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41.
Porous Cr3 C2 grains (∼300 to 500 μm) with ∼10 wt% of Cr2 O3 were prepared by heating a mixture of MgCr2 O4 grains and graphite powder at 1450° to 1650°C for 2 h in an Al2 O3 crucible covered by an Al2 O3 lid with a hole in the center. The porous Cr3 C2 grains exhibited a three-dimensional network skeleton structure. The mean open pore diameter and the specific surface area of the porous grains formed at 1600°C for 2 h were ∼3.5 (μm and ∼6.7 m2 /g, respectively. The present work investigated the morphology and the formation conditions of the porous Cr3 C2 grains, and this paper will discuss the formation mechanism of those grains in terms of chemical thermodynamics. 相似文献
42.
Takahiro Ohkubo Eiji Tsuchida Kenzo Deguchi Shinobu Ohki Tadashi Shimizu Toshiya Otomo Yasuhiko Iwadate 《Journal of the American Ceramic Society》2018,101(3):1122-1134
It remains a challenge to establish structural models of multicomponent oxide glass systems. In this study, we have investigated 68.3SiO2–16.1B2O3–4.2Al2O3–11.4Na2O glass and melt structures by ab initio molecular dynamics (AIMD) simulations. The atomic configurations obtained from AIMD simulations were validated against 17O solid‐state NMR spectrum under 24.0 T and neutron diffraction data, and excellent agreement was achieved. The bond lengths, angles, and coordination geometries were statistically analyzed for each atomic species. Here we particularly address the role of minor atomic species such as five‐coordinate Si (SiV) and Al (AlV). The SiV–O bond lengths and O–SiV–O angle distribution in the glass indicated 1.718 Å and three peaks at 90°, 120°, and 175°, which are assigned to a coordination geometry of the trigonal bipyramidal structure. Ring statistic analysis revealed that SiV and AlV were found to preferentially contribute to the formation of small ring sizes. 相似文献
43.
In adipocytes, short and long term stimulation of β adrenergic receptors (βAR) induces the desensitization to catecholamines,
leading to a decrease in the intracellular accumulation of cAMP, but the roles played by this in lipolysis is not clear. In
this study, we assessed the catecholamine-induced desensitization of lipolysis and compared this in adipocytes isolated from
visceral and subcutaneous fat tissues of rats. When adipocytes were pretreated with isoproterenol (ISO), the norepinephrine
(NE)-induced lipolysis was significantly reduced dose- and time-dependently. A similar reduction of the lipolytic response
was also found in NE-, dobutamine-, terbutaline- or BRL37344-induced lipolysis. The ISO- and each βAR agonist-induced lipolysis
in the visceral fat was not only higher than in the subcutaneous fat, but also markedly reduced by ISO- or NE-pretreatment.
These results showed that short-term treatment of three subtypes of βAR by each agonist induces a rapid reduction in the lipolytic
response to βAR stimulation. This suggests some common mechanism for the rapid desensitization of βAR-agonist-induced lipolysis,
in contrast with previous reports on the characteristics of βAR subtypes. In addition, the regional difference of adipose
tissue not only in inducing lipolysis but also in rapid desensitization was also apparent. 相似文献
44.
Some kinetic characteristics and hydrolytic action patterns on various β-D -galactosyl-maltooligosaccharides (Gal-Gn), ranging in size from D.P. (degree of polymerization) 5 to 8, of an exo-maltotetraose-forming amylase of Pseudomonas stutzeri (G4-amylase) were examined to produce a few p-nitrophenyl β-D -galactosyl-α-maltooligosaccharides (Gal-GnP, n = 4,5). The relative hydrolytic reaction rates for larger Gal-Gn by the enzyme were larger than those for smaller saccharides tough the values for unmodified linear maltooligosachharides were almost same. Michaelis constants (Km) for hydrolysis of Gal-G4, Gal-G5, Gal-G6 and Gal-G7 by the enzyme were 1.3, 1.9, 1.3 and 1.3mM, and apparent molecular activities (ko) for these saccharides were 5.9, 38, 91 and 126s−1, respectively. The values of ko/Km for them were remarkably smaller than those for unmodified linear maltooligosaccharides. The G4-amylase cleaved 2 points of the α-1,4-glucosidic linkage in β-1,4-Gal-G4 to give β-1,4-Gal-G2 and -Gal-G3 in the molar ratio of 3:1, whereas the enzyme attacked 3 points of the linkage in β-1,4-Gal-G5, -Gal-G6 and -Gal-G7 to form β-1,4-Gal-G2,-Gal-G3 and Gal-G4 in the molar ratios of 2:5:1, 1:3:6 and 1:3:6, in the early stage of the reaction, respectively. On the other hand, the enzyme showed no action on β-1,6-Gal-G4 and formed β-1,6-Gal-G4 solely from β-1,6-Gal-G5, and β-1,6-Gal-G4 and -Gal-G5 were from β-1,6-Gal-G6 and -Gal-G7 in the ratios of 8:1 and 2:1, respectively. The enzyme also catalyzed the transfer action to produce Gal-G3P, Gal-G4P and Gal-G5P, of which the formation ratio was coincided well with the hydrolytic action pattern on each Gal-Gn, from Gal-Gn tested as a donor and p-nitrophenyl α-glucoside (GP) as an acceptor in an aqueous solution containing 40% (v/v) methanol. By using this novel reaction, Gal-G5P is now producing on an industrial scale to apply as a substrate for the assay of human α-amylase. 相似文献
45.
Parallel BDD-based monolithic algorithms for acoustic fluid-structure interaction problems are developed. In a previous study, two schemes, NN-I + CGC-FULL and NN-I + CGC-DIAG, have been proven to be efficient among several BDD-type schemes for one processor. Thus, the parallelization of these schemes is discussed in the present study. These BDD-type schemes consist of the operations of the Schur complement matrix-vector (Sv) product, Neumann-Neumann (NN) preconditioning, and the coarse problem. In the present study, the Sv product and NN preconditioning are parallelized for both schemes, and the parallel implementation of the solid and fluid parts of the coarse problem is considered for NN-I + CGC-DIAG. The results of numerical experiments indicate that both schemes exhibit performances that are almost as good as those of single solid and fluid analyses in the Sv product and NN preconditioning. Moreover, NN-I + CGC-DIAG appears to become more efficient as the problem size becomes large due to the parallel calculation of the coarse problem. 相似文献
46.
Ranfeng Qiu Hongxin Shi Keke Zhang Yimin Tu Chihiro Iwamoto Shinobu Satonaka 《Materials Characterization》2010,61(7):684-688
The interfacial characteristics of resistance spot welded steel–aluminum alloy joint have been investigated using electron microscopy. The results reveal that reaction product FeAl3 is generated in the peripheral region of the weld while a reaction layer consisting of Fe2Al5 adjacent to steel and FeAl3 adjacent to aluminum alloy forms in the central region of the weld, and that the morphology and thickness of the reaction layer vary with the position at the welding interface. 相似文献
47.
Kitayama Shinobu; Conway Lucian Gideon III; Pietromonaco Paula R.; Park Hyekyung; Plaut Victoria C. 《Canadian Metallurgical Quarterly》2010,65(6):559
Contemporary U.S. culture has a highly individualistic ethos. Nevertheless, exactly how this ethos was historically fostered remains unanalyzed. A new model of dynamic cultural change maintains that sparsely populated, novel environments that impose major threats to survival, such as the Western frontier in the United States during the 18th and 19th centuries, breed strong values of independence, which in turn guide the production of new practices that encourage self-promotion and focused, competitive work. Faced with few significant threats to survival, residents in traditional areas are likely to seek social prestige by adopting existing practices of other, higher status groups. Because of both the massive economic success of the frontier and the official endorsement of the frontier by the federal government, eastern residents of the United States in the 18th and 19th centuries may have actively adopted the frontier practices of independence, thus incorporating the frontier ethos of independence to form the contemporary U.S. national culture. Available evidence is reviewed, and implications for further research on cultural change are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
48.
Kenji Nakamura Shinobu Satonaka Yoshiki Matsunaga Masahiro Kuronaga Chihiro Iwamoto 《Welding International》2017,31(6):435-444
In this study, new butt welding technique was proposed to join polymeric materials in which the polymeric material is softened by a heated tool due to the Joule effect heating of the electric current flow through the tool, and the coalescence of material is done by the stirring action due to the tool rotation. A 3 mm-thick Polycarbonate (PC) sheets were joined in various joining conditions, from which joining mechanism, mechanical properties of joints and process parameters affecting joint performance were investigated. In the experiments, in situ observation with a CCD camera and material temperature measurement during the process, as well as the observation of surface appearance and cross section of the joint and tensile test were performed for these purposes. It was shown from the in situ observation and material temperature measurement that the molten and softened region is formed around the weld tool. It was also shown that sufficient heat input was required to form sound joints with acceptable performance, which depended upon the joining speed and amount of electric current flow through the tool. The observation of joint appearance and cross section revealed that the joint with comparable thickness to base material was obtained under the condition of revolution pitch below 0.08 mm, defined by the ratio of joining speed to tool rotation. It is noticed that joints obtained from the proper conditions have the same mechanical properties as the base material, and that the process parameters of this method were tool rotation speed, welding speed and amount of electric current. These results suggest proposed method is useful for joining the polymeric materials. 相似文献
49.
The paper presents the highly ordered geometrical structures of laser induced periodic surface structure (LIPSS) in azobenzene urethane polymer (DR19 polymer) from 4-(N,N-dihydroxyethylamino)-4′-nitroazobenzene (Disperse red 19) with tolylene-2,4-diisocyanate (TDI). One or two regulated striped LIPSS was formed in confined spaces between surface relief gratings (SRG) induced by the s-polarized interfered beams. The pitch of LIPSS was one-half or one-third of SRG pitch. Standing wave with some selected mode between SRG in the surface waveguide is responsible for the formation of the regulated striped LIPSS. The crossed illumination of the interfered beams showed the waffle-like structure for s-polarization beam and the egg crate-like (ECL) structure for p-polarized beam. Photoinduced microscopic molecular ordering was also investigated. The linear polarized beam gave the large optical anisotropy in the polymer and the circularly polarized beam produced the chiral structure. The circular dichroism spectra showed the sharp peak due to the circular Bragg reflection from which the chiral pitch was evaluated. 相似文献
50.
Xi‐Ping Deng Lun Shan Shinobu Inanaga Mitsuhiro Inoue 《Journal of the science of food and agriculture》2005,85(8):1379-1388
The greatest fear of global climate change is drought. World‐wide, 61% of countries receive rainfall of less than 500 mm annually; domestication of wheat first occurred in such a semiarid region of southwestern Asia, and it seems that wheat foods originally came from dryland gardens. Wheat plants respond to drought through morphological, physiological and metabolic modifications in all plant parts. At the cellular level, plant responses to water deficit may result from cell damage, whereas other responses may correspond to adaptive processes. Although a large number of drought‐induced genes have been identified in a wide range of wheat varieties, a molecular basis for wheat plant tolerance to water stress remains far from being completely understood. The rapid translocation of abscissic acid (ABA) in shoots via xylem flux, and the increase of ABA concentration in wheat plant parts correlate with the major physiological changes that occur during plant response to drought. It is widely accepted that ABA mediates general adaptive responses to drought. For a relatively determinate target stress environment, and with stable genotype × environment interaction, the probability for achieving progress is high. This approach will be possible only after we learn more about the physiology and genetics of wheat plant responses to water stress and their interactions. The difficulties encountered by molecular biologists in attempting to improve crop drought tolerance are due to our ignorance in agronomy and crop physiology and not to lack of knowledge or technical expertise in molecular biology. Copyright © 2005 Society of Chemical Industry 相似文献