bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of muscle contraction with ultrasound imaging
Authors: Hodges P.W. , Pengel L.H.M. , Herbert R.D. , Gandevia S.C.
Published: May 2003

To investigate the ability of ultrasonography to estimate muscle activity, we measured architectural parameters (pennation angles, fascicle lengths, and muscle thickness) of several human muscles (tibialis anterior, biceps brachii, brachialis, transversus abdominis, obliquus internus abdominis, and obliquus externus abdominis) during isometric contractions of from 0 to 100% maximal voluntary contraction (MVC). Concurrently, electromyographic (EMG) activity was measured with surface (tibialis anterior only) or fine‐wire electrodes. Most architectural parameters changed markedly with contractions up to 30% MVC but changed little at higher levels of contraction. Thus, ultrasound imaging can be used to detect low levels of muscle activity but cannot discriminate between moderate and strong contractions. Ultrasound measures could reliably detect changes in EMG of as little as 4% MVC (biceps muscle thickness), 5% MVC (brachialis muscle thickness), or 9% MVC (tibialis anterior pennation angle). They were generally less sensitive to changes in abdominal muscle activity, but it was possible to reliably detect contractions of 12% MVC in transversus abdominis (muscle length) and 22% MVC in obliquus internus (muscle thickness). Obliquus externus abdominis thickness did not change consistently with muscle contraction, so ultrasound measures of thickness cannot be used to detect activity of this muscle. Ultrasound imaging can thus provide a noninvasive method of detecting isometric muscle contractions of certain individual muscles. Muscle Nerve 27: 682–692, 2003
Toxoplasmic myositis as a presenting manifestation of idiopathic CD4 lymphocytopenia
Authors: Plonquet Anne , Bassez Guillaume , Authier François‐Jérôme , Dray Jean Marc , Farcet Jean Pierre , Gherardi Romain K.
Published: May 2003

Toxoplasma gondii encysts in skeletal muscle. Although only rarely found at muscle biopsy, this parasite has previously been regarded as a possible cause of polymyositis. We report a case of biopsy‐proven toxoplasmic myositis in a non–HIV‐infected patient that led to recognition of idiopathic CD4 lymphocytopenia (ICL), a rare condition typically associated with opportunistic infections. Interestingly, the CD25+ subset that corresponds to the CD4+ regulatory T cells controlling autoimmune processes was lacking. Steroid and antiprotozoal therapy led to recovery. Muscle Nerve 27: 761–765, 2003
Breakdown of adenine nucleotide pool in fatiguing skeletal muscle in McArdle's disease: A noninvasive 31P‐MRS and EMG study
Authors: Zange Jochen , Grehl Torsten , Disselhorst‐Klug Catherine , Rau Günter , Müller Klaus , Schröder Rolf , Tegenthoff Martin , Malin Jean‐Pierre , Vorgerd Matthias
Published: May 2003

Energy metabolism and electrical muscle activity were studied in the calf muscles of 19 patients with proven McArdle's disease and in 25 healthy subjects. Phosphorus magnetic resonance spectroscopy and surface electromyography (S‐EMG) were performed during two isometric muscle contractions of 3 min at 30% maximum voluntary contraction, one performed during normal perfusion and the other during applied ischemia. After about 1 min of ischemic muscle contraction in diseased muscle a significant acceleration in phosphocreatine breakdown was observed, along with a significant decrease in adenosine triphosphate. During both contractions the absence of glycolysis was shown by a significant alkalinization. Furthermore, in patients we observed a greater increase in the S‐EMG amplitude than in control subjects. We conclude that early on during moderate exercise, a small number of muscle fibers reach metabolic depletion, indicated by a reduction in the adenine nucleotide pool. An increasing number of motor units, which are still in a high‐energy state, are continuously recruited to compensate for muscle fatigue. This functional compartmentation may contribute to the pathophysiology of exercise intolerance in McArdle's disease. Muscle Nerve 27: 728–736, 2003
Maximal voluntary ventilation in myasthenia gravis
Authors: Heliopoulos Ioannis , Patlakas Georgios , Vadikolias Kostantinos , Artemis Nicolaos , Kleopa Kleopas A. , Maltezos Eustratios , Piperidou Haritomeni
Published: May 2003

Assessment of respiratory muscle weakness is important at all stages of myasthenia gravis. The maximal voluntary ventilation (MVV) is an objective dynamic method for measuring the working capacity of respiratory muscles. The clinical value of this method was studied in 24 newly diagnosed patients with myasthenia gravis, classified according to Osserman criteria (grades I, IIa, and IIb). The MVV values were normal in group I, whereas a characteristic “myasthenic pattern” of decremental respiratory volumes was demonstrated during MVV in group IIa and IIb patients, with or without dyspnea. Despite some limitations and lack of specificity, MVV may be a valuable tool in the assessment of respiratory dysfunction in patients with myasthenia gravis. Muscle Nerve, 27: 715–719, 2003
Ambulatory foot temperature measurement: A new technique in polyneuropathy evaluation
Authors: Kang Peter B. , Hoffman Stuart N. , Krimitsos Ellen , Rutkove Seward B.
Published: May 2003

Complaints of abnormal foot temperature are common among patients with polyneuropathy. However, there is no published method of ambulatory foot temperature measurement to identify possible thermoregulatory disturbances in these patients. We configured a digital electronic thermometer and thermocouple to measure and record distal foot and ambient temperatures simultaneously every minute for 24 to 48 h. Sixteen patients with polyneuropathy and 5 normal subjects were studied; 12 patients with polyneuropathy and 4 normal subjects had at least 24 h of successful recording. The data obtained from these patients were consistent and easily summarized by standard statistical methods. In the others, technical difficulties produced nonphysiological readings. In the patients with polyneuropathy, changes in foot temperature mirrored ambient temperature fluctuations more closely than in normal subjects. This technique shows promise in studying temperature regulation in the feet and may provide new insights into neuropathy‐associated pain and the pathogenesis of polyneuropathy. Muscle Nerve 27: 737–742, 2003
Morphological changes in muscle tissue of patients with infantile Pompe's disease receiving enzyme replacement therapy
Authors: Winkel Léon P. F. , Kamphoven Joep H. J. , Van Den Hout Hannerieke J. M. P. , Severijnen Lies A. , Van Doorn Pieter A. , Reuser Arnold J. J. , Van Der Ploeg Ans T.
Published: May 2003

Pompe's disease (glycogen storage disease type II) is an autosomal recessive myopathy caused by lysosomal α‐glucosidase deficiency. Enzyme replacement therapy (ERT) is currently under development for this disease. We evaluated the morphological changes in muscle tissue of four children with infantile Pompe's disease who received recombinant human α‐glucosidase from rabbit milk for 72 weeks. The patients were 2.5–8 months of age at entry. Prior to treatment, all patients showed lysosomal glycogen storage in skeletal and smooth muscle cells, vascular endothelium, Schwann cells, and perineurium. The first response to treatment was noticed in vascular endothelium and in peripheral nerves after 12 weeks of treatment at an enzyme dose of 15–20 mg/kg. Increasing the dose to 40 mg/kg led, after 72 weeks of treatment, to a reduction of glycogen storage and substantial improvement of muscle architecture in the least affected patient. Not all patients responded equally well, possibly due to differences in degree of glycogen storage and concomitant muscle pathology at the start of treatment. We conclude that intravenous administration of recombinant human α‐glucosidase from rabbit milk can improve muscle morphology in classic infantile Pompe's disease when treatment is started before irreversible damage has occurred. Muscle Nerve 27: 743–751, 2003
Quantitative ultrasonography of skeletal muscles in children: Normal values
Authors: Scholten R.R. , Pillen S. , Verrips A. , Zwarts M.J.
Published: May 2003

The purpose of this study was to establish normal values of muscle thickness, ratio of muscle thickness to subcutaneous fat thickness, and muscle echo intensity in children between 11 weeks and 16 years of age. Transverse scans of four muscles were made by standardized real‐time ultrasound examination. The scans were digitized, and mean echo intensity was measured using gray‐scale analysis. A multiple regression equation was used to study which independent parameter (age, height, weight, or sex) influenced the variables for each muscle. Muscle thickness depended on the child's weight. The other parameters did not significantly influence muscle thickness after correction for weight. The ratio of muscle thickness to subcutaneous fat thickness depended on age. Echo intensity showed no correlation with either of the variables. As a result, all normal values, including the equation to calculate them, are described. These normal data may help to determine the diagnostic value of muscle ultrasound in children with suspected neuromuscular disease. Muscle Nerve 27: 693–698, 2003
Quantitative skeletal muscle ultrasonography in children with suspected neuromuscular disease
Authors: Pillen S. , Scholten R.R. , Zwarts M.J. , Verrips A.
Published: May 2003

We determined prospectively the diagnostic value of quantitative ultrasonography in detecting neuromuscular disorders in children. Ultrasonographic scans of four muscles were made in 36 children with symptoms or signs suggestive of neuromuscular disease, such as muscle weakness and hypotonia. The muscle thickness, ratio of muscle thickness to subcutaneous fat thickness, and echo intensity were determined in each muscle. The echo intensity was measured using computer‐assisted gray‐scale analysis. Thirteen of the 36 patients had a neuromuscular disorder (6 a myopathy and 7 a neuropathy). Differentiation between neuromuscular diseases and nonneuromuscular diseases could be made on the basis of echo intensities with a sensitivity of 92%, a specificity of 90%, a positive predictive value of 86%, and a negative predictive value of 95%. We conclude that computer‐assisted quantitative analysis of muscle echo intensity is a reliable method to discriminate between neuromuscular and nonneuromuscular diseases in children. Muscle Nerve 27: 699–705, 2003
Motoneuron excitability and the F wave
Authors: Espiritu M. Geraldine , Lin Cindy S.‐Y. , Burke David
Published: May 2003

For three motoneuron pools that differ in excitability to Ia inputs [tibialis anterior (TA), abductor pollicis brevis (APB), and soleus], F‐wave parameters were measured at rest, during voluntary contraction, and following prolonged vibration. There was an inverse relationship between F‐wave chronodispersion and F‐wave persistence at rest, and this appeared to be related to the ease of recording the H reflex for the motoneuron pool. During a steady voluntary contraction, overall F‐wave activity increased in amplitude but decreased in duration for TA and APB. Following vibration of the test muscle at 50 HZ for 10 min there was a long‐lasting depression of the H reflexes of TA and APB, but no significant change in F‐wave measurements. These findings are consistent with the view that reflex discharges can prevent F waves in low‐threshold motor units, and that chronodispersion is affected by the extent of reflex activity; that is, chronodispersion and related F‐wave measurements do not measure motor properties exclusively. The findings also suggest that F waves provide a flawed measure of the excitability of the motoneuron pool. Muscle Nerve 27: 720–727, 2003
Simultaneous backward stability of Gauss and Gauss–Jordan elimination
Authors: Peña J. M.
Published: May 2003

It is well known that some pivoting strategies are backward stable for Gauss elimination but are not backward stable for Gauss–Jordan elimination (GJE) when these procedures are used to solve a linear system Ax=b. We analyse the simultaneous backward stability for Gauss and GJE of several pivoting strategies, including a pivoting strategy which we call double partial pivoting. Copyright © 2002 John Wiley & Sons, Ltd.
Algebraic formulations for the solution of the nullspace‐free eigenvalue problem using the inexact Shift‐and‐Invert Lanczos method
Authors: Simoncini V.
Published: May 2003

Given the generalized symmetric eigenvalue problem Ax=λMx, with A semidefinite and M definite, we analyse some algebraic formulations for the approximation of the smallest non‐zero eigenpairs, assuming that a sparse basis for the null space is available. In particular, we consider the inexact version of the Shift‐and‐Invert Lanczos method, and we show that apparently different algebraic formulations provide the same approximation iterates, under some natural hypotheses. Our results suggest that alternative strategies need to be explored to really take advantage of the special problem setting, other than reformulating the algebraic problem. Experiments on a real application problem corroborate our theoretical findings. Copyright © 2002 John Wiley & Sons, Ltd.
A shell problem ‘highly sensitive’ to thickness changes
Authors: Bathe Klaus‐Jürgen , Chapelle Dominique , Lee Phill‐Seung
Published: May 2003

In general, shell structural problems can be identified to fall into one of the categories of membrane‐dominated, bending‐dominated and mixed shell problems. The asymptotic behaviour with a well‐defined load‐scaling factor shows distinctly into which category a given shell problem falls. The objective of this paper is to present a shell problem and its solution for which there is no convergence to a well‐defined load‐scaling factor as the thickness of the shell decreases. Such shells are unduly sensitive in their behaviour because the ratio of membrane to bending energy stored changes significantly and indeed can fluctuate with changes in shell thickness. We briefly review the different asymptotic behaviours that shell problems can display, and then present the specific problem considered and its numerical solution using finite element analysis. Copyright © 2003 John Wiley & Sons, Ltd.
Exploiting partial or complete geometrical symmetry in 3D symmetric Galerkin indirect BEM formulations
Authors: Bonnet Marc
Published: May 2003

Procedures based on group representation theory, allowing the exploitation of geometrical symmetry in symmetric Galerkin BEM formulations, are investigated. In particular, this investigation is based on the weaker assumption of partial geometrical symmetry, where the boundary has two disconnected components, one of which is symmetric; e.g. this can be very useful for defect identification problems. The main development is expounded in the context of 3D Neumann elastostatic problems, considered as model problems; and then extended to SGBIE formulations for Dirichlet and/or scalar problems. Both Abelian and non‐Abelian finite symmetry groups are considered. The effectiveness of the present approach is demonstrated through numerical examples, where both partial and complete symmetry are considered, in connection with both Abelian and non‐Abelian symmetry groups. Copyright © 2003 John Wiley & Sons, Ltd.
Mechanically based models: Adaptive refinement for B‐spline finite element
Authors: Kagan Pavel , Fischer Anath , Bar‐Yoseph Pinhas Z.
Published: May 2003

This article presents two new methods for adaptive refinement of a B‐spline finite element solution within an integrated mechanically based computer aided engineering system. The proposed techniques for adaptively refining a B‐spline finite element solution are a local variant of np‐refinement and a local variant of h‐refinement. The key component in the np‐refinement is the linear co‐ordinate transformation introduced into the refined element. The transformation is constructed in such a way that the transformed nodal configuration of the refined element is identical to the nodal configuration of the neighbour elements. Therefore, the assembly proceeds as with classic finite elements, while the solution approximation conforms exactly along the inter‐element boundaries. For the h‐refinement, this transformation is introduced into a construction that merges the super element from the finite element world with the hierarchical B‐spline representation from the computational geometry. In the scope of developing sculptured surfaces, the proposed approach supports C0 as well as the Hermite B‐spline C1 continuous shapes. For sculptured solids, C0 continuity only is considered in this article. The feasibility of the proposed methods in the scope of the geometric design is demonstrated by several examples of creating sculptured surfaces and volumetric solids. Numerical performance of the methods is demonstrated for a test case of the two‐dimensional Poisson equation. Copyright © 2003 John Wiley & Sons, Ltd.
On a consistent hourglass stabilization technique to treat large inelastic deformations and thermo‐mechanical coupling in plane strain problems
Authors: Reese Stefanie
Published: May 2003

In linear elasticity, the concept of reduced integration combined with hourglass stabilization can be directly derived from a mixed method, if certain assumptions are made. Such a derivation is much more difficult when the relation between stress and strain is highly non‐linear. Earlier works use the linearized form of a classical multi‐field functional in order to derive the hourglass stabilization analytically. In the present contribution, it is shown how such stabilization techniques can be directly derived at the level of the weak form. Crucial to the new concept is a Taylor expansion of the constitutively dependent quantities with respect to the centre of the element. The approach is suitable for various kinds of inelastic material models and thermo‐mechanical coupling. One of the important features of the new element technology is its computational efficiency which is especially visible when the numerical effort at the element level is very high. Copyright © 2003 John Wiley & Sons, Ltd.
Algebraic elimination of slide surface constraints in implicit structural analysis
Authors: Chow Edmond , Manteuffel Thomas A. , Tong Charles , Wallin Bradley K.
Published: May 2003

Slide surface and contact boundary conditions can be implemented via Lagrange multipliers in the algebraic equations in implicit structural analysis. This indefinite set of equations is difficult to solve by iterative methods and is often too large to be solved by direct methods. When there are m constraints and there exists a set of m variables where each variable is only involved in a single constraint, we advocate a direct elimination technique which leaves a sparse, positive definite system to solve by iterative methods. We prove that the amount of ‘fill‐in’ created by this process is independent of the size of the slide surfaces. In addition, the eigenvalues of the reduced matrix do not differ significantly from the eigenvalues of the unconstrained matrix. This method can be extended to the case where constrained surfaces intersect and leads to a graph theoretic approach for determining which variables can be eliminated efficiently for constraints with more general structure. Published in 2003 by John Wiley & Sons, Ltd.
Some observations on unsymmetric radial basis function collocation methods for convection–diffusion problems
Authors: Li Jichun , Chen C. S.
Published: May 2003

In this paper, we re‐investigate the unsymmetric radial basis function (RBF) collocation method for solving convection–diffusion problems with high Péclet number as in Power and Barraco (Computers and Mathematics with Applications 2002; 43:551). By testing different RBFs and different numbers of nodes, we found that the unsymmetric method can still solve high Péclet number problems reasonably well by using more nodes and domain decomposition techniques. Compared to solving one large problem, the domain decomposition method is shown to be very efficient and can improve the accuracy especially when the Péclet number is not that high. From our tests, it seems that the RBFs r4 ln r and r8 ln r are not very stable, while r6 ln r, r5 and r7 perform very well. Copyright © 2003 John Wiley & Sons, Ltd.
Topology optimization with implicit functions and regularization
Authors: Belytschko T. , Xiao S. P. , Parimi C.
Published: May 2003

Topology optimization is formulated in terms of the nodal variables that control an implicit function description of the shape. The implicit function is constrained by upper and lower bounds, so that only a band of nodal variables needs to be considered in each step of the optimization. The weak form of the equilibrium equation is expressed as a Heaviside function of the implicit function; the Heaviside function is regularized to permit the evaluation of sensitivities. We show that the method is a dual of the Bends–Kikuchi method. The method is applied both to problems of optimizing single material and multi‐material configurations; the latter is made possible by enrichment functions based on the extended finite element method that enable discontinuous derivatives to be accurately treated within an element. The method is remarkably robust and we found no instances of checkerboarding. The method handles topological merging and separation without any apparent difficulties. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and characterization of conducting copolymers from aniline and o‐anisidine in HCl solutions
Authors: Rehan HH , Al‐Mazroa SH , Al‐Fawzan FF
Published: May 2003

Conducting poly(aniline‐co‐o‐anisidine) (PAS) films with different ratios of aniline units in the polymer chain were prepared by oxidative polymerization of different molar ratios of aniline and o‐anisidine in 1 M HCl using cyclic voltammetry. Due to the much higher reactivity of o‐anisidine, the structure and properties of PASs were found to be dominated by the o‐anisidine units. The polymerization of poly‐o‐anisidine and PASs followed zero‐order kinetics with respect to formation of the polymer (film thickness) and the autocatalytic polymerization of aniline was completely inhibited. In contrast to polyaniline, a decrease in the polymerization temperature was found to increase the amount of copolymer formed and its redox charge. The presence of aniline units in PASs led to a pronounced increase in the molecular weight and conductivity, and a decrease in the solubility in organic solvents. Repetitive charging/discharging cycles showed that PASs resist degradation more than polyaniline. Copyright © 2003 Society of Chemical Industry
Study of the effect of BDMA catalyst in the epoxy novolac curing process by isothermal DSC
Authors: Firouzmanesh MR , Azar A Aref
Published: May 2003

Epoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry
Effect of solvent exposure on the properties of hydroxy‐terminated polybutadiene‐based polyurethanes
Authors: Gupta Tarakranjan , De Debasish , Adhikari Basudam
Published: May 2003

Hydroxy‐terminated polybutadiene‐based prepolyurethanes and diamine chain extended polyurethane‐ureas were prepared and treated with various organic solvents in the moisture‐cured state in order to modify their ultimate strength. FTIR studies with solvent‐treated polyurethanes and polyurethane‐ureas confirmed that organic solvents penetrated inside the polyurethane hard segments and affected hydrogen bonding. The polar and non‐polar solvents showed different abilities to penetrate into polyurethane hard segments. Solvent treatment after moisture curing increased the tensile strength of these polyurethanes and polyurethane‐ureas with respect to control samples. The stress–strain behaviour of solvent‐treated polyurethane follows the constrained junction model. The change in hard segment crystallinity on solvent treatment has been explained by wide‐angle X‐ray diffraction study. The better orientation in polybutadiene soft segments evidenced from SEM (scanning electron microscopy) pictures is believed to be the main reason behind the improved tensile properties of solvent‐treated polyurethane samples. The effect of solvent treatment, as well as stretching, on the diffusion coefficient of hexane in polyurethanes was investigated. Copyright © 2003 Society of Chemical Industry
Analysis of the swelling dynamics of crosslinked P(N‐iPAAm‐co‐MAA) copolymers, the corresponding homopolymers and their interpenetrating networks. Kinetics of water penetration into the gel above the pKaof MAA comonomeric units
Authors: Díez‐Peña E , Quijada‐Garrido I , Frutos P , Barrales‐Rienda JM
Published: May 2003

The effect of composition on the swelling kinetics of a series of crosslinked poly(N‐isopropylacrylamide)s [P(N‐iPAAm)] and poly(methacrylic acid)s [P(MAA)], their statistical copolymers P(N‐iPAAm‐co‐MAA), and some sequential interpenetrating networks (IPNs) has been studied at pHs above the pKa of MAA comonomeric units. The swelling process of the hydrogels upon immersion in buffer solutions was monitored by the weight change as a function of time. First‐order kinetics apply better than second‐order kinetics which fail, especially for predicting swelling equilibrium values. However, hydrogels presenting hydrogen bonding between MAA and N‐iPAAm units do not obey either first‐order or second‐order kinetics. The high n values found indicate that the swelling process is mostly controlled by polymer relaxation. Copyright © 2003 Society of Chemical Industry
Kinetic model of mechanism of alternating radical copolymerization and its quantitative treatment method
Authors: Liu Guo‐Dong , Zhang Yan , Qu Xiong‐Wei , Zhang Liu‐Cheng
Published: May 2003

A general mechanism is proposed in this paper with the assumption of homopolymerization, cross‐propagation and kinetically‐controlled termination and a quantitative treatment method is developed. The model proposed is different from that of Shirota and Shan. The kinetic models concerning the participation of charge‐transfer complexed (CTC) monomer and homopolymerization or otherwise, and kinetic‐ or diffusion‐controlled termination are generalized into one equation. The quantitative treatment method proposed can give monomer reactivity ratios without concerning the specific kinetic model. Meanwhile, information on the termination process can also be acquired from the quantitative treatment method. Copyright © 2003 Society of Chemical Industry
In situ polymerization and characterization of polyester‐based polyurethane/nano‐silica composites
Authors: Chen Xichong , Wu Limin , Zhou Shuxue , You Bo
Published: May 2003

Polyester‐based polyurethane/nano‐silica composites were obtained via in situ polymerization and investigated by Fourier‐transform infrared spectroscopy (FTIR), or FTIR coupled with attenuated total reflectance (FTIR‐ATR), Transmission electron microscopy (TEM), atomic force microscopy (AFM), an Instron testing machine, dynamic mechanical analysis (DMA) and ultraviolet‐visible spectrophotometry (UV‐vis). FTIR analysis showed that in situ polymerization provoked some chemical reactions between polyester molecules and nano‐silica particles. FTIR‐ATR, TEM and AFM analyses showed that both surface and interface contained nano‐silica particles. Instron testing and DMA data showed that introducing nano‐silica particles into polyurethane enhanced the hardness, glass temperature and adhesion strength of polyurethane to the substrate, but also increased the resin viscosity. UV‐vis spectrophotometry showed that nano‐silica obtained by the fumed method did not shield UV radiation in polyurethane films. Copyright © 2003 Society of Chemical Industry
Synthesis and solution properties of alternating maleimide/styrene hyperbranched copolymers via controlled radical mechanism
Authors: Ishizu Koji , Takashimizu Chisato , Shibuya Takeshi , Uchida Satoshi
Published: May 2003

Copolymerizations of (N,N‐diethyldithiocarbamyl)methylstyrene (inimer: DTCS) with maleimide (MI) were carried out under UV irradiation. DTCS monomers play an important role in this copolymerization system as an inimer that is capable of initiating radical polymerization of the vinyl group. Reactivity ratios (r1 = 0.15 and r2 = 0) were estimated by the curve‐fitting procedure (DTCS [M1]; MI[M2]). These reactivities show strong alternation, and the propagating copolymer radicals proceed with homopolymerization of 1:1 complexes formed between the donor and acceptor monomers. These alternating copolymers exhibit highly branched structure and are actually hyperbranched copolymers. The compact nature of the hyperbranched molecules was demonstrated by comparison of their dilute‐solution properties with those of the linear analogues. The hyperbranched macromolecules behave as single, well‐separated molecules (even in good solvent) and as hard spheres. Copyright © 2003 Society of Chemical Industry
Effect of synthesis parameters on the electrical conductivity of polypyrrole‐coated poly(ethylene terephthalate) fabrics
Authors: Kaynak Akif , Beltran Rafael
Published: May 2003

The effects of pyrrole, anthraquinone‐2‐sulphonic acid (AQSA) and iron(III) chloride (FeCl3) concentrations, reaction time and temperature on the electrical conductivity of polypyrrole (PPy)—coated poly(ethylene terephthalate) (PET) fabrics were investigated. With an increase in both the AQSA and FeCl3 concentrations, resistivity decreased to a point beyond which higher concentrations led to increased surface resistivity. Erosion of the polymer coating, in dynamic synthesis from continual abrasion, manifested as an exponential increase in the resistance of the coated textile substrate. This was not encountered in static synthesis conditions. Temperature affected the degree of surface and bulk polymerisation. The effect of polymerisation temperature on conductivity was negligible. Conductive polymer coating on textiles through chemical polymerisation enabled a smooth coherent film to encase individual fibres, which did not affect the tactile properties of the host substrate. The optimum FeCl3/pyrrole and AQSA FeCl3/pyrrole molar ratios were found to be 2.22 and 0.40 respectively. Copyright © 2003 Society of Chemical Industry
Flammability and thermal stability studies of ABS/Montmorillonite nanocomposite
Authors: Wang Shaofeng , Hu Yuan , Lin Zhihua , Gui Zhou , Wang Zhengzhou , Chen Zuyao , Fan Weicheng
Published: May 2003

Acrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry
Interpolymer complexes of novel linear and crosslinked acrylic acid–Schiff base copolymers
Authors: Zhumadilova Gulmira , Yashkarova Marziya , Bimendina Larisa , Kudaibergenov Sarkyt
Published: May 2003

Novel linear and crosslinked copolymers of acrylic acid and Schiff base, containing the amine groups in the main chain and the carboxylic groups in the side chain, have been synthesized by the Michael addition reaction followed by radical copolymerization. The copolymers that exhibited poly(ampholyte–electrolyte) behaviour were used to prepare complexes by reaction with anionic (poly(acrylic acid), poly(styrene sodium sulfonate)), cationic (polyethyleneimine, poly(hexamethylene guanidine)) and non‐ionic (poly(N‐vinylpyrrolidone), poly(ethylene glycol), poly(vinyl alcohol)) polymers. The influence of external factors, such as solvent quality, temperature, pH and ionic strength, on phase (coil–globule) and volume (swelling–collapse) transitions has been studied.

© 2003 Society of Chemical Industry
Mössbauer, infrared, and X‐ray studies of Ti‐doped CoCr1.2Fe0.8O4 ferrites
Authors: Amer M. A.
Published: May 2003

The spinel samples Co1+xTixCr1.2–2xFe0.8O4 (0 ≤ x ≤ 0.6) were investigated at room temperature using Mössbauer, X‐ray, and IR spectra. The Mössbauer spectra for x ≤ 0.1 showed only broad six‐lines patterns and for 0.2 ≤ x ≤ 0.5 showed, in addition to the broad six‐lines patterns, a central paramagnetic phase C. The spectrum for x = 0.6 showed only paramagnetic phase C. The six‐lines patterns were analysed to two magnetic patterns attributed to Fe3+ ions on the tetrahedral A‐sites and to Fe2+ and Fe3+ ions on the octahedral B‐sites. The broader B‐site pattern appeared to be composite for x ≤ 0.3, thus it has been analysed to its multicomponents. The paramagnetic phase C was analysed to two quadrupole doublets due to Fe3+ ions at the A‐ and B‐sites. The obtained hyperfine interaction parameters have been studied and discussed as functions of the composition factor x. The cation distributions have been estimated and supported by X‐ray studies. Six absorption bands were observed in the IR spectra and attributed to Fe3+ ions on the A‐ and B‐sites, to Fe2+ and Co2+ ions, and to the energy of the sublattices. The IR bands revealed the existence of Fe2+ ions in the samples. The true and theoretical lattice parameters, the oxygen positional parameter, and the ionic radii, bonds, and edges of the A‐ and B‐sites have been determined from the X‐ray analysis. They were studied and discussed in dependence of x.
Weak localization and the Mooij rule in disordered metals
Authors: Park Mi‐Ae , Savran Kerim , Kim Yong‐Jihn
Published: May 2003

Weak localization leads to the same correction to both the conductivity and the McMillan's electron–phonon coupling constantλ(andλtr, transport electron–phonon coupling constant). Consequently the temperature dependence of the thermal electrical resistivity is decreasing as the conductivity is decreasing due to weak localization, which results in the decrease of the temperature coefficient of resistivity (TCR) with increasing the residual resistivity. Whenλandλtrare approaching zero, only the residual resistivity part remains and it gives rise to the negative TCR. Accordingly, the Mooij rule is a manifestation of weak localization correction to the conductivity and the electron–phonon interaction. This understanding provides a new means of probing the phonon‐mechanism in exotic superconductors and an opportunity of fabricating new novel devices.
Magnetic characteristics and band structure calculations of Y2Co7–xNixB3 compounds
Authors: Mincic A. , Pop V.
Published: May 2003

The Y2Co7–xNixB3 compounds crystallize in a hexagonal structure of the Ce2Co7B3‐type for x ≤ 4. Magnetic measurements were performed in the temperature range 4–800 K and in fields up to 8 T. The compounds with x ≤ 3 are ferromagnetically ordered. Y2Co3Ni4B3 is found to be paramagnetic in the studied temperature range. The experimental data were compared with the results obtained from band structure calculations using the TB‐LMTO method in the ASA approximation. The magnetic behavior of cobalt in these compounds is analyzed within the theory of spin fluctuations.
Evidence of non‐adiabatic small polaron hopping conduction in Bi0.1A0.9MnO3 (A = Ca, Sr, Pb)
Authors: Pal Sudipta , Banerjee Aritra , Chatterjee P. , Chaudhuri B. K.
Published: May 2003

A detailed study of the electrical transport properties of semiconducting perovskites Bi0.1A0.9MnO3 (A = Ca, Sr, Pb of increasing ionic radius ri) have been made over a wide range of temperature 80–375 K. XRD studies indicate a change of structural differences with change of ionic radius ri of A. The dc conductivity of the Sr‐ and Pb‐doped samples with larger ri is much lower than that of the Ca‐doped sample of smaller ri. Unlike the Sr‐ and Pb‐doped samples, little negative magnetoresistance is also observed in the Ca‐doped sample (below 115 K at 1.5 T field). The resistivity data below θD/2 (θD is the Debye temperature) are fitted well with the Mott's variable range hopping (VRH) model, whereas the nearest‐neighbour small polaron hopping mechanism satisfactorily fitted the high‐temperature (above θD/2 ≈ 200 K) conductivity data. The condition of the non‐adiabatic small polaron hopping mechanism is valid for all the samples. The estimated electron–phonon interaction constant γp (= 2WH/hνph) of the highly resistive Sr‐ and Pb‐doped samples are much higher (≫4) than those of the low‐resistive Ca‐doped oxide sample (≈4). Large values of γp destroy spin ordering in the Sr‐ and Pb‐doped samples, while for the lower value of γp in the Ca‐doped sample spin ordering favours high conductivity and show a negative magnetoresistance (only in the low‐temperature region). Low‐temperature (T < θD/2) frequency‐dependent ac conductivity data indicate that the conduction mechanism in the highly resistive Sr‐ and Pb‐doped samples is primarily due to hopping of Anderson‐localized charge carriers.
Studies on the electrical conduction in silver telluride thin films
Authors: Gnanadurai P. , Soundararajan N. , Sooriamoorthi C. E.
Published: May 2003

The temperature dependence of the electrical resistance of unannealed and annealed silver telluride thin films of different thickness between 30 and 110 nm, prepared by thermal evaporation at a pressure of 2 × 10–5 mbar, has been studied. The films are polycrystalline. It is found that metastable defects influence the phase transition in unannealed films. The annealed films undergo a structural phase transition at around 410 K during heating and at around 380 K during cooling. Similar hysteresis has also been observed in the phase transition of bulk material in differential scanning calorimetry studies. It is found that the resistivity of silver telluride thin films decreases with decrease in film thickness. This may be due to the generation of free carriers by the increase of Frenkel defects due to silver atoms.
On the band gap of indium nitride
Authors: Nag B. R.
Published: May 2003

The controversy about the band gap of indium nitride is discussed. It is shown by considering the electron effective mass in different direct‐gap II–VI and III–V semiconducting compounds that the controversy may be resolved by measuring the electron effective mass in indium antimonide samples showing a band gap of 0.7 eV.
Deep and edge photoluminescence emission of CuInTe2
Authors: Jagomägi Andri , Krustok Jüri , Raudoja Jaan , Grossberg Maarja , Danilson Mati
Published: May 2003

Photoluminescence studies of chalcopyrite CuInTe2 were conducted. Three edge (1.041 eV, 1.030 eV, and 1.019 eV) and two deep level (0.999 eV and 0.957 eV) emission bands were observed at 11 K. The excitation intensity dependence of PL spectra was recorded. As possible band sources one excitonic and four band‐to‐defect recombination mechanisms are proposed in this paper.
The Wiener Index of simply generated random trees
Authors: Janson Svante
Published: May 2003

Asymptotics are obtained for the mean, variance, and higher moments as well as for the distribution of the Wiener index of a random tree from a simply generated family (or, equivalently, a critical Galton–Watson tree). We also establish a joint asymptotic distribution of the Wiener index and the internal path length, as well as asymptotics for the covariance and other mixed moments. The limit laws are described using functionals of a Brownian excursion. The methods include both Aldous' theory of the continuum random tree and analysis of generating functions. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 22: 337–358, 2003
Regular pairs in sparse random graphs I
Authors: Kohayakawa Y. , Rödl V.
Published: May 2003

We consider bipartite subgraphs of sparse random graphs that are regular in the sense of Szemerédi and, among other things, show that they must satisfy a certain local pseudorandom property. This property and its consequences turn out to be useful when considering embedding problems in subgraphs of sparse random graphs. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 22: 359–434, 2003
A note on scrambling permutations
Authors: Radhakrishnan Jaikumar
Published: May 2003

A family ℱ of permutations of [n] is completely k‐scrambling [Spencer,1972] if for every sequence 〈p1, p2, …, pk〉 of k distinct elements of [n], there is a permutation π ∈ ℱ with π(p1) < π(p2) < … < π(pk). We show that the size of the smallest completely k‐scrambling family of permutations of [n] is at least

This improves the previous best lower bound, due to Füredi 1996, by a factor of approximately 2/log2e. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 22: 435–439, 2003
Notes on the variance of the number of maxima in three dimensions
Authors: Carlsund Anna
Published: May 2003

We study the number of maxima on a d‐dimensional cube. We give an exact expression for the variance in three dimensions, which is easy to express as a polynomial in log n and therefore can be compared with approximations. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 22: 440–447, 2003
Intrapartum assessment of fetal head engagement: comparison between transvaginal digital and transabdominal ultrasound determinations
Authors: Sherer D. M. , Abulafia O.
Published: May 2003

Objective

To test the null hypothesis that no correlation exists between transvaginal digital examination and the gold standard technique of intrapartum transabdominal ultrasound determination of fetal head engagement, and secondarily to compare the performance of attending physicians and senior residents in depicting fetal head engagement by transvaginal digital examination.

Methods

Two hundred and twenty‐two consecutive patients in labor > 37 weeks' gestation with normal singleton cephalic‐presenting fetuses and with either ruptured or intact membranes were included. Of these, 119 were nulliparous and 103 were multiparous. Transvaginal digital examinations were performed by either attending physicians or senior residents and were followed immediately by transverse suprapubic sonographic assessments by a single sonographer. The fetal head was considered engaged on transvaginal digital examination if the leading part of the fetal head was positioned at least at maternal ischial spine station 0, and on transverse suprapubic ultrasound if the fetal biparietal diameter was below the maternal pelvic inlet. Examiners were blinded to each other's findings and the effect of examiner experience on the rate of agreement between the two techniques was assessed. The effect of several other independent variables upon the rate of agreement between the two modalities was also assessed.

Results

Overall, transvaginal digital examinations were consistent with ultrasound determinations with a raw percent agreement rate of 85.6% (95% confidence interval (CI), 80.8–90.3); κ = 69.5% (95% CI, 59.4–73.9; P < 0.001). When stratified according to parity, the raw percent agreement rate for nulliparous patients was 81.5% (95% CI, 73.4–88.0); κ = 60.7% (95% CI, 45.9–64.1; P < 0.001), and for multiparous patients it was 90.3% (95% CI, 84.1–95.9); κ = 80.4% (95% CI, 63.0–87.5; P < 0.001). Maternal age, gravidity, maternal body mass index, gestational age, cervical dilatation, effacement, membrane status, ischial spine station of the fetal head, fetal head position at ultrasound assessment, birth weight and mode of delivery did not significantly affect rate of agreement. Parity did not affect examination consistency in multiparous patients, but in the whole group increasing parity increased the rate of agreement between modalities. Presence of combined spinal epidural anesthesia significantly increased the rate of agreement in the complete group and among multiparous but not among nulliparous patients.

Conclusion

These data demonstrate a high rate of agreement (85.6%) between ultrasound determination and transvaginal digital assessment of fetal head engagement. Examiner experience had no effect. These data support the use of intrapartum transabdominal assessment of fetal head engagement. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Reference values for an index of fetal aortic isthmus blood flow during the second half of pregnancy
Authors: Ruskamp J. , Fouron J.‐C. , Gosselin J. , Raboisson M.‐J. , Infante‐Rivard C. , Proulx F.
Published: May 2003

Objective

During fetal life, the parallel position of the two cardiac ventricles confers a special status to the aortic isthmus. Flow through the isthmus reflects the balance between the performances of the two ventricles and their respective peripheral impedances. This study proposes a fetal aortic isthmus flow velocity index and its reference values defined on the basis of gestational age (GA).

Methods

Video recordings of 111 normal fetuses from 18 to 39 weeks of gestation were retrospectively reviewed. An isthmus flow velocity index (IFI) was calculated as follows: IFI = (systolic + diastolic)/systolic velocity integrals. GA‐specific reference ranges of IFI were constructed.

Results

An IFI of 1.33 ± 0.03 was found at 18 weeks. This value decreased slightly but steadily with GA to reach 1.23 ± 0.16 at 39 weeks. This change is mainly related to a decrease in diastolic velocity integrals.

Conclusion

The proposed IFI provides information on the direction and, indirectly, on the volume of blood flow through the fetal aortic isthmus. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Use of three‐dimensional ultrasound imaging in the diagnosis of prenatal‐onset skeletal dysplasias
Authors: Krakow D. , Williams J. , Poehl M. , Rimoin D. L. , Platt L. D.
Published: May 2003

Objective

Recognition of prenatal‐onset skeletal dysplasias has improved with advances in ultrasound imaging. Skeletal abnormalities can be recognized by two‐dimensional (2D) ultrasound, but generating a precise diagnosis can be challenging. We aimed to determine whether three‐dimensional (3D) imaging conferred any advantages over 2D imaging in these cases.

Methods

We studied five women with fetuses of 16–28 gestational weeks referred for abnormal ultrasound skeletal findings. First 2D and then 3D sonography was performed and the results compared.

Results

The pregnancies resulted in the following skeletal dysplasias: thanatophoric dysplasia, achondrogenesis II/hypochondrogenesis, achondroplasia, chondrodysplasia punctata (rhizomelic form) and Apert's syndrome. For all five fetuses, the correct diagnosis was made in the prenatal period by analysis of the 2D images. In each case the 3D images confirmed the preliminary diagnosis and for many findings it improved the visualization of the abnormalities.

Conclusion

The 3D imaging had advantages over the 2D imaging when it came to evaluation of facial dysmorphism, relative proportion of the appendicular skeletal elements and the hands and feet. Most importantly, the patient and referring physician appreciated the 3D images of the abnormal findings more readily which aided in counseling and management of the pregnancy. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.