This lent itself well to the contentious debate over assimilatory practices. In any case, it undergoes a variety of assimilatory processes. Sulfate reduction can be dissimilatory or assimilatory. Siroheme is a co-factor of both assimilatory and dissimilatory nitrite and sulfite reductases. There is no word-final or assimilatory devoicing in Ukrainian. She noted assimilatory raising of vowels in vowel sequences. Some assimilatory processes mentioned above also occur across word boundaries. The oxidation of methane (or methanol) can be assimilatory or dissimilatory in nature (see figure). Occasionally, such syllables may dropped entirely, leaving behind an assimilatory trace like the moraic obstruent. In assimilatory sulfate reduction, however, the sulfate is assimilated, or incorporated into organic compounds. Additionally, "H. larsenii" undergoes assimilatory nitrate reduction to nitrite to ammonia. The latter process is called assimilatory sulfate reduction because the sulfate sulfur is assimilated. Most importantly, there is very common external sandhi, and some assimilatory sound changes. Assimilatory nitrate reductase gene sequences are most similar to those described for the cyanobacteria. There is, however, assimilatory "voicing"&colon; voiceless obstruents are voiced when preceding voiced obstruents.