Finite Element Analysis Of Thermal Characteristics in Continuous Wave Long Wavelength Surface Emitting Lasers (I): Dielectric Cavity Structures

We numerically analyzed the thermal characteristic in continuous wave (cw) GalnAsP/InP surface emitting lasers with dielectric multilayer mirrors by using finite element method. From the simulation of temperature distribution in cw devices, we found that MgO/Si multilayer mirror which has a high thermal conductivity is effective for heat sinking; the thermal resistance of device using MgO/Si mirror is nearly half of that using SiO₂/Si one, almost independently of their thicknesses. It was also indicated that the optimum design for other structural parameters, especially the thickness of active region, is important to effectively suppress the temperature increase. The minimum threshold current was estimated to be 3 mA under cw condition for the active region diameter of 4 μm and thickness of 0.5 μm.     

A Microoptic Network Unit Using Planar Microlens Array

We propose a new concept for an optical network unit using planar microlens array for fiber to the home networks. It is expected from this modeling that an optical coupling loss of 2.5 dB, a polarization dependent loss of 0.5 dB and an extinction ratio larger than 50 dB can be achieved. The structure design and its fabrication method are discussed.     

Differential geometry of chemically reacting systems

This paper is a detailed differential geometrical study of chemically reacting systems. In particular the following coordinate-free properties of chemically reacting systems are obtained: 1) the general solution of the intrinsic reaction coordinate (IRC) (henceforth referred to as meta-IRC), 2) extended definitions of the Hessian matrix and normal vibrations at any non-equilibrium point on the surface, and 3) clarification of the close connection between the geometry of meta-IRC and the geography of the surface at a transition point. The theory is elucidated using a model potential surface.     

Diels-alder reactions of cyclohexadienes derived from decarboxylation of photo[4 + 2]cycloadducts between 4,6-dimethyl-2-pyrone and cyclic olefins

Labile photo [4 + 2] adducts between 4,6-dimethyl-2-pyrone and cyclic olefins reacted with second olefins to give cross adducts, and with acetylenes to afford both bis-adducts and benzene derivatives with the concurrent decarboxylation, respectively. The reaction mechanism of the latter was considered.     

Periodic surface calculations on chemisorption of H2 on a Ni surface

The periodic model of finite surfaces has been employed to investigate the localizability of the chemisorption interaction and to examine the validity of the cluster model. The adsorbate—surface interaction is estimated by the usual perturbation method. The model is applied to chemisorption of hydrogen molecule on a Ni(100) surface. As for the present calculations, the period model is shown to be advantageous over the cluster model in representing both the adsorbate-free surface state and the adsorbate—surface interaction.     

Theory of chemical bonds in metalloenzymes IV: Hybrid‐DFT study of Rieske‐type [2Fe?2S] clusters

The Rieske‐type [2Fe? 2S] cores of electron‐transfer (ET) proteins in the mitochondrial respiratory chain have unusual properties, such as redox potentials and spectroscopy. In this study, part IV of a series, the inherent molecular structures and characteristic electronic structures of the Rieske‐type [2Fe? 2S] clusters are investigated using broken‐symmetry hybrid density functional theory (BS‐HDFT). Geometry optimizations for the oxidized and reduced states were performed and their characteristic vibrational modes are assigned. Magnetic properties are investigated using model Hamiltonians to describe the electron delocalization and the unsymmetric property. The parameters of the model Hamiltonian, such as exchange coupling J, valence delocalization B, and potential energy difference Δ, are evaluated from the BS‐HDFT calculations. The valence localization and excitation energy (ΔE) of the Rieske‐type [2Fe? 2S] cluster are discussed. The chemical bond nature is characterized by chemical indices from natural orbital analysis. Our theoretical results are reasonably consistent with experimental results. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Functional vibrational spectroscopy of a cytochrome c monolayer: SEIDAS probes the interaction with different surface-modified electrodes

Electrochemically induced infrared difference spectra of cytochrome c on various chemically modified electrodes (CMEs) are recorded by exploiting the surface-enhancement exerted by a granular gold film. We have recently developed surface-enhanced infrared difference absorption spectroscopy (SEIDAS), which provides acute sensitivity to observe the minute enzymatic change of a protein on the level of a monolayer. By these means, we demonstrate that the relative band intensities in the potential-induced difference spectra of adsorbed cytochrome c are significantly dependent on the type of CME used (mercaptopropionic acid, mercaptoethanol, 4,4'-dithiodipyridine, or L-cysteine). These differences are attributed to the altered interaction of cytochrome c with the headgroup of the various CMEs leading to variations in surface orientation and relative distance from the surface. Nevertheless, the peak positions of the observed bands are identical among the CMEs employed. This implies that the internal conformational changes induced by the redox reaction of the adsorbed cytochrome c are not disturbed by the interaction with the CME and that full functionality of the protein is retained. Finally, we critically discuss our results within the framework of the different models for cytochrome c adsorption on CMEs.     

Mild and efficient removal of hydroxyethyl unit from 2-hydroxyethyl ether derivatives leading to alcohols

[reaction: see text]. CAN is a good reagent for the transformation of 2-hydroxyethyl ether units to alcohols. Significantly, many functional groups can tolerate the reaction conditions, although they do not survive under many previously reported removal conditions. The reaction mechanism is clarified.     

Properties and cage lactone synthesis of diels-alder adducts from 2-pyrones

New cage lactones were synthesized by the photocyclization of the tricyclodienolactones 1a, 1b, 2 which were available from the Diels-Alder reactions of 2-pyrones with p-benzoquinones or norbornadiene. Retro-Diels-Alder reactions of cross-adducts between 2-pyrone-mono-adducts and p-benzoquinone were also described.     

Preparation of 3-(2H-pyran-2-on-6-yl)indolizines and the diels-alder reactions with some olefinic and acetylenic dienophiles

3-(2H-Pyran-2-on-6-yl)indolizines 6a-d were prepared by 1,3-dipolar cycloaddition reactions of N-(2H-pyran-2-on-6-yl)methylpyridinium bromides 5a,b with dimethyl acetylenedicarboxylate (DMAD). All of the cycloaddition reactions of 6b with N-phenylmaleimide, p-benzoquinone, and DMAD took place at the 2-pyrone ring to give 3-substituted indolizines.