Highly regioselective [3 + 2] annulation of azomethine imines with 1-alkynyl Fischer carbene complexes to functionalized N,N-bicyclic pyrazolidin-3-ones

The highly regioselective [3 + 2] cycloaddition of azomethine imines to 1-alkynyl Fischer carbene complexes has been successfully realized under mild conditions. Oxidative demetalation of the newly formed pyrazolo-pyrazolone carbene complexes with pyridine-N-oxide or ceric ammonium nitrate efficiently afforded pyrazolo-pyrazolone derivatives as well as cycloprop-2-enone and trisubstituted 1H-pyrazoles in some cases, providing a novel route to versatile functionalized N,N-bicyclic pyrazolidin-3-ones.     

The Nonlinear Schr¨odinger Equations with Combined Nonlinearities of Power-Type and Hartree-Type

The primary goal of this paper is to present a comprehensive study of the nonlinear Schr?dinger equations with combined nonlinearities of the power-type and Hartree-type. Under certain structural conditions, the authors are able to provide a complete picture of how the nonlinear Schr?dinger equations with combined nonlinearities interact in the given energy space. The method used in the paper is based upon the Morawetz estimates and perturbation principles.     

一种基于分段能量分析的桥式吊车镇定控制器设计方法

针对欠驱动桥式吊车系统,提出了一种基于分段能量分析的桥式吊车镇定控制器没计方法.具体而言,首先通过对系统特性进行分段分析构造出一个新的能量函数;随后,在其基础上设计了一种新型的能量控制器,并借助Lyapunov方法和LaSalle不变性原理证明了闭环系统的渐近稳定性.利用数值仿真与实际实验验证了所提出的控制算法具有良好的控制性能,对外界干扰具有较强的鲁捧性.此外,实验结果进一步表明:相比常规的能量控制方法与时间最优控制方法,该控制方法可降低驱动能耗,保征台车的快速精确定位,同时负载的摆角被抑制在更小的范围内,几乎无残余摆动.     

由三个特殊次序向量对构造三对角对称矩阵

讨论利用给定的三个特殊次序向量对构造不可约三对角矩阵、Jacobi矩阵和负Jacobi矩阵的反问题.在求解方法中,将已知的一些关系式等价地转化为线性方程组,利用线性方程组有解的条件,得到了所研究问题有惟一解的充要条件,并给出了数值算法和例子.     

基于亮度均衡化的图像阈值分割技术在黄河冰凌监测中的应用

一种基于亮度均衡化的图像阈值分割算法被提出.该算法将冰凌图像亮度数据均衡化,以类间方差最大为标准,求得最佳阈值,并将冰凌图像转化为二值图像,通过冰凌像素统计,最终确定冰凌密度.该算法被应用于黄河河道冰凌图像密度的计算中,取得较好的效果.     

一般Hopf曲面上向量丛的结构

得到了非主Hopf曲面上连续复向量丛全纯结构的存在性及可滤性问题的充要条件.     

Detection of formate, rather than carbon monoxide, as the stoichiometric coproduct in conversion of fatty aldehydes to alkanes by a cyanobacterial aldehyde decarbonylase

The second of two reactions in a recently discovered pathway through which saturated fatty acids are converted to alkanes (and unsaturated fatty acids to alkenes) in cyanobacteria entails scission of the C1-C2 bond of a fatty aldehyde intermediate by the enzyme aldehyde decarbonylase (AD), a ferritin-like protein with a dinuclear metal cofactor of unknown composition. We tested for and failed to detect carbon monoxide (CO), the proposed C1-derived coproduct of alkane synthesis, following the in vitro conversion of octadecanal (R-CHO, where R = n-C(17)H(35)) to heptadecane (R-H) by the Nostoc punctiforme AD isolated following its overproduction in Escherichia coli. Instead, we identified formate (HCO(2)(-)) as the stoichiometric coproduct of the reaction. Results of isotope-tracer experiments indicate that the aldehyde hydrogen is retained in the HCO(2)(-) and the hydrogen in the nascent methyl group of the alkane originates, at least in part, from solvent. With these characteristics, the reaction appears to be formally hydrolytic, but the improbability of a hydrolytic mechanism having the primary carbanion as the leaving group, the structural similarity of the ADs to other O(2)-activating nonheme di-iron proteins, and the dependence of in vitro AD activity on the presence of a reducing system implicate some type of redox mechanism. Two possible resolutions to this conundrum are suggested.     

Direct analysis of oligosaccharides and alpha hydroxy acids in fruits using electrosonic spray ionization mass spectrometry

Electrosonic spray ionization (ESSI) is a derivative technique of electrospray ionization (ESI) for mass spectrometry (MS) in which droplets are charged in the course of sonic spray. In this study, we applied ESSI MS to direct analysis of oligosaccharides and alpha hydroxy acids (AHAs) in fruits. The components were extracted from fruit fleshes by a feasible method prior to ESSI MS analysis, but the fruit juices were analyzed without further pretreatment. The results demonstrate that mainly alkali metal adducts of oligosaccharides are favorably produced in positive ion mode, while deprotonated AHAs and oligosaccharides are produced in negative ion mode. Compared with mass spectra obtained using electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS), mass spectra using ESSI make the identification of oligosaccharides more straightforward in positive ion mode than in negative ion mode.     

A novel two-nozzle electrospinning process for preparing microfiber reinforced pH-sensitive nano-membrane with enhanced mechanical property

A novel pH sensitive membrane (pHS-M) with mechanical integrity is synthesized firstly by two nozzles electrospining in this work. We report an excellent strategy here to combine indicative nanofiber from 9% PAN solution and micro-sized fibers from 20% PA-66 solution homogeneously in one electrospinning setup. The pH indicative property of electrospun sheet can be achieved by PAN nanofibers that first aminating with ethylenediamine and then immobilizing phenolphthalein covalently through a Mannich reaction, while micro-sized PA-66 fibers are responsible for the improvement of mechanical property of electrospun mat due to their elastic and flexible behavior. The composite membrane was characterized by SEM, FTIR and UV–vis spectroscopy. Results show that two kinds of pH sensitive membranes (single PAN nanofibers (pHS-NF) or composite PAN/PA-66 fiber (pHS-CF)) all exhibited remarkable color change from pale yellow to violet in a wide range of alkaline solution and rapid response time within 100 s. But after added of microfiber, the tensile strength was enhanced from 1.3 MPa to 6.90 MPa prominently which is beneficial to put the membrane into practice.     

Polyynes from Toona ciliata var. ciliata and Related Cytotoxic Activity

A phytochemical investigation of Toona ciliata var. ciliata afforded three new polyynes, 1 – 3 . Their structures were elucidated on the basis of spectroscopic analysis and chemical methods. Only compound 3 exhibited potent cytotoxicity against the HL‐60 cell line with an IC₅₀ value of 6.7±0.27 μM .