Oronary heart disease is caused by a buildup of plaque in the arteries that supply blood to the heart. when the flow of blood to the heart is restricted or blocked, the heart can be damaged due to a lack of oxygen. further, if a large piece of plaque buildup gets dislodged from an artery wall, it can get stuck in other arteries throughout the body, including arteries in the brain. for simplicity, let's assume that the artery is cylindrical with a radius of r. the flow rate of a viscous fluid is given by poiseuille's law q=(π/8)(δp/ηl)r4.

Oronary heart disease is caused by a buildup of plaque in the arteries that supply blood to the heart. when the flow of blood to the heart is restricted or blocked, the heart can be damaged due to a lack of oxygen. further, if a large piece of plaque buildup gets dislodged from an artery wall, it can get stuck in other arteries throughout the body, including arteries in the brain. for simplicity, let's assume that the artery is cylindrical with a radius of r. the flow rate of a viscous fluid is given by poiseuille's law

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.