Effect of pore size on the capacity of sislca-immobilized 8-quinolinol

Optimization of the pore sizes of various silica gels used as supports in the immobilization of 8-quinolinol is described. Increased capacity is observed as pore size decrease to the opt? at about 6 nm. At smaller pore sizes, steric effects appear to predominate, ? capacities decrease sharply. An explanation for these effects is proposed, it was confirmed by using molecular models.     

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Nonequilibrium potential approach: Local and global stability of stationary patterns in an activator-inhibitor system with fast inhibition

We study the formation and global stability of stationary patterns in a finite one-dimensional reaction-diffusion model of the activator-inhibitor type. The analysis proceeds through the study of the nonequilibrium potential or Lyapunov functional for this system considering the fast inhibitor case and, in order to obtain analytical results, the adoption of a piecewise linear version of the model. We have studied the changes in relative stability among the different patterns as the ratio between the diffusion coefficients is varied and have discussed the meaning of the different contributions to the nonequilibrium potential.     

Pmr characterization of diastereomeric forms of acyclic compounds bearing two equivalent chiral atoms in 1,5-positions

Assignment of configurations to diastereomeric pairs was based on anisochronism of diastereotopic protons of suitable probe groups, at various distances from both chiral centers.     

Studies on the separation of anions with 8-hydroxy-quinolinium ion as counterion

Distribution constants, K_D, for 8-hydroxyquinolinium-anion pairs and for a series of inorganic and organic anions are reported between aqueous acidic phases and 1-butanol and 3-methyl-1-butanol. As expected, K_D values are larger for anions with relatively large crystal radius (e.g., Cl^- < I^- < R-SO₃^-), smaller for anions containing either hydroxyl or carboxyl groups favoring solvation by water (e.g., HSO₄^-, HSeO₃^-, H₂PO₄^-, C₆H₅COO^-, CH₃COO^-) and larger in solvents with larger solubility parameters (e.g., 4-methyl-2-pentanone < 3-methyl-1-butanol < 1-butanol). Distribution constants between aqueous solutions and 8-hydroxyquinoline immobilized (chemically) on controlled-pore glass are estimated for a series of aromatic and aliphatic sulfonates. Aromatic sulfonates show substantially larger K_D values than aliphatic sulfonates. Batch equilibration data were used to design chromatographic (liquid-solid) separation of a few sulfonates.     

The hydrogen atom as a projection of an homogeneous space

The Kustaanheimo-Stiefel transformation as applied to the nonrelativistic hydrogen atom provides one of the rare examples of a free particle moving on a four-dimensional homogeneous space.     

Friedel oscillations in a relativistic quantum plasma

The linear responce of a two-component plasma to a static test charge is analyzed at large distances from the impurity. The electrons are considered relativistic and degenerate and the ions classical and non-relativistic. The results show that the electrons give the principal contribution to the response, which is long ranged and characterized by the Friedel oscillatory behavior.