Experimental and simulational study of the operation conditions for a high transmission mass filter.

The operation conditions of a double pulsed field mass filter were studied using both experiment and simulation. The mass filter consists of two pairs of parallel plates and operates on the time-of-flight principle. The study showed that the ions' beam deflection angle is a critical factor in optimizing the mass filter transmission efficiency. This angle is dependent on the accelerating voltage, ion mass, and horizontal velocity of the ions. The optimum operating conditions for the mass filter were found and used to study the mass distribution of palladium ions produced by a magnetron sputtering source. The study shows that this mass filter is suitable for technological applications because of its high transmission and wide mass range.

Structure of oxidized bismuth nanoclusters.

Synchrotron X-ray diffraction has determined that beta-Bi(2)O(3) is the dominant oxide phase covering hexagonal bismuth nanoclusters produced in an inert gas aggregation source. Simulated Debye-Scherrer patterns have indicated that the oxide is 20 +/- 5 Angstroms thick on average, at the surface of 320 +/- 40 Angstroms diameter clusters. A Williamson-Hall analysis of the peak broadening was used to measure the non-uniform strain in clusters. The oxidized clusters were in -0.11 +/- 0.06% uniform compressive strain compared with other clusters without oxides detectable by X-ray diffraction which only have a small tensile uniform strain. High-resolution transmission electron microscopy (HRTEM) and multislice image simulations indicated a beta-Bi(2)O(3) thickness of 20-50 Angstroms. The HRTEM micrographs show the relative orientation between the oxide and the cluster core.

Effect of high pressure ammoniation procedure on the detoxification of aflatoxins.

Ammoniation represents the best technique to detoxify aflatoxin-contaminated grain and it is considered as economically practicable for commercial applications. In the present studyAspergillus parasiticus was used to contaminate yellow corn to produce the final concentration reached 4000 µg/kg corn total aflatoxin. Two procedures of ammoniation (in aqueous ammonia concentrations, 0.25, 0.5, 1, 1.5 and 2% ) were adopted for aflatoxin destruction. The first procedure was under atmospheric pressure at ambient temperature (AP/AT) for 24 hrs, and the second procedure was under high pressure (2 bar) at high temperature (121°C) (HP/HT ) for 15 min. Aflatoxin concentrations were determined by HPLC using fluorescence detection. The effect of HP/HT procedure was compared with the ammoniation procedure under AP/AT. The detoxification pattern of the two ammoniation procedures as well as the detoxification pattern of the different types of aflatoxins under the two procedures was studied.