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L'viv, Ukraine

Kuznik W.,Debrecen University | Kuznik W.,Czestochowa University of Technology | Rakus P.,Czestochowa University of Technology | Parasyuk O.V.,European University at Kiev | And 3 more authors.
Materials Letters

We present a growth and photoinduced piezeoelctricity for novel chalcogenide single crystalline alloys - AgGaGe3-xSnxSe8. The titled crystals possess promising laser-operated piezoelectric properties. A specific procedure of Bridgman-Stockbarger method synthesis is described. The effective piezoelectric tensor coefficient deff is reduced by 74% upon illumination with a 400 mW 532 nm continuous wave laser. The relaxation of the piezoelectricity after switching off of the laser is explored. A principal role of Sn ions is demonstrated. © 2015 Elsevier B.V. Source

Banakh T.,Lviv University | Petrenko O.,Kyiv University | Protasov I.,Kyiv University | Slobodianiuk S.,Kyiv University
Electronic Journal of Combinatorics

Let G be a group and X be a G-space with the action G× X → X, (g, x) → gx. A subset F of X is called a kaleidoscopical configuration if there exists a coloring X: X → C such that the restriction of X on each subset gF, g ∈ G, is a bijection. We present a construction (called the splitting construction) of kaleidoscopical configurations in an arbitrary G-space, reduce the problem of characterization of kaleidoscopical configurations in a finite Abelian group G to a factorization of G into two subsets, and describe all kaleidoscopical configurations in isometrically homogeneous ultrametric spaces with finite distance scale. Also we construct 2 c (unsplittable) kaleidoscopical configurations of cardinality c in the Euclidean space R n. Source

Bovgyra O.V.,Lviv University | Kurlak V.Y.,Lviv University | Chrunik M.,Military University of Technology | Majchrowski A.,Military University of Technology | And 2 more authors.
Optical Materials

Polarized optical functions near the fundamental absorption edge of novel Cs3Zn6B9O21 nonlinear optical crystals possessing a wide UV transparency down to 190nm were investigated. The anisotropy of optical functions is not well studied yet which restrains the further strategy of the formation on its base of solid state compounds with desirable properties. The studies were performed using a band structure calculations as well as the experimental measurements of fundamental polarized UV absorption edge and X-ray photoelectron spectra of the studied crystals. The experimental data were used for evaluation of scissor factors of the band structure. The results of the calculations were compared with the XPS and polarized absorption optical spectra of the investigated crystals. The introduction of the scissor factor was performed in order to obtain a sufficient agreement with experiment. The observed anisotropy of absorption may be explained by the anisotropy of carrier effective masses. © 2015 Elsevier B.V. Source

Bunio L.V.,Lviv University | Tsvilynjuk O.M.,Lviv University
Contemporary Problems of Ecology

Specific features of sedge (Carex hirta) development on oil-contaminated soils are studied for the first time. A decrease in morphometric parameters of leaves and rhizomes and the enlargement of roots under the effect of oil are revealed. The plants of sedge on oil-contaminated soils are characterized by a reduced period of morphogenesis and early ageing of leaves. Rhizomes of these plants are less branched. Their plagiotropic growth is short-term and soon gives way to orthotropic growth. Our investigations yield new data on the morphology, morphogenesis, and ecology of C. hirta. © 2015, Pleiades Publishing, Ltd. Source

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