Single-allele underdominance and single-locus engineered underdominance have the strongest confinement properties, but are difficult to engineer and require a high introduction frequency, respectively.
Thus the inducibility of HIPV emission, which ensures association with herbivore feeding, is likely essential for HIPV function, but it is difficult to engineer (Kos et al., 2009).
The engines are often simple and potentially more efficient than crankshaft engines but they are more difficult to engineer and exploit successfully.
A tunnel would be far cheaper, $11 million, and would gobble much less land, but would also be more difficult to engineer.
The concept of affordance is relatively easy to define, but has proved to be remarkably difficult to engineer.
Some trypsin-like proteases are endowed with Na+-dependent allosteric enhancement of catalytic activity, but this important mechanism has been difficult to engineer in other members of the family.
Some successes in altering non-cellulosic polysaccharides has been achieved, but it would appear that drastic changes in cellulose are more difficult to engineer.
It has been much more difficult to engineer than that sounds.
Although it will be very difficult to engineer such sweeping change in Russia, this is precisely the way to confront corruption.
The embarrassing lack of sportsmanship prompted FIFA to make it more difficult to engineer a result by playing the final group games simultaneously.
