Showing papers by "Ministry of Supply published in 1956"

Factors which interfere in the manometric assay of monoamine oxidase.

Abstract: Appleby, J. I., Gibson, G., Norymberski, J. K. & Stubbs, R. D. (1955). Biochem. J. 60, 453. Edwards, R. W. H., Kellie, A. E. & Wade, A. P. (1953). Mem. Soc. Endocrin. 2, 53. Norymberski, J. K. (1952). Nature, Lond., 170, 1074. Norymberski, J. K. & Sermin, A. T. (1953). Biochem. J. 55, 876. Norymberski, J. K. & Stubbs, R. D. (1954). Lancet, 2,386. Norymberski, J. K. & Stubbs, R. D. (1956). Biochem. J. 64, 168. Norymberski, J. K., Stubbs, R. D. & West, H. F. (1953). Lancet, 2, 1276. Schestakow, P. (1905). Chem. Zlb. 1, 1227. Smith, D. C. & Tompsett, S. L. (1955). Analy8t, 80, 397.

An antigen determining virulence in Pasteurella pestis.

Abstract: DESPITE assiduous search by many workers, the factor conferring the property of high virulence on strains of P. pestis has remained undetected. Virulent and protective avirulent strains have been studied comparatively by the methods of immunology, immunochemistry and biochemistry without yielding convincing evidence of a difference in their properties sufficient to account for their difference in virulence. This communication reports results showing that an important antigenic difference between virulent and protective avirulent strains does in fact exist.

Biochemical changes occurring during sporulation in Bacillus species.

Abstract: is too fast to be measured by the methods used. The second step, which involves the acylation of the enzyme and the concomitant liberation of pnitrophenol, is characterized by the rate constant k2= 3-15 sec.-'. The third step involves the liberation of acetate and reactivation of the enzyme; the rate of this reaction is defined by kI3= 0-0254 sec.-'. 2. The rate constant k2 for the second step is, within experimental error, the same at pH 6-45 and pH 7*75; from this and other available evidence it is suggested that it involves the acetylation of the OH group of a serine residue in the enzyme. The third step has a pH dependence similar to that previously found for the overall rate of reactions catalysed by chymotrypsin, and it is suggested that itinvolvesthe imidazole group ofa histidine residue ofthe enzyme.

Adenosine deaminase and ribosidase in spores of Bacillus cereus.

Abstract: Inosine is a more effective germination stimulant than adenosine for spores of Bacillus cereus and B. anthracis (Powell & Hunter, 1955). A crude method of assessment, based on the paper-ionophoresis technique of Wade & Morgan (1954), indicated that extracts from disintegrated resting spores of B. cereus converted adenosine into inosine. This suggested the possibility that inosine might be, in fact, the germination stimulant, and that germination of a given spore suspension in adenosine might depend, to some extent, on its adenosine-deaminase activity. We have now studied quantitatively the deamination of adenosine by resting and germinated spores of B. cereus, and also its further breakdown to the purine and free ribose. The possible relationships between these reactions and spore germination in B. cereus are discussed. Part of this work has already been briefly reported (Powell, 1955). 40 mm sodium potassium phosphate buffer pH 7-3. Resting and germinated spores were disintegrated in suspensions containing 2 x 1010 spores/ml., using the Mickle (1948) tissue disintegrator with Ballotini beads size 12. The suspensions were ice-cooled at 10 min. intervals during disintegration, which usually took 1 hr. Homogenates were separated by centrifuging for 30 min. at 6000 g to give extract and 'debris' preparations. For some experiments (see below) the deaminase was precipitated from extracts with 30% (v/v) ethanol at 0°. It redissolved readily in water and buffer solutions. A spore-coat preparation was obtained by disintegrating a resting-spore suspension for approximately 20 min., i.e. until the appearance of stained films indicated that disruption had occurred, but the suspension still consisted mainly of recognizable spore-coat fragments. Smaller particles of doubtful origin were removed by repeatedly suspending in

The composition of the spore coats of Bacillus megatherium, B. subtilis and B. cereus.

Abstract: A peptide containing glutamic acid, alanine, aediaminopimelic acid and hexosamine was found to be present in exudates from germinating spores and in extracts from disintegrated resting spores (Powell & Strange, 1953; Strange & Powell, 1954). It was suggested that the peptide might be derived from the spore coat when this underwent a change in permeability during germination or was damaged mechanically. In the present study of the chemical composition of spore coats, these were obtained by mechanical disintegration, a method which has been used by a number of workers to obtain bacterial cell walls (Salton & Home, 1951; Salton, 1953; Cunmmins, 1954). There seemed little hope of demonstrating the presence of the peptide in the coat of the resting spore by this method, as the peptide appeared to be so readily freed during disintegration. It was found, however, that sporecoat preparations of BaciUus mnegatherium still contained considerable amounts, and B. subtilis smaller amounts, of bound hexosamine which was slowly released in the form of the peptide previously isolated. This process and the effect of various enzymes on it are described. A similarity was found between the effect of lysozyme on spore peptide and lysozyme substrate, which is a mucopolysaccharide considered to exist within certain bacterial cell walls as an insoluble complex (Meyer, Palmer, Thompson & Khorazo, 1936; Epstein & Chain, 1940; Meyer & Hahnel, 1946; Salton, 1952), and this is also described.

The effects of a cold environment and of ammonia on the toxicity of sulphuric acid mist to guinea-pigs.

Abstract: Exposure of guinea pigs for 8 hr to H/sub 2/SO/sub 4/ mist (2.7 ..mu..m MMD) yielded an LC/sub 50/ of 6.8 ppM. Animals either became dyspneic within 3 hr and died within 8 hr or suffered little effect during exposure. Some animals were particularly resistant. LC/sub 50/ for mist of 0.8 ..mu..m MMD was 14.9 ppM at room temperature (20/sup 0/C) and 11.7 ppM at 0/sup 0/C. Decrease was significant at 2% level. That cold especially affects more resistant animals is suggested. No evidence for tolerance was observed. Ammonium carbonate (NH/sub 3/ to neutralize mist) negated mortal effect of mist sufficient to produce > 50% mortality. Fatal effect was laryngeal spasm and bronchoconstriction. Pathology included emphysematous lungs. No pathological findings were observed in animals surviving short LC/sub 50/, but prolonged exposure produced slowly-repairable pathological lesions including capillary engorgement (perhaps sequel to bronchospasm).

Infra-red Spectra of Chelating Agents: 2-Phenacylpyridine Derivatives

Abstract: IT has been suggested that in a conjugated system of the type (I), where XH and Y can form a hydrogen bond donor–acceptor system, there is a significant contribution of the ionic form (II) to the ground state of the chelate system.

Vowel sounds and perceptual constancy.

Abstract: IT has been known for some time that vowels are distinguished from one another mainly by the frequencies of the formants or regions of the auditory spectrum in which there is a comparatively large amount of energy. Recently, the hypothesis has been put forward by Joos1 that when a listener identifies the vowel in a particular word he does so not by considering the absolute value of the lowest two formant frequencies, as was previously thought, but by assessing the frequencies of these formants in relation to the formant frequencies of other vowels which he has heard pronounced by that speaker. On this hypothesis, the identification of a particular sound depends on the acoustic structure of the neighbouring sounds.

Experiments on Circular Cones at Yaw in Supersonic Flow

Abstract: T PROBLEM of supersonic flow past circular cones a t yaw has received considerable at tent ion from theoretical research workers in recent years. Several methods of solution have been proposed, 5 and those based on Stone's paper have been used as the basis for very extensive tables of data. I t is, therefore, ra ther surprising t ha t experimental information on this problem is comparatively scanty, and tha t no set of observed results comparable to the tables calculated by Kopal a t Massachusetts Ins t i tu te of Technology is available. In the present paper an account is given of measurements of pressure on two circular cones of semiapex angles 15° and 20° over a range of angles of yaw between 0° and 25°. T h e measurements are made a t one Mach Number in the Supersonic Wind Tunnel at tached to the Applied Mathematics and Mechanics Division a t For t Halstead. Existing results appear to refer to cones much thinner than these and are given a t somewhat arbi trary angles of yaw. The present results should, therefore, be of value in showing pressure distributions on cones producing shocks of considerable strength which, when yawed, display marked variations in entropy in the flow behind them. Further , the variation of pressure distribution with angle of yaw has been shown in a systematic manner, and the da ta given are probably more complete than those published previously. The results are of value in themselves, bu t they are also suitable as a s tandard against which the more firmly established theoretical methods can be tested Accordingly, the pressure distributions a t Mach Num-

Phase-Change in 1,2,4,5-Tetrabromobenzene investigated by Pure Quadrupole Resonance

Abstract: IT is the purpose of this communication to mention a result of a type which we believe to be hitherto unreported, which we obtained when the temperature dependence of the bromine-81 pure quadrupole resonance at about 240 Mc./s. in 1,2,4,5-tetrabromobenzene was investigated. Here, on raising the temperature above 20° C., there is as usual a linear decrease of frequency. However, a very sudden discrete drop occurs at 46.5° C., after which there is again a linear decrease. On then reducing the temperature, the increase of frequency is linear as far as 33.5° C., where there is a sudden discrete rise, the frequency returning to the original line and completing a hysteresis loop.

Alpha epsilon-Diaminopimelic acid in the peptide moiety of the cell wall polysaccharide of Bacillus anthracis.

Abstract: Bacillus anthracis contains a polysaccharide which appears to be part of the cell wall1. Ivanovics2 first isolated the polysaccharide which contained galactose 34 per cent, glucosamine 34 per cent, nitrogen 4.2 per cent and α-carboxyl amino-nitrogen 0.8 per cent. Strange and Belton3 obtained from culture filtrates of B. anthracis a polysaccharide which contained galactose 39–43 per cent, glucosamine 34 per cent, nitrogen 3.9 per cent and α-carboxyl amino-nitrogen 1.26 per cent. The differences between the total nitrogen and glucosamine nitrogen values together with the figures for α-carboxyl amino-nitrogen in these preparations indicated the presence of 5–10 per cent of amino-acid residues. Smith and Zwartouw4 obtained a polysaccharide from B. anthracisgrown in vivo. It contained galactose 38–43 per cent, glucosamine 38–44 per cent, nitrogen 4.0 per cent and α-carboxyl amino-nitrogen 0.3 per cent. Since this preparation satisfied a number of rigorous tests for homogeneity it was concluded that a small peptide moiety (2–3 per cent) was firmly attached to the polysaccharide. We are concerned here with the constitution of this peptide moiety.

Tridac, a large analogue computing machine

Abstract: Tridac is the name given to a large analogue computing machine installed at the Royal Aircraft Establishment The machine, which has been built to assist in solving guided-weapon problems, has electronic, mechanical and hydraulic components, and operates on a 1:1 time scale so that real components can be included in the computation Tridac is intended to assist system understanding and development by constructing system models with which mathematical computations can be carried out Each computing section, the parameters of which can be easily changed, represents a particular part of the real system The mathematical operations of summation, integration, multiplication and resolution are carried out using either drift-corrected dc amplifiers or electrically controlled servo motors, with hydraulic or electric power Connections to the servo motors and interconnections between the various cabinets, which contain in all some 2000 electronic units, are arranged to facilitate the simulation of the flight of a guided missile Principles of operation, computing methods and components, installation, and method of operation of the computer are discussed with reference to the problems to be solved

The spine pad; a discarded item of tropical clothing; an historical and physiological survey.

Abstract: THE spine pad has become a dull museum piece, and it is probable that specimens are nowadays not easy to find. Yet to those living in tropical areas during the early part of the century and to those serving with the British Army in hot climates during the First World War, memories may be evoked of a piece of cloth of cotton, silk or wool, plain or quilted, several inches wide, attachable to the shirt or coat along the spine, and sometimes with a coloured lining. It is now difficult to accept that this mere piece of cloth could in any way protect from the effects of the sun. But the purpose of the spine pad was so closely linked with the development of ideas concerning body heat,_ fever and sunstroke, that one must be prepared to explore many early lines of thought for an understanding of its origin and its demise.

A transducer for digital data-transmission systems

Abstract: Accurate information such as may be required for weapon control may best be transmitted over long-distance telegraph or voice communication circuits by using some form of digital representation or pulse code modulation. The paper describes a method by which the position of a scale attached to a datum shaft may be “read” photo-electrically as a binary number in much the same way as the scale of a surveying instrument is read in degrees and minutes. Data-transducers have been constructed to represent the angular position of a shaft as a 14-digit binary number, that is to an accuracy of rather better than one minute of arc. Special precautions have been taken in the design of the scale to prevent gross errors due to movement of the scale while it is being read. Such errors as do occur are examined in detail, since in some data-transmission applications they may not be sufficiently serious to justify the more complex equipment required for their complete elimination.

The Initial Behaviour of a Spherical Explosion. I. Theoretical Analysis

Abstract: The analysis of the disturbance near the source of spherical blast from a polytropic explosive in which $\gamma $ = 3, given in Berry & Holt (1954), is generalized to apply to an explosive gas and a surrounding medium governed by any equations of state. Most of the properties established in the special case are found to be generally true. In particular, a second blast wave is shown to be a consequence of the breakdown of continuous gas flow in the neighbourhood of a singular characteristic. The complete field near the origin of blast can be determined from series expansions similar in type to those in Berry & Holt (1954). Except in the gas expansion zone the coefficients in these expansions can be expressed in simple terms. The quantity defining the first departure of the second shock from the singular characteristic is given by an expression as simple as that in the polytropic case, although its derivation presents new difficulties. The analysis shows that, for all types of explosive, the second shock is a second-order effect in terms of the square root of the time from the end of detonation. This contradicts that conclusion reached earlier by Wecken (1951) on the basis of less detailed analysis. Application to actual explosions is described in the second part of this paper.

Pseudo-cholinesterase in Rat Erythrocytes

Abstract: ALTHOUGH there are many references in the literature to the existence of different types of cholinesterase in mammalian sera1, it is generally believed that human red cells contain only one type2. Furthermore, we can find no evidence in the literature for the existence of a pseudo-cholinesterase in any mammalian erythrocytes, although many workers have stated that benzoylcholine is hydrolysed by red cells. Since, however, the rate of hydrolysis is slow, this breakdown of a substrate formerly presumed to be specific for pseudo-cholinesterase has been attributed to true cholinesterase. Indeed, Adams3 has shown that purified true cholinesterase does hydrolyse benzoylcholine, at a rate which would account for such observations. In spite of this, some results obtained by Fraser with benzoylcholine4 imply the existence of more than one type of cholinesterase in red cells.

The airworthiness and reliability of aircraft electrical systems

Abstract: Standards for the airworthiness and reliability of electrical systems and equipment are discussed in relation to the overall standards for the aircraft and its engines, and the effect of duplication of systems and equipment is considered. The control and protection of generating systems is examined in relation to experience, particularly of total power failure, and it is concluded that systems have not proved sufficiently reliable in the past to justify entire reliance on them in aircraft which depend on electrical supply for their continued flight. Various methods of providing duplicate and emergency supplies are described. The electrical controls of engines and propellers is discussed in relation to engine reliability, and recommendations are made for improvement. Inadvertent operation of some services (e.g. control-surface trimmers, propeller reversing) may constitute a major hazard to the aircraft; a detailed assessment of the causes of such operation is made and of methods of avoiding it. In an aircraft which carries large quantities of fuel and uses other inflammable fluids at high pressures, the extensive use of electricity may involve a considerable risk of fire or explosion unless the most stringent precautions are taken. Some of the risks and the measures taken to combat them are described.

A Resonant-Cavity Torque-Operated Wattmeter for Microwave Power

Abstract: A sensitive method of microwave power measurement is described which makes use of the mechanical force exerted by the electromagnetic field on a small vane in a resonant cavity. It is shown that the force on the vane is a simple function of the Q-factor of the cavity, the power absorbed in it and the perturbation of its resonant frequency caused by the vane. The results of a comparison between an experimental wattmeter based on this principle and a water calorimeter are given, and the requirements of a practical instrument are discussed.

Agar diffusion plates: the recording of experimental data.

Abstract: Ein Auswertungsverfahren der Antigen-Antikorper-Analyse mittels der Geleediffusionsmethode vonOuchterlony wird beschrieben.

A servo system for digital data transmission

Abstract: Certain special features must be taken into account in the design of a servo system which is to operate satisfactorily with digital data. In particular, the data are quantized in amplitude, thereby introducing non-linear effects; they constitute a series of samples instead of a continuous function, and there may be significant delays due to low-speed transmission circuits or digital equipment or both. All of these contribute in various ways towards reducing the stability of the system. The method of synthesis takes full account of the sampling and delay features and enables a degree of prediction to be incorporated which ensures that the regenerated data do not lag on the original under steady-state conditions. Effects especially attributable to amplitude quantization are then studied qualitatively. Since stability diminishes and the sensitivity to noise and instrumental errors increases as the time of prediction is increased, it is essential that the delay involved in the transmission of each sample should be minimized. Furthermore, the sampling servo system is less efficient than a continuous one as a smoothing device, and as much smoothing as possible should be applied at the sending end before sampling.