1,687 research outputs found

    De beleving van watertypen : literatuuroverzicht en validatie van de indicator 'water' uit het BelevingsGis

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    Inventarisatie belevingsonderzoek natuur ten behoeve van het Natuurplanburea

    ESC NN-Potentials in Momentum Space. I. PS-PS Exchange Potentials

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    A momentum space representation is derived for the Nijmegen Extended-Soft-Core (ESC) interactions. The partial wave projection of this representation is carried through, in principle for Two-Meson-Exchange (TME) in general. Explicit results for the momentum space partial wave NN-potentials from PS-PS-Exchange are given.Comment: 23 pages, 2 PostScript figures, revtex

    Fast Searching in Packed Strings

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    Given strings PP and QQ the (exact) string matching problem is to find all positions of substrings in QQ matching PP. The classical Knuth-Morris-Pratt algorithm [SIAM J. Comput., 1977] solves the string matching problem in linear time which is optimal if we can only read one character at the time. However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation. Let m≀nm \leq n be the lengths PP and QQ, respectively, and let σ\sigma denote the size of the alphabet. On a standard unit-cost word-RAM with logarithmic word size we present an algorithm using time O\left(\frac{n}{\log_\sigma n} + m + \occ\right). Here \occ is the number of occurrences of PP in QQ. For m=o(n)m = o(n) this improves the O(n)O(n) bound of the Knuth-Morris-Pratt algorithm. Furthermore, if m=O(n/logâĄÏƒn)m = O(n/\log_\sigma n) our algorithm is optimal since any algorithm must spend at least \Omega(\frac{(n+m)\log \sigma}{\log n} + \occ) = \Omega(\frac{n}{\log_\sigma n} + \occ) time to read the input and report all occurrences. The result is obtained by a novel automaton construction based on the Knuth-Morris-Pratt algorithm combined with a new compact representation of subautomata allowing an optimal tabulation-based simulation.Comment: To appear in Journal of Discrete Algorithms. Special Issue on CPM 200

    Conservation of co‐evolved interactions: understanding the Maculinea–Myrmica complex

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    1. The six papers in this Special Issue of Insect Conservation and Diversity are presented as a gedenkschrift honouring ground‐breaking contributions made by the late Graham Elmes towards understanding the biology of Myrmica ants and their social parasites. 2. A common theme is that each research paper contributes new knowledge applicable to the future survival of Maculinea (= Phengaris) species of butterflies, which have become flagships for insect conservation across Europe. All Maculinea species are highly specialised, with larvae that feed briefly on a specific foodplant before living underground for 11–23 months as social parasites of Myrmica colonies. 3. This introductory overview provides a brief history of the research that has led to the current collection, with emphasis on Graham Elmes' life and work. It is followed by three research papers that illustrate the diversity, socio‐biology and ecology of Myrmica ants. A fourth describes an extreme adaptation that increases the efficiency with which some populations of Maculinea larvae exploit the resources within Myrmica nests. A fifth, more theoretical, paper models the constraints that typically lead to host specificity among social parasites and explores why host switches are rare and quick

    G3DV: A new 3D genome browser and experimental data viewer.

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    Genomes are tremendous co-evolutionary holistic systems for molecular storage, processing and fabrication of information. Their system-biological complexity remains, however, still largely mysterious, despite immense sequencing achievements and huge advances in the understanding of the general sequential, three-dimensional and regulatory organization. Here, we present the GLOBE 3D Genome Platform a completely novel grid based virtual “paper” tool and in fact the first system-biological genome browser integrating the holistic complexity of genomes in a single easy comprehensible platform: Based on a detailed study of biophysical and IT requirements, every architectural level from sequence to morphology of one or several genomes can be approached in a real and in a symbolic representation simultaneously and navigated by continuous scale-free zooming within a unique three-dimensional OpenGL and grid driven environment. In principle an unlimited number of multi-dimensional data sets can be visualized, customized in terms of arrangement, shape, colour, and texture etc. as well as accessed and annotated individually or in groups using internal or external data bases/facilities. Any information can be searched and correlated by importing or calculating simple relations in real-time using grid resources. A general correlation and application platform for more complex correlative analysis and a front-end for system-biological simulations both using again the huge capabilities of grid infrastructures is currently under development. Hence, the GLOBE 3D Genome Platform is an example of a grid based approach towards a virtual desktop for genomic work combining the three fundamental distributed resources: i) visual data representation, ii) data access and management, and iii) data analysis and creation. Thus, the GLOBE 3D Genome Platform is the novel system-biology oriented information system urgently needed to access, present, annotate, and to simulate the holistic genome complexity in a unique gateway towards a real understanding, educative presentation and curative manipulation planning of this tremendous evolutionary information grail – genomes

    ep → ep π⁰ Reaction Studied in the Δ(1232) Mass Region Using Polarization Asymmetries

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    Measurements of the angular distributions of target and double-spin asymmetries for the Δ+(1232) in the exclusive channel → p(→e,e\u27p)π0 obtained at the Jefferson Lab in the Q2 range from 0.5 to 1.5 GeV2/c2 are presented. Results of the asymmetries are compared with the unitary isobar model [D. Drechsel , Nucl. Phys. A645, 145 (1999)], dynamical models [T. Sato and T. S. Lee, Phys. Rev. C 54, 2660 (1996); S. S. Kamalov , Phys. Lett. B 27, 522 (2001)], and the effective Lagrangian theory [R. M. Davidson , Phys. Rev. D 43, 71 (1991)]. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly

    Resonance approximation and charge loading/unloading in adiabatic quantum pumping

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    Quantum pumping through mesoscopic quantum dots is known to be enhanced by resonant transmission. The pumped charge is close to an integer number of electrons when the pumping contour surrounds a resonance, but the transmission remains small on the contour. For non-interacting electrons, we give a quantitative account of the detailed exchange of electrons between the dot and the leads (to the electron reservoirs) during a pumping cycle. Near isolated distinct resonances, we use approximate Breit-Wigner expressions for the dot's Green function to discuss the loading/unloading picture of the pumping: the fractional charge exchanged between the dot and each lead through a single resonance point is related to the relative couplings of the dot and the leads at this resonance. If each resonance point along the pumping contour is dominated by the coupling to a single lead (which also implies a very small transmission), then the crossing of each such resonance results in a single electron exchange between the dot and that lead, ending up with a net quantized charge. When the resonance approximation is valid, the fractional charges can also be extracted from the peaks of the transmissions between the various leads.Comment: 10 pages, 4 figure

    Ground state at high density

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    Weak limits as the density tends to infinity of classical ground states of integrable pair potentials are shown to minimize the mean-field energy functional. By studying the latter we derive global properties of high-density ground state configurations in bounded domains and in infinite space. Our main result is a theorem stating that for interactions having a strictly positive Fourier transform the distribution of particles tends to be uniform as the density increases, while high-density ground states show some pattern if the Fourier transform is partially negative. The latter confirms the conclusion of earlier studies by Vlasov (1945), Kirzhnits and Nepomnyashchii (1971), and Likos et al. (2007). Other results include the proof that there is no Bravais lattice among high-density ground states of interactions whose Fourier transform has a negative part and the potential diverges or has a cusp at zero. We also show that in the ground state configurations of the penetrable sphere model particles are superposed on the sites of a close-packed lattice.Comment: Note adde

    Polydisperse star polymer solutions

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    We analyze the effect of polydispersity in the arm number on the effective interactions, structural correlations and the phase behavior of star polymers in a good solvent. The effective interaction potential between two star polymers with different arm numbers is derived using scaling theory. The resulting expression is tested against monomer-resolved molecular dynamics simulations. We find that the theoretical pair potential is in agreement with the simulation data in a much wider polydispersity range than other proposed potentials. We then use this pair potential as an input in a many-body theory to investigate polydispersity effects on the structural correlations and the phase diagram of dense star polymer solutions. In particular we find that a polydispersity of 10%, which is typical in experimental samples, does not significantly alter previous findings for the phase diagram of monodisperse solutions.Comment: 14 pages, 7 figure
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