User:DDeFigueroa
From MariachiWiki
Hi. Desiree graduated from Stony Brook University with a B.S. in Biochemistry and is currently the curator at Stony Brook in the Undergraduate Biology Department http://www.bio.sunysb.edu. As the curator she is responsible for the implementation of the lab curriculum as defined by the student lab manual. She is also an adjunct instructor in the Undergraduate Biology Department and has taught Biology 202: Molecules to Organisms and Biology 204: Fundamentals of Scientific Inquiry. She started teaching a few years ago and thoroughly enjoys the interaction between herself and the students.
Desiree has recently been able to get back into taking some courses of interest over the last year, which includes CEB558/PHY315 at present, and CEN 514 last semester. These classes will eventually lead to a master’s degree.
When Desiree isn’t at work in the lab or her office 
(it was Christmas), she can be found cooking and/or eating, gardening and spending time with her family enjoying the outdoors whenever possible. Skiing, hiking, biking, camping and the beach are among her favorite activities. Desiree has a daughter who attends college locally as a history major. She enjoys both shopping as well as the outdoors.
Me and the offspring. We couldn’t get boots to fit the cat. Hiking a mountain in the northeast.
Week 2
This week we used detectors to determine
1. optimal voltage
2. measurements when configuration is changed
3. effects of varying measurement times on the counts
1. The optimal voltage was determined by changing the voltage from 5.001-6.1. At 5.699 the readings began to level off and based on the Feb 5 data the best voltage was determined to be 5.906. Small voltage fluctuations will still be on the plateau where the voltage is good and the noise is low.
2. We changed the configuration by varying the displacement of detector 3. 
displacement
3. We varied the time intervals that measurements were taken. The results indicated that the average number of counts
/second was 19.5).
Contents |
Week 3 (Feb.12, 2008)
This week we discussed errors. Since no measurements are perfect, it is important to find out how close it is to the actual “answer”. In doing this, we have to discuss experimental errors.
Part of this discussion must include accuracy, precision and statistical evaluation of errors.
Errors in our case involve counts and rate. To determine count errors we use calculate the square root of N where N=counts. To determine rate, R=N/t and the error on the rate is R=sqrtN/t where R=Rate, t=Time and N=counts.
Sources of errors are typicaly systematic errors, which are equipment errors. A meter stick analogy was helpful to describe this. You can measure with a meter stick but if its missing a number then your measurements will always be wrong. Your equipment is not correct.
Another common source of error are ramdon errors where your answers are not the same. This can be minimized by taking a larger sample or more measurements.
A way to illustrate the errors in our measurements was using error bars in the graphs of the data, collected.
Gillian, Mildred and myself changed the configuration of the detectors prior to taking new data. We used 2 counters separated by about 3 feet. We took only 5 measurements at both 0 degrees and 45 degrees (facing North) before platting the data.
February 19, 2008
I wasn’t able to make it to class this week but Gillian and Mildred were there and took new data. Last week we had the detectors measure at 0 and 45 degrees facing north. Gillian found out that north facing was not good due to high concrete walls so they reoriented the detectors to face east. This week they took data at various angles and facing east and recorded the counts, count rates and error.
As expected, the count rates decreased as the angle increased. While we may image cosmic rays coming only from above, the sky (0 degrees) they do hit the detectors from various angles. Since its not such a clear, unobstructed path at angles other than 0 degrees, the measured rays decrease.
February 26, 2008
This week we discussed chi2 analysis and the implications of the values calculated. For our purposes chi2= [(average-data point)/error]2 where average is calculated values.
If the chi2 value is >>greater than 1 then we could say that the data or the model is bad If the chi2 value is <<less than 1 then we can say that the data may be good but the model is bad.
We added a trend line to graphed data to get an equation (if linear y=mx+b) that was used as the average value in the chi2 equation. We also discussed the importance of x error bars in data representation.
For our groups measurements, we were measuring at different angle facing East. If we were able to only measure the exact point( dashed line) at that angle then we would have data based on that exact angle. In reality however, our data is collected and measures a range of angles (solid lines) and that can be illustrated by the x error bars on our graphs.
We also began our powerpoint for the following week to present our data to the class.
Last week data was collected with the octagon facing east due to a high thick wall that may have interfered with taking measurements from the north. We re-oriented the octagon to face the north to see if in fact it was going to make a big difference in our detectors picking up rays. Based on the data, we can determine that with the exception of measurment, it didn't make much difference.
March 4, 2008
Today all of the groups presented their data and gave a description of the experiments they were running.
My groups experiment related to changing the angles and to a lesser extent, the direction in which the detectors faced. We were interested in determining if the count rate changed based on the angle as mentioned in previous entries. We presented our experimental data as a powerpointand gave what we hoped were good explanations for variations in measurements that we got.
Other groups presented information about measuring Flux, measurements using cosmic Chris on different floors in the builing, shower masurements and systematic errors.
March 11,2008
This week we switched groups around after dicussing ideas for the next part of the class.
We talked about what the detectors can actually measure-time,counts and some part of energy that is left in detector as particle passes through.
My group is going to try to measure the velocity of particles passing through the detectors. We are going to vary the distacnce between the detectors and vary the lengths of wire to determine speed. Other groups are measuring energy, using cosmic Chris, and continuing with detector separation measurements.
We began taking data that measured speed between both detectors. To do this we tried to determine the distance between peaks of both detectors. There is a difference in the time between when detector 1 and detector 2 measures a particle passing through.
We didn't have much tme to do any analysis of the data we collected but you can see that as the distance increases the time between peaks has increased as well. This was just the first set of data and gives us a jumping off point to continue with. We were not able to change the wire during the class so there isn't any data for that yet.
March 25, 2008
We continued with measurements this week using different lengths of cable.
Prof. Marx pointed out that our data indicated that we had measurements faster than the speed of light. Since that is unlikely, we had to explore errors in our measurements. Unfortunately, after collecting new data, our computer decided to stop working. This of course caused us to lose our data which indicated that based on published values of RG58 cables we had about a 19% error rate. This was error based on taking correct visual measurements. Our data indicated 1.59 m/ns and the published values indicated 1.96 m/ns.
We were able to collect some data here that was taken using RG8 cable.
April 1, 2008
During this class we continued taking readings and trying to eliminate or isolate some errors. Dima set up the computer to take 130 measurements at one time. This gave us a volume of data that would have taken us much too long to do without Dimas set up.
We also began working on the power point for our presentation
April 8, 2008
Todays class was devoted to the second set of presentations.
Vincent continued measurements with Cosmic Chris in both the physics and the math buildings. He took measurements on various floors using the bridge as a central location for measurements.
Harry, Tania and Joe presented information on cosmic ray energy. The measured the energy deposited in the detectors using various detector configurations.
Karyn and Tom measure cosmic ray showers by separating the detectors.
Mildred, Greg,Pat and Tom showed us data they had collected by varying a the angle and configuration of three detectors. They also changed the length of the wires that they used.
Gillian looked at some of the data collected for one week from Smithtown high school. She also obtained local weather data. Based on the data she collected from the school as well as weather data, Gillian was able to show a correlation between pressure and cosmic rays.
April 15, 2008
Last week we presented our data from the previous weeks experiments. This week we continued with our velocity measurements. Mildred and I began taking measurements using Dimas program which allows us to take large amounts of data. Using detector A and detector C we took data with our detectors together (separated by 32cm on center) and separated by 197cm.
We were collected data for 15 mins at a time at both of these distances. We were only able to collect one set of data and produce a histogram for each of these data sets. Next week we will continue to collect data using the same set up to be better able to have better error
April 22,2008
Mildred and I continued to collect data to try to get a better understanding as to the error in our velocity measurements. We have collected about 1000 measrements at 32 and 197 cm. These distances correspond to the distances the detectors are apart from one another.
Using the data we have collected to date we were able to determine the mean using the following Emean=RMS/sqrt(N). This gives us the error that we can use when plotting our data at both 32 and 197cm. We created a histogram as well as a scatter plot with error bars for both sets of data
April 29, 2008
This week Mildred and I tried to crunch some numbers to get an understanding of the data that we had been collecting.
Our intention was to figure out the speed of the cosmic rays were were detecting. We, using Dimas program were able to take a large amount of measurements at one time. This helped to eliminate the human error involved in trying to read the oscilliscope and a lot of aggravation.
Once we got these numbers we created some histograms to visualize the data we had collected and plotted this information. Using a formula Prof. Marx had given us we were able to plot the errors on our speed measurements instead of using error bars. This was good because it enabled us to "see" the errors and it helped us to see why we collected the data we did.
Dima later gave us a formula so that we would have a more accurate number to represent our error. This led to a powerpoint for our last powerpoint presention.
May 6,2008
This was our last class and everyone gave their last presentation. It was interesting to see what everyone was doing and how they would be using information from the class. Since most of the people in the class are teachers, they will be using the class to help with their own classes. Some of them have detectors in their schools and have collaborated on ways to make the information gathered in the schools useful to their students.
My final velocity presentation consisted of data that I had collected over the last half of the class. Some with Brad and James and some with Mildred. We were interested in determining the velocity of cosmic rays. To do this we needed to gain a better understanding of the errors that we are dealing with.
We examined the cables and found that the cables we were using have a velocity factor of 0.66 which means that the velocity is 66% the speed of light.
We continued to collect data and eventually collected what we felt was enough to be able to determine error using a histogram as well as a formula Prof. Marx and Dr. Vavilov had given us. The histogram and the graph associated with our data were good to give us a visual representation but the fourmula was what we used to get an accurate number of what our error was.
As it turned out, our data indicated that we measured cosmic rays that were pretty close to the speed of light even with our error. Whether or not the error is within an acceptable range, I don't know. We didn't get to that.
The class itself was enjoyable. I liked the mix of undergraduate students, teachers and graduate students. I think everyone brings something different to the group and its a great way to get other perspectives on the same topic. Prof. Marx and Dima were very helpful and patient even with a ton of emails on the weekends.
ddefigueroa@notes.cc.sunysb.edu
