Evolving east Asian river systems reconstructed by trace element and Pb and Nd isotope variations in modern and ancient Red River-Song Hong sediments

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q04039, doi:10.1029/2007GC001867.Rivers in east Asia have been recognized as having unusual geometries, suggestive of drainage reorganization linked to Tibetan Plateau surface uplift. In this study we applied a series of major and trace element proxies, together with bulk Nd and single K-feldspar grain Pb isotope ion probe isotope analyses, to understand the sediment budget of the modern Red River. We also investigate how this may have evolved during the Cenozoic. We show that while most of the modern sediment is generated by physical erosion in the upper reaches in Yunnan there is significant additional flux from the Song Lo, draining Cathaysia and the SW Yangtze Block. Nd isotope data suggest that 40% of the modern delta sediment comes from the Song Lo. Carbonates in the Song Lo basin make this a major control on the Red River Sr budget. Erosion is not a simple function of monsoon precipitation. Active rock uplift is also required to drive strong erosion. Single grain Pb data show a connection in the Eocene between the middle Yangtze and the Red River, and probably with rivers draining the Songpan Garze terrane. However, the isotope data do not support a former connection with the upper Yangtze, Mekong, or Salween rivers. Drainage capture appears to have occurred throughout the Cenozoic, consistent with surface uplift propagating gradually to the southeast. The middle Yangtze was lost from the Red River prior to 24 Ma, while the connection to the Songpan Garze was cut prior to 12 Ma. The Song Lo joined the Red River after 9 Ma. Bulk sample Pb analyses have limited provenance use compared to single grain data, and detailed provenance is only possible with a matrix of different proxies

Thermochronology of mineral grains in the Red and Mekong Rivers, Vietnam: Provenance and exhumation implications for Southeast Asia

Sand samples from the mouths of the Red and Mekong Rivers were analyzed to determine the provenance and exhumation history of their source regions. U-Pb dating of detrital zircon grains shows that the main sources comprise crust formed within the Yangtze Craton and during the Triassic Indosinian Orogeny. Indosinian grains in the Mekong are younger (210-240 Ma) than those in the Red River (230-290 Ma), suggesting preferential erosion of the Qiangtang Block of Tibet into the Mekong. The Red River has a higher proportion of 700-800 Ma grains originally derived from the Yangtze Craton. 40Ar/ 39Ar dating of muscovite grains demonstrates that rocks cooled during the Indosinian Orogeny are dominant in both rivers, although the Mekong also shows a grain population cooling at 150-200 Ma that is not seen in the Red River and which is probably of original Qiangtang Block origin. Conversely, the Red River contains a significant mica population (350-500 Ma) eroded from the Yangtze Craton. High-grade metamorphic rocks exposed in the Cenozoic shear zones of southeast Tibet-Yunnan are minority sources to the rivers. However, apatite and zircon fission track ages show evidence for the dominant sources, especially in the Red River, only being exhumed through the shallowest 5-3 km of the crust since ̃25 Ma. The thermochronology data are consistent with erosion of recycled sediment from the inverted Simao and Chuxiong Basins, from gorges that incise the eastern flank of the plateau. Average Neogene exhumation rates are 104-191 m/Myr in the Red River basin, which is within error of the 178 ± 35 m/Myr estimated from Pleistocene sediment volumes. Sparse fission track data from the Mekong River support the Ar-Ar and U-Pb ages in favoring tectonically driven rock uplift and gorge incision as the dominant control on erosion, with precipitation being an important secondary influence. © 2006 by the American Geophysical Union

The Duverger-Demsetz Perspective on Electoral Competitiveness and Fragmentation: With Application to the Canadian Parliamentary System, 1867–2011

We combine Duverger’s Law (1954) with Demsetz’s (1968) theory of natural monopoly to provide a novel perspective on electoral competitiveness in a single member district, plurality rule system. In the framework we develop, competitiveness depends on the contestability of elections, which declines as party fragmentation exceeds the long run level predicted by Duverger’s Law. We provide support for this Duverger-Demsetz perspective by studying the relationship between the concentration of vote shares and a new index of electoral contestability over the history of the Canadian parliamentary system from 1867. Extension of the argument to proportional electoral systems is also considered

Porphyromonas gingivalis induces RANKL in T-cells

Porphyromonas gingivalis is an oral pathogen highly implicated in chronic periodontitis, a disease characterized by inflammatory destruction of the tooth-supporting alveolar bone and eventually, tooth loss. T-cell innate immune responses are actively involved in this pathological process. Receptor activator of NF-kappaB Ligand (RANKL) is a cytokine that stimulates bone resorption, while its soluble decoy receptor osteoprotegerin (OPG) blocks its action. This study aimed to investigate in Jurkat T-cells the effects of P. gingivalis on the RANKL-OPG system and the major inflammatory mediator of bone resorption prostaglandin E(2) (PGE(2)). P. gingivalis caused concentration-dependent up-regulation of RANKL gene expression and protein production, assessed by quantitative PCR and ELISA, respectively. PGE(2) production was also enhanced. However, OPG was not detected. In conclusion, P. gingivalis induces RANKL and PGE(2) in T-cells, potentially favoring bone resorption. These T-cell responses to P. gingivalis may contribute to the pathogenesis of inflammatory alveolar bone destruction occurring in chronic periodontitis

Targeting Bcl-2 for the treatment of multiple myeloma

International audienceDespite advances in the treatment of multiple myeloma, the disease still remains incurable for the majority of patients. The overexpression of anti-apoptotic proteins (i.e., Bcl-2, Bcl-X L or Mcl-1) is a hallmark of cancer and favors tumor cell survival and resistance to therapy. The oral drug venetoclax is the first-in-class Bcl-2-specific BH3 mimetic. In myeloma, in vitro sensitivity to venetoclax is mainly observed in plasma cells harboring the t(11;14) translocation, a molecular subgroup associated with high Bcl-2 and low Mcl-1/Bcl-XL expression. In addition with Bcl-2 members expression profile, functional tests as BH3 profiling or in vitro BH3 mimetic drug testing also predict sensitivity to the drug. Phase 1 clinical trials recently confirmed the efficacy of venetoclax monotherapy in heavily pretreated myeloma patients, mostly in patients with t(11;14). In combination with the proteasome inhibitor bortezomib, venetoclax therapy was found to be feasible and allowed promising response rate in relapsed myeloma patients, independent of t(11;14) status. The present review summarizes the current knowledge, "from bench to bedside", about venetoclax for the treatment of multiple myeloma