Reaction between Fe-C Binary Alloys and Liquid Zinc

Twenty binary Fe-C alloys with a full-annealed structure were immersed in a pure zinc bath at 733 K for 600 s to clarify the reactivity of pearlite structure with liquid zinc. The structure of an alloy layer formed was observed and its thickness and the quantities of iron reacted with zinc were measured. The results obtained are as follows: (1) The alloy layer formed on a steel containing carbon up to a eutectoid level consists of a gamma layer next to the steel base, followed by a delta 1 layer and a zeta layer, and many ternary carbide particles are found in the alloy layer, increasing in number in propotion as a carbon concentration increases. Many cementite projections are found at an alloy layer / steel base interface, and the zeta layer grows irregularly in a hyper-eutectoid carbon level. (2) The thickness of the alloy layer and the quantities of iron having reacted with zinc do not depend on the carbon concentration up to the eutectoid level. (3) Cementite disrupts into the ternary carbide particles, and these particles are placed on the straight or curved line, or are distributed sparsely, depending on the cementite size and its relative position to the alloy layer/steel base interface. (4) The reactivity of pearlite structure is comparable with that of ferrite structure in 733 K, 600 s immersion

Reaction between Fe-0.10mass%Si Alloy(s) and Zinc(1)

An Fe-0.10mass%Si alloy was immersed in the pure zinc bath for a time up to 6 ks at various temperatures ranging from 713 K to 873 K. The morphology of the alloy layer was observed, and the thickness of the alloy layer and the quantities of iron having reacted with zinc were measured. The total thickness of the alloy layer formed at temperatures ranging from 713 K to 753 K is thicker than that of one formed at higher temperatures. The temperature dependence of the quantity of iron remaining in the alloy layer is similar to that of the total thickness of the alloy layer. An iron mass loss is greater in the temperature range from 713 K to 753 K, and above 813 K, it increases with the immersion temperature. To obtain information on the silicon reactivity in hot dip galvanizing, the results obtained for the Fe-0.10mass%Si alloy were compared with those obtained for pure iron under the same conditions used in this study. The addition of 0.10mass% Si influences the Fe-Zn reaction in the temperature range from 713 K to 753 K. The alloy layer formed in this temperature range comprises a gamma layer, a delta 1 layer, and a zeta layer. The zeta layer formed in this temperature range is a (zeta+eta) mixture layer, and is composed of granular or columnar zeta crystals. The growth of the zeta layer obeys the linear time law, disobeying the diffusion controlled process. The delta 1 layer formed in the temperature range from 713 K to 753 K is constant. This causes the growth of the zeta layer to obey the linear time law. The rapid reaction between the Fe-0.10mass%Si alloy and liquid zinc in the vicinity of 713 K is the effect of added silicon that allows the formation of the (zeta+eta) mixture layer

Corrosion Behavior of Zn - 5 mass% Al Alloy

The corrosion resistance of hot dip Zn-Al alloy coated steel sheet is shown to be improved through changing a cooling rate after hot dipping. The Zn-5 mass% Al alloy and Zn-5 mass% Al - Mischmetal alloy which were melted and cooled to room temperature with five different methods were corrosiontested in stagnant 2% HCI and 3% NaCl aqueous solution at 308 K. In 2% HCI solution, the corrosion behavior of Zn - 5 mass% Al alloy strongly depended on a cooling rate, while that of Zn - 5 mass% Al - Mischmetal alloy was almost independent of the cooling rate. The mischmetal addition makes the cooling rate dependence of the corrosion behavior of Zn - 5 mass% Al alloy less pronounced. In 3% NaCl solution, the corrosion behaviors of Zn - 5 mass% Al alloy and Zn - 5 mass% Al - Mischmetal alloy depended on the cooling rate complicatedly. A white product was formed on each sample after corrosion- testing in 3% NaCl solution. By adding mischmetal to the Zn - 5 mass% Al alloy, a pitting corrosion in 3% NaCl solution tended to be suppressed

Mini Screening of Kinase Inhibitors Affecting Period-length of Mammalian Cellular Circadian Clock

In mammalian circadian rhythms, the transcriptional-translational feedback loop (TTFL) consisting of a set of clock genes is believed to elicit the circadian clock oscillation. The TTFL model explains that the accumulation and degradation of mPER and mCRY proteins control the period-length (tau) of the circadian clock. Although recent studies revealed that the Casein Kinase Iεδ (CKIεδ) regurates the phosphorylation of mPER proteins and the circadian period-length, other kinases are also likely to contribute the phosphorylation of mPER. Here, we performed small scale screening using 84 chemical compounds known as kinase inhibitors to identify candidates possibly affecting the circadian period-length in mammalian cells. Screening by this high-throughput real-time bioluminescence monitoring system revealed that the several chemical compounds apparently lengthened the cellular circadian clock oscillation. These compounds are known as inhibitors against kinases such as Casein Kinase II (CKII), PI3-kinase (PI3K) and c-Jun N-terminal Kinase (JNK) in addition to CKIεδ. Although these kinase inhibitors may have some non-specific effects on other factors, our mini screening identified new candidates contributing to period-length control in mammalian cells

Haematopoietic development and immunological function in the absence of cathepsin D

Background: Cathepsin D is a well-characterized aspartic protease expressed ubiquitously in lysosomes. Cathepsin D deficiency is associated with a spectrum of pathologies leading ultimately to death. Cathepsin D is expressed at high levels in many cells of the immune system, but its role in immune function is not well understood. This study examines the reconstitution and function of the immune system in the absence of cathepsin D, using bone marrow radiation chimaeras in which all haematopoietic cells are derived from cathepsin D deficient mice.Results: Cathepsin D deficient bone marrow cells fully reconstitute the major cellular components of both the adaptive and innate immune systems. Spleen cells from cathepsin D deficient chimaeric mice contained an increased number of autofluorescent granules characteristic of lipofuscin positive lysosomal storage diseases. Biochemical and ultrastructural changes in cathepsin D deficient spleen are consistent with increased autolysosomal activity. Chimaeric mice were immunised with either soluble (dinitrophenylated bovine gamma globulin) or particulate (sheep red blood cells) antigens. Both antigens induced equivalent immune responses in wild type or cathepsin D deficient chimaeras.Conclusion: All the parameters of haematopoietic reconstitution and adaptive immunity which were measured in this study were found to be normal in the absence of cathepsin D, even though cathepsin D deficiency leads to dysregulation of lysosomal function

Selected Mutations in a Mesophilic Cytochrome c Confer the Stability of a Thermophilic Counterpart

Mesophilic cytochrome c551 of Pseudomonas aeruginosa (PA c551) became as stable as its thermophilic counterpart, Hydrogenobacter thermophilus cytochrome c552 (HT c552), through only five amino acid substitutions. The five residues, distributed in three spatially separated regions, were selected and mutated with reference to the corresponding residues in HT c552 through careful structure comparison. Thermodynamic analysis indicated that the stability of the quintuple mutant of PA c551 could be partly attained through an enthalpic factor. The solution structure of the mutant showed that, as in HT c552, there were tighter side chain packings in the mutated regions. Furthermore, the mutant had an increased total accessible surface area, resulting in great negative hydration free energy. Our results provide a novel example of protein stabilization in that limited amino acid substitutions can confer the overall stability of a natural highly thermophilic protein upon a mesophilic molecule.This work was supported by a grant from the Japanese Ministry of Education, Science and Culture