Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.     

Photoresponse of p-type zinc-doped iron(III) oxide thin films

Stable zinc-doped iron(III) oxide thin films that exhibit p-type behavior were synthesized by spray pyrolytic deposition (SPD) on conducting indium-doped tin oxide-coated glass substrate. The highest photocurrent density of 1.1 mA/cm2 was observed at an illumination intensity of 40 mW/cm2 at -0.8 V vs Pt for zinc-doped p-Fe2O3 samples prepared at an optimum substrate temperature of 663 K using an optimum spray time of 70 s. A quantum efficiency of 21.1% at 325 nm was found for SPD samples prepared using a dopant concentration of 0.0088 M zinc nitrate hexahydrate. X-ray diffraction results showed structures of alpha-Fe2O3 and ZnFe2O4. A direct band gap energy of 2.2 eV was found from monochromatic photocurrent density data and agrees closely with the band gap obtained from UV-vis absorption. The X-ray photoelectron spectroscopy results also confirm the presence of zinc dopant (4.0 atomic %) in thin films of zinc-doped p-Fe2O3.     

Rapid determination of total sulfur in fuels using gas chromatography with atomic emission detection

The purpose of this study is to determine whether gas chromatography (GC)-atomic emission detection (AED) can be used in a low-resolution mode for rapid, accurate determinations of total sulfur in fuels at trace levels to complement other popular methods of total sulfur analysis. A method for the rapid determination of total sulfur in fuels (called "fast GC-AED") is developed. The method is tested on gasoline, jet fuel, kerosene, and diesel fuel with sulfur concentrations ranging from 125 mg/L down to 2.5 mg/L. Fast GC-AED shows better performance than traditional GC-AED for total sulfur determinations, especially for complex mixtures containing many different sulfur-containing compounds at trace levels. This method also shows that GC-AED can be used for both rapid determinations of total sulfur and traditional determinations of speciated sulfur without requiring equipment changes. Fast GC-AED is competitive with other popular methods for sulfur analysis. The 5-min program that is developed for fast GC-AED is comparable with the time scale of other methods, such as wavelength dispersive X-ray fluorescence and UV-fluorescence (2 to 5 min). Fast GC-AED also compares favorably with UV-fluorescence for trace sulfur determinations, demonstrating accuracy down to 2.5-mg/L sulfur.     

Two connected inverse spectral transforms

We establish a transformation which connects the potentials of the one-dimensional Dirac and Klein-Gordon operators. This transformation links the solutions of the nonlinear evolution equations solvable by means of the two inverse spectral transforms which use the Dirac and Klein-Gordon direct and inverse spectral problems.