Immobilization of the thrombin inhibitor r-hirudin conserving its biological activity

Surface immobilization of the thrombin inhibitor r-hirudin was carried out on two different polymers. Linkage to poly(urethane-graft-acrylic acid) (PAC/PU) was done via carboxylic acid groups, using a water soluble carbodimide, while the immobilization on a modified poly[(ethene-co-vinyl acetate)-graft-vinyl chloride] (PVC/EVA) was achieved via the alcohol groups of the polymer using HDI as spacer. Direct immobilization of r-hirudin leaded to a remarkable loss of thrombin activity. As proved by means of protein chemical analysis, loss of activity was due to a selective coupling via the N-terminal amino group of r-hirudin, which is essential for its thrombin activity. Based on these results we developed an immobilization method via an -amino group of r-hirudin preserving full biological activity of the r-hirudin coated surface. © 2001 Kluwer Academic Publishers     

Influence of surface defects and corrosive medium on the fatigue resistance of ST17G1S steel

We study the influence of surface defects and corrosive medium on the characteristics of fatigue resistance of specimens of ST17G1S steel extensively used for the production of pipes in the oil-and-gas industry. The accumulated results enable us to estimate the degree of decrease in the limited fatigue strength for specimens of ST17G1S steel in the presence of surface defects and under the action of corrosive medium. __________ Translated from Problemy Prochnosti, No. 4, pp. 99–107, July–August, 2007.     

Influence of corrosive media on the fatigue strength of duralumin in relation to the loading frequency

Electrode potentials of D16T duralumin specimens during fatigue tests in a 3% NaCl solution at loading frequencies of 200 and 3000 cpm were measured and the fatigue strength of this material tested in air and water at loading frequencies of 200 and 6000 cpm was determined. It was established that the effect of corrosive media on the fatigue limit and endurance of duralumin depends on the loading frequency.     

Influence of freeze–thaw on the stored free energy in soils

In K₀ consolidation, i.e. laterally confined compression, the axial pressure creates some plastic work on the soil samples. Part of this plastic work is dissipated by friction between soil grains. The other part is stored as free energy (SFE) in the soil. When the soil micro-structure is disturbed, SFE is either accumulated or released. In this paper, formula for SFE is deduced under K₀ conditions. Lanzhou loess and Qinghai–Tibet silty clay were used as study objects. After freeze–thaw, changes in mechanical properties of the two soils lead to the changes in SFE. It is found that freeze–thaw has different effects on the soil density, and thus on SFE. They are increased for the soils with low original dry unit weight, and decreased for the soils with high original dry unit weight.     

Influence of polyacrylic acid on the protective properties of the KORSOL inhibitor

Polyacrylic acid (PAA) is a dispersant of hardness salts. Its anticorrosion properties are better than the anticorrosion properties of the dispersants produced by the Nalko Firm. In the KORSOL composition, it does not reveal the synergetic action but does not deteriorate the protective properties of the inhibitor.     

Effect of the corrosive medium on propagation of short cracks

Conclusions The results show that the crack depth in the range 0.2–1.3 mm affects the chemically determined crack growth rate in 50SiMn7 high-strength steel under the effect of the alkaline sulfate-saturated solution of Ca(OH)₂ (pH 12.1). In free corrosion conditions and a load constant with time, the upper boundary of the depth of the chemically small crack for the given system is 1.3 mm. In the saturated solution of CaSO₄ this boundary is below 0.2 mm. This experimentally confirmed effect of the chemically small cracks makes it possible to increase the crack depth from 0.12 to 0.25 mm at a given load of 900 MPa.The article was sent to the editorial board in the German language. Authorized translation by S. Ya. Yarema.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 2, pp. 13–20, March–April, 1990.     

Influence of the surface morphology and microstructure on the biological properties of Ti-Si-C-N-O coatings

Detailed structural, microstructural, biofilm formation and cytotoxicity studies were performed on Ti-Si-C-ON hard coatings prepared by DC reactive magnetron sputtering, in order to evaluate the relation among these properties. Compositional analysis showed the existence of two distinct regimens; regime I: high C/Si atomic ratio (C/Si ≥ 1.42) and intermediate N/Ti atomic ratio; regime II: low C/Si atomic ratio (C/Si ≤ 0.49) and low N/Ti atomic ratio. The structural analysis revealed that, in regime I, films crystallized in a B1-NaCl crystal structure typical of TiC_0.2N_0.8. In regime II, the decrease of C/Si and increase in silicon concentration led to the formation of Ti-Si-C-ON along with a reduction of grain size in the films. Atomic force microscopy observations showed that the surface morphology of these Ti-Si-C-ON films became smoother when the silicon content increased and the nitrogen content decreased, which is consistent with the formation of nanosized clusters. Concerning biological properties, it was observed that cytotoxicity could be related with the titanium concentration while biofilm formation ability was found to be related with the surface morphology of the films.     

Influence of EDTA washing on the species and mobility of heavy metals residual in soils

Aiming to estimate the potential risk of ethylenediaminetetraacetic acid (EDTA)-enhanced soil washing, the heavy metal species and their mobility in the washed soil under different combinations were investigated by batch leaching tests and the sequential extraction procedure. Results demonstrate that the metal removal efficiency was rather low (less than 12%), partially due to the significant Ca dissolution and strong bonding between metals and the soil as well as the insufficient EDTA dosage. The washing combination of 0.0005 M EDTA and half-an-hour washing can enhance the instant mobility of Ni, Zn and Pb possibly owing to the slow detachment of EDTA-destabilized metals. Metal fractionation also exhibits the corresponding increase in their labile exchangeable fractions. Therefore, a more concentrated EDTA solution for a longer duration often decreased their mobility. The increase in some fractions of a curtain metal implies the redistribution of this metal during the EDTA soil washing. The pathway of such a redistribution may vary for different metals, but the redistribution to organic matter is often a slow process, while that to carbonates or Fe/Mn oxides is a faster one and even may occur in a half hour washing with 0.0005 M EDTA solution. These redistribution processes may also increase the metal chemical availability. Therefore, we should prudently control the chelating reagent concentration and washing duration to finally minimize the mobility and availability of the remaining heavy metals when designing the soil washing for the remediation of metal-contaminated soils.