Theoretical investigation of the distributions of laser radiation intensities inside spherical gold nanoparticles
with radiuses in the range 5-100 nm during laser irradiation for wavelengths 400, 532, 800 nm was carried out.
Distributions of laser intensity are nonhomogeneous for some ranges of nanoparticle sizes and values of laser
wavelengths. These results can be applied for explanation of some experimental data of laser-induced
fragmentation, evaporation and formation of nanonetworks as a result of laser action on nanoparticles and for
laser technologies of nanoparticles.
Computer calculation of optical properties of core-shell metal nanoparticles was made for some laser
wavelengths. Efficiency factors of absorption, scattering and extinction by spherical core-shell gold-silver and
silver-gold nanoparticles of the radiuses in the range 5-100 nm and for laser wavelengths 400, 532 and 800 nm
were calculated. Analysis of influence of optical parameters of metals, radiuses of core and thicknesses of shell
on optical properties of nanoparticles was made.
Simulations of optical radiation transformation by spherical microparticles containing monomers of nanoparticles inside
or on the surface of them have been performed. Conditions of microparticle internal field variations are obtained under
changes of monomer concentration.
A computer model of the dynamics of temperature field in multilayer biological structure, containing a blood vessel, as a
result of the action of pulse laser radiation was worked out. The calculations were done with regard to the diffraction of
radiation and the heat exchange at the vessel boundary with the surroundings. The possibility of use of pulse modulated
laser radiation for the increase of the homogeneity of vessel walls coagulation and the decrease of the risk of tissue
injury, determined by phase transition, was considered.
A computer model of the dynamics of temperature field in multilayer biological structure, containing a blood vessel, as a
result of the action of pulse laser radiation was worked out. The calculations were done with regard to the diffraction of
radiation and the heat exchange at the vessel boundary with the surroundings. The possibility of use of pulse modulated
laser radiation for the increase of the homogeneity of vessel walls coagulation and the decrease of the risk of tissue
injury, determined by phase transition, was considered.
A computer model of blood vessel heating by pulse laser irradiation incident on the upper skin layer (epidermis) is suggested. The model is a multilayered half-infinite structure. The depths, optical (absorption and scattering), mechanical and thermal-optical properties of layers are in agreement with the real properties of epidermis and dermis of skin. The exterior of model object (epidermis) is illuminated by light beam of cylindrical form with homogeneous intensity distribution along the cross section. The blood vessel, situated in dermis, is simulated by infinite circular cylinder. Calculations of the dynamics of temperature field inside blood vessel taking into account an inhomogeneous distribution of volumetric heat release within it under the action of pulse laser irradiation of skin were made.
The influence of low-intensity laser radiation on the transport of human blood within skin capillaries is investigated in vivo on cardiac ischemia patients. For the sample as a whole the mean blood perfusion increased by thirty percent after exposure, for 10 minutes, to light from a Helium Neon laser at an irradiance level of 225 W/m2. In some individual patients the blood perfusion more than doubled. A two-dimensional theoretical model is developed that suggests that modest heating of the blood is induced by the incident radiation and could be responsible for the observed increase.
An advanced model of blood vessel heating by laser radiation is proposed for tasks of laser skin surgery and therapy. Blood vessel is modeled by infinite circular cylinder situated in skin dermis. Heat conduction equation taking into account the inhomogeneous internal source function is calculated. The source function inside the blood vessel is calculated according to the theory of diffraction of electromagnetic radiation on infinite circular cylinder. Dynamics of the temperature fields inside the vessels as a function of vessel diameters and duration of irradiance is calculated for the wavelength of 0.532 μm. It is determined the irradiance conditions whereby the near-homogeneous heating along the perimeter of walls of blood vessels on minimum laser exposure to surrounding tissues is achieved.
Spider leg veins represent an important aesthetic problem. This clinical study was performed to investigate the pulsed near-infrared diode laser (810 nm) treatment of spider leg veins. 35 female patients were enrolled in this study and treated twice with laser densities of energy (fluence) between 60 - 100 J/cm2 and a spot size of 50 mm2. Histological examinations were performed to investigate morphological and functional effects. Spectroscopic investigations were used as a non-invasive evaluation tool. After the first laser treatment 15 patients showed a complete disappearance (CR); in the remaining 20 patients a remarkable improvement (RI) was seen (N=35). After six months of follow-up
CR was noted in 6 patients, RI in 6, a stable situation in 9, and scar formation in one patient (N=21). The histological examination before and after laser treatment showed no cellular inflammatory reactions. The mean vascular areas were significantly reduced after the laser treatments. Vis-NIR spectroscopic investigations showed almost an immediate occurrence of the haemoglobin double peak and a prompt decrease of the visible remittance after laser treatment of
the skin. Pulsed diode laser therapy is a safe and effective option for the treatment of spider leg veins. Objective in vivo- monitoring by remission spectroscopy and the histology of biopsy specimens show the immediate and long-term laser effects of the irradiated skin in detail.
Theoretical and experimental studies of the influence of low-intensity laser radiation, on the velocity of microcirculation of the erythrocytes of patients with the cardiovascular disease “in vivo" are carried out. Dynamic light scattering techniques were used to monitor the variation in the perfusion of micro capillary blood flow during irradiation under "in vivo" conditions and compared to the change in average size of aggregates of the blood effects observed "in vitro" using static scattering of light. It is shown that the process of the fragmentation of erythrocytes depends on amount of energy absorbed by biological tissues. This conclusion is supported by the good qualitative agreement with the theoretical model, based on the heat transfer theory within the dermis.
Results of consideration for bimodal laser regime in aerosol micro particle under the action of the second harmonic of a Nd-doped power glass laser as a pumping source for the mixture of an active substance and a saturable absorber as micro impurity in a spherical micro particle are proposed. Bimodal radiation in aerosol microparticle as spherical cavity is considered. Interactions of modes in presence of impurity as absorber both and enlargement and inhibition effects are described to enlarge sensitivity to impurity.
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