bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sequence dependence of oxidation of some repeating pentapeptide sequences of elastin with electrolytically generated Mn(III): synthesis, kinetics and mechanistic study
Authors: Gowda D. Channe , Gowda B. K. Kempe , Rangappa K. S. 
Published: August 2002

AbstractThe repeating sequence of elastin, valylprolylglycylvalylglycine (VPGVG), its permutation pentamer glycylvalylglycylvalylproline (GVGVP), and its more hydrophobic pentamer glycylphenylalanylglycylvalylproline (GFGVP) were synthesized by classical solution‐phase methods and characterized. The kinetics of the oxidation of these pentapeptides (PP) by Mn(III) was studied in the presence of sulphate ions in acidic medium at 25 °C. The reaction was followed spectrophotometrically at λmax = 500 nm. A first‐order dependence of rate on both [Mn(III)] and [PP] was observed. The rate is independent of concentration of the reduction product, Mn(II) and hydrogen ions. Effects of varying dielectric constant of the medium and addition of anions such as sulphate, chloride and perchlorate were studied. Activation parameters were evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of PP with Mn(III) in the rate‐limiting step is suggested. An apparent correlation was noted between the rate of oxidation and the hydrophobicity of these sequences where increased hydrophobicity results in an increased rate of oxidation. Further, it was observed that the pentamers with Pro as C‐terminus are more susceptible to oxidation than the pentamer with Gly as C‐terminus. Copyright © 2001 John Wiley & Sons, Ltd.
Formation and polymorphic phase transitions of crystalline inclusion compounds between 2,2′‐bis(9‐hydroxy‐9‐fluorenyl)biphenyl host and acetone guest
Authors: Ibragimov Bakhtiyar T. , Beketov Kayrat M. , Weber Edwin , Seidel Jürgen , Sumarna Omay , Makhkamov Kabul K. , Köhnke Kurt 
Published: August 2002

AbstractThe 2,2′‐bis(9‐hydroxy‐9‐fluorenyl)biphenyl host compound (1) was found to form various crystalline inclusion compounds with acetone depending on the crystallization conditions or on the method of preparation (inclusion of acetone vapour, co‐crystallization from solution). In order to understand and control the formation of these pseudopolymorphic phases regarding potential uses, single crystals of the existing phases (two 1:2 and one 1:1 compound) were prepared, their structures were solved by single‐crystal x‐ray diffraction (XRD) analysis and the desolvation and phase transformations were studied using simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC) and variable‐temperature powder XRD. The results explain the inclusion and desolvation behaviour and also clarify the observed, apparently accidental formation of a 1:1 or 1:2 inclusion compound at ambient temperature. Copyright © 2001 John Wiley & Sons, Ltd.
Study of the decarboxylation mechanism of fluorobenzoic acids by strong N‐bases
Authors: Gierczyk Błażej , Wojciechowski Grzegorz , Brzezinski Bogumił , Grech Eugeniusz , Schroeder Grzegorz 
Published: August 2002

AbstractThe kinetics of the decarboxylation reactions of pentafluorobenzoic and tetrafluorobenzoic acids by various N‐bases were studied using 19F NMR spectroscopy. The rate constants of these reactions are dependent on the structure of the fluorinated acid and the pKa values of the N‐bases. Pentafluorobenzoic acid is decarboxylated about two orders of magnitude faster than tetrafluorobenzoic acid. With increasing pKa values of the protonated N‐bases these reactions became much slower. These results suggested that the rate‐determining step of the studied reactions is the attack of the conjugated acid (protonated N‐base) on carboxylate anion. Copyright © 2001 John Wiley & Sons, Ltd.
New silanization coating for DNA fragment analysis by capillary electrophoresis
Authors: Jung Ho Jin , Bae Young Chan 
Published: August 2002

AbstractWe propose a new coating technique for fused silica capillaries using silanization with trimethylchlorosilane and diethylamine as a mediating agent in DNA separation using capillary electrophoresis. The proposed coating technique is simple and stable at a high pH. Capillaries coated by the new preparation method give excellent reproducibility for DNA fragment analysis with a good relative standard deviation of less than 0.7% for 150 runs and good stability at pH 8.2. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1405–1420, 2002
Effect of the tail‐group length and degree of polymerization on the order parameter of side‐chain liquid‐crystalline polymethacrylates containing phenylbenzoate mesogenic groups
Authors: Barmatov E. B. 
Published: August 2002

AbstractThe orientation of the side‐chain liquid‐crystalline polymers (LCP) containing phenylbenzoate mesogenic groups in the magnetic field was examined with 2H NMR spectroscopy. The influence of the degree of polymerization as well as the length of the methylene tail group (n = 1–4) have been established. The decrease of the order parameter S of the LCPs with an increased length of the tail group was found. The order parameter S of LCPs does not depend on the degree of polymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2044–2048, 2002
Synthesis of multicyclic and grafted polystyrenes
Authors: Lepoittevin Bénédicte , Hemery Patrick 
Published: August 2002

AbstractWell‐defined multicyclic polystyrenes are prepared in two steps. The first step is the preparation of a cyclic difunctional polystyrene by the reaction of α,ω‐dilithiopolystyrene chains with 1,3‐bis(phenylethenyl)benzene. Then, this product is covalently grafted to poly(chloromethylstyrene) chains leading to the formation of a high molar mass product containing linear and cyclic parts. As a model reaction and to optimize the previous reaction, a study of coupling of the linear difunctional model polystyrene with poly(chloromethylstyrene) is performed leading to grafted polystyrene. The grafted products are analyzed by size‐exclusion chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and liquid chromatography at the exclusion‐adsorption transition point. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2723–2730, 2001
Incorporation of a photochromic hinge in a rodlike polypeptide and its influence on dielectric and optical properties
Authors: Williams Alveda J. , Gupta Vinay K. 
Published: August 2002

AbstractA hinged, photoresponsive polypeptide (PAzP) was prepared and the effect of the photochromic hinge on the dielectric and photoisomerization behavior of the polymer in solution was probed. Polymerization of N‐carboxyanhydride of γ‐benzyl‐L‐glutamate was carried out with two different bifunctional photochromic amine initiators: di[(mercaptoethylamine)‐methylpropanamide]azobenzene (DMMPAB) and diaminoazobenzene (DAAB). Careful structural comparison of the polymers revealed that the basicity of the initiator plays a key role in determining the shape and structure of the polymer. Specifically, the use of a novel initiator DMMPAB prepared by the addition of flexible aliphatic amine substituents onto DAAB resulted in a hinged polymer (PAzP1), in which a single photochromic hinge was located within the polymer chain (Mw ∼ 36 kDa). In contrast, direct initiation with DAAB resulted in a polymer (PAzP2) in which the photochromic moiety was preferentially near the terminus of the polymer chain (Mw ∼ 21 kDa) and the polymer possessed a significant degree of asymmetry. Dielectric spectroscopy revealed that, in spite of a higher molecular weight, PAzP1 had a lower rotational relaxation time (2.72 μs) in solution than that of PAzP2 (4.41 μs). The residual dipole moment for the hinged PAzP1 was also smaller than that observed for PAzP2. The hinged polypeptide PAzP1 prepared from DMMPAB showed uniform photoisomerization between cis and trans states. However, the presence of flexible aliphatic amine substituents on DMMPAB caused the rate of isomerization of PAzP1 to be similar to the initiator DMMPAB. Optical characterization revealed that heterogeneity in the structure of PAzP2 was manifested as nonuniform rates of photoisomerization and thermal relaxation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2759–2773, 2001
High‐pressure rheology and viscoelastic scaling predictions of polymer melts containing liquid and supercritical carbon dioxide
Authors: Royer Joseph R. , DeSimone Joseph M. , Khan Saad A. 
Published: August 2002

AbstractHigh‐pressure rheological behavior of polymer melts containing dissolved carbon dioxide (CO2) at concentrations up to 6 wt % were investigated using a high‐pressure extrusion slit die rheometer. In particular, the steady shear viscosity of poly(methyl methacrylate), polypropylene, low‐density polyethylene, and poly(vinylidene fluoride) with dissolved CO2were measured for shear rates ranging from 1 to 500 s−1and under pressure conditions up to 30 MPa. The viscosity of all samples revealed a reduction in the presence of CO2with its extent dependent on CO2concentration, pressure, and the polymer used. Two types of viscoelastic scaling models were developed to predict the effects of both CO2concentration and pressure on the viscosity of the polymer melts. The first approach utilized a set of equations analogous to the Williams–Landel–Ferry equation for melts between the glass‐transition temperature (Tg) andTg+ 100 °C, whereas the second approach used equations of the Arrhenius form for melts more than 100 °C aboveTg. The combination of these traditional viscoelastic scaling models with predictions forTgdepression by a diluent (Chow model) were used to estimate the observed effects of dissolved CO2on polymer melt rheology. In this approach, the only parameters involved are physical properties of the pure polymer melt that are either available in the existing literature or can be measured under atmospheric conditions in the absence of CO2. The ability of the proposed scaling models to accurately predict the viscosity of polymer melts with dissolved high‐pressure CO2were examined for each of the polymer systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3055–3066, 2001
Methanol vapor‐induced morphology and current–voltage characteristic changes in a cast‐coated nafion film/interdigitated microarray electrode
Authors: Umeda Minoru , Ojima Hiroyuki , Mohamedi Mohamed , Uchida Isamu 
Published: August 2002

AbstractMethanol vapor‐induced membranous changes in a cast‐coated Nafion thin film were studied through current–voltage (I–V) characteristics with an interdigitated microarray (IDA) electrode and atomic force microscopy (AFM). The obtained I–V curves showed that the as‐prepared Nafion film was stable under humidified nitrogen gas; however, the I–V profile dramatically changed with exposure to methanol vapor. Next, the morphology of the film was compared before and after methanol exposure with AFM images. On the basis of our observations, we found that the as‐prepared film had an irregularly complicated microstructure, whereas the structure became homogeneous in appearance after 30 min of exposure to methanol gas. The alternating‐current conductivity data, showing almost the same magnitude before and after exposure, strongly suggested that the I–V profile shift was based on a change in an electrode reaction mechanism induced by a change in the junction at the Nafion/IDA electrode interface. Furthermore, the methanol vapor‐pre‐exposed Nafion was stable for further exposure to methanol vapor, water vapor, or both. With the stabilized film used in combination with the IDA electrode, a reversible change in the magnitude of the current was observed when the methanol/water vapor ratio was varied. This indicated that the electrode reaction had good reproducibility after the treatment. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1103–1109, 2002
Clay‐reinforced polyamide: Preferential orientation of the montmorillonite sheets and the polyamide crystalline lamellae
Authors: Varlot K. , Reynaud E. , Kloppfer M. H. , Vigier G. , Varlet J. 
Published: August 2002

AbstractIntercalated and exfoliated nanocomposites were prepared by the extrusion and injection of polyamide‐6 and highly swollen or slightly swollen montmorillonite, respectively. The microstructure of pure compounds was characterized. The basal spacing was more homogeneous in swollen montmorillonite than in nontreated montmorillonite. This was attributed to the presence of a surfactant. Surfactant crystallites were observed in swollen montmorillonite and in the nanocomposites. Their distribution is discussed. The nanocomposites exhibited anisotropic properties attributed to the orientation of the montmorillonite sheets. The preferential orientation of the montmorillonite sheets was studied in detail by small‐angle X‐ray scattering (SAXS). It was found to be related to the injection direction. An average distance between two sheets was also measured from the SAXS spectra. The crystallographic state of the polyamide matrix was then analyzed. The orientation of the polymer lamellae relative to the montmorillonite sheets is discussed. The orientation of the montmorillonite sheets and the polyamide lamellae is expected to play a major role in the mechanical properties of nanocomposites. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1360–1370, 2001
Morphology and electrical breakdown properties of LDPE‐polypropylene copolymer blends
Authors: Zhang Chao , Mori Tatsuo , Mizutani Teruyoshi , Ishioka Mitsugu , Cheng Yonghong 
Published: August 2002

AbstractIn this study, the specimens of low‐density polyethylene (LDPE) and blend polymers of LDPE and a random copolymer of ethylene and propylene were prepared by the blowing process and T‐die method. The differences in electrical breakdown properties and morphology between the specimens made by the two different methods were studied. It was found that the specimen made by the T‐die method had a higher electrical breakdown strength than the specimen made by the blowing process, except for the DC breakdown strength in some cases at 30 °C. The morphology of the specimens was investigated by means of the measurements of thermal shrinkage, infrared dichroism, and X‐ray diffraction. The specimen made by the T‐die method has a stronger orientation in both the crystalline and amorphous phases than the specimen made by the blowing process. The difference in morphology is supposed to be correlated with the difference in electrical breakdown properties between the specimens made by the two different methods. It was concluded that the electrical breakdown properties are strongly affected by the orientation of chains in the specimen. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1741–1748, 2001
Prediction of polyimide materials with high glass‐transition temperatures
Authors: Liang Taining , Yang Xiaozhen , Zhang Xiangyu 
Published: August 2002

AbstractThe prediction of chemical structures that possess higher glass‐transition temperatures (Tg's) is crucial for designing polyimides. Because of a lack of suitable parameters, several estimation methods cannot be used for this purpose. In this study, therefore, we used molecular dynamic simulation with the DREIDING II force field to predict Tg's for polyimides. Simulated results indicated a good agreement with experimental observations. A barrier analysis of the bridging bonds between moieties along the main‐chain backbone showed a correlation between Tg and the barrier height. This proved to be helpful in a preliminary selection before the molecular dynamic simulation for accelerating the process of research and development on new polyimides. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2243–2251, 2001
Considerations of psychosocial illness phase in cancer survival
Authors: Clipp Elizabeth C. , Hollis Donna R. , Cohen Harvey J. 
Published: August 2002

AbstractRarely are biomedical, clinical and psychosocial data considered simultaneously as influences on cancer patient outcomes. This study utilized medical record and interview data from 152 adult cancer patients with various tumor types in a model of survival estimation. Predictors included disease stage of the neoplasm (TNM stage), clinical functioning of the patient (Karnofsky performance status), and psychosocial demands of the disease course (psychosocial illness phase). Psychosocial illness phase captures developmental time phases of illness (i.e. ‘crisis’, ‘early chronic’, ‘late chronic’ and ‘terminal’), essentially locating patients along the disease course relative to treatment and treatment response. The analysis utilized the Kaplan–Meier (product‐limit) method to estimate stratum specific survival functions. Model comparisons employed the differences in the likelihood ratio chi‐squares between nested models, and Cox proportional hazard models assisted in explaining the effects of the predictors on survival times. Results indicate that psychosocial illness phase makes an independent contribution to survival time estimation (p<0.05) when all three dimensions are considered simultaneously. Copyright © 2001 John Wiley & Sons, Ltd.
Improvements of lung function in cystic fibrosis
Authors: Tauber Erich , Eichler Irmgard , Gartner Christian , Halmerbauer Gerhard , Götz Manfred , Rath Regina , Wojnarowski Claudia , Frischer Thomas 
Published: August 2002

AbstractImproved care for patients with cystic fibrosis (CF) has led to their improved survival. We analyzed retrospectively whether improvements in lung function (LF) could be detected in our CF patients over the decade 1980–1990. In 72 patients, 153 LF measurements were performed in their first year of life (1980–1991), and then 189 LF measurements were performed again in 60 of those patients during their sixth year of life (1987–1997). Regression analysis was performed on LF parameters at age 6 years.When adjusting for weight, height, gender, and LF in the first year of life, the date of subsequent measurement was positively associated with FEV1 (P < 0.01) and MEF50% (P < 0.05) and negatively with FRCpleth (P < 0.05).The proposed model predicts a child's FEV1 at age 6 to be 75% of predicted if born in 1980, but 108% of predicted when born in 1990. Improved CF care is the most likely explanation for this observation. Pediatr Pulmonol. 2002; 33:263–268. © 2002 Wiley‐Liss, Inc.
Irreversible airway obstruction in childhood asthma? A clinician's viewpoint
Authors: König Peter 
Published: August 2002

AbstractEven though childhood asthma is assumed to comprise reversible airway obstruction, some children develop irreversible airway obstruction (not reversed by a bronchodilator or corticosteroids); this may be due to inflammation that has caused remodeling. Lately, it has been claimed that in the absence of treatment with inhaled corticosteroids, most patients will develop progressive irreversible obstruction. Several studies culminating with the Childhood Asthma Management Program (CAMP) study, which was the first randomized placebo‐controlled prospective long‐term study designed to test for irreversible obstruction, did not show the development of such progressive irreversible obstruction. Nevertheless, deterioration in pulmonary function does occur in some patients, probably due to inadequate anti‐inflammatory treatment, and possibly also due to maintenance adrenergic treatment. Most previous studies concentrated on forced expiratory volume in 1 sec (FEV1), a test assessing mostly large airway obstruction. More studies are needed to investigate the presence of small airway obstruction. Pediatr Pulmonol. 2002; 33:307‐310. © 2002 Wiley‐Liss, Inc.
Anaerobic fitness in children with asthma: Adaptation to maximal intermittent short exercise
Authors: Counil F.‐P. , Karila C. , Varray A. , Guillaumont S. , Voisin M. , Préfaut C. 
Published: August 2002

AbstractNineteen asthmatic boys (aged 13.4 years, 25–75 percentile: 11.5–15.1 years) performed short bouts of maximal exercise (force‐velocity test) to test their anaerobic fitness and tolerance of maximal anaerobic exercise. Fourteen healthy boys (aged 13.9 years, 25–75 percentile: 11.6–15.7 years) matched for anthropometric characteristics including lean body mass (LBM), pubertal stage, and weekly physical activity formed a control group. The maximal anaerobic power (Wana) was measured during the force‐velocity test. The maximal oxygen uptake (V′) was assessed during a standard graded exercise test. Pre‐ and post‐exercise pulmonary function was measured by body plethysmography.The asthmatic children exhibited lower Wana than the control group (8.2 watt·kg−1 LBM, 25–75 percentile: 7.55–10.6 vs. 11.3 watt·kg−1 LBM, 25–75 percentile: 9.46–14.1; P = 0.01). V′ was also diminished in the asthmatic group (P = 0.01). Multiple stepwise regression models revealed that Tanner's score (P < 0.001) and the diagnosis of asthma (P < 0.01) were the best predictors of Wana.In conclusion, a diminished anaerobic fitness could contribute to the overall exercise limitation in asthmatic children. Pediatr Pulmonol. 2001; 31:198–204. © 2001 Wiley‐Liss, Inc.
Glucocorticoids and lung development in the fetus and preterm infant
Authors: Bolt Roel J. , van Weissenbruch M.M. , Lafeber H.N. , Delemarre‐van de Waal H.A. 
Published: August 2002

AbstractDuring the final prenatal period of fetal lung development in humans, important maturational processes occur, including the production of surfactant necessary to decrease surface tension at the air‐liquid interface of the alveoli. During early gestation, the glucocorticoid receptor is expressed in the fetal lung, and glucocorticoids stimulate the production of surfactant‐associated proteins and increase phospholipid synthesis by enhancing the activity of phosphatidylcholine. Other glucocorticoid‐induced effects may include stimulation of cell maturation and differentiation, inhibition of DNA synthesis, changes in interstitial tissue components, stimulation of antioxidant enzymes, and regulation of pulmonary fluid metabolism. Recently, it was suggested that glucocorticoids are also important in postnatal pulmonary development, and may be related to the development of neonatal lung disease in preterm infants. Surfactant deficiency that can be prevented by antenatal corticosteroid treatment causes infant respiratory distress syndrome and requires mechanical ventilation. Ventilation by itself or in combination with high levels of oxygen, fluid overload, pulmonary infections, sepsis, and air leak syndrome causes an acute pulmonary inflammatory reaction that may result in chronic lung disease or bronchopulmonary dysplasia. Glucocorticoids are effective in the treatment of chronic lung disease of prematurity and regulate the inflammatory response by the interaction with transcription factors such as nuclear factor κB and activated protein 1. Indeed, inflammatory cells and the levels of chemokines and cytokines in bronchoalveolar fluid decrease after dexamethasone treatment. However, treatment of fetuses and preterm infants with repeated and/or high doses of corticosteroids may have considerable long‐term side effects on somatic, brain, and lung growth. The difficult balance between short‐term gain and the possible long‐term side effects of glucocorticoids in preterms remains a difficult issue. Pediatr Pulmonol. 2001; 32:76–91. © 2001 Wiley‐Liss, Inc.