@inbook{3568, author = {Edelsbrunner, Herbert}, booktitle = {Handbook of Convex Geometry}, isbn = {978-0-444-89596-7}, pages = {699 -- 735}, publisher = {North Holland}, title = {{Geometric algorithms}}, doi = {10.1016/C2009-0-15705-7}, year = {1993}, } @inbook{3569, author = {Edelsbrunner, Herbert}, booktitle = {Current Trends in Theoretical Computer Science, Essays and Tutorials}, isbn = {978-9810214623}, pages = {1 -- 48}, publisher = {World Scientific Publishing}, title = {{Computational geometry}}, year = {1993}, } @article{3643, abstract = {We investigate the establishment and spread of new adaptive peaks within Wright's ‘shifting balance’. The third phase of the ‘shifting balance’ involves a kind of group selection, since demes in which a superior peak has been established contain more individuals, and so send out more migrants. We assume that population size, N, increases with mean fitness, , according to the exponential relation, . Here, k is a measure of the weakness of density-dependent regulation, and equals the inverse of the regression of log (fitness) on log(N). In the island model, we find that just as with soft selection (k = 0), two distinct types of behaviour exist: group selection makes no qualitative difference. With low numbers of migrants, demes fluctuate almost independently, and only one equilibrium exists. With large numbers of migrants, all the demes evolve towards the same adaptive peak, and so the whole population can move towards one or other of the peaks. Group selection can be understood in terms of an effective mean fitness function. Its main consequence is to increase the effect of selection relative to drift (Ns), and so increase the bias towards the fitter peak. However, this increased bias depends on the ratio between k and the deme size (k/N), and so is very small when density-dependence is reasonably strong.}, author = {Rouhani, Shahin and Barton, Nicholas H}, issn = {0016-6723}, journal = {Genetical Research}, number = {2}, pages = {127 -- 136}, publisher = {Cambridge University Press}, title = {{Group selection and the 'shifting balance'}}, doi = {10.1017/S0016672300031232}, volume = {61}, year = {1993}, } @article{3644, abstract = {Wright proposed that there is a ' shifting balance' between selection within demes, random drift, and selection between demes at different 'adaptive peaks'. We investigate the establishment and spread of new adaptive peaks, considering a chromosome rearrangement, and a polygenic character under disruptive selection. When the number of migrants (Nm) is small, demes fluctuate independently, with a bias towards the fitter peak. When Nm is large, the whole population can move to one of two stable equilibria, and so can be trapped near the lower peak. These two regimes are separated by a sharp transition at a critical Nm of order 1. Just below this critical point, adaptation is most efficient, since the shifting balance greatly increases the proportion of demes that reach the global optimum. This is so even if one peak is only slightly fitter than the other (AWx \/N), and for both strong and weak selection (Ns <§ 1 or Ns > 1). Provided that Nm varies sufficiently gradually from place to place, the fitter peak can be established in regions where Nm « 1, and can then spread through the rest of the range. Our analysis confirms Wright's argument that if selection, migration and drift are of the same order, the ' shifting balance' leads to efficient evolution towards the global optimum.}, author = {Barton, Nicholas H and Rouhani, Shahin}, issn = {0016-6723}, journal = {Genetical Research}, number = {1}, pages = {57 -- 74}, publisher = {Cambridge University Press}, title = {{Adaptation and the 'shifting balance'}}, doi = {10.1017/S0016672300031098 }, volume = {61}, year = {1993}, } @article{4036, abstract = {This paper presents a randomized incremental algorithm for computing a single face in an arrangement of n line segments in the plane that is fairly simple to implement. The expected running time of the algorithm is O(nα(n)log n). The analysis of the algorithm uses a novel approach that generalizes and extends the Clarkson-Shor analysis technique [in Discrete Comput. Geom., 4(1989), pp. 387-421]. A few extensions of the technique, obtaining efficient randomized incremental algorithms for constructing the entire arrangement of a collection of line segments and for computing a single face in an arrangement of Jordan arcs are also presented.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Guibas, Leonidas and Sharir, Micha and Snoeyink, Jack}, issn = {0097-5397}, journal = {SIAM Journal on Computing}, number = {6}, pages = {1286 -- 1302}, publisher = {SIAM}, title = {{Computing a face in an arrangement of line segments and related problems}}, doi = {10.1137/0222077 }, volume = {22}, year = {1993}, } @article{4040, abstract = {A plane geometric graph C in ℝ2 conforms to another such graph G if each edge of G is the union of some edges of C. It is proved that, for every G with n vertices and m edges, there is a completion of a Delaunay triangulation of O(m2 n) points that conforms to G. The algorithm that constructs the points is also described.}, author = {Edelsbrunner, Herbert and Tan, Tiow}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {197 -- 213}, publisher = {Springer}, title = {{An upper bound for conforming Delaunay triangulations}}, doi = {10.1007/BF02573974}, volume = {10}, year = {1993}, } @article{4041, abstract = {The zone theorem for an arrangement of n hyperplanes in d-dimensional real space says that the total number of faces bounding the cells intersected by another hyperplane is O(n(d-1)). This result is the basis of a time-optimal incremental algorithm that constructs a hyperplane arrangement and has a host of other algorithmic and combinatorial applications. Unfortunately, the original proof of the zone theorem, for d greater-than-or-equal-to 3, turned out to contain a serious and irreparable error. This paper presents a new proof of the theorem. The proof is based on an inductive argument, which also applies in the case of pseudohyperplane arrangements. The fallacies of the old proof along with some ways of partially saving that approach are briefly discussed.}, author = {Edelsbrunner, Herbert and Seidel, Raimund and Sharir, Micha}, issn = {0097-5397}, journal = {SIAM Journal on Computing}, number = {2}, pages = {418 -- 429}, publisher = {SIAM}, title = {{On the zone theorem for hyperplane arrangements}}, doi = {10.1137/0222031}, volume = {22}, year = {1993}, } @article{4042, abstract = {It is shown that a triangulation of a set of n points in the plane that minimizes the maximum edge length can be computed in time 0(n2). The algorithm is reasonably easy to implement and is based on the theorem that there is a triangulation with minmax edge length that contains the relative neighborhood graph of the points as a subgraph. With minor modifications the algorithm works for arbitrary normed metrics.}, author = {Edelsbrunner, Herbert and Tan, Tiow}, issn = {0097-5397}, journal = {SIAM Journal on Computing}, number = {3}, pages = {527 -- 551}, publisher = {SIAM}, title = {{A quadratic time algorithm for the minmax length triangulation}}, doi = {10.1137/0222036 }, volume = {22}, year = {1993}, } @article{4044, abstract = {Edge insertion iteratively improves a triangulation of a finite point set in ℜ2 by adding a new edge, deleting old edges crossing the new edge, and retriangulating the polygonal regions on either side of the new edge. This paper presents an abstract view of the edge insertion paradigm, and then shows that it gives polynomial-time algorithms for several types of optimal triangulations, including minimizing the maximum slope of a piecewise-linear interpolating surface.}, author = {Bern, Marshall and Edelsbrunner, Herbert and Eppstein, David and Mitchell, Stephen and Tan, Tiow}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {47 -- 65}, publisher = {Springer}, title = {{Edge insertion for optimal triangulations}}, doi = {10.1007/BF02573962}, volume = {10}, year = {1993}, } @article{4045, abstract = {We apply Megiddo's parametric searching technique to several geometric optimization problems and derive significantly improved solutions for them. We obtain, for any fixed ε>0, an O(n1+ε) algorithm for computing the diameter of a point set in 3-space, an O(8/5+ε) algorithm for computing the width of such a set, and on O(n8/5+ε) algorithm for computing the closest pair in a set of n lines in space. All these algorithms are deterministic.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Guibas, Leonidas and Sharir, Micha}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {183 -- 196}, publisher = {Springer}, title = {{Diameter, width, closest line pair, and parametric searching}}, doi = {10.1007/BF02573973}, volume = {10}, year = {1993}, } @article{4175, abstract = {We have studied the effects of different neurotrophins on the survival and proliferation of rat cerebellar granule cells in culture. These neurons express trkB and trkC, the putative neuronal receptors for brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) respectively. Binding studies using iodinated BDNF and NT-3 demonstrated that both BDNF and NT-3 bind to the cerebellar granule neurons with a similar affinity of approximately 2 x 10(-9) M. The number of receptors per granule cell was surprisingly high, approximately 30 x 10(-4) and 2 x 10(5) for BDNF and NT-3, respectively. Both NT-3 and BDNF elevated c-fos mRNA in the granule neurons, but only BDNF up-regulated the mRNA encoding the low-affinity neurotrophin receptor (p75). In contrast to NT-3, BDNF acted as a survival factor for the granule neurons. BDNF also induced sprouting of the granule neurons and significantly protected them against neurotoxicity induced by high (1 mM) glutamate concentrations. Cultured granule neurons also expressed low levels of BDNF mRNA which were increased by kainic acid, a glutamate receptor agonist. Thus, BDNF, but not NT-3, is a survival factor for cultured cerebellar granule neurons and activation of glutamate receptor(s) up-regulates BDNF expression in these cells.}, author = {Lindholm, Dan and Dechant, Georg and Heisenberg, Carl-Philipp J and Thoenen, Hans}, issn = {0953-816X}, journal = {European Journal of Neuroscience}, number = {11}, pages = {1455 -- 1464}, publisher = {Wiley-Blackwell}, title = {{Brain-derived neurotrophic factor is a survival factor for cultured rat cerebellar granule neurons and protects them against glutamate-induced neurotoxicity}}, doi = {10.1111/j.1460-9568.1993.tb00213.x}, volume = {5}, year = {1993}, } @article{4177, abstract = {Thyroid hormones play an important role in brain development, but the mechanism(s) by which triiodothyronine (T3) mediates neuronal differentiation is poorly understood. Here we demonstrate that T3 regulates the neurotrophic factor, neurotrophin-3 (NT-3), in developing rat cerebellar granule cells both in cell culture and in vivo. In situ hybridization experiments showed that developing Purkinje cells do not express NT-3 mRNA but do express trkC, the putative neuronal receptor for NT-3. Addition of recombinant NT-3 to cerebellar cultures from embryonic rat brain induces hypertrophy and neurite sprouting of Purkinje cells, and upregulates the mRNA encoding the calcium-binding protein, calbindin-28 kD. The present study demonstrates a novel interaction between cerebellar granule neurons and developing Purkinje cells in which NT-3 induced by T3 in the granule cells promotes Purkinje cell differentiation.}, author = {Lindholm, Dan and Castrén, Eero and Tsoulfas, Pantelis and Kolbeck, Roland and Berzaghi, Maria and Leingärtner, Axel and Heisenberg, Carl-Philipp J and Tesarollo, Lino and Parada, Luis and Thoenen, Hans}, issn = {0021-9525}, journal = {Journal of Cell Biology}, number = {2}, pages = {443 -- 450}, publisher = {Rockefeller University Press}, title = {{Neurotrophin-3 induced by tri-iodothyronine in cerebellar granule cells promotes Purkinje cell differentiation}}, doi = {10.1083/jcb.122.2.443}, volume = {122}, year = {1993}, } @article{4299, abstract = {Evolutionary explanations of aging (or senescence) fall into two classes. First, organisms might have evolved the optimal life history, in which survival and fertility late in life are sacrificed for the sake of early reproduction or high pre-adult survival. Second, the life history might be depressed below this optimal compromise by the influx of deleterious mutations; since selection against late-acting mutations is weaker, deleterious mutations will impose a greater load on late life. We discuss ways in which these theories might be investigated and distinguished, with reference to experimental work withDrosophila. While genetic correlations between life history traits determine the immediate response to selection, they are hard to measure, and may not reflect the fundamental constraints on life history. Long term selection experiments are more likely to be informative. The third approach of using experimental manipulations suffers from some of the same problems as measures of genetic correlations; however, these two approaches may be fruitful when used together. The experimental results so far suggest that aging inDrosophila has evolved in part as a consequence of selection for an optimal life history, and in part as a result of accumulation of predominantly late-acting deleterious mutations. Quantification of these effects presents a major challenge for the future.}, author = {Partridge, Linda and Barton, Nicholas H}, issn = {0016-6707}, journal = {Genetica}, number = {1-3}, pages = {89 -- 98}, publisher = {Springer}, title = {{Evolution of aging: Testing the theory using Drosophila}}, doi = {10.1007/BF01435990}, volume = {91}, year = {1993}, } @article{4300, abstract = {Evolutionary explanations of ageing fall into two classes. Organisms might have evolved the optimal life history, in which survival and fertility late in life are sacrificed for the sake of early reproduction and survival. Alternatively, the life history might be depressed below this optimal compromise by deleterious mutations: because selection against late-acting mutations is weaker, these will impose a greater load on late life. Evidence for the importance of both is emerging, and unravelling their relative importance presents experimentalists with a major challenge.}, author = {Partridge, Linda and Barton, Nicholas H}, issn = {0028-0836}, journal = {Nature}, pages = {305 -- 311}, publisher = {Nature Publishing Group}, title = {{Optimality, mutation and the evolution of ageing}}, doi = {10.1038/362305a0}, volume = {362}, year = {1993}, } @inbook{4301, author = {Barton, Nicholas H and Gale, Katherine}, booktitle = {Hybrid zones and the evolutionary process}, editor = {Harrison, Richard}, isbn = { 0-19-506917-X}, pages = {13 -- 45}, publisher = {Oxford University Press}, title = {{Genetic analysis of hybrid zones}}, doi = {10.1046/j.1420-9101.1994.7050631.x}, year = {1993}, } @misc{4302, author = {Barton, Nicholas H}, booktitle = {Genetical Research}, issn = {0016-6723}, number = {1}, pages = {77 -- 85}, publisher = {Cambridge University Press}, title = {{Review of "The causes of molecular evolution" by J.H. Gillespie}}, doi = {10.1017/S001667230003158X }, volume = {62}, year = {1993}, } @article{4303, abstract = {In a stably subdivided population with symmetric migration, the chance that a favoured allele will be fixed is independent of population structure. However, random extinction introduces an extra component of sampling drift, and reduces the probability of fixation. In this paper, the fixation probability is calculated using the diffusion approximation; comparison with exact solution of the discrete model shows this to be accurate. The key parameters are the rates of selection, migration and extinction, scaled relative to population size (S = 4Ns, M = 4Nm, Λ = 4Nλ); results apply to a haploid model, or to diploids with additive selection. If new colonies derive from many demes, the fixation probability cannot be reduced by more than half. However, if colonies are initially homogeneous, fixation probability can be much reduced. In the limit of low migration and extinction rates (M, Λ 1), it is 2s/{1 + (Λ/MS)(1 −exp(−S))}, whilst in the opposite limit (S 1), it is 4sM/{Λ(Λ + M)}. In the limit of weak selection (M, Λ 1), it is 4sM/{Λ(Λ + M)}. These factors are not the same as the reduction in effective population size (Ne/N), showing that the effects of population structure on selected alleles cannot be understood from the behaviour of neutral markers.}, author = {Barton, Nicholas H}, issn = {0016-6723}, journal = {Genetics Research}, number = {2}, pages = {149 -- 158}, publisher = {Cambridge University Press}, title = {{The probability of fixation of a favoured allele in a subdivided population}}, doi = {10.1017/S0016672300031748}, volume = {62}, year = {1993}, } @article{4304, author = {Barton, Nicholas H}, issn = {0960-9822}, journal = {Current Biology}, number = {11}, pages = {797 -- 799}, publisher = {Cell Press}, title = {{Why species and subspecies?}}, doi = {10.1016/0960-9822(93)90036-N}, volume = {3}, year = {1993}, } @inproceedings{4506, abstract = {We propose a formal framework for designing hybrid systems by stepwise refinement. Starting with a specification in hybrid temporal logic, we make successively more transitions explicit until we obtain an executable system.}, author = {Henzinger, Thomas A and Manna, Zohar and Pnueli, Amir}, booktitle = {International Hybrid Systems Workshop}, editor = {Grossman, Robert and Nerode, Anil and Ravn, Anders and Rischel, Hans}, isbn = {978-3-540-57318-0}, pages = {60 -- 76}, publisher = {Springer}, title = {{Towards refining temporal specifications into hybrid systems}}, doi = {10.1007/3-540-57318-6_24}, volume = {736}, year = {1993}, } @article{4589, abstract = {The theory of the natural numbers with linear order and monadic predicates underlies propositional linear temporal logic. To study temporal logics that are suitable for reasoning about real-time systems, we combine this classical theory of infinite state sequences with a theory of discrete time, via a monotonic function that maps every state to its time. The resulting theory of timed state sequences is shown to be decidable, albeit nonelementary, and its expressive power is characterized by ω-regular sets. Several more expressive variants are proved to be highly undecidable. This framework allows us to classify a wide variety of real-time logics according to their complexity and expressiveness. Indeed, it follows that most formalisms proposed in the literature cannot be decided. We are, however, able to identify two elementary real-time temporal logics as expressively complete fragments of the theory of timed state sequences, and we present tableau-based decision procedures for checking validity. Consequently, these two formalisms are well-suited for the specification and verification of real-time systems. Copyright © 1993 Academic Press. All rights reserved.}, author = {Alur, Rajeev and Henzinger, Thomas A}, issn = {0890-5401}, journal = {Information and Computation}, number = {1}, pages = {35 -- 77}, publisher = {Elsevier}, title = {{Real-time logics: Complexity and expressiveness}}, doi = {10.1006/inco.1993.1025}, volume = {104}, year = {1993}, }