bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of linear polymer dimensions of poly(4‐chlorostyrene) in various solvents around the θ temperatures by intrinsic viscosity
Authors: Baysal Bahattin M. , Yilmaz Ferdane
Published: April 2007

Intrinsic viscosities of poly(4‐chlorostyrene) solutions in isopropyl‐benzene and n‐propylbenzene at temperatures above and below the theta (θ) temperatures of these solvents were measured using a capillary viscometer. The viscosity measurements were performed on three poly(4‐chlorostyrene) samples having molecular weights (M̄;v) 1.75 × 106, 6.5 × 105 and 2.7 × 105. A smooth and continuous contraction below the θ temperatures was observed for both solvents. The temperature dependence of [/eta] can be represented by a master curve in a plot of α3/eta|/tau|M1/2 (g1/2 mol−1/2) versus |/tau|M1/2 (g1/2 mol−1/2), where α/eta = [/eta(T)]/[/eta(θ)]1/3 is the expansion factor and /tau = (T ‐ θ)/T is the reduced temperature. A universal plot of reduced viscosity size (α/eta) versus reduced blob parameter (N/Nc) shows the achievement of collapsed state for T<θ. The prediction of thermal blob theory is also verified for T > θ. The temperature dependence of intrinsic viscosity, both below and above the θ temperature, exhibits similar behaviour to the temperature dependence of dipole moments for both of these solvents.
Structural change of cellulose contained in immature cotton boll during its growth
Authors: Matsuda Yukiko , Kowsaka Keisuke , Okajima Kunihiko , Kamide Kenji
Published: April 2007

An attempt was made to clarify the change in the structure of immature cotton (Gossypium spp.) boll during its growth. For this purpose, five immature cotton bolls with length less than 4.64 cm were adopted as samples and cellulose fibres taken from these bolls were subjected to SEM observation, 13C NMR, X‐ray diffraction and IR analysis. Intramolecular hydrogen bonds were progressively formed during the growth of first cell wall but crystallization did not occur at this stage. Crystallization, as detected by X‐ray diffraction, takes place after the formation of O3…O'5 and O2…O'6 intramolecular hydrogen bonds. The crystallization is well correlated with the formation of intermolecular hydrogen bonds, as detected by IR analysis. The conformational regularity of molecular chains (formation of intramolecular hydrogen bonds) is concluded to be prerequisite for the crystallization of cotton fibre.
Synthesis of ring‐shaped polyisoprene
Authors: Madani Abdelaziz El , Favier Jean‐Claude , Hémery Patrick , Sigwalt Pierre
Published: April 2007

Cyclization of α,ω;‐dilithiopolyisoprenes has been achieved in hexane solution in the presence of tetrahydrofuran (15% in volume) at −40 to ‐ 50°C. Using as linking agent the non‐conjugated diene 1,2‐bis(isopropenyl‐4‐phenyl)‐ethane, macrocyclic polyisoprenes could be obtained with yields of at least 90%, even for molecular weights as high as 30 000 mol g−1. With SiCl4 as coupling agent no gelation occurred and yields of about 70% in cyclic dimers, probably bicyclic, have been observed.

These results are compared to those obtained by various authors with α,ω;‐dilithiopolystyrenes or α,ω;‐disodiopolystyrenes and are attributed mainly to the presence, in the polyisoprene case, of predominant cyclic aggregates even at low organolithium concentration.
Modification of kaolinite by surface polymerization
Authors: Laslett Robert L. , Wansbrough Katherine M. , Mainwaring David E. , Rizzardo Ezio , Singh Sirgit
Published: April 2007

Kaolinite filler surfaces were modified by both surface adsorption and surface reaction. Their subsequent wetting and adhesion properties were determined by measurement of the contact angle of the powders by the Washburn technique using three probe liquids that spanned molecular polarity. Surface modification by adsorption utilized the kaolinite surface acidity to polymerize styrene. Surface reaction involved reaction of kaolinite hydroxyl groups with aryl diisocyanates and subsequent termination with a series of alcohols of increasing complexity.

It was shown that kaolinite surfaces could be modified to produce surfaces of controlled hydrophobicity that could exceed that of conventionally silanated kaolinite. The ability of phases to spread and wet these filler surfaces was analysed in terms of the thermodynamic functions—spreading coefficient S12 and spreading pressure πe.
Photodegradable high density polyethylene‐based shopping bags— environmental hazard or blessing?
Authors: Ferguson Grant M. , Hood Mark , Abbott Kerry
Published: April 2007

Plastics are popularly regarded as an environmental hazard. Ferric stearate photoinitiated high density polyethylene (HDPE) films manufactured as supermarket shopping bags were found to rapidly photodegrade after exposure to ultraviolet (UV) and visible light irradiation. Our studies confirmed manufacturer's claims that the bags would degrade more rapidly than standard UV stabilised bags. The photodegradable bags had the potential to completely degrade and be resorbed into the biosphere without adverse effects.
Effect of lewis acids on cure kinetics and mechanical properties of hydroxyterminated polybutadiene polymers
Authors: Ninan K. N. , Krishnan K.
Published: April 2007

The effect of two Lewis acids, viz. BF3 and AlCl3 on the cure reaction of hydroxy‐terminated polybutadiene: toluene diisocyanate systems has been studied in order to evaluate them as possible pot‐life extenders in solid propellant formulations. The enthalpy of the cure exotherm, evaluated from DSC curves, did not show any dependence on the concentration of the two acids. The kinetic parameters for the cure reaction showed an increase in both cases indicating the effectiveness of the acids as reaction retardants. However, BF3 is not a suitable candidate for pot‐life extension, because of its adverse effect on the elongation at break of the cured HTPB samples. The coefficient of thermal expansion is unaffected by the two additives, probably because of their negligible influence on the cross‐link density of the cured network.
Phenol novolac/poly(4‐ hydroxyphenylmaleimide) blend hardeners for DGEBA‐type epoxy resin
Authors: Matsumoto Akihiro , Hasegawa Kiichi , Fukuda Akinori
Published: April 2007

Phenol novolac/poly (4‐hydroxyphenylmaleimide) (PHPMI) blends were used as an epoxy resin hardener. The curing behavior of the above system and the thermal and mechanical properties of the cured epoxy resin were studied. It was not necessary to use a curing accelerator for this system, because PHPMI caused acceleration of the curing reaction. The curing mechanism of this system was investigated by using model compounds. Test pieces from the neat resins and the glass fiber reinforced resins were evaluated in terms of thermal and mechanical properties, respectively. It was found that heat resistance and mechanical properties were improved by increasing the amount of PHPMI in the hardener.
Curing studies on vinyl ester resin using acrylates as reactive diluents
Authors: Kant Krishna , Mishra A. , Rai J. S. P.
Published: April 2007

The curing behavior of bis(methacryloxy) derivatives of diglycidyl ether of bisphenol A (vinyl ester resin) containing acrylates (methyl, ethyl and butyl acrylate) as the reactive diluents (40% w/w) were studied by DSC analysis. Data found in this study indicated that an appreciable curing rate is obtained at lower temperature with increased concentrations of initiator. The acid value, activation energy, Arrhenius factor and specific heat are discussed.
Poly(4‐methylstyrene‐co‐chloromethylstyrene): A negative electron beam resist—synthesis and lithography evaluation
Authors: Affrossman Stanley , Bakshaee Massoud , Bramley David , Chow Fong , Dix Christopher , Hendy Paul , Jones Mervyn , Ledwith Anthony , Mills Margaret , Tate Phillip Miller , Pethrick Richard A.
Published: April 2007

Synthesis and lithographic characterization of a series of negative acting electron sensitive resists based on poly(4‐methylstyrene‐co‐chloromethylstyrene) are reported. The sensitivity and contrast of these resists were found to depend on the chloromethylstyrene (CMS) content and an optimum value of 5 wt% was determined from consideration of parameters associated with the reproducibility of the synthetic method and also the lithographic performance. Both the sensitivity and resolution were found to depend on the molecular weight and CMS content of the copolymer. Several methods of scale up for the synthesis were explored, the route having a very significant influence on the film formation characteristics of the resists. The reactivity ratios of the monomers were measured in order that the compositional drift, which occurs during the synthesis, could be quantified. The effect of solvent composition and molecular weight of the copolymer were explored in relation to the quality of the resulting lithography. These studies have indicated that the copolymer has the potential of being used as a VLSI sub‐micron resist with good plasma etch resistance.
Ionomer interpenetrating polymer networks from polyurethane anionomers and polyurethane isocyanurate
Authors: Ai‐Salah Hasan A. , Xiao Han X. , McLean John A. , Frisch Kurt C.
Published: April 2007

Two‐component interpenetrating polymer network (IPN) systems composed from polyurethane isocyanurate and polyurethane anionomer were prepared by simultaneous polymerization and crosslinking in solution. Specific attractive forces that occurred among various networks helped to make them compatible and led to the formation of true homogeneous topologically interpenetrating polymer networks. These ionomer IPNs were characterized by means of stress‐strain properties, hardness, thermogravimetric analysis, density and conductivity. The morphology of the IPNs was studied by thermomechanical analysis and dynamic mechanical analysis.
Effect of synthesis conditions on properties of poly(N‐isopropylacrylamide) gels
Authors: Gehrke Stevin H. , Palasis Maria , Akhtar M. Kamal
Published: April 2007

Properties of poly(N‐isopropylacrylamide) gels—equilibrium degree of swelling, shear modulus, effective crosslink density and clarity—depend significantly upon the conditions of synthesis. While it is well known that monomer and crosslinker concentrations affect gel properties, other variables are shown here to have significant effects on the properties of the resulting gels. Initiator type and concentration, synthesis temperature, mold geometry and polymerization time all significantly affect the properties, including the swelling degree. Evidence suggests that the microstructure of these gels is particularly sensitive to these variables.
Micellar polymerisation of ionic surfactants studied by conductimetry
Authors: Tribet C. , Gaboriaud R. , Lelievre J.
Published: April 2007

The micellar polymerisation of ionic surfactants such as allyldodecyl‐dimethylammonium bromide and 3‐dodecyl‐1‐vinyl imidazolium iodide has been studied by conductimetry in aqueous solution. The polymerisation was carried out using two different sources of γ rays directed into solutions of surfactant above the critical micellar concentration. Conductimetry is shown to be a very good physicochemical method for analysis of these solutions. The results showed different behaviour for the two surfactants, which has highlighted a change in the structure of their aggregates which led to the assumption of an interaction between the polymers of high mass and different products of the polymerisation (oligomers, products of degradation, monomers etc.). Ultrafiltration experiments coupled with 1H‐NMR and conductivity analysis confirm these assumptions.
Mechanical changes of electron beam irradiated ethylene–vinyl acetate copolymer (EVA) film (I)
Authors: Matsui Toshiro , Shimoda Mitsuya , Osajima Yutaka
Published: April 2007

Electron beam irradiation of ethylene‐vinyl acetate copolymer (EVA) film results in a marked depression of sorption of flavour compounds. This effect is presumed to be brought about by radical reactions, following changes in the structure. The crosslinking density and gel fraction increased with irradiation dose, and the maximum percent gel reached 70% for 20 Mrad‐50g kg−1 EVA film, 35% for 20 Mrad‐95g kg−1 EVA film and 50% for 10 Mrad‐150g kg−1 EVA film.

In calculating the ratio of scission to crosslinking events, it was found that EVA film is a polymer of the scission type. The degree of crystallinity, Xc decreased significantly with increasing irradiation dose in all irradiated films. For unirradiated films, Xc decreased with increase in vinyl acetate content, which suggests that crystalline regions of EVA film are primarily composed of ethylene units. Therefore, the scission reaction may predominantly take place in the crystalline region, resulting in the formation of methyl or end vinyl groups. This was supported by measuring the film density, peak melting temperature and stress at yield.
Dielectric and viscoelastic relaxations in poly(dicyclohexyl itaconate)
Authors: Díaz‐Calleja Ricardo , Gargallo Ligia , Radic Deodato
Published: April 2007

The relaxation spectrum of poly(dicyclohexyl itaconate) (PDCHI) was studied by dynamic mechanical, DC dielectric and thermally stimulated current measurements. Four relaxations, α, β, γ and δ, were obtained. The only method by which all four peaks were observed is that of dynamic dielectric measurements because of the broad range of frequencies employed. The β, γ and δ relaxations were characterized by the activation energy in a relaxation map. A tentative explanation of the molecular origin of each absorption is proposed. In the case of the α relaxation we have used two transformations, one from the permittivity to polarizability and the second from compliance to deformability in order to make evident the existence of this relaxation.
Diffusion and permeation of gases in undrawn and radially drawn films of native and commercial gutta‐percha (trans‐Polyisoprene)
Authors: Arvanitoyannis Loannis , Heath Richard , Embeoglou Loannis
Published: April 2007

The permeability of native and commercial grades of gutta‐percha (trans‐polyisoprene), was determined and related to diffusion rate both below and above the glass transition temperature (Tg) and the melting point (Tm). Both radially drawn and undrawn membranes were evaluated. Five gases (O2, N2, CO2, H2 and He) were used as permeants and the measurements were taken both above and below the polymers' crystalline Tm. The diffusivity of the gases was found to have an increased rate above the Tm. The reduction of solubility, diffusivity and permeability with increasing draw ratio was attributed to an increase in crystallinity.
Control of intrinsic brittleness and toughness of polymers and blends by chemical structure: A review
Authors: Wu Souheng
Published: April 2007

The intrinsic brittle‐ductile (craze‐yield) behavior of polymers and blends are controlled by two chain parameters: entanglement density ve and characteristic ratio Cx. These chain parameters can be predicted from chemical structure. Therefore, the intrinsic brittle‐ductile behavior of polymers and blends can be controlled by chemical structure using group additivity. The chemical composition and chain structure which can give the ultimate toughness in polymers and blends are discussed.
Solid state polyamidation processes
Authors: Papaspyrides Constantine D.
Published: April 2007

Low reaction rates and distinct transition phenomena from the solid to the melt state restrain solid state polymerisation (SSP) reactions of nylon salts for industrial application. To alleviate these problems, catalysts containing nylon salts are employed. In this study, hexamethylenediammonium adipate (HMA) particles were used containing a strictly controlled amount of catalyst, either phosphoric acid, sulphuric acid or boric acid. The results show considerable acceleration of the reaction rate, especially in the presence of boric acid, while the solid state character of the process is maintained throughout the total course of the reaction. Comparative polymerisation runs were monitored both by end‐group and quantitative water determinations of the reacting material to exclude any accumulation of the water of polycondensation within the reacting particles. The results obtained support further the mechanism proposed for the transition solid‐melt in SSP runs of nylon salts in the absence of catalysts. In the latter case extended water accumulation is the rule.
Castor‐oil‐modified epoxy resins as model systems of rubber‐modified thermosets. 1: Thermodynamic analysis of the phase separation
Authors: Ruseckaite Roxana A. , Williams Roberto J. J.
Published: April 2007

Castor oil (CO) was used to replace polydisperse commercial rubbers (carboxy‐ or epoxy‐terminated butadiene‐acrylonitrile random copolymers, CTBN or ETBN) in model systems developed to analyse the origin of the phase separation process in rubber‐modified thermosets. Mixtures of CO with an epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) showed a higher miscibility than a typical CTBN (18% acrylonitrile)‐DGEBA system. Thermodynamic factors accounting for this behaviour are discussed using the Flory‐Huggins lattice model. Addition of a stoichiometric amount of ethylenediamine (EDA) to a DGEBA‐CO solution increased the miscibility. A pseudo‐binary approach was used to fit the cloud point curve up to 30% volume fraction of CO. Percentage conversions at the cloud point during the DGEBA‐EDA polymerization were experimentally determined and compared with theoretical predictions using the pseudo‐binary approach in the framework of the Flory‐Huggins lattice model. Reasonable agreement was found, giving direct evidence of the fact that phase separation results from the decrease in the entropic contribution to the free energy of mixing during polymerization.
Raman spectroscopic studies of the polyacrylonitrile‐zinc complexes in aqueous solutions of zinc chloride and bromide
Authors: Edwards H. G. M. , Hoskins A. R. , Johnson A. F. , Lewis I. R.
Published: April 2007

Raman spectroscopic studies of the dissolution of polyacrylonitrile (PAN) in aqueous zinc halides are reported. The dissociation constants of aqueous PAN‐zinc chloride and PAN‐zinc bromide containing 60‐75% wt/wt and 65‐80% wt/wt zinc in aqueous polyacrylonitrile solutions, respectively, have been measured by Raman spectroscopy. Intensity measurements allowed for a quantitative measurement of the amount of free and complexed CN groups to be made, utilising the 2259 and 2290cm−1v(CN) stretching Raman bands. The degree of complexation was found to be small in many of the solutions. The effect of the addition of salt on the structure of thev(OH) band at 3000‐3800 cm−1was studied for the aqueous zinc salts and an aqueous sodium thiocyanate solution. The low wavenumber regions of the Raman spectra, Δv = 100‐350cm−1, for both zinc chloride and zinc bromide solutions of PAN have also been studied.
Thermal, spectral and morphological studies on cellulose, cellulose ethylthiophosphate and its metal complexes in air
Authors: Bhagwan Jai , Lal Krishan , Horrocks A. Richard , Price Dennis
Published: April 2007

Metal complexes of thiophosphorylated cellulose, when heated, give rise to high char yields. These and related observations suggest that such derivatisation may give rise to novel flame retardant treatments for cellulosic materials.

The kinetics of thermal degradation of cellulose, cellulose ethylthiophosphate (CESP) and metal complexes of the CESP have been studied by thermogravimetry (TG) and differential thermal analysis (DTA) from ambient temperature to 700°C in dynamic air to investigate the potential flame retardance of the CESP and its metal complexes. Various parameters such as energy, entropy, enthalpy and free energy of activation have been calculated using the Broido method and transition state theory. For the decomposition stage of thermal degradation, the activation energies of the CESP samples lie in the range 53‐133 kJmol−1 and of the metal complexes, 108‐177kJmol−1, which are found to be lower than that of cellulose (187 kJmol−1). Scanning electron micrographs of the CESP show that the fibrillar structure of cotton has become more evident and chars retain the general morphology of the original fibre although severe, localised zones of damage reflect the gross chemical and physical changes occurring during pyrolysis. The IR spectra of chars of modified samples indicate formation of compounds containing C=O, C=C and P=O groups. The mechanisms of thermal degradation of the CESP and its metal complexes have been proposed.
Studies on modified phenolic resin. Iv: Properties of phenolic resin modified with 4‐hydroxyphenyl‐ maleimide/n‐butylacrylate copolymers
Authors: Matsumoto Akihiro , Hasegawa Kiichi , Fukuda Akinori
Published: April 2007

Three 4‐hydroxyphenylmaleimide/ n‐butylacrylate (HPMI/n‐BuA) copolymers with different monomer ratios were synthesized. Their average molecular weights, glass transition temperatures (T,g), and thermal decomposition temperatures were measured. It was found that these copolymers had higher average molecular weights and higher thermal decomposition temperatures than novolac.

Modified phenolic resins were prepared by transfer moulding from moulding compounds consisting of novolac, the copolymer, hexamethylenetetramine (hexamine), and glass fibre. Properties of the three kinds of modified phenolic resins were examined by flexural test, impact test, dynamic thermomechanometry, and observation of morphology. It was found that phenolic resin modified with HPMI/ n‐BuA (1/3‐6) copolymer and modified with HPMI/n‐BuA (1/7‐0) copolymer showed good toughness and good heat resistance. It was also found that the heat resistance of modified phenolic resins was improved by after‐cure, but the mechanical properties were decreased by after‐cure: similar behaviour was observed for unmodified phenolic resin.
Synthesis of poly(4‐methylstyrene)‐ graft‐poly(ethylene oxide)s and application as polymeric dispersant in coal‐water mixture
Authors: Bonaccorsi F. , Lezzi A. , Prevedello A. , Lanzini L. , Roggero A.
Published: April 2007

Poly(4‐methylstyrene)‐graft‐poly(ethylene oxide)s were prepared via polymerisation of ethylene oxide on to poly(4‐methylstyrene)s functionalised with hydroxyl groups. In this way, many ‘comb‐like’ polymers having different hydrophobic backbone length, hydrophilic branch length and frequency of branches were synthesised. These polymers were tested as dispersants in coal‐water mixtures in order to correlate the dispersing properties of this class of polymers with the investigated parameters.
An examination of the CTONI utilizing Gc‐Gf theory: A comparison of the CTONI and WJ‐III
Authors: Lassiter Kerry S. , Matthews T. Darin , Feeback Greg
Published: April 2007

The present investigation examined the validity of the Comprehensive Test of Nonverbal Intelligence (CTONI) with the Woodcock‐Johnson III Tests of Cognitive Abilities (WJ‐III COG) by administering these instruments in counterbalanced order to 60 college students. Results indicated that the mean CTONI NIQ score was not significantly different from the mean WJ‐III COG General Intellectual Ability (GIA) score. However, mean score differences were found between the CTONI NIQ and the WJ‐III COG Verbal Ability, Thinking Ability, Comprehension‐Knowledge, and Fluid Reasoning cluster scores. Although the correlations between the CTONI and the WJ‐III COG cluster scores were generally of small magnitude, the CTONI Geometric Nonverbal IQ composite score demonstrated construct specificity, whereas the CTONI Pictorial Nonverbal IQ scale did not. The implications of the findings are discussed and practitioners are asked to use caution when using this instrument to assess the fluid reasoning abilities of college students. © 2007 Wiley Periodicals, Inc.
The successful resolution of armed hostage/barricade events in schools: A qualitative analysis
Authors: Daniels Jeffrey A. , Bradley Mary C. , Cramer Daniel P. , Winkler Amy J. , Kinebrew Kisha , Crockett Deleska
Published: April 2007

This article explores the perceptions and reactions of school and law enforcement personnel in the successful resolution of armed hostage and barricade events in schools. A total of 12 individuals from three schools were interviewed to determine (1) their salient roles related to the situations, (2) facilitative systemic conditions, (3) to what they attributed the successful resolution, and (4) their advice to other school professionals. Results suggest that establishment of trusting relationships between school personnel and all students is essential in successfully resolving school hostage and barricade events. In addition, respondents discussed the importance of awareness, training, and communications in resolving such events. Implications for school staff are included, along with limitations and future research directions. © 2007 Wiley Periodicals, Inc.
Effects of interspersing rates on students performance on and preferences for mathematics assignments: Testing the discrete task completion hypothesis
Authors: Cates Gary L. , Erkfritz Karyn N.
Published: April 2007

The current study investigated the discreet task completion hypothesis presented by C. H. Skinner (2002) by investigating how the rate of interspersing affects performance on and preferences for academic assignments. Specifically, 70 sixth‐, seventh‐, and eighth‐grade students were presented with four assignment pairs of multiplication problems. Each pair consisted of a control assignment (i.e., no interspersing) and an experimental assignment (i.e., interspersing) that interspersed at one of four rates (i.e., no interspersing, every other problem, every third problem, or every fifth problem). After working on each assignment pair, assignment acceptability was measured. Results indicated that although students completed the same number of target problems with the same level of accuracy within assignment pairs, total problem completion rates were affected by the rate of interspersing. In addition, students' acceptability of the assignments was strongly related to the discrepancy in total problems completed across assignment types within assignment pairs. Discussion focuses on predicting students' preferences for academic assignments, implications for practitioners, and directions for future research. © 2007 Wiley Periodicals, Inc.
The learning and study strategies of college students with ADHD
Authors: Reaser Abigail , Prevatt Frances , Petscher Yaacov , Proctor Briley
Published: April 2007

This study compared learning and study strategies of students with attention‐deficit/hyperactivity disorder (ADHD) to two groups: college students with learning disabilities (LD) and college students without disabilities. In addition, strengths and weaknesses within the ADHD group were examined on the Learning and Study Strategies Inventory, 2nd edition (LASSI; C.E. Weinstein & D.R. Palmer, 2002). The LASSI was also evaluated as a predictive measure for academic achievement for college students with ADHD compared to other students. Results indicate that several important differences may exist in the learning and study strategies of students with ADHD versus students with LD and students without disabilities. However, the LASSI may not be a useful tool for predicting academic achievement for college students with ADHD. Interventions for working with students with ADHD are given. © 2007 Wiley Periodicals, Inc.
Optically active electrochromism in polyanilines
Authors: Goto Hiromasa
Published: April 2007

The electrochemically driven control of the natural optical activity of polyanilines bearing chiral camphorsulfonic acid is reported. Aniline was polymerized in the presence of camphorsulfonic acid by oxidative electrochemical polymerization in water to afford polyanilines containing (+)‐ or (−)‐camphorsulfonic acid. This research elucidated that the polymerization, with cyclic voltammetry scanning up to 1.1 V, produced consistent optically active polyanilines. The polyaniline films thus prepared showed intense and tunable optical activity based on electrochemical reduction/oxidation in a 0.1 M sulfuric acid aqueous solution. The circular dichroism and optical rotation angle of the polymer were tunable by the appropriate adjustment of an externally applied potential as a form of optical modulation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2085–2090, 2007
Dispersion copolymerization of methyl methacrylate and n‐butyl acrylate
Authors: Jiang Sheng , Sudol E. David , Dimonie Victoria L. , El‐Aasser Mohamed S.
Published: April 2007

In the dispersion copolymerization of methyl methacrylate (MMA) and n‐butyl acrylate (BA), the particle size increases with an increasing MMA fraction in the comonomer. The power dependence of the particle size on the initiator concentration also increases with an increasing MMA concentration. Similar to what can be found in the homopolymerizations, two populations can be observed in the molecular weight distributions of the copolymers. Core–shell structured particles with a poly(methyl methacrylate)‐rich core and a poly(n‐butyl acrylate)‐rich shell result from the copolymerizations because of the significantly different reactivity ratios. The reaction rates of the dispersion copolymerization are lower than those of the homopolymerization of BA and close to or lower than those of the homopolymerization of MMA, depending on the ratio of the monomers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2105–2112, 2007
A first pan‐Arctic assessment of the influence of glaciation, permafrost, topography and peatlands on northern hemisphere lake distribution
Authors: Smith Laurence C. , Sheng Yongwei , MacDonald Glen M.
Published: April 2007

The locations of ∼200 000 large northern hemisphere lakes (sized 0.1 to 50 km2, northwards of ∼45°N latitude) are intersected with new global databases on topography, permafrost, peatlands and LGM glaciation to identify some first‐order controls on lake abundance and land area fraction at the pan‐Arctic scale. Of the variables examined here, glaciation history and the presence of some form of permafrost appear most important to the existence of lakes. Lake densities and area fractions average ∼300–350% greater in glaciated (versus unglaciated) terrain, and ∼100–170% greater in permafrost‐ influenced (versus permafrost‐free) terrain. The presence of peatlands is associated with additional ∼40–80% increases in lake density and ∼10–50% increases in area fraction. On average, lakes are most abundant in glaciated, permafrost peatlands (∼14.4 lakes/1000 km2) and least abundant in unglaciated, permafrost‐free terrain (∼1.2 lakes/1000 km2). Lake statistics are surprisingly similar across continuous, discontinuous and sporadic permafrost zones, decrease modestly in isolated permafrost, and drop sharply in the absence of permafrost. A simple calculation based on ‘space‐for‐time’ substitution for all glaciated/lowland terrain (∼2.7 × 107 km2, of which ∼48% is currently in some state of permafrost) suggests that in a ‘permafrost‐free’ Arctic, the number of lakes could be reduced from ∼192 000 to 103 000 (−46%) and their total inundation area reduced from ∼560 000 to 325 000 km2 (−42%). A more realistic scenario of thawed discontinuous, sporadic and isolated permafrost only, with a +10% lake increase in continuous permafrost and no change in permafrost‐free areas suggests reductions to ∼155 000 lakes (−15%) and ∼476 000 km2 (−15%), respectively. Copyright © 2007 John Wiley & Sons, Ltd.
Molecular domain organization of BldD, an essential transcriptional regulator for developmental process ofStreptomyces coelicolorA3(2)
Authors: Lee Chang‐Jin , Won Hyung‐Sik , Kim Jeong‐Mok , Lee Bong‐Jin , Kang Sa‐Ouk
Published: April 2007

A homodimeric protein, BldD is a key regulator for developmental process ofStreptomyces coelicolorand thebldDmutant exhibits severely pleiotropic defects in the antibiotic production and morphological differentiation of the bacterium. In the present work, we approached domain organization of BldD, to structurally and functionally characterize the protein as a DNA‐binding protein. We first observed a proteolytic cleavage of BldD by the cytoplasmic extracts ofS. coelicolor, which was highly dependent on the developmental stage of the bacterium. The resulting fragment of BldD was identified by mass spectrometry as the N‐terminal domain resistant to the proteolysis. Recombinant proteins corresponding to the intact BldD, the N‐terminal domain (residues 1–79) and the rest part (C‐terminal domain; residues 80–167) were used for comparative analyses by several spectroscopic, thermodynamic, and biochemical experiments, respectively. The results of circular dichroism and nuclear magnetic resonance spectroscopies certified each of the two determined domains could be regarded as an individual folding unit possessing an independent thermodynamic cooperativity. Structural interaction between the two domains was little observed in the DNA‐free and DNA‐bound states. Strikingly, it was revealed by gel permeation chromatography, chemical crosslink, gel mobility shift, and NMR‐monitored DNA‐binding experiments, that only the N‐terminal domain is responsible for the dimerization as well as DNA‐binding of BldD. Detailed inspection of the present results suggests that BldD function in a unique and complicated mode to totally regulate the diverse developmental stages ofS. coelicolor. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Stepwise prediction of conformational discontinuous B‐cell epitopes using the Mapitope algorithm
Authors: Bublil Erez M. , Freund Natalia Tarnovitski , Mayrose Itay , Penn Osnat , Roitburd‐Berman Anna , Rubinstein Nimrod D. , Pupko Tal , Gershoni Jonathan M.
Published: April 2007

Mapping the epitope of an antibody is of great interest, since it contributes much to our understanding of the mechanisms of molecular recognition and provides the basis for rational vaccine design. Here we present Mapitope, a computer algorithm for epitope mapping. The algorithm input is a set of affinity isolated peptides obtained by screening phage display peptide‐libraries with the antibody of interest. The output is usually 1–3 epitope candidates on the surface of the atomic structure of the antigen. We have systematically tested the performance of Mapitope by assessing the effect of the algorithm parameters on the final prediction. Thus, we have examined the effect of the statistical threshold (ST) parameter, relating to the frequency distribution and enrichment of amino acid pairs from the isolated peptides and the D (distance) and E (exposure) parameters which relate to the physical parameters of the antigen. Two model systems were analyzed in which the antibody of interest had previously been co‐crystallized with the antigen and thus the epitope is a given. The Mapitope algorithm successfully predicted the epitopes in both models. Accordingly, we formulated a stepwise paradigm for the prediction of discontinuous conformational epitopes using peptides obtained from screening phage display libraries. We applied this paradigm to successfully predict the epitope of the Trastuzumab antibody on the surface of the Her‐2/neu receptor in a third model system. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Can Batesian mimicry help plants to deter herbivores?
Authors: Massei Giovanna , Cotterill Jane V , Coats Julia C , Bryning Gareth , Cowan Dave P
Published: April 2007

Several authors have suggested that edible plants could avoid herbivory by mimicking olfactory cues of toxic plants. However, very few studies have been carried out to test this hypothesis. The aims of the present study were to identify the volatiles of three clover species and to test whether a species lacking chemical defences, such as red clover, could avoid being grazed by rabbits by mimicking the volatiles of the cyanogenic white clover. Two main volatiles were identified in all three clover species, and a further two volatiles were present in white clover only. Rabbits presented with a choice between white clover, red clover and red clover sprayed with white clover extract ate significantly more red clover than white or white‐flavoured red clover. The results suggest that the volatiles of toxic plants could be used and exploited as a source of natural, safe and effective repellents to control the impact of pest herbivores on plants. Copyright © 2007 Society of Chemical Industry
Repellence of the red bud borer Resseliella oculiperda from grafted apple trees by impregnation of rubber budding strips with essential oils
Authors: van Tol Rob WHM , Swarts Henk J , van der Linden Anton , Visser JH
Published: April 2007

The red bud borer Resseliella oculiperda (Rübs.) is a pest insect of apple trees when rootstocks are grafted with scion buds by ‘shield budding’. The female midges are attracted to the wounds of the grafted buds where they lay their eggs. The larvae feed on the cambium and destroy the buds completely or partially, leading to bad union of the buds with the rootstocks. Budding strips are used very often by growers to bind scion buds to rootstocks. These strips cannot prevent midges from reaching the damaged tissue. Chemical treatments applied to the grafts and other types of strip do not provide better protection against the pest and may cause other risks for growers. In orchard experiments in 2000 and 2001, the authors evaluated the repellent action provided by three essential oils and five compounds of plant origin against the midges by impregnating budding strips with them. The essential oils of lavender, Lavandula angustifolia (P. Mill.), and α‐terpineol decreased the infestation of buds by more than 95 and 80% respectively. The other potential repellents tested [the essential oil of Juniperus virginiana (L.), citronellal, the essential oil of Cinnamomum camphora (L.) J. Presl, R‐carvone, linalool and R‐fenchone] decreased infestation by 67, 66, 51, 45, 37 and 25% respectively. The formulation and commercial development of budding strips impregnated with lavender oil is discussed. Copyright © 2007 Society of Chemical Industry
Two‐colour spectroscopy of ZnSe:Cr
Authors: Ivanov Vitalii Yu. , Godlewski Marek , Gregorkiewicz Tom
Published: April 2007

Based on two‐colour spectroscopy, we identify origin of infrared emissions in Cr doped ZnSe. Near infrared emission at about 0.98 μm is related to Cr2+ intra‐shell process. Optical memory effect is observed related to metastability of light induced Cr1+ population. This effect can be used for optical detection of THz radiation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural properties of ZnO polymorphs
Authors: Wróbel Jan , Piechota Jacek
Published: April 2007

The first principles calculations by using the plane‐wave pseudopotential method in the scheme of density functional theory were performed for polymorphs of ZnO: wurzite‐, zinc‐blende‐, rocksalt‐structures, and yet experimentally undiscovered CsCl‐structure. The elastic behavior and the stability of the structures are investigated and compared to experimental data, where available. For each structure, electronic properties are calculated within the LDA+U approximation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photo‐induced changes of photoconductivity and exciton luminescence in ZnO crystals
Authors: Markevich I. V. , Kushnirenko V. I. , Bulakh B. M.
Published: April 2007

In ZnO crystals, the drop of photoconductivity as well as the change of exciton luminescence intensity and spectrum shape were found to occur under light irradiation in 300–800 K temperature range. The initial characteristics were restored with time in dark. Observed effects were shown to result from the variation of shallow donor density in the surface layer of the crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modification of the photoluminescence characteristics of CdZnTe/ZnTe QWs by CdTe monolayer film insertion
Authors: Borkovska L. V. , Korsunska N. O. , Sadofyev Yu. G. , Beyer R. , Weber J. , Kryshtab T. , Andraca‐Adame J. A. , Kazakov I. P. , Kushnirenko V. I.
Published: April 2007

In present work, the influence of single monolayer CdTe film insertion on the luminescence and structural characteristics of CdZnTe/ZnTe quantum well (QW) was investigated by the photoluminescence (PL) and the high resolution X‐ray diffraction (HRXRD) methods. The structures were grown by MBE on GaAs substrate and contained Cd0.4Zn0.6Te QW of 8 nm thickness with or without 1 monolayer CdTe film embedded in the middle of QW. The low temperature PL investigations showed that insertion of CdTe layer resulted in a “blue” shift of the QW PL peak position, in the two times narrowing of the QW PL band and one order of value increase of its intensity. Temperature dependencies of the QW PL spectra as well as time‐resolved PL investigations indicated that these changes are caused by the increase of shallow localized state density and the decrease of deep one. The degradation of interface quality as well as the change of the QW composition were found by the HRXRD profiles. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of oxygen content on the electrical characteristics of ZnO
Authors: Jung E. S. , Kim H. S. , Kong B. H. , Cho H. K. , Park N. K. , Lee H. S.
Published: April 2007

This work presents the influence of the variation of oxygen content in the ZnO films on their electrical characteristics. We applied the post‐thermal annealing in N2 and air ambient to control the oxygen content of ZnO films, which improved crystallinity and optical properties of ZnO films. The oxygen concentration was measured by Auger electron spectroscopy and the electrical characteristics were obtained by Hall measurement in the van der Pauw configuration and transmission line method. As result, it was shown that the electron concentration varies from 1016 to 1021/cm3, while the resistivity from 10−3 to tens ohm‐cm with respect to Zn/O concentration ratio. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanisms by which Astragalus membranaceus injection regulates hematopoiesis in myelosuppressed mice
Authors: Zhu Xiao‐Ling , Zhu Bi‐De
Published: April 2007

The aim of this study was to investigate the mechanism underlying the effects of Astragalus membranaceus injection (AMI) on myelopoiesis in myelosuppressed mice. At 72 h after cyclophosphamide injection (250 mg/kg), the mice were administered AMI (500 mg/kg) intraperitoneally for 6 consecutive days or an equivalent volume of saline as a control. Murine colony‐forming unit‐fibroblast (CFU‐F) formation, production of IL‐6 and GM‐CSF by bone marrow stromal cells (BMSC), and bcl‐2 protein and mRNA expression in BMSC were measured by CFU‐F assay, ELISA, immunohistochemistry and in situ hybridization. The results indicated that AMI improved the hematopoietic microenvironment by enhancing the BMSC survival and proliferation of CFU‐F, production of IL‐6 as well as GM‐CSF by BMSC and bcl‐2 protein and mRNA expression in BMSC, which promoted myelopoiesis. The data may provide a mechanistic basis for applying this ancient Chinese herb to promote hematopoiesis as an efficacious adjuvant therapy against myelosuppression induced by anti‐cancer therapy. Copyright © 2007 John Wiley & Sons, Ltd.
The theory of currents through small bridge molecules
Authors: Burrows B. L. , Amos A. T.
Published: April 2007

A model to treat the theory of currents through small bridge molecules connected to leads is constructed using the time‐dependent Schrödinger equation and the wide‐band approximation to treat the leads. It is shown that the behaviour of the current through the bridge may be summarized by considering three time periods: a transient period, a quasi‐steady ‐state period and a decaying period. The results obtained are compared with previous work and in particular it is shown that, under reasonable assumptions, they are in accord with the more conventional time‐independent scattering theory approaches in the steady‐state period. Illustrative calculations are presented for both chain and ring bridge molecules. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Probing the ultrafast photoelectron spectra of Br2 molecule
Authors: Hu Jie , Liu Feng , Meng Qing‐Tian , Han Ke‐Li
Published: April 2007

The time‐dependent‐wave‐packet method is applied to study the ionization of Br2 molecule with four ionization processes. The ground state absorption makes the photoelectron to be left in the three final ionic states: Br (X2∑), Br (A2∏u), and Br (B2∑), and each population of these ionic states is related with the laser intensities. The information of the dissociation can be got by analyzing the photoelectron features of the transient wave packet, which also suggests that an ionization process occurs during the dissociation, and the Br atoms that mainly resulted from the dissociation of Br2 (C1∏u) are ionized at later time delays as the dissociation is nearly complete. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Mapping disability‐adjusted life years: a Bayesian hierarchical model framework for burden of disease and injury assessment
Authors: MacNab Ying C.
Published: April 2007

This paper presents a Bayesian disability‐adjusted life year (DALY) methodology for spatial and spatiotemporal analyses of disease and/or injury burden. A Bayesian disease mapping model framework, which blends together spatial modelling, shared‐component modelling (SCM), temporal modelling, ecological modelling, and non‐linear modelling, is developed for small‐area DALY estimation and inference. In particular, we develop a model framework that enables SCM as well as multivariate CAR modelling of non‐fatal and fatal disease or injury rates and facilitates spline smoothing for non‐linear modelling of temporal rate and risk trends. Using British Columbia (Canada) hospital admission–separation data and vital statistics mortality data on non‐fatal and fatal road traffic injuries to male population age 20–39 for year 1991–2000 and for 84 local health areas and 16 health service delivery areas, spatial and spatiotemporal estimation and inference on years of life lost due to premature death, years lived
with disability, and DALYs are presented. Fully Bayesian estimation and inference, with Markov chain Monte Carlo implementation, are illustrated. We present a methodological framework within which the DALY and the Bayesian disease mapping methodologies interface and intersect. Its development brings the relative importance of premature mortality and disability into the assessment of community health and health needs in order to provide reliable information and evidence for community‐based public health surveillance and evaluation, disease and injury prevention, and resource provision. Copyright © 2007 John Wiley & Sons, Ltd.
Problems with credit rating and reporting systems in Mexico: A barrier to North America's full economic development?
Authors: Rose Peter S.
Published: April 2007

In many regions of the globe today outside the US and Canada, existing networks for evaluating borrowers' credit histories, for recording borrowers' pledges of assets backing loans, and for the legal enforcement of creditor claims are often poorly developed. Inside North America these problems with credit information flows and legal enforcement systems are most evident inside Mexico, where credit reporting networks and the courts work under a somewhat different set of rules than in Canada and the United States. A national mail survey of more than 300 US banks lending across international boundaries into Mexico found that many US bankers have reservations about the credibility of credit reporting and credit security systems inside Mexico. If these reservations persist, they can lead to a fundamental restructuring of that developing nation's industry that could discourage international capital inflows and curtail the emergence of small business. Indeed, unless current credit information flows are more fully integrated and are of more uniform quality throughout North America, the North American Free Trade Agreement (NAFTA) is likely to continue to fall short of its promise of significant job growth and improved living standards throughout the continent. © 1997 John Wiley & Sons, Inc.