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S Pivovarov

Publications and source records attributed to S Pivovarov.

6 recordsLinked to original sources
PubMed2006

The Third International Intercomparison on EPR Tooth Dosimetry: part 2, final analysis.

The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation.

Electron Spin Resonance Spectroscopy↗
PubMed2005

Dispersion of components in transport processes: velocity dispersion model.

This paper presents a new model of dispersion of components in transport processes. It is suggested that the flow velocity may be specified by a Gauss function with relative dispersion of flow velocity beta=sigmav/v; the overall dispersion of inert component (in porous as well as in homogeneous medium) may be calculated from the equation sigma=(2Dt/tau2 + (betavt)2)0.5, where D is the diffusion coefficient, t is time, tau is tortuosity, and v is flow velocity. The most common range of variability of relative dispersion of flow velocity in natural soils is 8-32%. The model is well applicable to column and field experiments.

Letter↗
PubMed2005

The 3rd international intercomparison on EPR tooth dosimetry: Part 1, general analysis.

The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.

Benchmarking↗
PubMed1998

Acid-Base Properties and Heavy and Alkaline Earth Metal Adsorption on the Oxide-Solution Interface: Non-Electrostatic Model.

A new approach was applied to the description of acid-base properties and heavy and alkaline earth metal adsorption on the oxide-solution interface. The acid-base properties of hematite have been determined at different temperatures. The adsorption of protons and hydroxyl ions on the hematite surface has a temperature independent character. The proton and hydroxyl ion adsorption in NaCl media was explained by the reactions. &tbond;H2O + H3O+ + Cl- = &tbond;H2OHCl + H2O &tbond;OH2 + OH- + Na+ = &tbond;OHNa + H2O. The modified equation of the Frumkin-Fouler-Guggenheim isotherm was used to simulate the experimental data (theta, relative adsorption): log[thetaHCl/(1 - thetaHCl)] - log[H+] - log[Cl-] = log KoHCl + log BH[NthetaHCl/(1 + (N - 1)thetaHCl)]; log[thetaNaOH/(1 - thetaNaOH)] - log[Na+] - log[OH-] = logKoNaOH + logBOH[NthetaNaOH/(1 + (N - 1)thetaNaOH)]. The model parameters were log BH = -4.92 +/- 0.1, log BOH = -2.61 +/- 0.05, N = 3.25 +/- 0.2. The site density of the hematite surface was determined to be 3.8 +/- 0.1 µ moles/m2. The values of the constants were log KoHCl (25-100 degreesC) = 9.50 +/- 0.1; log KoNaOH (25-100 degreesC) = 5.93 +/- 0.1. Copyright 1998 Academic Press.

Journal Article↗
PubMed1997

Surface Structure and Site Density of the Oxide-Solution Interface.

The site densities of the surface of different oxides and hydroxides have been calculated from crystallographic data. The following values for the common habits are recommended: 2.7 nm-2 (Corundum), 2.3 nm-2 (Boehmite and Gibbsite), 2.2 nm-2 (Hematite and Rutile), 2.1 nm-2 (Lepidocrokite), 1.9 nm-2 (Diaspore), and 1.7 nm-2 (Goethite). The probable deviations due to the variations in habits are about +/-0.2 nm-2, except Rutile (+/-0.4 nm-2). For the concrete faces the values of site density are adduced. Copyright 1997 Academic Press.

Journal Article↗