bluuebunny/crossref_metadata_2025_split huggingface dataset:
Socio‐economic, socio‐political and socio‐emotional variables explaining school bullying: a country‐wide multilevel analysis
Authors: Chaux Enrique , Molano Andrés , Podlesky Paola 
Published: September 2009

AbstractWhy do some countries, regions and schools have more bullying than others? What socio‐economic, socio‐political and other larger contextual factors predict school bullying? These open questions inspired this study with 53.316 5th‐ and 9th‐grade students (5% of the national student population in these grades), from 1,000 schools in Colombia. Students completed a national test of citizenship competencies, which included questions about bullying and about families, neighborhoods and their own socio‐emotional competencies. We combined these data with community violence and socio‐economic conditions of all Colombian municipalities, which allowed us to conduct multilevel analyses to identify municipality‐ and school‐level variables predicting school bullying. Most variance was found at the school level. Higher levels of school bullying were related to more males in the schools, lower levels of empathy, more authoritarian and violent families, higher levels of community violence, better socio‐economic conditions, hostile attributional biases and more beliefs supporting aggression. These results might reflect student, classroom and school contributions because student‐level variables were aggregated at the school level. Although in small portions, violence from the decades‐old‐armed conflict among guerrillas, paramilitaries and governmental forces predicted school bullying at the municipal level for 5th graders. For 9th graders, inequality in land ownership predicted school bullying. Neither poverty, nor population density or homicide rates contributed to explaining bullying. These results may help us advance toward understanding how the larger context relates to school bullying, and what socio‐emotional competencies may help us prevent the negative effects of a violent and unequal environment. Aggr. Behav. 35:520–529, 2009. © 2009 Wiley‐Liss, Inc.
Electric Field‐Directed Convective Assembly of Ellipsoidal Colloidal Particles to Create Optically and Mechanically Anisotropic Thin Films
Authors: Mittal Manish , Furst Eric M. 
Published: September 2009

AbstractA method of simultaneous field‐ and flow‐directed assembly of anisotropic titania (TiO2) nanoparticle films from a colloidal suspension is presented. Titania particles are oriented by an alternating (ac) electric field as they simultaneously advect towards a drying front due to evaporation of the solvent. At high field frequencies (ν > ∼25 kHz) and field strengths (E > 300 V cm−1), the particles orient with their major axis along the field direction. As the front recedes, a uniform film with thicknesses of 1–10 µm is deposited on the substrate. The films exhibit a large birefringence (Δn ≈ 0.15) and high packing fraction (ϕ = 0.75 ± 0.08), due to the orientation of the particles. When the frequency is lowered, the particle orientation undergoes a parallel–random–perpendicular transition with respect to the field direction. The orientation dependence on field frequency and strength is explained by the polarizability of ellipsoidal particles using an interfacial polarization model. Particle orientation in the films also leads to anisotropic mechanical properties, which are manifested in their cracking patterns. In all, it is demonstrated that the field‐directed assembly of anisotropic particles provides a powerful means for tailoring nanoparticle film properties in situ during the deposition process.
Conjugated Polymers Combined with a Molecular Beacon for Label‐Free and Self‐Signal‐Amplifying DNA Microarrays
Authors: Lee Kangwon , Rouillard Jean‐Marie , Kim Bong‐Gi , Gulari Erdogan , Kim Jinsang 
Published: September 2009

AbstractA conjugated polymer (CP) and molecular‐beacon‐based solid‐state DNA sensing system is developed to achieve sensitive, label‐free detection. A novel conjugated poly(oxadiazole) derivative exhibiting amine and thiol functional groups (POX‐SH) is developed for unique chemical and photochemical stability and convenient solid‐state on‐chip DNA synthesis. POX‐SH is soluble in most nonpolar organic solvents and exhibits intense blue fluorescence. POX‐SH is covalently immobilized onto a maleimido‐functionalized glass slide by means of its thiol group. Molecular beacons having a fluorescent dye or quencher molecule as the fluorescence resonance energy transfer (FRET) acceptor are synthesized on the immobilized POX‐SH layer through direct on‐chip oligonucleotide synthesis using the amine side chain of POX‐SH. Selective hybridization of the molecular beacon probes with the target DNA sequence opens up the molecular beacon probes and affects the FRET between POX‐SH and the dye or quencher, producing a sensitive and label‐free fluorescence sensory signal. Various molecular design parameters, such as the size of the stem and loop of the molecular beacon, the choice of dye, and the number of quencher molecules are systematically controlled, and their effects on the sensitivity and selectivity are investigated.
Silica‐Supported Zirconium Complexes and their Polyoligosilsesquioxane Analogues in the Transesterification of Acrylates: Part 2. Activity, Recycling and Regeneration
Authors: Salinier Valérie , Niccolai Gerald P. , Dufaud Véronique , Basset Jean‐Marie 
Published: September 2009

AbstractThe catalytic activity of both supported and soluble molecular zirconium complexes was studied in the transesterification reaction of ethyl acrylate by butanol. Two series of catalysts were employed: three well defined silica‐supported acetylacetonate and n‐butoxy zirconium(IV) complexes linked to the surface by one or three siloxane bonds, (SiO)Zr(acac)3 (1) (SiO)3Zr(acac) (2) and (SiO)3Zr(O‐n‐Bu) (3), and their soluble polyoligosilsesquioxy analogues (c‐C5H9)7Si8O12(CH3)2Zr(acac)3 (1′), (c‐C5H9)7Si7O12Zr(acac) (2′), and (c‐C5H9)7Si7O12Zr(O‐n‐Bu) (3′). The reactivity of these complexes were compared to relevant molecular catalysts [zirconium tetraacetylacetonate, Zr(acac)4 and zirconium tetra‐n‐butoxide, Zr(O‐n‐Bu)4]. Strong activity relationships between the silica‐supported complexes and their polyoligosilsesquioxane analogues were established. Acetylacetonate complexes were found to be far superior to alkoxide complexes. The monopodal complexes 1 and 1′ were found to be the most active in their respective series. Studies on the recycling of the heterogeneous catalysts showed significant degradation of activity for the acetylacetonate complexes (1 and 2) but not for the less active tripodal alkoxide catalyst, 3. Two factors are thought to contribute to the deactivation of catalyst: the lixivation of zirconium by cleavage of surface siloxide bonds and exchange reactions between acetylacetonate ligands and alcohols in the substrate/product solution. It was shown that the addition of acetylacetone to the low activity catalyst Zr(O‐n‐Bu)4 produced a system that was as active as Zr(acac)4. The applicability of ligand addition to heterogeneous systems was then studied. The addition of acetylacetone to the low activity solid catalyst 3 produced a highly active catalyst and the addition of a stoichiometric quantity of acetylacetone at each successive batch catalytic run greatly reduced catalyst deactivation for the highly active catalyst 1.
Highly Stereoselective Halocyclopropanation of α,β‐Unsaturated Amides
Authors: Concellón José M. , Rodríguez‐Solla Humberto , Blanco Elena G. , Villa‐García María A. , Alvaredo Noemí , García‐Granda Santiago , Díaz M. Rosario 
Published: September 2009

AbstractA convenient highly stereoselective synthesis of chloro‐ and bromocyclopropanamides from di‐ tri‐ or tetrasubstituted (E)‐ or (Z)‐α,β‐unsaturated amides with total or high stereoselectivity promoted by chromium dichloride or dibromide is described. The transformation of chlorocyclopropanamides into the corresponding ketones or amines is also reported. A mechanism to explain these transformations is proposed.
First Heterogeneous Ligand‐ and Salt‐Free Larock Indole Synthesis
Authors: Batail Nelly , Bendjeriou Anissa , Lomberget Thierry , Barret Roland , Dufaud Véronique , Djakovitch Laurent 
Published: September 2009

AbstractA new ligand‐ and salt‐free procedure using heterogeneous palladium catalysts for the Larock indole and benzofuran synthesis is reported. After optimisation of the reaction conditions, good to high isolated yields have been achieved for a variety of structures. Recycling studies have shown that the palladium catalysts can be readily recovered and reused. Reactions and recovery of the palladium catalysts can be carried out in the presence of air, without any particular precaution.
Association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and age of onset in schizophrenia
Authors: Vares Maria , Saetre Peter , Deng Hong , Cai Guiqing , Liu Xiehe , Hansen Thomas , Rasmussen Henrik B. , Werge Thomas , Melle Ingrid , Djurovic Srdjan , Andreassen Ole A. , Agartz Ingrid , Hall Håkan , Terenius Lars , Jönsson Erik G. 
Published: September 2009

AbstractDifferent lines of evidence indicate that methylenetetrahydrofolate reductase (MTHFR) functional gene polymorphisms, causative in aberrant folate–homocysteine metabolism, are associated with increased vulnerability to several heritable developmental disorders. Opposing views are expressed considering the possible association between MTHFR and susceptibility for schizophrenia. In order to evaluate if age of onset could explain some of this discrepancy we investigated the relationship between two functional MTHFR gene polymorphisms and age at onset in this disorder. Scandinavian patients (n = 820) diagnosed with schizophrenia, schizoaffective disorder, and schizophreniform disorder were investigated. Two functional MTHFR single nucleotide polymorphisms (SNPs; rs1801131 and rs1801133) were genotyped and the effect of MTHFR polymorphisms on the age of onset was examined with survival analysis. In an attempt to replicate the findings from the Scandinavian sample, the association between rs1801133 and age at onset was also analyzed in Chinese high‐risk families, with two or more affected siblings (n = 243). Among the Scandinavian patients the functional MTHFR SNP rs1801133 (C677T) significantly affected age at onset of schizophrenia in a dose‐dependent manner (P = 0.0015), with lower age of onset with increasing numbers of the mutant T‐allele. There was no evidence of rs1801131 (A1298C) affecting age of onset in schizophrenia. Within the Chinese high‐risk families carriers of the MTHFR 677T allele showed earlier age at onset than siblings being homozygous for the wild‐type allele (P = 0.008). The MTHFR C677T polymorphism may play a role as a modifying factor for age of onset in schizophrenia. © 2009 Wiley‐Liss, Inc.
The association of the dopamine transporter gene and the dopamine receptor 2 gene with delirium, a meta‐analysis
Authors: van Munster Barbara C. , de Rooij Sophia E.J.A. , Yazdanpanah Mojgan , Tienari Pentti J. , Pitkälä Kaisu H. , Osse Robert J. , Adamis Dimitrios , Smit Orla , van der Steen Marijke S. , van Houten Miriam , Rahkonen Terhi , Sulkava Raimo , Laurila Jouko V. , Strandberg Timo E. , Tulen Joke H.M. , Zwang Louwerens , MacDonald Alastair J.D. , Treloar Adrian , Sijbrands Eric J.G. , Zwinderman Aeilko H. , Korevaar Johanna C. 
Published: September 2009

AbstractDelirium is the most common neuropsychiatric syndrome in elderly ill patients. Previously, associations between delirium and the dopamine transporter gene (solute carrier family 6, member 3 (SLC6A3)) and dopamine receptor 2 gene (DRD2) were found. The aim of this study was to validate whether markers of the SLC6A3 and DRD2 genes are were associated with delirium in independent populations. Six European populations collected DNA of older delirious patients. Associations were determined per population and results were combined in a meta‐analysis. In total 820 medical inpatients, 185 cardiac surgery patients, 134 non‐cardiac surgery patients and 502 population‐based elderly subjects were included. Mean age was 82 years (SD 7.5 years), 598 (36%) were male, 665 (41%) had pre‐existing cognitive impairment, and 558 (34%) experienced delirium. The SLC6A3 rs393795 homozygous AA genotype was more frequent in patients without delirium in all populations. The meta‐analysis showed an Odds Ratio (OR) for delirium of 0.4 (95% confidence interval (C.I.) 0.2–0.6, P = 0.0003) for subjects with AA genotype compared to the AG and GG genotypes. SLC6A3 marker rs1042098 showed no association with delirium. In meta‐analysis the DRD2 rs6276 homozygous GG genotype showed an OR of 0.8 for delirium (95% C.I. 0.6–1.1, P = 0.24). When subjects were stratified for cognitive status the rs6276 GG genotype showed ORs of 0.6 (95% C.I. 0.4–1.0, P = 0.06) and 0.8 (95% C.I. 0.5–1.5, P = 0.51) for delirium in patients with and without cognitive impairment, respectively. In independent cohorts, a variation in the SLC6A3 gene and possibly the DRD2 gene were found to protect for delirium. © 2009 Wiley‐Liss, Inc.
Methods on erg9 gene deletion in Schizosaccharomyces pombe
Authors: Cheng Bing , Yuan Qi‐peng , Sun Xin‐xiao , Li Wen‐jin 
Published: September 2009

AbstractGene modification to key enzymes in biosynthesis pathway becomes familiar technology which can increase efficiency of industrial strains. In the current study, we established a desirable deletion approach based on homologous recombination. It was simple and available for spn5 gene deletion. Also, four kinds of erg9 gene deletion cassettes were constructed in similar manner. The lengths of flanking sequences for homologous integration were from 59 bp to more than 1 Kb, and three selective markers (G418, Zeocin and LEU2) were employed in these cassettes. However, Δerg9 mutant was not obtained in this work. The possible reason is that erg9 gene is an essential gene and a single copy in its chromosome. Deficiency of erg9 gene resulted in nonviability to the cells. In addition, LEU2 marker caused unspecific integration and the difficulty of screening mutants is increased during deletion procedures. This work provides important evidence to modify industrial strains by using deletion technologies. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Solar membrane natural gas steam‐reforming process: evaluation of reactor performance
Authors: De Falco M. , Basile A. , Gallucci F. 
Published: September 2009

AbstractIn this work, the performance of an innovative plant for efficient hydrogen production using solar energy for the process heat duty requirements has been evaluated via a detailed 2D model. The steam‐reforming reactor consists of a bundle of coaxial double tubes assembled in a shell. The annular section of each tube is the reaction zone in which Ni‐based catalyst pellets are packed, whereas the inner tube is a dense Pd‐based selective membrane that is able to remove hydrogen from the reaction zone. By coupling reaction and hydrogen separation, equilibrium constrains inside the reactor are circumvented and high methane conversions at relatively low temperatures are achieved. The heat needed for the steam‐reforming reaction at this low operating temperature can be supplied by using a molten salt stream, heated up to 550 °C by a parabolic mirror solar plant, as heating fluid. The effects on membrane reactor performance of some operating conditions, as gas mixture residence time, reaction pressure and steam‐to‐carbon ratio, are assessed together with the enhancement of methane conversion with respect to the traditional process, evaluated in the range 40.5–130.9% at the same operating conditions. Moreover, owing to the use of a solar source for chemical process heat duty requirements, the greenhouse gases (GHG) reduction is estimated to be in the range 33–67%. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Steered molecular dynamics simulation of the detaching process of two parallel surfaces glued together by a single polyethylene chain
Authors: Wang Yu , Zhang Linxi , Cheng Jun 
Published: September 2009

AbstractThe detaching process of two parallel surfaces glued together by a single polyethylene chain in vacuo was investigated with a steered molecular dynamics method. Various statistical properties were analyzed in detail, including the mean‐square end‐to‐end distance; parallel and perpendicular mean‐square radii of gyration; shape factor; segment density distribution; average percentages of the microstructure of the chain of the tail, train, bridge, and loop; average surface adsorption energy; average total energy; and average pulling force (〈f〉). All these properties depended strongly on the pulling velocity (v). There existed a peak in the curve of 〈f〉 as a function of the detaching distance. Further, the relation between the maximum value of 〈f〉 and v showed three distinctive regions: a region of weak dependence at v < 10−2 Å/ps, a region of strong dependence at 10−2 Å/ps < v < 6.50 Å/ps, and a region of weak dependence at v > 6.50 Å/ps. These investigations may provide some insight into the microcosmic principle of the failure process of polymeric adhesives. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Investigation on the mechanical performances of ternary nylon 6/SEBS elastomer/nano‐SiO2 hybrid composites with controlled morphology
Authors: Zhang Baoqing , Wong Julia Shuk‐Ping , Shi Dean , Yam Richard Ching‐Man , Li Robert Kwok‐Yiu 
Published: September 2009

AbstractThe distribution of maleated styrene‐hydrogenated butadiene‐styrene (mSEBS) elastomer and nano‐SiO2 in nylon 6 matrix was controlled by varying the blending procedure. Nano‐SiO2 particles with different surface properties (hydrophilic versus hydrophobic) were adopted to adjust their interactions with other components. Two different structures, separate dispersion of nano‐SiO2 and elastomer particles as well as encapsulation of nano‐SiO2 fillers by the elastomer, were obtained. The structures were confirmed through scanning electron microscope (SEM) investigation. The mechanical measurement results showed that the microstructure and the interactions among the components had dramatic influences on the final mechanical properties, especially Izod fracture toughness, for the ternary nanocomposites. The nanocomposites containing hydrophilic nano‐SiO2 had better mechanical performances compared with the composites filled with hydrophobic SiO2 when they were in the same microstructure. The nanocomposites with separate dispersion structure showed higher stiffness compared with those of encapsulation type. However, the separately dispersed nano‐SiO2 particles restricted the cavitation of elastomer phases that led to low toughening effectiveness. The difference of cavitation intensity for elastomer phase was revealed by SEM investigation on the facture surfaces for the nanocomposites with the two different microstructures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Improvement of permeation performance of polyethersulfone (PES) ultrafiltration membranes via addition of Tween‐20
Authors: Amirilargani Mohammad , Saljoughi Ehsan , Mohammadi Toraj 
Published: September 2009

AbstractIn this study, effects of Tween‐20 (polyoxyethylene sorbitan monolaurate) as a variable surfactant additive on morphology, permeation performance and antifouling properties of asymmetric polyethersulfone (PES) membranes were investigated. The membranes prepared from PES/polyethylene glycol (PEG)/N,N‐dimethylformamide (DMF) system via phase inversion induced by immersion precipitation in water coagulation bath. The membranes performances were evaluated using ultrafiltration (UF) experiments. The scanning electron microscope and atomic force microscopy analysis were performed to investigate the membrane morphology. The obtained results indicate that by increasing the concentration of Tween‐20, the membrane morphology changes slowly from thin finger‐like structure with spongy structure to long and wide finger‐like structure with some macrovoids. Addition of surfactant to the casting solution increases the porosity of the membrane sublayer. It was found out that the rejection ratio of Bovine serum albumin (BSA) decreases, while the flux recovery ratio remarkably increases and the degree of irreversible fouling decreases. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Microstructure determination of methyl methacrylate‐N‐arylsubstituted itaconimide copolymers by NMR spectroscopy
Authors: Chauhan Rashmi , Choudhary Veena 
Published: September 2009

AbstractThis article describes the homopolymerization and copolymerization of methyl methacrylate with N‐(5‐chloro‐2‐methoxyphenyl)itaconimide (OMCPI)/N‐(5‐chloro‐3‐methoxyphenyl)itaconimide (MCPI) monomers using AIBN as an initiator and THF as solvent at 60°C. Feed compositions having varying mole fractions of OMCPI and MCPI ranging from 0.1 to 0.5 were taken to prepare copolymers. Structural characterization of homopolymers and copolymers thus obtained was done using FT‐IR, 1H‐NMR, and elemental analysis. Copolymer composition was determined using percent nitrogen content. Comonomer reactivity ratios were determined using Kelen‐Tüdos and non‐linear error in variable model (EVM) method using RREVM computer program. Carbonyl carbon signals of MMA (M) as well as N‐aryl itaconimide (I) copolymers in the 13C{1H}‐NMR spectra were used for the determination of sequence distribution of M‐and I‐centered triads. Sequence distribution of M‐ and I‐ centered triads calculated using 13C{1H}‐NMR spectra are in good agreement with the theoretically calculated values using Harwood's model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Microwave preparation and adsorption properties of EDTA‐modified cross‐linked chitosan
Authors: Ge Huacai , Huang Shiying 
Published: September 2009

AbstractA novel chitosan‐based adsorbent (CCTE) was synthesized by the reaction between epichlorohydrin O‐cross‐linked chitosan and EDTA dianhydride under microwave irradiation (MW). The chemical structure of this new polymer was characterized by infrared spectra analysis, thermogravimetric analysis, and X‐ray diffraction analysis. The results were in agreement with the expectations. The static adsorption properties of the polymer for Pb2+, Cu2+, Cd2+, Ni2+, and Co2+ were investigated. Experimental results demonstrated that the CCTE had higher adsorption capacity for the same metal ion than the parent chitosan and cross‐linked chitosan. In particular, the adsorption capacities for Pb2+ and Cd2+ were 1.28 mmol/g and 1.29 mmol/g, respectively, in contrast to only 0.372 mmol/g for Pb2+ and 0.503 mmol/g for Cd2+ on chitosan. Kinetic experiments indicated that the adsorption of CCTE for the above metal ions achieved the equilibrium within 4 h. The desorption efficiencies of the metal ions on CCTE were over 93%. Therefore, CCTE is an effective adsorbent for the removal and recovery of heavy metal ions from industrial waste solutions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Novel crosslinked starch microspheres as adsorbents of Cu2+
Authors: Miao Zongcheng , Li Zhongjin , Deng Deng , Wang Lei , Liu Yong 
Published: September 2009

AbstractA novel adsorbent, a crosslinked starch microsphere (CSM), was prepared from soluble starch and N,N′‐methylenebisacrylamide. The microporous structure of the CSM was determined with scanning electron microscopy. The diameter distribution of the CSMs was quite uniform, and the average diameter of the microparticles was estimated to be 50 μm. Cu2+ was introduced into the CSM. The successful adsorption of Cu2+ in the CSM was confirmed with Fourier transform infrared spectroscopy. The crystal structure of the CSM was destroyed after the incorporation of Cu2+. This was proven with X‐ray diffraction. The thermal stability of the CSM was weakened with the introduction of Cu2+ during simultaneous thermal analysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010