Rapid detection of nitroaromatic and nitramine explosives on chromatographic paper and their reflectometric sensing on PVC tablets

Rapid and inexpensive sensing of explosive traces in soil and post-blast debris for environmental and criminological purposes with optical sensors has recently gained importance. The developed sensing method for nitro-aromatic and nitramine-based explosives is based on dropping an acetone solution of the analyte to an adsorbent surface, letting the solvent to dry, spraying an analytical reagent to produce a persistent spot, and indirectly measuring its reflectance by means of a miniature spectrometer. This method proved to be useful for on-site determination of nitro-aromatics (trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (tetryl) and dinitrotoluene (DNT)) and nitramines (1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)) pre-adsorbed on a poly vinyl chloride (PVC) surface, with the use of different spray reagents for each group of explosives producing different colors. The calibration equations of the tested compounds as reflectance vs. concentration showed excellent linearity (correlation coefficient: 0.998-0.999). The linear quantification interval in terms of absolute quantity of analyte was 0.1-0.5 μg. The developed method was successfully tested for the analysis of military explosives Comp B and Octol, and was validated against high performance liquid chromatography (HPLC). The reflectometric sensing method could also be used for qualitative identification of the nitrated explosives on a chromatographic paper. The reagent-impregnated paper could also serve as sensor, enabling semi-quantitative determinations of TNT and tetryl.     

太阳爆发日珥内双向喷流事件的紫外光谱研究

太阳双向喷流事件是过渡区重要的小尺度现象之一。双向喷流事件的光谱特征是强的展宽和非高斯形状。当双向喷流事件发生时,光谱像的红、蓝两翼分别或者同时明显增强,其相应的多普勒速度可达100 km·s-1以上。双向喷流事件的平均尺度约1 800 km, 寿命约60 s。双向喷流事件出现在磁对消区附近,且其速度与当地的阿尔芬速度相当,普遍认为其产生机制为小尺度快速磁重联。对其系统、全面地研究始于SOHO时代。SOHO/SUMER具有高时空和谱分辨率、宽的谱线覆盖,其观测的光谱数据为探究双向喷流事件提供了有力的光谱学诊断工具。双向喷流事件及其他过渡区小尺度现象的相互联系已被广泛研究,但双向喷流事件与日珥及其精细结构的关系研究还很少。文章通过SOHO/SUMER的Si Ⅲ谱线的定点观测,再现了爆发日珥演化的强度﹑多普勒速度和宽度演化图。通过Si Ⅲ谱线分析,找出宽度大于三个标准偏差的Si Ⅲ谱线,然后进行视像筛选出双向喷流事件,最终在爆发日珥中诊断出多个双向喷流事件,且大多数的双向喷流事件以准周期20 min重复出现在爆发日珥的中心区域。通过讨论,认为日珥中心磁流管之间的磁重联导致了双向喷流事件的重复出现,双向喷流事件产生的高速等离子体流可能是日面物质抛射的一部分,或是跟随日面物质抛射的太阳风的一部分。     

Estimation of spinodals from the density profile of the vapor–liquid interface

An extension of a recently proposed method for the calculation of the spinodals in pure fluid systems from the interfacial properties is elaborated, which requires the density profile as only input. The foundation of this approach is the so-called Fuchs-transformation which gives an estimate for the tangential pressure profile from the density profile. Using molecular dynamics simulation data for argon and carbon dioxide as well as lattice Boltzmann simulation data for the argon-like Shan–Chen fluid, the accuracy of the approach is analyzed. The Fuchs-transformation is qualitative, however it is possible to estimate the temperature–density projection of the spinodal. Depending on the underlying correlation function for the interfacial density profile reasonable results are obtained for the liquid and the vapor spinodal. The advantage of this method is that equilibrium data can be used to estimate the spinodal which is experimentally impossible to access because it is a highly non-equilibrium property. In the final consequence of this approach only the coexistence vapor and liquid densities are required to estimate the temperature–density projection of the spinodals.     

四苯乙烯的合成、表征及在爆炸物检测中的应用 ——介绍一个大学化学综合实验

因具有聚集诱导发光特性、螺旋桨结构的四苯乙烯及其衍生物,在有机光电材料、荧光传感和生物成像等领域表现出优异的荧光性能。本实验以二苯甲酮为原料,利用McMurry偶联反应合成四苯乙烯。采用萃取、干燥和柱层析等手段对产物进行分离和纯化,通过熔点测定、核磁共振氢谱、核磁共振碳谱和质谱对其结构进行表征后,使用苦味酸作为模型化合物,利用荧光光谱测定其对爆炸物的荧光检测极限。本实验寓科研热点于实验教学中,不仅提高了学生的实验操作技能,而且有助于学生了解具有聚集诱导发光性能的四苯乙烯及其衍生物的研究现状和应用前景,激发了学生的科研兴趣和创新意识。     

关于半线性椭圆型方程爆破解的存在性

文中得到半线性椭圆型方程的爆破问题解的存在性,其中或者是Rn中的有界区域,C3,C4,C5,C6是正常数,并且C5,C3（0,1）．     

缩短两级爆磁压缩发生器输出脉冲宽度的一种途径

 缩短两级爆磁压缩发生器输出脉冲宽度的一种有效办法是增大第二级螺旋线圈的锥角,但增大锥角会降低发生器电感压缩比,合理的锥角设计是此类发生器的关键。介绍了三种能带大电感负载、结构紧凑的两级爆磁压缩发生器,第一级结构参数相同,第二级螺旋线圈锥角分别为6°,8°,10°。在电感负载上进行的实验结果表明：其输出电流分别达到140,90和50 kA,电流脉冲宽度分别为12.5,8.5和6.3 μs,对应的名义输出功率分别为7,7和3 GW。     

Integrated explosive preconcentrator and electrochemical detection system for 2,4,6-trinitrotoluene (TNT) vapor

This article reports on an integrated explosive-preconcentration/electrochemical detection system for 2,4,6-trinitrotoluene (TNT) vapor. The challenges involved in such system integration are discussed. A hydrogel-coated screen-printed electrode is used for the detection of the thermally desorbed TNT from a preconcentration device using rapid square wave voltammetry. Optimization of the preconcentration system for desorption of TNT and subsequent electrochemical detection was conducted yielding a desorption temperature of 120 °C under a flow rate of 500 mL min⁻¹. Such conditions resulted in a characteristic electrochemical signal for TNT representing the multi-step reduction process. Quantitative measurements produced a linear signal dependence on TNT quantity exposed to the preconcentrator from 0.25 to 10 μg. Finally, the integrated device was successfully demonstrated using a sample of solid TNT located upstream of the preconcentrator.     

Weighted Limit Theorems for Continuous-Time Vector Martingales with Explosive and Mixed Growth

In this article, we establish the almost-sure central limit theorem (ASCLT) for a quasi-left continuous vector martingale with explosive and mixed (regular and explosive) growth. We also prove a quadratic extension and establish several new central limit theorems associated with the obtained ASCLT. Finally, we study the problem of parameter estimation in the particular case of multidimensional diffusion processes, which illustrates in a concrete manner the use of our results.     

Resonance of Feshbach-type and explosive instability of magnetoelastic waves in solids

In this paper, we theoretically describe a magnetoelastic system with an explosive instability in which the magnetic energy can be converted into the mechanical one via an extremely efficient channel. The principle is based on the amplification of acoustic waves traveling in an antiferromagnetic crystal under the action of transversal electromagnetic pumping. It is known that such parametric interaction can produce an exponential acoustic wave amplification. Our finding consists in the addition of another pumping channel by means of a discrete resonant acoustic mode whose impact is similar to the Feshbach resonance observed in another physical system (ultra-cold gazes). The addition of the second pumping mechanism results in the explosive instability having the dynamics of a singularity at a finite time instead of the exponential growth. In our example the traveling waves are Lamb waves in an antiferromagnetic plate, and the additional pumping is a shear resonance. We establish equations governing the considered three-phonon parametric instability, theoretically analyze the instability conditions, and give a relevant numerical example illustrating the explosive magneto-acoustic dynamics. It is shown that the explosive scenario can occur with a very low signal level i.e. Lamb waves amplitudes comparable to spontaneous noise in the system.     

Monte Carlo simulations of a D-T neutron generator shielding for landmine detection

Shielding for a D–T sealed neutron generator has been designed using the MCNP5 Monte Carlo radiation transport code. The neutron generator will be used in field for the detection of explosives, landmines, drugs and other ‘threat’ materials. The optimization of the detection of buried objects was started by studying the signal-to-noise ratio for different geometric conditions.