What are the typical metals used for implantable medical devices and why?
Typical implantable medical devices are made from either medical grade stainless steel (316L), Cobalt Chromium (CoCr), or Titanium Dioxide (TiO2). These three are the most common metals as they are biocompatible, and retain the usual strength associated with metals. Their biocompatibility is in large part due to the oxide layer on the metal surface, which prevents adverse reaction when in contact with living cells. The oxide layer also protects from degradation which could cause loss of strength and integrity of an implantable medical device. There are other metals that can be used, such as amalgam and gold. However, these metals have properties which make them soft and as such are not as useful in the load bearing scenarios common to implantable medical devices.
The recommended daily calcium intake for a 20-year-old is 1,000 milligrams (mg). One cup of milk contains 299 mg of calcium and one cup of juice contains 261 mg of calcium. Write an inequality to represent the possible number of cups of milk (m) and cups of juice (j) a 20-year-old could drink in a day to meet or exceed the recommended daily calcium intake from these drinks alone?
1000 <= 299*m + 261*j
Describe the relationship of position, velocity, and acceleration.
Position, velocity, and acceleration, are related to one another in that one is the derivative of the next with respect to time. For example, to find the position of an object, the formula is xcurrent = xoriginal + (velocity)*(time) + (acceleration)*(time^2). The derivative of this equation would yield the velocity. Therefore, vcurrent = voriginal + 2*(acceleration)*(time). This is also why the units of position are typically in meters, while velocity are in meters/second, and acceleration are in meters/(second^2).