silicon essays

silicon essays Silicon is an essential element in humans, found in significant concentrations in hair, bone, epidermis and dental enamel. It is also the second most abundant element on the earths crust, constituting about 28% by weight.(cite) Many foods and beverages, including certain vegetables, grains, rice, and beer have been shown to contain significant amounts of silicon. Silicone is a synthetic form of silicon and includes 40% silicon by weight. The silicones are synthetic polymers and are not therefore found naturally. They have a linear, repeating silicon-oxygen backbone akin to silica. However, organic groups attached directly to the silicon atoms by carbon-silicon bonds prevent formation of the three-dimensional network found in silica. These types of compound are also known as polyorganosiloxanes. Certain organic groups can be used to link two or more of these silicon-oxygen backbones and the nature and extent of this cross linking enables a wide variety of products to be manufacture d.(cite) The most important materials used in medical implants are fluids, gels and rubbers (elastomers) whose physical and chemical properties include, amongst others, a high degree of chemical inertness, thermal stability and resistance to oxidation. Silicone is used by many prosthesis, medical devices, and pharmaceutical products. The many silicone containing medical devices include artificial heart valves, artificial joints, Norplant contraceptive implants, pacemaker wires, and dialysis tubing. Of course silicone is probably best known for its use in breast implants. In 1992 the FDA pulled silicone-gel filled breast implants off the market as they were alleged to cause connective-tissue disorders such as systemic lupus erthematosus, rheumatoid arthritis and scleroderma, a hardening of the skin.(cite) Recent studies have disproven this, showing that connective-tissue diseases were no more common in women with implants than thos...