The characteristics and design of the conical log-spiral antenna

The balanced conical logarithmic-spiral antenna is considered as a slow-wave locally periodic structure with a slowly varying period. A study of the near fields and their relationship to the far fields has led to the identification of the active region or effective radiating aperture on the antenna and to a clearer understanding of its operating characteristics. Information of the near- and far-field characteristics and on the input impedance for a wide range of parameters is presented in a form suitable for use in the design of practical antennas.     

Simultaneous analysis of hydrocortisone and hydrocortisone phosphate by high-pressure liquid chromatography: reversed-phase, ion-pairing approach

The reversed-phase, ion-pairing approach to high-pressure liquid chromatography was applied to the simultaneous analysis of hydrocortisone and its phosphate ester in laboratory-prepared samples and injectable solutions. Results of this technique were evaluated and compared with results of the official procedure.     

A comparison of two sampling methods for the estimation of dry matter and mineral content of swede roots

The composition of swede roots is normally estimated from samples of cores, from which the outer tissue is cut off to minimise soil contamination. Cylindrical cores contain a disproportionally large amount of xylem tissue which has a relatively low dry matter (DM), N, Ca, Na and Mg content and a high K content. Segments are the only subsamples of swede roots which have the correct proportions of xylem, phloem and skin. Several hundred samples of cores and segments were analysed to determine whether correction factors could be applied to data obtained from the less laborious method of taking cores. The mean correction factors for the cultivar Doon Major were 1.08 for DM content and 1.11, 1.01, 0.75, 1.30, 1.48 and 1.55 for N, P, K, Ca, Na and Mg, respectively. However, these factors varied, depending on site, season, fertiliser treatment and root size. Therefore, constant correction factors can not be generally applied and cores must be regarded as unsatisfactory for estimating the composition and nutrient uptake of swedes. The errors involved in determining P content from core samples appeared to be relatively insignificant.     

Microprocessor-based IEEE-488 interfacing unit as a development aid

The IEEE-488 standard has become one of the major standards for instrument interfacing used today, finding wide application in automatic test equipment and microcomputer-based controllers. This article describes a microprocessor-based IEEE-488 interfacing unit that is now in use as a development aid in our digital control laboratories. The unit offers an answer to specialized signal generation and intelligent data acquisition.