Development of constrained DET for measurements of dissolved iron in surface sediments at sub-mm resolution.

The technique of diffusive equilibration in thin-films (DET) was used to measure pore-water concentrations of dissolved Fe at high (1 mm) and ultra-high (400 μm) spatial resolution in the surface sediments (0–12 mm) and immediate overlying water of Esthwaite Water, UK. DET measurements were made using an unconstrained DET probe and a new constrained DET probe with 200-μm wide compartments in a 400-μm thick ceramic sheet. Good agreement between profiles obtained by conventional and constrained DET measurements confirmed the performance of the new procedure, which in principle can be used to measure most major components of pore waters. Single point maxima observed with conventional DET were revealed as systematic peaks with constrained DET. All Fe pore-water profiles showed tightly defined maxima in the surface sediments. Double maxima observed for both spring and winter were probably due to tightly defined zones of bacterial oxidation of Fe(II) although sampling artifacts could not be completely ruled out. Differences in ultra-high resolution vertical concentration profiles measured only 2 mm apart provided evidence of small scale horizontal heterogeneity. Such observations suggest that fluxes through the sediment water interface calculated from concentration profiles should be treated as spatially specific values. Average fluxes can only be obtained from several replicate measurements

On the interpretation of micro-PIXE measurements on a prototype microstructured reference material

In order to determine the beam spot size and scanning properties of ion microbeam systems, a novel reference material has been developed, consisting of permalloy (81% Ni, 19% Fe) strip patterns on silicon substrate. Due to the choice of substrate and pattern materials, these samples exhibit a high elemental contrast suitable for analysis with X-ray detection and ion scattering techniques. The microlithographic production scheme is briefly described. A prototype chip of this material was investigated with PIXE and RBS analysis in a scanning nuclear microprobe. It proved to be extremely useful in the routine to focus the ion microbeam and to determine its spot size. Due to the microscopic structure of these samples, a geometric dependence of matrix effects in the production of Si X-rays from the substrate material could be shown. Even dead-time effects in the counting electronics, showing up as an apparent thickness gradient, could be observed. Besides its primary role in microbeam diagnostics, this reference material can serve an educational role in developing the analyst's ability to correctly identify and interpret such artefacts

Vojnovic B: The use of microbeams to investigate radiation damage in living cells. ApplRadiat Isot 2010

a b s t r a c t The micro-irradiation technique continues to be highly relevant to a number of radiobiological studies in vitro. In particular, studies of the bystander effect show that direct damage to cells is not the only trigger for radiation-induced effects, but that unirradiated cells can also respond to signals from irradiated neighbours. Furthermore, the bystander response can be initiated even when no energy is deposited in the genomic DNA of the irradiated cell (i.e. by targeting just the cytoplasm)

A Novel Micro-Structured Reference Material for Microbeam Analysis.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

The use of microbeams to investigate radiation damage in living cells.

The micro-irradiation technique continues to be highly relevant to a number of radiobiological studies in vitro. In particular, studies of the bystander effect show that direct damage to cells is not the only trigger for radiation-induced effects, but that unirradiated cells can also respond to signals from irradiated neighbours. Furthermore, the bystander response can be initiated even when no energy is deposited in the genomic DNA of the irradiated cell (i.e. by targeting just the cytoplasm)

Using aquatic macrophyte community indices to define the ecological status of European lakes

Defining the overall ecological status of lakes according to the Water Framework Directive (WFD) is to be partially based on the species composition of the aquatic macrophyte community. We tested three assessment methods to define the ecological status of the macrophyte community in response to a eutrophication pressure as reflected by total phosphorus concentrations in lake water. An absolute species richness, a trophic index (TI) and a lake trophic ranking (LTR) method were tested at Europe-wide, regional and national scales as well as by alkalinity category, using data from 1,147 lakes from 12 European states. Total phosphorus data were used to represent the trophic status of individual samples and were plotted against the calculated TI and LTR values. Additionally, the LTR method was tested in some individual lakes with a relatively long time series of monitoring data. The TI correlated well with total P in the Northern European lake types, whereas the relationship in the Central European lake types was less clear. The relationship between total P and light extinction is often very good in the Northern European lake types compared to the Central European lake types. This can be one of the reasons for a better agreement between the indices and eutrophication pressure in the Northern European lake types. The response of individual lakes to changes in the abiotic environment was sometimes represented incorrectly by the indices used, which is a cause of concern for the use of single indices in status assessments in practice