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排序方式: 共有263条查询结果,搜索用时 31 毫秒
41.
Back DF de Oliveira GN Burrow RA Castellano EE Abram U Lang ES 《Inorganic chemistry》2007,46(7):2356-2358
The reaction of Hg(TePh)2 with AgX (X = Cl, NO3) in the presence of PPh3 and PMePh2 in dimethylformamide (DMF) affords the cluster [Hg6Ag4(TePh)16] (1) at room temperature or [Hg6Ag4Te(TePh)14]2 (2) with heating. When Hg(TePh)2 is reacted with [Co(PPh3)2Cl2] or [Ni(PPh3)2Cl2], the clusters [Hg8Te(PhTe)12Cl4]Q [3; Q = [Co(DMF)6]2+ (3a), [Ni(DMF)6]2+ (3b)] are formed. The syntheses of 1 and 2 occur with the incorporation of AgI into the cluster, and the single-crystal analyses show that the two ternary clusters consist of Hg, Ag, and Te centers occupying well-defined positions. Compounds 3a and 3b do not show the incorporation of the metal into the cluster, but the CoII and NiII salts provide the Cl atom to generate the anionic cluster 3 stabilized by the [Co(DMF)6]2+ or [Ni(DMF)6]2+ ion. 相似文献
42.
The cyclization of gamma-chloroamine 11, derived from l-alanine, and acetylenic sulfone 12 afforded the dehydropiperidine 19 via conjugate addition followed by intramolecular alkylation of the corresponding sulfone-stabilized anion. An unexpected acid-catalyzed desulfonylation of 19 occurred in one step via desilylation and tautomerization of the enamine moiety to the corresponding aldehyde, followed by elimination of p-toluenesulfinic acid. The highly stereoselective reduction of the resulting unsaturated aldehyde 25 with sodium cyanoborohydride produced piperidine 23 with a diastereomeric ratio of >98:2. (-)-(ent)-Julifloridine (8) was obtained by Swern oxidation of 23, followed by Wittig olefination and hydrogenation/debenzylation. 相似文献
43.
E. Heindl C. Kefes M. Soda J. Vancea C.H. Back 《Journal of magnetism and magnetic materials》2009,321(22):3693-3697
We investigate spin-dependent hot electron transport through metallic epitaxial spin valves by ballistic electron magnetic microscopy (BEMM). By variation of the thickness of one of the ferromagnetic layers we determine the spin dependent attenuation lengths which reflect hot electron transport along the vicinity of the [1 0 0]-axis of the bcc Fe34Co66 lattice. The majority spin attenuation length is more than 6 times larger than that of the minority spins within the measured energy interval of 1.3 up to 2 eV above the Fermi level. Consequently a Magnetocurrent effect exceeding 1200% accompanied by a monotonic bias voltage behavior is observed at room temperature. 相似文献
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45.
AL Stein FN Bilheri JT da Rocha DF Back G Zeni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(34):10602-10608
A copper-catalyzed cyclization of (ortho-alkynyl)benzaldimines with diorganoyl dichalcogenides allowed the synthesis of 4-organochalcogen isoquinolines, whereas the presence of base in the reaction medium inhibited the product formation producing the undesirable isoquinoline without the organochalcogen atom at the 4-position. The cyclization reaction was carried out by using CuI (20?%) as a catalyst with diorganoyl dichalcogenides (1.5?equiv) in the presence of DMF at 100?°C. Furthermore, the reaction did not require an argon atmosphere and was carried out in an open flask. The cyclization reaction tolerated a variety of functional groups both in ortho-alkynylbenzaldimines and diorganoyl dichalcogenides, such as trifluoromethyl, chloro, fluorine, and methoxyl, to give the six-membered heterocyclic ring exclusively through a 6-endo-dig cyclization process. The organochalcogen group present at the 4-position of the isoquinoline ring was further subjected to a selective chalcogen-lithium exchange reaction followed by the addition of aldehydes to afford the desired secondary alcohols in good yields. The obtained isoquinolines also proved to be suitable substrates for the Suzuki and Sonogashira coupling conditions affording the corresponding products through C?C bond formation. 相似文献
46.
Heo SK Ju SA Kim GY Park SM Back SH Park NH Min YJ An WG Nguyen TT Kim SM Kim BS 《Experimental & molecular medicine》2012,44(2):149-158
The development of gastric cancer (GC) is closely related to chronic inflammation caused by Helicobacter pylori infection, and herpes virus entry mediator (HVEM) is a receptor expressed on the surface of leukocytes that mediates potent inflammatory responses in animal models. However, the role of HVEM in human GC has not been studied. Previously, we showed that the interaction of HVEM on human leukocytes with its ligand LIGHT induces intracellular calcium mobilization, which results in inflammatory responses including induction of proinflammatory cytokine production and anti-bacterial activities. In this study, we report that leukocytes from GC patients express lower levels of membrane HVEM (mHVEM) and have lower LIGHT-induced bactericidal activities than those from healthy controls (HC). In contrast, levels of soluble HVEM (sHVEM) in the sera of GC patients were significantly higher than in those of HC. We found that monocyte membrane-bound HVEM is released into the medium when cells are activated by proinflammatory cytokines such as TNF-α and IL-8, which are elevated in the sera of GC patients. mHVEM level dropped in parallel with the release of sHVEM, and release was completely blocked by the metalloprotease inhibitor, GM6001. We also found that the low level of mHVEM on GC patient leukocytes was correlated with low LIGHT-induced bactericidal activities against H. pylori and S. aureus and production of reactive oxygen species. Our results indicate that mHVEM on leukocytes and sHVEM in sera may contribute to the development and/or progression of GC. 相似文献
47.
J. Pedersen B. B. Back S. Bjørnholm J. Borggreen G. Sletten F. Azgui H. Emling H. Grein G. Seiler-Clark W. Spreng H. J. Wollersheim P. Walker 《Zeitschrift für Physik A Hadrons and Nuclei》1985,321(4):567-575
Results of a search for high-spin isomers in W and Os nuclei withN=104–107 are presented. Targets of48Ca and48, 50Ti are bombarded with a pulsed136Xe beam, and delayed gamma-radiation is detected by an array of NaI- and Ge-detectors. Several new isomers, with spin values up to ~22h, are found in178,180W and180, 182, 183Os. Markedly different decay patterns and hindrance factors are found in the Os isotopes as compared to the expectations based on theK-selection rule valid for axially symmetric nuclei. The findings are ascribed to the onset of triaxial distortions. 相似文献
48.
J.P. Seitz B.B. Back M.P. Carpenter I. Diszegi K. Eisenman P. Heckman D.J. Hofman M.P. Kelly T.L. Khoo S. Mitsuoka V. Nanal T. Pennington R.H. Siemssen M. Thoennessen R.L. Varner 《Nuclear Physics A》2005,750(2-4):245-255
The giant dipole resonance built on excited states was observed in very fissile nuclei in coincidence with evaporation residues. The reaction 48Ca + 176Yb populated evaporation residues of mass A=213–220 with a cross section of 200 μb at 259 MeV. The extracted giant dipole resonance parameters are in agreement with theoretical predictions for this mass region. 相似文献
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50.