Interfacial Activity of Trioctyloamine in Hydrocarbon/Water Systems with Nonorganic Electrolytes

Interfacial tension and surface excess isotherms for trioctylamine (TOA) were determined and interpreted. Despite its high hydrophobicity, TOA adsorbs at the hydrocarbon/water interfaces and decreases effectively the interfacial tension, especially in systems containing acidic aqueous phase. Interfacial activity of TOA rises with an increase of the aqueous phase acidity. The effect of amine protonation is clearly observed. Interfacial tension isotherms obtained experimentally can be well matched with the Szyszkowski equation. The interfacial activity of TOA is affected by the type of the organic diluent and the composition of the aqueous phase, i.e., the kind and concentration of nonorganic electrolyte present in the system. Copyright 2001 Academic Press.     

Tailoring the interface of hybrid microresonators in viscid fluids enhances their quality factor by two orders of magnitude

The application of microresonators in fluids is predominantly constrained by the strong damping caused by the viscid drag and the additional inertia of the liquid in the interfacial layer. In this paper we propose the new concept of partial wetting that exploits another property of liquids, its surface energy, to adapt physically the interface of the microresonator to the liquid by the formation of a meniscus. First experiments performed with technically simple batch-fabricated prototypes validate the potential of partial wetting as a vital route to improve the quality factor of microresonators in viscid fluids to values up to 600 exceeding those of conventional microresonators by almost two orders of magnitude.     

Off-line system for measurement of nitrous oxide concentration in gases leaving the irradiation chamber

The N₂O concentration in the gas leaving the irradiation chamber was determined by off-line gas chromatographic analysis. The grab sample system involved the scrubber with a 1.0 N NaOH solution and the drying columns. The paper presents preliminary results of N₂O concentration measurement for two different gas irradiation doses with other technological parameters of the pilot installation being constant.     

Compact basis sets for LCAO-LSD calculations. Part I: Method and bases for Sc to Zn

A method for preparing compact orbital and auxiliary basis sets for LCAO-LSD calculations has been developed. The method has been applied to construct basis sets for first row transition metal atoms from Sc to Zn for the 3d^n?14s¹ and 3d^n?24s² configurations. The properties of different expansion patterns have been tested in atomic calculations for the chromium atom.     

Compact basis sets for LCAO-LSD calculations. Part II: Tests for Cr2 and Ni4

The compact orbital and auxiliary basis sets for LCAO-LSD calculations introduced in Part I are tested in molecular calculations on Cr₂ and Ni₄. The present results for spectroscopic constants and valence orbital energies obtained using medium size orbital expansions with a double-zeta representation for valence orbitals are in very good agreement with those previously calculated with very extended sets. Since the computational time of the present calculations is reduced severalfold compared with the extended basis set calculations, the present basis sets allow increased efficiency of the LCAO-LSD calculations and allow the method to be extended to larger systems.     

Produktion von β-Lactamantibiotika durch Mikroorganismen

β-lactam antibiotics are commercially and clinically important compounds that are produced by bacteria as well as by filamentous fungi. There is a great interest not only to increase the yield of microbial antibiotic production but also to generate new and highly effective antibiotics. It may be foreseen that this aim is reached by the use of in vitro recombinant technology. The biochemical as well as the physiological data which seem to be important for the understanding of β-lactam biosynthesis is filamentous fungi are summarised. In addition, recent technical advances are mentioned which become available through molecular biology. Examples are given to demonstrate the feasability of DNA recombinant technology for biotcchnical applications by introducing novel biosynthetic pathways into fungal β-lactam producers.     

LCGTO-LSD calculations for CH2

LCGTO-LSD calculations for ground (³B₁) and excited (¹A₁) states of methylene, CH₂, have been performed. Various exchange-correlation potentials and a variety of basis sets (including f functions) have been used. For both states the LSD optimized geometry agrees well with both experimental and the most advanced ab initio results. The correct ground state is found, and the ¹A₁-³B₁ energy separation was found to be ～ 15 kcal/mol, using the “best” local exchange-correlation potential (VWN ), the experimental value being ～ 9 kcal/mol. This result compares favorably with the Hartree-Fock limit separation of 25 kcal/mol. The Kohn-Sham exchange potential leads to a gap of ～26 kcal/mol.     

Applicaition of the statistical method in the theory of intermolecular interactions

The approximate way of calculating the supermolecular density applied in the Gordon and Kim method is examined. If the supermolecular density is approximated by a sum of the subsystem densities, the results for the individual contributions to the interaction energy (kinetic, potential) appear to be incorrect as compared with those obtained in the SCF approach and in first-order perturbation theory. However, a considerable improvement of the statistical results is obtained if a more suitably calculated supermolecular density is used. All calculations have been carried out for the He₂ system.