Showing papers by "Ministry of Supply published in 1952"

The Absorption Spectra of Single Crystals of Lead Sulphide, Selenide and Telluride

Abstract: The absorption spectra of single crystals of PbS, PbSe and PbTe have been examined in the temperature range from 20°K to 600°K The spectra are characterized by a sharp absorption edge which comcides with the long wavelength limit of photoconductivity in each material. At longer wavelengths the absorption coefficient increases slowly with increasing wavelength, as in germanium and silicon

Flavin-adenine dinucleotide and diaphorase in resting and germinated spores, and vegetative cells of Bacillus subtilis and Bacillus megatherium

Abstract: The method described in the present work allows the purity of the solution under test for tocopherols to be assessed and also enables the separation of the commonly occurring a-, yand 8-tocopherols to be achieved. Applications of the method to the examination of several oils indicate the usefulness of the method. For example, the presence of 8tocopherol in soya-bean oil is readily ascertained, whereas its existence escaped detection by conventional methods for many years. In addition, the substance in cocksfoot grass which gives a colour with diazotized o-dianisidine is shown to be different from any of the known tocopherols in its behaviour on the chromatogram. Similarly, a non-tocopherol ferric-reducing substance which is not removed by the saponification, adsorption and crystallization processes is present in wheat-germ oil. Although the method will probably not be readily applicable to routine analysis, its value for reliably detecting the presence of naturally occurring tocopherols is apparent. Application of the method to the quantitative analysis of tocopherol mixtures is being undertaken and will be the subject ofa further communication.

Cross-polarization of the Radar Melting-Band

Abstract: WHEN plane-polarized radiation is scattered by meteorological precipitation particles other than spheres, a component of the back-scattered energy is polarized at right-angles to the plane of polarization of the incident wave. This component will be referred to as the ‘cross-polarized’ component in this communication. Recent observations at Cambridge and Malvern have shown that the melting particles found just below the freezing-level, which give rise to the well-known radar ‘melting-band’1, produce back-scattered radiation with a greater cross-polarized component than that given by the rain below and the snow above the freezing-level. These observations have been made using separate aerials for transmission and reception, by comparing the echo received when the aerials have their planes of polarization parallel with that received when the plane of polarization for reception is at right-angles to that for transmission.

A Wind Tunnel for the Study of Airborne Infections.

Abstract: A vertical closed circuit wind tunnel is described in which a spinning top sprayer is used as a source of homogeneous particles of pathogenic organisms. The dry particle size may be set at any figure between 1 and 20 µ, and the cloud concentration can be varied over wide limits. Provision is made for humidity control. Animals may be exposed to the cloud, and samples taken from it. The apparatus can be sterilized with flowing steam and formalin.An appendix giving details of the operational technique is available on request.

Use of Ion Exchange Resins to determine the Charge of an Ion in Aqueous Solution

Abstract: THE use of mono-functional ion-exchange resins with strongly acidic or basic groups provides an extremely simple and rapid technique for the determination of the ionic charge of an anion or cation in aqueous solution The method has the further advantage of being applicable to solutions containing only very small concentrations of the unknown ion

Polarographic Determination of Fluoride

Abstract: Willard and Dean1 have described a polarographic method for the determination of aluminium, based on the measurement of the polarographic step produced by the reduction of ‘Solochrome Violet R.S.’ (sodium salt of 5-sulpho-2 hydroxy-α-benzene azo-2 naphthol), which is known as ‘Pontachrome violet S.W.’ in the United States. This compound produces a step of half-wave potential about 0.3 V. vs. the saturated calomel electrode in an acetate buffer solution of pH 4.6. Addition of aluminium to a solution of this dye causes this polarographic step to be reduced in height and a second step to appear at a point about 0.2 V. more negative. The sum of the height of these two steps is equal to the height of the original step, and the size of the second step is proportional to the concentration of aluminium present.

Xix.—a microforge attachment for the biological microscope

Abstract: Synopsis The device described enables a standard biological microscope to be adapted to the manufacture of micromanipulator tools. It has most of the features of the de Fonbrune microforge, but costs much less. The design is largely based on de Fonbrune's.

Some factors affecting the performance of coaxial cables for permanent television links

Abstract: Transmission by long-distance cable and repeaters using a vestigial-sideband carrier is becoming standard practice in television The paper describes some factors affecting the performance of coaxial cables in such an application A brief description of the inherent properties of a typical coaxial cable and their effect on system design is given The main part of the paper describes an experimental programme for evaluating the irregularities of coaxial cable, and an estimate is given of their effect on television transmission It is found that the most probable magnitude of the distortion from this cause is lower than the distortion from other causes

The Formation of an Aerosol by Condensation of a Dilute Vapour in a Carrier Gas

Abstract: The formation of a dilute aerosol by supercooling a mixture of vapour and carrier gas is examined theoretically. It is shown how the partial differential equations of this kind of problem can be reduced approximately to a set of ordinary differential equations, much more easily handled by numerical methods. An approximate solution is obtained which shows how the average particle size depends on the rate of cooling and the time of quenching.

Basic Engineering Standards and Their Place in Design

Abstract: In this paper standardization in design is considered The argument is developed tat the detailed design of the parts of a mechanism demands a logical approach The designer should state on the drawing, in the simplest possible terms, what he really wants The necessary range of basic (or abstract) engineering standards, both for him to achieve this aim and to provide for economic production, are givenThe basic standards cover definitions, geometric analysis, ultimate standards of size, basic sizes, limits and fits, measurement, surface texture, drawing practice, standard forms (for example, screw threads), and standards of design Their nature and scope are examined in general terms and some of the main compromises necessary are discussedThe necessity is shown for a sound framework, wide enough to cover the normal needs of all engineers The dangers of a parochial outlook are stressed and the needs of both small and large producers are emphasized These standards are shown to be the essential prelimina

Tropospheric Wave Propagation in a Duct of Non-Uniform Height

Abstract: This paper describes an approximate method for extending the simple mode theory of tropospheric refraction (Booker and Walkinshaw 1947) to cover situations where the refractive index profile varies with range The transmission path is divided into a number of zones, in each of which the variation in the refractive index profile is small In each zone the profile is then taken to be independent of range, and given by the mean profile throughout the zone. The duct-width d and the lapse-rate of modified refractive index at infinite height kinfinity are found for each zone and are used, together with published propagation curves, to evaluate the distribution of radio field strength in the region beyond the horizon of a transmitter Although the method is a general one, the final formula refers specifically to situations in which the field can be adequately described by the first mode alone, and where the mean profile of refractive index in each zone may be represented analytically by a one-half power law curve. An example of the application of the method to a practical situation is given This shows good agreement between experiment and theory, and demonstrates the significant effect of changes in the refractive index profile on the level of field strength The limitations of the method are pointed out, and its extension to cover other types of refractive index profile and higher order modes is outlined

Multi-star Sextants

Abstract: Amongst the schemes for simplifying the processes of astronomical position fixing the family of multi-star sextants contains some interesting material. By the simultaneous observation of two or more stars through an optical system coupled to a gravity reference, it is possible to determine the observer's position directly in latitude and longitude, with little or no computation. The number of instruments on these lines which have been designed is very large and it would not be possible to describe them in detail in the course of a short paper. A few remarks about their principles may, however, be of interest since they are, in general, sound in theory and fall short of practical requirements only because, when used on an unstable platform such as a ship or aircraft, they make too heavy a demand on the skill of the observer.