Linker-free layer-by-layer self-assembly of gold nanoparticle multilayer films for direct electron transfer of horseradish peroxidase and H2O2 detection

Au nanoparticle (AuNP) multilayer films were fabricated by combining interfacial assembly and layer-by-layer assembly. The key point is that the procedure does not require assistance of organic linker molecules, thus providing a suitable platform for the modification of biological molecules. Direct electron transfer can easily take place between a glassy carbon electrode and horseradish peroxidase (HRP) molecules adsorbed on AuNP films. The current density of direct electron transfer was closely related to the layer number, m, and reached a maximum value for m = 4. The optimized HRP/AuNP multilayer film had a relatively rapid response and satisfactory selectivity for H₂O₂ detection. The linear range and the detection limit were 9.8 × 10⁻⁶ to 6 × 10⁻³ mol/L and ∼4.9 × 10⁻⁶ mol/L (S/N = 3), respectively.     

2,4-二甲基-3-氨基噻吩的合成

[方法]2,4-二甲基-3-氨基噻吩主要用于有机合成,是合成除草剂的重要中间体。以巯基乙酸和乙酰丙酮为起始原料,经过亲核加成、酯化、关环、水解、脱羧、还原等7步反应得到2,4-二甲基-3-氨基噻吩,并优化了关键的硝化反应。[结果]正交试验显示硝化反应的最优条件:反应温度15℃,3,5-二甲基噻吩-2-甲酸与乙酰硝酸酯的摩尔比1∶7,反应时间55 min。[结论]该路线简单经济,条件温和,收率高于其他路线,适合生产。     

Experimental and finite element analysis for fracture of coating layer of galvannealed steel sheet

Mechanical properties of galvannealed (GA) steel sheet used for automotive exposed panel and predicted failure phenomenon of its coating layer were evaluated using finite element method. V-bending test was performed to understand better the fracture of coating layer of GA steel sheet during plastic deformation. Yield strength of the coating layer was calculated by using a relative difference between hardness of coating layer measured from the nano-indentation test and that of substrate. To measure shearing strength at the interface between substrate and coating layer, shearing test with two specimens attached by an adhesive was carried out. Using the mechanical properties measured, a series of finite element analyses coupled with a failure model was performed. Results reveal that the fracture of coating layer occurs in an irregular manner at the region where compressive deformation is dominant. Meanwhile, a series of vertical cracks perpendicular to material surface are observed at the tensile stressed-region. It is found that 0.26-0.28 of local equivalent plastic strain exists at the coating and substrate at the beginning of failure. The fracture of coating layer depends on ductility of the coating layer considerably as well.     

High-temperature deformation behavior of a beta Ti-3.0Al-3.5Cr-2.0Fe-0.1B alloy

The high-temperature deformation behavior of a beta Ti-3.0 Al-3.5 Cr-2.0 Fe-0.1 B alloy was investigated by a Gleeble-1500 D thermal simulator. The height reduction was 50%, corresponding to a true strain of 0.693. The strain rate ranging from 0.01 to 10.00 s^-1 and the deformation temperature ranging from 800 to 950 ℃ were considered.The flow stress and the apparent activation energy for deformation, along with the constitutive equation, were used to analyze the behavior of the Ti-3.0 Al-3.5 Cr-2.0 Fe-0.1 B alloy. The processing map was established. The effect of strain rate on the microstructure at 850 ℃ was evaluated.The flow stress-strain curves indicated that the peak flow stresses increased along with an increase in the strain rate and decreased as the deformation temperature increased.Based on the true stress-true strain curves, the constitutive equation was established and followed as the ε= 6.58×10¹⁰[sinh(0.0113σ)]^3.44exp(-245481.3/RT). The processing map exhibited the "unsafe" region at the strain rate of10 s^-1 and the temperature of 850 ℃,and the rest region was "safe". The deformation microstructure demonstrated that both dynamic recovery(DRV) and dynamic recrystallization(DRX) existed during deformation. At the lower strain rate of 0.01 s^-1, the main deformation mechanism was the DRV, and the DRX was the dominant deformation mechanism at the higher strain rate of 1.00 s^-1.     

基于GIS的旧城改造开发容量的研究--以南阳市旧城更新改造为例

随着城市化进程的不断推进,旧城改造已经成为我国目前城市建设的重要任务,如何有效地进行旧城更新改造,对我国城市发展战略具有重要的意义。文章从城市经济定量分析角度入手,提出了旧城改造开发容量的概念、模型,土地等级评价指标体系及计算土地等级评价因素权重的AHP模型;以旧城生态环境和社会环境为约束条件,以经济作为目标函数,提出了基于旧城生态环境容量和社会环境目标确定旧城开发容量的上限模型,及基于市场行为的经济目标确定旧城开发容量的下限模型,使旧城改造始终处于经济、社会、环境持续协调发展的有序控制之中;并以ARCGIS为平台,结合南阳市旧城改造规划设计研究,得出旧城改造开发强度专题数据地图,对在GIS平台下合理确定旧城改造的开发容量,进行了尝试性探索。     

Topological structure evolvement of flow and temperature fields in deformable drop Marangoni migration in microgravity

Using the level-set method and the continuum interface model, the axisymmetric thermocapillary migration of a deformable liquid drop immerged in an immiscible bulk liquid with a temperature gradient is simulated numerically with constant material properties of the two phases. Steady terminal state of the motion can always be reached. The dimensionless terminal migration velocity decreases monotonously with the increase of the Marangoni number. Good agreements with space experimental data and most of previous numerical studies in the literature are evident. The terminal topological structure of flow field, in which a recirculation identical to Hill’s vortex exists inside the drop, does not change with the Marangoni number. Only slight movement of the location of vortex center can be observed. On the contrary, bifurcations of the terminal topological structure of temperature field occur twice with increasing Marangoni number. At first, the uniform and straight layer-type structure of temperature field at infinitesimal Reynolds and Marangoni numbers wraps inside of the drop due to convective transport of heat as the Marangoni number increases, resulting in the emergence of an onion-type local cooler zone around the center of the drop beyond a lower critical Marangoni number. Expanding of this zone, particularly in the transverse direction, with the increasing of the Marangoni number leads to a cap- or even shell-type structure. The coldest point within the liquid drop locates on the axis. There is a middle critical Marangoni number, beyond which the coldest point will jump from the rear stagnation into the drop, though the topological structure of the temperature field does not change. The second bifurcation occurs at an upper critical Marangoni number, where the shell-type cooler zone inside drops ruptures from the central point and then a torus-type one emerges. The coldest point departs from the axis, and the so-called “cold-eye” appears in the meridian. It is also found that the inner and outer thermal boundary layers along the interface may exist both inside and outside the drop if Ma > 70. But the thickness decreases with the increasing Marangoni number more slowly than the prediction of potential flow at large Marangoni and Reynolds numbers. A velocity shear layer outside the drop is also introduced formally, of which modality may be affected by the convective transports of heat and/or momentum.     

选矿厂循环水研究现状及其处理技术

选矿生产过程中耗水量大，为响应国家环保政策，实现选矿厂废水闭路循环，概述了铁矿石选厂、有色金属选矿厂、选煤厂及非金属选矿厂4种类型循环水特点及研究现状，讨论了混凝沉淀法、中和法、吸附法和膜分离法在循环水高效澄清方面的利用情况及存在的不足。指出去除可溶离子、残余药剂，降低循环水中的固体含量是循环水澄清回用的基本要求。对不同的循环水特性应使用不同的处理方法，一般需要联合使用。开发新型高效的澄清技术及工艺，改善现有循环水系统存在的不足将是推进绿色矿山建设重点与热点。     

Signal processing for real-time identification of similar metals by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy(LIBS) is regarded as a promising technique for realtime sorting of scrap metals due to its capability of fast multi-elemental and in-air analysis. This work reports a method for signal processing which ensures high accuracy and high speed during similar metal sorting by LIBS. Similar metals such as aluminum alloys or stainless steel are characterized by nearly the same constituent elements with slight variations in elemental concentration depending on metal type. In the proposed method, the original data matrix is substantially reduced for fast processing by selecting new input variables(spectral lines) using the information for the constituent elements of similar metals. Specifically, principal component analysis(PCA) of full-spectra LIBS data was performed and then, based on the loading plots, the input variables of greater significance were selected in the order of higher weights for each constituent element. The results for the classification test with aluminum alloy, copper alloy,stainless steel and cast steel showed that the classification accuracy of the proposed method was nearly the same as that of full-spectra PCA, but the computation time was reduced by a factor of 20 or more. The results demonstrated that incorporating the information for constituent elements can significantly accelerate classification speed without loss of accuracy.     

CaCu3Ti4O12陶瓷高介电性的起因机制

为了探索CaCu3Ti4O12(CCTO)高介电性的起因机制,利用固相反应工艺制备了CCTO陶瓷样品,对其电学性质进行了研究.在40 Hz～100 MHz测量范围内,其室温下的介电频谱在1 MHz附近呈现一个类Debye型弛豫,而高温介电频谱分别在1 kHz以下和1 MHz附近呈现两个类Debye型弛豫.抛除表面层的同一个样品分别溅射金电极和烧渗银电极后升温测量其介电频谱,发现低频介电弛豫对电极的金属类型高度敏感,而高频介电弛豫与电极的金属类型无关,与材料微观结构存在着密切的关系.因此推断:CCTO低频介电弛豫起源于样品与电极之间的耗尽层效应,而高频介电弛豫起源于高阻态的晶界与半导化的晶粒形成内部阻挡层电容效应.     

法国ESM500综合传动装置的技术特点分析

对法国ESM500综合传动装置的技术特点进行了介绍,通过与我国传动装置技术水平的对比分析,提出了借鉴国外的技术优势,提高我国现有传动装置技术水平的解决方案．