The opportunity of identification of a pathology of a cervical tissue on the reference interrelation of contributions of the basic endogenic fluorophors in fluorescence spectrum is researched. The mathematical model and results of calculations of contributions of fluorophors at norm and at some pathologies is submitted. The experimental fluorescence spectrum of a cervical tissue has been decomposed on the fluorophor spectrums calculated beforehand. Contributions of fluorophors are received on method of least squares.
The propagation of nanosecond laser pulses in solutions of large-scale carbon nanostructures has been theoretically and numerically investigated in this paper. The three-level ladder-type scheme was used to study the medium with RSA. Numerical simulation of the propagation of nanosecond laser pulses in RSA media was carried out using the classical transport equation for incoherent nonlinear interaction of radiation with the medium described by the proposed three-level model. It is shown that for sufficiently small relaxation times of the medium and high intensity of, a splitting of the transmitted pulse by two is possible.
Experiments and numerical simulations have been carried out to determine the synchronization precision for a laser with brief periodic Q switching which has the ability to synchronize ultrashort output pulses with an external electrical control pulse. For a generation pulse length of 1–2 μs, the physical limit on the synchronization precision is 0.04T, where T is the axial period of the cavity, when the rise time of the Q is 2T for the pulse train. The instability of the synchronization is due primarily to an instability of the rise time and the errors within which the front is coordinated with external processes through electrical sync pulses. When an air-gap switch is used to form the electrical control signal, control pulses with a rise time ∼ 20 ns lead to an instability of less than 1 ns in the synchronization, according to measurements.
The propagation of short light pulses in a three-level medium with reverse saturable absorption taking into account relaxation is considered. It is shown that in such a medium soliton-like pulses of constant duration can propagate. The areas in the five-dimensional parameter space in which such pulses can exist are determined by numerical methods. The parameters of the problem are the characteristics of the medium – the relaxation time, the ratio of the absorption cross sections of the first excited and ground states and the initial transmittance, as well as the characteristics of the pulse – the duration and intensity.
In this paper, the propagation of nanosecond laser pulses in various media with reverse saturable absorption is studied by numerical methods. Numerical simulation of the propagation of nanosecond laser pulses in a three-level medium with reverse saturable absorption was carried out using the classical transport equation for the case of incoherent nonlinear interaction of radiation with the medium described by the proposed three-level model. The degree of pulse deformation in such media is estimated. It is shown that with an increase in intensity, the pulse begins to deform, the pulse front shortens, the trailing edge becomes longer, the asymmetry coefficient increases. An additional maximum begins to form during a trailing edge with a further increase in intensity. As the additional maximum increases, the asymmetry coefficient monotonously decreases to negative values.
The method of analysis of supermodes composition in laser with short-term periodic modulation of losses--nonstationary supermodes--has been suggested and investigated. This method is based on the property of invariance supermode to Fourier-transformation. In experiment this is displayed by a regular modulation of integral spectrum of generation such laser in case, when individual supermode is generated. Realization of method makes possible to obtain detailed data about dynamics of generation laser and also to solve problems of control the parameters of characteristic for a given laser high-energy ultrashort pulses.
The possibilities of realizing an intracavity self injection regime in laser with short-term resonant modulation of losses (STRML) have been investigated. It is shown by calculations, analytically and experiments that natural chirp is proposer to USP of the STRML-laser. The monoblock construction of electrooptical double modulator for the STRML-laser has been represented.
Methods of pulse oximetry and photoplethysmography are widely used in clinical medicine and practice of biomedical research outside the clinic. The advantages of the method are high efficiency of preparation for the diagnostic procedure, non-invasive, complete safety for health. The method provides the possibility of unlimited long - term monitoring of the dynamics of saturation and desaturation of hemoglobin. In combination with the above, subject to the qualitative registration of photoplethysmograms, the method allows the calculation and analysis of a number of indicators of peripheral blood circulation: the total pulse blood flow to the study region, the tone of arterial vessels of different diameters, the state of capillary blood flow. Most modern foreign models of pulse oximeters are integrated devices that provide measurement of a very limited set of physiological parameters: the percentage of hemoglobin oxygen saturation and pulse rate. The range of pulse oximeters containing the interface with the personal computer and providing operational calculation of indicators of peripheral photoplethysmograms is small. Such devices have a fairlyhigh cost and are not portable. The development of domestic integrated electronic devices is extremely relevant, allowing along with obtaining information about blood oxygenation to perform continuous monitoring of peripheral blood circulation. The authors developed an electronic module that provides long-term registration of photoplethysmograms in the infrared and red areas of the light spectrum. The electronic module is made exclusively with the use of domestic active radio elements – discrete semiconductor devices and integrated circuits. The device was developed in full compliance with the import substitution policy pursued by the President and the Government of the Russian Federation. The advantage of the device is the "open architecture" of the electronic circuit, which provides four analog signals suitable for further digitization. The signals contain information about pulsating and non-pulsating components of the optical density of biological tissue in the infrared and red ranges of the spectrum. The device has an electronic filter of mains interference. Tests of the device demonstrated high quality of photoplethysmograms. This makes it possible tosuccessfullyuse the device for studies of hemoglobin oxygenation and peripheral hemodynamics.
Results of numerical model operation of the x-ray radiation spectra and values of the magnetic field induction of the laser plasma received on aluminium and copper targets under action of USP are presented in this work. In calculations the mathematcial model including combined equations of ideal magnetohydrodynamics in vie of tranpsor ot laser radiation and a self-radiation of laser plasm, supplemented by equations of state and tabulared absorption constant was used. Calculations have shown the oscillation of the x-rays in a pectral rang 1-10 keV with intensity up to 1011 W/cm2. It is revealed that the accoutn of a heating of plasma by the laser USP changes sharply the morphology of a powerful shock plams wave. Calucation has shown that near to a surface of a target there is an oscillation of spontaneous magnetic fields with an induction about 5•107 Gs. And medial value of a magnetic field induction on a copper target in 1. times is more than on an aluminium target. The electron concnetration in laser plams on a copper target, on the average, in 1.3 times is more than on an aluminium target. The velocity of a motion of front of laser plama is ovservationally estimaed at an optical breakdown in atmosphere which ahs made quantity about 7.5•106cm/s.
A model of the laser pulse propagation through a medium with a special mechanism of optical limiting - the effect of the reverse saturated absorption - was proposed. It is shown that the propagation through three-level medium with reverse saturable absorption leads to decrease duration and transformation of the profile of the pulse. Analytical expressions for the maximum intensity shift and change of duration of the laser pulse were obtained.
