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P Horwitz

Publications and source records attributed to P Horwitz.

3 recordsLinked to original sources
PubMed2003

Preconcentration of radium isotopes from natural waters using MnO2 Resin.

We have characterized "MnO2 Resin," a new resin developed by the PG Research Foundation, for radium adsorption over wide ranges of pH, reaction times and salt concentrations. We show that the sorption of 133Ba (used as a proxy for Ra) is highly dependent on pH with the most useful range from pH 4 to 8. The surface layers of the Mn oxides apparently become more positively charged under acidic conditions (below pH 4), which prevents diffusion of positively charged alkaline earth species (e.g. Ba2+, Ra2+) into the sorption sites. Adsorption at higher pH is thought to be inhibited because of carbonate complexation. We found that the sorption characteristics for radium onto MnO2 Resin are especially favorable for low-salinity waters but the sorption is still very satisfactory for highly salted solutions (KD=2.8x10(4) in both cases) but with slower kinetics. For analytical purposes, both column and pump experiments showed high recoveries with no measurable discrimination between Ra and Ba regardless of flow rates in fresh water. Seawater tests showed that recoveries of Ra and Ba are lower than fresh water at elevated flow rates with Ra adsorption higher than Ba at flow rates above 10 ml/min.

Barium Radioisotopes↗
PubMed1994

Personnel protection during aerosol ventilation studies using radioactive technetium (Tc99m)

Two commercially available nebulizing devices used for ventilation studies were evaluated. The nebulizers use radioactive Technetium-99m (Tc99m), a potential source of room air contamination. Ambient air concentrations of Tc99m were monitored, as were the exposures of department personnel not performing ventilation studies. Room surfaces and air vents were examined to determine the extent of contamination in the examination room. Personnel were evaluated for contamination on clothing, hair, and airways when hospital lab coats and latex gloves were the only protective apparel used. Though the maximum permissible concentration of 4 x 10(-5) microCi/c3 was not exceeded, preliminary results indicated levels as high as 11,000 disintegrations/min in the nasal passages of personnel. These findings clearly demonstrate the need for more effective personal protective devices. Personnel contamination resulted primarily from the patient, due to an inability to maintain a proper oral seal on the nebulizer mouthpiece. Conventional hospital surgical masks were ineffective in reducing internal deposition to tolerable levels. By comparison, levels were reduced by 19% (p > 0.10) through use of methods such as simple body substance isolation techniques and high-efficiency disposable respirators. Levels approaching 50 disintegrations/min or less were obtainable (p < 0.001), and overall levels of Tc99m were reduced by 78%.

Aerosols↗