bluuebunny/crossref_metadata_2025_split huggingface dataset:
An introduction to stem cells
Authors: Alison Malcolm R. , Poulsom Richard , Forbes Stuart , Wright Nicholas A. 
Published: October 2002

Abstract1998 saw the publication of two papers describing the growth in vitro of human embryonic stem (ES) cells derived either from the inner cell mass (ICM) of the early blastocyst or the primitive gonadal regions of early aborted fetuses. Work on murine ES cells over many years had already established the amazing flexibility of ES cells, essentially able to differentiate into almost all cells that arise from the three germ layers. The realization of such pluripotentiality (see below) has, of course, resulted in the field of stem cell research going into overdrive, the establishment of many new biotechnology companies (http://www.stemcellresearchnew.com/catalog1677.html), and a genuine belief that stem cell research will deliver a revolution in terms of how we treat cardiovascular disease, neurodegenerative disease, cancer, diabetes, and the like. However, many people believe that early human embryos should be accorded the same status as any sentient being and thus their ‘harvesting’ for stem cells is morally unjustifiable. With this in mind, other sources of malleable stem cells have been sought. In the adult, organ formation and regeneration was thought to occur through the action of organ‐ or tissue‐restricted stem cells (i.e. haematopoietic stem cells giving rise to all the cells of the blood, neural stem cells making neurons, astrocytes, and oligodendrocytes). However, it is now believed that stem cells from one organ system, for example the haematopoietic compartment can develop into the differentiated cells within another organ system, such as the liver, brain or kidney. Thus, certain adult stem cells may turn out be as malleable as ES cells and so also be useful in regenerative medicine. This brief overview summarizes the important attributes of tissue‐based stem cells and clarifies the terms used. Copyright © 2002 John Wiley & Sons, Ltd.
Preimplantation genetic diagnosis for single gene disorders: experience with five single gene disorders
Authors: Harper Joyce C. , Wells Dagan , Piyamongkol Wirawit , Abou‐Sleiman Patrick , Apessos Angela , Ioulianos Antonis , Davis Mary , Doshi Alpesh , Serhal Paul , Ranieri Massimo , Rodeck Charles , Delhanty Joy D. A. 
Published: October 2002

AbstractWe report our experience of 14 preimplantation genetic diagnosis (PGD) cycles in eight couples carrying five different single gene disorders, during the last 18 months. Diagnoses were performed for myotonic dystrophy (DM), cystic fibrosis (CF) [ΔF508 and exon 4 (621+1 G>T)], fragile X and CF simultaneously, and two disorders for which PGD had not been previously attempted, namely neurofibromatosis type 2 (NF2) and Crouzon syndrome. Diagnoses for single gene disorders were carried out on ideally two blastomeres biopsied from Day 3 embryos. A highly polymorphic marker was included in each diagnosis to control against contamination. For the dominant disorders, where possible, linked polymorphisms provided an additional means of determining the genotype of the embryo hence reducing the risk of misdiagnosis due to allele dropout (ADO). Multiplex fluorescent polymerase chain reaction (F‐PCR) was used in all cases, followed by fragment analysis and/or single‐stranded conformation polymorphism (SSCP) for genotyping. Embryo transfer was performed in 13 cycles resulting in one biochemical pregnancy for CF, three normal deliveries (a twin and a singleton) and one early miscarriage for DM and a singleton for Crouzon syndrome. In each case the untransferred embryos were used to confirm the diagnoses performed on the biopsied cells. The results were concordant in all cases. The inclusion of a polymorphic marker allowed the detection of extraneous DNA contamination in two cells from one case. Knowing the genotype of the contaminating DNA allowed its origin to be traced. All five pregnancies were obtained from embryos in which two blastomeres were biopsied for the diagnosis. Our data demonstrate the successful strategy of using multiplex PCR to simultaneously amplify the mutation site and a polymorphic locus, fluorescent PCR technology to achieve greater sensitivity, and two‐cell biopsy to increase the efficiency and success of diagnoses. Copyright © 2002 John Wiley & Sons, Ltd.
Paracetamol pack size restriction: the impact on paracetamol poisoning and the over‐the‐counter supply of paracetamol, aspirin and ibuprofen
Authors: Sheen Christopher L. , Dillon John F. , Bateman D. Nicholas , Simpson Kenneth J. , MacDonald Thomas M. 
Published: October 2002

AbstractPurposeSelf‐poisoning occurs with over‐the‐counter (OTC) drugs, particularly paracetamol (acetaminophen). In 1998, OTC pack sizes of paracetamol were reduced. We have studied the effect of this pack size restriction on OTC supply of paracetamol, aspirin and ibuprofen.MethodsIMS Health UK provided data on the UK sales of paracetamol, aspirin and ibuprofen. The total mass and number of packs of each drug supplied were compared for the years 1998, 1999 and 2000.ResultsThe mass of aspirin and paracetamol sold fell, that of ibuprofen increased. The number of paracetamol packs sold was unchanged, the analgesic dose of aspirin fell and ibuprofen supply increased.ConclusionsIt seems that the paracetamol pack size reduction has not achieved as large an overdose rate reduction as might have been expected. Instead, a shift to the use of ibuprofen may lead to an increase in gastrointestinal adverse events and continue the burden on healthcare resources. Copyright © 2002 John Wiley & Sons, Ltd.
Spectroelectrochemistry of pyrrole oligomers in the presence of acrylamide
Authors: Saraç A Sezai , Sönmez Gürsel 
Published: October 2002

AbstractSoluble pyrrole oligomers were characterized during electropolymerization of pyrrole in the presence of acrylamide (in acetonitrile) which stabilizes radical cations of pyrrole allowing the reaction to be followed by spectroscopic and spectroelectrochemical means. The role of the applied electrical conditions and the effect of the presence of acrylamide on the formation of pyrrole oligomers in solution, and on the resulting polymer on an electrode surface (both Pt and indium tin oxide), were investigated. The soluble and insoluble products were characterized using UV‐visible and FTIR spectroscopy, cyclic voltammetry and a four‐point probe technique. Polypyrrole and poly(pyrrole–acrylamide) free‐standing films had conductivity values of about 90 and 1 S cm−1, respectively. Spectroscopic, cyclovoltammetric and conductivity results support the incorporation of acrylamide into intermediate species that may have useful application in industry.© 2002 Society of Chemical Industry
Electrochemical behaviour and electrochemical polymerization of fluoro‐substituted anilines
Authors: Cihaner Atilla , Önal Ahmet M 
Published: October 2002

AbstractThe electrochemical behaviour of three fluoro‐substituted aniline monomers, 2‐fluoroaniline (2FAN), 3‐fluoroaniline (3FAN) and 4‐fluoroaniline (4FAN), was investigated in aqueous acidic and organic media by means of cyclic voltammetry (CV) studies. Constant potential electrolysis (CPE) of the monomers in acetonitrile–water mixture (1:1 by volume) using NaClO4 as supporting electrolyte yielded soluble polymers. The mechanism of electrochemical polymerization was investigated using in situ electron spin resonance (ESR) and in situ UV–VIS spectroscopic techniques for one of the monomers (4FAN). Both CV and in situ UV–VIS measurements indicated that the polymers obtained are in the emeraldine base form. In situ ESR studies indicated that electrochemical polymerization involves a radical‐cation as an intermediate. Characterization of polymer products have been carried out using FTIR and NMR spectroscopic techniques, and thermal behaviour was studied using differential scanning calorimetry (DSC). It was found that conductivity can be imparted to as‐synthesized polyfluoroanilines via iodine doping.© 2002 Society of Chemical Industry
Reliability and comparability of a Spanish‐language form of the preschool and kindergarten behavior scales
Authors: Carney Amy G. , Merrell Kenneth W. 
Published: October 2002

AbstractComparability of a Spanish language translation of the Preschool and Kindergarten Behavior Scales was examined in relation to the English language version. Children ages 3–6 enrolled in preschool, kindergarten, or Head Start programs were rated concurrently by respondents on English and Spanish versions of the PKBS. Results showed virtually identical internal consistency of scores on both forms on Social Skills (.93) and Problem Behavior (.96) Scales. Correlations between forms for Social Skills and Problem Behavior scores were .93 and .94, respectively. Implications of these findings, directions for future research and the importance of continued work toward development/translation of other Spanish language assessment instruments for the early childhood population are discussed. © 2002 Wiley Periodicals, Inc.
High‐pressure mechanistic delineation based on activation volumes
Authors: Jenner Gérard 
Published: October 2002

AbstractHigh‐pressure kinetics is a useful tool for the determination and the assessment of mechanisms in organic chemistry. The volume of activation ΔV* deduced from these kinetic measurements is an indicator of the position of the transition state. In addition, if accurately determined, ΔV* permits the detection of fine mechanistic effects such as alteration of mechanism according to substrates within the same reaction type, operation of secondary orbital interactions in Diels–Alder cycloadditions, angular hydrogen transfer in ene reactions, etc. Copyright © 2001 John Wiley & Sons, Ltd.
Spectrophotometric determination of the transition system for interactions involving model hydrogen bonds in acetonitrile
Authors: Magoński Józef 
Published: October 2002

AbstractThe bonds formed by interactions of picric acid (HA) with each of 12 (un)substituted pyridines (B) in acetonitrile (AN) were studied by UV–vis spectrophotometry to determine the $\Delta \hbox{p}K_{\rm a}^{\rm AN}=$ $\hbox{p}K_{{\rm BH}^{+}}^{\rm AN} - \hbox{p}K_{\rm HA}^{\rm AN}$ corresponding to the transition system. The choice of both model system and experimental technique enabled the effect of heteroconjugation to be observed and the effects of formation of two theoretically possible homoconjugates (AHA− and BHB+) to be eliminated. The relationship between the wavelength at the absorbance maximum (λmax) for 10−4 M solutions of complexes of picric acid with (un)substituted pyridines in acetonitrile and $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ was found to have a sigmoidal shape with an inflection point at $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ of ca −0.3. On the basis of this relationship and UV–vis spectra, the picric acid–3‐acetylpyridine system was recognized as that being the nearest to the transition system. The fact that the transition $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ was lower than zero has been explained by the remarkable effect of species having the average structures A−···+HB on the established λmax values. The general results of this work and our previous results based on IR and 1H NMR studies, and also the lack of any experimental counterexamples, indicate that the zero value of $\Delta \hbox{p}K_{\rm a}^{\rm AN}$ constitutes a fundamental basis for predicting which one, among the given family of protonic hetero systems, is the most likely to show transitional properties in acetonitrile. Finally, it is postulated that the protonic hetero systems which are the most likely to show transitional properties in a given solvent S are those for which $\Delta \hbox{p}K_{\rm a}^{\rm S}$ is close to zero, the eventual shift arising from peculiarity of the technique applied. Copyright © 2002 John Wiley & Sons, Ltd.
Space‐demanding intramolecular isomerizations in the solid state
Authors: Kaupp G. , Schmeyers J. , Kato M. , Tanaka K. , Toda F. 
Published: October 2002

AbstractThe thermal isomerizations of meso‐ and rac‐3,4‐dibromo‐1,6‐diphenyl‐1,6‐bis(p‐tolyl)‐1,2,4,5‐hexatetraene (1) to give stereospecifically the 3,4‐bis(phenyl‐p‐tolylmethylene)‐1,2‐dibromocyclobutenes 3 and 5 + 6 were studied in the solid state using atomic force microscopy (AFM) and interpreted on the basis of known crystal structural data. These isomerizations run to completion in the bulk and include highly space‐demanding internal rotations around the central bond. Far‐reaching anisotropic molecular movements are detected on the major faces that align the surface features along cleavage planes in the initial phase rebuilding stage. Only one of three identified cleavage planes of meso‐1 is successful, owing to closer interactions of the bromine substituents in the non‐used cleavage planes. Thus, very fine details can be correlated and predicted for the occurrence of internal rotations and molecular movements in the crystal lattice. The second stage in these intramolecular isomerizations, the phase transformation, produces very high features up to 100 nm and still parallel to the preferred cleavage plane of meso‐1 but in the µm range without relation to the initial crystal structure in the case of rac‐1. Copyright © 2002 John Wiley & Sons, Ltd.
An NMR, IR and theoretical investigation of the methyl effect on conformational isomerism in 3‐fluoro‐3‐methyl‐2‐butanone and 1‐fluoro‐3,3‐dimethyl‐2‐butanone
Authors: Tormena Cláudio F. , Rittner Roberto , Abraham Raymond J. 
Published: October 2002

AbstractThe solvent dependence of the 1H and 13C NMR spectra of 3‐fluoro‐3‐methyl‐2‐butanone (FMB) and 1‐fluoro‐3,3‐dimethyl‐2‐butanone (FDMB) was examined and the 4JHF, 1JCF and 2JCF couplings are reported. Density functional theory (DFT) at the B3LYP/6–311 ++ G(2df,2p) level with ZPE (zero point energy) corrections was used to obtain the conformer geometries. In both FMB and FDMB, the DFT method gave only two minima for cis (FCCO, 0°) and trans (FCCO, 180°) rotamers. Assuming the cis and trans forms, the observed couplings in FMB when analysed by solvation theory gave the energy difference E
cis − E
trans of 3.80 kcal mol−1 (1 kcal = 4.184 kJ) in the vapour phase (cf. the DFT value of 3.21 kcal mol−1), decreasing to 2.6 kcal mol−1 in CCl4 and to 0.27 kcal mol−1 in DMSO. In FDMB the observed couplings when analysed similarly by solvation theory gave E
cis − E
trans = 1.80 kcal mol−1 in the vapour phase, decreasing to 0.47 kcal mol−1 in CCl4 and to −1.25 kcal mol−1 in DMSO. The introduction of a methyl group geminal to the fluorine atom shifts the conformational equilibrium towards the trans rotamer, in contrast to no significant effect when the methyl group is introduced at the α‐carbon further from the fluorine atom. Copyright © 2002 John Wiley & Sons, Ltd.
Structure–reactivity correlation for the ligand‐decelerated catalytic osmium tetraoxide dihydroxylation of alkenes
Authors: Erdik Ender , Kâhya Didem 
Published: October 2002

AbstractKinetic studies on the ligand‐decelerated catalytic OsO4 dihydroxylation of seven substituted styrenes with trimethylamine‐N‐oxide in the absence and in the presence of pyridine ligand have been carried out. The rates correlate with the Hammett relationship and V‐shaped plots with a maximum are in agreement with the oxidation of osmate(VI) ester in the rate‐determining step. Copyright © 2002 John Wiley & Sons, Ltd.
The nitro anomaly and Brønsted βnuc values in SN2 reactions on chlorine
Authors: Eliad Linoam , Hoz Shmaryahu 
Published: October 2002

AbstractThe kinetics of chlorine transfer reactions between N‐chlorosuccinimide (NCS) and four carbon nucleophiles (the conjugated bases of phenyldinitromethane, Meldrum's acid, phenylmalononitrile and phenylnitro‐methane) in water were determined. A plot of log k for the SN2 reactions vs the pKa of the first three conjugated acids of the nucleophiles gave a straight line with a slope (βnuc) of 1.8. The data point for the mononitro derivative, phenylnitromethane, deviates negatively from the line by 6.7 log units. This deviation is typical of proton transfer reactions and was recently shown to occur also in SN2 reactions on bromine. Copyright © 2002 John Wiley & Sons, Ltd.
Vinyl‐ and ethynylsilanes, ‐germanes and ‐stannanes. A new case of dissociative proton attachment
Authors: Mó Otilia , Yáñez Manuel , Gal Jean‐François , Maria Pierre Charles , Guillemin Jean‐Claude 
Published: October 2002

AbstractThe gas‐phase protonation of H2CC(H)XH3and HC≡CXH3(X = Si, Ge, Sn) compounds was investigated through the use of high‐level density functional theory methods. The structures of neutral and protonated species were optimized at the B3LYP/6–31G* level of theory, while the final energies were obtained by single‐point B3LYP/6–311 + G(3df,2p) calculations. In the gas phase, vinyl‐ and ethynylsilanes, ‐germanes and ‐stannanes behave as carbon bases of moderate strength, with the only exception of vinylstannane, which is predicted to be about 20 kJ mol−1more basic than ammonia. In all cases Cαprotonation is the most favorable process. This protonation is followed by a C—X bond cleavage, so that the protonated form corresponds to a tightly bound complex between ethylene (or acetylene) and the corresponding XH3+cation. This implies that dissociative proton attachments can be observed when the basic center is an atom of low electronegativity, provided that the other atoms bonded to it are much less electronegative than the basic center itself, and that the fragments formed as products of the dissociation are intrinsically stable. Copyright © 2002 John Wiley & Sons, Ltd.
Induced intramolecularity in the reference reaction can be responsible for the low effective molarity of intramolecular general acid–base catalysis
Authors: Pascal Robert 
Published: October 2002

AbstractWhereas intramolecular catalysis by nucleophilic groups can be associated with values of effective molarities ranging from 105 to 108 M in the absence of strain, values below 10 M are usually observed for general acid–base catalysis. Based on the grounds that the efficiency of intramolecular reactions is related to the entropic disadvantage of bimolecular reactions, this low efficiency is usually explained by a loose transition state for proton transfer that is diffusion limited in the thermodynamically favorable direction. However, the transient formation of a hydrogen bond at an electronegative center provides another possibility that can account for the low efficiency of general acid–base catalysis when the reaction is not diffusion limited. Any proton transfer at a site that forms hydrogen bonds to the solvent and that is concerted with a slower process is likely to take place along a hydrogen bond with the catalyst and thus to have an intramolecular character. As a result, low benefits can be earned from further intramolecularity. This analysis has important consequences for intramolecular and enzymatic proton transfers to and from carbon atoms. Owing to the absence or the weak strength of hydrogen bonds capable of inducing intramolecularity in the non‐catalyzed mechanism, high effective molarities could be recovered. As a result, the existence of strong hydrogen bonds with carbon acids would no longer be needed to account for the high effective molarities that have been observed in some cases for intramolecular proton transfer to or from carbon. Moreover, the introduction of new concepts such as short, strong hydrogen bonds (low‐barrier hydrogen bonds) to account for the high efficiency of enzymatic proton abstraction from carbon would not be necessary. Copyright © 2002 John Wiley & Sons, Ltd.
Dual influence of lithium chloride on the anionic propagation of polystyryllithium in ethereal solvents
Authors: Verheyden Hilde , Van Lierde Paul , Szwarc Michael , Litvinenko Galina , Van Beylen Marcel 
Published: October 2002

AbstractThe addition of lithium chloride (LiCl) to a solution of polystyryllithium (PStLi) in tetrahydropyran (THP) reduces the rate of propagation of PStLi at a low concentration of the latter but accelerates it at higher concentrations of PStLi. Moreover, the addition of LiCl, which is dimeric in ethereal solutions, increases the conductance of PStLi solutions in tetrahydrofuran (THF) and THP to a much greater extent than expected from the separate conductances of PStLi and LiCl, which is itself even less dissociated than PStLi. These phenomena are fully explained by the dual action of LiCl. Below a certain concentration of PStLi, the dissociation, not of LiCl as such, as claimed before, but of its solvated dimer into free Li+ ions and ClLiCl− triple ions provides Li+ ions that repress the ionic dissociation of PStLi by a common ion effect. This, in turn, diminishes the concentration of free polystyryl anions, which are the dominating species responsible for the propagation of PStLi, resulting in retardation. However, at higher concentrations of PStLi, Li+ ions produced by its dissociation are scavenged by the scavenging action of LiCl dimers, producing quintuple cations. This reduces the concentration of free Li+ ions and, therefore, increases the concentration of the reactive free polystyryl anions, resulting in an acceleration of the propagation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2148–2157, 2002
Living cationic polymerization route to poly(oligooxyethylene carbonate) vinyl ethers
Authors: Feit Ben‐Ami , Halak Baruch 
Published: October 2002

AbstractThe addition of dialkyl (R = Me or Et) carbonates to poly(oxyethylene)‐based solid polymeric electrolytes resulted in enhanced ionic conductivities. Relatively high conductivities in lithium batteries with solutions of lithium salts in di(oligooxyethylene) carbonates such as R(OCH2CH2)nOC(O)O(CH2CH2O)mR (R = Et, n = 1, 2, or 3, m = 0, 1, 2, or 3) and related carbonates were obtained. In this respect, related comb‐shaped poly(oligooxyethylene carbonate) vinyl ethers of the type CH2CH(OR) were prepared [R = (OCH2CH2)nOC(O)O(CH2CH2O)mR′; (1) n = 2 or 3, m = 0, R′ = Et; (2) n = 2 or 3; m = 3, R′ = Me]. The direct preparation of derived target polymers of this class by polymerization of the corresponding vinyl ether‐type monomers could not be achieved because of a rapid in situ decarboxylative decomposition of these monomers (as formed) during the final step of their synthesis. Instead, a prepolymer was prepared by a living cationic polymerization of CH2CH(OCH2CH2)nOC(O)CH3 (n = 2 or 3). The hydrolysis of its pendant ester groups, followed by the reaction of the hydrolyzed prepolymer with each of several alkyl chloroformates of the type ClC(O)O(CH2CH2O)mR′ (m = 0, 2, or 3, R′ = Me or Et) resulted in the corresponding target polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2171–2183, 2002
Cationic copolymerization of indene with styrene derivatives: Synthesis of random copolymers of indene with high molecular weight
Authors: Kanaoka Shokyoku , Ikeda Nobuyuki , Tanaka Akira , Yamaoka Hitoshi , Higashimura Toshinobu 
Published: October 2002

AbstractRandom copolymers with high molecular weights of indene and p‐methylstyrene (pMeSt) were synthesized by cationic polymerization with trichloroacetic acid/tin tetrachloride in CH2Cl2 at low temperatures. When indene and pMeSt (1:1 v/v), for example, were polymerized at −40 °C, both monomers were consumed at very similar rates to give a copolymer with high molecular weight [number‐average molecular weight (Mn): 8–9 × 104]. This is indeed quite unexpected behavior for the combination of these two monomers because pMeSt polymerized over 1000 times faster than indene in the homopolymerization under the reaction conditions previously described. The product copolymer of indene and pMeSt had a random monomer sequence in it that was confirmed by NMR analyses and thermal‐property measurements. In sharp contrast with pMeSt, styrene and p‐chlorostyrene, which have no electron‐donating groups on the phenyl ring, led to low molecular weight polymers (Mn < 10,000) in the copolymerization with indene (1:1 v/v). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2449–2457, 2002