bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of a polyvinyl‐polyamino acid graft copolymer
Authors: Kimura Masatoshi , Egashira Toshiro , Nishimura Takao , Maeda Mizuo , Inoue Shohei 
Published: April 2003

AbstractA copolymer having reactive primary amino groups was synthesized by the copolymerization of styrene and N‐methyl‐N‐(4‐vinylphenethyl)ethylenediamine (1). Polymerization of N‐carboxy amino acid anhydrides (NCA's) of L‐alanine, γ‐benzyl‐L‐glutamate, or β‐benzyl‐L‐aspartate was initiated by the primary amino groups of this copolymer to give a novel polyvinyl‐polyamino acid graft copolymer.
13C NMR spectra of polymers made by ring‐opening polymerization of optically active and racemic 5,5‐dimethylbicyclo[2.2.1]hept‐2‐ene using metathesis catalysts
Authors: Ho Huu Thoi , Ivin Kenneth J. , Rooney John J. 
Published: April 2003

AbstractRing‐opened polymers of racemic and optically active 5,5‐dimethylbicyclo[2.2.1]hept‐2‐ene (6) (5,5‐dimethylnorbornene), with cis double bond contents of 0–100%, were prepared using various Mo‐, W‐, Re‐, Os‐, Ru‐, and Ir‐based olefin metathesis catalysts. The 13C NMR spectra of these polymers are interpreted in terms of TH, TT, HH, HT structures (T = tail, H = head, referring to the orientation of the methyl groups), also tt, tc, ct, cc structures (t = trans, c = cis double bonds), and m, r dyads (m = meso, r = racemic, referring to the relative configuration of adjacent cyclopentane rings in the chains). m/r splitting is observed for both the olefinic carbon (C3) and the adjacent ring carbon (C4) in the HH structures of the all‐trans polymer made from racemic monomer using RuCl3 as catalyst. All‐cis polymers are fully syndiotactic while all‐trans polymers have 58% isotactic (m) and 42% syndiotactic (r) dyads. A consistent set of substitution parameters is derived, the effect of two methyl substituents on the 13C chemical shifts being generally a little less than the sum of the effects of the individual substituents.
Triphenylphosphine catalyzed polymerization of maleic anhydride
Authors: Sahu Uma S. , Bhadani Suraj N. 
Published: April 2003

AbstractThe polymerization of maleic anhydride initiated by triphenylphosphine was investigated in acetic anhydride as well as in dimethylformamide. It was found that the polymer conversion increases with the increase of the concentration of monomer and initiator and the reaction temperature. It was also found that the rate of polymerization is higher in dimethylformamide than in acetic anhydride under the same set of experimental conditions. The apparent overall activation energy was found to be about 26,4kJ · mol‐1 and 39,8 kJ · mol‐1 in acetic anhydride and dimethylformamide, respectively. The polymerization rate depends upon the basicity of the initiator as well as on the dielectric constant of the solvent.
Constitution and properties of the coatings formed in situ by anodic oxidation of azophenols
Authors: Musiani Macro M. , Mengoli Giuliano , Pelli Beatrice , Folonari Carlo 
Published: April 2003

AbstractThree different azophenols were oxidized by both the system CuCl/O2 in pyridine and electrochemically (as coherent films) on Fe and Cu anodes in water/methanol mixtures. Products of the chemical and anodic oxidative coupling process are in any case very near each other. Poly(oxy‐4‐phenylazo‐1,2‐phenylene) and its 3‐allyl derivative are obtained from 4‐hydroxyazobenzene (1) and 3‐allyl‐4‐hydroxyazobenzene (2), respectively. The polymerization of 4‐hydroxy‐3,5‐dimethylazobenzene (3) mainly proceeds through elimination of the phenylazo group and formation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene). By oxidation of 2 at Cu anodes thin, adherent films having very good protective features are obtained in short electrolysis times.
Studies on syntheses and permeabilities of special polymer membranes, 52. Syntheses of p‐aminostyrene derivatives
Authors: Uragami Tadashi , Hachiya Hitoshi , Sugihara Mizuho 
Published: April 2003

AbstractFour kinds of p‐aminostyrene derivatives, i. e., methyl 4‐vinylsuccinanilate (9), ethyl 4‐vinyl‐sebacanilate (10), 4‐vinylsuccinanilic acid (11), and 4‐vinylsebacanilic acid (12), were synthesized and purely isolated. Their structures were identified by elementary analysis and by IR and 1H NMR spectroscopy.
Poly(organophosphazenes). Some aspects of synthesis, catalysis and characterization
Authors: Devadoss Eswaran , Nair Chethrappilly P. Reghunadhan 
Published: April 2003

AbstractThe catalytic effects of three typical metal salts, HgCl2, Hgl2, and ZnCl2, on the ringopening polymerization of (PNCl2)3/(PNCl2)4 in terms of the hard/soft concept for acids and bases were studied. The influence of the nature and the concentration of the initiators on the onset of gelation, the extent of polymerization, and on the polymer molecular weight is described. A new technique to follow the substitution reaction of chlorine in poly(dichlorophosphazene) by the 4‐methylphenoxy group is proposed.
Polymerization of lactams, 52. Anionic polymerization of 2‐pyrrolidone accelerated with CO2, part 1
Authors: Daniel Ladislav , Brožek Jiří , Roda Jan , Kŕlíček Jaroslav 
Published: April 2003

AbstractThe polymerization of 2‐pyrrolidone (1) initiated with its potassium salt (2‐oxo‐1‐pyrrolidinylpotassium) (2) and accelerated by the presence of CO2, was investigated. For the optimal concentration of 2 (≈5 mol‐%) and 0,5 mol‐% CO2, the most suitable polymerization temperature was found to the range between 45 and 55°C. The variation of CO2 concentration, 0,5 < [CO2] < 3 mol‐%, does not affect the polymerization yield under the optimal conditions. The similarity of the course of polymerization in the presence of CO2 directly introduced into the reaction mixture with that in the presence of isolated carboxylate of 1, is considered as a proof that CO2 is transformed into the active potassium carboxylate of 1. The order of polymerization reaction with respect to initiator was found to be ≈0,8 indicating the complexity of the reaction mechanism.
Oxydation du polypropylène atactique photocatalysée par des oxydes de zinc
Authors: Penot Gilles , Arnaud René , Lemaire Jacques 
Published: April 2003

AbstractThe chemical modification of atactic polypropylene samples by ZnO‐photocatalysed oxidation were investigated by IR spectrophotometry, chemical titration, and kinetic measurements, using different types of ZnO as photocatalysts. It was found that in pigmented samples, the formation and disappearance of the primary hydroperoxides are enhanced by the oxides. The inner filter effect of the pigment is antagonized by its photocatalytic effect. However, higher photostationary concentrations of hydroperoxides were observed in presence of ZnO. The main feature of the photocatalytic oxidation was found to be complete inhibition of Norrish type I and type II processes of the ketonic groups observed with type A and “active” ZnO; ketones and lactones accumulate in the matrix without any formation of acidic or unsaturated groups.
Anionic polymerization and copolymerization of 1,3‐ and 1,4‐diisopropenylbenzene
Authors: Lutz Pierre , Beinert Gérard , Rempp Paul 
Published: April 2003

AbstractThe anionic polymerization of 1,3 and 1,4‐diisopropenylbenzene (DIB) was found to be characterized by a rather low ceiling temperature and by rather strong differences in reactivity between the two double bonds. At low degrees of conversion the polymers formed are essentially linear and carry one pendant double bond per monomeric unit. Branching and crosslinking can occur only at higher conversion. 1,3‐DIB can be copolymerized anionically with α‐methylstyrene. Grafting reactions were carried out on polymer backbones with pendant unsaturated groups, using two different pathways. The occurence of coupling reaction can be avoided by a proper choice of experimental conditions.
Phase distribution chromatography (PDC) as a method for the investigation of polymers in solution, 3. Determination of narrow molecular weight distributions
Authors: Greschner Georg S. 
Published: April 2003

AbstractPhase distribution chromatography (PDC) is demonstrated to be a powerful method for the correct determination of narrow molecular weight distributions. This is shown by comparing the molecular weight distributions (MWD) of polystyrenes obtained from PDC measurements with those obtained by Baker‐Williams fractionation and by gel permeation chromatography. Four problems are formulated and analyzed which are closely connected with the calculation of the MWD from a measured PDC‐elution curve at temperatures below the theta point of the system. Thus, the theory of PDC outlined previously is tested.
Polymerization of lactams, 54. Anionic polymerization of 2‐pyrrolidone accelerated with CO2, part 3
Authors: Roda Jan , Brožek Jiří , Králíček Jaroslav , Tuzar Zdeněk 
Published: April 2003

AbstractIntrinsic viscosities in m‐cresol and weight average molecular weights, M̄w, were measured for samples of high molecular weight poly(2‐pyrrolidone) (poly (1)) prepared by anionic polymerization of 2‐pyrrolidone (1) accelerated with CO2. It was proved that the earlier found relationship [η] = 4 · 10−2 · M0,77 (in cm3 · g−1) holds for M̄Mw up to 8 · 105 g. mol−1. The probable reason for the formation of poly (1) with an exceptionally high molecular weight is discussed.
Light scattering from aqueous solutions of poly(acrylamide‐co‐maleic anhydride)
Authors: Ionescu Livia Maria , Petrea Ion , Bujor Ingrid Ionescu , Demetrescu Ioana 
Published: April 2003

AbstractLight scattering measurements from aqueous solutions for two samples of poly(acrylamide‐co‐maleic anhydride) in the presence of salt are conducted. One of the samples exhibits a negative initial slope and a minimum in the plot of the conventional reciprocal scattered intensity function of sin2 (θ/2). The explanation for this anomaly is a large optical anisotropy of the segment. A correction for this effect of segmental anisotropy is made. The behaviour of the other sample of this copolymer is typical for a polyelectrolyte. By analysing the disymmetry of the scattered light, the influence of the salt concentration on the polyion is evidenced by the determination of the macromolecular dimensions. Light scattering data allow the evaluation of the Mark‐Kuhn‐Houwink exponent a for various degrees of dissociation of the polyion; a correlation between the variation of a and the shape of the macromolecule is observed.
High temperature demixing of poly(decyl methacrylate) solutions in isooctane and its pressure dependence
Authors: Maderek Eugeniusz , Schulz G. V. , Wolf B. A. 
Published: April 2003

AbstractSolutions of poly (decyl methacrylate) in isooctane (2,2, 4‐trimethylpentane) show lower critical solution temperatures (LCST) that lie well below the thermal degradation of the polymer. The corresponding exothermal theta‐temperature (from the Shultz‐Flory plot) amounts to 210°C. The increase in solvent quality by pressure turns out to be very pronounced (d Tc/dp ≈ +1 K/bar). With solutions of the polymer in motor oils, high temperature demixing is unlikely to occur below their boiling point. The theoretical evaluation of published experimental data for 11 different systems exhibiting LCSTs demonstrates the following: Under the equilibrium vapour pressure of the solution high temperature demixing is generally observed withing the temperature interval between Tb, the boiling point of the pure solvent (1 bar), and 1,5 Tb. As Tc ‐ Tb increases, the heats of mixing and the pressure influence on Tc increase, too.
Polymers containing enzymatically degradable bonds, 7. Design of oligopeptide side‐chains in poly[N‐(2‐hydroxypropyl)methacrylamide] copolymers to promote efficient degradation by lysosomal enzymes
Authors: Duncan Ruth , Cable Hazel C. , Lloyd John B. , Rejmanová Pavla , Kopeček Jindřich 
Published: April 2003

AbstractN‐(2‐Hydroxypropyl)methacrylamide copolymers are considered to be a potential drug delivery system. To fulfil this role the drug‐polymer linkage must be susceptible to intralysosomal hydrolysis. Taking p‐nitroanilide as a drug analogue, copolymers were synthesized bearing oligopeptidyl‐p‐nitroanilide side‐chains designed to match known specificities of the lysosomal enzymes cathepsin L or cathepsin D. Degradation of side‐chains by rat liver lysosomal enzymes (measured by monitoring terminal p‐nitroaniline release) occurred only in the presence of reduced glutathione (5 mmol/l) and was effectively inhibited by leupeptin, indicating the involvement of thiol‐proteinases in every case. Depending on side‐chain composition, between 20 and more than 50% of the terminal p‐nitroaniline residues were liberated during a 5 h incubation. It has also been shown that 1) a polymer molecule may contain side‐chains of a single type that are nevertheless differentially susceptible to lysosomal hydrolysis; 2) two of the side‐chains studied liberate only a p‐nitroaniline residue, whereas the others also release amino‐acyl‐p‐nitroanilides; 3) the cleavage of all side‐chains displays a broad pH optimum pH 5 to pH 7; 4) the Michaelis‐Menten constant Km for side‐chain cleavage varied between 26,1 and 143,2 mg/ml, depending on the amino acid sequence of the side‐chain.
End groups in poly(vinyl chloride) and their influence on the thermal stability
Authors: Jurriaan C. , Van den Heuvel M. , Weber Anton J. M. 
Published: April 2003

AbstractEnd groups in a low molecular weight fraction of a commercial suspension poly(vinylchloride) were analysed by means of 1H NMR and IR spectroscopy and by size exclusion chromatography. The following groups were identified and quantified: ethoxycarbonyloxy (1), 1,2‐dichloroethyl (2), trans‐ and cis‐4‐chloro‐2‐butenyl (3 and 4), 2‐chloroethyl (5), and 2‐chloroethylidene (6). The influence of these groups on the degradation at 180°C was determined.
Hypoglycaemic and hypolipidaemic action of alcohol extract of Tinospora cordifolia roots in chemical induced diabetes in rats
Authors: Stanely Mainzen Prince P. , Menon Venugopal P. 
Published: April 2003

AbstractThe present investigation was undertaken to evaluate the hypoglycaemic and hypolipidaemic effects of an alcohol extract of Tinospora cordifolia roots, an indigenous plant used in Ayurvedic medicine in India. Oral administration of the extract of Tinospora cordifolia (TCREt) roots for 6 weeks resulted in a signiﬁcant reduction in blood and urine glucose and in lipids in serum and tissues in alloxan diabetic rats. The extract also prevented a decrease in body weight. Thus our study clearly shows that an alcohol TCREt has a hypoglycaemic and hypolipidaemic action. Copyright © 2003 John Wiley & Sons, Ltd.
A revenue management approach to demand management and order booking in assemble‐to‐order manufacturing
Authors: Harris Frederick H. deB. , Pinder Jonathan P. 
Published: April 2003

AbstractRevenue management is an order acceptance and refusal process that employs differential pricing strategies and stop sales tactics to reallocate capacity, enhance delivery reliability and speed, and realize revenue from change order responsiveness in order to maximize the revenue from pre‐existing capacity. While previously considered primarily as a tool of service operations, revenue management has considerable potential for assemble to order (ATO) manufacturing environments. Increasing demand for customer responsiveness has created service‐oriented manufacturing environments suitable for the application of revenue management methods. This paper applies revenue management concepts and techniques to ATO manufacturing environments and presents models for optimal pricing and capacity decisions.
Morphological distribution of MBP‐like immunoreactivity in the brain during development
Authors: Bjelke B. , Seiger Å. 
Published: April 2003

AbstractMyelin‐basic protein (MBP)‐like immunoreactivity was studied during development from postnatal day 1 to day 21 as a marker for the myelination process in the rat brain. Using monoclonal MBP antibodies, the caudo‐rostral successive progression of MBP immunoreactivity was mapped in 1‐, 7‐, 14‐, and 21‐day‐old animals using fluorescence microscopy of both coronal and sagittal sections. At 1 day of age, MBP‐immunoreactive single fibers were seen in the lower brain stem, especially in formatio reticularis, whereas the rest of the brain was negative. In 1‐week‐old animals, MBP‐positive fibers extended all the way into frontal cortex, but still in sparse arrays of single fibers with the largest number at the brain stem level. The 2‐week stage showed a dramatic increase in the number of MBP‐immunoreactive fibers. At the brain stem level, MBP‐positive fiber plexuses were mixed with MBP‐positive longitudinal axonal pathways. In cerebellar cortex, positive fibers began to radiate out from the white matter into the grey matter. A dense network of MBP‐positive fibers was located in thalamus, and dense fluorescent fiber bundles were seen in capsula interna piercing through striatum. In cerebral cortex positive radiating fibers were considerably more numerous than at the previous stage. At the age of 3 weeks, MBP‐immunoreactive fibers could be seen in networks and bundles in all parts of the brain. In the brain stem, a dense plexus of positive fibers filled formatio reticularis. In cortex cerebelli and cortex cerebri, a high density of radiating positive fibers was found. In striatum, a sparse distribution of single fibers was found in the neuropil surrounding the now strongly positive bundles of capsula interna.MBP‐like immunoreactivity was followed during postnatal rat brain development and seemed to serve as a good indicator of progression of the myelinization process. With the excellent signal‐to‐noise ratio and the detailed morphological description of the distribution of MBP‐like immunoreactivity, the present report can serve as a reference for studies of pathological disturbances of myelination in CNS as they relate to mechanical, chemical or hormonal perturbations.
Patterns of ethanol‐induced cell death in the developing nervous system of mice; Neural fold states through the time of anterior neural tube closure
Authors: Kotch Lori E. , Sulik Kathleen K. 
Published: April 2003

AbstractVital staining and routine histological analyses of mouse embryos 12 h after acute maternal ethanol administration (2.9 g/kg) illustrated that selected neuronal cell populations are killed. At the time of treatment, embryos had 5–15 somite pairs, corresponding to the developmental stages occurring in humans during the fourth week of post‐fertilization; i.e. when neural folds are present and neural tube fusion begins. Affected cell populations in embryos having 6–26 somite pairs (up to the stage of anterior neuropore closure) were in discrete locations in the alar and basal plates of the rhombencephalon, in the otic placode/vesicle, and in the regions of the epibranchial placodes, olfactory placodes and trigeminal ganglion. The potential basis for the vulnerability of these cell populations to ethanol‐induced cell death is discussed. Our understanding of the scope of ethanol‐induced CNS damage is dependent upon further defining ethanol‐sensitive cell populations at all stages of CNS development.
Cognitive deficits in long‐term survivors of childhood medulloblastoma and other noncortical tumors: Age‐dependent effects of whole brain radiation
Authors: Radcliffe Jerilynn , Bunin Greta R. , Sutton Leslie N. , Goldwein Joel W. , Phillips∥ Peter C. 
Published: April 2003

AbstractTwenty‐four children, aged 1.5–20 yr at diagnosis, with noncortical brain tumors, primarily medulloblastoma, have been followed for 3–4 yr for intellectual status. All the children received craniospinal irradiation, and 19 of 24 received chemotherapy as well. For the group as a whole, Full Scale IQ fell from 104 at baseline to 91 at final follow‐up. Children younger than 7 yr at diagnosis showed a significant decrease in IQ as early as year 1, and all changes from baseline to years 3 and 4 were significant. In contrast, children older than 7 yr at diagnosis did not show a significant IQ change from baseline to year 3 or 4. The Spearman correlation coefficient between IQ change and age at diagnosis from baseline to year 4 was 0.57 (P=0.003).This study supports the hypothesis that children treated with whole brain radiation at a younger age have more severe cognitive impairment than those treated at a later age. Limitations in sample size and duration of observations do not permit us to identify whether a true plateau occurs 2–4 yr after irradiation versus a continued progressive decline in intellectual performance. Moreover, we cannot at this time distinguish between a true dementing process versus failure to acquire new cognitive skills at a rate comparable to age‐matched peers.
Muscarinic cholinergic receptor regulation and acetylcholinesterase inhibition in response to insecticide exposure during development
Authors: Dvergsten C. , Meeker R.B. 
Published: April 2003

AbstractNeonatal rats were exposed to parathion, an acetylcholinesterase inhibiting organophosphorus pesticide, during a rapid phase of cholinergic receptor development. Rats were given subcutaneous injections of 1.5 mg/kg/day from postnatal days 8–20. The immediate effects of subchronic developmental exposure were assessed in 21‐day‐old animals and more persistent effects assessed in 36‐day‐old animals. There was a 61% inhibition of acetylcholinesterase and a 27% decrease of muscarinic receptor density in 21‐day‐old treated rats. The reduction in receptor density was dose‐dependent and a significant correlation was found between the level of acetylcholinesterase inhibition produced by parathion and the reduction in receptor density. It was estimated that a minimum of at least 15% prolonged inhibition of forebrain acetylcholinesterase by parathion was necessary to reduce receptor density. Regional analyses of receptor autoradiograms of 21‐day‐old animals indicated muscarinic receptors in the cortex and hippocampus were preferentially lost. The anterior thalamus was notable in having a high density of cholinergic receptors which were unaffected by parathion treatment. No changes were found in the affinity of [3H]QNB for the receptor or in the binding of the agonist, acetylcholine, in competition binding studies. AChE activity and muscarinic receptor density returned to normal after a 16 day recovery period. Parathion treated animals were growth inhibited but, growth retardation induced by undernutrition did not alter receptor density or affinity of QNB for muscarinic receptors. Thus, the transient decrease in receptor density in parathion exposed animals was similar to the response previously observed in adults and was not secondary to growth retardation or undernutrition. Receptor densities and acetylcholinesterase levels were regulated back to normal values after a 16 day recovery period in spite of the perturbation of cholinergic function during cholinergic synapse and receptor development.