bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and determination of the major constituents in traditional Chinese medicinal plant Polygonum multiflorum thunb by HPLC coupled with PAD and ESI/MS
Authors: Yi Tao , Leung Kelvin S. Y. , Lu Guang‐Hua , Zhang Hao , Chan Kelvin 
Published: March 2007

AbstractAn HPLC–PAD–MS method has been developed for the qualitative and quantitative analysis of the major chemical constituents in Polygonum multiflorum Thunb. Chromatographic separation was conducted on an Alltima C18 column using water:acetonitrile:acetic acid as the mobile phase. Altogether nine compounds of various classes, including stilbene glucosides, anthraquinone glucosides and anthraquinone derivates, were identified by online ESI/MS. Their identities were ascertained by comparison with data derived from the literature and/or standard compounds. Five components were quantified by HPLC–PAD and the method was fully validated. All the linear regressions were acquired with R2 > 0.99 and the quantification limits (with a signal‐to‐noise ratio of 3) ranged from 0.63 and 1.57 ng. Repeatability was evaluated by intra‐ and inter‐day assays and RSD value was within 2.47%. Recovery studies for the quantified compounds were found to be within the range 96.32–102.53% with RSD less than 2.35%. The overall procedure is rapid and reproducible and is considered suitable for qualitative and quantitative analysis of a large number of samples. Copyright © 2007 John Wiley & Sons, Ltd.
Structural control of rubber modified thermoplastic as produced by the mass process
Authors: Freeguard Graham F. 
Published: March 2007

AbstractCommercially important polyblends can be produced by a mass process which proceeds via the dispersion of a rubber solution phase. During the process several distinct stages can be identified and structural variation of the final polymer is achieved by controlled agitation. The relationship between the nature and structure of the dispersed phase and the mechanical properties of the polyblend are illustrated and discussed in the light of current theories of impact enhancement.
Preparation and properties of polymer lattices polymerised without surfactants
Authors: Ono Hiroshi , Saeki Hideo 
Published: March 2007

AbstractSeries of polystyrene and polymethyl methacrylate latex dispersions have been prepared in the absence of any surfactant using potassium persulphate as an initiator. The latex particles are stabilised by the electrical repulsion generated by the sulphate groups which are covalently linked to the polymer molecules and are not removed by dialysis. The effects of polymerisation temperature, monomer concentration and initiator concentration on the ultimate particle size and conversion were investigated for these two series of lattices. The modal diameters of these lattices were found to be in the range of 530 to 1550 nm for polystyrene lattices, and 140 to 270 nm for polymethyl methacrylate lattices. The surface charge densities were calculated from conductometric titration results for polymethyl methacrylate lattices and were found to increase almost linearly with increase of the concentration of potassium persulphate used.
Assessment of the high temperature performance of phenolic—phosphate resin composites
Authors: Hodd Kenneth A. , Reader Alan L. , Redfarn Cyril A. 
Published: March 2007

AbstractThe thermal stability of a phenolic‐phosphate resin, prepared by the transesterification of triphenyl phosphate and resorcinol and cured with hexamethylene tetraamine, has been compared with that of a conventional phenolic resin. Thermogravimetric analysis (TGA) of the resins, in air, demonstrated that the phenolic‐phosphate resin had the superior thermal resistance. Accordingly, to assess the performance of phenolic‐phosphate resins as thermally stable binders in composites, long‐term heating ageing studies at 250°C were carried out on asbestos‐filled moulded test specimens. The results of these tests were less welldefined than the TGA results, for the phenolic composite had the higher flexural strength (108.5 MNm−2) initially compared with 56.7 MNm−2 for the phenolic‐phosphate composite. However, after 1000 h heating at 250°C neither system retained a useful level of flexural strength, although the phenolic‐phosphate composite (18.35 MNm−2) was stronger than the phenolic composite (5.4 MNm−2).
A light scattering study of some solutions of triblock copolymers
Authors: Brown Bernar D. L. 
Published: March 2007

AbstractThree samples of polystyrene‐polybutadiene‐polystyrene block copolymers have been studied by means of the light scattering technique in several solvents. The light scattering measurements indicate the degree of heterogeneity of the samples. Further measurements which were made on the least heterogeneous of the samples in a solvent closely matching the refractive index of the centre block suggest that the two types of polymer are largely separate. In this case the angular intensity variation of the light scattering can be interpreted in terms of the scattering obtained from a “dumb‐bell” configuration.
Some aspects of the emulsion polymerisation of vinyl acetate
Authors: Stannett Vivian , Klein Andrew , Litt Morton 
Published: March 2007

AbstractThe present status of work on the mechanism of the emulsion polymerisation of vinyl acetate initiated by potassium persulphate is critically reviewed. In addition, some new data illustrating the effect of adding electrolytes is presented. The polymerisation proceeds by a mechanism different from that of most vinyl monomers. In particular, the rates are approximately zero order on monomer from 20 to 85% conversion with only a minor dependence on the soap concentration and the number of particles. The dependence of the rate on the initiator concentration varies with different investigators from 0.5–1.0 order. The results are discussed in terms of various current theories and an attempt is made to rationalise them in a reasonable way.
Chloromodified ethylene propylene diene polymers
Authors: Schoen Löwhardt A. A. , van Raaijen Wim , van'T Wout Johan W. F. 
Published: March 2007

AbstractThe heterogeneous gas/solid chlorination of various ethylene propylene diene polymers has been studied at temperatures between 0 and 75°C at conditions which are unfavourable for free radical reactions. The structure of the chloromodified polymers has been cleared by n.m.r. and from these data a chlorination mechanism has been proposed. An equation for the diffusion controlled chlorination rate has also been given as well as some cure characteristics and mechanical properties of allylic chlorine containing chloromodified ethylene propylene dicyclopentadiene polymers.
Electroinitiated emulsion polymerisation of vinyl acetate. I. The mechanism of initiation
Authors: Tidswell Bryan M. , Train Andrew W. 
Published: March 2007

AbstractVinyl acetate has been shown to polymerise during the electrolysis of its aqueous acidified emulsion. The stabilisation of the emulsion is difficult and sodium salts of ethoxylated fatty alcohols have been used as emulsifier. Polymerisation occurs only within a narrow, low pH range. Percentage conversion and molecular weight show a maximum at about pH = 1. Below this value, acid hydrolysis of monomer interferes with the polymerisation whilst at higher values a change in the electrode process may occur. Polymerisation is considered to occur through the presence of hydrogen radicals adsorbed on the mercury cathode.
Electroinitiated emulsion polymerisation of vinyl monomers. III. Homopolymerisation and copolymerisation with vinyl acetate
Authors: Tidswell Bryan M. , Train Andrew W. 
Published: March 2007

AbstractOf the monomers studied, vinyl acetate and vinyl n‐caproate are the only ones capable of electroinitiated homopolymerisation in aqueous acidic emulsion. Water solubility does not appear to be the overriding consideration. Activity of the radical would seem to be most important. Copolymerisation with monomers not undergoing homopolymerisation in this system produces good yields of copolymers low in vinyl acetate concentration.
Dynamic mechanical properties of polypentenamers with pendant ionic groups and their hydrogenated derivatives
Authors: Sanui K. , Macknight William J. 
Published: March 2007

AbstractDynamic mechanical properties of substituted polypentenamers having thioglycolate side groups and their hydrogenated derivatives have been studied. Methyl esters, acids and salts were investigated at two concentrations, 5.5 mole (%) and 9.2 mole (%). In the un‐hydrogenated derivatives one principal relaxation, labelled β, exists in the temperature range from‐160 to 100°C. This relaxation arises from microbrownian segmental motion accompanying the glass transition. Its temperature is affected by the concentration of substituent but not the chemical nature of the substituent. A ‘rubbery plateau’ region exists in the acid and salt derivatives and in the latter the salt groups act as reinforcing fillers in this plateau region, consistent with the ionic domain model for their structures.In the hydrogenated derivatives, three relaxations occur in the temperature range from −160 to 120°C and these are labelled α, β, and γ in order of decreasing temperature. The α relaxation arises from motions associated with the crystal phase except in the case of the 9.2 mole (%) sodium salt derivatives where it arises from motions occurring within ionic domains. The β relaxation arises from microbrownian segmental motions accompanying the glass transition, and the γ relaxation arises from localised motions which may involve both amorphous and crystalline phase components.
The effects of inorganic borates on the burning of PVC
Authors: Cowan J. , Manley T. R. 
Published: March 2007

AbstractThe flammability of flexible poly(vinyl chloride) sheet containing barium, calcium and zinc borates, alone and in combination with antimony oxide, was measured by BS2782‐508C and ASTM D2863. A statistical comparison of these tests was made. Barium and calcium borates, with or without antimony oxide, had little or no effect on flame retardancy, but zinc had a synergistic effect with antimony oxide.The value of these inorganic borates in reducing smoke is compared using the Stanton Redcroft F.T.B. Unit, an attachment of the manufacturer's Critical Oxygen Index (C.O.I.) test. This test consists of passing the smoke from the C.O.I, test directly into a chamber where the maximum smoke density is measured using a light source and photocell assembly. Formulations containing zinc borate and antimony oxide gave the least smoke.The advantages of zinc borate in flame retardant poly(vinyl chloride) were found to be offset by inferior mechanical and electrical properties and heat stability, unless small amounts of epoxidised oil were added. The degree of hydration of the zinc borate was not critical.
Studies of heterocyclic polymers. V. poly (1, 3′‐benzobis (iminopyrrolenones))
Authors: Hodd Kenneth A. , Hussein Mohammed 
Published: March 2007

AbstractThe synthesis of dimethyl‐2, 5‐dicyanoterephthalate from 2,5‐dibromo‐p‐xylene and its conversion to 1,3′‐benzobis (iminopyrrolenone) are reported.1,3 ‐Benzobis (N‐phenyliminopyrrolenone) was prepared by reaction of 1,3′‐benzobis (iminopyrrolenone) with aniline. The product was a bright yellow crystalline solid which was also formed when dimethyl‐2,5‐dicyanoterephthalate was condensed with aniline under suitable conditions.Poly (1,3′‐benzobis (iminopyrrolenones)) were synthesised by the condensation of 1,3′ ‐benzobis (iminopyrrolenone) with aromatic diamines and with 1,6‐diaminohexane at high temperatures in dimethyl sulphoxide. The degrees of polymerisation of the polymers obtained were low, as judged by the completeness of the condensation reaction.Thermogravimetric analyses of these polymers in air showed that they have 10% weight‐loss temperatures in the range 420 to 520°C, for the polymers prepared from aromatic diamines, and of 350°C for the polymer derived from 1,6‐diaminohexane. The insoluble, intractable nature of these polymers precluded a thorough study of their structure.
Polymers in contact lens applications. V. Design and calibration of a technique for “dissolved” oxygen permeability measurements
Authors: Ng Chiong O. , Tighe Brian J. 
Published: March 2007

AbstractThe importance of ‘in vitro’ measurements of ‘dissolved’ oxygen permeabilities of polymers for use in contact with the cornea (as in contact lenses) is discussed and a description given of the design and calibration of a technique suitable for the measurement of oxygen permeabilities in both the ‘dissolved’ (i.e. the transport of oxygen across a membrane separating two aqueous phases) and ‘gaseous’ (in which the membrane separates two gas phases) states.By the use of a thin film of hydrophobic but highly oxygen permeable polymer even very fragile high water content hydrogels can be supported and studied. Sources of error are discussed together with the conflicting literature values for the oxygen permeability of poly(2‐hydroxyethyl methacrylate) hydrogels. On the basis of the present work a value of 75 × 10−10 cm3 (STP) mm cm−2 s−1 cm−1 Hg is suggested for the ‘dissolved’ oxygen permeability of this polymer at 25 °C.
Relationship between substituent effect and aromaticity – Part III: naphthalene as a transmitting moiety for substituent effect
Authors: Krygowski Tadeusz M. , Palusiak Marcin , Płonka Anna , Zachara‐Horeglad Joanna E. 
Published: March 2007

AbstractMolecular geometry of 10 isomeric nitronaphtholate ions (excludingperi‐ andortho‐type substituted systems), 1‐ and 2‐naphtholate ions, 1‐ and 2‐nitronaphthalene,meta‐ andpara‐nitrophenolate, phenolate, and nitrobenzene were optimized at B3LYP/6‐311G** level of approximation. Substituent effect stabilization energy (SESE), geometry‐based aromaticity index HOMA, magnetism‐based indices NICS, NICS(1), NICS(1)zz, and parameters characterizing Bond Critical Points (BCP) (ρ, ▿2ρ, ellipticity, ion/cov) of the Bader AIM theory were used to characterize transmitting properties for substituent effect through the naphthalene moiety. It results from our study that the studied systems could be clearly divided into two groups, (i) apara‐type group, where the intramolecular charge transfer between theπ‐electron donating andπ‐electron accepting substituents can be described by canonical forms with charge separation (as in the case ofpara‐nitrophenolate) and (ii) ameta‐type group, where this transfer requires using canonical forms with double charge separation (as in the case ofmeta‐nitrophenolate). Copyright © 2007 John Wiley & Sons, Ltd.
Investigation of N‐carbamoylamino acid nitrosation by {NO + O2} in the solid‐gas phase. Effects of NOx speciation and kinetic evidence for a multiple‐stage process
Authors: Lagrille Olivier , Taillades Jacques , Boiteau Laurent , Commeyras Auguste 
Published: March 2007

AbstractNitrosation of N‐carbamoylamino acids (CAA) by gaseous NO + O2, an interesting synthetic pathway to amino acid N‐carboxyanhydrides (NCA), alternative to the phosgene route, was investigated on N‐carbamoyl‐valine either in acetonitrile suspension or solventless conditions, and compared to the classical nitrosating system NaNO2 + CF3COOH (TFA), the latter being quite less efficient in terms of either rate, stoichiometric demand, or further tractability of the product. The rate and efficiency of the NO + O2 reaction mainly depends on the O2/NO ratio. Evaluation of the contribution of various nitrosating species (N2O3, N2O4, HNO2) through stoichiometric balance showed the reaction to be effected mostly by N2O3 for O2/NO ratios below 0.3, and by N2O4 for O2/NO ratios above 0.4. The relative contribution of (subsequently formed) HNO2 always remains minor. Differential scanning calorimetry (DSC) monitoring of the reaction in the solid phase by either HNO2 (from NaNO2 + TFA), gaseous N2O4 or gaseous N2O3, provides the associated rate constants (ca. 0.1, 2 and 108 s−1 at 25°C, respectively), showing that N2O3 is by far the most reactive of these nitrosating species. From the DSC measurement, the latent heat of fusion of N2O3, 2.74 kJ · mol−1 at −105 °C is also obtained for the first time. The kinetics was investigated under solventless conditions at 0°C, by either quenching experiments or less tedious, rough calorimetric techniques. Auto‐accelerated, parabolic‐shaped kinetics was observed in the first half of the reaction course, together with substantial heat release (temperature increase of ca. 20°C within 1–2 min in a 20‐mg sample), followed by pseudo‐zero‐order kinetics after a sudden, important decrease in apparent rate. This kinetic break is possibly due to the transition between the initial solid‐gas system and a solid‐liquid‐gas system resulting from water formation. Overall rate constants increased with parameters such as the specific surface of the solid, the O2/NO ratio, or the presence of moisture (or equivalently the hydrophilicity of the involved CAA), however without precise relationship, while the last two parameters may directly correlate to the increasing acidity of the medium. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis of poly(L‐lysine)‐graft‐polyesters through Michael addition and their self‐assemblies in aqueous solutions
Authors: Xu Ning , Du Fu‐Sheng , Li Zi‐Chen 
Published: March 2007

AbstractA series of poly(L‐lysine)s grafted with aliphatic polyesters, poly(L‐lysine)‐graft‐poly(L‐lactide) (PLy‐g‐PLLA) and poly(L‐lysine)‐graft‐poly(ϵ‐caprolactone) (PLy‐ g‐PCL), were synthesized through the Michael addition of poly(L‐lysine) and maleimido‐terminated poly(L‐lactide) or poly(ϵ‐caprolactone). The graft density of the polyesters could be adjusted by the variation of the feed ratio of poly(L‐lysine) to the maleimido‐terminated polyesters. IR spectra of PLy‐g‐PCL showed that the graft copolymers adopted an α‐helix conformation in the solid state. Differential scanning calorimetry measurements of the two kinds of graft copolymers indicated that the glass transition temperature of PLy‐g‐PLLA and the melting temperature of PLy‐g‐PCL increased with the increasing graft density of the polyesters on the backbone of poly(L‐lysine). Circular dichroism analysis of PLy‐g‐PCL in water demonstrated that the graft copolymer existed in a random‐coil conformation at pH 6 and as an α‐helix at pH 9. In addition, PLy‐g‐PCL was found to form micelles to vesicles in an aqueous medium with the increasing graft density of poly(ϵ‐caprolactone). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1889–1898, 2007
Photolytic transformation of aryl benzobisoxazole and aryl benzobisthiazole compounds into carbon dioxide
Authors: So Ying‐Hung , Bell Bruce M. , Albers Dave R. 
Published: March 2007

AbstractSolid‐state aryl benzobisoxazole and aryl benzobisthiazole compounds photolyzed in the presence of O2 undergo cleavage to produce benzobisoxazoles (or benzobisthiazoles), benzonitriles, and benzamides. A very high percentage of the carbon atoms in one of the two segments from chain cleavage are converted to CO2. This very unusual observation has been carefully confirmed by gas chromatography/mass spectroscopy analysis of the gaseous components in the photolysis vessel before and after photolysis, labeling experiments, and the correlation of the mass reduction in photolyzed polymers and the amount of CO2 that evolves. The rate of CO2 generation is used to compare the relative photostability of aryl benzobisoxazole and aryl benzobisthiazole model compounds, films, and fibers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1868–1877, 2007
Fluorinated copolymers and terpolymers based on vinylidene fluoride and bearing sulfonic acid side‐group
Authors: Sauguet L. , Ameduri B. , Boutevin B. 
Published: March 2007

AbstractThe radical co‐ and terpolymerization of perfluoro(4‐methyl‐3,6‐dioxaoct‐7‐ene) sulfonyl fluoride (PFSVE) with 1,1‐difluoroethylene (or vinylidene fluoride, VDF or VF2), hexafluoropropene (HFP), chlorotrifluoroethylene (CTFE), and bromotrifluoroethylene (BrTFE) is presented. Although PFSVE could not homopolymerize under radical initiation, it could be copolymerized in solution under a radical initiator with VDF, while its copolymerizations with HFP or CTFE led to oligomers in low yields. The terpolymerizations of PFSVE with VDF and HFP, with VDF and CTFE, or with VDF and BrTFE also led to original fluorinated terpolymers bearing sulfonyl fluoride side‐groups. The conditions of co‐ and terpolymerization were optimized in terms of the nature and the amount of the radical initiators, of the nature of solvents (fluorinated or nonhalogenated), and of the initial amounts of fluorinated comonomers. The different mol % contents of comonomers in the co‐ and terpolymers were assessed by 19F NMR spectroscopy. A wide range of co‐ and terpolymers containing mol % of PFSVE functional monomer ranging from 10 to 70% was produced. The kinetics of copolymerization of VDF with PFSVE enabled to assess the reactivity ratios of both comonomers: rVDF = 0.57 ± 0.15 and rPFSVE = 0.07 ± 0.04 at 120 °C. The thermal and physicochemical properties were also studied. Moreover, the glass transition temperatures (Tgs) of poly(VDF‐co‐PFSVE) copolymers containing different amounts of VDF and PFSVE were determined and the theoretical Tg of poly(PFSVE) homopolymer was deduced. Then, the hydrolysis of the SO2F into SO3H function was investigated and enabled the synthesis of fluorinated copolymers bearing sulfonic acid functions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1814–1834, 2007
Efficacy of dexamethasone injection for acute bronchiolitis in hospitalized children: A randomized, double‐blind, placebo‐controlled trial
Authors: Teeratakulpisarn Jamaree , Limwattananon Chulaporn , Tanupattarachai Sureeporn , Limwattananon Supon , Teeratakulpisarn Somrak , Kosalaraksa Pope 
Published: March 2007

AbstractControversy over the efficacy of systemic corticosteroids for acute bronchiolitis initiated this study. We conducted a randomized, double‐blind, placebo‐controlled trial to examine the efficacy of single dexamethasone injection for the treatment of acute bronchiolitis in young hospitalized children. The study, performed at the pediatric wards of a University Hospital and its affiliated hospital in Thailand, included 174 previously healthy children under 2 years of age, hospitalized with acute bronchiolitis. Each child received either a single intramuscular injection of 0.6 mg/kg dexamethasone or a placebo in addition to regular management. The primary outcome was the time from study entry to resolution of respiratory distress, determined by a clinical score derived from the respiratory rate, occurrence of wheezing, chest retraction, and oxygen saturation. Survival analysis using the Kaplan–Meier method and a log‐rank test were performed. A single‐dose, dexamethasone injection versus placebo produced a significant: (1) decrease in the time needed for resolution of respiratory distress (hazard ratio 1.56; 95% CI, 1.14–2.13; P = 0.005), (2) decrease in the mean duration of symptoms of 11.8 hr (95% CI, 3.9–19.7; P = 0.004), (3) decrease in the mean duration of oxygen therapy of 14.9 hr (95% CI, 5.3–24.4; P = 0.003), and (4) decrease in the mean length of hospital stay of 13.4 hr (95%CI, 2.6–24.2; P = 0.02). In conclusion, a single injection of dexamethasone yielded a significant clinical benefit for the treatment of previously healthy, young children hospitalized with acute bronchiolitis. Pediatr Pulmonol. 2007; 42:433–439. © 2007 Wiley‐Liss, Inc.