Differential pulse voltammetric determination of famotidine

A differential pulse voltammetric method for the determination of famotidine in pharmaceutical preparations is described. The method is based on electrochemical oxidation of famotidine at a glassy carbon or platinum electrode. The proposed method shows good reproducibility, and sample preparation is simple.     

Classical Klingenberg generalized quadrangles

Research supported by I.W.O.N.L. grant no. 840037.     

Reactions of n-sulfinyl-p-toluenesulfonamide with alcohols

N-Sulfinyl p-toluenesulfonamide (1) reacted with triaryl- and diarylmethanols to give predominantly N- substiuted sulfonamides and SO₂ presumably via carbonium ion intermediates. When carbonium ion forming alchols, such as t-BuOH and Ph₂C(Me)OH, were used the predominant products were alkenes and p- toluenesulfonamide. Allytic alcohols afforded N- substiuted sulfonamides along with dienes andp-toluenesulfonamide. Alcohols which could not predictably give relatively stable intermediate carbonium ions, gave either dialkyl sulfites or dialkyl eithers, along with p-toluenesulfonamide. In one case, namely with 9-phenylfluorenol the 1:1 adduct with 1 (an amidosulfite) was isolated. A mechanism for the reactions is proposed.     

Optimal operation for a bi-fuel thermal power plant by mathematical programming

This study is an attempt to provide the management of the Electricity Generating Authority of Thailand with an effective tool for determining the best operation of thermal units. A bi-fuel thermal power plant at North Bangkok, consisting of three thermal units, is considered. One of these units is adaptable to both lignite and fuel oil use, while the others use only fuel oil. A general optimization model, applicable to most power plants, is developed and a simplified version is applied to the North Bangkok Power Plant. A 0–1 mixed integer linear programming technique is used to find a method of operating the thermal units, which minimizes total fuel costs. Comparing the optimal solutions with actual operating strategies shows that savings in costs can be realised by implementing the model solution. Moreover, since the framework developed is quite general, it may be usefully applied to other power plant studies.     

Stereochemical aspects of proton chemical shifts. III—Configurational assignments in pentacyclic systems without recourse to a karplus equation

It is shown that in contrast to the use of coupling constants, chemical shift criteria may lead to unambiguous structural elucidations in pseudorotational frameworks (pentacycles, heptacycles, etc.).     

Zur Quantentheorie der stimulierten RAMAN-Streuung in Molekülkristallen. II. Spezielle Fälle eines stationären RAMAN-Oszillators

Two kinds of stationary RAMAN oscillators are investigated theoretically for molecular crystals. The calculations are done firstly for the generation of one first order anti-STOKES mode and secondly for the generation of one second order STOKES mode. By using a quantum theoretical model described in an earlier paper for treatment of molecular crystals RAMAN scattering is assumed to be polariton scattering. Within this framework coupled nonlinear equations for the polariton operators of the excited modes are derived, stationary occupation numbers for the different modes and threshold conditions are calculated. The influence of phase fluctuations of the pump wave on the line widths of the RAMAN modes are investigated.