A proposta do trabalho e obter os valores dos níveis de energia do átomo de hélio ou de íons tipo hélio por meio de um hamiltoniano modelo que descreve os estados estacionários de um sistema de duas partículas de dirac em um centro coulombiano. A função de onda total e escrita como uma combinação de produtos diretos anti-simetrizados de bispinores similares as soluções para uma partícula. Parte dos espectros do átomo de hélio e do SI POT.12+ para os momentos angulares totais J = 0, 1, 2 (paridades par e ímpar, respectivamente) são obtidos. / The helium and helium-like ions energy levels are evaluated using a Hamiltonian operator that describes the stationary states of two-DIRAC particles system in an external Coulomb field. The total wave function of the system is an anti-simmetrized combination of tensor products of bispinors, similar to the one-particle DIRAC solutions. The partial helium and 51 12+ spectra are obtained for the total angular momenta J = 0,1,2 (even and odd parities, respectively).

A proposta do trabalho e obter os valores dos níveis de energia do átomo de hélio ou de íons tipo hélio por meio de um hamiltoniano modelo que descreve os estados estacionários de um sistema de duas partículas de dirac em um centro coulombiano. A função de onda total e escrita como uma combinação de produtos diretos anti-simetrizados de bispinores similares as soluções para uma partícula. Parte dos espectros do átomo de hélio e do SI POT.12+ para os momentos angulares totais J = 0, 1, 2 (paridades par e ímpar, respectivamente) são obtidos. / The helium and helium-like ions energy levels are evaluated using a Hamiltonian operator that describes the stationary states of two-DIRAC particles system in an external Coulomb field. The total wave function of the system is an anti-simmetrized combination of tensor products of bispinors, similar to the one-particle DIRAC solutions. The partial helium and 51 12+ spectra are obtained for the total angular momenta J = 0,1,2 (even and odd parities, respectively).

published_or_final_version / abstract / toc / Physics / Master / Master of Philosophy

Constructivist learning theory is based upon the tenets that students come to learning experiences with prior knowledge and experiences that the learner will choose from to make sense of the present situation. This leads to a mixture of understandings among students. This study proposed to reveal students‟ understanding of atomic structure and cell structure as well as the relationships between atoms and cells. High school students from one private school participated in a paper-and-pencil test to uncover conceptual understanding and content knowledge of atoms and cells. The 120 participants were from grades: 9 (13m, 15f), 10 (9m, 20f), 11 (21m, 17f), and 12 (17m, 8f). All 120 students took the paper-and-pencil test and 16 students (4 per grade) participated in a follow-up interview. Drawings were analyzed by individual characteristics then using groups of characteristics models classes were formed. Openended questions were scored holistically by rubric scores and then deconstructed into individual content statements. A limited number of findings follow. Students were more likely to draw a Bohr model. Freshmen were less likely to indicate living materials contained atoms and more likely to indicate forms of energy contained atoms. As students progressed through high school, details included in cells decreased. Students failed to recognize that the sum of the products from cell division will be larger than the original cell due to the two growth periods included in the division cycle. Students were often able to provide the correct yes or no answer to are atoms and cells similar, different, or related but the follow-up answers often included non-scientific conceptions. Recommendations include implementing instructional strategies that promote long-term retention of conceptual understanding and the underlying content knowledge. Design evaluation methods to monitor student understanding throughout a unit of study that go beyond traditional closed-ended questions. Many limitations related to this study suggest that results should not be generalized beyond the targeted population.

In accordance with the 2010 Dodd-Frank Act, conflict minerals refer to gold, tantalum, tin, and tungsten bearing minerals sourced from the Democratic Republic of Congo (DRC) that have been mined illegally and used to funnel funds to rebel forces. In response to an increasing demand for these metals used in cellphones, computers, and other popular technologies, Dodd-Frank mandates that industrial consumers demonstrate due diligence and assure that the materials they use have been extracted legally. Because current chain-of-custody methods have not been effective in sourcing ores, a study was undertaken whereby the range of mineralogical characteristics of 15 samples along the wolframite solid solution series were determined in order to ascertain if differences in these characteristics would permit fingerprinting of the source deposit of wolframite, of which the DRC is the world's fifth largest producer. For these 15 samples, single-crystal X-ray structure and powder X-ray diffraction studies have been conducted; major, minor and trace element chemistry has been determined using ICP-MS and ICP-OES; and Raman spectroscopy has been carried out. Finally, statistical methods were used to determine relationships between samples, and the results of that mathematical work show that there is no firm method at the present time of determining the provenance of a sample based on the information of the crystal structure, diffraction patterns, vibrational frequencies/scattering, or major and trace elemental chemistry. This study elucidates the range of mineralogical properties along the hübnerite-ferberite solid solution series while working towards to development of an analytical technique that is affordable, practical, accessible and effective for industrial consumers seeking product certification and compliance with the 2010 Dodd-Frank Act.

Theoretical study of energy levels, oscillator strengths, transition probabilities, and lifetimes of Si III lines has been reported in this thesis. These atomic parameters are required for the interpretation of emission and absorption lines of Si III and for the modeling of astrophysical plasmas including Galactic High Velocity Clouds (HVCs), the Sun, and white dwarf stars. We used Hartree-Fock (HF) and Multiconfiguration Hartree-Fock (MCHF) methods in our calculations. We have considered 58 levels of the 3s2, 3s3p, 3p2, 3s3d, 3s4s, 3s4p, 3s4d, 3s4f, 3s5s, 3s5p, 3s5d, 3s6s, and 3s5f configurations. The relativistic corrections are included in Breit-Pauli approximation by using one-body Darwin, mass correction, spin-orbit operators, and two-body spin-other-orbit and spin-spin operators. The results have been compared with previous theoretical results and available experimental data, and generally a good agreement is found.

An important direction in nanoscale science is to synthesize materials whereby atomic clusters serve as the building blocks. Properties of these clusters can be controlled through size and composition, and such an approach offers a pathway toward designing larger, customized materials. One way to stabilize such materials is through the use of ligated clusters. Ag4Ni2(DMSA)4 is one such cluster, the first with a bimetallic core, and has been stabilized by the experimental group of A. Sen at The Pennsylvania State University. The theoretical studies undertaken in this thesis were directed toward providing information on the atomic structure, nature of electronic states, optical spectra, and any magnetic information of this new species. Theoretical studies have also been carried out on various clusters to provide input into the fragmentation data obtained through MS/MS experiments.

Thesis (P.hD (Physics)) --University of Limpopo, 2013 / Titanium dioxide (TiO2) nanoparticles, nanowires, nanosheets and nanoporous are of great interest in many applications. This is due to inexpensive, safety and rate capability of the material. It has being considered as a replacement of graphite anode material in rechargeable lithium batteries. Much experimental work on pure and lithiated nanostructures of TiO2 has been reported, mostly with regards to their complex microstructures. In this work we employ molecular dynamics (MD) simulation to generate models of TiO2 nano-architectures including: nanosheet, nanoporous, nanosphere and bulk. We have successfully recrystallised all four nanostructures from amorphous precursors; calculated radial distribution functions (RDFs), were used to confirm crystallinity. Configuration energies, calculated as a function of time, were used to monitor the recrystallisation. Calculated X-Ray Diffraction (XRD) spectra, using the model nanostructures, reveal that the nanostructures are polymorphic with TiO2 domains of both rutile and brookite in accord with experiment. Amorphisation and recrystallisation was successful in generating complex microstructures. In particular, bulk and nanoporous structures show zigzag tunnels (indicative of micro-twinning) while nanosphere and nanosheet shows zigzag and straight tunnels in accord with experiment. All model nanostructures of TiO2 were lithiated with different lithium content. RDFs, microstructures, configuration energies, calculated as a function of time and XRDs of all lithiated structures are presented. / University of Limpopo Research Office,The Royal Institution(Ri),Granfield University,Materials Modelling Centre,UCL,and the CHPC

published_or_final_version / Physics / Master / Master of Philosophy

abstract / Physics / Doctoral / Doctor of Philosophy