Some morphological observations on polycaprolactam filament

Examination of longitudinal, cross, and skew sections of extruded polycaprolactam filaments with the polarizing light microscope reveal morphological features not previously described. In cross-sectional view, three distinct layers enclose a “homogeneous” central matrix. The outermost layer is characterized by large, birefringent, truncated cones extending upward from the surface. Associated with the cones and an entity in its own right is what appears to be a second layer of ultrafibrils. Below the latter is a fine-structured layer of submicroscopic spherulites. A combination of the above features forms the transcrystalline region of stressed melts. Row nucleation is evident on the surface of the filaments.     

An ultrasonic velocity borehole logger for use in rock

An ultrasonic velocity borehole logger has been developed for use in small diameter boreholes drilled in rock for probing ahead of tunnels. The paper gives details of its design and construction and examples of its use in logging boreholes drilled in a laboratory trial and in an underground stone quarry. Two special features of the logging tool are that the transducers are mechanically pressed against the rock in the borehole wall and therefore no liquid is needed in the borehole to provide a coupling for the signal, and that the whole tool has been made compact enough to fit into a 56 mm diameter borehole. The instrument measures the compressional wave velocity of the rock, which may be interpreted to provide a qualitative indication of rock properties. In addition a method of deriving the rock strength from the velocity is suggested and demonstrated for the two test boreholes. Recommendations for developing the prototype into an instrument for routine use are made.     

Some observations on the mechanisms of atomization in atomic absorption spectrometry with atom-trapping and electrothermal techniques

The mechanisms of collection and release of sixteen elements in atom-trapping atomic absorption spectrometry with a water-cooled silica trap in an air-acetylene flame are examined. Ag, Au, Cd, Co, Cu, Fe, Ni, Pb, Se and Zn appear to accumulate as metals whilst K, Li, Na, Cr, Mg and Mn are trapped as silicates or oxides. Al and V are also trapped as oxides, but were not studied further. No evidence could be found that the surface temperature of the trap exceeds 1700 K during the release cycle. Plots of appearance time of atoms vs. m.p. suggest that while direct evaporation can play a part in atomization, sputtering by energetic species in the scouring flame gases may explain the appearance of gaseous atoms at the relatively low temperatures involved. The atomization phenomena are related to those observed with electrothermal atomizers based on carbon and tantalum. It is suggested that sputtering processes may also be involved in such atomizers.     

Some optical studies with the air-acetylene flame

The application of Schlieren and shadow techniques for the study of flame processes is discussed in relation to analytically useful premixed flames. The information obtained, particularly with shadowgraphs, may be correlated with the measured signals and signal noise in atomic-absorption and flame-emission spectrometry.