We present simultaneous Hubble Space Telescope (HST) WFC3+Spitzer IRAC variability monitoring for the highly variable young (similar to 20 Myr) planetary-mass object PSO J318.5-22. Our simultaneous HST + Spitzer observations covered approximately two rotation periods with Spitzer and most of a rotation period with the HST. We derive a period of 8.6. +/-. 0.1 hr from the Spitzer light curve. Combining this period with the measuredvsinifor this object, we find an inclination of 56 degrees.2. +/-. 8 degrees.1. We measure peak-to-trough variability amplitudes of 3.4%. +/-. 0.1% for Spitzer Channel 2 and 4.4%-5.8% (typical 68% confidence errors of similar to 0.3%) in the near-IR bands (1.07-1.67 mu m) covered by the WFC3 G141 prism-the mid-IR variability amplitude for PSO J318.5-22 is one of the highest variability amplitudes measured in the mid-IR for any brown dwarf or planetary-mass object. Additionally, we detect phase offsets ranging from 200 degrees to 210 degrees (typical error of similar to 4 degrees) between synthesized near-IR light curves and the Spitzer mid-IR light curve, likely indicating depth-dependent longitudinal atmospheric structure in this atmosphere. The detection of similar variability amplitudes in wide spectral bands relative to absorption features suggests that the driver of the variability may be inhomogeneous clouds (perhaps a patchy haze layer over thick clouds), as opposed to hot spots or compositional inhomogeneities at the top-of-atmosphere level.

The use of alternative feedstock sources to enhance the energy production of anaerobic systems, and thus their economic value, is one of the current research areas in the field of bioenergy production. Marine biomass represents a unique source of organic matter for the optimisation of anaerobic digestion systems and can be regarded as a sustainable alternative to purposely grown energy crops requiring significant amounts of water, fertiliser and land for their cultivation. Seaweeds are of particular interest as they are characterised by high biomass yields and interesting conversion rates. In temperate seas, brown seaweed species generally dominate the flora and their relative abundance on the sublittoral zone of the British coastline make them a substrate of choice for anaerobic digestion. However, little information is available on commercial-scale anaerobic digestion of seaweed for biogas production and the potential factors that could impair its successful conversion. This work was proposed in order to establish the potential and optimise the use of seaweed as an additional source of organic matter for anaerobic digesters. The study also investigated the use of the Anaerobic Digestion Model No.1 (ADM1) as a platform for process simulation. The model original structure is inadequate to accurately represent the anaerobic co-digestion of seaweed and was therefore updated with the addition of specific processes. The study was carried out in three main experimental stages. In a first stage, the effect of seaweed salinity (represented by sodium ions) on anaerobic digestion was investigated using a mesophilic laboratory-scale anaerobic digester. It was found that a rapid increase in sodium ion levels can negatively impact on biogas production and result in the accumulation of volatile fatty acids. The ADM1 does not originally take into account the inhibitory effect of sodium and was therefore modified to include a function representing the effect of sodium ions on the rate of acetate uptake. The extended model was able to reproduce experimental observations and was used to predict the effect of sodium ions in the presence of other process inhibitors. Microbial adaptation to salinity was also investigated during batch assays. It was found that a suitable period of adaptation can significantly reduce the adverse effect of salinity on methanogens. The phenomenon was successfully implemented in the model through the addition of a specific inhibition function and the calibration of kinetic parameters. The second stage of this research focused on the effect and mode of action of phlorotannin (a phenolic compound found exclusively in brown seaweed) on mixed microbial cultures through the monitoring of intracellular material leakage and transmission electron microscopy observations. Results suggested that phlorotannin induces strong extra- and intra-cellular effects on cells exposed to the compound, thus adversely impacting on energy requirements and final methane yields. The effect of phlorotannin was found to be dependent on both the degree of polymerisation of the compound and the morphology of microorganisms. Furthermore, the effect of phlorotannin during the anaerobic co-digestion of brown seaweed (Laminaria digitata) and vegetable residues was also investigated. Experimental results were successfully modelled using an extensively modified version of the ADM1, which introduces an uncompetitive function to the rate of acetate uptake in order to represent the inhibition of methanogenesis by phlorotannin. The model was also updated with a combination module for the simulation of co-digestion processes. The third stage focused on establishing operational guidelines for the anaerobic co-digestion of brown seaweed and non-saline feedstocks. Results suggested that although seaweed can be an alternative organic substrate in anaerobic digestion systems, phlorotannin content might limit its use for commercial-scale application. Whilst this study identified salinity and phlorotannin as key barriers to the use of brown seaweed as a substrate for anaerobic systems, the adaptation of operating conditions to favour microbial adaptation could lead to its effective use in large-scale applications.

Disks around brown dwarfs (BDs) are excellent laboratories to study the first steps of planet formation in cold and low-mass disk conditions. The radial-drift velocities of dust particles in BD disks higher than in disks around more massive stars. Therefore, BD disks are expected to be more depleted in millimeter-sized grains compared to disks around T Tauri or Herbig Ae/Be stars. However, recent millimeter observations of BD disks revealed low millimeter spectral indices, indicating the presence of large grains in these disks and challenging models of dust evolution. We present 3 mm photometric observations carried out with the IRAM/Plateau de Bure Interferometer (PdBI) of three BD disks in the Taurus star-forming region, which have been observed with ALMA at 0.89 mm. The disks were not resolved and only one was detected with enough confidence (similar to 3.5 sigma) with PdBI. Based on these observations, we obtain the values and lower limits of the spectral index and find low values (alpha(mm) less than or similar to 3.0). We compare these observations in the context of particle trapping by an embedded planet, a promising mechanism to explain the observational signatures in more massive and warmer disks. We find, however, that this model cannot reproduce the current millimeter observations for BD disks, and multiple-strong pressure bumps globally distributed in the disk remain as a favorable scenario to explain observations. Alternative possibilities are that the gas masses in the BD disk are very low (similar to 2 x 10(-3) M-Jup) such that the millimeter grains are decoupled and do not drift, or fast growth of fluffy aggregates.

Please read the abstract in the thesis / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Biochemistry / unrestricted

No description available.

During the last 25 years, the Eastern Cape Province of South Africa has seen the establishment of many small to medium sized (≤ 440km2) game reserves. These reserves have reintroduced many of the larger indigenous wildlife that had been extirpated by the early 20th century. As such, these reserves and wildlife introductions have created many research opportunities, including investigations on the ecology of reintroduced carnivores in the Thicket biome. Brown hyaenas (Hyaena brunnea) are one of the large carnivore species that have been reintroduced into the area. As these animals have predominantly been studied in more open, arid systems, their reintroduction has provided an excellent opportunity to study the species in an alternate natural habitat. Information gathered from such investigations adds to our knowledge of the species and also provides information for the management of brown hyaenas within small, enclosed reserves. Data were collected over the period of one calendaryear, from February 2013 to February 2014 at Kwandwe Private Game Reserve in the Eastern Cape, South Africa. Brown hyaena population estimates were calculated using capture-recapture methods from individually identifiable images captured during a three month camera trapping survey. Images of brown hyaenas were separated into left- and right-side profiles. Twenty-eight individuals were positively identified from left-side images and 27 from right-side images. Non-spatial and spatially explicit capture-recapture analyses were both run in the program DENSITY 5.0. Density estimates ranged from 14 to 20 individuals/100km2 (equivalent to a total abundance of 26-37 individuals) depending on the method used. Despite the range of estimates, all are considerably higher than in other areaswhere densities have been calculated. Satellite/GPS collars were fitted to three individual brown hyaenas (two males and one female) to measure their home range size and use of space. Home range size was calculated using two different methods, Kernel utilisation distributions and Brownian bridges. Home range estimates were similar using both methods; however Brownian bridge methods appeared to exaggerate the use of space by individuals. Kernel home range sizes for the three individuals ranged between 42.62km2 and 79.88km2. These estimates are considerably smaller than previous findings from other parts of Africa and suggest that sufficient resources may be available within this enclosed system. The results from this study suggest that brown hyaenas are successful generalists in this enclosed system and are able to persist at high densities and occupy relatively small home ranges. This information is important for the managers of small reserves who wish to reintroduce brown hyaenas. Should brown hyaenas be introduced into reserves in the Thicket biome with sufficient resources, the numbers are likely to increase rapidly. If high numbers are not desired then preventative measures (e.g. contraception) should be investigated before release.

The Brown McDade Mine is a recent gold-silver discovery in the Yukon Territory, halfway between Whitehorse and Dawson. It lies in the area unglaciated during the Pleistocene Period. Diamond drilling and stripping in 1946 indicated commercial values across a width of 10 feet and over a length of 1000 ft. The geologic structure is that of a Late Tertiary, dyke-like body of quartz feldspar porphyry cutting quartz diorite of Jurassic or later age. This body has a Northwest strike and dips steeply west. The ore zone lies in the porphyry and is believed genetically related to it. The mineralization consists of a cherry-like fine grained blue quartz, with disseminated sulphides comprising less than 5% of the mass. Metallic minerals are pyrite, arsenopyrite, and sphalerite, with lesser amounts of galena, chalcopyrite, tetrahedrite, stibnite, bournonite, jamesonite and gold. The gold is associated with the pyrite in fine particles, the majority less than 150 microns in size. The gold-silver ratio is about one to ten. Sericitization and carbonatization are the chief forms of hydrothermal alteration, while considerable limonite, and around the ore zone, jarosite, have been produced by weathering. On the basis of comparisons with known deposits, the Brown McDade is considered to belong to the deeper epithermal type. It should continue to reasonable depths although the ore shoots are likely to be erratic. The area south of the main ore zone, underlain by schistose rocks will probably be unfavorable for the occurrence of ore. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The research work presented in this thesis comprises an electron microscopy and spectroscopy study of crystal defects that relate to the occurrence of different colours in natural and synthetic diamonds. Two principal lines of investigation have been covered, each with its own objective. The first aims to identify the source of brown colour in natural and synthetic diamond and the second to ascertain the distribution of colour inducing point defects in synthetic diamond. An outline of both areas of research is given below.1) Brown colour in natural and synthetic diamondsColour is a physical property that can be very difficult to characterise in diamond and consequently it receives regular attention from scientists working in the gem industry. In this work, the crystal structures of brown and colourless natural type IIa diamonds are compared along with brown coloured synthetic diamonds manufactured using the chemical vapour deposition (CVD) process. Numerous attempts have been made to trace the origin of brown tints in natural diamond, with the most likely sources, dislocations and nitrogen impurities, ruled out through the application of various analytical techniques. Recently more emphasis has been placed on the study of vacancy related defects in natural diamond and their influence on colour. Differences between the annealing characteristics of brown coloured natural and CVD diamonds suggest that the defect or defects responsible for the brown colour might be different for each type of diamond. The focus of this research work is the analysis of vacancy defects of the order of 1nm in size using aberration corrected scanning transmission electron microscopy (AC-STEM). The sub-nanometre size probe afforded by this technique allows such defect structures to be resolved much more readily than with conventional high resolution transmission electron microscopy (HR-TEM). Small-scale contrast variations are apparent in the lattice images of brown diamonds but not of the colourless variety. These features have been compared to simulated phase contrast images of vacancy clusters in diamond.2) Yellow / Green coloured synthetic diamonds grown using metal solvent catalystSynthetic diamonds for jewellery and industrial applications are routinely manufactured under high pressure-temperature (HPHT) conditions that closely resemble those found during the creation of natural diamonds. Although the manufacturing equipment can vary in design, the HPHT process that occurs inside the reaction vessel remains essentially the same. During processing, the carbon source material is dissolved into a molten metal and then precipitated onto tiny seed diamonds that are added to the reaction chamber. Much time and effort has been expended in refining this process to reduce impurities and defects in the finished diamonds. The presence of remnant transition metal atoms (e.g. nickel) in the crystal structure influences the electronic properties and in particular the colour of the diamonds. The position and configuration of these metallic defects has previously been studied by a variety of analytical techniques, including optical absorption-luminescence spectroscopy and electron paramagnetic resonance spectroscopy (EPR). These studies have proposed a number of optically active nickel centres at both substitutional and interstitial sites. Their association with vacancies and nitrogen atoms has also been highlighted. This work uses electron microscopy and spectroscopy to characterise the nickel defects in synthetic type 1b diamonds.

>Magister Scientiae - MSc / This thesis reports the results of a twofold study on the recently proposed phenomenon of 'stellar pulsations' in young brown dwarfs by the seminal study of Palla and Baraffe (2005) (PB05, thereafter). The PB05 study presents results of a non-adiabatic linear stability analysis showing that young brown dwarfs should become pulsationally unstable during the deuterium burning phase of their evolution. The PB05 calculations on which this prediction is based have already been applied in a number of ground and space-based observational campaigns aimed at searching for this newly proposed putative class of potential pulsators. However, despite their significance and implications, the theoretical calculations by PB05 have not yet, to date, been subjected to independent verification in a different computational framework. To achieve this, we have generated equilibrium brown dwarf models and performed non-adiabatic linear stability calculations similar to PB05 assuming their 'frozen-in convection' approximation and the relevant input physics. The calculations performed in this thesis show, in overall, that there is a good agreement between the results from our study and those in PB05. However, there seem to be significant differences for very low mass objects as pointed out in our comparative results. We attribute this difference to our different boundary conditions. Our outer boundary condition is equivalent to the Eddington approximation in the 3-D case (e.g see Unno and Spiegel (1966)), while PB05 use a combination of different atmospheric profiles as discussed in Chabriel and Baraffe (2000). The validity of the frozen-in assumption used by PB05, which is based on the argument that the convective time scales calculated for these objects are much less than the pulsation time scales, has not been investigated. In this thesis, we have invoked a time-dependent theory of convection similar to Kuhfuss (1986) and Stellingwerf (1982) which includes turbulent pressure, turbulent diffusion and turbulent viscosity to study the pulsations. We have also investigated the effects of varying a number of free parameters in the above theoretical models. Our results show that turbulent pressure dominates in driving the pulsations in young brown dwarfs yielding growth rates much higher than in the frozen-in scenario. This is a new result that requires further analysis. The perturbation in the convective flux is found to have a damping effect on the acoustic modes. Turbulent viscosity is found to lead to damping which increases with increase in the value of the turbulent viscosity parameter and is found to have very little effect on the fundamental mode pulsation periods. Variation in the turbulent diffusion parameter has a very small effect on the fundamental mode periods and e-folding times. As a side lobe, we have determined theoretical pulsation constants for the fundamental mode and calculated the period ratios for the fundamental mode to those of the first and second harmonics. We find values of pulsation constants falling within the theoretical values calculated for variable stars shown in Cox (1980). This is explained in relation to the terms that go into the theoretical formula discussed later in this thesis. We find a correlation between the period ratios and the BDs mass and argue that such plots of the period ratios vs mass of the BDs could be useful in constraining the masses, given known periods from observations.

“Southern Fringes: Little Magazines and Larry Brown’s Early Short Fiction” seeks to revitalize and expand the scholarly field of the New Southern Studies, employing textuality, book history, and postcritique perspectives towards the study of literary events and objects. Whereas the New Southern Studies rightly problematizes and dismantles notions of the signifier southern named in connection with literary works, such approaches often ignore paratextual elements, including material and sociological features, that work to frame and support these narratives. This dissertation addresses such shortcomings, arguing that paratextual formations function as vital spaces for constructing senses of southernness in service of both bibliographic identity and readers’ literary discernments. Exploring public epitext in a variety of locations, as well as four cases of Larry Brown’s short stories appearing in Mississippi Review, The Greensboro Review, and The Chattahoochee Review, this dissertation demonstrates how Brown’s writing emerges as southern fringe: a joint presence of autobiographic, material, perceptual, and other paratextual elements that frame Brown’s writing in unique locales outside of the literary mainstream. This dissertation's implications include adopting a mode of reading and analysis, focusing on case studies and surface readings of paratext serving specific bibliographic documents, as a way to move beyond generalizing and broad claims about the nature, function, and interpretation of literature. Additionally, this dissertation focuses on little magazines, materiality, and paratext as expanded sites and perspectives for the continued growth and development of interdisciplinary humanities fields such as the New Southern Studies. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection