Stabilization of the Surface of ZnO Films and Elimination of the Aging Effect

Zinc oxide is a promising multifunctional material. The practical use of nano- and polycrystalline ZnO devices faces a serious problem of instability of electrical and luminescent characteristics, due to the adsorption of oxygen by the surface during aging. In this paper, the aging effect in ZnO films and nanorod arrays was studied. It was found that ZnO samples demonstrate different behavior of the degradation process, which corresponds to at least two different types of adsorbing surface sites for O₂, where O₂ adsorption is of a different nature. The first type of surface sites is rapidly depassivated after hydrogen passivation and the aging effect takes place due to these centers. The second type of surface sites has a stable structure after hydrogen passivation and corresponds to HO–ZnO sites. The XPS components of these sites include the Zn2p_3/2 peak at 1022.2 ± 0.2 eV and Zn2p_1/2 peak at 1045.2 ± 0.2 eV, with a part of the XPS O1s peak at 531.5 ± 0.3 eV. The annealing transforms the first type of site into the second one, and the subsequent short-term plasma treatment in hydrogen results in steady passivation, where the degradation of characteristics is practically reduced to zero.     

An evidence-based approach to writing reviews as illustrated by treatment of erectile dysfunction

Reviews integrate the data from original sources of information on the given topic. The quality of the review of literature depends on the quality of initial information. The development of evidence-based medicine demands higher standards from clinical trials. The authors analyse available information on the treatment of erectile dysfunction basing on standard international requirements for clinical trials. A checking list is available for standardization of clinical assessment. The data obtained is ranged by the degree of statistical significance. Basing on the evidence-based approach, the conclusion on efficacy of the following modern drugs in the treatment of erectile dysfunction are made: sildenafil, iochimbin, prostaglandin E1 and tadalafil. The conclusion on efficacy of the other drugs against erectile dysfunction is impossible in view of methodological drawbacks of the trials.     

The effect of the time of methotrexate administration over 24 hours on the antitumor activity of the preparation, its concentration in the blood and in the tumor in Pliss' lymphosarcoma in rats]

A mismatch between a circadian rhythm of blood-methotrexate level and that of the drug concentration in rat transplanted lymphosarcoma tissue was established. The drug proved 3 times more effective when given at the time of the day when its concentration in tumor tissue was likely to be the highest.