bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological alterations of maximal voluntary quadriceps activation by changes of knee joint angle
Authors: Becker Roland , Awiszus Friedemann
Published: August 2002

The purpose of this study was to investigate the influence of different angles of the knee joint on voluntary activation of the quadriceps muscle, estimating the ability of a subject to activate a muscle maximally by means of voluntary contraction. Isometric torque measurement was performed on 6 healthy subjects in 5° intervals between 30° and 90° of knee joint flexion. Superimposed twitches at maximal voluntary contraction (MVC) and at a level of 60% and 40% of the MVC were applied and the voluntary activation estimated. At between 30° and 75° of knee flexion, the maximal extension torque increased at an average rate of 2.67 ± 0.6 Nm/degree, followed by a decline with further flexion. However, throughout the joint‐angle range tested, voluntary activation increased on average by 0.37%/degree with a maximum at 90° of flexion. Due to the influence of joint position it is not possible to generalize results obtained at the knee joint angle of 90° of flexion, which is usually used for the quadriceps twitch‐interpolation technique. Consequently, it is useful to investigate voluntary activation deficits in knee joint disorders at a range of knee joint angles that includes, in particular, the more extended joint angles used frequently during daily activity. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 667–672, 2001
Inelastic constitutive properties and shear localization in Tennessee marble
Authors: Holcomb D. J. , Rudnicki J. W.
Published: August 2002

The inelastic response of Tennessee marble is modelled by an elastic plastic constitutive relation that includes pressure dependence of yield, strain‐softening and inelastic volume strain (dilatancy). Data from 12 axisymmetric compression tests at confining pressures from 0 to 100 MPa are used to determine the dependence of the yield function and plastic potential, which are different, on the first and second stress invariants and the accumulated inelastic shear strain. Because the data requires that the strain at peak stress depends on the mean stress, the locus of peak stresses is neither a yield surface nor a failure envelope, as is often assumed. Based on the constitutive model and Rudnicki and Rice criterion, localization is not predicted to occur in axisymmetric compression although faulting is observed in the tests. The discrepancy is likely due to the overly stiff response of a smooth yield surface model to abrupt changes in the pattern of straining. The constitutive model determined from the axisymmetric compression data describes well the variation of the in‐plane stress observed in a plane strain experiment. The out‐of‐plane stress is not modelled well, apparently because the inelastic normal strain in this direction is overpredicted. In plane strain, localization is predicted to occur close to peak stress, in good agreement with the experiment. Observation of localization on the rising portion of the stress–strain curve in plane strain does not, however, indicate prepeak localization. Because of the rapid increase of mean stress in plane strain, the stress–strain curve can be rising while the shear stress versus shear strain curve at constant mean stress is falling (negative hardening modulus). Copyright © 2001 John Wiley & Sons, Ltd.
Comparison of a 3‐D DEM simulation with MRI data
Authors: Ng Tang‐Tat , Wang Changming
Published: August 2002

This paper presents a comparison of a granular material studied experimentally and numerically. Simple shear tests were performed inside the magnetic core of magnetic resonance imaging (MRI) equipment. Spherical pharmaceutical pills were used as the granular material, with each pill's centre location determined by MRI. These centre locations in the initial assembly were then used as the initial configuration in the numerical simulation using the discrete element method. The contact properties between pharmaceutical pills used in the numerical simulation were obtained experimentally. The numerical predication was compared with experimental data at both macroscopic and microscopic levels. Good agreement was found at both levels. Copyright © 2001 John Wiley & Sons, Ltd.
Iterative coloring extension of a maximum clique
Authors: Caramia Massimiliano , Dell'Olmo Paolo
Published: August 2002

In this paper we present an improved branch and bound algorithm for the vertex coloring problem. The idea is to try to extend the coloring of a maximum clique to its adjacent vertices. If this succeeds, its successive neighbors are considered; in case of failure (i.e., in the case the initial colors are not sufficient), working on the subgraph induced by the maximum clique and its neighborhood, the lower bound is improved by seeking for an optimal coloring of this subgraph by branch and bound. The process is repeated iteratively until the whole graph is examined. The iterative scheme exploits a further lower bound obtained by integrating a simple algorithm into the maximum clique search, and a new method to compute upper bounds on subgraphs. Furthermore, a new branching rule and a method for the selection of the initial maximum clique are presented. Extensive computational results and comparisons with existing exact coloring algorithms on random graphs and benchmarks are given. © 2001 John Wiley & Sons, Inc. Naval Research Logistic 48: 518–550, 2001
Blockade of the central generator of locomotor rhythm by noncompetitive NMDA receptor antagonists in Drosophila larvae
Authors: Cattaert Daniel , Birman Serge
Published: August 2002

The noncompetitive antagonists of the vertebrate N‐methyl‐D‐aspartate (NMDA) receptor dizocilpine (MK 801) and phencyclidine (PCP), delivered in food, were found to induce a marked and reversible inhibition of locomotor activity in Drosophila melanogaster larvae. To determine the site of action of these antagonists, we used an in vitro preparation of the Drosophila third‐instar larva, preserving the central nervous system and segmental nerves with their connections to muscle fibers of the body wall. Intracellular recordings were made from ventral muscle fibers 6 and 7 in the abdominal segments. In most larvae, long‐lasting (>1 h) spontaneous rhythmic motor activities were recorded in the absence of pharmacological activation. After sectioning of the connections between the brain and abdominal ganglia, the rhythm disappeared, but it could be partially restored by perfusing the muscarinic agonist oxotremorine, indicating that the activity was generated in the ventral nerve cord. MK 801 and PCP rapidly and efficiently inhibited the locomotor rhythm in a dose‐dependent manner, the rhythm being totally blocked in 2 min with doses over 0.1 mg/mL. In contrast, more hydrophilic competitive NMDA antagonists had no effect on the motor rhythm in this preparation. MK 801 did not affect neuromuscular glutamatergic transmission at similar doses, as demonstrated by monitoring the responses elicited by electrical stimulation of the motor nerve or pressure applied glutamate. The presence of oxotremorine did not prevent the blocking effect of MK 801. These results show that MK 801 and PCP specifically inhibit centrally generated rhythmic activity in Drosophila, and suggest a possible role for NMDA‐like receptors in locomotor rhythm control in the insect CNS. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 58–73, 2001
From medical images to anatomically accurate finite element grids
Authors: Cebral Juan Raul , Löhner Rainald
Published: August 2002

The successful application of computational modelling of blood flow for the planning of surgical and interventional procedures to treat cardiovascular diseases strongly depends on the rapid construction of anatomical models. The large individual variability of the human vasculature and the strong dependence of blood flow characteristics on the vessel geometry require modelling on a patient‐specific basis. Various image processing and geometrical modelling techniques are integrated for the rapid construction of geometrical surface models of arteries starting from medical images. These discretely defined surfaces are then used to generate anatomically accurate finite element grids for hemodynamic simulations. The proposed methodology operates directly in 3D and consists of three stages. In the first stage, the images are filtered to reduce noise and segmented using a region‐growing algorithm in order to obtain a properly defined boundary of the arterial lumen walls. In the second stage, a surface triangulation representing the vessel walls is generated using a direct tessellation of the boundary voxels. This surface is then smoothed and the quality of the resulting triangulation is improved. Finally, in the third stage, the triangulation is subdivided into so‐called discrete surface patches for surface gridding, the desired element size distribution is defined and the finite element grid generated. Copyright © 2001 John Wiley & Sons, Ltd.
On a two‐level finite element method for the incompressible Navier–Stokes equations
Authors: Franca L. P. , Nesliturk A.
Published: August 2002

We consider the Galerkin finite element method for the incompressible Navier–Stokes equations in two dimensions, where the finite‐dimensional space(s) employed consist of piecewise polynomials enriched with residual‐free bubble functions. To find the bubble part of the solution, a two‐level finite element method (TLFEM) is described and its application to the Navier–Stokes equation is displayed. Numerical solutions employing the TLFEM are presented for three benchmark problems. We compare the numerical solutions using the TLFEM with the numerical solutions using a stabilized method. Copyright © 2001 John Wiley & Sons, Ltd.
Working toward consensus: Providers' strategies to shift patients from curative to palliative treatment choices
Authors: Norton Sally A. , Bowers Barbara J.
Published: August 2002

End‐of‐life decision making is a complex phenomenon and providers, patients, and families often have different views about the appropriateness of treatment choices. The results presented here are part of a larger grounded‐theory study of reconciling decisions near the end of life. In particular, we examined how providers (N = 15) worked near the end of patients' lives toward changing the treatment decisions of patients and families from those decisions that providers described as unrealistic (i.e., curative) to those that providers described as more realistic (i.e., palliative). According to providers, shifting patients' and families' choices from curative to palliative was usually accomplished by changing patients' and families' understanding of the patient's overall “big picture” to one that was consistent with the providers' understanding. Until patients and families shifted their understanding of the patient's condition—the big picture—they continued to make what providers judged as unrealistic treatment choices based on an inaccurate understanding of what was really going on. These unrealistic choices often precluded possibilities for a “good death.” According to providers, the purpose of attempting to shift the patient or proxy's goals was that realistic goals lead to realistic palliative treatment choices that providers associated with a good death. In this article we review strategies used by providers when they believed a patient's death was imminent to attempt to shift patients' and families' understandings of the big picture, thus ultimately shifting their treatment decisions. © 2001 John Wiley & Sons, Inc. Res Nurs Health 24:258–269, 2001
Manual preparation of ground sections for the microscopy of natural bone tissue: update and modification of Frost's ‘rapid manual method’
Authors: Maat George J.R. , Van Den Bos Robert P.M. , Aarents Mj (Job)
Published: August 2002

Light microscopy should be a routine complementary diagnostic tool for osteoarchaeologists, palaeopathologists and forensic anthropologists. However, this well‐established and long existing technique is not widely utilized. It is a popular belief that the preparation of the required sections of bone tissue demands a lot of time, expensive instruments, and a knowledge of plastics. To show that this is not entirely the case, a long existing technique for the manual preparation of ground sections was brushed up and tested. Its application is simple, extremely cheap, rapid and reliable and the final product is a beautiful and intact ca. 10–15 micron or less thin section. A few modifications are proposed which further improve the feasibility of the technique, and which also make it very suitable for less well‐preserved, inhumed, and even cremated osteoarchaeological/forensic remains. As in the original method, the modifications need only a few extra, but still very basic and cheap products. A detailed step by step description of the procedure is presented. The advantages are then discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Effects of filler type and processing apparatus on the properties of the recycled “ light fraction” from municipal post‐consumer plastics
Authors: Dintcheva N. Tzankova , Mantia F.P. La , Trotta F. , Luda M. P. , Camino G. , Paci M. , Di Maio L. , Acierno D.
Published: August 2002

Plastic waste or scraps are generated from two main sources: industrial wastes and post‐consumer wastes. By using the flotation method, generally two fractions are obtained from municipal post‐consumer wastes: a light fraction, floating on water, and a heavy fraction. The former is essentially made of low and high density polyethylene—LDPE, HDPE—and polypropylene—PP; the heavy fraction is formed by poly(vinyl chloride)—PVC—and poly(ethylene terephthalate)—PET.

In this work, the recycling of a light fraction from municipal post‐consumer plastics has been studied, considering also the effect of filler type—glass fibres, calcium carbonate and wood fibres—and processing apparatus—discountinous mixer, single and twin screw extruder—on the properties.

Although the similar chemical nature of the two main components, polyethylene and polypropylene of the light fraction, the mechanical properties of the recycled mixture are quite scarce, mainly because of the incompatibility and the possible presence of some heterogeneous particles.

The recycling of the light fraction can significantly change the properties of the polymer system because of the thermomechanical stress and of the residence time during processing.

The adding of the three fillers type leads to an increase of the thermomechanical and of some of the mechanical properties. The elastic modulus increases with the three fillers; in particular, glass fibres show the best results. The effect of the three fillers is quite similar for tensile strength, elongation at break and impact strength. The adding of inert filler strongly improves the rigidity of light fraction from municipal post‐consumer plastics. Copyright © 2001 John Wiley & Sons, Ltd.
A systematic study of the microwave and thermal cure kinetics of the DGEBA/DDS and DGEBA/DDM epoxy‐amine resin systems
Authors: Hill David J. T. , George Graeme A. , Rogers David G.
Published: August 2002

The microwave and thermal cure processes for the epoxy‐amine systems (epoxy resin diglycidyl ether of bisphenol A, DGEBA) with 4,4′‐diaminodiphenyl sulphone (DDS) and 4,4′‐diaminodiphenyl methane (DDM) have been investigated for 1 : 1 stoichiometries by using fiber‐optic FT‐NIR spectroscopy. The DGEBA used was in the form of Ciba‐Geigy GY260 resin. The DDM system was studied at a single cure temperature of 373 K and a single stoichiometry of 20.94 wt% and the DDS system was studied at a stoichiometry of 24.9 wt% and a range of temperatures between 393 and 443 K. The best values of the kinetic rate parameters for the consumption of amines have been determined by a least squares curve fit to a model for epoxy/amine cure. The activation energies for the polymerization of the DGEBA/DDS system were determined for both cure processes and found to be 66 and 69 kJ mol−1 for the microwave and thermal cure processes, respectively. No evidence was found for any specific effect of the microwave radiation on the rate parameters, and the systems were both found to be characterized by a negative substitution effect. Copyright © 2002 John Wiley & Sons, Ltd.
Pre‐ and perinatal findings in partial trisomy 7q resulting from balanced parental translocations t(7;21) and t(4;7)
Authors: Courtens W. , Vroman S. , Vandenhove J. , Wiedemann U. , Schinzel A.
Published: August 2002

We report on a fetus and a newborn, both with partial trisomy 7q21→qter due to different familial translocations, t(7;21)(q21.2;p12) and t(4;7)(q35;q21.2). Postmortem examination of the 19‐week‐old female fetus disclosed dysmorphic features, cleft palate, anomalies of the great vessels, intestinal malrotation and uterus bicornis. The newborn girl revealed a pattern of minor anomalies, cleft palate, cerebellar hypoplasia, and anomalies of pancreas, gall bladder and appendix. The clinical findings in three other reported fetuses with partial trisomy 7q described so far are reviewed. A duplication 7q21→qter, as found in the propositi, has only been described in 11 patients who all had a concurrent partial monosomy. Patient 1 is particularly interesting since she is, to our knowledge, the first reported case with pure trisomy 7q21/22→qter. We reviewed the phenotype of the previously described patients, compared it with the propositae, and summarized the clinical features of pure trisomy 7q21/22→qter. Copyright © 2001 John Wiley & Sons, Ltd.
Is hormone replacement therapy protective for venous ulcer of the lower limbs?
Authors: Bérard Anick , Kahn Susan R. , Abenhaim Lucien
Published: August 2002

Purpose

Estrogen has been found to increase the risk of deep vein thrombosis (DVT), which is associated with venous ulcers. A matched case–control study was therefore performed to quantify the effect of hormone replacement therapy (HRT) on the occurrence of venous ulcers of the lower limbs.

Methods

Women presenting to a participating vascular surgery department between January and December 1997 with a first open venous ulcer served as cases. Controls were sampled among women with sub‐acute conditions such as skin problems, cold, headache/migraine, sore throat and mild ear infections, and were matched on referral site and age (±5 years). Subjects were eligible for this study if they were postmenopausal, and excluded if they had non‐palpable pedal pulse or any chronic active diseases. The study consisted of an interviewer‐administered risk factor questionnaire. Conditional multivariate logistic regression analyses were performed adjusting for history of DVT and unbalanced distributions in important covariates.

Results

Forty‐four cases and 80 matched controls were recruited. The mean age of participants was 64 years. HRT users were significantly thinner 27% with body mass index (BMI = (kg/height (m2)) ≥ 27 vs. 41%, p = 0.04) and less likely to have a history of DVT (12 vs. 33%, p = 0.02) and varicose veins (VV) (52 vs. 69%, p = 0.04) than non‐users. A matched univariate logistic regression analysis was performed to quantify the effect of HRT on venous ulcers and generated an odds ratio (OR) of 0.14 with 95% confidence interval of (0.04, 0.49)95%: adjusting for prior DVT resulted in an OR of 0.29 (0.09, 0.93)95%. When adjusting for BMI, history of VV, exercise, education, and smoking, the OR observed was 0.03 (0.01, 0.13)95%: further adjustment for prior DVT gave an OR estimate of 0.06 (0.01, 0.50)95%CI.

Conclusions

Our study demonstrates that HRT has a protective effect on the occurrence of venous ulcers of the lower limbs. Adjusting for prior DVT moves the estimate closer to the null. DVT is a strong contraindication for HRT and therefore must be considered in order to eliminate confounding by contraindication. Copyright © 2001 John Wiley & Sons, Ltd.
Copolymerization of a bisanthracene compound with bismaleimides by Diels–Alder cycloaddition
Authors: Grigoras Mircea , Colotin Georgiana
Published: August 2002

Four new polymers have been synthesized via succesive Diels–Alder cycloadditions of a bisdiene compound bearing two anthracene groups and four bisdienophiles, all containing bismaleimide functions. The polycondensation reaction was performed in N,N‐dimethylacetamide at 120 °C leading to polymers soluble in polar solvents having molecular weights lower than 6000 g mol−1.

© 2001 Society of Chemical Industry
Increasing Native American Indian involvement in gifted programs in rural schools
Authors: Montgomery Diane
Published: August 2002

Native American Indian students are not identified or served at the same rate as their majority counterparts. Javits Grants are part of a small federal program providing funding for direct service research and demonstration projects. The purpose of the grants is to resolve the problems in identifying and meeting the needs of underrepresented gifted populations. Herein is a description of Project LEAP, which was designed to identify and meet the needs of rural high school students who have gifts, talents, or high potential. The project was funded for three years. The information provided in this discussion was collected through on‐site interviews with all project staff and written reports from students at the end of each project year. The project was planned with four conceptual goals: community collaboration, partnership with parents, culturally relevant identification, and appropriate curriculum. Two themes emerged from an analysis of the interview and project documentation data regarding the implementation of the four Project goals: (a) the rural linkages that existed and were forged and (b) the authenticity infused into all project activities to discover and nurture gifts, talents, or high potential. © 2001 John Wiley & Sons, Inc.
NMR studies of hydrogen bonding interactions with secondary amide and urea groups
Authors: Deetz Martin J. , Fahey Julianne E. , Smith Bradley D.
Published: August 2002

The cis/trans ratios for six model secondary amides were determined by 1H NMR in a range of solvent systems. The trans to cis equilibrium in chloroform is only slightly affected by addition of the hydrogen bond donor, trifluorethanol, but the cis rotamer is stabilized by an average of 0.7 kcal mol−1 when acetic acid is used as an intermolecular donor–acceptor template. Conversely, amide interaction with anionic hydrogen bond acceptors decreases the percentage of cis rotamer. 15N NMR spectroscopy was used to determine the effect of hydrogen bonding on the trans amide structure. The direction and the magnitude of 15N complex‐induced‐shifts indicate that both hydrogen bond donors and acceptors raise the secondary amide rotational barrier by increasing the CN bond order. The relationship of these results to protein structure is discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Synthesis and characterization of nitroglycerin‐functionalized polystyrene
Authors: Raja S. , Dhamodharan R.
Published: August 2002

The synthesis and characterization of diethyl oxomalonate‐, glycerol‐, and nitroglycerin‐functionalized polystyrene (DPS, GPS, and NGPS) from polystyrene (PS) by the chemical‐modification route were explored. DPS was synthesized by the Friedel–Crafts acylation of PS with diethyl oxomalonate in the presence of SnCl4 by a batchwise‐addition process. Proton NMR studies indicate that the acylation was essentially quantitative. IR spectroscopy was additionally used to confirm the transformation. The reduction of DPS was carried out using various reduction agents and reaction conditions. The sodium hydride reduction in tetrahydrofuran resulted in a quantitative conversion to GPS as estimated by 1H NMR spectroscopy. Treatment of GPS with a nitrating mixture of nitric and sulfuric acids results in the formation of NGPS. All the polymers were characterized using gel permeation chromatography, IR, UV, 1H spectroscopic techniques, pyrolysis‐mass spectrometry, and thermogravimetric analysis. This is the first investigation on the syntheses of DPS, GPS, and NGPS. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1203–1215, 2001
Degradation behavior of stereoregular cis–transoidal poly(phenylacetylene)s
Authors: Karim S. M. Abdul , Nomura Ryouji , Masuda Toshio
Published: August 2002

The stability of poly(phenylacetylene)s in solution was systematically studied. Cis–transoidal poly(phenylacetylene) prepared with a Rh catalyst readily underwent autoxidative degradation into oligomers, whereas a W‐based polymer with a trans‐rich geometrical structure degraded slowly under similar conditions. The degradation of W‐based poly(phenylacetylene) was independent of the solvents, whereas the degradation of the cis–transoidal material strongly depended on the solvents, and very rapid degradation was observed in toluene and CHCl3. A reduction in the degradation rate in the absence of oxygen and the appearance of carbonyl groups in an IR spectrum and aldehyde protons in a 1H NMR spectrum of the resulting oligomers indicated the direct participation of oxygen in the degradation where light was supposed to assist the degradation by producing radicals on the main chain. The cis content of cis–transoidal poly(phenylacetylene) was unchanged during the degradation, unlike for the acid‐catalyzed decomposition, in which the cis content decreased linearly as the molecular weight decreased. Ring‐substituted poly(phenylacetylene)s degraded slowly compared with poly(phenylacetylene), regardless of the kind of substituent, which suggests that steric factors affected the degradation rate. The use of radical scavengers such as 2,2,6,6‐tetramethylpiperidine‐1‐oxyl and diphenylpicrylhydrazil suppressed the decomposition. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3130–3136, 2001
Morphology, crystalline structure, and properties of poly(vinylidene fluoride)/silica hybrid composites
Authors: Kim Jae‐Wan , Cho Won‐Jei , Ha Chang‐Sik
Published: August 2002

Poly(vinylidene fluoride)/silica (PVDF/SiO2) hybrid composite films were prepared via sol–gel reactions from mixtures of PVDF and tetraethoxysilane in dimethylacetamide. Their morphology, crystalline structure, and thermal, mechanical, and electrical properties were examined. For morphology measurements, scanning electron microscopy and optical microscopy were applied. X‐ray diffraction and infrared analyses showed that the crystalline structure of PVDF was not changed much by the addition of SiO2, indicating that there was no interaction between PVDF and SiO2. With increasing SiO2 content, the melting temperature rarely changed, the degree of crystallinity and the dielectric constant decreased, and the decomposition temperature slightly increased. A PVDF/SiO2 hybrid composite film with 5 wt % SiO2 exhibited balanced mechanical properties without a severe change in the crystalline structure of PVDF, whereas for the hybrid composites with higher SiO2 contents (>10 wt %), the mechanical properties were reduced, and the spherulite texture of PVDF was significantly disrupted by the presence of SiO2 particles. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 19–30, 2002
Effects of humidity on Young's modulus in poly(methyl methacrylate)
Authors: Ishiyama C. , Higo Y.
Published: August 2002

Tensile tests on poly (methyl methacrylate) (PMMA) were conducted to clarify the effects of humidity and strain rate on tensile properties, particularly Young's modulus. Prior to the tensile tests, specimens were kept under various humidity conditions at 293 K, which were the same as the test conditions, for a few months to adjust the sorbed water content in the specimens. The tensile tests were performed under each humidity condition at three different strain rates (approximately 1.4 × 10−3, 1.4 × 10−4, and 1.4 × 10−5 s−1). Stress‐strain curves changed with humidity and strain rate. Young's moduli were also measured at small applied stresses (below 6.7 MPa) under various humidity conditions at 293 K. Young's modulus decreases linearly with increasing humidity and a decreasing logarithm of strain rate. These results suggest that Young's modulus of PMMA can be expressed as a function of two independent parameters that are humidity and strain rate. A constitutive equation for Young's modulus of PMMA was proposed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 460–465, 2002; DOI 10.1002/polb.10107
Crystallinity changes in plastically deformed isotactic polypropylene evaluated by x‐ray diffraction and differential scanning calorimetry methods
Authors: Lima Martha Fogliato S. , Vasconcellos Marcos A. Zen , Samios Dimitrios
Published: August 2002

The crystallinity of isotactic polypropylene (iPP), when deformed with plastic plane‐strain compression, was studied with wide‐angle X‐ray scattering (WAXS) and differential scanning calorimetry (DSC) techniques. A comparison of the obtained crystallinity data with annealed iPP samples was performed. The material used in this study was commercial iPP (weight‐average molecular weight = 117.400 g/mol; number‐average molecular weight = 17.300 g/mol). A significant decrease in the crystallinity was observed with increasing deformation pressure when the X‐ray method was employed, whereas only a small decrease was registered when the DSC method of crystallinity determination was used. However, the annealed iPP samples demonstrated a slight crystallinity increase when evaluated by both techniques. The reason for the difference between WAXS and DSC crystallinity results is discussed. This study of iPP specimens subjected to large deformation led us to the conclusion that the WAXS method provides accurate crystallinity values for the deformed material, whereas the values obtained by the DSC method do not reproduce the real crystallinity of the deformed material. This is due to the inherent heating process of the method, which causes a relaxation process and a significant change in the crystallinity of the deformed material, providing values nearer to its intrinsic equilibrium state. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 896–903, 2002
Targeting novel folds for structural genomics
Authors: McGuffin Liam J. , Jones David T.
Published: August 2002

The ultimate goal of structural genomics is to obtain the structure of each protein coded by each gene within a genome to determine gene function. Because of cost and time limitations, it remains impractical to solve the structure for every gene product experimentally. Up to a point, reasonably accurate three‐dimensional structures can be deduced for proteins with homologous sequences by using comparative modeling. Beyond this, fold recognition or threading methods can be used for proteins showing little homology to any known fold, although this is relatively time‐consuming and limited by the library of template folds currently available. Therefore, it is appropriate to develop methods that can increase our knowledge base, expanding our fold libraries by earmarking potentially “novel” folds for experimental structure determination. How can we sift through proteomic data rapidly and yet reliably identify novel folds as targets for structural genomics? We have analyzed a number of simple methods that discriminate between “novel” and “known” folds. We propose that simple alignments of secondary structure elements using predicted secondary structure could potentially be a more selective method than both a simple fold recognition method (GenTHREADER) and standard sequence alignment at finding novel folds when sequences show no detectable homology to proteins with known structures. Proteins 2002;48:44–52. © 2002 Wiley‐Liss, Inc.
Contribution of Thr29 to the thermodynamic stability of goat α‐lactalbumin as determined by experimental and theoretical approaches
Authors: Horii Katsunori , Saito Minoru , Yoda Takao , Tsumoto Kouhei , Matsushima Masaaki , Kuwajima Kunihiro , Kumagai Izumi
Published: August 2002

The Thr29 residue in the hydrophobic core of goat α‐lactalbumin (α‐LA) was substituted with Val (Thr29Val) and Ile (Thr29Ile) to investigate the contribution of Thr29 to the thermodynamic stability of the protein. We carried out protein stability measurements, X‐ray crystallographic analyses, and free energy calculations based on molecular dynamics simulation. The equilibrium unfolding transitions induced by guanidine hydrochloride demonstrated that the Thr29Val and Thr29Ile mutants were, respectively, 1.9 and 3.2 kcal/mol more stable than the wild‐type protein (WT). The overall structures of the mutants were almost identical to that of WT, in spite of the disruption of the hydrogen bonding between the side‐chain OH group of Thr29 and the main‐chain CO group of Glu25. To analyze the stabilization mechanism of the mutants, we performed free energy calculations. The calculated free energy differences were in good agreement with the experimental values. The stabilization of the mutants was mainly caused by solvation loss in the denatured state. Furthermore, the OH group of Thr29 favorably interacts with the CO group of Glu25 to form hydrogen bonds and, simultaneously, unfavorably interacts electrostatically with the main‐chain CO group of Thr29. The difference in the free energy profile of the unfolding path between WT and the Thr29Ile mutant is discussed in light of our experimental and theoretical results. Proteins 2001;45:16–29. © 2001 Wiley‐Liss, Inc.
Coordination topology and stability for the native and binding conformers of chymotrypsin inhibitor 2
Authors: Baysal Canan , Atilgan Ali Rana
Published: August 2002

We demonstrate that the stabilization of the binding region is accomplished at the expense of a loss in the stability of the rest of the protein. A novel molecular mechanics (MM) approach is introduced to distinguish residue stabilities of proteins in a given conformation. As an example, the relative stabilities of folded chymotrypsin inhibitor 2 (CI2) in unbound form, and CI2 in complex with subtilisin novo is investigated. The conformation of the molecule in the two states is almost identical, with an ∼0.6‐Å root‐mean‐square deviation (RMSD) of the Cα atoms. On binding, the packing density changes only at the binding loop. However, residue fluctuations in the rest of the protein are greatly altered solely due to those contacts, indicating the effective propagation of perturbation and the presence of remotely controlling residues. To quantify the interplay between packing density, packing order, residue fluctuations, and residue stability, we adopt an MM approach whereby small displacements are inserted at selected residues, followed by energy minimization; the displacement of each residue in response to such perturbations are organized in a perturbation‐response matrix L. We define residue stability λi = ∑jLij/∑j Lji as the ratio of the amount of change to which the residue is amenable, to the ability of a given residue to induce change. We then define the free energy associated with residue stability, ΔGλ = −RT ln λ. ΔGλ intrinsically selects the residues that are in the folding core. Upon complexation, the binding loop becomes more resistant to perturbation, in contrast to the α‐helix that favors change. Although the two forms of CI2 are structurally similar, residue fluctuations differ vastly, and the stability of many residues is altered upon binding. The decrease in entropy introduced by binding is thus compensated by these changes. Proteins 2001;45:62–70. © 2001 Wiley‐Liss, Inc.
Activity against plant pathogenic fungi of phomalactone isolated fromNigrospora sphaerica
Authors: Kim Jin‐Cheol , Choi Gyung Ja , Park Joong‐Hyeop , Kim Heung Tae , Cho Kwang Yun
Published: August 2002

Phomalactone, 5,6‐dihydro‐5‐hydroxy‐6‐prop‐2‐enyl‐2H‐pyran‐2‐one, produced by the fungusNigrospora sphaerica, was testedin vitroagainst nine plant pathogenic fungi, and specifically inhibited the mycelial growth ofPhytophthora infestans, with an MIC value of 2.5 mg litre−1. Its inhibitory activities against sporangium and zoospore germination ofP infestanswere similar to those againstPhytophthora capsici. In vivo, at 100 and 500 mg litre−1, it reduced the development of tomato late blight caused byP infestans.

© 2001 Society of Chemical Industry
In vivo pharmacokinetics of pyribenzoxim in rats
Authors: Liu Kwang‐Hyeon , Moon Joon‐Kwan , Sung Ha‐Jung , Kang Seung‐Hun , Koo Suk‐Jin , Lee Hye‐Suk , Kim Jeong‐Han
Published: August 2002

Pyribenzoxim, benzophenone O‐[2,6‐bis(4,6‐dimethoxypyrimidin‐2‐yloxy)benzoyl]oxime, is a new post‐emergence herbicide providing broad‐spectrum weed control in rice fields. [14C]Pyribenzoxim was used to study the pharmacokinetics of the compound after oral administration of a dose of 1000 mg kg−1 to male Sprague–Dawley rats. The material balance ranged from 97.3 to 99.7% of the administered dose and urinary and fecal recovery accounted for 97.1%, with the majority of radioactivity recovered in feces (88.6%) by 168 h after treatment. Elimination as volatile products or as carbon dioxide was negligible. The following values were obtained for the compound in the blood: AUC0–168h, 28400 µg equiv h g−1; Tmax, 12 h; Cmax, 372 µg equiv g−1; half‐life, 53 h. Radioactivity in tissue decreased from 96.1% of applied radiocarbon at 6 h to 0.4% at 168 h and the highest concentration of radioactivity among the tissues was observed in liver while the lowest residues were found in brain. The elimination half‐lives of radioactivity from tissues was in the range of 7 to 77 h and Tmax values of 12, 24 and 12 h were observed for blood, liver and kidney, respectively. Except for that in the digestive tract, the tissue‐to‐blood ratio (TBR) was highest in the liver.

© 2001 Society of Chemical Industry
Latent production of angiotensin I‐converting enzyme inhibitors from buckwheat protein
Authors: Li Chun‐Hui , Matsui Toshiro , Matsumoto Kiyoshi , Yamasaki Rikio , Kawasaki Terukazu
Published: August 2002

The latent production of angiotensin I‐converting enzyme (ACE) inhibitors from tartary buckwheat (BW) was investigated, and the peptides responsible for ACE inhibition characterized. Intact buckwheat was found to exhibit ACE inhibitory activity having an IC50 value of 3.0 mg/ml. The activity of the protein fraction (IC50: 0.36 mg protein/ml) was not enhanced by pepsin treatment. Pepsin, followed by chymotrypsin and trypsin hydrolysis, resulted in a significant increase in the ACE inhibitory activity (IC50: 0.14 mg protein/ml). The rutin contained in the buckwheat did not exhibit any ACE inhibition. A single oral administration of BW digest lowered the systolic blood pressure of a spontaneously hypertensive rat. Thus, BW proteins offer a potential resource for producing ACE inhibitory peptides during the digestion process. From the di‐/tri‐peptide fraction (DTPF) of the BW digest, inhibitory peptides were identified. The magnitude (%) of the total ACE inhibitory contribution of each identified peptide, relative to the overall inhibition of the DTPF, was about 41%. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Contraceptive effects of Phyllanthus amarus in female mice
Authors: Rao Mandava V. , Alice Kurian M.
Published: August 2002

Antifertility effects of an alcohol extract of the whole plant, Phyllanthus amarus at a dose of 100 mg/kg body weight for 30 days orally was investigated in cyclic adult female mice. The results revealed no ­significant change in absolute body and organ weights in extract‐fed animals, indicating no alteration in general metabolic status. Further, feeding had no effect on haematological and clinical biochemical tests reflecting its non‐toxicity. Similarly, uterine and ovarian biochemical tests showed no change except in 3β and 17β hydroxy steroid dehydrgenase (HSDs) levels, probably affecting hormonal conversions in the latter. Cohabited females with normal male mice were unable to become pregnant as their cyclicity was affected. These factors are related to a change in the hormonal milieu that governs female reproductive function. Upon withdrawal of feeding for 45 days, these effects were reversible. Thus this extract manifests a definite contraceptive effect in female mice. Copyright © 2001 John Wiley & Sons, Ltd.
Cytostatic activity of Achillea ageratum L.
Authors: Gómez M. A. , García M. D. , Sáenz M. T.
Published: August 2002

The cytostatic activity of a chloroform extract and two isolated compounds from Achillea ageratum L. (Asteraceae) was determined in vitro against Hep‐2 and McCoy cells. The chloroform extract exhibited a high degree of growth inhibition compared with the values obtained with the 6‐mercaptopurine (positive control) against both cultures. Stigmasterol and β‐sitosterol, isolated from the chloroform extract, showed a high degree of growth inhibition. Copyright © 2001 John Wiley & Sons, Ltd.
Neurophysiological Effects of an Extract of Eschscholzia californica Cham. (Papaveraceae)
Authors: Rolland A. , Fleurentin J. , Lanhers M. C. , Misslin R. , Mortier F.
Published: August 2002

An aqueous alcohol extract of Eschscholzia californica (Ec) has been evaluated for benzodiazepine, neuroleptic, antidepressant, antihistaminic and analgesic properties, in order to complete the study of the sedative and anxiolytic effects previously demonstrated.

The plant extract did not protect mice against the convulsant effects of pentylenetetrazol, and did not cause muscle relaxant effects but appeared to possess an affinity for the benzodiazepine receptor: thus, flumazenil, an antagonist of these receptors, suppressed the sedative and anxiolytic effects of the extract. The Ec extract induced peripheral analgesic effects in mice but did not possess antidepressant, neuroleptic or antihistaminic effects.
Ab initio modeling of competitive drug–drug interactions: 5‐fluorouracil dimers in the gas phase and in solution
Authors: Alagona Giuliano , Ghio Caterina , Monti Susanna
Published: August 2002

5‐Fluorouracil (FU) is a halogen derivative of the uracil nucleoside widely used for treatment of solid tumors and in combination drug regimens for cancer chemotherapy. In drug delivery by biodegradable poly(ester‐ether‐ester)s, drug–drug interactions are competitive with respect to the drug–copolymer ones. The potential energy and free energy of association for a variety of FU–FU dimers (either H‐bonded or stacked) were therefore studied in the gas phase to shed some light on their absolute and relative strength, because competition between these two kinds of interactions was recently proposed [McCarthy et al. Mol Phys 1997, 91, 513] and examined with a combination of methods [Hobza et al. J Phys Chem A 1998, 102, 6921] for uracil dimers. The effect of the computational level [Hartree–Fock/second order Møller–Plesset (HF/MP2) or B3LYP, including or not counterpoise corrections to the basis set superposition error] was examined as well as that of the use of polarization functions more diffuse than usual 6‐31G*(0.25) more diffuse than usual. The MP2 level is necessary to describe stacking interactions, because B3LYP is inadequate for them, giving results very similar to the HF ones. The 6‐31G*(0.25) basis set produces very favorable interaction energies, but it is prone to basis set superposition error (BSSE). The binding free energy is noticeably less favorable than the potential energy, due to the increase in vibrational entropy for the association process. There is a good linear relationship between Svib and the binding energy for the HF/6‐31G* optimized structures. Estimates of the incidence of thermal corrections at the MP2 level were carried out on the MP2/3‐21G and B3LYP/6‐31G* structures, where possible. The solvation properties in chloroform or in water of the dimers kept rigid at their in vacuo geometries were examined in the polarizable continuum model framework. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 128–142, 2001
Screening for disulfide‐rich peptides in biological sources by carboxyamidomethylation in combination with differential matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Neitz Susanne , Jürgens Michael , Kellmann Markus , Schulz‐Knappe Peter , Schrader Michael
Published: August 2002

Peptides with biological functions often contain disulfide bridges connecting two cysteine residues. In an attempt to screen biological fluids for peptides containing cysteine residues, we have developed a sensitive and specific method to label cysteines selectively and detect the resulting molecular mass shift by differential mass spectrometry. First, reduction of disulfide bridges and carboxyamidomethylation of free thiols is adjusted to quantitatively achieve cysteine alkylation for complex peptide extracts. In a second step, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) before and after chemical derivatization is performed, followed by differential analysis to determine shifted peaks; shifted peaks belong to cysteine‐containing peptides, other peaks remain unchanged. The number of cysteines can then be determined by the resulting molecular mass shift. Free, reduced cysteines are shifted by 57 u, two oxidized cysteines involved in disulfide bridges (cystine) result in a shift to higher mass per disulfide bridge of 116 u. Disulfide bridges connecting different amino acid chains like insulin break up during reduction. In this case, two peaks with lower molecular masses result from a single one in the unmodified sample. With this technique, we were able to identify cysteine‐containing peptides and short fragments of proteins present in human blood filtrate. Copyright © 2001 John Wiley & Sons, Ltd.
Random regular graphs of high degree
Authors: Krivelevich Michael , Sudakov Benny , Vu Van H. , Wormald Nicholas C.
Published: August 2002

Random d‐regular graphs have been well studied when d is fixed and the number of vertices goes to infinity. We obtain results on many of the properties of a random d‐regular graph when d=d(n) grows more quickly than
$\sqrt{n}$. These properties include connectivity, hamiltonicity, independent set size, chromatic number, choice number, and the size of the second eigenvalue, among others. ©2001 John Wiley & Sons, Inc. Random Struct. Alg., 18: 346–363, 2001.
Interface evolution and bond strength when diffusion bonding materials with stable oxide films
Authors: Shirzadi A. A. , Assadi H. , Wallach E. R.
Published: August 2002

The effects of stable surface oxides on the interface morphologies and strengths of aluminium diffusion bonds are reviewed. Previous approaches, proposed to overcome problems with surface oxides when joining aluminium alloys and composites, are described and compared for both solid‐state diffusion bonding and conventional transient liquid‐phase diffusion bonding. Non‐conventional joining methods, particularly the new method of temperature‐gradient transient liquid‐phase diffusion bonding and its capability of producing high‐strength bonds reliably, also are considered. Copyright © 2001 John Wiley & Sons, Ltd.
Interactions of CO2 and CO at fractional atmosphere pressures with iron and iron oxide surfaces: one possible mechanism for surface contamination?
Authors: Miller D. J. , Biesinger M. C. , McIntyre N. S.
Published: August 2002

The interactions of carbon dioxide and carbon monoxide at moderately high pressures with clean iron surfaces have been studied using x‐ray photoelectron spectroscopy (XPS) and static time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Clean iron surfaces were analysed after exposure to CO2 or CO gas having pressures of 10–104 Pa at 25 °C. Exposure to either gas results first in a thin surface film of FeO. In addition, this oxide is completely or partially covered with a carbonaceous layer. The thickness of the carbon layer is influenced by the type of gas used and its pressure. The ToF‐SIMS studies using isotopically labelled 13CO2 under the same reaction conditions show that the labelled carbon is not enriched on the surface and therefore no direct reaction occurs between the labelled carbon and the surface. It is proposed that the influence of either gas on the carbonaceous layer formed may be indirect: these gases may alter the equilibrium partial pressures of other adsorbates on the walls of the vacuum chamber. Copyright © 2002 John Wiley & Sons, Ltd.