Home Institutions and Research Projects of 2004 REU Program Participants The SRI REU program assigns each student to work with a staff scientist on a separate research project. Typically these projects are a sub-task in a larger research program of the mentor. Some of these projects are independent with the mentor overseeing the students progress on a daily basis. The majority of the projects are experimental, with the student working in the laboratory side-by-side with a Ph.D. staff member. Since the student projects are each individually supervised, the SRI program can accommodate students with different starting and ending dates.
2004 REU Projects at SRI Christina Baer ( Wellesley College ) A green line located at 557.7 nm can be distinguished in spectra of the nightglow. The appearance of this line, characteristic of oxygen, demonstrated that the airglow could be associated with the photodissociation of O2 . In addition, another spectral line characteristic to oxygen is visible in the nightglow spectra, located at ~630 nm. While referred to as the “red line,” this spectral feature actually consists of two separate red lines occurring at 630 and 634 nm. In my experiments, atomic oxygen is produced by the photodissociation of molecular oxygen at 157 nm, the product atomic states are O(1D) and O(3P). The transition from the excited O(1D) state to O(3P), the ground state, produces a 630 nm emission (the red line) which can be detected by a photomultiplier tube (PMT) with the help of an interference filter or a monochromator . By varying the intensity of the laser light or composition of gas in the cell, it is possible to control the concentration of atomic oxygen in the resulting gas mixture. The evolution of the O(1D) concentration over time will be determined by studying the time dependence of the red line intensity. From this data, it is possible to determine the O(1D) + O(3P) rate coefficient. As of August 20th the initial experimental goals determined for this summer have been met. Despite our difficulties maintaining laser power from day to day, we managed to take data which allows us to calculate a preliminary rate constant for the deactivation of O(1D) by O(3P). Our initial values indicate that the constant is about 2 orders of magnitude slower than previously thought. Many more experimental checks must be made before we are certain that our data actually corresponds to the O(1D)+O(3P) collision. Analyzing the data and coming to understand the theory behind the O(1D) experiment was a truly valuable experience; forcing myself to work through the differential equations was not particularly pleasant but my understanding of the processes underlying the experiment definitely improved. In addition to working on the O(1D)+O(3P) experiment, I also had the opportunity to work with Rhiannon on her experiment concerning ammonia ice and hydrocarbons. It was a great opportunity for me to be involved with such different experiments; taking data on both setups exposed me to many different experimental techniques and allowed me to have more hands-on time in the lab. I only wish I had more time to follow through with my experiments, I feel like I've come to a deeper understanding of my experiment just in time to leave. I have really enjoyed working for Kostas , his enthusiasm, patience and inherent teaching ability greatly enriched my entire experience at SRI. The REU program offered me the chance to work with professional scientists in a research environment, an opportunity that is not available at Wellesley . Participating in experiments and interacting on a daily basis with the scientists in MPL allowed me to see what a career as a research scientist entails and I can't emphasize enough the importance of that experience. Zachary Campbell ( Texas A&M University ) Laboratory experiments were performed on mixtures of N2 , O2 , O3 , and CO2 gases. We excited the oxygen molecules in the mixture with one laser and detected the excited molecules with a second laser. We used REMPI ( R esonance E nhanced M ulti p hoton I onization) techniques in which only a particular excited species was ionized and detected by measuring the ion current. Varying the delay between the laser pulses allowed us to study the dependence of the concentration of particular O2 excited states. In the first part of the project, I became well acquainted with the experimental apparatus and assisted Dr. Dušan Pejaković and Dr. Rich Copeland in performing measurements of the rate constants of the reactions O2 ( X , ν= 1) + O and O2 ( a , ν= 1) + O. In the second part of the project, I independently performed measurements of the rate constants of the reactions O2 ( a , ν= 1) + O2 and O2 ( a , ν= 1) + CO2 at temperatures of 240 K and room temperature. Our measured room temperature rate constants are consistent with earlier SRI measurements, and the O2 ( a , ν= 1 ) + O2 rate constant does not show significant variation between room temperature and 240 K. However, the O2 ( a , ν= 1) + CO2 rate coefficient at 240 K is ~20% lower than that at room temperature. Yu Gu ( Cornell University ) I have accomplished three goals this summer. 1) I built a setup with a tunable diode laser with a range of 1520-1580nm, an Erbium-doped fiber amplifier, and a custom-designed microscope. 2) I showed that water droplets from 100um to 1mm could be moved and combined using the infrared beam. 3) I repeated a simple protein detection assay performed earlier by Ken (Horseradish Peroxidase + ABTS) with the new setup. I have also started the design process for performing performing further molecular analysis. In particular, I have done drawings for the creation of a doughnut-shaped beam using an axicon lens. The first eight weeks of the summer were devoted to building the setup and the microscope. I spent three weeks performing experiments and brainstorming about molecular analysis. Future work includes increasing the range in droplet size, maintaining a high contact angle, and facilitating molecular analysis. Andy Knyazik (University of California-Santa Cruz) My goal for the summer was to build an apparatus that will be used to demonstrate effects of Rayleigh and Brillouin Spectroscopy in supercritical fluids. The name of the technique is stimulated gain spectroscopy, which is when a powerful pump beam interferes with a probe beam. The signal spectrum of the probe beam is then measured, in which I plan to see traits of Rayleigh and Brillouin scattering. Throughout these 12 weeks, I intended to learn a lot about optical equipment and its practical applications, by using it to create our apparatus. I learned to work with mirrors, lenses, spatial filters, isolators, amplifiers, polarizers , half- and quarter- waveplates , and fibers. I believe I have achieved most of my goals for this summer, as I will illustrate below. I have built a system that took the output of an Nd : YAG laser operating at 1064 nm, separated it into probe and pulse beams, and interfered these in a sample cell further along the optical path. To create a pump beam I double passed a weak narrow-band laser through two gain amplifiers operating at 10 Hz. I optimized the two spatial filters that followed each gain amplifier, which would only keep the desired fundamental spatial mode passing through and block all other amplified modes. The probe laser was generated from the seed laser with a beam-splitter. I sent the probe beam through a single-mode fiber to filter out unwanted modes, and later on focused it inside a cell, where it interfered with the focused pulse beam. The probe beam then went inside another fiber where the output was monitored with a photodiode connected to an oscilloscope in order to detect the scattering of interest. Optimizing the amplification while keeping lasing under control took a lot of time, and therefore I did not collect any scattering signals inside supercritical fluids. The losses that the probe beam has when it passes through a single mode fiber are also very disappointing: I am only getting 25 tO30% of the power through the fiber. The apparatus otherwise is optimized and is done well enough to perform the scattering measurements. Rhiannon Meharchand ( Florida State University ) I began the summer by trying to climb the steepest learning curve imaginable. I spent a lot of time figuring out what spectroscopy was, and why on Earth (or Jupiter, for that matter) anyone would need it. I also spent a good deal of time familiarizing myself with the apparatus, and trying not to break things. I learned about Jupiter, and quite a bit about various spectroscopy experiments that had taken place with ammonia. Everything was quite confusing in the beginning, but things started to work out for the better as the summer continued. By mid-summer, I had figured out how to run experiments by myself and not break too many things (although I'm pretty sure the ion gauge and turbo-molecular pump hate me a little). I spent a lot of time collecting data, in an attempt to figure out how to get spectra that look like the literature. There were also a few weeks during the middle of the summer where I attempted to figure out what the data meant and where to get the constants and figures needed for calculations. This led me to the conclusion that Google hates me a little too. Throughout the summer we took various trips to companies and research facilities in the bay area, which was very enlightening. I had never seen the for-profit/industrial side of research, and I feel like a whole new horizon of opportunity was laid out for me during our trips. The end of summer rush was exhilarating. Experiments started to work, things started to make sense, and I started to become a little sad that everything would be ending soon. All considered , I discovered the following things: 1) It is possible to obtain and suppress ammonia features in the infrared absorption spectra by coating the ammonia films with hydrocarbons. 2) 12 weeks may seem like a long time, but it is nothing in the world of research. 3) I like the world of research. I never quite believed that this was a field that I could go into, but this summer has shown me that anything is possible once you just get over how little you know and jump in headfirst. I'm much more confident in my abilities now, and much more aware of what skills I will need for the real world. I had a wonderful summer, made a lot of new friends, and discovered a little bit about myself in the process. Thank you so much for the opportunity. Nader Moussa ( North
Carolina State University ) Some of the difficulties I faced this summer involved the implementation of the computer model. I worked in FORTRAN-77, which was a good experience with scientific computation, very different from my school curriculum in computer science (which is geared towards "modern business programming" techniques). The idiosyncrasies of this language provided a fun challenge. I also applied many techniques from diverse fields to implement my geometric model, which used Truncated Octahedron shapes instead of cubes for the individual ceramic grains. Turning these complex shapes into program-code exercised my skills in vectors and matrices. Lastly, I developed a good understanding of the timing, scheduling, and other issues involved in a research environment. These skills are independent of the project I worked on, and will be very portable to future work. My experience at SRI was fantastic. The work was stimulating and fun; the environment was conducive to productivity, with a great deal of self-direction. This gave me the opportunity to work at my own pace, which I think made for a balance between productivity and learning. In summary, I enjoyed working here this summer, and will definitely consider coming back in the future. Adam
Percival ( Reid College ) The primary goal of the summer was to complete an upconverting chelate -based immunoassay in a microscopic format including matrix effects for a cell culture. Completion of this assay would meet the requirements of our funding milestone, allowing further work in this area to proceed. To assist in achieving this goal, I performed a number of experiments. For erbium chelates , I helped investigate different chelating agents (DPA, DTPA, and DOTA) and excitation mechanisms (one-color excitation at both 810 nm and 980 nm, as well as two color 810 nm plus 980 nm). We found that we could produce upconversion using all three excitation methods, and that the best chelating agent was DPA, followed by DTPA and then DOTA. Secondly, we spent some time investigating the potential of silver island films to enhance the signal from lanthanides. In preliminary experiments using Eu -DTPA, we were able observe an increase in signal strength by a factor of ten in the chelate solution on a silver island film slide, as compared to an ordinary glass slide. In addition, we observed a significantly decreased fluorescence lifetime in the chelates on a silver island film compared with those on glass, as predicted by the theory of silver nanoparticle enhancement of electromagnetic fields. This provides us with further experimental confirmation that we are observing a true enhancement of our signal from the silver island film. Finally, I performed a number of experiments relating to a co-fluorescent solution that can be used for enhancing the signal from our chelates . Despite difficulties in reproducing the results from our experiments, and a number of problems resulting from europium contamination, we were able to consistently show a significant increase in our signal strength due to the co‑fluorescent solution. Unfortunately, to date it has been difficult to quantify this enhancement and determine our detection limit, due to poor reproducibility. We also are not yet certain of the extent of the europium contaminant in gadolinium of different purities, or of how the signal strength changes as the europium concentration varies. As a result, the co‑fluorescence technique is not quite to the point where it can be really useful in our assay, although several experiments that attempt to resolve these issues are currently in progress. Núria Queraltó ( Ramon Llull University , Spain ) In order to study all these processes I've been involved this summer in the research project "Oxidation of refractory ceramics in dissociated oxygen" with Dr. Jochen Marschall . My main goal was to study t he effect of dissociated oxygen on the oxidation of Si , polycrystalline SiC and LPCVD Si3 N4 . These systems are less complicated than UHTC and allow a better understanding of the processes involved in the oxidation. One of the steps was to investigate the oxidation environment because we really didn't know how many oxygen atoms are involved in the process. We ran some experiments measuring pressure and temperature at different points of the system. We have concluded that to know exactly the amount of oxygen atoms we would need a laser technique. In any case, we have estimated the loss of oxygen atoms due to the recombination process along the tube. Another step was to run some experiments changing the oxidation conditions like time or temperature. With these results we have been able to fit the data to the oxidation equation of Deal and Grove. From this part we have extracted some rate constants that have helped us to understand better the overall process. We have used two gases to obtain atomic oxygen: molecular oxygen (O2 ) and nitrogen oxide (N2 O). The first one was less dissociated than the second one because the bond between the nitrogen and the oxygen of the nitrogen oxide is weaker than the bond of the molecular oxygen, which is not 100% covalent. According to this, when we used N2 O instead of O2 the samples were more oxidized. There's a lot of controversy about which is the species that is diffusing through the silica layer. Everybody argues about three candidates: O2 , O, O2 - . After reading in the literature we believe that molecular oxygen is the one diffusing. In this hypothesis atomic oxygen remains in the surface when we dissociate the molecular oxygen and then recombines into molecular oxygen and diffuses. Nevena Rakuljic ( University of California , San Diego ) There are two measurement techniques that are used at SRI to characterize a tissue—a CW imaging and fiber optic frequency domain instrument. My job this summer has been working on the imaging setup for the frequency domain. I built a light intensifier circuit which detects light coming out of the rodent that allows us to separate absorption from scattering, and thus to quantify the characteristics of a tissue. The modulation frequency of the light and the detector is in the 100 MHz range. The detector is based on modulating the gain of an image intensifier at a frequency offset from the modulation of our source light, which allows us to look at the heterodyne detection of the signals. The intensifier acts as a mixer of the frequency offset optical signal and the 100 MHz amplified signal. This information allows us to compare RF amplitude and phase before and after entering the tissue, as well as the change in DC amplitude. Plugging this information into the frequency domain equation, we are able to quantify the values of absorption and scattering of the tissue, which are the numbers that we seek. The stability of the light source that has been mentioned in my goals statement has been addressed as well. Moreover, as we have realized, laser diodes are stable enough for our experiment (in terms of temperature), and thus all that needs to be done is purchase a couple of diodes at different NIR wavelengths, with the necessary power of 1 Watt or more. I have been imposed with many problems that I had to solve, such as impedance matching, dealing with RF pick-up and increasing the modulation depth of our signal. My electronics background has helped me, but without help of my mentors would not have been sufficient to successfully complete this portion of the project. Working in SRI has definitely been beneficial to my future career, and has helped me get a better grasp in the field of applied electronics. Brock
South (Rose-Hulman Institute or Technology) My contribution to this larger project for the most part dealt with improving the latter characteristic: selectivity. I set out to determine if the fragmentation patterns of the chemical agent simulant molecules change in a reproducible way as the wavelength of the ionizing photons changes. This could provide a highly selective means to identify particular agent molecules if there proved to be fragment pattern changes unique to each molecule. I collected and analyzed three-dimensional signal intensity vs. wavelength and mass spectra of two agent simulants under various conditions of temperature, laser focusing, and ionizing wavelength. The end result of my studies showed that each fragment of these simulant molecules behaved in the same way when the wavelength was scanned over the range of 270 nm to 250 nm. This means that there were no patterns appearing that could be used to uniquely identify the simulants in this wavelength region. Consequently, I showed that wavelength scanning in the investigated wavelength range was not a good route to take. My studies, however, opened up another possible route having to do with the power density of the laser beam in the ionization region which ultimately could greatly simplify the current system without limiting its potential usefulness as a detector. In addition to my project goals, I had many personal goals for this passing summer. I was able to absorb knowledge pertaining to a variety of fields—organic chemistry, laser physics, chemical agent studies, and mass spectroscopy. I had never worked with or even seen a mass spec system before this summer, and I certainly had not even a clue how they worked. Now I can say that I have a comfortable working knowledge of time-of-flight mass spectrometers—at the least, I could probably pick up and use similar time-of-flight mass specs without much training or hassle. In working with this system, it was required of me to learn some simple organic chemistry naming rules. I had seen chemical names quite a bit in my schoolwork, but it wasn't until I sat down with them here that I actually figured out that they really do correspond well to the structure of the molecules. Also, while working with the system I became reasonably familiar with the mass spec's laser system. Over the course of the summer I picked up a great deal of knowledge about chemical agents—what they are, what they do, how to detect them, and so on. If nothing else, that information is interesting, if perhaps not directly applicable in the near-term. What I will probably be using very soon, however, are the basic lab skills I honed during these months. These range from simple laser safety techniques to the habit of keeping a thorough lab notebook—honestly, the latter hadn't been a priority of mine until I learned firsthand the impossibility of keeping your figures and procedures just by memory even over the course of a week. Indara Suarez ( Pasadena City College ) Allison
Widhalm (University of Southen California ) In addition, the large telescopes have been used to study the atmosphere of Venus, and we have found both similarities and differences in the emission from the two environments, with the common thread being emission from oxygen atoms and molecules. We study the various emissions from both the earth and Venus to learn how the atmosphere changes in an hour, a night, a season, and a solar cycle. Work on this project involves learning how to handle the data files, and represents a unique opportunity to explore our environment as made accessible by the world's largest telescopes. Molecular Physics Laboratory REU 2004 Program Activities • Tutorial Seminars • Student Presentations • Academic/Industrial Visits • Social Events 1. Tutorial Seminars REU 2004 Tutorial Seminars
2.
Student Presentations REU 2004 Student Presentations
3.
Academic / Industrial Visits • On June 30, 2004, we visited and had a tour at SLAC in the morning, followed by a visit and tour of the laboratories of Profs. Steve Chu and Hongjie Dai at Stanford's Bio-X, Applied Physics, and Chemistry Departments. • Visit to Google Headquarters in Mountain View on (7/23/2004, host: Dyana Wong) • Visit to Intuitive Surgical in Sunnyvale (8/2/2004, host: Tom Nixon) • Visit to Arcturus Bioscience in Mountain View (8/12/2004, host: Tom Baer) • Tour and operation of SRI's Scanning Electron Microscope (SEM) Facility (7/28/2004, host: Jordi Perez) • Visit to SRI's Artificial Intelligence group and introduction to their robotics technologies (8/4/2004, host: Regis Vincent) • Tour of SRI's Engineering Demo Room and introduction to SRI's artificial muscle and diamagnetic levitation technologies (8/10/2004, host: Roy Kornbluh ) 4.
Social Events Contact Us:
For more information about SRI's REU Program, contact |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
About Us 
R&D Divisions Careers Newsroom Contact Us
©2008 SRI International 333 Ravenswood Avenue, Menlo Park, CA 94025-3493
SRI International is an independent, nonprofit corporation. Privacy policy