206 research outputs found
A Sampling of the Phenetic Diversity of Cacao in the International Cocoa Gene Bank of Trinidad
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Cacao
No full textCacao originates from the rainforests of South America, the centre of diversity being the Upper Amazon region. However, present-day cultivation extends through the humid tropics with the largest proportion being in West Africa. Ex situ conservation of cacao is particularly important due to the incremental loss of native (wild) habitats and replacement of traditional varieties on farms. It is estimated that over 24,000 cacao accessions are conserved in genebanks, many of which are associated with national research institutes. There are currently two international genebanks for cacao (in Trinidad and in Costa Rica) that have been put under the auspices of the International Treaty on Plant Genetic Resources for Food and Agriculture. Breeding approaches have tended to focus on improving yields and resistance to pests and diseases and have often utilised a relatively narrow genetic base. In order to meet on-going and future challenges to cocoa production, including the need for greater climate resilience and more easily managed, productive cacao farms, it is necessary to utilise a broader range of genetic resources. Advances in genomic technology may accelerate breeding efforts and can be used to identify off-types and redundancies in collections. Underlying breeding efforts, there is a critical need for on-going conservation, characterisation, evaluation and utilisation of cacao genetic resources
The compilation and analysis of a descriptor list for cocoa (Theobroma cacao L.).
No full textThe usefulness of several cocoa descriptors was assessed in this study. Thirty-five quantitative descriptors were analyzed to determine whether, and to what extent, they differentiate between fifty-three accessions. The latter represent a range of diversity. All the descriptors were discriminative. However, the leaf descriptors were more influenced by environment than the reproductive ones and the fruit descriptors displayed the most variability within the populations studied. There were several correlations between these descriptors. For the purpose of quick identification of accessions, the most discriminative were retained and those correlated with them discarded. The resulting subset of descriptors includes pod weight and length, total bean weight, bean length and width; staminode, petal and sepal lengths, ovule number; total leaf length and leaf apical angle. Information on the diversity of the accessions was important for assessing the usefulness of these descriptors. Seven homogeneous groups of accessions were identified by clustering with sixty-eight mixed variables. The presence of diversity was demonstrated and the accessions could be differentiated according to their geographic origin. No subsets of descriptors provided a classification identical to that of the full complement. However, a subset of thirty-four mixed descriptors furnished a similar classification. It may be appropriate for quick classification in the International Cocoa Genebank, Trinidad. Subsets of descriptors may be useful for differentiating between distinct accessions. However, as large a group of descriptors, as is practicable, is recommended for the reliable determination of the relationships between the accessions
Participatory Design Game for Urban Slum Upgrading in the context of Addis Ababa
No full textThe project uses a tangible and visual method for eliciting the shareholder’s spatial needs using a game-based approach. The design game resembles a board game in conjunction with Lego and functions on a more abstract level in relation to the built environment. The game is intended for use in a collaborative design that allows end users to collectively configure their space based on their spatial requirements and priorities which otherwise may not be met by standard conventional design in the top-down approach. The development of the design game abstracts the working spatial and social qualities of slum settlements within Ababa’s inner city (specifically kebele compound houses) and embeds them into a system of configurational elements and rules for configuring a low-rise courtyard-based incremental housing. This system of design flows a modular co-ordination system based upon a tartan grid. The end users use the game elements (boards, modules, activity cards & tokens) to configure their space based on the defined game rules. In the game play process, the stakeholders (players) will identify and weigh different domestic and commercial spaces, functions and sizes based upon their priority to form their configuration of hierarchic spatial framework and shared spaces. The method of developing the game can be replicated to create design games for different contexts. The game serves as a simulation of a design problem that facilitates trade-offs, design ideation, projection of stakeholder needs, preferences, and co-creation. At the basic level, the game can be used to collect information about end-user preferences regarding spatial configuration, the use of tokens creates a trade-off where players have to prioritize their immediate spatial needs. At a higher level, the game can be used in a bottom-up planning strategy for ideating new housing solutions and upgrading existing ones.Architecture, Urbanism and Building Sciences | Building Technolog
Slow dynamic diagnosis of asphalt concrete specimen to determine level of damage caused by static low temperature conditioning
No full textThe phenomenon of slow dynamics has been observed in a variety of materials which are considered as relatively homogeneous that exhibit nonlinearity due to the presence of defects or cracks within them. Experimental realizations in previous work suggest that slow dynamics can be in response to acoustic drives with relatively larger amplitude as well as rapid change of temperature. Slow dynamics as a nonlinear elastic response of damaged materials is manifested as a sharp drop and then recovery of resonance frequency linearly with logarithmic time. In this work, slow dynamics recovery is intended to be used as a means of identifying and evaluating thermal damage on an asphalt concrete specimen. The experimental protocol for measuring slow dynamics is based on the technique of nonlinear resonance spectroscopy and is set up with non-contact excitation using a loud speaker and the data acquisition tool box of Matlab. Sweeps of frequency with low amplitude are applied in order to probe the specimen at its linear viscoelastic state. The drop and then recovery in fundamental axially symmetric resonance frequency is observed after the specimen is exposed to sudden temperature change. The investigation of the viscoelastic contribution to the change in resonance frequency and slow dynamics can help identify micro-damage in asphalt concrete samples.</p
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