Lessing's work has always been difficult to define: a mix of classical realism, science-fiction, parable, memoir, fantasy and polemic.
At the Farmington Public Schools, Janet Collins, the food service director who has been working on a committee with Mr. Manfredi to develop a nutrition and wellness policy, said it has been difficult to define exactly what healthy is.
This relationship between heats of reaction and equilibrium allowed van 't Hoff to define chemical "affinity," an old concept in the history of chemistry that had been difficult to define in terms of its effects, specifically the amount of work that a reversible chemical reaction could perform.
Furthermore, what constitutes 'genuine' nursing has been difficult to define and 'caring' difficult to measure.
In the absence of specific high-affinity agonists and antagonists, it has been difficult to define the target genes and biological responses attributable to many of the orphan nuclear receptors (ONRs).
CD19-specific chimeric antigen receptor (CAR)–modified T cells have antitumor activity in B cell malignancies, but factors that affect toxicity and efficacy have been difficult to define because of differences in lymphodepletion and heterogeneity of CAR-T cells administered to individual patients.
