Fabrication of Periodic Waveguides Using Organic Crystals and Fluorinated Polyimides for Quasi-Phase-Matched Second-Harmonic Generation

We have developed a new method to fabricate periodic waveguide structures used for quasi-phase-matched second-harmonic generation, where nonlinear optical organic crystals and fluorinated copolyimides are alternately arranged. Quasi-phase-matched second-harmonic generation from an organic waveguide device has been demonstrated.     

A variational approach to distribution function theory

We present a novel formalism for the generation of integral equations for the distribution functions of fluids. It is based on a cumulant expansion for the free energy. Truncation of the expansion at theKth term and minimization of the resulting approximation leads to equations for the distribution functions up toKth order.The formalism is not limited to systems with two-body interactions and does not require the addition of closure relations to yield a complete set of equations. In fact, it automatically generates superposition approximations, such as the Kirkwood three-body superposition approximation or the Fisher-Kopeliovich four-body one.The conceptual approach is adapted from the cluster variation method of lattice theory.     

A heated-electrode discharge lamp for trace analysis by atomic emission spectroscopy

Graphite electrodes heated by d.c- power alone, or a combination of d.c- and r.f. power, are investigated for generating atomic emission from cadmium with specially designed discharge lamps. Best results are achieved if the plasma produced by both power sources can be concentrated within a cylindrical electrode.     

On the stability of characterizations of the exponential distribution

Summary It is shown that if the distribution of min {X ₁/a₁, X₂/a₂,…, X_N/a_N} is close to that ofX ₁, then the distribution is close to the exponential distribution. The paper was presented at the Conference on Mathematical Statistics and Probability Theory held at the New Delhi Centre of the Indian Statistical Institute, December, 1980. The Institute of Statistical Mathematics     

SCF MO calculations of heteroatomic systems with the variable Β approximation

In order to elucidate the electronic structure of protonated N-heterocycles, we have carried out SCF MO calculations, considering the -bond polarizations which are caused by the large net charge on nitrogen atom. Appropriate parametrizations of the valence state energies associated with the -bond polarization model have been proposed. Our calculations showed that a conventional covalent model for protonated N-heterocycles failed to explain the experimental electronic spectral data and an extremely polarized -core model gave quite good results in the whole. The present theory expected that the nature of electronic spectra of quinoline is considerably changed by the -bond polarization due to the protonation.

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Zusammenfassung Um die Elektronenstruktur von protonisierten N-Heterozyklen zu untersuchen, wurden SCF-MO-Rechnungen durchgeführt, bei denen die Polarisierung der -Bindung durch die Ladung am N-Atom berücksichtigt wird. Eine geeignete Parametrisierung der Valenzzustands-Energien in Verbindung mit dem Modell der Polarisierung der -Bindung wird vorgeschlagen. Die Rechnungen zeigen, da\ ein herkömmliches kovalentes Modell für die genannten Verbindungen bei der ErklÄrung des Elektronenspektrums versagt, wÄhrend ein Modell mit stark polarisierten -Bindungen befriedigende Ergebnisse liefert. Aus der vorliegenden Theorie lÄ\t sich folgern, da\ das Elektronenspektrum des Chinolins betrÄchtlich durch die Polarisierung der -Bindung infolge Protonisierung geÄndert wird.

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Résumé Afin d'éclaircir la structure électronique d'hétérocycles protonisés sur l'azote, nous avons effectué des calcules SCF MO en considérant la polarization des liaisons dûe à la forte charge nette sur l'atome d'azote. Des paramétrisations appropriées à ce modèle polarisé sont proposées pour les énergies des états de valence. Nos calculs ont montré qu'un modèle covalent conventionnel pour les N hétérocycles protonisés ne réussit pas à expliquer le spectre électronique expérimental alors qu'un modèle à forte polarisation du squelette donne des résultats dans l'ensemble satisfaisants. Cette théorie prévoit que la nature du spectre électronique de la quinoléine est considérablement modifiée par la polarisation dûe à la protonisation.

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Presented partly at the 23rd Symposium on Molecular Structure and Spectroscopy, The Ohio State University, Columbus, Ohio, U.S.A., September 1968.     

Efficient total synthesis of (+)-negamycin, a potential chemotherapeutic agent for genetic diseases

Herein, we describe an efficient strategy for the total synthesis of (+)-negamycin using commercially available achiral N-Boc-2-aminoacetaldehyde as starting material with 42% overall yield for a limited number of steps.