It took years, he says, to show that caffeine had a performance-enhancing effect.

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Keith Hylton of Boston University's law school estimates that the welfare-enhancing effect of making negligence more expensive would be the biggest economic benefit of loser-pays.

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"There's definitely a performance-enhancing effect if you use things that improve oxygen transport to the tissue, " says Larry Bowers, an expert on athletic drug testing and senior managing director of the U.S. Anti-Doping Agency.

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In addition, the Mood Lamp creates a soft, environment-enhancing lighting effect, while the Smart Sensor analyzes the amount of illumination being provided by ambient light sources.

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First, "greenhouse gases" refers to several gases recognized by scientists as enhancing the greenhouse effect.

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In a recent study, economists at the IMF analysed the respective impact of deficit reduction, global rebalancing and productivity-enhancing structural reforms on the growth prospects of big rich economies and found that by far the strongest positive effect came from structural reforms.

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"If it is true that the mechanism is all about rays enhancing diffuse radiation, it would mean that 'global dimming' and 'global brightening' would have a big effect on tree growth and therefore on the absorption of carbon dioxide, " warns Ms Dengel.

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