Energy Expenditures

Hydrocarbon, typically natural gas, is fed into the reactor to intersect with an electric arc stmck between a graphite cathode and a metal (copper) anode. The arc temperatures are in the vicinity of 20,000 K inducing a net reaction temperature of about 1500°C. Residence time is a few milliseconds before the reaction temperature is drastically reduced by quenching with water. Just under 11 kWh of energy is required per kg of acetylene produced. Low reactor pressure favors acetylene yield and the geometry of the anode tube affects the stabiUty of the arc. The maximum theoretical concentration of acetylene in the cracked gas is 25% (75% hydrogen). The optimum obtained under laboratory conditions was 18.5 vol % with an energy expenditure of 13.5 kWh/kg (4). 

Decrea.sed energy consumption. As mentioned previously, methods of energy conservation are often interrelated and complementary to each other. Energy expenditures associated with the treatment and transport of waste are usually but not always reduced when the amount of waste generated is lessened, while at the same time the pollution associated with energy consumed by these activities is abated. 

Traditionally ceramic raw materials have been dug out of the ground and used with little or no treatment or purification. Sand, fireclay, talc, and gypsum are examples. The energy expenditure for producing these materials is therefore small. Some of these materials can be found naturally in high purity. Silica sands (SiO,) with less than 100 ppm (parts per mil-... 

Many ceramic applications are high value and small volume, so energy expenditure is high. Ferroelectric magnets, electronic substrates, electrooptics, abrasives such as silicon carbide and diamond, are examples. Diamond is found naturally, and made synthetically by the General Electric Company at high pressure and temperature. Synthetic diamonds for abrasives require less energy to make than the value in Table 4 nevertheless, the market is carefully divided between natural and synthetic diamonds. 

Large quantities of uranium oxide are required for nuclear reactor fuel. The uranium ore must be carefully purified and processed to desired shapes, causing high energy expenditure. 

There has been considerable focus on the development of drugs that lead to a reduction in the total amount of adipose tissue. These include agents targeted at limiting fat absorption, the inhibition of appetite, and the stimulation of energy expenditure (thermogenesis)-or a combination thereof. The best example of drugs,... 

Obesity results from an energy imbalance, when energy intake exceeds energy expenditure over a prolonged period of time. The excess energy is stored in the form of triglycerides in the adipose tissue. 

Reduction of energy intake appetite and satiation Reduction of energy intake intestinal absoiption Increase of energy expenditure Modulation of fat storage... 

Additional effects LDL-C reduction Increased energy expenditure Metabolic effects... 

Despite tremendous efforts, research on energy expenditure did not yet lead to successful therapies. Much attention has been devoted to the stimulation of (33 receptors. The stimulation of these adrenergic receptors should lead to an increased expression of the... 

Homeostatic regulation of metabolic efficiency (i.e., caloric intake required to maintain body weight constant to maintain constant ratios of energy expenditure/ conservation). 

The cytokine leptin is secreted by adipocytes (fat cells) in proportion to the size of the adipose dq>ot and circulates via the bloodstream to the brain, where it ultimately affects feeding behavior, endocrine systems including reproductive function and, at least in rodents, energy expenditure. The major effect of Lqrtin is on the hy-pothalamous, where it suppresses appetite and hence food intake. Leptin exerts its effects via binding to the leptin receptor in the brain (specifically in the hypothalamus), which activates the JAK-STAT Pathway. 

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