Enhanced Hydrodynamic Radius of AOT/n-heptane/Water Reverse Micellar System Through Altered Electrostatic Interactions and Molecular Self-Assemblies

We have demonstrated a unique approach to alter the aqueous pool size of an AOT/n-heptane/water reverse micellar system. A positively charged dye Rhodamine B (RhB) and negatively charged Rose Bengal (RB) were incorporated in the reverse micellar pool to investigate the effect of electrostatic interactions and stacking effects among the dye molecules on the AOT/n-heptane/water interface. Dynamic light scattering revealed increase in reverse micellar pool size in presence of positively charged dye aggregates at the oil–water interface. However, less expansion was observed in presence of negatively charged dye aggregates (RB). This confirms the role of electrostatic interaction in modulating the hydrodynamic radius. A head-to-tail type of stacking of RhB molecules at the interface favors this expansion. The differences in stacking of the two dyes inside the reverse micelles and their torsional mobility indicated the role of the reverse micellar interface and H-bonding ability of the microenvironment on dye aggregation. Conductivity measurements demonstrated a significant drop in percolation temperature of the reverse micellar system in presence of dye aggregates. This confirms the effect of dye aggregation and electrostatic interaction on such expansion. This strategy can be exploited for solubilizing greater amounts and a wider variety of drug molecules in microemulsions.

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A simple fast microwave-assisted synthesis of thermoelectric bismuth telluride nanoparticles from homogeneous reaction-mixture

A new simple chemical method for synthesis of nanocrystalline bismuth telluride (Bi₂Te₃) has been developed by microwave assisted reduction of homogeneous tartrate complexes of bismuth and tellurium metal ions with hydrazine. The reaction is performed at pH 10. The nano-crystallites have rhombohedral phase identified by XRD. The size distribution of nanoparticle is narrow and it ranges between 50 to 70 nm. FESEM shows that the fine powders are composed of small crystallites. The TEM micrographs show mostly deformed spherical particles and the lattice fringes are found to be 0.137 nm. Energy dispersive X-ray spectroscopy (EDX) analysis shows the atomic composition ratio between bismuth and tellurium is 2:3. Thermoelectric properties of the materials are studied after sintering by spark plasma sintering method (SPS). The grain size of the material after sintering is in the nanometer range. The material shows enhanced Seebeck coefficient and electrical conductivity value at 300 K. The figure of merit is found to be 1.18 at 300 K.

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Azimuthal pion fluctuation in ultra relativistic nuclear collisions and centrality dependence—a study with chaos based complex network analysis

Various works on multiplicity fluctuation have investigated the dynamics of particle production process and eventually have tried to reveal a signature of phase transition in ultra-relativistic nuclear collisions. Analysis of fluctuations of spatial patterns has been conducted in terms of conventional approach. However, analysis with fractal dynamics on the scaling behavior of the void has not been explored yet. In this work we have attempted to analyze pion fluctuation in terms of the scaling behavior of the void probability distribution in azimuthal space in ultra-relativistic nuclear collisions in the light of complex networks. A radically different and rigorous method viz. Visibility Graph was applied on the data of ³²S-Ag/Br interaction at an incident energy of 200 GeV per nucleon. The analysis reveals strong scaling behavior of void probability distributions in azimuthal space and a strong centrality dependence.     

Electronic states and spectroscopic properties of GeSi

Electronic structure and spectroscopy of the GeSi molecule have been investigated by performing ab initio based multireference configuration interaction calculations. Potential energy curves of 29 Λ-S states of singlet, triplet, and quintet spin multiplicities have been constructed. Spectroscopic constants of 24 bound states within 36 000 cm⁻¹ are reported and compared with the available data. The calculated dissociation energy of GeSi in the ground state is 2.80 eV. Effects of the spin-orbit coupling on the spectroscopic properties of the molecule have been found to be small. However, the computed zero-field-splitting of the ground state compares well with the earlier prediction. Transitions such as 2³Σ⁻-X³Σ⁻, 3³Σ⁻-X³Σ⁻, 4³Π-A³Π, 5³Π-A³Π etc. are relatively strong. Radiative lifetimes for several dipole allowed and spin-forbidden transitions are calculated. The estimated lifetimes of the 2³Σ⁻, 3³Σ⁻, and 5³Π states are about 109, 33, and 62 ns, respectively. Dipole moments of most of the low-lying states of GeSi are also reported.     

An Aluminum Hydride That Functions like a Transition‐Metal Catalyst

The reaction of [LAlH₂] (L=HC(CMeNAr)₂, Ar=2,6‐iPr₂C₆H₃) with MeOTf (Tf=SO₂CF₃) resulted in the formation of [LAlH(OTf)] ( 1 ) in high yield. The triflate substituent in 1 increases the positive charge at the aluminum center, which implies that 1 has a strong Lewis acidic character. The excellent catalytic activity of 1 for the hydroboration of organic compounds with carbonyl groups was investigated. Furthermore, it was shown that 1 effectively initiates the addition reaction of trimethylsilyl cyanide (TMSCN) to both aldehydes and ketones. Quantum mechanical calculations were carried out to explore the reaction mechanism.     

Synthesis of libraries of quinoxalines through eco-friendly tandem oxidation-condensation or condensation reactions

A facile and expeditious solid-phase synthesis of libraries of quinoxalines promoted on KF-alumina surface via tandem oxidation-condensation or condensation reactions is reported. The reaction protocol is operationally simple and mild. Moreover, solvent-free reaction condition makes the reaction procedure eco-friendly and economically viable.     

Solving multi-objective parallel machine scheduling problem by a modified NSGA-II

In this paper, we modify a Multi-Objective Evolutionary Algorithm, known as Nondominated sorting Genetic Algorithm-II (NSGA-II) for a parallel machine scheduling problem with three objectives. The objectives are – (1) minimization of total cost due tardiness, (2) minimization of the deterioration cost and (3) minimization of makespan. The formulated problem has been solved by three Multi-Objective Evolutionary Algorithms which are: (1) the original NSGA-II (Non-dominated Sorting Genetic Algorithm–II), (2) SPEA2 (Strength Pareto Evolutionary Algorithm-2) and (3) a modified version of NSGA-II as proposed in this paper. A new mutation algorithm has also been proposed depending on the type of problem and embedded in the modified NSGA-II. The results of the three algorithms have been compared and conclusions have been drawn. The modified NSGA-II is observed to perform better than the original NSGA-II. Besides, the proposed mutation algorithm also works effectively, as evident from the experimental results.     

Co-existence of multiple attractors in the PWM controlled DC drives

DC shunt and series drives are extensively used in the industry. The occurrence of bifurcation and chaos in dc shunt and permanent magnet drives are well known. It is observed that the behavior of the drives not only depends on the value of system parameters but also on the value of initial conditions. Multiple attractors can exist for same parameter value. Different choice of initial conditions gives different periodic behavior of the system. The drive is intended to operate in a parameter range to give period-1 behavior. We report the existence of sub- harmonic oscillations in the period-1 region of the bifurcation diagram along with co-existing attractor with fractal basin boundaries in PWM controlled dc series drives. The series drive is extensively used in electric traction and other applications. The dc drives are run with dc input voltage. This dc voltage may be derived from a dc source or an ac source with a rectifier. The dc series drive shows different bifurcation behavior when different types of input voltage and switching elements are used. The existence of period-1, period-2 and period-4 orbits are observed with different initial conditions in the desired period-1 region of the bifurcation diagram. The dependence of system’s behavior on initial condition may render the system’s behavior unpredictable. These phenomena may have serious implication in performance.     

Dimethyl sulfoxide induced structural transformations and non-monotonic concentration dependence of conformational fluctuation around active site of lysozyme

Experimental studies have observed significant changes in both structure and function of lysozyme (and other proteins) on addition of a small amount of dimethyl sulfoxide (DMSO) in aqueous solution. Our atomistic molecular dynamic simulations of lysozyme in water-DMSO reveal the following sequence of changes on increasing DMSO concentration. (i) At the initial stage (around 5% DMSO concentration) protein's conformational flexibility gets markedly suppressed. From study of radial distribution functions, we attribute this to the preferential solvation of exposed protein hydrophobic residues by the methyl groups of DMSO. (ii) In the next stage (10-15% DMSO concentration range), lysozome partially unfolds accompanied by an increase both in fluctuation and in exposed protein surface area. (iii) Between 15-20% concentration ranges, both conformational fluctuation and solvent accessible protein surface area suddenly decrease again indicating the formation of an intermediate collapse state. These results are in good agreement with near-UV circular dichroism (CD) and fluorescence studies. We explain this apparently surprising behavior in terms of a structural transformation which involves clustering among the methyl groups of DMSO. (iv) Beyond 20% concentration of DMSO, the protein starts its final sojourn towards the unfolding state with further increase in conformational fluctuation and loss in native contacts. Most importantly, analysis of contact map and fluctuation near the active site reveal that both partial unfolding and conformational fluctuations are centered mostly on the hydrophobic core of active site of lysozyme. Our results could offer a general explanation and universal picture of the anomalous behavior of protein structure-function observed in the presence of cosolvents (DMSO, ethanol, tertiary butyl alcohol, dioxane) at their low concentrations.