bluuebunny/crossref_metadata_2025 huggingface dataset:
Lesbian, gay, bisexual, and transgender college students with disabilities: A look at multiple cultural minorities
Authors: Harley Debra A. , Nowak Theresa M. , Gassaway Linda J. , Savage Todd A.
Published: October 2002

College students with disabilities who are lesbian, gay, bisexual, or transgender (LGBT) represent diverse cultural minorities with multiple service needs involving disabilities, identities, and adjustment strategies. These students are usually accommodated in the college environment because of their disability while simultaneously marginalized based on their sexual orientation. This article discusses LGBT college students with disabilities as multiple cultural minorities with a focus on educational environments, institutional issues, and strategies for university personnel. © 2002 Wiley Periodicals, Inc.
Not all school dropouts are the same: Ethnic differences in the relation between reason for leaving school and adolescent substance use
Authors: Aloise‐Young Patricia A. , Chavez Ernest L.
Published: October 2002

Several national studies have revealed that students choose to drop out of school for a variety of reasons. Moreover, there are ethnic differences in the reasons dropouts give for leaving school. In the present study, the relation between reason for dropping out and substance use was explored in Mexican American and non‐Hispanic White adolescents. The results revealed that for Mexican American adolescents, substance use was highest among those who left school to be with their friends and lowest among those who left for family‐related reasons. Among non‐Hispanic White adolescents, there were no significant differences in substance use as a function of reason for leaving school. For both ethnicities, nearly one‐third of the dropouts reported that their substance use was an important contributor to their decision to leave school early. The theoretical and practical implications of these findings are discussed. Recommendations are made for ways in which the reasons that dropouts give for leaving school can be used to inform school programs. © 2002 John Wiley & Sons.
Thermal and hyperbaric addition of N,N‐ and N,O‐ binucleophiles on cycloalkylidenic bromo esters
Authors: Rulev Alexandre Y. , Maddaluno Jacques
Published: October 2002

The thermal and high‐pressure (11 kbar) induced reaction between 2‐bromo‐2‐(cycloalkylidene)acetates and N,O‐ and N,N‐binucleophiles (such as ethylenediamines or aminoethanols) provides morpholin‐2‐ones and piperazin‐2‐ones. Thus, in contrast to simple primary amines, binucleophiles do not form spirocyclic derivatives. The expected Michael addition competes with a cascade reaction consisting of a migration of the double bond followed by the substitution of the newly established allylic halogen and a lactonization (lactamization), and eventually ended by a back‐migration of the double bond. Copyright © 2002 John Wiley & Sons, Ltd.
Interactions of chiral quinuclidin‐3‐yl benzoates with butyrylcholinesterase: kinetic study and docking simulations
Authors: Primožič Ines , Hrenar Tomica , Tomić Srđanka , Meić Zlatko
Published: October 2002

Both enantiomers of quinuclidin‐3‐yl benzoate (RQBz and SQBz) were synthesized in order to examine the stereoselectivity of the hydrolysis of these esters catalyzed by horse serum butyrylcholinesterase (BChE). The hydrolysis of benzoylcholine (BzCh) was also studied in order to determine the influence of the alcohol part of ­the esters upon the kinetics. The kcat value for the substrates decreased in order BzCh > RQBz (4‐fold slower) ≫­SQBz (76‐fold slower reaction). KM values determined for quinuclidinium substrates revealed that the binding affinity of RQBz (0.28 mM) is approximately 2‐fold lower than that of SQBz (0.13 mM) towards BChE. From the ratio of the enantiomeric kcat/KM values, an enantiomeric excess of 78% was calculated, indicating that the resolution of racemic quinuclidin‐3‐yl benzoate can be achieved by hydrolysis with BChE. The orientations of all the studied benzoate esters and butyrylcholine (BuCh) in the active site of human BChE were proposed by flexible ligand docking with AutoDock 3.0. Analyses of the Michaelis complexes obtained revealed that there are numerous similar close contacts in the active site. The main difference in binding of quinuclidinium and choline esters was found in the ammonium electrostatic region which includes cation–π interaction of the ammonium moiety of substrates with the indole ring ­of Trp84. The important cation–π interaction with Trp84 was lowest in the case of the S‐enantiomer of QBz, which might be the main explanation for the slowest rate of hydrolysis of that compound. Copyright © 2002 John Wiley & Sons, Ltd.
Catalysis in electron transfer reactions: facts and mechanistic insights
Authors: Fukuzumi Shunichi
Published: October 2002

Catalysis in electron transfer reactions between electron donors and acceptors is described and the important mechanistic insight is provided by showing a number of examples of both thermal and photochemical reactions that involve metal ion‐catalyzed electron transfer processes as the rate‐determining steps. The quantitative measure of Lewis acidity of metal ions was obtained from the gzz values of ESR spectra of superoxide–metal ion complexes which vary significantly depending on the type of metal ions. Copyright © 2002 John Wiley & Sons, Ltd.
Strained hydrocarbons from cyclic diynes—preparation and reactivity
Authors: Bethke Sabine , Brand Stefan , Treptow Björn , Gleiter Rolf
Published: October 2002

The reaction of cyclic diynes with either CpCo(CO)2 or AlCl3 yielded strained hydrocarbons in which a Dewar benzene or a tricyclo[4.2.0.02,5]octa‐3,7‐diene frame is bridged by hydrocarbon chains. The photochemistry and thermochemistry of these species are discussed. Results of quantum chemical calculations (DFT, CASPT2) are used to discuss the thermochemistry of four different fourfold bridged tricyclo[4.2.0.02,5]octa‐3,7‐dienes. Depending on the bridging mode, either a Cope‐type rearrangement or a ring opening reaction is preferred. Copyright © 2002 John Wiley & Sons, Ltd.
Thermo‐solvatochromism in aqueous alcohols: effects of the molecular structures of the alcohol and the­solvatochromic probe
Authors: Antonious Maged S. , Tada Erika B. , Seoud Omar A. El
Published: October 2002

Thermo‐solvatochromism of 2,6‐diphenyl‐4‐(2,4,6‐triphenylpyridinium‐1‐yl)‐1‐phenolate, 2,6‐dichloro‐4‐(2,4,6‐triphenylpyridinium‐1‐yl) phenolate and 1‐methylquinolinium‐8‐olate in the temperature range 10–45 °C was studied in mixtures of water with methanol, ethanol, 1‐propanol, 2‐propanol, 2‐methyl‐2‐propanol, 2‐methoxyethanol and 1,2‐ethanediol. Plots of the solvent polarity parameter, ET in kcal mol−1, versus mole fraction of water in the binary mixture, χw, indicated that all probes are preferentially solvated by the alcohol. Thermo‐solvatochromic data for aqueous methanol, 2‐methoxyethanol and 1,2‐ethanediol were fitted to a simple solvent‐exchange model, in which water substitutes alcohol in the probe solvation micro‐sphere. Data for the remaining alcohols required a more elaborate model, where water and water–alcohol complex substitute alcohol and/or water in the probe solvation micro‐sphere. A temperature increase causes gradual desolvation of the probe, due to a decrease in the H‐bonding abilities of both components of the binary mixture. Copyright © 2002 John Wiley & Sons, Ltd.
Solute–solvent and solvent–solvent interactions in the preferential solvation of Brooker's merocyanine in binary solvent mixtures
Authors: da Silva Domingas C. , Ricken Ingrid , Silva Marcos A. do R. , Machado Vanderlei G.
Published: October 2002

The ET polarity values of 4‐[(1‐methyl‐4(1H)‐pyridinylidene)ethylidene]‐2,5‐cyclohexadien‐1‐one, better known as Brooker's merocyanine, were collected in binary mixtures comprising a non‐protic [acetonitrile, dimethyl sulfoxide (DMSO) and acetone] and a protic (water, methanol, ethanol, propan‐2‐ol and butan‐1‐ol) solvent. Data referring to mixed systems involving water and alcohols (methanol, ethanol, propan‐2‐ol and 2‐methylpropan‐2‐ol) were also collected. These data were used in the investigation of the preferential solvation of the dye. Each solvent system was analyzed in terms of both solute–solvent and solvent–solvent interactions. These latter interactions are responsible for the synergistic effects observed for the ET parameter in many binary mixtures. All data were successfully fitted to a model based on solvent exchange equilibria, which allowed the separation of the different contributions of the solvent species in the solvation shell of the dye. This model was then successfully applied to explain the kinetic behavior of the methylation of sodium 4‐nitrophenoxide in acetone–water mixtures. This result suggests that this solvatochromic strategy can be successful in the analysis of many other solvent‐dependent kinetic and thermodynamic processes occurring in mixed solvents. Copyright © 2002 John Wiley & Sons, Ltd.
Experimental and computational studies of α‐lactones: Structure and bonding in the three‐membered ring
Authors: Buchanan J. Grant , Charlton Michael H. , Mahon Mary F. , Robinson James J. , Ruggiero Giuseppe D. , Williams Ian H.
Published: October 2002

Crystallographic analysis of the bromo‐β‐lactones obtained by addition of bromine to aqueous solutions of disodium 2,3‐dimethylmaleate and 2,3‐dimethylfumarate reveals stereochemistries (4 from 1, and 3 from 2) opposite to those originally assigned (3 from 1, and 4 from 2). Specifically, the maleate leads to a bromo‐β‐lactone with the methyl groups in a trans relationship, whereas the fumarate leads to the corresponding cis isomer. To account for this observation, we suggest that the first‐formed intermediate in each case is an α‐lactone. B3LYP/6–31 + G(d) calculations in PCM water indicate that the cyclic chloronium and bromonium adducts of acrylate anion are not intermediates but transition structures for the degenerate rearrangement of halomethyl‐α‐lactones. Bader analysis of MP2/6–31 + G(d,p) electron density distributions indicates that oxiranone possesses considerable ionic character in the endocyclic Cα—On bond. In PCM water there is neither a ring critical point nor a bond critical point for Cα—On, although geometrically the molecule still possesses an acute‐angled three‐membered ring with a CαCOn angle of only 69°. Combined quantum/classical calculations for B3LYP/6–31 + G(d) oxiranone surrounded by about 600 explicit TIP3P water molecules indicate that the cyclic structure is an energy minimum in aqueous solution, and Bader analysis gives a result similar to that from the continuum model. Copyright © 2002 John Wiley & Sons, Ltd.
A stable β‐silyl carbocation with allyl conjugation
Authors: Lambert Joseph B. , Liu Chunqing , Kouliev Timur
Published: October 2002

The carbocation Et3SiCH2C+Ph(CHCHPh) has been found to be stable at room temperature with tetrakis(pentafluorophenyl)borate as the anion and benzene as the solvent. The cation constitutes the first stable β‐silyl carbocation in which positive charge is delocalized both allylically and benzylically. Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis and characterization of liquid‐crystalline polyphosphonates containing disubstituted ferrocene esters as mesogens
Authors: Senthil S. , Kannan P.
Published: October 2002

A series of ferrocene‐containing liquid‐crystalline polyphosphonates with an even number of methylene groups are reported. All the polymers gave birefringent melts. The mesophase was identified as transparent with an increase in the spacer. The effects of pendant substitution and the spacer were studied with thermogravimetric analysis and differential scanning calorimetry. The effects of the phosphonate group in the spacer and the ferrocene ester group in the mesogen were examined. The presence of a steplike mesogenic structure and a pendant phenyl group in the spacer led to reductions in the glass‐transition and melting temperatures. The ferrocene moiety in the mesogen might be one of the reasons for the increased thermal stability and decreased liquid crystallinity. An energy‐minimized structure for the mesogenic and spacer segments was created with computer‐modeling programs, and it suggested the reason for the reductions in the glass‐transition and melting temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2256–2263, 2002
Synthesis and characterization of new highly organosoluble poly(ether imide)s based on 3,3′,5,5′‐tetramethyl‐2,2‐bis[4‐(4‐dicarboxyphenoxy)phenyl]propane dianhydride
Authors: Liaw Der‐Jang , Chen I‐Wen , Chen Wen‐Hsiang , Lin Shu‐Ling
Published: October 2002

A new bis(ether anhydride), 3,3′,5,5′‐tetramethyl‐2,2‐bis[4‐(4‐dicarboxyphenoxy)phenyl]propane dianhydride (3), was prepared in three steps: the nitro displacement of 4‐nitrophthalonitrile with 2,2‐bis(4‐hydroxy‐3,5‐dimethylphenyl)propane, the alkaline hydrolysis of the intermediate bis(ether dinitrile), and the subsequent dehydration of the resulting bis(ether diacid). A series of new highly soluble poly(ether imide)s with tetramethyl and isopropylidene groups were prepared from the bis(ether anhydride) 3 with various diamines by a conventional two‐stage synthesis including polyaddition and chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.54–0.73 dL g−1. Gel permeation chromatography measurements revealed that the polymers had number‐average and weight‐average molecular weights of up to 54,000 and 124,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility and were readily dissolved in various solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, N,N‐dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. Most of the polymers could be dissolved with chloroform concentrations as high as 30 wt %. These polymers had glass‐transition temperatures of 244–282 °C. Thermogravimetric analysis showed that all polymers were stable, with 10% weight losses recorded above 463 °C in nitrogen. These transparent, tough, and flexible polymer films were obtained through solution casting from N,N‐dimethylacetamide solutions. These polymer films had tensile strengths of 81–102 MPa and tensile moduli of 1.8–2.0 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2556–2563, 2002
Kinetics of the polycondensation and copolycondensation of bis(3‐hydroxypropyl) terephthalate and bis(4‐hydroxybutyl) terephthalate
Authors: Kim Joon Ho , Park Jun Ho , Kwon Chang Hwan , Lyoo Won Seok
Published: October 2002

The kinetics of the polycondensation and copolycondensation reactions of bis(3‐hydroxypropyl) terephthalate (BHPT) and bis(4‐hydroxybutyl) terephthalate (BHBT) as monomers were investigated at 270 °C in the presence of titanium tetrabutoxide as a catalyst. BHPT was prepared by the ester interchange reaction of dimethyl terephthalate and 1,3‐propanediol (1,3‐PD). Through the same method adopted for BHPT synthesis, BHBT was prepared with 1,4‐butanediol instead of 1,3‐PD. With second‐order kinetics applied for polycondensation, the rate constants of the polycondensation of BHPT and BHBT, k11 and k22, were calculated to be 4.08 and 4.18 min−1, respectively. The rate constants of the cross reactions in the copolycondensation of BHPT and BHBT, k12 and k21, were calculated with results obtained from proton nuclear magnetic resonance spectroscopy analysis. The rate constants during the copolycondensation of BHPT and BHBT at 270 °C decreased in the order k12 > k22 > k11 > k21, indicating that the reactivity of BHBT was larger than that of BHPT at 270 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2435–2441, 2002
Synthesis of poly(p‐phenylene vinylene)‐ and poly(phenylene ethynylene)‐based polymers containing p‐terphenyl in the main chain with alkoxyphenyl side groups
Authors: Spiliopoulos Ioakim K. , Mikroyannidis John A.
Published: October 2002

Starting from the pyrylium salt and following a facile synthetic route, we synthesized and polymerized 4,4″‐diiodo‐2′,6′‐di[4‐(2′‐ethylhexyl)oxy]phenyl‐p‐terphenyl with p‐divinylbenzene or p‐diethynylbenzene. The resulting polymers had moderate molecular weights, were amorphous, and dissolved in tetrahydrofuran and chloroform, with glass‐transition temperatures of 120–131 °C. The polymers behaved as violet‐blue‐emitting materials with photoluminescence maxima around 420 and 450 nm in solution and in thin films, respectively. They possessed well‐defined chromophores resulting from steric interactions in the polymer chain. The photoluminescence quantum yields were up to 0.29. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2591–2600, 2002
Synthesis and properties of new aromatic polysquaramide by solid‐state thermal polycondensation of salt monomer composed of squaric acid and bis(4‐aminophenyl) ether
Authors: Imai Yoshio , Shiratori Motohito , Inoue Tatsuo , Kakimoto Masa‐aki
Published: October 2002

The 1:1 stoichiometric salt monomer composed of squaric acid and bis(4‐aminophenyl) ether was successfully prepared and subjected to solid‐state thermal polycondensation under ordinary or high pressure, giving quite readily the aromatic polysquaramide with moderately high molecular weight. The polysquaramide formed was actually the random copolymer consisting of two component polymers, one of the main component being the polymer with a quasi‐aromatic mesoionic structure. The aromatic polysquaramide was crystalline and had a glass‐transition temperature of 245 °C, with an initial weight‐loss temperature of 400 °C in nitrogen. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2648–2655, 2002
Highly luminescent diyne (CCCC) containing hybrid polyphenyleneethynylene/poly(p‐phenylenevinylene) polymer: Synthesis and characterization
Authors: Egbe Daniel Ayuk Mbi , Birckner Eckhard , Klemm Elisabeth
Published: October 2002

Luminophoric dialdehyde 1,4‐bis[4‐formylphenylethynyl‐(2,5‐dioctadecyloxyphenyl)‐buta‐1,3‐diyne] (4) enables the synthesis of diyne‐containing hybrid polyphenyleneethynylene/poly(p‐phenylenevinylene) polymer poly[1,4‐phenylene‐ethynylene‐1,4‐(2,5‐dioctadecyloxy)phenylene‐butadi‐1,3‐ynylene‐1,4‐(2,5‐dioctadecyloxy)phenylene‐ethynylene‐1,4‐phenylene‐ethene‐1,2‐diyl‐1,4‐(2,5‐dioctadecyloxy)phenylene‐ethene‐1,2‐diyl] (7) with a well‐defined general structure (PhCCArCCCCArCC PhCHCHArCHCH)n, which was confirmed by NMR and infrared spectroscopy. The highly luminescent material is thermostable, soluble in usual organic solvents through the grafting of octadecyloxy side groups, and can be processed into transparent films. With the aim to investigate the effect of CCCC in the photophysical behavior of 7, a comparison of the photophysics of monomers 3 [1,4‐bis(4‐formylphenylethynyl)‐2,5‐dioctadecyloxybenzene] and 4 and subsequently of their respective polymers 6 and 7 has been carried out. Similar photophysical behaviors for 6 (poly[1,4‐phenylenethynylene‐1,4‐(2,5‐dioctadecyloxyphenylene)ethene‐1,2‐diyl]) and 7 were observed in dilute CHCl3 solution as a result of an identical chromophore system responsible for the absorption (λa = 448 nm) and emission (λf = 490 nm) in both compounds. The increased planarization and enhanced rigidity of the conjugated backbone in the solid state at room temperature as well as in frozen dilute tetrahydrofuran solution at 77 K cause the bathochromic shift of the absorption and emission spectra. The large octadecyloxy side chains obviously limit strong π‐π interchain interactions in the solid films, which explains the high fluorescence quantum yields of 35 and 52% obtained for 6 and 7, respectively. The energetically arduous migration of the π electron through the diyne units not only requires a higher threshold voltage for the detection of photoconductivity in 7 but could possibly limit radiationless deactivation channels of the exciton, which explains the approximate 20% fluorescence quantum yields difference between 6 and 7 in the solid state. The electron‐withdrawing effect of the triple bonds confer both 6 and 7 with a good electron‐accepting property (Eox = 1.39 V vs Ag/AgCl) if used in light‐emitting diode devices. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2670–2679, 2002
Synthesis and functionalization of poly(ether sulfone)s based on 1,1,1‐tris(4‐hydroxyphenyl)ethane
Authors: Kricheldorf Hans R. , Vakhtangishvili Lali , Fritsch Detlev
Published: October 2002

Branched poly(ether sulfone)s were prepared from 1,1,1‐tris(4‐hydroxyphenyl) ethane and 4,4′‐difluorodiphenyl sulfone (DFDPS) either by polycondensation in dimethyl sulfoxide with the elimination of water or via the silyl method in N‐methylpyrrolidone. With an exact 1/1 stoichiometry, crosslinking was avoidable, but significant fractions of cyclic oligomers and polymers were detected by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Furthermore, bridged cycles (bicycles) were detected. For the silyl method, even an excess of DFDPS of 10 mol % did not result in crosslinking. The pendant OH groups were modified by acylation with acetic anhydride, methacrylic anhydride, undecylenoyl chloride, or cinnamoyl chloride. Alkylation was only successful in a one‐pot procedure via the silyl method. Alkylbromide, ethyl bromoacetate, 3‐chloropropionitrile, 4‐nitrobenzyl bromide, and 3,4‐dichlorobenzyl chloride served as alkylating agents. With 1,3‐propane and 1,4‐butane sultone, poly(ether sulfone)s with pendant sulfonate groups were obtained. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2967–2978, 2002
Copolymerization of 1,3‐butadiene and isoprene with cobalt dichloride/methylaluminoxane in the presence of triphenylphosphine
Authors: Nath Dilip C. D. , Shiono Takeshi , Ikeda Tomiki
Published: October 2002

The homopolymerization and copolymerization of 1,3‐butadiene and isoprene were achieved at 0 °C with cobalt dichloride in combination with methylaluminoxane and triphenylphosphine (Ph3P). For 1,3‐butadiene, highly cis‐specific and 1,2‐syndiospecific polymerization proceeded in the absence or presence of Ph3P, respectively, although the activity with Ph3P was much higher than that without Ph3P. Only a trace of the polymer was, however, obtained in isoprene polymerization when Ph3P had been added. For copolymerization, the polymer yield in the presence of Ph3P was about three times higher than that in its absence. Copolymerization in the presence of Ph3P was, therefore, investigated in more detail. Unimodal gel permeation chromatography elution curves with narrower polydispersity (weight‐average molecular weight/number‐average molecular weight ≈ 1.5) indicated that the propagation reaction proceeded by single‐site active species. Both the yield and molecular weight of the copolymer decreased with an increasing amount of isoprene in the feed, and this was followed by an increase in the isoprene content in the copolymer. The monomer reactivity ratios, r1 (1,3‐butadiene) and r2 (isoprene), were estimated to be 2.8 and 0.15, respectively. Although the 1,3‐butadiene content in the copolymer was strongly dependent on the comonomer composition in the feed, the ratio of 1,2‐inserted units to 1,4‐inserted units of 1,3‐butadiene was constant. Concerning the isoprene unit, the percentage of 1,2‐ and 3,4‐inserted units was increased at the expense of 1,4‐inserted units with an increasing isoprene content in the feed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3086–3092, 2002
Use of α‐diketones as visible photoinitiators for the photocrosslinking of waterborne latex paints
Authors: Bibaut‐Renauld C. , Burget D. , Fouassier J. P. , Varelas C. G. , Thomatos J. , Tsagaropoulos G. , Ryrfors L. O. , Karlsson O. J.
Published: October 2002

The efficiency of several α‐diketones as visible light photoinitiators for the crosslinking of waterborne latex dispersions in the presence of acrylic monomers was evaluated. Among the eight α‐diketones studied, camphorquinone allows the fastest curing speed, and the curing of the acrylic waterborne coating is not affected by the presence of oxygen. The properties of the sunlight‐cured volatile organic compound (VOC)‐free pigmented paints prepared from the waterborne latex are as good or better than the equivalent conventional paint containing VOCs. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3171–3181, 2002
Preparation and characterization of cyclic polystyrene with short poly(2‐tert‐butylbutadiene) sequences
Authors: Takano Atsushi , Nonaka Atsushi , Kadoi Osamu , Hirahara Kazuhiro , Kawahara Seiichi , Isono Yoshinobu , Torikai Naoya , Matsushita Yushu
Published: October 2002

A polystyrene‐block‐oligo(2‐tert‐butylbutadiene)‐block‐polystyrene triblock copolymer was prepared and cyclized by end‐to‐end ring closure. Ring‐shaped polystyrene‐block‐oligo(2‐tert‐butylbutadiene) was isolated from the coupling product via gel permeation chromatography (GPC) fractionation. The ring polymer was ozonized for decomposition of the oligo(2‐tert‐butylbutadiene) sequences selectively referring to the linear molecule. From GPC analysis of the decomposed products by ozonolysis, it was quantitatively confirmed that the fractionated product was 86% ring molecules. Single chain dimensions of the ring and linear molecules in a good solvent, benzene, and in a θ solvent, cyclohexane, were measured with small‐angle neutron scattering. The ratios of the radii of gyration, Rg(ring)/Rg(linear), were 0.780 in benzene and 0.789 in cyclohexane. These were compared with theoretically predicted values. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1582–1589, 2002
Investigation of the deformation of homogeneous poly(ethylene‐co‐1‐octene) by wide‐ and small‐angle X‐ray scattering using synchrotron radiation
Authors: Androsch R. , Stribeck N. , Lüpke T. , Funari S. S.
Published: October 2002

The deformation behavior of homogeneous ethylene‐1‐octene copolymers was investigated as a function of the crystallinity and the crystal size and perfection, respectively, by wide‐ and small‐angle X‐ray scattering using synchrotron radiation. The crystallinity and the crystal size and perfection, respectively, are controlled by the copolymer composition and the condition of melt crystallization. The deformation includes rotation of crystals, followed by plastic deformation and complete melting of the initial crystal population, and final formation of microfibrils. The process of rotation, plastic deformation, and melting of crystals of the initial structure is completed at lower strain if the size and perfection of the crystals, respectively, decrease, that is, if crystals thermally melt at lower temperature. The kinetics of the fibrillation of the initial structure seems independent of the crystal symmetry, that is, rotation and melting of pseudohexagonal and orthorhombic polyethylene crystals (as evident in low‐crystalline specimens) are similar. The structure of the microfibrils, before and after stress release, is almost independent of the condition of prior melt crystallization, which supports the notion of complete melting of the initial crystal population. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1919–1930, 2002
Interlocking shish‐kebab morphology in polybutene‐1
Authors: Kalay G. , Kalay C. R.
Published: October 2002

The aim of this research was to explore the effect of shear‐controlled orientation injection molding (SCORIM) on polybutene‐1 (PB‐1). This article describes the methods and processing conditions used for injection molding and discusses the properties of the moldings. Both conventional and SCORIM have been used for the production of moldings. SCORIM is based on the application of specific macroscopic shears to a solidifying melt that facilitates enhanced molecular alignment. The effect of the process was investigated by performing mechanical tests, X‐ray studies, differential scanning calorimetric studies, polarized light microscopy, and atomic force microscopy (AFM). Moldings exhibited an improved mechanical performance as compared with conventional moldings. Young's modulus was increased over twofold, and the impact energy was enhanced by 60%. The improvement in mechanical performance was combined with an increase in crystallinity and enhanced molecular orientation. The application of SCORIM also favored the formation of the stable Form I′ in PB‐1. The formation of interlocking shish‐kebab morphology following the application of SCORIM was observed in the AFM studies. Relationships between the mechanical properties of PB‐1 and the micromorphologies formed during processing are demonstrated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1828–1834, 2002
Synthesis and characterization of copolyperoxides of indene with styrene, α‐methylstyrene, and α‐phenylstyrene
Authors: De Priyadarsi , Sathyanarayana D. N.
Published: October 2002

The oxidative copolymerization of indene with styrene, α‐methylstyrene, and α‐phenylstyrene is investigated. Copolyperoxides of different compositions have been synthesized by the free‐radical‐initiated oxidative copolymerization of indene with vinyl monomers. The compositions of the copolyperoxides obtained from the 1H and 13C NMR spectra have been used to determine the reactivity ratios of the monomers. The reactivity ratios indicate that indene forms an ideal copolyperoxide with styrene and α‐methylstyrene and alternating copolyperoxides with α‐phenylstyrene. Thermal degradation studies via differential scanning calorimetry and electron‐impact mass spectroscopy support the alternating peroxide units in the copolyperoxide chain. The activation energy for thermal degradation suggests that the degradation is dependent on the dissociation of the peroxide (OO) bonds in the backbone of the copolyperoxide chain. Their flexibility has been examined in terms of the glass‐transition temperature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2004–2017, 2002
Synthesis by plasma and characterization of bilayer aniline–pyrrole thin films doped with iodine
Authors: Morales J. , Olayo M. G. , Cruz G. J. , Olayo R.
Published: October 2002

The synthesis by plasma and characterization of aniline–pyrrole bilayer polymers doped in situ with iodine were studied. The objective was to study the electrical conductivity of thin films composed of alternating layers of different polymers. The results indicated that the plasma technique is capable of forming chemically bonded layered polymers with several possible combinations. The electric conductivity was studied during heating–cooling cycles so the dependence of the bilayer polymers on temperature could be observed. The behavior was related with the Arrhenius model, with average activation energies of 0.4 ± 0.1 eV in the heating steps and 0.5 ± 0.1 eV in the cooling steps. The difference in both steps shows the influence of the aniline in the bilayer polymer network because polyaniline presents changes in the structure during heating processes. The bilayer aniline–pyrrole polymers had greater electric conductivity at room temperature than that shown by the separate homopolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1850–1856, 2002
Recurrent pneumothoraces associated with nocturnal noninvasive ventilation in a patient with muscular dystrophy
Authors: Choo‐Kang Lee R. , Ogunlesi Folasade O. , McGrath‐Morrow Sharon A. , Crawford Thomas O. , Marcus Carole L.
Published: October 2002

Although a common complication of mechanical ventilation in acute respiratory failure, spontaneous pneumothorax has been rarely reported among patients on chronic, intermittent, noninvasive positive pressure support. We report the first case of recurrent pneumothoraces associated with nocturnal bilevel positive airway pressure ventilation via a nasal mask.

A 26‐year old man with chronic respiratory failure secondary to an unclassified neuromuscular condition suffered four separate episodes of spontaneous pneumothorax over a 12‐month period. Two episodes occurred while he was asleep on bilevel positive airway pressure support. He was found to have numerous subpleural blebs, and we propose a mechanism for their development. Following open pleurodesis and blebectomy, the patient has not had another pneumothorax.

Given the increasing utilization of chronic nocturnal bilevel positive airway pressure ventilation, we suggest that healthcare providers and patients be made aware of this potentially life‐threatening complication. Pediatr Pulmonol. 2002; 34:73–78. © 2002 Wiley‐Liss, Inc.
Inflammatory endobronchial polyps in childhood: Clinical spectrum and possible link to mechanical ventilation
Authors: McShane D. , Nicholson A.G. , Goldstraw P. , Ladas G. , Travis W.D. , Ramanan R. , Balfour‐Lynn I.M. , Rosenthal M. , Bush A.
Published: October 2002

Inflammatory polyps of the airways are now regarded as histopathologically distinct nonneoplastic endobronchial lesions, which in adults are associated with a variety of chronic inflammatory insults. However, their clinical presentation in the pediatric population is extremely rare, with the etiology of such polyps poorly defined. The clinical and histopathological data from four pediatric patients, identified in the histopathology files of the Royal Brompton Hospital, were retrospectively reviewed.

Three out of 4 patients had a history of mechanical ventilation in the neonatal period. In these 3 patients, the polyps were all situated in the proximal airways on the right side. These 3 patients presented at 6 weeks, 7 weeks, and 2 years, respectively, and were successfully treated by polypectomy at rigid bronchoscopy, with subsequent return to normality. One patient, presenting at 12 years of age without history of iatrogenic intervention, underwent a left lower lobectomy for a polyp sited in a segmental bronchus. Presentation in 3 of the 4 patients was with lobar collapse. The fourth patient presented with hyperinflation.

We conclude that inflammatory endobronchial polyps may be associated with a history of mechanical ventilation in the neonatal period, polyp formation perhaps being secondary to airway trauma. The small caliber of the main airways in neonates may also be a contributory factor in presentation. Pediatr Pulmonol. 2002; 34:79–84. © 2002 Wiley‐Liss, Inc.
Normal values for maximal static inspiratory and expiratory pressures in healthy children
Authors: Tomalak Waldemar , Pogorzelski Andrzej , Prusak Jarosław
Published: October 2002

Maximal static respiratory pressures are a simple measure of respiratory muscle strength. In order to construct a set of equations describing normal values, we measured maximal inspiratory (PImax) and expiratory (PEmax) pressures in 296 children (144 boys and 152 girls), aged 7–14 years, in sitting and standing positions.

The boys reached higher values in sitting and standing positions for PImax (−8.29 ± 2.69 and −8.19 ± 2.73 kPa, respectively) and PEmax (8.02 ± 2.32 and 7.94 ± 2.32 kPa, respectively) than girls (−6.53 ± 1.99 and −6.60 ± 2.03 kPa for PImax and 6.91 ± 1.79 and 7.13 ± 1.81 kPa for PEmax for sitting and standing positions, respectively); the differences between boys and girls were highly significant (P < 0.001 in all instances). There were no differences regarding body position during measurements in both genders. Multiple correlation analysis showed significant correlations of pressures to age in boys in all cases, but in girls only for PImax in standing position. Therefore, equations describing reference values were constructed with respect to age as the independent variable. Maximal pressures also correlated with maximal inspiratory and expiratory flows.

The measurements of PImax and PEmax are useful in assessing respiratory muscle strength despite their relatively large variability. PImax and PEmax also correlate with maximum peak expiratory and inspiratory flows. Children generate lower pressures and lower maximal flows than adolescents and adults. Pediatr Pulmonol. 2002; 34:42–46. © 2002 Wiley‐Liss, Inc.
Incidence of respiratory syncytial virus‐related hospitalizations in high‐risk children: Follow‐up of a national cohort of infants treated with Palivizumab as RSV prophylaxis
Authors: Lacaze‐Masmonteil Thierry , Rozé Jean‐Christophe , Fauroux Brigitte
Published: October 2002

The prophylactic administration of Palivizumab, a monoclonal antibody binding the respiratory syncytial virus (RSV) fusion protein, was recently shown to significantly decrease the incidence of RSV‐related hospitalizations among high‐risk children (IMpact‐RSV trial). While awaiting marketing authorization in France and through a cohort of patients' name‐based national program temporarily authorized by the French Drug Agency, a prospective register of all Palivizumab‐treated patients in France was set up during the epidemic season 1999–2000. Based on this register, this study was carried out to evaluate the incidence of RSV‐related hospitalizations and the safety of prophylaxis among a national cohort of children at high‐risk of severe RSV disease.

During the study period, guidelines issued by the French Pediatric Society recommended prophylaxis for children either aged less than 6 months at inclusion and born at less than 33 weeks of gestation with a history of bronchopulmonary dysplasia (BPD) at 28 days of life, or aged less than 2 years, born at less than 36 weeks of gestation, and having required treatment for BPD over the previous 6 months. Once included in the program, investigators were to prospectively report the clinical and demographic characteristics of children, all hospitalizations, and reasons for the hospitalizations.

Five hundred and sixteen children were treated with 1–5 monthly doses. The median gestational age was 28 weeks, and children born at less than 33 weeks of gestation accounted for 88% of the cohort. The prevalence of BPD was 81%. Ninety children were hospitalized for respiratory illness. In 39 children, hospitalizations were attributed to RSV (7.6% of the total cohort). Among those 39 children, 10 (1.9% of the total cohort) required admission into an intensive care unit, and 4 required mechanical ventilation. No deaths or serious adverse events attributable to RSV infection or Palivizumab treatment were reported.

We conclude that the RSV‐related hospitalization rate in this high‐risk cohort was comparable to the rate observed in the subgroup of Palivizumab‐prophylaxed children with BPD in the IMpact‐RSV trial. Pediatr Pulmonol. 2002; 34:181–188. © 2002 Wiley‐Liss, Inc.
Mechanisms of the growth inhibitory effects of the isoflavonoid biochanin A on LNCaP cells and xenografts*
Authors: Rice Lori , Samedi Von G. , Medrano Theresa A. , Sweeney Carol A. , Baker Henry V. , Stenstrom Anne , Furman Jaime , Shiverick Kathleen T.
Published: October 2002

BACKGROUND

Isoflavones inhibit the growth of some types of tumor cells, including prostate adenocarcinoma. This study used LNCaP cells and xenografts to investigate the mechanisms of the antiproliferative effects of biochanin A, a major isoflavone present in red clover but not soy‐derived products.

METHODS

LNCaP cells were exposed to varying doses of biochanin A to evaluate viability, DNA synthesis, and DNA fragmentation (TUNEL) analysis. Regulation of gene expression was determined by using Western immunoblotting and cDNA microarrays. Anti‐tumorigenic effects were evaluated by using athymic mice with LNCaP flank tumors.

RESULTS

Biochanin A induced a dose‐dependent inhibition of proliferation and [3H]thymidine incorporation that correlated with increased DNA fragmentation, indicative of apoptosis. Western blot analyses of cell cycle regulatory proteins revealed that biochanin A significantly decreased expression of cyclin B and p21, whereas flow cytometry showed that cells were accumulating in the G0/G1 phase. cDNA microarray analyses identified 29 down‐regulated genes with six reduced below assay detection limits. Eleven genes were up‐regulated, including 9 that were undetectable in controls. In mice with LNCaP xenografts, biochanin A significantly reduced tumor size and incidence.

CONCLUSION

These results indicate that biochanin A inhibits prostate cancer cell growth through induction of cell cycle arrest and apoptosis. Biochanin A‐regulated genes suggest multiple pathways of action. Biochanin A inhibits the incidence and growth of LNCaP xenograft tumors in athymic mice. Prostate 52:201–212, 2002. © 2002 Wiley‐Liss, Inc.
Anti‐tumor effects of toxins targeted to the prostate specific membrane antigen
Authors: Fracasso Giulio , Bellisola Giuseppe , Cingarlini Sara , Castelletti Deborah , Prayer‐Galetti Tommaso , Pagano Francesco , Tridente Giuseppe , Colombatti Marco
Published: October 2002

BACKGROUND

There is presently no effective therapy for relapsing, metastatic, androgen‐independent prostate cancer. Immunotherapy with monoclonal antibody–vehicled toxins (Immunotoxins, ITs) may be a promising novel treatment option for the management of prostate cancer in these cases.

METHODS

Three anti–prostate specific membrane antigen (anti‐PSMA) monoclonals (J591, PEQ226.5, and PM2P079.1) were cross‐linked to ricin A‐chain (RTA; native or recombinant), and their cytotoxic effects were investigated in monolayer and three‐dimensional (3‐D) cell cultures of prostate carcinoma cells (LNCaP).

RESULTS

The various Immunotoxins showed effects in the nanomolar range (IC50s of 1.6–99 ng/ml) against PSMA+ cells (IC50 being the concentration inhibiting 50% cell proliferation or protein synthesis). PSMA− cell lines were 62‐ to 277‐fold less sensitive to anti‐PSMA ITs, evidencing an appreciable therapeutic window. Treatment with J591‐smpt‐nRTA (0.35–31.7ng/ml) resulted in complete eradication of 3‐D tumor micromasses or in 1.46‐ to 0.35‐log reduction of target cells number, depending on the dose.

CONCLUSION

Anti‐PSMA ITs appear to be promising for use in the eradication of small prostate tumor cell aggregates present in tissues and in the bone marrow. Prostate 53: 9–23, 2002. © 2002 Wiley‐Liss, Inc.
Induction of cell cycle arrest and apoptosis in human prostate carcinoma cells by a recombinant adenovirus expressing p27Kip1
Authors: Katner Adrienne L. , Hoang Quoc Bao Ly , Gootam Praveen , Jaruga Ewa , Ma Quangwei , Gnarra James , Rayford Walter
Published: October 2002

BACKGROUND

Adp27Kip1, a recombinant adenovirus, was evaluated for expression of p27, a cyclin‐dependent kinase inhibitor (CDKI) and tumor suppressor protein, in human prostate carcinoma cells. Effects of p27Kip1 on cell cycle and apoptosis were analyzed.

METHODS

We evaluated the effects of overexpression of p27Kip1 in the human prostate carcinoma cell lines LNCaP, DU‐145, and PC‐3 in vitro and in vivo. Growth curve studies, cell cycle analysis, terminal deoxynucleotidyl transferase‐mediated nick end‐labeling (TUNEL), and annexin V–fluorescein isothiocyanate apoptosis analyses were conducted to determine effects of p27Kip1 on cell cycle. CDKI activity assays and Westerns blots were conducted to determine presence/activities of CDKIs.

RESULTS

Adp27Kip1‐induced protein levels increased in a dose‐dependent manner; p27Kip1 protein was detected within 6 hr of infection with Adp27Kip1 and remained stable for at least 48 hr. The activities of Cdk2, Cdk4, and Cdc2 kinases were inhibited 24 hr after infection with Adp27Kip1. Bromodeoxyuridine incorporation demonstrated a dose‐dependent decrease in S‐phase cells 24 hr postinfection. TUNEL analysis revealed an induction of apoptosis (10 pfu/cell) within 48 hr of infection in all cell lines. Growth curve analyses demonstrated that Adp27Kip1 infection inhibited proliferation of all cell lines tested and decreased cell numbers for Adp27Kip1‐infected LNCaP and PC‐3 cells by 96 hr. Cell cycle analysis of DNA content demonstrated an accumulation of cells in G0/G1‐phase 24–120 hr after Adp27Kip1‐infection. In vivo studies demonstrated a reduction in LNCaP xenograft tumor growth rates in mice injected with Adp27Kip1.

CONCLUSION

Exogenous p27Kip1 overexpression results in cell cycle regulation in the human prostate carcinoma cell lines tested, representing the first use of this vector on prostate cancer cell lines in vitro and in vivo. Moreover, p27Kip1 expression is associated with an increase in early apoptosis, which represents a recently discovered function for this protein. It also represents the first time this association has been observed in prostate carcinoma cell lines. This study provides support for the further development of Adp27Kip1 as a potential therapeutic vector in the treatment of adenocarcinoma of the prostate. Prostate 53: 77–87, 2002. © 2002 Wiley‐Liss, Inc.
Signal transduction in the photoactive yellow protein. II. Proton transfer initiates conformational changes
Authors: Groenhof Gerrit , Lensink Marc F. , Berendsen Herman J. C. , Mark Alan E.
Published: October 2002

Molecular dynamics simulation techniques, together with semiempirical PM3 calculations, have been used to investigate the effect of photoisomerization of the 4‐hydroxy‐cinnamic acid chromophore on the structural properties of the photoactive yellow protein (PYP) from Ectothiorodospira halophila. In this bacteria, exposure to blue light leads to a negative photoactic response. The calculations suggest that the isomerization does not directly destabilize the protein. However, because of the isomerization, a proton transfer from a glutamic acid residue (Glu46) to the phenolate oxygen atom of the chromophore becomes energetically favorable. The proton transfer initiates conformational changes within the protein, which are in turn believed to lead to signaling. Proteins 2002;48:212–219. © 2002 Wiley‐Liss, Inc.
Inhibition of trypsin by cowpea thionin: Characterization, molecular modeling, and docking
Authors: Melo Francislete R. , Rigden Daniel J. , Franco Octávio L. , Mello Luciane V. , Ary Maria B. , Grossi de Sá Maria F. , Bloch Carlos
Published: October 2002

Higher plants produce several families of proteins with toxic properties, which act as defense compounds against pests and pathogens. The thionin family represents one family and comprises low molecular mass cysteine‐rich proteins, usually basic and distributed in different plant tissues. Here, we report the purification and characterization of a new thionin from cowpea (Vigna unguiculata) with proteinase inhibitory activity. Cowpea thionin inhibits trypsin, but not chymotrypsin, binding with a stoichiometry of 1:1 as shown with the use of mass spectrometry. Previous annotations of thionins as proteinase inhibitors were based on their erroneous identification as homologues of Bowman‐Birk family inhibitors. Molecular modeling experiments were used to propose a mode of docking of cowpea thionin with trypsin. Consideration of the dynamic properties of the cowpea thionin was essential to arrive at a model with favorable interface characteristics comparable with structures of trypsin‐inhibitor complexes determined by X‐ray crystallography. In the final model, Lys11 occupies the S1 specificity pocket of trypsin as part of a canonical style interaction. Proteins 2002;48:311–319. © 2002 Wiley‐Liss, Inc.
Variants of 310‐helices in proteins
Authors: Pal Lipika , Basu Gautam , Chakrabarti Pinak
Published: October 2002

An analysis of the shortest 310‐helices, containing three helical residues and two flanking capping residues that participate in two consecutive i + 3 → i hydrogen bonds, shows that not all helices belong to the classic 310‐helix, where the three central residues adopt the right‐handed helical conformation (αR). Three variants identified are: 3‐helix with all residues in the left‐handed helical region (αL), 3‐helix where the first residue is in the extended region followed by two residues in the αL conformation, and its mirror‐image, the 3‐helix. In the context of these helices, as well as the equivalent variants of α‐helices, the length dependence of the handedness of secondary structures in protein structure is discussed. There are considerable differences in the amino acid preferences at different positions in the various types of 310‐helices. Each type of 310‐helix can be thought to be made up of an extension of a particular type of β‐turn (made up of residues i to i + 3) such that the (i + 3)th residue assumes the same conformation as the preceding residue. Distinct residue preferences at i and i + 3 positions seem to decide whether a particular stretch of four residues will be a β‐turn or a 310‐helix in the folded structure. Proteins 2002;48:571–579. © 2002 Wiley‐Liss, Inc.