Mechanic-elastic properties and radiation attenuation efficiency of TeO2/WO3/K2O composite glass systems for nuclear and medical application.

WO3 effects on neutron and ionizing radiation defending factors of ternary tellurite-based glass blocks with molecular formula 80TeO2 -(20-x)WO3 - xK2O; x = 0-20 mol% (denoted as TKW-glass) has been reported via Phy-X theoretical calculations and Geant4 simulation code. Correlations between shielding factors and kinetics properties of the investigated glasses at different photon energy have been examined. The highest values of mass (MAC) attenuation coefficient were noted at 15 keV of the examined TKW-glass materials with the values of 38.408, 44.388, 49.855, 54.872, 59.492 cm2/g for TKW-0, TKW-5, TKW-10, TKW-15, and TKW-20, respectively. Generally, these values of the TKW-glasses obey the sequence: (TKW-0)MAC< (TKW-5)MAC < (TKW-10)MAC < (TKW-15)MAC < (TKW-20)MAC. The highest mean free path (MFP) values of TKW-glasses were registered at 15 MeV with the values of 6.101, 5.591, 5.097, 4.647, and 4.302 cm for TKW-0, TKW-5, TKW-10, TKW-15, and TKW-20, respectively. The two parameters half value layer (HVL) and MFP follow the pattern: (TKW-0)HVL, MFP > (TKW-5)HVL,MFP > (TKW-10)HVL,MFP > (TKW-15)HVL,MFP > (TKW-20)HVL,MFP. The maximum values of effective atomic number (EAN) took place at gamma energy of 15 keV corresponding to 44.35, 48.86, 52.63, 55.83, and 58.58 for TKW-0, TKW-5, TKW-10, TKW-15, and TKW-20, respectively. The trend of the buildup factors was similar for all of the glass specimens. The fast neutron removal cross-section (ΣR) enhanced as WO3 content increased in the specimens. Thus, the peaked value of ΣR is 0.1059 cm-1 was noted in the TKW-20 sample. Mechanical properties, neutron and γ-rays protection parameters were observed to improve with enhanced WO3 mol% in the TKW-glasses. The current results bear their utilization for neutron and gamma protection purposes.

Modelling of Nonthermal Dielectric Barrier Discharge Plasma at Atmospheric Pressure and Role of Produced Reactive Species in Surface Polymer Microbial Purification.

A nonthermal atmospheric plasma reactor was used to sterilize polymer surfaces and satisfy safety constraints in a biological medium. A 1D fluid model was developed using COMSOL Multiphysics software® 5.4 with a helium-oxygen mixture at low temperature for the decontamination of bacteria on polymer surfaces. An analysis of the evolution of the homogeneous dielectric barrier discharge (DBD) was carried out through studying the dynamic behavior of the discharge parameters including the discharge current, the consumed power, the gas gap voltage, and transport charges. In addition, the electrical characteristics of a homogeneous DBD under different operating conditions were studied. The results shown that increasing voltage or frequency caused higher ionization levels and maximum increase of metastable species' density and expanded the sterilization area. On the other hand, it was possible to operate plasma discharges at a low voltage and a high density of plasma using higher values of the secondary emission coefficient or permittivity of the dielectric barrier materials. When the discharge gas pressure increased, the current discharges declined, which indicated a lower sterilization efficiency under high pressure. A short gap width and the admixture of oxygen were needed for sufficient bio-decontamination. Plasma-based pollutant degradation devices could therefore benefit from these results.

Elucidating the Structural, Electronic, Elastic, and Optical Properties of Bulk and Monolayer MoS2 Transition-Metal Dichalcogenides: A DFT Approach.

Due to their outstanding properties for optoelectronic and versatile electronic applications, the atomically thin layers of transition-metal dichalcogenide (TMDC) materials have demonstrated a potential candidacy to succeed its analog silicon-based technology. Hence, the elucidation of the most important features of these materials is indispensable. In this study, we provide a theoretical elucidation of the structural, electronic, elastic, and optical characteristics of TMDCs. The study has been carried out by elucidating the material in its two particular forms, namely, bulk and two-dimensional (2D) layered (monolayer). The theoretical investigation was carried out within the framework of the density functional theory (DFT) method using first-principles calculations. The Perdew-Burke-Ernzerhof (PBE) variant of the generalized gradient approximation (GGA) scheme, as performed in the Quantum Espresso package, is used. Van der Waals density functional effects, involving the nonlocal correlation part from the rVV10 and vdW-DF2 methods, were treated to remedy the lack of the long-range vdW interaction. An illustration of the performance of both rVV10 and vdW-DF2 functionalities, with the popular PBE correlations, is elucidated. The Born stability criterion is employed to assess structural stability. The obtained results reveal an excellent stability of both systems. Furthermore, the theoretical results show that band-gap energy is in excellent agreement with experimental and theoretical data. Pugh's rule suggested that both the bulk and MoS2-2D layered systems are ductile materials. The refractive indices obtained herein are in good agreement with the available theoretical data. Moreover, the theoretical results obtained with the present approach demonstrate the ductility of both systems, namely, the bulk and the MoS2-2D layered. The results obtained herein hold promise for structural, elastic, and optical properties and pave the way for potential applications in electronic and optoelectronic devices.

Elucidating the Infrared Spectral Properties of Succinic Molecular Acid Crystals: Illustration of the Structure and the Hydrogen Bond Energies of the Crystal and Its Deuterated Analogs.

Herein, the infrared spectroscopic properties of molecular succinic acid crystals (SA) and their four isotopic analogs [C2H4(COOH)2, h6-SA; C2H4(COOD)2, d2-SA; C2D4(COOH)2, d4-SA; C2D4(COOD)2, d6-SA] are reported. The correlation between the structure of succinic acid molecules and their corresponding hydrogen bond energies is elucidated. The effects related to the isotopic dilution as well as the changes in the spectrum recording temperature on the fine structures of the vO-H and vO-D bands are interpreted. The infrared spectral anomalies detected in the spectra of isotopically neat succinic nanocrystal acids are confirmed by theoretical calculations using density functional theory (DFT). According to previous spectroscopic studies of succinic acid and those carried out for α,ω-dicarboxylic acids, a decent agreement between the experimental results and the theoretical DFT simulations is obtained. Moreover, the spectra of single crystals of the h6 and d4 succinic acid variants prove that the vibrational coupling mechanism between the (COOH)2 cycles is rigorously convergent to that detected in the spectra of aromatic carboxylic acids, suggesting thereby that the promotion of symmetry-forbidden high stretching IR transitions plays a crucial role. Furthermore, the obtained experimental results reveal that the succinic acid shows a spectral behavior significantly different from that characteristic of hydrogen associations of other acids of homologous series, such as the glutaric, adipic, malonic, and pimelic acid crystals. The results obtained herein shed light on the way to explore the revealed structure of isotopic derivatives of succinic acid crystals and may prove to be useful results for understanding the nature of unconventional interactions as well as the macroscopic energy effects directing the development of hydrogen associations.

A unified quantum model susceptible to elucidate the dissimilarity of IR spectral density of dicarboxylic acid crystals: Phthalic and terephthalic acid crystals cases.

Over the last decades, several approaches have been developed for elucidating the infrared spectral density of dicarboxylic acid crystals, which has been served as prototype for determining hydrogen bonds dynamics. These approaches differ in how accurately the simulated spectra can superimpose the experimental ones. In this study, we present a superdimer quantum approach susceptible to elucidate the infrared spectral properties of some particular dicarboxylic acid crystals using a newly proposed algorithm, which favors the rule of Davydov coupling in the generation of the spectra. The approach, which is herein effectively applied to terephthalic and phthalic acid dimer crystals, ascribes the non-conventional IR spectral properties of these particular acid crystals to the existence of superdimer structure in their lattices. In this superdimer structure, a strong vibronic coupling mechanism, namely Davydov coupling, takes place between the proton stretching vibrations in the (COOH)2 cycles. This strong coupling exciton, generated by the resonance arising in the two coupled (COOH)2 cycles of the aromatic rings of the superdimer, in conjunction with the strong anharmonic coupling between the fast and slow modes of each hydrogen bonds provide a strong support basis for a common explanation of the physical properties of these two different crystalline systems. The numerical simulations, involving the implications of the superdimer model, are systematically correlated with the experimental spectra. A decent agreement between the evaluated spectra and the experimental bandshapes of terephthalic and phthalic dicarboxylic acid crystals was obtained using a set of physically sound parameters as inputs in the theoretical formulation. The superdimer quantum approach thereby underscore the potential of the dynamical cooperative interactions between "Davydov coupling" and "strong anharmonic coupling" mechanisms in the generation of the spectral features of terephthalic and phthalic dicarboxylic acid crystals, suggesting that the congregated effects of these two mechanisms can be considered as the most reliable source of the non-conventional IR spectral properties observed. It is therefore expected that this novel algorithm reduces the discrepancies between the simulated spectra compared to the experimental one and simplify the computation of spectra in more complex hydrogen bonded systems.