Comparing a chemoautotrophic-based biofloc system and three heterotrophic-based systems receiving different carbohydrate sources

A 56-day study was conducted in which shrimp (Litopenaeus vannamei) were stocked at 300 m⁻³ into 16, 500-L tanks. Four treatments were created: chemoautotrophic (CA), heterotrophic sucrose (HS), heterotrophic molasses (HM), and heterotrophic glycerol (HG). The heterotrophic treatments were managed such that the C:N ratio of inputs (feed and carbohydrate source) was 22:1. The chemoautotrophic treatment received no added carbohydrate, only shrimp feed. Each treatment was assigned randomly to four replicate tanks. Nitrate-N was significantly greater in the CA treatment, accumulating to a peak mean concentration of 162 mg NO₃-N L⁻¹ and nitrate was typically below detection (<0.01 mg NO₃-N L⁻¹) in the heterotrophic treatments. 5-Day biochemical oxygen demand (BOD₅) was significantly greater in the heterotrophic treatments compared to the chemoautotrophic treatment. Total suspended solids concentration was significantly lower in the CA treatment compared to any other. Shrimp growth rate was significantly greater in the CA and HS treatments versus the HM treatment and there was no significant difference in growth rate between the HG treatment and any other treatment. These results indicate that differences in management and carbohydrate source can lead to substantial disparity in system function and shrimp production.     

牛奶检验与喷雾干燥中的粘度分析

根据中、澳两国两种牛奶流变试验结果,指出牛奶流变特性受浓度、温度和牛奶品种的影响,可以采用粘度分析法进行新鲜牛奶质量鉴定,并对牛奶喷雾干燥时的温度和浓度选择提出见解。     

复合酶对沙门氏菌杀灭作用的研究

通过研究复合酶对鼠伤寒沙门氏菌S0013(Salmonella typhimurium0013)的杀菌效果,筛选出最佳的复合杀菌酶配方,即溶菌酶0.03%,β-甘露聚糖酶0.03%,-β1,3-葡聚糖酶0.02%,中性蛋白酶0.01%。通过平板培养计数法,验证了该配方的杀菌效果。结果表明:经复合杀菌酶处理后,沙门氏菌数目比对照组减少了1 000倍,比正对照的溶菌酶组减少了10倍。     

多元校正紫外光谱法测定苹果汁含量研究

研究了多元校正紫外光谱测定苹果汁含量的方法。结果表明,苹果汁含量不同的样品有不同的紫外吸收曲线。含量小于70%时,曲线差异明显,噪音较小。当含量大于70%后,光谱噪音水平升高,不同含量的吸收曲线差异缩小,检测能力下降。利用偏差权重法选取280-365 nm区间的光程进行建模,用主成分分析法来压缩变量,然后用逐步回归法建立苹果汁含量的数学模型,再用完全交互验证法对模型进行验证,结果预测值与真实值相关性良好,偏差较小。通过优化建模条件,建立合适的UV光谱预测模型,可以对苹果汁及其饮料中原果汁含量进行快速检测。     

基于改进MCS算法的道路模拟机试验系统

通过增加积分环节,提出了改进的自适应最小控制合成算法( MCSI)作为道路模拟机试验系统的伺服控制系统外环,以克服振动台在测试中存在的未知时变参数及时变干扰的影响,以提高振动台位移跟踪精度.通过对单通道道路模拟机试验系统动力机构进行建模,并对PID、MCS和MCSI控制器进行了设计与仿真.仿真结果表明,MCS及MCSI控制器跟踪精度远远高于传统的PID控制器,而改进的MCS跟踪精度又优于MCS,并且具有在线调节参数的优点.基于快速原型的MCS算法,利用Matlab/Simulink建立振动台控制系统模块,在CCS集成开发环境中自动生成代码,然后将可执行代码下载到DSP TMS320C2812和TMS320C6713中,实现了基于MCSI的道路模拟机试验系统设计.     

8种杀菌剂对油菜菌核病菌室内生物活性测定

为筛选防治油菜菌核病菌的有效药剂,采用菌落直径法测定并比较了8种杀菌剂对油菜菌核病菌的室内生物活性。结果表明,咯菌腈对油菜菌核病菌抑菌活性最好,其它依次为己唑醇、啶菌噁唑、多菌灵、多氧霉素、嘧霉胺和噁霉灵,嘧菌酯的抑菌活性最差。试验结果可以为油菜菌核病的田间防治提供有益参考。     

Robustness in the mineral supply from temporary grasslands

Abstract

The current study examined the capacity of different temporary grassland legume–grass mixtures under different N supply levels to supply similar amounts of elements in systems where the herbage is cut for feed. Mixtures showed a good robustness in supplying equal amounts of mineral elements in the combined herbage as well as equal concentrations in dry matter of mineral elements compared with the same species in monocultures. The reasons for the mixed systems to be able to buffer differences in N supply levels as well as different compositions of the mixtures were that legume leaves and stems had similar concentrations of mineral elements, whether in monocultures or in mixtures with grasses. Grasses in mixture with legumes had however higher N, Ca, S, Zn, Cu and tended to have higher Mg concentration, both in stems and leaves, while Mn were less concentrated in mixtures’ dry matter. Further, the mixtures doubled their dry matter accumulation in the two weeks just around grass heading. The systems partly buffered the time-wise differences in the sense that the P accumulation paralleled dry matter but the N was diluted. This was mirrored in a decrease in N concentration and maintenance of the concentration level of P and other elements. As the stem–leaf ratio was higher (p<0.05) in festulolium than in ryegrass and as the stems of festulolium have lower concentrations of N, K, Ca, S, Mg, Fe and Cu than leaves, the mixtures including festulolium had a rapidly declining proportion of these elements in the combined mixtures’ dry matter. Management options in improving the mineral supplies are thus to choose species when establishing the temporary grasslands according to functionality, to manipulate the content of legumes by the N supply level, and to time the harvest of the herbage.     

玉米幼胚组织培养体系优化

以5个骨干玉米自交系幼胚为材料, 研究幼胚大小、2, 4-D浓度、KT浓度对幼胚愈伤组织诱导及分化的影响。结果表明, 5个骨干玉米自交系均可诱导出愈伤组织, 但不同条件下诱导率存在显著差异。最适幼胚大小为2.0～3.0 mm, 因基因型不同而有所变化;2, 4-D浓度在1.0～3.0 mg/L有利于愈伤组织诱导, 同一材料不同2, 4-D浓度对胚性愈伤组织诱导率的影响具有显著差异, 不能以初级愈伤诱导率高低作为选择胚性愈伤诱导率的标准;KT可显著提高愈伤组织的分化率, 随着KT浓度的增加分化率呈先上升后下降的趋势, 最适KT浓度为1.0～2.5 mg/L。     

噻苯隆对莴笋产量、品质的影响及药害症状初步研究

在一定范围内,使用高浓度噻苯隆,会直接导致莴笋的功能叶、幼叶受害,同时会因为代谢导致新生叶片受害。在摘除死亡叶片后,正常管理下,莴笋植株可恢复生长,最终成熟;使用高浓度（〉0．10％）噻苯隆,会使成熟莴笋植株的株高、茎粗、叶片质量、叶中脉质量、叶片长宽比、根部质量、产量下降,而叶面积指数、品质提高;使用低浓度（0．05％）噻苯隆,可提高莴笋植株的叶片质量、叶中脉质量、茎部质量、株高、茎粗、产量。     

超滤法浓缩麦芽糖的研究

[目的]研究采用超滤工艺浓缩麦芽糖液的效果。[方法]采用分子量为6 000 Da的超滤膜,分别浓缩40%、15%的麦芽糖液,考察麦芽糖液的超滤浓缩效果及反洗对膜性能的恢复效果。[结果]超滤膜浓缩40%的麦芽糖液时,超滤通量衰减迅速,堵塞明显;但采用同样的超滤膜浓缩15%的麦芽糖液时,超滤通量较大,且衰减较慢,效果理想。麦芽糖葡萄糖值(DE值)由滤前的43%达到滤后的50%;透光率由滤前的91%T达到滤后的98%T。[结论]该研究为提高麦芽糖产品的透明度、延长产品保质期等,提供了一种较为实用的技术方法。