@article{1449, abstract = {In this paper we consider a canonical compactification of M, the moduli space of stable Higgs bundles with fixed determinant of odd degree over a Riemann surface Σ, producing a projective variety M̄ = M ∪ Z. We give a detailed study of the spaces M̄, Z and M. In doing so we reprove some assertions of Laumon and Thaddeus on the nilpotent cone.}, author = {Hausel, Tamas}, issn = {1435-5345}, journal = {Journal fur die Reine und Angewandte Mathematik}, number = {503}, pages = {169 -- 192}, publisher = {Walter de Gruyter}, title = {{Compactification of moduli of Higgs bundles}}, doi = {10.1515/crll.1998.096}, volume = {1998}, year = {1998}, } @article{1450, abstract = {In this paper we consider the topological side of a problem which is the analogue of Sen's S-duality testing conjecture for Hitchin's moduli space M of rank 2 stable Higgs bundles of fixed determinant of odd degree over a Riemann surface ∑. We prove that all intersection numbers in the compactly supported cohomology of M vanish, i.e. "there are no topological L2 harmonic forms on M". This result generalizes the well known vanishing of the Euler characteristic of the moduli space of rank 2 stable bundles N of fixed determinant of odd degree over ∑. Our proof shows that the vanishing of all intersection numbers of H* cpt(M) is given by relations analogous to the Mumford relations in the cohomology ring of N.}, author = {Hausel, Tamas}, issn = {1095-0761}, journal = {Advances in Theoretical and Mathematical Physics}, number = {5}, pages = {1011 -- 1040}, publisher = {International Press}, title = {{Vanishing of intersection numbers on the moduli space of Higgs bundles}}, doi = {10.4310/ATMP.1998.v2.n5.a3}, volume = {2}, year = {1998}, } @inproceedings{11926, abstract = {We present the first polylog-competitive online algorithm for the general multicast problem in the throughput model. The ratio of the number of requests accepted by the optimum offline alaorithm to the exoected number of reauests accepted by our algorithm is O(jlog n + log log M)(log n + log M) log n), where M is the number of multicast groups and n is the number of nodes in the nraoh. We show that this is close to optimum by presenting-an*R(log nlog M) lower bound on this ratio for anv randomized online algorithm against an oblivious adversary, when M is much lar&r than the link capacities. Our lower bound applies even in the restricted case where the link capacities are much larger than bandwidth requested by a single multicast. We also present a simple proof showing that it is impossible to be competitive against an adaptive online adversary. As in the previous online routing algorithms, our algorithm uses edge-costs when deciding on which is the best path to use. In contrast to the nrevious comnetitive aleorithms in the throughput modei, our cost is-not a direct function of the edne load. The new cost definition allows us to decouple the effects of routing and admission decisions of different multicast groups. }, author = {Goel, Ashish and Henzinger, Monika H and Plotkin, Serge}, booktitle = {9th Annual ACM SIAM Symposium on Discrete Algorithms}, isbn = {0898714109}, location = {San Francisco, CA, United States}, pages = {97--106}, publisher = {Society for Industrial and Applied Mathematics}, title = {{An online throughput-competitive algorithm for multicast routing and admission control}}, year = {1998}, } @article{3487, abstract = {It is widely accepted that individual neurons in the central nervous system release only a single fast transmitter. The possibility of corelease of fast neurotransmitters was examined by making paired recordings from synaptically connected neurons in spinal cord slices. Unitary inhibitory postsynaptic currents generated at interneuron-motoneuron synapses consisted of a strychnine-sensitive, glycine receptor-mediated component and a bicuculline-sensitive, γ-aminobutyric acid (GABA)(A) receptor-mediated component. These results indicate that spinal interneurons release both glycine and GABA to activate functionally distinct receptors in their postsynaptic target cells. A subset of miniature synaptic currents also showed both components, consistent with corelease from individual synaptic vesicles.}, author = {Jonas, Peter M and Bischofberger, Joseph and Sandkühler, Jürgen}, issn = {0036-8075}, journal = {Science}, number = {5375}, pages = {419 -- 424}, publisher = {American Association for the Advancement of Science}, title = {{Corelease of two fast neurotransmitters at a central synapse}}, doi = {10.1126/science.281.5375.419}, volume = {281}, year = {1998}, } @article{3488, abstract = {We have examined gating and pharmacological characteristics of somatic K+ channels in fast-spiking interneurons and regularly spiking principal neurons of hippocampal slices. In nucleated patches isolated from basket cells of the dentate gyrus, a fast delayed rectifier K+ current component that was highly sensitive to tetraethylammonium (TEA) and 4-aminopyridine (4- AP) (half-maximal inhibitory concentrations <0.1 mM) predominated, contributing an average of 58% to the total K+ current in these cells. By contrast, in pyramidal neurons of the CA1 region a rapidly inactivating A- type K+ current component that was TEA-resistant prevailed, contributing 61% to the total K+ current. Both types of neurons also showed small amounts of the K+ current component mainly found in the other type of neuron and, in addition, a slow delayed rectifier K+ current component with intermediate properties (sow inactivation, intermediate sensitivity to TEA). Single-cell RT-PCR analysis of mRNA revealed that Kv3 (Kv3.1, Kv3.2) subunit transcripts were expressed in almost all (89%) of the interneurons but only in 17% of the pyramidal neurons. In contrast, Kv4 (Kv4.2, Kv4.3) subunit mRNAs were present in 87% of pyramidal neurons but only in 55% of interneurons. Selective block of fast delayed rectifier K+ channels, presumably assembled from Kv3 subunits, by 4-AP reduced substantially the action potential frequency in interneurons. These results indicate that the differential expression of Kv3 and Kv4 subunits shapes the action potential phenotypes of principal neurons and interneurons in the cortex.}, author = {Martina, Marco and Schultz, Jobst and Ehmke, Heimo and Monyer, Hannah and Jonas, Peter M}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {20}, pages = {8111 -- 8125}, publisher = {Society for Neuroscience}, title = {{Functional and molecular differences between voltage-gated K+ channels of fast-spiking interneurons and pyramidal neurons of rat hippocampus}}, doi = {10.1523/JNEUROSCI.18-20-08111.1998}, volume = {18}, year = {1998}, } @misc{3506, abstract = {A method of geometric morphing between a first object having a first shape and a second object having a second shape. The method includes the steps of generating a first Delaunay complex corresponding to the first shape and a second Delaunay complex corresponding to the second shape and generating a plurality of intermediary Delaunay complexes defined by a continuous family of mixed shapes corresponding to a mixing of the first shape and the second shape. The method further includes the steps of constructing a first skin corresponding to the first Delaunay complex and a second skin corresponding to the second Delaunay complex and constructing a plurality of intermediary skins corresponding to the plurality of intermediary Delaunay complexes. The first skin, second skin and plurality of intermediary skins may be visually displayed on an output device.}, author = {Edelsbrunner, Herbert and Fu, Ping}, title = {{Apparatus and method for geometric morphing}}, year = {1998}, } @article{3521, abstract = {Spike transmission probability between pyramidal cells and interneurons in the CA1 pyramidal layer was investigated in the behaving rat by the simultaneous recording of neuronal ensembles. Population synchrony was strongest during sharp wave (SPW) bursts. However, the increase was three times larger for pyramidal cells than for interneurons. The contribution of single pyramidal cells to the discharge of interneurons was often large (up to 0.6 probability), as assessed by the presence of significant (<3 ms) peaks in the cross-correlogram. Complex-spike bursts were more effective than single spikes. Single cell contribution was higher between SPW bursts than during SPWs or theta activity. Hence, single pyramidal cells can reliably discharge interneurons, and the probability of spike transmission is behavior dependent.}, author = {Csicsvari, Jozsef L and Hirase, Hajima and Czurkó, András and Buzsáki, György}, issn = {0896-6273}, journal = {Neuron}, number = {1}, pages = {179 -- 189}, publisher = {Elsevier}, title = {{Reliability and state dependence of pyramidal cell-interneuron synapses in the hippocampus: an ensemble approach in the behaving rat}}, doi = {10.1016/S0896-6273(00)80525-5}, volume = {21}, year = {1998}, } @article{3525, author = {Nádasdy, Zoltán and Jozsef Csicsvari and Hirase, Hajima and Czurkó, András and Buzsáki, György}, journal = {European Journal of Neuroscience}, number = {Suppl. 10}, pages = {9409 -- 9409}, publisher = {Wiley-Blackwell}, title = {{Persistence and temporal compression of spike sequences during fast field oscillation in the hippocampus}}, volume = {10}, year = {1998}, } @article{3527, author = {Jozsef Csicsvari and Czurkó, András and Hirase, Hajima and Buzsáki, György}, journal = {European Journal of Neuroscience}, number = {Suppl. 10}, pages = {2553 -- 2553}, publisher = {Wiley-Blackwell}, title = {{Monosynaptic interactions between CA1 Pyramidal cells and interneuron in the behaving rat}}, volume = {10}, year = {1998}, } @article{3535, author = {Hirase, Hajima and Czurkó, András and Jozsef Csicsvari and Buzsáki, György}, journal = {European Journal of Neuroscience}, number = {Suppl. 10}, pages = {9932 -- 9932}, publisher = {Wiley-Blackwell}, title = {{Hippocampal pyramidal neutrons “space-clamped” in a running wheel task: Place cells or path integrators?}}, volume = {10}, year = {1998}, } @inbook{3570, abstract = {Visualization of high-dimensional or large geometric data sets is inherently difficult, so we experiment with the use of audio to display the shape and connectivity of these data sets. Sonification is used as both an addition to and a substitution for the visual display. We describe a new algorithm called wave traversal that provides a necessary intermediate step to sonification of the data; it produces an ordered sequence of subsets, called waves, that allows us to map the data to time. In this paper we focus in detail on the mathematics of wave traversal, in particular, how wave traversal can be used as a discrete Morse function.}, author = {Axen, Ulrike and Edelsbrunner, Herbert}, booktitle = {Mathematical Visualization}, isbn = {9783662035672}, pages = {223 -- 236}, publisher = {Springer}, title = {{Auditory Morse analysis of triangulated manifolds}}, doi = {10.1007/978-3-662-03567-2_17}, year = {1998}, } @article{3627, abstract = {When a favourable mutation sweeps to fixation, those genes initially linked to it increase in frequency; on average, this reduces diversity in the surrounding region of the genome. In the first analysis of this 'hitch-hiking' effect, Maynard-Smith and Haigh followed the increase of the neutral allele that chanced to be associated with the new mutation in the first generation, and assumed that the subsequent increase was deterministic. Later analyses, based on either coalescence arguments, or on diffusion equations for the mean and variance of allele frequency, have also made one or both of these assumptions. In the early generations, stochastic fluctuations in the frequency of the selected allele, and coalescence of neutral lineages, can be accounted for correctly by following relationships between genes conditional on the number of copies of the favourable allele. This analysis shows that the hitch-hiking effect is increased because an allele that is destined to fix tends to increase more rapidly than exponentially. However, the identity generated by the selective sweep has the same form as in previous work, h[r/s] (2 Ns)(-2r/s), where h[r/s] tends to 1 with tight linkage. This analysis is extended to samples of many genes; then, genes may trace back to several families of lineages, each related through a common ancestor early in the selective sweep. Simulations show that the number and sizes of these families can (in principle) be used to make separate estimates of r/s and Ns.}, author = {Barton, Nicholas H}, issn = {0016-6723}, journal = {Genetical Research}, number = {2}, pages = {123 -- 133}, publisher = {Cambridge University Press}, title = {{The effect of hitch-hiking on neutral genealogies}}, doi = {10.1017/S0016672398003462}, volume = {72}, year = {1998}, } @article{3628, abstract = {Determining the way in which deleterious mutations interact in their effects on fitness is crucial to numerous areas in population genetics and evolutionary biology. For example, if each additional mutation leads to a greater decrease in log fitness than the last (synergistic epistasis), then the evolution of sex and recombination may be favored to facilitate the elimination of deleterious mutations. However, there is a severe shortage of relevant data. Three relatively simple experimental methods to test for epistasis between deleterious mutations in haploid species have recently been proposed. These methods involve crossing individuals and examining the mean and/or skew in log fitness of the offspring and parents. The main aim of this paper is to formalize these methods, and determine the most effective way in which tests for epistasis could be carried out. We show that only one of these methods is likely to give useful results: crossing individuals that have very different numbers of deleterious mutations, and comparing the mean log fitness of the parents with that of their offspring. We also reconsider experimental data collected on Chlamydomonas moewussi using two of the three methods. Finally, we suggest how the test could be applied to diploid species.}, author = {West, Stuart and Peters, Andrew and Barton, Nicholas H}, issn = {0016-6731}, journal = {Genetics}, number = {1}, pages = {435 -- 444}, publisher = {Genetics Society of America}, title = {{Testing for epistasis between deleterious mutations}}, doi = {10.1093/genetics/149.1.435}, volume = {149}, year = {1998}, } @article{3629, abstract = {This paper demonstrates the effect of habitat heterogeneity and a habitat preference on the genetic structure of a hybrid zone between the toads Bombina bombina and B. variegata (Anura: Discoglossidae); 1613 toads from 85 sites across a transect near Pešćenica, Croatia, were scored for five unlinked diagnostic allozyme markers. These were found to be largely concordant. Aside from minor systematic deviations, there was little variance in allele frequency among loci within sites. Yet the allele frequencies did not follow a smooth cline, but formed a mosaic in the center, such that neighboring sites could differ markedly in their enzyme score. A detailed ecological survey revealed a correlation between this pattern and habitat. In keeping with the typical breeding sites of the parental taxa, B. bombina-like hybrids were found more often in ponds, whereas B. variegata-like hybrids were more common in puddles. In addition, there was significant heterozygote deficit (FIS) and strong linkage disequilibrium (R), both of which were stronger on the B. bombina side of the transect, and stronger in puddles than ponds. Mark-recapture data showed: (1) that the animals disperse beyond the scale of the habitat pattern; (2) frequent turn-over of individuals within sites; and (3) nonrandom movement between two sites of different habitat type. We conclude that an active habitat preference must contribute to the observed association between marker alleles and habitat. As a consequence, there is incomplete mixing of the two gene pools, which could explain the high level of FIS and R. The asymmetry in these parameters may reflect asymmetry in the preference or in the distribution of habitats across the zone. We discuss the implications of habitat preference for the dynamics of hybrid zones.}, author = {Maccallum, Catriona and Nürnberger, Beate and Barton, Nicholas H and Szymura, Jacek}, issn = {0014-3820}, journal = {Evolution}, number = {1}, pages = {227 -- 239}, publisher = {Wiley-Blackwell}, title = {{Habitat preference in the Bombina hybrid zone in Croatia}}, doi = {10.1111/j.1558-5646.1998.tb05156.x}, volume = {52}, year = {1998}, } @article{3926, abstract = {Two components of sexual selection in the lesser wax moth, Achroia grisella, are clearly defined: females choose males based on characters of their ultrasonic advertisement signals, and males display agonistic behaviour patterns in contests over signalling stations. We conducted a series of laboratory trials to determine whether successes in these two sexual selection arenas were related. Our trials showed that winners in contests over signalling stations were characterized by earlier initiation of both signalling and aggression. These characteristics may indicate higher levels of ‘motivation,’ but it is unclear whether this level is a fixed trait. There was no relationship, however, between any measure of a male's attractiveness to females and his success in winning competition trials. Thus, inter- and intra-sexual selection may be acting on different, uncorrelated traits in A. grisella.}, author = {Cremer, Sylvia and Greenfield, Michael}, issn = {0044-3573}, journal = {Ethology}, number = {1}, pages = {1 -- 9}, publisher = {Wiley-Blackwell}, title = {{Partitioning the components of sexual selection: attractiveness and agonistic behaviour in male wax moths, Achroia grisella (Lepidoptera, Pyralidae)}}, doi = {10.1111/j.1439-0310.1998.tb00025.x}, volume = {104}, year = {1998}, } @article{4011, abstract = {The size and shape of macromolecules such as proteins and nucleic acids play an important role in their functions. Prior efforts to quantify these properties have been based on various discretization or tessellation procedures involving analytical or numerical computations. In this article, we present an analytically exact method for computing the metric properties of macromolecules based on the alpha shape theory. This method uses the duality between alpha complex and the weighted Voronoi decomposition of a molecule. We describe the intuitive ideas and concepts behind the alpha shape theory and the algorithm for computing areas and volumes of macromolecules. We apply our method to compute areas and volumes of a number of protein systems. We also discuss several difficulties commonly encountered in molecular shape computations and outline methods to overcome these problems. (C) 1998 Wiley-Liss, Inc.}, author = {Liang, Jie and Edelsbrunner, Herbert and Fu, Ping and Sudhakar, Pamidighantam and Subramaniam, Shankar}, issn = {0887-3585}, journal = {Proteins: Structure, Function and Bioinformatics}, number = {1}, pages = {1 -- 17}, publisher = {Wiley-Blackwell}, title = {{Analytical shape computation of macromolecules: I. molecular area and volume through alpha shape}}, doi = {10.1002/(SICI)1097-0134(19981001)33:1<1::AID-PROT1>3.0.CO;2-O}, volume = {33}, year = {1998}, } @article{4012, abstract = {The structures of proteins are well-packed, yet they contain numerous cavities which play key roles in accommodating small molecules, or enabling conformational changes. From high-resolution structures it is possible to identify these cavities. We have developed a precise algorithm based on alpha shapes for measuring space-filling-based molecular models (such as van der Waals, solvent accessible, and molecular surface descriptions). We applied this method for accurate computation of the surface area and volume of cavities in several proteins. In addition, all of the atoms/residues Lining the cavities are identified, We use this method to study the structure and the stability of proteins, as well as to locate cavities that could contain structural water molecules in the proton transport pathway in the membrane protein bacteriorhodopsin.}, author = {Liang, Jie and Edelsbrunner, Herbert and Fu, Ping and Sudhakar, Pamidighantam and Subramaniam, Shankar}, issn = {0887-3585}, journal = {Proteins: Structure, Function and Bioinformatics}, number = {1}, pages = {18 -- 29}, publisher = {Wiley-Blackwell}, title = {{Analytical shape computation of macromolecules: II. Inaccessible cavities in proteins}}, doi = {10.1002/(SICI)1097-0134(19981001)33:1<18::AID-PROT2>3.0.CO;2-H}, volume = {33}, year = {1998}, } @article{4013, abstract = {The shape of a protein is important for its functions, This includes the location and size of identifiable regions in its complement space. We formally define pockets as regions in the complement with limited accessibility from the outside. Pockets can be efficiently constructed by an algorithm based on alpha complexes. The algorithm is implemented and applied to proteins with known three-dimensional conformations. 1998 Published by Elsevier Science B.V. All rights reserved.}, author = {Edelsbrunner, Herbert and Facello, Michael and Liang, Jie}, issn = {0166-218X}, journal = {Discrete Applied Mathematics}, number = {1-3}, pages = {83 -- 102}, publisher = {Elsevier}, title = {{On the definition and the construction of pockets in macromolecules}}, doi = {10.1016/S0166-218X(98)00067-5}, volume = {88}, year = {1998}, } @inproceedings{4015, abstract = {The reconstruction of a shape or surface from a finite set of points is a practically significant and theoretically challenging problem. This paper presents a unified view of algorithmic solutions proposed in the computer science literature that are based on the Delaunay complex of the points.}, author = {Edelsbrunner, Herbert}, booktitle = {Proceedingsof the 3rd Latin American Symposium on Theoretical Informatics}, isbn = {9783540642756}, location = {Campinas, Brazil}, pages = {119 -- 132}, publisher = {Springer}, title = {{Shape reconstruction with Delaunay complex}}, doi = {10.1007/BFb0054315}, volume = {1380}, year = {1998}, } @inproceedings{4016, abstract = {Geomagic Wrap™ is a commercially available software for reconstructing shapes and surfaces from 3D scanning data. The data can be any arbitrary finite point set in 3D, and there are no requirements on local density or organization in slices etc. The software contains components for surface reconstruction, improvement, and analysis, and it supports a variety of input and output formats that make it compatible with scanning hardware and CAD and graphics software.}, author = {Edelsbrunner, Herbert and Facello, Michael and Fu, Ping and Qian, Jiang and Nekhayev, Dmitry}, pages = {148 -- 158}, publisher = {SPIE}, title = {{Wrapping 3D scanning data}}, doi = {10.1117/12.302448}, volume = {3313}, year = {1998}, }