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排序方式: 共有256条查询结果,搜索用时 46 毫秒
101.
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104.
Akerib DS Alvaro-Dean J Armel-Funkhouser MS Attisha MJ Baudis L Bauer DA Beaty J Brink PL Bunker R Burke SP Cabrera B Caldwell DO Callahan D Castle JP Chang CL Choate R Crisler MB Cushman P Dixon R Dragowsky MR Driscoll DD Duong L Emes J Ferril R Filippini J Gaitskell RJ Haldeman M Hale D Holmgren D Huber ME Johnson B Johnson W Kamat S Kozlovsky M Kula L Kyre S Lambin B Lu A Mahapatra R Manalaysay AG Mandic V May J McDonald R Merkel B Meunier P Mirabolfathi N Morrison S Nelson H Nelson R 《Physical review letters》2004,93(21):211301
We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6 live days, providing 19.4 kg d of Ge net exposure after cuts for recoil energies between 10 and 100 keV. A blind analysis was performed using only calibration data to define the energy threshold and selection criteria for nuclear-recoil candidates. Using the standard dark-matter halo and nuclear-physics WIMP model, these data set the world's lowest exclusion limits on the coherent WIMP-nucleon scalar cross section for all WIMP masses above 15 GeV/c2, ruling out a significant range of neutralino supersymmetric models. The minimum of this limit curve at the 90% C.L. is 4 x 10(-43) cm2 at a WIMP mass of 60 GeV/c2. 相似文献
105.
D L Boger S H Kim Y Mori J H Weng O Rogel S L Castle J J McAtee 《Journal of the American Chemical Society》2001,123(9):1862-1871
Full details of studies leading to the total synthesis of the teicoplanin aglycon are provided. Key elements of the first generation approach (26 steps from constituent amino acids, 1% overall) include the coupling of an EFG tripeptide precursor to the common vancomycin/teicoplanin ABCD ring system and sequential DE macrocyclization of the 16-membered ring with formation of the diaryl ether via a phenoxide nucleophilic aromatic substitution of an o-fluoronitroaromatic (80%, 3:1 atropisomer diastereoselection) followed by 14-membered FG ring closure by macrolactamization (66%). Subsequent studies have provided a second generation total synthesis which is shorter, more convergent, and highly diastereoselective (22 steps, 2% overall). This was accomplished by altering the order of ring closures such that FG macrolactamization (95%) preceded coupling of the EFG tripeptide to the ABCD ring system and subsequent DE ring closure. Notably, DE macrocyclization via diaryl ether formation on substrate 57, the key intermediate in the latter approach incorporating the intact FG ring system, occurred with exceptional diastereoselection for formation of the natural atropisomer (>10:1, 76%) without problematic C(2)(3) epimerization provided the basicity of the reaction is minimized. 相似文献
106.
M.J. Edgell R.W. Paynter J.E. Castle 《Journal of Electron Spectroscopy and Related Phenomena》1985,37(2):241-256
Resolution, sensitivity and calibration data are presented for a novel high energy XPS source, monochromated Ag Lα radiation (hv = 2984.3 eV). Adequate resolution is attainable for good signal/noise spectra, whilst values for experimental sensitivity factors agree well with theoretical cross section values calculated by Nefedov. This allows an evaluation of ESCA 3 Mk. II transmission function up to 3000 eV, which appears to obey an approximate E dependence. Monochromated Ag Lα (linewidth 1.3 eV) overcomes the problem of broad natural linewidths for high energy sources, such that chemical state information can be gained. Various new core level and Auger peaks are developed, a notable feature being the 1s core level and KLL Auger transition capability from Al through to Cl. Improved sensitivity is experienced for elements whose major peaks occur in the 1500–3000 eV BE range, whilst there is no serious reduction of sensitivity in the conventional XPS energy range. 相似文献
107.
M. J. Musmar Gary E. Martin Robert T. Gampe Vincent M. Lynch Stanley H. Simonsen Milton L. Lee Marvin L. Tedjamulia Raymond N. Castle 《Journal of heterocyclic chemistry》1985,22(2):545-553
1-Methylphenanthro[3,4-b]thiophene was prepared by the photocyclization of 1-(4′-methyl-2′-thienyl)-2-(2″-naphthyl)ethene. The 1H and 13C-nmr spectra were assigned using two-dimensional 1H/13C heteronuclear chemical shift correlation and relayed coherence transfer (RELAY) experiments. From nuclear Overhauser difference spectra, the H11-C1 methyl-H intramolecular distance was determined to be 2.10 Å. The molecule crystallized from chloroform in the monoclinic system, space group P21/c. A total of 3536 unique reflections were measured and the structure was solved by direct methods and refined to a final R = 0.049. The molecule is helical with both chiral forms observed in the crystal. The H11-C1 methyl-H distance in the crystal was 2.12(3)Å in excellent agreement with the distance measured in solution by NOE techniques. 相似文献
108.
Michiharu Sugiura Marvin L. Tedjamulia Yoshinori Tominaga Raymond N. Castle Milton L. Lee 《Journal of heterocyclic chemistry》1983,20(6):1453-1459
The synthesis of the potentially mutagenic 1-methyl- (11), 3-methyl- (12), 4-methyl- (21), 5-methyl- (27), 7-methyl- (58), 8-methyl- (61), 9-methyl- (59) and 10-methylbenzo[2,3]phenanthro[4,5-bcd]thiophene (60) is reported. 相似文献
109.
Marvin L. Tedjamulia Yoshinori Tominaga Raymond N. Castle Milton L. Lee 《Journal of heterocyclic chemistry》1983,20(6):1485-1495
The synthesis of all four isomers of the monoethyldibenzothiophenes and all of the sixteen isomers of the dimethyldibenzothiophenes has been accomplished. 相似文献
110.
Sunao Furukawa Mitsutaka Takada Raymond N. Castle 《Journal of heterocyclic chemistry》1981,18(3):581-585
Several pyrimidinylalkylthiols and furo[2,3-d]pyrimidines and their derivatives have been prepared as potential radiation-protection agents. 相似文献