Highly efficient antimicrobial electrospun PVP/CS/PHMGH nanofibers membrane: preparation,antimicrobial activity and in vitro evaluations

Research on Chemical Intermediates - A highly efficient oligomer antimicrobial agent, polyhexamethylene guanidine hydrochloride (PHMGH), is added to mixtures of polyvinylpyrrolidone (PVP)/chitosan...     

化学蒸气发生-电感耦合等离子体原子发射光谱法测定地质样品中痕量金

地质样品经盐酸-硝酸(3+1)混合酸溶解,活性炭分离富集后,于90℃用12g.L-1硼氢化钠溶液(溶于0.5g.L-1氢氧化钠溶液中)作还原剂,用化学蒸气发生-电感耦合等离子体原子发射光谱法测定其中痕量的金。金的质量浓度在1 500μg.L-1以内与其发射强度呈线性关系,方法的检出限(3s)为0.59μg.L-1。方法用于测定2个标准物质(GBW 07289和GBW 07291)中金含量,测定值与认定值相符。     

Joint optimal fair cooperative spectrum sensing and transmission in cognitive radio

Since the sensing power consumption of cooperative spectrum sensing (CSS) will decrease the throughput of secondary users (SU) in cognitive radio (CR), a joint optimal model of fair CSS and transmission is proposed in this paper, which can compensate the sensing overhead of cooperative SUs. The model uses the periodic listen-before-transmission method, where each SU is assigned a portion of channel bandwidth, when the primary user (PU) is estimated to be free by the coordinator. Then, a joint optimization problem of local sensing time, number of cooperative SUs, transmission bandwidth and power is formulated, which can compensate the sensing overhead of cooperative SUs appropriately through choosing suitable compensating parameter. The proposed optimization problem can be solved by the Polyblock algorithm. Simulation results show that compared with the traditional model, the total system throughput of the fairness cooperation model decreases slightly, but the total throughput of the cooperative SUs improves obviously.     

Carbon-Based Materials as Lithium Hosts for Lithium Batteries

Lithium (Li) metal has attracted significant attention in areas that range from basic research to various commercial applications due to its high theoretical specific capacity (3860 mA h g⁻¹) and low electrochemical potential (−3.04 vs. standard hydrogen electrode). However, dendrites often form on the surfaces of Li metal anodes during cycling and thus lead to battery failure and, in some cases, raise safety concerns. To overcome this problem, a variety of approaches that vary the electrolyte, membrane, and/or anode have been proposed. Among these efforts, the use of three-dimensional frameworks as Li hosts, which can homogenize and minimize the current density at the anode surface, is an effective approach to suppress the formation of Li dendrites. Herein, we describe the development of using carbon-based materials as Li hosts. While these materials can be fabricated into a variety of porous structures, they have a number of intrinsic advantages including low costs, high specific surface areas, high electrical conductivities, and wide electrochemical stabilities. After briefly summarizing the formation mechanisms of Li dendrites, various methods for controlling structural and surface chemistry will be described for different types of carbon-based materials from the viewpoint of improving their performance as Li hosts. Finally, we provide perspective on the future development of Li host materials needed to meet the requirements for their use in flexible and wearable devices and other contemporary energy storage techniques.     

Ferric chloride-promoted direct trifluoromethylselenolation of nitrogen-containing heterocyclic compounds by Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate in water

The ferric chloride-promoted direct trifluoromethylselenolation of indoles and other nitrogen-containing heterocyclic compounds in water was performed by employing TsSeCF₃ as a trifluoromethylselenolation reagent. The shelf-stable and readily accessible reagents, along with the environmentally friendly and mild reaction conditions make this method an effective alternative for the trifluoromethylselenolation of electron-rich aromatics.     

Room temperature ionic liquid electrolytes for redox flow batteries

Redox flow batteries (RFBs) usually contain aqueous or organic electrolytes. The aim of this communication is to explore the suitability of room temperature ionic liquids (RTILs) as solvents for RFBs containing metal complexes. Towards this aim, the electrochemistry of the metal acetylacetonate (acac) complexes Mn(acac)₃, Cr(acac)₃, and V(acac)₃ was studied in imidazolium-based RTILs. The V²⁺/V³⁺, V³⁺/V⁴⁺, and V⁴⁺/V⁵⁺ redox couples are quasi-reversible in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C₂C₁Im][N(Tf₂)]. The Mn(acac)₃ and Cr(acac)₃ voltammetry, on the other hand, is irreversible in [C₂C₁Im][N(Tf₂)] at glassy carbon (GC) but the rate of the Mn²⁺/Mn³⁺ reaction increases if Au electrodes are used. Charge–discharge measurements show that a coulombic efficiency of 72% is achievable using a V(acac)₃/[C₂C₁Im][N(Tf₂)]/GC cell.     

Asymptotic Formulas and Inequalities for the Gamma Function in Terms of the Tri-Gamma Function

Results in Mathematics - In the paper, the authors establish some asymptotic formulas and double inequalities for the factorial n! and the gamma function Γ in terms of the tri-gamma function...     

One-step synthesis of novel flower-like Sn-doped ZnO architectures with enhanced photocatalytic activity

A facile hydrothermal method to synthesize flower-like Sn-doped ZnO (FLSn-ZnO) nanostructures is described. The obtained hierarchical architectures of FLSn-ZnO are found to be assembled with abundant regular-shaped nanosheets and nanoparticles. A possible formation mechanism is proposed on the base of a series of control experiments. The tests show that FLSn-ZnO architectures exhibit higher photocatalytic activity in the degrading Rhodamine B and tetracycline aqueous solution than pure ZnO under UV-light irradiation. And photocurrent response and photoluminescence of ZnO and FLSn-ZnO demonstrates that in photocatalytic performance, the latter is higher.