Rank/select queries over mutable bitmaps

The problem of answering rank/select queries over a bitmap is of utmost importance for many succinct data structures. When the bitmap does not change, many solutions exist in the theoretical and practical side. In this work we consider the case where one is allowed to modify the bitmap via a flip(i) operation that toggles its ith bit. By adapting and properly extending some results concerning prefix-sum data structures, we present a practical solution to the problem, tailored for modern CPU instruction sets. Compared to the state-of-the-art, our solution improves runtime with no space degradation. Moreover, it does not incur in a significant runtime penalty when compared to the fastest immutable indexes, while providing even lower space overhead. (C) 2021 Elsevier Ltd. All rights reserved

Diversité des espèces cultivées et contraintes à la production en agriculture maraîchère au Togo

Cette étude vise à faire le point sur la diversité des espèces cultivées en agriculture maraîchère, leur distribution suivant les organes produits, la disponibilité des légumes ainsi que les contraintes qui entravent cette agriculture. Elle se fonde sur des enquêtes menées sous forme de "focus groups" auprès des maraîchers du pays. Les données recueillies et traitées ont révélé 43 espèces maraîchères qui se répartissent en 30 genres et 17 familles. Les légumes feuilles sont les plus fréquents quoique l’on puisse constater une prédominance de production de la carotte (Daucus carotta L.). Bien que Brassica oleracea var. capitata L. et Lactuca sativa L. soient cultivées dans tout le pays, elles semblent néanmoins être spécifiques des régions sèches de la Kara et des Savanes qui alimentent la capitale Lomé, en saison sèche (novembre à mars). Cette agriculture est soumise à des contraintes mais, celle qui semble avoir le plus d’impact est liée au foncier. En agissant sur celui-ci, on peut faire évoluer l’agriculture maraîchère au Togo vers des futurs prometteurs.Mots clés : Diversité, espèces cultivées, contraintes, agriculture maraîchère, Tog

Urban energy exchanges monitoring from space

One important challenge facing the urbanization and global environmental change community is to understand the relation between urban form, energy use and carbon emissions. Missing from the current literature are scientific assessments that evaluate the impacts of different urban spatial units on energy fluxes; yet, this type of analysis is needed by urban planners, who recognize that local scale zoning affects energy consumption and local climate. However, satellite-based estimation of urban energy fluxes at neighbourhood scale is still a challenge. Here we show the potential of the current satellite missions to retrieve urban energy budget, supported by meteorological observations and evaluated by direct flux measurements. We found an agreement within 5% between satellite and in-situ derived net all-wave radiation; and identified that wall facet fraction and urban materials type are the most important parameters for estimating heat storage of the urban canopy. The satellite approaches were found to underestimate measured turbulent heat fluxes, with sensible heat flux being most sensitive to surface temperature variation (-64.1, +69.3 W m-2 for ±2 K perturbation); and also underestimate anthropogenic heat flux. However, reasonable spatial patterns are obtained for the latter allowing hot-spots to be identified, therefore supporting both urban planning and urban climate modelling

Characterization of vacancy defects in Cu(In,Ga)Se2 by positron annihilation spectroscopy

The photovoltaic performance of Cu(In1-x,Gax)Se2 (CIGS) materials is commonly assumed to be degraded by the presence of vacancy-related defects. However, experimental identification of specific vacancy defects remains challenging. In this work we report positron lifetime measurements on CIGS crystals with x = 0, and x = 0.05, saturation trapping to two dominant vacancy defect types, in both types of crystal, is observed and found to be independent of temperature between 15–300 K. Atomic superposition method calculations of the positron lifetimes for a range of vacancy defects in CIS and CGS are reported. The calculated lifetimes support the assignment of the first experimental lifetime component to monovacancy or divacancy defects, and the second to trivacancies, or possibly the large In-Se divacancy. Further, the calculated positron parameters obtained here provide evidence that positron annihilation spectroscopy has the capability to identify specific vacancy-related defects in the Cu(In1-x,Gax)Se2 chalcogenides