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Biomedical subjects

I Kobal

Publications and source records attributed to I Kobal.

At least 19 recordsLinked to original sources
PubMed2006

High natural radiation exposure in radon spa areas: a detailed field investigation in Niska Banja (Balkan region).

The measurement campaigns have been done in the rural community of Niska Banja, a spa town located in southern Serbia, to evaluate population exposure to natural radioactivity. After a screening survey in 200 houses, annual radon and thoron concentrations were measured in 34 houses, and in 2004 a detailed investigation was carried out at six houses with elevated indoor radon concentrations. The paper presents the results of these detailed measurements. The complementary techniques were applied to determine radon and thoron concentrations in indoor air, in soil gas, radon exhalation from soil, soil permeability, and indoor and outdoor gamma doses. Soil and water samples were collected and analysed in the laboratory. Indoor radon and thoron concentrations were found to be more than 1kBqm(-3) and 200Bqm(-3), respectively. Extremely high concentrations of soil-gas radon (>2000kBqm(-3)) and radon exhalation rates (1.5mBqm(-2)s(-1)) were observed. These results will be utilised to set up the methodology for a more systematic investigation.

Air Pollution, Indoor↗
PubMed2006

Radon in a thermal spring: identification of anomalies related to seismic activity.

Anomalies have been observed in the radon content of thermal spring water at the Italian-Slovenian border. To distinguish the anomalies caused by environmental parameters (air and water temperature, barometric and hydrostatic pressure, rainfall) from those ascribed solely to earthquakes with M(L) from 1.2 to 2.5 and epicentres, R(E), within 2R(D) (R(D)--Dobrovolsky's radius), two approaches have been used: (i) correlation between time gradients of radon concentration and hydrostatic pressure, and (ii) regression trees within machine learning programs. The regression trees approach has been improved by introducing additional environmental parameters and prolonging the measuring period.

Disasters↗
PubMed2003

Application of decision trees to the analysis of soil radon data for earthquake prediction.

Different regression methods have been used to predict radon concentration in soil gas on the basis of environmental data, i.e. barometric pressure, soil temperature, air temperature and rainfall. Analyses of the radon data from three stations in the Krsko basin, Slovenia, have shown that model trees outperform other regression methods. A model has been built which predicts radon concentration with a correlation of 0.8, provided it is influenced only by the environmental parameters. In periods with seismic activity this correlation is much lower. This decrease in predictive accuracy appears 1-7 days before earthquakes with local magnitude 0.8-3.3.

Decision Trees↗
PubMed2002

Soil radon monitoring in the Krsko Basin, Slovenia.

In order to support the safe operation of the Krsko Nuclear Power Plant (Westinghouse, 676 MWe PWR), the seismotectonic structure of the Krsko basin has been thoroughly investigated. As part of a wider study, a study on radon in soil gas was started in April 1999. Combined barasol detectors buried in six boreholes, two along the Orlica fault and four on either side of it, measure and record radon activity, temperature and pressure every 60 min. The results have been evaluated and the possibility of a correlation with seismic activity is discussed. Correlation between radon concentration and barometric pressure has been observed for all barasols. Preliminary results show that, at one location, the correlation coefficient between radon and barometric pressure changed sign before earthquakes.

Journal Article↗
PubMed2002

Geochemical monitoring of thermal waters in Slovenia: relationships to seismic activity.

Thermally anomalous fluids released in seismic areas in Slovenia were the subjects of geochemical monitoring. Thermal waters were surveyed from the seismically active area of Posocje (Bled and Zatolmin; NW Slovenia) and from Rogaska Slatina in eastern Slovenia. Continuous monitoring of geochemical parameters (radon concentration, electrical conductivity, and water temperature) was performed with discrete gas sampling for their (3)He/(4)He ratio. The observed values were correlated with meteorological parameters (rainfall, barometric pressure and air temperature) and with seismic activity. Only a few earthquakes occurred in the vicinity of the measuring sites during the monitoring period. Nevertheless, changes in radon concentration, water temperature, electrical conductivity and helium isotopic ratio were detected at the three thermal springs in the periods preceding the earthquakes. A close correlation was also observed of both water temperature and electrical conductivity with the Earth tide, making the observations in the selected sites a promising tool for addressing the widely debated question of earthquake prediction.

Journal Article↗
PubMed2002

Correlation between short-term and long-term radon measurements.

In selected kindergartens and schools, long-term average indoor air radon concentrations were measured by two-month exposure of etched track detectors. Short-term average concentrations were obtained from 7-10 day continuous radon recordings during the exposure of etched track detectors. Only in about 1/3 of cases both averages did agree within +/- 20%; otherwise they differ considerably. The assumption that short-term results can substitute for long-term data, which is sometimes made to correct radon exposure estimated on the basis of concentrations obtained by etched track detectors, should therefore be treated with caution.

Air Pollution, Indoor↗
PubMed2001

Carbon isotope fractionation in the decarboxylation of phenylpropiolic acid in hydrogen donating media.

13C kinetic isotope effect (KIE) in the decarboxylation of phenylpropiolic acid (PPA) in tetralin medium (Tn) has been determined at 409-432 K and found to be of magnitude similar to the 13C KIE observed in the decarboxylation of malonic acid where the rupture of the C-C bond is the rate determining step. 13C KIE equals 1.0318/at 136 degrees C in the decarboxylation of PPA in Tn medium. Intramolecular 13C KIE in the decarboxylation of malonic acid equals 1.0316 at this temperature. Thus it has been shown that the nearly "full" 13C KIE can be achieved by providing the excess hydrogen to Calpha of PPA (or to triple acetylene bond) using not only strong mineral acids as the source of protons but also by carrying out the decarboxylation in organic medium like tetralin. A mechanism of decarboxylation of PPA in Tn is suggested.

Carbon Isotopes↗
PubMed2001

Radon exposure in slovene kindergartens based on continuous radon measurements.

Contiunuous measurements of concentration of radon and radon decay products, and equilibrium factor were carried out in the indoor air of 13 kindergartens at the beginning of 2000. Average values of the parameters measured during working time only and during the whole period, were compared and applied to estimate effective doses to the personnel. Results of short-term continuous measurements were used to correct the exposure, based generally on the radon concentration.

Air Pollution, Indoor↗
PubMed2001

Radon exposure in Slovenian spas.

Radon and gamma dose rates were surveyed in five Slovenian spas, at Rogaska Slatina, Radenci, Moravci, Podcetrtek, and Catez. Due to effective ventilation systems, the indoor air radon concentration rarely exceeds 200 Bq x m(-3) and is usually lower. Uncer the present operationsal conditions and working regimes of the spas, there is no basis for concern about elevated exposure of personnel to radon.

Air Pollutants, Radioactive↗
PubMed2001

Methodology of radon monitoring and dose estimates in Postojna Cave, Slovenia.

Due to the specific work regime in the Postojna Cave, which depends primarily on the daily number of visitors, and on seasonal variations in air radon concentrations, an optimal methodology for radon and progeny measurement and dose calculation was sought. The program of measurement throughout the years was optimized, and now comprises 3-mo exposures of etched-track detectors, and twice a year, 8-10-d measurements using continuous monitors. Radon concentrations range from about 500 Bq m(-3) in winter to about 6,000 Bq m(-3) in summer, and equilibrium factors range from 0.42 to 0.69 in winter and from 0.33 to 0.86 in summer. Radiation doses from radon decay products for employees in the cave were calculated according to the ICRP 65 methodology. The basic input data are radon concentrations and equilibrium factors at two selected locations in the cave and the records of the time spent by a worker in the cave. Effective doses received by employees annually ranged from 0.02 to 8.4 mSv.

Environmental Exposure↗
PubMed2000

Systematic indoor radon and gamma-ray measurements in Slovenian schools.

During the winter months of 1992/93 and 1993/94, instantaneous indoor radon concentrations and gamma dose rates were measured in 890 schools in Slovenia attended in total by about 280,000 pupils. Under "closed conditions," the room to be surveyed was closed for more than 12 h prior to sampling, the air was sampled into alpha scintillation cells with a volume of 700 cm3, and alpha activity was measured. An arithmetic mean of 168 Bq m(-3) and a geometric mean of 82 Bq m(-3) were obtained. In 67% of schools, indoor radon concentrations were below 100 Bq m(-3), and in 8.7% (77 schools with about 16,000 pupils) they exceeded 400 Bq m(-3), which is the proposed Slovene action level. In the majority of cases, radon concentrations were high due to the geological characteristics of the ground. Approximately 70% of schools with high radon levels were found in the Karst region. Gamma dose rates were measured using a portable scintillation counter. An arithmetic mean of 102 nGy h(-1) and a geometric mean of 95 nGy h(-1) were obtained. No extraordinarily high values were recorded.

Adolescent↗
PubMed1997

Investigation of the Electrical Double Layer in a Metal Oxide/Monovalent Electrolyte Solution System

Adsorption of the monovalent cations Cs+ and Na+ from mixed solutions of NaCl and CsCl at the TiO2(anatase)/water interface was studied. Higher adsorption of Cs+ than Na+ was observed from solutions of similar electrolyte concentration. The surface ionization and complexation constants of surface hydroxyl groups were determined using potentiometric titration data. Results for the adsorption of Cs+ and Na+ from mixed electrolyte solutions showed that these ions adsorb at different distances from the metal oxide surface.

Journal Article↗
PubMed1994

Systematic indoor radon and gamma measurements in kindergartens and play schools in Slovenia.

Systematic measurements of indoor radon concentrations and gamma dose rates were carried out in the 730 kindergartens and play schools in Slovenia that, together, care for 65,600 children. The main method for indoor radon measurement was direct sampling in alpha scintillation cells, but in cases with an increased instantaneous radon concentration, the additional methods of track-etch detectors and alpha spectroscopy were applied. In 528 kindergartens and play schools (72%), radon concentrations were below 100 Bq m-3, with a geometric mean of 58 Bq m-3. In 16 kindergartens and play schools (2.2%), radon concentrations exceeded 800 Bq m-3. In all cases, the main reason for a high indoor radon concentration was the geological structure of the soil. Gamma dose rates were measured with a portable scintillation counter, but in the Ljubljana region thermoluminescence dosimeters were also exposed. The results ranged from 30 to 295 nGy h-1, with a geometric mean of 88 nGy h-1.

Air Pollution, Indoor↗
PubMed1994

Radon level reduction in two kindergartens in Slovenia.

Remedial actions were carried out in two kindergartens with average heating season radon concentrations of about 2,000 Bq m-3. The first kindergarten is built on sedimentary gravel and the second one on fly ash and cinder fill. In both cases, radon accumulated in a sub-floor channel (service tunnel). The channels were opened at both ends. Natural ventilation of the tunnels did not produce a sufficient reduction in radon concentration. A fan was mounted in one kindergarten to ventilate the channel for 20 min three times each day, thus reducing radon levels to an acceptable value.

Air Pollution, Indoor↗
PubMed1993

Preliminary indoor radon investigations in Lublin region, Poland.

Indoor air radon concentrations in all kindergartens and play schools in Lublin, Poland, were determined in grab samples by using alpha scintillation cells. In addition, some public buildings and homes in Lublin and several places in Eastern Poland were surveyed for radon. For kindergartens and play schools, the geometric mean was 23 Bq m-3 with a standard deviation of 1.4 Bq m-3, while in public buildings and homes, these values were 26 and 1.6 Bq m-3, respectively.

Air Pollution, Indoor↗
PubMed1988

Atmospheric radon concentrations in dwellings in Slovenia, Yugoslavia.

About 120 homes in Slovenia, Yugoslavia, were selected in urban areas, in a uranium rain and mill region, around coal-fired plants and around a phosphate mill. Radon-222 in air was determined using alpha scintillation cells and the gamma dose rate measured with thermoluminescent dosimeters. The levels obtained were explained by differences in building materials and ventilation rates of homes, as well as by the influence of man-made radioactivity sources. The results show that in the same region radon concentration, expressed as geometric mean, can be up to eight times higher in winter than in the autumn (Pohorje) or nine times higher in one region relative to another (Zirovski vrh-Zasavje).

Air Pollutants↗