Light-Induced Transitions of Polar State and Domain Morphology of Photo-Ferroelectric Nanoparticles

Using the Landau-Ginzburg-Devonshire approach, we study light-induced phase transitions, evolution of polar state and domain morphology in photo-ferroelectric nanoparticles (NPs). Light exposure increases the free carrier density near the NP surface and may in turn induce phase transitions from the nonpolar paraelectric to the polar ferroelectric phase. Using the uniaxial photo-ferroelectric Sn2P2S6 as an example, we show that visible light exposure induces the appearance and vanishing of striped, labyrinthine or curled domains and changes in the polarization switching hysteresis loop shape from paraelectric curves to double, pinched and single loops, as well as the shifting in the position of the tricritical point. Furthermore, we demonstrate that an ensemble of non-interacting photo-ferroelectric NPs may exhibit superparaelectric-like features at the tricritical point, such as strongly frequency-dependent giant piezoelectric and dielectric responses, which can potentially be exploited for piezoelectric applications.Comment: 42 pages, 7 figures, including 14 pages Supplement with 6 figure

The strain-induced transitions of the piezoelectric, pyroelectric and electrocaloric properties of the CuInP2_2S6_6 films

The low-dimensional ferroelectrics, ferrielectrics and antiferroelectrics are of urgent scientific interest due to their unusual polar, piezoelectric, electrocaloric and pyroelectric properties. The strain engineering and strain control of the ferroelectric properties of layered 2D Van der Waals materials, such as CuInP$_2$(S,Se)$_6$ monolayers, thin films and nanoflakes, are of fundamental interest and especially promising for their advanced applications in nanoscale nonvolatile memories, energy conversion and storage, nano-coolers and sensors. Here, we study the polar, piezoelectric, electrocaloric and pyroelectric properties of thin strained films of a ferrielectric CuInP$_2$S$_6$ covered by semiconducting electrodes and reveal an unusually strong effect of a mismatch strain on these properties. In particular, the sign of the mismatch strain and its magnitude determine the complicated behavior of piezoelectric, electrocaloric and pyroelectric responses. The strain effect on these properties is opposite, i.e., "anomalous", in comparison with many other ferroelectric films, for which the out-of-plane remanent polarization, piezoelectric, electrocaloric and pyroelectric responses increase strongly for tensile strains and decrease or vanish for compressive strains.Comment: 16 pages, 5 figures, to be presented at the VI Lithuanian-Polish Meeting on Physics of Ferroelectric

Electrocaloric Response of the Dense Ferroelectric Nanocomposites

Using the Landau-Ginzburg-Devonshire approach and effective media models, we calculated the spontaneous polarization, dielectric, pyroelectric, and electrocaloric properties of BaTiO$_3$ core-shell nanoparticles. We predict that the synergy of size effects and Vegard stresses can significantly improve the electrocaloric cooling (2- 7 times) of the BaTiO$_3$ nanoparticles with diameters (10-100) nm stretched by (1-3)% in comparison with a bulk BaTiO$_3$. To compare with the proposed and other known models, we measured the capacitance-voltage and current-voltage characteristics of the dense nanocomposites consisting of (28 -35) vol.% of the BaTiO$_3$ nanoparticles incorporated in the poly-vinyl-butyral and ethyl-cellulose polymers covered by Ag electrodes. We determined experimentally the effective dielectric permittivity and losses of the dense composites at room temperature. According to our analysis, to reach the maximal electrocaloric response of the core-shell ferroelectric nanoparticles incorporated in different polymers, the dense composites should be prepared with the nanoparticles volume ratio of more than 25 % and fillers with low heat mass and conductance, such as Ag nanoparticles, which facilitate the heat transfer from the ferroelectric nanoparticles to the polymer matrix. In general, the core-shell ferroelectric nanoparticles spontaneously stressed by elastic defects, such as oxygen vacancies or any other elastic dipoles, which create a strong chemical pressure, are relevant fillers for electrocaloric nanocomposites suitable for advanced applications as nano-coolers.Comment: 38 pages, including 10 figures and 2 appendixe

A key to the species of Hyphodontia sensu lato

A dichotomous key to all currently accepted species of Hyphodontia in the broad sense is presented. It consists of a key to genera (Alutaceodontia, Botryodontia, Chaetoporellus, Deviodontia, Hastodontia, Hyphodontia s. str., Kneiffiella, Lagarobasidium, Lyomyces, Palifer, Rogersella, Schizopora, Xylodon) and detailed keys to species level within genera. The key also includes taxa which were published under preliminary names (such as ‘Hyphodontia species A’) and some taxa which require taxonomic clarification (like Hyphodontia macrescens). Some recently describes Hyphodontia species are placed in the keys to Palifer and Xylodon due to their morphology

Research on the basis of foam glass substrates with additions of copper compounds

Obtained artificial substrates, representing a porous glass (foam glass) with additives of 3 to 10% of the mass. copper ions. Glass raw materials were used as raw materials for the synthesis of substrates. In order to create open porosity, a carbonate blowing agent (chalk) was introduced into the initial mixture. Foaming additive served as sodium nitrate, a source of copper ions - copper sulfate (copper sulfate). A distinctive feature of the synthesis method was the combination of wetting the initial mixture and its rapid heating to maximum temperature. This mode was used to increase the porosity of the resulting structure. It was found that the water absorption of the obtained substrates increases with an increase in the concentration of copper ions in them. The resulting materials, due to the increased content of copper ions in them, may have a fungicidal effect. Perhaps their use in crop production, landscape design, the construction industry in conditions of high humidity

Phylogenetic and morphological studies in Xylodon (Hymenochaetales, Basidiomycota) with the addition of four new species

Gefördert durch den Publikationsfonds der Universität Kasse

Xylodon lanatus complex and other additions to Xylodon

Peer reviewe

Phase Transitions in Ferroelectric Domain Walls

Despite multiple efforts, there exist many unsolved fundamental problems related with detection and analysis of internal polarization structure and related phase transitions in ferroelectric domain walls. Their solution can be very important for the progress in domain wall nanoelectronics and related applications in advanced memories and other information technologies. Here we study theoretically the features of phase transitions in the domain walls, which are potentially detectable by the scanning probe capacitance microwave microscopy. The finite element modeling based on the Landau-Ginzburg-Devonshire theory is performed for the capacitance changes related with the domain wall motion in a multiaxial ferroelectric BaTiO3.Comment: 12 pages, 4 figure

Rad51 Protein from the Thermotolerant Yeast Pichia angusta as a Typical but Thermodependent Member of the Rad51 Family

The Rad51 protein from the methylotrophic yeast Pichia angusta (Rad51(Pa)) of the taxonomic complex Hansenula polymorpha is a homolog of the RecA-RadA-Rad51 protein superfamily, which promotes homologous recombination and recombination repair in prokaryotes and eukaryotes. We cloned the RAD51 gene from the cDNA library of the thermotolerant P. angusta strain BKM Y1397. Induction of this gene in a rad51-deficient Saccharomyces cerevisiae strain partially complemented the survival rate after ionizing radiation. Purified Rad51(Pa) protein exhibited properties typical of the superfamily, including the stoichiometry of binding to single-stranded DNA (ssDNA) (one protomer of Rad51(Pa) per 3 nucleotides) and DNA specificity for ssDNA-dependent ATP hydrolysis [poly(dC) > poly(dT) > φX174 ssDNA > poly(dA) > double-stranded M13 DNA]. An inefficient ATPase and very low cooperativity for ATP interaction position Rad51(Pa) closer to Rad51 than to RecA. Judging by thermoinactivation, Rad51(Pa) alone was 20-fold more thermostable at 37°C than its S. cerevisiae homolog (Rad51(Sc)). Moreover, it maintained ssDNA-dependent ATPase and DNA transferase activities up to 52 to 54°C, whereas Rad51(Sc) was completely inactive at 47°C. A quick nucleation and an efficient final-product formation in the strand exchange reaction promoted by Rad51(Pa) occurred only at temperatures above 42°C. These reaction characteristics suggest that Rad51(Pa) is dependent on high temperatures for activity