No description available.

No description available.

No description available.

No description available.

Single molecule magnets (SMMs) posses multi-level energy structures with properties that make them attractive candidates for implementation into quantum information technologies. However there are some major hurdles that need to be overcome if these systems are to be used as the fundamental components of an eventual quantum computer. One such hurdle is the relatively short coherence times these systems display which severely limits the amount of time quantum information can remain encoded within them. In this dissertation, recent experiments conducted with the intent of bringing this technology closer to realization are presented. The detailed knowledge of the spin Hamiltonian and mechanisms of decoherence in SMMs are absolutely essential if these systems are to be used in technologies. To that effect, experiments were done on a particularly promising SMM, the complex K₆[V[superscript IV over subscript 15As[superscript III over subscript 6]O₄₂(H₂O)] ⋅ 8H₂O, known as V₁₅. High-field electron spin resonance (ESR) measurements were performed on this system at the National High Magnetic Field Laboratory. The resulting spectra allowed for detailed analysis of the V₁₅ spin Hamiltonian which will be presented as well as the most precise values yet reported for the g-factors of this system. Additionally, the line widths of the ESR spectra are studied in depth and found to reveal that fluctuations within the spin-orbit interaction are a mechanism for decoherence in V₁₅. A new model for decoherence is presented that describes very well both the temperature and field orientation dependences of the measured ESR line widths. Also essential is the ability to control spin-states of SMMs. Presented in this dissertation as well is the demonstration of the coherent manipulation of the multi-state spin system Mn[subperscript 2+] diluted in MgO by means of a two-tone pulse drive. Through the detuning between the excitation and readout radio frequency pulses it is possible to select the number of photons involved in a Rabi oscillation as well as increase the frequency of this nutation. Experimental findings fit well the analytical model developed. This process could lead to the use of multi-level spin systems as tunable solid state qubits. Finally, if quantum computing technologies are to be commercially realized, an on-chip method to address qubits must be developed. One way to incorporate SMMs to an on-chip device is by way of a coplanar waveguide (CPW) resonator. Efforts to create a resonator of this type to be used to perform low-temperature ESR on-chip will be described. Our work is focused on implementing such on-chip techniques in high magnetic fields, which is desirable for ESR-type of experiments in (quasi-)isotropic spin systems. Considerable attention is given to the coupling of these devices and a geometry is presented for a superconducting CPW resonator that is critically coupled. The effect of the magnetic field on the resonance position and its quality factor is addressed as well. Our devices show robust performance in field upwards of 1 Tesla and their use in performing on-chip ESR measurements seem promising. / A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2015. / July 14, 2015. / electron spin resonance, multi-level spin system, single molecule magnets, spin coherence, superconducting resonator, vanadium 15 / Includes bibliographical references. / Irinel Chiorescu, Professor Directing Dissertation; Naresh Dalal, University Representative; Jorge Piekarewicz, Committee Member; Vladimir Dobrosavljevic, Committee Member; Ryan Baumbach, Committee Member.

Anammox process is happening to be in the center of interest for several years. Implementing partial nitrification/Anammox process into main stream of wastewater would result in a great improvement of sustainable technologies for reducing nitrogen in environment. However, Great chalange fo Anammox bacteria in main stream is the low temperature which is a strong inhibiting factor for them. In this study pilot-scale MBBR reactor was operated to investigate the influence of low temperatures in Anammox process. Two different phases operated at 13 and 16°C were investigated during five months. SAA, OUR and online measurements were used to observe process capacity in low temperatures. Deammonification process was found to be stable in 13°C. Moreover, Anammox bacteria capacity to convert nitrogen to nitrogen gas was found in even 5°C. Satisfactory results for Deammonification process in low temperatures may result in future application of Anammox process in full-scale plant for main stream of wastewater.

A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science / The role of intersite electron correlation effects and the possible occurrence of the metal-insulator transition in carbon-ion implanted type IIa diamond samples have been studied at very low temperatures, using four- and two-point probe contact electrical conductivity measuring techniques. The measurements were extended to ruthenium oxide thin films in the presence and absence of a constant magnetic field of B = 4.0 T down to 100 mK, using a 3He-4He dilution refrigerator. The effect of the Coulomb gap in the variable range hopping regime has been well studied by other workers. The results tend to follow the Efros-Shklovskii behaviour with a trend towards the Mott T- 114 law for diamond samples far removed from the metal insulator transition, on the insulating side at low temperatures. / Andrew Chakane 2019

No description available.

For microelectronics used in the low-temperature applications, the understanding of their reliability and performance has become an important research subject characterised as electronics to serve under the severe or extreme service conditions. Along with the impact from the increased miniaturization of devices, the various properties and the relevant thermo-mechanical response of the interconnection materials to temperature excursion at micro-scale become a critical factor which can affect the reliable performance of microelectronics in various applications. Pure indium as an excellent interconnection material has been used in pixellated detector systems, which are required to be functional at cryogenic temperatures. This thesis presents an extensive investigation into the thermo-mechanical properties of indium joints as a function of microstructure, strain (loading histories-dependent) and temperature (service condition-sensitive), specifically in the areas as follows: (i) the interfacial reactions and evolution between indium and substrate during the reflow process (liquid-solid) and thermal aging (solid-solid) stages by taking low-temperature cycling into account; (ii) determination of the effects of joint thickness and the types of substrate (e.g. Cu or Ni) on the mechanical properties of indium joints, and the stress- and temperature-dependent creep behaviour of indium joints; (iii) the establishment of a constitutive relationship for indium interconnects under a wide range of homologous temperature changes that was subsequently implemented into an FE model to allow the analysis of the evolution of thermally-induced stresses and strains associated with a hybrid pixel detector.

Low Temperature Nuclear Orientation (LTNO) is an important technique in the study of nuclei far from stability. The theory of LTNO and its application to the measurement of static nuclear moments and other quantities of spectroscopic interest are reviewed. The off-line facility at Oxford was used to study the decay of ¹³³I→¹³³Xe and ¹³⁵I→¹³⁵Xe. ¹³³I having Z=53 and N=80 has three protons above the closed shell Z=50 and two neutrons holes in N=82 shell, while ¹³⁵I has fully closed neutron shell since it has N=82, and they are of considerable theoretical interest since a wide variety of the theoretical nuclear models may be used to describe the observed levels close to the stable double closed shell structure. Another aim is to search for the nuclear magnetic dipole moment of the ground state of ¹³⁵I. Nuclear orientation of ¹³³IFe and ¹³⁵IFe enabled the mixing ratios of several transitions in the decay scheme of ¹³³I and ¹³⁵I to be determined. From temperature dependence for ¹³⁵I, the nuclear magnetic moment of ¹³⁵I has been deduced. Also temperature dependence for ¹³³I, analysed using a simple model, gave value for the magnetic hyperfine field that differed from previous published values. The method of combining nuclear orientation with NMR has become a very popular technique in recent years for determining nuclear magnetic dipole moments very precisely. The purpose of the NMR/ON experiment was to measure the hyperfine field with greater precision and to get some idea of the proportion of nuclei subject to it. Light Eu and Sm nuclei have attracted attention as systems with the number of protons right below the Z=64 subshell gap and the number of neutrons approaching N=82 major shell closure. Odd-proton, odd-neutron and odd-odd nuclei near the A=140 region have been investigated in the framework of the particle-triaxial rotor model. Main attention has been paid to explanation of experimental magnetic dipole and electric quadrupole moments of ground and isomeric states. Model predictions for deformation parameters of ^136-142Sm even-even cores have been extracted.