Abstract: An apparatus adapted to be implanted in a patient for electrically stimulating the heart and analyzing the heart's stimulated response, and a method of operating the apparatus, are disclosed. The apparatus operates to reduce the stimulation polarization artifact that normally accompanies such stimulation, allowing accurate measurement of stimulated cardiac potentials. The apparatus is useful in such devices as cardiac pacemakers, tachycardia reversion devices, and defibrillators. Optimizing features are provided to allow the apparatus to function properly in noisy environments and with suboptimal leads. In addition, provision is included to make the apparatus capable of performing self-diagnosis for determining when accurate sensing is not possible.

Abstract: Alpha-Olefins are polymerized in the presence of a catalyst which comprises (A) the reaction product of (1) a tetrahydrocarbyloxy zirconium compound such as tetraisopropoxy zirconium or a tetravalent hydrocarbyloxy zirconium halide such as triisopropoxy zirconium halide with (2) a chromium compound such as CrO.sub.3 ; (B) a solid catalyst support; (C) an organometallic activating agent or cocatalyst and (D) a trivalent or tetravelent titanium compound. The resultant polymers have a high molecular weight and a narrow molecular weight distribution.

Abstract: Olefins are polymerized in the presence of chromium-containing catalysts which have been improved by depositing the chromium onto the inorganic oxide support in the vapor phase rather than as an inorganic or organic compound. The resulting polymers exhibit a higher molecular weight as compared to those polymers prepared in the presence of such chromium-containing catalysts prepared in the conventional manner.

Abstract: Dual transition metal compounds containing zirconium and chromium are prepared by reacting a tetrahydrocarbyloxy zirconium compound such as tetraisopropoxy zirconium or a tetravalent hydrocarbyloxy zirconium halide such as triisopropoxy zirconium halide with a chromium compound such as CrO.sub.3. These compounds, as well as combinations of other soluble chromium and zirconium compounds, are useful in the polymerization of .alpha.-olefins to produce polymers having a high molecular weight and a narrow molecular weight distribution.

Abstract: Inorganic oxide supported chromium-containing catalysts are improved by depositing the chromium onto the inorganic oxide support in the vapor phase rather than as an inorganic or organic compound. Polymers resulting from polymerizing one or more .alpha.-olefins in the presence of such catalysts exhibit a higher molecular weight as compared to those polymers prepared in the presence of such chromium-containing catalysts prepared in the conventional manner.

Abstract: Dual transition metal compounds containing titanium and chromium are prepared by reacting a hydrocarbyloxy titanium halide with CrO.sub.3. The compounds are useful in catalysts for the polymerization of .alpha.-olefins.

Abstract: A catalyst mixture containing at least two independently supported catalysts, at least one of which is an inorganic halide supported titanium and/or vanadium Ziegler type catalyst and at least one other is an inorganic oxide supported, chromium catalyst.These catalyst mixtures are suitable for polymerizing one or more .alpha.-olefins.

Abstract: Alpha-olefins are polymerized in the presence of at least two independently supported catalysts, one of which is an inorganic halide supported titanium and/or vanadium Ziegler type catalyst and at least one other is inorganic oxide supported, chromium catalyst. This dual catalyst increases catalyst efficiency and/or provides more flexible control of the properties of the resulting polymers.

Abstract: .alpha.-olefins are polymerized with a catalyst prepared from (1) an inert support, (2) the reaction product of a tetravalent hydrocarbyloxy titanium halide such as di-n-butoxy titanium dichloride and hexavalent chromium oxide and (3) an organometal activating agent such as a tri alkyl aluminum.