Toeplitz定理的推广

本文将Ｔｏｅｐｌｉｔｚ定理推广到函数情形，为证明和计算一类函数极限提供了一种方法。     

多元校正双指示电极电位沉淀滴定法同时测定混合卤素离子

建立一种可同时测定混合卤素离子的电位滴定新方法.在这种方法中,滴定剂是硝酸银和氟化钠的混合溶液,被滴定液中同时插入了氟离子指示电极和银离子指示电极.在滴定过程中的任一滴定点,溶液中Ag 的浓度和滴定剂的加入体积可由两个电极的电位测定值同时获得,从而可应用多元校正法由相应的滴定曲线求得混合卤素离子中每一种离子的含量.用该方法对混合物样品中的Cl-、Br-、I-进行了同时测定,测定结果的相对标准偏差为0.13%～0.45%(n=5),回收率为97.3%～103.4%.     

A novel sensor based on multi-walled carbon nanotubes and boron-doped double-layer molecularly imprinted membrane for the analysis of SCZ in pharmaceutical and biological samples

ABSTRACT

A molecularly imprinted electrochemical sensor for the rapid detection of the anti-parasitic drug Secnidazole (SCZ) is reported. In this work, the build electrochemical sensor was based on a carbon paste electrode (CPE) modified with multi-wall carbon nanotubes (MWCNTs) and boron-embedded duplex molecularly imprinted composite membranes (B-DMICMs), that significantly increased the efficiency of the sensor for the detection of template molecule SCZ. Density functional theory (DFT) was employed to study the interactions between the template and monomers to select appropriate functional monomers for rational design of the B-DMICMs.The optimal experimental conditions were optimised for the factors affecting the performance of the sensor. Under the optimal conditions, the reduction peak currents of SCZ by differential pulse voltammetry increased linearly with SCZ concentration in the range from 3.0 × 10^?4 to 1.0 × 1.0^?6 mol L^?1 and 1.0 × 1.0^?6 to 1.91 × 10^?8 mol L^?1 with a detection limit of 1.72 × 10^?8 mol L^?1 for secnidazole, which is significantly lower than those in the currently used methods and in previous reports. This method offers low cost, sensitive and effective determination of SCZ and can potentially be used for detection of SCZ in pharmaceutical and biological samples with good precision and accuracy.     

Separation and determination of trace uranium using a double-receptor sandwich supramolecule method based on immobilized salophen and fluorescence labeled oligonucleotide

A double-receptor sandwich supramolecule method for the separation and determination of trace uranium was proposed in this paper. One receptor is a salophen which can react with uranyl to form a uranyl-salophen complex, and another receptor is an oligonucleotide which can bind uranyl to form oligonucleotide-uranyl-salophen supramolecule. The salophen was immobilized on the surface of silica gel particles and used as the solid phase receptor for separating uranium from solution. The oligonucleotide was labeled with a fluorescent group and used as the labeled receptor for quantitatively analyzing uranium. In the procedure of separation and determination, uranyl ion was first combined with the solid phase receptor and then conjugated with the labeled receptor to form the sandwich-type supramolecule. The labeled receptor in the sandwich supramolecule was then eluted and determined by fluorescence analysis. The experimental results demonstrate that this method has a number of advantages such as high selectivity, excellent pre-concentration capability, high sensitivity, good stability and low cost. Under optimal conditions, the linear range for the detection of uranium is 0.5–30.0 ng mL⁻¹ with a detection limit of 0.2 ng mL⁻¹. The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0–105.5%.     

流动注射多元校正-络合滴定法同时测定混合金属离子

将流动注射应用于电位络合滴定分析法,建立了一种可同时测定混合金属离子的电位滴定方法。在该方法中,用EDTA与氟化钠的混合溶液作为滴定剂,在流通池中同时插入汞膜电极和氟离子指示电极,在滴定过程中的任一滴定点,流出液的汞电位和反应物的混合比例可由两个电极的电位测定值同时获得,从而可应用多元校正法由相应的滴定曲线求得混合金属离子中每一种组分的含量。应用该方法对混合样品中的Cu2+、Pb2+、Zn2+进行了同时测定,测定结果的相对标准偏差均在0.14%~0.48%(n=5)之间,回收率均在97.3%~103.9%之间。     

啁啾脉冲堆积宽带激光非线性传输时域调制特性

为避免时域调制增长形成的高强度时间尖峰对光学元件的损坏,数值研究了啁啾堆积脉冲宽带激光非线性传输的时域调制增长规律。结果表明:对于正常色散介质,子脉冲间干涉引入的时间调制与外加调制随着传输距离的增加,不断振荡减弱;相反,对于反常色散介质,无外加时间噪声时,堆积子脉冲间的相互干涉引入的时间调制有微弱增长,但当传输距离进一步增加时,子脉冲间干涉引入的调制可以获得快速增长;而当外加非线性最快增长时间调制时,时间调制发生迅速增长,具有破坏威胁的时间尖峰易于形成。     

A resonance light scattering method for the determination of uranium based on a water-soluble salophen and oxalate

A resonance light scattering (RLS) method for the direct detection of uranium (VI) or uranyl in aqueous solution without separation procedure has been reported in this paper. Sulfo-salophen, a water-soluble tetradentate Schiff base ligand of uranyl, reacted with uranyl to form a complex. The complex reacted further with oxalate to form supramolecular dimer with large molecular volume, resulting in a production of strong RLS signal. The amount of uranium (VI) was detected through measuring the RLS intensity. A linear range was found to be 0.2–30.0 ng/mL under optimal conditions with a detection limit of 0.15 ng/mL. The method has been applied to determine uranium (VI) in environmental water samples with the relative standard deviations of less than 5 % and the recoveries of 98.8–105.8 %. The present technique is suitable for the assay of uranium (VI) in environmental water samples collected from different sources.     

Determination of fructose 1,6-bisphosphate using a double-receptor sandwich type fluorescence sensing method based on uranyl–salophen complexes

In this paper, we report a double-receptor sandwich type fluorescence sensing method for the determination of fructose bisphosphates (FBPs) using fructose 1,6-bisphosphate (F-1,6-BP) as a model analyte based on uranyl–salophen complexes. The solid phase receptor is an immobilized uranyl–salophen (IUS) complex which is bound on the surface of glass slides by covalent bonds. The labeled receptor is another uranyl–salophen complex containing a fluorescence group, or uranyl–salophen–fluorescein (USF). In the procedure of determining F-1,6-BP in sample solution, F-1,6-BP is first adsorbed on the surface of the glass slide through the coordination reaction of F-1,6-BP with IUS. It then binds USF through another coordination reaction to form a sandwich-type structure of IUS-F-1,6-BP-USF. The amount of F-1,6-BP is detected by the determination of the fluorescence intensity of IUS-F-1,6-BP-USF bound on the glass slide. Under optimal conditions, the linear range for the detection of F-1,6-BP is 0.05–5.0 nmol mL⁻¹ with a detection limit of 0.027 nmol mL⁻¹. The proposed method has been successfully applied for the determination of F-1,6-BP in real samples with satisfactory results.     

The Crucial Role of Charge Accumulation and Spin Polarization in Activating Carbon‐Based Catalysts for Electrocatalytic Nitrogen Reduction

Cost‐effective carbon‐based catalysts are promising for catalyzing the electrochemical N₂ reduction reaction (NRR). However, the activity origin of carbon‐based catalysts towards NRR remains unclear, and regularities and rules for the rational design of carbon‐based NRR electrocatalysts are still lacking. Based on a combination of theoretical calculations and experimental observations, chalcogen/oxygen group element (O, S, Se, Te) doped carbon materials were systematically evaluated as potential NRR catalysts. Heteroatom‐doping‐induced charge accumulation facilitates N₂ adsorption on carbon atoms and spin polarization boosts the potential‐determining step of the first protonation to form *NNH. Te‐doped and Se‐doped C catalysts exhibited high intrinsic NRR activity that is superior to most metal‐based catalysts. Establishing the correlation between the electronic structure and NRR performance for carbon‐based materials paves the pathway for their NRR application.