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正OPINION The Role of Risk China should keep an eye on debt risks.In an increasingly volatile financial market,risks may have positive effects,as market participants can better weigh risks and returns,and respond to changes in a more accurate way.Recent financial reforms,such as the central bank’s policy on deposit certificates in the interbank market and the initial public     

Preparation of pyrolysis reference samples: evaluation of a standard method using a tube furnace

A new, simple method for the reproducible creation of pyrolysis products from different materials that may be found at a fire scene is described. A temperature programmable steady-state tube furnace was used to generate pyrolysis products from different substrates, including softwoods, paper, vinyl sheet flooring, and carpet. The temperature profile of the tube furnace was characterized, and the suitability of the method to reproducibly create pyrolysates similar to those found in real fire debris was assessed. The use of this method to create proficiency tests to realistically test an examiner's ability to interpret complex gas chromatograph-mass spectrometric fire debris data, and to create a library of pyrolsates generated from materials commonly found at a fire scene, is demonstrated.     

Forensic Analysis of Human Autopsy Tissue for the Presence of Polydimethylsiloxane (Silicone) and Volatile Cyclic Siloxanes using Macro FT‐IR,FT‐IR Spectroscopic Imaging and Headspace GC‐MS

This study describes effective and straightforward primary and secondary methods for the detection of silicone in human autopsy tissue. The primary method is polydimethylsiloxane (PDMS) specific and employs either macro‐attenuated total reflection Fourier transform infrared (ATR‐FT‐IR) spectroscopy for samples with a high PDMS concentration (relative to that of the matrix) or micro‐FT‐IR spectroscopic imaging in a reflection/absorption modality for samples with a low PDMS concentration. Although the secondary method is not PDMS specific, it employs headspace gas chromatography with mass spectrometric detection (HS/GC‐MS) for the detection of low molecular weight volatile cyclic siloxanes (VCS), which are characteristic marker compounds for PDMS. Overall, the combined results from the primary and secondary analyses provide reliable evidence for the presence of silicone.     

Volatile organic compounds from the combustion of human and animal tissue

The volatile by-products of the combustion of ordinary fuels such as wood, polystyrene, polyethylene, urethane foam, PVC and the like are well known to the forensic fire debris examiner. When a fire involves a human body, volatile species are produced that are not so well known, including various alkenes and aldehydes. These have sometimes been mistaken for the residues of unusual accelerants. In an attempt to document what volatiles are produced by the combustion of animal fat and human fat, the authors have used an open-tube pyrolysis probe as a microfurnace to burn small samples of unembalmed subcutaneous fat from human, avian and porcine sources, and collect volatiles by charcoal strip adsorption. The volatile products were analyzed by GC/MS. Predominant species included aldehydes in the C6-C10 range, homologous series of alkenes and alkanes, and other hydrocarbon products. These results were compared to those obtained by free-burning (open flame in air) of similar specimens and to the volatiles detected in debris from beneath a human cadaver in a test fire. Differences between the volatile profiles produced by human fat as compared to pork and chicken fat and adventitious sources of such volatiles are discussed.     

亳州产4种药用菊花栽培品种内在质量的比较研究

目的 通过比较亳州地区4种药用菊花栽培品种的化学成分,为药用菊花的质量评价提供参考。方法以绿原酸、木犀草苷、3,5-O-二咖啡酰基奎宁酸、总挥发油含量为检测指标,对同一栽培环境下的4种药用菊花栽培品种的化学成分含量进行测定。结果 4种药用菊花栽培品种的绿原酸、木犀草苷、3,5-O-二咖啡酰基奎宁酸含量以杭白菊最高,亳菊最低;总挥发油含量以杭白菊最高,小白菊最低,亳菊挥发油颜色为蓝色。结论 菊花的主要化学成分含量因栽培品种不同而存在明显差异,亳菊挥发油颜色与其他3种不同,即品种与质量之间存在一定的相关性。     

The Stability of Collected Human Scent Under Various Environmental Conditions*,†

Abstract: Human scent evidence collected from objects at a crime scene is used for scent discrimination with specially trained canines. Storage of the scent evidence is usually required yet no optimized storage protocol has been determined. Storage containers including glass, polyethylene, and aluminized pouches were evaluated to determine the optimal medium for storing human scent evidence of which glass was determined to be the optimal storage matrix. Hand odor samples were collected on three different sorbent materials, sealed in glass vials and subjected to different storage environments including room temperature, ?80°C conditions, dark storage, and UVA/UVB light exposure over a 7‐week period. Volatile organic compounds (VOCs) in the headspace of the samples were extracted and identified using solid‐phase micro‐extraction–gas chromatography/mass spectrometry (SPME–GC/MS). Three‐dimensional covariance mapping showed that glass containers subjected to minimal UVA/UVB light exposure provide the most stable environment for stored human scent samples.     

油樟叶挥发油水乳剂对家兔自然感染皮肤真菌病的疗效观察

从患皮肤真菌病家兔的皮屑、被毛中分离病原真菌,并进行病原鉴定;分别用5、10、30mL/L油樟叶挥发油水乳剂通过皮肤涂擦法进行治疗试验,以观察油樟叶挥发油水乳剂对家兔皮肤真菌病的疗效。结果显示,分离得到的2种病原真菌经培养特性、菌落性状、菌丝形态和孢子性状特征等鉴定,为须毛癣菌和犬小孢子菌;3种剂量组的油樟叶挥发油水乳剂对家兔皮肤真菌病均有较好的疗效,其中以10mL/L油樟叶挥发油水乳剂对于家兔自然感染皮肤真菌病的疗效最好。试验表明油樟叶挥发油水乳剂对兔自然感染的皮肤真菌病具有一定的疗效。     

韭菜挥发油成分的气相色谱-质谱分析及抗常见病原菌活性研究

采用水蒸气蒸馏法提取韭菜挥发油,通过体外抑菌试验检测其抑菌活性,确定体外最小抑菌浓度(MIC);并采用气相色谱-质谱(GC-MS)法分离检测韭菜挥发油成分。结果显示,韭菜挥发油具有广谱的抑菌活性,且对不同细菌的MIC不同。在韭菜挥发油中鉴定出17个组分,主要为二丙烯基-双硫醚(39.308%)、甲基-丙烯基-双硫醚(32.763%)、甲基-丙烯基-三硫醚(12.157%)、二丙烯基-三硫醚(7.330%)。结果表明,韭菜挥发油具有研发成新型抗菌药物与食品防腐剂的潜力。     

白鸡屎藤挥发油主要成分的定性定量分析

为了探讨白鸡屎藤挥发油的药代动力学特征及其药物残留检测方法,采用化学试剂法对白鸡屎藤挥发油进行定性分析,然后通过柱前衍生高效液相色谱技术对白鸡屎藤挥发油的主要成分进行了定量检测。化学试剂定性方法的研究结果表明,白鸡屎藤挥发油含有酸类、酚类、醛或酮类、醇类、酯或内酯类(包括△α,β-γ内酯环)以及被还原性成分;高效液相色谱技术分析结果表明,白鸡屎藤挥发油含有丁香酚、异丁香酚、左旋α-松油醇、右旋α-松油醇、芳樟醇、水杨酸甲酯、樟脑、龙脑等药理活性成分,以芳樟醇、水杨酸甲酯、龙脑的含量最高,丁香酚、异丁香酚、左旋α-松油醇、右旋α-松油醇、樟脑的含量相对较高。通过白鸡屎藤挥发油柱前衍生化处理,建立的白鸡屎藤挥发油主要成分的高效液相色谱检测方法具有简单、快速的特点,在30min内可完成对白鸡屎藤挥发油主要活性物的分析,适用于白鸡屎藤挥发油的质量控制、药代动力学研究和药物残留检测。     

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.