Visualization of latent fingermark corrosion of brass, climatic influence in a comparison between the U.K. and Iraq

Through a comparison of fingermark sweat corrosion of α phase brass in both the U.K. and Iraq, we show how samples from Iraq have improved fingermark corrosion over U.K. samples that require no additional enhancement prior to visualization. Over 50% of Iraqi samples produced fingermark corrosion with full ridge detail compared with 0% from the U.K. X-ray photoelectron spectroscopy analysis of the fingermark corrosion products showed that Iraqi samples exhibit more dezincification with the Zn:Cu ratio averaging 1:1.82 compared with 1:3.07 for U.K. samples. Auger spectroscopy showed the presence of both zinc oxide and copper (I) oxide. No copper (II) was observed on the surface of the corroded brass. Opportunities to exploit the optical properties of these thin film oxides to enhance the visualization of fingermark corrosion are considered, and the potential to use fingermark corrosion of metal as a means of visualizing fingerprints in war zones is discussed.     

High Resolution Imaging of Latent Fingerprints by Localized Corrosion on Brass Surfaces

Abstract:  The Atomic Force Microscope (AFM) is capable of imaging fingerprint ridges on polished brass substrates at an unprecedented level of detail. While exposure to elevated humidity at ambient or slightly raised temperatures does not change the image appreciably, subsequent brief heating in a flame results in complete loss of the sweat deposit and the appearance of pits and trenches. Localized elemental analysis (using EDAX, coupled with SEM imaging) shows the presence of the constituents of salt in the initial deposits. Together with water and atmospheric oxygen—and with thermal enhancement—these are capable of driving a surface corrosion process. This process is sufficiently localized that it has the potential to generate a durable negative topographical image of the fingerprint. AFM examination of surface regions between ridges revealed small deposits (probably microscopic "spatter" of sweat components or transferred particulates) that may ultimately limit the level of ridge detail analysis.     

A Comparison of Cleaning Regimes for the Effective Removal of Fingerprint Deposits from Brass

Abstract:  Effective removal of fingerprint deposits is crucial for experimentation related to the corrosion of metals by fingerprint deposits. Such removal is also necessary prior to deposition of test fingerprints. The effectiveness of four regimes in removing fingerprint deposits from brass is considered. Sustained wiping of the deposit with a tissue at applied pressures of up to c . 1430 Pa or rubbing while the brass was immersed in acetone both failed to remove completely all traces of fingerprint deposits. Heating the brass to 600°C was an effective remover; however, this also oxidized the surface of the metal except where inhibited by fingerprint deposits. The most effective regime, and the only one of the four that removed all traces of deposit without affecting the properties of the metal surface, was immersion in warm soapy water while rubbing with a tissue. We propose this as the preferred method for fingerprint removal.     

1,2,4‐Triazine‐Based Chromogenic Reagents for the Detection of Microtraces of Various Metals Left on Human Skin*

Abstract: This article extends the application of 1,2,4‐triazine‐based chromogenic reagents to the detection of nonferrous metal traces left on contact with canvas and human skin. The possibility of detection of iron traces resulting from contact with objects made of stainless steel was investigated as well. Additionally, the ability of triazines to form chromatic complexes with Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺, Cr³⁺, and Al³⁺ ions was studied spectrophotometrically. Molar absorption coefficients, ranging from 8.8 to 29.9 × 10³/M/cm, provide high sensitivity of 1,2,4‐triazines toward nonferrous ions, thus, enabling the detection at concentrations as low as a few μM. The method was sensitive enough to detect traces resulting from a 1‐min contact with a stainless steel made object, which is commonly considered as a corrosion‐resistant material. The amounts of metal ions transferred to the skin after a 2‐min contact with objects made of brass, zinc, and copper were sufficient to develop chromatic imprints.     

开发金属纤维燃烧器——提高天然气应用技术

阐述了我国天然气的发展概况,提出为迎接来自四面八方的天然气,必须具备各种行业的先进燃气应用技术,并且根据目前我国情况,强调提高天然气应用技术的迫切性.同时介绍了国外一种新型金属纤维燃烧器的优越特性.     

论海洋法中的剩余权利

《联合国海洋法公约》的许多规则和原则已经成为习惯国际法,为世界各国所遵守。但是,该公约在扩大沿海国的管辖权和缩小公海自由的调整过程中留下了余地和空间,也就是海洋法中的剩余权利问题。尤其是在专属经济区这一新的区域内,沿海国的主权权利和专属管辖权与公海自由及其他国家的权利划分不是十分确定。如,剩余捕鱼权,"自由权利"的行使与"适当顾及"的关系,"用于和平目的"和军事用途等解释问题,都已引起多方的关注。这些问题值得我们认真研究和探讨,以期维护国家海洋权益,促进海洋法的发展。     

用发射光谱分析测定电流斑中的金属元素

<正> 电流斑由肉眼或组织学观察有时难以确认,尤其是凶杀案件中,在电击死亡后,尸体经伪装或因腐败,从形态学确诊电流斑困难更大。因此,如能在可疑电流斑部位的皮肤组织中,检出接触皮肤导体的金属元素,对确认电击致死具有重要意义。作者结合两起案例,利用原子发射光谱分析法,对人体皮肤电流斑进行检验。现将结果报告于下。     

上转换发光微粒悬浮液显现手印技术初探

目的 建立NaYF4∶Er,Yb微粒悬浮液显现手印技术方法并界定适用范围与条件.方法 用NaYF4∶Er,Yb微粒悬浮液显现瓷砖、玻璃等19种（各50枚）不同客体上皮脂汗手印,并对结果进行分析比较.结果 该方法对背景复杂的非渗透性客体上的油汗手印显现良好,其效果优于普通ZnO小颗粒悬浮液.结论 该方法操作简便、适用客体广泛、背景干扰少,适合进一步研究推广.     

真空镀膜与“502”熏显法显现非渗透性客体上汗潜手印的比较研究

目的探索真空镀膜手印显现技术,提高现场潜在手印显现率。方法通过真空镀膜与＂502＂熏显法显现常见非渗透性客体上汗潜手印的对比实验,比较二者显现效果优劣。结果真空镀膜法对于显现常见非渗透性客体上的新鲜和陈旧汗潜手印都有着明显的优势。结论真空镀膜是一种更为灵敏的非渗透性客体手印显现方法,是现有手印显现方法的重要补充。     

Effect of chloride ion concentration on the galvanic corrosion of α phase brass by eccrine sweat

Inductively coupled plasma mass spectrometry measurement of the relative concentration of sodium, chloride, calcium, and potassium ions in eccrine sweat deposits from 40 donors revealed positive correlations between chloride and sodium (ρ = 0.684, p < 0.01) and chloride and calcium ions (ρ = 0.91, p < 0.01). Correlations between ion concentration and the corrosion of α phase brass by the donated sweat were investigated by visual grading of the degree of corrosion, by measuring the copper/zinc ratio using energy-dispersive X-ray spectroscopy, and from a measurement of the potential difference between corroded and uncorroded brass when a large potential was applied to the uncorroded brass. An increasing copper/zinc ratio (indicative of dezincification) was found to correlate positively to both chloride ion concentration and visual grading of corrosion, while visual grading gave correlations with potential difference measurements that were indicative of the preferential surface oxidation of zinc rather than copper.