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Professional competence, critical thinking, teamwork ability, foreign language contribute to competitiveness of a modern graduating student. Project-based learning has a proven educational potential: motivates research, creates opportunities to express oneself, develops communicative competence and abilities to work in a team. This paper researches the conditions for the use of project-based learning at foreign language classes; the stages for the project realization; offers approved project on the topic «Sport». Methodology: theoretical analysis of psychological, pedagogical and methodical literature, personal work experience analysis. Practical implications: foreign language teaching.

The examination of all persons suspected in the use narcotics (including suppliers and vendors of drugs) in Svetlogorsk (Belarus) for the presence of antibodies to HIV revealed 811 cases of HIV infection, i.e. 1% of the whole population was found to be infected by HIV. More than 90% of all HIV-infected persons were drug addicts introducing narcotic intravenously; young people aged 18 to 29 years constituted 81% (of these, 76% were males and 24% were females). The rapid spread of HIV was caused by the use of a ready-made HIV-infected drug which had been supplied for sale and could have been infected in the process of manufacture or packing.

The paper presents laser sets, including forsterite laser, applicable for the HpD therapy. We describe the laser sets pumped by the Q-switched Nd:YAG laser pulse (20 ns), generating radiation within a therapeutic range (λ = 630 nm) and diagnostic one (λ = 410 nm). The tunable range of the set is λ = ± 20 nm for FH (λ = 1260 nm) and Δλ = ± 10 nm for the SH of forsterite laser (λ = 630 nm).

The paper presents laser set, including forsterite laser, applicable for the HpD therapy. The forsterite laser pumped by the q-CW Nd:YAG laser, at 20 W of a pump power, (Nd:YAG q-cw laser with a wide TM00 mode) can generate radiation of average power of about 400 mW at wavelength of λ = 1270 nm or radiation of average power of 25 mW at wavelength of 630 nm. The tunable range of the set is λ = ± 20 nm for FH (λ = 1260 nm) and Δλ = ± 10 nm for the SH of forsterite laser (λ = 630 nm).

The paper presents laser sets, including forsterite laser, applicable for the HpD therapy. We describe the laser sets pumped by the Q-switched Nd:YAG laser pulse, generating radiation within a therapeutic range and diagnostic one as well as the set generating within the q-W regime. We discuss the results of investigations carried out with the laser set for diagnosis. The set comprises the KZnF3 laser with a ruby pump. The forsterite laser pumped by the q-CW Nd:YAG laser, at 20 W of a pump power, can generate radiation of average power of about 400 mW at wavelength of (lambda) equals 1270 nm or radiation of average power of 150 mW at wavelength of 630 nm. The tunable range of the set is (lambda) equals +/- 20 nm FH and (Delta) (lambda) equals +/- 10 nm for the SH of forsterite laser. We have also analyzed other laser sets fulfilling requirements of the HpD diagnosis and therapy.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The possible laser systems for HpD tumors diagnostics and therapy are presented in this paper. The principal laser system for those applications is based on Forsterite laser. Generation two wavelengths -- for therapy ((lambda) equals 630 plus or minus 10 nm) and diagnostics ((lambda) equals 400 plus or minus 5 nm) are possible in those systems.

Cr4+ doped forsterite crystal is an easily lasing medium. The first laser action in this crystal has been achieved by Petricevic et. al. [1]. Many authors have described their experiments presented Cr:Forsterite laser actions in different regimes (CW, pulsed, mode-locked) [2, 3, 4]. It has been established that stimulated transitions between 3T2 and 3 A2 levels of the Cr4+ ion are responsible for lasing of this medium in the range of wavelength 1, 15 — 1.35 μm [5]. The Cr:Forsterite laser is usually pumped by 1.06 um Nd:YAG laser radiation. The absorption at 1.06 μm results in population of the 3T2 state (an upper laser level) and depopulation of the ground 3A2 state. The ground 3A2 state may be strongly depopulated till complete blenching of the Cr:Forsterite crystal. This is a characteristic behaviour of a saturable absorber.

The forsterite laser Mg2 SiO 4:Cr4+ is an effective tunable source in the spectral range 1,15–1,35 μm [l] and it is a subject of interest for a number of researches. The laser in this wavelength range is expected to be useful in medical, diagnostic and laboratory applications.

As it was mentioned in the papers [1,2] the Ti:Sapphire and Cr:Forsterite tunable lasers can be used as basic sources for getting tunable coherent radiation in the spectral range 0,2–5,5 μm and even wider. The central part of this range 0,68–1,37 μm is covered by the main frequency generation of Ti:Sapphire and Cr:Forsterite lasers. The short-wavelength is covered by harmonic generation of the new nonlinear crystals, such as BBO, LBO, KTP [3 – 5]. The long-wavelength part of the above mentioned range was gained by the differece frequency generation of tunable lasers (in the dual-wavelength regime) or tunable and pump lasers. In this case the main problem is the synchronization of pulses to be mixed. Different methods were used for this problem solution [6,7]. Besides the synchronization difficulty, this method has a principal deficiency - energetic efficiency limit at a given wavelength. In this proces the long-wavelength is loosing and the energetic efficiency is less than one. The middle and far IR generation efficiency is especially noneffective. In this case the long-wavelength quantum energy (hv l) is comparable with short-wavelength quantum hv s .

Results of tuned Ti:sapphire laser investigations are presented in this paper. Shortening and stabi 1 i zat ion of pulse durat ion have been achieved us ing the SBS cell inside of the laser cavity. The main advantages of this laser and its features are shown. i:© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Tetrahydropyran (THP) forms a clathrate hydrate THP·17H2O of cubic structure II which melts at P = 1 atm, T= – 0.8°C decomposing into two liquids with an upper consolute temperature of dissolution of 226 °C. It is destabilized by pressure and at P > 1.15 kbar, T= – 4.3°C cubic structure I hydrate appears to become stable.

A source of tunable coherent radiation based on the use of Ti(3+):Al(2)O(3) crystals pumped by Cu-vapor laser radiation is studied experimentally. This source is promising for applications to atmospheric sensing as well as for use in applied optics and spectroscopy studies. Energy, kinetic, spectral, and spatial characteristics of lasing in nonselective and selective cavities and in the master oscillator power amplifier system are measured. Based on the latter scheme an experimental model of the source is developed. It permits continuously tunable radiation to be obtained in two spectral regions, i.e., within the fundamental band from 680 to 980 nm with a maximum average output power of ~2.6 W and in its second harmonic range from 340 to 490 nm with a maximum average output power of 450 mW. The linewidth of the emission is ~2 pm everywhere in the operating wavelength ranges, and the beam divergence is close to that of the diffraction. The pulse repetition rate is 5 kHz. A further increase in the output power is possible.

Observations of the deformations caused by construction of the Nurek hydroelectric station (on the Vakhsh River, USSR) were carried out during and after the construction period. Observations were made both in the dam foundation and in the reservoir flanks in vertical and horizontal directions. Observation data indicate that the dam foundation experienced uneven settling both over area and in time. The maximum deformations were found to correspond to the maximum loads. These actual data indicate that the construction of a dam and creation of a reservoir cause deformations of the rock mass in an extensive region, and the specific settlement depends upon the strength and density of the rocks composing the foundations and also upon the pressure created by the dam's weight. The geodetic observations are continuing at the Nurek hydroelectric station to monitor the possible movements of the rock blocks and the effects of these movements on the normal operation of individual structures of the hydrostation. 3 references, 2 figures, 4 tables.

To study the role of stepwise and relaxation processes under effective excitation of anti-Stokes luminescence of rare-earth (RE) ions in crystals the time-shifted pulse method is used. It is shown that direct comparison of measured single- and two-photon luminescence excitation spectra often enables one to make immediate conclusions on the position and classification of electron levels of RE ions. The Tb3+ and Eu3− level structures (crystal CaF2) in the near ultraviolet are considered as an example. The peculiarities connected with the polarization characteristics of the two-photon absorption of radiation by the trivalent RE ions in a crystal matrix are discussed. To obtain the two-photon spectra a frequency-tunable organic dye solution laser (ODSL) is used. [Russian Text Ignored].

In tunable travelling wave lasers a ring resonator is often used with an amplitude gate consisting of output and return mirrors situated perpendicular to the optical axis of the resonator. To obtain narrow-band output a selector is additionally placed in the negative feedback path. Here the selection, accomplished due to the competition of the waves passing through the negative feedback path and the waves forming inside the ring portion of the resonator, slowly grows in time. The disadvantage of the time required for selection under these conditions is pronounced in pulsed lasers where the time to form narrow-band generation is equivalent to the pumping pulse duration. To overcome this a gain medium is usually introduced into the negative feedback path. This paper examines another means for increasing the effectiveness of selection of the negative feedback path which involves the use of ring antiresonance. A mathematical model depicting this technique is constructed and experimental verification of the method is carried out in a dye laser pumped by a YAG laser. The ring antiresonance resonator is found to be superior to both a linear resonator and a traditional ring resonator both energetically and in its spectral characteristics.

Stable 4,4′-diethoxydiphenyl nitric oxide radicals can be used as effective inhibitors of the thermal polymerization of styrene and polymerization initiated with azoisobutyrodinitrile and benzoyl peroxide. Rate constants and activation energies of inhibition of polymerization o styrene with 4,4′-diethoxydiphenyl nitric oxide were calculated.

The spectroscopic and lasing characteristics of laser-pumped Al2O3:Ti3+ crystals are presented. A conversion efficiency of 42% was achieved in a nonselective resonator. In a selective resonator, the output wavelength was tunable in the range 675–945 nm and the maximum efficiency was 25%. In the pulse-periodic regime, pulse energies of up to 40 mJ were obtained and the average power was ~1.5 W with a divergence of ~1.2 mrad. The lasing kinetics were studied. When excitation by a dye laser was used (τp=5μsec), the characteristic features of free lasing were investigated and the Q-switched regime was realized. A study was made of the influence of the structural characteristics of the Al2O3:Ti3+ crystals on the spectral, energy, and other lasing characteristics.

Invention and scientific and technological progress. One of the main tasks before us in the development of the national economy of our country in light of the decisions of the XXVI Congress of the CPSU is increasing the pace of scientific and technological progress as a decisive condition for transferring the economy to a path of intensive development and raising the effectiveness of public production.1 Scientific and technological progress is a dynamic and multifaceted process of improving all aspects of public production on the basis of science, technology, and the leading experience. Its essence consists in the fact that scientific progress joins technological progress in the single process of the scientific and technological development of society.2

An investigation was made of the output characteristics of an Al2O3:Ti3+ crystal laser pumped by radiation from a copper vapor laser. An average output power of 1.5 W was obtained when the pump power absorbed in the crystal was 15 W and the differential efficiency (in terms of the absorbed energy) was ~ 29%. A dispersive resonator with a diffraction grating on an autocollimation configuration was used to tune the output wavelength within the range 700–900 nm and the spectral width of the line was ~ 0.8 nm. An analysis was made of the influence of the temperature of the crystal on the output characteristics of the laser.