The phrase "already been ascertained" is correct and usable in written English.
It can be used when indicating that something has been determined or established prior to the current moment.
Example: "The results of the experiment have already been ascertained, confirming our initial hypothesis."
Alternatives: "already been determined" or "already been established".
Additionally, a past study examining ENGAGE8 indicated that the behaviourally rated treatment gains over 12 months occurred above any beyond the natural reductions found in their comparison no treatment group, and as such this has already been ascertained with regard to treatment effects over time.
The most obvious experimental precedent in photogeochemistry is a natural photoreaction that has already been ascertained.
Antibody specificity had already been ascertained in a previous study [ 22].
Sunflower genome composition has already been ascertained using other methods, i.e. biochemical analyses [ 40], sequencing and analysis of a small insert library [ 20], whole genome 454 sequencing [ 21].
The validity of such positive effects of cross-linking has already been ascertained by hip joint simulator study under nonabrasive/abrasive conditions demonstrating a significant reduction in volumetric wear for XLPE liner compared to non-cross-linked liner [ 44] despite having high anisotropy on its surface (cf. Figure 5(c)).
Although the positive correlation between SES and health has already been well established, no consensus on how this correlation may change with age has been ascertained.
In general, two big problems with Ecstasy have been ascertained.
Although many drugs are already being screened, their efficacy cannot be ascertained to the fullest extent due to a shortage of histone lysine methylation detection and evaluation methods.
As in live scientific controversies, courts observe science in the making, because the facts needed to resolve legal disputes, and even the methods by which such facts might be ascertained, are seldom already out there in the existing scientific literature (Jasanoff 1995).
According to reports whose accuracy cannot be ascertained, the Turkish government is already engaged in discussions concerning the day after in Syria.
A limitation of the current analysis is the possibility of reverse causation; since vitamin D levels were assessed at baseline when participants were already HIV-infected, the temporal relationship between HIV and vitamin D status could not be ascertained.
