text: To estimate the effect of adsorbates on the electrical con- 
  ductance of doped CNTs, we ﬁrst consider the change in con- 
  ductance when a single molecule is adsorbed on a metal site of 
  an otherwise pristine CNT. In Fig. 2(b) we show the calculated 
  change in conductance relative to the metal site with no ad- 
  sorbate. In contrast to the binding energies, there are no clear 
  trends in the conductances. The sensitivity of the conductance 
  is perhaps most clearly demonstrated by the absence of cor- 
  relation between different types of vacancies, i.e. between the 
  three panels in Fig. 2(b). Close to the Fermi level, the conduc- 
  tance of a perfect armchair CNT equals 2G0. The presence 
  of the metal dopant leads to several dips in the transmission 
  function known as Fano antiresonances [20]. The position 
  and shape of these dips depend on the d-levels of the transi- 
  tion metal atom, the character of its bonding to the CNT, and 
  is further affected by the presence of the adsorbate molecule. 
  The coupling of all these factors is very complex and makes 
  it difﬁcult to estimate or rationalize the value of the conduc- 
  tance. For the spin polarized cases, we use the spin-averaged 