TY - JOUR
AB - We report the molecular characterization of two novel rat helix-loop-helix (HLH) proteins, designated HES-1 and HES-3, that show structural homology to the Drosophila hairy and Enhancer of split [E(spl)] proteins, both of which are required for normal neurogenesis. HES-1 mRNA, expressed in various tissues of both embryos and adults, is present at a high level in the epithelial cells, including the embryonal neuroepithelial cells, as well as in the mesoderm-derived tissues such as the embryonal muscle. In contrast, HES-3 mRNA is produced exclusively in cerebellar Purkinje cells. HES-1 represses transcription by binding to the N box, which is a recognition sequence of E(spl) proteins. Interestingly, neither HES-1 nor HES-3 alone interacts efficiently with the E box, but each protein decreases the transcription induced by E-box-binding HLH activators such as E47. Furthermore, HES-1 also inhibits the functions of MyoD and MASH1 and effectively diminishes the myogenic conversion of C3H10T1/2 cells induced by MyoD. These results suggest that HES-1 may play an important role in mammalian development by negatively acting on the two different sequences while HES-3 acts as a repressor in a specific type of neurons.
AU - Sasai, Yoshiki
AU - Kageyama, Ryoichiro
AU - Tagawa, Yoshiaki
AU - Ryuichi Shigemoto
AU - Nakanishi, Shigetada
ID - 2535
IS - 12 B
JF - Genes and Development
TI - Two mammalian helix-loop-helix factors structurally related to Drosophila hairy and Enhancer of split
VL - 6
ER -
TY - JOUR
AB - 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.
AU - Herbert Edelsbrunner
AU - Tan, Tiow Seng
AU - Waupotitsch, Roman
ID - 4043
IS - 4
JF - SIAM Journal on Scientific Computing
TI - An O(n^2 log n) time algorithm for the MinMax angle triangulation
VL - 13
ER -
TY - JOUR
AB - 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.
AU - Chazelle, Bernard
AU - Herbert Edelsbrunner
ID - 4046
IS - 1
JF - Journal of the ACM
TI - An optimal algorithm for intersecting line segments in the plane
VL - 39
ER -
TY - JOUR
AB - 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.
AU - Herbert Edelsbrunner
AU - Guibas, Leonidas
AU - Pach, János
AU - Pollack, Richard
AU - Seidel, Raimund
AU - Sharir, Micha
ID - 4047
IS - 2
JF - Theoretical Computer Science
TI - Arrangements of curves in the plane - topology, combinatorics, and algorithms
VL - 92
ER -
TY - JOUR
AB - 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.
AU - Aggarwal, Alok
AU - Herbert Edelsbrunner
AU - Raghavan, Prabhakar
AU - Tiwari, Prasoon
ID - 4048
IS - 1
JF - Information Processing Letters
TI - Optimal time bounds for some proximity problems in the plane
VL - 42
ER -
TY - CONF
AB - 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.
AU - Bern, Marshall
AU - Herbert Edelsbrunner
AU - Eppstein, David
AU - Mitchell, Stephen
AU - Tan, Tiow Seng
ID - 4049
TI - Edge insertion for optimal triangulations
VL - 583
ER -
TY - JOUR
AU - Herbert Edelsbrunner
ID - 4050
IS - 1
JF - Discrete & Computational Geometry
TI - Guest editor's foreword
VL - 8
ER -
TY - JOUR
AB - 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.
AU - Aronov, Boris
AU - Herbert Edelsbrunner
AU - Guibas, Leonidas J
AU - Sharir, Micha
ID - 4053
IS - 3
JF - Combinatorica
TI - The number of edges of many faces in a line segment arrangement
VL - 12
ER -
TY - JOUR
AB - 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.
AU - Heisenberg, Carl-Philipp
AU - Thoenen, Hans
AU - Lindholm, Dan
ID - 4195
IS - 8
JF - Neuroreport
TI - Triiodothyronine Regulates Survival and Differentiation of Rat Cerebellar Granule Neurons
VL - 3
ER -
TY - JOUR
AB - 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.
AU - Hatfield, Todd
AU - Nicholas Barton
AU - Searle, Jeremy B
ID - 4305
IS - 4
JF - Evolution; International Journal of Organic Evolution
TI - A model of a hybrid zone between two chromosomal races of the common shrew (Sorex araneus)
VL - 46
ER -