First-Principles Simulation of Dielectric Function in Biomolecules

The dielectric spectra of complex biomolecules reflect the molecular heterogeneity of the proteins and are particularly important for the calculations of electrostatic (Coulomb) and electrodynamic (van der Waals) interactions in protein physics. The dielectric response of the proteins can be decomposed into different components depending on the size, structure, composition, locality, and environment of the protein in general. We present a new robust simulation method anchored in rigorous ab initio quantum mechanical calculations of explicit atomistic models, without any indeterminate parameters to compute and gain insight into the dielectric spectra of small proteins under different conditions. We implement this methodology to a polypeptide RGD-4C (1FUV) in different environments, and the SD1 domain in the spike protein of SARS-COV-2. Two peaks at 5.2–5.7 eV and 14.4–15.2 eV in the dielectric absorption spectra are observed for 1FUV and SD1 in vacuum as well as in their solvated and salted models.

FTIR and dielectric relaxation analysis for PVC-Pb3O4 polymer nanocomposites

This work studies the FTIR as well as dielectric characteristics of the PVC-Pb3O4 nanocomposite films. FTIR analysis shows the small shift in 650, 845 and 1732 cm− 1 band positions as a confirmation of interaction between Pb3O4 nanoparticles with PVC polymer matrix. The real permittivity (ε1) decreases with increasing frequency for all samples with the appearance of a relaxation peak at high temperatures. The dielectric loss data (ε2) of the PVC-Pb3O4 nanocomposite revealed a shift of the dielectric absorption peak towards high frequency with increasing the temperature. The activation energy values for both α and β relaxations almost decreased with increasing the Pb3O4 concentration. The energy density of samples containing Pb3O4 has a lower energy density than the pure PVC polymer film. The exponent s often increased with increasing the temperature, and this behavior is consistent with overlapping large-polaron tunneling model. The DC activation energy decreased when the percentage of Pb3O4 increased to 3.0 wt% and then increased at 4.0 wt%. Additionally, a convergence between these values and the activation energies of α and β relaxations observed, which is indicates that the same type of charge carriers participate in the processes.

THE STUDY OF CURVES OF THE TRANSIENT CURRENT IN POLYTETRAFLUOROETHYLENE BY MEANS OF FOURIER ANALYSIS

Experimental transition current curves for polytetrafluoroethylene after exposure to high-energy ionizing radiation are obtained. The transient current curves in irradiated polytetrafluoroethylene are analyzed based on the discrete Fourier transform. It is shown that there is an intense maximum of dielectric absorption in the infralow frequency region. This maximum is characterized by abnormally large values of the dielectric increment, permittivity, and the dielectric loss factor. It is concluded that the volume polarization of the irradiated polytetrafluoroethylene is uniform. The polarization observed in this frequency range is associated with the activation of migration of trapped charge carriers within microscopic regions.

Effects of Electromagnetic Fields and their Shielding on the Growth of Dwarf Runner Beans

The aim of the study was to determine the effect of electromagnetic fields and their shielding on the growth of dwarf runner bean Phaseolus coccineus L. Three sectors were separated on the device emitting electromagnetic fields: “E” - sector emitting electromagnetic radiation with the predominance of the electrical component, “EM” - sector emitting electromagnetic radiation without domination of its components and “M” - sector with a predominance of magnetic component. Fields generated by the device were also shielded with ADR TEX, a screen based on a nanocomposite in which the electric component of the electromagnetic radiation is absorbed by water dispersed within a dielectric matrix in various ways. The composites exhibit high dielectric absorption and shield electric fields within the frequency range from ~100 mHz to ~100 kHz. Electromagnetic fields with the predominance of the electrical component and without domination of its components delayed the initial emergence of runner bean seedlings. Shielding of electromagnetic field without domination of its components with ADR TEX screen protected against this negative impact on the emergence rate of young runner bean seedlings. Exposure of plants to differentiated electromagnetic fields adversely affected their growth. Plants exposed to electromagnetic radiation without domination of its components had the lowest height and the shortest internodes. Shielding of electromagnetic fields with ADR TEX screen efficiently protected against their negative impact on the plant growth. Electromagnetic fields and their shielding did not influence the size of leaves and the index leaf greenness (SPAD).

Growth and Property Investigations of Two Organic–Inorganic Hybrid Molecular Crystals with High Thermal Stability: 4-Iodoanilinium perchlorate 18-crown-6 and 4-Iodoanilinium Borofluorate 18-crown-6

Two new organic–inorganic hybrid molecular single crystals, 4-Iodoanilinium perchlorate 18-crown-6 (1) and 4-Iodoanilinium borofluorate 18-crown-6 (2), with large sizes and high thermal stability were successfully synthesized by solution method. Their structures, phase purities, thermal stability, dielectric, absorption and fluorescence spectra were systematically investigated for potential applications. Compounds 1 and 2 crystallize in orthorhombic crystal system, in same space group, namely Pnma. The thermal measurements shown 1 and 2 maintain high thermal stability up to 150 °C. The temperature dependency of dielectric constant was studied, and no distinct anomaly was observed. The band gap were calculated to be 3.38 eV and 3.57 eV for 1 and 2, respectively, slightly smaller than those of layer perovskite (benzylammonium)2PbCl4 semiconducting materials, which have potential applications in optoelectronic detection field. The investigations throw light on the semiconductor properties of organic–inorganic hybrid crown type material and provide two types of crown compounds with high thermal stability.