Composition and in vitro antibacterial activity of essential oils from four Satureja species growing in Iran

The composition and in?vitro antibacterial activity of essential oils from four Satureja species (S. bachtiarica, S. khuzistanica, S. mutica and S. rechingeri) growing in Iran were determined. According to the results of GC-FID and GC-MS analysis, all oil samples were principally composed of phenolic constituents (carvacrol and/or thymol) with the percentages ranging from 41.2% (S. bachtiarica) to 77.7% (S. rechingeri). Determining antibacterial activities by the disc diffusion method against two Gram-positive and two Gram-negative bacteria revealed the maximum activity against Bacillus cereus with a range of minimum inhibitory concentration values from 0.25 to 1?mg?mL(-1) and minimum bactericidal concentration values from 0.5 to 1?mg?mL(-1). The oils of S. khuzistanica and S. rechingeri appeared to be more active in general than those of other species. In conclusion, the essential oils of studied Satureja species have the potential to be considered as alternatives for synthetic food preservatives.     

Pd-poly(N-vinyl-2-pyrrolidone)/KIT-6 nanocomposite: Preparation,structural study,and catalytic activity

The Pd-poly(N-vinyl-2-pyrrolidone)/KIT-6 nanocomposite was prepared by an in situ polymerization method and used as an efficient heterogeneous catalyst for C–C bond formation through the Heck coupling reaction of aryl iodides, bromides and chlorides with styrene. The physical and chemical properties of the catalyst were characterized by XRD, BET, FT-IR, TGA, UV-Vis and TEM techniques. The reactions were performed in methanol-water as solvent and the products were obtained in high yield and purity after a simple work-up. The stability of the nanocomposite catalyst was excellent and could be reused 8 times without much loss of activity in the Heck coupling reaction.     

Zinc oxide nanoparticles:A highly efficient and readily recyclable catalyst for the synthesis of xanthenes

A novel and efficient route for the synthesis of 1,8-dioxooctahydroxanthenes and 14-aryl-14H-dibenzo[a,j]xanthenes is described through one-pot multi-component reaction of dimedone and 2-naphthol with various aryl aldehydes using ZnO nanoparticles under solvent-free conditions.This method provides a novel and improved pathway for the synthesis of xanthenes in the terms of excellent yields,short reaction times,reusability and low catalyst loading.     

Effects of substrate on surface morphology, crystallinity, and photoluminescence properties of sputtered ZnO nano films

Effects of substrate on crystallinity, surface morphology, and luminescence properties of radio frequency sputtered zinc oxide (ZnO) thin films were investigated. A variety of materials such as Si (100), Si (111), Al₂O₃, quartz, and silicon carbide (SiC) wafers were examined as substrates for deposition of ZnO thin films. The results showed smooth and uniform growth of c-axis orientation films. The thickness of the layers was about 50 nm. The average grain sizes of films were about 10, 13, and 12 nm for Si (111), quartz, and SiC samples, respectively. The deposited film on Al₂O₃ showed the largest grain size, about 500 nm. Grazing incidence x-ray diffraction patterns of the samples revealed that sputtered layers on Al₂O₃ and quartz had better crystallinity with higher peak at (002) orientation compared to Si and SiC substrates. Moreover, the Al₂O₃ sample exhibited a weak peak at position of (100) planes of ZnO too. The photoluminescence spectra of the samples showed a typical luminescence behavior with a broad UV band, including a main peak at around 388 nm and a weak shoulder peak at around 381 nm, corresponding with bound excitonic recombination and free excitonic recombination, respectively. The luminescence peak revealed that the intensity of UV emission is not necessarily dependent on the grain sizes and the micro-structural quality of ZnO films.     

Balanced fuzzy particle swarm optimization

In the present study an extension of particle swarm optimization (PSO) algorithm which is in conformity with actual nature is introduced for solving combinatorial optimization problems. Development of this algorithm is essentially based on balanced fuzzy sets theory. The classical fuzzy sets theory cannot distinguish differences between positive and negative information of membership functions, while in the new method both kinds of information “positive and negative” about membership function are equally important. The balanced fuzzy particle swarm optimization algorithm is used for fundamental optimization problem entitled traveling salesman problem (TSP). For convergence inspecting of new algorithm, method was used for TSP problems. Convergence curves were represented fast convergence in restricted and low iterations for balanced fuzzy particle swarm optimization algorithm (BF-PSO) comparison with fuzzy particle swarm optimization algorithm (F-PSO).     

B12N12纳米笼：潜在的二氧化氮检测传感器

利用密度泛函理论通过计算吸附能量、HOMO/LUMO能隙变化、电荷转移、结构扭曲等研究二氧化氮分子在B12N12纳米笼的吸附．此外,通过计算B₁₂N₁₂的电子结合能、Gibbs自由能、态密度和分子表面的静电势研究其稳定性和其它特性．B₁₂N₁₂纳米笼吸附二氧化氮显示三种构型．B₁₂N₁₂团簇的HOMO/LUMO能隙变化对二氧化氮分子的存在非常敏感,从自由团簇的6.84 eV降为NO₂/团簇稳定团簇的3.23 eV．团簇的导电性被极大地提高,表明B₁₂N₁₂纳米簇可能是潜在的二氧化氮气体分子检测传感器.     

H2TPP organocatalysis in mild and highly regioselective ring opening of epoxides to halo alcohols by means of halogen elements

We found that elemental iodine and bromine are converted to trihalide nucleophiles (triiodine and tribromide anion, respectively) in the presence of catalytic amounts of meso-tetraphenylporphyrins (H2TPP). Therefore a highly regioselective method for the synthesis of beta-haloalcohols through direct ring opening of epoxides with elemental iodine and bromine in the presence of H2TPPs as new catalysts is described. At room temperature a series of epoxide derivatives were converted into the corresponding halohydrins resulting from an attack of trihalide species anion atoms at the less substituted carbon atom. This method occurs under neutral and mild conditions with high yields in various aprotic solvents, even when sensitive functional groups are present.     

Synthesis and characterization of P4VP/SBA-15 composite by in situ polymerization

Abstract  

Poly(4-vinylpyridine)/SBA-15 (P4VP/SBA-15) composites with various amounts of SBA-15 were prepared and characterized. The physical and chemical properties of P4VP/SBA-15 were investigated by XRD, BET, FT-IR, TGA, and SEM techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compounds and ethyl cyanoacetate in the presence of water as a solvent. The effects of reaction temperature, the amount of catalyst, amount of support, solvent, and the amount of benzoyl peroxide during the synthesis of P4VP/SBA-15 were investigated, as well as the recyclability of the heterogeneous composite. The catalyst used for this synthetically useful transformation showed a considerable level of reusability as well as very good activity. This reaction occurred rapidly when water was used as a solvent, so we assume it to be a green reaction.     

Interactive effect of oxygen diffusion and volatiles advection on transient thermal degradation of poly methyl methacrylate (PMMA)

A transient, one-dimensional model has been presented to formulate the substantial role of polymer gasification in the early stages of fire growth. The present model comprises the interaction between the oxygen diffusion and the released volatiles on the rate of polymer gasification, when the polymeric sample is subjected to an external radiative source. The model also includes different mechanisms affecting the degradation process such as in-depth thermal and oxidative decomposition, in-depth absorption of radiation and heat and mass transfer in the both gas and solid phases. The results for two different radiative heat sources (17 and 40 kW m⁻²) are reported and yielded realistic results, comparing to the published experimental data. It was found that an increase in the oxygen concentration will lead to a considerable decrease in the surface temperature as well as significant increase of gasification rate at 17 kW m⁻²; nevertheless this effect is less apparent at 40 kW m⁻².     

Analysis of regular and irregular acoustic streaming patterns in a rectangular enclosure

This study reports an experimental investigation of the non-linear phenomena of regular (classical) and irregular streaming patterns generated in an air-filled rigid-walled square channel subjected to the acoustic standing waves of different frequencies and intensities. The interaction of acoustic waves and thermoviscous fluids is responsible for these phenomena. The resonator’s walls are maintained at isothermal condition. Synchronized particle image velocimetry (PIV) technique has been used to measure the streaming velocity fields. The experimental results show that at a given excitation frequency, regular streaming flow patterns are observed up to a certain value of the excitation amplitude. As the amplitude increases beyond this limit, the regular streaming is distorted to an irregular flow structure. The regular and irregular streaming are classified in terms of streaming Reynolds number . It is found that for Re_s2<50, classical streaming flow patterns are established and then deform to irregular and complex shapes as Re_s2 exceeds 50.