Protein adsorption capability of zinc ferrite nanoparticles formed by a low-temperature solution-based process

We report successful synthesis of zinc ferrite nanoparticles (ZFs) by a facile low-temperature (90 °C) solution-based process from ferric nitrate nonahydrate and zinc nitrate hexahydrate precursors in presence of hydrazine hydrate. X-ray diffraction analysis and transmission electron microscopy confirmed the presence of ZFs, which were further characterized by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric measurements for identification of characteristic chemical bond vibrations and thermal weight loss behavior, respectively. Measurements of magnetic properties at room temperature revealed that the sample showed quite high saturation magnetization (22.0 emu/g at ~19,200 G), implying the presence of less impurities/surface defects in the ZFs. The material also showed zero coercivity as a soft-magnetic material. The protein adsorption performance of the ZFs was checked using bovine serum albumin (BSA) as model protein. Excellent protein adsorption capacity of 210 mg/g (close to the value of 218.81 mg/g calculated using the Langmuir model) for BSA concentration of 0.3 mg/mL was obtained at optimized solution pH of 5. This simple process could be adopted for synthesis of different magnetic nanomaterials for use in biomedical applications.     

Transient thermoelastic waves in an anisotropic hollow cylinder due to localized heating

This paper presents a theoretical study of transient ultrasonic guided waves generated by concentrated heating of the outer surface of an infinite anisotropic hollow circular cylinder. Generalized thermoelastic theory proposed by Lord and Shulman is adopted to model the dynamic thermoelastic behavior of the cylinder. The concentrated heat source model used is to represent heating due to a pulsed laser beam, which is focused on the outer surface of the cylinder. A semi-analytical finite element (SAFE) method is employed to evaluate guided wave modes in the cylinder. Using integral transform techniques, the modal wave forms are obtained in frequency and wave number domains. Time histories of the propagating modes are then calculated by applying inverse Fourier transformation in the time domain. Numerical results showing the dispersion curves for the group velocities of the propagating modes and transient radial displacements are presented. For this purpose it is assumed that the cylinder is made of transversely isotropic silicon nitride (Si₃N₄). Attention is focused on the propagation characteristics of longitudinal and flexural modes separately.     

Standing waves in a non-linear 1D lattice: Floquet multipliers, Krein signatures, and stability

We construct a class of exact commensurate and incommensurate standing wave (SW) solutions in a piecewise smooth analogue of the discrete non-linear Schrödinger (DNLS) model and present their linear stability analysis. In the case of the commensurate SW solutions the analysis reduces to the eigenvalue problem of a transfer matrix depending parametrically on the eigenfrequency. The spectrum of eigenfrequencies and the corresponding eigenmodes can thereby be determined exactly. The spatial periodicity of a commensurate SW implies that the eigenmodes are of the Bloch form, characterised by an even number of Floquet multipliers. The spectrum is made up of bands that, in general, include a number of transition points corresponding to changes in the disposition of the Floquet multipliers. The latter characterise the different band segments. An alternative characterisation of the segments is in terms of the Krein signatures associated with the eigenfrequencies. When one or more parameters characterising the SW solution is made to vary, one occasionally encounters collisions between the band-edges or the intra-band transition points and, depending on the the Krein signatures of the colliding bands or segments, the spectrum may stretch out in the complex plane, leading to the onset of instability. We elucidate the correlation between the disposition of Floquet multipliers and the Krein signatures, presenting two specific examples where the SW possesses a definite window of stability, as distinct from the SW’s obtained close to the anti-continuous and linear limits of the DNLS model.     

Synthesis of mesoporous Stöber silica nanoparticles: the effect of secondary and tertiary alkanolamines

The effect of secondary (diethanolamine) and tertiary (triethanolamine) alkanolamines as catalysts on the formation of mesoporous Stöber silica nanoparticles by sol–gel method was studied. The particles were characterized by thermogravimetry and differential thermal analysis, Fourier transform infrared spectroscopy, N₂ physisorption measurements, and field emission scanning electron microscopy. By using ammonia and different alkanolamines as catalysts, the Brunauer–Emmet–Teller (BET) surface area and pore volume increased in the order of ammonia < diethanolamine < triethanolamine. A maximum BET surface area of 140.1 m² g^?1 and pore volume of 0.66 cm³ g^?1 were obtained from triethanolamine catalyzed silica particles. The average particle size of silica prepared by ammonia and different alkanolamines as catalysts decreased in the order of ammonia > diethanolamine > triethanolamine. The role of different alkanolamines on the textural properties and particle size of silica is explained in terms of their relative steric hindrance and basicity.     

Exposure to underground radon in and around Kolkata Municipal Corporation area: an exhaustive study

Air radon survey was carried out at different underground locations at Kolkata using radon monitor. Average radon concentration for basements was found to be 22.70 ± 1.12 Bq/m³ with maximum 59.00 ± 7.18 Bq/m³ and minimum 8.50 ± 3.14 Bq/m³. Average level for sub-ways was 23.05 ± 2.59 Bq/m³ fluctuating between maximum 39.00 ± 1.24 Bq/m³ and minimum 13.50 ± 1.78 Bq/m³. In comparison, open air background at basement entrance was 19.44 ± 1.06 Bq/m³ and subway entrance was 18.58 ± 1.14 Bq/m³. Annual effective dose was calculated to assess probable health risk. Radon concentration level and annual effective dose were found well below safe levels recommended by International Agencies WHO and UNSCEAR.

     

Selection of Suitable Combination of Nonfunctional Micellar Catalyst and Heteroaromatic Nitrogen Base as Promoter for Chromic Acid Oxidation of Ethanol to Acetaldehyde in Aqueous Medium at Room Temperature

The effect of the promoter and micellar catalyst on chromic acid on the oxidation of ethanol in aqueous acid media has been studied. Picolinic acid (PA), 1,10‐phenanthroline (phen), and 2,2′‐bipyridine (bipy) are used as promoters. Sodium dodecyl sulfate (SDS), cetyl pyridinium chloride (CPC), and Triton‐X‐100 (TX‐100) are tested as micellar catalysts. Hexavelent chromium is an active species in the absence of the promoter. In the presence of the heteroaromatic nitrogen bases used as the promoter, Cr(VI)–PA, Cr(VI)–bipy, and Cr(VI)–phen complexes have been proposed as the active oxidants. The time taken for completion of the reaction using different combinations of promoter and micellar catalysts are different. Although the rate is highest (12.5 times) in TX‐100 in the absence of the promoter, it is observed that the rate is almost 737 times faster for the combination of SDS and bipy compared to the unpromoted and uncatalyzed path. CPC inhibits the oxidation process. The observed acceleration and retardation of the rate of oxidation process has been explained on the basis of partitioning of the reactants in the micellar and aqueous phase. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 175–186, 2013     

Temperature‐dependent self‐assembly and rheological behavior of a thermoreversible pmma–PnBA–PMMA triblock copolymer gel

Self‐assembly and mechanical properties of triblock copolymers in a mid‐block selective solvent are of interest in many applications. Herein, we report physical assembly of an ABA triblock copolymer, [PMMA–Pn BA–PMMA] in two different mid‐block selective solvents, n‐butanol and 2‐ethyl‐1‐hexanol. Gel formation resulting from end‐block associations and the corresponding changes in mechanical properties have been investigated over a temperature range of ?80 °C to 60 °C, from near the solvent melting points to above the gelation temperature. Shear‐rheometry, thermal analysis, and small‐angle neutron scattering data reveal formation and transition of structure in these systems from a liquid state to a gel state to a percolated cluster network with decrease in temperature. The aggregated PMMA end‐blocks display a glass transition temperature. Our results provide new understanding into the structural changes of a self‐assembled triblock copolymer gel over a large length scale and wide temperature range. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 877–887     

Novel Route for the Synthesis of 3-(Pyrrol-1-yl)-indolin-2-ones in Aqueous Micellar Medium

A high-yielding environmentally benign protocol has been developed for the synthesis of 3-(pyrrol-1-yl)-indolin-2-ones from the reaction of isatin and trans-4-hydroxy-L-proline in aqueous micellar medium. The method is operationally simple and more effective than the previous methods in terms of the yield of the products and the reaction time.     

The Korteweg-de Vries hierarchy: structure and solution

We attempt to realize the structure of the Korteweg-de Vries (KdV) hierarchy by using a simple dimensional analysis. The specific results presented refer to equations of the hierarchy and conserved Hamiltonian densities associated with them. Based on the Gel’fand-Levitan-Marchenko equation we construct a series expansion for the unstable solution of the KdV-like equations by using the continuous part of the spectrum for the Schrödinger operator. Our result is in exact agreement with that obtained from the Sabatier’s formulation of the inverse problem for rational reflection coefficients.