bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization and chain conformation of semicrystalline and amorphous polymer blends studied by wide‐angle and small‐angle scattering
Authors: Huang Ching‐I , Chen Jun‐Rong 
Published: September 2002

AbstractWe examine the crystallization and chain conformation behavior of semicrystalline poly(ethylene oxide) (PEO) and amorphous poly(vinyl acetate) (PVAc) mixtures with wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and small‐angle neutron scattering (SANS) experiments. For blends with PEO weight fractions (wtPEO) greater than or equal to 0.3, below the melting point of PEO, the WAXD patterns reveal that crystalline PEO belongs to the monoclinic system. The unit‐cell parameters are independent of wtPEO. However, the bulk crystallinity determined from WAXD decreases as wtPEO decreases. The scattered intensities from SAXS experiments show that the systems form an ordered crystalline/amorphous lamellar structure. In a combination of WAXD and SAXS analysis, the related morphological parameters are assigned correctly. With the addition of amorphous PVAc, both the average amorphous layer thickness and long spacing increase, whereas the average crystalline layer thickness decreases. We find that a two‐phase analysis of the correlation function from SAXS, in which the scattering invariant is linearly proportional to the volume fraction of lamellar stacks, describes quantitatively the crystallization behavior of PEO in the presence of PVAc. When wtPEO is close to 1, the samples are fully spaced‐filled with lamellar stacks. As wtPEO decreases from 1.0 to 0.3, more PVAc chains are excluded from the interlamellar region into the interfibrillar region. The fraction outside the lamellar stacks, which is completely occupied with PVAc chains, increases from 0 to 58%. Because the radius of gyration of PVAc with a random‐coil configuration determined from SANS is smaller than the average amorphous layer thickness from SAXS, we believe that the amorphous PVAc chains still persist with a random‐coil configuration even when the blends form an ordered structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2705–2715, 2001
Ryanodine receptor acts as a sensor for redox stress
Authors: Pessah Isaac N 
Published: September 2002

AbstractRyanoids have not attained importance as insecticides, but the increasing number of xenobiotic effectors known to influence Ca2+ signalling by interaction with ryanodine receptors (RyRs) may serve to identify new targets for insect control. A historical review of redox control of microsomal Ca2+ transport is given here, followed by recent evidence indicating that hyperactive Cys residues are an essential component of a transmembrane redox sensor. Focus is on the role of sulfhydryl chemistry in RyR regulation; metabolic quinonoid intermediates from pesticides and other environmental contaminants are of interest in this context.© 2001 Society of Chemical Industry
Sensitivity of Venturia inaequalis to trifloxystrobin
Authors: Küng Färber Ruth B , Chin Khoon Min , Leadbitter Neil 
Published: September 2002

AbstractThe sensitivity of Venturia inaequalis to trifloxystrobin was monitored by both in vitro (spore germination) and in vivo tests (on apple seedlings). There was good correlation between the in vitro and in vivo results. Baseline sensitivity was established with 95 bulk isolates from Europe between 1995 and 1998 which showed a narrow sensitivity range‐factor of up to 17 between the least and most sensitive isolates. Monitoring of populations originating from trifloxystrobin‐treated and untreated orchards between 1995 and 1999 showed only sensitive isolates and no performance deficiencies were reported. Data also show that trifloxystrobin is not cross‐resistant to anilinopyrimidines and triazoles, but is cross‐resistant to kresoxim‐methyl, another strobilurin which also inhibits the cytochrome bc1 enzyme complex at the Qo‐site in the respiration chain of fungal mitochondria (QoI inhibitors). Under experimental conditions from a specific trial site in Switzerland, where trifloxystrobin has been tested since 1994, isolates containing conidia resistant to Qo inhibitors were detected in 1997 and 1999. However no obvious performance deficiencies were reported. Nevertheless these results demonstrate a risk for the development of practical resistance in V inaequalis to Qo inhibitors and therefore a need to apply resistance management principles strictly.© 2002 Society of Chemical Industry
High level methoprene resistance in the mosquito Ochlerotatus nigromaculis (Ludlow) in Central California
Authors: Cornel Anthony J , Stanich Matthew A , McAbee Rory D , Mulligan F Steve 
Published: September 2002

AbstractIn the summer of 1998, failures of methoprene field applications to control the mosquito Ochlerotatus nigromaculis (Ludlow) were noticed in several pastures in the outskirts of Fresno, California, USA. Effective control with methoprene had been achieved for over 20 years prior to this discovery. Susceptibility tests indicated that the Fresno Oc nigromaculis populations had developed several thousand‐fold higher LC50 and LC90 tolerance levels to methoprene compared with methoprene‐naïve populations. The synergists piperonyl butoxide (PBO), S,S,S‐tributyl phosphorotrithioate and 3‐octylthio‐1,1,1‐trifluoro‐2‐propanone had little synergistic effect, suggesting that the mechanism of methoprene tolerance was not mediated by P450 monooxygenase or carboxylesterase enzyme degradation. As part of initiating a resistance management strategy, partial reversion back to methoprene susceptibility was achieved in a resistant population after six consecutive applications of Bacillus thuringiensis israelensis Goldberg & Marga coupled with two oil and two pyrethrum + PBO applications.© 2002 Society of Chemical Industry
Field‐simulator studies of insecticide resistance to dimethylcarbamates and pyrethroids conferred by metabolic‐ and target site‐based mechanisms in peach‐potato aphids, Myzus persicae (Hemiptera: Aphididae)
Authors: Foster Stephen P , Denholm Ian , Devonshire Alan L 
Published: September 2002

AbstractA range of insecticides was applied at recommended application rates against populations of Myzus persicae (Sulzer) carrying various combinations of three insecticide resistance mechanisms (carboxylesterase‐based metabolic resistance and two target‐site mechanisms, known as MACE and kdr), supported on either Chinese cabbage or potatoes in field simulator cages. Patterns of response were similar on both host species. MACE conferred extreme resistance to pirimicarb and triazamate (dimethylcarbamate insecticides). The kdr mechanism was associated with resistance to lambda‐cyhalothrin, cypermethrin and deltamethrin (pyrethroid insecticides). A mixture of pirimicarb plus lambda‐cyhalothrin was only effective against M persicae not carrying kdr or carrying kdr and low carboxylesterase‐based resistance. None of the insecticides tested was effective against M persicae carrying both MACE and kdr resistance. The implications of these findings for the formulation of control strategies, based on regular monitoring of resistance genotype frequencies, are discussed.© 2002 Society of Chemical Industry
Antibacterial activity of bactenecin 5 fragments and their interaction with phospholipid membranes
Authors: Tokunaga Yoko , Niidome Takuro , Hatakeyama Tomomitsu , Aoyagi Haruhiko 
Published: September 2002

AbstractBactenecin 5 (Bac 5) is an antibacterial 43mer peptide isolated from bovine neutrophils. It consists of an Arg‐rich N‐terminal region and successive repeats of Arg‐Pro‐Pro‐Ile (or Phe). We synthesized Bac 51‐23 and several related peptides to clarify the roles these regions play in antibacterial activity. An assay of antibacterial activity revealed that such activity requires the presence of Arg residues at or near the N‐terminus, as well as a chain length exceeding 15 residues. None of the peptides exhibited haemolytic activity. Polyproline II‐like CD curves were observed for most of the peptides. Measurements of the membrane perturbation and fusion indicated that the perturbation and fusogenic activities of the peptides were, generally, parallel to their antibacterial activities. Amino acid substitution in the repeating region had some effect on antibacterial activity. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd.
Configuration and racemization determination of cysteine residues in peptides by chiral derivatization and HPLC: application to oxytocin peptides
Authors: Szabó Sándor , Szókán Gyula , Khlafulla Abdulrahim M. , Almás Márta , Kiss Csaba , Rill Attila , Schön István 
Published: September 2002

AbstractAn improved RP‐HPLC method was developed for the determination of the configuration and stereochemical purity of cysteine residues in peptides. The method consists of oxidation of cysteine and cystine residues to cysteic acid, followed by hydrolysis and pre‐column chiral derivatization with Val‐Marfey's reagent. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd.
Synthesis of linear and comb‐like peptide constructs containing up to four copies of a T cell epitope and their capacity to stimulate T cells
Authors: Mack Jürgen , Falk Kirsten , Rötzschke Olaf , Walk Tilmann , Strominger Jack L. , Jung Günther 
Published: September 2002

AbstractPolypeptide constructs containing up to four copies of the T cell epitope 306‐318 of influenza virus haemagglutinin have been synthesized on solid phase. Between the copies, a non‐natural PEG‐based spacer amino acid has been introduced. The oligomeric epitopes were analysed by RP‐HPLC and ES‐MS. The arrangement of the epitopes within the peptide constructs was either linear or comb‐like. The proliferative response in a T helper cell assay induced by these oligomerized epitopes has been tested, showing that the linearly arranged epitopes are more effective than the comb‐like oligomers. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd.
Amino acid modifications in the wild type sequence p53 232–240 overcome the poor immunogenicity of this self tumour epitope
Authors: Baratin Myriam , Kayibanda Michèle , Ziol Marianne , Romieu Raphäelle , Briand Jean‐Paul , Guillet Jean‐Gérard , Viguier Mireille 
Published: September 2002

AbstractA major limitation in antigen‐specific cancer vaccines is that most of the tumour antigens that are potent candidates for broad applicability originate from self proteins. The peptides presented by tumour cells are derived from tissue‐specific differentiation proteins, from proteins altered by genetic mutation or by non mutated proteins that are normally silent in most adult tissues. As a consequence, T‐cell responses elicited against those antigens are rather weak. Several data showed that amino acid modifications could enhance the immunogenicity of such antigens by priming T‐cells that have escaped central tolerance based on a poor avidity. In this regard, this strategy could be powerful for inducing immunity against tumours. The present report focuses on the murine wild type epitope p53 232–240 that is poorly immunogenic. It shows that substitution of the two cysteine residues by serine or amino butyric acid derivatives and substitution of the two methionine residues by norleucine residues resulted in enhanced stability of the MHC/peptide complex. The MHC binding affinity of analogue peptides was enhanced between 10 and 100 fold. They were also potent immunogens, stronger than was the original wild type epitope; T‐cell responses were increased up to 50 times. Moreover, the effector T‐cells elicited by three of these peptides cross reacted with the natural epitope. These observations have important implications for strategies that use the modified‐peptide epitope. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Study of the yeast Saccharomyces cerevisiae F1FO‐ATPase ε‐subunit
Authors: Aznar‐Derunes Céline , Manigand Claude , Picard Philippe , Dautant Alain , Goetz Michael , Schmitter Jean‐Marie , Precigoux Gilles 
Published: September 2002

AbstractThe yeast Saccharomyces cerevisiae F1FO‐ATPase ε‐subunit (61 residues) was synthesized by the solid‐phase peptide approach under both acidic and basic strategies. Only the latter strategy allowed us to obtain a pure ε‐subunit. The strong propensity of the protein to produce few soluble dimeric species depending on pH has been proved by size‐exclusion chromatography, electrophoresis and mass spectrometry. A circular dichroism study showed that an aqueous solution containing 30% trifluoroethanol or 200 mM sodium dodecyl sulphate is required for helical folding. In both solvents at acidic pH, the ε‐subunit is soluble and monomeric. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Transient rate matrix determination for the complex system
Authors: Qamber Isa S. 
Published: September 2002

AbstractThis paper presents new techniques dealing with the reliability of complex systems. A power station reliability assessment model is used to illustrate the approach. Before calculating the state transient probabilities for the overall electrical power plant, the failure and repair rates of each generating unit are needed. These two coefficients can form a transition rate matrix, which represents each generator. To form the overall system a special technique is required. In the present study the direct‐differentiation and the Kronecker algebra methods are used to form the overall transition rate matrix, which represents the whole system. Forming the overall system is the first part (major part) of the current study. The second part is to calculate the state transient probabilities, following the Adams method. Two electric power plants from the State of Bahrain are analysed as examples. Copyright © 2001 John Wiley & Sons, Ltd.
Arsenosugar identification in seaweed extracts using high‐performance liquid chromatography/electrospray ion trap mass spectrometry
Authors: Miguens‐Rodriguez Maria , Pickford Russell , Thomas‐Oates Jane E. , Pergantis Spiros A. 
Published: September 2002

AbstractThe development of analytical techniques suitable for providing structural information on a wide range of elemental species is a growing necessity. For arsenic speciation a variety of mass spectrometric techniques, mainly inductively coupled plasma mass spectrometry (ICP‐MS) and electrospray tandem mass spectrometry (ES‐MS/MS) coupled on‐line with high‐performance liquid chromatography (HPLC), are in use. In this paper we report the identification of arsenic species present in samples of marine origin (seaweed extracts) using ES ion trap mass spectrometry (IT) multistage mass spectrometry (MSn). Both reversed‐phase and anion‐exchange HPLC have been coupled on‐line to ES‐ITMS. Product ion scans with multiple stages of tandem MS (MSn; n = 2–4) were used to acquire diagnostic data for each arsenosugar. The spectra contain structurally characteristic fragment ions for each of the arsenosugars examined. In addition it was observed that upon successive stages of collision‐induced dissociation (CID) a common product ion (m/z 237) was formed from all four arsenosugars examined. This product ion has the potential to be used as an indicator for the presence of dimethylated arsenosugars (dimethylarsinoylribosides). The HPLC/ES‐ITMSn method developed allows the sensitive identification of arsenosugars present in crude seaweed extracts without the need for extended sample preparation. In fact, sample preparation requirements are identical to those typically employed for HPLC/ICP‐MS analysis. Additionally, the resulting product ions are structurally diagnostic of the arsenosugars examined, and tandem mass spectra are reproducible and correspond well to those obtained using other low‐energy CID techniques. As a result, the HPLC/ES‐ITMSn approach minimises the potential for arsenic species misidentification and has great potential as a means of overcoming the need for characterised standards. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of the saliva from patients with oral cancer by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Chen Yu‐Chie , Li Tzu‐Ying , Tsai Ming‐Fei 
Published: September 2002

AbstractUsing matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS), this study analyzed the saliva obtained from patients with oral cancer and compared these mass spectra with those obtained from healthy controls. Saliva without pre‐treatment was mixed directly with a sinapinic acid matrix. Alpha‐amylase (57 kDa) dominated the high mass range in the MALDI mass spectra of the saliva from healthy subjects, but the peak was suppressed for patients with oral cancer and was replaced by a peak at m/z 66 k in the spectra of patients' samples (15 out of 20). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) with in‐gel tryptic digestion combined with matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) was employed to characterize this 66‐kDa protein, which was thus shown to be albumin. However, based on SDS‐PAGE results, concentrations of both alpha‐amylase and albumin in patients' saliva were significantly higher than those in healthy subjects. This discrepancy was shown to be due to MALDI suppression effects due to the albumin. MALDI‐MS thus has potential as a possible rapid diagnostic screening tool for oral cancer. Copyright © 2002 John Wiley & Sons, Ltd.
In situ analysis of solvents on breath and blood: a selected ion flow tube mass spectrometric study
Authors: Wilson Paul F. , Freeman Colin G. , McEwan Murray J. , Milligan Daniel B. , Allardyce Randall A. , Shaw Geoffrey M. 
Published: September 2002

AbstractWe report measurements of residual vapour levels of xylenes and trimethylbenzenes, present following a floor re‐surfacing procedure, using the technique of selected ion flow tube mass spectrometry (SIFT‐MS). A subject exposed to controlled amounts of xylene and mesitylene was monitored by direct breath exhalation over a 4‐hour period after exposure to the volatile organic compounds (VOCs) had stopped. The headspace gases above 5‐mL blood samples taken over this period were also monitored. The decays of the solvent levels with time were fitted to a two‐compartment model with residence times for xylene and mesitylene of 0.37 h and 0.38 h, respectively (compartment one) and 2.5 h and 2.8 h, respectively (compartment two). Copyright © 2002 John Wiley & Sons, Ltd.
Small angle neutron scattering measurements of synthetic polymer dispersions in matrix‐assisted laser desorption/ionization matrixes
Authors: Bauer Barry J. , Byrd H. C. Michelle , Guttman Charles M. 
Published: September 2002

AbstractSmall angle neutron scattering (SANS) is used to measure the size and the dispersion of synthetic polymers in matrix‐assisted laser desorption/ionization (MALDI) matrixes. Deuterated polystyrene (DPS) and dithranol in tetrahydrofuran were deposited by electrospray onto a substrate for small angle neutron scattering (SANS) measurements. DPS with 6050 and 27 000 g mol−1 molecular masses were prepared at mass fractions between 0.2 and 6%. All samples contained large aggregates of DPS with characteristic sizes >200 Å that represent hundreds of aggregated chains. Samples of mass fraction 1% DPS (6050 g mol−1) in 2,5‐dihydroxybenzoic acid, all‐trans‐retinoic acid, and sinapinic acid also have large zero angle scattering characteristic of large aggregates. The morphological trend obtained from the SANS measurements of the DPS aggregate size in the four matrixes is dithranol > 2,5‐dihydroxybenzoic acid > all‐trans‐retinoic acid > sinapinic acid. These measurements indicate that DPS in dithranol exhibits the most strong phase separation, while DPS in sinapinic acid shows considerable domain mixing. All of these matrixes produce MALDI signal strength under appropriate conditions, suggesting that strong phase separation does not diminish the signal‐to‐noise ratio. DPS (188 000 g mol−1) in biphenyl was used as a model system of a matrix that can be either crystalline or amorphous. SANS data shows that above the biphenyl melting point, a conventional solution is formed that has molecularly dispersed polymers. Upon crystallization, there is strong aggregation of the DPS into large domains. Therefore, the crystalline matrixes commonly used in MALDI measurements probably cause large aggregations of polymers to be present during the MALDI process. Published in 2002 by John Wiley & Sons, Ltd.
Generic fast gradient liquid chromatography/tandem mass spectrometry techniques for the assessment of the in vitro permeability across the blood–brain barrier in drug discovery
Authors: Chu Inhou , Liu Fei , Soares Anthony , Kumari Pramila , Nomeir Amin A. 
Published: September 2002

AbstractRapid, generic gradient liquid chromatography/tandem mass spectrometry (LC/MS/MS) assays, designed to accelerate sample analyses, have been developed to keep pace with the productivity of advanced synthetic procedures. In this study, LC/MS/MS was combined with an in vitro, cell‐based, blood–brain barrier (BBB) model to evaluate the potential of new chemical entities (NCEs) to cross the BBB. This in vitro assay provides the permeability of discovery compounds across a monolayer of a primary culture of bovine brain microvessel endothelial cells in a fraction of the time that is required for in vivo studies (brain/plasma concentrations), using only 2 mg of the compound. The results are consistent with in vivo brain/plasma concentration ratio data. Copyright © 2002 John Wiley & Sons, Ltd.
Poly(amide ester)s from 2,6‐pyridinedicarboxylic acid and ethanolamine derivatives: identification of macrocycles by matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Chevallier Pascale , Soutif Jean‐Claude , Brosse Jean‐Claude , Brunelle Alain 
Published: September 2002

AbstractThe influence of the polycondensation pathway and aminoalcohol structure was investigated in the synthesis of poly(amide ester)s by polytransesterification from ethyl pyridine‐2,6‐dicarboxylate and 2‐amino‐2‐methylpropan‐1‐ol or the corresponding bis(amide alcohol), or by polycondensation from the diacid dichloride. Both linear and cyclic structures were identified by steric exclusion chromatography (SEC) and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS). Transesterification led to cyclic oligomers (macrocycles) with 2–14 pyridine moities in the ring whereas polycondensation from the diacid dichloride gave low molecular weight polymers (Mn = 1800) and macrocycles. Copyright © 2002 John Wiley & Sons, Ltd.
A theorem for UGAS and ULES of (passive) nonautonomous systems: robust control of mechanical systems and ships
Authors: Fossen Thor. I. , Loría Antonio , Teel Andrew 
Published: September 2002

AbstractThe main contribution of this paper is a theorem to guarantee uniform global asymptotic stability (UGAS) and uniform local exponential stability (ULES) for a class of nonlinear non‐autonomous systems which includes passive systems. These properties (and a uniform local Lipschitz condition) guarantee robustness of stability while weaker properties, like uniform global stability plus global convergence, do not. Our main result is then used in the tracking control problem of mechanical systems and ships. We use an adaptive backstepping design and prove UGAS of the closed‐loop tracking error system, in particular, we obtain that both the tracking and parameter estimation errors converge uniformly globally to zero. Copyright © 2001 John Wiley & Sons, Ltd.