A new ternary layered carbide, ZrAl 4 C 4 , has been synthesized and characterized by X-ray powder diffraction. The crystal structure was successfully determined using direct methods and further refined by the Rietveld method. The crystal is trigonal (space group P3m1, Z 5 2) with lattice dimensions a 5 0.332471(3) nm, c 5 2.19717(2) nm, and V 5 0.210330(3) nm 3 . The final reliability indices calculated from the Rietveld refinement were R wp 5 6.56% (S 5 1.58), R p 5 4.92%, R B 5 1.90%, and R F 5 0.98%. The compound shows an intergrowth structure with NaCl-type [Zr 2 C 3 ] thin slabs separated by Al 4 C 3 -type [Al 8 C 7 ] layers.Ã All distances shorter than 0.33 nm (metal-metal) and 0.25 nm (metal-carbon) are given.
The isolated rat heart is perfused with adenosine-8-C14, or a mixture of ATP-8-C14 and ATP-r-P32 of known isotope (C14/P32) ratio. The results indicate that any difference between the rate of incorporation of adenosine-C14 or ATP-C14 into myocardial nucleosides and nucleotides fraction did not show significance, and also that any difference of the C14 distribution in the perfusates between adenosine-C14 and ATP-C14 perfused by the isolated rat hearts did not show singnificance. When perfused with C14-and P32-ATP of known isotope ratio, ATP isolated from the myocardium showed an isotope ratio (C14/P32) approximately 5 times greater than that of ATP in perfusion fluid. These results suggest that ATP might be first degraded and later resynthesized intracellularly.
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