Search

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged)., Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editing

La prise de conscience collective de la nature systemique du changement climatique est recente. Elle a notamment emerge dans le contexte de reunions internationales placees sous l’egide de l’Organisation des Nations Unies (ONU) et des rapports du Groupe intergouvernemental d’experts sur le climat (GIEC), qui ont reconnu la responsabilite de l’homme dans ce changement. Elle a ete beaucoup plus tardive dans le domaine economique et financier ou, en depit d’une acceleration de la mobilisation des autorites et des acteurs depuis 2015, les institutions financieres peinent a prendre en compte cette nature systemique du changement climatique et a l’integrer dans leur cadre de gestion des risques financiers et extra-financiers. Une modification de la regulation financiere est egalement necessaire pour accelerer cette prise en compte.

Les stress tests constituent, depuis la crise financiere de 2008, l'un des outils privilegies des superviseurs pour evaluer les risques et les vulnerabilites auxquels sont exposees les institutions financieres. Leur usage reste toutefois encore limite pour evaluer les risques financiers associes au changement climatique. En s'appuyant sur l'exemple de l'exercice pilote mis en œuvre en 2020 par l'Autorite de controle prudentiel et de resolution, cet article presente les caracteristiques essentielles de ces stress tests climatiques, les scenarios sur lesquels ils reposent avant d'aborder les difficultes auxquelles les superviseurs et les institutions financieres qui les mettent en œuvre sont confrontes ainsi que certaines de leurs limites.Classification JEL : G21, G28, H23, Q48, Q54.

Les neobanques rassemblent un ensemble heteroclite de nouveaux intermediaires financiers, offrant des services bancaires en ligne ou via des applications mobiles. Leurs caracteristiques ont evolue depuis leur apparition dans les annees 2000 ainsi que la nature de leurs relations avec les banques traditionnelles. Toutefois, leurs objectifs de rentabilite n’ont jusqu’a present guere ete atteints, en partie en raison de la difficulte et du cout d’acquisition de nouveaux clients. La nouvelle generation de neobanques, 100 % digitale et principalement accessible par des applications mobiles, est-elle de nature a bouleverser le paysage bancaire ? Classification JEL : G18, G21, G28.

In order to reduce the consumption of energy and the emissions of greenhouse gases and CO2 generated by the construction industry, bio-based concretes made of plant aggregates are increasingly used in the optimization of building envelopes thanks to their good hydrothermal performances, their renewable origin, and biodegradability. These insulation materials are considered as a promising alternative to synthetic systems made of mineral wool. This study investigates the use of a bio-based concretes performed with a mixture of eco-aggregates derived from rice plant and lime as thermal insulation materials. The effect of combining different proportions of rice straw (RS) with rice husks (RH) (100%, 66%, 50%, and 33%) on both mechanical and hydrothermal properties of bio-based concretes are investigated. The characterization seeks to evaluate the thermal conductivity, moisture buffer value (MBV) and mechanical compressive properties of the rice straw/rice husk concretes. Results show that the thermal conductivity of the bio-based concretes slightly decreased with increasing rice straw content. The MBV values measured showed that rice straw confers to concretes an excellent moisture buffering capacity according to the Nordtest project classification. The compression test result also revealed that rice straw concretes have high mechanical deformability. Straw concretes do not break but continuously deform.

Stone slate used for roofing is often considered as a key element of architectural heritage, especially in the French ‘‘Massif Central’’ region, where it contributes to the Mediterranean agropastoral cultural landscape of the “Causses and Cevennes” perimeter registered on the UNESCO World Heritage List. This material is subjected in service to severe and cycled climatic conditions (freeze-thaw) that may lead from mechanical damage to failure and thus compromise its use. In this paper, a damage assessment strategy of limestone roofing tiles samples during freeze-thaw cycles, based on the monitoring of their impulse vibration response, is proposed. Variations of the modal parameters such as resonant frequencies, damping ratios and mode shapes are analyzed through a 3D finite element model of each sample. This allows quantifying the loss of dynamic stiffness due to the ongoing damage and drawing comparisons between the studied materials in relation to their microstructural and mesostructural damages. Thus presence of pre-existing diagenetic features, such as stylolites (Ds in Nicholson classification), inside limestone tilestone with unimodal micropore, or with presence of high porosity volume, constitute weaknesses of the stone that can lead to damage.

This paper proposes an analytical framework to quantify the impacts of climate policy and transition narratives on economic and financial variables necessary for financial risk assessment. Focusing on transition risks, the scenarios considered include unexpected increases in carbon prices and productivity shocks to reflect disorderly transition processes. The modelling framework relies on a suite of models, calibrated on the high-level reference scenarios of the Network for Greening the Financial System (NGFS). Relying on this approach, the ACPR has selected a number of quantitative scenarios to be submitted to a group of voluntary banks and insurance companies to conduct the first bottom-up pilot climate-related risk assessment.

Les monnaies digitales, dont la part dans les transactions reste faible, ne constituent a ce jour un danger ni pour la conduite de la politique monetaire ni pour la stabilite financiere. Toutefois, leur essor est spectaculaire. Combinant une nouvelle forme de monnaie et un nouveau systeme de paiement, elles pourraient s’averer, dans un futur proche, « disruptives » pour le systeme bancaire et les banques centrales. Face a de telles evolutions, les banques centrales pourraient etre conduites a emettre elles-memes de la monnaie digitale selon differentes modalites, que nous presenterons dans cet article. La plupart d’entre elles ont pour corollaire la disparition du systeme des reserves fractionnaires et, eventuellement, celle du cash et des depots bancaires, avec des consequences importantes pour le mecanisme de creation monetaire.

International audience; Lime and hemp concretes are used as infill materials manually tamped in timber stud walls or more recently in the form of precast blocks. In either case, the structural design practice of wood frame construction associated with hemp concrete does not assume any contribution of the plant-based concrete whereas it may contribute towards the racking strength of the wall. This work is intended to evaluate the shear behaviour of two different bio-based concretes by means of triaxial compression. Hemp shives and whole rice husks were mixed with a lime-based binder according to the same mix proportioning and mixes were vibro-compacted in cylindrical forms. Then, samples were cured at 23 degrees C - 65%RH before being tested under unconfined and triaxial compression. The triaxial shear test was performed after 60 days of curing on unsaturated specimens under drained conditions at air pressure and for increasing effective confining pressure (from 25 to 150 kPa). It was possible to estimate the shear strength parameters (peak friction angle and cohesion) of the two plant-based concretes. Comparing results, it appears a consistent value of cohesion but a different friction angle related to the binder and the aggregate contributions respectively. This leads to a first analysis of the relationship between the composition of the concrete (plant aggregates cemented with a binder) and its shear strength. Furthermore, the ductility of plant-based concretes is markedly enhanced as the mean effective pressure increases. Finally, the shear strength of plant-based concretes should be considered as part of the design practice of building envelopes.

In this paper, I analyse house price developments in a set of 18 OECD countries. I find some evidence that global financial conditions have played an important role in shaping house price developments in these countries, especially in the run-up to the financial crisis. The current very accommodative monetary policy environment may already have triggered a new build-up of financial imbalances in some countries. However, while the synchronicity in housing cycles has increased across countries, the amplitude of these cycles continues to be influenced by domestic factors and local structural features, leaving national macroprudential authorities with some leeway to address these imbalances.

Alors que la notion de politique macroprudentielle fait l’objet de nombreux travaux, la question de sa coordination au niveau global reste tres peu debattue. Elle est pourtant essentielle pour en assurer l’efficacite, garantir des conditions saines de concurrence entre institutions ou juridictions, et eviter le risque de redondance ou de conflits d’objectifs entre differents niveaux de decision : national, regional et mondial. Dans cet article, on presente dans un premier temps les principales justifications pour penser la politique macroprudentielle dans un cadre global avant d’en preciser, dans un second temps, les modalites.Classification JEL : F38, F42, G28.

International audience; The purpose of this paper is to investigate the mechanical properties and the lime-based binder hardening of green concretes made of rice husk or hemp hurd. Concrete specimens were subjected to different curing conditions. Under natural carbonation, specimens were cured during 10 months either in a climate-controlled room (20 degrees C - 50%RH) or exposed outdoors. The work also focused on an accelerated carbonation curing (CO2 curing) aiming to improve the short term compressive strength (1-2 months) of the concrete materials. Compressive strength tests were conducted at different dates until 10 months of natural carbonation and after CO2 curing. Powdered matrix samples were collected in the bulk and on the surface of the specimens to investigate carbonation and hydration of the binder by thermal analysis and a phenolphthalein test was used to provide information about the carbonation depth. Under natural carbonation, the results indicated that the lime-based binder was almost hardened in the same way for both concretes with a similar rate of carbonation. However, the rice husk concrete was characterized by a ceiling effect of mechanical performances overtime, which was attributed to the lower bonding strength between rice husks and lime. Concerning specimens exposed outdoors, the strength gain over time was more significant owing to more favorable humidity conditions for carbonation. The accelerated carbonation curing led to an increase of mechanical properties of the concretes in the short term. The compressive strength after CO2 curing was approximately equivalent to those obtained after 10 months of outdoor exposure under natural carbonation.

The results reported in this document first contribute to the development of an innovative plant-based concrete using raw rice husk. This crop residue is available throughout the year at low cost and its use to manufacture bio-based concretes for green building provides a new recovery sector for a local by-product coming from rice farming in France.

Unlike Portland cement, the use of lime goes back much further in time. During the Greco-Roman period, walls were built of lime-based mortars blended with fine sand and pozzolanic additives (volcanic ash).

Many by-products of plant origin have been incorporated in mineral binders. However, it is important to distinguish plant fibers used as reinforcement in cement composite materials from plant-derived aggregates used for the manufacturing of lightweight insulating concretes (bio-based concretes).

Hemp concrete is obtained from the mix of hemp shiv, water and a mineral binder (which can be itself a mixture of different binders).

Mise en cause des le declenchement de la crise financiere en 2007, en raison de sa dimension procyclique, la « juste valeur » reste, sept ans plus tard, le mode unique de valorisation comptable du portefeuille de negociation (trading) des banques. Cette situation souleve une question importante pour le regulateur dans la perspective de la prevention du risque systemique. Elle part de l’observation que l’evaluation comptable des portefeuilles de trading au « prix de marche » est en fait tres marginale par rapport a l’evaluation au « prix de modele ». Dans cet article, nous mesurons tout d’abord la repartition de la valorisation des portefeuilles de trading, entre le mark to market et le mark to model. Nous calculons ensuite une mesure du return on equity (ROE) des activites de trading, en rapportant le resultat brut au montant des fonds propres reglementaires assis sur la value at risk (VaR), et constatons que ce ROE est non seulement anormalement eleve mais egalement qu’il est reste stable depuis le declenchement de la crise. En outre, nous etablissons que la rentabilite des activites de trading des banques est positivement et significativement correlee au poids du mark to model dans le total du portefeuille, et en particulier au poids des actifs de « niveau 3 ». Classification JEL : G15, G21, G28, M48.

We investigate the extent to which it is possible to detect asset-price booms and banking crises according to alternative identification strategies and we assess their robustness. We find some evidence that house price-booms are more likely to turn into costly recession or to trigger a banking crisis than stock-price booms. Resorting both to a non-parametric approach and a discrete-choice (logit) model, we analyze the ability of a wide set of indicators to robustly explain costly asset-price booms. According to our results, real long-term interest rates and real stock prices tend to increase the probability of a costly housing-price boom, whereas real GDP tends to increase the probability of a costly stock-price boom. Interestingly, the credit-to-GDP gap indicator, sometimes put forward in the literature as a key reference for setting countercyclical capital buffers, does not seem to be a robust leading indicator of costly booms or banking crises.

The incorporation of an elastomer phase into a poly(ether ether ketone) (PEEK) matrix was carried out using two different processing methods (melt blending (MB) and dry blending) to improve the damping factor (tan δ) of the composite with a minimal change in the PEEK stiffness. A cross-linked fluoroelastomer (CFE) was carefully chosen according to its high glass transition temperature ( Tα), high thermal stability and high modulus. The blends were characterized by scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), modified Oberst test, flexural test and pyrolysis combustion flow calorimeter. According to SEM micrographs, an original well-dispersed PEEK-elastomer composite was obtained. The tan δ of the materials was evaluated using DMTA and modified Oberst test. Both techniques indicate that the incorporation of 5–20 wt% of CFE fine powders only slightly increased the tan δ of the material. Moreover, a decrease in flexural modulus and thermal stability of the blends was detected when there was an increase in the CFE content. Even if the properties are not yet significantly improved, it was well ascribed that the MB method was suitable to mix elastomer particles within a PEEK matrix. Poor interfacial adhesion has been identified as the main key parameter, which should be improved in further work.

Using a wide range of macroeconomic and econometric models we assess the long-term economic impact of the Basel III reform. Our main results are the following. (1) The economic costs of the new regulatory standards for bank capital and liquidity are considerably below existing estimates of the benefits that the reform should have by reducing the probability of banking crises (Basel Committee on Banking Supervision (2010) ‘An Assessment of the Long-term Impact of Stronger Capital and Liquidity Requirements’, Basel). (2) The reform dampens output volatility modestly, although there is some heterogeneity across models. (3) The adoption of countercyclical capital buffers can substantially amplify the dampening effect on output volatility.

La doctrine des banques centrales ainsi que leur cadre strategique ont ete soumis a rude epreuve lors de la crise financiere : leur objectif de stabilite des prix etait defini de facon trop etroite et les considerations de stabilite financiere laissees au second plan. Lorsque les taux d’interet directeurs nominaux ont heurte leur « contrainte zero », les banques centrales ont du mettre en œuvre des mesures non conventionnelles les conduisant a sortir tres largement des limites fixees par leur mandat de stabilite des prix. Paradoxalement, au sortir de la crise, le cadre strategique des banques centrales ne semble pas fondamentalement remis en cause. Leur mandat a meme ete etendu pour integrer de nouvelles missions en matiere de politique macroprudentielle et, dans certains cas, la supervision microprudentielle. Le principal defi souleve par la centralisation de toutes ces fonctions au sein des banques centrales est leur capacite a les mener en toute independance. Or l’independance est la condition premiere du succes de leurs missions traditionnelles de maintien de la stabilite des prix et de preteur en dernier ressort.Classification JEL : E41, E52, E58, E63.

At the onset of the financial crisis in 2007, ?fair value? accounting came under fire for its pro-cyclical effects. Seven years on, fair value remains the sole method of accounting valuation of banks? trading books. One concern, which is relevant to regulations aimed at preventing systemic risk, is based on the observation that accounting valuation of trading portfolios at ?market price? is in fact minimal compared to ?model price? valuation. In this paper, we assess the distribution of the valuation of trading portfolios, between ?mark-to-market? and ?mark-to-model?, at the international level. Then, we calculate a measure of return on equity (ROE) on trading activities by comparing the gross income to the amount of regulatory capital based on ?value at risk? (VaR) and find that this ROE is not only abnormally high, but has also generally remained stable since the onset of the crisis. In addition, we establish that returns on banks? trading activities are positively and significantly correlated to the share of assets subject to mark-to-model in the total portfolio, and particularly the share of ?Level 3? assets. Classification JEL: G15, G21, G28, M48.

Le financement de l’activite economique a connu de profondes transformations au cours des deux dernieres decennies. Ainsi, une part grandissante des credits au secteur prive a ete distribuee en dehors du secteur bancaire traditionnel. Dans le meme temps, les banques sortaient de leurs bilans une part importante des credits tout en modifiant leurs structures de financement. De telles evolutions ont ete considerees par de nombreux observateurs comme l’une des causes principales de la crise actuelle. Elles ont en particulier mis en evidence le role cle joue par le shadow banking dans ces evolutions. Si ce phenomene touche principalement les Etats-Unis, il s’est fortement developpe en Europe, notamment au Royaume-Uni mais aussi dans la zone euro. En depit des efforts de la Commission europeenne, les retards pris dans l’harmonisation de la reglementation et la supervision financiere en Europe posent des problemes specifiques dans le suivi et la surveillance du shadow banking.Classification JEL : G01, G21, G23, G24, G28.

article i nfo Monetary union can benefit countries suffering from policy credibility problems if it eliminates the inflation bias and also allows for more efficient management of certain shocks. But it also carries costs as some stabilization may be feasible even in the absence of credibility, and this may be more than what an individual country can hope for in a monetary union. In this paper, we combine the stabilization and credibility branches of the currency union literature and construct a simple welfare criterion that can be used to evaluate alternative monetary arrangements. We produce examples where monetary union may be welfare improving even for low-modest levels of inflation bias (2-3%) as long as business cycles are not too a-synchronized across countries.

Results concerning γ-irradiation of polymer blends such as HDPE/ground tire rubber (GTR) and PP/HDPE are reported in this article with a special emphasis on the order of processing steps. Irradiation dose varied in the range 0–100 kGy. The two first polymers (HDPE and rubber) are preferentially crosslinked under γ irradiation while PP undergoes chain scission. Mechanical tests and differential scanning calorimetry (DSC) analysis show that the efficiency of the reactive compatibilization by γ irradiation depends greatly on the chronology of γ-irradiation and injection-molding steps. Electron spin resonance (ESR) results reveal that numerous radicals remain trapped in the materials after γ-irradiation even after a long time. Then the effect of irradiation on material properties is different if polymers are melted after irradiation or not. Crosslinking and chain scission are not affected in an equivalent way by the order of processing steps. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

International audience; This paper deals with the compatibilization between recycled HDPE matrix and ground tyre rubber powder, through a free radical mechanism, by adding a peroxide. Mechanical tests show competition between the crosslinking of HDPE and the formation of interfacial bonding. The addition of more than 1 %wt of peroxide results in a strong improvement of interfacial adhesion and elongation at break. The performance is also compared to that resulting from gamma irradiation of the same blends.In the second part of this article, experimental tests and simulation by finite elements analysis were performed and showed the non-possibility of obtaining a “thermoplastic elastomer” by blending and compatibilizing HDPE and ground tyre rubber powder, since perfect interfacial adhesion still results in decohesion between matrix and particles.