Correlation of the Solubilizing Abilities of 1-Butyl-1-methyl-pyrrolidinium Tris(pentafluoroethyl)trifluorophosphate, 1-Butyl-1-methylpyrrolidinium Triflate and 1-Methoxyethyl-1-methylmorpholinium Tris(pentafluoroethyl)trifluorophosphate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrolidinium tris(pentafluoroethyl)trifluorophosphate ([BMPyrr]⁺[FAP]^?), 1-butyl-1-methylpyrrolidinium triflate, ([BMPyrr]⁺[Trif]^?), and 1-methoxyethyl-1-methylmorpholinium tris(pentafluoroethyl)trifluorophosphate, ([MeoeMMorp]⁺[FAP]^?), stationary phases at (323, 353 and 383) K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) and water-to-anhydrous IL partition coefficients. The three sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL (log₁₀ K) and water-to-IL (log₁₀ P) partition coefficient data to within average standard deviations of about 0.11 and 0.15 log₁₀ units, respectively.     

Protein-Polysaccharide Interactions for Stabilization of Food Emulsions

Proteins, polysaccharides and their blends, as examples of natural biopolymers, are surface active materials. Biopolymers may be considered as amphiphilic macromolecules that play an essential role in stabilizing food formulations (foams, emulsions and dispersions). Under specific conditions (such as protein-to-polysaccharide ratio, pH, ionic strength, temperature, mixing processing), it has been stated that proteins and polysaccharides form hybrids (complexes) with enhanced functional properties in comparison to the proteins and polysaccharides alone. Different protein-polysaccharide pairs are reviewed with particular attention to the emulsification capability of their mixtures. In the case of uncomplexed blends of biopolymers, competitive adsorption onto hydrophobic surfaces is generally reported. Conversely, electrostatic complexation between oppositely charged proteins and polysaccharides allows better anchoring of the new-formed macro-molecular amphiphile onto oil-water interfaces. Moreover, improved thermal stability and increased resistance to external treatment (high pressure) involved in food processing are obtained. This review presents basic and applied knowledge on protein-polysaccharide interactions in aqueous medium and at the oil-water interface in food emulsion systems. Electrostatic interactions and thermodynamic incompatibility in mixed biopolymer solutions are correlated to the functional properties (rheology, surface hydrophobiciry, emulsification power) of these interesting blends. Basic and industrial selected systems of different families of hydrocolloids (as gum Arabic, galactomannans, pectins) and protein (caseins, whey, soya, gelatin) mixtures are reviewed.     

Crystallization of Celecoxib in Microemulsion Media

Celecoxib belongs to a new NSAID family specifically inhibiting cyclooxygenase‐2 (COX‐2). The present formulations require high dosage since the transmembrane transport fluctuates and is very difficult to control. We solubilized celecoxib in micelles of nonionic microemulsions and hydrophilic surfactant. The supersaturated solubilized drug was precipitated from the nano‐droplets to form a new solid structure with improved dissolution properties. The selected microemulsion systems loaded with celecoxib were characterized by SAXS, SD‐NMR, viscosity, and electrical conductivity techniques. Precipitation was conducted from W/O as well as from O/W U‐type microemulsions. The crystals obtained by the precipitation were characterized by x‐ray powder scattering, differential scanning calorimetry, FTIR measurements, and microscopic scans.     

Surface morphological and impedance spectroscopic studies on the interaction of polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) with mild steel in acid solutions

The inhibition of mild steel corrosion in aerated acid mixture of 0.5 N H₂SO₄ and 0.5 N HCl solution was investigated using potentiodynamic polarization studies, linear polarization studies, electrochemical impedance spectroscopy, adsorption, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, degree of surface coverage, adsorption kinetics, and surface morphology is investigated. The inhibition efficiency increased markedly with increase in additive concentration. The presence of PEG and PVP decreases the double-layer capacitance and increases the charge-transfer resistance. The inhibitor molecules first adsorb on the metal surface following a Langmuir adsorption isotherm. Both PEG and PVP offer good inhibition properties for mild steel and act as mixed-type inhibitors. Surface analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that PVP offers better protection than PEG.     

Electrochemical studies on the interaction of l-cysteine with metallic copper in sulfuric acid

Amino acids have been widely used as green corrosion inhibitors for an array of metals. Considering its importance in corrosion chemistry, studies were undertaken with the objective to discovering the inhibitory effect of a sulfur-containing amino acid, l-cysteine, on copper in different concentrations of sulfuric acid (0.5, 1.0, and 1.5 M) at different temperatures. Techniques like the weight loss method, electrochemical impedance spectroscopy, potentiodynamic polarization (Tafel), and adsorption studies were employed. Results revealed that l-cysteine do offer an attractive inhibition efficiency. However, with an increase in the concentration of the inhibitor, corrosion rates decreased irrespective of the temperature gradients. This is due to surface adsorption of the inhibitor molecules on the metal which has contributed to a decreased double-layer capacitance and increased polarization resistance. With the increase in the concentration of the medium, the corrosion rate was also enhanced and this is due the liberation of a high quantum of H⁺ ions. Based on the results of Tafel polarization studies, it is evident that the amino acid, l-cysteine, could act as a mixed type inhibitor. The importance of l-cysteine in the corrosion of copper metal has been highlighted in this paper.     

Physicomechanical properties of nanocomposites based on cellulose nanofibre and natural rubber latex

Cellulose nanofibres (CNF) with diameter 10–60 nm were isolated from raw banana fibres by steam explosion process. These CNF were used as reinforcing elements in natural rubber (NR) latex along with cross linking agents to prepare nanocomposite films. The effect of CNF loading on the mechanical and dynamic mechanical (DMA) properties of NR/CNF nanocomposite was studied. The morphological, crystallographic and spectroscopic changes were also analyzed. Significant improvement of Young’s modulus and tensile strength was observed as a result of addition of CNF to the rubber matrix especially at higher CNF loading. DMA showed a change in the storage modulus of the rubber matrix upon addition of CNF which proves the reinforcing effect of CNF in the NR latex. A mechanism is suggested for the introduction of the Zn–cellulose complex and its three dimensional network as a result of the reaction between the cellulose and the Zinc metal which is originated during the composite formation.     

Graph‐based resource allocation algorithms for multiuser downlink MIMO‐OFDMA networks

Multiuser multiple‐input multiple‐output orthogonal frequency division multiple access (MIMO‐OFDMA) is considered as the practical method to attain the capacity promised by multiple antennas in the downlink direction. However, the joint calculation of precoding/beamforming and resource allocation required by the optimal algorithms is computationally prohibitive. This paper proposes computationally efficient resource allocation algorithms that can be invoked after the precoding and beamforming operations. To support stringent and diverse quality of service requirements, previous works have shown that the resource allocation algorithm must be able to guarantee a specific data rate to each user. The constraint matrix defined by the resource allocation problem with these data rate constraints provides a special structure that lends to efficient solution of the problem. On the basis of the standard graph theory and the Lagrangian relaxation, we develop an optimal resource allocation algorithm that exploits this structure to reduce the required execution time. Moreover, a lower‐complexity suboptimal algorithm is introduced. Extensive simulations are conducted to evaluate the computational and system‐level performance. It is shown that the proposed resource allocation algorithms attain the optimal solution at a much lower computational overhead compared with general‐purpose optimization algorithms used by previous MIMO‐OFDMA resource allocation approaches. Copyright © 2012 John Wiley & Sons, Ltd.     

Direct Addition of Grignard Reagents to Aliphatic Carboxylic Acids Enabled by Bulky turbo-Organomagnesium Anilides

The synthesis of ketones through addition of organometallic reagents to aliphatic carboxylic acids is a straightforward strategy that is limited to organolithium reagents. More desirable Grignard reagents can be activated and controlled with a bulky aniline-derived turbo-Hauser base. This operationally simple procedure allows the straightforward preparation of a variety of aliphatic and perfluoroalkyl ketones alike from functionalized alkyl, aryl and heteroaryl Grignard reagents.     

A sustainable method of mitigating acid corrosion of mild steel using jackfruit pectin (JP) as green inhibitor: Theoretical and electrochemical studies

This study is attempted to develop a green corrosion inhibitor from a waste material of Jack fruit (Artocarpus heterophyllus). This method is therefore quite valuable to health, environment, and economic point of view. Pectin is isolated from the jackfruit peel waste using 0.05 ?N oxalic acid and used as an inhibitor for mild steel corrosion in acidic environment as it is highly water soluble. 250–1000 ?ppm of pectin was used in this study at a temperature range of 303–323 ?K. The protection efficiency of jack fruit pectin (JP) in 0.5 ?M HCl was evaluated by conventional weight loss and electrochemical techniques. The potentiodynamic polarization results revealed that JP could effectively reduce the corrosion of mild steel in acidic medium at 1000 ?ppm concentration with an inhibition efficiency of 89.75% and corrosion rate of 2.392 mpy. The mixed type behavior of the inhibitor is identified from Tafel polarization studies. Electrochemical impedance spectroscopy (EIS) measurements suggest that the corrosion inhibition process is kinetically controlled. adsorption and kinetic behavior of the inhibitor also have been studied. Surface manifestations were followed using FESEM and AFM techniques. DFT calculations and Monte Carlo simulations were also carried out to corroborate the experimental results with theoretical outputs and succeeded to a great extent.     

On exponential stability of second order delay differential equations

We propose a new method for studying stability of second order delay differential equations. Results we obtained are of the form: the exponential stability of ordinary differential equation implies the exponential stability of the corresponding delay differential equation if the delays are small enough. We estimate this smallness through the coefficients of this delay equation. Examples demonstrate that our tests of the exponential stability are essentially better than the known ones. This method works not only for autonomous equations but also for equations with variable coefficients and delays.