[The formation of trihalomethanes precursor in anionic surfactant biodegradation].
Trihalomethanes (THMs) formed by chlorination of precursor substances in raw water, are found in drinking water. They are found at concentration levels higher than those of other organic contaminants. In the present study, the relationship between the formation of THM precursors and anionic surfectants biodegradation was investigated. Three anionic surfectants (LAS, AS and soap), dissolved in river
Biodegradation of α-Olefin Sulfonates (AOS) and Other Surfactants
To follow the progress of biodegradation of anionic surfactants, the methylene blue method is the most widely employed for quantitative analysis. But, there is unaccountably the case in which the activity to methylene blue disappeared even before surfactant has not yet completely been biodegraded into inorganic compounds. And so, we examined the biodegradability of several surfactants by measuring the residual carbonaceous materials in comparison with the colorimetric analysis.Sodium α-olefin sulfonates (AOS) and other ten anionic and three nonionic surfactants were taken as test materials. In the shake culture test method, it was found that surfactants containing straight alkyl chain such as AOS, alcohol sulfate and soap were degraded in shorter period necessary for the disappearance of the carbonaceous materials during biodegradation. However, surfactants having benzene ring or ethoxylate chain in their molecules were slow in decrease of the concentration of organic carbon during biodegradation, and there was a large discrepancy between the biodegradation rates obtained by colorimetric analysis and measurement of organic carbon.
Thermally Induced Dynamics of Satellite Solar Panels
Thermally induced structural motions are known to affect the attitude dynamics of low Earth orbiting satellites during eclipse transitions. Motions of e exible appendages such as solar panels lead to rigid body rotations of the entire satellite because the total angular momentum of the system is conserved. These potentially large attitude disturbances may violate pointing accuracy and jitter requirements. One type of thermally induced dynamics exhibited by solar panels is thermal snap. The Upper Atmosphere Research Satellite is a prominent example of a satellite that experiences thermal snap disturbances during eclipse transitions. This paper describes recent studies of thermally induced dynamicsof solarpanels, including an analysisofsatelliteattitudedynamics resulting from thermally induced structural motions and a laboratory investigation of the thermal-structural performance of a satellite solar panel. Analytical and experimental results demonstrate thermal bending deformations with acceleration transients that have characteristic thermal snap disturbance histories in response to rapid changes in heating. The studies show that solar panel thermal snap disturbances are caused by through-the-thickness temperature differences that vary at a nonconstant rate. Finite element analysis correctly predicts the thermal snap phenomenon observed in the solar panel experiments.