Biological damage threshold induced by ultrashort fundamental, 2nd, and 4th harmonic light pulses from a mode-locked Nd: glass laser. Final report, April 1978-January 1980
Selected biological macromolecules and 20 Macaca fascicularis monkey eyes were irradiated with ultrashort pulses of light of various wavelengths derived from a mode-locked Nd:Glass laser in order to determine threshold damage mechanisms. Macromolecules such as calf-thymus DNA, dipalmitoyl phosphatidyl choline vesicles, and egg-yolk lecithin vesicles, which are similar to the constituents of living cells that may be susceptible to damage, were irradiated with single picosecond pulses and entire mode-locked pulse trains of 1060-nm and 530-nm light. DNA was not damaged at any energy density available including levels sufficient to cause dielectric breakdown in water. Experimental studies of electromagnetic stress-induced birefringence in DNA base-pairs were also carried out in an attempt to establish a lower limit on the restraining forces governing tilting of the DNA bases with respect to the helix axis. The irradiation experiments at 1060 nm with the bilipid layer vesicles indicated a damage threshold of approx. 600 mJ/sq cm for entire pulse trains of approx. 100 pulses and approx. 9 mJ/sq cm for single pulses. It appears likely that direct electrostrictive forces disrupted the vesicle membranes and facilitated their transition to stacked lamellar structures known as liposomes. Retinal damage thresholds in M. fascicularis were determined for irradiation with single ultrashort pulses and entire pulse trains of 2nd harmonic light. Disruption of the cellular membranes is suggested as the threshold damage mechanism. It is postulated that for pulse trains, irreversible damage occurs very early in the train, at the first pulse to attain or exceed the threshold electric field.
- Research Organization:
- Washington Univ., Seattle (USA)
- OSTI ID:
- 5509587
- Report Number(s):
- AD-A-104821/4
- Country of Publication:
- United States
- Language:
- English
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ELECTRIC FIELDS
BIOLOGICAL EFFECTS
NEODYMIUM LASERS
CELL MEMBRANES
DAMAGE
DEOXYCYTIDYLIC ACID
EYES
IRRADIATION
LIPIDS
MACACUS
RETINA
ANIMALS
BODY
BODY AREAS
CELL CONSTITUENTS
FACE
HEAD
LASERS
MAMMALS
MEMBRANES
MONKEYS
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANS
PRIMATES
SENSE ORGANS
SOLID STATE LASERS
VERTEBRATES
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