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51.
52.
Mathematics and art converge in the fractal forms that also abound in nature. We used molecular self-assembly to create a synthetic, nanometer-scale, Sierpinski hexagonal gasket. This nondendritic, perfectly self-similar fractal macromolecule is composed of bis-terpyridine building blocks that are bound together by coordination to 36 Ru and 6 Fe ions to form a nearly planar array of increasingly larger hexagons around a hollow center.  相似文献   
53.
In India, systematic genotype replacement has been observed for serotype A foot-and-mouth disease virus. After a decade of co-circulation of genotypes VI and VII, genotype VII emerged as the single dominant genotype since 2001. To derive possible explanations for such epochal evolution dynamics, in vitro intergenotype growth competition experiments involving both co- and superinfection regimes were conducted. Coinfection of BHK-21 cells demonstrated abrupt loss in the genotype VI viral load with commensurate increase in the load of genotype VII as measured by the genotype differentiating ELISA, RT-PCR and real-time RT-PCR. The superinfection dynamics was shaped by temporal spacing of infection, where the invading genotype VII took more number of passages than coinfection to eventually overtake the resident genotype VI. It was speculated that such superior replicative fitness of genotype VII could have been a possible factor for the ultimate dominance of genotype VII in nature.  相似文献   
54.
Attempts were made to estimate the area under the disease progress curve (AUDPC) of rice blast disease caused by Pyricularia grisea from two data points on the disease progress curve. Forty-two rice genotypes were exposed to high disease pressure in a nursery over nine seasons. A conducive condition was created for maximum disease development through high nitrogen application, close spacing and maintenance of high relative humidity. Disease severity was recorded on alternate days beginning from disease initiation until the end of the epidemic. The estimation of AUDPC, and logistic and Gompertz apparent infection rates using either all-points (AP) or two-point (TP) methods revealed significant correlations among them. This was also confirmed through regression analysis and factor analysis. Hence, the estimation of AUDPC from two data points i.e. initial and final disease scores of the disease progress curves is recommended as providing information similar to that from all the data points; this should save valuable time, labour and economic resources.  相似文献   
55.
Labeo rohita (139.92 ± 0.76 mm/24.33 ± 0.45 g) was reared for 92 days in floating square cages (10 m2 area, 1.5 m height) in a pond (2 ha) at six stocking densities (5, 7.5, 10, 15, 20 and 25 fish m?2) each with 3 replicates. Fish were fed daily once in the morning with rice polish and groundnut oil cake (1:1) in dough form at 3 % of the total body weight. Survival ranged from 96 to 100 % in different stocking densities. Final average body weight, average body weight gain, mean daily body weight gain and SGR decreased (P < 0.05) with increasing stocking density. Conversely, final biomass, biomass gain and FCR increased (P < 0.05) with increasing stocking density. The highest growth rate of fish could be achieved up to 60 days at 5 fish m?2 and 92 days at other densities. The reduced growth rate at 10–25 fish m?2 for 60 days of culture indicated that stress is related to size and density of the fish, suggesting that utmost care is required to reduce the stress at high densities. Maximum production and profit was observed at the highest stocking density. Non-lethal levels of water and soil qualities at different sites (cage premises, and 20 and 200 m away from cage area) suggested that cage aquaculture could be done safely covering 0.9 % of pond area. Production of advanced fingerlings in cages was found a viable alternative to their culture in pond.  相似文献   
56.
Aquaculture is emerging as one of the most viable and promising enterprises for keeping pace with the surging need for animal protein, providing nutritional and food security to humans, particularly those residing in regions where livestock is relatively scarce. With every step toward intensification of aquaculture practices, there is an increase in the stress level in the animal as well as the environment. Hence, disease outbreak is being increasingly recognized as one of the most important constraints to aquaculture production in many countries, including India. Conventionally, the disease control in aquaculture has relied on the use of chemical compounds and antibiotics. The development of non-antibiotic and environmentally friendly agents is one of the key factors for health management in aquaculture. Consequently, with the emerging need for environmentally friendly aquaculture, the use of alternatives to antibiotic growth promoters in fish nutrition is now widely accepted. In recent years, probiotics have taken center stage and are being used as an unconventional approach that has numerous beneficial effects in fish and shellfish culture: improved activity of gastrointestinal microbiota and enhanced immune status, disease resistance, survival, feed utilization and growth performance. As natural products, probiotics have much potential to increase the efficiency and sustainability of aquaculture production. Therefore, comprehensive research to fully characterize the intestinal microbiota of prominent fish species, mechanisms of action of probiotics and their effects on the intestinal ecosystem, immunity, fish health and performance is reasonable. This review highlights the classifications and applications of probiotics in aquaculture. The review also summarizes the advancement and research highlights of the probiotic status and mode of action, which are of great significance from an ecofriendly, sustainable, intensive aquaculture point of view.  相似文献   
57.
Taxus wallichiana is one of the most important medicinal tree species of the Himalayan region. Leaf and bark of the species yield an important drug called taxol, which is used for treatment of many types of cancer. There is a serious threat to the existence of the species due to over exploitation in its native habitat. Adequate information on the nature and the extent of genetic diversity in this important species is required for developing suitable strategy for its conservation. Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) were used to assess genetic variation in nine natural populations of T. wallichiana from western part of the Himalayan ranges. Both the markers revealed low genetic diversity in these populations. Average heterozygosity for AFLP and RAPD were 0.3715 and 0.3072, respectively. ΦST values derived from molecular variance were 0.0855 and 0.1005 for AFLP and RAPD, respectively, whereas the corresponding GST values were 0.1796 and 0.2140. Most part of the genetic variation was present within the populations. However, between population variation was low but statistically significant, which suggested that the sampled populations might not constitute a single panmictic population. Cluster analysis and Mantel’s correlation revealed that genetic differentiation broadly followed geographic distribution of the populations. T. wallichiana thus urgently needs to be conserved using both in situ and ex situ conservation approaches.  相似文献   
58.
Suspensions of soil repeatedly treated with carbofuran under glasshouse conditions enhanced the degradation of carbofuran significantly in a mineral salts medium. Ninety-seven per cent of the applied carbofuran degraded in a medium inoculated with soil suspensions treated with carbofuran, compared to 15% in uninoculated medium in 10 days. Out of the seven bacterial cultures isolated from the enrichment culture, two cultures identified as Pseudomonas stutzeri and Bacillus pumilis enhanced carbofuran degradation, resulting in more than 98% loss of the applied carbofuran in 30 days. The other cultures enhanced the degradation up to 70% within the same period. The mixture of all the seven cultures, however interacted synergistically, enhancing the degradation of carbofuran residues to 96% in 10 days. © 1997 SCI.  相似文献   
59.
Bacillus circulans PB7, isolated from the intestine of Catla catla, was evaluated for use as a probiotic supplement in the feeds for the fingerlings of Catla catla. The effect of supplement on the growth performance, feed utilization efficiency, and immune response was evaluated. Catla fingerlings (ave. wt. 6.48 ± 0.43 g) were fed diets supplemented with 2 × 104 (feed C1), 2 × 105 (feed C2), and 2 × 106 (feed C3) B. circulans PB 7 cells per 100 g feed for 60 days at 5% of the body weight per day in two equal instalments in triplicate treatments. The control feed (CC) was not supplemented with the B. circulans. All the feeds were isocaloric and isonitrogenous. Fish fed with feed C2 displayed better growth, significantly (P ≤ 0.05) highest RNA/DNA ratio, a lower feed conversion ratio (FCR), and a higher protein efficiency ratio (PER) than the other experimental diets. Highest carcass protein and lipid was also observed in the fish fed C2 feed compared to the others. Significantly (P ≤ 0.05), highest protease was recorded in fish fed feed C2 (47.9 ± 0.016) and lowest in fish fed feed C3 (32.10 ± 0.009), where α-amylase activity did not differ significantly (P ≤ 0.05) beyond the lowest inclusion level. ALP, ACP, GOT, and GPT in the liver of Catla catla were the highest (P ≤ 0.05) in fish fed C2 feed. The highest TSP, albumin, and globulin was observed in fish treated with C2 feed after 60 days feeding trial, but the lowest glucose level was observed in the same treatment. After the feeding trial, the non-specific immunity levels and disease resistance of fish were also studied. Phagocytic ratio, phagocytic index, and leucocrit value were the highest in fish fed feed C2. After the feeding trial, the fish were challenged for 10 days by bath exposure to Aeromonas hydrophila (AH1) (105c.f.u. ml−1 for 1 h, and, after 7 days, 107c.f.u. ml−1 for 1 h). Highest survival percentage was observed in fish fed with feed C2 compared with only 6.66% in the controls, which indicated the effectiveness of B. circulans PB 7 in reducing disease caused by A. hydrophila.  相似文献   
60.
Summary Ovary culture has been employed for the production of interspecific hybrids of a partially compatible cross of Brassica juncea (2n=36) × Brassica campestris (2n=20). Five to seven days old ovaries cultured on White's medium supplemented with casein hydrolysate (300 mg/l) and sucrose (5%) produced more seeds than any other media tried, but seed development was better on media fortified with plant hormones. The seed yield was better in B. juncea × B. campestris than their reciprocal cross. The plants obtained from ovary-derived seeds were transferred to the field; they were intermediate in some morphological characters and chromosome number (2n=28) as compared to their parents. The flower buds generally did not open and had poorly developed anthers with mostly sterile pollen. The pod size/setting was very much reduced, but healthy seeds were obtained.  相似文献   
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