Assay of p-aminobenzenesulphonamides with chloramine-T

New spectrophotometric and titrimetric methods for the assay of p-aminobenzenesulphonamides with chloramine-T have been developed. They are simple, reproducible and accurate within the limits described (+/-3%) and are useful at high concentration levels. These methods are also applicable to the assay of p-aminobenzenesulphonamides in rat urine.     

Magnetic properties of amorphous heisenberg ferromagnet with random anisotropy

Magnetization, susceptibility, and the critical temperature for a spin-one amorphous Heisenberg ferromagnet with random local anisotropy are calculated in the molecular field approximation for the exchange interactions. The effects of random fluctuations of the magnitude of the local anisotropy about its crystalline value are studied for various probability distributions. It is found that for a given randomness, measured in terms of the root mean square fluctuation of the magnitude of the local anisotropy, the magnetization and the critical temperature depend more on the range, denned as the magnitude of the maximum value of the fluctuation from its mean value, than the shape of the probability distribution function. The effect of randomness decreases as the crystalline value of the anisotropy increases. Calculation of the susceptibility shows that above the critical temperature, randomness has no effect.     

Photomutagenic properties of terfenadine as revealed by a stepwise photostability,phototoxicity and photomutagenicity testing approach

Administration of the second-generation antihistamine, terfenadine, is sometimes associated with photosensitivity and other skin reactions. To obtain information on its photoreactivity, we used a stepwise experimental approach involving tests for photostability, phototoxicity (PT) (mouse fibroblast cell line [3T3] neutral red uptake [NRU] test) and photomutagenicity (with standard Ames salmonella tester strains TA98, TA100 and TA102). Terfenadine was not phototoxic to cultured mammalian cells under the conditions used (i.e. 5000/161 mJ cm(-2) UVA-UVB). Natural sunlight and UV radiations caused considerable drug decomposition and formation of several photoproducts. Addition of the irradiated terfenadine solution (i.e. a mixture of photoproducts) to the tester did not significantly increase background mutation frequency. Irradiation of terfenadine coplated with the TA102 strain induced a clear-cut photomutagenic response, the magnitude of which was dependent upon the precursor compound concentration and the UV dose (212/7 to 339/11 mJ cm(-2) UVA-UVB). These findings demonstrate that in vitro terfenadine is photomutagenic in absence of PT. Further in vitro and in vivo studies are therefore needed to provide an adequate safety assessment of the photochemical genotoxicity--carcinogenicity potential of terfenadine. In the meantime, patients should be advised to avoid excessive exposure to sunlight.     

Chaotic spatial bifurcation by complex coupling

A spatial bifurcation (a transition from stationary to oscillatory regime) in a chain of unidirectionally coupled phase systems is studied. It is shown that complication of coupling terms can make this bifurcation spatially chaotic in contrast to the previously observed "regular" and "predictable" type. It is demonstrated that the found type of spatial bifurcation corresponds to a smooth (predictable) manifold in the parameter space, while its spatial location gets actually unpredictable being governed by regularities of chaotic behavior. We infer that complex collective dynamics may arise in networks with plain architecture and simple dynamics of individual elements if nontrivial coupling is realized.     

Topological and Nonstandard Extensions

We introduce a notion of topological extension of a given set X. The resulting class of topological spaces includes the Stone-ech compactification X of the discrete space X, as well as all nonstandard models of X in the sense of nonstandard analysis (when endowed with a natural topology). In this context, we give a simple characterization of nonstandard extensions in purely topological terms, and we establish connections with special classes of ultrafilters whose existence is independent of ZFC.     

Topological and Nonstandard Extensions

We introduce a notion of topological extension of a given set X. The resulting class of topological spaces includes the Stone-ech compactification X of the discrete space X, as well as all nonstandard models of X in the sense of nonstandard analysis (when endowed with a natural topology). In this context, we give a simple characterization of nonstandard extensions in purely topological terms, and we establish connections with special classes of ultrafilters whose existence is independent of ZFC.     

On a quadratic difference assuming three values

Aequationes mathematicae - The aim of this work is to investigate the alternative quadratic functional equation $$\begin{aligned} f(x+y)+f(x-y)-2f(x)-2f(y)\in \{0,1,2\}, \end{aligned}$$ where $$f{:...