V. Múčka

The protection of Escherichia coli bacteria and the yeast Saccharomyces cerevisiae against UV-C radiation by ethanol was studied. It was found that the fraction of surviving cells increases with increasing ethanol concentration. The specific protection depends on the dose rate, concentration range of ethanol, and it is higher for yeast compared to the bacteria.

Abstract Radiation induced dechlorination of trichloroethylene (TCE) and tetrachloroethylene (PCE) in aqueous solutions containing the active carbon (AC) or cupric oxide (CuO) as the modifiers was studied. The obtained results were compared to the previously studied dechlorination of polychlorinated biphenyls (PCBs). Both modifiers were found to decrease the efficiency of dechlorination. The AC modifier acts mainly via adsorption of the aliphatic (unlike the aromatic) hydrocarbons and the CuO oxide mainly inhibits the mineralization of the perchloroethylene. The results presented in this paper will be also helpful for the studies of the impact of chlorinated hydrocarbons on the membrane permeability of living cells.

The influence of selected adsorbents (active carbon, bentonite and zeolite) on the radiation removal of lead from its aqueous solution using electron beam radiation was investigated. Both positive and negative effects on radiation reduction of Pb2+ ions depending on the dose applied were observed in presence of these solid modifiers. Besides deaeration with nitrogen, the efficiency of the process under

Gradual dechlorination of the polychlorinated biphenyls (PCBs) in alkaline solutions in 2-propanol under the effect of high energy electrons (4.5 MeV) produced by electron accelerator has been studied using a flow-through apparatus of the volume of about 50 L. The dependence of both relative radiation chemical yield and the dechlorination degree on the initial concentration of OH- ions or PCBs, absorbed dose as well as on dose rate has been investigated.

The catalytic systems NiO–ZnO covering the whole interval 0–100wt% of one component were studied. The systems were prepared from the oxide and the nitrate of one and the other metal component. The catalytic and some physico-chemical properties of the catalysts before and after γ or electron irradiation were compared with those found earlier with the same system prepared in other

Abstract The catalytic and some physico-chemical properties of a variety of ferric oxides have been studied. Most of the catalysts prepared consisted of hematite and magnetite. The specific catalytic activities of the samples were found to be very different and their values appeared not to be determined by the ratio of the hematite and the magnetite present in the sample. Heat treatment of the samples changed their catalytic efficiency. γ-Irradiation (60Co) of the catalysts with the dose of 1 MGy led to a lower catalytic activity, β-irradiation (90Sr-90Y) with a dose of 10 kGy enhanced their catalytic efficiency and a neutron-irradiation (252Cf) with the dose of 425 Gy generated positive or negative radiation catalytic effects. The observed changes in catalytic activity of the treated samples may be explained in terms of the principle of bivalent catalytic sites provided that the surface concentration of the Fe2+-Fe3+ sites determines the catalytic activity of the ferric oxide.

Abstract The effect of ionizing radiation ( 60 Co γ-rays) on Pt-supported catalyst used for the dearomatization of jet fuel with distillation in the range 395–534 K has been studied. Pre-irradiation of the catalyst with doses in the range 10 2 −5 × 10 4 Gy leads to the partial catalyst activation. Irradiation of the catalyst enhances its resistance to catalyst poisons, particularly to sulphur-compounds, and this is probably the reason for its catalytic activity being ∼60–100% greater than that of un-irradiated catalyst. Optimum conditions for dearomatization on the irradiated catalyst were found and, by means of a rotary three-factorial experiment, it was shown that these lie at lower temperatures and lower pressures than those for un-irradiated catalyst.

Radiation removal of Co2+ and Ni2+ ions from aqueous solutions containing Me2+ and various scavengers for OH radicals has been studied. In nondeaerated solutions containing HCOOK as OH radical scavenger, two mechanisms of removal were found: reduction leading to the insoluble colloidal metals and precipitation causing predominant formation of carbonate. The processes taking place are mainly affected by the concentration

Abstract Some physico-chemical and catalytic properties of NiO-Bi 2 0 3 catalysts containing various amounts of components in the range 0–100 wt% of one component have been studied before and after 1-MGy-γ irradiation in air or in water using the hydrogen peroxide decomposition as a test reaction. Irradiation, when performed in water, led to a decrease in catalytic activity but did not lead to modification of the mutual influence of both components of the catalysts. The annealing of radiation effects was observed at temperatures above 50°C.

Abstract The catalytic activities and some physico-chemical properties of NiO-ZnO catalysts prepared by precipitation of mixtures of carbonates and nitrates of both metals and subsequent calcination have been tested before and after irradiation, using the decomposition of hydrogen peroxide as a test reaction. A mutual influence of both oxides and their sensitivities to ionizing radiation have been proved.

A gradual degradation of polychlorinated biphenyls (PCBs) was found under the influence of accelerated electrons (4.5 MeV) absorbed in alkaline 2-propanol solutions containing 0.3–1.0 vol.% of PCBs. A degree of dechlorination grows with increasing dose of irradiation from 2 to 100 kGy. The inhibiting effects of acetone as well as of oxygen were observed.

Abstract Some physico-chemical and catalytic properties of two-component CuOBi 2 O 3 catalysts containing various ratios of both components in the range 0–100 wt% of one component have been tested before and after γ- and electron-irradiation, using the decomposition of hydrogen peroxide as a test reaction. Irradiation led to modification of mutual influence of both components in the system accompanied by creation of radiolytically induced catalytic sites.

The process of activation is an important part of wastewater treatment technology. It can be affected in many ways, not least by using radiation. The paper describes effects of pre-irradiation of small part of biomass on activated sludge process. It has been shown, that relatively low dose of accelerated electrons can positively affect many parameters of the system.

The radiation dechlorination of tetrachloroethylene (PCE) caused by both γ- and EB (accelerated electrons)-irradiation in aqueous solutions, containing oxygen, nitrous oxide, HCO3−- or NO3−-ions, was studied. The promoting and inhibiting effects of the two firstly and lastly mentioned species were observed, respectively. The influence of pH on this process was also investigated.

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A radiation dechlorination of PCE and TCE initiated by both γ and EB irradiation in aqueous solutions was studied. A promoted effect of ozone was observed in this process. The dependences of degree of dechlorination and radiation yield on the dose and on the initial concentration of the organics as well as of the dose constant on the initial concentration

Besides common chemical and biological methods, the radiation technology is a promising way of sludge treatment. The paper describes possibilities of combined accelerated electrons/biological processing of both anaerobic and aerobic sludge. Besides one-shot experiments, experimental reactors for the simulation of anaerobic processes have been used. Main effort has been aimed to decrease organic compounds concentration and overall volume of solids,

One of the methods of determining cell concentrations in solutions is to apply a suitably diluted cell suspension to agar plates and count the resultant colonies. For this method to be correct it must be assumed tha t one colony grows from every living cell. In addition to single cells, however, a bacterial culture contains a considerable number of cells in pairs, chains and large groups, which, when transferred to agar, also give rise to only one colony (St~rka, 1959). These pseudomycelia do not divide into individual cells even after multiple progressive dilution of the culture. Our experiments showed tha t when we diluted a culture to 10 -4 of the original cell concentration, the numbers of pairs of cells, expressed as a percentage of the total count, varied by maximally + 5 % . This means tha t all measurements based on the above method are loaded with a standard error producing lower results than the actual cell concentration in the solution (determined, for example, by counting the cells directly in a counting chamber). The aim of the present s tudy was to correct these results so as to eliminate, or at least modify, the error of such measurements. Our method is based on the premises submitted below. We denote the number of pseudomycelia in a medium volume unit as m and assume tha t each of them is composed of s cells. I f the cell concentration determined by a colony count on agar is denoted as n, then assuming tha t every individual cell and every pseudomycelium gives rise to one colony, the actual number of cells in the given volume unit will be determined by the relationship

X-ray-excited luminescence and time-resolved UV-excited photoluminescence were employed to evidence energy transfer processes between two main emission components in PbWO4 scintillating single crystals. It was found that energy transfer from the blue to green emission centres occurs via free-charge carriers above 150 K. This process causes a redistribution of the emitted energy in favour of the green emission component. At