Detonation-Wave Phenomena

Abstract

Study of detonation-wave phenomena in high explosives is a necessary adjunct to the understanding of explosive effects and their practical applications. The phenomena associated with a single detonation wave are complex; the collision of several may be spectacular. The sequence of ultra-high speed photographs on the front cover of this issue of Science shows the collision of eight waves. These photographs, made by the Naval Weapons Laboratory, Dahlgren, Virginia, are a by-product of a general study of initiation, propagation, and interaction of detonation waves undertaken as an aid to explosive system design. The action which occurs in just a few microseconds shows a symmetry in the detonating explosive which rivals that of the snowflake. When photographed in color, the growth and fading of this rather strange explosive "snowflake" give an appearance of unreal beauty.These photographs were made with a Beckman and Whitley model 189 framing camera operating at about 600,000 frames per second, with individual exposure times of about 0.6 microsecond. A disk of DuPont EL 506C sheet explosive 25.4 centimeters in diameter by 0.379 centimeter thick was mounted on plywood. The explosive was initiated simultaneously at eight equidistant points on its rear surface with exploding bridge-wire detonators.A frame-by-frame description (beginning with the upper left-hand corner and reading downward) follows: 1) A still shot of the disk mounted on plywood.2-3) Detonation begins simultaneously and expands uniformly. 4-9) Extreme pressures at the collision of wave fronts produce lines of intense luminosity resulting from the ionization of the air. 10) Collision lines reach the center. 11-15) Reflected shock waves pro- DECEMBER 1964 Detonation-Wave PhenomenaStudy of detonation-wave phenomena in high explosives is a necessary adjunct to the understanding of explosive effects and their practical applications. The phenomena associated with a single detonation wave are complex; the collision of several may be spectacular. The sequence of ultra-high speed photographs on the front cover of this issue of Science shows the collision of eight waves. These photographs, made by the Naval Weapons Laboratory, Dahlgren, Virginia, are a by-product of a general study of initiation, propagation, and interaction of detonation waves undertaken as an aid to explosive system design. The action which occurs in just a few microseconds shows a symmetry in the detonating explosive which rivals that of the snowflake. When photographed in color, the growth and fading of this rather strange explosive "snowflake" give an appearance of unreal beauty.These photographs were made with a Beckman and Whitley model 189 framing camera operating at about 600,000 frames per second, with individual exposure times of about 0.6 microsecond. A disk of DuPont EL 506C sheet explosive 25.4 centimeters in diameter by 0.379 centimeter thick was mounted on plywood. The explosive was initiated simultaneously at eight equidistant points on its rear surface with exploding bridge-wire ...

Relation between Subunit Structure and Temperature-Sensitivity of Mutant Phenylalanyl RNA Synthetases of Escherichia coli

“…The ready dissociation of the mutant and revertant enzymes prompted us to study dissociation of the wild type enzyme in order to compare the size of possibly resulting subunits with those present in mutant extracts. For this purpose a preparation of purified phenylalanyl RNA synthetase of wild type NP3 was dialyzed for different lengths of time against 1 .O M guanidine hydrochloride containing 10 mM 2-mercaptoethanol [19] and was then subsequently fractionated by gel filtration. The fractions were analyzed for enzyme activity and cross-reacting material (Fig.…”

“…For this purpose a preparation of purified phenylalanyl RNA synthetase of wild type NP3 was dialyzed for different lengths of time against 1 .O M guanidine hydrochloride containing 10 mM 2-mercaptoethanol [19] and was then subsequently fractionated by gel filtration. The fractions were analyzed for enzyme activity and cross-reacting material (Fig.…”

On the dissociation of the sheep haemoglobin molecule at neutral pH I. Osmotic pressure measurements

“…Extrapolating to zero NaCl concentration, the limiting AG® is 8 kcal/mol (33 kJ/mol), close to the published value (8.2) of Kawahara et al (1965) for human HbCO a t 25 °C in a variety of inorganic salt solutions. The nonlinearity of the plot in figure 6 suggests, according to Tanford (1964), th a t specific ion-binding, probably of Cl-ions, occurs. The available experimental d ata in phosphate solutions do not allow a quantitative extrapola tion, b u t a higher extrapolation lim it ife suspected (see Johnson & Perrella 1970).…”

“…Recent investigations on human haemoglobin at neutral pH have been carried out by Tanford (1964), Kirschner & Tanford (1964), Kawahara, Kirschner & Tanford (1965 using sedimentation velocity and assuming certain sedimentation coefficients for the undissociated molecule and its subunits, by Guidotti (1967) using osmometry, and by Chiancone, Gilbert, Gilbert & Kellett (1968) using gel filtration.…”