Beam-propagation method for analysis of z -dependent structures that uses a local oblique coordinate system

In the most current beam-propagation method (BPM), the coupling between the transverse and the longitudinal fields in z -dependent structures is ignored under the staircase approximation, which results in violation of power conservation. We propose a novel BPM that is derived in a local oblique coordinate system to analyze z -dependent structures accurately and efficiently without taking the staircase approximation. The coupling between the transverse and the longitudinal fields is automatically included in the local oblique coordinate system, and power is thus conserved if the reflection is neglected.     

Evaluation of the thermal stability of some nonlinear optical chromophores

Optical data storage is poised to benefit from a new class of advanced polymeric materials engineered to exhibit photorefractivity. Likewise, the transmission and processing of data will also benefit from a related class of materials with electro-optic activity. Organic chromophores are critical constituents of these materials which function due to a change of index of refraction in response to an electric field. However, a number of materials and processing problems remain to be solved before devices incorporating these optically nonlinear chromophores are practical. For example, for electrooptical applications the NLO waveguide should be able to withstand short duration processing temperatures in excess of 300°C and long duration use temperatures of at least 80°C. The requirement for thermochemical stability follows from the need to implement highT _g matrices to provide stability of the orientational or polar order required for long-term device performance and reliability. As a result, the thermal stability of chromophores is now more closely evaluated in addition to their transparency and optical nonlinearity properties. Some chromophore classes, such as the azo dyes studied here, have attractive properties for these applications but further enhancements in overall properties are needed. Identification of the fundamental chemical processes in thermal decomposition of these dyes should lead to introduction of structural changes which provide better stability. Here thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA/MS) is used to provide an assay of thermochemical stability with an added benefit that insight into the mechanisms of thermal decomposition may by identified. In this initial study diaryl substitution of the amine in derivatives of 4-amino-4-nitroazobenzene was observed to greatly enhance thermal stability relative to dialkyl substitution. Substitution of phenyl for alkyl eliminates structural features involved in the most facile degradation mechanism available to the alkyl derivative.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe authors acknowledge contributions by colleagues at IBM including H. Truong and R. Siemens for the thermal analysis. This work was supported by the Air Force Office of Scientific Research and the National Institute of Science and Technology Advanced Technology Program.     

Spectroscopic correlations between supermolecules and molecules. Anatomy of the ion-modulated electronic properties of the nitrogen donor in monoazacrown-derived intrinsic fluoroionophores

The synthesis, absorption and emission spectra, fluorescence quantum yields, and fluorescence lifetimes of three compound series of trans-4,4'-disubstituted aminostilbenes (1-3) are reported. The chromo-/fluoroionophoric behavior of the monoaza-15-crown-5- (A15C5) and monoaza-18-crown-6 (A18C6)-derived species (1A(5)()-3A(5)() and 1A(6)()-3A(6)()) in acetonitrile and dichloromethane are also investigated. Great similarities in electronic spectroscopic properties (chemical shifts, wavelength, intensity, and lifetime) between the metal ion-complexed supermolecules and the corresponding chloro-substituted molecules have been observed: namely, 1A(5)()/Ca(2+)-3A(5)()/Ca(2+) approximately 1A(6)()/Ba(2+)-3A(6)()/Ba(2+) approximately 1C-3C in acetonitrile and 1A(5)()/Na(+)-2A(5)()/Na(+) approximately 1A(6)()/K(+)-2A(6)()/K(+) approximately 1C-2C in dichloromethane. Such spectroscopic correlations allow us to define the metal ion-modulated electronic character of the azacrown nitrogen atom in the ground and excited states and, in turn, to gain insights into the observed fluoroionophoric behavior of these probes in terms of the size and direction of fluorescence shifts and intensity variations.     

Separation and Determination of Chemical Constituents in the Roots of Rhus Javanica L. Var. Roxburghiana

From the roots of Rhus javanica L. var. roxburghiana, totally thirty‐seven known compounds have been isolated and identified. Their structures were elucidated based on their spectral analysis as well as comparison with authentic samples. These compounds were grouped to be fifteen triterpenoids, five steroids, two lignans, two flavonoids, nine phenolics, and four other aromatic derivatives. Their cytotoxicities toward two cell lines NUGC‐3 and HONE‐1 were also evaluated.     

Influence of a Nonionic Surfactant (Triton X-100) on Contaminant Distribution between Water and Several Soil Solids

The influence of a nonionic surfactant (Triton X-100) on the contaminant distribution coefficients in solid-water mixtures was determined for a number of relatively nonpolar compounds (contaminants) on several natural solids. The studied compounds consisted of BTEX (benzene, toluene, ethylbenzene, and p-xylene) and chlorinated pesticides (lindane, alpha-BHC, and heptachlor epoxide), which span several orders of magnitude in water solubility (S(w)); the solid samples comprised a bentonite, a peat, and two other soils, which cover a wide range of solid organic matter (SOM) content. The applied surfactant concentrations (X) ranged from below the (nominal) CMC to 2-3 times the CMC. For relatively water-soluble BTEX compounds, the distribution coefficients with surfactant (K(d)*) all exceeded those without surfactant (K(d)); the K(d)*/K(d) ratios increased with increasing S(w) from p-xylene to benzene on each solid at a given X, with increasing X for each compound on a solid, and with decreasing solid SOM content for each compound over the range of X studied. For the less-soluble pesticides, the K(d)*/K(d) ratios exhibited a large increase with X for bentonite, a marginal change (increase or decrease) for a soil of 2.4% SOM, and a moderate-to-large decrease for two soils of 14.8% and 86.4% SOM. These unique observations were rationalized in terms of the properties of the compound, the amount of surfactant sorbed on the solid, the enhanced solubilization of the compound by surfactant in water, and the relative effects of the surfactant when adsorbed on minerals and when partitioned into SOM. Copyright 2000 Academic Press.     

Configurational assignment of several 1,4-substituted adamantanes

The configurations of several 1,4- (= 2,5-) disubstituted adamantanes have been determined by means of X-ray diffraction. Since these compounds have rigid skeletons and since there is almost no difference in stability or steric requirements between the geometric isomers, these epimers are expected to be very useful for stereochemical studies.     

Application of crown ethers as modifiers for the separation of amines by capillary electrophoresis

The separation of amines with capillary electrophoresis (CE) was made possible by applying crown ethers such as 18-crown-6 and 15-crown-5 as modifiers. Crown ether 18-crown-6 performed better as a modifier than 15-crown-5. The mobility change of primary amines with 18-crown-6 was larger than that for secondary and tertiary amines. The mobility change of various amines with 18-crown-6 were in the order: 1-aminobutane>2-aminobutane>2-amino-2-methylpropane. Effects of crown ether concentration, pH and cations in the eluent of CE were also investigated and discussed. Some neurotransmitters such as dopamine, serotonin, epinephrine, isoproterenol and phenylalanine were separated successfully by using crown ethers in CE analysis.     

Industrial Protease “Alcalase” as a Catalyst in Organic Synthesis: Resolution of Natural and Unnatural Amino Acids

Procedures have been developed for the resolution of natural and unnatural amino acids using soluble or immobilized industrial enzyme “Alcalase” as catalyst. The specificity of enzyme on different amino acids and the stability of both free and immobilized enzyme have been studied.