Efficient removal for multiple pollutants via Ag2O/BiOBr heterojunction: A promoted photocatalytic process by valid electron transfer pathway

Multiple pollutants including pathogenic microorganism contaminations and emerging organic contaminations (EOCs) have shown a growing threat to the environment, especially the natural waters. However, the control and removal of pathogenic microorganism contaminations and EOCs have been greatly limited since limited knowledge of their environmental behaviors. Thus, a novel and efficient photocatalyst Ag₂O/BiOBr heterojunction was synthesized and used for removal of multiple pollutants including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), tetracycline and acetaminophen under visible light. The results showed that there were valid electron transfer pathways between BiOBr and Ag₂O, the main electron transfer direction was the BiOBr to Ag₂O. Photo-generated electrons were stored in Ag₂O and thus separation efficiency between holes and photo-generated electrons was obviously enhanced. Active oxygen species were highly produced and eventually end up with the high efficiency of removal of multiple pollutants. For Ag₂O/BiOBr with Ag₂O content at 3% (the best performance) under visible light, log decrease of E. coli was 7.16 (removal efficiency was 100%) in 120 min, log decrease of S. aureus was 7.23 (removal efficiency was 100%) in 160 min, C/C₀ of tetracycline was 0.06 in 180 min, C/C₀ of acetaminophen was 0.17 in 180 min. This work could provide a promising candidate in the actual contaminated natural waters for cleaning multiple pollutants.     

Effect of methoxy position on dynamic mechanical and shape memory properties of methoxyphenol-based polybenzoxazines

Abstract

Two series of benzoxazines were synthesized from o-, m-, and p-methoxyphenols, two polyetheramines with different molecular weights, and formaldehyde. The glass transition temperatures (T _gs) of m-methoxyphenol-based polybenzoxazines are respectively higher than those of o- and p-methoxyphenol-based counterparts. The polybenzoxazines exhibit thermally induced one-way dual-shape memory behavior based on T _g, and the o- and p-methoxyphenol-based polybenzoxazines exhibit higher shape memory performance than m-methoxyphenol-based counterparts under motion constraints.     

Discrete element simulation of effects of multicontact loading on single particle crushing

Particle crushing commonly occurs in granular materials and affects their structures and mechanical properties. Unlike idealized particles in experimental single particle crushing tests with two loading points, natural particles are crushed under multicontact loading. To date, the criteria and patterns of particle crushing under multicontact conditions are not fully understood. By using the three-dimensional discrete element method, this report explores the effect of multicontact loading on the crushing criterion of a single particle, the crushing pattern, and the relationship between the particle crushing strength and loading distribution. The particles are modelled as aggregates of glued Voronoi polyhedra. The numerical results indicate that the logarithm of the mean principal stress has a good linear correlation with the coordination number. For a specific coordination number, the number of child particles presents a significant normal distribution. For a specific number of child particles, the volumes of child particles can be statistically described as normal or gamma distribution. Three typical models are proposed to qualitatively analyse the relationship between the loading distribution and crushing strength. The relevant conclusions can be helpful in engineering practice and in further studies on crushable granular materials via the discrete element method.     

Theoretical investigation on submicron particle penetration through circular tubes inside a porous medium

The analytical infinite series solution of submicron particle transport in a circular tube bounded by a porous wall, such as a pinhole, is determined under the slip velocity boundary condition, and the solution is verified by using the experimental data in the previous studies for the specific cases. The results show that particle penetration rate increases with the increase of the porous parameter, the axial pressure drop, and the pinhole radius, whereas it decreases with increasing the pinhole length. The penetration rate of nano-particles are more sensitive to the variation of these parameters. However, the differences between the penetrations of particles ranging from 0.3 μm to 1 μm are not evident because the diffusion becomes weak gradually in this size range. In addition, a further comparison is performed between the analytical solution and the existing studies, and approximate expressions are presented for accurate calculation of particle penetration rate through pinholes appearing in porous materials including filter devices and masks.     

Ge adsorption on Ag(111): A density-functional theory investigation

First-principles density-functional theory has been used to investigate the adsorptions of Ge on Ag(111) surfaces for a wide range of coverage. Preferred adsorption sites, adsorption energies, surface structures, and the electronic properties are studied. Our results show that adsorption on the surface in fcc- sites is energetically favorable. The adsorption energies decrease as increasing Ge atoms, while the work functions of Ag surface decrease. The contour maps of the difference charge show that there exists covalent bonding in lower coverage systems to some extent for Ge on Ag(111) surface, and the interaction of Ge and Ag atoms becomes weaker with the increase of adsorption degree. The calculated density of states indicates that the adsorption structures have metallic character, while the number of electron transition is small and the interaction is not strong between Ge and Ag atoms.     

Valuation and risk assessment of participating life insurance in the presence of credit risk

In participating life insurance, management decisions regarding the asset composition can substantially impact the value of a policy from the policyholders’ perspective as well as the insurer’s risk situation. Due to the long-term guarantees often embedded in these contracts, life insurers typically invest a considerable portion of their capital in long-term assets such as corporate and government bonds. Besides interest rate risk, the value of these bond investments is thus particularly influenced by credit risk. Thus, the aim of this paper is to examine the impact of market risk associated with the asset composition on fair valuation and risk assessment with focus on credit risk and its interaction with equity risk and interest rate risk. Our analysis emphasizes that the consideration of credit risk associated with bonds has a strong impact on the fair valuation and risk measurement in the context of participating life insurance contracts, even in case of higher grade bond exposures.     

Flame retardancy and mechanical properties of poly(decamethylene terephthalamide) filled with metal phosphinates

Flame retardancy and mechanical properties of poly(decamethylene terephthalamide) (PA10T) containing aluminum diethlyphosphinate (BEPAL) were investigated. The influence of BEPAL on the thermal degradation behavior of PA10T was studied using thermogravimetry, flammability test and chemical analysis. A decomposition model was given on the basis of Lewis acid-base interaction. The introduction of BEPAL led to reduced decomposition temperature, while the limiting oxygen index was greatly improved. The investigation of mechanical properties of PA10T/BEPAL composites indicated that the tensile strength firstly increased when low content BEPAL was added, then decreased with further increasing the concentration of BEPAL due to the agglomeration of filler particles. Dynamic mechanical analysis (DMA) results revealed that the presence of BEPAL hindered the movement of molecular chain.     

Fluorinated vs hydrogenated surfactants in mixtures with valinomycin—The Langmuir monolayer study

Selected fluorinated and hydrogenated surfactants, namely a semifluorinated alkane (SFA): 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-henicosafluorononacosane (F10H19), two long chain alcohols: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-ol (F8H10OH) and octadecane-1-ol (C18OH) and with two long chain thiols of the analogous apolar part structure to the above-mentioned alcohols, i.e.: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-thiol (F8H10SH) and octadecane-1-thiol (C18SH) have been tested in mixtures with valinomycin as potential artificial matrixes for its immobilization. The thermodynamic analysis (ΔG^exc vs X_val plots) based on surface pressure–area isotherm registration for particular valinomycin/surfactant mixtures, complemented with BAM images of the films structure indicate that only fluorinated surfactants are suitable materials for valinomycin incorporation as they form homogeneous miscible monolayers at X_val below 0.5.     

Extending slow manifold near generic transcritical canard point

We consider the dynamics of planar fast-slow systems near generic transcritical type canard point. By using geometric singular perturbation theory combined with the recently developed blow-up technique, the existence of canard cycles, relaxation oscillations and solutions near the attracting branch of the critical manifold is established. The asymptotic expansion of the parameter for which canard exists is obtained by a version of the Melnikov method.     

Isolation and Purification of Unstable Iridoid Glucosides from Traditional Chinese Medicine by Preparative High Performance Liquid Chromatography Coupled with Solid-phase Extraction

An efficient preparative method was successfully developed for isolation and purification of unstable components from medicinal plant extracts, using a combined method of preparative high performance liquid chro-matography(HPLC) and solid-phase extraction(SPE). The aim of this study was to obtain an effective method with high preparative efficiency and importantly to avoid the transformation of unstable compounds. The preparative HPLC system was based on an LC/MS controlled four-channel autopurification sys...