Corrosion of novel rail steels in 3.5 % NaCl solution

Eutectoid steels, which are traditionally used as rails in railway systems, are prone to corrosion, especially in coastal environments. In order to minimize this problem, four new rail steel compositions, with different combinations of microalloying elements Cu, Cr, Ni and Si, were designed and processed as per the thermomechanical schedule for normal rail steel processing in industry. Corrosion behavior of the rail steels were studied by weight loss measurement after immersion test and Tafel polarization in freely aerated 3.5 % NaCl. The rust obtained after immersion test were characterized by Fourier transform infrared spectroscopy (FTIR). Corrosion rate obtained weight loss measurement was similar for all the rail steels. γ-FeOOH (lepidocrocite) and δ-FeOOH were identified as the major rust phases from the FTIR spectra of the rail steels. The relative absorption intensities of these rust phases were similar for all the rail steels. Corrosion rates calculated from Tafel polarization tests were similar for all the rail steels. The corresponding free corrosion potentials were also similar for all the rail steels. The zero corrosion potential obtained from Tafel polarization of Cu-Mo, Cr-Mn, Cu-Ni, Cr-Cu-Ni and Cr-Cu-Ni-Si rail steels was more noble compared to C-Mn and Cu-Si rail steels indicating better corrosion resistance of these alloys. The importance of conducting alternate wetting and drying test has been emphasized.     

Influence of crystallographic texture and microstructure on elastic modulus of steels

In this paper the effects of crystallographic texture and microstructure on the elastic modulus of different grades of steel have been collected from the available literature and put in one place. It is expected that this will help researchers in their understanding of both the fundamental and the practical aspects of the different grades of steel used for various purposes.

Dans cet article, on a recueilli à partir de la littérature disponible et rassemblé en un seul lieu les effets de la texture cristallographique et de la microstructure sur le module l’élasticité de différentes nuances d’acier. On s’attend à ce que cela aide les chercheurs dans leur compréhension tant des aspects fondamentaux que pratiques des différentes nuances d’acier utilisées à diverses fins.     

Differential divalent cation requirements uncouple the assembly and catalytic reactions of human immunodeficiency virus type 1 integrase

Previous in vitro analyses have shown that the human immunodeficiency virus type 1 (HIV-1) integrase uses either manganese or magnesium to assemble as a stable complex on the donor substrate and to catalyze strand transfer. We now demonstrate that subsequent to assembly, catalysis of both 3' end processing and strand transfer requires a divalent cation cofactor and that the divalent cation requirements for assembly and catalysis can be functionally distinguished based on the ability to utilize calcium and cobalt, respectively. The different divalent cation requirements manifest by these processes are exploited to uncouple assembly and catalysis, thus staging the reaction. Staged 3' end processing and strand transfer assays are then used in conjunction with exonuclease III protection analysis to investigate the effects of integrase inhibitors on each step in the reaction. Analysis of a series of related inhibitors demonstrates that these types of compounds affect assembly and not either catalytic process, therefore reconciling the apparent disparate results obtained for such inhibitors in assays using isolated preintegration complexes. These studies provide evidence for a distinct role of the divalent cation cofactor in assembly and catalysis and have implications for both the identification and characterization of integrase inhibitors.     

Quantum dots monitor TrkA receptor dynamics in the interior of neural PC12 cells

Can quantum dots (QDs) serve as physiologically relevant receptor probes in the interior of cells? We directly visualize endocytosis, redistribution, and shuttling of QD bound-TrkA receptors to PC12 neural processes and far-reaching growth cone tips. Internalized QDs are contained in microtubule-associated vesicles and possess transport properties that reflect TrkA receptor dynamics. This opens up new possibilities for the development of QD platforms as molecular tools to image biochemical signaling and transport cargo in the cell interior.     

Synthesis of spodumene and spodumene — zirconia composite powders using aqueous sol-gel method

Pure spodumene and spodumene-zirconia (5, 10, 15 mol%) composite powders were prepared using aqueous sol-gel method employing lithium formate, aluminium formate, zirconium formate and tetraethoxy silane (TEOS) as starting materials in aqueous medium. The gels prepared by this method were dried at 100°C for 24h and then calcined for 2h at different temperatures ranging from 500°C to 800°C. X-ray powder diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA) and infra-red spectroscopy analysis (IR) were utilized to characterize the gel powders and calcined powders. Transmission electron microscope (TEM) was used to measure the average particle size of the calcined powders.     

Effect of Co Addition on the Microstructure, Martensitic Transformation and Shape Memory Behavior of Fe-Mn-Si Alloys

The effect of Co addition has been studied in Fe-30Mn-6Si-xCo (x = 0 to 9 wt pct) shape memory alloys in terms of their microstructure, martensitic transformation and shape recovery. Microstructural investigations reveal that in Fe-Mn-Si-Co alloys, the microstructure remains single-phase austenite (??) up to 5 pct Co and beyond that becomes two-phase comprising ?? and off-stoichiometric (Fe,Co)₅Mn₃Si₂ intermetallic ??-phases. The forward ??-?? martensite transformation start temperature (M _S) decreases with the addition of Co up to 5 pct, and alloys containing more than 5 pct Co, show slightly higher M _S possibly on account of two-phase microstructure. Unlike M _S, the ??-?? reverse transformation start temperature (A _S) has been found to remain almost unaltered by Co addition. In general, addition of Co to Fe-Mn-Si alloys deteriorates shape recovery due to decreasing resistance to plastic yielding concomitant with the formation of stress induced ?? martensite. However, there is an improvement in shape recovery beyond 5 pct Co addition, possibly due to the strengthening effect arising from the presence of (Fe,Co)₅Mn₃Si₂ precipitates within the two-phase microstructure and due to higher amount of stress induced ?? martensite.     

Synthesis of nano particle of inorganic oxides by polymer matrix

Ultrafine (⩽ 150 nm) powders of spinels [MFe₂O₄ where M = Ni(II), Co(II) and Zn(II)]; rare-earth orthoferrites [RFeO₃ where R = Sm, Nd and Gd], and rare-earth garnets [R₃Fe₃O₁₂ where R = Sm, Nd and Gd] with good purity and chemical homogeneity were prepared through two new versatile chemical routes. The first route involved the coprecipitation of the desired metal nitrates from their aqueous solution, in presence of a water soluble polymer-polyvinyl alcohol (PVA), by triethyl ammonium carbonate solution. The other process involved complete evaporation of a mixture of optimum amounts of PVA and the desired aqueous metal nitrate solutions, with and without the addition of optimum amounts of urea when the mixture was evaporated to a pasty mass. In addition, detailed study on the reported potassium ferricyanide route was also carried out for the production of the rare-earth orthoferrite powders. The various precursor as well as the heat-treated mixed-oxide powders, prepared through each of the routes, were compared by the physical characterization studies involving thermal gravimetry and differential scanning calorimetry, infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, and room temperature magnetic measurements.     

Preparation and photocatalytic activity of nano-sized nickel molybdate (NiMoO4) doped bismuth titanate (Bi2Ti4O11) (NMBT) composite

Various compositions of nano-sized (NiMoO₄)_x-doped Bi₂Ti₄O₁₁ (x = 0.01, 0.05, 0.1) composites have been prepared by chemical solution decomposition (CSD) method using triethanolamine (TEA) as complexing agent. Ni(II) is one of reactive species on the catalyst surface and Mo(VI) ion helps to compensate the charge of the lattice. The photocatalysts based on the above compositions have been tested for photobleaching of methyl orange (MO) solution under Hg-lamp. The prepared nanopowders are characterized by XRD, EDAX, UV–vis spectra, specific surface area (BET), zeta potential, ESR and HRTEM analyses. The average particle size of nickel molybdate-doped bismuth titanate lies around 30 ± 2 nm measured from TEM. Result shows nickel molybdate-doped bismuth titanate (NiMoO₄)_x(Bi₂Ti₄O₁₁)_1−x (NM_xBT_1−x; x = 0.01) composite is found to be more photoactive compared all the compositions studied except degussa P25 titania.     

Cloning, characterization and identification of the gene encoding phosphatidylinositol 4-kinase

The vast majority of AIDS-related deaths are associated with opportunistic infections. For fungal infections, there are few effective antifungals, particularly for systemic use. The discovery that very low doses of the bleomycin family of anticancer chemical congeners compromise the integrity of fungal cell walls led to our approach to identify genes that complement-cell wall defects, and develop methods to facilitate the identification of new antifungals targeted to fungal cell walls. This report describes one of the genes cloned by complementation of the blm1-1 mutation of S. cerevisiae using a YCp50-based yeast genomic library. Characterization and identification of the gene were carried out using drug screening tests, Southern hybridization analyses, DNA sequencing and DNA sequence similarity searches in databases. The gene STT4, is essential for viability and encodes a phosphatidylinositol 4-kinase that plays an important role in the phosphatidylinositol-mediated signal transduction pathway required for cell wall integrity. Like blm1-1 mutant strains, stt4 cells arrest mostly in the G2/M phase of the cell cycle. Further studies using this approach should help us understand the role of PI4-K in maintaining fungal cell-wall integrity, identify additional genes affecting potential target structures in cell walls of opportunistic fungal pathogens in AIDS patients, and assist in drug discovery and antifungal drug design.