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The mesomorphic phase transitions of sodium stearate occurring between 23°C. and 200°C. were investigated by means of the nuclear magnetic resonance of the hydrogen nuclei in sodium stearate. The changes in the nuclear magnetic resonance line width as the temperature increased revealed three phase transitions. These are the supercurd-subwaxy transition at 114°C., the subwaxy-waxy at 130°C., and the waxy-superwaxy transition at approximately 165°C.. Since the nuclear magnetic resonance line width is reduced as molecular motion increases, a general explanation of the phase transitions has been attempted. Stearic acid was also investigated by means of nuclear magnetic resonance at temperatures between 24°C. and 90°C.. Only one transition, the melting point at 70°C. could be detected. / Science, Faculty of / Chemistry, Department of / Graduate

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There is growing awareness in the physics education research community about the importance of using representations in physics teaching and the need for lecturers to reflect on their practice. This research study adopted a design-based research approach in an attempt to design a reliable, valid and practically useful artefact (framework/strategy) that could be used to trigger introductory physics lecturers’ reflections on their instructional use of representations. The artefact, which was instantiated with physics lecturers, comprised an observation protocol, an accompanying definitions key, a communication platform, and an instrument to assess the outcome (the levels of reflection). The video-data of lecturer practice were analysed using a priori codes to generate profiles of teaching practice. The resulting profiles were used to trigger individual video-stimulated reflection. The levels of reflection were assessed using a purpose-designed ‘Expectations of Reflection’ taxonomy. Thereafter a set of design guidelines and design principles were generated to guide further similar design-based educational studies. The process was validated via interview data but, while it was deemed a valid and reliable solution to the research problem, there were varying levels of perceived value of the artefact among the participating lecturers.

The literature on isolated bursts and possible mechanisms of origin has been critically reviewed, and observations point to a mechanism involving omission of electromagnetc radiation from plasma oscillations in the solar corona excited by outward travelling disturbances. Solar noise observations on 125 Mc./s. recorded at Rhodes University during the period November 26 1957 - February 6 1958 have been analysed by the author for isolated bursts, and these observations show the same general features reported by previous investigators. In interpretation of these records particular attention has been devoted to two aspects of isolated bursts; namely the preponderance on single frequency records of double-humped bursts, and the shape of isolated burst profiles. The authors suggests that a probable explanation of double-humped bursts observed on any frequency f is that the first hump represents omission at or near the level of zero refractive index for f radiation, and that the second hump corresponds to harmonic omission at the f/2 level. Source velocities may be calculated from the time delay between the peaks and an average value of 2 x 10⁴ km./sec. was obtained from an analysis of 21 double-humped bursts. This value is in very good agreement with that deduced by Wild (1950b) from the rate of frequency drift of peak intensity of isolated bursts. Simple isolated bursts had decay profiles which are approximatley exponential in shape, and this is usually interpreted in terms of the natural decay of plasma oscillations in the medium of origin. The author has verified that the exponential function is a good fit to the observed decay profiles, but shows that a relation of the form I - ¹/n (superscript) ⋉ t (where I is intensity and t is time) fits just as well. An alternative model is suggested which would lead to an exponential-like decay profile which is not determined by the natural decay of plasma oscillations. The work concludes with some suggestions for further research.

Dissertation presented in ful lment of the requirements for the degree of: Master of Science in Physics 2016 / The Phase-II upgrade of the Large Hadron Collider at CERN in the early 2020s will enable an order of magnitude increase in the data produced, unlocking the potential for new physics discoveries. In the ATLAS detector, the upgraded Hadronic Tile Calorimeter (TileCal) Phase-II front end read out system is currently being prototyped to handle a total data throughput of 5.1 TB/s, from the current 20.4 GB/s. The FPGA based Super Read Out Driver (sROD) prototype must perform an energy reconstruction algorithm on 2.88 GB/s raw data, or 275 million events per second. Due to the very high level of pro ciency required and time consuming nature of FPGA rmware development, it may be more e ective to implement certain complex energy reconstruction and monitoring algorithms on a general purpose, CPU based sROD co-processor. Hence, the feasibility of a general purpose ARM System on Chip based co-processing unit (PU) for the sROD is determined in this work. A PCI-Express test platform was designed and constructed to link two ARM Cortex-A9 SoCs via their PCI-Express Gen-2 x1 interfaces. Test results indicate that the latency of the PCI-Express interface is su ciently low and the data throughput is superior to that of alternative interfaces such as Ethernet, for use as an interconnect for the SoCs to the sROD. CPU performance benchmarks were performed on ve ARM development platforms to determine the CPU integer, oating point and memory system performance as well as energy e ciency. To complement the benchmarks, Fast Fourier Transform and Optimal Filtering (OF) applications were also tested. Based on the test results, in order for the PU to process 275 million events per second with OF, within the 6 s timing budget of the ATLAS triggering system, a cluster of three Tegra-K1, Cortex-A15 SoCs connected to the sROD via a Gen-2 x8 PCI-Express interface would be suitable. A high level design for the PU is proposed which surpasses the requirements for the sROD co-processor and can also be used in a general purpose, high data throughput system, with 80 Gb/s Ethernet and 15 GB/s PCI-Express throughput, using four X-Gene SoCs.

Quantization and renormalization of non-Abelian gauge fields is studied. Yang-Mills theory is renormalized up to two-loops using the background field method retaining arbitrary value of the gauge parameter. The result confirms the expectations for calculations performed in background field gauge. Namely, the counter-term depending on the background field only is a renormalization constant times the square of the field strength of the background field, and the constant upon renormalization of the gauge parameter is independent of the gauge parameter. Finally, the three-loop contribution to the renormalization group β function of pure Yang-Mills theory is calculated in the background field gauge. / Ph. D.

This work presents a new form of microscopy, the instrument constructed to demonstrate it, the images produced and the image contrast mechanisms seen for the first time. Some of its future scientific potential is described and finally, recent work towards advancing the method is discussed. Many forms of microscopy exist, each with unique advantages. Of several broad categories that they could be grouped into, those that use particle beams have proven very generally useful for micro and nano-scale imaging, including Scanning Electron, Transmission Electron, and Ion Beam microscopes. These have the disadvantage, however, of implanting electric charges into the sample, and usually at very high energy relative to the binding energy of molecules. For most materials this modifies the sample at a small scale and as we work increasingly towards the nano-scale, this is a serious problem. The Neutral Atom Microscope (NAM) uses a beam of thermal energy (under 70 meV) non-charged atoms or molecules to probe an atomic surface. For several decades scientists have been interested in this possibility, using a focused beam. Scattering of neutral atoms provides a uniquely low-energy, surface-sensitive probe, as is known from molecular beam experiments. We have developed a new approach, operating with the sample at a close working distance from an aperture, the need for optics to focus the beam is obviated. The demonstrated, practical performance of this "Pinhole" NAM exceeds all other attempts by great lengths by many measures. The unique images resulting and contrast mechanism discoveries are described. The future potential for nano-scale resolution is shown.

This thesis is a history of the beginnings of nuclear research and education in India, between 1938 and 1959, through the trajectories of particle accelerator building activities at three institutions: the Department of Physics, Indian Institute of Science, Bangalore, the Palit Laboratory of Physics, University Science College, Calcutta, later (Saha) Institute of Nuclear Physics, and the Tata Institute of Fundamental Research, Bombay. The two main arguments in this thesis are: First, the beginnings of nuclear research in India were rooted in the "modernist imperative" of the research field. However, post-war organisation of nuclear research came to be inextricably imbricated in processes of state-formation in independent India in a manner such that failure to actively engage with the bureaucratic state implied death of a laboratory project or constraints upon legitimately possible research. Second, state-formation, like the pursuit of nuclear research in India for the period of my study, became about India's participation and claim upon the universal. State-formation was equally a modernist imperative. Powerful sections of the nationalist bourgeoisie in India understood "Science" and the "State" as universals in World History, and India, they were convinced, had to confirm its place in history as an equal among equals. These two arguments combined explain how nuclear research came to be established, transformed, and extended through the gradual assembly of material infrastructure to realistically enable the new country take a capable decision on the nuclear question.

Since 1982, the Si (111)-(7x7) surface has been extensively studied both theoretically and experimentally with the modern powerful tools of STM and Scanning Tunneling Spectroscopy (STS). In this work, a simple atomic orbital model for the Si (111)-(7x7) surface is developed to simulate the experimental results of STM and STS. Based on Tersoff-Hamann’s theory for the tunneling current, simulations of clean Si (111)-(7x7) constant-current images are presented. The direct, real-space simulated topographic images of the surface are compared to experimental results qualitatively and quantitatively. The simulation of spectroscopic imaging and normalized conductance spectra are also included. The adsorption of atomic hydrogen atoms onto the Si (111)-(7x7) surface is also simulated. / xiv, 146 leaves ; 29 cm.