Drying and Heating Modelling of Granular Flow: Application to the Mix-Asphalt Processes

Concrete asphalt is a hydrocarbon material that includes a mix of mineral components along with a bituminous binder. Prior to mixing, its production protocol requires drying and heating the aggregates. Generally performed in a rotary drum, these drying and heating steps within mix asphalt processes have never been studied from a physical perspective. We are thus proposing in the present paper to analyze the drying and heating mechanisms when granular materials and hot gases are involved in a co-current flow. This process step accounts for a large proportion of the overall energy consumed during hot-mix asphalt manufacturing. In the present context, the high energy cost associated with this step has encouraged developing new strategies specifically for the drying process. Applying new asphalt techniques so that an amount of moisture can be preserved in the asphalt concrete appears fundamental to such new strategies. This low-energy asphalt, also referred to as the "warm technique", depends heavily on a relevant prediction of the actual moisture content inside asphalt concrete during the mixing step. The purpose of this paper is to present a physical model dedicated to the evolution in temperature and moisture of granular solids throughout the drying and heating steps carried out inside a rotary drum. An initial experimental campaign to visualize inside a drum at the pilot scale (i.e. 1/3 scale) has been carried out in order to describe the granular flow and establish the necessary physical assumptions for the drying and heating model. Energy and mass balance equations are solved by implementing an adequate heat and mass transfer coupling, yielding a 1D model from several parameters that in turn drives the physical modeling steps. Moreover, model results will be analyzed and compared to several measurements performed in an actual asphalt mix plant at the industrial scale (i.e. full scale)

Adaptation of the forecasting system to control Black Leaf Streak Disease of banana in the specific conditions of Dominican Republic

Introduction. Black Leaf Streak Disease (BLSD) is the most important foliar disease affecting banana production worldwide. A forecasting system has been developed and implemented in various countries aiming at optimal control of BLSD through minimum applications of fungicide. In Dominican Republic, favorable dry climatic conditions contrast with serious organizational issues for BLSD control. Our objective was to evaluate the adaptation of this forecasting strategy in these specific conditions. Materials and methods. Fungicide resistance analyses were carried out in the northwestern region of Dominican Republic, in order to determine the appropriate spectrum of systemic fungicides for the forecasting strategy. Three field experiments were set up on commercial farms where disease evolution was monitored every week, on reference plots, in order to decide the pertinence of fungicide applications. Results. Fungicide resistance to QoI fungicides and strong sensitivity reduction to DMI (Demethylation Inhibitor) fungicides were detected in all farms. In spite of these limitations in the use of some fungicide groups, disease control was achieved with a limited number of fungicide applications (6–9), as compared with 13–26 applications in most commercial farms of Dominican Republic over the same period. Discussion. The calculation of an indicator of the efficiency of the chemical control confirmed the potential of the forecasting strategy, underlining the influence of crop management as well as the neighboring environment of the farms on its efficiency. The requirements for further generalization of this system to commercial farms of this country are discussed. (Résumé d'auteur

Background Light in Potential Sites for the ANTARES Undersea Neutrino Telescope

The ANTARES collaboration has performed a series of {\em in situ} measurements to study the background light for a planned undersea neutrino telescope. Such background can be caused by $^{40}$K decays or by biological activity. We report on measurements at two sites in the Mediterranean Sea at depths of 2400~m and 2700~m, respectively. Three photomultiplier tubes were used to measure single counting rates and coincidence rates for pairs of tubes at various distances. The background rate is seen to consist of three components: a constant rate due to $^{40}$K decays, a continuum rate that varies on a time scale of several hours simultaneously over distances up to at least 40~m, and random bursts a few seconds long that are only correlated in time over distances of the order of a meter. A trigger requiring coincidences between nearby photomultiplier tubes should reduce the trigger rate for a neutrino telescope to a manageable level with only a small loss in efficiency.Comment: 18 pages, 8 figures, accepted for publication in Astroparticle Physic

HHEX is a transcriptional regulator of the VEGFC/FLT4/PROX1 signaling axis during vascular development.

Formation of the lymphatic system requires the coordinated expression of several key regulators: vascular endothelial growth factor C (VEGFC), its receptor FLT4, and a key transcriptional effector, PROX1. Yet, how expression of these signaling components is regulated remains poorly understood. Here, using a combination of genetic and molecular approaches, we identify the transcription factor hematopoietically expressed homeobox (HHEX) as an upstream regulator of VEGFC, FLT4, and PROX1 during angiogenic sprouting and lymphatic formation in vertebrates. By analyzing zebrafish mutants, we found that hhex is necessary for sprouting angiogenesis from the posterior cardinal vein, a process required for lymphangiogenesis. Furthermore, studies of mammalian HHEX using tissue-specific genetic deletions in mouse and knockdowns in cultured human endothelial cells reveal its highly conserved function during vascular and lymphatic development. Our findings that HHEX is essential for the regulation of the VEGFC/FLT4/PROX1 axis provide insights into the molecular regulation of lymphangiogenesis