BedMachine v3: Complete Bed Topography and Ocean Bathymetry Mapping of Greenland From Multibeam Echo Sounding Combined With Mass Conservation.

Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine-terminating glaciers. Here we present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation approach. A new 150 m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yielding major improvements over previous data sets, particularly in the marine-terminating sectors of northwest and southeast Greenland. Our map reveals that the total sea level potential of the Greenland ice sheet is 7.42 ± 0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine-based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing.

Proton tracks and the formation of pores in poly[diethylene glycol bis-(allyl carbonate)].

Modern dosimetry needs efficient detectors for registering light ions, especially light ions having energies of up to 10 MeV/amu. That is why this research pays attention to the development of materials for such a task. In this work, a CR-39 detector, which is the most efficient detector, was used. It was irradiated with low-energy protons. Using sensitive electrolytic etching and electron scanning microscopy, a complete analysis was carried out of the process of the formation of a pore starting from its opening to the final stage of its formation. The process of sequential track breakthroughs was observed. The data obtained on the shape of the pore and the parameters of its formation allow simulation of the process of etching. The etch rates and sensitivity of etching are determined. The influence of energy losses on the geometry of the pore is considered.

Determination of the calibration factor of polysulphone film UV dosemeters for terrestrial solar radiation.

Polysulphone film is used as a personal UV dosemeter in dermatological or epidemiological studies. The relative efficiency of this detector does not exactly match the action spectrum as proposed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and to which the UV dose and exposure limits refer. Therefore, the calibration of the dosemeter depends on the spetrum. In the present paper the variation of the calibration factor for terrestrial solar UV spectra is analysed on the basis of a two year observation period at a site near Munich. Germany. A detailed error estimation is included. It is shown that the variation of the calibration factor within this class of spectra is the main contribution to the total uncertainty of the dose determination, which can be up to 40%. The shape of the spectrum of terrestrial solar UV radiation is mainly determined by the total ozone column and the solar elevation angle. It is shown how the calibration depends on these two parameters and how this additional information can help to reduce the measurement error to a residual uncertainty of 17%. Exposure studies of terrestrial solar UV radiation using polysulphone film as a dosemeter would gain in accuracy if total ozone column values at the study's site could be measured or taken from satellite or weather service data. The interpretation of the magnitude of the dose uncertainty depends on the further use of these data.

Report on the third annual meeting of the Society for Biological Radiation Research, GBS '99.

During the past few decades radiation research has developed into specialized sub-disciplines, ranging from basic physics and chemistry to tumor biology and experimental radiotherapy. Scientific issues as well as the techniques and methodologies applied are subject to diverging discussion. The annual scientific meetings of the German "Gesellschaft für Biologische Strahlenforschung (GBS)" were established with the primary aim of allowing up-to-date transfer of current knowledge in any of the topics in radiation research and of promoting interaction between different research groups. This report provides a summary of the presentations at the third annual meeting which took place in 1999 in Dresden, Germany. The meeting particularly focussed on frontline research in radiation chemistry, modeling of radiation effects, dosimetry of non-ionizing radiation and unconventional radiation qualities, e.g., heavy ions or soft x-rays, stochastic radiation effects, DNA repair, and various aspects of radiobiological research of cells, normal tissues and tumors.

Laboratory facilities and recommendations for the characterization of biological ultraviolet dosimeters.

A laboratory facility for characterizing biological dosimeters for the measurement of UV radiation has been built and tested. The facility is based on a solar simulator, stabilized by photofeedback, and monitored by a spectroradiometer, with a versatile filter arrangement. This enables the following characteristics of the dosimeters to be ascertained: spectral response, linearity, and reciprocity; angular acceptance and response; calibration in simulated sunlight. The system has been tested on a variety of dosimeters and has the potential to be used with other radiometers, subject currently to the size of their active surface.

[Measurement and evaluation of natural and artificial UV radiation]. / Messung und Bewertung natürlicher und künstlicher UV-Strahlung.

Natural and artificial UV radiation are environmental factors with both beneficial and harmful biological effects. This article will explain the physical measurement quantities and their relation to the biologically effective dose and will summarize the present technical state of the art of personal UV monitoring. In practical use are dosimeters based on polysulphone, a polymer which undergoes changes in its optical properties upon irradiation with UV. Other systems determine the UV dose by quantifying damage induced in Bacillus subtilis spores upon UV exposure. An electronic UV sensor represents a new and interesting development. Personal UV dosimeters will become an useful tool in both clinical and scientific areas within dermatology.

Dynamic X-ray compensation for conformal radiotherapy by means of multi-leaf collimation.

The application of a multiple fixed field technique employing individually shaped and intensity-modulated beams makes it possible to produce dose distributions of high conformity even in the case of concave target volumes. With the technique presented here arbitrary intensity-modulated beams for the practical solution of the inverse problem can be generated. It is also possible to omit wedges, blocks and compensators in conventional radiotherapy. A continuous unidirectional sweep of independently computer-controlled leaves of a multi-leaf collimator is used to modulate the primary uniform beam. A new algorithm is introduced that computes the leaf trajectories. Also, a method is presented that accounts for leaf penumbra and transmission, which causes the generated fluence distribution to deviate from the desired fluence distribution. An optimization algorithm minimizing this deviation is described. The algorithm calculating the leaf trajectories, as well as the method considering penumbra and transmission and the successive optimization technique are used to calculate examples. Treatment times are calculated and compared to those needed when using compensators. A relationship between the treatment time and the maximum leaf speed is also deduced. To achieve good performance the maximum leaf speed should be no less than 20 mm/s.