The origin and composition of carbonatite-derived carbonate-bearing fluorapatite deposits

Carbonate-bearing fluorapatite rocks occur at over 30 globally distributed carbonatite complexes and represent a substantial potential supply of phosphorus for the fertiliser industry. However, the process(es) involved in forming carbonate-bearing fluorapatite at some carbonatites remain equivocal, with both hydrothermal and weathering mechanisms inferred. In this contribution, we compare the paragenesis and trace element contents of carbonate-bearing fluorapatite rocks from the Kovdor, Sokli, Bukusu, Catalão I and Glenover carbonatites in order to further understand their origin, as well as to comment upon the concentration of elements that may be deleterious to fertiliser production. The paragenesis of apatite from each deposit is broadly equivalent, comprising residual magmatic grains overgrown by several different stages of carbonate-bearing fluorapatite. The first forms epitactic overgrowths on residual magmatic grains, followed by the formation of massive apatite which, in turn, is cross-cut by late euhedral and colloform apatite generations. Compositionally, the paragenetic sequence corresponds to a substantial decrease in the concentration of rare earth elements (REE), Sr, Na and Th, with an increase in U and Cd. The carbonate-bearing fluorapatite exhibits a negative Ce anomaly, attributed to oxic conditions in a surficial environment and, in combination with the textural and compositional commonality, supports a weathering origin for these rocks. Carbonate-bearing fluorapatite has Th contents which are several orders of magnitude lower than magmatic apatite grains, potentially making such apatite a more environmentally attractive feedstock for the fertiliser industry. Uranium and cadmium contents are higher in carbonate-bearing fluorapatite than magmatic carbonatite apatite, but are much lower than most marine phosphorites

Chasing feet in the wild: A proposed egocentric motion-aware gait assessment tool

Despite advances in gait analysis tools, including optical motion capture and wireless electrophysiology, our understanding of human mobility is largely limited to controlled conditions in a clinic and/or laboratory. In order to examine human mobility under natural conditions, or the 'wild', this paper presents a novel markerless model to obtain gait patterns by localizing feet in the egocentric video data. Based on a belt-mounted camera feed, the proposed hybrid FootChaser model consists of: 1) the FootRegionProposer, a ConvNet that proposes regions with high probability of containing feet in RGB frames (global appearance of feet), and 2) LocomoNet, which is sensitive to the periodic gait patterns, and further examines the temporal content in the stacks of optical low corresponding to the proposed region. The LocomoNet signicantly boosted the overall model's result by ltering out the false positives proposed by the FootRegionProposer. This work advances our long-term objective to develop novel markerless models to extract spatiotemporal gait parameters, particularly step width, to complement existing inertial measurement unit (IMU) based methods

Environmental policies in European aviation: a stakeholder management perspective

Aviation contributes to economic and social development, but air traffic congestion and aircraft-related gas emissions damage the environment; hence, appropriate policies should be introduced to ensure sustainable growth. This paper highlights the interdependence of environmental reforms in aviation by thoroughly investigating two major European policy schemes, i.e. the European Union Emissions Trading Scheme and the Single European Sky. Emphasis is given on policy aspects of multi-stakeholder governance. Based on focus group interviews with thirty-nine senior managers and in-depth interviews with seven experts, transaction costs are highlighted and a stakeholder power vs. interest grid is developed to identify and, most importantly, to address governance failure, thus effectively linking different aviation policies in a holistic manner