96 resultados para Photon sources
Resumo:
The profiling of MDMA tablets can be carried out using different sets of characteristics. The first type of measurements performed on MDMA tablets are physical characteristics (i.e. post-tabletting characteristics). They yield preliminary profiling data that may be valuable in a first stage for investigation purposes. However organic impurities (i.e. pre-tabletting characteristics) are generally considered to bring more reliable information, particularly for presentation of evidence in court. This work aimed therefore at evaluating the added value of combining pre-tabletting characteristics and post-tabletting characteristics of seized MDMA tablets. In approximately half of the investigated cases, the post-tabletting links were confirmed with organic impurities analyses. In the remaining cases, post-tabletting batches (post-TBs) were divided in several pre-tabletting batches (pre-TBs), thus supporting the hypothesis that several production batches of MDMA powder (pre-TBs) were used to produce one single post-TB (i.e. tablets having the same shape, diameter, thickness, weight and score; but different organic impurities composition). In view of the obtained results, the hypotheses were discussed through illustrating examples. In conclusion, both sets of characteristics were found relevant alone and combined together. They actually provide distinct information about MDMA illicit production and trafficking.
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An intercomparison of the response of different photon and neutron detectors was performed in several measurement positions around a spent fuel cask (type TN 12/2B) filled with 4 MOX and 8 UO2 15 x 15 PWR fuel assemblies at the nuclear power plant Gosgen (KKG) in Switzerland. The instruments used in the study were both active and passive, photon and neutron detectors calibrated either for ambient or personal dose equivalent. The aim of the measurement campaign was to compare the responses of the radiation instruments to routinely used detectors. It has been shown that especially the indications of the neutron detectors are strongly dependent on the neutron spectra around the cask due to their different energy responses. However, routinely used active photon and neutron detectors were shown to be reliable instruments. (C) 2012 Elsevier Ltd. All rights reserved.
Resumo:
Photons participate in many atomic and molecular interactions and processes. Recent biophysical research has discovered an ultraweak radiation in biological tissues. It is now recognized that plants, animal and human cells emit this very weak biophotonic emission which can be readily measured with a sensitive photomultiplier system. UVA laser induced biophotonic emission of cultured cells was used in this report with the intention to detect biophysical changes between young and adult fibroblasts as well as between fibroblasts and keratinocytes. With suspension densities ranging from 1-8 x 106 cells/ml, it was evident that an increase of the UVA-laser-light induced photon emission intensity could be observed in young as well as adult fibroblastic cells. By the use of this method to determine ultraweak light emission, photons in cell suspensions in low volumes (100 microl) could be detected, in contrast to previous procedures using quantities up to 10 ml. Moreover, the analysis has been further refined by turning off the photomultiplier system electronically during irradiation leading to the first measurements of induced light emission in the cells after less than 10 micros instead of more than 100 milliseconds. These significant changes lead to an improvement factor up to 106 in comparison to classical detection procedures. In addition, different skin cells as fibroblasts and keratinocytes stemming from the same donor were measured using this new highly sensitive method in order to find new biophysical insight of light pathways. This is important in view to develop new strategies in biophotonics especially for use in alternative therapies.
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Keywords Diabetes mellitus; coronary artery disease; myocardial ischemia; prognostic value; single-photon emission computed tomography myocardial perfusion imaging Summary Aim: To determine the long-term prognostic value of SPECT myocardial perfusion imaging (MPI) for the occurrence of cardiovascular events in diabetic patients. Methods: SPECT MPI of 210 consecutive Caucasian diabetic patients were analysed using Kaplan-Meier event-free survival curves and independent predictors were determined by Cox multivariate analyses. Results: Follow-up was complete in 200 (95%) patients with a median period of 3.0 years (0.8-5.0). The population was composed of 114 (57%) men, age 65±10 years, 181 (90.5%) type 2 diabetes mellitus, 50 (25%) with a history of coronary artery disease (CAD) and 98 (49%) presenting chest pain prior to MPI. The prevalence of abnormal MPI was 58%. Patients with a normal MPI had neither cardiac death, nor myocardial infarction, independently of a history of coronary artery disease or chest pain. Among the independent predictors of cardiac death and myocardial infarction, the strongest was abnormal MPI (p<.0001), followed by history of CAD (Hazard Ratio (HR)= t 5.9, p=0.0001), diabetic retinopathy (HR=10.0, p=0.001) and inability to exercise (HR=7.7, p=0.02). Patients with normal 1VIPI had a low revascularisation rate of 2.4% during the follow-up period. Compared to normal MPI, cardiovascular events increased 5.2 fold for reversible defects, 8.5 fold for fixed defects and 20.1 fold for the association of both defects. Conclusion: Diabetic patients with normal MPI had an excellent prognosis independently of history of CAD. On the opposite, an abnormal MPI led to a > 5 fold increase in cardiovascular events. This emphasizes the value of SPECT MPI in predicting and risk-stratifying cardiovascular events in diabetic patients. Mots-Clés Diabète; maladie coronarienne; ischémie myocardique; valeur pronostique; tomoscintigraphie myocardique de perfusion par émission monophotonique Résumé Objectifs: Déterminer la valeur pronostique à long terme de la tomoscintigraphie myocardique de perfusion (TSMP) chez les patients diabétiques pour prédire les événements cardiovasculaires (ECV). Méthodes: Etude de 210 diabétiques caucasiens consécutifs référés pour une TSMP. Les courbes de survie ont été déterminées par Kaplan-Meier et les facteurs prédictifs indépendants par analyses multivariées de type Cox. Résultats: Le suivi a été complet chez 200 (95%) patients avec une durée médiane de 3.0 ans (0.8-50). La population était composée de 114 (57%) hommes, âge moyen 65±10 ans, avec 181 (90.5%) diabète de type 2, 50 (25%) antécédents de maladie coronarienne (AMC) et 98 (49%) patients connus pour un angor avant la TSMP. La prévalence de TSMP anormales était de 58%. Aucun décès d'origine cardiaque ou infarctus du myocarde n'est survenu chez les patients avec une TSMP normale, ceci indépendamment de leurs AMC et des douleurs thoraciques. Les facteurs prédictifs indépendants pour les ECV sont une TSMP anormale (p<.0001), les AMC (Hazard Ratio (HR)=15.9, p-0.0001), suivi de la rétinopathie diabétique (HR-10.0, p=0.001) et de l'incapacité à effectuer un exercice (HR=7.7, p=0.02). Les patients avec une TSMP normale ont présenté un taux de revascularisations de 2.4%. La présence de défauts mixtes accroît le risque d'ECV de 20.1 fois, les défauts fixes de 8.5 fois et les défauts réversibles de 5.2 fois comparés aux sujets avec une TSMP normale. Conclusion: Les patients diabétiques, coronariens ou non, avec une tomoscintigraphie myocardique de perfusion normale ont un excellent pronostique. A l'opposé, une TSMP anormale est associée à une augmentation du risque d'ECV de plus de 5 fois. Ceci confirme l'utilité de la TSMP dans la stratification du risque chez les patients diabétiques.
Resumo:
Résumé Lors d'une recherche d'information, l'apprenant est très souvent confronté à des problèmes de guidage et de personnalisation. Ceux-ci sont d'autant plus importants que la recherche se fait dans un environnement ouvert tel que le Web. En effet, dans ce cas, il n'y a actuellement pas de contrôle de pertinence sur les ressources proposées pas plus que sur l'adéquation réelle aux besoins spécifiques de l'apprenant. A travers l'étude de l'état de l'art, nous avons constaté l'absence d'un modèle de référence qui traite des problématiques liées (i) d'une part aux ressources d'apprentissage notamment à l'hétérogénéité de la structure et de la description et à la protection en terme de droits d'auteur et (ii) d'autre part à l'apprenant en tant qu'utilisateur notamment l'acquisition des éléments le caractérisant et la stratégie d'adaptation à lui offrir. Notre objectif est de proposer un système adaptatif à base de ressources d'apprentissage issues d'un environnement à ouverture contrôlée. Celui-ci permet de générer automatiquement sans l'intervention d'un expert pédagogue un parcours d'apprentissage personnalisé à partir de ressources rendues disponibles par le biais de sources de confiance. L'originalité de notre travail réside dans la proposition d'un modèle de référence dit de Lausanne qui est basé sur ce que nous considérons comme étant les meilleures pratiques des communautés : (i) du Web en terme de moyens d'ouverture, (ii) de l'hypermédia adaptatif en terme de stratégie d'adaptation et (iii) de l'apprentissage à distance en terme de manipulation des ressources d'apprentissage. Dans notre modèle, la génération des parcours personnalisés se fait sur la base (i) de ressources d'apprentissage indexées et dont le degré de granularité en favorise le partage et la réutilisation. Les sources de confiance utilisées en garantissent l'utilité et la qualité. (ii) de caractéristiques de l'utilisateur, compatibles avec les standards existants, permettant le passage de l'apprenant d'un environnement à un autre. (iii) d'une adaptation à la fois individuelle et sociale. Pour cela, le modèle de Lausanne propose : (i) d'utiliser ISO/MLR (Metadata for Learning Resources) comme formalisme de description. (ii) de décrire le modèle d'utilisateur avec XUN1 (eXtended User Model), notre proposition d'un modèle compatible avec les standards IEEE/PAPI et IMS/LIP. (iii) d'adapter l'algorithme des fourmis au contexte de l'apprentissage à distance afin de générer des parcours personnalisés. La dimension individuelle est aussi prise en compte par la mise en correspondance de MLR et de XUM. Pour valider notre modèle, nous avons développé une application et testé plusieurs scenarii mettant en action des utilisateurs différents à des moments différents. Nous avons ensuite procédé à des comparaisons entre ce que retourne le système et ce que suggère l'expert. Les résultats s'étant avérés satisfaisants dans la mesure où à chaque fois le système retourne un parcours semblable à celui qu'aurait proposé l'expert, nous sommes confortées dans notre approche.
Resumo:
A forensic intelligence process was conducted over cross-border seizures of false identity documents whose sources were partly known to be the same. Visual features of 300 counterfeit Portuguese and French identity cards seized in France and Switzerland were observed and integrated in a structured database developed to detect and analyze forensic links. Based on a few batches of documents known to come from common sources, the forensic profiling method could be validated and its performance evaluated. The method also proved efficient and complementary to conventional means of detecting connections between cases. Cross-border links were detected, highlighting the need for more collaboration. Forensic intelligence could be produced, uncovering the structure of counterfeits' illegal trade, the concentration of their sources and the evolution of their quality over time. In addition, two case examples illustrated how forensic profiling may support specific investigations. The forensic intelligence process and its results will underline the need to develop such approaches to support the fight against fraudulent documents and organized crime.
Resumo:
The late Variscan (275-278 Ma) Pribram uranium deposit is one of the largest known accumulations of uraniferous bitumens in hydrothermal veins. The deposit extends along the northwestern boundary of the Central Bohemian pluton (345-335 Ma) with low-grade metamorphosed Late Proterozoic and unmetamorphosed Cambrian rocks. From a net uranium production of 41,742 metric tons (t), more than 6,000 t were extracted from bitumen-uraninite ores during 43 years of exploration and mining. Three morphological varieties of solid bitumen are recognized: globular, asphaltlike, and cokelike. While the globular bitumen is uranium free, the other two types are uraniferous. The amount of bitumen in ore veins gradually decreases toward the contact with the plutonic body and increases with depth. Two types of bitumen microtextures are recognized using high-resolution transmission electron microscopy: amorphous and microporous, the former being less common in uraniferous samples. A lower Raman peak area ratio (1,360/1,575 cm(-1)) in mineralized bitumens (0.9) compared with uranium-free samples (2.0) indicates a lower degree of microtextural organization in the latter The H/C and O/C atomic ratios in uranium-free bitumens (0.9-1.1 and 0.09, respectively) are higher than those in mineralized samples (H/C = 0.3-0.8, O/C = 0.03-0.09). The chloroform extractable matter yield is Very low in uranium-free bitumens (0.30-0.35% of the total organic carbon,TOC) and decreases with uranium content increase. The extracted solid uraniferous bitumen infrared spectra show depletion in aliphatic CH2 and CH3 groups compared to uranium-free samples. The concentration of oxygen-bearing functional groups relative to aromatic bonds in the IR spectra of uranium-free and mineralized bitumen, however, do not differ significantly. C-13 NMR confirmed than the aromaticity of a uraniferous sample is higher (F-ar = 0.61) than in the uranium-free bitumen (F-ar = 0.51). Pyrolysates from uraniferous and nonuraniferous bitumens do not differ significantly, being predominantly cresol, alkylphenols, alkylbenzenes, and alkylnaphthalenes. The liquid pyrolysate yield decreases significantly with increasing uranium content. The delta(13)C Values of bulk uranium-free bitumens and low-grade uraniferous, asphaltlike bitumens range from -43.6 to 52.3 per mil. High-grade, cokelike, uraniferous bitumens are more C-13 depleted (54.5 to -58.4 parts per thousand). In contrast to the very light isotopic ratios of the high-grade uraniferous cokelike bitumen bulk carbon, the individual n-alkanes and isoprenoids (pristane and phytane) extracted from the same sample are significantly C-13 enriched. The isotopic composition of the C13-24 n-alkanes extracted from the high-grade uraniferous sample (delta(13)C = -28.0 to 32.6 parts per thousand) are heavier compared with the same compounds in a uranium-free sample (delta(13)C = 31.9 to 33.8 parts per thousand). It is proposed that the bitumen source was the isotopically light (delta(13)C = 35.8 to 30.2 parts per thousand) organic matter of the Upper Proterozoic host rocks that were pyrolyzed during intrusion of the Central Bohemian pluton. The C-13- depleted pyrolysates were mobilized from the innermost part of the contact-metamorphic aureole, accumulated in structural traps in less thermally influenced parts of the sedimentary complex and were later extracted by hydrothermal fluids. Bitumens at the Pribram deposit are younger than the main part of the uranium mineralization and were formed through water-washing and radiation-induced polymerization of both the gaseous and liquid pyrolysates. Direct evidence for pyrolysate reduction of uranium in the hydrothermal system is difficult to obtain as the chemical composition of the original organic fluid phase was modified during water-washing and radiolytic alteration. However, indirect evidence-e.g., higher O/C atomic ratios in uranium-free bitumens (0.1) relative to the Upper Proterozoic source rocks (0.02-0.05), isotopically very light carbon in associated whewellite (delta(13)C = 31.7 to -28.4 parts per thousand), and the striking absence of bitumens in the pre-uranium, hematite stage of the mineralization-indicates that oxidation of organic fluids may have contributed to lowering of aO(2) and uraninite precipitation.