Zs. Varga

Measurement of radon, radon daughters and thoron concentrations by multi-detector devices

Abstract There is a growing interest in collection of data concerning human exposures to naturally occurring alpha-emitting radionuclides (e.g. in mines, dwellings, building materials, industrial wastes, coal fuel cycle, water supply, soil, plants, etc). Most of such studies is incomplete for the following reasons: 1) In radon measurements the contribution of thoron is generally neglected. 2) The determination of equilibrium factor is complicated or not possible at all. 3) Short- and long-term concentration fluctuations cause difficulties in obtaining representative mean values. 4) The plate-out effect is generally not taken into account. We have studied a variety of simple methods that could be used to overcome some of these difficulties by using cups equipped with two or more alpha-sensitive nuclear track detectors. A theoretical foundation of the quantitative measurements with such devices is presented. Experimental data are reported on radon, radon daughters and thoron concentrations measured by multi-detector devices in cave soil gas and in air of Hungarian dwellings.

Cell surface markers, inositol phosphate levels and membrane potential of lymphocytes from young and old human patients

It is well known that most physiological functions change with aging, including the immune response. Data concerning the aging of lymphocyte subpopulations are conflicting. The antigen density of peripheral blood lymphocytes has been determined by fluorescently tagged OKT-3, OKT-4, OKT-8, OKT-11 and OKM1 monoclonal antibodies in a carefully selected aged (over 87 years) population, and compared to that of young subjects. A substantial difference was found in the percentage distribution of OKT8 and OKM1 subsets. The volume of lymphocytes of the elderly population was significantly less than that of the young. The effect of various monoclonal antibodies on phosphatidylinositol breakdown has also been studied. It was found that only OKT3, acting through the CD3 antigen receptor, was able to induce inositol phosphate formation in both young and elderly, although in the latter population this occurred at a lower level. Because the plasma membrane plays a regulatory role in this process, an important and sensitive functional parameter, the membrane potential, was also monitored and influenced by changing the extracellular K+ concentration. The lymphocytes of the elderly population responded less sensitively to changes in extracellular potassium concentration.

Spark counting of α-radiograms recorded on LR-115 strippable cellulose nitrate film

Abstract In this paper a study on the spark counting of etch-holes of α-particle tracks recorded on 13 μm strippable cellulose nitrate track detectors (Kodak-Pathe LR-115 films) is described. Results for the counting characteristics as a function of etching and irradiation parameters are given. Applications of the spark counting technique to α-radiograms obtained by the ( p , α) nuclear reaction and soil-radon exhalation measurements are presented.

In vitro testing of the anti-mycoplasma effect of some anti-coccidial drugs

The anti-mycoplasma effects of the ionophores (lasalocid sodium, monensin and nigericin) were compared with that of tylosin tartrate and tiamulin in vitro. Forty-four strains representing 14 avian and 10 mammalian Mycoplasma species and serotypes and 5 Acholeplasma species were tested. The ionophores showed average minimal inhibitory concentration (MIC) values between 3.65 and 4.93 micrograms ml-1 for all strains, the MIC values for glucose-fermenting strains were between 2.26 and 3.75 micrograms ml-1, significantly lower than for arginine-hydrolysing strains (9.27-13.12 micrograms ml-1). These values were significantly higher than those obtained with tylosin tartrate (0.45 micrograms ml-1) or tiamulin (0.13 micrograms ml-1). The ionophores were more efficacious against acholeplasmas (0.06-0.25 micrograms ml-1) than against mycoplasmas.

Formation of ion-beam images in gelatine and various polymers

Abstract It has recently been reported by Najzer, Humar and Ilic (1982) that the pure gelatine can be used for producing relief images of high-fluence ion-beams after a treatment in water at room temperature for few minutes. The new method is proposed for high-resolution microradiography of boron in metals via 10B(n,α)7Li reaction. In our present work studies are performed to understand the phenomenon observed. We have simulated the image formation by accelerated electron, proton and alpha-particle beams at different fluences. A narrow fluence region is found in which a highly enhanced dissolution rate of the irradiated gelatine is induced. We assume that when the fluence exceeds a critical value (tipically 1012–1013 ions·cm-2) the damage zones of individual tracks cover almost completely the irradiated area, transforming the irradiated layer into a huge damage zone. In this case the effective diameter of damage zone around a single track has to be d eff= =φ c -1 2 ≅(3–10) nm . We have found that the ion-induced image formation phenomenon observed in gelatine is a more general one and the method may be extended to almost all the etch-track and non-etch-track forming polymers and perhaps to insulating silicates. For example high-resolution α- microradiographs have been obtained with CR-39, CN-85, PC and PET sheets and even with hydrate-cellulose known as a non-track-forming material.

Study of the transport process of uranyl ions in an ion-exchange membrane by solid-state track detector fissionography

Abstract A study was made of the diffusion of uranyl ions in an ion-exchange membrane of polystyrenesulphonic acid type. The solid-state track detector technique was used to prepare radiograms on the diffusion concentration profiles in the interior of the membrane at various diffusion times and temperatures. Fission fragments from 238 U were detected in mica plates, and the local variations in the uranyl ion concentration were employed to determine the characteristic parameters of the transport process: the diffusion coefficients, the frequency factor and the activation energy.

Neutron-induced autoradiography based on relief and dyed image formation in polymers

Abstract Neutron-induced autoradiography utilizing formation of a dyed and/or relief image in polymers was developed. The method is based on the detection of neutron-induced charged particles, via (n,p), (n, a ), (n,f) reactions and those neutron capture processes leading to internal conversion and/or β-decay. Irradiated polymers are treated in water containing an organic dye or in pure water for a few minutes to obtain a dyed and/or relief image, respectively. The fluence of charged particles required to produce a dyed image is between 10 11 –10 12 cm -2 which is one order of magnitude less than that for a relief image. Various procedures based on utilization of optical and electron microscopy for contrast enhancement were developed. The techniques were applied to image boron, uranium and gadolinium in solids. Samples were irradiated in the core of a nuclear reactor. The required thermal neutron fluence was between 10 14 –10 16 cm -2 .

Development of the dyed-track method for kodak CN-85 detector

Abstract The dyed-track method has been successfully developed for cellulose derivatives. The track parameters (width, colouration deepness, contrast, registration sensitivity), however, proved to be very dependent on the detector material and on the track processing conditions. In our previous works optimum conditions were presented mostly for cellulose acetate sheets. In the present work we have studied the influence of track processing parameters on the dyed-track formation in Kodak cellulose nitrate detector called CN-85. It is found that in this material optimum dyed-tracks can be produced with using no swelling but with a thermal annealing at 100 °C for 1 hour after particles irradiation. For sensitization a treatment with 15% HCl at 22°C for 20 hours and for dyeing 0.3 wt% Rhodamine-B at 100°C for 1 hour proved to be the best. For better understanding the track dyeing phenomenon we have studied the colouration behaviour of electron-irradiated CN-85 detectors.