4 resultados para Ink-stones.
em Université de Lausanne, Switzerland
Resumo:
The level of information provided by ink evidence to the criminal and civil justice system is limited. The limitations arise from the weakness of the interpretative framework currently used, as proposed in the ASTM 1422-05 and 1789-04 on ink analysis. It is proposed to use the likelihood ratio from the Bayes theorem to interpret ink evidence. Unfortunately, when considering the analytical practices, as defined in the ASTM standards on ink analysis, it appears that current ink analytical practices do not allow for the level of reproducibility and accuracy required by a probabilistic framework. Such framework relies on the evaluation of the statistics of the ink characteristics using an ink reference database and the objective measurement of similarities between ink samples. A complete research programme was designed to (a) develop a standard methodology for analysing ink samples in a more reproducible way, (b) comparing automatically and objectively ink samples and (c) evaluate the proposed methodology in a forensic context. This report focuses on the first of the three stages. A calibration process, based on a standard dye ladder, is proposed to improve the reproducibility of ink analysis by HPTLC, when these inks are analysed at different times and/or by different examiners. The impact of this process on the variability between the repetitive analyses of ink samples in various conditions is studied. The results show significant improvements in the reproducibility of ink analysis compared to traditional calibration methods.
Resumo:
For more than a decade scientists tried to develop methods capable of dating ink by monitoring the loss of phenoxyethanol (PE) over time. While many methods were proposed in the literature, few were really used to solve practical cases and they still raise much concern within the scientific community. In fact, due to the complexity of ink drying processes it is particularly difficult to find a reliable ageing parameter to reproducibly follow ink ageing. Moreover, systematic experiments are required in order to evaluate how different factors actually influence the results over time. Therefore, this work aimed at evaluating the capacity of four different ageing parameters to reliably follow ink ageing over time: (1) the quantity of solvent PE in an ink line, (2) the relative peak area (RPA) normalising the PE results using stable volatile compounds present in the ink formulation, (3) the solvent loss ratio (R%) calculated from PE results obtained by the analyses of naturally and artificially aged samples, (4) a modified solvent loss ratio version (R%*) calculated from RPA results. After the determination of the limits of reliable measurements of the analytical method, the repeatability of the different ageing parameters was evaluated over time, as well as the influence of ink composition, writing pressure and storage conditions on the results. Surprisingly, our results showed that R% was not the most reliable parameter, as it showed the highest standard deviation. Discussion of the results in an ink dating perspective suggests that other proposed parameters, such as RPA values, may be more adequate to follow ink ageing over time.
Resumo:
In liver, the glyoxylate cycle contributes to two metabolic functions, urea and glucose synthesis. One of the key enzymes in this pathway is glyoxylate reductase/hydroxypyruvate reductase (GRHPR) whose dysfunction in human causes primary hyperoxaluria type 2, a disease resulting in oxalate accumulation and formation of kidney stones. In this study, we provide evidence for a transcriptional regulation by the peroxisome proliferator-activated receptor alpha (PPARalpha) of the mouse GRHPR gene in liver. Mice fed with a PPARalpha ligand or in which PPARalpha activity is enhanced by fasting increase their GRHPR gene expression via a peroxisome proliferator response element located in the promoter region of the gene. Consistent with these observations, mice deficient in PPARalpha present higher plasma levels of oxalate in comparison with their wild type counterparts. As expected, the administration of a PPARalpha ligand (Wy-14,643) reduces the plasma oxalate levels. Surprisingly, this effect is also observed in null mice, suggesting a PPARalpha-independent action of the compound. Despite a high degree of similarity between the transcribed region of the human and mouse GRHPR gene, the human promoter has been dramatically reorganized, which has resulted in a loss of PPARalpha regulation. Overall, these data indicate a species-specific regulation by PPARalpha of GRHPR, a key gene of the glyoxylate cycle.
Resumo:
Si le passage d'un calcul rénal est souvent considéré comme un événement médical mineur, quoique très douloureux, de plus en plus d'études indiquent qu'il doit être pris au sérieux puisqu'il peut indiquer un risque cardiovasculaire augmenté. Nous revoyons ici les études qui associent risque cardiovasculaire et calcul rénal et les liens physiopathologiques qui les unissent. Nous montrons que la lithiase est un événement intervenant tôt dans la vie d'un individu à risque de développer des complications cardiovasculaires. Ainsi, la lithiase ne doit pas être banalisée, mais doit être considérée comme une première alerte devant inciter le médecin traitant à recenser précocement les facteurs de risque cardiovasculaires et à mettre en place une stratégie de prévention. Cette approche pourrait permettre de diminuer l'incidence d'événements cardiovasculaires chez les patients formeurs de lithiases. Most of the time, kidney stones are considered as minor, but painful events. However, several studies have recently shown an association between kidney stone and an increased cardio-vascular risk. We review here these studies and explore the underlying pathophysiological hypotheses. At the end, we propose that lithiasis should be considered as a red flag intervening early during life-time and allowing a check of cardiovascular risk factors and early preventive intervention. Such approach may be successful in reducing the incidence of cardio-vascular events in stone formers.