Efforts to ablate soft tissue with conventional lasers have been limited by collateral damage and by concern over potential photochemical effects. Motivated by the thermal-confinement model, past infrared investigations targeted the OH-stretch mode of water with fast pulses from lasers emitting near 3,000 nm (refs 1, 7-9). What does a free-electron laser offer for the investigation of tissue ablation? Operating at non-photochemical single-photon energies, these infrared sources can produce trains of picosecond pulses tunable to the vibrational modes of proteins, lipids and/or water. We report here that targeting free-electron laser radiation to the amide II band of proteins leads to tissue ablation characterized by minimal collateral damage while maintaining a substantial ablation rate. To account for these observations we propose a novel ablation mechanism based on compromising tissue through resonant denaturation of structural proteins.
Proponents have long argued that small‐scale mining, given proper direction and support, can contribute substantively to the socioeconomic development of rural areas in developing countries. The attitudes of governments, commercial mining companies and donor agencies have been coloured by the haphazard, informal, often dangerous and seemingly wasteful character of much local mining activity, especially at the smallest scale. Yet this ‘artisanal’ activity has come to assume a critical economic welfare function in many countries, especially those which have suffered through extended periods of environmental and economic stress. This paper argues that this type of mining, because of both its upside potential and its problematic nature, cannot be ignored: neither can it be eradicated. Instead, explicit and sustained attention from governments, non‐government organizations, the private sector and donor agencies is advocated for an effort to rationalize and formalize this type of mining, to increase its economic and technical efficiency, and to maximize its social benefits and minimize its disadvantages.
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