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.     

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.     

A rapid and sensitive high-performance liquid chromatography assay for rofecoxib in human serum

Rofecoxib is a selective cyclooxygenase (COX)-2 inhibitor that is approved for the treatment of acute pain and osteoarthritis in adults. A sensitive and rapid high-performance liquid chromatographic (HPLC) method of determining rofecoxib in human serum is described. Alkalinized plasma samples are extracted into an organic solvent containing an internal standard and evaporated under nitrogen. The dried sample residues are reconstituted with mobile phase and analyzed by HPLC. The method uses 100 microL of the sample and is linear from 20 to 2000 ng/mL of rofecoxib. Precision and accuracy studies are performed. Stability of the drug in serum over four weeks is documented. This new method is simple, sensitive, precise, and accurate. Its use will translate into faster laboratory turnaround time, and the small sample volume required (100 microL) makes this assay suitable for pediatric patients. This assay will expedite pharmacokinetic studies and the therapeutic drug monitoring of rofecoxib and possibly other COX-2 inhibitors.