Characteristics of Wave Induced Oscillations in Mesospheric O2 Emission Intensity and Temperature

Gravity wave and tidal signatures in mesospheric emissions can be characterized using a quantity η which relates the wave intensity perturbations to the corresponding induced temperature oscillation. The quasi-monochromatic wave induced oscillations in the O2 (0–1) atmospheric emission observed from Maui, Hawaii (20.8 N, 156.2 W) have been investigated for the periods ranging from 1–12 hours. Our results clearly show that ∣η∣ increases from 0.5 to 10 with the increasing wave periods while the phase Ø exhibits a decreasing trend (+75 to −100°). When compared with model, observed trends agree well while significant differences in the absolute values are noted, possibly due to complex chemical and dynamical processes at mesospheric altitudes

The occurrence altitudes of middle atmospheric temperature inversions and mesopause over low-latitude Indian sector

We study the occurrence characteristics of mesospheric inversion layers (MILs) in the 60–105 km altitude region over the low-latitude Indian sector. We note that lower inversions in the mesospheric temperatures occur in the 70–75 km altitude regions while the upper inversions occur in 90–95 km altitude regions. The mesopause altitude is mostly noted to be ~ 98 km with the night-time mesopause (particularly in the year 2002) showing a small peak in the mesopause occurrence at ~ 75 km altitude. We note higher occurrence rate of MILs during high solar activity year compared to low solar activity year. It is also observed that night time MILs show a systematic seasonal variability, with higher occurrence of single and double temperature inversions during equinoxes

Lyngbyastatins 8–10, Elastase Inhibitors with Cyclic Depsipeptide Scaffolds Isolated from the Marine Cyanobacterium Lyngbya semiplena

Investigation of an extract from the marine cyanobacterium Lyngbya semiplena, collected in Tumon Bay, Guam, led to the identification of three new cyclodepsipeptides, lyngbyastatins 8–10 (1–3). The structures of 1–3 were determined by NMR, MS, ESIMS fragmentation and chemical degradation. Compounds 1–3 are closely related to lyngbyastatins 4–7. Like the latter compounds, we found 1–3 to inhibit porcine pancreatic elastase, with IC50 values of 123 nM, 210 nM and 120 nM, respectively

Response of OH airglow emissions to mesospheric gravity waves and comparisons with full-wave model simulation at a low-latitude Indian station

Quasi-monochromatic gravity-wave-induced oscillations, monitored using the mesospheric OH airglow emission over Kolhapur (16.8° N, 74.2° E), India, during January to April 2010 and January to December 2011, have been characterized using the Krassovsky method. The nocturnal variability reveals prominent wave signatures with periods ranging from 5.2 to 10.8 h as the dominant nocturnal wave with embedded short-period waves having wave periods of 1.5–4.4 h. The results show that the magnitude of the Krassovsky parameter, viz. |η|, ranged from 2.1 to 10.2 h for principal or long nocturnal waves (5.2–10.8 h observed periods), and from 1.5 to 5.4 h for the short waves (1.5–4.4 h observed periods) during the years of 2010 and 2011, respectively. The phase (i.e., Φ) values of the Krassovsky parameters exhibited larger variability and varied from −8.1 to −167°. The deduced mean vertical wavelengths are found to be approximately −60.2 ± 20 and −42.8 ± 35 km for long- and short-period waves for the year 2010. Similarly, for 2011 the mean vertical wavelengths are found to be approximately −77.6 ± 30 and −59.2 ± 30 km for long and short wave periods, respectively, indicating that the observations over Kolhapur were dominated by upward-propagating waves. We use a full-wave model to simulate the response of OH emission to the wave motion and compare the results with observed values