Then the oligonucleotide sequences can be annealed and ligated into the digested and purified vector. The wire itself is most often fully annealed, electrolytically refined copper. Tempered and heat strengthened glass can be three to seven times stronger than annealed glass. Gene specific primers are then annealed to the single stranded DNA. Most atomized powders are annealed, which helps reduce the oxide and carbon content. Grinding tantalum is difficult, especially so for annealed tantalum. To achieve a fully ferritic matrix the alloy must be annealed. Steel weldments are occasionally annealed in a low-temperature oven to relieve residual stresses. Gilding metal may be annealed by heating to between . They are then annealed again to remove any strain hardening. Triton's surface is covered with a transparent layer of annealed frozen nitrogen. Initially, the wire is fully annealed. The obtained glass is usually annealed to prevent breakage during processing. In the alloy name the appended 'A' indicates the alloy has been annealed. Typical tempers are soft annealed and rolled hard.