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41.
The conformations of a number of cyano-substituted aromatic model mesogens with actual or potential application in liquid crystals have been obtained using density functional B-LYP/6-311G(d) methodology. Dipole polarizability tensors have been computed at Hartree-Fock and B3-LYP levels of theory using Spackman's recommended basis sets, in order to obtain polarizability anisotropies, and to compare them with those of the parent compounds. The results indicate that 6-cyanoazulene is a potentially important mesogenic component, having a polarizability anisotropy not much less than 4-cyano-2,2'-bipyridyl. Electric dipole transition moments and oscillator strengths to the lowest singlet and triplet excited states have also been estimated for the cyanoazulenes, using a Configuration-Interaction Singles CIS/6-311G(d) approximation.  相似文献   
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Total cross section measurements for the 102Pd(p, γ)103Ag and 116Sn(p, γ)117Sb reactions have been performed in the proton energy range 2.6 to 4.25 MeV, and for the 112Sn(α, γ)116Te reaction over the alpha beam energy range 7.0 to 10.5 MeV. An activation technique was used in which gamma rays from decays of the reaction products were detected off-line by two hyper-pure germanium detectors in a low background environment. Where possible, reaction rates are derived and the results compared to those of calculations generated by the NON-SMOKER and the MOST statistical model codes so as to judge their applicability for describing the cross sections needed for network calculations of nucleosynthesis in explosive astrophysical environments via the γ- and rp-processes.  相似文献   
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July 1969, 528 pages, illustrated, $25.50  相似文献   
47.
The structure and superconducting properties of high temperature hydrogenated calcium-graphite intercalation compound, CaC6 have been investigated using room temperature X-ray diffraction, and temperature and field dependence of magnetisation. It is found that the hydrogenation can only decompose the CaC6 phase, and generate a mixture of CaH2 and graphite as the final compound. The hydrogenation of CaC6 also reveals a degradation of its superconducting properties. The experimental results are discussed in detail and it is found that the formation of stable CaH2 and deintercalation are the main source for observed phase separation and suppression in superconductivity.  相似文献   
48.
A correlated three-parameter variational ground-state Ψ(r1,r2,r12) proposed by Chandrasekhar for helium-like ions gives a high percentage of the electron correlation energy resulting from the interaction energy e2/r12 and also yields an analytic ground-state electron density ρ(r). Here, we extract via Schrödinger equation an exact Hamiltonian for which the Chandrasekhar wave function is the ground-state. Properties of the potential energy function in this Hamiltonian are quantified. Finally, kinetic energy densities are plotted and related to the Laplacian of ρ(r).  相似文献   
49.
On the planar hexagonal lattice , we analyze the Markov process whose state (t), in , updates each site v asynchronously in continuous time t0, so that v (t) agrees with a majority of its (three) neighbors. The initial v (0)'s are i.i.d. with P[ v (0)=+1]=p[0,1]. We study, both rigorously and by Monte Carlo simulation, the existence and nature of the percolation transition as t and p1/2. Denoting by +(t,p) the expected size of the plus cluster containing the origin, we (1) prove that +(,1/2)= and (2) study numerically critical exponents associated with the divergence of +(,p) as p1/2. A detailed finite-size scaling analysis suggests that the exponents and of this t= (dependent) percolation model have the same values, 4/3 and 43/18, as standard two-dimensional independent percolation. We also present numerical evidence that the rate at which (t)() as t is exponential.  相似文献   
50.
Nanotechnology is touted as a transformative technology in that it is predicted to improve many aspects of human life. There are hundreds of products in the market that utilize nanostructures in their design, such as composite materials made out of carbon or metal oxides. Potential risks to consumers, to the environment, and to workers from the most common passive nanomaterial—carbon nanotubes—are emerging through scientific research. Newer more active nanostructures—such as cancer therapies and targeted drug systems—are also increasing in use and are raising similar risk concerns. Governing the risks to workers is the subject of this commentary. The Occupational Safety and Health Act of 1970 grants the Occupational Safety and Health Administration the legal authority to set occupational health standards to insure that no worker suffers material impairment of health from work. However, setting a standard to protect workers from nanotechnology risks may occur some time in the future because the risks to workers have not been well characterized scientifically. Alternative risk governances—such as dynamic oversight through stakeholder partnerships, “soft law” approaches, and national adoption of international consensus standards—are evaluated in this article.  相似文献   
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