Enzymatic Digestion Method Coupled with Artificial Intelligence Techniques in Forensic Drowning Diatom Detection / 中山大学学报(医学科学版)

ObjectiveArtificial intelligence （AI） full smear automated diatom detection technology can perform forensic pathology drowning diatom detection more quickly and efficiently than human experts.However， this technique was only used in conjunction with the strong acid digestion method， which has a low extraction rate of diatoms. In this study， we propose to use the more efficient proteinase K tissue digestion method （hereinafter referred to as enzyme digestion method） as a diatom extraction method to investigate the generalization ability and feasibility of this technique in other diatom extraction methods. MethodsLung tissues from 6 drowned cadavers were collected for proteinase K ablation and made into smears， and the smears were digitized using the digital image matrix cutting method and a diatom and background database was established accordingly.The data set was divided into training set， validation set and test set in the ratio of 3：1：1， and the convolutional neural network （CNN） models were trained， internally validated， and externally tested on the basis of ImageNet pre-training. ResultsThe results showed that the accuracy rate of the external test of the best model was 97.65 %， and the area where the model features were extracted was the area where the diatoms were located. The best CNN model in practice had a precision of more than 80 % for diatom detection of drowned corpses. ConclusionIt is shown that the AI automated diatom detection technique based on CNN model and enzymatic digestion method in combination can efficiently identify diatoms and can be used as an auxiliary method for diatom detection in drowning identification.

Relationship between Postmortem Interval and FTIR Spectroscopy Changes of the Rat Skin / 法医学杂志

Objective To infer postmortem interval （PMI） based on spectral changes of the dorsal skin of rats within 15 days postmortem using Fourier transform infrared （FTIR） spectroscopy. Methods The rats were sacrificed by cervical dislocation after anesthesia, and then placed at 25 ℃ and relative humidity of 50%. The FTIR spectral data collected from the dorsal skin at PMI points were modeled with machine learning technique. Results There was no significant difference of absorption peak location among all the PMI groups but their peak intensities changed as a function of PMIs. The model for PMI estimation was constructed using partial least squares （PLS） regression, reaching a R2 of 0.92 and a root mean square error （RMSE） of 1.30 d. As shown in variable importance for projection （VIP）, four spectral bands including 1 760-1 700 cm-1, 1 660-1 640 cm-1, 1 580-1 540 cm-1 and 1 460-1 420 cm-1 were determined as important contributions to model prediction. Conclusion Application of the FTIR technique to detect postmortem spectral changes of the rat skin provides a novel proposal for PMI estimation.

Expression of caspase-3 and HAX-1 after cerebral contusion in rat / 法医学杂志

OBJECTIVE@#To observe the expression pattern of caspase-3 and HCLS1-associated protein X-1 (HAX-1) at different time after cerebral contusion in rat, and explore the new method for estimating the injury interval.@*METHODS@#The cerebral contusion model was established using adult SD male rats. Then the rats were randomly allocated into 8 groups: 2 h, 6 h, 12 h, 1 d, 3 d, and 7 d after cerebral contusion, sham-operation and normal control. Expression of caspase-3 and HAX-1 protein after cerebral contusion in rat was detected by Western blotting. Laser scanning confocal microscope was used to observe the number of HAX-1 positive cells and TUNEL-stained cells after cerebral contusion.@*RESULTS@#The expression of caspase-3 increased parallelly with the time after cerebral contusion and reached the peak value on 3 d. The expression of caspase-3 decreased gradually and still maintained a high level expression on 7 d (P < 0.05). The expression of HAX-1 positive cell went up after injury, and reached the peak value at 6 h (P < 0.05), then turned down gradually after 12 h and went out of detection after 3 d. The number of TUNEL-stained cells increased obviously at 2 h and reached the peak value on 3 d. The number of TUNEL-stained apoptotic cells decreased gradually and still maintained a high level expression on 7 d (P < 0.05).@*CONCLUSION@#The expression of caspase-3 and HAX-1 after cerebral contusion has time sequential regularity, which may provide new evidence for forensic diagnosis of cerebral contusion interval.

Time-order expression of caspase-3 and iNOS in contused human brain tissue / 法医学杂志

OBJECTIVE@#To investigate the expression of caspase-3 and iNOS in different intervals and to provide evidence for estimation of injury intervals after brain contusion in human.@*METHODS@#Thirty cases died of serious brain injury were included into the injury groups and 5 cases died of non-brain injury were served as control group. To analyze the changes of caspase-3 and iNOS expression in brain samples at different intervals (2h, 4-8h, 10-14h, 1-2d, 3-5d, 8-11d) by immunohistochemistry and auto-image analysis system.@*RESULTS@#The level of caspase-3 expression started to increase in 2 hours after brain contusion compared to the control group (P<0.05). The level of caspase-3 expression continued to increase in 1-2 days and maintained high level in 3-5 days compared to the control group (P<0.05), then decreased gradually. There was no statistically significant difference between the expression level of iNOS in 2 hours with the control group (P>0.05). But the expression level of iNOS began to increase in 4-8 hours after brain contusion and reached its maximum in 1-2 days, then decreased. Weak expression of iNOS still could be detected in 8-11 days.@*CONCLUSION@#The expression of caspase-3 and iNOS can be used as effective evidence for human brain contusion interval.