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81.
Muhammad Omer Aijaz Sajjad Haider Fahad S. Al-Mubaddel Rawaiz Khan Adnan Haider Abdulaziz Abdullah Alghyamah Waheed A. Almasry Mohammad Sherjeel Javed Khan Muhammad Javid Wajahat Ur Rehman 《Fibers and Polymers》2017,18(4):611-618
The present study is focused on studying the swelling kinetics, thermal and aqueous stabilities, and determination of various forms of water in the chitosan (CS) and polyacrylonitrile (PAN) blend and semi-interpenetrating polymer network (sIPN). CS/PAN blend hydrogel films were prepared by solution casting technique. The blend film with optimum swelling properties was selected for the synthesis of sIPN. CS in the blend was crosslinked with the vapors of Glutaraldehyde (GTA) to prepare sIPN. The fabricated CS/PAN blend and sIPN hydrogels films were characterized with Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and field emission scanning electron microscope (FESEM). The kinetics of swelling, bound and unbound waters and aqueous stability were determined experimentally. FESEM showed good miscibility between CS and PAN, FTIR showed no chemical interaction between CS and PAN; however, it did show a doublet for the sIPN, TGA showed improved thermal stability and swelling kinetic followed second order kinetics. The degree of swelling of the sIPN hydrogels samples at room temperature varied from ~2200 % (with a fair degree of stability (~30 %)) to ~1000 % (with high degree of aqueous stability (43 %)) with increase in the crosslinking time. The calculated unbound water (WUB) max., for the blend was 52.3 % whereas for the bound (WB) the max., was 41.9 %. However, for sIPN hydrogel films, the WUB water decreased (max. 21.0 %) where as the WB increased (max. 52.0 %). The decrease in WUB and increase in the WB is attributed to the formation of a compact structure and increase in the contact area between the water and polymers in sIPN hydrogels due to the induction of new water contacting point in these hydrogel films, respectively. 相似文献
82.
Effects of dietary protein and lipid levels on growth performance,fatty acid composition and antioxidant‐related gene expressions in juvenile loach Misgurnus anguillicaudatus 下载免费PDF全文
Jie Yan Yang Li Xiao Liang Yin Zhang Mahmoud A.O. Dawood Daniel Matuli'c Jian Gao 《Aquaculture Research》2017,48(10):5385-5393
Dojo loach (Misgurnus anguillicaudatus) is one of the most important cultured freshwater fish in several East Asian countries. However, a little information is available in its nutritional requirements. Thus, this study was conducted to evaluate the effects of feeding varying levels of dietary protein and lipid on growth, fatty acid composition and antioxidant‐related gene expressions in juvenile loach. Six practical diets at three levels of protein (30%, 40% and 50%) and two levels of lipid (6% and 12%) were fed to loach juveniles (initial weight 0.40 g) in triplicated groups (20 fish per replicated) for a period of 8 weeks. Results showed that regardless of lipid level, body weight gain of fish was significantly increased with incremental dietary protein level. Meanwhile, feed conversion ratio was significantly decreased by dietary protein levels, and the lowest value was observed in fish fed dietary protein levels of 50%, regardless of dietary lipid level. Moreover, the percentage of 22:6n‐3 in viscera was significantly increased by different protein levels. The expression level of catalase was significantly increased with incremental dietary protein level with both lipid levels. Meanwhile, the expression level of hepatic nuclear factor erythroid 2‐related factor 2 (Nrf2) was downregulated with incremental dietary protein level with 6% of lipid level, but the expression was upregulated with incremental dietary protein level with 12% of lipid level. In conclusion, these data suggested that 6% lipid and 50% protein in diet was optimal for loach during early development stage. 相似文献
83.
Dorothee Ehrich Maite Cerezo Anna Y. Rodnikova Natalya A. Sokolova Eva Fuglei Victor G. Shtro Aleksandr A. Sokolov 《BMC ecology》2017,17(1):32
Background
High latitude ecosystems are at present changing rapidly under the influence of climate warming, and specialized Arctic species at the southern margin of the Arctic may be particularly affected. The Arctic fox (Vulpes lagopus), a small mammalian predator endemic to northern tundra areas, is able to exploit different resources in the context of varying tundra ecosystems. Although generally widespread, it is critically endangered in subarctic Fennoscandia, where a fading out of the characteristic lemming cycles and competition with abundant red foxes have been identified as main threats. We studied an Arctic fox population at the Erkuta Tundra Monitoring site in low Arctic Yamal (Russia) during 10 years in order to determine which resources support the breeding activity in this population. In the study area, lemmings have been rare during the last 15 years and red foxes are nearly absent, creating an interesting contrast to the situation in Fennoscandia.Results
Arctic fox was breeding in nine of the 10 years of the study. The number of active dens was on average 2.6 (range 0–6) per 100 km2 and increased with small rodent abundance. It was also higher after winters with many reindeer carcasses, which occurred when mortality was unusually high due to icy pastures following rain-on-snow events. Average litter size was 5.2 (SD = 2.1). Scat dissection suggested that small rodents (mostly Microtus spp.) were the most important prey category. Prey remains observed at dens show that birds, notably waterfowl, were also an important resource in summer.Conclusions
The Arctic fox in southern Yamal, which is part of a species-rich low Arctic food web, seems at present able to cope with a state shift of the small rodent community from high amplitude cyclicity with lemming dominated peaks, to a vole community with low amplitude fluctuations. The estimated breeding parameters characterized the population as intermediate between the lemming fox and the coastal fox ecotype. Only continued ecosystem-based monitoring will reveal their fate in a changing tundra ecosystem.84.
Calibration and validation of optical chlorophyll‐measuring devices for use in predicting crude protein concentration in tropical grass herbage 下载免费PDF全文
M. P. Hughes C. H. O. Lallo V. Mlambo P. G. A. Jennings 《Grass and Forage Science》2017,72(1):118-136
The objective of this experiment was to evaluate the Fieldscout CM 1000 NDVI and Yara N‐Tester as easy‐to‐use and cost‐effective tools for predicting foliar chlorophylls (a, b and total) and crude protein (CP) concentrations in herbage from three tropical grass species. Optical chlorophyll measurements were taken at three stages (4, 8 and 12 weeks) of regrowth maturity in Guinea grass (Panicum maximum) and Mulato II (Brachiaria hybrid) and at 6 and 12 weeks maturity in Paspalum spp (Paspalum atratum). Grass samples were harvested subsequent to optical measurements for laboratory analysis to determine CP and solvent‐extractable chlorophylls (a, b and total) concentrations. Optical chlorophyll measurements and CP concentrations were highly correlated (Yara N‐Tester: r2 = 0·77–0·89; Fieldscout CM 1000 NDVI: r2 = 0·52–0·84). Crude protein prediction models from the Yara N‐Tester and Fieldscout CM 1000 NDVI accounted for 70–89% and 44–73% CP variability, respectively, in Mulato II and Guinea grass. The Yara N‐tester produced more accurate and reliable CP estimates based on very high concordance correlation coefficient [CCC (0·73–0·91)] and low rMSPE, mean and regression bias. It is concluded that the Yara N‐Tester produces more accurate and reliable CP estimates of tropical pastures. 相似文献
85.
Resource Use Assessment of Shrimp,Litopenaeus vannamei and Penaeus monodon,Production in Thailand and Vietnam 下载免费PDF全文
Claude E. Boyd Aaron A. McNevin Phoebe Racine Huynh Quoc Tinh Hang Ngo Minh Rawee Viriyatum Duangchai Paungkaew Carole Engle 《Journal of the World Aquaculture Society》2017,48(2):201-226
Resource use was investigated at 34 Litopenaeus vannamei and five Penaeus monodon farms in Thailand and 30 L. vannamei and 24 P. monodon farms in Vietnam. Farms varied in water surface areas for production, reservoirs, canals, and settling basins; in pond size and depth; and in water management, stocking density, feeding rate, amendment input, aeration rate, crop duration, and crops per year. Production of L. vannamei averaged 17.3 and 10.9 m.t./ha/yr, and feed conversion ratio averaged 1.49 and 1.33 in Thailand and Vietnam, respectively. On average, production of 1 m.t. of L. vannamei required 0.58 ha land, 5,400 m3 water, 60 GJ energy, and 1218 kg wildfish in Thailand and 1.76 ha land, 15,100 m3 water, 33.7 GJ energy, and 1264 kg wildfish in Vietnam. Resource use per metric ton of shrimp declined with greater production intensity. In Thailand, P. monodon was produced at 0.2–0.4 m.t./ha/yr, with no inputs but water and postlarvae. In Vietnam, P. monodon production averaged 3.60 m.t./ha/yr. Production of 1 m.t. of P. monodon required 0.80 ha land, 36,000 m3 water, 47.8 GJ energy, and 1180 kg wildfish, and resource use per ton production declined with increasing production intensity. 相似文献
86.
Rapid salinity changes affect the survival and physiology of a penaeid prawn: Implications of flood events on recruitment to the fishery 下载免费PDF全文
K. J. Tyler A. Becker N. A. Moltschaniwskyj M. D. Taylor 《Fisheries Management and Ecology》2017,24(6):478-487
Estuaries act as nurseries for many penaeid prawns, but these habitats are highly susceptible to salinity decline through flooding. The rate of salinity decline and duration of exposure to non‐optimal salinity may affect survival and subsequent recruitment of prawns to the fishery. This study aimed to determine the effect of salinity fluctuations observed in local estuaries during flood events using a novel dilution approach. Mortality of juvenile Melicertus plebejus (Hess) was assessed after 24 hr exposure to 24 rates of salinity decline ranging from 0.01% to 20% per hr. After the salinity decline, prawns were held at the final salinities for five days before again assessing mortality as well as aerobic metabolic rate and prawn water content. Salinity decline from 36 to ~0.8 led to 50% mortality, but continued exposure to low salinity for five days increased mortality at this salinity to 99% and shifted the 50% mortality point to salinity ~5. Aerobic metabolic rate and water content data suggested the cause of mortality due to exposure to salinities < 5 was osmoregulatory failure. Rapid salinity declines over 24 hr and sustained low salinity due to flooding could compromise the survival of juvenile prawns, potentially reducing recruitment to the fishery. 相似文献
87.
Mycobacteriosis caused by Mycobacterium marinum in reared mullets: first evidence from Sardinia (Italy) 下载免费PDF全文
E Antuofermo A Pais M Polinas T Cubeddu M Righetti M A Sanna M Prearo 《Journal of fish diseases》2017,40(3):327-337
Mycobacterium marinum is a slow‐growing non‐tuberculous mycobacterium, and it is considered the most common aetiologic agent of mycobacteriosis in wild and cultured fish. The diagnosis is principally made by histology when positive Ziehl–Neelsen stain granulomas are detected. The aim of this study was to investigate the occurrence of mycobacteriosis in extensively cultured Mugilidae of two lagoons (Cabras and San Teodoro) from Sardinia by the use of histology, microbiology, PCR and DNA sequencing. Nine of 106 mullets examined were affected by mycobacteriosis, and the spleen was the most affected organ. The histology detected higher rate (100%) of infection in spleen than the culture and PCR (75% and 62.5%, respectively). The sequencing of hsp65 gene identified M. marinum as the primary cause of mycobacteriosis in the mullets examined. Mullets affected by mycobacteriosis were mainly fished in the San Teodoro lagoon characterized by critical environmental conditions. Histology remains the most common method in detecting fish affected by mycobacteriosis, and PCR‐based methods are essential for species identification. Our finding are worthy of attention because mycobacteriosis caused by M. marinum in reared mullets was evidenced for the first time in Sardinia, suggesting that this disease may be underestimated also in other cultured fish species. 相似文献
88.
M. A. Abd El-baky 《Fibers and Polymers》2017,18(12):2417-2432
A study on the tensile and flexural properties of jute-glass-carbon fibers reinforced epoxy hybrid composites in inter-ply configuration is presented in this paper. Test specimens were manufactured by hand lay-up process and their tensile and flexural properties were obtained. The effects of the hybridization, different fibers content and plies stacking sequence on the mechanical properties of the tested hybrid composites were investigated. Two-parameter Weibull distribution function was used to statistically analyze the experimental results. The failure probability graphs for the tested composites were drawn. These graphs are important tools for helping the designers to understand and choose the suitable material for the required design and development. Results showed that the hybridization process can potentially improve the tensile and flexural properties of jute reinforced composite. The flexural strength decreases when partial laminas from a carbon/epoxy laminate are replaced by glass/epoxy or jute/epoxy laminas. Also, it is realized that incorporating high strength fibers to the outer layers of the composite leads to higher flexural resistance, whilst the order of the layers doesn’t affect the tensile properties. 相似文献
89.
M. Bjørnevik H. Hansen B. Roth A. Foss E. Vikingstad C. Solberg A.K. Imsland 《Aquaculture Nutrition》2017,23(2):285-292
The study was designed to investigate the effect of four cycles of 5 weeks starvation followed by 10‐week refeeding compared with daily feeding under either natural photoperiod or continuous light (LL) regime on body composition and flesh quality in Atlantic cod in sea cages, northern Norway. The fish were sampled for body composition and flesh quality parameters at the start of the trial, twice at the end of a 10‐week feeding period and twice at the end of a 5‐week starvation period. There was effect of both feeding and light regime on growth, the two starving groups losing weight during starvation and regaining weight during refeeding, and the group under LL being heavier. But, the mean overall growth did not vary between groups. Starvation/refeeding regime resulted in higher slaughter yield, but no overall effect was seen on hepatosomatic index, water content, water holding capacity (WHC), muscle pH, hardness or flesh colour compared with control groups. Continuous light increased gutted weight and slaughter yield, lowered WHC and depressed maturation compared with fish under natural light regime. Increased growth rate resulted in softer fillets and lower muscle pH. 相似文献
90.
Large-scale deployment of a rice 6 K SNP array for genetics and breeding applications 总被引:1,自引:0,他引:1
Michael J. Thomson Namrata Singh Maria S. Dwiyanti Diane R. Wang Mark H. Wright Francisco Agosto Perez Genevieve DeClerck Joong Hyoun Chin Geraldine A. Malitic-Layaoen Venice Margarette Juanillas Christine J. Dilla-Ermita Ramil Mauleon Tobias Kretzschmar Susan R. McCouch 《Rice》2017,10(1):40