Kinetic simulation of oxidative coupling of methane over perovskite catalyst by genetic algorithm： Mechanistic aspects

The reaction kinetics of oxidative coupling of methane catalyzed by perovskite was studied in a fixed bed flow reactor. At atmospheric pressure, the reactions were carried out at 725, 750 and 775 ℃, inlet methane to oxygen ratios of 2 to 4.5 and gas hourly space velocity (GHSV) of 100 min-1. Correlation of the kinetic data has been performed with the proposed mechanisms. The selected equations have been regressed with experimental data accompanied by genetic algorithm (GA) in order to obtain optimized parameters. After investigation the Langmuir-Hinshelwood mechanism was selected as the best mechanism, and Arrhenius and adsorption parameters of this model were obtained by linear regression. In this research the Marquardt algorithm was also used and its results were compared with those of genetic algorithm. It should be noted that the Marquardt algorithm is sensitive to the selection of initial values and there is possibility to trap in a local minimum.     

Efficient and Ecofriendly Route for the Solvent-Free Synthesis of 4-Alkoxy-5H-chromen[2,3-d]pyrimidines Using Phosphonic Acid Functionalized KIT-6 Confined Ionic Liquid as Recoverable Catalyst

Phosphonic acid functionalized KIT-6 confined ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIm][BF₄]) catalyzed the one-pot condensation reaction of iminochromenes and salicylaldehydes with different primary alcohols to achieve the corresponding 4-alkoxy-5H-chromen[2,3-d]pyrimidines under solvent-free conditions and in good yields. This efficient nanocatalyst can be recovered for at least five reaction runs without significant loss of either activity or confined IL.     

Density functional study on the sensing properties of nano-sized BeO tube toward H2S

Using density functional calculations, we have investigated the adsorption of a H₂S molecule on the pristine and Si-doped BeO nanotubes (BeONT). It was found that the H₂S molecule is physically adsorbed on the pristine BeONT with adsorption energies ranging from 3.0 to 4.2 kcal/mol. Substituting a Be or O atom of the tube by Si increases the adsorption energy to 6.9–17.2 kcal/mol. We found that substituting an O atom by Si makes the electronic properties of the BeONT strongly sensitive to the H₂S molecule. Therefore, the process of Si doping provides a good strategy for improving the sensitivity of BeONT to toxic H₂S, which cannot be trapped and detected by the pristine BeONT. Also, the emitted electron current density from the Si_O–BeONT will be significantly increased after the H₂S adsorption.     

Solvent‐Dependent Enantiodivergence in the Chlorocyclization of Unsaturated Carbamates

A remarkable solvent‐controlled enantiodivergence is seen in the hydroquinidine 1,4‐phthalazinediyl diether ((DHQD)₂PHAL)‐catalyzed chlorocyclization of unsaturated carbamates. Eyring plot analyses of this previously unreported reaction are used to probe and compare the R‐ and S‐selective pathways. In the CHCl₃/hexanes solvent system, the pro‐R process shows a surprising increase in selectivity with increasing temperature. These studies point to a strongly solvent‐dependent entropy–enthalpy balance between the pro‐R and pro‐S pathways.     

A unique circular path of moving single bubble sonoluminescence in water

Based on a quasi-adiabatic model,the parameters of the bubble interior for a moving single bubble sonoluminescence (m-SBSL) in water are calculated.By using a complete form of the hydrodynamic force,a unique circular path for the m-SBSL in water is obtained.The effect of the ambient pressure variation on the bubble trajectory is also investigated.It is concluded that as the ambient pressure increases,the bubble moves along a circular path with a larger radius and all bubble parameters,such as gas pressure,interior temperature and light intensity,increase.A comparison is made between the parameters of the moving bubble in water and those in N-methylformamide.With fluid viscosity increasing,the circular path changes into an elliptic form and the light intensity increases.     

Protein Engineering of Bacillus thermocatenulatus Lipase via Deletion of the α5 Helix

Lipases from Bacillus thermocatenulatus are a member of superfamily of α/β hydrolase, but there are structural differences between them. In this work, we focused on the α5 helix of B. thermocatenulatus lipase (BTL2) which is absent in canonical α/β hydrolase fold. In silico study showed that the α5 helix is a region that causes disorder in BTL2 protein. So, the α5 helix (residues 131 to 150) has been deleted from the B. thermocatenulatus lipase gene (BTL2) and the remain (Δα5-BTL2) has been expressed in Pichia pastoris yeast. The α5 deletion results in increase of enzyme-specific activity in the presence of tributyrin, tricaproin, tricaprylin, tricaprin, trilaurin, and olive oil (C18) substrates by 1.4-, 1.7-, 2.0-, 1.2-, 1.75-, and 1.95-fold, respectively. Also, deletion leads to increase in enzyme activity in different temperatures and pHs, whereas it did not significantly affect on enzyme activity in the presence of organic solvents, metal ions, and detergents.     

Dihaloplatinum(II) complexes having diimine ligands: crystal structure,thermal properties,cytotoxicity effects against breast cancer cells and application as a precursor towards nanoparticles

The reaction of potassium tetrachloroplatinate(II) with dimethylsulfide and a mixture of HBr/KBr affords trans-[PtBr₂(SMe₂)₂]; [PtBr₂(Me₂bpy)] (Me₂bpy = 4,4'-dimethyl-2,2'-bipyridine) was prepared from the reaction of trans-[PtBr₂(SMe₂)₂] with Me₂bpy. The crystal structure of the yellow form of [PtBr₂(bu₂bpy)] (bu₂bpy = 4,4'-di-tert-butyl-2,2'-bipyridine) was determined by X-ray crystallography. The X-ray single-crystal structure determination of complex [PtBr₂(bu₂bpy)] reveals that the platinum adopts a square planar geometry with a twofold axis through the platinum atoms. Thermal properties of the related series of diimine platinum(II) complexes [PtX₂(bu₂bpy)] (X?=?Cl, Br, I) reveal that the thermal stabilities increase [PtI₂(bu₂bpy)]?<?[PtCl₂(bu₂bpy)]?<?[PtBr₂(bu₂bpy)]. [PtBr₂(bpy)] (bpy = 2,2'-bipyridine), [PtBr₂(Me₂bpy)] and [PtX₂(bu₂bpy)] (X?=?Cl, Br, I) were studied by MTT assay against two human breast cancer cell lines of MCF-7 and MDA-MB-468 with [PtCl₂(bu₂bpy)] having a higher cytotoxic effect towards both cancer cell lines, which shows the significant role of the halide and diimine ligand. Semi-spherical Pt(0) nanoparticles (NPCs) were prepared by the simple calcination of [PtX₂(bu₂bpy)] (X?=?Cl, Br, I) at 800?°C in air.     

Transient bioelectronics: Electronic properties of silver microparticle‐based circuits on polymeric substrates subjected to mechanical load

Transient soft bioelectronics are capable of forming conformal contacts with curvilinear surfaces of biological host tissues and organs. Such systems are often subject to continuous static and dynamic loads from the biological host. In this article, we present investigation of electronic attributes of transient soft bioelectronic circuits subjected to mechanical force and influence of substrate's transiency on the transiency of the whole device; also, characterize and quantify loss of functionality in triggered devices. Variations in the electrical conductivity of circuits as a function of applied mechanical load was used as a means to deduce electronic characteristics under stress. The experimental results suggest that there exists a correlation between electronic properties of circuits and applied mechanical strain; no clear correlation was, however, observed between electronic properties of circuits and frequency of the applied dynamic load. Control over transiency rate of identical circuits utilizing the transiency characteristics of the poly(vinyl alcohol)l‐based substrates is also studied and demonstrated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1603–1610