Graphite Pore Structure Evaluation by Serial Section Kinematography

The method and techniques employed in the investigation of the pore structure of graphites by serial sectioning combined with kinemicrography are discussed. Some of the simpler problems associated with the working of graphite somples to a good finish and yet with reasonable speed are also reviewed.     

The Translation of Colours into Black-and-White Photographs

Usual chromatic sensitization of black-and-white films attempts to translate a completely natural subject, rich in tone values and colours. into a monochrome representation. To remind an observer of the subject is only possible when taking both into account. A theoretical spectral sensitivity like that of the eye, neither at normal nor at increased contrast, is satisfactory in spite of the apparent obviousness of its choice, because the exact rendering of relative luminosities must be disturbed if objects of different hue, but of equal visual luminosity, are to be distinguished. The usual chromatic sensitivity of block-and-white films is sotisfactary; it might be improved further by slightly reducing the sensitivity to blue light, and increasing that to green light.     

On the Influence of Polyvinylpyrrolidone (PVP) during the Synthesis of Ultrafine Emulsions

The influence of PVP as well as the influence of the excess of silver ions, and the quantity of silver iodide in the crystal phase, on the physical ripening of Lipmann’s emulsions are investigated. It is established that PYP favours the formation of ultrafine emulsions. Its inhibitory influence on physical ripening makes it possible to regulate and equalize the activity of the gelatins, used in the synthesis of Lipmann’s emulsions.

Emulsions with a resolving power of 3200 1/mm satisfactory sensitivity and edge sharpness are synthesized.     

Behaviour of Thiosulphate in Electrodialysis in the Presence of Photographic Gelatin

Electrodialysis of a 10 per cent solution of gelatin containing 30 /M of thiosulphate labelled 3,S in the outer sulphur atom was carried out with a brentzinger apparatus. Forty-five per cent of the radioactivity appeared in the anodic liquid, thirty per cent in the cathodic and the remaining twenty-five per cent in the gelatin solution. The validity of these results is discussed also in relation to other experiments carried out with ,SS labelled sulphate and :aP labelled phosphate.     

The Photography of Radioactive Materials

This paper discusses some or the many problems peculiar to the photography or radioactive materials. Specialized apparatus and techniques are described, such as telephotography via mirrors, illumination systems and macro techniques.     

Photographic Procedure for Complex Chart Visual Interpretation Records*

Comparison of complicated chart records is not an easy task, even if great trouble is taken to produce transparent film copies dye-toned to contrasting colours. The lines may cross and re-cross so frequently that the sequence of events is difficult to see. In suchcases superimposition of above-the-line and below-the-line silhouettes is helpful, since it permits both the sign and the magnitude of the error at any point to be readily seen. Photographic procedures are described for making such silhouettes from commercially available materials.     

Photofabricated Focussing Diffracting Optics

Optical components such as zone plates which operate by diffraction can be formed from a recording, in a photosensitive layer, of the intensity distribution created by the interaction of two coherent wavefronts.

This paper describes some examples of such components and discusses the practical aspects of photofabrication. Examples of wavefront aberration introduced by a wavelength change and two methods of aberration correction are shown.     

Optical Character Generation for a High-Speed Non-Impact Printer

The requirements for optical character generation for a commercial electrophotographic high-speed printer—more than 10,000 1pm—are given. They lead to the conclusion that the principal elements of a character generator will he a laser, an acousto-optic deflector and a polygon mirror.

The arrangement of a character generator which has been realized in a commercial printer is described in detail. Its performance characteristics are calculated and compared to experimental results.     

Mechanisms of Adsorption from Aqueous Solutions: Some Basic Problems

Despite its wide occurrence and practical importance, adsorption at the interface between a solid and an aqueous solution still presents one of the most complicated problems in surface chemistry. Some of the factors known to influence adsorption processes are pointed out and the present need for more thorough investigation of well-characterized systems is emphasized.     

An authenticated secure image hiding scheme

Abstract

Image hiding involves the concealment of an embedded secret image within a cover image to form a stego-image. The secret image can be used for transmission across the public networks without its presence being detected. Image hiding thus serves as a way of secure message communication; therefore, except for the platitudinous issues of image quality and hiding capacity, it is necessary to pay more attention to the means to assure the origin and integrity of the delivered content. In this paper, a digital signature scheme is skillfully applied so as to guarantee the integrity and the origin of the transmitted message and a behind-the-scenes guide to recover the hidden secret. Our idea launches realistic feints and ambushes to enhance the effect of camouflage.