The phrase "additionally a subset of" is correct and usable in written English.
It can be used when you want to introduce an extra piece of information that specifies a smaller group within a larger category.
Example: "The research focuses on renewable energy sources; additionally, a subset of these sources includes solar and wind energy."
Alternatives: "also a part of" or "furthermore a division of".
Additionally, a subset of 20 of these taxa that were highly abundant in our dataset was analyzed to examine species-level patterns of fragmentation (Fig. 5b) and DNA damage (Fig. 5d).
Additionally, a subset of samples was analyzed for tryptophan content and the ratio of tryptophan to other large neutral amino acids.
Additionally, a subset of 71 S. Kentucky isolates from chickens were analyzed via this procedure.
Additionally, a subset of 80 samples from the Ngerenya 1998 cohort were independently dialysed and tested in GIAs against 3D7 and W2mef.
Additionally, a subset of these genes were over-expressed in RNA from clinical BPH tissues, and the levels of many were found to correlate with disease status.
Additionally, a subset of these androgen regulated genes were found to be over-expressed in RNA from clinical BPH tissues, and the levels of many were found to correlate with disease severity.
Additionally, analyzing a subset of painting grounds (Fig. 3) further confirms the use of lead white for grounds far into the twentieth century.
Additionally, only a subset of the injected CSC population resulted in metastatic nodules.
Additionally, only a subset of the sample experienced what might be considered clinically meaningful weight loss.
Additionally, in a subset of the study population of RCT2, additional electroencephalographic measurements were performed to assess underlying synaptic function.
Additionally, in a subset of mt2 mutant embryos the morphology of the PHBC clusters was affected, with the ECs forming ectopic sprouts (arrowhead, Fig. 2e).
