Luminescence properties and time-resolved spectroscopy of rare-earth doped SrMoO4 single crystals

The work of V. Pankratova was supported by the financial support of Scientific Research Project for Students and Young Researchers (SJZ/2020/05) realized at Institute of Solid State Physics, University of Latvia. The Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.Luminescence properties of nominally pure and doped with Eu3+ and Pr3+ ions SrMoO4 single crystals grown by the Czochralski method have been studied. Thermal quenching of intrinsic emission of pure and doped SrMoO4 single crystals has been observed, as well as a correlation of thermal quenching activation energies with rare-earth ion concentration has been observed. Tunable laser was used to study time-resolved luminescence in a range from 10 K to room temperature. The effect of dopant nature and concentration on intrinsic emission and decay kinetics has been elucidated. --//-- Viktorija Pankratova, Elizaveta E. Dunaeva, Irina S. Voronina, Anna P. Kozlova, Roman Shendrik, Vladimir Pankratov, Luminescence properties and time-resolved spectroscopy of rare-earth doped SrMoO4 single crystals, Optical Materials: X, Volume 15, 2022, 100169, ISSN 2590-1478, https://doi.org/10.1016/j.omx.2022.100169. Article published under the CC BY-NC-ND licence.Scientific Research Project for Students and Young Researchers (SJZ/2020/05); the Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Social representations of HIV/AIDS in five Central European and Eastern European countries: A multidimensional analysis

Cognitive processing models of risky sexual behaviour have proliferated in the two decades since the first reporting of HIV/AIDS, but far less attention has been paid to individual and group representations of the epidemic and the relationship between these representations and reported sexual behaviours. In this study, 494 business people and medics from Estonia, Georgia, Hungary, Poland and Russia sorted free associations around HIV/AIDS in a matrix completion task. Exploratory factor and multidimensional scaling analyses revealed two main dimensions (labelled ‘Sex’ and ‘Deadly disease’), with significant cultural and gender variations along both dimension scores. Possible explanations for these results are discussed in the light of growing concerns over the spread of the epidemic in this region

Values of sexual behaviour in Central and Eastern Europe

Despite the profusion of social cognitive models for the prediction of sexual behaviour, we have only limited knowledge as to the role of individual values in predicting risky sexual activity. This study assessed the relationship between a recently developed value structure and sexual behaviour in the context of rising HIV infection in central and eastern Europe. Five hundred and three respondents (business people, doctors and nurses) from Estonia, Georgia, Hungary, Poland and Russia completed Schwartz’s Portrait Values Questionnaire and reported their condom use, partnership history and record of sexual disease. Results indicated that values had a moderate but consistent relationship with sexual behaviour, with riskier sexual activity reported by those high on Openness to Change, Hedonism and Self-Enhancement. These findings are discussed in the context of the need for culturally sensitive interventions in order to tackle the growing HIV epidemic in this region.This project was supported by a research grant from the Research Support Scheme operated by the Soros Foundation, Prague

Reducing Drag of Body by Adding a Plate

This paper focuses on theoretical investigations of the location of a separation point laminar boundary layer on the surface of a circular cylinder. The investigations were carried out by CFD software FlowSimulation. The displacement of the separation point on the surface of the circular cylinder is achieved by installing a flat plate in front of the cylinder parallel to the flow. It was found that the greatest displacement of the separation point to the back of the cylinder is possible when the chord of the plate equals to a quarter of the diameter of the circular cylinder. The flat plate allows not only to change the position of the separation point but also to reduce the drag by about 25%

Reducing Drag of Body by Adding a Plate

This paper focuses on theoretical investigations of the location of a separation point laminar boundary layer on the surface of a circular cylinder. The investigations were carried out by CFD software FlowSimulation. The displacement of the separation point on the surface of the circular cylinder is achieved by installing a flat plate in front of the cylinder parallel to the flow. It was found that the greatest displacement of the separation point to the back of the cylinder is possible when the chord of the plate equals to a quarter of the diameter of the circular cylinder. The flat plate allows not only to change the position of the separation point but also to reduce the drag by about 25%

Impedance spectroscopy study of lanthanum-gallium tantalate single crystals grown under different conditions

The effect of the growth atmosphere and the type of deposited current conductive coatings on the impedance/admittance of La3Ta0.5Ga5.5O14 lanthanum-gallium tantalate has been revealed. The lanthanum-gallium tantalate single crystals have been grown in argon and argon with admixture of oxygen gas atmospheres. Current conductive coatings of iridium, gold with a titanium sublayer, and silver with a chromium sublayer have been deposited onto the single crystals. The tests have been carried out taking into account the polarity of the specimens. The temperature and frequency dependences of the admittance of lanthanum-gallium tantalate have been measured in an alternating electric field at frequencies in the 5 Hz to 500 kHz range and temperatures from 20 to 450 °C. The specimens with gold current conductive coating have the lowest admittance. Analysis of the temperature and frequency functions of the dielectric permeability has shown the absence of any frequency dependence in the entire test range. Equivalent electric circuits have been constructed. Graphic-analytic and numeric analysis of the equivalent electric circuits of the electrode/langatate/electrode cells has shown that the admittance of the metal/langatate/metal cells is controlled by the electrochemical processes at the electrode/electrolyte/electrode interface. The absolute values of the impedance components depend on the langatate growth conditions and the type of the electrodes. Our measurements suggest that the material of the current conductive coating has a greater effect on the absolute values of the measured parameters than the growth atmosphere

Impedance spectroscopy study of lanthanum-gallium tantalate single crystals grown under different conditions

The effect of the growth atmosphere and the type of deposited current conductive coatings on the impedance/admittance of La3Ta0.5Ga5.5O14 lanthanum-gallium tantalate has been revealed. The lanthanum-gallium tantalate single crystals have been grown in argon and argon with admixture of oxygen gas atmospheres. Current conductive coatings of iridium, gold with a titanium sublayer, and silver with a chromium sublayer have been deposited onto the single crystals. The tests have been carried out taking into account the polarity of the specimens. The temperature and frequency dependences of the admittance of lanthanum-gallium tantalate have been measured in an alternating electric field at frequencies in the 5 Hz to 500 kHz range and temperatures from 20 to 450 °C. The specimens with gold current conductive coating have the lowest admittance. Analysis of the temperature and frequency functions of the dielectric permeability has shown the absence of any frequency dependence in the entire test range. Equivalent electric circuits have been constructed. Graphic-analytic and numeric analysis of the equivalent electric circuits of the electrode/langatate/electrode cells has shown that the admittance of the metal/langatate/metal cells is controlled by the electrochemical processes at the electrode/electrolyte/electrode interface. The absolute values of the impedance components depend on the langatate growth conditions and the type of the electrodes. Our measurements suggest that the material of the current conductive coating has a greater effect on the absolute values of the measured parameters than the growth atmosphere