The phrase "activity was defined by" is correct and usable in written English.
It can be used when explaining the parameters or characteristics that determine or describe a specific activity.
Example: "The success of the project was largely due to how the activity was defined by clear objectives and measurable outcomes."
Alternatives: "activity was characterized by" or "activity was determined by".
According to these thresholds, 'epidemic influenza activity' was defined by rates at or above 35 cases per 1000 consultations.[12] We restricted our analysis to patients who presented for medical attention at any of the sentinel surveillance sites and who subsequently had a swab taken for the identification of influenza virus by RT-PCR.
The beginning of ventricular electrical activity was defined by the beginning of the QRS complex.
Intensity of activity was defined by the number of gait cycles per minute.
Disease activity was defined by the SLE Disease Activity Index (SLEDAI).
Physical activity was defined by the seven-day physical activity recall questionnaire [ 52].
The minimum level of disease activity was defined by the number of swollen joints at physical examination ≥6.
That strongly suggests that activity is defined by a good contact between Cu0 and ZnO, whereas the selectivity depends on the morphology of copper nanoparticles.
If something is going on, then some action seems to be required somewhere; and in the nature of things, the domain of activity is defined by the classification of goings on.
Each state variable σi can take a discrete number of states which denote the level of activity of the signaling element represented by node i, and where each level of activity is defined by its regulatory effect on the state variables of its target nodes.
In this discussion, human economic activity is defined by the regenerative power of the ecosystem (e.g., the ability of the forest to regenerate once timber has been cut) and absorbency (e.g., the ability of the atmosphere and ocean to take in and cleanse pollutants).
The covariance function of the atrial activity is defined by: ρ s A = E s A ( t + τ ) s A ( t ) ≃ ρ s A ( τ + n P ) (3). corresponding to one entry in the diagonal of the covariance matrix of the source signals R s = E [s(t + τ)s(t)T].
