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71.
This Letter reports on the acceleration of the rate of formation of the boron–oxygen defect in p‐type Czochralski silicon with illumination intensities in excess of 2.1 × 1017 photons/cm2/s. It is observed that increased light intensities greatly enhance the rate of defect formation, without increasing the saturation concentration of the defect. These results suggest a dependence of the defect formation rate upon the total majority carrier concentration. Finally, a method using temperatures up to 475 K and an illumination intensity of 1.68 × 1019 photons/cm2/s is shown to result in near‐complete defect formation within seconds. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
72.
Dr. Luke D. Elliott Dr. Jonathan P. Knowles Dr. Paul J. Koovits Katie G. Maskill Michael J. Ralph Dr. Guillaume Lejeune Lee J. Edwards Richard I. Robinson Ian R. Clemens Brian Cox David D. Pascoe Guido Koch Martin Eberle Malcolm B. Berry Prof. Kevin I. Booker‐Milburn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15226-15232
The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20 % lower than that of batch, whereas three‐layer reactors were 20 % more productive. Finally, the utility of flow chemistry was demonstrated in the scale‐up of the ring‐opening reaction of a potentially explosive [1.1.1] propellane with butane‐2,3‐dione. 相似文献
73.
This paper describes an attempt to design, analyse and refine professional development (PD) resources that encourage the implementation of inquiry-based learning (IBL). We describe the iterative development of the resources in England with over 100 mathematics teachers from secondary, tertiary and adult education and then analyse the impact these resources had on teachers’ beliefs and practices and the issues arising. This evaluation revealed that teachers had moved away from transmission-based orientations, encouraged by the use of less structured tasks and sample lesson plans, but some found it difficult to adopt IBL pedagogies. The most significant issues for teachers may be summarised as: confusing IBL with ‘discovery’ learning; developing and managing collaborative cultures within the classroom; and planning lessons that adapt to the emerging needs of learners. 相似文献
74.
Yuhua Huang Frank Bennett Vishal Verma F. George Njoroge Malcolm MacCoss 《Tetrahedron letters》2012,53(26):3203-3205
A direct conversion of a thiolacetate to its corresponding sulfonyl chloride in the presence of acid and base sensitive functional groups is described. 相似文献
75.
Malcolm Mackley 《Rheologica Acta》2010,49(5):443-458
This paper is based on a presentation given at the de Gennes discussion meeting held at Chamonix in February 2009. The paper
gives a personal review of the way developments relating to the stretching of polymer chains has taken place over the last
40 years. de Gennes was very influential in relation to chain dynamics concepts at the University of Bristol, where many pioneering
concepts relating to chain stretching were developed by the late Sir Charles Frank and Andrew Keller. The paper reviews basic
concepts on extensional rheology, droplet deformation, chain extension from extensional flow and the achievement of high chain
extension for high-modulus polyethylene. The paper also reviews recent developments concerning the influence of chain stretching
on polymer melt processing. 相似文献
76.
Malcolm Greig 《Designs, Codes and Cryptography》2002,27(1-2):25-47
Batten and Beutelspacher have characterized Finite Linear Spaces with lines of size n,n + 1 and n + 2, and with v (n + 1)2for n 22, and some of the cases for smaller n. In this article, using the structuredapproach we presented in our earlier article [8], we complete this characterization for smalln. 相似文献
77.
Liu X McLaughlin AC de Miranda MP McInnes EJ Kilner CA Halcrow MA 《Chemical communications (Cambridge, England)》2002,(24):2978-2979
The complex [[Cu3(HpztBu)4(mu-pztBu)2(mu-F)2(mu 3-F)]2]F2 (HpztBu = 3[5]-tert-butylpyrazole) has a cyclic, C2v-symmetric hexacopper core. The two non-coordinated F- anions are encapsulated within cavities formed by three HpztBu ligands. 相似文献
78.
Yao-Yi Cheng Peggy Cebe Malcolm Capel Heidi Schreuder-Gibson Aaron Bluhm Walter Yeomans 《Journal of Polymer Science.Polymer Physics》1995,33(17):2331-2341
Crystallization and melting behavior are studied by small-angle X-ray scattering (SAXS) for a series of recently synthesized monotropic liquid crystalline polycarbonates based on α-methyl stilbene mesogen and methylene flexible spacer. The one-dimensional electron density correlation function is used to obtain long period, crystal thickness, and linear crystallinity from the Lorentz-corrected SAXS intensity. Changes in these parameters during nonisothermal crystallization and melting are explained by a model of dual crystal populations. The primary crystals form first using the liquid crystalline phase as crystal nuclei, while smaller and less perfect crystals form later from the isotropic phase at low temperature. The results of the real-time SAXS study of isothermal crystallization also support the view that the nematic phase serves as crystal nuclei for fast crystallization. An odd-even effect in crystal thickness and linear crystallinity is observed in all the SAXS experiments mentioned above. The results of this study and our complementary wide-angle X-ray scattering (WAXS) investigation show clearly that the difference in the position of the neighboring carbonate dipoles on a chain affects structural organization both at the unit cell level and at the level of the crystal in these monotropic LCPs. © 1995 John Wiley & Sons, Inc. 相似文献
79.
Malcolm S. Cresser Anthony C. Edwards 《Spectrochimica Acta Part B: Atomic Spectroscopy》1984,39(4):609-612
The operating pressure of a pneumatic nebulizer has been measured. The rsult has been used to explain the problems associated with the variation in flame spectroscopy signal with sample position when a capillary T piece is used for continuous addition of releasing agent. The way to minimize this variation is outlined. 相似文献
80.
G. N. Malcolm C. E. Baird G. R. Bruce K. G. Cheyne R. W. Kershaw M. C. Pratt 《Journal of Polymer Science.Polymer Physics》1969,7(9):1495-1511
Measurements are reported of the vapor pressures and the heats and volumes of mixing of solutions of poly(ethylene glycol dimethyl ether) in chloroform and in carbon tetrachloride. The measurements have been used to calculate the thermodynamic mixing functions for mixing with zero volume change. These values have been compared with the predictions of the lattice theory of mixtures at three different levels of approximation, viz., the generalized “first approximation” theory of Barker, the “zeroth approximation” theory, and the Flory theory. In the hydrogen-bonding chloroform solutions the Barker theory is more successful than the other forms of the lattice theory. The results have also been used, in conjunction with those for solutions of poly(propylene glycol dimethyl ether) in the same two solvents, to test the ability of the Barker theory to correlate the properties of related systems. Good correlation is found between the two carbon tetrachloride solutions but not between the chloroform solutions. It is probable that the side-chain methyl groups in the propylene oxide repeating unit cause the hydrogen-bonding interaction to be weaker in this polymer than it is in the polymer with the ethylene oxide repeating unit. 相似文献