High Zn content of Randall's plaque: A μ-X-ray fluorescence investigation

Kidney stone disease, or nephrolithiasis, is a common ailment. Among the different risk factors usually associated with nephrolithiasis are dehydration, metabolic defects (especially with regard to calcium and oxalate). The presence of a mineral deposit at the surface of the renal papilla (termed Randall's plaque) has all been recently underlined. Of note, Randall's plaque is made of the calcium phosphate, carbapatite, and serves as a nucleus for kidney stone formation. The process by which apatite nanocrystals nucleate and form Randall's plaque remains unclear. This paper deals with the possible relationship between trace elements and the formation of this mineral. The investigation has been performed on a set of Randall's plaques, extracted from human kidney stones, through μ-X-ray diffraction and μ-X-ray fluorescence analyses in order to determine the chemical composition of the plaque as well as the nature and the amount of trace elements. Our data provide evidence that Zn levels are dramatically increased in carbapatite of RP by comparison to carbapatite in kidney stones, suggesting that calcified deposits within the medullar interstitium are a pathological process involving a tissue reaction. Further studies, perhaps including the investigation of biomarkers for inflammation, are necessary for clarifying the role of Zn in Randall's plaque formation

Exploring the electrochemical behavior of InSb as negative electrode for Mg-ion batteries

International audienceMagnesium metal has a tendency to react with conventional electrolytes to form a barrier on its surface[1], rendering cations exchange impossible, and thus dramatically limiting reversible stripping/deposition of Mg. Unlike Mg metal, alloys based on p-block elements (Sn, Sb, In, Pb, Bi) do not appear to suffer from the formation of a blocking passivation layer in conventional electrolytes. These substitute electrodes appear therefore as a promising solution to overcome the problem of compatibility with electrolytes, even if the reaction mechanisms behind their operation in conventional electrolytes are still unsolved. In order to improve the performance of these electrodes, we evaluated a possible synergy effect between p-block elements, as already shown for SnSb[2] and BiSb[3]. We chose to work on InSb that may combine the high theoretical capacity of Sb and the lowest working potential reported for In. InSb, synthetized by ball-milling, shows an electrochemical behavior (Figure 1) drastically different from those of the lone elements. We will demonstrate that the combination of In and Sb is beneficial as it promotes the reactivity of Sb, similarly to BiSb alloy[3]. Structural and morphological ex situ characterization will also be described in details and correlated with the peculiar electrochemical behavior of InSb. Figure 1: Voltage profile of an InSb-based electrode cycled at a rate of C/100 in an electrolyte based of EtMgCl and Et2AlCl in THF

Formation and characterization of hydride blisters in Zircaloy 4 cladding tubes

International audienceThis article is focused on the formation of hydride blisters in zirconium alloys an experimental and theoretical standpoint, and their characterization in terms of morphology, hydrides crystallographic phases, hardness and hydrogen concentration. An experimental setup was developed to grow hydride blisters on pre-hydrided Zircaloy-4 cladding tubes by thermo-diffusion. The thermal conditions were optimized based on thermo-diffusion calculations, that take into account the hysteresis in the hydrogen solubility limit, to obtain a high blister growth rate. Micro-X-ray Diffraction (XRD), nano-hardness and Elastic Recoil Detection Analysis (ERDA) showed that the blisters contain a hydrogen gradient, with pure δδ-hydride phase close to the external surface over one third of the blister depth. Thermo-diffusion calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys

Silicon Sheets By Redox Assisted Chemical Exfoliation

In this paper, we report the direct chemical synthesis of silicon sheets in gram-scale quantities by chemical exfoliation of pre-processed calcium di-silicide (CaSi2). We have used a combination of X-ray photoelectron spectroscopy, transmission electron microscopy and Energy-dispersive X-ray spectroscopy to characterize the obtained silicon sheets. We found that the clean and crystalline silicon sheets show a 2-dimensional hexagonal graphitic structure.Comment: Accepted in J. Phys.: Condens. Matte

Assessment of the real contact area of a multi-contact interface from electrical measurements

The electrical supply of moving trains is provided by a sliding contact between the train's pantographs and the catenary. This electromechanical interface is composed of the pantograph's strips ? made mainly of carbon ? and the catenary contact wire. The temperature rising induces the rising of the carbon strip wear. Moreover, the heating produced at the interface depends on the surface quality. Indeed, the smaller is the surface contact, the greater is the electrical resistance which implies more heat production because of the Joule effect. The problem is multi-physical, there is a coupling between mechanical, electrical and thermal states. The objective is to define the real contact area with a simple electrical measurement. In many practical or fundamental situations involving contacting solids, the relevant notion of the real contact area is a very delicate one and especially its experimental assessment. Based on the Drude's classical transport model and within the linear elasticity approximation, a phenomenological model of a metal/metal contact is built up, offering a simplified interpretation framework of experimental data. The model accounts for the influence of the mechanical state of the contacting zone upon its electrical properties, such as its impedance. Interpreting available data within this framework leads to the assessment of the spots' number. The total contact force works on the spots and on the average contact length. In this model, the interface is treated as a new medium with its own conductivity and mean free time between ionic collisions. There are two types of measurement: - Electrical measurements carried out on two copper sheets with dimensions 50X50X1 mm3 acted upon with an external compression force, allowed to check and validate the model. In agreement with the conditions of the model and to avoid the complexification of the model due to the intricacy between thermal and electrical processes at the contact interface, the measurements were operated in alternative current at low voltages. - Additional measurements of surface states have been realized to join the electrical measure with roughness and the nature of the metal.  In the case of contact between train's pantograph and catenary, this method allows predicting electric transfer's quality to control the heating of the interface. Being sensitive to the spots' mechanical solicitation conditions, properly interpreted, electrical impedance measurements should lead to a better understanding of the complex mechanical responses of these interfaces and their ageing process or even to detect a fatigue and prevent a potential failure

Production of H2 by water radiolysis in cement paste under electron irradiation: A joint experimental and theoretical study

International audienceLong-term confinement of nuclear waste is one of the main challenges faced by the nuclear industry. Fission products such as 90 Sr and 137 Cs, both β − emitters known to induce serious health hazards, represent the largest fraction of nuclear waste. Cement is a good candidate to store them, provided it can resist the effects of irradiation over time. Here, we have investigated the effects of β − decay on cement by performing electron irradiation experiments on different samples. We show that H 2 production in cement, the main effect of water radiolysis, depends strongly on composition and relative humidity. First-principles calculations indicate that the water-rich interlayer regions with Ca 2+ ions act as electron traps that promote the formation of H 2. They also show that holes localize in water-rich regions in low Ca content samples and are then able to participate in H 2 production. This work provides new understanding of radiolysis effects in cements

The effect of priority setting decisions for new cancer drugs on medical oncologists' practice in Ontario: a qualitative study

<p>Abstract</p> <p>Background</p> <p>Health care policies, including drug-funding policies, influence physician practice. Funding policies are especially important in the area of cancer care since cancer is a leading cause of death that is responsible for a significant level of health care expenditures. Recognizing the rising cost of cancer therapies, Cancer Care Ontario (CCO) established a funding process to provide access to new, effective agents through a "New Drug Funding Program" (NDFP). The purpose of this study is to describe oncologists' perceptions of the impact of NDFP priority setting decisions on their practice.</p> <p>Methods</p> <p>This is a qualitative study involving semi-structured, in-depth interviews with 46 medical oncologists in Ontario. Oncologists were asked to describe the impact of CCO's NDFP drug funding decisions on their practice. Analysis of interview transcripts commenced with data collection.</p> <p>Results</p> <p>Our key finding is that many of the medical oncologists who participated in this study did not accept limits when policy decisions limit access to cancer drugs they feel would benefit their patients. Moreover, overcoming those limits had a significant impact on oncologists' practice in terms of how they spend their time and energy and their relationship with patients.</p> <p>Conclusion</p> <p>When priority setting decisions limit access to cancer medications, many oncologists' efforts to overcome those limits have a significant impact on their practice. Policy makers need to seriously consider the implications of their decisions on physicians, who may go to considerable effort to circumvent their policies in the name of patient advocacy.</p

Les structures des sols analysées en microscopie optique et par des techniques submicroscopiques

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L’emploi de l’alun dans les recettes métallurgiques à la lumière de l’expérimentation: L’exemple de la falsification de l’argent

International audienceReferences to the use of alum [as a reactant] can be found in many ancient metallurgical texts while its identification on site, in correspondence to the metallurgical workshop, remains uncertain. Nevertheless, the use of an experimental approach, based on recipes described in the papyrus of Leyde and Stockholm (3rd century AD), provides a way to elucidate both the practical features and the nature of the products obtained. In order to understand the role of alum in metalworking, our study focuses on the question related to the forgery of silver by addiction of copper hammer scale. An experimental laboratory protocol has been established and it allows to follow the evolution of the products from the raw materials to the copper-alloyed silver. The materials obtained from such experimentation systematically characterized by structural and elemental analysis and the results provided a way to have a better understanding on the functionality of the recipes. A new hypothesis on the interpretation of the texts is proposed.L’alun est un matériau qui apparaît assez classiquement comme réactif dans plusieurs textes métallurgiques. Son identification sur le terrain, au sein d’ateliers métallurgiques, reste encore à démontrer. En revanche, il est possible d’organiser une réflexion autour de l’approche expérimentale afin d’apprécier autant le caractère opératoire que la nature des produits formés à partir de ces recettes dont les plus anciennes remontent aux papyrus de Leyde et de Stockholm (iiie siècle après J.-C.).Pour tenter de comprendre quelle place fonctionnelle peut occuper l’alun dans le travail des métaux, nous nous sommes focalisés sur la question liée à la falsification de l’argent par ajout de battitures de cuivre. Un protocole expérimental de laboratoire a été mis en place permettant de suivre l’évolution des produits depuis les matières premières jusqu’à l’argent allié au cuivre. Dans la logique de ces séries expérimentales, les matériaux mis en œuvre comme les produits issus des expériences ont fait l’objet d’une caractérisation structurale et élémentaire qui permet de mieux apprécier la fonctionnalité des recettes. Cette approche autorise une nouvelle hypothèse quant à l’interprétation de ces texte