bluuebunny/crossref_metadata_2025 huggingface dataset:
Approaches to Terminal Diacetylenes, Precursors to New Substituted Polyacetylenes
Authors: Gibson Harry W. , Weagley Ronald J.
Published: April 2007

A number of synthetic routes to substituted 1,6‐heptadiynes, specifically 3,3,5,5‐tetramethyl‐1,6‐heptadiyne (5), cis‐1,3‐dimethyl‐1,3‐diethynylcyclopentane (3, R=CH3) and cis‐1,3‐diethynylcyclopentane (3, R=H), have been examined. These diacetylenes are precursors to new substituted polyacetylenes via cyclopolymerisation. Two major synthetic difficulties were encountered: (1) low reactivity of neopentyl systems to nucleophilic displacement in the cases of 3, R=CH3 and 5, and, conversely, (2) lability of isoalkyl type structures such as the intermediates for 3, R=H toward elimination during nucleophilic displacement reactions. These fundamental problems were compounded by the fact that all the intermediates are difunctional, giving rise to the statistical problem of mixed functionalities. While none of the desired diacetylenes was prepared in a pure state, a number of new intermediate compounds were synthesised. Furthermore, an impure sample of 3, R=H did yield a polymer film in preliminary experiments.
1H Nuclear Magnetic Resonance Study of Melt Polycondensation of 4,4′‐Sulphonyldiphenol with Methyl‐ and Chloromethylphosphonic Dichloride
Authors: Natansohn Almeria
Published: April 2007

Melt polycondensation of 4,4′‐sulphonyldiphenol with methylphosphonic dichloride and chloromethylphosphonic dichloride, respectively, was studied by taking samples from time to time and recording their 1H n.m.r. spectra. Analysis of the spectra provided identification of the intermediate structures present during the reaction. Complete spectral assignments were made, and the effect of the substitution on the chemical shifts was measured. No kinetic calculations were made, owing to the inhomogeneity of the reaction mixtures.
The Technology of Phenol‐Formaldehyde Moulding Powders 1 ‐ Characterisation of Novolak Resins and Derived Moulding Powders
Authors: Birley Arthur W. , Blinkhorn Arthur
Published: April 2007

This research programme has been concerned with the technology of phenol‐formaldehyde resins and of moulding powders based on them. This paper reports the characterisation of the prepolymer (Novolak) and concentrates on the results obtained by gel permeation chromatography with an infrared detector. A variety of frequencies have been employed, corresponding to different components in the resin, and the best separation was obtained by monitoring the phenolic hydroxyl at 3400 cm−1. It has been concluded that both commercial Novolak and prepolymer extracted from moulding powder contain a substantial fraction of high molecular weight material.
A Comparative Study of the Thermal Stability and Mechanism of Degradation of Poly(arylene sulphones)
Authors: Crossland B. , Knight G. J. , Wright W. W.
Published: April 2007

Three poly(arylene sulphones) have been studied by thermogravimetry to ascertain their relative thermal stabilities in both inert and oxidising atmospheres. Experiments have been carried out at a rate of temperature rise of 2°C min−1 and isothermally at a number of temperatures. The level of stability found compared favourably with that of other heat‐resistant materials, for example the addition type polyimides. The polymers have also been examined by pyrolysis gas chromatography mass spectrometry using two different procedures. In the first, fresh samples were pyrolysed at a number of increasing temperatures, whereas in the second, the sample was subjected to successive pyrolyses at the same temperature intervals.
Synthesis of Poly(4,5‐bis‐hydroxy‐1,3‐cyclopentadienylene vinylene) from Poly(6,8‐(1,5‐dichloro‐2,4‐dioxa‐3‐keto)‐bicyclo[3.3.0]octylene vinylene). Generation of a Conjugated Polymer by Hydrolysis of a Precursor Polymer
Authors: James Feast W. , Harper Kevin
Published: April 2007

Hydrolysis of poly(6,8‐(1,5‐dichloro‐2,4‐dioxa‐3‐keto)bicyclo[3.3.0]octylene vinylene) results in the formation of poly(4,5‐bis‐hydroxy‐1,3‐cyclopentadienylene vinylene), a new conjugated polymer. This new system can be generated as a surface layer on its precursor polymer. The conversion process has been studied with the aid of infrared and optical spectroscopy, elemental analysis, microscopy and conductivity measurements.
Molten State Transition in Thermoplastic Rubber
Authors: Canevarolo Sebastião V. , Birley Arthur W. , Hemsley Derek A.
Published: April 2007

The flow characteristics of styrene‐butadiene‐styrene thermoplastic rubbers have been studied and the results compared with earlier static measurements. Computer best‐fitting shift factors and inverse Melt Flow Index were plotted according to two mathematical models, Arrhenius and Vogel. Fulcher, Tamman and Hesse (VFTH). One transition was observed in both models, with appreciable reduction in the apparent activation energy of flow above this transition. This melt transition was associated with the temperature above which the PS chains can be removed from the PS rich phase by the rubbery chains. This allows rearrangement of the domain structure in a static condition or facilitates flow. Birefringence measurements support the model proposed.
‘Ordered’ Structure of Polyallylamine Hydrochloride in Dilute Solutions as Studied by Small Angle X‐ray Scattering
Authors: Yoshikawa Yukihiro , Matsuoka Hideki , Ise Norio
Published: April 2007

Aqueous solutions of polyallylamine hydrochloride were examined by small angle x‐ray scattering. When the polymer concentration of coexisting simple salt was low, a single, broad peak was observed. The peak was interpreted as indicating the presence of an ordered arrangement of macroions in the solutions. The intermacroion spacing was calculated by the Bragg equation and found to be much smaller than the average intermacroion spacing calculable from the polymer concentration, suggesting that there exist ordered regions and at the same time disordered regions in the solutions. The Bragg spacing decreased with increasing polymer concentration and increased with increasing salt concentration. Mixing of two samples of different molecular weights gave a new scattering peak in between the original peaks of the mother samples, which supports the intermolecular nature of the ordering. The peak height was lowered with increasing temperature. The scattering peak was found to stay unaffected for 21 days.
Behaviour of Composites Used in the Confinement of Nuclear Wastes 2 ‐ Water Absorption in Particle‐filled Epoxide Networks
Authors: Nicaise E. , Gandini A. , Cheradame H.
Published: April 2007

The diffusion of water into epoxide composites containing sand or glass beads has been studied as a function of temperature, type of filler and its surface treatment. This investigation falls within a broader context whose aim is to assess the possibility of embedding nuclear wastes into polymer matrices. The quality of polymer‐filler adhesion was checked by scanning electron microscopy. The best filler was found to be siliceous sand in particles of about 30 μm diameter, which could be added to epoxide networks in large proportions and provide a better material than the polymer alone.
Anionic Graft Polymerisation of Styrene from Polyisoprene. Dependence of Grafting Efficiency on Polyisoprene Structure
Authors: Al‐Jarrah Mustafa M. F. , Al‐Kafaji Jawad K. H. , Apikian Rita L.
Published: April 2007

Styrene was grafted from polyisoprene forming poly(isoprene‐g‐styrene) graft polymers. N,N,N',N'‐Tetramethylene diamine and s‐butyllithium were used to create active centres on the polyisoprene backbone in cyclohexane under anionic living polymerisation conditions. The stereoregularity of polyisoprene is shown to influence the grafting efficiency. Addition of small amounts of tetrahydrofuran increased grafting efficiency and decreased polydispersity of the graft polymers obtained. Polystyrene branches are shown to be syndiotactic rich.
The Computer Simulation of the Continuous Vulcanisation of High Pressure Hose
Authors: Evans Colin W. , Manley Thomas R.
Published: April 2007

The use of molten salt in the pressurised liquid continuous vulcanisation system enables most of the disadvantages of steam continuous vulcanisation to be overcome. To reduce the time needed to introduce this novel process into production a computer was used to simulate the pressurised liquid continuous vulcanisation system. Computer simulation can greatly reduce the costs of introducing new processes.
The Cure of Carboxy‐terminated Diene Polymers and the Role of a Polymer‐supported Catalyst
Authors: Willoughby Bryan G.
Published: April 2007

Both infrared spectroscopy and wet chemical techniques reveal that the terminal acid groups of carboxyl‐terminated polybutadiene behave in the same manner as in representative low molecular weight dilute solution systems. Contrary to previous expectations the chromium(III)‐catalysed epoxy chain extension shows third‐order character, and the slow progress of reaction at high conversions can be rationalised on simple kinetic grounds and without recourse to considerations of limited functional group accessibility. The parallels between bulk polymer and classical solution reactions anticipate the effectiveness of a system in which the catalyst is also a polymer: the synthesis and evaluation of two such catalysts are described. Whilst gel times are no slower for the polymer‐catalysed cures, product properties may be actually improved, thus, the unreinforced product of a liquid nitrile rubber cure may achieve a tensile strength of 4.5 MPa when the initial catalyst is chromium(III) supported on the same polymer, an improvement which can be rationalised in terms of classical concepts of polymer reactivity and step growth processes.
Investigation and Development of Epoxy Foams
Authors: Hajimichael Michael , Lewis Annette , Scholey Dave , Simmonds Clive
Published: April 2007

The development of low toxicity rigid epoxy foams as an alternative to polyurethane foams for electronics encapsulation is described. The basic foam components ‐ epoxy resin, hardener, accelerator, blowing agent and surfactant ‐ are blended to form a two part system which is mixed and foamed when required. Each foam component is selected for its contribution to the foaming reaction and the final foam properties. The balance of component miscibility, viscosity, reaction rate and exotherm determine foam quality. Foam properties are affected by (1) density (2) cell structure and (3) the molecular structure of the reactants. Initial foam development utilised epoxy/amine chemistry and produced two foams, Feldex F3 and F4. Subsequently, use of a more reactive polymercaptan hardener improved foam strength and process times, resulting in Feldex F5 and F6 which have been used successfully to prepare quality mouldings and encapsulated electronics. Recently, development has been extended to new areas of application, e.g. high temperature foams. The mechanical, electrical, thermal and chemical properties of the best epoxy foams have been evaluated; selected results are reported. The epoxy foams developed offer low density, high strength, low dielectric constant and loss tangent, high volume resistivity, good thermal insulation, low corrosivity and low toxicity. In addition, epoxy foams soften in acetone, an advantage over their polyurethane counterparts since encapsulated electronics may be retrieved without employing corrosive solvents. (Feldex is a registered trade mark of THORN EMI Electronics.)
Structure and Properties Relationships of Epoxy Resins Part 1: Crosslink Density of Cured Resin: (II) Model Networks Properties
Authors: Lau Chung H. , Hodd Kenneth A. , Wright William W.
Published: April 2007

Carefully designed resin precursors of high purity, viz. N,N‐bis‐(2,3‐epoxypropyl)‐N',N‐dimethyl‐4,4′‐diaminodiphenylenemethane (G2A) and N,N‐bis‐(2,3‐epoxypropyl)‐N,N‐dimethyl‐4,4′‐diamino‐diphenylenemethane (G2S) were used in combination with N,N,N',N‐tetrakis‐(2,3‐epoxypropyl)‐4,4′‐diaminodiphenylene methane, TGDDM, and cured with stoichiometric amounts of 4,4′‐diamino‐diphenylene methane (DDM) to produce networks with a range of controlled crosslink density. The tensile moduli E of the networks in the rubbery state, at Tg+30°C, Tg+45°C and Tg+60°C, were measured using a thermal mechanical analyser. Using the statistical theory of rubber elasticity and the observed values of E, the number average molecular weights between crosslink points Mc for the cured resins were deduced. The experimental Mc values were then compared with those derived by calculations based on a probabilistic model of the network proposed by Chu and Seferis.1 The experimental Mc values were 2.5 to 5.5 times larger than the calculated ones. The differences were attributable to a consumption of only 40% of the available secondary amino hydrogen via epoxy‐amine reaction. A direct relationship was established between the glass transition temperature and the crosslink density 1/Mc for the resins, and the dynamic mechanical properties were studied. The thermal stability of cured resins studied by thermo‐gravimetric analysis indicated an enhancement of stability as 1/Mc was reduced. The amount of water absorbed by cured resin was directly proportional to 1/Mc.
Modelling of the Hydrolysis of Benzylpenicillin to 6‐Aminopenicillanic Acid and Phenyl Acetic Acid by an Immobilised Penicillin Amidase in a Small Pilot Plant Batch Recirculated Reactor
Authors: Cardoso Joaquim Pereira , Da Costa Manuel Bento Correia
Published: April 2007

This paper deals with the modelling of the hydrolysis of benzylpenicillin to 6‐aminopenicillanic acid (6‐APA) and phenyl acetic acid (PAA) in a small pilot plant batch recirculated reactor by an immobilised penicillin amidase preparation. By using the following linearised form for an integrated Michaelis‐Menten equation Et/V0X=α+β| In (1‐X)/X| where α and β are reaction kinetic parameters, good correlations are obtained of α and β with linear velocity across the reactor, substrate concentration and temperature of operation. A process to determine α and β from initial velocity measurements is outlined. The applicability of the above equation to published data is also analysed.
Crosslink Enhancement in Polypropylene Film by Gamma Irradiation in the Presence of Acetylene
Authors: Ken Busfield W. , Appleby Rodney W.
Published: April 2007

The effects of crosslink enhancement by the presence of acetylene during gamma irradiation, on the physical and mechanical properties of polypropylene film are reported. Gel contents show that crosslink enhancement is considerably greater if the sample is highly annealed (PPA) than if it is quenched (PPQ). For PPA, thermal analysis suggests only minor damage to the crystalline lamellae, but significant stabilisation of lamellae by crosslink formation in the lamellar surface regions. This is supported by an increased resistance to the yielding process observed in tensile stress/strain and creep tests. The effects in PPQ is less.
Size‐exclusion Chromatography of Urea‐Formaldehyde Resins
Authors: Hlaing Tin , Gilbert Adrian , Booth Colin
Published: April 2007

Samples of urea‐formaldehyde resin have been investigated by means of size‐exclusion chromatography systems: (A) Zorbax PSM packing with either pure N,N‐dimethylacetamide (DMA) eluant or DMA+0.1 mol dm−3 LiNO3 eluant; (B) Styragel packing with DMA eluant. In addition to separation by size‐exclusion, adsorption/partition and hydrodynamic effects were observed. The influence of reaction time and conditions on the production of large soluble aggregates was investigated briefly.
Polymeric Routes to Silicon Carbide
Authors: Schilling Curtis L.
Published: April 2007

Several classes of organosilicon polymers are effective precursors for silicon carbide ceramic compositions. These include polydimethylsilane (via a two‐step process), ‘polysilastyrene’, polycarbosilazanes or polysilazanes, and certain siloxanes, plus the branched polycarbosilanes, branched polysilahydrocarbons, and vinylic polysilanes developed at Union Carbide. The latter three classes are prepared by active metal dechlorinations of appropriate chlorosilane blends, leading to recognition of branching at backbone silicon atoms (either as prepared or during processing) as a prerequisite for obtaining useful ceramic yields. Fundamental reactivity differences between the active metals (potassium and sodium) allow the preparation of sodium‐derived vinylic polysilanes. The latter offer certain economic and performance advantages as ceramic precursors.
The Thermal Degradation of Some Polymers Based Upon p‐Hydroxybenzoic Acid
Authors: Crossland The Late Barbara , Knight Graham J. , Wright William W.
Published: April 2007

Three polymers based upon p‐hydroxybenzoic acid have been studied by thermogravimetry to ascertain their relative thermal stabilities in both inert and oxidising atmospheres. Experiments have been carried out at a rate of temperature rise of 2°C min−1 and isothermally at a number of temperatures. The polymers have good thermal stability. They have also been examined by pyrolysis gas chromatography mass spectrometry using two different procedures. In the first, fresh samples were pyrolysed at a number of increasing temperatures, whereas in the second, the same sample was subjected to successive pyrolyses at the same temperature intervals. The results are compared with those of other authors derived using different techniques.
Studies of Partially Metallated Poly(2‐vinylfluorene)'s in Solution 1 ‐ Ion Pair Structure and the Concentration Effects of Carbanion Salts Along the Polymer Chain
Authors: Watanabe Akira , Matsuda Minoru
Published: April 2007

Partially metallated polymers of 2‐vinylfluorene in tetrahydrofuran THF and THF‐dimethoxyethane mixtures were studied by electronic absorption spectroscopy. Effects arising from interaction of the ion pairs within the polymer chain were clearly observed. Conversion of the contact ion pairs with lithium and sodium cations into the solvent‐separated ion pairs is influenced by interactions between the solvent‐separated ions pairs. The polymer carbanions with bulky K+ and Cs+ cations exhibited a shift of λ with increasing carbanion concentration, suggesting the formation of an extended polymer chain in solution.
Size Exclusion Chromatography of Poly(ethylene glycol)
Authors: Güven Olgun
Published: April 2007

Size exclusion chromatography calibrations for polystyrene and poly(ethylene glycol) standard samples in the molecular weight range of (600‐11000) have been obtained in tetrahydrofuran. The Kuhn‐Mark‐Houwink‐Sakurada constants of poly(ethylene glycol) in tetrahydrofuran were determined, and poly(ethylene glycol) chromatograms were evaluated according to primary and universal calibration methods. The molecular weights determined from universal curves were substantially lower than those obtained from primary curves. The Coll and Prusinowski universal calibration procedure gave better results than the calibration of Benoit et al.
Synthesis, characterization and curing of m‐diethylaminophenol‐formaldehyde resin
Authors: Patel Pradip S. , Patel Shanti R.
Published: April 2007

Polycondensation of m‐diethylaminophenol with formaldehyde has been studied under various reaction conditions. The resins formed are fusible and soluble in common organic solvents. All the resin samples have been characterized by spectral studies, measurement of solution viscosity, estimation of M̄n and by t.g.a. The curing of selected resin samples by hexamine has been studied both by measuring percentage of cured material as a function of time at different temperatures and by differential scanning calorimetry. The d.s.c. data have been analyzed by various methods to evaluate the gross kinetic parameters of the curing reactions.
Determination of average molecular weights of a polyelectrolyte by meniscus‐depletion sedimentation equilibrium
Authors: Budd Peter M.
Published: April 2007

Long‐column meniscus‐depletion sedimentation equilibrium has been used to determine M̄n, M̄w and M̄z for the Na+ and (CH3)4N+ salts of a high molecular weight poly(styrene sulphonate). Consideration has been given to ways of avoiding the need for dialysis when dealing with polyelectrolyte solutions.
Use of DTA with infrared analysis of evolved gas to investigate the effect of flame retardants on gas evolution from pyrolysed cellulose (cotton)
Authors: Price Dennis , (Dick) Horrocks A. R. , Akalin Mehmet
Published: April 2007

DTA combined with infrared analysis of the evolved gas (EGA) has been used to study the temperature behaviour, both in air and nitrogen, of commercial phosphorus‐ and nitrogen‐ and/or bromine‐containing flame retardants applied to cotton. By reference to the DTA traces and also the maxima occurring in the CO, CO2 and H2O evolution rates, seven significant peak temperatures were assigned. Two new relatively low temperature peaks have been observed: the higher of these is DTA‐sensitive and occurs in all unretarded and retarded samples and is ascribed to the formation of an ‘activated cellulose’ state previously proposed by Bradbury, Sakai and Shafizadeh;17 the lower peak is an exotherm (188‐220°C) associated with H2O and CO2 evolution from flame‐retarded samples only. These observations are interpreted in terms of the mechanism of the cellulose pyrolysis/combustion and the influence of the flame retardants.
Ring‐opening polymerization of 1 ‐ethylbicyclo[2.2.1] hept‐2‐ene
Authors: Hamilton James G. , Ivin Kenneth J. , Rooney John J.
Published: April 2007

1‐Ethylbicyclo[2.2.1]hept‐2‐ene has been polymerized using a range of metathesis catalysts and the structure of the polymers determined by 13C n.m.r. spectroscopy. For a given catalyst the cis double bond content was lower and the head‐tail bias greater than for polymers of the 1‐methyl analogue. This is interpreted in terms of enhanced steric and polar effects brought about by the ethyl substituent.
Thermal behaviour of films of partially neutralized poly(acrylic acid). 3: Effect of magnesium and calcium ions
Authors: Nicholson John W. , Wasson Eleanor A. , Wilson Alan D.
Published: April 2007

Partially neutralized polyacrylates of calcium and magnesium have unexpectedly been found not to undergo thermal decarboxylation at 250°C, unlike partial polyacrylates of lithium, sodium or potassium. Reflectance infrared spectroscopy has confirmed that the partial polyacrylate of calcium is predominantly ionic but as with the magnesium compound, this does not promote decarboxylation. Further study of the partial lithium salt of poly(acrylic acid) has confirmed that lithium ions exhibit some degree of covalency, and hence are probably site‐bound. Despite this, they succeed in promoting decarboxylation. It is concluded that the main factor which prevents calcium and magnesium facilitating decarboxylation is their divalency, rather than any inherent tendency to become site‐bound. Reasons for this are discussed.
Some thermodynamic properties of tetrafluoroethene‐hexafluoropropene copolymers
Authors: Simeone Giovanni , Bonardelli Piergiorgio , Moggi Giovanni , Bart Jan C. J.
Published: April 2007

Copolymers of tetrafluoroethene (TFE) with hexafluoropropene (HFP) have been prepared in the 0‐14mol% HFP composition range. Their melting temperatures (Tm), enthalpies (ΔHf) and entropies (ΔSf) of first and second fusion, and crystallinities (X) according to x‐ray diffraction(x.r.d.) and differential scanning calorimetry (d.s.c.) have been determined. The results indicate that ΔHf/Xx.r.d of the polymer crystals decreases with higher HFP content.
Theoretical and experimental considerations on poly(dihalophenylene oxide)s
Authors: Türker Lemi , Kisakürek Duygu
Published: April 2007

The decomposition of copper(II) trihalophenoxides in acetonitrile yields poly(dihalophenylene oxide)s. A 1H n.m.r. study has shown that a bromine atom in the 4‐position of the trihalophenoxides results in polymers having higher linearity. Various dynamic and static methods, within the framework of Hückel molecular orbital theory, have been used to explain the product distribution.
Metal aerosol jet printing for solar cell metallization
Authors: Mette A. , Richter P. L. , Hörteis M. , Glunz S. W.
Published: April 2007

Metal aerosol jet printing is a new non‐contact direct‐write technique for the front side metallization of highly efficient industrial silicon solar cells. With this technique the first layer of a two‐layer contact structure is created. It features a low contact resistance and good mechanical adhesion to the silicon surface. The second layer is formed by light‐induced silver plating (LIP) to increase the line conductivity. To form the first layer a metal‐containing aerosol is created in the printer and focused via a second surrounding gas stream through a nozzle and deposited onto the substrate. The focussing gas avoids the contact between the aerosol and the nozzle tip. In addition, line widths significantly smaller than the outlet diameter of the nozzle tip can be reached. Fine and continuous lines with a width of 14 µm were printed using a metal organic ink. As the adhesion of these layers was not sufficient, a commercially available screen‐printing paste for solar cell metallization was modified and tested. Monocrystalline silicon solar cells of 12·5 cm × 12·5 cm with an aluminum back surface field were processed, achieving energy conversion efficiencies up to 17·8%. Copyright © 2007 John Wiley & Sons, Ltd.
Structural and electrical properties of Zn(Al)O layers for transparent metal oxide applications
Authors: Kwon Y. B. , Abouzaid M. , Ruterana P. , Je J. H.
Published: April 2007

The microstructure and electrical properties of low temperature (250 °C) RF sputtered Al doped ZnO layers are investigated. By varying the Al composition from 0 to 15 at%, it is shown that the morphology of the layers is improved whereas the crystalline structure changes from highly oriented monocrystalline domains to textured and misoriented nanocrystallites. It is also noticed that the best metallic properties are attained for a quite low Al concentration in the AZO (3 at%), when the Al content is further increased, the mobility, carrier density and resistivity saturate. The annealing in air at higher temperatures does not seem to improve the conduction properties, instead at 800 °C, the resistivity drops by more than one order of magnitude and the carrier density by almost five orders of magnitude. At this high temperature, the strong increase of the mobility is tentatively attributed to the better crystalline quality of the annealed layers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A theoretical investigation of ZnOxS1–x alloy band structure
Authors: Rozale H. , Beldi L. , Bouhafs B. , Ruterana P.
Published: April 2007

We report the properties of ordered ZnOx S1–x alloys calculated in various structures (CuAu–I, Cu3Au, Luzonite and Famatinite) using a first‐principles total‐energy formalism based on the hybrid full‐potential augmented plane‐wave plus local orbitals (APW + lo) method, within the local‐density approximation (LDA). The calculated band gaps of the alloys are direct and range from 0.49 for O‐rich to 1.55 eV for S‐rich ZnOx S1–x . The non linear variation of the band gap energy is related to the large electronegativity difference between O and S. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical properties of zinc oxide films deposited by wire explosion technique
Authors: Snitka Valentinas , Jankauskas Vytenis , Žunda Audrius , Mizariene Vida , Seniunas Gediminas
Published: April 2007

Nanostructured ZnO films were deposited on glass, quartz and Al on silicon mono‐crystal Si (100) substrates by using the wire explosion technique. The growth process, structure and photoluminescence (PL) properties were studied by X‐ray diffraction (XRD), UV–VIS spectroscopy, scanning electron (SEM) and atomic force microscopy (AFM) and photoluminescence measurements. X‐ray diffraction measurements have shown that ZnO films are composed of (100), (002), (101) orientation crystallites. The post‐deposition thermal treatment at 600 °C temperature in air has shown that the composite of Zn/ZnO film was fully oxidized to ZnO film. XRD spectra of the film deposited in oxygen atmosphere at room temperature presents high intensity dominating peak at 2θ = 36.32° corresponding to the (101) ZnO diffraction peak. The small fraction of the film (7%) correspond to (002) peak intensity at 2θ = 34.42°. This result indicates the good crystal quality of the film and hexagonal wurtzite‐type structure deposited by zinc wire explosion. The SEM analysis shows that ZnO films presented different morphologies from fractal network to porous films depending on deposition conditions. AFM analysis revealed the grain size range from 50 to 500 nm. The deposited in air films have shown the weak PL peak at ∼373 nm and a strong green luminescence band. The films deposited in oxygen atmosphere demonstrate increased UV band PL intensity and decreased intensity of green PL band. The obtained PL spectra are similar to powder ZnO and it correlates with the size of ZnO nanoparticles (10–30 nm) measured by AFM. These results demonstrated that the wire explosion technique is a feasible method to produce high‐quality ZnO nanocrystalline thin films and quantum dots. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Involvement of morbilliviruses in the pathogenesis of demyelinating disease
Authors: Sips G. J. , Chesik D. , Glazenburg L. , Wilschut J. , De Keyser J. , Wilczak N.
Published: April 2007

Two members of the morbillivirus genus of the family Paramyxoviridae, canine distemper virus (CDV) and measles virus (MV), are well‐known for their ability to cause a chronic demyelinating disease of the CNS in their natural hosts, dogs and humans, respectively. Both viruses have been studied for their potential involvement in the neuropathogenesis of the human demyelinating disease multiple sclerosis (MS). Recently, three new members of the morbillivirus genus, phocine distemper virus (PDV), porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV), have been discovered. These viruses have also been shown to induce multifocal demyelinating disease in infected animals. This review focuses on morbillivirus‐induced neuropathologies with emphasis on aetiopathogenesis of CNS demyelination. The possible involvement of a morbillivirus in the pathogenesis of multiple sclerosis is discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Automated tether management system for extravehicular activities
Authors: Minor Mark A. , Hirschi Christopher R.
Published: April 2007

Safe extravehicular activity (EVA) requires astronauts to employ tethers to ensure proximity to their spacecraft. This research strives to improve EVA efficiency by allowing crew members to remotely release and retract their safety tether from extended distances using a tether management system consisting of a remotely releasable robotic gripper and a retractor that controls the length of tether. This circumvents the current need to travel back to the tether anchor and manually release the tether, which requires the crew member to travel three times further than necessary. The automated tether management system is essentially a multifunctional teleoperated robotic system that has the potential to improve EVA efficiency, reduce crew‐member fatigue, and improve efficiency of existing robots such as Robonaut. Design and performance requirements are specified to comply with current safety standards. The multifunctional gripper is designed to provide fail‐safe self‐locking positive engagement on a variety of spacecraft anchors. The retractor employs motorized and passive retraction to minimize power consumption, allow the retractor to mimic existing retractable safety tethers functionality, and facilitate control over gripper flight. A nonconductive fiber‐optic core structural tether is designed to transmit commands to the gripper while reducing the risk of developing electrical charges at orbital velocities. Experiments in a simulated microgravity environment evaluate behavior during gripper release and retraction and provide guidelines for improved system operation. Based on these guidelines, the system is then further optimized via simulation for improved retraction considering orbital dynamics. These results provide a recommended operating envelope to allow safe automated gripper retraction. © 2007 Wiley Periodicals, Inc.
Sensor architecture for the robotic control of large flexible space structures
Authors: Bilton Amy , Ishijima Yoshiyuki , Lichter Matthew , Dubowsky Steven
Published: April 2007

The future construction and maintenance of very large space structures such as orbital solar power stations and telescopes will require teams of free‐flying space robots. For robots to effectively perform these tasks, they will require knowledge of the structure's vibrations. Here, a robotic based sensor architecture for the vibration estimation of very large structures is presented. It is shown that this information can be effectively estimated by combining data provided by free‐flying remote robot “observers” equipped with range sensors with structure‐mounted acceleration sensors. A modified Kalman filter fuses low‐bandwidth vision data from the remote sensing robots with the high bandwidth, but spatially sparse structure‐mounted acceleration sensors. Results from experimental studies are presented that confirm the effectiveness of this approach. 2007 Wiley Periodicals, Inc.
Efficient support for content‐aware request distribution and persistent connection in Web clusters
Authors: Liu Ho‐Han , Chiang Mei‐Ling , Wu Men‐Chao
Published: April 2007

To support Web clusters with efficient dispatching mechanisms and policies, we propose a light‐weight TCP connection transfer mechanism, TCP Rebuilding, and use it to develop a content‐aware request dispatching platform, LVS‐CAD, in which the request dispatcher can extract and analyze the content in requests and then dispatch each request by its content or type of service requested. To efficiently support HTTP/1.1 persistent connection in Web clusters, request scheduling should be performed per request rather than per connection. Consequently, multiple TCP Rebuilding, as an extension to normal TCP Rebuilding, is proposed and implemented. On this platform, we also devise fast TCP module handshaking to process the handshaking between clients and the request dispatcher in the IP layer instead of in the TCP layer for faster response times. Furthermore, we also propose content‐aware request distribution policies that consider cache locality and various types of costs for dispatching requests in this platform, which makes the resourceutilization of Web servers more effective. Experimental results of a practical implementation on Linux show that the proposed system, mechanisms, and policies can effectively improve the performance of Web clusters. Copyright © 2007 John Wiley & Sons, Ltd.
Assessing the reliability of the chernobyl shelter
Authors: Sidorenko M. V.
Published: April 2007

The reliability assessment is performed for a highly critical existing structure under lack of information on the actual state of its elements. A non‐standard probabilistic method is adopted: it makes use of “retrospective information”.
Self‐deployable structures with “scissor‐like‐elements”: Problems of simulation and control
Authors: Barsotti A. , de Barbieri F.
Published: April 2007

The scope of the work has been to study the static and dynamic behaviour of deployable or self‐deployable structures composed by rigid elements interconnected by pin‐jointed ends and intermediate pivots, that can be assembled in order to form movable roofing systems or similar applications. Modelling of the behaviour of self‐deployable systems has been approached both during the deployment and in the fully deployed configuration. In particular, the non‐linear dynamic simulation of the deployment phase is approached as a coupled problem of dynamics and kinematics leading to a non‐linear model of the system. The problem of applying active control techniques to the resulting system is also faced, leading to the solution of the non‐linear control problem for the deployment phase, and to a bounded ‐state approach for the in‐service phase. Numerical developments have been performed in the MATLAB environment.
Design and test of a multi‐input multi‐output adaptive active flutter suppression system based on neural network for a wing model
Authors: Rendina M. , Mazzoni G.
Published: April 2007

This paper describes the application of a recurrent dynamic neural network to the problem of adaptive active flutter suppression. A significant feature of the neural controller is its application to an unstable and non‐minimum phase system. The development of the system and its experimental verification are carried out on a wing model with two control surfaces, one on the leading and one at the trailing edge, and two accelerometers. The controller combines a first network for the identification of the variables to be controlled, i.e. the two wing tip accelerations at the leading and trailing edge, with a second network, that commands the deflection required to the control surfaces. It is used for the control task using the output generated by the first network. Adaptivity is obtained by maintaining an on‐line training on both of the neural networks. Extensive preliminary numerical simulations have permitted the authors to define the values of the design parameters aimed at the achievement of an optimal compromise between computational requirements and system performances. The results of the application to the real wing model have shown the effectiveness of such a controller in adapting to different operational conditions, extending flutter free envelope of the wing model up to a speed 30% higher than the uncontrolled flutter onset.
Active vibration control of a monopile offshore structure
Authors: Nielsen S. R. K. , Kirkegaard P. H. , Thesbjerg L.
Published: April 2007

In the Danish part of the North Sea monopile platforms with a cylindrical shaft have been used at the exploitation of marginal fields. In the paper a new principle for active vibration control of such structures is suggested. The principle is based on a control of the boundary layer flow around the cylinder of the platform, so the drag force in the generalized Morison equation is increased whenever it is acting in the opposite direction of the cylinder motion, whereas an unchanged drag force is applied, whenever it is acting co‐directionally to the cylinder motion. The inertial force of the wave load is not subjected to control. The increased drag force is obtained by forcing the boundary layers to separate by blowing air into the boundary layer from the inside through small holes in the cylinder surface placed at a relatively large distance from the water surface. The control is specified by the sign of the fluid velocity relative to the platform, and only this quantity need to be measured, which is easily performed by a flow meter fixed to the platform. The efficiency of the described closed loop control system has been verified by model tests in a wave flume in both regular and irregular wave conditions, where reductions in the vibration level of up to 50% have been registered.
Some experiences on vibrations and noise suppression with piezoelectric active control systems
Authors: Ghiringhelli Gian Luca
Published: April 2007

In this paper a research activity, aimed at verifying the possibility of designing active vibration control systems based on piezoelectric devices, is reported. A full analogic controller has been developed to suppress the vibrations in a clamped rectangular flat panel using piezoceramic patches. Vibration reduction tests and their correlations to numerical predictions, based on an integrated piezo‐structural model, are presented. Only simple co‐located direct feed‐back laws have been used to point out problems related to measurements. Self sensing actuators were also tested. The correlation with numerical prediction shows that the adopted approach is capable of supplying a suitable design tool.
Distributed sensor for detection of impending structural failure along a 25km optical fibre with 2 metres spatial resolution
Authors: Lecœuche V. , Webb D. J. , Pannell C. N. , Jackson D. A.
Published: April 2007

We describe an experimental set‐up designed for detection of impending structural failure in large‐scale structures such as bridges or dams. Strain applied on any 2 metres section along a 25km standard telecommunication fibre can be detected. We demonstrate sufficient signal to noise ratio with a very limited number of acquisitions, which could be performed in less than 3 seconds with custom‐build electronics. All electrical instrumentation is located on one end of the sensing fibre, permitting an easy installation.
Serial multiplexing of optical fibers for sensing of structural strains
Authors: Chen Z. , Li Q. , Ansari F. , Mendez A.
Published: April 2007

Condition Monitoring of civil structures is best accomplished by way of distributed sensors. Sensors capable of making distributed measurements allow for monitoring the entire structure. Optical fiber sensors are especially very attractive for this purpose, since they are geometrically versatile and they can be readily integrated within various types of structures and materials. The research presented here describes the development of a new optical fiber sensor system for measurement of structural strains based on white light interferometry. Individual sensors are linked in series and an optical switch provides for multiplexing of strain signals from various locations in the structure. Bragg grating type fiber optic sensors as well as strain gauges were employed for comparison and verification of strain signals as measured by the new system. The system provides capability for distributed sensing of strains in large structures.
Limiting control possibilities of multi‐mass flexible structures
Authors: Balandin D.
Published: April 2007

The limiting control possibilities of multi‐mass flexible systems subjected to disturbances from a certain class are studied. A general method of estimating these possibilities is suggested. This method is discussed for the systems described by the ordinary differential equations. The relationship between estimating limiting control possibilities and calculating optimal control with respect to a criterion of minimal guaranteed result is discussed. The mathematical models presented in this paper can be applied to a wide class of actual flexible systems, in particular, to buildings and structures under seismic or wind loads.
Nonlinear analysis of stochastic stability problems
Authors: Griesbaum R. , Wedig W.
Published: April 2007

For stability investigations of elastic structures subjected to parametric excitations by white noise we follow Khas'minskii's concept introducing projections on unit hyperspheres which separate all stationary solutions of the linear systems from their instationary part. The projection processes are investigated by Monte‐Carlo simulations and by Fourier expansions of the associated Fokker‐Planck equations in order to obtain the invariant measures of the systems and corresponding top Lyapunov exponents.
Numerical methods for the control of flexible structures extended abstract of briffaut's thesis
Authors: Bourquin F.
Published: April 2007

This paper is an extended abstract of the thesis of J.‐S. Briffaut. It treats the active control of flexible structures. In the first part the design of open‐loop control laws for beams is considered. In the second the implementation of Komornik's full state feed‐back law. In the third and fourth numerical results for the control of frames made of beams under bending and traction‐compression.
Active control in civil engineering: From conception to full scale applications
Authors: Aupérin M. , Dumoulin C. , Magonette G. E. , Marazzi F. , Försterling H. , Bonefeld R. , Hooper A. , Jenner A. G.
Published: April 2007

An active tendon control system for civil engineering cable‐supported structures is proposed. The technique is based on a tendon actuator collocated with a force sensor. A large‐scale mock‐up using industrial components has been built and widely tested. The test‐bed is a model of cable‐stayed bridge during its construction phase, equipped with hydraulic actuators on the two longest stay‐cables. The results of several damping experiences are presented; they clearly demonstrate the efficiency of the active damping system. The proposed technology is directly applicable to real structures by scaling up the devices.
Asymptotics of forced vibrations of bases, foundations and seismoisolators
Authors: Aghalovyan L. A. , Gevorgyan R. S. , Sahakyan A. V. , Aghalovyan M. L.
Published: April 2007

Vibrations of plate‐like bases, foundations and seismoisolators caused, in particular, by seismic loading are studied. Asymptotic solutions of relevant dynamic equations of elasticity theory are constructed. Resonance conditions are derived, ways to avoid hazardous resonances are discussed.
Seismic control of regular and irregular buildings using viscoelastic passive dampers
Authors: Sophocleous A. A.
Published: April 2007

This paper illustrates the vibration control effectiveness of passive viscoelastic dampers for regular or irregular structures. Its optimum installation location is determined from the controlled mode shape values and the optimal system parameters of the viscoelastic passive dampers are evaluated by minimizing the modal displacement response and maximizing the damping energy dissipation capacity between the structure with and the structure without the dampers. The analytical results of the parametric investigation show that the seismic response of regular or irregular structures are greatly improved by using viscoelastic dampers, leading to an alternative method of strengthening compared to the traditional rehabilitation techniques.
A PET study of effects of chronic 3,4‐methylenedioxymethamphetamine (MDMA, “ecstasy”) on serotonin markers in Göttingen minipig brain
Authors: Cumming Paul , Møller Mette , Benda Kjeld , Minuzzi Luciano , Jakobsen Steen , Jensen Svend B. , Pakkenberg Bente , Stark Anette K. , Gramsbergen Jan Bert , Andreasen Mette F. , Olsen Aage K.
Published: April 2007

The psychostimulant 3,4‐methylendioxymethamphetamine (MDMA, “ecstasy”) evokes degeneration of telencephalic serotonin innervations in rodents, nonhuman primates, and human recreational drug users. However, there has been no alternative to nonhuman primates for studies of the cognitive and neurochemical consequences of serotonin depletion in a large‐bodied animal. Therefore, we used positron emission tomography (PET) with [11C]DASB to map the distribution of plasma membrane serotonin transporters in brain of Göttingen minipigs, first in a baseline condition, and again at 2 weeks after treatment with MDMA (i.m.), administered at a range of doses. In parallel PET studies, [11C]WAY‐100635 was used to map the distribution of serotonin 5HT1A receptors. The acute MDMA treatment in awake pigs evoked 1°C of hyperthermia. MDMA at total doses greater than 20 mg/kg administered over 2–4 days reduced the binding potential (pB) of [11C]DASB for serotonin transporters in porcine brain. A mean total dose of 42 mg/kg MDMA in four animals evoked a mean 32% decrease in [11C]DASB pB in mesencephalon and diencephalon, and a mean 53% decrease in telencephalic structures. However, this depletion of serotonin innervations was not associated with consistent alterations in the binding of [11C]WAY‐100635 to serotonin 5HT1A receptors. Stereological cell counting of serotonin‐positive neurons, which numbered 95,000 in the dorsal raphé nucleus of normal animals, was unaffected in MDMA‐treated group. group. Synapse 61:478–487, 2007. © 2007 Wiley‐Liss, Inc.