Complexes of biologically important ligands. I. Ternary complexes of nickel(II) comprising 1,10-o-phenanthrolineazosulfonamide derivatives and alkyldithiophosphates

5-[p-(R-Sulfonyl)phenylazo]-1,10-o-phenanthroline (L) and its octahedral complexes of the type [Ni(R₂dtp)₂(L)] (where R₂dtp = diethyl-or dipropyldithiophosphate) with the core NiN₂S₄ have been prepared and characterized by spectral, magnetic, and thermogravimetric methods. The thermal decomposition mechanism of the compounds was proposed and the kinetic parameters of decomposition were calculated making use of the Coats—Redfern and Horowitz—Metzger equations.     

Different alternatives for stability constant determination of Zr and Hf 2-methyl lactate complexes by cation exchange

Three different alternatives are applied for the determination of the stability constants of zirconium and hafnium complexes with 2-methyl lactic acid using cation exchange. Calculations based on the exchange equilibria of the highly charged metal cations and the positively charged ligand complexes rather than that of the hydrolysed complex species are worked out according to SCHUBERT and FRONAEUS, respectively. The third alternative adopted in this work, is principally based on the consideration of all complexed species produced by hydrolyses in the aqueous phase. The B-values obtained by the different methods are intercorrelated and discussed.     

Effect of some environmental ligands and fertilizers on humic acid complexation with strontium

The effect of some environmental ligands and certain fertilizers on the complexation of strontium with humic acid wasinvestigated colorimetrically and radiometrically. The results indicate that Na₂-EDTA, Na₃-citrate and NaCl compete to complex strontium in solution with the sequence: chloride < citrate < EDTA while Na₃-phosphate has the reverse behavior. In the case of nitrogen containing fertilizers, the results show that urea, Mg-ammonium nitrate and ammonium nitrate increase the availability of strontium to plants and microorganisms.     

Generalized Weber Problem with Rectangular Regions

The problem of locating one or more new facilities relative to a number of existing rectangular regions is treated for the case where the rectilinear norm is used. The new facilities are to be located such that the total weighted distance is minimized. If there is interfacility interaction among the new facilities, a gradient-free nonlinear search algorithm is utilized. Computational experience suggests that this algorithm is expedient even in the solution of large problems.     

Steiner's problem and fagnano's result on the sphere

This note describes the nature of optimal solutions for the spherical Steiner-Weber location problem for the case of unit weights and either 3 or 4 demand points (requireing 4 demand points to lie in an open hemisphere). Geometrically appealing results which are necessary conditions for optimum solutions and spherical analogs of known planar results are obtained.     

Numerical computation of optimal control problems with unknown final time

This paper presents a numerical computational method for the solution of optimal control problems with unknown final time. The method presented is based on a transformation and a modified quasilinearization technique. A numerical example is included for illustration.