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101.
The neutral, bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) coordinates to Cu(I) halides via the imine nitrogen, and the complexes are stabilized by intramolecular NH...X interactions (X = Cl, Br) or are partially dissociated (X = I) in the solid state; in all cases, fluxional behavior is observed in solution. Selected complexes have been tested as catalysts for the polymerization of methyl methacrylate. 相似文献
102.
Francisco Prieto Emma Hill Barry A. Coles Richard G. Compton John H. Atherton 《Journal of Solid State Electrochemistry》1999,3(4):187-192
A high-speed channel flow cell is used to study the reaction of solid p-chloranil with basic aqueous solutions. Dissolution of the solid is shown to be induced by reaction of OH− ions at the solid/liquid interface and appropriate kinetic parameters are reported.
Received: 1 September 1998 / Accepted: 2 November 1998 相似文献
103.
Spatial Regression Models for Extremes 总被引:2,自引:0,他引:2
Meteorological data are often recorded at a number of spatial locations. This gives rise to the possibility of pooling data through a spatial model to overcome some of the limitations imposed on an extreme value analysis by a lack of information. In this paper we develop a spatial model for extremes based on a standard representation for site-wise extremal behavior, combined with a spatial latent process for parameter variation over the region. A smooth, but possibly non-linear, spatial structure is an intrinsic feature of the model, and difficulties in computation are solved using Markov chain Monte Carlo inference. A simulation study is carried out to illustrate the potential gain in efficiency achieved by the spatial model. Finally, the model is applied to data generated from a climatological model in order to characterize the hurricane climate of the Gulf and Atlantic coasts of the United States. 相似文献
104.
F. Javier Del Campo B. A. Coles F. Marken R. G. Compton E. Cordemans 《Ultrasonics sonochemistry》1999,6(4):H63
The use of high frequency ultrasound in electrochemical systems is of major interest for the optimisation of electrosynthetic and electroanalytical procedures, especially when the strong mechanical effects of 20 kHz ultrasound are detrimental. The characterisation of a 500 kHz ultrasound reactor for sonoelectrochemical experiments by voltammetric and potentiometric measurements revealed the presence of considerable thermal, as well as mass transport, effects depending on geometric parameters and the material used for the construction of the working electrode. Micromixing and cavitation processes govern the mass transport to and from the electrode surface and are shown by atomic force microscopy (AFM) to cause erosion on the electrode surface. Electrochemically active films of Prussian blue are shown to be gradually removed by cavitation erosion. Degassing the solution prior to sonication increases the efficiency of cavitation processes. 相似文献
105.
Andrey Petrov Lawrence Conrad Dr. Nathan T. Coles Manuela Weber Priv.-Doz. Dr. Dirk Andrae Dr. Almaz Zagidullin Dr. Vasili Miluykov Prof. Dr. Christian Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(67):e202203056
A diglyme solution of Na[cyclo-P5] ( 1 ) reacts with alkynes and isolobal nitriles and phosphaalkynes to afford the otherwise elusive (aza)phospholide anions 2 a – c , 4 a,b , and 6 . The reaction of Na[cyclo-P5] with alkynes and nitriles was studied by means of DFT methods, which suggested a concerted mechanism for the formation of 2 a and 4 b . The anions 2 a – c , 4 a,b , and 6 coordinate in an η5-fashion towards FeII to give the sandwich (aza)phosphametallocenes 3 a – c , 5 a,b and 7 in moderate to good yields. The new compounds were characterized by means of multinuclear NMR spectroscopy, single-crystal X-ray diffraction and cyclic voltammetry. 相似文献
106.
Previous work has shown that guest-host ferroelectric systems incorporating dichroically absorbing dyes are suitable for use in colour display applications. These utilize either the dichroic absorption of a conventional dye, or the emission of a fluorescent dye. We present here the electrooptical properties of several advanced ferroelectric liquid crystals doped with a new fluorescent dye, coloured blue in emission. The data consists of measurements of tilt angle, response time, spontaneous polarization, and rotational viscosity, from which we conclude that certain hosts are not adversely affected by the fluorescent dopants. These results are then discussed in connection with the use of these mixtures in two novel colour display configurations, which are also presented, utilizing either the dichroic absorption or the polarized fluorescence of the fluorophore guests. 相似文献
107.
We report laser cooling of trapped 171Yb+ ions. The ions are confined in a linear Paul trap. Temperatures below 1 K have been achieved, and evidence of a phase transition to a crystal-like state has been observed. The metastable 2
D
3/2 level is drained using a transition at 609.1 nm not previously used for this purpose. Laser cooling of 171Yb+ may be of importance to the development of new microwave frequency standards. 相似文献
108.
We demonstrate that the addition of small amounts of a novel azo-dye to a ferroelectric liquid crystal and illumination with low intensity (∼ 0.8 mW cm-2) UV light can result in reversible, isothermal phase transitions and dramatic changes in the properties of the system. In particular we examine light induced transitions between the S*1, and S*C phases and the consequent photomechanical regulation of spontaneous polarization. 相似文献
109.
Mohammed Ibn-elhaj Antoine Skoulios Daniel Guillon Joanna Newton Philip Hodge Harry J. Coles 《Liquid crystals》1995,19(3):373-378
The phase behaviour and the structural characterization of a new series of linear dimeric and cyclic tetrameric molecules which contain three distinct parts, a cyanobiphenyl aromatic core (A), a paraffin chain (P) and a central siloxane group (B) with the A-P-B-P-A sequence, are described. Incompatible with one another, these parts tend to locate themselves in three separate sub-layers superposed in a partially bilayered smectic A structure. Each sub-layer adapts its internal structure in order to be appropriate for superposition, as in the case of organosiloxane molecules with the A-P-B sequence reported previously. 相似文献
110.
Investigation of the structure of the lithiated bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) has led to the reproducible isolation of compounds containing the 'Li9(hpp)7(O2)' core, in which a peroxide dianion has been encapsulated within a mono-capped, cubic array of lithium ions. 相似文献