Sentence examples for have often proven difficult from inspiring English sources
Biomarkers originating from tissues have often proven difficult to discover in blood because of the dilutive factor.
In the past decade, the plethora of candidate genes and regions emerging from genetic linkage and smaller-scale association studies yielded intriguing 'hits' that have often proven difficult to replicate consistently.
While there are charter schools led by visionary, experienced educators with a true commitment to improving achievement in poor communities of color, they are few and their programs have often proved difficult to replicate.
Proinflammatory cytokines such as IL-1 and TNF-α are abundant in rheumatoid synovium, whereas the T cell-derived cytokines, especially IL-4 and interferon-γ, have often proved difficult to detect in RA synovium [ 24].
In the case of asthma, some measure of support for this hypothesis is provided by the observation that already in 2006 (prior to the first GWAS for asthma) variation in more than 100 genes was implicated in asthma susceptibility (33), yet many variants show only weak associations that have often proved difficult to replicate (34– 34).
The expression of parasite genes has often proven difficult in heterologous systems such as yeast or E. coli.
Critiquing such theories has often proven difficult, not least because of the imprecise dating of many aspects of the palaeoclimate or archaeological records and the difficulties of merging the two strands of research.
However, the path from QTL to the identification of causative genes has often proven difficult.
The management of the unstable elbow, whether resulting from acute trauma, its sequelae, or chronic disease, has often proven difficult [ 13, 16].
Unfortunately, this has often proved difficult.
