bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rigid PVC/(layered silicate) nanocomposites produced through a novel melt‐blending approach
Authors: Matuana Laurent M. 
Published: April 2009

AbstractOn the basis of the fusion behavior of poly(vinyl chloride) (PVC), the influence of compounding route on the properties of PVC/(layered silicate) nanocomposites was studied. Four different compounding addition sequences were examined during the melt compounding of PVC with montmorillonite (MMT) clay, including (a) a direct dry mixing of PVC and nanoclay, (b) an addition of nanoclay at compaction, (c) an addition of nanoclay at the onset of fusion, and (d) an addition of nanoclay at equilibrium torque. Both unmodified sodium montmorillonite (Na+‐MMT) and organically modified montmorillonite (Org.‐MMT) clays were used, and the effect of the addition sequence of the clay during compounding on its dispersion in the matrix was evaluated by X‐ray diffraction and transmission electron miscroscopy. The surface color change, dynamic mechanical analysis, and flexural and tensile properties of PVC/clay nanocomposites were also studied. The experimental results indicated that both the extent of property improvement and the dispersion of nanoparticles in PVC/(layered silicate) nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing. The addition of nanoclay to PVC must be accomplished at the onset of fusion, when PVC particles are reduced in size, in order to produce nanocomposites with better nanodispersion and enhanced mechanical properties. Overall, rigid PVC nanocomposites with unmodified clay (Na+‐MMT) were more thermally stable and exhibited better mechanical properties than their counterparts with organically modified clay (Org.‐MMT). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers
Policy‐based scanning with QoS support for seamless handovers in wireless networks
Authors: Yoo Sang‐Jo , Golmie Nada 
Published: April 2009

AbstractSupporting seamless handovers between different wireless networks is a challenging issue. One of the most important aspects of a seamless handover is finding a target network and point of attachment (PoA). This is achieved by performing a so‐called channel scanning. In most handovers, such as between universal mobile telecommunications system (UMTS), wireless local area network (WLAN), and worldwide interoperability for microwave access (WiMAX), channel scanning causes severe service disruptions with the current PoA and degrades the quality of service (QoS) during the handover. In this paper, a new architecture for QoS supported scanning that can be generalized to different wireless networks is proposed. It employs two techniques. The first is for determining a policy‐based order for the channel scanning sequence. With this technique, depending on the network costs and user requirements, the policy engine determines the channel scanning order for different network types and sets up a scanning sequence of PoAs for a given network type. This policy‐based scanning order provides a faster discovery of the target PoA that meets the QoS demands of the user. The second technique consists of a QoS supported dynamic scanning algorithm where the scanning frequency and duration are determined based on the user QOS requirements. Most importantly, the scanning duration is scheduled to guarantee the user QoS requirements while the scan progresses. Simulation results show that the proposed mechanism achieves relatively short service disruptions and provides the desired quality to users during the scanning period. Copyright © 2009 John Wiley & Sons, Ltd.
Hybrid TOA/AOA estimation error test and non‐line of sight identification in wireless location
Authors: Wann Chin‐Der , Lin Han‐Yi 
Published: April 2009

AbstractIn this paper, a modified time‐of‐arrival (TOA) estimation error test and a hybrid time‐of‐arrival/angle‐of‐arrival (TOA/AOA) estimation error test for identification of line of sight (LOS) base stations (BSs) are proposed. The proposed schemes aim to improve the location accuracy of wireless location systems suffering from the non‐line of sight (NLOS) propagation errors. The modified TOA‐based estimation error test is considered a straightforward approach in identifying the LOS‐BS set when the number of LOS BSs is greater than or equal to three. When both TOA and AOA metrics are available, hybrid TOA/AOA squares of normalized estimation errors are formulated by adopting the approximate maximum likelihood (AML) estimation. The proposed hybrid estimation error test scheme is capable of identifying the LOS/NLOS status of each BS, and performing location estimation in the situation where only two LOS BSs exist. Simulation results show that the proposed schemes are capable of correctly identifying the LOS BSs and improving the overall location accuracy. Copyright © 2009 John Wiley & Sons, Ltd.
Drug‐eluting stent coatings
Authors: Puskas Judit E. , Muñoz‐Robledo Lyn G. , Hoerr Robert A. , Foley John , Schmidt Steven P. , Evancho‐Chapman Michelle , Dong Jinping , Frethem Chris , Haugstad Greg 
Published: April 2009

AbstractThis paper reviews the development of coronary stents from a polymer scientist's view point, and presents the first results of an interdisciplinary team assembled for the development of new stent systems. Poly(styrene‐b‐isobutylene‐b‐styrene) block copolymer (SIBS), a nanostructured thermoplastic elastomer, is used in clinical practice as the drug‐eluting polymeric coating on the Taxus coronary stent (trademark of Boston Scientific Co.). Our group has been developing new architectures comprising of arborescent (dendritic) polyisobutylene cores (D_SIBS), which were shown to be as biocompatible as SIBS. ElectroNanospray (Nanocopoeia Inc.™) was used to coat test coupons and coronary stents with selected DSIBS polymers loaded with dexamethasone, a model drug. The surface topology varied from smooth to nanosized particulate coating. This paper will demonstrate how drug release profiles were influenced by both the molecular weight of the polyisobutylene core and spraying conditions of the polymer‐drug mixture. Copyright © 2009 John Wiley & Sons, Inc.This article is categorized under:

Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials
The Hsp90/Cdc37p chaperone system is a determinant of molybdate resistance in Saccharomyces cerevisiae
Authors: Millson Stefan H. , Nuttall James M. , Mollapour Mehdi , Piper Peter W. 
Published: April 2009

AbstractSaccharomyces cerevisiae lacks enzymes that contain the molybdopterin co‐factor and therefore any requirement for molybdenum as a trace mineral supplement. Instead, high molybdate levels are inhibitory to its growth. Low cellular levels of heat shock protein 90 (Hsp90), an essential chaperone, were found to enhance this sensitivity to molybdate. Certain Hsp90 point mutations and co‐chaperone protein defects that partially compromise the function of the Hsp90/Cdc37p chaperone system also rendered S. cerevisiae hypersensitive to high molybdate levels. Sensitivity was especially apparent with mutations close to the Hsp90 nucleotide binding site, with the loss of the non‐essential co‐chaperone Sti1p (the equivalent of mammalian Hop), and with the abolition of residue Ser14 phosphorylation on the essential co‐chaperone Cdc37p. While it remains to be proved that these effects reflect direct inhibition of the Hsp90 of the cell by the MoO42+ oxyanion in vivo; this possibility is suggested by molybdate sensitivity arising with a mutation in the Hsp90 nucleotide binding site that does not generate stress sensitivity or an impaired stress response. Molybdate sensitivity may therefore be a useful phenotype to score when studying mutations in this chaperone system. Copyright © 2009 John Wiley & Sons, Ltd.
$^{2}_{\infty}\rm [Tb(Tz\ast)_{3}]$, A Homoleptic 2‐Dimensional Framework from a Solvent Free Synthesis of Terbium Metal with 1H‐1,2,3‐Triazole
Authors: Rybak Jens‐Christoph , Müller‐Buschbaum Klaus 
Published: April 2009

AbstractSingle crystalline $^{2}_{\infty}\rm [Tb(Tz\ast)_{3}]$, (Tz*)– = 1,2,3‐triazolate anion, C2H2N3–, was obtained by the reaction of terbium metal with the amine 1H‐1,2,3‐triazole. As no additional solvent was used, the formation of a homoleptic framework without additional co‐ligands is accessible. Furthermore molecular hydrogen is produced. $^{2}_{\infty}\rm [Tb(Tz\ast)_{3}]$ is a 2‐dimensional framework with a (6,6) topology including (Tz*)– double bridges. The structure can be deduced from a basic structure type as it adopts the AlCl3 structure with the triazolate ligands establishing the package. (Tz*)– thus function as μ‐η1:η2/μ‐η2:η1 linkers between trivalent terbium ions that have a C.N. of nine. The framework exhibits an exceptional thermal stability up to 380 °C considering the three neighbouring nitrogen atoms of the triazolate ligands. At this point the framework decomposes in one single exothermic step under release of N2.
Metal(II) Cyamelurates Prepared from Aqueous Ammonia
Authors: Sattler Andreas , Budde Michael R. , Schnick Wolfgang 
Published: April 2009

AbstractWe identified three metal(II) salts of cyameluric acid, namely CaNH4(H2C6N7O3)(HC6N7O3)·6H2O, [Cu(NH3)2]3(C6N7O3)2·2H2O and (NH4)2[Zn(H2O)6](HC6N7O3)2·2H2O. All three compounds were prepared by crystallization from aqueous ammonia solutions containing the respective metal(II) ions. Apparently, the copper salt is identical with a compound claimed in the literature with formula CuNH4C6N7O3·NH3. We studied the structure of all three compounds using single‐crystal XRD (CaNH4(H2C6N7O3)(HC6N7O3)·6H2O: P\bar{1} (no. 2), a = 6.6428(13), b = 8.7159(17), c = 19.245(4) Å, α = 92.52(3), β = 92.22(3), γ = 106.95(3)°, V = 1063.3(4) Å3, Z = 2), ([Cu(NH3)2]3(C6N7O3)2·2H2O: P\bar{1} (no. 2), a = 7.1732(14), b = 9.2338(18), c = 9.994(2) Å, α = 94.15(3), β = 106.13(3), γ = 106.28(3)°, V = 602.3(3) Å3, Z = 1), ((NH4)2[Zn(H2O)6](HC6N7O3)2·2H2O: P\bar{1} (no. 2), a = 6.7568(14), b = 8.7252(17), c = 10.505(2) Å, α = 77.03(3), β = 77.08(3), γ = 82.95(3)°, V = 586.5(2) Å3, Z = 1). With the present work we provide the first structural investigation of cyamelurate salts containing divalent metal ions. We studied the occurrence of special structural features for the title compounds which have been claimed for copper salts of cyameluric acid by earlier works. We also made some fundamental discoveries about the crystal growth in these systems. The copper compound was studied further, using magnetic measurements and thermal analysis.
Hyperparathyroidism and Malnutrition with Severe Vitamin D Deficiency
Authors: Agarwal Amit , Gupta Sushil Kumar , Sukumar Ranjith 
Published: April 2009

AbstractBackgroundVitamin D deficiency and its associated problems are common in developing Asian countries and countries of the Middle East. Various factors, including poor nutritional status and other compounding factors such as dietary, cultural, ethnic, and environmental factors, play a major role in contributing to the poor calcium and vitamin D homeostasis. Vitamin D deficiency is thought to exacerbate signs and symptoms of hyperparathyroidism (HPT). In this overview, we present evidence of the impact of vitamin D and calcium deficiency on primary HPT (PHPT).MethodsWe performed an evidence‐based review of articles published in the English language between January 1960 and June 2008.ResultsLevel IV evidence suggests widespread calcium and vitamin D deficiency in developing countries (issue 1). Limited level IV evidence suggests malnutrition as a primary cause of calcium and vitamin D deficiency (issue 2). Level IV evidence suggests that calcium and vitamin deficiencies cause secondary HPT and possibly PHPT as well (issues 3 and 4). A literature search revealed only six studies that correlated vitamin D levels with clinical, biochemical, and pathologic features of PHPT (issue 5). These studies provide level IV evidence suggesting that vitamin D deficiency causes some specific clinical features of PHPT as well as exacerbating other features of the disease.ConclusionsIn the developing countries, which have severe vitamin D and calcium deficient population, PHPT patients present with advanced disease and particularly severe bone symptoms. There is presently only level IV evidence of vitamin D status affecting the clinical severity of PHPT.
Gastroesophageal Reflux Disease and Morbid Obesity: Is There a Relation?
Authors: Fisichella Piero M. , Patti Marco G. 
Published: April 2009

AbstractGastroesophageal reflux disease (GERD) is highly prevalent in morbidly obese patients, and a high body mass index (BMI) is a risk factor for the development of GERD. However, the mechanism by which the BMI affects esophageal acid exposure is not completely understood. Although many advances have been made in the understanding of the pathophysiology of GERD, many aspects of the pathophysiology of this disease in morbidly obese patients remain unclear. The following review describes the current evidence linking esophageal reflux to obesity, covering the pathophysiology of the disease and the implications for treatment of GERD in the obese patient.
Normal growth and development in mice over‐expressing the CCN family member WISP3
Authors: Nakamura Yukio , Cui Yajun , Fernando Carol , Kutz Wendy E. , Warman Matthew L. 
Published: April 2009

AbstractLoss‐of‐function mutations in the gene WISP3 cause the autosomal recessive human skeletal disease Progressive Pseudorheumatoid Dysplasia, whereas mice with knockout mutations of Wisp3 have no phenotype. The lack of a phenotype in the Wisp3 knockout mice has constrained studies of the protein’s in vivo function. Over‐expression experiments in zebrafish indicated that WISP3 may function as a BMP and Wnt signaling modulator. To determine whether these biologic activities are retained in mice, we created two strains of transgenic mice that over‐express WISP3 in a broad array of tissues. Despite strong and persistent protein over‐expression, the transgenic mice remained phenotypically indistinguishable from their non‐transgenic littermates. Surprisingly, WISP3 contained in conditioned medium recovered from transgenic mouse primary kidney cell cultures was able to bind BMP and to inhibit BMP signaling in vitro. Factors that account for the difference between the in vitro and in vivo activities of WISP3 remain unknown. At present, the mouse remains a challenging model organism in which to explore the biologic function of WISP3.Summary of article. Transgenic mice that broadly over‐express WISP3 were created to search for in vivo biologic activities, since mice that lack WISP3 were normal. Surprisingly, transgenic mice were also phenotypically indistinguishable from wild‐type animals. The mouse is a challenging model organism in which to explore the biologic function of WISP3.
New data on Ordovician–Silurian conodonts and stratigraphy from the Severnaya Zemlya Archipelago, Russian Arctic
Authors: MÄNNIK P. , BOGOLEPOVA O. K. , PÕLDVERE A. , GUBANOV A. P. 
Published: April 2009

AbstractThirty samples from 22 sections collected by the SWEDARCTIC international expedition to Severnaya Zemlya in 1999 contained Ordovician and Silurian conodont faunas. Several taxa, includingApsidognathuscf.milleri,Aulacognathuscf.kuehni,Nudibelodina sensitiva,Ozarkodina broenlundiandPterospathodus eopennatus, allow precise dating of the strata in this region for the first time. The occurrence ofAphelognathus pyramidalisandRhipidognathusaff.R. symmetricusin samples from the Strojnaya Formation fits well with the earlier dating of these strata as latest Ordovician. However,Aphelognathussp. in sample BG-99/14-a, collected from the upper Ushakov Formation, indicates that at least in the lower reaches of the Ushakov River the top of this formation is considerably younger than considered earlier: the sampled strata are Late, not Early Ordovician in age. In the Ordovician and Silurian the present-day Severnaya Zemlya region was dominated by extensive shallow-water, mainly semi-restricted basin environments with habitat specific faunas. The occurrence ofRiphidognathusaff.R. symmetricusat some levels in the Upper Ordovician suggests extreme shallowing episodes in the basin. On Severnaya Zemlya, ‘normal-marine’ faunas (includingPt. eopennatus) invaded the distal peripheral regions of the wide shallow-water platform at times of maximum sea-level rise only. The occurrence ofOz. broenlundiandN. sensitivaindicates that in the early Silurian the Severnaya Zemlya basin was quite well connected to the basins over modern North Greenland as well as to the Baltic Palaeobasin. The lower Silurian conodont assemblages in the Vodopad to Samojlovich formations are most similar to those described from the eastern Timan–northern Ural region.
Feature map management for mobile robots in dynamic environments
Authors: Lee Se-Jin , Park Byung-Jae , Lim Jong-Hwan , Cho Dong-Woo 
Published: April 2009

SUMMARYThis paper presents a new approach to the management of the environmental map for mobile robots in dynamic environments. The environmental map is built of primitive features, such as lines, points, and even circles, extracted from ambiguous data captured by the robot's sonar sensor ring. The feature map must be managed because the indoor surroundings where mobile robots operate are continuously changing due to nonstationary objects, such as wastebaskets, tables, and people. The features are processed by trimming, division, or removal, depending on the dynamic circumstances. All processing refers to the occupancy probabilities of grid squares generated for the map features. The occupancy probabilities of the squares are updated using the Bayesian updating model with the sonar sensor data. Experimental results demonstrate the validity of the proposed method.
Design, implementation, and performance evaluation of a 4-DOF parallel robot
Authors: Choi Hee-Byoung , Konno Atsushi , Uchiyama Masaru 
Published: April 2009

SUMMARYThis paper deals with the design, implementation, and performance evaluation of a new type of 4-DOF parallel mechanism providing three translations and one rotation for high-speed handling and machining. This parallel mechanism is named H4. A necessary condition and system configuration of the H4 are also described. Hardware and kinematics of the H4 is addressed and the manipulability ellipsoid which is one of the widely used methods to examine the design of parallel mechanisms is addressed. The performance evaluation is carried out to demonstrate the H4 robot. The simulation and experimental results show that three different controllers, the PD, PD + velocity feed-forward, and dynamic compensation controller, dramatically improve the trajectory tracking accuracy.
Subgraphs of Randomk-Edge-Colouredk-Regular Graphs
Authors: LIEBY PAULETTE , McKAY BRENDAN D. , McLEOD JEANETTE C. , WANLESS IAN M. 
Published: April 2009

LetG=G(n) be a randomly chosenk-edge-colouredk-regular graph with 2nvertices, wherek=k(n). Such a graph can be obtained from a random set ofkedge-disjoint perfect matchings ofK2n. Leth=h(n) be a graph withm=m(n) edges such thatm2+mk=o(n). Using a switching argument, we find an asymptotic estimate of the expected number of subgraphs ofGisomorphic toh. Isomorphisms may or may not respect the edge colouring, and other generalizations are also presented. Special attention is paid to matchings and cycles.The results in this paper are essential to a forthcoming paper of McLeod in which an asymptotic estimate for the number ofk-edge-colouredk-regular graphs fork=o(n5/6) is found.
Expressing Combinatorial Problems by Systems of Polynomial Equations and Hilbert's Nullstellensatz
Authors: LOERA J. A. , LEE J. , MARGULIES S. , ONN S. 
Published: April 2009

Systems of polynomial equations over the complex or real numbers can be used to model combinatorial problems. In this way, a combinatorial problem is feasible (e.g., a graph is 3-colourable, Hamiltonian, etc.) if and only if a related system of polynomial equations has a solution.For an infeasible polynomial system, the (complex) Hilbert Nullstellensatz gives a certificate that the associated combinatorial problem is infeasible. Thus, unless P = NP, there must exist an infinite sequence of infeasible instances of each hard combinatorial problem for which the minimum degree of a Hilbert Nullstellensatz certificate of the associated polynomial system grows.In the first part of the paper, we show that the minimum degree of a Nullstellensatz certificate for the non-existence of a stable set of size greater than the stability number of the graph is the stability number of the graph. Moreover, such a certificate contains at least one term per stable set of G. In contrast, for non-3-colourability, we proved that the minimum degree of a Nullstellensatz certificate is at least four. Our efforts so far have only yielded graphs with Nullstellensatz certificates of precisely that degree.In the second part of this paper, for the purpose of computation, we construct new polynomial encodings for the problems of finding in a graph its longest cycle, the largest planar subgraph, the edge-chromatic number, or the largest k-colourable subgraph. We include some applications to graph theory.
In vitro fertilization efficiency in coral Acropora digitifera
Authors: Iguchi Akira , Morita Masaya , Nakajima Yuichi , Nishikawa Akira , Miller David 
Published: April 2009

SummaryWe performed fertilization experiments with Acropora digitifera, which is one of the dominant scleractinian corals in the Ryukyu Archipelago, Japan, to determine optimal conditions for in vitro manipulations. Our result suggests that conspecific fertilization is essentially complete within 30 min under the experimental conditions used in usual fertilization experiments in corals. Previous in vitro experiments (1 × 105–106 sperm/ml, 4–8 h) are likely to have overestimated the efficiency of fertilization of Acropora spp. in the field. Therefore, we suggest that incubation periods shorter than those used to date (i.e. complete exclusion of sperm 1 h after their addition) would be more appropriate for the estimation of fertilization rates in corals.
Subcellular localization of calcium and Ca-ATPase activity during nuclear maturation inBufo arenarumoocytes
Authors: Ramos Inés , Cisint Susana B. , Crespo Claudia A. , Medina Marcela F. , Fernández Silvia N. 
Published: April 2009

SummaryThe localization of calcium and Ca-ATPase activity inBufo arenarumoocytes was investigated by ultracytochemical techniques during progesterone-induced nuclear maturation, underin vitroconditions. No Ca2+deposits were detected in either control oocytes or progesterone-treated ones for 1–2 h. At the time when nuclear migration started, electron dense deposits of Ca2+were visible in vesicles, endoplasmic reticulum cisternae and in the space between the annulate lamellae membranes. Furthermore, Ca-ATPase activity was also detected in these membrane structures. As maturation progressed, the cation deposits were observed in the cytomembrane structures, which underwent an important reorganization and redistribution. Thus, they moved from the subcortex and became located predominantly in the oocyte cortex area when nuclear maturation ended. Ca2+stores were observed in vesicles surrounding or between the cortical granules, which are aligned close to the plasma membrane. The positive Ca-ATPase reaction in these membrane structures could indicate that the calcium deposit is an ATP-dependent process. Our results suggest that during oocyte maturation calcium would be stored in membrane structures where it remains available for release at the time of fertilization. Data obtained under our experimental conditions indicate that calcium from the extracellular medium would be important for the oocyte maturation process.