Search results for " Periodic table"
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From Masurium to Trinacrium: The Troubled Story of Element 43
2005
The first man-made chemical element was that with atomic number 43. It was produced at the University of Californiaâ€sA„A¬Berkeley (by neutron bombardment of a molybdenum plate and was chemically identified at the University of Palermo (Italy) in 1937 by Segre and Perrier. Previous attempts to identify it in natural ore had been unsuccessful, owing to the short life of its isotopes. Notwithstanding, several claims of its discovery had appeared in the chemical literature. The history of this discovery clearly shows the dramatic improvements of chemical analytical techniques and criteria in the first half of 20th century. In 1949 its discoverers proposed to call it technetium, which means pro…
Molecular Classification of Pesticides Including Persistent Organic Pollutants, Phenylurea and Sulphonylurea Herbicides
2014
Pesticide residues in wine were analyzed by liquid chromatography–tandem mass spectrometry. Retentions are modelled by structure–property relationships. Bioplastic evolution is an evolutionary perspective conjugating effect of acquired characters and evolutionary indeterminacy–morphological determination–natural selection principles; its application to design co-ordination index barely improves correlations. Fractal dimensions and partition coefficient differentiate pesticides. Classification algorithms are based on information entropy and its production. Pesticides allow a structural classification by nonplanarity, and number of O, S, N and Cl atoms and cycles; different behaviours depend …