Benchmarking Block Ciphers for Wireless Sensor Networks

Choosing the most storage- and energy-efficient block cipher specifically for wireless sensor networks (WSNs) is not as straightforward as it seems. To our knowledge so far, there is no systematic evaluation framework for the purpose. We have identified the candidates of block ciphers suitable for WSNs based on existing literature. For evaluating and assessing these candidates, we have devised a systematic framework that not only considers the security properties but also the storage- and energy-efficency of the candidates. Finally, based on the evaluation results, we have selected the suitable ciphers for WSNs, namely Rijndael for high security and energy efficiency requirements; and MISTY1 for good storage and energy efficiency

Survey and Benchmark of Block Ciphers for Wireless Sensor Networks

Cryptographic algorithms play an important role in the security architecture of wireless sensor networks (WSNs). Choosing the most storage- and energy-efficient block cipher is essential, due to the facts that these networks are meant to operate without human intervention for a long period of time with little energy supply, and that available storage is scarce on these sensor nodes. However, to our knowledge, no systematic work has been done in this area so far.We construct an evaluation framework in which we first identify the candidates of block ciphers suitable for WSNs, based on existing literature and authoritative recommendations. For evaluating and assessing these candidates, we not only consider the security properties but also the storage- and energy-efficiency of the candidates. Finally, based on the evaluation results, we select the most suitable ciphers for WSNs, namely Skipjack, MISTY1, and Rijndael, depending on the combination of available memory and required security (energy efficiency being implicit). In terms of operation mode, we recommend Output Feedback Mode for pairwise links but Cipher Block Chaining for group communications

A comparison of the responses of mature and young clonal tea to drought.

To assist commercial producers with optimising the use of irrigation water, the responses to drought of mature and young tea crops (22 and 5 years after field planting respectively) were compared using data from two adjacent long-term irrigation experiments in Southern Tanzania. Providing the maximum potential soil water deficit was below about 400-500 mm for mature, and 200-250 mm for young plants (clone 6/8), annual yields of dry tea from rainfed or partially irrigated crops were similar to those from the corresponding well-watered crops. At deficits greater than this, annual yields declined rapidly in young tea (up to 22 kg (ha mm)-1) but relatively slowly in mature tea (up to 6.5 kg (ha mm)- 1). This apparent insensitivity of the mature crop to drought was due principally to compensation that occurred during the rains for yield lost in the dry season. Differences in dry matter distribution and shoot to root ratios contributed to these contrasting responses. Thus, the total above ground dry mass of well-irrigated, mature plants was about twice that for young plants. Similarly, the total mass of structural roots (>1 mm diameter), to 3 m depth, was four times greater in the mature crop than in the young crop and, for fine roots (<1 mm diameter), eight times greater. The corresponding shoot to root ratios (dry mass) were about 1:1 and 2:1 respectively. In addition, each unit area of leaf in the canopy of a mature plant had six times more fine roots (by weight) available to extract and supply water than did a young plant. Despite the logistical benefits resulting from more even crop distribution during the year when crops are fully irrigated, producers currently prefer to save water and energy costs by allowing a substantial soil water deficit to develop prior to the start of the rains, up to 250 mm in mature tea, knowing that yield compensation will occur later

Audiencing Artscapes: Encounters between art and audience at Yorkshire Sculpture Park

This thesis explores the ways in which the meanings of site art are inscribed by different audiences and their spatially contingent processes of audiencing. Theoretically and empirically it suggests the importance of the verb ‘audiencing’ over the static noun ‘audience’ to activate the dynamic processes involved in the production of art’s meaning. The thesis is based upon qualitative research undertaken over one year spent at Yorkshire Sculpture Park, West Yorkshire. It tailors archival, ethnographic and visual methodologies to address how examples of site art within their spatial context are audienced from a range of roles and positionalities. Audiencing is shown to occur non-linearly, with meaning inscribed variously during the processes of making, installation and exhibiting. Each chapter explores different facets of the relationship between site, art and audience, tracing the histories, discourses and situated knowledges that shape the meanings of the sculpture park and its art. Overall the thesis develops understandings of the geographies of art, suggesting how memory, environmental history and situated knowledges are essential to the embodied dimensions of interpreting site art, and exploring the ways in which audiences have read, produced and practiced the local landscape in differently scaled geographical contexts. This project also considers the ways in which the public can be convened and formed in different spaces, using the sculpture park as a case study to develop critical discussion on non-urban site art and non-urban public space. Together the chapters offer new methodological and analytic approaches to framing the cultural and social meaning of art. Mixed qualitative methods are adopted to explore the in-depth, complex meanings of site art within a range of peoples’ lives, revealing the creativity, relational geography and site specificity that lie at the heart of arts’ audiencing

An overview of tea research in Tanzania - with special reference to the Southern Highlands.

The history of tea development in Tanzania from the early part of this century to the present is summarised. Average yields of made tea from well managed estates in the Mufindi district have increased from around 600 kg ha-1 in the late 1950s to 3000 kg ha-1 at the present time: by comparison, yields from smallholder farms have remained much lower, averaging only 400-500 kg ha-1. There have been a large number of technical, economic and other changes over the last 30 to 40 years. The removal of shade trees, the use of herbicides, the application of NPK compound fertilisers, the introduction of irrigation (on some estates) and changes in harvesting policy have all contributed to the increases in yield. Financial and infrastructural problems have contributed to the low yields from many smallholders and others, and have limited the uptake of new technology. The contribution of research is reviewed, from the start of the Tea Research Institute of East Africa in Kenya in 1951, through to the development of the Marikitanda Tea Research Centre in Amani in 1967; the Ngwazi Tea Research Unit in Mufindi (1967 to 1970, and from 1986), and lastly the Kifyulilo Tea Research Station, also in Mufindi in 1986. The yield potential of well fertilized and irrigated clonal tea, grown at an altitude of 1800 m, is around 6000 kg ha-1. This potential is reduced by drought, lack of fertilizer, bush vacancies and inefficient harvesting practices. The corresponding potential yields at high (2200 m) and low (1200 m) altitude sites range from 3000-3500 kg ha-1 up to 9000-10000 kg ha-1 and are largely a function of temperature. The opportunities for increasing yields of existing tea, smallholder and estate, are enormous. Tea production in the Southern Highlands of Tanzania is about to expand rapidly. Good, appropriate research is needed to sustain this development over the long term, and suggestions on how best this is done in order to assist the large scale producers as well as the smallholders, are discussed

The economic value of biodiversity in New Zealand: Results from a household survey

This paper presents the results of a national study examining the economic value of biodiversity in New Zealand. Three valuation techniques were used to collect information from respondents: the contingent valuation method, the well-being method and the choice modelling method. Results revealed that respondents were familiar with the native plants and animals in their areas and valued them highly, therefore having a strong value for native biodiversity

Evaluation of Morphological Diversity in South Indian Tea Clones Using Statistical Methods

Morphological diversity of three Camellia (Theaceae) taxa conserved in an ex situ gene bank was studied and the importance of different descriptors in categorising accessions into distinct groups was also determined. Twelve accessions were characterised using 15 morphological descriptors of IPGRI guidelines. The results of principal component analysis (PCA) on morphological characters showed that the first two principal components accounted for 44.77 % of the total variance. In the evaluated quantitative characters, all three taxa had a coefficient of variation (CV) greater than 24.85%, and within the taxon the CV was greater than 9.59%. The qualitative characters showed a wide range of variations and yielded significant differences (p<0.05). Phenotypic data had high contributing component loadings from characters such as leaf area, weight of harvested shoots, stem colour, leaf pubescence and young shoot colour. Cluster analysis delineated the accessions into three groups. The implications of our results hold promise for assessing genetic diversity in germplasm collections, which is a prerequisite for their utilisation, effective management and crop improvement

Floral Pigments of the Yellow Camellia, Camellia Chrysantha (Theaceae)

Floral pigments of Camellia chrysantha consist of three flavonoids (quercimeritrin, rutin, and isoquercitrin) and two xanthophylls (neoxanthin and an unidentified xanthophyll). The transfer of yellow petal coloration from C. chrysantha to other Camellia species may be hampered by interspecific genetic incompatibilities and by the complexities of genetic regulation of biosynthesis of the pigments involved

Rubisco-bis-phosphate oxygenase (RuBP)- A potential housekeeping gene for qPCR assays in tea

The present experiment is an effort to find a stable reference gene in Camellia sinensis and Camellia assamica under different biotic and abiotic stresses. This study evaluate the variation in gene expression across tea leaf tissues in nine experiments. The suitability of 18S rRNA, 26S rRNA, rubiscobis- phosphatase oxygenase (RuBP) and Camellia tubulin (CaT) as reference genes were validated by geNorm and BestKeeper programs. The finding reveals 18S rRNA and RuBP to be the most stably expressed housekeeping genes, the latter being the first report of its kind in tea. The finding paves the way for their application in accurate quantification of trait specific gene expression and other genomic studies in tea.Keywords: Camellia sinensis, Camellia assamica, qPCR, BestKeeper, geNorm, housekeeping gen

INVESTIGATION ON POLYPHENOLIC COMPOUNDS DERIVED FROM TROPICAL HERBS FOR INHIBITING SILICATE SCALES

Silicate scale deposition in region around the wellbore or in any parts of the production system is a serious production problem. During hydrofluoric acidizing treatments, the release of silicon and aluminum sets off a series of reactions that include hydrolysis of silicic acid, condensation and eventual polymerization of amorphous silica. These reactions negate the original aim of inhibiting silicate scales. Currently, most chemical inhibitors are harmful and not environmental friendly. Therefore, environmental friendly scale inhibitors extracted from plants are beginning to get attention as possible alternative. This paper presents experimental findings on tropical herbs such as premna cordifolia, camellia sinensis, and piper betle and abelmoschus esculentus for preventing silicate scales. Effects of polyphenolic compounds were examined in mitigating the polymerization and condensation of the silicic acid. The performance of selected herbs was evaluated at different concentrations and a range of pH before comparing them against the conventional green inhibitor, polyaspartate (PASP). Experimentally, 100 ml samples of brines representing formation water were added with 100 ppm, 500 ppm and 1000 ppm polyphenolic compounds from the four herbs respectively. Observation was made for 24 hours at 90oC during the compatibility test and at interval of 1,2,3,4,5 and finally 24 hours for turbidity test at pH 1-5. The loss of transparency due to the presence of suspended particulate, colloidal material, or both represents the degree of turbidity. Results showed that green inhibitors at concentrations of 100 ppm, 500 ppm and 1000 ppm did not cause precipitation. Turbidity of all samples decreased when concentration of polyphenolic compounds increased. Camellia sinensis, due to its high content of polyphenolic compounds caused the least turbidite compared to the other green inhibitors. This finding justifies other published works where polyphenolic compounds had acted as a chelating agent in the form of silicon-polymerizing complexes to condense and polymerize silicic acid in brines to prevent formation of silicate scaling. Nevertheless, turbidity of all brines added with green inhibitors showed higher turbidity values than that of brines added with PASP. It might be attributed to the high concentration of chlorophyll since the extracts were used in their pure forms without other treatments