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排序方式: 共有1711条查询结果,搜索用时 15 毫秒
121.
Yuji Shimada Akio Sugihara Yumi Minamigawa Kenichi Higashiyama Kengo Akimoto Shigeaki Fujikawa Sadao Komemushi Yoshio Tominaga 《Journal of the American Oil Chemists' Society》1998,75(9):1213-1217
An attempt was made to enrich arachidonic acid (AA) from Mortierella single-cell oil, which had an AA content of 25%. The first step involved the hydrolysis of the oil with Pseudomonas sp. lipase. A mixture of 2.5 g oil, 2.5 g water, and 4000 units (U) Pseudomonas lipase was incubated at 40°C for 40 h with stirring at 500 rpm. The hydrolysis was 90% complete after 40 h, and the resulting
free fatty acids (FFA) were extracted with n-hexane (AA content, 25%; recovery of AA, 91%). The second step involved the selective esterification of the fatty acids with
lauryl alcohol and Candida rugosa lipase. A mixture of 3.5 g fatty acids/lauryl alcohol (1:1, mol/mol), 1.5 g water, and 1000 U Candida lipase was incubated at 30°C for 16 h with stirring at 500 rpm. Under these conditions, 55% of the fatty acids were esterified,
and the AA content in the FFA fraction was raised to 51% with a 92% yield. The long-chain saturated fatty acids in the FFA
fraction were eliminated as urea adducts. This procedure raised the AA content to 63%. To further elevate the AA content,
the fatty acids were esterified again in the same manner with Candida lipase. The repeated esterification raised the AA content to 75% with a recovery of 71% of its initial content. 相似文献
122.
Takuya Akiyama Kengo Magara Gyosuke Meshitsuka Knut Lundquist Yuji Matsumoto 《木材化学与工艺学杂志》2015,35(1):8-16
In this study, we investigated the proportion of erythro- and threo-forms of β-O-4-ether structures and their enantiomeric compositions in hardwood lignin by applying the ozonation method to birch wood meal. Optical activity was not substantially observed in either the erythronic or threonic acids obtained as the ozonation products of β-O-4-structures in birch wood meal. The proportions of the four stereoisomeric forms {(αS,βR)-erythro, (αR,βR)-threo, (αS,βS)-threo, and (αR,βS)-erythro forms} were estimated to be 37-38%, 13-14%, 12-13%, and 36-37% based on the yields of erythronic and threonic acids, and on their optical activities. The proportions suggest that the entire components of β-O-4-ether structures in birch wood lignin have R- and S-configurations at the β-carbon in approximately the same quantities {(βR)-β-O-4-structure: (βS)-β-O-4-structure = 50–52:48–50}; i.e., that the β-ether structures are essentially racemic. This estimation implies that, during lignin biosynthesis, an equal number of enantiomeric forms of β-O-4-bonded quinone methides were formed by radical coupling reactions. 相似文献
123.
以聚丙烯酸钠(PAAS)为调控剂,采用化学沉淀法在室温下合成了亚微米级硫酸钡。采用扫描电子显微镜(SEM)、激光粒度分析仪、X射线衍射(XRD)仪对硫酸钡微粒的形貌、粒度分布和结构进行表征。研究了PAAS加入量对硫酸钡颗粒形貌和粒度分布的影响。以硫酸作为沉淀剂时,当PAAS加入量为硫酸钡理论产量的1.0%(质量分数)时,得到平均粒径为0.5μm的球形硫酸钡颗粒,并进一步探讨了PAAS的作用机理。Zeta电位测定结果显示,PAAS吸附到硫酸钡颗粒表面,翻转了颗粒表面的电性,使其带有较强的负电性。提出了硫酸钡颗粒固体-溶液界面的双电层模型。以硫酸铵作为沉淀剂时,副产物氨水(NH3·H2O)电离出的氢氧根(OH-)减缓了表面吸附层变薄的趋势,当PAAS加入量为硫酸钡理论产量的0.4%(质量分数)时,获得平均粒径为0.45μm的硫酸钡颗粒。 相似文献
124.
Hiroaki Inoue Yuji Arai Tsunao Kishida Ryu Terauchi Kuniaki Honjo Shuji Nakagawa Shinji Tsuchida Tomohiro Matsuki Keiichirou Ueshima Hiroyoshi Fujiwara Osam Mazda Toshikazu Kubo 《International journal of molecular sciences》2015,16(1):1043-1050
Hypoxia-inducible factor (HIF)-2α is considered to play a major role in the progression of osteoarthritis. Recently, it was reported that pressure amplitude influences HIF-2α expression in murine endothelial cells. We examined whether hydrostatic pressure is involved in expression of HIF-2α in articular chondrocytes. Chondrocytes were cultured and stimulated by inflammation or hydrostatic pressure of 0, 5, 10, or 50 MPa. After stimulation, heat shock protein (HSP) 70, HIF-2α, nuclear factor kappa B (NF-κB), matrix metalloproteinase (MMP)-13, MMP-3, and vascular endothelial growth factor (VEGF) gene expression were evaluated. The levels of all gene expression were increased by inflammatory stress. When chondrocytes were exposed to a hydrostatic pressure of 5 MPa, HIF-2α, MMP-13, and MMP-3 gene expression increased significantly although those of HSP70 and NF-κB were not significantly different from the control group. In contrast, HIF-2α gene expression did not increase under a hydrostatic pressure of 50 MPa although HSP70 and NF-κB expression increased significantly compared to control. We considered that hydrostatic pressure of 5 MPa could regulate HIF-2α independent of NF-κB, because the level of HIF-2α gene expression increased significantly without upregulation of NF-κB expression at 5 MPa. Hydrostatic pressure may influence cartilage degeneration, inducing MMP-13 and MMP-3 expression through HIF-2α. 相似文献
125.
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128.
Yang Gao Junya Iihama Daiki Hamana Ryo Iwasaki Sawao Honda Toru Asaka Munni Kumari Tomokatsu Hayakawa Samuel Bernard Philippe Thomas Yuji Iwamoto 《International Journal of Applied Ceramic Technology》2023,20(2):768-779
A series of β-SiAlON:Eu2+ phosphors were synthesized from single-source precursors, perhydropolysilazane chemically modified with Al(OCH(CH3)2)3, AlCl3, and EuCl2. The single-source precursors were converted to β-SiAlON:Eu2+ phosphors by pyrolysis under flowing N2 or NH3 at 1000°C, followed by heat treatment at 1800°C under an N2 gas pressure at 980 kPa. By varying the molar ratio of the chemical modifiers, β-SiAlON:Eu2+ with the compositions close to the theoretical ones expressed as Si6−zAlzOz−2yN8−z+2y:yEu2+ were synthesized, where the z values and Eu2+ contents were controlled in the ranges of .44–.78 and .35–1.48 mol%, respectively. The polymer-derived β-SiAlON:Eu2+ phosphors exhibited green emission under excitation at 460 nm attributed to the 4f7–4f6(7f3)5d1 transition of dopant Eu2+. High-angle annular dark-field-scanning transmission microscopy analysis confirmed that the doped-Eu2+ existed interstitially within the channels along the c axis of host β-SiAlON. Compared with the conventional powder metallurgy route, the polymer-derived ceramic route in this study offers some advantages in the grain growth of host β-SiAlON and photoluminescence properties in terms of green emission intensity under excitation at 460 nm, and the highest intensity was achieved for the polymer-derived β-SiAlON:Eu2+ with z = .64 and .37 mol% Eu2+. 相似文献
129.
Isobe K Shoji K Nakanishi Y Yokoe M Wakao N 《Journal of Bioscience and Bioengineering》2003,95(3):257-263
Cholesterol oxidase (CHO) with high stability in detergents was found from an isolated strain, Y-134, belonging to the gamma-subclass of Proteobacteria. CHO production reached its maximum by incubation at 30 degrees C for 12 d. It was purified from cell-free extract prepared by mixing the cells with 0.4% Triton X-100. The absorption spectrum of the purified enzyme exhibited maxima at 274 and 410 nm, and a shoulder at 330 nm. The molecular mass was 115 kDa with two identical subunits of 58 kDa. The enzyme oxidized cholest-5-en-3beta-ol (cholesterol) and 5alpha-cholestan-3beta-ol (dihydrocholesterol) at a high reaction rate, and the K(m) value for cholesterol was 65 microM. The stability of the enzyme was higher than other CHOs in nonionic detergents with high values of hydrophilelipophile balance (HLB) such as Triton X-450 and sodium cholate. NH2-terminal sequence analysis showed a high similarity to CHO from Burkholderia cepacia, but not to CHOs from Streptomyces or Brevibacterium. 相似文献
130.
主要从鳄鱼皮的粒面特点、形态结构及应用等方面出发 ,充分考虑了制革过程中机械磨耗对鳄鱼皮的作用 ,加强了对化工材料的选择 ,同时在灰碱烧鳞、漂色、鞣制、复鞣、染色、加脂、整饰等几个技术关键进行了细致的研究 ,提出了制造高档鳄鱼皮革的制革工艺。 相似文献