An Efficient Three‐Component Synthesis of Pyranoquinoline Derivatives

Pyranoquinoline derivatives have been synthesized via three‐component reaction of 4‐hydroxy‐1‐methyl‐2(1H)‐quinolinone and dialkyl acetylenedicarboxylates in the presence of nucleophiles such as alkyl isocyanides and triphenylphosphine.     

Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling

Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M – 2H]^2– ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M – 3H]^3– ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M – 2H]^2– ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M – 3H]^3– ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.

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Full polysaccharide chitosan‐CMC membrane and silver nanocomposite: synthesis,characterization, and antibacterial behaviors

Chitosan‐carboxymethyl cellulose (CMC) full polysaccharide membrane was prepared by cross‐linking of chitosan with CMC dialdehyde and subsequent reductive amination. CMC dialdehyde molecule was prepared by periodate oxidation of CMC and then applied as a cross‐linking agent to form a new membrane network. The properties of oxidized CMC were investigated by various methods such as Fourier transform infrared (FT‐IR) spectroscopy, ¹H NMR spectroscopy, and viscosity test. Then, novel chitosan‐CMC silver nanocomposite was prepared using chitosan‐CMC as a carrier. The structure of the chitosan‐CMC membrane and the silver nanocomposite were confirmed by FT‐IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). TEM images indicate that the chitosan‐CMC nanocomposite comprises silver nanoparticles with diameters in the range of about 5–20 nm. The antibacterial studies of the nanocomposite were also evaluated. The chitosan‐CMC silver nanocomposite demonstrates good antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Copyright © 2016 John Wiley & Sons, Ltd.     

Vitamin C functionalized multi-walled carbon nanotubes and its reinforcement on poly(ester-imide) nanocomposites containing L-isoleucine amino acid moiety

The aim of this research was to prepare poly(ester–imide) (PEI)-based nanocomposites (NCs) through the functionalization of carboxylated-multiwalled carbon nanotubes (MWCNT)s with ascorbic acid, in order to ensure better filler dispersion and good interfacial adhesion between filler and matrix. Chiral and biodegradable PEI was synthesized from amino acid-based diacid with 4,4′-thiobis(2-tert-butyl-5-methylphenol) by a direct polycondensation method. Using the solution mixing technique, the NCs containing modified MWCNTs with different loading levels of 5,10, 15 wt% were produced and examined in terms of chemical structure, morphology, and thermal stability by FT-IR spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). TEM and FE-SEM photographs of the obtained NCs indicated well-dispersed morphologies and strong interaction between the functionalized MWCNTs and the polymer matrix. TGA results revealed that the addition of MWCNT resulted in a significant increase of the thermal stability and char yields of the NCs compared to those of the neat PEI.     

Time growth rate optimisation of terahertz electromagnetic wave generation by converting occupied plasma region from annular plasma to filled plasma in the core,in an elliptical Cherenkov maser with two energy sources

A theoretical model is described here for studying the effect of temperature on nanomaterials. The thermodynamic equation of state (EoS) proposed by Goyal and Gupta in High Temp.-High Press. 45, 163 (2016); Oriental J. Chem. 32(4), 2193 (2016), is extended in the present study using Qi and Wang model [Mater. Chem. Phys. 88, 280 (2004)]. The thermal expansion coefficient is expressed in terms of shape and size and used to obtain the isobaric EoS of nanomaterials for the change in volume \(V/{V_0}\). The variation in \(V/{V_0}\) with temperature is estimated for spherical nanoparticles, nanowires and nanofilms. It is found that the volume thermal expansivity decreases as size of the nanomaterial increases, whereas \(V/{V_0}\) increases with temperature across nanomaterials of different sizes. The lattice parameter variation with temperature is studied in Zn nanowires, Se and Ag nanoparticles. It is found that lattice constant increases with increase in temperature. Also, bulk modulus is found to increase with temperature in nanomaterials. The results obtained from the present model are compared with the available experimental data. A good consistency between the compared results confirms the suitability of the present model for studying thermal properties of the nanomaterials.     

Fractal Coding Metamaterials

The concept of fractal coding metamaterials is proposed here, which can be used to design reflective metasurfaces with self‐similar pseudo‐random phase responses based on the coding strategy utilizing fractal interpolation functions (FIF). The class of fractals whose FIF is formed by a contraction mapping on the y‐coordinate and an arbitrary linear function of the x‐coordinate is considered. This formulation is used in deriving the theoretical model and in the experimental realization. An analytical relation between the reflection phase distribution in the form of the above‐mentioned FIF and the far‐field radiation pattern of the structure is derived. In the numerical example, a reflecting metasurface formed by slotted metallic patches of varying sizes is considered. A number of full wave scattering simulations for such a metamaterial reflectarray are performed and the optimal designs which make the response of the structure more accurate as compared with the analytical predictions are identified. Following the simulation results, the array is built and a number of measurements are performed. The results of this work may find applications in phased antenna array design and beam forming.     

Ultrasound‐assisted Synthesis of Ag‐ZnS/rGO and its Utilization in Photocatalytic Degradation of Tetracycline Under Visible Light Irradiation

Recent improvements based on heterojunction nanocomposites have opened new possibilities in photocatalysis. In this research, an ultrasound‐assisted coprecipitation method was used to fabricate silver, zinc sulfide and reduced graphene oxide (Ag‐ZnS/rGO) nanocomposite, and characterization results indicated that 3% Ag‐ZnS spherical nanoparticles are successfully embedded in rGO matrix. The potential of the Ag‐ZnS/rGO, as a visible light active photocatalyst, was assessed through optimizing degradation of Tetracycline (TC) by response surface methodology. It was found that the photocatalytic degradation of TC increased with an increase in the amount of nanocomposite and irradiation time, whereas it decreased with increasing the initial TC concentration. Under the optimal conditions (10 mg L^?1 of TC, 1.25 g L^?1 of Ag‐ZnS/rGO, at pH = 7, and irradiation duration 110 min), more than 90% of the TC was degraded. The study of the mechanism of the photocatalytic process disclosed that the synergistic role of surface plasmon resonance (SPR) induced by Ag nanoparticles and p‐type semiconductor feature of rGO leads to ZnS semiconductor stimulation in the visible light region. Eventually, a pseudo‐first order kinetics model was developed based on the proposed mechanism. The obtained results highlight the role of Ag‐ZnS/rGO nanophotocatalyst toward degradation of some antibiotics under visible light.