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111.
We investigate rational approximations (r/p,q/p) or (r/p,q/r) to points on the curve (α,ατ) for almost all α>0, where p,q,r are all primes. We immediately obtain corollaries on making p,[αp], [ατp] simultaneously prime. 相似文献
112.
Love JC Wolfe DB Chabinyc ML Paul KE Whitesides GM 《Journal of the American Chemical Society》2002,124(8):1576-1577
This paper describes microcontact printing (muCP) of long-chain alkanethiolates on palladium, followed by solution-phase etching with an iron(III)-based etchant, to make patterned structures. The commonly used soft-lithographic procedure for fabricating microstructures-muCP of SAMs on gold-has three shortcomings: a significant surface density of pinhole defects, substantial edge roughness, and incompatibility with processes used in CMOS fabrication. Microcontact printing on palladium gives fewer defects and smaller edge roughness than on gold, and is compatible with CMOS. The mechanism by which etch-resistant patterns are formed is different for palladium and gold. The Pd/S interfacial layer formed by the reaction of palladium films with sulfur-containing compounds provides good resistance to etches independently of the barrier to access the surface provided by the film of (CH2)n groups in the long-chain SAMs. This barrier is the basis of the etch resistance of SAMs on gold, but only supplements the etch resistance of the sulfur-containing interfacial layer on palladium. Characterization of the SAM formed from hexadecanethiol on palladium is described. 相似文献
113.
Suppiah Navaratnam Edward J. Land Barry J. Parsons Iqbal Ahmad Glyn O. Phillips 《Photochemistry and photobiology》1983,38(2):153-159
Abstract— Transient absorption spectra produced by laser flash-photolysis of an aqueous solution of ephedrine have been measured under a variety of conditions. Ephedrine was found to photoionise via a biphotonic process. The apparent yield of photoionisation increases with lowering of pH, a value of 8.8 being found for the p K a associated with this change. The cation radical absorption spectrum has been determined using the techniques of both pulse radiolysis and laser flash photolysis. The extinction coefficient of the cation at 295 nm was determined to be 1.37 × 104 dm3 mol-1 cm-1 and 1.2 × 104 dm3 mol-1 cm-1 by the two techniques, respectively, at pH 11. It is also shown that the rate constant for electron abstraction by the azide radical to form the ephedrine cation is controlled by protonation of the amine group in the side chain. The ephedrine anion radical spectrum and its extinction coefficient at 305 nm were also determined. The excited states responsible for photoionisation and photodegradation are discussed. 相似文献
114.
Glyn R. John Leon A. P. Kane-Maguire Dwight A. Sweigart 《Journal of organometallic chemistry》1976,120(3)
Phosphonium adduct formation via attack of tri-n-butylphosphine on the cations [(C7H7)M(CO)3]+ (M = Cr, Mo, W) obeys the rate law, Rate = k [complex] [PBu3]. The very similar rate constants for the Cr, Mo and W complexes confirm the similar electrophilicities of the tropylium rings in these cations, and also support the view that there is direct addition to the rings. The related complexes [(C6H7)Fe(CO)3]BF4 and [(C6H6)Mn(CO)3]BF4 also form adducts with PBu3, and the quantitative reactivity order [(C6H7)Fe(CO)3]+ > [(C7H7)Cr(CO)3]+ » [(C6H6)Mn(CO)3]+ (160:60:1) has been established. 相似文献
115.
Philip J. Cox Susan Blaney Steve W. Love Norman Shankland David B. Sheen 《Journal of chemical crystallography》1995,25(12):845-850
The solid solution formed by the title compound, C9H16NO3, has been examined by a variety of techniques and shown to be an equi-molecular mixture of the two enantiomers. Refinement of the disordered structure was based on the orthorhombic space groupPnma witha=8.023(2),b=10.030(3), andc=12.352(2)Å, finalR=0.055. The oxygens of the carboxyl group are disordered and both enantiomers can occupy the same, rather than alternate, crystallographic sites. Results from studies involving IR, GC-MS, and chiral chromatography are also presented. In addition we report on the use of synchrotron X-ray topography to investigate strain in crystals of the solid solution. 相似文献
116.
Anomolous spikes in the loss spectrum of practical depressed-cladding fibres with a finite cladding and absorbing jacket can be explained in terms of a combination of three effects — the excitation conditions, the absorption behaviour of core and cladding modes, and the slight variation in the fibre diameter along its length. 相似文献
117.
Fungal metabolite oosporein was prepared in four steps and 24% overall yield starting from 2,5-dimethoxytoluene. It was demonstrated that treatment of phoenicin with pyrrolidine and copper(II) acetate led to oosporein, whereas similar treatment of the isomeric ‘isophoenicin’ produced a benzofuran diquinone. No chromatography was required during any step of the synthesis. 相似文献
118.
Micallef R. W. Kivshar Yu. S. Love J. D. Burak D. Binder R. 《Optical and Quantum Electronics》1998,30(7-10):751-770
We investigate how two-dimensional spatial optical solitons can be generated in a non-linear Kerr medium using the non-linear guided modes of a weakly-guiding slab waveguide with a linear core and a non-linear cladding as the source of excitation. Symmetric, antisymmetric and asymmetric non-linear modes are considered, from which we determine the parameters of single solitons, oscillating two-soliton bound states, and two repelling solitons, respectively. Both the beam propagation method and inverse scattering transform are used. 相似文献
119.
Zeitschrift für Physik C Particles and Fields - We list all dimension sixSU(3)×SU(2)×U(1) invariant operators which can be used in a phenomenological analysis of deviations from the... 相似文献
120.
James A. Besley John D. Love François Ladouceur Graeme Maxwell 《Optical and Quantum Electronics》2002,34(4):317-330
We investigate the higher-order supermodes of symmetric buried channel waveguide (BCW) couplers with cores of square, rectangular, and trapezoidal geometries. We show how the cutoff wavelengths of these supermodes can be used to interpret the spectral response of a practical single-mode BCW coupler. Our results highlight the design constraints imposed by second-order supermodes. We also compare the behaviour of these couplers with that of circular-core couplers to illustrate how the geometry of each core affects the coupler cutoff characteristics. 相似文献