bluuebunny/crossref_metadata_2025 huggingface dataset:
Flame‐retardant epoxy resins from o‐cresol novolac epoxy cured with a phosphorus‐containing aralkyl novolac
Authors: Liu Ying Ling , Wu Chuan Shao , Hsu Keh Ying , Chang Teh Chou
Published: October 2002

A novel phosphorus‐containing aralkyl novolac (Ar‐DOPO‐N) was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) first with terephthaldicarboxaldehyde and subsequently with phenol. The chemical structures of the synthesized compounds were characterized with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. Ar‐DOPO‐N blended with phenol formaldehyde novolac was used as a curing agent for o‐cresol formaldehyde novolac epoxy, resulting in cured epoxy resins with various phosphorus contents. The epoxy resins exhibited high glass‐transition temperatures (159–177 °C), good thermal stability (>320 °C), and retardation on thermal degradation rates. High char yields and high limited oxygen indices (26–32.5) were observed, indicating the resins' good flame retardance. Using a melamine‐modified phenol formaldehyde novolac to replace phenol formaldehyde novolac in the curing composition further enhanced the cured epoxy resins' glass‐transition temperatures (160–186 °C) and limited oxygen index values (28–33.5). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2329–2339, 2002
End‐group modification of poly(butyl acrylate) prepared by atom transfer radical polymerization: Mechanistic study using gradient polymer elution chromatography
Authors: Snijder Auke , Klumperman Bert , Van Der Linde Rob
Published: October 2002

The introduction of a functional group into a poly(butyl acrylate) polymer prepared by copper‐mediated atom transfer radical polymerization and the characterization of the prepared polymer by gradient polymer elution chromatography are reported. The bromo end group of the initial polymer can be transformed into a different functional group with several functionalization reactions, including nucleophilic substitution and atom transfer radical addition (ATRA), in combination with comonomers, addition–fragmentation transfer agents, or stable radicals. Several new functionalization agents are reported, including ATRA using 1‐(3‐hydroxymethyl‐phenyl)‐pyrrole‐2,5‐dione and trimethyl{1‐[4‐(2‐trimethylsiloxyethoxy)]phenylethenyloxy}silane and nucleophilic substitution using 2‐mercapto ethanol. The rate constant of the functionalization reaction and the final functionality are determined with gradient polymer elution chromatography, a technique by which qualitative and quantitative information about the conversion can be obtained. Polymers with a functionality greater than 95% are reported. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2350–2359, 2002
Ruthenium‐based metathesis initiators: Development and use in ring‐opening metathesis polymerization
Authors: Frenzel Ulrich , Nuyken Oskar
Published: October 2002

For many years, olefin metathesis has been a central topic of industrial and academic research because of its great synthetic utility. The employed initiators cover a wide range of compounds, from simple transition‐metal salts to highly sophisticated and well‐defined alkylidene complexes. Currently, ruthenium‐based catalysts are at the center of attention because of their remarkable tolerance toward oxygen, moisture, and numerous functionalities. This article focuses on recent developments in the field of ring‐opening metathesis polymerization using ruthenium‐based catalysts. ruthenium‐based initiators and their applications to the preparation of advanced polymeric materials are briefly reviewed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2895–2916, 2002
Controlled‐release systems based on the intercalation of polymeric metribuzin onto montmorillonite
Authors: Rehab Ahmed , Akelah Ahmed , El‐Gamal Maisa M.
Published: October 2002

A series of polymer–clay composites carrying metribuzin as herbicide moieties were prepared. Linear copolymers containing metribuzin via an imide linkage were prepared by the free‐radical polymerization of metribuzin monomer (N,N‐diacryloyl metribuzin) with different comonomers. The intercalation of the copolymers onto montmorillonite through a cationic exchange process was carried out and yielded metribuzin composite products. The prepared materials were characterized with a wide variety of analytical techniques, including gel permeation chromatography, NMR, IR, elemental microanalysis, gravimetric analysis (calcination), and swelling measurements. The release rates for the prepared materials were investigated in media of different pHs with an ultraviolet spectrophotometer. Also, these compounds were studied for the control of herb growth. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2513–2525, 2002
Synthesis of model polycyclohexylene/polyethylene miktoarm star copolymers with three and four arms
Authors: Tsoukatos Thodoris , Hadjichristidis Nikos
Published: October 2002

The synthesis of well‐defined 3‐ and 4‐miktoarm star copolymers of the A2B and A3B types is described, where A is 1,4‐polybutadiene and B is poly(1,3‐cyclohexadiene). The synthetic approach involves the reaction of poly(1,3‐cyclohexadienyl)lithium with an excess of methyltrichlorosilane or tetrachlorosilane followed, after the removal of excess silane, by a small excess of polybutadienyllithium. Characterization was carried out by size exclusion chromatography, low‐angle laser light scattering, laser differential refractometry, and NMR spectroscopy. The complete heterogeneous catalytic hydrogenation of the A2B and A3B miktoarm stars, with a calcium carbonate‐supported palladium catalyst, leads to the formation of A2B and A3B miktoarm stars with one amorphous polycyclohexylene arm with an extremely high glass‐transition temperature and two or three crystalline polyethylene arms. Differential scanning calorimetry was used to determine the glass‐transition temperature of the amorphous blocks of the starting and hydrogenated stars and the melting temperature of polyethylene. Solid‐state 13C NMR spectroscopy was performed to ensure the complete saturation of the polycyclohexadiene and polybutadiene arms. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2575–2582, 2002
Preparation of novel, high‐modulus, swollen‐ or jungle‐gym‐type polyimide gels end‐crosslinked with 1,3,5‐tris(4‐aminophenyl)benzene
Authors: He Jionghao , Machida Shinjiro , Kishi Hiromitsu , Horie Kazuyuki , Furukawa Hidemitsu , Yokota Rikio
Published: October 2002

A novel preparation approach for high‐performance polyimide gels that are swollen or have a jungle‐gym‐type structure is proposed. A new rigid and symmetric trifunctional amine, 1,3,5‐tris(4‐aminophenyl)benzene (TAPB), was synthesized as a crosslinker. Three different kinds of amic acid oligomers derived from pyromellitic dianhydride (PMDA), 4,4′‐oxydiphthalic anhydride (ODPA), p‐phenylenediamine (PDA), and 4,4′‐oxydianiline (ODA) were end‐crosslinked with TAPB at a high temperature to make polyimide networks with different structures. Transparent polyimide gels were obtained from the ODPA–ODA/TAPB series with high compression moduli of about 1 MPa at their equilibrium swollen states in N‐methylpyrrolidone. Microscopic phase separation occurred during the gelation–imidization process when polyimide networks were generated from PMDA–PDA/TAPB and PMDA–ODA/TAPB. After these opaque polyimide networks were dried, a jungle‐gym‐like structure was obtained for the PMDA–PDA/TAPB and PMDA–ODA/TAPB series; that is, there was a high void content inside the networks (up to 70%) and little volume shrinkage. These polyimide networks did not expand but absorbed the solvent and showed moduli as high as those of solids. Therefore, using the highly rigid crosslinker TAPB combined with the flexible monomers ODPA and ODA and the rigid monomers PMDA and PDA, we prepared swollen, high‐performance polyimide gels and jungle‐gym‐type polyimide networks, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2501–2512, 2002
Synthesis and characterization of poly(ethylene oxide)/polylactide/poly(ethylene oxide) triblock copolymer
Authors: Lee Soo‐Hong , Kim Soo Hyun , Han Yang‐Kyoo , Kim Young Ha
Published: October 2002

Poly(ethylene oxide/polylactide/poly(ethylene oxide) (PEO/PL/PEO) triblock copolymers, in which each block is connected by an ester bond, were synthesized by a coupling reaction between PL and PEO. Hydroxyl‐terminated PLs with various molecular weights were synthesized and used as hard segments. Hydroxyl‐terminated PEOs were converted to the corresponding acid halides via their acid group and used as a soft segment. Triblock copolymers were identified by Fourier transform infrared spectroscopy, 1H NMR, and gel permeation chromatography. Differential scanning calorimetry (DSC) and X‐ray diffractometry of PEO/PL/PEO triblock copolymers suggested that PL and PEO blocks were phase‐separated and that the crystallization behavior of the PL block was markedly affected by the presence of the PEO block. PEO/PL/PEO triblock copolymers with PEO 0.75k had two exothermic peaks (by DSC), and both peaks were related to the crystallization of PL. According to thermogravimetric analysis, PEO/PL/PEO triblock copolymer showed a higher thermal stability than PL or PEO. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2545–2555, 2002
Synthesis and properties of new soluble aromatic polyamides and polyimides on the basis of N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine
Authors: Liou Guey‐Sheng , Hsiao Sheng‐Huei
Published: October 2002

A new N‐phenylated amide (N‐phenylamide) unit containing aromatic diamine, N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was prepared by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 3‐nitrobenzoyl chloride, followed by catalytic reduction. Two series of organosoluble aromatic poly(N‐phenylamide‐imide)s and poly(N‐phenylamide‐amide)s with inherent viscosities of 0.58–0.82 and 0.56–1.21 dL/g were prepared by a conventional two‐stage method and the direct phosphorylation polycondensation, respectively, from the diamine with various aromatic dianhydrides and aromatic dicarboxylic acids. All polyimides and polyamides are amorphous and readily soluble in many organic solvents such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with high tensile strengths. These polyimides and polyamides had glass‐transition temperatures in the ranges of 230–258 and 196–229 °C, respectively. Decomposition temperatures of the polyimides for 10% weight loss all occurred above 500 °C in both nitrogen and air atmospheres. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2564–2574, 2002
Preparation of poly(arylenediphosphine)s by palladium‐catalyzed polycondensation: Formation of polymer transition‐metal complexes and catalytic reactions
Authors: Kanbara Takaki , Takase Syuichi , Hayashi Rika , Kagaya Shigehiro , Hasegawa Kiyoshi , Yamamoto Takakazu
Published: October 2002

The palladium‐catalyzed polycondensation of aryl diiodides with 1,3‐bis(phenylphosphino)propane afforded poly(arylenediphosphine)s in good yields. Treatment of the polyphosphine with elemental sulfur and hydrogen peroxide efficiently converted the polyphosphine into poly(arylenediphosphine sulfide) and poly(arylenediphosphine oxide), respectively. Treatment of the polyphosphines with Pd(II) and Pt(II) yielded corresponding polymer‐metal complexes with high metal contents. Application of the polymer‐Pd complexes in homogeneous and heterogeneous aryl alkynylation and carbonylation was examined. The polymer‐Pd complexes showed good catalytic activity similar to that of the corresponding low molecular weight Pd complex, and reuse of the polymer catalysts was easily achieved. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2637–2647, 2002
Supported stereospecific metallocene binary catalyst for propylene polymerization
Authors: de Fátima Vieira Marques Maria , Camargo Pombo Carla , Azevedo Silva Rodrigo , Conte Anunciata
Published: October 2002

In this work, propylene was polymerized with isospecific and syndiospecific catalysts in homogeneous and heterogeneous systems. The binary metallocene system of both isospecific and syndiospecific catalysts in the heterogeneous system was also used. Besides the type of catalyst, parameters such as polymerization temperature and pressure were varied to achieve the better conditions for the polymerization. The objective of this work is to investigate the influence of these parameters on the characteristics of the produced polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2979–2986, 2002
Novel tricomponent membranes containing poly(ethylene glycol)/poly(pentamethylcyclopentasiloxane)/poly(dimethylsiloxane) domains
Authors: Kurian Pious , Kennedy Joseph P.
Published: October 2002

The 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

Seven 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

Blends 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

A 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

We 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

One‐ 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

Random 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

Amorphous 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

The 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

Here 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

The 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

Fluorescent 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

The 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

The 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

The 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

Process 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.
Construction of double sampling s‐control charts for agile manufacturing
Authors: He David , Grigoryan Arsen
Published: October 2002

Double sampling (DS) $\overline{X}$‐control charts are designed to allow quick detection of a small shift of process mean and provides a quick response in an agile manufacturing environment. However, the DS $\overline{X}$‐control charts assume that the process standard deviation remains unchanged throughout the entire course of the statistical process control. Therefore, a complementary DS chart that can be used to monitor the process variation caused by changes in process standard deviation should be developed. In this paper, the development of the DS s‐charts for quickly detecting small shift in process standard deviation for agile manufacturing is presented. The construction of the DS s‐charts is based on the same concepts in constructing the DS $\overline{X}$‐charts and is formulated as an optimization problem and solved with a genetic algorithm. The efficiency of the DS s‐control chart is compared with that of the traditional s‐control chart. The results show that the DS s‐control charts can be a more economically preferable alternative in detecting small shifts than traditional s‐control charts. Copyright © 2002 John Wiley & Sons, Ltd.
Theoretical studies on transimination of vitamin B6 analogs
Authors: Salvà Antoni , Donoso Josefa , Frau Juan , Muñoz Francisco
Published: October 2002

The transimination reaction of vitamin B6 analogs has been studied by semiempirical quantum mechanics calculations (PM3 Hamiltonian) on a model reactive system consisting of the Schiff base made from a pyridoxal‐5'‐phosphate (PLP) model compound, methylamine and two auxiliary water molecules. The mechanism of this reaction has been theoretically established through the description of the energy and the geometric parameters of the intermediates and transition‐state structures in the gas phase and in water solution by means of the use of two different solvation models. The description of the reaction pathway for transimination through the structures that have resulted from the calculations supports the existence of a geminal diamine as the main intermediate. The reaction also involves the occurrence of internal hydrogen transfers and water‐mediated hydrogen transfers as rate‐limiting steps. This study highlights the key role of water molecules not only in the formation of selected hydrogen bonds but also as true reactives. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Discrete and continuum quantum states for the Kratzer oscillator
Authors: Matamala Adelio R.
Published: October 2002

Kratzer oscillator is a realistic zero‐order model for describing the anharmonic ro‐vibrational motion in diatomic molecules. Kratzer oscillator has an energy spectrum containing both discrete and continuum parts. Wavefunctions belonging to the continuum would be useful in the study of transitions to the continuum in molecular dissociation processes. In this article, bound and scattering wavefunctions of the Kratzer oscillator are reviewed and the bound–bound and the bound–free matrix elements are obtained. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Variational problem for ground and excited rovibronic states on the basis of a molecular Hamiltonian in the principal central axes
Authors: Tsaune A. Y. , Podolyak Y. A. , Glushkov V. N. , D'Yachenko M. P.
Published: October 2002

A general scheme of realization of nonempirical methods for calculation of the ground and excited rovibronic states of flexible molecules is proposed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Derivation of shell effects and magic numbers in metal clusters by the application of Strutinsky's method to the Clemenger–Nilsson and q‐deformed 3‐D harmonic oscillator models
Authors: Bonatsos D. , Kuleff A. I. , Maruani J. , Raychev P. P. , Terziev P. A.
Published: October 2002

Strutinsky's standard averaging method is applied to metal clusters described by two different potentials—Clemenger–Nilsson (CN) and q‐deformed 3‐D (Q3D) harmonic oscillator (HO). In addition, a new approximate fitting formula—of the liquid drop model type—is derived for the smooth part of the energy. The results obtained for the oscillating part of the energy (shell correction term) with the two cluster potentials through the two averaging methods are compared and discussed. It is found that with both CN and Q3D HO potentials the standard and approximate methods give similar results for clusters with a large number of particles, whereas for smaller clusters significant differences appear. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Two charged particles in a two‐dimensional well
Authors: Salter Edward A. , Wierzbicki A.
Published: October 2002

Numerical solutions are obtained for the time‐independent Schrödinger equation for a system of two particles of the same charge, repelled by the Coulomb force and confined to a two‐dimensional infinite well. The eigenfunctions are expanded in a basis set of product delta functions; the Coulomb potential's singularity is thereby removed. We discuss our findings regarding correlated behavior in the lowest energy states of a well of width and length 3 bohr and the ordering of symmetric and antisymmetric states. Presented are conditional‐probability densities in which Coulomb and Fermi holes are featured. The method is useful for treating other two‐particle interactions in two dimensions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Rapid 18O analysis of small water and CO2 samples using a continuous‐flow isotope ratio mass spectrometer
Authors: Fessenden Julianna E. , Cook Craig S. , Lott Michael J. , Ehleringer James R.
Published: October 2002

High‐frequency throughput is often needed in isotopic studies in biological and medical fields. Here we report that high‐precision oxygen isotope ratio measurements of water (±0.13‰) were rapidly and routinely made on small samples (40–100 µL) using an isotope ratio mass spectrometer operated in continuous‐flow mode. Simple modifications to existing instrumentation allow for rapid manual analyses of dilute CO2 (10% CO2/90% N2), including the addition of a septum port and water trap prior to the gas chromatography (GC) column (elemental analyzer column in this study) and the extension of fused‐silica capillary tubing between the mass spectrometer source and the effluent tubing from the GC column (located within the CONFLO unit on Finnigan mass spectrometers). We routinely analyzed 20 small‐volume samples per hour using this technique, without sacrificing precision of the oxygen isotope ratio measurement. Copyright © 2002 John Wiley & Sons, Ltd.
High‐throughput logP measurement using parallel liquid chromatography/ultraviolet/mass spectrometry and sample‐pooling
Authors: Zhao Yining , Jona Janan , Chow David T. , Rong Haojing , Semin David , Xia Xiaoyang , Zanon Roger , Spancake Chris , Maliski Ed
Published: October 2002

A novel approach to high‐throughput logP measurement based on liquid chromatography/ultraviolet/mass spectrometry (LC/UV/MS) is proposed. The logP value is determined by correlation with the logk value, where k is the capacity factor k = (tr−t0)/t0, with the logP value using a defined set of standards. Since the analyte retention time (tr) is determined from the appropriate extracted ion chromatogram (EIC), there are no interferences from impurities and this allows the pooling of multiple compounds into one injection. To ensure the accuracy and instrument robustness in a routine high‐throughput environment, a simple and MS‐friendly mobile phase consisting of 20 mM ammonium carbonate (pH 8.0) for basic compounds or 20 mM ammonium formate (pH 1.0) for acidic compounds, both in combination with methanol at a ratio of 45:55, is used. This approach has been successfully used on single as well as parallel multi‐channel LC/UV/MS systems to screen small to large sets of lead compounds and their analogs. A high‐throughput capability to analyze over 1000 compounds per day has been achieved. Copyright © 2002 John Wiley & Sons, Ltd.
Application of Biobarriers for Groundwater Containment at Fractured Bedrock Sites
Authors: Ross Nathalie , Bickerton Greg
Published: October 2002

Biological barriers are a beneficial application of biofilms that aim at reducing the hydraulic conductivity
(K) in geological formations. Several studies have shown the potential benefits of creating such
barriers either by stimulating the indigenous microbial community (biostimulation) or injecting
bacteria (bioaugmentation). For example, laboratory experiments show that groundwater microorganisms
attached to a ceramic surface and generated a biofilm as thick as 1,100 μm. In a limestone fracture, this
bacterial community clogged a single fracture up to 99.2 percent within 22 days. At the field scale,
applications in porous aquifers led to a five‐fold decrease in K after 2.5 days of biostimulation, and a
bioaugmentation with a starved, adapted bacterial culture decreased K by 99.4 percent. One promising development
of the biobarrier concept is a field application at a fractured bedrock site. Using a multidisciplinary approach
and focusing on a well‐characterized fracture system, a field trial was undertaken in Southern Ontario to
measure the extent of bioclogging and the stability over time. This article focuses on the literature pertinent
to the preparation of this field trial and presents the innovative approach selected to monitor the bioclogging
in such a challenging environment.
Treatment of MTBE‐Contaminated Waters with Fenton's Reagent
Authors: Ray Asim B. , Selvakumar Ariamalar , Tafuri Anthony N.
Published: October 2002

Methyl tertiary‐butyl ether (MTBE) is commonly used as a fuel additive because of its many favorable properties that allow it to improve fuel combustion and reduce resulting concentrations of carbon monoxide and unburnt hydrocarbons. Unfortunately, increased production and use have led to its introduction into the environment. Of particular concern is its introduction into drinking water supplies. Accordingly, research studies have been initiated to investigate the treatment of MTBE‐contaminated soil and groundwater. The summer 2000 issue of Remediation reported the results of an initial study conducted by the authors to evaluate the treatment of MTBE using Fenton's reagent. In this follow‐up study, experiments were conducted to further demonstrate the effectiveness of using Fenton's reagent (H2O2:Fe+2) to treat MTBE‐contaminated groundwater. The concentration of MTBE was reduced from an initial concentration of 1,300 μg/l (14.77 μ moles) to the regulatory level of 20 μg/l (0.23 μ moles) at a H2O2:Fe+2 molar ratio of 1:1, with ten minutes of contact time and an optimum pH of 5. The by‐products, acetone and tertiary butyl alcohol, which are always present in MTBE in trace amounts, were not removed even after 60 minutes of reaction time. © 2002 Wiley Periodicals, Inc.*
A Slice of Guidance Provides Some Insight to Addressing Contaminated Sediments
Authors: Sears Ted
Published: October 2002

The U.S. Environmental Protection Agency (EPA) has issued guidance to improve cleanup risk
management decisions at sites involving contaminated sediments. The guidance is titled Principles for
Managing Contaminated Sediment Risks at Hazardous Waste Sites and is important because sediment cleanup
decisions are often very technical and complex. While the guidance is not a step‐by‐step
“how to” document, it does provide the framework for risk‐based decision making and national
consistency. Although it does not answer the more technical questions associated with remediation, it will
likely provide site managers with greater certainty related to their decisions and help determine what questions
need to be asked for many complex issues. Additional and forthcoming EPA reports, seminars, and products will be
useful in building upon this framework. This article provides an overview of the risk management principles
presented in the guidance. © 2002 Wiley Periodicals, Inc.