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Effects of white-tailed deer herbivory on a tallgrass prairie remnantGooch, Scott 11 January 2010 (has links)
A study was conducted to determine what impact high white-tailed deer (Odocoileus virginianus) densities were having on the native grasslands of a tallgrass: aspen forest tract embedded within an agro-urban setting. Due to excessive spring moisture, row-crops were unavailable the first year. Using microhistological fecal analysis to determine dietary composition, deer were assessed to be placing the site’s favoured native plant species at risk of extirpation. Measuring woody stem abundance and height along and near the prairie: forest ecotone, deer were found to restructure woody growth but not directly influence encroachment rates. Indirectly, however, deer facilitated forest encroachment and prairie degradation through seed dispersal, nitrogen deposition, gap-dynamics, and trampling. Comparing dietary composition to nutritional data, deer grazed to maximize fitness, selecting foods high in IVDMD, minimizing energy expenditure, and optimizing CP. High crop CP was offset by intensively grazing particular native plants. ADF was an effective nutritional marker, not AIA.
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Foraging and menstruation in the Hadza of TanzaniaFitzpatrick, Katherine January 2018 (has links)
The Hadza, residing near Lake Eyasi in northern Tanzania, represent one of the last remaining hunter-gatherer populations. Inhabiting the same area as our hominin ancestors and exploiting very similar resources, the Hadza maintain a foraging lifestyle characterised by a sexual division of labour. Studies of their foraging and food sharing habits serve as the foundation to numerous hypotheses of human behaviour and evolution. Data from the Hadza have featured heavily in debates on the sexual division of labour. These debates focus predominantly on men’s foraging, including how and why men provision. Women’s provisioning, on the other hand, is seldom explicitly examined and is often presumed to be constrained by reproduction. This thesis contributes to debates on the sexual division of labour by investigating how a woman’s reproductive status affects her foraging behaviours. Observational data on women’s foraging are investigated from 263 person/day follows (1,307 hours total) across 10 camps between 2004 and 2006. These data present the first quantitative documentation of forager women’s eating and sharing outside of camp. Interview data on women’s reproductive timeline are also analysed from in-depth interviews with 58 women from 9 camps in 2015. Spanning from menarche to menopause, these data offer the first quantitative and qualitative documentation of forager women’s menstruation. The results demonstrate that Hadza women eat and share over 800 kilocalories outside of camp per person/day. They regularly give and receive food, including gifts of honey from men. Breastfeeding women are more likely to give gifts and give more gifts than non-breastfeeding women. When they bring nurslings with them outside of camp, they forage less kilocalories per hour. Post-menopausal women eat less relative to what they forage, are less likely to receive gifts, rest less and forage more than pre-menopausal women. Although Hadza women describe their foraging workload as most difficult during late pregnancy, no significant differences in eating, sharing, resting or foraging are observed for pregnant women. Menstrual data from the Hadza reveal that menstruation is not only culturally relevant to the sexual division of labour, but it is also biologically relevant to current understandings of fertility. The majority (60%) of Hadza women report not doing their normal work during menstruation. They also report menstruation-related taboos for berry picking. The thesis presents an in-depth review of women’s menstruation, from the duration of menses to the menstrual cleaning process.
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COMBUSTION CHARACTERISTICS OF ADDITIVELY MANUFACTURED GUN PROPELLANTSAaron Afriat (10732359) 05 May 2021 (has links)
<p>Additive manufacturing of gun
propellants is an emerging and promising field which addresses the limitations
of conventional manufacturing techniques. Gun propellants are manufactured
using wetted extrusion, which uses volatile solvents and dies of limited and
constant geometries. On the other hand, additive techniques are faced with the challenges
of maintaining the gun propellant’s energetic content as well as its structural
integrity during high pressure combustion. The work presented in this thesis demonstrates
the feasibility of producing functioning gun propellant grains using vibration-assisted
3D printing, a novel method which has been shown to extrude extremely viscous materials
such as clays and propellant pastes. At first, the technique is compared to
screw-driven additive methods which have been used in printing gun propellant
pastes with slightly lower energetic content. In chapter two, diethylene glycol dinitrate (DEGDN), a
highly energetic plasticizer, was investigated due to its potential to replace
nitroglycerin in double base propellants with high nitroglycerin content. A
novel isoconversional method was applied to analyze its decomposition kinetics.
The ignition and lifetime values of diethylene
glycol dinitrate were obtained using the new isoconversional method, in
order to assess the safety of using the plasticizer
in a modified double base propellant. In chapter three, a modified double base
propellant (M8D) containing DEGDN was additively manufactured using VAP. The
printed strands had little to no porosity, and their density was nearly equal
to the theoretical maximum density of the mixture. The strands were burned at
high pressures in a Crawford bomb and the burning was visualized using high
speed cameras. The burning rate equation as a function of the M8D propellant as
a function of pressure was obtained. Overall, this work shows that VAP is
capable of printing highly energetic gun propellants with low solvent content,
low porosity, with high printing speeds, and which have consistent burning
characteristics at high pressures. </p>
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