非传统稳定同位素在土壤重金属源解析方面的应用

随着工业发展,土壤中累积的重金属对人类产生健康威胁。在全面评估土壤重金属污染的情况下,通过非传统稳定同位素测量可以对其来源进行有效解析。鉴于这一新兴领域的快速发展,对非传统稳定同位素在土壤重金属源解析中的作用进行了阐述。在此基础上,提出了现有的问题和展望,为土壤重金属污染源解析理论、技术的研究与应用提供借鉴,推进土壤重金属污染防控的建立与完善。     

辨微识源: 纳米颗粒物溯源技术的新进展※

随着纳米技术在医药、工业催化、食品及农业生产等领域的广泛应用, 人造纳米颗粒被大量生产并最终不可避免地进入自然环境, 进而造成潜在的环境和健康风险. 目前, 纳米材料已经被认为是一类潜在的环境污染物. 准确示踪纳米颗粒的来源和环境转化过程是评价其毒理学效应和进行精准污染管控的重要前提. 综述了近年来纳米颗粒溯源技术的新进展, 包括多维化学指纹技术、非传统稳定同位素技术、同位素标记技术和环境DNA标记技术等, 并对纳米颗粒溯源技术的未来发展方向进行了展望.     

Migration,Crystallization and Dissolution Changes of Salt Solution with Color Rendering Property in Porous Quartz Materials

In order to visually display the migration and crystallization process of salt solution in porous cultural relics, copper sulfate solution with color rendering property was selected to record the migration, crystallization and resolution of salt solution in simulated SiO₂ samples under different environmental conditions in real time through high-resolution recording system, scanning electron microscope system, salt phase X-ray diffraction system, and so on. The results showed the migration of salt solution in porous samples was related to the structural characteristics of the porous samples, the migration rate of salt solution, the evaporation rate and the change frequency of crystallization–resolution, etc., in which the large pore size of the sample, the higher the concentration and the faster migration and evaporation rate of salt solution, the greater the change rate of the brine accumulation zone or salt crystallization zone in the different porous samples. During the humidification–drying cycles of rainfall, the higher the cycle frequency of humidification–drying was, the higher the drying temperature was, the more frequent the crystallization-analysis change of salt in the salt-bearing sample was, and the more extensive the distribution of salt crystal zone was. This is the first time to visualize the salt belt by simulating the changing process of a salt solution with a color rendering property in porous samples. This has scientific theoretical guidance for the study of the migration–crystallization changes of soluble salts contained in porous silicate cultural relics. The visibility analysis results of multilayer salt crystal belts can also provide the preliminary basis for further effective desalination of salt bearing cultural relics.     

A note on the proper frequency resolution for the room transfer function in the phased beam tracing method

In the simulation of acoustic response of a room, one cannot satisfactorily estimate the transfer function or the impulse response with a sparse frequency resolution. We have studied about the frequency resolution for a satisfactory estimation of room transfer function or the reverberation time using the phased beam tracing method. In order to investigate what happens with the frequency resolution, a number of frequency resolution (0.01-1 Hz), which are usually employed in the numerical analysis, was tested for a room model. It was found that the total accumulated phase in a transfer function and the late part of an impulse response of a room are influenced by the frequency resolution. Main reason for the difference is the correct detection of non-minimum phase zeros, depending on the frequency resolution. A criterion for a proper frequency resolution was suggested by considering the modal density of three-dimensional space. When a sparse dataset was initially given, we showed that cubic spline interpolation can be used to enhance the precision of detection for non-minimum phase zeros.     

Suppression of primary chromatic aberration by genetic algorithm in an advanced telephoto lens

This paper proposes a new method for finding a suitable glass combination set for an advanced telephoto lens via a genetic algorithm (GA). Normally, glass properties, inclusive of index and Abbe number, play a significant role in the elimination of primary chromatic aberration. So many optical glasses (over 300 different refractive types) have been developed hitherto that it is difficult to choose a state-of-the-art glass combination quickly. According to the newly developed GA operations in this paper, however, several suitable glass combinations can be found quickly through a unique sequence of function selection, crossover and mutation. An advanced telephoto lens design is employed in this research, which has the characteristic of being more sensitive to axial aberrations than lateral chromatic aberrations. The GA operations are described in the macro of the optical software program, CODE V. The simulation results in this research show that the primary chromatic aberration is efficiently eliminated after the application of GA. The main goal of this research is that during optimization, error function could be minimized only if primary aberrations are well under control in our first step; in a telephoto lens, the secondary spectrum of longitudinal chromatic aberration and lateral chromatic aberration caused by distortion play a role in chromatic aberration control as well; however, optimization with a combination of both primary chromatic aberration and secondary chromatic aberration will complicate the process with a lot of working variables. The GA method introduced in this paper might efficiently eliminate the primary chromatic aberration first by finding the best glass combination and its trend and then simplifying the following optimization process for all optical systems.     

An approximate treatment of reflection coefficient in the phased beam tracing method for the simulation of enclosed sound fields at medium frequencies

The phased beam tracing method (PBTM) was suggested as a medium-frequency simulation technique for the calculation of impulse response, although main assumptions of geometric acoustics still hold. The phased method needs the reflection coefficient for characterizing the acoustic property of a surface and the complex wave number for describing the propagation characteristics. In this study, two types of approximate real reflection coefficients derived from the measured absorption coefficient were tested for a practical applicability. As a test example, pressure impulse responses and energy impulse responses computed from the PBTM were compared with those from the measurement and the ordinary beam tracing method. The PBTM employing the approximate reflection coefficients greatly increased the accuracy of the prediction compared to the ordinary beam tracing method, in particular at the medium-frequency range in octave bands above the Schroeder cutoff frequency. A comparison was made between angle-dependent and angle-independent reflection coefficients in the calculation of acoustic measures. Although the angle-dependent reflection coefficient yielded best matched results with measured data, but the simple angle-independent reflection coefficient can be also used with a reasonably good precision.     

基于软光刻的多层光互连垂直耦合结构

设计并试制了一种新型垂直耦合光互连线路结构,可用于高速计算机内部等垂直堆叠的多层连通光互连的芯片间光信息通讯。其结构简单,且具有较小的连接损耗(可低至0.05dB)。对四种不同的典型波导截面(分别为30μm×30μm,50μm×50μm,100μm×100μm,200μm×200μm),利用蒙特卡罗多光线追迹分析法对跨越1~6层的垂直耦合结构进行了性能分析,发现当该结构的跨越高度与横向跨越距离的比值约为0.128时,可实现较理想的低损耗(低于1dB)光传输。采用软光刻的方法制备了实验多层光互连线路,其性能测试与理论结果基本相符。     

Optical Code Generating Device Using 1×N Asymmetric Hollow Waveguide Couplers

An optical code generating device for security access system application is presented. The code generating device constructed using asymmetric hollow optical waveguide coupler design provides a unique series of output light intensities which are successively used as an optical code. The design of the waveguide is made using two major components which are asymmetric Yjunction splitter and a linear taper. Waveguiding is done using a hollow waveguide structure. Construction of higher level 1×N hollow waveguide coupler is done utilizing a basic 1×2 asymmetric waveguide coupler design together with a cascaded design scheme. Nonsequential ray tracing of the asymmetric hollow optical waveguide couplers is performed to predict the optical transmission properties of the waveguide. A representation of the code combination that can be generated from the device is obtained using combinatory number theory.     

Light propagation in multi‐step index optical fibres

This paper reviews the theoretical analysis of light propagation we have carried out on multimode multi‐step index (MSI) optical fibres. Starting from the Eikonal equation, we derive the analytical expressions that allow calculating the ray trajectories inside these fibres. We also analyse the effects of leaky rays on the transmission properties of MSI fibres. For this purpose, a single analytical expression for the evaluation of the ray power transmission coefficient is calculated. Afterwards, we investigate the effects of extrinsic and intrinsic coupling losses on the performance of MSI fibres, providing analytical expressions to calculate the coupling loss and, also, determining the most critical parameters. Finally, we carry out a comprehensive numerical analysis of the fibre bandwidth under different source configurations.     

同位素示踪技术定量分析肿瘤细胞中的代谢重编

肿瘤代谢在最近几年重新获得重视,讨论肿瘤代谢我们无法避开瓦伯格效应,尽管瓦伯格效应在20世纪20年代就提出来了。瓦伯格效应也称需氧糖酵解,是指在有氧的条件下癌细胞过量摄取葡萄糖,产生更多的乳酸。此外,癌细胞也可摄取其他物质,如谷氨酰胺、丝氨酸和甘氨酸等作为能量需求与营养来源。为了描述癌细胞中改变了的代谢通路,同位素标记示踪技术提供了一种新的全局观点,让我们更好地理解在癌基因或抑癌基因调控下的代谢切换。色谱与质谱联用是一种重要的分析工具,可定量检测带有同位素标记的代谢物,从而剖析肿瘤细胞中的生物化学反应。在本文中,我们总结了基于质谱的肿瘤代谢分析的研究概况并提出未来的研究方向。重点讨论碳-13标记与氘代标记的示踪技术分析中间代谢产物,包括还原型烟酰胺腺嘌呤二核苷酸磷酸(NADPH)。目前生物化学教科书中认为NADPH主要来源于磷酸戊糖途径。然而,氘代示踪技术分析表明,包括一碳代谢在内的其他代谢通路对产生NADPH也很重要。以上内容都在本文中进行了讨论。