A modified simulated annealing algorithm for parameter determination for a hybrid virtual model.

In this work we present an algorithm based on the simulated annealing (SA) method for electron beam spectrum reconstruction from central axis PDD data. We use a simulated beam in order to assess the accuracy of the method, and compare it with others usually employed. We found that our modified SA algorithm produced excellent reconstructed PDDs and beam profiles and improved reconstructed spectra. We also tested our method for the simultaneous determination of an electron energy spectrum and the position of a trimmer from central axis PDD data, and found this to be sufficient for the determination of the physical parameters of this hybrid model.

Biological weighting function for the mortality of Boeckella gracilipes (Copepoda, Crustacea) derived from experiments with natural solar radiation.

We performed in situ experiments during the austral summer of 1998 to quantify the mortality of the fresh-water copepod Boeckella gracilipes as a function of the UV dose. The copepods were exposed to solar radiation at the water-surface for approximately 24-34 h. Long-pass cut-off filters (Schott) were used in the exposure experiments. UV radiation and PAR were measured with an IL-1700 (International Light Inc.) and a PUV-500 radiometer (Biospherical Instruments Inc.). A biological weighting function for UV-induced mortality was calculated by fitting a model based on a logistic curve. Our results show that UV damage in this species is strongly wavelength- and dose-dependent. B. gracilipes was highly vulnerable to both UV-B (290-320 nm) and UV-A radiation (< 360 nm). The shape of the BWF obtained for B. gracilipes resembles more closely the action spectra (AS) for UV-induced erythema, than the AS for naked DNA.

Photodegradation of natural organic matter exposed to fluctuating levels of solar radiation.

Irradiation of natural water samples with natural or artificial UVR typically results in a progressive loss of color and decreased absorbance; a process often referred to as photobleaching. In a typical photobleaching experiment, samples are exposed to a relatively constant level of artificial or natural UVR. However, under most natural situations, the vertical mixing of the water within the upper mixed layer results in strong and periodic fluctuations in UV irradiance. In this paper, we present the results of an experiment in which natural lake water was exposed to solar radiation in quartz tubes that were incubated either at fixed depths or rotating within the water column. We found differences between rotating and fixed samples in (i) photobleaching, (ii) nutrient release, and (iii) subsequent use by algae and bacteria. The evidence presented in this study demonstrated that photochemical processes might be affected by vertical water motion. The reasons for such differences remain largely unknown. Although we offer a potential explanation for such differences, our proposed mechanism is based on a post-hoc analysis of the data and should be taken solely as a working hypothesis for future research.

Radioluminescence of red-emitting Eu-doped phosphors for fiberoptic dosimetry.

Fiberoptic dosimetry (FOD) technique has become an attractive method for real-time dosimetry. Al(2)O(3):Cis one of the most used radioluminescence materials for FOD due to its high efficiency but it presents the drawback of emitting in the spectral region, where spurious luminescence is also important. Optical filtering is the simplest technique to remove spurious luminescence, but is useful when red-emitting scintillators are employed. In this work, the feasibility of using red-emitting Eu-doped phosphors as FOD scintillators has been investigated.