bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymeric herbicide–Montmorillonite composite: synthesis, characterization and release studies
Authors: Rehab Ahmed 
Published: August 2002

AbstractThe production of polymeric herbicide intercalated onto montmorillonite interlayer through the process of cation exchange, in order to produce chemically bound polymeric herbicide with clay, has been reported. This was carried out by cation exchange of clay with onium salts of preformed polymeric pentachlorophenyl methacrylate. The products were characterized by various techniques including IR spectroscopy and elemental microanalysis. The interlayer spacing was determined by X‐ray diffraction and thermogravimetric analysis (TGA) and calcination investigated the thermal stability. The morphology of the composite was investigated by scanning electron microscopy. The swelling behaviors in different solvents and release of pentachlorophenol (PCP) in different medium have been described. Copyright © 2001 John Wiley & Sons, Ltd.
Structural characteristics of phenol formaldehyde novolak resin depending on polycondensation type using molecular simulation
Authors: Choi Sung‐Seen 
Published: August 2002

AbstractPhenol formaldehyde novolak resins have various structures depending on the polycondensation types. Their structures were characterized using molecular mechanics and molecular dynamics. Dimer, tetramer, hexamer, octamer, and decamer of the resins with the ortho–ortho, ortho–para, and para–para sequences were calculated. The ortho–ortho resins have the structural characteristics of intramolecular hydrogen bonds between hydroxyl groups of the adjacent phenolic units. For the ortho–para and para–para resins, the intramolecular hydrogen bonds are formed mainly between hydroxyl groups of the backbone phenolic units. The para–para resins also have intramolecular hydrogen bonds between hydroxyl groups of the branched phenolic units. A factor determining the structural characteristics of the resins was found to be the geometry of the basic unit (dimer). The order of the end‐to‐end distances between hydrogen atoms on the para‐position of the basic units of the resins is ortho–ortho resin < ortho–para resin < para–para resin. The calculational results were found to be consistent with the gel permeation chromatography (GPC) analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Euglycaemic diabetic ketoacidosis – is it on the rise?
Authors: De P. , Child D.F. 
Published: August 2002

AbstractWe present two cases of diabetic ketoacidosis in type 1 diabetic patients who presented with normal glucose levels. The clinical picture and biochemical profile were typical of diabetic ketoacidosis, although if only the blood glucose level at presentation had been taken into account the unwary would have missed the diagnosis. The two cases highlight that ketoacidosis in diabetes can occur with near‐normal blood glucose and that levels of blood glucose and development of ketoacidosis do not necessarily correlate. ‘Euglycemic ketoacidosis’ was originally described whereby the initial blood glucose was less than 16.7 mmol/L and plasma bicarbonate equal to or less than 10 mmol/L. The cause of preserved ‘euglycemia’ could be greater urinary loss of glucose triggered by counter‐regulatory hormones or decreased rate of hepatic glucose production observed during a fast as in a state of diabetic ketoacidosis. Better education and home blood glucose monitoring with appropriate increase in insulin doses during intercurrent illness may be another factor responsible for the rising incidence of euglycemia. One must use urinary ketones and arterial blood gas measurement in all known diabetic patients who are unwell on presentation to diagnose ‘euglycaemic diabetic ketoacidosis’ and treat them with cautious use of low‐dose insulin infusion and intravenous fluids, otherwise a potentially treatable condition may be missed. We discuss euglycaemic diabetic ketoacidosis, an entity we believe is possibly on the rise and discuss the available, albeit controversial and scarce, literature. Copyright © 2001 John Wiley & Sons, Ltd.
Antihypertensives and myocardial infarction risk: the modifying effect of history of drug use
Authors: Bourgault Chantal , Elstein Eleanor , Baltzan Marc A. , Lorier Jacques Le , Suissa Samy 
Published: August 2002

AbstractPurposeConfounding by indication is common in observational studies of outcomes that treatment is intended to affect. In light of the stepped‐care approach to hypertension management, we reexamined the controversy around myocardial infarction (MI) risk in relation to antihypertensive agents by considering past drug history both as a confounder and as an effect modifier.MethodsCase–control design nested within a cohort of 19 501 adults initiating therapy with angiotensin‐converting enzyme inhibitors (ACEI), calcium channel blockers (CCB) or β‐blockers in Saskatchewan (1990–93) and followed up to 1997. MI cases were identified using death certificates and hospital discharge diagnoses (ICD‐9 410). Four controls were matched to each case to account for duration and timing of follow‐up.Results812 MI cases were identified, of which 26% were fatal. At first, current use of CCB and ACEI (versus β‐blockers) appeared to be associated with an increased risk of MI (RR = 2.2; 95% CI = 1.8–2.7 and RR = 1.3; CI = 1.0–1.6 respectively). Adjustment for drug use history attenuated both associations (RR = 1.6; CI = 1.1–2.2 and RR = 1.0; CI = 0.7–1.4). Moreover, the risk for CCB use disappeared when restricted to patients who had already used these agents in the past (RR = 1.1; CI = 0.77–1.7) whereas a high risk of MI for ACEI was found in digoxin users (RR = 9.4; CI = 3.2–27.5).ConclusionPast drug history can be both a confounder and an effect modifier in observational studies. We found adjustment for medication history to attenuate the associations between antihypertensive agents and MI risk. In addition, the estimates significantly varied across drug history profiles thus suggesting the presence of preferential prescribing of specific drug classes to high‐risk patients. Copyright © 2001 John Wiley & Sons, Ltd.
Use of cold medications for upper respiratory tract infections in children
Authors: Jhaj R. , Bhargava V. K. , Uppal R. , Lekha S. , Reeta Kh. , Kaur N. 
Published: August 2002

AbstractPrescribing practices in the treatment of upper respiratory tract infections (URTI) in children were studied, with particular emphasis on overuse of antibiotics, combination cold medications, and off‐label use of medicines in children. Prescriptions with the diagnosis of URTI were studied over a period of 5 months in a general pediatric clinic. Out of 224 prescriptions scrutinized, a cold medication was prescribed in 88.4% of cases and 50.9% prescriptions contained a combination preparation. Antihistamines (50.9%), α‐adrenoceptor agonist decongestants (50.0%) and opioid anti‐tussives (24.5%) were the common ingredients of cold medications. Antihistamines (35.7%) were also used alone. Of the children 18.2% were receiving a drug contraindicated or not recommended in their age group. Antibiotics were prescribed in only 8.5% of cases, and for appropriate indications, reflecting a more restrained use of antibiotics. Copyright © 2001 John Wiley & Sons, Ltd.
Blending of styrene‐block‐butadiene‐block‐styrene copolymer with sulfonated vinyl aromatic polymers
Authors: Picchioni Francesco , Giorgi Ivan , Passaglia Elisa , Ruggeri Giacomo , Aglietto Mauro 
Published: August 2002

AbstractDifferent polymers containing sulfonic groups attached to the phenyl rings were prepared by sulfonation of polystyrene (PS) and styrene‐block‐(ethylene‐co‐1‐butene)‐block‐styrene (SEBS). The sulfonation degree (SD) was varied between 1 and 20 mol% of the styrene units.Polyphase materials containing sulfonated units were prepared by blending styrene‐block‐butadiene‐block‐styrene (SBS), with both sulfonated PS and sulfonated SEBS in a Brabender mixer. Such a procedure was performed as an alternative route to direct sulfonation of SBS which is actually not selective towards benzene rings because of the great reactivity of the double bonds in polybutadiene (PB) blocks to sulfonation agents. Thermal and dynamic‐mechanic analysis, together with morphology characterization of the blends, is consistent with obtaining partially compatible blends characterized by higher Tg of the polystyrene domains and improved thermal stability.© 2001 Society of Chemical Industry
Copolyesters of hydroxyphenylalkanoic acids: synthesis and thermal properties of poly{(4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]} and poly{(3‐bromo‐4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]}
Authors: Abraham Shiney , Prasad V S , Pillai C K S , Ravindranathan M 
Published: August 2002

AbstractCopolyesters of 8‐(3‐hydroxyphenyl)octanoic acid (HPOA), a monomer with kink and flexible segment derived from cardanol, and 4‐hydroxybenzoic acid (HBA) or its brominated derivative, 3‐bromo‐4‐hydroxybenzoic acid (BrHBA), were synthesized by acidolysis melt polycondensation of the in situ generated acetoxyderivative in the presence of magnesium acetate as catalyst by a one‐pot method and characterized. The formation of the copolyester was confirmed by elemental analysis, FTIR and 1H NMR spectroscopy. These polymers were highly insoluble in most solvents except highly polar solvents, such as trifluoroacetic acid. The inherent viscosities of the soluble polymers were in the range of 0.8–1.1 dlg−1. The thermal and phase behaviour of the copolyesters were studied by DSC and polarized light microscopy. Poly{(4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]} with 50 mole% of HPOA showed a birefringent melt with opalescence and a worm‐like texture of a nematic phase. The effect of bromine substitution in the analogue poly{(3‐bromo‐4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]} was evident when it showed a lower transition with minimum 45% Br‐HBA at 225 °C showing enhanced melt processability. These copolymers, with hydrolytically degradable aliphatic carbonyl group and better crystallinity compared to poly(hydroxyalkanoate)s, are interesting in possible biomedical applications.© 2002 Society of Chemical Industry
Grid‐connected photovoltaic systems: the Brazilian experience and the performance of an installation
Authors: Ferreira de Oliveira Sérgio Henrique , Zilles Roberto 
Published: August 2002

AbstractJust as in several other countries, the Brazilian experience of installing in place solar photovoltaic technology was first aimed at meeting the needs of rural areas. More recently, the effects of the international trend towards grid‐connected photovoltaic systems are beginning to be felt in Brazil. In less than five years, the first four grid‐connected photovoltaic systems have been installed, and other projects are in progress. This work presents the overall characteristics of the first four systems and the technical performance achieved by one of them, with an annual production in the range of 1500 kW h/kWp. Copyright © 2001 John Wiley & Sons, Ltd.
Radical stabilization energy as a measure of the spectral properties and reactivity trends in homologous groups
Authors: Finkelshtein E. I. 
Published: August 2002

AbstractThe existence of linear relationships has been demonstrated between stretching frequencies of R—H, RO—H, CH3CON(R)—H and R—OX (X = H for alcohols and O for peroxy radicals) bonds and radical stabilization energies, Es(R·), of related radicals. The correlation equations of Es(R·) and R—H bond dissociation energies (BDE), D(R—H), with the above stretching frequencies were obtained. From the equations the D(R—H) values for different hydrocarbons were calculated and compared with the experimental data. The mean difference between calculated and experimental values for saturated hydrocarbons is 2.3 kJ mol−1. The greater differences for some unsaturated hydrocarbons are discussed and explained. The BDEs calculated from the D(R—H = f (ν) equations may be regarded as the best. The IR spectra of menthol, menadione, 3‐methylpent‐2‐en‐4‐yn‐1‐ol and retinol were recorded in solution and the Es(R·) values of the corresponding radicals and the D(R—H) values of the related C—H bonds in the parent hydrocarbons were estimated for the first time. It is also shown that the radical stabilization energy may be used to estimate the reactivity of organic compounds in free radical reactions. One may conclude that the stabilization energy of the radicals of many organic compounds could be estimated from the vibrational spectra. The Es(R·) itself is a useful quantity for predicting kinetic and spectral properties of organic compounds. Copyright © 2001 John Wiley & Sons, Ltd.
Synthesis and characterization of new aromatic tweezers and complex formation with tropylium ion in 1,2‐dichloroethane
Authors: Lämsä Markku , Kiviniemi Sari , Kettukangas Eeva‐Riitta , Nissinen Maija , Pursiainen Jouni , Rissanen Kari 
Published: August 2002

AbstractA series of benzene and pyridine tweezers bearing phenyl, naphthyl and anthryl receptor units was prepared and characterized. The x‐ray crystal structure of the 1,3‐bis(9‐methanolanthracene)methylbenzene ligand (5) is reported. UV–visible and NMR spectroscopy were used to investigate the host–guest chemistry of the new ligands in complexation with tropylium tetrafluoroborate as a model aromatic cationic guest in 1,2‐dichloroethane. The appearance of coloured charge‐transfer absorption bands demonstrates the complex formation with a tropylium ion. The enlargement of aryl receptor size from phenyl and naphthyl to anthryl increases the stability of complexes. Electron donor–acceptor interactions are an important driving force for complexation by molecular tweezers. The results are discussed and compared with those of previously studied systems containing crown ethers and podands. The bisanthracenes 5 and 1,3‐bis(9‐methanolanthracene)methylpyridine (6) are especially interesting in displaying both complexation ability and intramolecular cycloaddition via charge‐transfer excitation. Copyright © 2001 John Wiley & Sons, Ltd.
Tautomerism in 4‐substituted 1‐phenyl‐3‐methyl‐pyrazolin‐5‐ones—a theoretical ab initio and 13C NMR study
Authors: Kleinpeter E. , Koch A. 
Published: August 2002

AbstractThe tautomeric equilibria between the CH, OH and NH forms in a series of 4‐substituted 1‐phenyl‐3‐methyl‐pyrazolin‐5‐ones have been studied using ab initio calculations at various levels of theory and comparison made with the experimental results obtained from NMR measurements. Quantitative comparison of both the relative energies and the 13C chemical shifts of the tautomers constituting the tautomeric equilibria were made by calculation of both sets of parameters. The influence of the solvent was included by employing various models of the self‐consistent reaction field theory. Initially, the solvent was included in the calculations by applying a continuum of differing polarity over the surface of isolated tautomers (self‐consistent isodensity polarized continuum model method), then later by assuming formation of an adduct between the solute and the solvent (thereby simulating effectively the hydrogen bonding in the OH and NH tautomers) and finally by calculating dimer or trimer complexes of the various tautomers. In this manner, the agreement between the theoretically calculated and the experimentally determined tautomeric equilibria was improved significantly. The theoretically calculated 13C chemical shifts of the tautomers were found to be viable for the assignment of the tautomers, particularly the preferred tautomer in the OH/NH equilibrium, which remains fast on the NMR time scale even at low temperatures. Copyright © 2001 John Wiley & Sons, Ltd.
Tetraalkylalkene vertical ionization potentials revisited
Authors: Nelsen Stephen F. , Reinhardt Laurie A. 
Published: August 2002

AbstractThe vertical ionization potentials for three tetra‐α‐branched‐alkyl‐substituted alkenes (13–15) are reported, compared with literature data for other tetralkylalkenes, and the values discussed with reference to AM1 semiempirical and B3LYP density functional calculations. Copyright © 2001 John Wiley & Sons, Ltd.
(Thiocarbonyl‐α‐thio)carboxylic acid derivatives as transfer agents in reversible addition–fragmentation chain‐transfer polymerizations
Authors: Farmer Steven C. , Patten Timothy E. 
Published: August 2002

AbstractEthyl S‐(thiobenzoyl)thioacetate, ethyl S‐thiobenzoyl‐2‐thiopropionate, and S‐(thiobenzoyl)thioglycolic acid were used as chain‐transfer agents for the reversible addition–fragmentation chain‐transfer (RAFT) polymerizations of styrene, methyl methacrylate, and butyl acrylate. Of these polymerizations, only those of styrene and butyl acrylate with any of the transfer agents showed molecular weight control corresponding to controlled/living polymerizations. The best molecular weight control was observed for the polymerizations of styrene and butyl acrylate with ethyl (S)‐thiobenzoyl‐2‐thiopropionate. Semiempirical PM3 calculations were performed for the investigation of the relative heats of reaction of the chain‐transfer equilibria between the aforementioned chain‐transfer agents and dimer radicals of the three monomers. The molecular weight control of the polymerizations correlated with the stability trend of the leaving‐group radical of the chain‐transfer agent. This relatively simple computational model offered some value in determining which transfer agents would show the best molecular weight control in RAFT polymerizations. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 555–563, 2002; DOI 10.1002/pola.10143
Poly(pentamethylcyclopentasiloxane). I. Synthesis and characterization
Authors: Kurian P. , Kennedy J. P. , Kisluik A. , Sokolov A. 
Published: August 2002

AbstractWe have discovered that pentamethylcyclopentasiloxane (D5H) can be readily polymerized into poly(pentmethylcyclopentasiloxane) (PD5) with a Pt (Karstedt) catalyst in the presence of water in bulk or in solution at 100 °C and that the product is a solid with extraordinary properties. The polymerization starts with the oxidation of the SiH groups by water into an intermediate containing SiOH groups (SiH + H2O → SiOH + H2), which is followed immediately by the condensation (2SiO → SiOSi) of D5H rings into complex aggregates of cyclosiloxane moieties. According to Raman spectroscopy, an average of three of the five SiH functionalities are converted, and the final product contains only a negligible number of SiOH groups. The melting and glass‐transition temperatures of the monomer are exceptionally low: Tm,D5H = −137.6 ± 1 and Tg,D5H = −152 ± 2 °C. The polymer exhibits an unprecedented combination of properties: it is a stiff and brittle solid, is insoluble in common solvents, does not exhibit a melting endotherm but has an extremely low glass transition (Tg,PD5 = −151 ± 0.5 °C), and is thermally stable up to at least 700 °C. Brillouin scattering indicates very slow variation of the relaxation time with temperature, a property characteristic of strong glass‐forming systems such as silica glass. This characteristic may account for the unique combination of properties of the new polymer: an extremely low glass‐transition temperature combined with solidlike properties even at ambient temperature (more than twice its glass‐transition temperature). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1285–1292, 2002
Synthesis and characterization of novel polyimides bearing a side chain composed of stilbene mesogen and undecyl spacer and the alignment ability of nematic liquid‐crystal molecules
Authors: Park J. H. , Sohn B.‐H. , Jung J. C. , Lee S. W. , Ree M. 
Published: August 2002

AbstractFour different polyimides with side chains containing undecyl spacers and 4‐fluorostilbene mesogen end groups were prepared, and their structures and the controllability of the liquid‐crystal (LC) alignment with rubbing were investigated. From X‐ray scattering and differential scanning calorimetry data, pyromellitic dianhydride (PMDA)‐, benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA)‐, and 4,4′‐oxydi(phthalic anhydride) (ODPA)‐based polyimides were shown to have layered structures and short‐range ordering. Pretilt angles of LCs on the rubbed surfaces were 1–9°, depending on the rubbing density and backbone. In particular, the long undecyl spacers caused the mesogenic stilbene end groups to lie next to the main chain, resulting in a reduction in the pretilt angles. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1800–1809, 2001
One‐step preparation of polyurethane dispersions by miniemulsion polyaddition
Authors: Tiarks Franca , Landfester Katharina , Antonietti Markus 
Published: August 2002

AbstractThe application of the miniemulsion process to synthesize polyurethane dispersions with diameters of about 200 nm in a one‐step procedure, free of molecular weight restrictions, is described. With IR and NMR spectroscopy, it is shown that the reaction of the diisocyanate with the diol is the main reaction, whereas the reaction with water is only a side reaction. Differential scanning calorimetry measurements and transmission electron microscopy are used to characterize both polymer and latex properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2520–2524, 2001
Synthesis, characterization, and biodegradability of novel regular‐network polyester‐amines based on 1,1,1‐triethanolamine
Authors: Nagata Minoru , Morooka Takashi , Sakai Wataru , Tsutsumi Naoto 
Published: August 2002

AbstractRegular‐network polyester‐amines were prepared from 1,1,1‐triethanolamine (YN) and various dicarboxylic acids [HOOC(CH2)n−2COOH, n = 6–14]. A prepolymer prepared by melt polycondensation was cast from dimethylformamide solution and postpolymerized at 220 °C in a nitrogen flow for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyester‐amines obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density, DSC, and thermomechanical analysis. The biodegradation experiments for the network polyester‐amine films were carried out in enzymatic solution with Rhizopus delemar or Pseudomonas cepacia lipase and in an activated sludge. The degree and rate of biodegradation were estimated by the weight loss of the films. After incubation in Rhizopus delemar lipase solution for 24 h, weight loss was hardly observed for YN6–7, whereas it increased greatly for YN8–13 (13–51 g/m2), and then it decreased rapidly for YN14. The methylene‐chain dependence of degradation was essentially the same as in the case of network polyesters from glycerol and various aliphatic dicarboxylic acids reported previously. Psedomonas cepacia lipases also degraded YNn films, but the rate of degradation was much slower than Rhizopus delemar lipase. In the exposure to activated sludge for 30 days, the network polyester films with medium methylene‐chain lengths (YN7–11) showed the lager weight loss, as in the case of the enzymatic degradation, whereas the rate of biodegradation was much slower than that of the enzymatic degradation with Rhizopus delemar lipase. The effect of the protonation of the film with hydrochloric acid on the enzymatic degradation was also examined. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2896–2903, 2001