Ultrafast strain engineering in complex oxide heterostructures

We report on ultrafast optical experiments in which femtosecond midinfrared radiation is used to excite the lattice of complex oxide heterostructures. By tuning the excitation energy to a vibrational mode of the substrate, a long-lived five-order-of-magnitude increase of the electrical conductivity of NdNiO(3) epitaxial thin films is observed as a structural distortion propagates across the interface. Vibrational excitation, extended here to a wide class of heterostructures and interfaces, may be conducive to new strategies for electronic phase control at THz repetition rates.     

Band gap narrowing and fluorescence properties of nickel doped SnO2 nanoparticles

Nickel-doped tin oxide nanoparticles (sub-5 nm size) with intense fluorescence emission behavior have been synthesized by sol-gel route. The structural and compositional analysis has been carried out by using XRD, TEM, FESEM and EDAX. The optical absorbance spectra indicate a band gap narrowing effect and it was found to increase with the increase in nickel concentration. The band gap narrowing at low dopant concentration (<5%) can be assigned to SnO₂−SnO_2−x alloying effect and for higher doping it may be due to the formation of defect sub-bands below the conduction band.     

Studies on Intermolecular Interactions in Liquid Mixtures of Alkoxyalkanols and Branched Alcohols by Volumetric and Acoustic Measurements at Different Temperatures

Densities and speeds of sound for binary mixtures of diethylene glycol monomethyl ether and triethylene glycol monomethyl ether with 3-methyl-1-butanol and 2-methyl-2-butanol were measured at 288.15, 298.15 and 308.15 K, over the entire range of compositions at atmospheric pressure, using an Anton Paar DSA 5000 density meter. The experimental densities and speeds of sound have been used to calculate excess molar volumes and excess molar isentropic compressibilities. The speed of sound data are compared with theoretical speeds of sound calculated using several approaches.     

Sonochemical degradation of martius yellow dye in aqueous solution

The sonolytic degradation of the textile dye martius yellow, also known as either naphthol yellow or acid orange 24, was studied at various initial concentrations in water. The degradation of the dye followed first-order kinetics under the conditions examined. Based on gas chromatographic results and sonoluminescence measurements of sonicated aqueous solutions of the dye, it is concluded that pyrolysis does not play a significant role in its degradation. The chromatographic identification of hydroxy added species indicates that an OH radical induced reaction is the main degradation pathway of the dye. Considering the non-volatility and surface activity of the dye, the degradation of the dye most probably takes place at the bubble/solution interface. The quantitative and qualitative formation of the degradation intermediates and final products were monitored using HPLC and ESMS. The analytical results suggest that the sonolytic degradation of the dye proceeds via hydroxylation of the aryl ring and also by C-N bond cleavage of the chromophoric ring, either through OH radical attack or through another unidentified process. The identification of various intermediates and end products also imply that the degradation of martius yellow proceeds through multiple reaction pathways. Total organic carbon (TOC) analyses of the dye solutions at various times following sonication revealed that sonolysis was effective in the initial degradation of the parent dye but very slow in achieving mineralization. The slow rate of mineralization is likely to be due to the inability of many of the intermediate products such as, the carboxylic acids, to accumulate at the bubble (air/water) interface and undergo decomposition due to their high water solubility (low surface activity).     

Excess molar volumes of methylcyclohexane+benzene, +methylbenzene, +1,4-dioxane,and +tetrahydrofuran at 303.15 K

Excess molar volumes V_m^E as function of mole fraction x for methylcyclohexane + benzene, + methylbenzene, + 1,4-dioxane, and + tetrahydrofuran are reported at 303.15 K. The excess molar volumes are positive and indicate the presence of weak interactions.     

Linear balls and the multiplicity conjecture

A linear ball is a simplicial complex whose geometric realization is homeomorphic to a ball and whose Stanley–Reisner ring has a linear resolution. It turns out that the Stanley–Reisner ring of the sphere which is the boundary complex of a linear ball satisfies the multiplicity conjecture. A class of shellable spheres arising naturally from commutative algebra whose Stanley–Reisner rings satisfy the multiplicity conjecture will be presented.     

Accuracy of the multipole expansion applied to a sphere in a creeping flow parallel to a wall

An example system is studied to discuss precision of the multipoleexpansion, applied to determine forces exerted on particlesby a viscous low-Reynolds-number fluid flow. A single spherein an ambient flow (pure shear, quadratic, and modulated shear)parallel to a close plane wall is considered. Forces and torquesexerted by the ambient flow on a motionless sphere are evaluated.Their precision is determined and related to a multipole orderof the truncation. Similar analysis is performed for a movingsphere with no ambient flow and for a freely moving sphere.Relative motion of the sphere with respect to the wall givesrise to strong lubrication interactions. It is analysed howthese interactions affect accuracy of the pure multipole expansion,and what are the smallest distances where it becomes insufficient.An alternative precise method is applied, in which lubricationexpressions are subtracted from the hydrodynamic forces andtorques, and the residue is evaluated as a fast-convergent seriesof inverse powers of the distance between the sphere centreand the wall. The accuracy of this procedure is carefully analysed.     

Structural, thermal and conductive properties of Bi4−xMxV2O11 (M = La, Gd; 0 x 0.4) compounds

Bi_4−xM_xV₂O₁₁ (M = La, Gd) was prepared by solid state reactions. The amount of La and Gd in the (Bi_4−xM_xV₂O₁₁) was varied in the range of (0 x 0.4). The addition of La and Gd to Bi₄V₂O₁₁ electrolyte was found to stabilize the β crystalline phase for x 0.3. In addition, the phase transition corresponding β- to γ-phases are evident in the ionic conductivity plots as well as in XRD, DSC profiles of x 0.3 samples. The highest ionic conductivity was observed in Bi_3.9La_0.1V₂O₁₁ and Bi_3.8Gd_0.2V₂O₁₁ samples in the range of 10⁻³–10⁻⁴ S/cm for 700–500 °C. These results were supported by impedance spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC).