bluuebunny/crossref_metadata_2025_split huggingface dataset:
A DRD1 haplotype is associated with risk for autism spectrum disorders in male‐only affected sib‐pair families
Authors: Hettinger Joe A. , Liu Xudong , Schwartz Charles E. , Michaelis Ron C. , Holden Jeanette J.A. 
Published: January 2008

AbstractIndividuals with autism spectrum disorders (ASDs) have impairments in executive function and social cognition, with males generally being more severely affected in these areas than females. Because the dopamine D1 receptor (encoded by DRD1) is integral to the neural circuitry mediating these processes, we examined the DRD1 gene for its role in susceptibility to ASDs by performing single marker and haplotype case–control comparisons, family‐based association tests, and genotype–phenotype assessments (quantitative transmission disequilibrium tests: QTDT) using three DRD1 polymorphisms, rs265981C/T, rs4532A/G, and rs686T/C. Our previous findings suggested that the dopaminergic system may be more integrally involved in families with affected males only than in other families. We therefore restricted our study to families with two or more affected males (N = 112). There was over‐transmission of rs265981‐C and rs4532‐A in these families (P = 0.040, P = 0.038), with haplotype TDT analysis showing over‐transmission of the C‐A‐T haplotype (P = 0.022) from mothers to affected sons (P = 0.013). In addition, haplotype case–control comparisons revealed an increase of this putative risk haplotype in affected individuals relative to a comparison group (P = 0.004). QTDT analyses showed associations of the rs265981‐C, rs4532‐A, rs686‐T alleles, and the C‐A‐T haplotype with more severe problems in social interaction, greater difficulties with nonverbal communication and increased stereotypies compared to individuals with other haplotypes. Preferential haplotype transmission of markers at the DRD1 locus and an increased frequency of a specific haplotype support the DRD1 gene as a risk gene for core symptoms of ASD in families having only affected males. © 2008 Wiley‐Liss, Inc.
In‐situ‐Funktionalisierung von Polyolefinen mit Heteroatomen: Reaktionswege und katalytische Kettenübertragung
Authors: Amin Smruti B. , Marks Tobin J. 
Published: January 2008

AbstractKettenübertragungen sind effiziente und selektive chemische Prozesse für die d‐ und f‐Metall‐katalysierte In‐situ‐Funktionalisierung von Polyolefinen. Eine Reihe höchst unterschiedlicher elektronenarmer wie auch elektronenreicher Kettenüberträger eignet sich dafür, bei der Single‐Site‐Polymerisation von Olefinen einen selektiven Kettenabbruch mit gleichzeitiger Kohlenstoff‐Heteroelement‐Verknüpfung herbeizuführen. Als Kettenüberträger finden z. B. Silane, Borane, Alane, Phosphine und Amine Verwendung. Mit ihnen sind hohe Polymerisationsaktivitäten, eine Kontrolle von Molekulargewicht und Mikrostruktur der Polyolefine und eine selektive Kettenfunktionalisierung möglich. Für elektronenarme und elektronenreiche Reagentien findet man deutlich unterschiedliche Mechanismen. Als Katalysatoren für diese selektiven Kettenabbruchs‐/Funktionalisierungsprozesse eignen sich vielfältige Metallzentren (frühe Übergangsmetalle, Lanthanoide, späte Übergangsmetalle) und Single‐Site‐Hilfsliganden (Metallocene, Halbmetallocene, Nichtmetallocene).
Versatile Pathways for In Situ Polyolefin Functionalization with Heteroatoms: Catalytic Chain Transfer
Authors: Amin Smruti B. , Marks Tobin J. 
Published: January 2008

AbstractChain‐transfer processes represent highly effective chemical means to achieve selective, in situ d‐ and f‐block‐metal catalyzed functionalization of polyolefins. A diverse variety of electron‐poor and electron‐rich chain‐transfer agents, including silanes, boranes, alanes, phosphines, and amines, effect efficient chain termination with concomitant carbon–heteroelement bond formation during single‐site olefin‐polymerization processes. High polymerization activities, control of polyolefin molecular weight and microstructure, and selective chain functionalization are all possible, with distinctly different mechanisms operative for the electron‐poor and electron‐rich reagents. A variety of metal centers (early transition metals, lanthanides, late transition metals) and single‐site ancillary ligand arrays (metallocene, half‐metallocene, non‐metallocene) are able to mediate these selective chain‐termination/functionalization processes.
Structure dependence of photochromism of azobenzene‐functionalized polythiophene derivatives
Authors: Zhao Xiong‐Yan , Wang Ming‐Zhu , Liu Hong‐Jie 
Published: January 2008

AbstractTwo novel azobenzene‐functionalized polythiophene derivatives, poly[4‐((4‐(phenyl)azo)phenoxy)butyl‐3‐thienylacetate] (PATh‐4) and the copolymer of 3‐hexylthiophene and 4‐((4‐(phenyl)azo)phenoxy)butyl‐3‐thienylacetate (COP‐64) were synthesized. The structure and photoelectronic behavior of both polythiophene derivatives were characterized by NMR, FTIR, UV–vis, XRD, GPC, modulated DSC, and photoluminescence spectroscopy. These new polymers combine photoluminescence property and photochemical behavior of both polythiophene‐conjugated backbones and the photoisomerizable moieties in the side chains. The photoluminescence property of polymers so obtained can be modified reversibly through the photochemical isomerization reaction of the photoactive groups in side chains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Functional copolymer of geraniol and acrylonitrile: Synthesis and characterization
Authors: Sharma Saroj , Srivastava A. K. 
Published: January 2008

AbstractThe radical copolymerization of acyclic terpene namely geraniol [GER] with acrylonitrile [AN] in DMF at (70 ± 0.1)°C for 1 h, using benzoylperoxide (BPO) as an initiator has been carried out under inert atmosphere of nitrogen. The kinetic expression for reaction is Rp ∝ [BPO]0.5 [AN]1.0 [GER]1.0. The IR spectrum of the copolymer shows bands at 3432 and at 2244 cm−1 due to OH group of GER and CN group of AN, respectively. The 13C‐NMR spectrum shows peaks at 73–75 δ ppm and 116–120 δ ppm due to OH group of GER and CN group of AN, respectively. The thermogravimetric analysis and differential scanning calorimetry study shows that copolymer is thermally stable up to 407°C and has glass transition temperatures (Tg) 56°C. The reactivity ratios r1 (AN) and r2 (GER) have been calculated as 0.05 and 0.005, respectively. The Alfrey‐Price Q‐e parameter for GER has been calculated as 0.094 and −2.0, respectively. The molecular weights of the copolymers have been evaluated by gel‐permeation chromatography. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of thermal treatments on the miscibility of poly(vinyl cinnamate) binary blends
Authors: Hsu Wen‐Ping 
Published: January 2008

AbstractPoly(vinyl cinnamate) (PVCN) could undergo thermal or photo crosslinking. PVCN was previously found to be miscible with poly(vinyl phenol) (PVPh) [also named poly(hydroxystyrene)]. In this article, the miscibility between PVCN with or without thermal crosslinking and poly(styrene‐co‐hydrostyrene) (designated as MPS) was investigated. PVCN was determined to be miscible with MPS with 15% of hydroxystyrene (MPS‐15) at two compositions but partially miscible or immiscible at PVCN/MPS‐15(50/50) composition. For MPS with 5% of hydroxystyrene (MPS‐5), two Tg values were detected indicating mostly immiscibility. However, PVCN after thermal crosslinking was determined to be miscible with both MPS‐5 and MPS‐15. Immiscibility was found between thermally crosslinked PVCN and PVPh different from miscibility in the original PVCN/PVPh blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
The skin‐core structure of poly(acrylonitrile‐itaconic acid) precursor fibers in wet‐spinning
Authors: Ge Heyi , Liu Huashi , Chen Juan , Wang Chengguo 
Published: January 2008

AbstractThe skin‐core structure of poly(acrylonitrile‐itaconic acid) [P(AN‐IA)] precursor fibers in wet‐spinning has been analyzed by the means of electron probe microanalyser (EPMA), scanning electron microscope (SEM), and transmission electron microscope. The numerical solution of Fick's second law equations for diffusion in the nascent fiber was obtained by using the Method of Lines. It has been found that [P(AN‐IA)] precursor fiber composed of four parts had remarkable skin‐core structure. The sheet‐like skin, which was compact and homogeneous, had high crystallization and highly oriented structure. However, the core with low crystallization and some voids was loose, somewhat disorderly and unsystematic. Moreover, the precursor fiber had a pillar‐like layered structure along the fiber axis. The average thickness of each layer increased gradually from the skin to the endothecium. Meanwhile, a structural model of PAN precursor fiber has been built. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and light‐emitting properties of a novel π‐conjugated poly[di(p‐phenyleneethynylene)‐alt‐ (p‐phenylenecyanovinylene)] containing n‐octyloxy side branches
Authors: Chi Jun Ho , Lee Chang‐Lyoul , Kim Jang‐Joo , Jung Jin Chul 
Published: January 2008

AbstractA novel π‐conjugated poly[di(p‐phenyleneethynylene)‐alt‐(p‐phenylenecyanovinylene)] having n‐octyloxy side chains (PPE‐C8PPE‐PPV) was prepared by polymerization of the monomer DEDB with BCN. Chemical structure of the polymer obtained was confirmed by 1H NMR, FTIR, and EA. PPE‐C8PPE‐PPV had a molecular weight enough to fabricate the electroluminescent (EL) device, and showed a good organosolubility, excellent thermal stability, and film‐forming property. In UV absorption and PL spectra in film it showed a maximum at 430 and 543 nm, respectively, which appeared 5 and 41 nm longer wavelengths than that of the solution, respectively. HOMO, LUMO energy levels and band gap were determined to be −5.70, −3.29, and 2.41 eV, respectively. Two EL devices with low‐work function cathodes were fabricated with the structures of ITO/PEDOT/PPE‐C8PPE‐PPV/cathodes (LiF/Al and Mg:Ag/Ag). The both devices exhibited a bright green light emission at 545 nm and the maximum luminescence of 197 cd/cm2 (LiF/Al) and 158 cd/cm2 (Mg:Ag/Ag). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Comparative study of the elasticity and permeability of vulcanized films made with skim and cream natural rubber latex
Authors: Winsunthorn Suwaluk , Bonfils Frédéric , Pochat‐Bohatier Céline , Bouyer Denis , Deratani André , Dupuy Claude 
Published: January 2008

AbstractThe purpose of this study was to gain a clearer picture of the structure and properties of vulcanized films made with skim and cream latex from Hevea brasiliensis. The two properties targeted for this study were the elasticity of the films and their permeability to acetone. Surface characterization by atomic force microscopy revealed that vulcanization substantially modified the structure of the films compared to unvulcanized films. Unlike unvulcanized films, particle identity was retained in the vulcanized films made with cream latex, even after 4 weeks of aging. In addition, skim latex gave vulcanized films with greater elasticity than those obtained with cream latex. On the basis of the structural characterization carried out on the latex and films and information from the literature, the greater elasticity of the skim films arose from more entanglements between polyisoprene chains and associations between proteins. Despite differences in the structure, the acetone permeability was very similar for skim and cream vulcanized films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Swelling properties of chemically modified oil palm empty fruit bunch based polyurethane composites
Authors: Tay G. S. , Rozman H. D. 
Published: January 2008

AbstractIn this study, the diffusion of various types of solvent in oil palm empty fruit bunch/polyurethane composites, produced from chemically modified empty fruit bunches, was investigated. The solubility parameters and polymer–solvent interaction parameters of the produced composites were determined. The void contents of the composites were also determined before swelling tests to eliminate the free solvent present in the system. From the results obtained, we found that the diffusion of the solvents was dependent on the compatible group available and the voids present in the system. The solubility parameters of the empty fruit bunch/polyurethane composites with different degrees of chemical modification were 11.6 and 11.7 (cal/cm−3)1/2. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Morphology, thermal expansion, and electrical conductivity of multiwalled carbon nanotube/epoxy composites
Authors: dos Santos Alexandre S. , Leite Thiago de O. N. , Furtado Clascídia A. , Welter Cezar , Pardini Luiz C. , Silva Glaura G. 
Published: January 2008

AbstractMultiwalled carbon nanotube/epoxy composites loaded with up to 0.5 wt % multiwalled carbon nanotubes were prepared and characterized. Infrared microscopy, scanning electron microscopy, thermogravimetry, differential scanning calorimetry, thermomechanical analysis, and electrical conductivity measurements of the composites were performed. Infrared microscopy and scanning electron microscopy images showed that the debundled nanotubes were well dispersed. The thermal expansion coefficients, before and after the glass transition, remained approximately constant with the addition of nanotubes, whereas the electrical conductivity at room temperature increased approximately 5 orders of magnitude. This result was attributed to the thermal expansion coefficients of the intertube gap on the carbon nanotube bundles, which were in the same range as that of the epoxy resin. Therefore, nanocomposites capable of electrostatic dissipation can be processed as neat epoxy materials with respect to the volume changes with temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
On the electrospinning of poly(vinyl alcohol) nanofiber mats: A revisit
Authors: Supaphol Pitt , Chuangchote Surawut 
Published: January 2008

AbstractElectrospinning was used to fabricate mats of poly(vinyl alcohol) (PVA; Mw = 72,000 Da, degree of hydrolysis ≈ 97.5–99.5) nanofibers from PVA solutions in reverse osmotic water. The effects of solution concentration, applied electrical potential, sonication, and collection distance on morphological appearance and diameters of the as‐spun fiber mats as well as those of the individual fibers were carefully investigated mainly by scanning electron microscopy. The effect of the distance from the center of the as‐spun fiber mat on morphological appearance and diameters of the as‐spun fibers was also investigated. The mechanical integrity of some as‐spun PVA fiber mats was also investigated. At all concentrations and applied electrical potentials investigated, the average diameters of the as‐spun PVA fibers ranged between 85 and 647 nm. The use of sonication to prepare a PVA solution caused the viscosity of the solution to decrease; hence, the observed decrease in the average diameters of the as‐spun fibers and the average diameters of the as‐spun fibers were practically the same throughout the as‐spun fiber mat. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
The modified‐single fiber test: A methodology for monitoring ballistic performance
Authors: Kim J. , McDonough W. G. , Blair W. , Holmes G. A. 
Published: January 2008

AbstractA minimally invasive testing methodology was developed to monitor the in‐service performance of soft body armor. In the spirit of the single fiber test standard, ASTM C 1557‐03, the fiber diameter was measured at five equally spaced locations along a 6‐cm gauge length specimen. In addition, the single fiber test specimen was modified by placing reflecting tape just outside the specimen gauge length to allow the use of a laser extensometer for directly measuring fiber displacement and hence, strain. This modified testing methodology was found to be reproducible and provide data that was normally distributed based on descriptive statistics when variations in the fiber diameters along the length of the specimen were considered. The abnormality in the data, identified using Pierce's outlier criterion, may be associated with processing variations during the fiber manufacture and/or the woven fabrics and not associated with the testing methodology. Furthermore, the failure strain was found to be drastically reduced when the minimum fiber diameter along the length of the test specimen was less than 11 μm. This suggests that a methodology that accurately profiles fiber diameter changes along the gauge length of the fiber may be useful in analyzing single fiber test results. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Crystallization and melting of a polyethylene copolymer: In situ observation by atomic force microscopy
Authors: Mirabella Francis M. 
Published: January 2008

AbstractThe isothermal crystallization and subsequent melting of a narrow composition distribution polyethylene (PE) copolymer (containing a few mole percent of an α‐olefin) was observed by hot‐stage atomic force microscopy (AFM). The observations revealed that a thicker lamellae population formed first, followed by a thinner population. This indicated that the crystallization process occurred in two sequential steps. Initially, a single population of uniform lamellar thickness appeared rapidly and progressively occupied the surface. These skeletal lamellae typically ranged in thickness from about 10–15 nm. Progressively, upon isothermal storage, a second, bridging population of lamellae filled in between this initial skeletal population. This second population was thinner with thicknesses of about 4–6 nm. Upon heating, the second, thinner, bridging population of lamellae melted first, leaving the initial, skeletal population, which melted at higher temperatures. These results indicate that PE copolymers crystallize in a stepwise fashion; this was envisioned to begin with a first step in which the thickest lamellae crystallize from the folding of the longest ethylene sequences, followed by a second step in which shorter sequences, constrained between thicker lamellae, crystallize into a population of thinner crystals. The melting of this presumed bimodal population of crystal thicknesses would produce a broad and bimodal endotherm; the bimodal melting endotherm was observed by differential scanning calorimetry. Furthermore, the lamellar thickness dimensions measured by AFM were in approximately the same range as those calculated from the melting endotherm by means of Gibbs–Thompson theory. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Aromaticity and Diatropicity of Polyacenequinododimethides
Authors: Aihara Jun‐ichi , Makino Masakazu 
Published: January 2008

AbstractTypical polyacenequinododimethides exist only in a single classical structure. These hydrocarbons are moderately aromatic and diatropic, although they have no aromatic conjugated circuits. This apparent dichotomy was resolved with our graph theory of aromaticity and magnetotropicity. Many nonconjugated circuits were found to contribute collectively to aromaticity and diatropicity. For individual molecules, local aromaticity increases with distance from theexo‐methylene groups. This fact indicates that the conjugated‐circuit model is not always applicable to semibenzenoid hydrocarbons such as polyacenequinododimethides.
Reversible Double‐Helix–Random‐Coil Transition Process of Bis{hexa(ethynylhelicene)}s
Authors: Sugiura Hiroki , Amemiya Ryo , Yamaguchi Masahiko 
Published: January 2008

AbstractTwo compounds with two hexa(ethynylhelicene) parts connected by a flexible haxadecamethylene and a rigid butadiyne linker were synthesized. The 1H NMR spectroscopic and CD analyses and vapor‐pressure osmometry (VPO) of these two compounds revealed intramolecular double‐helix formation. Upon heating a 5‐μM solution in toluene, the double‐helix structure unfolded to form a random coil, and on cooling it folded again into a double helix. The thermodynamic stabilities of both structures were dependent on temperature, and the structural change in both compounds is due to the large enthalpies and entropies under equilibrium. The rate constants of their unfolding were obtained by assuming a pseudo‐first‐order reaction; the compound with a rigid linker unfolded slower than that with a flexible linker. The former has a larger activation energy, and its double‐helix and random‐coil conformers were separated by chromatography. The rate of folding was also faster for the flexible‐linker compound with larger activation energy. The rate constants for the folding of both compounds slightly decreased with increasing temperature, which was ascribed to the presence of exothermic pre‐equilibrium and rate‐determining steps. The folding was markedly accelerated with increasing random‐coil concentration, which suggests the involvement of self‐catalysis. A mechanism of folding was proposed. The involvement of different mechanisms of folding and unfolding was suggested by the kinetic studies, and it was confirmed by the presence of hysteresis in the melting profiles. The difference in linker structure also affected the thermal‐switching profiles of the double‐helix–random‐coil structural changes.
Total Synthesis of 2‐Hydroxytetracosanolide and 2‐Hydroxy‐24‐oxooctacosanolide By Using an Effective Lactonization
Authors: Shiina Isamu , Sasaki Akane , Kikuchi Takaaki , Fukui Hiroki 
Published: January 2008

AbstractWe have developed effective methods for the total synthesis of 2‐hydroxytetracosanolide and 2‐hydroxy‐24‐oxooctacosanolide, the defensive salivary secretions of termites. The former natural product isolated from Armitermes neotenicus, a species of termite that inhabits Guyana, contains a 25‐membered lactone backbone, and the latter, extracted from Pseudacanthoterme springer, an African termite, includes a 29‐membered lactone moiety. The key cyclization to produce the 25‐ or 29‐membered lactone core is performed by using 2‐methyl‐6‐nitrobenzoic anhydride (MNBA) with a stoichiometric amount of 4‐(dimethylamino)pyridine (DMAP) or a catalytic amount of 4‐(dimethylamino)pyridine N‐oxide (DMAPO).
The Catalytic Acylcyanation of Imines
Authors: Pan Subhas Chandra , List Benjamin 
Published: January 2008

AbstractThe catalytic acylcyanation of aldimines with acylcyanides and a direct three‐component variant involving the generation of an imine in situ have been developed. Furthermore, a highly enantioselective version has been established, culminating in the first organocatalytic asymmetric three‐component Strecker reaction. Jacobsen thiourea catalysts were found to catalyze the reaction with excellent enantioselectivities, whereas binol phosphates (binol=1,1′‐bi‐2,2′‐naphthol) proved to be catalytically active but only modestly enantioselective. A large number of different substrates could be used in the processes described, thus illustrating the potential of our reaction for the generation of diversity within the attractive α‐amino carbonyl framework. Furthermore, a novel cyclic amidine was obtained from the reaction of acetyl cyanide with ketimines.
Asymmetric 1,3‐Dipolar Cycloadditions of N‐Benzyl and N‐Diphenylmethyl Nitrones and α,β‐Unsaturated Aldehydes Catalyzed by Bis‐Titanium Chiral Lewis Acids
Authors: Hashimoto Takuya , Omote Masato , Hato Yoshio , Kano Taichi , Maruoka Keiji 
Published: January 2008

AbstractBis‐titanium chiral Lewis acids that contain two oxygen‐bridged titanium centers were successfully applied to the asymmetric 1,3‐dipolar cycloaddition of nitrones and α,β‐unsaturated aldehydes. The introduction of the diphenylmethyl group as the N substituent on the nitrones, with the aim of destabilizing the nitrone–Lewis acid complex, led to the drastic enhancement of not only the reactivity but also the enantioselectivity. By employing this approach, 1,3‐dipolar cycloadditions of nitrones and the rather unreactive methacrolein were facilitated to give cycloadducts that bear one all‐carbon quaternary center with unique regioselectivity and excellent stereoselectivity.