纸张物证的分析检验方法

纸张是犯罪现场经常出现的物证。对纸张物证的分析检验在案件侦破中有着重要作用,因此,法庭科学工作者一直对纸张物证的检验方法进行深入研究。随着法庭科学实验室的发展,纸张的检验技术得到了长足的进步,由传统的单一仪器分析方法发展到现在多种分析技术的联合应用,从而建立了快速、有效、灵敏的检验方法,为涉及纸张物证的案件侦破做出了显著的贡献。本文对纸张物证的分析检验方法进行了介绍和讨论。     

A first example of macromolecular Ti(IV) Lewis acid in the catalytic enantioselective Mukaiyama reaction

The preparation and characterization of a soluble copolymer P1 between styrene, divinylbenzene (DVB) and the enantiomerically pure salicylaldimine ligand 3c is described. The Lewis acid prepared from this macromolecular chiral ligand and Ti(OⁱPr)₄ has been used in the catalytic Mukaiyama reaction to afford benzyl (R)-3-hydroxy-3-phenylpropanoate 7.     

Effects of multi-frequency ultrasound on physicochemical properties,structural characteristics of gluten protein and the quality of noodle

In this study, the influence of multi-frequency ultrasound irradiation on the functional properties and structural characteristics of gluten, as well as the textural and cooking characteristics of the noodles were investigated. Results showed that the textural and cooking characteristics of noodles that contain less gluten pretreated by multi-frequency ultrasonic were ultrasonic frequency dependent. Moreover, the noodles that contain a smaller amount of sonicated gluten could achieve the textural and cooking quality of commercial noodles. There was no significant difference in the cooking and texture characteristics between commercial noodles and noodles with 12%, 11%, and 10% gluten pretreated by single-frequency (40 kHz), dual-frequency (28/40 kHz), and triple-frequency sonication (28/40/80 kHz), respectively. Furthermore, the cavitation efficiency of triple-frequency ultrasound was greater than that of dual-frequency and single-frequency. As the number of ultrasonic frequencies increased, the solubility, water holding capacity and oil holding capacity of gluten increased significantly (p < 0.05), and the particle size was reduced from 197.93 ± 5.28 nm to 110.15 ± 2.61 nm. Furthermore, compared to the control group (untreated), the UV absorption and fluorescence intensity of the gluten treated by multi-frequency ultrasonication increased. The surface hydrophobicity of gluten increased from 8159.1 ± 195.87 (untreated) to 11621.5 ± 379.72 (28/40/80 kHz). Raman spectroscopy showed that the α-helix content of all sonicated gluten protein samples decreased after sonication, while the β-sheet and β-turn content increased, and tryptophan and tyrosine residues were exposed. Through scanning electron microscope (SEM) analysis, the gluten protein network structure after ultrasonic treatment was loose, and the pore size of the gluten protein network increased from about 10 μm (untreated) to about 26 μm (28/40/80 kHz). This work elucidated the effect of ultrasonic frequency on the performance of gluten, indicating that with increasing frequency combination increases, the ultrasound effect became more pronounced and protein unfolding increased, thereby impacting the functional properties and the quality of the final product. This study provided a theoretical basis for the application of multi-frequency ultrasound technology in the modification of gluten protein and noodle processing.     

全波形激光雷达回波信号建模仿真与分析

全波形回波信号建模仿真与分析是全波形激光雷达探测技术的一项重要研究内容。针对激光束在目标场景中投影点的获取问题,提出了一种基于激光束空间边界的光线求交快速算法,运算效率高,稳定性好。基于激光雷达信号的时空分布特性,推算出目标场景对信号的响应函数,建立二者的作用过程模型。并针对全回波检测技术中的距离选通探测模式,对目标回波信号与距离选通门限的位置关系进行了分类建模和分析。在研究以上三项关键技术的基础上,构建了全波形激光雷达回波信号仿真系统,仿真实现和分析了不同距离选通门限条件下的全波形回波信号特性,并生成了复杂场景下隐蔽目标的全波形激光雷达数据。     

同位素稀释液相色谱-串联质谱法测定动物性食品中的双酚A、壬基酚及辛基酚

建立了动物性食品肉、蛋和奶中双酚A、壬基酚和辛基酚的超高效液相色谱-串联质谱( UPLC-MS/MS)检测方法.比较了固相萃取法(SPE)和凝胶渗透色谱法(GPC)两种前处理技术,探讨了前处理过程中目标化合物背景污染的来源.最终采用乙酸乙酯-环己烷(1∶1,V/V)超声提取,经GPC净化后进行超高效液相色谱串联质谱分析.3种目标化合物的线性范围为0.25～1600 μg/L,相关系数R2＞ 0.999;对肉和鸡蛋样品,方法的定量限( LOQ)为0.2μg/kg;奶粉样品的LOQ为0.4 μg/kg.目标化合物在3个不同水平的加标回收率为85.9％～117.0％,RSD＜ 20％.应用本方法对市售动物性食品肉、蛋和奶进行了分析,壬基酚的检出率最高,含量为0.27～1357 μg/kg,此外还检出了双酚A.     

Evaluation of the zinox and zeolite materials as adsorbents to remove H2S from natural gas

Mesoporous materials can be generally used as adsorbents to remove impurities from gases. During the past few years, H₂S has been removed from natural gas using materials such as dolomite, zeolites, and industrial compounds, which can be widely used by oil and natural gas companies. The present study focused on the use of Zeolite 13X and Zinox 380 as H₂S adsorbent at 25 °C. They were characterized by chemical analyses (X-ray fluorescence and atomic absorption), X-ray diffraction, particle size distribution analyses and FT Infrared spectroscopy. Adsorption reactions were carried out using proposed models. The results revealed that both materials studied could be used as H₂S adsorbents in natural gas exceeding the capabilities of industrial compounds.     

图像比色法测定有色溶液

根据溶液中有色物质颜色值与其质量浓度成正比的原理及数字图像红绿蓝色彩模式,通过采集样品溶液的图像信息,采用图像比色法对有色溶液进行定量分析。以蓝色硫酸铜溶液为研究对象,在实验箱内采集图像和建立统计回归模型。结果表明:方法测量误差为5%,线性范围为10.0~50.0g·L-1,相关系数大于0.990。     

火灾现场燃烧残留物检验研究进展

从火场燃烧残留物检验方法、基质干扰和数据解读等方面综述了火场燃烧残留物检验鉴定的研究进展,重点介绍了检验方法的研究成果与该领域常见的化学计量学方法,并对该领域的研究方向进行了展望(引用文献56篇)。     

First Total Synthesis of 3α,4α-Oxidoagarofuran and (-)-3β,4α-Dihydroxy-β-dihydroagarofuran

The first stereoselective total synthesis of (–)-3β, 4α-dihydroxy-β-dihydroagarofuran (1) and 3α, 4α-oxidoagarofuran (2) has been described. The key step is the epoxidation of α-agarofuran (6) with dimethyldioxirane.