Production and properties of crude enterotoxin of Pseudomonas aeruginosa

Pseudomonas aeruginosa CTM-3 was found to be the most potentially enteroxigenic strain out of the 12 isolates recovered from milk, as a high fluid length ratio, i.e. F/L (1.1) in rabbit gut and a strong permeability response in rabbit skin (38.5 mm² necrotic zone) was obtained with this culture. No clear-cut relationship between the two tests was observed. Six of the ethidium bromide (300 μg/ml) cured variants of this culture completely lost their ability to produce enterotoxin indicating the possible involvement of a plasmid in enterotoxin synthesis. The crude enterotoxin from P. aeruginosa CTM-3 was completely inactivated in 15 s at 72°C. However, it was fairly stable at pH values in the range 4.5–7.5. Both pepsin and trypsin inactivated the enterotoxin activity at a concentration of 40 μg/ml. Organic acids, formalin and hydrogen peroxide had no significant effect on the enterotoxin activity. The need for further investigations with purified preparations is emphasized.     

26—A STUDY OF LIGHT DAMAGE TO UNDYED TEXTILE YARNS UNDER A FADING LAMP AT A FIXED HUMIDITY

An investigation is described in which the effect of light on several undyed textile fibres was studied with two sources of light, (i)natural sunlight and (ii) a Light-fastness Tester. The exposures were carried out in an atmosphere of controlled humidity, i.e., at 45% r.h., and behind glass. The results in terms of percentage loss in tensile strength, elongation, and energy to break are found to be identical for both types of exposure. Tendering by the Tester is shown to be twice as rapid as that by natural sunlight. By using the Tester for 24 hours per day as against 8 hours per day for sunlight, results could be obtained in one-sixth of the time. Moreover, the Light-fastness Tester is cheap and easy to handle compared with other sources of artificial light.     

Trends and Profile in Enzyme Engineering Research during 1971–98

There is sufficient evidence to prove the potential of immobilized enzymes to be commercially successful in many industries, but a survey of products in biotechnology and some reports indicate its limited success. To visualize the factual status, the present study looks into trends and profiles of this field using scientometric methods. The salient results show a steady decline in outputs in the form of patents and publications since 1993 along with a decline in the number of groups from academics and industries. Among the countries involved, there is also a decline, though USA and Japan show some strength in basic and applied research, respectively.     

Development of a novel metal hydride–air secondary battery

A laboratory metal hydride/air cell was evaluated. Charging was via a bifunctional air gas-diffusion electrode. Mixed nickel and cobalt oxides, supported on carbon black and activated carbon, were used as catalysts in this electrode. At 30mAcm–2 in 6m KOH, the air electrode potentials were –0.2V (oxygen reduction) and +0.65V (oxygen evolution) vs Hg/HgO. The laboratory cell was cycled for 50 cycles at the C/2 rate (10mAcm–2). The average discharge/charge voltages of the cell were 0.65 and 1.6V, respectively. The initial capacity of the metal hydride electrode decreased by about 15% after 50 cycles.     

The use of tin and bronze in prehistoric southern Indian metallurgy

Conclusions Although the findings are from disparate contexts, they demonstrate a long familiarity of Indian metal workers with the use of tin and with manipulating bronze alloys to exploit the functional properties of phases and intermetallic compounds. Thus, the copper-bronze tradition in southern Indian antiquity and in the Indian subcontinent has more depth than suspected, with some evidence for the use of local tin sources in southern India. Some of the findings are reasonably peculiar to the region, such as the solid-cast bronze images, β bronze coinage, δ bronze mirrors, and α bronze slags, while the high-tin β bronzes and vessels from Indian prehistory predate those known elsewhere and probably go back to the Indus Valley. All of this strengthens the case for indigenous copper-bronze traditions. Sharada Srinivasan earned her Ph.D. in southern Indian archaeometallurgy from the Institute of Archaeology, University College, London, in 1996. She is currently a Homi Bhabha Fellow in archaeometallurgy at the Department of Metallurgy, Indian Institute of Science, Bangalore, India.     

Electrochemical oxidation of boron containing compounds on titanium carbide and its implications to direct fuel cells

Electrochemical oxidation of sodium borohydride (NaBH₄) and ammonia borane (NH₃BH₃) (AB) have been studied on titanium carbide electrode. The oxidation is followed by using cyclic voltammetry, chronoamperometry and polarization measurements. A fuel cell with TiC as anode and 40 wt% Pt/C as cathode is constructed and the polarization behaviour is studied with NaBH₄ as anodic fuel and hydrogen peroxide as catholyte. A maximum power density of 65 mW cm⁻² at a load current density of 83 mA cm⁻² is obtained at 343 K in the case of borhydride-based fuel cell and a value of 85 mW cm⁻² at 105 mA cm⁻² is obtained in the case of AB-based fuel cell at 353 K.