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Experimental results obtained by in situ machining within a Scanning Electron Microscope of a resulphurized steel containing Type I manganese sulphide inclusions are presented. The data obtained from slow speed machining tests show that chip formation in these steels involves decohesion and cavitation at the sulphide-matrix interface as well as fracture of sulphide inclusions. While these processes promote fracture in the shearing region during chip formation (confirming an earlier hypothesis due to Tipnis and Cook), it is argued that these phenomena cannot be responsible for better tool life, surface finish, and lowered power requirements usually encountered with free machining alloys under typical industrial cutting conditions. The role of thermal dissipation during machining and its effect in altering the chip formation through thermally induced changes in plastic flow behavior of Type I sulphide inclusions are discussed.

A simple technique for designing low-pass recursive digital filters with nearly linear phase characteristic is presented. The linearity of phase is obtained by placing the poles in the neighbourhood of the passband at equal intervals on a circle of radius r, inside the unit circle on the z-plane. The zeros are placed in the stopband on another circle of radius 1/r. The phase characteristics of these filters are shown to be linear with a maximum periodic error of r m radian, where m is the sum of the number of poles and zeros of the filter. This error can be made small by suitably choosing m and r. Stop-band transmission characteristics of these filters are also examined and an upper bound obtained for the asymptotic db-loss.

Detailed cytological studies have been carried out on nine species and varieties under the genus Sida. Some varieties of S. rhombifolia showed the presence of accessory chromosomes and so populations of these varieties from different ecological habitats were collected. Paradichlorobenzene and aesculin were found to be the most effective pretreating chemicals in studying their somatic chromosomes. The chromosome numbers reveal that polyploidy, both inter- and intraspecific, has played a role in evolution in the genus, in addition to aneuploidy. Of the different basic numbers (n=7, 8, 9) 7 is found to be deep seated.In addition to polyploidy, structural rearrangements of chromosomes have been observed in all cases showing their prominent role in speciation within this genus. Moreover, regular bivalent formation even in intraspecific tetraploids suggests structural changes during evolution. However homogeneity of the genus as a whole is indicated in the general pattern of the karyotypes of different species and varieties and also in the similarity in their total chromatin length. Within this genus at least polyploidy in speciation has not been associated with diminution in chromosome size.The constant presence of accessory chromosomes in a phenotypically distinct population of S. rhombifolia, indicates some selective advantage. Regarding the origin of accessory chromosomes, it has been suggested that some of the extra chromosomes of high polyploid cells which are often found in the individuals bearing accessories, may lose their function and undergo heterochromatinization and as such are transformed into accessory, ones.