However, there are some problems facing this approach, which we outline in the supplemental document Problems for Wide-Scoping.
But a major difficulty facing this approach is that the localization process is extremely sensitive to errors in the assumed propagation model and array calibration.
One challenge facing this approach is to express adequate levels of the therapeutic transgene in a regulated and sustained fashion, eventually restricting expression to a single lineage developing from the transduced stem cells.
The challenges facing this approach are no greater - and may be less - than those facing other means of addressing the threat of global climate change.
A significant challenge facing this approach is that of reproducibility: signatures developed on a set of patients may fail to perform well on different sets of patients.
The major challenges facing this approach are finding an adequate supply of islet cells and preventing transplanted or regenerated cells from being killed by immune destruction from autoimmunity and/or transplant rejection.
However, one fundamental issue facing this approach is the high interconnectivity seen in the biological networks due to the presence of a small number of hubs, that is, network nodes with hundreds or even thousands of connections [ 8].
For example, while the group-based approach is effective with adult men and women in this context, the restricted mobility and time constraints young married girls face made this approach more challenging.
In the face of this approach to fiscal policy, so aptly labeled by Keith Hennessey as a strategy of "whistling past the graveyard" and so at odds with the self-righteous tone of President Obama's first budget with its cover proclaiming "A New Era of Responsibility," it is difficult to blame Republicans for pushing for fiscal restraint in any way possible.
While he acknowledges that Facebook has a strong brand and a familiar interface in its favor, it doesn't insulate it from the same problems those earlier companies faced with this approach.
