Apparent molar heat capacities of aqueous solutions of acetic,propanoic and succinic acids,sodium acetate and sodium propanoate from 300 to 525 K and a pressure of 28 MPa

The apparent molar heat capacities of dilute aqueous solutions of acetic, propanoic and succinic acid and sodium salts of the two monofunctional acids were measured at 300 Kp,2 ^o . After subtracting the heat capacity of a point mass, the remaining heat capacity was successfully decomposed into functional group contributions at all temperatures. Together with the results of our previous paper on alcohols and diols the heat capacity contributions of the CH₂, CH₃, OH, COOH, (COOH)₂, and COONa groups are now available and these allow reasonably accurate predictions of the heat capacities of all compounds composed of these groups in this temperature range.     

MCM-41分子筛负载钼钴系催化剂的噻吩HDS研究

通过氧吸附量、噻吩吸附热及反应速率常数的测定，研究了MoO3/MCM-41、MoO3-CoO(NiO)/MCM-41系列催化剂，发现，对于MoO3/MCM-41催化剂，当MoO3的质量分数（以MCM－41为底数，即MCM－41＝1g时，MoO3含量为0．15g，下同）从15％增加到20％时，其噻吩的加氢硫（HDS）活性增大，至25％时活性下降，所对应的氧吸附量（mL/g催化剂）也是先增大后减少，并且两者有很好的线性对应关系，而且噻吩吸附热则基本保持不变，采用不同的MoO3-CoO(NiO)浸渍顺序制备的MoO3-CoO(NiO)/MCM-41催化剂中，先浸渍CoO(NiO）再浸渍MoO3的催化剂，其噻吩HDS活性明显优于对其它浸渍顺序制备的催化剂，同时催化剂的氧吸附量和噻吩吸附热也最大。     

Spectroelectrochemical and Voltammetric Studies of L‐DOPA

The electrooxidation of L -dopa at GC electrode was studied by in situ UV-vis spectroelectrochemistry (SEC) and cyclic voltammetry. The mechanism of electrooxidation and some reaction parameters were obtained. The results showed that the whole electrooxidation reaction of L -dopa at glassy carbon (GC) electrode was an irreversible electrochemical process followed by a chemical reaction in neutral solution (EC mechanism). The spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E⁰=228 mV, the apparent electron-transfer number of the electrooxidation reaction αn=0.376 (R=0.99, SD=0.26), the standard electrochemical rate constant k⁰=(3.93±0.12)×10⁻4 cm s⁻¹ (SD=1.02×10⁻²), and the formation equilibrium constant of the following chemical reaction k_c=(5.38±0.34)×10⁻¹ s⁻¹ (SD=1.02×10⁻²) were also obtained.     

A Self‐Sampling‐and‐Flow Biosensor for Continuous Monitoring

A self‐sampling‐and‐flow biosensor was fabricated by sandwiching a nitrocellulose strip on the working electrode side of the double‐sided microporous gold electrodes and a wicking pad on the counter electrode side. The double‐sided microporous electrodes were formed by plasma sputtering of gold on a porous nylon substrate. Sample was taken up to the enzyme‐immobilized working electrode by the capillary action of the front nitrocellulose strip dipped into the sample solution, analyzed electrochemically at the enzyme‐immobilized electrode, and diffuses out to the backside wicking pad through the micropores of the electrodes, constituting a complete flow cell device with no mechanical liquid‐transporting device. Biosensor was formed by co‐immobilizing the glucose oxidase and electron transfer mediator (ferrocene acetic acid) on the thioctic acid self‐assembled monolayer‐modified working electrode. A typical response time of the biosensor was about 5 min with the sensitivity of 2.98 nA/mM glucose, providing linear response up to 22.5 mM. To demonstrate the use of self‐sampling‐and‐flow biosensor, the consumption rate of glucose in the presence of yeast was monitored for five days.     

Some model theory for monotone quantifiers

A generalization of the existential and universal quantifier, the monotone quantifiers, are studied. It is shown that the model theory for monotone quantifiers behaves very much like classical model theory. Completeness theorems, definability theorems and preservation theorems are given. Ultraproducts, reduced products and Back and Forth arguments are studied.This work is part of the research program of the G.N.S.A.G. group of the Italian C.N.R.     

Complexation of Ni, Cu, Zn, and Cd by DOC in some metal-impacted freshwater lakes: a comparison of approaches using electrochemical determination of free-metal-ion and labile complexes and a computer speciation model, WHAM V and VI

Complexation of Ni(II), Cu(II), Zn(II), and Cd(II) by dissolved organic carbon (DOC) in some freshwater lakes in Rouyn-Noranda, Québec, Canada, where they were impacted by effluents from a nearby copper smelter, was measured by kinetic and equilibrium methods using cathodic and anodic stripping voltammetry. The measured free-metal-ion and labile metal-complex concentrations were compared with the predictions made by a widely-used computer speciation model, the Windermere Humic Aqueous Model (WHAM): WHAM V and its improved version WHAM VI. If it is assumed that 65% of the DOC is “active”, i.e. behaving as isolated humic substances such as fulvic acid, both versions of WHAM are able to predict the labile and free-metal-ion concentrations of Ni, Zn, and Cd reasonably well; however, both underestimate the free-copper-ion concentration by one to two orders of magnitude. WHAM VI is generally better than or equal to WHAM V for successfully predicting most of the free-metal-ion concentrations. The modelled competition by Al(III) and Fe(III) in the lake surface waters showed that in most cases Cu(II) was most affected by this competition. WHAM VI predicts a larger effect from the Al(III) and Fe(III) competition than does WHAM V.     

Heat Capacities of Aqueous Solutions of Acetone; 2,5-Hexanedione; Diethyl Ether; 1,2-Dimethoxyethane; Benzyl Alcohol; and Cyclohexanol at Temperatures to 523 K

The heat capacities of aqueous solutions of acetone, 2,5-hexanedione, diethyl ether, 1,2-dimethoxyethane, benzyl alcohol and cyclohexanol at concentrations of 0.1 to 1.0 mol⋅kg⁻¹ were determined at temperatures of 298.15, 423.15, 473.15 and 523.15 K and pressures up to 28 MPa. The measurements were performed at ambient conditions using the commercial Picker differential flow calorimeter and at high temperatures and pressures with a customized Picker type calorimeter constructed at the Blaise Pascal University, Clermont-Ferrand. Standard molar heat capacities were obtained by weighted extrapolation to the infinite dilution limit. The contributions of –CO–, –O– and –OH groups to the standard molar volume and standard molar heat capacity were determined from the newly determined and literature data. The variation of the three oxygen-containing group contributions with temperature and molecular structure is examined qualitatively.     

在N—甲基吡咯烷酮中聚苯硫醚合成的宏观动力学

研究了无水硫化钠与对二氯苯（以Ｎ－甲基吡咯烷酮为溶剂）合成聚苯硫醚反应的宏观动力学，该反应是一个小分子缩合串联自缩聚的过程，通过测定不同反应聚合体系中氯化钠的徨成率和硫化内的转化率，建立了该反应的宏观动力学方程：１／（１－ＰＮａＣｌ＋ＰＮａ２ｓ）＝Ｃ０Ｋｔ＋１；并计算得到２２０、２５０℃的表观反应速率为４．５×１０＾－４和３．０×１０＾－３ｋｇ／（ｍｏｌ．ｓ），表观活化能为１３４ｋＪ／ｍｏｌ。     

Multidimensional separation of isomeric species of chlorinated hydrocarbons such as PCB,PCDD, and PCDF

A multidimensional GC-system containing two capillary columns of different polarities, operated within a double oven instrument, was used for the optimized separation of complex isomeric mixtures of various types of chlorinated aromatic compounds such as PCB, PCDD, or PCDF. Electron capture was applied parallel to flame ionization detection to obtain sensitive signals of the PCB or PCDD and the n-alkane standards required for identification by Kovats indices, respectively. Electron capture detection within a valvelessly operated MDGC system forced changes in the usual instrumental set-up, the live-switching coupling piece being located within the second oven of the double oven instrument. This oven is operated isothermally to ensure optimal and interference-free detection, for stable flow conditions within the coupling piece and for the determination of the isothermal retention indices (Kovats), which are much more suitable for identification by retention than the so-called “linear” indices.     

Magnesium substitution in Nd0.7Sr0.3MnO3

Magnesium substitution in Nd_0.7Sr_0.3MnO₃ has been studied by neutron powder diffraction. Polycrystalline samples of nominal compositions Nd_0.7Sr_0.3Mn_1−yMg_yO₃ with y=0.0, 0.1, 0.2 and 0.3 were synthesized by the standard solid-state reaction method. Rietveld refinements of the neutron powder diffraction data showed that all samples had distorted perovskite structure of orthorhombic symmetry. Mg initially preferred to substitute for Nd and only at Mg concentration greater than 0.1, a substantial substitution for Mn occurred. Our study also showed that Mg-substitution did not change the crystal structure of Nd_0.7Sr_0.3MnO₃.