Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D" layer

The Earth's lower mantle is believed to be composed mainly of (Mg,Fe)SiO3 perovskite, with lesser amounts of (Mg,Fe)O and CaSiO3). But it has not been possible to explain many unusual properties of the lowermost 150 km of the mantle (the D" layer) with this mineralogy. Here, using ab initio simulations and high-pressure experiments, we show that at pressures and temperatures of the D" layer, MgSiO3 transforms from perovskite into a layered CaIrO3-type post-perovskite phase. The elastic properties of the post-perovskite phase and its stability field explain several observed puzzling properties of the D" layer: its seismic anisotropy, the strongly undulating shear-wave discontinuity at its top and possibly the anticorrelation between shear and bulk sound velocities.Comment: PUBLISHED IN Nature 430, 445-448 (2004

Characteristics of the secondary electrons calibration beam of the accelerator S-25R "Pakhra"

The characteristics of the secondary electrons` calibration quasi-monochromatic beam of the accelerator S-25R "Pakhra" of the Lebedev Physical Institute of the Russian Academy of Sciences (LPI) on the basis of magnet SP-57 are presented. With an electron energy in the range of 45-280 MeV, a collimator diameter in front of the trigger counters of 3 mm and copper Converter thicknesses of 1-3 mm, the energy resolution and beam intensity were 4.4-2.2% and around 16 e/sec, respectively

Creation and decay of eta-mesic nuclei

First experimental results on photoproduction of eta-mesic nuclei are analyzed. In an experiment performed at the 1 GeV electron synchrotron of the Lebedev Physical Institute, correlated pi+n pairs arising from the reaction gamma + 12C -> N + eta(A-1) -> N + pi+ + n + (A-2) and flying transversely to the photon beam have been observed. When the photon energy exceeds the eta-meson production threshold, a distribution of the pi+n pairs over their total energy is found to have a peak in the subthreshold region of the internal-conversion process eta p -> pi+ n which signals about formation of eta-mesic nuclei.Comment: 6 pages, 6 figures. Talk at CIPANP, May 2000, Quebe

Clinical, morphological and molecular biological examination of the myocardium in COVID-19 patients

The presence of coronavirus-associated myocarditis remains controversial despite elevations in cardiac troponin and natriuretic peptide in many patients.Aim. To assess the morphological changes in the myocardium of patients who died due to coronavirus disease 2019 (COVID-19) and compare them with the intravital level of cardiac biomarkers.Material and methods. A total of 420 hospital charts and 77 autopsies of those who died from COVID-19 were analyzed. In 15 of 77 cases (19%) with histologically suspected myocarditis, an immunohistochemical examination of the myocardium with antibodies to CD3, CD45, CD8, CD68, CD34, Ang1, VWF, VEGF, HLA-DR, MHC1, C1q, VP1 of enteroviruses was performed, and in 8 patients with immunohistochemically confirmed myocarditis (10%) — polymerase chain reaction for SARS-CoV-2.Results. Hemorrhage, intramural thrombosis, necrosis of non-coronary origin, myocardial infarction and lymphocytic myocarditis were detected in 43%, 10%, 17%, 19% and 10% of cases, respectively, without coronavirus N and E gene sequences in the myocardium. Dysplasia, hyperplasia and hypertrophy of the vascular endothelium, expression of Ang1, VWF, VEGF, MHC1, C1q, VP1 of enteroviruses were determined in 100, 100, 87, 100, 75 and 62% of cases of myocarditis, respectively. There were no significant correlations between inflammatory biomarkers and myocarditis.Conclusion. The main morphological manifestation of COVID-19 in the myocardium is the so-called endotheliitis with dysplasia and endothelial activation, leading to hemorrhages, intramural thrombosis and necrosis. There is no convincing evidence of a direct involvement of coronavirus in myocarditis induction

ОБЕСПЕЧЕНИЕ ИЗМЕРЕНИЙ ОПТИЧЕСКИХ СВОЙСТВ МОНОКРИСТАЛЛОВ И ЗАГОТОВОК НА ИХ ОСНОВЕ СТАНДАРТНЫМИ ОБРАЗЦАМИ ПРЕДПРИЯТИЯ

The effectiveness of metrological control and consequently the credibility of test results directly depend on the level of certified reference material completeness in laboratory. In the sphere of single crystals optical parameters measurement the deficiency of state and manufactured certified reference materials takes place. Therefore, the development and application of certified reference materials of organization are reasonable and effective. The experience of development and application of organization certified reference materials designed for control of stability and guaranteeing of measurement traceability in the testing laboratory «Single crystals and stocks on their base» of National University of Science and Technology «MISIS» is considered.Эффективность метрологического контроля, а в итоге достоверность получаемых результатов напрямую связаны с уровнем обеспечения лаборатории стандартными образцами (СО). В области измерений параметров оптических монокристаллов и заготовок на их основе существует дефицит государственных стандартных образцов, а также промышленно производимых стандартных образцов. Поэтому для данной области исследований целесообразно и эффективно разрабатывать и применять стандартные образцы предприятия (СОП). Рассмотрен опыт разработки и применения стандартных образцов предприятия, предназначенных для контроля стабильности и обеспечения прослеживаемости измерений параметров оптических монокристаллов и заготовок на их основе, в аккредитованной межкафедральной учебно-испытательной лаборатории полупроводниковых материалов и диэлектриков «Монокристаллы и заготовки на их основе» Национального исследовательского технологического университета «МИСиС»