The radiative capture cross section of a highly pure (99.999%), 6.125(2) grams 238U sample ((9.56±05)e-4 atoms/barn) has been measured in the 185 m flight path at the CERN neutron time-of-flight facility n_TOF in the energy range 0.3 eV-20 keV. The Total Absorption Calorimeter (TAC) detection system, an array of 40 BaF2 crystals, was used utilising the total absorption technique, where all the γ-rays from the capture cascades are detected. These data have undergone careful background subtraction, with special care being given to the background originating from neutrons scattered by the 238U sample. Pile-up and dead-time effects have been corrected for using an innovative correction method valid for variable high count rates within a complex detection system such as the TAC. The resulting capture yield has an uncertainty of up to 2.2% below 5 keV and up to 3.7% between 5 and 20 keV, in line with the accuracy requested in the NEA High Priority Request List. A resonance analysis has been performed up to 5 keV with the code SAMMY. Between 5 and 20 keV, the cross section is treated as unresolved and averaged. The results confirm the excellent quality of the most recent nuclear data evaluations within quoted uncertainties and suggest some improvements. In particular, these TAC data suggest a 2% increase in the average cross section in the energy range 2-9 keV and a 5% reduction in the energy range 9-20 keV.

Thesis advisor: James P. Morken / The development of boron and palladium ligands for conjunctive cross-coupling provides access to new reactivity. Some of these advances are outlined in this dissertation. Chapter one describes an enantioselective and diastereoselective palladium catalyzed conjunctive cross-coupling of β-substituted alkenyl boron “ate” complexes to afford contiguous benzylic stereocenters. “Mac” diol was discovered as a useful boron ligand in conjunctive cross-coupling by reducing unwanted Suzuki-Miyaura cross-coupling. Chapter two describes the utilization of “mac” diol in the enantioselective conjunctive cross-coupling of α-substituted alkenyl boron “ate” complexes with carbamoyl chlorides. This transformation affords tertiary, β-boryl amides, which provide a complementary approach to Mannich, aldol, and conjugate borylation products. Water was an essential additive to enable high yield and high enantioselectivity, and its reaction role was investigated. The synthetic utility of this cross-coupling was demonstrated with the asymmetric synthesis of (+)-adalinine. Chapter three describes the thought process behind discovering a new palladium ligand for conjunctive cross-coupling. Phosphinooxazolines (PHOX) are useful and inexpensive ligands for enantioselective palladium-catalyzed conjunctive cross-coupling. A stereochemical model of this cross-coupling with this ligand was examined. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

This thesis presents MCNPX simulations of the SCANDAL set-up used at the Theodor Svedberg Laboratory for neutron scattering cross-section measurements. The thesis describes processes and data important for the upcoming off-line data analysis. In the experiment, neutrons scattered off the target are converted to protons which are stopped in scintillator crystals. The results of presented simulations include a description of the proton spectra in dependence of the neutron-to-proton conversion angle, calculation of the hit position gates and a study of the converter describing the role of its chemical composition and also the role of other plastic scintillator on the proton spectra. / QC 20100520

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Electron Compton scattering is the best known fundamental QED process, however, a precision measurement of its cross section for a beam energy above 1 GeV has been lacking up to now. An updated high precision measurement of the neutral pion lifetime via the Primakoff effect (PrimEx-II) experiment was performed in Hall B of Jefferson Lab in 2010. The experiment used small angle coherent photoproduction of πO's in the Coulomb field of a nucleus, i.e. the Primakoff effect, to determine the lifetime with a precision of less than $1.5%. It therefore requires thorough understanding of the underlying systematic uncertainties. To facilitate that data for well known electromagnetic processes were taken concurrently with the photoproduction data. This analysis pertains to measuring the Compton scattering cross section, which occurs with similar kinematics to the primary process. The combination of the well established theory for this process with large collected statistics allowed to extract this cross section with high precision in an energy region of 4-5 GeV for 12C and 28Si targets. The results of this analysis will be presented.

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A primary purpose of this study was to develop and test a model of adaptation for children and adolescents who move to a foreign country. The model was developed from existing literature on adult migration, and from the small fund of knowledge which exists on immigrant children. Adaptation was conceptualized into two kinds - sociocultural and psychological. It was proposedthat sociocultural adaptation would mediate the relationship between a number of independent variables (coping strategies, life events, length of stay, social support, and cultural distance) andthe dependent variable, which was psychological adaptation. Use of Path analytical techniques demonstrated the poor utility of this model. There was no support for a linear relationship between psychological adaptation and sociocultural adaptation. Exploratory, data-based analyses were then carried out to determine significant predictors for sociocultural and psychological adaptation. While a significant set of predictors emerged for sociocultural adaptation, few individual significant variables emerged for psychological adaptation. Limitations of this study are noted.The implications for intervention of this finding to migrant children and adolescents are discussed. / Master of Science

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