Aerospace Medicine and Biology

N95-32722*# Justus Liebig-Univ., Giessen (Germany). Cell and Radiation Biophysics. ESTIMATION OF SPATIALLY RESTRICTED LET USING TRACK STRUCTURE MODELS J. KIEFER In NASA. Ames Research Center, Minutes of the 12th Joint NASA/DARA-DLR Life Sciences Program Working Group Meeting p 11-13 1994 Avail: CASI HC A01/MF A03 The spatial distribution of energy deposition is an important determinant in the formation of biologically significant lesions. It has been widely realized that Linear Energy Transfer (LET) being an average quantity is not sufficient to describe the situation at a submicroscopic scale. To remedy this to some extent ‘energy-cutoff’ values are sometimes used but since they are related to secondary electron energy and only indirectly to their range they are also not adequate although they may be easily calculated. ‘Rangerestricted LET’ appears to be better but its determination is usually quite involved. Xapsos (1992) suggested a semi-empirical approximation based on a modified Bethe-formula which contains a number of assumption which are difficult to verify. A simpler and easier way is to use existing beam-models which describe energy deposition around an ion’s path. They all agree that the energy density (i. e., energy deposited per unit mass) decreases with the inverse square of the distance from the track center. This simple dependence can be used to determine the fraction of total LET which is deposited in a cylinder of a given radius. As an example our own beam model. Energy density depends on distance x (measured in m) from the track center according to the presented formula. Derived from text N95-32723*# Justus Liebig-Univ., Giessen (Germany). Cell and Radiation Biophysics. HEAVY ION INDUCED DNA-DSB IN YEAST AND MAMMALIAN CELLS Status Report M. LOEBRICH, S. IKPEME, and J. KIEFER In NASA. Ames Research Center, Minutes of the 12th Joint NASA/DARA-DLR Life Sciences Program Working Group Meeting p 15-17 1994 Avail: CASI HC A01/MF A03 Molecular changes at the DNA are assumed to be the main cause for radiation effects in a number of organisms. During the course of the last decades techniques have been developed for measuring DNA double-strand breaks (dsb), generally assumed to 51 LIFE SCIENCES (GENERAL) A95-96275 DENTAL RESTORATIVE MATERIAL-TOOTH INTERFACES SALLY J. MARSHALL Univ of California, San Francisco, CA, United States, GRAYSON W. JR. MARSHALL, JOHN H. KINNEY, and MEHDI BALOOCH Scripta Metallurgica et Materialia (ISSN 0956716X) vol. 31, no. 8 October 15 1994 p. 983-988 refs (BTN-94-EIX94522406268) Copyright The interface between the tooth and a restorative element is crucial to the quality of restoration. Secondary dental caries may ensue at the site of interface if the restorative material is ineffective. Current research is being made on developing new techniques to enhance bonding composites to dentin. Amalgam bonding is of particular interest since this might promote impenetrability to secondary caries thereby strengthening its durability. EI N95-32719*# National Aeronautics and Space Administration. Ames Research Center, Moffett Field, CA. MINUTES OF THE 12TH JOINT NASA/DARA-DLR LIFE SCIENCES PROGRAM WORKING GROUP MEETING Final Report RONALD J. WHITE 1994 234 p Meeting held in Moffett Field, CA, 26-27 Oct. 1994 (NASA-TM-110655; NAS 1.15:110655) Avail: CASI HC A11/MF A03 This report contains the final minutes of the 12th Joint NASA/ DARA-DLR Life Sciences Program Working Group Meeting and includes the presentations made by participants. For individual titles, see N95-32720 through N95-32731. N95-32720*# Siegen Univ., (Germany). Dept. of Physics. PROTON-INDUCED FRAGMENTATION OF CARBON AT ENERGIES BELOW 100 MEV M. SCHMITZ, T. STREIBEL, H. ROECHER, J. DREUTE, S. E. HIRZEBRUCH, G. HUENTRUP, and WOLFGANG HEINRICH In NASA. Ames Research Center, Minutes of the 12th Joint NASA/ DARA-DLR Life Sciences Program Working Group Meeting p 1-3 1994 Avail: CASI HC A01/MF A03 Radiation effects caused by single cosmic ray particles have been studied for many years in radiobiological experiments for different biological objects and biological end-points. Additionally, single event effects in microelectronic devices have gained large interest. There are two fundamental mechanisms by which a single particle can cause radiation effects. On the one hand, a cosmic ray ion with high linear energy transfer can deposit a high dose along its path. On the other hand, in a nuclear collision, a high dose can be deposited by short range particles emitted from the target nucleus. In low earth orbits a large contribution to target fragmentation events originates from trapped protons which are encountered in the South Atlantic Anomaly. These protons have energies up to a few hundred MeV. We study the fragmentation of C, O and Si nuclei the target nuclei of biological material and microelectronic devices in nuclear collisions.