Effect of temperature on rectifying Schottky barriers formed from fingerprint sweat corrosion of brass

Corrosive electrochemical processes of brass, including those resulting from fingerprint sweat, continue to be studied because of the widespread industrial use of brass. Here, we examine how increased temperature affects the relative abundance of fingerprint sweat corrosion products and the rectifying Schottky barrier formed between p-type copper (I) oxide corrosion and brass. X-ray photoelectron spectroscopy confirms increasing dezincification with increasing temperature. This leads to n-type zinc oxide replacing copper (I) oxide as the dominant corrosion product, which then forms a rectifying Schottky barrier with the brass, instead of copper oxide, when the temperature reaches c. 600°C. Using X-ray diffraction, resulting diodes show polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional current/voltage (I/V) characteristics of these diodes show good rectifying qualities. At temperatures between c. 100 and c. 600°C, when neither oxide dominates, the semiconductor/brass contact displays an absence of rectification.     

热敏纸与压敏纸上的汗液手印显现

根据热敏纸与压敏纸的特性,研制了一种新的汗液手印显现方法,该方法能有效的保持检材原貌,不破坏检材.     

Dual fingerprint reagents with enhanced sensitivity: 5-methoxy- and 5-methylthioninhydrin

"Dual fingerprint reagents" are chemical formulations which produce with latent fingerprints in a single step, impressions that are both colored and fluorescent. Pre-mixed solutions of the two commercially available ninhydrin analogues, 5-methoxyninhydrin (MN) and 5-methylthioninhydrin (MTN) with zinc or cadmium salts, are true dual reagents. They are much more sensitive than the parent dual reagent, ninhydrin/ZnCl(2). The main advantage of the new formulations is that they can be used at room temperature, with no need to cool the sample to liquid nitrogen temperature. At 0.05% concentration, which is 10-fold lower than the common ninhydrin working solution, MTN/ZnCl(2) is as sensitive as DFO in the fluorescence mode and considerably more sensitive in the color mode. MTN is also slightly cheaper than DFO.     

Visualization of latent fingerprint corrosion of metallic surfaces

Abstract:  Chemical reactions between latent fingerprints and a variety of metal surfaces are investigated by heating the metal up to temperatures of ∼600°C after deposition of the fingerprint. Ionic salts present in the fingerprint residue corrode the metal surface to produce an image of the fingerprint that is both durable and resistant to cleaning of the metal. The degree of fingerprint enhancement appears independent of the elapsed time between deposition and heating but is very dependent on both the composition of the metal and the level of salt secretion by the fingerprint donor. Results are presented that show practical applications for the enhancement to fingerprints deposited in arson crime scenes, contaminated by spray painting, or deposited on brass cartridge cases prior to discharge. The corrosion of the metal surface is further exploited by the demonstration of a novel technique for fingerprint enhancement based on the electrostatic charging of the metal and then the preferential adherence of a metallic powder to the corroded part of the metal surface.     

Toward a quantitative typology of burglars: a latent profile analysis of career offenders

Burglary is a serious, costly, and prevalent crime but prior typologies of burglars are mostly speculative and based on qualitative data. Using a sample of 456 adult career criminals, the current study used latent profile analysis to construct a methodologically rigorous quantitative typology. Four classes of burglars emerged: young versatile, vagrant, drug-oriented, and sexual predators. All groups demonstrated significant involvement in varied forms of crime, but the sexual predator group was the most violent and had the most serious criminal careers. Connections to the criminal career literature are offered and suggestions for further empirical study of offender typologies are discussed.     

子代孝道类别对亲代福祉的影响探究——基于CFPS2014的实证检验

弘扬孝亲敬老传统美德在支持家庭养老保障机制的有效运转和提升老年福祉水平方面具有积极作用,亦是践行党的二十大报告中“弘扬中华传统美德,加强家庭家教家风建设”的有益探索。研究发现子代持有的孝道观念在具备相互性和权威性双元面向的基础上,可进一步被划分为“高认同型”“分化型”“矛盾型”“低认同型”四个潜在类别;“孝道—福祉增进效应”具有稳定性,子代对相互性孝道认同程度越高,其亲代产生高福祉水平的可能性更大;该效应在亲代群体间具有异质性,拥有养老资源较为匮乏的亲代,能够从孝道对福祉的正向效应中获得更多回报。下一步政策取向是强化新时代家庭观的制度保障,进一步发挥家风建设和家庭美德发展对实现代际之间紧密的情感联结和高度的责任认同的有效力量。     

凤丹皮总苷高效液相色谱特征指纹图谱研究

目的 建立凤丹皮总苷的指纹图谱，为科学评价及有效控制其质量提供可靠依据。方法 采用Agilent TC-C18(2)（250 mm×4.6 mm，5 μm）色谱柱；乙腈（A）-0.05%磷酸水（B）为流动相，梯度洗脱，流速1.0 mL/min，检测波长230 nm，进样容积20 μL。结果 建立了凤丹皮总苷高效液相色谱特征指纹图谱的共有模式，指定18个共有峰，统计结果显示，11批凤丹皮总苷样品高效液相色谱特征指纹图谱相似度均大于0.80。结论 建立的特征指纹图谱方法快速、准确、简便，可用于凤丹皮总苷的质量控制。