PROBLEMS OF COEXISTENCE OF SUPERCONDUCTIVITY AND MAGNETIC ORDERING OF COPPER SUBLATTICES IN YBa2Cu3-XFeXO7-X CERAMICS

The article studies the problems of coexistence of superconductivity and magnetic ordering of copper sublattices in YBa2Cu3-xFexO7-x ceramics. It is known that in superconducting ceramics YBa2Cu3O7-z with orthorhombic lattice as the oxygen content decreases, the transition temperature in superconducting state Tc decreases, and at z>0.6 superconductivity disappears, the lattice becomes tetragonal and at the same time, antiferromagnetic ordering of sublattices Cu (2) appears. The substitution in ceramics of YBa2Cu3O7 part of copper atoms by iron atoms (i.e., the formation of a solid solution of YBa2Cu3-xFexO7+y) is accompanied by similar effects: as x increases, Tc decreases, at x>0.05 the orthorhombic lattice becomes tetragonal, at x>0.45 the superconductivity disappears. The most significant moment is the fact of coexistence in ceramics YBa2Cu3-xFexO7+y in the region of compositions 0.03 < x < 0.45 of superconductivity and magnetic ordering of iron atoms in copper nodes (the latter is established by Mossbauer spectroscopy on isotope 57Fe in a large number of works. However, it remains unclear whether the magnetic ordering of iron atoms in the YBa2Cu3-xFexO7+y lattice is related to the magnetic ordering of copper atoms

In Situ Proteolysis Condition-Induced Crystallization of the XcpVWX Complex in Different Lattices

Although prevalent in the determination of protein structures; crystallography always has the bottleneck of obtaining high-quality protein crystals for characterizing a wide range of proteins; especially large protein complexes. Stable fragments or domains of proteins are more readily to crystallize; which prompts the use of in situ proteolysis to remove flexible or unstable structures for improving crystallization and crystal quality. In this work; we investigated the effects of in situ proteolysis by chymotrypsin on the crystallization of the XcpVWX complex from the Type II secretion system of Pseudomonas aeruginosa. Different proteolysis conditions were found to result in two distinct lattices in the same crystallization solution. With a shorter chymotrypsin digestion at a lower concentration; the crystals exhibited a P3 hexagonal lattice that accommodates three complex molecules in one asymmetric unit. By contrast; a longer digestion with chymotrypsin of a 10-fold higher concentration facilitated the formation of a compact P212121 orthorhombic lattice with only one complex molecule in each asymmetric unit. The molecules in the hexagonal lattice have shown high atomic displacement parameter values compared with the ones in the orthorhombic lattice. Taken together; our results clearly demonstrate that different proteolysis conditions can result in the generation of distinct lattices in the same crystallization solution; which can be exploited in order to obtain different crystal forms of a better quality

Orthorhombic distortion in Au nanoparticles induced by high pressure

A shape-dependent orthorhombic lattice distortion is induced in Au nanoparticles below 12 GPa in a DAC.

3D superstructures with an orthorhombic lattice assembled by colloidal PbS quantum dots

We report a new type of metamaterial comprising a highly ordered 3D network of 3–7 nm lead sulfide quantum dots self-assembled in an organic matrix formed by amphiphilic ligands (oleic acid molecules).

Особенности формирования магнитокалорических явлений в системах Mn-=SUB=-1-t-=/SUB=-Ti-=SUB=-t-=/SUB=-As и Mn-=SUB=-1-x-=/SUB=-Cr-=SUB=-x-=/SUB=-NiGe

The magnetocaloric properties of the systems exhibiting magnetic (paramagnetism (PM)–ferromagnetism (FM)) and structural (hexagonal lattice–orthorhombic lattice) transitions separated (overlapped) in temperature are analyzed in terms of a model of interacting parameters of magnetic and structural orders. It is shown that the magnetocaloric characteristics of the system can increase or decrease during overlapping of the structural ( P 6_3/ mmc – P _ nma ) and magnetic (PM–FM) transitions in the dependence of the character of combination of the low-symmetric orthorhombic ( P _ nma ) and high-symmetric hexagonal ( P 6_3/ mmc ) phases with a ferromagnetic order.