A combination of organic and inorganic cations in the synthesis of transition metal nitrates: preparation and characterization of canted rectangular Ising antiferromagnet (PyH)CsCo2(NO3)6.

Pyridinium cesium cobalt nitrate, (PyH)CsCo2(NO3)6, obtained from a nitric acid solution crystallizes in the orthorhombic space group Pnma with unit cell parameters a = 8.6905(14) Å, b = 11.9599(18) Å, c = 18.386(3) Å, V = 1911.0(5) Å3, and Z = 4. It consists of [Co(NO3)3]- layers, in which each Co2+ ion is connected with four monodentate bridging NO3-groups and one bidentate terminal NO3-group, forming a corrugated rectangular net. Magnetization and specific heat measurements show that (PyH)CsCo2(NO3)6 undergoes a long-range canted antiferromagnetic ordering in two steps at TC1 = 5.0 K and TC2 = 2.6 K. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization measured for (PyH)CsCo2(NO3)6 show that it is an Ising antiferromagnet. In support of these observations, our DFT + U + SOC calculations show that the Co2+ ions of (PyH)CsCo2(NO3)6 have an easy-axis magnetic anisotropy with preferred spin orientation along the b-axis. To a first approximation, the spin lattice of (PyH)CsCo2(NO3)6 is a weakly alternating Ising antiferromagnetic chain (J1/J2 ∼ 0.85), and these chains interact weakly (J3/J2 ∼ 0.07) to form a rectangular Ising antiferromagnetic lattice. In agreement with the prediction for a rectangular Ising antiferromagnet by Onsager, (PyH)CsCo2(NO3)6 undergoes a long-range antiferromagnetic ordering.

A cascade of magnetic phase transitions and a 1/3-magnetization plateau in selenite-selenate Co3(SeO3)(SeO4)(OH)2 with kagomé-like Co2+ ion layer arrangements: the importance of identifying a correct spin lattice.

We prepared a new compound, Co3(SeO3)(SeO4)(OH)2, having layers in a kagomé-like arrangement of Co2+ (spin S = 3/2) ions. This phase crystallizes in the orthorhombic space group Pnma (62) with unit cell parameters a = 11.225(9) Å, b = 6.466(7) Å and c = 11.530(20) Å. Its layers, parallel to the ab-plane, are made up of Co1O5 square pyramids and Co2O6 and Co3O6 octahedra. As the temperature is lowered, Co3(SeO3)(SeO4)(OH)2 undergoes three successive magnetic transitions at 27.5, 19.4 and 8.1 K, and the magnetization of Co3(SeO3)(SeO4)(OH)2 measured at 2.4 K exhibits a 1/3-magnetization plateau between 7.8 and 19.9 T. The H-T magnetic phase diagram constructed for Co3(SeO3)(SeO4)(OH)2 from ac and dc magnetic susceptibility, specific heat and magnetization measurements contains three magnetic phases I, II and III. Phase I is antiferromagnetic, while phases II and III are ferrimagnetic and responsible for the 1/3-magnetization plateau. To interpret these complex magnetic properties, we identified the correct spin lattice for Co3(SeO3)(SeO4)(OH)2 by evaluating its intralayer and interlayer spin exchanges based on spin-polarized DFT+U calculations.

[Study of Multiple Enzymatic Incorporation of Modified Nucleotides of Purine and Pyrimidine Nature in the Growing DNA Chain].

The substrate properties of nitrogen-base modified derivatives of purine and pyrimidine deoxynucleoside triphosphates during their simultaneous pairwise insertion into the growing DNA strand have been studied. Modified nucleotides were introduced using real-time PCR and the primer extension reaction; in one reaction, derivatives with both different and similar functional substituents were used. Genomic bacterial DNA, specially constructed synthetic DNA fragments, and SELEX libraries were used as templates. The reactions were performed using DNA polymerases with no 3'-5' correcting exonuclease activity: Taq, Vent (exo-), DeepVent (exo-), and KOD XL. It was shown that the substrate efficiency is affected by both the size of the substituent group and the chemical nature of deoxynucleoside triphosphate. The effectiveness varies significantly depending on the polymerase used. The most effective of the studied substrates are pyrimidine deoxynucleoside triphosphates in combination with Vent (exo-) DNA polymerase. DNAs modified by pairs of dissimilar nucleotides (dU + dC, dU + dA, dC + dA) with similar and different functional substituents were obtained.

[Liver and COVID-19: possible mechanisms of damage].

The global epidemic of a new coronavirus infection caused by SARS-CoV-2 is a major threat to human health. In the clinical picture, along with acute respiratory distress syndrome, liver lesions are also noted. The following mechanisms are currently being considered: direct damaging effects of SARS-CoV-2, immuno-mediated inflammation, hypoxia, drug exposure, and reactivation of pre-existing liver disease. We studied 150 patients with COVID-pneumonia who are under inpatient treatment at the University Clinical Hospital No. 1 of Sechenov First Moscow State Medical University. Of these, the presence of SARS-CoV-2 RNA was confirmed by polymerase chain reaction in 84 (56.0%) patients. In 55 (36.7%) patients, an increase in serum aminotransferases was registered, mainly alanine aminotransferase max. up to 572 U/L and aspartate aminotransferase up to a max. of 232 U/L. The long-term consequences are unknown and require monitoring of these patients.

Structure, conductivity and magnetism of orthorhombic and fluorite polymorphs in MoO3-Ln2O3 (Ln = Gd, Dy, Ho) systems.

Phase-pure orthorhombic compositions at a Ln/Mo ratio ∼ 5.2-5.7 (Ln = Gd, Dy, Ho) have been obtained for the first time by prolonged (40-160 h) heat treatment of mechanically activated 5Ln2O3 + 2MoO3 (Ln = Gd, Dy, Ho) oxide mixtures at 1200 °C. Although the starting Ln : Mo ratio was 5 : 1 (Ln10Mo2O21 (Ln = Dy, Ho)), it changed slightly in the final product due to the volatility of molybdenum oxide at 1200 °C (40-160 h) (ICP-MS analysis). Brief high-temperature firing (1600 °C, 3 h) of 5Ln2O3 + 2MoO3 (Ln = Gd, Dy, Ho) oxide mixtures leads to the formation of phase-pure fluorites with compositions close to Ln10Mo2O21 (Ln = Gd, Dy, Ho). Gd10Mo2O21 molybdate seems to undergo an order-disorder (orthorhombic-fluorite) phase transition in the range of 1200-1600 °C. For the first time, using the neutron diffraction method, it was shown that low-temperature phases with a Ln/Mo ratio ∼ 5.2-5.7 (Ln = Gd, Dy, Ho) have an orthorhombic structure rather than a tetragonal structure. Proton contribution to the total conductivity of Ln10Mo2O21 (Ln = Gd, Dy, Ho) fluorites and gadolinium and dysprosium orthorhombic phases in a wet atmosphere was observed for the first time. In both orthorhombic and fluorite phases, the total conductivity in wet air decreases with decreasing lanthanide ionic radii. In a wide temperature range, the compounds under study exhibit paramagnetic behaviour. However, the orthorhombic phases of Dy and Ho compounds reach the antiferromagnetic state at 2.4 K and 2.6 K, respectively.

[Risk factors for the early development of septic shock in patients with severe COVID-19].

AIM: In a retrospective study, we evaluated factors associated with the early development of septic shock in patients with severe COVID-19. MATERIALS AND METHODS: We collected medical records of the intensive care unit patients submitted by the local COVID-19 hospitals across Russia to the Federal Center for the Critical Care at the Sechenov First Moscow State Medical University (Sechenov University). Septic shock in crticially ill patients requiring mechanical ventilation was defined as a need in vasopressors to maintain blood pressure. RESULTS: We studied 1078 patients with severe COVID-19 who were admitted to the intensive care units for respiratory support. There were 611 males and 467 females. The mean age was 61.013.7 years. Five hundred twenty five medical records (48.7%) were received from the Moscow hospitals, 159 (14.7%) from the Moscow region, and 394 (36.5%) from the hospitals located in 58 regions of the Russian Federation. In 613 (56.9%) patients, diagnosis of SARS-CoV-2 infection was confirmed by PCR, and in the other cases it was established on the basis of the clinical picture and the results of the chest CT scan. Septic shock developed in 214 (19.9%) of 1078 patients. In the logistic regression model, the risk of septic shock in patients older than 50 years was higher than in patients of a younger age (OR 2.34; 95% CI 1.533.67; p0.0001). In patients with more severe SARS-CoV-2 infection, there was an increase in the prevalence of cardiovascular diseases, including coronary heart disease and atrial fibrillation, type 2 diabetes and malignant tumors. The risk of septic shock in patients with three or more concomitant diseases was higher than in patients without any concomitant chronic diseases (OR 1.76; 95% CI 1.762.70). CONCLUSION: The risk of septic shock in patients with acute respiratory distress syndrome induced by SARS-CoV-2 is higher in patients older than 50 years with concomitant diseases, although a severe course of the disease is also possible in younger patients without any concomitant disorders.

Synthesis, structure and magnetic ordering of the mullite-type Bi2Fe(4-x)CrxO9 solid solutions with a frustrated pentagonal Cairo lattice.

Highly homogeneous mullite-type solid solutions Bi2Fe(4-x)CrxO9 (x = 0.5, 1, 1.2) were synthesized using a soft chemistry technique followed by a solid-state reaction in Ar. The crystal structure of Bi2Fe3CrO9 was investigated using X-ray and neutron powder diffraction, transmission electron microscopy and (57)Fe Mössbauer spectroscopy (S.G. Pbam, a = 7.95579(9) Å, b = 8.39145(9) Å, c = 5.98242(7) Å, RF(X-ray) = 0.022, RF(neutron) = 0.057). The ab planes in the structure are tessellated with distorted pentagonal loops built up by three tetrahedrally coordinated Fe sites and two octahedrally coordinated Fe/Cr sites, linked together in the ab plane by corner-sharing forming a pentagonal Cairo lattice. Magnetic susceptibility measurements and powder neutron diffraction show that the compounds order antiferromagnetically (AFM) with the Néel temperatures decreasing upon increasing the Cr content from TN ∼ 250 K for x = 0 to TN ∼ 155 K for x = 1.2. The magnetic structure of Bi2Fe3CrO9 at T = 30 K is characterized by a propagation vector k = (1/2,1/2,1/2). The tetrahedrally coordinated Fe cations form singlet pairs within dimers of corner-sharing tetrahedra, but spins on the neighboring dimers are nearly orthogonal. The octahedrally coordinated (Fe,Cr) cations form antiferromagnetic up-up-down-down chains along c, while the spin arrangement in the ab plane is nearly orthogonal between nearest neighbors and collinear between second neighbors. The resulting magnetic structure is remarkably different from the one in pure Bi2Fe4O9 and features several types of spin correlations even on crystallographically equivalent exchange that may be caused by the simultaneous presence of Fe and Cr on the octahedral site.

Anisotropy of magnetic properties of Fe(1+y)Te.

The magnetic properties of Fe(1+y)Te single crystals (y ≃ 0.1 ÷ 0.18) were studied at temperatures 4.2 ÷ 300 K. At an ambient pressure, with decreasing temperature a drastic drop in χ(T) was confirmed at T ≃ 60 ÷ 65 K, which appears to be closely related to the antiferromagnetic (AFM) ordering. It is found that the magnitudes of the anisotropy of magnetic susceptibility Δχ in the AFM phase are close in the studied samples, whereas the sign of the anisotropy apparently depends on the small variations of the excess iron y in Fe(1+y)Te samples. The performed DFT calculations of the electronic structure and magnetic properties for the stoichiometric FeTe compound indicate the presence of frustrated AFM ground states. There are very close energies and magnetic moments for the double stripe configurations, with the AFM axes oriented either on the basal plane or along the [0 0 1] direction. Presumably, both these configurations can be realized in Fe(1+y)Te single crystals, depending on the variations of the excess iron. This can provide different signs of magnetic anisotropy in the AFM phase, presently observed in the Fe(1+y)Te samples. For these types of AFM configuration, the calculations for the FeTe values of Δχ are consistent with our experimental data.

Magnetic properties of superconducting FeSe in the normal state.

A detailed magnetization study for the novel FeSe superconductor is carried out to investigate the behavior of the intrinsic magnetic susceptibility χ in the normal state with temperature and under hydrostatic pressure. The temperature dependences of χ and its anisotropy Δχ = χ([parallel]) - χ([perpendicular]) are measured for FeSe single crystals in the temperature range 4.2-300 K, and a substantial growth of susceptibility with temperature is revealed. The observed anisotropy Δχ is very large and comparable to the averaged susceptibility at low temperatures. For a polycrystalline sample of FeSe, the significant pressure effect on χ is determined to be essentially dependent on temperature. Ab initio calculations of the pressure-dependent electronic structure and magnetic susceptibility indicate that FeSe is close to magnetic instability, with dominating enhanced spin paramagnetism. The calculated paramagnetic susceptibility exhibits a strong dependence on the unit cell volume and especially on the height Z of chalcogen species from the Fe plane. The change of Z under pressure determines a large positive pressure effect on χ, which is observed at low temperatures. It is shown that the literature experimental data on the strong and nonmonotonic pressure dependence of the superconducting transition temperature in FeSe correlate qualitatively with the calculated behavior of the density of electronic states at the Fermi level.

Quasiparticle dynamics and phonon softening in FeSe superconductors.

Quasiparticle dynamics of FeSe single crystals revealed by dual-color transient reflectivity measurements (ΔR/R) provides unprecedented information on Fe-based superconductors. The amplitude of the fast component in ΔR/R clearly gives a competing scenario between spin fluctuations and superconductivity. Together with the transport measurements, the relaxation time analysis further exhibits anomalous changes at 90 and 230 K. The former manifests a structure phase transition as well as the associated phonon softening. The latter suggests a previously overlooked phase transition or crossover in FeSe. The electron-phonon coupling constant λ is found to be 0.16, identical to the value of theoretical calculations. Such a small λ demonstrates an unconventional origin of superconductivity in FeSe.

Pressure effects on the magnetic susceptibility of FeTe(x)(x approximately 1.0).

The magnetic susceptibility χ of FeTe(x) compounds (x approximately 1.0) was studied under hydrostatic pressure up to 2 kbar at fixed temperatures of 55, 78 and 300 K. Measurements were taken both for polycrystalline and single crystalline samples. At ambient pressure, with decreasing temperature a drastic drop in χ(T) was confirmed at T approximately 70 K, which appears to be closely related to antiferromagnetic ordering. The obtained results have revealed a puzzling growth of susceptibility under pressure, and this effect is enhanced by lowering the temperature. To shed light on the pressure effects in the magnetic properties of FeTe, ab initio calculations of its volume dependent band structure and the exchange enhanced paramagnetic susceptibility were performed within the local spin density approximation.