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A family of chromium complexes bearing tridentate pyridine-based ligands are disclosed as highly active precatalysts for the oligomerization of ethylene. The ligands are comprised of two distinct types: Type 1, in which both ketone groups of 2,6-diacetylpyridine are converted to imines to produce pyridine bisimine NNN ligands; and Type 2, in which only one ketone group of 2,6-diacetylpyridine is condensed with an aniline derivative to give monoimine NNO coordination sets. Ligands of either type are coordinated to chromium(II) or chromium(III) chlorides, and activation of the resultant complexes with methylaluminoxane (MAO) produces highly active ethylene oligomerization and polymerization catalysts. Catalysts of Type 1 (NNN set) generally produce 1-butene when only two ortho alkyl substituents are present but switch to making waxes or polyethylene when the size and/or number of ortho substituents are increased. Catalysts of Type 2 (NNO set) produce waxes and polyethylene under all of the substitution pat...

Cytokines are polypeptides that are produced by various cell types and act in an autocrine or paracrine manner. They have many different biological actions and have been used in dermatology to treat a wide range of dermatologic diseases. In this paper we review some of the more commonly used cytokines in dermatology, including interferon-alpha and -gamma, interleukins-2 and -10, and granulocyte-macrophage colony-stimulating factor. We specifically examine their roles in the treatment of condyloma and verruca, hemangiomas, keloids, skin cancers, atopic dermatitis, psoriasis, Behcet disease, chronic granulomatous disease, wound healing, and cutaneous T cell lymphoma. In addition, some of the adverse effects associated with these cytokines are discussed.