Operator substitution

Insertion Operator for Bayesian Tree Substitution Grammars

We propose a model that incorporates an insertion operator in Bayesian tree substitution grammars (BTSG). Tree insertion is helpful for modeling syntax patterns accurately with fewer grammar rules than BTSG. The experimental parsing results show that our model outperforms a standard PCFG and BTSG for a small dataset. For a large dataset, our model obtains comparable results to BTSG, making the ...

Lac operator analogues: bromodeoxyuridine substitution in the lac operator affects the rate of dissociation of the lac repressor.

As measured by a decreased rate of dissociation, lac repressor binds 10-times tighter to 5-bromodeoxyuridine-substituted lac operator than it does to normal lac operator. This result is obtained both in the absence and in the presence of isopropylthiogalactoside, an inducing ligand. These data are significant with regard to the mechanism of sequence-specific protein-DNA interaction, and also su...

Operator Theory and Operator Algebras

Operator programs and operator processes

We define a notion of program which is not a computer program but an operator program: a detailed description of actions performed and decisions taken by a human operator (computer user) performing a task to achieve a goal in a simple setting consisting of that user, one or more computers and a work environment. Our definition and notations are based on the program algebra PGA: a small body of ...

Systematic Underestimation of Tree Branch Lengths by Lake’s Operator Metrics: An Effect of Position-dependent Substitution Rates

Lake has proposed a method, which he calls “operator metrics,” for estimating branch lengths (as transversion differences) on an unrooted phylogenetic tree of nucleotide sequences. Examination of published applications of operator metrics reveals that it often assigns branch lengths that sum to less than the observed sequence differences, indicating a substantial systematic bias. The problem oc...