1] The M w 7.9 Wenchuan earthquake of 12 May 2008 was the most destructive Chinese earthquake since the 1976 Tangshan event. Tens of thousands of people were killed, hundreds of thousands were injured, and millions were left homeless. Here we infer the detailed rupture process of the Wenchuan earthquake by back-projecting teleseismic P energy from several arrays of seismometers. This technique has only recently become feasible and is potentially faster than traditional finite-fault inversion of teleseismic body waves; therefore, it may reduce the notification time to emergency response agencies. Using the IRIS DMC, we collected 255 vertical component broadband P waves at 30-95°from the epicenter. We found that at periods of 5 s and greater, nearly all of these P waves were coherent enough to be used in a global array. We applied a simple down-sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function (ARF). We also considered three regional subarrays of seismometers in Alaska, Australia, and Europe that had apertures less than 30°and P waves that were coherent to periods as short as 1 s. Individual ARFs for these subarrays were skewed toward the subarrays; however, the linear sum of the regional subarray beams at 1 s produced a symmetric ARF, similar to that of the groomed global subarray at 5 s. For both configurations we obtained the same rupture direction, rupture length, and rupture time. We found that the Wenchuan earthquake had three distinct pulses of high beam power at 0, 23, and 57 s after the origin time, with the pulse at 23 s being highest, and that it ruptured unilaterally to the northeast for about 300 km and 110 s, with an average speed of 2.8 km/s. It is possible that similar results can be determined for future large dip-slip earthquakes within 20-30 min of the origin time using relatively sparse global networks of seismometers such as those the USGS uses to locate earthquakes in near-real time.

Leaf senescence is an important biological process that contributes to grain yield in crops. To study the molecular mechanisms underlying natural leaf senescence, we harvested three different developmental ear leaves of maize, mature leaves (ML), early senescent leaves (ESL), and later senescent leaves (LSL), and analyzed transcriptional changes using RNA-sequencing. Three sets of data, ESL vs. ML, LSL vs. ML, and LSL vs. ESL, were compared, respectively. In total, 4,552 genes were identified as differentially expressed. Functional classification placed these genes into 18 categories including protein metabolism, transporters, and signal transduction. At the early stage of leaf senescence, genes involved in aromatic amino acids (AAAs) biosynthetic process and transport, cellular polysaccharide biosynthetic process, and the cell wall macromolecule catabolic process, were up-regulated. Whereas, genes involved in amino acid metabolism, transport, apoptosis, and response to stimulus were up-regulated at the late stage of leaf senescence. Further analyses reveals that the transport-related genes at the early stage of leaf senescence potentially take part in enzyme and amino acid transport and the genes upregulated at the late stage are involved in sugar transport, indicating nutrient recycling mainly takes place at the late stage of leaf senescence. Comparison between the data of natural leaf senescence in this study and previously reported data for Arabidopsis implies that the mechanisms of leaf senescence in maize are basically similar to those in Arabidopsis. A comparison of natural and induced leaf senescence in maize was performed. Athough many basic biological processes involved in senescence occur in both types of leaf senescence, 78.07% of differentially expressed genes in natural leaf senescence were not identifiable in induced leaf senescence, suggesting that differences in gene regulatory network may exist between these two leaf senescence programs. Thus, this study provides important information for understanding the mechanism of leaf senescence in maize.

Three new diarylheptanoids and one new monoterpenoid were isolated from the rhizomes of Zingiber officinale together with four known diarylheptanoids, 5-8. Their structures were elucidated mainly by spectroscopic methods, and they were deduced as 5-[4-hydroxy-6-(4-hydroxyphenethyl)tetrahydro-2 H-pyran-2-yl]-3-methoxybenzene-1,2-diol (1), sodium (E)-7-hydroxy-1,7-bis(4-hydroxyphenyl)hept-5-ene-3 S-sulfonate (2), sodium (E)-7-hydroxy-1,7-bis(4-hydroxyphenyl)hept-5-ene-3 R-sulfonate (3), and hydroxycineole-10-O-beta-D-glucopyranoside (4), respectively. Among the isolated compounds, compounds 1, 5, and 8 exhibited strong superoxide anion radical scavenging activities in a phenazine methosulfate-NADH system. In a more biological system, these compounds were demonstrated to exhibit potent protection against lipid peroxidation in mouse liver microsomes exposed to oxidative conditions. These compounds were subsequently tested on primary cultures of rat hepatocytes exposed to oxidative damage, and definitive cytoprotective actions were found.

We identify and document microseisms produced by wave action in six lakes: The Great Slave Lake, Lake Ontario, Yellowstone Lake, Dianchi Lake, Fuxian Lake, and Erhai Lake. The lakes span more than 2 orders of magnitude in size (areas of 210–27,000 km2) and sample a range of climatic and tectonic regimes in Canada, the U.S., and China. Lake‐generated microseisms create spectral peaks at periods near 1 s and are often polarized as Rayleigh waves propagating away from the lake. In contrast to ocean‐generated microseisms, lake‐generated microseisms are only observed within about 25–30 km of the shoreline. This is consistent with the well‐known high attenuation of short‐period Rayleigh waves (Rg). It is unclear if lake‐generated microseisms are produced by a linear shoaling process, analogous to primary ocean microseisms, or a nonlinear wave‐wave interaction process, analogous to secondary ocean microseisms. If they are mainly produced by shoaling, lake‐generated microseisms might provide a spatially integrated measure of shoreline erosion. Regardless of the source mechanism, lake‐generated microseisms appear to provide a record of ice phenology for lakes that freeze in the winter. Such data could contribute to assessing the effects of climate change on high‐latitude lakes in remote areas. Finally, it is likely that lake‐generated microseisms are useful for imaging the geological structure of the shallow crust, information that is important for quantifying seismic hazard and can be difficult to obtain in urban areas where active source imaging is not feasible.

No abstract