The synthesis of highly crystalline covalent organic frameworks via the monomer crystal induction for the photocatalytic asymmetric α-alkylation of aldehydes

Covalent organic frameworks (COFs) are ordered porous organic frameworks, which found wide applications in gas sorption and separation, catalysis, sensoring, and many others owing to their permanent porosity and designable structural motifs. To take full advantage of the well-defined porous structure, COFs need to be synthesized with high crystallinity. However, the synthesis of COFs with high crystalline is a general challenge, which requires dedicated linker design and reaction condition optimization. To achieve this, we developed a monomer crystal-induced strategy to construct crystalline COFs. The synthesized COFs have higher crystallinity, surface area, and thermal stability than those prepared without monomer crystal induction. Furthermore, the high crystalline COFs exhibit excellent performance in the photocatalytic asymmetric alkylation of aldehydes. The monomer crystal-induced method not only represents a new route for the synthesis of crystalline COFs but also sheds light on the mechanism of the formation of COFs.     

AN ADAPTIVE TRUST-REGION METHOD FOR GENERALIZED EIGENVALUES OF SYMMETRIC TENSORS

For symmetric tensors,computing generalized eigenvalues is equivalent to a homogenous polynomial optimization over the unit sphere.In this paper,we present an adaptive trustregion method for generalized eigenvalues of symmetric tensors.One of the features is that the trust-region radius is automatically updated by the adaptive technique to improve the algorithm performance.The other one is that a projection scheme is used to ensure the feasibility of all iteratives.Global convergence and local quadratic convergence of our algorithm are established,respectively.The preliminary numerical results show the efficiency of the proposed algorithm.     

关于"圆盘定理的改进与弱连对角占优矩阵"一文的注记

本文指出《应用数学学报》中一文的错误,分析了产生错误的原因,同时给出修正的矩阵谱包含域及特征值定理,推广与改进了佟文廷（１９７７）以及叶伯英（１９８５）的相应结果。     

关于Brualdi定理的注记

本文首先确定了弱不可约矩阵Ｃａｓｓｉｎｉ卵形域与Ｂｒｕａｌｄｉ谱包含域之间的包含关系，进而将Ｂｒｕａｌｄｉ谱包含推广到一般矩阵及分块矩阵上，并得到特征值分布定理，所得结果推广了（１）－（５）的相应结果。     

连续流动法同时测定污水中氨氮和总磷

采用连续流动分析法测定污水中氨氮、总磷的含量。比较了污水样品不同的稀释倍数对测定结果的影响。实验结果表明:氨氮和总磷的质量浓度在0.1~8 mg/L范围内线性良好,线性相关系数均为0.99997;测量结果的相对标准偏差分别为2.01%,0.84%(n=7);方法检出限分别为0.012,0.009 mg/L;质控样测量值均在标示值范围内;样品加标回收率为93.4%~101.1%。污水的洁净程度对测定结果影响较大。洁净度高的污水,直接测定与稀释后测定,测定值无显著性差异;而洁净度低的污水,直接测定与稀释后测定结果差异比较大。该法采用全谱直读CCD检测方式,灵敏度高,稳定性好,无光谱干扰,且支持氨氮和总磷同时测定,方便快捷,适合污水中氨氮和总磷的测定。     

A partially insulated interface crack between a graded orthotropic coating and a homogeneous orthotropic substrate under heat flux supply

In this paper, thermal response of an orthotropic functionally graded coating-substrate structure with a partially insulated interface crack under heat flux supply is considered. It is assumed that there exists thermal resistance to heat conduction through the crack region. The mixed boundary value problems are reduced to a system of singular integral equations and solved numerically. Higher order asymptotic terms for the singular integral kernels are considered to improve the accuracy and the convergence efficiency of the numerical integrals. Numerical results are presented to show the effects of the orthotropy parameters, thermo-elastic nonhomogeneity parameters, and dimensionless thermal resistance on the temperature distribution and the thermal stress intensity factors (SIFs).     

A ratiometric fluorescent probe for specific detection of cysteine over homocysteine and glutathione based on the drastic distinction in the kinetic profiles

The first ratiometric fluorescent probe for specific detection of cysteine over homocysteine and glutathione was developed based on the drastic distinction in the kinetic profiles.     

Controllable synthesis and enhanced visible photocatalytic degradation performances of Bi2WO6–carbon nanofibers heteroarchitectures

Bi₂WO₆–carbon nanofibers (Bi₂WO₆–CNFs) heteroarchitectures were fabricated by two steps consisting of the preparation of CNFs by electrospinning and growth of Bi₂WO₆ on the CNFs through ethylene glycol solvothermal processing. The results showed that the loading amounts of Bi₂WO₆ on the surface of CNFs could be controlled by adjusting the precursor concentration for the fabrication of Bi₂WO₆–CNFs heteroarchitectures during the solvothermal process. The photocatalytic tests revealed that the obtained Bi₂WO₆–CNFs heteroarchitectures showed higher photocatalytic property under visible light to degrade Rhodamine B than pure Bi₂WO₆ synthesized by solvothermal process in the absence of CNFs owing to improved separation efficiency of photogenerated electrons and holes. Moreover, the Bi₂WO₆–CNFs heteroarchitectures could be separated easily by sedimentation due to their one-dimensional nanostructural property. Meanwhile, the photocatalytic activity of Bi₂WO₆–CNFs heteroarchitectures was stable during the recycling due to the strong interactions between Bi₂WO₆ nanosheets and CNFs. Trapping experiment suggested that ${\text{O}}_{ 2}^{ \cdot - }$ , instead of OH·, was the main active species during the photocatalytic process of the Bi₂WO–CNFs heteroarchitectures.     

Tm2CrFe14.5Si1.5化合物的反常热膨胀性质研究

通过X射线衍射手段研究了Tm2CrFe14.5 Si1.5化合物的热膨胀性质及本征磁致伸缩性质.研究结果表明,Tm2CrFe14.5Si1.5化合物在303～623 K范围内,具有单相的Th2Ni17型结构;Tm2CrFe14.5Si1.5化合物的居里温度约为453 K,比其母合金Tm2 Fe17高约163 K;沿a轴方向上,Tm2CrFe 14.5 Si1.5化合物在423～448 K温度范围内出现负热膨胀现象,其热膨胀系数(α)a为-0.716×10-5/K;沿c轴方向上,在303～398 K温度范围内也出现负热膨胀现象,其热膨胀系数(α)c为-0.547×10-5/K.两者综合的结果使得在423～448 K温度范围内,Tm2CrFe14.5Si1.5化合物的体热膨胀系数(α)为-0.794 × 10-5/K.对本征磁致伸缩的研究结果表明,Tm2CrFe14.5 Si1.5化合物中存在着较强的各向异性的本征磁致伸缩.