Firebrand spotting is one of the most vexing problems associated with wildland fires, challenging the lives and efforts of fire-fighting planners. This work is an effort to model numerically the event of firebrand spotting for the purposes of reviewing past modelling approaches and of demonstrating a more current coupled fire/atmosphere approach. A simple, two-dimensional treatment of the process of firebrand lofting is examined under the restrictive conditions typical of a classical plume modelling approach. Using this approach, the differences in trajectories of combusting and non-combusting particles are investigated. Next, firebrand spotting is examined using a coupled fire/atmosphere LES (Large Eddy Simulator) in which the processes of firebrand lofting, propagation, and deposition are connected. The behaviour of combusting and non-combusting firebrands released from a moving grassfire into three-dimensional time-varying coupled atmosphere-wildfire induced circulations is examined. When these results are compared to the results of a classical plume model for firebrand spotting, it is found that firebrand propagation in the coupled LES simulated flow is significantly different from that obtained by the two-dimensional empirically-derived plume model approach. The coupled atmosphere-wildfire LES results are explorative and need to be subjected to direct testing.
Follicular unit extraction (FUE) is an accepted method of extracting individual follicular unit grafts for hair transplant surgery. Since follicles are harvested from the back of the scalp using tiny punches resulting in minimal scarring, it has gained rapid acceptance among the patients. However, due care needs to be exercised while performing FUE. FUE should not be confused with the older plug graft extraction methods of coring out hair-bearing skin plugs. Lack of due diligence while performing such extractions can lead to subluxation of the grafts into the subdermal layer of scalp. Overtumescence of the scalp donor area, use of blunt punches and trying to “core” out the full thickness grafts can all contribute to this. The following cases illustrate some pitfalls to be avoided while performing FUE and the adverse consequences if they occur.
Thermospheric zonal winds at altitudes of 140 to 250 km are shown to reverse from eastward to strong westward between 100° and 200° in geographic longitude and 60°S to 70°S latitude in the Southern Hemisphere. The reversal also occurs at the same latitude in the Northern Hemisphere, but from 200° to 340° longitude. The phenomenon has been previously described as a “wind wall.” Observations by the Wind Imaging Interferometer (WINDII) on the National Aeronautics and Space Administration's Upper Atmosphere Research Satellite (UARS) and simulations by the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM‐X) are utilized to explore the characteristics of what has been called a wind wall. In order to study the dependence on solar radio flux and geomagnetic activity, the relationships of the maximum zonal wind and F10.7 (the solar radio flux at 10.7 cm) and ap indices are investigated. The results show that WINDII observations and WACCM‐X simulations agree well in describing this wind signature. Moreover, the appearance of the wind wall is found to have a strong dependence on the solar radio flux and geomagnetic activity. In addition, WINDII winds have a stronger response to geomagnetic activity than WACCM‐X winds.
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