A laboratory model of a cooled continental shelf

A laboratory model of wintertme cooling over a continental shelf has a water surface cooled by air in an annular rotating tank. A flat shallow outer "continental shelf" region is next to a conical "contiental slope" bottom and a flat "deep ocean" center. The shelf flow consists of cellular convection cells descending into a region with very complicated baroclinic eddies. Extremely pronounced fronts are found at the shelf break and over the slope. Associated with these are sizable geostrophic currents along the shelf and over shelf break contour. Eddies are particularly energetic there. Cooling rate is compared with temperature difference between "continental shelf" and "deep ocean". Scaling considerations produce an empirical best fit formula for temperature difference as a function of cooling rate. This produces a relatively straight regression line over a wide range of rotation rates, shelf depths and cooling rates. If this formula is valid for the ocean, water over continental shelves will be much colder due to constraints imposed by rotation of the earth than if the fluid were not rotating.Funding was provided by the Office of Naval Research under Contract No. N00014-89-J-1037

Single-cell delineation of lineage and genetic identity in the mouse brain

During neurogenesis, mitotic progenitor cells lining the ventricles ofthe embryonic mouse brain undergo their final rounds of cell division, giving rise to a wide spectrum of postmitotic neurons and glia(1,2). The link between developmental lineage and cell-type diversity remains an open question. Here we used massively parallel tagging of progenitors to track clonal relationships and transcriptomic signatures during mouse forebrain development. We quantified clonal divergence and convergence across all major cell classes postnatally, and found diverse types of GABAergic neuron that share a common lineage. Divergence of GABAergic clones occurred during embryogenesis upon cell-cycle exit, suggesting that differentiation into subtypes is initiated as a lineage-dependent process at the progenitor cell level