Ultrasound-assisted regeneration of zeolite/water adsorption pair.

The use of ultrasound to enhance the regeneration of zeolite 13X for efficient utilization of thermal energy was investigated as a substitute to conventional heating methods. The effects of ultrasonic power and frequency on the desorption of water from zeolite 13X were analyzed to optimize the desorption efficiency. To determine and justify the effectiveness of incorporating ultrasound from an energy-savings point of view, an approach of constant overall input power of 20 or 25 W was adopted.

Protonation thermochemistry of selected hydroxy- and methoxycarbonyl molecules.

The gas-phase basicities of a representative set of hydroxy- and methoxycarbonyl compounds (hydroxyacetone, 1, 3-hydroxybutanone, 2, 3-hydroxy-3-methylbutanone, 3, 1-hydroxy-2-butanone, 4, 4-hydroxy-2-butanone, 5, 5-hydroxy-2-pentanone, 6, methoxyacetone, 7, 3-methoxy-2-butanone, 8, 4-methoxy-2-butanone, 9, and 5-methoxy-2-pentanone, 10) were experimentally determined by the equilibrium method using Fourier transform ion cyclotron resonance and high-pressure mass spectrometry techniques. The latter method allows the measurement of proton transfer equilibrium constants at various temperatures and thus the estimate of both the proton affinities and the protonation entropies of the relevant species. Quantum chemical calculations at the G3 and the B3LYP/6-311+G(3df,2p)//6-31G(d) levels of theory were undertaken in order to find the most stable structures of the neutrals 1-10 and their protonated forms.

Reassessing the level of unintended pregnancy and its correlates in Vietnam.

Despite rapidly increasing contraceptive use and rapidly declining fertility, unintended pregnancy and induced abortion remain common in Vietnam. This study reassesses the level of unintended pregnancy in Vietnam and its correlates, drawing on retrospective calendar data gathered for the Vietnam Demographic and Health Survey II. Data from 13,540 "segments" of outcomes and contraceptive practice were analyzed.