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991.
A new method for studying the kinetics of the expansion of explosion products based on measuring the time elapsed from explosion initiation to the short-circuiting of the discharge gap by the products was proposed. It was revealed that, at the initial stage of expansion of the silver azide explosion products, they move with uniform acceleration, a behavior suggestive that, during this period, the exothermic reaction 2N3 → 3N2 occurs.  相似文献   
992.
The influence of a large signal on the characteristics of a small signal near the frequency of the former is experimentally studied for the case of their simultaneous propagation through a resonant transmission line based on backward volume magnetostatic waves. The effects observed are caused by the excitation of spin waves in a ferromagnetic film at different large-signal frequencies and by the back influence of excited spin-wave packets on the amplitude and phase characteristics of the small signal.  相似文献   
993.
Ivanov  E. 《Russian Physics Journal》2002,45(7):695-708
We give a brief account of supersymmetric Born–Infeld theories with extended supersymmetry, including those with partially broken supersymmetry. Some latest developments in this area are presented. One of them is N = 3 supersymmetric Born–Infeld theory which admits a natural off-shell formulation in N = 3 harmonic superspace.  相似文献   
994.
We investigate the exclusive photoproduction of a heavy timelike photon which decays into a lepton pair, . This can be seen as the analog of deeply virtual Compton scattering, and we argue that the two processes are complementary for studying generalized parton distributions in the nucleon. In an unpolarized experiment the angular distribution of the leptons readily provides access to the real part of the Compton amplitude. We estimate the possible size of this effect in kinematics where the Compton process should be dominated by quark exchange. Received: 9 October 2001 / Published online: 5 April 2002  相似文献   
995.
Ethylene/1‐hexene copolymerizations with disiloxane‐bridged metallocenes, rac‐ and meso‐1,1,3,3‐tetramethyldisiloxanediyl‐bis(1‐indenyl)zirconium dichloride (rac‐ 1 , meso‐ 1 ) activated by modified methylaluminoxane were performed to investigate the influence of conformational dynamics on comonomer selectivity. Although 1H NOESY (nuclear Overhauser and exchange spectroscopy) analysis indicated that the most stable conformation for the meso isomer in solution was that in which both indenes project over the metal coordination site, this isomer showed higher 1‐hexene selectivity in copolymerization (re = 140 ± 30, rh = 0.024 ± 0.004) than the rac isomer with only one indene over the coordination site (re = 240 ± 20, rh = 0.005 ± 0.001). The meso isomer showed high 1‐hexene selectivity, a high product of reactivity ratios (rerh = 3.3 ± 0.5) and produced copolymers that could be separated into fractions with different ethylene content suggesting that the active species exhibited multisite behavior and populated conformations with different comonomer selectivities during the copolymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3323–3331, 2004  相似文献   
996.
Recent developments in desorption/ionisation mass spectrometry techniques have made their application to biological analysis a realistic and successful proposition. Developments in primary ion source technology, mainly through the advent of polyatomic ion beams, have meant that the technique of secondary ion mass spectrometry (SIMS) can now access the depths of information required to allow biological imaging to be a viable option.Here the role of the primary ion C60+ is assessed with regard to molecular imaging of lipids and pharmaceuticals within tissue sections. High secondary ion yields and low surface damage accumulation are demonstrated on both model and real biological samples, indicating the high secondary ion efficiency afforded to the analyst by this primary ion when compared to other cluster ion beams used in imaging. The newly developed 40 keV C60+ ion source allows the beam to be focused such that high resolution imaging is demonstrated on a tissue sample, and the greater yields allow the molecular signal from the drug raclopride to be imaged within tissue section following in vivo dosing.The localisation shown for this drug alludes to issues regarding the chemical environment affecting the ionisation probability of the molecule; the importance of this effect is demonstrated with model systems and the possibility of using laser post-ionisation as a method for reducing this consequence of bio-sample complexity is demonstrated and discussed.  相似文献   
997.
We consider some initial-boundary value problems for the linear and nonlinear heat equation where the gradient of the solution is prescribed on the boundary. Assuming that a solution exists, we obtain bounds for the solution and its gradient by maximum principle arguments or by means of differential and integral inequalities.  相似文献   
998.
Kalvius  G. M.  Wagner  F. E.  Halevy  I.  Gal  J. 《Hyperfine Interactions》2003,151(1-4):195-207
Hyperfine Interactions - The YFe4Al8 and ErFe4Al8 intermetallics were studied by57Fe Mössbauer spectroscopy between 2 K and room temperature. The spectra are consistent with iron occupying 8f...  相似文献   
999.
In a previous paper we gave a new formulation and derived the Euler equations and other necessary conditions to solve strong, pathwise, stochastic variational problems with trajectories driven by Brownian motion. Thus, unlike current methods which minimize the control over deterministic functionals (the expected value), we find the control which gives the critical point solution of random functionals of a Brownian path and then, if we choose, find the expected value.This increase in information is balanced by the fact that our methods are anticipative while current methods are not. However, our methods are more directly connected to the theory and meaningful examples of deterministic variational theory and provide better means of solution for free and constrained problems. In addition, examples indicate that there are methods to obtain nonanticipative solutions from our equations although the anticipative optimal cost function has smaller expected value.In this paper we give new, efficient numerical methods to find the solution of these problems in the quadratic case. Of interest is that our numerical solution has a maximal, a priori, pointwise error of O(h3/2) where h is the node size. We believe our results are unique for any theory of stochastic control and that our methods of proof involve new and sophisticated ideas for strong solutions which extend previous deterministic results by the first author where the error was O(h2).We note that, although our solutions are given in terms of stochastic differential equations, we are not using the now standard numerical methods for stochastic differential equations. Instead we find an approximation to the critical point solution of the variational problem using relations derived from setting to zero the directional derivative of the cost functional in the direction of simple test functions.Our results are even more significant than they first appear because we can reformulate stochastic control problems or constrained calculus of variations problems in the unconstrained, stochastic calculus of variations formulation of this paper. This will allow us to find efficient and accurate numerical solutions for general constrained, stochastic optimization problems. This is not yet being done, even in the deterministic case, except by the first author.  相似文献   
1000.
In this work, we reexamine the time scale Laplace transform as defined by Bohner and Peterson [M. Bohner, A. Peterson, Dynamic Equations on Time Scales: An Introduction with Applications, Birkhäuser, Boston, 2001; M. Bohner, A. Peterson, Laplace transform and Z-transform: Unification and extension, Methods Appl. Anal. 9 (1) (2002) 155-162]. In particular, we give conditions on the class of functions which have a transform, develop an inversion formula for the transform, and further, we provide a convolution for the transform. The notion of convolution leads to considering its algebraic structure—in particular the existence of an identity element—motivating the development of the Dirac delta functional on time scales. Applications and examples of these concepts are given.  相似文献   
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