油菜籽油分及脂肪酸同时测定的气相色谱快速方法

本文拟定了对菜籽油分与脂肪酸组分同时测定的气谱快速方法,基于使用氢氧化四甲铵为催化剂,酯交换在汽化室以热解方式进行,可使油分定量地转换成脂肪酸甲酯。甲酯总峰面积的大小,可作为含油量的量度,与外标作比较,求得菜籽的含油率;再对各脂肪酸甲酯的峰面积作归一化法处理,便可求得各脂肪酸的含量;与油重法和IUPAC庚烷法测定结果相比较,其相对误差分别为±3％和±3—10％,符合快速分析的要求。     

Towards an improved and more flexible representation of water stress in coupled photosynthesis-stomatal conductance models

Coupled photosynthesis-stomatal conductance (A-g_s) models are commonly used in ecosystem models to represent the exchange rate of CO₂ and H₂O between vegetation and the atmosphere. The ways these models account for water stress differ greatly among modelling schemes. This study provides insight into the impact of contrasting model configurations of water stress on the simulated leaf-level values of net photosynthesis (A), stomatal conductance (g_s), the functional relationship among them and their ratio, the intrinsic water use efficiency (A/g_s), as soil dries. A simple, yet versatile, normalized soil moisture dependent function was used to account for the effects of water stress on g_s, on mesophyll conductance (g_m) and on the biochemical capacity. Model output was compared to leaf-level values obtained from the literature. The sensitivity analyses emphasized the necessity to combine both stomatal and non-stomatal limitations of A in coupled A-g_s models to accurately capture the observed functional relationships A vs. g_s and A/g_svs. g_s in response to drought. Accounting for water stress in coupled A-g_s models by imposing either stomatal or biochemical limitations of A, as commonly practiced in most ecosystem models, failed to reproduce the observed functional relationship between key leaf gas exchange attributes. A quantitative limitation analysis revealed that the general pattern of C₃ photosynthetic response to water stress may be well represented in coupled A-g_s models by imposing the highest limitation strength to g_m, then to g_s and finally to the biochemical capacity.     

Effect of elevated carbon dioxide and water stress on gas exchange and water use efficiency in corn

CO₂ has been predicted to increase in the future, and thus leading to possible changes in precipitation patterns. The objectives of this study were to investigate water use and canopy level photosynthesis of corn plants, and to quantify water use efficiency in corn plants under two different CO₂ levels combined with four different water stress levels. Corn plants were planted in sunlit plant growth chambers and a day/night temperature of (28/18 °C) was applied. From 21 days after emergence (DAE), the eight treatments including two levels of carbon dioxide concentrations (400 and 800 μmol mol⁻¹) and four levels of water stress (well-watered control, “mild”, “moderate”, and “severe” water stress) treatments at each CO₂ level were imposed. Height, number of leaves, leaf lengths, and growth stages of corn plants were monitored from nine plants twice a week. Corn plants were separately collected, dried, and analyzed for the biomass accumulation at 21 and 60 DAE. Soil water contents were monitored by a time domain reflectometry (TDR) system (15 probes per chamber). The “breaking points” (changes from high to low rates of soil water uptake) were observed in the bottom of soil depth for the water stressed conditions, and the “breaking points” under ambient CO₂ appeared 6-9 days earlier than under elevated CO₂. Although approximately 20-49% less water was applied for the elevated CO₂ treatments than for ambient CO₂ from 21 DAE, higher soil water contents were recorded under elevated CO₂ than under ambient CO₂. However, corn growth variables such as height, leaf area, and biomass accumulation were not significantly different in CO₂ or water stressed treatments. This result may be explained by considering that significant differences in canopy level gross photosynthesis among the water stress treatments was observed only toward the end of the experiment. The higher soil water contents observed under elevated CO₂ resulted mainly from less water use than under ambient CO_2. WUE (above ground biomass per water use since 21 DAE) at the final harvest was consistently higher and varied with a smaller range under elevated CO₂ than under ambient CO₂. This study suggests that less water will be required for corn under high-CO₂ environment in the future than at present.     

西气东输管道工程与我国天然气工业发展

西气东输管道工程是一项世界级的宏大工程，该工程作为我国西部大开发标志性工程之一，不但有利于加快新疆以及我国西部地区经济的发展，促进我国能源结构的调整，有效治理大气污染，促进长江三角洲地区的经济快速发展，而且标志着我国天然气工业发展新时期的到来，极大地带动了整个天然气工业的全面发展，是一个非常重要而具有划时代意义的里程碑，从四个方面论述了西气东输管道工程对我国天然气工业发展的重要意义。     

乙草胺,喹禾灵的同柱气相色谱分析

采用气相色谱法,氢焰离子化检测器,选择２．５％ＳＰ２４０１／ｃｈｒｏｍｏｓｏｒｂ Ｗ－ＨＰ（８０￣１００目）色谱柱,以乙二酸二正辛酯为内标,在相同的气相色谱条件下,完成乙草胺、喹禾灵的有效成分定量分析。     

CO2体积分数倍增对4种植物幼苗气体交换及水分利用效率的影响

在CO2体积分数倍增的条件下,研究了油松(Pinus tabulaeformis)、侧柏(Platycladus orientalis)、元宝枫(Acer truncatum)和刺槐(Robinia pseudoacacia)叶片的气体交换及水分利用效率的变化。结果表明:CO2体积分数倍增条件下,4个树种的净光合速率均高于对照,油松、侧柏和元宝枫的日平均蒸腾速率分别较对照降低4.2%、17.5%和29.9%,其水分利用效率的日变化明显高于对照,分别提高25.6%、42.1%和52.2%。在CO2体积分数倍增条件下培养30、60和90d后,植物的水分利用效率明显提高,90d时油松、侧柏、刺槐和元宝枫分别为对照的224.9%、162.9%、154.3%和108.1%。     

Measurement of dough specific volume in chemically leavened dough systems

Gas production and gas retention properties of doughs are pivotal to the manufacture of bread of good quality, but these properties are rarely measured directly in fermenting dough due to a paucity of suitable instrumentation. A digital image analysis-based method was used to measure the dynamic specific volume (DSV) of various chemically leavened dough systems. Sodium bicarbonate (1.4–4.2 g per 100 g of flour) in combination with equivalent neutralizing amounts of the leavening acidulants glucono-delta-lactone, potassium acid tartrate, adipic acid or sodium acid pyrophosphate consistently increased the specific volume of bread dough so that void fractions in the dough spanned between 5 and 67% at ordinary fermentation temperatures. The relationship between the specific volume of dough at the end of fermentation and the actual gas evolved (measured independently) was essentially linear and was characterized by a slope that provided a good index of the actual gas-trapping properties of dough. Therefore, the use of the DSV technique in conjunction with chemical leaveners offers the possibility of obtaining quantitative, real time information on the gassing capacity of the leavening system and the gas-holding capacity of the dough.     

中缅天然气管道高陡边坡管段清管安全分析

中缅天然气管道某80°高陡边坡管段在进行清管作业时,清管器极易对管底弯头造成巨大冲击,可能引发天然气泄漏等灾难性后果.利用OLGA软件获得该边坡管段的清管器运行压力、运行速度及持液率等工艺参数,利用ANSYS与CAESARII有限元软件,建立清管过程中的应力与位移模型并进行有限元分析,进而提出安全清管建议.结果 表明:...     

气相色谱/质谱(GC/MS)测定蔬菜中甲基对硫磷农药和呋喃丹的优化

利用气相色谱/质谱(GC/MS)同时测定及确定蔬菜中甲基对硫磷农药和克百威(呋喃丹)的残留量。研究了振荡提取时间、提取剂用量、盐加入量、浓缩条件等操作条件对分析方法的影响。得到的优化分析条件如下:振荡提取时间为90 min、提取剂用量为70 mL、盐加入量为3 g、浓缩条件为温度50℃低压0.09 atm;该方法的相对标准偏差<10%,样品的加标回收率为甲基对硫磷82.5%、克百威为93.5%。本方法可以满足这2种杀虫剂在蔬菜中的检测要求。