Enhancing forensic investigations: Identifying bloodstains on various substrates through ATR-FTIR spectroscopy combined with machine learning algorithms.

The forensic analysis of bloodstains on various substrates plays a crucial role in criminal investigations. This study presents a novel approach for analyzing bloodstains using Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) in combination with machine learning. ATR-FTIR offers non-destructive and non-invasive advantages, requiring minimal sample preparation. By detecting specific chemical bonds in blood components, it enables the differentiation of various body fluids. However, the subjective interpretation of the spectra poses challenges in distinguishing different fluids. To address this, we employ machine learning techniques. Machine learning is extensively used in chemometrics to analyze chemical data, build models, and extract useful information. This includes both unsupervised learning and supervised learning methods, which provide objective characterization and differentiation. The focus of this study was to identify human and porcine blood on substrates using ATR-FTIR spectroscopy. The substrates included paper, plastic, cloth, and wood. Data preprocessing was performed using Principal Component Analysis (PCA) to reduce dimensionality and analyze latent variables. Subsequently, six machine learning algorithms were used to build classification models and compare their performance. These algorithms comprise Partial Least Squares Discriminant Analysis (PLS-DA), Decision Trees (DT), Logistic Regression (LR), Naive Bayes Classifier (NBC), Support Vector Machine (SVM), and Neural Network (NN). The results indicate that the PCA-NN model provides the optimal solution on most substrates. Although ATR-FTIR spectroscopy combined with machine learning effectively identifies bloodstains on substrates, the performance of different identification models still varies based on the type of substrate. The integration of these disciplines enables researchers to harness the power of data-driven approaches for solving complex forensic problems. The objective differentiation of bloodstains using machine learning holds significant implications for criminal investigations. This technique offers a non-destructive, simple, selective, and rapid approach for forensic analysis, thereby assisting forensic scientists and investigators in determining crucial evidence related to bloodstains.

In Vivo Degradation Behavior of Magnesium Alloy for Bone Implants with Improving Biological Activity, Mechanical Properties, and Corrosion Resistance.

This study aimed to establish a surface modification technology for ZK60 magnesium alloy implants that can degrade uniformly over time and promote bone healing. It proposes a special micro-arc oxidation (MAO) treatment on ZK60 alloy that enables the composite electrolytes to create a coating with better corrosion resistance and solve the problems of uneven and excessive degradation. A magnesium alloy bone screw made in this way was able to promote the bone healing reaction after implantation in rabbits. Additionally, it was found that the MAO-treated samples could be sustained in simulated body-fluid solution, exhibiting excellent corrosion resistance and electrochemical stability. The Ca ions deposited in the MAO coating were not cytotoxic and were beneficial in enhancing bone healing after implantation.

The Effect of Oxalic Acid as the Pre-Activator for the Electropolishing of Additive Manufactured Titanium-Based Materials and Its Characterization.

The use of additive manufactured (AM) titanium-based materials has increased substantially for medical implants and aerospace components. However, the inferior surface roughness of additive manufactured products affects the outward appearance and reduces performance. This study determines whether activation treatment prior to electropolishing produces a better surface. Oxalic acid (OA) is used as a pre-activator using different experimental conditions and the surface roughness is reduced by electropolishing with an electrolyte of perchloric acid and glacial acetic acid. The SEM surface morphology, mechanical properties, phase transformation and electrochemical properties are measured to determine the effect of different degrees of roughness on the surface. The results show that the surface roughness of AM titanium-based samples decreases from 8.47 µm to 1.09 µm after activation using OA as a pre-treatment for electropolishing. After electropolishing using optimal parameters, the hardness and resistance to corrosion resistance are increased.

A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy.

This study characterizes and determines the corrosion resistance of Mn-Ce conversion coated LZ91 magnesium alloy that undergoes pretreatments. It is challenging to process large and curved workpieces in the industry because the geometric shapes are complex if they are mechanically ground. This study uses acid pickling instead of mechanical grinding, and a nitric acid solution is used for pickling. After pretreatments, the samples are immersed for 30 s in a conversion coating solution containing 0.1 M KMnO4 and 0.025 M Ce(NO3)3 with a pH of 1.5, as demonstrated in previous studies by the authors. The microstructure of the coating layer and electrochemical behavior of conversion coated samples exposed to 3.5 wt.% NaCl solution are studied. The corrosion behavior of Mn-Ce conversion coating specimens is determined using a salt spray test (SST). Scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS) are used to analyze the interface between the coating layer and the underlying magnesium substrate and to investigate the microstructure of the specimens. The roughness of the coatings is measured using 3D white light interferometry. The results show that the deteriorated area ratio for conversion coated LZ91 decreases to less than 5% after 72 h of SST exposure, and the corrosion resistance is improved 2.25 times with the Mn-Ce conversion coating on LZ91 magnesium alloy.

Antimicrobial and Anticorrosion Activity of a Novel Composite Biocide against Mixed Bacterial Strains in Taiwanese Marine Environments.

Taiwan is an island with a humid subtropical climate. The relatively warm seawater results in biofouling of the surfaces of marine facilities. Biocide application is a common practice for combating and eliminating adhesive fouling. However, a single type of biocide may have limited antimicrobial effects due to the relatively high microbial diversity in marine environments. Therefore, applying a mixture of various biocides may be necessary. In this study, the antimicrobial and anticorrosion properties of a newly designed composite biocide, namely a combination of thymol and benzyldimethyldodecylammonium chloride, were investigated by applying the biocide to 304 stainless steel substrates immersed in inocula containing bacterial strains from Tamsui and Zuoying harbors. The ability of 3TB and 5TB treatments to prevent sessile cells and biofilm formation on the 304 stainless steel coupon surface was determined through scanning electron microscopy investigation. In addition, confocal laser scanning microscopy indicated that the 5TB treatment achieved a greater bactericidal effect in both the Tamsui and Zuoying inocula. Moreover, electrochemical impedance spectroscopy revealed that the diameter of the Nyquist semicircle was almost completely unaffected by Tamsui or Zuoying under the 5TB treatment. Through these assessments of antimicrobial activity and corrosion resistance, 5TB treatment was demonstrated to have superior bactericidal activity against mixed strains in both southern and northern Taiwanese marine environments.

The Potential of Calcium/Phosphate Containing MAO Implanted in Bone Tissue Regeneration and Biological Characteristics.

Micro arc oxidation (MAO) is a prominent surface treatment to form bioceramic coating layers with beneficial physical, chemical, and biological properties on the metal substrates for biomaterial applications. In this study, MAO treatment has been performed to modify the surface characteristics of AZ31 Mg alloy to enhance the biocompatibility and corrosion resistance for implant applications by using an electrolytic mixture of Ca3(PO4)2 and C10H16N2O8 (EDTA) in the solutions. For this purpose, the calcium phosphate (Ca-P) containing thin film was successfully fabricated on the surface of the implant material. After in-vivo implantation into the rabbit bone for four weeks, the apparent growth of soft tissues and bone healing effects have been documented. The morphology, microstructure, chemical composition, and phase structures of the coating were identified by SEM, XPS, and XRD. The corrosion resistance of the coating was analyzed by polarization and salt spray test. The coatings consist of Ca-P compounds continuously have proliferation activity and show better corrosion resistance and lower roughness in comparison to mere MAO coated AZ31. The corrosion current density decreased to approximately 2.81 × 10-7 A/cm2 and roughness was reduced to 0.622 µm. Thus, based on the results, it was anticipated that the development of degradable materials and implants would be feasible using this method. This study aims to fabricate MAO coatings for orthopedic magnesium implants that can enhance bioactivity, biocompatibility, and prevent additional surgery and implant-related infections to be used in clinical applications.