Low-frequency quantum oscillations in LaRhIn5_5: Dirac point or nodal line?

In the recent paper [1], a new method based on measuring a temperature correction to a quantum-oscillation frequency was proposed to study an energy-band dispersion of charge carriers in small Fermi surface (FS) pockets of crystals. To illustrate their approach, Guo et al. [1] applied it to a number of materials and, in particular, to the multiband metal LaRhIn$_5$ which, apart from high-frequency oscillations associated with a large FS, also exhibits the oscillations with the low frequency $F\approx 7$ T. Although the method of Ref. [1] really detects charge carriers with a linear dispersion, it does not distinguish between the carriers near a Dirac point and near a nodal line, since all such quasiparticles disperse linearly. Here we ask what is the nature of the carriers associated with the frequency $F$ in LaRhIn$_5$ and call attention to the puzzling origin of this frequency.Comment: This is matters arising from C. Guo et al. Nature Communications 12, 6213 (2021); 6 pages, 2 figure

The Berry phase and the phase of the Shubnikov-de Haas oscillations in three-dimensional topological insulators

Within the semiclassical approach, we calculate contributions of the Berry phase and of the Zeeman coupling of the electron moment with the magnetic field to the phase of the Shubnikov - de Haas oscillations for the surface electrons in the Bi$_2$X$_3$ family of three-dimensional topological insulators (X stands for Te or Se). We also discuss a relation of the obtained results with published experimental data on the Shubnikov-de Haas oscillations for this family of topological insulators.Comment: 4 pages, submitted to Phys. Rev.

Origin of the peaks in the Nernst coefficient of bismuth in strong magnetic fields

We explain the origin of most of the peaks in the Nernst coefficient that were recently observed at magnetic fields directed along the trigonal axis and the bisectrix direction in bismuth. Additional experiments are discussed that enable one to verify our explanation.Comment: Submitted to Physical Review B. 4 pages, 5 figure

The levels of markers of the myocardium damage and state of the oxygen budget in patients, suffering the mitral valve insufficiency in surgical correction, using crystalloid cardioplegia

Objective. Аnalysis of levels of the myocardium damage markers and state of the oxygen budget in patients, suffering the mitral valve insufficiency, in surgical correction, using crystalloid cardioplegia, was performed. Маterials and methods. There were examined 40 patients, suffering the mitral valve insufficiency and ageing (56.2 ± 4.5) yrs old, admitted to the Institute of the Heart MH of Ukraine for surgical correction of the failure. The therapy and operative intervention, the mitral valve prosthesis, were conducted in the patients in accordance to actual local protocol of intraoperative cardioprotection, using the crystalloid cardioplegia (Bretschtider’s solution). The markers levels, concerning the myocardium affection (troponin I, sodiumuretic peptide, alaninaminotranspherase, aspartataminotransphefase, creatinphosphokinase, МВ fraction of creatinephosphokinase), indices of the oxygen budget (hemoglobin, hematocrit, hemoglobin saturation by oxygen in arterial and venous blood, partial pressure of oxygen in arterial and venous blood, lactate) were performed in the patients while exit from perfusion, before admittance to the Department of Intensive Therapy and discharge from it. There were calculated: the ratio of creatinephosphokinase-MB towards creatinephosphokinase, аrterio-venous difference of hemoglobin saturation by the oxygen, content of oxygen in arterial and venous blood, transport, consumption of oxygen and coefficient of the oxygen extraction by the tissues. Results. The levels of markers investigated, concerning affection of myocardium in the patients, did not exceeded the norm range, while statistically significant dynamics was registered only for concentration of sodiumuretic peptide and ratio of creatinephosphokinase-MB towards creatinephosphokinase. The indices of hemic chain of the oxygen transport trustworthily lowered while exit from perfusion only. Тhe oxygen transport and consumption after the failure correction have reduced trustworthily, while coefficient of the oxygen extraction by the tissues did not change essentially. Arterio-venous difference for the oxygen content have reduced trustworthily, but on this background the lactate level have raised significantly. Conclusion. The levels of markers studied, concerning the myocardium damage, did not differ during the investigation course essentially, what witnesses satisfactory state of myocardium

Энергетическая оценка влияния левосимендана на кислородный бюджет при экстренном аортокоронарном шунтировании у больных с острым коронарным синдромом

Цель. Оценка эффективности левосимендана как инотропного препарата в периоперационном периоде при выполнении аортокоронарного шунтирования (АКШ) в экстренном порядке у больных с острым коронарным синдромом (ОКС) на основе исследования энергетики кровообращения. Материалы и методы. АКШ в экстренном порядке выполнено 80 пациентам с ОКС. В 1–й группе (40 больных) использовали локальный протокол анестезии и интенсивной терапии, больным 2–й группы (40) дополнительно вводили левосимендан. Фиксировали фракцию выброса (ФВ) левого желудочка, сердечный выброс (СВ), уровень лактата, доставку, потребление и потребность в добутамине. Рассчитывали предложенный энергетический индекс, отражающий степень удовлетворения тканей в кислороде. Результаты. Левосимендан способствует более быстрому восстановлению СВ и транспорта кислорода без повышения энергозатрат, энергетический индекс при этом достоверно выше – 10,73 ± 3,50 по сравнению с 8,74 ± 2,47 (p < 0,05). Выводы. Кальциевый сенситизатор левосимендан при экстренном АКШ у больных с ОКС способствует более быстрому восстановлению насосной функции миокарда и снижает потребность в добутамине. Применение левосимендана у больных с ОКС при выполнении экстренного АКШ позволяет повысить энергетическую эффективность транспорта кислорода и обеспечивает антигипоксический эффект