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Tagging is demonstrated in argon and nitrogen gases using a femtosecond laser with pulse energies of approximately 70 μJ through a nonresonant ionization process at 267 nm. The signal fluorescence lifetime in pure argon and nitrogen-argon mixtures are measured and found to be long enough to make mean velocity and turbulence measurements in a subsonic flow. In pure argon, the dominating processes involve atomic transitions between 700 and 900 nm. In argon-nitrogen mixtures, nitrogen quenches atomic argon species and the dominant radiating processes are transitions in the nitrogen second positive system. In pure nitrogen, emission on the microsecond time scale comes from the nitrogen first positive system. Lower energy density is needed for tagging and narrower tagged lines are produced using 267 nm as compared to femtosecond laser tagging in argon and nitrogen using 400 nm or 800 nm. Velocimetry using the 267 nm line is demonstrated in a turbulent argon pipe flow and the Taylor microscale of the flow is determined.
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Transmission of intense ultrashort laser pulses through hollow-core fibers (HCFs) is investigated for molecular-tagging velocimetry. A low-vacuumed HCF beam-delivery system is developed to transmit hi...
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Progressive mental disturbances and unconsciousness due to breathing mixtures of oxygen and inert gases (argon, helium, xenon, krypton, and atmospheric nitrogen) at high pressure.
Argon. A noble gas with the atomic symbol Ar, atomic number 18, and atomic weight 39.948. It is used in fluorescent tubes and wherever an inert atmosphere is desired and nitrogen cannot be used.
A method of tissue ablation and bleeding control that uses argon plasma (ionized argon gas) to deliver a current of thermocoagulating energy to the area of tissue to be coagulated.
A technique utilizing a laser coupled to a catheter which is used in the dilatation of occluded blood vessels. This includes laser thermal angioplasty where the laser energy heats up a metal tip, and direct laser angioplasty where the laser energy directly ablates the occlusion. One form of the latter approach uses an EXCIMER LASER which creates microscopically precise cuts without thermal injury. When laser angioplasty is performed in combination with balloon angioplasty it is called laser-assisted balloon angioplasty (ANGIOPLASTY, BALLOON, LASER-ASSISTED).
Techniques using laser energy in combination with a balloon catheter to perform angioplasty. These procedures can take several forms including: 1, laser fiber delivering the energy while the inflated balloon centers the fiber and occludes the blood flow; 2, balloon angioplasty immediately following laser angioplasty; or 3, laser energy transmitted through angioplasty balloons that contain an internal fiber.