@inproceedings{4058, abstract = {We present 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.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Guibas, Leonidas and Sharir, Micha and Snoeyink, Jack}, booktitle = {Proceedings of the 2nd annual ACM-SIAM symposium on Discrete algorithms}, isbn = {978-0-89791-376-8}, location = {San Francisco, CA, United States of America}, pages = {441 -- 448}, publisher = {SIAM}, title = {{Computing a face in an arrangement of line segments}}, year = {1991}, } @inproceedings{4055, 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 O(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}, booktitle = {32nd Annual Symposium of Foundations of Computer Science}, location = {San Juan, PR, United States of America}, pages = {414 -- 423}, publisher = {IEEE}, title = {{A quadratic time algorithm for the minmax length triangulation}}, doi = {10.1109/SFCS.1991.185400}, year = {1991}, } @article{4051, abstract = {An algorithm is presented that constructs the convex hull of a set of n points in three dimensions in worst-case time O(n log2h) and storage O(n), where h is the number of extreme points. This is an improvement of the O(nh) time gift-wrapping algorithm and, for certain values of h, of the O(n log n) time divide-and-conquer algorithm.}, author = {Edelsbrunner, Herbert and Shi, Weiping}, issn = {1095-7111}, journal = {SIAM Journal on Computing}, number = {2}, pages = {259 -- 269}, publisher = {SIAM}, title = {{An O(n log^2 h) time algorithm for the three-dimensional convex hull problem}}, doi = {10.1137/0220016 }, volume = {20}, year = {1991}, } @article{4057, author = {Edelsbrunner, Herbert}, issn = {1090-2724}, journal = {Journal of Computer and System Sciences}, number = {2}, pages = {249 -- 251}, publisher = {Elsevier}, title = {{Corrigendum}}, doi = {10.1016/0022-0000(91)90013-U}, volume = {42}, year = {1991}, } @article{3468, abstract = {Two types of metabolically regulated K channels have been identified for the first time in enzymatically demyelinated fibres of amphibian sciatic nerve using the patch-clamp technique. A maxi K channel with a single-channel conductance of 132 pS (105 mM K on both sides of the membrane, 15°C) is activated both by micromolar concentrations of internal Ca and by depolarization. A second type of K channel with a conductance of 44 pS is inhibited by intracellular adenosine 5'-triphosphate (ATP) with a half-maximal inhibitory concentration (IC50) of 35 μM. It is blocked by submicromolar concentrations of external glibenclamide. Both channels are sensitive to external tetraethylammonium chloride (IC50 = 0.2 mM for the maxi K channel and 4.2 mM for the ATP-sensitive channel). They may be part of a complex feedback system regulating axonal excitability under various metabolic conditions. }, author = {Jonas, Peter M and Koh, Duk and Kampe, Knut and Hermsteiner, Markus and Vogel, Werner}, issn = {1432-2013}, journal = {Pflügers Archiv : European Journal of Physiology}, number = {1-2}, pages = {68 -- 73}, publisher = {Springer}, title = {{ATP-sensitive and Ca-activated K channels in vertebrate axons: novel links between metabolism and excitability}}, doi = {10.1007/BF00370453}, volume = {418}, year = {1991}, } @article{3646, abstract = {We compare the pattern of morphological and electrophoretic variation in the hybrid zone between Bombina bombina and B. variegata across two transects: one near Cracow and one 200 km away, near Przemysl in southeastern Poland. Morphological variation across the Przemysl transect had been surveyed more than 50 years ago; though we found a significant shift at one site, there is no evidence for gross movement over this period. Morphological and electrophoretic changes coincide, and the average shape of the clines is the same across both transects. At the center, most of the change in frequency of six diagnostic allozymes occurs within w = 6.05 km (2-unit support limits 5.56-6.54 km). These steep gradients are generated not by selection on the allozymes themselves, but by associations with other loci: though these markers are unlinked, they are in strong linkage disequilibrium with each other [R = D/ = 0.22 (0.15-0.29) at the center]. Disequilibria are broken up as alleles diffuse away from the zone and flow into the new genetic background. The net barrier to the flow of genes from bombina into variegata, which is generated by these disequilibria, is B = 51 (22-81) km. The fitness of hybrids must be substantially reduced to produce such a barrier [W̄H/W̄P = 0.58 (0.54-0.68)], and this selection must be spread over many loci [N = 55 (26-88)]. Alleles introgress significantly less far than would be expected from the age of the zone and the estimated dispersal rate [σ = 0.99 (0.82-1.14) km gen.-1/2]: this implies selection of se = 0.37 (0.15-0.58)% on the enzymes themselves. There is weak but significant linkage disequilibrium well away from the center of the zone; this, together with the presence of parental and F1 genotypes, suggests some long-range migration. However, such migration is not likely to cause significant introgression. }, author = {Szymura, Jacek and Barton, Nicholas H}, issn = {1558-5646}, journal = {Evolution}, number = {2}, pages = {237 -- 261}, publisher = {Wiley-Blackwell}, title = {{The genetic structure of the hybrid zone between the fire-bellied toads Bombina bombina and B. variegata: comparisons between transects and between loci}}, doi = {10.1111/j.1558-5646.1991.tb04400.x}, volume = {45}, year = {1991}, } @article{3647, abstract = {A method is developed that describes the effects on an arbitrary number of autosomal loci of selection on haploid and diploid stages, of nonrandom mating between haploid individuals, and of recombination. We provide exact recursions for the dynamics of allele frequencies and linkage disequilibria (nonrandom associations of alleles across loci). When selection is weak relative to recombination, our recursions provide simple approximations for the linkage disequilibria among arbitrary combinations of loci. We show how previous models of sex-independent natural selection on diploids, assortative mating between haploids, and sexual selection on haploids can be analyzed in this framework. Using our weak-selection approximations, we derive new results concerning the coevolution of male traits and female preferences under natural and sexual selection. In particular, we provide general expressions for the intensity of linkage-disequilibrium induced selection experienced by loci that contribute to female preferences for specific male traits. Our general results support the previous observation that these indirect selection forces are so weak that they are unlikely to dominate the evolution of preference-producing loci.}, author = {Barton, Nicholas H and Turelli, Michael}, issn = {0016-6731}, journal = {Genetics}, number = {1}, pages = {229 -- 255}, publisher = {Genetics Society of America}, title = {{Natural and sexual selection on many loci}}, doi = {10.1093/genetics/127.1.229}, volume = {127}, year = {1991}, } @article{3648, abstract = {We investigate the probability of fixation of a chromosome rearrangement in a subdivided population, concentrating on the limit where migration is so large relative to selection (m ≫ s) that the population can be thought of as being continuously distributed. We study two demes, and one- and two-dimensional populations. For two demes, the probability of fixation in the limit of high migration approximates that of a population with twice the size of a single deme: migration therefore greatly reduces the fixation probability. However, this behavior does not extend to a large array of demes. Then, the fixation probability depends primarily on neighborhood size (Nb), and may be appreciable even with strong selection and free gene flow (≈exp(-B·Nb) in one dimension, ≈exp(-B\cdotNb) in two dimensions). Our results are close to those for the more tractable case of a polygenic character under disruptive selection.}, author = {Barton, Nicholas H and Rouhani, Shahin}, issn = {1558-5646}, journal = {Evolution}, number = {3}, pages = {499 -- 517}, publisher = {Wiley-Blackwell}, title = {{The probability of fixation of a new karyotype in a continuous population}}, doi = {10.1111/j.1558-5646.1991.tb04326.x}, volume = {45}, year = {1991}, } @inproceedings{4059, abstract = {Let P be a simple polygon with n vertices. We present a simple decomposition scheme that partitions the interior of P into O(n) so-called geodesic triangles, so that any line segment interior to P crosses at most 2 log n of these triangles. This decomposition can be used to preprocess P in time O(n log n) and storage O(n), so that any ray-shooting query can be answered in time O(log n).The algorithms are fairly simple and easy to implement. We also extend this technique to the case of ray-shooting amidst k polygonal obstacles with a total of n edges, so that a query can be answered in O(radicklog n) time.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Grigni, Michelangelo and Guibas, Leonidas and Hershberger, John and Sharir, Micha and Snoeyink, Jack}, booktitle = {18th International Colloquium on Automata, Languages and Programming}, location = {Madrid, Spain}, pages = {661 -- 673}, publisher = {Springer}, title = {{Ray shooting in polygons using geodesic triangulations}}, doi = {10.1007/3-540-54233-7_172}, volume = {510}, year = {1991}, } @article{4061, abstract = {We present an algorithm to compute a Euclidean minimum spanning tree of a given set S of N points in Ed in time O(Fd (N,N) logd N), where Fd (n,m) is the time required to compute a bichromatic closest pair among n red and m green points in Ed . If Fd (N,N)=Ω(N1+ε), for some fixed e{open}>0, then the running time improves to O(Fd (N,N)). Furthermore, we describe a randomized algorithm to compute a bichromatic closest pair in expected time O((nm log n log m)2/3+m log2 n+n log2 m) in E3, which yields an O(N4/3 log4/3 N) expected time, algorithm for computing a Euclidean minimum spanning tree of N points in E3. In d≥4 dimensions we obtain expected time O((nm)1-1/([d/2]+1)+ε+m log n+n log m) for the bichromatic closest pair problem and O(N2-2/([d/2]+1)ε) for the Euclidean minimum spanning tree problem, for any positive e{open}.}, author = {Agarwal, Pankaj and Edelsbrunner, Herbert and Schwarzkopf, Otfried and Welzl, Emo}, issn = {1432-0444}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {407 -- 422}, publisher = {Springer}, title = {{Euclidean minimum spanning trees and bichromatic closest pairs}}, doi = {10.1007/BF02574698}, volume = {6}, year = {1991}, } @article{4062, abstract = {We prove that for any set S of n points in the plane and n3-α triangles spanned by the points in S there exists a point (not necessarily in S) contained in at least n3-3α/(c log5 n) of the triangles. This implies that any set of n points in three-dimensional space defines at most {Mathematical expression} halving planes.}, author = {Aronov, Boris and Chazelle, Bernard and Edelsbrunner, Herbert and Guibas, Leonidas and Sharir, Micha and Wenger, Rephael}, issn = {1432-0444}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {435 -- 442}, publisher = {Springer}, title = {{Points and triangles in the plane and halving planes in space}}, doi = {10.1007/BF02574700}, volume = {6}, year = {1991}, } @inproceedings{4508, abstract = {We extend the specification language of temporal logic, the corresponding verification framework, and the underlying computational model to deal with real-time properties of concurrent and reactive systems. A global, discrete, and asynchronous clock is incorporated into the model by defining the abstract notion of a real-time transition system as a conservative extension of traditional transition systems: qualitative fairness requirements are replaced (and superseded) by quantitative lower-bound and upperbound real-time requirements for transitions. We show how to model real-time systems that communicate either through shared variables or by message passing, and how to represent the important real-time constructs of priorities (interrupts), scheduling, and timeouts in this framework. Two styles for the specification of real-time properties are presented. The first style uses bounded versions of the temporal operators; the real-time requirements expressed in this style are classified ...}, author = {Henzinger, Thomas A and Manna, Zohar and Pnueli, Amir}, booktitle = {Proceedings of the 18th ACM SIGPLAN-SIGACT symposium on Principles of programming languages}, isbn = {978-0-89791-419-2}, location = {Orlando, FL, United States of America}, pages = {353 -- 366}, publisher = {ACM}, title = {{Temporal proof methodologies for real-time systems}}, doi = {10.1145/99583.99629}, year = {1991}, } @phdthesis{4516, abstract = {We extend the specification language of temporal logic, the corresponding verification framework, and the underlying computational model to deal with real-time properties of reactive systems. Semantics We introduce the abstract computational model of timed transition systems as a conservative extension of traditional transition systems qualitative fairness requirements are superseded by quantitative real-time constraints on the transitions. Digital clocks are introduced as observers of continuous real-time behavior. We justify our semantical abstractions by demonstrating that a wide variety of concrete real-time systems can be modeled adequately. Specification We present two conservative extensions of temporal logic that allow for the specification of timing constraints while timed temporal logic provides access to time through a novel kind of time quantifier, metric temporal logic refers to time through time-bounded versions of the temporal operators. We justify our choice of specification languages by developing a general framework for the classification of real-time logics according to their complexity and expressive power. Verification We develop tools for determining if a real-time system that is modeled as a timed transition system meets a specification that is given in timed temporal logic or in metric temporal logic. We present both model-checking algorithms for the automatic verification of finite-state real-time systems and proof methods for the deductive verification of real-time systems.}, author = {Henzinger, Thomas A}, pages = {295}, publisher = {Stanford University}, title = {{The temporal specification and verification of real-time systems }}, year = {1991}, } @article{4592, author = {Alur, Rajeev and Henzinger, Thomas A}, issn = {0163-5700}, journal = {SIGACT News}, number = {3}, pages = {6 -- 12}, publisher = {ACM}, title = {{Time for logic}}, volume = {22}, year = {1991}, } @inproceedings{4621, abstract = {The most natural, compositional, way of modeling real-time systems uses a dense domain for time. The satisfiability of timing constraints that are capable of expressing punctuality in this model, however, is known to be undecidable. We introduce a temporal language that can constrain the time difference between events only with finite, yet arbitrary, precision and show the resulting logic to be EXPSPACE-complete. This result allows us to develop an algorithm for the verification of timing properties of real-time systems with a dense semantics.}, author = {Alur, Rajeev and Feder, Tomás and Henzinger, Thomas A}, booktitle = {Proceedings of the 10th Annual ACM Symposium on Principles of Distributed Computing}, isbn = {978-0-89791-439-0}, location = {Montreal, Canada}, pages = {139 -- 152}, publisher = {ACM}, title = {{The benefits of relaxing punctuality}}, doi = {10.1145/227595.227602}, year = {1991}, }