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91.
92.
E.J.W Whittaker 《Journal of Non》1978,28(2):293-304
The cavities in the random close packing of spheres are re-examined with a view to considering the possible applicability of the structure as a model for the arrangement of oxygen atoms in a silicate melt. For this purpose a limit of 1.20 diameters is used to define near contacts between spheres, and this leads to substantial changes in both the numbers and the types of polyhedral cavities found. Serious limitations are deduced for the Si: O ratios of silicate structures for which the random close packing might serve directly as a model, but suggestions are made as to how the introduction of ionic charges might itself tend to modify the packing into a more appropriate form. 相似文献
93.
C. W. Whittaker F. O. Lundstrom und A. R. Merz 《Fresenius' Journal of Analytical Chemistry》1931,84(1-2):35-36
Ohne Zusammenfassung 相似文献
94.
The advent of the quantum cascade laser (QCL) with emission wavelengths available in the infrared range from 3 μm through
more than 100 μm opens up the possibility of exploiting infrared atmospheric transparency windows for free space optical communications.
In an effort to establish the efficacy of using directly modulated QCLs for free space communications we have conducted a
series of investigations that demonstrate the potential advantages of this technology. In these experiments we first establish
that the QCL has very high modulation bandwidth. We then implement a practical free space communications link that under
conditions of atmospheric fog, dust and other obscurants offers significant transparency advantage when compared with near
infrared wavelength sources presently used in commercial free space optical communications links. 相似文献
95.
96.
Raymond J. Abraham Collette M. Holden Philip Loftus David Whittaker 《Magnetic resonance in chemistry : MRC》1974,6(3):184-189
The 13C spectra of α-thujene ( 1 ), isothujone ( 2 ), (?)isothujol ( 3 ), (+)neoisothujol ( 4 ), sabinol ( 5 ), dihydroumbellulone ( 6 ) and umbellulone ( 7 ) and the alcohol acetates are recorded and assigned. The C-6 chemical shift may be used in conjunction with the steric shift mechanism as a conformational probe in these molecules. The results obtained indicate that isothujol, neoisothujol, isothujone and dihydroumbellulone adopt boat-like conformations whilst sabinol has a much flatter conformation. Conjugation of the isolated double bond of α-thujene and the carbonyl group of dihydroumbellulone with the cyclopropane ring has virtually no effect on the 13C shifts, but those of umbellulone itself are anomalous, indicating conjugation of the α,β unsaturated ketone system with the cyclopropyl ring. 相似文献
97.
Coldham I Patel JJ Raimbault S Whittaker DT Adams H Fang GY Aggarwal VK 《Organic letters》2008,10(1):141-143
Asymmetric lithiation of substituted benzylamines, N-Boc-pyrrolidine, or N-Boc-indoline using Beak's methodology was followed by electrophilic quench with trialkylboranes. The resulting borate intermediates rearrange with concomitant C-N bond breakage to give, after oxidation, chiral secondary alcohols with high enantioselectivity. 相似文献
98.
Boyer C Soeriyadi AH Roth PJ Whittaker MR Davis TP 《Chemical communications (Cambridge, England)》2011,47(4):1318-1320
In this communication, we report on a new route to the functionalization of ATRP polymers exploiting their halide end-groups, which were converted successfully into reactive disulfide end-groups, using sodium methanethiosulfonate. The resultant disulfide-terminated polymers could then be reacted with different functional thiols to yield functional polymers exploiting either thiol/disulfide exchange chemistry or thiol/ene "click" reactions. 相似文献
99.
Rucker RP Whittaker AM Dang H Lalic G 《Angewandte Chemie (International ed. in English)》2012,51(16):3953-3956
No longer a hindrance: copper-catalyzed electrophilic amination of aryl boronic esters is accomplished under mild reaction conditions using 2.5-5.0 mol % of a catalyst derived from copper tert-butoxide and Xantphos ligand. The reaction tolerates a wide range of functional groups and can be used to prepare some of the most hindered anilines made to date. 相似文献
100.
Davide Bacciu Terence A. Etchells Paulo J. G. Lisboa Joe Whittaker 《Computational Statistics》2013,28(2):621-646
Conditional independence graphs are now widely applied in science and industry to display interactions between large numbers of variables. However, the computational load of structure identification grows with the number of nodes in the network and the sample size. A tailored version of the PC algorithm is proposed which is based on mutual information tests with a specified testing order, combined with false negative reduction and false positive control. It is found to be competitive with current structure identification methodologies for both estimation accuracy and computational speed and outperforms these in large scale scenarios. The methodology is also shown to approximate dense networks. The comparisons are made on standard benchmarking data sets and an anonymized large scale real life example. 相似文献