References of "Lepot, Laurent"
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See detailDichroism measurements in forensic fibre examination: Part 5—Pigmented fibres
De Wael, K.; Lepot, Laurent ULg

in Science & Justice : Journal of the Forensic Science Society (2012), 52(3), 161-167

A number of pigmented fibre samples were examined with plane polarized light on their dichroic behaviour by optical light microscopy (OLM) and microspectrophotometry with plane polarized light (MSP-PPL ... [more ▼]

A number of pigmented fibre samples were examined with plane polarized light on their dichroic behaviour by optical light microscopy (OLM) and microspectrophotometry with plane polarized light (MSP-PPL). It was found that about half of the samples show a strong dichroic effect and another 20% have a weak dichroism. Both regular (80%) and inversed dichroic effects (20%) occur. The dichroic characteristics of pigmented fibres can be compared to these of sheet polarizers. It is suggested that the dichroic behaviour of pigmented fibres depends strongly on the crystal structure (shape of the pigment grains) and the draw ratio (orientation of the polymer chains). [less ▲]

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See detailThe use of linear dichroism in forensic fibre examinations — Part 6. Validation and practical aspects of MSP-PPL
De Wael, K.; Lepot, Laurent ULg

in Science & Justice : Journal of the Forensic Science Society (2012), 52(4), 249258

This paper summarizes the results of previous work on the microscopic observation of linear dichroism found in dyed fibres (polyesters, polyamides, wool, silk, cotton, viscose, acrylics and acetates) and ... [more ▼]

This paper summarizes the results of previous work on the microscopic observation of linear dichroism found in dyed fibres (polyesters, polyamides, wool, silk, cotton, viscose, acrylics and acetates) and in pigmented fibres as well as the measurements on these fibre classes using microspectrophotometry with plane polarized light (MSP-PPL). The validation of this method is discussed and a practical tool is proposed for comparing fibre traces with control fibres. The limitations and strengths of this method are also revised. [less ▲]

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See detailApplication de la spectroscopie Raman à l’analyse de colorants sur fibres de coton dans le contexte de la criminalistique
Lepot, Laurent ULg

Doctoral thesis (2011)

Forensic examination of textile fibres is based on fibre morphology and on fibre material and dyes characterization. Cotton is the most frequently used fibre in textiles but also the most encountered in ... [more ▼]

Forensic examination of textile fibres is based on fibre morphology and on fibre material and dyes characterization. Cotton is the most frequently used fibre in textiles but also the most encountered in casework. While man-made fibres show various morphologies and materials, cotton is a natural cellulosic fibre with constant morphology. Cotton fibres examination can consequently be summarized in the characterization of fibre dyes. However forensic needs require non-destructive, fast and sensitive techniques. For fibres microspectrophotometry (MSP) is the commonly used technique and the obtained UV-Vis absorption spectrum reflects dyes used to colour the fibre. Any other technique suitable for dye characterization is thus helpful to reinforce MSP results on cotton fibres. Raman spectroscopy is a fast non-destructive technique, easy to integrate into the fibre analytical sequence without any additional sample preparation. Moreover it provides specific molecular information and seems convenient for the study of coloured molecules. This work allowed to demonstrate the potential of the technique in dyed cotton fibres examination through the characterization of pure dyes but also the ability to detect different components in dye mixtures. In order to help dye identification spectral databases were built using Raman spectra collected in the present work. Unfortunately such a database will never be exhaustive and the identification of an unknown dye would be compromised. An interesting option is to identify the general chemical class of the unknown dye, especially to evaluate its rarity. The recognition of some dye chemical classes has been made by the mean of characteristic peaks but this method remains somewhat subjective. This subjectivity can be bypassed using chemometric techniques; they are able to predict chemical class membership on the basis of Raman specific information. Some experiments have been performed on Raman spectra using PCA models and the SIMCA classification tool. [less ▲]

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See detailLa spectroscopie Raman au service de l’archéométrie
Lepot, Laurent ULg

Scientific conference (2011, August 31)

La spectroscopie Raman est une technique particulièrement bien adaptée à l'analyse des oeuvres d'art et des pièces archéologiques. Cette présentation illustre, sans être exhaustive, plusieurs domaines d ... [more ▼]

La spectroscopie Raman est une technique particulièrement bien adaptée à l'analyse des oeuvres d'art et des pièces archéologiques. Cette présentation illustre, sans être exhaustive, plusieurs domaines d'application comme l'étude des pigments, des molécules organiques, des produits de corrosion et des minéraux et gemmes. Elle se focalise ensuite sur deux exemples détaillées concernant l'étude des peintures murales de la Cathédrale de Tournai et celle des restes colorés d'un insigne d'épaule retrouvé sur la dépouille d'un soldat australien de la première guerre mondiale. [less ▲]

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See detailRaman spectroscopy of dye mixtures on cotton fibres
Lepot, Laurent ULg

Conference (2011, June 17)

Raman spectroscopy is becoming a routine technique in numerous forensic labs since it is fast and non-destructive. Recent work has shown that Raman spectra of dyes depend on the excitation laser ... [more ▼]

Raman spectroscopy is becoming a routine technique in numerous forensic labs since it is fast and non-destructive. Recent work has shown that Raman spectra of dyes depend on the excitation laser wavelength used (resonance effects) and on the scattering ability of the dye molecule itself. Both factors together with fluorescence emission may affect the detection of a dye, especially within a mixture. In order to obtain a better understanding of their Raman behavior binary mixtures at various ratios have been prepared using five known dyes showing different scattering and fluorescent abilities. Their Raman investigation at 514 and 785 nm highlights the complementarity of these two resonant and non-resonant sources and the limitations of the Raman technique in the detection of both major and minor components of a dye mixture. Other investigations have been performed on binary and ternary known dye mixtures on cotton fibres by Raman spectroscopy and MSP-Vis. The combination of two laser sources leads in most cases to the detection of both or two out of three dye components. This Raman information reinforces clearly the confidence in MSP-Vis results. Indeed the contribution of the minor dye component is sometimes very small in the MSP spectrum and a visual inspection of the spectra in addition to inhomogeneous dyeing on cotton may result in difficult interpretation. For these reasons Raman spectroscopy is a very convenient technique to confirm or maybe specify the MSP results, especially for fibre types with common MSP spectra. Furthermore, MSP-Vis also showed some limitations with very light or very dark colored fibres whereas Raman spectroscopy could still discriminate between fibre types. [less ▲]

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See detailOn the frequency of occurrence of a peculiar polyester fibre type found in blue denim textiles
De Wael, Kris; Baes, Christiaan; Lepot, Laurent ULg et al

in Science & Justice (2011), 51(4), 154-162

In a double murder investigation, the victims were found after a prolonged stay in a drainage canal. In spite of the expectations, fibre examination established a multitude of primary and secondary ... [more ▼]

In a double murder investigation, the victims were found after a prolonged stay in a drainage canal. In spite of the expectations, fibre examination established a multitude of primary and secondary transferred fibres. One of these fibre types was a colourless polyester fibre possessing a blue coloured molten fibre end. These matched one of the types present in the suspect's blue denim trousers. The aim of this study was to verify the rarity of this peculiar fibre type and more precisely its presence in blue denim textiles. Over five hundred different blue jeans textiles were examined and only one of these presented exactly the same type. The comparison involved microscopy, microspectrophotometry in the visible range and Raman spectroscopy. The results indicate this fibre type is extremely rare in a blue jeans fabrics and that "standard" blue denim should not be disregarded in case work. [less ▲]

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See detailDichroism measurements in forensic fibre examination: Part 3 -- Dyed cotton and viscose fibres
De Wael, Kris; Lepot, Laurent ULg

in Science & Justice (2011), 51(4), 173-186

A number of dyed cellulosic fibres were examined with plane polarized light on their dichroic behavior by microscopy and microspectrophotometry (MSP-PPL). Significant dichroic effects (mostly hypochromic ... [more ▼]

A number of dyed cellulosic fibres were examined with plane polarized light on their dichroic behavior by microscopy and microspectrophotometry (MSP-PPL). Significant dichroic effects (mostly hypochromic effects and hypsochromic bands shifts) were reported. The effect is related to the chemical structure: some dye structures always possess dichroism (azo, stilbene, thiazole and oxazine), some dyes demonstrate sometimes dichroic effects (anthraquinoid, indigoid) while other structures never demonstrate dichroic effects (sulphur, diphenylmethanes, triarylmethanes, phthalocyanines). In some cases a different dichroic behavior was found for the same dyes applied on cotton and on viscose. [less ▲]

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See detailEvaluation of the shedding potential of textile materials
De Wael, K.; Lepot, Laurent ULg; Lunstroot, K. et al

in Science & Justice : Journal of the Forensic Science Society (2010), 50(4), 192-194

A practical method is proposed to assess the shedding potential of textile materials. The evaluation of the sheddability is based on the use of adhesive tapes and on comparison, using three different ... [more ▼]

A practical method is proposed to assess the shedding potential of textile materials. The evaluation of the sheddability is based on the use of adhesive tapes and on comparison, using three different sheddability scales for cotton, wool and fine man-made fibres. (c) 2010 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved. [less ▲]

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See detailIn search of blood – detection of minute particles using spectroscopic methods
Lepot, Laurent ULg; Gilbert, Bernard ULg; De Wael, Kris et al

in Forensic Science International (2008), 180(1), 37-42

An examination protocol for rapid detection of remnants of blood particles on garments of suspects in bloody murder cases is described. Micro particles of blood are sampled along with fibres and hairs ... [more ▼]

An examination protocol for rapid detection of remnants of blood particles on garments of suspects in bloody murder cases is described. Micro particles of blood are sampled along with fibres and hairs using the tape lifting method. The tapings are searched with a low power microscope for red particles with morphology similar to blood. Presumed blood traces are further examined using microspectrophotometry on the cut out piece of taping. The typical visible spectrum of haemoglobin is characteristic for blood. Alternatively Raman spectroscopy can be used to measure the characteristic vibrational spectrum of haemoglobin. At a later stage, these particles may be removed from the piece of taping in order to extract the blood and attempt to obtain a genetic profile. [less ▲]

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See detailApplication of Raman spectroscopy to forensic fibre cases
Lepot, Laurent ULg; Gilbert, Bernard ULg; De Wael, Kris et al

in Science & Justice : Journal of the Forensic Science Society (2008), 48(3), 109-117

Five forensic fibre cases in which Raman spectroscopy proved to be a good confirmatory method for microspectrophotometry (MSP) are described. Absorption spectra in the visible range are indeed sometimes ... [more ▼]

Five forensic fibre cases in which Raman spectroscopy proved to be a good confirmatory method for microspectrophotometry (MSP) are described. Absorption spectra in the visible range are indeed sometimes characteristic of a certain dye but this one can be subsequently identified unambiguously by Raman spectroscopy using a spectral library. In other cases the comparison of Raman spectra of reference fibres and suspect fibres led to an improvement of the discrimination power. The Raman measurements have been performed directly on mounted fibres and the spectra showed only little interference from the mounting resin and glass. Raman spectroscopy is therefore a powerful method that can be applied in routine fibre analysis following optical microscopy and MSP measurements. [less ▲]

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See detailA propos des peintures romanes de la cathédrale de Tournai
Lepot, Laurent ULg; Gilbert, Bernard ULg; Denoël, Sophie

in Denoël, Sophie (Ed.) Les peintures murales, Les techniques : Actes du colloque (2008)

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See detailEtude in situ de colorants sur fibres de coton par spectrométrie Raman
Lepot, Laurent ULg

Master of advanced studies dissertation (2006)

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See detailThe technique of the mural paintings of the Tournai Cathedral
Lepot, Laurent ULg; Gilbert, Bernard ULg; Denoël, Sophie

in Journal of Raman Spectroscopy (2006), 37(10), 1098-1103

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See detailIn situ study of cotton dyed fibres by Raman spectroscopy
Lepot, Laurent ULg

Conference (2006)

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See detailTechnique of mural paintings from the Tournai Cathedral
Lepot, Laurent ULg; Denoël, Sophie; Gilbert, Bernard ULg

Poster (2005)

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