MSCPNT / Department of Food Science and Technology / The study aimed to determine the physicochemical properties, extract and characterise pectin from three varieties (green, purple and orange) of prickly pear (Opuntia spp) fruit peel. Research samples were collected from Bothlokwa Mphakane village in Limpopo province of South Africa. The experimental design for this study was randomized complete block design and each treatment was conducted in triplicate. Pectin was extracted using sulphuric acid at four different pH levels (1, 2, 3 & 4) and microwave power levels (low, medium & high). The characterisation of extracted pectin was done by calculating the ash, moisture, equivalent weight, anhydrouronic acid, methoxyl content, and degree of esterification. Functional groups present in extracted and commercial pectin were investigated for similarities using Fourier Transform Infrared Spectroscopy. The yield of pectin for purple ranged from 2.9% to 13.8%, orange from 1.4% to 9.8% and from 2.3% to 10.0% for green prickly pear peel. A decrease in pH resulted in an increased pectin yield and an increase in microwave power level increased the pectin yield. Maximum yields of 13.8% on purple, 10.0% on green and 9.8% on orange were obtained at pH 1.0 and medium power level. The best condition for extraction using sulphuric acid was at a medium power level and pH 1.0. The pectins obtained were compared against each other in terms of yield, physicochemical characteristics and chemical structure. The ash content of the extracted pectin was significantly higher at 25.16 ± 0.69, 34.26 ± 1.92 and 36.30 ± 1.07, however the pectin showed lower moisture content and equivalent weight. The methoxyl contents were 2.28 ± 0.26, 2.38 ± 0.21 and 3.86 ±0.31, anhydrouronic acid contents were 25.58 ± 2.03, 25.93 ± 2.35 and 38.84 ± 2.29, and degree of esterification were 49.87 ± 0.17, 50.63 ± 4.76 and 56.39 ± 1.60 across the orange, purple and green varieties, respectively. The prickly pear peel pectin spectra exhibited similarities in its absorption pattern to that of commercial citrus pectin. Therefore, the extraction of pectin from prickly pear peels is feasible in viewpoint of yield and quality, and that the pectin has potential for substitution of citrus pectin in the food processing industry. / NRF

Made available in DSpace on 2015-03-05T16:20:40Z (GMT). No. of bitstreams: 0 Previous issue date: 27 / Nenhuma / A conversão de florestas naturais em monoculturas arbóreas vem formando mosaicos heterogêneos na paisagem, onde é desconhecida a capacidade de colonização das espécies vegetais do sub-bosque. Essa mudança no uso da terra leva a modificações na composição de espécies de plantas, podendo alterar o seqüestro de carbono em florestas. Este estudo procurou caracterizar diferenças na composição, riqueza de espécies, riqueza funcional e abundância de plantas que colonizam o sub-bosque de florestas e monoculturas arbóreas, investigando também como a diversidade de espécies e diversidade de grupos funcionais podem influenciar no acúmulo de biomassa no sub-bosque. O estudo foi conduzido na Floresta Nacional de São Francisco de Paula, RS, Brasil, em três repetições de cada um dos seguintes ambientes: áreas de monoculturas de Pinus, Eucalyptus e Araucaria angustifolia e Floresta Ombrófila Mista. Em cada uma das 12 áreas de estudo, foram demarcadas 5 parcelas de 8m² e 5 parcelas de 1m³. Foram realizados levantamentos de ri / The conversion of native forests to tree monocultures have been producing an heterogeneus landscape mosaic where the capacity of colonization of understorey plants from adjacent forest is still unknown. These changes in land use may lead to modifications on plant species composition which can alter forest carbon storage. These study investigates differences in species composition, species richness, abundance and functional richness of plants that colonized the understorey of forests and tree monocultures. It also investigates how species diversity and the diversity of functional groups could influence biomass storage in the understorey. The study was conducted at the São Francisco de Paula National Forest, RS, Brazil, using three replicates of each of the following habitas monocultures of Pinus, Eucalyptus and Araucaria angustifolia and Araucaria forest. In each of the 1 study sites five 8m² plots and five 1m³ plots were defined. Richness, abundance and biomass storage of plant species were surveyed and sepa

Coral reefs, seagrass beds and mangroves constitute a complex mosaic of habitats referred to as the tropical seascape. Great gaps exist in the knowledge of how these systems are interconnected. This thesis sets out to examine ecological connectivity, i.e. the connectedness of ecological processes across multiple scales, in Zanzibar and Mafia Island, Tanzania. Paper I examined the current knowledge of interlinkages and their effect on seascape functioning, revealing that there are surprisingly few studies on the influences of cross-habitat interactions and food-web ecology. Furthermore, 50% of all fish species use more than one habitat and 18% of all coral reef fish species use mangrove or seagrass beds as juvenile habitat in Zanzibar. Paper II examined the seascape of Menai Bay, Zanzibar using a landscape ecology approach and studied the relationship between fish and landscape variables. The amount of seagrass within 750m of a coral reef site was correlated with increased invertebrate feeder/piscivore fish abundance, especially Lethrinidae and Lutjanidae, which are known to perform ontogenetic and feeding migrations. Within patch seagrass cover was correlated with nursery species abundance. Paper III focused on a seagrass-dominated seascape in Chwaka Bay, Zanzibar and showed that small-scale habitat complexity (shoot height and density) as well as large-scale variables such as distance to coral reefs affected abundance and distribution of a common seagrass parrotfish Leptoscarus vaigiensis. Paper IV studied the connectivity and functional role of two snappers (Lutjanus fulviflamma and L. ehrenbergii) using stable isotopes (δ15N and δ13C) and found that connectivity between habitats was maintained by ontogenetic and foraging migrations by these species. The thesis concludes that ecological connectivity and multi-habitat usage by fish is a general and important characteristic in the Western Indian Ocean and should be considered in management planning. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Submitted.</p>

Piers-Rubinsztajn (P-R) conditions, involving catalysis by tris(pentafluorophenyl)borane, were applied to siliconize triarylamines. A phenylated linear methylhydrosiloxane copolymer was utilized to create a hydrolytically-stable composite with promising optical, electrochemical and thermal properties. However, the reaction was highly exothermic, had rapid uncontrollable kinetics and produced methane as a byproduct; problematic characteristics for larger scale syntheses. Thereafter, triarylamines with bulkier substituents were studied to determine whether the kinetics could be slowed and a less volatile byproduct created. The rate of conversion was retarded significantly as expected, but not all derivatives reacted quantitatively in ambient conditions. Finally, P-R conditions were applied to methylhydrosiloxane-dimethylsiloxane copolymers. Gelation in air upon extended reaction time was effectively avoided by “finishing” excess Si-H sites using anisole. The result was the preparation of composites with up to 61 wt % arylamine content, which are expected to have significant applications as cost-effective flexible hole transport layers in organic electronic devices.

Piers-Rubinsztajn (P-R) conditions, involving catalysis by tris(pentafluorophenyl)borane, were applied to siliconize triarylamines. A phenylated linear methylhydrosiloxane copolymer was utilized to create a hydrolytically-stable composite with promising optical, electrochemical and thermal properties. However, the reaction was highly exothermic, had rapid uncontrollable kinetics and produced methane as a byproduct; problematic characteristics for larger scale syntheses. Thereafter, triarylamines with bulkier substituents were studied to determine whether the kinetics could be slowed and a less volatile byproduct created. The rate of conversion was retarded significantly as expected, but not all derivatives reacted quantitatively in ambient conditions. Finally, P-R conditions were applied to methylhydrosiloxane-dimethylsiloxane copolymers. Gelation in air upon extended reaction time was effectively avoided by “finishing” excess Si-H sites using anisole. The result was the preparation of composites with up to 61 wt % arylamine content, which are expected to have significant applications as cost-effective flexible hole transport layers in organic electronic devices.

Experimental measurement of fuel properties are expensive, require sophisticated instrumentation and are time consuming. Mathematical models and approaches for predicting fuel properties can help reduce time and costs. A new approach for characterizing petroleum fuels called the functional group approach was developed by disassembling the innumerable fuel molecules into a finite number of molecular fragments or ‘functional groups’. This thesis proposes and tests the following hypothesis, Can a fuels functional groups be used to predict its combustion properties? Analytical techniques like NMR spectroscopy that are ideally suited to identify and quantify the various functional groups present in the fuels was used. Branching index (BI), a new parameter that quantifies the degree and quality of branching in a molecule was defined. The proposed hypothesis was tested on three classes of fuels namely gasolines, diesel and heavy fuel oil. Five key functional groups namely paraffinic CH3, paraffinic CH2, paraffinic CH, naphthenic CH-CH2 and aromatic C-CH groups along with BI were used as matching targets to formulate simple surrogates of one or two molecules that reproduce the combustion characteristics. Using this approach, termed as the minimalist functional group (MFG) approach surrogates were formulated for a number of standard gasoline, diesel and jet fuels. The surrogates were experimentally validated using measurements from Ignition quality tester (IQT), Rapid compression machine (RCM) and smoke point (SP) apparatus. The functional group approach was also employed to predict research octane number (RON) and motor octane number (MON) of fuels blended with ethanol using artificial neural networks (ANN). A multiple linear regression (MLR) based model for predicting derived cetane number (DCN) of hydrocarbon fuels was also developed. The functional group approach was also extended to study heavy fuel oil (HFO), a viscous residual fuel that contains heteroatoms like S, N and O. It is used in ships as marine fuel and also in boilers for electricity generation. 1H NMR and 13C NMR measurements were made to analyze the average molecular parameters (AMP) of HFO molecules. The fuel was divided into 19 different functional groups and their concentrations were calculated from the AMP values. A surrogate molecule that represents the average structure of HFO was then formulated and its properties were predicted using QSPR approaches.

Moderate livestock grazing is often identified as a useful management tool for sustaining biodiverse grassland communities and has long been practiced in Scandinavian mountains. Despite of a growing number of studies focusing on grazing effects along elevational gradients worldwide, there is still limited knowledge of how grazing intensity varies over time and how it affects plant communities on species and functional group level. Moreover, the majority of existing studies are conducted in enclosures with controlled stocking rate, while free-range grazing with a highly varied livestock number is the common practise in Scandinavia. Therefore, the aim of this study was to quantify free-range grazing intensity over the growing season along an elevational gradient and to evaluate how grazing affects plant communities on species, functional group and community level. In order to quantify grazing intensity, we conducted a grazer exclusion experiment along an elevational gradient in Norway in the growing season of 2019. We quantified grazing intensity as the difference in dry above-ground biomass between grazed and caged plots and analyzed plant composition on community and functional group level as well as recorded species-specific grazing damage and potentially influential abiotic factors. To capture the effects of temporal variation in grazing we also relocated caged and grazed plots in four-week intervals during the growing season. We demonstrated that grazing intensity gradually decreased with elevation and elevation explained 77% of the variation in grazing among sites. Lower grazing intensity at high elevation is likely related to decreasing plant productivity and differences in plant community composition along the gradient. Grazers reduced the biomass of graminoids and forbs in the intensively grazed lower sites. Grazing damage varied among sites for five of the eight most commonly grazed plant species, which was mainly driven by a higher grazing damage in the intermediate site (900m a.s.l.). Selective grazing was observed in three sheep-dominated study sites. Grazing intensity did not significantly vary during the growing season at any site, possibly due to weak temporal effects of an overall short growing season. In accordance with other studies, we demonstrated that grazing homogenized plant community composition in actively grazed sites that were relatively species rich. To conclude, livestock grazing can help maintain biodiverse semi-natural grasslands, yet when grazing is applied as a management tool in the mountainous landscapes, we suggest considering that grazing intensity, and therefore its effects, will vary with elevation.

No description available.

<p>In this thesis I examine and evaluate the effects of a documented large-scale eutrophication on macroalgal vegetation on the Swedish coast. During the past century the load of nutrients has increased manifold in the Baltic Sea area, increasing primary production and organic sedimentation significantly. By re-investigating a unique reference material of macroalgal vegetation from the 1940-60s and by conducting new diving studies at the same sites, I showed that long-term trends in macroalgal community composition and species’ distributions are consistent with changes expected from an increased nutrient availability. In the Öregrund archipelago (northern Baltic Sea), I documented a declined depth distribution of the dominant canopy forming alga, <i>Fucus vesiculosus</i>, and an increased abundance of opportunistic ephemeral algae compared to 52-53 years ago. In the Gullmar Fjord area (Skagerrak), trends included increased abundances of functional groups with opportunistic algae, decreased abundances of large perennial algae and a general decline in the depth distribution of the vegetation compared to 36-57 years ago. Sediment removal experiments in the northern Baltic Sea confirmed the hypothesis that sedimentation influences macroalgal community composition. Species depending on short periods of reproduction were clearly favoured by sediment removal, especially <i>F. vesiculosus</i> that seemed limited in depth by the local sediment load. Species with long continuous periods of dispersal by spores and/or fragments (for example the ephemerals <i>Cladophora glomerata</i>, <i>Ceramium tenuicorne</i> and <i>Enteromorpha</i> spp.) were more tolerant to the natural sediment load. In general, sediment removal favoured macroalgal establishment and development, indicating that variation in the natural sediment load is an important constraint for sublittoral rocky-shore macroalgal community development. I conclude by suggesting that the documented long-term changes in macroalgal vegetation on the Swedish coast partly are explained by an increased organic sedimentation in these areas.</p>

In this thesis I examine and evaluate the effects of a documented large-scale eutrophication on macroalgal vegetation on the Swedish coast. During the past century the load of nutrients has increased manifold in the Baltic Sea area, increasing primary production and organic sedimentation significantly. By re-investigating a unique reference material of macroalgal vegetation from the 1940-60s and by conducting new diving studies at the same sites, I showed that long-term trends in macroalgal community composition and species’ distributions are consistent with changes expected from an increased nutrient availability. In the Öregrund archipelago (northern Baltic Sea), I documented a declined depth distribution of the dominant canopy forming alga, Fucus vesiculosus, and an increased abundance of opportunistic ephemeral algae compared to 52-53 years ago. In the Gullmar Fjord area (Skagerrak), trends included increased abundances of functional groups with opportunistic algae, decreased abundances of large perennial algae and a general decline in the depth distribution of the vegetation compared to 36-57 years ago. Sediment removal experiments in the northern Baltic Sea confirmed the hypothesis that sedimentation influences macroalgal community composition. Species depending on short periods of reproduction were clearly favoured by sediment removal, especially F. vesiculosus that seemed limited in depth by the local sediment load. Species with long continuous periods of dispersal by spores and/or fragments (for example the ephemerals Cladophora glomerata, Ceramium tenuicorne and Enteromorpha spp.) were more tolerant to the natural sediment load. In general, sediment removal favoured macroalgal establishment and development, indicating that variation in the natural sediment load is an important constraint for sublittoral rocky-shore macroalgal community development. I conclude by suggesting that the documented long-term changes in macroalgal vegetation on the Swedish coast partly are explained by an increased organic sedimentation in these areas.