Galactic cosmic rays on extrasolar Earth-like planets: II. Atmospheric implications

(abridged abstract) Theoretical arguments indicate that close-in terrestial exoplanets may have weak magnetic fields. As described in the companion article (Paper I), a weak magnetic field results in a high flux of galactic cosmic rays to the top of the planetary atmosphere. We investigate effects that may result from a high flux of galactic cosmic rays both throughout the atmosphere and at the planetary surface. Using an air shower approach, we calculate how the atmospheric chemistry and temperature change under the influence of galactic cosmic rays for Earth-like (N_2-O_2 dominated) atmospheres. We evaluate the production and destruction rate of atmospheric biosignature molecules. We derive planetary emission and transmission spectra to study the influence of galactic cosmic rays on biosignature detectability. We then calculate the resulting surface UV flux, the surface particle flux, and the associated equivalent biological dose rates. We find that up to 20% of stratospheric ozone is destroyed by cosmic-ray protons. The reduction of the planetary ozone layer leads to an increase in the weighted surface UV flux by two orders of magnitude under stellar UV flare conditions. The resulting biological effective dose rate is, however, too low to strongly affect surface life. We also examine the surface particle flux: For a planet with a terrestrial atmosphere, a reduction of the magnetic shielding efficiency can increase the biological radiation dose rate by a factor of two. For a planet with a weaker atmosphere (with a surface pressure of 97.8 hPa), the planetary magnetic field has a much stronger influence on the biological radiation dose, changing it by up to two orders of magnitude.Comment: 14 pages, 9 figures, published in A&

Galactic cosmic rays on extrasolar Earth-like planets I. Cosmic ray flux

(abridged abstract) Theoretical arguments indicate that close-in terrestial exoplanets may have weak magnetic fields, especially in the case of planets more massive than Earth (super-Earths). Planetary magnetic fields, however, constitute one of the shielding layers that protect the planet against cosmic-ray particles. In particular, a weak magnetic field results in a high flux of Galactic cosmic rays that extends to the top of the planetary atmosphere. We wish to quantify the flux of Galactic cosmic rays to an exoplanetary atmosphere as a function of the particle energy and of the planetary magnetic moment. We numerically analyzed the propagation of Galactic cosmic-ray particles through planetary magnetospheres. We evaluated the efficiency of magnetospheric shielding as a function of the particle energy (in the range 16 MeV $\le$ E $\le$ 524 GeV) and as a function of the planetary magnetic field strength (in the range 0 ${M}_\oplus$ $\le$ {M} $\le$ 10 ${M}_\oplus$). Combined with the flux outside the planetary magnetosphere, this gives the cosmic-ray energy spectrum at the top of the planetary atmosphere as a function of the planetary magnetic moment. We find that the particle flux to the planetary atmosphere can be increased by more than three orders of magnitude in the absence of a protecting magnetic field. For a weakly magnetized planet (${M}=0.05\,{M}_{\oplus}$), only particles with energies below 512 MeV are at least partially shielded. For a planet with a magnetic moment similar to Earth, this limit increases to 32 GeV, whereas for a strongly magnetized planet ($M=10.0\,{M}_{\oplus}$), partial shielding extends up to 200 GeV. We find that magnetic shielding strongly controls the number of cosmic-ray particles reaching the planetary atmosphere. The implications of this increased particle flux are discussed in a companion article.Comment: 10 pages, 9 figures; accepted in A&

Evaluation du projet SPAS-PMU REVIAC

Le projet REVIAC: Le projet REVIAC (Réinsertion vie active) est un projet de collaboration entre le Service de prévoyance et d'aides sociales (SPAS) et la Policlinique médicale universitaire (PMU) pour améliorer les possibilités de démarches de réinsertion chez les bénéficiaires du revenu d'insertion (RI) avec certificat d'incapacité de travail. En effet, certains bénéficiaires ont des certificats médicaux d'incapacité récurrents et les assistants sociaux (AS) ne peuvent entreprendre les démarches nécessaires. Le projet développé par le SPAS et la PMU comprend deux axesa : ? La création à la PMU d'une consultation pour les bénéficiaires du RI dont l'état de santé compromet toute démarche d'insertion/d'activation. ? Le développement de l'information et de la formation : a) des médecins, principalement de premier recours, sur les thématiques sociales liées au RI et le réseau socio-sanitaire existant, et b) des assistants sociaux sur les pratiques des médecins traitants. Les objectifs du projet sont : Encourager l'élaboration de projets favorisant l'autonomie des bénéficiaires (autonomie sociale comme professionnelle et financière), compatibles avec leur état de santé, réalistes et réalisables ; Apporter un soutien médical aux bénéficiaires entrant dans une démarche d'insertion ou en cours d'insertion, en collaboration avec leurs médecins traitants ; Fournir aux AS les informations nécessaires leur permettant d'initier, au besoin, une collaboration avec l'AI dans le cadre de mesures de prévention et d'insertion ; Permettre aux AS de diriger et accompagner les bénéficiaires dont l'état de santé est incompatible avec une démarche d'insertion vers d'autres types de mesures ou d'autres prises en charge plus adéquates (rentes AI, etc.) ; Améliorer la collaboration entre les médecins traitants des bénéficiaires et les assistants sociaux en charge de leur dossier ; Proposer, à terme, le développement de nouvelles mesures adaptées aux problématiques de santé des bénéficiaires

The murine male reproductive organ at a glance: Three-dimensional insights and virtual histology using label-free light sheet microcopy

Background:The unique anatomy of the male reproductive organ reflects its complex function from sperm maturation to their storage for months until emission. Since light microscopy in two dimensions (2d) cannot sufficiently demonstrate its complex morphology, a comprehensive visualization is required to identify pathologic alterations in its entire anatomical context.Objectives:Aim of this study was to use three-dimensional (3d) light sheet fluorescence microscopy (LSFM) to visualize entire murine testes in 3d, label-free and at subcellular resolution, and to assign local autofluorescence to testicular and deferent structures.Materials and methods:Murine testes were fixed with four different fixatives and subsequently cleared with benzoic acid/benzyl benzoate. Hereafter, complete murine testes were scanned with LSFM with different fluorescence filter sets and subsequently embedded in paraffin for further conventional planar histology.Results:Autofluorescence signals of the murine reproductive organ allowed the unambiguous identification of the testicular anatomy from the seminiferous tubules to the vas deferens with their specific stratification independent of the used fixative. Blood vessels were visualized from the pampiniform plexus to the small capillaries of single tubules. Moreover, due to the specific intrinsic fluorescence properties of the efferent ducts and the epididymis, luminal caliber, the epithelial stratification and retronuclear cytoplasmic inclusions gave a unique insight into the interface of both morphological structures. Subsequent 2d histology confirmed the identified morphological structures.Discussion:LSFM analysis of the murine reproductive organ allows due to its intrinsic fluorescence a simple, label-free 3d assessment of its entire duct morphology, the epithelial composition, and the associated blood supply in its anatomical relation.Conclusion:LSFM provides the technical basis for comprehensive analyses of pathologically altered murine testes in its entirety by depicting specific autofluorescence. Thereby it facilitates mouse studies of testicular disease or their drug-related alterations in more detail potentially for clinical translation assessing human testicular biopsies.<br

Data scientists

What is a data scientist? How can you become one? How can you form a team of data scientists that fits your organization? In this chapter, we trace the skillset of a successful data scientist and define the necessary competencies. We give a disambiguation to other historically or contemporary definitions of the term, and show how a career as a data scientist might get started. Finally we will answer the above mentioned third question, i.e. how to build analytics teams within a data-driven organization

One dimensional exciton luminescence induced by extended defects in nonpolar (Al,Ga)N/GaN quantum wells

In this study, we present the optical properties of nonpolar GaN/(Al,Ga)N single quantum wells (QWs) grown on either a- or m-plane GaN templates for Al contents set below 15%. In order to reduce the density of extended defects, the templates have been processed using the epitaxial lateral overgrowth technique. As expected for polarization-free heterostructures, the larger the QW width for a given Al content, the narrower the QW emission line. In structures with an Al content set to 5 or 10%, we also observe emission from excitons bound to the intersection of I1-type basal plane stacking faults (BSFs) with the QW. Similarly to what is seen in bulk material, the temperature dependence of BSF-bound QW exciton luminescence reveals intra-BSF localization. A qualitative model evidences the large spatial extension of the wavefunction of these BSF-bound QW excitons, making them extremely sensitive to potential fluctuations located in and away from BSF. Finally, polarization-dependent measurements show a strong emission anisotropy for BSF-bound QW excitons, which is related to their one-dimensional character and that confirms that the intersection between a BSF and a GaN/(Al,Ga)N QW can be described as a quantum wire