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Semester 2 Examinations 2010/ 2011
Exam Code(s) 2 BG Exam(s) 2 nd^ Biomedical Engineering Module Code(s) ME Module(s) Introduction to Biomedical Engineering Paper No. 1 Repeat Paper External Examiner(s) Professor David Taylor Internal Examiner(s) Professor Peter McHugh Dr. Laoise McNamara Dr. Patrick McGarry Instructions: (^) Answer 3 questions All questions will be marked equally. Use a separate answer book for each section.
Duration 2 Hours
No. of Pages 5 Department(s) Mechanical & Biomedical Engineering Course Co-ordinator(s) Dr. Laoise McNamara, Dr. Patrick McGarry Requirements: Statistical/ Log Tables Graph Paper Log Graph Paper Release to Library: Yes
Section A Question 1 (a) Briefly describe the methods by which cells can generate motion. In your answer indicate the cellular components that are involved in movement of the cell and briefly describe the mechanism by which they operate together to generate movement. [3] (b) Briefly describe the principle of aseptic technique used for in vitro cell culture. [4] (c) Discuss the differences between the structure and function of osteocyte and osteoblast cells. In your answer detail how the cells are distinguished from each other in vitro. [4] (d) During a cell culture experiment, you perform a trypan blue stain and count your cells using a haemocytometer and microscope. During staining you dilute 70 l of cell suspension with 70 l of trypan blue. You find that there are 8 cells stained blue and 11 unstained cells in 1 square of the haemocytometer (Figure Q1(a)). Estimate the % viability and the total number of viable cells in a 10 ml suspension assuming a 1:2 dilution. [ 5 ] (e) Estimate the proliferation constant for your cells using the graph in Figure Q1(b). Calculate the number of cells expected after two days of culture using the equation below. [4] N(t) = Ce t/d where N(t) is the number of cells at time t (in days); C is the initial number of cells; t is time (in days); and d is the proliferation constant of the cell line. Figure Q 1 : (a) Haemocytometer, (b) Graph of MC3T3 proliferation rate.
Section B
Question 3 Figure Q Figure Q3(a) shows a person performing lower leg flexion/extension exercises to strengthen the quadriceps muscles. A weight, Wo, is attached at the heel. Figure Q3(b) shows a free body diagram of the lower leg, indicating the position of the attached weight (Wo), the self weight of the lower leg (W 1 ) and the tensile force exerted by the quadriceps muscles through the patellar ligament (FM). Note that the presence of the patella results in an angle between the patellar ligament and the tibia. (a) Derive an expression for the muscle force FM. [7] (b) If removal of the patella reduces from 15 o to 2 o what is the percentage increase in muscle force FM required to maintain static equilibrium for =45o? [4] (c) Based on the result of (b) comment on the role of the patella in extension of the lower leg. [3] (d) Calculate the magnitude and direction of the tibiofemoral joint reaction force for the following parameters: a=10cm; b=20cm; c=50cm; W 1 =100N; Wo=100N; = o ; = o
. [ 6 ]
(a) (b)
O
A
B
C
a
b
c W 1
Wo
Fm
Question 4 (a) Derive the general equation for a Maxwell viscoelastic model (spring and dash-pot in series). [3] (b) Determine the response of a Maxwell model to a stress-relaxation test. Provide a sketch of this behaviour. [3] (c) Derive the general equation for a Kelvin-Voigt viscoelastic model (spring and dash-pot in parallel). [3] (d) Determine the response of a Kelvin-Voigt model to a creep test. Provide a sketch of this behaviour. [3] (e) Derive the constitutive equation for the viscoelastic model shown in Figure Q4 below. [6] (f) Sketch the response of the model shown in Figure 4 to a creep test. Why is this response more realistic for the creep of cartilage than the response of a Kelvin-Voigt model? [2] Figure Q
