We present the design of a novel metal micro-aperture surface emitting laser for tera byte optical data storage. The field distribution near micro-aperture is calculated by 2-dimensional finite element method, and it is shown that a spot size as narrow as 100 nm beyond a diffraction limit is obtainable. 相似文献
As the production of engineered nanomaterials quantitatively expands, the chance that workers involved in the manufacturing
process will be exposed to nanoparticles also increases. A risk management system is needed for workplaces in the nanomaterial
industry based on the precautionary principle. One of the problems in the risk management system is difficulty of exposure
assessment. In this article, examples of exposure assessment in nanomaterial industries are reviewed with a focus on distinguishing
engineered nanomaterial particles from background nanoparticles in workplace atmosphere. An approach by JNIOSH (Japan National
Institute of Occupational Safety and Health) to quantitatively measure exposure to carbonaceous nanomaterials is also introduced.
In addition to real-time measurements and qualitative analysis by electron microscopy, quantitative chemical analysis is necessary
for quantitatively assessing exposure to nanomaterials. Chemical analysis is suitable for quantitative exposure measurement
especially at facilities with high levels of background NPs. 相似文献
A system consisting of finitely many nonrelativistic particles bound on an external potential and minimally coupled to a massless quantized radiation field without the dipole approximation is considered. An ultraviolet cut-off is imposed on the quantized radiation field. The Hamiltonian of the system is defined as a self-adjoint operator in a Hilbert space. The existence of the ground states of the Hamiltonian is established. It is shown that there exist asymptotic annihilation and creation operators. Hence the location of the absolutely continuous spectrum of the Hamiltonian is specified.
Summary: A diastereomeric pair of novel N‐propargylphosphonamidates, HCCCH2NHP(O)(CH3)O‐L ‐menthyl was synthesized by the successive condensations of methylphosphonic dichloride with L ‐menthol and propargylamine. The (R)‐P‐isomer ( 1a ) was isolated, and the absolute configuration was determined by XRD. Polymerization of 1a , and a mixture of 1a and (S)‐P‐isomer ( 1b ) was carried out with a zwitterionic Rh complex as a catalyst. cis‐Stereoregular polymers with number‐average molecular weights of 5 600–9 800 were obtained in good yields. Poly( 1a ) and poly( 1a 29‐co‐ 1b 71) exhibited large specific rotations (+408 and −146°), and intense Cotton effects ([θ] = +2.25 and −0.9 × 104 deg · cm2 · dmol−1) based on the conjugated polyacetylene backbone around 325 nm in CHCl3, indicating that these polymers have helical structures, whose predominant helical senses are opposite.
Polymerization of N‐propargylphosphonamidate. 相似文献
The chemical reactions between (−)-deprenyl and ·OH or ·OOH were studied using molecular orbital theory, with N,N-dimethylpropargylamine as a model. (−)-Deprenyl was confirmed to be a good radical scavenger. The active site was the acetylenic
part and ·OH- or ·OOH was trapped on either acetylenic carbon. The activation energies were about 10–20 kcal/mol. The resulting ·OH- or ·OOH-adducts, still radicals, trapped further radicals on the remaining carbon of the acetylenic part. The final double trapping
products were at extraordinarily lower energy levels than the original reactants by 50–70 kcal/mol. The secondary transition
states were not detected, suggesting that the reactions occurred at once or in a cascade. Some results with the model system
were verified by the results with the real (−)-deprenyl system.
Received: 6 October 1999 / Accepted: 5 March 2000 / Published online: 21 June 2000 相似文献
Effects of internal rotations of chromophores under the energy transfer interaction in proteins on the time-resolved fluorescence were examined by numerical calculations. Expressions used for the calculations are based on the approximations that the energy transfer takes place according to Foöurster's mechanism and the rotational motions of the energy donor and acceptor along the surfaces of cones are described by a set of rotational diffusion equations. The intensity decay of the donor depended a little on the rotational diffusion coefficient of the donor in some cases, while that of the acceptor did very little. Anisotropy of the donor decayed faster as the diffusion coefficient of the donor increased. Anisotropy decay of the acceptor markedly depended not only on the mutual configuration of the pair in the protein, but also on the diffusion coefficient of the donor. The dependence of the time-resolved fluorescence on the diffusion coefficient of the acceptor was not as great as that of the donor. 相似文献