bluuebunny/crossref_metadata_2025_split huggingface dataset:
Re‐examination of the Reactivity of N‐Carboxy Amino Acid Anhydrides 1. Polymerisation of Amino Acid NCAs in Acetonitrile and in the Solid State in Hexane
Authors: Kanazawa Hitoshi , Inada Aya , Kawana Nobukazu 
Published: November 2006

AbstractRing‐opening polymerisation of N‐carboxy anhydrides of γ‐benzyl‐L‐ glutamate, L‐alanine and L‐leucine by a primary amine initiator in acetonitrile and in hexane was examined, with care taken to avoid contamination by moisture. The polymerisation of amino acid NCAs initiated by butylamine in hexane proceeded in the crystalline state (solid state) because the NCA crystals did not dissolve in hexane. Although amino acid NCAs were believed to polymerise completely in acetonitrile, polymerisation of the amino acid NCAs in acetonitrile was found to stop at around 20% conversion. As resulting polypeptides did not dissolve in acetonitrile, the polymer terminals were considered to be occluded in the polymer precipitate. On the other hand, each amino acid NCA was much more reactive in the solid state in hexane than in acetonitrile. Especially, L‐leucine NCA showed remarkable reactivity in the solid state. The reactivity in the solid state was explained with reference to the crystal structure.
Structural and Dynamical Properties of n‐Alkane Molecules in Clathrate Phase of Syndiotactic Polystyrene
Authors: Kaneko Fumitoshi , Uda Yukihiro , Kawaguchi Tatsuya , Ute Koichi , Yamamuro Osamu 
Published: November 2006

AbstractSyndiotactic polystyrene (sPS) forms a clathrate phase with a variety of compounds. Not only rigid molecules but also flexible molecules can be stored in the cavities of the clathrate phase. To clarify the adjustment mechanism of a flexible guest molecule to the sPS clathrate system, the host and guest structures were investigated by means of solid‐state 13C NMR and Raman spectroscopy, and X‐ray diffractometry for the sPS clathrates with a series of n‐alkanes from n‐hexane to n‐decane. Although the 010 spacing of the host sPS lattice expanded slightly on going from n‐hexane to n‐heptane, it decreased markedly at n‐octane and then increased gradually with the chain length of guest n‐alkane. The conformational change of guest n‐alkane molecules was involved in this anomalous change in the 010 spacing. Majority of the n‐hexane and n‐heptane molecules took extended chain structures in the clathrates, whereas all longer n‐alkanes took bent chain structures. The mean‐square displacement of hydrogen atoms in the clathrates was estimated by quasielastic neutron scattering experiments. It was confirmed that the host lattice contraction suppressed thermal motion of the clathrate system.
Melting Processing of Biodegradable Cellulose Diacetate/Starch Composites
Authors: Lee S. Y. , Cho M. S. , Nam J. D. , Lee Y. 
Published: November 2006

AbstractNatural polymers and their derivatives are attracting increasing interest as promising biodegradable materials that can meet the environmental and recycling demands from society. This study prepared biodegradable composites of cellulose diacetate and starch, and examined their physical and thermal properties. In addition, the morphology of the composites was examined by scanning electron microscopy. For melt processing, epoxidized soybean oil, as a lubricant, and triacetine, as a plasticizer, were added to the composites. The optimal conditions for the preparation of the biodegradable composites were determined. Increasing the amount of starch in the composites resulted in further enhancement of the processability of cellulose diacetate. The tensile strength and Young's modulus decreased, and the amount of elongation and Tg value increased with increasing amount of starch.
Interpenetrating Polymer Networks with Spatially Graded Morphology Controllable by UV‐Radiation Curing
Authors: Nakanishi Hideyuki , Namikawa Nobuhiro , Norisuye Tomohisa , Tran‐Cong‐Miyata Qui 
Published: November 2006

AbstractInterpenetrating Polymer Networks (IPNs) composed of polystyrene (PS) and poly(methyl methacrylate) (PMMA) were synthesized from a precursor mixture by using dissimilar photo‐cross‐link reactions. When the reation yields exceeded a certain threshold, the mixture was quenched from one‐phase region into two‐phase region, leading to phase separation. Upon irradiation with strong UV‐light, an intensity gradient was formed along the propagating direction of the exciting light, generating a gradient of quench depth via the spatial inhomogeneity of the cross‐link reactions. As a consequence, a gradient of the characteristic length scales was continuously generated from the top to the bottom of the mixture. The resulting three‐dimensional (3‐D) morphology was in‐situ observed at different depths of the mixture by using a laser‐scanning confocal microscope (LSCM). From this 3‐D observation, it was found that phase separation was accelerated at the bottom of the mixture and proceeded in an autocatalytic fashion. The mechanism for the formation of the graded morphology was discussed in conjunction with the kinetics of the autocatalytic phase separation.
Ultrafast Optical Responsive SWNT/Polymer Thin Films in Guided Wave Mode Geometry
Authors: Ryu Jang‐Hyun , Nagamura Toshihiko , Shigeta Masahiro , Nakashima Naotoshi 
Published: November 2006

AbstractSingle walled carbon nanotubes (SWNT) having good optical and electrochemical properties were solublized by aromatic polymers. The polymer‐wrapped SWNT film cast from solution showed transient bleaching with a time constant of recovery less than 1 ps in both the visible and optical telecommunication wavelength region. Polymer thin film containing SWNT was assembled into the guided wave mode geometry with a low refractive index polymer.
Curing of Styrene‐Free Unsaturated Polyester Alkyd and Development of Novel Related Clay Nanocomposites
Authors: Mironi‐Harpaz I. , Narkis M. , Siegmann A. 
Published: November 2006

AbstractThermoset unsaturated polyesters (UP) are usually obtained by crosslinking of alkyd chains dissolved in an unsaturated reactive monomeric diluent, usually styrene. Recently we found that UP‐alkyd chains (without styrene) are intrinsically cured into a crosslinked matrix in the presence of peroxide. The thermal, mechanical, dynamic mechanical and chemorheological properties and the network molecular structure of the crosslinked UP‐alkyd are a function of the peroxide content used. All properties change considerably upon the addition of small amounts of peroxide (between 1 and 2%wt.) and change to a lesser extent upon employing higher peroxide concentrations (up to 6%wt.). Due to co‐occurrence of crosslinking and scission events, the crosslinked system contains both gel and sol fractions. The sol fraction demonstrates a plasticizing effect on the crosslinked network, affecting the thermal and mechanical properties of the crosslinked polymer. The new materials developed in this work are interesting for utilization in innovative styrene‐free UP‐alkyd/organo‐clay nanocomposites. It was found that inducing high shear levels for prolonged durations promotes the intercalation and exfoliation of the silicate layers, resulting in a better dispersion of clay particles. Crosslinking of the UP‐alkyd/organo‐clay nanocomposites alters their nanostructure, particularly affected by the peroxide content used. Thus, depending on the content employed, either an exfoliated or a combined intercalated/exfoliated structure may be realized.
Ultrasonic Investigation of the Gelation Process of Poly(Acrylamide) Gels
Authors: Norisuye Tomohisa , Strybulevych Anatoliy , Scanlon Martin , Page John 
Published: November 2006

AbstractThe time evolution of ultrasonic velocity and attenuation has been investigated in‐situ during the gelation process of polyacrylamide (PAAm) hydrogels. Longitudinal ultrasonic pulses were transmitted through the gel samples and continuously recorded to obtain the magnitude and phase of the waves as a function of time and frequency, enabling the attenuation coefficient, α, and phase velocity, vp, of PAAm gels to be determined. The reaction was characterized by (1) an initial rapid increase in α and vp, and (2) a subsequent reduction after both quantities passed through a peak associated with the exothermic reaction for the PAAm gelation. The square of vp is proportional to the longitudinal modulus of the sample and inversely proportional to the density, and the values of vp for the aged gels were smaller than those before the gelation. The cross‐linker concentration dependence was further examined in order to investigate the gelation process accompanied by phase separation.
Measurement System for Very Small Photoelastic Constant of Polymer Films
Authors: Tsukiji Mitsuo , Kowa Hiroyuki , Muraki Kanae , Umeda Norihiro , Imoto Kenji , Kanasaki Masayoshi , Tahara Komei , Morii Katsunori , Tajitsu Yoshiro 
Published: November 2006

AbstractWe produced a new system for measuring the small photoelastic constant of a polymer thin film with a small birefringence. Using our mesurement system, we evaluated the photoelastic constant of a polymer film in real time by quantitative analysis. Photoelastic constants of 11.30 × 10−12 Pa−1 for a cellulose triacetate film and 78.38 × 10−12 Pa−1 for a polycarbonate film were obtained. Furthermore, we obtained a small photoelastic constant of 0.12 × 10−12 Pa−1 for a cycloolefin film for liquid crystal displays, using our new measurement system. This value is very small. We emphasize that, if a small change in retardation and stress cannot be detected simultaneously using our system, then we cannot obtain such a small photoelastic constant.
Dynamical Mechanical Analysis and Curing Analysis of Fouling Release Coatings and Components
Authors: Provder Ted , Malliprakash Shyam , Amin Sarjak Hemantkumar , Majid Atheer , Texter John 
Published: November 2006

AbstractA commercially available fouling release (adsorbed foulants removed by shear flow) coating based on poly(dimethylsiloxane) and a commercial marine epoxy primer have been analyzed by diffusing wave spectroscopy and by thermal and dynamical mechanical methods. Diffusing wave spectroscopy reveals 7–9 distinct relaxation intervals over short (minutes) to long (20 hour) time scales. Several junctures of these intervals are shown to correlate with mechanically determined film formation parameters, such as set to touch times, tack free times, and dry through times. Thickness series of coatings made by casting illustrate similarities and distinct differences between the epoxy primer and poly(dimethylsiloxane)‐based fouling release coating formulations. Several low temperature β transitions are resolved in the fouling release coatings in addition the α (Tg) transition in both formulations. A scaling analysis of the thickness series data shows that both the primer and the top coat exhibit a negative exponent for thickness; −0.77 for the epoxy; −1.2 for the top coat. Stress‐strain experiments reveal further significant difference between these two types of elastomers. The elastic modulus for the epoxy is 1000‐fold higher than for the topcoat. A small elastic modulus is thought to be key in the successful functioning of fouling release coatings. Analyses of substrate effects (wire mesh, fiberglass braid) and of coating or loading levels on dynamical mechanical properties, in comparison with thickness series of thin films are presented. The woven braid offers the advantage that it can be loaded more easily than can wire mesh substrates. The negative exponents show that thinner coatings may be more mechanically resilient than thicker coatings, as the ability to store and dissipate mechanical energy decreases as thickness increases.
Self‐Assembly and Liquid Crystalline Properties of Ionic Polymers and Their Nonionic Family
Authors: Yoshimi Takeshi , Ujiie Seiji 
Published: November 2006

AbstractLangmuir‐Blodgett (LB) monolayers with an extremely dense azobenzene moiety in a unit area, were prepared using a series of ionic liquid crystalline polymers (ILCPs) and their nonionic family (NLCPs). The isober curves and the compression‐expansion isotherms of the ILCPs and NLCPs on water showed that the polymer Langmuir monolayers have good quality. The molecular organization of these polymers on the water surface depended on the length of spacer alkyl chains and the existence of ammonium salts. Low‐molecular‐weight liquid crystals between the LCP monolayer dipped glass substrates showed a homeotropic alignment.
Search of Optimum Conditions for Sublimation Growth of Thiophene/Phenylene Co‐Oligomer Crystals
Authors: Yamao Takeshi , Kawasaki Yasuhiro , Ota Satoshi , Hotta Shu , Azumi Reiko 
Published: November 2006

AbstractOptimum crystal growth conditions of thiophene/phenylene co‐oligomers (TPCOs) have been studied by means of sublimation recrystallization method with changing both gas flow rate and gas pressure. The largest flaky crystal, more than 10 mm2, was produced at the gas flow rate ∼50 ml/min and reduced pressure ∼0.05 Mpa, while no crystals were obtained at pressure less than 0.01 MPa. Excess supply of N2 gas or reduced pressure for accelerating sublimation might obstruct the crystal growth of TPCOs.
Increased proximal urethral sensory threshold after radical pelvic surgery in women
Authors: Kessler Thomas M. , Studer Urs E. , Burkhard Fiona C. 
Published: November 2006

AbstractAimTo identify factors that potentially influence urethral sensitivity in women.Patients and MethodsThe current perception threshold was measured by double ring electrodes in the proximal and distal urethra in 120 women. Univariate analysis using Kaplan–Meier models and multivariate analysis applying Cox regressions were performed to identify factors influencing urethral sensitivity in women.ResultsIn univariate and multivariate analysis, women who had undergone radical pelvic surgery (radical cystectomy n = 12, radical rectal surgery n = 4) showed a significantly (log rank test P < 0.0001) increased proximal urethral sensory threshold compared to those without prior surgery (hazard ratio (HR) 4.17, 95% confidence interval (CI) 2.04–8.51), following vaginal hysterectomy (HR 4.95, 95% CI 2.07–11.85), abdominal hysterectomy (HR 5.96, 95% CI 2.68–13.23), or other non‐pelvic surgery (HR 4.86, 95% CI 2.24–10.52). However, distal urethral sensitivity was unaffected by any form of prior surgery. Also other variables assessed, including age, concomitant diseases, urodynamic diagnoses, functional urethral length, and maximum urethral closure pressure at rest had no influence on urethral sensitivity in univariate as well as in multivariate analysis.ConclusionsIncreased proximal but unaffected distal urethral sensory threshold after radical pelvic surgery in women suggests that the afferent nerve fibers from the proximal urethra mainly pass through the pelvic plexus which is prone to damage during radical pelvic surgery, whereas the afferent innervation of the distal urethra is provided by the pudendal nerve. Better understanding the innervation of the proximal and distal urethra may help to improve surgical procedures, especially nerve sparing techniques. Neurourol. Urodynam. 26:208–212, 2007. © 2006 Wiley‐Liss, Inc.
A multi‐term semi‐energy finite strip method for post‐buckling analysis of composite plates
Authors: Assaee H. , Ovesy H. R. 
Published: November 2006

AbstractIn this paper a finite strip approach based on the concept of a rigorous post‐buckling solution for composite plates, namely the semi‐energy approach, is presented. Moreover, in semi‐energy finite strip approach, the out‐of‐plane displacement field of the finite strip is the only displacement which is postulated by a deflected form. The postulated deflected form is substituted into von Kármán's compatibility equation which is solved exactly to obtain the corresponding forms of the mid‐plane stresses and displacements. The solution of von Kármán's compatibility equation and the postulated out‐of‐plane deflected form are then used to evaluate the potential energy of the related finite strip. Finally, by invoking the principle of minimum potential energy, the equilibrium equations of the finite strip are derived. The developed finite strip method (FSM) is applied to analyse the post‐buckling behaviour of laminated composite plates. As far as, the validity and numerical efficiency of the developed semi‐energy FSM is concerned, the results obtained from semi‐energy FSM approach are compared with those obtained from a fairly conventional and well exploited finite strip technique, namely the full‐energy finite strip method. The study of the results revealed that the developed semi‐energy FSM provides a very higher convergence and stress distribution properties in comparison with the full‐energy solution by incorporating considerably less number of degrees of freedom. This means that from the computational economy point of view, the developed semi‐energy FSM is superior to the full energy FSM. Copyright © 2006 John Wiley & Sons, Ltd.
Free vibration of generally supported rectangular Kirchhoff plates: State‐space‐based differential quadrature method
Authors: Lü C. F. , Zhang Z. C. , Chen W. Q. 
Published: November 2006

AbstractThe title problem is investigated using the differential quadrature method based on the state‐space formalism. The plates, with mixed boundary conditions, may cross over one‐way internal rigid line supports that impose zero transverse displacement constraints. Differential quadrature procedure is applied in the direction of line supports, while exact solution is sought in the transfer domain perpendicular to the line supports using the state space method. To avoid numerical instability in the transfer matrix method, joint coupling matrices are introduced, mainly according to the continuity conditions at line joints. Natural frequencies of rectangular Kirchhoff plates with general boundary conditions are calculated and compared with the results from other methods. Effects of location of internal line supports and the mixed boundary conditions on the frequency parameters are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
A meshless method for axi‐symmetric poroelastic simulations: numerical study
Authors: Ferronato Massimiliano , Mazzia Annamaria , Pini Giorgio , Gambolati Giuseppe 
Published: November 2006

AbstractA meshless model, based on the meshless local Petrov–Galerkin (MLPG) approach, is developed and implemented for the solution of axi‐symmetric poroelastic problems. The solution accuracy and the code performance are investigated on a realistic application concerning the prediction of land subsidence above a deep compacting reservoir. The analysis addresses several numerical issues, including the parametric selection of the optimal size of the local sub‐domains for the weak form and the nodal supports, the appropriate integration rule, and the linear system solver. The results show that MLPG can be more accurate than the standard finite element (FE) method on coarse discretizations, with its superiority decreasing as the nodal resolution increases. This is due to both a slower convergence rate and a progressively higher computational cost compared to FE. These drawbacks can be partially mitigated by improving the efficiency of the numerical integration and the system solver with the aid of projection techniques based on Krylov subspace methods. The outcome of the present analysis supports the development of coupled methods where a limited number of MLPG nodes are used to locally improve a FE solution. Copyright © 2006 John Wiley & Sons, Ltd.
Synthesis and Rh(I)‐catalyzed polymerization of 1,3‐diphenylyne–calix[4]arene compounds: Novel conjugated, calixarene‐based polymers
Authors: Costa Alexandra I. , Prata José V. 
Published: November 2006

AbstractThe synthesis of two 1,3‐bis(4‐ethynylbenzyloxy)calix[4]arenes, 5,11,17,23‐tetrakis(1,1‐dimethylethyl)‐25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene (1) and 25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene (2), was accomplished through Sonogashira coupling of appropriate calixarene derivatives. Methods for the polymerization of these bifunctional building blocks with Rh(I) as a catalyst, leading ultimately to conjugated polymers having calix[4]arene units incorporated into the main chain, were explored. Calixarenes 1 and 2 were efficiently polymerized with rhodium‐based initiators and afforded the conjugated polymers poly{5,11,17,23‐tetrakis(1,1‐dimethylethyl)‐25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene} (poly 1) and poly{25,27‐bis(4‐ethynylbenzyloxy)‐26,28‐dihydroxycalix[4]arene}. Depending on the conditions, high conversions and good yields were obtained. The effects of adding cocatalysts (NHEt2 and/or PPh3) were studied in connection with the number‐average molecular weight and the molecular weight distribution of the resultant polymer (poly 1) and tentatively correlated with the formation of low‐molecular‐weight materials. A catalytic system containing triphenylphosphine as the sole additive ([Rh(nbd)Cl]2; [Rh]/[PPh3] = 0.5) proved to be the best for the polymerization of p‐tert‐butylcalixarene compound 1. Linear polymers having high number‐average molecular weights (up to 1.1 × 105 g mol−1) with low polydispersities were produced under these conditions. For debutylated homologue 2, its polymerization was best carried out in the absence of any added cocatalyst. A cyclopolymerization route, comprising the intramolecular ring closing of the calix[4]arene pendant ethynyl groups followed by an intermolecular propagation step, is advanced to explain the results. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 7054–7070, 2006
A study of the In Vivo activity of the leaf extract of Alchornea cordifolia against multiply antibiotic resistant S. aureus isolate in mice
Authors: Igbeneghu O. A. , Iwalewa E. O. , Lamikanra A. 
Published: November 2006

AbstractThe effect of a 50% aqueous ethanol extract of Alchornea cordifolia (Schum and Thonn) Muell. Arg. leaf was investigated in mice which had been infected intraperitoneally with 5.0 × 109 cfu of Staphylococcus aureus. Dose‐dependent antibacterial activity was demonstrated and the rate of survival of infected mice was improved significantly by doses between 25 and 200 mg/kg of injected extract when compared with untreated infected controls. The intraperitoneal median lethal dose of the extract was found to be 800 mg/kg. Copyright © 2006 John Wiley & Sons, Ltd.
Additional antiprotozoal flavonol glycosides of the aerial parts of Helianthemum glomeratum
Authors: Calzada Fernando , Alanís Alma Delia 
Published: November 2006

AbstractBioassay‐guided fractionation of the methanol extract of aerial parts from Helianthemum glomeratum afforded five antiprotozoal flavonol glycosides: tiliroside, kaempferol‐3‐O‐(3″,6″di‐O‐E‐p‐coumaroyl)‐βd‐glucopyranoside, astragalin, quercitrin and isoquercitrin. The in vitro antiprotozoal assay showed that tiliroside was the most potent antiamoebic and antigiardial compound with IC50 values of 17.5 µg/mL for Entamoeba histolytica and 17.4 µg/mL for G. lamblia. Isoquercitrin showed selectivity against E. histolytica (IC50 14.7 µg/mL) and quercitrin toward G. lamblia (IC50 24.3 µg/mL). All isolated compounds were less active than metronidazole and emetine, two antiprotozoal drugs used as positive controls. Copyright © 2006 John Wiley & Sons, Ltd.