Effect of dispersed oxides of rare earths and other reactive elements on the high temperature oxidation resistance of Fe-20Cr alloy

The isothermal oxidation resistance in air at 1273, 1323, and 1373 K of Fe-20Cr alloys with 1 wt pct dispersoid of Y₂0₃, La₂O₃, A1₂O₃, TiO₂, SiO₂, Cr₂O₃ and without dispersoid prepared by a conventional sintering and rolling procedures was examined. It was found that SiO₂ dispersoid reduced, while A1₂O₃ dispersoid slightly increased the oxidation resistance. The dispersoids of TiO₂ and Cr₂O₃ showed no beneficial effect on the oxidation resistance except for the oxidation after 10 h at 1373 K. The oxidation behavior after 10 h at 1373 K was rather complex including accelerated oxidation. The beneficial effect of La₂O₃ and Y₂O₃ dispersoids was excellent at all temperatures. The oxidation rates during the early stage of oxidation for the alloys with dispersoid were apparently dependent on the type of the dispersoid. There was no evidence that dispersoid accumulated at the scale-alloy interface. Comparison of results obtained for the oxidation of the alloys prepared by a powder metallurgical procedure with results for the alloys by arc-melting procedure indicated that the grain size of the alloy is an important factor for reduction of oxidation rate but does not seem to be critical, because the grain size of the alloys with dispersoid was not dependent on the type of the dispersoid. Ion Microanalyses of the Cr₂O₃ scale formed after 1 h oxidation at 1373 K showed an interesting feature in that all the dispersed elements were incorporated in the scale and the iron content of the scale was lower on the alloys which exhibited better oxidation resistance.     

Phospholipids and oxophospholipids in atherosclerotic plaques at different stages of plaque development

We identified and quantified the hydroperoxides, hydroxides, epoxides, isoprostanes, and core aldehydes of the major phospholipids as the main components of the oxophospholipids (a total of 5–25 pmol/μmol phosphatidylcholine) in a comparative study of human atheroma from selected stages of lesion development. The developmental stages examined included fatty streak, fibrous plaque, necrotic core, and calcified tissue. The lipid analyses were performed by normal-phase HPLC with on-line electrospray MS using conventional total lipid extracts. There was great variability in the proportions of the various oxidation products and a lack of a general trend. Specifically, the early oxidation products (hydroperoxides and epoxides) of the glycerophosphocholines were found at the advanced stages of the plaques in nearly the same relative abundance as the more advanced oxidation products (core aldehydes and acids). The anticipated linear accumulation of the more stable oxidation products with progressive development of the atherosclerotic plaque was not apparent. It is therefore suggested that lipid infiltration and/or local peroxidation is a continuous process characterized by the formation and destruction of both early and advanced products of lipid oxidation at all times. The process of lipid deposition appears to have been subject to both enzymatic and chemical modification of the normal tissue lipids. Clearly, the appearance of new and disproportionate old lipid species excludes randomness in any accumulation of oxidized LDL lipids in atheroma.     

Phase transformations and some laws obeyed by nonvariant reactions in binary Plutonium systems

Fifty-three eutectoid reactions detected in thirty of the virtually all known binary phase diagrams of plutonium are analyzed. It is shown that they obey a universal empirical dependence relating the parameters of nonvariant (eutectoid and peritectoid) transformations and the temperatures of phase formation. Cases of deviation from this dependence are described, which require amendment of the phase diagrams (of Pu with Cm, Hf, and Al). The dependence is used for analyzing the parameters of eutectoid decomposition of the -solid solution of Pu in plutonium alloys with elements of the IIIB group at atmospheric and enhanced pressure and variants of nonvariant reactions in the Pu - Al (-phase and Pu₃Al and PuAl compounds) and Pu - Np (four eutectoid and four peritectoid transformations) systems. It is shown that the dependence can be used for amending and predicting the parameters of nonvariant reactions in the Pu - Np system     

A novel transfection method for mammalian cells using calcium alginate microbeads

The direct transfer of genetic materials into mammalian cells is an indispensable technique. We have developed calcium alginate (CA) microbeads which can deliver plasmid DNAs and yeast artificial chromosomes into plant and yeast cells. In this paper, we demonstrate the effective transfection of mammalian cells by CA microbeads immobilizing plasmid DNAs. The transfection was performed using the pEGFP-C1 plasmid containing the cytomegalovirus (CMV) promoter and enhanced green fluorescent protein (EGFP) gene. The transient expression of EGFP was observed 24 h after transfection. The expression efficiency was maximum when the concentration of sodium alginate was 1% and the amount of plasmid DNA was increased to 100 microg. The expression efficiency of our method using CA microbeads is 2-10 times higher than that of the polyethylene glycol (PEG) method. Our results suggest that the CA microbead mediated transfection of mammalian cells effectively delivers genetic materials into mammalian suspension cells.     

Development of new dosimetry using extended DNA fibers

We applied fluorescent microscopy to monitor the damage of DNA upon exposure to gamma radiation. Our developed dosimetry demonstrated that the number of breaks in DNA is proportional to the dose of the irradiation but is not dependent on dose rate of the irradiation and the GC content of DNA.     

Production of vitamin B12 in genetically engineered Propionibacterium freudenreichii

Since the chemical synthesis of vitamin B12 requires more than 70 steps, the production of vitamin B12 has been achieved by microorganism fermentation with additional brief chemical modifications. In an effort to increase the productivity of vitamin B12, we tried to express 10 genes belonging to the hem, cob and cbi gene families involved in the synthesis of vitamin B12 in Propionibacterium freudenreichii, which is a known producer of vitamin B12. In a recombinant P. freudenreichii clone that harbored the expression vector containing a cobA, cbiLF, or cbiEGH, we obtained an increase in vitamin B12 production of 1.7-, 1.9-, and 1.5-fold higher, respectively, than that in the microorganism without any cloned genes in the expression vector pPK705. The cobU and cobS genes caused a slight increase in the production of vitamin B12. Furthermore, we achieved multigene expression in P. freudenreichii. In a recombinant P. freudenreichii clone that harbored an exogenous gene, hemA, from Rhodobacter sphaeroides and endogenous hemB and cobA genes, we successfully achieved the production of about 1.7 mg/l vitamin B12, 2.2-fold higher than that produced by P. freudenreichii harboring pPK705.     

Dendrimer-immobilized culture surface as a tool to evaluate formation of cellular cytoskeleton of anchorage-dependent cells

Anchorage-dependent cultivation of human epithelial and keratinocyte cells was carried out on surfaces modified with synthesized dendrimers. Notable elongation of the epithelial cells was recognized on the culture surface immobilized with a dendrimer having D-glucose as a functional ligand, but not when a dendrimer having L-glucose was used or when the dendrimer was ligand-free. This morphological change was attributable to a temporary grasping of the cells at the D-glucose moiety via a glucose transporter-mediated mechanism present in the cell membrane. Following visualization of the actin filaments of the cells, it was considered that the cellular elongation on the D-glucose-bound dendrimer surface reflected the degree of formation of the cellular cytoskeleton. The cellular roundness was calculated by means of image analysis of the individual cells and employed as a parameter to evaluate the formation of the cellular cytoskeleton. In the culture of keratinocytes on the D-glucose-bound dendrimer surface, it was demonstrated that the decrease in the ratio of elongated cells (i.e., cells with a low roundness value) was correlated with the deterioration in the growth potential associated with cellular senescence.     

Simulation of characteristics of a SiO2/c-axis-oriented LiNbO3/diamond surface acoustic wave

High-frequency surface acoustic wave (SAW) devices based on diamond that have been realized to date utilize c-axis-oriented ZnO as the piezoelectric thin film. This material, with SiO2 overlay, shows excellent characteristics of a high phase velocity of over 10,000 m/s and a zero temperature coefficient, and it has been successfully applied to high-frequency SAW filters and resonators. To expand on materials used on diamond, the theoretical calculation has been carried out for LiNbO3/diamond, and a high electromechanical coupling coefficient up to 9.0% is expected. In this work, the characteristics of SiO2/LiNbO3/diamond were studied by computer simulation, emphasizing a zero temperature coefficient with a high coupling coefficient. Calculations are carried out for the phase velocity, the electromechanical coupling coefficient, and the temperature coefficient of the Rayleigh wave and its higher mode Sezawa wave. As a result, SiO2/IDT/LiNbO3/diamond is found to offer a zero temperature coefficient with a very high coupling coefficient up to 10.1% in conjunction with a high phase velocity of 12,100 m/s.     

Cyclic deformation behavior and dislocation structure of Ti-2 at. Pct Al single crystals oriented for double prism slip

Cyclic deformation behavior and dislocation substructure in the single crystals of Ti-Al alloy containing 2.0 pct Al (by atom) with double prism slip at different cyclic strain amplitudes were examined. The testing results showed that Ti-2Al displayed an initial slight cyclic hardening followed by a striking softening period, and a saturation stage was reached finally. Secondary cyclic hardening was observed for most specimens before failure, specifically at the high cyclic strain amplitudes. The cyclic resolved shear stress-strain curve (CSSC) was observed to contain a plateau in the testing strain range with a saturation plateau stress of about 55 MPa. Trace analysis on the surface of specimens with an optical microscope shows that the (10 0) and (1 00) double prism slips can be distinguished from the traces on the (0001) surface of the fatigued specimens. The dislocation substructure in the fatigued specimens was examined using a transmission electron microscope (TEM). The typical dislocation configuration is the saturated dislocation bundles, which are tangled on the (10 0) and (1 00) slip planes and arranged parallel to the [0001] direction.