Quasars: What Turns Them Off?

Quasars: What Turns Them Off?

While the high-redshift quasar luminosity function closely parallels the hierarchical growth of dark matter halos, at lower redshifts quasars exhibit an anti-hierarchical turn-off, which moves from the most luminous objects to the faintest. We explore the idea that this may arise from self-regulating feedback, caused by quasar outflows. Using a detailed hydrodynamic simulation we calculate the ...

Overweight and obese adolescents: what turns them off physical activity?

A systematic review of qualitative studies was undertaken to understand the barriers to physical activity experienced by adolescents who were overweight or obese. From a search of electronic databases and 'grey' literature, published between 1950 and 2009, 15 studies met the inclusion criteria. Bronfenbrenner's model of human development provided an ecological lens for identifying and synthesis...

Young galaxies : what turns them on ?

Lyman break galaxies (LBGs) at z ∼ 3 exhibit number densities and clustering similar to local L∗ galaxies; however, their star formation rates (SFRs) are much higher. We explore the scenario in which LBGs are starburst galaxies triggered by collisions, and thus provide an explanation for these key properties. The relative paucity of starburst galaxies at low redshift can be attributed to a much...

Off-label prescriptions: how to identify them, frame them, announce them and monitor them in practice?

Following the Mediator crisis and the passage of the Health and Safety Law of December 2011, off-label prescriptions are a real concern shared by all those involved in healthcare system. Off-label, in the strictest sense of the term, is defined as all prescriptions that do not correspond to the summary of product characteristics (SPC), particularly those that fail to comply with the indications...

Polymeric Gas Separation Membranes: What Makes them Industrially more Attractive?