高分子玻璃化熵理论研究进展

玻璃化问题的理论描述是凝聚态物理中的重要基础科学研究课题.高分子是研究玻璃化的典型模型体系,其独有的分子特征为发展有效、普适的玻璃化理论提供了新的机遇.构型熵是发展玻璃化理论的一个核心物理量.基于构型熵的模型可追溯至近一个世纪前观察到的熵与动力学关联的实验现象,并且近年来该理论的发展进入了一个新的阶段,特别是在高分子玻璃化的研究中.本文首先对玻璃化经典熵理论的发展进行了回顾,并介绍了高分子玻璃化熵理论的基本框架.之后,从分子细节影响高分子玻璃化的物理机制、热力学标度与活化体积的理论描述和高分子过冷液体的热力学-动力学关系三个方面阐述了本课题组近年来基于高分子玻璃化熵理论的研究进展,重点强调了该理论在理解高分子玻璃化关键问题中的价值和优势.最后,探讨了高分子玻璃化熵理论进一步发展面临的问题与挑战,并且对玻璃化理论研究的未来发展方向进行了展望.     

概念密度泛函理论及近来的一些进展

概念密度泛函理论(又称密度泛函活性理论或化学密度泛函理论)是密度泛函理论(DFT)的化学活性理论. 本文对其理论框架和最新进展进行了概述, 包括电负性、硬度、软度、福井函数、亲电性, 及其从这些概念中得到的原理. 介绍了二元描述符和立体效应定量描述的新进展, 并对今后的发展作出了展望.     

价层电子对互斥理论教学中几个问题的讨论

针对大学课程中价层电子对互斥（VSEPR）理论教学过程中存在的问题,对VSEPR理论的理论基础、过渡金属不适用于VSEPR理论的原因以及与杂化轨道理论之间的关系进行了讨论,并提出了教学建议。     

多组分聚合物体系热力学理论研究进展

概述了多组分聚合物体系热力学理论研究中,从经典的Flory-Huggins平均场理论到Prigogine-Flory现代状态方程理论(EOS)的发展历程,着重讨论了用Flory的EOS及其简化理论研究各种类型聚合物共混体系相容性的发展状况.     

基于链端体积分数的聚合物溶液理论

提出“链端体积分数”的概念以克服Flory-Huggins(FH)理论中的平均场假设.将聚合物多链体系看成一条“间隔连续链”,使一些热力学量写成路径积分的形式.在聚合物/溶剂体系中,保留了FH理论的无热熵假设,把总熵分为两部分,建立了一个新的聚合物溶液理论.计算了聚苯乙烯/环己烷体系的FH相互作用参数和相分离曲线,并与实验数据和FH理论作了比较,结果表明,我们的理论结果比FH的理论结果有了很大的改进.     

van der Waals状态方程与溶液理论

阐明了van der Waals状态方程与溶液理论间的密切关系。由van der Waals状态方程中的内压力和自由体积简捷地导得Scatchard-Hildebrand正规溶液理论、无热溶液理论和Flory-Huggins聚合物溶液理论。表明这些理论都是建立在van der Waals流体的基础上,为进一步改进这些理论提供了一条切实可行的思路。     

化学计量学的基础算法与应用研究

本文综合讨论了化学计量学的一些基础问题,包括分析信息理论、实验设计与优化、采样理论、分析检测理论、校正理论、分析信号处理、化学模式识别和计算机数字模拟等,并介绍了作者实验室的部分近期工作。     

灌浆理论浅析

详细分析了两种灌浆液体的类型牛顿体和宾汉姆体的力学特征以及二者之间异同和联系,介绍了岩土体结构的基本理论、灌浆的基本理论、渗透灌浆理论机制及内容、劈裂灌浆理论机制及内容、压密灌浆理论机制及内容。     

现代酸碱理论在有机化学中的应用

简要介绍现代酸碱理论的建立及其基本概念。现代酸碱理论包括了Brφnsted-Lowry酸碱理论、Lewis酸碱理论、HSAB理论和超酸理论。举例介绍了与物理有机化学、有机合成、有机催化等领域相关的现代酸碱理论的广泛应用。     

相图边界理论与相区接触定律及Gupta方法的比较

综述了恒压相图中与相邻相区及其边界关系有关的经验规则和理论法则, 重点比较了相图的边界理论和相区接触定律, 着重指出相区接触定律的不足, 并显示相图边界理论的确是一个比较基本的相理论. 还比较了Gupta方法和相图边界理论的方法在根据有限的信息构筑多元复杂恒压水平截面图上的优劣.     

Real‐Time Monitoring of Phosphorylation Kinetics with Self‐Assembled Nano‐oscillators

Phosphorylation is a post‐translational modification that is involved in many basic cellular processes and diseases, but is difficult to detect in real time with existing technologies. A label‐free detection of phosphorylation is reported in real time with self‐assembled nano‐oscillators. Each nano‐oscillator consists of a gold nanoparticle tethered to a gold surface with a molecular linker. When the nanoparticle is charged, the nano‐oscillator can be driven into oscillation with an electric field and detected with a plasmonic imaging approach. The nano‐oscillators measure charge change associated with phosphorylation of peptides attached onto a single nanoparticle, allowing us to study the dynamic process of phosphorylation in real time without antibodies down to a few molecules, from which Michaelis and catalytic rate constants are determined.     

Long-Range Transport in an Assembly of ZnO Quantum Dots: The Effects of Quantum Confinement,Coulomb Repulsion and Structural Disorder

We have studied the storage and long-range transport of electrons in a porous assembly of weakly coupled ZnO quantum dots permeated with an aqueous and a propylene carbonate electrolyte solution. The number of electrons per ZnO quantum dot is controlled by the electrochemical potential of the assembly; the charge of the electrons is compensated by ions present in the pores. We show with optical and electrical measurements that the injected electrons occupy the S, P, and D type conduction electron levels of the quantum dots; electron storage in surface states is not important. With this method of three-dimensional charge compensation, up to ten electrons per quantum-dot can be stored if the assembly is permeated with an aqueous electrolyte. The screening of the electron charge is less effective in the case of an assembly permeated with a propylene carbonate electrolyte solution. Long-range electron transport is studied with a transistor set-up. In the case of ZnO assemblies permeated with an aqueous electrolyte, two quantum regimes are observed corresponding to multiple tunnelling between the S orbitals (at a low occupation) and P orbitals (at a higher occupation). In a ZnO quantum-dot assembly permeated with a propylene carbonate electrolyte solution, there is a strong overlap between these two regimes.     

Electrostatic energies and forces computed without explicit interparticle interactions: a linear time complexity formulation

A rapid method for the calculation of the electrostatic energy of a system without a cutoff is described in which the computational time grows linearly with the number of particles or charges. The inverse of the distance is approximated as a polynomial, which is then transformed into a function whose terms involve individual particles, instead of particle pairs, by a partitioning of the double sum. In this way, the electrostatic energy that is determined by the interparticle interactions is obtained without explicit calculation of these interactions. For systems of positive charges positioned on a face-centered cubic lattice, the calculation of the energy by the new method is shown to be faster than the calculation of the exact energy, in many cases by an order of magnitude, and to be accurate to within 1-2%. The application of this method to increase the accuracy of conventional truncation-based calculations in condensed-phase systems is also demonstrated by combining the approximated long-range electrostatic interactions with the exact short-range interactions in a "hybrid" calculation. For a 20-A sphere of water molecules, the forces are shown to be six times as accurate using this hybrid method as those calculated with conventional truncation of the electrostatic energy function at 12 A. This is accomplished with a slight increase in speed, and with a sevenfold increase in speed relative to the exact all-pair calculation. Structures minimized with the hybrid function are shown to be closer to structures minimized with an exact all-pair electrostatic energy function than are those minimized with a conventional 13-A cutoff-based electrostatic energy function. Comparison of the energies and forces calculated with the exact method illustrate that the absolute errors obtained with standard truncation can be very large. The extension of the current method to other pairwise functions as well as to multibody functions, is described.     

Microchip analysis of lithium in blood using moving boundary electrophoresis and zone electrophoresis

The determination of inorganic cations in blood plasma is demonstrated using a combination of moving boundary electrophoresis (MBE) and zone electrophoresis. The sample loading performed under MBE conditions is studied with the focus on the quantitative analysis of lithium. A concentration adjustment takes place when the sample components migrate into the chip during the sample loading step. Using a heart-cutting method, a diluted sample plug is subsequently separated with capillary zone electrophoresis. The excessive dispersion that is typical of the samples with a high ionic strength is thereby prevented. The method can be easily applied to commercially available capillary electrophoresis microchips under the condition that the electroosmotic flow is suppressed. For the first time the lithium concentration is determined in the blood plasma from a patient on lithium therapy without sample pretreatment. Using a microchip with conductivity detection, a detection limit of 0.1 mmol/L is obtained for lithium in a 140 mmol/L sodium matrix.     

Theoretical Definition of a Functional Group and the Molecular Orbital Paradigm

It is the purpose of this review to demonstrate that the empirical classification of the observations of chemistry in terms of the properties assigned to functional groups is a consequence of and is predicted by physics. This is accomplished by showing that the atoms and functional groups of chemistry can be identified with bounded space-filling objects whose properties are defined by quantum mechanics. The quantum mechanical definition of a group is combined with a new pictorial representation of its form to obtain a unified picture which should make it eminently recognizable to chemists. This picture, when combined with the demonstrated ability of these groups to recover the measured properties of atoms in molecules, is offered as one which meets the expectations a chemist associates with the concept of a functional group. The manner in which this physical definition of a group differs fundamentally from models of functional groups based upon molecular orbital theory is discussed.     

CALCULATION OF THE YOUNG''''S MODULUS OF AN ADSORBED POLYMER LAYER

Polymer layers adsorbed to a surface or in a confined environment often change their mechanical properties. There is even the possibility of solidification of the confined layer. To judge the stiffness of such a layer, we used the Hertz model to calculate the Young's modulus of the polymer layer in the confinement of AFM experiments with silicon nitride tip with a radius of curvature of R≈50 nm and a glass sphere attached to the cantilever R = 5μm. Since there is no visible indentation of the layer in the AFM experiments, the layer is either penetrated very easily, or the indentation is too small to be seen in a force curve. The latter would be the case for a polymer layer with a Young's modulus above 4×108 Pa in case of an experiment with a silicon nitride tip and 4×105 Pa in case of a glass sphere.     

Nonenzymatic Electrochemical Sensor for Wearable Interstitial Fluid Glucose Monitoring

We report on a nonenzymatic electrochemical sensor for wearable glucose monitoring in interstitial fluid. The sensor exhibited acceptable selectivity and reliability for continuous glucose detection for up to 30 days. The sensor tip is coated with polyurethane, and the biocompatibility of the tip is investigated by tissue staining. A fully integrated wearable glucose monitoring system is developed with a wireless connection with a smartphone. The test results are in agreement with reference methods. So, we believe the sensor is promising for the development of a continuous glucose monitoring system and diabetes management.     

Enhancing detectability in CE by combining an isotachophoretic preconcentration with capillary zone electrophoresis in a single capillary

Summary This paper describes a strategy where a major part of a single capillary is filled with sample which when is isotachophoretically (ITP) preconcentrated while a hydrodynamic backpressure is applied to keep the analytes in the capillary. In the subsequent analysis of the test compounds, amitriptyline and metoprolol, capillary zone electrophoresis is used. The concentration limit of detection is lowered at least 170 times. Preliminary results where an ITP-preconcentration is combined with micellar electrokinetic chromatography with a neutral micellar agent is also presented.     

Tandem mass spectrometry in metallomics and the involving role of ICP-MS detection: A review

Metallomics is a relatively new branch of omics with a growing interest. The study of metallomes is becoming more focused in certain metabolites and the screening of various categories of analytes using a robust analytical methodology is more than appealing. In this context, when dealing with the challenge of identifying a certain species or specify a particular molecular structure, tandem mass spectrometry (MS/MS) is a reliable tool. Moreover, MS/MS instrumentation is recommended in hyphenated chromatographic techniques with MS detection such as LC–MS, where primary molecular species suffer minor fragmentation (soft-ionization techniques). ICP–MS is widely used in metallomics with its main advantages being the provided high sensitivity and selectivity. Usually, analyzes utilize ICP–MS as the main detection. Its role in proteomics is significant as an alternating choice for protein and peptide quantifications.     

哒螨灵在苹果和土壤上残留以及降解行为研究

本研究建立了基于高效液相色谱为基础的哒螨灵分析方法,并对哒螨灵在安徽淮北和陕西咸阳两地苹果上的消解和残留行为进行了研究,同时还考察了哒螨灵在两地土壤中的降解和残留行为．哒螨灵在苹果中的消解动态方程：陕西咸阳为C=0．4007e^-0.1535t,半衰期T1/2=4．5天;安徽淮北=0．1096e^-0.1464t,半衰期T1/2=4．7天;在土壤中的消解动态方程：陕西咸阳为C=0．7978e^0.1218t,半衰期T1/2=5．7天;安徽淮北C=1．4024e^-0.0912t,半衰期T1/2=7．6天．在推荐使用高剂量和推荐高剂量1．5倍情况下,施药1-2次,末次药后7天,哒螨灵在苹果中的残留为0．02～0．14mg／kg;药后14天为0．01—0．12mg／kg．试验结果表明,药后7天,苹果中哒螨灵的残留量低于2mg／kg,用药次数1-2次,每次间隔7天的情况下,在苹果上的安全间隔期可定为7天．