All Direct Subsidized and Unsubsidized Loans disbursed between July 1, 2014 and June 30, 2015 carry a fixed interest rate of 4.66% for undergraduates. Graduate or professional students receiving a Direct Unsubsidized Loan disbursed between July 1, 2014 and June 30, 2015 will have a fixed interest rate of 6.21%.
There is a problem when the valve that controls what blood is good and what blood is used, no longer is strong enough to control this flow. Heart valves get damaged or simply wear out. I think you are asking what causes blood to flow in the wrong direction. My guess is that it would be a faulty heart valve.
Slow blood flow can occur if there is a narrowing of the blood vessel. This can obstruct the flow. One common cause is atherosclerosis. There are deposition of cholesterol or lipids in the wall of the arteries which can narrow it. Other causes can be an inflammation. In the veins there can be slow flow where there is difficulty in pumping blood from legs towards the heart. If you feel any symptom, you should get an examination you need to get it checked by doctor. Any query, please feel free to ask.