71,446 research outputs found
The effect of stirring on the heterogeneous nucleation of water and of clathrates of tetrahydrofuran/water mixtures
The statistics of liquid-to-crystal nucleation are measured for both water
and for clathrate-forming mixtures of tetrahydrofuran (THF) and water using an
automatic lag time apparatus (ALTA). We measure the nucleation temperature
using this apparatus in which a single sample is repeatedly cooled, nucleated
and thawed. The effect of stirring on nucleation has been evaluated numerically
and is discussed. We find that stirring of the solution makes no difference to
the nucleation temperature of a given solution in a given tube.Comment: 4 pages, 4 figure
Cellular repair/misrepair track model
A repair/misrepair cell kinetics model is superimposed onto the track structure model of Katz to provide for a repair mechanism. The model is tested on the repair-dependent data of Yang et al. and provides an adequate description of that data. The misrepair rate determines the maximum relative biological effectiveness (RBE), but similar results could arise from indirect X-ray lethality not include in the present model
Vacuum thermal conductivity measurements of NASA E4A1 elastomeric heat shield material
Line source vacuum thermal conductivity measures for elastomeric heat shield materia
On the potential impact of the newly proposed quality factors on space radiation protection
The recently proposed changes in the defined quality factor hold great potential for easing some of the protection requirements from electrons and protons in the near-Earth environment. At the same time, the high Linear Energy Transfer (LET) components play an even more important role which must be further evaluated. Several recommendations are made which need to be addressed before these new quality factors can be implemented into space radiation potection practice
Target correlation effects on neutron-nucleus total, absorption, and abrasion cross sections
Second order optical model solutions to the elastic scattering amplitude were used to evaluate total, absorption, and abrasion cross sections for neutron nucleus scattering. Improved agreement with experimental data for total and absorption cross sections is found when compared with first order (coherent approximation) solutions, especially below several hundred MeV. At higher energies, the first and second order solutions are similar. There are also large differences in abrasion cross section calculations; these differences indicate a crucial role for cluster knockout in the abrasion step
Quasi-elastic nuclear scattering at high energies
The quasi-elastic scattering of two nuclei is considered in the high-energy optical model. Energy loss and momentum transfer spectra for projectile ions are evaluated in terms of an inelastic multiple-scattering series corresponding to multiple knockout of target nucleons. The leading-order correction to the coherent projectile approximation is evaluated. Calculations are compared with experiments
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