ABSTRACT
We report the production and characterization of a form of amorphous carbon with s p-s p(2) hybridization (atomic fraction of sp hybridized species > or =20%) where the predominant sp bonding appears to be (=C=C=)(n) cumulene. Vibrational and electronic properties have been studied by in situ Raman spectroscopy and electrical conductivity measurements. Cumulenic chains are substantially stable in high vacuum conditions for temperatures lower than 250 K and they influence the electrical transport properties of the s p-s p(2) carbon through a self-doping mechanism by pinning the Fermi level closer to one of the mobility gap edges. Upon heating above 250 K the cumulenic species decay to form graphitic nanodomains embedded in the s p(2) amorphous matrix thus reducing the activation energy of the material. This is the first example of a pure carbon system where the s p hybridization influences bulk properties.
Subject(s)
Anemia, Hypochromic , Anemia, Pernicious , Thalassemia , Anemia, Hypochromic/history , Anemia, Hypochromic/therapy , Anemia, Pernicious/history , Anemia, Pernicious/therapy , Blood Substitutes/therapeutic use , Ferric Compounds/therapeutic use , History, 20th Century , Humans , Thalassemia/genetics , Thalassemia/history , Thalassemia/therapy , Vitamin B 12/therapeutic useSubject(s)
Erythrocytes/physiology , Hemolysis , Publishing/history , History, 18th Century , Humans , Italy , Microscopy/historyABSTRACT
On the basis of clonal development of leukemias, the beginning of the true preleukemias should antedate the overt leukemia by at least 37 doubling times (e.g., at least 4 years in the chronic granulocytic leukemia).