The forbidden line (6sp³P₀ - 6s²¹S₀ ) λ2656Å is forbidden for all multipole transitions if the nucleus of Hg isotope has no magnetic moment. For Hg¹⁹⁹ the selection rule is broken by the interaction of the nuclear magnetic dipole moment with the atomic electrons. In this thesis the Zeeman effect of the line is discussed in detail. In particular, the intensity of the Zeeman components is calculated as a function of the external magnetic field. It turns out that even for an external magnetic field sufficient to produce the Back-Goudsmit effect (30,000 gauss) the intensity of Zeeman components changes by less than one percent. Also the effect of the interaction of the nuclear magnetic moment and atomic electrons on the intensity of forbidden lines (6 ¹S₀ - 6³P₁) λ4618Å and (6 ¹S₀ - 6³P₂) λ5313Å of Pb²⁰⁹ is calculated (in absence of external magnetic field). The effect is very small. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This experiment was aimed at the determination of the dipole moment of the diatomic molecule HC1⁺ (in the ²π½ state). The method was to observe the Stark splitting optically by using a 3.4 meter Jarrell ash spectrograph. The charged diatomic molecule was obtained by passing HCl gas through a LoSurdo discharge tube in which a high electric field was applied; optical plates were obtained from the spectrograph and analysed. Dipole moment of HC1⁺ in the ²π½ state was found to be smaller than 0.8 debye. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The theory of the quadrupole interaction in nuclear magnetic resonance spectroscopy and relaxation measurements is presented in detail, with applications to ²H-NMR studies of order and dynamics in bilayers of deuterated lipids. Investigations of lipid-protein interactions in reconstituted membrane systems and intact biological membranes are reviewed. An experimental program is described which uses a synthetic amphiphilic polypeptide, with known geometry and variable length, to isolate questions about the geometrical interpretation of orientational order in lipid-protein interactions. A report is presented of an investigation of the effects of this polypeptide, Lys₂-Gly-Leu₂₀-Lys₂-Ala-amide, on the mixed bilayer system: Dimyristoylphosphatidylcholine Di-per-deuterio-myristoylphosphatidic Acid. The addition of the peptide was found to have little effect (≤5%) on the first and second moments of the distribution of quadrupole splittings in the liquid crystalline phase. Similarly, the spin-lattice relaxation time constants were affected by ≤10% in the liquid crystalline phase. The time constant for the decay of the quadrupole echo decreased dramatically above the phase transition with the addition of peptide, a phenomenon which is explained in terms of the presence of a new slow motion in the lipid-peptide systems. A simple model of the slow motion induced by the peptide is proposed, in which the lipid molecules undergo a rapid exchange between boundary and bulk sites. An effective correlation time is determined from an average over the rotations on each of these sites. Using this model, estimates are made of the change in the second moment brought about by the onset of the rotations, and. of the number of binding sites on the peptide. These estimates are found to be in agreement with independent measurements of the change in the second moment, and the number of binding sites is within the range predicted by simple considerations of charge balance. The change in the lineshape with the variation of the spacing of the pulses in the quadrupole echo experiment was investigated, and it was determined that the transverse relaxation time constants have a slight orientation dependence. It was also determined that the addition of the peptide has no significant effect on the variation of the lineshape. Some experiments which could answer some of the questions raised by these results are suggested. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Despite the impressive performance of deep neural networks (DNNs) on numerous vision tasks, they still exhibit yet-to-understand uncouth behaviours. One puzzling behaviour is the reaction of DNNs to various noise attacks, where it has been shown that there exist small adversarial noise that can result in a severe degradation in the performance of DNNs. To rigorously treat this, we derive exact analytic expressions for the first and second moments (mean and variance) of a small piecewise linear (PL) network with a single rectified linear unit (ReLU) layer subject to general Gaussian input. We experimentally show that these expressions are tight under simple linearizations of deeper PL-DNNs, especially popular architectures in the literature (e.g. LeNet and AlexNet). Extensive experiments on image classification show that these expressions can be used to study the behaviour of the output mean of the logits for each class, the inter-class confusion and the pixel-level spatial noise sensitivity of the network. Moreover, we show how these expressions can be used to systematically construct targeted and non-targeted adversarial attacks. Then, we proposed a special estimator DNN, named mixture of linearizations (MoL), and derived the analytic expressions for its output mean and variance, as well. We employed these expressions to train the model to be particularly robust against Gaussian attacks without the need for data augmentation. Upon training this network on a loss that is consolidated with the derived output probabilistic moments, the network is not only robust under very high variance Gaussian attacks but is also as robust as networks that are trained with 20 fold data augmentation.

Theory on leadership has emphasised the need for contributing towards leadership in extreme context. Give the rise in crisis, and the study aims to contribute by exploring how crucible moments can contribute towards leader’s development for crisis management. The objective of the study is to use the insights gained from the leader’s journey to develop a framework to contribute towards leadership development for crisis management. A narrative approach is used in this qualitative study and explores the themes identified from the leader's life journey. Semi-structured interviews were conducted with 13 executives in manufacturing organisation within the automotive sector, in the eThekwini region in Kwa-Zulu Natal. The research found that crucible experiences have contributed towards developing leader’s identity through self-awareness and discovering their potential. They learned decision making and allowed for change to occur. Crucible experience is also related to transformational learning, as it provided a trigger for learning. Leaders developed their approach for crisis management through applied experience and stepping up in a crisis. This crucible experience has found to contribute towards the leader's approach to crisis management. / Mini Dissertation (MBA)--University of Pretoria, 2021. / Gordon Institute of Business Science (GIBS) / MBA / Unrestricted

Ultracold bialkali polar molecules present a wealth of opportunities in quantum science research and technology; including fields such as quantum simulation, quantum chemistry, quantum metrology, precision measurement and quantum computation. A great deal of interest lies in their rich internal rotational and vibrational state structure and their large electric dipole moment. However, the additional complexity also provides significant challenges. To date, only a limited number of molecular species are available at ultracold temperatures below 1 microkelvin. The assembly of heteronuclear ground state molecules from ultracold atoms has emerged as a promising approach for creating ultracold molecules. In this thesis, I will present the creation of the first ultracold gases of NaCs ground state molecules. First, we produce an ultracold mixture of Na and Cs. Second, we associate weakly bound molecular pairs from the Na-Cs mixture. Finally, we apply a two-photon stimulated Raman adiabatic passage (STIRAP) pulse to transfer the weakly bound NaCs molecules into the deeply bound rovibrational ground state. I report on the construction of a new apparatus that produces ultracold mixtures of Na and Cs. We use this apparatus to assemble weakly bound NaCs molecules and successfully transfer up to 20,000 ultracold dipolar NaCs molecules to their rovibrational ground state in each experimental run. On the way to these results, we demonstrated a pathway towards creating the first quantum degenerate mixtures of Na and Cs. We identified and characterized an interspecies Feshbach resonance at 864.12(5) G, adiabatically sweeping across it to form weakly bound NaCs Feshbach molecules. We characterized the Feshbach molecule formation in various parameter regimes. Next, we performed a study of accessible NaCs excited states and identified a pathway to the rovibrational ground state using one- and two-photon spectroscopy. Finally, we demonstrated STIRAP to the rovibrational ground state, and investigated basic properties of the ground state molecules.

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No description available.

For years track and field athletes have worn spiked shoes to enhance performance. This study was conducted to determine the effect of track spikes on hip, knee, and ankle peak joint moments (PJM) in collegiate and elite athletes while running. To measure differences in joint moments, ten intercollegiate and post graduate male distance runners from Brigham Young University ran at a four-minute-mile pace (6.7 m/s) across a force plate synched with infrared cameras tracking body positioning in each shoe condition. Repeated measures ANOVA (p < 0.05) revealed no significant peak joint differences between running shoes and track spikes. The minimum hip and peak knee PJM approached significance (F = 3.221, P = 0.116 and F = 2.875, P = 0.134 respectively). The high variability of joint moments between trials made it difficult to detect differences between conditions. The variability may be explained by any number of factors including: biomechanical differences in running form, running at high speeds, type of subjects, and potentially other factors.

Spectral Moment Analysis has helped further our understanding of the spectral properties of obstruent speech production; however, the physiologic correlates of these spectral measures are not well understood. The aim of the present study was to examine the possible correlations between the linguapalatal contact patterns used to produce the fricatives /s/ and /ʃ/ and the resulting spectral characteristics. Using spectral moment analysis and electropalatography (EPG), the real-word productions of eight speakers of American English were investigated. The spectral measures for the fricative tokens in the present study were found to be similar to data reported in previous research with adult speakers. Although the majority of the correlations examined in this study were found to be statistically significant, none of the correlations accounted for a large proportion of the variance in the data. Generally the strongest correlations were found between the spectral mean and the symmetry of the contact pattern in the anterior region of the hard palate and the width of the contact pattern in the medial region of the palate. These findings may indicate that although the width and symmetry of linguapalatal contact contributes to the spectral signature /s/ and /ʃ/ fricatives, they are likely only part of a much more complex process that may involve other mechanisms such as lip rounding, tongue groove depth and shape, aerodynamic factors, and the shape of the vocal tract in other regions.