bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel tricomponent membranes containing poly(ethylene glycol)/poly(pentamethylcyclopentasiloxane)/poly(dimethylsiloxane) domains
Authors: Kurian Pious , Kennedy Joseph P. 
Published: October 2002

AbstractThe synthesis and characterization of novel tricomponent networks consisting of well‐defined poly(ethylene glycol) (PEG) and poly(dimethylsiloxane) (PDMS) strands crosslinked and reinforced by poly(pentamethylcyclopentasiloxane) (PD5) domains are described. Network synthesis occurred by dissolving α,ω‐diallyl PEG and α,ω‐divinyl PDMS prepolymers in a common solvent (toluene), introducing a stoichiometric excess of pentamethylcyclopentasiloxane (D5H) to the charge, inducing the cohydrosilation of the prepolymers by Karstedt's catalyst and completing network formation by the addition of water. Water in the presence of the Pt‐based catalyst oxidizes the SiH groups of D5H to SiOH functions that immediately polycondense and bring about crosslinking. The progress of cohydrosilation and polycondensation was followed by monitoring the disappearance of the SiH and SiOH functions by Fourier transform infrared spectroscopy. Because cohydrosilation and polycondensation are essentially quantitative, overall network composition can be controlled by calculating the stoichiometry of the three network constituents. The very low quantities of extractable (sol) fractions corroborate efficient crosslinking. The networks swell in both water and hexanes. Differential scanning calorimetry showed three thermal transitions assigned, respectively, to PEG (melting temperature: 46–60 °C depending on composition), PDMS [glass‐transition temperature (Tg) = ∼−121 °C], and PD5 (Tg = ∼−159 °C) and indicated a phase‐separated tricomponent nanoarchitecture. The low Tg of the PD5 phase is unprecedented. The strength and elongation of PEG/PD5/PDMS networks can be controlled by overall network composition. The synthesis of networks exhibiting sufficient mechanical properties (tensile stress: 2–5 MPa, elongation: 100–800%) for various possible applications has been demonstrated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3093–3102, 2002
Effect of the initial matrix material on the structure of radiation‐grafted ion‐exchange membranes: Wide‐angle and small‐angle X‐ray scattering studies
Authors: Jokela K. , Serimaa R. , Torkkeli M. , Sundholm F. , Kallio T. , Sundholm G. 
Published: October 2002

AbstractSeven different fluoropolymer films were used as matrix materials for radiation‐grafted ion‐exchange membranes. The crystallinity and preferred orientation of these membranes were studied with wide‐angle X‐ray scattering, and the lamellar structure of the membranes was examined with small‐angle X‐ray scattering. The crystallinity of poly(vinylidene fluoride) (PVDF)‐based matrix materials varied between 57 and 40%, and the crystallinity of the sulfonated samples varied between 34 and 23%. The lamellar periods of PVDF‐based matrix materials were about 115 Å, and the lamellar periods of poly(ethylene‐alt‐tetrafluoroethylene) and poly(tetrafluoroethylene‐co‐hexafluoropropylene) were 250 and 212 Å, respectively. When the samples were grafted, the lamellar periods increased. Correlation function analysis showed very clearly that the long‐range order decreased because of grafting and sulfonation processes. For those samples that showed good proton conductivity, the lamellar period also increased because of sulfonation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1539–1555, 2002
Morphological changes during heating in poly(L‐lactic acid)/poly(butylene succinate) blend systems as studied by synchrotron X‐ray scattering
Authors: Park Jun Wuk , Im Seung Soon 
Published: October 2002

AbstractBlends of poly(L‐lactic acid) (PLA) and poly(butylene succinate) (PBS) were prepared in various compositions via melt mixing, and the morphological changes were investigated with differential scanning calorimetry and synchrotron wide‐angle and small‐angle X‐ray scattering techniques at a heating rate of 10 °C/min. Differential scanning calorimetry thermograms of PLA/PBS blends showed two distinct melting peaks over the entire composition range. The exothermal peak for PLA shifted significantly to a lower temperature and overlapped with that of PBS around 100 °C. A depression of the melting point of the PLA component via blending was observed. The synchrotron wide‐angle X‐ray scattering during heating revealed that there was no cocrystallization or crystal modification via blending. The synchrotron small‐angle X‐ray scattering data showed that well‐defined double‐scattering peaks (or peaks with a clear scattering shoulder) appeared during crystallization, indicating that this system possessed dual lamellar stacks. These peaks were deconvoluted into two components with a peak separation computer program, and then the morphological parameters of each component were obtained by means of the correlation function. The long period and average lamellar thickness of the two components before melting decreased with an increasing content of the other polymer component. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1931–1939, 2002
Morphology and structure of nylon‐2,14 single crystals from dilute solution
Authors: Li Yongjin , Zhang Guosheng , Yan Deyue , Zhou Enle 
Published: October 2002

AbstractA perfect single crystal of nylon‐2,14 was prepared from 0.02% (w/v) 1,4‐butanediol solution by a “self‐seeding” technique and isothermal crystallization at 120 and 145 °C. The morphology and structure features were examined by transmission electron microscopy with both image and diffraction modes, atomic force microscopy, and wide‐angle X‐ray diffraction (WAXD). The nylon‐2,14 single crystal grown from 1,4‐butanediol at 145 °C inhabited a lathlike shape with a lamellar thickness of about 9 nm. Electron diffraction and WAXD data indicated that nylon‐2,14 crystallized in a triclinic system with lattice dimensions a = 0.49 nm, b = 0.51 nm, c = 2.23 nm, α = 60.4°, β = 77°, and γ = 59°. The crystal structure is different from that of nylon‐6,6 but similar to that of other members of nylon‐2Y. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1913–1918, 2002
Normal‐stress differences and the detection of disclinations in nematic elastomers
Authors: Fried Eliot , Todres Russell E. 
Published: October 2002

AbstractWe used a continuum model to investigate the isochoric radial expansion of a right circular cylindrical specimen composed of a nematic elastomer that is crosslinked in a uniaxial state and then annealed. Numerical solutions show that, above a certain radial expansion, the material has a definitive energetic preference for a state involving a disclination of strength +1 along the cylinder axis. Surrounding such a disclination is a core with radial dimension on the order of 10−2 μm, which coincides with observations in conventional liquid‐crystal melts. Examination of the normal‐stress differences indicates that the first of these differences depends nonmonotically on the extent of radial expansion and possesses a local minimum at the point where a disclination becomes energetically preferred. This suggests a practical experimental method for testing the predictions of our model. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2098–2106, 2002
Gas sorption environments in poly(2,6‐dimethyl‐1,4‐phenylene oxide) by xenon‐129 nuclear magnetic resonance: Effects of processing
Authors: Wang Yingzi , Inglefield Paul T. , Jones Alan A. 
Published: October 2002

AbstractOne‐ and two‐dimensional xenon‐129 nuclear magnetic resonance (129Xe NMR) experiments were performed on a series of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PXE) samples to characterize the sorption environments and the relative mobility of xenon in the samples. Samples of PXE in sealed NMR tubes pressurized with xenon were studied as a function of temperature, pressure, and processing. In a dense cast film of PXE, the shift relative to the free gas resonance is smaller than that observed for typical glassy polymers, indicating a higher free volume environment. Solubility rises rapidly as temperature decreases. The lower shift and rapid increase in solubility with decreasing temperature are consistent with a relatively high free volume environment for gas sorption. If PXE is antiplasticized, the shift is slightly larger, the increase in signal intensity with decreasing temperature is smaller, and the line widths are greater. This sample is a better packed glass with less free volume and slower diffusion. Samples of PXE produced by rapid precipitation have broad lines and even lower shifts corresponding to a wide distribution of higher free volume environments. The appearance of two lines at low temperatures is consistent with the presence of a bimodal distribution of environments similar to what has been observed with positron annihilation lifetime spectroscopy. The resonance closest to the free gas resonance is associated with very large free volume elements relative to those of traditional glassy polymers. In two‐dimensional experiments, there is a rapid exchange of xenon by diffusion between the two environments, indicating the close spatial proximity of the environments. Two‐dimensional experiments and one‐dimensional progressive saturation experiments reflect a rapid exchange of xenon between the sorbed state and the free gas resonance for the precipitated samples. At low temperatures, the high field peak exchanges more rapidly with the free gas. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1965–1974, 2002
Electromechanical properties of poly(vinylidene fluoride‐trifluoroethylene) networks
Authors: Casalini R. , Roland C. M. 
Published: October 2002

AbstractRandom copolymers of 65% vinylidene fluoride and 35% trifluoroethylene were reacted with an organic peroxide, in combination with a free‐radical trap, to yield networks of high crosslink density. Crystallization subsequent to the crosslinking yielded ferroelectric materials exhibiting large electrostrictive strains. The magnitude of the electromechanical response increased with an increasing degree of crosslinking, even though this reduced the crystallinity. For the most crosslinked sample, longitudinal (thickness) strains as high as 12% were induced at an electric field of 9 MV/m. This electrostrictive performance exceeded that obtained to date with any poly(vinylidene fluoride) material. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1975–1984, 2002
Modeling structural recovery in glasses: An analysis of the peak‐shift method
Authors: Zheng Y. , Simon S. L. , McKenna G. B. 
Published: October 2002

AbstractAmorphous polymers below their glass‐transition temperature are inherently not at equilibrium. As a result, their structures continuously relax in an attempt to reach the equilibrium state. The current models of structural recovery can quantitatively describe the process. One of the parameters needed for the models is the nonlinearity parameter x. It has been proposed that x can be obtained from experimental data with the so‐called peak‐shift method. In this work, we use the Tool–Narayanaswamy–Moynihan model to identify the factors that determine the accuracy of the peak‐shift method and to quantify the errors in the value of x obtained from the peak‐shift method. In addition, we determine the influence of the error in x on the evaluation of the nonexponential model parameter β. Finally, the peak‐shift method is compared with the traditional curve‐fitting method for model parameter determination. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2027–2036, 2002
Evaluation of the surface free energy of spin‐coated photodefinable epoxy
Authors: Turunen Markus P. K. , Laurila Tomi , Kivilahti Jorma K. 
Published: October 2002

AbstractThe surface free energy of crosslinked photodefinable epoxy (PDE) was evaluated from the advancing contact angles measured by the sessile drop method. Poly(tetrafluoroethylene) (PTFE) was used as a reference material in the evaluation of the surface free energies by various models. Pure water, diiodomethane, formamide, ethylene glycol, diethylene glycol, glycerol, 1‐bromonaphthalene, decane, and tetradecane were used as the probing liquids. The surface free energies for PDE and PTFE were calculated to be 43.6 and 21.2 mJ/m2, respectively. The contact‐angle measurements indicated the isotropy of the PDE surface with respect to the surface free energy. The PDE coating was further characterized with scanning electron microscopy and atomic force microscopy. The PDE surface was treated chemically and by reactive ion etching (RIE) to determine their impact on the wettability and adhesion. The treatments resulted in decreased contact angles between the crosslinked PDE surface and water as the polarity of the surface increased from about 9% to 18 and 43% by the chemical and RIE treatments, respectively. On the contrary, the surface free energy of the treated PDEs, as calculated by the geometric mean model, did not change markedly (to 47.4 and 41.8 mJ/m2 by the chemical and RIE treatments, respectively). Consequently, the contact angles of diiodomethane and the PDE solution on the treated surfaces did not decrease noticeably. The stud‐pull test showed improved adhesion strength for PDE that was left less crosslinked and, therefore, had residual affinity against the sequential PDE layer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2137–2149, 2002
Flexible protein alignment and hinge detection
Authors: Shatsky Maxim , Nussinov Ruth , Wolfson Haim J. 
Published: October 2002

AbstractHere we present a novel technique for the alignment of flexible proteins. The method does not require an a priori knowledge of the flexible hinge regions. The FlexProt algorithm simultaneously detects the hinge regions and aligns the rigid subparts of the molecules. Our technique is not sensitive to insertions and deletions. Numerous methods have been developed to solve rigid structural comparisons. Unlike FlexProt, all previously developed methods designed to solve the protein flexible alignment require an a priori knowledge of the hinge regions. The FlexProt method is based on 3‐D pattern‐matching algorithms combined with graph theoretic techniques. The algorithm is highly efficient. For example, it performs a structural comparison of a pair of proteins with 300 amino acids in about 7 s on a 400‐MHz desktop PC. We provide experimental results obtained with this algorithm. First, we flexibly align pairs of proteins taken from the database of motions. These are extended by taking additional proteins from the same SCOP family. Next, we present some of the results obtained from exhaustive all‐against‐all flexible structural comparisons of 1329 SCOP family representatives. Our results include relatively high‐scoring flexible structural alignments between the C‐terminal merozoite surface protein vs. tissue factor; class II aminoacyl‐tRNA synthase, histocompatibility antigen vs. neonatal FC receptor; tyrosine‐protein kinase C‐SRC vs. haematopoetic cell kinase (HCK); tyrosine‐protein kinase C‐SRC vs. titine protein (autoinhibited serine kinase domain); and tissue factor vs. hormone‐binding protein. These are illustrated and discussed, showing the capabilities of this structural alignment algorithm, which allows un‐predefined hinge‐based motions. Proteins 2002;48:242–256. © 2002 Wiley‐Liss, Inc.
Kinetic analysis of the interaction between the QutA and QutR transcription‐regulating proteins
Authors: Watts Carys , Si‐Hoe Shi Ming , Lamb Heather K. , Levett Lisa J. , Coggins John R. , Hawkins Alastair R. 
Published: October 2002

AbstractThe QutR protein is a multidomain repressor protein that interacts with the QutA activator protein. Both proteins are active in the signal transduction pathway that regulates transcription of the quinic acid utilization (qut) gene cluster of the microbial eukaryote Aspergillus nidulans. In the presence of quinate, production of mRNA from the eight genes of the qut pathway is stimulated by the QutA activator protein. The QutR protein plays a key role in signal recognition and transduction, and a deletion analysis has shown that the N‐terminal 88 amino acids are sufficient to inactivate QutA function in vivo. Using surface plasmon resonance we show here that the N‐terminal 88 amino acids of QutR are able to bind in vitro to a region of QutA that genetic analysis has previously implicated in transcription activation. We further show that increasing the concentration of a full‐length (missense) mutant QutR protein in the original mutant strain can restore its repressing function. This is interpreted to mean that the qutR mutation in this strain increases the equilibrium dissociation constant for the interaction between QutA and QutR. We propose a model in which the QutA and QutR proteins are in dynamic equilibrium between bound (transcriptionally inactive) and unbound (transcriptionally active) states. Proteins 2002;48:161–168. © 2002 Wiley‐Liss, Inc.
Dissipation of triclopyr herbicide applied in Lake Minnetonka, MN concurrently with Rhodamine WT dye
Authors: Fox Alison M , Haller William T , Getsinger Kurt D , Petty David G 
Published: October 2002

AbstractFluorescent dye was applied concurrently with triclopyr in two 6.5‐ha treatment plots in Lake Minnetonka, MN for data collection to support full aquatic registration of this herbicide. The herbicide and dye mixture was applied by airboat to Phelps Bay with weighted, trailing hoses to maximize uniform distribution of these materials in the water column. A surface application was made to the Carsons Bay plot to attain theoretical triclopyr and dye concentrations of 2500 and 10 µg litre−1, respectively. Water samples collected at various times following application showed very little movement of the herbicide and dye out of the Carsons Bay plot. Triclopyr residues moved to a greater extent out of the Phelps Bay plot. The dye was easily tracked in real‐time using field fluorometers, which allowed new sampling stations to be established to monitor this movement. Dye concentrations were strongly correlated to herbicide concentrations (r2 = 0.97 in both plots) but were less predictive of the triclopyr metabolite 3,5,6‐trichloropyridinol (TCP; r2 = 0.82 in Phelps and r2 = 0.73 in Carsons), probably due to its differential metabolism and degradation. The inert dye can be used to compare the dissipation of herbicide residues by dilution versus microbial or other breakdown processes. Vertical sampling of dye in the water column showed that surface applications of aquatic herbicides can delay uniform mixing in the water column by several days. Although the dye aided the tracking of residues outside the treatment areas, predetermined sampling times and stations were still needed if very low concentrations of herbicide were to be detected at times and stations where the dye had been diluted below its limit of detection.© 2002 Society of Chemical Industry
Effect of diphacinone on blood coagulation in Spermophilus beecheyi as a basis for determining optimal timing of field bait applications
Authors: Whisson Desley A , Salmon Terrell P 
Published: October 2002

AbstractThe effect was determined of a single dose of 2 mg kg−1 diphacinone on three blood‐clotting parameters [Prothrombin Time (PT), Partial Thromboplastin Time (PTT), and Protein Induced by Vitamin K Absence or Antagonists (PIVKA)] over a 120‐h period in California ground squirrels, Spermophilus beecheyi. Diphacinone resulted in elevated PT, PTT and PIVKA within 24 h of squirrels receiving the dose. The most significant change was observed 72 h after dosing. As time following diphacinone dosing increased, there was higher individual variation in blood‐clotting time. We suggest that increasing the interval between field bait applications should still result in squirrel mortality but reduce the potential for secondary hazards that may occur when squirrels have the opportunity to consume more than one lethal dose of diphacinone.© 2002 Society of Chemical Industry
Flow cytometric estimation on cytotoxic activity of leaf extracts from seashore plants in subtropical Japan: isolation, quantification and cytotoxic action of (‐)‐deoxypodophyllotoxin
Authors: Masuda Toshiya , Oyama Yasuo , Yonemori Shigetomo , Takeda Yoshio , Yamazaki Yuko , Mizuguchi Shinichi , Nakata Mami , Tanaka Tomochika , Chikahisa Lumi , Inaba Yuzuru , Okada Yoshihiko 
Published: October 2002

AbstractThe cytotoxic activity of methanol extracts of leaves collected from 39 seashore plants in Iriomote Island, subtropical Japan was examined on human leukaemia cells (K562 cells) using a flow cytometer with two fluorescent probes, ethidium bromide and annexin V‐FITC. Five extracts (10 μg/mL) from Hernandia nymphaeaefolia, Cerbera manghas, Pongamia pinnata, Morus australis var. glabra and Thespesia populnea greatly inhibited the growth of K562 cells. When the concentration was decreased to 1 μg/mL, only one extract from H. nymphaeaefolia still inhibited the cell growth. A cytotoxic compound was isolated from the leaves by bioassay‐guided fractionation and was identified as (‐)‐deoxypodophyllotoxin (DPT). The fresh leaves of H. nymphaeaefolia contained a remarkably high amount of DPT (0.21 ± 0.07% of fresh leaf weight), being clarified by a quantitative HPLC analysis. DPT at 70–80 pM started to inhibit the growth of K562 cells in an all‐or‐none fashion and at 100 pM or more it produced complete inhibition in all cases. Therefore, the slope of the dose‐response curve was very steep. DPT at 100 pM or more decreased the cell viability to 50%–60% and increased the number of cells undergoing apoptosis (annexin V‐positive cells). The results indicate that DPT contributes to the cytotoxic action of the extract from the leaves of H. nymphaeaefolia on K562 cells. Copyright © 2002 John Wiley & Sons, Ltd.
Anticonvulsant and sedative effects of Salvadora persica L. stem extracts
Authors: Monforte M. T. , Trovato A. , Rossitto A. , Forestieri A. M. , d'Aquino A. , Miceli N. , Galati E. M. 
Published: October 2002

AbstractThe effect of Salvadora persica L. stem extracts on the potentiation of sodium pentobarbital activity and on generalized tonic‐clonic seizure produced by pentylenetetrazol (PTZ) on the rat is reported. The extracts of Salvadora persica L. extended sleeping‐time and decreased induction‐time induced by sodium pentobarbital; in addition it showed protection against pentylenetetrazol‐induced convulsion by increasing the latency period and diminishing the death rate. Copyright © 2002 John Wiley & Sons, Ltd.
Statistical analysis of process capability indices with measurement errors
Authors: Bordignon Silvano , Scagliarini Michele 
Published: October 2002

AbstractProcess capability indices (PCIs) have been widely used in manufacturing industries to provide a quantitative measure of process potential and performance. While some efforts have been dedicated in the literature to the statistical properties of PCIs estimators, scarce attention has been given to the evaluation of these properties when sample data are affected by measurement errors. In this work we deal with the problem of measurement‐error effects on the performance of PCIs. The analysis is illustrated with reference to $C_p$ and $C_{pk}$, i.e. the two most common measures suggested to evaluate process capability. Copyright © 2002 John Wiley & Sons, Ltd.