bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bounding the expected number of rectilinear full Steiner trees
Authors: Wulff‐Nilsen Christian 
Published: August 2009

AbstractGiven a finite set Z of n points, called terminals, in ℝd, the Rectilinear Steiner Tree Problem asks for a tree of minimal L1‐length spanning Z. An optimal solution has a unique decomposition into full Steiner trees (FSTs). By using geometric properties and combinatorial arguments, we bound the expected number of FSTs satisfying simple necessary conditions for being part of an optimal solution. More specifically, we show that the expected number of FSTs spanning exactly K terminals and satisfying the empty lune property, a weak version of the bottleneck property, and the so‐called empty hyperbox property is O(n(log log n)2(d−1)) for K = 3 and O(n(log log n)d−1 log K−2n) for K > 3, assuming terminals are randomly distributed in a hypercube with a uniform distribution. In the plane, we improve an earlier bound by showing that the expected number of FSTs with the Hwang form spanning exactly K terminals and satisfying the empty lune property and the so‐called disjoint lunes property is O(nπK). © 2009 Wiley Periodicals, Inc. NETWORKS, 2010
Constraint preconditioning for nonsymmetric indefinite linear systems
Authors: Sun Li‐Ying , Liu Jun 
Published: August 2009

AbstractThis paper introduces and presents theoretical analyses of constraint preconditioning via a Schilders'‐like factorization for nonsymmetric saddle‐point problems. We extend the Schilders' factorization of a constraint preconditioner to a nonsymmetric matrix by using a different factorization. The eigenvalue and eigenvector distributions of the preconditioned matrix are determined. The choices of the parameter matrices in the extended Schilders' factorization and the implementation of the preconditioning step are discussed. An upper bound on the degree of the minimum polynomial for the preconditioned matrix and the dimension of the corresponding Krylov subspace are determined, as well as the convergence behavior of a Krylov subspace method such as GMRES. Numerical experiments are presented. Copyright © 2009 John Wiley & Sons, Ltd.
An enhanced‐physics‐based scheme for the NS‐α turbulence model
Authors: Miles William W. , Rebholz Leo G. 
Published: August 2009

AbstractWe study a new enhanced‐physics‐based numerical scheme for the NS‐alpha turbulence model that conserves both energy and helicity. Although most turbulence models (in the continuous case) conserve only energy, NS‐alpha is one of only a very few that also conserve helicity. This is one reason why it is becoming accepted as the most physically accurate turbulence model. However, no numerical scheme for NS‐alpha, until now, conserved both energy and helicity, and thus the advantage gained in physical accuracy by modeling with NS‐alpha could be lost in a computation. This report presents a finite element numerical scheme, and gives a rigorous analysis of its conservation properties, stability, solution existence, and convergence. A key feature of the analysis is the identification of the discrete energy and energy dissipation norms, and proofs that these norms are equivalent (provided a careful choice of filtering radius) in the discrete space to the usual energy and energy dissipation norms. Numerical experiments are given to demonstrate the effectiveness of the scheme over usual (helicity‐ignoring) schemes. A generalization of this scheme to a family of high‐order NS‐alpha‐deconvolution models, which combine the attractive physical properties of NS‐alpha with the high accuracy gained by combining α‐filtering with van Cittert approximate deconvolution. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010
Circulating tumour tissue fragments in patients with pulmonary metastasis of clear cell renal cell carcinoma
Authors: Kats‐Ugurlu Gursah , Roodink Ilse , de Weijert Mirjam , Tiemessen Dorien , Maass Cathy , Verrijp Kiek , van der Laak Jeroen , de Waal Rob , Mulders Peter , Oosterwijk Egbert , Leenders William 
Published: August 2009

AbstractTumour metastasis is the result of a complex sequence of events, including migration of tumour cells through stroma, proteolytic degradation of stromal and vessel wall elements, intravasation, transport through the circulation, extravasation and outgrowth at compatible sites in the body (the ‘seed and soil’ hypothesis). However, the high incidence of metastasis from various tumour types in liver and lung may be explained by a stochastic process as well, based on the anatomical relationship of the primary tumour with the circulation and mechanical entrapment of metastatic tumour cells in capillary beds. We previously reported that constitutive VEGF‐A expression in tumour xenografts facilitates this type of metastatic seeding by promoting shedding of multicellular tumour tissue fragments, surrounded by vessel wall elements, into the circulation. After transport through the vena cava, such fragments may be trapped in pulmonary arteries, allowing them to expand to symptomatic lesions. Here we tested whether this process has clinical relevance for clear cell renal cell carcinoma (ccRCC), a prototype tumour in the sense of high constitutive VEGF‐A expression. To this end we collected and analysed outflow samples from the renal vein, directly after tumour nephrectomy, in 42 patients diagnosed with ccRCC. Tumour fragments in venous outflow were observed in 33% of ccRCC patients and correlated with the synchronous presence or metachronous development of pulmonary metastases (p < 0.001, Fisher's exact test). In patients with tumours that, in retrospect, were not of the VEGF‐A‐expressing clear cell type, tumour fragments were never observed in the renal outflow. These data suggest that, in ccRCC, a VEGF‐A‐induced phenotype promotes a release of tumour cell clusters into the circulation that may contribute to pulmonary metastasis. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
New evidence for tumour embolism as a mode of metastasis
Authors: Hart Ian R 
Published: August 2009

AbstractThe demonstration that a significant proportion of patients with renal carcinomas of the clear cell type have tumour cell clumps or aggregates in venous outflow from the kidney has interest from two viewpoints. Firstly, the association of this occurrence with high VEGF‐A production by the cancer seems to suggest a novel mode of ‘budding’ invasion where nests of tumour cells enter the dilated and mechanically fragile new vessels supplying the cancerous growth. Secondly, with the association of fragment occurrence and metastatic development, the entrance of clumps into the circulation indicates that epithelial–mesenchymal transition (EMT) is not an obligatory step for the disseminatory behaviour of all cancers. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Dynamic mechanical analysis of pineapple leaf/glass hybrid fiber reinforced polyester composites
Authors: Devi L. Uma , Bhagawan S.S. , Thomas S. 
Published: August 2009

AbstractThe dynamic mechanical properties of randomly oriented intimately mixed hybrid composites based on pineapple leaf fibers (PALF) and glass fibers (GF) in unsaturated polyester (PER) matrix were investigated. The PALFs have high‐specific strength and improve the mechanical properties of the PER matrix. In this study, the volume ratio of the two fibers was varied by incorporating small amounts of GF such as PALF/GF, 90/10, 80/20, 70/30, and 50/50, keeping the total fiber loading constant at 40 wt%. The dynamic modulus of the compositeswas found to increase on GF addition. The intimately mixed (IM) hybrid composites with PALF/GF, 80/20 (0.2 Vf GF) showed highest E′ values and least damping. Interestingly, the impact strength of the composites was minimum at this volume ratio. The composites with 0.46 Vf GF or PALF/GF (50/50) showed maximum damping behavior and highest impact strength. The results were compared with hybrid composites of different layering patterns such as GPG (GF skin and PALF core) and PGP (PALF skin and GF core). IM and GPG hybrid composites are found more effective than PGP. The activation energy values for the relaxation processes in different composites were calculated. The overall results showed that hybridization with GF enhanced the performance properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Fabrication and electrical properties of CNT/PP conductive composites with low percolation threshold by solid state alloying
Authors: Gao D.L. , Zhan M.S. 
Published: August 2009

AbstractThe carbon nanotube/polypropylene conductive composites with a percolation threshold as low as 0.25 wt% were fabricated by solid state alloying. This solid state alloying method uses the super‐high speed mechanical shearing (at 10,000 rpm) to process the entangled catalytically grown carbon nanotubes (CNTs) and the polymer matrix in solid state. The electrical properties of the nanocomposites and the structure and distribution of CNTs were investigated. The results indicated that via the shear‐intensive process, CNTs were truncated and dispersed effectively, and their length could be controlled properly to fully exert the advantage of high aspect ratios (length‐to‐diameter ratios). At the same time, a linear structure conductive network which may considerably lower the percolation threshold was also formed by this method. Moreover, the CNTs could be further dispersed under the action of thermo energy provided by increasing the processing temperature. The super‐high speed solid state alloying method is a favorable approach for the production of low percolation threshold conductive composites of CNTs filled high viscosity resins. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Aspirin increases mortality in diabetic patients without cardiovascular disease: a Swedish record linkage study
Authors: Welin Lennart , Wilhelmsen Lars , Björnberg Arne , Odén Anders 
Published: August 2009

AbstractPurposeAspirin is effective in secondary prevention of cardiovascular disease. The results are less convincing when aspirin is used for primary prevention even in high‐risk patients (i.e., patients with diabetes). We therefore analyzed the effect of aspirin on mortality and serious bleeding in diabetic patients with and without cardiovascular disease.MethodsWe performed a record linkage study of the patient registry of the Västra Götaland region in south‐western Sweden, the Swedish mortality register and the Swedish register of dispensed drugs. All diabetic patients (n = 58 465) from 1 July 2005 to 30 June 2006 were followed up with respect to bleeding until 31 October 2006, and mortality until 31 December 2006.ResultsWhen 19 confounding factors (diseases and interventions) were assessed, aspirin significantly increased mortality in diabetic patients without cardiovascular disease from 17% (95% confidence interval; 95%CI, 1–36) at age 50 years to 29% (16–43) at age 85 years. In contrast aspirin tended to decrease mortality among elderly diabetic patients with cardiovascular disease. Theoretical calculations indicated that aspirin caused 107 excess deaths among diabetic patients without cardiovascular disease and prevented 164 deaths among diabetic patients with cardiovascular disease. Aspirin also increased the risk of serious bleeding by 46% (95%CI, 22–75) in diabetic patients without cardiovascular disease but decreased the risk among those with cardiovascular disease.ConclusionAspirin use in diabetes patients without cardiovascular disease remains controversial and current guidelines should be revised until results from ongoing large randomized controlled trials become available. Copyright © 2009 John Wiley & Sons, Ltd.
A systematic narrative review of the studies on structured child‐centred interventions for families with a parent with cancer
Authors: Niemelä Mika , Hakko Helinä , Räsänen Sami 
Published: August 2009

AbstractObjective: To perform a systematic narrative review of the current state of published articles on the structured interventions targeted at children with a parent suffering from cancer.Methods: The study was based on a narrative synthesis approach. Eleven structured child‐centred intervention studies were systematically searched through PubMed, PsycINFO and MEDLINE. The interventions were grouped into two main categories: ‘structured family interventions’ and ‘structured peer group interventions’. Special attention was focused on the preventive purpose of the interventions.Results: The participants (children, parents and health professionals) reported several positive impacts of interventions on children's and parents' psychosocial well‐being, although no improvement or changes were also observed. The effect of interventions on the children was evaluated by structured methods only in five studies.Conclusions: This review showed the lack of valid psychosocial preventive intervention methods focusing on children with parental cancer and highlighted the need of intervention research with controlled study designs and long follow‐up periods. However, an intervention method should be easy to train and applicable to the clinical practice of healthcare professionals. By refining the practice‐based experiences with scientific research evidence it is possible to move to the next level in providing psychosocial support and prevention for children living in families with parental cancer. Copyright © 2009 John Wiley & Sons, Ltd.
Role of Chlamydophila pneumoniae in children hospitalized for community‐acquired pneumonia in Vienna, Austria
Authors: Kurz Herbert , Göpfrich Hubert , Wabnegger Leila , Apfalter Petra 
Published: August 2009

AbstractBackgroundNo recent Austrian data are available on the epidemiology and morbidity of Chlamydophila pneumoniae (C. pneumoniae) as causative agent in youths and children hospitalized with community‐acquired pneumonia (CAP). These data would serve as a rationale for empiric antimicrobial therapy.MethodsDuring winter months 2006/7 112 immunocompetent youths and children between 2 months and 18 years hospitalized consecutively with CAP were prospectively enrolled. Microbiological detection of conventional bacteria, Mycoplasma pneumoniae as well as respiratory viruses was performed, and clinical signs as well as indices of inflammation were documented. Diagnosis of C. pneumoniae was performed by means of species‐specific real‐time PCR as well as cell culture from respiratory secretions.ResultsPCR for C. pneumoniae was performed in 60 patients. In 4 cases (6.7%) C. pneumoniae was found as causative agent. In 1 case C. pneumoniae could be confirmed by cell‐culture. All children with C. pneumonia were ≥5 years of age. All but 1 child received clarithromycin together with cefuroxime. The number of days with fever >38,5°C was between 1 and 7, the number of days in hospital was between 4 and 7, all children recovered completely.ConclusionC. pneumoniae was found in 6.7% of children and youths hospitalized with CAP in a community hospital during the winter months 2006/07. Children and youths with lower respiratory infections should further be tested for C. pneumoniae to elucidate the actual epidemiological situation and to guide empiric antimicrobiotic therapy. Pediatr Pulmonol. 2009; 44:873–876. © 2009 Wiley‐Liss, Inc.
Analysis of the plasticity of location of the Arg244 positive charge within the active site of the TEM‐1 β‐lactamase
Authors: Marciano David C. , Brown Nicholas G. , Palzkill Timothy 
Published: August 2009

AbstractA large number of β‐lactamases have emerged that are capable of conferring bacterial resistance to β‐lactam antibiotics. Comparison of the structural and functional features of this family has refined understanding of the catalytic properties of these enzymes. An arginine residue present at position 244 in TEM‐1 β‐lactamase interacts with the carboxyl group common to penicillin and cephalosporin antibiotics and thereby stabilizes both the substrate and transition state complexes. A comparison of class A β‐lactamase sequences reveals that arginine at position 244 is not conserved, although a positive charge at this structural location is conserved and is provided by an arginine at positions 220 or 276 for those enzymes lacking arginine at position 244. The plasticity of the location of positive charge in the β‐lactamase active site was experimentally investigated by relocating the arginine at position 244 in TEM‐1 β‐lactamase to positions 220, 272, and 276 by site‐directed mutagenesis. Kinetic analysis of the engineered β‐lactamases revealed that removal of arginine 244 by alanine mutation reduced catalytic efficiency against all substrates tested and restoration of an arginine at positions 272 or 276 partially suppresses the catalytic defect of the Arg244Ala substitution. These results suggest an evolutionary mechanism for the observed divergence of the position of positive charge in the active site of class A β‐lactamases.
The Drosophila G protein‐coupled receptor, Methuselah, exhibits a promiscuous response to peptides
Authors: Ja William W. , Carvalho Gil B. , Madrigal Marisol , Roberts Richard W. , Benzer Seymour 
Published: August 2009

AbstractMethuselah (Mth) is a G protein‐coupled receptor (GPCR) associated with longevity in Drosophila melanogaster. Previously, Stunted (Sun) was identified as a peptide agonist of Mth. Here, we identify two additional activators of Mth signaling: Drosophila Sex Peptide (SP) and a novel peptide (Serendipitous Peptide Activator of Mth, SPAM). Minimal functional sequences and key residues were identified from Sun and SPAM by studying truncation and alanine‐scanning mutations. These peptide agonists share little sequence homology and illustrate the promiscuity of Mth for activation. mth mutants exhibit no defects in behaviors controlled by SP, casting doubt on the biological significance of Mth activation by any of these agonists, and illustrating the difficulty in applying in vitro studies to their relevance in vivo. Future studies of Mth ligands will help further our understanding of the functional interaction of agonists and GPCRs.
Thermochromic VO2‐based multilayer films with enhanced luminous transmittance and solar modulation
Authors: Mlyuka Nuru R. , Niklasson Gunnar A. , Granqvist Claes G. 
Published: August 2009

AbstractVanadium dioxide (VO2) shows an abrupt and reversible change in optical and electrical properties when the temperature is raised beyond a critical point of ∼68 °C. Films made from this material have a potential to be used in energy efficient “smart” windows with temperature‐dependent throughput of solar radiation. Two of the drawbacks of this material have been its low luminous transmittance and limited solar modulation of transmittance during switching. In this work we report calculations and experiments on multilayers of VO2 and TiO2, produced by reactive DC magnetron sputtering, that significantly improve the luminous transmittance and solar modulation of the films during switching. We also explore the angular‐dependent transmittance of five‐layer TiO2/VO2/TiO2/VO2/TiO2 films and demonstrate that the modulation of luminous and solar transmittance can be enhanced at non‐normal angles of incidence.
Thermal conductivity reduction in fullerene‐enriched p‐type bismuth telluride composites
Authors: Gothard N. , Spowart J. E. , Tritt T. M. 
Published: August 2009

AbstractWe present a systematic study of the effects of fullerene nanoinclusions upon a p‐type bismuth–antimony–telluride matrix, where the ultimate goal is maximizing the figure of merit by reducing the thermal conductivity (TC). Nanocomposites consisting of a bismuth–telluride matrix with fullerene inclusions have been prepared both by mechanical mixing and ball milling, with the final consolidation in each case achieved by uniaxial hot pressing. A series of samples was produced with fullerene concentrations ranging from fractional levels to several molar percent, and the effects of the fullerene additions upon the resulting microstructure have been considered. Thermal and electrical transport properties have been measured from 10 to 300 K, and the data are discussed in light of the underlying physical mechanisms.
Anomalous ferromagnetic behaviour of Y2O3 and CuO nanoparticles in YBa2Cu3Oy superconductor
Authors: Yanmaz E. , Basoglu M. , Grovenor C. R. M. 
Published: August 2009

AbstractAnomalous ferromagnetic behaviour of the Y2O3 and CuO components in YBa2Cu3Oy (Y123) was observed after severe reduction of particle size. The particle size reduction was performed in two ways. First, Y2O3, BaCO3 and CuO were ground for different times to reduce the particle size to the nanoscale. It was found that the superconducting phase could not be obtained without heat treatment, but a weak ferromagnetic behaviour of the mixture was observed at liquid and room temperatures. Second, preheated Y123 powders were subjected to grinding for various times followed by a second sintering process. It was found that the superconducting transition temperature, Tc, was strongly suppressed by increasing grinding time, and ferromagnetic behaviour at both room and liquid nitrogen temperatures was also observed. In order to understand which compound is responsible for this weak ferromagnetism, the Y2O3, BaCO3 and CuO powders were separately ground and M‐H loops taken at 290 K. The results indicated that both Y2O3 and CuO powders showed weak ferromagnetism, but BaCO3 showed anti ferromagnetism. It is thought that energy transfer to the powder particles by grinding results in severe plastic deformation of the particles to produce dislocations, vacancies and atomic disorder. We discuss then the observations in the context of recent studies of the magnetic properties of nanoscale oxide materials.
Saturation of luminescence from Si nanocrystals embedded in SiO2
Authors: Timmerman D. , Izeddin I. , Gregorkiewicz T. 
Published: August 2009

AbstractWe present a photoluminescence excitation study of silicon nanocrystals in a SiO2 matrix. We show that although the excitation cross‐section is wavelength‐dependent and increases for shorter excitation wavelengths, the maximum time‐integrated photoluminescence signal for a given sample saturates at the same level independent of excitation wavelength or amount of generated electron‐hole pairs per nanocrystal after a laser pulse. We demonstrate explicitly that saturation is achieved when every nanocrystal has absorbed at least one photon. In nanocrystals where several electron‐hole pairs have been created during the excitation pulse, fast non‐radiative recombinations reduce their number, leading to the situation that only a single electron‐hole pair per nanocrystal can recombine radiatively, producing a photon and contributing to the photoluminescence. In this way a natural limit is set for photoluminescence intensity from an ensemble of Si nanocrystals excited with a laser pulse with a short duration in comparison with the radiative recombination time.
Ferrimagnetic magnetizations in a thin film described by the transverse Ising model
Authors: Kaneyoshi T. 
Published: August 2009

AbstractThe two surfaces of a thin film with a thickness L described by the transverse Ising model are coupled to the inner next layer with a negative exchange interaction, so that the spin direction at the surfaces is opposite to that of the inner layers. The influences of exchange interactions, transverse fields and thickness on the longitudinal and transverse magnetizations of the thin film are investigated by the use of the standard mean‐field theory. The longitudinal magnetization of a thin film is strongly affected by the ratios of the exchange interactions and the transverse fields between the surfaces and the bulk. In particular, some typical ferrimagnetic behaviours are found for the temperature dependence of longitudinal magnetization in the thin film, depending on these ratios and the transverse field in the bulk. The possibility of two compensation points is also found for the system with L = 10.