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Objective. To identify the major confounding factors of primary venous thromboses and embolisms associated with reproductive behavior of women. Subjects and methods. Retrospective analysis of risk factors for venous thromboembolic events (VTEEs) was made in 53 reproductive-aged (18-45-year-old) women with no history of severe somatic diseases and thromboses. Results. In 67.9% of the patients, the major triggers of primary VTEEs were the use of combined oral contraceptive (COC) pills (43.4%) and pregnancy/postpartum (24.5%). The most common cofactors were lower extremity varices (79.2%), over 35 years of age (62.4%), a sedentary lifestyle (60.4%), smoking (33.9%), obesity (33.9%), and positive family history of thromboses/genetically verified thrombophilia (20.8%). The mean number of background risk factors was 3.4±0.1 in COC users, 3.7±0.2 in pregnant women, and 5.0±0.1 in puerperas. Conclusion. When prescribing COC pills, planning, and managing pregnancy/postpartum, it is necessary to keep in mind that the risk of VTEEs is increased, to thoroughly assess the already existing risk factors, and to take every measure for their prevention.

A stochastic theory of quasi-phase-matched consecutive processes, which takes into account peculiarities of the method of creating a nonlinear lattice in crystals, is developed. The influence of aperiodicity of a certain type on the efficiency of the process of consecutive parametric interaction of light waves with nonmultiple frequencies in crystals with irregular poled structure is studied. It has been established that in aperiodically poled nonlinear crystals the regime of exponentially changing intensity of interacting waves can be implemented. A particular case of nondegenerate parametric amplification is also discussed.

A theory of the interaction between light waves in polydomain crystals with a random variation in the domain thickness described by a random telegraph process is developed. The second harmonic generation and parametric amplification upon high-frequency pumping are considered. It is found that the maximum efficiency of nonlinear conversion is achieved when the phase mismatch between the interacting waves is equal to the doubled spatial frequency at which the nonlinearity sign is changed (the condition of stochastic quasi-phase matching).

The process of parametric amplification with low frequency pumping in the case of aliquant frequencies of interacting waves has been studied. It has been shown that this process can be realized in a periodically poled LiNbO3 crystal. It has been established that in periodically poled nonlinear crystals the regime of exponential changing intensity of interacting waves can be implemented. The highest possible conversion efficiency in the parametrically amplified wave reaches approximately 70%.

A brief review of recent advances in the studies of two coupled three-wave nonlinear optical processes with multiple frequencies, which possess a number of special properties compared to conventional three-wave processes, is presented. The consecutive interactions of co-propagating and counter-propagating light waves in a LiNbO3 crystal with a regular domain structure are considered. The energy exchange upon consecutive interactions of the waves with frequencies ω, 2ω and 3ω is analysed. The prospects of using consecutive nonlinear optical processes in quantum electronics and nonlinear optics are discussed.

The spatial coherence of the radiation emitted by a single-frequency ring Nd : YAG chip laser with a diode pumping was determined. The maximum value of the degrees coherence was 0.99994±0.00003. The factors limiting the spatial coherence of the radiation of low-power diode-pumped solid-state lasers was discussed.

We present results of theoretical and experimental study of the consecutive third harmonic generation in a periodically poled bulk LiNbO/sub 3/:Y crystal. It is shown theoretically that under certain conditions for nonlinear coefficients the energy of wave with frequency /spl omega/ in the consecutive considered interaction can be almost completely converted to the energy of wave with frequency 3/spl omega/.

The possibility of the quasi-phase-matched generation of the second harmonic (λ = 0.542 μm) by self-doubling of the fundamental radiation frequency in an Nd:Mg:LiNbO3 crystal laser having a regular domain structure and pumped by a diode laser (λpump = 0.81 μm) was demonstrated.

Consecutive generation of the third harmonic (i.e. generation of radiation with the doubled frequency followed by frequency summation) radiation from a Q-switched Nd:YAG laser (λ = 1.064 μm) was observed in a Y:LiNbO3 crystal polarised periodically along the z axis. The modulation period of the nonlinear susceptibility was ~ 60 μm. The second and third harmonics of the radiation were generated respectively in the ninth and thirty-third quasi-phase-matching orders.