Novel Quinolone Derivatives: Synthesis and Antioxidant Activity

Russian Journal of General Chemistry - Novel quinolone derivatives have been designed and readily synthesized according to a simple protocol including O-alkylation and Claisen rearrangement...     

Regioselective synthesis of spiro isoxazole-oxindole-tetrahydrothiophene hybrids via cascade reactions under catalyst-free conditions

Catalyst-free synthesis of the isoxazole-spirooxindole-tetrahydrothiophene hybrids is reported. Formation of 1,4-thia-Michael and intramolecular aldol reactions were observed (instead of 1,6-thia-Michael followed by vinylogous Henry reactions) in a regioselective fashion to give new isoxazole-spirooxindole-tetrahydrothiophene hybrids with excellent yields.     

Bivariate q-Bernstein-Schurer-Kantorovich Operators

Results in Mathematics - The purpose of this paper is to construct a bivariate generalization of a new kind of Kantorovich type q-Bernstein-Schurer operators. We give the rate of convergence by...     

Viscoelastic behavior of PMMA/grafted PBA nanoparticle systems in the molten state

The viscoelastic properties of poly(methyl methacrylate) (PMMA)/grafted poly(butyl acrylate) (PBA) nanoparticle systems were investigated. The rubber particles consist of PBA core (60 nm in diameter) and grafted PMMA shell. The grafting degree, defined as the weight ratio of grafted PMMA to PBA particles, ranges from 0.8 to 1.5. Two series of samples, A series with 7.5 wt.% of PBA content and B series with 12 wt.% of PBA content, were used. The systems exhibited fast and slow relaxation process, the former reflecting the relaxation of the matrix PMMA chains and the latter being attributed to grafted PBA particles. For A series samples, time-temperature superposition (TTS) was held well over the frequency (ω) and temperature (T) ranges measured. However, for B series samples, TTS was not satisfied at low ω due to the particle-particle interaction of grafted PBA particles, although the samples obeyed TTS at high ω associated with the relaxation with entanglement of matrix PMMA. At high T and low ω region, the B series samples showed a sol-gel transition at elevating T and the critical gel behavior characterized with a power-law relationship, G′ = G″/tan(nπ/2) ∝ ωⁿ, was observed. This behavior suggested formation of a self-similar, fractal structure of grafted PBA particles. The critical gel temperature (T _gel) and the critical exponent (n) were determined for the B series samples. TEM observations revealed that as-prepared A and B samples had well-dispersed particles but the B samples after viscoelastic measurements had fragmented networks of the PBA particles, confirming that the sol-gel transition occurred for the PMMA/grafted PBA systems at elevating T.     

Application of selected natural sources on mulberry silk fabric

Silk finds an important place for its elegance, softness, luster, sheen, strength, uniformity suitable for the production of respective valuable textile garments and apparels. Due to the amphoteric character of silk protein polymer, the overall behavior of silk will be enriched when it is applied with natural resources. Based on these considerations, it is proposed in this research work to treat mulberry silk fabric with recovered sericin protein in addition with natural finishing sources like aloevera, amla and nochi in varied combinations followed by coloration with some selected natural sources. After these applications, the silk fabric was undergone for some testing for the determination of color value, fastness behavior, tensile strength, absorbency character, anti-odor and retention aspects, and FTIR graphs. The outcome of the results are convinced to the expectations suitable for the applications in the textile industries for garment and apparel utilities.     

Residual stress distribution on surface-treated Ti-6Al-4V by X-ray diffraction

The x-ray diffraction technique has been used to measure surface residual stress in Ti-6Al-4V samples subjected to shot peening (SP), laser shock peening (LSP) and low plasticity burnishing (LPB). The magnitude, spatial and directional dependence and uniformity of the surface residual stresses have been investigated. The results show that residual stresses due to SP are uniform and independent of direction. LSP has been observed to produce non-uniform residual stress varying from one region to another, and also within a single laser shock. In the case of LPB, residual stresses have uniform spatial distribution but have been observed to be direction-dependent. Various components of the residual stress tensor in the LPB sample have been determined following the Dolle-Hauk method. The results of the residual stress due to three surface treatments are compared, and possible reasons for spatial and directional dependence are discussed.     

β,β′‐Bipyrrole Fusion‐Driven cis‐Bimetallic Complexation in Isomeric Porphyrin

An unprecedented cis‐bimetallic complex of dinaphthoporphycene (DNP), namely [Pd₂(μ‐DNP)(μ‐OAc)₂], is reported. The most striking feature of this complex is that two palladiums coordinate to the macrocycle on the same side and are closely held together (Pd? Pd: 2.67 Å) by two bridging acetate ligands exhibiting significant metal–metal bonding interaction (bond order 0.18 evaluated by NBO analysis). Interestingly, replacing acetate with acetylacetonate (acac) could stabilize an unusual mono‐palladium complex of DNP, where Pd coordinates unsymmetrically to two ring Ns above the macrocyclic plane, as well as coordinating with two Os of the acac ligand. Remarkably, the rigid DNP core displays enhanced complexation induced aromaticity (as per NICS and HOMA analysis), despite undergoing severe core deformation during complexation with metal ion(s) as noticed from their solid‐state structures.     

A Self-Organized Ensemble of Fluorescent 3-Hydroxyflavone-Al (III) Complex as Sensor for Fluoride and Acetate Ions

Aluminum chloride addition results in a self-organized TURN-ON fluorescence of 3-hydroxyflavone (3HF) by a complexation reaction in MeOH and subsequent ligand exchange reaction with fluoride or acetate ions causes a fluorescence TURN-OFF of this complex, delivering a quantitative estimation route for fluoride and acetate ions. The ternary complex of 3HF with Al (III), a hard acid provides for a sensitive signalling system for fluoride ion, a hard base in the concentration range from 6 μM to 50 mM by a concerted co-ordination of fluoride ion involving an intermediate mechanistic pathway, while the complex is sensitive to acetate addition between 0–68 μM. The ligand exchange reaction of Al (3HF)₂ complex by fluoride or acetate ion, without interference from other common anions, has been investigated by UV-visible and fluorescence spetroscopies. The structure of the in-situ intermediate isolated at higher Al (3HF)₂ complex and acetate concentrations was inferred from the FT-IR spectrum and ESI-MS of the sample.     

Performance investigation on fin type solar still with paraffin wax as energy storage media

Journal of Thermal Analysis and Calorimetry - It is indispensable to enhance the performance of a conventional solar still in order to increase its productivity. It has been effectively done by...     

A Proficient approach to enhance heat transfer using cupric oxide/silica hybrid nanoliquids

Journal of Thermal Analysis and Calorimetry - High performance cooling anticipated in smaller size heat transfer equipment is the most significant challenge in many industries including CPU...