High-pressure area Hadley cells help form the subtropical ridge, steer tropical waves and tropical cyclones across the ocean and is strongest during the summer. The subtropical ridge also helps form most of the world's deserts. On English-language weather maps, high-pressure centers are identified by the letter H. Weather maps in other languages may use different letters or symbols. The direction of wind flow around an atmospheric high-pressure area and a low-pressure area, as seen from above, depends on the hemisphere. High-pressure systems rotate clockwise in the northern Hemisphere; low-pressure systems rotate clockwise in the southern hemisphere. The scientific terms in English used
Low pressure molding to keep the desired form upon cooling down. These polyamide materials differ from other thermoplastics in two main areas: One: Viscosity: At processing temperature (410F/210C) the viscosity is very low, typically around 3,000 centipoise (similar to pancake syrup). Low viscosity materials require low injection pressure in order to inject into a cavity. In fact it is normal to use a simple gear pump to inject the polyamide material. Low injection pressure is paramount, when over-molding relatively fragile electronic component. Two: Adhesion: Polyamide materials are basically high performance hot-melt adhesives. The adhesive properties of polyamide is what seals a chosen substrate.