A gradient liquid chromatographic (LC) method for control of emtricitabine (FTC) was validated for the analysis of FTC formulations (capsules and oral solution) and fixed-dose-combination tablets containing FTC [FTC combined with tenofovir disoproxil fumarate (TDF) and FTC combined with TDF and efavirenz (EFV)]. The method is based on the purity test recently prescribed in the International Pharmacopoeia and uses a Hypersil BDS C18 column (25 cm × 4.6 mm i.d.), 5 μm kept at a temperature of 35 °C. Other reversed-phase columns were also investigated. The mobile phases for gradient elution consist of acetonitrile, phosphate buffer and water. The flow rate is 1.0 mL min−1 and UV detection is performed at 280 nm. The method is capable of separating the main components from one another, from the inactive ingredients and from the main degradation products. The method was validated with respect to accuracy, precision, sensitivity and linearity for each component and the solution media were optimized. Finally, commercial FTC capsules, FTC oral solution, FTC/TDF tablets and FTC/TDF/EFV tablets were examined.
True coincidence summing correction factors for 133Ba, 152Eu and 125Sb were determined experimentally for a small volume source and compared with correction factors obtained with three softwares (EFFTRAN-X, GESPECOR and VGSL). The radionuclides investigated have a relatively challenging decay scheme and their spectra are known to suffer from losses due to summation (γ–γ, γ–X and X–X) when measured at close distances on a HPGe detector sensitive to low energy photons. This study shows that the softwares were in good agreement with each other and the experimental data and the calculated activity was consistent with the activity in the volume source.
We study tail probabilities of the suprema of Lévy processes with subexponential or exponential marginal distributions over compact intervals. Several of the processes for which the asymptotics are studied here for the first time have recently become important to model financial time series. Hence our results should be important, for example, in the assessment of financial risk. 相似文献
We consider stimulated pair production employing strong-field QED in a high-intensity laser background. In an infinite plane wave, we show that light-cone quasi-momentum can only be transferred to the created pair as a multiple of the laser frequency, i.e. by a higher harmonic. This translates into discrete resonance conditions providing the support of the pair creation probability which becomes a delta-comb. These findings corroborate the usual interpretation of multi-photon production of pairs with an effective mass. In a pulse, the momentum transfer is continuous, leading to broadening of the resonances and sub-threshold behaviour. The peaks remain visible as long as the number of cycles per pulse exceeds unity. The resonance patterns in pulses are analogous to those of a diffraction process based on interference of the produced pairs. We finally comment on the dependence of the peak positions, and in turn the effective mass, on the pulse shape. 相似文献