Biotechnological progress in producing fuels and valuable chemicals and in bioremediating environmental impacts

Applied Biochemistry and Biotechnology - The 71 poster papers presented at the 16th Symposium on Biotechnology for Fuels and Chemicals provided new information on ethanol production, feedstock...     

On cardioactive steroids. XII. The synthesis of (natural) bufalin and α′-isobufalin

An efficient and simple synthesis of bufalin (1) via furan-containing intermediates is described. The same method was also used for the synthesis of α-isobufalin (2) which was prepared with equal simplicity, but in lower yield.     

Analytical Chemistry — today''s definition and interpretation

Conclusion Analytical Chemistry is an applied, experimental field of natural science and is based not only on chemistry, but also on physics, biology, information theory and many fields of technology. The purpose of Analytical Chemistry is to provide information on the chemical composition of natural and synthetic objects and the changes in this composition over space and time. It is a typical multidisciplinary subject with many feedback links emphasizing teamwork in solution of problems.     

Determination of gold in leach liquors by anodic stripping voltammetry in non-aqueous medium

The anodic stripping voltammetry of gold in butyl acetate/methanol (2 + 1) mixture is reported. The tetrachloroaurate(III) complex is extracted into butyl acetate, lithium perchlorate in methanol is added, and gold is deposited on a glassy carbon rotating disk cathode at ?0.6 V vs. SCE. The deposited gold is stripped in the same medium at a scan rate of 50 mV s^?1. The method is suitable for the determination of gold (0.1–1 mg l^?1) in chloride leach liquors.     

Multiphase equilibria in solutions of polydisperse homopolymers. I. Three-phase equilibria in ternary and quasiternary systems

A recent critique of the mechanism of three-phase separation suggested by Tompa for ternary system solvent–polymer (1)–polymer (2) is shown to be invalid, and Tompa's account is reinforced by analytical arguments and numerical results. In particular it is proven that the critical point in some simple Flory–Huggins systems is thermodynamically unstable, rather than just metastable. Three-phase separations in quasiternary systems cannot be studied by simple methods advanced for treatment of true ternary systems. Rather a new, more general, approach is required for these cases.     

Influence of reactant adsorption on limiting currents in normal pulse polarography: Part V. Theory for non-linear adsorption

The analytical theory for adsorption-influenced limiting currents in normal pulse polarography is extended to conditions where the adsorption isotherm is non-linear. The case of Langmuirian adsorption at a stationary planar electrode is treated in detail, using the Reinmuth series for the dependence of surface coverage on time, and it is explained how the measured currents are affected by the isotherm parameters. The approach to Langmuirian adsorption at stationary spherical and expanding plane electrodes is briefly indicated. Finally it is pointed out how the problem can be solved for an arbitrary type of isotherm.     

On extendibility of unavoidable sets

A subset X of a free monoid A¹ is said to be unavoidable if all but finitely many words in A¹ contain some word of X as a subword. A. Ehrenfeucht has conjectured that every unavoidable set X is extendible in the sense that there exist x ? X and a ? A such that (X ? {x}) ∪ {xa} is itself unavoidable. This problem remains open, we give some partial solutions and show how to efficiently test unavoidability, extendibility and other properties of X related to the problem.