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排序方式: 共有515条查询结果,搜索用时 31 毫秒
471.
Masatoshi Futakawa Hiroyuki Kogawa Yujiro Ikeda Mark Wendel Günter Bauer Kohei Okita Yoichiro Matsumoto 《Journal of Nuclear Materials》2008,377(1):182-188
Liquid-mercury target systems for MW-class spallation neutron sources are being developed around the world. Proton beams are used to induce the spallation reaction. At the moment the proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. In order to estimate the cavitation erosion, i.e. the pitting damage formed by the collapse of cavitation bubbles, off-beam tests were performed by using an electric magnetic impact testing machine (MIMTM), which can impose equivalent pressure pulses in mercury. The damage potential was defined based on the relationship between the pitting damage and the time-integrated acoustic vibration induced by impact due to the bubble collapses. Additionally, the damage potential was measured in on-beam tests carried out by using the proton beam at WNR (Weapons Neutron Research) facility in Los Alamos Neutron Science Center (LANSCE). In this paper, the concept of the damage potential, the relationship between the pitting damage formation and the damage potential both in off-beam and on-beam tests is shown. 相似文献
472.
473.
Shirasuna K Shimizu T Sayama K Asahi T Sasaki M Berisha B Schams D Miyamoto A 《Reproduction (Cambridge, England)》2008,135(4):519-525
Angiogenesis, changes in blood flow, and extracellular matrix remodeling are the processes associated with the development and demise of the bovine corpus luteum (CL) during the estrous cycle. APJ (putative receptor protein related to angiotensin type 1 receptor) is a G-protein-coupled receptor, and its ligand, apelin, has been identified as a novel regulator of blood pressure and as an angiogenic factor. We hypothesized that the apelin-APJ system is involved in luteal function. This study investigated whether apelin-APJ exists in bovine CL and determined their expression profiles and localization during luteal phase and prostaglandin F(2)(alpha) (PGF(2)(alpha))-induced luteolysis. During the luteal phase, apelin mRNA expression increased from early to late CL and decreased in regressed CL. APJ mRNA expression increased from early to mid-CL and remained elevated in late and regressed CL. Apelin and APJ proteins were immunohistochemically detected only in the smooth muscle cells of intraluteal arterioles during the luteal phase. PGF(2)(alpha) stimulated apelin and APJ mRNA expression at 0.5-2 and 2 h respectively, and then the mRNA expression of apelin-APJ was inhibited from 4 h during PGF(2)(alpha)-induced luteolysis. Additionally, apelin mRNA and protein were stimulated at 1 h after PGF(2)(alpha) injection only in the periphery of mid- but not early CL. The present study indicated that the apelin-APJ was localized in the smooth muscle cells of intraluteal arterioles, and responded to PGF(2)(alpha) at the periphery of mid-CL in the cow. Thus, the apelin-APJ system may be involved in the maturation of CL and the luteolytic cascade as a regulator of intraluteal arterioles in cow. 相似文献
474.
Nakanishi N Takeuchi F Park SY Hori H Kiyota K Uno T Tsubaki M 《Journal of Bioscience and Bioengineering》2008,105(6):604-613
A genetically engineered porcine myoglobin triple mutant (H64V/V68H/H93A) (VHA-Mb) contains 6 non-axial His residues (His24, His36, His48, His81, His82, and His119) besides two candidate axial His residues (His68 and His97). Although previous resonance Raman study on the ferric VHA-Mb were not conclusive for its coordination structure, present EPR parameters of the ferric VHA-Mb were consistent with bis-imidazole coordination of His68/His97. We further investigated the reactivity of these possible His ligands with diethylpyrocarbonate (DEPC) to clarify the coordination structure and their protonation states in ferric form. We found that the non-axial His residues were easily modified with a low concentration of DEPC based on UV spectral changes and MALDI-TOF-MS analyses. On the other hand, the two candidate axial His ligands were protected from the modification due to a limited steric exposure of their imidazoles to solvent, the Fe(3+)-N(epsilon2) coordination bond, and the protonation of N(delta1) by forming a hydrogen bond with their immediate surroundings. However, once N-carbethoxylation occurred at N(epsilon2) of His97, resulting in a disruption of the heme Fe(3+)-N(epsilon2) coordination bond, it facilitated the second N-carbethoxylation to take place at N(delta1) of the same imidazole ring, leading to a bis-N-carbethoxylated derivative and further to a ring-opened derivative. These phenomena were consistent with the bis-His68/His97 coordination. Further, these were not observed at all for cytochrome b(561), a transmembrane di-heme containing protein responsible for the ascorbate-specific transmembrane electron transfer, where only a specific N(delta1)-carbethoxylation of axial His occurred at a low concentration of DEPC, leading to an inhibition of the electron acceptance from ascorbate without a release of the heme. These distinct results might be related to a specific physiological mechanism being operative at the cytosolic heme center of cytochrome b(561). 相似文献
475.
Hyun-Suk Choo Taro Kinumoto Masafumi Nose Kohei Miyazaki Takeshi Abe Zempachi Ogumi 《Journal of power sources》2008
Oxidation of highly oriented pyrolytic graphite (HOPG) under potential cycling conditions is investigated to understand the stability of graphite used in polymer electrolyte fuel cells (PEFCs) under their dynamic operation conditions. Electrochemical methods, AFM and XPS are applied to examine the surface oxidation of HOPG. The current peaks corresponding to quinone–hydroquinone redox reaction begin to appear on cyclic voltammograms after potential cycling between 0.6 V and 0.8 V vs. SHE (standard hydrogen electrode), indicating that the surface of HOPG is partially oxidized to form surface functional groups containing oxygen, whereas HOPG is relatively stable during potential cycling between 0.4 V and 0.6 V. An increase in potential range to 0.8–1.0 V extends the oxidation and forms pits on the surface of HOPG that is caused by the loss of surface carbon through the oxidation to gaseous products. The high rate of potential cycling accelerates the surface oxidation of HOPG. 相似文献
476.
A convenient method was developed for preparation of FAME in small amounts from glycerolipids of blood or breast milk. Initially,
0.04–0.06 mL blood or breast milk was spotted onto a small piece of filter paper (1.5×1.5 cm) that had been washed with acetone
containing 0.05% 2,6-di-tert-butyl-p-cresol (BHT). Fach piece, once it had dried, was put in a small test tube, to which 2 mL hexane and 0.2 mL 2 M KOH/methanol
were added. After vigorous mixing or sonication for 2 min at room temperature, the solution was neutralized or acidified by
the addition of a few drops of acetic acid. To the solution was added 2 mL H2O, and then the hexane layer that separated was concentrated to dryness in vacuo. The FAME obtained were analyzed by GC. The method was applicable to the analysis of a large number of blood and breast milk
samples, and the arachidonate/(eicosapentaenoate +docosahexaenoate) ratios could be determined rapidly. 相似文献
477.
cis-Vaccenic acid in pulp lipids of commonly available fruits 总被引:1,自引:1,他引:0
Akira Shibahara Kohei Yamamoto Takao Nakayama Goro Kajimoto 《Journal of the American Oil Chemists' Society》1987,64(3):397-401
Fatty acids of commonly available fruit pulps have been analyzed by capillary gas chromatography of their methyl esters and
by gas chromatography-mass spectrometry as their dimethyl disulfide adducts. The gas chromatographic and mass spectrometric
data proved that these fruits always containedcis-vaccenic (cis-11-octadecenoic) acid as a component fatty acid of their pulp lipids. The concentration ofcis-vaccenic acid in total octadecenoic acids ranged from 1.9% to 95.1% in the fruit pulps examined. The highest concentration
of this acid was detected in pulp lipids of Japanese persimmon (Diospyros kaki). In fruit pulp lipids,cis-vaccenic acid was a common octadecenoic acid as well as oleic acid. 相似文献
478.
479.
Titanium oxide nanotubes for bone regeneration 总被引:3,自引:0,他引:3
Kubota S Johkura K Asanuma K Okouchi Y Ogiwara N Sasaki K Kasuga T 《Journal of materials science. Materials in medicine》2004,15(9):1031-1035
Titanium oxide nanotubes with Ca ions on their surfaces were prepared as 2 mm cylindrical inserts and placed into surgically created bone defects in the femurs of Wistar rats. On day 3, fibroblast-like cells were present on the surface of the nanotube inserts and fibers were observed by scanning electron microscopy (SEM). On day 7, cells with alkaline phosphatase activity were present and identified as osteoblasts by SEM and transmission electron microscopy. New bone matrices were observed in and around the porous nanotube inserts by light microscopy. Compared with clinically used hydroxyapatite and tricalcium phosphate, beta-titanium oxide nanotubes promote faster acquisition and development of osteoblasts and bone tissues and have better bone regenerating ability after one week. 相似文献
480.