synopsisTwo water-soluble synthetic polymers and several polysaccharides were compared for friction reduction effectiveness during increased exposure to turbulent flow. Solutions were passed through a 0.117 X 41.0 cm fine bore tube at a constant solvent wall shear stress of 4200 dynes/cm2 and wall shear rate of 4 X 1W sec-'. After one pass through the tube, greatest friction reduction at low polymer concentrations waa in the order poly(ethy1ene oxide) > polyacrylamide > bacterial polysaccharide from Xanthomonas campesbis > guar gum. As a result of mechanical degradation, after 40 passes of 40 ppm solutions, friction reduction effect.iveness was in the order polyacrylamide > polysaccharide from Xunthomonas cumpestris > poly(ethy1ene oxide) > guar gum. Degradation curves, the effect of concentration on degradation, and boundary layer and pipe flow applications are discussed.
The reduction of light intensity in bioluminescent bacteria upon exposure to toxic substances can be used for rapid screening of materials. Results are often comparable to more expensive standard bioassays.A commercially available system was used to determine the relative response of bioluminescent bacteria to a number of alkyltin compounds: R4Sn, R3SnX, R2SnX2, and RSnX3, where R = alkyl group and X = halide, Within a series of compounds differing only in the number of R groups attached to the central tin atom, the most toxic compound was always the trialkyltin compound. The greatest difference in toxicity was found in the butyltin series of compounds: tributyltin was -35 times more toxic than dibutyltin and -750 times more toxic than (mono)butyltin. When trialkyltin compounds were compared, the toxicity to these bacteria increased with the number of carbons in the alkyl chain: the tributyltin compounds are -150 times more toxic than trimethyltin compounds.
Vibrio marinus MP-1, an obligate psychrophilic marine bacterium, was severely damaged when heat-shocked in growth medium. Cells heat-shocked at 20, 23, and 25 C in growth medium released 260 mμ absorbing material (nucleic acids and nucleotides), orcinol-reacting material (RNA), ninhydrin-reacting material (amino acids), malic dehydrogenase, and glucose-6-phosphate dehydrogenase increasingly at higher temperatures. Older cultures were found to be more resistant to thermal death, lysis, and leakage. No significant leakage or lysis could be detected after the heat-shocking of stationary phase cells in growth medium for 120 min when more than 99.9% were killed. Cells in the log phase of growth were the most sensitive to death, leakage, and lysis. After 95% were killed at 25 C, and 94% at 20 C, cells began to release intracellular materials. Leakage and lysis occurred concomitantly after death. Loss of membrane permeability control before death would, therefore, not be indicated. It is suggested that the increased sensitivity to heat in young cultures may be attributed to thermolabile synthetic mechanisms involved in rapidly growing cultures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.