Spare Part Surgery Flashcards
Ethical Frameworks
characterise the thought process we go through, the reasons we give when deciding how to act in a certain situation
Utilitarianism
believe the best course of action is the one giving way to the most happiness
Divine Command
using religions writings to guide the decision
Virtue Ethics
the right course of action is that which is considered ‘virtuous’ (morally correct)
Rights and Duties
people have certain rights and other people have a duty to grant them this right (e.g. patient has right to treatment and doctor has to grant it to them)
Good bone substitute
- material must be strong enough to withstand and exert forces involved in movement
- mechanical properties must be similar to those of real bone
Smooth material
has a low friction surface
Durable material
can withstand repeated loading and unloading
Tensile stress
when the sample is pulled
Compressive stress
when the sample is squashed
Ultimate compressive/tensile stress
stress needed to break a material
Strain
the ratio of compression/extension to the original length
Young’s modulus
stress/strain
limit of proportionality
when the two variables no longer create a straight line
elastic limit
beyond this point the material will be plastically deformed so won’t go back to original shape/size
What is the area under a force extension graph?
the elastic energy (1/2fx)
What is the gradient of a stress strain graph?
Young’s Modulus
What is the area under a stress strain graph?
energy density
Yield point
dip on stress strain graph after elastic limit reached - after this point the material becomes plastic
Ultimate tensile strength/stress
highest point on a stress strain graph - this is the maximum stress the material can take before breaking
What are diffraction patterns used for?
to identify the structure of small materials
Why are we looking into polymers for replacement body parts?
because they have similar properties to bones:
are strong and have an ultra high molecular weight
Converging lens (Convex)
- brings light together at a focal point
- fattest in middle
- real image
Diverging lens (Concave)
- spreads light out
- thinnest in middle
- virtual image
Drawing ray diagrams
- draw a ray parallel to principle axis (from object to lens)
- draw refracted ray from principle axis through focal point
- draw undeviated ray through the middle of the lens from object
- draw image where the two rays cross
Object position: Outside 2F
- Image position: between F and 2F
- real
- inverted
- diminished
Object position: At 2F
- Image position: At 2F
- real
- inverted
- same size
Object position: Between F and 2F
- Image position: outside 2F
- real
- inverted
- magnified
Object position: At F
- Image position: at ∞
- real
- inverted
- at ∞
Object position: Inside F
- Image position: -between F and 2F
- virtual
- upright
- magnified
What is a real image?
can be projected onto a screen (is on the other side of the lens from the object)
Diverging lens image
- virtual
- upright
- diminished
- closer to lens than object
What sound frequencies can we hear?
20-20000Hertz
Above 20000Hz
Ultrasound
Below 20Hz
Infrasound
Uses of ultrasound in medicine:
- check blood flow
- break up kidney stones
- pictures of developing foetuses
Sound
- is a longitudinal wave
- through air at 340m/s
- can reflect, refract, superpose and form standing waves
Ultrasonic probe
has a piezo-electric transducer
Why is coupling gel used?
so the ultrasound doesn’t reflect off the skin
How does ultrasound work?
It will travel at different speeds in different materials so we measure the time taken for the echo to return. This will depend on the material as well as the distance. The wavelength of the ultrasound will change.
At each boundary some of the ultrasound will reflect and some will refract
Doppler Effect (Towards)
Moving source towards you means more waves per second so it has a higher frequency and higher pitch than the emitted ones. The wavelength received will be shorter than emitted
Doppler Effect (Away from)
Moving source away from you means the wavelength will be longer than the emitted. This causes the frequency and pitch to decrease so they’ll be lower than the original
