Background airborne radioactivity in an equatorial Brazilian town

The aim of this work was to determine the background airbome radioactivity in the town of Natal, Brazil. Indoor radon concentrations were measured inside 24 buildings using solid state nuclear track detectors which were exposed for a period of about 180 days. The average indoor radon level resulted to be 15.4±10.6 Bq·m^–3. Measurements of gross - and -activities were performed at six different sites for airbome particulate samples collected over cellulose nitrate filters. Mean values of 0.15±0.06 mBq·m^–3 and 0.42±0.10 mBq·m^–3 were obtained for the gross -and gross -activity, respectively.     

Radiation dose contribution from coal-slags used as structural building material

A significant dose contribution on the population could be derived from coal slags used as isolation material. Extremely high natural activities are measured in the coal slag, derived from the region of the settlement Ajka, Hungary. In some buildings monitored, the elevated -doses were nearly 5–10 times higher than the world average ones. The annual average indoor radon concentrations from the slag exceeded 400 Bq/m³ and in some cases up to 1200 Bq/m³. Due to the elevated exposure and the radon concentrations in the dwellings the annual dose was estimated to 8–24 mSv/y more than 5–10 times of the world average one.     

Experimental and theoretical considerations on the calibration factor K between α-activity concentration and track density for application in radon dosimetry

This paper describes a new version of the measurement of the calibration factor, K, between radon activity concentration and track density. The use of Solid State Nuclear Track Detectors (SSNTDs) is one of the most convenient techniques to assess the radiation level of -activities in the environment. Exposed plastic films are chemically and electrochemically etched in an alkali solution and the -tracks are evaluated under an optical microscope. The detailed procedure for this study and the caliabration of the etched films for conversion of track density to radon exposure in (Bq·m^–3) are given in this paper. It was found the experimental and theoretical values of K were 1.37 and 1.27 (track·cm^–2·kBq^–1·h^–1·m³), respectively, for plastic detectors CR-39.     

Rn-222 air concentrations in Chihuahua State (Mexico) dwellings and in the U.S./Mexico border

Using charcoal detectors and electrets, radon concentrations were measured at 12 different locations in Mexico, homes in particular, throughout Chihuahua State. While these measurements were short-term, long-term measurements were also conducted around Chihuahua and Aldama cities using LR-115 II type detectors. In addition, LR-115 II type detectors were deployed for comparative purposes between Ciudad Juarez (Mexico) and El Paso (Texas). Significant average radon values were obtained in Aldama and Parral at 225 and 173 Becquerel per cubic meter (Bq m^− 3), respectively. Over 30% of the homes sampled in Aldama, Cuauhtemoc, Parral and Chihuahua had radon concentrations greater than 148 Bq m^− 3.     

90Sr and137Cs in fallout from Chernobyl in the Bucharest-Măgurele area during 1986–1987

This work shows the variation of⁹⁰Sr and¹³⁷Cs in atmospheric fallout in the Bucharest-Mgurele area during 1986–1987. The amount of⁹⁰Sr in the fallout was estimated to be about 900 Bq.m^–2 in 1986 and about 9.2 Bq.m^–2 in 1987. The amount of¹³⁷Cs was estimated to be 13300 and 615 Bq.m^–2 in 1986 and 1987, respectively.     

Radon measurement by coincidence gamma-ray spectrometry

A method of radon measurement by a multidetector -ray spectrometer,based on coincidence counting of 609 keV photons from two-step cascade transitionsthat follow â – decay of 214 Bi, is proposed. Besides a good accuracy,the method has better sensitivity than some standard methods of radon measurementcurrently in use. Applying this method to the PRIPJAT-2M spectrometer with6 NaI(Tl) detectors, and counting a 1 l sample of well water for 30 minutes,a minimum detectable radon activity of 0.25 Bq/l is experimentally determined.     

Influence of pollution and building materials on domestic radioactivity in Marrakechi dwellings

Domestic radioactivity has been studied by using LR-115 and CR-39 solid state nuclear track detectors (SNTD) and a suitable beta- and gamma-gaseous counter. A new calibration method, based on measuring thoron (²²⁰Rn) to radon (²²²Rn) ratios, has been developed for determining the -activity originating from radon in different Marrakechi dwellings. The influence of building materials as well as pollution and airing factors, on domestic radioactivity has been investigated.     

Spectrophotometric extractive determination of thiolactams with picric acid and silver

Summary Spectrophotometric Extractive Determination of Thiolactams with Picric Acid and Silver The thiolactams (Tpl, Tpr, Tkl, Tel) form with Ag⁺ and picric acid in solutions a complex with a molar ratio of AgTLpicric acid=1:1:1, which can be extracted into chloroform. The composition of the solid complexes of thiolactam is 121 (AgTLR). The formation of ternary complexes was used in the spectrophotometric determination of thiolactams in a concentration range of 0.2–5.0g/ml. Lactams do not influence the analytical response. The method is applicable to the determination of the thiolactams in a mixture of caprolactam and in xylene solutions during their synthesis.Communication presented at the European Conference on Analytical Chemistry (Euroanalysis V) Cracow, Poland, August 26–31, 1984.     

Determination of Radon Equivalent Alpha-Doses in Different Human Organs from Water Ingestion Using SSNTD and Dosimetric Compartmental Models

Radon -activities per unit volume have been measured in different drinking water samples belonging to different aquifers and sources by using CR-39 and LR-115 solid state nuclear track detectors (SSNTD). Radon initial equivalent -dose rates due to water ingestion have been evaluated in the stomach assuming that all the radon ingested appears in this organ. The influence of the origin and quality of the water samples studied has been investigated. Committed equivalent doses have been determined in different human organs by using dosimetric compartment models. The influence of the radon mean residence time on the committed equivalent doses in the different compartments of the gastrointestinal system has been studied. The committed equivalent dose per unit activity of radon ingested has been evaluated in the stomach tissue and compared with literature data.     

Stratigraphical Study of Quaternary Travertine Samples by Using CR-39 and LR-115 Solid State Nuclear Track Detectors

Radon -activity, uranium content and activity ratios of uranium and thorium [A _c (²³⁸U)/A _c (²³²Th)] have been determined in different layers of stratigraphical quaternary travertine deposits in the Errachidia area (High-Atlas, Morocco), by using two solid state nuclear track detectors (SSNTD), of CR-39 and LR-115 type II. The mineralogy of samples has been determined by X-ray diffraction. Correlation between the stratigraphy, uranium content and radon -activity has been investigated. An uranium-aragonite association has been found.     

Novel studies on the temperature-dependence of electric and photovoltaic properties of thin CdSe films for solar cells

Thin CdSe films were prepared under vacuum at different glass substrate temperatures. The effects of substrate heating and temperature on the X-ray diffraction patterns, electrical, DC current-voltage characteristics and photovoltaic properties were investigated in detail. the results obtained were interpreted mathematically, which led to a hopping conduction mechanism. Valuable semiconducting parameters were evaluated for the thin films investigated, for their useful application in photovoltaic or solar cell industries: surface charge density (4.8×10¹² cm^–2), thickness of depletion layer (7.4×10^–7 cm) and donor concentration (6.5×10¹⁸cm^–3).

---

Zusammenfassung Dünne Cd-Se-Filme wurden unter Vakuum bei verschiedenen Glassubstrattemperaturen hergestellt. Die Auswirkung der Substraterhitzung und -temperatur auf die röntgendiffraktogramme, die elektrische und Gleichstromspannungscharakteristik und die Sperrschichtphotoeigenschaften wurden detailliert untersucht. Die erhaltenen Ergebnisse wurden mathematisch interpretiert, was zu einem Sprungleitungsmechanismus führte. Halbleiter-Parameter der Untersuchten dünnen Filme wurden für den Gebrauch in der Sperrschicht- und Solarzellen herstellenden Industrie ermittelt: Dichte der Oberflächenladung (4,8·10¹² cm^–2), Dicke der trägerverarmten Schicht (7,4·10^–7 cm) und Donorkonzentration (6,5·10¹⁸ cm^–3).

---

CdSe . , , . , . , : 4,8·10^{12 –2}, 7,4·10^–7 6,5·10^{18 –3}.

     

Determination of137Cs and134Cs in air samples collected near Belgrade /Yugoslavia/ following the Chernobyl accident

This paper presents the results of measurements of¹³⁷Cs and¹³⁴Cs content in air sampled during May 1986. Maximum concentrations:¹³⁷Cs 2.94±0.01 Bq m^–3 and¹³⁴Cs 1.38±0.01 Bq m^–3 were registered on May 3. Several other long lived radionuclides having -energies in the region 33 keV to 1365 keV were registered in the same samples two years later. The results of measurements of the total -activity in air for the same period are also presented.     

Radon in the spa of Bizovac

The radon concentration in the air and water of the Bizovac spa was measured by the Radhome silicon detector and the average values were obtained as 70 Bq/m³ in the indoor pool, 40 Bq/m³ in the hotel room, 135 Bq/m³ in the closed therapeutic bathroom, but the geothermal water had a Rn concentration of 25.3 kBq/m³ and the potable one 2.7 kBq/m³. The Rn transfer factor (f) from water to air in the indoor pool and therapeutic bathroom was 10 and 40 times higher than for normal dwellings (f _n=10^–4), respectively. The effective equivalent dose of inhaled radon for permanent personnel under the worst conditions in the spa was 5.4 mSv/y, but visitors spending two weeks in the spa could receive the dose of 77 Sv.     

Calibration coefficient of the SSNTD and equilibrium factor for radon

Disintegration, ventilation and deposition were considered as removal processes of the radon and its short-lived daughters in air and the respective concentration equations were applied. Calibration coefficient (K_F) of the solid state nuclear track detector (SSNTD) LR-115 for radon and the equilibrium factor (F) were related to track densities of the bare detector (D) and the filtered one (D_o). A useful relationship between K_F, F and detector sensitivity coefficient (k) was derived. Using the calibrated value k=3.29×10^–3 m, the exposed detectors gave the average values of the equilibrium factor, calibration coefficient and indoor radon concentration of a single house living room in Osijek 0.46, 142.3 m^–1 and 37.8 Bq m^–3, respectively.     

Non-destructive determination of low-level210Pb and226Ra with an ordinary high-purity Ge-detector

A convenient non-destructive method for the determination of low level²¹⁰Pb and²²⁶Ra with an ordinary high-purity Ge-detector is presented. The ordinary Ge-detectors used in this work were available to measure 46.5 keV -rays of²¹⁰Pb. These detectors were also useful for the non-destructive analysis of low-level²²⁶Ra in lime-stone and calcium chemicals when a stream of nitrogen gas was maintained around the detectors. By this method, measurements could be carried out not only for²¹⁰Pb and²²⁶Ra but also for other -emitting radionuclides simultaneously, using the same detector. The detection limits of about 1 Bq per sample for²¹⁰Pb and about 0.05 Bq per sample for²²⁶Ra, respectively, were estimated, when the samples were counted for 1–2 days.     

Oxidation of toluene on lanthanum cobaltite perovskite (LaCoO3) catalyst

Vapor phase oxidation of toluene to benzaldehyde has been studied on lanthanum cobaltite, LaCoO₃, with a perovskite structure. Experimental data were obtained in the temperature range 350 to 600°C and contact time 0.2 to 2 h. The overall kinetic analysis indicated the oxidation of toluene to benzaldehyde to be first order, with a frequency factor of 0.62 h^–1 and an activation energy of 38.29 kJ mol^–1.

---

, LaCoO₃, . 350 600°C 0,2 2 . , 0,62 ^–1 38, 29 ·^–1.

     

Withanolides of Physalis I. Physalactone

Summary 1. A new withanolide, which has been called physalactone, has been isolated fromPhysalis alkekengi L. growing in Turkmenia. It has the structure of 4,17,20(R)-trihydroxy-3-methoxy-1-oxo-5,6-epoxy-22R-witha-8(14), 24-dienolide.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 531–534, July–August, 1977.     

Levels of artificial radionuclides and uranium in rain water collected from Ibaraki (Japan) following the Tomsk-7 accident in Russia

Measurements of some selected radionuclides were carried out in rain waters collected from Ibaraki Prefecture, Japan, following the nuclear accident at Tomsk-7, Russian Federation, in April 1993. The concentrations obtained for artificial radionuclides were⁹⁰Sr1.8 mBq l^–1,¹³⁷Cs0.1 Bq l^–1,¹³¹I0.1 Bq l^–1 and¹²⁹I4 Bq l^–1. Uranium (²³⁸U) concentrations in rainfalls in April 1993 were 6.3–39 ng l^–1. These data were compared to control values obtained previously and there was no appreciable influence on the radioactivity levels in Japan after the Tomsk-7 accident. Since only limited data on the concentrations of¹²⁹I and uranium in rain water are available, these new analytical results contribute to understanding the background levels for these nuclides.     

The influence of the lithology and depth on water recharge of wells in two Moroccan Atlantic coastal regions by using solid state nuclear track detectors and radon as a natural tracer

Uranium and thorium contents as well as radon and thoron -activity concentrations were evaluated inside different underground water samples by using a method based on calculating the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) detection efficiencies for the emitted -particles and measuring the resulting track density rates. The validity of the SSNTD technique utilized was checked by analysing uranium nitrate standard solutions. A relationship between water radon concentration and recharge of wells dug in two Moroccan Atlantic coastal regions, for a given lithology, was found. The influence of the lithology and depth on radon concentration and salinity of well waters studied was investigated.     

Electrostriction of polymethylmethacrylates

Electrostriction of tactic polymethylmethacrylates in response to step-on and step-offdc-fields was investigated in the field strength range from 1 to 5 MV m^–1 at room temperature; one example of electrostriction under sinusoidal field is given.Three principal retardation time regions were found: ₁=1.5 s, ₂=30 s, and ₃=140 s, each field strength independent. The retardation strengths belonging to these electrostrictive processes depend on tacticity.The low frequency limit of the electrostrictive volume compliance for the investigated PMMA is _a =–1.2×10^–15 m² V ^–2 for atactic, _S =–2.3×10^–14 m² V ^–2 for syndiotactic, and _i=–4.5 × 10^–14 m² V ^–2 for isotactic PMMA.Herrn Prof. Dr. F. H. Müller gewidmet.