Chemically-bonded stationary phases for thin-layer chromatography of metal ions

Summary A numer of bonded stationary phases were investigated for the separation of Cd²⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ by thin-layer chromatography. The effect of structure, surface loading, type of silica gel and mobile phase concentration was considered.     

The canonical ensemble via symplectic integrators using Nosé and Nosé-Poincaré chains

Simulations that sample from the canonical ensemble can be generated by the addition of a single degree of freedom, provided that the system is ergodic, as described by Nosé with subsequent modifications by Hoover to allow sampling in real time. Nosé-Hoover dynamics is not ergodic for small or stiff systems and the addition of auxiliary thermostats is needed to overcome this deficiency. Nosé-Hoover dynamics, like its derivatives, does not have a Hamiltonian structure, precluding the use of symplectic integrators which are noted for their long term stability and structure preservation. As an alternative to Nosé-Hoover, the Hamiltonian Nosé-Poincaré method was proposed by Bond, Laird, and Leimkuhler [J. Comput. Phys. 151, 114 (1999)], but the straightforward addition of thermostatting chains does not sample from the canonical ensemble. In this paper a method is proposed whereby additional thermostats can be applied to a Hamiltonian system while retaining sampling from the canonical ensemble. This technique has been used to construct thermostatting chains for the Nosé and Nosé-Poincaré methods.     

Preparation of methyl (1R,2S,5S)- and (1S,2R,5R)-2-amino-5-tert-butyl-cyclopentane-1-carboxylates by parallel kinetic resolution of methyl (RS)-5-tert-butyl-cyclopentene-1-carboxylate

Comparison of the kinetic and parallel kinetic resolutions of methyl (RS)-5-tert-butyl-cyclopentene-1-carboxylate allows for the efficient synthesis of both (1R,2S,5S)- and (1S,2R,5R)-enantiomers of methyl 2-amino-5-tert-butyl-cyclopentane-1-carboxylate.     

Synthesis of s-triazolocycloalkyl-, s-triazolobenzocycloalkyl-, and s-triazolocycloalkylhydrothiadiazines

The reaction of cyclic-α-haloketones with 5-subslituted-4-amino-4H-1,2,4-triazole-3-lhiols gave s-triãzolocycloalkylhydrothiadiazines and s-triazolobenzocycloalkylthiadiazines. Reduetion of the 5,5a-imine bond of the s-triazoloeycloalkylthiadiazines gave s-triazolocycloalkylhydrothia-diazines.     

Nonlinear Boundary Value Problems on Sequence Spaces

In this paper we study the solvability of nonlinear, discrete-time boundary value problems for functional equations. Conditions are established for the existence of solutions to problems of the form $$x(k + 1) = f(k, x(k)) + \lambda g(k, x(k)); \quad k = 0, 1, 2, \ldots$$