龙竹竹材纵向气体渗透性测定

参照木材流体渗透特性相关理论和研究方法,对大型丛生竹种———龙竹竹材的纵向气体渗透性进行了测定和分析,结果表明预处理方法和含水率对竹材纵向渗透性有显著影响。预处理可提高竹材气体渗透性,水煮预处理试件的渗透性优于汽蒸预处理试件的渗透性;随竹材试件含水率降低,竹材纵向气体渗透性增加。这些结论可为竹材防霉处理、染色处理、防火处理等改性处理提供有益的参考。     

毛细管气相色谱法测定天然冰片遗留物中右旋龙脑的含量

采用气相色谱方法HP-5规格(30m×0.32mm0.25μm)石英弹性毛细管柱,进样口温度200℃、氢火焰检测器(FID)220℃、程序升温,初始温度70℃,以3℃/min升到120℃,保持5min,在此色谱条件下,右旋龙脑峰与其他峰能有效分离。经重复试验,测得遗留物中的右旋龙脑在67%～70%。     

升高气温对旱柳光合和生长的影响

工业革命以来 ,大气ＣＯ2 含量增加了 30 % ,预计到 2 1世纪中叶大气ＣＯ2 含量将增加 1倍。与此同时 ,ＣＨ4、Ｎ2 Ｏ、ＣＦＣｓ等温室气体的排放也不断增加 (Ｖｉｔｏｕｓｅｋ ,1 994)。这些温室气体含量的增加必将导致全球性气候变化 (Ｖｉｔｏｕｓｅｋ ,1 994;Ｍｃｌｅｏｄｅｔａｌ.,1 999)。根据大气环流模型 (ｇｅｎｅｒａｌｃｉｒｃｕｌａｔｉｏｎｍｏｄｅｌｓ,ＧＣＭｓ)的预测 ,2 1世纪全球气温将可能平均升高 1 5～ 4 5℃ (Ｈｏｕｇｈｔｏｎｅｔａｌ.,1 996)。在 1 95 1～ 1 989年的约 40ａ间 ,中国半干旱区的平均气温升高了 0 5…     

城市燃气置换期内天然气利用对策

天然气是一种清洁、经济、高效的能源。2006年，天然气进入了广东。作为目前最清洁的一次能源，天然气的到来，为整个广东的能源结构带来了改变。本文介绍天然气的特性及优点，简要回顾广州市天然气利用工程的历程，简述广州市天然气置换工程概况，评述在广州城市燃气管网置换期内天然气的利用对策。     

干燥方式对九制陈皮挥发性风味物质的影响

[目的]香气是衡量食品品质的重要评价指标之一.九制陈皮以其独特的香气而闻名,比较不同干燥方式对九制陈皮香气的影响.[方法]采用气相离子迁移谱(Gas Chromatography-Ion Mobility Spectroscopy,GC-IMS)对烘干与晒干两种干燥方式九制陈皮的挥发性风味化合物进行比较分析,根据其特征...     

Effects of different ventilation strategies on gas exchange and extravascular lung water during early stage of acute lung injury in a canine model

AIM: To evaluate the effects of different ventilation strategies on gas exchange and extravascular lung water during early stage of acute lung injury (ALI). METHODS: Upon the establishment of oleic acid-induced ALI (diagnostic standard: PaO₂/FiO₂ ≤ 300 mmHg), 24 adult mongrel dogs were randomly divided into 3 groups (n=8 each) according to different ventilation strategies: controlling high-concentration oxygen therapy (O₂) group, continuous positive airway pressure (CPAP) group and bi-level positive airway pressure (BiPAP) group. The parameters of gas exchange and hemodynamics including the values of normal baseline, at ALI early stage (positive control) and from 1 to 4 h after treatment were recorded continuously. RESULTS: Compared with the value at the beginning of ALI, after 4 h of artificial ventilation, the improvement in oxygenation index (PaO₂/FiO₂) in BiPAP group (375.83±81.55, P<0.01) and CPAP group (327.17±78.82, P<0.01) were better than that in O₂ group (255.00±49.85, P>0.05). The ratio of alveolar dead space to tidal volume [V_D(alv)/V_T]in O₂ group further increased (P<0.01), while it obviously declined in CPAP group and BiPAP group (P<0.01). Oxygen delivery (DO₂) in BiPAP group (P<0.01) was much higher than that in CPAP group and O₂ group, while oxygen consumption (VO₂) and oxygen extraction rate (O₂ER) in O₂ group were evidently higher than those in CPAP group and BiPAP group (P<0.05, P<0.01). After treatment, the alveolar-arterial oxygen differences [P_(A-a)O₂] of the 3 ventilation groups were significantly higher than the normal baseline values and the values at early ALI stage (P<0.01). BiPAP and CPAP greatly reduced the ratio of shunted blood to total perfusion (Qs/Qt) as compared with O₂ group (P<0.01). Some parameters including pulmonary arterial wedge pressure (PAWP) and index of cardiac output (CI) kept stable, while mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) further increased in CPAP group and BiPAP group (P<0.05,P<0.01). Three ventilation strategies did not effectively control the increase in extravascular lung water index (ELWI). CONCLUSION: During early stage of ALI, BiPAP and CPAP make active effects on improving gas exchange and tissue oxygenation. BiPAP displays more significant therapeutic effect than CPAP and oxygen therapy. The 3 ventilation strategies have no obvious effects on reducing extravascular lung water.     

固相萃取-气相色谱法检测烟叶中18种有机氯类杀虫剂残留

[目的]建立固相萃取-气相色谱法检测烟草中18种有机氯类杀虫剂多残留检测分析方法。[方法]烟草样品经正己烷超声提取、Florisil固相萃取柱净化后,用气相色谱电子捕获检测器(ECD)进行有机氯类杀虫剂残留检测。[结果]在0.05～0.50μg/g浓度范围内,18种有机氯类杀虫剂的线性关系良好,回收率在81.82%～101.50%,相对标准偏差为1.95%～4.56%(n=6),检测限均为0.01μg/g。[结论]该方法灵敏、快速、简便,适用于烟叶中有机氯类杀虫剂多残留分析。     

罗勒子挥发油成分及抗氧化活性分析

[目的]研究新疆和田罗勒子挥发油的化学成分和抗氧化活性。[方法]采用挥发油提取器对罗勒子挥发油进行提取,用GC-MS联用仪进行测定,并结合计算机检索技术对分离的化合物进行鉴定,应用色谱峰面积归一化法计算各成分的相对含量,并通过研究罗勒子提取物的清除DPPH.自由基能力来探索其抗氧化活性。[结果]共分离出65种成分,确认了其中的60种成分,占挥发油总成分的92.59%。其中主要成分为亚麻油酸(13.83%)、正棕榈酸(13.80%)、长叶薄荷酮(8.31%)和反式斯巴醇(6.72%)等;利用水蒸气蒸馏所提取的新疆和田产罗勒子中的挥发油具有较好的清除DPPH.自由基的作用。[结论]新疆和田产罗勒子挥发油中醇、酮类化合物含量较多,酸、烯类化合物次之,且其挥发油具有一定清除DPPH.自由基能力。     

石韦浸膏动态逆流提取及其在卷烟中的应用研究

采用正交设计试验优化石韦的动态逆流提取工艺,利用气相色谱-质谱联用技术对提取物进行分析,测定其百分含量。确定石韦动态逆流提取的最佳工艺条件是提取溶剂为50%乙醇、原料溶剂质量比1∶12、提取温度75℃、提取时间为2 h;此工艺条件的浸膏得率为16.7%。气相色谱-质谱联用技术共鉴定出74种成分,其中主要成分为3-甲氧基苯甲醛、苯酚、4-乙烯基-2-甲基-苯酚、异芒果苷、7,3,4-三甲基-榭皮黄酮、木樨草素等,它们的总含量为67.59%。通过卷烟加香试验发现,石韦浸膏具有明显增加烟气甜润度、协调香气、细腻烟气、干净口腔等功效。