bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymeric Photoinitiators Containing Side‐chain Ketoaromatic Moieties for Fast Ultraviolet Initiated Polymerisation of Acrylic Monomers
Authors: Carlini Carlo 
Published: April 2007

AbstractThe synthesis of polymeric photoinitiators having side‐chain cyclohexylphenylketone as well as benzophenone moieties at different distances from the backbone is described. Study of the activity of the former systems, in the ultraviolet initiated polymerisation of acrylic monomers, indicates that a remarkable increase in the polymerisation rate is observed when the cyclohexylphenylketone chromophore is attached to the main chain through an ethereal linkage rather than an ester group. In the case of the latter systems, considerable improvement is observed in the photoinitiating activity with respect to the corresponding low molecular weight model compounds in the polymerisation of acrylic monomers. Moreover, in general the copolymers of benzophenone‐containing monomers show higher activity than the corresponding homopolymers. These results are discussed in terms of photoexcitation energy migration along the polymer chain, as well as of intramolecular hydrogen abstraction from both main and side chains. This last occurrence seems to be the main activation process, as suggested by a strict correlation between activity and hydrogen‐donating properties of the co‐units in the copolymers, Photophysical evidence supporting this point is also reported. Finally, the synthesis of polymeric photoinitiators, containing both benzophenone and tertiary amine groups in the same macromolecule, has been accomplished via copolymerisation of 4‐acryloxybenzophenone with 4‐(N,N‐dimethylamino)styrene. Preliminary data concerning photoinitiating activity of these last copolymers indicate that conformational mobility affects the formation capability of exciplexes and then the activity itself.
Behaviour of Composites Used in the Confinement of Nuclear Wastes 1 ‐ Water Absorption of Polymer Matrices
Authors: Nicaise E. , Gandini A. , Cheradame H. 
Published: April 2007

AbstractThe diffusion of water into typical epoxide and polyester materials has been studied as a function of temperature, temperature cycles and polymer structure. A reversible uptake characterised by a diffusion coefficient and an equilibrium absorption was accompanied by an irreversible water uptake due to hydrolysis. Polyesters showed a pronounced tendency to degradation, particularly above room temperature. This preliminary investigation was conducted within the broader scope of a study dealing with the feasibility of embedding nuclear wastes in polymer matrices. The results obtained thus far are encouraging, notably with epoxide networks.
Mechanical Properties of Alkyl Isocyanate Modified Scots Pine Wood Surfaces
Authors: Banks William B. , Jones Gwynn Lloyd 
Published: April 2007

AbstractThin longitudinal sections (100 μm thick) were reacted with butyl isocyanate and octadecyl isocyanate under dry conditions. Weight gain and nitrogen analysis demonstrated reaction to degree of substitution about 0.9 (based on published wood cell wall analytical data). Infrared spectra data gave good evidence for the formation of carbamate ester (urethane bonds). Up to weight gain of about 30% no practically significant loss of tensile strength or toughness was observed. Above this level, strength and toughness was observed to fall as a function of weight increase, similarly with both reagents. Over the range examined the precise degree of substitution (loss of hydroxyl functionality) appeared to have no direct effect on mechanical properties. The strength losses seem to be related to cell wall rupture resulting from excessive swelling occurring at the higher levels of reaction.
Application of New Radiochemical Methods to the Study of the Cure of Epoxies by Various Imidazoles
Authors: Jones John R. , Poncipe Carlo , Barton John M. , Wright William W. 
Published: April 2007

AbstractThe reaction between phenylglycidyl ether and a number of substituted imidazoles has been investigated using a combination of tritium nuclear magnetic resonance spectroscopy and radio‐high performance liquid chromatography, two methods that have not been used previously in this area. For more volatile catalysts such as aromatic amines radio‐gas chromatography can be employed to good effect.
Use of the Exponential Model of Enzyme Decay to Plan a Strategy for Enzymatic Batch Reactions and to Assess the Industrial Applicability of Immobilised Enzyme Preparations
Authors: Cardoso Joaquim Pereira 
Published: April 2007

AbstractThis paper is concerned with the development of a model to plan a strategy for an enzymatic batch process whereby the enzyme is subjected to deactivation as described by the exponential (first‐order) decay model. The particular system used was the enzymatic hydrolysis of penicillin to 6‐aminopenicillanic acid, but the model can be utilised with other batch systems, provided that decay of the immobilised enzyme preparation is described by the exponential decay model. The model developed is eminently practical and simple, and several examples of its application are given. Experimental data obtained in a small pilot plant batch recirculated reactor could, on average, be well fitted by this model.
Borides and Silicides ‐ New Chemistry and Applications
Authors: Aylett Bernard J. 
Published: April 2007

AbstractA general survey is presented of the preparation, physical and chemical properties, and structural patterns of transition metal borides and silicides. The appropriateness of their description as inorganic homopolymers stabilised by electron transfer from metal centres is discussed. Finally, applications are outlined, with particular reference to the fabrication of thin films and their use in advanced microelectronic devices.
Polymerization of ethyl 2‐cyanoacrylate in the presence of poly(butadiene‐co‐acrylonitrile)
Authors: Dikov Valentin K. , Kotzev Dimitar L. , Kabaivanov Vladimir S. 
Published: April 2007

AbstractRadical graft copolymers of ethyl 2‐cyanoacrylate on to poly(butadiene‐co‐acrylonitrile), were prepared and characterized by infrared spectroscopy. Simultaneous homopolymerization of ethyl 2‐cyanoacrylate also occurred. The polymerization of ethyl 2‐cyanoacrylate is significantly affected by the presence of the pre‐formed dissolved elastomer, the overall activation energies in the presence and absence of elastomer being 80.8 ± 0.4 kJ mol−1 and 77.0 ± 0.4 kJ mol−1, respectively. In each case the reaction was first‐order with respect to the monomer.
Particulate stabilisers for drops in suspension polymerisation: Use of a wax model
Authors: Brooks Brian W. , Bygate Fiona , Lane Andrew C. 
Published: April 2007

AbstractFinely divided inorganic solids can be used for drop stabilisation in suspension polymerisation. In order to clarify the role of these solids, experiments have been carried out using a model system in which wax drops were dispersed in water in the presence of magnesium hydroxide. Drop sizes were reduced if the hydroxide was precipitated in situ before dispersion of the wax. As the loading of this precipitate increased, the average drop size passed through a minimum. The presence of a surfactant modified the effect of the hydroxide. Electrolyte, which is formed in the precipitation reaction, also influences the drop size. The separate effects of solid hydroxide, surfactant and electrolyte are not additive. There is some evidence for a nucleating effect which may not be desirable in suspension polymerisation.
Magnetic and optical properties of single crystals of transition metal doped ZnO
Authors: Kane M. H. , Fenwick W. E. , Strassburg M. , Nemeth B. , Varatharajan R. , Song Q. , Keeble D. J. , El‐Mkami Hassane , Smith G. M. , Zhang Z. J. , Nause J. , Summers C. J. , Ferguson I. T. 
Published: April 2007

AbstractConsiderable effort has been devoted to the study of transition metal doped zinc oxide following various theoretical predictions of room temperature ferromagnetism in these materials. Near equilibrium growth techniques may be suitable for the production of dilute transition metal doped ZnO because the transition metal solubility in ZnO can be relatively high. This work reports on the optical, structural, and magnetic properties of single crystals of Co‐ and Mn‐doped ZnO grown by a modified melt‐growth technique. X‐ray diffraction reveals that the as grown crystals are pure single crystals with no second phases. Mn doping up to 5% results in an increase in c‐axis lattice parameter (5.207 Å to 5.211 Å), and X‐ray linewidths (78 arcsec to 252 arcsec) at doping levels of 5% Mn. Optical transmission shows distinct absorption spectra related to the color of the Zn1–x TMx O sample resulting from interatomic transitions within the divalent transition metal ion. Electron paramagnetic resonance confirms the divalent nature of the substitutional transition metal ions. Raman spectroscopy shows the predominantly the E2 (high) peak at 407 cm–1, but with increasing doping shows additional disorder‐related modes. The magnetic behavior reveals a paramagnetic behavior at all temperatures for both Mn‐ and Co‐doped ZnO up to transition metal doping levels of 5% and 3% respectively. The dominant exchange mechanism in the Mn‐ and Co‐doped ZnO crystals is found to be antiferromagnetic superexchange. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical observation of discrete well width fluctuations in wide band gap III‐nitride quantum wells
Authors: Haratizadeh H. , Monemar B. , Paskov Plamen P. , Holtz Per Olof , Valcheva E. , Persson P. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I. 
Published: April 2007

AbstractA detailed observation of discrete well width fluctuations via localized excitons in the photoluminescence (PL) spectra of MOCVD‐grown undoped GaN/Al0.07Ga0.93N multiple quantum wells (MQWs) has been reported. Doublet excitonic features with a distance varying between 10 and 25 meV for different well widths (1.5 to 4.5 nm) are observed in the PL spectra. They are explained in terms of discrete well width variations by onec‐lattice parameter, i.e. two GaN monolayers. By mapping the PL measurements across the samples with different excitation spot size, it is shown that the extension of areas with a constant well width is less than 1 μm2. TEM pictures give evidence of interface roughness, although the contrast is weak at this low Al composition. In addition we observe a long‐range variation of the PL peak position across the sample, interpreted as a fluctuation in Al composition in the barriers. The residual broadening of an excitonic peak (apart from the splitting related to well width fluctuations) is about 10 meV, somewhat larger for larger well widths, and is mainly ascribed to hole localisation potentials in the QWs. Additional broadening occurs in the MQWs due to inequivalent properties of each QW within the excitation spot. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of annealing atmosphere on the quality of ZnO crystal surface
Authors: Grasza K. , Łusakowska E. , Skupiński P. , Kopalko K. , Bąk‐Misiuk J. , Mycielski A. 
Published: April 2007

AbstractZinc oxide crystals were grown by CVT contactless technique and thermally annealed in the air, nitrogen or oxygen atmospheres, or zinc or arsenic vapours. Wide ranges of annealing times and temperatures were applied. The variety of morphology and quality of the crystal surface was investigated by AFM and XRD. It was found, that thermal annealing in the air, nitrogen, oxygen and zinc resulted in similar evolution of the crystal surface, although there are observed differences in the rate of the changes. The annealing in zinc vapour resulted in roughness (RMS) lower than 1 nm. The annealing in arsenic vapour leads to degradation of the crystal surface. The improvement of the surface was not observed in case of thermal annealing of the rough ZnO surfaces obtained by ALE homoepitaxy on the smooth CVT as‐grown ZnO surfaces. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of treatment on the CdTe, Cd1–xMnxTe and Cd1–xZnxTe surface stoichiometry
Authors: Dremlyuzhenko S. G. , Zakharuk Z. I. , Savchuk A. I. , Fochuk P. M. 
Published: April 2007

AbstractThe effects of treatment in several etchants on CdTe, Cd1–x Mnx Te, Cd1–x Znx Te surface stoichiometry are studied. Simple chemical etching of CdTe, Cd1–x Mnx Te, Cd1–x Znx Te causes a relief and contamination of near‐surface layer with etchant components. It was determined that Cd, Mn, Zn are washed out into the solution as a result of material treatment in bromine‐methanol etchant, and, consequently, the surface is enriched with elemental tellurium and its oxides. Treatment in alkaline solutions allows minimizing the violation of surface stoichiometry. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and characterization study of multidimensional hierarchical ZnO nanostructures
Authors: Park Dong Jun , Kim Dong Chan , Lee Jeong Yong , Cho Hyung Koun 
Published: April 2007

AbstractZnO multidimensional hierarchical structure was successfully fabricated with the sequence of ZnO top layers/ZnO nanorods/ZnO buffer/Si(111) substrate by continuous controlling growth condition in metal organic chemical vapor deposition (MOCVD) system. Transmission electron microscopy (TEM) showed that ZnO nanorods in hierarchical structure had a single crystal hexagonal wurtzite structure with 〈0001〉ZnO growth direction. Only near band edge (NBE) emissions with very weak deep level emission are observed around 3.28 eV. This indicates that ZnO hierarchical structure grown by MOCVD shows a good optical quality and less interior defects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoconductivity of Ga doped polycrystalline ZnO films grown by reactive plasma deposition
Authors: Kishimoto Seiichi , Hayashi Kunihiko , Hamaguchi Hirofumi , Makino Hisashi , Yamada Takahiro , Miyake Aki , Yamamoto Tetsuya 
Published: April 2007

AbstractPhotoconductivity and photo‐absorption of polycrystalline Ga‐doped ZnO (GZO) thin films with film thickness of 200 nm have evaluated compared with undoped ZnO films. The GZO and undoped ZnO thin films were deposited on alkali‐free glass substrate at 200 °C by a reactive plasma deposition with DC arc discharge technique under an oxygen gas flow rate from 0 to 30 sccm. Undoped ZnO films with carrier concentration of 2.50 × 1018 and 7.96 × 1018 cm–3 have exciton absorption at about 3.28 eV. For these films, the photoconductivity peak is agreement with the photon‐energy of exciton absorption in the optical‐absorption. The optical band edge of undoped ZnO films estimated from the optical‐absorption shows a shift to higher energy with increasing the carrier concentration. The increase of oxygen gas flow rate led to the resistivity change of GZO films from 2.15 × 10–4 to 4.54 × 10–3 Ω cm, corresponding to the carrier concentration change from 1.39 × 1021 to 1.05 × 1020 cm–3. The photoconductivity of GZO film is larger than that of undoped ZnO film. The peak energy of photoconductivity spectra of GZO films are seen to little shift to higher energy with increasing the carrier concentration. The GZO film exhibited the larger photoconductivity at the wavelength, ranging widely less than 380 nm. GZO film with carrier concentration more than 1 × 1021 cm–3 indicated much larger photoconductivity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of effect of casein phosphopeptides on zinc binding using mass spectrometry
Authors: Wang Jiaxi , Green Kirk , McGibbon Graham , McCarry Brian 
Published: April 2007

AbstractPhosphorylation is one of the key events in signal transduction and zinc plays an important catalytic and/or structural role in many biological systems. The binding of Zn to a phosphopeptide will alter the physiological functions of a peptide. The binding of casein phosphopeptides (CPPs) to Zn has been analyzed using nanospray mass spectrometry. Electrospray ionization (ESI) spectra of peptides produced by tryptic digestion of α‐casein incubated with Zn show both free and Zn‐bound phosphopeptides. The interaction of CPPs and the corresponding dephosphorylated peptides with zinc is compared. This study demonstrates that the phosphorylation state of a peptide dramatically affects Zn binding, with the decrease in Zn‐bound forms of peptide paralleling the decrease in phosphorylation as casein is chemically dephosphorylated, although, in some cases, a small amount of residual Zn‐binding capacity remains in the completely dephosphorylated peptide. The observed fragmentation patterns of the Zn‐bound CPPs support the thesis that nonphosphorylated residues are involved in the metal binding. Copyright © 2007 John Wiley & Sons, Ltd.
Autonomous capture of a tumbling satellite
Authors: Rekleitis Ioannis , Martin Eric , Rouleau Guy , L'Archevêque Régent , Parsa Kourosh , Dupuis Eric 
Published: April 2007

AbstractIn this paper, we describe a framework for the autonomous capture and servicing of satellites. The work is based on laboratory experiments that illustrate the autonomy and remote‐operation aspects. The satellite‐capture problem is representative of most on‐orbit robotic manipulation tasks where the environment is known and structured, but it is dynamic since the satellite to be captured is in free flight. Bandwidth limitations and communication dropouts dominate the quality of the communication link. The satellite‐servicing scenario is implemented on a robotic test‐bed in laboratory settings. The communication aspects were validated in transatlantic tests. © 2007 Canadian Space Agency
Highly Ordered Nanostructured Surfaces Obtained with Silica‐Filled Diblock‐Copolymer Micelles as Templates
Authors: Frömsdorf Andreas , Kornowski Andreas , Pütter Sabine , Stillrich Holger , Lee Li‐Ting 
Published: April 2007

AbstractIn this work, we present the size‐controlled preparation of silica‐filled micelle cores and their self‐assembly behavior, which is dependent on the block lengths, different coating techniques, and substrates. Furthermore, we present a way to use these structures as templates for highly ordered magnetic nanostructures, revealed by Ar‐ion milling. The resulting structures were characterized by different imaging and scattering techniques and model simulations were performed. The characterization of the obtained nanostructured surfaces has be performed with atomic force microscopy, by scanning electron microscopy, grazing‐incidence X‐ray small‐angle scattering, and X‐ray reflectivity measurements. The magneto‐optical Kerr effect was utilized to investigate magnetic properties.
High damping natural rubber seismic isolators
Authors: Fuller K. N. G. , Gough J. , Pond T. J. , Ahmadi H. R. 
Published: April 2007

AbstractLaminated high damping rubber bearings provide a simple means of isolating structures from horizontal earthquake ground motions. The key properties of the rubber compounds are dynamic shear modulus and damping. The effect of strain amplitude, repeated cycling and temperature on these properties is given. The need to prevent changes in modulus associated with low temperature crystallization of rubber is discussed. Assessment of the long term stability of rubber properties from both accelerated ageing tests and measurements on bearings removed after prolonged service is considered. A model for the behaviour of high damping rubber is presented, and used to show how the response of a structure to ground acceleration depends upon the level of damping.
PATHOLEX ‐ an expert system for a pathology in the construction: Case of drought
Authors: Madiou H. , Lechani M. , Hannachi N. 
Published: April 2007

AbstractThe drought is the result of a deep anomaly of the natural hydraulic balance, affecting certain areas for periods of time varying from one year to several years. The periods of drought and the anomalies, they bring about in the hydraulic balance of affected areas, have drawn the specialists' attention, particularly those in the construction field because of the damages they may cause on the constructions. The objectives of our research consists of designing an expert system for the diagnosis of drought as a cause of disorders in the constructions. The automatisation of the diagnosis problem improves highly the quality and the efficiency of its process. As a result, it is recommended to record this expertise in a computer in such a way it can be used by less qualified personnel.
Design of linear active control algorithms for non‐stationary unknown forcing function
Authors: Baratta A. , Cennamo C. , Voiello G. 
Published: April 2007

AbstractThe object of the research is the design procedure of a linear control algorithm able to mitigate the effects of seismic shaking as far as possible, maintaining the running and installation costs within admissible bounds. The procedure starts from approaching the solution of the equation of motion of a SDOF structure in the norm sense, as explained in Secs. 2–3, which allows to obtain results that do not depend on the details of the forcing function. The approach is generalized to MDOF structures by modal decomposition, and it is shown that the control algorithm can be designed by independent modal control, by applying at each mode the procedure outlined for a SDOF system. Robustness of the algorithm with reference to uncertain identification of the structural properties is successfully investigated, both by theoretical tools and by numerical simulation. The whole pattern proves to be effective and poorly conditioned by the peculiar characters of the excitation.
The static electromechanical coupling factor in linear piezoelectric material
Authors: Davi F. 
Published: April 2007

AbstractWe show that the electromechanical coupling factor is the solution of two eigenvalue problems which depends on the piezoelectric, elastic and dielectric properties of the materials. We show that there are at most three eigenvalues and three associated strain eigentensors which render extremum the ratio of mechanical energy converted into electric energy: their value is the same if the three eigenvalues whose associated electric field eigenvectors render extremum the ratio of electrical energy converted into mechanical.