四驱汽车电控分动器性能预测与试验

为了探讨四驱汽车电控分动器的传动性能,以带多片式离合器式的电控分动器为研究对象,提出一种基于遗传PID控制的电控分动器性能预测方法。首先通过分析分动器各部件功耗损失,构建电控分动器传动特性预测模型;其次探讨离合器摩擦副数、摩擦片内外径、润滑油粘度等参数对其性能传递的影响规律;最后在电控分动器试验台上开展了分动器性能试验。试验结果表明,所提性能预测方法能较好地预测行驶过程中电控分动器传动特性,为后期控制系统设计提供理论依据。     

受固氮活性制约的蓝藻固氮去铵阻抑及其与生理条件的关系

在不同气体环境中培养的蓝藻Ａｎａｂａｅｎａ７１２０固氮活性各异，Ａｒ＋ＣＯ２中最大，空气中次之，Ａｒ中最小。固氮活性高者去铵阻抑速率大，反之则小。它们对各种生理条件的反应不一样，固氮活性高者，其去铵阻抑速率受氧和氮的抑制小。在氢和氧加合条件下，三种活性的蓝藻去铵阻抑均加快，但活性低者慢而小些。光强减弱或加光合抑制剂时，固氮活性低者去铵阻抑速率显著小于活性高者，而添加外源的蔗糖或丙酮酸时，也是固氮活     

Stable C and N isotope values of selected components of a tropical australian sugarcane ecosystem

The ¹³C and ¹⁵N values of sugarcane plant tissues, decomposing harvest residues, soil and the casts and body tissues of the earthwormPontoscolex corethrurus were determined. Little variation in ¹³C values was found between plant parts. The ¹³C values of the decomposing harvest residues declined and became more variable after 148 days of exposure in the field. In the decomposing residues, ¹³C values of the neutral detergent fibre fraction were similar to those of the whole tissues while those of the proximate lignin were more negative. The ¹⁵N values of the residues also declined over time after a short initial delay.P. corethrurus populations are more intimately associated with the roots of sugarcane than with the bulk soil. Tissue ¹³C values suggest that the earthworm diet is similar to or more enriched in¹³C than sugarcane tissues and is substantially more enriched than the soil C. Earthworm tissues have similar levels of¹⁵N enrichment to both the soil and plant tissues. These data are consistent with the hypothesis that this earthworm derives much of its assimilated C relatively directly from organic matter associated with the roots and decomposing harvest residues.     

不同形态氮素比例对不同小白菜品种生物量和硝酸盐含量的影响

利用NO-3 N∶NH 4 N为 10 0∶0、5 0∶5 0和 0∶10 0三个硝铵配比的营养液对 12个不结球小白菜品种进行水培试验。结果表明 :不同的硝铵配比对不同品种小白菜的生物量、叶绿素SPAD值、硝酸盐积累量等有着显著的影响 ,同一氮源培养下不同的小白菜品种间也表现出显著的差异 ;12个小白菜品种叶绿素SPAD值随营养液中的NH 4 N比例的增加而升高 ,两者间存在着显著的正相关 ;单株生物量除亮白叶 1号和五月慢在全硝培养中生物量较其他两种配比大外 ,其他 10个品种均在 5 0∶5 0硝铵营养液中表现最好 ;供试的 12个小白菜品种中有 9个品种的硝酸盐积累量随着NH 4 N比例的增加而下降 ,表明适当地配施铵态氮较纯硝营养液能获得更好的产量、更高的叶绿素SPAD值和较低的硝酸盐积累量。     

苏云金芽孢杆菌抗癌的研究进展

最近研究发现某些非杀虫的苏云金芽孢杆菌（Bacillus thuringiensis,Bt)株系的伴孢蛋白对体外培养的人癌细胞（MOLT－4，HeLa)具有毒杀能力。这类蛋白不属于已知的任何一种Cry/Cyt蛋白，其抗癌活性需经蛋白酶水解活化，所导致的细胞病变有明显的核凝聚和细胞肿胀过程。这个发现可能导致Bt在医疗上的新应用。文章综述了国外一些研究的新进展以期对国内的Bt研究提供新的思路。     

不同液土比和温度条件下塿土铵离子吸附

Effects of NH₄⁺ concentration, solution/soil ratio and temperature on NH₄⁺ adsorption were studied in a Eum-Orthic Anthrosol. The slopes of the soil NH₄⁺ adsorption isotherms and the fitted n, the coefficient for the adsorption intensity, and k, the coefficient related to adsorption capacity, of the Freundlich equation increased with increasing solution/soil ratio (SSR) and with decreasing temperature (T). For the range of experimental conditions, the value of ∂q/∂c, the rate of change of the amount of NH₄⁺ adsorbed in the soil solid phase (q) with respect to the equilibrium concentration of NH₄⁺ in soil solution (c), was 0.840, indicating that q increased with increasing c. From 2 to 45 ℃, ∂q/∂SSR, the rate of change of q with respect to SSR, decreased from 2.598 to 1.996, showing that q increased with increasing SSR, while its increasing rate decreased with temperature. From SSR 1:1 to 20:1, ∂q/∂T, the rate of change of q with respect to T, decreased from -0.095 to -0.361, indicating that q decreased with increasing temperature, and at the same time the negative effect of temperature became larger as SSR increased. Thus under the experimental conditions the order of importance in determining the amount of NH₄⁺ adsorbed in the soil solid phase was ∂q/∂SSR > ∂q/∂c > |∂q/∂T|, indicating that the greatest effect on the amount of NH₄⁺ adsorbed was with the solution/soil ratio; the equilibrium concentration of NH₄⁺ had a lesser effect; and temperature had the least effect.     

猪5-HT4b受体基因cDNA克隆和序列分析

利用RT—PCR技术克隆了猪5-HT4bR基因的核苷酸序列，并利用生物信息学手段进行了验证。核苷酸序列测定与分析表明，该基因片段全长1209bp且包含一个完整的开放阅读框，编码402个氨基酸。该序列已在GenBank登录（Accession No．AY566638）。序列分析结果表明，该基因与已报道的人、鼠等5种动物5-HT4bR基因具有较高的核酸序列和氨基酸序列同源性，分别为92．56％和93．63％。该基因编码的蛋白具有7次跨膜结构，属于G蛋白偶联受体超家族。     

沼泽垦殖前后土壤呼吸与CH_4通量变化

湿地是陆地生态系统的重要组成部分,在碳的储存中起着重要作用。湿地垦殖后,在相同季节根层土壤温度明显高于沼泽湿地土壤,但垦殖后土壤有机碳、氮素含量明显降低,C:N比值减小,土壤呼吸通量增大,且具有季节性变化。垦殖8年的农田土壤,呼吸通量大于垦殖15年的农田土壤,弃耕后土壤有机碳含量及土壤呼吸强度有所增加,土壤呼吸通量与土壤温度呈显著正相关关系。沼泽湿地土壤为大气CH4的重要源,通量季节性变化明显,沼泽垦殖后农田土壤成为CH4的汇,不同垦殖年限土壤间CH4通量差异性不大。     

Microbial use of organic amendments in saline soils monitored by changes in the C/C ratio

An incubation experiment was carried out to investigate whether salinity at high pH has negative effects on microbial substrate use, i.e. the mineralization of the amendment to CO₂ and inorganic N and the incorporation of amendment C into microbial biomass C. In order to exploit natural differences in the ¹³C/¹²C ratio, substrate from two C₄ plants, i.e. highly decomposed and N-rich sugarcane filter cake and less decomposed N-poor maize leaf straw, were added to two alkaline Pakistani soils differing in salinity, which had previously been cultivated with C₃ plants. In soil 1, the additional CO₂ evolution was equivalent to 65% of the added amount in the maize straw treatment and to 35% in the filter cake treatment. In the more saline soil 2, the respective figures were 56% and 32%. The maize straw amendment led to an identical immobilization of approximately 48 μg N g⁻¹ soil over the 56-day incubation in both soils compared with the control soils. In the filter cake treatment, the amount of inorganic N immobilized was 8.5 μg N g⁻¹ higher in soil 1 than in soil 2 compared with the control soils. In the control treatment, the content of microbial biomass C₃-C in soil 1 was twice that in soil 2 throughout the incubation. This fraction declined by about 30% during the incubation in both soils. The two amendments replaced initially similar absolute amounts of the autochthonous microbial biomass C, i.e. 50% of the original microbial biomass C in soil 1 and almost 90% in soil 2. The highest contents of microbial biomass C₄-C were equivalent to 7% (filter cake) and 11% (maize straw) of the added C. In soil 2, the corresponding values were 14% lower. Increasing salinity had no direct negative effects on microbial substrate use in the present two soils. Consequently, the differences in soil microbial biomass contents are most likely caused indirectly by salinity-induced reduction in plant growth rather than directly by negative effects of salinity on soil microorganisms.     

脲酶/硝化抑制剂对土壤脲酶活性、有效态氮及春小麦产量的影响

通过田间随机区组试验,就缓释尿素对土壤脲酶活性,土壤有效态氮及小麦产量的影响进行了研究。本试验设置4个处理,1)普通尿素(U);2)U+脲酶抑制剂LNS(SRU1);3)SRU1+硝化抑制剂双氰胺(DCD)(SRU2);4)SRU1+硝化抑制剂3,5-二甲基吡唑(DMP)(SRU3)。结果表明,在整个春小麦(TriticumaestivumL.)生育期内,SRU1、SRU2和SRU3处理的土壤脲酶活性低于U处理,且SRU2、SRU3处理的土壤NH4+-N含量在较长时间内维持在较高水平;小麦成熟期,SRU1、SUR2和SRU3处理土壤有效态N含量显著高于U处理(p<0.05);SRU1、SRU2、SRU3处理小麦的生物学性状和产量略高于U处理,但是处理间没有显著差异。