Fine-Tuning the Physical Properties of Perovskite Related La-Ti-Oxides by Merely Altering the Oxygen Stoichiometry

2000 ◽  
Vol 658 ◽  
Author(s):  
Olav Becker ◽  
Stefan Ebbinghaus ◽  
Bernd Renner ◽  
Armin Reller
Keyword(s):  
Physical Properties ◽  
Structural Changes ◽  
Mixed Valence ◽  
Fine Tuning ◽  
Oxygen Stoichiometry ◽  
Electron Microscopic ◽  
Structural Mechanism ◽  
Oxidation Processes ◽  
Structural Framework ◽  
Intermediate Phases

ABSTRACTThe isostructural oxides LaTiO3.5, SrNbO3.5 and CaNbO3.5 adopt layered structures made up of perovskite related slabs intermitted by layers of non-linking BO6-octahedra (B=Ti, Nb). In these phases the transition metals Ti and Nb are in their highest oxidation states +IV and +V, respectively. They are insulators, in the case of the Ti phase a ferroelectric insulator with the highest known Tc (above 1700°C). By changing the oxygen stoichiometry, i.e. by controlled reduction or re-oxidation processes in the range of 2ABO3.5 ø 2ABO3 + ½ O2 (A=La or Sr, B=Ti or Nb) mixed valence phases are obtained. Accordingly, the physical properties of the different phases alter from insulating to semiconducting or to conducting. Detailed studies on the structural changes reveal, however, that the sublattice of the metal cations is basically conserved. In principle the reduction corresponds to a condensation of the perovskite layers leading to intermediate phases such as the semiconducting LaTiO3.4, in which five TiO6-octahedra thick perovskite slabs constitute the structural framework and 20% of the Ti+IV cations are reduced to Ti+III. Conductivity measurements using single crystals of the corresponding Ti and Nb phases reveal that these mixed valence oxides must be considered as one-dimensional conductors. The fully reduced phases La+IIITi+IIIO3 and Sr+IINb+IVO3 adopt distorted perovskite structures. Extensive high resolution electron microscopic and light microscopic investigations have been carried out in order to characterize the structural mechanism of the reversible, highly topotactic reduction and re-oxidation processes. Thermogravimetric measurements in reducing and oxidizing atmospheres have been performed for the identification of the temperature ranges wherein the decisive mass changes take place. The results of the described experiments support that the properties of such metal oxides can be finely and reversibly tuned by merely changing the oxygen stoichiometries.

Electron microscopic study of the structural changes as a function of temperature in anorthite*

1973 ◽  
Vol 138 (1-4) ◽  
pp. 403-418
Author(s):  
M. Czank ◽  
J. Van Landuyt ◽  
H. Schulz ◽  
F. Laves ◽  
S. Amelinckx
Keyword(s):  
Microscopic Study ◽  
Electron Microscopic Study ◽  
Structural Changes ◽  
Electron Microscopic

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

New insights into the structural basis of integrin activation

Blood ◽  
2003 ◽  
Vol 102 (4) ◽  
pp. 1155-1159 ◽  
Author(s):  
Jian-Ping Xiong ◽  
Thilo Stehle ◽  
Simon L. Goodman ◽  
M. Amin Arnaout
Keyword(s):  
Conformational Changes ◽  
Structural Changes ◽  
Structural Basis ◽  
Integrin Activation ◽  
Cellular Functions ◽  
Electron Microscopic ◽  
The Past ◽  
Intracellular Signals ◽  
Bidirectional Signaling ◽  
New Hypothesis

Abstract Integrins are cell adhesion receptors that communicate biochemical and mechanical signals in a bidirectional manner across the plasma membrane and thus influence most cellular functions. Intracellular signals switch integrins into a ligand-competent state as a result of elicited conformational changes in the integrin ectodomain. Binding of extracellular ligands induces, in turn, structural changes that convey distinct signals to the cell interior. The structural basis of this bidirectional signaling has been the focus of intensive study for the past 3 decades. In this perspective, we develop a new hypothesis for integrin activation based on recent crystallographic, electron microscopic, and biochemical studies.

scholarly journals The effects of simulated microgravity on skeletal muscle of Japanese quail: transmission electron microscopic study

2011 ◽  
Vol 80 (1) ◽  
pp. 119-124 ◽  
Author(s):  
Katarína Holovská ◽  
Viera Almášiová ◽  
Viera Cigánková ◽  
Peter Škrobánek
Keyword(s):  
Skeletal Muscle ◽  
Japanese Quail ◽  
Structural Changes ◽  
Simulated Microgravity ◽  
Negative Impact ◽  
Electron Microscopic ◽  
Giant Mitochondria ◽  
Transmission Electron ◽  
Muscle Tissues ◽  
And Control

The aim of the present study was to investigate the effects of simulated microgravity (hypodynamia) on the structure of the skeletal muscle (m. gastrocnemius) in developing Japanese quail by transmission electron microscopy. Samples of muscle tissues from experimental (n = 28) and control (n = 28) birds were collected at day 7, 14, 28, 42 and 56 of age. The structure of m. gastrocnenmius was changed depending on hypodynamia length. The first extensive structural changes were found on day 14 of age. The mitochondria were enlarged and the spaces between the myofibrils were slightly extended compared to control. The sarcomeres were irregular and lipid droplets occurred in the sarcoplasm. Further developmental changes occurred on day 28 of age. Mitochondria fused into the giant mitochondria which frequently exceeded the length of one sarcomere. Moreover, at 42 days of age, beside the above mentioned changes, sarcoplasmic reticulum was dilated and the number of mitochondrial cristae was reduced. However, the structure of m. gastrocnemius on day 56 was less damaged compared to the damage observed on day 42 of age. Presented results indicate that the continuous stay of male Japanese quail under simulated microgravity has a negative impact on the structure of m. gastrocnemius, but also the ability of muscle tissue to cope with these specific conditions.

scholarly journals Proteolytic and Structural Changes in Rye and Triticale Roots under Aluminum Stress

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 3046
Author(s):  
Joanna Szewińska ◽  
Elżbieta Różańska ◽  
Ewa Papierowska ◽  
Mateusz Labudda
Keyword(s):  
Heavy Metals ◽  
Structural Changes ◽  
Transcript Level ◽  
Fine Tuning ◽  
Gelatinolytic Activity ◽  
Border Cells ◽  
Aluminum Stress ◽  
Transcript Levels ◽  
Root Border Cells ◽  
Level Analysis

Proteolysis and structural adjustments are significant for defense against heavy metals. The purpose of this study was to evaluate whether the Al3+ stress alters protease activity and the anatomy of cereale roots. Azocaseinolytic and gelatinolytic measurements, transcript-level analysis of phytocystatins, and observations under microscopes were performed on the roots of Al3+-tolerant rye and tolerant and sensitive triticales exposed to Al3+. In rye and triticales, the azocaseinolytic activity was higher in treated roots. The gelatinolytic activity in the roots of rye was enhanced between 12 and 24 h in treated roots, and decreased at 48 h. The gelatinolytic activity in treated roots of tolerant triticale was the highest at 24 h and the lowest at 12 h, whereas in treated roots of sensitive triticale it was lowest at 12 h but was enhanced at 24 and 48 h. These changes were accompanied by increased transcript levels of phytocystatins in rye and triticale-treated roots. Light microscope analysis of rye roots revealed disintegration of rhizodermis in treated roots at 48 h and indicated the involvement of root border cells in rye defense against Al3+. The ultrastructural analysis showed vacuoles containing electron-dense precipitates. We postulate that proteolytic-antiproteolytic balance and structural acclimation reinforce the fine-tuning to Al3+.

scholarly journals STRUCTURAL CHANGES IN THE MICROCIRCULATORY BED OF THE PANCREAS IN RATS WITH EXPERIMENTAL METABOLIC SYNDROME

2018 ◽  
Vol 15 (3) ◽  
pp. 347-353
Author(s):  
T. E. Kuznetsova ◽  
E. L. Ryzhkovskaya ◽  
E. I. Kalinovskaya
Keyword(s):  
Metabolic Syndrome ◽  
Glucose Oxidation ◽  
Structural Changes ◽  
Krebs Cycle ◽  
Electron Microscopic ◽  
Microcirculatory Bed ◽  
The Metabolic Syndrome ◽  
Marginal State ◽  
Inflammatory Changes ◽  
Blood Elements

A complex histological, histochemical and electron microscopic study of the state of the microcirculatory bed of the pancreas and conjugate transformations in the parenchyma of the organ after modeling the metabolic syndrome using a diet high in fats and carbohydrates was carried out. Spasm of arterioles, the marginal state of leukocytes and the desquamation of endotheliocytes into the lumen of a vessel, the stasis of erythrocytes in capillaries were revealed. The endothelial cells of capillaries had signs of increased transport of substances through the vessel walls: pinocytosis, fenestration, loosening of basal membranes. It was observed that capillaries are filled with shaped blood elements, on the luminal surface of endotheliocytes nuclei are protruded and the cytoplasm outgrowth into the lumen of the vessel is formed. At the same time, glucose oxidation accelerated both in the Krebs cycle and along the glycolytic pathway in the endotheliocytes of the vessels of the microcirculatory bed, indicating that the energy was supplied to the cells at a higher level. Disturbances of microcirculation were accompanied by focal destructive and inflammatory changes in the parenchyma of the organ.

scholarly journals A study into the structure and physical properties of the Cr18Ni9-grade steel following long-term irradiation as part of the BN-600 reactor internals

2020 ◽  
Vol 6 (1) ◽  
pp. 1-6
Author(s):  
Irina A. Portnykh ◽  
Aleksandr V. Kozlov ◽  
Valery L. Panchenko ◽  
Vyacheslav S. Shikhalev
Keyword(s):  
Physical Properties ◽  
Young’S Modulus ◽  
Structural Changes ◽  
Young's Modulus ◽  
Void Size ◽  
Initial State ◽  
Porosity Distribution ◽  
Grade Steel ◽  
Reactor Internals

The microstructures and physical properties of the austenitic Cr18Ni9-grade steel after 22 and 33 years of operation as part of the reactor internals were tested for assessing the conditions of the BN-600 reactor non-replaceable components (internals) and the potential of their subsequent use in predicting the reactor ultimate life. The paper presents histograms of the porosity distribution depending on the void size, in samples taken from portions that were subjected to neutron irradiation with displacement rates ranging from 1.0×10–9 to 4.3×10–8 dpa/s at temperatures from 370 to 440 °C. The elasticity characteristics were measured by resonance-type ultrasonic technique for the samples taken from the same portions of material. It was demonstrated that swelling calculated using the histograms of the porosity distribution depending on the void size has the maximum value at ~415 °C and after 33 years of irradiation reaches values of ~3%. Long-term variations of Young’s modulus demonstrate non-monotonous dependence on the damage dose. The maximum relative variation of Young’s modulus after 22 and 33 years of operation does not exceed 2% and 6%, respectively, of the values corresponding to the initial state. It was shown that along with the irradiation-induced swelling the changes in the physical properties are also affected in the process of irradiation by other structural changes and, in particular, by the formation of secondary phases. As shown by the results of the studies, operation of the BN-600 reactor internals made of Cr18Ni9-grade steel can be extended beyond 33 years of service. The comparison of the results obtained for the material after 22 and 33 years of operation contains information required for describing subsequent changes of the structure and properties of the Cr18Ni9 internals. The obtained results can be used for forecasting the reactor ultimate life within the framework of existing and developed models.

scholarly journals Zika virus replication in glioblastoma cells: electron microscopic tomography shows 3D arrangement of endoplasmic reticulum, replication organelles, and viral ribonucleoproteins

2021 ◽  
Author(s):  
Johannes Wieland ◽  
Stefan Frey ◽  
Ulrich Rupp ◽  
Sandra Essbauer ◽  
Rüdiger Groß ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Line ◽  
Zika Virus ◽  
Structural Changes ◽  
Electron Tomography ◽  
Glioblastoma Cells ◽  
Electron Microscopic ◽  
N Protein ◽  
Ribonucleoprotein Complexes ◽  
Infected Cells

AbstractStructural changes of two patient-derived glioblastoma cell lines after Zika virus infection were investigated using scanning transmission electron tomography on high-pressure-frozen, freeze-substituted samples. In Zika-virus-infected cells, Golgi structures were barely visible under an electron microscope, and viral factories appeared. The cytosol outside of the viral factories resembled the cytosol of uninfected cells. The viral factories contained largely deranged endoplasmic reticulum (ER), filled with many so-called replication organelles consisting of a luminal vesicle surrounded by the ER membrane. Viral capsids were observed in the vicinity of the replication organelles (cell line #12537 GB) or in ER cisternae at large distance from the replication organelles (cell line #15747 GB). Near the replication organelles, we observed many about 100-nm-long filaments that may represent viral ribonucleoprotein complexes (RNPs), which consist of the RNA genome and N protein oligomers. In addition, we compared Zika-virus-infected cells with cells infected with a phlebovirus (sandfly fever Turkey virus). Zika virions are formed in the ER, whereas phlebovirus virions are assembled in the Golgi apparatus. Our findings will help to understand the replication cycle in the virus factories and the building of the replication organelles in glioblastoma cells.

Sign in / Sign up

Export Citation Format

Share Document