The effect of local electronic interaction on the optical properties of boron–nitride nanotubes

We investigate the behavior of optical absorption of boron–nitride nanotubes (6,0) in the context of Hubbard model at the paramagnetic sector. GW approximation has been implemented in order to make self-energy matrix of electronic system. Afterwards, the real and imaginary parts of transverse dielectric functions have been obtained using linear response theory. The results show that the frequency gap in the optical absorption decreases with Coulomb repulsion strength. Moreover the results show that the local Coulomb interaction leads to the appearance of the excitonic effects in the optical spectrum. Finally the effects of electronic concentration on the frequency behavior of imaginary part of dielectric function have been investigated.     

Dispersion and localisation in structured Rayleigh beams

This paper brings a comparative analysis between dynamic models of couple-stress elastic materials and structured Rayleigh beams on a Winkler foundation. Although physical phenomena have different physical origins, the underlying equations appear to be similar, and hence mathematical models have a lot in common. In the present work, our main focus is on the analysis of dispersive waves, band-gaps and localised waveforms in structured Rayleigh beams. The Rayleigh beam theory includes the effects of rotational inertia which are neglected in the Euler–Bernoulli beam theory. This makes the approach applicable to higher frequency regimes. Special attention is given to waves in pre-stressed Rayleigh beams on elastic foundations.     

Conducting moisture sensitive reactions under mechanochemical conditions

Dry organic solvents are used for various organic reactions that employ moisture sensitive reagents. The processes to dry these solvents are hazardous and costly. Setting up reactions in an open atmosphere while using moisture sensitive reagents has little to no effect on the rate or yield of the reaction under mechanochemical conditions. We believe this is partly due to the gaseous nature of the water vapor in the air compared to the dissolved water and oxygen in solution.     

非平稳确定性信号与非平稳随机信号统一分类法的探讨

根据信号通过线性系统可产生新信号的理论,对非平稳确定性信号与非平稳随机信号的统一分类方法进行了深入研究,分别给出格林函数描述的线性时变系统法、调制函数作用于边界稳定线性系统的自激振荡正弦波法、随机输入线性时不变系统与边界稳定的与不稳定的线性系统组合法。这3种分类法便于对非平稳确定性信号与非平稳随机信号进行统一分类研究,并具有比较全面与系统性好的优点。     

Polyethylene glycol (PEG-400): An efficient one-pot green synthesis and anti-viral activity of novel α-diaminophosphonates

Abstract

An efficient and eco-friendly protocol has been accomplished for a series of novel α-diaminophosphonates by a one-pot, three-component system via Kabachnik-Fields reaction of 4,4′-methylenedianiline, a variety of aryl/heteroaryl aldehydes and diphenylphosphite employing polyethylene glycol (PEG-400) as a green solvent at 80?°C. All products were obtained in good to excellent yields (80–95%). The identity of the new synthesized compounds was confirmed by IR, ¹H, 13C, and 31P NMR, LC-MS and elemental analysis. In vivo anti-viral activity was evaluated against tobacco mosaic virus (TMV). Compounds 4b, 4c, 4j and 4k exhibited the highest anti-viral activities against tobacco mosaic virus (TMV) when compared with the standard drug ningnanmycin.     

Microwave Irradiation for Accelerating Synthesis of New Chiral Nanostructured Poly(amide-imide)s Having a Thiazole Pendant Group

Microwave irradiation was used to accelerate the polycondensation of a new thiazole-containing diamine with several chiral diacids. Polymerization reactions were carried out in molten tetrabutylammonium bromide as a green molten salt medium and triphenyl phosphite as the homogenizer. A series of new compounds were characterized by Fourier transform-infrared spectroscopy, nuclear magnetic resonance spectroscopy, and elemental analysis techniques. The polymeric samples showed high thermal stability with decomposition temperature being above 360°C; they were in a nanoscale size and were assembled uniformly and randomly in a sponge-like morphology.     

Natural deep eutectic solvents as new potential media for green technology

Developing new green solvents is one of the key subjects in Green Chemistry. Ionic liquids (ILs) and deep eutectic solvents, thus, have been paid great attention to replace current harsh organic solvents and have been applied to many chemical processing such as extraction and synthesis. However, current ionic liquids and deep eutectic solvents have still limitations to be applied to a real chemical industry due to toxicity against human and environment and high cost of ILs and solid state of most deep eutectic solvents at room temperature. Recently we discovered that many plant abundant primary metabolites changed their state from solid to liquid when they were mixed in proper ratio. This finding made us hypothesize that natural deep eutectic solvents (NADES) play a role as alternative media to water in living organisms and tested a wide range of natural products, which resulted in discovery of over 100 NADES from nature. In order to prove deep eutectic feature the interaction between the molecules was investigated by nuclear magnetic resonance spectroscopy. All the tested NADES show clear hydrogen bonding between components. As next step physical properties of NADES such as water activity, density, viscosity, polarity and thermal properties were measured as well as the effect of water on the physical properties. In the last stage the novel NADES were applied to the solubilization of wide range of biomolecules such as non-water soluble bioactive natural products, gluten, starch, and DNA. In most cases the solubility of the biomolecules evaluated in this study was greatly higher than water. Based on the results the novel NADES may be expected as potential green solvents at room temperature in diverse fields of chemistry.     

Green chemistry for the synthesis of methacrylate-based hydrogels crosslinked through Diels–Alder reaction

This study describes an environmentally friendly and green synthetic approach for the preparation of poly(aminoethylmethacrylate)-based hydrogels crosslinked through Diels–Alder (DA) reaction in water. This “click” reaction offers the possibility of preparing chemically crosslinked hydrogels in the absence of any catalyst, initiator or coupling agent, thus preserving the biocompatibility of the material. The suitable furan diene was obtained by modifying a methacrylate polymer by its reaction with furfural, a first generation compound derived from renewable resources. Methacrylate-based complementary polymeric dienophiles were also prepared by introducing maleimide groups into the structure. The products obtained at different steps were characterized by FTIR, NMR and TGA techniques. The study of the rheological properties of the hydrogels proved the success of this green “click” synthetic strategy confirming the formation of chemically crosslinked networks by the use of the Diels–Alder reaction. Furthermore, SEM studies revealed promising morphological properties of the ensuing hydrogels in terms of biomedical applications.     

Synthesis in Water and Antimicrobial Activity of 5-Trichloromethyl-4,5-dihydroisoxazoles

Two series of 5-trichloromethylisoxazoles were synthesized from the cyclocondensation of 1,1,1-trichloro-4-methoxy-3-alken-2-ones [Cl₃CC(O)C(R²) = C(R¹)OMe, where R¹ = H, Me, Et, Pr, iso-Pr, cyclo-Pr, Bu, terc-Bu, CH₂Br, CHBr₂, CH(Me)SMe, (CH₂)₂Ph, and Ph, and R² = H; R¹ = H and R² = Me and Et; R¹ and R² = -(CH₂)₄- and -(CH₂)₅-; and R¹ = Et and Ph and R² = Me] with hydroxylamine hydrochloride through a rapid one-pot reaction in water. The 5-trichloromethyl-4,5-dihydroisoxazoles were aromatized by reaction with concentrated sulfuric acid to obtain the respective 5-trichloromethylisoxazoles. Their structures were confirmed by elemental analysis, ¹H/¹³C nuclear magnetic resonance, and electron impact mass spectroscopy. Crystal structure analysis for 5-triclhoromethyl-5-hydroxy-3-propyl-4,5-dihydroisoxazole (2d) and 5-trichloromethyl-5-hydroxy-3,4-hexamethylene-4,5-dihydroisoxazole (2o) is presented. The antimicrobial activities of the 5-trichloromethyl-4,5-dihydroisoxazole derivatives were examined using the standard twofold dilution method against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and yeasts (Candida spp. and Cryptococcus neoformans). All of the tested 5-trichloromethyldihydroisoxazoles exhibited antibacterial and antifungal activities at the tested concentrations.

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