The problem with using CO2 is that the system has to run at 1, 500psi, about five times the pressure in a typical refrigeration cycle.

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There will be further upwards price pressure from investors looking to cycle back into commodities, and particularly oil after the start of the New Year.

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The daily cycle of higher pressure in the morning and lower pressure in the evening results from daytime heating of the atmosphere by the sun.

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The home-appliance maker is caught in a vicious spin cycle of rising expenses and intensified pressure from Korean rivals.

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Foreclosures place downward pressure on house prices, contributing to a vicious cycle of economic pain.

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Paul Zwillenberg, managing director, says the typical start-up's financing cycle has greatly shortened, putting new pressure on firms to grow quickly.

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Under pressure to shrink overhead and telescope the new-product cycle, big companies are more likely to turn to universities or small companies to help develop ideas.

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If energy prices, already on the rise, continue to trend upward, it could put further pressure on producers and on consumers, who are stuck in a cycle of deleveraging.

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The Stirling cycle describes a phenomenon where a confined volume of gas expands at high pressure and contracts at low pressure.

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