紫外光谱法对维生素E油酸酯、维生素E与油酸的同时测定

建立了混合体系中维生素E、油酸和维生素E油酸酯同时测定的方法,用光纤光谱仪获取混合体系紫外-可见透射光谱.实验按均匀设计建立校正集和预测集,在255 ～315 nm波段采用偏最小二乘法建立了同时定量测定该3组分的校正模型,并用间隔区间偏最小二乘法(iPLS)通过优选建模区间改进油酸的预测模型.采用iPLS能够显著提高模型准确度,尤其对光谱弱响应的物质,最大相对误差从PLS直接建模的54.7%降至iPLS的8.98%,建立的模型可满足动力学研究的原位分析需要.     

区间偏最小二乘结合差分进化算法应用于鱼粉近红外光谱波长筛选

蛋白质含量是评价鱼粉质量的重要指标,该文采用近红外(NIR)光谱分析技术结合特征筛选方法建立了鱼粉蛋白质含量的快速定量分析模型,并结合区间偏最小二乘(iPLS)和二进制变异策略的差分进化(DE)算法建立了区间偏最小二乘差分进化(iPLS-DE)的波长筛选优化模式,对鱼粉NIR光谱数据进行特征波长筛选。iPLS-DE通过调试iPLS中等分子区间的数量,优选出9个最优特征波段,再采用二进制变异策略的DE算法在最优特征波段内筛选离散特征波长组合,最后根据模型的评价指标确定iPLS-DE优选模型并与iPLS优选模型进行比较。结果表明,将鱼粉全谱等分为5个子区间时,iPLS-DE筛选出50个离散特征波长建立的优选模型对测试集样品的预测均方根误差和相对分析误差分别为1.033%和4.058,而iPLS优选模型对测试集样品的预测均方根误差和相对分析误差分别为1.131%和3.855。表明iPLS-DE方法能够有效地提高NIR光谱分析模型对鱼粉蛋白质定量检测的预测能力。     

拉曼光谱结合后向间隔偏最小二乘法用于调和汽油辛烷值定量分析

采用后向间隔偏最小二乘(Backward interval partial least squares,BiPLS)提取汽油拉曼光谱特征谱段,并用于研究法辛烷值(Research octane number,RON)的定量分析。实验中首先使用SPXY(Sample set partitioning based on joint x-y distances)方法划分训练集、交叉验证集和测试集,并采用稳健回归方法剔除异常的样本数据,再结合BiPLS方法筛选特征谱段,利用特征谱段建立偏最小二乘模型。与全谱段偏最小二乘模型的预测性能对比结果表明,后向间隔偏最小二乘方法可使输入模型的特征数据维数降低50.00%,交叉验证均方根误差(Root mean square error of cross validation,RMSECV)降低18.92%,预测均方根误差(Root mean square error of prediction,RMSEP)降低13.86%。后向间隔偏最小二乘方法可有效提取汽油拉曼光谱的特征谱段,降低模型复杂度,同时提高模型预测精度,在调和汽油研究法辛烷值定量分析方面有较好的应用前景。     

激光诱导击穿光谱检测青菜中镉元素的多变量筛选研究

利用激光诱导击穿光谱(LIBS)技术与常规化学分析方法获取28个浓度梯度含Cd元素的青菜样品的LIBS谱线信息以及Cd含量信息.对获取的光谱信息结合标准归一化处理(SNV)、一阶导数(FD)、二阶导数(SD)、中心化处理(Center)作为偏最小二乘法(PLS)模型的优选方法;再根据4种预处理方法的预测结果选取最佳方法,同时将该方法作为间隔偏最小二乘法(iPLS)与联合区间间隔偏最小二乘法(SiPLS)优选青菜LIBS谱线的最佳波长区间.结果表明:通过SiPLS优选的特征波长区间分别为214.72 ～ 215.82 nm,215.88～ 216.97 nm,225.08 ～ 226.35 nm,并且经过中心化预处理后建立的验证模型效果最好,结果显示交叉验证均方根误差(RMSECV)为1.487,验证均方根误差(RMSEP)为1.094,相关系数(R)为0.9942,平均相对误差(ARE)为11.60％.研究结果表明,所选优化方法适合青菜中重金属Cd元素的LIBS校正模型的建立,且具有较好的预测效果.     

基于组合偏最小二乘的特征波段优选方法在氨、碱化处理玉米秸秆粗蛋白检测中的研究

该文构建了玉米秸秆粗蛋白定量分析模型,并对光谱特征波段选取方法进行探讨及验证。首先对107个样本进行预处理,剔除两个异常样本后采用DB2小波缺省阈值4层分解方式进行光谱重构,预处理后粗蛋白模型交互验证决定系数R2CV从0.788 9提高至0.920 8,采用间隔偏最小二乘(IPLS)及其改进型方法后向区间间隔偏最小二乘(BIPLS)、组合间隔偏最小二乘(SIPLS)进行特征波段选取,并对比主成分分析、竞争性自适应重加权采样法、相关系数法、遗传算法、移动窗口最小二乘等结果,发现基于IPLS及其改进型BIPLS、SIPLS均可有效、准确定位特征波段区间,其中采用SIPLS 30 波段间隔在10 128~10 398 cm-1与11 196~11 462 cm-1时具有最优模型,验证集相关系数(rp)为0.978 4,验正集决定系数(R2P)为0.957 2,验正集均方误差根(RMSEP)为0.221 1,相比于其他波段选取方法表现出较好的实时准确性,该方法可为玉米秸秆氨碱化最优条件判定提供重要的数据支撑。     

icPL-ANN近红外光谱分析方法在航空燃料中的应用研究

以航空燃料的闪点预测为例,针对数据分布分散不连续,与光谱信息的线性关联偏弱的情况,提出一种将波段间隔组合与线性-人工神经网络(icPLANN)相结合的近红外光谱定量分析方法。该方法利用分段建模考核进行波段优选,最大程度地提取了有效信息,并结合PL-ANN方法建立了近红外光谱定量分析模型。最终把预测结果与间隔组合偏最小二乘法(icPLS)的实验结果进行了对比。结果表明,间隔组合PL-ANN模型的校正标准偏差(SEC)为0.75,预测标准偏差(SEP)为0.86,而间隔组合偏最小二乘法SEC为1.48,SEP为1.08,因此前一种方法的预测精度更高,预测决定系数(Rp2)能达到0.8971。可见,针对分散不连续数据与近红外光谱的复共线性影响预测模型准确度和稳定性的问题,间隔组合PL-ANN方法是一种有效的近红外光谱定量方法。     

CARSiPLS用于烟煤中水分与挥发分的近红外光谱测定

将竞争自适应重加权采样(CARS)与区间偏最小二乘回归(iPLS)相结合的变量筛选建模方法 CARSiPLS,用于烟煤中水分与挥发分的近红外光谱测定。以CARS逐步筛选出每个区间与待测量相关的变量,建立烟煤中水分与挥发分近红外光谱测定的偏最小二乘回归模型。结果表明:与PLS、iPLS相比,CARSiPLS可以显著减少变量数,同时提高模型预测性能;挥发分建模变量从1557个减少至15个,水分建模变量从1557个减少至317个;挥发分、水分的预测平均绝对百分误差分别从0.031 5降至0.018 4、从0.188 4降至0.094 6;挥发分、水分的预测均方差分别从0.010 8降至0.006 7、从0.005 0降至0.002 8。     

CARSiPLS用于烟煤中水分与挥发分的近红外光谱测定北大核心CSCD

将竞争自适应重加权采样(CARS)与区间偏最小二乘回归(iPLS)相结合的变量筛选建模方法 CARSiPLS,用于烟煤中水分与挥发分的近红外光谱测定。以CARS逐步筛选出每个区间与待测量相关的变量,建立烟煤中水分与挥发分近红外光谱测定的偏最小二乘回归模型。结果表明:与PLS、iPLS相比,CARSiPLS可以显著减少变量数,同时提高模型预测性能;挥发分建模变量从1557个减少至15个,水分建模变量从1557个减少至317个;挥发分、水分的预测平均绝对百分误差分别从0.031 5降至0.018 4、从0.188 4降至0.094 6;挥发分、水分的预测均方差分别从0.010 8降至0.006 7、从0.005 0降至0.002 8。     

红外光声光谱技术结合区间、组合区间偏最小二乘测定油菜籽含氮量和含油量

应用红外光声光谱技术结合区间、组合区间偏最小二乘,建立了油菜籽含氮量和含油量的校正模型。结果表明,红外光声光谱技术可以应用于油菜籽品质的快速测定。相对于全谱偏最小二乘建模,区间、组合区间偏最小二乘的采用筛选出了含氮量和含油量的相关波段,使模型简化,并提高了模型预测精度。     

Bagging偏最小二乘和Boosting偏最小二乘算法的金银花醇沉过程近红外光谱定量模型预测能力研究

建立金银花醇沉过程中稳健的近红外光谱( Near infrared spectroscopy,NIR)定量模型,为金银花醇沉过程的快速评价提供方法。研究基于金银花醇沉过程绿原酸的 NIR 数据,通过建立 Bagging 偏最小二乘(Bagging-PLS)模型、Boosting偏最小二乘(Boosting-PLS)模型与偏最小二乘(Partial Least Squares,PLS)模型,实现对模型性能比较;在此基础上,采用组合间隔偏最小二乘法( Synergy interval partial least squares,siPLS)和竞争自适应抽样( Competitive adaptive reweighted sampling,CARS )法分别对光谱进行变量筛选,建立模型,实现了对模型预测性能的考察。实验结果表明, Bagging-PLS和Boosting-PLS(潜变量因子数设为10)的预测性能均优于 PLS 模型。在此基础上,两批样品采用 siPLS 筛选变量,第一个批次金银花筛选波段820~1029.5 nm和1030~1239.5 nm,第二个批次金银花醇沉筛选波段为820~959.5 nm和960~1099.5 nm;采用CARS方法变量筛选,两批样品分别选择5折交叉验证和10折交叉验证,取交叉验证均方根误差( RMSECV)值最小的子集作为最终变量筛选的结果。经过变量筛选的两批金银花醇沉过程中的绿原酸含量Bagging-PLS和Boosting-PLS模型的预测均方根误差(RMSEP)值降低了0.02~0.04 g/L,预测相关系数提高了4%~5%。综上,Baggning-PLS和Boosting-PLS算法可作为金银花醇沉过程NIR定量模型的快速预测方法。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.