Natural Occurrence of Undecaenes in Some Fruits and Vegetables

1-(E,Z)-3,5-undecatriene and 1-(E,Z,Z)-3,5,8-undecatetraene were isolated under enzyme inhibition from edible parts of peach, passion fruit, and kiwi; the triene only was found in celery, parsley, mandarine, apple and pear. Capillary gas chromatography, sniffing-capillary gas chromatography, and combined “live”-capillary gas chromatography-mass spectrometry of the concentrated liquid-liquid extracts were used to establish their identity. Owing to their ultra-low odor detection thresholds and the proposed biogenesis, these trace compounds may be “character impacts” in a wide variety of food flavors of plant origin.     

Spontaneous Cracking in Unfired Magnesia Compacts Upon Standing in Air

Analytical-grade magnesium oxide powder without binder was compressed hydrostatically to 50,000 lb. per sq. in. to form compacts. When exposed to moist air immediately after pressing, these compacts developed irregularly shaped cracks. Controlled tests, in which these compacts were exposed for various lengths of time to various atmospheres, indicated that in general water vapor, carbon dioxide, and residual stresses had to be present if cracking was to occur. The probable cause of the cracking was the formation of a less dense and mechanically weak basic carbonate of magnesium at crystallite surface points of high stress concentration which developed during the compacting. The adsorption of dry CO₂ at such sites prevented subsequent delayed fracture.     

Aerosol Sampling Efficiency in a Model Room

The sampling process of a model room with a suction nozzle in a calm or low movement environment was numerically simulated and experimentally analyzed. Computational fluid dynamics (CFD) software, Fluent (Fluent Inc.), was used for the numerical simulation. The flow was considered to be compressible and turbulent, and particles were considered to be spheres of constant density. A good agreement was found between the numerical and experimental results (maximum difference of 15% in the overlapping zone), and the numerical model was further extended and used for parametric analysis. The influence of sampling velocity and shape of the suction nozzle on sampling efficiency was investigated experimentally and numerically in a particle size range of 2–45 µm. It was found that sampling efficiency is smaller for V-shaped nozzles, mainly for lower velocities. Sampling efficiency was calculated for each particle diameter and for the whole particle size distribution as well. Sampling efficiency decreases as particle size increases. It is concluded that knowledge of sampling efficiency for each of the sampled particle sizes may indicate the concentration and size distribution in the sampled space.     

An extended X-ray absorption fine structure investigation on the local environment of niobium ions in Nb2O5-doped SrTiO3 glass ceramics

The dielectrical properties of glass ceramics derived from SrO–B2O3–Al2O3–TiO2 glasses are improved by doping the starting material with Nb2O5 and judicious choice of heat treatment conditions. In order to understand this effect the local environment of the niobium ions is studied by EXAFS (extended X-ray absorption fine structure) investigations at the Nb-K edge. For comparison purposes Ti-K and Sr-K EXAFS spectra have also been measured. The experiments suggest that the niobium ions are incorporated onto titanium sites in the crystalline SrTiO3 phase formed during the thermal treatment. This revised version was published online in November 2006 with corrections to the Cover Date.