In the econometric terminology, it will be challenging to isolate or identify the causal effect of s 2, ∂θ 2/∂s 2. If research cannot achieve such identification, then no evidence-based policy on school inputs is feasible.
Given the interest and use of educational technologies and consequent interest by researchers, it is often challenging to isolate the major issues that have been or can be addressed by academic research.
Because children are likely to be exposed to multiple environmental chemicals, and because these chemical exposures may be correlated with each other, it is challenging to isolate associations.
This bacterium is challenging to isolate and cultivate, as it replicates in short lifespan cells (i.e. polynuclear cells), which rapidly undergo autolysis after sampling.
While it is important to recognize that these two main populations of EVs have distinct biogenesis pathways, it remains technically challenging to isolate their respective pure populations due to their overlapping size distributions and most preparations are therefore heterogeneous [ 3].
The causes of change (or stasis) in policy and practice are difficult to predict ahead of time and are often just as challenging to isolate and identify after the fact.
Due to lung structural complexity with cellular diversity and slow epithelial cell turnover rates, it is still a challenge to isolate and characterize lung stem/progenitor cells for exploring the lung disease processes and endogenous repair mechanisms.
It is still a great challenge to isolate genes by map-based cloning for the huge genome size of peanut.
Second, in studies dealing with differential exposures to macronutrients, it is a major challenge to isolate the macronutrient truly responsible for the nutrigenetic effects, particularly for fat and carbohydrates as they tend to be manipulated in such a way that one is compensated by the other.
