Extraction separation of Sr2+ from Ba2+ in the system cobalt dicarbollide-polyethylene glycol-nitrobenzene-CCl4-cyclohexaned iaminetetraacetate

The kinetics of Sr and Ba distribution both for extraction and back-extraction processes has been investigated. The influence of the equilibrium pH, the CDTA concentration and the Na/Li ratio on the distribution of the metals to be separated was established. Separation factors (Ba/Sr) achieved were not altered by replacing PEG 400 as the synergic agent by the cheaper technical product Slovafol 909. Practical hints for carrying out the separation for analytical purposes. are given.     

Periodic solutions of dry friction problems

Dry friction problems lead to discontinuous differential equations, e.g. to

On approximation by bivariate incomplete polynomials

In this paper we prove that given certain convex domains Δ on the plane, ε>0, andf∈C(Δ) such thatf=0 on θ²Δ={(θ² x,θ² y):(x,y)?Δ} (0<θ<1), a polynomialp(x, y) of the form $$p(x,y) = \sum\limits_{\theta n \leqslant k + l \leqslant n} {a_{kl} x^k y^l }$$ exists such that ∥f?p∥ _C(Δ) ≤ε. The admissible convex domains include triangles and parallelograms with a vertex at the origin and sections of unit disk.