Discovery of Bragg confined hybrid modes with high Q-factor in a hollow dielectric resonator

The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4 $GHz$ with an unloaded Q-factor of order $2\times10^5$, which is more than a factor of 6 above the dielectric loss limit. Previously such modes have only been realized from pure Transverse Electric modes with no azimuthal variations and only the $E_{\phi}$ component. From rigorous numeric simulations it is shown that the mode is a hybrid mode with non-zero azimuthal variations and with dominant $E_r$ and $E_{\phi}$ electric field components and $H_z$ magnetic field component.Comment: Accepted to be published in Applied Physics Letter

Greffage de molécules électroactives sur carbone pour les électrodes de supercondensateur hybride

Aujourd'hui, la planète entière est consciente de la nécessité de développer de nouvelles sources d'énergie durables et respectueuses de l'environnement. Ces sources pour la plupart intermittentes (solaire, éolien) doivent être associées à des systèmes de stockage. Parmi les dispositifs de stockage électrochimique de l'énergie, on distingue principalement les batteries et les supercondensateurs. Les batteries stockent l'énergie de façon faradique et présentent donc des énergies spécifiques élevées. Le stockage des charges dans les supercondensateurs est basé sur des processus capacitifs qui assurent de fortes puissances spécifiques et des durées de vie quasi-infinie. Les systèmes hybrides combinent une électrode de batterie avec une électrode de supercondensateur. L'électrode faradique augmente la capacité stockée pendant que l'électrode capacitive maintient des cinétiques de réaction rapides. Dans cette thèse nous avons développé des stratégies pour augmenter la densité d'énergie stockée de ces systèmes. L'approche retenue a été le greffage covalent de molécules électroactives à la surface d'un carbone poreux pour ajouter une contribution faradique à la capacité totale de l'électrode de supercondensateur. La chimie des sels de diazonium a été utilisée pour la modification des poudres de carbone. Un intérêt particulier a été porté sur le choix de la molécule. La formation d'une liaison forte entre la molécule et le substrat a été démontrée par différentes techniques de caractérisation. Finalement, l'assemblage et le cyclage de dispositifs complets ont prouvés que le greffage permet une augmentation de la densité d'énergie sans impacter sur la densité de puissance

Perceptions and relation-mediating mechanisms in human-wildlife conflicts

Human-wildlife conflict represents a recurring challenge in the history of humankind. Since the 1970s and the environmental awakening of consciousnesses, the problem took a new dimension through competitions between people with different views about nature and wildlife. Some would consider it as an utilitarian object to manage and exploit while others would adopt a more empaphetic and ecological attitude, thus causing disagreements. This study takes a perception-based approach to unravel the conflict surrounding the reintroduction of the brown bear (Ursus arctos) in the French Pyrenees, in order to understand how individuals in this case of human-wildlife conflict perceive the animal, and to identify the key-components that contribute to the creation of those perceptions. The findings reveal that people share a connection with bears, positive or negative, which results from their initial perception and whose elaboration is continuously influenced by various relation-mediated mechanisms. The analysis of specific historical events and cultural factors related to bears shows that perceptions are prone to change and relations between humans and bears are never simple. In addition, it demonstrates that as an animal, the bear has always left a significant impression on human communities, either as a magnificent entity worthy of respect or a powerful creature deemed too dangerous to be allowed near their habitations and activities

Using emerging technology to draw learning across the curriculum

To drive the wider adoption of STEM in schools, researchers have promoted the benefits of teaching STEM subjects integrated across the curriculum. This integration can support more authentic learning opportunities where learning is framed in real-world application or driven through problem/project based learning. The integration of digital technologies (DT), where the learning moves away from consumption to creation, provides for further application of learning where the development of artefacts can be situated within other subjects. This integration, however, raises new challenges for effective teaching and learning, and while new technologies and approaches can support this practice, this is still evolving. In this study we explore how one high school in New Zealand has integrated the creation of digital artefacts situated, in the digital technologies (DT) class, with learning in the Māori Performing Arts class. The study explores how mixed reality (MR), combined with design thinking approaches, provide new opportunities to integrate learning and support engagement in STEM. Drawing on a participatory action research methodology, this article explores the experiences and perceptions of three teachers as they adopt MR to engage and teach students drawing on critical DT skills

Angers – Îlot Quatrebarbes-Pignerolles

La construction d’immeubles au pied du coteau de l’Esvière, en bordure de la Maine, a permis quelques constatations sur ce quartier en dehors des trois enceintes urbaines, malgré l’arasement des niveaux anciens par les constructions modernes. L’époque gallo-romaine est représentée par des constructions légères (trous de poteaux, briques crues), un sol de galets damés et quelques fosses-dépotoirs. Les niveaux gallo-romains reposent sur une couche épaisse de sable qui a été déposée sur le subst..

The VIPERS Multi-Lambda Survey. II. Diving with massive galaxies in 22 square degrees since z = 1.5

We investigate the evolution of the galaxy stellar mass function (SMF) and stellar mass density from redshift z=0.2 to z=1.5 of a $K_{AB}$<22-selected sample with highly reliable photometric redshifts and over an unprecedentedly large area. Our study is based on NIR observations carried out with WIRCam at CFHT over the footprint of the VIPERS spectroscopic survey and benefits from the high quality optical photometry from the CFHTLS and UV observations with the GALEX satellite. The accuracy of our photometric redshifts is $\sigma_z$ < 0.03 and 0.05 for the bright ($i_{AB}$22.5) samples, respectively. The SMF is measured with ~760,000 galaxies down to $K_s$=22 and over an effective area of ~22.4 deg$^2$, the latter of which drastically reduces the statistical uncertainties (i.e. Poissonian error & cosmic variance). We point out the importance of a careful control of the photometric calibration, whose impact becomes quickly dominant when statistical uncertainties are reduced, which will be a major issue for future generation of cosmological surveys with, e.g. EUCLID or LSST. By exploring the rest-frame (NUV-r) vs (r-$K_s$) color-color diagram separating star-forming and quiescent galaxies, (1) we find that the density of very massive log($M_*/ M_{\odot}$) > 11.5 galaxies is largely dominated by quiescent galaxies and increases by a factor 2 from z~1 to z~0.2, which allows for additional mass assembly via dry mergers, (2) we confirm a scenario where star formation activity is impeded above a stellar mass log($M^*_{SF} / M_{\odot}$) = 10.64$\pm$0.01, a value that is found to be very stable at 0.2 < z < 1.5, (3) we discuss the existence of a main quenching channel that is followed by massive star-forming galaxies, and finally (4) we characterise another quenching mechanism required to explain the clear excess of low-mass quiescent galaxies observed at low redshift.Comment: 22 pages, 20 figures. Accepted for publication in A&A. Version to be publishe

POV: Obama's ban on juvenile solitary confinement

Point of view article in BU Toda

Controlling spatial distributions of molecules in multicomponent organic crystals, with quantitative mapping by confocal Raman microspectrometry

We report four experimental strategies for controlling the three-dimensional arrangement of molecules in multicomponent organic crystals, exploiting confocal Raman microspectrometry to quantify the three-dimensional spatial distributions. Specifically, we focus on controlling the distribution of two types of guest molecule in solid organic inclusion compounds to produce composite core–shell crystals, crystals with a homogeneous distribution of the components, crystals with continuous compositional variation from the core to the surface, and crystals with alternating shells of the components. In this context, confocal Raman microspectrometry is particularly advantageous over optical microscopy as it is nondestructive, offers micrometric spatial resolution, and relies only on the component molecules having different vibrational properties