29 research outputs found
Binding polynomial in molecular self-assembly
In the present work the concept of a binding polynomial is revisited for the most widely used case of self-assembly of identical molecular units and results in the re-construction of a link to the grand partition function of such a system. It is found that if the self-assembly process is not pronounced (i.e., the product of the equilibrium constant and the monomer concentration is close to zero), the binding polynomial has the meaning of a molecular partition function that is given by the summation over energy levels of any molecule in the system. In other cases the concept of a binding polynomial may be misleadin
Fractal C60 fullerene aggregation: Equilibrium thermodynamics approach
Using dynamic light scattering (DLS) data we showed that the main physico-chemical parameters characterizing C60 fullerene aggregation in solution, viz. equilibrium aggregation constant and fractal number, may be obtained from equilibrium thermodynamics approac
Post-COVID immunopatology syndrome: characteristics of phenotypical changes in the immune system in post-COVID patients
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
Phase formation and relaxor properties of lead-free perovskite ceramics on the base of sodium-bismuth titanate
The work was supported by the Russian Foundation for Basic Research (Projects 16-53-48009, 17-03-00542)
Effects of boundary conditions on magnetization switching in kinetic Ising models of nanoscale ferromagnets
Magnetization switching in highly anisotropic single-domain ferromagnets has
been previously shown to be qualitatively described by the droplet theory of
metastable decay and simulations of two-dimensional kinetic Ising systems with
periodic boundary conditions. In this article we consider the effects of
boundary conditions on the switching phenomena. A rich range of behaviors is
predicted by droplet theory: the specific mechanism by which switching occurs
depends on the structure of the boundary, the particle size, the temperature,
and the strength of the applied field. The theory predicts the existence of a
peak in the switching field as a function of system size in both systems with
periodic boundary conditions and in systems with boundaries. The size of the
peak is strongly dependent on the boundary effects. It is generally reduced by
open boundary conditions, and in some cases it disappears if the boundaries are
too favorable towards nucleation. However, we also demonstrate conditions under
which the peak remains discernible. This peak arises as a purely dynamic effect
and is not related to the possible existence of multiple domains. We illustrate
the predictions of droplet theory by Monte Carlo simulations of two-dimensional
Ising systems with various system shapes and boundary conditions.Comment: RevTex, 48 pages, 13 figure
Binding polynomial in molecular self-assembly
In the present work the concept of a binding polynomial is revisited for the most widely used case of self-assembly of identical molecular units and results in the re-construction of a link to the grand partition function of such a system. It is found that if the self-assembly process is not pronounced (i.e., the product of the equilibrium constant and the monomer concentration is close to zero), the binding polynomial has the meaning of a molecular partition function that is given by the summation over energy levels of any molecule in the system. In other cases the concept of a binding polynomial may be misleadin
Ferroelectric composites and ceramics based on stillwellite-like solid solutions
Stillwellite-like LaBGeO5 exhibits promising pyroelec. properties that were obsd. for both single crystal and glass-ceramic textures. To increase pyroelec. coeff. in the room temp. range, it is worth trying to create stillwellite-like solid solns. diminishing ferroelec. phase transition point, Tc. However such an attempt has been carried out only for LaBSiO5 stillwellite doped with Pb(Ca)BPO5. Taking into account the higher pyroelec. activity of LaBGeO5 as compared to LaBSiO5, in the present work existence of solid solns. in the LaBGeO5-LaBSiO5 and LaBGeO5-Pb(Ca)BPO5 systems was explored and Tc compn. dependency was detd. It can be supposed that compns. in the range LaBGe0.2-0.4Si0.8-0.6O5 are good candidates to develop new high-effective pyroelecs. in form of ceramics, composites or texture
Processing and characterization of lead-free ceramics on the base of sodium–potassium niobate
Lead-free sodium–potassium niobate-based piezoelectric materials are most intensively studied in order to replace the widely used Pb-based ones. In this work, the effects of modification of compositions by donor and acceptor dopants in the A- and B-sites of perovskite lattice on structure, dielectric, ferroelectric, and piezoelectric properties of ceramics from Morphotropic Phase Boundary in the (1−x)(K0.5Na0.5)NbO3–xBaTiO3 system and in compositions with x=0.05 and 0.06 additionally doped by Ni3+ cations have been studied