Effects of the evolution of two cross‐focused Gaussian laser beams on the terahertz generation in thermal collisional plasma

Generation of the terahertz (THz) radiation based on the beating of two cross‐focused high intensity Gaussian laser beams in a warm rippled density plasma is numerically investigated, taking into account the ponderomotive force, Ohmic heating, and collisional nonlinearities. The beat ponderomotive force as a result of cross‐focusing of beams induces a vertical velocity component that by coupling with the rippled density gives rise to a nonlinear current deriving THz radiation. The effect of laser beams spot size evolution and plasma parameters on the THz generation is studied. It was found that there exist special electron temperature and laser intensity ranges with “turning points” where the generation of THz radiation reaches its maximum value and outside of these ranges, it disappears. The results also indicated that increasing the background electron density as well as taking into account the collision frequency help THz generation. Moreover, the maximum yield of THz radiation occurs when the beat wave frequency approaches the plasma frequency.     

The study of the weibel electromagnetic instability growth rate in the presence of the body stress

Body stress flow can be expected in the fast ignition imploding of the inertial fusion process that strongly damps small‐scale velocity structures. The Weibel instability is one of the plasma instabilities that require anisotropy in the distribution function. The body stress effect was neglected in the calculation of the Weibel instability growth rate. In this article, the propagation condition of impinging waves and the growing modes of the Weibel instability on the plasma density gradient of the fuel fusion with the body stress flow are investigated. Calculations show that the minimum value of the body stress rate threshold in the linear polarization is about 2.96 times greater than that of the circular polarization. Increasing 10 times of the density gradient and decreasing 2 times of the wavelength in the linear polarization and the circular polarization, respectively, lead to about 1.78 × 10⁶ times increment and 0.019 times decrement in the maximum of the Weibel instability growth rate. Also, the Weibel instability growth rate maximum in the circular polarization is about 10⁷ times greater than that of the linear polarization. The body stress flow and the density gradient tend to stabilize the Weibel instability in the circular polarization and act as a destabilizing source in the linear polarization. Therefore, by increasing steps of the density gradient plasma near the relativistic electron beam‐emitting region, in the circular polarization, the Weibel instability occurs at a higher stress flow.     

Design,synthesis, and in silico studies of novel eugenyloxy propanol azole derivatives having potent antinociceptive activity and evaluation of their β-adrenoceptor blocking property

The design, synthesis, antinociceptive and β-adrenoceptor blocking activities of several eugenyloxy propanol azole derivatives have been described. In this synthesis, the reaction of eugenol with epichlorohydrin provided adducts 3 and 4 which were N-alkylated by diverse azoles to obtain the eugenyloxy propanol azole analogues in good yields. Adducts 3 and 4 were also reacted with azide ion to obtain the corresponding azide 6. The ‘Click’ Huisgen cycloaddition reaction of 6 with diverse alkynes afforded the title compounds in good yields. The synthesized eugenyloxy propanol azole derivatives were in vivo studied for the acute antinociception on male Spargue Dawley rats using tail-flick test. Compounds 5f, 5g, 7b and 11a exhibited potent analgesic properties in comparison with eugenol as a standard drug. In addition, all compounds were ex vivo tested for β-adrenoceptor blocking properties on isolated left atrium of male rats which exhibited partial antagonist or agonist behaviour compared to the standard drugs. The molecular docking study on the binding site of transient receptor potential vanilloid subtype 1 (TRPV1) has indicated that like capsaicin, eugenyloxy propanol azole analogues exhibited the strong affinity to bind at site of TPRV1 in a “tail-up, head-down” conformation and the presence of triazolyl moieties has played undeniable role in durable binding of these ligands to TRPV1. The in silico pharmacokinetic profile, drug likeness and toxicity predictions carried out for all compounds determined that 5g can be considered as potential antinociceptive drug candidate for future research.

     

Improving the Sound Absorption Properties of Flexible Polyurethane (PU) Foam using Nanofibers and Nanoparticles

Polyurethane foam as the most well-known absorbent materials has a suitable absorption coefficient only within a limited frequency range. The aim of this study was to improve the sound absorption coefficient of flexible polyurethane (PU) foam within the range of various frequencies using clay nanoparticles, polyacrylonitrile nanofibers, and polyvinylidene fluoride nanofibers. The response surface method was used to determine the effect of addition of nanofi- bers of PAN and PVDF, addition of clay nanoparticles, absorbent thickness, and air gap on the sound absorption coefficient of flexible polyurethane foam (PU) across different frequency ranges. The absorption coefficient of the samples was measured using Impedance Tubes device. Nano clay at low thicknesses as well as polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers at higher thicknesses had a greater positive effect on absorption coefficient. The mean sound absorption coefficient in the composite with the highest absorption coeffi- cient at middle and high frequencies was 0.798 and 0.75, respectively. In comparison with pure polyurethane foam with the same thickness and air gap, these values were 2.22 times at the middle frequencies and 1.47 times at high frequencies, respectively. Surface porosity rose with increasing nano clay, but decreased with increasing polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers. The results indicated that the absorption coefficient was elevated with increasing the thickness and air gap. This study suggests that the use of a combination of nanoparticles and nanofibers can enhance the acoustic properties of flexible polyurethane foam.     

Substituent effect on structure,stability, and aromaticity of novel BnNmC20–(n+m) heterofullerenes

We are focusing our calculations on the structural stabilities and electronic properties of 26 novel B_nN_mC_20–(n+m) heterofullerenes, with n, m = 1 ? 5, at B3LYP/6‐311++G** and B3LYP/AUG‐cc‐pVTZ levels of theory. Vibrational frequency calculations on C₂₀ and its analogues show that except B₂N₂C₁₆ (1) and B₂N₂C₁₆ (2), all other heterofullerenes are true minima. The heats of atomization energies, binding energy, band gaps (ΔE_HOMO‐LUMO), aromaticity, nucleus‐independent chemical shifts, thermodynamic stability, kinetic stability against electronic excitation, binding energy as a stability criterion of different configurations, geometrical parameters, conformational structures, conductivity, charge transfer, and possibility for hydrogen storage of these heterofullerenes strongly depend on their number of heteroatoms, topology, filling patterns, and locations as well as “B‐site and N‐site attachments.” B₅N₅C₁₀ contains 5 alternating boron and nitrogen atoms in the equatorial position. It is predicted to be thermodynamically and kinetically the most stable against electron excites. Thus, it is energetically favorable and its electronic properties as well as stabilities make it perhaps a good candidate for an experimental investigation and testing verification.     

Ground State Solutions for a Semilinear Elliptic Equation Involving Concave-convex Nonlinearities

This work is devoted to the existence and multiplicity properties of the ground state solutions of the semilinear boundary value problem $-Δu=λa(x)u|u|^{q-2}+ b(x)u|u|^{2^∗-2}$ in a bounded domain coupled with Dirichlet boundary condition. Here $2^∗$ is the critical Sobolev exponent, and the term ground state refers to minimizers of the corresponding energy within the set of nontrivial positive solutions. Using the Nehari manifold method we prove that one can find an interval L such that there exist at least two positive solutions of the problem for $λ∈Λ$.     

Dimension of quantum channel of radiation in pure Lovelock black holes

The effects of a running gravitational coupling and the entropic force on future singularities are considered. Although it is expected that the quantum corrections remove the future singularities or change the singularity type, treating the running gravitational coupling as a function of energy density is found to cause no change in the type of singularity but causes a delay in the time that a singularity occurs. The entropic force is found to replaces the singularity type $II\, \hbox {by} \overline{III} (a=\hbox {const.}, H=\hbox {const.}, \dot{H} \rightarrow \infty , p \rightarrow \infty , \rho \rightarrow \infty )$ which differs from previously known type $III$ and to remove the $w$ -singularity. We also consider an effective cosmological model and show that the types $I$ and $II$ are replaced by the singularity type $III$ .     

A note on the dynamic liquidity trading problem with a mean-variance objective

This note studies the dynamic liquidity trader’s problem with a mean-variance objective function. Independent of the market impact functions and the market price dynamics, we provide a necessary and sufficient condition under which the dynamic programming equation (Bellman equation) can be extended to mean-variance objectives. Evaluation of this condition involves solving an optimization problem and taking variance of its optimal value. This computation may be difficult even when random disturbances in the market price dynamics follow a well-known distribution. To avoid this pitfall, we then provide some sufficient condition which can be assessed very easily.     

Near infrared organic light-emitting diodes based on acceptor-donor-acceptor (ADA) using novel conjugated isatin Schiff bases

Fabrications of a single layer organic light emitting diodes (OLEDs) based on two conjugated acceptor-donor-acceptor (ADA) isatin Schiff bases are described. The electroluminescent spectra of these materials range from 630 to 700 nm and their band gaps were measured between 1.97 and 1.77 eV. The measured maximum external quantum efficiencies (EQE) for fabricated OLEDs are 0.0515% and 0.054% for two acceptor-donor-acceptor chromophores. The Commission International De L’Eclairage (CIE) (1931) coordinates of these two compounds were attained and found to be (0.4077, 0.4128) and (0.4411, 0.4126) for two used acceptor-donor-acceptor chromophores. The measured I-V curves demonstrated the apparent diode behavior of two ADA chromophores. The turn-on voltages in these OLEDs are directly dependent on the thickness. These results have demonstrated that ADA isatin Schiff bases could be considered as promising electroluminescence-emitting materials for fabrication of OLEDs.     

Design,synthesis, and biological activities of novel azole-bonded \upbeta -hydroxypropyl oxime O-ethers

The synthesis and biological effects of 15 novel azole-bonded \(\upbeta \) -hydroxypropyl oxime \(O\) -ethers have been described. In this synthesis, the oximation of aromatic ketones followed by an \(O\) -alkylation reaction with epichlorohydrin and/or epibromohydrin led to the corresponding \(O\) -oxime ether adducts. Subsequently, the attained \(O\) -oxime ether adducts were used to synthesize the target molecules after treating them with the appropriate azole derivatives. The in vitro antifungal and antibacterial activities of title compounds were obtained against several pathogenic fungi, Gram-positive and/or Gram-negative bacteria. Benzophenone \(O\) -2-hydroxy-3-(2-phenyl-1 \(H\) -imidazol-1-yl) propyl oxime and 9 \(H\) -fluoren-9-one \(O\) -2-hydroxy-3-(2-phenyl-1 \(H\) -imidazol-1-yl)propyl oxime proved to have considerable antifungal activity against Candida albicans, Candida krusei, Aspergillus niger, and Trichophyton rubrum. These two compounds demonstrated comparable antifungal activity to clotrimazole and fluconazole (standard drugs). All compounds were also tested against Escherichia coli and Staphylococcus aureus as Gram-negative and Gram-positive bacteria, respectively, and their activities were compared to gentamycin and ampicillin (reference drugs). In general, marginal antibacterial activity against tested bacteria was observed for the title compounds. A molecular docking study is also discussed for the two most potent compounds against fungi. The docking study reveals a considerable interaction between the two most potent compounds and the active site of Mycobacterium P450DM. Moreover, these two compounds are much strongly bound to the active site of Mycobacterium P450DM compared to fluconazole.