NMR and potentiometric determination of the high pK values and protonation sequence of dipyridino-hexaaza-28-crown-8 and its interactions with selenate,sulfate and nitrate ions in aqueous solution

The aqueous protonation and anion-binding SeO ₂ ^–/4 SO _2– ⁴ , and NO _– ³ ) constants of the macrocyclic polyamine ligand, dipyridino-hexaaza-28-crown-8(L), were measured in 0.1M KCl using a potentiometric titration technique. The protonation sequence of the aza groups of L was studied in D₂O from the chemical shifts of the nonlabile protons so as to find the charge distribution geometry as a function of pD. The study indicates that in 0.1M KC1 fully protonated L forms stable l: 1 complexes with SeO _2– ⁴ (logK=3.68) and SO _2– ⁴ (logK=3.55), but not with NO _– ³ (logK < l.5). All of the amine pK values were above 6.3, thus allowing the use of the protonated form of this ligand over a wide pH range.     

Effect of Ce<Superscript>3+</Superscript> on spectral characteristic of D1/D2/Cytb559 complex from spinach

It was studied by spectroscopy that PSII reaction center complex consisting of three polypeptides, D₁, D₂ and Cytb559, were purified from PSII particle of CeCl₃ treated spinach. The results of the experiment show that Ce³⁺ could improve the growth of spinach, and accelerate electron transport of PSII particles. Of chl-a of UV-Vis spectrum of D1/D2/Cytb559 complex, Soret band was blue-shifted by 3 nm and Q band by 2 nm, respectively, and the fluorescence emission peak was blue-shifted by 5 nm in CeCl₃-treated spinach compared with the one in control. By the extended X-ray absorption fine structure (EXAFS) spectroscopy methods, it has been found that Ce³⁺ is coordinated with 8 nitrogen atoms in the first coordination shell with Ce-N bond length of 0.253 nm, and Ce³⁺ with 6 oxygen atoms in the second coordination shell with Ce-O bond length of 0.32 nm. However, the secondary structure of D1/D2/Cytb559 complex by circular dichroism (CD) spectroscopy has no significant change after CeCl₃ treated. It might be that Ce³⁺ binds to porphyrin rings of chlorophyll and oxygen of amino acid residue of polypeptide in D1/D2/Cytb559 complex, and then accelerates the primary reaction of PSII, intensifies function of P680⁺ primary electron donor of D1/D2/Cytb559, but there is little change in conformation of PSII reaction center complex.     

When does gradient Ricci soliton have one end?

Annals of Global Analysis and Geometry - In this paper, we study a problem of finding compact hypersurfaces of prescribed mean curvature with free boundary in a ball. We transform the problem to an...     

A CS-AdaBoost-BP model for product quality inspection

Quality inspection is essential in preventing defective products from entering the market. Due to the typically low percentage of defective products, it is generally challenging to detect them using algorithms that aim for the overall classification accuracy. To help solve this problem, we propose an ensemble learning classification model, where we employ adaptive boosting (AdaBoost) to cascade multiple backpropagation (BP) neural networks. Furthermore, cost-sensitive (CS) learning is introduced to adjust the loss function of the basic classifier of the BP neural network. For clarity, this model is called a CS-AdaBoost-BP model. To empirically verify its effectiveness, we use data from home appliance production lines from Bosch. We carry out tenfold cross-validation to evaluate and compare the performance between the CS-AdaBoost-BP model and three existing models: BP neural network, BP neural network based on sampling, and AdaBoost-BP. The results show that our proposed model not only performs better than the other models but also significantly improves the ability to identify defective products. Furthermore, based on the mean value of the Youden index, our proposed model has the highest stability.

     

Construction of Spatiotemporal-Coupling Optimal Low-Dimensional Dynamical Systems for Compressible Navier-Stokes Equations; [可压缩 Navier-Stokes 方程的时空耦合优化低维动力系统建模方法]北大核心CSCD

For the low-dimensional dynamical system model to study dynamics properties of Navier-Stokes equations, it is very important that the attraction domain of the low-dimensional model is the same as that of Navier-Stokes equations. However, to date, there is no universal approach to ensure this purpose for general problems. Herein, it is found that any low-dimensional model based on spatial bases, such as proper orthogonal decomposition bases, optimal spatial bases, and other classical spatial bases, is not predictable, i.e., the error increases with the time evolution of the flow field. With the theoretical framework for building optimal dynamical systems and the new concept of spatiotemporal-coupling spectrum expansion, the low-dimensional model for compressible Navier-Stokes equations was constructed to approximate the numerical solution to large-eddy simulation equations, and the numerical results and novel time evolution of spatiotemporal-coupling bases were given. The entire field error is typically below 10−2%, and the average error at each grid point is below 10−8%. The spatiotemporal-coupling optimal low-dimensional dynamical systems can ensure that the attraction domain of the low-dimensional model is the same as that of Navier-Stokes equations. Therefore, characteristic dynamics properties of spatiotemporal-coupling optimal low-dimensional dynamical systems are the same as those of real flow. © 2022 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

Normalized Dynamic Characterization and Application of Multiple Heat Storage Materials Based on Standard Thermal Resistance北大核心CSCD

基于标准热阻和能量流法,推导出储热材料与换热流体的瞬态换热热阻,通过类比电路分析法,获得了储热-换热过程的瞬态热量流模型及动态响应时间常数。进一步引入节点温度,重新定义换热热阻,获得了储热与换热过程耦合的三阶电路瞬态热量流模型,求解得到了加热、储热和释热三类时间常数,可用于协同表征储热材料中储热与释热的快慢程度,从而实现了多类储热材料的归一化动态表征。通过数值模拟验证与应用对比分析,发现基于多时间常数的归一化动态模型用于表征储热材料的动态特性是可行的,可直接对不同换热、储热材料进行对比分析。案例分析发现与固体储热材料换热时,液态金属的动态换热能力优于熔融盐,而相比于水蒸气和CO₂,空气与陶瓷材料换热能更快达到稳态。     

油菜花粉气味成分研究

为了提高气相色谱/质谱的检出灵敏度,采用进样新方法对油菜花粉气味组分进行分离测定,对下列11种成分作了鉴定:二甲二硫;正辛烷;1,3-二甲苯,异硫氰酸丙烯酯;1,4-二甲苯;1,2-二甲苯;3,4-二甲基庚烷;二甲三硫;2-甲基-5-已烯腈;萘;对-甲氧基苯丙烯。     

The Regularity of Stochastic Convolution Driven by Tempered Fractional Brownian Motion and Its Application to Mean-field Stochastic Differential Equations

In this paper, some properties of a stochastic convolution driven by tempered fractional Brownian motion are obtained. Based on this result, we get the existence and uniqueness of stochastic mean-field equation driven by tempered fractional Brownian motion. Furthermore, combining with the Banach fixed point theorem and the properties of Mittag-Leffler functions, we study the existence and uniqueness of mild solution for a kind of time fractional mean-field stochastic differential equation driven by tempered fractional Brownian motion.