Abstract In nonlinear greedy approximation theory, bidemocratic bases have traditionally played the role of dualizing democratic, greedy, quasi-greedy, or almost bases. this article we shift viewpoint and study them for their own sake, just as would with any other kind greedy-type particular show that need not be despite fact they retain a strong unconditionality flavor which brings very close ...

substituted schiff bases (hydrazones) 5a-j have been prepared from the starting material 2-chloro pyridine-3-carboxylic acid 1 by a sequence of reactions like reaction with 2-amino-6-nitro benzothiazole (ullamann condensation), thionyl chloride, hydrazine hydrate and different aromatic aldehydes. on cyclocondensation of 5a-j with thioglycolic acid in dry 1,4-dioxane furnished desired compounds ...

in this paper, we investigate duality of modular g-riesz bases and g-riesz basesin hilbert c*-modules. first we give some characterization of g-riesz bases in hilbert c*-modules, by using properties of operator theory. next, we characterize the duals of a giveng-riesz basis in hilbert c*-module. in addition, we obtain sucient and necessary conditionfor a dual of a g-riesz basis to be again a g...