Profiling the scent of weathered training aids for blood-detection dogs

At outdoor crime scenes, cadaver-detection and blood-detection dogs may be tasked with locating blood that is days, weeks or months old. Although it is known that the odour profile of blood will change during this time, it is currently unknown how the profile changes when exposed to the environment. Such variables must be studied in order to understand when the odour profile is no longer detectable by the scent-detection dogs and other crime scene tools should be implemented. In this study, blood was deposited onto concrete and varnished wood surfaces and weathered in an outdoor environment over a three-month period. Headspace samples were collected using solid phase microextraction (SPME) and analysed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC–TOFMS). The chemical odour profiles were compared with the behavioural responses of cadaver-detection and blood-detection dogs during training. Data interpretation using principal component analysis (PCA) and hierarchical cluster analysis (HCA) established that the blood odour could no longer be detected using SPME–GC×GC–TOFMS after two months of weathering on both surfaces. Conversely, the blood-detection dogs had difficulty locating the blood samples after one month of weathering on concrete and after one week of weathering on varnished wood. The scent-detection dogs evaluated herein had not been previously exposed to environmentally weathered blood samples during training. Given that this study was conducted to test the dogs' baseline abilities, it is expected that with repeated exposure, the dogs' capabilities would likely improve. The knowledge gained from this study can assist in providing law enforcement with more accurate training aids for blood-detection dogs and can improve their efficiency when deployed to outdoor crime scenes.     

美国关键矿产安全的脆弱性识别与韧性操作逻辑

关键矿产安全是满足国防工业基础建设、助推清洁能源产业转型以及实现诸多高新技术研发与落地等国家安全需要的核心要素。供应链的安全则是关键矿产安全的核心,而生产与开发能力、回收技术发展、地缘政治竞争等因素皆会影响供应链的稳定性。存在严重对外依赖的现实使得美国为摆脱关键矿产安全的脆弱性,开始追求关键矿产的安全韧性。但在全球实力和地位相对下降的背景下,美国将地缘政治竞争视为影响供应安全的最重要因素。因此,美国在关键矿产安全领域表现出双重叙事：一方面,美国秉持生存叙事,力图通过减少关键矿产供应链的脆弱性,增强韧性,以保障国家安全的基本需求;另一方面,美国又主张权力叙事,将关键矿产安全韧性视为操作工具,以谋求全球控制和主导地位。在双重叙事的交织下,美国通过政治化关键矿产评估、构建排他性供应链等策略,意图在国际舞台上塑造有利于己的格局。而此种刻意制造安全焦虑、拉动“小圈子”、分割全球发展力量的举措给全球安全韧性带来严重冲击,威胁全人类的福祉,中国要高度警觉其进一步的举措,并积极进行应对。     

关于汽车弯路事故的几种受力分析

汽车转弯时发生的交通事故,除了因抢行或者瞭望不佳而引发事故以外,绝大多数是在侧滑力的作用下导致车辆驶离本车道发生碰撞或者追尾、倾翻的,此类问题易引发重特大交通事故。为了说明车辆转弯侧滑事故的机理,文章对车辆常见的几种转弯现象进行了受力分析,以期为事故处理提供可以借鉴的分析资料。     

全球化语境中的英语文化圈及其语言教学

英语全球化致使出现了更多的英语变体,并蕴涵各自的文化.探讨文化教育的内涵,旨在使英语教育适应英语的演变和实现提高学生综合运用英语能力的总体目标.英语文化教育既涵盖"内圈"文化又必须涉及"外圈"和"扩张圈"文化;文化教育不仅为了提高学生的英语交际能力和批评性文化意识,而且注重培育学生的世界胸怀;教材内容应该国际化,包含"内圈"、"外圈"和"扩张圈"文化.     

The Unidad Popular Process as Represented through Siglo XXI Publishers: Between Local Reception and the Construction of a Global Event

This article deals with the role played by books and publishing houses in the representations and circulation of ideas relating to the Chilean Unidad Popular process (1970–1973). Due to its transnational nature, Siglo XXI stands out as a privileged object of analysis. This publishing house was founded by Orfila Reynal in Mexico in 1965, and opened a branch in Buenos Aires in 1971. Amidst political and cultural radicalisation, Siglo XXI Argentina factored in the local reception of ideas about the Chilean road to socialism, and its shaping into a global event.