Variation of the Diameter of the Sun as Measured by the Solar Disk Sextant (SDS)

The balloon-borne Solar Disk Sextant (SDS) experiment has measured the angular size of the Sun on seven occasions spanning the years 1992 to 2011. The solar half-diameter -- observed in a 100-nm wide passband centred at 615 nm -- is found to vary over that period by up to 200 mas, while the typical estimated uncertainty of each measure is 20 mas. The diameter variation is not in phase with the solar activity cycle; thus, the measured diameter variation cannot be explained as an observational artefact of surface activity. Other possible instrument-related explanations for the observed variation are considered but found unlikely, leading us to conclude that the variation is real. The SDS is described here in detail, as is the complete analysis procedure necessary to calibrate the instrument and allow comparison of diameter measures across decades.Comment: 41 pages; appendix and 2 figures added plus some changes in text based on referee's comments; to appear in MNRA

The influence of ambipolarity on plasma confinement and the performace of ECRIS

International audienceCharge diffusion in an ECRIS discharge is usually characterized by non ambipolar behavior. While the ions are transported to the radial walls, electrons are lost axially from the magnetic trap. Global neutrality is maintained via compensating currents in the conducting walls of the vacuum chamber. It is assumed that this behavior reduces the ion breeding times compared to a truly ambipolar plasma. We have carried out a series of dedicated experiments in which the ambipolarity of the ECRIS plasma was influenced by inserting special metal-dielectric structures (MD layers) into the plasma chamber of the Frankfurt 14GHz ECRIS. The measurements demonstrate the positive influence on the source performance when the ECR plasma is changed towards more ambipolar behavior

Dealing with flood damages: will prevention, mitigation and ex-post compensation provide for a resilient triangle?

There is a wealth of literature on the design of ex-post compensation mechanisms for natural disasters. However, more research needs to be done on the manner in which these mechanisms could steer citizens toward adopting individual level preventive and protection measures in the face of flood risks. This paper provides a comparative legal analysis of the financial compensation mechanisms following floods, be it through insurance, public funds or a combination of both, with an empirical focus on Belgium, the Netherlands, England and France. Similarities and differences between the methods in which these compensation mechanisms for flood damages enhance resilience are analyzed. The comparative analysis especially focuses on the link between the recovery strategy on the one hand and prevention and mitigation strategies on the other. There is great potential within the recovery strategy for promoting preventive action, for example in terms of discouraging citizens from living in high-risk areas, or encouraging the uptake of mitigation measures, such as adaptive building. However, this large potential is yet to be realized, in part due to insufficient consideration and promotion of these connections within existing legal frameworks. Recommendations are made about how the linkages between strategies can be further improved. These recommendations relate to, amongst others, the promotion of resilient reinstatement through recovery mechanisms and the removal of legal barriers preventing the establishment of link-inducing measures

Inverse identification processes of elastoplastic constitutive models using advanced optimisation strategies

The success of simulation tools in reproducing the mechanical behaviour of materials, particularly for metals, depends on the quality of the models and their inherent material parameters. However, the commonly used parameter identification strategies are still expensive and non-robust. The robustness and efficiency of these strategies are closely related with the single-stage optimisation methods adopted. The aim of this work is to implement and analyse optimisation strategies such as sequential, parallel and hybrid approaches in a parameter identification problem using full-field methods, particularly the Virtual Fields Method (VFM) and the Finite Element Model Updating (FEMU). The definition of the objective functions of both VFM and FEMU methods is also discussed in the framework of optimisation.publishe

Material parameters identification: Gradient-based, genetic and hybrid optimization algorithms

This paper presents two procedures for the identification of material parameters, a genetic algorithm and a gradient-based algorithm. These algorithms enable both the yield criterion and the work hardening parameters to be identified. A hybrid algorithm is also used, which is a combination of the former two, in such a way that the result of the genetic algorithm is considered as the initial values for the gradient-based algorithm. The objective of this approach is to improve the performance of the gradient-based algorithm, which is strongly dependent on the initial set of results. The constitutive model used to compare the three different optimization schemes uses the Barlat'91 yield criterion, an isotropic Voce type law and a kinematic Lemaitre and Chaboche law, which is suitable for the case of aluminium alloys. In order to analyse the effectiveness of this optimization procedure, numerical and experimental results for an EN AW-5754 aluminium alloy are compared.http://www.sciencedirect.com/science/article/B6TWM-4SJGWMW-1/1/01e8be60ce61e8fc30473d85439fbe3

Prediction of the bending behavior after pre-strain of an aluminum alloy

The present work is focused on the modeling of sheet metal mechanical behavior up to rupture, including anisotropy and hardening. The mechanical behavior of an AA6016 alloy was characterized at room temperature in tension, simple shear and hydraulic bulging. The initial anisotropy was described with the Yld2004-18p yield criterion coupled to a mixed hardening law. Concerning rupture, an uncoupled phenomenological criterion of Mohr-Coulomb type will be used. For the material parameter identification, an inverse methodology was used with the objective of reducing the gap between experimental and numerical data. Finally, validation of the results was performed on bending tests with different amplitudes of tension pre-strain in order to reach or not rupture in the bent area

The mechanisms by which lipids coordinately regulate the formation of the protein and lipid domains of the stratum corneum: Role of fatty acids, oxysterols, cholesterol sulfate and ceramides as signaling molecules

The formation of a permeability barrier between the external environment and the host is essential for survival. To provide this barrier keratinocytes undergo a complex pathway of differentiation, which culminates in keratinocyte cornification and the formation of extracellular lipid enriched lamellar membranes in the stratum corneum. The mechanisms that coordinately regulate the parallel formation of the corneocytes and lamellar membranes are unknown. The extracellular lamellar membranes are derived from the exocytosis of lamellar bodies and to synthesize lamellar bodies the keratinocyte must have abundant quantities of cholesterol, fatty acids and ceramides. These lipids could serve as signaling molecules and thereby coordinately regulate the formation of the stratum corneum. Fatty acids activate PPARs and studies have shown that PPAR activation stimulates keratinocyte differentiation. Cholesterol is converted to oxysterols that activate LXR and studies have shown that LXR activation also stimulates keratinocyte differentation. Additionally, PPAR and LXR activation also facilitates the formation of the lipid enriched lamellar membranes. Ceramides, via a number of mechanisms also stimulate keratinocyte differentiation. Recently, studies have shown that ceramides by increasing PPAR delta also increase the expression of ABCA12, which would facilitate the formation of lamellar bodies. Finally, keratinocytes accumulate a large quantity of cholesterol sulfate, which plays a key role in regulating desquamation. Cholesterol sulfate has also been shown to stimulate keratinocyte differentiation. Thus, cholesterol, cholesterol sulfate, fatty acids and ceramides all stimulate keratinocyte differentiation and thereby could coordinately regulate the formation of the stratum corneum

The acceleration and storage of radioactive ions for a neutrino factory

The term beta-beam has been coined for the production of a pure beam of electron neutrinos or their antiparticles through the decay of radioactive ions circulating in a storage ring. This concept requires radioactive ions to be accelerated to a Lorentz gamma of 150 for 6He and 60 for 18Ne. The neutrino source itself consists of a storage ring for this energy range, with long straight sections in line with the experiment(s). Such a decay ring does not exist at CERN today, nor does a high-intensity proton source for the production of the radioactive ions. Nevertheless, the existing CERN accelerator infrastructure could be used as this would still represent an important saving for a beta-beam facility. This paper outlines the first study, while some of the more speculative ideas will need further investigations.Comment: Accepted for publication in proceedings of Nufact02, London, 200

Contribution of Large Pig for Renal Ischemia-Reperfusion and Transplantation Studies: The Preclinical Model

Animal experimentation is necessary to characterize human diseases and design adequate therapeutic interventions. In renal transplantation research, the limited number of in vitro models involves a crucial role for in vivo models and particularly for the porcine model. Pig and human kidneys are anatomically similar (characterized by multilobular structure in contrast to rodent and dog kidneys unilobular). The human proximity of porcine physiology and immune systems provides a basic knowledge of graft recovery and inflammatory physiopathology through in vivo studies. In addition, pig large body size allows surgical procedures similar to humans, repeated collections of peripheral blood or renal biopsies making pigs ideal for medical training and for the assessment of preclinical technologies. However, its size is also its main drawback implying expensive housing. Nevertheless, pig models are relevant alternatives to primate models, offering promising perspectives with developments of transgenic modulation and marginal donor models facilitating data extrapolation to human conditions