Design criteria and performance parameters of an alpha irradiation device for cell studies

An alpha irradiation device is described that utilises a commercially available disc-shaped americium-241 source of 8 cm diameter. The alpha particles traverse a moving collimator and the source is rotated to reduce the influence of source inhomogeneities. Source, collimator and a shutter disc are mounted in a container which is flushed with helium to reduce energy losses of the alpha particles before reaching the exit foil. The shutter disc is activated by a computer-controlled step motor. The broad beam of alpha particles emerges from the exit window of the container with a remaining range in tissue of about 15 mu m. An intermittent computer-controlled use of a preabsorber makes it possible to reduce dose differences within a depth up to 12.5 mu m to not more than +or-3%. With the commercially available americium sources a dose rate of 0.2 Gy min-1 is reached; this can be increased by utilising a somewhat wider collimator

A slowly rotating perfect fluid body in an ambient vacuum

A global model of a slowly rotating perfect fluid ball in general relativity is presented. To second order in the rotation parameter, the junction surface is an ellipsoidal cylinder. The interior is given by a limiting case of the Wahlquist solution, and the vacuum region is not asymptotically flat. The impossibility of joining an asymptotically flat vacuum region has been shown in a preceding work.Comment: 7 pages, published versio

Microdosimetry of diagnostic X-rays: applications of the variance-covariance method.

Microdosimetric measurements in beams of diagnostic X rays (between 30 and 125 kV) have been performed. In these pulsed radiation fields, microdosimetric measurements are possible only by application of the variance-covariance technique. The dose mean lineal energy, yD, is determined for various simulated diameters, at different depths in the absorber, and at different points within the pulse intervals. From the measured temporal dependences one can also obtain values of yD for different X-ray pulse generators. The results demonstrate the potential of the variance-covariance method for a diversity of microdosimetric measurements in radiation protection and in the quality control of radiation beams

Criteria of applicability for autoradiography of tritium

Autoradiography is an effective tool for the imaging of radionuclide distributions in various samples. In sophisticated applications with special preparation and development of sample-emulsion combinations and subsequent grain counts it can be highly quantitative, but it requires carefully controlled conditions and a variety of counter-checks, for example through scintillation spectroscopy. Less refined applications use X-ray films as detectors, and their seeming simplicity tends to invite artefacts and misinterpretations. Particular care needs to be taken, if one deals, or presumes to deal, with the low-energy ß-emitter tritium. Because of the short electron ranges the film must be in intimate contact with the sample, which tends to produce chemographic artefacts; without added spectroscopic measurements it is impossible to discriminate the spurious signals from a blackening of the film due to tritium. Recent statements concerning autoradiographic tritium measurements in tree samples have created considerable public concern and have demonstrated the pitfalls of uncritical use. This paper presents order-of-magnitude criteria for the detection threshold in the autoradiography of tritium; they can serve as an exclusion principle for some of the more extravagant misinterpretations. Dedication to Prof. Wolfgang Jacobi on the occasion of his 65th birthda

An eco-solution for track & trace of goods and third party logistics

This paper presents a new economic cost-effective solution known as the Web and telephony based method for tracking and tracing of goods and small and medium sized third party logistic providers. Considering that these companies usually operate on very flat margins, a comparison is made of the available track and trace technologies like GPS, mobile phone approximated GPS and Java based cell tracking in terms of costs, operating risks, and other evaluation criteria