The helical melamine–Keggin hybrid nanorods: syntheses and characterizations with two strategies,one-step solid-state chemical reaction and experimental solvent diffusion method

Two new Melamine-Keggin hybrid nanorods, MELH-PMo₁₂ and MELH-PW₁₂, for the first time are successfully synthesized by two chemical methods, one-step solid-state chemical reaction method and experimental solvent diffusion method at room temperature. One-step solid-state reactions involve grounded nanorod materials along with grinding of row material and with solvent diffusion method these nanorods synthesized in single crystals form. These compounds crystallized in trigonal space groups P-3. Elemental analysis, infrared spectroscopy, UV spectroscopy and XRD analysis results prove that the samples still possess Keggin type structure. Transmittance electron microscopy and single-crystal X-ray have shown that the samples have nanorod structures.     

Mg(OH)2 nanostructures using impure brine: optimization of synthesis parameters by Taguchi robust design and study of optical properties

Research on Chemical Intermediates - In this research, high purity magnesium hydroxide (Mg(OH)2) nanoparticles were successfully synthesized by the wet chemical precipitation method from an impure...     

Application of chemometric methods in modeling of competitive multidye biosorption from ternary system

Simultaneous biosorption properties of three cationic dyes (Methylene blue, Crystal violet and Safranin) on Sargassum glaucescens were studied. In the most of previous papers in the field of dye biosorption, one dye or dyes with nearly separate spectra were used and dye concentration was determined by Beer’s law at different λ _max. Significant of this study is application of dyes with highly overlapped spectra (as many real situations) that their concentrations can be determined by chemometric methods. Plackett–Burman design was applied to identify the most significant factors, Box–Behnken design was used to determine optimal conditions, and principal component-wavelet neural network was used for the simultaneous determination of dye concentrations in ternary solutions. The optimum biosorption conditions were determined as dye concentration 10^?4 mol L^?1, biosorbent dosage 0.1 g L^?1 and biosorbent particle size 0.188 µm. At this condition, maximum biosorption capacity was 0.80 mmol g^?1. The biosorption process was slightly slower in the ternary system comparing with single system which was related to competition phenomena between dyes. It was found that the overall biosorption data were described by the pseudo-second-order kinetic model. Fourteen isotherm models were applied to experimental data, and it was concluded that Hill model had the best correlation.     

Optimization and characterization of electrospun chitosan/poly(vinyl alcohol) nanofibers as a phenol adsorbent via response surface methodology

Fabrication and characterization of chitosan/poly(vinyl alcohol) electrospun nanofibers for adsorption of phenol from water were investigated. The effects of voltage (15–30 kV), solution injection flow rate (0.5–1.5 ml/hr), distance of needle and collector (10–20 cm) and chitosan/poly(vinyl alcohol) ratio (25/75, 50/50, 75/25) were studied to obtain the optimum electrospinning conditions for the maximum adsorption capacity of phenol. Central composite design (CCD) was used to investigate and optimize the processing factors for production of chitosan/poly(vinyl alcohol) nanofibers from aqueous solutions. The nanofibers were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR). Uniform beadless nanofibers with the minimum diameters of 3–11 nm were obtained at chitosan/poly(vinyl alcohol) ratio of 50/50, voltage of 22.5 kV, distance of 15 cm and injection flow rate of 1.99 ml hr^?1. Fourier transform infrared spectrum of chitosan/poly(vinyl alcohol) exhibited the existence of relevant functional groups of both poly(vinyl alcohol) and chitosan in the blends. Results of CCD show that among all processing factors, rate of electrospinning will highly affect the nanofiber adsorption. The response surface quadratic order model presented correlation coefficient explaining 69.5% of the variability in the adsorption. Copyright © 2017 John Wiley & Sons, Ltd.     

Supercyclicity in the operator algebra using Hilbert-Schmidt operators

We prove that the Supercylicity Criterion for any operatorT on a Hilbert space is equivalent to the supercyclicity of the left multiplication operator induced byT in the strong operator topology.     

Double-charged ionic liquid-functionalized layered double hydroxide nanomaterial as a new fiber coating for solid-phase microextraction of phenols

Double-charged diazabicyclo[2.2.2]octane (DABCO) was immobilized on the inner surface of a nanomaterial composed of the layered double hydroxides (LDHs) of Zn(II) and Cr(III). The resulting material was characterized by SEM, FT-IR and XRD techniques. This novel nanocomposite has been used as a highly porous fiber coating for solid-phase microextraction (SPME) of phenol and various chloro-, nitro- and aminophenols. The LDH nanocomposite was deposited on a stainless steel wire and then evaluated with respect to the extraction of phenolic compounds from water samples. The effects of temperature, extraction time, ionic strength, stirring rate, pH, and desorption temperature and time on the extraction were optimized. The compounds were then separated and quantified by GC-MS. Under optimum conditions, the repeatability for a single fiber (for n = 3 and expressed as the relative standard deviation) is between 2.3 and 7.2 %. The detection limits are between 0.02 and 6.3 pg mL⁻¹. The method is simple, rapid, and inexpensive. The fiber is thermally stable and its use gives high recoveries.

Double-charged diazabicyclo[2.2.2]octane (DABCO) was immobilized on the inner surface of a nanomaterial composed of the layered double hydroxides (LDHs) of Zn(II) and Cr(III). This novel nanocomposite has been used as a highly porous fiber coating for solid-phase microextraction (SPME) of phenol and various chloro-, nitro- and aminophenols.

     

The synergistic chaperoning operation in a Bi-chaperone system consisting of alpha-crystallin and beta-casein: bovine pancreatic insulin as the target protein

While chaperone activity of alpha-crystallin (α-Crs) is important in maintaining lens transparency that of beta-casein (β-CN) is vital to prevent the development of corpora amylacea (accumulation of amyloid deposits in mammary glands). These two chaperone proteins are amphiphilic, each contains distinct polar and non-polar regions in the structure. While polar domain of α-Crs is highly electropositive, the counterpart domain in β-CN is strongly electronegative. In this study a Bi-chaperone system consisting of α-Crs and β-CN with different molar ratios were used to prevent the chemical-induced insulin aggregation spectroscopically. As shown, α-Crs and β-CN in the Bi-chaperone system exhibit synergistic chaperoning operation which strongly depends to the specific ratio of the chaperone components. The results of both fluorescence study and native gel electrophoresis confirmed the non-covalent interactions between α-Crs and β-CN. Consequently the synergistic activity can be explained with the possible electrostatic interactions between their polar/charged domains which bring them in close proximity, allowing their synergistic chaperoning operation in the Bi-chaperone system.     

Determination of a time-dependent diffusivity from nonlocal conditions

The inverse problem of determining the temperature and the time-dependent thermal diffusivity from various additional nonlocal information is investigated. These nonlocal conditions can come in the form of an internal or boundary energy, or, in the one-dimensional case, as a difference boundary temperature or heat flux so as to ensure the uniqueness of solution for the heat conduction equation with unknown thermal diffusivity coefficient. The Ritz-Galerkin method with satisfier function is employed to solve the inverse problems numerically. Numerical results are presented and discussed.     

Computational studies of the purine-functionalized graphene sheets

We performed a computational work to investigate the properties of functionalized graphene sheets (S) by adenine (A) and guanine (G) purine nucleobases. To achieve the purpose of this work, we examined the functionalization of armchair and zigzag tips of the S model by each of the A and G purines. The results indicated that the optimized properties for the investigated hybrid structures are different depending on the tip of functionalization and the used purine nucleobase. Moreover, the atomic level properties of the investigated structures were investigated by evaluating quadrupole coupling constants (C_Q) for the atoms of the optimized structures. The remarkable trend of the C_Q parameters is that the changes of atomic properties are many more significant for the functionalization of the zigzag-tip by the G nucleobase, which is in agreement with the results of the optimized properties.     

Numerical solution of the nonlinear age-structured population models by using the operational matrices of Bernstein polynomials

In this paper a numerical method for solving the nonlinear age-structured population models is presented which is based on Bernstein polynomials approximation. Operational matrices of integration, differentiation, dual and product are introduced and are utilized to reduce the age-structured population problem to the solution of algebraic equations. The method in general is easy to implement, and yields good results. Illustrative examples are included to demonstrate the validity and applicability of the new technique.