Showing papers by "Brunel University London published in 1975"
TL;DR: An algorithm to detect structure is described and this algorithm identifies sets of variables and the corresponding constraint relationships so that the total number of GUB-type constraints is maximized.
Abstract: Large practical linear and integer programming problems are not always presented in a form which is the most compact representation of the problem. Such problems are likely to posses generalized upper bound(GUB) and related structures which may be exploited by algorithms designed to solve them efficiently. The steps of an algorithm which by repeated application reduces the rows, columns, and bounds in a problem matrix and leads to the freeing of some variables are first presented. The ‘unbounded solution’ and ‘no feasible solution’ conditions may also be detected by this. Computational results of applying this algorithm are presented and discussed. An algorithm to detect structure is then described. This algorithm identifies sets of variables and the corresponding constraint relationships so that the total number of GUB-type constraints is maximized. Comparisons of computational results of applying different heuristics in this algorithm are presented and discussed.
252 citations
TL;DR: An investigation was carried out into the part played by background stimuli during Pavlovian conditioning, and it was found that the degree to which rats avoided the environment was inverselyrelated to the probability of the CS being followed by a US and directly related to the level of US intensity.
Abstract: An investigation was carried out into the part played by background stimuli during Pavlovian conditioning. Groups of rats were presented with tone CSs and unavoidable foot-shock USs. Both CS-US con...
144 citations
TL;DR: In this paper, the Isotherm migration method is extended to two dimensions and a convenient finite-difference method of solution is described for a variety of initial and boundary conditions.
107 citations
TL;DR: In this article, subject preferences and subject choices of 1,204 pupils in 19 secondary schools were investigated and the effect of attitudes towards teachers on subject preference and subject choice was found to be more marked in co-educational than in single sex schools.
Abstract: Summary The subject preferences and subject choices of 1,204 pupils in 19 secondary schools were investigated Sex-linked polarisation of subject preferences were more marked in co-educational than in single-sex schools An investigation of the effect of attitudes towards teachers showed a relationship between liking for teacher and subject preference, but not subject choice The results are discussed in relation to the current reorganisation of secondary schools along co-educational, as well as comprehensive, lines
104 citations
TL;DR: Oocysts were the most accessible parasite stage for investigation but sporozoites and merozoites of an embryo-adapted strain of E. tenella were also examined for enzyme activity.
Abstract: A method for the biochemical identification of protozoa belonging to the genus Eimeria is described for the first time. Starch gel electrophoresis of the enzymes lactate dehydrogenase, glucose phosphate isomerase, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase from parasite extracts revealed both intra- and inter-species differences when 11 strains representative of 6 species of Eimeria were examined. Oocysts were the most accessible parasite stage for investigation but sporozoites and merozoites of an embryo-adapted strain of E. tenella were also examined for enzyme activity.
95 citations
TL;DR: The degree to which rats failed to avoid this environment was found to relate to CS duration by an inverted U curve, and the manipulation of the trace interval however did not significantly affect avoidance.
Abstract: An experiment was carried out to investigate the part played by background stimuli during Pavlovian conditioning. Groups of rats were presented with tone CSs and unavoidable footshock USs. Two components of the inter-stimulus interval, namely CS duration and the duration of a trace interval, were manipulated across groups. Subsequently subjects were tested for their reactions to background stimuli by being re-exposed to the training environment in the absence of both the CS and US. The degree to which rats failed to avoid this environment was found to relate to CS duration by an inverted U curve. The manipulation of the trace interval however did not significantly affect avoidance.
80 citations
TL;DR: In this paper, the authors proposed a method for smooth interpolation to boundary data on a triangle, and sufficient conditions are given so that the functions when pieced together form a C N−1 (Ω) function over a triangular subdivision of a polygonal region Ω and the precision sets of the interpolation functions are derived.
69 citations
TL;DR: In this article, the results of past work in the field of ultrasonic machining are reviewed and the effects of process parameters isolated, and it is shown that, in the past, conclusions have been drawn for specific conditions and that it is unwise to accept the results as those generally prevailing.
Abstract: The result of past work in the field of ultrasonic machining is reviewed and the effects of process parameters isolated. The review shows that, in the past, conclusions have been drawn for specific conditions and it is unwise to accept the results as those generally prevailing. It is also clear that whilst there is general agreement concerning some parameter effects, there is contradictory evidence regarding others.
69 citations
TL;DR: The influence of persulphate ions on the radiosensitivity of dilute aqueous solutions of ribonuclease and lysozyme has been studied under a variety of conditions and a chain reaction has been demonstrated in nitrous-oxide-saturated persULphate solution.
Abstract: SummaryThe influence of persulphate ions on the radiosensitivity of dilute aqueous solutions of ribonuclease and lysozyme has been studied under a vatiety of conditions. Rate-constants for reactions of the sulphate radical, SO4, with a variety of solutes and transient product spectra of some of these reactions are reported.The presence of persulphate ions in general enhances the radiation sensitivity; in nitrous-oxide-saturated persulphate solution, a chain reaction has been demonstrated.
66 citations
TL;DR: Boronising is a surface diffusion treatment analogous to carburising, but produces harder surfaces without recourse to quenching as mentioned in this paper, and has been evaluated on steels and grey cast iron under dry sliding conditions.
63 citations
TL;DR: In this paper, error bounds for interpolation remainders on triangles are derived by means of extensions of the Sard Kernel Theorems and applied to the Galerkin method for elliptic boundary value problems.
Abstract: Error bounds for interpolation remainders on triangles are derived by means of extensions of the Sard Kernel Theorems. These bounds are applied to the Galerkin method for elliptic boundary value problems. Certain kernels are shown to be identically zero under hypotheses which are, for example, fulfilled by tensor product interpolants on rectangles. This removes certain restrictions on how the sides of the triangles and/or rectangles tend to zero. Explicit error bounds are computed for piecewise linear interpolation over a triangulation and applied to a model problem.
TL;DR: In this article, the unsaturated constituents of the long-chain component phenols in cashew nut-shell liquid from Anacardium occidentale were analyzed by means of combined thin-layer chromatography and liquid chromatography.
TL;DR: Experiments show that the drug reacts with an iron–cysteine complex over time scales of the order of a second, which means that the ability of the cell to repair radiation-induced free radical lesions by hydrogen or electron donation would be lowered.
Abstract: THE possibility of using hypoxic cell radiosensitising drugs as adjuncts in the radiotherapy of some forms of cancer has received renewed attention1–4. In particular administration of metronidazole (Flagyl, May and Baker Ltd) to tumour bearing mice before exposure to X rays, has been found to reduce the radiation dose required to control 50% of the tumours by a factor of 1.2–1.3 (refs 5 and 6). Preliminary clinical trials are now in progress7. The drug was originally chosen for study because of its constituent nitro group (which suggested it was a strong radical oxidant) and its extremely favourable pharmacological and toxicological properties8. Previously the activity of a large number of radiosensitisers had been attributed to their ability to react with intracellular sulphydryl compounds9,10. The ability of the cell to repair radiation-induced free radical lesions by hydrogen11 or electron donation12 would thus be lowered. Measurements13 of anoxic solutions over a period of 2 h did not, however, show any appreciable reaction between metronidazole (8 × 10−4 M) and the sulphydryl groups of cysteamine (8 ×10−4 M) or dithiothreitol (4 ×10−4 M). Recent associated pharmacological studies with rat intestinal contents have prompted us to re-examine the reaction of metronidazole with sulphydryl compounds and to investigate the possibility of catalysis by ferrous ions. We now report experiments which show that the drug reacts with an iron–cysteine complex over time scales of the order of a second. A drug–iron–cysteine complex is formed which is subsequently reduced over a period of minutes.
TL;DR: In this paper, two numerical methods, an integral equation method and a conformal transformation method, are described for the solution of harmonic boundary value problems, which are designed to deal with problems involving curved boundaries, boundary singularities and discontinuous boundary conditions.
TL;DR: In this article, the measured response of grid turbulence to three limiting types of uniform homogeneous strain: plane straining, axisymmetric elongation and axisymmetric flattening was described.
Abstract: This paper describes the measured response of grid turbulence to three limiting types of uniform homogeneous strain: plane straining, axisymmetric elongation and axisymmetric flattening. Straining was achieved by allowing the turbulence to be convected through suitable distorting ducts; the maximum strain ratios were 5·8, 6·0 and 2·3, respectively. An attempt is made, using rapid-distortion theory, to specify an effective strain which accounts for the initial anisotropy of the grid turbulence; in the experiments, this effect was most important for the third species of strain. The maximum effective strain ratios were calculated as 4·05, 7·2 and 2·75, respectively. The rapid-distortion results are able to describe several features of the response of the turbulence with good accuracy: (i) the variation of total turbulence energy through the experimental ducts; (ii) the tendency of one component (that in the direction of the (larger) negative strain) to contain one-half of the turbulence energy after only moderate straining; and (iii) the changes in dimensionless structure parameters composed of ratios of component intensities. The first kind of prediction requires that the concurrent decay be specified in a simple way; (ii) and (iii) require that the initial anisotropy be taken into account. The predictions (iii) are generally less accurate than the others. The degree of success achieved by the rapid-distortion hypo-thesis is rather surprising, since the strain rates in the experiments were not as large as those for which the theory might have been expected to be valid. It is concluded that successful models of turbulence must provide a vorticity amplification essentially like that of rapid-distortion theory. However, the simple distorting flows considered here may not provide severe tests of more refined models, since many features of the response have already been accounted for.
TL;DR: The stoichiometry problem of fixation of surface chromium (II) on Silicagel has been studied in this paper, showing that the metal is bound prediminantly (if not only) in chromate-like units up to a concentration of 2,8% CrII.
Abstract: Die thermogravimetrische Analyse eines reduzierten Phillips-Kontakts (Trager: Silicagel „Merck 7733”) zeigt, das CrII. Ionen bis zu einer Konzentration von 2.8% CrII uberwiegend, wenn nicht ausschlieslich in Chromat-analogen Einheiten gebunden werden. Bei hoherem Chrom(II)-Gehalt. bis zur maximal erreichbaren Konzentration von 3.5%, werden von dem zusatzlich fixierten Chrom keine weiteren durch die Messung erfasbaren OH-Gruppen verbraucht (Bildung von Polychromat-analogen Strukturen und/oder Verwendung von nichtbenachbarten OH-Gruppen). Die Analyse ergibt weiterhin. das nicht alle thermogravimetrisch erfasten OH-Gruppen zur Fixierung von Chrom in der Lage sind.
Ein Vergleich der quantitativen Ergebnisse mit Silicagel-Modellen macht die Verwendung von vicinalen Paaren fur die Bindung des Chroms unterhalb 2.8% wahrscheinlich.
On Surface Compounds of Transition Metals. X. The stoichiometry Problem of Fixation of Surface Chromium (II) on Silicagel.
Thermogravimetric analysis of a reduced Philips catalyst (support: silicagel “Merck 7733”) shows that the metal is bound prediminantly (if not only) in chromate-like units up to a concentration of 2,8% CrII. At higher CrII contents. up to the maximum of 3.5%, the additionally fixed chromium does not consume further OHs, within the scope of the thermogravimetric method formation of polychromatelike structures and/or use of not-neighbouring OH groups. The analysis further demonstrates that not all the SiOh groups comprised by the method are able to accommodate surface chromium.
The fixation of the metal seems to proceed most likely by reaction with the vicinal pairs of SiOH, as a correlation of our data with silica models shows.
TL;DR: It is demonstrated that HPE is a relatively potent carcinostatic agent in vitro in the tumour lines tested in this study and results obtained under conditions in vitro do not distinguish between a direct cytotoxic effect of HPE on the ascitic tumour cells or a possible extension in the generation time of these cells.
TL;DR: In this article, a relatively non-polar stationary phase at a high temperature was used to avoid tailing by initial conversion of the unsaturated constituents into the common saturated member by hydrogenation and to obtain anacardic acid, the principal component of natural CNSL, in the form of the volatile methyl ester.
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TL;DR: In this article, the relative molar response values for the main constituent phenols and the use of an internal standard have led to a quantitative procedure by isocratic elution under reversed-phase partition, preferably with the solvent acetonitrile-water.
TL;DR: In this article, the constants in Sobolev norm error bounds for interpolation remainders on triangles were derived for finite element analysis of elliptic equations on a triangulation of a polygonal region.
Abstract: The constants in Sobolev norm error bounds are derived for interpolation remainders on triangles. These bounds can be applied to the finite element analysis of elliptic equations on a triangulation of a polygonal region Ω.
TL;DR: A short review of free radicals can be found in this paper, where the general structures of the free radicals are discussed. But the analysis is limited to a few types of free radical molecules.
Abstract: Free radicals are molecules or molecular fragments containing a single unpaired electron. In general, free radicals are reactive chemically, some (e.g. HO•) being extremely reactive. However, certain types of free radical, such as nitroxyl-radicals and free radicals stabilized by steric or derealization features, are much less reactive and a few (e.g. diphenyl picryl hydrazyl) are stable enough to be crystallised and stored at temperatures above 0°. Table 1 gives the general structures of free radicals that will be discussed in this short review.
01 Sep 1975
TL;DR: A survey on the use of classifications of pores in solid materials can be found in this article, where different methods for surface determination and characterisation of pore structure from adsorption measurements are compared.
Abstract: A survey is given on the present use of classifications of pores in solid materials. Different types of adsorption isotherms are presented. The interpretation of physisorption isotherms is discussed. Different methods for surface determination and characterisation of pore structure from adsorption measurements are compared.
Es wird eine Ubersicht uber die in Gebrauch befindlichen Klassifizierungen von Poren in Festkorpern gegeben. Verschiedene Typen von Adsorptionsisothermen werden vorgefuhrt. Die Interpretation von Physisorptionsisothermen wird diskutiert. Verschiedene Methoden zur Oberflachenbestimmung und zur Charakterisierung der Porenstruktur mit Hilfe von Adsorptionsmessungen werden verglichen.
TL;DR: By measuring the intensity of the scattered light, the electric polarisability of Escherichia coli could be monitored as small quantities of antibiotics were added to the suspensions, and it is taken to suggest that the antibiotic molecules were adsorbed on to the bacterial surface thereby reducing the surface charge.
TL;DR: Three dyslexic patients were found to show performance corrrelating with the imageability of the material, but not with its concreteness; indeed, derived nouns were easier to read than simple nouns.
Abstract: Subjects with acquired dyslexia sometimes find abstract words more difficult to read than concrete words. Three dyslexic patients were found to show performance corrrelating with the imageability of the material, but not with its concreteness. This could not be explained in terms of lexical complexity; indeed, derived nouns were easier to read than simple nouns. These effects were reliable across the three subjects. It was suggested that they were naming imaginal representations of the referents of imageable nouns.
TL;DR: The work described here explores the possibility and confirms that one of the functions of the brain hormone is to retain the blood in the mid-gut until development of the oöcytes is complete.
Abstract: Development of the oocytes after a blood-meal in the mosquito Aedes aegypti occurs in two phases: initiation , which is independent of hormonal action, and promotion to maturity, which is dependent on a neurosecretory hormone from the brain (acting through the endocrine system of the thorax). During the promotion-phase, material for the growth of the oocytes is mobilized from the blood in the mid-gut. The work described here explores the possibility and confirms that one of the functions of the brain hormone is to retain the blood in the mid-gut until development of the oocytes is complete.
TL;DR: In this paper, Dinonylnaphthalenesulphonic acid in solution in n-heptane when equilibrated with an aqueous solution imbibes a considerable amount of water and forms micelles.
TL;DR: In this article, the d.c. electrical properties of Au-SiO/TiO-Au thin film devices have been studied and their properties including electroforming and electron emission into a vacuum have been determined.
TL;DR: In this paper, a comparison of the mechanical properties of ionic polymer cements, prepared by reacting an aqueous poly(acrylic acid) solution with ion-leachable inorganic powders, is made.
Abstract: A comparison is made of the mechanical properties of ionic polymer cements, prepared by reacting an aqueous poly(acrylic acid) solution with ion-leachable inorganic powders. Out of the wide range of powders investigated, specially formulated aluminosilicate glasses gave the most promising results, and the properties of cements made from them are discussed in greater detail. In particular, the dependence of compressive strength on cement age is described, and the loss of water from the material when exposed to atmospheres of low relative humidity is shown to be related to property changes which occur under these conditions. An interpretation of these detrimental effects is presented in terms of variation in the cement microstructure, and methods of minimising the effects by various modifications to the basic system are reviewed.
TL;DR: In this paper, electric birefringence studies have been made on some five samples of sodium carboxymethyl cellulose of different molecular weights (M) in water and the orientational relaxation times were evaluated from the decay rates of pulsed field experiments.