Oxygen Content and Thermodynamic Stability of YBaCo2O6-delta Double Perovskite

The thermodynamic stability of the double perovskite YBaCo2O6−δ was studied using the coulometric titration technique and verified by measurements of the overall conductivity depending on oxygen partial pressure at a given temperature. As a result, the stability diagram of YBaCo2O6−δ was plotted. YBaCo2O6−δ was found to be thermodynamically stable in air at 850°C and higher temperatures, whereas its thermodynamic stability at 900°C is limited by the range of oxygen partial pressures −3.56 ≤ log(pO2/atm) ≤ −0.14. Oxygen content in YBaCo2O6−δ slightly decreases at 900°C from 5.035 at log(pO2/atm) = −0.14 to 4.989 in the atmosphere with log(pO2/atm) = −3.565 indicating a crucial role which variation of Co+3/Co+2 ratio plays in its stability. YBaCo2O6−δ decomposes into the mixture of YCoO3 and BaCoO3−z at the high pO2 stability limit, whereas YBaCo4O7, BaCo1−xYxO3−γ, and Y2O3 were identified as the products of its decomposition at the low pO2 one

Abnormal methylation of PRDM16 and PTPRN2 genes in chorionic villi in miscarriage

Relevance. Abnormal epigenetic regulation of genes responsible for the development of the embryo and placenta is associated with many pregnancy pathologies. Aim. The aim of this work was to analyze the prevalence of abnormal methylation of the PRDM16 and PTPRN2 genes in chorionic villi of spontaneous abortions with normal karyotype and with the most frequent aneuploidies (trisomy 16 and monosomy X). Materials and Methods. The methylation profile was evaluated using targeted bisulfite massive parallel sequencing in chorionic villi of induced abortions (n = 10), spontaneous abortions with normal karyotype (n = 39), trisomy 16 (n = 17) and monosomy X (n = 20) and peripheral blood lymphocytes of healthy volunteers (n = 6). Results and Discussion. In analyzed genes, differential methylation of individual CpG sites was found in chorionic villi of spontaneous abortions. Despite the absence of significant differences between the groups in the average level of methylation in analyzed gene regions, abnormal methylation of the PRDM16 and PTPRN2 genes were detected for 33 % and 5 % of spontaneous abortions, respectively, indicating a high incidence of epigenetic abnormalities in these genes in the chorionic villi of spontaneous abortions. The level of methylation of the PRDM16 gene significantly correlated with the level of methylation of the retrotransposon LINE-1, which indicates the generalized nature of methylation disorders in spontaneous abortions. Finally, the level of methylation of the PTPRN2 gene depended on the age of mothers of spontaneous abortions with monosomy X, which raises the question of the influence of maternal factors on the methylation profile in this group of spontaneous abortions. Conclusion. The results indicate that epigenetic disorders of the PRDM16 gene may be associated with spontaneous termination of pregnancy in the first trimester

Growth, Diet and Fatty Acid Composition of Gibel Carp Carassius Gibelio in Lake Shira, a Brackish Water Body in Southern Siberia

For the first time the presence of gibel carp Carassius gibelio has been detected in the brackish meromictic Lake Shira (Southern Siberia, Republic of Khakassia). Lake Shira has been continuously studied since the late 19th century, and it has been considered so far that there is no ichthyofauna in the lake. This work investigates the growth and population characteristics, as well as food spectra and fatty acid composition of C. gibelio specimen at different ages that were fished out in the summers of 2007 and 2008. The water salinity at the fishing point was 15 g l-1. The food spectrum of one- and two-year old C. gibelio was dominated by diatomic, green and blue-green algae, while four- to sixyear old species had an increased share of copepods, beetles and chironomids in their food spectrum, and beginning from the age of six years the amphipods Gammarus lacustris consisted significant part of gibel carp diet. Thus, it was shown that C. gibelio is a carnivore with regard to the population of amphipods Gammarus lacustris, which have been regarded so far as the upper link in the trophic cascade of Lake Shira. One of the possible reasons for appearance of fish is the decreased water salinity caused by rising of the lake level. In the recent years, the level of Lake Shira exceeded all the values that had been registered since the late 19th century, and the lakes salinity decreased correspondingly to its smallest value for the whole period of observation.В солоноватом меромиктическом оз. Шира (Южная Сибирь, Республика Хакасия) зарегистрировано присутствие серебряного карася Carassius gibelio. Озеро Шира непрерывно изучается с конца XIX в., и до сих пор считалось, что ихтиофауна в данном озере отсутствует. В настоящей работе исследуются морфологические характеристики, спектр питания и жирнокислотный состав особей Carassius gibelio различного возраста, выловленных в оз. Шира в летнее время 2007 и 2008 гг. Соленость воды в местах вылова была около 15 г/л. Среди пищевых компонентов особей возраста 1-2 лет преобладали диатомовые, зеленые и сине-зеленые водоросли. У особей от четырех до семи лет в пище увеличивалась доля копепод, жуков и хирономид. Начиная с шестилетнего возраста значительную долю в рационе составляли бокоплавы Gammarus lacustris. Таким образом, серебряный карась может быть хищником по отношению к популяции Gammarus lacustris, который до сих пор считался верхним звеном трофического каскада в экосистемы оз. Шира. Одна из возможных причин появления карася в озере - снижение солености, обусловленное повышением уровня озера. В последнее десятилетие уровень оз. Шира превысил все значения, известные для данного озера с конца XIX в. Соответственно, соленость воды в озере снизилась до минимального значения из всех зарегистрированных ранее

Thermodynamics of Formation and Disordering of YBaCo₂O_6-δ Double Perovskite as a Base for Novel Dense Ceramic Membrane Materials

Differential scanning calorimetry studies of the complex oxide YBaCo2O6-δ (YBC), combined with the literature data, allowed outlining the phase behavior of YBC depending on the oxygen content and temperature between 298 K and 773 K. The oxygen nonstoichiometry of single-phase tetragonal YBC was measured at different temperatures and oxygen partial pressures by both thermogravimetric and flow reactor methods. The defect structure of YBC was analyzed. As a result, the thermodynamic functions (∆Hi○, ∆Si○) of the defect reactions in YBC were determined. Experimental data on the oxygen content and those calculated based on the theoretical model were shown to be in good agreement. Standard enthalpies of formation at 298.15 K (∆Hf○) were obtained for YBC depending on its oxygen content using solution calorimetry. It was found that ∆Hf○ = f(6-δ) function is linear in the range of (6-δ) from 5.018 to 5.406 and that its slope is close to the value of the enthalpy of the quasichemical reaction describing oxygen exchange between the oxide and ambient atmosphere, which confirms the reliability of the suggested defect structure model

Phase Behavior and Defect Structure of HoBaCo₂O_6-δ

The differential scanning calorimetry study showed that the double perovskite HoBaCo2O6-δ (HBC), depending on its oxygen content, undergoes three phase transitions in the temperature range 298–773 K. Their origin was tentatively explained using the relevant literature data. For the single-phase tetragonal HBC, the oxygen nonstoichiometry dependences on the oxygen partial pressure were investigated by thermogravimetric and flow reactor methods in the intermediate-temperature range of 573–773 K. The proposed defect structure of HBC was successfully verified using the obtained data on its oxygen nonstoichiometry combined with those reported earlier. As a result, the values of the thermodynamic parameters (∆Hi∘, ∆Si∘) of the defect reactions proceeding in HBC were determined. The defect structure of HBC was shown to be similar to that of YBaCo2O6-δ (YBC) likely due to similar ionic radii of Ho3+ and Y3+

Nonstoichiometry, Defect Chemistry and Oxygen Transport in Fe-Doped Layered Double Perovskite Cobaltite PrBaCo2−xFexO6−δ (x = 0–0.6) Membrane Materials

Mixed conducting cobaltites PrBaCo2−xFexO6−δ (x = 0–0.6) with a double perovskite structure are promising materials for ceramic semi-permeable membranes for oxygen separation and purification due to their fast oxygen exchange and diffusion capability. Here, we report the results of the detailed study of an interplay between the defect chemistry, oxygen nonstoichiometry and oxygen transport in these materials as a function of iron doping. We show that doping leads to a systematic variation of both the thermodynamics of defect formation reactions and oxygen transport properties. Thus, iron doping can be used to optimize the performance of mixed conducting oxygen-permeable double perovskite membrane materials

Growth, Diet and Fatty Acid Composition of Gibel Carp Carassius Gibelio in Lake Shira, a Brackish Water Body in Southern Siberia

For the first time the presence of gibel carp Carassius gibelio has been detected in the brackish meromictic Lake Shira (Southern Siberia, Republic of Khakassia). Lake Shira has been continuously studied since the late 19th century, and it has been considered so far that there is no ichthyofauna in the lake. This work investigates the growth and population characteristics, as well as food spectra and fatty acid composition of C. gibelio specimen at different ages that were fished out in the summers of 2007 and 2008. The water salinity at the fishing point was 15 g l-1. The food spectrum of one- and two-year old C. gibelio was dominated by diatomic, green and blue-green algae, while four- to sixyear old species had an increased share of copepods, beetles and chironomids in their food spectrum, and beginning from the age of six years the amphipods Gammarus lacustris consisted significant part of gibel carp diet. Thus, it was shown that C. gibelio is a carnivore with regard to the population of amphipods Gammarus lacustris, which have been regarded so far as the upper link in the trophic cascade of Lake Shira. One of the possible reasons for appearance of fish is the decreased water salinity caused by rising of the lake level. In the recent years, the level of Lake Shira exceeded all the values that had been registered since the late 19th century, and the lakes salinity decreased correspondingly to its smallest value for the whole period of observation.В солоноватом меромиктическом оз. Шира (Южная Сибирь, Республика Хакасия) зарегистрировано присутствие серебряного карася Carassius gibelio. Озеро Шира непрерывно изучается с конца XIX в., и до сих пор считалось, что ихтиофауна в данном озере отсутствует. В настоящей работе исследуются морфологические характеристики, спектр питания и жирнокислотный состав особей Carassius gibelio различного возраста, выловленных в оз. Шира в летнее время 2007 и 2008 гг. Соленость воды в местах вылова была около 15 г/л. Среди пищевых компонентов особей возраста 1-2 лет преобладали диатомовые, зеленые и сине-зеленые водоросли. У особей от четырех до семи лет в пище увеличивалась доля копепод, жуков и хирономид. Начиная с шестилетнего возраста значительную долю в рационе составляли бокоплавы Gammarus lacustris. Таким образом, серебряный карась может быть хищником по отношению к популяции Gammarus lacustris, который до сих пор считался верхним звеном трофического каскада в экосистемы оз. Шира. Одна из возможных причин появления карася в озере - снижение солености, обусловленное повышением уровня озера. В последнее десятилетие уровень оз. Шира превысил все значения, известные для данного озера с конца XIX в. Соответственно, соленость воды в озере снизилась до минимального значения из всех зарегистрированных ранее