Metallic and nonmetallic shine in luster: An elastic ion backscattering study

Luster is a metal glass nanocomposite layer first produced in the Middle East in early Islamic times ( 9th AD) made of metal copper or silver nanoparticles embedded in a silica-based glassy matrix. These nanoparticles are produced by ion exchange between Cu+ and Ag+ and alkaline ions from the glassy matrix and further growth in a reducing atmosphere. The most striking property of luster is its capability of reflecting light like a continuous metal layer and it was unexpectedly found to be linked to one single production parameter: the presence of lead in the glassy matrix composition. The purpose of this article is to describe the characteristics and differences of the nanoparticle layers developed on lead rich and lead free glasses. Copper luster layers obtained using the ancient recipes and methods are analyzed by means of elastic ion backscattering spectroscopy associated with other analytical techniques. The depth profile of the different elements is determined, showing that the luster layer formed in lead rich glasses is 5–6 times thinner and 3–4 times Cu richer. Therefore, the metal nanoparticles are more densely packed in the layer and this fact is related to its higher reflectivity. It is shown that lead influences the structure of the metal nanoparticle layer through the change of the precipitation kinetics

Dose reconstruction in the context of tomotherapy

In vivo dosimetry is a way to verify the radiation dose delivered to the patient in measuring the dose generally during the first fraction of the treatment. It is the only dose delivery control based on a measurement performed during the treatment. In today's radiotherapy practice, the dose delivered to the patient is planned using 3D dose calculation algorithms and volumetric images representing the patient. Due to the high accuracy and precision necessary in radiation treatments, national and international organisations like ICRU and AAPM recommend the use of in vivo dosimetry. It is also mandatory in some countries like France. Various in vivo dosimetry methods have been developed during the past years. These methods are point-, line-, plane- or 3D dose controls. A 3D in vivo dosimetry provides the most information about the dose delivered to the patient, with respect to ID and 2D methods. However, to our knowledge, it is generally not routinely applied to patient treatments yet. The aim of this PhD thesis was to determine whether it is possible to reconstruct the 3D delivered dose using transmitted beam measurements in the context of narrow beams. An iterative dose reconstruction method has been described and implemented. The iterative algorithm includes a simple 3D dose calculation algorithm based on the convolution/superposition principle. The methodology was applied to narrow beams produced by a conventional 6 MV linac. The transmitted dose was measured using an array of ion chambers, as to simulate the linear nature of a tomotherapy detector. We showed that the iterative algorithm converges quickly and reconstructs the dose within a good agreement (at least 3% / 3 mm locally), which is inside the 5% recommended by the ICRU. Moreover it was demonstrated on phantom measurements that the proposed method allows us detecting some set-up errors and interfraction geometry modifications. We also have discussed the limitations of the 3D dose reconstruction for dose delivery error detection. Afterwards, stability tests of the tomotherapy MVCT built-in onboard detector was performed in order to evaluate if such a detector is suitable for 3D in-vivo dosimetry. The detector showed stability on short and long terms comparable to other imaging devices as the EPIDs, also used for in vivo dosimetry. Subsequently, a methodology for the dose reconstruction using the tomotherapy MVCT detector is proposed in the context of static irradiations. This manuscript is composed of two articles and a script providing further information related to this work. In the latter, the first chapter introduces the state-of-the-art of in vivo dosimetry and adaptive radiotherapy, and explains why we are interested in performing 3D dose reconstructions. In chapter 2 a dose calculation algorithm implemented for this work is reviewed with a detailed description of the physical parameters needed for calculating 3D absorbed dose distributions. The tomotherapy MVCT detector used for transit measurements and its characteristics are described in chapter 3. Chapter 4 contains a first article entitled '3D dose reconstruction for narrow beams using ion chamber array measurements', which describes the dose reconstruction method and presents tests of the methodology on phantoms irradiated with 6 MV narrow photon beams. Chapter 5 contains a second article 'Stability of the Helical TomoTherapy HiArt II detector for treatment beam irradiations. A dose reconstruction process specific to the use of the tomotherapy MVCT detector is presented in chapter 6. A discussion and perspectives of the PhD thesis are presented in chapter 7, followed by a conclusion in chapter 8. The tomotherapy treatment device is described in appendix 1 and an overview of 3D conformai- and intensity modulated radiotherapy is presented in appendix 2. - La dosimétrie in vivo est une technique utilisée pour vérifier la dose délivrée au patient en faisant une mesure, généralement pendant la première séance du traitement. Il s'agit de la seule technique de contrôle de la dose délivrée basée sur une mesure réalisée durant l'irradiation du patient. La dose au patient est calculée au moyen d'algorithmes 3D utilisant des images volumétriques du patient. En raison de la haute précision nécessaire lors des traitements de radiothérapie, des organismes nationaux et internationaux tels que l'ICRU et l'AAPM recommandent l'utilisation de la dosimétrie in vivo, qui est devenue obligatoire dans certains pays dont la France. Diverses méthodes de dosimétrie in vivo existent. Elles peuvent être classées en dosimétrie ponctuelle, planaire ou tridimensionnelle. La dosimétrie 3D est celle qui fournit le plus d'information sur la dose délivrée. Cependant, à notre connaissance, elle n'est généralement pas appliquée dans la routine clinique. Le but de cette recherche était de déterminer s'il est possible de reconstruire la dose 3D délivrée en se basant sur des mesures de la dose transmise, dans le contexte des faisceaux étroits. Une méthode itérative de reconstruction de la dose a été décrite et implémentée. L'algorithme itératif contient un algorithme simple basé sur le principe de convolution/superposition pour le calcul de la dose. La dose transmise a été mesurée à l'aide d'une série de chambres à ionisations alignées afin de simuler la nature linéaire du détecteur de la tomothérapie. Nous avons montré que l'algorithme itératif converge rapidement et qu'il permet de reconstruire la dose délivrée avec une bonne précision (au moins 3 % localement / 3 mm). De plus, nous avons démontré que cette méthode permet de détecter certaines erreurs de positionnement du patient, ainsi que des modifications géométriques qui peuvent subvenir entre les séances de traitement. Nous avons discuté les limites de cette méthode pour la détection de certaines erreurs d'irradiation. Par la suite, des tests de stabilité du détecteur MVCT intégré à la tomothérapie ont été effectués, dans le but de déterminer si ce dernier peut être utilisé pour la dosimétrie in vivo. Ce détecteur a démontré une stabilité à court et à long terme comparable à d'autres détecteurs tels que les EPIDs également utilisés pour l'imagerie et la dosimétrie in vivo. Pour finir, une adaptation de la méthode de reconstruction de la dose a été proposée afin de pouvoir l'implémenter sur une installation de tomothérapie. Ce manuscrit est composé de deux articles et d'un script contenant des informations supplémentaires sur ce travail. Dans ce dernier, le premier chapitre introduit l'état de l'art de la dosimétrie in vivo et de la radiothérapie adaptative, et explique pourquoi nous nous intéressons à la reconstruction 3D de la dose délivrée. Dans le chapitre 2, l'algorithme 3D de calcul de dose implémenté pour ce travail est décrit, ainsi que les paramètres physiques principaux nécessaires pour le calcul de dose. Les caractéristiques du détecteur MVCT de la tomothérapie utilisé pour les mesures de transit sont décrites dans le chapitre 3. Le chapitre 4 contient un premier article intitulé '3D dose reconstruction for narrow beams using ion chamber array measurements', qui décrit la méthode de reconstruction et présente des tests de la méthodologie sur des fantômes irradiés avec des faisceaux étroits. Le chapitre 5 contient un second article intitulé 'Stability of the Helical TomoTherapy HiArt II detector for treatment beam irradiations'. Un procédé de reconstruction de la dose spécifique pour l'utilisation du détecteur MVCT de la tomothérapie est présenté au chapitre 6. Une discussion et les perspectives de la thèse de doctorat sont présentées au chapitre 7, suivies par une conclusion au chapitre 8. Le concept de la tomothérapie est exposé dans l'annexe 1. Pour finir, la radiothérapie «informationnelle 3D et la radiothérapie par modulation d'intensité sont présentées dans l'annexe 2.

Selective regulation of acid-sensing ion channel 1 by serine proteases.

Acid-sensing ion channels (ASICs) are neuronal Na(+) channels that belong to the epithelial Na(+) channel/degenerin family. ASICs are transiently activated by a rapid drop in extracellular pH. Conditions of low extracellular pH, such as ischemia and inflammation in which ASICs are thought to be active, are accompanied by increased protease activity. We show here that serine proteases modulate the function of ASIC1a and ASIC1b but not of ASIC2a and ASIC3. We show that protease exposure shifts the pH dependence of ASIC1a activation and steady-state inactivation to more acidic pH. As a consequence, protease exposure leads to a decrease in current response if ASIC1a is activated by a pH drop from pH 7.4. If, however, acidification occurs from a basal pH of approximately 7, protease-exposed ASIC1a shows higher activity than untreated ASIC1a. We provide evidence that this bi-directional regulation of ASIC1a function also occurs in neurons. Thus, we have identified a mechanism that modulates ASIC function and may allow ASIC1a to adapt its gating to situations of persistent extracellular acidification.

Evaluation of Different Methods to Calculate Heavy-Truck VMT, Final Report, December 2004

Reliable estimates of heavy-truck volumes are important in a number of transportation applications. Estimates of truck volumes are necessary for pavement design and pavement management. Truck volumes are important in traffic safety. The number of trucks on the road also influences roadway capacity and traffic operations. Additionally, heavy vehicles pollute at higher rates than passenger vehicles. Consequently, reliable estimates of heavy-truck vehicle miles traveled (VMT) are important in creating accurate inventories of on-road emissions. This research evaluated three different methods to calculate heavy-truck annual average daily traffic (AADT) which can subsequently be used to estimate vehicle miles traveled (VMT). Traffic data from continuous count stations provided by the Iowa DOT were used to estimate AADT for two different truck groups (single-unit and multi-unit) using the three methods. The first method developed monthly and daily expansion factors for each truck group. The second and third methods created general expansion factors for all vehicles. Accuracy of the three methods was compared using n-fold cross-validation. In n-fold cross-validation, data are split into n partitions, and data from the nth partition are used to validate the remaining data. A comparison of the accuracy of the three methods was made using the estimates of prediction error obtained from cross-validation. The prediction error was determined by averaging the squared error between the estimated AADT and the actual AADT. Overall, the prediction error was the lowest for the method that developed expansion factors separately for the different truck groups for both single- and multi-unit trucks. This indicates that use of expansion factors specific to heavy trucks results in better estimates of AADT, and, subsequently, VMT, than using aggregate expansion factors and applying a percentage of trucks. Monthly, daily, and weekly traffic patterns were also evaluated. Significant variation exists in the temporal and seasonal patterns of heavy trucks as compared to passenger vehicles. This suggests that the use of aggregate expansion factors fails to adequately describe truck travel patterns.

Jambes lourdes, insuffisance veineuse des membres inférieurs et hormonothérapie substitutive [Heavy legs, venous insufficiency of the legs and hormone substitution therapy]

The effects of estrogens and gestagens on veins and circulation have been studied since prescription of these hormones as oral contraception and description of related thromboembolic events. The identification of different receptors and the description of these receptors in venous walls have helped to understand some hormonal effects. However, the actual knowledge remains insufficient to explain the complexity of the actions of hormones on venous function. The distribution, the density and the receptor types vary with age, gender, hormonal status and vascular bed. Gestagens mainly reduce the tone of venous walls, whereas estrogens have various effects. Between 25% and 50% of European adults and even 80% or more in some risk groups complain about heavy legs, with or without chronic venous insufficiency. The number of women to whom hormonal substitution is or could be prescribed increases along with aging of populations and the better understanding of potential benefits. The need for a better understanding of vascular effects of sexual hormones is growing, since the incidence of chronic venous insufficiency of the legs increases with age. The life prognosis will not be affected by a deterioration of a chronic venous insufficiency. In contrast, the quality of life, morbidity and the cost of treatment will be expected to change. In addition, thromboembolic events have to be considered, as has been shown in recent studies. These findings outline the need for further studies on the relation between hormones and venous function and for some caution when prescribing hormonal substitution.

Panorama des environs de Londres / Par A. M. Perrot ; Ad. Hocquart Dir[ec]t[ion]

Échelle(s) : [ca 1:365 000], échelle de 4 lieues de poste de France [= 4,7 cm]

Subtype-specific Modulation of Acid-sensing Ion Channel (ASIC) Function by 2-Guanidine-4-methylquinazoline.

Acid-sensing ion channels (ASICs) are neuronal Na(+)-selective channels that are transiently activated by extracellular acidification. ASICs are involved in fear and anxiety, learning, neurodegeneration after ischemic stroke, and pain sensation. The small molecule 2-guanidine-4-methylquinazoline (GMQ) was recently shown to open ASIC3 at physiological pH. We have investigated the mechanisms underlying this effect and the possibility that GMQ may alter the function of other ASICs besides ASIC3. GMQ shifts the pH dependence of activation to more acidic pH in ASIC1a and ASIC1b, whereas in ASIC3 this shift goes in the opposite direction and is accompanied by a decrease in its steepness. GMQ also induces an acidic shift of the pH dependence of inactivation of ASIC1a, -1b, -2a, and -3. As a consequence, the activation and inactivation curves of ASIC3 but not other ASICs overlap in the presence of GMQ at pH 7.4, thereby creating a window current. At concentrations >1 mm, GMQ decreases maximal peak currents by reducing the unitary current amplitude. Mutation of residue Glu-79 in the palm domain of ASIC3, previously shown to be critical for channel opening by GMQ, disrupted the GMQ effects on inactivation but not activation. This suggests that this residue is involved in the consequences of GMQ binding rather than in the binding interaction itself. This study describes the mechanisms underlying the effects of a novel class of ligands that modulate the function of all ASICs as well as activate ASIC3 at physiological pH.

Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice.

In vitro studies suggested that sub-millisecond pulses of radiation elicit less genomic instability than continuous, protracted irradiation at the same total dose. To determine the potential of ultrahigh dose-rate irradiation in radiotherapy, we investigated lung fibrogenesis in C57BL/6J mice exposed either to short pulses (≤ 500 ms) of radiation delivered at ultrahigh dose rate (≥ 40 Gy/s, FLASH) or to conventional dose-rate irradiation (≤ 0.03 Gy/s, CONV) in single doses. The growth of human HBCx-12A and HEp-2 tumor xenografts in nude mice and syngeneic TC-1 Luc(+) orthotopic lung tumors in C57BL/6J mice was monitored under similar radiation conditions. CONV (15 Gy) triggered lung fibrosis associated with activation of the TGF-β (transforming growth factor-β) cascade, whereas no complications developed after doses of FLASH below 20 Gy for more than 36 weeks after irradiation. FLASH irradiation also spared normal smooth muscle and epithelial cells from acute radiation-induced apoptosis, which could be reinduced by administration of systemic TNF-α (tumor necrosis factor-α) before irradiation. In contrast, FLASH was as efficient as CONV in the repression of tumor growth. Together, these results suggest that FLASH radiotherapy might allow complete eradication of lung tumors and reduce the occurrence and severity of early and late complications affecting normal tissue.

Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings

1. Sex-biased mortality in adult vertebrates is often attributed to lower immunocompetence and higher parasite susceptibility of males. Although sex-specific mortality has also been reported during growth, the importance of sex-specific immunocompetence and parasite susceptibility in explaining male-biased mortality remains ambiguous in growing individuals because of potentially confounding sources of mortality such as sexual dimorphism. 2. Here, we investigated sex-specific susceptibility to the blood-sucking louse fly Crataerina melbae and sex differences in cell-mediated immunity in a bird species that is sexually monomorphic both in size and plumage coloration at the nestling stage, the Alpine Swift, Apus melba. 3. For this purpose, we manipulated ectoparasite loads by adding or removing flies to randomly chosen nests in two years, and injected nestlings with mitogenic phytohaemagglutinin (PHA) in another year. 4. There were no significant differences between male and female offspring in immune response towards PHA, parasite load, and parasite-induced decrease in growth rate. Secondary sex ratios were however biased toward males in parasitized broods, and this was explained by a greater mortality of females in parasitized than deparasitized broods. 5. Our findings are in contrast to the widely accepted hypothesis that males suffer a greater cost of parasitism. We discuss alternative hypotheses accounting for female-specific mortality.

Fábrica de "Metalheads" : arquetipo de la representación del aficionado al Heavy Metal en España

El presente estudio expone los resultados del tema desarrollado en la línea investigativa de culturas urbanas contemporáneas y procesos comunicacionales. Trabajo que describe (construye) el arquetipo del aficionado al heavy metal en España.

Subsampling the mean of heavy-tailed dependent observations

We establish the validity of subsampling confidence intervals for themean of a dependent series with heavy-tailed marginal distributions.Using point process theory, we study both linear and nonlinear GARCH-liketime series models. We propose a data-dependent method for the optimalblock size selection and investigate its performance by means of asimulation study.