@article{3472, abstract = {A novel potassium-selective channel which is active at membrane potentials between -100 mV and +40 mV has been identified in peripheral myelinated axons of Xenopus laevis using the patch-clamp technique. At negative potentials with 105 mM-K on both sides of the membrane, the channel at 1 kHz resolution showed a series of brief openings and closings interrupted by longer closings, resulting in a flickery bursting activity. Measurements with resolution up to 10 kHz revealed a single-channel conductance of 49 pS with 105 mM-K and 17 pS with 2.5 mM-K on the outer side of the membrane. The channel was selective for K ions over Na ions (PNa/PK = 0.033). The probability of being within a burst in outside-out patches varied from patch to patch (> 0.2, but often > 0.9), and was independent of membrane potential. Open-time histograms were satisfactorily described with a single exponential (tau o = 0.09 msec), closed times with the sum of three exponentials (tau c = 0.13, 5.9, and 36.6 msec). Sensitivity to external tetraethylammonium was comparatively low (IC50 = 19.0 mM). External Cs ions reduced the apparent unitary conductance for inward currents at Em = -90 mV (IC50 = 1.1 mM). Ba and, more potently, Zn ions lowered not only the apparent single-channel conductance but also open probability. The local anesthetic bupivacaine with high potency reduced probability of being within a burst (IC50 = 165 nM). The flickering K channel is clearly different from the other five types of K channels identified so far in the same preparation. We suggest that this channel may form the molecular basis of the resting potential in vertebrate myelinated axons.}, author = {Koh, Duk and Jonas, Peter M and Bräu, Michael and Vogel, Werner}, issn = {0022-2631}, journal = {Journal of Membrane Biology}, pages = {149 -- 162}, publisher = {Springer}, title = {{A TEA-insensitive flickering potassium channel active around the resting potential in myelinated nerve}}, doi = {10.1007/BF00231893}, volume = {130}, year = {1992}, } @article{3581, abstract = {A number of rendering algorithms in computer graphics sort three-dimensional objects by depth and assume that there is no cycle that makes the sorting impossible. One way to resolve the problem caused by cycles is to cut the objects into smaller pieces. In this paper we address the problem of estimating how many such cuts arc always sufficient. We also consider a few related algorithmic and combinatorial geometry problems. For example, we demonstrate that n lines in space can be sorted in randomized expected time O(n4’st’), provided that they define no cycle. We also prove an 0(n7’4) upper bound on the number of points in space so that there are n lines with the property that for each point there are at least three noncoplanar lines that contain it. }, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Guibas, Leonidas and Pollack, Richard and Seidel, Raimund and Sharir, Micha and Snoeyink, Jack}, issn = {0925-7721}, journal = {Computational Geometry: Theory and Applications}, number = {6}, pages = {305 -- 323}, publisher = {Elsevier}, title = {{Counting and cutting cycles of lines and rods in space}}, doi = {10.1016/0925-7721(92)90009-H}, volume = {1}, year = {1992}, } @article{3645, abstract = {Three components of mating call (pulse duration, cycle length, and fundamental frequency) were measured and six diagnostic enzyme loci scored across the hybrid zone between the toads Bombina bombina and B. variegata. All three call components differ significantly, but only cycle length is diagnostic. The clines in call coincide with those for enzymes, and have similar widths. This suggests that there is no strong selection on any of these characters. There are significant correlations between electrophoretic markers and call components, but these are no stronger than would be expected if the electrophoretic loci and the genes causing mating call were neutral. The selection differential on the call is no greater than 6% of the difference in mean cycle length between the two taxa. There is a substantial increase in the variance of cycle length in the center of the zone, suggesting that a small number of loci are involved (≈ three). Recombination between these loci will hinder the evolution of reinforcement and may partly be responsible for the lack of premating isolation between B. bombina and B. variegata.}, author = {Sanderson, Neil and Szymura, Jacek and Barton, Nicholas H}, issn = {0014-3820}, journal = {Evolution}, number = {3}, pages = {595 -- 607}, publisher = {Wiley-Blackwell}, title = {{Variation in mating call across the hybrid zone between the fire-bellied toads Bombina bombina and B. variegata}}, doi = {10.1111/j.1558-5646.1992.tb02068.x}, volume = {46}, year = {1992}, } @article{4043, abstract = {It is shown that a triangulation of a set of n points in the plane that minimizes the maximum angle can be computed in time O(n2 log n) and space O(n). The algorithm is fairly easy to implement and is based on the edge-insertion scheme that iteratively improves an arbitrary initial triangulation. It can be extended to the case where edges are prescribed, and, within the same time- and space-bounds, it can lexicographically minimize the sorted angle vector if the point set is in general position. Experimental results on the efficiency of the algorithm and the quality of the triangulations obtained are included.}, author = {Edelsbrunner, Herbert and Tan, Tiow and Waupotitsch, Roman}, issn = {1095-7111}, journal = {SIAM Journal on Scientific Computing}, number = {4}, pages = {994 -- 1008}, publisher = {Society for Industrial and Applied Mathematics }, title = {{An O(n^2 log n) time algorithm for the MinMax angle triangulation}}, doi = {10.1137/0913058}, volume = {13}, year = {1992}, } @article{4046, abstract = {The main contribution of this work is an O(n log n + k)-time algorithm for computing all k intersections among n line segments in the plane. This time complexity is easily shown to be optimal. Within the same asymptotic cost, our algorithm can also construct the subdivision of the plane defined by the segments and compute which segment (if any) lies right above (or below) each intersection and each endpoint. The algorithm has been implemented and performs very well. The storage requirement is on the order of n + k in the worst case, but it is considerably lower in practice. To analyze the complexity of the algorithm, an amortization argument based on a new combinatorial theorem on line arrangements is used.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert}, issn = {1557-735X}, journal = {Journal of the ACM}, number = {1}, pages = {1 -- 54}, publisher = {ACM}, title = {{An optimal algorithm for intersecting line segments in the plane}}, doi = {10.1145/147508.147511}, volume = {39}, year = {1992}, } @article{4047, abstract = {Arrangements of curves in the plane are fundamental to many problems in computational and combinatorial geometry (e.g. motion planning, algebraic cell decomposition, etc.). In this paper we study various topological and combinatorial properties of such arrangements under some mild assumptions on the shape of the curves, and develop basic tools for the construction, manipulation, and analysis of these arrangements. Our main results include a generalization of the zone theorem of Edelsbrunner (1986) and Chazelle (1985) to arrangements of curves (in which we show that the combinatorial complexity of the zone of a curve is nearly linear in the number of curves) and an application of that theorem to obtain a nearly quadratic incremental algorithm for the construction of such arrangements.}, author = {Edelsbrunner, Herbert and Guibas, Leonidas and Pach, János and Pollack, Richard and Seidel, Raimund and Sharir, Micha}, issn = {0304-3975}, journal = {Theoretical Computer Science}, number = {2}, pages = {319 -- 336}, publisher = {Elsevier}, title = {{Arrangements of curves in the plane - topology, combinatorics, and algorithms}}, doi = {10.1016/0304-3975(92)90319-B}, volume = {92}, year = {1992}, } @article{4048, abstract = {Given a sequence of n points that form the vertices of a simple polygon, we show that determining a closest pair requires OMEGA(n log n) time in the algebraic decision tree model. Together with the well-known O(n log n) upper bound for finding a closest pair, this settles an open problem of Lee and Preparata. We also extend this O(n log n) upper bound to the following problem: Given a collection of sets with a total of n points in the plane, find for each point a closest neighbor that does not belong to the same set.}, author = {Aggarwal, Alok and Edelsbrunner, Herbert and Raghavan, Prabhakar and Tiwari, Prasoon}, issn = {1872-6119}, journal = {Information Processing Letters}, number = {1}, pages = {55 -- 60}, publisher = {Elsevier}, title = {{Optimal time bounds for some proximity problems in the plane}}, doi = {10.1016/0020-0190(92)90133-G}, volume = {42}, year = {1992}, } @inproceedings{4049, abstract = {The edge-insertion paradigm improves a triangulation of a finite point set in R2 iteratively by adding a new edge, deleting intersecting old edges, and retriangulating the resulting two polygonal regions. After presenting an abstract view of the paradigm, this paper shows that it can be used to obtain polynomial time algorithms for several types of optimal triangulations.}, author = {Bern, Marshall and Edelsbrunner, Herbert and Eppstein, David and Mitchell, Stephen and Tan, Tiow}, booktitle = {1st Latin American Symposium on Theoretical Informatics}, editor = {Simon, Imre}, isbn = {978-3-540-55284-0}, location = {São Paulo, Brazil}, pages = {46 -- 60}, publisher = {Springer}, title = {{Edge insertion for optimal triangulations}}, doi = {10.1007/BFb0023816}, volume = {583}, year = {1992}, } @article{4050, author = {Edelsbrunner, Herbert}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {217 -- 217}, publisher = {Springer}, title = {{Guest editor's foreword}}, doi = {10.1007/BF02293046}, volume = {8}, year = {1992}, } @article{4053, abstract = {We show that the maximum number of edges bounding m faces in an arrangement of n line segments in the plane is O(m2/3n2/3+nα(n)+nlog m). This improves a previous upper bound of Edelsbrunner et al. [5] and almost matches the best known lower bound which is Ω(m2/3n2/3+nα(n)). In addition, we show that the number of edges bounding any m faces in an arrangement of n line segments with a total of t intersecting pairs is O(m2/3t1/3+nα(t/n)+nmin{log m,log t/n}), almost matching the lower bound of Ω(m2/3t1/3+nα(t/n)) demonstrated in this paper.}, author = {Aronov, Boris and Edelsbrunner, Herbert and Guibas, Leonidas and Sharir, Micha}, issn = {0209-9683}, journal = {Combinatorica}, number = {3}, pages = {261 -- 274}, publisher = {Springer}, title = {{The number of edges of many faces in a line segment arrangement}}, doi = {10.1007/BF01285815}, volume = {12}, year = {1992}, } @article{4195, abstract = {The effects of tri-iodothyronine (T3), which are known to affect cerebellar development, were tested on neuronal survival and differentiation of cultured cerebellar granule neurons. T3 in physiological concentrations increased both granule neuron survival after three days in culture and synaptic vesicle protein formation, as shown by immunostaining with antibodies against synaptophysin. Likewise, T3 increased the mRNA level for synapsin(I), but not that for GAP43 in granule neurons. Antibodies against microtubule associated protein Tau, which is expressed in developing neurites, showed that T3 also enhanced neurite formation.}, author = {Heisenberg, Carl-Philipp J and Thoenen, Hans and Lindholm, Dan}, issn = {1473-558X}, journal = {Neuroreport}, number = {8}, pages = {685 -- 688}, publisher = {Lippincott, Williams & Wilkins}, title = {{Triiodothyronine Regulates Survival and Differentiation of Rat Cerebellar Granule Neurons}}, doi = {10.1097/00001756-199208000-00008 }, volume = {3}, year = {1992}, } @article{4305, abstract = {The common shrew (Sorex araneus) is subdivided into several karyotypic races in Britain. Two of these races meet near Oxford to form the "Oxford-Hermitage" hybrid zone. We present a model which describes this system as a "tension zone," i.e., a set of clines maintained by a balance between dispersal and selection against chromosomal heterozygotes. The Oxford and Hermitage races differ by Robertsonian fusions with monobrachial homology (kq, no versus ko), and so F1 hybrids between them would have low fertility. However, the acrocentric karyotype is found at high frequency within the hybrid zone, so that complex Robertsonian heterozygotes (kq no/q ko n) are replaced by more fertile combinations, such as (kq no/k q n o). This suggests that the hybrid zone has been modified so as to increase hybrid fitness. Mathematical analysis and simulation show that, if selection against complex heterozygotes is sufficiently strong relative to selection against simple heterozygotes, acrocentrics increase, and displace the clines for kq and no from the cline for ko. Superimposed on this separation is a tendency for the hybrid zone to move m favor of the Oxford (kq no) race. We compare the model with estimates of linkage disequilibrium and cline shape made from field data.}, author = {Hatfield, Todd and Barton, Nicholas H and Searle, Jeremy}, issn = {1558-5646}, journal = {Evolution; International Journal of Organic Evolution}, number = {4}, pages = {1129 -- 1145}, publisher = {Wiley-Blackwell}, title = {{A model of a hybrid zone between two chromosomal races of the common shrew (Sorex araneus)}}, doi = {10.1111/j.1558-5646.1992.tb00624.x}, volume = {46}, year = {1992}, } @misc{4306, author = {Barton, Nicholas H and Goldman, Nick}, booktitle = {Nature}, pages = {440 -- 441}, publisher = {Nature Publishing Group}, title = {{Genetics and geography}}, doi = {10.1038/357440a0}, volume = {357}, year = {1992}, } @inbook{4307, author = {Barton, Nicholas H}, booktitle = {Animal dispersal: small mammals as a model}, editor = {Stenseth, Nils and Lidicker, William}, pages = {37 -- 60}, publisher = {Chapman Hall}, title = {{The genetic consequences of dispersal}}, doi = {10.1007/978-94-011-2338-9_3}, year = {1992}, } @article{4308, author = {Barton, Nicholas H}, issn = {1558-5646}, journal = {Evolution; International Journal of Organic Evolution}, number = {2}, pages = {551 -- 557}, publisher = {Wiley-Blackwell}, title = {{On the spread of new gene combinations in the third phase of Wright's shifting balance}}, volume = {46}, year = {1992}, } @inproceedings{4504, abstract = {Real-time systems operate in “real,” continuous time and state changes may occur at any real-numbered time point. Yet many verification methods are based on the assumption that states are observed at integer time points only. What can we conclude if a real-time system has been shown “correct” for integral observations? Integer time verification techniques suffice if the problem of whether all real-numbered behaviors of a system satisfy a property can be reduced to the question of whether the integral observations satisfy a (possibly modified) property. We show that this reduction is possible for a large and important class of systems and properties: the class of systems includes all systems that can be modeled as timed transition systems; the class of properties includes time-bounded invariance and time-bounded response.}, author = {Henzinger, Thomas A and Manna, Zohar and Pnueli, Amir}, booktitle = {19th International Colloquium on Automata, Languages and Programming}, location = {Vienna, Austria}, pages = {545 -- 558}, publisher = {Springer}, title = {{What good are digital clocks?}}, doi = {10.1007/3-540-55719-9_103}, volume = {623}, year = {1992}, } @inproceedings{4505, abstract = {We describe finite-state programs over real-numbered time in a guarded-command language with real-valued clocks or, equivalently, as finite automata with real-valued clocks. Model checking answers the question which states of a real-time program satisfy a branching-time specification (given in an extension of CTL with clock variables). We develop an algorithm that computes this set of states symbolically as a fixpoint of a functional on state predicates, without constructing the state space. For this purpose, we introduce a mu-calculus on computation trees over real-numbered time. Unfortunately, many standard program properties, such as response for all nonzeno execution sequences (during which time diverges), cannot be characterized by fixpoints: we show that the expressiveness of the timed mu-calculus is incomparable to the expressiveness of timed CTL. Fortunately, this result does not impair the symbolic verification of "implementable" real-time programs--those whose safety constraints are machine-closed with respect to diverging time and whose fairness constraints are restricted to finite upper bounds on clock values. All timed CTL properties of such programs are shown to be computable as finitely approximable fixpoints in a simple decidable theory.}, author = {Henzinger, Thomas A and Nicollin, Xavier and Sifakis, Joseph and Yovine, Sergio}, booktitle = {Proceedings of the 7th Annual IEEE Symposium on Logic in Computer Science}, isbn = {0-8186-2735-2}, location = {Santa Cruz, CA, United States of America}, pages = {394 -- 406}, publisher = {IEEE}, title = {{Symbolic model checking for real-time systems}}, doi = {10.1109/LICS.1992.185551}, year = {1992}, } @inbook{4507, abstract = {We incorporate time into an interleaving model of concurrency. In timed transition systems, the qualitative fairness requirements of traditional transition system are replaced (and superseded) by quantitative lower-bound and upperbound timing constraints on transitions. The purpose of this paper is to explore the scope of applicability for the abstract model of timed transition systems. We demonstrate that the model can represent a wide variety of phenomena that routinely occur in conjunction with the timed execution of concurrent processes. Our treatment covers both processes that are executed in parallel on separate processors and communicate either through shared variables or by message passing, and processes that time-share a limited number of processors under a given scheduling policy. Often it is this scheduling policy that determines if a system meets its real-time requirements. Thus we explicitly address such questions as time-outs, interrupts, static and dynamic priorities.}, author = {Henzinger, Thomas A and Manna, Zohar and Pnueli, Amir}, booktitle = {Real Time: Theory in Practice}, pages = {226 -- 251}, publisher = {Springer}, title = {{Timed transition systems}}, doi = {10.1007/BFb0031995}, volume = {600}, year = {1992}, } @article{4517, abstract = {It has been observed repeatedly that the standard safety-liveness classification for properties of reactive systems does not fit for real-time properties. This is because the implicit “liveliness” of time shifts the spectrum towards the safety side. While, for example, response—that “something good” will happen eventually—is a classical liveness property, bounded response—that “something good” will happen soon, within a certain amount of time—has many characteristics of safety. We account for this phenomenon formally by defining safety and liveness relative to a given condition, such as the progress of time.}, author = {Henzinger, Thomas A}, issn = {0020-0190}, journal = {Information Processing Letters}, number = {3}, pages = {135 -- 141}, publisher = {Elsevier}, title = {{Sooner Is Safer Than Later}}, doi = {10.1016/0020-0190(92)90005-G}, volume = {43}, year = {1992}, } @article{2482, abstract = {The complementary DNA of a metabotropic glutamate receptor coupled to inositol phosphate/Ca2+ signal transduction has been cloned and characterized. This receptor shows no sequence similarity to conventional G protein-coupled receptors and has a unique structure with large hydrophilic sequences at both sides of seven putative membrane-spanning domains. Abundant expression of this messenger RNA is observed in neuronal cells in hippocampal dentate gyrus and CA2-3 and in cerebellar Purkinje cells, suggesting the importance of this receptor in specific hippocampal and cerebellar functions.}, author = {Masu, Masayuki and Tanabe, Yasuto and Tsuchida, Kunihiro and Shigemoto, Ryuichi and Nakanishi, Shigetada}, issn = {1476-4687}, journal = {Nature}, number = {6312}, pages = {760 -- 765}, publisher = {Nature Publishing Group}, title = {{Sequence and expression of a metabotropic glutamate receptor}}, doi = {10.1038/349760a0}, volume = {349}, year = {1991}, }