Joint signal extraction from galaxy clusters in X-ray and SZ surveys: A matched-filter approach

The hot ionized gas of the intra-cluster medium emits thermal radiation in the X-ray band and also distorts the cosmic microwave radiation through the Sunyaev-Zel'dovich (SZ) effect. Combining these two complementary sources of information through innovative techniques can therefore potentially improve the cluster detection rate when compared to using only one of the probes. Our aim is to build such a joint X-ray-SZ analysis tool, which will allow us to detect fainter or more distant clusters while maintaining high catalogue purity. We present a method based on matched multifrequency filters (MMF) for extracting cluster catalogues from SZ and X-ray surveys. We first designed an X-ray matched-filter method, analogous to the classical MMF developed for SZ observations. Then, we built our joint X-ray-SZ algorithm by combining our X-ray matched filter with the classical SZ-MMF, for which we used the physical relation between SZ and X-ray observations. We show that the proposed X-ray matched filter provides correct photometry results, and that the joint matched filter also provides correct photometry when the $F_{\rm X}/Y_{500}$ relation of the clusters is known. Moreover, the proposed joint algorithm provides a better signal-to-noise ratio than single-map extractions, which improves the detection rate even if we do not exactly know the $F_{\rm X}/Y_{500}$ relation. The proposed methods were tested using data from the ROSAT all-sky survey and from the Planck survey.Comment: 22 pages (before appendices), 19 figures, 3 tables, 5 appendices. Accepted for publication in A&

The differential view of genotype–phenotype relationships

International audienceAn integrative view of diversity and singularity in the living world requires a better understanding of the intricate link between genotypes and phenotypes. Here we re-emphasize the old standpoint that the genotype–phenotype (GP) relationship is best viewed as a connection between two differences, one at the genetic level and one at the phenotypic level. As of today, predominant thinking in biology research is that multiple genes interact with multiple environmental variables (such as abiotic factors, culture, or symbionts) to produce the phenotype. Often, the problem of linking genotypes and phenotypes is framed in terms of genotype and phenotype maps, and such graphical representations implicitly bring us away from the differential view of GP relationships. Here we show that the differential view of GP relationships is a useful explanatory framework in the context of pervasive pleiotropy, epistasis, and environmental effects. In such cases, it is relevant to view GP relationships as differences embedded into differences. Thinking in terms of differences clarifies the comparison between environmental and genetic effects on phenotypes and helps to further understand the connection between genotypes and phenotypes

Handles: Behavior-Propagating First Class References For Dynamically-Typed Languages

Preprint, Accepted with minor revisionsInternational audienceControlling object graphs and giving specific semantics to references (such as read-only, own- ership, scoped sharing) has been the focus of a large body of research in the context of static type systems. Controlling references to single objects and to graphs of objects is essential to be able to build more secure systems, but is notoriously hard to achieve in absence of static type systems. In this article we embrace this challenge by proposing a solution to the following question: What is the underlying mechanism that can support the definition of properties (such as revocable, read-only, lent) at the reference level in the absence of a static type system? We present handles: first class references that propagate behavioral change dynamically to the object subgraph during program execution. In this article we describe handles and show how handles support the implementation of read-only references and revocable references. Handles have been fully implemented by modifying an existing virtual machine and we report their costs

Study of geopolymerization mechanisms by 27Al-NMR and calorimetry correlation

Geopolymers are alumino-silicate binders prepared by reacting a powdered alumino-silicate source (metakaolin) with an alkali silicate “activating” solution. The geopolymerization reaction is a complex process but it is consensual that geopolymers are formed by dissolution of the metakaolin and condensation reactions between silicates and aluminates initially in solution or as dissolution products. However, those two processes occur concomitantly during the geopolymerization. It makes it difficult to study geopolymerization mechanisms in detail for kinetics or thermodynamics purposes. This could explain why detailed mechanistic descriptions are scarce in the literature and why this topic is still a matter of debate. In this study, an experimental method highlighting the different mechanisms involved in the geopolymerization is proposed, allowing the determination of a thermodynamic parameter of the system. The different processes constituting the geopolymerization were dissociated by varying the metakaolin content in geopolymers, for a given activating solution. Reactivity of such mixes was investigated by isothermal conduction microcalorimetry (ICC). Time resolved 27Al static Nuclear Magnetic Resonance (NMR) was used to monitor the concentration of aluminate centers in solution during the reaction. The correlation as function of time of the total heat release measured by ICC with the aluminate centers concentration in solution exhibited the existence of a master curve allowing the determination of a reaction enthalpy. The influence of alkali cations, silicate species and aluminate ions on this reaction enthalpy was then investigated. For the first time, the dependence of the geopolymer thermodynamics over the initial composition of the system was highlighted

Epidemic models in measure spaces: persistence, concentration and oscillations

We investigate the long-time dynamics of a SIR epidemic model in the case of a population of pathogens infecting a single host population. The pathogen population is structured by a phenotypic variable. When the initial mass of the maximal fitness set is positive, we give a precise description of the convergence of the orbit, including a formula for the asymptotic distribution. We also investigate precisely the case of a finite number of regular global maxima and show that the initial distribution may have an influence on the support of the eventual distribution. In particular, the natural process of competition is not always selecting a unique species, but several species may coexist as long as they maximize the fitness function. In many cases it is possible to compute the eventual distribution of the surviving competitors. In some configurations, species that maximize the fitness may still get extinct depending on the shape of the initial distribution and some other parameter of the model, and we provide a way to characterize when this unexpected extinction happens. Finally, we provide an example of a pathological situation in which the distribution never reaches a stationary distribution but oscillates forever around the set of fitness maxima

Magnetic manipulation with several mobile coils towards gastrointestinal capsular endoscopy.

Traditional techniques of endoscopy based on flexible endoscopes are fairly reliable but poorly tolerated by patients and do not give access to the small bowel. It has been demonstrated that magnetic fields are usable for manipulating an untethered magnet, either using fixed coils or mobile permanent magnets.We introduce a novel approach for magnetic manipulation and present the preliminary results obtained by simulating a planar manipulation system including multiple mobile coils

New insights into the role of hydroxide ions and silicate species during geopolymerization

The specific role of hydroxide ions in highly alkaline silicate solutions has been hardly investigated due to the difficulty to quantify them. In this study, Hammet acidity functions of sodium silicate solutions have been assessed for the first time. The low acidity function values found in these solutions, when compared to pure sodium hydroxide solutions, has been explained by the buffering effect of silicate species using liquid state 29Si NMR. Such a parameter has then been used to quantify the hydroxide ions ability to react during mixing alkali silicate solutions with metakaolin. Despite lower initial acidity function values for equivalent sodium hydroxide additions when compared to silicate-free solutions, it has been demonstrated that dissolution of the studied metakaolin is much more efficient in presence of silicate species. Such a phenomenon has been attributed to the gradual release of hydroxide ions resulting from silicate species condensation during the metakaloin dissolution

Geometric analysis of the singularities of a magnetic manipulation system with several mobile coils.

International audienceIt has been demonstrated that magnetic fields are relevant for manipulating an untethered magnet, either using fixed coils or mobile permanent magnets. This paper shows however, that any magnetic manipulation method is prone to singular configurations and that the simple numerical analysis of the rank of the "manipulation matrix" is not enough to detect them. Alternatively, we propose a geometrical analysis to interpret and detect the singularities as well as to decide on the acceptability of a reference trajectory. Then, we present results obtained by simulating a planar manipulation system including a multiple mobile coils and a Helmholtz like set-up

Handles: Behavior-Propagating First Class References For Dynamically-Typed Languages

International audienceControlling object graphs and giving specific semantics to references (such as read-only, ownership, scoped sharing) have been the focus of a large body of research in the context of static type systems. Controlling references to single objects and to graphs of objects is essential to build more secure systems, but is notoriously hard to achieve in the absence of static type systems. In this article we embrace this challenge by proposing a solution to the following question: What is an underlying mechanism that can support the definition of properties (such as revocable, read-only, lent) at the reference level in the absence of a static type system? We present handles: first-class references that propagate behavioral change dynamically to the object subgraph during program execution. In this article we describe handles and show how handles support the implementation of read-only references and revocable references. Handles have been fully implemented by modifying an existing virtual machine and we report their costs

Advocacy for Multi Mobile Coil Magnetic Manipulation in Active Digestive Endoscopy.

International audienceTraditional techniques of endoscopy based on flexible endoscopes are fairly reliable but poorly tolerated by patients and do not give access to the small bowel. Magnetic fields have been shown usable for manipulating endoscopic capsules, either using static coils with varying currents or mobile permanent magnets. In this short paper, we propose a novel approach which combines electromagnetic and kinematic effects and outline our research