Solid-phase microextraction of hop volatiles. Potential use for determination and verification of hop varieties.

The composition of hop essential oil is an important tool for evaluation of hop quality. As each hop variety has a typical essential oil pattern (fingerprint), hop oil analyses can be used to distinguish between hop varieties. The headspace solid-phase microextraction (SPME) method as described in this contribution is a simple sample preparation technique and represents an alternative procedure for essential oil fingerprint determination. Different SPME parameters (extraction temperature, extraction time and sample mass) were studied and the results were compared with those obtained by the routine distillation method. It is shown that SPME results can be used for determination and verification of varieties grown in Slovenia by means of principal components analysis.

Update in the treatment of schizophrenia.

The large number of drugs available to treat schizophrenia and the emergence of atypical and newer agents that provide efficiency with lessening of side effects may not only serve to provide more amelioration against this disease, but may also help us to unravel the neurochemical defects of the disorder. Despite these encouraging trends, the reality is that schizophrenia is still a devastating illness for a sizeable minority affected with the condition, that a 'cure' is not yet possible, and that drug therapies alone will not provide all that is required in acute or continuing management. Supporting care in the community for patient and family are just as important as pharmacotherapy in managing this problem.

On some modified spherical models.

A one parameter family of models is considered which for zero value of the parameter alpha reduces to the familiar spherical model. The models for alpha > 0 have a symmetry close to that of an Ising model. A heuristic discussion of phase transitions in these models leads to the conjecture that, if the spherical model (alpha = 0) exhibits a phase transition, then so do the models with alpha > 0, and that moreover the critical temperature remains the same, at least for sufficiently small alpha. The conjecture is checked on a mean field model.

A complete solution of the periodic Toda problem.

The motion of the periodic Toda lattice is explicitly determined in terms of Abelian integrals.

On some periodic toda lattices.

A discrete version of Floquet's theory is developed and applied to a system of non-linear differential equations related to the periodic Toda lattice. A special solution previously found by Toda is thus seen to fit into the formalism of inverse scattering problems.

On some isospectral second order differential operators.

A method of exhibiting potentials which are uniquely determined by their spectra is discussed and illustrated in an example.