function y = trovuTemperaturoj(u)

  numberOfElements = 1000;
  bigDiameter = 0.44;

  Delta_r = -bigDiameter*0.5/numberOfElements;
  r = linspace(bigDiameter*0.5,0.00000001,numberOfElements);


  numOfEl=numberOfElements;
  y(2+numOfEl:2*numOfEl-1) = \
      (  (1./r(2:numberOfElements-1)) .* \
       ((u(2+numOfEl-1:numOfEl-1+numOfEl-1) - \
	 u(2+numOfEl:numOfEl-1+numOfEl))./(Delta_r)));

endfunction