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Using the newly published Yb isotopic abundances and the mass bias relationship between Yb and Hf, we carried out an analysis of Hf isotopes in the standard zircon.

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The Encyclopedia of Scientific Dating Methods has been selected to receive the 2016 GSIS Mary B. Ansari Best Reference Work Award. J.W. Jack Rink and Jeroen W. Thompson are the editors of this reference work published by Springer in 2015.

The Geoscience Information Society has presented the GSIS Mary B. Ansari Best Reference Work Award annually since 1988. The award honors an outstanding reference work published in the field of geoscience information during the previous three years.

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As in simpler alkanes , carbon in the CFCs bonds with tetrahedral symmetry. Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, the methane-derived CFCs deviate from perfect tetrahedral symmetry. [4]

The densities of CFCs are higher than their corresponding alkanes. In general the density of these compounds correlates with the number of chlorides.

CFCs and HCFCs are usually produced by halogen exchange starting from chlorinated methanes and ethanes. Illustrative is the synthesis of chlorodifluoromethane from chloroform :

The National Weather Service Storm Prediction Center expects a slight risk of severe weather on Thursday. The areas of concern are in the Four Corners Region. The primary threats with these storms will be damaging winds and hail. Read More

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Using the newly published Yb isotopic abundances and the mass bias relationship between Yb and Hf, we carried out an analysis of Hf isotopes in the standard zircon.

Hafnium is a chemical element with symbol Hf and atomic number 72. A lustrous , silvery gray, tetravalent transition metal , hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, by Dr Alexander Scott, making it the last stable element to be discovered. Hafnium is named after Hafnia , the Latin name for Copenhagen , where it was discovered. [4] [5]

Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nm and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination with niobium , titanium , or tungsten.

Hafnium's large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plants , but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.