Tanacetamide D: A New Ceramide from Tanacetum artemisioides

One new ceramide (=long‐chain base linked to a fatty acid via an amide bond), tanacetamide D ( 1 ), was isolated from Tanacetum artemisioides. Besides this, the two known constituents 5‐demethylnobiletin ( 2 ) and 5‐hydroxy‐3,6,7,8,3′,4′‐hexamethoxyflavone ( 3 ) were isolated for the first time from this species. The structure elucidation of the isolated compounds were based primarily on 2D‐NMR techniques including correlation spectroscopy (COSY), heteronuclear multiple‐quantum coherence (HMQC), heteronuclear multiple‐bond correlation (HMBC), and nuclear Overhauser effect spectroscopy (NOESY) experiments.     

Influence of pH on the preparation of dispersed Ag–TiO<Subscript>2</Subscript> nanocomposite

In this paper, data concerning the effect of pH on the morphology of Ag–TiO₂ nanocomposite during photodeposition of Ag on TiO₂ nanoparticles is reported. TiO₂ nanoparticles prepared by sol–gel method were coated with Ag by photodeposition from an aqueous solution of AgNO₃ at various pH levels ranging from 1 to 10 in a titania sol, under UV light. The as-prepared nanocomposite particles were characterized by UV–vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and N₂ adsorption/desorption method at liquid nitrogen temperature (−196 °C) from Brunauer–Emmett–Teller (BET) measurements. It is shown that at a Ag loading of 1.25 wt.% on TiO₂, a high-surface area nanocomposite morphology corresponding to an average of one Ag nanoparticle per titania nanoparticle was achieved. The diameter of the titania crystallites/particles were in the range of 10–20 nm while the size of Ag particles attached to the larger titania particles were 3 ± 1 nm as deduced from crystallite size by XRD and particle size by TEM. Ag recovery by photo harvesting from the solution was nearly 100%. TEM micrographs revealed that Ag-coated TiO₂ nanoparticles showed a sharp increase in the degree of agglomeration for nanocomposites prepared at basic pH values, with a corresponding sharp decrease in BET surface area especially at pH > 9. The BET surface area of the Ag–TiO₂ nanoparticles was nearly constant at around a value of 140 m² g⁻¹ at all pH from 1–8 with an anomalous maximum of 164 m² g⁻¹ when prepared from a sol at pH of 4, and a sharp decrease to 78 m² g⁻¹ at pH of 10.     

Large amplitude Fourier transformed ac voltammetry at a rotating disc electrode: a versatile technique for covering Levich and flow rate insensitive regimes in a single experiment

The theory for large amplitude Fourier transformed ac voltammetry at a rotating disc electrode is described. Resolution of time domain data into dc and ac harmonic components reveals that the mass transport for the dc component is controlled by convective-diffusion, while the background free higher order harmonic components are flow rate insensitive and mainly governed by linear diffusion. Thus, remarkable versatility is available; Levich behaviour of the dc component limiting current provides diffusion coefficient values and access to higher harmonics allows fast electrode kinetics to be probed. Two series of experiments (dc and ac voltammetry) have been required to extract these parameters; here large amplitude ac voltammetry with RDE methodology is used to demonstrate that kinetics and diffusion coefficient information can be extracted from a single experiment. To demonstrate the power of this approach, theoretical and experimental comparisons of data obtained for the reversible [Ru(NH(3))(6)](3+/2+) and quasi-reversible [Fe(CN)(6)](3-/4-) electron transfer processes are presented over a wide range of electrode rotation rates and with different concentrations and electrode materials. Excellent agreement of experimental and simulated data is achieved, which allows parameters such as electron transfer rate, diffusion coefficient, uncompensated resistance and others to be determined using a strategically applied approach that takes into account the different levels of sensitivity of each parameter to the dc or the ac harmonic.     

Influence of cotton variety on compression and destructuration abilities under elevated pressure

Fourteen cotton samples of various strength, maturity and fineness were compressed in the same conditions at elevated pressure (2.0 GPa) and temperature (120 °C) in a home-made Bridgman anvil press designed to process samples of about 20 mm diameter. The influence of cotton properties to the abilities to be compacted into a solid 3D object was studied by mechanical measurements (nano-indentation and DMA) and scanning electron morphology observations. No influence of maturity ratio was observed. But strength and fineness were important parameters. It was shown that the lower are the mechanical properties of the cotton fibres (low strength or large fineness value), the easier it is to compact them. By observing the morphology of compacted samples, it was shown that compaction is linked to the destructuration of fibres under pressure down to the nanofibrillar level.     

Role of Copper Oxide on Epoxy Coatings with New Intumescent Polymer-Based Fire Retardant

Epoxy resins (EP) have been used as a thermos-setting material in the field of coating, casting, bonding agent, and laminating. However, a major drawback associated with its use is the lack of good flaming properties, and it is responsible for heavy smoke along with hazardous gases considerably limiting its uses in various fields. In this study, N-ethanolamine triazine-piperizine, a melamine polymer (ETPMP), was established as a new charring-foaming agent and was successfully synthesized with ethanolamine, piperizine, cyanuric chloride, and melamine as precursor molecules via the nucleophilic substitution reaction method. Elemental analysis and Fourier transform infrared (FTIR) spectroscopy analysis were applied to approve the synthesis of ETPMP and confirmation of its structure and characterization. The epoxy coating of intumescent flame retardant (IFR) was equipped by introducing ETPMP, ammonium polyphosphate (APP), and copper oxide (CuO) in multiple composition ratios. CuO was loaded at various amounts into the IFR-coating system as a synergistic agent. The synergistic action of CuO on IFR coatings was scientifically examined by using different analytical tests such as vertical burning test (UL-94V), limited oxygen index (LOI), thermal gravimetric analysis (TGA), cone calorimeter, and scanning electron microscope (SEM). The results showed that small changes in the amount of CuO expressively amplified the LOI results and enhanced the V-0 ratings in the UL-94V test. The TGA data clearly demonstrate that the inclusion of CuO can transform the thermal deprivation behavior of coatings with a growing char slag proportion with elevated temperatures. Information from cone calorimeter data affirmed that CuO can decrease the burning factors by total heat release (THR) together with peak heat release rate (PHRR). The SEM images indicated that CuO can enrich the power and compression of the intumescent char that restricts the movement of heat and oxygen. Our results demonstrate a positive influence of CuO on the epoxy-headed intumescent flame retardant coatings.     

Micellar and Solvent Effects on the Rate of Reaction Between L-Tyrosine and Ninhydrin

Kinetics of the reaction of L-tyrosine and ninhydrin has been studied spectrophotometrically at pH = 5.0 and temperature 80°C in aqueous, aqueous-organic and aqueous cationic micelles of cetyltrimethylammonium bromide (CTAB). The product formed in all the media remains the same. Also, the reaction is catalyzed in both organic solvent and CTAB micellar media. The results obtained in micellar media are treated quantitatively in terms of pseudo-phase model. The rate constants and binding constants with the micelles have been evaluated.     

Resonance Rayleigh Scattering,Second-Order Scattering and Frequency Doubling Scattering Spectra of Copper(II)-Flutamide System with Anionic Surfactants and its Analytical Application

A simple, sensitive, and rapid method based on ion association, for the determination of FLD has been developed. Flutamide (FLD) can react with Cu(II) to form 1:1 cationic chelate at pH 2.2–7.0 Mclivaine buffer medium, which can further react with anionic surfactants (AS) such as sodium dodecyl sulfate (SDS), sodium lauryl sulfonate (SLS) and sodium dodecylbenzene sulfonate (SDBS) to form 1:1 ion-association complexes. As a result, the resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) were enhanced to the highest degree. The maximum RRS, SOS and FDS wavelengths of three ion-association complexes were located at 345/345 nm, 610/305 nm and 430/860 nm, respectively. The increments of scattering intensity (ΔI) were directly proportional to the concentration of FLD in certain ranges. The detection limits (3σ) of FLD for SDS, SLS and SDBS systems were 1.9 ng ml⁻¹, 2.1 ng ml⁻¹ and 2.2 ng ml⁻¹(RRS method), 2.4 ng ml⁻¹, 2.7 ng ml⁻¹ and 2.6 ng ml⁻¹ (SOS method) and 2.3 ng ml⁻¹, 2.4 ng ml⁻¹ and 2.5 ng ml⁻¹ (FDS method), separately. The sensitivity of RRS method was higher than those of FDS and SOS methods. The optimum conditions of RRS method and the influence factors, the composition and the reaction mechanism have been discussed. Since the method is highly selective, it does not interference concomitant substances. These methods were applied successfully for the determination of FLD in pharmaceutical formulation and urine samples.     

Comparative analysis of oil composition and antibacterial activity of aerial parts of Terminalia arjuna (Roxb.)

Abstract

Volatile oil composition of leaves and fruits of Terminalia arjuna (Roxb.) was reported for the first time. Oils were extracted by microwave assisted hydrodistillation where yield of both oils were found to be 0.20% and their GC-MS analyses led to the identification of 65 and 48 constituents, respectively. Major constituents of leaves were carvacrol (11.17%), thymol (6.52%), α-terpinyl acetate (5.92%) and anethole (5.13%) while that of fruits were (E)-isoeugenol (11.48%), furfural (8.25%), p-vinylguaiacol (6.8%) and p-ethylguaiacol (5.72%) that demonstrated a significant difference between composition of its aerial parts, however, 33 constituents were identical that showed similarity characteristics in quality of these oils. Both leaf and fruit oils were found active against pathogenic and drug-resistant microbes: E. coli, Methicillin-resistant S. aureus, P. aeruginosa, Total-drug-resistant P. aeruginosa and K. pneumoniae with MIC values of 0.32, 0.32, 0.64, 0.64, 2.56?mg/mL and 0.16, 0.16, 0.32, 0.64, 1.28?mg/mL, respectively.     

Electro-optic response of metal halide $$\hbox {CsPbI}_3$$: A first-principles study

In this work, we have obtained energy levels and charge radius for the β-stability line nucleus, in relativistic shell model. In this model, we considered a close shell for each nucleus containing double magic number and a single nucleon energy level. Here we have taken ⁴¹Ca with a single neutron in the ⁴⁰Ca core as an illustrative example. Then we have selected the Eckart plus Hulthen potentials for interaction between the core and the single nucleon. By using parametric Nikiforov–Uvarov (PNU) method, we have calculated the energy values and wave function. Finally, we have calculated the charge radius for ¹⁷O, ⁴¹Ca, ⁴⁹Ca and ⁵⁷Ni. Our results are in agreement with experimental values and hence this model can be applied for similar nuclei.     

Kinetic and mechanistic investigation of the oxidation of the antibacterial agent levofloxacin by permanganate in alkaline medium

The kinetics and mechanism of oxidation of levofloxacin (LF) by manganese(VII) in alkaline medium at constant ionic strength was studied spectrophotometrically. The reaction exhibits 2:1 Mn:LF stoichiometry and is first order in permanganate but fractional order in both LF and alkali. Decrease in the dielectric constant of the medium results in a decrease in the rate of reaction. The effects of added products and ionic strength have also been investigated. The main products identified were hydroxylated LF and Mn(VI). A mechanism involving free radicals is proposed. In a composite equilibrium step, levofloxacin binds to MnO₄ ⁻ to form a complex that subsequently decomposes to the products. Investigations of the reaction at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism.