Cooking schedule of alkyd resin preparation. I. Effect of cooking schedule on viscosity-molecular weight relationship

The two constants in the equation log η = A + C′ M?_n^1/2 (η is the viscosity of molten alkyd and M?_n the number average molecular weight) were determined at 110°C for two kinds of alkyd resin prepared with the same formulation but with different cooking schedules. It was found that the magnitude of the slope C′ was larger for the alkyd which was prepared by raising the reaction temperature directly up to 230°C, in comparison with that of the alkyd which was prepared by maintaining the temperature at 170°C for an hour and then raising it up to 230°C. Measurements of η and M?_n were carried out until the gelation occurred. Both upward and downward breaks were observed in log η vs. M?_n^1/2 plot. Based on these viscometric data, the gel point mechanism was discussed. Disagreements between the molecular weight observed and that calculated from the Flory's theoretical equation became more remarkable as the esterification proceeded. This suggested that a large extent of intraesterification reaction is taking place in alkyd synthesis.     

Rapid Formation of α-Al2O3 Scale on an Fe–Al Alloy by Pure-Metal Coatings at 900 °C

Rapid formation of an α-Al₂O₃ scale on Fe–50 at.%Al by pure metal thin coatings of Ni, Al, Ti, Cr or Fe was investigated, and the effects of those elements on Al₂O₃-scale evolution were assessed. The oxidation behavior of samples with and without coatings could be divided into two groups: the samples with/without Ni and Al, and those with Ti, Cr and Fe. The mass gains of samples coated with Al and Ni were almost the same as that of non-coated Fe–50 at.%Al alloy. The mass gains of samples coated with Ti, Cr, and Fe were much lower than that of the Fe–50 at.%Al alloy. A stable α-Al₂O₃ scale was found to develop from the beginning of oxidation on the samples coated with Ti, Cr and Fe. However metastable θ-Al₂O₃ remained after long-time oxidation of non-coated and Ni- and Al-coated samples. The direct α-Al₂O₃ scale formation on the samples with Cr or Fe coatings was speculated to be due to sympathetic nucleation of α-Al₂O₃ on the surface of Al-supersaturated Fe₂O₃ for Fe-coated sample, and composition changes from (Cr,Al)₂O₃ to (Al,Cr)₂O₃ for the Cr-coated sample. Initial formation of an oxide having a corundum structure was inferred to provide a nucleation site for precipitation of α-Al₂O₃ without prior formation of a metastable Al₂O₃ scale.     

Ablation of Selenbp1 Alters Lipid Metabolism via the Pparα Pathway in Mouse Kidney

Selenium-binding protein 1 (Selenbp1) is a 2,3,7,8-tetrechlorodibenzo-p-dioxin inducible protein whose function is yet to be comprehensively elucidated. As the highly homologous isoform, Selenbp2, is expressed at low levels in the kidney, it is worthwhile comparing wild-type C57BL mice and Selenbp1-deficient mice under dioxin-free conditions. Accordingly, we conducted a mouse metabolomics analysis under non-dioxin-treated conditions. DNA microarray analysis was performed based on observed changes in lipid metabolism-related factors. The results showed fluctuations in the expression of numerous genes. Real-time RT-PCR confirmed the decreased expression levels of the cytochrome P450 4a (Cyp4a) subfamily, known to be involved in fatty acid ω- and ω-1 hydroxylation. Furthermore, peroxisome proliferator-activated receptor-α (Pparα) and retinoid-X-receptor-α (Rxrα), which form a heterodimer with Pparα to promote gene expression, were simultaneously reduced. This indicated that reduced Cyp4a expression was mediated via decreased Pparα and Rxrα. In line with this finding, increased levels of leukotrienes and prostaglandins were detected. Conversely, decreased hydrogen peroxide levels and reduced superoxide dismutase (SOD) activity supported the suppression of the renal expression of Sod1 and Sod2 in Selenbp1-deficient mice. Therefore, we infer that ablation of Selenbp1 elicits oxidative stress caused by increased levels of superoxide anions, which alters lipid metabolism via the Pparα pathway.     

尿素中添加腐植酸、黄腐酸、重过磷酸钙和氯化钾能抑制氨的挥发

该试验比较了不同混合物,尿素-重过磷酸钙-氯化钾、尿素-重过磷酸钙-氯化钾-腐植酸、尿素-重过磷酸钙-氯化钾-黄腐酸、尿素-重过磷酸钙-氯化钾-酸性混合物(黄腐酸+腐植酸)在对氨损失,土壤pH值,铵态氮和可利用硝态氮积累等方面的影响,以尿素单独施用作为对照。方法:在实验室条件下,利用一个封闭式动态空气流量系统来评估是否混有重过磷酸钙、氯化钾、腐植酸、黄腐酸的情况下尿素的有效性。氨损失、土壤pH值、土壤中铵态氮以及可利用硝态氮是由标准程序测定的。结果:与对照组(单独施用尿素)相比,处理尿素-重过磷酸钙-氯化钾,尿素-重过磷酸钙-氯化钾-腐植酸,尿素-重过磷酸钙-氯化钾-黄腐酸,尿素-重过磷酸钙-氯化钾-酸性混合物(黄腐酸+腐植酸)中氨损失明显地减少,减少率由12.92%、20.12%、25.94%达到100%,土壤中的铵态氮也有类似的变化。从所有的处理来看,只有尿素-重过磷酸钙-氯化钾-黄腐酸,尿素-重过磷酸钙-氯化钾-酸性混合物(腐植酸+黄腐酸)明显地积累了土壤中可利用硝态氮,这一结果与本研究中pH值的结果一致。结论:尿素、重过磷酸钙、氯化钾中混合腐植酸或者酸性的腐植酸和黄腐酸混合物能够显著减少氨损失。这项研究结果有助于提高尿素中N,P,K使用的有效性,同时减少环境污染。     

Incorporation of Halogenated Amino Acids into Antibody Fragments at Multiple Specific Sites Enhances Antigen Binding

Expansion of the amino-acid repertoire with synthetic derivatives introduces novel structures and functionalities into proteins. In this study, we improved the antigen binding of antibodies by incorporating halogenated tyrosines at multiple selective sites. Tyrosines in the Fab fragment of an anti-EGF-receptor antibody 059–152 were systematically replaced with 3-bromo- and 3-chlorotyrosines, and simultaneous replacements at four specific sites were found to cause a tenfold increase in the affinity toward the antigen. Structure modeling suggested that this effect was due to enhanced shape complementarity between the antigen and antibody molecules. On the other hand, we showed that chlorination in the constant domain, far from the binding interface, of Rituximab Fab also increased the affinity significantly (up to 17-fold). Our results showed that antigen binding is tunable with the halogenation in and out of the binding motifs.     

Inhibition effect of metal cations to intergranular stress corrosion cracking of sensitized Type 304 stainless steel

Inhibition effect of metal cation to intergranular stress corrosion cracking (IGSCC) of sensitized Type 304 stainless steel has been investigated by slow strain rate technique (SSRT) with a dynamic crack observation system. The SCC tests were conducted in fully-deaerated aqueous solutions containing various metal sulfates of 10⁻⁵ kmol/m³ at 95 °C. Metal cations of Na⁺, Ca²⁺, Mn²⁺ and Zn²⁺ were selected in this study, and were characterized by a hardness based on the hard and soft acids and bases (HSAB) concept. As a result, it was found that a hard metal cation in the test solution increased crack initiation time and decreased mean crack initiation frequency. In other words, metal cations with larger hardness have an ability of suppressing initiation process of the IGSCC. On the other hand, apparent mean crack velocity was independent of the hardness of metal cation. The finding that the metal cations with large hardness inhibit initiation of the IGSCC was able to be rationally explained on the basis of the passive film model combined with the HSAB concept.