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Despite being the most prevalent eating disorder amongst individuals with developmental disabilities and may occur in as many as 25%-33% of children, there is much that is still unknown about pica. There has been little advancement in finding out what causes this disorder and because of that, treating and even diagnosing pica can be difficult. In addition to that, pica can have health consequences that range from mild to severe so, when coupled with the difficulty in treatment and lack of breakthrough
however kerosene-fueled engines would "knock" and crack the cylinder head and pistons. This then led to the long search for antiknock agents, culminating in tetra ethyl lead. Typical mid-1920's gasoline was 40-60 octane. The 1950s saw the start of the increase of the compression ratio, requiring higher octane fuels. Octane ratings, lead levels, and vapor pressure increased, whereas sulfur content decreased. Minor improvements were made to gasoline formulations to improve yields and octane until
Catalysts speed up the rate of reaction and remain chemically unchanged or being used up in the process, and are widely used in industry. Enzymes are biological catalysts made up of proteins, and can be used a lot in industry since they operate best close to room temperature and pressure which can be maintained in industrial processes. Catalysts will speed up rate of reaction and can also be used to change properties of a product to increase it’s usefulness – it can turn light, bendy poly(ethene)
Lead is a heavy, low melting, bluish-gray metal that is found naturally in the Earth's crust.Before 3000 B.C. the Egyptians used lead in glaze pottery while ancient romans used this metal for two purposes: • To join the water pipes • To flavor wines and food ( Though, it is scarcely found naturally as a metal but combined with two or moreother elements to form lead compounds mainly in the ores Galena (PbS), Cerussite(PbCO3), and Anglesite(PbSO4) (Infoplease, 2012). Metallic lead is resilient to
Chapter 1 INTRODUCTION In thermodynamics Refrigeration is the major application area, in which the heat is transferred from a lower temperature region to a higher temperature region. The devices which produce refrigeration are known as Refrigerators and the cycle on which it operates are called refrigeration cycles. Vapour compression refrigeration cycle is the most regularly used refrigeration cycle in which the refrigerant is alternately vaporized and condensed and in the vapor