Bouncing universe models in an extended gravity theory

Some bouncing models are investigated in the framework of an extended theory of gravity. The extended gravity model is a simple extension of the General Relativity where an additional matter geometry coupling is introduced to account for the late time cosmic speed up phenomena. The dynamics of the models are discussed in the background of a flat FRW universe. Some viable models are reconstructed for specifically assumed bouncing scale factors. The behavior of the models are found to be decided mostly by the parameters of the respective models. The extended gravity based minimal matter-geometry coupling parameter has a role to remove the omega singularity occurring at the bouncing epoch. It is noted that the constructed models violate the energy conditions, however, in some cases this violation leads to the evolution of the models in phantom phase. The stability of the models are analyzed under linear homogeneous perturbations and it is found that, near the bounce, the models show instability but the perturbations decay out smoothly to provide stable models at late times.     

Exponential Stability for Time-changed Stochastic Differential Equations

Acta Mathematicae Applicatae Sinica, English Series - So far there have been few results presented on the exponential stability for time-changed stochastic differential equations. The main aim of...     

“Quad-band flexible magnesium zinc ferrite (MgZnFe2O4)-based double negative metamaterial for microwave applications”

This article presents vertically coupled, rectangular complementary split-ring resonator-shaped quad-band double-negative (DNG) metamaterial unit cells, that is, having both negative permittivity and permeability, which redirect negative refractive and also are not found in nature. The metamaterial is fabricated on magnesium zinc ferrite-based flexible microwave substrates, and the flexible substrates are chosen with two different concentrations of magnesium (Mg) denoted by Mg₃₀ and Mg₅₀ for 30% and 50% of Mg, which possess dielectric constants of 4.32 and 3.15 and loss tangents of 0.003 and 0.005, respectively. The proposed metamaterials are demonstrated by utilizing the CST microwave simulator, and their effective parameters are extracted according to the Nicolson-Ross-Wire method. With Mg_30, the prepared, flexible metamaterial shows measured resonances at 3.70 GHz, 7 GHz, 8.60 GHz, and 9.78 GHz, whereas with Mg₅₀ it shows the measured resonances at 4.10 GHz, 7.70 GHz, 9.33 GHz, and 10.62 GHz. Very good effective medium ratios (EMR) along with DNG properties are obtained, namely 6.5 and 5.85 for Mg₃₀ and Mg_50, respectively, with a physical dimension of 12.5 × 9.5 mm² for both of the unit cells_. Also, the electric field, magnetic field, and surface current distribution at different resonances and the polarization insensitivity at different polarization angles were observed. Thus, the designed new flexible substrate microwave materials based on DNG metamaterials are potential candidates for S-, C- and X-band applications, as well as for flexible microwave technologies.     

Spectroscopic properties of the low-lying electronic states and laser cooling feasibility for the SrI molecule

Laser cooling of a molecule with heavy nuclei is often complicated because of the density distribution of the electronic states. Here, we evaluate the feasibility of the laser cooling of the SrI molecule by calculating the potential energy curves and transition dipole moments of the ground and low-lying excited states using the multi-reference configuration interaction plus Davidson corrections (MRCI + Q) and the all-electron basis sets of ANO-RCC. The relativistic effect and the spin-orbit coupling splits are included, because both Sr and I are heavy atoms. Based on the obtained potential energy curves, we solve the Schrödinger equation of nuclear motion to determine the rovibrational energy levels and the Franck-Condon factors. The spectroscopic parameters are obtained by fitting the rovibrational energy levels with the Dunham expression. The radiation lifetimes, the Doppler and recoil temperatures between the X²Σ⁺ and the ²Π_1/2/²Π_3/2/B²Σ⁺ states are calculated. 5-color laser cooling schemes for the molecule are proposed, which can lead to the total effective Franck-Condon factors being 0.99983, 0.99979, and 0.99941 for the three transitions, respectively. All the obtained results suggest that the SrI molecule is a feasible candidate for laser cooling.     

A chlorinated non-fullerene acceptor for efficient polymer solar cells

Improving the performance and reducing the manufacturing costs are the main directions for the development of organic solar cells in the future. Here, the strategy that uses chemical structure modification to optimize the photoelectric properties is reported. A new narrow bandgap (1.30 eV) chlorinated non-fullerene electron acceptor (Y15), based on benzo[d][1,2,3] triazole with two 3-undecyl-thieno[2′,3′:4,5] thieno[3,2-b] pyrrole fused -7-heterocyclic ring, with absorption edge extending to the near-infrared (NIR) region, namely A-DA'D-A type structure, is designed and synthesized. Its electrochemical and optoelectronic properties are systematically investigated. Benefitting from its NIR light harvesting, the fabricated photovoltaic devices based on Y15 deliver a high power conversion efficiency (PCE) of 14.13%, when blending with a wide bandgap polymer donor PM6. Our results show that the A-DA'D-A type molecular design and application of near-infrared electron acceptors have the potential to further improve the PCE of polymer solar cells (PSCs).     

Enhanced uranium bioleaching high-fluorine and low-sulfur uranium ore by a mesophilic acidophilic bacterial consortium with pyrite

The high level of fluorine and low sulfur in the ore could significantly undermine the bioleaching effectiveness. Here, a strategy to improve the bioleaching efficiency by introducing fluoride-resistant mesophilic eosinophils coupled with pyrite supplement was investigated in a bioleaching system with such ore. The results of column and heap bioleaching showed that 89.25% and 90.40% of uranium were recovered with the consortium and pyrite addition, which increased the uranium leaching rates by 13.22% and 8.96% as compared with the sulfuric acid leaching. Hence, it provides a method to improve uranium bioleaching efficiency of the high-fluorine and low-sulfur uranium ore by the consortium adding pyrite.

     

Construction of a novel ZnCo2O4/Bi2O3 heterojunction photocatalyst with enhanced visible light photocatalytic activity

A novel ZnCo₂O₄/Bi₂O₃ heterojunction photocatalyst was prepared via balling method. The enhanced photocatalytic activity is mainly attributed to the broad photoabsorption and low recombination rate of photogenerated electron-hole pairs, which is driven by the photogenerated potential difference formed at the ZnCo₂O₄/Bi₂O₃ heterojunction interface.     

In silico identification of natural products with anticancer activity using a chemo-structural database of Brazilian biodiversity

Cancer is one of the leading causes of death worldwide, and the number of patients has only increased each year, despite the considerable efforts and investments in scientific research. Since natural products (NPs) may serve as suitable sources for drug development, the cytotoxicity against cancer cells of 2221 compounds from the Nuclei of Bioassays, Ecophysiology, and Biosynthesis of Natural Products Database (NuBBE_DB) was predicted using CDRUG algorithm. Molecular modeling, chemoinformatics, and chemometric tools were then used to analyze the structural and physicochemical properties of these compounds. We compared the positive NPs with FDA-approved anticancer drugs and predicted the molecular targets involved in the anticancer activity. In the present study, 46 families comprising potential anticancer compounds and at least 19 molecular targets involved in oncogenesis. To the best of our knowledge, this is the first large-scale study conducted to evaluate the potentiality of NPs sourced from Brazilian biodiversity as anticancer agents, using in silico approaches. Our results provided interesting insights about the mechanism of action of these compounds, and also suggested that their structural diversity may aid structure-based optimization strategies for developing novel drugs for cancer therapy.