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Yap Siaw-Yang 《Fisheries Research》1984,2(4):299-314
An earlier cohort analysis using catch-at-length data (for the period May 1979–April 1980) on the stock of Osteochilus hasselti C. & V. computes statistics on: (1) the total stock at the start of the cohort (N = 22.7 × 105) (these stock numbers decrease progressively at successive lengths, in a steady state and assuming constant natural mortality rate, M = 2.1); (2) catch numbers in a cohort totalling 780 940 individuals; (3) the exploitation rate of the cohort of E = 0.34, suggesting moderate exploitation of the species at Bukit Merah Reservoir, Malaysia.However, the validity of cohort analysis on a species exploited at a very early age depends on the input value of the variables natural mortality rate (M), fishing mortality rate of terminal largest fish (Fter), and growth parameters (L∞, K). Because of the methodological difficulties in estimation and verification of M, Fter and K values of O. hasselti, a range of values of input variables is adopted for comparison. The effect of the variability of M values (0.5, 1.0, 1.5 and 2.5) on the computation results of smaller size-class fishes NL is significantly different from that based on M = 2.1, showing a much lower population size.The variability of input values of Fter (range 0.5–2.5) and K (0.28–2.62) is tested on their effects on the population size of recruits. The combined effect of M and K in the relationship of ranging from 0.8 to 2.5 is varied to decide the possible values of K. In general, the different input values of M, Fter and K result in lower estimates of the population size of recruits, Nr This is about 28% lower than Nr = 22.7 × 105 when M = Fter = 2.1 and K = 1.15. With an inherent computational bias, the population size of Nr = 22.7 × 105 is probably an under-estimate, but it is both reasonable and biologically possible for O. hasselti at Bukit Merah Reservoir, Malaysia, since the input variables are generated from representative length composition data of commercial catches and tagging data. 相似文献
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Multiplex PCR genotyping for five bacterial blight resistance genes applied to marker‐assisted selection in rice (Oryza sativa) 
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下载免费PDF全文 Bacterial blight (BB) is the most economically damaging disease of rice in Asia and other parts of the world. In this study, a multiplex PCR genotyping method was developed to simultaneously identify genotypes of five BB resistance genes, Xa4, xa5, Xa7, xa13 and Xa21. The resistance R alleles were amplified using five functional markers (FMs) to generate amplicons of 217, 103, 179, 381 and 595 bp in IRBB66. Amplicons of 198, 107, 87, 391 and 467 bp corresponded to susceptible alleles in Taiwanese japonica rice cultivars. In backcross breeding programmes, the multiplex PCR assay was integrated into selection from a population using BB resistance donor IRBB66 crossed to rice cultivar ‘Tainung82’. Two plants with homozygosity for Xa4, xa5, Xa7, xa13 and Xa21 were selected from 1100 BC2F2 plants. In addition, the five BB resistance genes were also accurately identified in F2 populations. This multiplex PCR method provides a rapid and efficient method for detecting various BB resistance genes, which will assist in pyramiding genes to improve durability of BB resistance in Taiwanese elite rice cultivars. 相似文献
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We developed new assessment methods for Acropora coral recruitment using coral settlement devices (CSDs) and holes of a marine block. Both devices were deployed in situ before mass spawning of Acropora corals. The CSDs were sampled after 3–4 months of spawning to measure early recruitment, whereas holes of the marine block were observed underwater or MB was sampled to observe holes after 1 year of spawning to measure the recruitment. By combining the results, we would know the recruitment (visually identified underwater) in reefs, including the amount of early recruitment (identified by stereomicroscopic methods), and the environmental condition of the coral reef. These results would help to predict the future of a reef. Nagura Bay had a high early Acropora recruitment; however, due to competition with algae and sedimentation, the recruitment of juvenile corals was extremely low. The reef would possibly be healthy and sustainable at sites where both the early recruitment and recruitment are high. However, if both are low, the reef will be in a critical condition where urgent restoration will be required. 相似文献
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The standard method for culturing human embryonic stem cells (hESC) uses supporting feeder layers of cells or an undefined substrate, Matrigel(?), which is a basement membrane extracted from murine sarcoma. For stem cell therapeutic applications, a superior alternative would be a defined, artificial surface that is based on immobilized human plasma vitronectin (VN), which is an adhesion-mediating protein. Therefore, VN adsorbed to diverse polymer surfaces was explored for the continuous propagation of hESC. Cells propagated on VN-coated tissue culture polystyrene (TCPS) are karyotypically normal after >10 passages of continuous culture, and are able to differentiate into embryoid bodies containing all three germ layers. Expansion rates and pluripotent marker expression verified that a minimal VN surface density threshold is required on TCPS. Further exploration of adsorbed VN was conducted on polymer substrates with different properties, ranging from hydrophilic to hydrophobic and including cationic and anionic polyelectrolyte coatings. Despite differing surface properties, these substrates adsorbed VN above the required surface density threshold and were capable of supporting hESC expansion for >10 passages. Correlating wettability of the VN-coated surfaces with the response of cultured hESC, higher cell expansion rates and OCT-4 expression levels were found for VN-coated TCPS, which exhibits a water contact angle close to 65°. Importantly, this simple, defined surface matches the performance of the benchmark Matrigel, which is a hydrogel with highly complex composition. 相似文献
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Disha Varijakzhan Jiun-Yan Loh Wai-Sum Yap Khatijah Yusoff Rabiha Seboussi Swee-Hua Erin Lim Kok-Song Lai Chou-Min Chong 《Marine drugs》2021,19(5)
Marine sponges are sessile invertebrates that can be found in temperate, polar and tropical regions. They are known to be major contributors of bioactive compounds, which are discovered in and extracted from the marine environment. The compounds extracted from these sponges are known to exhibit various bioactivities, such as antimicrobial, antitumor and general cytotoxicity. For example, various compounds isolated from Theonella swinhoei have showcased various bioactivities, such as those that are antibacterial, antiviral and antifungal. In this review, we discuss bioactive compounds that have been identified from marine sponges that showcase the ability to act as antibacterial, antiviral, anti-malarial and antifungal agents against human pathogens and fish pathogens in the aquaculture industry. Moreover, the application of such compounds as antimicrobial agents in other veterinary commodities, such as poultry, cattle farming and domesticated cats, is discussed, along with a brief discussion regarding the mode of action of these compounds on the targeted sites in various pathogens. The bioactivity of the compounds discussed in this review is focused mainly on compounds that have been identified between 2000 and 2020 and includes the novel compounds discovered from 2018 to 2021. 相似文献
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Das Sourav Baumgartner John B. Esperon-Rodriguez Manuel Wilson Peter D. Yap Jia-Yee S. Rossetto Maurizio Beaumont Linda J. 《Landscape Ecology》2019,34(12):2883-2896
Landscape Ecology - Climate refugia—areas that remain suitable for species during periods of climate disruption—have played an important role in species persistence over time.... 相似文献
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Chad Shouquan Cheng Monica Campbell Qian Li Guilong Li Heather Auld Nancy Day David Pengelly Sarah Gingrich David Yap 《Water, air, and soil pollution》2007,182(1-4):117-130
Using within-weather-group air pollution prediction models developed in Part I of this research, this study estimates future air pollution levels for a variety of pollutants (specifically, carbon monoxide – CO, nitrogen dioxide – NO2, ozone – O3, sulphur dioxide – SO2, and suspended particles – SP) under future climate scenarios for four cities in south-central Canada. A statistical downscaling method was used to downscale five general circulation model (GCM) scenarios to selected weather stations. Downscaled GCM scenarios were used to compare respective characteristics of the weather groups developed in Part I; discriminant function analysis was used to allocate future days from two windows of time (2040–2059 and 2070–2089) into one of four weather groups. In Part I, the four weather groups were characterised as hot, cold, air pollution-related, and other (defined as relatively good air quality and comfortable weather conditions). In estimating future daily air pollution concentrations, three future pollutant emission scenarios were considered: Scenario I – emissions decreasing 20% by 2050, Scenario II – future emissions remaining at the same level as at the end of the twentieth century, and Scenario III – emissions increasing 20% by 2050. The results showed that, due to increased temperatures, the average annual number of days with high O3 levels in the four selected cities could increase by more than 40–100% by the 2050s and 70–200% by the 2080s (from the current areal average of 8 days) under the three pollutant emission scenarios. The corresponding number of low O3 days could decrease by 4–10% and 5–15% (from the current areal average of 312 days). For the rest of the pollutants, future air pollution levels will depend on future pollutant emission levels. Under emission Scenarios II and III, the average annual number of high pollution days could increase 20–40% and 80–180%, respectively, by the middle and late part of this century. In contrast, under Scenario I, the average annual number of high pollution days could decrease by 10–65%. 相似文献
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It is well documented that marine oysters are net bioaccumulators of trace metals and they can be employed as biomonitors of time-integrated measurements of bioavailable metal fractions over their lifetime. In this study, the Malaysian mangrove flat tree oyster Isognomon alatus collected from the estuaries of Lukut River (five sites), Sepang Besar River (one site), and one metal-polluted site at Kg. Pasir Puteh were dissected into muscle, mantle plus gills, byssus, and remaining soft tissues. All the four different soft tissues were analyzed for Fe, Cu, and Ni. Significant spatial differences in the accumulated metal concentrations of the oysters were found between sampling sites, and these could be attributed to anthropogenic inputs including discharges of shrimp ponds (Lukut), animal husbandry (Sepang Besar), sewage, shipping, and industrial effluents (Kg. Pasir Puteh). For Fe, the tissue distribution followed: byssus > mantle plus gill >muscle > remaining soft tissues, while for Cu and Ni, both followed byssus > remaining soft tissues > mantle plus gill > muscle. This indicated that byssus could act as an excretion route for the metals. Based on a correlation analysis between oyster tissues and sediments, selected tissues of I. alatus were shown to be good biomonitors of Ni and Cu contamination, while high regulative capacity of Fe in the oyster tissues could hardly reflect the actual Fe levels in the surroundings. However, the clustering patterns based on metal levels in the four different soft tissues were not in agreement with those based on the geochemical fractions of sediment data. This phenomenon which was due to the metal contamination might not necessarily create high bioavailabilities of metals to the biomonitor I. alatus, which might involve differences in uptake, excretion, and sequestration of metals. Similarly to the Mussel Watch approach, this study points to the very potential use of the different soft tissues of I. alatus as biomonitors for regular biomonitoring in the mangrove area of Peninsular Malaysia. 相似文献