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211.
212.
Tatarakis M Beg FN Clark EL Dangor AE Edwards RD Evans RG Goldsack TJ Ledingham KW Norreys PA Sinclair MA Wei MS Zepf M Krushelnick K 《Physical review letters》2003,90(17):175001
Measurements of energetic electron beams generated from ultrahigh intensity laser interactions (I>10(19) W/cm(2)) with dense plasmas are discussed. These interactions have been shown to produce very directional beams, although with a broad energy spectrum. In the regime where the beam density approaches the density of the background plasma, we show that these beams are unstable to filamentation and "hosing" instabilities. Particle-in-cell simulations also indicate the development of such instabilities. This is a regime of particular interest for inertial confinement fusion applications of these beams (i.e., "fast ignition"). 相似文献
213.
Fan Y Tysoe B Sim J Mirkhani K Sinclair AN Honarvar F Sildva H Szecket A Hardwick R 《Ultrasonics》2003,41(5):369-375
A resonance acoustic spectroscopy technique is assessed for nondestructive evaluation of explosively welded clad rods. Each rod is modeled as a two-layered cylinder with a spring-mass system to represent a thin interfacial layer containing the weld. A range of interfacial profiles is generated in a set of experimental samples by varying the speed of the explosion that drives the copper cladding into the aluminum core. Excellent agreement is achieved between measured and calculated values of the resonant frequencies of the system, through appropriate adjustment of the interfacial mass and spring constants used in the wave scattering calculations. Destructive analysis of the interface in the experimental specimens confirms that key features of the interfacial profile may be inferred from resonance acoustic spectroscopy analysis applied to ultrasonic measurements. 相似文献
214.
Allan M. Sinclair Roger R. Smith 《Transactions of the American Mathematical Society》2003,355(2):465-475
The Laplacian (or radial) masa in a free group factor is generated by the sum of the generators and their inverses. We show that such a masa is strongly singular and has Popa invariant . This is achieved by proving that the conditional expectation onto is an asymptotic homomorphism. We also obtain similar results for the free product of discrete groups, each of which contains an element of infinite order.
215.
A detailed study of the detection of trace gases at atmospheric pressure using tunable diode lasers is described. The influence of multipass cells, retroreflectors and topographical targets is examined. The minimum detectable infrared absorption ranges from 0.1% for a pathlength of 1.2 km to 0.01% over short pathlengths. The factors which limit this sensitivity are discussed, and the techniques are illustrated by monitoring atmospheric CO2 and CH4. 相似文献
216.
J. Bartholomew Stephen H. Shenker J. Sloan J. Kogut M. Stone H.W. Wyld J. Shigmetsu D.K. Sinclair 《Nuclear Physics B》1984,230(2):222-240
Chiral symmetry breaking is studied in lattice quantum electrodynamics in the quenched approximation by computer simulation methods. Simulations at zero temperature show that is non-zero for all couplings e2 greater than a critical value ec2. The sensitivity of to short-distance features of the lattice action is studied by simulating variant gauge actions. Simulations on asymmetric lattices do not reveal significant temperature dependence in the symmetry breaking dynamics. Subtle effects and limitations of quenched calculations are discussed. 相似文献
217.
D. Sinclair I. Paschopoulos H.S. Bradlow P.S. Fisher A.A. Pilt W.D.M. Rae 《Nuclear Physics A》1976,261(3):511-532
Reactions induced by 126 MeV 16O ions on 26Mg have been investigated in the angular range 5° to 12°. Optical model parameters were derived from the elastic scattering data and were used in a DWBA analysis of the inelastic scattering and single-nucleon transfer data. Satisfactory agreement was obtained for the angular distributions and for the spectroscopic factors. The two-nucleon transfer reactions appear to excite vibrational states. A DWBA analysis correctly describes the angular distributions for the two-proton transfer data. Most of the other few-nucleon transfer spectra exhibit little selective excitation but give a maximum at an energy consistent with the optimum Q-value predicte for direct transfer. Both the one- and twonucleon transfer data require that the 26Mg ground state contains considerable (λ, μ) = (4. 8) components and is not pure (10, 2) as predicted by simple SU(3) calculations. 相似文献
218.
219.
A general method for solving the low-energy spectrum of an infrared unstable field theory is presented. The method involves a strong coupling expansion of the lattice approximation to the theory. Ultimately the results must be continued to zero-coupling constant in accord with the asymptotic freedom of such theories. The method is applied to the pure gauge field (glueball) part of quantum chromodynamics. The spectrum of lowest-lying states consists of a scalar and tensor which are almost degenerate and an axial vector with mass ≈1.6 times the scalar mass.The same procedure applied to the Abelian gauge theory yields unstable results which may indicate the presence of a phase transition. 相似文献
220.
A Simple,Broad‐Scope Nickel(0) Precatalyst System for the Direct Amination of Allyl Alcohols
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Prof. Joseph B. Sweeney Dr. Anthony K. Ball Philippa A. Lawrence Mackenzie C. Sinclair Luke J. Smith 《Angewandte Chemie (International ed. in English)》2018,57(32):10202-10206
The preparation of allylic amines is traditionally accomplished by reactions of amines with reactive electrophiles, such as allylic halides, sulfonates, or oxyphosphonium species; such methods involve hazardous reagents, generate stoichiometric waste streams, and often suffer from side reactions (such as overalkylation). We report here the first broad‐scope nickel‐catalysed direct amination of allyl alcohols: An inexpensive NiII/Zn couple enables the allylation of primary, secondary, and electron‐deficient amines without the need for glove‐box techniques. Under mild conditions, primary and secondary aliphatic amines react smoothly with a range of allyl alcohols, giving secondary and tertiary amines efficiently. This “totally catalytic” method can also be applied to electron‐deficient nitrogen nucleophiles; the practicality of the process was demonstrated in an efficient, gram‐scale preparation of the calcium antagonist drug substance flunarizine (Sibelium®). 相似文献