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Mostrando 1-12 de 56 artigos, teses e dissertações.
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1. Encoding of Luminescent Ink Markers Using Low-Level Data Fusion and Chemometrics
The identification and analysis of documentary fraud is always a challenge for forensic science. Document analysis has proven to be an important branch of forensics in elucidating the authenticity of documents. The development and incorporation of luminescent inks in authentic documents have proved to be an excellent security feature. This paper purposes the
Journal of the Brazilian Chemical Society. Publicado em: 2023
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2. A multivariate approach to differentiate yerba mate (Ilex paraguariensis) commercialized in the southern Brazil on the basis of phenolics, methylxanthines and in vitro antioxidant activity
Abstract The consumption of yerba mate beverages is related to several health benefits. These desirable properties are mainly due to the bioactive compounds. However, the levels of those compounds are directly affected by factors such as geographical origin. This study aimed to use chemometrics to evaluate the antioxidant compounds of yerba mate (consumed as
Food Sci. Technol. Publicado em: 2020-09
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3. FASE SENSORA DE POLI(CLORETO DE VINILA) NA DETECÇÃO DE 17β-ESTRADIOL EM MEIO AQUOSO UTILIZANDO ESPECTROSCOPIA NO INFRAVERMELHO MÉDIO E QUIMIOMETRIA
In recent years, estrogens have gained notable attention among emerging pollutants, increasingly leading to the need for less laborious analytical methods. Optical sensors are a promising technology for the determination of chemical contaminants in water, acting as an alternative screening method. The aim of this work was to evaluate the performance of poly(
Quím. Nova. Publicado em: 2020-09
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4. 1H NMR and Chemometric Methods to Estimate the Octane Number in Brazilian C Gasolines
Brazilian gasoline type C can be purchased with octane number as the main difference. This quality parameter directly affects the price. Intermediate formulations may not be easily distinguished from conform samples due to similarity in visual appearance and physicochemical properties. The use of anhydrous ethanol as an additive also influences the octane va
J. Braz. Chem. Soc.. Publicado em: 2020-08
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5. Estimation of soil phosphorus availability via visible and near-infrared spectroscopy
ABSTRACT: Spectroscopic techniques have great potential to evaluate soil properties. However, there are still questions regarding the applicability of spectroscopy to analyze soil phosphorous (P) availability, especially in tropical soils with low nutrient contents. Therefore, this study evaluated the possibility to estimate P availability in soil and its po
Sci. agric. (Piracicaba, Braz.). Publicado em: 20/12/2019
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6. NMR-based metabolomics to select a surgical method for treating papillary thyroid carcinoma
OBJECTIVE: This study aims to investigate differences in the metabolomic profiles of patients who received different surgeries for papillary thyroid carcinoma (PTC). METHODS: Two surgical methods, i.e., unilateral and total thyroidectomy, were employed according to different disease conditions. Sera from patients who were treated with levothyroxine sodium
Clinics. Publicado em: 14/11/2018
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7. AVALIAÇÃO DE FRAGMENTOS DE LENHOS CARBONIZADOS DE ARAUCARIACEAE POR MEIO DE TERMOGRAVIMETRIA E INFRAVERMELHO ASSOCIADAS À ANÁLISE MULTIVARIADA
The aim of the study is to evaluate the physical and chemical changes that occur on wood fragments submitted to different temperatures, verifying their influence on significant chemical characteristics in the forming process. Carbonization process in muffle associated to the techniques of Thermogravimetry, Fourier Transform Infrared Spectroscopy (FTIR) and m
Quím. Nova. Publicado em: 2017-09
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8. Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry
A fast procedure using time-domain nuclear magnetic resonance (TD-NMR) to detect olive oil adulteration with polyunsaturated vegetable oils in filled bottles is proposed. The 1H transverse relaxation times (T2) of 37 commercial samples were measured using low-field nuclear magnetic resonance (LF-NMR) spectrometer and a unilateral nuclear magnetic resonance (
J. Braz. Chem. Soc.. Publicado em: 2017-02
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9. Multivariate Analysis of Perfumes by Ultraviolet Spectrophotometry
An efficient, fast and cost-effective method for detecting adulteration in perfumes by UV spectroscopy and multivariate analysis is proposed. Classification of perfumes, either as original or fake, was accomplished with the spectroscopic data using chemometric techniques such as principal component analysis (PCA), soft independent modeling of class analog
J. Braz. Chem. Soc.. Publicado em: 2015-08
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10. Quimiometria: conceitos, métodos e aplicações
A quimiometria surgiu da necessidade de extrair informações químicas da profusão de dados resultantes da moderna instrumentação. Neste livro são abordados os principais métodos de tratamento de dados de natureza multivariada, iniciando com a apresentação das técnicas utilizadas na sua preparação. A seguir, são abordados os métodos de análise exploratória: análise de componentes principais (PCA) e análise de agrupamentos por métodos hierárquicos (HCA). Modelos quantitativos são construídos utilizando os métodos de regressão linear múltipla (MLR), componentes principais (PCR) e quadrados mínimos parciais (PLS). Métodos supervisionados de reconhecimentos de padrões do k-ésimo vizinho mais próximo (k-NN), SIMCA, e a análise discriminante PLS-DA são discutidos na construção dos modelos de classificação. Todos os capítulos incluem rotinas computacionais e vários exemplos.
Autor(es): Ferreira, Márcia Miguel Castro
Editora da Unicamp. Publicado em: 2015
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11. Non-destructive NIR spectrometric cultivar discrimination of castor seeds resulting from breeding programs
Este artigo propõe um método de espectrometria no infravermelho próximo (NIR) de reflectância difusa para a discriminação não-destrutiva de sementes de mamona das cultivares mais comumente empregadas nas plantações brasileiras (BRS Nordestina e BRS Paraguaçu). Para esta finalidade, duas técnicas de classificação são comparadas, o SIMCA (modelag
J. Braz. Chem. Soc.. Publicado em: 2014-05
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12. UV-Vis spectrometric detection of biodiesel/diesel blend adulterations with soybean oil
Um método para detecção de adulterações de misturas de biodiesel/diesel (B5) com óleo de soja empregando espectrometria UV-Vis é proposto. O estudo envolve 90 amostras compreendendo misturas B5 com e sem a adição de óleo de soja (0,5 a 2,5% v/v). Uma discriminação apropriada foi obtida utilizando classificadores SIMCA (modelagem independente e fl
J. Braz. Chem. Soc.. Publicado em: 2014-01