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Time variations of lightning activity in the three main tropical thunderstorm centers located in the Maritime Continent (Pakistan, India, Southeast Asia, Indonesia, and Australia), Africa, and the Americas are analyzed using a lightning activity index IRS, which is calculated from the resonances of magnetic field in the extremely low frequency range—the Schumann resonances—which were observed at Hylaty station (Poland) in the time interval July 2005–May 2006. Power spectrum analysis of the IRS series is carried out for this time interval. The annual and semiannual variations are shown in all of the series together with the following characteristic periodicities: 45 (Madden–Julian oscillation), 17.6, 13.5, and 4.8 days, seen mainly in the series describing the lightning activity of the Maritime Continent. In addition, maps of the dynamical power spectrum are constructed. They present variability both in the values of characteristic periods 26–30, 17–22, 12–14, 9–10, and 5–7 days and in their duration. During the studied time interval, according to these indices, the African center was the most active, whereas the American and Maritime Continent centers showed a similar level of activity. The largest differences among the centers were observed in the summer months in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

The occurrence of similar glass beads at archaeological sites in Africa and Asia bears witness to the trade relationship between the two continents. This paper reports elemental analysis results from a recent in-depth laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) study of a group of archaeological glass beads with a specific alumina-rich composition from East Africa, India and Sri Lanka. Based on the concentrations of the trace elements, two different subgroups were identified. One subgroup occurs at early periods (fourth centurybce to fifth centuryace) in South India and Sri Lanka. The second subgroup appears at later dates in Africa and was identified at different Kenyan sites dated from the ninth to the 19th centuryace, and at the contemporaneous site of Chaul in western India. [ABSTRACT FROM AUTHOR]