Experimentally determined oscillator strengths and linewidths for the Schumann-Runge band system of molecular oxygen—III. The (7-0) to (19-0) bands

Experimental oscillator strengths and predissociation linewidths have been derived from equivalent width measurements at room temperature for the (11-0) to (15-0) Schumann-Runge bands of molecular oxygen, and at low temperature for the (15-0) to (19-0) bands, using the Adelaide 6 m vacuum ultraviolet monochromator operated at a resolution of 0.006 nm. Photometric methods were used to measure the ultraviolet absorption for 40 groups of ratational lines, and the resulting data were interpreted using a curve of growth type of analysis to give oscillator strengths and pre-dissociation linewidths. The variation of the oscillator strengths with N? within each band was found to agree well with the theoretical predictions of Allison, while the mean band oscillator strengths derived from the results are in good agreement with previous measurements. The results demonstrate the need for accurate data about multiplet line splittings. A revised analysis of previous data for the (7-0) to (14-0) bands is also presented.     

Contraction of convex surfaces by nonsmooth functions of curvature

We consider the motion of convex surfaces with normal speed given by arbitrary strictly monotone, homogeneous degree one functions of the principal curvatures (with no further smoothness assumptions). We prove that such processes deform arbitrary uniformly convex initial surfaces to points in finite time, with spherical limiting shape. This result was known previously only for smooth speeds. The crucial new ingredient in the argument, used to prove convergence of the rescaled surfaces to a sphere without requiring smoothness of the speed, is a surprising hidden divergence form structure in the evolution of certain curvature quantities.     

Molecular flexibility effects upon liquid dynamics

Simulation results for the diffusive behavior of polymer chain/penetrant systems are analyzed. The attractive range and flexibility of simple chain molecules were varied in order to gauge the effect on dynamics. In all cases, the dimensionless diffusion coefficient, D*, is found to be a smooth, single-valued function of the packing fraction, eta. The functions D*(eta) are found to be power laws with exponents that are sensitive to both chain stiffness and particle type. For a specific system type, the D*'s for both penetrant and chain-center-of-mass extrapolate to zero at the same packing fraction, eta0. This limiting packing fraction is interpreted to be the location of the glass transition, and (eta0-eta), the distance to the glass transition.     

Chemoselective derivatization of alkaloids in periwinkle

The terpene indole alkaloid biosynthetic pathway can utilize a secologanin substrate analog containing a handle for functionalization, and the resulting non-natural alkaloids can be chemoselectively derivatized in crude extracts of plant tissue.     

Lifespan theorem for constrained surface diffusion flows

We consider closed immersed hypersurfaces in ${\mathbb R^{3}}$ and ${\mathbb R^4}$ evolving by a class of constrained surface diffusion flows. Our result, similar to earlier results for the Willmore flow, gives both a positive lower bound on the time for which a smooth solution exists, and a small upper bound on a power of the total curvature during this time. By phrasing the theorem in terms of the concentration of curvature in the initial surface, our result holds for very general initial data and has applications to further development in asymptotic analysis for these flows.     

Probing the dependence of long-range, four-atom interactions on intermolecular orientation: 3. Hydrogen and iodine

Two-laser, action spectroscopy experiments have been performed in the I(2)B-X, υ'-0 spectral region on H(2)···I(2) and D(2)···I(2) complexes to investigate the dependence of the H(2)/D(2) + I(2) intermolecular interactions on orientation. The spectra contain features associated with at least two different conformers of the ground-state H(2)/D(2)···I(2)(X,υ' = 0) complexes; one conformer has a preferred T-shaped geometry with the H(2)/D(2) moiety localized in a potential minimum that is orthogonal to the I-I bond axis, and the second conformer has a linear geometry with the H(2)/D(2) moiety positioned in minima at either end of the I(2) molecule, along the bond axis. Those features associated with complexes containing para-H(2)(j = 0), ortho-H(2)(j = 1), ortho-D(2)(j = 0), and para-D(2)(j = 1) are also assigned. The linear conformers are found to be more strongly bound than the T-shaped conformers with binding energies of 118.9(1.9) cm(-1) versus 91.3-93.3 cm(-1) for the ortho-H(2)···I(2) complexes and 144.2(2.1) cm(-1) versus 107.9 cm(-1) for the para-D(2)···I(2) complexes, respectively. Electronic structure calculations of the complexes containing ICl and I(2) with H(2), He, Ne, and Ar were performed to reveal the nature of the interactions and to shed insight into the origins of the different binding energies. The most stable minima in the H(2)/D(2) + I(2)(B,υ') excited-state potentials have T-shaped geometries. Calculated energies and probability amplitudes of the excited-state levels provide insight into the different excited-state intermolecular vibrational levels accessed by transitions of the two ground-state conformers.     

Bi2223带材临界电流沿长度方向的统计分布

本文采用四引线法测量了Bi2223带材临界电流沿长度方向的分布,采用正态分布、对数正态分布、威布尔分布和最小极值分布对临界电流分布进行了拟合检验,确定了临界电流的最优统计分布模型.     

Willmore energy for joining of carbon nanostructures

Numerous types of carbon nanostructure have been found experimentally, including nanotubes, fullerenes and nanocones. These structures have applications in various nanoscale devices and the joining of these structures may lead to further new configurations with more remarkable properties and applications. The join profile between different carbon nanostructures in a symmetric configuration may be modelled using the calculus of variations. In previous studies, carbon nanostructures were assumed to deform according to perfect elasticity, thus the elastic energy, depending only on the axial curvature, was used to determine the join profile consisting of a finite number of discrete bonds. However, one could argue that the relevant energy should also involve the rotational curvature, especially when its size is comparable to the axial curvature. In this paper, we use the Willmore energy, a natural generalisation of the elastic energy that depends on both the axial and rotational curvatures. Catenoids are absolute minimisers of this energy and pieces of these may be used to join various nanostructures. We focus on the cases of joining a fullerene to a nanotube and joining two fullerenes along a common axis. By comparing our results with the earlier work, we find that both energies give similar joining profiles. Further work on other configurations may reveal which energy provides a better model.