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排序方式: 共有432条查询结果,搜索用时 15 毫秒
91.
Tetsuya Tanigami Hitoshi Ohta Ryuji Orii Kazuo Yamaura Shuji Matsuzawa 《Journal of Inorganic and Organometallic Polymers》1995,5(2):135-153
Three polymers of poly[bis(ethylamino)phosphazene] (PBEAP) containing different amounts of the residual P–Cl moieties, which had been hydrolyzed into P OH in the following sample purification processes, were prepared by substitution of the chlorines on poly(dichlorophosphazene) with ethylamine. Only the polymer which had the highest side-chain content of ethylamino groups (ca. 93°o) had a film-forming ability and a crystalline nature. The hydrolytic degradation of PBEAP in acidic solutions was investigated using the solution viscosity data obtained as a function of standing time. Acetic acid, 0.5 and 1N, pure acetic acid, and 2.2.2-trifluoroethanol were used as solvents. The degradation was composed of random breaking processes along the polymer chain, especially at the-N=P(OH)2-and-N=P(OH)(NHC2H5)-units, and an unzippering-like breaking process which was started at the chain ends produced by the former random breaking. The random breaking caused an abrupt decrease in viscosity at the beginning of the degradation, and on the contrary, the unzippering-like breaking appeared as a gradual decrease in viscosity at the later stages of degradation. The total rate of degradation depended on the concentration of the ethylamino groups. 相似文献
92.
Yuji Shimada Akio Sugihara Hirofumi Nakano Tomomi Yokota Toshihiro Nagao Sadao Komemushi Yoshio Tominaga 《Journal of the American Oil Chemists' Society》1996,73(11):1415-1420
An attempt was made to produce structured lipids containing essential fatty acid by acidolysis with 1,3-positional specificRhizopus delemar lipase. The lipase was immobilized on a ceramic carrier by coprecipitation with acetone and then was activated by shaking
for 2 d at 30°C in a mixture of 5 g safflower or linseed oil, 10 g caprylic acid, 0.3 g water and 0.6 g of the immobilized
enzyme. The activated enzyme was transferred into the same amount of oil/caprylic acid mixture without water, and the mixture
was shaken under the same conditions as for the activation. By this reaction, 45–50 mol% of the fatty acids in oils were exchanged
for caprylic acid, and the immobilized enzyme could be reused 45 and 55 times for safflower and linseed oils, respectively,
without any significant loss of activity. The triglycerides were extracted withn-hexane after the acidolysis and then were allowed to react again with caprylic acid under the same conditions as mentioned
above. When acidolysis was repeated three times with safflower oil as a starting material, the only products obtained were
1,3-capryloyl-2-linoleoylglycerol and 1,3-capryloyl-2-oleoyl-glycerol, with a ratio of 86∶14 (w/w). Equally, the products
from linseed oil were 1,3-capryloyl-2-α-linolenoyl-glycerol, 1,3-caprylol-2-linoleoyl-glycerol, and 1,3-capryloyl-2-oleoly-glycerol
(60∶22∶18, w/w/w). All fatty acids at the 1,3-positions in the original oils were exchanged for caprylic acid by the repeated
acidolyses, and the positional specificity ofRhizopus lipase was also confirmed to be strict. 相似文献
93.
Makoto Takahashi Yuuko Tomioka Toshiyuki Miyauchi Shoji Sato Asami Murai Toshiyuki Ido Koichi Wakita Hiroshi Terada Sadao Ohkido Masanori Matsubara 《Journal of the American Ceramic Society》2007,90(7):2032-2037
A slurry containing YBa2 Cu3 O7− x particles and a fine YBa2 Cu3 (OH) x colloid solution was prepared, and a large-scale bulk YBa2 Cu3 O7− x superconductor (about 50 mm × 35 mm × 2 mm) was produced by plastic forming without high-pressure molding. The samples molded from the slurry were dried and then fired at 1223 K in air. X-ray diffraction data indicated that the samples had the characteristic orthorhombic YBa2 Cu3 O7− x structure. Measurements of electrical resistance were carried out between 300 and 50 K by the standard four-probe DC electrical measurement. The samples began superconducting at an onset temperature around 92 K, and the full-transition temperature (critical temperature) ( T c ) was 88.7±1.4 K. The critical current density ( J c ) measured at 77 K was about 440 A/cm2 , the value of J c was improved by the heat treatment under an oxygen atmosphere, and J c =1.6 × 103 A/cm2 was observed. Under the magnetic field (B=1 T), the sample held its superconductivity, and demonstrated that this method can be used to produce the magnetic shielding used in magnetic resonance imaging diagnosis. 相似文献
94.
Gels of syndiotacticity-rich poly(vinyl alcohol) (s-PVA) in mixed solvents of water/dimethyl sulfoxide (DMSO) or water/ethylene glycol (EG) were made by chilling at the temperatures of 0–70°C from those solutions with the polymer concentrations below 10g/dL. The melting points of the gels were measured warming the gel from the gelling temperature (Tgel) at a constant heating rate. The apparent enthalpy of fusion of a junction of gel, ΔH was estimated from the relation between the apparent melting temperature and the polymer concentration. The s-PVA gels made from the mixtures of the water/lower contents of DMSO or EG had a minimum at lower Tgel and a maximum ΔH at a higher Tgel. On the other hand, the s-PVA gels made from the mixtures of the water/higher contents of them had nearly a maximum ΔH at a higher Tgel. From those results, it was considered that the former gels received a high thermal history while the latter gels received only slight thermal history. 相似文献
95.
Norimitsu Sakagami Kouhei Ishimaru Sadao Kawamura Mizuho Shibata Hiroyuki Onishi Shigeo Murakami 《野外机器人技术杂志》2013,30(4):624-640
This paper reports the development of a robotic inspection system using a mechanical contact mechanism that enhances the positioning stability of a small and lightweight underwater robot to take clear images of underwater targets and to work with manipulators for inspections under external disturbances. As described in this paper, first we perform a two‐dimensional numerical analysis based on force and moment acting on an underwater robot with a contact mechanism. Second, we experimentally investigate the friction coefficients of several soft and high friction materials for the contact points of a prototype contact mechanism to enhance the positioning stability of the robot. Based on the results of numerical analysis and the experimental investigation, we design and develop a prototype contact mechanism for an underwater robot. Moreover, we experimentally test the stability of the underwater robot with the contact mechanism in a test tank. Finally, a ship hull inspection is conducted as a field test in a port using the robot with the developed contact mechanism. The experimentally obtained results indicate that the proposed contact mechanism is a useful tool for underwater visual inspections and manipulator tasks of a small and lightweight underwater robot. 相似文献
96.
The quality of the image signal obtained from the environmental secondary electron detector (ESED) employed in a variable pressure (VP) SEM can be dramatically improved by using helium gas. The signal-to-noise ratio (SNR) increases gradually in the range of the pressures that can be used in our modified SEM. This method is especially useful in low-voltage VP SEM as well as in a variety of SEM operating conditions, because helium gas can more or less maintain the amount of unscattered primary electrons. In order to measure the SNR precisely, a digital scan generator system for obtaining two images with identical views is employed as a precondition. 相似文献
97.
98.
MD Gunn S Kyuwa C Tam T Kakiuchi A Matsuzawa LT Williams H Nakano 《Canadian Metallurgical Quarterly》1999,189(3):451-460
Secondary lymphoid organ chemokine (SLC) is expressed in high endothelial venules and in T cell zones of spleen and lymph nodes (LNs) and strongly attracts naive T cells. In mice homozygous for the paucity of lymph node T cell (plt) mutation, naive T cells fail to home to LNs or the lymphoid regions of spleen. Here we demonstrate that expression of SLC is undetectable in plt mice. In addition to the defect in T cell homing, we demonstrate that dendritic cells (DCs) fail to accumulate in spleen and LN T cell zones of plt mice. DC migration to LNs after contact sensitization is also substantially reduced. The physiologic significance of these abnormalities in plt mice is indicated by a markedly increased sensitivity to infection with murine hepatitis virus. The plt mutation maps to the SLC locus; however, the sequence of SLC introns and exons in plt mice is normal. These findings suggest that the abnormalities in plt mice are due to a genetic defect in the expression of SLC and that SLC mediates the entry of naive T cells and antigen-stimulated DCs into the T cell zones of secondary lymphoid organs. 相似文献
99.
Y Terauchi Y Tsuji S Satoh H Minoura K Murakami A Okuno K Inukai T Asano Y Kaburagi K Ueki H Nakajima T Hanafusa Y Matsuzawa H Sekihara Y Yin JC Barrett H Oda T Ishikawa Y Akanuma I Komuro M Suzuki K Yamamura T Kodama H Suzuki K Yamamura T Kodama H Suzuki S Koyasu S Aizawa K Tobe Y Fukui Y Yazaki T Kadowaki 《Canadian Metallurgical Quarterly》1999,21(2):230-235
100.
Indentation fatigue testing is carried out for four kinds of zirconia ceramics; 6Y-FSZ, 3Y-TZP, Mg-PSZ and Ce-TZP; which have different strengthening-toughening mechanisms one another. Each material shows different indentation fatigue behavior. Large sized surface chipping is produced easily in early cycles for non-toughened 6Y-FSZ, while 3Y-TZP toughened by anelasticity has high resistance against chipping. There is a possibility that anelastic characteristic works as resistance against indentation fatigue damage. Stress induced phase transformation also improves fatigue damage, but this effect depends on the extent of transformation and/or occurrence of microcracking. 相似文献