Refine
Year of publication
- 2006 (840) (remove)
Document Type
- Article (581)
- Doctoral Thesis (82)
- Monograph/Edited Volume (54)
- Conference Proceeding (32)
- Postprint (26)
- Preprint (24)
- Review (18)
- Other (17)
- Master's Thesis (3)
- Working Paper (2)
Language
- English (840) (remove)
Keywords
- climate change (4)
- polyelectrolyte (4)
- Fluoreszenz-Resonanz-Energie-Transfer (3)
- Immunoassay (3)
- Nanopartikel (3)
- Nichtlineare Dynamik (3)
- Optimality Theory (3)
- Polyelektrolyt (3)
- metabolite profiling (3)
- metabolomics (3)
Institute
- Institut für Physik und Astronomie (159)
- Institut für Biochemie und Biologie (128)
- Institut für Chemie (81)
- Institut für Geowissenschaften (73)
- Institut für Mathematik (71)
- Institut für Informatik und Computational Science (55)
- Department Linguistik (46)
- Extern (37)
- Department Psychologie (36)
- Institut für Anglistik und Amerikanistik (34)
Semiclassical asymptotics for the scattering amplitude in the presence of focal points at infinity
(2006)
Semiclassical asymptotics for the scattering amplitude in the presence of focal points at infinity
(2006)
We consider scattering in $\R^n$, $n\ge 2$, described by the Schr\"odinger operator $P(h)=-h^2\Delta+V$, where $V$ is a short-range potential. With the aid of Maslov theory, we give a geometrical formula for the semiclassical asymptotics as $h\to 0$ of the scattering amplitude $f(\omega_-,\omega_+;\lambda,h)$ $\omega_+\neq\omega_-$) which remains valid in the presence of focal points at infinity (caustics). Crucial for this analysis are precise estimates on the asymptotics of the classical phase trajectories and the relationship between caustics in euclidean phase space and caustics at infinity.
A new large set of reciprocal recombinant inbred lines (RILs) was created between the Arabidopsis accessions Col-0 and C24 for quantitative trait mapping approaches, consisting of 209 Col-0 x C24 and 214 C24 x Col-0 F-7 RI lines. Genotyping was performed using 110 evenly distributed framework single nucleotide polymorphism markers, yielding a genetic map of 425.70 cM, with an average interval of 3.87 cM. Segregation distortion (SD) was observed in several genomic regions during the construction of the genetic map. Linkage disequilibrium analysis revealed an association between a distorted region at the bottom of chromosome V and a non-distorted region on chromosome IV. A detailed analysis of the RILs for these two regions showed that an SD occurred when homozygous Col-0 alleles on chromosome IV coincided with homozygous C24 alleles at the bottom of chromosome V. Using nearly isogenic lines segregating for the distorted region we confirmed that this genotypic composition leads to reduced fertility and fitness.
Classical SDRT (Asher and Lascarides, 2003) discussed essential features of dialogue like adjacency pairs or corrections and up-dating. Recent work in SDRT (Asher, 2002, 2005) aims at the description of natural dialogue. We use this work to model situated communication, i.e. dialogue, in which sub-sentential utterances and gestures (pointing and grasping) are used as conventional modes of communication. We show that in addition to cognitive modelling in SDRT, capturing mental states and speech-act related goals, special postulates are needed to extract meaning out of contexts. Gestural meaning anchors Discourse Referents in contextually given domains. Both sorts of meaning are fused with the meaning of fragments to get at fully developed dialogue moves. This task accomplished, the standard SDRT machinery, tagged SDRSs, rhetorical relations, the up-date mechanism, and the Maximize Discourse Coherence constraint generate coherent structures. In sum, meanings from different verbal and non-verbal sources are assembled using extended SDRT to form coherent wholes.
Received views of utterance context in pragmatic theory characterize the occurrent subjective states of interlocutors using notions like common knowledge or mutual belief. We argue that these views are not compatible with the uncertainty and robustness of context-dependence in humanhuman dialogue. We present an alternative characterization of utterance context as objective and normative. This view reconciles the need for uncertainty with received intuitions about coordination and meaning in context, and can directly inform computational approaches to dialogue.
Forum: EU-Diplomatie im Jahre 2020
In semi-arid savannas, unsustainable land use can lead to degradation of entire landscapes, e.g. in the form of shrub encroachment. This leads to habitat loss and is assumed to reduce species diversity. In BIOTA phase 1, we investigated the effects of land use on population dynamics on farm scale. In phase 2 we scale up to consider the whole regional landscape consisting of a diverse mosaic of farms with different historic and present land use intensities. This mosaic creates a heterogeneous, dynamic pattern of structural diversity at a large spatial scale. Understanding how the region-wide dynamic land use pattern affects the abundance of animal and plant species requires the integration of processes on large as well as on small spatial scales. In our multidisciplinary approach, we integrate information from remote sensing, genetic and ecological field studies as well as small scale process models in a dynamic region-wide simulation tool. <hr> Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006.
Rezensiertes Werk:
Frank, Robert: Phrase Structure Composition and Syntactic Dependencies. - Cambridge, MA : MIT Press, 2002. - xiv + 326 S.
In most cases where ring closing metathesis is applied to the synthesis of heterocycles, alpha,omega-dienes are used as precursors. If substrates containing more than two double bonds are subjected to a metathesis reaction, carba- or heterocycles bearing additional exocyclic alkene functionality result, or multiple ring closing processes occur. This offers interesting and potentially very useful synthetic perspectives. On the other hand, selectivity problems need to be addressed as the cyclization of substrates with more than two double bonds available for olefin metathesis may result in constitutional isomers or stereoisomers. This review highlights problems and opportunities evolving from ring closing metathesis of tri-, tetra-, and polyenes as a strategy for the selective synthesis of functionalized heterocycles. The chapter on RCM of trienes is subdivided according to the symmetry of the metathesis precursor. The following two chapters deal with the double or multiple RCM of tetra- or polyenes. These processes are further classified according to the preferred cyclization mode. Finally, the application of cascade or domino metathesis reactions to the synthesis of heterocycles will be discussed. These processes can be classified into those where exclusively C-C-double bonds take part in the metathesis reaction, and those where one or more C-C-triple bonds are involved
The results of the theoretical consideration of stochastic resonance in overdamped bistable oscillators are given. These results are founded not on the model of two states as in [McNamara B, Wiesenfeld K. Theory of stochastic resonance. Phys Rev A 1989;39:4854-69], but on splitting of motion into regular and random and the rigorous solution of the Fokker-Planck equation for the random component. We show that this resonance is caused by a change, under the influence of noise, of the system's effective stiffness and damping factor contained in the equation for the regular component. For a certain value of the noise intensity the effective stiffness is minimal, and this fact causes non-monotonic change of the output signal amplitude as the noise intensity changes. It is important that the location of the minimum and its value depend essentially on the signal frequency.
Rhodobacter capsulatus xanthine dehydrogenase (XDH) is a cytoplasmic enzyme with an (alpha beta) 2 heterodimeric structure that is highly identical to homodimeric eukaryotic xanthine oxidoreductases. The crystal structure revealed that the molybdenum cofactor (Moco) is deeply buried within the protein. A protein involved in Moco insertion and XDH maturation has been identified, which was designated XdhC. XdhC was shown to be essential for the production of active XDH but is not a subunit of the purified enzyme. Here we describe the purification of XdhC and the detailed characterization of its role for XDH maturation. We could show that XdhC binds Moco in stoichiometric amounts, which subsequently can be inserted into Moco-free apo-XDH. A specific interaction between XdhC and XdhB was identified. We show that XdhC is required for the stabilization of the sulfurated form of Moco present in enzymes of the xanthine oxidase family. Our findings imply that enzyme-specific proteins exist for the biogenesis of molybdoenzymes, coordinating Moco binding and insertion into their respective target proteins. So far, the requirement of such proteins for molybdoenzyme maturation has been described only for prokaryotes
This paper tries to apply common methods to estimate unbiased coefficients for the return to schooling in Germany for the year 2004. Based on the simple Mincer-type wage equation, the return to schooling is around 9.5% per year. There is no sheepskin effect. As expected the return in the private sector is higher than in the public sector. Females have a higher return than males, but there are no differences between East and West Germans. An Instrumental Variables and a 3-Stage-Least-Squares approach give very high returns. For correcting the sample selection, the Heckman Two Step Procedure and the Heckman Maximum Likelihood Approach are used. For both methods, the coefficients are very similar, but higher than without correcting for it.
Earthquakes form by sudden brittle failure of rock mostly as shear ruptures along a rupture plane. Beside this, mechanisms other than pure shearing have been observed for some earthquakes mainly in volcanic areas. Possible explanations include complex rupture geometries and tensile earthquakes. Tensile earthquakes occur by opening or closure of cracks during rupturing. They are likely to be often connected with fluids that cause pressure changes in the pore space of rocks leading to earthquake triggering. Tensile components have been reported for swarm earthquakes in West Bohemia in 2000. The aim and subject of this work is an assessment and the accurate determination of such tensile components for earthquakes in anisotropic media. Currently used standard techniques for the retrieval of earthquake source mechanisms assume isotropic rock properties. By means of moment tensors, equivalent forces acting at the source are used to explain the radiated wavefield. Conversely, seismic anisotropy, i.e. directional dependence of elastic properties, has been observed in the earth's crust and mantle such as in West Bohemia. In comparison to isotropy, anisotropy causes modifications in wave amplitudes and shear-wave splitting. In this work, effects of seismic anisotropy on true or apparent tensile source components of earthquakes are investigated. In addition, earthquake source parameters are determined considering anisotropy. It is shown that moment tensors and radiation patterns due to shear sources in anisotropic media may be similar to those of tensile sources in isotropic media. In contrast, similarities between tensile earthquakes in anisotropic rocks and shear sources in isotropic media may exist. As a consequence, the interpretation of tensile source components is ambiguous. The effects that are due to anisotropy depend on the orientation of the earthquake source and the degree of anisotropy. The moment of an earthquake is also influenced by anisotropy. The orientation of fault planes can be reliably determined even if isotropy instead of anisotropy is assumed and if the spectra of the compressional waves are used. Greater difficulties may arise when the spectra of split shear waves are additionally included. Retrieved moment tensors show systematic artefacts. Observed tensile source components determined for events in West Bohemia in 1997 can only partly be attributed to the effects of moderate anisotropy. Furthermore, moment tensors determined earlier for earthquakes induced at the German Continental Deep Drilling Program (KTB), Bavaria, were reinterpreted under assumptions of anisotropic rock properties near the borehole. The events can be consistently identified as shear sources, although their moment tensors comprise tensile components that are considered to be apparent. These results emphasise the necessity to consider anisotropy to uniquely determine tensile source parameters. Therefore, a new inversion algorithm has been developed, tested, and successfully applied to 112 earthquakes that occurred during the most recent intense swarm episode in West Bohemia in 2000 at the German-Czech border. Their source mechanisms have been retrieved using isotropic and anisotropic velocity models. Determined local magnitudes are in the range between 1.6 and 3.2. Fault-plane solutions are similar to each other and characterised by left-lateral faulting on steeply dipping, roughly North-South oriented rupture planes. Their dip angles decrease above a depth of about 8.4km. Tensile source components indicating positive volume changes are found for more than 60% of the considered earthquakes. Their size depends on source time and location. They are significant at the beginning of the swarm and at depths below 8.4km but they decrease in importance later in the course of the swarm. Determined principle stress axes include P axes striking Northeast and Taxes striking Southeast. They resemble those found earlier in Central Europe. However, depth-dependence in plunge is observed. Plunge angles of the P axes decrease gradually from 50° towards shallow angles with increasing depth. In contrast, the plunge angles of the T axes change rapidly from about 8° above a depth of 8.4km to 21° below this depth. By this thesis, spatial and temporal variations in tensile source components and stress conditions have been reported for the first time for swarm earthquakes in West Bohemia in 2000. They also persist, when anisotropy is assumed and can be explained by intrusion of fluids into the opened cracks during tensile faulting.
We examined chemical communication in male and female European pond turtles (Emys orbicularis). In simultaneous binary choice tests, a focal animal was given a choice between pheromones from a conspecific and a choice chamber containing untreated water. Females did not show a preference, both when male and when female stimuli were presented. On the contrary, males preferred the odor of a female over untreated water, suggesting that males actively search for females. The strength of preference was positively correlated with the body size difference between the female and the focal male, indicating that males prefer to mate with larger females. Female fecundity is positively correlated with female size in E. orbicularis, which may account for male choosiness. No overall preference for the stimulus animal was observed when males were presented cues from another male. However, the strength of preference was negatively correlated with the difference in body size. Males avoided large males, but oriented towards smaller stimulus males. This reflects that males form dominance hierarchies, where large males aggressively attack smaller ones. Far-range chemical communication probably enables males to minimize the risk of costly aggressive interactions. This is, to our knowledge, the first study on the role of chemical cues for inter-and intrasexual communication in the European pond turtle
We prove the existence of sectors of minimal growth for general closed extensions of elliptic cone operators under natural ellipticity conditions. This is achieved by the construction of a suitable parametrix and reduction to the boundary. Special attention is devoted to the clarification of the analytic structure of the resolvent.