bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lovastatin protects mesenchymal stem cells against hypoxia‐ and serum deprivation‐induced apoptosis by activation of PI3K/Akt and ERK1/2
Authors: Xu Ruixia , Chen Jinghai , Cong Xiangfeng , Hu Shengshou , Chen Xi 
Published: May 2007

AbstractCell therapy with bone marrow‐derived mesenchymal stem cells (MSCs) has been shown to have great promises in cardiac repair after myocardial infarction. However, poor viability of transplanted MSCs in the infracted heart has limited the therapeutic efficacy. Our previous studies have shown in vitro that rat MSCs undergo caspase‐dependent apoptosis in response to hypoxia and serum deprivation (Hypoxia/SD). Recent findings have implicated statins, an established class of cholesterol‐lowering drugs, enhance the survival of cells under various conditions. In this study, we investigated the effect of lovastatin on rat MSCs apoptosis induced by Hypoxia/SD, focusing in particular on regulation of mitochondrial apoptotic pathway and the survival signaling pathways. We demonstrated that lovastatin (0.01–1 µM) remarkably prevented MSCs from Hypoxia/SD‐induced apoptosis through inhibition of the mitochondrial apoptotic pathway, leading to attenuation of caspase‐3 activation. The loss of mitochondrial membrane potential and cytochrome‐c release from mitochondria to cytosol were significantly inhibited by lovastatin. Furthermore, the antiapoptotic effect of lovastatin on mitochondrial apoptotic pathway was effectively abrogated by both PI3K inhibitor, LY294002 and ERK1/2 inhibitor, U0126. The phosphorylations of Akt/GSK3β and ERK1/2 stimulated by lovastatin were detected. The activation of ERK1/2 was inhibited by a PI3K inhibitor, LY294002, but U0126, a ERK1/2 inhibitor did not inhibit phosphorylation of Akt and GSK3β. These data demonstrate that lovastatin protects MSCs from Hypoxia/SD‐induced apoptosis via PI3K/Akt and MEK/ERK1/2 pathways, suggesting that it may prove a useful therapeutic adjunct for transplanting MSCs into damaged heart after myocardial infarction. J. Cell. Biochem. 103: 256–269, 2008. © 2007 Wiley‐Liss, Inc.
Modulation of the amplitude of NAD(P)H fluorescence transients after synaptic stimulation
Authors: Brennan A.M. , Connor J.A. , Shuttleworth C.W. 
Published: May 2007

AbstractIn brain slices, excitatory synaptic stimulation results typically in transient initial decreases in NAD(P)H fluorescence, followed by longer‐lasting NAD(P)H increases that overshoot pre‐stimulus NAD(P)H levels before returning slowly to baseline. We concluded recently that mitochondrial metabolism (rather than NADH generation by glycolysis) was responsible for the “overshoot” phase of responses evoked in murine hippocampal slices. The present study examined factors that may influence the amplitude of the overshoot phase, without necessarily directly influencing mitochondrial or glycolytic metabolism. The amplitudes of overshoots were influenced strongly by changes in pre‐stimulus NAD(P)H fluorescence levels produced by a prior electrical stimulus. In contrast, these changes in pre‐stimulus redox state had little effect on the amplitude of evoked initial NAD(P)H decreases. Resting NAD(P)H fluorescence levels differed significantly across sub‐regions of each slice, however, this is not due to differences in resting redox state, and the relative amplitude of NAD(P)H overshoots were not different in different slice regions. Exposure to an A1 receptor agonist (CPA) reduced the amplitude of postsynaptic potentials, and preferentially reduced the amplitude of NAD(P)H overshoots, before initial oxidizing components of biphasic transients were reduced significantly. These results suggest that amplitudes of NAD(P)H overshoots may not be good quantitative measures of the intensity of a discrete stimulus, under some conditions where the stimulus is small relative to recent activity in the slice. Comparison of flavoprotein autofluorescence with NAD(P)H levels seems useful when making quantitative comparisons of responses from different regions of slices, where optical properties and ongoing activity may be substantially different. © 2007 Wiley‐Liss, Inc.
Neuroinflammation and regulation of glial glutamate uptake in neurological disorders
Authors: Tilleux Sébastien , Hermans Emmanuel 
Published: May 2007

AbstractOxidative stress, neuroinflammation, and excitotoxicity are frequently considered distinct but common hallmarks of several neurological disorders, including Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and Alzheimer's disease. Although neuron degeneration and death are the ultimate consequences of these pathological processes, it is now widely accepted that alterations in the function of surrounding glial cells are key features in the progression of these diseases. In response to alteration in their local environment, microglia, commonly considered the resident immune cells of the nervous parenchyma, become activated and release a variety of soluble factors. Among these, proinflammatory cytokines and free radicals actively participate in the degenerative insults. In addition, excitotoxic neuronal damage resulting from excessive glutamate is frequently associated with impaired handling of extracellular glutamate by gliotic astrocytes. Although several research projects have focused on the biochemical mechanisms of the regulation of glial glutamate transporters, a relationship between activation of microglia and modulation of astrocytic glutamate uptake is now suggested. The aim of this review is to summarize and discuss the data showing an influence of inflammatory mediators and related free radicals on the expression and activity of glial glutamate transporters. © 2007 Wiley‐Liss, Inc.
Construction of efficient tree networks: The pipeline problem
Authors: Zadeh N. 
Published: May 2007

AbstractIt is observed that sample cost functions for the pipeline problem [1] are discretely convex, i.e., their graphs are discrete subsets of graphs of convex functions. As a result, it is shown that the pipeline problem may be attacked by using either a minimum cost flow approach, or a combination of dynamic programming and sorting. Problems with concave cost functions are shown to be relatively easy. Even for problems which are neither convex nor concave, it is shown that in certain instances, only a subset of the data for each cost function is relevant. Error bounds are presented when approximations to the original cost functions are used. Results obtained in [4] for a related problem are summarized.
On the existence of N‐connected graphs with prescribed degrees (n ≧ 2)
Authors: Wang D. L. , Kleitman D. J. 
Published: May 2007

AbstractIn this paper we provide a simple algorithm for constructing an n‐ (vertex) connected graph with no multiple edges or loops having degree sequence satisfying the conditions indicated below. We prove these to be necessary and sufficient for the existence of such a graph.Our algorithm consists of constructing the graph in stages. An explicit construction is given if all degrees are n or n+1. Otherwise we choose a vertex with either the largest or smallest degree and connect it with a set of the remaining vertices having largest degrees, leaving a residual degree sequence for the rest of the graph which later can then be constructed by iteration. We connect the vertex of smallest degree above if the residual degrees after its connection are all at least n. Otherwise we connect the vertex of largest degree.The conditions on the degree sequence are that it must be realizable by a graph, all degrees must be at least n, and the number of edges which can avoid touching the n‐1 largest degree vertices are sufficient to form a tree among the other vertices.
On building minimum cost communication networks
Authors: Zadeh N. 
Published: May 2007

AbstractThe notion of an „exact”︁ test for improving network solutions is discussed. Computational results are presented which indicate the power of „exact”︁ tests relative to current marginal pricing schemes. It is conjectured that each cycle in an optimal solution must contain at least \documentclass{article}\pagestyle{empty}\begin{document}$ 1 + \frac{1}{{1^\alpha - 1}} $\end{document} links, where the cost of a link of length l and capacity y is proportional to 1·yα, 0 ≦ α ≦ 1.A simple „exact”︁ test is presented for the one termianl TELPAK problem.
A fundamental problem in vehicle routing
Authors: Orloff C. S. 
Published: May 2007

AbstractAn important but difficult combinatorial problem, in general, is to find the optimal route for a single vehicle on a given network. This paper defines a problem type, called the General Routing Problem, and gives an algorithm for its solution. The classical Traveling Salesman Problem and the Chinese Postman Problem are shown to be special limiting cases of the General Routing Problem. The algorithm provides a unified approach to both node and arc oriented routing problems, and exploits special properties of most real transportation networks such as sparsity of the associated adjacency matrix, and the tendency for arc symmetry at many nodes. For node oriented routing problems, this approach tends to produce large reduction in effective problem size.
Exact calculation of computer network reliability
Authors: Hänsler E. , McAuliffe G. K. , Wilkov R. S. 
Published: May 2007

AbstractIn designing a distributed computer network, the reliability and availability of the communication paths between all pairs of centers is a primary consideration. Many different approaches have been taken to calculate exactly the probability of successful communication between any specified pair of centers, for a given failure probability of the individual computer systems and communication facilities. However, almost all of these methods are not computationally feasible for large networks. Consequently, approximate calculations of network reliability have been suggested. In this paper a procedure is given for the exact calculation of the probability that all paths between a pair of nodes in a given network are interrupted. The procedure generates mutually exclusive sets of cutting states and calculates the probability of the related events. Summing these values one obtains the probability of service interruption between the specified pair of nodes. If all links fail with equal probability p, the coefficients of a polynomial can be calculated, describing the service disruption probability as a function of p.
Generalized Ramsey theory for graphs IV, the Ramsey multiplicity of a graph
Authors: Harary F. , Prins G. 
Published: May 2007

AbstractA Proper graph G has no isolated points. Its Ramsey number r(G) is the minimum p such that every 2‐coloring of the edges of Kp contains a monochromatic G. The Ramsey multiplicity R(G) is the minimum number of monochromatic G in any 2‐coloring of Kr(G). With just one exception, namely K4, we determine R(G) for proper graphs with at most 4 points. For the stars K1,n, it is shown that R = 2n when n is odd and R = 1 when n is even. We conclude with the conjecture that for a proper graph, R(G) = 1 if and only if G = K2 or K1,n with n even.
Shortest alternating path algorithms
Authors: Brown J. R. 
Published: May 2007

AbstractThe concept of an alternating path has been very useful in analyzing matching problems and has formed the basis for a number of matching algorithms. However, no techniques have been devised to find the shortest alternating path in a weighted graph. This paper defines different types of directed and undirected alternating paths, and shows how the problem of finding the shortest directed alternating path can be transformed into a problem of finding the shortest path in a directed graph. Utilizing this transformation, an efficient algorithm is developed for finding the shortest undirected alternating path. Computational experience is given. Extensions of the techniques in this paper to other types of alternating paths are discussed.
A bit‐pushing shortest distance algorithm
Authors: Rosenthal A. 
Published: May 2007

AbstractA bit manipulation method is given for finding shortest distances from an origin in an unweighted graph, or alternatively, for finding connected components. The basic approach is similar to some component algorithms already in the literature but an easy implementation is given that overcomes the problem which prevents the others from being efficient–namely, the problem of identifying the ones in a sparse bit string without checking all the bits. The algorithm would be most effective for moderate sized graphs (about 20–100 nodes). Computational results are given.
Minimal complete matchings and negative cycles
Authors: Tobin R. L. 
Published: May 2007

AbstractConditions are developed which relate the existence of negative and nonpositive simple cycles in an undirected network to minimal complete matchings on a derived network. These conditions are then used to develop a test to determine whether or not an undirected network contains nonpositive simple cycles. Also, it is shown that, in certain cases, the solution to the matching problem gives information about the location of the nonpositive cycles.
An algorithm for the longest cycle problem
Authors: Dixon E. T. , Goodman S. E. 
Published: May 2007

AbstractAn algorithm is presented which solves the problem of finding the longest simple cycle in an undirected edge‐weighted network. The properties of the vector spaces associated with the fundamental cycles of a network are used to develop a suitable algorithm for finding simple cycles, and this is imbedded into a branch and bound scheme that solves the longest cycle problem.
A new deterministic network reliability measure
Authors: Tainiter M. 
Published: May 2007

AbstractWe introduce and study properties of a new definition of connectivity and reliability which we call “mean connectivity.” The usual definition of cohesion which is used in survivability or reliability analysis is local in that it is the minimum size of an edge cutset. Mean connectivity involves an average time to connectivity, where the average is over random sequences of the edges of a graph. Aside from intuitive appeal, the new definition is shown to have desirable mathematical properties.
A generalized upper bounding approach to a communications network planning problem
Authors: McCallum C. J. 
Published: May 2007

AbstractAn important network optimization problem is to determine the routing of circuits and construction of additional are capacity in a communications network so as to satisfy forecasted circuit requirements at minimum cost. This paper considers the single‐time‐period version of the problem formulated as a linear program in the arc‐chain form. The special structure of this linear program is exploited to develop an efficient solution procedure. In particular, the generalized upper bounding technique devised by Dantzig and Van Slyke is applied. The computer implementation of the procedure is discussed and computational experience is reported. Brief mention is also made of certain extensions that are being pursued.
Measures of the restrictiveness of project networks
Authors: Thesen A. 
Published: May 2007

AbstractThe concept of the restrictiveness of project networks is defined to reflect the degree to which precedence requirements eliminate possible scheduling sequences. A suitable measure of restrictiveness is presented, as published related materials are shown not to apply. To extend the computational feasibility of the concept to larger networks, three indirect estimators of the measure are introduced. Relationships between these and related statistical properties of networks are shown. Finally, an algorithm to generate random networks with a specified restrictiveness is given.
A product form representation of the inverse of a multicommodity cycle matrix
Authors: Helgason R. V. , Kennington J. L. 
Published: May 2007

AbstractWhen solving multicommodity network flow problems with either a primal or a dual partitioning technique one must carry and update a working basis inverse whose size need never exceed the number of saturated arcs (i.e. arcs for which there is no excess capacity). Efficient procedures have appeared in the literature for updating this inverse if it is carried in explicit form. However, for real world multicommodity network flow problems, this inverse may become quite large. In addition, this matrix may be quite dense even though the working basis may be sparse. In an attempt to obtain a sparse representation of this inverse matrix and simplify the computational burden, we present a new data structure along with the updating formulae for storing and updating this matrix. This data structure is a generalization of the well‐known product form procedure frequently used in mathematical programming codes.
Color‐feasible sequences of a multigraph
Authors: de Werra D. 
Published: May 2007

AbstractGiven a multigraph G, a sequence (h1,…, hm) of nonnegative integers h1 ≥… ≥ hm is color‐feasible for G if there is an edge‐coloring H1,…, Hm where Hi has exactly hi edges (i=1,…, m). It is known that the set C(G) of color‐feasible sequences of G is partially ordered. We show that if G is simple with maximum degree d, then all maximal sequences of C(G) have at most d+1 nonzero entries. This result can be extended to multigraphs. Furthermore, if the odd elementary cycles of a multigraph G satisfy some specified conditions then all maximal sequences have at most d+1 nonzero entries.
A mean‐time comparison of algorithms for the all‐pairs shortest‐path problem with arbitrary arc lengths
Authors: Kelton W. D. , Law A. M. 
Published: May 2007

AbstractA mean‐time comparison of the algorithms of Floyd, Dantzig, Tabourier, and of repeated application of several single‐source algorithms, for the all‐pairs shortest‐path problem with arbitrary arc lengths clearly demonstrates the superiority of the Tabourier procedure for networks in which an average of at least 25% of the potential direct arcs are present. For very sparse networks, repeated application of a single‐source label‐correcting algorithm is found to be preferable.
On the numerical evaluation of some basic traffic formulae
Authors: Farmer R. F. , Kaufman I. 
Published: May 2007

AbstractThe problem of evaluating some basic traffic tormulae is considered here from a computational point of view. The specific problems include the evaluation of Poisson, Erlang B and Erlang C blocking functions and their associated inverses. Formulae related to Wilkinson's nonrandom traffic theory are also included. The methods presented are simple, efficient and accurate. They are based on several newly derived formulae and are ideally suited for extensive computerized network analysis, design and optimization problems. These methods have been incorporated into the simulator of the Canadian network. This simulator is widely used in analyzing the usage of the network as well as in assessing the impact of changing loads which arise from shifts in the economy, demand or rates.
Systematic searches for hypohamiltonian graphs
Authors: Collier J. B. , Schmeichel E. F. 
Published: May 2007

AbstractA graph G is called hypohamiltonian if G is not hamiltonian but every vertex‐deleted subgraph G‐v is hamiltonian. The existence of a p‐vertex hypohamiltonian graph is open only for p = 14,17, and the existence of a p‐vertex, cubic hypohamiltonian graph is open only for p = 14,16,24,32. With the aid of a computer we have established that there is no hypohamiltonian graph of order 14, and no cubic hypohamiltonian graph of order 14 or 16. In addition, there is no hypohamiltonian graph of order 17 with girth ≥ 5. On the other hand, new p‐vertex, cubic hypohamiltonian graphs have been found for p = 18,22.
Link designs and probability analyses for a class of connecting networks
Authors: Hwang F. K. 
Published: May 2007

AbstractWe study a class of five‐stage connecting networks which are generalizations of the AMDF networks recently proposed. The terminals of a network in this class are partitioned into various zones while two terminals of the same zone have a larger number of distinct paths connecting them than two terminals of different zones. Furthermore, to facilitate the analysis of blocking probabilities, we require that the linear graphs (union of all connecting paths) for all intrazone pairs of terminals be isomorphic and fixed, and the linear graphs for all interzone pairs be isomorphic.We show that balanced incomplete block designs can be used to construct large classes of such networks. For a fixed number of distinct paths, we also determine the symmetric linear graph which has the smallest blocking probability, and show that the network which yields this linear graph (for interzone pairs) can always be constructed if a certain balanced incomplete block design exists.
Shortest paths with euclidean distances: An explanatory model
Authors: Golden B. L. , Ball M. 
Published: May 2007

AbstractThis paper considers the problem of finding the shortest path between an origin and destination pair in networks whose arc lengths are Euclidean distances. Dijkstra's algorithm and a modified version of Dijkstra's algorithm which is more adaptive to network topology are compared. We demonstrate on the infinite lattice network with diagonal arcs (a prototype of more general sparse Euclidean networks) that on the average the adaptive algorithm expands less than 8.3% the area that would be expanded by the Dijkstra algorithm and in the worst case it expands less than 10.7%. In addition, we present computational results for more general networks.
A new shortest path updating algorithm
Authors: Goto S. , Sangiovanni‐Vincentelli A. 
Published: May 2007

AbstractA new algorithm for updating shortest paths from all vertices to a set of vertices following a decreasing‐length‐modification of some arcs, is presented. The algorithm is based on a formula which has an algebraic analogy with the well‐known Householder formula for inverting modified matrices. The number of operations (i.e., additions and comparisons) required for solving the modified shortest path problem is estimated as 0(mn2), where n is the overall number of vertices and m is a parameter related to the arcs which have been updated. The algorithm proposed here is particularly powerful for solving large‐scale networks with sparse structure.
The largest minimal rectilinear steiner trees for a set of n points enclosed in a rectangle with given perimeter
Authors: Chung F. R. K. , Hwang F. K. 
Published: May 2007

AbstractSuppose P is a set of points in the plane with rectilinear distance. Let ls(P) denote the length of a Steiner minimal tree for P. Let lr(P) denote the semiperimeter of the smallest rectangle with vertical and horizontal lines which encloses P. It is well known that ls(P) ≥ lr(P) for ∣P∣ ≥ 3 where ∣P∣ denotes the cordinality of P.In designing placement algorithms for printed circuits, lr(P) has been used as an estimate of ls(P) when ∣P∣ is small. Therefore, it is of some interest to know the value of

In this paper we show ρn tends to (√n+1)/2 and we give the exact value of ρn for n ≤ 10.
Exact and approximate algorithms for optimal network design
Authors: Dionne R. , Florian M. 
Published: May 2007

AbstractABSTRACTIn this paper, we present exact and approximate algorithms for the problem of optimal network design, which was first studied by Ridley [15], Stairs [17] and Scott [16], among others. Given a network, the problem consists in selecting a subset of links that minimizes the sum of shortest routes between all nodes subject to a budget constraint. Congestion effects are not considered. First, we refine a branch‐and‐bound algorithm proposed by Hoang [7] and we compare the resuling algorithm to an algorithm developed by Boyce et al. [1]. Our conclusion is that these exact algorithms perform adequately on medium size problems; however, for larger problems, approximate methods based on heuristic approaches are necessary. We then introduce two new heuristic approaches and test their computational efficiency as well as that of two other already known heuristics. The new heuristics presented produce excellent results. Finally, we consider more general versions of the problem.