Banca de DEFESA: VICTOR GABRIEL DE PAULA SAIDE

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : VICTOR GABRIEL DE PAULA SAIDE
DATE: 29/04/2022
TIME: 13:00
LOCAL: Ambiente virtual, GoogleMeet
TITLE:

CHEMICAL ANALYSIS OF THE LEAD CORE OF RIFLE PROJECTILES BY WAVELENGTH DISPERSION X-RAY FLUORESCENCE (WDXRF) AND CHEMOMETRICS FOR FORENSIC PURPOSES

KEY WORDS:

HCA, PCA, SIMCA, k-NN, WDXRF

PAGES: 102
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Analítica
SPECIALTY: Métodos Óticos de Análise
SUMMARY:

Rifle bullets are usually deformed after firing, hampering the identification of the firearm that made the shot and consequently the shooter by ballistic comparison using optical microscopy. In such cases, knowledge of the composition of the bullets can be an alternative means of identifying their origin. In this work, wavelength dispersion X-ray fluorescence (WDXRF) was used for the first time as a tool to identify the origin of rifle projectiles, with the aid of chemometrics. A total of 66 samples of lead core from 7.62 caliber rifle projectiles were analyzed. These samples form 6 distinct groups of projectiles, considering the manufacturer and the year of manufacture: Companhia Brasileira de Cartuchos (CBC) of the year 2009 and of the year 2016, Israel Military Industries (IMI), Federal Cartridge (FC), Fray Luiz Beltrán (FLB) and Zavod Vlasim (ZV). Principal component analysis (PCA) on the spectral data discriminated these 6 projectile groups. The first 3 principal components (PC) were responsible for more than 99% of the variability in the samples. The spectral regions of antimony and X-ray scattering were decisive for the discrimination of the groups. The dendrogram obtained in the hierarchical cluster analysis (HCA) showed the formation of 6 groups with a relative distance of 0,85. The k-nearest neighbor (k-NN) analysis was able to correctly classify all 17 samples used in the test set, using 1 ≥ k ≥ 8. The smooth modeling analysis independent of class analogies (SIMCA) correctly classified all samples in the test set. The results were promising for forensic investigation purposes. The WDXRF technique proved to be viable for the analysis of lead core samples from rifle projectiles and the applied statistical analysis proved to be adequate for the discrimination of rifle projectiles from the spectral data. The percentage of elements obtained by the method of fundamental parameters were investigated by the same techniques (PCA and HCA), however the 6 groups of projectiles were not fully discriminated. The percentage of antimony proved to be decisive for the separation of some groups, mainly the CBC group of the year 2016, due to the high content of antimony that this group presented. Welch's analysis of variance (ANOVA), followed by the Games-Howell test, of the percentage of antimony confirmed that this element alone can differentiate almost all projectile groups. The WDXRF technique has the advantage of being simple and fast, in addition to preserving evidence as it is a non-destructive method.

BANKING MEMBERS:
Presidente - 2626414 - JOSE GERALDO ROCHA JUNIOR
Externo ao Programa - 2630672 - FLAVIO COUTO CORDEIRO
Externa à Instituição - MARTHA MARIA ANDREOTTI FAVARO - UNICAMP
Externo à Instituição - LUIZ FERNANDO SILVA CALDAS - UFF
Externo à Instituição - ANDRE VINICIUS DOS SANTOS CANUTO - UFRRJ