Fragmentation patterns of newly isolated cassane butenolide diterpenes and differentiation of stereoisomer by tandem mass spectrometry

Different stereoisomers of active molecules often cause different physiological responses and hence pose a challenge for their identification. This study involves perceptive fragmentation behavior of newly isolated cassane butenolides, caesalpinolide A [1] and caesalpinolide B [2] (epimeric at the hemiketal position) by tandem MS. The electrospray ionization-mass spectrometry (ESI-MS)/collision-induced dissociation (CID; ESI-MS(2) and ESI-IT-MS(n)) were investigated. The effect of orientations of hemiketal hydroxyl at C-12 was clearly observed in the mass spectrum. Tandem mass spectra of 1, 1(A) or 2, 2(A) show stereospecific fragmentation resulting in significant abundance dissimilarity of [MH - H(2)O](+) as well as differences in fragmentation pathway. Both of these pathways seem to be influenced by the stereochemistry of the molecule. The differentiation can be clearly visualized from the [M + H - H(2)O](+)/[M + H](+) ratio of the two isomers where beta-isomer 2 was found to be five times higher than that of alpha-isomer 1 in full scan liquid chromatography-electrospray ionization mass spectrometry(LC-ESI-MS). In high-energy CID, the mass fingerprint of 1, 2, 1(A), and 2(A) was found to be different from one another.     

全息光盘存储器的数据存取与像素匹配

全息光盘存储(HDS)技术作为一种非常具有潜力的新型信息存储技术, 是下一代光盘发展的目标。在全息光盘存储系统中, 为了实现数据精确快速地写入和读出, 降低误码率, 需要在整个高分辨率页面上实现空间光调制器(SLM)与光电阵列耦合器(CCD)之间1∶1像素匹配。在体全息存储理论和光学设计理论基础上, 研究实现SLM和CCD像素1∶1匹配的方法, 提出了实现像素匹配的要求和条件, 并且按照此要求完成该全息光盘存储器的光学系统。实验中, 分别使用随机数据掩膜版和SLM实现了对CCD的512×512精确像素匹配, 在光学系统中引入存储介质条件下, 图像质量良好, 掩膜版和SLM原始误码率分别为2.5×10-4和1.5×10-4。     

一种红外与可见光融合的“双双目”立体视觉系统的标定方法研究

针对红外相机与可见光相机联合标定的问题,利用不同物体红外辐出度的差异,设计了可同时应用于红外相机与可见光相机标定的平面靶标。利用"最大稳定极值区域"(MSER)算法,检测靶标的镂空深色区域。为克服图像可能存在较大畸变的问题,通过相邻最大稳定极值区域质心的位置关系预估角点所在位置,在预估位置内进行角点检测,提取用于标定的亚像素角点位置。结果表明:新型靶标及相应的角点提取方法能够同时满足于红外相机与可见光相机内外参数标定的需要。通过红外与可见光"双双目"立体视觉系统的融合重构效果可看出,提供的标定数据能够满足系统需求。     

用最小二乘法求旋光实验中未知溶液的浓度

本用曲线拟合的最小二乘法求旋光实验中未知溶液的浓度,并由这种方法的原理可知,用这种方法求得的数据能够具有最小的误差。     

X射线衍射多谱峰匹配强度比定量相分析方法

提出了1种采用x射线衍射多谱峰匹配强度比进行定量相分析的新方法;该法是利用混合物样品x射线衍射谱图中的多谱峰数据,结合ICDD卡中的各相标准谱峰的相对强度分布数据进行最小二乘法回归分析,求得混合物样品中各相间的多谱峰匹配强度比;以多谱峰匹配强度比取代通常采用的特定单一谱线强度比,用于混合物样品的x射线衍射定量相分析,有利于提高定量相分析的精度;采用多谱峰匹配强度比结合绝热法和基体清洗法X射线衍射定量相分析原理,通过对4组分混合物样品的分析,证实实验结果和理论完全一致。     

高阶控制增稳系统等效拟配参数时域在线辨识方法

现代控制增稳飞机是高达几十阶的复杂系统,将其降阶为特定形式的低阶等效系统才能与已有飞行品质规范进行比较,进而预测和评价飞机飞行品质.从时域角度出发,提出了一种高阶控制增稳系统等效拟配参数在线辨识方法.分析了时域等效系统拟配的基本方法,提出了等效系统实时在线拟配的系统框架思路,基于Tustin变换法推导了由高阶系统时域响应获取四阶等效系统参数的数学公式,应用最小二乘法在MATLAB中实现了算法编程,并用试飞数据验证了所提方法的可行性.计算结果表明,所提方法可以快速准确地实现高阶控制增稳系统的等效系统参数辨识.     

曲率限制的红外焦平面告警系统目标搜索算法

为了降低红外焦平面告警系统中较高的虚警率,提出了一种速度限制基础上基于曲率限制的目标搜索算法。以视场角5.34.0凝视型红外告警系统为例,在MATLAB中对红外图像序列进行了目标搜索实验,验证了该算法的可行性。按照蒙特卡罗法思路模拟了包含大量随机噪声的目标场景,研究了该算法相比传统多帧检测算法对随机噪声的抗干扰性。对该算法的搜索帧数进行了扩展,给出了不同搜索帧数的搜索效果和时效性表现。     

场景轮廓的动态规划立体匹配算法

立体匹配算法是三维重建的关键步骤。由于实际场景中经常存在大片灰度相近的区域,稠密三维重建存在计算时间长、实时性差的问题。采用了场景的轮廓来重建场景的方法。基于场景中相邻点之间的视差应当是连续的假设,解决了轮廓在匹配时存在的"噪点"的问题,利用动态规划法对轮廓上各个点的视差进行约束以及求解最优解。由于提取轮廓后需要匹配的点数大为减少,用时可减少为原来的10%,得到与场景一致的轮廓视差图。     

用扫描式电感耦合等离子体光谱仪测定红矾钾产品中的杂质

应用电感耦合等离子体发射光谱法测定了铬盐清洁工艺红矾钾产品中的微量元素硅、铝、铁、钙、锰、镁和氯。采用基体匹配法消除了大量基体的干扰。实验的优化条件为RF发生器的入射功率095kW;载气压力013MPa,流量12L·min-1;辅助气流量02L·min-1。元素氯用氯化银沉淀间接测定,在6%的硝酸体系中氯离子形成氯化物完全沉淀,在50℃陈化2h后进行测定。样品的加标回收率在90%～104%,RSD<4%,检出限在10-4%～10-5%。随机抽样的分析结果与标准加入法吻合较好,相对误差在-427%～ 526%。本方法用于实际样品分析,快速简单,结果令人满意。     

Different responses of E:Z‐isomers of pesticides in liquid chromatography–electrospray ionization–mass spectrometry

The mass spectrometric behavior of four pairs of stereoisomers was investigated by liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI–MS). The E‐ and Z‐isomers of the pesticides chlorfenvinphos, dimethomorph, mevinphos and phosphamidon—each with one double bond—were chosen for this study. The MS response of the individual isomers was investigated by infusing the isomers individually into the MS or after the separation of isomer mixtures via high‐performance liquid chromatography(HPLC). In the case of dimethomorph, the same MS response was found for the two isomers. In contrast to that, the individual isomers of chlorfenvinphos, mevinphos and phosphamidon showed different MS response both in the single ion monitoring (SIM) mode in single quadrupole MS and multiple reaction monitoring (MRM) mode in tandem MS. The MS response of the isomers partly depends on (1) the declustering potential of the precursor ion in the SIM mode, (2) the selected transition and (3) the collision energy in the MRM mode. Consequently, quantification by summation of the peak areas of the isomers is inaccurate due to over‐ or underestimating of one of the stereoisomers. Accurate quantitative results can only be achieved when the compound‐specific MS parameters are separately determined for each isomer. This can be done by using pure isomers or by the determination of the MS parameters after HPLC separation and the measurement of the actual isomer ratio with an independent technique. Copyright © 2010 John Wiley & Sons, Ltd.