An analysis of peak overpressures in vented gaseous explosions

Experimental data from vented explosion tests using stoichiometric methane–air and 18% hydrogen–air mixtures in a 63.7 m³ chamber with a 2.7 or 5.4 m² vent are presented. Results from experiments conducted using stoichiometric propane–air in 2.42 m³ vessel with a 0.26 m² vent are also reported. The tests were focused on the effect of fuel, enclosure size, ignition location, vent size, and obstacles on the pressure development of a propagating flame in a vented enclosure. The dependence of the maximum pressure generated on the experimental parameters was analyzed. It was found that the pressure maxima may be caused by pressure transients controlled by the interplay of the maximum-flame area, the burning velocity, and the overpressure generated by an external explosion. A simple model was proposed to estimate the maximum pressure for each of the main pressure transients. The model was found to agree with the experimental data within the experimental uncertainty.     

High‐order implicit time integration for unsteady incompressible flows

The spatial discretization of unsteady incompressible Navier–Stokes equations is stated as a system of differential algebraic equations, corresponding to the conservation of momentum equation plus the constraint due to the incompressibility condition. Asymptotic stability of Runge–Kutta and Rosenbrock methods applied to the solution of the resulting index‐2 differential algebraic equations system is analyzed. A critical comparison of Rosenbrock, semi‐implicit, and fully implicit Runge–Kutta methods is performed in terms of order of convergence and stability. Numerical examples, considering a discontinuous Galerkin formulation with piecewise solenoidal approximation, demonstrate the applicability of the approaches and compare their performance with classical methods for incompressible flows. Copyright © 2011 John Wiley & Sons, Ltd.     

FEW: A workflow tool for free energy calculations of ligand binding

In the later stages of drug design projects, accurately predicting relative binding affinities of chemically similar compounds to a biomolecular target is of utmost importance for making decisions based on the ranking of such compounds. So far, the extensive application of binding free energy approaches has been hampered by the complex and time‐consuming setup of such calculations. We introduce the free energy workflow (FEW) tool that facilitates setup and execution of binding free energy calculations with the AMBER suite for multiple ligands. FEW allows performing free energy calculations according to the implicit solvent molecular mechanics (MM‐PB(GB)SA), the linear interaction energy, and the thermodynamic integration approaches. We describe the tool's architecture and functionality and demonstrate in a show case study on Factor Xa inhibitors that the time needed for the preparation and analysis of free energy calculations is considerably reduced with FEW compared to a fully manual procedure. © 2013 Wiley Periodicals, Inc.     

Antibacterial and Antifungal Activities—Surface Active Properties Relation of Novel Dischiff Base Cationic Gemini Amphiphiles Bearing Homogeneous Hydrophobes

A novel series of cationic Gemini amphiphiles containing Dischiff base species were synthesized and their chemical structures were determined using different analytical tools. Their surface properties were determined using surface tension measurements. The adsorption and micellization thermodynamic parameters were calculated using Gibb's equations at 25°C. The surface parameters were also determined including critical micelle concentration, effectiveness, efficiency, maximum surface excess, minimum surface area, interfacial tension, and emulsification power. The synthesized cationic Gemini surfactants were evaluated as bactericides for gram negative and gram positive bacteria and also against sulfur reducing bacteria (SRB). The results of the cytotoxicity of the synthesized compounds against the targeted bacterial strains were promising and completely dependent on the surface activity of these compounds.     

Pairwise decomposition of an MMGBSA energy function for computational protein design

Computational protein design (CPD) aims at predicting new proteins or modifying existing ones. The computational challenge is huge as it requires exploring an enormous sequence and conformation space. The difficulty can be reduced by considering a fixed backbone and a discrete set of sidechain conformations. Another common strategy consists in precalculating a pairwise energy matrix, from which the energy of any sequence/conformation can be quickly obtained. In this work, we examine the pairwise decomposition of protein MMGBSA energy functions from a general theoretical perspective, and an implementation proposed earlier for CPD. It includes a Generalized Born term, whose many‐body character is overcome using an effective dielectric environment, and a Surface Area term, for which we present an improved pairwise decomposition. A detailed evaluation of the error introduced by the decomposition on the different energy components is performed. We show that the error remains reasonable, compared to other uncertainties. © 2014 Wiley Periodicals, Inc.     

Nanocast mesoporous mixed metal oxides for catalytic applications

Since the initial discovery of ordered mesoporous silica in early 1990s, considerable innovations were achieved regarding their synthesis, characterization and applications. One of the best outcomes of these intense research efforts is the development of a solid templating method called “nanocasting”, which is based on using mesoporous silica (or carbon) as a rigid template. This solid-to-solid replication method opened the pathway for synthesizing high surface area non-silica mesostructured materials that are challenging to obtain through conventional self-assembly processes which are based on amphiphilic soft structure-directing agents. In particular, the replicated metal oxide mesostructures obtained by this method were found to be highly versatile for a wide range of applications, especially in catalysis, owing to their large specific surface area. Furthermore, the nanocasting method is particularly suited for the synthesis of mixed metal compositions, favored by the possible confinement of mixed precursors in the nanopores of the template. In this account, we discuss some of the recent developments regarding the synthesis of nanocast mixed metal oxides and their perspectives of catalytic applications. It is here the choice of the authors to place emphasis on a few representative examples of compositions (e.g., non-noble metal-based catalysts, perovskites) and catalytic reactions (e.g., hydrogen production, gas-phase oxidation).     

A Highly Sensitive and Selective Label-free Electrochemical Biosensor with a Wide Range of Applications for Bisphenol A Detection

A label-free DNA-based electrochemical biosensor owning high sensitivity and selectivity has been established for detecting bisphenol A in a wide range of applications. Coupling the high electrochemical performance of graphene oxide-thionine-Au nanomaterial with the specific binding capacity of the aptamers to BPA, the monitoring of trace amount of BPA was realized, the detection limit was 3.3 pg ⋅ mL⁻¹ with strong anti-interference. Besides, using molecular docking, it was found that BPA binds to the bases DC-49, DC-51, DG-52, DG-53 and DA-63 on the aptamer via hydrogen bonding and π-π stacking interactions. Finally, the biosensor had been successfully applied in different real samples.     

Synthesis of activated carbon foams with high specific surface area using polyurethane elastomer templates for effective removal of methylene blue

Carbon foams have gained significant attention due to their tuneable properties that enable a wide range of applications including catalysis, energy storage and wastewater treatment. Novel synthesis pathways enable novel applications via yielding complex, hierarchical material structure. In this work, activated carbon foams (ACFs) were produced from waste polyurethane elastomer templates using different synthesis pathways, including a novel one-step method. Uniquely, the produced foams exhibited complex structure and contained carbon microspheres. The ACFs were synthesized by impregnating the elastomers in an acidified sucrose solution followed by direct activation using CO₂ at 1000 ℃. Different pyrolysis and activation conditions were investigated. The ACFs were characterized by a high specific surface area (S_BET) of 2172 m²/g and an enhanced pore volume of 1.08 cm³/g. Computer tomography and morphological studies revealed an inhomogeneous porous structure and the presence of numerous carbon spheres of varying sizes embedded in the porous network of the three-dimensional carbon foam. X-ray diffraction (XRD) and Raman spectroscopy indicated that the obtained carbon foam was amorphous and of turbostratic structure. Moreover, the activation process enhanced the surface of the carbon foam, making it more hydrophilic via altering pore size distribution and introducing oxygen functional groups. In equilibrium, the adsorption of methylene blue on ACF followed the Langmuir isotherm model with a maximum adsorption capacity of 592 mg/g. Based on these results, the produced ACFs have potential applications as adsorbents, catalyst support and electrode material in energy storage systems.     

二维过渡金属硫属化合物的大面积制备与应用研究进展

二维过渡金属硫属化合物(TMDs)因具有可调带隙、 谷电子学性质和高催化活性等优点, 在电子学、 光电子学和能源相关领域受到广泛关注. 为了实现以上应用, 实现大面积、 厚度均匀TMDs薄膜的批量制备至关重要. 化学气相沉积法(CVD)是制备大面积均匀、 高质量二维材料普遍使用的方法. 本文从前驱体的供给和衬底的设计两个角度, 总结了目前合成大面积TMDs薄膜的CVD方法, 并讨论了高质量TMDs的生长机制和参数优化方法; 介绍了高质量TMDs在电子学、 光电子学和电/光催化等方面的应用; 讨论了目前合成大面积均匀、 高质量TMDs所面临的挑战, 并对该领域的发展方向进行了展望.     

Asymptotically exact a posteriori local discontinuous Galerkin error estimates for the one‐dimensional second‐order wave equation

In this article, we analyze a residual‐based a posteriori error estimates of the spatial errors for the semidiscrete local discontinuous Galerkin (LDG) method applied to the one‐dimensional second‐order wave equation. These error estimates are computationally simple and are obtained by solving a local steady problem with no boundary condition on each element. We apply the optimal L² error estimates and the superconvergence results of Part I of this work [Baccouch, Numer Methods Partial Differential Equations 30 (2014), 862–901] to prove that, for smooth solutions, these a posteriori LDG error estimates for the solution and its spatial derivative, at a fixed time, converge to the true spatial errors in the L²‐norm under mesh refinement. The order of convergence is proved to be , when p‐degree piecewise polynomials with are used. As a consequence, we prove that the LDG method combined with the a posteriori error estimation procedure yields both accurate error estimates and superconvergent solutions. Our computational results show higher convergence rate. We further prove that the global effectivity indices, for both the solution and its derivative, in the L²‐norm converge to unity at rate while numerically they exhibit and rates, respectively. Numerical experiments are shown to validate the theoretical results. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1461–1491, 2015