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Showing papers by "Brunel University London published in 1983"


Journal ArticleDOI
TL;DR: Experimental elastic moduli of the pure vitreous inorganic oxides SiO2, GeO 2, P2O5, B2O3, and As2O 3 were compared with simple theoretical models of elastic deformation involving the use of available estimates for the anioncation (first order) stretching force constants.
Abstract: Experimental elastic moduli of the pure vitreous inorganic oxides SiO2, GeO2, P2O5, B2O3, and As2O3, are compared with simple theoretical models of elastic deformation involving the use of available estimates for the anion-cation (first order) stretching force constants. On the basis of this comparison it is concluded that all of these glasses are essentially three-dimensionally-connected ring structures: the average ring size, in each case, being similar to the sizes found in corresponding crystalline forms of these oxides. Les modules experimentals elastiques des oxydes inorganiques purs et vitreux, SiO2, GeO2, P2O5, B2O3, et As2O3, sont consideres par comparaison avec les modeles, simples et theoriques, de la deformation elastique, qui enveloppent les evaluations dont on dispose pour les constants, de premier ordre des forces d'elongation. Par suite de cette comparaison, on conclut que tous ces verres sont essentiellement en forme de structures circulaire en trois dimensions: la dimension moyenne des cercles est pareil aux dimensions qu'existent dans les formes cristallines de ces oxydes.

245 citations


Journal ArticleDOI
TL;DR: The results give the first clear picture of the interrelationships between some of the major hormones known to be involved in salmonid reproduction and provide further evidence for the important role of 17 alpha-hydroxy-20 beta-dihydroprogesterone in the processes of oocyte maturation and ovulation.

230 citations


Journal ArticleDOI
TL;DR: The annual profile of steroids and of vitellogenin, and the relationships between these parameters, were similar in the two strains, except that most changes occurred 2 months later in the winter-spawning strain than they did in the autumn- spawning strain.

156 citations


Book ChapterDOI
01 Jan 1983
TL;DR: Vitamin E and total lipid-soluble, chain-breaking antioxidant concentrations in some normal and cancerous tissues have been measured and a number of unresolved problems relating to the action of vitamin E in vivo are discussed.
Abstract: Measurements of the absolute rate constants for the reaction with peroxyl radicals of alpha, beta, gamma and delta-tocopherol and several model compounds are described. The peroxyl radicals were obtained either by the autoxidation of styrene or by the flash photolysis of di-t-butyl ketone in an oxygen-saturated environment. The kinetic data are discussed in stereoelectronic terms. Vitamin E and total lipid-soluble, chain-breaking antioxidant concentrations in some normal and cancerous tissues have been measured. In human blood plasma and erythrocyte ghost membranes vitamin E is the major, and possibly the only, chain-breaking antioxidant. Lipid extracts of Novikoff ascites hepatoma cells contain considerably more vitamin E relative to lipid than do extracts of normal rat liver. These tumour lipids contain relatively fewer highly unsaturated fatty acids and are present at lower lipid/wet tissue ratios than the normal liver lipids. A number of unresolved problems relating to the action of vitamin E in vivo are discussed.

142 citations


Journal ArticleDOI
TL;DR: It is suggested that the noradrenergic system may be involved in the expression of extinction behavior by a role in selective attention, the dopamine system via an involvement with secondary reinforcement, the cholinergic system by a mechanism of response inhibition and the barbiturates and benzodiazepines by a block of nonreward.

81 citations


Journal ArticleDOI
TL;DR: In this article, the enhancement of Misonidazole radiosensitization by an inhibitor of Glutathione Biosynthesis was discussed, and the effects of the inhibitor on the Glutathi biosynthesis were investigated.
Abstract: (1983). Enhancement of Misonidazole Radiosensitization by an Inhibitor of Glutathione Biosynthesis. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine: Vol. 43, No. 2, pp. 179-183.

78 citations


Journal ArticleDOI
TL;DR: The absolute rates of reaction of the trichloromethylperoxy radical derived from carbon tetrachloride and the halothane peroxy radical with oleic, linoleic, Linolenic and arachidonic acids have been determined using the fast reaction technique of pulse radiolysis.

73 citations


Journal ArticleDOI
TL;DR: The sulphur-containing drugs, metiazinic acid, piroxicam, penicillamine and sulindac as well as the indole derivative indomethacin, protect the virus from inactivation by the model peroxy radical CC13O2.

67 citations


Journal ArticleDOI
TL;DR: In this article, three different pipe-grade polyethylenes, in the form of one large and three small diameter pipe systems, have been tested at elevated temperatures, using constant and fluctuating internal pressure loadings that resulted in brittle fractures.
Abstract: Three different pipe-grade polyethylenes, in the form of one large and three small diameter pipe systems, have been tested at elevated temperatures, using constant and fluctuating internal pressure loadings that resulted in brittle fractures. The behaviour under fatigue of two of the three types of small diameter polyethylene pipes was substantially described by a cumulative damage model, whilst the third exhibited a fatigue weakness, an observation not previously reported. The performance of the large diameter pipes under fatigue was dominated by the presence of large voids in the pipe wall that arose from incorrect processing and resulted in premature failure. The sites of crack initiation in one material grade of the small diameter systems were examined in detail. In particular the size, position and composition of particles initiating fracture were determined. The maximum particle size on the fracture surface of the pipe was found to correlate reasonably well with a measure of pipe lifetime, as predicted by a fracture mechanics approach, and indicated that the lifetime of this one type of polyethylene pipe was dependent on the size of the inclusions initiating fracture.

64 citations


Book ChapterDOI
01 Jan 1983
TL;DR: The possibility that in vivo these compounds may sometimes act synergistically is discussed in the light of recent information on hydrogen atom and electron transfer reactions and the long-established findings that vitamin C can augment the antioxidant action of vitamin E whereas iron salts can have a deleterious effect as discussed by the authors.
Abstract: There is increasing evidence that as a result of infection or the action of toxic chemicals or radiation, the body may be continuously exposed to the damaging action of free radicals. While previous results have suggested that zinc may be involved in limiting the formation of these highly reactive species, natural organic antioxidants such as vitamin E may also play an important role in reducing their effect. Recent results showing quantitative and qualitative differences in the free radical reactivity of vitamin E, vitamin C, beta-carotene and glutathione are reported. The possibility that in vivo these compounds may sometimes act synergistically is discussed in the light of recent information on hydrogen atom and electron transfer reactions and the long-established findings that vitamin C can augment the antioxidant action of vitamin E whereas iron salts can have a deleterious effect.

55 citations


Journal ArticleDOI
TL;DR: In this article, the fundamental absorption edges of some samples of V2O5-P2O-5 and V2 O 5-P 2O 5-TeO2 glasses were measured in the short wavelength part of the visible region, and it was found that their fundamental absorption is dependent on composition and arises from direct forbidden transitions and occurs at a photon energy in the range 1.9 to 2.6 eV, depending on composition.
Abstract: The fundamental absorption edges of some samples of V2O5-P2O5 and V2O5-P2O5-TeO2 glasses were measured in the short wavelength part of the visible region, and it was found that the fundamental absorption of these glasses is dependent on composition and arises from direct forbidden transitions and occurs at a photon energy in the range 1.9 to 2.6 eV, depending on composition.

Journal ArticleDOI
TL;DR: Cell viability measurements show that halothane metabolism in both hypoxic and aerobic conditions can lead to cell death, and oxidative lipid damage could be a cause of cell damage, as judged by cell viability, additional to covalent binding.


Journal ArticleDOI
TL;DR: In this article, the solvent extract of the outer green shell of the pistachio nut, Pistachia vera, was found to contain a mixture of phenolic acids.

Journal ArticleDOI
04 Aug 1983-Nature
TL;DR: It is reported here that both the lower threshold of motion and adaptation to motion are uniform for M-scaled stimuli, and are related to the velocity of the ‘cortical image’.
Abstract: Recent studies have revealed some remarkably simple relationships between visual performance and the neuroanatomy of the visual pathways. The visual field is mapped topographically on the surface of the striate cortex in man; the projection is large for the central visual field and is progressively compressed towards the periphery. Visual acuity decreases with distance from the fovea in proportion to the estimated cortical magnification factor, M (the extent of striate cortex in millimetres corresponding to a degree of arc in visual space). If a stimulus is magnified at peripheral locations in proportion to 1/M, it becomes equally resolvable across the visual field. This scaling procedure (M-scaling) maintains equivalence of the cortical projection of stimuli with different visual field loci. We have used M-scaling to investigate motion perception as a visual field variable. We report here that both the lower threshold of motion and adaptation to motion are uniform for M-scaled stimuli, and are related to the velocity of the 'cortical image'.


Journal ArticleDOI
TL;DR: Evidence is presented that this resulted from iron catalysed decomposition of the lipid hydroperoxide, and suggests a role for free iron or iron chelates in the propagation of lipid peroxidation stimulated by other systems.
Abstract: SummaryThe generation of hydroxyl free radicals in 60Co γ-irradiation of a dilute aqueous suspension of phosphatidyl choline liposomes, resulted in the rapid accumulation of lipid hydroperoxides (linearly with time), but only small concentrations of malondialdehyde. Incubation of the irradiated liposomes with ferric chloride was found to significantly increase the malondialdehyde, and evidence is presented that this resulted from iron catalysed decomposition of the lipid hydroperoxide. This suggests a role for free iron or iron chelates in the propagation of lipid peroxidation stimulated by other systems.

Journal ArticleDOI
TL;DR: Micromorphologie d'un copolyester d'acide paracetoxybenzoique et d'acetoxynaphtalique par diffraction RX et microscopie electronique a balayage.
Abstract: Micromorphologie d'un copolyester d'acide paracetoxybenzoique et d'acide acetoxynaphtalique par diffraction RX et microscopie electronique a balayage

Journal ArticleDOI
TL;DR: In this paper, the formation of CdSnO3 and Cd2SnO4 from closed vessels was studied over a range of temperature by thermal analysis, X-ray powder diffraction and electron spectroscopy.
Abstract: The formation of CdSnO3 and Cd2SnO4 from cadmium and tin oxides in closed vessels was studied over a range of temperature by thermal analysis, X-ray powder diffraction and electron spectroscopy. The results, presented in diagrammatic form, enable suitable reaction conditions to be chosen for the formation of either stannate in the monophase form. ESCA and SIMS examination of the reactants and products indicates that the commercial CdO starting material contains small amounts of carbonate and suboxide impurities, which however have no effect on the formation of the final product. Electron spectroscopy also indicates that the cadmium stannates, once formed, are significantly more resistant to atmospheric carbonation or hydration than is the parent CdO.

Journal ArticleDOI
TL;DR: The n-tuple recognition net is seen as a building brick of a progression of network structures and the emergent 'intelligent' properties of such systems are discussed.

Journal ArticleDOI
TL;DR: In this paper, a numerical method based on the integral equation formulation of Symm is described for computing approximations to the mapping functions which accomplish the following conformal maps: (a) the mapping of a domain interior to a closed Jordan curve onto the interior of the unit disc, (b) mapping of an exterior domain exterior to closed Jordan curves onto the exterior of a unit disc.
Abstract: A numerical method, based on the integral equation formulation of Symm, is described for computing approximations to the mapping functions which accomplish the following conformal maps: (a) the mapping of a domain interior to a closed Jordan curve onto the interior of the unit disc, (b) the mapping of a domain exterior to a closed Jordan curve onto the exterior of the unit disc, (c) the mapping of a doubly-connected domain bounded by two closed Jordan curves onto a circular annulus. The numerical method is based on approximating the unknown source density by cubic splines and "singular" functions, and is particularly suited for the mapping of difficult domains having sharp corners.

Journal ArticleDOI
01 Jun 1983-Wear
TL;DR: Pins of aluminium, Al-16%Si and Al 16%Si-1%Cu were rubbed against a steel disc (1%C-1.5%Cr) in the oxidative (mild) region and the wear surfaces were studied using electron spectroscopy.

Journal ArticleDOI
01 Jan 1983
TL;DR: In this article, a novel fluorescence procedure has been used to study the binding characteristics of DNA with three modern fluorochromes currently used in chromosome cytochemistry, i.e., ethidium bromide, berberine sulphate and quinacrine mustard.
Abstract: A novel fluorescence procedure has been used to study the binding characteristics of DNA with three modern fluorochromes currently used in chromosome cytochemistry. The transient changes in the polarised components of fluorescence have been recorded for dye-tagged DNA solutions when subjected to short duration electric pulses. From these data, it has been inferred that, like ethidium bromide, berberine sulphate and quinacrine mustard both intercalate the DNA structure whilst the bi-benzimidazole derivative Hoechst 33258 binds with a distinctively different geometry, probably within the helical grooves.

Journal ArticleDOI
TL;DR: The midsagittal plane of the human thorax is represented by a two-dimensional finite-element model and Interpretations in terms of current density show that variations of bone conductivity have little influence on the fields.
Abstract: The midsagittal plane of the human thorax is represented by a two-dimensional finite-element model. Solutions of steady-state potential fields of bipolar epidural stimulation are computer generated. Effects of biological tissue conductivity and geometry on the fields are studied. Interpretations in terms of current density show that variations of bone conductivity have little influence on the fields. For constant current stimulation, the presence of the tough dura mater, irrespective of its thickness, does not seem to be significant. In contrast, the crucial factor affecting the field is the width of subarachnoid space which contains the highly conductive cerebrospinal fluid.

Book ChapterDOI
TL;DR: A review of the early history of work on hydrogen spillover during the decade 1960-1970 can be found in this paper, where a summary of the present state of knowledge of the phenomenon is presented.
Abstract: After a short review of the early history of work on hydrogen spillover during the decade 1960–1970, this paper presents a summary of the present state of knowledge of the phenomenon. Its effects are classified in terms of the nature of the hydrogen acceptor: (i) irreducible oxides, (ii) partially reducible oxides and related systems, (iii) oxides capable of forming hydrogen bronzes, (iv) reducible oxides not forming bronzes, and (v) carbon. The reversibility of hydrogen spillover is then briefly treated, and rate effects discussed in terms of the movement of mobile species across the various phase boundaries present in typical systems. Finally there is a short assessment of the possible importance of spillover during normal catalysed processing. The need for further systematic studies (e.g. on the effect of metal dispersion) and the wider use of isotopic tracer methods is strongly urged.

Journal ArticleDOI
TL;DR: In this paper, the pituitary gland of the rainbow trout was radioimmunoassayed for alpha-melanocyte-stimulating hormone (α-MSH), β-msH, adrenocorticotrophin (ACTH), and endorphin.

Journal ArticleDOI
TL;DR: It is concluded that TEA may have a direct post-synaptic action, in addition to releasing ACh from the presynaptic nerve terminals, which produces more contracture tension than does ACh for a given level of membrane depolarization.

Journal ArticleDOI
TL;DR: The role of iron(III) picolinate as a possible intracellular catalyst of the Haber-Weiss reaction was discussed in this paper, where it was found to enhance the rate of formation of hydroxyl radicals.

Journal ArticleDOI
TL;DR: In this paper, an operational system composed of a number of independent but similar units is described and a maintenance float is provided to ensure that a given number N must be in service and to ensure this, a float comprises units under repair and in an equipment reserve.
Abstract: This paper describes an operational system composed of a number of independent but similar units. A given number N must be in service and to ensure this a maintenance float is provided. The float comprises units under repair and in an equipment reserve. Float factors are estimated using a Weibull distribution for failures and a log-normal function for repairs. Both functions are applied to an engineering case study and the estimated float levels are compared with a simulation of the field data. Optimum float levels are developed using a simple cost model.

Journal ArticleDOI
TL;DR: Methyl α-chloro-α-phenylthio acetate (α-CHI) as mentioned in this paper regiospecifically alkylates O-silylated enolates to form γ-keto esters.