Screening Approach for the Discovery of New Hybrid Perovskites with Efficient Photoemission

Owing to quantum confinement, low‐dimensional hybrid perovskite materials have recently shown a great potential for applications in optoelectronics. Such compounds can exhibit broad‐ or narrow‐band light emission, low‐temperature solution processability, high thermal stability, and relatively high photoluminescence quantum yields (PLQY). However, the search for efficient phosphors with a specific set of characteristics remains difficult because the family of hybrid perovskites consists in an extremely large chemical system (i.e., different halides, metals, and organic molecules), and optical properties are not predictable prior to material synthesis and characterization. Here, is proposed a simple approach to screen a significant amount of new hybrid lead halide perovskites. The synthetic method by fast crystallization at low temperature enables the rapid identification of the materials exhibiting the targeted photoluminescence properties. This approach is tested for the discovery of hybrid lead halide perovskites with efficient white‐light emission. Among 100 newly synthesized compounds, 5 exhibit intense white emission, and the in‐depth characterization of a selected candidate shows high color rendering index (CRI) = 78 and a PLQY of 9%, which is equivalent to the record reported for hybrid perovskites. This compound exhibits a new structure type for warm white‐light emitting hybrid perovskites with chains of corner‐sharing PbX₆.     

Application of socio-technical systems models to Martian colonisation and society build

Abstract

The human desire for exploration, together with an increasingly demanding potential need for establishing a human colony away from Earth has stimulated the concept and early planning for Mars colonisation. Successful delivery of such a challenging and expensive technological feat requires a highly informed and supportive general society. Although the ergonomic constraints on astronauts living and working in space is well documented, no study has employed the use of ergonomics tools to explore colony and societal build on other worlds. We have employed Cognitive Work Analysis to derive an abstraction hierarchy for both colony establishment and maintenance with the vision of building a new Martian society. We find that our model will accommodate five major challenge themes collected from over 800 members from twenty two United Kingdom - based astronomical societies and scientific groups and propose that this study may have utility in guiding mission planners in the early colonisation phase and later stage expansion processes. Using the proposed architecture for the Mars One mission, we have performed a basic human factors analysis and propose a number of key design features which may enable long term habitation.     

In search of the lost polychromy of English medieval alabaster panels in the Southwest of France

Polychrome alabaster carvings, representing religious scenes, constitute England's major contribution to European mediaeval sculpture. During the period between 1350 and 1550, large number of alabaster carvings were produced in the Midlands. Despite their massive destruction during the English Reformation (ca.1534), more than 2500 of them still survive, either legally exported or sold clandestinely to the Continent. With more than 100 panels still existing, the Bordeaux region holds one of the largest concentrations of these reliefs. Most of them have unfortunately lost their medieval polychromy, but 20 can still provide valuable information. They are currently studied in our multidisciplinary research program “ALBATRES” (Polychromie, pigments, perception: les albâtres anglais de la fin du Moyen Âge conservés sur le territoire aquitain. Labex LaScArBx project [2018-2020]). Focused on the panels' polychromy, the project links art history, archaeometry, optical and 3D engineering, and experimental archeology. The first aim is to obtain complete information on the materials and techniques used by medieval painters. The second consists in studying the functions of polychromy and its perception, by determining and interpreting the selection criteria and aesthetic uses of colors and gilding. The polychrome remains of the Aquitaine corpus are studied by means of visual examination, macrophotographic documentation, and noninvasive portable spectroscopic analyses (reflectance spectroscopy by fiber optics in visible and infrared ranges, fluorimetry, etc.). They reveal, among others, the presence of cinnabar, red lead, red ochre, copper green pigments, yellow ochre, gold, lead white, and others. The results allow the production of model samples to help understand the medieval color organization before proposing the coloring of a real copy of one of the studied panels (Virgin's Assumption, Musée d'Aquitaine, Bordeaux). The shape and the appearance of the color rendering could be improved thanks to a special device built at the IOGS to develop a shader that approximates as closely as possible the appearance of the panels. Finally, all information will be integrated on 3D model panels for better appreciation of the carvings and the artistic taste of medieval spectators.     

Toward green three‐phase composites with enhanced dielectric permittivity

This work aims to investigate the dielectric potential of microcrystalline cellulose, a green biosourced material, as a third constituent in the three‐phase composites based on ethylene vinyl acetate‐vinyl ester of versatic acid (EVA‐VeoVa) terpolymer and BaTiO₃. For that, new green three‐phase composites were prepared using an economic and green process, with simple implementation at room temperature and using water as a solvent. Compared with the binary composite EVA‐VeoVa/BaTiO₃, the three‐phase composite EVA‐VeoVa/BaTiO₃/microcrystalline cellulose showed an improvement of the BaTiO₃ particles dispersion, enhanced relative permittivity, and reduced dielectric loss, which explains the significance of this study. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46147.     

Impact of Thermodiffusion on the Initial Vertical Distribution of Species in Hydrocarbon Reservoirs

In this work we propose a methodology, based on molecular dynamics simulations, to quantify the influence of segregation and thermodiffusion on the initial state distribution of the fluid species in hydrocarbon reservoirs. This convection-free approach has been applied to a synthetic oil composed of three normal alkanes and to a real acid gas. It has been found that the thermodiffusion effect induced by the geothermal gradient is similar (but opposite in sign) to that due to segregation for both mixtures. In addition, because of the combined effect of thermal expansion and thermodiffusion, it has been observed that the density gradient can be reversed, in the presence of a geothermal gradient. These numerical results emphasize the need of improving our quantification of thermodiffusion in multicomponent mixtures. The SCCO-SJ10 experiments will be a crucial step towards this goal.     

35 years of Multilateral Environmental Agreements ratifications: a network analysis

With the ratification of Multilateral Environmental Agreements (MEAs) the countries of the international community or of intentional communities—be they political, economic, financial, securitarian or strategic—endow these instruments of international cooperation with significant autonomy. From the 3550 dates of ratification of these MEAs recorded from 1979 to mid-September 2014, we produce a graph whose vertices are the 48 MEAs (ratified at least once) and whose links are induced by the succession of ratifications in time. On this basis we propose a diagnosis on the international acceptance of this type of legal instruments and their vulnerability in a global context that builds on the change in the balance of powers as a result of globalization, the break of the bipolar and then unipolar system, and the rise of new powers. Thus, it appears that a global environmental order has been promoted and implemented with some success in the 90s mainly by liberal Western countries who were then able to lead other countries less likely to bind to the fulfillment of environmental obligations. However, the expansion of this global environmental order now seems frozen, due to the current crisis of multilateralism. The rise of many countries, particularly in the South, whose environmental, political and economic weight grew, confronted with the “stable community” formed in the past 35 years suggests that there is a real power shift in the international arena and consequently, multilateralism needs to reflect this new reality. In other terms, the global environmental order is being slowly reformed. As a consequence, the treaties formed clusters in the past but they did not follow the same pattern since the twenty-first century began.     

Periodic Arrays of Diamond‐Shaped Silver Nanoparticles: From Scalable Fabrication by Template‐Assisted Solid‐State Dewetting to Tunable Optical Properties

Periodic arrays of anisotropic silver nanoparticles having peculiar optical properties are fabricated at a macroscopic scale. The proposed scalable method is based on temperature‐assisted solid‐state dewetting of a continuous thin layer deposited on a silica substrate patterned by the nanoimprint technique. The resulting nanoparticles are shaped like diamonds and are half‐embedded into the patterned silica. A period‐dependent optimum in film thickness for the quality of spatial organization is found and discussed in terms of thermodynamics and, for the first time, in terms of the role of grains in the dewetting process. The optical properties of the arrays are driven by not only simply the particle shape but also the lattice period and the degree of order. A surface lattice resonance that disperses with the underlying period is evidenced experimentally and confirmed by optical simulations. The opportunity to fabricate and tune such an assembly of plasmonic particles on transparent substrate opens interesting perspectives for not only fundamental photonics but also potential optical applications.     

An empirical study on the impact of static typing on software maintainability

Static type systems play an essential role in contemporary programming languages. Despite their importance, whether static type systems impact human software development capabilities remains open. One frequently mentioned argument in favor of static type systems is that they improve the maintainability of software systems—an often-used claim for which there is little empirical evidence. This paper describes an experiment that tests whether static type systems improve the maintainability of software systems, in terms of understanding undocumented code, fixing type errors, and fixing semantic errors. The results show rigorous empirical evidence that static types are indeed beneficial to these activities, except when fixing semantic errors. We further conduct an exploratory analysis of the data in order to understand possible reasons for the effect of type systems on the three kinds of tasks used in this experiment. From the exploratory analysis, we conclude that developers using a dynamic type system tend to look at different files more frequently when doing programming tasks—which is a potential reason for the observed differences in time.