The phrase "ascertained when a" is correct and usable in written English.
It can be used when discussing the determination of a specific time or condition related to an event or situation.
Example: "The results of the experiment were ascertained when a significant change in temperature was observed."
Alternatives: "determined when a" or "established when a".
The duration of breast feeding in months between 0 and 7 was ascertained when an infant was at 6 or 7 months of age; therefore, the chance of recall bias seems unlikely.
However, anticipatory situation detection has to predict the future deployment of the situational variables in order to ascertain when a situation starts.
Care homes are one big target market for SiempreSecos, with the system providing professional caregivers with a more discreet way of ascertaining when a dementia patient, for instance, who is also incontinent needs their adult diaper changing.
It's now seeking to build the best system of micro-assessments anywhere that can be delivered on demand, such that it will be able to ascertain when a student has truly mastered a concept.
Brenner and Hakulinen (2009) performed a study based on failure to ascertain when a registered case has died comparing overall and relative survival for a range of scenarios.
Of equal importance is ascertaining when a treatment induces metabolic changes that are recordable with PET that do not translate into an anti-tumoural action such as inhibition of growth.
Since variation is often part of the routine process of perfecting surgical techniques, it becomes difficult to ascertain when a surgical innovation becomes an experiment that requires research ethics approval.
An extraordinary shift of the antiferrodistortive transition temperature (Ta) is ascertained when just a small percentage of any of the dopants is used.
According to Article 580, referenced in the charges, a crime is only ascertained when intent to commit the crime has been established.
