A Mathematical Model of Digital Linear Tomography

Russian Journal of Nondestructive Testing - A mathematical model of digital linear tomography has been developed that takes into account the geometrical parameters of the scheme of testing, the...     

Segregation of impurities,temper brittleness,and hydrogen embrittlement of steel 30KhNMA with different concentrations of molybdenum

In recent years practical and scientific interest in investigating segregation processes to assess the mechanism of steel embrittlement by impurity elements has grown. This interest was noticeably stimulated by industrial use of new metallurgical technologies that ensure higher purity of steel with respect to impurity elements. It has become possible to decrease the content of expensive molybdenum due to the higher purity of steels without substantial change in their properties. In the present work the structure and properties of steel 30KhNMA with conventional and elevated purities, standard and reduced concentrations of molybdenum, and microadditions of V, Ti, and Nb are investigated.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 21–24, May, 1995.     

Polyurethane/poly(hydroxyethyl methacrylate) semi-interpenetrating polymer networks for biomedical applications

The thermodynamic miscibility, morphology, phase distribution, mechanical properties, surface properties, water sorption, bacterial adhesion and cytotoxicity of semi-interpenetrating polymer networks (semi-IPNs) based on crosslinked polyurethane (PU) and poly(hydroxyethylmethacrylate) (PHEMA) were studied to give an insight into their structure and properties. The free energies of mixing of the two polymers in semi-IPNs have been determined and it was shown that the values are positive and depend on the amount of PHEMA. This demonstrates that the components are immiscible, the extent of which is dependent upon variations in composition. The morphology of the semi-IPNs was analyzed with scanning electron microscopy and tapping mode atomic force microscopy (TMAFM). The micrographs of the semi-IPNs and TMAFM phase images indicated that distinct phase separation at the nanometer scale is observed. The mechanical properties reflect the changes in structure of semi-IPNs with composition. The stress at break increases from 3.4 MPa to 23.9 MPa, and the Young’s modulus from 12.7 MPa up to 658.5 MPa with increasing amounts of PHEMA, but strain at break has a maximum at 40.4% PHEMA. The bacterial adhesion and cytotoxicity data suggest that semi-IPNs with PHEMA content above 22% may be used for biomedical material applications.     

Hydroxyapatite-calcium carbonate ceramic composite materials

Hydroxyapatite/calcium carbonate (CC) composite powders containing up to 50 wt % CO₃²⁻, have been prepared via precipitation from aqueous solutions. According to chemical analysis data, the CO₃²⁻ content of the powders coincides with the intended one over the entire composition range studied. With increasing CO₃²⁻ content, the specific surface area of the powders decreases because of the formation and growth of large needlelike CC crystals up to 1.5 μm in size. The addition of low-melting-point alkali carbonates to the starting powder mixture reduces the sintering temperature of the powders to below 720°C, thereby preventing the thermal decomposition of CC. The highest bending strength, up to 76 MPa, is offered by the materials with the lowest CC content, about 20 wt %, and an average crystal size of 100 nm. The solubility of the composites gradually increases with CC content. In vitro experiments with a human fibroblast model (MTT test) demonstrate that the composites have zero cytotoxicity.     

Immunochemical study of antigens in the ascitic fluid of patients with ovarian cancer

5 antigens are identified in ascitic fluid from patients with ovarian tumours--AgA, AgB, AgV, AgG and AgD. Specific antisera are produced in rabbits by immunization with different protein and glycoprotein fractions of this fluid and by simultaneous injections of gamma-globulin fraction from antihuman plasma protein and pool of 25 ascitic fluids to rabbits. By the double immunodiffusion technique with standard test-systems for these antigens. It is found that all of them are absent in donor blood serum, but are present in certain normal and fetal tissues. AgA and AgD are also found in some extracts of lung, stomach, colon, and connective tissue tumours. The immunohistochemical and high-sensitive serological methods are necessary for determination of the usefulness of these antigens as tumour markers.