This is a patent interference case. Ronald Hitzeman, Arthur Levinson, and Daniel Yansura (collectively, “the Hitzeman inventors” or “Hitzeman”) are the junior parties in the two interferences at issue. William Rutter, Pablo Valenzuela, Benjamin Hall, and Gustav Ammerer (collectively, “the Rutter inventors” or “Rutter”) are the senior parties. On July 30, 1990, the United States Patent and Trademark Office (“PTO”) declared Interference No. 102,416 (“the ’416 interference”) between U.S. Application Serial No. 07/209,504 by Rutter, entitled to a filing date of August 4, 1981 (“the ’504 Rutter application”), and U.S. Patent No. 4,803,164 to Hitzeman, entitled to a filing date of August 31, 1981 (“the ’164 Hitzeman patent”). On October 22, 1992, the PTO declared Interference No. 102,989 (“the ’989 interference”) between U.S. Patent No. 4,769,238 to Rutter, entitled to a filing date of August 4, 1981 (“the ’238 Rutter patent”), and U.S. Application Serial No. 07/248,863 by Hitzeman, entitled to a filing date of August 31, 1981 (“the ’863 Hitzeman application”). On June 30, 1999, the Board of Patent Appeals and Interferences (“Board”) issued separate Final Decisions in each of the interferences, awarding priority in both interferences to Rutter. On August 27, 1999, Hitzeman filed a timely notice of appeal to this court. We have jurisdiction pursuant to 35 U.S.C. � 141 (West Supp. 2000). We heard oral arguments in this case on January 9, 2001. The issues raised on appeal are nearly identical in the two interferences, and so we address both interferences in this opinion, with distinctions noted between the two interferences where appropriate. Because we conclude that the Board properly determined that the particle size and sedimentation rate limitations recited in both counts are material limitations, and because substantial evidence supports the Board’s conclusion that Hitzeman had not conceived of the particle size and sedimentation rate limitations prior to Rutter’s reduction to practice of the invention, and because the legal standards applied by the Board were correct, we affirm.
I. Factual and Procedural Background
A. Overview of the Technology
