Relationship Between Electronic and Crystal Structure in Nd1 + xBa2 − xCu3O6 + δ

In accordance with a relation between the lattice parameter c and the concentration of holes p, which has been found earlier for the YBa2Cu3O6+δcompound, we obtain the p parameter in the same manner for the solid solution Nd1.2Ba1.8Cu3O6+δwith substitution of Nd3+for Ba2+in barium sites. For this, structural and superconducting properties of the Nd1.2Ba1.8Cu3O6+δsamples stored for specified times τ after quenching from annealing temperatures have been studied. The investigation shows that Nd1.2Ba1.8Cu3O6+δstored for a long time has quite a low critical temperature Tcextending only to Tconset = 55 K for the most oxidized sample with δ = 0.953. We find that the δ-dependence of the lattice parameter c significantly changes with time τ. When using the relation between c and p, the existence of electron doping of 0.045 per Cu in Nd1.2Ba1.8Cu3O6+δcan be inferred. This doping explains well-reduced Tcin Nd1.2Ba1.8Cu3O6+δ. In addition, we observe a local drop of Tcby up to 20 K for the samples with p˜0.095 (δ˜0.8) similar to decreasing Tcknown as “anomaly 1/8”. © 2017, Springer Science+Business Media New York

Estimation of the Operating Parameters of Miniature Radioisotope Thermoelectric Power Unit Based on the Th-228 Isotope

The article considers the construction of a miniature radioisotope power unit based on thermoelectric conversion of thermal energy released during nuclear decay. It is proposed to use thin fluoropolymer films (membranes) as a dielectric heat-insulating material. The results of numerical simulation of a prototype of a miniature radioisotope thermoelectric battery unit based on the thorium-228 isotope in the ANSYS program are presented. The geometry of the system has been optimized. It was established that the temperature of the source can reach about 1033 K, and the efficiency of the considered battery unit can reach 16.8%, which corresponds to modern power supplies of this type

Current Density Distribution in 2G HTS Tape in an External Magnetic Field

AbstractThis paper describes the method of study of the critical current density distribution across a tape in a background magnetic field. We measured the current distribution by the scanning Hall probe method. Then we measured field across a tape by a set of 10 Hall probes placed on a single substrate. By comparison of data from these two experiments we determined positions of Hall probes at a tape. Then we measured the current distribution of current density across a tape inside a magnet in parallel and perpendicular magnetic field of 30 mT. The details of measuring method and results are presented

Evolution of the Crystal and Electronic Structures of the RBa 2 Cu 3 O 6 + δ Cuprates in Annealing

Abstract: The crystal structure and the magnetic properties of the HTSC cuprates YBa 2 Cu 3 O 6 + δ , Y 1 ‒   x Ca x Ba 2 Cu 3 O 6 + δ , and Nd 1 + x Ba 2 – x Cu 3 O 6 + δ (x = 0.2) with the structure of a layered perovskite are studied. The well-known aging effect detected in these HTSC materials during storage under standard conditions, namely, an increase in their critical temperature T c and a decrease in lattice parameter c in time, is investigated. Using YBa 2 Cu 3 O 6 + δ as an example, we show that the dependence of c on the oxygen content undergoes the following changes in time: (1) the negative slope of the dependence with respect to axis δ increases and (2) nonlinearity appears and grows in time according to a quadratic law. The first type of changes is explained by an increase in the valence of copper ions, which is accompanied by a decrease in their radius. The second type is explained by the electrostatic interaction of structural CuO 2 planes due to the accumulation of electron holes, which come from CuO δ planes, in them. The calculation of the second type of changes in parameter c in the YBa 2 Cu 3 O 6 + δ cuprate exhibits good quantitative agreement with the experimental data. The second-type changes in the Y 1 – x Ca x Ba 2 Cu 3 O 6 + δ compound (hole doping of CuO 2 planes) turn out to be identical to those in YBa 2 Cu 3 O 6 + δ . However, the differently directed (in time) changes in lattice parameter c in Nd 1 + x Ba 2 – x Cu 3 O 6 + δ indicate that the CuO 2 planes in the neodymium cuprate are doped by electrons at the initial stage of aging. However, when these planes are saturated with holes in time, the type of doping changes from n to p without a noticeable change in the crystal structure, which has been considered to be impossible for layered cuprates to date. © 2018, Pleiades Publishing, Inc

Инвагинация червеобразного отростка

The pathology of the appendix remains one of the topical areas of abdominal surgery. Its rare diseases can be difficult to diagnose and treat, and are accompanied by the development of serious complications. One of them is  intussusception of the appendix to the cecum. Intussusception can be caused by previously undiagnosed primary lesions of the appendix. At the same time, it can simulate tumor and tumor-like formations of the cecum and lead to  diagnostic errors. The literature review provides modern data on the history of the study of the problem, the epidemiology of classification, the causes and mechanisms of the development of appendiceal intussusception, the methods of its diagnosis and treatment.  Патология червеобразного отростка остается одним из актуальных разделов абдоминальной хирургии. Его редкие заболевания могут представлять сложности для диагностики и лечения и сопровождаться развитием серьезных осложнений. Одно из них — инвагинация червеобразного отростка в слепую кишку. Инвагинация может быть вызвана ранее  недиагностированными первичными поражениями отростка. В  то же время инвагинат может симулировать опухолевые и опухолеподобные образования слепой кишки и приводить к  диагностическим ошибкам. В обзоре литературы приведены  современные данные об истории изучения проблемы,  эпидемиологии, классификации, причинам и механизмам развития инвагинации червеобразного отростка, методах ее диагностики и лечения.