a special role of the tricritical point for the Standard Model Higgs sector in the scope of the latest experimental results, which suggests the unexpected relevance of tricritical behavior in the electroweak interactions. © 2013 Elsevier B.V. All rights reserved. Source


Mischke S.,Free University of Berlin | Zhang C.,Lanzhou University
Global and Planetary Change | Year: 2010

A lake sediment core from the eastern Tibetan Plateau was investigated by multi-proxy geochemical, sedimentological and magnetic analyses and its age determined using 14C AMS dating in an approach to use short-lived climate periods for a spatial assessment of the Holocene climate history on the Tibetan Plateau. Six cold events were identified from the Lake Ximencuo record which occurred between 10.3-10.0, 7.9-7.4, 5.9-5.5, 4.2-2.8, 1.7-1.3 and 0.6-0.1cal ka BP. A comparison with previously published Holocene records from lake and peat sections, ice cores and glacial remains of the Tibetan Plateau revealed that the cold event starting around 4.2cal ka BP had the most significant and widespread impact on almost all of the examined sites. This cold event lasted about a millennium in the western and central part of the Tibetan Plateau and possibly several hundred years longer at some sites in its eastern realm. The cold event inferred between 7.9 and 7.4cal ka BP from Lake Ximencuo was recorded at a number of sites on the eastern Tibetan Plateau too and probably corresponds to a cold event identified around 8.2cal ka BP at the sites on the western and central Tibetan Plateau. The coincidence with the 8.2ka event of the North Atlantic region implies that the latter exerted a significant environmental impact on the Tibetan Plateau too. The cold spell between 10.3 and 10.0cal ka BP was recorded at some marginal sites of the Tibetan Plateau but had apparently a less significant environmental impact. The more irregular pattern of cold events between about 7cal ka BP and the onset of the cold event after 4.2cal ka BP might be related to the catchment-specific response of the lake sediment and peat accumulation to the termination of the Holocene 'climatic optimum' on the Tibetan Plateau. The final two cold events between 1.7 and 1.3cal ka BP and in the last several hundred years representing the Little Ice Age are more widely seen on the Tibetan Plateau although they did not reach the significance of the cold event at 4.2cal ka BP. However, the three cold periods since 4.2cal ka BP are apparently coeval with the decline and establishment of Chinese Dynasties implying a remarkable impact on the social systems in eastern China. The consistent inference of cold events around 8.2cal ka BP or a few hundred years later and starting at 4.2cal ka BP is evidence for a temporary trans-regional climatic response on the Tibetan Plateau in the Holocene regardless of the catchment-specific response of complex natural systems. © 2010 Elsevier B.V. Source


The paper presented is the first comprehensive, fully quantitative, high resolution study of marine palynology from an OAE3 black-shale environment. It is based on 175m core spanning the upper Turonian to lower Santonian at Tarfaya, Morocco, NW Africa, which has been sampled from centimetre to 3m intervals. The results are integrated and discussed with lithology and geochemistry data to (1) distinguish between potential changes in production and preservation of total organic carbon (TOC) accumulation and (2) constrain the stratigraphic position of the Oceanic Anoxic Event 3 (OAE3).The succession is characterized by increased total organic carbon (TOC), varying between 1% and 19% (average about 6%). Distinct black-shale horizons of variable thickness appear episodically throughout the succession, with higher frequency in the late Turonian. Higher TOC contents do not strictly correlate to lithologic black-shales or peaks of a specific taxon of organic-walled algae. The palynomorph spectrum is strongly dominated by organic-walled algae, with the ratio of terrigenous sporomorphs to organic-walled algae (t/m index) varying between zero and 0.05 (average 0.01). The dominance of algal organic matter is corroborated by the prevalence of Type I kerogen identified using Rock-Eval pyrolysis. Dinocyst diversity is low, with the absolute taxa number varying from 7 to 27 between single samples. The peridinioid/gonyaulacoid ratio of dinocysts (p/g ratio) shows strong fluctuations, varying between 1 and 283 (average of about 100).The upper Turonian interval is dominated by Bosedinia spp., a dinocyst taxon formerly described as abundant only in lacustrine sediments from the Oligocene and Miocene of SE Asia. This dominance is episodically modified by the increase of the warm-temperate waters dinocysts fraction, here mainly represented by the genera Alterbidinium, Isabelidinium and Spinidinium. Within the Coniacian-Santonian, black-shale horizons are limited in number and are concentrated within the upper Coniacian to lower Santonian interval. The dinocysts show alternating, prominent peak abundances of Palaeohystrichophora spp. and the warm-temperate water dinocysts fraction, here mainly represented by the genera Trithyrodinium and Chatangiella. However, a final episode of increased proportions of Bosedinia spp. is confined to a 5m thick black-shale horizon closely spanning the Coniacian-Santonian boundary.Changes in the ratio of total sulphur to total organic carbon (TS/TOC) reflect fluctuating oxygen contents of bottom waters throughout the late Turonian to Santonian. These are significantly parallelled by the alternation of dinocysts assemblages suggestive of enhanced upwelling and water column stratification respectively, probably reflecting changes in the mode of TOC accumulation. Accordingly, preservation largely prevails during the late Turonian interval and changes towards increased production within the Coniacian-Santonian. However, a final preservation-event is probably represented by the black-shale horizon closely spanning the Coniacian-Santonian boundary (top Dicarinella concavata foraminifera zone), which may reflect an episodic shutdown of a major upwelling cell. It is thus proposed, that the "culmination" of the OAE3 at Tarfaya may represent intermittent preservation of TOC within an otherwise high productivity environment related to a global cooling trend. © 2014 Elsevier Ltd. Source


Richter A.M.,Humboldt University of Berlin | Povolotsky T.L.,Humboldt University of Berlin | Wieler L.H.,Free University of Berlin | Hengge R.,Humboldt University of Berlin
EMBO Molecular Medicine | Year: 2014

In 2011, nearly 4,000 people in Germany were infected by Shiga toxin (Stx)-producing Escherichia coli O104:H4 with > 22% of patients developing haemolytic uraemic syndrome (HUS). Genome sequencing showed the outbreak strain to be related to enteroaggregative E. coli (EAEC), suggesting its high virulence results from EAEC-typical strong adherence and biofilm formation combined to Stx production. Here, we report that the outbreak strain contains a novel diguanylate cyclase (DgcX)-producing the biofilm-promoting second messenger c-di-GMP-that shows higher expression than any other known E. coli diguanylate cyclase. Unlike closely related E. coli, the outbreak strain expresses the c-di-GMP-controlled biofilm regulator CsgD and amyloid curli fibres at 37°C, but is cellulose- negative. Moreover, it constantly generates derivatives with further increased and deregulated production of CsgD and curli. Since curli fibres are strongly proinflammatory, with cellulose counteracting this effect, high c-di-GMP and curli production by the outbreak O104:H4 strain may enhance not only adherence but may also contribute to inflammation, thereby facilitating entry of Stx into the bloodstream and to the kidneys where Stx causes HUS. © 2014 The Authors. Source


Sinnhuber B.-M.,Karlsruhe Institute of Technology | Meul S.,Free University of Berlin
Geophysical Research Letters | Year: 2015

Bromine from very short lived substances (VSLS), primarily from natural oceanic sources, contributes substantially to the stratospheric bromine loading. This source of stratospheric bromine has so far been ignored in most chemistry climate model calculations of stratospheric ozone trends. Here we present a transient simulation with the chemistry climate model EMAC for the period 1960-2005 including emissions of the five brominated VSLS CHBr3, CH2Br2, CH2BrCl, CHBrCl2, and CHBr2Cl. The emissions lead to a realistic stratospheric bromine loading of about 20 pptv for present-day conditions. Comparison with a standard model simulation without VSLS shows large differences in modeled ozone in the extratropical lowermost stratosphere and in the troposphere. Differences in ozone maximize in the Antarctic Ozone Hole, resulting in more than 20% less ozone when VSLS are included. Even though the emissions of VSLS are assumed to be constant in time, the model simulation with VSLS included shows a much larger ozone decrease in the lowermost stratosphere during the 1979-1995 period and a faster ozone increase during 1996-2005, in better agreement with observed ozone trends than the standard simulation without VSLS emissions. ©2015. American Geophysical Union. All Rights Reserved. Source


Motta R.,Free University of Berlin
Journal of Agrarian Change | Year: 2016

The introduction of biotechnology is part of a global process of structural change in agriculture characterized by an increased integration of world agriculture with high corporate control. However, as the legal competence to allow the planting and trade of genetically modified (GM) crops commonly lies at the level of the nation state, this remains strategic in the politics of GM crops, both for actors promoting the technology and for social movements struggling against it. This paper illustrates this argument with an analysis of the struggles over GM crops in Brazil. It shows how the implementation of a food regime based on biotechnology, corporate control and neoliberal globalism depended on the state and was a contested process. © 2016 John Wiley & Sons Ltd. Source


Plattner N.,Free University of Berlin | Doll J.D.,Brown University | Meuwly M.,University of Basel
Journal of Chemical Theory and Computation | Year: 2013

Infinite swapping (INS) is a recently developed method to address the rare event sampling problem. For INS, an expanded computational ensemble composed of a number of replicas at different temperatures is used, similar to the widely used parallel tempering (PT) method. While the basic concept of PT is to sample various replicas of the system at different temperatures and exchange information between the replicas occasionally, INS uses the symmetrized distribution of configurations in temperature space, which corresponds to the infinite swapping limit of PT. The effect of this symmetrization and the enhanced information exchange between replicas is evaluated for three different biological systems representing different sampling problems in biology: (1) blocked alanine dipeptide, which is a small system and therefore optimal to evaluate sampling efficiency quantitatively, (2) Villin headpiece, which is used as a test case for the protein folding process, and (3) neuroglobin, which is used to evaluate the effects of enhanced information exchange between replicas for sampling the substate space of a folded protein. For these three test systems, PINS is compared to PT, and it is found that in all cases the sampling with PINS is substantially more efficient. © 2013 American Chemical Society. Source


Kraub M.,Leibniz Institute for Molecular Pharmacology | Haucke V.,Leibniz Institute for Molecular Pharmacology | Haucke V.,Free University of Berlin
Nature Cell Biology | Year: 2016

Contact sites between the endoplasmic reticulum and the plasma membrane mediate receptor signalling. How this function is controlled physically and functionally is poorly understood. Extended synaptotagmins are now shown to shuttle the lipid metabolite diacylglycerol from the plasma membrane to the endoplasmic reticulum in receptor-stimulated cells. © 2016 Macmillan Publishers Limited. Source


Simon O.,Free University of Berlin
Journal of Animal and Feed Sciences | Year: 2010

An interdisciplinary research group granted by the German Research Foundation (FOR 438) tested various hypotheses and tired to develop a model for the mode of action of probiotics in pigs. The study included the fields of animal nutrition/digestion physiology, anatomy and histology of the intestinal mucosa, transport and secretory properties of the mucosa, microbiology of the intestinal tract, immune system (classes of intraepithelial lymphocytes, humoral responses), gene expression of the mucosa and finally the in vitro and in vivo resistance against infection with Salmonella. Five trials with ten sows per treatment each and their piglets and two probiotic strains were included in this study. The studied bacterial strains were Enterococcus faecium NCIMB 10415 and Bacillus cereus var. toyoi NCIMB 40112. Concluding from our studies and the published data of others, the effects of probiotics on performance are rarely significant. However, with one exception the incidence of post-weaning diarrhoea under the effect of both probiotics was significantly reduced in the trials of the research group. Furthermore, the identification frequency of various E. coli sero-pathovars relevant in post weaning diarrhoea was reduced in these animals. On the other hand, no significant modifications were found for the morphology and histology of the intestinal mucosa and also not on transport properties of this tissue. A further important finding was that the mode of action for probiotics is not unique but species or even strain specific. Most probably the studied probiotics act directly and/or via modifications of the intestinal microbiota on the immune system (intraepithelial lymphocyte population). Source


Vent-Schmidt T.,Albert Ludwigs University of Freiburg | Riedel S.,Free University of Berlin
Inorganic Chemistry | Year: 2015

The chemistry of the lanthanides is mostly dominated by compounds in the oxidation state +III. Only few compounds of Ce, Pr, and Tb are known with the metal in the +IV oxidation state. Removal of the last f-electron on praseodymium +IV would lead to a closed-shell system with formal oxidation state V. In this work we investigated the stability of the PrF5 molecule by theory and matrix-isolation techniques through the reaction of laser-ablated praseodymium atoms with fluorine in excess of neon, argon, krypton, or neat fluorine. Besides the known PrF3 molecule, unreported IR bands for PrF4 could be observed, and there is evidence for the formation of PrF and PrF2 but not for the formation of PrF5. © 2015 American Chemical Society. Source


Perez-Torres J.F.,Free University of Berlin
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

A theoretical study of the electronic and nuclear flux densities of a vibrating H2+ molecular ion is presented. The time-dependent wave function is represented in the basis of vibronic eigenstates which are numerically obtained from the complete nonrelativistic Hamiltonian without the clamped-nuclei approximation. A one-center expansion in terms of B-splines and Legendre polynomials is employed to solve the corresponding eigenvalue equation. The electronic and nuclear flux densities are then calculated from the total wave function through their quantum-mechanical definition. Analysis of the flux densities close to the turning points shows that the nuclear wave packet takes longer time (1.4 fs) to change its direction compared to the electronic one (1 fs). © 2013 American Physical Society. Source


Bonthuis D.J.,TU Munich | Gekle S.,TU Munich | Netz R.R.,Free University of Berlin
Langmuir | Year: 2012

We derive the theoretical framework to calculate the dielectric response tensor and determine its components for water adjacent to hydrophilic and hydrophobic surfaces using molecular dynamics simulations. For the nonpolarizable water model used, linear response theory is found to be applicable up to an external perpendicular field strength of ∼2 V/nm, which is well beyond the experimental dielectric breakdown threshold. The dipole contribution dominates the dielectric response parallel to the interface, whereas for the perpendicular component it is essential to keep the quadrupole and octupole terms. Including the space-dependent dielectric function in a mean-field description of the ion distribution at a single charged interface, we reproduce experimental values of the interfacial capacitance. At the same time, the dielectric function decreases the electrostatic part of the disjoining pressure between two charged surfaces, unlike previously thought. The difference in interfacial polarizability between hydrophilic and hydrophobic surfaces can be quantized in terms of the dielectric dividing surface. Using the dielectric dividing surface and the Gibbs dividing surface positions to estimate the free energy of a single ion close to an interface, ion-specific adsorption effects are found to be more pronounced at hydrophobic surfaces than at hydrophilic surfaces, in agreement with experimental trends. © 2012 American Chemical Society. Source


Seiffert S.,Helmholtz Center Berlin | Seiffert S.,Free University of Berlin
Macromolecular Rapid Communications | Year: 2012

Thermoresponsive polymer gels exhibit pronounced swelling and deswelling upon changes in temperature, rendering them attractive for various applications. This transition has been studied extensively, but only little is known about how it is affected by nano- and micrometer-scale inhomogeneities in the polymer gel network. In this work, droplet microfluidics is used to fabricate microgel particles of strongly varying inner homogeneity to study their volume phase behavior. These particles exhibit very similar equilibrium swelling and deswelling independent of their inner inhomogeneity, but the kinetics of their volume phase transition is markedly different: while gels with pronounced micrometer-scale inhomogeneity show fast and affine deswelling, homogeneous gels shrink slowly and in multiple steps. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Raz R.,University of Leipzig | Raz R.,Leibniz Institute for Molecular Pharmacology | Rademann J.,University of Leipzig | Rademann J.,Free University of Berlin
Organic Letters | Year: 2012

Rapid and efficient preparation of peptide thioacids from 2-cyanoethyl peptide thioesters has been accomplished. S-2-Cyanoethyl peptide thioesters were obtained cleanly without the need for purification from resin-bound tert-butyl peptide thioesters using 3-mercaptopropionitrile as a nucleophile. Elimination of the 2-cyanoethyl group proceeded rapidly (t1/2 < 8 min) under mild conditions and furnished peptide thioacids up to the size of a 16-mer. Peptide thioacids could be isolated or formed in situ and reacted smoothly with electron-deficient azides yielding an amide as the ligation product. © 2012 American Chemical Society. Source


Leonori D.,Max Planck Institute of Colloids and Interfaces | Seeberger P.H.,Free University of Berlin
Organic Letters | Year: 2012

The cell-surface glycans on bacteria contain many monosaccharides that cannot be obtained by isolation from natural sources. Availability of differentially protected monosaccharides is therefore often limiting access to potential oligosaccharide vaccine antigens. D-Fucosamine, Dbacillosamine, and D-xylo-2,6-deoxy-4-ketohexosamine building blocks were prepared via a divergent de novo synthesis from L-Garner aldehyde. The route relies on a chelation-control assisted organometallic addition and an anti-selective dihydroxylation reaction. © 2012 American Chemical Society. Source


Al-Jibbouri H.,Free University of Berlin | Pelster A.,University of Kaiserslautern
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We study the collective excitation frequencies of a harmonically trapped 85Rb Bose-Einstein condensate (BEC) in the vicinity of a Feshbach resonance. To this end, we solve the underlying Gross-Pitaevskii (GP) equation by using a Gaussian variational approach and obtain the coupled set of ordinary differential equations for the widths and the center of mass of the condensate. A linearization shows that the dipole-mode frequency decreases when the bias magnetic field approaches the Feshbach resonance, so the Kohn theorem is violated. © 2013 American Physical Society. Source


O'Hara R.,Free University of Berlin | Barnes D.,Aberystwyth University
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2012

We have developed a new optimisation based shape from shading algorithm which is able to make use of sophisticated camera and reflectance models and does not require a good initialising surface. Surface shape consistent with ground truth is obtained when the technique is applied to both synthetic rendered surfaces and real images captured by the Mars Express orbiter and HRSC instrument. The obtained surfaces provide improved fine surface detail over that found using stereo techniques and demonstrate the applicability of the technique to real images. © 2011 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Source


Kaufer B.B.,Free University of Berlin | Flamand L.,Laval University
Current Opinion in Virology | Year: 2014

HHV-6 integrates its genome into telomeres of human chromosomes. Integration can occur in somatic cells or gametes, the latter leading to individuals harboring the HHV-6 genome in every cell. This condition is transmitted to descendants and referred to as inherited chromosomally integrated human herpesvirus 6 (iciHHV-6). Although integration can occur in different chromosomes, it invariably takes place in the telomere region. This integration mechanism represents a way to maintain the virus genome during latency, which is so far unique amongst human herpesviruses. Recent work provides evidence that the integrated HHV-6 genome can be mobilized from the host chromosome, resulting in the onset of disease. Details on required structural determinants, putative integration mechanisms and biological and medical consequences of iciHHV-6 are discussed. © 2014, Elsevier B.V. All rights reserved. Source


Seiffert S.,Helmholtz Center Berlin | Seiffert S.,Free University of Berlin
Macromolecular Rapid Communications | Year: 2012

Microgel particles can be fabricated with great control by droplet-based microfluidics; however, to this end, their shape is intrinsically limited to be spherical. Existing approaches to circumvent this limitation rely on the rapid interception of transient non-spherical preparticle shapes, greatly limiting their versatility. This paper presents a facile microfluidic approach that overcomes this limitation. The method utilizes the injection of scaffolding microgel particles into droplets that have insufficient volumes to host the microgels in a spherical shell. As a result, the drops adopt non-spherical equilibrium shapes that serve to template non-spherical soft supraparticles by slow and gentle chemical reactions. Non-spherical microgel particles can be fabricated by simple droplet-based templating: injecting spherical microgels into droplets that have insufficient volumes to host them in a spherical shell forces the drops to adopt non-spherical equilibrium shapes that can be fixed by slow and gentle chemical reactions. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Gramelsberger G.,Free University of Berlin
Studies in History and Philosophy of Science Part C :Studies in History and Philosophy of Biological and Biomedical Sciences | Year: 2013

Synthetic biology and systems biology are often highlighted as antagonistic strategies for dealing with the overwhelming complexity of biology (engineering versus understanding; tinkering in the lab versus modelling in the computer). However, a closer view of contemporary engineering methods (inextricably interwoven with mathematical modelling and simulation) and of the situation in biology (inextricably confronted with the intrinsic complexity of biomolecular environments) demonstrates that tinkering in the lab is increasingly supported by rational design methods. In other words: Synthetic biology and systems biology are merged by the use of computational techniques. These computational techniques are needed because the intrinsic complexity of biomolecular environments (stochasticity, non-linearities, system-level organization, evolution, independence, etc.) require advanced concepts of bio bricks and devices. A philosophical investigation of the history and nature of bio parts and devices reveals that these objects are imitating generic objects of engineering (switches, gates, oscillators, sensors, etc.), but the well-known design principles of generic objects are not sufficient for complex environments like cells. Therefore, the rational design methods have to be used to create more advanced generic objects, which are not only generic in their use, but also adaptive in their behavior. Case studies will show how simulation-based rational design methods are used to identify adequate parameters for synthesized designs (stability analyses), to improve lab experiments by 'looking through noise' (estimation of hidden variables and parameters), and to replace laborious and time-consuming post hoc tweaking in the lab by in-silico guidance (in-silico variation of bio brick properties). The overall aim of these developments, as will be argued in the discussion, is to achieve adaptive-generic instrumentality for bio parts and devices and thus increasingly merging systems and synthetic biology. © 2013 Elsevier Ltd. Source


Hassan B.A.,Center for the Biology of Disease | Hiesinger P.R.,Free University of Berlin | Hiesinger P.R.,Charite - Medical University of Berlin
Cell | Year: 2015

Molecular codes, like postal zip codes, are generally considered a robust way to ensure the specificity of neuronal target selection. However, a code capable of unambiguously generating complex neural circuits is difficult to conceive. Here, we re-examine the notion of molecular codes in the light of developmental algorithms. We explore how molecules and mechanisms that have been considered part of a code may alternatively implement simple pattern formation rules sufficient to ensure wiring specificity in neural circuits. This analysis delineates a pattern-based framework for circuit construction that may contribute to our understanding of brain wiring. © 2015 Elsevier Inc. Source


Klatt S.,Max Planck Institute for Molecular Genetics | Klatt S.,Free University of Berlin | Konthur Z.,Max Planck Institute for Molecular Genetics
Microbial Cell Factories | Year: 2012

Background: Secretory signal peptides (SPs) are well-known sequence motifs targeting proteins for translocation across the endoplasmic reticulum membrane. After passing through the secretory pathway, most proteins are secreted to the environment. Here, we describe the modification of an expression vector containing the SP from secreted acid phosphatase 1 (SAP1) of Leishmania mexicana for optimized protein expression-secretion in the eukaryotic parasite Leishmania tarentolae with regard to recombinant antibody fragments. For experimental design the online tool SignalP was used, which predicts the presence and location of SPs and their cleavage sites in polypeptides. To evaluate the signal peptide cleavage site as well as changes of expression, SPs were N-terminally linked to single-chain Fragment variables (scFv's). The ability of L. tarentolae to express complex eukaryotic proteins with highly diverse post-translational modifications and its easy bacteria-like handling, makes the parasite a promising expression system for secretory proteins.Results: We generated four vectors with different SP-sequence modifications based on in-silico analyses with SignalP in respect to cleavage probability and location, named pLTEX-2 to pLTEX-5. To evaluate their functionality, we cloned four individual scFv-fragments into the vectors and transfected all 16 constructs into L. tarentolae. Independently from the expressed scFv, pLTEX-5 derived constructs showed the highest expression rate, followed by pLTEX-4 and pLTEX-2, whereas only low amounts of protein could be obtained from pLTEX-3 clones, indicating dysfunction of the SP. Next, we analysed the SP cleavage sites by Edman degradation. For pLTEX-2, -4, and -5 derived scFv's, the results corresponded to in-silico predictions, whereas pLTEX-3 derived scFv's contained one additional amino-acid (AA).Conclusions: The obtained results demonstrate the importance of SP-sequence optimization for efficient expression-secretion of scFv's. We could successfully demonstrate that minor modifications in the AA-sequence in the c-region of the natural SP from SAP1, based on in-silico predictions following the (-3, -1) rule, resulted in different expression-secretion rates of the protein of interest. The yield of scFv production could be improved close to one order of magnitude. Therefore, SP-sequence optimization is a viable option to increase the overall yield of recombinant protein production. © 2012 Klatt and Konthur; licensee BioMed Central Ltd. Source


Kleinert H.,Free University of Berlin
Electronic Journal of Theoretical Physics | Year: 2011

With the help of a simple variational procedure it is possible to convert the partial sums of order N of many divergent series expansions f(g) = σ∞n=0 angn into partial sums σ Nn=0 bng-ωn, where 0 < ω < 1 is a parameter that parametrizes the approach to the large-g limit. The latter are partial sums of a strong-coupling expansion of f(g) which converge against f(g) for g outside a certain divergence radius. The error decreases exponentially fast for large N, like e-const.×N1-ω. We present a review of the method and various applications. © Electronic Journal of Theoretical Physics. Source


Shahid S.A.,Leibniz Institute for Molecular Pharmacology | Shahid S.A.,Max Planck Institute For Entwicklungsbiologie | Bardiaux B.,Leibniz Institute for Molecular Pharmacology | Franks W.T.,Leibniz Institute for Molecular Pharmacology | And 5 more authors.
Nature Methods | Year: 2012

Membrane proteins are largely underrepresented among available atomic-resolution structures. The use of detergents in protein purification procedures hinders the formation of well-ordered crystals for X-ray crystallography and leads to slower molecular tumbling, impeding the application of solution-state NMR. Solid-state magic-angle spinning NMR spectroscopy is an emerging method for membrane-protein structural biology that can overcome these technical problems. Here we present the solid-state NMR structure of the transmembrane domain of the Yersinia enterocolitica adhesin A (YadA). The sample was derived from crystallization trials that yielded only poorly diffracting microcrystals. We solved the structure using a single, uniformly 13 C- and 15 N-labeled sample. In addition, solid-state NMR allowed us to acquire information on the flexibility and mobility of parts of the structure, which, in combination with evolutionary conservation information, presents new insights into the autotransport mechanism of YadA. © 2012 Nature America, Inc. All rights reserved. Source


Guzman A.,Free University of Berlin
The Journal of biological chemistry | Year: 2012

Bone (or body) morphogenetic proteins (BMPs) belong to the TGFβ superfamily and are crucial for embryonic patterning and organogenesis as well as for adult tissue homeostasis and repair. Activation of BMP receptors by their ligands leads to induction of several signaling cascades. Using fluorescence recovery after photobleaching, FRET, and single particle tracking microscopy, we demonstrate that BMP receptor type I and II (BMPRI and BMPRII) have distinct lateral mobility properties within the plasma membrane, which is mandatory for their involvement in different signaling pathways. Before ligand binding, BMPRI and a subpopulation of BMPRII exhibit confined motion, reflecting preassembled heteromeric receptor complexes. A second free diffusing BMPRII population only becomes restricted after ligand addition. This paper visualizes time-resolved BMP receptor complex formation and demonstrates that the lateral mobility of BMPRI has a major impact in stabilizing heteromeric BMPRI-BMPRII receptor complexes to differentially stimulate SMAD versus non-SMAD signaling. Source


Quitzow R.,Free University of Berlin
Environmental Innovation and Societal Transitions | Year: 2015

The rise of Chinese solar energy firms has taken many experts by surprise. German policy makers and researchers alike had suggested that the country's ambitious deployment policies would translate into a competitive advantage for the German solar photovoltaics industry. This paper argues that these expectations rested on an outdated model of the international diffusion of innovation. Building on the technological innovation system (TIS) framework and the related system functions approach, the paper thus proposes a new approach for capturing the global dynamics of innovation and industrial development in emerging technology fields. Focusing on a period of dynamic growth in the field of crystalline-based PV technologies, the paper highlights how a set of dynamic and mutual inter-dependencies between an industrialized country (i.e. Germany) and an emerging economy (i.e. China) have driven the development and diffusion of technology in the field. © 2015 Published by Elsevier B.V. All rights reserved. Source


The term "performance-related health disorders" has been defined by BERGMANN (1992) as catabolic phenomena and pathological processes that are related to or caused by high productivity levels. In the past few years, a cause and effect relationship has been determined between numerous health disorders found in farm animals and their increased productivity. In contrast to the classic hereditary diseases, the performance-related health disorders are anthropogenic diseases. The severity of these disorders is, as a rule, determined by anthropogenic environmental factors. Breeding and keeping animals in such a way that they suffer from performance-related health disorders therefore is an ethical problem. Furthermore, it has also been a legal problem since the implementation of Section 11b of the German Protection of Animals Act (TierSchG) in 1986. However, this ban has not been enforced; the federal ministry responsible argues that this is because there is still a "very controversial discussion" on the question of when the "line that separates breeding from 'problem' or 'agony breeding' (Qualzucht)" has been reached or overstepped. The following article takes a close look at the almost 20-year-old debate on the lack of enforcement. There is a large amount of circumstantial evidence that indicates that the problems that arise in determining whether specific animals fall under Section 11b TierSchG do not arise from a veterinary dispute but rather from the difficulty of identifying responsibilities. The traditional ethical model used to appeal to the feelings of responsibility in a layperson is the so-called Golden Rule ("do unto others as you would have them do unto you") which so far has not been applied to the area of animal breeding. The following article presents a model on how to create an awareness for ethical malpractice. The model makes it possible to use the change of perspective demanded by the Golden Rule and apply it to the area of animal breeding. This provides what could potentially be a useful aid in understanding ones own responsibility. While looking at possible solutions, two aspects are differentiated: the chronic non-enforcement of Section 11b TierSchG and the complete abolition of the problem. Possible solutions are presented for both areas and put up for discussion. © Verlag Eugen Ulmer, Stuttgart. Source


Stevenson P.A.,University of Leipzig | Rillich J.,Free University of Berlin
PLoS ONE | Year: 2013

Population density has profound influences on the physiology and behaviour of many animal species. Social isolation is generally reported to lead to increased aggressiveness, while grouping lowers it. We evaluated the effects of varying degrees of isolation and grouping on aggression in a territorial insect, the Mediterranean field cricket, Gryllus bimaculatus. Substantiating early observations, we show that dyadic contests between weight-matched, adult male crickets taken from groups rarely escalate beyond threat displays, whereas interactions between pairs of previously isolated crickets typically escalate to physical fights lasting several seconds. No significant differences were found between 1, 2 and 6-day isolates, or between individuals grouped for a few hours or lifelong. Unexpectedly, crickets grouped in immediate proximity within individual mesh cages that precluded fighting while permitting visual, olfactory and mechanical, antennal contact, were as aggressive as free isolates. This suggests that reduced aggression of grouped animals may be an acquired result of fighting. Supporting this notion, isolated crickets initially engage in vigorous fights when first grouped, but fighting intensity and duration rapidly decline to the level of life-long grouped crickets within only 10 min. Furthermore, grouped crickets become as aggressive as life-long isolates after only 3 hours of isolation, and on the same time course required for crickets to regain their aggressiveness after social defeat. We conclude that the reduced aggressiveness of grouped crickets is a manifestation of the loser effect resulting from social subjugation, while isolation allows recovery to a state of heightened aggressiveness, which in crickets can be considered as the default condition. Given the widespread occurrence of the loser effect in the Animal Kingdom, many effects generally attributed to social isolation are likely to be a consequence of recovery from social subjugation. © 2013 Stevenson et al. Source


Aziz E.F.,Helmholtz Center Berlin | Aziz E.F.,Free University of Berlin
Journal of Physical Chemistry Letters | Year: 2011

Reactions catalyzed by metalloproteins occur at the active centers, making them the focus of many spectroscopic investigations in an attempt to determine their structure. Here, an overview of the recent achievements and the current developments of X-ray spectroscopies using synchrotron light sources is presented. Their potential for investigating protein structure and dynamics is discussed. © 2011 American Chemical Society. Source


Bennemann K.H.,Free University of Berlin
Journal of Physics Condensed Matter | Year: 2011

Optically induced ultrafast electronic excitations with sufficiently long lifetimes may cause strong effects on phase transitions like structural and nonmetal →metal ones and on supercooling, supersaturation, etc. Examples are the transitions diamond→graphite, graphite→graphene, non-metal→ metal, solid→ liquid and vapor →liquid, solid. Photoinduced formation of graphene and water condensation of saturated or supersaturated vapor due to increased bonding amongst water molecules are of particular interest. These nonequilibrium transitions are an ultrafast response, on a few hundred fs time scale, to the fast low to large energy electronic excitations. The energy of the photons is converted into electronic energy via electronic excitations changing the cohesive energy. This changes the chemical potential controlling the phase transition. In view of the advances in laser optics photon induced transitions are expected to become an active area in nonequilibrium physics and phase transition dynamics. Conservation laws like energy or angular momentum conservation control the time during which the transitions occur. Since the photon induced effects result from weakening or strengthening of the bonding between the atoms or molecules transitions like solid/liquid, etc can be shifted in both directions. Photoinduced transitions will be discussed from a unified point of view. © 2011 IOP Publishing Ltd. Source


Olias P.,Free University of Berlin | Schade B.,Bavarian Animal Health Service | Mehlhorn H.,Heinrich Heine University Dusseldorf
Infection, Genetics and Evolution | Year: 2011

Until recently, besnoitiosis has been a neglected disease of domestic animals. Now, a geographic expansion of the causing protozoan parasite Besnoitia besnoiti in livestock has been recognized and the disease in cattle is considered emerging in Europe. Bovine besnoitiosis leads to significant economic losses by a decline in milk production, sterility, transient or permanent infertility of bulls, skin lesions and increase of mortality in affected cattle population. Phylogenetically, the Besnoitia genus is closest related to the well studied and medically important protozoans, Toxoplasma gondii and Neospora caninum. In contrast, discriminative molecular markers to type and subtype large mammalian Besnoitia species (B. besnoiti, B. caprae, B. tarandi, B. bennetti) on a relevant level of species and strains are lacking. Similarly, these cyst-forming parasites may use two hosts to fulfill their life cycle, but this has not been proven for all large mammalian Besnoitia species yet. Most important though, the final hosts and transmission routes of these Besnoitia species remain mysterious. Here, we review aspects of parasite's pathology, speciation, phylogeny, epidemiology and transmission with a special focus on recent molecular studies of all to date known Besnoitia species. Using an integrated approach, we have tried to highlight some promising directions for future research. © 2011 Elsevier B.V. Source


Mukherjee B.,Max Planck Institute for Polymer Research | Delle Site L.,Free University of Berlin | Kremer K.,Max Planck Institute for Polymer Research | Peter C.,Max Planck Institute for Polymer Research
Journal of Physical Chemistry B | Year: 2012

We present a systematic derivation of a coarse grained (CG) model for molecular dynamics (MD) simulations of a liquid crystalline (LC) compound containing an azobenzene mesogen. The model aims at a later use in a multiscale modeling approach to study liquid crystalline phase transitions that are (photo)induced by the trans/cis photoisomerization of the mesogen. One of the major challenges in the coarse graining process is the development of models that are for a given chemical system structurally consistent with for example an all-atom reference model and reproduce relevant thermodynamic properties such as the LC phase behavior around the state point of interest. The reduction of number of degrees of freedom makes the resulting coarse models by construction state point dependent; that is, they cannot easily be transferred to a range of temperatures, densities, system compositions, etc. These are significant challenges, in particular if one wants to study LC phase transitions (thermally or photoinduced). In the present paper we show how one can systematically derive a CG model for a LC molecule that is highly consistent with an atomistic description by choosing an appropriate state point for the reference simulation. The reference state point is the supercooled liquid just below the smectic-isotropic phase transition which is characterized by a high degree of local nematic order while being overall isotropic. With the resulting CG model it is possible to switch between the atomistic and the CG levels (and vice versa) in a seamless manner maintaining values of all the relevant order parameters which describe the smectic A (smA) state. This model will allow us in the future to link large length scale and long time scale CG simulations of the LC state with chemically accurate QM/MM simulations of the photoisomerization process. © 2012 American Chemical Society. Source


Casiraghi C.,University of Manchester | Casiraghi C.,Free University of Berlin
Physica Status Solidi (B) Basic Research | Year: 2011

The Raman scattering process in graphene is always resonant, i.e. involves real electronic states, and this affects the Raman intensity. Thus, a detailed analysis of the Raman intensity of graphene can provide useful information on the Raman scattering process itself, in particular on the interaction between the fundamental excitations in graphene, such as electron-phonon and electron-defect interactions, which can be studied only by transport or complex techniques. Here a detailed analysis of the dependence of the Raman intensity of graphene on doping and disorder is presented. While the intensity of the G peak, I(G), is not strongly affected by small amount of doping or disorder, the intensity of the 2D peak strongly decreases with increasing doping or disorder. By analyzing the dependence of I(2D) with doping in the framework of a fully resonant process, we measured the total electron-phonon scattering rate. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Lehmann J.,Cornell University | Rillig M.C.,Free University of Berlin | Thies J.,Cornell University | Masiello C.A.,Rice University | And 2 more authors.
Soil Biology and Biochemistry | Year: 2011

Soil amendment with biochar is evaluated globally as a means to improve soil fertility and to mitigate climate change. However, the effects of biochar on soil biota have received much less attention than its effects on soil chemical properties. A review of the literature reveals a significant number of early studies on biochar-type materials as soil amendments either for managing pathogens, as inoculant carriers or for manipulative experiments to sorb signaling compounds or toxins. However, no studies exist in the soil biology literature that recognize the observed large variations of biochar physico-chemical properties. This shortcoming has hampered insight into mechanisms by which biochar influences soil microorganisms, fauna and plant roots. Additional factors limiting meaningful interpretation of many datasets are the clearly demonstrated sorption properties that interfere with standard extraction procedures for soil microbial biomass or enzyme assays, and the confounding effects of varying amounts of minerals. In most studies, microbial biomass has been found to increase as a result of biochar additions, with significant changes in microbial community composition and enzyme activities that may explain biogeochemical effects of biochar on element cycles, plant pathogens, and crop growth. Yet, very little is known about the mechanisms through which biochar affects microbial abundance and community composition. The effects of biochar on soil fauna are even less understood than its effects on microorganisms, apart from several notable studies on earthworms. It is clear, however, that sorption phenomena, pH and physical properties of biochars such as pore structure, surface area and mineral matter play important roles in determining how different biochars affect soil biota. Observations on microbial dynamics lead to the conclusion of a possible improved resource use due to co-location of various resources in and around biochars. Sorption and thereby inactivation of growth-inhibiting substances likely plays a role for increased abundance of soil biota. No evidence exists so far for direct negative effects of biochars on plant roots. Occasionally observed decreases in abundance of mycorrhizal fungi are likely caused by concomitant increases in nutrient availability, reducing the need for symbionts. In the short term, the release of a variety of organic molecules from fresh biochar may in some cases be responsible for increases or decreases in abundance and activity of soil biota. A road map for future biochar research must include a systematic appreciation of different biochar-types and basic manipulative experiments that unambiguously identify the interactions between biochar and soil biota. © 2011 Elsevier Ltd. Source


Gramelsberger G.,Free University of Berlin
Studies in History and Philosophy of Science Part B - Studies in History and Philosophy of Modern Physics | Year: 2010

The scientific understanding of atmospheric processes has been rooted in the mechanical and physical view of nature ever since dynamic meteorology gained ground in the late 19th century. Conceiving the atmosphere as a giant 'air mass circulation engine' entails applying hydro- and thermodynamical theory to the subject in order to describe the atmosphere's behaviour on small scales. But when it comes to forecasting, it turns out that this view is far too complex to be computed. The limitation of analytical methods precludes an exact solution, forcing scientists to make use of numerical simulation. However, simulation introduces two prerequisites to meteorology: First, the partitioning of the theoretical view into two parts-the large-scale behaviour of the atmosphere, and the effects of smaller-scale processes on this large-scale behaviour, so-called parametrizations; and second, the dependency on computational power in order to achieve a higher resolution. The history of today's atmospheric circulation modelling can be reconstructed as the attempt to improve the handling of these basic constraints. It can be further seen as the old schism between theory and application under new circumstances, which triggers a new discussion about the question of how processes may be conceived in atmospheric modelling. © 2010 Elsevier Ltd. Source


Eisler V.,Copenhagen University | Peschel I.,Free University of Berlin
Annalen der Physik (Leipzig) | Year: 2010

We study the ground-state entanglement of two halves of a critical transverse Ising chain, separated by an interface defect. From the relation to a two-dimensional Ising model with a defect line we obtain an exact expression for the continuously varying effective central charge which governs the asymptotic behaviour of the entanglement entropy. The result is relevant also for other fermionic chains. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Weser M.,Fritz Haber Institute | Voloshina E.N.,Free University of Berlin | Horn K.,Fritz Haber Institute | Dedkov Yu.S.,Fritz Haber Institute
Physical Chemistry Chemical Physics | Year: 2011

The electronic structure and magnetic properties of the graphene/Fe/Ni(111) system were investigated via combination of the density functional theory calculations and electron-spectroscopy methods. This system was prepared via intercalation of thin Fe layers (1 ML) underneath graphene on Ni(111) and its inert properties were verified by means of photoelectron spectroscopy. Intercalation of iron in the space between graphene and Ni(111) changes drastically the magnetic response from the graphene layer that is explained by the formation of the highly spin-polarized 3dz 2 quantum-well state in the thin iron layer. © the Owner Societies. Source


Von Blanckenburg F.,Helmholtz Center Potsdam | Von Blanckenburg F.,Free University of Berlin | Bouchez J.,Helmholtz Center Potsdam
Earth and Planetary Science Letters | Year: 2014

The ratio of the meteoric cosmogenic radionuclide 10Be to the stable isotope 9Be is proposed here to be a flux proxy of terrigenous input into the oceans. The ocean's dissolved 10Be/9Be is set by (1) the flux of meteoric 10Be produced in the atmosphere; (2) the denudational flux of the rivers discharging into a given ocean basin; (3) the fraction of 9Be that is released from primary minerals during weathering (meaning the 9Be transported by rivers in either the dissolved form or adsorbed onto sedimentary particles and incorporated into secondary oxides); and (4) the fraction of riverine 10Be and 9Be actually released into seawater. Using published 10Be/9Be data of rivers for which independent denudation rate estimates exist we first find that the global average fraction of 9Be released during weathering into river waters and their particulate load is 20% and does not depend on denudation rate. We then evaluate this quantitative proxy for terrigenous inputs by using published dissolved seawater Be isotope data and a compilation of global river loads. We find that the measured global average oceanic dissolved 10Be/9Be ratio of about 0.9 × 10 -7 is satisfied by the mass balance if only about 6% of the dissolved and adsorbed riverine Be is eventually released to the open ocean after escaping the coastal zone. When we establish this mass balance for individual ocean basins good agreement results between 10Be/9Be ratios predicted from known river basin denudation rates and measured ocean 10Be/9Be ratios. Only in the South Atlantic and the South Pacific the 10Be/9Be ratio is dominated by advected Be and in these basins the ratio is a proxy for ocean circulation. As the seawater 10Be/9Be ratio is faithfully recorded in marine chemical precipitates the 10Be/9Be ratio extracted from authigenic sediments can now serve to estimate relative changes in terrigenous input into the oceans back through time on a global and on an ocean basin scale. © 2013 Elsevier B.V. Source


Bertin A.,BAM Federal Institute of Materials Research and Testing | Bertin A.,Free University of Berlin
Advances in Polymer Science | Year: 2014

This review gives representative examples of the various types of synthetic cationic polymers or polyampholytes (chemical structure, architecture, etc) that can be used to complex DNA (forming polyplexes) for their application in gene delivery. In designing polycations for gene delivery, one has to take into account a balance between protection of DNA versus loss of efficiency for DNA condensation and efficient condensation versus hindering of DNA release. Indeed, if the polyplexes are not stable enough, premature dissociation will occur before delivery of the genetic material at the desired place, resulting in low transfection efficiency; on the other hand, a complex that is too stable will not release the DNA, also resulting in low gene expression. The techniques generally used to determine these properties are gel electrophoresis to test the DNA/polymer complexation, ethidium bromide or polyanion displacement to test the affinity of a polymer for DNA, and light scattering to determine the extent of DNA condensation. Moreover, with the development of more precise instruments for physico-chemical characterization and appropriate biochemical and biophysical techniques, a direct link between the physico-chemical characteristics of the polyplexes and their in vitro and in vivo properties can be drawn, thus allowing tremendous progress in the quest towards application of polyplexes for gene therapy, beyond the research laboratory. © Springer-Verlag Berlin Heidelberg 2013. Source


Shegokar R.,Free University of Berlin
Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques | Year: 2011

Nanotechnology has offered enormous improvement in field of therapeutics by means of designing of drug delivery systems and opened the possibility of controlling infections at the molecular level. Nanocarriers can cross biological barriers and are able to target cellular reservoirs of Mycobacterium tuberculosis (M. tuberculosis). Nanoparticle-based systems have significant potential for treatment and prevention of tuberculosis (TB). A variety of nanocarriers have been widely evaluated as potential drug delivery systems for various administration routes. Targeting the drugs to certain physiological sites such as the lymph nodes has emerged as a promising strategy in treating TB with improved drug bioavailability and reduction of the dosing frequency. Nanotechnology based rational targeting may improve therapeutic success by limiting adverse drug effects and requiring less frequent administration regimes, ultimately resulting in more patients compliance and thus attain higher adherence levels. The development of nanoparticle based aerosol vaccine is undergoing which could serve as new platform for immunization. Present article compiles the general physiological aspects of the infection along with the relevance nanocarriers used in prevention of tuberculosis. Source


Basilio Janke E.M.,Free University of Berlin | Riechert-Krause F.,University of Greifswald | Weisz K.,University of Greifswald
Journal of Physical Chemistry B | Year: 2011

Base pairs formed by the inosine nucleoside (I) play an important role in many physiological processes as well as in various DNA technologies. Relative stabilities and favored base pair geometries of free inosine wobble base pairs in aprotic solvents have been determined through 1H NMR measurements at room temperature and at very low temperatures in a freonic solvent. As indicated by its significantly deshielded imino proton, the Watson-Crick-type I•C base pair forms a remarkably strong NHN hydrogen bond. For the thermodynamically less stable I•A wobble base pair, two configurations of similar population coexist at 133 K in the slow hydrogen bond exchange regime, namely a Watson-Crick(I)-Watson-Crick(A) geometry and a Watson-Crick(I)- Hoogsteen(A) geometry. I•U base pairs are stabilized by two rather weak hydrogen bonds and are significantly disfavored over inosine self-associates in a low-temperature Freon solution. © 2011 American Chemical Society. Source


Tapia E.,Free University of Berlin
Pattern Recognition Letters | Year: 2011

The integral image approach allows optimal computation of Haar-based features for real-time recognition of objects in image sequences. This paper describes a generalization of the approach to high-dimensional images and offers a formula for optimal computation of sums on high-dimensional rectangles. © 2010 Elsevier B.V. All rights reserved. Source


Specimens of three populations of Halicephalobus Timm, 1956 from rotten wood and slime flux were studied and compared with measurements of the original descriptions of the wood-inhabiting H. minutus, H. parvus and H. similigaster. The main distinguishing features such as vulva position and tail length are highly variable in the specimens of the isolates studied here and include the ranges given in the descriptions of the three Halicephalobus species known from similar habitats so far. This study shows that the differentiating characters used in the literature are not possible to apply for the wood-inhabiting Halicephalobus species when studying cultured live specimens. In conclusion, the three nominal species of wood-inhabiting Halicephalobus are based on type specimens that actually belong to the same species. Halicephalobus minutus syn. n. and H. parvus syn. n. are therefore proposed as junior synonyms of H. similigaster. A description of H. similigaster is given. © 2011 Brill. Source


Noe F.,Free University of Berlin | Clementi C.,Rice University
Journal of Chemical Theory and Computation | Year: 2015

Characterizing macromolecular kinetics from molecular dynamics (MD) simulations requires a distance metric that can distinguish slowly interconverting states. Here, we build upon diffusion map theory and define a kinetic distance metric for irreducible Markov processes that quantifies how slowly molecular conformations interconvert. The kinetic distance can be computed given a model that approximates the eigenvalues and eigenvectors (reaction coordinates) of the MD Markov operator. Here, we employ the time-lagged independent component analysis (TICA). The TICA components can be scaled to provide a kinetic map in which the Euclidean distance corresponds to the kinetic distance. As a result, the question of how many TICA dimensions should be kept in a dimensionality reduction approach becomes obsolete, and one parameter less needs to be specified in the kinetic model construction. We demonstrate the approach using TICA and Markov state model (MSM) analyses for illustrative models, protein conformation dynamics in bovine pancreatic trypsin inhibitor and protein-inhibitor association in trypsin and benzamidine. We find that the total kinetic variance (TKV) is an excellent indicator of model quality and can be used to rank different input feature sets. © 2015 American Chemical Society. Source


Wloka C.,University of Pennsylvania | Wloka C.,Free University of Berlin | Bi E.,University of Pennsylvania
Cytoskeleton | Year: 2012

Cytokinesis is essential for cell proliferation in all domains of life. Because the core components and mechanisms of cytokinesis are conserved from fungi to humans, the budding yeast Saccharomyces cerevisiae has served as an attractive model for studying this fundamental process. Cytokinesis in budding yeast is driven by two interdependent cellular events: actomyosin ring (AMR) constriction and the formation of a chitinous cell wall structure called the primary septum (PS), the functional equivalent of extracellular matrix remodeling during animal cytokinesis. AMR constriction is thought to drive efficient plasma membrane ingression as well as to guide PS formation, whereas PS formation is thought to stabilize the AMR during its constriction. Following the completion of the PS formation, two secondary septa (SS), consisting of glucans and mannoproteins, are synthesized at both sides of the PS. Degradation of the PS and a part of the SS by a chitinase and glucanases then enables cell separation. In this review, we discuss the mechanics of cytokinesis in budding yeast, highlighting its common and unique features as well as the emerging questions. © 2012 Wiley Periodicals, Inc. Source


Ehrlich M.,Tel Aviv University | Gutman O.,Tel Aviv University | Knaus P.,Free University of Berlin | Henis Y.I.,Tel Aviv University
FEBS Letters | Year: 2012

Transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) cytokines participate in a multiplicity of ways in the regulation of numerous physiological and pathological processes. Their wide-ranging biological functions are controlled by several mechanisms, including regulation of transcription, complex formation among the signaling receptors (oligomerization) and with co-receptors, binding of the receptors to scaffolding proteins or their targeting to specific membrane domains. Here, we address the generation of TGF-β and BMP receptor homo- and hetero-oligomers and its roles as a mechanism capable of fast regulation of signaling by these crucial cytokines. We examine the available biochemical, biophysical and structural evidence for the ternary structure of these complexes, and the possible roles of homomeric and heteromeric receptor oligomers in signaling. © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved. Source


Tumaneng K.,University of California at San Diego | Schlegelmilch K.,Harvard University | Schlegelmilch K.,Free University of Berlin | Russell R.C.,University of California at San Diego | And 7 more authors.
Nature Cell Biology | Year: 2012

Organ development is a complex process governed by the interplay of several signalling pathways that have critical functions in the regulation of cell growth and proliferation. Over the past years, the Hippo pathway has emerged as a key regulator of organ size. Perturbation of this pathway has been shown to play important roles in tumorigenesis. YAP, the main downstream target of the mammalian Hippo pathway, promotes organ growth, yet the underlying molecular mechanism of this regulation remains unclear. Here we provide evidence that YAP activates the mammalian target of rapamycin (mTOR), a major regulator of cell growth. We have identified the tumour suppressor PTEN, an upstream negative regulator of mTOR, as a critical mediator of YAP in mTOR regulation. We demonstrate that YAP downregulates PTEN by inducing miR-29 to inhibit PTEN translation. Last, we show that PI(3)K-mTOR is a pathway modulated by YAP to regulate cell size, tissue growth and hyperplasia. Our studies reveal a functional link between Hippo and PI(3)K-mTOR, providing a molecular basis for the coordination of these two pathways in organ size regulation. © 2012 Macmillan Publishers Limited. All rights reserved. Source


Hepworth M.R.,Free University of Berlin
Gut microbes | Year: 2012

Recently, we demonstrated a novel role for gastrointestinal mast cells (MCs) in the early events that lead to the generation of Th2 immunity to helminth infection. Mice lacking MCs (Kit(W) /Kit(W-v) and Kit(W-Sh)) showed a significant inhibition of Th2 cell priming following infection with the parasitic helminth Heligmosomoides polygyrus bakeri (Hp). We showed that MCs degranulate during the early stages of infection when the helminth larvae invade the small intestinal tissue. Furthermore, MC degranulation was required for the enhanced expression and production of the tissue-derived cytokines IL-25, IL-33 and TSLP, which are required for the optimal orchestration and priming of type 2 immunity. In this addendum we aim to address several questions raised by our findings - in particular, the mechanisms through which MCs may recognize helminth exposure in the early stages of infection and by which they may enhance expression of critical tissue cytokines thus, enabling Th2 priming. Furthermore, we will discuss these findings in the context of recently described novel innate immune cells, such as type 2 hematopoietic progenitors and type 2 innate lymphoid cells. Source


Russia is usually considered as being obstructive to European integration in the EU's Eastern neighbourhood, while the EU is portrayed as being the key promoter of convergence with EU rules. Thus, strong economic dependence on Russia and EU active leverage should account for cross-policy variation in convergence with EU rules. By comparing convergence in Ukraine's telecommunications and food safety regulations, I show that active leverage exerted by Western European multinationals rather than by the EU accounts for divergent outcomes. Further, Russia's 'bad guy' image does not hold if we stop treating Russia as a unitary actor but distinguish between passive and active leverage exerted by Russian government policies, the Russian market and Russian multinationals investing in the Eastern neighbourhood countries on domestic policy choices. © 2013 Copyright University of Glasgow. Source


Nassauer A.,Free University of Berlin
Policing | Year: 2015

Purpose-The purpose of this paper is to connect sociology, criminology, and social psychology to identify specific factors that keep protests peaceful, discusses empirical examples of effective peacekeeping, and develops practical peacekeeping guidelines. Design/methodology/approach-The analysis systematically compared 30 peaceful and violent protests in the USA and Germany to identify peaceful interaction routines and how they are disrupted. It employed a triangulation of visual and document data on each demonstration, analyzing over 1,000 documents in total. The paper relies on qualitative analysis based on the principles of process tracing. Findings-Results show that specific interaction sequences and emotional dynamics can break peaceful interaction routines and trigger violence. Single interactions do not break these routines, but certain combinations do. Police forces and protesters need to avoid these interaction dynamics to keep protests peaceful. Communication between both sides and good police management are especially important. Research limitations/implications-The paper highlights the need to examine the role of situational interactions and emotional dynamics for the emergence and avoidance of protest violence more closely. Practical implications-Findings have implications for police practice and training and for officers’and protesters’safety. Originality/value-Employing recent data and an interdisciplinary approach, the study systematically analyzes peacekeeping in protests, developing guidelines for protest organizers and police. ©, 2015. Emerald Group Publishing Limited. Source


Spencer J.R.,Southwest Research Institute | Denk T.,Free University of Berlin
Science | Year: 2010

The extreme albedo asymmetry of Saturn's moon lapetus, which is about 10 times as bright on its trailing hemisphere as on its leading hemisphere, has been an enigma for three centuries. Deposition of exogenic dark material on the leading side has been proposed as a cause, but this alone cannot explain the global shape, sharpness, and complexity of the transition between lapetus' bright and dark terrain. We demonstrate that all these characteristics, and the asymmetry's large amplitude, can be plausibly explained by runaway global thermal migration of water ice, triggered by the deposition of dark material on the leading hemisphere. This mechanism is unique to lapetus among the satumian satellites because its slow rotation produces unusually high daytime temperatures and water ice sublimation rates for a given albedo. Source


Seiffert S.,Helmholtz Center Berlin | Seiffert S.,Free University of Berlin
Macromolecular Rapid Communications | Year: 2011

Monodisperse polymer gel particles with micrometer-scale dimensions serve for a variety of applications, including those as microcapsules for actives or as micrometer-sized matrixes for mesoscopic additives. These particles can be produced with exquisite control through the use of droplet-based microfluidic templating followed by subsequent droplet solidification. This can be achieved by two ways: One way is to use pre-microgel solutions of low molecular weight monomers and to form microgels by polymerizing these monomers. Another way is to use pre-polymerized, high molecular weight precursors and to gel them by polymer-analogous crosslinking. Both approaches have their specific advantages, allowing microgels to be tailored and optimized for specific needs such as those as delivery systems or scaffolds for living cells. This article highlights some recent achievements in the development and use of these microfluidic techniques to fabricate functional microgel particles. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Krucken J.,Free University of Berlin
Trends in parasitology | Year: 2012

The broad-spectrum anthelmintic cyclooctadepsipeptide PF1022A is a fungal metabolite from Rosellinia sp. PF1022, which is a Mycelia sterilia found on the leaves of Camellia japonica. A broad range of structurally related cyclooctadepsipeptides has been characterized and tested for anthelmintic activities. These metabolites have been used as starting points to generate semisynthetic derivatives with varying nematocidal capacity. Predominant among these compounds is emodepside, which exhibits a broad nematocidal potential against gastrointestinal and extraintestinal parasites. Here we review the chemical biology and mode of action of cyclooctadepsides with particular attention to PF1022A and emodepside. We illustrate how they target nematode neuromuscular function, opening up new avenues for antiparasitic treatments with potential capability for important selective toxicity. Copyright © 2012 Elsevier Ltd. All rights reserved. Source


Kyba C.C.M.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Kyba C.C.M.,Free University of Berlin | Hanel A.,Museum am Scholerberg | Holker F.,Leibniz Institute of Freshwater Ecology and Inland Fisheries
Energy and Environmental Science | Year: 2014

Improvements in the luminous efficiency of outdoor lamps might not result in energy savings or reductions in greenhouse gas emissions. The reason for this is a rebound effect: when light becomes cheaper, many users will increase illumination, and some previously unlit areas may become lit. We present three policy recommendations that work together to guarantee major energy reductions in street lighting systems. First, taking advantage of new technologies to use light only when and where it is needed. Second, defining maximum permitted illuminances for roadway lighting. Third, defining street lighting system efficiency in terms of kilowatt hours per kilometer per year. Adoption of these policies would not only save energy, but would greatly reduce the amount of light pollution produced by cities. The goal of lighting policy should be to provide the light needed for any given task while minimizing both the energy use and negative environmental side effects of the light. This journal is © the Partner Organisations 2014. Source


Sammler D.,Max Planck Institute for Human Cognitive and Brain Sciences | Novembre G.,Max Planck Institute for Human Cognitive and Brain Sciences | Koelsch S.,Free University of Berlin | Keller P.E.,Max Planck Institute for Human Cognitive and Brain Sciences
Cortex | Year: 2013

Syntactic operations in language and music are well established and known to be linked in cognitive and neuroanatomical terms. What remains a matter of debate is whether the notion of syntax also applies to human actions and how those may be linked to syntax in language and music. The present electroencephalography (EEG) study explored syntactic processes during the observation, motor programming, and execution of musical actions. Therefore, expert pianists watched and imitated silent videos of a hand playing 5-chord sequences in which the last chord was syntactically congruent or incongruent with the preceding harmonic context. 2-chord sequences that diluted the syntactic predictability of the last chord (by reducing the harmonic context) served as a control condition. We assumed that behavioural and event-related potential (ERP) effects (i.e., differences between congruent and incongruent trials) that were significantly stronger in the 5-chord compared to the 2-chord sequences are related to syntactic processing. According to this criterion, the present results show an influence of syntactic context on ERPs related to (i) action observation and (ii) the motor programming for action imitation, as well as (iii) participants' execution times and accuracy. In particular, the occurrence of electrophysiological indices of action inhibition and reprogramming when an incongruent chord had to be imitated implies that the pianist's motor system anticipated (and revoked) the congruent chord during action observation. Notably, this well-known anticipatory potential of the motor system seems to be strongly based upon the observer's music-syntactic knowledge, thus suggesting the " embodied" processing of musical syntax. The combined behavioural and electrophysiological data show that the notion of musical syntax not only applies to the auditory modality but transfers - in trained musicians - to a " grammar of musical action" . © 2012 Elsevier Ltd. Source


Schulz H.,Free University of Berlin | Salzarulo P.,University of Florence
Sleep Medicine Reviews | Year: 2012

The development of sleep research can be divided into two main periods. The first one was initiated in 1863 by the first systematic measurement of the depth of sleep, the second in 1953 by the discovery of recurrent episodes of rapid eye movements in sleep. The main methodological procedure in the first of these two periods was the measurement of a single physiological variable, while beginning with long-term measurements of the electroencephalogram (EEG) in sleep, multi-channel, polygraphic recording became the method of choice for sleep studies. Although rhythmic changes in the ultradian frequency range of one to 2h were observed early in many variables during sleep (movements, autonomic functions, penile erections), the recognition of the existence of two different states of sleep (rapid eye movement (REM) and non-rapid eye movement (NREM sleep)) was contingent upon a 'synthetic' view, which focus on the coalescence of multiple variables. The dual concept of sleep organization evolved stepwise in parallel to the rapid growth of neurophysiological knowledge and techniques in the first half of the 20th century, culminating in the discovery of REM sleep. © 2011 Elsevier Ltd. Source


The invention of feed-in tariffs to support renewable energy is analysed. The invention of this policy instrument was the product of a long process of evolutionary tinkering that started in the 1970s, beginning with policies originally implemented to support cogeneration power plants, followed by many small and seemingly irrelevant modifications in order to meet the needs of renewable energy producers. Only by unpacking the policy into its design elements can the long, drawn-out process of policy invention be fully understood. Policymakers adjusted the policy design over time, learning by trial and error. This learning was only possible because the initial effects of the policy were underestimated and natural opponents were distracted by other policies and activities. To allow policy inventions to occur, policymakers should provide protective space to make the necessary amendments for policy success. © 2014 © 2014 Taylor & Francis. Source


Babujian H.M.,Alikhanian Brothers 2 | Foerster A.,Federal University of Rio Grande do Sul | Karowski M.,Free University of Berlin
Nuclear Physics B | Year: 2010

The general SU (N) form factor formula is constructed. Exact form factors for the field, the energy-momentum and the current operators are derived and compared with the 1 / N-expansion of the chiral Gross-Neveu model and full agreement is found. As an application of the form factor approach the equal time commutation rules of arbitrary local fields are derived and in general anyonic behavior is found. © 2009 Elsevier B.V. All rights reserved. Source


Schneider I.,Free University of Berlin
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2013

The modest aim of this case study is the non-invasive and pattern-selective stabilization of discrete rotating waves ('ponies on a merry-go-round') in a triangle of diffusively coupled Stuart-Landau oscillators. We work in a setting of symmetry-breaking equivariant Hopf bifurcation. Stabilization is achieved by delayed feedback control of Pyragas type, adapted to the selected spatio-temporal symmetry pattern. Pyragas controllability depends on the parameters for the diffusion coupling, the complex control amplitude and phase, the uncontrolled super-/sub-criticality of the individual oscillators and their soft/hard spring characteristics. We mathematically derive explicit conditions for Pyragas control to succeed. © 2013 The Author(s) Published by the Royal Society. All rights reserved. Source


Gilmore K.,Max Planck Institute of Colloids and Interfaces | Seeberger P.H.,Max Planck Institute of Colloids and Interfaces | Seeberger P.H.,Free University of Berlin
Chemical Record | Year: 2014

Due to the narrow width of tubing/reactors used, photochemistry performed in micro- and mesoflow systems is significantly more efficient than when performed in batch due to the Beer-Lambert Law. Owing to the constant removal of product and facility of flow chemical scalability, the degree of degradation observed is generally decreased and the productivity of photochemical processes is increased. In this Personal Account, we describe a wide range of photochemical transformations we have examined using both visible and UV light, covering cyclizations, intermolecular couplings, radical polymerizations, as well as singlet oxygen oxygenations. The efforts of the Seeberger group in continuous photochemical reactions, both visible and UV light, are described. These transformations include cyclizations, intermolecular couplings, radical polymeriztions, as well as a range of singlet oxygen oxygenations. Copyright © 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Abdel-Latief M.,Free University of Berlin | Hoffmann K.H.,University of Bayreuth
Peptides | Year: 2014

Allatotropin (AT) and allatostatin (AS) neuropeptides are known to regulate the biosynthesis of juvenile hormones (JH) in insects. Furthermore, they possess myoregulatory and other activities in a wide range of insect species. The genome of Tribolium castaneum encodes two AS and one AT precursors. Here we cloned the cDNAs of the precursors, followed their expression patterns during the pupal stage, and established their putative roles in adult development and oviposition of the females using RNA interference (RNAi). Cloning of the cDNA and gene structure analyses of the Tc-AT gene confirmed that the gene is expressed in three mRNA isoforms. Real-time PCR data demonstrate that the Tc-AT isoforms and the AS genes, Tc-AS C and Tc-AS B, are expressed in discerning developmental and tissue-specific patterns. Single injections of dsRNAi (targeted against the Tc-AT, Tc-AS C, and Tc-AS B, respectively), into young pupae resulted in abnormal adult phenotypes, whereby about half of the animals (P1 phenotype) looked relatively normal, but the females laid low numbers of eggs. The other halves (P2) exhibited strong developmental defects with abnormal duration of the pupal stage, abnormal head and body sizes, short elytra, and incomplete sclerotization. Moreover, these females deposited no eggs and died within one week after emergence. Individual silencing of the Tc-AT mRNA isoforms showed that Tc-AT3 had the most disruptive influence on adult development and fecundity of the females. Our findings clearly indicate a significant role of AT and AS neuropeptides in the pupa. The distinct mechanisms of action, however, remain to be determined. © 2013 Elsevier Inc. Source


Freund H.-J.,Fritz Haber Institute of the Max Planck Society | Nilius N.,Carl von Ossietzky University | Risse T.,Free University of Berlin | Schauermann S.,Fritz Haber Institute of the Max Planck Society
Physical Chemistry Chemical Physics | Year: 2014

The development of model catalyst systems for heterogeneous catalysis going beyond the metal single crystal approach, including phenomena involving the limited size of metal nanoparticles supported on oxide surfaces, as well as the electronic interaction through the oxide-metal interface, is exemplified on the basis of two case studies from the laboratory of the authors. In the first case study the reactivity of supported Pd nanoparticles is studied in comparison with Pd single crystals. The influence of carbon contaminants on the hydrogenation reaction of unsaturated hydrocarbons is discussed. Carbon contaminants are identified as a key parameter in those reactions as they control the surface and sub-surface concentration of hydrogen on and in the particles. In the second case study, scanning probe techniques are used to determine electronic and structural properties of supported Au particles as a function of the number of Au atoms in the particle. It is demonstrated how charge transfer between the support and the particle determines the shape of nanoparticles and a concept is developed that uses charge transfer control through dopants in the support to understand and design catalytically active materials. © 2014 the Owner Societies. Source


Slaby J.,Free University of Berlin
Medical Humanities | Year: 2015

This programmatic theory paper sketches a conceptual framework that might inspire work in critical Medical Humanities. For this purpose, Kaushik Sunder Rajan’s account of biocapital is revisited and discussed in relation to the perspective of a critical neuroscience. Critical neuroscience is an encompassing positioning towards the recent public prominence of the brain and brain-related practices, tools and discourses. The proposed analytical scheme has five focal nodes: capital, life, technoscience, (neoliberal) politics and subjectivity. A special emphasis will be placed on contemporary framings of subjectivity, as it is here where deepreaching entanglements of personhood with scientific practice and discourse, medical and informational technologies, and economic formations are most evident. Notably, the emerging subject position of the ‘prospective health consumer’ will be discussed as it figures prominently in the terrain between neuroscience and other medico-scientific disciplines. © 2015, Medical Humanities. All rights reserved. Source


Engels B.,Free University of Berlin
Canadian Journal of Development Studies | Year: 2015

In reaction to the global food price crisis, people marched in the streets of numerous cities of the Global South, protesting against unaffordable prices for foodstuffs. This article investigates the conditions that enabled this mobilisation. It analyses the case of Burkina Faso, where protests were particularly intense. Building on approaches from social movement studies, it is argued that in Burkina Faso, temporal political opportunities (the price crisis opening up a window of opportunity) and dynamic politico-institutional structures ("cycles of contention"), in combination with social movements organisational resources, explain the way the price issue was framed and why mobilisation was possible. © 2015 Canadian Association for the Study of International Development (CASID). Source


Ruckert H.-W.,Free University of Berlin
Mental Health and Prevention | Year: 2015

Facts and figures on mental health of students and the provision of counselling services will be presented in this article, gathered by the former European Student Counsellors network Forum Européenne de l'Orientation Académique/European Forum on Student Guidance (FEDORA). The Center for Academic Advising and Psychological Counselling of the Freie Universität in Berlin can serve as an example for a typical institution. After the Bologna reform in Europe, putting students under more stress than before, and ever more students coming to European universities with preexisting mental conditions and subsequent adjustment issues, integrated learning support and mental health strategies are called. © 2015 Elsevier GmbH. Source


Beheshti H.,Free University of Berlin
Energy Policy | Year: 2011

Nuclear energy has direct impacts on the environment. Uranium mining, milling, and enrichment affect the livelihoods around and stress on the water resources. In addition, nuclear power plants consume huge amount of water and elevate the water temperature of the ambient water resources. The Iranian nuclear program has pledged for 20,000 MW of nuclear energy by 2025. The fulfillment of such ambitious target stresses the environment and increases the environmental degradation cost of the country. Iran central semi-arid area and the Persian Gulf are the major regions with high risk of impacts from the current nuclear program. © 2011 Elsevier Ltd. Source


Pelargonium species contribute significantly to the health care of a large population in the Southern African region, as part of a long-standing medical system intimately linked to traditional healing practices. Most notably, extracts of the roots of P. sidoides have commonly been applied for the treatment of dysentery and diarrhoea but only occasionally for respiratory complaints. Clinical trials have shown that a modern aqueous-ethanolic formulation of P. sidoides extracts (EPs® 7630) is an efficacious treatment for disorders of the respiratory tract, for example bronchitis and sinusitis. It should be noted that EPs® 7630 is the most widely investigated extract and therefore is the focus of this review. In order to provide a rationale for its therapeutic activity extracts have been evaluated for antibacterial activity and for their effects on non-specific immune functions. Only moderate direct antibacterial capabilities against a spectrum of bacteria, including Mycobacteria strains, have been noted. In contrast, a large body of in vitro studies has provided convincing evidence for an anti-infective principle associated with activation of the non-specific immune system. Interestingly, significant inhibition of interaction between bacteria and host cells, a key to the pathogenesis of respiratory tract infections, has emerged from recent studies. In addition, antiviral effects have been demonstrated, including inhibition of the replication of respiratory viruses and the enzymes haemagglutinin and neuraminidase. Besides, an increase of cilliary beat frequency of respiratory cells may contribute to the beneficial effects of P. sidoides extracts. This example provides a compelling argument for continuing the exploration of Nature and traditional medical systems as a source of therapeutically useful herbal medicines. © 2011 by the authors; licensee MDPI, Basel, Switzerland. Source


Cephalopods are extraordinary molluscs equipped with vertebrate-like intelligence and a unique buoyancy system for locomotion. A growing body of evidence from the fossil record, embryology and Bayesian molecular divergence estimations provides a comprehensive picture of their origins and evolution. Cephalopods evolved during the Cambrian (∼530Ma) from a monoplacophoran-like mollusc in which the conical, external shell was modified into a chambered buoyancy apparatus. During the mid-Palaeozoic (∼416Ma) cephalopods diverged into nautiloids and the presently dominant coleoids. Coleoids (i.e. squids, cuttlefish and octopods) internalised their shells and, in the late Palaeozoic (∼276Ma), diverged into Vampyropoda and the Decabrachia. This shell internalisation appears to be a unique evolutionary event. In contrast, the loss of a mineralised shell has occurred several times in distinct coleoid lineages. The general tendency of shell reduction reflects a trend towards active modes of life and much more complex behaviour. © 2011 WILEY Periodicals, Inc. Source


Strassheim J.,Free University of Berlin
Journal of Pragmatics | Year: 2010

Two seminal but unconnected relevance theories of communication are compared: one found in Alfred Schutz's philosophy, and one developed by Dan Sperber and Deirdre Wilson in a cognitive-science framework. The comparison is meant to strengthen both sides by integrating their advantages, and to prompt further discussion between these and other relevance accounts. Both theories, it is argued, aim to grasp and explain the fact, unaccounted for by code-like rules (e.g. of language), that people interact in context in a routine yet flexible way. Both investigate a dynamics of selectivity in experience making certain selections 'relevant' to an individual, which interactants exploit for coordination. Three differences between the theories are examined, and specific integrations encouraged: (a) The central problematic of inter-individual ascriptions of relevance remains underdeveloped with Sperber/Wilson. Schutz's idea of ongoing 'typification' is proposed as an amendment. (b) Schutz lacks a concise notion of relevance. Sperber/Wilson's two-sided concept paves the way for a different concept meeting requirements identified in the article and captures the interlocking of routine and flexibility in interaction. (c) Sperber/Wilson overly restrict the range of experience powering their theory. This is shown for individual goals, whose inclusion via the recommended concepts of typification and relevance is suggested. © 2009 Elsevier B.V. All rights reserved. Source


Cipollini D.,Wright State University | Rigsby C.M.,Wright State University | Barto E.K.,Free University of Berlin
Journal of Chemical Ecology | Year: 2012

Studies of allelopathy in terrestrial systems have experienced tremendous growth as interest has risen in describing biochemical mechanisms responsible for structuring plant communities, determining agricultural and forest productivity, and explaining invasive behaviors in introduced organisms. While early criticisms of allelopathy involved issues with allelochemical production, stability, and degradation in soils, an understanding of the chemical ecology of soils and its microbial inhabitants has been increasingly incorporated in studies of allelopathy, and recognized as an essential predictor of the outcome of allelopathic interactions between plants. Microbes can mediate interactions in a number of ways with both positive and negative outcomes for surrounding plants and plant communities. In this review, we examine cases where soil microbes are the target of allelopathic plants leading to indirect effects on competing plants, provide examples where microbes play either a protective effect on plants against allelopathic competitors or enhance allelopathic effects, and we provide examples where soil microbial communities have changed through time in response to allelopathic plants with known or potential effects on plant communities. We focus primarily on interactions involving wild plants in natural systems, using case studies of some of the world's most notorious invasive plants, but we also provide selected examples from agriculturally managed systems. Allelopathic interactions between plants cannot be fully understood without considering microbial participants, and we conclude with suggestions for future research. © 2012 Springer Science+Business Media, LLC. Source


Kenfack A.,Free University of Berlin | Singh K.P.,Indian Institute of Science
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

We study onset and control of stochastic resonance (SR) phenomenon in two driven bistable systems, mutually coupled and subjected to independent noises, taking into account the influence of both the inertia and the coupling. In the absence of coupling, we found two critical damping parameters: one for the onset of SR and another for which SR is optimum. We then show that in weakly coupled systems, emergence of SR is governed by chaos. A strong coupling between the two oscillators induces coherence in the system; however, the systems do not synchronize no matter what the coupling is. Moreover, a specific coupling parameter is found for which the SR of each subsystem is optimum. Finally, a scheme for controlling SR in such coupled systems is proposed by introducing a phase difference between the two coherent driving forces. © 2010 The American Physical Society. Source


Robinson P.N.,Charite - Medical University of Berlin | Robinson P.N.,Max Planck Institute for Molecular Genetics | Robinson P.N.,Free University of Berlin | Webber C.,University of Oxford
PLoS Genetics | Year: 2014

The use of model organisms as tools for the investigation of human genetic variation has significantly and rapidly advanced our understanding of the aetiologies underlying hereditary traits. However, while equivalences in the DNA sequence of two species may be readily inferred through evolutionary models, the identification of equivalence in the phenotypic consequences resulting from comparable genetic variation is far from straightforward, limiting the value of the modelling paradigm. In this review, we provide an overview of the emerging statistical and computational approaches to objectively identify phenotypic equivalence between human and model organisms with examples from the vertebrate models, mouse and zebrafish. Firstly, we discuss enrichment approaches, which deem the most frequent phenotype among the orthologues of a set of genes associated with a common human phenotype as the orthologous phenotype, or phenolog, in the model species. Secondly, we introduce and discuss computational reasoning approaches to identify phenotypic equivalences made possible through the development of intra- and interspecies ontologies. Finally, we consider the particular challenges involved in modelling neuropsychiatric disorders, which illustrate many of the remaining difficulties in developing comprehensive and unequivocal interspecies phenotype mappings. © 2014 Robinson, Webber. Source


Adelle C.,University of East Anglia | Weiland S.,Free University of Berlin
Impact Assessment and Project Appraisal | Year: 2012

Policy assessment has spread rapidly around the world in the last few decades providing an opportunity for further innovation and understanding in the way in which assessment is conceived, practised and researched. The extension of assessment from project and programme level to policy level was in part intended to improve its effectiveness by moving the focus of study upstream in the policy-making process. This paper reflects on the state of the art in policy assessment. It illustrates how the diffusion of policy assessment has led not to one standard 'correct' way of conducting policy assessment but to a great deal of diversity in how policy assessment is practised as well as researched and even theorized. Although the 'textbook' concept and everyday practices of policy assessment are based on a traditional rational linear concept of policy-making, policy assessment has become the latest arena for post-positivist conceptions of policy-making and assessment to resurface. This paper suggests that the future agenda for both research and practices could - indeed should - attempt to straddle these two theoretical approaches. © 2012 Copyright IAIA. Source


Lehmann A.,Free University of Berlin | Ittel A.,TU Berlin
International Journal of Law and Psychiatry | Year: 2012

Studies concerning inmate psychopathy (as measured by Psychopathy-Checklist-Revised, PCL-R; Hare, 1991) have predominantly been concerned with male inmates. This study was the first to look into psychopathy using the PCL-R with the whole required procedure in German prisons with female inmates. The aims of the present study were to gain data about the prevalence of psychopathy in this sample and to examine potential relations between the types and motive of aggression, prosocial behavior and scores on the PCL-R. Sixty female inmates were examined.We obtained a prevalence rate of psychopathy of 17% (. N=. 10, with a cut-off score of 25). Considering a wide range of subtypes of aggressive behaviors, we found that physical proactive, and relational reactive aggression as well as age predicted high scores of psychopathy. However, prosocial or helping behavior was not associated with psychopathy. Implications for diagnostic issues in forensics concerning female prisoners are discussed. © 2012 Elsevier Ltd. Source


Niemitz C.,Free University of Berlin
Naturwissenschaften | Year: 2010

During the last century, approximately 30 hypotheses have been constructed to explain the evolution of the human upright posture and locomotion. The most important and recent ones are discussed here. Meanwhile, it has been established that all main hypotheses published until the last decade of the past century are outdated, at least with respect to some of their main ideas: Firstly, they were focused on only one cause for the evolution of bipedality, whereas the evolutionary process was much more complex. Secondly, they were all placed into a savannah scenario. During the 1990s, the fossil record allowed the reconstruction of emerging bipedalism more precisely in a forested habitat (e.g., as reported by Clarke and Tobias (Science 269:521-524, 1995) and WoldeGabriel et al. (Nature 412:175-178, 2001)). Moreover, the fossil remains revealed increasing evidence that this part of human evolution took place in a more humid environment than previously assumed. The Amphibian Generalist Theory, presented first in the year 2000, suggests that bipedalism began in a wooded habitat. The forests were not far from a shore, where our early ancestor, along with its arboreal habits, walked and waded in shallow water finding rich food with little investment. In contrast to all other theories, wading behaviour not only triggers an upright posture, but also forces the individual to maintain this position and to walk bipedally. So far, this is the only scenario suitable to overcome the considerable anatomical and functional threshold from quadrupedalism to bipedalism. This is consistent with paleoanthropological findings and with functional anatomy as well as with energetic calculations, and not least, with evolutionary psychology. The new synthesis presented here is able to harmonise many of the hitherto competing theories. Source


Jones G.J.,University of Cardiff | Robertazzi A.,Free University of Berlin | Platts J.A.,University of Cardiff
Journal of Physical Chemistry B | Year: 2013

Anion-π interactions are attractive interactions between electron-poor aromatic rings and electron-rich negative ions or groups. Predicted by theoretical studies in the late 1990s, the first experimental evidence of anion-π interactions was provided by two independent studies in 2004. Since then, the role of these interactions in chemical and in biochemical systems has been investigated. In this work we report benchmark interaction energies, estimated from the extrapolated MP2 basis set limit with CCSD(T) correction, for several model complexes. These are then used to assess faster, more approximate methods including MP2 and its local approximation, along with various forms of Density Functional Theory (DFT). The most promising of these are then used to describe the geometries and interaction energies of a series of complexes between electron-poor substituted benzene rings and anions as well as examples of such interactions in models of proteins. © 2013 American Chemical Society. Source


Prechelt L.,Free University of Berlin
IEEE Transactions on Software Engineering | Year: 2011

Background: For developing Web-based applications, there exist several competing and widely used technological platforms (consisting of a programming language, framework(s), components, and tools), each with an accompanying development culture and style. Research question: Do Web development projects exhibit emergent process or product properties that are characteristic and consistent within a platform, but show relevant substantial differences across platforms or do team-to-team individual differences outweigh such differences, if any? Such a property could be positive (i.e., a platform advantage), negative, or neutral, and it might be unobvious which is which. Method: In a nonrandomized, controlled experiment, framed as a public contest called "Plat-Forms", top-class teams of three professional programmers competed to implement the same requirements for a Web-based application within 30 hours. Three different platforms (Java EE, PHP, or Perl) were used by three teams each. We compare the resulting nine products and process records along many dimensions, both external (usability, functionality, reliability, security, etc.) and internal (size, structure, modifiability, etc.). Results: The various results obtained cover a wide spectrum: First, there are results that many people would have called "obvious" or "well known", say, that Perl solutions tend to be more compact than Java solutions. Second, there are results that contradict conventional wisdom, say, that our PHP solutions appear in some (but not all) respects to be actually at least as secure as the others. Finally, one result makes a statement we have not seen discussed previously: Along several dimensions, the amount of within-platform variation between the teams tends to be smaller for PHP than for the other platforms. Conclusion: The results suggest that substantial characteristic platform differences do indeed exist in some dimensions, but possibly not in others. © 2011 IEEE. Source


Cuesta-Seijo J.A.,Carlsberg Laboratory | Nielsen M.M.,Carlsberg Laboratory | Marri L.,Carlsberg Laboratory | Tanaka H.,Carlsberg Laboratory | And 4 more authors.
Acta Crystallographica Section D: Biological Crystallography | Year: 2013

Starch, a polymer of glucose, is the major source of calories in the human diet. It has numerous industrial uses, including as a raw material for the production of first-generation bioethanol. Several classes of enzymes take part in starch biosynthesis, of which starch synthases (SSs) carry out chain elongation of both amylose and amylopectin. Plants have five classes of SS, each with different roles. The products of the reaction of SS are well known, but details of the reaction mechanism remain obscure and even less is known of how different SSs select different substrates for elongation, how they compete with each other and how their activities are regulated. Here, the first crystal structure of a soluble starch synthase is presented: that of starch synthase I (SSI) from barley refined to 2.7 14;Å resolution. The structure captures an open conformation of the enzyme with a surface-bound maltooligosaccharide and a disulfide bridge that precludes formation of the active site. The maltooligosaccharide-binding site is involved in substrate recognition, while the disulfide bridge is reflective of redox regulation of SSI. Activity measurements on several SSI mutants supporting these roles are also presented. © 2013 International Union of Crystallography. Source


Hass U.,Free University of Berlin | Massmann G.,Carl von Ossietzky University
Water Research | Year: 2012

The occurrence and distribution of six psychoactive compounds (primidone, phenobarbital, oxazepam, diazepam, meprobamate, and pyrithyldione) and a metabolite of primidone (phenylethylmalonamide) were investigated in wastewater treatment plant (WWTP) effluents, surface water, groundwater of a bank filtration site, raw and final drinking water, and in groundwater affected by former sewage irrigation.Primidone and its metabolite phenylethylmalonamide were found to be ubiquitous in environmental water samples in Berlin. Maximum concentrations of 0.87 and 0.42 μg/L, respectively, were encountered in WWTP effluents. Both compounds are apparently not removed when passaging through the different compartments of the water cycle and concentrations are only reduced by dilution. Phenobarbital was present at nearly every stage of the Berlin water cycle with the exception of raw and final drinking water. The highest concentrations of phenobarbital (up to 0.96 μg/L) were measured in groundwater influenced by former sewage irrigation. Oxazepam was only present in WWTP effluents and surface waters (up to 0.18 μg/L), while diazepam was not detected in any matrix. Due to their withdrawal from the German market years ago, the pharmaceuticals meprobamate and pyrithyldione were only found in sewage farm groundwater (up to 0.50 and 0.04 μg/L, respectively) and, in case of meprobamate, also in decade old bank filtrate (0.03 μg/L).Our results indicate a high persistence of some of the investigated compounds in the aquatic system. As a consequence, these pollutants may potentially reach drinking water resources via bank filtration if present in WWTP effluents and/or surface waters in partly closed water cycles such as Berlin's. © 2012 Elsevier Ltd. Source


Weisse A.Y.,Free University of Berlin | Huisinga W.,University of Potsdam
Journal of Computational Physics | Year: 2011

We propose a novel strategy for global sensitivity analysis of ordinary differential equations. It is based on an error-controlled solution of the partial differential equation (PDE) that describes the evolution of the probability density function associated with the input uncertainty/variability. The density yields a more accurate estimate of the output uncertainty/variability, where not only some observables (such as mean and variance) but also structural properties (e.g., skewness, heavy tails, bi-modality) can be resolved up to a selected accuracy. For the adaptive solution of the PDE Cauchy problem we use the Rothe method with multiplicative error correction, which was originally developed for the solution of parabolic PDEs. We show that, unlike in parabolic problems, conservation properties necessitate a coupling of temporal and spatial accuracy to avoid accumulation of spatial approximation errors over time. We provide convergence conditions for the numerical scheme and suggest an implementation using approximate approximations for spatial discretization to efficiently resolve the coupling of temporal and spatial accuracy. The performance of the method is studied by means of low-dimensional case studies. The favorable properties of the spatial discretization technique suggest that this may be the starting point for an error-controlled sensitivity analysis in higher dimensions. © 2011 Elsevier Inc. Source


Risse T.,Free University of Berlin
Global Policy | Year: 2012

One cannot begin to understand EU foreign policy without taking identity politics into account. First, the differential Europeanization of national identities explains to a large degree why the current European Security and Defence Policy (ESDP) has not been supranationalized. Second, the gap between the EU's grandiose rhetoric of being a 'force for good' in the world and its inability to put this foreign policy identity at work into practice, largely results from the fact that the EU's construction of a distinct foreign policy identity is inward rather than outward-oriented. Last, but not least, the EU enlargement discourse, particularly about Turkey, has as much to do with contested self-descriptions of the EU and what follows for its boundaries than with any security or economic considerations. The article starts with conceptual remarks on collective identity, followed by three case studies focusing on the lack of supranationalization of the ESDP, the EU's foreign policy construction as a civilian power, and the enlargement discourse, particularly with regard to Turkey. I conclude with some policy recommendations. © 2012 London School of Economics and Political Science and John Wiley & Sons Ltd. Source


Yousef K.P.,Free University of Berlin
Journal of Acquired Immune Deficiency Syndromes | Year: 2016

BACKGROUND:: While HIV continues to spread globally, novel intervention strategies such as treatment as prevention (TasP) may bring the epidemic to a halt. However, their effective implementation requires a profound understanding of the underlying transmission dynamics. METHODS: : We analyzed parameters of the German HIV epidemic based on phylogenetic clustering of viral sequences from recently infected seroconverters with known infection dates. Viral base-line and follow-up pol sequences (n=1943) from 1159 drug-naïve individuals were selected from a nationwide long-term observational study initiated in 1997. Putative transmission clusters were computed based on a maximum likelihood phylogeny. Utilizing individual follow-up sequences, we optimized our clustering threshold to maximize the likelihood of co-clustering individuals connected by direct transmission. RESULTS: : The sizes of putative transmission clusters scaled inversely with their abundance and their distribution exhibited a heavy tail. Clusters based on the optimal clustering threshold were significantly more likely to contain members of the same or bordering German federal states. Inter-infection times between co-clustered individuals were significantly shorter (26 weeks; IQR: 13-83) than in a null model. CONCLUSION:: Viral intra-individual evolution may be used to select criteria that maximize co-clustering of transmission pairs in the absence of strong adaptive selection pressure. Inter-infection times of co-clustered individuals may then be an indicator of the typical time to onwards transmission. Our analysis suggests that onward transmission may have occurred early after infection, when individuals are typically unaware of their serological status. The latter argues that TasP should be combined with HIV testing campaigns to reduce the possibility of transmission before TasP initiation. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Source


Biedermann S.,Washington State University | Biedermann S.,Free University of Berlin | Hellmann H.,Washington State University
Trends in Plant Science | Year: 2011

The ubiquitin proteasome pathway is one of the major regulatory tools used by eukaryotic cells. E3 ligases, which allow controlled modification of proteins with ubiquitin, are crucial for the specificity of the pathway. Recently, an additional plant cullin-based E3 ligase complex was described which contains cullin 4 (CUL4) and DAMAGED DNA BINDING 1 protein as core subunits. Our knowledge of this E3 ligase has increased tremendously since its first description, and it seems to be involved in many developmental and physiological processes. Here, we review the most recent studies on CUL4 E3 complexes, with a focus on their substrate recognition and the plethora of processes that they regulate in plants, such as photomorphogenesis, flowering and abiotic stress response. © 2010 Elsevier Ltd. Source


Georgieva Y.,Max Planck Institute for Molecular Genetics | Konthur Z.,Free University of Berlin
Molecules | Year: 2011

The last decade has seen a steady increase in screening of cDNA expression product libraries displayed on the surface of filamentous bacteriophage. At the same time, the range of applications extended from the identification of novel allergens over disease markers to protein-protein interaction studies. However, the generation and selection of cDNA phage display libraries is subjected to intrinsic biological limitations due to their complex nature and heterogeneity, as well as technical difficulties regarding protein presentation on the phage surface. Here, we review the latest developments in this field, discuss a number of strategies and improvements anticipated to overcome these challenges making cDNA and open reading frame (ORF) libraries more readily accessible for phage display. Furthermore, future trends combining phage display with next generation sequencing (NGS) will be presented. © 2011. Source


Witte C.-P.,Free University of Berlin
Plant Science | Year: 2011

Urea is a plant metabolite derived either from root uptake or from catabolism of arginine by arginase. In agriculture, urea is intensively used as a nitrogen fertilizer. Urea nitrogen enters the plant either directly, or in the form of ammonium or nitrate after urea degradation by soil microbes. In recent years various molecular players of plant urea metabolism have been investigated: active and passive urea transporters, the nickel metalloenzyme urease catalyzing the hydrolysis of urea, and three urease accessory proteins involved in the complex activation of urease. The degradation of ureides derived from purine breakdown has long been discussed as a possible additional metabolic source for urea, but an enzymatic route for the complete hydrolysis of ureides without a urea intermediate has recently been described for Arabidopsis thaliana. This review focuses on the proteins involved in plant urea metabolism and the metabolic sources of urea but also addresses open questions regarding plant urea metabolism in a physiological and agricultural context. The contribution of plant urea uptake and metabolism to fertilizer urea usage in crop production is still not investigated although globally more than half of all nitrogen fertilizer is applied to crops in the form of urea. Nitrogen use efficiency in crop production is generally well below 50% resulting in economical losses and creating ecological problems like groundwater pollution and emission of nitric oxides that can damage the ozone layer and function as greenhouse gasses. Biotechnological approaches to improve fertilizer urea usage bear the potential to increase crop nitrogen use efficiency. © 2010 Elsevier Ireland Ltd. Source


Tawfik A.,Cairo University | Tawfik A.,Free University of Berlin
Indian Journal of Physics | Year: 2012

We have studied the event-by-event dynamical fluctuations of some particle yield ratios at various incident energies. We have assumed that the particle production in the final state is due to chemical equilibrium processes. We have compared the results from the hadron resonance gas (HRG) model with the available experimental data. At energies up to SPS,the HRG model can very well reproduce the experimentally measured fluctuations. To reproduce RHIC results, the quark phase space occupancy parameter is allowed to vary. Furthermore, we have made predictions for the dynamical fluctuations ofstrange and non-strange particle ratios. We have found that the overall energy-dependence is non-monotonic. We have alsofound that the fluctuations strongly depend on the various species of particle ratios. © 2012 IACS. Source


Robertazzi A.,Free University of Berlin
Chemphyschem : a European journal of chemical physics and physical chemistry | Year: 2014

Combination of an electron-rich molecule (e.g. chloride anion or nitrile group) with a chlorinated cyclohexasilane ring produces a supramolecular inverse sandwich complex formed by two guests (Cl(-) or R C≡N) strongly bonded to both faces of a planar host (Si6 ring). In-depth theoretical studies were carried out to investigate the nature of the bonding interactions that generate such a stable complex. Second-order Møller-Plesset perturbation theory (MP2) calculations confirmed that the presence of the Cl substituents is fundamental to the stability of the supramolecular assemblies. The density functional theory (DFT) functional wB97XD gave an estimation of the contribution of dispersion interactions to the binding energy. These interactions become more important as the Cl atoms of the rings are systematically replaced by methyl groups or hydrogen atoms. Analysis of the topology of the electron density and the reduced density gradient gave insight into the binding of the studied supramolecular assemblies. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Bluetongue virus (BTV) can infect most species of domestic and wild ruminants causing substantial morbidity and mortality and, consequently, high economic losses. In 2006, an epizootic of BTV serotype 8 (BTV-8) started in northern Europe that caused significant disease in cattle and sheep before comprehensive vaccination was introduced two years later. Here, we evaluate the potential of equine herpesvirus type 1 (EHV-1), an alphaherpesvirus, as a novel vectored DIVA (differentiating infected from vaccinated animals) vaccine expressing VP2 of BTV-8 alone or in combination with VP5. The EHV-1 recombinant viruses stably expressed the transgenes and grew with kinetics that were identical to those of parental virus in vitro. After immunization of mice, a BTV-8-specific neutralizing antibody response was elicited. In a challenge experiment using a lethal dose of BTV-8, 100% of interferon-receptor-deficient (IFNAR(-/-)) mice vaccinated with the recombinant EHV-1 carrying both VP2 and VP5, but not VP2 alone, survived. VP7 was not included in the vectored vaccines and was successfully used as a DIVA marker. In summary, we show that EHV-1 expressing BTV-8 VP2 and VP5 is capable of eliciting a protective immune response that is distinguishable from that after infection and as such may be an alternative for BTV vaccination strategies in which DIVA compatibility is of importance. Source


Bolhuis J.J.,University Utrecht | Okanoya K.,RIKEN | Okanoya K.,University of Tokyo | Scharff C.,Free University of Berlin
Nature Reviews Neuroscience | Year: 2010

Vocal imitation in human infants and in some orders of birds relies on auditory-guided motor learning during a sensitive period of development. It proceeds from 'babbling' (in humans) and 'subsong' (in birds) through distinct phases towards the full-fledged communication system. Language development and birdsong learning have parallels at the behavioural, neural and genetic levels. Different orders of birds have evolved networks of brain regions for song learning and production that have a surprisingly similar gross anatomy, with analogies to human cortical regions and basal ganglia. Comparisons between different songbird species and humans point towards both general and species-specific principles of vocal learning and have identified common neural and molecular substrates, including the forkhead box P2 (FOXP2) gene. © 2010 Macmillan Publishers Limited. All rights reserved. Source


Koelsch S.,Free University of Berlin
Annals of the New York Academy of Sciences | Year: 2015

This paper describes principles underlying the evocation of emotion with music: evaluation, resonance, memory, expectancy/tension, imagination, understanding, and social functions. Each of these principles includes several subprinciples, and the framework on music-evoked emotions emerging from these principles and subprinciples is supposed to provide a starting point for a systematic, coherent, and comprehensive theory on music-evoked emotions that considers both reception and production of music, as well as the relevance of emotion-evoking principles for music therapy. © 2015 New York Academy of Sciences. Source


Yang H.,University of Southern California | Robinson P.N.,Charite - Medical University of Berlin | Robinson P.N.,Max Planck Institute for Molecular Genetics | Robinson P.N.,Free University of Berlin | Wang K.,University of Southern California
Nature Methods | Year: 2015

Prior biological knowledge and phenotype information may help to identify disease genes from human whole-genome and whole-exome sequencing studies. We developed Phenolyzer (http://phenolyzer.usc.edu), a tool that uses prior information to implicate genes involved in diseases. Phenolyzer exhibits superior performance over competing methods for prioritizing Mendelian and complex disease genes, based on disease or phenotype terms entered as free text. © 2015 Nature America, Inc. Source


Rubin N.,Free University of Berlin
Proceedings - Annual IEEE Symposium on Foundations of Computer Science, FOCS | Year: 2013

Let P be a collection of n points in the plane, each moving along some straight line at unit speed. We obtain an almost tight upper bound of O(n 2+ε), for any ε > 0, on the maximum number of discrete changes that the Delaunay triangulation DT(P) of P experiences during this motion. Our analysis is cast in a purely topological setting, where we only assume that (i) any four points can be co-circular at most three times, and (ii) no triple of points can be collinear more than twice; these assumptions hold for unit speed motions. Copyright © 2013 by The Institute of Electrical and Electronics Engineers, Inc. Source


Raz R.,Leibniz Institute for Molecular Pharmacology | Raz R.,Free University of Berlin | Rademann J.,University of Leipzig | Rademann J.,Leibniz Institute for Molecular Pharmacology
Organic Letters | Year: 2011

tert-Butyl thioesters display an astonishing stability toward secondary amines in basic milieu, in contrast to other alkyl and aryl thioesters. Exploiting this enhanced stability, peptide thioesters were synthesized in a direct manner, applying a tert-butyl thiol linker for Fmoc-based solid-phase peptide synthesis. © 2011 American Chemical Society. Source


Maletz J.,Free University of Berlin
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2014

The Hemichordata are generally interpreted as early deuterostomes, closely related to the chordates, a notion important for modern analyses of the origin of the deuterostomes. Because their fossil record is quite scanty, modern phylogenetic interpretations largely rely on the analysis of DNA of the available extant taxa. The tripartite body plan of the group of worm-like hemichordates, the Enteropneusta, may be traced back in deep time to a few poorly known Middle Cambrian (Series 3, Stage 5) taxa from the Burgess Shale biota. The derived small, colonial or pseudocolonial Pterobranchia (Cephalodiscida and Graptolithina) have a more complete fossil record due to their preservable housing construction, the tubarium. The relationships of fossil taxa, putatively identified as early deuterostomes and possible hemichordates or even as pterobranchs of Lower to Middle Cambrian age (e.g. Galeaplumosus, Herpetogaster), cannot be substantiated. The Pterobranchia and their housing construction are first seen in the Middle Cambrian Series 3, Stage 5 but a clonal, colonial organization of the tubaria can only be recognized in the basal Drumian. The fossil enteropneust Mazoglossus ramsdelli Bardack, 1997 from the Carboniferous Mazon Creek Biota is re-described, its lectotype designated and illustrated for the first time. © 2013 Elsevier B.V. Source


Gonska B.,Free University of Berlin
Discrete and Computational Geometry | Year: 2016

We show that for every simplicial polytope an inscribed simplicial polytope exists that has the same dimension, number of vertices, number of edges, and number of 2-faces. This proves that the g-theorem for simplicial polytopes also holds for the class of inscribed simplicial polytopes (up to dimension 7). The proof includes an incremental construction scheme for Delaunay triangulations. © 2016 Springer Science+Business Media New York Source


Fones H.,Free University of Berlin | Preston G.M.,University of Oxford
FEMS Microbiology Reviews | Year: 2013

Metals play essential roles in many biological processes but are toxic when present in excess. This makes their transport and homoeostatic control of particular importance to living organisms. Within the context of plant-pathogen interactions the availability and toxicity of transition metals can have a substantial impact on disease development. Metals are essential for defensive generation of reactive oxygen species and other plant defences and can be used directly to limit pathogen growth. Metal-based antimicrobials are used in agriculture to control plant disease, and there is increasing evidence that metal hyperaccumulating plants use accumulated metal to limit pathogen growth. Pathogens and hosts compete for available metals, with plants possessing mechanisms to withhold essential metals from invading microbes. Pathogens, meanwhile, use low-metal conditions as a signal to recognise and respond to the host environment. Consequently, metal-sensing systems such as fur (iron) and zur (zinc) regulate the expression of pathogenicity and virulence genes; and pathogens have developed sophisticated strategies to acquire metal during growth in plant tissues, including the production of multiple siderophores. This review explores the impact of transition metals on the processes that determine the outcome of bacterial infection in plants, with a particular emphasis on zinc, iron and copper. This review discusses the pivotal role of transition metals such as zinc, copper and iron in determining the outcome of plant-pathogen interactions, both as essential mineral nutrients for plant and pathogen, and as anti-microbial agents that inhibit pathogen growth. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved. Source


Schwiete G.,Free University of Berlin | Oreg Y.,Weizmann Institute of Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We extend previous theoretical studies of the contribution of fluctuating Cooper pairs to the persistent current in superconducting rings subjected to a magnetic field. For sufficiently small rings, in which the coherence length ξ exceeds the radius R, mean-field theory predicts the emergence of a flux-tuned quantum-critical point separating metallic and superconducting phases near half-integer flux through the ring. For larger rings with Rξ, the transition temperature is periodically reduced but superconductivity prevails at very low temperatures. We calculate the fluctuation persistent current in different regions of the metallic phase for both types of rings. Particular attention is devoted to the interplay of the angular momentum modes of the fluctuating order parameter field. We discuss the possibility of using a combination of different pair-breaking mechanisms to simplify the observation of the flux-tuned transition in rings with ξ>R. © 2010 The American Physical Society. Source


Jetchev N.,Free University of Berlin | Toussaint M.,University of Stuttgart
Autonomous Robots | Year: 2014

Learning complex skills by repeating and generalizing expert behavior is a fundamental problem in robotics. However, the usual approaches do not answer the question of what are appropriate representations to generate motion for a specific task. Since it is time-consuming for a human expert to manually design the motion control representation for a task, we propose to uncover such structure from data-observed motion trajectories. Inspired by Inverse Optimal Control, we present a novel method to learn a latent value function, imitate and generalize demonstrated behavior, and discover a task relevant motion representation. We test our method, called Task Space Retrieval Using Inverse Feedback Control (TRIC), on several challenging high-dimensional tasks. TRIC learns the important control dimensions for the tasks from a few example movements and is able to robustly generalize to new situations. © 2014 Springer Science+Business Media New York. Source


Glockner G.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Glockner G.,Free University of Berlin | Glockner G.,University of Cologne | Noegel A.A.,University of Cologne
Biological Reviews | Year: 2013

Amoeboid life forms can be found throughout the evolutionary tree. The greatest proportion of these life forms is found in the Amoebozoa clade, one of the six major eukaryote evolutionary branches. Despite its common origin this clade exhibits a wide diversity of lifestyles including free-living and parasitic species and species with multicellular and multinucleate life stages. In this group, development, cooperation, and social behaviour can be studied in addition to traits common to unicellular organisms. To date, only a few Amoebozoa genomes have been sequenced completely, however a number of expressed sequence tags (ESTs) and complete and draft genomes have become available recently for several species that represent some of the major evolutionary lineages in this clade. This resource allows us to compare and analyse the evolutionary history and fate of branch-specific genes if properly exploited. Despite the large evolutionary time scale since the emergence of the major groups the genomic organization in Amoebozoa has retained common features. The number of Amoebozoa-specific genetic inventions seems to be rather small. The emergence of subgroups is accompanied by gene and domain losses and acquisitions of bacterial gene material. The sophisticated developmental cycles of Myxogastria and Dictyosteliida likely have a common origin and are deeply rooted in amoebozoan evolution. In this review we describe initial approaches to comparative genomics in Amoebozoa, summarize recent findings, and identify goals for further studies. © 2012 Cambridge Philosophical Society. Source


Malic E.,TU Berlin | Maultzsch J.,TU Berlin | Reich S.,Free University of Berlin | Knorr A.,TU Berlin
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We have performed microscopic calculations of the Rayleigh scattering cross section for arbitrary metallic single-walled carbon nanotubes. The focus of our investigations lies on excitonic effects and their influence on the characteristic features in a Rayleigh scattering spectrum. Our approach is based on density-matrix theory including tight-binding energies, the carrier-light coupling as well as the carrier-carrier interaction. Due to the refractive-index contribution to the scattering cross section, we observe characteristic features in Rayleigh spectra, such as a strong deviation from the Lorentz peak shape and the larger oscillator strength of the lower-lying transition M ii - in the double-peaked structure, independently of the chiral angle and the diameter of the investigated nanotubes. We observe excitonic binding energies in the range of 60-80 meV for metallic nanotubes with diameters of 1.5-2.5 nm. The overlap of the excitonic transition with the close-by continuum has a significant influence on the peak shape and a minor influence on the peak intensity ratios. The presented results are in good agreement with recent experimental data. © 2010 The American Physical Society. Source


Felderer M.,University of Innsbruck | Schieferdecker I.,Free University of Berlin
International Journal on Software Tools for Technology Transfer | Year: 2014

Software testing has often to be done under severe pressure due to limited resources and a challenging time schedule facing the demand to assure the fulfillment of the software requirements. In addition, testing should unveil those software defects that harm the mission-critical functions of the software. Risk-based testing uses risk (re-)assessments to steer all phases of the test process to optimize testing efforts and limit risks of the software-based system. Due to its importance and high practical relevance, several risk-based testing approaches were proposed in academia and industry. This paper presents a taxonomy of risk-based testing providing a framework to understand, categorize, assess, and compare risk-based testing approaches to support their selection and tailoring for specific purposes. The taxonomy is aligned with the consideration of risks in all phases of the test process and consists of the top-level classes risk drivers, risk assessment, and risk-based test process. The taxonomy of risk-based testing has been developed by analyzing the work presented in available publications on risk-based testing. Afterwards, it has been applied to the work on risk-based testing presented in this special section of the International Journal on Software Tools for Technology Transfer. © 2014 Springer-Verlag Berlin Heidelberg. Source


We introduce the software package ReaDDy for simulation of detailed spatiotemporal mechanisms of dynamical processes in the cell, based on reaction-diffusion dynamics with particle resolution. In contrast to other particle-based reaction kinetics programs, ReaDDy supports particle interaction potentials. This permits effects such as space exclusion, molecular crowding and aggregation to be modeled. The biomolecules simulated can be represented as a sphere, or as a more complex geometry such as a domain structure or polymer chain. ReaDDy bridges the gap between small-scale but highly detailed molecular dynamics or Brownian dynamics simulations and large-scale but little-detailed reaction kinetics simulations. ReaDDy has a modular design that enables the exchange of the computing core by efficient platform-specific implementations or dynamical models that are different from Brownian dynamics. Source


Zentek J.,Free University of Berlin
Animal health research reviews / Conference of Research Workers in Animal Diseases | Year: 2011

Medium-chain fatty acids (MCFAs) are found at higher levels in milk lipids of many animal species and in the oil fraction of several plants, including coconuts, palm kernels and certain Cuphea species. Medium-chain triglycerides (MCTs) and fatty acids are efficiently absorbed and metabolized and are therefore used for piglet nutrition. They may provide instant energy and also have physiological benefits beyond their energetic value contributing to several findings of improved performance in piglet-feeding trials. MCTs are effectively hydrolyzed by gastric and pancreatic lipases in the newborn and suckling young, allowing rapid provision of energy for both enterocytes and intermediary hepatic metabolism. MCFAs affect the composition of the intestinal microbiota and have inhibitory effects on bacterial concentrations in the digesta, mainly on Salmonella and coliforms. However, most studies have been performed in vitro up to now and in vivo data in pigs are still scarce. Effects on the gut-associated and general immune function have been described in several animal species, but they have been less studied in pigs. The addition of up to 8% of a non-esterified MCFA mixture in feed has been described, but due to the sensory properties this can have a negative impact on feed intake. This may be overcome by using MCTs, allowing dietary inclusion rates up to 15%. Feeding sows with diets containing 15% MCTs resulted in a lower mortality of newborns and better development, particularly of underweight piglets. In conclusion, MCFAs and MCTs offer advantages for the improvement of energy supply and performance of piglets and may stabilize the intestinal microbiota, expanding the spectrum of feed additives supporting piglet health in the post-weaning period. Source


Zhang Y.J.,Free University of Berlin
Plasmonics | Year: 2011

Efficient conversion of absorbed light to heat energy and strong scattering by gold and silver nanoparticles suggest these nanoparticles as the agents of heating and imaging. Absorption efficiency and scattering efficiency of gold and silver nanoparticles were studied through numerical simulation using the discrete dipole approximation method. This study shows that the size of gold and silver nanoparticles can effect gold and silver nanoparticles' absorption efficiency and scattering efficiency. The gold nanoparticle is found to possess the maximum absorption efficiency when the size of gold nanoparticle is 50 nm and the incident wavelength is 540 nm, and the increasing scattering efficiency with the increasing size of gold nanoparticle in the medium, and refractive index of the medium is around 1.33. However, the silver nanoparticle owns the maximum absorption efficiency when the size of silver nanoparticle is 20 nm and the incident wavelength is 396 nm, and the maximum scattering efficiency when the size of silver nanoparticle is 30 nm and the incident wavelength is 410 nm in the same medium. The conditions for achieving the maximum adsorption efficiency and scattering efficiency of gold and silver nanoparticle can be used for heating and imaging using visible and near-infrared light. © Springer Science+Business Media, LLC.2011. Source


Drenkhahn K.,Free University of Berlin
Behavioral Sciences and the Law | Year: 2013

Secure preventive detention of dangerous offenders has been a major source of debate in German law and practice. Unlike the other two custodial measures of correction and security in the Penal Code (confinement in a psychiatric hospital and in a detoxification clinic), it has served mainly as incapacitation. Judgments by the German Federal Constitutional Court and the European Court of Human Rights challenged this traditional concept of secure preventive detention, which led to a redefinition of the measure. It is now conceived as an offending behavior treatment measure in a secure environment. This article reports on the background of this development and analyzes its implications. © 2013 John Wiley & Sons, Ltd. Source


Salfner F.,Humboldt University of Berlin | Wolter K.,Free University of Berlin
Journal of Systems and Software | Year: 2010

In this paper we investigate the effect of three time-triggered system rejuvenation policies on service availability using a queuing model. The model is formulated as an extended stochastic Petri net using a variety of distributions for times between state changes. We define a metric for steady-state service availability and derive how it can be estimated from the models in a hybrid approach combining simulation and analytical reasoning. We further analyze time-to-failure of systems with rejuvenation. Experiments show that the optimal rejuvenation interval as well as the achievable service availability improvement depend significantly on system utilization. The experiments also show that service availability can deviate significantly from steady-state system availability. For low utilization all rejuvenation policies perform well. For medium utilization, one policy is significantly inferior to the other two, while for high utilization, no rejuvenation should be performed at all. © 2009 Elsevier Inc. Source


Wilrich P.-T.,Free University of Berlin
Accreditation and Quality Assurance | Year: 2010

In analogy to quantitative measurements, the precision of qualitative measurement methods can be characterised by the repeatability standard deviation and the reproducibility standard deviation of the sensitivity. In order to determine these standard deviations, the ISO 5725-2 approach is used. A simulation study and an example demonstrate the advantages of the method. © 2010 Springer-Verlag. Source


Micklitz T.,Free University of Berlin | Levchenko A.,Argonne National Laboratory | Levchenko A.,Michigan State University
Physical Review Letters | Year: 2011

We study the problem of energy relaxation in a one-dimensional electron system. The leading thermalization mechanism is due to three-particle collisions. We show that for the case of spinless electrons in a single channel quantum wire the corresponding collision integral can be transformed into an exactly solvable problem. The latter is known as the Schrödinger equation for a quantum particle moving in a Pöschl-Teller potential. The spectrum for the resulting eigenvalue problem allows for bound-state solutions, which can be identified with the zero modes of the collision integral, and a continuum of propagating modes, which are separated by a gap from the bound states. The inverse gap gives the time scale at which counterpropagating electrons thermalize. © 2011 American Physical Society. Source


Levesque F.,Max Planck Institute of Colloids and Interfaces | Seeberger P.H.,Max Planck Institute of Colloids and Interfaces | Seeberger P.H.,Free University of Berlin
Angewandte Chemie - International Edition | Year: 2012

Malaria is a serious global health issue. Artemisinin combination treatments are the first-line drugs, but supplies are limited because artemisinin is obtained solely by extraction from Artemisia annua. A continuous-flow process that converts dihydroartemisinic acid into artemisinin (see scheme) was shown to be an inexpensive and scalable process that can ensure a steady, affordable supply of artemisinin. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Ahsanullah,Free University of Berlin | Rademann J.,University of Leipzig | Rademann J.,Leibniz Institute for Molecular Pharmacology
Angewandte Chemie - International Edition | Year: 2010

Support and guidance: Azidopeptidyl phosphoranes on a solid support react very efficiently through cyclative cleavage to yield cyclopeptides with an incorporated triazole ring. The solid support is advantageous as cyclization is favored strongly over oligomerization reactions and thus only cyclized products are released. "Chemical equation presented". © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Source


Menzel R.,Free University of Berlin
Journal of Physiology Paris | Year: 2014

The insect mushroom body is a higher order integration center involved in cross-sensory integration and memory formation. The relatively large mushroom bodies of social Hymenoptera (e.g. bees) have been related to the demands of a social system and the neural processes required to allow the animal to navigate in an ever-changing environment. Here I review studies aiming to elucidate the neural processes that take place at the input and the output sites of the mushroom bodies and that underlie cross-sensory integration, associative learning, memory storage and retrieval. Highly processed sensory information is received at modality-specific compartments of the input site, the calyx. The large number of intrinsic neurons of the mushroom body receive multiple sensory inputs establishing combinations of processed sensory stimuli. A matrix-like memory structure characterizes the dendritic area of the intrinsic neurons allowing storage of rich combinations of sensory information. The rather small number of extrinsic neurons read out from multiple intrinsic neurons, thereby losing their sensory coding properties. The response properties of these neurons change according to the value of stimulus combinations experienced. It is concluded that the mushroom bodies transform the highly dimensional sensory coding space into a low dimensional coding space of value-based information. A model of such an experience-dependent recoding device is presented and compared with the available data. © 2014 Elsevier Ltd. Source


Wischnath G.,Peace Research Institute Oslo PRIO | Wischnath G.,Free University of Berlin | Buhaug H.,Peace Research Institute Oslo PRIO
Climatic Change | Year: 2014

Effects of climate change are frequently claimed to be responsible for widespread civil violence. Yet, scientists remain divided on this issue, and recent studies suggest that conflict risk increases with higher rainfall, loss of rainfall, higher temperatures or none of the above. Lack of scientific consensus is driven by differences in data, methods, and samples, but may also reflect a fragile and inconsistent correlation for the habitual spatiotemporal domain, Sub-Saharan Africa post-1980. This study presents a comprehensive, multi-scale empirical evaluation of climate-conflict connections across Asia, the continent with the highest conflict rate per country. We find little evidence that interannual climate variability and anomalies are linked to historical conflict risk in the simple and general manner proposed by some earlier research. Although a significant parameter coefficient can be obtained under certain specifications, the direction and magnitude of the climate effects are inconsistent and sensitive to research design. Instead, Asian civil wars share central features with violent events elsewhere, proving the main correlates of contemporary armed conflict to be economic and socio-political rather than climatological. © 2014 The Author(s). Source


Jiang L.,California Institute of Technology | Pekker D.,California Institute of Technology | Alicea J.,University of California at Irvine | Refael G.,California Institute of Technology | And 2 more authors.
Physical Review Letters | Year: 2011

A junction between two topological superconductors containing a pair of Majorana fermions exhibits a "fractional" Josephson effect, 4π periodic in the superconductors' phase difference. An additional fractional Josephson effect, however, arises when the Majorana fermions are spatially separated by a superconducting barrier. This new term gives rise to a set of Shapiro steps which are essentially absent without Majorana modes and therefore provides a unique signature for these exotic states. © 2011 American Physical Society. Source


Rare codons can influence the stability of messenger RNAs, promote regular spacing of ribosomes on a transcript, or modulate stability and proper folding of nascent proteins. The mRNA specifying the stationary phase master regulator RpoS, which belongs to the RpoD family of sigma factors, contains a high number of rare codons, including many codons at positions corresponding to more frequent codons encoding the same amino acids in the homologous RpoD sequence. Substituting these rare codons in rpoS by the more frequent synonymous rpoD codons resulted in decreased transcript and protein levels compared to the natural rare-codon wildtype version of rpoS. The frequent-codon mutant rpoS transcript exhibited faster turnover than the rare-codon wildtype mRNA. Studies with endoribonuclease-deficient strains revealed RNase E to be crucial for this accelerated mRNA degradation. Thus, in the case of RpoS expression, "less is obviously more", as our data suggest a model, in which slowing down translational speed by ribosomal pausing at many rare codons along a transcript could reduce ribosome spacing and thereby protect the transcript against ribonucleolytic attack by RNase E. Such a mechanism may be especially important for translationally controlled genes like rpoS where the formation of secondary structure in the translational initiation region competes with (therefore relatively inefficient) ribosome loading. Moreover, strong codon differences in genes encoding isoenzymes expressed in exponential and stationary phase suggest that transcript protection by repetitive ribosome pausing at multiple rare codons in stationary phase-expressed transcripts may be a general principle to save resources under nutrient-limited conditions. Source


Gramelsberger G.,Free University of Berlin
Simulation and Gaming | Year: 2011

Meteorology has employed automatic computing machines since the early days of electronic computers. From the 1950s on, a large body of models used for "in silico" experiments (numerical simulation) has been built up, together with an international infrastructure of measuring, modeling, and testing. These outstanding developments- unique in science-led not only to an increasing standardization in developing and applying models but also to deepening the interlinking between modeling and generating evidence. The article explores needs and strategies for evaluating scientific results based on mass data output devices. © 2011 SAGE Publications. Source


Pfluger H.-J.,Free University of Berlin | Duch C.,Arizona State University
Physiology | Year: 2011

Skeletal muscle innervation differs between vertebrates and insects. Insect muscle fibers exhibit graded electrical potentials and are innervated by excitatory, inhibitory, and also neuromodulatory motoneurons. The latter form a unique class of unpaired neurons with bilaterally symmetrical axons that release octopamine to alter the efficacy of synaptic transmission and regulate muscle energy metabolism by activating glycolysis. Octopaminergic neurons that innervate muscles with a high energy demand, for example, flight muscles that move the wings of a locust up and down, are active during rest but are inhibited during flight and its preparatory phase, a jump. Therefore, it is argued that these neurons are involved in providing locusts with the necessary fuel at takeoff, but then may aid the switch to lipid oxidation during flight. In general, the octopaminergic system may switch the whole organism from a tonic to a dynamic state. 2011 Int. Union Physiol. Sci./Am. Physiol. Soc. Source


Animal researchers are increasingly interested in individual differences in behavior. Their interpretation as meaningful differences in behavioral strategies stable over time and across contexts, adaptive, heritable, and acted upon by natural selection has triggered new theoretical developments. However, the analytical approaches used to explore behavioral data still address population-level phenomena, and statistical methods suitable to analyze individual behavior are rarely applied. I discuss fundamental investigative principles and analytical approaches to explore whether, in what ways, and under which conditions individual behavioral differences are actually meaningful. I elaborate the meta-theoretical ideas underlying common theoretical concepts and integrate them into an overarching meta-theoretical and methodological framework. This unravels commonalities and differences, and shows that assumptions of analogy to concepts of human personality are not always warranted and that some theoretical developments may be based on methodological artifacts. Yet, my results also highlight possible directions for new theoretical developments in animal behavior research. © 2011 Wiley Periodicals, Inc. Source


Marciani M.,Leiden University | Brouwer P.W.,Free University of Berlin | Beenakker C.W.J.,Leiden University
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We derive the statistics of the time-delay matrix (energy derivative of the scattering matrix) in an ensemble of superconducting quantum dots with chaotic scattering (Andreev billiards), coupled ballistically to M conducting modes (electron-hole modes in a normal metal or Majorana edge modes in a superconductor). As a first application we calculate the density of states ρ0 at the Fermi level. The ensemble average ©ρ0=δ0-1M[max(0,M+2α/β)]-1 deviates from the bulk value 1/δ0 by an amount depending on the Altland-Zirnbauer symmetry indices α,β. The divergent average for M=1,2 in symmetry class D (α=-1, β=1) originates from the midgap spectral peak of a closed quantum dot, but now no longer depends on the presence or absence of a Majorana zero mode. As a second application we calculate the probability distribution of the thermopower, contrasting the difference for paired and unpaired Majorana edge modes. © 2014 American Physical Society. Source


Gusy B.,Free University of Berlin
Pravention und Gesundheitsforderung | Year: 2010

Objective: Little research has been done on student health in Germany. High well-being scores but risky health behaviors (e.g., substance use) have been stated but are often not linked with the university context. Method: To promote health assessment in Germany that includes the university context, empiric research was reviewed. Results: Best-practice models are based on theoretical models that integrate health indicators as well as personal and university conditions. To assess stress and resources in the university context, new questionnaires were developed and evaluated. Positive and negative aspects of health and personal circumstances were measured by established questionnaires. Conclusions: To promote the health assessment of college students in Germany, the development of instruments and data-based interventions should be continued. © 2010 Springer Medizin Verlag. Source


Liu Z.,Beijing Computational Science Research Center | Liu Z.,CAS Institute of Physics | Bergholtz E.J.,Free University of Berlin
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

The possibility of realizing lattice analogs of fractional quantum Hall (FQH) states, so-called fractional Chern insulators (FCIs), in nearly flat topological (Chern) bands has attracted a lot of recent interest. Here, we make the connection between Abelian as well as non-Abelian FQH states and FCIs more precise. Using a gauge-fixed version of Qi's Wannier basis representation of a Chern band, we demonstrate that the interpolation between several FCI states, obtained by short-range lattice interactions in a spin-orbit-coupled kagome lattice model, and the corresponding continuum FQH states is smooth: the gap remains approximately constant and extrapolates to a finite value in the thermodynamic limit, while the low-lying part of the orbital entanglement spectrum remains qualitatively unaltered. The orbital entanglement spectra also provide a first glimpse of the edge physics of FCIs via the bulk-boundary correspondence. Corroborating these results, we find that the squared overlaps between the FCI and FQH ground states are as large as 98.7% for the 8-electron Laughlin state at ν=13 (consistent with an earlier study) and 97.8% for the 10-electron Moore-Read state at ν=12. For the bosonic analogs of these states, the adiabatic continuity is also shown to hold, albeit with somewhat smaller associated overlaps, etc. Although going between the Chern bands to the Landau-level problem is often smooth, we show that this is not always the case by considering fermions at filling fraction ν=45, where the interpolation between Hamiltonians describing the two systems results in a phase transition. © 2013 American Physical Society. Source


Slaby J.,Free University of Berlin
Journal of Consciousness Studies | Year: 2013

We propose an action-oriented understanding of emotion. Emotions are modifications of a basic form of goal-oriented striving characteristic of human life. They are appetitive orientations: pursuits of the good, avoidances of the bad. Thus, emotions are not truly distinct from, let alone opposed to, actions - as erroneously suggested by the classical understanding of emotions as 'passions'. In the present paper, we will outline and defend this broadly enactive approach and motivate its main claims. Our proposal gains plausibility from a literature- and interview-based investigation of emotional changes characteristic of clinical depression. Much narrative evidence from patient reports points towards the conclusion that many of those changes might result from a catastrophic alteration of the basic form of goal-pursuit at the root of human emotionality. The experience of profound depression could in this respect be a kind of inverted image of non-pathological emotionality - a highly unnatural passivity, giving rise to a profound - and quite horrifying - sense of incapacity. Source


Svoboda J.,Academy of Sciences of the Czech Republic | Fischer F.D.,University of Leoben | Abart R.,Free University of Berlin
Acta Materialia | Year: 2010

In many multi-component systems, phases can be considered stoichiometric. If two phases not stably coexisting are brought into contact, multiple new phases may nucleate at the interface and develop into a sequence of layers with different phase compositions, which grow between the original phases. Inert markers at the original contact may show "splitting" of the marker (Kirkendall) plane, called polyfurcation. Nearly exclusively binary systems have been studied theoretically or experimentally. A thermodynamic model for the kinetics of diffusional phase transformation in multi-component systems and motion of the polyfurcated Kirkendall plane is derived by the thermodynamic extremal principle. The degrees of freedom of the system are discussed rigorously. The model is demonstrated on simulations of kinetics in binary three-phase and ternary four-phase systems. © 2010 Acta Materialia Inc. Source


Gruber C.,Free University of Berlin | Luongo O.,University of Naples Federico II | Luongo O.,National Institute of Nuclear Physics, Italy | Luongo O.,National Autonomous University of Mexico
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Cosmography is used in cosmological data processing in order to constrain the kinematics of the universe in a model-independent way, providing an objective means to evaluate the agreement of a model with observations. In this paper, we extend the conventional methodology of cosmography employing Taylor expansions of observables by an alternative approach using Padé approximations. Due to the superior convergence properties of Padé expansions, it is possible to improve the fitting analysis to obtain numerical values for the parameters of the cosmographic series. From the results, we can derive the equation of state parameter of the universe and its first derivative and thus acquire information about the thermodynamic state of the universe. We carry out statistical analyses using observations of the distance modulus of type 1a supernovae, provided by the union 2.1 compilation of the supernova cosmology project, employing a Markov chain Monte Carlo approach with an implemented Metropolis algorithm. We compare the results of the original Taylor approach to the newly introduced Padé formalism. The analyses show that experimental data constrain the observable universe well, finding an accelerating universe and a positive jerk parameter. We demonstrate that the Padé convergence radii are greater than standard Taylor convergence radii, and infer a lower limit on the acceleration of the universe solely by requiring the positivity of the Padé expansion. We obtain fairly good agreement with the Planck results, confirming the ΛCDM model at small redshifts, although we cannot exclude a dark energy density varying in time with negligible speed of sound. © 2014 American Physical Society. Source


Peschel I.,Free University of Berlin | Eisler V.,University of Vienna
Journal of Physics A: Mathematical and Theoretical | Year: 2012

We consider fermionic and bosonic quantum chains where a defect separates two subsystems and compare the corresponding entanglement spectra. With these, we calculate their Rényi entanglement entropies and obtain analytical formulae for the continuously varying coefficient of the leading logarithmic term. For the bosonic case we also present numerical results. © 2012 IOP Publishing Ltd. Source


Stein C.,Free University of Berlin | Baerwald C.,University of Leipzig
Expert Opinion on Pharmacotherapy | Year: 2014

Introduction: Centrally acting opioids are well established in the treatment of acute, surgical and cancer pain. However, their use in chronic noncancer pain (CNCP) is controversial because of side effects such as tolerance, somnolence, respiratory depression, confusion, constipation and addiction. Chronic arthritis and other musculoskeletal diseases are among the leading causes of CNCP. Areas covered: This manuscript will discuss the role of conventional opioids in chronic arthritis. In addition, future developments and strategies exploiting peripheral effects of opioids on pain and inflammation will be outlined. Expert opinion: Aims in drug development include the design of peripherally restricted opioid agonists, selective targeting of endogenous opioids to sites of painful injury and the augmentation of peripheral ligand and receptor synthesis, for example, by gene therapy. Although a large number of peripherally acting opioid compounds have been developed, clinical Phase III studies have not been published so far. Another strategy is to augment the effects of endogenously released opioid peptides by the inhibition of their degrading enzymes. Technology-oriented research is needed to find novel ways of peripheral restriction of opioids. Such analgesics would be desirable for their lack of central side effects and of adverse effects typical of nonsteroidal anti-inflammatory drugs (gastrointestinal ulcers, bleeding, myocardial infarction and stroke). © Informa UK, Ltd. Source


Janicke M.,Free University of Berlin
Energy Policy | Year: 2012

There are many questionable assumptions in the discussion of economic growth. One of them is the idea that governments are able to achieve sustained high growth. Another one is the believe that the solution to pressing financial and social problems centers on higher growth. It is also questionalble, however, to say that giving up on economic growth as a paradigm is the necessary condition to tackle the environmental crisis. In actuality, solving such problems is about radical growth in environmental and resource-saving technologies. It is also about radical "de-growth" in products and processes that undermine long-term living and production conditions. This paper describes some best practice cases of "green growth" and the conceptual generalisations given by the OECD and other established institutions in Europe and Asia. It traces the transformation of the concept of "green growth" and evaluates the strategy that accompanies it. © 2012 Elsevier Ltd. Source


An overview of the established developmental models of antisocial behavior in children and adolescents is presented. Most of the established developmental models (e. g., by Patterson, Moffitt, or Loeber) consider - at least - an early-starter and a late-starter pathway. Additionally, several other pathways limited to childhood or adulthood have been suggested. Several recently conducted studies have revealed results which make a critical discussion and revision of the established developmental models necessary. The developmental models are summarized and results from recently conducted studies are discussed with regard to their implications for intervention and prevention strategies. © Hogrefe Verlag, Göttingen 2010. Source


Sommer C.,Free University of Berlin
Bioacoustics | Year: 2011

Potential predators elicit alarm calls in many birds and mammals. The context-specific occurrence of acoustically distinct alarm call types may allow conclusions about their functions and/or the underlying call system. Furthermore, many group-living species exhibit a co-operative system of vigilance in terms of predator avoidance. In a descriptive field study I investigated alarm calling and sentinel activity in group-living Arabian Babblers Turdoides squamiceps focussing on the context-specificity of call type occurrence in relation to the caller's behaviour. The results revealed that two of the three different alarm call types were correlated to the distance to the predator: Barks were uttered more frequently to distant and tzwicks to close predators. Sentinels were more likely to utter barks and trills, but foraging group members tzwicks. Results suggest that sentinels detect potential dangers in greater distances and start calling earlier, whereas foraging birds detect predators only closer and therefore utter higher urgency calls. Finally, the results added to the current knowledge of the urgency-based call system of Arabian babblers, in which information can be provided on different levels: Variation in the call structure of single call types, combined use of different call types and discrete use of different call types in different contexts. © 2011 AB Academic Publishers. Source


Horenko I.,Free University of Berlin
Dynamics of Atmospheres and Oceans | Year: 2010

A method for clustering of multidimensional non-stationary meteorological time series is presented. The approach is based on optimization of the regularized averaged clustering functional describing the quality of data representation in terms of several regression models and a metastable hidden process switching between them. Proposed numerical clustering algorithm is based on application of the finite element method (FEM) to the problem of non-stationary time series analysis. The main advantage of the presented algorithm compared to Hidden Markov Models (HMMs) and to finite mixture models is that no a priori assumptions about the probability model for the hidden and observed processes (e.g., Markovianity or stationarity) are necessary for the proposed method. Another attractive numerical feature of the discussed algorithm is the possibility to choose the optimal number of metastable clusters and a natural opportunity to control the fuzziness of the resulting decomposition a posteriory, based on the statistical distinguishability of the resulting persistent cluster states. The resulting FEM-K-trends algorithm is compared with some standard fuzzy clustering methods on toy model examples and on analysis of multidimensional historical temperature data locally in Europe and on the global temperature data set. © 2009 Elsevier B.V. All rights reserved. Source


Kuwert P.,University of Greifswald | Knaevelsrud C.,Free University of Berlin | Pietrzak R.H.,Yale University
American Journal of Geriatric Psychiatry | Year: 2014

Objectives: This study examined the current prevalence, and demographic, military, health, and psychosocial correlates of loneliness in a contemporary nationally representative sample of older U.S. veterans. Methods: Two thousand twenty-five veterans aged 60 years and older participated in the National Health and Resilience in Veterans Study. Loneliness was assessed using a questionnaire adapted from the Revised UCLA Loneliness Scale. A broad range of demographic, military, health, and psychosocial variables was also assessed. Results: 44% of veterans reported feeling lonely at least some of the time (10.4% reported often feeling lonely). Greater age, disability in activities of daily living, lifetime traumas, perceived stress, and current depressive and post-traumatic stress disorder symptoms were positively associated with loneliness, and being married/cohabitating, higher income, greater subjective cognitive functioning, social support, secure attachment, dispositional gratitude, and frequency of attending religious services were negatively associated with loneliness. The largest magnitude associations were observed for perceived social support, secure attachment style, and depressive symptoms. Conclusions: Loneliness is prevalent among older veterans in the United States, and associated with several health and psychosocial variables. These results suggest that multifactorial interventions that emphasize bolstering of social support and reduction of depressive symptoms may help mitigate loneliness in the rapidly growing population of older veterans. © 2014 American Association for Geriatric Psychiatry. Source


Nishimura K.,Free University of Berlin
Energy, Sustainability and Society | Year: 2012

Background: This article examines the policymaking process of Ontario's Green Energy Act (GEA) which enabled the introduction of the first comprehensive feed-in tariff (FIT) in North America. The FIT, which is a payback system for renewable energy (RE) producers, was implemented in order to make Ontario a Green Leader in North America. This article analyzes this process through a consideration of the role played by grassroots action. Methods: The Green Energy Act Alliance (GEAA) succeeded in the implementation of the GEA. Using Lober's collaborative window, this article explores factors that led to the realization of the FIT. The conclusion will show that the GEAA succeeded in opening the collaborative window, even though the model's prerequisites were not completely fulfilled, namely there was a lack of public awareness. Results: The diffusion of innovation theory helps us to understand this, with regard to the GEAA's strategy. The policymakers had recognized the importance of RE but had not yet been motivated to develop RE generating capacity in the region. The GEAA changed their opinion by showing the success of the FIT in Europe in boosting the economy. Conclusions: After the European study tour, the Minister of Energy, George Smitherman, as one of the important policymakers, started to support the GEA, and this was the key factor leading to the introduction of the FIT, despite a lack of public awareness. © 2012 Nishimura; licensee Springer. Source


Mez L.,Free University of Berlin
Wiley Interdisciplinary Reviews: Energy and Environment | Year: 2012

Since the report of Club of Rome, 'The Limits to Growth', the exhaustion of fossil energy sources has been under discussion. Coal, oil, and gas-and energy technologies relying upon them-will be exhausted in the future. High expectations for nuclear energy have given way to the insight that nuclear fission is at best a bridging technology. The risks of this technology became apparent by nuclear catastrophes such as Chernobyl and Fukushima, and uranium resources are limited. Furthermore, fast breeder technology has failed and fourth generation reactors are still pure fiction. Before the industrial revolution, nearly all energy demands were supplied by renewable energy worldwide. From the beginning of the nineteenth century, fossil fuel was used in a steadily increasing amount for heating, lighting, transport, and other energy purposes. Electricity as scientific form of energy played an important role in the transformation of agricultural to industrial societies. Electricity systems are the basic infrastructure of modern societies, influencing the industrial organization, the degree of automation, the communication system, and the industrial future. Today the electrical power industry is at a crossroads, last but not least for environmental reasons. Beside the large cathedrals of electricity generation, other types of generation technologies, each of which brings totally different social relations between energy producers and consumers, have a historical chance to emerge. The solar age will replace the fossil and the nuclear age sooner or later. This transformation is not only a technical and economic, but also a social and political problem. © 2012 John Wiley & Sons, Ltd. Source


Mez L.,Free University of Berlin
Energy Policy | Year: 2012

For the future of nuclear power it will be decisive whether or not nuclear fission technologies offer a sustainable solution to global energy problems. The impressive expansion of nuclear reactors in the 1960s and 1970 slowed down after the meltdown in Harrisburg and the nuclear explosion in Chernobyl. Since the end of the 1980s installed nuclear capacity has stagnated, and in Europe declined. However, a nuclear revival or renaissance has been predicted for 30 years. This article reviews global scenarios and national nuclear programmes and analyses problems in the nuclear industry. Special attention is given to nuclear power and global warming and the nexus between nuclear power and nuclear proliferation. © 2012 Elsevier Ltd. Source


Schwemmer T.,Humboldt University of Berlin | Schwemmer T.,Free University of Berlin | Baumgartner J.,Max Planck Institute of Colloids and Interfaces | Faivre D.,Max Planck Institute of Colloids and Interfaces | Borner H.G.,Humboldt University of Berlin
Journal of the American Chemical Society | Year: 2012

The peptide-mediated functionalization of inorganic particle surfaces is demonstrated on gadolinium oxide (GdO) particles, revealing specific means to functionalize nano- or microparticles. Phage display screening is exploited to select 12mer peptides, which exhibit sequence-specific adhesion onto surfaces of GdO particles. These peptide adhesion domains are exploited to effectively decorate GdO particles with fluorescently labeled poly(ethylene oxide) (PEO), proving to result in a stable surface modification as shown by significant reduction of protein adsorption by 80%, compared to nonfunctionalized particles. Peptide adhesion and stability of the noncovalent coating are investigated by adsorption/elution experiments and Langmuir isotherms. Fluorescence microscopy, contact angle, and energy dispersive X-ray (EDX) measurements confirmed the sequence specificity of the interactions by comparing adhesion sequences with scrambled peptide sequences. Noncovalent, but specific modification of inorganic particle surfaces represents a generic strategy to modulate functionality and function of nano- or microparticle surfaces. © 2011 American Chemical Society. Source


Schreurs M.A.,Free University of Berlin
Energy Policy | Year: 2012

The slow pace of progress in the international climate negotiations is contrasted by the dynamic changes occurring on the ground as competition among countries for green technology leadership heats up. China, Germany, Japan, and the United States all exhibit interest in being green technology leaders although the United States could fall behind due to lack of strong federal government support for climate action. © 2012 Elsevier Ltd. Source


Krumnow C.,Free University of Berlin | Pelster A.,Bielefeld University | Pelster A.,University of Duisburg - Essen
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

A homogeneous polarized dipolar Bose-Einstein condensate is considered in the presence of weak quenched disorder within mean-field theory at zero temperature. By first solving perturbatively the underlying Gross-Pitaevskii equation and then performing disorder ensemble averages for physical observables, it is shown that the anisotropy of the two-particle interaction is passed on to both the superfluid density and the sound velocity. © 2011 American Physical Society. Source


Bredtmann T.,Universite de Sherbrooke | Bredtmann T.,Free University of Berlin | Chelkowski S.,Universite de Sherbrooke | Bandrauk A.D.,Universite de Sherbrooke
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

A pump-probe scheme for preparing and monitoring electron-nuclear motion in a dissociative coherent electron-nuclear wave packet is explored from numerical solutions of a non-Born-Oppenheimer time-dependent Schrödinger equation. A mid-ir intense few-cycle probe pulse is used to generate molecular high-order-harmonic generation (MHOHG) from a coherent superposition of two or more dissociative coherent electronic-nuclear wave packets, prepared by a femtosecond uv pump pulse. Varying the time delay between the intense ir probe pulse and the uv pump pulse by a few hundreds of attoseconds, the MHOHG signal intensity is shown to vary by orders of magnitude, thus showing the high sensitivity to electron-nuclear dynamics in coherent electron-nuclear wave packets. We relate this high sensitivity of MHOHG spectra to opposing electron velocities (fluxes) in the electron wave packets of the recombining (recolliding) ionized electron and of the bound electron in the initial coherent superposition of two electronic states. © 2011 American Physical Society. Source


Lima A.R.P.,Free University of Berlin | Pelster A.,University of Duisburg - Essen
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We investigate the influence of quantum fluctuations upon dipolar Bose gases by means of the Bogoliubov-de Gennes theory. Thereby, we make use of the local density approximation to evaluate the dipolar exchange interaction between the condensate and the excited particles. This allows to obtain the Bogoliubov spectrum analytically in the limit of large particle numbers. After discussing the condensate depletion and the ground-state energy correction, we derive quantum-corrected equations of motion for harmonically trapped dipolar Bose gases by using superfluid hydrodynamics. These equations are subsequently applied to analyze the equilibrium configuration, the low-lying oscillation frequencies, and the time-of-flight dynamics. We find that both atomic magnetic and molecular electric dipolar systems offer promising scenarios for detecting beyond mean-field effects. © 2011 American Physical Society. Source


Bonthuis D.J.,TU Munich | Gekle S.,TU Munich | Netz R.R.,Free University of Berlin
Physical Review Letters | Year: 2011

The framework for deriving tensorial interfacial dielectric profiles from bound charge distributions is established and applied to molecular dynamics simulations of water at hydrophobic and hydrophilic surfaces. In conjunction with a modified Poisson-Boltzmann equation, the trend of experimental double-layer capacitances is well reproduced. We show that the apparent Stern layer can be understood in terms of the dielectric profile of pure water. © 2011 American Physical Society. Source


Imhof P.,Free University of Berlin
Methods in Enzymology | Year: 2016

Modeling enzymatic reactions is a demanding task due to the complexity of the system, the many degrees of freedom involved and the complex, chemical, and conformational transitions associated with the reaction. Consequently, enzymatic reactions are not determined by precisely one reaction pathway. Hence, it is beneficial to obtain a comprehensive picture of possible reaction paths and competing mechanisms. By combining individually generated intermediate states and chemical transition steps a network of such pathways can be constructed. Transition networks are a discretized representation of a potential energy landscape consisting of a multitude of reaction pathways connecting the end states of the reaction. The graph structure of the network allows an easy identification of the energetically most favorable pathways as well as a number of alternative routes. © 2016 Elsevier Inc. Source


Erbas A.,Free University of Berlin | Erbas A.,TU Munich | Netz R.R.,University of North Carolina at Chapel Hill
Biophysical Journal | Year: 2013

Friction within globular proteins or between adhering macromolecules crucially determines the kinetics of protein folding, the formation, and the relaxation of self-assembled molecular systems. One fundamental question is how these friction effects depend on the local environment and in particular on the presence of water. In this model study, we use fully atomistic MD simulations with explicit water to obtain friction forces as a single polyglycine peptide chain is pulled out of a bundle of k adhering parallel polyglycine peptide chains. The whole system is periodically replicated along the peptide axes, so a stationary state at prescribed mean sliding velocity V is achieved. The aggregation number is varied between k = 2 (two peptide chains adhering to each other with plenty of water present at the adhesion sites) and k = 7 (one peptide chain pulled out from a close-packed cylindrical array of six neighboring peptide chains with no water inside the bundle). The friction coefficient per hydrogen bond, extrapolated to the viscous limit of vanishing pulling velocity V/0, exhibits an increase by five orders of magnitude when going from k = 2 to k = 7. This dramatic confinement-induced friction enhancement we argue to be due to a combination of water depletion and increased hydrogen-bond cooperativity. © 2013 by the Biophysical Society. Source


Stein C.,Free University of Berlin | Stein C.,Helmholtz Virtual Institute
Annual Review of Medicine | Year: 2016

Opioids are the oldest and most potent drugs for the treatment of severe pain. Their clinical application is undisputed in acute (e.g., postoperative) and cancer pain, but their long-term use in chronic pain has met increasing scrutiny. This article reviews mechanisms underlying opioid analgesia and other opioid actions. It discusses the structure, function, and plasticity of opioid receptors; the central and peripheral sites of analgesic actions and side effects; endogenous and exogenous opioid receptor ligands; and conventional and novel opioid compounds. Challenging clinical situations, such as the tension between chronic pain and addiction, are also illustrated. © 2016 by Annual Reviews. Source


Ghabour M.,Free University of Berlin | Pelster A.,University of Kaiserslautern
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We consider a dilute homogeneous Bose gas with both an isotropic short-range contact interaction and an anisotropic long-range dipole-dipole interaction in a weak random potential at low temperature in three dimensions. Within the realm of Bogoliubov theory, we analyze how both condensate and superfluid are depleted due to quantum and thermal fluctuations as well as disorder fluctuations. © 2014 American Physical Society. Source


Steinigeweg R.,TU Braunschweig | Khodja A.,University of Osnabruck | Niemeyer H.,University of Osnabruck | Gogolin C.,Free University of Berlin | Gemmer J.,University of Osnabruck
Physical Review Letters | Year: 2014

In the ongoing discussion on thermalization in closed quantum many-body systems, the eigenstate thermalization hypothesis has recently been proposed as a universal concept and has attracted considerable attention. So far this concept is, as the name states, hypothetical. The majority of attempts to overcome this hypothetical character are based on exact diagonalization, which implies for, e.g., spin systems a limitation of roughly 15 spins. In this Letter we present an approach that pushes this limit up to system sizes of roughly 35 spins, thereby going significantly beyond what is possible with exact diagonalization. A concrete application to a Heisenberg spin ladder which yields conclusive results is demonstrated. © 2014 American Physical Society. Source


Herbst F.,Martin Luther University of Halle Wittenberg | Seiffert S.,Helmholtz Center Berlin | Seiffert S.,Free University of Berlin | Binder W.H.,Martin Luther University of Halle Wittenberg
Polymer Chemistry | Year: 2012

Mono- and bifunctional supramolecular poly(isobutylene)s (PIBs) bearing hydrogen-bonding motifs (barbituric acid or a Hamilton wedge) are prepared by a combination of living carbocationic polymerization (LCCP) and azide-alkyne "click" reactions to investigate their dynamics and self-healing behaviour. Barbituric acid (7) or Hamilton wedge (8) functionalized polymers (3a-c, 4a-d, 5a-c, 6a) with molecular weights of ∼3000 up to 30000 g mol -1 exhibit complete end group transformation as proven by NMR and MALDI methods. Temperature-dependent rheology in the melt reveals thermoreversible formation of supramolecular clusters. Stoichiometric mixing of the polymers by solution blending affects the extent of clustering by specifically interacting barbituric acid/Hamilton wedge moieties. Frequency-dependent measurements on bifunctional barbituric acid functionalized PIBs reveal a strong rubbery plateau and terminal flow, caused by the formation of dynamically bridged clusters. In addition, fluorescence recovery after photobleaching (FRAP) measurements on the same supramolecular polymers reveal a multitude of different chain dynamics. Small discs of these polymers show self-healing at room temperature after being cut and brought into contact at the fractured surface. © 2012 The Royal Society of Chemistry. Source


Zilberberg O.,Weizmann Institute of Science | Romito A.,Karlsruhe Institute of Technology | Romito A.,Free University of Berlin | Gefen Y.,Weizmann Institute of Science
Physical Review Letters | Year: 2011

A protocol employing weak values (WVs) to obtain ultrasensitive amplification of weak signals in the context of a solid-state setup is proposed. We consider an Aharonov-Bohm interferometer where both the orbital and the spin degrees of freedom are weakly affected by the presence of an external charge to be detected. The interplay between the spin and the orbital WVs leads to a significant amplification even in the presence of finite temperature, voltage, and external noise. © 2011 American Physical Society. Source


Lehmann S.,RWTH Aachen | Seiffert S.,Helmholtz Center Berlin | Seiffert S.,Free University of Berlin | Richtering W.,RWTH Aachen
Journal of the American Chemical Society | Year: 2012

Thermosensitive composite hydrogels that consist of a poly(acrylamide) hydrogel matrix with embedded micrometer-sized poly(N-isopropylacrylamide) microgel beads are promising models for complex, heterogeneous gels. We investigate the coupling of the microgel beads with the gel matrix and the formation of interpenetrating networks inside the microgels by confocal two-focus fluorescence correlation spectroscopy (2fFCS). This technique serves to study the effects of the heterogeneous structure of the composite hydrogels on the diffusive mobility of nanoscopic dextran tracers within the gels. Our investigations reveal that the formation of interpenetrating networks inside the embedded microgel beads depends on their cross-link density: whereas interpenetrating networks are formed inside weakly cross-linked beads, they are not formed inside strongly cross-linked beads. If the formation of interpenetrating networks occurs, the temperature-dependent swelling and deswelling of the beads is obstructed. In addition, the mobility of dextran tracers inside the embedded microgel beads is hindered compared to those in free beads and in the surrounding gel matrix. Surprisingly, the surrounding poly(acrylamide) hydrogel matrix swells inhomogeneously when the embedded poly(N-isopropylacrylamide) beads collapse upon heating. This indicates the formation of pores near the surface of the collapsed beads, offering promising means to tailor composite hydrogels for applications as membranes with tunable permeability. Our experiments also demonstrate the utility of 2fFCS to study spatially resolved diffusion in complex environments, which is of great interest in biomaterials research. © 2012 American Chemical Society. Source


Brembs B.,Free University of Berlin
Proceedings of the Royal Society B: Biological Sciences | Year: 2011

Until the advent of modern neuroscience, free will used to be a theological and a metaphysical concept, debated with little reference to brain function. Today, with ever increasing understanding of neurons, circuits and cognition, this concept has become outdated and any metaphysical account of free will is rightfully rejected. The consequence is not, however, that we become mindless automata responding predictably to external stimuli. On the contrary, accumulating evidence also from brains much smaller than ours points towards a general organization of brain function that incorporates flexible decisionmaking on the basis of complex computations negotiating internal and external processing. The adaptive value of such an organization consists of being unpredictable for competitors, prey or predators, as well as being able to explore the hidden resource deterministic automats would never find. At the same time, this organization allows all animals to respond efficiently with tried-and-tested behaviours to predictable and reliable stimuli. As has been the case so many times in the history of neuroscience, invertebrate model systems are spearheading these research efforts. This comparatively recent evidence indicates that one common ability of most if not all brains is to choose among different behavioural options even in the absence of differences in the environment and perform genuinely novel acts. Therefore, it seems a reasonable effort for any neurobiologist to join and support a rather illustrious list of scholars who are trying to wrestle the term 'free will' from its metaphysical ancestry. The goal is to arrive at a scientific concept of free will, starting from these recently discovered processes with a strong emphasis on the neurobiological mechanisms underlying them. © 2010 The Royal Society. Source


Klein R.,Free University of Berlin
Annual Review of Fluid Mechanics | Year: 2010

Atmospheric flows feature length scales from 10-5 to 10 5 m and timescales from microseconds to weeks or more. For scales above several kilometers and minutes, there is a natural scale separation induced by the atmosphere's thermal stratification, together with the influences of gravity and Earth's rotation, and the fact that atmospheric-flow Mach numbers are typically small. A central aim of theoretical meteorology is to understand the associated scale-specific flow phenomena, such as internal gravity waves, baroclinic instabilities, Rossby waves, cloud formation and moist convection, (anti-)cyclonic weather patterns, hurricanes, and a variety of interacting waves in the tropics. Single-scale asymptotics yields reduced sets of equations that capture the essence of these scale-specific processes. For studies of interactions across scales, techniques of multiple-scales asymptotics have received increasing recognition in recent years. This article recounts the most prominent scales and associated scale-dependent models and summarizes recent multiple-scales developments. Copyright © 2010 by Annual Reviews. All rights reserved. Source


Mayer M.,Free University of Berlin
Theoretical Criminology | Year: 2010

While in broad agreement about the growing importance of workfare and punitive tendencies in contemporary politics, this article raises four questions about Wacquant's model of a neoliberal state. Besides pointing out the fuzzy definition of the target group of punitive regulation, it questions whether penal containment is generalizable as 'core' of the neoliberal state. Third, it critiques the selective treatment of contemporary poverty policies (excluding a variety of, for example, activating, neoliberal policies), built on a skewed view of the transition from a supposedly generous 'nanny state' to a strict 'daddy state'. Fourth, it challenges the claim of 'overall fitness' of punitive containment of urban marginality and the absence of agency and contradictions from the model. © The Author(s), 2010. Source


Breuer F.,Free University of Berlin
Discrete and Computational Geometry | Year: 2010

Let μ 1,...,μ n be continuous probability measures on ℝ n and α 1,...,α n∈[0,1]. When does there exist an oriented hyperplane H such that the positive half-space H + has μ i(H +)=α i for all i∈[n]? It is well known that such a hyperplane does not exist in general. The famous Ham Sandwich Theorem states that if α i=1/2 for all i, then such a hyperplane always exists. In this paper we give sufficient criteria for the existence of H for general α i∈[0,1]. Let f 1,...,f n:S n-1→ℝ n denote auxiliary functions with the property that for all i, the unique hyperplane H i with normal v that contains the point f i(v) has μ i(H i +)=α i. Our main result is that if Im f 1,...,Im f n are bounded and can be separated by hyperplanes, then there exists a hyperplane H with μ i(H +)=α i for all i. This gives rise to several corollaries; for instance, if the supports of μ 1,...,μ n are bounded and can be separated by hyperplanes, then H exists for any choice of α 1,...,α n∈[0,1]. We also obtain results that can be applied if the supports of μ 1,...,μ n overlap. © 2009 Springer Science+Business Media, LLC. Source


Janicke M.,Free University of Berlin
Journal of Cleaner Production | Year: 2012

This article explores the governmental means to accelerate technical progress in climate protection. It is based on selected "best practice" cases in which the diffusion of low-carbon technologies has been accelerated by ambitious policies. The empirical cases involve not just renewable energies, but also energy efficiency (the latter being considered more difficult in terms of governance). The examples are taken from advanced OECD countries as well as from emerging economies. This article will explore, which factors have caused this dynamic development. The conclusion reached will show that the interaction of positive feedback mechanisms - which has already been described as "virtuous cycle" - provides only a plausible theoretical explanation, if the policy cycle is added to the market cycle and the innovation cycle. Climate policy should not only define ambitious targets but also address all three feedback mechanisms. © 2011 Elsevier Ltd. All rights reserved. Source


Anish C.,Max Planck Institute of Colloids and Interfaces | Guo X.,Max Planck Institute of Colloids and Interfaces | Wahlbrink A.,Max Planck Institute of Colloids and Interfaces | Seeberger P.H.,Max Planck Institute of Colloids and Interfaces | Seeberger P.H.,Free University of Berlin
Angewandte Chemie - International Edition | Year: 2013

The sugar coat of "Black Death" betrays it. The plague can be detected by monoclonal anti-carbohydrate antibodies. In a new technique, a plague-specific oligosaccharide antigen (see structure) is synthesized. With the help of lipopolysaccharide (LPS)-specific monoclonal antibodies (mAbs), the presence of the plague pathogen Yersinia pestis can then be detected in serum from patients by using a glycan microarray. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Hahn J.,Free University of Berlin
PloS one | Year: 2013

Giardiasis, a gastrointestinal disease caused by Giardia duodenalis, is currently treated mainly with nitroimidazoles, primarily metronidazole (MTZ). Treatment failure rates of up to 20 percent reflect the compelling need for alternative treatment options. Here, we investigated whether orlistat, a drug approved to treat obesity, represents a potential therapeutic agent against giardiasis. We compared the growth inhibitory effects of orlistat and MTZ on a long-term in vitro culture adapted G. duodenalis strain, WB-C6, and on a new isolate, 14-03/F7, from a patient refractory to MTZ treatment using a resazurin assay. The giardiacidal concentration of the drugs and their combined in vitro efficacy was determined by median-effect analysis. Morphological changes after treatment were analysed by light and electron microscopy. Orlistat inhibited the in vitro growth of G. duodenalis at low micromolar concentrations, with isolate 14-03/F7 (IC50(24h) = 2.8 μM) being more sensitive than WB-C6 (IC50(24h) = 6.2 μM). The effect was significantly more potent compared to MTZ (IC50(24h) = 4.3 μM and 11.0 μM, respectively) and led to specific undulated morphological alterations on the parasite surface. The giardiacidal concentration of orlistat was >14 μM for 14-03/F7 and >43 μM for WB-C6, respectively. Importantly, the combination of both drugs revealed no interaction on their inhibitory effects. We demonstrate that orlistat is a potent inhibitor of G. duodenalis growth in vitro and kills parasites at concentrations achievable in the gut by approved treatment regimens for obesity. We therefore propose to investigate orlistat in controlled clinical studies as a new drug in giardiasis. Source


Baberschke K.,Free University of Berlin
Journal of Physics: Conference Series | Year: 2011

Both techniques went different routes: The EPR explored an enormous variety of paramagnets in solids, liquids, and gas phase. The focus was to determine orbital- and spin-magnetic moments (g-tensor), hyperfine interactions, and from the linewidth the spin dynamics (T 1, T 2 relaxation). In FMR most of the experiments and theory assumed the total value M to be constant in the equation of motion and used only one effective damping parameter (Gilbert). This is an enormous, unnecessary limitation for today's analysis of magnetism in nanostructures and ultrathin films. To assume M = const ignores spin wave excitations, scattering between longitudinal and transverse components of M. Moreover, in the framework of itinerant ferromagnetism, the magnetic moment/atom μ was assumed to be isotropic with g≈2! That ignores the anisotropy of μ in nanostructures and the importance of the orbital magnetic moments with μ L/μ S = (g - 2)/2. Without finite μ L we would have no magnetic anisotropy energy (MAE), no hard magnets, no magnetic storage media. Only recently the "language" of EPR was adapted to FMR in ultrathin films. A g-tensor is discussed and its interrelation with the MAE is pointed out. Also recent theory points out, that" there is no reason to assume a fixed magnetization length for nanoelements". This allows a detailed discussion of magnon-magnon scattering, spin-spin, and spin-lattice relaxation - useful, for example, for fs spin dynamics. Recent FMR experiments using frequencies from 1 GHz up to several hundred GHz, will allow measuring the proper g-factor components and μ L,μ S. From the frequency dependent linewidth magnon-magnon scattering can be separated from dissipative spin-lattice damping. Source


Inhofer A.,Albert Ludwigs University of Freiburg | Bercioux D.,Albert Ludwigs University of Freiburg | Bercioux D.,Free University of Berlin
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We propose a device that allows for the emission of pairs of spin-polarized electrons into the edge states of a two-dimensional topological insulator. Charge and spin emission is achieved using a periodically driven quantum dot weakly coupled to the edge states of the host topological insulator. We present calculations of the emitted time-dependent charge and spin currents of such a dynamical scatterer using the Floquet scattering matrix approach. Experimental signatures of spin-polarized two-particle emission can be found in noise measurements. Here a new form of noise suppression, named Z2 antibunching, is introduced. Additionally, we propose a setup in which entanglement of the emitted electrons is generated. This entanglement is based on a postselection procedure and becomes manifest in a violation of a Clauser-Horne-Shimony-Holt inequality. © 2013 American Physical Society. Source


Malic E.,TU Berlin | Maultzsch J.,TU Berlin | Reich S.,Free University of Berlin | Knorr A.,TU Berlin
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We present microscopic calculations of the absorption spectra of metallic single-walled carbon nanotubes. We address the controversial question of the excitonic binding energies in metallic nanotubes as well as the excitonic character of higher transitions. In spite of the strong screening, we observe binding energies in the range of 100 meV for metallic nanotubes with diameters in the range of 1-2.2 nm. Characteristic features of the absorption spectra, such as peak splitting and an asymmetric peak shape, are observed. The splitting is due to the trigonal warping effect. The peak shoulder at high energies is a result of an overlap of the excitonic excitation with the free-particle Van Hove singularity. Furthermore, we find higher transitions to be also significantly influenced by excitons. Our approach is based on density matrix, which allows the investigation of the chirality and diameter dependence of the excitonic binding energy for the first four optical transitions for a variety of different metallic and semiconducting nanotubes. © 2010 The American Physical Society. Source


Daumke O.,Max Delbruck Centrum fur Molekulare Medizin | Daumke O.,Free University of Berlin | Roux A.,University of Geneva | Haucke V.,Leibniz Institute for Molecular Pharmacology | Haucke V.,Charite - Medical University of Berlin
Cell | Year: 2014

Biological membranes undergo constant remodeling by membrane fission and fusion to change their shape and to exchange material between subcellular compartments. During clathrin-mediated endocytosis, the dynamic assembly and disassembly of protein scaffolds comprising members of the bin-amphiphysin-rvs (BAR) domain protein superfamily constrain the membrane into distinct shapes as the pathway progresses toward fission by the GTPase dynamin. In this Review, we discuss how BAR domain protein assembly and disassembly are controlled in space and time and which structural and biochemical features allow the tight regulation of their shape and function to enable dynamin-mediated membrane fission. © 2014 Elsevier Inc. Source


A model for treating excitation and relaxation of adsorbates at metallic surfaces induced by non-adiabatic coupling is developed. The derivation is based on the concept of resonant electron transfer, where the adsorbate serves as a molecular bridge for the inelastic transition between an electron source and a sink. In this picture, energy relaxation and scanning tunneling microscopy (STM) at metallic surfaces are treated on an equal footing as a quasi-thermal process. The model goes beyond the local harmonic approximation and allows for an unbiased description of floppy systems with multiple potential wells. Further, the limitation of the product ansatz for the vibronic wave function to include the position-dependence of the non-adiabatic couplings is avoided by explicitly enforcing detailed balance. The theory is applied to the excitation of hydrogen on palladium, which has multiple local potential minima connected by low energy barriers. The main aspects investigated are the lifetimes of adsorbate vibrations in different adsorption sites, as well as the dependence of the excitation, response, and transfer rates on an applied potential bias. The excitation and relaxation simulations reveal intricate population dynamics that depart significantly from the simplistic tunneling model in a truncated harmonic potential. In particular, the population decay from an initially occupied local minimum induced by the contact with an STM tip is found to be better described by a double exponential. The two rates are interpreted as a response to the system perturbation and a transfer rate following the perturbation. The transfer rate is found to obey a power law, as was the case in previous experimental and theoretical work. © 2013 AIP Publishing LLC. Source


Vacha R.,Masaryk University | Marsalek O.,Czech Institute of Organic Chemistry And Biochemistry | Willard A.P.,University of Texas at Austin | Bonthuis D.J.,TU Munich | And 2 more authors.
Journal of Physical Chemistry Letters | Year: 2012

Classical molecular dynamics simulations point to an anisotropy of water-water hydrogen bonding at the water surface. Approaching from the gas phase, a region of primarily dangling hydrogens is followed by dangling oxygens before the isotropic bulk region. Using ab initio calculations, we translate this hydrogen bonding anisotropy to charge transfer between water molecules, which we analyze with respect to both instantaneous and averaged positions of the water surface. Similarly to the oil/water interface, we show that there is a region of small net negative charge extending 0.2 to 0.6 nm from the Gibbs dividing surface in the aqueous phase. Using a simple continuum model, we translate this charge profile to a zeta potential, which acquires for realistic positions of the shear surface the same negative sign as that observed experimentally, albeit of a smaller absolute value. © 2011 American Chemical Society. Source


Kleinert H.,Free University of Berlin
Electronic Journal of Theoretical Physics | Year: 2011

We recall the successes of the Hubbard-Stratonovich Transformation (HST) of many-body theory, point out its failure to cope with competing channels of collective phenomena and show how to overcome this by Variational Perturbation Theory. That yields exponentially fast converging results, thanks to the help of a variety of collective classical fields, rather than a fluctuating collective quantum field as suggested by the HST. © Electronic Journal of Theoretical Physics. Source


Geiger I.,Free University of Berlin | Parlamis J.,University of San Francisco
Computers in Human Behavior | Year: 2014

Email has profoundly influenced the way we communicate personally and professionally and, for many, email negotiations have become a common, every day experience. While many studies have investigated email negotiations by relying on and discussing the characteristics of the medium, this paper focuses on the user's attitude toward the medium and its respective influence on email negotiation. Specifically, we investigate which dimensions make up negotiators' attitude toward email, i.e. their email affinity, and how these attitudes, in turn, influence the negotiation outcomes. In our scale development, three facets of email affinity are theoretically considered, empirically explored and validated: email preference, email comfort and email clarity. Our negotiation study contains a quasi-experimental email negotiation exercise where subjects were paired according to their email affinity. Email comfort emerged as a significant predictor of individual profit, joint gain, and different dimensions of subjective value. Theoretical implications and further research are discussed. © 2013 Elsevier Ltd. All rights reserved. Source


Lotze C.,Free University of Berlin
Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2012

Reversible isomerization processes are rarely found when organic molecular switches are adsorbed on metal surfaces. One obstacle is the large energy difference of the isomeric forms, since usually the most planar conformer has the largest adsorption energy. In the example of an imine derivative, we show a strategy for also stabilizing the non-planar isomer by intermolecular bonding to its neighbors. Tunneling electrons from the tip of a scanning tunneling microscope can then be used to induce reversible switching between the trans and cis-like state. Supported by model force-field calculations, we illustrate that the most probable cause of the enhanced stability of the three-dimensional cis state at specific adsorption sites is the electrostatic interaction with N sites of the neighboring molecule. Source


Grosu C.,Free University of Berlin
Journal of Combinatorial Theory. Series B | Year: 2016

The present paper is concerned with the various algebraic structures supported by the set of Turán densities.We prove that the set of Turán densities of finite families of r-graphs is a non-trivial commutative semigroup, and as a consequence we construct explicit irrational densities for any r≥. 3. The proof relies on a technique recently developed by Pikhurko.We also show that the set of all Turán densities forms a graded ring, and from this we obtain a short proof of a theorem of Peng on jumps of hypergraphs.Finally, we prove that the set of Turán densities of families of r-graphs has positive Lebesgue measure if and only if it contains an open interval. This is a simple consequence of Steinhaus's theorem. © 2016 Elsevier Inc. Source


Voloshina E.,Humboldt University of Berlin | Paulus B.,Free University of Berlin
Journal of Chemical Theory and Computation | Year: 2014

Existence of the sp-d hybridization of the valence band states of the fcc Ca and Sr in the vicinity of the Fermi level indicates that their electronic wave function can have a multireference (MR) character. We performed a wave-function-based correlation treatment for these materials by means of the method of increments. As opposed to the single-reference correlation treatment (here, coupled cluster), which fails to describe cohesive properties in both cases, employing the MR averaged coupled pair functional, one can achieve almost 100% of the experimental correlation energy. © 2014 American Chemical Society. Source


Micklitz T.,Free University of Berlin | Norman M.R.,Argonne National Laboratory
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We derive the spin Hamiltonian for the quantum spin liquid Na 4Ir3O8, and then estimate the direct and superexchange contributions between near neighbor iridium ions using a tight-binding parametrization of the electronic structure. We find a magnitude of the exchange interaction comparable to experiment for a reasonable value of the on-site Coulomb repulsion. For one of the two tight-binding parametrizations we have studied, the direct exchange term, which is isotropic, dominates the total exchange. This provides support for those theories proposed to describe this quantum spin liquid that assume an isotropic Heisenberg model. © 2010 The American Physical Society. Source


Lawaczeck R.,Free University of Berlin | Jost G.,Bayer AG | Pietsch H.,Bayer AG
Investigative Radiology | Year: 2011

Aim: To contribute to the understanding of the pharmacokinetics of intravenously administered, renally excreted contrast media with circulation, distribution, and renal excretion providing access to optimized and patient-based administration protocols. Method: Numerical solutions of the pharmacokinetic equations are presented where the physiological parameters (organ volumes, blood flows) and administration parameters (dose, concentration, and velocity) are fixed and the variable parameters (the exchange rates between plasma and interstitium, the rate for renal excretion) are adjusted to results from clinical studies of healthy individuals. Results: Recirculation, organ plasma concentrations, and renal excretion are adequately modeled. With the calculated distribution and renal excretion rates, 3 time periods are discriminated: 1. Mixing period (initial 100 seconds). Bolus decay; 2. Distribution period (about 500 seconds). Volume of distribution approaches a constant value; 3. Equalization period (about 1200 seconds or ≥55 circulations). Ratios of the organ concentrations reach constant values with kidneys, the location of excretion, showing the lowest ratios. Conclusion: The model describes bolus tracking, recirculation, plasma to interstitium distribution, and renal excretion. For known administration parameters, the relevant pharmacokinetic parameters can be achieved from the results of clinical studies. If the arguments are reversed, the pharmacokinetic parameters obtained allow the calculation of personalized administration protocols for computed tomography and magnetic resonance imaging examinations where the 2 initial time periods are essential. Copyright © 2011 by Lippincott Williams & Wilkins. Source


Deffner S.,University of Maryland University College | Lutz E.,Free University of Berlin | Lutz E.,Friedrich - Alexander - University, Erlangen - Nuremberg
Physical Review Letters | Year: 2013

We derive a Margolus-Levitin-type bound on the minimal evolution time of an arbitrarily driven open quantum system. We express this quantum speed limit time in terms of the operator norm of the nonunitary generator of the dynamics. We apply these results to the damped Jaynes-Cummings model and demonstrate that the corresponding bound is tight. We further show that non-Markovian effects can speed up quantum evolution and therefore lead to a smaller quantum speed limit time. © 2013 American Physical Society. Source


Schroer B.,Free University of Berlin | Schroer B.,Brazilian Center for Research in Physics (CBPF)
Studies in History and Philosophy of Science Part B - Studies in History and Philosophy of Modern Physics | Year: 2015

Recent insights into the conceptual structure of localization in QFT (modular localization) led to clarifications of old unsolved problems. The oldest one is the Einstein-Jordan conundrum which led Jordan in 1925 to the discovery of quantum field theory. This comparison of fluctuations in subsystems of heat bath systems (Einstein) with those resulting from the restriction of the QFT vacuum state to an open subvolume (Jordan) leads to a perfect analogy; the globally pure vacuum state becomes upon local restriction a strongly impure KMS state. This phenomenon of localization-caused thermal behavior as well as the vacuum-polarization clouds at the causal boundary of the localization region places localization in QFT into a sharp contrast with quantum mechanics and justifies the attribute "holstic". In fact it positions the E-J Gedankenexperiment into the same conceptual category as the cosmological constant problem and the Unruh Gedankenexperiment. The holistic structure of QFT resulting from "modular localization" also leads to a revision of the conceptual origin of the crucial crossing property which entered particle theory at the time of the bootstrap S-matrix approach but suffered from incorrect use in the S-matrix settings of the dual model and string theory.The new holistic point of view, which strengthens the autonomous aspect of QFT, also comes with new messages for gauge theory by exposing the clash between Hilbert space structure and localization and presenting alternative solutions based on the use of stringlocal fields in Hilbert space. Among other things this leads to a reformulation of the Englert-Higgs symmetry breaking mechanism. © 2015. Source


Lange K.M.,Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy | Lange K.M.,Helmholtz Center Berlin | Aziz E.F.,Helmholtz Center Berlin | Aziz E.F.,Free University of Berlin
Chemical Society Reviews | Year: 2013

Soft X-ray spectroscopies are powerful tools for probing the local electronic and molecular orbital structures of materials in different phases and various environments. While modern spectroscopic tools using soft X-ray synchrotron photons perspicuously reveal the molecular orbital (MO) structure in detail, structures remain widely unknown in the liquid phase since many of these techniques could only be applied to solutions very recently. Furthermore, the interactions and dynamics of molecules in the liquid phase are especially complicated compared to those in gas and solid phases and thereby impede the understanding of functional materials in solution. This review presents recent developments using soft X-ray radiation for probing the electronic structure of ions and molecules in solution. The presented X-ray absorption, emission, and photo-electron spectroscopy studies exhibit the powerful contributions of soft X-ray liquid spectroscopies in the last few years. © 2013 The Royal Society of Chemistry. Source


Buzogany A.,Free University of Berlin
Environment and Planning C: Government and Policy | Year: 2015

Establishing structures of environmental governance is an important goal of external policy actors but a notoriously difficult one to achieve in states with weak regulatory capacities. Building on newer developments in governance research, this contribution offers contextual specifications for factors mediating external regulatory influence. The paper analyses the emergence and the effectiveness of environmental governance in two explorative case studies dealing with the provision of drinking water and, respectively, nature protection from Romania. The main finding is that external influence can lead to the emergence of new modes of environmental governance if supported by capable sectoral administration and pro-change stakeholders. © 2015, The Author(s) 2015. Source


Campbell E.T.,University of Sheffield | Campbell E.T.,Free University of Berlin
Physical Review Letters | Year: 2014

Error-correcting codes protect quantum information and form the basis of fault-tolerant quantum computing. Leading proposals for fault-tolerant quantum computation require codes with an exceedingly rare property, a transversal non-Clifford gate. Codes with the desired property are presented for d-level qudit systems with prime d. The codes use n=d-1 qudits and can detect up to ∼d/3 errors. We quantify the performance of these codes for one approach to quantum computation known as magic-state distillation. Unlike prior work, we find performance is always enhanced by increasing d. © 2014 Published by the American Physical Society. Source


Dewey M.,Free University of Berlin
Cardiac CT | Year: 2011

Computed tomography of the heart has become a highly accurate diagnostic modality that is attracting increasing attention. This extensively illustrated book aims to assist the reader in integrating cardiac CT into daily clinical practice, while also reviewing its current technical status and applications. Clear guidance is provided on the performance and interpretation of imaging using the latest technology, which offers greater coverage, better spatial resolution, and faster imaging. The specific features of scanners from all four main vendors, including those that have only recently become available, are presented. Among the wide range of applications and issues to be discussed are coronary artery bypass grafts, stents, plaques, and anomalies, cardiac valves, congenital and acquired heart disease, and radiation exposure. Upcoming clinical uses of cardiac CT, such as plaque imaging and functional assessment, are also explored. © Springer-Verlag Berlin Heidelberg 2011. Source


Rinne O.,Max Planck Institute for Physics | Rinne O.,Free University of Berlin
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We study various aspects of black holes and gravitational collapse in Einstein-Yang-Mills theory under the assumption of spherical symmetry. Numerical evolution on hyperboloidal surfaces extending to future null infinity is used. We begin by constructing colored and Reissner-Nordström black holes on surfaces of constant mean curvature and analyze their perturbations. These linearly perturbed black holes are then evolved into the nonlinear regime and the masses of the final Schwarzschild black holes are computed as a function of the initial horizon radius. We compare with an information-theoretic bound on the lifetime of unstable hairy black holes derived by Hod. Finally we study critical phenomena in gravitational collapse at the threshold between different Yang-Mills vacuum states of the final Schwarzschild black holes, where the n=1 colored black hole forms the critical solution. The work of Choptuik et al. [Phys. Rev. D 60, 124011 (1999)] is extended by using a family of initial data that includes another region in parameter space where the colored black hole with the opposite sign of the Yang-Mills potential forms the critical solution. We investigate the boundary between the two regions and discover that the Reissner-Nordström solution appears as a new approximate codimension-two attractor. © 2014 American Physical Society. Source


Kunec D.,Free University of Berlin
Avian Diseases | Year: 2013

Proteomics is the application of rapidly evolving high-throughput technologies that enable analysis of proteins on a large scale. Recent advances in instrumentation have allowed detection, identification, and quantification of proteins with unparalleled precision and reproducibility, and this, in combination with novel bioinformatics tools, has helped to move proteomics from the simple cataloging of expressed proteins toward discovery of operating mechanisms in the biological systems. Proteomics holds great promise for advancing the understanding of viral pathogenesis, immunity, and the dynamics of virus-host protein interactions. Nevertheless, only a small number of proteomic studies have been done on animal viruses and avian herpesviruses in particular. This review summarizes the basic concepts and technologies used in proteomics and highlights the most successful applications of different proteomic approaches that resulted in identification of new virus-host protein interactions, mechanisms of genetic resistance and susceptibility to Marek's disease in chickens, and profiling and analysis of proteomes of Gallid herpesvirus 2 (GaHV-2), GaHV-3, and Meleagrid herpesvirus 1 infected or transformed cells. This review also discusses current limitations and potential future applications of proteomic methods in avian herpesvirus research. © American Association of Avian Pathologists. Source


He Z.,South University of Science and Technology of China | Jiang W.,South University of Science and Technology of China | Schalley C.A.,Free University of Berlin
Chemical Society Reviews | Year: 2015

Large protein-sized synthetic supramolecular architecture is rare and certainly has not yet achieved the structural and functional complexity of biomolecules. As multiple, identical copies of a few building blocks are repetitively used, a highly symmetrical architecture results with limitations in function. In marked contrast, functional structures in nature are often assembled with high geometric precision from many different building blocks. They cooperate in a complex way realizing energy conversion, mechanical motion or transport phenomena. Beyond self-assembly, the structurally and functionally complex biomolecular machines rely on self-sorting to correctly position all subunits through orthogonal recognition sites. Mimicking such self-sorting processes is a promising strategy for supramolecular synthesis - resulting in higher structural complexity and promising access to a more sophisticated function. The term "integrative self-sorting"was coined to describe the strategy to form well-defined assemblies with well-controlled subunit positions. The key process is the incorporation of two or more orthogonal binding motifs into at least some of the subunits. Modularity and programmability based on orthogonal yet similar binding motifs generate diversity and complexity. Integrative self-sorting is thus inherently related to systems chemistry. Depending on the individual binding motifs, (multi-)stimuli responsiveness can be achieved. When different recognition events en route to the final assembly occur on significantly different time scales, kinetic pathway selection is observed. In this account, we review the modularity, programmability, and emergent properties of integrative self-sorting, emphasizing its utility and perspective for complex supramolecular architectures. © The Royal Society of Chemistry 2015. Source


Thomas U.,Leibniz Institute for Neurobiology | Sigrist S.J.,Free University of Berlin
Advances in Experimental Medicine and Biology | Year: 2012

The molecular and cellular mechanisms that control the composition and functionality of ionotropic glutamate receptors may be considered as most important "set screws" for adjusting excitatory transmission in the course of developmental and experience-dependent changes within neural networks. The Drosophila larval neuromuscular junction has emerged as one important invertebrate model system to study the formation, maintenance, and plasticity-related remodeling of glutamatergic synapses in vivo. By exploiting the unique genetic accessibility of this organism combined with diverse tools for manipulation and analysis including electrophysiology and state of the art imaging, considerable progress has been made to characterize the role of glutamate receptors during the orchestration of junctional development, synaptic activity, and synaptogenesis. Following an introduction to basic features of this model system, we will mainly focus on conceptually important findings such as the selective impact of glutamate receptor subtypes on the formation of new synapses, the coordination of presynaptic maturation and receptor subtype composition, the role of nonvesicularly released glutamate on the synaptic localization of receptors, or the homeostatic feedback of receptor functionality on presynaptic transmitter release. © 2012 Springer-Verlag/WIen. Source


Schulze M.S.E.D.,Dana-Farber Cancer Institute | Schulze M.S.E.D.,Free University of Berlin | Wucherpfennig K.W.,Dana-Farber Cancer Institute | Wucherpfennig K.W.,Harvard University
Current Opinion in Immunology | Year: 2012

HLA-DM serves a critical function in the loading and editing of peptides on MHC class II (MHCII) molecules. Recent data showed that the interaction cycle between MHCII molecules and HLA-DM is dependent on the occupancy state of the peptide binding groove. Empty MHCII molecules form stable complexes with HLA-DM, which are disrupted by binding of high-affinity peptide. Interestingly, MHCII molecules with fully engaged peptides cannot interact with HLA-DM, and prior dissociation of the peptide N-terminus from the groove is required for HLA-DM binding. There are significant similarities to the peptide loading process for MHC class I molecules, even though it is executed by a distinct set of proteins in a different cellular compartment. © 2011 Elsevier Ltd. Source


Marquardt J.,Free University of Berlin
Environmental Innovation and Societal Transitions | Year: 2015

It is argued that transition management can be a useful analytical approach for clarifying how development aid can stimulate economic development. To illustrate this, potential applications are suggested. Three similarities between transition management and development aid are identified. In addition, the reverse potential influence, from development aid thinking to transition management, is briefly discussed. © 2014 Elsevier B.V. Source


Seppelt K.,Free University of Berlin
Chemical Reviews | Year: 2015

The chemistries and physics of the molecular hexafluorides are well-developed. The hexafluorides of radioactive elements are insufficiently developed. Sulfur hexafluoride is an extreme unreactive, even physiologically inert gas. It is the model compound for octahedral symmetry. Xenon hexafluoride is not monomeric in the solid and liquid or dissolved state, and the molecule does not adopt the octahedral structure. Nine transition metal hexafluorides exists that are best prepared by direct fluorination of the metals. Molybdenum and tungsten hexafluoride have been known for more than 80 years and are the only transition metal hexafluorides that are commercially available. Both compounds are made from the elements. Source


Ozkahya L.,Istanbul Bilgi University | Person Y.,Free University of Berlin
Journal of Combinatorial Theory. Series B | Year: 2012

For a given graph H let φ H(n) be the maximum number of parts that are needed to partition the edge set of any graph on n vertices such that every member of the partition is either a single edge or it is isomorphic to H. Pikhurko and Sousa conjectured that φ H(n)=ex(n, H) for χ(H)≥3 and all sufficiently large n, where ex(n, H) denotes the maximum size of a graph on n vertices not containing H as a subgraph. In this article, their conjecture is verified for all edge-critical graphs. Furthermore, it is shown that the graphs maximizing φ H(n) are (χ(H)-1)-partite Turán graphs. © 2011 Elsevier Inc. Source


Cheng H.,Free University of Berlin | Stark C.B.W.,University of Leipzig
Angewandte Chemie - International Edition | Year: 2010

"Chemical Equation Presented" Double, double, no toll and trouble: Enantiomerically pure tetrahydrofurans are obtained with high position- and stereoselectivity through a ruthenium(Vll)-catalyzed oxidative cyclization of 5,6dihydroxy alkenes (see scheme TPAP = tetrapropylammonium perruthenate). A dual activation modifies the reactivity and increases the carbophilicity of the transition metal so that an otherwise unusual dioxygenation with perruthenate occurs. © 2010 Wlley-VCH Verlag GmbH & Co. KGaA. Source


Briest F.,Medizinische Klinik 1 CBF | Briest F.,Free University of Berlin | Grabowski P.,Medizinische Klinik 1 CBF
Theranostics | Year: 2014

Gastroenteropancreatic neuroendocrine neoplasms are heterogeneous in their clinical behavior and require therapies specially tailored according to staging, grading, origin and expression of peptide receptors. Despite extensive scientific efforts, the therapy options are still not satisfactory. The main reasons are due to the lack of a broad mechanistic knowledge, an insufficient classification of specific diagnostic sub-groups, and predictive markers. GEP-NEN tumors evade early diagnosis because of slow asymptomatic growth behavior and are frequently not detected until metastasized. How signaling networks contribute to tumor progression and how these networks interact remains unclear in large parts. In this review we summarize the knowledge on the growth factor responsive non-angiogenetic pathways in sporadic GEP-NENs, highlight promising mechanistic research approaches, and describe important therapy targets. © Ivyspring International Publisher. Source


Wurst S.,Free University of Berlin
Frontiers in Plant Science | Year: 2013

Most studies on plant-mediated above-belowground interactions focus on soil biota with direct trophic links to plant roots such as root herbivores, pathogens, and symbionts. Detritivorous soil fauna, though ubiquitous and present in high abundances and biomasses in soil, are under-represented in those studies. Understanding of their impact on plants is mainly restricted to growth and nutrient uptake parameters. Detritivores have been shown to affect secondary metabolites and defense gene expression in aboveground parts of plants, with potential impacts on aboveground plant-herbivore interactions. The proposed mechanisms range from nutrient mobilization effects and impacts on soil microorganisms to defense induction by passive or active ingestion of roots. Since their negative effects (disruption or direct feeding of roots) may be counterbalanced by their overall beneficial effects (nutrient mobilization), detritivores may not harm, but rather enable plants to respond to aboveground herbivore attacks in a more efficient way. Both more mechanistic and holistic approaches are needed to better understand the involvement of detritivores in plant-mediated above-belowground interactions and their potential for sustainable agriculture. © 2013 Wurst. Source