Nonlinear effects of electrolyte diodes and transistors in a polymer gel medium

The polarization curve of an acid-base interface in a hydrogel medium has a diode characteristic. Two of each such electrolyte diodes can be combined to give an electrolyte transistor. When a salt is added to the alkaline or to the acidic part of a reverse biased electrolyte diode, the current response is highly nonlinear. If the salt is added to the acidic side, even bistability can be observed. This bistability can generate complex oscillations in a base-acid-base electrolyte transistor. These nonlinear effects are studied experimentally and theoretically. While the nonlinear salt effect can be explained with the Nernst-Planck equations, to understand the bistable behavior further investigations are necessary. (c) 1999 American Institute of Physics.     

Effects of chlorine gas exposure on the optical properties of rhodium phthalocyanine films

We investigated the effects of exposing rhodium phthalocyanine films deposited on glass substrates by the Lagmuir-Blodgett technique to chlorine gas. The visual aspect of the films is altered upon chlorination, changing in color from blue to transparent. We performed optical absorption and Raman Scattering measurements on our films prior to and after exposing it to chlorine gas. We observed a pronounced quenching of the characteristic triplet centered around the Q-absorption band at 662 nm as a result of chlorine incorporation. Another absorption band, in the near UV part of the spectrum, is not greatly affected by the process. No new optical structures appear as a consequence of chlorination. Equivalent effects were observed in the Raman spectra. Leaving the previously exposed films in air for several hours results in a slow partial recovery of the optical spectra. This recovery, as well as the amount of original quenching, depends on the amount of time during which the film was exposed to chlorine.     

The Electron Density is Smooth Away from the Nuclei

We prove that the electron densities of electronic eigenfunctions of atoms and molecules are smooth away from the nuclei.     

A Total Synthesis of (±)- Aphidicolin: Regio- and stereoselective conversion of 3α,18-Di-O-benzyl-17-nor-14-aphidicolen-16-one into (±)-aphidicolin

A regio- and steroselective conversion of the totally synthetic 3α, 18-di-O-benzyl-17-nor-14-aphidicolen-16-one (5), into (±)-aphidicolin 1 , by hydroxylation of the 2-methylidenebicyclo[3.2.1] oct-3-ene derivative 6 is described. Compound 5 was a key intermediate in our previously described total synthesis of 2 , which represented a formal synthesis of 1 .     

On the loss of information due to fuzziness in experimental observations

The absence of exactness in the observation of the outcomes of a random experiment always entails a loss of information about the experimental distribution. This intuitive assertion will be formally proved in this paper by using a mathematical model involving the notions of fuzzy information and fuzzy information system (as intended by Tanaka, Okuda and Asai) and Zadeh's probabilistic definition. On the basis of this model we are first going to consider a family of measures of information enclosing some well-known measures, such as those defined by Kagan, Kullback-Leibler and Matusita, and then to establish methods for removing the loss of information due to fuzziness by increasing suitably the number of experimental observations.     

Modified clenshaw-curtis method for the computation of Bessel function integrals

The numerical evaluation of Bessel function integrals may be difficult when the Bessel function is rapidly oscillating in the interval of integration. In the method presented here, the smooth factor of the integrand is replaced by a truncated Chebyshev series approximation and the resulting integral is computed exactly. The numerical aspects of this exact integration are discussed.     

Zur Polymorphie von Dapson und Ethambutoldihydrochlorid

Zusammenfassung Bei den Arzneistoffen Dapson und Ethambutoldihydrochlorid liegen außergewöhnlich komplizierte Polymorphieverhältnisse vor. In beiden Fällen wurden vier Modifikationen nachgewiesen, beiDapson existiert außerdem noch ein Hydrat. Das Dapson-Anhydrat liegt als enantiotrope Mod. III vor, die bei 80° in Mod. II übergeht. Diese Form ist meist bis zu ihrem Schmelzpunkt beständig. Mod. I, die aus der Schmelze kristallisiert, ist ebenfalls mit Mod. II enantiotrop. Außerdem besteht zwischen Mod. I und Mod. III Enantiotropie. Die Umwandlung Mod. IIIMod. II erfolgt spontan und unabhängig von Keimen, so daß der Schmelzpunkt von Mod. III nicht bestimmt werden kann. Bei Mod. IV konnte keine Enantiotropie mit einer anderen Kristallform nachgewiesen werden. Ethambutoldihydrochlorid weist nur enantiotrope Umwandlungen durch Umklappen ganzer Kristalle in das Gitter der anderen Modifikation auf, so daß nur der Schmelzpunkt der Hochtemperaturform bestimmbar ist. Die Tieftemperaturform besteht aus Mod. II, Mod. IV ist bei Raumtemperatur metastabil, während die instabile Mod. III nur ein ganz schmales Existenzgebiet zwischen ca. 40 und 45° besitzt, da sie sowohl mit Mod. IV als mit Mod. I enantiotrop ist.

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On the polymorphism of dapsone and ethambutol dihydrochloride

Summary There are extraordinarily complicated polymorphism conditions in the drugs dapsone and ethambutol chloride. In both cases, four modifications were detected, and in the case of dapsone there exists a hydrate in addition. The dapsone anhydrate is present as enantiotropic Mod. III, which transforms into Mod. II at 80°. This form is mostly stable up to its melting point. Mod. I, which crystallizes from the melt, is likewise enantiotropic with Mod. II. In addition, there is enantiotropy between Mod. I and Mod. III. The transformation of Mod. IIIMod. II takes place continuously and independently from nuclei, so that the melting point of Mod. III cannot be determined. In Mod. IV, no enantiotropy with another crystal form could be detected.Ethambutol dihydrochloride only displays enantiotropic transformations by folding over of entire crystals into the lattice of the other modification, so that only the melting point of the high temperature form can be determined. The low temperature form consists of Mod. II, Mod. IV is metastable at room temperature, whereas the unstable Mod. III only possesses a quite narrow range of existence between about 40 and 45°, since it is enantiotropic both with Mod. IV and with Mod. I.