Shape fluctuation-induced dynamic hysteresis

We consider a system of Brownian particles confined in a two-dimensional bilobal enclosure whose walls are driven in time periodically by an external perturbation. The response of the particles under shape modulation is characterized by a relaxational delay which results in a non-vanishing area of the response function-field loop, response function being the integrated probability of residence of the particles in any of the lobes. This phenomenon is an entropic analogue of dynamical hysteresis, which vanishes in the quasi-static limit. The hysteresis loop area depends on temperature, strength of modulating field, and the geometrical parameters of the enclosure and exhibits a turnover as a function of frequency of the field.     

Structural characterization and spectroelectrochemical, anion sensing and solvent dependence photophysical studies of a bimetallic Ru(II) complex derived from 1,3-di(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)benzene

The X-ray crystal structure of a mixed-ligand bimetallic ruthenium(II) complex of composition [(bipy)(2)Ru(H(2)Impib)Ru(bipy)(2)](ClO(4))(4) (1), where H(2)Impib = 1,3-di(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)benzene and bipy = 2,2'-bipyridine, has been determined and showed that the compound crystallized in monoclinic form with the space group P2(1)/c. The absorption, steady state and time-resolved luminescence spectral properties of the complex were thoroughly investigated in different solvents. The compound displays strong luminescence at room temperature with lifetimes in the range of 140-470 ns, depending upon the nature of the solvent. Solvent-induced lifetime tuning makes the complex a suitable solvatochromic probe. The complex is found to undergo one simultaneous two-electron reversible oxidation in the positive potential window (0 to +1.6 V) and four quasi-reversible reductions in the negative potential window (0 to -2.2 V). Spectroelectrochemical studies have also been carried out for the bimetallic compound in the range of 300-1600 nm. With stepwise oxidation of the Ru(ii) centers replacement of MLCT bands by LMCT bands occur with the development of a broad band at λ(max) = 1260 nm, which is ascribed to inter-valence charge-transfer (IVCT) transition for the mixed-valence Ru(II)Ru(III) species. The anion sensing properties of the receptor were thoroughly investigated in acetonitrile solution using absorption, steady state and time-resolved emission spectroscopic studies. The anion sensing studies revealed that the receptor acts as sensor for F(-), AcO(-) and H(2)PO(4)(-). It is evident that in the presence of excess F(-) and AcO(-) ions, deprotonation of the imidazole N-H fragments of the receptor occurs, an event which is signaled by the change of color from yellow to orange visible to the naked eye. From the absorption and emission titration studies the binding/equilibrium constants of the receptor with the anions have also been determined. Anion-induced lifetime quenching by F(-) and AcO(-) and enhancement by H(2)PO(4)(-) makes the receptor a suitable lifetime-based sensor for selective anions. Cyclic voltammetry (CV) measurements of the compound carried out in acetonitrile have provided evidence in favor of anion-dependent electrochemical responses with F(-) and AcO(-) ions.     

Quarkonia production at forward rapidity in Pb+Pb collisions at {\sqrt{{s}_{\rm NN}}=2.76} TeV with the ALICE detector

The study of formation of heavy quarkonia in relativistic heavy-ion collisions provides important insight into the properties of the produced high-density QCD medium. Lattice QCD studies show sequential suppression of quarkonia states with increasing temperature; which affirms that a full spectroscopy can provide us a thermometer for the matter produced under extreme conditions in relativistic heavy-ion collisions and one of the most direct probes of deconfinement. Muons from the decay of charmonium resonances are detected in ALICE experiment in p?+?p and Pb+Pb collisions with a muon spectrometer, covering the forward rapidity region (2.5?<?y?<?4). The analysis of the inclusive J/?? production in the first Pb+Pb data collected in the fall of 2010 at a centre of mass energy of $\sqrt{s_{\rm NN}}=2.76$ ?TeV is discussed. Preliminary results on the nuclear modification factor (R _AA) and the central to peripheral nuclear modification factor (R _CP) are presented.     

Ultrasound-assisted aza-Michael reaction in water: a green procedure

The conjugate addition of amines to conjugated alkenes (commonly known as aza-Michael reaction) constitutes a key step for the synthesis of various complex natural products, antibiotics, α-amino alcohols and chiral auxiliaries. Ultrasound-induced addition of several amines to α, β-unsaturated ketones, esters and nitriles has been carried out very efficiently in water as well as under solvent-free conditions. No catalysts or solid supports have been used in this method. Remarkable enhancement of reaction rate has been observed in water under ultrasound-induced method. This environmentally benign procedure has provided clean formation of the products with better selectivity.     

Combined effects of blockage and yield stress on drag and heat transfer from an in-line array of three spheres

This work reports results on the drag and heat transfer from an in-line array of three isothermal spheres falling in a cylindrical confinement filled with Bingham plastic fluids. The effects of dimensionless parameters, such as the Reynolds number (1 ≤ Re?≤?100), Prandtl number (1 ≤ Pr?≤?100), Bingham number (0 ≤ Bn?≤?100), blockage ratio (2 ≤ β?≤?4) and sphere-to-sphere distance (1.5 ≤ t?≤?6) have been elucidated. The flow and heat transfer characteristics were analysed in terms of yielded/unyielded regions, streamline and isotherm contours, drag coefficient, pressure coefficient, and local and average Nusselt number. Broadly, the drag coefficient shows a positive dependence on Bn and sphere-to-sphere distance (t) while it exhibits an inverse dependence on Re and β. On the other hand, the Nusselt number shows a positive dependence on Re, Pr, Bn and β; and a complex dependence on t for each sphere. Simple predictive expressions for the average Nusselt number for each sphere are formulated, thereby enabling its prediction in a new application.     

Jeans Instability of Self Gravitating Dust Cloud in Presence of Effective Electrostatic Pressure

The role of viscosity coefficient (η'), coulomb coupling parameter (Γ) and dust mass on the growth of jeans mode is investigated in strongly coupled dusty plasma using equations of Generalized Hydrodynamics (GH) Model. The novel aspect of this work is that the force arising due to electrostatic pressure caused by grain grain interaction has been included in the dynamics of dust particles. This force is found to play a significant role in counter balancing the self gravity effect, thereby reducing the growth rate of jeans instability. The present work may provide more physical insight in understanding the mechanisms behind formation of planetesimals, stars etc.     

A conductivity study of polyelectrolytes based on 4-vinyl pyridine and butylmethacrylate

Abstract  In this paper, the chain flexibility of P4-VP was tried to increase by lowering its glass transition temperature (T _g) and by increasing its amorphous region by copolymerizing with butyl methacrylate. The copolymers were prepared in five different feed molar ratios to optimize the required properties such as higher room temperature conductivity and film-forming capacity. The conductivity and conduction behavior of the copolymers, as well as their hydrochloride and hydrobromide salts, have been reported. The copolymers were prepared by solution polymerization technique, using tetrahydrofuran as solvent at 60 °C, and the salts were prepared by simple acidification. The copolymers and their salts were characterized by scanning electron micrographs, infrared, proton nuclear magnetic resonance, thermogravimetric, differential scanning calorimetry and AC impedance measurements. There was about 10³- to 10⁴-fold increase in room temperature conductivity of these plasticized polyelectrolytes. The conduction behavior was found to be predominantly ionic. The scientific importance of this paper is that, unlike polymer electrolytes, no external salt is used; instead the virgin polymer and polyelectrolytes are used for conductivity measurements.     

Optimization of plasma parameters for high rate deposition of titanium nitride films as protective coating on bell-metal by reactive sputtering in cylindrical magnetron device

Nano-structured titanium nitride (TiN) thin film coating is deposited by reactive sputtering in cylindrical magnetron device in argon and nitrogen gas mixtures at low temperature. This method of deposition using DC cylindrical magnetron configuration provides high uniform yield of film coating over large substrate area of different shapes desirous for various technological applications. The influence of nitrogen gas on the properties of TiN thin film as suitable surface protective coating on bell-metal has been studied. Structural morphological study of the deposited thin film carried out by employing X-ray diffraction exhibits a strong (2 0 0) lattice texture corresponding to TiN in single phase. The surface morphology of the film coating is studied using scanning electron microscope and atomic force microscope techniques. The optimized condition for the deposition of good quality TiN film coating is found to be at Ar:N₂ gas partial pressure ratio of 1:1. This coating of TiN serves a dual purpose of providing an anti-corrosive and hard protective layer over the bell-metal surface which is used for various commercial applications. The TiN film's radiant golden colour at proper deposition condition makes it a very suitable candidate for decorative applications.     

Sorption of uranium on magnetite nanoparticles

Magnetite (Fe₃O₄) nanoparticle was synthesized using a solid state mechanochemical method and used for studying the sorption of uranium(VI) from aqueous solution onto the nanomaterial. The synthesized product is characterized using SEM, XRD and XPS. The particles were found to be largely agglomerated. XPS analysis showed that Fe(II)/Fe(III) ratio of the product is 0.58. Sorption of uranium on the synthesized nanomaterials was studied as a function of various operational parameters such as pH, initial metal ion concentration, ionic strength and contact time. pH studies showed that uranium sorption on magnetite is maximum in neutral solution. Uranium sorption onto magnetite showed two step kinetics, an initial fast sorption completing in 4–6 h followed by a slow uptake extending to several days. XPS analysis of the nanoparticle after sorption of uranium showed presence of the reduced species U(IV) on the nanoparticle surface. Fe(II)/Fe(III) ratio of the nanoparticle after uranium sorption was found to be 0.48, lower than the initial value indicating that some of the ferrous ion might be oxidized in the presence of uranium(VI). Uranium sorption studies were also conducted with effluent from ammonium diuranate precipitation process having a uranium concentration of about 4 ppm. 42% removal was observed during 6 h of equilibration.     

Adsorptive removal of Cr(III) from aqueous solution using tripolyphosphate cross-linked chitosan beads

Chitosan tripolyphosphate (CTPP) beads were prepared at two different cross-linking densities and adsorption of Cr(III) onto it were studied as a function of different operational parameters such as solution pH, equilibration time and initial Cr(III) ion concentration. Higher cross-linked beads were found to have more adsorption capacity at all the experimental pH employed (pH = 3–5), whereas adsorption capacity is found to increase with increase in pH. Adsorption data were analyzed using Langmuir and Freundlich isotherm models. Langmuir model is found be more suitable to explain the experimental results with a monolayer adsorption capacity of 469.5 mg/g. Among the kinetic models used, pseudo-second order kinetic model could best describe the adsorption process. Competition experiments done in presence of Na(I), Mg(II), Ca(II), Al(III) and Fe(III) revealed that, except in the case of Al(III), adsorption of Cr(III) is not significantly affected by the presence of foreign cations. NaCl is found to be a suitable leaching agent for the desorption of adsorbed Cr(III) from CTPP beads. FTIR spectroscopic investigations confirmed that phosphate groups are the principal binding site responsible for the sorption of Cr(III) onto CTPP beads.