Mantle Layering across Central South America

Imaging of seismic velocity discontinuities along a 3000 km profile across central South America at 20°S suggests that the depth variations of the 410-km (d410) and 660-km (d660) discontinuities are closely associated with the high-velocity Nazca slab and juxtaposed low-velocity oceanic mantle beneath the slab. The mantle transition zone thickness ranges from 220 km in the oceanic mantle to 270 km in a 600-km-wide area occupied by the deflected Nazca slab. The slab deflection has also been suggested by previous studies of seismic tomography and seismicity. This 50 km difference in the thickness corresponds to a lateral temperature variation of about 370°C between the two areas. The depth of d410 shows a gradual eastward decrease of about 10 km along the profile, corresponding to a temperature that is about 75°C cooler to the east. This variation is probably related to changes in the upper mantle geotherms associated with the transition from tectonically active to stable upper mantle. A low-velocity anomaly in the upper mantle and mantle transition zone beneath eastern Brazil, previously detected by seismic tomography and interpreted as a fossil plume, produced no detectable perturbation in transition zone thickness. It is thus unlikely to extend to the transition zone or alternatively is not thermal in origin. Finally, we have observed several possible second-order discontinuities at the depths of 230, 500, 600, 840, and 915 km beneath the western part of the study area

Widespread Hypomethylation Occurs Early and Synergizes with Gene Amplification during Esophageal Carcinogenesis

Although a combination of genomic and epigenetic alterations are implicated in the multistep transformation of normal squamous esophageal epithelium to Barrett esophagus, dysplasia, and adenocarcinoma, the combinatorial effect of these changes is unknown. By integrating genome-wide DNA methylation, copy number, and transcriptomic datasets obtained from endoscopic biopsies of neoplastic progression within the same individual, we are uniquely able to define the molecular events associated progression of Barrett esophagus. We find that the previously reported global hypomethylation phenomenon in cancer has its origins at the earliest stages of epithelial carcinogenesis. Promoter hypomethylation synergizes with gene amplification and leads to significant upregulation of a chr4q21 chemokine cluster and other transcripts during Barrett neoplasia. In contrast, gene-specific hypermethylation is observed at a restricted number of loci and, in combination with hemi-allelic deletions, leads to downregulatation of selected transcripts during multistep progression. We also observe that epigenetic regulation during epithelial carcinogenesis is not restricted to traditionally defined “CpG islands,” but may also occur through a mechanism of differential methylation outside of these regions. Finally, validation of novel upregulated targets (CXCL1 and 3, GATA6, and DMBT1) in a larger independent panel of samples confirms the utility of integrative analysis in cancer biomarker discovery

Small earthquakes in NE Kansas and their possible causes

During the past few years the geophysics group at Kansas State University (KSU) has installed and operated two transportable seismic arrays and a permanent seismic station in Kansas. One of the purposes of the experiments is to detect small earthquakes in the area, and another is to study the velocity and anisotropic structure of the crust and the mantle, aiming at finding a possible explanation for the occurrence of intraplate earthquakes in this area, which has experienced a few MMI 7 earthquakes since 1867. The first transportable experiment was conducted between June, 2000 and February, 2001. Eight broadband seismic stations were deployed along a 450-km-long, EW profile between Palco and Atchison, Kansas. The second transportable experiment took place between April and October, 2001, during which eight short-period stations were deployed along the periphery of an approximate circle with a radius of about 20 km, centered at Manhattan, KS. The permanent station is located on the KSU Konza Prairie Biological Research Station. So far it is the second permanent broadband seismic station in Kansas. While the data sets are still being analyzed, we have identified tens of small earthquakes, most of which have occurred in NE Kansas. In addition, by stacking P-to-S converted seismic waves from the the base of the crust, we have found that the crust beneath the Midcontinent rift (MCR) and the areas within about 120 km on each side of the rift axis is thickened by up to 12 km relative to the adjacent areas. The thickening was likely the result of the lateral compression during the closure of the MCR about 1.1 billion years ago. Based on previous data and our new crustal thickness measurement, we hypothesize that the long-lasting uplift of the Nemaha Ridge is the result of the uplift of the Moho toward isostatic balance. Such an uplift is possibly the ultimate cause of earthquakes in NE Kansas

Small Earthquakes in NE Kansas and their Possible Causes

During the past few years the geophysics group at Kansas State University (KSU) has installed and operated two transportable seismic arrays and a permanent seismic station in Kansas. One of the purposes of the experiments is to detect small earthquakes in the area, and another is to study the velocity and anisotropic structure of the crust and the mantle, aiming at finding a possible explanation for the occurrence of intraplate earthquakes in this area, which has experienced a few MMI 7 earthquakes since 1867. The first transportable experiment was conducted between June, 2000 and February, 2001. Eight broadband seismic stations were deployed along a 450-km-long, EW profile between Palco and Atchison, Kansas. The second transportable experiment took place between April and October, 2001, during which eight short-period stations were deployed along the periphery of an approximate circle with a radius of about 20 km, centered at Manhattan, KS. The permanent station is located on the KSU Konza Prairie Biological Research Station. So far it is the second permanent broadband seismic station in Kansas. While the data sets are still being analyzed, we have identified tens of small earthquakes, most of which have occurred in NE Kansas. In addition, by stacking P-to-S converted seismic waves from the the base of the crust, we have found that the crust beneath the Midcontinent rift (MCR) and the areas within about 120 km on each side of the rift axis is thickened by up to 12 km relative to the adjacent areas. The thickening was likely the result of the lateral compression during the closure of the MCR about 1.1 billion years ago. Based on previous data and our new crustal thickness measurement, we hypothesize that the long-lasting uplift of the Nemaha Ridge is the result of the uplift of the Moho toward isostatic balance. Such an uplift is possibly the ultimate cause of earthquakes in NE Kansas