You are investigating the role of physical activity in heart disease and suggest that physical activity protects against having a heart attack. while presenting these data to your colleagues, someone asks if you have thought about confounders such as factor x. this factor x could have confounded your interpretation of the data if it: a. is a factor for some other disease, but not heart disease. b. is a factor associated with physical activity and heart disease. c. is a part of the pathway by which physical activity affects heart disease. d. has caused a lack of follow-up of test subjects.

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?

Which of the following is the most important advantage of a large field of view? a. allows larger areas to be examined b. relieves eyestrain c. minimizes parallax errors. d. increases precision in proportion to the in- crease in field of view

A)-explain briefly the importance of standards in engineering design. b)- what is patent? c)-explain the relationship between these standards: b.s. and b.s.en d)- in engineering design concepts, types of loads and how they act are important factors. explain.