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31.
Itaka K Kanayama N Nishiyama N Jang WD Yamasaki Y Nakamura K Kawaguchi H Kataoka K 《Journal of the American Chemical Society》2004,126(42):13612-13613
An siRNA nanocarrier formed through self-assembly of PEG-based block catiomer possessing two distinct amino groups with different pKa values in a side chain was developed. This design provided the carrier with a sufficient siRNA complexation and an assumed buffering capacity in the endosomes, allowing it to exhibit remarkable gene knockdown abilities as well as sufficient serum tolerability. 相似文献
32.
Zegers RG Abend H Akimune H van den Berg AM Fujimura H Fujita H Fujita Y Fujiwara M Galès S Hara K Harakeh MN Ishikawa T Kawabata T Kawase K Mibe T Nakanishi K Nakayama S Toyokawa H Uchida M Yamagata T Yamasaki K Yosoi M 《Physical review letters》2003,90(20):202501
The excitation and subsequent proton decay of the isovector spin-flip giant monopole resonance (IVSGMR) is studied via the 208Pb(3He,t) reaction at 410 MeV. In the inclusive spectrum (60+/-5)% of the non-energy-weighted sum-rule strength for this 2 variant Planck's over 2h omega resonance was found in the region 29相似文献
33.
Yamasaki R Tanatani A Azumaya I Saito S Yamaguchi K Kagechika H 《Organic letters》2003,5(8):1265-1267
[reaction: see text] Introduction of an electron-withdrawing group on the aromatic ring of N-methylacetanilide decreased the ratio of the cis conformer, and the ratio correlates well with the Hammett sigma values of the substituents. These steric properties can be applied to achieve amide conformational switching by protonation at the aromatic substituent of 4-[bis(dimethylamino)]-N-methylacetanilide or N-[p-(dimethylamino)phenyl]-N-phenylacetamide. 相似文献
34.
S. V. Buldyrev F. Pammolli M. Riccaboni K. Yamasaki D.-F. Fu K. Matia H. E. Stanley 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(2):131-138
We present a preferential attachment growth model to obtain the
distribution P(K) of number of units K in the classes which may
represent business firms or other socio-economic entities. We found
that P(K) is described in its central part by a power law with an
exponent ϕ = 2+b/(1-b) which depends on the probability of entry of new
classes, b. In a particular problem of city
population this distribution is equivalent to the well known Zipf
law. In the absence of the new classes entry, the
distribution P(K) is exponential.
Using analytical form of P(K) and assuming proportional growth
for units, we derive P(g), the distribution of business firm
growth rates. The model predicts that P(g) has a Laplacian cusp
in the central part and asymptotic power-law tails with an exponent
ζ = 3. We test the analytical expressions derived using
heuristic arguments by simulations. The model might also explain the
size-variance relationship of the firm growth rates. 相似文献
35.
36.
Ductile nickel-tungsten (Ni-W) alloys containing about 20–21 at.%W were electroplated onto copper substrates. The development
of the amorphous/nanocrystalline microstructure towards a complete crystallization by isochronal heat treatments in vacuum
was monitored by different methods. For medium annealing temperatures a solid-solution of W in the fcc-Ni lattice was achieved
resulting in an increased hardness. For temperatures of 600 °C and upward recrystallization started and thermodynamically
stable intermetallic compounds like Ni4W and NiW were formed. A third phase, containing more than 80 at.%W was also detected but could not be identified so far.
Only by combination of different methods and especially by use of analytical TEM structural analysis and phase identification
in these amorphous-nanocrystalline Ni-W alloys were successful. 相似文献
37.
M Uchida S Morita M Chihiro T Kanbe K Yamasaki Y Yabuuchi K Nakagawa 《Chemical & pharmaceutical bulletin》1989,37(6):1517-1523
Many 8-[(2-benzimidazolyl)sulfinyl]-5,6,7,8-tetrahydroquinolines were synthesized and examined for their (H+ + K+) adenosine triphosphatase ATPase-inhibitory and antisecretory activities. These sulfinyl compounds could be considered to be rigid analogues of the 2-[(2-pyridyl)methylsulfinyl]benzimidazole class of antisecretory agents. All the compounds tested were potent inhibitors of (H+ + K+)ATPase. Most of the compounds also inhibited histamine-induced gastric acid secretion in rats. Among them, 8-[(5-fluoro-2-benzimidazolyl)sulfinyl]-3-methyl-5,6,7,8-tetrahydroqu inoline (XIVm) was found to have the most potent activity. The structure-activity relationships are discussed. 相似文献
38.
Nitroxyl radicals (nitroxides) with unpaired electron are widely used as antioxidants, contrast agents, and spin probes. Although piperidine nitroxyl radicals have many applications, these are mainly tetramethylpiperidine compounds, and only a few reports consider the substitution of N-O surround as a reaction site, such as 2,2,6,6-tetrasubstituted piperidine nitroxyl radicals. Our results revealed that the 2,6-position of the 2,2,6,6-tetramethylpiperidin-4-one compound was substituted by cyclohexyl groups to produce 2,2,6,6-tetrasubstituted piperidin-4-one derivatives under mild reaction conditions. An interesting result was obtained by using 15N-labeled NH4Cl instead of 14NH4Cl: it gave 15N-labeled 2,2,6,6-tetrasubstituted piperidin-4-one-1-oxyls with a high 15N content. In conclusion, the new method for the synthesis of nitroxyl radicals readily yields 2,2,6,6-tetrasubstituted piperidin-4-one under mild conditions. 相似文献
39.
Corrosion and passivation behavior of Mg-Zn-Y-Al alloys prepared by cooling rate-controlled solidification 总被引:1,自引:0,他引:1
Michiaki Yamasaki Shogo IzumiYoshihito Kawamura Hiroki Habazaki 《Applied Surface Science》2011,257(19):8258-8267
Highly corrosion-resistant nanocrystalline Mg-Zn-Y-Al multi-phase alloys have been prepared by consolidation of rapidly solidified (RS) ribbons. The relation between corrosion behavior and microstructure evolution of Mg-Zn-Y-Al alloys with a long period stacking ordered phase has been investigated. In order to clarify the influence of rapid solidification on the occurrence of localized corrosion such as filiform corrosion, several Mg96.75Zn0.75Y2Al0.5 (at.%) alloys with different cooling rates are fabricated by the gravity casting, copper mould injection casting and melt-spinning techniques and their corrosion behavior and microstructures are examined by the salt water immersion test, electrochemical measurements, GDOES, XRD, SEM and TEM. To clarify the effect of aluminium addition on the improvement in corrosion resistance of the alloys, several Mg97.25−xZn0.75Y2Alx alloys with different aluminium contents are fabricated by consolidating RS ribbons and the formation of corroded films on the Mg-Zn-Y-Al alloys have been investigated. Rapid solidification brings about the grain refinement and an increase in the solid solubility of zinc, yttrium and aluminium into the magnesium matrix, enhancing microstructural and electrochemical homogeneity, which in turn enhanced corrosion resistance. The addition of aluminium to magnesium can modify the structure and chemical composition of surface films and improves the resistance to local breakdown of the films. 相似文献