高精度玻璃折射率测量仪的研制及应用

目的 研制一种测量任意形状和大小玻璃物证折射率的精密测量仪并将其应用于法庭科学领域.方法 利用玻璃折射率匹配法原理,通过温度的精确测量与控制、成像和图像处理技术,对非规则形状玻璃的折射率进行测量.结果 在传统玻璃折射率匹配测量技术的基础上,研制出一种高精度玻璃折射率测量的新设备,该折射率测量仪的分辨能力可达10-5数量级.结论 具有测量精度高、重复性好、操作简单快捷、与国外同类产品相比成本低廉等显著特点,在案件侦破中发挥了重要作用.     

汽车风挡玻璃的鉴别方法研究

目的研究油浸法和X射线荧光光谱法对汽车风挡玻璃的鉴别能力。方法应用油浸法对30个风挡玻璃样品进行折射率测试，并将所得数据进行t检验分析。对不能区分的样品再用X射线荧光光谱进行元素成分分析。结果30个样品共组成的435对中，折射率t检验在置信度959／5时区分427对，其余8对通过元素成分实现区分。结论折射率测试和元素分析相结合，可对常见汽车风挡玻璃进行有效区分。     

玻璃折射率数据处理方法初探

目的探讨玻璃折射率数据处理方法。方法将案件中收集到的45个玻璃样品和同一个车灯不同部位的45块玻璃样品进行折射率测定。用独立样本Student’st检验、welch检验以及方差分析（ANOVA）对数据进行成对检验。结果方差分析法中Dunnett’s C法处理玻璃折射率数据,有效控制了第一类和第二类错误。当α=0．05时,犯第一类错误的概率约为4．44％,犯第二类错误的概率约为3．54％。     

油浸法鉴别汽车后视镜玻璃的研究

目的研究油浸法对汽车后视镜玻璃的鉴别能力。方法应用油浸法对20种汽车后视镜玻璃进行折射率值测定并用t检验法对数据进行处理。结果在置信度为95％时，20个后视镜玻璃样品的区分率为97．9％。结论油浸法对汽车后视镜玻璃有很好的区分能力，而且使用样品量少，可以达到微克级，是一种鉴别后视镜玻璃的有效方法。     

混和硅油测定玻璃折射率

目的建立混合硅油测定单纯用B油和C油无法测定的玻璃折射率的方法。方法将B油和C油分别按1：2和2：3的体积比配成两种混合硅油,用此两种混合硅油测定同一块玻璃的折射率。结果用此两种硅油测得的玻璃的折射率结果无显著性差异。该方法克服了玻璃折射率仪温度范围窄（25℃～125℃）的缺点。     

基于折射率数据的玻璃物证比对检验似然比模型建立及评估

玻璃是常见微量物证，目前国内微量物证检验报告通常只列出检验数据或定性给出比对检验结论，无法量化表达物证比对鉴定结论。似然比证据价值评价方法在全世界被广泛接受，但在中国，针对玻璃物证的定量价值评价方法还未建立，给检察官和法官准确利用玻璃物证带来困难。为提升玻璃物证的证据价值，本文拟建立量化比对检验结论的似然比方法模型并进行评估。基于四大类150个玻璃样品共750个折射率的检验数据，采用高斯核密度估计方法建立似然比(LR)模型，采用直方图和两类错误率对该模型进行评估。通过建立的似然比模型计算得出同源样品间的LR值在6.58～204 500范围内，不同源的样品间的LR值在0～0.68范围内，在150个样品的自身比对中，仅有一个样品自身比对的LR<1，错误排除率为0.67%；对150个不同来源玻璃样品进行两两比对，在C²₁₅₀=11 175对比对中，有173对LR>1，错误接纳率为1.55%，两个错误率均较低，在可接受范围内。基于高斯核密度估计建立的似然比模型能够对基于玻璃折射率数据的样品比对给出满意的比对结果，可为法庭提供玻璃样品比对的...     

保存温度与时间对生物样品中氯胺酮稳定性的影响

目的研究不同温度和时间条件保存时生物样品中氯胺酮的稳定性。方法家兔以氯胺酮150mg/kg灌胃,30min后处死,取其血、肝、肾、脑,分别在室温（18～24℃）和冷冻（-20℃）条件下保存,并用气相色谱-质谱法定性分析、气相色谱-氮磷检测器法测定不同时间各样品中氯胺酮含量。结果血、肝、肾、脑冷冻保存至第30天氯胺酮含量均降低（P〈0.05）;室温条件下各样品中氯胺酮含量自第5天起均升高（P〈0.05）。结论生物样品在冷冻条件下保存时氯胺酮稳定性较好,怀疑氯胺酮中毒或死亡的检材应冷冻保存,尽快检测。     

油浸法测定玻璃折射率的不确定度评定

目的建立油浸法测定玻璃折射率不确定度的评定方法。方法按照不确定度的A类和B类评定方法,对未知玻璃折射率测定过程中不确定度分量进行计算,最终确定扩展部不确定度。结果油浸法测定玻璃折射率的扩展不确定度约为4×10-5。结论根据不确定度计算出来的折射率的变化范围与实际分析中折射率的变化范围完全吻合。     

原子吸收分光光度法鉴别窗玻璃的研究

玻璃碎片是刑事案件现场常见的一种物证。在司法鉴定实践中,通过玻璃碎片的鉴别和同一认定,确定其来源,对侦破案情有较大的价值。目前国内公、检、法部门鉴别玻璃碎片,主要放在受力情况、折射率等物理机械性能的测试,玻璃碎片化学成分的鉴定未见报导。玻璃的主要成分是硅酸盐。不同型号的玻璃,使用性能有不同要求,其成分有较大     

血液样品中乙醇稳定性的实验研究

目的考察在不同存放条件下含乙醇的血液样品中乙醇浓度的变化情况。方法采用顶空-气相色谱法,以异丙醇为内标,对存放条件不同的血液样品中乙醇进行检测。结果冷冻(-10℃)条件存放1至30天,血液样品中乙醇含量无显著变化;冷藏(4℃)条件存放1至30天,血液样品中乙醇含量变化不显著;室温(28℃~33℃)条件存放1至30天,血液样品中乙醇含量显著改变。结论含有乙醇的血液样品,在冷冻、冷藏条件下可较稳定的存放30天;在室温条件下存放30天血液样品中乙醇浓度发生显著变化,不可在此条件下存放。     

Bayesian mixture modelling for glass refractive index measurement

Glass is a common type of physical evidence in forensic science. Broken glass recovered from a suspect may have similar physical characteristics to glass collected at a crime scene and therefore can be used as evidence. Statistical treatment of this evidence involves computing a measure of the weight of evidence. This may be done in a Bayesian framework that incorporates information from the circumstances of the crime. One of the most crucial quantities in this calculation is the assessment of the relative rarity of the characteristics of the glass, essentially the probability distribution used to model the physical characteristics of recovered glass. Typical characteristics used in casework are the elemental composition of glass and the refractive index measurement. There is a considerable body of scientific literature devoted to the modelling of this information. For example a kernel density estimation has been used to model the background population of glass based on the refractive index measurement and a multivariate Gaussian finite mixture model has been used to model the elemental composition of glass. In this paper, we present an alternative approach, the Dirichlet Process Mixture Model, to model the glass refractive index measurement in a Bayesian methodology. A key advantage is that using this method allows us to model the probability density distribution of refractive index measurements in a more flexible way.     

An investigation of bulk and surface refractive indices for flat window glasses,patterned window glasses and windscreen glasses

The bulk and surface refractive indices have been measured for 20 float window glasses, 20 non-float window glasses, 20 patterned window glasses and 20 toughened float windscreen glasses.The refractive index of the tin-contact surface of the float glasses was always greater than that of the bulk, typically by 0.002 (range 0.00053–0.00307). In contrast the refractive indices of the two surfaces and the bulk of the sheet window glasses were in agreement within accepted experimental error in each case. A number of patterned window glasses showed significantly different refractive indices between the plain and patterned surfaces, the largest difference obtained (0.00021) being an order of magnitude smaller than that found for a typical float glass.Nine of the 40 float glasses examined yielded abnormal fragments from the upper surface in the sense that they did not disappear at the match temperature of the bulk glass. The refractive index measured from these abnormal fragments for two of these glasses was lower than the refractive index from the bulk glass.The variation in the bulk refractive index for the sheet and float window glasses produced an estimated standard deviation (E.S.D.) of 1.2 × 10^?5. However, the patterned glasses were nearly three times as variable (E.S.D. = 3.3 × 10^?5) and the toughened float glasses were, on average, almost seven times as variable (E.S.D. = 8.0 × 10^?5).The value of making surface as well as bulk refractive index measurements in routine casework is discussed in the light of the above results.     

A survey of glass fragments recovered from clothing of persons suspected of involvement in crime

The refractive indices (RI) of over 2000 glass fragments recovered from items of clothing submitted to the Birmingham and Wetherby Home Office forensic science laboratories in connection with crimes involving broken glass have been measured. The glass fragments have been classified according to their location on the clothing, and a grouping algorithm has been applied to the data.The refractive index distribution was found to be dependent on the location of the glass on the clothing. The significance of the results in the interpretation of glass evidence is discussed.     

The effect of re-annealing on the distribution of refractive index in a windscreen and a windowpane classification of glass samples

Tiny glass fragments of two typical objects being of interest in forensic investigations: car windscreen and windowpane were examined from the point of view of their importance as crime evidence. Both examined objects were made from float glass and were toughened. The present paper concerns examination of refractive index distribution across the objects under investigation before and after the glass fragments were annealed according to previously chosen procedure. The annealing procedure was carried out in order to increase discrimination power of refractive index (RI). The following conclusions can be drawn from the results obtained. For both examined objects the mean RI was significantly higher after annealing and, at the same time, standard deviations in RI were smaller. The distributions of RI for both examined objects appeared not to be normal; the deviations from normality were observed at both sides of RI distributions. It was found that the difference in the values DeltaRI (difference between mean values of RI after annealing and before annealing) for both examined object was not significant and thus it would be not a good parameter to differentiate between two heat strengthen objects. The attempt to classify 181 glass samples on the basis of theirs RI and DeltaRI was performed. Increased discrimination of glass samples was observed.     

Determining the Refractive Index Variation within Panes of Vehicle Windshield Glass

Refractive indices of seven double‐paned vehicle windshields were measured to assess the variation across the pane of glass and to evaluate collection techniques for known glass standards by comparing false negative rates. Measurements were made using a Foster and Freeman GRIM3 instrument, and a minimum of 240 measurements were made per pane. The mean SD of the windshields was 0.00004. It was further determined that collecting a known sample from two different sections of a shattered windshield gave the lowest rate of false negatives when using ± 2 standard deviations to estimate the RI variation of the known glass. Additionally, refractive indices often were highest in the center of the windshield and decreased toward the left and right edges; in approximately half the sample set, the two panes of a single windshield were differentiated by one or more properties.     

Mixed effects modelling for glass category estimation from glass refractive indices

520 Glass fragments were taken from 105 glass items. Each item was either a container, a window, or glass from an automobile. Each of these three classes of use are defined as glass categories. Refractive indexes were measured both before, and after a programme of re-annealing. Because the refractive index of each fragment could not in itself be observed before and after re-annealing, a model based approach was used to estimate the change in refractive index for each glass category. It was found that less complex estimation methods would be equivalent to the full model, and were subsequently used. The change in refractive index was then used to calculate a measure of the evidential value for each item belonging to each glass category. The distributions of refractive index change were considered for each glass category, and it was found that, possibly due to small samples, members of the normal family would not adequately model the refractive index changes within two of the use types considered here. Two alternative approaches to modelling the change in refractive index were used, one employed more established kernel density estimates, the other a newer approach called log-concave estimation. Either method when applied to the change in refractive index was found to give good estimates of glass category, however, on all performance metrics kernel density estimates were found to be slightly better than log-concave estimates, although the estimates from log-concave estimation prossessed properties which had some qualitative appeal not encapsulated in the selected measures of performance. These results and implications of these two methods of estimating probability densities for glass refractive indexes are discussed.     

Heat stroke deaths caused by electric blankets: case report and review of the literature

Heat stroke is the most serious and potentially life-threatening condition of the heat-related illnesses. Heat stroke deaths caused by electric blanket are rarely reported. In this paper, we report 2 cases of fatal heat stroke caused by overheating from electric blankets in winter. One was a 41-year-old man who was found unresponsive in bed on an electric blanket. His wife shared the same bed with him and was found unconscious. The wife's axillary temperature was 40 degrees C (104 degrees C) when she was admitted to the hospital. She fully recovered after medical treatment. The husband was pronounced dead at scene, with rectal temperature at 41.2 degrees C (106.2 degrees C). The other was a 13-year-old girl who was found dead in bed on an electric blanket, with rectal temperature at 41 degrees C (105.8 degrees F). The literature is reviewed, and the pertinent findings, including scene investigations, postmortem examination, the risk and mechanism of fatal heat stroke caused by using electric blanket, are discussed.     

Application of false discovery rate procedure to pairwise comparisons of refractive index of glass fragments

This study was undertaken to apply a new method of controlling type I error when performing pairwise comparisons. The Benjamini and Hochberg false discovery rate (FDR) controlling procedures have proved to be very powerful tools in solving many practical problems but have not yet been applied to pairwise comparisons of refractive index of glass samples. Students t-test and Welch test (unequal variance Student's t-test) were applied to all possible pairwise comparisons. The comparisons were made on the basis of refractive index values of 72 glass fragments from different car windows and 69 different fragments from one windscreen. The type I error was controlled by the use of Benjamini and Hochberg false discovery rate (FDR) controlling procedure. To illustrate the importance of controlling type I error when using pairwise comparisons, results of pairwise comparisons with the FDR controlling procedure were compared to those comparisons made without any controlling procedure. Significantly fewer false negative results (false rejection of H0) were found during the use of FDR procedure in the comparison of refractive indices from the same windscreen than when comparing without controlling type I error. The results of application of FDR method were also compared to the results of other post-hoc tests, such as Tukey HSD test and Bonfferoni test. The FDR method has higher power than Bonferroni method and Tukey HSD method and control errors better than comparing without controlling type I error. The method of choice, for pairwise comparison of glass fragments on the basis of refractive index is Welch test with FDR adjustment. The method gave type I errors at level about 5.3% and type II error at about 3.7%.     

The classification and discrimination of glass fragments using non destructive energy dispersive X-ray microfluorescence

Frequency of analytical characteristics is best estimated on glass recovered at random. However, as such data were not available to us, we decided to use control windows for this estimation. In order to use such a database, one has to establish that the recovered fragment comes from a window. Therefore, elemental analysis was used both for classification and discrimination of glass fragments. Several articles have been published on the subject, but most methods alter the glass sample. The use of non destructive energy dispersive X-ray microfluorescence (microXRF) for the analysis of small glass fragments has been evaluated in this context. The refractive index (RI) has also been measured in order to evaluate the complementarity of techniques. Classification of fragments has been achieved using Fisher's linear discriminant analysis (LDA) and neural networks (NN). Discrimination was based on Hotelling's T2 test. Only pairs that were not differentiated by RI followed by the Welch test were studied. The results show that neural network and linear discriminant analysis using qualitative and semi-quantitative data establishes a classification of glass specimens with a high degree of reliability. For discrimination, 119 windows collected from crime scene were compared: using RI it was possible to distinguish 6892 pairs. Out of 129 remaining pairs, 112 were distinguished by microXRF.     

The consequences of potentially differing distributions of the refractive indices of glass fragments from control and recovered sources

In forensic cases involving glass evidence, the variance of the recovered glass refractive index (RI) has been observed to be larger than the variance of the control glass RI. This has consequences for subsequent interpretation. To investigate this phenomenon, a study was made of the probable distributions of refractive indices of the recovered glass given a range of casework type scenarios involving breakage and backscatter. An investigation of the consequences of any distribution differences with regard to casework was also made. It was discovered that the inclusion of surface fragments from the float surface of the glass can have a profound effect on the comparison of recovered and control glass samples. The effect was largest when a breaker was striking the float surface of a window. In particular, it was found that the inclusion of a few surface fragments even post grouping is sufficient by itself to explain the observed differences in variance of RI between control and recovered groups. Surface fragments, if present, are very likely to be treated as outliers and to be deemed as non-matching. The findings of this paper challenge routine glass examination procedure and suggest that knowledge of which surface is facing the striker is valuable information in interpretation.