The detailed amino acid analysis of several strains of tobacco mosaic virus carried out by Knight (1) has revealed interesting chemical similarities and differences among these strains, although they are morphologically very similar (2). In the present work the isoelectric points of the strains which Knight has analyzed were determined by a method developed by the author (3). The virus strains ...

The detailed amino acid analysis of several strains of tobacco mosaic virus carried out by Knight (1) has revealed interesting chemical similarities and differences among these strains, although they are morphologically very similar (2). In the present work the isoelectric points of the strains which Knight has analyzed were determined by a method developed by the author (3). The virus strains ...

In this paper, we continue the study of domino-tilings of Aztec diamonds (introduced in [1] and [2]). In particular, we look at certain ways of placing “barriers” in the Aztec diamond, with the constraint that no domino may cross a barrier. Remarkably, the number of constrained tilings is independent of the placement of the barriers. We do not know of a simple combinatorial explanation of this ...

We study the concept of jointness for guessing principles, such as ♦κ and various Laver diamonds. A family of guessing sequences is joint if the elements of any given sequence of targets may be simultaneously guessed by the members of the family. We show that, while equivalent in the case of ♦κ, joint Laver diamonds are nontrivial new objects. We give equiconsistency results for most of the lar...