Medical and industrial applications of nuclear reaction physics

An understanding of the interactions of neutrons and protons below a few hundred MeV with nuclei is important for a number of applications. In this paper, two new applications are discussed: radiation transport calculations of energy deposition in fast neutron and proton cancer radiotherapy to optimize the dose given to a tumor; and intermediate-energy proton accelerators which are currently being designed for a range of applications including the destruction of long-lived radioactive nuclear waste. We describe nuclear theory calculations of direct, preequilibrium, and compound nucleus reaction mechanisms important for the modeling of these systems.     

Applications of molecular orbital theory to the interpretation of mass spectra. Prediction of primary fragmentation sites in organic molecules

Semi-empirical molecular orbital calculations have been carried out on the steroidal hormone estrone, both as a neutral molecule and the corresponding positively charge molecular ion. These calculations provide estimates of bond densities and net atomic charges, factors deemed important in past correlations of observed mass spectra with molecular structure. Calculated net charges appear to be unrelated to fragmentation processes. Calculated bond densities of the ground state molecular ion of estrone allow prediction of gross features of fragmentation. Bond densities of excited electronic states of the molecular ion may provide a basis for finer distinction among sites of initial bond cleavage, which is information crucial to rationalization of subsequent fragmentation of the molecular ion.     

Calibration laws based on multiple linear regression applied to matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry

Operation of any mass spectrometer requires implementation of mass calibration laws to translate experimentally measured physical quantities into a m/z range. While internal calibration in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) offers several attractive features, including exposure of calibrant and analyte ions to identical experimental conditions (e.g. space charge), external calibration affords simpler pulse sequences and higher throughput. The automatic gain control method used in hybrid linear trap quadrupole (LTQ) FT-ICR-MS to consistently obtain the same ion population is not readily amenable to matrix-assisted laser desorption/ionization (MALDI) FT-ICR-MS, due to the heterogeneous nature and poor spot-to-spot reproducibility of MALDI. This can be compensated for by taking external calibration laws into account that consider magnetic and electric fields, as well as relative and total ion abundances. Herein, an evaluation of external mass calibration laws applied to MALDI-FT-ICR-MS is performed to achieve higher mass measurement accuracy (MMA).