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排序方式: 共有390条查询结果,搜索用时 203 毫秒
91.
Prof. Dr. Tomoaki Tanase Dr. Kanako Nakamae Prof. Dr. Yasutaka Kitagawa Prof. Dr. Takayuki Nakajima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(51):12953-12958
Reactions of Pd8 strings supported by meso-Ph2PCH2P(Ph)CH2P(Ph)CH2PPh2 (meso-dpmppm) ligands, [Pd8(meso-dpmppm)4(L)2]4+ (L=CH3CN ( 1 ), XylNC ( 2 )) with C60 resulted in the exclusive formation of unprecedented metal-chain-wired C60 bucky balls, [{Pd4(meso-dpmppm)2(L)}2(C60)]4+ (L=CH3CN ( 11 ), XylNC ( 12 )), in which a C60 fullerene is trapped in the central Pd–Pd junction, as unambiguously established by spectroscopic, X-ray crystallographic, and theoretical techniques. The similar reaction of Pd8 strings supported by rac-dpmppm, [Pd8(rac-dpmppm)4(CH3CN)2]4+ ( 3 ) also afforded a racemic mixture of [{Pd4((R*,R*)-dpmppm)2(CH3CN)}2(C60)]4+ ( 13 ) without scrambling the Pd4 fragments with (R,R)- and (S,S)-dpmppm ligands. Consequently, those of enantiopure chiral Pd8 strings, [Pd8((R*,R*)-dpmppm)4(CH3CN)2]4+, certainly afforded chiral bucky balls of [{Pd4((R*,R*)-dpmppm)2(CH3CN)}2(C60)]4+ ( 13 RR and 13 SS ), that exhibit mirror-image circular dichroism spectra. The reactions of 1 and 2 were also applied for trapping a C70 fullerene to give 2 : 1 adducts of [{Pd4(meso-dpmppm)2(L)}2(C70)]4+ (L=CH3CN ( 21 ), XylNC ( 22 )). These results provide useful information for creating a platform to develop dimensionally and chirality controlled metal–carbon nanocomposite materials. 相似文献
92.
93.
Gold Nanoparticles: Fabrication of NIR‐Excitable SERS‐Active Composite Particles Composed of Densely Packed Au Nanoparticles on Polymer Microparticles (Part. Part. Syst. Charact. 4/2015) 下载免费PDF全文
94.
Hirofumi Hattori Tomoya Houra Yasutaka Nagano 《International Journal of Heat and Fluid Flow》2007,28(6):1262-1271
This paper presents direct numerical simulations (DNS) of stable and unstable turbulent thermal boundary layers. Since a buoyancy-affected boundary layer is often encountered in an urban environmental space where stable and unstable stratifications exist, exploring a buoyancy-affected boundary layer is very important to know the transport phenomena of the flow in an urban space. Although actual observation may qualitatively provide the characteristics of these flows, the relevant quantitative turbulent quantities are very difficult to measure. Thus, in order to quantitatively investigate a buoyancy-affected boundary layer in detail, we have here carried out for the first time time- and space-developing DNS of slightly stable and unstable turbulent thermal boundary layers. The DNS results show the quantitative turbulent statistics and structures of stable and unstable thermal boundary layers, in which the characteristic transport phenomena of thermally stratified boundary layers are demonstrated by indicating the budgets of turbulent shear stress and turbulent heat flux. Even though the input of buoyant force is not large, the influence of buoyancy is clearly revealed in both stable and unstable turbulent boundary layers. In particular, it is found that both stable and unstable thermal stratifications caused by the weak buoyant force remarkably alter the structure of near-wall turbulence. 相似文献
95.
Shintaro Hatanaka Yasushi Obora Dr. Yasutaka Ishii Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(6):1883-1888
A novel iridium‐catalyzed intermolecular coupling reaction of primary alcohols or aldehydes with 2‐alkynes was successfully achieved with high regioselectivity to give hydroacylation products such as α,β‐unsaturated ketones in good yields. The mechanistic investigation of the reaction strongly indicated that the coupling proceeds through the initial formation of homoallylic alcohols followed by dehydrogenation to β,γ‐unsatutated ketones and then isomerisation, which leads to the hydroacylation products. 相似文献
96.
Ito M Ogino H Oshima H Shiraki N Shibamoto Y Kasai H Mase M Kawamura Y Miyati T 《Magnetic resonance imaging》2006,24(5):625-630
PURPOSE: A newly developed contrast material, CH3-DTPA-Gd (NMS60), a trimer containing 3 Gd(3+) atoms per molecule, has been shown to offer greater enhancement and longer vascular retention than gadopentetate dimeglumine (Gd-DTPA) in animals. We report on our early phase II study on NMS60 in brain tumor patients together with supplementary investigations. METHODS AND MATERIALS: The longitudinal relaxation rate (R(1)=1/T(1)) and the transverse relaxation rate (R(2)*=1/T(2)*) of NMS60 and Gd-DTPA were determined at 20 degrees C in water at 1.5 T. An NMS60 dose of 0.1 or 0.2 mmol (Gd)/kg was randomly assigned and administered to 10 patients (five women, five men; mean age: 49 years) with brain tumors. Safety and contrast-enhancing ability of NMS60 were evaluated. Dual dynamic contrast-enhanced T(1) and R(2)* studies (DUCE imaging) were also carried out in two patients. RESULTS: Regarding the relaxivity per Gd, R(1) and R(2)* of NMS60 were 9.5 and 11.0 (mmol/L x s)(-1), respectively, compared to 4.8 and 7.2 (mmol/L x s)(-1) for Gd-DTPA. Although a transient slight increase of alanine aminotransferase was observed in one case, no other adverse reactions were observed after administration of NMS60. Contrast enhancement by NMS60 was excellent at both concentrations, and when tumor detectability was assessed with a five-point scale, the diagnostic usefulness was 4 or higher in all cases. In DUCE imaging, NMS60 appeared to show high signal intensity, when compared with the data obtained separately for Gd-DTPA. CONCLUSION: NMS60 had a high contrasting effect and little toxicity, and is expected to be clinically useful. 相似文献
97.
Yuji Hirai Hiroshi Yabu Yasutaka Matsuo Kuniharu Ijiro Masatsugu Shimomura 《Macromolecular Symposia》2010,295(1):77-80
Summary: Self-organized honeycomb-patterned polymer films were prepared by using condensed water droplet arrays as templates. Porous polymer masks for dry etching were easily prepared on Si substrates by peeling off the honeycomb-patterned films. After dry etching, hexagonally-arranged micro-pores were formed on the surface of Si substrates. 相似文献
98.
Yohji Akama Kei Irie Akitoshi Kawamura Yasutaka Uwano 《Discrete and Computational Geometry》2010,44(3):589-598
Motivated by statistical learning theoretic treatment of principal component analysis, we are concerned with the set of points
in ℝ
d
that are within a certain distance from a k-dimensional affine subspace. We prove that the VC dimension of the class of such sets is within a constant factor of (k+1)(d−k+1), and then discuss the distribution of eigenvalues of a data covariance matrix by using our bounds of the VC dimensions
and Vapnik’s statistical learning theory. In the course of the upper bound proof, we provide a simple proof of Warren’s bound
of the number of sign sequences of real polynomials. 相似文献
99.
Sachio Fukuoka Yasutaka Nakajima Wataru Watanabe Atsunori Mori Tatsuro Matsumura Kenji Takeshita 《Tetrahedron》2010,66(9):1721-6513
N,N,N′,N′-(Tetrakis-2-pyridylmethyl)ethylenediamine (TPEN) derivatives bearing the different number (1-4) of a double bond moiety on the pyridine ring are synthesized and subjected to copolymerization with N-isopropylacrylamide in the presence of AIBN. The obtained poly(TPEN-NIPA) gels show thermo-responsive swelling/shrinking behaviors and are employed for the extraction of cadmium(II) ion from the aqueous solution to examine the relationship of the gel characteristics and the extraction performance. The polymer gels composed of the TPEN derivative bearing three or four double bonds exhibit temperature-dependent change of swelling and shrinking in water. These gels extract CdII ion efficiently from the aqueous solution in the swelling state at 5 °C, while little extraction was observed at 45 °C with shrinking. 相似文献
100.
Saito T Nishihara S Kataoka Y Nakanishi Y Kitagawa Y Kawakami T Yamanaka S Okumura M Yamaguchi K 《The journal of physical chemistry. A》2010,114(45):12116-12123
In the present study, the concerted and stepwise reaction mechanisms for 1,3-dipole cycloaddition of ozone with ethylene (1) and acrylonitrile (2) are investigated. The stationary points are optimized by using four hybrid R(U)DFT methods. A geometry optimization method based on an approximate spin projection (AP-opt method) is applied to eliminate a spin contamination from the broken-symmetry (BS) solution. The AP-opt method reveals that a diradical intermediate for the stepwise pathway is spurious due to the spin contamination. The revised reaction profile with no diradical intermediate supports the stereospecificity. On the basis of the experimental data, the RCCSD(T) method outperforms AP-UCCSD(T), AP-UBD(T), and MkMRCCSD(4e,4o) for the systems, indicating that the RCCSD(T) method can describe the diradical character of ozone within a framework of single reference wave function. The subsequent single point energy calculations show that the highly synchronous transition state is much more favorable than the asynchronous one for 1. In the case of 2, there is not much difference between two transition states because of its asymmetric structure and charge separations in the transition states. 相似文献