Durabilité de la culture cotonnière selon l'utilisation des insecticides : cas du Togo de 1991-2010

Dans la perception des profanes, le coton est encore associé à la culture consommant le plus d'insecticides néfastes pour la santé et l'environnement. Une telle mauvaise image n'est plus méritée selon une étude internationale, mais les pays producteurs ont peu analysé et informé sur l'évolution de l'utilisation d'insecticides. Cette communication comble la lacune dans le cas du Togo. L'étude est basée sur la reconstitution des séries de données des surfaces emblavées et d'insecticides distribués aux producteurs de coton du Togo, de 1990 à 2010. Les données sur les insecticides concernent les volumes distribués ainsi que leurs compositions en matières actives, permettant ainsi de déduire la consommation de matières actives par hectare. Par ailleurs, les charges toxicologiques vis-à-vis de divers éléments de la faune ont été calculées à partir des indices d'écotoxicité établis par la FAO pour chaque matière active. La consommation de matières actives insecticides au Togo a chuté régulièrement jusqu'à un litre/hectare, du même niveau que l'Australie qui recourt par ailleurs aux variétés génétiquement modifiées. La charge toxicologique, pesant sur l'homme mais aussi sur divers éléments de la faune comme les abeilles ou les daphnés des cours d'eau, a diminué quoique de manière moins régulière. Cette évolution est la conséquence d'une protection limitée depuis trois décennies à moins de six traitements et de l'adoption de nouvelles générations de molécules insecticides. Au Togo, l'utilisation des insecticides dans la culture cotonnière a évolué dans une direction plus compatible avec le souci de la santé humaine et de la préservation de l'environnement, mais cette évolution est extrapolable à tous les pays cotonniers de l'Afrique francophone. Il convient de poursuivre l'évolution engagée dans les décisions relatives aux insecticides à commander, en s'inspirant des indicateurs utilisés dans cette étude. (Résumé d'auteur

Structure design for high performance n-type polymer thermoelectric materials

Organic thermoelectric (OTE) materials have been regarded as a potential candidate to harvest waste heat from complex, low temperature surfaces of objects and convert it into electricity. Recently, n-type conjugated polymers as organic thermoelectric materials have aroused intensive research in order to improve their performance to match up with their p-type counterpart. In this review, we discuss aspects that affect the performance of n-type OTEs, and further focus on the effect of planarity of backbone on the doping efficiency and eventually the TE performance. We then summarize strategies such as implementing rigid n-type polymer backbone or modifying conventional polymer building blocks for more planar conformation. In the outlook part, we conclude forementioned devotions and point out new possibility that may promote the future development of this field.</jats:p

Analytical Study on Time-Dependent Stiffness of Stud Shear Connectors

Concrete creep weakens the spring stiffness of stud shear connectors (SSCs) and increases the long-term deflection of long-span composite beams. The time-dependent properties of SSC are of great importance for the long-term evaluation of composite steel construction. This paper proposes the time-dependent stiffness (TDS) method based on the analytical solution of the beam on a viscoelastic foundation to simulate the SSC under the sustained push-out load. TDS method combines beam theory and the viscoelastic property of hardened concrete. The long-term slip of SSC is predicted by hand calculation of the explicitly expressed governing equation, and it is close to the refined finite element analysis (FEA) results. The constants and parameters used to determine TDS seem to be insensitive regarding geometric and material variation. TDS may provide a simplified method to incorporate the time-dependent partial interaction into complex composite structures by saving the consumption of computer storage and advanced modeling time which are usually required in the refined modeling at the steel-concrete interface, especially when the long-term properties of concrete are of interest.</jats:p

n-Type organic electrochemical transistors: materials and challenges

Organic electrochemical transistors (OECTs) have emerged as an enabling technology for the development of a variety of applications ranging from digital logic circuits to biosensors and artificial synapses for neuromorphic computing. To date, most of the reported OECTs rely on the use of p-type (hole transporting) conducting and semiconducting polymers as the channel material, while electron transporting (n-type) OECTs are yet immature, thus precluding the realization of advanced complementary circuitry. In this highlight, we review and discuss recent achievements in the area of n-type OECTs, in particular targeting recently reported n-type channel materials and how these have enabled a considerable advancement of OECT circuit capabilities. Further, the critical challenges currently limiting the performance of n-channel OECTs are summarized and discussed, setting material design guidelines for the next generation n-type and complementary OECTs.Funding Agencies|Swedish Research Council [2016-03979]; Swedish Governmental Agency for Innovation Systems - VINNOVA [2015-04859]; Swedish Foundation for Strategic Research [SE13-0045, RIT15-0119]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]</p

Smart textiles for human–machine interface fabricated <i>via</i> a facile on-site vapor-phase polymerization

PEDOT deposition on 1D to 3D textiles is achieved by an on-site vapor polymerization and their application in human–machine interfaces is then explored.</jats:p

Charge generation mechanism of tandem organic light emitting diodes with pentacene/C₇₀ organic heterojunction as the connecting layer

Charge generation mechanism of a pentacene/C70 planar organic heterojunction is discussed in detail to fabricate high performance tandem OLEDs.</p