bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical analysis of cost outcomes in a randomized controlled clinical trial
Authors: Rutten‐van Mölken Maureen P. M. H. , Van Eddy K. A. , van Vliet René C. J. A. 
Published: May 2007

AbstractThis paper suggests an approach to deal with an estimation problem which is often encountered in analyzing the longitudinal cost data gathered in a clinical trial. The source of that estimation problem is twofold: 1) a considerable number of missing data due to treatment‐related withdrawal of severely affected patients with high health care costs in only one the treatment groups and 2) a heavily skewed cost distribution due to rare high‐cost events. The approach is illustrated using data from a trial comparing 3 different drug regimes.In order to calculate costs per patient‐year in case of selectively missing data we extrapolated the costs of patients with incomplete follow‐up. Due to the skewness and the associated large variance in costs per patient‐year, these costs cannot be analyzed using common parametric statistical methods relying on underlying normal distributions. A logarithmic transformation was performed to approximate a normal distribution, reduce the impact of extreme values and create similar size variances in the treatment groups. An ordinary least squares regression analysis of transformed data then standardized for differences in patient characteristics between the groups. For the retransformation, the so‐called smearing estimate was used. This ‘transformation‐standardization‐retransformation’ approach enabled us to provide more consistent and efficient estimates of cost differences that were shown to be statistically significant and judged to be important.
The demand for cigarettes in california and behavioural risk factors
Authors: Hu Teh‐Wei , Ren Qui‐Fang , Keeler Theodore E. , Bartlett Joan 
Published: May 2007

AbstractThis study contributes to the understanding of the demand for cigarettes by taking into account the interdependence of smoking and other behavioural risk factors. Information on smoking and other behavioural risk factors including drinking, alcohol use, and obesity were obtained from the California Behavioural Risk Factor Survey for the period 1985–91. A monthly cigarette price index for California was constructed based on data obtained from the Bureau of Labor Statistics. A two‐part model was used to examine separately the effect of price on the decision to be a smoker, and on the amount of cigarettes smoked by smokers. The overall price elasticity of cigarettes was estimated at −0.46, with a price elasticity of −0.33 for smoking participation and of −0.22 for the amount of cigarettes consumed by smokers. The inclusion of other behavioural risk factors reduced the estimated price elasticity for smoking participation substantially, but had no effect on the conditional price elasticity for the quantity of cigarettes smoked.
On approximations in treatment costing
Authors: Whynes David K. , Walker Andrew R. 
Published: May 2007

AbstractAs detailed costing may be a time‐consuming and expensive exercise within an evaluation, economists will be conscious of the possibilities of taking short‐cuts. To explore the viability of such approaches in the context of acute care (the surgical treatment for colorectal cancer), we compare the results of a detailed costing study with reduced list costing and econometric estimation. We conclude, first, that use of a reduced list is likely to generate substantial research economies only at the expense of inaccuracy. Second, crude costing, based upon average costs of the specialty, is acceptable when the frame of reference is the aggregate. Such crude costing, however, is vulnerable to bias when specific sub‐samples of patients are to be considered. Finally, total costs are predictable from a restricted list of cost and event variables, and with a high degree of accuracy, although ex ante specification of the functional form is problematic.
The impact of nursing grade on the quality and outcome of nursing care
Authors: Carr‐Hill Roy A. , Dixon Paul , Griffiths Mary , Higgins Moira , McCaughan Dorothy , Rice Nigel , Wright Ken 
Published: May 2007

AbstractThe large industry which has grown up around the estimation of nursing requirements for a ward or for a hospital takes little account of variations in nursing skill; meanwhile nursing researchers tend to concentrate on the appropriate organisation of the nursing process to deliver best quality care. This paper, drawing on a Department of Health funded study, analyses the relation between skill mix of a group of nurses and the quality of care provided.Detailed data was collected on 15 wards at 7 sites on both the quality and outcome of care delivered by nurses of different grades, which allowed for analysis at several levels from a specific nurse‐patient interaction to the shift sessions. The analysis shows a strong grade effect at the lowest level which is 'diluted' at each succeeding level of aggregation; there is also a strong ward effect at each of the lower levels of aggregation. The conclusion is simple; you pay for quality care.
Nitric oxide‐releasing polyurethane–PEG copolymer containing the YIGSR peptide promotes endothelialization with decreased platelet adhesion
Authors: Taite Lakeshia J. , Yang Peter , Jun Ho‐Wook , West Jennifer L. 
Published: May 2007

AbstractThrombosis and intimal hyperplasia are the principal causes of small‐diameter vascular graft failure. To improve the long‐term patency of polyurethane vascular grafts, we have incorporated both poly(ethylene glycol) and a diazeniumdiolate nitric oxide (NO) donor into the backbone of polyurethane to improve thromboresistance. Additionally, we have incorporated the laminin‐derived cell adhesive peptide sequence YIGSR to encourage endothelial cell adhesion and migration, while NO release encourages endothelial cell proliferation. NO production by polyurethane films under physiological conditions demonstrated biphasic release, in which an initial burst of 70% of the incorporated NO was released within 2 days, followed by sustained release over 2 months. Endothelial cell proliferation in the presence of the NO‐releasing material was increased as compared to control polyurethane, and platelet adhesion to polyethylene glycol‐containing polyurethane was decreased significantly with the addition of the NO donor. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
Evidence that PI3K, Rac, Rho, and Rho kinase are involved in basic fibroblast growth factor‐stimulated fibroblast–Collagen matrix contraction
Authors: Abe Masatoshi , Sogabe Yoko , Syuto Tomoko , Yokoyama Yoko , Ishikawa Osamu 
Published: May 2007

AbstractFibroblast–collagen matrix contraction has been used as a model system to study how cells organize connective tissue. Previous work showed that lysophosphatidic acid (LPA)‐stimulated floating collagen matrix contraction is independent of Rho kinase while platelet‐derived growth factor (PDGF)‐stimulated contraction is Rho kinase‐dependent. The current studies were carried out to determine the signaling mechanisms of basic fibroblast growth factor (bFGF)‐stimulated fibroblast–collagen matrix contraction. Both bFGF and LPA promoted equally collagen matrix contraction well. Three different inhibitors, LY294002 for phosphatidylinositol‐3‐kinase (PI3K), C3 exotransferase for Rho and Y27632 for Rho kinase, suppressed the bFGF‐stimulated fibroblast–collagen matrix contraction. With bFGF stimulation, fibroblasts spread with prominent stress fiber network formation and focal adhesions. In the presence of Rho kinase inhibitor, focal adhesions and stress fibers were mostly lost. We demonstrated that bFGF stimulation for fibroblast caused transient Rac and Rho activation but did not activate Cdc42. In addition, bFGF enhanced fibroblast migration in wound healing assay. The present study implicates PI3K, Rac, Rho, and Rho kinase as being involved in bFGF‐stimulated collagen matrix contraction. The elucidation of bFGF‐triggered signal transduction may be an important clue to understand the roles of bFGF in wound healing. J. Cell. Biochem. 102: 1290–1299, 2007. © 2007 Wiley‐Liss, Inc.
Role of aralar, the mitochondrial transporter of aspartate‐glutamate, in brain N‐acetylaspartate formation and Ca2+ signaling in neuronal mitochondria
Authors: Satrústegui Jorgina , Contreras Laura , Ramos Milagros , Marmol Patricia , del Arco Araceli , Saheki Takeyori , Pardo Beatriz 
Published: May 2007

AbstractAralar, the Ca2+‐dependent mitochondrial aspartate‐glutamate carrier expressed in brain and skeletal muscle, is a member of the malate–aspartate NADH shuttle. Disrupting the gene for aralar, SLC25a12, in mice has enabled the discovery of two new roles of this carrier. On the one hand, it is required for synthesis of brain aspartate and N‐acetylaspartate, a neuron‐born metabolite that supplies acetate for myelin lipid synthesis; and on the other, it is essential for the transmission of small Ca2+ signals to mitochondria via an increase in mitochondrial NADH. © 2007 Wiley‐Liss, Inc.
Among the branched‐chain amino acids, only valine metabolism is up‐regulated in astrocytes during glutamate exposure
Authors: Bak Lasse K. , Johansen Maja L. , Schousboe Arne , Waagepetersen Helle S. 
Published: May 2007

AbstractGlutamate homeostasis during glutamatergic neurotransmission is predominantly maintained via functioning of the glutamate‐glutamine cycle. However, the glutamate‐glutamine cycle explains only the fate of the carbon atoms but not that of the accompanying transfer of nitrogen from neurons to astrocytes. In this respect, a putative branched‐chain amino acid (BCAA) shuttle has been suggested for transfer of amino nitrogen. Metabolism of BCAAs was investigated in cultured cerebellar astrocytes in a superfusion paradigm employing 15N‐labeled leucine, isoleucine, or valine. Some cultures were exposed to pulses of glutamate (50 μM; 10 sec every 2 min; 75 min in total) to mimic conditions during glutamatergic synaptic activity. 15N labeling of glutamate, aspartate, glutamine, alanine, and the three BCAAs was determined by using mass spectrometry. Incorporation of 15N into intracellular glutamate from [15N]leucine, [15N]isoleucine, or [15N]valine amounted to about 40–50% and differed only slightly among the individual BCAAs. Interestingly, label (%) in glutamate from [15N]valine was not decreased upon exposure to exogenous glutamate, which was in contrast to a marked decrease in labeling (%) from [15N]leucine or [15N]isoleucine. This suggests an up‐regulation of transamination involving only valine during repetitive exposure to glutamate. It is suggested that valine in particular might have an important function as an amino acid translocated between neuronal and astrocytic compartments, a function that might be up‐regulated during synaptic activity. © 2007 Wiley‐Liss, Inc.
A systematic review of the evidence for cranberries and blueberries in UTI prevention
Authors: Jepson Ruth G. , Craig Jonathan C. 
Published: May 2007

AbstractIn this review we assess the effectiveness of cranberry and blueberry products in preventing symptomatic urinary tract infections (UTIs). Selection criteria were randomised or quasi‐randomised controlled trials of cranberry or blueberry juice/products for the prevention of symptomatic UTIs. A comprehensive search was undertaken in November 2006 whereupon two reviewers independently assessed and extracted data. Quality was assessed using Cochrane criteria. Relative risks (RR) were calculated where appropriate; otherwise a narrative synthesis was undertaken. No relevant trials of blueberry products were identified. Nine trials of cranberry products met the inclusion criteria. In four good quality randomised controlled trials (RCTs), cranberry products significantly reduced the incidence of symptomatic UTIs in 12 months (overall RR 0.65, 95% CI: 0.46–0.90) compared with placebo/control. Five trials were not included in the meta‐analyses due to the lack of appropriate data. However, only one reported a significant result. Side effects were common, and losses to followup/withdrawals in several of the trials were high (> 40%). There is some evidence from four good quality RCTs that cranberry juice may decrease the number of symptomatic UTIs over a 12‐month period, particularly in women with recurrent UTIs. It is uncertain whether it is effective in other susceptible groups.
Minimum cost routing for dynamic network models
Authors: Yaged B. 
Published: May 2007

AbstractThis paper presents a heuristic technique which attempts to minimize the present worth of first costs (PWFC) needed to satisfy the growth in point‐to‐point flow requirements for a dynamic (in time) model of the long‐haul communications network which spans the United States. This extends earlier work on the design of static (in time) multicommodity flow networks in which each link cost function is a concave function of the link flow. The cost reduction techniques presented here are based upon the coupling between network structure, routing techniques, and economies of scale evident in transmission system costs. The technique does not change any circuit routings performed prior to the study interval. The network model studied is normative, not predictive, and cannot be used to predict the outcome of short range issues (e.g. ‐ impact of rate changes).
Algorithms for a maximum clique and a maximum independent set of a circle graph
Authors: Gavril F. 
Published: May 2007

AbstractConsider a family of chords in a circle. A circle graph is obtained by representing each chord by a vertex, two vertices being connected by an edge when the corresponding chords intersect. In this paper, we describe efficient algorithms for finding a maximum clique and a maximum independent set of circle graphs. These algorithms require at most n3 steps, where n is the number of vertices in the graph.
Cost allocation in networks: The bulk supplier problem
Authors: Claus A. , Kleitman D. J. 
Published: May 2007

AbstractWe consider the cost allocation problem faced by a large scale supplier (the telephone company) who rents telephone circuits to its customers. A number of possible allocation rate structures are analyzed, as are some of the criteria that they may be measured by. Finally, we draw conclusions and make recommendations for cost allocation in these circumstances.
On building minimum cost communication networks over time
Authors: Zadeh N. 
Published: May 2007

AbstractThis paper deals with the problem of minimizing the present worth of expenditures needed to enlarge the capacity of a communications network over time so as to meet rising traffic demands. Eight general “tests” are given for improving network solutions. The tests require only a moderate amount of computation and have the property that they will improve a wide class of non‐optimal solutions. It is observed that for a large subclass of practical problems, the dynamic problem of building a network over time may be converted to a static problem for most of the computations. This suggests a strong similarity between the optimal solutions to both problems.
On general routing problems
Authors: Lenstra J. K. , Kan A. H. G. Rinnooy 
Published: May 2007

AbstractIn two recent papers by C. S. Orloff (Networks, 4(1974)35–64, 147–162) general routing problems for one or more vehicles on a graph G = (N,A) are introduced and discussed. The single vehicle problem is to find an optimal tour on G, containing required subsets Q ⊆ N and R ⊆ A. We show that a proposed conversion of required nodes to required arcs is not allowed and that the problem remains polynomial complete if Q = θ. Furthermore, the proposed transformations from M vehicle to single vehicle problems are shown to be incorrect; correct transformations are presented as well.
On optimum path problems
Authors: Thomas R. E. 
Published: May 2007

AbstractThis tutorial paper is concerned with network problems characterized as finding optimum paths in given networks and with synthesizing networks with given optimum paths. Optimum paths are best with respect to path weights where the path weights can represent such‐diverse path parameters as distances, costs, flows, or reliabilities. This paper surveys these problems and the known results by considering specific but simple generic examples while avoiding any detailed or rigorous proofs. The final example uses a mathematical equivalence and combines known optimum path results to obtain new results regarding the synthesis of optimum networks with specified point‐to‐point reliabilities.
A good algorithm for smallest spanning trees with a degree constraint
Authors: Gabow H. N. 
Published: May 2007

AbstractGiven a connected graph with edge costs, we seek a spanning tree having a specified degree at one vertex r, with cost as small as possible. A previous algorithm, using edge exchanges, has run time 0(V2); we improve this to 0(E log log V+V log V). Here V and E are the number of vertices and edges. The algorithm uses edge exchanges ordered efficiently on a reduced graph; it also uses efficient algorithms for minimum spanning trees and priority queues.
A note on finding optimum branchings
Authors: Camerini P. M. , Fratta L. , Maffioli F. 
Published: May 2007

AbstractThe subject of this note is Tarjan's algorithm for finding an optimum branching in a directed graph. Two errors are pointed out, namely (i) an incorrect claim involving branching uniqueness, and (ii) an imprecise way of updating edge values in each iteration. These two inaccuracies do not affect the basic validity of the algorithm. It is shown here that they may be fixed via a simple modification, which leaves unchanged the overall time and space performances.
An integer linear programming approach to the steiner problem in graphs
Authors: Aneja Y. P. 
Published: May 2007

AbstractConsider a connected undirected graph G[N; E] with N = S ∪ P, the set of nodes, where P is designated as the set of Steiner points. A weight is associated with each edge ei of the set E. The problem of obtaining a minimal weighted tree which spans the set S of nodes has been termed in literature as the Steiner problem in graphs. A specialized integer programming (set covering) formulation is presented for the problem. The number of constraints in this formulation grows exponentially with the size of the problem. A method called the row generation scheme is developed to solve the above problem. The method requires knowing the constraints only implicitly. Several other problems which can be put in a similar framework can also be handled by the above scheme. The generality of the scheme and its efficiency is discussed. Finally the computational result is demonstrated.
Graphs as models of communication network vulnerability: Connectivity and persistence
Authors: Boesch Frank T. , Harary Frank , Kabell Jerald A. 
Published: May 2007

AbstractIt is well known that the maximum connectivity k of a graph G with p points and q lines is given by [2 q/p]. This is restated in two useful alternative forms which minimize q given p and k, and which maximize p in terms of q and k. We define the persistence of a graph as the smallest number of points whose removal increases the diameter. It is shown that the persistence of a graph of diameter d is the minimum over all pairs of nonadjacent points of the maximum number of disjoint paths of length at most d joining them. A similar result is obtained for line‐persistence and it is shown that these invariants are independent of each other.
The cohesiveness of a point of a graph
Authors: Akiyama Jin , Boesch Frank , Era Hiroshi , Harary Frank , Tindell Ralph 
Published: May 2007

AbstractThe connectivity contribution or cohesiveness of a point v of graph G is defined as the difference k(G) ‐ k(G ‐ v) where kappa is the usual connectivity symbol. It is shown that if a point v of G has negative cohesiveness, then the set of points adjacent to v is the unique minimum size disconnecting set of G. This theorem has several corollaries including the result that if v has negative cohesiveness in G, then it does not in Γ. Finally we define a cohesiveness triple (n_, n0, n+) of a graph by taking these, respectively, as the number of negative, zero, and positive cohesiveness points of G. The necessary and sufficient conditions for an arbitrary triple to be the cohesiveness triple of a graph are derived.
Mean flow scheduling and optimal construction of a treelike communication network
Authors: Perl Yehoshua , Yesha Yaacov 
Published: May 2007

AbstractHorn's algorithm for weighted mean flow scheduling with treelike precedence constraints is reexamined. A new analysis of an efficient implementation of Horn's algorithm shows an O(n log n) complexity. This is an improvement on the known O(n2) complexity of this algorithm. An application of Horn's algorithm to a problem of optimal scheduling of a treelike communication network is presented.
Complexity of vehicle routing and scheduling problems
Authors: Lenstra J. K. , Kan A. H. G. Rinnooy 
Published: May 2007

AbstractThe complexity of a class of vehicle routing and scheduling problems is investigated. We review known NP‐hardness results and compile the results on the worst‐case performance of approximation algorithms. Some directions for future research are suggested. The presentation is based on two discussion sessions during the Workshop to Investigate Future Directions in Routing and Scheduling of Vehicles and Crews, held at the University of Maryland at College Park, June 4–6, 1979.
Series‐parallel reduction for difficult measures of network reliability
Authors: Rosenthal Arnon 
Published: May 2007

AbstractFormulas for series and parallel reductions are obtained for difficult measures of network reliability. Examples considered include “traffic to center,” “total traffic carried,” “minimum cut,” and “all demanding vertices communicate.” We find general properties of “distribution‐preserving” and “average‐preserving” replacements, and present several examples. For systems analyzed by Monte‐Carlo sampling, we find that the estimator variance is reduced by the replacement.
A new approach to near‐optimal path assignment through electric‐circuit modeling
Authors: Smolleck Howard A. , Chen Mo‐Shing 
Published: May 2007

AbstractThis paper introduces a new philosophy and an associated computational algorithm for obtaining near‐optimal path assignments in a connected network. The method, which differs completely from traditional and other currently used techniques, is based upon the performance of successive computational examinations of the distribution of currents in the electric‐circuit model of the network under observation. Fast sparse‐matrix techniques originally developed for real‐time studies in the electric power sector are introduced in order to make the algorithm feasible for large‐system applications.Small illustrative examples are presented, and observations concerning the use of the authors' algorithm in the solution of a large transportation system problem are discussed. Some unique characteristics of the algorithm are explored.
Aggregation and disaggregation in convex network problems
Authors: Zipkin Paul H. 
Published: May 2007

AbstractThis article considers the error induced when the nodes of a large convex‐cost network problem are aggregated to form a smaller problem. First, I formalize the notion of aggregation, focusing on disaggregation of the solution and construction of the cost functions of the aggregate problem. I then explore qualitatively the conditions under which the error is likely to be small, and show how to compute bounds on the error.