Comparative Study of the Structure, Composition, and Electrocatalytic Performance of Hydrogen Evolution in MoSx~2+δ/Mo and MoSx~3+δ Films Obtained by Pulsed Laser Deposition.

Systematic and in-depth studies of the structure, composition, and efficiency of hydrogen evolution reactions (HERs) on MoSx films, obtained by means of on- and off-axis pulsed laser deposition (PLD) from a MoS2 target, have been performed. The use of on-axis PLD (a standard configuration of PLD) in a buffer of Ar gas, with an optimal pressure, has allowed for the formation of porous hybrid films that consist of Mo particles which support a thin MoSx~2+δ (δ of ~0.7) film. The HER performance of MoSx~2+δ/Mo films increases with increased loading and reaches the highest value at a loading of ~240 µg/cm2. For off-axis PLD, the substrate was located along the axis of expansion of the laser plume and the film was formed via the deposition of the atomic component of the plume, which was scattered on Ar molecules. This made it possible to obtain homogeneous MoSx~3+δ (δ~0.8-1.1) films. The HER performances of these films reached saturation at a loading value of ~163 µg/cm2. The MoSx~3+δ films possessed higher catalytic activities in terms of the turnover frequency of their HERs. However, to achieve the current density of 10 mA/cm2, the lowest over voltages were -162 mV and -150 mV for the films obtained by off- and on-axis PLD, respectively. Measurements of electrochemical characteristics indicated that the differences in the achievable HER performances of these films could be caused by their unique morphological properties.

[MORPHOLOGICAL CHARACTERIZATION OF OXYS AND WISTAR RAT HIPPOCAMPUS IN THE AGING PROCESS].

Using light and electron microscopy, the structural changes in the hippocampus of senescence-accelerated OXYS rats (n = 20) and Wistar (n = 20) were examined in the age aspect. By light microscopy, the neurons with the signs of chromatolysis and hyperchromatic neurons were detected in CA1, CA3 fields and the dentate gyrus of the hippocampus, suggesting the presence of the signs of degeneration already in 4 month-old OXYS rats. By the age of 18 months, severe structural changes occured in all the regions of the hippocampus of OXYS rats. Ultramicroscopically, in 4 month-old OXYS rats the. initial manifestation of destruction of mitochondria and accumulation of lipofuscin granules were found. These changes were shown to progress with age; 18-month-old animals were characterized by more significant degradation of organelles. These findings indicate more pronounced age-related changes of neurons in OXYS rats as compared to those in in Wistar rats.