Explosive charges are delivered by a number of methods including hand-tossed charges, helicopter-dropped bombs, Gazex concussion lines, and ballistic projectiles launched by air cannons and artillery. Passive preventive systems such as snow fences and light walls can be used to direct the placement of snow. Snow builds up around the fence, especially the side that faces the prevailing winds. Downwind of the fence, snow build-up is lessened. This is caused by the loss of snow at the fence that would have been deposited and the pickup of the snow that is already there by the wind, which was depleted of snow at the fence. When there is a sufficient density of trees, they can greatly reduce the strength of avalanches. They hold snow in place and when there is an avalanche, the impact of the snow against the trees slows it down. Trees can either be planted or they can be conserved, such as in the building of a ski resort, to reduce the strength of avalanches.
Poliosis (also called poliosis circumscripta), is the decrease or absence of melanin (or colour) in head hair, eyebrows, eyelashes or any other hairy area. It is popularly known as white forelock when it affects hair directly above the forehead. This condition can cause single or, less commonly, multiple white patches on the hair. Some mistake these white patches for simple birth marks. In poliosis there is decreased or absent melanin in the hair bulbs of affected hair follicles; the melanocytes of the skin are usually not affected. Associated medical conditions
Poliosis occurs in several genetic syndromes such as piebaldism, Waardenburg syndrome, neurofibromatosis type I, and tuberous sclerosis. It can also occur in conditions such as vitiligo, Vogt–Koyanagi–Harada disease, alopecia areata, sarcoidosis, and in association with neoplasms and some medications. Popular culture
It is sometimes called a Mallen streak, after a fictional family with hereditary poliosis. The Mallen family featured in a sequence of novels by Catherine Cookson, of which The Mallen Streak was the first. She later adapted them into a TV series called The Mallens.Sports presenter Dickie Davies, runner Sam Brown, punk singer Dave Vanian, and fashion expert Stacy London are also known for their Mallen streaks.During his tenure as the host of Talk Soup, host John Henson repeatedly referred to his own poliosis as a "skunk spot".In DC Comics one of Batmans Robins, Jason Todd, is sometimes portrayed with a white forelock.In Marvel Comics, the X-Men member Rogue has a prominent Mallen streak which is a consistent visual trademark of the character.