不同水稻品种对铵态氮和硝态氮吸收特性的研究

采用水培方法研究了不同形态氮素对武育粳 3号 (常规粳稻 )和扬稻 6号 (常规籼稻 )生长的影响及其水稻苗期对NH 4 N和NO-3 N的吸收动力学特征。结果表明 :不同形态氮素对水稻生长影响差异显著 ,铵硝混合营养下水稻的生长最优 ;扬稻 6号比武育粳 3号具有更强的氮素吸收能力 ;不论武育粳 3号或是扬稻 6号 ,单一氮源时NO-3 的Km 值均大于NH 4 ,说明水稻对NH 4 的亲和力大于NO-3 ,武育粳 3号对NH 4 的最大吸收速率小于NO-3 ,而扬稻 6号则极为接近 ;NH 4 的存在均显著降低两个水稻品种对NO-3的吸收速率 ,武育粳 3号和扬稻 6号的NO-3 的Vmax分别比单一硝营养减小 1/ 2和 2 / 3,NO-3 的存在不影响武育粳 3号对NH 4 的吸收速率 ,但使扬稻 6号对NH 4 的吸收速率减小     

Microbial activity in soils frozen to below −39 °C

Recent research on life in extreme environments has shown that some microorganisms metabolize at extremely low temperatures in Arctic and Antarctic ice and permafrost. Here, we present kinetic data on CO₂ and ¹⁴CO₂ release from intact and ¹⁴C-glucose amended tundra soils (Barrow, Alaska) incubated for up to a year at 0 to −39°C. The rate of CO₂ production declined exponentially with temperature but it remained positive and measurable, e.g. 2-7 ng CO₂-C cm⁻³ soil d⁻¹, at −39 °C. The variation of CO₂ release rate (v) was adequately explained by the double exponential dependence on temperature (T) and unfrozen water content (W) (r²>0.98): v=A exp(λT+kW) and where A, λ and k are constants. The rate of ¹⁴CO₂ release from added glucose declined more steeply with cooling as compared with the release of total CO₂, indicating that (a) there could be some abiotic component in the measured flux of CO₂ or (b) endogenous respiration is more cold-resistant than substrate-induced respiration. The respiration activity was completely eliminated by soil sterilization (1 h, 121 °C), stimulated by the addition of oxidizable substrate (glucose, yeast extract), and reduced by the addition of acetate, which inhibits microbial processes in acidic soils (pH 3-5). The tundra soil from Barrow displayed higher below-zero activity than boreal soils from West Siberia and Sweden. The permafrost soils (20-30 cm) were more active than the samples from seasonally frozen topsoil (0-10 cm, Barrow). Finding measurable respiration to −39 °C is significant for determining, understanding, and predicting current and future CO₂ emission to the atmosphere and for understanding the low temperature limits of microbial activity on the Earth and on other planets.     

土壤钾解吸的动力学方程和大麦反应的关系

本文应用Ｅｌｏｖｉｃｈ、抛物线扩散、权函数和指数方程研究电超滤恒电场下１２种土壤钾解吸的动力学。Ｅｌｏｖｉｃｈ、抛物线扩散和权函数方程具有高的相关系数和小的标准差，可以很好地描述土壤钾解吸的动力学，而指数方程的相关系数低和标准差大而不适宜应用。本文成功地建立了动力学方程与大麦多点田间试验钾肥反应和土壤钾素状况之间的相关关系，Ｅｌｏｖｉｃｈ、抛物线扩散和权函数方程的常数（斜率或截距）与土壤速效钾、大     

挖坑机弯曲振动特征对的理论计算与实验验证

用动力分析与动态设计方法，研究了农业机械的弯曲振动问题，以拖拉机后悬挂式挖同为例，通过对研究系统非链状结构的链状简化，建立了系统的动力学模型，求得了系统的固有频率和主振型，对固有频率的实验测试结果，证实了本文研究的正确性。     

动态水压下非旋转式折射喷头水力特性

为解决非旋转式折射喷头水量分布集中,打击动能较大的问题,构建了动态水压喷灌测试平台。选择Nelson D3000型喷头为研究对象,施加以三角函数型动态变化的水压,对喷头的径向水量分布与能量分布进行测试,并与恒压条件下的水量和能量分布进行对比。结果表明:构建的动态水压测试平台能够满足对动态供水压力的要求,施加了动态水压的Nelson D3000型喷头径向湿润范围由恒压时的0.85~1.36 m增加到2.55~4.42 m,喷灌强度最大值降低67.6%~78.4%,能量通量密度最大值降低52.9%~71.6%,说明采用动态水压供水可以有效地改善Nelson D3000型喷头的径向水量分布和能量分布。     

旋耕机运动参数动态试验方法的研究

介绍了通过计算机的处理与控制，在试验过程中用直接实现改变台车前进速度或动力输出轴转速的试验方法（简称动态试验法）来获取旋耕机运动参数与功率消耗的关系曲线，从而大大减少了试验次数，提高了试验的可比性及精度。本试验方法也适用于其它耕种机具。     

树莓果汁中花色苷降解动力学的研究

通过研究树莓果汁花色苷在不同pH值和贮藏温度下的热稳定性,建立了花色苷降解动力学模型,研究结果表明：树莓果汁花色苷对pH和热不稳定,花色苷的降解符合一级反应动力学,随着pH值和温度的升高,树莓花色苷热降解活化能（Ea）和半衰期（tl／2）显著下降。经验证实验表明,该降解动力学模型有效,可用于树莓果汁贮藏温度的选择和预测不同温度下的贮藏期。     

Numerical study of dense solid-liquid flow in hydrodynamic vortex separator applied in recirculating biofloc technology system

Hydrocyclone separation technique has commonly been applied in engineering for solid-liquid separation. In aquaculture, since Hydrodynamic Vortex Separator (HDVS) is able to control flocs concentration effectively, the Recirculating Biofloc Technology (RBFT) has been gradually acknowledged (Zhu et al., 2016). In order to operate RBFT system at maximum performance, the removal efficiency of HDVS at different Hydraulic Retention Time (HRT) must be fully predictable. The aim of this work is to investigate the relationship between separation efficiency and HRT of HDVS applied in RBFT system, through Computational Fluid Dynamics (CFD) method. For this, a three-dimensional unsteady transient model was developed to simulate the hydrodynamics in HDVS based on the commercial software Workbenching 17.0. A Two Fluid Model (TFM) using kinetic theory of granular flow (KTGF) has been developed to describe the dense solid-liquid (flocs-water) flow field of HDVS in RBFT system. Additionally, the Reynolds averaged Navier-Stokes (RANS) equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. Finally, pilot-scale studies were conducted to evaluate the accuracy and precision of simulation models applied. The results indicate that the flocs removal efficiency of HDVS obtained from tests were less than that from the simulation results at three different HRTs. But it decreased with the decline of HRT both for experiment and simulation. Additionally, the CFD model proposed can enhance the fundamental understanding of the effects of HRT on separation efficiency and at the same time, probably coupled with physical experiment whenever necessary, offer a more reliable way for optimum control of HDVS under varying conditions. Based on the simulation results, the flocs management in RBFT system is briefly discussed.     

两个棉铃虫酯酶基因(001f和001g)在杆状病毒表达载体系统(BEVS)中的表达及酶活分析

昆虫羧酸酯酶(carboxylesterases,CarEs)对有机磷、拟除虫菊酯、氨基甲酸酯等三大类化学杀虫剂的代谢解毒作用是昆虫代谢抗性产生的一种重要机制.为明确棉铃虫(Helicoverpa armigera)两个酯酶基因001f和001g在代谢抗性中的作用,本研究基于杆状病毒表达载体系统(BEVS)在草地夜蛾(Spodoptera frugiperda)Sf9细胞系中成功表达了酯酶基因001f和001g,表达产物经非变性聚丙烯酰胺凝胶电泳和α-乙酸萘酯染色,结果表明,两个酯酶的条带染色很深,染色条带主要分布在相对迁移率(Rm)值为0.27～0.36和0.37～0.48之间的两个区域.进一步采用酶标仪测定了表达产物对α-乙酸萘酯(α-naphthyl acetate)和4-硝基苯基乙酸酯(para-nitrophyl acetate)的酶促代谢动力学特性,结果表明,两个酯酶对底物均有极强的亲和力和非常高效的催化效率,其对α-乙酸萘酯的亲和系数(Km值)分别为(3.9±0.6)和(3.3±0.4) μmol/L,速率常数(kcat/Km值)高达(95±9.3)和(26.5±1.9) μmol-1·s-1·L；相比较而言对于4-硝基苯基乙酸酯的kcat/Km值较低(分别为(4.47±0.33)和(12.8±0.10) μmol-1 ·s-1·L).上述结果在生化水平上证实了两个酯酶均具有较强代谢作用,预示着这两个酯酶基因与棉铃虫的代谢抗性可能相关,并可能对有机磷、拟除虫菊酯等化学杀虫剂也具有一定代谢解毒作用.     

Acetylcholinesterase in selected plant-parasitic nematodes: Inhibition, kinetic and comparative studies

The in vitro inhibition potency of some organophosphates (OPs) and carbamates (CAs) which are widely used to control plant-parasitic nematodes on acetylcholinesterase (AChE) of Meloidogyne javanica, Heterodera avenae and Tylenchulus semipenetrans, the major pathogens responsible for the damage of a wide range of crops in Al-Qassim region, Saudi Arabia was examined. AChE of H. avenae activity was 1.58- and 1.51-fold greater than that of T. semipenetrans or M. javanica, respectively. The order of inhibition potency of the tested compounds against T. semipenetrans AChE was: carbofuran > paraoxon > oxamyl > fenamiphos > phorate-sulfoxide > aldicarb, where the corresponding concentrations that inhibited 50% of the nematode AChE activity (I₅₀) were 5 × 10⁻⁸, 7 × 10⁻⁷, 7.5 × 10⁻⁷, 2 × 10⁻⁶, 2 × 10⁻⁴ and 2 × 10⁻³ M, respectively. Paraoxon, fenamiphos and carbofuran exhibited high inhibition potency against M. javanica AChE where the I₅₀ values were below 1 nM. Phorate-sulfoxide and aldicarb were potent inhibitors of M. javanica AChE with I₅₀ values of 3.8 and 8 nM, respectively, while oxamyl exhibited low inhibition potency with I₅₀ of 15 nM. Fenamiphos and paraoxon showed the highest I₅₀ values of <100 μM against H. avenae followed by oxamyl (I₅₀ < 1 mM), whereas paraoxon, carbofuran and aldicarb showed low potency with I₅₀ values >1 mM. All the tested compounds exhibited high inhibition potency to AChE of M. javanica than T. semipenetrans or H. avenae. Except phorate-sulfoxide in M. javanica the inhibition pattern and implied mechanism for all the tested compounds for the three nematodes is suggested to be a linear mixed type (a combination of competitive and non-completive type).