Minerals, metals and mining are the cornerstone of technological development and play an essential role in achieving the United Nations Sustainable Development Goals. Mining, however, is not a wastefree process, with mine wastes being a source of a host of environmental problems. One of these is acid rock drainage (ARD), which forms through a complex series of acid formation (mainly via sulfide oxidation), neutralisation (primarily by carbonates) and gangue mineral dissolution reactions in waste rock and tailings storage piles. The resulting drainage waters are often acidic, highly saline and may contain elevated levels of deleterious elements. Effective ARD mitigation requires accurate ARD characterisation and prediction strategies. To date, standard guidelines recommend a suite of geochemical static (characterisation) and kinetic (prediction) tests. Characterisation tests such as acid-base accounting (ABA) and net acid generation (NAG) tests provide a quick and relatively inexpensive estimate of the "worst case" scenario for acid formation and neutralisation, while kinetic tests (commonly humidity or column leach tests) aim to predict the longterm weathering potential of waste material. The UCT biokinetic test (not currently industry standard practice) was developed to address the effect of microorganisms on ARD formation and allow for the collection of relative kinetic data on neutralisation and acidification within a shortened time period. None of these tests, however, account for the additional layer of complexity introduced by mineral texture, which describes the interrelationship of mineral grains to one another, their shapes and sizes, with some frequently studied textural parameters including mineral liberation, association, grain size distribution and particle size. Mineralogical and textural analyses are infrequently practiced in the context of ARD assessment due to the difficulty in obtaining statistically sound quantitative textural data, high costs of measurement, and standard ARD assessment protocols recommending (rather than necessitating) these assessments. An ARD assessment approach that includes static, kinetic, mineralogical and textural assessments has nonetheless been suggested by several researchers. This project assessed the dominating textural parameters on the scales of kinetic (humidity cell) test (HCT) feed material (meso-scale) and characterisation (static and UCT batch biokinetic) test (SCT) feed material (micro-scale) using four waste rock samples (A, B, C and D) from a greenstone belt gold deposit as a case study. More specifically, the study aimed to assess the role of mineralogy and texture in the ARD assessment "toolbox" and to investigate the role of coarse material sampling for ARD assessment. Data sets collected included the PSD of the micro- and meso-scale material, sample chemistry data obtained from XRF spectrometry and LECO total sulfur, bulk mineralogy data from QXRD and QEMSCAN, as well as textural and mineralogical data from QEMSCAN for sized and unsized micro- and meso-scale material. ARD-specific data sets included results of geochemical characterisation tests such as ANC and single-addition NAG tests, the UCT batch biokinetic test with and without pH control for samples C and D, as well as prediction test data from water-fed and modified humidity cell tests. The geochemical static tests performed on samples A, B, C and D classified them as PAF, PAF, uncertain and NAF, respectively. Non-pH-controlled UCT batch biokinetic tests remained circumneutral for samples B, C and D over the duration of 90 days, while for sample A the pH became acidic over time. The pH-controlled tests demonstrated a steady depletion of neutralisation potential over the first 30 days. Humidity cell test results demonstrated no acidic leachate formation for waterfed tests over 40 weeks, while modified tests showed a decreasing pH over time as the neutralisation capacity was reduced. The mineralogy was important for the interpretation of test results on both the micro-and meso-scales and was assessed in terms of both discrete minerals and reactivity groupings (Fe-Sulfide, other sulfide, dissolving (carbonate), fast weathering, intermediate weathering, slow weathering, inert and other). For sample A the mineralogy was dominated by the inert (quartz), slow weathering (magnetite, plagioclasealbite) and intermediate weathering (Fe-amphibole) categories, with lesser contributions from the FeSulfide (pyrrhotite), dissolving (calcite) and fast weathering (epidote) groups. The main groups contributing to the sample B mineralogy were the slow weathering (plagioclase-albite, magnetite, Kfeldspar), inert (quartz) and intermediate weathering (Fe-mica, chlorite) groups, followed by Fe-Sulfide (pyrite), dissolving (calcite) and fast weathering (epidote) mineral groups. Sample C mineralogy comprised predominantly inert (quartz, titanite), Fe-Sulfide (pyrrhotite), dissolving (calcite) and intermediate weathering (Fe-mica, chlorite) minerals, with lesser contributions from slow weathering (K-feldspar) and fast weathering (epidote) minerals. Sample D comprised intermediate weathering (Feamphibole, chlorite, Fe-mica) and slow weathering minerals, with lesser contributions from slow weathering (magnetite), dissolving (calcite) and Fe-Sulfide (pyrrhotite) minerals. Textural parameters (liberation and association, grain size distribution and liberation spectrum) were evaluated for the FeSulfide and dissolving minerals. On the micro-scale, a large portion of the Fe-Sulfide and dissolving minerals in the samples was found in the liberated category (50%) of the texturally significant size fractions (>1mm), which comprised predominantly locked Fe-Sulfide and dissolving minerals. Evidence of a bimodal distribution was, however, found for sample C via the liberation spectrum and grain size distribution (early liberation size of 8mm), which accounted for the larger degree of liberation observed in the >1mm size fractions, and a larger degree of liberation for the sample overall. The association of Fe-Sulfide and dissolving minerals for all samples was found to be primarily to inert, intermediate weathering and slow weathering minerals, with a larger degree of association of Fe-Sulfide to dissolving minerals observed in sample C. On the micro-scale the mineralogy helped inform the placement of the samples on the geochemical classification plot based on the Fe-Sulfide, dissolving and intermediate weathering mineral contents. For the non-pH-controlled UCT batch biokinetic test, the presence and abundance of calcite was thought to dictate the PAF/NAF nature of the test, as even relatively low amounts of calcite rendered the pH circumneutral for the duration of the test (sample B). For pH-controlled tests, however, the calcite was depleted over time, which led to a favourable acidic environment for the acidophilic bacteria used in the batch biokinetic test. For both the geochemical characterisation and the pH-controlled UCT batch biokinetic tests there was evidence to suggest the contribution of intermediate weathering (Feamphibole, Fe-mica, chlorite) and slow weathering (magnetite) minerals to the neutralisation potential in the sample. On the meso-scale the effects of mineralogy were most prominent for the modified humidity cell tests, which showed some pH fluctuations and a steady depletion of the primary neutralisation potential. The pH fluctuation after the depletion of the dissolving minerals was attributed to the dissolution of intermediate weathering minerals over the 40 weeks of the tests. These effects were not observed during the 40 weeks of the water-fed experiments. Given sufficient time for the latter test, however, it would be expected that upon the onset of acidification, similar effects of the mineralogy on the leachate quality would be observed as in the modified tests. Knowledge of the Fe-sulfide and dissolving mineral texture yielded several insights. on the micro-scale, the liberation and grain size distribution data provided an indication that a sample-customised grinding size should be established to ensure adequate "worst case" scenario determination via characterisation tests, as material with fine Fe-Sulfide or dissolving mineral grains may not be fully liberated at the recommended 75µm top size. On the meso-scale, the texture yielded insight into the circumneutral behaviour of the water-fed HCT, as most of the acid-forming minerals were contained in size fractions where the liberation was either limited or negligible, with predominant association to slow weathering, intermediate weathering and inert minerals. These findings highlighted the importance of considering mineralogy, texture and the PSD of the material for HCT result interpretation. When considering texture as a parameter for ARD assessment, the potential for sampling and mineralogical errors arose due to the coarse material size (specifically on the meso-scale) and the limitations on the number of particles that could be assessed. Quantitative mineralogy and texture data allowed for the quantitative assessment of the sampling and mineralogical errors, which were investigated through Pierre Gy's fundamental sampling error (FSE) equation, the binomial distribution approximation and the plotting of confidence intervals over the Fe-Sulfide liberation data. The results showed that although tools such as Gy's "safety line" provide a useful quick means of sampling error assessment, this approach may yield excessively large sample mass requirements for coarse material. Calculating the sampling error from the textural and mineralogical data provided a useful tool to estimate sample representativeness. Additionally, the estimation of sampling errors may help in the planning of an appropriate sampling approach, which may ultimately provide a means to relate data sets to one another across scales based on how representative samples are of one another, and therefore of the parent lot. The current study showed how mineralogy and texture are not simply "tools" in the ARD assessment "toolbox", but rather a key means for interpreting characterisation and prediction test data. Additionally, the quantitative assessment of mineralogy and texture provided the opportunity to assess the materialspecific sampling error, which, in turn, may allow for the correlation of data sets across various scales and for the planning of appropriate sampling strategies. Recommendations for future work include: the quantitative assessment of the ARDI for meso-scale material; the assessment of detailed characterisation and prediction test leachate chemistry; trace element assessment and deportment throughout UCT batch biokinetic and humidity cell testing; mineralogical and textural assessment on characterisation and prediction test residues during and after tests; an in-depth analysis of the minimal/optimal sample block/sub-sample mass required for minimal error; the assessment of samples using X-ray microcomputed tomography to assess and decrease the effects of stereological bias prevalent in 2D measurements; and the application of a similar texture and mineralogy assessment to additional waste types (such as coal wastes, or waste material containing non-Fe-bearing sulfides).

Gun barrels are an important component in advanced defence systems. The gun barrels are used for direct and indirect fire and the material of the gun barrel is exposed to great strains and high temperatures. This sets high demands on the material of the gun barrel. During firing the gun barrel can be damaged. The first damage in gun barrels is the wear of the rifling followed by fatigue. When fatigue occurs cracks can propagate downwards into the bore and could result in catastrophic failure. Therefore investigation regarding the wear, the mechanisms and the underlying factors causing the damage will be performed. How and where the wear in gun barrels occur and also which wear mechanisms causing the wear. Wear in gun barrels involves extreme conditions during firing such as high gas pressure and high temperature from the burning propellant. This thesis work aims to understand how and why wear and damaging mechanisms in gun barrels occurs. Moreover how other ballistic factors influences have on the wear. The wear in gun barrels is caused by erosion from the combustion gases or/and sliding wear caused by the high-speed projectile. The phenomena of wear are complicated and factors like deformation state, types of wear, environment and process are interrelated with each other. These give the rise of wear. In this thesis, samples from three gun barrels were analysed. A new unworn gun barrel, a medium worn gun barrel and a severely worn gun barrel. From the used gun barrels 4 critical positions were identified, then samples from both surface and cross-section were obtained from the gun barrels. The surface and cross-section were analysed using different methods including optical light microscopy and scanning electron microscopy to characterise the surface damage and wear mechanisms. The results from the investigation revealed the dominating wear mechanism to be thermal and chemical erosion at the positions closest to the combustion chamber with heat checks as its signature feature. The heat checks are associated with fatigue cracks developed at the surface and during thermo-mechanical loading, allows it to propagate down into the surface. For both samples at position 2, after the start of the rifling, adhesive wear was obtained too. The adhesive wear was induced by material pick-up from the driving band of the projectile during sliding. In other meaning, the material is transferred from the counter-face to the bore surface. The severely worn gun barrel had been subjected to sliding wear at the muzzle end compared to the medium worn gun barrel which hadn’t experience the same wear rate at the same position. The analysis of the cross-section examination revealed information about the structure and condition of the material. To obtain more information about mechanical properties, a hardness test was performed. The hardness test revealed a hard but brittle surface which can be sheared by the frictional force caused by the sliding projectile. The analysis of the gun barrels revealed information about wear mechanisms and damages in medium and severely worn gun barrels. The detected wear mechanism was thermal erosion, chemical erosion, mechanical erosion and sliding wear.

The Rhizobiaceae bacteria are known for its varied nitrogen metabolism: especially its nitrogen fixation, so called diazotrofia, its capability of symbiosis with plants, or on the contrary plant pathogenesis (genus Agrobacterium). Rhizobium radiobacter R89 (stored in Czech Collection of Microorganism, in Brno as R89-1) is bacteria strain capable of codeine and morphine biotransformation to whole spectrum of pharmacologically significant derivates. This work is focused on purification and characterization of two selected enzymes that catalyze oxidation-reduction reactions, the crucial beginning of morphine skelets biodegradation. At the first, the biotransformational potential of the strain was evaluated and biochemical, molecular biological and bioinformatical approaches were employed to purify the responsible enzymes. Considering unsuccessful purification from Rhizobium radiobacter R89-1, the proteins structural genes were cloned and heterologously expressed in bacterial system and afterward characterized. Found protein sequence and enzyme characterization (basic kinetic measurements, substrate specificity and thermo- stability) have revealed different origin of the enzymes and clarify reasons why the original purification procedure was not successful.

This essay will exlopre the character of one of our times most beloved fictional characters, Harry Potter. The purpose of this esay is to investigate Harry's character in J.K. Rowling's first novel and to show that it is his his character that is one of the chief reasons for the popularity of the book, and indeed, of the entire series. The various different passages in Harry's role are well-illustrated by close reading of the significant passages in different parts of the novel.

Submitted in the fulfillment of the requirements for the degree of the DOCTOR OF PHILOSOPHY In the Department of African Languages, at the University of Zululand, 2010. / This study gives the critical analysis of Ngcobo’s sociological radio plays. The written plays are examined. The work is arranged as follows: Chapter one is the general introduction of the study. It paves the way the study will be conducted which includes among other things; hypothesis, aim of study, scope of study, definition of concepts, research methodology, theoretical approaches to the study, the characteristic nature of radio drama, an influence of traditional drama and the synopsis of all serial radio plays. Chapter two explores the various theoretical approaches that are applicable in such the study of radio plays; inter alia; sociological, structuralism, reader, moral – philosophical, reception, intention, historical – biographical, semiotics and New Criticism approaches. Chapter three looks at the understanding structure of the radio plays where amongst other things explores the aspects of society that radio play addresses. It gives comparisons of social aspects, social disorder / revolt and looks at how Ngcobo addresses such social revolts in order to bring about social restoration. Chapter four focuses on the comparisons of the radio plays with regard to style, temporal which includes time and space. It further focuses characters / actors and narration. Chapter five looks at the linguistic appropriateness of the radio plays. It seeks to ascertain Ngcobo’s language how it suits his characters, situation, addresses the questions and answers’ relationships as they crop up in the plays. Monologue as an integral part of psychological process describes a mode of mental processes which include sadness, elation and desolation as felt by characters. It assesses Ngcobo’s usage of dialogue and also looks at other factors such as mood, place, sound effects, music and sound effectiveness as important components that heighten the development of the play to the horizons for its effectiveness. Chapter six deals with meaning and interpretation of the radio plays whereby it deals with the intention, significance, emerging factors that arise further enhance the development of the plays. Apparent and challenges that the playwright poses on his plays are also highlighted. Chapter seven is the concluding chapter. This looks at the thesis in its final analysis which gives the summary, findings and observations. It examines the challenges and contributions of the study with a critical overview and conclusions. Lastly it suggests some future research on the study of serial radio drama by showing the important elements as discovered in this study.

<p>  </p> <p>Architectured metamaterials are artificial systems with unique structural characteristics. They show distinct deformation behaviors and improved mechanical properties compared to regular materials. For example, mechanical metamaterials demonstrate negative Poisson's ratios, whereas regular materials have positive values. In theory, the auxetic behaviors arise from periodic cellular architectures regardless of the materials utilized. While this premise is mostly true for macroscopic metamaterials, it may not work well at a very small lengthscale since chemistry may play a critical role in nanostructures. However, this fundamental idea has not been addressed due to the lack of powerful manufacturing strategies at the nanoscale. The majority of architectured metamaterials are manufactured from top down with their unit size of microns or larger. On the other hand, there are also molecular auxetics which are natural crystals and thus are not designable. Therefore, there is a significant gap in lengthscale from 10 nm to 1 µm. DNA self-assembly is a bottom-up approach that can construct complex nanostructures based on sequence complementarity. Examples include DNA origami structures and DNA tile assemblies. This dissertation bridges the gap in the lengthscale by introducing nanoscale auxetic units from DNA and investigates relevant structural properties and mechanical behaviors. This study addresses the premise of metamaterials and elucidates the structure-property relation. The findings from this work formulate design principles for DNA based auxetic metastructures. </p> <p>In this work, we built several two-dimensional (2D) auxetic nanostructures from wireframe DNA origami. They serve as the model systems to demonstrate the feasibility of constructing nanoscale auxetics via DNA self-assembly. DNA origami structures are commonly constructed by a long ‘scaffold’ strand with many ‘staple’ oligonucleotides. Since the DNA metastructures are too small to directly apply external forces, we implemented chemical deformation by inserting ‘jack’ edges. Like a car jack, the length of the jack edges can be modulated via two-step DNA reactions: toehold-mediated strand displacement and annealing with a new set of jack staples. The DNA nanostructures reconfigure accordingly. To complement the experiment, we performed molecular dynamics (MD) simulations based on coarse-grained models using an open-source oxDNA platform. In the numerical computation, external loads were directly applied to deform the metastructures, providing details of structural deformation. We discovered that the auxetic behaviors of DNA metamaterials can be estimated by architectural designs, however the material properties are also crucial in the structures and deformations. Our mechanistic study provided general design guidelines for 2D auxetic DNA metamaterials. We also designed and constructed a Hoberman flight ring from DNA, a simplified planar version of Hoberman sphere. This structure consists of six equilateral triangles that are topologically organized into two layers, resembling a trefoil knot. The DNA flight ring deploys upon external forces, expanding (open state) or contracting (closed state) by sliding the two layers of triangles. This is the first synthetic deployable nanostructure and offers a versatile platform for topological research.</p> <p>This thesis also investigates 3D effects in DNA assemblies and related mechanics. We used a DNA origami tile designed with an intrinsic twist as a model system and explored its cyclization process using MD simulations. The numerical computation revealed the detailed process where the structure untwists and curves for cyclization simultaneously under external forces. The force and energy required to overcome the initial curvature and cause the 3D deformation were also calculated. The results agree well with the previous experiment and theory, further verifying the simulation method. Direct mechanical forces and DNA responses were realized experimentally with 3D DNA crystals built from triangular DNA tiles. Nanoindentation was performed on macroscopic ligated crystals using atomic force microscopy (AFM). MD simulations were performed in parallel, which revealed the full spectrum of several distinct deformation modes from linear elasticity to structural failure. The combined experiment, computation, and theoretical calculation showed that the complex behaviors can only be understood fully by considering the structure and its components. </p> <p>The scientific findings from this thesis should contribute to the construction of auxetic metastructures, the design methods for DNA based metamaterials as well as the prediction of their structural properties and mechanical behaviors. This thesis will pave the way for building architectured materials from DNA with tailored properties and functionalities, opening the door for new opportunities and unique applications.</p>

Clay, quartz and feldspar are widely available in Uganda. The location and properties of various clay deposits are reported in the literature, but little is reported on feldspar and quartz deposits. In this work an extended literature on ceramics and porcelains in particular, is documented. Samples from two deposits of feldspar and two deposits of quartz are characterised and found to possess requisite properties for making porcelain insulators. Sample porcelain bodies are made from materials collected from selected deposits using different mixing proportions of clay, feldspar and quartz. Their properties in relation to workability, firing temperature, dielectric and bending strengths are studied. It is found that a mixture consisting of 30% Mutaka kaolin, 15% Mukono ball clay, 30% Mutaka feldspar and 25% Lido beach flint yields a body with highest mechanical strength (72MPa) and dielectric strength (19kV/mm) when fired at 1250°C. The strength (both mechanical and dielectric) is found to decrease with increasing firing temperature. At high firing temperatures, the undissolved quartz in the body decreased, the glass content increases and pores are formed. Mullite content on the other hand does not change at temperatures above 1200°C but there are significant differences in the morphologies of the mullite crystals in the samples. Optimum mechanical and electrical properties are found at maximum virtification and a microstructure showing small closely packed mullite needles. / QC 20101122

Yes / In this paper, a 2.45 GHz band microwave sensor design is introduced to be utilized for the dielectric constant determination of ethanol-water solutions. The introduced microwave sensor is composed of two symmetrically positioned, directly coupled inter-connected split-ring resonators with a circular ring-shaped detection area in the middle region, into which a small amount of ethanol-water solution is dropped. The fabricated prototype of the microwave sensor has a total component size of 12 mm x 30 mm on Rogers RO4003 substrate. The sensor measurement performance is numerically evaluated and experimentally validated in good agreement. The introduced microwave sensor has the structural design novelty of possessing the main detection region in a form of a circular hollow where a disposable 3D printed fluid cup can be accommodated for multiple uses. The introduced microwave sensor has technical feasibility to be used as an ingredient identification device for the chemical solutions to figure out complex dielectric parameters of ethanol-water specimens with small, low-cost, reusable, easy-to-fabricate features as well as the determination of volume percentage concentration of ethanol content.

<p dir="ltr">Repeated loading and unloading cycles lead to the formation of strain in the material which causes initiation of the crack formation this phenomenon is called fatigue. Fatigue properties are critical for structures subject to cyclic load; hence fatigue analysis is used to predict the life of the material. Fatigue analysis plays an important role in optimizing the design of the 3D printed material and predicting the fatigue life of the 3D printed component.</p><p><br></p><p dir="ltr">The main objective of this thesis is to predict the fatigue behavior of different microstructures of Ti-64 titanium alloy by using the PRISMS-Fatigue open-source framework. To achieve this goal Ti-64 microstructure models were created using programming scripts, then the structures were exported to a finite element visualization software package, with all the required properties embedded in the pipeline. The PRISMS-Fatigue framework is used to conduct a fatigue analysis on 3D printed materials, using the Fatigue Indicator Parameters (FIP), which measure the driving force of fatigue crack formation in the microstructurally small crack growth.</p><p><br></p><p dir="ltr">Three different microstructures, i.e., cubic equiaxed, random equiaxed, and rolled equiaxed microstructures, are analyzed. The FIP results show that the cubic equiaxed grains have the best fatigue resistance due to their isotropic structural characteristics. Additionally, the grain size effect using 1 and 10 micrometers is investigated. The results show that the 1 micrometer grain size cubic equiaxed microstructure has a better fatigue resistance because as grains are small and they have a higher mechanical strength.</p>

Yes / This study investigates the acoustic performance of materials made using various amounts of bio-binder (cis-1,4-polyisoprene). The filler used in making these materials was from recycled tyres which consist of nylon 6,6 fibres bonded to rubber grains known as tyre shred residue (TSR). The materials have shown high acoustical performance especially at low binder levels, due mainly to the open porosity of the tested samples. The paper begins with a discussion of materials made using recycled granulates. The macroscopic properties (e.g. flow resistivity, porosity, tortuosity, etc.) that control the acoustical behaviour of these materials are then defined as are methods for their measurements. The acoustical characterisation of porous media is considered next, followed by discussion of the acoustic performance of the materials. The characteristics of these novel materials are illustrated through experimental and theoretical models involving sound absorption and transmission.