钠离子和钾离子通道噪声扰动对神经网络 时空模式的影响

研究了钠离子和钾离子通道噪声扰动对Hodgkin-Huxley神经网络放电时空模式的影响. 发现无论钠离子通道噪声还是钾离子通道噪声扰动, 当取定一组温度、噪声强度, 随着耦合强度的增大, 神经网络放电时空斑图总能演化出螺旋波, 而且存在形成螺旋波所需的临界耦合强度. 分析发现钠离子通道噪声有利于神经网络螺旋波的形成, 而钾离子通道噪声不利于螺旋波形成. 结果还表明较低的温度能够使神经网络对噪声更加敏感. 最后, 讨论了特定参数下螺旋波与靶波之间的转化现象.     

基于碳纳米管的纳米连接技术的研究进展

纳米连接技术是构筑纳电子器件的关键技术。但鉴于目前纳米连接机理不甚明确、纳米连接技术不甚成熟,阻碍了纳电子器件的进一步研制和应用。因此如何形成碳纳米管与金属电极间可靠、稳定、有效的互连已成为该领域的研究难点和热点。本文综述了近年来改善纳米连接性能的多种方法,并对其原理和特点进行了分析和比较。最后,对该领域未来发展的趋势进行了展望。     

水油两相体系生物还原-化学沉淀耦合反应制备纳米二硫化锡

针对Sn4+易于水解而难以在水相稳定存在的不利条件,尝试了在水油两相体系中应用生物转化-化学沉淀耦合反应工艺制备SnS2纳米材料。研究了水油两相体系制备SnS2的优化条件,并借助XRD、SEM、EDS表征了制备材料的结构、形貌和物相。研究表明,生物水相pH值7、水油两相反应温度35℃,油相Sn4+与水相SO42-之物质的量浓度比1∶2的条件下有利于SnS2的生成。制备的SnS2为纳米片花瓣,纳米片平均厚度约为30 nm,花状微晶直径约1~5μm,纯度高,无杂质。     

Dynamical response of a neuron–astrocyte coupling system under electromagnetic induction and external stimulation

Previous studies have observed that electromagnetic induction can seriously affect the electrophysiological activity of the nervous system. Considering the role of astrocytes in regulating neural firing, we studied a simple neuron–astrocyte coupled system under electromagnetic induction in response to different types of external stimulation. Both the duration and intensity of the external stimulus can induce different modes of electrical activity in this system, and thus the neuronal firing patterns can be subtly controlled. When the external stimulation ceases, the neuron will continue to fire for a long time and then reset to its resting state. In this study, "delay" is defined as the delayed time from the firing state to the resting state, and it is highly sensitive to changes in the duration or intensity of the external stimulus. Meanwhile, the self-similarity embodied in the aforementioned sensitivity can be quantified by fractal dimension. Moreover, a hysteresis loop of calcium activity in the astrocyte is observed in the specific interval of the external stimulus when the stimulus duration is extended to infinity, since astrocytic calcium or neuron electrical activity in the resting state or during periodic oscillation depends on the initial state. Finally, the regulating effect of electromagnetic induction in this system is considered. It is clarified that the occurrence of "delay" depends purely on the existence of electromagnetic induction. This model can reveal the dynamic characteristics of the neuron–astrocyte coupling system with magnetic induction under external stimulation. These results can provide some insights into the effects of electromagnetic induction and stimulation on neuronal activity.     

光催化还原制备Au/Ag核壳结构纳米粒子及其修饰电极的电催化性能

以Keggin结构硅钨杂多酸H4SiW12O40(SiW12)为光催化还原剂,通过光化学还原法制备Au/Ag核壳结构纳米粒子. 透射电子显微镜分析显示,所得纳米粒子粒径为30～40 nm,呈均匀分散的球形颗粒,该制备方法的特点是可以较好的避免单金属纳米粒子的形成. 将Au/Ag核壳纳米粒子修饰到具有PVP膜的玻碳电极表面,得到SiW12-(Au/Ag)-PVP多层膜修饰电极. 该修饰电极在0.5 mol/L H2SO4介质中具有良好的电化学响应,在0～-0.75 V电位范围内,出现了3对归属于SiW12的氧化还原峰,且电极性能稳定,灵敏度高. 对H2O2的电催化还原性能明显优于单金属Ag纳米粒子修饰电极,说明Au核的存在可以很好的改善Ag的电催化性能,Au和Ag之间存在相互协同催化作用.     

Photothermal biological effects of monomeric erythrocyte using optical tweezers

The changes of mechanical properties and biological activities of monomeric erythrocytes are studied using optical tweezers micromanipulation technology. Firstly, the mechanical properties of irradiated erythrocyte membranes are obtained. Weaker power laser irradiation can delay the decay of the mechanical properties of erythrocytes and promote the biological activity of erythrocytes, while higher power laser irradiation damages erythrocytes. The stronger the laser irradiation is, the more obvious and rapid the damage will be. The temperature of the cell surface will be changed by regulating the laser power and irradiation time, so the biological functions of erythrocyte can be controlled. Secondly, the finite element simulation of the temperature change on the cell surface under the condition of laser irradiation is carried out using simulation software, and the precise temperature of the cell surface irradiated cumulatively by a laser with different powers is obtained. Finally, the processes of abscission, unfolding, and denaturation of hemoglobins in erythrocytes at different temperatures due to the photothermal effect are analyzed using the model. The mechanism of laser irradiation on the elasticity of erythrocyte membranes is also obtained.     

高灵敏银纳米棒阵列对农药啶虫脒的表面增强拉曼散射快速检测

The determination of pesticide residue on agricultural products is increasingly important.Exposure to pesticides can cause severe acute reactions in humans,including aplastic anemia and leukemia.In this work,we developed a rapid and sensitive method to detect acetamiprid pesticide residue based on surface-enhanced Raman scattering.Silver nanorod (AgNR) arrays were fabricated by oblique angle deposition technology and were used as SERS substrates.Prior to detection,the AgNR arrays were cleaned with nitric acid solution or a mixture of methanol and acetone.Compared to the unwashed AgNR arrays,the AgNR arrays washed with methanol and acetone shows a signal enhancement 1000 times greater than the unwashed AgNR array due to the effective removal of the impurities on its surface.The limit of detection of acetamiprid was determined to be 0.05 mg/L.In addition,the molecular structure of acetamiprid was simulated and the corresponding vibration modes of the characteristic bands of acetamiprid were calculated by density function theory.To demonstrate its practical application,the AgNRs array substrates were applied successfully to the rapid identification of acetamiprid residue on a cucumber''s surface.These results confirmed possibility of utilizing the AgNRs SERS substrates as a new method for highly sensitive pesticide residue detection.     

中性微乳液介质增敏鲁米诺电化学发光研究

磷酸盐缓冲的中性溴化十六烷基三甲基铵-正戊醇-正庚烷微乳液介质体系对鲁米诺的电化学发光有显著的增敏作用,本文对此增敏作用进行了研究,并在此介质体系中采用电化学发光淬灭法测定了生物活性分子褪黑素,此法可用于测定脑白金胶囊中的褪黑素。     

硫化镉纳米膜的生物还原-化学沉淀耦合制备及其性能表征

本文应用生物还原-化学沉淀耦合反应(CRBRCP-EDTA)制备出硫化镉纳米薄膜,并借助XRD和SEM对合成材料的物相、结构、形貌进行了表征。研究表明,以铝片为基底时CdS难以沉积,CdS纳米薄膜不能形成;以导电玻璃和单晶硅片为基底时CdS纳米薄膜方可生成。导电玻璃和单晶硅片薄膜都是双层结构,导电玻璃薄膜下层厚度大约40~50 nm,上层厚度大约450~500 nm,整体厚度大约500~550 nm;硅片薄膜的上下两层厚度基本相等,均为300 nm左右,而整体厚度达到600~650 nm。Cd²⁺浓度增加和分散剂PAM加入显著改善了导电玻璃薄膜质量,膜的致密性、均匀性和光催化活性都有所提高。     

冷质部件支撑结构中压杆的热过屈曲分析

以圆杆式冷质量支撑结构中的压杆为研究对象,考虑了材料线膨胀系数α随温度非线性变化的特性及材料本构关系的非线性,基于轴线可伸长原理建立了压杆的热过屈曲数学模型;利用打靶法分别分析了材料本构关系取线性模型和非线性模型时的压杆热屈曲过程,并对二者进行了对比。研究结果表明:无论材料本构关系采用线性模型还是非线性模型,当α取常数时临界屈曲温度与柔度无关;而当α随温度非线性变化时,柔度则对临界屈曲温度产生影响;在同一柔度下,考察α对屈曲特性参数的影响规律时材料本构关系的非线性特性不可忽略;在非线性本构关系下线膨胀系数随温度非线性变化时可得到最大轴向载荷、最小横向支座反力、最小轴线总伸长量;较小的横向支座反力可以有效减小支撑结构中心收缩位移,较小的轴线总伸长量可以有效减小压杆周向固定端连接处应力。