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1.
For fairly high concentrations, the effective arsenic diffusioncoefficient is known to grow linearly with the concentration.In this paper, we consider the strongly enhanced diffusion ofarsenic by asymptotic methods, and extend the results of a previouspaper (King & Please, 1987) in three ways: we characterizean additional (low-concentration) region; we consider the influenceof the initial data; and we consider the case of constant surfaceconcentration. 相似文献
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R. B. KING 《Molecular physics》2013,111(10):1567-1577
Topological representations (top-reps), which originally were developed to model molecular polyhedral isomerization processes, can be extended to depict the relationships between the polygons and polyhedra involved in Jahn-Teller (JT) distortions. Using this approach, the top-rep of the E ? (b 1g + b 2g) distortion of square planar molecules to rectangle and rhombus isomers becomes a rhombus in which the vertices alternately represent distortions to the rectangle and rhombus isomers. Similarly the top-rep of the E ? e distortion of regular Oh octahedra to elongated D4h tetragonal bipyramids becomes a triangle in which the vertices represent the three distinct tetragonal bipyramids from a given octahedron and the edge midpoints represent lower symmetry rhombic D2h intermediates. A regular octahedron can be used as a top-rep for the T ? (e + t 2) distortions of regular octahedra if the 6 vertices represent distortions to D4h tetragonal bipyramid isomers, the 8 face midpoints represent distortions to D3d trigonal antiprism isomers, and the 12 edge midpoints represent lower symmetry rhombic D2h intermediates. In the case of Jahn-Teller T ? h distortions of regular Ih icosahedra, the corresponding top-rep becomes a regular icosahedron in which the 12 vertices represent distortions to pentagonal D5d isomers, the 20 face midpoints represent distortions to trigonal D3d isomers, and the 30 edge midpoints represent D2h intermediates. A 4-dimensional analogue of the tetrahedron (i.e. the 4-simplex) can be used as a top-rep for the G ? g problem and the H ? g component of the H ? (g + 2h) problem for JT distortions of regular icosahedra. In this case the 5 vertices and the 10 edge midpoints correspond to Th isomers and D3d intermediates, respectively. 相似文献
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In this paper, we have calculated the elastic scattering of high energy electrons with nuclei C12 by phase shift calculation.We take the charge distribution of the nucleus C12 as following:(1) exponential distribution:ρ(x)=ρ0θ-x/a, (2) gaussian distribution:ρ(x)=ρ0e(-x2/a2),(3) uniform distribution: ρ(x) ={ρ0 when 0kR, where a and b are the parameters, and the constant R is the radius of the nucleus C12. The energy of the electrons is 187 Mev.The result of the calculation shows that the gaussian distribution confirms the experimental result better than the other two kinds of distributions, and gives R=(12)1/3r0, where r0=1.35×10-13 cm. 相似文献
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Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14
Background
We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.Results
Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Conclusion
Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. 相似文献9.
J. A. BURNS B. B. KING D. RUBlO 《International Journal of Computational Fluid Dynamics》2013,27(1-2):93-112
Abstract In his paper we consider the problem of designing a feedback controller for a thermal fluid. Any practical feedback controller for a fluid flow system must incorporate some type of state estimator. Moreover, regardless of the approach, one must introduce approximations at some point in the analysis. The method presented here uses distributed parameter control theory to guide the design and approximation of practical slate estimators. Wc use finite clement techniques to approximate optimal infinite dimensional controllers based on linear quadratic Gaussian lpar;LQG) and MinMax theory for the Bonssincsq equations. These designs are then compared to full state feedback. We present several numerical experiments and we describe how these techniques can also be applied to sensor placement problems. 相似文献
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