A Systematic Study to Understand the Effects of Particle Size Distribution of Magnetic Fingerprint Powders on Surfaces with Various Porosities

This study intends to design magnetite (Fe₃O₄)‐based magnetic fingerprint powders with different particle size distributions. It also investigates the influence of particle size distribution on the visualization of latent fingermarks with as little background staining as possible on the surfaces with various porosities in a systematic way. Two strategies were used to prepare the magnetic fingerprint formulations for this study: milling of coarse magnetite particles for different durations, and mixing of sieved fine particles with different size ranges with coarse particles. Particle size analyses of the prepared magnetic powders, optical microscopy‐based roughness analysis of the surfaces and SEM measurements of the visualized fingerprints and representative powders were performed. Mag2 of the formulations prepared through milling and Mag5 and Mag6 of the formulations prepared through sieving and mixing were more successful in the development of latent prints than the rest of the solutions.     

Identification of 2‐(ethylamino)‐1‐(4‐methylphenyl)‐1‐pentanone (4‐MEAP), a New “Legal High” Sold by an Internet Vendor as 4‐Methyl Pentedrone

Online vendors are offering a new legal high, 4‐methylpentedrone (4‐MPD). Information for potential users provided by internet vendors of 4‐MPD includes incorrect structures and nonexistent CAS numbers. A sample of 4‐MPD was obtained and analyzed using GC‐MS, NMR, and LC‐EIS. The fragmentation data from the GC‐MS and LC‐EIS produced an M‐1 ion that suggested the molecular mass was 219 amu, rather than 205 amu as calculated for 4‐methylpentedrone. The difference in molecular mass corresponded to the addition of a methyl group. Based on the mass and fragmentation pattern, two standards were synthesized, 2‐(ethylamino)‐1‐(4‐methylphenyl)‐1‐pentanone and 1‐(4‐methylphenyl)‐2‐(propylamino)‐1‐butanone. The synthesis involved bromination of the appropriate ketone followed by the reaction with ethylamine or propylamine. Based on the NMR data and unique fragmentation patterns produced by these molecules, the sample was identified as 2‐(ethylamino)‐1‐(4‐methylphenyl)‐1‐pentanone, not 4‐methylpentedrone.     

核磁共振技术在控制柴油车尾气污染中的应用

为解决柴油车在道路行驶过程中流动污染问题 ,采用核磁共振技术改善燃油品质 ,以控制减少外排污染物对环境的危害 ,净化城市交通道路环境     

Rapid Localization of Bone Fragments on Surfaces using Back‐Projection and Hyperspectral Imaging

Manual localization of bone fragments on the ground or on complex surfaces in relation to accidents or criminal activity may be time‐consuming and challenging. It is here investigated whether combining a near‐infrared hyperspectral camera and chemometric modeling with false color back‐projection can be used for rapid localization of bone fragments. The approach is noninvasive and highlights the spatial distribution of various compounds/properties to facilitate manual inspection of surfaces. Discriminant partial least squares regression is used to classify between bone and nonbone spectra from the hyperspectral camera. A predictive model (>95% prediction ability) is constructed from raw chicken bones mixed with stone, sand, leaves, moss, and wood. The model uses features in the near‐infrared spectrum which may be selective for bones in general and is able to identify a wide variety of bones from different animals and contexts, including aged and weathered bone.     

Characterization of Blue Pigments Used in Automotive Paints by Raman Spectroscopy

Micro‐Raman spectroscopy was applied to forensic identification of pigments in paint chips and provided differentiation between paint samples. Sixty‐six blue automotive paint samples, 26 solid and 40 metallic were examined. It was found that the majority of the collected Raman spectra provided information about the pigments present. However, in some cases, fluorescence precluded pigment identification. Using laser excitation at longer wavelengths or pretreatment to effect photobleaching often resulted in reduced fluorescence, particularly for solid color samples, and allowed pigment identification. The examined samples were compared pairwise taking into account number, location, and intensity of absorption bands in their infrared spectra. The estimated discrimination power ranged from 97% for solid paint samples to 99% for metallic paint samples.     

应用磁珠法提取陈旧骨骼DNA

目的探讨采用磁珠法提取陈旧骨骼DNA的可行性。方法取经土埋或室外暴露下存放1~5年不等的10根长骨,经水洗、刮净,钻取骨密质骨粉3g,应用EQ1000磁珠试剂盒提取DNA,经复合扩增,ABI 3130XL基因分析仪电泳分离,进行STR分型检测。结果 10根长骨均获得完整的STR分型,电泳图谱基线干净,除个别大片段基因座外,等位基因荧光信号分布均衡性较好。结论采用磁珠法提取陈旧骨骼的DNA,能满足分型要求,可在实际检案中选用。     

拉曼光谱技术在物证鉴定中的应用

拉曼光谱技术具有不接触样品、不破坏样品、无需样品制备等优点,适用于法庭科学领域不同种类物证的分析.本文综述了拉曼光谱技术在物证鉴定中的应用,并对该技术的发展趋势进行了展望.     

荧光检验法在朱墨时序鉴定中的应用研究

朱墨时序鉴定一直是文书司法鉴定实践中常见的鉴定项目,也是研究的热点和疑难问题.通过实验研究并结合检案实践,较系统地阐述了视频荧光光谱检验法和显微荧光检验法在朱墨时序鉴定的具体应用,探讨了荧光检验的技术要点.研究表明,荧光检验法（特别是显微荧光检验法）具有普通显微检验法的优点,同时对普通显微检验法中难以观察到的印文或文字色料荧光特性及色料的微观分布状态,具有明显的检验效果,是普通显微检验法有效的补充检验手段.     

基于拉曼光谱的血液遗留时间研究与模型预测

目的针对犯罪现场血液遗留时间的判断问题,实验以不同遗留时间的血液为研究对象,建立基于拉曼光谱的血液遗留时间的辨别方法。方法采集遗留时间为0.5h~240h的指尖血液样本,获取其拉曼光谱数据,经校正和平滑处理后,对数据进行归一化。利用RSD值评价光谱的稳定性,选取前10个主成分和6个重要波段分别建立模型,利用预测集测试模型效果。结果相同遗留时间血液的拉曼光谱具有较好的稳定(RSD<0.2),不同遗留时间血液的拉曼光谱在680cm^-1等6个波段有明显的强度变化。前10个主成分建立的PLSR模型,其r²=0.9927。6个重要波段建立的PLSR模型,预测集效果r²=0.8797。结论利用拉曼光谱结合建模分析是一种无损快速的评估血液遗留时间的方法。     

Analysis and discrimination of electrical tapes: part II. Backings

The backings of 90 black electrical tapes were analyzed to evaluate the chemical components of these films, the ability of individual techniques to discriminate samples, and the ability of the techniques combined to distinguish samples. The techniques utilized and their respective discrimination results were stereomicroscopy and physical measurements, to include observation of surface features of the backing, width, and thickness measurements (c. 64%); Fourier transform infrared spectroscopy (FTIR) using a microscope accessory (c. 83%); pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS; c. 81%); and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS; c. 87%). Ninety-four percent of the backings were discriminated through this combination of analytical methods. Finally, evaluating these results in conjunction with previously published data on the analysis of the adhesives from the same set of electrical tapes provided an overall discrimination of nearly 96%.