bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered expression of connexins 26 and 43 in Sertoli cells in seminiferous tubules infiltrated with carcinoma‐in‐situ or seminoma
Authors: Brehm Ralph , Marks Alexander , Rey Rodolfo , Kliesch Sabine , Bergmann Martin , Steger Klaus 
Published: October 2002

AbstractThe expression of connexins (cx) 26 and 43 in testis infiltrated with carcinoma‐in‐situ (CIS) or seminoma was examined to gain insight into the relationship between aberrant gap junctional communication and spermatogenic impairment in the neoplastic testis. In uninvolved tubules with normal spermatogenesis, cx43 immunostaining was localized to the Sertoli–Sertoli junctional complex and cx26 was absent. In contrast, infiltrated tubules with spermatogonial arrest or CIS‐only were negative for cx43, but displayed strong intracytoplasmic Sertoli cell staining for cx26. The Sertoli cells in these tubules re‐expressed cytokeratin 18 (ck18), signifying a reversion to a less differentiated state. Western blot analysis for cx43 revealed a single immunoreactive band at 43 kD (normal spermatogenesis) and three bands at 43, 41, and 39 kD (impaired spermatogenesis with CIS or seminoma). For cx26, a doublet band at 26/28 kD (normal spermatogenesis) and an additional doublet band at 52/54 kD (impaired spermatogenesis with CIS or seminoma) were observed. The altered expression of cx26 and cx43 in Sertoli cells in testes infiltrated with CIS or seminoma suggests that a derangement in intercellular communication between Sertoli cells and between Sertoli cells and germ cells may play a role in the resulting spermatogenic impairment and possibly in the proliferation and neoplastic progression of CIS cells. Copyright © 2002 John Wiley & Sons, Ltd.
Non‐disclosing preimplantation genetic diagnosis for Huntington disease
Authors: Stern Harvey J. , Harton Gary L. , Sisson Michael E. , Jones Shirley L. , Fallon Lee A. , Thorsell Lilli P. , Getlinger Michael E. , Black Susan H. , Schulman Joseph D. 
Published: October 2002

AbstractObjectivesIndividuals at risk for Huntington disease face difficult decisions regarding their reproductive options. Most do not wish to pass on the gene for Huntington disease to their children, but may not be prepared themselves to undergo presymptomatic testing and learn their genetic status. For these reasons, many at‐risk individuals with a family history of HD would choose a method of genetic diagnosis that would assure them that they can have children unaffected with HD without revealing their own genetic status (non‐disclosing). We have shown that, with a carefully designed and executed programme of non‐disclosing preimplantation genetic testing, one can successfully assist at‐risk couples to have their own biological children who are free from Huntington disease, without forcing parents to confront knowledge of their own genetic status.MethodsCouples where one partner was at 50% risk for Huntington disease underwent in vitro fertilization with preimplantation embryo biopsy and molecular analysis for Huntington disease where appropriate.ResultsAfter extensive counselling and informed consent, 10 couples underwent 13 in vitro fertilization and two frozen embryo transfer cycles in a programme for non‐disclosing preimplantation genetic diagnosis for Huntington disease. In 11 cycles, embryos determined to be free of Huntington disease were transferred, resulting in five clinical pregnancies. One set of twins and three singleton pregnancies have delivered. One pregnancy resulted in a first‐trimester loss.ConclusionsThe option of non‐disclosing preimplantation genetic diagnosis should be reviewed, along with other relevant medical options, when counselling at‐risk Huntington disease families. Copyright © 2002 John Wiley & Sons, Ltd.
Attitude of at‐risk subjects towards preimplantation genetic diagnosis of α‐ and β‐thalassaemias in Hong Kong
Authors: Wah Hui Pui , Lam Yung Hang , Chen Min , Tang Mary Hoi Yin , Yeung William Shu Biu , Ng Ernest Hung Yu , Ho Pak Chung 
Published: October 2002

AbstractObjectivesThe aim of the study was to assess whether preimplantation genetic diagnosis (PGD) was an acceptable alternative to prenatal diagnosis in couples at risk of giving birth to a child with α‐ or β‐thalassaemia in an Asian population.MethodsAn information leaflet was distributed to the women at risk. They were asked to complete a questionnaire after having an interview with a designated investigator.ResultsA total of 141 valid questionnaires were analysed; 82.3% of the women considered PGD either the same or better than conventional prenatal diagnosis. Women with an affected child or a subfertility problem were more willing to accept PGD and to undergo this procedure in their future pregnancies. Their main concern about PGD was damage to the embryo during the PGD procedure. The most important perceived advantage of PGD was avoidance of termination of an affected pregnancy.ConclusionsPGD is an acceptable alternative to conventional prenatal diagnosis in women at risk of giving birth to a child with α‐ or β‐thalassaemia in an Asian population. This is particularly true in women with a subfertility problem and in women who already have an affected child. Copyright © 2002 John Wiley & Sons, Ltd.
The structure of negative emotion scales: generalization over contexts and comprehensiveness
Authors: Smits Dirk J. M. , De Boeck Paul , Kuppens Peter , Van Mechelen Iven 
Published: October 2002

In this article, we tested whether a four‐dimensional individual‐difference structure of negative emotions (Sadness, Fear, Anger, Shame) as described e.g. by Diener, Smith and Fujita can be found in self‐report data when the emotions are explicitly linked to three different specific contexts. In addition, we check the comprehensiveness of the structure by adding terms people spontaneously use to directly express negative affect. A situational questionnaire was constructed, based on the emotion terms from Diener et al., and it was administered to 161 participants. The structure we obtained was five dimensional instead of four dimensional: the Shame scale turned out to be two dimensional, with guilt and regret defining one factor, and shame and embarrassment defining another factor. Between these two, there is a moderate positive correlation. The structure is shown to be nearly identical for all three situations. The minor differences we found do contextualize the meaning of the emotional responses. The newly added terms could be captured quite well by the factor Anger. No separate factor was needed, meaning that the obtained five‐dimensional structure may be considered comprehensive enough for the field of negative emotions. Copyright © 2002 John Wiley & Sons, Ltd.
Towards a one‐pot synthesis of a polystyrene–PMMA block copolymer via atom‐transfer radical polymerization
Authors: Keary Claire , Zhang Xi , Hogen‐Esch Thieo E , Wang Jin‐Shan 
Published: October 2002

AbstractThe solution atom‐transfer radical copolymerization of styrene and methyl methacrylate in butyl acetate at 110 °C in the presence of Cu(II) bromide and 2,2′‐bipyride was investigated. Polystyrene was polymerized by atom‐transfer radical polymerization using benzyl bromide as initiator and MMA was then added to the system. Block copolymers were formed when MMA was added at ≤90% styrene conversion. Molecular weight distributions (Mw/Mn) of the block copolymers were ≤1.5. The possibility of end‐capping the polystyrene precursor as a means of improving its initiating efficiency towards MMA was also investigated but did not improve the system.© 2002 Society of Chemical Industry
Effects of poly(ethylene‐co‐propylene) elastomer on mechanical properties and combustion behaviour of flame retarded polyethylene/magnesium hydroxide composites
Authors: Wang Zhengzhou , Shen Xiaofeng , Fan Weicheng , Hu Yuan , Qu Baojun , Gui Zhou 
Published: October 2002

AbstractMagnesium hydroxide‐based halogen‐free flame retarded linear low density polyethylene composites containing poly(ethylene‐co‐propylene) elastomer were prepared in the melt process and subsequently vulcanized thermally. Influences of the elastomer on the mechanical properties, combustion characteristics and crystallization behaviour of polyethylene/magnesium hydroxide composites have been investigated. The results from the mechanical tests show that the incorporation of a suitable amount of elastomer into polyethylene/magnesium hydroxide composites after vulcanization can increase both the tensile strength and elongation greatly, compared with those of the composites without the elastomer. It has been found that the properties such as limiting oxygen index, UL‐94 rating, the time to ignition and the rate of heat release of polyethylene/magnesium hydroxide/elastomer composites are all improved in comparison with polyethylene/magnesium hydroxide composites at the same retardant level. Scanning electron microscopy studies show that the incorporation of the elastomer into polyethylene/magnesium hydroxide composites improves the compatibility between the filler and the polymer substrate. The degrees of crystallinity of polyethylene/magnesium hydroxide/elastomer composites decrease with increasing the elastomer content.© 2002 Society of Chemical Industry
The effect of the anion on the chemical shifts of the aromatic hydrogen atoms of liquid 1‐butyl‐3‐methylimidazolium salts
Authors: Headley Allan D. , Jackson Nichole M. 
Published: October 2002

AbstractThe NMR chemical shifts of the aromatic hydrogen atoms of 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate $(\hbox{BMI}^{+}\hbox{BF}_{4}^{-})$ and 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate $(\hbox{BMI}^{+}\hbox{PF}_{6}^{-})$ have been determined in nine deuterated solvents. The aromatic hydrogen atoms of $\hbox{BMI}^{+}\hbox{PF}_{6}^{-}$ are more sensitive to solvation effects than the hydrogen atoms of $\hbox{BMI}^{+}\hbox{BF}_{4}^{-}$. The interaction of the hydrogen atoms of the imidazolium cation with the relatively small and basic $\hbox{BF}_{4}^{-}$ anion is more intimate than the interaction with the fairly large, polarizable and less basic $\hbox{PF}_{6}^{-}$ anion. For both salts, the interaction involving the anion and the hydrogen atoms of the imidazolium cation is more intimate for H2, compared with H4 or H5. Owing to the intimate interaction of the ions of $\hbox{BMI}^{+}\hbox{BF}_{4}^{-}$, its aromatic hydrogen atoms are less sensitive to solvation effects than the hydrogen atoms of $\hbox{BMI}^{+}\hbox{PF}_{6}^{-}$. Copyright © 2001 John Wiley & Sons, Ltd.
Modeling intrinsic basicities and acidities
Authors: Alcamí Manuel , Mó Otilia , Yáñez Manuel 
Published: October 2002

AbstractWe illustrate the potential of ab initio and density functional theory (DFT) methods to model and gain some understanding of the intrinsic reactivity of molecules. We show how the use of high‐level ab initio or DFT calculations permit to rationalize (a) basicity and acidity trends along a series of homologous compounds, namely thiocarbonyl and selenocarbonyl derivatives, α,β‐unsaturated amines, phosphines and arsines, and α,β‐unsaturated alkanes, silanes, germanes and stannanes, (b) the role of intramolecular hydrogen bonds in intrinsic acidities and basicities, (c) the incidence of induced proton transfer process effects on the intrinsic basicity of compounds stabilized by intramolecular hydrogen bonds, (d) hybridization effects on intrinsic basicities, (e) the role of non‐classical structures in intrinsic basicities and (f) the observation of bond cleavage associated with gas‐phase protonation and the influence of these dissociative proton attachment mechanisms on the intrinsic basicity of the system. Copyright © 2002 John Wiley & Sons, Ltd.
Mechanism of hydrogen abstraction from methane and hydrofluoromethanes by hydroxyl radical
Authors: Korchowiec Jacek 
Published: October 2002

AbstractThe self‐consistent charge and configuration method for subsystems (SCCCMS) is applied to discuss the mechanism of hydrogen abstraction from methane and hydrofluoromethanes by hydroxyl radicals. All calculations are done at the B3LYP level of theory with the 6–311G(d,p) basis set. The results of energy partitioning, performed for transition‐state structures and two additional points on the minimum energy paths, demonstrate that the perturbation in the external potential (due to nuclei), namely classical/non‐classical electrostatic and polarization energies, is the most important. The formation of a pre‐reaction molecular adduct is controlled by electrostatic interactions due to their long‐range character. The charge‐transfer energy is unimportant for the hydrogen abstraction reactions. Copyright © 2002 John Wiley & Sons, Ltd.
Density functional theory study of the Lewis acid‐catalyzed Diels–Alder reaction of nitroalkenes with vinyl ethers using aluminum derivatives
Authors: Domingo Luis R. , Asensio Amparo , Arroyo Pau 
Published: October 2002

AbstractThe inverse electron demand Diels–Alder reaction of nitroalkenes with vinyl ethers catalyzed by Lewis acids based on aluminum metal, AlMe3, Al(OMe)3 and AlCl3 was studied using density functional theory methods. A continuum model was selected to represent the effects of dichloromethane used as solvent. For this cycloaddition reaction two reactive channels corresponding to the endo and exo approach modes of the vinyl ether to the Lewis acid‐coordinated nitroalkene were studied. Coordination of the aluminum metal to an oxygen atom of the nitroalkene increases the electrophilicity of the heterodiene, decreasing the activation energy of the cycloaddition. The substitution effect on the aluminum metal with Me, OMe and Cl on the activation energy and the stereoselectivity is discussed. An analysis of the static electrophilicity on reactants allows an explanation of the behavior of these Lewis acid‐catalyzed cycloadditions. Copyright © 2002 John Wiley & Sons, Ltd.
A radical route in the biomimetic oxidation of a tertiary amine
Authors: Cuppoletti Andrea , Galli Carlo , Gentili Patrizia , Petride Horia 
Published: October 2002

AbstractWhereas the biomimetic oxidative N‐dealkylation of tertiary amines with t‐BuOOH and an iron(III) tetraphenylporphyrin typically proceeds by an electron transfer (ET) route, a radical H‐atom transfer (HAT) route has been found to operate with N‐benzylaziridine (1), an amine that is fairly resistant towards one‐electron oxidation for steric reasons. New mechanistic information is presented in favour of this radical route, and the exclusive formation of the dimeric product N,N′‐dibenzylpiperazine (2) is explained in the light of the Baldwin's rules. Flash photolysis data provide a rate constant of 1.7 × 105 s−1 for the ring opening of the aziridine radical (1.) to the imine radical (4.) in the early stages of the process leading to 2. Semiempirical calculations indicate the ring‐opened radical 4. to be more stable than 1.. Copyright © 2002 John Wiley & Sons, Ltd.
Preparation of amphiphilic statistical copolymers of 2‐hydroxyethyl methacrylate with 2‐diethylaminoethyl methacrylate, precursors of water‐soluble copolymers
Authors: Martinez Gerardo , Sanchez‐Chaves Manuel , Lopez Madruga Enrique 
Published: October 2002

AbstractStatistical copolymers of 2‐hydroxyethyl methacrylate (HEMA) and 2‐diethylaminoethyl methacrylate (DEA) were synthesized at 50 °C by free‐radical copolymerization in bulk and in a 3 mol L−1 N,N′‐dimethylformamide solution with 2,2′‐azobisisobutyronitrile as an initiator. The solvent effect on the apparent monomer reactivity ratios was attributed to the different aggregation states of HEMA monomer in the different solvents. The copolymers obtained were water‐insoluble at a neutral pH but soluble in an acidic medium when the molar fraction of the DEA content was higher than 0.5. The quaternization of DEA residues increased the hydrophilic character of the copolymers, and they became water‐soluble at a neutral pH when the HEMA content was lower than 0.25. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2427–2434, 2002
Photocrosslinking system based on a poly(vinyl phenol)/thermally degradable diepoxy crosslinker blend
Authors: Okamura Haruyuki , Toda Shogo , Tsunooka Masahiro , Shirai Masamitsu 
Published: October 2002

AbstractPhotocrosslinkable systems with thermally cleavable properties based on blends of poly(vinyl phenol) (PVP) and diepoxides were investigated. Thermally cleavable diepoxides as crosslinkers were prepared and characterized. As a thermally cleavable linkage, a tertiary ester moiety was incorporated into the crosslinker molecule. PVP/crosslinker blended films containing photoacid generators (PAGs) became insoluble in solvents after UV irradiation and subsequent post‐exposure‐bake (PEB) treatment. With a rise in the PEB temperature, the insoluble fraction of the irradiated films increased, passed through a maximum value, decreased, and increased again at elevated baking temperatures. The insolubilization profiles of the irradiated films were complicated and strongly dependent on the type of PAG used, the structure of the crosslinkers, and the PVP/crosslinker ratio. A mechanism for the thermal degradation was studied with Fourier transform infrared spectroscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3055–3062, 2002
Solvent‐induced crystallization in poly(ethylene terephthalate) during mass transport
Authors: Ouyang Hao , Lee Wen‐Hao , Shiue Sham‐Tsong , Lin Tsang‐Lang 
Published: October 2002

AbstractSolvent transport in poly(ethylene terephthalate) (PET) and related phase transformation were investigated. The data of mass sorption were analyzed according to Harmon's model for Case I (Fickian), Case II (swelling), and anomalous transport. This transport process in PET is accompanied by the induced crystallization of the original amorphous state. The transformation was examined by wide‐angle X‐ray scattering, small‐angle X‐ray scattering, differential scanning calorimetry, and Fourier transform infrared spectroscopy. During this process, the matrix is under a strain state that causes different kinetic paths of crystallization as compared with that by thermal annealing. This state of strain assists the development of the solvent‐induced crystallization. The model regarding crystallization was proposed in terms of the study of long period L, the crystal thickness lc, and the thickness of amorphous layer la obtained from the one‐dimensional correlation function and interface distribution function. Different kinetic paths were discovered for different crystallization processes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1444–1453, 2002
Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends
Authors: Varghese Hima , Johnson T. , Bhagawan S. S. , Joseph Seena , Thomas Sabu , Groeninckx G. 
Published: October 2002

AbstractThe dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass‐transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δmax were in accordance with morphology changes in the blends. From tan δ values of peroxide‐cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide‐angle X‐ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002
Ring‐chain interactions in solutions of cyclic and linear poly(methylene) ester oligomers in p‐dioxan and chloroform
Authors: Xu R. , Leonard J. , Bui V. T. 
Published: October 2002

AbstractThe thermodynamic behavior of ternary solutions containing one cyclic (CYC10 and CYC20) and one linear (LIN10 and LIN20) poly(methylene) ester oligomer, respectively, in p‐dioxan and chloroform were investigated through vapor‐pressure measurements. Experiments were carried out at 25, 30, 35, and 40 °C. The ring‐chain interaction parameters χ″ were evaluated using the Leonard's equation for a ternary polymer solution containing one ring polymer. Results indicated that the values of χ″ are concentration and solvent dependent, and they vary with molecular size and slightly with temperature. All χ″ values were positive for both CYC10/LIN10 and CYC20/LIN20 blends, with the higher values for the former system, indicating that both ring‐chain oligomer blends are nearly immiscible, and the difference between cyclic and linear oligomers decreases as molecular size increases. The positive χ″ agrees with differential scanning calorimetric measurements performed on ring‐chain oligomer blends that show two distinct endotherms for the blends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1425–1433, 2002
Effect of inert diluent segment on the miscibility behavior of poly(vinylphenol) with poly(acetoxystyrene) blends
Authors: Kuo Shiao‐Wei , Chang Feng‐Chih 
Published: October 2002

AbstractPolymer blends of poly(vinylphenol) (PVPh) and poly(styrene‐co‐vinylphenol) with poly(p‐acetoxystyrene) (PAS) were prepared by solution casting from tetrahydrofuran solution. The thermal properties and hydrogen bonding of the blends were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. Although hydrogen bonding existed between the PVPh and PAS segments, the experimental results indicated that PVPh is immiscible with PAS as shown by the existence of two glass‐transition temperatures over the entire composition range by DSC. This phenomenon is attributed to the strong self‐association of PVPh, intramolecular screening, and functional group accessibility effects of the PVPh/PAS blend system. However, the incorporation of an inert diluent moiety such as styrene into the PVPh chain renders the modified polymer to be miscible with PAS. Copolymers containing between 16 and 51 mol % vinylphenol were fully miscible with PAS according to DSC studies. These observed results were caused by the reduction of the strong self‐association of PVPh and the increase of the interassociation between PVPh and PAS segments with the incorporation of styrene on the PVPh chain. According to the Painter‐Coleman association model, the interassociation equilibrium constant of PVPh/PAS blends was determined by a model compound and polymer blend. Good correlation between these two methods was obtained after considering the intramolecular screening and functional group accessibility effect in the polymer blend. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1661–1672, 2002