• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1846
  • 1022
  • 325
  • 218
  • 178
  • 175
  • 55
  • 54
  • 43
  • 42
  • 39
  • 37
  • 37
  • 30
  • 18
  • Tagged with
  • 4875
  • 767
  • 442
  • 392
  • 378
  • 333
  • 302
  • 246
  • 237
  • 218
  • 217
  • 206
  • 205
  • 202
  • 200
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
531

Static axial pile foundation response using seismic piezocone data

Niazi, Fawad Sulaman 27 August 2014 (has links)
Ever since the use of cone penetration testing (CPT) in geotechnical site investigations, efforts have been made to correlate its readings with the components of static axial pile capacity: unit base resistance (qb) and unit shaft resistance (fp). Broadly, the pile capacity analysis from CPT data can be accomplished via two main approaches: rational (or indirect) methods, and direct methods. The rational methods require a two-step approach, whereby CPT data are first used to provide assessments of geoparameters that are further utilized as input values within a selected analytical framework to enable the evaluation of the pile capacity components. In contrast, direct CPT methods use the measured penetrometer readings by scaling relationships or algorithms in a single-step process to obtain fp and qb for full-size piling foundations. The evolution of the CPT from mechanical to electrical to electronic versions and single-channel readings (i.e., measured tip resistance, qc) to the piezocone penetration test (CPTu), that provides three readings of point stress (qt), sleeve friction (fs), and porewater pressure (u1 or u2), has resulted in the concurrent development of multiple CPT-based geotechnical pile design methods. It is noted, however, that current CPT-based methods focus only on an estimate of "axial pile capacity", corresponding to a limiting load or force at full mobilization. A more comprehensive approach is sought herein utilizing the CPT readings towards producing a complete nonlinear load-displacement-capacity (Q-w-Qcap) on axial pile response. In particular, the seismic cone penetration test (SCPT) provides the profile of shear wave velocity (Vs) that determines the fundamental small-strain shear modulus: Gmax = gt?Vs2, where gt = total mass density of soil. With the penetrometer readings useful in assessing foundation capacity, the stiffness Gmax finds application within elastic continuum solutions towards evaluating the load-displacement (Q-w) response. In this study, a concise review of the deep foundation systems is presented, including pile types and characteristics, various arrangements of axial pile load testing in static mode, and interpretations of the load test data. In addition a comprehensive state-of-the-art review of CPT-based rational and direct methods of pile capacity evaluations is compiled. It is recognized that the direct methods offer more convenience in their straightforward approach in estimation of the pile capacity. The piezocone-based UniCone direct method proposed by Eslami and Fellenius (1997) is selected for further refinements, as it utilizes all three CPT readings in its design formulations. Concerning the analysis of pile deformations under axial loading, a brief review covers designs employing empirical formulations, analytical solutions, load-transfer (t-z) methods, numerical simulations, variational approaches, and those using hybrid methods. Specifically, the analytical elastic solution by Randolph and Wroth (1978; 1979) is covered in more detail since it is simple and convenient in application with extended applications to uplift and bidirectional O-cell types of loadings. This elastic approach also serves well in modeling a stacked pile solution for layered soil profiles. The last part of the review covers various shear modulus reduction schemes, since evaluation of the applicable stiffnesses is considered to be the most delicate phase in the nonlinear Q-w response analysis of axially loaded piles. It is identified that the most appropriate scheme applicable to static axial loading of pile foundations is the one that can be derived from the back-analyses of actual load tests within the framework of analytical elastic solution. In order to conduct a comprehensive research study on the axial Q-w-Qcap response of deep foundations from CPT readings, a large database is compiled. This includes 330 case records of pile load tests at 70 sites from 5 continents and 19 different countries of the world, where pile foundations were load tested under top-down compression or top-applied uplift (tension) loading, or both, or by bi-directional Osterberg cell setups. All test sites had been investigated using CPT soundings; in most cases by the preferred SCPTu that provides all four readings from the same sounding: qt, fs, u2, and Vs. In a few cases, sites were subjected to CPT or CPTu and the profiles of shear wave velocities were obtained by other field geophysical techniques, otherwise by empirical estimations. Results of the new correlation efforts are offered to derive coefficients Cse for shaft component and Cte for base component of the axial pile capacity from CPTu data. The UniCone type of soil classification chart is refined by delineating 11 soil sub-zones along with their respective Cse, in contrast to the 5 zones originally proposed. The CPT material index, Ic (Robertson, 2009) is then used to establish direct correlations linking Cse vs. Ic and Cte vs. Ic. Statistical relationships offer continuous functions for estimating the coefficients over a wide range of Ic values, thereby eliminating the need for use of the soil classification chart as well as improving the reliability in the evaluations of fp and qb. The effects of the pile loading direction (compression vs. uplift) and loading rate are also incorporated in the proposed design formulations. New sets of shear stiffness reduction curves are developed from the back-analysis of pile load tests and Gmax profiles obtained from the SCPT data. Alternative functions formats are provided in terms of hyperbolic tangent expressions or exponential curves, developed as normalized shear stiffness (G/Gmax) vs. logarithm of percent pseudo-strain (gp = w/d, where w = pile displacement and d = pile diameter). These charts offer convenience in the axial Q-w analysis of different pile categories within the framework of analytical elastic solution. The results also account for the plasticity characteristics of the soil formations within the database. A stacked pile model for Q-w analysis is presented in which certain adaptations are proposed in the elastic continuum solution. These adaptations enable plotting of separate modulus reduction curves (G/Gmax vs. gp) as function of depth for each layer, and treating pile as a stack of smaller pile segments embedded in a multi-layered soil media. The solution can be used to address the question of progressive failure with depth in a multi-layer soil media that exhibits nonlinear soil stiffness response. Finally, the closed-from analytical elastic pile solution for predicting the Q-w response is decoupled and modified to account for different setup cases and multi-stage loading of bi-directional O-cell tests. The decoupling accounts for separate assessments of the response to axial loading for different segments of pile shaft and different stages of loading, while the modifications include: (1) reduced maximum radius of influence for the upward displacements of the upper shaft segment, and (2) modeling the non-linear ground stiffness from the back-analysis of a well-documented dataset of O-cell load tests.
532

GFRP-reinforced concrete exterior beam-column joints subjected to seismic loading

Hasaballa, Mohamed 29 October 2014 (has links)
Glass fibre-reinforced polymer (GFRP) reinforcement is used in reinforced concrete (RC) infrastructure to avoid steel corrosion problems. The behaviour of GFRP reinforcement under seismic loading in RC frame structures has not been widely investigated. The behaviour of beam-column joints significantly influences the response of the Seismic Force Resisting Systems. Therefore, both the design and detailing of the beam-column joints are critical to secure a satisfactory seismic performance of these structures. However, the current Canadian FRP design codes (CSA 2012, CSA 2006) have no considerable seismic provisions, if any, due to lack of data and research in this area. Such lack of information does not allow for adequate designs and subsequently limits the implementation of FRP reinforcement as a non-corrodible and sustainable reinforcement in new construction. Therefore, it deemed necessary to track areas of ambiguity and lack of knowledge to provide design provisions and detailing guidelines. This study investigated the seismic behaviour of the GFRP-RC exterior beam-column joints. The study consisted of an experimental phase, in which ten full-scale T-shaped GFRP-RC specimens were constructed and tested to failure, and an analytical phase using finite element modelling (FEM). Specimens in the experimental phase were designed to investigate the anchorage detailing of beam longitudinal reinforcement inside the joint (using either bent bars or headed bars) and to evaluate the shear capacity of the joint. In the analytical phase, a commercial FEM software (ATENA-3D) was used to run a parametric study that investigated the influence of the presence of lateral beams, axial load on the column, applied shear stresses in the joint, and the concrete strength. Test results showed that the performance of the specimens reinforced with GFRP headed bars was comparable to their counterparts reinforced with bent bars up to 4.0% drift ratio. The difference in the reinforcement surface conditions had insignificant influence on the overall behaviour. Moreover, it was concluded that the shear capacity of GFRP-RC beam-column joints is 0.85 √f'c. Furthermore, an evaluation of the relevant seismic provisions in the CSA/S806-12 (CSA 2012) was carried out and some recommendations were proposed for consideration in the future updates of the CSA/S806-12.
533

Climate Change Vulnerability Assessment for Sustainable Urban Development : A Study on Slum Population of Kota, India

Akhter Feroz, Raisin January 2012 (has links)
The urban centres are becoming more vulnerable to climate change because of the rapid urbanization and the inequality of urban development. This study assesses the urban vulnerability in an integrated approach focusing the slum people as the targeted group. The slum people are severely exposed to climate risks in terms of city‟s overall development. The negative indications of the indicators of person‟s vulnerability represent their high sensitivity to the adverse impact of climate change. The determinants of adaptive capacity also confirm that the slum people are more vulnerable to climate change with having lower adaptive capacity; though, the city is possessing high development indexes. In this context, an institutional structure is developed to build multi-level urban climate governance with the involvement of all relevant stakeholders based on the case study and literature review to integrate the vulnerable group in development planning for climate change adaptation.
534

Test Performance: the Influence of Cognitive Load on Reading Comprehension

Clevinger, Amanda 12 August 2014 (has links)
Scores from high-stakes tests such as the Scholastic Aptitude Test (SAT) are commonly used as criteria for college admission decisions. So, it is of implied importance to identify factors that contribute to susceptibility to failure on these tests. One potential factor addressed in the current study was whether emotional cognitive load differentially impacts those with low working memory capacity or trait anxiety. Individual differences in subjective arousal were also tested as a mechanism contributing to this effect. In Experiment 1, a reading comprehension task revealed that type of cognitive load affected accuracy. In Experiment 2, state anxiety was induced using methods from previous research. The results revealed that, again, only type of cognitive load affected comprehension accuracy. Together, results suggest that arousal induced via disturbing words negatively influence reading performance regardless of superior working memory capacity. These findings are not based on cognitive load in general, but the semantic value of the words processed, in particular, that led to comprehension difficulty. Results are discussed in terms of theoretical and practical implications.
535

The role of local economic development in building capacity and growth for small, medium and micro enterprises in Sedibeng District Municipality / Mavi Sintu

Mavi, Sintu January 2012 (has links)
South Africa as a developing country experienced high levels of poverty and unemployment. These levels emanate from skills gap and low literacy rate in the townships populated by low income households. To an extent some households lacked access to participate in the economic sector, resulting from fragmented policies and apartheid regime. The lack of participation among the households placed pressure on government. These problems forced the state to provide social protection (grants). Such allowances are expensive especially where there are fewer opportunities for employment activities. The promotion of entrepreneurship and small business remains an important priority of the government of South Africa. The South African government is acknowledged for its commitments to ensure that small businesses progressively contribute to growth and performance of the South African economy. Globally, numerous policy legislative frameworks have been developed to support the SMMEs. This study aimed to discover the support given to the SMMEs by the South African government. In particular, the study is situated within the SMMEs in the SDM. The hypothesis for this study is premised on the fact that SMME`s can contribute immensely to job creation. The outcomes of this argument relies on the provisions based on a conducive environment which can enable the SMME`s to thrive. This statement was validated by means of literature review, interviews and site visits. This study found that the SMMEs are indeed the cornerstone of job creation and for sustainable livelihoods. LED programmes can create more jobs through the SMME sector. Literature worldwide confirms that the SMMEs are vital in creating employment opportunities. This research also confirmed that this is possible only if the environment in which SMMEs operate in is favourable for the SMMEs to prosper. In this regard many policy documents were developed to emphasize the stance of government to develop, grow and capacitate SMMEs in South Africa. It is indeed true that the LED can be used to grow and capacitate SMMEs in South Africa. Despite the progress being made on the development of the SMMEs, few issues need to be taken care off. The municipality indicated that there are no monitoring procedures in place which make it difficult to measure the infectiveness of their interventions and they further pointed out that they are working on the matter. The measurement of these milestones is not properly recorded to inform future generations. It is suggested that more research should be emphasised on the SMME sector, especially being the mandate of the municipality. / Thesis (M. Development and Management (Public Management and Government))--North-West University, Vaal Triangle Campus, 2013
536

A description of the electricity system in Spain since 2005 and the economic potential for renewable energy technologies

Izquierdo-Millan, Javier 24 January 2014 (has links)
The energy system in Spain can be characterized as being high energy intensive when compared to the rest of Europe and because of its high dependence on imported resources (around 84%). The focus of this document is to explore a novel approach to describe, as part of this energy system, the electricity system in Spain since 2005 and the economic potential for renewable energy technologies (RET) to replace the electricity generated from fossil resources by 2050. The heart of the design and implementation of any RET policy should be the reduction or elimination of fossil fuel dependency. This document aims at describing the evolution of the Spanish electricity system in the last decade, and addressing the possible influence of certain factors in the design and implementation of the electricity system by using modern modeling technologies to evaluate the potential of RET. This will represent a novel approach to bridge the results from modeling technologies to policy makers. To ensure the credibility and reliability of the data researched, validation criteria has been used which includes the accuracy of information, the content (whether factual or opinion), time (limited to certain periods), format (validity of internet sources, journals, etc), authority (reputable authors and sources), objective reasoning, currency and links to other resources, and the quality of writings and its review among others. The proposed research approach follows a methodology where the first step is to understand the electricity system in Spain, followed by the definition of the model of interest (optimization models) and the design of three different scenarios (Business as Usual, FIT and High fossil prices) for the evaluation of the potential of RET, finishing with the analysis of the results from the model and data collected from the perspectives of what has been done in previous RET policies and plans, and the possible influence of factors such as organizations and corporations on those policies and plans. The results obtained from the model are analysed and compared to the Business as Usual scenario. The amount of electricity generated from fossil resources and to be replaced by RET is calculated using the scenarios, as well as the evolution of primary energy, imports, final energy consumptions and CO2 emissions. In order to test the applicability of this approach, the results of the model have been compared with the current situation of the Spanish electricity system. Calculations using capacity factors of the RET and their share in the current electricity generation are performed in order to identify the final amount of power (MW) to be installed in order to replace the electricity generated (GWh) by fossil resources by 2050. Based on the conclusions, RET has the potential to replace the generation of electricity from fossil fuels but improvements in the efficiency of RET will be needed. In addition, it is recommended that significant considerations in RET policy like the energy and electricity systems should be a strategic component of the Spanish policy system, be done in order to set the Spanish electricity system in a more sustainable path .
537

Agriculture and Tourism Development: The Case of St. Kitts

Jenkins, Rae-Gean January 2014 (has links)
In 2005, the Government of St. Kitts and Nevis officially closed the sugar industry, ending mono-crop agriculture and opening a space for a new chosen economic driver, tourism. Newly available lands, an agricultural- based workforce and a push into tourism led to this research examining the state of agricultural tourism development in a transitioning region. Interviews with key public and private sector personnel, coupled with an evaluation of official policies and plans, were used in this qualitative case study to explore the state of agricultural tourism development (opportunities and barriers) and the role that stakeholders play in its creation. This research not only found common geographic and technical barriers but also endemic mental and behavioural characteristics of the local populace, which hinder agricultural development and, by extension, agricultural tourism. Negative attitudes towards agriculture and a lack of entrepreneurial spirit pervade, which hampers agricultural tourism development. Hence, this research shows that local attitudes towards agriculture play an important role in successfully diversifying agriculture via tourism. Many studies focus on the addition of tourism to an agricultural product without first ensuring the successful production of agricultural products themselves so that agricultural tourism can develop. Hence, this research asserts the need for the agricultural industry to upgrade its products to meet expected tourism standards before moving into agricultural tourism. Additionally, for the successful development of agricultural tourism, there needs to be a focused and sustained plan aimed at changing the mindset of the local populace towards agriculture and entrepreneurship, coupled with the government providing a facilitative environment conducive to developing agricultural tourism.
538

The Replicator And Scheffler’s Distributive Hybrid: Deriving Moral Obligations From Ability To Aid

Griffith, Adam 01 January 2014 (has links)
If one can do a good thing, ought one do it? In this paper, I argue that capability is a strong source of moral obligation that can, in proper doses, override things like property rights. I will build a hypothetical case based on a fictional invention called the Replicator with enormous potential for use as a humanitarian tool and I’ll use it to display the way that capability to aid imposes powerful moral obligations on both individuals and organizations. Ultimately, I will use the model that I will develop to demonstrate that some real-world entities are not satisfying their moral responsibilities with regards to aiding the global poor, and will suggests ways in which they can fulfill those obligations.
539

Die ontwikkeling en evaluering van 'n kapasiteitsbouprogram vir boere ter fasilitering van lewenskwaliteit / Abraham Carel Botma

Botma, Abraham Carel January 2004 (has links)
The origin of this study is due to research Botma (1999) undertook among Free State farmers in order to determine what the global level of perceived stress was, but also to determine which specific stressors they experienced and what its intensity was. With this study Botma (1999) found that the stressors by which the farmers are confronted, hold negative implications for their quality of life. The purpose of the current study namely to develop a capacity building programme by means of which quality of life can be facilitated, resulted therefore from the abovementioned research. The capacity building programme entailed the following components: stress, psychological well-being, quality of life and subjective well-being. The capacity building programme was also subjected to evaluation in order to determine its effect on the participants. In order to achieve this objective, the following scales were used in the empirical study: Quality of Lie Questionnaire (Evans & Cope, 1989), Sense of Coherence Scale (Antonovsky, 1993), Satisfaction with Life Scale (Diener, Larsen & Griffen, 1985), Affectometer 2 (Kamman & Flett, 1983), COPE (Carver, Scheier & Weintraub, 1989) and the Spiritual Well- Being Scale (Ellison & Smith, 1991). All these scales showed satisfactory reliability indices. A sample of 60 participants from three districts in the Free State was used. As far as the qualitative component of this research was concerned, focus groups were led with 10 participants, and in-depth interviews were conducted with four respondents. The empirical part of this study indicated that there was no difference between the experimental and control group before the intervention had VII taken place. On conclusion of the program, clear differences could be detected within the experimental group as well as between the experimental and control group. The experimental group showed an improvement in spirituality, subjective well-being and quality of life. These results were also reflected by the focus groups and by the in-depth interviews. It is however interesting to note that the above-mentioned changes that had taken place in the participants are mainly concerned with their affect and not with their behaviour as such. The reason being the fact that the focus of the programme is spiritual and mainly emphasises the improvement of the affective quality of life of the participants. The results of the in-depth interviews indicate the fact that the capacity building programme still has a long-term effect on the participants. Recommendations are made with regard to the capacity building programme in terms of changes to for example the inclusion of behavioural change. This research contributed to the understanding of spirituality, psychological well-being, subjective well-being and quality of life as well as to its application in a capacity building programme for farmers. / Thesis (Ph.D. (Psychology))--North-West University, Potchefstroom Campus, 2004.
540

Polyphenols, ascorbate and antioxidant capacity of the Kei-apple (Dovyalis caffra) / Tersia de Beer

De Beer, Tersia January 2006 (has links)
There is a close relationship between the susceptibility to disease and nutritional state, in the sense that an adequate diet enhances resistance to disease. There is an increasing interest in this beneficial relationship among scientists, food manufacturers and consumers. The trend is moving towards functional foods and their specific health benefits. The results of numerous epidemiological studies and recent clinical trials provide consistent evidence that diets rich in fruits and vegetables can reduce the risk of chronic diseases. These protective effects are mediated through multiple groups of beneficial nutrients contained in the fruits and vegetables, one of these being polyphenol antioxidants. The intake of the polyphenols plays an important role in the reduction and prevention of coronary heart disease (CHD), cardiovascular disease and cancer, as a consequence of their associated antioxidant properties. Fruits contain an array of polyphenols with antioxidant capacity. Polyphenols may be classified in two broad groups namely: flavonoids and non-flavonoids. Flavonoid subgroups in fruits are further grouped as catechins, anthocyanins, procyanidins and flavonol among others. Phenolic acids occur as hydroxylated derivatives of benzoic acid and cinnarnic acid, and are classified as non-flavonoids. Polyphenols have redox properties allowing them to act as reducing agents, hydrogen donators and singlet oxygen quenchers, and thus contribute to the antioxidant capacity of fruits and vegetables. Because of the numerous beneficial effects attributed to these antioxidants, there is renewed interest in finding vegetal species with high phenolic content and relevant biological activities. In view of the importance of these substances towards health and food chemistry, this study will focus on the polyphenol and Vitamin C characterisation and quantification of an indigenous South African fruit, the Kei-apple (Dovyalis cafra), thought to have antioxidant properties. Due to the fact that polyphenol content influences the colour, taste and possible health benefits of the fruit / processed food product, this study will supply valuable information to industry in choosing the best fruit processing methods to attain the desired end product. The exploitation of indigenous South African fruits (Marula and Kei-apple) is receiving increasing prominence, not only due to their health benefits, but also the opportunities these present to rural based economics. Furthermore, this research will serve as a platform for further research on the Kei-apple and other indigenous South African fruits with possible health benefits. Aims: The overall aim of this study is the quantification and characterisation of various nutritionally important antioxidants (polyphenols and ascorbate) in the Kei-apple fruit in its entirety, as well as in its individual fruit components (peel, flesh and seeds). In addition, the total antioxidant capacity of the entire fruit and the various fruit components will be determined in the unfractionated and fractionated fruit extracts. Gas chromatography coupled mass spectrometry (GC-MS) characterisation of the individual polyphenol components will also be analyzed in order to speculate on possible specific health benefits which the Kei-apple may possess. Methods: The study was designed to ensure that a representative fruit sample was collected. Approximately 100 kg Kei-apples were picked in the month of November 2004 from the Bloemhof area in South Africa. A sample of 50 fruits was rinsed and separated into the various components (peel, flesh and seeds). An additional 50 fruits were randomly selected, cleaned and used in their entirety for data representative of the entire fruit. The sample extracts were prepared, after being grounded and lyophilized, by a method described by Eihkonen et al. (1999) using 70% aqueous acetone. The C18-fractionation on the fruit and separated fruit components resulted in four fractions containing (1) phenolic acids; (2) procyanidins, catechins and anthocyanin monomers; (3) flavonols and (4) anthocyanin polymers. The total polyphenol content of the fruit and fruit components as well as the above mentioned C18-fractions were determined by Folin-Ciocalteu's method (Singleton & Rossi, 1965). Both free and total ascorbate concentrations in these samples were determined as described by Beutler (1984), in addition to total sugar content of these via standard methods. Apart from their nutritional interest, both these measurements are necessary for the correction of the total polyphenol concentrations. The total antioxidant capacity of the entire fruit and various fruit components was determined by measuring the oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) of the unfractionated and fractionated extracts. Using GC-MS analysis, the various individual polyhenol compounds contributing to the total polyphenol content of the Kei-apple was separated, identified and quantified. This quantitative data was captured and statistically analysed. The analysis of variation was performed using the Tukey Honest Significant Difference test for post-hoc comparison. ORAC, FRAP and polyphenol Pearson correlation analyses were performed using Statistics (Statsoft Inc., Tulsa, Oklahoma, USA) with significance set at P ≤ 0.05. Results and discussion: This study determined the presence of various nutritionally important antioxidants (polyphenols and ascorbate), the total antioxidant capacity in the entire fruit as well as in the individual fruit components (peel, flesh and seeds) and their polyphenol sub group fractions. Total phenol content: The Kei-apple, in its entirety, has a polyphenol concentration of 943 ± 20.3 mg GAE/100g dry weight. Comparison of the individual fruit components showed the seeds to have the highest total polyphenol concentration with 1990 ± 31.3 mg GAE/100g dry weight, followed by that of the peel, 1126 ± 45.8 mg GAE/100g dry weight and then that of the flesh, 521 ± 1.01 mg GAE/100g dry weight. Total, L-ascorbic (ASC) and L-dehydroascobic (DHA) concentration: The total ascorbate of Kei-apple fruit is 517 ± 0.92 mg/100g dry weight. In contrast to the polyphenol content, the flesh of the Kei-apple had significantly the highest concentration of total ascorbate 778 ± 1.20 mg/100g dry weight, Gascorbic 241 ± 21.0 mg/100g dry weight, as well as Gdehydroascobic 537 ± 22.2 mg/100g dry weight. The ratio of Lascorbic acidltotal ascorbate for the flesh, entire fruit, peel and seed is 0.31,0.43,0.49,0.95, respectively, indicating the seeds are the most stable source of biologically active Vitamin C, with 95% of the total ascorbate occurring as G ascorbate. This is also in line with the total polyphenol content of these components, confirming a polyphenol sparing effect on ascorbate. C18-fractionation extracts: Solid phase (C18) fractionation of the Kei-apple fruit and fruit components showed that the fruit, peels and seeds consist predominantly of phenolic acids, followed by procyanidin, catechin and anthocyanin monomers and thereafter varying amounts of anthocyanin polymers and flavonols. Antioxidant capacity: The antioxidant capacity of the entire fruit and individual fruit components as determined by ORAC, (r=0.76) and FRAP, (r=0.95) significantly correlated with the total polyphenol content, as well as to each other (r=0.88), indicating both to be good predictors of antioxidant capacity. GC-MS polyphenol characterisation of the Kei-apple: Caffeic acid and hydro-p-coumaric acid were seen to be the phenolic acids occurring in the highest concentrations in the Kei-apple fruit. The majority of these are concentrated in the flesh and in the case of caffeic acid, also in the peel. The order of predominance of other major non-flavonoid components in the whole fruit analysis are m-hydroxybenzoic acid > p-hydroxyphenyl acetic acid > 3-methoxy-4- hydroxyphenylpropionic acid > p-coumaric acid. The peel of the Kei-apple, apart from caffeic acid, has exceptionally high concentrations of ferulic acid and also serves as a source of protocatechuic acid. Syringic acid was most prominent in the seeds. Although the total flavonoid concentration in the Kei-apple was low, taxifolin and catechin were identified and the seeds almost entirely accounting for these. Conclusion: From this study it was concluded the Kei-apple is a rich source of antioxidant compounds (polyphenols and ascorbate), with a strong antioxidant capacity, and hence may be associated with health promotion properties, particularly in the prevention of cancer, cardiovascular disease, and neurodegeneration. Additionally, due to the increased scientific and commercial interest in this fruit, it is essential to take into consideration the various factors (agronomic, genomic, pre- and post harvest condition and processing) and tissues. This might affect the chemical composition of the final marketed product, which may play a significant role in determining the polyphenol and ascorbate composition and bioactivity of these compounds during food processing procedures. Hence, the polyphenol composition of the various fruit components should be taken into consideration when selecting a method of fruit processing into the desired end product. / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2007.

Page generated in 0.0677 seconds