Distribution by Scientific Domains

Kinds of Vertices

  • adjacent vertex
  • common vertex
  • distinct vertex
  • k vertex
  • n vertex
  • one vertex

  • Terms modified by Vertices

  • vertex set
  • vertex v

  • Selected Abstracts

    In vitro adhesion of Candida species to denture base materials

    MYCOSES, Issue 2 2006
    X. Y. He
    Summary Adhesion of Candida species to prosthetic acrylic resins is an essential first step in the pathogenesis of denture stomatitis. Data on the relative adhesion of pathogenic non- albicans Candida species to different denture base materials are sparse. The purpose of the present study was to investigate in vitro adhesion of C. albicans, C. glabrata, C. krusei and C. dubliniensis to four different denture base materials. Specimens of both heat-cured resins (VertexTM Rapid Simplified and ProBaseTM Hot) and cold-cured resins (Paladur® A and Paladur® B) were prepared using a novel method and the adhesion of four strains each of the foregoing Candida species evaluated microscopically using a soft imaging system. There was a significant difference in yeast adherence between Vertex and the other resins. Only C. glabrata attached to Vertex, while all the remainder of the tested species adhered to all other resins tested except ProBase, which resisted C. krusei adhesion. There was a significant difference in candidal adhesion between cold-cured and heat-cured resins for three Candida species (C. albicans, P = 0.039; C. glabrata, P = 0.002 and C. krusei, P = 0.000). The type of denture base material and whether they are heat-cured or cold-cured play an important role in modifying candidal adhesion. [source]

    Vertex disjoint routings of cycles over tori

    Jean-Claude Bermond
    Abstract We study the problem of designing a survivable WDM network based on covering the communication requests with subnetworks that are protected independently from each other. We consider here the case when the physical network is T(n), a torus of size n by n, the subnetworks are cycles and the communication scheme is all-to-all or total exchange (where all pairs of vertices communicate). We will represent the communication requests by a logical graph: a complete graph for the scheme of all-to-all. This problem can be modeled as follows: find a cycle partition or covering of the request edges of K, such that for each cycle in the partition, its request edges can be routed in the physical network T(n) by a set of vertex disjoint paths (equivalently, the routings with the request cycle form an elementary cycle in T(n)). Let the load of an edge of the WDM network be the number of paths associated with the requests using the edge. The cost of the network depends on the total load (the cost of transmission) and the maximum load (the cost of equipment). To minimize these costs, we will search for an optimal (or quasi optimal) routing satisfying the following two conditions: (a) each request edge is routed by a shortest path over T(n), and (b) the load of each physical edge resulting from the routing of all cycles of S is uniform or quasi uniform. In this article, we find a covering or partition of the request edges of K into cycles with an associated optimal or quasi optimal routing such that either (1) the number of cycles of the covering is minimum, or (2) the cycles have size 3 or 4. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 49(3), 217,225 2007 [source]

    Efficient three-dimensional scene modeling and mosaicing

    Tudor Nicosevici
    Scene modeling has a key role in applications ranging from visual mapping to augmented reality. This paper presents an end-to-end solution for creating accurate three-dimensional (3D) textured models using monocular video sequences. The methods are developed within the framework of sequential structure from motion, in which a 3D model of the environment is maintained and updated as new visual information becomes available. The proposed approach contains contributions at different levels. The camera pose is recovered by directly associating the 3D scene model with local image observations, using a dual-registration approach. Compared to the standard structure from motion techniques, this approach decreases the error accumulation while increasing the robustness to scene occlusions and feature association failures, while allowing 3D reconstructions for any type of scene. Motivated by the need to map large areas, a novel 3D vertex selection mechanism is proposed, which takes into account the geometry of the scene. Vertices are selected not only to have high reconstruction accuracy but also to be representative of the local shape of the scene. This results in a reduction in the complexity of the final 3D model, with minimal loss of precision. As a final step, a composite visual map of the scene (mosaic) is generated. We present a method for blending image textures using 3D geometric information and photometric differences between registered textures. The method allows high-quality mosaicing over 3D surfaces by reducing the effects of the distortions induced by camera viewpoint and illumination changes. The results are presented for four scene modeling scenarios, including a comparison with ground truth under a realistic scenario and a challenging underwater data set. Although developed primarily for underwater mapping applications, the methods are general and applicable to other domains, such as aerial and land-based mapping. © 2009 Wiley Periodicals, Inc. [source]

    On Vertices of outdegree n in minimally n -connected digraphs

    W. Mader
    Abstract Let |D| and |D|+n denote the number of vertices of D and the number of vertices of outdegree n in the digraph D, respectively. It is proved that every minimally n -connected, finite digraph D has |D|+n,,,n,+,1 and that for n,,,2, there is a cn,>,0 such that for all minimally n -connected, finite digraphs D. Furthermore, case n,=,2 of the following conjecture is settled which says that every minimally n -connected, finite digraph has a vertex of indegree and outdegree equal to n. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 129,144, 2002 [source]

    Site-Selective Internal Cross-Linking between Mercury(II)-Centered Vertices of an Octahedral Mercury(II) Capsule by a Rod-Shaped Ditopic Ligand,

    ANGEWANDTE CHEMIE, Issue 1 2010
    Shuichi Hiraoka Dr.
    Ein oder zwei stabförmige Bissulfonat-Brückenliganden wurden durch positionsselektive Verdrängung innerer TfO, -Liganden in eine selbstorganisierte HgII -Kapsel eingebaut. Durch einen Ligandenaustausch der verbleibenden inneren TfO, -Liganden wurden TsO, -Liganden im Innern der resultierenden Kapsel angeordnet, in welcher der/die Bissulfonat-Ligand(en) zwei gegenüberliegende HgII -Ecken verbrücken (siehe Bild). Tf=Trifluormethansulfonyl, Ts=p -Toluolsulfonyl. [source]

    Combined compression and simplification of dynamic 3D meshes

    Libor Vá
    Abstract We present a new approach to dynamic mesh compression, which combines compression with simplification to achieve improved compression results, a natural support for incremental transmission and level of detail. The algorithm allows fast progressive transmission of dynamic 3D content. Our scheme exploits both temporal and spatial coherency of the input data, and is especially efficient for the case of highly detailed dynamic meshes. The algorithm can be seen as an ultimate extension of the clustering and local coordinate frame (LCF)-based approaches, where each vertex is expressed within its own specific coordinate system. The presented results show that we have achieved better compression efficiency compared to the state of the art methods. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Discrete Distortion in Triangulated 3-Manifolds

    Mohammed Mostefa Mesmoudi
    Abstract We introduce a novel notion, that we call discrete distortion, for a triangulated 3-manifold. Discrete distortion naturally generalizes the notion of concentrated curvature defined for triangulated surfaces and provides a powerful tool to understand the local geometry and topology of 3-manifolds. Discrete distortion can be viewed as a discrete approach to Ricci curvature for singular flat manifolds. We distinguish between two kinds of distortion, namely, vertex distortion, which is associated with the vertices of the tetrahedral mesh decomposing the 3-manifold, and bond distortion, which is associated with the edges of the tetrahedral mesh. We investigate properties of vertex and bond distortions. As an example, we visualize vertex distortion on manifold hypersurfaces in R4 defined by a scalar field on a 3D mesh. distance fields. [source]

    SIMD Optimization of Linear Expressions for Programmable Graphics Hardware

    Chandrajit Bajaj
    Abstract The increased programmability of graphics hardware allows efficient graphical processing unit (GPU) implementations of a wide range of general computations on commodity PCs. An important factor in such implementations is how to fully exploit the SIMD computing capacities offered by modern graphics processors. Linear expressions in the form of, where A is a matrix, and and are vectors, constitute one of the most basic operations in many scientific computations. In this paper, we propose a SIMD code optimization technique that enables efficient shader codes to be generated for evaluating linear expressions. It is shown that performance can be improved considerably by efficiently packing arithmetic operations into four-wide SIMD instructions through reordering of the operations in linear expressions. We demonstrate that the presented technique can be used effectively for programming both vertex and pixel shaders for a variety of mathematical applications, including integrating differential equations and solving a sparse linear system of equations using iterative methods. [source]

    Age-related changes in transient and oscillatory brain responses to auditory stimulation during early adolescence

    Catherine Poulsen
    Maturational changes in the capacity to process quickly the temporal envelope of sound have been linked to language abilities in typically developing individuals. As part of a longitudinal study of brain maturation and cognitive development during adolescence, we employed dense-array EEG and spatiotemporal source analysis to characterize maturational changes in the timing of brain responses to temporal variations in sound. We found significant changes in the brain responses compared longitudinally at two time points in early adolescence, namely 10 years (65 subjects) and 11.5 years (60 of the 65 subjects), as well as large differences between adults, studied with the same protocol (Poulsen, Picton & Paus, 2007), and the children at 10 and 11.5 years of age. The transient auditory evoked potential to tone onset showed decreases in the latency of vertex and T-complex components, and a highly significant increase in the amplitude of the N1 wave with increasing age. The auditory steady state response to a 40-Hz frequency-modulated tone increased in amplitude with increasing age. The peak frequency of the envelope-following response to sweeps of amplitude-modulated white noise also increased significantly with increasing age. These results indicate persistent maturation of the cortical mechanisms for auditory processing from childhood into middle adulthood. [source]

    Involvement of the thalamocortical network in TLE with and without mesiotemporal sclerosis

    EPILEPSIA, Issue 8 2010
    Susanne G. Mueller
    Summary Purpose:, The thalamus plays an important role in seizure propagation in temporal lobe epilepsy (TLE). This study investigated how structural abnormalities in the focus, ipsilateral thalamus and extrafocal cortical structures relate to each other in TLE with mesiotemporal sclerosis (TLE-MTS) and without hippocampal sclerosis (TLE-no). Methods:, T1 and high-resolution T2 images were acquired on a 4T magnet in 29 controls, 15 TLE-MTS cases, and 14 TLE-no. Thalamus volumes were obtained by warping a labeled atlas onto each subject's brain. Deformation-based morphometry was used to identify regions of thalamic volume loss and FreeSurfer for cortical thickness measurements. CA1 volumes were obtained from high-resolution T2 images. Multiple regression analysis and correlation analyses for voxel- and vertex-based analyses were performed in SPM2 and FreeSurfer. Results:, TLE-MTS had bilateral volume loss in the anterior thalamus, which was correlated with CA1 volume and cortical thinning in the mesiotemporal lobe. TLE-no had less severe volume loss in the dorsal lateral nucleus, which was correlated with thinning in the mesiotemporal region but not with extratemporal thinning. Discussion:, The findings suggest that seizure propagation from the presumed epileptogenic focus or regions close to it into the thalamus occurs in TLE-MTS and TLE-no and results in circumscribed neuronal loss in the thalamus. However, seizure spread beyond the thalamus seems not to be responsible for the extensive extratemporal cortical abnormalities in TLE. [source]

    Slow Repetitive TMS for Drug-resistant Epilepsy: Clinical and EEG Findings of a Placebo-controlled Trial

    EPILEPSIA, Issue 2 2007
    Roberto Cantello
    Summary:,Purpose: To assess the effectiveness of slow repetitive transcranial magnetic stimulation (rTMS) as an adjunctive treatment for drug-resistant epilepsy. Methods: Forty-three patients with drug-resistant epilepsy from eight Italian Centers underwent a randomized, double-blind, sham-controlled, crossover study on the clinical and EEG effects of slow rTMS. The stimulus frequency was 0.3 Hz. One thousand stimuli per day were given at the resting motor threshold intensity for 5 consecutive days, with a round coil at the vertex. Results:"Active" rTMS was no better than placebo for seizure reduction. However, it decreased interictal EEG epileptiform abnormalities significantly (p < 0.05) in one-third of the patients, which supports a detectable biologic effect. No correlation linked the rTMS effects on seizure frequency to syndrome or anatomic classification, seizure type, EEG changes, or resting motor threshold (an index of motor cortex excitability). Conclusions: Although the antiepileptic action was not significant (p > 0.05), the individual EEG reactivity to "active" rTMS may be encouraging for the development of more-powerful, noninvasive neuromodulatory strategies. [source]

    Magneto,Structural Correlations in Discrete MnII -WV Cyano-Bridged Assemblies with Polyimine Ligands

    Robert Podgajny
    Abstract We present the magneto,structural correlations for two novel discrete cyano-bridged assemblies based on cationic complexes of manganese(II) with diimine ligands and octacyanotungstate(V) ions. The crystal structure of [MnII(terpy)(dmf)(H2O)2][MnII(terpy)(H2O)(dmf)(,-NC)WV(CN)7]2·6H2O (1) (terpy = 2,2,;6,,2,-terpyridine, dmf = dimethylformamide) contains dinuclear {MnIIWV}, cyano-bridged anions, while the crystal structure of [MnII(phen)3]2[MnII(phen)2(,-NC)2WV(CN)6]2(ClO4)2·9H2O (2) (phen = 1,10-phenanthroline) is built of tetranuclear {MnII2WV2}2, square anions. Intramolecular Mn,W magnetic interactions through the cyano bridges are represented by magnetic coupling constants J = ,39 cm,1 for the {MnIIWV}, unit in 1 and J1 = ,25.7 and J2 = ,16.7 cm,1 for the {MnII2WV2}2, unit in 2. J and J1 represent relatively strong W,CN,Mn interactions and are ascribed to the bridges in b positions of TPRS-8 (trigonal prism square-face bicapped) of [W(CN)8]3, polyhedra, favoring the strongest electronic interactions between the d,d orbital of W and the ,* orbitals of CN,, whereas J2 is related to the m vertex of [W(CN)8]3,. The magnetic properties of 1 and 2 are compared with reference compounds and discussed in the context of the type of coordination polyhedra of [W(CN)8]3, as well as the metric parameters of cyano-bridged W,CN,Mn linkages. We found the type of coordination polyhedra and bridging mode of [W(CN)8]3, to be the most important factors influencing the magnitude of the Mn,W magnetic interaction. [source]

    Functional topography of the human nonREM sleep electroencephalogram

    Luca A. Finelli
    Abstract The sleep EEG of healthy young men was recorded during baseline and recovery sleep after 40 h of waking. To analyse the EEG topography, power spectra were computed from 27 derivations. Mean power maps of the nonREM sleep EEG were calculated for 1-Hz bins between 1.0 and 24.75 Hz. Cluster analysis revealed a topographic segregation into distinct frequency bands which were similar for baseline and recovery sleep, and corresponded closely to the traditional frequency bands. Hallmarks of the power maps were the frontal predominance in the delta and alpha band, the occipital predominance in the theta band, and the sharply delineated vertex maximum in the sigma band. The effect of sleep deprivation on EEG topography was determined by calculating the recovery/baseline ratio of the power spectra. Prolonged waking induced an increase in power in the low-frequency range (1,10.75 Hz) which was largest over the frontal region, and a decrease in power in the sigma band (13,15.75 Hz) which was most pronounced over the vertex. The topographic pattern of the recovery/baseline power ratio was similar to the power ratio between the first and second half of the baseline night. These results indicate that changes in sleep propensity are reflected by specific regional differences in EEG power. The predominant increase of low-frequency power in frontal areas may be due to a high ,recovery need' of the frontal heteromodal association areas of the cortex. [source]

    Interaction between genioglossus and diaphragm responses to transcranial magnetic stimulation in awake humans

    Wei Wang
    The modulation of activity of the upper airway dilator and respiratory muscles plays a key role in the regulation of ventilation, but little is known about the link between their neuromuscular activation processes in vivo. This study investigated genioglossus and diaphragm responses to transcranial magnetic stimulation applied in different facilitatory conditions. The amplitude and latency of motor-evoked potential responses and the stimulation intensity threshold leading to a motor response (motor threshold) were recorded with stimulation applied at the vertex and anterolateral area in 13 awake normal subjects. Stimuli were applied during inspiration with and without resistance, during expiration with and without maximal tongue protrusion and during deep inspiration. In each stimulation location and condition, no diaphragmatic response was obtained without previous genioglossus activity (diaphragmatic and genioglossus responses latencies during expiration: 18.1 ± 2.9 and 6.3 ± 2.6 ms, respectively, mean ±s.d., P < 0.01). Genioglossus motor-evoked potential amplitude, latency and motor threshold were significantly modified with tongue protrusion with a maximal effect observed for stimulation in the anterolateral area. Deep inspiration was associated with a significant facilitatory effect on both genioglossus and diaphragm motor responses. The facilitatory effects of respiratory and non-respiratory manoeuvres were also observed during focal stimulation where isolated genioglossus responses were observed. Genioglossus and diaphragm differed in their motor threshold both at baseline and following facilitatory manoeuvres. Conclusions: (1) transcranial magnetic stimulation-induced genioglossus response systematically precedes that of diaphragm; (2) this sequence of activation is not modified by respiratory and non-respiratory manoeuvres; and (3) the genioglossus and diaphragm are differently influenced by these manoeuvres in terms of latency of the motor response and of motor threshold. [source]


    INSECT SCIENCE, Issue 4 2000
    ZHENG Zhe-min
    Abstract, A new species of the genus Formosatettix Tinkham 1937, Formosatettix tiantangensis sp. nov. from Dabie Mountains in Hubei Province is described. The new species is allied to Formosatettix henanensis Liang, but differs in: 1) width of vertex about 1.6 times the width of an eye; 2) length of antennae about 1.6,1.7 times the length of anterior femora; 3) upper margin of pronotum distinctively arched; 4) ventral margin of posterior pronotal process arched, lateral carinae curvingigly arched and 5) posterior margin of subgenital plate of female concave, median keel present on the plate. The type specimens are deposited in the Institute of Zoology, Shaanxi Normal University and Department of Biology, Huanggang Normal College, Hubei Province respectively. [source]


    INSECT SCIENCE, Issue 1 2000
    LI Qiang
    Abstract, Two new species of the subgenus Calceorhopalum Tsuneki of the genus Rhopalum Stephens are described. The new species, Rhopalum (Calceorhopalum) odontodorsale sp. nov. from Sichuan and Guizhou Province, is similar to R. (C.) spinicollum Tsuneki, but can be distinguished from the latter in the shape of clypeus, vertex with denser and larger punctures, anterior lateral corner of collar with a small tooth, tarsomere I of fore legs rather broad in male, and the shape of male genitalia. Holotype (,) is deposited in the Insect Collections of Institute of Zoology, Chinese Academy of Sciences. Paratypes (9 ,, 14 2 2) are deposited in the Insect Collections of Institute Zoology, Chinese Academy of Sciences and the Insect Collections of Zhejiang Agricultural University separately. The other new species, Rhopalum (Calceorhopalum) rubigabdominale sp. nov. from Sichuan Province, is similar to R (C.) spinicollum Tsuneki also, but can be distinguished from the latter by the characters of the vertex concave, anterior lateral comer of collar rounded, posterior lateral corner of propleuron with a coarse and long tooth, prepectus with blunt comer medially, head and thorax with denser and larger punctures, abdomen yellowish or reddish brown, and the shape of male genitalia. Holotype (,) and paratypes (3,,) are kept in the Insect Collections of Institute Zoology, Chinese Academy of Sciences. [source]

    Source signature and elastic waves in a half-space under a sustainable line-concentrated impulsive normal force

    Moche Ziv
    Abstract First, the response of an ideal elastic half-space to a line-concentrated impulsive normal load applied to its surface is obtained by a computational method based on the theory of characteristics in conjunction with kinematical relations derived across surfaces of strong discontinuities. Then, the geometry is determined of the obtained waves and the source signature,the latter is the imprint of the spatiotemporal configuration of the excitation source in the resultant response. Behind the dilatational precursor wave, there exists a pencil of three plane waves extending from the vertex at the impingement point of the precursor wave on the stress-free surface of the half-space to three points located on the other two boundaries of the solution domain. These four wave-arresting points (end points) of the three plane waves constitute the source signature. One wave is an inhibitor front in the behaviour of the normal stress components and the particle velocity, while in the behaviour of the shear stress component, it is a surface-axis wave. The second is a surface wave in the behaviour of the horizontal components of the dependent variables, while the third is an inhibitor wave in the behaviour of the shear stress component. An inhibitor wave is so named, since beyond it, the material motion is dying or becomes uniform. A surface-axis wave is so named, since upon its arrival, like a surface wave, the dependent variable in question features an extreme value, but unlike a surface wave, it exists in the entire depth of the solution domain. It is evident from this work that Saint-Venant's principle for wave propagation problems cannot be formulated; therefore, the above results are a consequence of the particular model proposed here for the line-concentrated normal load. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Vibration analysis of conical panels using the method of discrete singular convolution

    Ömer CivalekArticle first published online: 16 NOV 200
    Abstract A discrete singular convolution (DSC) free vibration analysis of conical panels is presented. Regularized Shannon's delta kernel (RSK) is selected as singular convolution to illustrate the present algorithm. In the proposed approach, the derivatives in both the governing equations and the boundary conditions are discretized by the method of DSC. Effects of boundary conditions, vertex and subtended angle on the frequencies of conical panel are investigated. The effect of the circumferential node number on the vibrational behaviour of the panel is also analysed. The obtained results are compared with those of other numerical methods. Numerical results indicate that the DSC is a simple and reliable method for vibration analysis of conical panels. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    The stability of stars of triangular equilibrium plate elements

    E. A. W. Maunder
    Abstract Equilibrium models for finite element analyses are becoming increasingly important in complementary roles to those from conventional conforming models, but when formulating equilibrium models questions of stability, or admissibility of loads, are of major concern. This paper addresses these questions in the context of flat plates modelled with triangular hybrid elements involving membrane and/or flexural actions. Patches of elements that share a common vertex are considered, and such patches are termed stars. Stars may be used in global analyses as assemblies of elements forming macro-elements, or in local analyses. The conditions for stability, or the existence and number of spurious kinematic modes, are determined in a general algebraic procedure for any degree of the interpolation polynomials and for any geometric configuration. The procedure involves the determination of the rank of a compatibility matrix by its transformation to row echelon form. Examples are presented to illustrate some of the characteristics of spurious kinematic modes when they exist in stars with open or closed links. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    A non-iterative derivation of the common plane for contact detection of polyhedral blocks

    Shu-Wei Chang
    Abstract A non-iterative derivation for finding the common plane between two polyhedral blocks is presented. By exploiting geometric relations between the normal of a plane and the closest vertex on a block, the common plane can be resolved without resorting to an iterative method. To facilitate derivations, normals in half-space are decomposed into finite subsets in which each subset corresponds to the same closest vertex on a block. The gap function, originally dependent on the normal and the two closest vertices, becomes a function of the normal only. To compute the gap for a given normal subset, the maximum theorem and the maximum projection theorem are introduced. The maximum theorem reduces finding the maximum in a subset to its boundary. Calculating the gap in 2D in a given subset thus reduces to checking two inner products. The maximum projection theorem further reduces finding the maximum on a 3D boundary to an explicit form. Three numerical examples are used to demonstrate the accuracy and efficiency of the proposed scheme. The example in which the blocks are in contact further shows the existence of a local maximum while calculating the gap and illustrates the potential deficiencies in using the Cundall's iterative scheme. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    A vertex-based finite volume method applied to non-linear material problems in computational solid mechanics

    G. A. Taylor
    Abstract A vertex-based finite volume (FV) method is presented for the computational solution of quasi-static solid mechanics problems involving material non-linearity and infinitesimal strains. The problems are analysed numerically with fully unstructured meshes that consist of a variety of two- and three-dimensional element types. A detailed comparison between the vertex-based FV and the standard Galerkin FE methods is provided with regard to discretization, solution accuracy and computational efficiency. For some problem classes a direct equivalence of the two methods is demonstrated, both theoretically and numerically. However, for other problems some interesting advantages and disadvantages of the FV formulation over the Galerkin FE method are highlighted. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Automatic construction of non-obtuse boundary and/or interface Delaunay triangulations for control volume methods

    Nancy Hitschfeld
    Abstract A Delaunay mesh without triangles having obtuse angles opposite to boundary and interface edges (obtuse boundary/interface triangles) is the basic requirement for problems solved using the control volume method. In this paper we discuss postprocess algorithms that allow the elimination of obtuse boundary/interface triangles of any constrained Delaunay triangulation with minimum angle ,. This is performed by the Delaunay insertion of a finite number of boundary and/or interface points. Techniques for the elimination of two kinds of obtuse boundary/interface triangles are discussed in detail: 1-edge obtuse triangles, which have a boundary/interface (constrained) longest edge; and 2-edge obtuse triangles, which have both their longest and second longest edge over the boundary/interface. More complex patterns of obtuse boundary/interface triangles, namely chains of 2-edge constrained triangles forming a saw diagram and clusters of triangles that have constrained edges sharing a common vertex are managed by using a generalization of the above techniques. Examples of the use of these techniques for semiconductor device applications and a discussion on their generalization to 3-dimensions (3D) are also included. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    An augmented spatial digital tree algorithm for contact detection in computational mechanics

    Y. T. Feng
    Abstract Based on the understanding of existing spatial digital tree-based contact detection approaches, and the alternating digital tree (ADT) algorithm in particular, a more efficient algorithm, termed the augmented spatial digital tree (ASDT) algorithm, is proposed in the present work. The ASDT algorithm adopts a different point representation scheme that uses only the lower corner vertex to represent a (hyper-)rectangle, with the upper corner vertex serving as the augmented information. Consequently, the ASDT algorithm can keep the working space the same as the original n -dimensional space and, in general, a much better balanced tree can be expected. This, together with the introduction of an additional bounding subregion for the rectangles associated with each tree node, makes it possible to significantly reduce the number of node visits in the region search, although each node visit may be slightly more expensive. Three examples arising in computational mechanics are presented to provide an assessment of the performance of the ASDT. The numerical results indicate that the ASDT is, at least, over 3.9 times faster than the ADT. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Application of two-state M -integral for analysis of adhesive lap joints

    Yongwoo Lee
    Abstract With the aid of the two-state M -integral and finite element analysis, the asymptotic solution in terms of the complete eigenfunction expansion is obtained for adhesive lap joints. The notch stress intensity is introduced to characterize the singular stress field near the notch vertex of adhesive lap joints. The proposed scheme enables us to extract the intensity of each eigenfunction term from the far field data without resort to special singular elements at the vertex. It turns out that a weak stress singularity is not negligible around the vertex when it exists in addition to the major singularity. For a thin adhesive layer, there exist two asymptotic solutions: one is the inner solution approaching the eigenfunction solution for the vertex at which the adherend meets with the adhesive and the other is intermediate solution represented by the eigenfunction series that would be obtained in the absence of the adhesive layer. An appropriate guideline for choosing the geometric parameters in designing the adhesive lap joints, particularly the overlap length or the size of the adhesive zone, is suggested from the viewpoint of minimizing the notch stress intensity. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    5,-Reductase type 2 gene variant associations with prostate cancer risk, circulating hormone levels and androgenetic alopecia

    Vanessa M. Hayes
    Abstract Controversy exists over the significance of associations between the SRD5A2 (5,-reductase type 2) polymorphisms, A49T and V89L, and risk of prostate cancer. These potentially functional polymorphisms may alter life-long exposure to androgens with subsequent effects on male health and aging. The aim of this study was to examine the association of these variants with prostate cancer risk, plasma hormone levels and androgenetic alopecia. Subjects include 827 cases and 736 controls from an Australian population-based case,control study of prostate cancer. Information on prostate cancer risk factors and patterns of balding were collected. Plasma levels of testosterone, 3,-diol glucuronide (3,-diolG), dehydroepiandrosterone sulfate, androstenedione, sex hormone-binding globulin and estradiol were measured for controls. No associations with the V89L polymorphism were found. Carriers of the rarer A49T A allele were at a 60% higher risk of prostate cancer (OR = 1.60; 95% CI 1.09,2.36; p = 0.02) and 50% lower risk of vertex and frontal balding (p = 0.03) compared with men homozygous for the more common G allele. Although we found little evidence of association between this variant and plasma levels of 5 measured androgens, circulating 3,-diolG levels were 34% lower in A49T A allele carriers (p < 0.0001). Our study provides evidence that the SRD5A2 A49T A variant is associated with an increased risk of prostate cancer, lower levels of circulating 3,-diolG and decreased risk of baldness. These findings raise important questions with respect to previous assumptions concerning hormonal influences on prostate cancer risk in ageing males. © 2006 Wiley-Liss, Inc. [source]

    A new distributed approximation algorithm for constructing minimum connected dominating set in wireless ad hoc networks

    Bo Gao
    Abstract In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub-graph. However, finding the minimum connected dominating set (MCDS) is a well-known NP-hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one-hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Chronic telogen effluvium or early androgenetic alopecia?

    Rodney Sinclair MBBS
    A 16-year-old girl presented with a 12-month history of generalized hair shedding from the scalp. The onset of shedding coincided with the development of Hashimoto's thyroiditis and iron deficiency. At the time of initial presentation, the Hashimoto's thyroiditis had been treated with Neo-Mercazole and she was euthyroid. Her iron stores were low, with a ferritin level of 13 µg/L. As she was vegetarian, oral iron replacement therapy was commenced without further investigation. On follow-up 6 months later, her iron stores were normal (ferritin, 36 µg/L), but the hair shedding had continued. On examination, there was a positive hair pull test from both the vertex of the scalp and the occipital scalp. There was mild bitemporal recession, but no widening of the central part, and she appeared to have a full, thick head of hair (Fig. 1). Additional investigations at that time revealed normal thyroid function and negative antinuclear antibody (ANA) and syphilis serology. She was on no medication other than Neo-Mercazole. Serum testosterone, dihydroepiandosterone sulphate (DHEAS) and sex hormone binding globulin (SHBG) were normal. Two 4-mm punch biopsies were taken from the vertex of the scalp; one was sectioned horizontally and the other vertically. The vertical section was unremarkable. On the horizontal section, there were 32 hair follicles in total, 30 of which were terminal hairs and two of which were vellus hairs. One hair was in telogen. The ratio of terminal to vellus hairs was 15 : 1. Figure 1. Initial presentation A diagnosis of chronic telogen effluvium was made. The condition was explained to the patient and she was reassured that chronic telogen effluvium is not a progressive condition and does not lead to baldness. No treatment was recommended. At follow-up 12 months later, the hair loss had obviously progressed and the patient was assessed as having Ludwig Stage 1 androgenetic alopecia with widening of the central part (Fig. 2). Repeat blood tests showed normal iron studies, thyroid function, and hormone parameters. Three 4-mm punch biopsies were taken from the vertex of the scalp and all were sectioned horizontally. The terminal to vellus hair ratios were 1 : 1, 2.6 : 1, and 1.9 : 1. A diagnosis of androgenetic alopecia was made and she was commenced on oral spironolactone, 200 mg/day. Figure 2. Presentation after 12 months [source]

    Pyoderma gangrenosum of the scalp treated with cyclosporine A

    Pasquale Patrone MD
    A 56-year-old woman presented with an ulcer, with a depth of 9 mm, on the vertex and frontal parietal regions of the scalp. The lesion had a round shape (diameter, 7 cm), with clear-cut margins and vertical borders sinking vertically to a bottom that was entirely covered with purulent fibrinous yellowish matter and greenish colored necrotic tissue. Other numerous small roundish ulcers were present next to the large ulcer. These had irregular margins with a yellowish fibrinous bottom (Fig. 1). The patient reported the appearance of two small ulcers on the left and on the right frontal parietal regions about 1 year earlier. These had been treated locally with antimicrobials and antiseptics with no result. During the 2 months prior to our evaluation, a few small round-shaped ulcers had appeared on the scalp. These had progressively increased in size and number. Figure Figure 1 . Large ulcer with clear-cut margins, covered by purulent fibrinous matter, and other small roundish ulcers The patient had been an insulin-dependent diabetic for 23 years. Hematochemical examinations showed no significant alterations, except for a rise in glycemia. Urine examination gave normal results. Carcinoembryonic antigen and lymphocytic phenotyping indices were normal. Echographic, endoscopic, and radiocontrast studies of the abdomen did not reveal the presence of lesions either in the gastrointestinal tract or in other organs. Samples of ulcerous tissue were collected from the scalp to perform histologic and microbiologic analysis in search of fungi and bacteria. This last examination revealed the presence of Staphylococcus aureus and Candida parapsylosis. Direct search for mycobacteria was negative. Histology indicated the presence of dermal granulomatous inflammation with giant multinucleate cells, associated with large zones of suppuration and colliquative necrosis. While waiting to complete the diagnostic course, topical antiseptic, antimicrobial, and fibrinolytic therapy was administered; subsequently, as this did not lead to any improvement, systemic treatment with cyclosporine A (5 mg/kg/day) was started. Rapid improvement of the clinical picture occurred. The ulcers appeared cleaner from the first 2 weeks of treatment, radial growth stopped, and the margins were slightly more superficial. The patient continued with immunomodulating therapy at home over a period of 7 months. The dose was progressively reduced until, over a period of about 3 months, complete re-epithelialization of the lesion, with subsequent partial regrowth of the hair, was obtained (Figs 2 and 3). No relapses were observed 1 year after treatment was suspended. Figure 2. Partial re-epithelialization of the lesion with partial regrowth of the hair Figure 3. Scar and hair regrowth [source]

    Lichen planopilaris [cicatricial (scarring) alopecia] in a child

    FNASC, FRAS (Lond.), Virendra N. Sehgal MD
    A mother of a 12-year-old boy, 2 years ago, noticed that he showed patchy loss of hair on the vertex of the scalp. It was asymptomatic and progressive. Subsequently, similar patches appeared elsewhere on the scalp. Some of these patches joined to form a large bald patch. This was accompanied by dusky blue eruptions over the left upper lip and eyebrows. Later, there was localized loss of hair. A family history of a similar ailment was absent. Examination of the scalp revealed plaques of alopecia with mild to moderate erythema. The skin was smooth, shiny, and atrophic (Fig. 1). Atrophy was apparent by the presence of wrinkles in places, and by holding the skin between the thumb and the index finger. The periphery of the lesions was well demarcated and was occupied by erythematous, scaly, follicular papules. Lesions were also located on the patches of alopecia. In addition, flat-topped, dusky blue, papules/plaques were present over the upper lip. Figure 1. Lichen planopilaris: plaques of alopecia showing smooth, shiny, atrophic skin with erythema A study of hematoxylin and eosin-stained microsections prepared from the upper lip and vertex of the scalp was undertaken. The former revealed hyperkeratosis, hypergranulosis, sawtooth irregular acanthosis, and destruction of the basal cell layer which, in turn, was embraced by a lymphohistiocytic infiltrate disposed in a band-like fashion. A few cells were seen invading the epidermis. Pigment-laden histiocytes were found intermingled with the infiltrate. In the scalp skin, on the other hand, atrophy of the epidermis with punctuation of keratin plugs, together with fibrosis of the dermis, was prominent. The walls of the hair follicles were hyperkeratotic, while their lumina were conspicuous by their dilatation and contained keratotic plugs (Fig. 2a,b). Sebaceous and sweat glands were absent. Figure 2. Lichen planopilaris showing atrophy of the epidermis, fibrosis of the dermis, dilatation of the hair follicle lumina containing keratotic plug(s), and hyperkeratosis of the wall of the follicle (hematoxylin and eosin: a , ×,40; b , ×,100) Response to treatment, comprising ultramicronized griseofulvin (Gris O.D.) 375 mg/day (Sehgal VN, Abraham GJS, Malik GB. Griseofulvin therapy in lichen planus ,- a double blind controlled trial. Br J Dermatol 1972; 86: 383,385; Sehgal VN, Bikhchandani R, Koranne RV et al. Histopathological evaluation of griseofulvin therapy in lichen planus. A double blind controlled study. Dermatologica 1980; 161: 22,27) and prednisolone 20 mg/day for 6 months, was excellent (Fig. 3). Topical betamethasone dipropionate (Diprovate) lotion was used as a supplement. Figure 3. Perceptible decline in band-like lymphohistiocytic inflammatory infiltrate (hematoxylin and eosin, a, × 40; b, ×,100) [source]

    Addressing agent loss in vehicle formations and sensor networks

    Tyler H. Summers
    Abstract In this paper, we address the problem of agent loss in vehicle formations and sensor networks via two separate approaches: (1) perform a ,self-repair' operation in the event of agent loss to recover desirable information architecture properties or (2) introduce robustness into the information architecture a priori such that agent loss does not destroy desirable properties. We model the information architecture as a graph G(V, E), where V is a set of vertices representing the agents and E is a set of edges representing information flow amongst the agents. We focus on two properties of the graph called rigidity and global rigidity, which are required for formation shape maintenance and sensor network self-localization, respectively. For the self-repair approach, we show that while previous results permit local repair involving only neighbours of the lost agent, the repair cannot always be implemented using only local information. We present new results that can be applied to make the local repair using only local information. We describe implementation and illustrate with algorithms and examples. For the robustness approach, we investigate the structure of graphs with the property that rigidity or global rigidity is preserved after removing any single vertex (we call the property as 2-vertex-rigidity or 2-vertex-global-rigidity, respectively). Information architectures with such properties would allow formation shape maintenance or self-localization to be performed even in the event of agent failure. We review a characterization of a class of 2-vertex-rigidity and develop a separate class, making significant strides towards a complete characterization. We also present a characterization of a class of 2-vertex-global-rigidity. Copyright © 2008 John Wiley & Sons, Ltd. [source]