bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new MRI method, tested in vitro for the assessment of thermal coagulation and demonstrated in vivo on focused ultrasound ablation
Authors: Carasso Dina , Hanannel Arik , Navon Gil 
Published: December 2007

AbstractA new MRI method is described. It is implemented for the assessment of thermal coagulation after thermal treatment. The method does not require injection of a contrast agent. The image is based on the amount of magnetization exchange between macromolecules and water in the tissue. Coagulated tissue has a faster magnetization exchange rate, forming the new contrast. In this study, the new imaging method is shown to have good contrast between coagulated and untreated excised tissues of porcine liver and muscle. The method is also successfully demonstrated in vivo in rat thigh muscle thermally treated with focused ultrasound. Copyright © 2007 John Wiley & Sons, Ltd.
Some edge‐fault‐tolerant properties of the folded hypercube
Authors: Hsieh Sun‐Yuan 
Published: December 2007

AbstractIn this article, we analyze some edge‐fault‐tolerant properties of the folded hypercube, a variant of the regular hypercube that is obtained by adding an edge to every pair of nodes with complementary addresses. We show that ann‐dimensional folded hypercube is (n− 2)‐edge‐fault‐tolerant Hamiltonian‐connected whenn(≥ 2) is even, (n− 1)‐edge‐fault‐tolerant strongly Hamiltonian‐laceable whenn(≥ 1) is odd, and (n− 2)‐edge‐fault‐tolerant hyper Hamiltonian‐laceable whenn(≥ 3) is odd. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
The maximum congested cut problem and its robust counterpart: Exact and approximation algorithms for the single and the multicommodity case
Authors: Scutellà Maria G. 
Published: December 2007

AbstractWe study an optimization problem which can be interesting in several network applications, especially in telecommunication. Given a capacitated directed network G in which a flow, related to a certain commodity, has to be sent from a given set of origins to a given set of destinations, we want to compute a maximum congested cut, i.e., a cut (S,T) of G which maximizes the ratio between the net demand of T and the capacity of the cut. We will show that a maximum congested cut can be computed in polynomial time by formulating the problem as a special maximum mean‐weight cut problem, and solving it by Newton's method for linear fractional combinatorial optimization (Radzik, Complexity in Numerical Optimization, World Scientific, Singapore, 1993). The introduced formulation will be extended to the case in which the flow demands vary in a polyhedron D, and a cut has to be determined which maximizes the congestion with respect to the flow demands in D, addressing a robust version of the problem. We will prove that the robust maximum congested cut problem is coNP‐Hard. Special cases solvable in polynomial time as well as approximation algorithms for some relevant hard cases will be proposed. The specialization of the proposed approaches to the well‐studied class of Hose models (Duffield et al., Proc., Conf Appl Technol Architect Protocol Comp Comm 29 (1999), 95–108) will be discussed. Then, in the second part of the paper, we will investigate the case in which k commodities are given, and a maximum congested cut has to be computed in such a multicommodity flow context. This problem is NP‐Hard. Some algorithmic considerations will be formulated in order to approximate the maximum congested cut in multicommodity networks, also addressing the robust version of the problem. A consequence of the stated results is a polynomial time algorithm for the sparsest cut problem in undirected graphs, for the special case in which k is O(log n), and an O(${{k}\over{\log n}}$)‐approximationalgorithm for the general case, where n denotes the cardinality of the node set. Furthermore, a new heuristic approach for the directed sparsest cut problem will be suggested. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
Transversals of subtree hypergraphs and the source location problem in digraphs
Authors: van den Heuvel Jan , Johnson Matthew 
Published: December 2007

AbstractA hypergraph H = (V,E) is a subtree hypergraph if there is a tree T on V such that each hyperedge of E induces a subtree of T. Since the number of edges of a subtree hypergraph can be exponential in n = |V|, one can not always expect to be able to find a minimum size transversal in time polynomial in n. In this paper, we show that if it is possible to decide if a set of vertices W ⊆ V is a transversal in time S(n) (where n = |V|), then it is possible to find a minimum size transversal in O(n3S(n)). This result provides a polynomial algorithm for the Source Location Problem: a set of (k,l)‐sources for a digraph D = (V,A) is a subset S of V such that for any v ∈ V there are k arc‐disjoint paths that each join a vertex of S to v and l arc‐disjoint paths that each join v to S. The Source Location Problem is to find a minimum size set of (k,l)‐sources. We show that this is a case of finding a transversal of a subtree hypergraph, and that in this case S(n) is polynomial. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
New facets for the planar subgraph polytope
Authors: Hicks Illya V. 
Published: December 2007

AbstractThis study describes certain facet classes for the planar subgraph polytope. These facets are extensions of Kuratowski facets and are of the form 2x(U) + x(E(G)\U) ≤ 2|U| + |E(G)\U| − 2 where the edge set U varies and can be empty. Two of the new types of facets complete the class of extended subdivision facets, explored by Jünger and Mutzel. In addition, the other types of facets consist of a new class of facets for the polytope called 3‐star subdivisions. It is also shown that the extended and 3‐star subdivision facets are also equivalent to members of the class of facets with coefficients in {0, 1, 2} for the set covering polytope. Computational results displaying the effectiveness of the facets in a branch‐and‐cut scheme for the maximum planar subgraph problem are presented. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
Cycle‐based algorithms for multicommodity network flow problems with separable piecewise convex costs
Authors: de Souza Mauricio C. , Mahey Philippe , Gendron Bernard 
Published: December 2007

AbstractWe present cycle‐based algorithmic approaches to find local minima of a nonconvex and nonsmooth model for capacity expansion of a network supporting multicommodity flows. By exploiting complete optimality conditions for local minima, we give the convergence analysis of the negative‐cost cycle canceling method. The cycle canceling method is embedded in a tabu search strategy to explore the solution space beyond the first local optimum. Reaching a local optimum, the idea is to accept a cost‐increasing solution by pushing flow around a positive‐cost cycle, and then to make use of the cycle cancelling method incorporating tabu search memory structures to find high quality local optima. Computational experiments on instances of the literature show that the tabu search algorithm can significantly improve feasible solutions obtained by the local optimization procedure, and it outperforms the capacity and flow assignment heuristic in terms of solution quality. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
A graph theory approach for designing conservation reserve networks with minimal fragmentation
Authors: Önal Hayri , Wang Yicheng 
Published: December 2007

AbstractHabitat fragmentation is often cited as one of the most important factors that adversely affect species persistence and survival ability. Contiguity of habitat sites is usually desirable when designing a conservation reserve. If a contiguous reserve is not feasible, due to landscape characteristics or economic constraints, designing a reserve network with minimal fragmentation may be a viable strategy. This article presents a linear integer programming formulation of the problem using graph theory concepts. A graph is constructed where nodes correspond to individual sites and directed arcs are defined for pairs of nodes corresponding to adjacent sites. The model determines a minimal representative tree as a subgraph where each node in the tree corresponds to either a selected reserve site or a gap site. Reserve fragmentation is defined as the sum of gap sites, which is to be minimized. An important computational problem is the formation of cycles when determining the minimal representative tree. This problem is resolved using an iterative procedure that utilizes Dantzig‐cuts when a cycle occurs in the solution. Arbitrarily generated data sets are used to explore the computational efficiency of this approach. Finally an empirical application of the model to a real data set involving 744 sites and 32 endangered/threatened bird species is presented. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
New dynamic programming algorithms for the resource constrained elementary shortest path problem
Authors: Righini Giovanni , Salani Matteo 
Published: December 2007

AbstractThe resource constrained elementary shortest path problem (RCESPP) arises as a pricing subproblem in branch‐and‐price algorithms for vehicle‐routing problems with additional constraints. We address the optimization of the RCESPP and we present and compare three methods. The first method is a well‐known exact dynamic‐programming algorithm improved by new ideas, such as bidirectional search with resource‐based bounding. The second method consists in a branch‐and‐bound algorithm, where lower bounds are computed by dynamic‐programming with state‐space relaxation; we show how bounded bidirectional search can be adapted to state‐space relaxation and we present different branching strategies and their hybridization. The third method, called decremental state‐space relaxation, is a new one; exact dynamic‐programming and state‐space relaxation are two special cases of this new method. The experimental comparison of the three methods is definitely favorable to decrement state‐space relaxation. Computational results are given for different kinds of resources, arising from the capacitated vehicle‐routing problem, the vehicle‐routing problem with distribution and collection, and the vehicle‐routing problem with capacities and time windows. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
Techniques for analyzing dynamic random graph models of web‐like networks: An overview
Authors: Cami Aurel , Deo Narsingh 
Published: December 2007

AbstractVarious random graph models have recently been proposed to replicate and explain the topology of large, complex, real‐life networks such as the World Wide Web and the Internet. These models are surveyed in this article. Our focus has primarily been on dynamic random graph models that attempt to account for the observed statistical properties of web‐like networks through certain dynamic processes guided by simple stochastic rules. Particular attention is paid to the equivalence between mathematical definitions of dynamic random graphs in terms of inductively defined probability spaces and algorithmic definitions of such models in terms of recursive procedures. Several techniques that have been employed for studying dynamic random graphs—both heuristic and analytic—are expounded. Each technique is illustrated through its application in analyzing various graph parameters, such as degree distribution, degree‐correlation between adjacent nodes, clustering coefficient, distribution of node‐pair distances, and connected‐component size. A discussion of the most recent salient work and a comprehensive list of references in this rapidly‐expanding area are included. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
The fractional congestion bound for efficient edge disjoint routing
Authors: Baveja Alok 
Published: December 2007

AbstractThis article investigates the following problem: Given the fractional relaxation of the edge disjoint routing problem, how small a fractional congestion is sufficient to guarantee efficient edge disjoint routing? That is, what is the largest possible valuevsuch that a fractional flow with congestion at mostv, can be efficiently converted into an edge disjoint routing? Leighton, Lu, Rao, and Srinivasan (SIAM J Comput 2001) have established that fractional congestion of at most the order ofO(1/(dlogk)) is sufficient, wheredis the maximum path length in the fractional relaxation, andkis the number of pairs to be routed. It is also known thatΘ(1/d) is the correct bound, if we are only interested in an existence result (Leighton, Rao, and Srinivasan, Hawaii International Conference on System Sciences, 1998). Motivated by the fact thatdis small for many types of routing problems, specifically, polylogarithmic for expander graphs, this article improves upon the former result by showingO(1/(dlogd)) fractional congestion to suffice. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
Sufficient conditions for a graph to be super restricted edge‐connected
Authors: Wang Shiying , Lin Shangwei 
Published: December 2007

AbstractRestricted edge connectivity is a more refined network reliability index than edge connectivity. A restricted edge cut F of a connected graph G is an edge cut such that G‐F has no isolated vertex. The restricted edge connectivity λ′ is the minimum cardinality over all restricted edge cuts. We call G λ′‐optimal if λ′ = ξ, where ξ is the minimum edge degree in G. Moreover, a λ′‐optimal graph G is called a super restricted edge‐connected graph if every minimum restricted edge cut separates exactly one edge. Let D and g denote the diameter and girth of G, respectively. In this paper, we first present a necessary condition for non‐super restricted edge‐connected graphs with minimum degree δ ≥ 3 and D ≤ g − 2. Next, we prove that a connected graph with minimum degree δ ≥ 3 and D ≤ g − 3 is super restricted edge‐connected. Finally, we give some sufficient conditions on the conditional diameter and the girth for super restricted edge‐connected graphs. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
On a graph coloring problem arising from discrete tomography
Authors: Bentz C. , Costa M.C. , de Werra D. , Picouleau C. , Ries B. 
Published: December 2007

AbstractAn extension of the basic image reconstruction problem in discrete tomography is considered: given a graph G = (V,E) and a family $\cal {P}$ of chains Pi together with vectors h(Pi) = (h,…,h), one wants to find a partition V1,…,Vk of V such that for each Pi and each color j, |Vj ∩ Pi| = h. An interpretation in terms of scheduling is presented. We consider special cases of graphs and identify polynomially solvable cases; general complexity results are established in this case and also in the case where V1,…,Vk is required to be a proper vertex k‐coloring of G. Finally, we examine also the case of (proper) edge k‐colorings and determine its complexity status. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
A Reach and Bound algorithm for acyclic dynamic‐programming networks
Authors: Bailey Matthew D. , Smith Robert L. , Alden Jeffrey M. 
Published: December 2007

AbstractNode pruning is a commonly used technique for solution acceleration in a dynamic‐programming network. In pruning, nodes are adaptively removed from the dynamic programming network when they are determined not to lie on an optimal path. We introduce an ε‐pruning condition that extends pruning to include a possible error in the pruning step. This results in a greater reduction of the computation time; however, as a result of the inclusion of this error, the solution can be suboptimal or possibly infeasible. This condition requires the ability to compare the costs of an optimal path from a node to a terminal node. Therefore, we focus on the class of acyclic dynamic programming networks with monotonically decreasing optimal costs‐to‐go. We provide an easily implementable algorithm, Reach and Bound, which maintains feasibility and bounds the solution's error. We conclude by illustrating the applicability of Reach and Bound on a problem of single location capacity expansion. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
Spectral bounds for the maximum cut problem
Authors: Ben‐Ameur Walid , Neto José 
Published: December 2007

AbstractThe maximum cut problem is a classical combinatorial optimization problem that is known to be NP‐hard in general. In the present article, we provide some new lower and upper bounds that are based on the eigenvalues of the weight matrix with modified diagonal entries. Namely, we show that some upper bounds presented here are generally better than the SDP bound introduced by Goemans and Williamson, JACM 42 (1995), 1115–1145. We also discuss the complexity of computing these bounds and provide some preliminary computational results. © 2007 Wiley Periodicals, Inc. NETWORKS, 2008
Polynomial preserving recovery for meshes from Delaunay triangulation or with high aspect ratio
Authors: Zhang Zhimin 
Published: December 2007

AbstractA newly developed polynomial preserving gradient recovery technique is further studied. The results are twofold. First, error bounds for the recovered gradient are established on the Delaunay type mesh when the major part of the triangulation is made of near parallelogram triangle pairs with ε‐perturbation. It is found that the recovered gradient improves the leading term of the error by a factor ε. Secondly, the analysis is performed for a highly anisotropic mesh where the aspect ratio of element sides is unbounded. When the mesh is adapted to the solution that has significant changes in one direction but very little, if any, in another direction, the recovered gradient can be superconvergent. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008
Finite element study of time‐dependent Maxwell's equations in dispersive media
Authors: Li Jichun , Chen Yitung 
Published: December 2007

AbstractIn this article, we consider the time‐dependent Maxwell's equations in a bounded domain when dispersive media are involved. The Crank‐Nicolson scheme is developed to approximate the electric field equation by Nedelec edge elements and is proved to be optimal convergent in energy norm. The analysis is carried out for Debye medium, but the same results hold true for other dispersive media such as plasma and Lorentz medium. Furthermore, our analysis extends straightforward to cases when a dispersive medium and a simple medium (such as air) are coupled. Mathematics Subject Classification (2000): 65N30, 35L15, 78‐08. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008
Equilibrated error estimators for discontinuous Galerkin methods
Authors: Cochez‐Dhondt Sarah , Nicaise Serge 
Published: December 2007

AbstractWe consider some diffusion problems in domains of ℝd, d = 2 or 3 approximated by a discontinuous Galerkin method with polynomials of any degree. We propose a new a posteriori error estimator based on H(div)‐conforming elements. It is shown that this estimator gives rise to an upper bound where the constant is one up to higher order terms. The lower bound is also established with a constant depending on the aspect ratio of the mesh, the dependence with respect to the coefficients being also traced. The reliability and efficiency of the proposed estimator is confirmed by some numerical tests. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008
Impfung gegen humane Papillomaviren. Eine neue Präventionsstrategie gegen Krebs
Authors: Hampl Monika 
Published: December 2007

AbstractDas Humane Papillomvirus (HPV) ist das häufigste durch Geschlechtsverkehr übertragene Virus weltweit. Circa 70 bis 80 % der Bevölkerung macht in ihrem Leben die meist asymptomatisch verlaufende Infektion durch. Wird die Infektion nicht ausgeheilt, kann es zu einem Einbau der Virus‐DNA in das Wirtsgenom kommen und damit zu einer persistierenden Infektion mit Expression der beiden viralen Onkogene E6 und E7, die in den Zellzyklus eingreifen. Eine persistierende HPV‐Infektion ist eine notwendige Voraussetzung für die Entstehung des Zervix‐ und in vielen Fällen des Vulva‐ und Analkarzinoms, sowie deren Vorstufen.
Trends in der Impfstoffentwicklung. DNA‐ und zellbasierte Impfstoffe
Authors: Scherer Jürgen , Hinz Thomas , Cichutek Klaus 
Published: December 2007

AbstractFür eine Reihe von Infektionskrankheiten sowohl bakterieller, parasitärer als auch viraler Genese wurde vor allem im 20. Jahrhundert eine Vielzahl von Impfstoffen entwickelt, die Impflinge erfolgreich schützen konnten. Dies führte zu einer drastisch verminderten Krankheitslast in der Bevölkerung, zu einer deutlich verringerten Säuglingssterblichkeit und zu einer Erhöhung der Lebenserwartung. Aktuell werden die globalen Bemühungen intensiviert, das Poliomyelitis‐ und das Masern‐Virus auszurotten.
Herstellung und Qualitätskontrolle von Impfstoffen. “The process is the product”
Authors: Pfleiderer Michael 
Published: December 2007

AbstractDer Nutzen von Impfstoffen zur Prophylaxe von Infektionskrankheiten wurde bereits vor mehr als 200 Jahren wissenschaftlich belegt. In der Folge wurden seit den Tagen Edward Jenners, der 1798 überzeugend darstellen konnte, dass Kuhpocken am Menschen zum Schutz vor Pockenvirusinfektionen angewendet werden können, fortwährend neue oder optimierte Impfstoffe entwickelt. Dadurch haben viele der ansonsten lebensbedrohlichen viralen und bakteriellen Infektionskrankheiten heute ihren Schrecken verloren.
Die Empfehlungen der Ständigen Impfkommission am Robert Koch‐Institut. Standardimpfungen sind erstattungsfähig
Authors: Meyer Christiane , Wiese‐Posselt Miriam , Deleré Yvonne , Reiter Sabine 
Published: December 2007

AbstractImpfungen gehören zu den wirksamsten, nebenwirkungsarmen und kostengünstigsten Maßnahmen des Infektionsschutzes, weshalb es von öffentlichem Interesse ist, Impfungen zum Schutz des Einzelnen, aber auch – insbesondere durch das Erreichen einer Herdenimmunität – zum Schutz von Bevölkerungsgruppen allgemein zu empfehlen.
Impfskeptiker – Impfgegner. Von einer anderen Realität im Internet
Authors: Maurer Wolfgang 
Published: December 2007

AbstractObwohl die Durchimpfungsrate in Deutschland gestiegen ist, gibt es noch genügend Impflücken, so dass impfpräventable Infektionserreger, deren Wirt nur der Mensch ist, noch weiter zirkulieren können. Zugleich sind Impfungen unter manchen wissenschaftsfernen Menschen verpönt, ja manche bekämpfen Impfungen auf das heftigste. Impfgegner sind heterogen zusammengesetzt, die härtesten Impfgegner bezweifeln, dass es überhaupt humanpathogene Viren gibt. Eltern werden von solchen Scharlatanen aufgefordert, ihre Kinder nicht zu impfen. Impfen ist jedoch medizinischer Standard, auf den alle – auch Kinder – ein Anrecht haben. Gegen ärztliche Impfgegner sollte hart durchgegriffen werden, da sie die ärztliche Sorgfaltspflicht grob verletzen, wenn sie die STIKO‐Impfempfehlungen ablehnen.