A comparative investigation of the properties of nickel-graphite materials from electrolytic and carbonyl nickel powders

Summary The substitution of carbonyl nickel powder for electrolytic powder raises the strength, as well as the corrosion and oxidation resistance of nickel-graphite materials. The particle size and ash content of the graphite exert no marked influence on the strength characteristics.Translated from Poroshkovaya Metallurgiya, No. 11(47), pp. 35–38, November, 1966.     

Effect of the physicochemical properties of molten copper on the structure and properties of the atomized powders

Translated from Poroshkovaya Metallurgiya, No. 7 (343), pp. 1–5, July, 1991.     

Development of hydroxyapatite derived from Indian coral

A simple method of converting the calcium carbonate skeleton of the corals available in the Indian coast into hydroxyapatite granules has been developed. By heating the coral to 900 degrees C, the organic materials were eliminated. Powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were employed to characterize the coral and to optimize the processing parameters as well as to confirm the hydroxyapatite formation. The coral used exhibits the presence of both aragonite and calcite phases (dimorphism). At a temperature of 900 degrees C the coral was found to decompose all the carbonate phases. The pre-heated coral is converted into hydroxyapatite by a chemical exchange reaction with di-ammonium phosphate under hydrothermal conditions. The hydroxyapatite obtained was in powder form and does not contain any impurities. The in vitro solubility test of the apatite granules performed in Gomoris, Michalelis, Sorensens, Ringer's and phosphate buffer of pH 7.2 and de-ionized water indicated the stability of the coralline hydroxyapatite.     

Biochemical properties of amylase isozymes from Gammarus palustris. A comparative study

Two major alpha-amylase isozymes from Gammarus palustris were purified and characterized. These isozymes, Amy IW and Amy Ic, exhibit a seasonal pattern of expression. In this article we investigate whether the seasonal variation has an adaptive significance. In addition, the species-specific properties of amylases were studied. Purification of the isozymes was achieved by sequential glycogen-ethanol precipitation, Sephadex G-200 and ion exchange chromatography. Characterization in terms of Km, activity patterns at different temperatures, pH values and salt concentrations was done for both isozymes. In addition, the distribution of enzymatic products was analyzed in a high-performance liquid chromatography system. In all conditions tested, the two isozymes gave similar results. This observation suggests that the seasonal change in amylase expression pattern does not result in enzymes differentially suited for seasonal variation in conditions. A comparative analysis showed that G. palustris amylases are apparently distinct from other amylases. These distinctions were seen as an unusually low Km value, an activity peak at low NaCl concentration, a relatively high pH optimum and the predominant formation of maltotriose.     

A comparative study of the properties of the diffusion-alloyed and homogeneously alloyed powders of the N2MD1,5 low-alloy steel

Translated from Poroshkovaya Metallurgiya, No. 1(349), pp. 11–13, January, 1992.     

A comparative study of physicochemical and photocatalytic properties of visible light responsive Fe,Gd and P single and tri-doped TiO2 nanomaterials

High performance Fe-Gd-P tri-doped TiO_2 nanoparticles(1 at% for each dopant) were successfully synthesized by a modified sol-gel method. Various analytical and spectroscopic techniques were carried out to determine the physicochemical properties of the prepared samples, including XRD, EDX, FESEM,BET, FTIR, XPS, PL, EIS and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activities of prepared samples were evaluated by photo degradation of methyl orange(MO) and 4-chlorophenol(4-CP) as model pollutants under visible light irradiation. Effects of each dopant on different properties of TiO_2 nanoparticles were investigated. Results show that Gd and P doping enhances TiO2 surface textural properties by forming Ti-O-Gd and Ti-O-P bonds. It is found that Gd plays a superior role in increasing oxygen vacancies and organic species on TiO_2 surface. Gd doping also facilitates transferring of the photo-induced charge carriers to the surface adsorbed species. The enhanced electronic band structure and visible light response, as well as high electron lifetime of Fe-Gd-P tri-doped sample is mainly attributed to Fe and Gd doping. The tri-doped TiO_2 with rate constant of k_(app)= 1.28 × 10~(-2) min~(-1) for MO and k_(app) = 0.94 × 10~(-2) min~(-1) for 4-CP, shows the highest photodegradation rate among all samples including undoped and single doped samples. The improved photocatalytic performance of Fe-Gd-P tridoped TiO_2 is due to the synergistic effect of enhanced surface chemistry and textural properties,increased number of surface adsorbed hydroxyl groups and organic species, improved visible light absorption, increased lifetime of the photo-induced electron/hole pairs and boosted interfacial charge transfer.     

Total solid phase synthesis of gamma-subunit of cGMP phosphodiesterase from bovine retina and physicochemical properties of synthetic protein

The 87-membered polypeptide with the sequence of the gamma subunit of cGMP phosphodiesterase from bovine retina rods (PDE gamma) was synthesized by the solid phase method. Two synthetic approaches, which were based on the Boc/Bzl-strategy, were used; both syntheses were carried out in a continuous-flow reactor with swellographic monitoring. In the first approach, five Arg residues were coupled in the form of Boc-Arg(Z)2-OH and the final cleavage of the peptide from the support was effected by the mixture of CF3SO2SiMe3 and thionisole in trifluoroacetic acid. There resulted a heterogeneous, ornitine-rich, and absolutely inactive peptide material which was insoluble in aqueous alkali. In the second approach, Arg(Tos) and the HF low-high cleavage procedure were used, which resulted in a homogeneous polypeptide (according to HPLC and capillary electrophoresis) that manifested correct molecular mass under ion-spray mass spectrometry and the full functional activity characteristic of the native protein. The effect of zinc salts on the PDE gamma fluorescence in solutions and on its solubility was established. This demonstrated a significant PDE gamma affinity with Zn2+ ions and appeared to be connected with the functioning of the protein in the retina cells. For the first time, the dynamics of the peptidylpolymer swelling in different solvents was studied during the synthesis of peptides with very long sequences.     

A comparative investigation of the properties of ferritic stainless steel powders produced by various methods

Translated from Poroshkovaya Metallurgiya, No. 11(311), pp. 25–27, November, 1988.     

A comparative analysis of embryos derived from routine in-vitro fertilization and subzonal microinsemination

Embryos obtained from patients undergoing routine in-vitro fertilization (IVF) and embryo transfer were compared with those undergoing subzonal microinsemination (SUZI) for male factor infertility. Overall, the proportion of cleaved embryos was significantly higher in the IVF group in comparison with the SUZI group at 48 h post-insemination [1533 out of 1609 (95.3%) versus 776 out of 952 (81.5%)]. The mean +/- SD grading score of the IVF-derived embryos of 3.61 +/- 0.50 was significantly better than that for SUZI of 2.97 +/- 0.86 (P < 0.0005) at the same time. The implantation rates following the replacement of IVF or SUZI embryos at 48 h were comparable: 14.3 and 10.0% respectively. However, the IVF embryo implantation rate of 15.1% at 72 h was significantly better than that following the replacement of SUZI embryos at either 48 (10.0%) or 72 h (8.0%). The replacement of SUZI-derived embryos at 48 h resulted in significantly higher pregnancy (25.0%) and implantation rates (10.0%) than at 72 h, with rates of 10.8 and 8.0% respectively. Similarly, the overall embryo quality deteriorated following in-vitro culture for up to 72 h. The clinical pregnancy loss rate (33.0%) was highest following the replacement of SUZI embryos at 72 h, although the data were limited. It is suggested that these data indicate that a combination of in-vitro manipulation, the injection of multiple spermatozoa into the subzonal space and probably the genomic capacity of spermatozoa derived from poor-quality semen may contribute to the poorer outcome of embryo development following SUZI. Prolonged in-vitro culture beyond 48 h appears to be deleterious to the development of SUZI cleaved embryos and the subsequent outcome of treatment, and hence should be avoided.     

A properties comparison for porous materials from various metallic fibers and powders

Conclusions Powder fiber materials have a more finely porous structure than is the case with drawn fiber materials under conditions of equal porosity and a single fiber diameter, however they are characterized by lower permeability and mechanical strength indices; the specific surface of powder fiber materials is twice that of drawn fibers, ali other conditions being equal.Powder fiber materials exhibit a more uniform structure and better permeability than powder materials given the same porosity; they also differ in terms of the greater strength at the same permeability.In effectiveness terms, powder fiber materials that have the same o B value are typified by the K value and the overall K/D_max parameter, and occupy an intermediate position between porous drawn fiber materials and powders.Translated from Poroshkovaya Metallurgiya, No. 1(349), pp. 45–48, January, 1992.     

Cathepsin D from horse spleen. I. Purification and study of certain physicochemical properties

Horse spleen cathepsin D (3.4.23.5.) was purified from crude extract by sodium chloride and ethanol precipitation, column chromatography fractionation on DEAE cellulose and CM Sephadex, re-chromatography on DEAE cellulose and gel filtration. The enzyme has been purified about 3.000 folds with a yield of 30 per cent. The purified enzyme seems to be homogeneous on Sephadex G100, one protein band is apparent on disc electrophoresis. Determined by dansylation the N-terminal amino acid is glycine. A molecular weight of 42,500 +/- 3,000 was obtained with Sephadex G100 gel filtration and light scattering measurements. Amino acid analysis and chemical determinations were performed: cathepsin D is a glycoprotein (2 or 3 osamine residues) including 344 amino acids and 4 disulfide bonds. Spectrophotometric data show that E1cm/1 mg/ml = 1.01 at lambda = 280 nm. ORD measurements indicate about 20 per cent of helicoidal content in the molecule.     

A comparative study of fatigue properties of two face-centered-cubic metals

Fatigue tests were performed on two sets of specimens made of aluminum and nickel. The cyclic stress strain curve (CSSC) of aluminum exhibited a cyclic hardening response, in which the saturation stress increased with plastic strain amplitude, whereas the CSSC of nickel exhibited cyclic hardening in two stages: a stage at which saturation stress increases with plastic strain amplitudes and a second stage, which exhibits a semiplateau showing a slight increase in saturation stress with plastic strain amplitudes. Transmission electron microscopy (TEM) analysis of both materials showed that nickel contains elongated dislocations and persistent slip bands, while aluminum contains dislocation cells. This article is based on a presentation made in the symposium entitled “Fourth International Alloy Conference”, which occurred in Kos, Greece, from June 26 to July 1, 2005, and was sponsored by Engineering Conferences International (ECI) and co-sponsored by Lawrence Livermore National Laboratory and Naval Research Laboratory, United Kingdom.