bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prenatal diagnosis of female monozygotic twins discordant for Turner syndrome: implications for prenatal genetic counselling
Authors: Gilbert B. , Yardin C. , Briault S. , Belin V. , Lienhardt A. , Aubard Y. , Battin J. , Servaud M. , Philippe H. J. , Lacombe D. 
Published: October 2002

AbstractWe describe a set of monozygotic (MZ) female twins, one of whom presented with a typical Turner syndrome (TS) phenotype and the other a normal female phenotype. Prenatal fetal ultrasonographic examination showed a monochorial diamniotic pregnancy with a hygroma colli and growth delay in Twin A and no anomalies in Twin B. Karyotypic analysis performed on fetal blood samples demonstrated a 46,XX/45,X (23/2) mosaicism in Twin A and a normal 46,XX chromosome constitution in Twin B. At birth, Twin A presented with a typical TS and Twin B had a normal female phenotype. Postnatal cytogenetic investigation of blood lymphocytes showed the same 46,XX/45,X mosaicism in both twins: 46,XX/45,X (40/7) in Twin A and 46,XX/45,X (40/5) in Twin B. Further investigations at the age of 10 months showed in Twin A a 46,XX/45,X (98/2) mosaicism in lymphocytes and 100% of 45,X (50 analysed cells) in fibroblasts, and in Twin B a normal 46,XX (100 analysed cells) chromosome constitution in lymphocytes but a mild 46,XX/45,X (78/2) mosaicism in fibroblasts. Monozygosity was confirmed by molecular analysis. To our knowledge, this is the first report of prenatal diagnosis of MZ female twins discordant for TS. Review of reported sets of MZ female twins (eight cases) or triplets (one case) discordant for TS shows, as in the present case, that the phenotype correlates better with the chromosomal distribution of mosaicism in fibroblasts than in lymphocytes. In the blood of MZ twins chimerism may modify the initial allocation of the mosaicism. These results suggest that, in cases of prenatal diagnosis of MZ female twins discordant for TS, the phenotype of each twin would be better predicted from karyotype analysis of cells from amniotic fluid than from fetal blood. Copyright © 2002 John Wiley & Sons, Ltd.
Study on polypropylene/natural rubber blend with polystyrene‐modified natural rubber as compatibilizer
Authors: Hashim Azanam S , Ong S K 
Published: October 2002

AbstractPolystyrene‐modified natural rubber (SNR) was prepared in the laboratory and subsequently used as compatibilizer in polypropylene/natural rubber (PP/NR) blends. The effect of SNR (at 5%, 10%, 15% and 20% by volume) in PP/NR (70/30) blend was studied by maintaining the rubber volume while PP volume was replaced by SNR accordingly. The sequence of mixing was found to affect the blend morphology and tensile properties. The effect of curatives on the tensile properties of the blends was also investigated. The addition of curatives into the rubbers in PP/NR/SNR improved the tensile properties significantly compared with the PP/NR reference blend. For a semi‐efficient curative system, SNR loading at 10% gave the best overall tensile properties, while for an efficient curative system, 5% SNR loading resulted in improvements in tensile strength and stiffness of over 20% and 40%, respectively, compared with the reference.© 2002 Society of Chemical Industry
Acidity and basicity of primary N‐phenylnitramines: catalytic effect of protons on the nitramine rearrangement
Authors: Daszkiewicz Zdzisław , Spaleniak Grzegorz , Kyzioł Janusz B. 
Published: October 2002

AbstractPara‐substituted N‐phenylnitramines were prepared either by oxidation of diazonium salts or by nitration under alkaline or acidic conditions. Isotopic [15N‐NO2] labelling indicated that the bands characteristic of the N‐nitro group appear in the 1318–1323 and 1585–1607 cm−1 regions. In the nitrogen NMR spectra, the nitramino group gives two resonances at −193 ± 3 (NH) and −32 ± 3 ppm (NO2). The chemical shifts in proton and carbon NMR spectra are predictable, based on increments and the additivity rule. The spectral data indicate the lack of conjugation between the nitramino group and another substituent bound to the ring. It seems to contradict the well‐known fact that substituents strongly (ρ = 4) influence the rate of nitramine rearrangement. The acidities of primary N‐phenylnitramines (3.77 < pKA < 5.62) are similar to those of benzoic acids and weakly dependent (ρ = 1) on the electronic character of a substituent. Based on the analogy with benzoic acids, it has been calculated that basicities of nitramines (pKB ≈ 21) are extremely low. Consequently, addition of protons to an intact nitramine molecule, as the preliminary step of the rearrangement, seems to be improbable. Migration of the N‐nitro group precedes protonation; the latter process facilitates transformation of intermediates into stable final products. Copyright © 2001 John Wiley & Sons, Ltd.
Anisotropic molecular movements in organic crystals by mechanical stress
Authors: Kaupp Gerd , Schmeyers Jens , Hangen Ude D. 
Published: October 2002

AbstractNanoindents and nanoscratching on organic crystals with their anisotropic molecular packing explore far‐reaching molecular movements or abrasion of material by the application of mechanical stress. Only intermolecular hydrogen bonds and van der Waals ‘bonds’ are broken in these experiments. Thiohydantoin (1) is a particularly suitable model owing to its well‐defined layered crystal packing and its cleavability at the (10–2)‐planes. Indents with a cube corner indenter on the natural (110)‐face give piling‐up of material by molecular movements only to one side by following the direction of the slopes of the molecular monolayers. Four orthogonal nanoscratches along and across the long crystal edge (each back and forth) on (110) give four different very distinct results: (1) molecular movements to both sides and in front with symmetric piling‐up, (2) abrasion of material, (3) molecular movements to the right and (4) molecular movements to the left. The influence of the single molecular layers that stand 66° steep is clearly expressed by these results. No molecular movement but abrasion of material occurs upon nanoscratching on the (10–2) cleavage plane of 1, now with the molecular monolayers flat. These anisotropic molecular responses to mechanical stress are detected by atomic force microscopy. They may be of use in nanotechnology, but cannot be predicted by the more common collective mechanical properties such as hardness or Young's elasticity modulus, quantities that do not at all relate to the extreme anisotropies that are reported here for the first time. Copyright © 2002 John Wiley & Sons, Ltd.
Looking for a contribution of the non‐equilibrium solvent polarization to the activation barrier of the SN2 reaction
Authors: Jaworski Jan S. 
Published: October 2002

AbstractThe solvent effect on the activation free energy of the Finkelstein reaction between methyl iodide and Cl− ions was analysed in terms of the recent Marcus theory unifying the SN2 and the electron transfer reactions. The homolytic bond dissociation energy and the related resonance energy of interaction of the states seem to be almost solvent independent. The sum of the work term wr and the solvent reorganization energy λ0/4 depends strongly on the solvent acidity parameter, e.g. ETN, describing the solvation/desolvation of anions. However, after removing the contribution of the specific solvation the linear increase of the remaining part of λ0/4 with the Pekar factor, describing the non‐equilibrium solvent polarization, was observed for six aprotic solvents. Copyright © 2002 John Wiley & Sons, Ltd.
Kinetic and mechanistic studies on the inhibition of free radical‐initiated polymerization of styrene by β‐carotene and α‐tocopherol
Authors: Li Zhaolong , Cui Jian , Hong Xiaoyin , Liu Youcheng , Liu Zhongli 
Published: October 2002

AbstractThe inhibition of free radical‐initiated polymerization of styrene by β‐carotene (βC) and α‐tocopherol (TOH) was studied by dilatometry. The polymerization was initiated by 2,2′‐azobis(isobutyronitrile) at 50 °C in chlorobenzene and inhibited by βC and/or TOH. It was found that βC and TOH could efficiently inhibit the polymerization, either used individually or in combination, and a significant synergistic effect was observed when they were used in combination. It is proposed that retinal, which is the principal oxidation product of βC, may be involved in the synergistic inhibition reaction of βC and TOH. Copyright © 2002 John Wiley & Sons, Ltd.
Acid‐catalyzed hydrolysis of bridged bi‐ and tricyclic compounds. XXXIX—Kinetics and mechanisms of the hydration reactions of 1‐ and 3‐acetylnortricyclanes
Authors: Lajunen Martti , Salmi Jani , Limnell Taru 
Published: October 2002

AbstractThe disappearance of 1‐ and 3‐acetylnortricyclanes (1‐Ac and 2‐Ac) in aqueous perchloric acid was followed by capillary gas chromatography at different temperatures and acid concentrations. 1‐Ac is much less reactive than 2‐Ac. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products studied. 1‐Acetylnortricyclane is hydrated according to the A‐2 mechanism, i.e. the carbonyl oxygen is protonated in the fast pre‐equilibrium and one water molecule attacks at the rate‐limiting stage the partially open cyclopropane ring, producing 6‐acetyl‐2‐norborneols. 3‐Acetylnortricyclane is hydrated according to the AdE2 mechanism, i.e. the cyclopropane ring is slowly protonated and opened, with subsequent fast attack of water producing 3‐, 5‐ and 7‐acetyl‐2‐norborneols. Copyright © 2002 John Wiley & Sons, Ltd.
Controlled ring‐opening polymerization of cyclic carbonates and lactones by an activated monomer mechanism
Authors: Endo Takeshi , Shibasaki Yuji , Sanda Fumio 
Published: October 2002

AbstractThis article reviews recent topics in the controlled synthesis of polycarbonates and polylactones with small polydispersity indices by activated monomer cationic ring‐opening polymerizations, especially with new initiator systems, such as alcohol/protonic acid and boron alkoxide/protonic acid. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2190–2198, 2002
Single‐electron and two‐electron transfer in the anionic polymerization of vinyl monomers and the ring‐opening polymerization of lactones*
Authors: Jedliński Zbigniew 
Published: October 2002

AbstractSingle‐electron‐transfer (SET) and two‐electron‐transfer reactions and their mechanisms were examined in the anionic polymerization of vinyl monomers and in the ring‐opening polymerization of lactones. SET resulted in the formation of radical anions or enolates at the initiation step of styrene or lactone polymerization with naphthalene sodium as a catalyst. However, alkali‐metal supramolecular complexes such as M+crown–M− (M = Na or K) were able to transfer two electrons to both these monomers to form carbanions as reactive intermediates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2158–2165, 2002
Flame‐retardant epoxy resins from o‐cresol novolac epoxy cured with a phosphorus‐containing aralkyl novolac
Authors: Liu Ying Ling , Wu Chuan Shao , Hsu Keh Ying , Chang Teh Chou 
Published: October 2002

AbstractA novel phosphorus‐containing aralkyl novolac (Ar‐DOPO‐N) was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) first with terephthaldicarboxaldehyde and subsequently with phenol. The chemical structures of the synthesized compounds were characterized with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. Ar‐DOPO‐N blended with phenol formaldehyde novolac was used as a curing agent for o‐cresol formaldehyde novolac epoxy, resulting in cured epoxy resins with various phosphorus contents. The epoxy resins exhibited high glass‐transition temperatures (159–177 °C), good thermal stability (>320 °C), and retardation on thermal degradation rates. High char yields and high limited oxygen indices (26–32.5) were observed, indicating the resins' good flame retardance. Using a melamine‐modified phenol formaldehyde novolac to replace phenol formaldehyde novolac in the curing composition further enhanced the cured epoxy resins' glass‐transition temperatures (160–186 °C) and limited oxygen index values (28–33.5). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2329–2339, 2002
End‐group modification of poly(butyl acrylate) prepared by atom transfer radical polymerization: Mechanistic study using gradient polymer elution chromatography
Authors: Snijder Auke , Klumperman Bert , Van Der Linde Rob 
Published: October 2002

AbstractThe introduction of a functional group into a poly(butyl acrylate) polymer prepared by copper‐mediated atom transfer radical polymerization and the characterization of the prepared polymer by gradient polymer elution chromatography are reported. The bromo end group of the initial polymer can be transformed into a different functional group with several functionalization reactions, including nucleophilic substitution and atom transfer radical addition (ATRA), in combination with comonomers, addition–fragmentation transfer agents, or stable radicals. Several new functionalization agents are reported, including ATRA using 1‐(3‐hydroxymethyl‐phenyl)‐pyrrole‐2,5‐dione and trimethyl{1‐[4‐(2‐trimethylsiloxyethoxy)]phenylethenyloxy}silane and nucleophilic substitution using 2‐mercapto ethanol. The rate constant of the functionalization reaction and the final functionality are determined with gradient polymer elution chromatography, a technique by which qualitative and quantitative information about the conversion can be obtained. Polymers with a functionality greater than 95% are reported. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2350–2359, 2002
Ruthenium‐based metathesis initiators: Development and use in ring‐opening metathesis polymerization
Authors: Frenzel Ulrich , Nuyken Oskar 
Published: October 2002

AbstractFor many years, olefin metathesis has been a central topic of industrial and academic research because of its great synthetic utility. The employed initiators cover a wide range of compounds, from simple transition‐metal salts to highly sophisticated and well‐defined alkylidene complexes. Currently, ruthenium‐based catalysts are at the center of attention because of their remarkable tolerance toward oxygen, moisture, and numerous functionalities. This article focuses on recent developments in the field of ring‐opening metathesis polymerization using ruthenium‐based catalysts. ruthenium‐based initiators and their applications to the preparation of advanced polymeric materials are briefly reviewed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2895–2916, 2002
Controlled‐release systems based on the intercalation of polymeric metribuzin onto montmorillonite
Authors: Rehab Ahmed , Akelah Ahmed , El‐Gamal Maisa M. 
Published: October 2002

AbstractA series of polymer–clay composites carrying metribuzin as herbicide moieties were prepared. Linear copolymers containing metribuzin via an imide linkage were prepared by the free‐radical polymerization of metribuzin monomer (N,N‐diacryloyl metribuzin) with different comonomers. The intercalation of the copolymers onto montmorillonite through a cationic exchange process was carried out and yielded metribuzin composite products. The prepared materials were characterized with a wide variety of analytical techniques, including gel permeation chromatography, NMR, IR, elemental microanalysis, gravimetric analysis (calcination), and swelling measurements. The release rates for the prepared materials were investigated in media of different pHs with an ultraviolet spectrophotometer. Also, these compounds were studied for the control of herb growth. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2513–2525, 2002
Synthesis of model polycyclohexylene/polyethylene miktoarm star copolymers with three and four arms
Authors: Tsoukatos Thodoris , Hadjichristidis Nikos 
Published: October 2002

AbstractThe synthesis of well‐defined 3‐ and 4‐miktoarm star copolymers of the A2B and A3B types is described, where A is 1,4‐polybutadiene and B is poly(1,3‐cyclohexadiene). The synthetic approach involves the reaction of poly(1,3‐cyclohexadienyl)lithium with an excess of methyltrichlorosilane or tetrachlorosilane followed, after the removal of excess silane, by a small excess of polybutadienyllithium. Characterization was carried out by size exclusion chromatography, low‐angle laser light scattering, laser differential refractometry, and NMR spectroscopy. The complete heterogeneous catalytic hydrogenation of the A2B and A3B miktoarm stars, with a calcium carbonate‐supported palladium catalyst, leads to the formation of A2B and A3B miktoarm stars with one amorphous polycyclohexylene arm with an extremely high glass‐transition temperature and two or three crystalline polyethylene arms. Differential scanning calorimetry was used to determine the glass‐transition temperature of the amorphous blocks of the starting and hydrogenated stars and the melting temperature of polyethylene. Solid‐state 13C NMR spectroscopy was performed to ensure the complete saturation of the polycyclohexadiene and polybutadiene arms. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2575–2582, 2002
Preparation of novel, high‐modulus, swollen‐ or jungle‐gym‐type polyimide gels end‐crosslinked with 1,3,5‐tris(4‐aminophenyl)benzene
Authors: He Jionghao , Machida Shinjiro , Kishi Hiromitsu , Horie Kazuyuki , Furukawa Hidemitsu , Yokota Rikio 
Published: October 2002

AbstractA novel preparation approach for high‐performance polyimide gels that are swollen or have a jungle‐gym‐type structure is proposed. A new rigid and symmetric trifunctional amine, 1,3,5‐tris(4‐aminophenyl)benzene (TAPB), was synthesized as a crosslinker. Three different kinds of amic acid oligomers derived from pyromellitic dianhydride (PMDA), 4,4′‐oxydiphthalic anhydride (ODPA), p‐phenylenediamine (PDA), and 4,4′‐oxydianiline (ODA) were end‐crosslinked with TAPB at a high temperature to make polyimide networks with different structures. Transparent polyimide gels were obtained from the ODPA–ODA/TAPB series with high compression moduli of about 1 MPa at their equilibrium swollen states in N‐methylpyrrolidone. Microscopic phase separation occurred during the gelation–imidization process when polyimide networks were generated from PMDA–PDA/TAPB and PMDA–ODA/TAPB. After these opaque polyimide networks were dried, a jungle‐gym‐like structure was obtained for the PMDA–PDA/TAPB and PMDA–ODA/TAPB series; that is, there was a high void content inside the networks (up to 70%) and little volume shrinkage. These polyimide networks did not expand but absorbed the solvent and showed moduli as high as those of solids. Therefore, using the highly rigid crosslinker TAPB combined with the flexible monomers ODPA and ODA and the rigid monomers PMDA and PDA, we prepared swollen, high‐performance polyimide gels and jungle‐gym‐type polyimide networks, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2501–2512, 2002
Synthesis and characterization of poly(ethylene oxide)/polylactide/poly(ethylene oxide) triblock copolymer
Authors: Lee Soo‐Hong , Kim Soo Hyun , Han Yang‐Kyoo , Kim Young Ha 
Published: October 2002

AbstractPoly(ethylene oxide/polylactide/poly(ethylene oxide) (PEO/PL/PEO) triblock copolymers, in which each block is connected by an ester bond, were synthesized by a coupling reaction between PL and PEO. Hydroxyl‐terminated PLs with various molecular weights were synthesized and used as hard segments. Hydroxyl‐terminated PEOs were converted to the corresponding acid halides via their acid group and used as a soft segment. Triblock copolymers were identified by Fourier transform infrared spectroscopy, 1H NMR, and gel permeation chromatography. Differential scanning calorimetry (DSC) and X‐ray diffractometry of PEO/PL/PEO triblock copolymers suggested that PL and PEO blocks were phase‐separated and that the crystallization behavior of the PL block was markedly affected by the presence of the PEO block. PEO/PL/PEO triblock copolymers with PEO 0.75k had two exothermic peaks (by DSC), and both peaks were related to the crystallization of PL. According to thermogravimetric analysis, PEO/PL/PEO triblock copolymer showed a higher thermal stability than PL or PEO. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2545–2555, 2002
Synthesis and properties of new soluble aromatic polyamides and polyimides on the basis of N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine
Authors: Liou Guey‐Sheng , Hsiao Sheng‐Huei 
Published: October 2002

AbstractA new N‐phenylated amide (N‐phenylamide) unit containing aromatic diamine, N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was prepared by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 3‐nitrobenzoyl chloride, followed by catalytic reduction. Two series of organosoluble aromatic poly(N‐phenylamide‐imide)s and poly(N‐phenylamide‐amide)s with inherent viscosities of 0.58–0.82 and 0.56–1.21 dL/g were prepared by a conventional two‐stage method and the direct phosphorylation polycondensation, respectively, from the diamine with various aromatic dianhydrides and aromatic dicarboxylic acids. All polyimides and polyamides are amorphous and readily soluble in many organic solvents such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with high tensile strengths. These polyimides and polyamides had glass‐transition temperatures in the ranges of 230–258 and 196–229 °C, respectively. Decomposition temperatures of the polyimides for 10% weight loss all occurred above 500 °C in both nitrogen and air atmospheres. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2564–2574, 2002
Preparation of poly(arylenediphosphine)s by palladium‐catalyzed polycondensation: Formation of polymer transition‐metal complexes and catalytic reactions
Authors: Kanbara Takaki , Takase Syuichi , Hayashi Rika , Kagaya Shigehiro , Hasegawa Kiyoshi , Yamamoto Takakazu 
Published: October 2002

AbstractThe palladium‐catalyzed polycondensation of aryl diiodides with 1,3‐bis(phenylphosphino)propane afforded poly(arylenediphosphine)s in good yields. Treatment of the polyphosphine with elemental sulfur and hydrogen peroxide efficiently converted the polyphosphine into poly(arylenediphosphine sulfide) and poly(arylenediphosphine oxide), respectively. Treatment of the polyphosphines with Pd(II) and Pt(II) yielded corresponding polymer‐metal complexes with high metal contents. Application of the polymer‐Pd complexes in homogeneous and heterogeneous aryl alkynylation and carbonylation was examined. The polymer‐Pd complexes showed good catalytic activity similar to that of the corresponding low molecular weight Pd complex, and reuse of the polymer catalysts was easily achieved. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2637–2647, 2002
Supported stereospecific metallocene binary catalyst for propylene polymerization
Authors: de Fátima Vieira Marques Maria , Camargo Pombo Carla , Azevedo Silva Rodrigo , Conte Anunciata 
Published: October 2002

AbstractIn this work, propylene was polymerized with isospecific and syndiospecific catalysts in homogeneous and heterogeneous systems. The binary metallocene system of both isospecific and syndiospecific catalysts in the heterogeneous system was also used. Besides the type of catalyst, parameters such as polymerization temperature and pressure were varied to achieve the better conditions for the polymerization. The objective of this work is to investigate the influence of these parameters on the characteristics of the produced polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2979–2986, 2002