电解冷蒸气发生原子荧光法测定痕量汞

以电解冷蒸气发生技术结合原子荧光光谱仪,采用自行设计的圆盘电解池,进行汞的电解还原冷蒸气发生情况的研究.实验表明,铂作为阴极时,Hg的电化学发生响应信号与化学还原法获得的信号强度相当;同时发现,载气引入位置是影响Hg响应信号强度的重要因素.在1.0 mol/L H2SO4作为阴极液及0.8 A的电解电流条件下,Hg的检出限为1.2 ng/L(3σ); 相对标准偏差为1.7%(n=11).利用此体系分析了标准物质及生物样品中的痕量汞,结果满意.     

A high‐performance liquid chromatography assay with a triazole‐bonded column for evaluation of d‐amino acid oxidase activity

Elution profiles of kynurenic acid (KYNA) and 7‐chlorokynurenic acid (Cl‐KYNA) were examined by high‐performance liquid chromatography (HPLC) using a triazole‐bonded stationary phase column (Cosmosil® HILIC) under isocratic elution of a mobile phase consisting of CH₃CN–aqueous 10 mm ammonium formate between pH 3.0 and 6.0. The capacity factors of KYNA and Cl‐KYNA varied with both the CH₃CN content and the pH of the mobile phase. The elution order of KYNA and Cl‐KYNA was reversed between the CH₃CN‐ and H₂O‐rich mobile phases, suggesting that hydrophilic interactions and anion‐exchange interactions caused retention of KYNA and Cl‐KYNA in the CH₃CN‐ and H₂O‐rich mobile phases, respectively. The present HPLC method using a triazole‐bonded column and fluorescence detection (excitation 250 nm, emission 398 nm) was applied to monitor in vitro production of KYNA from d ‐kynurenine (d ‐KYN) by d ‐amino acid oxidase (DAO) using Cl‐KYNA as an internal standard. A single KYNA peak was clearly observed after enzymatic reaction of d ‐KYN with DAO. Production of KYNA from d ‐KYN was suppressed by the addition of commercial DAO inhibitors. The present HPLC method can be used to evaluate DAO activity and DAO inhibitory effects in candidate drugs for the treatment of schizophrenia. Copyright © 2015 John Wiley & Sons, Ltd.     

Cold Sintering: A Paradigm Shift for Processing and Integration of Ceramics

This paper describes a sintering technique for ceramics and ceramic‐based composites, using water as a transient solvent to effect densification (i.e. sintering) at temperatures between room temperature and 200 °C. To emphasize the incredible reduction in sintering temperature relative to conventional thermal sintering this new approach is named the “Cold Sintering Process” (CSP). Basically CSP uses a transient aqueous environment to effect densification by a mediated dissolution–precipitation process. CSP of NaCl, alkali molybdates and V₂O₅ with small concentrations of water are described in detail, but the process is extended and demonstrated for a diverse range of chemistries (oxides, carbonates, bromides, fluorides, chlorides and phosphates), multiple crystal structures, and multimaterial applications. Furthermore, the properties of selected CSP samples are demonstrated to be essentially equivalent as samples made by conventional thermal sintering.     

Aa1Dd1-Aa2Dd2型氢键体系的网络结构参数

利用溶胶-凝胶分配理论对氢键溶液的模型体系进行研究, 给出了体系的凝胶化条件以及凝胶点后氢键网络中各类结构参数的计算方案, 并进行了相应的数值计算. 结果表明, 当两类质子受体基团的活性不同时, 质子受体基团的竞争作用对网络结构有一定影响. 这为控制氢键网络结构特征提供了可能的理论线索.     

Theoretical study of neutral and protonated triple bonded molecules formed between C, N, Si, P, B and Al

A theoretical study of the possible protonation sites of simple molecules formed by C, N, Si, P, B and Al that present a triple bond between those atoms has been carried out. The calculations performed include MP2 and CCSD(T) methods with the aug-cc-pVTZ basis set. The nature of the protonated species has been analyzed with the Atoms In Molecules methodology. To Serafin, a free spirit and a good friend. Contribution to the Serafin Fraga Memorial Issue.     

_(a_1)_(d_1)-A_(a_2)D_(d_2)型氢键体系的网络结构参数

利用溶胶-凝胶分配理论对氢键溶液的模型体系进行研究,给出了体系的凝胶化条件以及凝胶点后氢键网络中各类结构参数的计算方案,并进行了相应的数值计算.结果表明,当两类质子受体基团的活性不同时,质子受体基团的竞争作用对网络结构有一定影响.这为控制氢键网络结构特征提供了可能的理论线索.     

Surface diffusion in reversed-phase liquid chromatography using silica gels bonded with C1 and C18 ligands of different densities

Surface diffusion in reversed-phase liquid chromatography (RPLC) using silica gels bonded with C₁ and C₁₈ alkyl ligands of different densities was studied from the viewpoints of two extrathermodynamic relationships, i.e., enthalpy-entropy compensation (EEC) and linear free energy relationship (LFER). First, according to the four methods proposed by Krug et al., the values of surface diffusion coefficient (D_s) were analyzed to confirm that an actual EEC resulting from substantial physico-chemical effects takes place for surface diffusion. Then, it was also demonstrated that a LFER is observed between surface diffusion and the retention equilibrium. The establishment of EEC and LFER suggests a mechanistic similarity of molecular migration by surface diffusion, irrespective of the alkyl chain length and the densities of C₁ and C₁₈ ligands. Finally, a thermodynamic model for the LFER based on the real EEC was used to estimate D_s values under various RPLC conditions. The D_s values can be estimated with a mean square deviation of about 25–30%. The agreement between the D_s values estimated and those experimentally measured suggests that the total mass flux by surface diffusion consists of the two contributions due to C₁ and C₁₈ ligands and that the contribution of each ligand is proportional to the ligand density.     

Molecular dynamics simulations on the structures and properties of ε-CL-20-based PBXs ——Primary theoretical studies on HEDM formulation design

Five polymer bonded explosives (PBXs) with the base explosive ε-CL-20 (hexanitrohexaazaisowurtzi- tane), the most important high energy density compound (HEDC), and five polymer binders (Estane 5703, GAP, HTPB, PEG, and F2314) were constructed. Molecular dynamics (MD) method was employed to investigate their binding energies (Ebind), compatibility, safety, mechanical properties, and energetic properties. The information and rules were reported for choosing better binders and guiding formula- tion design of high energy density material (HEDM). According to the calculated binding energies, the ordering of compatibility and stability of the five PBXs was predicted as ε-CL-20/PEG > ε-CL-20/ Estane5703 ≈ε-CL-20/GAP > ε-CL-20/HTPB > ε-CL-20/F2314. By pair correlation function g(r) analyses, hydrogen bonds and vdw are found to be the main interactions between the two components. The elasticity and isotropy of PBXs based ε-CL-20 can be obviously improved more than pure ε-CL-20 crystal. It is not by changing the molecular structures of ε-CL-20 for each binder to affect the sensitivity. The safety and energetic properties of these PBXs are mainly influenced by the thermal capability (C°p) and density (ρ) of binders, respectively.     

Study on the nature of interaction of BrCl with HF,H2O,and NH3

By counterpoise‐corrected optimization method, the interactions of BrCl with the first‐row hydrides (HF, H₂O, NH₃) have been investigated at the MP2/6–311++G(3d,3p) level. To understand that the X? Br‐type (X = F, O, N) structure is more stable than the corresponding hydrogen‐bonded structure in these complexes, the electronic properties were also investigated. Symmetry‐adapted perturbation theory (SAPT) analysis has been carried out to understand the nature of the weak hydrogen bond and X? Br‐type interactions. On the other hand, for the weak hydrogen‐bonded complexes and the X? Br‐type complexes charges transfer is well correlated with the total induction energies. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Effect of Al2O3 nanoparticles on the steel-glass/epoxy composite joint bonded by a two-component structural acrylic adhesive

This paper reports a study on the effect of Al₂O₃ nanoparticles on the adhesion strength of steel-glass/epoxy composite joints bonded by a two-component structural acrylic adhesive. The addition of Al₂O₃ nanoparticles to the two-component acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strength of the adhesive joints increased by addition of Al₂O₃ up to 1.5 wt%, which decreased by further addition of the nanofiller. Introduction of the nanoparticles caused a reduction in the peel strength of the joints. DSC analysis revealed that the glass transition temperature (Tg) of the adhesives rose by increasing the nanofiller content. The advancing water contact angle was decreased for adhesives containing nanoparticles. SEM micrographs indicated good dispersions of the Al₂O₃ nanoparticles within the acrylic matrix in the specimens with up to 1.5 wt% Al₂O₃ and revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces.