bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atom transfer radical polymerization of n‐butyl acrylate catalyzed by CuBr/N‐(n‐hexyl)‐2‐pyridylmethanimine
Authors: Zhang Huiqi , Van Der Linde Rob 
Published: October 2002

AbstractThe homogeneous atom transfer radical polymerization (ATRP) of n‐butyl acrylate with CuBr/N‐(n‐hexyl)‐2‐pyridylmethanimine as a catalyst and ethyl 2‐bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different solvents such as toluene, anisole, N,N‐dimethylformamide, and 1‐butanol were linear throughout the reactions, and the experimental molecular weights increased linearly with increasing monomer conversion and were very close to the theoretical values. These, together with the relatively narrow molecular weight distributions (polydispersity index ∼ 1.40 in most cases with monomer conversion > 50%), indicated that the polymerization was living and controlled. Toluene appeared to be the best solvent for the studied ATRP system in terms of the polymerization rate and molecular weight distribution among the solvents used. The polymerization showed zero order with respect to both the initiator and the catalyst, probably because of the presence of a self‐regulation process at the beginning of the reaction. The reaction temperature had a positive effect on the polymerization rate, and the optimum reaction temperature was found to be 100 °C. An apparent enthalpy of activation of 81.2 kJ/mol was determined for the ATRP of n‐butyl acrylate, corresponding to an enthalpy of equilibrium of 63.6 kJ/mol. An apparent enthalpy of activation of 52.8 kJ/mol was also obtained for the ATRP of methyl methacrylate under similar reaction conditions. Moreover, the CuBr/N‐(n‐hexyl)‐2‐pyridylmethanimine‐based system was proven to be applicable to living block copolymerization and living random copolymerization of n‐butyl acrylate with methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3549–3561, 2002
Spectroscopic characterization and preparation of low molecular, water‐soluble chitosan with free‐amine group by novel method
Authors: Nah Jae‐Woon , Jang Mi‐Kyeong 
Published: October 2002

AbstractLow molecular, water‐soluble chitosan (LMWSC) with a free amine group was prepared by the novel salts‐removal method described in this study. A weight‐average molecular weight and degree of deacetylation (DDA) of LMWSC were determined by viscometry and Kina titration, resulting in 18,579 Da and 93% DDA, respectively. In the Fourier transform infrared spectroscopic, 1H NMR, and 13C NMR spectra the absorption band by the carboxyl group derived from lactic acid and the impurities formed in the enzymatic process disappeared or were significantly lower than that of the control chitosan. Also, from the 1H NMR and 13C NMR spectra the empirical value for the area ratio of the proton and carbon corresponds nearly to its theoretical values. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum identified the difference in the two adjacent peaks as 161. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3796–3803, 2002
Synthesis and in vitro degradation of poly(N‐vinyl‐2‐pyrrolidone)‐based graft copolymers for biomedical applications
Authors: Brunius Carl F. , Edlund Ulrica , Albertsson Ann‐Christine 
Published: October 2002

AbstractThis work is devoted to the design of a novel family of hydrosoluble biomaterials: poly(N‐vinyl‐2‐pyrrolidone) (PVP)‐based graft copolymers. A synthesis route has been elaborated in which ω‐functionalized PVP is prepared via chain‐transfer radical polymerization, end‐group modified, and subsequently grafted onto a polyhydroxylated backbone, typically dextran or poly(vinyl alcohol). The resulting graft copolymer biomaterials are designed for use in various biomedical applications, particularly as materials with a stronger potential for plasma expansion than already existing products have. The graft copolymers are potentially degradable because the PVP grafts are connected to the polyol backbone via a hydrolytically labile carbonate or ester linkage. The degradation of the graft copolymers was performed in vitro over a period of 6 weeks. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3652–3661, 2002
Correlation between the tacticity and content of labile nondefect structures in poly(vinyl chloride)
Authors: Martinez Gerardo , Millan Jose Luis 
Published: October 2002

AbstractThe content of mm isotactic triads taking the GTTG− conformation for samples of poly(vinyl chloride) (PVC) fractions of different tacticities was measured through a substitution reaction with sodium benzenethiolate. This quantity changed linearly with the ratio of rmmmrx to mmmmrx (x = m or r), as accurately determined by 13C NMR spectroscopy. In a comparison of this correlation and that obtained between the thermal degradation stability and overall isotactic content, as studied previously, some novel evidence for the GTTG− conformation of a few mm triads, termini of isotactic sequences no shorter than one heptad as specific labile sites in PVC, was obtained. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3944–3949, 2002
Synthesis and characterization of hyperbranched polyimides with good organosolubility and thermal properties based on a new triamine and conventional dianhydrides
Authors: Chen Huan , Yin Jie 
Published: October 2002

AbstractA triamine monomer, 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB), was synthesized from phloroglucinol and 4‐chloronitrobenzene, and it was successfully polymerized into soluble hyperbranched polyimides (HB PIs) with commercially available dianhydrides: 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA). Different monomer addition methods and different monomer molar ratios resulted in HB PIs with amino or anhydride end groups. From 1H NMR spectra, the degrees of branching of the amino‐terminated polymers were estimated to be 0.65, 0.62, and 0.67 for 6FDA–TAPOB, ODPA–TAPOB, and BTDA–TAPOB, respectively. All polymers showed good thermal properties with 10% weight‐loss temperatures (T10's) above 505 °C and glass‐transition temperatures (Tg's) of 208–282 °C for various dianhydrides. The anhydride‐terminated HB PIs showed lower T10 and Tg values than their amino‐terminated counterparts. The chemical conversion of the terminal amino or anhydride groups of the 6FDA‐based polyimides into an aromatic imido structure improved their thermal stability, decreased their Tg, and improved their solubility. The HB PIs had moderate molecular weights with broad distributions. The 6FDA‐based HB PIs exhibited good solubility even in common low‐boiling‐point solvents such as chloroform, tetrahydrofuran, and acetone. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3804–3814, 2002
Reverse atom transfer radical solution polymerization of methyl methacrylate under pulsed microwave irradiation
Authors: Cheng Zhenping , Zhu Xiulin , Chen Gaojian , Xu Wenjian , Lu Jianmei 
Published: October 2002

AbstractThe reverse atom transfer radical polymerization (RATRP) of methyl methacrylate (MMA) was successfully carried out under pulsed microwave irradiation (PMI) at 69 °C with N,N‐dimethylformamide as a solvent and with azobisisobutyronitrile (AIBN)/CuBr2/tetramethylethylenediamine as an initiation system. PMI resulted in a significant increase in the polymerization rate of RATRP. A 10.5% conversion for a polymer with a number‐average molecular weight of 34,500 and a polydispersity index of 1.23 was obtained under PMI with a mean power of 4.5 W in only 52 min, but 103 min was needed under a conventional heating process (CH) to reach a 8.3% conversion under identical conditions. At different [MMA]0/[AIBN]0 molar ratios, the apparent rate constant of polymerization under PMI was 1.5–2.3 times larger than that under CH. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3823–3834, 2002
Effects of organophilic clay on the solvent‐maintaining capability, dimensional stability, and electrochemical properties of gel poly(vinylidene fluoride) nanocomposite electrolytes
Authors: Liu H. J. , Hwang J. J. , Chen‐Yang Y. W. 
Published: October 2002

AbstractFour quaternary alkyl ammonium salts were used in an organophilic procedure, performed on montmorillonite clay, and resulted in intercalation in dimethylformamide (DMF) or ethylene carbonate (EC)/propylene carbonate (PC) as a cosolvent between poly(vinylidene fluoride) (PVdF) and the organophilic clay. An examination using X‐ray diffraction revealed that PVdF entered galleries of montmorillonite clay, and it exhibited exfoliation and intercalation phenomena when it was analyzed with transmission electron microscopy. Gel PVdF nanocomposite electrolyte materials were successfully prepared by the addition of the appropriate percentages of DMF or PC/EC as a cosolvent, organophilic clay, and lithium perchlorate to PVdF. The maximum ionic conductivity was 1.03 × 10−2 S/cm, and the materials exhibited better film formation, solvent‐maintaining capability, and dimensional stability than electrolyte films without added organophilic clays. The results of cyclic voltammetry testing showed that the addition of the organophilic clays significantly enhanced the electrochemical stability of the polymer electrolyte system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3873–3882, 2002
π‐Conjugated oligomers containing tropone in the main chain: Synthesis, characterization, and optical properties
Authors: Takagi Koji , Nishikawa Yukimi , Nishioka Naomi , Kunisada Hideo , Yuki Yasuo 
Published: October 2002

AbstractThe synthesis and characterization of tropone‐containing π‐conjugated oligomers were investigated. Two kinds of oligomers [1,4‐phenylene type (4a–4e) and 2,5‐thienylene type (5)] were successfully obtained by the Wittig polycondensation technique, in which the tropone content could be controlled by the monomer feed ratio for the 1,4‐phenylene‐type oligomers. The absorption maximum blueshifted and the emission intensity decreased with an increase in the tropone content in the oligomers. The emissive color could be tuned by the selection of the aromatic ring; that is, 4a–4e emitted orange‐yellow light and 5 emitted either orange‐yellow or red light according to the excitation wavelength. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3927–3937, 2002
Spatially heterogeneous dynamics during physical aging far below the glass transition temperature
Authors: Thurau Courtney T. , Ediger M. D. 
Published: October 2002

AbstractPhysical aging experiments after a deep quench were performed via an optical photobleaching technique to examine the evolution of the segmental dynamics of a polystyrene melt far below the glass transition temperature (Tg). Both rotational and translational diffusion measurements of dilute tetracene probes dispersed in the polymer matrix were monitored as a function of aging time. Following a temperature quench from Tg +2 °C deep into the glass (with isothermal aging temperatures ranging from Tg −15 to Tg −67 °C), either rotational or translational diffusion measurements were performed for up to 105 s of elapsed time. During this period, relaxation times for both observables were retarded by at least a factor of 3. Rotational and translational observables respond differently to the initial temperature quench and to the subsequent isothermal aging. These differences likely indicate that the dynamics responsible for physical aging in a quenched glass are spatially heterogeneous. Immediately following the quench, regions of faster mobility age toward equilibrium faster than regions of slower mobility. These findings compliment recent aging experiments close to Tg and bolster the conclusion that heterogeneous dynamics are important for the accurate description of physical aging. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2463–2472, 2002
Polypeptide‐based nanocomposite: Structure and properties of poly(L‐lysine)/Na+‐montmorillonite
Authors: Krikorian Vahik , Kurian Mary , Galvin Mary E. , Nowak Andrew P. , Deming Timothy J. , Pochan Darrin J. 
Published: October 2002

AbstractThe feasibility of constructing polymer/clay nanocomposites with polypeptides as the matrix material is shown. Cationic poly‐L‐lysine · HBr (PLL) was reinforced by sodium montmorillonite clay. The PLL/clay nanocomposites were made via the solution‐intercalation film‐casting technique. X‐ray diffraction and transmission electron microscopy data indicated that montmorillonite layers intercalated with PLL chains coexist with exfoliated layers over a wide range of relative PLL/clay compositions. Differential scanning calorimetry suggests that the presence of clay suppresses crystal formation in PLL relative to the neat polypeptide and slightly decreases the PLL melting temperature. Despite lower crystallinity, dynamic mechanical analysis revealed a significant increase in the storage modulus of PLL with an increase in clay loading producing storage modulus magnitudes on par with traditional engineering thermoplastics. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2579–2586, 2002
Preliminary measurements on methane content in permafrost, Central Yakutia, and some experimental data
Authors: Brouchkov Anatoli , Fukuda Masami 
Published: October 2002

AbstractThe concentration of methane in air bubbles within permafrost was sampled from both alluvial deposits and ice wedges in Eastern Siberia. The values of methane concentration were as high as 6000 ppmv in both frozen soil and ice wedges. The anti‐proportional relationship between methane and carbon dioxide concentration values in permafrost was examined. Values of methane concentration in ice wedges are smaller than those in frozen soils. Values of total volumetric air content, water content and density were obtained by on‐the‐spot investigation. Increases of methane and carbon dioxide concentrations were detected in accordance with increases of water content of frozen soil. Geologically older permafrost contained higher values of methane concentration than younger permafrost. Samples of frozen soils were incubated at temperature −5°C in order to study possible methane production. A slow production in different soils was observed, although the experiments took a long time before measurable changes of methane content could be found. The rate of methane production decreases in time; therefore, long‐term forecasts of methane content in frozen soils are still problematical. Copyright © 2002 John Wiley & Sons, Ltd.
Acute renal failure in cystic fibrosis: Association with inhaled tobramycin therapy
Authors: Hoffmann Ingrid M. , Rubin Bruce K. , Iskandar Samy S. , Schechter Michael S. , Nagaraj Shashi K. , Bitzan Martin M. 
Published: October 2002

AbstractWe describe a 20‐year‐old patient with cystic fibrosis who developed acute nonoliguric renal failure associated with inhaled tobramycin. Clinical evaluation and renal biopsy findings were consistent with aminoglycoside‐induced changes. Renal failure due to inhaled aminoglycosides has not been previously reported. The incidence may rise, however, with the increased use of this treatment modality. Measurable tobramycin levels due to inhalational therapy with conventional dosing in the reported patient indicate that the drug can be systemically absorbed, and renal tubular toxicity may occur. Pediatr Pulmonol. 2002; 34:375–377. © 2002 Wiley‐Liss, Inc.
Construction and characterization of β‐lactoglobulin chimeras
Authors: Kobayashi Takuji , Ikeguchi Masamichi , Sugai Shintaro 
Published: October 2002

AbstractAt neutral pH, equine β‐lactoglobulin (ELG) is monomeric, whereas bovine β‐lactoglobulin (BLG) exists as a dimer. To understand the difference in the oligomerization properties between ELG and BLG, three mutants of ELG (LP, I, and LPI) were constructed by substituting amino acids responsible for important interactions at the dimer interface of BLG into ELG. The mutant LP has an AB loop mutation (S34A/E35Q), the mutant I has an I strand mutation (G145M/R146H/V147I/Q148R/I149L/V150S/P151F/D152N/L153P) and the mutant LPI includes both the LP and I mutations. The far‐ and near‐UV CD spectra of the three mutants are similar to that of the wild‐type ELG, indicating that the secondary and the tertiary structures of ELG are not significantly affected by the mutations. Ultracentrifuge analysis shows that all three mutants are monomeric at neutral pH, suggesting that the protein sequences in the AB loop and I strand of BLG alone cannot support dimerization of ELG. Thus, structural differences must exist between ELG and BLG that prevent the ELG mutants from forming the same interactions as BLG at the dimer interface. Proteins 2002;49:297–301. © 2002 Wiley‐Liss, Inc.
Activation of octopaminergic receptors by essential oil constituents isolated from aromatic plants: possible mode of action against insect pests
Authors: Kostyukovsky Moshe , Rafaeli Ada , Gileadi Carina , Demchenko Nataly , Shaaya Eli 
Published: October 2002

AbstractAs a result of screening a large number of essential oils from Israeli aromatic plants and their biologically active constituents, we isolated two oils with high activity against several stored‐product insects. In this study the effect of these compounds on the acetylcholinesterase and the octopamine systems in insects was studied in order to elucidate their mode of action. Inhibition of acetylcholinesterase activity in vitro was evident only at high concentrations (10−3 M) and could not account effectively for the low‐dose mortality for some stored‐product insects observed in vivo. However, the essential oil constituents were found to cause a significant increase in the levels of the intracellular messenger, cyclic AMP of abdominal epidermal tissue in the model insect, Helicoverpa armigera Hübn. The effect was significant even at low, physiological concentrations (10−8 M) when tested directly on abdominal epidermal tissue preparations in vitro. This intracellular response was found to resemble closely the significant increases in the levels of the cyclic AMP of abdominal epidermal tissue due to treatment with the neurotransmitter/neuromodulator, octopamine. Subsequent treatment with the octopaminergic antagonist, phentolamine, effectively inhibited the cyclic AMP levels induced by essential oil treatment, indicating possible competitive activation of octopaminergic receptors by essential oil constituents.© 2002 Society of Chemical Industry
Production of patchouli mild mosaic virus resistant patchouli plants by genetic engineering of coat protein precursor gene
Authors: Kadotani Naoto , Ikegami Masato 
Published: October 2002

AbstractPatchouli (Pogostemon cablin (Blanco) Benth), an aromatic crop which yields an essential oil, is widely cultivated in South‐east Asia. Patchouli mild mosaic virus (PaMMV) infects patchouli plants and causes decrease in leaf biomass and essential oil yield. Transgenic patchouli plants with PaMMV coat protein precursor (CP‐P) gene have been produced by Agrobacterium‐mediated transformation. PaMMV CP‐P gene integration into the patchouli genome was confirmed by the PCR method and by Southern blot analysis. The transformants were estimated to contain one to three copy genes using Southern blot analysis. The transformant with three copy genes was tested for the resistance to PaMMV by artificially inoculating plants grown in an environmentally controlled cabinet, and this transformant was found to be highly resistant to PaMMV. The transgenic patchouli plant with PaMMV CP‐P gene should provide valuable material for protecting against PaMMV.© 2002 Society of Chemical Industry
Antiinflammatory investigation of some species of Mikania
Authors: Suyenaga E. S. , Reche E. , Farias F. M. , Schapoval E. E. S. , Chaves C. G. M. , Henriques A. T. 
Published: October 2002

AbstractMikania laevigata Schultz Bip. ex Baker, M. involucrata Hook. et Arn. and M. hirsutissima DC. (Asteraceae), commonly occurring in the southern Brazilian State of Rio Grande do Sul, were submitted to biological tests to evaluate their potential antiinflammatory activity. Decoctions from the leaves and stems were analysed by the induced rat paw oedema and pleurisy models. The animals were treated orally with different decoction doses. In the induced rat paw oedema test, the animals treated with leaf decoctions from M. laevigata (200 mg/ kg) and M. involucrata (50 mg/ kg) presented an oedema inhibition of 81.56% and 81.67%, respectively, 3 h after the administration of the phlogistic agent. Leaf decoctions from M. hirsutissima (400 mg/ kg) did not show such an activity. Stem decoctions displayed lower antiinflammatory activity when compared with the same doses and response time of the leaf decoctions for all analysed species. In the pleurisy assay, leaf decoctions from M. laevigata (400 mg/ kg) and M. involucrata (200 mg/ kg) inhibited leukocyte migration to the pleural exudate by 28.26% and 54.35%, respectively. Copyright © 2002 John Wiley & Sons, Ltd.
Antioxidative components of Psoralea corylifolia (Leguminosae)
Authors: Haraguchi Hiroyuki , Inoue Junji , Tamura Yukiyoshi , Mizutani Kenji 
Published: October 2002

AbstractA meroterpene and four flavonoids were isolated from the seeds of Psoralea corylifolia as antioxidative components. Their structures were elucidated by spectral data and identified as bakuchiol (1), bavachinin (2), bavachin (3), isobavachin (4) and isobavachalcone (5). In particular, meroterpene 1 and flavonoids 4 and 5 showed broad antioxidative activities in rat liver microsomes and mitochondria. They inhibited NADPH‐, ascorbate‐, t‐BuOOH‐ and CCl4‐induced lipid peroxidation in microsomes. They also prevented NADH‐dependent and ascorbate‐induced mitochondrial lipid peroxidation. Bakuchiol (1) was the most potent antioxidant in microsomes and the inhibition of oxygen consumption induced by lipid peroxidation was time‐dependent. Furthermore, bakuchiol (1) protected human red blood cells against oxidative haemolysis. These phenolic compounds in P. corylifolia were shown to be effective in protecting biological membranes against various oxidative stresses. Copyright © 2002 John Wiley & Sons, Ltd.
Modulation of serum phosphatases activity in Swiss albino mice against gamma irradiation by Mentha piperita Linn.
Authors: Samarth R. M. , Goyal P. K. , Kumar Ashok 
Published: October 2002

AbstractThe modulatory influence of mentha oil (Mentha piperita Linn.) against a lethal dose (8.0 Gy) of gamma irradiation on the activities of serum phosphatases in Swiss albino mice was studied at various post‐irradiation intervals between 6 h and 30 days. Mentha oil (40 μL/animal/day) given orally for 3 consecutive days prior to whole‐body irradiation (8.0 Gy) showed a modulation of activity of serum phosphatases. The values of acid phosphatase activities were significantly higher in the irradiated groups throughout the experiment compared with the mentha treated unirradiated animals. However, the acid phosphatase activity of mentha treated irradiated animals showed a significant decline over untreated irradiated animals at all autopsy intervals, which attained the normal value on day 5. On the contrary, a marked decrease in serum alkaline phosphatase activity was noted in both irradiated groups but in the mentha treated irradiated group the values of alkaline phosphatase activity were found to be significantly higher than the respective control during the period of study being normal at day 5 post‐irradiation and onwards. Copyright © 2002 John Wiley & Sons, Ltd.