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Acute COVID-19 is a viral infection caused by a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in dramatically decreased peripheral blood CD3+T cell count apparently due to alterations of thymic T cell maturation, that can persist long term afterwards. Therefore, we analyzed the levels of peripheral blood TRECs (T-cell receptor excision circles), and investigated the main alterations in peripheral blood T cell subsets in COVID-19 convalescents. We performed molecular quantification of TRECs with “TREC/KREC-AMP PS” kit and flow cytometric analysis of peripheral blood lymphocytes from three groups of patients. The first group contained 109 samples from COVID-19 convalescents (6–12 month post-acute COVID-19) with normal levels of TRECs (TRECn); the second was formed from COVID-19 convalescents (6–12 month post-acute COVID-19) with decreased levels of TRECs (TREClow, n = 29), and healthy control group (HC, n = 18). We noticed no significant differences between all three groups in CD3+T cell relative and absolute numbers. However, CD4+T cell frequencies were decreased in TREClow and TRECn groups compared to HC (40.8% (31.6; 50.1) and 46.4% (40.0; 53.0) vs 53.5% (47.36; 56.9), p 0.001 and р = 0.004, respectively). Furthermore, Th cell levels were decreased in TREClow patients vs HC and TRECn groups (701 cell/1 µL (478; 807) vs 1005 cell/1 µL (700; 1419), р = 0.020, and 876 cell/ 1 µL (661; 1046), р = 0.008, respectively). Finally, both groups of COVID-19 convalescents had increased frequencies of circulating CD8+T cells — 29.4% (20.7; 39.7) in TREClow group, 26.5% (21.1; 32.7) in TRECn group vs 21.3% (17.1; 26.0) in healthy controls (p = 0.024 and р = 0.026, respectively). In TRECn group, CD8+T cell count was elevated vs control range (508 cell/1 µL (372; 622) vs 356 cell/1 µL (247; 531), р = 0.044). Thus, COVID-19 convalescents (6–12 month post-acute COVID-19) showed an imbalance in CD4+and CD8+T cell level even at 6–12 months post-acute SARS-CoV-2 infection, and the observed changes in peripheral blood T cells could be closely related to the alterations in thymic T cell maturation and differentiation. Such a long-term decline in TREC levels in the circulation may have a profound impact on immune system functions and requires immunocorrection therapy.

The aim of this study was to evaluate the activity of 225Ac in urine of patients undergoing radionuclide therapy with 225Ac-DOTA-TATE. Activity concentration was determined in the urine samples collected within 72 hours after injection of 225Ac-DOTA-TATE, using the ORTEC semiconductor gamma spectrometer, model TSP-DX-100T-PAC-PKG-1. Calculation of excreted activities was additionally performed based on scintig- raphy scans of patients receiving 225Ac-DOTA-TATE. Scans were conducted 5 times for each patient: immedi- ately after injection, at 4 hours, and on the 1st, 2nd, and 3rd days after injection of the radiopharmaceutical. Absolute activity values and fractions of the injected activity were calculated based on the specific activity values. The results of the calculated activity concentration values demonstrate that maximum excretion was observed within the four hours after 225Ac-DOTA-TATE injection. Significant differences between the two methods of determining 225Ac activity were observed only on the third day after radiopharmaceutical injection, which allows for the simplification of future experimental work by using indirect radioactivity measurement methods for activity calculations. There were no significant differences between patient groups with different number of 225Ac-DOTA-TATE injection, which allows for the exclusion of this parameter in the evaluation of experimental results. The results of this study represent the first published experimental data on the determi- nation of actinium excretion in patients.

Abstract Using AFM methods in air under normal conditions in a wide range of local force effects ( $${F}_{const}$$ F const 21 nN) stimulation ( $${F}_{const}$$ F const ) is a non-trivial selective process and exhibits a correspondingly elastic ( $$K=$$ K = 67.4 N/m), active ( $$K=$$ K = 80.2 N/m) and passive ( $$K=$$ K = 84.5 N/m) responses. $$K=K({F}_{const})$$ K = K ( F const ) and $$E=E({F}_{const})$$ E = E ( F const ) depend on $${F}_{const}$$ F const . Having undergone slight plastic deformations $${\Delta h}_{stiff}$$ Δ h stiff < 300 nm, the membrane is capable of restoring its shape. We mapped ( $$E=E(x;y)$$ E = E ( x ; y ) , $${D}_{f}$$ D f = 2.56; $${\Delta h}_{dfrm}={\Delta h}_{dfrm}(x;y)$$ Δ h dfrm = Δ h dfrm ( x ; y ) , $${D}_{f}$$ D f = 2.68; $${\Delta h}_{stiff}={\Delta h}_{stiff}(x;y)$$ Δ h stiff = Δ h stiff ( x ; y ) , $${D}_{f }$$ D f = 2.42, $$A=A\left(x;y\right)$$ A = A x ; y and $${F}_{adh}={F}_{adh}(x;y)$$ F adh = F adh ( x ; y ) ) indicating its complex cavernous structure.

This study examines the long-term effects of SARS-CoV-2 infection on immune status. Given the prolonged and profound immune dysregulation observed during acute SARS-CoV-2 infection, it remains to be determined whether these changes translate into subsequent immune system dysfunction in recovering individuals. In this sense, the aim of the study was to study the parameters of the immune system in patients who had undergone SARS-CoV-2 infection. 150 patients who underwent SARS-CoV-2 infection were examined according to 96 parameters using flow cytometry. A complete blood count was performed using a Medonic device (Sweden); ELISA method determined the levels of general and specific IgM, IgG, IgA, compliment fragments (JSC Vector-Best, Russia). The activity of the phagocytes was studied according to the generally accepted method. The study found that at least four phenotypes of immune system disorders are detected in patients. The first two phenotypes are related to the impairment of innate immune system factors and are associated with a decrease in the number of CD46+ and NK cells. It has been observed that a decrease in CD46+ persists for a long time in a significant number of recovered patients, highlighted by the impaired expression of this marker in various subpopulations of lymphocytes. The decrease in the level of natural killers was accompanied by a compensatory increase in the number of T lymphocytes, mainly due to T helpers and TNK lymphocytes, and the growth of total memory B cells. Two other identified phenotypes are characterized by damage to acquired immune response factors and are associated with damage to B cells and T cytotoxic cells. The relationship of such disorders with damage to hematopoiesis erythrocyte and platelet sprouts, which contribute to the appearance of hypoxia and possible violation of the blood coagulation system, has been shown. Therefore, the results obtained indicate a long-term pronounced damage to the immune system in postCOVID patients that requires immunocorrection of these disorders.

The federal forms of statistical reporting (3-DOZ form, form No. 30 of the Ministry of Health of the Russian Federation and radiation-hygienic passports of the subjects of the Russian Federation for 2015–2020) were analyzed in order to estimate the current status of nuclear medicine and assess the perspective and developing proposals for improving the national system of radiation protection in nuclear medicine. Over the past six years, the number of radionuclide examinations in the Russian Federation has been at the same level: on average 530 thousand per year. In 2020 the number of examinations decreased that was caused by the epidemic of coronavirus infection. The largest number of examinations in 2015-2020 were performed in Moscow (21%) and St. Petersburg (11%). Federal medical centers equipped with high-tech equipment are located in these cities, and patients from different regions are examined in these centers. The examination of bone is the most common examination in Russia: 40% from all of nuclear medicine examination; there is a moderate increase of that examinations. There is a high number of renal examinations (17%). The next most frequent are examinations of myocardium, thyroid, liver and lungs; the number of these examinations are decrease. Due to the development of modern diagnostic technologies, installation of new positron emission tomography departments and replacement of the old equipment with the new one (decrease in the number of renographs and increase the number of positron emission tomographs), the number of “other” examinations are increased with a factor of 3.7 since 2015 but the number of “functional” examinations is decreased. About two thousand studies per year were examined on a scanner (renograph, gamma camera, single-photon emission tomography), and about 0.6 thousand hybrid imaging examinations per year were performed on a single-photon emission tomography combined with computed tomography. The annual collective dose of radionuclide diagnosis in the country has increased from 1.2 to 3.7 thousand man-Sv since 2015. The main contribution to the collective dose in Russia was associated with “other” examinations, which include hybrid imaging and whole body positron emission tomography: 55% (39% in St. Petersburg, 60% in Moscow). Due to the limitations and heterogeneous content of the federal forms of statistical reporting it is difficult to assess the current state of nuclear medicine in the Russian Federation. The authors of the study were updated of the data collection system in the radionuclide diagnosis in 3-DOZ forms; it is under approval. For detailed and reliable assessment of the nuclear medicine in the country, it is necessary to conduct a separate survey to determine the types of nuclear medicine examinations, the gender and age profile of patients and patient doses. That survey should be conducted in St. Petersburg or Moscow, as model subjects of the Russian Federation.

Abstract In this work demostrates a unique method for determining the absolute value of the friction force of a nanoobject on the surface of a cell membrane using atomic force microscopy. The tribological properties of membranes of adult human buccal epithelium cells in the presence of a protective adsorption buffer layer of ~ 100 nm on their surface were studied using atomic force microscopy in the contact scanning mode. Local mapping of the tribological characteristics of the surface was carried out, viz. friction F L = F L (x, y) and adhesion F adh = F adh (x, y) forces were measured. Studies of the friction force F fr on the membrane surface at the nanolevel showed that its value varies discretely with an interval equal to l LF ≈ 100 nm. It was shown that such discreteness is determined by the interval l LF of the action of adhesive forces F adh and indicates the fractal nature of the functional dependence of the friction force on the coordinate F fr = F fr (x). Thus, for nano-objects with dimensions ≤ l LF , the absolute value of F fr decreases according to a power law with an increase in the size of the object, which contradicts the similar dependence of the friction force for macro-objects in the global approximation.

The evolution of the single-particle characteristics of neutron- and proton-rich isotones with the new magic numbers , in the range from 8 to 20 in the dispersive optical model was traced. The calculated energy gaps and widened with the increase in excess of protons and neutrons, respectively. At the same time, the deviation of half-sum of the single-particle energies of the last predominantly occupied and the first predominantly unoccupied states from the Fermi energy decreased. The widening of the gaps were enhanced under the assumption of an increase in the diffuseness of the Hartree–Fock component of the dispersive optical model potential with an increase in the neutron excess over the range of numbers considered. The bubble structure manifests itself clearly in the neutron density distribution of the proton-unstable nucleus Ca. [ABSTRACT FROM AUTHOR]

Single phase ceramic samples of new compositions (1 − x)NaNbO3 – хLiNbO3 (x = 0; 0.05; 0.10; 0.15), modified with a LiF additive, are prepared through solid state reactions, and their crystal structure, microstructure and dielectric and nonlinear optical properties are studied. A drop from 108.1 to 42.8 nm of the volume-weighted crystallite size distribution function corresponding to coherent scattering regions is observed. A rise in the temperature of phase transitions and a weakening of nonlinear optical properties are revealed as the concentration of Li cations grows. [ABSTRACT FROM AUTHOR]

Ceramic samples of new compositions (1−x)(0.9NaNbO3 − 0.1BaTiO3) − xBaZrO3 (x = 0 ÷ 0.05) modified by SiO2 oxide additive were prepared; their phase composition, structure parameters, microstructure, dielectric and ferroelectric properties were studied. Formation of a phase with a perovskite structure with a tetragonal unit cell was established, which volume increased due to partial replacement of A and B cations by Ba2+ and Zr4+ ones with large ionic radii. Decrease in the temperature of ferroelectric phase transitions and corresponding increase in polarization and electrocaloric effect indicates a positive effect of doping on the functional properties of sodium niobate-based ceramics. [ABSTRACT FROM AUTHOR]

Na3Sc2−xRx(PO4)3 (R = Eu, Tb, Dy; 0 ≤ x ≤ 0.2) phosphors were synthesized by a high-temperature solid-state reaction. Sc : R ratios for the NSP:xR samples were determined by ICP-MS, EDX-SEM and TEM-EDX measurements. An X-ray diffraction study revealed that solid solutions with a NASICON-type structure were formed at 0 ≤ x ≤ 0.1. The luminescence properties of Na3Sc2(PO4)3 and Na3Sc2−xRx(PO4)3 (R = Eu, Tb, Dy) were studied in the range of 80–500 K. The highest R3+ luminescence intensity in Na3Sc2−xRx(PO4)3 (R = Eu, Tb, Dy) depending on R was found for x = 0.05 in the case of Dy and x = 0.1 in the case of Eu and Tb. The temperature behaviour of the R3+ emission intensity of Na3Sc2−xRx(PO4)3 (R = Eu, Tb, Dy) depends on R that replaces Sc. The decrease of the Eu3+ emission intensity depending on the transition energy by ∼26% and 18% at ∼420 K compared to TR allowed us to consider NSP:0.1Eu3+ as a suitable phosphor for pc-LEDs. The temperature dependence of the Dy3+ emission for NSP:0.05Dy3+ demonstrates a strong thermal quenching. Different temperature dependences of the Tb3+ emission intensity of NSP:0.1Tb3+ were found for two excitation bands at λex = 220 and 378 nm representing f–d and f–f intracentre transitions. No thermal quenching for f–f transitions takes place while the emission intensity for f–d transitions increases with a temperature rise from 80 to 500 K. The dielectric measurements for Na3Sc2(PO4)3 and Na3Sc1.9Eu0.1(PO4)3 were provided on ceramic pellets sintered under vacuum using a spark plasma sintering technique. Different dependences of conductivity were found for two samples. The calculated conductivity for Na3Sc1.9Eu0.1(PO4)3 with an R3¯c structure (σbulk = 6.4 × 10−5 S cm−1 at 300 K, 1.14 × 10−3 S cm−1 at 360 K and 5.0 × 10−2 S cm−1 at 500 K) is higher than that for pure α-Na3Sc2(PO4)3 but lower than that for β- and γ-Na3Sc2(PO4)3. [ABSTRACT FROM AUTHOR]

Single-phase ceramic samples of new compositions (Na1 –хSrх)0.5Bi0.5TiO3 (x = 0–0.5), including those modified by additives of SiO2 and ZnO oxides, have been obtained by solid-phase synthesis. The crystal structure and microstructure of these samples, as well as their dielectric, nonlinear optical, and local piezoelectric properties, have been studied. The formation of a perovskite-type phase with a pseudocubic unit cell in all synthesized samples and an increase in the cell volume as a result of partial substitution of perovskite structure cations are established. A decrease in the temperature of ferroelectric phase transitions (confirmed by the methods of dielectric spectroscopy and laser second-harmonic generation) to the tetragonal paraelectric phase is revealed. Remanent piezoelectric hysteresis loops are obtained for the synthesized samples in the polarization switching mode; this result confirms the occurrence of ferroelectric polarization switching. [ABSTRACT FROM AUTHOR]

Polymethylmethacrylate (PMMA) is the most commonly used bone void filler in orthopedic surgery. However, the biocompatibility and radiopacity of PMMA are insufficient for such applications. In addition to insufficient biocompatibility, the microbial infection of medical implants is one of the frequent causes of failure in bone reconstruction. In the present work, the preparation of a novel PMMA-based hydroxyapatite/ZnFe2O4/ZnO composite with heterophase ZnFe2O4/ZnO NPs as an antimicrobial agent was described. ZnFe2O4/ZnO nanoparticles were produced using the electrical explosion of zinc and iron twisted wires in an oxygen-containing atmosphere. This simple, highly productive, and inexpensive nanoparticle fabrication approach could be readily adapted to different applications. From the findings, the presented composite material showed significant antibacterial activity (more than 99% reduction) against P. aeruginosa, S. aureus, and MRSA, and 100% antifungal activity against C. albicans, as a result of the combined use of both ZnO and ZnFe2O4. The composite showed excellent biocompatibility against the sensitive fibroblast cell line 3T3. The more-than-70% cell viability was observed after 1–3 days incubation of the sample. The developed composite material could be a potential material for the fabrication of 3D-printed implants. [ABSTRACT FROM AUTHOR]

Single-phase ceramic samples with new compositions (1 – x – у)(Na0.5Bi0.5)TiO3–хBaTiO3–у(K0.5Na0.5)NbO3 (x = 0.05, у = 0–0.15) modified with ZnO and GeO2 additions were obtained by solid-phase synthesis. Their crystal structure, microstructure, and dielectric and local piezoelectric properties were studied. A phase with a perovskite structure with a pseudocubic unit cell was found to form in all of the synthesized samples; it was shown that the unit cell volume increased as a result of the partial replacement of base cations by complex additive cations. The ferroelectric phase transitions were confirmed by dielectric spectroscopy. Residual piezoelectric hysteresis loops were obtained for the synthesized samples in the polarization switching spectroscopy mode, which confirmed the switching of ferroelectric polarization. [ABSTRACT FROM AUTHOR]

Single-phase (1 – x)(K0.5Na0.5)NbO3⋅xBaZrO3 (x = 0–0.06) ceramics with new compositions, including those modified with SiO2 and ZnO oxide additions, have been prepared and their crystal structure, microstructure, and dielectric and nonlinear optical properties have been studied. A phase with the perovskite structure and an orthorhombic unit cell has been shown to form in all of the synthesized materials. Partial replacement of cations of the basic composition by cations of the combined additive has been demonstrated to cause an increase in unit-cell volume. The ferroelectric phase transitions in the ceramics have been confirmed by dielectric spectroscopy and laser radiation second harmonic generation measurements. Doping with SiO2 and ZnO oxide additions has been shown to lower the temperatures of the transitions from the orthorhombic ferroelectric phase to a tetragonal ferroelectric one and then to a cubic paraelectric phase. [ABSTRACT FROM AUTHOR]