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991.
Microbial sensor for preliminary screening of mutagens utilizing a phage induction test 总被引:1,自引:0,他引:1
For the preliminary screening of mutagens, a novel microbial sensor system was developed utilizing a phage induction test. Escherichia coli lysogenic strain GY5027 and nonlysogenic strain GY5026 were used in this study. The number of living cells was determined by measuring the respiration of cells immobilized onto an oxygen electrode. The injection of a mutagen, such as AF-2 and MNNG, caused the phage induction in the lysogenic strain, resulting in the decreased respiration of only the lysogenic strain immobilized onto the oxygen electrode but not of nonlysogenic strain. The rate of current increase correlated well with the concentration of mutagens. The sensor responses to the antibiotics and bactericides were definitely different from those of mutagens. Therefore, utilization of this microbial sensor system makes possible the estimation of a substrate's mutagenicity. 相似文献
992.
X. S. Ning K. Suganuma T. Okamoto A. Koreeda Y. Miyamoto 《Journal of Materials Science》1989,24(8):2879-2883
Two kinds of additive-free silicon nitride ceramics were brazed with aluminium; one was with as-ground faying surfaces and
the other was with faying surfaces heat-treated at 1073K for 1.8 ksec in air. The heat-treatment of the silicon nitride ceramics
formed a silicon oxynitride layer on the faying surfaces and increased the brazing strength of the joints. A silica-alumina
non-crystalline layer and a β′-sialon layer were formed successively from the aluminium side at the interface of the joints.
The heat-treatment which made the former layer thicker is a necessary process in making reliable, strong brazed joints. 相似文献
993.
994.
995.
The change in polystyrene (PS) layer thickness, which has been simultaneously determined during post-yield deformation, shows
that crazing is the basic mechanism of toughening in all laminated films, and that shear deformation supplements the contribution
of crazing especially for samples with high polyethylene (PE) volume fractions. Crazes formed in PS layers in the laminated
films are slender and regular compared with the short and lenticular crazes formed in bulk PS film. When PE volume fraction
increased, craze advance speed decreased because of the reduction of the stress concentration effect at craze tips. The life-time
of the first mature craze to be formed at a given strain rate increased with PE volume fraction because the PE supporting
the mature crazes could effectively inhibit craze rupture and blunt out the propagating crack by absorbing the stored elastic
energy in the PS layer that would have been dissipated as fracture surface energy. 相似文献
996.
997.
J. M. Richards M. I. Darby R. Baggott G. H. Wosteim Holm B. Yates G. Dorey L. N. Phillips 《Journal of Materials Science》1989,24(2):584-589
The effects of defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates have been measured. The defects studied were cut fibre plies, omission of polymer films and local delamination produced by the inclusion of foreign matter. Of these it was found that only cut plies had a significant detrimental effect on the strength of a laminate. For specimens with two cut plies, the failure stress, tensile, flexural and compressive in the remaining continuous plies was the same as in the defect-free material, provided that the cut plies were widely separated. However the failure stresses were 15–18% lower in the continuous plies in the specimens containing two cut plies which were more closely spaced and in specimens containing four cut plies. 相似文献
998.
A. Sadananda Chary S. Narender Reddy T. Chiranjivi 《Journal of Materials Science》1989,24(6):2199-2202
Dielectric properties, dielectric constant (k), dielectric loss (tan δ) and a.c. conductivity (σ) in the solution-grown single crystals of RbNO3 are presented from room temperature to about 200°C covering the frequency range 102 to 105 Hz. A broad peak observed in tan δ-frequency data between 103 and 105Hz is thought to be due to impurity-vacancy dipoles. The sudden rise of three parameters near 160°C is attributed to the known
phase transition from trigonal to CsCl structure. 相似文献
999.
1000.
This paper derives the governing equations for the thermomechanical behaviour of composites. When the basic equations for the thermoelastic behaviour of solids were first derived in the nineteenth century several approximations were made. The effect of these assumptions are discussed and illustrated by the results of a simple laboratory test. The implications of this work on the analysis of impact damaged laminates are then discussed. 相似文献