Determining triple half-twist of optical Möbius strips in electromagnetic fields with a non-planar structure.

Polarization ellipses in a nonparaxial field form twisted strips when traced along closed contours around a circular polarization singularity line. We found an analytical expression for the twist number of the strip when the contour is coplanar with the polarization ellipse in its center. Necessary and sufficient conditions for strips having one or three half-twists are found. A set of five parameters of electromagnetic field at the polarization singularity point is found which definitely determines the value of the twist number of the strip.

Indices of polarization Möbius strips surrounding lines of circular polarization in nonparaxial optical fields.

Detailed analysis of polarization ellipse strips constructed on small circular contours surrounding a single polarization singularity line of an electromagnetic field is carried out. It is shown that the strips formed by major and minor axes of polarization ellipses are nonorientable Möbius strips with opposite directions of twist. Explicit analytical expressions relating the direction of the strip twist to the orientation of its construction contour and the parameters of the electromagnetic field at the polarization singularity point are found.

Transformation of spin and orbital angular momentum in second-harmonic generation process by the near-surface layer of isotropic nonlinear medium.

We investigate the conversion between orbital and spin components of the angular momentum of light beams in the second-harmonic generation process from the near-surface layer of the nonlinear isotropic medium without spatial dispersion at oblique incidence of the elliptically polarized fundamental beam. The conservation of the projection of both spin and orbital angular momenta onto the normal to the surface of the medium during the transformation of the incident wave into a reflected double frequency wave has been demonstrated.

PDSTP Is the First Drug in Class to Treat Coronavirus Infection.

The results of a comprehensive study are presented on the development and creation of an original small PDSTP molecule, able to prevent the SARS-CoV-2 coronavirus infection from binding to the host cell. The PDSTP molecule was designed to electrostatically interact with heparan sulfate proteoglycans on the cell surface, and coronaviruses, particularly SARS-CoV-2, use this mechanism as the first stage of interaction with the cell. By blocking this process, it is possible to stop the life cycle of the virus, thus leading to its death. The drug candidate PDSTP, with its unique mechanism of action, is characterized by a very low toxicity and a high safety profile and demonstrates good efficacy in animal experiments.

Interconversion between OAM and SAM in five-wave mixing process in medium with the fourth-order optical susceptibility.

We investigate the interconversion between spin components of the angular momentum (SAM) and orbital components of the angular momentum (OAM) of collinear elliptically polarized monochromatic fundamental beams with frequencies ω1 and ω2 in the five-wave mixing process in homogeneous isotropic nonracemic mixtures of chiral molecules with nonlinear fourth-order susceptibility. Fundamental beams have helicoidal wavefronts and arbitrary radial distributions of intensity. The discovered non-conservation of the total SAM and OAM projections on the direction of propagation of the interacting waves during the generation of radiation at the frequency 3ω1 - ω2 compensate each other, ensuring the conservation of the total angular momentum projection. A straightforward classical and quantum interpretation of the results is given.

Transformation of spin and orbital angular momentum in second-harmonic generation process at oblique incidence of light from the surface of an isotropic medium with spatial dispersion of quadratic nonlinearity.

We discuss key features of the conversion of spin and orbital angular momentum of electromagnetic waves in the process of second-harmonic generation from the surface of the isotropic medium at oblique incidence. Conservation of the projections of spin and orbital parts of angular momentum of interacting waves onto the normal to the surface is shown for an arbitrary case of polarization and mode structure of the incident light beam.

Three-dimensional structure of polarization singularities of a light field near a dielectric spherical nanoparticle.

We numerically study the structure of polarization singularity lines in a near-field of the sub-wavelength dielectric particle when it is irradiated by a monochromatic elliptically polarized plane wave. For the various values of the ellipticity degree of the incident radiation, we trace the CT and LT-lines on which the polarization ellipse turns into a circle or a line, respectively. The continuous variation of the isotropy parameters of the singularities is visualized along the lines. The main rules of CT and LT-lines deformation, emergence, and vanishing are revealed.

Interconversion between the orbital and spin angular momentum of light beams in three-wave mixing processes in the bulk of an isotropic chiral medium.

A phenomenological description of nondegenerate and degenerate three-wave mixing in the bulk of an isotropic chiral medium is given for the wide class of fundamental light beams with nonuniform polarization distribution and multimode transverse structure. Special attention is paid to the classical and quantum interpretation of interconversion between spin and orbital parts of the angular momentum of the input and output beams.

Structure of polarization singularities of a light beam at triple frequency generated in isotropic medium by singularly polarized beam.

The components of electric field of the third harmonic beam, generated in isotropic medium with cubic nonlinearity by a monochromatic light beam carrying polarization singularity of an arbitrary type, are found analytically. The relation between C-points characteristics in the fundamental and signal beams are determined, as well as the impact of the phase mismatch on the shape of the C-lines.

Antiretroviral Activity Of a Novel Pyrimidyl-Di(Diazaspiroalkane) Derivative.

A novel compound, 3,3'-(5-nitropyrimidine-4,6-diyl)bis-3,12-diaza-6,9-diazoniadispiro[5.2.5.2]hexadecane tetrachloride dihydrochloride, was synthesized. The compound was found to inhibit the replication of various viral families by blocking specific heparan sulfate receptors on the host cell's surface. In experiments, the compound was found to be highly effective against several strains of HIV retroviruses.

Second harmonic generation in isotropic chiral medium with nonlocality of nonlinear optical response by heterogeneously polarized pulsed beams.

The second harmonic generation in the bulk of an isotropic chiral liquid with spatial or temporal nonlocality of its quadratic response is studied analytically. The fundamental pulsed beam has Gaussian time envelope and carries a polarization singularity at its axis. The influence of the topological charge and the handedness of the polarization singularity on the polarization state of the signal beam is revealed.

"Suppressor Factor" of Neutrophils: A Short Story of a Long-Term Misconception.

A large body of evidence obtained during the last decade has demonstrated that neutrophils suppress T cell proliferation in different models of inflammation and cell interaction. The commonly used method for assessing cell proliferation and proliferation inhibition is measuring [3H]thymidine incorporation into cells. Earlier, we observed inhibition of [3H]thymidine uptake in experiments on neutrophil-mediated regulation of T cell response in tuberculosis immunity. Here, we used different types of proliferating cells to analyze the nature of the soluble "neutrophil factor" by a variety of methods (dialysis, HPLC, mass spectrometry, and NMR) and unambiguously demonstrated that neutrophils do not synthesize a specific factor inhibiting cell proliferation, but secrete high concentrations of extracellular thymidine that competitively inhibit [3H]thymidine incorporation. Although the physiological significance of thymidine secretion by neutrophils remains unknown, this phenomenon should be carefully considered when designing test systems for studying cell-cell interactions.

Ultrabroad Terahertz Spectrum Generation from an Air-Based Filament Plasma.

We have solved the long-standing problem of the mechanism of terahertz (THz) generation by a two-color filament in air and found that both neutrals and plasma contribute to the radiation. We reveal that the contribution from neutrals by four-wave mixing is much weaker and higher in frequency than the distinctive plasma lower-frequency contribution. The former is in the forward direction while the latter is in a cone and reveals an abrupt down-shift to the plasma frequency. Ring-shaped spatial distributions of the THz radiation are shown to be of universal nature and they occur in both collimated and focusing propagation geometries. Experimental measurements of the frequency-angular spectrum generated by 130-fs laser pulses agree with numerical simulations based on a unidirectional pulse propagation model.

New uses of LFPs: Pathway-specific threads obtained through spatial discrimination.

Local field potentials (LFPs) reflect the coordinated firing of functional neural assemblies during information coding and transfer across neural networks. As such, it was proposed that the extraordinary variety of cytoarchitectonic elements in the brain is responsible for the wide range of amplitudes and for the coverage of field potentials, which in most cases receive contributions from multiple pathways and populations. The influence of spatial factors overrides the bold interpretations of customary measurements, such as the amplitude and polarity, to the point that their cellular interpretation is one of the hardest tasks in Neurophysiology. Temporal patterns and frequency bands are not exclusive to pathways but rather, the spatial configuration of the voltage gradients created by each pathway is highly specific and may be used advantageously. Recent technical and analytical advances now make it possible to separate and then reconstruct activity for specific pathways. In this review, we discuss how spatial features specific to cells and populations define the amplitude and extension of LFPs, why they become virtually indecipherable when several pathways are co-activated, and then we present the recent advances regarding their disentanglement using spatial discrimination techniques. The pathway-specific threads of LFPs have a simple cellular interpretation, and the temporal fluctuations obtained can be applied to a variety of new experimental objectives and improve existing approaches. Among others, they facilitate the parallel readout of activity in several populations over multiple time scales correlating them with behavior. Also, they access information contained in irregular fluctuations, facilitating the testing of ongoing plasticity. In addition, they open the way to unravel the synaptic nature of rhythmic oscillations, as well as the dynamic relationships between multiple oscillatory activities. The challenge of understanding which waves belong to which populations, and the pathways that provoke them, may soon be overcome.

Prophylactic Admission of an In Vitro Reconstructed Complexes of Human Recombinant Heat Shock Proteins and Melanoma Antigenic Peptides Activates Anti-Melanoma Responses in Mice.

Tumor-derived autologous antigenic peptides when bound to endogenous 70 kDa family heat shock proteins (HSP70) are able to induce effective T-cell responses against tumors. However, efficacy of HSPbased vaccines in clinical practical stand point still has a number of certain limitations including an activation of immune responses against alien non-human HSPs. In this study we reconstructed the complexes of human recombinant HSPs70 (human recombinant HSP70A1B and HSC70 mixture; hrHSPs70) with antigenic lowweight peptides derived from mice B16F10 melanoma cell lysate (PepMCL) in vitro and investigated the prophylactic potential of these complexes to activate anti-tumor immunity in melanoma mouse model. Our results demonstrate that the developed prophylactic vaccine elicits melanoma-specific immune responses and anti-tumor effects against melanoma. These results suggest that hrHSPs70 has capability to reconstitute complexes with peptides obtained from tumor cells lysates in vitro and, therefore, can be used for delivery of multiple antigenic peptides into antigen-presenting cells (APCs) to activate effectors cells. Designed in such a way hrHSPs70-based prophylactic vaccines induce immune responses resulting in a significant efficient prevention of tumor growth and metastases.

Adiabatic modulation of a cnoidal wave by a breather with orthogonal circular polarization in an isotropic gyrotropic nonlinear medium.

An approximate analytical solution of the non-integrable problem of steady-state adiabatic interaction of a cnoidal wave with a breather is obtained. The solving algorithm is described by the example of one-dimensional problem of steady-state interaction of a plane cnoidal wave with circular polarization (the "information" signal) with orthogonally polarized rational soliton (the "control" signal) in an isotropic nonlinear gyrotropic medium with Kerr nonlinearity and second-order group-velocity dispersion. It is shown that such the interaction results in a strong amplitude and frequency modulation of the information signal and this modulation is localized in the region where intensity of the control signal changes.

[Antiaggregation activity of arachidonic acid conjugates with neurotropic peptides proglyprol and semax].

The influence two original derivatives of a therapeutically important peptide, bearing arachidonic acid residue with semax and proglyprol, upon platelet aggregation have been studied in vitro. It is established that both derivatives, in contrast to the parent peptide, possess moderate anti-aggregant properties and produce a dose-dependent decrease in the interplatelet interaction induced by ADP, epinephrine, and arachidonic acid within the concentration range of 0.018 - 1.8 mM. This activity was more pronounced for arachidonoylsemax in comparison with arachidonoylproglyprol.

Modeling of nonlinear optical activity in propagation of ultrashort elliptically polarized laser pulses.

We propose a general model of third-order nonlinear optical susceptibility of isotropic gyrotropic medium with frequency and spatial dispersion. Our model allows for the description of the propagation of ultrashort (several oscillations) elliptically polarized laser pulses in such a medium and does not require smallness of the characteristic nonlocality dimension, unlike the conventional phenomenological model. We implemented our model numerically by means of a modified finite-difference time-domain method with an auxiliary differential equation. We have validated the correctness of our model by the comparison of the results obtained in our numerical simulations with generally known effects observed experimentally and described earlier theoretically for the monochromatic radiation or within the slowly varying envelope approach. We investigated effects accompanying the propagation of ultrashort (several oscillations) light pulses in nonlinear isotropic gyrotropic medium with frequency and spatial dispersion of cubic nonlinearity.

Spatial modules of coherent activity in pathway-specific LFPs in the hippocampus reflect topology and different modes of presynaptic synchronization.

Ongoing network activity often manifests as irregular fluctuations in local field potentials (LFPs), a complex mixture of multicellular synaptic currents of varying locations and extensions. Among other conditions, for synchronously firing presynaptic units to generate sizable postsynaptic LFPs, their axonal territories should overlap. We have taken advantage of anatomical regularity of the rat hippocampus and combined multiple linear recordings and spatial discrimination techniques to separate pathway-specific LFPs with enough spatial resolution to discriminate postsynaptic regions of varying activation, and to investigate their presynaptic origin, chemical nature, and spatial extension. We identified 6 main excitatory and inhibitory LFP generators with different synaptic territories in principal cells and hippocampal subfields matching anatomical pathways. Some recognized pathways did not contribute notably to LFPs. Each showed different septo-temporal spatial modules over which the field potential fluctuations were synchronous. These modules were explained by either the strong overlap of synaptic territories of coactivated afferent neurons (e.g., CA3 clusters for CA1 Schaffer LFPs), or widespread coalescence of postsynaptic territories (granule cell somatic inhibition). We also show evidence that distinct modes of afferent synchronization generate stereotyped spatial patterns of synchronous LFPs in one pathway. Thus, studying spatial coherence of pathway-specific LFPs provides remote access to the dynamics of afferent populations.

Aptamer RA36 inhibits of human, rabbit, and rat plasma coagulation activated with thrombin or snake venom coagulases.

RA36 DNA aptamer is a direct anticoagulant prolonging clotting time of human, rabbit, and rat plasma in the thrombin time test. Anticoagulant activity of RA36 is lower than that of recombinant hirudin. During inhibition of human plasma clotting activated with echitox (coagulase from Echis multisquamatus venom), the aptamer presumably binds to meisothrombin exosite I. The sensitivity of human plasma to the aptamer 5-fold surpasses that of rat plasma. Analysis of RA36 binding to coagulase of Agkistrodon halys venom (ancistron) is required for proving the effect of aptamer on polymerization of human fibrinogen.