NASA Technical Reports Server (NTRS) 20140000785: A Radiation Chemistry Code Based on the Green-s Functions of the Diffusion EquationReportar como inadecuado




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Autor: NASA Technical Reports Server (NTRS)

Fuente: https://archive.org/


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A radiation chemistry code based on the Green’s functions of the Diffusion Equation Ianik Plante Universities Space Research Association Division of Space Life Sciences NASA Johnson Space Center, Houston TX NASA Human Research Program Investigators’ Workshop February 11-13, 2014 Page No.
1 The space radiation problem  Space radiation is comprised of high-energy protons and heavy ions (HZE’s) and secondary protons, neutrons, and heavy ions produced in shielding  Unique damage to biomolecules, cells, and tissues occurs from HZE ions that is qualitatively distinct from Xrays and gamma-rays on Earth  No human data to estimate risk from heavy ions, thus requiring use of biological models and theoretical understanding to assess and mitigate risks  Shielding has excessive costs and will not eliminate galactic cosmic rays (GCR) Single HZE ions in cells And DNA breaks Page No.
2 Cucinotta and Durante, Lancet Oncology (2006) Radiation tracks and energy deposition  The energy deposition by heavy ions is highly heterogeneous and dependent on the type and energy of the ion  The interactions of radiation with matter are stochastic in nature and therefore often studied by Monte-Carlo simulations Primary energy loss events in low-LET tracks Primary energy loss events in high-LET tracks Penumbra ~100 to 500 eV blobs Track core ~100 Å s s ~500 eV to 5 keV 5 keV Delta rays Single HZE ions in cells C.
Ferradini (1979) J.
Chim.
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76, 636 A.
Mozumder and J.L.
Magee (1966) Radiat.
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28, 203 And DNA breaks Page No.
3 Radiation effects: time sequence of events Time (s) 10-15 10-12 10-9 Stage Events Physical Energy absorption Physico- Reorganization chemical Electron thermalization Chemical Radical diffusion Modeling Particle transport Cross sections Green’s functions Chemical reactions 10-6 10-3 Biological DNA repair Kinetics models Molecular dynamics Page No.
4 Radiation effects: time sequence of events H2O Physica...






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