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排序方式: 共有61条查询结果,搜索用时 15 毫秒
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Alejandra Salerno Vanina Ceriani Isabel A. Perillo 《Journal of heterocyclic chemistry》1997,34(3):709-716
1H-4,5-Dihydroimidazolium salts 1 react readily with nucleophilic reagents originating cyclic products which may be stable or become transformed into acyclic compounds maintaining the structural ethylenediamine unit. With methylmagnesium iodide compound 1e affords the expected imidazolidine, but in the case of substituted 1-aryl-3-methyl-2-phenyl salts 1b-d the N-aryl-N′-methylethylenediamines 3b-d and acetophenone ( 4 ) were isolated, the process representing the transfer of the C-2 unit to a nucleophilic carbon. With alkaline cyanides salts 1 react efficiently affording α,α-diaminonitriles 5 . In these compounds the cyano group may be readily substituted by nucleophiles (hydroxyl anion, species with nucleophilic carbon and reagents that act by hydride ion transfer), in a way similar to the salts but with better yields. 相似文献
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Claire Besson Djamaladdin G. Musaev Vanina Lahootun Rui Cao Lise‐Marie Chamoreau Richard Villanneau Françoise Villain René Thouvenot Yurii V. Geletii Craig L. Hill Anna Proust 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(39):10233-10243
Reaction of the divacant polyoxometalate K8[γ‐XW10O36] (X=Si, Ge) with two equivalents of the metal‐nitrido precursor Cs2[RuVINCl5], at room temperature in water, produces K2(Me2NH2)2H2[γ‐XW10O38{RuN}2], X=Si ( DMA ‐ 1 a ) or Ge ( DMA ‐ 1 b ). The X‐ray crystal structures of both complexes show monomeric complexes with highly unusual vicinal terminal metal‐nitrido units. The Ru?N bond lengths are 1.594(10) and 1.612(11) Å in 1 a and 1 b , respectively. EXAFS studies confirmed the key structural assignments from X‐ray crystallography. The XANES spectrum of DMA‐1 a , diamagnetism, NMR (29Si and 183W) chemical shifts, voltammetric behavior, reductive titrations with [PW12O40]4?, and computational data are all consistent with d2 RuVI centers in these complexes. The FT‐IR and Raman spectra show the expected vibrational modes of the {γ‐XW10} unit and the Ru?N stretch at 1080 cm?1, respectively. Interestingly, reduction of DMA‐1 a by 4 equivalents of [PW12O40]4? produces NH3 in nearly quantitative yield. Cyclic voltammetry versus pH and calculations provide the energetics for the possible two‐electron reduction and two‐proton addition processes in this reaction. 相似文献
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Vladimir Zakharov Ludmila Echevskaya Tatiana Mikenas Mikhail Matsko Andrey Tregubov Marina Vanina Marina Nikolaeva 《高分子科学》2008,(5):553-559
The effect of chemical composition of highly active supported Ziegler-Natta catalysts with controlled morphology on the MWD of PE has been studied.It was shown the variation of transition metal compound in the MgCl_2-supported catalyst affect of MWD of PE produced in broad range:Vanadium-magnesium catalyst(VMC)produce PE with broad and bimodal MWD(M_w/M_n=14-21).MWD of PE,produced over titanium-magnesium catalyst(TMC)is narrow or medium depending on Ti content in the catalyst(M_w/M_n=3.1-4.8).The oxidati... 相似文献
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MP Blencowe 《Contemporary Physics》2013,54(4):249-264
Nanoelectromechanical systems (NEMS) are nano-to-micrometer scale mechanical resonators coupled to electronic devices of similar dimensions. NEMS show promise for fast, ultrasensitive force microscopy and for deepening our understanding of how classical dynamics arises by approximation to quantum dynamics. This article begins with a survey of NEMS and then describes certain aspects of their classical dynamics. In particular, we show that for weak coupling the action of the electronic device on the mechanical resonator can be effectively that of a thermal bath, this despite the device being a driven, far-from-equilibrium system. 相似文献
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MP Janawadkar R Baskaran R Nagendran K Gireesan N Harishkumar Rita Saha L S Vaidhyanathan J Jayapandian Y Hariharan TS Radhakrishnan 《Pramana》2002,58(5-6):1159-1164
A program has been developed and initiated at the Indira Gandhi Centre for Atomic Research (IGCAR) for the utilization of
SQUID sensors in various application areas. DC SQUID sensors based on Nb-AlO
x
-Nb Josephson junctions have been designed and developed inhouse along with associated flux-locked loop (FLL) electronics.
A compact low field SQUID magnetometer insertible in a liquid helium storage dewar has also been developed inhouse and is
in use. Efforts to build a high field SQUID magnetometer, SQUID-DAC system, are in progress. A planar gradiometric DC SQUID
sensor for non-destructive evaluation (NDE) application to be used in relatively unshielded environment has been designed
and developed. An easily portable NDE cryostat with a small lift-off distance, to be used in external locations has been designed
and tested. The magnetic field produced by a given two-dimensional current density distribution is inverted using the Fourier
transform technique. 相似文献