@inbook{3455, abstract = {At a synapse, the transmitter is stored in synaptic vesicles and is released into the synaptic cleft almost instantaneously upon fusion of these vesicles with the presynaptic membrane. Subsequently, the transmitter diffuses to ligand-gated ion channels in the postsynaptic density, binds to them, and thereby causes channel activation. Unfortunately, we have estimates neither of the exact amount of transmitter in the synaptic vesicle nor of the concentration in the synaptic cleft reaching the postsynaptic receptors, and in some cases even the identity of the transmitter is unknown. These questions may be addressed by modeling of release and diffusion. Such a theoretical approach, however, is based on several assumptions, some of which lack experimental evidence.}, author = {Jonas, Peter M}, booktitle = {Single-channel recording}, editor = {Sakmann, Bert and Neher, Erwin}, isbn = {978-0-306-44870-6}, pages = {231 -- 243}, publisher = {Plenum}, title = {{Fast application of agonists to isolated membrane patches}}, doi = {10.1007/978-1-4419-1229-9_10}, year = {1995}, } @article{3461, author = {Jonas, Peter M and Burnashev, Nail}, issn = {0896-6273}, journal = {Neuron}, number = {5}, pages = {987 -- 990}, publisher = {Elsevier}, title = {{Molecular mechanisms controlling calcium entry through AMPA-type glutamate receptor channels}}, doi = {10.1016/0896-6273(95)90087-X}, volume = {15}, year = {1995}, } @article{3478, abstract = {1. Properties of dendritic glutamate receptor (GluR) channels were investigated using fast application of glutamate to outside-out membrane patches isolated from the apical dendrites of CA3 and CA1 pyramidal neurons in rat hippocampal slices. CA3 patches were formed (15-76 μm from the soma) in the region of messy fibre (MF) synapses, and CA1 patches (25-174 μm from the soma) in the region of Schaffer collateral (SC) innervation. 2. Dual-component responses consisting of a rapidly rising and decaying component followed by a second, substantially slower, component were elicited by 1 ms pulses of 1 mM glutamate in the presence of 10 μM glycine and absence of external Mg2+. The fast component was selectively blocked by 2-5 μM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and the slow component by 30 μM D-2-amino-5-phosphonopentanoic acid (D-AP5), suggesting that the fast and slow components were mediated by the GluR channels of the L-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and NMDA type, respectively. The peak amplitude ratio of the NMDA to AMPA receptor-mediated components varied between 0.03 and 0.62 in patches from both CA3 and CA1 dendrites. Patches lacking either component were rarely observed. 3. The peak current-voltage (I-V) relationship of the fast component was almost linear, whereas the I-V relationship of the slow component showed a region of negative slope in the presence of 1 mM external Mg2+. The reversal potential for both components was close to 0 mV. 4. Kainate-preferring GluR channels did not contribute appreciably to the response to glutamate. The responses to 100 ms pulses of 1 mM glutamate were mimicked by application of 1 mM AMPA, whereas 1 mM kainate produced much smaller, weakly desensitizing currents. This suggests that the fast component is primarily mediated by the action of glutamate on AMPA-preferring receptors. 5. The mean elementary conductance of AMPA receptor channels was about 10 pS, as estimated by non-stationary fluctuation analysis. The permeability of these channels to Ca2+ was low (~5% of the permeability to Cs+). 6. The elementary conductance of NMDA receptor channels was larger, with a main conductance state of about 45 pS. These channels were 3.6 times more permeable to Ca2+ than to Cs+. 7. AMPA receptor-mediated currents activated rapidly in response to 1 ms pulses of 1 mM glutamate and deactivated with a predominant, fast time constant and a smaller, slower component (τ1≃2 ms, τ2≃8 ms, contributing ~80 and ~20% to the total decay amplitude, respectively). Desensitization of the current during a 100 ms pulse was best fitted by two time constants (τ1≃10 ms, ~60%; τ2≃34 ms, ~40%). 8. NMDA receptor-mediated currents in response to 1 ms pulses of 1 mM glutamate activated and deactivated much more slowly than AMPA receptor-mediated currents. The time course could be described by a single exponential rising phase (τ≃7 ms) followed by a double exponential decay (τ1≃200 ms, ~80%; τ2≃1-3 s, ~20%). 9. Mg2+ blocked the NMDA component in a voltage-dependent manner, with a half-maximal inhibitory concentration (IC50) of 21 μM at -80 mV. At physiological Mg2+ concentrations, block of the NMDA component could be rapidly relieved with voltage jumps from negative to positive potentials. Block of the current upon return to negative potentials occurred almost instantaneously. 10. Zn2+ also selectively-blocked the NMDA receptor-mediated current with an IC50 of 22 μM, but this block differed from that of Mg2+ in that it showed little voltage dependence. Rapid application of Zn2+ together with glutamate produced partial block of the current. More block was observed if Zn2+ and glutamate were co-applied when NMDA receptor channels were already open. 11. The functional properties of dendritic GluRs were similar to those found at the soma. Knowledge of these properties facilitated simulations investigating the contribution of coactivated AMPA and NMDA receptors to synaptic depolarization and Ca2+ entry into dendritic spines. Because of its slow deactivation, the NMDA receptor-mediated current contributes substantially to depolarization and Ca2+ entry and is susceptible to modulation over a period of seconds, either by backpropagating action potentials or by the release of Zn2+ from presynaptic boutons.}, author = {Spruston, Nelson and Jonas, Peter M and Sakmann, Bert}, issn = {0022-3751}, journal = {Journal of Physiology}, number = {Pt 2}, pages = {325 -- 352}, publisher = {Wiley-Blackwell}, title = {{Dendritic glutamate receptor channels in rat hippocampal CA3 and CA1 pyramidal neurons}}, doi = {10.1113/jphysiol.1995.sp020521}, volume = {482}, year = {1995}, } @article{3479, abstract = {1. Glutamate receptor (GluR) channels were studied in basket cells in the dentate gyrus of rat hippocampal slices. Basket cells were identified by their location, dendritic morphology and high frequency of action potentials generated during sustained current injection. 2. Dual-component currents were activated by fast application of glutamate to outside-out membrane patches isolated from basket cell somata (10 μM glycine, no external Mg2+). The fast component was selectively blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the slow component by D-2-amino-5-phosphonopentanoic acid (D-AP5). This suggests that the two components were mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR)/kainate receptor and N-methyl-D-aspartate receptor (NMDAR) channels, respectively. The mean ratio of the peak current of the NMDAR component to that of the AMPAR/kainate receptor component was 0.22 (1 ms pulses of 10 mM glutamate). 3. The AMPAR/kainate receptor component, which was studied in isolation in the presence of D-AP5, was identified as AMPAR mediated on the basis of the preferential activation by AMPA as compared with kainate, the weak desensitization of kainate-activated currents, the cross-desensitization between AMPA and kainate, and the reduction of desensitization by cyclothiazide. 4. Deactivation of basket cell AMPARs following 1 ms pulses of glutamate occurred with a time constant (τ) of 1.2 ± 0.1 ms (mean ± S.E.M.). During 100 ms glutamate pulses, AMPARs desensitized with a τ of 3.7 ± 0.2 ms. 5. The peak current-voltage (I-V) relation of AMPAR-mediated currents in Na+-rich extracellular solution showed a reversal potential of -4.0 ± 2.6 mV and was characterized by a doubly rectifying shape. The conductance of single AMPAR channels was estimated as 22.6 ± 1.6 pS using non-stationary fluctuation analysis. AMPARs expressed in hippocampal basket cells mere highly Ca2+ permeable (P(Ca)/P(K) = 1.79). 6. NMDARs in hippocampal basket cells were studied in isolation in the presence of CNQX. Deactivation of NMDARs activated by glutamate pulses occurred bi-exponentially with mean τ values of 266 ± 23 ms (76%) and 2620 ± 383 ms (24%). 7. The peak I-V relation of the NMDAR-mediated component in Na+-rich extracellular solution showed a reversal potential of 1.5 ± 0.6 mV and a region of negative slope at negative membrane potentials in the presence of external Mg2+, due to voltage-dependent block by these ions. The conductance of single NMDAR channels in the main open state was 50.2 ± 1.8 pS. NMDARs in hippocampal basket cells were highly permeable to Ca2+ (P(Ca)/P(K) = 6.68). 8. AMPARs in hippocampal basket cells are characterized by about threefold faster kinetics and twentyfold higher Ca2+ permeability than AMPARs in hippocampal granule or pyramidal cells. Simulations show that the Ca2+ influx through basket cell AMPARs is comparable to that through NMDARs at negative membrane potentials with physiological concentrations of Ca2+ and Mg2+. This suggests a dual pathway of synaptically mediated Ca2+ entry into interneurones.}, author = {Koh, Duk and Geiger, Jörg and Jonas, Peter M and Sakmann, Bert}, issn = {0022-3751}, journal = {Journal of Physiology}, number = {Pt 2}, pages = {383 -- 402}, publisher = {Wiley-Blackwell}, title = {{Ca(2+)-permeable AMPA and NMDA receptor channels in basket cells of rat hippocampal dentate gyrus}}, doi = {10.1113/jphysiol.1995.sp020737}, volume = {485}, year = {1995}, } @article{3480, abstract = {Recording of glutamate-activated currents in membrane patches was combine with RT-PCR-mediated AMPA receptor (AMPAR) subunit mRNA analysis in single identified cells of rat brain slices. Analysis of AMPARs in principal neurons end interneurons of hippocampus and neocortex and in auditory relay neurons and Bergmann glial cells indicates that the GluR-B subunit in its flip version determines formation of receptors with relatively slow gating, whereas the GluR-D subunit promotes assembly of more rapidly gated receptors. The relation between Ca 2+ permeability of AMPAR channels and the relative GluR-B mRNA abundance is consistent with the dominance of this subunit in determining the Ca 2+ permeability of native receptors. The results suggest that differential expression of GluR-B and GluR-D subunit genes, as well as splicing end editing of their mRNAs, account for the differences in gating and Ca 2+ permeability of native AMPAR channels.}, author = {Geiger, Jörg and Melcher, Thorsten and Koh, Duk and Sakmann, Bert and Seeburg, Peter and Jonas, Peter M and Monyer, Hannah}, issn = {0896-6273}, journal = {Neuron}, number = {1}, pages = {193 -- 204}, publisher = {Elsevier}, title = {{Relative abundance of subunit mRNAs determines gating and Ca(2+) permeability of AMPA receptors in principal neurons and interneurons in rat CNS}}, doi = {10.1016/0896-6273(95)90076-4}, volume = {15}, year = {1995}, } @article{3481, abstract = {1. The influence of intracellular factors on current rectification of different subtypes of native α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) was studied in rat brain slices by combining fast application of glutamate with patch pipette perfusion. 2. The peak current-voltage (I-V) relation of the AMPARs expressed in Bergmann glial cells of cerebellum and dentate gyrus (DG) basket cells of hippocampus was weakly rectifying in outside-out patches and nystatin-perforated vesicles, but showed a doubly rectifying shape with a region of reduced slope between 0 and +40 mV in nucleated patches. The I-V relation of AMPARs expressed in hippocampal CA3 pyramidal neurones was linear in all recording configurations. 3. Intracellular application of 2.5 μM spermine, a naturally occurring polyamine, blocked outward currents in outside-oat patches from Bergmann glial cells and DG basket cells in a voltage-dependent manner, generating I-V relations with a doubly rectifying shape which were similar to those recorded in nucleated patches. AMPARs in CA3 pyramidal cell patches were unaffected by 25 μM spermine. 4. The half-maximal blocking concentration of spermine at +40 mV was 0.3 μM in Bergmann glial cell patches and 1.5 μM in DG basket cell patches, whereas it was much higher (≥ 100 μM) for CA3 pyramidal. cell patches. Spermidine also affected current rectification, but with lower affinity. The block of outward current by polyamines following voltage jumps developed within < 0.5 ms. 5. We conclude that current rectification, rather than being an intrinsic property of the Ca2+ permeable AMPAR channel, is generated by polyamine block.}, author = {Koh, Duk and Burnashev, Nail and Jonas, Peter M}, issn = {0022-3751}, journal = {Journal of Physiology}, number = {Pt 2}, pages = {305 -- 312}, publisher = {Wiley-Blackwell}, title = {{Block of native Ca(2+)-permeable AMPA receptors in rat brain by intracellular polyamines generates double rectification}}, doi = {10.1113/jphysiol.1995.sp020813}, volume = {486}, year = {1995}, } @inproceedings{3551, abstract = {Common geometric models for proteins and other molecules are the space filling diagram, the solvent accessible surface, and the molecular surface. We describe software that computes metric properties of these models, including volume and surface area. It also measures voids or empty space enclosed by the protein, and it keeps track of surface area contributions of individual atoms. The software is based on 3-dimensional alpha complexes and on inclusion-exclusion formulas with terms derived from the simplices in this complex.}, author = {Edelsbrunner, Herbert and Facello, Michael and Fu, Ping and Liang, Jie}, booktitle = {Proceedings of the 28th Annual Hawaii International Conference on System Sciences}, isbn = {0-8186-6930-6}, location = {Wailea, HI, United States of America}, pages = {256 -- 264}, publisher = {IEEE}, title = {{Measuring proteins and voids in proteins}}, doi = {10.1109/HICSS.1995.375331}, year = {1995}, } @inproceedings{3552, abstract = {The concept of an α-shape of a finite set of points in R^d, with weights, is defined and illustrated. An α-shape is a polytope which is not necessarily convex nor connected and can be derived from the (weighted) Delaunay triangulation of the point set, with a parameter controlling the desired level of detail. The set of all α values leads to a descrete family of shapes capturing the intuitive notion of ``crude'' versus ``fine'' shapes of a point set. Software that computes such shapes in R^2 and R^3 is available via anonymous ftp from: ftp://ftp.ncsa.uiuc.edu/Visualization/Alpha-shape/ }, author = {Akkiraju, Nataraj and Edelsbrunner, Herbert and Facello, Michael and Fu, Ping and Mücke, Ernst and Varela, Carlos}, pages = {63 -- 66}, publisher = {Elsevier}, title = {{Alpha shapes: definition and software}}, year = {1995}, } @misc{3597, author = {Kirkpatrick, Mark and Barton, Nicholas H}, booktitle = {Nature}, issn = {0028-0836}, pages = {388 -- 389}, publisher = {Nature Publishing Group}, title = {{Déjà vu all over again}}, doi = {10.1038/377388a0}, volume = {377}, year = {1995}, } @article{3636, abstract = {Observations on the means, variances, and covariances of quantitative traits across hybrid zones can give information similar to that from Mendelian markers. In addition, they can identify particular traits through which the cline is maintained. We describe a survey of six traits across the hybrid zone between Bombina bombina and Bombina variegata (Amphibia: Discoglossidae) near Pescenica in Croatia. We obtained laboratory measuments of the belly pattern, skin thickness, mating call, skeletal form, egg size, and the developmental time of tadpoles. Although offspring from hybrid populations showed no evidence of reduced viability, a third of the F1 families failed completely, irrespective of the direction of the cross. All traits differed significantly between the taxa. Clines in belly pattern, skin thickness, mating call, and skeletal form were closely concordant with clines in four diagnostic enzyme loci. However, the cline in developmental time was displaced towards bombina, and the cline in egg size was displaced towards variegata. This discordance could be because the traits are not inherited additively or because they are subject to different selection pressures. We favor the latter explanation in the case of developmental time. We show that moderate selection acting directly on a trait suffices to shift its position; rather stronger selection is needed to change its width appreciably. Within hybrid populations, there are significant associations among quantitative traits, and between traits and enzymes. Phenotypic variances also increase in hybrid populations. These observations can be explained by linkage disequilibria among the underlying loci. However, the average magnitude of the covariance between traits is about half that expected from the linkage disequilibria between enzyme loci. The discrepancy is not readily explained by nonadditive gene action. This puzzle is now unresolved and calls for further investigation.}, author = {Nürnberger, Beate and Barton, Nicholas H and Maccallum, Catriona and Gilchrist, Jason and Appleby, Michael}, issn = {0014-3820}, journal = {Evolution}, number = {6}, pages = {1224 -- 1238}, publisher = {Wiley-Blackwell}, title = {{Natural selection on quantitative traits in the Bombina hybrid zone}}, doi = {10.1111/j.1558-5646.1995.tb04449.x}, volume = {49}, year = {1995}, } @article{3637, abstract = {Hybridizing taxa remain distinct for two main reasons. Natural selection acts against hybrids either because of their incompatible genome, or because of differential adaptation of the pure types across an environmental gradient. Here, we provide experimental evidence that the location of the Bombina (Anura: Discoglossidae) hybrid zone in Croatia is, at least in part, determined by differential adaptation. B. bombina typically breeds in permanent water in the lowland, whereas B. variegata reproduces in puddles at higher elevations. In a reciprocal translocation, pure bombina and variegata tadpoles were introduced in equal proportions into lowland pond enclosures and upland puddles. After three weeks, variegata exceeded bombina in survival and growth in both habitats. The effect was most pronounced in puddles, where the few surviving bombina tadpoles had hardly grown at all. In comparison to variegata, the smaller hatchlings of bombina grew relatively faster in ponds, but remained smaller in absolute terms. Nevertheless, B. bombina appears better adapted to ponds than to puddles. The mechanisms by which variegata is excluded from ponds remain to be demonstrated. These data show that habitat dependent selection prevents the invasion of bombina tadpole traits into the variegata gene pool. Given the strong linkage disequilibria in hybrid populations, differential selection on tadpoles may be sufficient to maintain the integrity of the two gene pools.}, author = {Maccallum, Catriona and Nürnberger, Beate and Barton, Nicholas H}, issn = {0962-8452}, journal = {Proceedings of the Royal Society of London Series B Biological Sciences}, number = {1359}, pages = {257 -- 264}, publisher = {Royal Society of London}, title = {{Experimental evidence for habitat dependent selection in a Bombina hybrid zone}}, doi = {10.1098/rspb.1995.0089}, volume = {260}, year = {1995}, } @article{3638, abstract = {Any sample of genes traces back to a single common ancestor. Each gene also has other properties: its sequence, its geographic location and the phenotype and fitness of the organism that carries it. With sexual reproduction, different genes have different genealogies, which gives us much more information, but also greatly complicates population genetic analysis. We review the close relation between the distribution of genealogies and the classic theory of identity by descent in spatially structured populations, and develop a simple diffusion approximation to the distribution of coalescence times in a homogeneous two-dimensional habitat. This shows that when neighbourhood size is large (as in most populations) only a small fraction of pairs of genes are closely related, and only this fraction gives information about current rates of gene flow. The increase of spatial dispersion with lineage age is thus a poor estimator of gene flow. The bulk of the genealogy depends on the long-term history of the population; we discuss ways of inferring this history from the concordance between genealogies across loci.}, author = {Barton, Nicholas H and Wilson, I}, issn = {0962-8436}, journal = {Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences}, number = {1327}, pages = {49 -- 59}, publisher = {Royal Society, The}, title = {{Genealogies and geography}}, doi = {10.1098/rstb.1995.0090}, volume = {349}, year = {1995}, } @article{3639, abstract = {A general representation of multilocus selection is extended to allow recombination to depend on genotype. The equations simplify if modifier alleles have small effects on recombination. The evolution of such modifiers only depends on how they alter recombination between the selected loci, and does not involve dominance in modifier effects. The net selection on modifiers can be found explicitly if epistasis is weak relative to recombination. This analysis shows that recombination can be favoured in two ways: because it impedes the response to epistasis which fluctuates in sign, or because it facilitates the response to directional selection. The first mechanism is implausible, because epistasis must change sign over periods of a few generations: faster or slower fluctuations favour reduced recombination. The second mechanism requires weak negative epistasis between favourable alleles, which may either be increasing, or held in check by mutation. The selection (si) on recombination modifiers depends on the reduction in additive variance of log (fitness) due to linkage disequilibria (υ1 < 0), and on non-additive variance in log (fitness) (V′2, V′3,.. epistasis between 2, 3.. loci). For unlinked loci and pairwise epistasis, si = − (υ1 + 4V2/3)δr, where δr is the average increase in recombination caused by the modifier. The approximations are checked against exact calculations for three loci, and against Charlesworth's analyses of mutation/selection balance (1990), and directional selection (1993). The analysis demonstrates a general relation between selection on recombination and observable components of fitness variation, which is open to experimental test.}, author = {Barton, Nicholas H}, issn = {0016-6723}, journal = {Genetical Research}, number = {2}, pages = {123 -- 144}, publisher = {Cambridge University Press}, title = {{A general model for the evolution of recombination}}, doi = {10.1017/S0016672300033140}, volume = {65}, year = {1995}, } @article{3640, abstract = {The probability of fixation of a favorable mutation is reduced if selection at other loci causes inherited variation in fitness. A general method for calculating the fixation probability of an allele that can find itself in a variety of genetic backgrounds is applied to find the effect of substitutions, fluctuating polymorphisms, and deleterious mutations in a large population. With loose linkage, r, the effects depend on the additive genetic variance in relative fitness, var(W), and act by reducing effective population size by (N/Ne) = 1 + var(W)/2r2. However, tightly linked loci can have a substantial effect not predictable from Ne. Linked deleterious mutations reduce the fixation probability of weakly favored alleles by exp (-2U/R), where U is the total mutation rate and R is the map length in Morgans. Substitutions can cause a greater reduction: an allele with advantage s < scrit = (pi 2/6) loge (S/s) [var(W)/R] is very unlikely to be fixed. (S is the advantage of the substitution impeding fixation.) Fluctuating polymorphisms at many (n) linked loci can also have a substantial effect, reducing fixation probability by exp [square root of 2Kn var(W)/R] [K = -1/E((u-u)2/uv) depending on the frequencies (u,v) at the selected polymorphisms]. Hitchhiking due to all three kinds of selection may substantially impede adaptation that depends on weakly favored alleles.}, author = {Barton, Nicholas H}, issn = {0016-6731}, journal = {Genetics}, number = {2}, pages = {821 -- 841}, publisher = {Genetics Society of America}, title = {{Linkage and the limits to natural selection}}, doi = {http://www.genetics.org/content/140/2/821.long}, volume = {140}, year = {1995}, } @article{4028, abstract = {Efficient algorithms are described for computing topological, combinatorial, and metric properties of the union of finitely many spherical balls in R(d) These algorithms are based on a simplicial complex dual to a decomposition of the union of balls using Voronoi cells, and on short inclusion-exclusion formulas derived from this complex. The algorithms are most relevant in R(3) where unions of finitely many balls are commonly used as models of molecules.}, author = {Edelsbrunner, Herbert}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {415 -- 440}, publisher = {Springer}, title = {{The union of balls and its dual shape}}, doi = {10.1007/BF02574053}, volume = {13}, year = {1995}, } @article{4029, abstract = {A general and direct method for computing the Betti numbers of a finite simplicial complex in Bd is given. This method is complete for d less than or equal to 3, where versions of this method run in time O(n alpha(n)) and O(n), n the number of simplices. An implementation of the algorithm is applied to alpha shapes, which is a novel geometric modeling tool.}, author = {Delfinado, Cecil and Edelsbrunner, Herbert}, issn = {0167-8396}, journal = {Computer Aided Geometric Design}, number = {7}, pages = {771 -- 784}, publisher = {Elsevier}, title = {{An incremental algorithm for Betti numbers of simplicial complexes on the 3-sphere}}, doi = {10.1016/0167-8396(95)00016-Y}, volume = {12}, year = {1995}, } @inproceedings{4034, abstract = {Any arbitrary polyhedron P contained as a subset within Rd can be written as algebraic sum of simple terms, each an integer multiple of the intersection of d or fewer half-spaces defined by facets of P. P can be non-convex and can have holes of any kind. Among the consequences of this result are a short boolean formula for P, a fast parallel algorithm for point classification, and a new proof of the Gram-Sommerville angle relation.}, author = {Edelsbrunner, Herbert}, booktitle = {Proceedings of IEEE 36th Annual Foundations of Computer Science}, issn = {0272-5428}, location = {Milwaukee, WI, United States of America}, pages = {248 -- 257}, publisher = {IEEE}, title = {{Algebraic decomposition of non-convex polyhedra}}, year = {1995}, } @article{4035, abstract = {Let S be a set of n points in ℝd . A set W is a weak ε-net for (convex ranges of)S if, for any T⊆S containing εn points, the convex hull of T intersects W. We show the existence of weak ε-nets of size {Mathematical expression}, where β2=0, β3=1, and βd ≈0.149·2d-1(d-1)!, improving a previous bound of Alon et al. Such a net can be computed effectively. We also consider two special cases: when S is a planar point set in convex position, we prove the existence of a net of size O((1/ε) log1.6(1/ε)). In the case where S consists of the vertices of a regular polygon, we use an argument from hyperbolic geometry to exhibit an optimal net of size O(1/ε), which improves a previous bound of Capoyleas.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Grigni, Michelangelo and Guibas, Leonidas and Sharir, Micha and Welzl, Emo}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {1 -- 15}, publisher = {Springer}, title = {{Improved bounds on weak ε-nets for convex sets}}, doi = {10.1007/BF02574025}, volume = {13}, year = {1995}, } @article{4153, author = {Ransom, D. and Brownlie, Alison and Haffter, Pascal and Odenthal, Jörg and Kelsh, Robert and Brand, Michael and Furutani Seiki, Makoto and Granato, Michael and Hammerschmidt, Matthias and Heisenberg, Carl-Philipp J and Jiang, Yunjin and Kane, David and Mullins, Mary and Van Eden, Fredericus and Warga, Rachel and Nüsslein Volhard, Christiane and Zon, L.}, issn = {0006-4971}, journal = {Blood}, number = {10}, pages = {1912 -- 1912}, publisher = {American Society of Hematology}, title = {{Hematopoietic mutants identified in a saturation screen of the zebrafish genome}}, volume = {86}, year = {1995}, } @article{4296, abstract = {Three replicate lines of Drosophila melanogaster were cultured at each of two temperatures (16.5⚬C and 25⚬C) in population cages for 4 yr. The lifespans of both sexes and the fecundity and fertility of the females were then measured at both experimental temperatures. The characters showed evidence of adaptation; flies of both sexes from each selection regime showed higher longevity, and females showed higher fecundity and fertility, than flies from the other selection regime when they were tested at the experimental temperature at which they had evolved. Calculation of intrinsic rates of increase under different assumptions about the rate of population increase showed that the difference between the lines from the two selection regimes became less the higher the rate of population increase, because the lines were more similar in early adulthood than they were later. Despite the increased adaptation of the low-temperature lines to the low temperature, like the high temperature lines they produced progeny at a higher rate at the higher temperature. The lines may have independently evolved adaptations to their respective thermal regimes during the experiment, or there may have been a trade-off between adaptation to the two temperatures, or mutation pressure may have lowered adaptation to the temperature that the flies no longer encountered.}, author = {Partridge, Linda and Barrie, Brian and Barton, Nicholas H and Fowler, Kevin and French, Vernon}, issn = {0014-3820}, journal = {Evolution}, number = {3}, pages = {538 -- 544}, publisher = {Wiley-Blackwell}, title = {{Rapid laboratory evolution of adult life history traits in Drosophila melanogaster in response to temperature}}, doi = {10.1111/j.1558-5646.1995.tb02285.x}, volume = {49}, year = {1995}, }