As previously mentioned [22, 23], a dense layer of Na secondary phase was formed onto the surface of barium-containing titanate catalysts in the Na-doped system.
This may be attributed to the formation of a dense layer of Na secondary phase on the oxides that plugged the pores.
This may be attributed to the formation of a dense layer of Na secondary phase on the oxides and plugged the pores.
Since the discovery of Na layer in the late 1930s, several investigators have studied the origin and variation of this layer and the Na airglow originated therein (Blamont and Donahue 1961; Gibson and Sandford 1972; Kirchhoff and Clemesha 1983; Zahn et al. 1988; Clemesha et al. 1995; She et al. 2000; Fan et al. 2007; Kumar 2007; Sarkhel et al. 2009).
To further assess tight junction (TJ) integrity of endothelial cell layers, paracellular permeabilities of Na-F (MW 376.27) and LY (MW 550.39) were measured.
Later on, Dou et al. (2013) analyzed Na lidar data from four sites (40° N, 31° N, 30° N, 19° N) representing mid- and low latitudes in China and found that the occurrence rate of Na sporadic layers were similar at locations less than 31° N but about 3 time smaller at 40° N. Nas layers are common at low and high latitudes (Batista et al., 1989; Kwon et al., 1988; Hansen and von Zahn, 1990).
They demonstrated that the layer structure for the case of Na and Fe is mainly determined by chemistry, while the correlation between the two species is governed by gravity wave-induced density fluctuations.
A more comprehensive comparison of Na and Fe layers at mid-latitudes showed sporadic activity to be very prominent for Fe but not so for Na (Kane and Gardner, 1993).
The evidence comes from similarity between the lower boundary of Na and Fe layers as observed in the data presented in this study (Figs. 1 and 4), which is consistent with earlier observations (Yi et al., 2008; Yue et al. 2013).
We then computed average profiles for Nas layers of differing strengths, with strength defined as the concentration at the peak divided by the mean of the concentrations at the upper and lower boundaries.
