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1,753 results on '"Andreeva, L."'

4. Modeling the Process of Laser Cladding of HPT Blade Scallops

Author

Silensky, M., Latypov, R., Greshilov, K., Andreeva, L., Razin, A., Chaari, Fakher, Series Editor, Gherardini, Francesco, Series Editor, Ivanov, Vitalii, Series Editor, Haddar, Mohamed, Series Editor, Cavas-Martínez, Francisco, Editorial Board Member, di Mare, Francesca, Editorial Board Member, Kwon, Young W., Editorial Board Member, Tolio, Tullio A. M., Editorial Board Member, Trojanowska, Justyna, Editorial Board Member, Schmitt, Robert, Editorial Board Member, Xu, Jinyang, Editorial Board Member, Radionov, Andrey A., editor, and Gasiyarov, Vadim R., editor

Published
2024
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12. Physicochemical Research of Clinically Retrieved CU-NI-TI Orthodontic Archwires

Author

Stoyanova-Ivanova A., Petrov V., Petrova V., Andreeva L., Ilievska I., Zaleski A., and Mikli V.

Subjects
35 °c thermo-active copper niti (cuniti), autoclaving process, dsc, xrd, sem, edx, Medicine
Abstract

In modern orthodontics, thermally activated archwires are used more widely in clinical practice, because they have unique properties like superelasticity and bio-compatibility. The aim of the present study was to characterize commercial 35° C Cu-NiTi archwires in terms of their phase transition behavior, chemical composition, surface topography properties after clinical usage, as well as the influence of the autoclaving process. Materials and methods. 35° C Thermo-Active Copper NiTi (CuNiTi) of ORMCO, Glendora, CA, USA (as-received, as-received autoclaved and clinically retrieved) with rectangular cross-section and dimension 0.016x0.022 inch, were investigated. The physicochemical research was conducted via Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX) and X-ray Diffraction Analysis (XRD). The autoclaving was done in Runyes model B autoclave. Results. The DSC results revealed the austenite start (9.8° C; 26.47° C) and austenite finish (28° C; 31.74° C) temperatures for the as-received and autoclaved archwires respectively. For clinically retrieved samples the austenite finish temperature (Af) is around 27° C. The XRD patterns of the as-received and clinically retrieved samples show almost identical diffraction patterns. Rough surface of the CuNiTi alloy was revealed by the SEM analysis. Autoclaving process seems to have no effects on archwires’ structure and chemical composition. Chemical content of the investigated as-received CuNiTi are Ni, Ti and Cu: 47.07 wt% and 46.81 wt% and 6.11 wt%, respectively. The autoclaving process seems to have little influence on the transition temperature. The results from our study showed little difference (~7 °C) in the finish transition temperatures (Af), compared to the manufacturer’s claim. No intermediate R phase was detected by DSC. Conclusion. A good knowledge of the structural changes that occur in CuNiTi alloys in the oral cavity is useful for the orthodontists in order to optimize orthodontic treatment.

Published
2021
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44. The Social and Political Role of the Russian Orthodox Church as Perceived by College Students

Author

Andreeva, L. A. and Andreeva, L. K.

Abstract

The article compares the data from a survey reflecting college students' perception of the social and political role of the Russian Orthodox Church with the results of nationwide Russian surveys for the purpose of determining the degree to which the basic conclusions coincide or differ. [This article was translated by Kim Braithwaite.]

Published
2015
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47. The Use of D2 and Deuterated Water for the Introduction of a Label into 4-Aminobutanoic Acid.

Author

Shevchenko, V. P., Shevchenko, K. V., Andreeva, L. A., Nagaev, I. Yu., and Myasoedov, N. F.

Subjects
DEUTERIUM, TRIFLUOROACETIC acid, GABA, CATALYTIC converters for automobiles, ACIDS, ISOTOPE exchange reactions
Abstract

The efficiency of incorporating deuterium into 4-aminobutanoic acid (GABA) has been studied. The use of D2O at 200°C makes it possible to introduce into GABA an average of about 0.5 deuterium atoms, D2O with trifluoroacetic acid (1 : 1) at 250°C, an average 1.49 deuterium atoms with a yield of 15%. The solid-phase method permits introducing about 3 deuterium atoms per GABA molecule. During isotopic exchange with D2O, the use of a palladium–rhodium mixture pretreated with deuterium gas made it possible to produce [D]GABA with the deuterium content of 4.5–4.6 atoms. But in both cases, the yields of [D]GABA were low. Preparative amounts of [D]GABA were produced engaging additional supports. The best result was obtained when applying GABA to zeolite. Using D2O with 5% Pd/BaSO4–GABA–zeolite pretreated with deuterium gas, allows producing [D]GABA with an average content of 1.5–2.0 deuterium atoms and a yield of about 30%. [ABSTRACT FROM AUTHOR]

Published
2024
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