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The hot convective drying of fresh tilapia fillets was evaluated in a heat pump dryer. The influence of the drying temperature (35, 45 and 55°C), hot air velocity (1.50, 2.50 and 3.50 m/s) and thickness (3, 5 and 7 mm) of the tilapia fillets on the moisture ratio and drying rate has been studied. It shows that drying process took place in falling rate periods. The experimental drying data of fresh tilapia fillets under different conditions was fitted to nine different commonly used thin-layer drying models by nonlinear fitting methods and all the models were compared according to three statistical parameters, i.e. coefficient of determination, the reduced chi-square and the root mean square error. It was found that the coefficient of determination values of Page were higher than 0.99254, and the corresponding reduced chi-square and the root mean square error values were lower than 0.000632219 and 0.023854, respectively, indicating that the Page model is the best to describe drying curves of fresh tilapia fillets among them. Effective moisture diffusivity ranged from 6.55×10–10 to 1.23×10–9 m2/s calculated using the Fick’s second law. With the increase of the drying temperature and the hot air velocity, the effective moisture diffusivities Deff increased. The value of drying activation energy of tilapia fillets with thickness of 3 mm at hot air velocity 2.50 m/s was 17.66 kJ/mol, as determined from the slope of the Arrhenius plot, ln(Deff) versus 1/Ta.
The position of the Palaeozoic Anthracoptilidae has been a major problem of insect systematics for over a century. The previous hypotheses suggested affinities of Anthracoptilidae with the Palaeodictyopteroida, Protorthoptera, Hypoperlida, stem-Mantodea, Paraneoptera, Holometabola, or Eoblattida. Herein we put forward a new hypothesis based mainly on a comprehensive re-evaluation of the wing venation characters and re-examination of the type material of Anthracoptilus perrieri and Mesoptilus dolloi. The Anthracoptilidae are considered as belonging to the paoliid lineage, sister group of the Dictyoptera. In particular this result refutes the presence of Mantodea in the Paleozoic fossil record. The two families Strephocladidae and Strephoneuridae, are considered as junior synonyms of the Anthracoptilidae, while the previous synonymy of the Anthracoptilidae with the Ischnoneuridae is rejected. We consider the Permarrhaphidae, previously considered as synonym of the Anthracoptilidae, (and Permarrhaphus) as Insecta incertae sedis. The following new taxa are proposed: Mesoptilus carpenteri sp. nov. from the early Permian of Wellington Formation in Oklahoma (USA) which extends the range and distribution of the genus; Pseudomesoptilus gen. nov. is designated to include Mesoptilus sellardsi; Strephocladus permianus sp. nov. from the middle Permian of South of France; Westphaloptilus gallicus gen. et sp. nov. from the Bashkirian of the North of France.
Background. Arachidonic acid (ARA) is one of the three essential fatty acids, and it is important for human body to keep healthy and is widely used. At present, expensive materials such as glucose and yeast extract are generally reported to be optimal for ARA production. A new cost-effective fermentation process including cheaper material for ARA production is of great significance. Material and methods. Feasibility of using com meal and powdered soybean for fungal growth and lipid accumulation was evaluated by means of single factor test. N-hexadecane concentration was optimized, and the effect of temperature on biomass and ARA content was examined. Results. Mortierella alpina made better use of the aforementioned material as carbon and nitrogen sources for both hyphae growth and ARA production compared with glucose and yeast extract. Maximal levels of 10.9 g/L ARA and 26.1 g/L total lipids were obtained when 66 g/L com meal, 54 g/L soybean meal and 6% (v/v) n-hexadecane were supplemented. A temperature-shift strategy involved three steps, namely, 30°C (3 days) - 25°C (4 days) - 20°C (4 days), which further improved ARA production by 24.7%. Conclusion. Several factors such as carbon and nitrogen sources, temperature and dissolved oxygen had great influence on biomass and microbial oil production. Mortierella alpina preferred com and soybean meal compared with glucose and yeast extract, which would surely alleviate the high cost of ARA production. Based on this study, the new process is both low cost and practicable.
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