toan vo

Closed-basin alkaline lakes record climate change particularly well because they generally contain a sedimentary record that is high in carbonate mineral content from which climate proxies can be determined. Various approaches are used to estimate paleo-lake level and volume (δ18O, dating of “shoreline” tufas, biotic proxies, etc.), yet all carry certain caveats that limit their usefulness. Ultimately, the relationship between the chemistry of the lake, the volume of the lake, and the response of the proxy will determine how well a proxy serves a paleolimnologic purpose. Here, we discuss the use of carbonate-associated sulfate (CAS), the sulfate contained within the lattice of carbonate minerals that precipitate in lake water, as a proxy for lake water chemistry and by extension, lake volume. Walker Lake, an alkaline closed-basin lake in western Nevada, has experienced a well-documented lake-level decline since 1880 and provides a test case for CAS as a lake-level proxy. By extracting the CAS from sedimentary carbonate and tufas that have been age dated, we can relate these values to lake sulfate content based on historical or other proxy data. We confirm that CAS tracks lake sulfate. Our study of sedimentary carbonates demonstrates that CAS is a linear function of lake sulfate through a range of 10–25 mM, which corresponds to a change in lake level of 30 m. As confirmation of the CAS technique, we analyzed a stromatolitic tufa dated using AMS 14C. The CAS trend in the stromatolite suggested that it grew during a lake-level decline, a result consistent with other proxy data. Finally, laboratory experiments were conducted that demonstrate CAS is monotonically correlated with sulfate concentration and that precipitation kinetics are not likely a major control on CAS in alkaline lakes, but that ionic strength of the solution exerts a strong control on CAS.

... Nguyen Thanh Phuong, Vu Nam Son, Vo Thanh Toan, Tran Thi Thanh Hien and Pham Minh Duc ... Classification of land mapping units based on soil and hydrological characteristics of Tan Phu Thanh village, Chau Thanh A ... Hai, TN, TTT Hien, DH Tam, VT Toan and NT Phuong). ...

Some of the spin-on interlayer dielectrics (ILD) with dielectric constant k below 2.3, targeted for the 65 nm node and below, are available with their spin-on hard masks (SoHM) to reduce the total effective capacitance and to provide high selectivity to their respective ILDs during integration. In this work, FF-02, JSR’s SoHM is characterised. Its thermal stability, chemical compatibility to stripping solutions and resistance to moisture are investigated. Methods to seal the surface of FF-02 to chemicals are explored. Electrical properties including the dielectric constant, leakage current and breakdown fields are evaluated in planar capacitors and in single damascene structures.