An impedance analyzer method to simulate the oscillating characteristic of a series piezoelectric sensor in oscillators with zero or non-zero phases

An impedance analyzer method is employed to simulate the oscillation frequency of a series piezoelectric quartz crystal (SPQC) in electrolyte or non-electrolyte solutions. The influence of the oscillator phase on the oscillation frequency and response sensitivity are theoretically derived and experimentally verified. In non-electrolyte liquids, the oscillator phase has little effect on both the oscillation frequency and the response to the permittivity. But in electrolyte solutions, the oscillator phase has a significant influence on the oscillation frequency and the response sensitivity to the conductivity. Depending on the oscillator phase, the oscillation frequency of the SPQC may increase, be maintained or decrease with increasing conductivity in low or high conductive solutions. The dependence of the oscillation frequency of the SPQC on the supply voltage is explained. As an example of the applications, the SPQC is applied to the determination of the critical micelle concentration of ionic surfactants in aqueous solutions.     

The effects of media properties on the horseradish peroxidase-catalyzed fluorogenic reaction

The effects of media properties including buffers, acidity, solvents and surfactant on horseradish peroxidase-catalyzed fluorogenic reaction were investigated. The results showed that the so-called non-fluorescent hydrogen donors were in fact fluorescent. There existed an acid—base equilibrium in the fluorescent dimer product. For p -hydroxyphenylpropionic acid, a pK_a value of 8.0 for the product was obtained from its titration curve. The product fluorescence increased with higher pH, however, a longer time was needed to reach the reaction equilibrium due to the pH mismatch problem. Cationic micelles cetyltrimethylammonium bromide and cetyltrimethylammonium chloride could reduce the pH mismatch and offered a way to further increase the determination sensitivity. Finally, a micelle-enhanced flow-injection analysis of horseradish peroxidase is suggested.     

NLS-tupe equations in 2+1 dimensions: New type of solutions and non-isospectral problems

Integrable systems of NLS type in 2+1 dimensions are studied in three ways: their special solutions by Lie point symmetries, breaking-solutions by the ISM, as well as the non-isospectral problems.Department of Mathematics, Statistics and Computing Science, University of New England, Armidale N.S.W. 2351, Australia. E-mail: zhuhan@neumann.une.edu.au, xhe@metz.une.edu.au Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 99, No. 3, pp. 382–389, June, 1994.     

Separation of polycyclic aromatic hydrocarbons by micellar electrokinetic chromatography with aqueous short-chain alcohol solvent

Micellar electrokinetic capillary chromatography (MEKC) with aqueous organic solvent has been developed to separate polycyclic aromatic hydrocarbons (PAHs). Methanol, ethanol or propanol as an organic modifier was added to sodium dodecyl sulfate (SDS) micellar solution in order to increase the solubility of very hydrophobic solutes in mobile phase. Both methanol and ethanol can be used as co-solvents for the separation of PAHs. Use of ethanol resulted in a shorter analysis time than use of methanol. The separations of some PAHs were unsatisfactory using propanol although the analysis time was much shorter than with ethanol. The influence of ethanol content, SDS concentration and temperature on the separations was studied. Benzene and nine polycyclic aromatic hydrocarbons were successfully separated using 50 mM SDS-20 mM phosphate-5 mM borate, containing 40% (v/v) ethanol at 35 degrees C. The relative standard deviation (R.S.D.) of t(R) ranged from 0.5 to 1.5% for six repeat injections.     

TheΛ b →Λ c decay form factors

The recently measured cross-sections for diffractive dissociation of nuclei in high-energy proton nucleus (pA) collisions show a strikingA ^1/3 dependence on the target massA. Such a dependence emerges from an optical model which incorporates a simple mechanism to produce the absorption fluctuations required for inelastic diffraction. The observed momentum transfer (t) dependence of the differential cross-section, dσ/dt∝ exp(?B|t|), is described in terms of a correlation length \(R_F = \sqrt {2B} \) of the absorption fluctuations which turns out to be of the size of a nucleon. The excitation massM dependence, dσ/dM ²∝M ^?2, is explained by a bremsstrahlung mechanism.