A STUDY OF THE PHOTODYNAMIC EFFICIENCIES OF SOME EYE LENS CONSTITUENTS

We have studied the photochemical quantum yields of singlet oxygen production (using the RNO bleaching method) and superoxide production (using the EPR-spin trapping method and the SOD-inhibitable ferricytochrome c reduction spectral assay) of kynurenine (Ky), N-formylkynurenine (NFK), 3-hydroxykynurenine (3HK), kynurenic acid (KUA), and the flavins, riboflavin (RF) and flavin mononucleotide (FMN). Such a study of the photodynamic efficiencies is important since these compounds appear endogenously in the eye. The singlet oxygen quantum yields of the flavins and KUA are high, while Ky and 3HK generate no detectable amounts of singlet oxygen. The superoxide quantum yields of the sensitizers are low compared to their singlet oxygen, and Ky and 3HK produce no detectable amounts of superoxide. The production of the superoxide radical is enhanced in the presence of electron donor molecules such as EDTA and NADH. These results suggest that the production of oxyradicals in the lens may be modulated by the presence of endogenous electron donor molecules such as the coenzymes NADH and NADPH, which are present in significant amounts in some lenses. They also suggest that Ky and 3HK, which are known to be present in aged lenses, might play a protective rather than a deleterious role in the eye.     

Ab Initio Construction of Quasiadiabatic Potential-Energy Surfaces for Cycloaddition Reactions of Ethene and Substituted Allylic Cations

The nature of some well known 2π + 2π cycloaddition reactions was studied by explicit construction of the quasiadiabatic potential-energy surfaces for the cycloaddition of ethene and various monosubstituted allylic cations. Such surfaces determined by ab initio MO computations are particularly suitable for analysis of symmetry selection rules. By examining the characteristics of such surfaces, we have studied the substituent effect and the role played by the positive charge in such systems. Qualitative discussion based on simplified MO, involving fewer electrons, is also given.     

Determination of fatty acids in vegetable oil by reversed-phase liquid chromatography with fluorescence detection.

The effect of temperature and organic solvent composition (acetonitrile and methanol) on the reversed-phase separation of coumarin-derivatized fatty acids according to their carbon number (C14 to C22), the degree of unsaturation, as well as cis/trans (C18:1 c/t, C18:2 cc/tt, C18:3 ccc/ttt) configuration was investigated to find out the effective separation condition. Based on the linear plots of the logarithm of the capacity factor of saturated fatty acids versus their carbon number, the equivalent chain length (ECL) of unsaturated fatty acids was calculated. The ECL values were found to be significantly altered and the differentiation between cis and trans fatty acids was increased when either the temperature or organic solvent composition was decreased. These results generally led to a better resolution at the expense of separation time. A ternary gradient composed of water, acetonitrile, and methanol was then developed to elute the solutes at 55 degrees C within a separation time of 40 min with a minimum resolution of 1.0 for the worst pair. This method was demonstrated to resolve the fatty acids in a vegetable shortening.     

Laguerre polynomials and the inverse Laplace transform using discrete data

We consider the problem of finding a function defined on (0,∞) from a countable set of values of its Laplace transform. The problem is severely ill-posed. We shall use the expansion of the function in a series of Laguerre polynomials to convert the problem in an analytic interpolation problem. Then, using the coefficients of Lagrange polynomials we shall construct a stable approximation solution. Error estimate is given. Numerical results are produced.     

<Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> Observer-Based Control for a Class of Uncertain Neutral Time-Delay Systems via LMI Optimization Approach

In this paper, the H_∞ observer-based control for a class of uncertain neutral time-delay systems is considered. The linear matrix inequality (LMI) optimization approach is used to design the H_∞ robust control with disturbance attenuation. Two classes of observer-based controls are proposed and their H_∞-norm bounds are given. The control and observer gains are given from the LMI feasible solutions. A numerical example is given to illustrate the results. The research reported here was supported by the National Science Council of Taiwan under Grant NSC 93-2213-E-214-020.     

Phonon-assisted tunneling and shot noise in double barrier structures in a longitudinal magnetic field

The phonon-assisted resonant tunneling is studied for the double barrier structures in a longitudinal magnetic field. Using the scattering matrix approach with an appropriate one-particle Green's function we are able to calculate the current and the zero frequency shot noise power spectrum in a large range of the magnetic field and to any order of the electron-phonon interaction. Obtained results describe well the relevant experimental data and provide new suggestions for further examinations.     

Non-oscillatory shock-capturing finite element methods for the one-dimensional compressible Euler equations

A class of shock-capturing Petrov–Galerkin finite element methods that use high-order non-oscillatory interpolations is presented for the one-dimensional compressible Euler equations. Modified eigenvalues which employ total variation diminishing (TVD), total variation bounded (TVB) and essentially non-oscillatory (ENO) mechanisms are introduced into the weighting functions. A one-pass Euler explicit transient algorithm with lumped mass matrix is used to integrate the equations. Numerical experiments with Burgers' equation, the Riemann problem and the two-blast-wave interaction problem are presented. Results indicate that accurate solutions in smooth regions and sharp and non-oscillatory solutions at discontinuities are obtainable even for strong shocks.     

Studies of single-neutron holes in the transitional nuclei N = 83–89: The 142Ce(d,t)141Ce and 142Ce(3He, α)141Ce pick-up reactions

The level structure of ¹⁴¹Ce up to 3.7 MeV excitation energy has been investigated by the (d, t) and (³He, α) reactions using 17 MeV deuteron and 24 MeV ³He beams respectively. The angular distributions have been analyzed with standard DWBA calculations and spectroscopic factors are deduced. The experimental information is compared to unified model calculations involving both one-particle and two-particle one-hole configurations with quadrupole and octupole vibrations of the underlying N = 82 and N = 84 core.     

Level structure of123, 125I from the 122, 124Te(3He,d) reactions

The energy levels of ¹²³I and ¹²⁵I have been studied in the ^{122, 124}Te(³He, d)^{123, 125}I reactions at 24 MeV bombarding energy. The reaction products were analysed with an Enge split-pole magnetic spectrograph. A total of 57 levels below 3.3 MeV in ¹²³I and 79 levels below 4.1 MeV in ¹²⁵I were observed. Angular distributions were measured and compared with DWBA calculations to obtain orbital angular momentum transfers and spectroscopic strengths. The results were compared to previous radioactive decay studies and to theoretical energy level calculations.     

Synthesis of 2-alkoxy 1,4-naphthoquinone derivatives as antiplatelet,antiinflammatory, and antiallergic agents

In our continuing search for novel antiplatelet, antiallergic, and antiinflammatory agents, 2-alkoxy derivatives of 1,4-naphthoquinone were prepared. Some of these compounds showed significant antiplatelet, antiallergic, and antiinflammatory activities. Among them, 2-propoxy-1,4-naphthoquinone and 2-butoxy-1,4-naphthoquinone exhibited potent inhibitory effect on neutrophil superoxide anion formation. These two compounds are worthy of further exploration.