Upward propagation of lightning-generated whistler waves into the radiation belts

Lightning-generated whistler (LGW) waves which induce energetic electron precipitation provide an important coupling between the ionosphere and radiation belts. Using the ray-tracing technique, we examine the propagation behaviour of LGW waves and show that they can travel upward into the radiation belts during higher geomagnetic activities due to the plasmapause inward compression, particularly in cases of lower wave frequencies, lower wave normal angles and azimuthal angles. Both perpendicular and parallel group velocities of LGW waves remain in relatively small values inside the plasmasphere but change rapidly to high values outside the plasmasphere. The launching latitude increases with increasing LGW wave normal angle. These results here further reveal a detailed picture on how LGW waves escape out of the plasmasphere and onto the radiation belts.     

Effect of liquid-solid ratio on the morphology,structure, conductivity,and electromagnetic characteristics of iron particles

Using a ball-milling technique, polymorphous iron particles were prepared by changing only the liquid-solid ratio λ. Effects of λ on their morphology, structure, conductivity, and electromagnetic properties were studied. The results show that an increase of λ from 0 to 0.25 causes a nonlinear decrease of the conductivity in the ranges of 88.50–2.25 S cm^?1 and a regular variation of the electromagnetic parameters, corresponding to the as-obtained iron particles. This is ascribed to a combination of the increased shape anisotropy and the decreased fresh surface with active atoms deriving from the weakened welding-on action and the enhanced micro-malleation action in the ball-milling process. Hereinto, the iron flakes formed at wet-milling with λ=0.08?0.25 have lower conductivity, higher permittivity and permeability, and more excellent absorption property compared with the irregular iron particles obtained at dry-milling with λ=0. It is a consequence of the synergistic effect of dielectric relaxation loss, exchange energy and conductance loss originating from the flake-shape structures. This indicates that the morphology, structure, conductivity, and electromagnetic properties of the products can be effectively controlled by changing λ.

     

A robust polyacrylic acid/chitosan cryogel for rapid hemostasis

Science China Technological Sciences - Currently, it is a challenge to develop hemostatic materials with high water absorption capacity and anti-fatigue properties for quickly preventing massive...