Identification and analysis of repetitive elements (motifs) in DNA, RNA, and protein macromolecules is an important step in studying structure and functions of these biopolymers. Functional role of NA-BSE (non-adjacent base-stacking element, a widespread tertiary structure motif in various RNAs) in RNA–RNA interactions at various stages of the ribosome function during translation has been investigated in this work. Motifs of this type have been described to date that are reversibly formed during mRNA decoding, moving of the ribosome subunits relative to each other, and moving mRNA and tRNA along the ribosome during translocation. The EF-G-dependent NA-BSE formation involving 5S rRNA and 23S rRNA nucleotide residues is considered separately.

The effect of single overloads on the assessment of the threshold range of stress intensity factor in aluminum alloy AA7085 is analyzed. It is shown that in the cases where the testing procedure for measuring the ∆K threshold includes periodic overloads, the real threshold value might be underestimated by up to 49

The operation of a small-size Cherenkov gamma-ray telescope TAIGA-IACT with camera on SiPMs OnSemi MicroFJ-60035 has been modelled by multiparticle Monte Carlo (MC) methods. The model implies that telescope camera is equipped with two specific types of filters of 290-590 nm (visible+NUV) and 220-320 nm (MUV+UVB)-bands, each covering half of the camera pixels in some uniform order. This allows one to measure the fraction of UV-radiation in total amount of Cherenkov radiation of an extensive air shower (EAS), that can be used for efficient gamma-hadron separation. The corresponding quality factor takes values up to 5.07 in the 10-100 TeV range depending on the distance to EAS axis and camera orientation.

Chloramphenicol (CHL) is an antibiotic targeting the peptidyl transferase center in bacterial ribosomes. We synthesized a new analog, CAM-BER, by substituting the dichloroacetyl moiety of CHL with a positively charged aromatic berberine group. CAM-BER suppresses bacterial cell growth, inhibits protein synthesis in vitro, and binds tightly to the 70S ribosome. Crystal structure analysis reveals that the bulky berberine group folds into the P site of the peptidyl transferase center (PTC), where it competes with the formyl-methionine residue of the initiator tRNA. Our toe-printing data confirm that CAM-BER acts as a translation initiation inhibitor in stark contrast to CHL, a translation elongation inhibitor. Moreover, CAM-BER induces a distinct rearrangement of conformationally restrained nucleotide A2059, suggesting that the 23S rRNA plasticity is significantly higher than previously thought. CAM-BER shows potential in avoiding CHL resistance and presents opportunities for developing novel berberine derivatives of CHL through medicinal chemistry exploration.

The study of spin effects in elastic proton–proton and antiproton–proton scattering in the SPASCHARM experiment at U-70 accelerator facility (Institute for High Energy Physics, National Research Centre Kurchatov Institute, Protvino, Moscow oblast) is discussed. Polarized beams or a polarized target of the experiment will be used to measure the analyzing power A_N of elastic scattering of protons and antiprotons. The possibility of using two different types of the detectors to register recoil particles of elastic scattering of protons is analyzed. In the first case, it is proposed to use scintillation counters, the second option is a detector based on proportional chambers. A comparison of the registration efficiency of elastic pp scattering for two configurations of the experimental setup is carried out, and the required measurement time is determined.

The study of spin effects in elastic proton-proton and antiproton-proton scattering in the SPASCHARM experiment at U-70 accelerator facility (Institute for High Energy Physics, National Research Centre Kurchatov Institute, Protvino, Moscow oblast) is discussed. Polarized beams or a polarized target of the experimentwill be used to measure the analyzing powerAN of elastic scattering of protons and antiprotons. The possibility of using two different types of the detectors to register recoil particles of elastic scattering of protons is analyzed. In the first case, it is proposed to use scintillation counters, the second option is a detector based on proportional chambers. A comparison of the registration efficiency of elastic pp scattering for two configurations of the experimental setup is carried out, and the required measurement time is determined.

The effect of creep development that occurs under cyclic loading of polyetheretherketone (PEEK) is studied, where the cyclic creep parameter is used to quantitatively characterize the structure rearrangement. The magnitude of cyclic creep was calculated from mechanical hysteresis loops. To obtain the dependence of the magnitude of cyclic creep on the amplitude of the external cyclic stress, block loading was carried out with a stepwise increase in the amplitude. It is shown that the mechanism of development of cyclic creep under block loading has a two-stage character. The first stage is responsible for the adaptation of the polymer to an increase in the applied load. The second stage corresponds to stabilization, when the rate of creep development slows down, and its further development stops. It was found that despite the restructuring of the structure and the hardening caused by it, the degree of crystallinity under cyclic loading did not change and amounted to 59%. At the same time, the value of microstresses decreased from 6 to 0.9 MPa. It has been shown that cyclic strain hardening with a block increase in load can lead to an increase in the fatigue life of PEEK (which can reach 90% of the ultimate strength of the material).

The effect of high dose implantation of Ta+ ions (Dion = 5 ' 1016 cm -2) into samples from a TiNi shape memory alloy (SMA) on patterns of deformation and fracture mechanisms under quasi-static uniaxial tensile loads was studied. Using X-ray diffractometry, transmission electron microscopy, and scanning electron microscopy, it was shown that ion implantation resulted in amorphization of the surface layer with a thickness of -100 nm due to the formation of a chemical composition of approximately Ti36Ni41Ta23 (at.%), thermodynamically corresponding to the highest glass forming ability in the Ti-Ni-Ta system. In the implanted surface layer, both the microstructure and crystal structure defects subsystem were modified at a depth of -5 mm. Using the digital image correlation (DIC) method, the dynamics of changes in the integral and local (eyy longitudinal, exy shear and exx transverse) strain components were investigated in the tensile tests of both as-received and implanted TiNi SMA samples. On the basis of the obtained results, both integral and local stress-strain diagrams were plotted. In all studied cases, the main contribution to strain accumulation was made by the eyy and exx strains, which differed significantly for the as-received and implanted TiNi SMA samples. It was concluded that the positive effect of ion implantation was manifested in loading ranges close to the martensitic yield stress (at strain range of 1-6%), despite a noticeable decrease in the ultimate tensile strength and plasticity of the implanted TiNi samples.

The surface structure and mechanical surface and bulk properties of TiNi samples with surface treatment of different types (from mechanical grinding (MG) to mirror shine and jewelry vibromechanical (JVM) treatment) are compared. It has been found that, unlike MG, the JVM treatment does not lead to changes in the mechanical properties of the TiNi samples. The main reason for these differences is the formation of an outer amorphous layer 100 nm thick and a sublayer with a submicrocrystalline polygonized B2 structure more than 10 μm thick in the near-surface region of the TiNi samples with surface JVM treatment.

In this work, the relationship was considered between the structure and cyclic loading resistance of a layered composite consisting of PEI (PEEK) plate/PEI (PEEK) film/PEI-impregnated carbon-fiber fabric prepreg/PEI (PEEK) film/PEI (PEEK) plate by analyzing the time variation in the parameters of mechanical hysteresis loops calculated using digital image correlation. It was shown that the polyetherimide-based layered composite has low fatigue life under cyclic loading (0.8 of the yield strength), resulting from incompatible deformation between the PEI plates and the prepreg due to a layer interface formed by low-melting TecaPEI film. In the PEEK layered composite, the layer interface was formed by neat PEEK energy director and therefore had a little amount of defects, due to which the load was well transferred from the PEEK plates to the middle reinforcement layer. As a result, the fatigue life at a load level of 0.8 of the yield strength corresponded to high-cycle fatigue (more than 86000 cycles).

The antimicrobial resistance crisis along with challenges of antimicrobial discovery revealed the vital necessity to develop new antibiotics. Many of the animal proline-rich antimicrobial peptides (PrAMPs) inhibit the process of bacterial translation. Genome projects allowed to identify immune-related genes encoding animal host defense peptides. Here, using genome mining approach, we discovered a family of proline-rich cathelicidins, named rumicidins. The genes encoding these peptides are widespread among ruminant mammals. Biochemical studies indicated that rumicidins effectively inhibited the elongation stage of bacterial translation. The cryo-EM structure of the Escherichia coli 70S ribosome in complex with one of the representatives of the family revealed that the binding site of rumicidins span the ribosomal A-site cleft and the nascent peptide exit tunnel interacting with its constriction point by the conservative Trp23-Phe24 dyad. Bacterial resistance to rumicidins is mediated by knockout of the SbmA transporter or modification of the MacAB-TolC efflux pump. A wide spectrum of antibacterial activity, a high efficacy in the animal infection model, and lack of adverse effects towards human cells in vitro make rumicidins promising molecular scaffolds for development of ribosome-targeting antibiotics. The antimicrobial resistance crisis calls for development of new classes of antibiotics. Here, authors use genome mining approach to discover a distinct family of ribosome-targeting proline rich antimicrobial peptides.

Quantitative modeling of a system of optical concentrators based on an improved design of Winston hexagonal cones, providing a possibility of using light filters and intended for the registration camera of a small-size Cherenkov gamma-ray telescope, has been performed. The transmission of the cones is calculated, and the intensity distributions of the photon flux in the detector plane are given. Based on the results obtained, an optimal configuration of optical concentrators is proposed with an account for design features of the TAIGA-IACT mount, mirror, and camera, as well as of new detector units. The results obtained for the considered system are compared with the previously published models.

The nature of the change in creep under the cyclic loading on composites based on polyimide (PI) and polyetherimide (PEI) loaded with short carbon fibers (CFs) has been established. It is shown that in the low-cycle fatigue (LCF) mode, the durability of PI composites is several times higher, and the growth rate of cyclic creep is several times lower than for identically filled PEI-based composites. The higher growth rate of cyclic creep for the CF-loaded PEI is explained by the greater flexibility of the polymer macromolecule and, as a result, the ability to rearrange the microstructure.

The effect of creep development has been studied to clarify the nature of fatigue failure in neat polyetheretherketone (PEEK). The cyclic creep parameter was utilized to quantitatively characterize the structure rearrangement. The magnitude of cyclic creep was calculated taking into account the parameters of mechanical hysteresis loops. To reveal the dependence of the cyclic creep magnitude on the external cyclic stress, block loading was implemented with a stepwise increase in the amplitude. It has been shown that the mechanism of cyclic creep exhibited a two-stage pattern (under the block loading). The first stage is responsible for the polymer adaptation to an increase in the applied load, and the second stage corresponds to the steady state in which the rate of creep development slows down. It has been found that despite the cyclic loading induced structure conformation (rearrangement) and the strain hardening, the degree of crystallinity did not change a lot and amounted to 20

In this work the behavior of near β titanium alloy VT22 treated by radial shear rolling is studied and compared at the mesoscale level under low-frequency (5 Hz, stress ratio 0.1) and high-frequency (20 kHz, stress ratio –1.0) loading at stresses below the yield stress of the material. It is found that, in comparable ranges of applied stresses of 950–600 MPa, the fatigue life of the material at low loading frequency is three orders of magnitude lower than the very high cycle fatigue life at high-frequency loading. This effect is studied by fractographic analysis providing the crack growth stages and lives and the relative crack growth period at the stage of fatigue striation formation, as well as by analyzing mechanical hysteresis loops. The low fatigue life of an ultrafine-grained material is associated with its sensitivity to loading frequency. The material behavior under low-frequency loading is mainly determined by the zones with reduced plasticity, because even at high applied stresses, though below the yield stress, the alloy cannot relax the cyclic loading energy for a long time, which accelerates the fatigue crack nucleation.

The temperature dependences of the dark count and efficiency of single-photon detection for two silicon avalanche photodetectors of ultraviolet radiation (OnSemi/SensL MicroFJ-60035 and Hamamatsu VUV4 S13371-6050CQ-02) operating at a wavelength of 277 nm are studied experimentally in the context of development of a new recording camera for the TAIGA-IACT gamma-telescope. It is shown that the main characteristics of these detectors correspond to the manufacturer certification. The signal readout systems have been developed and tested. It is concluded that such detectors are applicable in recording cameras of Cherenkov gamma telescopes.

In this work we generalize the notion of superscattering and associate it with a symmetry group of a scattering object. Using the group theory approach we describe a way to spectrally overlap several eigenmodes of a resonator in order to achieve scattering enhancement. Importantly, this can be done by simple variation of geometric parameters of the system, implying that the symmetry is preserved. We also demonstarte that a scattering cross-section limit of a spherical object is not valid for the case of non-spherical geometries. As an example, we use finite-size ceramic cylinder and demonstrate that a dipolar scattering cross-section limit of a spherical object can be exceeded by more then 3 times. The obtained results may be promising for design of antennas and radio frequency identification systems.

Received 2 September 2021DOI:https://doi.org/10.1103/PhysRevApplied.16.039901© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMie scatteringOptical & microwave phenomenaRadio frequency techniquesPhysical SystemsCeramicsDielectricsTechniquesCavity resonatorsGroup theoryTransfer matrix methodAtomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics