Search

The Chinese mitten crab (Eriocheir sinensis) is an important economic crab in China. Across most of China, juvenile Chinese mitten crabs are cultured in earthen ponds. Juvenile crab cultured in rice fields is mainly restricted to the northeastern region. Rice-crab coculture is a new mode of sustainable development, which has developed over the past 30 years in China with progress in field engineering, culture density of the Chinese mitten crab, and ecological benefits. However, there are no reports on appropriate feeds in rice-crab coculture. Presently, crabs reared in an earthen pond consume a traditional diet (including soybean meal, corn, bran, and wheat) or formulated feed. Due to the numerous advantages of formulated feed (including comprehensive nutrition, stable quality, and ease of feeding) the development of practical and cheap formulated feed for Chinese mitten crab is the latest focus for promoting the sustainable development of the Chinese mitten crab industry. Although researchers have developed a series of formulated feed for Chinese mitten crab, traditional feed is more commonly used in the culture of Chinese mitten crab due to farmers feeding habits and the low price of traditional products. However, numerous studies have shown that feeding Chinese mitten crabs formulated diets has many advantages, for example: it improves the survival rate, reduces the early maturity rate, improves non-specific immunity and disease resistance of juvenile crabs, improves the quality and culture performance of crab species, and economic benefits, etc. However, research were usually conducted under indoor or pond culture conditions. The culture environment of rice fields and ponds are quite different to each other. The feed sources and environmental stress on juvenile crabs may also be quite different between the culture environments. Therefore, it is important to explore the feeding mode of juvenile crabs cultured in rice fields. However, the optimum feed and the effect of different diets on the growth and physiological metabolism of Chinese mitten crab reared in rice fields remains unclear. It is important to optimize the rice-crab breeding mode to achieve a high-quality Chinese mitten crab industry. Formulated diets and traditional diets (soybean meal, bran, corn, and wheat) were fed to juvenile E. sinensis cultured in a rice field for 152 days. Each feeding group included three replicates. This study was conducted to compare formulated diets with traditional diets using culture performance, protein metabolism, digestive enzymes, and the antioxidant and immune indexes of juvenile crabs. The results showed that: (1) the body weights of female and male crabs from the formulated diet group were higher than those in the traditional diet group, but the differences were not significant (P > 0.05) (Fig.1–3); (2) in terms of culture performance, the average body weight and yield of juvenile crabs, 1-year-old precocious crabs, and the overall total yield and survival rate of juvenile crabs in the formulated diet group were slightly higher than those of the traditional diet group. The feed conversion ratio of the formulated diet group was much lower than that of the traditional diet group (P < 0.05); (3) in terms of protein metabolism, the total protein content in the hemolymph of both female and male crabs fed the formulated diet was significantly higher than that in the traditional diet group (P < 0.05). Conversely, the contents of urea nitrogen in the hemolymph of male crabs and the activity of glutamic oxaloacetic transaminase in the hepatopancreas of the traditional diet group were significantly higher than those of the formulated diet group (P < 0.05); (4) lipase in the hepatopancreas of female and male crabs in the formulated feed group was significantly higher than that in the traditional diet group (P < 0.05). Conversely, the α-amylase activity of the male crabs in the formulated diet group was significantly lower than that of the traditional diet group; (5) the total antioxidant capacity, alkaline phosphatase, and acid phosphatase activities in the hemolymph of female crabs and the acid phosphatase activity in the hepatopancreas of the formulated diet group were significantly higher than those of the traditional feed group (P < 0.05). In conclusion, feeding a formulated diet can improve the culture performance, promote protein deposition and lipid absorption, and enhance the antioxidant and immune capacity of juvenile E. sinensis reared in a rice field. These factors result in improved crab quality. This study provides a basis for optimizing the culture technology of Chinese mitten crab and the development of a formulated diet for improved rice-crab coculture.

The geochemical characteristics and genesis of Paleozoic natural gas in the Ordos Basin are complex, with some disputes on the gas source of Lower Paleozoic. In order to better grasp the overall geochemical characteristics and variation laws of Paleozoic natural gas in the basin, the geochemical data of more than 700 natural gas samples from the whole basin are comprehensively analyzed based on the systematic collection, collation and analysis of previous data, and the genesis of natural gas is explored by combining the analysis of key elements such as natural gas formation, hydrocarbon formation and reservoir formation. The results show that the main body of Upper Paleozoic natural gas is coal-based gas controlled by maturity, with maturity increasing from northeast to southwest, and the southern part of the basin has a mixture of Upper and Lower Paleozoic gas. The Lower Paleozoic gas is dominated by oil-type gas from marine carbonate formations, of which the upper combination is characterized by a two-source composite reservoir of Upper Paleozoic coal-type gas and Lower Paleozoic oil-type gas; the middle-lower combination is a relatively independent oil-type gas reservoir, subject to different degrees of secondary transformation based on geological conditions and the degree of thermal evolution of organic matter, resulting in significant anomalies in its carbon isotope composition. The research has proved that marine hydrocarbon sources including carbonate rocks exist in the Lower Paleozoic of the basin, and the natural gas in the Upper and Lower Paleozoic has mixed to varying degrees in different locations of the basin.

High-frequency power supply is an important component of high-discharge glass curing systems for high level radioactive waste (HLLW) of cold crucibles, but because the parameters of each set of high-frequency power supply are not adjustable from the factory and are expensive, it is impossible to study the matching of the power supply parameters to the cold crucible and determine the optimal combination of parameters and the best matching state for the high-frequency power supply. The use of a small, inexpensive and fine-tunable high-frequency power supply to set up a Φ100 cold crucible experimental setup and to investigate the match between the power supply and the crucible is an effective way to solve this problem, but due to the large number of experimental variables and the small amount of valid data available from actual measurements, it is decided to carry out a simulation study of the multi-physics field coupling of a Φ100 cold crucible glass-curing high-frequency power supply. In this paper, COMSOL was used to carry out a multi-physical field coupling simulation of the temperature, flow and magnetic fields of the molten glass liquid, using current strength, frequency and number of turns of the coil as variables. The results show that increasing the current strength and frequency improves the melting capacity, increasing the coil diameter, spacing and number of turns improves the energy utilisation, the coil height is lower in the middle to improve the temperature field and magnetic field distribution, and the round coil and cold crucible are more advantageous than the oval. The initial optimization of the power supply parameters results in a 22.8% increase in the melt cell volume and a 35% increase in the average temperature of the cold crucible, which significantly improves the melting effect of the cold crucible. The simulated experiments provide guidance for the development of the Φ100 cold crucible experiments and lay the foundation for the optimisation of the high frequency power supply and coil parameters.

The prototype basin has become a hot nomenclature, which is widely used in the geoscience field. However, in a large number of publications, the understanding and expression of the prototype basin are quite different. Based on the analyses of the published and intramural documents, we believe that the prototype basin was newly defined by ZHU Xia in 1982, proposing that the prototype basin refers to a structural form and sedimentary entity formed in a geodynamic context (environment) during a certain geological history. A simple (small scale) basin is a prototype basin, and a large complex basin always contains several different prototype basins, which means the prototype basin varies over time. The nomenclature of the prototype basin should be an important part of ZHU Xia's academic thought and scientific theoretical system, which has a specific scientific connotation and nomenclature. It is suggested that the prototype basin and its synonymous nomenclature should be used in specific contexts for those basins whose original conditions have not been obviously transformed in the course of basin development. The original conditions contain the formation, evolution and hydrocarbon accumulation (mineralization) and several other related aspects of the basin. It is very difficult to reconstruct a reformed basin and get its prototype due to the complicated formation process, complex late reformation and uncertainty of reconstruction evidence and interpretations. The key points to reconstruct the original basin or the prototype basin can be summarized as: searching the evidence, determining the basin attributes, modeling the original state and remodeling the process, all of which need to be interrelated and carried out step-by-step.