Specific heat capacity and Debye temperature of zirconia and its solid solution

Specific heat C_P of zirconia and yttria stabilized zirconia doped or not with erbia and ceria was measured from 128 to 823 K and of yttria stabilized zirconia doped with erbia and plutonia from 443 to 1573 K. The new determined data were modelled using Debye theory. Data for the tetravalent oxide and for the studied solid solutions show that the extended Dulong and Petit law in Neumann-Kopp rule is verified for zirconia and the quaternary compounds. The Debye temperature of zirconia (590 K) and its yttria, erbia and ceria doped solid solutions (575-625 K) derived from these C_P measurements between 150 and 823 K is discussed and compared with that reported for other tetravalent metal oxides.     

Multicomponent analysis of electrochemical signals in the wavelet domain

Successful applications of multivariate calibration in the field of electrochemistry have been recently reported, using various approaches such as multilinear regression (MLR), continuum regression, partial least squares regression (PLS) and artificial neural networks (ANN). Despite the good performance of these methods, it is nowadays accepted that they can benefit from data transformations aiming at removing baseline effects, reducing noise and compressing the data. In this context the wavelet transform seems a very promising tool. Here, we propose a methodology, based on the fast wavelet transform, for feature selection prior to calibration. As a benchmark, a data set consisting of lead and thallium mixtures measured by differential pulse anodic stripping voltammetry and giving seriously overlapped responses has been used. Three regression techniques are compared: MLR, PLS and ANN. Good predictive and effective models are obtained. Through inspection of the reconstructed signals, identification and interpretation of significant regions in the voltammograms are possible.     

Characterisation of macroporous poly(methyl methacrylate) coated with plasma-polymerised poly(2-hydroxyethyl acrylate)

Macroporous poly(methyl methacrylate) networks with varying cross-linking density and porosity were coated with plasma-polymerised poly(2-hydroxyethyl acrylate) grafted on the pores surface. The result is a mechanically reinforced hydrogel (PMMA-gr-plPHEA) whose properties are characterised in this work using several experimental techniques. Bulk PMMA and bulk PHEA were also characterised as reference materials. The diffusion and water sorption properties of these hydrogels were studied through equilibrium water sorption isotherms and desorption starting with the sample equilibrated in immersion in liquid water or in a vapour atmosphere. Glass transition, dynamic-mechanical relaxation and thermal degradation were characterised in order to study the interphase interaction in these biphasic systems. All these experimental techniques suggested that plasma-polymerised PHEA is more homogeneously interpenetrated with highly cross-linked macroporous PMMA than if the porous substrate is a loosely cross-linked polymer network.     

Voltammetric Determination of Selected Aminoquinolines Using Carbon Paste Electrode

Optimum conditions have been found for voltammetric determination of mutagenic 5‐aminoquinoline, 6‐aminoquinoline and 3‐aminoquinoline by differential pulse voltammetry and adsorptive stripping differential pulse voltammetry on carbon paste electrode. The lowest limits of determination were found for adsorptive stripping differential pulse voltammetry in 0.1 mol dm^?3 H₃PO₄ (5×10^?7 mol dm^?3 , 1×10^?7 mol dm^?3, and 1×10^?7 mol dm^?3 for 5‐aminoquinoline, 6‐aminoquinoline and 3‐aminoquinoline, respectively). The possibility to determine mixtures of 8‐aminoquinoline with 3‐aminoquinoline or 5‐aminoquinoline or 6‐aminoquinoline, and mixtures of 5‐aminoquinoline with 3‐aminoquinoline or 6‐aminoquinoline by differential pulse voltammetry was verified. Binary mixtures of 8‐aminoquinoline with 3‐aminoquinoline or 6‐aminoquinoline, and of 3‐aminoquinoline with 5‐aminoquinoline could be successfully analyzed.     

精确固定节面量子Monte Carlo差值法

提出了精确固定节面量子Monte Carlo差值法, 这个新算法能够在精确固定节面量子Monte Carlo方法的基础上直接计算两个体系之间的能量差, 且使计算结果的统计误差达到10-5 hartree 数量级, 获得电子相关能90%以上. 我们把这个新算法应用于分子势能面的研究中, 使用一个“刚性移动”模型, 利用Jacobi变换使分子两个几何构型的能量计算具有很好的正相关性, 因而能得到准确的能量差值, 由此就可以得到精确的分子势能面.     

Thermal transitions of gluten-free doughs as affected by water, egg white and hydroxypropylmethylcellulose

The thermal performance of a gluten-free bread dough consisting of a blend of non allergenic corn and cassava starches (75:25) with hydroxypropylmethylcellulose (HPMC) as gluten mimetic hydrocolloid in conjunction with egg white (EW) was determined by differential scanning calorimetry. In order to analyse the effects of different levels of the components (water: 80-110%, HPMC: 0-2% and EW: 0-10% over the starch blend) on the thermal transitions of the dough, a Doehlert design and a response surface methodology were used.The analysis of variance showed that EW did not affect the onset temperature of gelatinisation and HPMC did not affect the peak and conclusion temperatures. HPMC-water interactions mainly controlled the onset temperature of starch gelatinisation. On the other hand, the peak and conclusion temperatures were determined by the additive and opposite effects of water and EW.     

不同结晶度的乙二醇及其水溶液玻璃化转变与焓松弛

为了考察晶体成分对无定形成分玻璃化转变和结构松弛行为的影响,利用差示扫描量热法(DSC),结合低温显微技术,研究了乙二醇(EG)及其50％水溶液在不同结晶度时的玻璃化转变和焓松弛行为.采用等温结晶方法控制骤冷的部分结晶玻璃体中的晶体份额.DSC结果表明,对于部分结晶的EG,只有单一的玻璃化转变过程,而对于50％EG,当结晶度不同时,不同程度地表现出两次玻璃化转变（无定形相Ⅰ和无定形相Ⅱ）.相Ⅰ的玻璃化转变温度和完全无定形态的含水EG的玻璃化转变温度相一致;相Ⅱ的玻璃化转变温度要比此温度约高6 ℃.低温显微观察结果印证了DSC实验结果.DSC等温退火的实验和KWW(Kohlrausch-Williams-Watts)衰变函数分析结果表明,EG无定形和50％EG中的两种无定形有不同的焓松弛行为.     

Donor/Acceptor Effects on the Linear and Nonlinear Optical Properties of Geminal Diethynylethenes (g‐DEEs)

A series of geminal diethynylethenes (g‐DEEs) with electron‐donating and/or electron‐accepting (D/A) groups were synthesized via a Pd‐catalyzed cross‐coupling sequence. The UV/VIS spectra for donor–acceptor (D–A) functionalized g‐DEEs 5, 8 , and 11 show distinctive absorption trends attributable to intramolecular charge‐transfer (ICT). The bond‐length‐alternation (BLA) index for the cross‐conjugated enediyne framework varies slightly with different terminal substituents as determined by density‐functional theory (DFT) calculations and single‐crystal X‐ray analysis. Ultrafast third‐order optical nonlinearities for the g‐DEEs were measured by the differential optical Kerr effect (DOKE) technique and show that terminal donor–acceptor substitution of g‐DEEs enhances molecular second hyperpolarizabilities (γ) in comparison to donor or acceptor g‐DEEs. A small increase in the two‐photon‐absorption cross‐section (σ⁽²⁾) is observed in the series 9 – 11 as a result of increased functionalization. The effects of donor/acceptor substitution on electron delocalization along the cross‐conjugated enediyne structure are evaluated on the basis of natural‐bond‐orbital (NBO) analysis. Solid‐state structures of the four derivatives 3b, 4b, 7 and 8 were characterized by single‐crystal X‐ray structural analysis and show an asymmetric unit cell for one derivative, D–A g‐DEE 8 .     

Structures, magnetic, and thermal properties of Ln3MoO7 (Ln=La, Pr, Nd, Sm, and Eu)

Ternary lanthanide-molybdenum oxides Ln₃MoO₇ (Ln=La, Pr, Nd, Sm, Eu) have been prepared. Their structures were determined by X-ray diffraction measurements. They crystallize in a superstructure of cubic fluorite and the space group is P2₁2₁2₁. The Mo ion is octahedrally coordinated by six oxygens and the slightly distorted octahedra share corners forming a zig-zag chain parallel to the b-axis. These compounds have been characterized by magnetic susceptibility and specific heat measurements. The La₃MoO₇ shows complex magnetic behavior at 150 and 380 K. Below these temperatures, there is a large difference in the temperature-dependence of the magnetic susceptibility measured under zero-field-cooled condition and under field-cooled condition. The Nd₃MoO₇ show a clear antiferromagnetic transition at 2.5 K. From the susceptibility measurements, both Pr₃MoO₇ and Sm₃MoO₇ show the existence of magnetic anomaly at 8.0 and 2.5 K, respectively. The results of the specific heat measurements also show anomalies at the corresponding magnetic transition temperatures. The differential scanning calorimetry measurements indicate that two phase-transitions occur for any Ln₃MoO₇ compound in the temperature range between 370 and 710 K.     

Effect of citric acid and hydrochloric acid on the polarographic behaviour of tin: Application to the determination of tin(II) in presence of tin(IV) in the activating solutions of the electroless plating of polymers

A new method for the determination of tin(II) in presence of tin(IV) is described. The method is based on differential pulse polarography on the hanging mercury drop electrode (HMDE). The effect of citric acid and hydrochloric acid concentrations on the polarographic peaks of tin(II) and tin(IV) has been studied. In 1 M HCl, the total quantity of tin can be determined, as under these conditions, in the absence of complexing agents, eventual variations in the oxidation states, in any concentration ratio, do not affect the peak height and the peak potential. In 0.2 M HCl and 0.2 M citric acid, tin(II) can be determined selectively in presence of tin(IV), as under these conditions, tin(IV) does not present polarographic response, while a well-defined peak is observed for tin(II). The method is applied to determine tin(II) and total tin in the activating solutions of the electroless plating of polymers.