A novel method for the synthesis of sulfur substituted-cyclopyrophosphate of cADPR analogs

A facile and efficient protocol for the synthesis of sulfur substituted-cyclopyrophosphate of cIDPRE(P_S~1-cIDPRE) was developed.The key step was the cyclization process which was completed by the sulfur substituted cyclization precursor 1b via the one-pot phosphoramidite strategy.     

Synthesis of biodiesel over ZnO/Ca(OH)2/KF catalyst prepared by the grinding method

A novel ZnO/Ca(OH)₂/KF solid base catalyst was prepared by the grinding method and applied to biodiesel synthesis by the transesterification of soybean oil. The effect of various parameters such as KF molar amount, calcination temperature, the amount of catalyst, molar ratio of methanol to oil, reaction temperature, and time on the activity of the catalyst were investigated. The catalysts were characterized by several techniques of thermogravimetry/derivative thermogravimetry, X–ray diffraction, Hammett indicator method, and scanning electron microscopy. The analysis results indicated that the KF interacted with Ca(OH)₂ and formed KCaF₃ phase before calcination of the catalyst. The formed KCaF₃ crystal phase was the main catalytic active component for the catalyst activity. In addition, the basicity of ZnO/Ca(OH)₂/KF was greatly influenced by the different calcination temperates, and the catalyst activity was correlated closely with the basicity. A desired biodiesel yield of 97.6 % was obtained at catalyst amount of 3 %, methanol/oil of 12:1, and reaction time of 1.5 h at 65 °C.     

Enantioseparation and molecular modeling study of eight psychoactive drugs on a coated polysaccharide-based chiral stationary phase

The enantioseparation of eight psychoactive drugs has been firstly performed on a coated cellulose-based chiral stationary phase (Chiralcel OJ-H). To obtain optimum separation conditions, the influences of alcohol modifiers and basic/acidic additives have been studied. As a result, except for the partial separation of oxybutynin enantiomers, the other seven drug enantiomers, including mirtazapine, sulpiride, promethazine, citalopram, oxazepam, donepezil, and cyamemazine, have been completely separated. Additionally, for gaining a better insight into the chiral recognition mechanisms, molecular docking was carried out using the Autodock software. Herein, binding energy and conformations of the chiral stationary phase complexes were provided, and it was found that the distinction in enantiomeric conformation determined the number and strength of intermolecular interactions between analytes and chiral stationary phase which resulted in the difference in binding energies of two enantiomers, and ultimately led to the different migration. These modeling results were in accordance with the observed enantioseparation results in high performance liquid chromatography experiments. At last, chiral separation mechanisms have been discussed in detail, and it has been confirmed that hydrogen bond, π–π, hydrophobic interactions, and some special interactions synergistically contributed to the enantioseparation of psychoactive drugs.     

Multiple Stimuli-Responsive Conformational Exchanges of Biphen[3]arene Macrocycle

Conformational exchanges of synthetic macrocyclic acceptors are rather fast, which is rarely studied in the absence of guests. Here, we report multiple stimuli-responsive conformational exchanges between two preexisting conformations of 2,2′,4,4′-tetramethoxyl biphen[3]arene (MeBP3) macrocycle. Structures of these two conformations are both observed in solid state, and characterized by ¹H NMR, ¹³C NMR and 2D NMR in solution. In particular, conformational exchanges can respond to solvents, temperatures, guest binding and acid/base addition. The current system may have a role to play in the construction of molecular switches and other stimuli-responsive systems.     

Chaotic resonance in Izhikevich neural network motifs under electromagnetic induction

Nonlinear Dynamics - Chaotic resonance (CR) is the response of a nonlinear system to weak signals enhanced by internal or external chaotic activity (such as the signal derived from Lorenz system)....     

Effects of nonlinearity of restoring springs on propulsion performance of wave glider

Nonlinear Dynamics - Wave glider is an unmanned surface vehicle that can directly convert wave energy into forward propulsion and fulfill long-term marine monitoring. A previous study suggested...     

关于《线性代数》教材改革的几点想法

随着现代科学技术的迅猛发展,尤其是计算机技术的广泛应用,我们应当在工科数学课程的教学内容、教学方法和教学手段上积极改革,与时俱进,以改进教学方法,提高教学质量,使得工科学生能借助于计算机,学好本专业所需的数学知识.在这篇短文中,我们想就《线性代数》的教学内容的改革     

阳离子交换皂石黏土在基质辅助激光解吸电离飞行时间质谱分析中的应用

将一种人工合成的无机聚合物——蒙脱石皂石黏土（smectite,Sm）应用于基质辅助激光解吸电离飞行时间质谱分析（matrix-assisted laser desorption/ionization time of flight mass spectrometry, MALDI-TOF-MS）,以检测糖类化合物。 将传统的有机基质2,4,6-三羟基苯乙酮（trihydroxyacetophenone, THAP）与阳离子交换后的皂石黏土混合制备成新型复合基质,应用于糖类化合物的检测。通过比较不同的制样方法,测定不同分子直径的糖类化合物,发现由于受复合基质晶面间距的限制,只有小分子糖类化合物能进入晶面间隙充分接触有机基质并被离子化,从而实现对小分子糖类化合物的选择性检测。     

X射线荧光分析中X射线管原级能谱分布的测定

确切知道X射线管激发的原级能谱分布是X射线荧光分析中的一个重要前提,所用能谱分布函数的准确度大大影响了最终的测量结果。提出利用间接测量法,选用合适的参量模型来描述X射线的原级能谱分布。依靠实验测得的厚靶纯元素样品的荧光强度,利用已知的理论公式,建立非线性方程,优化得到参量模型中的参量值。通过比较实验测得的元素的荧光强度值和利用得到的能谱分布函数计算的理论值,证明此种方法是可行的。     

Discovering Phase Field Models from Image Data with the Pseudo-Spectral Physics Informed Neural Networks

In this paper,we introduce a new deep learning framework for discovering the phase-field models from existing image data.The new framework embraces the approxim...