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991.
Michio Yamada Dr. Mayuko Okamura Satoru Sato Chika I. Someya Naomi Mizorogi Dr. Takahiro Tsuchiya Dr. Takeshi Akasaka Prof. Tatsuhisa Kato Prof. Shigeru Nagase Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(40):10533-10542
The two regioisomers of endohedral pyrrolidinodimetallofullerenes M2@Ih‐C80(CH2)2NTrt (M=La, Ce; Trt=trityl) were synthesized, isolated, and characterized. X‐ray crystallographic analyses of [6,6]‐La2@Ih‐C80(CH2)2NTrt and [6,6]‐Ce2@Ih‐C80(CH2)2NTrt revealed that the encapsulated metal atoms are located at the slantwise positions on the mirror plane that parallels the pyrrolidine ring. Paramagnetic NMR analyses of [6,6]‐ and [5,6]‐Ce2@Ih‐C80(CH2)2NTrt were also carried out to clarify the metal positions. As for the [6,6]‐adduct, the metal positions obtained by paramagnetic NMR analysis agree well with the X‐ray structure. In contrast, paramagnetic NMR analysis of the [5,6]‐adduct showed that the two Ce atoms are collinear with the pyrrolidine ring. We also compared the observed paramagnetic effects of the pyrrolidinodimetallofullerenes with those of other cerium‐encapsulating fullerene derivatives such as bis‐silylated Ce2@Ih‐C80 and a carbene adduct of Ce2@Ih‐C80. We found that the metal positions can be explained by the electrostatic potential maps of the corresponding [6,6]‐ and [5,6]‐adducts of [Ih‐C80(CH2)2NTrt]6?. These findings clearly show that metal positions inside fullerene cages can be controlled by means of the addition positions of the addends. In addition, the radical anions of the pyrrolidinodimetallofullerenes were prepared by bulk controlled‐potential electrolysis and characterized by X‐band EPR spectral study. 相似文献
992.
Kenji Fujito Shuichi Kubo Hirobumi Nagaoka Tae Mochizuki Hideo Namita Satoru Nagao 《Journal of Crystal Growth》2009,311(10):3011-3014
We succeeded in preparing very thick c-plane bulk gallium nitride (GaN) crystals grown by hydride vapor phase epitaxy. Growth of the bulk GaN crystals was performed on templates with 3 μm GaN layer grown by metal organic chemical vapor deposition on (0 0 0 1) sapphire substrates. Colorless freestanding bulk GaN crystals were obtained through self-separation processes. The crystal's diameter and thickness were about 52 and 5.8 mm, respectively. No surface pits were observed within an area of 46 mm diameter of the bulk GaN crystal. The dislocation density decreased with growth direction (from N-face side to Ga-face side) and ranged from 5.1×106 cm−2 near the N-face surface to 1.2×106 cm−2 near the Ga-face. A major impurity was Si, and other impurities (O, C, Cl, H, Fe, Ni and Cr) were near or below the detection limits by SIMS measurements. 相似文献
993.
Satoru Fujishige 《Combinatorica》2010,30(2):247-252
Recently Kamiyama, Katoh, and Takizawa have shown a theorem on packing arc-disjoint arborescences that is a proper extension of Edmonds’ theorem on disjoint spanning branchings. We show a further extension of their theorem, which makes clear an essential rôle of a reachability condition played in the theorem. The right concept required for the further extension is “convexity” instead of “reachability”. 相似文献
994.
We study positive linear Volterra integro-differential equations in Banach lattices. A characterization of positive equations
is given. Furthermore, an explicit spectral criterion for uniformly asymptotic stability of positive equations is presented.
Finally, we deal with problems of robust stability of positive systems under structured perturbations. Some explicit stability
bounds with respect to these perturbations are given. 相似文献
995.
In the many studies done on informational masking, interfering speech reduces speech intelligibility. This effect is often used to secure privacy in public spaces. These applications require estimates of how much masking is required. In general, masking effects are estimated by using spectrum information as excitation patterns. However, estimates of informational masking can hardly be obtained by only using spectrum information. Therefore, we estimated the effects of informational masking using time-domain information. Then, we calculated the cepstra of the envelopes’ magnitude histograms. If these cepstra are different between the target and the masker, the signals are not similar in the time-domain. Furthermore, the effect of informational masking would be low. Therefore, we considered the histograms’ cepstra distances (HCD) to estimate signal similarities. The signal similarities in our first experiment were estimated using five maskers by utilizing the HCD. These maskers were random noise, music, female speech, male speech, and target speaker’s speech. Male and female speech were more similar to the target speech than music and noise. Also, the same speaker’s speech was the most similar in the set of maskers. A listening test was carried out in the second experiment to verify the HCD. A double masker was used in this experiment as an effective informational masker. It has similar characteristics to reversal speech. The listening test results suggest the double-masker’s masking effects has the same relation with HCD. This suggests informational masking can be estimated by signal similarity using the HCD. 相似文献
996.
The carboxylic acids are stably adsorbed on TiO2(1 1 0) surfaces at room temperature. To demonstrate the neutralization mechanism proposed by Ashima et al. [H. Ashima, W.-J. Chun, K. Asakura, Surf. Sci. 601 (2007) 1822.] that explains the stable adsorption of carboxylic acids, we studied the full-coverage adsorption structure of acetic anhydride on a TiO2(1 1 0) surface by STM (scanning tunneling microscopy). We directly observed three postulated species on the TiO2(1 1 0) surface; normal acetates (termed acetate A) forming a (2 × 1) ordered structure, a minor acetate species (termed acetate B) which was present between the bridging oxygen and the 5-fold Ti, and the oxygen vacancies. We determined the ratio of these three species. This ratio was in good agreement with the postulated conversion reaction of acetate B to A. 相似文献
997.
Hironori Yamaguchi Shojiro Kimura Masayuki Hagiwara Yusuke Nambu Satoru Nakatsuji Yoshiteru Maeno Koichi Kindo 《Applied magnetic resonance》2009,36(2-4):285-289
We report the experimental results of electron spin resonance in high magnetic fields up to about 53 T on the quasi-two-dimensional triangular lattice antiferromagnet NiGa2S4. The temperature dependence of the resonance field at 584.8 GHz shows a steep change below about 30 K, indicating a development of the short-range correlation. The frequency dependence of the resonance field at the lowest temperature for H∥c is explained by one of the helical resonance modes. These experimental results suggest that the short-range order is well developed at low temperatures, and the resonance mode is described by a conventional spin wave theory. 相似文献
998.
999.
Ruthenium complexes are well known to catalyze the oxidation of alcohols,1 where a ruthenium alkoxide has been assumed as a key intermediate. The formation of symmetrical ethers from certain carbinols is also catalyzed by ruthenium in a similar manner.2 We now wish to report that the mixed etherification of allyl alcohols is catalyzed by RuCl3, which acts as a Lewis acid to cleave the allylic carbon—oxygen bond. 相似文献
1000.
Ryuichi Watanabe Hajime Uchida Toshiyuki Suzuki Ryoji Matsushima Mika Nagae Yoshikazu Toyohara Masayuki Satake Yasukatsu Oshima Akio Inoue Takeshi Yasumoto 《Tetrahedron》2013
A novel epoxy polyether compound named gambieroxide was isolated from the benthic dinoflagellate Gambierdiscus toxicus (GTP2 strain) collected at Papeete, Tahiti, French Polynesia and its structure comprising of a ladder-frame polyether with twelve contiguous trans-fused ether rings (6/7/6/6/6/7/6/8/6/6/6/6), a sulfate ester group, an epoxide, and two olefines in side chains was elucidated by detailed NMR and MS analysis. It is interesting that the structure strikingly resembles yessotoxin, one of lipophilic toxins in shellfish originating from the dinoflagellate Protoceratium reticulatum. 相似文献