We prove (under some technical assumptions) that each surface in R3 containing two arcs of parabolas with axes parallel to Oz through point has a parametrization (P(u,v)R(u,v),Q(u,v)R(u,v),Z(u,v)R2(u,v)) for P,Q,R,Z∈R[u,v] such P,Q,R have degree at most 1 u and v, Z 2 v. The proof is based on the observation one can consider parabola vertical axis as an isotropic circle; this allows us use meth...

necessary conditions for callus production from leaf and stem explants of norfolk island pine (araucaria excelsa l.) have been studied. ms and bm culture media containing 0.2, 0.5, 1, 2 and 5 mg/l naa, iba, 2,4-d and picloram supplemented with 30 g/l sucrose were used. callus was initiated in both culture media only in the presence of picloram and in the dark, but bm culture medium produced mor...