[en] The adsorption of NO₂ molecules on (8,0) zigzag single-walled boron nitride nanotube surface is investigated using density functional theory calculations. Two interaction modes, nitro (interacting atom is N) and nitrite (O interacts with BNNT) have been studied with increase in number of NO₂ molecules. The adsorption of single NO₂ molecule in both configurations is observed to be exothermic and physical in nature. However, in nitrite configuration, NO₂ molecules are chemisorbed on the surface leading to the dissociation of NO₂ molecules into NO and O. The density of states, natural bond orbital analysis and frontier orbital pictures provide rational understanding of the charge transfer involved in the process and predict significant enhancement in the conductivity of the BNNT after NO₂ adsorption. The DFT calculations show that NO₂ adsorption introduces new impurity states in the band gap of bare BNNT and expand their applications as NO₂ molecule gas sensor and catalytic surface for N-O dissociation depending upon the mode of adsorption.

[en] Growth of Young diagrams, equipped with Plancherel measure, follows the automodel equation of Kerov. Using the technology of unitary matrix model we show that such growth process is exactly same as the growth of gap-less phase in Gross-Witten and Wadia (GWW) model. The limit shape of asymptotic Young diagrams corresponds to GWW transition point. Our analysis also offers an alternate proof of limit shape theorem of Vershik-Kerov and Logan-Shepp. Using the connection between unitary matrix model and free Fermi droplet description, we map the Young diagrams in automodel class to different shapes of two dimensional phase space droplets. Quantising these droplets we further set up a correspondence between automodel diagrams and coherent states in the Hilbert space. Thus growth of Young diagrams are mapped to evolution of coherent states in the Hilbert space. Gaussian fluctuations of large N Young diagrams are also mapped to quantum (large N) fluctuations of the coherent states.

[en] Highlights: • The study reports density, ultrasonic speed and viscosity data of l-threonine in aqueous-sucrose solutions. • The study elucidates interactions of l-threonine with sucrose in aqueous media. • Provides data to estimate physicochemical properties of proteins in these media. • Correlates physicochemical properties of l-threonine with its behaviour in aqueous-sucrose solutions. -- Abstract: Densities, ρ of solutions of l-threonine in aqueous-sucrose solvents 5%, 10%, 15%, and 20% of sucrose, w/w in water at T = (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K; and ultrasonic speeds, u and viscosities, η of these solutions at 298.15, 303.15, 308.15, 313.15, and 318.15 K were measured at atmospheric pressure. From these experimental results, the apparent molar volume, V_ϕ, limiting apparent molar volume, V_ϕ^∘ and the slope, S_v, apparent molar compressibility, K_s,ϕ, limiting apparent molar compressibility, K_s,ϕ^∘ and the slope, S_k, transfer volume, V_ϕ,tr^∘, transfer compressibility, K_s,ϕ,tr^∘, limiting apparent molar expansivity, E_ϕ^∘, Hepler’s constant, (∂²V_ϕ^∘/dT²), Falkenhagen coefficient, A, Jones–Dole coefficient, B and hydration number, n_H have been calculated. The results have been interpreted in terms of solute–solvent and solute–solute interactions in these systems. The Gibbs energies of activation of viscous flow per mole of solvent, Δμ₁^{∘numbersign} and per mole of solute, Δμ₂^{∘numbersign} were also calculated and discussed in terms of transition state theory. It has been observed that there exist strong solute–solvent interactions in these systems and these interactions increase with increase in sucrose concentration in solution

[en] Highlights: • Li_2O·ZnO·Bi_2O_3·SiO_2 glasses have been synthesized. • Complex impedance plots suggest non-Debye relaxation behavior. • Charge carrier ions face same energy barrier during conduction and relaxation. • Hruby’s parameter reveals the high stability of glasses. - Abstract: Lithium zinc bismuth silicate glasses having composition 30Li_2O·20ZnO·xBi_2O_3·(50−x)SiO_2, (10 ⩽ x ⩽ 40 mol%) were prepared by using normal melt quenching technique. Physical, optical, electrical and thermal properties have been investigated in order to understand mixed former effect because of the presence of Bi_2O_3 and SiO_2 in these glasses. The compositional variations of density (D_g) and molar volume (V_g) have been examined. From the optical absorption spectra, the cut-off wavelength (λ_g), optical band gap (E_g) and Urbach’s energy (ΔE) have been determined and are related with the structural changes occurring in these glasses with increase in bismuth oxide content. The electronic polarizability of the oxide ion and optical basicity has also been obtained from the calculated values of the optical band gap. The ac and dc conductivities, activation energy for dc conduction (E_d_c) and for relaxation frequency (E_M_″) were calculated from the impedance spectra. The results obtained from dc conductivity depicted that the lithium ions are mainly responsible for the conduction mechanism and it also confirmed the network forming role of zinc oxide in these glasses. The temperature dependence of the relaxation dynamics in these glasses has been interpreted by using the scaling of the conductivity spectra. The observed conductivity spectra follows power law with exponent ‘s’ which decreases with temperature and satisfies the correlated barrier hopping (CBH) model. The exact overlying of normalized plots of electrical modulus on a single ‘master curve’ indicates temperature independent dynamical process at various frequencies. The non-linear compositional change in optical band gap, activation energies as well as glass transition temperature reveals the mixed glass former effect. The increase in the values of thermal parameters such as glass stability factor and Hruby’s parameter, suggests large stability of glasses

[en] In this paper we construct a unitary matrix model that captures the asymptotic growth of Young diagrams under q-deformed Plancherel measure. The matrix model is a q analog of Gross-Witten-Wadia (GWW) matrix model. In the large N limit the model exhibits a third order phase transition between no-gap and gapped phases, which is a q-deformed version of the GWW phase transition. We show that the no-gap phase of this matrix model captures the asymptotic growth of Young diagrams equipped with q-deformed Plancherel measure. The no-gap solutions also satisfy a differential equation which is the q-analogue of the automodel equation. We further provide a droplet description for these growing Young diagrams. Quantising these droplets we identify the Young diagrams with coherent states in the Hilbert space. We also elaborate the connection between moments of Young diagrams and the infinite number of commuting Hamiltonians obtained from the large N droplets and explicitly compute the moments for asymptotic Young diagrams.

[en] Highlights: • Provides density and viscosity data for l-arginine in aqueous-arabinose/xylose solutions. • Elucidates interactions of l-arginine in aqueous-arabinose/xylose solutions. • Correlates physicochemical properties of l-arginine with its behaviour in solution. -- Abstract: Densities, ρ of l-arginine in water and in aqueous–d-xylose/l-arabinose (2.5% and 5% of d-xylose/l-arabinose, w/w in water) mixed solvents were measured at temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K, and viscosities, η of these solutions at temperatures (298.15, 303.15, 308.15, 313.15 and 318.15) K were measured at atmospheric pressure. From the density values, the apparent molar volume, V_ϕ, limiting apparent molar volume, V_ϕ^°, slope, S_v and transfer volume, V_ϕ,tr^° and hydration number, n_H were calculated. The viscosity values have been analysed on the basis of the Jones–Dole equation; and Falkenhagen Coefficient, A and Jones–Dole coefficient, B were calculated. The Gibbs energies of activation of viscous flow per mole of solvent, Δμ₁^°numbersign and per mole of solute, Δμ₂^°numbersign were also calculated. The results indicate that there exist strong solute–solvent interactions in these systems, which increase with increase in carbohydrate concentration in both the solvents. It is observed that l-arginine act as a structure-maker in both these solvent systems

[en] Highlights: • The study reports density, ultrasonic speed and viscosity data of l-phenylalanine in aqueous-carbohydrate solutions. • The study elucidates interactions of l-phenylalanine with carbohydrates in aqueous media. • Correlates physicochemical properties of l-phenylalanine with its behavior in aqueous-carbohydrate solutions. • The structure-making/breaking ability of l-phenylalanine in these aqueous-carbohydrate solutions is reported. -- Abstract: The values of density, ρ and ultrasonic speed, u of solutions of l-phenylalanine in aqueous-carbohydrate solvents (2.5 and 5% of arabinose/glucose/sucrose, w/w in water) at T = (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K; and viscosities, η of these solutions at (298.15, 303.15, 308.15, 313.15, and 318.15) K and at atmospheric pressure were measured. From these experimental results, the apparent molar volume, V_ϕ, limiting apparent molar volume, V_ϕ^° and the slope, S_v, transfer volume, V_ϕ,tr^°, apparent molar compressibility, K_s,ϕ, limiting apparent molar compressibility, K_s,ϕ^° and the slope, S_k, transfer volume, V_ϕ,tr^°, transfer compressibility, K_s,ϕ,tr^°, limiting apparent molar expansivity, E_ϕ^°, Hepler’s constant, (∂²V_ϕ^°/dT²), Falkenhagen Coefficient, A, Jones–Dole coefficient, B and hydration number, n_H were calculated. The Gibbs free energies of activation of viscous flow per mole of solvent, Δμ₁^°numbersign and per mole of solute, Δμ₂^°numbersign, entropies, ΔS^° and enthalpies, ΔH^° of activation of viscous flow were also calculated and discussed in terms of transition state theory. The structure-making/breaking ability of the amino acid has also been discussed in terms of the sign of (∂²V_ϕ^°/dT²) and dB/dT. The results have been interpreted in terms of solute–solvent and solute–solute interactions in these systems

[en] Highlights: • Quaternary Li₂O ZnO Bi₂O₃ B₂O₃ glasses were synthesized using melt-quench method. • Bi₂O₃ acts as network former as well as network modifier. • Impedance data were analyzed using conductivity and modulus formalisms. • Normalized plots of electrical modulus overlap on a single ‘master curve’. - Abstract: The quaternary glass system 30Li₂O⋅20ZnO⋅xBi₂O₃⋅(50−x)B₂O₃ (with x = 0, 10, 20, 30, 40 and 50 mol%), were fabricated by the conventional melt quench technique. The characterization of the samples include physical properties (density and molar volume), thermal properties using differential scanning analysis, structural studies using IR spectroscopy, optical properties using UV–VIS–NIR spectroscopy and dielectric properties using impedance spectroscopy. Density and molar volume variations with glass composition have been discussed. The non-linear compositional change in glass transition temperature and result obtained from IR studies confirm that Bi₂O₃ play dual role i.e. as network modifying oxide as well as network forming oxide. Also, the significant shifting of band at 1384–1305 cm⁻¹ with increase in Bi₂O₃ content in the glass matrix suggests the formation of new boron–oxygen ring. The presence of sharp cut-off and large transmission in UV–VIS–NIR regime make these glasses suitable for spectral devices. The cut-off wavelength, optical band gap and Urbach’s energy were determined from the absorption spectra and were related with the structural changes occurring in these glasses with increase in Bi₂O₃:B₂O₃ ratio. The complex impedance plots show depressed semicircles that shift towards origin with increase in temperature. This reveals the migration of charge carrier ions in glass matrix is thermally stimulated. The frequency-dependent complex impedance data were analyzed in the framework of conductivity and modulus formalisms. The dc conductivity decreases with increase in Bi₂O₃ content (<40 mol%) because of blocking effect of the Bi ions on the migration of mobile ions. The observed maximum in E_dc for LZBB 4 sample implies the existence of mixed former effect in these glasses. The perfect overlapping of normalized plots of electrical modulus on a single ‘master curve’ suggests temperature independent dynamical process at different frequencies

[en] Highlights: •Single phased Sr substituted BaTiO₃ ceramics prepared via solid state reaction. •Rietveld refinement of the ceramics showed tetragonal symmetry, P4mm space group. •Linear decrease in Curie temperature was observed with increase in Sr substitution. •Multiple activation energies revealed electrically heterogeneous microstructure. •Conduction and relaxation were attributed to oxygen vacancies. -- Abstract: Single phased Sr substituted BaTiO₃ ceramics were synthesized via solid state reaction technique and were found to crystallise in tetragonal symmetry with P4mm space group using Rietveld refinement. With increase in Sr content the tetragonality was reduced and the Curie temperature decreased at rate of 3 K/mol%. The contribution of grain interiors and grain boundaries to conduction and relaxation mechanisms was discerned on basis of ac conductivity, impedance and modulus formalisms. Three conduction mechanisms were observed in grain interiors; two via conducting electrons from V_O^′ and V_O^″ and third one via oxygen vacancies itself. The relaxation at grain boundaries was attributed to the defect associate (V_o^″-2Ti³⁺). Saturated hysteresis loops confirmed the ferroelectric nature of the ceramics. The remnant polarization P_r and the coercive fields E_c decrease with increase in Sr content

[en] Synthesis of Bi_0_._8Ba_0_._2Fe_1_−_xV_xO_3 multiferroics (with x=0.0, 0.02 and 0.04 having code V0, V2 and V4, respectively) have been done by solid-state reaction technique. The structural, magnetic and electrical characterization of the prepared ceramics have been carried out using X-ray diffraction, Vibrating sample magnetometry and impedance spectroscopy, respectively. Rietveld refinement studies show that all samples have rhombohedral structure (R3c). The observed lattice distortion is due to the difference in the ionic radii of parent ions and doped ions. Sizeable M–H hysteresis loops revealed the transformation of antiferromagnetic BiFeO_3 (BFO) into ferromagnetic with Ba and V addition. The highest values of coercive field ~4.5 kOe and saturation magnetization ~1.14 emu/g are observed for V0 and V2 samples, respectively. The dielectric properties were improved with the co-doping as compared with the pure BFO compound due to structural distortion and decrease of oxygen vacancies by addition of higher valence V"5"+ cation. - Highlights: • Refinement has been done by hexagonal representation of R3c space group. • Magnetic properties are affected by the distortion in Fe–O octahedral. • Dielectric properties have improved on co-doping.