Summer Research Projects for Bucknell Students
Click on the project name for a more detailed description of the project
Project Name: Chaotic mixing, propagating reaction
fronts, and swimming bacteria
Project Mentor: Tom Solomon
Project Code: (THS-1)
In a forest fire, the dividing line between burned and unburned trees is called a front. The motion of this front determines how the fire spreads through the forest. Similar front dynamics characterize the spreading of a disease in society, as well as numerous chemical processing applications, biological processes in cells and developing embryos, and plasmas in fusion reactors. We are currently conducting experiments that explore how the motion of fronts is affected by fluid mixing, e.g., forced flows in a chemical processor, winds in a forest fire, or the motion of people in society while a disease spreads. Table-top experiments using a simple chemical reaction (the well-known Belousov-Zhabotinsky reaction) focus on how fronts are affected by simple flow patterns -- vortices (whirlpools) and jets.
We are testing theories of "burning invariant manifolds" that predict barriers that stop the motion of reaction fronts in laminar (smooth) fluid flows. We have already done several experiments that have verified these predictions in two-dimensional flows, and we are currently extending these experiments to three-dimensional fluid flows.
We have also initiated studies of the motion of swimming bacteria in fluid flows. It turns out that the same theories that predict barriers for the motion of chemical fronts also predicts barriers in the motion of mutated "smooth-swimming" bacteria. We are doing experiments that study these barriers for bacteria swimming in microfluidic channel flows.
There is a lot of "hands-on" work involved in these projects, including the designing, building and testing of the experimental apparatus, mixing chemicals for the reaction, culturing of bacteria, and doing numerous experimental data runs. The experimental work also involves a substantial amount of computer-aided image analysis, almost exclusively on Linux workstations running a program called IDL. We also frequently conduct numerical simulations of the phenomena, also with IDL. Although experience in computer analysis is useful, it is not required as long as the student involved is willing and eager to learn IDL.
Project Name: Jamming and flow of granular
and granular-fluid materials
Project Mentor: Brian Utter
Project Code: (BU-1)
The stability and flow of granular and granular-fluid systems (individual solid grains with or without an interstitial fluid) exhibit striking features with implications for both industrial processing and natural phenomena such as erosion and slope failure. In these complex systems, many simple building blocks interact through nonlinear forces such that complicated behavior emerges, such as the sudden and unpredictable avalanching of a slope of frictional grains. We perform experimental work to study these granular flows, particularly at the jamming transition, this transition between static and flowing regimes.
Specific experiments for this summer may include the jamming of granular suspensions in microfluidic networks related to filtration and plugging of porous materials, use of photoelasticity (a tool in which light transmitted through a material is related to the local force acting on it) to measure sparse force networks in three dimensional granular suspensions, or similar experiments imaging and characterizing granular flows. This work generally includes a fair amount of “hands-on” construction of experimental apparatuses and experimental optimization and measurement. Data collected will be processed using image analysis to extract useful quantitative statistics from image sequences of the experimental flow. We use a program called IDL to facilitate this analysis, but no prior programming experience is required.
Project Name: Non-equilibrium Thermodynamics and Quantum Statistics
Project Mentor: Martin Ligare
Project Code: (MKL-1)
Most introductory thermodynamics is limited to the study of systems in equilibrium. Recently there have been many advances in the field of classical non-equilibrium thermodynamics, and in this project we will generalize these advances to quantum systems of identical particles to study how the bosonic or fermionic nature of the particles in the system effects the thermodynamics.
Recent observations of anomalous light propagation include light that refracts "the wrong way" in so-called negative-index materials, "superluminal" light that appears to travel faster than the speed of light c, and ultraslow light. I have investigated theoretical models in which the electromagnetic field and the medium are both treated in a fully quantum mechanical manner in order to understand these anomalous effects at the level of a single photon. Topics for investigation in the summer of 2015 might include the following:
- Photon transport in metamedia with negative index of refraction
- Negative group velocities in media with gain
- Photon propagation in evanescent waves
- Photon transport and localization in disordered media
This project will involve theoretical calculations and work with a computer algebra system. Applicants for this project should have completed a quantum mechanics course at the junior/senior level.
Dynamics of integrable quantum many body systems
Project Mentor: Deepak Iyer
Project Code: (DI-1)
In this project, we will apply a recently developed formalism to study the dynamics of one-dimensional systems that are integrable, i.e., they have an infinite number of conserved quantities. These models show unique away from equilibrium behavior -- for instance, they violate the ergodic hypothesis. We will study these models under a variety of dynamical situations, and try to explain their behavior using computational tools.
Localization in disordered nonlinear classical systems
Project Mentor: Deepak Iyer
Project Code: (DI-2)
In the presence of disorder, like random scatterers, several systems that support waves undergo "localization", i.e., waves that start at one end are unable to reach the other. One can also think of it as becoming insulating. When one adds nonlinearities to the story, some of this localized behavior goes away, and there are as yet many open questions regarding the onset of such "delocalization", how it occurs in classical vs. quantum systems, and whether one can make any universal statements about the phenomenon. We will study this using numerical methods to solve the partial differential equations that describe these models.
A large number of phenomena are explained by studying so-called "lattice models", which essentially describe the dynamics and collective behavior of particles hopping around on a discrete lattice. For instance, ferromagnetism can be described very well by a simple model called the Ising model involving spins interacting on a square lattice. A variety of techniques have been developed to study and solve such models, and some work better than the others. Our goal here is study why one particular method, "linked cluster expansions", is very efficient at obtaining the thermodynamics of unordered phases. The method involves the use of sublattices (called lattice animals for their varied shapes) to build up the lattice, and it is as yet unknown what aspect of this counting allows an efficient solution. This project will study the combinatorics of these sub-lattices in detail using numerical and analytical techniques to get at this problem.
Project name: Development of low-noise electronics
for atomic magnetometry
Project Mentor: Ibrahim Sulai
Project Code: (IS-1)
The interaction of atoms and magnetic fields can be exploited to make extremely sensitive magnetic field detectors. Such atomic magnetometers have applications ranging from medical imaging to fundamental physics. In order to realize the promise that using large numbers of atoms to detect magnetic fields, other sources of noise and interference must be understood and eliminated. Most physical systems have characteristic noise distributions that decay with frequency – the so called “1/f noise”. This poses a challenge for detecting signals at low frequency. The first project for the summer involves designing and characterizing low noise current supplies in the 0 to 10 Hz range. A second and related project involves developing electronics that can achieve photon shot noise limited detection of laser intensity. The student will learn the basics of atom – light interactions, as well as experimental techniques in the field. Applicants should have taken PHYS 235.
Project Name: Discovering Planetary-mass Brown Dwarfs
Project Mentor: Katelyn Allers
Project Code: (KNA-1)
Brown dwarfs (objects with masses too low to sustain hydrogen burning) are the bridge between planets and stars. Young brown dwarfs are particularly exciting as objects with masses in the range of extrasolar planets are within the reach of direct observations in the near and mid-infrared. This project involves reducing and analyzing images of star-forming regions to identify new planetary-mass brown dwarfs. This project may involve planning and executing observations. Familiarity with IDL or Python is desirable but not required.
Project name: Eclipse Manager for Total Solar Eclipse, 21 August 2017
Project Mentor: Ned Ladd
Project Code: (NL-1)
On Monday, 21 August, a total solar eclipse will sweep across the United States, starting on the Oregon coast, and finishing the the Atlantic Ocean off the shores of South Carolina. More than 200 million Americans live in or near the path of totality. We are mounting an expedition to observe and document the eclipse from a site in South Carolina. The summer student Eclipse Manager will participate in the planning and execution of this expedition. Duties will include:
- eclipse planning and logistics
- design of the observational program
- field testing of astronomical equipment
- documentation of the event through social and traditional media outlets
Contact Information:Professor Tom Solomon