RESUMEN
For the first time, using sturgeon sperm as a model system, sensitive to optical radiation, the comparative studies of biological effect of continuous wave, quasi-continuous wave, nano- and picosecond laser radiation under conditions with equal average irradiance (3 mW/cm2) and wavelength (532 nm) have been carried out. Analyzing the parameters of spermatozoa motion it has been shown that, depending on the energy dose and mode of laser operation, the radiation may have both stimulatory and inhibitory effect on the velocity of motion and spermatozoa motility duration as well as on sustaining of functional characteristics of cold-stored sperm. The possibility of increasing the fertilization rate due to use of the sperm preliminary treated with laser radiation is demonstrated. For the first time, the possibility of enhancement of biological effect going from continuous wave to quasi-continuous wave laser radiation at equal irradiance and wavelength has experimentally been proven. It is shown that the difference in biological effect of continuous wave, quasi-continuous wave, nano- and picosecond laser radiation is due to amplitude (peak) values of intensity. Using fluorescence analysis and luminol-dependent chemiluminescence assay, evidence for the participation of endogenous flavins and metal-free porphyrins in sensitized ROS formation (singlet oxygen, hydrogen peroxide, and hydroxyl radicals) in sturgeon sperm was obtained. Mechanisms of photochemical and photothermal reactions explaining the difference in efficacy of action of laser radiation in above modes are discussed.
Asunto(s)
Fertilización/efectos de la radiación , Fármacos Fotosensibilizantes/química , Espermatozoides/efectos de la radiación , Animales , Cordados , Relación Dosis-Respuesta en la Radiación , Flavinas/química , Flavinas/metabolismo , Peróxido de Hidrógeno/química , Peróxido de Hidrógeno/metabolismo , Radical Hidroxilo/química , Radical Hidroxilo/metabolismo , Rayos Láser , Mediciones Luminiscentes , Masculino , Procesos Fotoquímicos , Porfirinas/química , Porfirinas/metabolismo , Especies Reactivas de Oxígeno/química , Especies Reactivas de Oxígeno/metabolismo , Motilidad Espermática/efectos de la radiación , Nanomedicina TeranósticaRESUMEN
The low-temperature cavitational disruption by trains of laser pulses was demonstrated in water. The trains used in the experiment were generated by a Raman laser at a wavelength of 1626 nm. The mean value of the fragmentation threshold energy density per pulse in a train was estimated to be equal to 7.2x10(6) J/m(3). The corresponding amplitude of the negative pressure had the order of 6-7 bars at a temperature jump of only about 2 degrees C. This result opens up prospects for developing precision nonthermal cavitational laser surgery.
Asunto(s)
Gases/química , Gases/efectos de la radiación , Terapia por Láser , Rayos Láser , Agua/química , Relación Dosis-Respuesta en la Radiación , Rayos Infrarrojos , Microburbujas , Presión , Dosis de RadiaciónRESUMEN
Continuous-wave Raman generation in a compact solid-state laser system pumped by a multimode diode laser is demonstrated. The Stokes radiation of stimulated Raman scattering at 1.181 microm is generated as a result of self-frequency conversion of the 1.067 microm laser radiation in Nd3+:KGd(WO4)2 crystal placed in the cavity. The Raman threshold was measured at 1.15 W of laser diode power. The highest output power obtained at the Stokes wavelength was 54 mW. The anomalous delay of Raman generation relative to the start of laser generation (the oscillation buildup) due to slow accumulation of Stokes photons in the cavity at low Raman gain and Raman threshold dependence not only on the laser intensity but also on the time of laser action are observed.
RESUMEN
We demonstrate the continuous-wave operation of a solid-state Raman laser containing a barium nitrate crystal as the Raman medium. The Raman laser, which has a singly resonant cavity, is pumped by multimode radiation. The Raman oscillation threshold is reached at approximately 2 W of pump power. As much as 500 kW/cm2 of Stokes power density at 60-kW/cm2 pump power density is obtained in the cavity.
RESUMEN
Raman conversion of femtosecond pulses in a solid-state medium is reported. Stimulated Raman scattering (SRS) was observed in an impulsive SRS regime when the pump pulse's duration was comparable with the period of Raman-active vibration. The generation of super broadband radiation, which is a distinguishing feature of impulsive SRS, is shown.
