bluuebunny/crossref_metadata_2025_split huggingface dataset:
Untersuchung der teilschritte der ethylen‐hochdruck‐polymerisation, 1. Druckabhängigkeit der einzelnen geschwindigkeitskonstanten
Authors: Luft Gerhard , Lim Pe‐Chin , Yokawa Masaru 
Published: April 2003

AbstractIn order to calculate the average molecular weight, the molecular weight distribution or the branching of low density polyethylene, the individual values of the rate constants of the different reactions involved in the free radical polymerization are required. The method of rotating sector was applied to determine the rate constants of chain propagation and chain termination in a wide range of temperatures and pressures. This first part of the work reports the influence of the pressure. It was found that the rate constant kp of the chain propagation increases with rising pressure whereas the rate constant kt of chain termination decreases. The effect of the pressure on kp can be explained in terms of the activation volume. The decrease of kt with pressure is caused by a diffusion controlled termination reaction.
On the mechanism of the flow process of poly(ethylene terephthalate)
Authors: Sasano Haruko , Kawai Tohru 
Published: April 2003

AbstractThe mechanism of “flow process” defined as drawing by which neither crystallization nor molecular orientation takes place was clarified on the basis of its direct experimental evidences on drawing of “amorphous” poly(ethylene terephthalate) films. In a certain temperature range above Tg, the polymer molecules are deformed and oriented on drawing, “inter‐molecular secondary linkage” playing an important role in the transmission of the applied force. When this intermolecular linkage breaks down above a certain critical temperature, the polymer molecules may slip past each other and flow independently, resulting in a large deformation without inducing any molecular orientation and crystallization. At higher temperatures crystallization occurs inducing the orientation as well.
Absolute determination of molar masses of standard polystyrenes by means of sedimentation‐diffusion measurements in cyclohexane
Authors: Petrus Vladimír , Porsch Bedr̂ich , Nyström Bo , Sundelöf Lars‐Olof 
Published: April 2003

AbstractAccurate measurements of the sedimentation coefficients at unit pressure and zero‐concentration s, the diffusion coefficients at zero concentration D0, and the intrinsic viscosities [η] were conducted at theta‐conditions (cyclohexane, 34,5°C) on 11 polystryrene standard samples with narrow molar mass distribution. These samples with nominal mass‐average molar masses (5 · 104 < Mw < 2 · 106 g · mol−1), provided by three manufacturers for the use as calibration standards, were the same as in the previous paper of this series summarizing our measurements in toluene. Logarithmic correlations between s, D0 and [η] are linear with deviations lower than ± 3% and indicate good consistency of all three independent sets of measured quantities. The molar masses MsD as determined from s and D0 by means of the Svedberg equation are in very good accordance with those previously determined in toluene, but for most samples the MsD are lower than the nominal values Mw as given by the manufacturers. For some standards the deviations amount to 15−35% and cannot be explained by experimental errors or by the polydispersity of the samples. On the other hand, two pairs of standards exhibit the same values of s, D0 and [η] in both solvents, although the nominal molar masses differ by 20%. These results lead to the conclusion that the experimentally determined MsD values are more reliable characteristics of the standard samples than the nominal Mw values and that the sedimentation‐diffusion technique is a powerful, though laborious, tool for an absolute determination of the molar mass.
Etude des prépolymères époxydes par chromatographie et 1H NMR à 350 MHz
Authors: Gulino Danièle , Galy Jocelyne , Pascault Jean‐Pierre , Tighzert Lan , Pham Quang Tho 
Published: April 2003

AbstractThe epoxy resins (DGEBA) obtained from 4,4′‐isopropylidendiphenol (bisphenol A) and 1‐chloro‐2,3‐epoxypropane (epichlorohydrin) and synthetized by the “taffy” process were found to consist of oligomers. The composition of prepolymers could be deduced from gel permeation chromatography (GPC), and particularly by high pressure liquid chromatography (HPLC). In the more resolved HPLC spectrum each oligomer was found to be accompanied by satellite peaks. The functionality of the prepolymers, determined by 1H NMR spectroscopy and cryometric or vapour pressure osmometric measurements was found to be less than two. These phenomena are due to the existence of abnormal chain ends having no epoxy group. The structure of the main components spearated by preparative GPC was studied by 1H NMR. For the impurities, the two indentified structures of chain ends are primary and secondary alcohol functions. Finally the compositions of three DGEBA were determined.
Polymères porteurs de dérivés du glycérol, 1. Polymérisation du méthacrylate d'époxy‐2,3 propyle et du méthacrylate‐phényl‐2 butyrate d'hydroxy‐2 triméthylène
Authors: Brosse Jean‐Claude , Mouity‐Moussounda François , Soutif Jean‐Claude 
Published: April 2003

AbstractRadical polymerizations and copolymerizations of 2,3‐epoxypropyl methacrylate (1) and its reaction product with 2‐phenylbutyric acid (2), 2‐hydroxytrimethylene methacrylate 2‐phenylbutyrate (3), were studied using 2,2′‐azodiisobutyronitrile, benzoyl peroxide, or H2O2 (with UV irradiation) as initiators, and also the influence of the experimental conditions (temperature, concentration, time) on the yield. Due to the reactivity of the oxirane moiety, poly(2,3‐epoxy‐propyl methacrylate) can easily be modified by ring opening reactions, e.g. with carboxylic acids.
Syntheses and characterization of polycondensation products derived from β‐(4‐methoxy‐3‐methyl)phenylglutaconic acid and diols
Authors: Mehta Ashok , Patel Rajni , Dave Harshad , Patel Kanti 
Published: April 2003

AbstractFive new copolyesters 3a – e were prepared by reacting β‐(4‐methoxy‐3 methyl)phenylglutaconic acid dichloride (1 b) with diols 2 a – e. The polymers were characterized by IR and TG. All polymers were found to decompose in the range of ≈200 to ≈650°C.
Studies of functional diene oligomers with an amino end group, 1. Synthesis of functional oligomers of isoprene with one diisopropylamino end group
Authors: Yoshino Norio , Yamaki Yoshitaka , Nagasaki Yukio , Tsuruta Teiji 
Published: April 2003

AbstractLithium diisopropylamide in the presence of diisopropylamine initiates the polymerization of isoprene to form oligomers with one diisopropylamino end group. The molecular weight of the oligomers formed is strongly dependent on the mole ratio diisopropylamine/lithium diisopropylamide. For instance, more than 70% of the oligomers obtained have an average molecular weight of 1 000, provided the reaction is run with an initial mole ratio 1:2 of amine to amide. Reactivities of several allylamine derivatives including the oligomers with amino end groups were studied in regard to their ability as chain transfer agents in the anionic polymerization of isoprene. According to the 1H NMR analysis, these oligomers contain 90% 1,4‐ and 10% 3,4‐enchainments.
Behaviour of poly(N‐vinylcarbazole) in 1,3‐dichlorobenzene/methanol mixtures
Authors: González M. C. , Zamora F. , Guzmán G. M. , León L. M. 
Published: April 2003

AbstractThe behaviour of poly(N‐vinylcarbazole) in a mixture of 1,3‐dichlorobenzene and methanol (solvent/non‐solvent system) is studied. The non‐solvent, methanol, is more strongly adsorbed than 1,3‐dichlorobenzene as judged from changes in the unperturbed dimensions and intrinsic viscosity. Therefore the Mark‐Houwink‐Sakurada constant and the flexibility parameter decrease with increasing methanol contents. A relation between the preferential adsorption parameter and the segment density is given.
Synthesis, characterization and conformational transition in poly(cyclohexylmethyl methacrylate)
Authors: Gargallo Ligia , Mendez Inés , Radic Deodato 
Published: April 2003

AbstractPoly(cyclohexylmethyl methacrylate), (poly[1‐(cyclohexylmethoxycarbonyl)‐1‐methylethylene]) was prepared and characterized by osmometric and viscometric measurements. The temperature dependences of the viscosity data and of the refractive index increment of the polymer were investigated in isobutyl methyl ketone solution. A discontinuity of the intrinsic viscosity [η] was observed over the temperature range 5°C – 10°C. Also sharp changes of the unperturbed dimensions parameter K⊖ and the thermodynamic parameter B from the Stockmayer‐Fixman plot were observed in the same temperature range. Similar discontinuities occur with the refractive index increments dn/dc. This phenomenon can be accounted for by assuming conformational changes of the chain in the chosen solvent at a specific temperature range. The results are compared with that obtained in poly(cyclohexyl methacrylate). The influence of the spacer group CH2 in the conformational behaviour of poly(cyclohexylmethyl methacrylate) is analyzed.
The cationic polymerisation of 2‐alkenylfurans, 3. Spectroscopic study of the alkylation as important side reaction leading to branched products
Authors: Gandini Alessandro , Martínez Ricardo 
Published: April 2003

AbstractA spectroscopic (UV, IR, 1H NMR) study of the cationic polymerisation of 2‐vinylfuran (1a) and 2‐isopropenylfuran (2a) showed the existence of an important alkylation reaction at C5 which competes with normal propagation. The extent of this competition depends on the monomer used and the polymerisation temperature. A comparison of the spectra of standard polymers (prepared by radical or stereospecific polymerisation) with those of polymers obtained by cationic initiation allowed to assess the extent of alkylation and its regiospecificity at C5 2‐Methyl‐5‐vinylfuran (1b) and 2‐methyl‐5‐isopropenylfuran (2b) were found to undergo cationic polymerisation without any interference from alkylation reactions. Reactions between these four monomers and 2‐methylfuran in the presence of typical acidic catalysts gave very high yields of alkylated products and no polymerisation, thus confirming the importance of this electrophilic reaction and its possible application to synthetic uses.
Polymerization of lactams, 64. Nonactivated anionic polymerization of 2‐pyrrolidone in the presence of quaternary ammonium cations
Authors: Roda Jan , Králíček Jaroslav , Šubr Vladimír , Stehlíček Jaroslav 
Published: April 2003

AbstractThe effect of addition of quaternary ammonium halides was studied in the nonactivated polymerization of 2‐pyrrolidone (1) initiated with the potassium salt of 2‐pyrrolidone (2‐oxo‐1‐pyrrolidinylpotassium) (2). The polymerization was accelerated upon small additions of Me4NCl, whereas addition of Et4NBr and Bu4NBr rather had a retardation effect and reduced the molecular weight of polymer. The formation of the corresponding quaternary ammonium salts of 2‐pyrrolidone in situ is analogous to the formation of the pure salts in their synthesis from the ammonium halides. The nonactivated polymerization of 1 initiated with the pure tetramethylammonium salt of 2‐pyrrolidone (3) showed all kinetic features of other nonactivated polymerizations of 1. High yields and molecular weights of poly(2‐pyrrolidone) and a higher number of growth centers during polymerization are evidence of a higher dissociation of 3 dissolved in 1 in comparison with 2 as the initiator. The activation energy of polymerization activated with 3 (47,9 kJ · mol−1 in the range 35 to 55°C) and the reaction order with respect to 3 (1,3 at 45°C) were determined.
Orientation of ketones embedded in a polyethylene matrix. Infrared dichroic study
Authors: Schmidt Pavel , Schneider Bohdan 
Published: April 2003

AbstractLow‐molecular weight ketones embedded in polyethylene films were oriented by cold drawing of the films and the effect of temperature on the orientation was studied by IR dichroism. The loss of orientation of the low‐molecular weight ketones with temperature is discussed on the basis of the Cohen‐Turnbull model of “free volumes”.
Characterization of microgel‐containing polymers by the light scattering method: A new method of evaluation and its comparison with other procedures
Authors: Procházka Ondřej , Tuzar Zdeněk , Kratochvíl Pavel 
Published: April 2003

AbstractA new method suitable for computer treatment was suggested for the evaluation of data obtained by light scattering from polymer solutions containing microgel. The method is based on the assumption of bimodal molar mass distribution and requires no additional data and/or restrictions. The accuracy of the present method was compared with that of other evaluation procedures (suggested by Lange, Gruber and Schurz, Strazielle, and Kratochvíl) using model mixtures consisting of two polymers differing by 2 to 3 orders of magnitude in molar mass. The values of molecular parameters (Mw,1, Mw, z2, (rz,12)1/2, (rz,22)1/2) obtained by the present method are in general more reliable then those calculated by means of the other evaluation procedures.
Lichtinitiierte polymer‐ und polymerisationsreaktionen, 10. Photoinduzierte zersetzung von diareniodonium‐ und triarensulfoniumsalzen durch kaliumtrisoxalatoferrat
Authors: Baumann Harald , Strehmel Bernd , Timpe Hans‐Joachim , Rehorek Detlef 
Published: April 2003

AbstractIn order to elucidate kinetics and mechanism of photoinitiation processes based on potassium trioxalatoferrate(III) (K3[Fe(cx)3])/ onium compounds/acrylamide (AA) interactions, photolysis and stationary photopolymerization were carried out. Diphenyliodonium chloride (Ph2I⊕Cl⊖) and triphenylsulfonium tetrafluoroborate (Ph3S⊕BF⊖4) were used as onium compounds. These compunds react with photolytically formed ˙CO⊖2 radicals by an electron transfer mechanism. The resulting phenyl radicals were detected by spin trapping with nitrosodurene. The quantum yield of the decomposition of onium salts, ϕIn, depends both on their reduction potentials and concentrations. Thus, an efficient redox reaction between ˙CO⊖2 radical and Ph3S⊕BF⊖4 is impossible because the former reacts faster with the Fe(III) complex. The ratio between rate constants of these competitive reactions (onium compound/Fe(III)) are 0,1 (Ph2I⊕Cl⊖) and 4 · 10−4 (Ph3S⊕BF⊖4). Only with the system K3[Fe(ox)3]/Ph2I⊕Cl⊖/AA a radically induced photopolymerization was observed. Both the rate and the quantum yield (ϕBr) depend on the Ph2I⊕Cl⊖ concentration. A correlation between ϕBr and √ϕIn was found.
Syntheses and chelating properties of polymer‐supported macrocyclic polythioethers
Authors: Tomoi Masao , Abe Osamu , Takasu Nobutaka , Kakiuchi Hiroshi 
Published: April 2003

AbstractPolymer‐supported macrocyclic polythioethers (7a, b, and 8) were prepared from chloromethylated polystyrene resins (6) and 14‐ or 20‐membered a hydroxyl group containing polythioethers (3a, b, and 5), which were synthesized by the reaction of the corresponding dithiols with 1,3‐dichloro‐2‐propanol (2). The polymer‐supported polythioethers were found to be highly efficient adsorbents of Ag(I), moderately effective for Cu(II), but less effective for Cd(II). For Ag(I) the binding ability of 7a is almost independent of the morphology of the polymer support, whereas for Cu(II) the binding ability depends on the morphology. Adsorbed Ag(I) or Cu(II) were removed by treatment with an ammonia solution from the polymer‐supported macrocyclic polythioethers, which can be re‐used without a significant decrease in binding ability.
Resines époxydes, 1. Mécanisme de polycondensation entre le bis[(époxy‐2,3 propoxy)‐4 phényl]‐2,2 propane et la m‐phénylénediamine par 13C NMR
Authors: Grenier‐Loustalot Marie‐Florence , Grenier Philippe 
Published: April 2003

AbstractCuring of 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane (diglycidyl ether of bisphenol A) (1) with m‐phenylenediamine (2) was performed in a variable temperature probe of a 13C FT NMR spectrometer (62,89 MHz). The formation of an initial adduct was directly observed and the progress of polymerisation was followed by recording the 13C NMR spectra at time intervals. Unreacted epoxide carbon atoms were detected in one sample as well as in a sample of 1 cured by a standard procedure.
Poly(ethylene glycol)s grafted onto crosslinked polystyrenes, 2. Multidetachably anchored polymer systems for the synthesis of solubilized peptides
Authors: Hellermann Heidi , Lucas Heinz‐Werner , Maul Jürgen , Pillai V. N. Rajasekharan , Mutter Manfred 
Published: April 2003

AbstractPoly(ethylene glycol)s grated onto suitably functionalized, crosslinked polystyrenes were introduced as a new class of multidetachably immobilized hydrophilic macromolecular supports for the synthesis of peptides. This new polymeric carrier system facilitates both the homogeneous solvation of the reaction site and the insolubilization of the substrate, which are prerequisites for an efficient multistep synthesis using polymeric supports. In these support systems, a strongly solvated hydrophilic linear chain molecule, poly(ethylene glycol) (PEG)Systematic IUPAC name: α‐Hydro‐ω‐hydroxypoly(oxyethylene).
, is attached to an insoluble, crosslinked polystyrene through suitable anchoring linkages. At the free chain end of this supported PEG, amino acid residues were stepwise incorporated following the standard synthetic methodology for peptides. A special feature of these new carriers is that the use of an orthogonal set of anchoring linkages to connect the polystyrene, PEG and the peptide provides access to the PEG‐bound solubilized peptide or to the free peptide, as desired. The applications of these new polymeric supports are illustrated by the synthesis of thioredoxin partial sequences in the free and PEG‐bound solubilized forms.
Accuracy of antenatal fetal ultrasound in the diagnosis of duplex kidneys
Authors: Whitten S. M. , McHoney M. , Wilcox D. T. , New S. , Chitty L. S. 
Published: April 2003

AbstractObjectivesTo assess the accuracy of ultrasound diagnosis of duplex kidneys in the fetus and to identify prognostic features of antenatal sonography associated with this diagnosis.MethodsRetrospective identification of cases with an antenatal diagnosis of duplex kidney was made from computerized databases. Results of postnatal radiological investigations were obtained from the unit where delivery took place.ResultsA total of 75% of cases seen in a multidisciplinary fetal renal clinic were correctly diagnosed as having a duplex kidney. Prognostic sonographic features are described. Detection of two separate poles or a ureterocele were strongly associated with a correct diagnosis. Accuracy was increased when two or more prognostic features were seen.ConclusionAccurate sonographic diagnosis of duplex kidneys in the fetus is possible in a dedicated multidisciplinary setting. Antenatal counseling and planning of postnatal care for the infant can be made with a high degree of certainty. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Multivariable analysis of tests for the diagnosis of intrauterine growth restriction
Authors: Bachmann L. M. , Khan K. S. , Ogah J. , Owen P. 
Published: April 2003

AbstractObjectivesTo describe how data from antenatal fetal ultrasound biometry, amniotic fluid index and umbilical artery Doppler can be appropriately combined using multivariable models and to investigate how the addition of these ultrasound parameters influences the ability to predict intrauterine growth restriction (IUGR).MethodsThis was a prospective cohort study involving 274 low‐risk pregnancies undergoing serial ultrasound examination at predetermined intervals. Standard deviation (Z) scores of the last values for fetal abdominal area (FAA), growth velocity of the FAA, amniotic fluid index (AFI) and umbilical artery Doppler pulsatility index prior to delivery were calculated for 260 fetuses. Customized estimated fetal weight (cEFW) centiles were also calculated using the last EFW before delivery after adjustment for fetal gender, gestational age, birth order and maternal weight, height and ethnic origin. Following delivery the neonatal ponderal index was calculated and centile position obtained. A neonatal ponderal index <25th centile served as the main outcome measure for diagnosis of IUGR. Logistic regression analysis was used to delineate the predictive value of the three fetal growth tests FAA, FAA growth velocity and cEFW and the additional values of AFI and pulsatility index of the umbilical artery.ResultsThe areas under the receiver–operating characteristics (ROC) curves (95% confidence interval) for FAA, FAA growth velocity and cEFW alone were 0.819 (0.748–0.891), 0.784 (0.699–0.869) and 0.74 (0.643–0.837), respectively, in the prediction of a neonatal ponderal index <25th centile. The addition of both the AFI and pulsatility index to FAA, FAA growth velocity and cEFW generated small increases in the areas, to 0.831 (0.758–0.904), 0.817 (0.735–0.899) and 0.766 (0.672–0.859), respectively. These improvements in diagnostic prediction were not statistically significant.ConclusionsThe addition of AFI and umbilical artery pulsatility index to the fetal biometry parameters did not significantly increase the ROC areas in the study population. The approach applied in this study is useful in the context of hypothesis generation. Further studies using larger data sets and other predictors should be carried out using the analytical techniques outlined in this paper to determine the contribution of various antenatal tests in the prediction of IUGR. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Epignathus: always a simple teratoma? Report of an exceptional case with two additional fetiforme bodies
Authors: Sarioglu N. , Wegner R. D. , Gasiorek‐Wiens A. , Entezami M. , Schmock J. , Hagen A. , Becker R. 
Published: April 2003

AbstractWe report on a case of a fetal epignathus combined with two fetus‐like structures resembling acardius acranius. The anomaly was detected at 23 weeks of gestation and led to termination of pregnancy at 24 weeks. This is the first description of epignathus with parasitic fetuses detected prenatally. It shows that the boundary between fetal teratoma and multiple pregnancy in special cases may be difficult to define. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Prenatal diagnosis of total anomalous pulmonary venous connection to the portal vein associated with right atrial isomerism
Authors: Boopathy Vijayaraghavan S. , Rao A. R. , Padmashree G. , Raman M. L. 
Published: April 2003

AbstractWe report the prenatal diagnosis of total anomalous pulmonary venous connection to the portal system in a 20‐week fetus with right atrial isomerism. The apex of the fetal heart pointed to the left, the fetal stomach was on the right, there was a common atrioventricular valve, the left ventricle was small and the abdominal aorta and inferior vena cava were on the left side; all these features were suggestive of right atrial isomerism. An anomalous vein was connected to the portal vein which ascended above the diaphragm and ended in a confluence of pulmonary veins, posterior to the common atrium. Color Doppler imaging helped confirm the diagnosis of total anomalous pulmonary venous connection. The prenatal findings were confirmed on autopsy. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Management of irritable bowel syndrome
Authors: Gunn M C , Cavin A A , Mansfield J C 
Published: April 2003

Abstract
The diagnosis of irritable bowel syndrome (IBS) is made on clinical grounds with appropriate limited investigations to exclude organic disease. IBS is common and may have a significant impact on a patient’s quality of life. Psychological symptoms are common. IBS may benefit from pharmacological and non-pharmacological management. Specific measures should be directed towards the dominant symptoms of constipation or diarrhoea. Several new drugs are currently under evaluation and may prove valuable for subgroups of patients with IBS. Successful management requires a combination of reassurance and explanation about the natural history of the condition.