It is difficult to characterize an emerging outbreak, for example, when only a handful of known genomes exist.
It is indeed difficult to characterize an entity that existed billions of years ago using information in molecules of life that are modern.
The built environment is multidimensional, which makes it difficult to characterize any given area as having a "good" or "bad" built environment.
Its sharp, assertive flavor is difficult to characterize without a torrent of descriptors, like trying to devise a one-line plot summary for a Georges Perec novel.
If the genius of the 13th-century stained glass lay in its epic sense of monumentality and that of the early 14th century in its warmth of human feeling, that of the late 14th and early 15th centuries is far more difficult to characterize in a phrase.
Phase separation mechanisms can produce a variety of complicated and intricate microstructures, which often can be difficult to characterize in a quantitative way.
These factors make passive system operation difficult to characterize within a traditional probabilistic framework that only recognizes discrete operating modes and does not allow for the explicit consideration of time-dependent boundary conditions.
Beyond these direct implications, our experimental design has broad applications in clinical research and basic sciences: it serves as a simple, robust, low cost, easy-to-use tool to reconstruct living membranes, which are difficult to characterize in a conventional laboratory setup.
