310 Final

ndifranco94's version from 2015-05-06 01:29

Gratzl Final

Question Answer
Accuracy% error; ex. 3% error = 97% accurate
Precisionstandard deviation
Standard Deviation
Two types of precisionresolution of output display, resolution of measurement
Conditions for Linear RegressionError follow NORMAL DISTRIBUTION, Variance is CONSTANT over entire dynamic range, Uniformity of data is CONSTANT
Sensitivityslope of data; ex. 0.1mV/cm
Lower Limit of Detectionsingle value; ex. 0.1mV
Calcium ISE
pH Glass Electrode
Combination Electrode (CO2 gas electrode)
O2 Electrode (can measure glucose levels)
Beer's Law ; where a=absorption coefficient, d=optical pathlength, c=conc.
Beer's Law w/ Standard Addition
Energy of a photon
Percent NRG radiated back as fluorescencefluorescent NRG/maximum absorption NRG
Absorption in terms of intensity islog(T), where T is transmitted intensity/input intensity
Transmittancetransmitted intensity/input intensity
Beer-Lambert Law w/ Intensity
3 Ways Signal Loss occursvibrational/thermal forces of molecules; Inner Filter Effect; photodestruction
3 Ways to Measure Glucose levels?O2-Linked Sensor, H2O2-Linked Sensor, Gluconic Acid Sensor
Entrapment membrane of O2 electrodehydrophobic, allows O2 in, allows H2O2 & H+ out
Current vs. glucose conc, O2 electrode
Current vs. glucose conc, pH electrode
Current vs. glucose conc, H2O2 electrode
Absorption and Fluorescence peaks vs wavelength
Two-Photon ExcitationTwo photons hit sample at the same time, excite to higher NRG level than individual photon w/ lower input NRG
Advantages of two-photon excitationphotobleaching is negligible, much higher resolution & lower illumination
Spectrophotometermeasures liquid sample concentrations using absorption or fluorescence
Absorbance Saturationtoo many molecules in soln, absorbance no longer inc prop. w/ conc b/c molecules block each other!, causes upper Absorbance limit
Background AbsorptionCauses plot of A vs c to shift UPWARDS
2 Sources of Absorption ErrorSaturation, Background Absorption
How to calibrate to remove background error?Dilution, Standard Addition
Standard Additionadd small volume, high conc of diff molecule to solution; measure change in absorbance and extrapolate back to zero
Standard Addition conditionsVst << Vsoln & cst >> cx
Absorbance vs conc plotLinear, positive
Intensity vs conc lotExponential decay
Inner Filter Effectdistorting molecule excites at similar wavelength, overlaps desired excitation peak and distorts measurement
Reflectance modalitystereo microscopy
Absorption modalitytransmission microscopy
Fluorescence modalityfluorescence microscopy
X-ray A1 Filterremoves low NRG x-rays that cannot penetrate body
Collimatorrestricts path of x-rays
Primary radiationstrikes the screen phosphor and creates light that exposes the film
Seconary radiationtrapped by grid
X-ray intensity errors are described byPoisson Distribution
Poisson distribution for discrete hits
Quality of spatial sampling is determined bysize of the pixels relative to the size of the smallest object to be recognized
spatial frequency of the smallest object1/l0 = fs0
full period of obejct and voidfsp = 1/2fs0, where Nyquist freq fsn = 2fsp
Modulation Transfer FunctionAnalagous to LPF Bode Plot, plots probability of detecting object of given size vs. spatial frequency,
Noise Equivalent Bandwidthanalogous to cutoff freq for imaging, equal to the integral of MTF^2
With same MTF @ lower contrast, the size of the SMALLEST object you can detect islarger
Forward Problem in Imaginghow does an imaging system create from an actual input image an output image? --> This is modeled as a spatial convolution of the input image with the MTF (Actual Image --> Detected Image)
Inverse Problem in Imaginghow can the actual image be reconstructed from the measured image? --> this is a deconvolution of MTF from the output image (Detected Image --> Actual Image)

Gratzl In Class Questions

Question Answer
What equation is used with a confluent monolayer?Cottrell's Equation
What equation is used with a single cell?microelectrode equation
What is the difference b/n mass transport and ISE equations?a conversion factor that gives you current instead of conc.
When do you need biosensors instead of base sensors?convert metabolities, glucose, etc... into something electroactive you can measure
How to modify a pH electrode into a CO2 electrode?start w/ pH electrode, coat w/ CO2-permeable membrane --> no other components can get in, so pH change is entirely based on CO2 levels
What does a biosensor consist of?Base sensor + biological component
How do you measure urea levels, knowing that it consumes O2 to form uric acid + hydrogen peroxide?measure O2, H2O2 levels
What direction is the shift in emitted NRG of a photon?red shifft --> towards lower NRG
What can cause a shift towatds higher NRG?If 2 photons hit simultaneously, can emit higher NRG than individual photons w/out photobleaching
What law defines intensity?Beer's; -log(It/I0)=acd
What is the range of transmittance values?0 to 1
What is the range of absorption values?0 to infinity
When is standard addition used?you have a very complex system w/ many types of molecules, calibrate the complex soln w/ small volumes of high conc molecules
Why would you use 4 or 5 standard additions to determine k?Linear calibration data = linear regression; non-linear calibration data = non-linear regression
Beer's Law is exponential and the emission equation is linear. What is the problem w/ this contradiction?Emission only looks linear b/c it is over such a small concentration range
Why is electroneutrality a problem in optical sensors but not ISEs?The color must be distributed throughout the entire membrane, not just one surface. If only at one surface --> too weak to see! Need chromionophore that moves based on pH AND displays a color
Why are ISEs faster than optical sensors ?No need to wait for diffusion through membrane
How to measure NO3 levels w/ bacteria that consume NO3 & have decreased O2 output?O2 amperometric sensor w/ Pt wire
At low glucose levels, sensor is orange, but at high glucose levels, sensor is blue. Why?low pH = blue, high pH = orange --> more glucose = more gluconic acid --> turns blue
Is there current flow in a thermocouple?NO
Is V vs. T for a thermocouple linear?Yes, for a narrow range of temps, modeled by a Taylor series though so not always linear
What does V do as T inc for a thermocouple?V inc b/c electrons move faster as T inc and can cross junction
Why is the voltage vs. T the same for a thermocouple no matter what you are measuring?B/c it is dependent on the metal properties!
What do you measure in a thermistor? How do you measure it?Measure change in resistance, can determine based on change in voltage or current
What is better, current-driven or voltage-driven thermistor?CURRENT-DRIVEN. As T inc, R decreases. For voltage, P=V^2/R --> P inc at low R = instability...For current, P=I^2R --> P dec at low R = stability