An Sn Application of Homotopy Continuation in Neutral Particle Transport

The objective of this dissertation is to investigate the usefulness of homotopy continuation applied in the context of neutral particle transport where traditional methods of acceleration degrade. This occurs in higher dimensional heterogeneous problems [51]. We focus on utilizing homotopy continuation as a means of providing a better initial guess for difficult problems. We investigate various homotopy formulations for two primary diffcult problems: a thick-diffusive fixed internal source, and a k-eigenvalue problem with high dominance ratio. We also investigate the usefulness of homotopy continuation for computationally intensive problems with 30-energy groups. We find that homotopy continuation exhibits usefulness in specific problem formulations. In the thick-diffusive problem it shows benefit when there is a strong internal source in thin materials. In the k-eigenvalue problem, homotopy continuation provides an improvement in convergence speed for fixed point iteration methods in high dominance ratio problems. We also show that one of our imbeddings successfully stabilizes the nonlinear formulation of the k-eigenvalue problem with a high dominance ratio

Aeronautical Engineering: A special bibliography with indexes, supplement 54

This bibliography lists 316 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1975

Guidance, flight mechanics and trajectory optimization. Volume 6 - The N-body problem and special perturbation techniques

Analytical formulations and numerical integration methods for many body problem and special perturbative technique

The Advancement of Mass Spectrometry-based Hydroxyl Radical Protein Footprinting: Application of Novel Analysis Methods to Model Proteins and Apolipoprotein E

Fast photochemical oxidation of proteins: FPOP) has shown great promise in the elucidation of the regions of a protein\u27s structure that are changed upon interaction with other macromolecules, ligands, or by folding. The advantage of this protein footprinting method is that it utilizes the reactivity of hydroxyl radicals to stably modify solvent accessible residues non-specifically in a microsecond. The extent of *OH labeling at sites assays their solvent accessibility. We have corroborated the predicted profoundly short timescale of labeling empirically, by FPOP-labeling three oxidation-sensitive proteins and examining their global FPOP product outcomes. The novel test developed to validate conformational invariance during labeling can be applied generally to any footprinting methodology where perturbation to protein structure by the footprint labeling is suspected. The stable modifications can be detected and quantified by the same proteolysis, chromatography, and mass spectrometry techniques employed in proteomics studies; however, proteomics software does not automatically report the residue-resolved full-sequence-coverage footprint information found in proteomics-like FPOP data. Here we report the development of software tools to facilitate a comprehensive and efficient analysis of FPOP data, and demonstrate their use in a study of barstar in its unfolded and native states. We next show that SO4-* can serve as an alternative non-specific labeling agent that can be generated by the FPOP apparatus on the same fast timescale as *OH. This demonstrates the tunable nature of FPOP. We have used FPOP to characterize the oligomeric structures of three human apolipoprotein E: ApoE) isoforms and a monomeric mutant in their lipid-free states. Only one isoform of ApoE is strongly associated with Alzheimer\u27s disease; unfortunately, the structural reason for this association is not known, in part because no high resolution structure exists of any isoform. We find that the three common isoforms of ApoE are very similar in their solvent accessible footprint, that their oligomeric interactions involve several regions in the C-terminal domain, and that the N-terminal domain of each resembles the monomeric mutant\u27s N-terminal domain, the truncated form of which has been characterized as a four-helix bundle. Finally, we find by FPOP that ApoE interacts with beta-amyloid peptide 1-42 at a specific site in its N-terminal domain

CEM03.03 and LAQGSM03.03 Event Generators for the MCNP6, MCNPX, and MARS15 Transport Codes

A description of the IntraNuclear Cascade (INC), preequilibrium, evaporation, fission, coalescence, and Fermi breakup models used by the latest versions of our CEM03.03 and LAQGSM03.03 event generators is presented, with a focus on our most recent developments of these models. The recently developed "S" and "G" versions of our codes, that consider multifragmentation of nuclei formed after the preequilibrium stage of reactions when their excitation energy is above 2A MeV using the Statistical Multifragmentation Model (SMM) code by Botvina et al. ("S" stands for SMM) and the fission-like binary-decay model GEMINI by Charity ("G" stands for GEMINI), respectively, are briefly described as well. Examples of benchmarking our models against a large variety of experimental data on particle-particle, particle-nucleus, and nucleus-nucleus reactions are presented. Open questions on reaction mechanisms and future necessary work are outlined.Comment: 94 pages, 51 figures, 5 tables, invited lectures presented at the Joint ICTP-IAEA Advanced Workshop on Model Codes for Spallation Reactions, February 4-8, 2008, ICTP, Trieste, Italy; corrected typos and reference