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Let Abe a unital Hermitian Banach algebra with the spectrum of a∈Adenoted by σA(a). We show that if a continuous and multiplicative function ϕ:A→Csatisfies ϕ(a)∈σ(a)for all a∈A, then ϕis linear and hence a character of A.

Active learning algorithms allow neural networks to dynamically take part in the selection of the most informative training patterns. This paper introduces a new approach to active learning, which combines an unsupervised clustering of training data with a pattern selection approach based on sensitivity analysis. Training data is clustered into groups of similar patterns based on Euclidean distance, and the most informative pattern from each cluster is selected for training using the sensitivity analysis incremental learning algorithm in (Engelbrecht and Cloete, 1999). Experimental results show that the clustering approach improves on standard active learning as presented in (Engelbrecht and Cloete, 1999).

Abstract: Levels of some of the most essential minerals in liver tissue of wild animals living in game reserves in South Africa were studied by instrumental thermal neutron activation analysis and a Ge(Li) detector. In addition, some of the most important trace elements were determined by atomic absorption spectrometry. The distribution of the content of the various elements was followed for about two years and attempts have been made to explain the influence of seasonal fluctuations of the micronutrients determined.

Summary The elements Ga, La and Sm were determined in the NIMROC geological standards by the standard addition method. After addition of standard quantities of the elements, the samples were irradiated with neutrons in a reactor. Radioactive sodium was radiochemically separated and the elemental concentrations were then determined by precision?-spectrometry.

Abstract: An activation analysis method has been developed for the routine determination of43Ca. The calcium is chemically separated and converted to fluoride. When activated for 2 hours with 4.50 MeV protons,43Sc and48Sc are produced and the ratio of their activities is a measure of the isotopic concentrations of43Ca.48Ca serves as an internal standard to represent total natural calcium. The relative standard deviation is ±1.5% and the method can determine a change of +0.004 atom %43Ca in natural calcium.42Ca may interfere, if present in enriched concentrations.

14 C in the Atmosphere from 1952 to 1971 According to Measurements of Wine Ethanol Previous measurements of 14 C in German wines (vintages 1952 — 1967) have been extended up to 1971 and are supple-mented by a series of samples from the southern hemisphere.