Characterization of the Oxide Scale Formed on T12 Water Wall Tube After Long-term Service in Supercritical Power Plant

Oxidation of Metals - Oxide scale control is one of the critical maintenance issues in fossil fuel power plant. Hence, the water treatment of the feed water has been changed from all-volatile...     

High-melt-strength polypropylene with electron beam irradiation in the presence of polyfunctional monomers

High-melt-strength polypropylene (PP) was achieved with irradiation by an electron beam generated from an accelerator in the presence of polyfunctional monomers (PFM). Among 16 PFMs, the relatively shorter molecular chain bifunctional monomers such as 1,4-butanediol diacrylate (BDDA) and 1,6-hexanediol diacrylate (HDDA) were the most effective for enhancing the melt strength of PP. The concentration and dose of the HDDA to obtain the high melt strength PP in irradiation under nitrogen gas atmosphere were 1.5 mmol/100 g PP and 1 kGy, respectively. DSC measurement and dynamic mechanical analysis showed that the thermal behavior of the high-melt-strength PP was different from that of the original PP. Crystallinity and crystallization temperature during cooling after heating were lower and higher in high melt strength PP than original PP, respectively. Elongational viscosity at 180°C of the high-melt-strength PP showed a remarkable increase at a certain elongational time with constant strain rate, demonstrating the typical property of high-melt-strength samples. This implies that a few higher molecular chains of PP, formed by intermolecular combination of its chain by HDDA in irradiation, give higher melt strength to induce entanglement of molecular chains. © 1996 John Wiley & Sons, Inc.     

Spray-dry synthesis of β-Cu1.8Zn0.2V2O7 ceramic fine particles showing giant negative thermal expansion

We used spray-dry method to synthesize fine powder of β-Cu_1.8Zn_0.2V₂O₇ showing large negative thermal expansion (NTE) linearly to temperature over a wide temperature range. The NTE of β-Cu_1.8Zn_0.2V₂O₇ is produced by microstructures consisting of voids and anisotropic thermal deformation of crystal grains in ceramics. By reducing the size of the microstructures that produce NTE, large NTE equivalent to that of bulk was realized, even for ceramic particles of about 2 μm size. Comparison with particles produced using a conventional method demonstrates that the particle size distribution is narrow and that the particles are nearly spherical. This achievement is expected to pave the way to use of NTE materials in micrometer-scale control of thermal expansion.     

Effect of Storage Conditions on 2–Acetyl-1–pyrroline Content in Aromatic Rice Variety, Khao Dawk Mali 105

ABSTRACT: The effect of package and temperature on 2–acetyl-1–pyrroline content in milled aromatic rice during storage was investigated. 2 -Acetyl-1 -pyrroline content was decreased faster at higher storage temperature. However, fat acidity of rice was increased during storage and inversely correlated with 2–acetyl-1–pyrroline content at an early stage of storage. The difference in 2–acetyl-1 -pyrroline recovery from the samples, which were extracted with ethanol at 40 °C and 75 °C, revealed that the starch bound and free forms of 2–acetyl-1–pyrroline may occur in aromatic rice. These results suggested that the biosynthesis of 2–acetyl-1 -pyrroline before starch structure formation in rice kernel could play a key role in the aroma quality of aromatic rice.     

Relationship between local structure and stability in hen egg white lysozyme mutant with alanine substituted for glycine

We prepared five mutant lysozymes in which glycines whose dihedralangles are located in the region of the left-handed helix, Gly49,Gly67, Gly71, Gly102 and Gly117, were mutated to an alanineresidue. From analyses of their thermal stabilities using differentialscanning calorimetry, most of them were more destabilized thanthe native lysozyme, except for the G102A mutant, which hasa stability similar to that of the native lysozyme at pH 2.7.As for the destabilized mutant lysozymes, their X-ray crystallographicanalyses showed that their global structures did not changebut that the local structures changed slightly. By examiningthe dihedral angles at the mutation sites based on X-ray crystallographicresults, it was found that the dihedral angles at these mutationsites tended to adopt favorable values in a Ramachandran plotand that the extent and direction of their shifts from the originalvalue had similar tendencies. Therefore, the change in dihedralangles may be the cause of the slight local structural changesaround the mutation site. On the other hand, regarding the mutationof G102A, the global structure was almost identical with thatof the native structure but the local structure was drasticallychanged. Therefore, it was suggested that the drastic localconformational change might be effective in releasing the unfavorableinteraction of the native state at the mutation site.     

Contrasting effects of water-soluble and water-insoluble dietary fibers on bile acid conjugation and taurine metabolism in the rat

The effect of the type of dietary fiber on the bile acid and taurine metabolism was examined in rats. Diets containing 10% of various water-soluble fibers (citrus pectin, konjak mannan, guar gum) as compared to a fiber-free diet increased biliary excretion of total bile acids. In contrast, water-insoluble dietary fibers (cellulose, corn bran, chitin; 10% in the diets) as well as cholestyramine (5% in the diet) considerably, decreased bile acid excretion. Water-soluble dietary fibermediated increases in bile acid excretion were totally attributable to increases in glycine-conjugates. Thus, these fibers greatly increased by the bile acid glycine-to-taurine ratio (G/T). Excretio of glycine conjugates decreased more than that of taurine conjugates in rats fed various water-insoluble dietary fibers. As a results, G/T in rats fed water-insoluble fibers was significantly lowered as compared to G/T in animals fed a fiber-free diet. Cholestyramine did not affect the G/T ratio of bile acids. Fecal bile acid excretion and the activities of hepatic cholesterol 7α-hydroxylase (EC 1.14.13.17) in rats fed various water-soluble dietary fibers approximately doubled as compared to the respective values for rats fed a fiber-free diet. Whereas cholestyramine greatly increased these parameters, water-insoluble fibers did not significantly affect them. Various water-soluble fibers decreased hepatic concentration and urinary excretion of taurine as well as the activity of hepatic cysteine dioxygenase (EC 1.13.11.20). In contrast, water-insoluble fibers considerably increased hepatic taurine concentrations and enzyme activities. The parameters for taurine metabolism were unaffected by cholestyramine. It was suggested that the types of dietary fiber affected hepatic taurine synthesis and thus modified bile acid glycine/taurine ratios.     

Carbon Dioxide Sensor Mechanism of Porous Hydroxyapatite Ceramics

Hydroxyapatite and Cl⁻ -containing hydroxyapatite powders are prepared and characterized. Reversible substitution of CO^2-₃ for OH⁻ at the surface is presumed to be responsible for the sensor function. The role of Cl⁻, which is necessary to realize the sensor function and is incorporated during soaking treatment, is considered as follows. It may reduce the strain caused by the incorporation of CO^2-₃ (which is larger than OH⁻), and, hence, promote the reversible substitution reaction. This behavior is presumed because Cl⁻ -containing hydroxyapatite samples exhibit sensor characteristics typical of CO₂ without any treatment.     

Oxidation kinetics for <Emphasis Type="Italic">cis</Emphasis>-9,<Emphasis Type="Italic">trans</Emphasis>-11 and <Emphasis Type="Italic">trans</Emphasis>-10,<Emphasis Type="Italic">cis</Emphasis>-12 isomers of CLA

The autoxidation processes of the cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) isomers of CLA were separately observed at ca. 0% RH and different temperatures. The t10,c12 CLA oxidized faster than the c9,t11 isomer at all tested temperatures. The first half of the oxidation process of t10,c12 CLA obeyed an autocatalytic-type rate expression, but the latter half followed first-order kinetics. On the other hand, the entire oxidation process of c9,t11 CLA could be expressed by the autocatalytic-type rate expression. The apparent activation energies and frequency factors for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested that the autoxidation mechanisms for the CLA and PUFA were essentially the same.     

深基坑工程动态施工反演分析与变形预报

提出了动态施工反演分析的思想，即在常规的反分析过程中引入逐步开挖和逐道支撑的动态施工因素，以求仿真模拟工程实际情况，进而为相继施工阶段的变形预报提供可靠保证。文中基于任意施工阶段间围护墙体变形与内支撑梁轴力的增量测值和施工ＦＥＭ优化反演分析法，反推了各土层的弹性模量系数，给出了作用在墙体两侧的土压力分布，并预报各相继施工阶段的墙体和土体变形、内力及内支撑梁轴力。