Biomedical subjects

M Tarvainen

Publications and source records attributed to M Tarvainen.

3 recordsLinked to original sources

PubMed2005

Plutonium in the air in Kurchatov, Kazakhstan.

Weekly air samples of 25000 m(3) volume were taken with two air samplers over a period of one year in 2000-2001 in the town of Kurchatov in Kazakhstan. For another three-month period in 2001, the samplers were run in the city of Astana, about 500 km west of Kurchatov. (137)Cs, Pu and U concentrations were determined from the filters. Pu activities in Kurchatov varied in a 100-fold range; median (239,240)Pu activities were 100 nBq/m(3) and (238)Pu activities 34 nBq/m(3). The corresponding values for Astana were considerably lower: 29 and 9 nBq/m(3), respectively, and in half of the filters the (238)Pu activity was below the detection limit. Plutonium concentration correlated with the amount of dust retained on the filters only at the highest dust loads. Also no correlation between wind speed and the plutonium activity in the filters was observed. Thus, resuspension does not seem to be the mechanism responsible for the airborne plutonium. No clear seasonal variation of Pu air concentration was observed, though levels were somewhat elevated in February to April. There was no correlation between the plutonium and (137)Cs concentrations. In most of the filters the cesium concentration was below the detection limit, but in those filters where it could be detected the cesium concentration was practically constant at 3.9+/-1.6 microBq/m(3). Dose estimation for the inhalation of the airborne plutonium gave a low value of 0.018 microSv/a for the inhabitants in Kurchatov, which is about a thousand times lower than the dose caused by the naturally occurring (210)Po. Air parcel trajectory analysis indicated that the observed Pu activities in the air could not unambiguously be attributed to the most contaminated areas at the Semipalatinsk Test Site.

Air Pollutants, Radioactive↗

PubMed2001

Predicting plasticization efficiency from three-dimensional molecular structure of a polymer plasticizer.

PURPOSE: In polymeric coatings, plasticizers are used to improve the film-forming characteristic of the polymers. In this study, a computerized method (VolSurf with GRID) was used as a novel tool for the prediction plasticization efficiency (beta) of test compounds, and for determining the critical molecular properties needed for polymer plasticization. METHODS: The film-former, starch acetate DS 2.8 (SA), was plasticized with each of 24 tested compounds. A decrease in glass transition temperature of the plasticized free films (determined by differential scanning calorimeter (DSC)) was used as an indicator for beta. Partial least squares discriminant analysis was used to correlate the experimental data with the theoretical molecular properties of the plasticizers. RESULTS: A good correlation (r2 = 0.77, q2 = 0.58) between the molecular modeling results and the experimental data demonstrated that beta can be predicted from the three-dimensional molecular structure of a compound. Favorable structural properties identified for the potent SA plasticizer were strong hydrogen bonding capacity and a definitive hydrophobic region on the molecule. CONCLUSIONS: The VolSurf method is a valuable tool for predicting the plasticization efficiency of a compound. The correlation between experimental and calculated glass transition temperature values verifies that physicochemical properties are primary factors influencing plasticization efficiency of a compound.

Models, Chemical↗

PubMed1979

In vitro measurement of phosphorus in small bone biopsies using 14 MeV neutron activation analysis.

In studying diseases of bone such as osteoporosis and renal osteodystrophy it is important to have an index of change in bone mineral content. For this purpose we describe a method for measuring the phosphorus content of 100--150 mg bone biopsies. Femoral and iliac crest biopsies from 6 cadavers were each paired with a standard bone of similar size and irradiated with 14 MeV neutrons for 10 minutes. A special rotor ensured the same activating flux across both sample and standard bone which were both wrapped in aluminium foil. The 28Al generated from bone phosphorus (31P(n,alpha)28Al) and the 27Mg generated from the aluminium foils (27Al(n,p)27Mg), which undergo beta-decay have useful gamma rays at 1779 keV and 844 keV respectively. These gamma rays were counted using a 110 cm3 Ge(Li) detector and a rotating frame permitting four 30 s counts of sample and standard alternately (interval for rotation 10 seconds) in identical geometries. Using this system the phosphorus content of the biopsies could be determined with a coefficient of variation of 4.6% using the standard bone as reference and 6% using aluminium foil as reference. In dense bone the P/dry weight ratio was 30--50% greater than in spongy bone. The clinical value of the method is discussed.

Activation Analysis↗