Oxalic acid as a simple and efficient organocatalyst for three-component synthesis ofα-amino nitriles

A simple,efficient,and general method has been developed for the synthesis ofα-amino nitriles.Oxalic acid as a BrФnsted acid promotes the addition of TMSCN to various imines(generated in situ).     

Applications of Raman Spectroscopy in Dentistry: Analysis of Tooth Structure

Abstract: Tooth enamel is the most mineralized tissue in the human body, and in this article the use of Raman spectroscopy for the analysis of tooth structure, a comparison with synthetic apatites, and use in dentistry are described. Spectral peaks that are related to dental hard and soft tissues are discussed, which provide crucial data in understanding the chemical structural properties of dentin and enamel. The Raman spectrum of dentin confirms the presence of crystalline phosphate-based minerals in dentin. Both dentin and enamel consist of two primary components: an inorganic or mineral phase that closely resembles hydroxyapatite and the Raman spectrum of dentin that confirms the presence of crystalline phosphate-based minerals in dentin. Hence, the mineral phase in dentin and enamel may be characterized essentially as nonstoichiometric substituted apatite. The presence of carbonate (A and B type) incorporated in the hydroxyapatite lattice is also confirmed by the presence of spectral bands. The organic phase, which is mainly composed of type I collagen, is confirmed by the spectral bands of amide I and amide II bands, tryptophan, and phenylalanine. Furthermore, these spectral bands associated with organic and inorganic parts of the enamel and dentin are useful in predicting early formation of carries formation.     

Experiments on New Arrangements of Convex and Concave Corrugated Tubes through a Double-pipe Heat Exchanger

The main scope of this article paper is to experimentally clarify the effects of outer-tube and inner-tube corrugations on thermal and frictional characteristics in a horizontal double-pipe heat exchanger. Nusselt number, friction factor, and thermal performance factor are evaluated for new various arrangements of convex and concave corrugated tubes. Smooth tubes were corrugated by means of a special machine. Findings indicate that the arrangement type of corrugated tubes has a significant effect on the mentioned parameters. The best performance was obtained for a heat exchanger made of a concave corrugated outer tube and a convex corrugated inner tube.     

Interaction between protoporphyrin IX and tryptophan silver nanoparticles

Silver nanoparticles (AgNPs) have been intensively studied for several purposes including therapeutic applications in cancer. When prepared with tryptophan and photoreduction, silver nanoparticles (TrpAgNPs) become an alternative to conventional anticancer drugs. In this study, the anticancer activity of synthesized TrpAgNPs against MCF-7 breast cancer cells was evaluated, and the inhibitory concentration (IC50) was found to be ~3.4 mg/mL. Since the protoporphyrin IX (PPIX) concentrations in tumor cells are elevate compared to normal cells, the PPIX-TrpAgNP interaction was studied to investigate if it could contribute for cell apoptosis. The investigation was performed using PPIX solution (0.9 μg/mL) with different TrpAgNP concentrations (from 0 to 13 mg/mL). PPIX was characterized by UV-Vis spectroscopy, steady-state and time-resolved fluorescence spectroscopy. The results have shown that the presence of spherical TrpAgNps with 16-nm diameter quench the PPIX fluorescence intensity. This quenching is strongly dependent on the concentration of the TrpAgNPs, and it is caused by a combination of a static and a dynamic process. The chemical binding leads to oxidation of tryptophan and formation of kynurenine, observed in the emission spectra around 470 nm. The strong reduction of the PPIX fluorescence decay lifetime with nanoparticle increasing concentration confirms the quenching processes due to charge transfer from the excited PPIX states to the resonant silver states. The present study confirms the anticancer activity of TrpAgNPs on the human breast cancer cell line (MCF-7) in vitro and indicates that PPIX-AgNP interaction could contribute with MCF-7 apoptosis.

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Graphical abstract Interaction between TrpAgNPs and PPIX

     

A note on the generalized Friedmann equations for a thick brane

Within our thick brane approach previously used to obtain the cosmological evolution equations on a thick brane embedded in a five-dimensional Schwarzschild Anti-de Sitter spacetime it is explicitly shown that the consistency of these equations with the energy conservation equation requires that, in general, the thickness of the brane evolves in time. This varying brane thickness entails the possibility that both Newton’s gravitational constant G and the effective cosmological constant Λ₄ are time dependent.     

Magnetic moments ofb-quark baryons in broken SU(5) symmetry

The magnetic moments ofb-quark baryons within the framework of five quark models are derived. Also the transition magnetic moments of variousb-quark baryons are calculated.     

A novel electrochemical biosensor based on the electrospun nanofibrous nanocomposites of PCL-PPy-MWCNT towards determination of TNF-α biomarker

Journal of Solid State Electrochemistry - For TNF detection, a novel electrochemical biosensor based on the PCL-PPY-MWCNT electrospun nanofiber was developed in this study. TNF is a potent...     

An inimitable and ecological pleasant technique for the assessment of trace amount of copper (II) in tangible samples with new complexing reagent

A simple and rapid spectrophotometric technique has been designed for the trace copper analysis employing 1-(2-Thiazolylazo)-2-naphthol (TAN) reagent in aqueous micellar solution of cetyl trimethylammonium bromide (CTAB) as a surfactant. Copper complexed with 1-(2-Thiazolylazo)-2-naphthol to form bis[1-(2-Thiazolylazo)-2-naphthol]copper. The present spectrophotometric technique was very important since the micellar system was used in place of the toxic, high cost and time-consuming solvent extraction steps. The technique showed an enhanced detection efficiency, specificity, and molar absorptivity. It was found that the molar absorption coefficient and sensitivity of Sandel were ε 2.45 × 10⁴ L mol^?1cm^?1 and 2.6 ngcm^?2 at λ_max 578.4 nm. A linear calibration plot in the range 0.12–5.0 μg mL^?1 was obtained; a stoichiometric metal ligand ratio [M:L] of 1:2 was found for the formation of Cu-[TAN]₂. The complex was formed at pH 9.5 and was stable up to 24 h. The proposed technique has been employed to study copper from different alloys, biological, environmental and pharmaceutical samples.     

Enhancement of tribological performance of epoxy bulk composites and composite coatings using micro/nano fillers: a review

Epoxies in the form of bulk and coatings have been used throughout the years for a wide spectrum of applications in various industries ranging from aerospace, oil and gas, petrochemical and marine to several others. Their use in tribological applications, those involving a range of contact conditions and where the requirement is exceptionally low wear and friction coefficient, is often limited by the properties of the pristine epoxy matrix such as low load bearing capacity combined with low thermal conductivity values. These properties have been improved by the addition of nano‐fillers, and numerous studies have been carried out in this regard. This paper presents a detailed review of the works carried out in the recent years where addition of nano‐fillers to formulate epoxy‐based composites and coatings has shown a substantial improvement in wear and friction properties thereby enhancing their potential to be used in demanding tribological applications such as solid lubricant in bearings, as wear‐resistant protective coatings in rotating and stationary equipment and for applications in the construction industry such as floorings and airport runway repairs. Copyright © 2016 John Wiley & Sons, Ltd.