"further narrowed down" is correct and usable in written English.
You can use it to indicate that a selection or focus has been made even more focused or specific. For example, "The list of possible solutions was further narrowed down to two options."
Those 125 were further narrowed down to 26 finalists prior to the announcement of the final cash prize-winners.
The GO annotation analysis further narrowed down the list to three TFs: SIX1, SIX2, and FOXC1 (Fig. 1f, Supplementary Fig. S1d).
We further narrowed down our roster of potential candidates by selecting only those companies that trade for less than 20 times 2004 estimated earnings.
The ASL3 locus was further narrowed down to a 32-kb region between P3 and P4 (Figure 3B), which included 3 putative open reading frames (ORFs) (http://rice.plantbiology.msu.edu) (Figure 3C).
While we were conducting the fine mapping, Ngangkham et al. ([2010]) reported that Rf4 was located in a region between RM6737 and RM6100 with a distance of 104 kb in the Nipponbare genome, which further narrowed down the candidate region.
After identifying the lncRNA locus, Zhou et al. ([2012]) further narrowed down its functional form to a small, 21-nt RNA, designated as osa-smR5864w osa-smR5864m864m for the wild-type and mutant allele, respectively.
Search for companies based on your major (or intended major) and further narrow down your search by geographic location.
During the surgery, the team did extensive testing on the exposed brain tissue to further narrow down the location.
To further narrow down the TF list, we used previously published transcriptome data of various organs ref. 21 and examined the expression of the 17 TFs (Fig. 1e).
Once Home Depot assesses the damage in each location — from power failures to flooding to roof damage — it can further narrow down what supplies to send where.
To further narrow down to the interacting domains, we created smaller GST-tagged TRIM24 truncation mutants of the N-terminal region and second-round of GST pull-down pinpointed the B1B2 domain (aa100 260) as essential for TRIM28 interaction (Fig. 2e).
