منابع مشابه
Simultaneous amino acid substitutions at antigenic sites drive influenza A hemagglutinin evolution.
The HA1 domain of HA, the major antigenic protein of influenza A viruses, contains all of the antigenic sites of HA and is under continual immune-driven selection. To resolve controversies on whether only a few or many residue sites of HA1 have undergone positive selection, whether positive selection at HA1 is continual or punctuated, and whether antigenic change is punctuated, we introduce an ...
متن کاملHigh apparent rate of simultaneous compensatory base-pair substitutions in ribosomal RNA.
We present a model for the evolution of paired bases in RNA sequences. The new model allows for the instantaneous rate of substitution of both members of a base pair in a compensatory substitution (e.g., A-U-->G-C) and expands our previous work by allowing for unpaired bases or noncanonical pairs. We implemented the model with distance and maximum likelihood methods to estimate the rates of sim...
متن کاملDelayed Substitutions
This paper investigates an approach to substitution alternative to the implicit treatment of the λ-calculus and the explicit treatment of explicit substitution calculi. In this approach, substitutions are delayed (but not executed) explicitly. We implement this idea with two calculi, one where substitution is a primitive construction of the calculus, the other where substitutions is represented...
متن کاملGeneric substitutions
Up to equivalence, a substitution in propositional logic is an endomorphism of its free algebra. On the dual space, this results in a continuous function, and whenever the space carries a natural measure one may ask about the stochastic properties of the action. In classical logic there is a strong dichotomy: while over finitely many propositional variables everything is trivial, the study of t...
متن کاملSimple Sentences , Substitutions , and
Many competent speakers initially judge that (i) is true and (ii) is false, though they know that (iii) is true. (i) Superman leaps more tall buildings than Clark Kent. (ii) Superman leaps more tall buildings than Superman. (iii) Superman is identical with Clark Kent. Semantic explanations of these intuitions say that (i) and (ii) really can differ in truthvalue. Pragmatic explanations deny thi...
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ژورنال
عنوان ژورنال: Science
سال: 2009
ISSN: 0036-8075,1095-9203
DOI: 10.1126/science.325_657c