基于亮蓝为显色剂的高酸度试纸

研究了色素亮蓝对氢离子浓度大于1 mol/L溶液的颜色响应及其变色机理,并将其作为显色剂应用于高酸度试纸的研发。 研究表明,固定于改性基纸上的亮蓝处于氢离子浓度为0.1~9.0 mol/L范围的介质溶液中时,其颜色变化表现出明显的酸度响应特征,即随着溶液酸度的提高,亮蓝逐渐由蓝色转化为蓝绿色、绿色、黄绿色直至黄色。 该响应具有普适性,不受无机酸的种类与氧化性强弱的影响。 采用分光光度法研究了溶液酸度对亮蓝光吸收特性的影响,提出其可能的变色机理。 以亮蓝为显色剂开发出高酸度试纸,该试纸可以直接检测溶液中0.1~9.0 mol/L范围内的氢离子平衡浓度,精确度为±1 mol/L。     

2014年广东高考理综化学试题赏析及思考

对2014年广东高考理综化学试题进行研究,先整体分析试题特点,后局部赏析试题内容亮点,挖掘试题功能,继而反思试题启示与备考策略,以达到探究命题规律和助推教学研究的目的。     

巧用具支试管改进化学实验

巧用具支试管改进了“钠与硫酸铜溶液的反应”“氢氧化亚铁的制备”“铜与浓硫酸反应”等实验,不仅节约药品、操作简便、快捷,而且现象明显,既适合教师演示实验,更利于学生开展探究实验。     

Large deflections of a beam subject to three-point bending

In this paper, a solution for the equilibrium configuration of an elastic beam subject to three-point bending is given in terms of Jacobi elliptical functions. General equations are derived, and the domain of the solution is established. Several examples that illustrate a use of the solution are discussed. The obtained numerical results are compared with the results of other authors. An approximation formula by which the beam load is given as a polynomial function of beam deflection is also derived. The range of applicability of the approximation is illustrated by numerical examples.     

On the modeling of fiber dispersion in fiber-reinforced elastic materials

When an isotropic material is subject to a uniaxial tension, the principal strain transverse to the direction of applied load is always negative. However, in fiber reinforced materials the transverse principal strain can change its sign as the load increases, passing through the zero-points, known as perversions. We investigate how the number of perversions in a material reinforced by two symmetrically aligned families of distributed fibers depends both on the degree of fiber dispersion and the model used for fiber dispersion. Angular integration and three variants of the generalized structure tensor approach are considered and discussed. The study of perversions clearly demonstrates the qualitative difference between these approaches in the case of high dispersion of fibers. The results suggest that this difference is primarily due to the way compressive fibers are modeled.     

豚鼠内耳前庭-半规管生物力学模型研究

人体维持平衡主要依靠前庭、视觉及本体感觉3个系统的相互协调来完成,其中前庭系统最为重要.因其结构细微且位置深在,传统方法难以满足现代前庭医学定位、定性、定量的研究需要,而生物数值模拟研究方法在现代耳科学研究中优势显著.建立精准的生物数值模型是其重点之一.本研究通过连续组织切片技术获取豚鼠内耳膜性结构的二维解剖数据,进一步建立同时包括前庭和3个半规管的宏观三维生物数值模型,其空间结构特征及尺寸与解剖学观察一致;数值模拟临床医学冷热实验,量化描述了不同环境温度激励下半规管内壶腹嵴顶位移、速度和压强等参数随时间变化的生物力学特征,其与临床观察到的眼震结果一致.总之,通过连续组织切片技术获取内耳膜性结构二维解剖数据并据此建立内耳三维生物数值模型的研究方法可行,所建立的生物模型可满足前庭-半规管平衡功能定位、定性、定量的研究需要.      

Modulation of the PGE2-Mediated Pathway in the Eclosion Blocking Effect of Flumethrin and Terpenoid Subfraction Isolated from Artemesia nilagirica in Rhipicephalus annulatus

Prostaglandins are a group of important cell-signaling molecules involved in the regulation of ovarian maturation, oocyte development, egg laying and associated behaviors in invertebrates. However, the presence of prostaglandin E₂ (PGE₂), the key enzymes for PGE₂ biosynthesis and its interference by drugs were not investigated previously in the ovary of ticks. The present study was undertaken to assess the modulation of the PGE₂-mediated pathway in the eclosion blocking effect of flumethrin and terpenoid subfraction isolated from Artemisia nilagirica in Rhipicephalus annulatus ticks. The acaricidal activities and chemical profiling of the terpenoid subfraction were performed. The localization of the cyclooxygenase1 (COX1) and prostaglandin E synthase (PGES) enzymes and the quantification of PGE₂ in the ovaries of the ticks treated with methanol (control), flumethrin and terpenoid subfraction were also undertaken. In addition, the vitellogenin concentration in hemolymph was also assayed. Both flumethrin and the terpenoid subfraction of A. nilagirica elicited a concentration-dependent inhibition of fecundity and blocking of hatching of the eggs. The COX1 could not be detected in the ovaries of treated and control ticks, while there was no significant difference observed in the concentration of vitellogenin (Vg) in them. The presence of PGES in the oocytes of control ticks was confirmed while the immunoreactivities against PGES were absent in the vitellogenic oocytes of ticks treated with flumethrin and terpenoid subfraction. The levels of PGE₂ were below the detection limit in the ovaries of the flumethrin-treated ticks, while it was significantly lower in the ovaries of the terpenoid subfraction-treated ticks. Hence, the prostaglandin E synthase and PGE₂ were identified as very important mediators for the signaling pathway for ovarian maturation and oviposition in ticks. In addition, the key enzyme for prostaglandin biosynthesis, PGES and the receptors for PGE₂ can be exploited as potential drug targets for tick control. The detection of PGES by immunohistochemistry and quantification of PGE₂ by LC-MSMS can be employed as valuable tools for screening newer compounds for their eclosion blocking acaricidal effects.     

Comparative study of InGaP/GaAs heterojunction bipolar transistors (HBTs) with different base surface treatments

The interesting InGaP/GaAs heterojunction bipolar transistors (HBTs) with different surface passivations on the base surface are fabricated and studied. Experimentally, the HBT device with sulfur treatment passivation displays the lowest offset voltage. However, the device with a 0.02 μm-thick emitter ledge structure reveals better transistor behaviors such as higher current gain and lower base surface recombination current. In addition, it also exhibits improved thermal stability. For the reliability test, the device with a 0.02 μm-thick emitter ledge structure shows the best performance. Therefore, from experimental results, the HBT device performance could be improved by appropriate base surface treatments, e.g., sulfur passivation and emitter ledge structure.     

Effective interactions of colloids on nematic films

The elastic and capillary interactions between a pair of colloidal particles trapped on top of a nematic film are studied theoretically for large separations d. The elastic interaction is repulsive and of quadrupolar type, varying as d^-5. For macroscopically thick films, the capillary interaction is likewise repulsive and proportional to d^-5 as a consequence of mechanical isolation of the system comprised of the colloids and the interface. A finite film thickness introduces a nonvanishing force on the system (exerted by the substrate supporting the film) leading to logarithmically varying capillary attractions. However, their strength turns out to be too small to be of importance for the recently observed pattern formation of colloidal droplets on nematic films.     

Phase shifting grating-slit test utilizing a liquid crystal display

A quantified focal plane testing method, termed phase-shifting grating-slit test, is demonstrated by utilizing a micro liquid crystal display. In contrast to the setup in the Ronchi Test, an incoherent illuminating grating is used and an optical slit is located at the image plane of the tested lens to modulate the aberrated wavefront. With the micro liquid crystal display generating and phase shifting the incoherent illuminating grating with variable frequency, a higher measurement dynamic range can be achieved on demand.