DNA repair and cell survival in haploid and its diploid derivative strains of Saccharomyces cerevisiae were studied after 100 krad X-ray irradiation. The cells were in the G1 stage of the cell cycle, where haploid cells had only one copy of genetic material per genome and diploid had two copies. It was found that diploid could repair double-strand breaks in its DNA after 48 hr of liquid holding which was accompanied by a four-fold rise in survival. In contrast a haploid strain failed to repair its DNA and showed no increase in survival after liquid holding. It is concluded that (1) repair of DNA double-strand breaks requires the availability of two homologous DNA duplexes, (2) restoration of cell viability during liquid holding is connected with repair of DNA double-strand breaks and (3) this repair is a slow process possibly associated with slow finding and conjugation of homologous chromosomes.

The results of an analytical review of publications on the process of inactivation of pathogenic microorganisms in groundwater are considered. The process of inactivation is described by a mathematical model based on an exponential dependence. The values of the inactivation rate factor for a number of pathogenic microorganisms are given. Recommendations are given regarding formulas for determining the dependence of the inactivation rate factor of bacteria and viruses on water temperature.

No abstract

Keywords:Groundwater and surface water interactions Riverbank filtration Riverbed clogging Hydraulic conductivity MODFLOW s u m m a r y A steady-state flow regime in riverbank well fields is often violated by fluctuations in river stages and variations in groundwater extraction. In this study, a criterion of quasi-steady flow during filtration processes at riverbank well fields was introduced. Under the assumption of steady-state flow, an analytical approach for determining the key hydraulic parameters (aquifer transmissivity and riverbed filtration resistance) between a stream and a hydraulically connected aquifer during riverbank filtration was presented. An optimal regular observation network (consisting of the locations of monitoring wells and the observation regime), which is based on the model-oriented approach using an example of a riverbank well field near the Kuybyshev Reservoir, Russia, was designed to minimise the uncertainty in the estimates of hydraulic parameters. The analyses showed that the initial recession in the surface water levels for the simplest constant groundwater withdrawal patterns can be used to determine the key hydraulic parameters; the error in these estimated parameters was less than 7% or 12%, depending on the designed monitoring network. When comparing the two typical monitoring networks, observation line A-A that passes midway through the water supply wells performed better than observation line B-B that passes through the water supply wells when estimating the hydraulic parameters. The results of this study can be used as a reference for designing and optimising a monitoring network that aims to determine the key hydraulic parameters at riverbank well fields.

No abstract