bluuebunny/crossref_metadata_2025 huggingface dataset:
Explaining English Language Proficiency Among Adolescent Immigrant Students
Authors: Carhill Avary , Suárez-Orozco Carola , Páez Mariela
Published: July 2008

This study aims to increase understanding of factors that account for academic English language proficiency in a sample of 274 adolescent first-generation immigrant students from China, the Dominican Republic, Haiti, Central America, and Mexico. Previous research has shown the importance of English language proficiency in predicting academic achievement measured by GPA and achievement tests. The present study describes the academic English language proficiency of immigrant youth after, on average, 7 years in the United States and models factors that contribute to variation. Findings show that although differences in individual student characteristics partially explain variation in English language proficiency, the schools that immigrant youth attended are also important. The amount of time that students spent speaking English in informal social situations is predictive of English language proficiency. These findings demonstrate that social context factors directly affect language learning among adolescent immigrant youth and suggest a crucial role for school and peer interventions.
Information Equation of State
Authors: Gough M. Paul
Published: July 2008

Landauer’s principle is applied to information in the universe. Once stars began forming there was a constant information energy density as the increasing proportion of matter at high stellar temperatures exactly compensated for the expanding universe. The information equation of state was close to the dark energy value, w = -1, for a wide range of redshifts, 10 > z > 0.8, over one half of cosmic time. A reasonable universe information bit content of only 1087 bits is sufficient for information energy to account for all dark energy. A time varying equation of state with a direct link between dark energy and matter, and linked to star formation in particular, is clearly relevant to the cosmic coincidence problem. In answering the ‘Why now?’ question we wonder ‘What next?’ as we expect the information equation of state to tend towards w = 0 in the future.c
Background music as noise abatement in open‐plan offices: A laboratory study on performance effects and subjective preferences
Authors: Schlittmeier Sabine J. , Hellbrück Jürgen
Published: July 2008

Continuous noise is played in many open‐plan offices to partially mask ambient sounds, in particular background speech. With this, the detrimental impact of background sounds on cognitive performance is intended to be reduced as well as subjectively perceived disturbance. Our experiments explored whether background music can achieve the same effects. Besides collecting subjective rating data, we tested cognitive performance using verbal serial recall. This is the standard task for exploring verbal short‐term memory, which is central to human information processing. Either staccato music, legato music or continuous noise was superimposed on office noise. In Experiment 1 (N = 30), only continuous noise reduced the detrimental impact of office noise significantly. Legato music did not qualify in this respect although it did not diminish cognitive performance when presented in isolation in Experiment 2 (N = 20). Subjective ratings in both experiments revealed that most participants would prefer legato music to continuous noise in office environments. Copyright © 2008 John Wiley & Sons, Ltd.
Dependence of Transformation Temperatures of NiTi‐based Shape‐Memory Alloys on the Number and Concentration of Valence Electrons
Authors: Zarinejad Mehrdad , Liu Yong
Published: July 2008

Dependence of transformation temperatures of ternary and quaternary NiTi‐based shape memory alloys on the number (ev/a) and concentration (cv) of valence electrons is investigated. Two distinct trends of transformation temperatures with respect to the number of valence electrons per atom are found depending on whether ev/a = 7 or ev/a ≠ 7. Clear correlations between transformation temperatures and cv exist. Ms and As decrease consistently from 900 to −100 °C, and 950 to −30 °C, respectively, with increasing cv from 0.145 to 0.296. The relationship of electron concentration on the elastic moduli of the NiTi‐based alloys is discussed. The possible influence of the atomic size of alloying elements on transformation hysteresis is introduced.
The Effect of Poly(3‐hexylthiophene) Molecular Weight on Charge Transport and the Performance of Polymer:Fullerene Solar Cells
Authors: Ballantyne Amy M. , Chen Lichun , Dane Justin , Hammant Thomas , Braun Felix M. , Heeney Martin , Duffy Warren , McCulloch Iain , Bradley Donal D. C. , Nelson Jenny
Published: July 2008

The time‐of‐flight method has been used to study the effect of P3HT molecular weight (Mn = 13–121 kDa) on charge mobility in pristine and PCBM blend films using highly regioregular P3HT. Hole mobility was observed to remain constant at 10−4 cm2V−1s−1 as molecular weight was increased from 13–18 kDa, but then decreased by one order of magnitude as molecular weight was further increased from 34–121 kDa. The decrease in charge mobility observed in blend films is accompanied by a change in surface morphology, and leads to a decrease in the performance of photovoltaic devices made from these blend films.
Efficient Polythiophene/Polyfluorene Copolymer Bulk Heterojunction Photovoltaic Devices: Device Physics and Annealing Effects
Authors: McNeill Christopher R. , Halls Jonathan J. M. , Wilson Richard , Whiting Gregory L. , Berkebile Stephen , Ramsey Michael G. , Friend Richard H. , Greenham Neil C.
Published: July 2008

Here the influence of annealing on the operational efficiency of all‐polymer solar cells based on blends of the polymers poly(3‐hexylthiophene) (P3HT) and poly((9,9‐dioctylfluorene)‐2,7‐diyl‐alt‐[4,7‐bis(3‐hexylthiophen‐5‐yl)‐2,1,3‐benzothiadiazole]‐2′,2″‐diyl) (F8TBT) is investigated. Annealing of completed devices is found to result in an increase in power conversion efficiency from 0.14 to 1.20%, while annealing of films prior to top electrode deposition increases device efficiency to only 0.19% due to a lowering of the open‐circuit voltage and short‐circuit current. By studying the dependence of photocurrent on intensity and effective applied bias, annealing is found to increase charge generation efficiency through an increase in the efficiency of the separation of bound electron‐hole pairs following charge transfer. However, unlike many other all‐polymer blends, this increase in charge separation efficiency is not only due to an increase in the degree of phase separation that assists in the spatial separation of electron‐hole pairs, but also due to an order of magnitude increase in the hole mobility of the P3HT phase. The increase in hole mobility with annealing is attributed to the ordering of P3HT chains evidenced by the red‐shifting of P3HT optical absorption in the blend. We also use X‐ray photoelectron spectroscopy (XPS) to study the influence of annealing protocol on film interface composition. Surprisingly both top and bottom electrode/blend interfaces are enriched with P3HT, with the blend/top electrode interface consisting of more than 95% P3HT for as‐spun films and films annealed without a top electrode. Films annealed following top electrode deposition, however, show an increase in F8TBT composition to ∼15%. The implications of interfacial composition and the origin of open‐circuit voltage in these devices are also discussed.
A Fluorescent Cobalt Probe with a Large Ratiometric Fluorescence Response via Modulation of Energy Acceptor Molar Absorptivity on Metal Ion Binding
Authors: Lin Weiying , Yuan Lin , Long Lingliang , Guo Cancheng , Feng Jianbo
Published: July 2008

Probe 1 has been synthesized as the first ratiometric fluorescent cobalt probe, and it exhibits several highly favorable features, in particular a remarkable ratiometric fluorescence response at two wavelengths. Importantly, the electronic energy transfer (EET) efficiency of the probe is modulated by the energy acceptor molar absorptivity variations on cobalt binding, which then transforms to a large ratiometric fluorescence response at two wavelengths. This signaling mechanism should open a new avenue for the development of powerful ratiometric probes with large emission signal ratios at two wavelengths for exciting applications in many fields.
Association of ADHD with genetic variants in the 5′‐region of the dopamine transporter gene: Evidence for allelic heterogeneity
Authors: Brookes K.J. , Xu X. , Anney R. , Franke B. , Zhou K. , Chen Wai , Banaschewski T. , Buitelaar J. , Ebstein R. , Eisenberg J. , Gill M. , Miranda A. , Oades R.D. , Roeyers H. , Rothenberger A. , Sergeant J. , Sonuga‐Barke E. , Steinhausen H.‐C. , Taylor E. , Faraone S.V. , Asherson P.
Published: July 2008

Multiple studies have reported an association between attention deficit hyperactivity disorder (ADHD) and the 10‐repeat allele of a variable number tandem repeat (VNTR) polymorphism in the 3′‐untranslated region (3′UTR) of the dopamine transporter gene (DAT1). Yet, recent meta‐analyses of available data find little or no evidence for this association; although there is strong evidence for heterogeneity between datasets. This pattern of findings could arise for several reasons including the presence of relatively rare risk alleles on common haplotype backgrounds or the functional interaction of two or more loci within the gene. We previously described the importance of a specific haplotype at the 3′ end of DAT1, as well as the identification of associated single nucleotide polymorphisms (SNPs) within or close to 5′ regulatory sequences. In this study we replicate the association of SNPs at the 5′ end of the gene and identify a specific risk haplotype spanning the 5′ and 3′ markers. These findings indicate the presence of at least two loci associated with ADHD within the DAT1 gene and suggest that either additive or interaction effects of these two loci on the risk for ADHD. Overall these data provide further evidence that genetic variants of the dopamine transporter gene confer an increased risk for ADHD. © 2008 Wiley‐Liss, Inc.
Variability of height, weight, and body mass index in a Swiss armed forces 2005 census
Authors: Rühli Frank , Henneberg Maciej , Woitek Ulrich
Published: July 2008

The influence of the environment and genetics on individual biological characteristics, such as body mass and stature is well known. Many studies of these relationships have been based on conscript data. These studies often suffer from the fact that their data cover only a part of the population. Characterized by prosperity, democratic stability and enormous micro‐regional cultural diversity, Switzerland is in the unique situation of offering data covering more than 80% of annual male birth cohorts. The aim of this study is to assess the impact of socioeconomic success, cultural differences, month of birth, and altitude (among other factors) on individual anthropometric characteristics of conscripts (N ∼ 28,000) in the 2005 census. Our result highlights in such a large male sample the relationship between economic environment, regional cultural diversity, climate, and other factors, such as individual month of birth on stature and weight. Socioeconomic status, culture (as reflected by mother tongue), and month of birth were found to have significant effects on height and weight, while altitude did not show such effects. In general, weight is more affected by all these variables than height. Taking weight‐dependent mortality and morbidity into account, it is of foremost public interest to know more about paired effects of living conditions on stature and weight in a highly developed society. Am J Phys Anthropol, 2008. © 2008 Wiley‐Liss, Inc.
Frontotemporal dementia and related disorders: Deciphering the enigma
Authors: Josephs Keith A.
Published: July 2008

In the past century, particularly the last decade, there has been enormous progress in our understanding of frontotemporal dementia, a non‐Alzheimer's type dementia. Large clinicopathological series have been published that have clearly demonstrated an overlap between the clinical syndromes subsumed under the term frontotemporal dementia and the progressive supranuclear palsy syndrome, corticobasal syndrome, and motor neuron disease. There have also been significant advancements in brain imaging, neuropathology, and molecular genetics that have led to different approaches to classification. Unfortunately, the field is complicated by a barrage of overlapping clinical syndromes and histopathological diagnoses that does not allow one to easily identify relations between individual clinical syndromic presentations and underlying neuropathology. This review deciphers this web of terminology and highlights consistent, and hence important, associations between individual clinical syndromes and neuropathology. These associations could ultimately allow the identification of appropriate patient phenotypes for future targeted treatments. Ann Neurol 2008;64:4–14
Rapidly progressive dementia
Authors: Geschwind Michael D. , Shu Huidy , Haman Aissa , Sejvar James J. , Miller Bruce L.
Published: July 2008

In contrast with more common dementing conditions that typically develop over years, rapidly progressive dementias can develop subacutely over months, weeks, or even days and be quickly fatal. Because many rapidly progressive dementias are treatable, it is paramount to evaluate and diagnose these patients quickly. This review summarizes recent advances in the understanding of the major categories of RPD and outlines efficient approaches to the diagnosis of the various neurodegenerative, toxic‐metabolic, infectious, autoimmune, neoplastic, and other conditions that may progress rapidly. Ann Neurol 2008;64:97–108
Leuchtdioden mit Halbleiternanokristallen
Authors: Rogach Andrey L. , Gaponik Nikolai , Lupton John M. , Bertoni Cristina , Gallardo Diego E. , Dunn Steve , Li Pira Nello , Paderi Marzia , Repetto Piermario , Romanov Sergei G. , O'Dwyer Colm , Sotomayor Torres Clivia M. , Eychmüller Alexander
Published: July 2008

Kolloidale Halbleiternanopartikel sind vielversprechende Luminophore für die Entwicklung einer neuen Generation von Elektrolumineszenzeinheiten. Bei Halbleiternanokristall‐LEDs wurden im Laufe eines Jahrzehnts enorme Fortschritte erzielt: So ließ sich die externe Quantenausbeute um mehr als zwei Größenordnungen verbessern, und Funktionseinheiten mit hoch gesättigten Farbemissionen sind heute Standard. Wenngleich die Geräteeffizienz immer noch eine Größenordnung kleiner ist als bei rein organischen LEDs, haben die Nanokristall‐LEDs eine ganze Reihe potenzieller Vorteile, z. B. spektralreine Emissionsfarben, was ein lohnender Forschungszweig für künftige Entwicklungen scheint. Weitere technische Verbesserungen von Nanokristall‐LEDs zielen auf höhere Materialstabilitäten, eine gezielte Steuerung chemischer und physikalischer Vorgänge an den Grenzflächen und die Optimierung der Ladungsinjektion und des Ladungstransports ab.
Light‐Emitting Diodes with Semiconductor Nanocrystals
Authors: Rogach Andrey L. , Gaponik Nikolai , Lupton John M. , Bertoni Cristina , Gallardo Diego E. , Dunn Steve , Li Pira Nello , Paderi Marzia , Repetto Piermario , Romanov Sergei G. , O'Dwyer Colm , Sotomayor Torres Clivia M. , Eychmüller Alexander
Published: July 2008

Colloidal semiconductor nanocrystals are promising luminophores for creating a new generation of electroluminescence devices. Research on semiconductor nanocrystal based light‐emitting diodes (LEDs) has made remarkable advances in just one decade: the external quantum efficiency has improved by over two orders of magnitude and highly saturated color emission is now the norm. Although the device efficiencies are still more than an order of magnitude lower than those of the purely organic LEDs there are potential advantages associated with nanocrystal‐based devices, such as a spectrally pure emission color, which will certainly merit future research. Further developments of nanocrystal‐based LEDs will be improving material stability, understanding and controlling chemical and physical phenomena at the interfaces, and optimizing charge injection and charge transport.
Kinetic monitoring of trisubstituted organotins in soil after sewage sludge application
Authors: Dubascoux S. , Lespes G. , Denaix L. , Gautier M. Potin
Published: July 2008

Organotin compounds (OTC) are widely used for their biocidal effects in various agricultural or industrial activities, leading to their environmental presence. Among the organotin species, tributyltin (TBT) and triphenyltin (TPhT) are the most used and are generally considered the most toxic. So it is important to understand their behaviour in soils and obtain data about their persistence and phytoavailability. Many works deal with OTC speciation in various matrices, but few are concerned with OTC degradation in soil. The present study focuses on kinetic monitoring of TBT and TPhT in an agricultural soil. These compounds were introduced into the soil by the way of spiked sewage sludge, simulating agricultural practice and diffuse contamination. The influence of time and initial OTC concentration on the species preservation was evaluated. TBT concentration was shown to have a positive effect on TBT preservation. Corresponding half‐lives were calculated. They were 6 ± 1 days and over 39 days for TPhT and TBT, respectively. Degradation compounds, mono‐ and dibutyltin, and mono‐ and diphenyltin, were produced by both direct and successive dealkyl and dearylation processes. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis, spectral characterization, electrochemical studies and catalytic properties in Suzuki–Miyaura coupling reactions of the mononuclear PdII, trinuclear PdII(BPh2)2 and RuIIPdIIRuII type complexes containing 4‐amino‐1‐benzyl piperidine and phenyl groups
Authors: Kilic Ahmet , Yilmaz Ismail , Ulusoy Mahmut , Tas Esref
Published: July 2008

The ligand containing the 4‐amino‐1‐benzyl piperidine group, N, N′‐(4‐amino‐1‐benzyl piperidine)‐glyoxime, (LH2) (1) was prepared from 4‐amino‐1‐benzyl piperidine with anti‐dichloroglyoxime at − 15 °C in absolute Tetrahydrofuran (THF). In the trinuclear [Pd(L)2Ru2(phen)4](ClO4)2 (4) and [Pd(L)2Ru2(bpy)4](ClO4)2 (5) metal complexes, the PdII ion centered into the main oxime core by the coordination of the imino groups while the two RuII ions coordinated dianionic oxygen donors of the oxime groups and linked to the ligands of 1,10‐phenanthroline and 2,2′‐bipyridine. The mono and trinuclear metal complexes were characterized by elemental analyses, FT‐IR, UV–vis, 1H and 13C‐NMR spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass spectra, X‐ray powder techniques and their morphology by SEM measurements. The cyclic voltammetric results show that the cathodic peak (Epc) potential of (3) shifts towards more positive values compared with that of (2) as a result of the BPh2+‐bridged complex formation. The Suzuki–Miyaura reaction was used to investigate their activity as catalyst either prepared in‐situ or from well‐defined complexes. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis of substituted vinylgermanes and germylsilylethenes via ruthenium complex catalyzed germylation of olefins
Authors: Marciniec Bogdan , Ławicka Hanna
Published: July 2008

A series of substituted vinylgermanes and divinylgermanes have been synthesized in moderate or high yield via two reactions of olefins and dienes catalyzed by [RuHCl(CO) (PCy3)2], i.e. germylative coupling with vinylgermanes and dehydrogenative germylation with hydrogermanes. While the former reaction can be a versatile way of regioselective synthesis of products (particularly useful for the stereoselective synthesis of germylsilylethenes), the latter could be used as a complement, especially in synthesis of germylate dioxol ethene and vinyl ethers. Copyright © 2008 John Wiley & Sons, Ltd.
Tin dithiocarbamates: applications and structures
Authors: Tiekink Edward R. T.
Published: July 2008

The uses and potential utility of tin/organotin dithiocarbamate,−S2CNR′2, compounds are reviewed. Various derivatives exhibit exciting potential as anti‐cancer agents, anti‐microbial agents and insecticides, e.g. against mosquito larvae. Tin dithiocarbamates have also proven useful as precursors for tin sulfide nanoparticles. There is a wealth of structural data available for such compounds and with the exception of the diorganotin bis(dithiocarbamate) compounds, R2Sn(S2CNR′2)2, compounds for which different structural motifs are evident, there is a certain degree of homogeneity in the molecular structures for each class of compound unless there are additional coordination sites on the R and/or R′ groups. Owing to the strong coordination potential of the dithiocarbamate ligand for tin, supramolecular aggregates involving secondary Sn…S interactions are the exception rather than the norm. Copyright © 2008 John Wiley & Sons, Ltd.
Superparamagnetic iron oxide as an efficient and recoverable catalyst for rapid and selective trimethylsilyl protection of hydroxyl groups
Authors: Mojtahedi Mohammad M. , Abaee M. Saeed , Eghtedari Mohammad
Published: July 2008

At room temperature and under solvent‐free conditions, various types of alcohols and phenols were efficiently protected within a few minutes using hexamethyldisilazane and magnetically recoverable Fe3O4. Preferential protection of primary alcohols was observed when they competed with secondary or tertiary alcohols. Highly selective protection of phenols in the presence of aromatic amines or thiophenol was also observed. Copyright © 2008 John Wiley & Sons, Ltd.
Influence of solid lubricant reinforcement on wear behavior of Kevlar fabric composites
Authors: Guo Fang , Zhang Zhao‐Zhu , Liu Wei‐min , Su Feng‐hua , Zhang Hui‐juan
Published: July 2008

The friction and wear behavior of Kevlar fabric composites reinforced by PTFE or graphite powders was investigated using a Xuanwu‐III friction and wear tester at dry sliding condition, with the unfilled Kevlar fabric composite as a reference. The worn surfaces were analyzed by means of scanning electron microscope, and X‐ray photoelectron spectroscopy. It was found that PTFE or graphite as fillers could significantly improve the tribological behavior of the Kevlar fabric composites, and the Kevlar fabric composites filled with 20% PTFE exhibited the best antiwear and antifriction ability among all evaluated cases. The transfer films established with two lubricants in sliding wear of composites against metallic counterparts made contributions to reducing friction coefficient and wear rate of Kevlar fabric composites. In particular, FeF2 generated in the sliding of Kevlar fabric composites filled with PTFE against counterpart pin improved the bonding strength between the transfer film and counterpart surface, which accounted for the lowest friction coefficient and wear rate of the Kevlar fabric composites filled with PTFE measured in the testing. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.
Kinetic study of the free‐radical polymerization of vinyl acetate in the presence of deuterated chloroform by 1H‐NMR spectroscopy
Authors: Semsarzadeh Mohammad Ali , Abdollahi Mahdi
Published: July 2008

The free‐radical polymerization of vinyl acetate was performed in the presence of deuterated chloroform (CDCl3) as a chain‐transfer agent (telogen) and 2,2′‐azobisisobutyronitrile as an initiator. The effects of the initiator and solvent concentrations (or equivalent monomer concentration) and the reaction temperature on the reaction kinetics were studied by real‐time 1H‐NMR spectroscopy. Data obtained from analysis of the 1H‐NMR spectra were used to calculate some kinetic parameters, such as the initiator decomposition rate constant (kd), kp(f/kt)1/2 ratio (where kp is the average rate constant for propagation, f is the initiator efficiency, and kt is the average rate constant for termination), and transfer constant to CDCl3 (C). The results show that kd and kp(f/kt)1/2 changed significantly with the solvent concentration and reaction temperature, whereas they remained almost constant with the initiator concentration. C changed only with the reaction temperature. Attempts were made to explain the dependence of kp(f/kt)1/2 on the solvent concentration. We concluded from the solvent‐independent C values that the solvent did not have any significant effect on the kp values. As a result, changes in the kp(f/kt)1/2 values with solvent concentration were attributed to the solvent effect on the f and/or kt values. Individual values of f and kt were estimated, and we observed that both the f and kt values were dependent on the solvent (or equivalent monomer) concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and phase transition of cellulose‐graft‐poly(ethylene glycol) copolymers
Authors: Li Yanxiang , Liu Ruigang , Huang Yong
Published: July 2008

Cellulose‐graft‐poly(ethylene glycol) copolymers were synthesized, and the thermal properties of the copolymers were investigated. The cellulose‐graft‐poly(ethylene glycol) copolymers showed solid–solid phase‐transition behavior with a high thermal storage density and good thermal stability in the temperature region of 25–250°C. The phase‐transition temperature and enthalpy of the cellulose‐graft‐poly(ethylene glycol) copolymers could be adjusted through changes in the poly(ethylene glycol) content. The prepared copolymers could be used as thermal energy storage materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
PS/EPDM blends prepared by in situ polymerization of styrene
Authors: Lourenço Emerson , Felisberti Maria Isabel
Published: July 2008

PS/EPDM blends formed by in situ polymerization of styrene in the presence of EPDM were prepared. EPDM has excellent resistance to factors such as weather, ozone and oxidation and it could be a good alternative for substituting polybutadiene‐based rubbers in PS toughening. The PS/EPDM blends present two phases, an EPDM elastomeric phase dispersed into a rigid matrix. The blends show higher thermal stability than polystyrene homopolymer due to the stabilizing effect of EPDM incorporation. The mechanical properties of in situ polymerized PS/EPDM blends with different compositions were evaluated before and after accelerated photoaging and compared with the properties of HIPS submitted to the same aging conditions. The blend containing 17 wt % of EPDM presents an increase in the impact resistance of 210% in comparison with the value of PS. Although the initial mechanical properties of HIPS are superior, a pronounced drop was observed after an exposure time. For example, after the aging period, all PS/EPDM blends showed higher strain at break than HIPS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
The swelling behaviors and network parameters of cationic starch‐g‐acrylic acid/poly(dimethyldiallylammonium chloride) semi‐interpenetrating polymer networks hydrogels
Authors: Li Xin , Xu Shimei , Pen Yang , Wang Jide
Published: July 2008

Amphiphilic semi‐interpenetrating polymer networks (semi‐IPN) hydrogels were prepared by a sequential‐IPN method by acrylic acid graft copolymerization into cationic starch in mild aqueous media of poly(dimethyldiallylammonium chloride). Some main factors were investigated to evaluate the swelling of hydrogels, and the network parameters Mc were given accordingly to elaborate the interaction between polymers. The chemical structure of the resulting hydrogel was confirmed using Fourier transform infrared spectroscopy. The cationic starch‐based semi‐IPN hydrogels achieved a high swelling capacity of 1070 g/g in deionized water and 94 g/g in 0.9 wt % NaCl solution, respectively) and high compressive stress in a high water content. Besides, a different pH‐dependent behavior was found for this semi‐IPN hydrogel. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Association and effective hydrodynamic thickness of hydrophobically associating polyacrylamide through porous media
Authors: Lu Hongsheng , Feng Yujun , Huang Zhiyu
Published: July 2008

This study was aimed at the association and effective hydrodynamic thickness of hydrophobically associating polyacrylamide (HAPAM) through porous media with coreflow experiment. It shows that there is strong hydrophobic association for HAPAM in porous media but not for polyacrylamide (PAM). The resistance factor and effective hydrodynamic thickness of HAPAM are obviously superior to those of PAM. HAPAM exhibits much stronger shear thinning behavior than PAM due to the ability to form transitional network structure. It also indicates that PAM can exhibit a transition from shear thinning behavior to shear thickening behavior at low polymer concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of adhesives on thermal conductivity of laminated veneer lumber
Authors: Kurt Şeref , Uysal Burhanettin , Özcan Cemal
Published: July 2008

In this study, it is aimed to describe the effect of adhesives (PVAc‐polyurethane and urea formaldehyde) on wooden materials (Scotch pine and oriental beech) cut tangentially and radially and layers in laminated veneer lumber (LVL; 3, 4, 5) on thermal conductivity. The lowest thermal conductivity of 0.105 kcal/(m h °C) was obtained in Scotch pine, cut tangentially, bonded with polyurethane, and three‐layer LVL. The highest thermal conductivity of 0.159 kcal/m h °C was obtained in oriental beech, cut radially, bonded with PVAc, and five‐layer LVL. Consequently, oriental beech wood cut radially and bonded with PVAc adhesive and five layers in LVL can be used as a material in construction where the thermal conductivity is required. Scotch pine wood cut tangentially and bonded with polyurethane adhesive and three layers in LVL can be used as a material in construction where the insulation is required. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Polyamide 6/maleated ethylene–propylene–diene rubber/organoclay composites with or without glycidyl methacrylate as a compatibilizer
Authors: Zhang Lingyan , Wan Chaoying , Zhang Yong
Published: July 2008

Polyamide 6 (PA6)/maleated ethylene–propylene–diene rubber (EPDM‐g‐MA)/organoclay (OMMT) composites were melt‐compounded through two blending sequences. Glycidyl methacrylate (GMA) was used as a compatibilizer for the ternary composites. The composite prepared through via the premixing of PA6 with OMMT and then further melt blending with EPDM‐g‐MA exhibited higher impact strength than the composite prepared through the simultaneous blending of all the components. However, satisfactorily balanced mechanical properties could be achieved by the addition of GMA through a one‐step blending sequence. The addition of GMA improved the compatibility between PA6 and EPDM‐g‐MA, and this was due to the reactions between PA6, EPDM‐g‐MA, and GMA, as proved by Fourier transform infrared analysis and solubility (Molau) testing. In addition, OMMT acted as a compatibilizer for PA6/EPDM‐g‐MA blends at low contents, but it weakened the interfacial interactions between PA6 and EPDM‐g‐MA at high contents. Both OMMT and GMA retarded the crystallization of PA6. The complex viscosity, storage modulus, and loss modulus of the composites were obviously affected by the addition of OMMT and GMA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and physical properties of low‐molecular‐weight redistributed poly(2,6‐dimethyl‐1,4‐phenylene oxide) for epoxy resin
Authors: Hwang Hann‐Jang , Hsu Su‐Wen , Wang Chun‐Shan
Published: July 2008

Low‐molecular‐weight poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) was prepared by the redistribution of regular PPO with 4,4′‐isopropylidenediphenol (bisphenol A) with benzoyl peroxide as an initiator in toluene. The redistributed PPO was characterized by proton nuclear magnetic resonance, mass spectra, and Fourier transform infrared spectroscopy. The redistributed PPO oligomers with terminal phenolic hydroxyl groups and low molecular weights (weight‐average molecular weight = 800–4000) were used in the modification of a diglycidyl ether of bisphenol A/4,4′‐diaminodiphenylmethane network system. The curing behaviors were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The effect of molecular weight and the amount of redistributed PPO oligomers incorporated into the network on the physical properties of the resulting systems were investigated. The thermal properties of the cured redistributed PPO/epoxy resins were studied by dynamic mechanical analysis, thermal mechanical analysis, thermogravimetric analysis, and dielectric analysis. These cured redistributed PPO/epoxy resins exhibited lower dielectric constants, dissipation factors, coefficients of thermal expansion, and moisture absorptions than those of the control diglycidyl ether of bisphenol A based epoxy. The effects of the composition on the glass‐transition temperature and thermal stability are discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and properties of homopolyamide and copolyamides fibers based on 2,6‐bis(p‐aminophenyl)benzo[1,2‐d;5,4‐d′]bisoxazole
Authors: Chen Xiangqun , Sun Qiu , Huang Yudong , Cai Wei
Published: July 2008

A novel aromatic homopolyamide with benzobisoxazole units in the main chain was synthesized with 2,6‐bis(p‐aminophenyl)benzo[1,2‐d;5,4‐d′]bisoxazole and terephthaloyl chloride by low temperature solution polycondensation, the inherent viscosity of which was 1.98 dL/g. The diamine and p‐phenylendiamine with terephthaloyl chloride were used to synthesize the copolyamides. The structures of homopolyamide and copolyamides were characterized by IR spectra, elemental analysis, and wide‐angle X‐ray diffraction. Wide‐angle X‐ray diffraction measurements showed that homopolyamide and copolyamides were predominantly crystallinity. The results of thermal analysis indicated that the thermal stabilities of the copolymer increased with an increase of the molar fraction of benzobisoxazole in the copolymers. The thermal stability of the copolyamides with decomposition temperatures (at 10% weight loss) above 570°C was better than that of poly(p‐phenylene terephthalamide) (PPTA). Fibers of homopolyamide and copolyterephthalamides were spun from lyotropic liquid crystal dope in 100% H2SO4. When compared with PPTA fibers prepared under the same conditions, the tensile strengths of copolyamides fibers improved by 20–33% with tensile strengths of 1.81 GPa, tensile moduli of 76 GPa, and elongations at break of 3.8–4.1%, which indicated that copolyamides fibers had outstanding mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Shear flow behaviors of poly(p‐phenylene benzobisoxazole) spinning dope
Authors: Chen Xiaojun , Liu Xiaoyun , Qian Jun , Zhuang Qixin , Li Xinxin , Han Zhewen
Published: July 2008

In this study, the shear flow properties of Poly(p‐phenylene benzobisoxazole) (PBO)/poly(phosphoric acid) (PPA) spinning dope were studied by means of capillary rheometer. The effect of shear stress, temperature, PBO concentration, and PBO molecular weight on the apparent viscosity of PBO/PPA dope was discussed. The results showed that the apparent viscosity of the dope decreased with the increase of the shear stress and the temperature. The flow behavior index increased with the increase of temperature, which indicated that the non‐Newtonian behavior of the dope became weaker at high temperature. Moreover, it was also found that at high shear stress, the apparent viscosity of the dope was insensitive to the temperature, PBO molecular weight, and PBO concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Copolymers of unsaturated and saturated poly(ether ester amide)s: Synthesis, characterization, and biodegradation
Authors: Guo Kai , Chu C. C.
Published: July 2008

A series of biodegradable random unsaturated/saturated poly(ether ester amide)s copolymers (USPEEAs) were synthesized by an active solution polycondensation of unsaturated and saturated dicarboxylic acid‐based diester monomers with diamine salts of phenylalanine and saturated oligo(ethylene glycol) (OEG). These USPEEA copolymers were obtained with fairly good yields in DMA solvent. The chemical structures of the USPEEA copolymers were confirmed by both IR and NMR spectra. The molecular weights (Mn and Mw) of USPEEAs measured by GPC ranged from 3 to 27 kg/mol with the molecular weight distribution (MWD) ranging from 1.52 to 2.13. USPEEA copolymers obtained had Tg lower than that of the pure UPEEAs but higher than that of pure saturated poly(ether ester amide)s (SPEEA). An increase in the unsaturated component in USPEEAs led to an increase in their Tg. A preliminary in vitro biodegradation property of USPEEA copolymers were investigated in both pure PBS buffer and α‐chymotrypsin solutions. The USPEEA copolymers showed a pronounced weight loss in enzyme solutions, but a smaller weight loss in a pure PBS. The biodegradation rates of USPEEA copolymers in α‐chymotrypsin solution were much slower than those of pure PEEAs. Therefore, upon adjusting monomers feed ratio, USPEEA copolymers could have controlled chemical, physical, and biodegradation properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A Femtosecond Study of the Interaction of Human Serum Albumin with a Surfactant (SDS)
Authors: Mandal Ujjwal , Ghosh Subhadip , Mitra Gopa , Adhikari Aniruddha , Dey Shantanu , Bhattacharyya Kankan
Published: July 2008

The interaction of a protein, human serum albumin (HSA) with a surfactant (sodium dodecyl sulfate, SDS) was studied by femtosecond up‐conversion. HSA was labeled covalently with a probe (CPM, 7‐dimethylamino‐3‐(4‐maleimidophenyl)‐4‐methylcoumarin). Binding of SDS to HSA is found to accelerate the solvation dynamics ∼1.3‐fold. The solvation dynamics in HSA displays two time components: 30 ps (20 %) and 800 ps (80 %). When ∼10 SDS molecules bind to HSA the components are 15 ps (40 %) and 800 ps (60 %). It is argued that SDS may increase the solvent exposure of the probe (CPM); it may also displace the buried water molecules in the immediate vicinity of CPM.
PdII‐Catalyzed Asymmetric Addition Reactions of 1,3‐Dicarbonyl Compounds: Mannich‐Type Reactions with N‐Boc Imines and Three‐Component Aminomethylation
Authors: Hamashima Yoshitaka , Sasamoto Naoki , Umebayashi Natsuko , Sodeoka Mikiko
Published: July 2008

This paper describes catalytic asymmetric Mannich‐type reactions of β‐ketoesters and malonates using chiral palladium complexes. Although readily enolizable, carbonyl compounds are attractive substrates, the use of such compounds as nucleophiles in Mannich‐type reactions has not been extensively investigated. In the presence of chiral Pd aqua complexes (2.5 mol %), β‐ketoesters reacted with various N‐Boc imines (Boc=tert‐butoxycarbonyl) to afford the desired β‐aminocarbonyl compounds in good yield with high to excellent stereoselectivity (up to 96:4 d.r., 95–99 % ee in most cases). In these reactions, construction of highly crowded vicinal quaternary and tertiary carbon centers was achieved in one step. A chiral Pd enolate is considered to be the key intermediate. To elucidate the stereoselectivity observed in the reaction, possible transition‐state models are discussed, taking into account steric and stereoelectronic effects. Furthermore, this catalytic system was applied to the Mannich‐type reaction of malonates with N‐Boc imine as well as one‐pot classical aminomethylation of β‐ketoesters using benzylamine salt and formalin. The reactions proceeded smoothly, and the corresponding Mannich products were obtained in high yield with moderate to good enantioselectivity.
Tin‐Free Radical Carbonylation of Alkylsulfonyl Derivatives into Alkylcarbonyl Derivatives
Authors: Kim Sangmo , Lim Kyoung‐Chan , Kim Sunggak
Published: July 2008

A simple radical approach based on tin‐free radical carbonylation is devised for the direct conversion of alkylthiosulfonates, alkylsulfonyl cyanides, and alkylsulfonyl oxime ethers into the corresponding alkyl thiol esters, acyl cyanides, and acylated oxime ethers in a single step. The present approach is very simple, highly efficient, and minimizes the formation of byproducts.
Phosphine‐Free Cp*Ru(Diamine) Catalysts in the Hydrogenation of Imines
Authors: Cheruku Pradeep , Church Tamara L. , Andersson Pher G.
Published: July 2008

We previously reported the phosphine‐free Cp*Ru(diamine)‐catalyzed hydrogenation of aryl methyl ketones. Herein we present the first report of ruthenium–diamine‐catalyzed imine hydrogenation to form amines. The most effective catalyst, I/KOtBu, completely converted several imines to amines at room temperature. The effect of electron‐donating and ‐withdrawing groups on the reaction was investigated using a suitable series of substrates. The asymmetric version of the reaction was studied for two substrates, and the chiral amine products could be obtained in moderate enantiomeric excess.
Comment: Advancing public sector performance analysis by Professor C. J. Heinrich
Authors: Farewell V. T.
Published: July 2008

Random assignment experiments are discussed by drawing parallels between issues in performance management studies and in clinical trials. In addition, the need for statistical rigour and for measures of uncertainty in performance management tools is highlighted. Copyright © 2008 John Wiley & Sons, Ltd.
Soft tissue anatomy around the hip and its implications for choice of entry point in antegrade femoral nailing
Authors: Moein C.M. Ansari , Verhofstad M.H.J. , Bleys R.L.A.W. , van der Werken Chr.
Published: July 2008

Antegrade intramedullary nailing is an accepted method of treatment for femoral shaft fractures. Entrance of the nail through the trochanteric fossa is currently recommended by some surgeons. This approach results in some cases, however, in loss of abduction strength and persistent pain. Nail insertion at the tip of the greater trochanter may be more favorable. In this study the anatomical relationships of the trochanteric fossa and of the tip of the greater trochanter were explored. Dissection was carried out in 10 fresh human cadaver femurs. The risks and safety of the two entry points with respect to the adjacent soft tissues were assessed. Abductor muscles and tendons, branches of the medial circumflex femoral artery and the hip joint capsule were at risk during nail insertion through the trochanteric fossa. These structures were not endangered during insertion through the trochanteric tip. The reported clinical morbidity after nailing through the trochanteric fossa may result from direct soft tissue injury and may be reduced by choosing the route through the greater trochanter. Clin. Anat. 21:568–574, 2008. © 2008 Wiley‐Liss, Inc.
Probing the Compatibility of Type II Ketosynthase–Carrier Protein Partners
Authors: Worthington Andrew S. , Hur Gene H. , Meier Jordan L. , Cheng Qian , Moore Bradley S. , Burkart Michael D.
Published: July 2008

Drug discovery often begins with the screening of large compound libraries to identify lead compounds. Recently, the enzymes that are involved in the biosynthesis of natural products have been investigated for their potential to generate new, diverse compound libraries. There have been several approaches toward this end, including altering the substrate specificities of the enzymes involved in natural product biosynthesis and engineering functional communication between enzymes from different biosynthetic pathways. While there exist assays to assess the substrate specificity of enzymes involved in these pathways, there is no simple method for determining whether enzymes from different synthases will function cooperatively to generate the desired product(s). Herein we report a method that provides insight into both substrate specificity and compatibility of protein–protein interactions between the acyl carrier protein (ACP) and ketosynthase (KS) domains involved in fatty acid and polyketide biosynthesis. Our technique uses a one‐pot chemoenzymatic method to generate post‐translationally modified ACPs that are capable of covalently interacting with KS domains from different biosynthetic systems. The extent of interaction between ACPs and KSs from different systems is easily detected and quantified by a gel‐based method. Our results are consistent with previous studies of substrate specificity and ACP–KS binding interactions and provide new insight into unnatural substrate and protein interactions.
Preparation and Properties of Stable Nanocrystalline Anatase TiO2 Colloids
Authors: Chen X.‐Q. , Shen W.‐H.
Published: July 2008

The nanocrystalline anatase TiO2 colloid has widely been applied in solar energy conversion, photo‐degradation of organic pollutions, photochemical disinfection, processing of sensors, and papermaking. It can be obtained from the hydrolysis of titanyl organic compounds [TiO(OOCCH3)2 and Ti2O(OC4H9)2(OOCCH3)4] at low temperature and normal pressure. TEM (Transmission Electron Microscope), SEM (Scattering Electron Microscope), and LS (Layer Scattering) analysis showed that the colloidal particles are spherical and possess a narrow size distribution, that the mean size (80 °C, 2 h, sample B) is 8.9 nm and its isoelectric point is 6.67. The SBET of the gel powders are 262.7457 m2/g (60 °C, 2 h, sample A) and 258.0024 m2/g (80 °C, 2 h, sample B). Research experiments showed that the turbidities of colloidal solutions decreased along with the decrease of water content in the mixed water‐alcohol dispersants, which predicated that the colloidal stability fell when lowering the electrical conductivity of the dispersant. The zeta potentials of the colloids are 14 mV ∼ 30 mV at pH 4.5 ∼ 6.0 in the presence of 0.5 · 10–2 mol L–1 NaNO3 electrolyte. Furthermore, the UV absorbance of the nanocrystalline TiO2 colloidal solutions increased with a decrease in particle size. The experimental results of photocatalytic degradation of the dye rhodamine revealed that the nanocrystalline TiO2 colloidal particles from this preparation method have good photocatalytic activity, which is better if doped with 0.2 % Fe3+.
The Transient Dynamics of a Small Bubble Rising in a Low Morton Number Regime
Authors: Ohta M. , Tsuji M. , Yoshida Y. , Sussman M.
Published: July 2008

The effect of initial bubble conditions on the transient dynamics of a small bubble (d = 1.5 mm) rising in water is computationally considered by a fully three‐dimensional direct numerical simulation. The numerical algorithm is based on the coupled level set/volume‐of‐fluid (CLSVOF) method for representing and updating the air‐water interface and the sharp interface approach is used to treat the air‐water interfacial boundary conditions. The transient bubble dynamics are investigated using bubbles with five different kinds of shapes as initial bubble conditions. It is shown computationally that the states of bubble shape, bubble trajectory, and terminal velocities greatly depend on initial conditions. As a consequence, the computational results have led us to conclusions in support of the experimental findings by Wu and Gharib [1] and Tomiyama et al. [2]. That is, the dynamic behavior of a rising bubble in a surface tension force dominant system is effected by the initial conditions.
Modeling and Characterization of Air Emissions from Laboratory and Industrial Fluidized Beds
Authors: Whitcombe J. M. , Braddock R. D. , Agranovski I. E.
Published: July 2008

A fluidized bed model using several elutriation correlations was developed and tested against an operating fluidized bed used in a Fluidized Catalytic Cracker Unit (FCCU) and a 1:8.5 scale laboratory system. It was found that there was little variation between the emission rates predicted using different elutriation correlations, although the newly developed equations were slightly more accurate for the laboratory‐scale system. Although total emission rates were predicted with reasonable accuracy, the actual volatility and fluctuations seen in real fluidized beds emissions were not predicted. When the model was used to predict particle emission from the industrial FCCU, they preformed poorly, grossly overestimating the actual levels. It was determined that the attrition terms used in emission modeling were inappropriate and that the model preformed better without them, but still overestimated the actual emissions. This overestimation was greater in the industrial system compared with the smaller laboratory system. It was also found that the older elutriation terms were better for predicting industrial emissions compared with those of the smaller scale units.