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Gossans, the brightly coloured oxidation products of sulphide mineralised rocks, have acted as an exploration target for base and precious metals and sulphur for thousands of years. They are easily identified from remote sensing and field-based reconnaissance, and once found may be drilled to determine the character of mineralisation below. The number of targets drilled could potentially be reduced if gossans overlying significant mineralisation can be discriminated from their field relations, mineralogy and geochemistry. Previous such studies have focussed on porphyry-type systems, with less attention on the generally much lower tonnage volcanogenic massive sulphide (VMS) deposits. However, VMS continue to provide an economically important source of metals in Europe and elsewhere. The Troodos Massif in Cyprus was chosen for this study as it hosts a currently active Cu mine along with historically worked VMS, is little deformed and has a relatively well understood geological framework. Of particular interest are secondary Cu deposits (SCUD) which form due to weathering of primary massive sulphides (PMS). These can be worked at relatively lower financial and environmental cost, and at much lower grades (down to around 0.1 % Cu). The only currently mined SCUD in Cyprus is the Phoenix ore body at Skouriotissa, which lies immediately adjacent to, and structurally below the Phoukasa PMS. The questions addressed in this study are: 1) Do Cypriot PMS that were mined for Cu show original Cu enrichments, or is their elevated Cu content a result of supergene enrichment to form an SCUD? This was addressed by comparing the mineralogical, chemical and S isotopic compositions of PMS mined for Cu with those mined for pyrite only from across the Troodos; 2) Do gossans formed from Cu-rich sulphides show distinctive mineralogical and chemical signatures? The characteristics of gossans known to overlie prospective sulphide bodies were compared with those from barren PMS; 3) What circumstances promote the formation of SCUDs? In particular, did sulphide oxidation occur on the sea floor or in a terrestrial environment? It was considered likely that SCUD formation may require sea floor oxidation because this will result in limited Cu dispersion, due to both sharp pH and redox gradients and limited fluid flow when compared with terrestrial weathering, where the depth to the water table can be considerable. The question was addressed by comparing the field relations, chemistry and S and O isotope compositions of gossans thought to have formed on the sea floor (Skouriotissa - Phoenix) with those generated in a terrestrial setting (Kokkinopezoula, Mathiati and Sia). The remnants of primary VMS deposits mined for Cu in Cyprus (Phoukasa, Sia and Troulli) almost exclusively contain primary Cu sulphides such as chalcopyrite. Secondary Cu sulphides, mainly chalcocite and covellite, are only present in significant concentrations at Phoukasa and Troulli, with Cu oxides being found in Phoenix. At Phoukasa, secondary Cu sulphides have a mean δ34S = 3.69±0.08 ‰ similar to primary pyrite and chalcopyrite (mean δ34S = 3.78±0.08 ‰) suggesting formation from Cu-rich fluids that scavenged S from primary sulphides. Sulphide material collected from copper mines has Cu = 840 to > 10,000 ppm at Phoukasa; 167 to 3573 ppm at Sia; 288 to > 10,000 ppm at Troulli, while the Cu-barren deposits have generally lower Cu grades (Cu = 170 to 433 ppm at Kokkinopezoula; 327 to 1303 ppm at Mathiati north). There are no systematic differences in the S isotope compositions of pyrite between deposits mined for Cu and those not (average δ34S = 1.68, 3.74 and 7.1 ‰ for Cu-rich Sia, Lysos and Phoukasa, and 5.03 and 3.70 ‰ for Cu-poor Kokkinopezoula and Mathiati North sulphides, respectively). No consistent chemical differences (including chalcophile elements) could be identified between gossans overlying Cu-rich as opposed to barren PMS. Gossans overlying the Lysos and Sia Cu-rich PMS, however, show an enrichment in Pb and Zn not observed in other gossans, and umbers, which are chemical sediments associated with VMS systems, often overlying gossans, show strong Cu enrichments in the vicinity of Cu-rich PMS. Umber samples from near the Cu-rich Phoukasa sulphide body contain > 10,000 to 35,400 ppm Cu, while those around Cu-poor Mathiati North contain 669 to 819 ppm Cu. There were no differences in the S isotope compositions of gypsum from sulphide bodies which were Cu-rich (δ34S = 5.9 to 6.9 ‰ for Sia, Phoukasa and Troulli) and Cu-poor (δ34S = 5.0 to 7.3 ‰ for Kokkinopezoula, Mathiati North). Regarding the environment of formation of SCUDs, an initial submarine oxidation of the Phoukasa VMS is considered likely as it is immediately overlain by marine pelagic sediments, while all other deposits studied are overlain by volcanics. In addition, volcanics in the vicinity of Phoukasa show large negative Ce anomalies (Ce/Ce* = 0.90 to 0.38, average = 0.71), consistent with sea floor alteration, compared with other localities such Kokkinopezoula (Ce/Ce* = 0.89 to 1.08, average = 0.97) and Sia (Ce/Ce* = 0.92 to 1.03, average = 0.99). Unfortunately, the S isotope composition of gypsum could not be used to determine the nature of the gossan-forming environment. Gypsums from all locations (average δ34S = 6.74±0.08 ‰) have δ34S values similar to, but slightly 34S enriched compared with their associated sulphides (average δ34S = 2.9±0.08 ‰) which indicates that their S isotope signature largely reflects that of S released during sulphide oxidation, as opposed to evaporation of sulphate-rich waters or direct precipitation from a similar solution (i.e., seawater). However, the oxygen isotope composition of gypsum (average δ18O = 6.2 ‰) from Sia (average δ18O = 2.4 ‰) reflects a mixture of atmospheric O (δ18O = 23.6 ‰) and Mediterranean meteoric water O (δ18O ≈-5.0 ‰), indicating a terrestrial environment of formation. Gypsum from Skouriotissa has an average δ18O = 6.6 ‰ which most likely indicates a combination of seawater and seawater-dissolved O (δ18O ≈23.5 ‰), despite some overlap with the composition of meteoric water and atmospheric O. In summary, it is proposed that the currently unique nature of Skouriotissa as hosting the only major SCUD in Cyprus is due largely to initial sea water alteration of the Phoukasa PMS resulting in limited Cu dispersion and localised Cu enrichment within the primary ore body. Subsequent uplift and alteration of the Phoukasa PMS led to the formation of a relatively high grade SCUD in the Phoenix deposit. The main outcomes of the study are a series of models for the development of gossans and associated lithologies in terrestrial and seafloor weathering environments in Cyprus. These incorporate a new term (retali) for acid leached volcanics in the footwall of PMS, and exploration-relevant field, mineralogical and chemical criteria for their discrimination from gossans, which overlie PMS. In agreement with an existing model, the formation of the Phoenix SCUD is interpreted as having been due to the downward migration of Cu-bearing acid fluids from the seafloor oxidation of the upper parts of the Phoukasa deposit. Secondary Cu mineralisation is thought to have taken place within the relatively reducing environment below the water table in lavas stratigraphically below the Phoukasa deposit. That the formation of SCUDs may require seafloor sulphide oxidation, and that this can be recognised in the mineralogy and chemical compositions of associated volcanics and gossans, provides new exploration criteria for SCUDs. However, it should be noted that the Phoenix deposit was the only SCUD examined in this study, and that this model should therefore be tested elsewhere.

The Galactic transient V1309 Sco was the result of a merger in a low-mass star system, while V838 Mon was thought to be a similar merger event from a more massive B-type progenitor. In this paper, we study a recent optical and infrared (IR) transient discovered in the nearby galaxy NGC4490 named NGC4490-OT2011 (NGC 4490-OT hereafter), which appeared similar to these merger events (unobscured progenitor, irregular multi-peaked light curve, increasingly red colour, similar optical spectrum, IR excess at late times), but which had a higher peak luminosity and longer duration in outburst. NGC4490-OT has less in common with the class of SN 2008S-like transients. A progenitor detected in pre-eruption Hubble Space Telescope (HST) images, combined with upper limits in the IR, requires a luminous and blue progenitor that has faded in late-time HST images. The same source was detected by Spitzer and ground-based data as a luminous IR (2-5 mu m) transient, indicating a transition to a self-obscured state qualitatively similar to the evolution seen in other stellar mergers and in luminous blue variables. The post-outburst dust-obscured source is too luminous and too warm at late times to be explained with an IR echo, suggesting that the object survived the event. The luminosity of the enshrouded IR source is similar to that of the progenitor. Compared to proposed merger events, the more massive progenitor of NGC4490-OT seems to extend a correlation between stellar mass and peak luminosity, and may suggest that both of these correlate with duration. We show that spectra of NGC4490-OT and V838 Mon also resemble light-echo spectra of eta Car, prompting us to speculate that eta Car may be an extreme extension of this phenomenon.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Two of the most prominent techniques to meet the next generation wireless communication system's demands are cognitive radio and massive MIMO systems. Cognitive radio systems improve radio spectrum utilization either by spectrum sharing or by opportunistically utilizing the spectrum of the licensed users. Employing multiple antennas at the transmitter and/or the receiver of the radio can further improve the overall performance of the wireless systems. Massive MIMO systems, on the other hand, improve the spectral and energy efficiencies of currently deployed systems by reaping all the benefits of the multi-antenna systems at a very large scale. The price paid for employing a large number of antennas either at the transmitter or receiver is the high hardware cost. Judicious transmit or receive antenna selection can reduce this cost, while retaining most of the benefits offered by multiple antennas. In my doctoral research, we have presented both upper and lower bounds on the capacity of a general selection diversity system. These novel bounds are simple to compute and can be used in a variety of different fading environments. We have also proposed and analyzed the performance of different antenna selection schemes for both an underlay cognitive radio and a massive MIMO system. Specifically, we have considered both receive and transmit antenna selection in an underlay cognitive radio based on the maximization of secondary link signal-to-interference plus noise ratio. Exact and asymptotic performance analyses of the secondary system with such selections are carried out, and numerical examples are presented to verify the correctness of the analytical results. Several sub-optimal antenna subset selection schemes for both a single-cell and a multi-cell multi-user massive MIMO system are also proposed. Numerical results on the sum rate of the system in different scenarios are presented to verify the superior performance of the proposed schemes over the existing sub-optimal antenna subset selection schemes. Lastly, we have also presented three novel hybrid analog/digital precoding schemes to reduce the hardware and software complexities of a sub-connected massive MIMO system. / Graduate / 0544

Nesta tese foi feito um estudo dos eventos cíclicos em Carinae em diversas faixas espectrais. A presença de um buraco na região polar do Homúnculo foi confirmada pelos mapas de velocidade da linha do [Fe II] 12567. A componente em emissão da linha do He I 10830, detectada na linha de visada do lóbulo NW e que apresenta velocidades negativas, foi mapeada e está contida no plano equatorial. Foi observado que durante um período de 206 dias, centrado na fase zero, a linha do He I 10830 apresenta um aumento na velocidade máxima da componente em absorção, atingindo 1800 km/s. Tal comportamento favorece orientações orbitais onde a passagem pelo periastro ocorre próximo à oposição. O Pequeno Homúnculo apresenta a mesma distribuição espacial da emissão em rádio e, considerando que esta seja proveniente principalmente da secundária, o fluxo de fótons no contínuo de Lyman é compatível com uma estrela de tipo espectral O5.5O7. A variabilidade das componentes largas e estreitas das linhas em diversas faixas espectrais apresenta um período bem definido (2022.1±0.6 dias) e extremamente estável ao longo dos últimos 60 anos, sendo que as variações observadas no período são devido aos erros nas medidas. Utilizando a componente estreita da linha do He I 6678 foi possível determinar a fase zero do ciclo #11 (T0=2452819.8). Os eventos espectroscópicos são compostos de dois regimes: um de variações lentas e outro de colapso. A primeira é revelada por variações lentas no nível de ionização do meio circunstelar ao longo de todo o ciclo e está associada a variações graduais no cone de choque dos ventos (abertura angular e conteúdo). O regime de colapso é observado ao redor do mínimo e é causado por um colapso temporário do cone de choque. Os fenômenos de alta energia são sensíveis somente ao regime de colapso, enquanto os de baixa energia, ao de variação lenta. Os fenômenos que envolvem energias intermediárias, respondem aos dois regimes. Foi observado uma anti-correlação entre a linha do Fe II 6455 e a do He I 7065, indicando que a primeira é formada nas regiões mais externas do vento da primária e a segunda, na secundária ou no cone de choque dos ventos. A curva de luz do He II 4686 apresenta dois picos antes da fase zero e outro logo após. Os dois picos antes do mínimo apresentam uma correlação com os picos na faixa dos raios-X, porém estes ocorrem 16.5 dias antes daqueles. O mecanismo mais provável para explicar a luminosidade observada do He II 4686 é a produção de fótons com 1215 Å através do fluxo de fótons na faixa do ultra-violeta extremo/raios-X moles produzidos na região próxima ao ápex do cone de colisão dos ventos. Como este mecanismo é extremamente sensível à densidade do meio, a região mais favorável para produzir a luminosidade observada do He II 4686 é a região do cone de choque voltada para a primária. / In this thesis, a multi-wavelength study on the cyclic events of Eta Carinae was performed. The presence of a hole in the polar region of the Homunculus was confirmed by the velocity maps of the [Fe II] 12567 line. The blue-shifted component of the He I 10830, detected towards the NW lobe, was mapped and it is in the equatorial plane. It was observed that within a short period of 206 days, centered on phase zero, the He I 10830 line shows an increase in the maximum velocity of the absorption component, which reaches up to -1800 km/s. Such behavior favors orbital orientation with periastron passage around oposition. The Little Homunculus shows the same spatial distribution as the radio emission and considering that the radio flux comes mainly from the secondary, then the photon flux in the Lyman continuum is comparable to a star with spectral type in the range O5.5-O7. The variability of the narrow and broad lines from many spectral regions shows a well-defined period (2022.1+/-0.6 days), which is also extremely stable along the last 60 years, during which the observed variations in the period are due to measurement errors. Using the narrow component of the He I 6678 it was possible to determine the phase zero of the cycle #11 (T_0=2452819.8). The spectroscopic events are a combination of two components: slow variation and collapse. The former is revealed by slow changes in the ionization level of circunstellar matter across the whole cycle and is associated to gradual changes in the wind-wind collision shock-cone (angular opening and gaseous content). The collapse component is restricted to around the minimum and is caused by a temporary collapse of the wind-wind collision shock. High-energy phenomena are sensitive only to the collapse component, while low-energy only to the slow variation component. Intermediate-energy phenomena are sensitive to both components. It was observed an anti-correlation between the Fe II 6455 and He II 7065, suggesting that the former is formed in the outer parts of the primary\'s wind, while the latter is associated to the secondary or to the wind-wind shock cone. The lightcurve of He II 4686 shows two peaks before phase zero and another one short after it. The two peaks before phase zero are correlated to the peaks seen in the X-rays. However, the X-ray peaks occur 16.5 days before those seen in the He II 4686 lightcurve. The most likely mechanism to explain the observed peak luminosity of the He II 4686 is the creation of ~1215 Angstroms photons by the extreme ultra-violet/soft X-rays photons, which are produced near the apex of the wind-wind shock-cone. Since this mechanism is extremely sensitive to the density, the most likely region to form the observed peak luminosity of the He II 4686 is on the primary\'s side of the wind-wind shock-cone.

Many uncertainties remain as to how the most massive stars are formed and how they interact with their environment via radiative and mechanical processes. This feedback may affect future generations of star formation -- triggering it by compressing gas, or hindering it by dispersing reservoirs. These scenarios can be simulated by solving the equations of hydrodynamics and radiative transfer. However, the latter is usually simplified due to its computational expense, despite its importance in determining the dynamics. In this thesis, I describe how I increased the efficiency of the radiation hydrodynamics code, TORUS, which uses a Monte Carlo approach to solving the radiative transfer. Tens of millions of energy packets are propagated through a domain split over hundreds of processors running in parallel with Message Passing Interface (MPI). By re-examining and improving communication algorithms, I lowered the radiation run time by about a factor of ten, making it tractable to run three-dimensional simulations of massive star feedback in clusters. This includes both the stellar and diffuse radiation fields, with multiple atomic species and silicate dust grains. The full ionization states and temperatures can then be fed in to produce self-consistent synthetic observations. I applied this to clouds of 1000 and 10,000 solar masses with surface density 0.01 g/cm^2, containing a 34 solar mass star, with photoionization and radiation pressure feedback. Photoionization is efficient at shaping and dispersing clouds. The expanding ionization front forms dense, spherical knots with pillars pointing away from the emitting star. These resemble the Pillars of Creation in the Eagle Nebula, and the proplyds observed in the Orion Nebula. In the lower-mass model, almost all material is removed from the (15.5 pc)^3 grid within 1.6 Myr; the higher mass cloud is somewhat more resistant, with 25 per cent remaining inside (32.3 pc)^3 after 4.3 Myr. Radiation pressure has a negligible effect, but will be more important for denser clouds or higher luminosities.

The past decade has seen an enormous increase in the number of connected wireless devices, and currently there are billions of devices that are connected and managed by wireless networks. At the same time, the applications that are running on these devices have also developed significantly and became more data rate insatiable. As the number of wireless devices and the demand for a high data rate will always increase, in addition to the growing concern about the energy consumption of wireless communication systems, the future wireless communication systems will have to meet three main requirements. These three requirements are: i) being able to achieve high throughput; ii) serving a large number of users simultaneously; and iii) being energy efficient (less energy consumption). Massive multiple-input multiple-output (MIMO) technology can satisfy the aforementioned requirements; and thus, it is a promising candidate technology for the next generations of wireless communication systems. Massive MIMO technology simply refers to the idea of utilizing a large number of antennas at the base station (BS) to serve a large number of users simultaneously using the same time-frequency resources. The hypothesis behind using a massive number of antennas at the BS is that as the number of antennas increases, the channels become favourable. In other words, the channel vectors between the users and their serving BS become (nearly) pairwisely orthogonal as the number of BS antennas increases. This in turn enables the use of linear processing at the BS to achieve near optimal performance. Moreover, a huge throughput and energy efficiency can be attained due to users multiplexing and array gain. In this thesis, we investigate the performance of massive MIMO systems under different scenarios. Firstly, we investigate the performance of a single-cell multi-user massive MIMO system, in which the channel vectors for the different users are assumed to be correlated. In this aspect, we propose two algorithms for users grouping that aim to improve the system performance. Afterwards, the problem of pilot contamination in multi-cell massive MIMO systems is discussed. Based on this discussion, we propose a pilot allocation algorithm that maximizes the minimum achievable rate in a target cell. Following that, we consider two different scenarios for pilot sequences allocation in multi-cell massive MIMO systems. Lower bounds on the achievable rates are derived for two linear detectors, and the performance under different system settings is analysed and discussed for both scenarios. Finally, two algorithms for pilot sequences allocation are proposed. The first algorithm takes advantage of the multiplicity of pilot sequences over the number of users to improve the achievable rate of edge cell users. While the second algorithm aims to mitigate the negative impact of pilot contamination by utilizing more system resources for the channel estimation process to reduce the inter-cell interference.

Massive sequencing has transformed the field of genome biology due to the continuous introduction and evolution of new methods. In recent years, the technologies available to read through genomes have undergone an unprecedented rate of development in terms of cost-reduction. Generating sequence data has essentially ceased to be a bottleneck for analyzing genomes instead to be replaced by limitations in sample preparation and data analysis. In this work, new strategies are presented to increase both the throughput of library generation prior to sequencing, and the informational content of libraries to aid post-sequencing data processing. The protocols developed aim to enable new possibilities for genome research concerning project scale and sequence complexity. The first two papers that underpin this thesis deal with scaling library production by means of automation. Automated library preparation is first described for the 454 sequencing system based on a generic solid-phase polyethylene-glycol precipitation protocol for automated DNA handling. This was one of the first descriptions of automated sample handling for producing next generation sequencing libraries, and substantially improved sample throughput. Building on these results, the use of a double precipitation strategy to replace the manual agarose gel excision step for Illumina sequencing is presented. This protocol considerably improved the scalability of library construction for Illumina sequencing. The third and fourth papers present advanced strategies for library tagging in order to multiplex the information available in each library. First, a dual tagging strategy for massive sequencing is described in which two sets of tags are added to a library to trace back the origins of up to 4992 amplicons using 122 tags. The tagging strategy takes advantage of the previously automated pipeline and was used for the simultaneous sequencing of 3700 amplicons. Following that, an enzymatic protocol was developed to degrade long range PCR-amplicons and forming triple-tagged libraries containing information of sample origin, clonal origin and local positioning for the short-read sequences. Through tagging, this protocol makes it possible to analyze a longer continuous sequence region than would be possible based on the read length of the sequencing system alone. The fifth study investigates commonly used enzymes for constructing libraries for massive sequencing. We analyze restriction enzymes capable of digesting unknown sequences located some distance from their recognition sequence. Some of these enzymes have previously been extensively used for massive nucleic acid analysis. In this first high throughput study of such enzymes, we investigated their restriction specificity in terms of the distance from the recognition site and their sequence dependence. The phenomenon of slippage is characterized and shown to vary significantly between enzymes. The results obtained should favor future protocol development and enzymatic understanding. Through these papers, this work aspire to aid the development of methods for massive sequencing in terms of scale, quality and knowledge; thereby contributing to the general applicability of the new paradigm of sequencing instruments. / <p>QC 20121126</p>

This is a spectroscopic and photometric study of suspected close binary systems among the massive stars. The stars studied here include stars with temperatures ranging from 45,000 Kelvin (K) to 15,000 K, corresponding to spectral types ranging from O3 V to B5 III, masses between 47 Solar Masses and 5 Solar Masses, and absolute V magnitudes from -6.28 to -2.0. I categorize 30 targets according to my spectroscopic observations into groups with no radial velocity variability, single-lined, and double-lined variability. My analysis of the 18 constant velocity stars results in estimates of stellar effective temperature, Teff, gravity, log g, projected rotational velocity, v sin i, and spectral classification. Analyzing single-lined systems, I find the same stellar parameters for five more systems, and also present the first orbits for these systems. I also explore the probable characteristics of the unseen companions in these systems. Three double-lined systems, two eclipsing and one with an ellipsoidal variation in the light curve, are fully analyzed, and I present important astrophysical parameters for each of these systems, including stellar masses, radii, ages, and distances to each system. The masses are accurate to 4.3% and 3.6% for the primary and secondary for LH 54-425, 2.1% and 1.6% for HI Mon, and 1.1% and 0.6% for HD 42401. Two more double-lined systems are studied, and preliminary results are presented. Photometric observations are analyzed for 56 targets from the All Sky Automated Survey in order to facilitate spectroscopic observations at key points in the binary orbit where spectral features of both components will be well separated. New spectroscopic observations of these eclipsing binaries with my computed ephemerides will allow us to obtain double-lined orbital elements and determine their masses, radii, ages, and distances. These computed parameters will then allow for comparison with theoretical stellar models, and a better understanding of the evolution of massive stars.