POWER OF ATTORNEY


     The undersigned Susan A. Keller hereby designates, constitutes and appoints
each of William B. Danzell,  Nigel P. Hebborn and Benjamin M. Alexander  singly,
my true and lawful  attorney and  authorizes  each of them singly to sign for me
and in my name any Initial  Statement of  Beneficial  Ownership of Securities on
Form 3,  Statement  of  Changes  in  Beneficial  Ownership  on Form 4, or Annual
Statement of Changes in Beneficial Ownership on Form 5, such power and authority
to remain in force until December 31, 2006.


     IN  WITNESS  WHEREOF,  the  undersigned  has duly  executed  this  Power of
Attorney as a sealed instrument this 17th day of December 2003.



                                                     /s/ Susan A. Keller
                                                     -------------------------
                                                     Susan A. Keller