bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of organoclay on the mechanical properties and morphology of injection‐molded polyamide 6/polypropylene nanocomposites
Authors: Chow W. S. , Ishak Z. A. Mohd. , Ishiaku U. S. , Karger‐Kocsis J. , Apostolov A. A. 
Published: November 2003

AbstractNanocomposites containing a thermoplastic blend and organophilic layered clay (organoclay) were produced by melt compounding. The blend composition was kept constant [polyamide 6 (PA6) 70 wt % + polypropylene (PP) 30 wt %], whereas the organoclay content was varied between 0 and 10 wt %. The mechanical properties of the nanocomposites were determined on injection‐molded specimens in both tensile and flexural loading. Highest strength values were observed at an organoclay content of 4 wt % for the blends. The flexural strength was superior to the tensile one, which was traced to the effect of the molding‐induced skin‐core structure. Increasing organoclay amount resulted in severe material embrittlement reflected in a drop of both strength and strain values. The morphology of the nanocomposites was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersion X‐ray analysis (EDX), and X‐ray diffraction (XRD). It was established that the organoclay is well dispersed (exfoliated) and preferentially embedded in the PA6 phase. Further, the exfoliation degree of the organoclay decreased with increasing organoclay content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 175–189, 2004
Novel degradable superabsorbent materials of silicate/acrylic‐based polymer hybrids
Authors: Ye Hua , Zhao Jian‐Qing , Zhang Yong‐Hua 
Published: November 2003

AbstractNovel superabsorbent materials, inorganic–organic hybrids, were synthesized by polymerizing acrylic acid or acrylamide with sodium silicate without any other crosslinking agent. The crosslinking bonds of SiOC form through the reaction of carboxyl groups with silanol groups (SiOH) existing in reaction system. Results of FTIR, swelling, and degrading experiments show that the crosslinking degree increased as the mol ratio of silicate increased in a certain range. The hybrids possess the properties of high absorbency and high absorption rate in both distilled water and normal saline solution. Because of the hydrolysis of SiOC bonds in aqueous solution, the hybrid hydrogels can degrade in days, and maybe beneficial to environment protection. This property is quite different from those superabsorbent polymer crosslinked with organic crosslinking agent. By monitoring the temperature of the reaction system, sodium silicate was also found to facilitate the trommsdorff effect in polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 936–940, 2004
Mechanical properties of glass fabric/polyester composites: Effect of silicone coatings on the fabrics
Authors: Pavlidou S. , Mai S. , Zorbas T. , Papaspyrides C. D. 
Published: November 2003

AbstractAn experimental investigation was carried out to study the effect of a silicone coating on the mechanical properties of polyester/woven glass fabric composites, fabricated by resin transfer molding. E‐glass woven fabrics were coated with a silicone elastomer by solution dip coating. The effect of variation of silicone amounts on the impact resistance, toughness, and mechanical properties of the composite was determined. Short beam shear tests were performed to assess the effect of coating on the adhesion of the fiber to the matrix. The coated specimens exhibited worse interlaminar shear strength over that of uncoated fabrics. Three‐point bending tests were also performed to investigate the effect of the coating on flexural properties. Whereas flexural strength and Young's modulus decreased with increasing amount of coating, the toughness, represented by the area under the stress–strain curve, presented a maximum. Finally, notched Izod impact tests were carried out and the curve for the energy absorbed during impact versus the amount of coating also appeared to have a maximum, indicating an interesting slot for optimum impact performance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1300–1308, 2004
Synthesis and characterization of water‐dispersed flame‐retardant polyurethane resin using phosphorus‐containing chain extender
Authors: Çelebi Funda , Polat Osman , Aras Leyla , Gündüz Güngör , Akhmedov Idris M. 
Published: November 2003

AbstractIn this research, a flame‐retardant water‐dispersed polyurethane resin was synthesized through incorporating phosphonate groups into the polyurethane structure in the chain‐extension step. A phosphorus‐containing reactive flame‐retardant compound was synthesized for this purpose. First, bis(4‐nitrophenyl)phenyl phosphine oxide was synthesized and then converted to bis(4‐amino phenyl)phenyl phosphine oxide (BAPPO) by reducing its nitro groups into amines. The obtained products were characterized by IR, 1H‐NMR, and 31P‐NMR, and the thermal properties of the polymers were determined by DSC analysis. The BAPPO‐containing polyurethane showed physical properties that were almost similar to those of phosphorus‐free polyurethane and exhibited good flame resistance with a limiting oxygen index value of 27. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1314–1321, 2004
Polymer gel electrolytes prepared from P(EG‐co‐PG) and their nanocomposites using organically modified montmorillonite
Authors: Jung H. R. , Cho M. S. , Ahn J. H. , Nam J. D. , Lee Y. 
Published: November 2003

AbstractPolymer gel electrolytes were prepared by thermal crosslinking reaction of a series of acrylic end‐capped poly(ethylene glycol) and poly(propylene glycol) [P(EG‐co‐PG)] having various geometries and molecular weights. Acrylic end‐capped prepolymers were prepared by the esterification of low molecular weight (Mn: 1900–5000) P(EG‐co‐PG) with acrylic acid. The linear increase in the ionic conductivity of polymer gel electrolyte films was observed with increasing temperature. The increase in the conductivity was also monitored by increasing the molecular weight of precursor polymer. Nanocomposite electrolytes were prepared by the addition of 5 wt % of organically modified layered silicate (montmorillonite) into the gel polymer electrolytes. The enhancement of the ionic conductivity as well as mechanical properties was observed in the nanocomposite systems. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 894–899, 2004
Nonisothermal crystallization of PP/nano‐SiO2 composites
Authors: Qian Jiasheng , He Pingsheng , Nie Kangming 
Published: November 2003

AbstractThe kinetics of nonisothermal crystallization of polypropylene (PP) containing nanoparticles of silicon dioxide (SiO2) were investigated by differential scanning calorimetry (DSC) at various cooling rates. Several different analysis methods were used to describe the process of nonisothermal crystallization. The results showed that the Ozawa equation and Mo's treatment could describe the nonisothermal crystallization of the composites very well. The nano‐SiO2 particles have a remarkable heterogeneous nucleation effect in the PP matrix. The rate of crystallization of PP/nano‐SiO2 is higher than that of pure PP. By using a method proposed by Kissinger, activation energies have been evaluated to be 262.1, 226.5, 249.5, and 250.1 kJ/mol for nonisothermal crystallization of pure PP and PP/nano‐SiO2 composites with various SiO2 loadings of 1, 3, and 5%, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1013–1019, 2004
Mechanical properties of polyurethane film exposed to solutions of nonoxynol‐9 surfactant and poly(ethylene glycol)
Authors: McDermott Martin K. , Schroeder LeRoy W. , Balsis Shay L. , Paradiso Nicole A. , Byrne Michelle L. , Briber Robert M. 
Published: November 2003

AbstractMechanical properties of two polyether urethane films (Estane and Tecoflex) were studied after exposure to solutions of nonoxynol 9 (N9) surfactant and poly(ethylene glycol) 400 (PEG) for various times. Large amounts of N9 were absorbed from N9/PEG solutions, resulting in soft‐segment plasticization and lower mechanical properties. As the N9 concentration increased, Estane absorbed more liquid and its mechanical properties decreased more compared to Tecoflex, although the mechanical properties of Estane were higher than Tecoflex at low concentrations of N9. Hard‐segment domain disruption is probably not occurring because the relationship between the elastic modulus and polymer volume fraction followed Flory's theory for swollen elastic rubber networks and the liquids do not fully dissolve the polymers. The diffusion behavior of N9 and PEG was observed to follow Fickian behavior. Most of the absorption and decrease in mechanical properties occurred within the first 20 h after soaking, implying that additional loss in strength over longer times would be minimal. Mechanical property anisotropy suggests that condoms should be cut from Estane film in an orientation that optimizes the property–orientation relationship for specific end uses. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1086–1096, 2004
Electrically conductive composites based on epoxy resin containing polyaniline–DBSA‐ and polyaniline–DBSA‐coated glass fibers
Authors: Jia W. , Tchoudakov R. , Segal E. , Narkis M. , Siegmann A. 
Published: November 2003

AbstractFour kinds of polyaniline (PANI)‐coated glass fibers (GF–PANI) combined with bulk PANI particles were synthesized. GF–PANI fillers containing different PANI contents were incorporated into an epoxy–anhydride system. The best conductivity behavior of the epoxy/GF–PANI composites was obtained with a GF–PANI filler containing 80% PANI. Such a composite shows the lowest percolation threshold at about 20% GF–PANI or 16% PANI (glass fiber‐free basis). The PANI‐coated glass fibers act as conductive bridges, interconnecting PANI particles in the epoxy matrix, thus contributing to the improvement of the conductivity of the composite and the lower percolation threshold, compared with that of a epoxy/PANI–powder composite. Particularly, the presence of glass fibers significantly improves the mechanical properties, for example, the modulus and strength of the conductive epoxy composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1329–1334, 2004
Effect of ethylphosphate on azobenzene‐containing thermotropic liquid‐crystalline polymers
Authors: Kumaresan S. , Kannan P. 
Published: November 2003

AbstractA new series of liquid‐crystalline polymers with azobenzene mesogens and an even number of methylene spacers along with phosphorus heterogeneity were synthesized. The structures of the monomers and polymers were characterized with various spectral techniques. The thermal analyses were performed with thermogravimetric analysis and differential scanning calorimetry (DSC). The formation of the liquid‐crystalline phase was confirmed with hot‐stage optical polarizing microscopy. All the polymers exhibited grainy and nematic textures during melting; this was confirmed by DSC analysis. The char yield of the polymers was quite high and was related to the formation of phosphoric acid. The glass‐transition temperature, melting temperature, and isotropization temperature were quite low. The reduction in the transition temperature could be attributed to the incorporation of the phosphorus heterogeneity and pendant ethyl group. Molecular modeling studies supported the experimental data obtained. The suitability of these polymers for optical data storage was studied with ultraviolet spectroscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 455–462, 2004
Resonance Raman scattering of cytochrome P450 BM3 and effect of imidazole inhibitors
Authors: Smith S. J. , Munro A. W. , Smith W. E. 
Published: November 2003

AbstractResonance Raman scattering from cytochrome P450 BM3 is obtained with a Raman microprobe using 406‐nm excitation with an accumulation time of a few seconds. The small sample size and rapid measurement time make the routine characterization of P450 systems by resonance Raman spectroscopy easier. Addition of imidazole and imidazole derivatives as inhibitors causes the appearance of additional peaks due to vinyl modes, increases the relative intensity of symmetric modes that would be A1g in D4h symmetry, and causes a large drop in the intensity of ν11. This information indicates that the ligation of imidazoles to the heme iron causes the alignment of the vinyl modes with the plane of the heme ring and reduces the out of plane distortion of the ring. The effect of both inhibitors is similar but there is a subtle difference in the extent of the reduction in the intensity of ν11, which suggests that steric effects within the pocket are having some effect. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 620–627, 2003
Conformational analysis of melittin in solution phase: Vibrational circular dichroism study
Authors: Wang Feng , Polavarapu Prasad L. 
Published: November 2003

AbstractThe vibrational absorption and vibrational circular dichroism (VCD) spectra of melittin in D2O solutions at different pH values, different salt concentrations, or different 2,2,2‐trifluoroethanol (TFE) concentrations are recorded in the amide I′ (1850–1600 cm−1) region. Two models are used to simulate this peptide in different conditions, and a coupled oscillator program is used to obtain the calculated absorption and VCD spectra. This study indicates that melittin adopts a mixed structure in D2O solution at low pH, low salt concentration, or low TFE concentration. With an increase in pH, salt concentration, or TFE concentration, the structure changes to α‐helix and further increases lead to aggregation. These results demonstrate the versatility of VCD in probing the conformations of peptides under different environmental perturbations. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 614–619, 2003
Conformational and biological characterization of human parathyroid hormone hPTH(1–34) analogues containing β‐amino acid residues in positions 17–19
Authors: Schievano E. , Mammi S. , Carretta E. , Fiori N. , Corich M. , Bisello A. , Rosenblatt M. , Chorev M. , Peggion E. 
Published: November 2003

AbstractThe N‐terminal 1–34 fragment of parathyroid hormone (PTH) elicits the full spectrum of bone‐related biological activities of the intact native sequences. It has been suggested that the structural elements essential for bioactivity are two helical segments located at the N‐terminal and C‐terminal sequences, connected by hinges or flexible points around positions 12 and 19. In order to assess the relevance of the local conformation around Gly18 upon biological function, we synthesized and characterized the following human (h) PTH(1–34) analogues containing β‐amino acid residues:

equation image

equation image

equation image

equation image

equation image

equation image

Biological activity and binding affinity of analogue I are one order of magnitude lower than those of the parent compound. In analogue II, both binding affinity and biological activity are partially recovered. Analogues III and V have no binding affinity and very low biological activity. Both bioactivity and binding affinity are partially recovered in analogue IV. The conformational properties of the analogues in aqueous solution containing dodecylphosphocholine micelles were studied by CD, 2D‐nuclear magnetic resonance and molecular dynamics calculations. The results confirmed the presence in all analogues of two helical segments located at the N‐terminal and C‐terminal sequences. The insertion of β‐amino acid residues around position 18 does not cause appreciable conformational differences in the five analogues. The differences in biological activity and binding affinity among the five analogues cannot be related to structural differences in the membrane mimetic environment reported in this study. Our results stress the importance of the side‐chain functionalities in the sequence 17–19 for biological function. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 534–547, 2003
Use of residual dipolar couplings as restraints in ab initio protein structure prediction
Authors: Haliloglu Turkan , Kolinski Andrzej , Skolnick Jeffrey 
Published: November 2003

AbstractNMR residual dipolar couplings (RDCs), in the form of the projection angles between the respective internuclear bond vectors, are used as structural restraints in the ab initio structure prediction of a test set of six proteins. The restraints are applied using a recently developed SICHO (SIde‐CHain‐Only) lattice protein model that employs a replica exchange Monte Carlo (MC) algorithm to search conformational space. Using a small number of RDC restraints, the quality of the predicted structures is improved as reflected by lower RMSD/dRMSD (root mean square deviation/distance root mean square deviation) values from the corresponding native structures and by the higher correlation of the most cooperative mode of motion of each predicted structure with that of the native structure. The latter, in particular, has possible implications for the structure‐based functional analysis of predicted structures. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 548–562, 2003
Brownian dynamics simulations of glycolytic enzyme subsets with F‐actin
Authors: Lowe S. L. , Adrian C. , Ouporov I. V. , Waingeh V. F. , Thomasson K. A. 
Published: November 2003

AbstractPrevious Brownian dynamics (BD) simulations identified specific basic residues on fructose‐1,6‐bisphophate aldolase (aldolase) (I. V. Ouporov et al., Biophysical Journal, 1999, Vol. 76, pp. 17–27) and glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) (I. V. Ouporov et al., Journal of Molecular Recognition, 2001, Vol. 14, pp. 29–41) involved in binding F‐actin, and suggested that the quaternary structure of the enzymes may be important. Herein, BD simulations of F‐actin binding by enzyme dimers or peptides matching particular sequences of the enzyme and the intact enzyme triose phosphate isomerase (TIM) are compared. BD confirms the experimental observation that TIM has little affinity for F‐actin. For aldolase, the critical residues identified by BD are found in surface grooves, formed by subunits A/D and B/C, where they face like residues of the neighboring subunit enhancing their electrostatic potentials. BD simulations between F‐actin and aldolase A/D dimers give results similar to the native tetramer. Aldolase A/B dimers form complexes involving residues that are buried in the native structure and are energetically weaker; these results support the importance of quaternary structure for aldolase. GAPDH, however, placed the critical residues on the corners of the tetramer so there is no enhancement of the electrostatic potential between the subunits. Simulations using GAPDH dimers composed of either S/H or G/H subunits show reduced binding energetics compared to the tetramer, but for both dimers, the sets of residues involved in binding are similar to those found for the native tetramer. BD simulations using either aldolase or GAPDH peptides that bind F‐actin experimentally show complex formation. The GAPDH peptide bound to the same F‐actin domain as did the intact tetramer; however, unlike the tetramer, the aldolase peptide lacked specificity for binding a single F‐actin domain. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 456–470, 2003
Application of statistical potentials to protein structure refinement from low resolution ab initio models
Authors: Lu Hui , Skolnick Jeffrey 
Published: November 2003

AbstractRecently ab initio protein structure prediction methods have advanced sufficiently so that they often assemble the correct low resolution structure of the protein. To enhance the speed of conformational search, many ab initio prediction programs adopt a reduced protein representation. However, for drug design purposes, better quality structures are probably needed. To achieve this refinement, it is natural to use a more detailed heavy atom representation. Here, as opposed to costly implicit or explicit solvent molecular dynamics simulations, knowledge‐based heavy atom pair potentials were employed. By way of illustration, we tried to improve the quality of the predicted structures obtained from the ab initio prediction program TOUCHSTONE by three methods: local constraint refinement, reduced predicted tertiary contact refinement, and statistical pair potential guided molecular dynamics. Sixty‐seven predicted structures from 30 small proteins (less than 150 residues in length) representing different structural classes (α, β, α˜/β) were examined. In 33 cases, the root mean square deviation (RMSD) from native structures improved by more than 0.3 Å; in 19 cases, the improvement was more than 0.5 Å, and sometimes as large as 1 Å. In only seven (four) cases did the refinement procedure increase the RMSD by more than 0.3 (0.5) Å. For the remaining structures, the refinement procedures changed the structures by less than 0.3 Å. While modest, the performance of the current refinement methods is better than the published refinement results obtained using standard molecular dynamics. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 575–584, 2003
Prognostic significance of metastatic lymph node size in patients with gastric cancer
Authors: Dhar D K , Kubota H , Kinukawa N , Maruyama R , Kyriazanos I D , Ohno S , Nagasue N 
Published: November 2003

Abstract

Background
Patients with gastric cancer that has metastasized to the lymph nodes are a heterogeneous population with a variable prognosis. Stratification of these patients into prognostic groups is necessary for optimal adjuvant therapy.

Methods
The study comprised 715 patients who had undergone curative resection of a gastric neoplasm. Lymph nodes were sectioned, stained with haematoxylin and eosin, and the diameter of the largest metastatic lymph node (MLN) was measured. Patients with metastatic nodes were divided into groups n1 and n2 according to the size of the MLN. The cut-off level was set at 7 mm by a two-sample log rank test; patients in group n1 had a MLN size of 7 mm or less and those in group n2 had a MLN of 8 mm or more.

Results
Patients were stratified into significant prognostic groups by both the Union International Contra la Cancrum (UICC) node (N) stage and MLN size (n group). The UICC N-stage subcategories were further divided into prognostic groups according to MLN size (n group). On multivariate analysis the MLN size remained independently significant in terms of overall and disease-free survival rates, and the UICC N stage was not significant, independently of the n group. Node-positive patients with fewer than 15 lymph nodes removed at operation could also be stratified into prognostic groups by the n group. Stratification according to the TNM stage and by MLN size was superior to existing UICC TNM staging.

Conclusion
This new method may help clinicians to design a more appropriate treatment strategy for patients with gastric cancer.
Arterial problems in athletes
Authors: Mosley J G 
Published: November 2003

AbstractBackgroundAthletes may present with arterial problems that are unusual in the typical patient with peripheral vascular disease. They are often handicapped only at the extremes of physical exertion and may have normal arterial pulses beyond any arterial occlusion.MethodsA Medline search was undertaken for articles on arterial disease in athletes. Further papers were identified by cross-referencing from the reference lists.ResultsA variety of syndromes has been described that result from unusual trauma to arteries, causing occlusion or rupture. Frequently the blood flow and pressures distal to the arterial disease are normal at rest, and diagnosis is often confused with venous, musculoskeletal or nerve disease. A variety of operative interventions has been described.ConclusionAthletes may experience arterial problems that may jeopardize their careers. If recognized promptly, operative intervention may permit a return to the highest level of sporting achievement.