bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling effects of forest canopies on slope stability
Authors: Keim Richard F. , Skaugset Arne E. 
Published: April 2003

AbstractWe investigated the potential effects of rainfall intensity smoothing by forest canopies on slope stability by modelling soil responses to measured rainfall and throughfall during high‐intensity rain. Field measurements showed that maximum intensities of precipitation were generally reduced under forest canopies at two sites in the Pacific Northwest, USA. Modelling soil water pore‐pressure responses of a hypothetical hillslope to the field data resulted in estimates of slope stability that were generally greater under forest canopy than for the same hillslope without forest canopy. Results indicate that smoothing of precipitation intensities may translate into overall greater stability of hillslopes under forest canopies. Copyright © 2003 John Wiley & Sons, Ltd.
Knowledge management: New York City taxi cab case study
Authors: Skok Walter 
Published: April 2003

AbstractThis paper discusses and analyses a case study of the New York City Medallion Taxi Cab Service (NYC MTCS), which has been operating successfully for many years and is a visible sign of the vibrancy of the ‘Big Apple’. The case study introduces the main stakeholders associated with the medallion cabs' licensing system, discusses current application and examination processes, and outlines how prospective cab drivers acquire knowledge of the possible routes. A comparison is then made with an earlier case study based on acquiring the ‘Knowledge’ to become a cab driver in London. This compares some theoretical perspectives with the practical situation in both cities in order to identify similarities and differences in the way knowledge is created and managed. Copyright © 2003 John Wiley & Sons, Ltd.
Recent advances in the chemistry of parainfluenza‐1 (Sendai) virus inhibitors
Authors: Saladino Raffaele , Ciambecchini Umberto , Nencioni Lucia , Palamara Anna Teresa 
Published: April 2003

AbstractPurine and pyrimidine derivatives, antioxidants, fusion inhibitors, statins, prostaglandins, antibiotic nucleosides, inhibitors of Ca2+ homeostasis, carbohydrate derivatives, antisense polynucleotides and chimeras, are described as inhibitors of parainfluenza‐1 (Sendai) viral infections. © 2003 Wiley Periodicals, Inc. Med Res Rev, 23, No. 4, 427–455, 2003
Polymerization by transition metal derivatives XI. Stereospecific polymerization of butadiene in the presence of π‐allyl nickel halogenoacetates
Authors: Dawans F. , Teyssié Ph. 
Published: April 2003

AbstractThe catalytic properties of a series of π‐allyl nickel halogenoacetates are reported for the cis‐1,4 polymerization of butadiene. Correlations between the catalytic activity of the complexes and the electron‐with‐drawing properties of their counter‐anions were made.
Correlation between the enthalpy of fusion and the specific volume of crystallized polycarbonate of bisphenol A.
Authors: Mercier J. P. , Legras R. 
Published: April 2003

AbstractSeveral measurements of the heat of fusion and of specific volume were carried out on bisphenol A‐polycarbonate of varying degrees of crystallinity. A linear correlation was established between these two physical variables and from this an enthalpy of fusion for the polycarbonate crystal of 26 Kcal. was deduced.
Linear polymerization of 2‐methylbut‐3YN‐2‐OL in the presence of CIS‐(PPh3)2 PtCl2
Authors: Furlani A. , Bicev P. , Carusi P. , Russo M. V. 
Published: April 2003

Abstract2‐methylbut‐3‐yn‐2‐ol is polymerized to linear polymers of medium molecular weight (ca. 1700) in the presence of cis(PPh3)2PtCl2.Trans(PPh3)2Pt(C≡C—C(CH3)2OH)2and trans (PPh3)2PtCl(C≡C—C(CH3)2OH) have been isolated in the course of the reaction. The property of (triphenylphosphine)‐Pt complexes of giving almost exclusively linear polymers of mono‐substituted acetylenes and the formation of σ‐Pt‐acetylides as active intermediates in the course of the polymerization reaction have been corroborated.
Polymerization of ethylene oxide with a calixarene‐based precursor: Synthesis of eight‐arm poly(ethylene oxide) stars by the core‐first methodology
Authors: Taton Daniel , Saule Myriam , Logan Jennifer , Duran Randolph , Hou Sijian , Chaikof Elliot L. , Gnanou Yves 
Published: April 2003

AbstractEight‐arm poly(ethylene oxide) (PEO) stars were prepared by the core‐first method with a newly designed octahydroxylated precursor. This compound was readily obtained in two steps from commercially available tert‐butylcalix[8]arene. The choice of the proper solvent of polymerization proved crucial to obtain PEO star materials with a narrow distribution of molar masses. For instance, the use of dimethyl sulfoxide (DMSO) resulted in PEO samples of rather large polydispersities (PDI: 1.3–1.5). In this solvent, the calixarene‐based precursor was only sparingly soluble, and an attempt to metalate its eight hydroxyl groups produced insoluble alkoxides. In addition, the presence of a side population of low‐molar‐mass species attributable to linear chains was detected because of the chain transfer of propagating alkoxides to DMSO. Polymerization experiments carried out in tetrahydrofuran (THF) as solvent afforded better control over the molar masses and PDIs. This was related to the better solubility of the octafunctional calixarene‐based precursor in THF and to the small tendency of the alkoxides formed to aggregate in that solvent. Under such conditions, all eight hydroxyl functions efficiently initiated the polymerization of ethylene oxide. In this way, well‐defined PEO stars (PDI < 1.2) of tunable molar masses incorporating a calixarene‐based core could be obtained, as it was supported by the characterization of the samples by size exclusion chromatography, NMR, and viscometry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1669–1676, 2003
Identification of free radicals trapped in solid methacrylated resins
Authors: Truffier‐Boutry Delphine , Gallez Xavier A. , Demoustier‐Champagne Sophie , Devaux Jacques , Mestdagh Michèle , Champagne Benoît , Leloup Gaëtane 
Published: April 2003

AbstractPhotopolymerization of methacrylated dental resins at room temperature leads to the appearance of long‐life free radicals because of system vitrification. These free radicals were observed by electronic paramagnetic resonance (EPR), and their characterization was undertaken by reference to the reactional mechanism, from the comparison with the model EPR signal and from theoretical simulation. Overlapping of two EPR signals assigned to two different kinds of radicals because of methacrylate end groups accounted for all the experimental and theoretical results. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1691–1699, 2003
Modeling the reversible addition–fragmentation transfer polymerization process
Authors: Wang Aileen R. , Zhu Shiping 
Published: April 2003

AbstractA kinetic model has been developed for reversible addition–fragmentation transfer (RAFT) polymerization with the method of moments. The model predicts the monomer conversion, number‐average molecular weight, and polydispersity of the molecular weight distribution. It also provides detailed information about the development of various types of chain species during polymerization, including propagating radical chains, adduct radical chains, dormant chains, and three types of dead chains. The effects of the RAFT agent concentration and the rate constants of the initiator decomposition, radical addition, fragmentation, disproportionation, and recombination termination of propagating radicals and cross‐termination between propagating and adduct radicals on the kinetics and polymer chain properties are examined with the model. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1553–1566, 2003
Syntheses of stereoregular and optically active polyamides from active 4‐chloro‐1‐benzotriazolyl diesters and diamines
Authors: Overberger C. G. , Lu C. X. , Chen C. C. 
Published: April 2003

AbstractA new route to prepare optically active polyamides was established, based on the polycondensation of two new active diesters: the active diesters of 4‐chloro‐1 hydroxybenzotriazole, such as 1,1'‐(terephthaloyldioxy)bis(4‐chloro‐benzotriazole), and 1,1'‐(isophthaloyldioxy)bis(4‐chlorobenzotriazole), with optically active isomers of 2,4‐diaminopentane. Dipolar aprotic solvents such as N,N‐dimethylformamide and dimethyl sulfoxide were used as reaction solvents. The solution polycondensation carried out in solution at room temperature afforded optically active polyamides. The aminolysis of the two active diesters was carried out as a model reaction study.
Preparation of aromatic polyesters by direct polycondensation with thionyl chloride in pyridine
Authors: Higashi Fukuji , Mashimo Toshio , Takahashi Ikuo 
Published: April 2003

AbstractMechanistic features of the reaction with thionyl chloride in pyridine were studied in a model reaction of benzoic acid with p‐chlorophenol or aniline. The yields were significantly affected by the amounts of pyridine, favorably by four equivalents, and the nature of pyridine, suggesting that pyridines are not only HCl scavengers, but are also involved in the reaction itself. The reaction was assumed to proceed via a carboxylic sulfinic‐anhydride intermediate different from acyl chloride, and the intermediate was found to be not so reactive that it was completely alcoholyzed by the phenol at high temperatures of more than 60°C. The reaction was successfully applied to the preparation of aromatic polyesters of high molecular weights by the direct polycondensation of aromatic dicarboxylic acids and bisphenols in pyridine at 80°C.
Boron–nitrogen polymers. I. Mechanistic studies of borazine pyrolyses
Authors: Paciorek K. J. L. , Harris D. H. , Kratzer R. H. 
Published: April 2003

AbstractPyrolyses of B‐triamino‐N‐triphenyl‐, B‐triamino‐N‐trimethyl‐, and B‐trianilino‐borazines were performed between 150 and 300°C. Initial stages of degradation were accompanied by liberation of ammonia in addition to the expected aniline or methylamine; this was most pronounced for the methyl borazine. Aniline elimination proceeded more readily with the B‐anilino than the B‐amino isomer. Data obtained support a ring opening mechanism resulting in telomerizaton accompanied by aniline liberation and formation first of singly then doubly bridged dimers and finally doubly bridged tetramers. Thermal exposure up to 1000°C failed to give pure boron nitride; carbon was invariably retained.
Polymerization of para‐xylylene derivatives (parylene polymerization). III. Heat effects during deposition of parylene N at different temperatures
Authors: Gazicki M. , Surendran G. , James W. , Yasuda H. 
Published: April 2003

AbstractThermal effects accompanying the vacuum deposition of poly‐para‐xylene (Parylene N) at different temperatures have been studied by following the changes in the temperature of the substrate. Similarly to the case of polychloro‐para‐xylylene (Parylene C), two distinct exothermic effects were observed; one discrete, resulting in sharp exothermic spikes and the other continuous, resulting in the shift of the baseline. The spike effect, attributed to the solid‐state polymerization of para‐xylylene, is observed at the low‐temperature range, the upper limit of which moves higher for higher deposition rates. The shift of a baseline as a function of deposition temperature exhibits two maxima, one independent of deposition rate and the second moving toward higher temperatures (that is, toward the first maximum) for higher deposition rates. First maximum falls at about 72°C and is attributed to the melting point of para‐xylylene crystals. X‐ray diffraction studies of polymer samples have shown that the existence of the second maximum is always followed by the appearance of an additional crystalline phase in the respective range of deposition temperatures. When the deposition rate is high enough, the second maximum merges with the first one, or virtually disappears. Under such conditions the new crystalline phase is no more detectable. It is postulated that the evolution of the additional amount of heat resulting in the appearance of the second maximum is due to the cyclization reaction and the formation of cyclic oligomers. This reaction very likely requires a particular spatial arrangement of monomer molecules and, therefore, it is suggested to take place in certain domains of the crystalline lattice.
Synthesis of polyamide containing optically active thymine derivative as a grafted pendant
Authors: Lu C. X. , Ji Aixue , Overberger C. G. 
Published: April 2003

AbstractA new route to polyamides containing optically active thymine groups as pendants has been established. The method is based on the grafting of (–) and (±)‐2‐(thymin‐1‐yl)propionic acid [(–) and (±) TPA] onto a polyamide containing hydroxyl groups. The hydroxy polyamide was prepared by selective N‐acylation of an active diester of N‐hydroxy‐5‐norborene‐2,3‐dicarboxamide (HONB), N,N'‐(isophthaloyl‐dioxy)‐bis(5‐norbornene‐2,3‐dicarboximide) (IPBONB), with 1,3‐diamino‐2‐hydroxypropane (AHP). Model compounds (−) and (±)‐(1,3‐dibenzoylamino‐2‐propyl)2‐(thymin‐1‐yl)propionate[(−) and (±) (BAPTP)] were prepared by direct, low‐temperature esterification before synthesizing the polymer.
Step‐growth cationic polymerization of α‐hydroxyisopropylferrocene
Authors: Zhan‐Ru Lin , Gonsalves Kenneth , Lenz Robert W. , Rausch Marvin D. 
Published: April 2003

Abstractα‐Hydroxyisopropylferrocene, HPF, was synthesized in good yield and polymerized at 20°C with either SnCl4 or BF3OEt2. The polymerization proceeds by self‐alkylation of the stable intermediate ferrocenylcarbenium ion on the cyclopentadienyl ring to form oligomers that contain both homoannular and heteroannular links. The unusually high stability of the α‐isopropylferrocenylcarbenium ion was demonstrated by synthesizing and isolating α‐isopropylferrocenylcarbenium tetrafluoborate from HPF and using it to initiate the polymerization of styrene. Initiation was successful at 20° and at 0°C, but no polymerization occurred −78°C. The condensation of ferrocene and acetone in the presence of AlCl3 gave oligomers having structures very similar to those obtained from the cationic polymerization of isopropenylferrocene.
Investigation of miscibility by spectroscopic methods IV. How far is poly(vinyl chloride) miscible with s‐poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)? An answer from nonradiative energy transfer
Authors: Albert B. , Jerome R. , Teyssie Ph. 
Published: April 2003

AbstractMiscibility of PVC with s.PMMA and SAN, respectively, has been investigated by nonradiative energy transfer. Blended by using a common solvent, the two polymer pairs are not homogeneous at a molecular level. They are likely to contain heterogeneities of a few nanometers depending on blend composition. At a comparable number average molecular weight, but a different polydispersity, SAN is seemingly less miscible with PVC than s.PMMA. That this behavior is of enthalpic or entropic origin, or mainly due to the method of mixing, cannot be settled so far.
Plasma polymerization of phenylsilane
Authors: Inagaki N. , Hirao H. 
Published: April 2003

AbstractComparative studies on plasma polymerizations of phenylsilane (PhSiH3) and toluene (PhCH3) have been carried out to prepare plasma polymers containing aromatic groups. The IR and ESCA spectra show that PhSiH3 and PhCH3 are subjected to ring‐opening reactions in a discharge state to form polymers involving alkyl chains as well as aromatic groups. The ring‐opening reactions are more feeble in the PhSiH3 system than in the PhCH3 system, which may be due to stabilization of phenyl–Si bonds in PhSiH3 by contribution of pπ−dπ bonding. Aromatic groups incorporated into the plasma polymers from PhSiH3 are mono‐substituted.
Polymers from renewable resources. II. Synthesis of polyamideimides by triphenyl‐phosphine–polyhalocompound activated polycondensation
Authors: Ray Sabyasachi Sinha , Kundu Achintya K. , Ghosh Malay , Maiti Sukumar 
Published: April 2003

AbstractA comparative evaluation of triphenylphosphine–polyhalocompound‐activated polycondensation of amino carboxylic acid as well as amino carboxylic acid containing an imidogroup with thionyl chloride activated polycondensation of the above two types of acids has been discussed. The role of different polyhalocompounds, acid acceptors, sequence of addition of reactants, temperature of reaction, etc. has been studied. It was observed that the molecular weight of the polyamide and polyamideimide, as evident from their inherent viscosity data, is generally higher, but the yield is lower than those obtained by thionyl chloride method. The reaction by the former method appears to be faster than the latter. The influence of various reaction conditions and possible mechanism of the polycondensation have been discussed.
Synthesis of aliphatic polyesters containing tetracyanoquinodimethane units by low‐temperature polycondensation reactions
Authors: Day Roger W. , Karimi Houshang , Francis Cecil V. , Kinstle James F. , Chambers James Q. 
Published: April 2003

AbstractThe low‐temperature solution polycondensation reaction between 1,4‐bis‐(2′‐hydroxy‐ethoxy)benzene and adipyl chloride has been studied in N,N‐dimethylacetamide. The effect of temperature, concentration, and reaction time on the percent yield and product viscosity has been determined. Optimum conditions were established for the preparation of high molecular weight products and then applied to the synthesis of novel tetracyanoquinodimethane polyesters. Products were characterized by gel permeation chromatography.
The glass‐to‐gel transition in solvent‐swollen polystyrene networks
Authors: Gutierrez Mario H. , Ford Warren T. 
Published: April 2003

AbstractGlass transition temperatures have been determined for polystyrenes crosslinked with 1–10% divinylbenzene and swollen with toluene, chloroform, N,N‐dimethylformamide, and tetrahydrofuran to as high as 0.7 weight fraction solvent. The Tg′s depend approximately on the weight fractions and the Tg′s of the components according to the empirical equation 1nTg = m1 1nTg1 + m2 1nTg2 of Pochan. The Tg′s of the networks swollen with toluene also fit approximately a quasithermodynamic equation of Karasz based on the Tg′s and the ΔCp′s at Tg of the components.
A 13C‐NMR spectral study of cellulose and glucopyranose dissolved in the NH3/NH4SCN solvent system
Authors: Degroot A. W. , Carroll F. I. , Cuculo J. A. 
Published: April 2003

AbstractThe 13C‐NMR chemical shifts of a cellulose with a DPw of 23 dissolved in the NH3/NH4SCN solvent system were found to be very similar to those of cellulose dissolved in DMSO (cellulose oligomers), in the LiCl/DMAC system and in the N‐methylmorpholine N‐oxide/DMSO system. It was concluded from this that cellulose does not react with the NH3/NH4SCN solvent. It was found, however, that glucose reacts with the solvent at C‐1 to form β‐D‐glucopyranosy‐lamine. Separation of this compound from the solvent resulted in another compound which was determined to be β,β‐di‐D‐glucopyranosylamine. The compounds β‐D‐glucopyranosylamine, N‐acetyl‐2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosylamine, β,β‐di‐D‐glucopyranosylamine, α,β‐di‐D‐glucopyranosylamine, 2,3,4,6,2′,3′,4′,6′‐octa‐O‐acetyl‐α,β‐di‐D‐glucopyranosylamine were all synthesized and the 13C‐NMR chemical shifts of these compounds are reported. It was also found that for the low‐DP cellulose sample which was used the reducing end group existed and had reacted with the solvent to form an amine at C‐1.
Plasma polymerization of phenyl isothiocyanate
Authors: Czeremuszkin G. , Wróbel A. M. , Kryszewski M. 
Published: April 2003

AbstractThin polymer films were obtained by plasma polymerization of phenyl isothiocyanate. Polymerizations were carried out in rf (13.56 MHz) glow discharge generated in an electrodeless flow system. It was found that this monomer produces uniform films with a wide range of thicknesses, from hundreds of nanometers to tens of micrometers. The deposition rate appeared to be dependent on the substrate distance from the monomer inlet. The chemical structure of plasma polymer was characterized by using elemental analysis, IR spectroscopy, gas chromatography, and mass spectrometry. Elemental analysis showed that the composition of polymer depends on the substrate position in the reactor. It was observed that sulphur content decreased with increasing the substrate distance from the monomer inlet, whereas nitrogen content appeared to increase. The IR data revealed significant decrease in —NCS groups content in the polymer as compared with the monomer spectrum and indicated for the appearance of new absorption bands corresponding to the CN and CH aliphatic, groups. The results account for a strong fragmentation of monomer in plasma involved in decomposition of isothiocyanate group and phenyl ring. The soluble fraction of polymeric material was examined by gas chromatography and then the separated products were analyzed by mass spectrometry. The soluble fraction was found to be composed of numerous low molecular‐weight compounds. Identification of their structure revealed the presence of residual monomer, thiophenol, cyanobenzene, diphenyl, diphenyl sulphide, diphenyl disulphide, phenyl thiocyanate, dicyanobenzene, phenatroline, and some other oligomeric products. Formation of these compounds proves high susceptibility of NCS group in the monomer towards different fragmentation reactions. The surface free energy and electrical conductivity of polymer films were evaluated. The surface free energy value was very close to those estimated for plasma polymers deposited from other benzene derivatives. The low electrical conductivity manifested by the investigated polymeric material indicated for its dielectric character. The photoelectrical measurements revealed some photoconductivity effect in this material.
An ESCA study of chemical reactions on the surfaces of cellulose fibers
Authors: Zadorecki Pawel , Rönnhult Tore 
Published: April 2003

AbstractCellulose fibers in the form of paper sheets were chemically modified with different functional groups using trichloro‐s‐triazine as coupling moiety. The treatments made the paper surfaces hydrophobic, as was indicated by an increase in contact angle against water. ESCA was used for the chemical characterization of the paper surfaces. The shape of the carbon 1s peak depended on the chemical functionality of the triazine derivatives. As a reference, ESCA spectra were also recorded for the triazine derivatives precipitated on aluminum plates. The chemical composition of modified cellulose surfaces could then be determined using a computer program for the peak separation and peak area measurement.