Molecular and genetic study of wheat rusts

Puccinia triticina, Puccinia graminis and Puccinia striiformis cause leaf, stem and yellow rust, respectively. Wheat rusts can cause losses as high as 70%. The rusts ability to evolve fungicide resistance has resulted in the use of resistant cultivars as the primary method of control. Breeding resistant cultivars is a long process and requires an accurate picture of the current and future pathogen population. Differentiation of wheat rust pathotypes using conventional plant pathology techniques is time consuming, labour intensive and requires the services of a highly skilled and experienced plant pathologist. Modern molecular biology techniques have the potential to aid the conventional techniques and provide fast, accurate same-day results. Microsatellite markers were used to differentiate P. triticina and P. striiformis pathotypes. Amplified fragment length polymorphisms (AFLP) were used to differentiate stem rust P. graminis pathotypes. Phylogenetic trees were created for leaf and stem rust pathotypes. Field isolates of leaf, stem and yellow rust were collected from eleven sites across the Western Cape Province. Microsatellite markers were used to type leaf and yellow rust isolates. AFLP markers could not be used on field isolates due to the presence of plant DNA. Novel alleles found in the Leaf and yellow rusts isolates prevented the assigning of a specific pathotype to each isolate. UVPrt10 (25.2%) and UVPrt9 (21.5%) were the most prevalent leaf rust pathotypes. Only 6E16A+ was identified in the yellow rust isolates. Pathotype incidence was similar to previous studies. The prevalence of multiple pathotypes with a variety of virulence genes in the rust population shows that breeding lines with single major resistance genes will not be effective and breeding programmes should concentrate on lines that exhibit quantitative resistance.Keywords: Prevalence, microsatellite, amplified fragment length polymorphisms (AFLP), phylogeny, PucciniaAfrican Journal of Biotechnology Vol. 12(42), pp. 6068-607

An assessment of the recreational fishery in the St Lucia estuarine system, KwaZulu-Natal, South Africa

St Lucia is one of the largest estuarine systems in Africa, and attracts thousands of anglers each year. Catch card data from the National Marine Linefish System for the years 1986–1999 were analysed to determine catch composition, catch per unit effort (cpue) and seasonality of catches by recreational anglers. Because not all anglers completed catch cards, estimates of total catch were made using additional data on the number of private boat outings, the number of boat trailers at boat slipways and the number of boats recorded entering the campsite gates during 1992 and 1993. In all, 27 fish families, constituting 55 species, were recorded by recreational anglers. Dusky kob Argyrosomus japonicus, spotted grunter Pomadasys commersonnii, perch Acanthopagrus berda, Natal stumpnose Rhabdosargus sarba, springer Elops machnata and mini-kob Johnius dorsalis were the most prominent species caught in terms of numbers and mass. Catch rates expressed numerically (fish angler-1 h-1) peaked during the summer and early winter. However, in terms of mass, catch rates peaked during late winter and spring, when there were increased landings of large dusky kob. Fluctuations in cpue were linked to salinity and estuary mouth conditions (i.e. mouth closure). Despite annual fluctuations in cpue, regression analysis revealed an overall downward trend for the dominant species (dusky kob and spotted grunter) and a gradual increase for stumpnose, perch and springer, but with the exception of stumpnose, these trends were not significant. Socio-economic aspects of the fishery were also investigated by conducting an independent boat-angler survey. The value of the recreational fishery, in terms of accommodation and direct angler expenditure, was estimated to be in the region of R9 million during 1992. Angler attitudes towards fishing regulations were positive and anglers generally had a good knowledge of the regulations for target species. Based on this assessment, a number of suggestions are made regarding the future management of the recreational fishery at St Lucia.Keywords: catch and effort, management, recreational angling, socio-economics, St Lucia estuarine systemAfrican Journal of Marine Science 2002, 24: 263–27

ROI detection in SPR measurements and molecule binding parameter estimation

Since 1983 when Surface Plasmon Resonance (SPR) was first proposed, it has become a widelyusedmethodology for various biosensing applications. In a SPR biosensing system in arrayformat, locating the region of interest (ROI) and estimating themolecule binding parametersfrom the SPR measurements are of great importance. In this thesis, we addressed these twochallenges by detecting the ROIs automatically and estimating the parameters optimally throughthe minimization of the mean square error (MSE).We first pre-processed the SPR video frame images to help enhance the ROI detectionperformance, and then applied the randomized Hough transformto automatically detect theROIs. With hundreds or even thousands of ROIs on a single SPR video frame image, our procedureto automatically detect the ROIs greatly reduced the labor to assign the ROIs.We then extracted the image gray level intensity data fromthe ROIs as a function of time,which were used to estimate the molecule binding parameters, ka (the rate of association) andkd (the rate of dissociation). These binding parameters are vital in biosensing applications. Inthis research we use a Particle SwarmOptimization (PSO) algorithm to estimate the parametersand compared the performance to the commercially used Levenberg-Marquardt (LM) algorithm,a gradient based algorithm. Our PSO algorithm performed better than LM achieving a muchlower MSE for all the active ROIs

Sculpture as systematic growth

The foundation of my work is built upon the idea that everything is comprised of constituent components in which all of the components serve a function in the creation of the integrated whole. This way of thinking is consistent with the principles of systems, however large or small, complex or simple. Every system has parameters that define and frame the behavior of its set of interacting and interdependent components. What I am interested in is not necessarily the final output of the system, but rather, the process in which the components interact within the parameters of the system and how the relationships of these interactions affect the outcome

RATIONALE, MOTIVATION AND EFFECT OF FOREIGN INVESTMENT IN VIETNAMESE COMPANIES

Existing literatures have documented that foreign investors in developed markets hold disproportionately more shares of firms with high turnover rates. In Vietnam, I find evidence that foreign investor ownership percentage is higher in firms with lower turnover rates, firms located in the south of Vietnam, firms listed on the Hochiminh stock exchange, firms that are listed longer on the exchange, large firms, and firms with low past returns. The effect of turnover rate on foreign ownership percentage is weak, while the coefficients of firm size and firm age since IPO are consistently robust. I find that foreign investors hold more in firms with lower government ownership, and firms audited by a prestigious international audit company only holds for firms listed on the Hanoi exchange. I find that the thesis that foreign investor percentage ownership stakes are higher in firms with higher current ratios holds only for the firms listed on the Hochiminh stock exchange. Although average firm size is higher for State-Owned Enterprises (SOEs) and foreign investors strongly prefer investing in large size firms, they strongly show their preference in firms other than SOEs. By excluding the effect of size, I find that foreign ownership percentage stakes in firms listed on the Hanoi exchange are lower than foreign ownership percentage stakes in firms listed on the Hochiminh exchange. Interestingly, since dividend began being taxed, foreigner ownership percentage has been lower in firms with high dividend yields

Midday measurements of leaf water potential and stomatal conductance are highly correlated with daily water use of Thompson Seedless grapevines

A study was conducted to determine the relationship between midday measurements of vine water status and daily water use of grapevines measured with a weighing lysimeter. Water applications to the vines were terminated on August 24th for 9 days and again on September 14th for 22 days. Daily water use of the vines in the lysimeter (ETLYS) was approximately 40 L vine−1 (5.3 mm) prior to turning the pump off, and it decreased to 22.3 L vine−1 by September 2nd. Pre-dawn leaf water potential (ΨPD) and midday Ψl on August 24th were −0.075 and −0.76 MPa, respectively, with midday Ψl decreasing to −1.28 MPa on September 2nd. Leaf g s decreased from ~500 to ~200 mmol m−2 s−1 during the two dry-down periods. Midday measurements of g s and Ψl were significantly correlated with one another (r = 0.96) and both with ETLYS/ETo (r = ~0.9). The decreases in Ψl, g s, and ETLYS/ETo in this study were also a linear function of the decrease in volumetric soil water content. The results indicate that even modest water stress can greatly reduce grapevine water use and that short-term measures of vine water status taken at midday are a reflection of daily grapevine water us

Forward osmosis–membrane distillation hybrid system for desalination using mixed trivalent draw solution

© 2020 Elsevier B.V. Finding suitable draw solutions is still a major problem when developing FO technologies. This study represents the first time a mixed trivalent draw solution containing of EDTA–2Na and Na3PO4 was systemically studied for FO performance. The objective here was to achieve simultaneously low reverse salt flux and high water flux. The FO results showed that the mixed trivalent draw solution-based 0.3 M EDTA–2Na and 0.55 M Na3PO4 underwent higher water flux (Jw = 9.17 L/m2⋅h) than that of pure 0.85 M EDTA-2Na (Jw = 7.02 L/m2⋅h) due to its lower viscosity. Additionally, the specific reverse salt flux caused by mixing 0.3 M EDTA–2Na with 0.55 M Na3PO4 draw solution was only 0.053 g/L using DI water as the feed solution. Donnan equilibrium force and formed complexation of [EDTANa]3-, [HPO4Na]- with the FO membrane are believed to constitute the main mechanism for minimizing salt leakage from the mixed draw solution. Moreover, the FO desalination process utilizing the mixed trivalent draw solution achieved water fluxes of 6.12 L/m2⋅h with brackish water (TDS = 5000 mg/L) and 3.10 L/m2⋅h with seawater (TDS = 35,000 mg/L) as the feed solution. Lastly, diluted mixed trivalent draw solution following the FO process was effectively separated using the MD process with salt rejection >99.99% at a mild feed temperature of 55 °C

Applicability of an integrated moving sponge biocarrier-osmotic membrane bioreactor MD system for saline wastewater treatment using highly salt-tolerant microorganisms

© 2017 Elsevier B.V. Osmotic membrane bioreactors (OsMBRs) are a recent breakthrough technology designed to treat wastewater. Nevertheless, their application in high-salinity wastewater treatment is not widespread because of the effects of saline conditions on microbial community activity. In response, this study developed an integrated sponge biocarrier-OsMBR system using highly salt-tolerant microorganisms for treating saline wastewater. Results showed that the sponge biocarrier-OsMBR obtained an average water flux of 2 L/m2 h during a 92-day operation when 1 M MgCl2 was used as the draw solution. The efficiency in removing dissolved organic compounds from the proposed system was more than 99%, and nutrient rejection was close to 100%, indicating excellent performance in simultaneous nitrification and denitrification processes in the biofilm layer on the carriers. Moreover, salt-tolerant microorganisms in the sponge biocarrier-OsMBR system worked efficiently in salt concentrations of 2.4%. A polytetrafluoroethylene MD membrane (pores = 0.45 μm) served to regenerate the diluted draw solution in the closed-loop system and produce high-quality water. The moving sponge biocarrier-OsMBR/MD hybrid system demonstrated its potential to treat salinity wastewater treatment, with 100% nutrient removal and 99.9% conductivity rejection

Perovskite/Colloidal Quantum Dot Tandem Solar Cells: Theoretical Modeling and Monolithic Structure

Metal-halide perovskite-based tandem solar cells show great promise for overcoming the Shockley-Queisser single-junction efficiency limit via low-cost tandem structures, but so far they employ conventional bottom-cell materials that require stringent processing conditions. Meanwhile, difficulty in achieving low-bandgap (11% absolute gain) to the ultimate efficiency via photon recycling. We report initial experimental demonstration of a solution-processed monolithic perovskite/CQD tandem solar cell, showing evidence for subcell voltage addition. We model that a power-conversion efficiency of 29.7% is possible by combining the state-of-the-art perovskite and CQD solar cells