bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical properties of blends of nylon with chemically modified ABS
Authors: Nelson T. J. , Subramanian N. 
Published: April 2007

AbstractTensile, flexural and impact properties were measured of a heterogeneous polymer blend system, consisting of nylon 6 and a chemically modified ABS (MABS). It was found from the tensile tests that nylon‐richer blends show yielding behaviour and nylon‐leaner blends show necking behaviour. The addition of MABS increases the modulus, whereas the tensile strength and percentage elongation at break decrease and go through a minimum. The impact strength is increased to a maximum of approximately three times when 20 wt% of MABS is added to nylon 6. In order to interpolate the mechanical properties observed, empirical equations are given which are found to describe the experimental data rather well. Photomicrographs were taken of the tensile fractured surfaces using a scanning electron microscope.
Rubber‐modified epoxies. I. Influence of presence of a low level of rubber on the polymerization
Authors: Chen Dong , Pascault Jean Pierre , Sautereau Henry 
Published: April 2007

AbstractButadiene‐acrylonitrile random copolymers with various molecular weights and end‐groups were introduced into a system consisting of the diglycidyl ether of bisphenol A (DGEBA) and 3,3′‐dimethyl‐4,4′‐diamino dicyclohexyl methane (3DCM) cured at 50°C. We studied the influence of a low level of soluble additive on the polymerization rate, evolution of viscosity, gelation and vitrification times, and the final network in the cases of different additive molecular weight and end groups of the additive. It was found that the additive influences the final network only by dissolving in the matrix and that the dilution effect plays a minor role, but the catalytic effect of an additive can play a significant role on the polymerization depending on the additive end groups. However, in all the rubber‐modified systems, the phase separation has no direct influence on the polymerization rate and the change of viscosity.
Dielectric properties of amorphous cellulose acetate‐butyrate polymer films
Authors: Reddy N. Venugopal , Kumar C. Ramesh , Rao V. V. R. Narasimha 
Published: April 2007

AbstractThe dielectric constant, loss tangent and AC conductivity of solution grown cellulose acetate‐butyrate films of 5μm thickness were studied as a function of temperature (300‐450 K) in the frequency range 10 Hz‐10 MHz. The decrease in dielectric constant was observed with the increase in frequency as well as with temperature. A loss peak was observed in the dielectric loss spectra and was identified as the β‐relaxation peak. The frequency‐dependent conductivity was also studied. The results were interpreted in terms of electronic conduction via hopping processes.
Azeotropy in terpolymerisation reactions of glycidylmethacrylate with alkyl acrylates and acrylonitrile
Authors: El‐Hamouly S. H. 
Published: April 2007

AbstractTernary copolymerisation of glycidylmethacrylate (GMA), with different alkyl acrylates (methylacrylate (MA), methylmethacrylate (MMA), butylacrylate (BuA) and n‐butylmethacrylate (n‐BuMA)) and acrylonitrile (AN)) were carried out in solution at 65°C in the presence of a free radical initiator. Experimental terpolymerisation data agree well with calculations based on the Alfrey‐Goldfinger equation. The determination of unitary, binary and ternary azeotropes of the various systems studied was easily handled by a computer. Ternary azeotropic compositions for GMA‐MMA‐AN and GMA‐nBuMA‐AN systems were found to be 17‐50:68‐50:14‐00 and 51‐00:3‐00:46‐00 mol%, respectively. Also, 'pseudo‐azeotropic' regions were identified where the deviation between feed and polymer compositions was very small.
Use of glycidyls in the modification of polyurethane membrane structures
Authors: Bezdadea Mariana , Savin Alexandru , Ciobanu Gabriela 
Published: April 2007

AbstractAromatic glycidyl ethers have been used for modifying the structure of polyurethane membranes and improving their properties. The changes of chemical structure of the polyurethane in the membrane network have been followed by IR spectroscopy. The structural uniformity of the membrane has been elucidated by osmotic measurements and SEM. The structure of the membranes obtained has been related to their permeability towards distilled water.
Photosensitive polymers containing pendent chalcone moieties via oxyethylene group
Authors: Akelah A. , Selim A. , El‐Deen N. Salah 
Published: April 2007

AbstractVinylchalcone derivatives were prepared by the reaction of the sodium salt of 4‐hydroxychalcone with 2‐chloroethanol, followed by esterfication of the hydroxy groups with methacryloyl chloride in the presence of triethylamine as a base. The photosensitive monomers, 4‐(methacryloyloxyethoxy)chalcone and its 4′‐methyl and 4′‐chloro‐derivatives, have been homo‐ and copolymerized with p‐nitrophenylmethacrylate under free radical conditions to give the copolymers containing different ratios of photosensitizer group. The photosensitivities of the polymeric chalcone derivatives were investigated through their photochemical reactions on exposure to UV light and measuring the changes in UV spectra before and after irradiation. The results of these measurements indicate that the insolubilization percentage, i.e. the rate of the double bond disappearance depends on the effects of (i) the time of exposure to UV light, (ii) the position of the substituent in the phenyl ring of the chalcone, (iii) the spacer between the active moiety and the polymer backbone, and (iv) the ratio of the photosensitizer group.
Experimental and theoretical push‐pull Chemo‐ and regioselectivity in 1,3‐Dipolar cycloaddition reactions: the case of benzotriazepin‐5‐one with mesitylnitrile oxide
Authors: Azzouzi Saida , Jalal Rachid , El Messaoudi Malika , Domingo Luis R. , Esseffar M'hamed , Aurell M. José 
Published: April 2007

AbstractA novel heterocyclic compound 3‐mesityl‐5‐methyl‐4,5,11,11a‐tetrahydro‐6H‐[1,2,4]oxadiazolo [5,4‐b][1,3,4]benzotriazépin‐6‐one 4 has been synthesised by a 1,3 dipolar cycloaddition (13DC) reaction of 1,3,4‐benzotriazepin‐5‐one 1 with mesitylnitrile oxide 3. The reaction, beside its synthetic interest, has shown to be completely chemo‐ and regioselective. The structure of the compound was determined by X‐ray crystallography and analysed by spectral methods (NMR and mass spectrometry). The molecular mechanism for the reaction has been studied using quantum mechanical calculations at the B3LYP/6‐31G* theory level. Two mechanisms are possible for the formation of the cycloadduct 4. The first one involves a 13DC reaction between 1, as dipolarophile and 3, as dipole. Analysis of the results indicates that it takes place along asynchronous concerted bond‐formation process with a very low polar character. The regioselectivity obtained from the calculations are in complete agreement with the unique formation of the cycloadduct 4. The second mechanism is initiated by the nucleophilic attack of the N3 nitrogen of the tautomer form of 2, to the C5 carbon of the nitrile oxide 3 to yield an amidoxime. However, the large energy involved in this addition prevents this mechanism. The large energy difference between the tautomers 1 and 2, makes that only the CN site of benzotriazepin‐5‐one 1 could act as a dipolarophile site. This fact makes the 13DC reaction to be chemoselective. The analysis of global electrophilicity of the reagents allows explaining the low polar character of these 13DC reactions. Copyright © 2007 John Wiley & Sons, Ltd.
A novel probe for determination of electrical surface potential of surfactant micelles: N,N'‐di‐n‐octadecylrhodamine
Authors: Mchedlov‐Petrossyan Nikolay O. , Vodolazkaya Natalya A. , Yakubovskaya Anna G. , Grigorovich Aleksey V. , Alekseeva Vera I. , Savvina Lyubov P. 
Published: April 2007

AbstractThe peculiarities of the structure of the fluorescent dye N,N'‐di‐n‐octadecylrhodamine advantage its using as an interfacial acid–base probe in aqueous micellar solution of colloidal surfactants. Two long hydrocarbon tails of the dye provide similar orientation of both cation and zwitterion on the micelle/water interface, with the ionizing group COOH exposed to the Stern region in all the systems studied. Further, the charge type of the acid–base couple, A+B±, ensures similar values of the ‘intrinsic’ contribution, pK, to the ‘apparent’ pK value in micelles of different surfactants. This makes the indicator suitable for determination of electrical surface potentials, Ψ. The pKs have been obtained in cationic, anionic, zwitterionic, and nonionic surfactant systems, at various salt background. In total 17 systems were studied. At bulk counterion concentration of ca. 0.05 M, the pK values vary from 2.14 ± 0.07 in n–C18H37N(CH3)Cl– micelles to 5.48 ± 0.06 in n–C16H33OSONa+ micelles. The Ψ values, corresponding to the Stern region of micelles, have been evaluated as Ψ = 59.16 pK–pK for T = 298.15 K. The pK parameter was equated to the average value of 4.23 in nonionic surfactants (4.12–4.32, depending on the surfactant type). For cetyltrimethylammonium bromide and sodium n‐dodecylsulfate micelles, the Ψ values (±(7–11) mV) appeared to be +118 mV and at bulk Br− concentration 0.019 M and −76 mV at bulk Na+ concentration 0.020 M, respectively. This satisfactorily agrees with the theoretical values +111 and −84 mV, estimated using the Oshima, Healy, and White equation for these well‐defined colloidal systems. Finally, not only absorption, but also fluorescence spectra display the same response to changes in bulk pH. Copyright © 2007 John Wiley & Sons, Ltd.
Modulating testosterone stimulated prostate growth by phenethyl isothiocyanate via Sp1 and androgen receptor down‐regulation
Authors: Beklemisheva Anastasia A. , Feng Jingyang , Yeh Yunshin Albert , Wang L. G. , Chiao J. W. 
Published: April 2007

AbstractBACKGROUNDThe effects of phenethyl isothiocyanate (PEITC), present naturally in cruciferous vegetables, on androgen‐influenced growth of the prostate such as benign hyperplasia, was investigated.METHODSRats dosed with cyproterone acetate and testosterone, were fed at the same time with either PEITC or vehicle control. The growth of the prostates was compared to untreated rats.RESULTSWhile testosterone increased the prostate mass (30%) and hyperplastic seminiferous tubules as compared to the untreated rats, PEITC feeding decreased the prostate mass and hyperplasia to roughly the levels of untreated rats (P < 0.05). PEITC negated the testosterone‐mediated enhancement of the androgen receptor (AR), via down‐regulating transcription factor Sp1 expression and Sp1 binding complex formation. Cell cycle progression was attenuated with decreases of cyclins, Rb, and up‐regulates p27.CONCLUSIONSPEITC modulates the testosterone‐influenced growth by repressing Sp1, thus down‐regulating AR and proliferation. PEITC from cruciferous vegetables may represent a regulator for hormone‐dependent growth of the prostate. Prostate 67: 863–870, 2007. © 2007 Wiley‐Liss, Inc.
Orientational vibrations of 2D molecular layers with quadrupolar interaction
Authors: Lykah V. A. , Syrkin E. S. 
Published: April 2007

AbstractMolecular layers with rotational degrees of freedom and quadrupolar interaction between linear molecules are investigated theoretically. Rotation of the molecules in the plane of an adsorbing surface is considered; centers of gravity of the molecules are pinned to sites of a rectangular lattice. The energy of the system contains an additional parameter ρ (ratio of the lattice constants of a 2D system), in comparison with the 1D case. It is found that alternating orientation of the adsorbed molecules along both sides of the rectangular unit cell corresponds to the minimum of the energy. Equations of rotational movement are derived for linear oscillations of molecules near the equilibrium positions in a 2D lattice. Dispersion relations are obtained and analyzed. The Brillouin zone cannot be divided as in the 1D case after unit‐cell doubling. The parameter B (k), which describes the topology of the dispersion surfaces, is introduced. It is shown that both branches of the spectrum have optical behavior. The gaps and bandwidths are found as functions of ρ. The method of calculation of the density of states (DOS) for translational oscillations of a 2D rectangular lattice with one atom per unit cell is generalized for rotational oscillations of a 2D two‐sublattice molecular lattice. The diagram describing three regions with different analytical properties of the DOS which correspond to different topologies of the isofrequency lines is introduced. This diagram is a portrait in the plane of the parameters B and ρ. The DOS is found in terms of complete elliptic integrals of the first kind. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Grain boundary‐modified dielectric spectra of electroceramics: the occurrence of ‘unexpected' thermal dielectric loss peaks
Authors: Antonelli Eduardo , M'Peko Jean‐Claude , Hernandes Antonio Carlos 
Published: April 2007

AbstractManifestation of dielectric/magnetic anomalies is often used to postulate or corroborate occurrence of structural phase transitions in both single‐crystal and polycrystalline materials. In the latter case, furthermore, some important aspects of grain‐boundary influence on the overall electrical response of materials have been more or less extensively characterized elsewhere. Nevertheless, the possible occurrence of ‘anomalous' thermal dielectric loss peaks, not associated with phase transitions or any other potential source, but still arising from grain boundary‐induced effects, has been less considered and explored. Here, BaZrO3 ceramics, commonly proposed to be attractive in the capacitor industry, are found to qualitatively and quantitatively help discussing and approaching this question by measuring, deeply treating and analyzing fixed‐frequency and frequency‐dependent impedance data. The overall work shows that grain boundary‐induced thermal dielectric peaks may occur, with temperature locations that may also be reasonably predicted. © 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Bound electron pairs on a triangular lattice in an extended Hubbard model
Authors: Bak M. 
Published: April 2007

AbstractThe properties of the bound states on a lattice is an interesting problem related to the properties of superconductivity and Bose–Einstein condensation in a given model. By means of the exact solution of the Schrödinger equation the properties of the bound pairs on a frustrated, triangular lattice are examined within extended Hubbard model. Dispersion curves and mobilities are calculated for both positive and negative sign of the hopping integral. The possibility of increasing the mobility with increasing intersite Coulomb interaction is found. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Field tunable spin/orbital correlations in Ca‐based ruthenates
Authors: Cuoco Mario , Forte Filomena , Noce Canio 
Published: April 2007

AbstractWe consider the field response of correlated t2g electrons within the layered Ca‐based ruthenates. Our analysis shows that, as a consequence of a fine interplay between the spin–orbit interaction and the octahedral distortions, the application of the field along different directions can bring to polarized configurations with inequivalent spin and orbital character. In particular, we underline how such behavior manifests at the boundary between an antiferromagnetic state with ferro‐type orbital correlations, and a ferromagnetic configuration with an antiferro‐type orbital character. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin‐charge rotating local reference frames: a unified U(2) = U(1) ⊗ SU(2) approach to the interacting electrons
Authors: Kopeć T. K. 
Published: April 2007

AbstractA spin‐charge unifying description for the Hubbard model based on the time dependent local gauge transformations is developed. The collective variables for charge and spin are isolated in the form of the space‐time fluctuating U(1) phase field and rotating spin quantization axis governed by the SU(2) symmetry, respectively. As a result interacting electrons appear as a composite objects consisting of bare fermions with attached U(1) and SU(2) gauge fields. We elaborate on the microscopic origins of the effective action with the Coulomb interaction that contain topological theta terms. Furthermore, we unravel the link between non‐trivial multiply‐connected topological structure of the U(2) = U(1) ⊗ SU(2) configurational space for gauge fields and the instanton contribution to the statistical sum. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved electroluminescence on nonpolar m ‐plane InGaN/GaN quantum wells LEDs
Authors: Kim Kwang‐Choong , Schmidt Mathew C. , Sato Hitoshi , Wu Feng , Fellows Natalie , Saito Makoto , Fujito Kenji , Speck James S. , Nakamura Shuji , DenBaars Steven P. 
Published: April 2007

AbstractImproved nonpolar m ‐plane $\bar 1$ light emitting diodes (LEDs) with a thick InGaN multi‐quantum‐well (MQW) structure have been fabricated on low extended defect bulk m ‐plane GaN substrates using metal organic chemical vapor deposition (MOCVD). The peak wavelength of the electroluminescence emission from the packaged LEDs was 402 nm, which is in the blue‐violet region. The output power and EQE were 28 mW and 45.4%, respectively, at a pulsed driving current of 20 mA. With increasing current, the output power increased linearly, and fairly flat EQE was observed with increasing drive current. At 200 mA, the power and EQE were 250 mW and 41%, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
H∞ filtering for a class of stochastic Markovian jump systems with impulsive effects
Authors: Dong Yuewu , Sun Jitao , Wu Qidi 
Published: April 2007

AbstractIn this paper, we discuss the problem of H∞ filtering for a class of stochastic Markovian jump systems with impulsive effects. The aim is to design a stochastically stable filter, using the locally sampled measurements, which guarantee both the stochastic stability and a prescribed level of H∞ performance for the filtering error dynamics. A sufficient condition for the existence of such a filter is given in terms of certain linear matrix inequalities (LMIs). When these LMIs are feasible, an explicit expression of a desired filter is obtained. A numerical example is provided to show the effectiveness of the proposed results. Copyright © 2007 John Wiley & Sons, Ltd.
An extended age period cohort model for analysing (age, period)‐tabulated data
Authors: Hanayama Nobutane 
Published: April 2007

AbstractA model of an extended version of the age period cohort (APC) model is proposed for analysing (age, period)‐tabulated data on mortality of some chronic diseases. Estimable functions of the parameters in the proposed model for ML estimation are elucidated, and the result of fitting the proposed model to the data on breast cancer mortality for females in the U.S. is shown, where it is seen that the proposed model provides a better fit to the data than APC model in terms of AIC. Copyright © 2007 John Wiley & Sons, Ltd.
Blade load mitigation control design for a wind turbine operating in the path of vortices
Authors: Hand M. Maureen , Balas Mark J. 
Published: April 2007

AbstractAs wind turbine rotor size continues to increase, load mitigation becomes an important control objective. Turbines with hub heights of nearly 100m operate in the stable, nocturnal boundary layer where coherent turbulence can be generated by atmospheric phenomena outside the surface layer. These coherent turbulent structures may contribute to blade fatigue loads that can be mitigated with advanced control algorithms. Disturbance accommodating control (DAC) methods were implemented in a wind turbine structural dynamics simulation code to mitigate transient blade load response induced by a simple, Rankine vortex in the inflow. As a best‐case scenario, a full‐state feedback controller (which included a very detailed disturbance model) showed that blade flap damage equivalent load caused by the vortex passing through the rotor could be reduced by 30% compared to one that resulted from simulation of a typical proportional‐integral (PI) controller. A realizable DAC controller that incorporates only the vertical shear component of the vortex reduced loads by 9% compared to that resulting from simulation of a PI controller. The load reduction was even greater when the vortex was superimposed over full‐field, homogeneous turbulence. DAC methods have the flexibility to incorporate properties of coherent turbulent inflow structures in the controller design to mitigate blade fatigue loads. Further work must be done to develop disturbance models as more details about the turbulent structures are identified. Copyright © 2007 John Wiley & Sons, Ltd.
The use of a European coinage alloy to compare the detection limits of mobile XRF systems. A feasibility study
Authors: Cesareo R. , Ferretti M. , Gigante G. E. , Guida G. , Moioli P. , Ridolfi S. , Roldán Garcia C. 
Published: April 2007

AbstractThe investigation of archaeological and historical materials makes use of techniques that, though borrowed from other fields of research and industrial production, frequently have to be ‘re‐invented’ because of peculiar characteristics of the analysed objects. Artistic relevance, limited movability, compositional and structural heterogeneity radically change the experimental approach and often require ad hoc designed equipment. These considerations also apply to x‐ray fluorescence, especially regarding mobile systems. The extensive development and use of mobile spectrometers has produced an extremely diversified context and created the need for common criteria to evaluate their performances as well as the advisability of a survey on the existing equipment.This paper shows the feasibility of such an idea through a demonstrative survey that was carried out among users of different mobile x‐ray fluorescence spectrometry (XRF) systems in the areas of Rome, Italy and Valencia, Spain. The experimental protocol was based on measuring spectrometer detection limits with the single standard method. The standard was the 50 eurocent coin, whose alloy is made of 89% Cu, 5% Al, 5% Zn, 1% Sn; the large spread of the European currency guarantees maximum availability. The experimental data show that the use of different x‐ray tubes and detectors results in detection limits that may differ from each other by a factor of 6 for Zn and almost 100 for Sn; despite the large number of variables that in principle affect the performance, it was observed that the high voltage of the x‐ray tube is the most important parameter. Copyright © 2007 John Wiley & Sons, Ltd.
Accurate efficiency calibration of a low‐energy HPGe detector using a monochromatic x‐ray source
Authors: Plagnard Johann , Bobin Christophe , Lépy Marie‐Christine 
Published: April 2007

AbstractHPGe detector efficiency has been calibrated using complementary methods involving radioactive x‐ray standards, reference synchrotron flux (Super ACO, LURE, France) and a monochromatic x‐ray source (SOLEX), combined with Monte Carlo simulation. In the study described here, SOLEX was used to determine the thickness of detector components that create absorption sites in front of the active zone of the detector, by energy scanning in the vicinity of their K and L binding energies. The layers of aluminium (infrared shielding), nickel (electrical contact) and germanium (dead layer) have been measured. This approach ensures accurate determination of the thickness of each component and enables the detector efficiency calculation by Monte Carlo simulation. Differences between simulated data and experimental efficiency values are about 1–5% at energies above 1400 eV and reach 20% at lower energies. Copyright © 2007 John Wiley & Sons, Ltd.