bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical characterization of concentrated dispersions: applications to laboratory analyses and on‐line process monitoring and control
Authors: Buron H , Mengual O , Meunier G , Cayré I , Snabre P 
Published: June 2004

AbstractLight scattering methods are often used to study the stability of suspensions or emulsions and to estimate the dispersed phase properties such as particle size and volume fraction. However, such optical methods often require a previous dilution of the dispersion because of a limited measurement range, and are then unable to give information about the real physical state of dense heterogeneous media. A new technology based on multiple light scattering analysis and called Turbiscan has been recently developed by a French company, Formulaction, to fill this gap and to characterize both diluted and concentrated dispersions. In the first part, we review the physical concepts of multiple light scattering by dispersions. In relation to the optical analyser Turbiscan, we present physical and statistical models for the radiative transfer in dense suspensions. In the second part, we investigate the influence of particle volume fraction and particle size (polystyrene latex bead suspensions) on the backscattered and transmitted light fluxes measured by Turbiscan. The experimental data are compared with results from the physical models. In the last section, we use the optical analyser Turbiscan Lab to detect and characterize various concentrated dispersions destabilization (coalescence, flocculation, creaming and sedimentation), and then the Turbiscan On Line to monitor and characterize an emulsification process under ultrasonic agitation. Copyright © 2004 Society of Chemical Industry
Characterization and properties of UV‐curable polyurethane‐acrylate/silica hybrid materials prepared by the sol‐gel process
Authors: Zhang Ling , Zeng Zhaohua , Yang Jianwen , Chen Yonglie 
Published: June 2004

AbstractUV‐curable, transparent hybrid material of urethane‐acrylate resin was prepared by the sol‐gel process using 3‐(trimethoxysilyl)propylmethacrylate (TMSPM) as a coupling agent between the organic and inorganic phases. The effects of the content of acid and silica on the morphology and mechanical properties of UV‐curable polyurethane‐acrylate/silica hybrid (UA‐TMSPM)/SiO2 materials have been studied. The results of thermogravimetric analysis for the (UA‐TMSPM)/SiO2 hybrid materials indicated that the thermal stability of the hybrids is greatly improved. It was found that with the increase of HCl content, the interfacial interaction between organic and inorganic phases had been strengthened, as demonstrated by field emission scanning electron microscopy. Without sacrificing flexibility, the hybrid materials showed improved hardness with increasing content of acid and silica. Compared with the pure organic counterpart UA/hexanediol diacrylate (UA/HDDA) system, abrasion resistance of the hybrids improved with increasing acid content, at low silica content. Copyright © 2004 Society of Chemical Industry
Synthesis and characterisation of organosoluble polyimides containing the anisyl moiety
Authors: Ramalingam Hariharan , Sowrirajalu Bhuvana , Ganesan Anuradha , Muthusamy Sarojadevi 
Published: June 2004

AbstractA new type of diamine monomer containing the anisyl moiety was synthesized via a straight‐forward one‐step procedure. Anisaldehyde was reacted with 2,6‐dimethylaniline in the presence of dry HCl to attain bis(4‐amino‐3,5‐dimethylphenyl)anisylmethane. A series of organo‐soluble polyimides were prepared using the anisyl diamine and various aromatic dianhydrides via a two step method involving thermal imidization. All polyimides are soluble in strong polar solvents such as N‐methyl‐2‐pyrollidone, N,N‐Dimethylformamide, and N,N‐DimethylAcetamide. The polyimides show excellent thermal stability and good mechanical properties. The glass transition temperatures of the polyimides are in the range 265–294 °C. The tensile strengths are in the range 79–99 MPa and the temperatures at which 10 % weight loss occurs are in the range 460–496 °C. Copyright © 2004 Society of Chemical Industry
Numerical simulation of the effect of nanotube orientation on tensile modulus of carbon‐nanotube‐reinforced polymer composites
Authors: Zhu Linjie , Narh Kwabena A 
Published: June 2004

AbstractBy correlating the curvature of carbon nanotubes to the orientation of fibers in a polymer, the effect of the curvature of nanotubes on the tensile modulus of carbon‐nanotube‐reinforced polymer composites was investigated with a numerical simulation method. The simulation results showed that the tensile modulus of a nanotube‐reinforced composite drops sharply when the nanotubes diverge from their orientation in the axial direction, and the presence of curved nanotubes in the polymer matrix significantly decreases the modulus of the composite. This finding could explain, partly, why in most cases, the predicted tensile modulus of a carbon‐nanotube‐reinforced composite, based on the assumption that the nanotubes are fully isolated and aligned in the polymer matrix, is much higher than the value obtained from experiments. Copyright © 2004 Society of Chemical Industry
Effect of aluminoxane on molecular weight and molecular weight distribution of polyethylene prepared by an iron‐based catalyst
Authors: Wang Qi , Li Lidong 
Published: June 2004

AbstractA series of aluminoxanes, tetraethylaluminoxane (TEAO), tetraalkylaluminoxane (TAAO), Et2AlOB(4 − F − C6H4)OAlEt2 (BTEAO) and ethyl‐iso‐butylaluminoxane modified with p‐fluorophenylboric acid (BEBAO), were prepared and their effects on molecular weight (MW) and molecular weight distribution (MWD) of polyethylene prepared by the iron‐based catalyst [(ArNC(Me))2C5H3N]FeCl2 (Ar2,6‐dimethylphenyl) (1) were investigated. It was found that TEAO and BTEAO were highly efficient activators for iron‐based catalysts and introducing the branched bulky group (eg iso‐Bu) into the aluminoxane activator could improve the MW of the resulting polyethylene. The MW of polyethylene produced by activators modified by p‐fluorophenylboric acid was higher than for other aluminoxane activators. The TEAO‐ and TAAO‐based polyethylene exhibited attractive bimodal MWD, and the lower MW fraction of bimodal MWD was shown to be produced in the early stage of polymerization due to chain transfer to the aluminium activator. Copyright © 2004 Society of Chemical Industry
Zirconocene‐catalyzed copolymerization of methyl methacrylate with other methacrylate monomers
Authors: Karanikolopoulos Giorgos , Batis Christos , Pitsikalis Marinos , Hadjichristidis Nikos 
Published: June 2004

AbstractStatistical copolymers of methyl methacrylate (MMA) with n‐butyl‐, s‐butyl, t‐butyl‐, n‐hexyl‐, decyl‐, stearyl‐, allyl‐, trimethylsilyl‐ and trimethylsilyloxyethyl methacrylate were prepared by zirconocene‐catalyzed copolymerization. The reactivity ratios of MMA copolymers with butyl‐, hexyl‐, and stearyl methacrylate were estimated using the Finemann–Ross, the inverted Finemann–Ross, and the Kelen–Tüdos graphical methods. Structural parameters of the copolymers were obtained from the calculated dyad sequences, derived by using the reactivity ratios. The effect of the nature of the methacrylate ester group and the catalytic system used on the copolymer structure is discussed. The glass‐transition temperature (Tg) values of MMA copolymers with butyl‐ and hexyl methacrylate were measured and examined in the frame of several theoretical equations, allowing the prediction of these Tg values. The best fit was obtained using Barton and Johnston equations, taking the monomer sequence distribution of the copolymers into account. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3761–3774, 2004
An electrostatic basis for the stability of thermophilic proteins
Authors: Dominy Brian N. , Minoux Hervé , Brooks Charles L. 
Published: June 2004

AbstractTwo factors provide key contributions to the stability of thermophilic proteins relative to their mesophilic homologues: electrostatic interactions of charged residues in the folded state and the dielectric response of the folded protein. The dielectric response for proteins in a “thermophilic series” globally modulates the thermal stability of its members, with the calculated dielectric constant for the protein increasing from mesophiles to hyperthermophiles. This variability results from differences in the distribution of charged residues on the surface of the protein, in agreement with structural and genetic observations. Furthermore, the contribution of electrostatic interactions to the stability of the folded state is more favorable for thermophilic proteins than for their mesophilic homologues. This leads to the conclusion that electrostatic interactions play an important role in determining the stability of proteins at high temperatures. The interplay between electrostatic interactions and dielectric response also provides further rationalization for the enhanced stability of thermophilic proteins with respect to cold‐denaturation. Taken together, the distribution of charged residues and their fluctuations have been shown to be factors in modulating protein stability over the entire range of biologically relevant temperatures. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Wave function and quasi‐energy of conduction electrons in a field of coherent light beams
Authors: Semchuk O. Yu. , Willander M. , Karlsteen M. 
Published: June 2004

AbstractIn this work the influence of high‐frequency coherent light beams (CLB) on the motion of conduction electrons in a crystalline phase is studied. The wave function and the quasi‐energy of conduction electrons are calculated. It is shown that a force that is associated with a pressure from the CLB influences the conduction electrons. A new approach to construct the kinetic equation, that takes into account the effects due to a CLB field that acts as the elementary processes for quasi‐particle interaction in a crystalline phase, is presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of germanium content on the medium range order and the vibrational analysis of Ge–Se chalcogenide glass system
Authors: Jayakumar S. , Predeep P. , Unnithan C. Harikuttan 
Published: June 2004

AbstractAn attempt is made to explain the Medium Range Order in the chalcogenide glass system Gex–Se1–x by computing the radial distribution function, g(r) from the available data of the structure factor, S(q). The results obtained are compared with pioneer works. The above obtained value of g(r) together with the effective interatomic potential calculated from S(q) applying Rao–Joarder equation is used for studying the vibrational eigen frequencies of the system both in the transverse and longitudinal phonon modes. From the long wavelength limit of the phonon frequency spectrum, the elastic and the thermal properties are also estimated. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band structure, metallization and superconductivity of GaP and GaN under high pressure
Authors: Louis C. Nirmala , Iyakutti K. , Nandhini K. S. Hema , Sivakumar M. , Palaniyandi E. 
Published: June 2004

AbstractThe electronic band structure, metallization, structural phase transition and superconductivity of cubic zinc blende‐type GaP and GaN are investigated. The equilibrium lattice constant, bulk modulus and pressure at which the compounds undergo a structural phase transition from ZnS structure to NaCl structure are predicted from the total energy calculations. The density of states at the Fermi level (N(EF)) is enhanced after metallization, which leads to the superconductivity in GaP and GaN. The superconducting transition temperatures (Tc) of GaP and GaN are obtained as a function of pressure for both the ZnS and NaCl structures and GaP and GaN come under the category of pressure‐induced superconductors. When pressure is increased Tc increases in both the normal and high‐pressure structures. The dependence of Tc on the electron–phonon mass enhancement factor λ shows that GaP and GaN are electron–phonon‐mediated superconductors. Also, it is found that GaP and GaN retained in their normal structure under high pressure give appreciably high Tc. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Screening dependence of superconducting state parameters of Cu–Zr metallic glasses
Authors: Sharma S. , Khan H. , Sharma K. S. 
Published: June 2004

AbstractThe screening dependence of superconducting state parameters (λ, μ*, Tc, α and N0V) of nine metallic glasses of the Cu–Zr system has been studied in the BCS–Eliashberg–McMillan framework by employing five forms of dielectric screening function in conjunction with Ashcroft's potential. It is observed that the electron–phonon coupling strength (λ) and transition temperature (Tc) are quite sensitive to the form of the dielectric screening, whereas the Coulomb pseudopotential (μ*), isotope effect exponent (α) and effective interaction strength (N0V) show weak dependences on screening function. The RPA form of dielectric screening is observed to yield the best results for all the glasses of the Cu–Zr system studied in the present work. Present computations yield almost linear variation of Tc with concentration x of Cu in the Cu–Zr system, which is in agreement with the experimental data. A linear Tc equation is proposed by fitting the present results for RPA screening, which is in conformity with other results for the experimental data. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localization of electronic eigenstates and spin waves in diluted magnetic semiconductors at low carrier densities
Authors: Berciu Mona , Bhatt R. N. 
Published: June 2004

AbstractUsing mean‐field and random‐phase approximations, we perform numerical simulations on finite‐size systems to investigate the effects of disorder on the nature (localized or extended ) of both electronic states and collective magnetic (spin‐wave) excitations for a prototypical disordered system with both electronic (fermionic) and magnetic degrees of freedom. We use a simple impurity model appropriate for dilute magnetic semiconductors at low charge carrier concentrations, below and near the metal‐insulator transition. In our model, the positional disorder of the magnetic dopants is taken into account at the outset. We find that enhanced disorder implies significant inhomogeneity in magnetic properties, leading to appearance of localized electron states as well as localized collective magnetic excitations. As a result, positional disorder of the dopants can significantly influence transport and magnetic properties in such materials at low dopant and carrier densities. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Roles of interactions in electronic properties of quantum disordered wires
Authors: Mori H. , Takeuchi Y. 
Published: June 2004

AbstractWe studied electronic transport properties of quantum wires with electron–electron interactions and random potentials. We focus in particular on the roles of the interactions in various situations. In a single wire system the interactions would enhance the random potential effect in some cases while they would suppress it in other cases. Taking analytical and numerical approaches, we clarified the roles in Hubbard wire based on the analysis of 4kF impurity scattering. We also studied the influence of inter‐wire interactions between parallel wires in the presence of random potentials and found a rather different role of the interactions on the localization phenomena. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic transport in nanoparticle arrays: The effect of structural disorder
Authors: Nikolić K. 
Published: June 2004

AbstractSelf‐assembled nanoparticle structures represent a very promising way of achieving nanoelectronic devices and even circuits. In this paper we analyse the electronic transport properties of nanoparticle arrays formed on the surface of ionic crystals. Results for the numerical simulations of the quantum percolation problem in the nanoparticle arrays or discontinuous metal films are given. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conductance fluctuations in one‐ and two‐dimensional localized systems
Authors: Ortuño M. , Somoza A. M. , Prior J. 
Published: June 2004

AbstractWe study quantum fluctuations in the localized regime of one‐dimensional systems. We calculate the variable‐range hopping conductance including fluctuations in the size of the states. Quantum effects increase the average resistance without qualitatively changing Mott's law and cannot be neglected for a proper interpretation of experimental results. We also discuss the effects of these fluctuations in two‐dimensional systems. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Critical points and quenched disorder: From Harris criterion to rare regions and smearing
Authors: Vojta Thomas , Sknepnek Rastko 
Published: June 2004

AbstractWe consider the influence of quenched spatial disorder on phase transitions in classical and quantum systems. We show that rare strong disorder fluctuations can have dramatic effects on critical points. In classical systems with sufficiently correlated disorder or in quantum systems with overdamped dynamics they can completely destroy the sharp phase transition by smearing. This is caused by effects similar to but stronger than Griffiths phenomena: True static order can develop on a rare region while the bulk system is still in the disordered phase. We discuss the thermodynamic behavior in the vicinity of such a smeared transition using optimal fluctuation theory, and we present numerical results for a two‐dimensional model system. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and identification of two potential oxidation degradants of oxymetazoline
Authors: Leader Ian P. , Halket John , Finch Paul 
Published: June 2004

AbstractTwo potential oxidation degradants of oxymetazoline have been isolated by liquid chromatography and monitored by electrospray single quadrupole mass spectrometry. The structures of the products are shown to be oxymetazoline N‐oxide and hydroxyamine by multiple‐stage fragmentation ion trap mass spectrometry. The product ion spectra were installed in a library database and the library was used to examine an aged commercial product; one of the degradants was detected, but at a level of less than 0.1% of the parent. Copyright © 2004 John Wiley & Sons, Ltd.
Parenting and adolescent self‐regulation
Authors: Purdie Nola , Carroll Annemaree , Roche Lawrence 
Published: June 2004

AbstractThis study examined the relationship between adolescents’ academic and non‐academic self‐regulation (SR), authoritative parenting (as demonstrated by high levels of Involvement, Strictness, and Autonomy Granting), and parent self‐efficacy in four areas. Participants were 214 Australian high school students and their parents. There was a moderate correlation (r=0.63) between academic and non‐academic SR. Adolescents and their parents differed significantly in their perceptions of parenting behaviours, with parents rating themselves higher than their children on Involvement, Autonomy Granting, and Strictness behaviours. A model of the relationships between the constructs was developed showing a strong path from parent self‐efficacy to both academic and non‐academic SR via high parental Involvement (as perceived by adolescents). Strict parenting and the granting by parents of psychological autonomy to their adolescent children did not appear to be important in the development of young people's self‐regulatory behaviours.
Adolescent drug trafficking trends in the United Kingdom—a 10‐year retrospective analysis
Authors: Vale Ellen Louise Eva , Kennedy Patrick John 
Published: June 2004

AbstractThis paper reports data from HM Customs and Excise (HMCE) of recorded cases of adolescent drug trafficking through all sea and air points of entry into the UK over a 10‐year period (May 1992–May 2002). We report the characteristics of 38 cases of mixed gender and nationality ranging in age between 13 and 18 years who have been apprehended by HMCE due to the illegal importation of drugs. Highlighted is an increasing trend in UK national male and female adolescents being apprehended for drug trafficking. Of particular note is the observation that more young adolescent females were apprehended importing large consignments of Class A substances than their male counterparts.
Human chorionic gonadotrophin and progesterone levels in pregnancies of unknown location
Authors: Condous G. , Lu C. , Van Huffel S.V. , Timmerman D. , Bourne T. 
Published: June 2004

AbstractObjective: To evaluate accuracy, user variability and impact of experience on the use of serum hCG and progesterone in women who have a pregnancy of unknown location (PUL's). Materials and methods: This was a retrospective study. Presenting 1932 consecutive women to an Early Pregnancy Unit had a transvaginal scan. The location of the pregnancy could not be found in 189 women (Pregnancy of unknown location, PUL), and so blood was taken to measure serum hCG and progesterone at presentation and subsequently after 48 h, according to the protocol. All women were monitored at regular intervals until the final outcome was known, which was a failing PUL, a viable or failing intra‐uterine pregnancy, an ectopic pregnancy or a persisting PUL. The final study group comprised 185 PUL, as four cases of persisting PUL were treated and excluded from the analysis. Five investigators assessed the hormonal data independently. The investigator's experience as defined by the number of years working in obstetrics and gynecology ranged from 2 to 15 years. Each investigator knew the women were clinically stable and that the scan result was consistent with a PUL, i.e. there were no signs of intra‐ or extra‐uterine pregnancy, and there was no hemoperitoneum on TVS. When assessing the PUL's, each investigator was given the hormonal results at time 0 and 48 h for serum hCG and progesterone and asked to classify the PUL's as failing PUL's, immediately viable intra‐uterine PUL's and ectopic PUL's. No other clinical information about the women was made available. Results: Complete data 185 women (89%): 102 failing PUL's, 63 immediately viable intra‐uterine PUL's and 20 ectopic PUL's (total 185). The most experienced investigator obtained the best accuracy 163/185 (88.1%); not significantly different from those obtained by less experienced investigators (range 85.9–87.6%). Mean correct classification of failing PUL and immediately viable intra‐uterine PUL's was 93% (range 89–95%); corresponding value for ectopic PUL's was 42% (range 25–60%). Agreement between observers for classification of failing PUL's and immediately viable intra‐uterine PUL's was almost perfect (Cohen's kappa 0.86–0.90), whereas the value for ectopic PUL's group was fair to moderate (Cohen's kappa 0.39–0.67). All 5 investigators misdiagnosed same 35% of ectopic PUL's. Conclusions: Serum hCG and progesterone levels at defined times can be used to predict the immediate viability of a PUL, but cannot be used reliably to predict its location. Clinical experience does not significantly improve the ability to assess PUL outcome.