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Showing papers by "Brunel University London published in 1974"


Journal ArticleDOI
TL;DR: It is concluded that the nitro-group plays a major role in metronidazole action and that at least four mechanisms may be operative under hypoxic conditions.
Abstract: SummaryRadiation biochemical and bacterial studies have been undertaken to investigate possible mechanisms of radiosensitization by metronidazole. It is concluded that the nitro-group plays a major role in its action and that at least four mechanisms may be operative under hypoxic conditions.(i) enzyme-catalysed depletion of nucleophiles,(ii) fixation of organic radicals,(iii) interference with recombination reactions,(iv) formation of toxic products.

95 citations


Journal ArticleDOI
22 Nov 1974-Nature
TL;DR: The protective effect of the nucleophilic compound, cysteamine, has been attributed to its ability to scavenge these species thereby preventing their reaction or to reduce chemically the free radical lesion thereby resulting in its repair.
Abstract: THE lethal action of ionising radiation or alkylating drugs is thought to involve the formation of electrophilic species (many of which are free radical in nature) which interact with essential molecules such as nucleic acid. The protective effect of the nucleophilic compound, cysteamine, has been attributed to its ability, first, to scavenge these species thereby preventing their reaction or, second, to reduce chemically the free radical lesion thereby resulting in its repair1,2. A similar mechanism has been postulated to explain the protective effect of promethazine against carbon tetrachloride-induced liver damage3,4.

89 citations


Journal ArticleDOI
TL;DR: In this article, a study was made of the kinetics of the reduction of molybdenum trioxide by hydrogen in the temperature range 480-600 °C, and the subsequent reduction of the dioxide to metal in the range 650-800 °C.
Abstract: A study has been made of the kinetics of the reduction of molybdenum trioxide to molybdenum dioxide by hydrogen in the temperature range 480–600 °C, and the subsequent reduction of the dioxide to molybdenum metal in the range 650–800 °C. The activation energies, E , and frequency factors, A , found for a sample of sublimed molybdenum trioxide were: MoO 3 + H 2 → MoO 2 + H 2 O E = 113 kJ mol −1 , A = 4.2 × 10 −1 s −1 , MoO 2 + 2H 2 → Mo + 2H 2 O E = 98.6 kJ mol −1 , A = 2.2 × 10 −2 s −1 , The reduction of the trioxide follows a linear rate equation and an explanation of this somewhat unusual result is presented. However, reduction of the dioxide to the metal followed the more usual deceleratory path characteristic of the contracting sphere model. The results obtained in the present work are compared with the results of previous investigations.

64 citations


Journal ArticleDOI
TL;DR: In this article, a Taylor's expansion in space and time dimensions is used to solve the moving boundary problem in a grid system, and a practical diffusion problem is solved and the results are compared with those obtained from other methods.

37 citations


Journal ArticleDOI
TL;DR: The effect of interstimulus interval (ISI) variation on the acquisition of a classically conditioned emotional response was investigated using a one-trial conditioning procedure and control groups demonstrated that conditioning was not a function of either pseudoconditioning, sensitization or stimulus novelty.
Abstract: The effect of interstimulus interval (ISI) variation on the acquisition of a classically conditioned emotional response was investigated using a one-trial conditioning procedure. The optimum ISI was found to be 10 s with a bidirectional gradient for conditioned suppression at ISI above and below 10 s. Control groups demonstrated that conditioning was not a function of either pseudoconditioning, sensitization or stimulus novelty.

30 citations


Journal ArticleDOI
TL;DR: In this paper, a procedure for the design of an observer of reduced order, with arbitrary dynamics, to provide an estimate of a single linear functional of the state vector of a linear system, is extended to the case in which a number of linear functionals are required.
Abstract: A procedure [1] for the design of an observer of reduced order, with arbitrary dynamics, to provide an estimate of a single linear functional of the state vector of a linear system, is extended to the case in which a number of linear functionals are required.

29 citations


Journal ArticleDOI
TL;DR: In this paper, values of the nitrogen BET specific surface areas calculated from data supplied by many laboratories on four currently available surface area standards are presented and compared, and analytical data, representative adsorption isotherms and typical BET plots are given.
Abstract: Values of the nitrogen BET specific surface areas calculated from data supplied by many laboratories on four currently available surface area standards are presented and compared. Analytical data, representative adsorption isotherms and typical BET plots are given. Various factors affecting the accuracy of nitrogen BET surface area measurements are summarised.

28 citations


Journal ArticleDOI
TL;DR: In this article, the reduction of molybdenum trioxide by hydrogen is catalysed by mechanically admixed supported palladium catalysts; the process has been followed by differential thermal analysis and by thermogravimetry.
Abstract: The reduction of molybdenum trioxide by hydrogen is catalysed by mechanically admixed supported palladium catalysts; the process has been followed by differential thermal analysis and by thermogravimetry. An oxide approximating to Mo 2 O 5 is formed by dehydration of a hydrogen molybdenum bronze below 300 °C; characterisation of this and other products has been attempted using e.s.r. and i.r. spectroscopy, and X-ray diffraction.

28 citations


Journal ArticleDOI
TL;DR: Circadian flight activity in the males and females of Anopheles gambiae Giles species A and B, A. melas (Theo.) and A. merus Don has been investigated using the acoustic actograph technique.
Abstract: Circadian flight activity in the males and females of Anopheles gambiae Giles species A and B, A. melas (Theo.) and A. merus Don. has been investigated using the acoustic actograph technique. In each species the pattern and timing of activity in males and females is almost identical. Cyclical activity continues in constant dark; the period of the cycle is approximately half-an-hour shorter in A. gambiae species A and half-an-hour longer in A. merus than in the other two species. In alternating 12 h light: 12 h dark, both sexes are active during the dark period, with peaks of activity following light-off and light-on. After light-off, the species become active in the following order: A. gambiae species A, A. melas, A. gambiae species B, A. merus. A. merus is approximately 20 min later than species A.

27 citations


Journal ArticleDOI
01 Oct 1974
TL;DR: In this article, the electrical properties of E. coli were characterized by predominant permanent dipole moments across and predominant induced dipoles along their major axis, and the induced moments were better accounted for in terms of a Maxwell-Wagner type of surface polarization rather than a bulk polarization process.
Abstract: E. coli is a short rod-like bacterium which, in aqueous suspension, scatters visible light in such a way that peaks are encountered in the angular scattering diagram. With a polydisperse sample this fine structure is lost. Because of this, it has been possible to make meaningful interpretation of the measurements of the changes in the scattered light when the suspensions were subjected to either pulsed or continuous direct current and alternating current electric fields. Apart from indicating particle size, the electrical properties of the bacteria were revealed. The bacteria were characterized by predominant permanent dipole moments across and predominant induced dipoles along their major axis. The induced moments seem to be better accounted for in terms of a Maxwell-Wagner type of surface polarization rather than a bulk polarization process. These electrical properties are compared with the results of other workers.

24 citations



Journal ArticleDOI
TL;DR: In this article, the authors studied diamond-pyramid indentations, made with loads of 1 to 100 g at room temperature on {111, {110} and {112} faces of germanium crystals, by scanning electron microscopy.
Abstract: Diamond-pyramid indentations, made with loads of 1 to 100 g at room temperature on {111}, {110} and {112} faces of germanium crystals, were studied by scanning electron microscopy. The Vickers-hardness number, which was highest for {111} faces, increased with the square root of the load by a factor of about 10 on any given surface, ranging from values as low as 60 to about 850, the latter corresponding to the VHN reported in the literature. The lengths of major cracks, generally seen on the surface of the crystal as an extension of the indentation diagonals, were found to be proportional tod-d 0, whered 0, equal to about 3 μm, represents a lower limiting value of the indentation diagonald, below which cracks do not seem to form. The increase of the VHN and of the crack-lengths with load is explained in terms of a tentative model involving the formation and the stress-induced growth of laminar “plastic” patches in a volume surrounding the indentation.

Journal ArticleDOI
TL;DR: It is suggested that bile flow in the rat is seriously affected by disturbances to the canalicular membrane, and preliminary biochemical investigations of these disturbances are reported here.
Abstract: An isolated perfused rat liver preparation has been developed to aid the study of the mechanisms underlying the secretion of bile and the cholestatic actions of two naturally occurring agents, icterogenin and sporidesmin. The perfused liver produced bile for 3-5 h at a steady rate slightly above that observed in intact rats possessing external biliary cannulae. During this period of perfusion detailed biochemical and physiological studies on the behaviour of the liver were carried out. Morphological examination of the livers after several hours of perfusion was performed by means of electron microscopy and quantitative analysis of the pictures for certain structural elements has been performed. The addition of ethanol (final concentration 27 mM) to control perfusion had no significant effect on bile flow or liver morphology except that there was a decrease in the numbers of multi- and mono-vesicular bodies and in their relative proportions in the cytoplasm. There was a large though transient increase in perfusate lactate to pyruvate ratio and a sharp fall in the perfusate pH. Sporidesmin (2 mg in ethanol-buffer solution) rapidly decreased bile flow, and retarded the increase in the lactate to pyruvate ratio and the decrease in the pH of the perfusate seen in ethanol controls. Electron micrographs of the livers following sporidesmin administration showed large regions of the bile canaliculi devoid of microvilli and there was the appearance in the cytoplasm of lysosomal-like structures containing numerous glycogen granules. Icterogenin (4 mg in ethanol-buffer solution) produced a rapid cholestasis, inhibited the changes in the lactate to pyruvate ratio and the perfusate pH seen in the ethanol control preparations. Electron micrographs of the icterogenin-treated livers revealed changes in the canalicular membrane, extrusion of material into the canalicular lumen and aggregation of lysosomes in the cytoplasm. These studies suggest that bile flow in the rat is seriously affected by disturbances to the canalicular membrane, and preliminary biochemical investigations of these disturbances are reported here.


Journal ArticleDOI
TL;DR: In this paper, a co-evaporated thin films of SiO and BaO were used as the insulator material in MIM and MIMIM structures, where the metal M was Al, Ag or Cu.

Journal ArticleDOI
01 Apr 1974-Wear
TL;DR: In this article, the friction and wear characteristics of grey cast iron, aluminium bronze and phosphor bronze rubbing against channel type and conventionally ground surfaces of chromium plating were studied.

Journal ArticleDOI
TL;DR: Measurements of the apical body in virgin male flies show that mated males have thinner apical bodies than virgin males of the same age, but individual deviations from this relation were considerable.
Abstract: The male accessory glands of Glossina austeni Newst. contain an apical secretion—a dense, opaque, whitish secretion at the apical end of the gland, and a diffuse secretion—a bulkier, more mobile, translucent, whitish secretion occupying nearly all the remainder of the gland. There is also a plug of clear solidified accessory material preventing the outflow of secretions from the resting gland. By immersing the whole accessory gland in a saline medium at pH 2·2, and then transferring the specimen to distilled water, the apical secretion can be separated manually from the rest of the gland, as an apical body. Measurements of the apical body in virgin male flies show that the apical body increases in width according to the equation: Age ≐ constant Χ width 2.5 , but individual deviations from this relation were considerable. Immediately after mating the apical body is long and thin; recovery to approximately the resting condition is complete after 48 h, but, on average, mated males have thinner apical bodies than virgin males of the same age. The use of apical secretion measurements to assess mating frequency under field conditions might be possible if adequate samples of males were available.

Journal ArticleDOI
TL;DR: Pulse radiolysis data show that metronidazole reacts rapidly with ·CH2OH, ·CMe2OH and ·CO2H; the spectrum of an intermediate in these reactions is attributed to the metronidsazole radical-anion.
Abstract: SummaryThe rates of reaction of ‘metronidazole’ [1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole] with e−aq, ·OH, ·CO−2, ·CH2OH, ·CHMeOH and ·CMe2OH have been measured by pulse radiolysis.E.s.r. data also show that metronidazole reacts rapidly with ·CH2OH, ·CMe2OH and ·CO2H; the spectrum of an intermediate in these reactions is attributed to the metronidazole radical-anion.

Journal ArticleDOI
01 May 1974-Nature
TL;DR: In this article, the major dimension of a particle of the order of the wavelength (λ) of the light incident on the system was measured using the Rayleigh-Gans-Debye (RGD) scattering theory.
Abstract: THE light scattering method is an accepted procedure for the measurement of the molecular weight (M) and the size of macromolecules in solution. This information is most readily available for particles the major dimension (ζ) of which is of the order of the wavelength (λ) of the light incident on the system. Provided that they are not too optically dense, such particles satisfy the conditions and are described in terms of the Rayleigh–Gans–Debye1,2 (RGD) scattering theory. In this equation, m is the ratio of the refractive index (n) of the solute to that of the solvent (n0).

Journal ArticleDOI
01 Nov 1974-Nature
TL;DR: In this article, the first realisation of laser-induced changes in the orientation of macromolecules and particles in a liquid medium was reported, and the effects accompanied particle orientation rather than local heating or refractive index changes.
Abstract: WE report here the first realisation of laser-induced changes in the orientation of macromolecules and particles in a liquid medium. We give preliminary data on the induced birefringence of two, very dilute, macromolecular suspensions; and we show that the effects accompany particle orientation rather than local heating or refractive index changes, and that they therefore indicate the foundation of a new method for characterising macromolecules.

Journal ArticleDOI
TL;DR: The increased rate of protein synthesis by the liver appeared to compensate for the increased loss of protein into the intestine and clinical disease only arises when this compensatory mechanism fails.

Journal ArticleDOI
01 Mar 1974
TL;DR: In this paper, a modified analysis of the convertor-controlled d.c. drive is presented, and a suitable method for solving the system equations is presented to solve the problem.
Abstract: The existing analysis of the convertor-controlled d.c. drive is suitable only for the operation of the system under certain conditions; it does not take into account some modes of operation that appear to have been overlooked in the past. This paper redefines modes of operation of the drive, and presents a modified analysis and a suitable method for solving the system equations. Although the analysis is confined to single-phase systems, a similar analysis would apply to more complex configurations.

Journal ArticleDOI
01 Mar 1974-Vacuum
TL;DR: In this paper, mass spectra are given of the gas atmospheres in an r.f. getter sputtering plant when depositing tantalum, and it is shown that gettering reduces the gaseous impurities.

Journal ArticleDOI
TL;DR: In this paper, the authors show that the currentvoltage characteristic of CaBr2 samples is not immediately reversible and depends on the maximum voltage level of the previous characteristic, and the electron emission is observed.
Abstract: Vacuum-deposited Au–CaBr2–Au thin film sandwich structures undergo a forming process when a de voltage of 4.5 to 7.5 V is applied. Prior to forming, very high current levels are drawn, possibly due to the presence of absorbed water vapour in the hygroscopic CaBr2 layer. After forming, the samples show a negative resistance region in the current-voltage characteristic, and electron emission is observed. In contrast with similar widely reported SiOx samples, the current-voltage characteristic of CaBr2 samples is not immediately reversible and depends on the maximum voltage level of the previous characteristic. Les structures en forme de couches minces de Au–CaBr2–Au preparees par evaporation dans le vide montrent l'evidence de formation electrique si l'on applique une tension directe de 4,5 a 7,5 V. Avant la formation, les grands courants electriques passent, possiblement comme consequence de l'eau absorbee dans la couche mince hygroscopique de CaBr2. Apres la formation, les specimenes montrent une region de resistance negative et l'emission des electrons dans le vide est observee. Par comparaison avec les resultats pour des specimenes de SiOx, la caracteristique tension-courant des specimenes de CaBr2 ne se renverse pas immediatement mais le courant resulte de la tension appliquee pour observer la caracteristique precedente.

Journal ArticleDOI
TL;DR: In this paper, the tope electrodes of silver or copper from which electron emission occurs, were studied for M-I-M structures of AgSiO/B[2]O3Cu and Ag
Abstract: The tope electrodes of silver or copper from which electron emission occurs, are studied for M-I-M structures of AgSiO/B[2]O3Cu and AgSiO/B2O3Ag while the specimens are contained in the chamber of a scanning electron microscope and subjected to bias voltages. Electroforming of the samples and their subsequent operation as negative resistance and electron-emitting devices lead to characteristic disturbances of the top electrodes which are consistent with the idea of filamentary conduction processes.

Journal ArticleDOI
TL;DR: A new general predictive model for computing the probability of winning is developed, and the method of computation is illustrated by a simple worked example.
Abstract: A company bidding by sealed tender needs to know the relationship between their bid price and their chances of winning the contract. Previously published models for computing the probability of winning are examined and found to be inaccurate. The problem is reformulated, and a new general predictive model for computing the probability of winning is developed. The method of computation is illustrated by a simple worked example.

Journal ArticleDOI
01 Aug 1974
TL;DR: In this paper, the Kerr constant (B ) of aqueous solution of polyvinylpyrrolidone (PVP) changed drastically when certain concentrations of the surfactant sodium dodecyl sulphate (SDS) were added to the PVP solutions.
Abstract: The Kerr constant ( B ) of aqueous solutions of polyvinylpyrrolidone (PVP) changed drastically when certain concentrations of the surfactant sodium dodecyl sulphate (SDS) were added to the PVP solutions. Three distinct regions were observed in the variation of B. These corresponded to the stages of interaction between the polymer and detergent indicated in previous papers by other workers using more laborious experimental methods. Using the transient birefringence technique, molecular relaxation times (τ) were determined at the same time as B . Insignificant variations of r were accompanied by order of magnitude changes in B . It is proposed that the electrical properties are far more sensitive indicators of polymer-surfactant interactions than are geometric parameters. Furthermore, the Kerr constant (and other electro-optic parameters) should provide a novel, sensitive and rapidly obtainable parameter for the increasingly popular studies on polymer-surfactant systems.

Journal ArticleDOI
TL;DR: In this article, the products of titration of pre-reduced supported metal catalysts with an alkene allowed separation of metal-held from support-held hydrogen, and the crystallite size of platinum supported on silica was estimated.
Abstract: Analysis of the products of titration of pre-reduced supported metal catalysts with an alkene allows separation of metal-held from support-held hydrogen. This has enabled the crystallite size of platinum supported on silica to be estimated and has also provided direct evidence of hydrogen spillover in these catalysts.

Journal ArticleDOI
TL;DR: In this paper, the decomposition of four dihalogenato complexes of manganese(II) and 1:10 phenanthroline has been studied by thermogravimetry and differential thermal analysis.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the molecules of nitrocellulose of this order of molecular weight and in this type of solvent are better regarded as extremely stiff and extended.