Avocados are becoming an increasingly important crop in South Africa, where the main producing areas include Limpopo, Mpumalanga and KwaZulu-Natal provinces. The South African avocado industry faces considerable challenges including increasing competition exporting avocados, particularly to the European market. The processes involved to export avocados has markedly improved over the past two decades, however there is always room for improvement and it is necessary to remain competitive on a global scale. Issues such as fruit being partially soft on arrival, quality defects and cold chain management breakdown are still present. It is necessary to investigate new aspects of cold storage such as extending the storage period and understanding the physiological aspects involved. To improvement such issues, an investigation was conducted on ultra-low temperature shipping (1°C) as well as the use of 1-MCP; the implementation of deliberate cold chain breaks to achieve a better understanding as to the quality influences involved; an extended storage period of 56 days to assess the quality issues and benefits involved; as well as investigating the physiological aspects involved with all above treatments on 'Hass' avocados. An initial study saw early-, mid- and late-season 'Hass' avocados stored at 1°C or 5.5°C for 28 days. Additional treatments included fruit treated and not treated with 1-MCP as well as waxed and unwaxed fruit. Storage at 1°C was comparable with 1-MCP treatment for both fruit softening in storage and extending the ripening period. Storage at 5.5°C resulted in partial in-transit ripening, if 1-MCP was not used. Early-season fruit incurred the most external chilling injury but overall levels were minimal and not concerning. Mid-season fruit were the most sound in terms of quality. It is suggested that 1°C can be used as a viable economic alternative to 1-MCP for long distance shipping of 'Hass' up to 28 days. The cold chain break trial included a 24 hour delay before cold storage, a deliberate 8 hour break at day 14 of cold storage where fruit were removed from cold storage and a control of 28 days cold storage where no break was involved. Early-, mid- and late-season 'Hass' avocados were stored at 1°C or 5.5°C for 28 days. Additional treatments included fruit treated and not treated with 1-MCP as well as waxed and unwaxed fruit. It was found that cold chain breaks do influence the amount of water loss, fruit softening and days taken to ripen. Storage at 1°C did not entirely negate the effects of cold chain breaks compared with 5.5°C, but did result in fruit which were harder at the end of storage and took longer to ripen. The use of 1-MCP also had advantageous effects with respect to significantly lengthening the ripening period, even when a cold chain break occurred, compared with fruit not treated with 1-MCP. As results of the study differed in some respects to those of previous studies, it is recommended that further work be conducted to determine what fruit or pre-harvest factors affect the fruit physiological changes which take place when cold chain breaks occur. Having the option to make use of an extended storage period would be of benefit to the industry if delays occur and fruit have to be maintained under cold storage. Extended storage of South African avocados, especially at the end of the season would also allow for the option of strategically holding back fruit from the export market in order to extend the supply period. It would not only benefit export options, but would also be highly beneficial to local pre-packers, as it would reduce the need to import fruit from the Northern hemisphere production areas during the South African off-season. Early-, mid- and late-season 'Hass' avocados were stored at 1°C or 5.5°C for 56 days. Additional treatments included fruit treated and not treated with 1-MCP as well as waxed and unwaxed fruit. The combination of 1°C with the use of 1-MCP resulted in a good shelf life as well as maintenance of internal quality and integrity. External chilling injury is of concern for early-season fruit, however, mid- and late-season fruit did not incur extensive damage. It is, therefore, advised that fruit placed in extended storage are marketed through the 'Ready ripe' program to mask any chilling injury on the 'Hass' fruit. Avocados are renown as a "healthy food" due to their nutritional value as well as containing relatively high concentrations of antioxidants. The fruit also contain high amounts of C7 sugars which can act as antioxidants. Additionally, C7 sugars and other antioxidants play important roles in fruit quality. Therefore, it is important to understand how varying storage conditions and treatments affect the levels of these physiological parameters. Treatments of cold chain break/delay included a deliberate 8 hour break at day 14 of cold storage where fruit were removed from cold storage, a 24 hour delay before cold storage and a control of 28 days where no break was involved. A 56 day extended storage period was also used. Early-, mid- and late-season 'Hass' avocados were stored at 1°C or 5.5°C for 28 days. Additional treatments included fruit treated and not treated with 1-MCP as well as waxed and unwaxed fruit. The use of 1-MCP maintained higher levels of antioxidants, ascorbic acid and C7 sugars for both the 28 day and the 56 day storage periods. The 24 hour delay had a tendency to increase consumption of anti-oxidant and sugar reserves. The use of 1°C resulted in antioxidant and ascorbic acid levels decreasing while maintaining higher sugar levels. Overall, high stress imposed on fruit decreased reserves resulting in poor quality fruit. The use of 1°C and 1-MCP treatments maintained fruit quality. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

A subsurface flow constructed wetland planted with the common reed (Phragmites australis) and softstem bulrush (Scirpus validus) was built in East Central Indiana. The objective of this study was to determine if temperature had an effect on nitrogen (N) removal from the wetland. The research was conducted from the first week of October 3, 1995 to the first week in December 5, 1995 why the wetland froze. Water samples were taken from 5 samplings sites in the system. Each sample was analyzed for organic-N, ammonia, nitrate, and total-N. In the system statistically significant amounts of organic-N, nitrate, and total-N were removed. Ammonia lever reductions, however, were not significant. Organic-N had a mean removal of 37% (8 mg/1) 'Nitrate had a mean removal of 96% (2.3 mg/1). Total-N removal over the sampling period averaged 30% (12 mg/1). The N results were regressed against air and wastewater temperatures. Wastewater temperature was more important because it had a direct impact can the plants and microbes in the system. Warmer temperatures sustained a higher metabolism for the biota in the system. Air temperature had an indirect impact on efficiency of N removal from the wastewater flowing through the wetland. The primary impact .: f the air temperature was on water temperature which then affected the metabolism of or a nc ns in the wetland cell. Greater removal efficiencies were seen during high temperature periods and lower removal efficiencies were noted when the temperatures were low. / Department of Natural Resources and Environmental Management

Tree-rings were analyzed to assess the relative importance of slope position and aspect as determinants of the climate-sensitivity of sugar maple and white oak radial growth. Tree size, crown condition, forest and soil composition, and site indices were assessed to document environmental differences between site-types and to verify similarity of stands within the same site-type. Climate-sensitivity was assessed using mean between-tree correlation, principal components analysis, mean sensitivity, regression analysis, and analysis of radial growth decline after severe drought. Ecological differences were found between high and low sites on north and south facing aspects. Sugar maple did not exhibit greater climate-sensitivity than white oak. Both species showed greater climate-sensitivity on upper and south-facing slopes. / Department of Biology

Maternal colonies of the big brown bat, Eptesicus fuscus were studied in Delaware and Grant Counties from 21 May to 22 September, 1992. Nineteen colonies of bats were located and revisited several times during the summer. Bats were captured, sexed, aged, weighed and banded at each site. The weight gain pattern of the bats was related to rainfall and temperature during the summer. Other factors that might affect weight gain such as ectoparasites, tooth wear, and wing damage were also measured.The summer of 1992 had below normal rainfall in May and above normal rainfall in June and July. Temperatures were below normal during the study period. The weights of captured bats were compared to weights of bats captured at similar colonies during the same period in 1988, a dry year, and 1989 a wet year. Both of these years had near normal temperatures. Lower weight gain for juveniles and for adult females in late spring and early summer of 1992 was associated with higher than average precipitation and lower than average temperatures during the period. / Department of Biology

Inoculation studies were conducted in controlled environments with isolates of a Phoma sue. collected from leaf spot lesions on the weed giant foxtail. Limited host specificity studies resulted in this potential bioherbicide fungus killing all three foxtail species tested including Setaria faberi (giant), a. viridis (green) and S. lutescens (yellow). Several agronomically important plant species tested exhibited a hypersensitive-type response to infection, but these plants soon grew out of this symptom and appeared healthy. This bioherbicide preferred cool temperatures, exhibiting optimal biomass loss (100%) or death against foxtail seedlings following 120 hours leaf wetness with plants incubated at 20°C. At more conducive growth temperatures for the weed (25'C-300C), optimum biomass loss achieved was only 70% following 50 hours leaf wetness. Susceptibility to this Phoma sue. greatly decreased as foxtail seedlings attained 4 or more leaves per plant. To kill this weed, the author recommends inoculation of foxtail seedlings in early evening to take advantage of cooler temperatures and to inoculate plants between cotyledon to 3-leaf stages of growth. / Department of Biology

Spatial distribution of species and thus the composition of deciduous forests are expected to change in response to global climatic warming. Climate-growth response algorithms in forest simulation models that represent the influence of climate on tree growth are based on the geographic range limits of a species. These models assume that temperature limitations control the latitudinal range boundaries for tree species in the eastern United States, and that water limitations control the western range boundary. This study investigated spatial variation of tree-growth responses to historical variations in climate using tree-ring data for Quercus rubra L. from 71 study sites across latitudinal and longitudinal temperature and precipitation gradients in eastern North America. Correlation analyses were used to identify significant site-specific associations between radial growth indices and 130 climate variables for the common time interval 1930-1980. Geographic information systems (GIS), and Mantel and partial Mantel spatial correlation analyses were used to map, identify, and measure spatial associations between oak sensitivity to climate and regional climate patterns to test the hypothesis that climate controls the spatial distributions of species range limits.Seasonal climate variables exhibited the strongest correlations with radial growth most consistently across the 71 study sites. However, spatial patterns in regional climate were only weakly associated with spatial variation in red oak sensitivity to climate variables. Contrary to expectations, correlations between red oak radial growth indices and temperature variables at northern and southern sites were not significant, failing to support the hypothesis that latitudinal range limits are defined by temperature effects on mature tree growth. High early growing season temperature reduced growth mostly at sites in the southwest region, which concomitantly experienced high inter-annual variability in soil moisture. Increased early growing season site water balance and precipitation was associated with greater radial growth in the western third of red oak's range, partially supporting the hypothesis that the western range limit is defined by limited water availability. These results indicate that climate only partially determines range limit locations; thus model projections may exaggerate forest responses to climate change. / Department of Biology

The purpose of this study was to determine whether deep-cryogenic freezing produces a change in the timbre or playing characteristics of brass trumpets. The experimental procedure consisted of two parts: quantitative analysis and qualitative analysis. For qualitative analysis a panel of four professional trumpet players evaluated five trumpets: four were frozen and re-evaluated, and one served as the experimental control. Analysis of the harmonic spectra of tones from each instrument provided quantitative data. Since previous studies requiring the analysis of musical instrument tones have suffered from a high degree of variation among tones played by human performers, I constructed a mechanical device that could play tones on the test instruments with greater consistency than is possible with live performers.The changes observed in the qualitative and quantitative analyses are very small, and possibly contradictory. The test panel rated all of the instruments higher after they had been frozen, and any actual improvement in the playing characteristics is suspect because the control instrument received the second highest improvement of the five instruments in the study. In the quantitative analysis, I observed some slight changes in the amplitudes of some of the harmonics in the spectral graphs, but I also observed slight variations in some of the harmonics of the control instrument. Inconsistencies in the performance of the electronic equipment used in the study could account for some of the variation. The instrument that showed the most statistically significant improvements was rated significantly higher in intonation after cryogenic processing, but I was unable to measure any frequency changes in the tones the mechanical embouchure played on the test instruments.Although one may not actually be able to measure differences reported in the qualitative analysis, it is not possible to rule out any acoustical change from cryogenic freezing. In fact, in the quantitative measurements, three of the instruments showed changes greater (some positive and some negative) than the "experimental error" seen in the control instrument's measurements. Additionally, one member of the test panel is convinced that cryogenic freezing has improved his instrument significantly, but the other three trumpeters are ambivalent. / School of Music

The rheological, color, micro-structural, and electrical properties of surimi seafood gels were investigated. Various starches and protein additives at different ratios were evaluated with Alaska pollock surimi under ohmic heating at different heating rates to determine their functional properties and further to compare these properties with those of conventionally cooked gels. Native starches at low concentration were able to enhance rheological properties due to their gelatinization during heating. Pregelatinized starch decreased texture properties; however, it could suppress the undesirable appearance of the final product because its granules could absorb the surrounding water during chopping and perform a higher degree of retrogradation when cooling. A mixture of native and pregelatinized starches showed a positive trend at high concentration. The more starch added, the lower the L* and b* values of the gels. Protein additives improved textural properties, but negatively affected gel colors. Lower moisture content of the final products showed higher strength in texture, but lower lightness values. Gels cooked under ohmic heating with a slow heating rate mostly exhibited better texture properties than conventionally cooked gels. Electrical conductivities increased when temperature increased, resulting in a linear relationship. Electrical conductivity also significantly increased with moisture content, and slightly increased with applied frequency and voltage. There were some changes in the magnitude of electrical conductivity of surimi-starch paste when temperature increased, most obviously seen at a high concentration of native starch with slow ohmic heating. This indicated that starch gelatinization affected the electrical conductivity of surimi-starch paste while heating. / Graduation date: 2003

he extent of BiInO₃ substitution in the perovskite system xBiInO(₃)-(1 - x)PbTiO₃ and the corresponding raise in the transition temperature were investigated using thermal analysis, dielectric measurements, x-ray diffraction, and electron microscopy. Maximum tetragonal perovskite distortion (c/a = 1.082) was obtained for x = 0.20, with a corresponding Curie temperature of 582°C. Phase-pure tetragonal perovskite was obtained for x less than or equal to 0.25. Compound formation after calcining mixed oxide powders resulted in agglomerated cube-shaped tetragonal perovskite particles, which could be fired to 94.7% of theoretical density (TD). Niobium-modified BIPT ceramics with PT contents of 80% and 85% were found to possess significantly lower dielectric loss at elevated temperatures, making it possible to polarize the materials. Piezoelectric properties were measured for a 1.5 mol% Nb -0.15BI-0.85PT composition with a transition temperature of 542°C; the longitudinal piezoelectric coefficient and coercive field were found to be 60 pC/N and 125 kV/cm, respectively. Compositions of xBiLaO₃-(1 − x)PbTiO₃ over the range 0 < x < 0.225 were calcined and sintered. Dielectric constant with temperature and differential scanning calorimetry measurements were in excellent agreement with respect to a Curie-like tetragonal to cubic transformations starting at 495°C for pure PbTiO₃, shifting to lower temperatures with increasing x. For compositions of x > 0.05, a second higher-temperature (∼600°C) endotherm, and matching dielectric anomaly, were consistently observed, for which there were no structural changes indicated by hot-stage x-ray diffraction. This transformation was interpreted to be similar to a Curie transformation in relaxor ferroelectrics in which localized segregation of B-site cations (below the resolution limit of x-ray diffraction) facilitated ferroelectric behavior.

Copies of author's previously published articles inserted. / Bibliography: leaves 143-167. / xvi, 176 leaves, [17] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Temperature may affect fruit-set in grapevines through its effect on the development of the flowers up to flower opening and on pollination, be it on the germination of the pollen and the growth of the pollen tube, or on the post-fertilisation growth of the ovule. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1996