基于少模长周期光纤叠栅的模式转换器

本文提出一种在同一段少模光纤上写入两个不同周期Λ1和Λ2的长周期光纤光栅构成叠栅的方法,实现了纤芯基模LP_(01)向高阶纤芯模LP_(11)模式转换的宽带宽的新型的全光纤模式转换器.利用有限元法和耦合模理论建立了模式转换器的理论分析模型.数值仿真分析了叠栅中两个子光栅周期间隔、光栅长度、耦合系数等光栅参数对模式转换器的影响.仿真分析和实验结果表明,通过改变两个子光栅的周期间隔来改变两个损耗峰的位置,形成一个损耗峰,从而可以实现宽带宽的模式转换器,其10dB带宽约是单栅的2倍.与传统的模式转换器相比,该转换器带宽宽、转换效率高,尺寸小、抗干扰能力强,可以在模分复用系统和光通信中得到广泛的应用.     

柑橘叶片叶绿素含量拉曼光谱定量分析方法研究

柑橘叶片叶绿素含量的准确检测对柑橘营养状况和生长态势具有极其重要的意义。研究了快速无损诊断柑橘叶片中叶绿素含量的方法,以期为拉曼光谱检测技术用于柑橘叶片叶绿素含量检测提供参考。采集不同冠层高度和不同地理分布的柑橘叶片120片,拭去叶片表面的灰尘,用去离子水对其清洗、晾干装入密封袋中并用标签分类标注。然后对柑橘叶片进行拉曼光谱采集,参数设置如下：分辨率为3 cm-1,积分时间为15 s;激光功率为50 mW。分别采用BaselineWavelet、迭代限制最小二乘（IRLS）和不对称最小二乘(ALS)三种算法对柑橘叶片的拉曼光谱背景进行扣除,使用偏最小二乘（PLS）方法建立定量模型;四种光谱预处理方法归一化(Normalization),Savitzky-Golay卷积平滑(SG smoothing, SG平滑)、多元散射校正(MSC)和Savitzky-Golay一阶导数(SG 1st Der)对扣除背景后的光谱进行进一步的优化处理。结果表明：采用原始光谱、BaselineWavelet、IRLS、ALS背景扣除处理后的光谱建立PLS模型,模型的相关系数r分别为0.858,0.828,0.885和0.862,交互验证均方根误差(RMSECV)分别为5.392,5.870,4.934和5.336,最佳因子数分别为8,3,8和8;IRLS背景扣除处理后的PLS模型的RMSECV最小,相关系数最高,建模效果最好。分别采用SG平滑、归一化、MSC和SG 1st Der预处理方法对IRLS背景扣除后光谱进行预处理并建立PLS模型,结果表明：IRLS光谱及其结合SG平滑、归一化、MSC和SG 1st Der四种预处理方法的PLS模型的R分别为0.885,0.897,0.852,0.863和0.888,RMSECV分别为4.934,4.715,5.595,5.182和4.962;最佳因子数分别为8,8,8,8和5;IRLS-SG平滑后PLS模型的RMSECV最小,模型效果最优。对IRLS-SG平滑预处理后的PLS模型展开验证,预测相关系数r为0.844,预测均方根误差(RMSEP)为5.29,预测精确度较高。采用拉曼光谱结合三种光谱背景扣除方法和四种预处理方法对柑橘叶片叶绿素含量进行定量分析表明：采用IRLS背景扣除结合SG平滑预处理后的PLS模型最优,建模集r为0.897,RMSECV为4.715;预测集r为0.844,RMSEP为5.29,预测精度较高。拉曼光谱结合背景扣除方法可以为柑橘叶片叶绿素含量的定量分析提供一种快速简便的分析方法。     

Two new 2-arylbenzofurnan derivatives from the leaves of Morus alba

Two new 2-arylbenzofuran derivatives, moracinfurol A and B (1–2), and ten known compounds (3–12) were isolated from the leaves of Morus alba. Their structures were determined on the basis of spectroscopic analysis including 1D, 2D NMR and HR-ESI-MS. All of the 2-arylbenzofuran derivatives were evaluated for cytotoxicity against A549 cells. Some cytotoxic 2-arylbenzofuran derivatives might induce autophagy characterized by the accumulation of LC-3 Ⅱ.     

Random Sequential Adsorption: Relationship to Dead Leaves and Characterization of Variability

A new construction for the planar unbounded random sequential adsorption (RSA) model is presented, which allows for a direct comparison with Matheron's dead leaves model. Furthermore, for the case of disks with random radii the problem of statistical determination of the proposal radius distribution is discussed. Finally, second order characteristics related to the pair correlation function are suggested for describing the variability of the RSA disk systems.     

Statistical mixture design--principal component optimization for selective compound extraction from plant material

A simplex centroid design is used to optimize solvent mixtures for selective extraction of compounds from Erythrina speciosa Andrews leaves. Three main groups of compounds characterized by chromatographic retention times of 1.7, 3.1, and 6.6 min were extracted. The chromatographic peak heights registered at 1407 equally spaced times for each design extract were converted into principal components (PCs). Three PCs account for 89.1% of the data variance and have important loading values at the above retention times. Quadratic mixture models were found to adequately describe the response surfaces of their PC score values. Maximizing the first PC scores while minimizing the second and third ones results in an optimum 83% dichloromethane-17% acetone mixture that selectively extracts the group of compounds with retention times around 3.1 min. Maximizing the second PC scores and minimizing the third PC scores leads to a 78% hexane-22% acetone mixture adequate for extracting the 6.6 min retention time compounds as well as other compounds with high retention times. The 1.7 min group of compounds is most efficiently extracted on maximizing the third PC that results in a 50% ethanol-50% acetone mixture. The Derringer-Suich algorithm confirmed the determination of these optimized mixtures.     

直观推导式演进特征投影算法-气相色谱-质谱联用测定烟叶中挥发性组分

应用气相色谱-质谱法及直观推导式演进特征投影(HELP)算法测定了烟叶中的挥发性组分.取经干燥及粉碎的烟叶样品用加速溶剂萃取法在160℃用乙醇提取15 min,所得提取液经吹氮蒸缩至1.5 mL,取1μL进样分析,采用DB-5MS毛细管柱进行分离.质谱分析采用电子轰击离子源,在质荷比(m/z)30～500范围内进行扫描...     

超声强化超临界CO2萃取樟树叶精油的研究

采用超声波强化超临界CO2萃取樟树叶精油,并采用正交实验对萃取工艺进行了优化.研究结果表明:当萃取压力为16MPa、温度为50℃、时间为80min、CO2流量为16kg/h、超声波功率为240W、超声波频率为20KHz时,能获得比较好的效果,精油的平均提取率可达1.92％.GC-MS的分析结果表明:樟树叶精油中樟脑+β...     

Fatty acid neutral losses observed in tandem mass spectrometry with collision‐induced dissociation allows regiochemical assignment of sulfoquinovosyl‐diacylglycerols

A full characterization of sulfoquinovosyldiacylglycerols (SQDGs) in the lipid extract of spinach leaves has been achieved using liquid chromatography/electrospray ionization‐linear quadrupole ion trap mass spectrometry (MS). Low‐energy collision‐induced dissociation tandem MS (MS/MS) of the deprotonated species [M ? H]^? was exploited for a detailed study of sulfolipid fragmentation. Losses of neutral fatty acids from the acyl side chains (i.e. [M ? H ? RCOOH]^?) were found to prevail over ketene losses ([M ? H ? R'CHCO]^?) or carboxylates of long‐chain fatty acids ([RCOO]^?), as expected for gas‐phase acidity of SQDG ions. A new concerted mechanism for RCOOH elimination, based on a charge‐remote fragmentation, is proposed. The preferential loss of a fatty acids molecule from the sn‐1 position (i.e. [M ? H ? R₁COOH]^?) of the glycerol backbone, most likely due to kinetic control of the gas‐phase fragmentation process, was exploited for the regiochemical assignment of the investigated sulfolipids. As a result, 24 SQDGs were detected and identified in the lipid extract of spinach leaves, their number and variety being unprecedented in the field of plant sulfolipids. Moreover, the prevailing presence of a palmitic acyl chain (16:0) on the glycerol sn‐2 position of spinach SQDGs suggests a prokaryotic or chloroplastic path as the main route for their biosynthesis. Copyright © 2013 John Wiley & Sons, Ltd.     

桑叶HILIC特征指纹图谱研究

应用亲水色谱法(HILIC)建立了桑叶药材的指纹图谱,并对10批桑叶样品进行分析,为桑叶药材的真伪鉴别及质量控制提供了新方法。采用HILIC XBridgeTMAmide色谱柱,以乙腈-水(含0.2%甲酸、20mmol/L甲酸铵、20%甲醇)为流动相,梯度洗脱,流速为0.8 mL/min,柱温为25℃,检测波长为322 nm,进样量为20μL。该方法具有良好的精密度、重现性和稳定性,检测的10批桑叶指纹图谱有17个共有峰,4个特征峰,采用ESI-TOF/MS对4个特征峰进行了指认,结合相似度分析可以用于不同产区桑叶药材的鉴别。桑叶HILIC指纹图谱有望成为桑叶药材真伪鉴别及质量控制的有力工具。