Cash and short-term investments were $141.5 million at December 31, 2012, which compares to $105.8 million at September 30, 2012. Cash flow from operating activities for the fourth quarter of 2012 was $73.2 million, led by higher net income and working capital improvements during the quarter.
E&C segment sales increased 70% to $94.8 million for the fourth quarter of 2012 compared with $55.6 million for the same quarter in the prior year. Revenue from large projects in backlog continues to accelerate. E&C orders for the fourth quarter of 2012 were $62.2 million, up 10% from the $56.4 million reported in the third quarter of 2012. E&C gross profit margins were 31.0% in the 2012 quarter compared with 24.8% in the same quarter of 2011. Higher volume, improved project mix and pricing, particularly in our brazed aluminum heat exchanger business, led to the margin improvement. In addition, several emergency short lead time opportunities during the fourth quarter of 2012 contributed 1.5% to E&C gross margin.
D&S segment sales improved 22% to $139.3 million for the fourth quarter of 2012 compared with $114.4 million for the same quarter in the prior year. Additional LNG equipment shipments in 2012, especially in Asia, led the improvement. D&S gross profit margin improved to 29.5% in the quarter compared with 26.6% a year ago. Improved volume, pricing, and lower material costs offset changes in geographic sales mix.
BioMedical segment sales improved 41% to $69.8 million for the fourth quarter of 2012 compared with $49.7 million for the same quarter in the prior year. This increase is due to the AirSep acquisition, which closed in August. The acquired revenues offset overall lower sales of respiratory therapy equipment due to continued weakness in Europe and the impact of Medicare physician audits and the competitive bidding process in the U.S. BioMedical gross profit margin decreased to 21.5% in the quarter compared with 39.9% for the same period in 2011. The decrease is primarily due to lower volume, additional restructuring costs, and changes in product mix, with lower margin oxygen concentrators representing a much larger share of the mix following the AirSep acquisition.