龙眼果皮干燥前后挥发性化学成分的GC-MS分析

采用同时蒸馏萃取与GC-MS联用技术对龙眼(Dimocarpus longan Lour.)果皮干燥前后的挥发性化学成分进行分析和鉴定。鲜果皮中共鉴定出35种成分,相对含量前5位的有罗勒烯异构体混合物(35.44%)、3-甲基-2-丁烯-1-醇(26.14%)、ɑ-古芸烯(11.33%)、δ-榄香烯(4.54%)、角鲨烯(6.29%);干燥后果皮中共鉴定出34种成分,相对含量前5位的有ɑ-古芸烯(24.54%)、3-甲基-2-丁烯-1-醇(17.21%)、棕榈酸(8.07%)、罗勒烯异构体混合物(5.55%)、δ-榄香烯(4.15%)。龙眼果皮干燥前后共有成分有13种,但含量不同。独有成分新鲜组22种,干燥组21种。     

采用有限差分法计算阶梯轴的弯曲刚度

以轴的弯曲变形微分方程的基础;利用有限差分法推导出阶梯轴弯曲变形三对角线性方程组,建立了计算化轴挠曲线的数学模型,并通过计算机进行数值运算,为求解阶梯轴的弯曲刚度提供了快速、准确的计算方法。     

基于混合效应模型的杉木人工林蓄积联立方程系统

建立江西杉木人工林基于非线性混合效应方法的林分优势木平均高和断面积模型以及基于对数形式线性混合效应蓄积模型的联立方程组,利用验证数据与传统模型回归方法的模拟结果进行比较分析。结果表明,优势木平均高是联立方程组最基本的组成部分。通过考虑优势木平均高和林分断面积模型中参数的随机效应以及3个因变量间的相关性,则蓄积模型中参数的随机效应可以忽略。优势木平均高决定着林分断面积预测的准确性,而优势木平均高和林分断面积又是预测蓄积的主要误差来源。基于混合效应模型方法的模拟结果明显好于传统回归估计方法。进行预测时,通过解释联立方程组中因变量相互间的相关性,利用已被观测的变量能够提高未观测变量的估计精度。     

Structure of mixed Picea abies (L) Karst,and Betula pendula Roth and Betula pubescens Ehrh. stands in South and middle Sweden

Observed diameter distributions of forest stands are adapted to the Johnson S _b probability function. The stands investigated are untreated mixed stands of Norway spruce (Picea abies (L.) Karst.) and birch (Betula pendula Roth and Betula pubescens Ehrh.) aged between 20 and 32 years. The adaptation of the Johnson S_b probability function is made both on mixed spruce and birch, and on each species separately. Altogether 156 observations were tested with observed distributions against calculated distributions in the Kolmo‐gorov‐Smirnov test. The fractiles are predicted with multiple regression and two multivari‐ate techniques, simultaneous‐equation models (multivariate regression) and partial least squares with latent variables. The independent variables are characteristics of site and stand. Both multivariate methods predict diameter distribution well when tested.     

东北野生香薷挥发油香味成分分析及在卷烟中的应用

为研究东北野生香薷不同部位化学成分的差异及其挥发油对卷烟感官质量的影响,采用同时蒸馏萃取法分别提取东北野生香薷花（籽）、叶、茎中的挥发油,GC-MS技术分析并比较不同部位挥发性成分的差异。由峰面积归一化法分析可知,挥发油的主要成分是香薷酮、去氢香薷酮,它们在花中含量分别为19.93%,57.19%;叶中含量为20.39%,50.31%;茎中含量为18.02%,44.68%。将所得挥发油加入单料烟,对加料前后的卷烟进行感官质量评价,结果显示添加挥发油可提高烟气柔顺、细腻程度,并呈现出独特的清香气息。     

Farm Households' Simultaneous Use of Sources to Access Information on Cotton Crop Production

This study has investigated farm households' simultaneous use of social networks, field extension, traditional media, and modern information and communication technologies (ICTs) to access information on cotton crop production. The study was based on a field survey, conducted in Punjab, Pakistan. Data were collected from 399 cotton farm households using the multistage sampling technique. Important combinations of information sources were found in terms of their simultaneous use to access information. The study also examined the factors influencing the use of various available information sources. A multivariate probit model was used considering the correlation among the use of social networks, field extension, traditional media, and modern ICTs. The findings indicated the importance of different socioeconomic and institutional factors affecting farm households' use of available information sources on cotton production. Important policy conclusions are drawn based on findings.     

普洱茶香气成分的提取及其微胶囊化技术研究*

 主要分离鉴定普洱茶陈香味成分,并将其提取物微胶囊化,扩大其用途。提取采用常压水蒸汽蒸馏萃取法（SDE）对普洱茶香气成分进行提取,经气相色谱（GC）和气质联用色谱分析（GC/MS）鉴定,结果表明构成普洱茶的主要香气成分为：氧化芳樟醇Ⅰ（顺式呋喃型）、氧化芳樟醇Ⅱ（反式呋喃型）、2,2,6-三甲基-6-乙烯基四氢吡喃、1,2,3-三甲氧基苯等。同时,本实验以β-环糊精和魔芋胶为壁材对普洱茶香气成分进行微胶囊化;通过正交实验得到微胶囊化最佳包埋工艺为：普洱茶香气成分与壁材的比例为1∶6,β-环糊精与魔芋胶的比例为500∶1,固形物浓度为20%,干燥温度为25℃。     

蜡梅花挥发油成分的GC-MS分析

采用同时蒸馏萃取法提取蜡梅鲜花与干花中的挥发油,并利用毛细管气相色谱-质谱(GC-MS)联用仪对蜡梅鲜花与干花挥发油的成分进行定性和定量分析。结果表明:蜡梅鲜花与干花的挥发油提取率分别为0.57%、0.71%。从蜡梅鲜花挥发油中鉴定出45种化学物质,占挥发油色谱总峰面积的92.62%;从蜡梅干花中鉴定出41种化学物质,占挥发油色谱总峰面积的87.08%。蜡梅鲜花与干花挥发油的化学成分基本一致,主要成分为石竹烯、长叶烯、β-揽香烯、大叶香烯、茅苍术醇、α-愈创木烯。     

目标因子分析-UV分光光度法对混用除草剂组分的同时测定

采用目标因子分析技术并结合紫外吸收光谱,建立了一种对混用除草剂的各组分不经分离进行同时测定的方法。参照均匀设计表配制9组不同浓度组合的混合物标准液,在200~230 nm波段(间隔3 nm)测10个波长点,再在相同实验条件下测定未知样品的吸光度,将数据输入MATLAB目标因子分析程序,即可求得各组分含量。该方法对3种除草剂的回收率分别为氰草津99.30%~101.60%,异丙甲草胺97.97%~101.36%,莠去津97.30%~101.50%。3种除草剂回收率的标准偏差分别为氰草津1.06%、异丙甲草胺1.49%、莠去津1.88%,相对标准偏差 分别为氰草津1.05%、异丙甲草胺1.48%、莠去津1.89%。实验结果表明,目标因子分析方法对此类混用除草剂的同时测定具有较高的准确度和精密度。     

Biomass,stem basic density and expansion factor functions for five exotic conifers grown in Denmark

Adequate allometric equations are needed for estimating carbon pools of fast growing tree species in relation to international reporting of CO₂ emissions and for assessing their possible contribution to increasing forest biomass resources. We developed models for predicting biomass, stem basic density and expansion factors of stem to above-ground biomass for five fast growing conifers. Data included destructive measurements of 236 trees from 14 sites, covering a wide range of growth conditions. To ensure model efficiency, models for predicting stem, crown and total above-ground biomass for the five species were estimated simultaneously using a linear, mixed effects model that allowed contemporaneous correlations between the different tree components. Models differed among species and included dbh and tree height. The models explained more than 98% of the variation in above-ground biomass and reflected differences in the allometry between tree species. Stem density differed among species but generally declined with increasing site index and dbh. The overall model for predicting stem basic density included dbh, H₁₀₀ and site index and explained 66% of the total variation. Expansion factors decreased from 1.8–2.0 in small trees (dbh < 10 cm) to 1.1–1.2 for large trees (dbh > 25 cm), but differed among species. The overall model explained 86% of the variation and included quadratic mean diameter and dbh.