脂肪酸甲酯生物柴油改善低硫柴油的润滑性能

生物柴油可作为改善低硫柴油润滑性能的天然添加剂。该文将豆蔻酸甲酯(C14:0)、棕榈酸甲酯(C16:0)、硬脂酸甲酯(C18:0)、油酸甲酯(C18:1)、亚油酸甲酯(C18:2)、亚麻酸甲酯(C18:3)、蓖麻醇酸甲酯(C18:1 OH)及蓖麻油甲酯和餐饮废油甲酯按照0.5%、1.0%、1.5%和3.0%的体积分数添加到低硫柴油中,在高频往复试验机(high-frequency reciprocating rig,HFRR)上进行润滑性能测试,探究脂肪酸甲酯的碳链长度、不饱和度及含羟基等结构特征对润滑性能的影响。结果表明,长碳链脂肪酸甲酯一般比短链润滑效果好;碳链长度为十八的脂肪酸酯中,不饱和程度即碳碳双键数目越高则润滑性能越好;而在相同碳链长度和不饱和度条件下,含羟基的蓖麻醇酸甲酯的润滑改善效果优于油酸甲酯。由多种脂肪酸酯构成的混合物生物柴油的润滑性能要优于某单一的纯脂肪酸甲酯。在低硫柴油中,当某饱和脂肪酸甲酯的体积分数比例达3.0%时,或不饱和酯的体积分数达到1.5%时,或生物柴油的体积分数达1.0%时,可使低硫柴油的润滑性能指标满足相关标准。研究脂肪酸甲酯的各种结构特征对其润滑性能的影响及作用机制,有助于筛选合适的生物柴油组分及其添加浓度作为低硫柴油的润滑添加剂。     

Allelopathic potential and an allelopathic substance in mango leaves

The present study was aimed to determine the allelopathic potential of mango (Mangifera indica L.) leaves and to identify allelopathic substances in the leaves. The aqueous methanol extracts of mango leaves inhibited seedling growth of garden cress, radish, rapeseed, foxtail fescue and crabgrass, and the inhibitory effects increased with the increasing extract concentration, suggesting that mango leaves may contain allelopathic substances. The extract was then purified by several chromatographic runs through a bioassay-directed fractionation, and an growth inhibitory substance was isolated and identified by spectral data as methyl-3,4,5-trihydroxybenzoate (methyl gallate). Methyl gallate at the concentration of 10 mM inhibited 98.6% and 99.8% of root and shoot growth of garden cress relative to the control, respectively, and 94.4% and 49.3% of those of foxtail fescue, respectively. The concentrations of methyl gallate required for 50% growth inhibition (I₅₀) on garden cress roots and shoots were 3.9 and 3.3 mM, and those on foxtail fescue roots and shoots were 1.5 and 9.5 mM, respectively. It is the first report of an allelopathic substance in mango leaves and allelopathic activity of methyl gallate. Therefore, the mango leaves may have potential as a soil additive material for the weed management options.     

基于模糊数学法评价甲基溴及其替代技术

为履行《关于消耗臭氧层物质的蒙特利尔议定书》规定,运用模糊数学综合评判法,探讨了甲基溴及其替代技术在土壤熏蒸过程中的各项因素,构建了作物产量、作物品质、病虫害防治效果、技术安全、操作过程、环境影响、应用时长和投入成本8个指标集,并划分了模糊评判集,综合评估了生姜、草莓作物甲基溴及其替代技术。生姜作物综合评估结果为甲基溴(83.61)氯化苦(79.06)棉隆(78.03)威百亩(69.07),草莓作物综合评估结果为甲基溴(69.13)氯化苦(64.60)棉隆(56.80)。各单项指标评价结果表明,甲基溴在作物产量、作物品质、防治效果以及应用时长等4个指标上均高于各项替代技术,但由于自身毒性、对臭氧层物质消耗以及受生产管控等因素的影响,在其余指标上低于替代技术;氯化苦在作物产量、作物品质和病虫害防治效果等6项指标上均高于其他替代技术,但由于为剧毒农药,而在技术安全和操作过程2项指标上低于其余替代技术。以上结果表明,生姜作物和草莓作物主流替代技术的消毒效果并不具备甲基溴的广谱性,当前最佳替代技术为氯化苦。     

四川四倍体小麦地方品种酯酶同工酶

对30份产于四川的四倍体小麦地方品种(T.TurgidumL.)的酯酶同工酶分析表明,四倍体小麦的幼苗、剑叶和幼穗间酯酶同工酶存在较大差异。其中,幼苗有14条带,12种类型;剑叶15条带,13种类型;幼穗13条带,11种类型。3次测定合并分析,则产生21种类型。若仅以1次测定看,多样性指数以剑叶最高,为0 1119,说明剑叶酯酶同工酶能更好地反映其遗传多样性。同时酯酶同工酶的差异证明,来源相同又同名但原始编号不同的两份"棒棒南麦"和两份"早佐"具有不同的基因型,应视为不同的品种。     

宝收75%干悬浮剂在大豆和土壤中的残留动态研究

应用高效液相色谱,对宝收75%干悬浮剂在大豆及土壤中的残留动态进行了试验测定,结果表明,宝收(噻吩磺隆)在大豆植株中的半衰期为3.8～4.1 d,在土壤中的半衰期为4.3～4.8 d;大豆和土壤中的最终残留量均为未检出。以此制订宝收的合理使用准则:按推荐剂量26.7～33.3 g/hm2土壤喷雾使用1次。     

Enzyme activities and microbial community structure in semiarid agricultural soils

This study investigated the effect of management on -glucosidase, -glucosaminidase, alkaline phosphatase, and arylsulfatase activities and the microbial community structure in semiarid soils from West Texas, USA. Surface samples (0–5 cm) were taken from a fine sandy loam, sandy clay loam, and loam that were under continuous cotton ( Gossypium hirsutum L.) or in cotton rotated with peanut ( Arachis hypogaea L.), sorghum ( Sorghum bicolor L.), rye ( Secale cereale) or wheat ( Triticum aestivum L.), and had different water management (irrigated or dryland), and tillage (conservation or conventional). The enzyme activities were higher in the loam and sandy clay loam than in the fine sandy loam. Soil pH was not affected by management, but the soil organic C and total N contents were generally affected by the different crop rotations and tillage practices studied. The trends of the enzyme activities as affected by management depended on the soil, but in general crop rotations and conservation tillage increased the enzyme activities in comparison to continuous cotton and conventional tillage. The soil enzyme activities were significantly correlated with the soil organic C ( r -values up to 0.90, P< 0.001), and were correlated among each other ( r -values up to 0.90, P <0.001). There were differences in the fatty acid methyl ester profiles between the fine sandy loam and the sandy clay loam and loam, and they reflected the differences in the enzyme activities found among the soils. For example, a 15:0 ranged from 1.61±0.25% in cotton-peanut/irrigated/no-till in the fine sandy loam to 3.86±0.48% in cotton-sorghum/dryland/conservation tillage in the sandy clay loam. There were no differences due to management within the same soil.Trade names and company names are included for the benefit of the reader and do not infer any endorsement or preferential treatment of the product by USDA-ARS     

水杨酸甲酯诱抗黑杨对杨扇舟蛾生长发育的影响

为了进一步探讨木本植物的诱导抗性对昆虫生长发育的影响并了解诱导抗性的作用机理,作者于2003年在北京林业大学采用生物测定的方法,研究了水杨酸甲酯熏蒸24 h后的黑杨对杨扇舟蛾生长发育的影响.结果表明,水杨酸甲酯熏蒸能够诱导黑杨启动防御系统产生诱导抗性,取其叶片喂食的杨扇舟蛾生长发育受阻,表现为体重减轻,营养代谢能力明显下降.证明降低昆虫体重及营养代谢能力是诱导抗性的生理机制之一.      

脂肪酶和酯酶指纹分析在嗜酸耐热菌快速鉴定中的应用

【目的】采用反相高效液相色谱建立嗜酸耐热菌的脂肪酶和酯酶指纹图谱,为建立基于脂肪酶和酯酶指纹分析的嗜酸耐热菌快速鉴定方法提供参考。【方法】将5个脂肪酶和酯酶底物直接与嗜酸耐热菌反应,通过反相高效液相色谱检测得到了9株嗜酸耐热菌的脂肪酶和酯酶指纹色谱图,并对色谱数据进行系统聚类分析。【结果】所得脂肪酶和酯酶指纹图谱能将脂环酸芽孢杆菌和芽孢杆菌明显分为2个类群,且同一属的2个不同种的细菌也能得到正确归类。【结论】脂肪酶和酯酶指纹分析能够用于嗜酸耐热菌的快速鉴别,且简便快速、重现性好、经济成本低,具有广阔的应用前景。     

W/O微乳液体系中SA和MS清除·O_2~-的研究

以水溶液体系作为对照,利用分光光度法研究了W/O型微乳液体系中水杨酸（SA）和水杨酸甲酯（MS）清除超氧阴离子自由基（·O2-）的性能.结果发现,在水浴时间为20min、pH值为8.20和邻苯三酚加入量适宜的情况下,W/O微乳液体系中SA、MS对·O2-的清除率分别可达72.92%、81.47%.微小的pH值变化会引起邻苯三酚自氧化速率的显著变化,电解质溶液对其也有明显的影响,但对SA、MS清除·O2-的能力影响不大.     

Inhibition of juvenile hormone biosynthesis and methyl farnesoate epoxidase activity by 1,5-disubstituted imidazoles in the cockroach,Diploptera punctata

Seventeen substituted imidazoles were tested as inhibitors of juvenile hormone (JH) III synthesis by cockroach corpora allata in an in-vitro radio-chemical assay. Most of these 1,5-disubstituted imidazoles were highly potent, with IC₅₀ values of less than 100nM. The compounds differed in their ability to cause an accumulation of the precursor methyl farnesoate in the glands. Four of the imidazoles were tested by topical application to previtellogenic adult females, and all caused a significant inhibition of JH synthesis and an accumulation of intraglandular methyl farnesoate for at least three days after treatment. Methyl farnesoate epoxidase activity of homogenates of corpora allata was inhibited by the compounds TH -14 and TH -27. This P450-dependent epoxidase activity was inhibited at less than 10 nM. The results show that the 1,5-disubstituted imidazoles are powerful inhibitors of the last step of juvenile synthesis in this cockroach.