Study of the fatigue delamination behaviour of adhesive joints in carbon fibre reinforced epoxy composites, influence of the period of exposure to saline environment.

This work analyses the fatigue delamination and fracture stress behaviour under mode I of adhesive joints made on an epoxy matrix composite material with unidirectional carbon fibre reinforcement and a commercial epoxy-based adhesive. DCB type tests (for mode I) were used with the aim to quantify the influence of the period of exposure to a degradation process in a salt spray chamber, to which the tested samples were subjected, on their fatigue behaviour. For this purpose and after a previous static characterisation of the material in which the critical values of the energy release rate for different exposure periods were determined, the levels of the energy release rate to be applied in the fatigue tests and the exposure periods to be considered (no exposure, exposure during one week and twelve weeks) and a ratio of fatigue stress levels of R = Gmin/Gmax = 0.1 were defined. From this experimental data, the G-N fatigue initiation curves and the G-da/dN growth curves were obtained. The experimental data obtained, in the fatigue initiation phase of the delamination process, have been treated by means of a probabilistic model based on a Weibull distribution, the application of models of these characteristics has allowed a better interpretation of the experimental results obtained. The most relevant result of the work is that, in general, the fatigue limits obtained for the adhesive joint, under mode I fracture, when subjected to a degradation process in a saline environment, do not translate into a relevant loss of its resistance capacity against this fatigue delamination phenomenon, in its initiation phase. On the other hand, the crack growth rates of the material subjected to different periods of exposure to a saline environment are similar and higher than those obtained for the material without exposure.

[New data on the potentials and prospects for the use of immobilized enzymes in medicine]. / Novye dannye o vozmozhnostiakh i perspektivakh primeneniia immobilizovannykh fermentov v meditsine.

The data on the completing level of a number of medical preparations on the basis of immobilized proteins, in particular, on the basis of enzymes are given. The firms and companies which successfully cooperate in the field of development of commercial programs for such preparations are listed. On the basis of own study a possibility to create some effective antitumor compounds in the next future is shown. The urgent and prospective application of the immobilized enzymes instead of the native ones in the medicine is grounded.

[High molecular weight L-asparaginase derivatives based on a water-soluble carboxymethyl cellulose: biological properties]. / Vysokomolekuliarnye proizvodnye L-asparaginazy na osnove vodorastvorimoi karboksimetiltselliulozy: biologicheskie svoistva.

L-asparaginase, covalently bound with water-soluble CM-cellulose, exhibited the elevated antileukemic activity in mice with inoculated lymphoid leukemia L5178y as compared with the native enzyme. The antileukemic activity of the immobilized enzyme was shown to depend on the content of the polymer bound with the enzyme; the polymer amount may be altered during the enzyme modification. The prolonged effect of immobilized L-asparaginase was observed in rabbit circulation.

[Effective complexes of the antileukemic enzyme L-asparaginase with dextran sulfate]. / Effektivnye kompleksy protivoleikoznogo fermenta L-asparaginazy s dekstransul'fatom.

Enzymatic and antileukemic effects of the complexes of L-asparaginase from E. coli and biologically active polymer dextran sulfate were studied to increase their therapeutic properties. The complex was characterized by more distinct substrate specificity, by an increase in the stability during storage, in thermostability as well as in the resistance to proteolysis. The increased antileukemic activity of the complex was observed in experimental lymphoid leukemia L5178y in mice. Use of the complex of L-asparaginase and dextran sulfate enabled to decrease distinctly the therapeutic dose of the enzyme.