Rapid oxygen exchange between hematite and water vapor

Oxygen exchange at oxide/liquid and oxide/gas interfaces is important in technology and environmental studies, as it is closely linked to both catalytic activity and material degradation. The atomic-scale details are mostly unknown, however, and are often ascribed to poorly defined defects in the crystal lattice. Here we show that even thermodynamically stable, well-ordered surfaces can be surprisingly reactive. Specifically, we show that all the 3-fold coordinated lattice oxygen atoms on a defect-free single-crystalline “r-cut” ($$1\bar{1}02$$ 1 1 ¯ 02 ) surface of hematite (α-Fe2O3) are exchanged with oxygen from surrounding water vapor within minutes at temperatures below 70 °C, while the atomic-scale surface structure is unperturbed by the process. A similar behavior is observed after liquid-water exposure, but the experimental data clearly show most of the exchange happens during desorption of the final monolayer, not during immersion. Density functional theory computations show that the exchange can happen during on-surface diffusion, where the cost of the lattice oxygen extraction is compensated by the stability of an HO-HOH-OH complex. Such insights into lattice oxygen stability are highly relevant for many research fields ranging from catalysis and hydrogen production to geochemistry and paleoclimatology.

Analysis of microcirculatory disorders in men with more than 10 years’ experience on night work

Aim. To study the nature and extent of the effects of long-term sleep and wake phase disorders (working at night for more than 10 years) on the characteristics of microcirculation in men. Methods. Laser Doppler flowmetry and spectophotometry, optical tissue oximetry, and laser-induced fluorescence spectroscopy were performed in 34 male patients with a mean age of 40.30.9 years and more than 10 years experience of night work to assess the effectiveness of microcirculation. 25 men with a mean age of 40.21.2 without night work experience were used as a control group. Microcirculation was studied on the laser diagnostic complex LAKK-M (LAZMA, Russian Federation). The measurement was carried out on the skin of the palmar surface of the terminal phalanx of the second finger of the hand. The following indicators were analyzed in automatic mode: the mean perfusion value, the index of specific oxygen consumption in the tissue, capillary blood saturation, the relative volume of the red blood cell fraction, arterial blood oxygen saturation, the index of perfusion oxygen saturation in the microcirculation, the efficiency of oxygen exchange and the fluorescent indicator of oxygen consumption. Statistical processing of the results was carried out using the Student's t-test for independent samples. Results. In patients working at night for more than 10 years, a decrease in microcirculation efficiency was revealed. The index of specific oxygen consumption in the tissue was lower than that of healthy volunteers by 34.1% (p=0.000255), and the index of oxygen exchange efficiency by 56.3% (p 0.001). Long-term night work (10 years) can lead to violations of microcirculation parameters and an irreversible decrease in the efficiency of oxygen exchange compared with the control group by an average of 56.3% (18.00.5 for the group with night work experience, 41.20.6 for the group of healthy volunteers, p 0.001), the index of specific oxygen consumption in the tissue by an average of 34.1% (1.530.03 for the group with night work experience, 2.320.2 for the group of healthy volunteers, p=0.000255) and an increase in the index of perfusion oxygen saturation in the microcirculation by 2 times compared with the control group (6.20.05 for the group with night work experience, 3.670.09 for the group of healthy volunteers, p 0.001), which is accompanied by an increase in the saturation of mixed (and venous) blood. Conclusion. The nature of the revealed violations of microcirculatory parameters in the long-term night work suggests their significance in the development of diseases that are currently attributable to the so-called group of diseases of civilization.