The phrase "are sometimes derived" is correct and usable in written English.
It can be used when discussing the origin or source of something that occurs occasionally or under certain conditions.
Example: "The conclusions of the study are sometimes derived from the data collected during the experiments."
Alternatives: "are occasionally obtained" or "are sometimes obtained from".
Always abstract, to avoid the distortion that occurs when representational images are subjected to the folds of hanging cloth, the designs, often geometric, are sometimes derived from folk art motifs.
(4) Other uses: Improved cookstoves do not usually cater to a few other uses and benefits that are sometimes derived from cookstoves such as lighting, space heating, reduction of insects and pests, and drying of thatched roof [30].
This is due to the fact that the K-type reference strain and the taxonomic type strain or other laboratory strains are sometimes derived from the same initial strain.
Studies of shamanism indicate that individual totemism may have predated group totemism, as a group's protective spirits were sometimes derived from the totems of specific individuals.
These redox cycles of FeII FeIII− were sometimes derived by biogeochemical pathway [1, 11].
Initial codes were sometimes derived from participants' words in vivo and sometimes from the categories that appeared in the existing literature on this topic (Barbour 1997; Shipman et al. 2002; Nord 1999).
Another source of information is seismic anisotropy, which is sometimes derived at high resolution using both approaches above, and also with seismic wave splitting measurements (Long and van der Hilst 2006).
But because I suffered from accent confusion, I just chalked up the talk to a case of giddiness that's sometimes derived from the thrill of speaking about inappropriate topics in public places.
The authors' own experiments seem to suggest that this variability may be sometimes derived from differences in preparation (they show that variation in cell freezing rate can dramatically affect occupancy at stop codons).
However, during evolution, organs and structures often change form and function and are sometimes present as derived or even rudimentary structures.
Knowledge-based models of such engines are sometimes difficult to derive and when they are available, their simulation may be numerically a rather heavy task given the control updating period that may be needed.
