In the comminution industry, cone crushers are widely used for secondary and subsequent stages of size reduction. For a given crusher, the achieved size reduction is governed by the closed-side setting. Hadfield Steel is commonly used to line the crushing members to minimize wear. Yet, liner wear caused by some rock types can still be excessive. Enlargement of discharge opening induced by wear of liners produces a drift in product size which, if unchecked, can lead to high volumes of re-circulating load. Alteration of closed-side setting is now commonly achieved via hydraulic means. However, compensation of liner wear still involves plant shut down and loss of production.

The problem initially presented was the structural elucidation of a compound obtained when 2,5-dimethylpyrrole was subjected to conditions of acidic reduction. Previous workers had assigned a molecular formula C₁₂H₁₇N to this product and a partial structure had been put forward based on the indolenine system. In the course of this work it was found that the compound obtained by these earlier workers was the result of a reductive self-condensation of 2,5-dimethylpyrrole, and Its structure was conclusively established as 1,3,4,7-tetramethylisoindoline. The methods used in the structural elucidation of this product included elemental analysis of its derivatives, measurement of its basicity and equivalent weight, infrared and ultraviolet spectroscopic evidence, oxidative degradation, and its proton magnetic resonance spectrum. Two related isoindolines were prepared by different routes. 2,4,7-trimethylisoindoline was synthesised by methods analogous to those already known, and the ultraviolet spectrum of its methiodide, when compared with that of the methiodide from 1,3,4,7-tetramethylisoindoline, reinforced the structural assignment of the latter. 1,3-diphenyl-4,7-dimethylisoindoline was obtained by the reductive condensation of acetonylacetone with 2,5-diphenylpyrrole (which did not undergo self-condensation). The favourable result of this reaction suggested that a similar condensation may have occurred to give the 1,3,4,7-tetramethylisoindoline and also admitted the possibility of a general synthesis of substituted isoindolines by this route. An attempt was made to resolve the mechanism of the 2,5-dimethylpyrrole condensation, for which either a Diels-Alder reaction or a ring-opening process may be postulated. The failure of the dimethylpyrrole to show dienic character, even in the presence of very strong dienophiles, together with positive evidence for ring-opening and ketone-pyrrole condensation argued forcibly for the latter mechanism. / Science, Faculty of / Chemistry, Department of / Graduate

L'émergence est parfois présentée comme ce qui expliquerait l'entropie alors que l'entropie expliquerait l'émergence. Tels quels ces deux énoncés ne peuvent être tous deux vrais. Face à la polysémie déconcertante des concepts 'émergence, d'entropie et d'explication, je soutiens que cet apparent paradoxe peut être résolu formellement ainsi: l'émergence (en un sens A) explique (en un sens B) l'entropie (en un sens C) et l'entropie (en un sens D) explique (en un sens E) l'émergence (en un sens F). La solution revient donc à préciser A, B, C, D, E, et F. Pour ce faire, je propose un modèle pluraliste (restreint) de l'explication et un examen critique du concept d'entropie.Dans le cas de l'entropie comme explanandum de l'émergence (A, B et C), ce qui émerge est l'irréversibilité comme propriété essentielle de l'entropie thermodynamique, mais l'émergence ne peut être synonyme de non-explicabilité. Je montre alors trois possibilités où l'émergence peut expliquer l'entropie thermodynamique: selon (i) un sens fort, comme une modalité ontologique, (ii) selon un sens intermédiaire d'après ce que j'appelle l'émergence méthodologique, ou (iii) un sens faible, comme sa désignation comme membre d'une classe d'émergents. Dans le cas de l'entropie comme explanans de l'émergence (D, E, et F), il faut distinguer l'approche substantielle de l'approche analogique. Dans le premier cas, l'entropie renvoie à une propriété macroscopique robuste et autonome pouvant être mobilisée au sein d'un explanans de l'émergence de nouvelles structures complexes. Dans le second cas, l'entropie exemplifie la réalisabilité multiple et peut être mobilisée, nonobstant une justification, au sein d'un explanans de l'émergence de propriétés à des niveaux supérieurs. En définitive, la polysémie de ces concepts peut être fructueuse au sein de ce cadre explicatif de phénomènes divers et complexes, de la physique à la biologie. / Entropy is generally considered as an emergent property, while the emergence of certain organized structures is supposed tobe the result of entropy dissipation. Thus, emergence is sometimes seen as explaining entropy, whereas sometimes the explanation is the other way around, as entropy would explain emergence. As such both statements cannot be true. Faced with the daunting polysemy of these concepts of emergence, entropy and explanation, I argue that this apparent paradox can be formally solved as follows: the emergence (in a sense A) explains (in a sense B ) entropy (in a sense, C ) and entropy (in a sense D ) explains (in a sense E ) emergence (in a sense F ). The solution is therefore to specify A, B, C, D, E, and F. To do this, I suggest a (restricted) pluralistic model of explanation and a critical examination of the concept of entropy. In the case of entropy as explanandum of emergence (A, B and C), what is emerging is irreversibility as an essential property of thermodynamic entropy, but it cannot be emergence of synonymous of non-explicability. I then show three possibilities that can explain the emergence of thermodynamic entropy : (i) in a strong sense,as an ontological modality, (ii) in an intermediate sense, from what I call ‘methodological emergence’(where there is a possibility of reductive explanation but no derivational reduction), or (iii) in a weak sense, as its designation as a member of an emergence class.In the case of entropy as explanans of emergence (D, E, and F), one must distinguish the substantive approach from the analogical approach. In the first case, entropy refers to a robust and autonomous macroscopic property that can be mobilized in an explanans of the emergence of new complex structures. In the second case, the entropy exemplifies multiple realizability and can be mobilized, with a proper justification, within an explanans of the emergence of properties at higher levels. Ultimately, the polysemy of these concepts can be fruitful in this explanatory framework for various complex phenomena, from physics to biology.

To improve upon the understanding and efficiency of the crushing/ i screening process, the Brenda Mines Limited secondary crushing plant was simulated. The plant consists of two stages of crushing, with a single stage of screening employed in closed circuit with the latter crushing stage. Acquisition of plant data was carried out according to full or modified factorial designs intended to cover normal operating ranges. The units sampled include a Symons Nordberg 7 - foot standard cone crusher, a Symons Nordberg 7 - foot short-head cone crusher and two Allis-Chalmers 8ft.x20ft. double deck virbrating screens. Sampling was carried out under conditions as close to steady state as was possible. All samples were screened at the plant using a standarized procedure. Raw data obtained around the screens was later adjusted by means of a least squares technique that assumes all measured values are in error. The models developed to describe both crushing operations are modifications of those used at Mt. Isa Mines Limited. The model parameters were empirically fitted to the observed data. Both models gave satisfactory performance. The model proposed for the vibrating screens was derived from small particle statistics. It is continuous over all size ranges and was judged to perform satisfactorily. Models for the short-head crushers and the screens can be extrapolated approximately twenty percent beyond their fitted data ranges. The fitted models were combined to enable a steady-state simulation of the complete secondary crushing plant. A study of the simulation was performed in accordance with a full factorial design modified to include intermediate ranges. Operating variables whose values were generated during the simulation remained within their fitted ranges, with the exception of the short-head crusher feedrate. Preliminary analysis of the simulation output shows that the results conform to expected and observed plant behavior. Further analysis with respect to short-head crusher power draw indicates that it may be possible to increase plant capacity under some conditions. The economic advantage of a digital simulation is demonstrated by the fact that the average cost for one computer run is approximately twenty cents. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

M.Sc. / An Acinetobacter sp. strain RFB1 isolated in our laboratory has been shown to have the ability to metabolise inorganic cyanide salts, CO 2, and bicarbonate. The enzyme aggregate responsible for the conversion of these substrates, is located extra-cellularly. Resolution of the extra-cellular complex, a crude enzyme filtrate, was attempted in order to characterise the protein responsible for the reduction of CO 2. The crude enzyme filtrate was separated by means of molecular exclusion chromatography and afforded three fractions with molecular masses ranging from 76 000 to 191 000. Analysis by SDS-electrophoresis, showed that the first protein fraction contained more than ten proteins. Certain of these proteins were identified in the second fraction and other proteins in the third protein fraction. This implies that some denaturation already occurred during molecular exclusion separation. The functionali7ation of CO 2 by protein fractions 1 and 3 supports this argument, and, in addition , cyanide ions were only reduced by fractions 1 and 2. Fatty acids, ranging with chainlengths between C5 and C25, were shown to be present and certain fatty acids were unequivocally identified by GC-mass spectroscopy as the products resulting from CO2 functionali7ation and carbon-carbon bond formation. Ferrous ions, in an optimal concentration of 250 gg cm', were necessary and served as an essential ingredient of the reaction mixture. A rather unusual result was, however, that apart from an initial, relatively small uptake of Fe(II), significant amounts of Fe(III) were not formed and the Fe(II) concentration remained approximately constant during the reaction. This implies that the formed Fe(M) is rapidly reduced to Fe(II) again. Spectroscopic measurements, furthermore, strongly suggested the involvement of an iron-sulphur cluster in a cyclic redox process wherein both Fe(II) and Fe(III) are involved. Carefully conducted experiments pointed to light as the outside source of energy. Qualitative similarities with an artificial photosynthetic process, formulated earlier by J-M. Lehlliii, can be drawn and used partly to explain the experimental results.

(1) In a variety of experimental procedures for Birch reduction at dry-ice temperature (-65 to -78°C), benzamide was reduced to 1,4-dihydrobenzamide: (a) By using Niem’s procedure (27), with lithium and ethanol in liquid ammonia at dry-ice temperature and where ethanol was added slowly after lithium addition, benzamide was reduced to 1,4-dihydrobenzamide., (b) By using Kuehne and Lambert’s method (20), with sodium and ethanol in liquid ammonia at dry-ice temperature, benzamide was reduced to 1,4-dihydrobenzamide., (c) Using Kuehne and Lambert’s method (20), with sodium and ethanol in liquid ammonia at -33°C (the boiling point of NH3), benzamide was reduced to a new compound (possibly 3-cyclohexene-carboxamide) not fully characterized. (2) m-Methoxybenzaminde when subjected to Birch reduction at -78°C or -33°C and with a 3.3 or 8 equivalents of sodium and ethanol by Kuehne and Lambert’s procedure (20), gave the following results: (a) With 3.3 equivalents of sodium and ethanol in liquid ammonia at -78°C, m-methoxybenzamide was reduced to 1,4-dihydro-3-methoxybenzamide.; (b) A reduction similar to (a) with added iron (1 p.p.m.), was done with no noticeably large effects.; (c) Birch reduction of m-methoxybenzamide at -33°C (the boiling point of ammonia), gave a new compound, not identified.; (d) m-Methoxybenzamide, with excess sodium (8 equivalent) at dry-ice temperature, was reduced to a light brownish liquid, not characterized. (3) Terephthalic acid on Birch reduction with lithium and ethanol in liquid ammonia was reduced to a mixture of cis- and trans- 1,4-dihydroterephthalic acid. Cis- and trans- isomers were separated on the basis of difference in solubility, as cis-isomer is more soluble in cold water than trans-isomer.

L’utilisation des acides de Lewis dérivés du bore tels que les boranes, les acides boroniques et les acides boriniques a émergée récemment comme une alternative intéressante aux métaux de transitions dans le domaine de la catalyse. Lors des travaux précédemment effectués au laboratoire par Tharwat Mohy El Dine, la synthèse d’acides boriniques originaux a été effectuée. Ces catalyseurs ont montrés une activité remarquable et supérieure aux dérivés boroniques correspondants pour la synthèse catalytique de dipeptides et la réaction de formylation d’amines. Au cours de nos travaux, il nous a été possible d’évaluer l’apport des acides boriniques pour la catalyse de la réduction des amides dans des conditions douces avec une bonne compatibilité fonctionnelle, le mécanisme réactionnel a également pu être rationnalisé. Nous avons ensuite évalué l’activité du même acide borinique pour la réaction de réduction des oxydes de phosphines, des sulfoxydes et des N-oxydes d’amines. Après une étude mécanistique portant sur le transfert d’hydrure d’un hydrosilane vers un acide borinique, l’apport des acides boriniques pour l’hydrosilylation des cétones, aldéhydes et imines a également été étudié. Une méthodologie coopérative entre un hydrosilane et un acide borinique pour la catalyse de la réaction d’amidation a été développée. Enfin, une étude théorique utilisant la RMN et la DFT a permis de rationnaliser la relation structure activité de nos catalyseurs. L’ensemble de ces travaux confirme le potentiel des acides boriniques en tant que catalyseurs efficaces pour de nombreuses réactions. / Boron based Lewis acid such as borane, boronic and borinic acids, has recently emerged as a strong alternative to transition metal catalysts for catalysis. During Tharwat Mody El Dine thesis, a range of original borinic acids have been synthetized. These catalysts have been used to investigate catalytic peptides synthesis and amines formylation. This thesis work with aimed the association between borinic acids and hydrosilanes for organic synthesis. In the first part a borinic acid catalyzed amides reductions have been developed, our methodology work in mild conditions and displayed high chemoselectivities. In a second chapter, we will study the activity of borinic acids for the reduction of phosphine oxides, sulfoxides and amine N-oxide. After a study on the formation of previously observed amine-borane, a borinic acid mediated ketones, aldehydes and imines hydrosilylation have been demonstrated in the third chapter. In the fourth chapter a cooperative borinic acid-hydrosilane mediated amide bond formation has been developed, the mild conditions and the absence of racemization appear as the keys elements of this methodology. Finally, RMN and DFT instruments have been used to understand the relationship between structure and reactivity of borinic acids.All this study confirms the potential of borinic acids as efficient metal-free catalysts in many organic transformations.Mots clés : catalyse, acide borinique, hydrosilane, réduction, amides.

NR 20140805

Nitrogen (N) is a chemical constituent for almost all biological molecules including proteins, DNA, RNA, lipids and is therefore vital for life. The ultimate source of nitrogen is the atmospheric dinitrogen (N2) but that only becomes bioavailable through a process of nitrogen fixation, the process that converts N2 to ammonia (NH3). The industrial Haber-Bosch process and biological nitrogen fixation account for the majority of nitrogen fixed every year. However, due to its high temperature, pressure and fossil fuel requirements, Haber-Bosch is an expensive process. Every year, approximately 3% of the global energy demand is used to manufacture ammonia through Haber-Bosch process. On the other hand, biological systems produce ammonia by reducing dinitrogen at ambient temperature and pressure using an anaerobic enzyme called nitrogenase. Research in understanding the mechanism of nitrogenase could eventually allow researchers to mimic the enzyme and fix nitrogen efficiently at standard temperature and pressure. In this research nitrogenase of Azotobacter vinelandii was studied to understand the mechanism of delivery of electrons/protons to the active site and how these accumulated reducing equivalents are used for substrates reduction. Through a series of studies, it has been demonstrated that the electrons and protons are added to the active site in a concerted manner which are then stored as bridging hydrides. The accumulated hydrides are used in four different mechanisms, namely reductive elimination, hydride protonolysis, migratory insertion and proton coupled electron transfer, to catalyze the reduction of varieties of unsaturated molecules. This fundamental understanding of molecular detail of nitrogenase catalysis could eventually help in development of more efficient, robust and selective catalysts.

Few model reduction techniques exist for dynamical systems whose parameters vary with time. We have particular interest here in linear time-periodic dynamical systems; we seek a structure-preserving algorithm for model reduction of linear time-periodic (LTP) dynamical systems of large scale that generalizes from the linear time-invariant (LTI) model reduction problem. We extend the familiar LTI system theory to analogous concepts in the LTP setting. First, we represent the LTP system as a convolution operator of a bivariate periodic kernel function. The kernel suggests a representation of the system as a frequency operator, called the Harmonic Transfer Function. Second, we exploit the Hilbert space structure of the family of LTP systems to develop necessary conditions for optimal approximations. Additionally, we show an a posteriori error bound written in terms of the $\\mathcal H_2$ norm of related LTI multiple input/multiple output system. This bound inspires an algorithm to construct approximations of reduced order. To verify the efficacy of this algorithm we apply it to three models: (1) fluid flow around a cylinder by a finite element discretization of the Navier-Stokes equations, (2) thermal diffusion through a plate modeled by the heat equation, and (3) structural model of component 1r of the Russian service module of the International Space Station. / Master of Science