What is an endophenotype?

The highest contact stresses in a gear tooth usually occur at which location?

A 55-tooth spur gear is in mesh with a 35-tooth pinion. Consider full-depth teeth with a pressure angle of ϕ=25° and the highest point of single tooth contact (HPSTC) loading. What is the bending geometry factor, J, for the gear?

The absolute viscosity of an SAE 20 engine oil at 110F is most nearly…

Problem #6 A rectangular key is used to connect a shaft of diameter d = 30 mm to a pulley. The key (see image) has a width of w = 10 mm, height of h = 6 mm, and length of L = 30 mm (into the page). The system is subject to a time-varying torque (T) that leads to the following forces on the key: Fmin = 40 kN and Fmax = 60 kN.   (a) What are the alternating and mean shear stresses of the key? Note: You do not have to find the von Mises effective stresses. Express your answer in MPa.

Problem #2 A three-stage compound gear train is shown below. What is the overall gear ratio expressed in terms of the number of teeth (e.g., N2 to N7, as needed)?  

Problem #3(a) Design suitable deep-groove ball bearings for a 10% failure rate to support the load shown below for at least 100×106 cycles at 1800 rpm. Take the shaft diameter to be 40 mm and the reaction force on the left bearing to be Rleft = 6275 N and the reaction force on the right bearing to be Rright = 7525 N. (a) Which bearing would you select for the left bearing? Show your work.    

The addition of two planets in the planetary (epicyclic) gear train below would increase the load experienced on the original planet.

Problem #4 A bearing with a diameter of 30 mm and length of 25 mm has a diametral clearance of cd = 45 μm. Consider lubrication with an oil that has an absolute viscosity of η=16 cP (recall that 1 cP = 10-3 Pa⋅s). Utilize a design load of P = 7.2 kN, a rotational speed of 1500 rpm, and an Ocvirk number of ON = 30 for the bearing.   (a) What is the no-load torque, To? Express your answer in N-m.

Many neurological conditions can be described as “synaptopathies,” reflecting their dependance on dysfunction at the level of the synapse. List three or more potential mechanisms whereby a synapse might be rendered dysfunctional (aka, how do you break a synapse?).