Solid-Solution Effect on Grain Boundary Character Distribution and Corrosion Resistance of 304 Stainless Steel

Russian Journal of Electrochemistry - In this study, we focus on the effect of solid-solution treatment on the susceptibility to intergranular corrosion and electrochemical corrosion of 304...     

OCT图像法测量折射率

基于光程匹配原理提出了一种用光学相干断层成像(OCT)系统获得的图像测量样品折射率的方法。通过分析光程匹配原理,给出用OCT图像法测量样品折射率的原理及过程。以玻璃载波片和黄瓜组织为样品进行实验。实验结果表明,用OCT图像法获得的载玻片和黄瓜组织的折射率测量值分别为1.499和1.353,与发表或已知的折射率结果相吻合,测试结果的随机误差可小于0.01。另外,使用OCT图像法通过短时间所采集的两幅图像可对横向扫描任意位置的折射率同时进行测量。该方法进一步简化了基于光程匹配原理的折射率测量法的过程,缩短了测量时间,是一种快速测量样品折射率的实用方法。     

多元统计分析在塔里木瓦吉里塔格钒钛磁铁矿床多元素相关性及成矿预测研究中的应用

塔里木巴楚县瓦吉里塔格地区出露有与塔里木早二叠世大火成岩省的形成密切相关的大型钒钛磁铁矿床. 基于多元统计分析对该矿区露头和大量钻孔岩心样品中Fe-Ti-V元素和部分主量元素数据开展了元素地球化学相关性研究. 采用SPSS软件对大量数据进行相关分析和回归分析,计算各元素间的相关系数,Fe、Ti、V 3种元素的相关性分析结果表明： 矿床中Fe、Ti和V之间均呈正相关, 成矿元素与造岩元素之间存在负相关关系;建立伴生钒元素与铁和钛元素之间关系的回归方程V=-4.984+0.360 Fe+0.984Ti,由Fe和Ti元素质量分数可以估算伴生组分V的质量分数.利用Matlab软件的可视化功能,绘制了Fe-Ti-V元素质量分数的三维立体图,建立空间模型,发现Fe₂O_3T、TiO₂和V₂O₅品位较高的位置相对一致,均主要分布于研究区北部中间一带,富集在辉石岩中. 该空间模型的建立有助于识别矿体和非矿体的分布范围和富集趋势,并进行成矿预测. 此项研究对钒元素含量的精确估算和矿藏勘探有一定的指导意义.     

酶水解和脱磷对卵黄高磷蛋白高乳化性的影响

卵黄高磷蛋白的乳化性尤其乳液稳定性比别的食品蛋白质高。蛋白酶和磷酸酯酶可使乳化活性和乳液稳定性明显降低，卵黄高磷蛋白的蛋白酶水解导致大肽链(高磷酸化核心区50～210个肽)和小肽链(N-端1～49个肽和C-端211～217个肽)裂解。不含小肽的肽不具备优异的乳化特性，蛋白质中一部分小肽在乳化特性中起着重要角色。换句话说，磷酸酯酶处理后，卵黄高磷蛋白中磷酸酯的静电排斥力对乳化性有显著影响，磷酸充分作用后的残基的这部分蛋白质对高乳化特性至关重要。     

Effect of Asymmetric Anchoring Groups on Electronic Transport in Hybrid Metal/Molecule/Graphene Single Molecule Junctions

A combined experimental and theoretical study on molecular junctions with asymmetry in both the electrode type and in the anchoring group type is presented. A scanning tunnelling microscope is used to create the “asymmetric” Au-S-(CH₂)n-COOH-graphene molecular junctions and determine their conductance. The measurements are combined with electron transport calculations based on density functional theory (DFT) to analyze the electrical conductance and its length attenuation factor from a series of junctions of different molecular length (n). These results show an unexpected trend with a rather high conductance and a smaller attenuation factor for the Au-S-(CH₂)_n-COOH-graphene configuration compared to the equivalent junction with the “symmetrical” COOH contacting using the HOOC-(CH₂)_n-COOH series. Owing to the effect of the graphene electrode, the attenuation factor is also smaller than the one obtained for Au/Au electrodes. These results are interpreted through the relative molecule/electrode couplings and molecular level alignments as determined with DFT calculations. In an asymmetric junction, the electrical current flows through the less resistive conductance channel, similarly to what is observed in the macroscopic regime.     

微波消解-氢化物发生原子吸收光谱法测定大米中铅

采用微波消解方式处理样品,建立了氢化物发生-原子吸收光谱法测定大米中痕量铅的分析方法。对载气流速、硼氢化钠浓度、溶液酸度以及铅反应试剂加入量进行了研究。在选择了最佳实验条件下,方法的检出限为0.05μg/L,加标回收率在96.8%~103.8%。     

Engineering a Highly Regioselective Fungal Peroxygenase for the Synthesis of Hydroxy Fatty Acids

The hydroxylation of fatty acids is an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. In this study, we have engineered a highly regioselective fungal peroxygenase for the ω-1 hydroxylation of fatty acids with quenched stepwise over-oxidation. One single mutation near the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward subterminal hydroxylation with a drop in the over-oxidation activity. While crystallographic soaking experiments and molecular dynamic simulations shed light on this unique oxidation pattern, the selective biocatalyst was produced by Pichia pastoris at 0.4 g L⁻¹ in a fed-batch bioreactor and used in the preparative synthesis of 1.4 g of (ω-1)-hydroxytetradecanoic acid with 95 % regioselectivity and 83 % ee for the S enantiomer.     

Revisit to the symmetry relations in diffusely backscattered polarization patterns of turbid media

As there exists an inconsistency in claiming the symmetrical relations in the 16 Mueller matrix elements used to describe a turbid medium, the author restudies the symmetrical relationships between diffusely backscattered polarization patterns in isotropic turbid media and simulates all two-dimensional elements of diffusely backscattered Mueller matrix in both cases of Rayleigh and Mie scatterings using the doublescattering approximation and the Monte Carlo algorithm, respectively. The previous experimental observatious are compared with the numerically determined matrix elements, showing a good agreement in both double-scattering model and Monte Carlo simulation. The symmetrical relations between the Mueller matrix elements are clarified.