Predicting the particle-induced background for future x-ray astronomy missions: the importance of experimental validation for GEANT4 simulations

Particle-induced background, or “instrument background”, produced from the interaction of background photons and charged particles with a detector, either as primaries or through the generation of secondary photons or particles, is one of the major sources of background for the focal plane sensors in X-ray astronomy missions. In previous studies for the European Space Agency (ESA) X-ray Multi Mirror (XMM-Newton) mission, the dominant source of background was found to be caused by the knock-on electrons generated as high-energy protons pass through the shielding materials surrounding the detector. From XMM-Newton, the contribution of Compton and other photon-generated background was small in comparison to the knock-on electron component. However, for the Wide Field Imager (WFI) on board the ESA Advanced Telescope for High-ENergy Astrophysics (ATHENA) mission Athena, which houses much thicker silicon in the depleted p-channel field effect transistor (DEPFET) active pixel sensors of the focal plane when compared to the Charge Coupled Devices (CCDs) used in the XMM-Newton EPIC MOS cameras, this photon component may no longer be expected to have such a minimal impact and therefore both the photon and proton-induced components must be considered in more detail. In order to minimise the background, studies have been conducted on the use of a graded-Z shield in addition to an aluminium proton shield (employed for radiation damage minimization). For thin detectors, a low-Z component alone may suffice, reducing the fluorescence components of the background. However, with thicker detectors a high-Z component may give added benefit through the combination of the high-Z component to reduce the photon-induced effects and a low-Z component to reduce the fluorescence components from the shielding’s inner-surfaces, thus creating an “aluminium sandwich”. In all cases, careful optimization of the shielding configuration is required to balance each component of background specific to the design of the instrument involved. The optimization of any shielding relies heavily upon a validated and verified simulation toolkit. Here we present the latest progress on our ongoing validation and verification studies of the GEANT4 simulations used for such an optimization process through a series of experimental test campaigns

What in the World are Possible Worlds?

Ted Sider writes that "many are impressed with the utility of possible worlds in linguistics and philosophy", and this is true, in particular, of those with an interest in modal logic. However, in the midst of the marvelous milieu brought on by the development of possible world semantics, some have stopped to ask just what it is that possible worlds are. They certainly seem useful, and we seem to understand how to use them and talk about them, but what precisely is it that we're talking about when we talk of possible worlds? In this thesis, I will attempt to outline the most significant and well-recognized view in this debate: that of David Lewis. Through my discussion of him, I will find occasion to discuss some alternative views that have arisen. After finishing my presentation of Lewis, I will discuss where people have begun to take this debate and address the question of whether progress can be made towards a substantive answer. In Chapter I, I begin by presenting the motivation of the question of possible worlds found in the study of modal logic. I then present the major approaches taken to answering the questions that were raised, leading into my discussion of David Lewis's famous and robust account. I present key features of Lewis's view and then move into his criticisms of the other major responses. This much should suffice as a relatively thorough treatment of the answers that have come before. In Chapter II, I discuss the current state of the debate. I begin by mentioning several problems that can be spotted in Lewis's views in particular. I then move to Menzel's account, which tries to answer the question of possible worlds from a new angle, jettisoning the direction taken by Lewis and his contemporaries. I explain why Menzel has taken this new approach, and then move into another new approach, this time given by Stephen Yablo. I discuss how these two approaches can help serve each other in helpful ways. But, at last, I present several hurdles these two views would have to overcome in order to play together nicely

La stratification temporelle dans l’image scientifique

Notre article développe une analyse des méthodes et stratégies de représentation visuelle de la stratification de couches temporelles dans deux disciplines qui visent la datation de phénomènes et d’objets : l’astrophysique et l’archéologie. Cette analyse vise à un inventaire des différents statuts des images mis en jeu par ces deux disciplines dans le but commun de représenter la stratification temporelle. Il s’agit en effet de montrer comment ce même objectif peut impliquer des techniques et des résultats iconographiques très différents dans les deux cas et de voir comment ces différentes solutions peuvent être comparables. Plus spécifiquement, l’analyse sémiotique porte sur la comparaison entre les images produites en astrophysique par l’analyse spectrale (du domaine radio au domaine gamma) et les images produites dans le domaine de l’archéologie, à savoir les images des stratifications des sols et des installations enfouies obtenues à travers des méthodes non invasives, telles la prospection aérienne et les prospections géophysiques. On part de l’hypothèse que les méthodes de fabrication d’images de ces disciplines sont comparables parce que toutes deux relèvent de visualisations qui reconstruisent les données en laboratoire (imagerie), mais on étudie aussi les différents niveaux d’« allographisation » (Nelson Goodman) de ces données requis par les deux disciplines (très élevé dans le cas de l’astrophysique, moins élevé dans le cas de l’archéologie) en faisant l’hypothèse que ces niveaux d’allographisation sont liés et justifiés par des sous-objectifs concernant la représentation de la succession temporelle. En effet, les images en archéologie ont pour but de mettre en évidence les différentes couches temporelles du passé cachées à notre perception directe, tandis que les images en astrophysique visent à construire une mosaïque temporelle du passé, du présent et du futur des astres. La visée principale de l’analyse des corpus consiste enfin à comprendre comment les images incarnent les différents sous-objectifs des deux disciplines : compacter ce qui est diffusé dans l’univers dans un cas, exfolier ce qui est stratifié dans le sous-sol dans l’autre.My article develops an analysis of methods and strategies of visual representation of temporal layers in two disciplines, which aim at the dating of phenomena and objects: astrophysics and archaeology. This analysis aims to establish an inventory of the different status of images brought into play by these two disciplines, in the common objective of representing temporal stratification. It involves showing how this same objective can involve very different techniques and iconographic results in the two cases, and to see how these different solutions can be comparable. More specifically, semiotic analysis is about the comparison between images produced in astrophysics by spectral analysis (from the domain of radio to the domain of gamma), and the images produced in the domain of archaeology, that is to say the images of soil stratifications and buried installations obtained by non-invasive methods such as aerial prospecting and geophysical prospecting. We begin with the hypothesis that the methods of image fabrication of these two disciplines are comparable, because both come from visualisations which reconstruct data in the laboratory (imaging), but the different levels of “allographing” (Nelson Goodman) of this data required by the two disciplines (very high in the case of astrophysics, less so in the case of archaeology), are studied by hypothesising that these levels of allographing are linked, and justified by sub-objectives concerning the representation of temporal succession: indeed, the images in archaeology aim to show the different temporal layers of the past that are hidden from our direct perception, while the images in astrophysics aim to construct a temporal cartography of the past, present and future of stars. The principal aim of the analysis of corpora involves finally understanding how images are the incarnation of the different sub-objectives of the two disciplines: compacting what is in the universe in one case, exfoliating what is stratified underground in the other

Light stop cornered

Electro-weak scale supersymmetry (SUSY) is the most promising extension of the Standard Model, allowing the solution of the naturalness problem and offering a dark matter candidate. Within this scenario the search for the top quark supersymmetric partner, the stop, plays a key role. Despite the fact that ATLAS analyses have excluded large portions of the stop phase space, there are uncovered corners at low mass that may hide a light stop. Several ATLAS searches are actually addressing these regions. These new results, obtained using the complete 2012 statistics from the Large Hadron Collider (LHC) operating at √s = 8TeV, will be presented

Les images anachroniques de l'histoire de l'univers

peer reviewedCet article étudie les techniques de détection utilisées par l’astrophysique permettant la formulation d’hypothèses sur la vie et les parcours des astres (extinction, explosion, etc.). Le corpus se constitue d’images tirées du dernier livre du célèbre astrophysicien Jean-Pierre Luminet "Le destin de l’Univers. Trous noirs et énergie sombre". Cet ouvrage de vulgarisation savante montre que ce sont les rapports entre images prises selon différentes longueurs d’onde (radio, infrarouge, spectre visible, ultraviolet, rayons X, gamma) et à différents moments qui permettent de visualiser des données, de les manipuler, de dater les phénomènes, de confirmer des hypothèses et de relancer l’investigation. Ce travail montre que les images en astrophysique sont des mosaïques construites à partir de mesures effectuées à travers une longue série de réglages des paramètres (température, composition chimique, vitesse de rotation, etc.) dont les couleurs surtout rendent compte. On y distingue les différentes fonctions des images à partir des processus qu’elles entendent détecter, mesurer, visualiser, imaginer à partir de la « densité » des agencements entre elles. On s’y enquête aussi sur des images à statut « artistique » qui sont contenue dans l’ouvrage de Luminet et on fait des hypothèses sur le rôle qu’elles jouent dans l’état d’acquisitions théoriques et de recherches en cours sur les trous noirs et d’autres phénomènes encore méconnus par la discipline

Photography as a Witness of Theatre

My paper investigates the meeting of theatre and photography in ‘theatre photography’. Recognizing that both art forms can determine theoretical and philosophical views on representation and self-representation, I aim to compare their visual strategies and the way they construct point of view. In the process several questions are raised: do qualities of photographs belong to objects photographed or to photographs themselves? How important is the object that ‘triggers’ the view? Should the theatre photographer place his camera anywhere? What of framing?In the second section I offer an analysis of photographs taken by Roger Pic in 1957 during the Paris performance of Brecht’s Mother Courage and Her Children by the Berliner Ensemble. This analysis seeks to demonstrate that theatre photography, which often seen as an example of documentary photography, can reach artistic status, provided it relies on enunciative strategies that express what cannot otherwise be photographed in a ‘direct’ manner, namely the characters’ words and emotions.Cet article se penche sur la photographie de théâtre. Partant de l’axiome selon lequel théâtre et photographie peuvent générer des questionnements théoriques et philosophiques concernant la représentation et l’auto-représentation, mon étude vise à comparer les stratégies visuelles et la construction du point de vue dans ces deux arts. Plusieurs autres questions sont également soulevées : les qualités d’une photo appartiennent-elles à l’objet saisi par la lentille ou à l’oeil du photographe ? Quelle importance accorder à l’objet qui ‘provoque’ la vision ? Le photographe de théâtre peut-il placer son appareil où il le désire ? Quelle est la fonction de l’énonciation photographique par rapport à l’énonciation théâtrale ?En second lieu, mon étude offre une analyse de certaines photos de Mère Courage et ses enfants prises par Roger Pic au cours de la performance parisienne du Berliner Ensemble en 1957. L’analyse vise à démontrer que la photographie de théâtre, habituellement conçue sous l’angle du documentaire, peut acquérir un statut artistique, à condition de s’appuyer sur des stratégies énonciatives capables de signifier ce qui ne peut être photographié de manière directe : les mots et les émotions des personnages

Soft Skill Development through the Agricultural Ambassador State Conference

Planning for the 2019 Agricultural Ambassador State Conference began in late spring of 2018. Throughout the duration of the planning of the conference, the author will study the soft skill development of the committee members hosting. In the past, this project has served its purpose by measuring the soft skill development of the students who attended the conference. However, in 2019 the project will evaluate the soft skill development of the committee members because they will be developing and implementing soft skills to help plan a successful conference. Through this project the author is looking to evaluate students’ soft skill development through leadership positions

Transcriptomic effects of the non-steroidal anti-inflammatory drug Ibuprofen in the marine bivalve Mytilus galloprovincialis Lam

The transcriptomic effects of Ibuprofen (IBU) in the digestive gland tissue of Mytilus galloprovincialis Lam. specimens exposed at low environmental concentrations (250 ng L-1) are presented. Using a 1.7 K feature cDNA microarray along with linear models and empirical Bayes statistical methods 225 differentially expressed genes were identified in mussels treated with IBU across a 15-day period. Transcriptional dynamics were typical of an adaptive response with a peak of gene expression change at day 7 (177 features, representing about 11% of sequences available for analysis) and an almost full recovery at the end of the exposure period. Functional genomics by means of Gene Ontology term analysis unraveled typical mussel stress responses i.e. aminoglycan (chitin) metabolic processes but also more specific effects such as the regulation of NF-kappa B transcription factor activity. (C) 2016 Elsevier Ltd. All rights reserved