Calcined Mg-Fe-CO(3) LDH as an adsorbent for the removal of selenite

Mg-Fe-CO(3) layered double hydroxide (LDH) with a Mg/Fe molar ratio of 2.0 was synthesized by co-precipitation method and its calcined product (CLDH) was obtained by heating Mg/Fe-LDH at 500 degrees C. Sorption of SeO(2-)(3) on CLDHs was studied and the results indicate that the sorption capacity of CLDHs was higher than that of uncalcined LDHs. Isotherms for SeO(2-)(3) sorption by CLDHs were well described using the Freundlich and Langmuir equations. The thermodynamic parameters, viz. DeltaG*, DeltaH*, DeltaS* were calculated to predict the nature of adsorption. The negative and positive values of DeltaG* and DeltaH* indicate that the adsorption process is spontaneous and endothermic in nature, respectively. The adsorption process followed first-order kinetics.     

Standardization of the ayurvedic formulation Haridra Khanda using high-performance thin-layer chromatography-densitometry

The present study aimed to standardize the Ayurvedic preparation Haridra Khanda containing Curcuma longa as a major ingredient. Various physicochemical parameters such as alcohol-soluble extractive, water-soluble extractive, total ash, and acid-insoluble ash were determined according to the Ayurvedic Pharmacopoeia of India. Microscopic evaluation of the formulation revealed the presence of various diagnostic cell structures of C. longa. Trace metal analysis indicated the absence of toxic metals such as As, Cd, Hg, and Pb. High-performance thin-layer chromatographic (HPTLC) fingerprint patterns at multiple wavelengths (254, 366, and 430 nm) identified the number of components present at each wavelength. The bioactive markers curcumin (C1), demethoxycurcumin (C2), and bisdemethoxycurcumin (C3) were quantified by using a simple, rapid, and efficient HPTLC method using plates precoated with silica gel 60F254 stationary phase. The instrumental precision [coefficient of variation (CV)] was 0.51, 0.64, and 0.79% and the repeatability of the method (CV) was 0.89, 1.11, and 0.95%, respectively, for C1 to C3. Limits of detection and quantitation for compounds C1 to C3 were 20, 20, and 15 ng and 50, 40, and 50 ng, respectively. Response was a linear function in the ranges of 50-350, 40-240, and 50-300 ng with correlation coefficient (r) = 0.9998, 0.9995, and 0.9992, respectively, for C1 to C3. The mean recovery values of 99.63 (C1), 98.65 (C2), and 98.97% (C3) indicated the excellent accuracy of the method. It is shown that HPTLC can be applied successfully for the marker evaluation of the formulation containing C. longa.     

Electronic and magnetic properties at rough alloyed interfaces of Fe/Co on Au substrates: An augmented space study

We studied the interface electronic and magnetic properties of Fe/Co deposited on Au substrate and researched the effects of roughness at the interfaces within augmented space formalism(ASF). The full calculation is carried out by recursion and tight-binding linear muffin tin orbital(TB-LMTO) methods. The amount of roughness is different at different atomic layers. The formalism is also applied to sharp interface, when interdiffusion of atoms is negligible. Our results of one monolayer transition metal agree with other reported results. A realistic rough interface is also modeled with three and four monolayers of transition metals, deposited on Au substrates.     

The defining role of interface crystallography in corrosion of a two-phase pearlitic steel

ABSTRACT

This study involved thermomechanically processed fine (few hundred nanometers of interlamellar spacing) pearlite wire rods of the different axial alignment of the pearlite colonies, and coarse (several micron interlamellar spacing) pearlite colonies. In the former, appropriate microstructural tailoring, and corresponding axial alignment, reduced the corrosion rate, in chloride solution, by nearly 6.4 times. In the coarse pearlite, on the other hand, dissolution and aqueous corrosion, influenced by microgalvanic coupling, was shown to be restricted to the ferrite side of the ferrite-cementite interface. The orientation relationship between ferrite and cementite determined localised corrosion. In summary, remarkable improvements in the resistance to galvanic corrosion were shown, in coarse two-phase pearlite, by enhancing the population of good-fit interfaces. Though the same observation was not possible, experimentally, in the fine pearlite colonies, the remarkable improvement in the corrosion resistance of aligned pearlite wire rods appears real and extremely reproducible.     

Gold Doping of Silver Nanoclusters: A 26‐Fold Enhancement in the Luminescence Quantum Yield

A high quantum yield (QY) of photoluminescence (PL) in nanomaterials is necessary for a wide range of applications. Unfortunately, the weak PL and moderate stability of atomically precise silver nanoclusters (NCs) suppress their utility. Herein, we accomplished a ≥26‐fold PL QY enhancement of the Ag₂₉(BDT)₁₂(TPP)₄ cluster (BDT: 1,3‐benzenedithiol; TPP: triphenylphosphine) by doping with a discrete number of Au atoms, producing Ag_29?xAu_x(BDT)₁₂(TPP)₄, x=1–5. The Au‐doped clusters exhibit an enhanced stability and an intense red emission around 660 nm. Single‐crystal XRD, mass spectrometry, optical, and NMR spectroscopy shed light on the PL enhancement mechanism and the probable locations of the Au dopants within the cluster.     

Semilocal convergence of a family of third-order methods in Banach spaces under Hölder continuous second derivative

In this paper, the semilocal convergence of a family of multipoint third-order methods used for solving F(x)=0$F\left(x\right)=0$ in Banach spaces is established. It is done by using recurrence relations under the assumption that the second Fréchet derivative of F$F$ satisfies Hölder continuity condition. Based on two parameters depending upon F$F$, a new family of recurrence relations is defined. Using these recurrence relations, an existence–uniqueness theorem is established to prove that the R$R$-order convergence of the method is (2+p)$(2+p)$. A priori error bounds for the method are also derived. Two numerical examples are worked out to demonstrate the efficacy of our approach.     

Preparation, characterization, and photocatalytic activity of sulfate-modified titania for degradation of methyl orange under visible light

Hydrated titania was prepared by a sol-gel method, taking tetraisopropyl orthotitanate as starting material, and then promoted with different weight percentages of sulfate by an incipient wetness impregnation method. The materials were characterized by various advanced techniques such as PXRD, BET surface area, N(2) adsorption-desorption measurements, FTIR, and SEM. Analytical results demonstrated that TiO(2) is mesoporous in nature, and sulfate modification could inhibit the phase transformation and enhance the thermal stability of TiO(2). It was also found that sulfate modification could reduce the crystallite size and increase the specific surface area of the catalysts. The degradation of methyl orange under solar radiation was investigated to evaluate the photocatalytic activity of these materials. Effects of different parameters such as pH of the solution, amount of catalyst, additives, and kinetics were investigated. At 2.5 wt% sulfate loading, the average percentage of degradation of methyl orange was nearly two times than that of neat TiO(2). The photocatalytic degradation followed first-order kinetics.     

Dramatic promotion of gold/titania for CO oxidation by sulfate ions

The activity of gold/titania catalysts for the room-temperature oxidation of CO can be dramatically enhanced by the addition of sulfate ions to the support; it appears that anion promotion of gold may be a general phenomenon and may be related to the direct modification of active gold sites in the case of sulfate ions, as evidenced by secondary ion mass spectrometry.     

Recurrence relations for a Newton-like method in Banach spaces

The convergence of iterative methods for solving nonlinear operator equations in Banach spaces is established from the convergence of majorizing sequences. An alternative approach is developed to establish this convergence by using recurrence relations. For example, the recurrence relations are used in establishing the convergence of Newton's method [L.B. Rall, Computational Solution of Nonlinear Operator Equations, Robert E. Krieger, New York, 1979] and the third order methods such as Halley's, Chebyshev's and super Halley's [V. Candela, A. Marquina, Recurrence relations for rational cubic methods I: the Halley method, Computing 44 (1990) 169–184; V. Candela, A. Marquina, Recurrence relations for rational cubic methods II: the Halley method, Computing 45 (1990) 355–367; J.A. Ezquerro, M.A. Hernández, Recurrence relations for Chebyshev-type methods, Appl. Math. Optim. 41 (2000) 227–236; J.M. Gutiérrez, M.A. Hernández, Third-order iterative methods for operators with bounded second derivative, J. Comput. Appl. Math. 82 (1997) 171–183; J.M. Gutiérrez, M.A. Hernández, Recurrence relations for the Super–Halley method, Comput. Math. Appl. 7(36) (1998) 1–8; M.A. Hernández, Chebyshev's approximation algorithms and applications, Comput. Math. Appl. 41 (2001) 433–445 [10]].