Thesis (M.Sc.) -- Memorial University of Newfoundland, 1987. / Typescript. Bibliography: leaves 56-64. Also available online.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In 2012, a three-axis HTS-SQUID magnetometer project for geomagnetic measurements has been started at SANSA Space Science in Hermanus, South Africa. The goal of this project was to replicate a three-axis SQUID magnetometer for geomagnetic field measurements at LSBB at Rustrel, France. This is to allow better characterizing of faint, low frequency geomagnetic and ionospheric phenomena. To record the output signals of the SQUID magnetometers, a measurement system had to be developed. To utilise the full sensitivity of the SQUID magnetometers, the output signals have to be recorded with high accuracy. A high-speed and high-accuracy data acquisition system was installed and software was developed to record data from it. The software is capable of sending the recorded data to a web server as it is being recorded. Basic hardware control of the SQUID magnetometers has also been implemented from this data acquisition system, by monitoring conditions with its software. Timing accuracy is an important aspect of this system, in order to enable comparisons with measurements from LSBB and from different locations in the world. A GPS receiver was used to obtain the current UTC time accurately in order to timestamp measurements. A software method was devised for timestamping, to improve accuracy by triggering measurements directly from the GPS receiver. A hardware real-time clock between the GPS receiver and the rest of the system has been avoided using this method. For research purposes, this measurement data must be available on the internet for the lifetime of the system. A data server was set up and a large database of recorded data has been generated over two years of this project. Long term implementation issues have also been addressed. A web interface was developed for the data server to enable live viewing of the recorded data. This web interface also facilitates access to the raw measurements for public use. Analysis of phenomena in the recorded data has been performed by other students from Stellenbosch University. / AFRIKAANSE OPSOMMING: In 2012 is daar by SANSA Space Science in Hermanus, Suid-Afrika begin met 'n drie-as HTS-SQUID magnetometerprojek vir die opneem van geomagnetiese metings. Die doel van hierdie projek was om die drie-as SQUID magnetometer vir geomagnetiese veldmetings by LSBB naby Rustrel in Frankryk te dupliseer. Dit sou dit moontlik maak om subtiele, laefrekwensie geomagnetiese en ionosferiese verskynsels beter te beskryf. Om die uittreeseine wat deur die SQUID magnetometers voortgebring word op te neem, moes n data-opnemerstelsel ontwikkel word. Ten einde die volle sensitiwiteit van die SQUID magnetometers te benut, moes die seine baie akkuraat gemeet word. 'n Hospoed- en ho-akkuraatheidsdata-opnemer is genstalleer en die nodige sagteware is ontwikkel om hierdie data op te neem. Die sagteware is in staat om die data, soos dit opgeneem word, na 'n webbediener te stuur. Basiese hardewarebeheer van die SQUID magnetometers is ook vanaf hierdie data-opnemerstelsel gemplementeer deur toestande met die sagteware te monitor. Akkurate tydmeting is 'n belangrike aspek van hierdie sisteem, sodat metings met die van LSBB en ander soortgelyke projekte in ander posisies op die aarde vergelyk kan word. 'n GPS-ontvanger is gebruik om die UTC-tyd akkuraat te ontvang, ten einde akkurate tydstempeling by metings te voeg. 'n Sagtewaremetode vir tydstempeling is ontwikkel om akkuraatheid te bevorder deur metings direk vanaf die GPS-ontvanger te sneller. Deur hierdie metode te gebruik, is dit onnodig om n intydse hardewaretydhouer tussen die GPS-ontvanger en die res van die sisteem te gebruik. Vir navorsingsdoeleindes moet hierdie metingsdata op die internet beskikbaar wees vir die duur van die stelsel se leeftyd. 'n Databediener is opgestel en 'n baie groot databasis van opgeneemde data is oor die twee jaar van hierdie projek gegenereer. Langtermynimplementeringskwessies het ook aandag geniet. 'n Webblad is vir die databediener ontwikkel sodat die data onmiddellik besigtig kan word soos dit opgeneem word. Hierdie webblad fasiliteer ook toegang tot die rou data-opnames vir openbare gebruik. Verskynsels in die data-opnames is by SANSA geanaliseer deur ander studente van die Universiteit van Stellenbosch.

We have performed detailed measurements of magnetic and dielectric properties of high quality magnetite (Fe3O4) single crystals in weak magnetic and electric fields. These measurements can reveal details of phase transitions and other features that are not yet fully understood. We focused not only at the Verwey transition - a well known phase transition taking place at about 120 K in stoichiometric samples - but we also explored and described new relaxation effects in magnetite at low temperatures. The low-temperature properties were also found to be exceptionally sensitive to sample quality, stoichiometry and homogeneity. The results presented in this thesis were acquired on sensitive non-commercial SQUID magnetometer complemented by four-probe dielectric spectroscopy and dc conductivity measurements.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-10-11T14:26:18Z No. of bitstreams: 1 rafaelguzelladecarvalho.pdf: 5817882 bytes, checksum: 3cecfbefd0364ef85d5c3183dcbdfc47 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-10-16T14:07:21Z (GMT) No. of bitstreams: 1 rafaelguzelladecarvalho.pdf: 5817882 bytes, checksum: 3cecfbefd0364ef85d5c3183dcbdfc47 (MD5) / Made available in DSpace on 2018-10-16T14:07:21Z (GMT). No. of bitstreams: 1 rafaelguzelladecarvalho.pdf: 5817882 bytes, checksum: 3cecfbefd0364ef85d5c3183dcbdfc47 (MD5) Previous issue date: 2015-07-23 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Glicosaminoglicanos (GAGs) são heteropolissacarídeos lineares ligados a um núcleo proteico dos proteoglicanos (PGs). Condroitim sulfato (CS) é GAG sulfatado composto por unidades dissacarídicas repetidas de ácido D-glucurônico e N-acetil-galactosamina, esse composto possui atividades biológicas associadas à interação com diferentes elementos da matriz. Estas ações têm sido relacionadas às suas características estruturais relativas ao elevado teor de grupos sulfato e carboxila que originam domínios estruturais que são conhecidos por participar de funções fisiológicas específicas. O presente trabalho teve por objetivo a identificação e caracterização estrutural dos GAGs extraídos de diferentes tecidos de lula (Doryteuthis plei) bem como a avaliação da atividade anticoagulante destes compostos. Para isso inicialmente determinamos a técnica de extração dos GAGs dos tecidos de manto, nadadeira, tentáculos e pele utilizando degradação com enzimas proteolíticas e purificação utilizando a técnica de cromatografia de troca iônica. Realizamos a identificação dos GAGs com degradações com liases específicas (chases AC e B de F. heparinum), em que ficou evidenciado que CS é o GAG majoritário dos tecidos de D. plei. Os CS encontrados tiveram peso molecular detectados na faixa de 30-50 kDa. A dosagem química de sulfato demonstrou que estes CS possuíam relação superior a 1,2 sulfato/hexosamina o que nos forneceu o indicativo que estas macromoléculas eram supersulfatadas. Este fato foi confirmado pela análise por FACE dos produtos da digestão de CS de manto e nadadeira com chase AC de A. aurescens em que a maior sulfatação foi relacionada à presença de alta proporção de resíduos di-sulfatados, ΔDi4,6S (≈55%). Técnicas espectroscópicas de Raman e RMN permitiram confirmar a maior substituição e sulfatação nas posições 4- e 6- da GalNAc, respectivamente. Os CS de manto e nadadeira ainda demonstraram atividade anticoagulante associada à inibição da via intrínseca da coagulação sendo detectada inibição dos fatores IIa e Xa. Desta forma concluímos que CS-E é o tipo de glicosaminoglicano constituinte nos tecidos de lula e que ele possui características tecido-específica, desempenhando sua atividade anticoagulante de acordo com o padrão de sulfatação. / Glycosaminoglycans (GAGs) are linear heteropolysaccharides attached to a core protein of proteoglycans (PGs). Chondroitin sulfate (CS) is sulfated GAG composed of repeating disaccharide units of D-glucuronic acid and N-acetyl-galactosamine, this compound has biological activities associated to their interaction with different components of the extracellular matrix. These activities have been related to their structural characteristics due to the high content of sulfate and carboxyl groups originating structural domains which are known to participate in specific physiological functions. This aim of this study was the identification and structural characterization of glycosaminoglycans extracted from squid different tissues (Doryteuthis plei) as well as evaluation of the anticoagulant activity of these compounds. Initially, we determined the procedures GAGs extraction in mantle tissue, fin, tentacles and skin using degradation with proteolytic enzymes and purification using ion exchange chromatography. We carried out the identification of GAG to degradation with specific lyases (chases AC and B from F. heparinum), wherein we evidenced that CS is the principal GAG of the D. plei tissues. Molecular weight of CS had a range of 30-50 kDa. Quantification of sulfate groups demonstrated that these CS had higher ratio of sulfate/hexosamine (1.2), a indicative that these macromolecules were oversulfated. This fact was confirmed by FACE analysis of CS from mantle and fin after digestion with chase AC from A. aurescens where most sulfation was related to the presence of high proportion of di-sulfated residues, ΔDi4,6S (≈55%). Raman spectroscopic and NMR techniques confirmed the increased substitution and sulfation in positions 4 and 6 of GalNAc, respectively. CS of the mantle and fin demonstrated anticoagulant activity associated with inhibition of the intrinsic coagulation pathway by inhibition of factors Xa and IIa. Thus, we conclude that CS-E is the kind of glycosaminoglycan constituent in squid tissues and it has tissue-specific characteristics, playing their anticoagulant activity according to the sulfation pattern.

Stable isotope analysis is an emerging tool to examine trophic pathways and migratory patterns of marine organisms. Squid are widely distributed in coastal and deep water regions of the Gulf of Mexico. Stable isotope ratios of carbon and nitrogen found within cephalopod tissues can provide information on both trophic level and habitat of their food sources. More recently, ontogenetic changes in stable isotope ratios within squid eye lenses have been documented. Concentric layers of crystallin proteins are added to the lens as the squid ages; the center of the lens contains the oldest layer and the youngest layers are on the outermost surface. The crystallin proteins are rich in carbon and nitrogen, providing suitable sources for isotopic analysis of both δ15N and δ13C. Doryteuthis plei is a common inshore squid in coastal waters of the western Atlantic region. This study identifies the geographic movements of D. plei in the eastern Gulf of Mexico using changes in isotope ratios in eye-lens layers. Isotopic analyses suggest that these squid begin their lives in the deep chlorophyll maximum of the outer shelf and move inshore as they age.

Erratic and highly variable catches in the South African chokka squid Loligo vulgaris reynaudii fishery, cause socio-economic hardship for the industry and uncertainty for resource managers. Catch forecasting can reduce this problem as it is believed that catch variability is strongly influenced by environmental factors. In this study, data were collected at varying temporal and spatial scales. Data for the hourly time-scale study were collected from 1996-1998, aboard commercial vessels, whilst for the longer time-scales, data were extracted for Kromme Bay (a single fishing area) from existing databases (1991-1998) that were comprised of compulsory catch returns and oceanographic data. The environment-catch relationship for chokka squid on the inshore spawning grounds was then investigated using multiple correlation and regression analysis, analysis of variance, contingency table analysis and cross-correlation statistical techniques. This simple, direct, 'black box' statistical approach was relatively successful in developing a predictive capability. On a short time-scale (hourly), the regression model accounted for 32% of the variability in catch, with turbidity the main determinant (13%). On a daily monthly time-scale, the best prediction model was on a monthly scale, accounting for 40% of the variability in catch. The principal determinant, bottom temperature anomaly (11 %), was found to lag one month forward. Seasonal and diel catch variations induced changes in the relative importance of turbidity, water temperature and wind direction on catches. A strong, positive relationship was found between easterly winds (which cause upwelling) and catch, particularly in summer. Catch rates, however, decreased with an increase in turbidity. The correlation between temperature and catch was generally negative, however, higher catches were associated with a temperature range of 13-18°C. Highest catch rates were associated with easterly winds, zero turbidity conditions and sea surface temperatures from 15.0-16.9°C. Selected case studies (in situ observations) suggested that upwelling and turbidity events act as environmental triggers for the initiation or termination of the spawning process, respectively. A holistic approach is required to improve predictive capability of chokka squid abundance. Although short-term predictability remains essential (i.e. hourly-scale), future research should concentrate on long-term prediction models (e.g., monthly time-scales) involving greater spatial variation, which are the most important for management.

The objective of this thesis is to analyse the management and redistribution policies implemented in the South African squid industry. This is done within the broader context of fisheries policies that have been implemented within the South African fishing industry as the squid industry has developed. The study therefore has an institutional basis, which reviews the development of institutional mechanisms as they have evolved to deal fisheries management problems. These mechanisms (which can either be formal or informal) consist of committees, laws and constitutions that have developed as society has progressed. Probably the most prominent of these, in terms of current fisheries policy, is the Marine Living Resources Act (MLRA) of 1998. The broad policy prescription of the MLRA basically advocates the sustainable utilisation of marine resources while outlining the need to restructure the fishing industry to address historical imbalances and to achieve equity. It is this broad objective that this thesis applies to the squid fishery. The primary means of achieving the above objective, within the squid industry, has been through the reallocation of permit rights. These rights also provide the primary means by which effort is managed. A disruption in the rights allocation process therefore has implications for resource management as well. Permits rights can be described as a form of use right or propertY right. These rights are structured according to their operational-level characteristics, or rules. Changing these rules can thus affect the efficiency or flexibility of a rights based system. This is important because initial reallocation of rights, by the Department of Environmental Affairs and Tourism (DEAT), was based on an incomplete set of rights. This partly led to the failure of early redistribution attempts resulting in a "paper permit" market. Nevertheless, this thesis argues that redistribution attempts were based on ill-defined criteria that contributed to the failure described above. In addition to this the method through which redistribution was attempted is also questionable. This can be described as a weak redistribution strategy that did not account for all equity criteria (i.e. factors like capital ownership, employment or relative income levels). This thesis thus recommends, among other things, that an incentive based rights system be adopted and that the design of this system correctly caters of the operational-level rules mentioned above. In addition to this a strong redistribution, based on fishing capital, ownership, income and the transfer of skills, should be implemented. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in

The simplest model for superconductor electrodynamics are the London equations, which treats the impact of electromagnetic fields on the current density as a localized phenomenon. However, the charge carriers of superconductivity are quantum mechanical objects, and their wavefunctions are delocalized within the superconductor, leading to non-local effects. The Pippard equation is the generalization of London electrodynamics which incorporates this intrinsic non-locality through the introduction of a new superconducting characteristic length, \xi_0, called the Pippard coherence length. When building nano-scale superconducting devices, the inclusion of the coherence length into electrodynamics calculations becomes paramount. In this thesis, we provide numerical calculations of various electrodynamic quantities of interest in the non-local regime, and discuss their implications for building superconducting devices. We place special emphasis on Superconducting QUantum Inteference Devices (SQUIDs), and their usage as flux quantum bits (qubits) in quantum computation. One of the main limitations of these flux qubits is the presence of intrinsic flux noise, which leads to decoherence of the qubits. Although the origin of this flux noise is not known, there is evidence that it is related to spin impurities within the superconducting material. We present calculations which show that the flux noise in the non-local regime is signi cantly different from the local case. We also demonstrate that non-local electrodynamics greatly affect the self-inductance of the qubit. / Graduate

Molecular Nanomagnets have been proposed as plausible candidates in a variety of futuristic applications. Thorough understanding of the magnetic properties of these systems is therefore necessary to develop devices that include such units. The aim of this thesis is to synthesise and structurally and magnetically characterise a range of systems that could be used as elementary units in three proposed applications such as: data storage devices, magnetic refrigerants and qubits for quantum computing. A series of mixed 3d/4f metal complexes were synthesised through solvothermal reactions and characterised by X-ray single crystal diffraction and SQUID magnetometry. Through indirect methods it was possible to obtain high magnetic entropy change for some systems. It was also possible to obtain some insight into the magnetic interactions within the systems through modelling the magnetic data. The role of the 4f-4f and 3d-4f interactions in two sets of molecules is also described. The first study is in an asymmetric dysprosium dimer, where through a range of experimental techniques and advanced theoretical methods, such ab-initio calculations we are able to explain the role of the intramolecular interactions and their effect on the SMM properties of this system. Similarly, insight into the role of the 3d-4f interactions is achieved through the observation of the magnetic behaviour of a family of 27 tetranuclear systems, though SQUID data and ab-initio calculations. Finally, chemical functionalization of a well-proposed qubits, namely {Cr7Ni} and subsequent reaction with a redox active metal ion, CoII/III, two {Cr7Ni} systems are linked. The magnitude of the exchange interaction between the {Cr7Ni}-CoII-{Cr7Ni} was determined through Electron Paramagnetic Resonance. Furthermore, by chemical oxidation/reduction of the cobalt between paramagnetic and diamagneticstates, i.e. CoII and CoIII respectively, we demonstrate that the interaction can be switched ON/OFF. This characteristic makes of these systems candidates to function as a SWAP gate.

Within this thesis, (ultra)thin NiFe2O4 (NFO) and CoFe2O4 (CFO) films are prepared via reactive molecular beam epitaxy (RMBE) on MgO(001) and SrTiO3(001) substrates and are characterized in terms of their structural, electronic, and magnetic properties. In a first step, the structural properties of ultrathin off-stoichiometric NixFe(3-x)O4 films (0<x<1.5) deposited via RMBE on MgO(001) are investigated in situ during film deposition by means of synchrotron radiation-based x-ray diffraction (XRD) and ex situ after film growth by high energy surface x-ray diffraction (HESXRD). In the second major step of this work, a more extensive study on the dependence of the cationic ratio in NixFe(3-x)O4 thin films (0<x<2.07) grown on MgO(001) is conducted. The film surface structure and chemical composition is characterized in situ by low energy electron diffraction (LEED) and laboratory-based soft x-ray photoelectron spectroscopy (XPS), respectively. Film thicknesses are determined via analysis of x-ray reflectivity (XRR) data, while the film structure is analyzed by XRD measurements. Further, chemical properties and the electronic structure of the NFO films with focus on the cationic valencies of Ni and Fe cations with varying x is investigated by means of (angle-resolved) hard x-ray photoelectron spectroscopy [(AR-)HAXPES]. Complementary x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) investigations are conducted to obtain information on the cationic site occupancies and on the element-specific magnetic moments. The latter are compared to magnetic properties characterized via superconducting quantum interference device (SQUID) magnetometry. In a third step, the type of substrate is changed to SrTiO3(001) to investigate the influence of a larger strain applied by the substrate to NFO films with varying thicknesses. Structural characterization at the surfaces and in the films is conducted by means of LEED, XRR, and (grazing incidence) XRD, whereas XPS and HAXPES provide information on the chemical composition and electronic structure in the near-surface region and in deeper subsurface layers, respectively. Magnetic properties are characterized by SQUID magnetometry. In a fourth step, an alternative pathway for the formation of ferrite thin films is demonstrated exemplarily for CoFe2O4 films on SrTiO3(001), which are formed by interdiffusion of Fe3O4/CoO bilayers. The interdiffusion process was monitored via XRR, soft XPS and AR-HAXPES to determine the bilayer/film structure, stoichiometry, and chemical properties. Analysis of complementary XAS measurements provides additional information on the occupancies of Fe and Co cations during interdiffusion. Final SQUID magnetometry measurements are performed to gain information on the magnetic properties before and after complete interdiffusion. Overall, within this thesis, it was demonstrated that NFO and CFO thin films can be prepared in high structural quality with sharp interfaces and surfaces, which is crucial for the applicability in the fields of spintronics and spincaloritronics.