BMC Pre-Lab
INCLUDE THIS SHEET AS THE FIRST PAGE OF YOUR REPORT.
Student's Name: ______________________________________________________________
Partner's Name: ______________________________________________________________
Before the 1st Day of Lab
Pre-lab Discussion Questions
It is your responsibility to discuss this lab with an instructor before your first day of your scheduled lab period. This signed sheet must be included as the first page of your report. Without it you will lose grade points. You should be prepared to discuss at least the following before you come to lab:
- What are the masses of the various nanoparticles you will be observing in the lab? How many molecules are in a single particle? What is the uncertainty in these numbers? Data sheets for the nanoparticles are available on the BMC Reprint List.
- We assume that particles in the fluid are in the non-inertial regime. What statistical assumption does that allow us to make?
- Consider a 1-d random walk of N steps, where the probability of moving left equals the probability of moving right at each step. This allows us to define a random variable X which represents the final displacement of the walker (its location after N steps). Calculate: $\langle X \rangle $ and $\langle X^{2} \rangle$. To do this, write$X = \sum_{1}^{N} S_{i}$ , where $S_{i}$ is an indicator on the ith step (explicitly, $S_{i} = -1$if the ith step was to the left, and $S_{i} = 1 $if the ith step was to the right). Keep in mind that the $S_{i} $ are independent when calculating $\langle X^{2} \rangle$ .
Staff Signature ______________________________________________ Date ____________
Completed on before the first day of lab? (circle) Yes / No
Questions to complete on the 1st day of lab
These questions can be answered after you read through the Simulating Brownian Motion. Make sure to copy and execute the scripts on the computer's MATLAB as you read so that you can understand the program structure and the different variable names. If you take your time and just work slowly through the page, these questions should be straightforward.
- Using the microscope, you will observe a minimum of two different-size particles in at least four solvents with different viscosity. Choose the conditions you plan to observe and simulate them in Matlab. (You should choose at least one particle with 1 μm in size or larger and one smaller.)
$\checkmark$This is a checkpoint. Plot the Displacement Squared for the different diffusion coefficients on the same graph (see the Hold command used in the write-up). Then call over the GSI to sign you off. - Use your simulated data to calculate the diffusion coefficient, D in each case. Explain how you arrived at your answer.
- What is the uncertainty of your estimation of D? How does it vary with the number of simulated data points? Explain your strategy for making observations in the lab. What additional sources of error (these are significant) will come in to play? How will you account for them?
Keep these scripts. When analyzing your data you can create artificial data sets on which to test your analysis techniques.
Staff Signature ______________________________________________ Date ____________
Completed before the second day of lab? (circle) Yes / No
Mid-lab Questions
On day 3 of this lab, you should have completed the following; Show them to an instructor and ask for a signature.
Mid-lab Questions Part I
- Using a slide with a combination of 10 μm and 0.44 μm polystyrene spheres, show how to set up Köhler illumination.
- How many nanometers per pixel are captured at 10x, 20x, and 40x magnification?
- Draw a diagram to show dark-field illumination. Explain how it is possible to see 40 nm objects with visible light (400-750 nm wavelengths).
- Set up dark-field illumination.
Staff Signature ______________________________________________ Date ____________
Completed by the second day of lab? (circle) Yes / No
Mid-lab Questions Part II
By day three of this lab, you should have collected some particle tracks and made several movies. Show one of the particle tracks to an instructor. What value of D did you obtain from the track? How close is this to the theoretical value? You can do this either with the BMC application or with the Matlab scripts. Show and explain your averaging and centroiding code. How do they work?
Staff Signature ______________________________________________ Date ____________
Completed by the third day of lab? (circle) Yes / No