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排序方式: 共有238条查询结果,搜索用时 31 毫秒
91.
A Green's function formalism incorporating broadened density of states (DOS) is proposed for the calculation of electrical conductance. In cluster-molecule-cluster systems, broadened DOS of the clusters are defined as continuous DOS of electrodes and used to calculate Green's function of electrodes. This approach combined with density functional theory is applied to the electrical transmission of gold atomic wires and molecular wires consisting of benzene-1,4-dithiolate, benzene-1,4-dimethanethiolate, 4,4(')-bipyridine, hexane dithiolate, and octane dithiolate. The B3LYP, B3PW91, MPW1PW91, SVWN, and BPW91 functionals with the LANL2DZ, CEP, and SDD basis sets are employed in the calculation of conductance. The width parameter was successfully determined to reproduce the quantum unit of conductance 2e(2)/h in gold atomic wires. The combination of the B3LYP hybrid functional and the CEP-31G basis set is excellent in reproducing measured conductances of molecular wires by Tao et al. [Science 301, 1221 (2003); J. Am. Chem. Soc. 125, 16164 (2003); Nano Lett. 4, 267 (2004)]. 相似文献
92.
Yuya Tanaka Yuya Kato Kaho Sugimoto Reo Kawano Tomofumi Tada Shintaro Fujii Manabu Kiguchi Munetaka Akita 《Chemical science》2021,12(12):4338
Here, we report multinuclear organometallic molecular wires having (2,5-diethynylthiophene)diyl-Ru(dppe)2 repeating units. Despite the molecular dimensions of 2–4 nm the multinuclear wires show high conductance (up to 10−2 to 10−3G0) at the single-molecule level with small attenuation factors (β) as revealed by STM-break junction measurements. The high performance can be attributed to the efficient energy alignment between the Fermi level of the metal electrodes and the HOMO levels of the multinuclear molecular wires as revealed by DFT–NEGF calculations. Electrochemical and DFT studies reveal that the strong Ru–Ru interaction through the bridging ligands raises the HOMO levels to access the Fermi level, leading to high conductance and small β values.Multinuclear organometallic molecular wires having (diethynylthiophene)diyl-Ru(dppe)2 repeating units show high conductance with small attenuation factors. The strong Ru–Ru interaction is the key for the long-range carrier transport. 相似文献
93.
Mohamed Elbandy Tomofumi Miyamoto Marie‐Aleth Lacaille‐Dubois 《Helvetica chimica acta》2007,90(2):260-270
Six new triterpene glycosides, repensosides A–F ( 1 – 6 , resp.), were isolated from the roots of Gypsophila repens L. Their structures, established by extensive 1D‐ and 2D‐NMR spectroscopic experiments as well as MS analyses, were found to be based on gypsogenic acid (or gypsogenin) as aglycone, with three to nine branched or unbranched sugar moieties. 相似文献
94.
H. Sakaue F. Maruta H. Fujimaki S. Tonouchi T. Hashimoto 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(1):123-127
Cesium-137 distribution in several rivers, lakes and their sediments was investigated with HPGe detectors to elucidate the
source of this isotope in some fresh waters from Kashiwazaki-Kariwa area, Niigata, Japan. It was suggested that there exists
a place abundant in fallout radionuclides in the east side of a mountain which is located by the coast. Great westerly monsoon
will contribute significantly to this phenomenon, which seems to be characteristic of mountains along the Sea of Japan. 相似文献
95.
Anderson RF Shinde SS Maroz A Boyd M Palmer BD Denny WA 《Organic & biomolecular chemistry》2008,6(11):1973-1980
The reduction chemistry of the new anti-tuberculosis drug PA-824, together with a more water-soluble analogue, have been investigated using pulse and steady-state radiolysis in aqueous solution. Stepwise reduction of these nitroimidazo-dihydrooxazine compounds through electron transfer from the CO(2) (-) species revealed that, unlike related nitroimidazoles, 2-electron addition resulted in the reduction of the imidazole ring in preference to the nitro group. In mildly acidic solution a nitrodihydroimidazo intermediate was formed, which was reduced further to the amine product. In both alkaline and neutral solution, an intermediate produced on 2-electron reduction was resistant to further reduction and reverted to parent compound on extraction or mass spectrometric analysis of the solution. The unusual reduction chemistry of these nitroimidazole compounds, exhibiting ring over nitro group reduction, is associated with alkoxy substitution in the 2-position of a 4-nitroimidazole. The unique properties of the intermediates formed on the reduction of PA-824 need to be considered as playing a possible role in its bactericidal action. 相似文献
96.
Belhouchet Z Sautour M Miyamoto T Lacaille-Dubois MA 《Chemical & pharmaceutical bulletin》2008,56(9):1324-1327
Two new steroidal saponins (1, 2) were isolated from the roots of Smilax aspera subsp. mauritanica (POIR.) ARCANG. (Liliaceae), together with the known curillin G (3), asparagoside E (4), asparoside A (5), asparoside B (6) and the phenolic compound resveratrol (7). Their structures were established mainly on the basis of 600 MHz 2D-NMR spectral data. 3 exhibited antifungal activity against the human pathogenic yeasts Candida albicans, C. glabrata and C. tropicalis (minimum inhibitory concentrations of 25, 25 and 50 microg/ml, respectively) whereas the other compounds were inactive. 相似文献
97.
Maruta T Saito T Inagaki M Shibata O Higuchi R 《Chemical & pharmaceutical bulletin》2005,53(10):1255-1258
A new glucocerebroside, linckiacerebroside A (1) and a known glucocerebroside S-2a-3 (2), have been isolated from the cerebroside molecular species obtained from the less polar fraction of the CHCl3/MeOH extract of the starfish Linckia laevigata, together with three pseudo homogeneous glucocerebroside, 3, 4, and 5. The structures of these cerebrosides were determined on the basis of chemical and spectroscopic evidence. 相似文献
98.
Saha PK Fukuda T Imoto W Ahn JK Ajimura S Aoki K Bhang HC Fujioka H Hotchi H Hwang JI Itabashi T Kang BH Kim HD Kim MJ Kishimoto T Krutenkova A Maruta T Miura Y Miwa K Nagae T Noumi H Outa H Ohtaki T Sakaguchi A Sato Y Sekimoto M Shimizu Y Tamura H Tanida K Toyoda A Ukai M Yim HJ 《Physical review letters》2005,94(5):052502
In order to produce a neutron-rich Lambda hypernucleus for the first time, we carried out an experiment by utilizing the (pi-,K+) double charge-exchange reaction on a 10B target. We observed the production of a 10LambdaLi hypernucleus. The cross section for the Lambda bound region was found to be 11.3+/-1.9 nb/sr with the 1.2 GeV/c incident momentum, which is compared with the 10LambdaB hypernucleus production cross section, 7.8+/-0.3 microb/sr, in the (pi+,K+) reaction with a 1.05 GeV/c incident momentum beam. 相似文献
99.
Shannon L. Black Patrick D. OConnor Maruta Boyd Adrian Blaser Jackie D. Kendall 《Tetrahedron》2018,74(22):2797-2806
A wide range of novel and known alkyl substituted pyrazolo[4,3-c]quinolines and related compounds were synthesized. Some of these compounds can undergo tautomerism and differences have been noted in the structural assignments already published. For each of these compounds, a complete assignment was made using 1H, 13C and 15N one- and two-dimensional NMR measurements, including NOESY, COSY, 1H-13C HSQC and 1H-13C HMBC. 1H-15N HMBC NMR has proved crucial in determining the relevant tautomeric and protonated state of the compounds. 相似文献
100.
We study nonlinear pulse propagation in an optical transmission system with dispersion compensation. A chirped nonlinear pulse can propagate in such a system, but eventually it decays into dispersive waves in a way similar to the tunneling effect in quantum mechanics. The pulse consists of a quadratic potential that is due to chirp in addition to the usual self-trapping potential and is responsible for the power enhancement and the decay. 相似文献