1. 
   R factor
   R plasmid.
   Found op http://www.mercksource.com/pp/us/cns/cns_hl_dorlands.jspzQzpgzEzzSzppdocszS
   
   
2. 
   R factor
   (from the article `plasmid`) ...of plasmids, colicinogenic (or Col ) factors, determines the production of proteins called colicins, which have antibiotic activity and can kill ...
   Found op http://www.britannica.com/eb/a-z/r/1
   
   
3. 
   R-factor
   R-factor is an old name for a plasmid that codes for antibiotic resistance. Often, R-factors code for more than one antibiotic resistance factor: genes that encode resistance to unrelated antibiotics may be carried on a single R-factor, sometimes up to 8 different resistances. Many R-factors can pa...
   Found op http://en.wikipedia.org/wiki/R-factor
   
   
4. 
   R-Factor
   See R-Value.
   Found op http://www.electromn.com/glossary/r.htm
   
   
5. 
   r.m.s.-ripple factor
   the ratio of the r.m.s. value of the ripple content to the absolute value of the direct component of a pulsating quantity
   Found op http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=161-02-27
   
   

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