Direct versus resonances mediated F+OH collisions on a new 3A" potential energy surface

A theoretical study of the F(2P) + OH(2Pi) --> HF(1Sigma+) + O(3P) reactive collisions is carried out on a new global potential energy surface (PES) of the ground 3A" adiabatic electronic state. The ab initio calculations are based on multireference configuration interaction calculations, using the aug-cc-pVTZ extended basis sets of Dunning et al. A functional representation of the PES shows no nominal barrier to reaction, contrary to previous results by others. Wave packet and quasiclassical trajectory calculations have been performed for this PES to study the F + OH(v = 0,j) reactive collision. The comparison was performed at fixed and constant values of the total angular momentum from 0 to 110 and relative translational energy up to 0.8 eV. The reaction presents a dynamical barrier, essentially due to the zero-point energy for the bending vibration near the saddle point. This determines two different reaction mechanisms. At energies higher than approximately 0.125 eV the reaction is direct, while below that value it is indirect and mediated by heavy-light-heavy resonances. Such resonances, also found in the simulations of the photodetachment spectrum of the triatomic anion, manifest themselves in the quasiclassical simulations, too, where they are associated to periodic orbits.     

Derivatization of tertiary amphetamines with 9-fluorenylmethyl chloroformate for liquid chromatography: determination of N-methylephedrine

The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) was evaluated for the derivatization of tertiary amphetamines prior to liquid chromatographic analysis. Conditions for the derivatization were investigated, including the reaction time, the derivatization reagent concentration and the pH, using N-methylephedrine as a model compound. On the basis of these studies, a method for the quantification of N-methylephedrine is presented. The method involves derivatization with FMOC at ambient temperature and separation of the derivatives formed on a LiChrospher C18, 5 microns, 125 x 4 mm id column using acetonitrile-water gradient elution. The proposed procedure shows good linearity, accuracy and reproducibility in the 1.0-25.0 micrograms mL-1 concentration range. The limit of detection was 0.1 microgram mL-1 and the limit of quantification was 0.5 microgram mL-1. The utility of the assay was demonstrated by determining N-methylephedrine in water and urine samples.     

Absolute line intensity measurements of hot bands for carbonyl sulfide at 12 microm

Using diode-laser spectroscopy, the intensities of 58 lines of the v(1) + v(1/2) - v(1/2) band and 36 lines of the 2v(1) - v(1) band of OCS have been measured. The corresponding band strengths S(0)(v) and the vibrational transition dipoles micro(v) have been derived through least squares fitting of these individual intensities. The band strengths values have been determined with a precision better than 2.5%.     

Extraction of cesium into nitrobenzene using hydrogen dicarbollylcobaitate in the presence of dibenzo-24-crown-8

Extraction of microamounts of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibenzo-24-crown-8 (DB24C8,L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺ and CsL⁺ are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Extraction--spectrophotometric determination of oxalate in urine and blood serum

An extraction--spectrophotometric method is described for the determination of oxalate, based on the formation of a mixed ligand vanadium (V)--mandelohydroxamic acid--oxalate complex. The complex was extracted into a solution of trioctylmethylammonium chloride (Adogen 446) in toluene and the absorbance measured at 535 nm. The experimental variables and interferences in this determination were studied. The detection limit is 0.5 microgram ml-1 and the range of application is between 2 and 8 micrograms ml-1. The method was applied to the determination of oxalate in urine and blood serum.     

Photochemical degradation of hyaluronic acid by singlet oxygen

Changes of the rheological properties of hyaluronic acid (sodium-magnesium salt) solutions after exposure to UV radiation indicate a vigorous decrease in their viscosity, but its still strong shear rate dependence. Whereas the presence of the singlet oxygen sensitizer (anthracene-1-sulphonic acid) brings about a loss of shear dependence; the studied solutions show newtonian behavior.     

Longitudinal acceptance computation for A 50 MeV race track microtron

The algorithm for analysing of longitudinal motion and for calculating phase trajectory in race track microtron (RTM) with small injection energy and small energy gain per turn is described. A longitudinal acceptance is calculated.We are indebted to E. A. Perelshtein and N. Ju. Kazarinov and A. Ju. Molodozhencev for stimulating advices. We thank M. Slodika for work with program coding.     

Molecular intercalates

The paper deals with the relations between host lattices and guest molecules. Several types of interaction of the guest molecules and the host material are explained and some conclusions are made about the arrangement of various guest molecules in the van der Waals' gap.