Simulation studies on the effects of solar heat on egg-laying, development and survival of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) in stored bambara groundnut Vigna subterranea (L.) Verdcourt

The effects of simulated solar heat on oviposition, development and survival of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) in stored bambara groundnut, Vigna subterranea (L.) Verdcourt, were evaluated at three high temperatures (40°C, 45°C and 50°C) at a constant, low humidity (30% relative humidity). Exposure to these temperatures for 6 h significantly reduced oviposition in C. maculatus and C. subinnotatus females. Females of both species that were exposed to 50°C laid significantly fewer eggs than those exposed to 40°C; and in the case of C. maculatus, females exposed to 45°C also laid significantly fewer eggs than those exposed to 40°C. The percentage of eggs laid by females of both species that reached adulthood after exposure to 50°C for 2–6 h was significantly lower than the percentage that developed from eggs laid by females that were exposed to 40°C. No adult developed from eggs of C. maculatus exposed for 6 h at 50°C or from eggs of C. subinnotatus exposed for 2 h at this temperature. For both species, no adult progeny subsequently emerged from seeds harbouring first instar larvae when exposed at 50°C for 2, 4 or 6 h. Older larvae of C. maculatus were more tolerant of exposure at 50°C: 26.8, 10.2 and 0.9% of late instar larvae exposed for 2, 4 and 6 h, respectively, developed to the adult stage. In contrast, no adults of C. subinnotatus emerged from seeds harbouring late instar larvae when exposed at 45°C for 6 h nor in seeds exposed to the temperature of 50°C for 4 or 6 h. On average, immature stages of C. subinnotatus were more susceptible to heat treatment than those of C. maculatus.     

Technique to isolate Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) eggs

A simple technique to isolate the eggs of Callosobruchus chinensis from the surface on which they are laid is described. An aqueous extract of their natural food, green gram, Vigna radiata, is used to coat glass beads that attract adult females for oviposition. The thin layer of extract on the glass beads allows separation of the eggs from the bead surface after a 15–20 s immersion in water. When transplanted onto fresh grain treated with glue, the separated eggs exhibit normal development and up to 97% hatching.     

杨木与辐射松树脂增强及其热处理材用做实木地板性能分析

对脲醛树脂浸渍增强杨木和辐射松及其180 ℃真空热处理的树脂浸渍材用做实木地板的性能进行了测试分析。结果表明,树脂浸渍杨木、树脂浸渍辐射松木材、热处理树脂浸渍杨木和热处理树脂浸渍辐射松木材的性能均能够满足《实木地板第1部分:技术要求》的要求;热处理树脂浸渍杨木和热处理树脂浸渍辐射松木材吸湿平衡含水率未达到《热处理实木地板》要求,其余指标满足要求;树脂浸渍改性材与真空热处理树脂浸渍改性材的甲醛释放量(干燥器法)分别为(0.1～0.3)mg/L和(0.06～0.2)mg/L;树脂浸渍改性与真空热处理树脂浸渍改性木材涂饰后材色加深,其纹理更加清晰美观,表面更加富有光泽。     

绿豆淀粉/PVA复合膜的制备及性能研究

采用流延法,制备一种含绿豆淀粉与聚乙烯醇(PVA)复合膜,并对其性能进行评价。采用单因素实验研究了绿豆淀粉与PVA比例、交联剂、增塑剂等因素对膜性能的影响,并利用正交实验法对绿豆淀粉与PVA质量比、增塑剂用量和交联剂用量进行的优化。结果表明,以绿豆淀粉∶PVA质量比、甘油和乙二醛的质量分数分别为7∶3(g/g)、20%、8%制备的膜的拉伸强度、断裂伸长率、透光率最佳,分别为(17.3±0.25)MPa、112%±2.15%、28.2%±0.23%。      

Nutritional value of cowpea (Vigna unguiculata L. Walp) meals as ingredients in diets for Pacific white shrimp (Litopenaeus vannamei Boone)

The nutritional value of cowpea (Vigna unguiculata L. Walp) meals, as ingredients in diets for Litopenaeus vannamei, was evaluated. Five experimental meals were prepared in the laboratory: whole raw cowpea (WRC), dehulled (DC), cooked (CC), germinated (GC) and extruded (EXC). The crude protein content of WRC (26.1%) increased after germination (29.5%). Carbohydrates ranged from 69.4% to 85.9%. The trypsin inhibitor activity of WRC meal was low (7.52 U/mg dry matter), and was reduced or eliminated by cooking and extrusion. Apparent digestibility of dry matter, protein and carbohydrate of the diet containing whole raw cowpea meal (71.1%, 85.9% and 76.7%, respectively) was similar to the control diet. Cooking and extruding of cowpea significantly increased dry matter, protein and carbohydrate digestibility in the diets. The results suggest that cowpea meals are good sources of nutrients and can be used as ingredients in diets for L. vannamei.