Water and Metasomatism in the Slave Cratonic Lithosphere (Canada): An FTIR Study

Water in the mantle influences melting, viscosity, seismic velocity, and electrical conductivity. The role played by water in the long-term stabilization of cratonic roots is currently being debated. This study focuses on water contents of mantle minerals (olivine, pyroxene and garnet) from xenoliths found in kimberlites of the Archean Slave craton. 19 mantle xenoliths from central Lac de Gras, and 10 from northern Jericho were analyzed by FTIR for water, and their equilibration depths span the several compositional layers identified beneath the region. At both locations, the shallow peridotites have lower water contents in their olivines (11-30 ppm H2O) than those from the deeper layers (28-300 ppm H2O). The driest olivines, however, are not at the base of the cratonic lithosphere (>6 GPa) as in the Kaapvaal craton. Instead, the deepest olivines are hydrous (31-72 ppm H2O at Lac de Gras and 275 ppm H2O at Jericho). Correlations of water in clinopyroxene and garnet with their other trace element contents are consistent with water being added by metasomatism by melts resembling kimberlite precursors in the mantle approx.0.35 Ga ago beneath Lac de Gras. The northern Jericho xenoliths are derived from a region of the Slave craton that is even more chemically stratified, and was affected at depth by the 1.27 Ga Mackenzie igneous events. Metasomatism at Jericho may be responsible for the particularly high olivine water contents (up to 300 ppm H2O) compared to those at Lac de Gras, which will be investigated by acquiring trace-element data on these xenoliths. These data indicate that several episodes of metasomatic rehydration occurred in the deep part of the Slave craton mantle lithosphere, with the process being more intense in the northern part beneath Jericho, likely related to a translithospheric suture serving as a channel to introduce fluids and/or melts in the northern region. Consequently, rehydration of the lithosphere does not necessarily cause cratonic root delamination and these peridotites may represent localized metasomatic zones - the wall rocks to kimberlite magma passage

Navigating and negotiating ethnographies of urban hustle in Nairobi slums

This paper reflects on doing and writing ethnography on the urban margins, where uncertainty and provisionality mark the everyday city. The discussion is situated within a postcolonial approach to ethnographies of ‘hustle’ in Nairobi slums, critically reflecting on methodological choices made to facilitate the licence to linger in intimate and interstitial spaces of neighbourhoods often closed off to visitors. The paper argues that while urban ethnography is foundational to postcolonial scholarship on African cities, it is also vexed with tensions between ethnographic experience of the provisional and uncertain lived reality in which ethnographers seek to embed themselves for periods of time, and the ethnographic representation that emerges in the form of ethnographic authorship. The paper engages with the methodological tactic of engaging in waste work as an ‘apprentice researcher’; and with the theoretical choice of deploying the very vocabularies and expressions of struggle of interlocutors living and working in the ‘slums’ of Nairobi

Hydrogen Contents of the Lithospheric Mantle Beneath the Canadian Cordillera and Slave Craton

Trace levels of hydrogen in mantle minerals can significantly influence the physical properties of the mantle, and identifying the processes that affect hydrogen incorporation in the main minerals of the lithospheric mantle is vital to our understanding of geodynamics. In particular, results from this dissertation are used to investigate the role of hydrogen in the longevity of ancient cratonic lithosphere and how melting, metasomatism and oxygen fugacity conditions affect hydrogen in the lithosphere. This is accomplished by measuring hydrogen contents, as well as major and trace elements contents of peridotite minerals from mantle xenoliths derived from the lithosphere beneath Alligator Lake in the northern Canadian Cordillera and three locales from the Slave craton. The Alligator Lake lithosphere has a heterogeneous composition resulting from modification by fluids derived from a subducting slab, followed by melting and metasomatism by carbonatite-like melts initiated by the opening of a slab window. Not only is subduction lithosphere not more hydrous than lithosphere in other tectonic settings, but it is also highly heterogeneous in hydrogen content locally. Moreover, in Alligator Lake, oxidation is not correlated to subduction metasomatism. The Slave cratonic lithosphere is chemically stratified vertically, and the hydrogen contents of its peridotite minerals replicate this stratification. Xenoliths from the Slave lithosphere provide evidence of localized metasomatism unique to each region (Jericho in the north, Lac de Gras in the center and Gahcho Kue in the southeast) and each chemical stratum at depth. These metasomatic processes resulted in addition and/or removal of hydrogen in the lithosphere, including by silicate melts, hydrous fluids, kimberlite-like melts and carbonatite-like melts. High hydrogen contents in olivine near the base of cratonic lithosphere resulting from metasomatism by H-bearing melts and fluids, as observed beneath the Slave craton, do not necessarily result in cratonic root delamination. Hydrogen addition caused by metasomatism might be localized in some lithospheres, and kimberlites that entrain mantle xenoliths follow conduits of weakness through the lithosphere, preferentially sampling the most metasomatized parts of the lithosphere. Therefore, the highest hydrogen contents recorded in mantle xenoliths might not be representative of the overall lithosphere.Earth and Atmospheric Sciences, Department o

National Beef Quality Audit–2016: assessment of cattle hide characteristics, offal condemnations, and carcass traits to determine the quality status of the market cow and bull beef industry

To continue the series that began in 1994, the National Beef Quality Audit (NBQA) – 2016 was conducted to quantify the quality status of the market cow and bull beef sector, as well as determine improvements made in the beef and dairy industry since 2007. The NBQA-2016 was conducted from March through December of 2016, and assessed hide-on carcasses (n = 5,278), chilled carcasses (n = 4,285), heads (n = 5,720), and offal items (n = 4,800) in 18 commercial processing facilities throughout the United States. Beef cattle were predominantly black-hided; 68.0% of beef cows and 67.2% of beef bulls possessed a black hide. Holstein was the predominant type of dairy animal observed. Just over half (56.0%) of the cattle surveyed had no mud contamination on the hide, and when mud was present, 34.1% of cattle only had small amounts. Harvest floor assessments found 44.6% of livers, 23.1% of lungs, 22.3% of hearts, 20.0% of viscera, 8.2% of heads, and 5.9% of tongues were condemned. Liver condemnations were most frequently due to abscess presence. In contrast, contamination was the primary reason for condemnation of all other offal items. Of the cow carcasses surveyed, 17.4% carried a fetus at the time of harvest. As expected, mean carcass weight and loin muscle area values observed for bulls were heavier and larger than cows. The marbling scores represented by cull animal carcasses were most frequently slight and traces amounts. Cow carcasses manifested a greater amount of marbling on average than bull carcasses. The predominant fat color score showed all carcasses surveyed had some level of yellow fat. Only 1.3% of carcasses exhibited signs of arthritic joints. Results of the NBQA-2016 indicate there are areas in which the beef and dairy industries have improved and areas that still need attention to prevent value loss in market cows and bulls

Amino Acid Nanofibers Improve Glycemia and Confer Cognitive Therapeutic Efficacy to Bound Insulin

Diabetes poses a high risk for debilitating complications in neural tissues, regulating glucose uptake through insulin-dependent and predominantly insulin-independent pathways. Supramolecular nanostructures provide a flexible strategy for combinatorial regulation of glycemia. Here, we compare the effects of free insulin to insulin bound to positively charged nanofibers comprised of self-assembling amino acid compounds (AACs) with an antioxidant-modified side chain moiety (AAC2) in both in vitro and in vivo models of type 1 diabetes. Free AAC2, free human insulin (hINS) and AAC2-bound-human insulin (AAC2-hINS) were tested in streptozotocin (STZ)-induced mouse model of type 1 diabetes. AAC2-hINS acted as a complex and exhibited different properties compared to free AAC2 or hINS. Mice treated with the AAC2-hINS complex were devoid of hypoglycemic episodes, had improved levels of insulin in circulation and in the brain, and increased expression of neurotransmitter taurine transporter, Slc6a6. Consequently, treatment with AAC2-hINS markedly advanced both physical and cognitive performance in mice with STZ-induced and genetic type 1 diabetes compared to treatments with free AAC2 or hINS. This study demonstrates that the flexible nanofiber AAC2 can serve as a therapeutic platform for the combinatorial treatment of diabetes and its complications

Agricultural Landscapes: History, Status and Challenges

Agricultural landscapes (rural landscapes, agrolandscapes) are territories shaped by agricultural production. They have enabled the development of human civilizations and are a cultural achievement. Peasants, farmers and agricultural enterprises feed society. They have created agricultural landscapes for their business and habitats for their life. To understand transformation processes in agricultural landscapes, we analyse the history of agriculture with a special focus on Europe and Eurasia. Current agricultural landscapes in a crowded, globalized world are multifunctional, highly complex systems. They not only serve to produce food commodities and energy for the increasing and expanding urban population but also provide diverse ecosystem services and need to cater for the demands of the rural population. Current agriculture is highly productive in wealthy countries, but due to high inputs it is also responsible for environmental problems such as water pollution and loss of biodiversity. Industrial-style agriculture in large fields has resulted in increased productivity but simplified the structure of landscapes and eliminated elements of nature and rural culture. Major problems that urgently need to be addressed include trends towards disrupting natural cycles in agricultural production, soil and water degradation, ageing populations in villages and the breakdown of rural infrastructure. Agricultural landscape research provides analyses to understand these processes and helps elaborate sustainable scientific, technical and cultural solutions