Structural phase transitions and their influence on Cu+ mobility in superionic ferroelastic Cu6PS5I single crystals

The structural origin of Cu+ ions conductivity in Cu6PS5I single crystals is described in terms of structural phase transitions studied by X-ray diffraction, polarizing microscope and calorimetric measurements. Below the phase transition at Tc=(144-169) K Cu6PS5I belongs to monoclinic, ferroelastic phase, space group Cc. Above Tc crystal changes the symmetry to cubic superstructure, space group F-43c (a=19.528); finally at 274K disordering of the Cu+ ions increases the symmetry to F-43m, (a=9.794). The phase transition at 274K coincides well with a strong anomaly in electrical conductivity observed in the Arrhenius plot. Diffusion paths for Cu+ ions are evidenced by means of the atomic displacement factors and split model. Influence of the copper stechiometry on the Tc is also discussed.Comment: conference pape

Kinetics of killer toxin production by Deabryomyces hansenii yeasts

Celem pracy była charakterystyka kinetyki syntezy toksyn killerowych przez 3 szczepy drożdży. Biosynteza toksyn killerowych przebiegała wraz ze wzrostem drożdży, a w przypadku szczepu KI2a również po jego zakończeniu. Aktywność bójcza środowiska hodowlanego wzrastała w trakcie trwania procesów, osiągając poziom 60-70 uU/mL. Szybkość właściwa wzrostu i szybkość właściwa tworzenia toksyn killerowych były najwyższe w przypadku szczepu KI2a i wynosiły odpowiednio μ max = 0,27 h-1 i qur = 0,97 aU/mg biomasy/h.The aim of study was the characterization of killer toxin production kinetics by 3 strains of Debaryomyces hansenii. Biosynthesis of killer toxins was associated with yeasts growth or was elongated afterwards in a case of KI2a strain. Killer activity of toxins increased during the process, reaching the level of 60-70 uU/mL. The strain KI2a showed both the highest growth rate and the specific rate of killer toxins production equal to μmax= 0.27 h-1 and qnr= 0.97uU/mgh, respectively

Ferroelastic domain wall orientations in the (NH₄)₃H(SeO₄)₂ crystal

Experimental and theoretical studies of the ferroelastic domain structure of the (NH₄)₃H(SeO₄)₂ crystal in phases III and IV are performed. Using the refined structural data the orientations of W - and W′-type domain walls, as well as the temperature evolution of the domain structure are investigated. It is shown that in spite of the fact that the room temperature phase III has a triclinic symmetry with small deviations from monoclinic, the domain structure in this phase differs strongly from the structure in the case of a monoclinic symmetry which has been previously accepted in this temperature range. In the monoclinic phase IV all the W′-type domain walls lie almost in parallel to the (001)-plane which explains the invisibility of W′ walls after III-IV phase transition during the observation of the domain structure in the (001)-plane.В роботі проведено експериментальне й теоретичне вивчення доменної структури кристалу (NH₄)₃H(SeO₄)₂ у фероеластичних фазах III і IV. Використовуючи найновіші структурні дані, досліджено орієнтації доменних стінок типу W та W′. Показано, що незважаючи на те, що при кімнатній температурі кристал має триклінну симетрію з незначними відхиленнями від моноклінної, доменна структура сильно відрізняється від тієї, яка отримується для фази з моноклінною симетрією, що було прийнято раніше для цього температурного інтервалу. У моноклінній фазі IV доменні стінки типу W′ майже паралельні до площини (001), що пояснює факт їх зникнення при оптичних спостереженнях у цій площині

Superionic Phase Transition in Rb4\text{}_{4}LiH3\text{}_{3}(SeO4\text{}_{4})4\text{}_{4} Single Crystals

Derivatographic, dielectric and complex impedance studies of Rb$\text{}_{4}$LiH$\text{}_{3}$(SeO$\text{}_{4}$)$\text{}_{4}$ crystals revealed a superionic phase transition at T$\text{}_{s}$ ≈ 448 K. The bulk conductivity rises from 10$\text{}^{-6}$ to 10$\text{}^{-4}$ (Ωm)$\text{}^{-1}$ at T$\text{}_{s}$, and the activation energy of conductivity in the direction of crystal axes a and b (where a = b for tetragonal symmetry) W$\text{}_{a}$ = W$\text{}_{b}$ decreases from 0.94 eV in the low temperature phase to the value of 0.27 eV at T > T$\text{}_{s}$. The analysis of the results of X-ray studies at room temperature and at 450 K indicates that the fast ion transport, characterized by low activation energy, is related to the delocalization of the H2 protons in the O(12)-H2-O(24) bonds linking the Se(1)O$\text{}_{4}$ and Se(2)O$\text{}_{4}$ tetrahedra. The "cogwheel" mechanism is suggested to be involved in the fast proton transport

Fourier Transform Near Infrared Raman Spectroscopy in Studies on Connective Tissue

Studies of tissue such as bones and veins often are carried out by means of microscopic and ultrasonographic methods. Therefore studies of changes caused by pathological or physical factors often are limited to morphological level. Application of Raman spectroscopy permits to associate morphological changes and molecular changes. The paper presents preliminary studies of temperature and ionizing radiation effects on Raman spectra of bone and collagen. Furthermore, effects of pathological factors on Raman spectra of human veins had been studied. It was noticed that heating of bone collagen up to 110°C gives the reversible changes in spectra. In the case of γ-irradiation, any effects were observed up to the dose of 1 MGy on mineral component of bone, whereas the influence on collagen was observed for doses higher than 100 kGy. The Raman spectra of varicose vs. normal veins permit to conclude some important changes observed for veins from chronic venous insufficiency patients