"Biomaterials Characterization Using Nanoindentation"
Did you ever wonder why it is so hard to break an abalone shell even though it is made primarily of chalk? Or why some polymers are stiff and some are stretchy? Many materials have structures, chemistry, or mechanical properties at the micro- or nanoscale that affect their physical properties at the macroscale (i.e. fracture resistance, strength). In order to better understand the relationships between structure and properties in biomaterials it is important to study natural materials at small length scales. Tools such as scanning electron microscopes let us look at structures at small length scales, smaller than a single human cell. Nanoindentation is a state-of- the-art materials characterization technique that allows us to measure the mechanical properties of materials at equally small length scales. In a nanoindentation test, a small tip is pressed into a sample, creating a small indent. Mechanical properties can be determined by analyzing the resulting data.
Research in Professor Ebenstein’s lab focuses on measuring mechanical properties of biomaterials using this technique. Current nanoindentation projects in the lab include: characterization of cat whiskers using nanoindentation and scanning electron microscopy and measuring the mechanical properties of soft tissues and hydrogels with biomedical applications. The project that you would get to focus on this summer is characterization of stiffness, hardness, and fracture resistance of different artificial tooth (denture) materials for an international dental materials company. || Learn more about Professor Ebenstein.
"Field Investigations of a Slurry Wall"
The STEM scholar will work with Professor Jeffrey Evans and two additional students to perform field investigations of a soil-bentonite slurry trench cutoff wall constructed with a research grant from the National Science Foundation. Slurry walls are widely used to repair dams and levees and to control contaminant transport in the subsurface. The research will include field cone penetration and Marchetti dilatometer testing at our field site near campus intermixed with engineering analysis conducted on campus in the Jeffrey C Evans Geotechnical Engineering Laboratory. The field investigations are aimed at better understanding the in place, post-construction, strength, compressibility and permeability of the completed cutoff wall.
The mixture of field and office research under the mentoring of Professor Evans will provide the STEM scholar opportunity to learn civil engineering principles associated with water and soils and at the same time gain practical field experience so necessary to a successful engineering career. || Learn more about Professor Evans.
"Cognitive Abilities in Primates"
Our lab focuses on discovering what evolutionary pressures may have led to the development of cognitive abilities in primates. To answer this question, we explore how socially housed primates learn, remember, and organize information. By comparing cognitive abilities across individuals within a species and between members of closely related species, we can identify factors that have made cognitive skills advantageous and better understand the origins of our own minds and brains. Students who join the lab will work in the Bucknell University Animal Behavior facility with our non-human primate collection. In addition to coding and analyzing data, students will be involved with conducting behavioral observations and cognitive experiments using touch screen computer technology.
Successful students will have an interest in working with animals, as well as experience (or interest in learning!) computer programming. Ongoing projects include comparative studies of learning, numerical cognition, spatial cognition, and memory. || Learn more about Professor Gazes.
"Sex Differences in Voluntary Exercise"
Females are more active than males in every species examined except for humans, but the causes of this sexual dimorphism are unknown. Our hypothesis is that females engage in more activity as a coping mechanism-- in other words, exercise is especially helpful in reducing anxiety in females, a sex that is well known to be more susceptible to stress. We'll study the behavioral and neuroendocrine response to running wheel access in male and female mice in order to better understand the variables associated with sex differences in voluntary activity. || Learn more about Professor Grisel.
"Investigating How Springs Respond to Storms"
As part on an on-going National Science Foundation project with Temple University, we are examining storm flows at karst springs to interpret flow dynamics in karst aquifers. Karst terrains are characterized by bedrock that dissolves forming caves, springs, sinkholes, and other characteristic features. Water flow in these areas is different than flow in porous media, and our methods of investigation differ as well. Data loggers collect water level, pH, and other data, and automatic storm samplers collect water samples during storms at several sites in the karst of central Pennsylvania. We analyze the water samples for content (including ions, rare Earth elements, isotopes, and carbon) and use the data to assess patterns in how water reaches the springs.
During this project, the STEM scholar will gain experience with field monitoring of springs, processing of geochemical data in the lab, and analysis of large data sets. The scholar will work closely with a rising senior in geology who has been involved with the project for a year. || Learn more about Professor Herman.
"Environmental Impacts of Coal Mining in Pennsylvania"
Over 8000 km of streams in Pennsylvania’s coal mining regions are affected by abandoned mine drainage (AMD), resulting in very high concentrations of iron and sulfate. The processes that lead to precipitation of Fe-bearing minerals and their deposition to the streambed affect the transport and fate of contaminants in these waters. We are particularly interested in the formation and stability of colloids – the very small particles that remain suspended - and their role in contaminant mobility. This project provides an opportunity to work as part of an interdisciplinary team in the environmental sciences. The research involves a combination of sample collection in the field, analyses of AMD water samples, and laboratory investigations of the chemical and hydrological variables that control the composition and stability of AMD colloids. || Learn more about Professors Herman and McGuire.
"High Efficiency Emulsion-based Liquid-Liquid Extraction"
The Jablonski group has proposed an innovative device that combines milli-fluidic emulsion-based liquid-liquid extraction with a continuous passive emulsion separation technique recently developed in the Jablonski laboratory. These novel fluidic devices allow for the co-current laminar flow of immiscible liquids at the 103 m to 102 m length scale and can process liquids at rates of several mL/min. These co-laminar flow devices have successfully been used to passively separate organic-in-aqueous and aqueous-in-organic emulsions.
Early experiments using these co-laminar flow devices for aqueous/ organic liquid-liquid extraction studies to accurately determine mass transfer coefficients have also been successful. The co-laminar flow technique provides an excellent method for determining mass transfer coefficients due to the well-defined interface between the immiscible liquids and the ability to sample the effluent streams immediately upon exiting the device. The proposed milli-fluidic extraction process has improved separation and decreased power requirements when compared with conventional liquid-liquid extraction methods. The proposed method will employ emulsion-forming and co-laminar flow milli-fluidic devices in series, and greater volumetric flow rates will be achieved by stacking several such two-device combinations to operate in parallel. || Learn more about Professor Jablonski.
"Chemical Models of Metalloproteins"
A dozen or so metals from the periodic table are essential for life and about a third of all proteins require metal ions to achieve their intended biological function. Proteins are synthesized in cells without metals and must somehow find the correct one to become active.
We are interested in how nature has tuned the structure of proteins to select for a specific metal ion. We prepare organic molecules (ligands) that mimic the metal binding sites of proteins. We study how mixtures of metals compete for the ligand, with the goal of understanding how the structure of the ligand and its 3D arrangement in space affect metal binding affinity. || Learn more about Professor Kerber.
The STEM scholar will work within the Mather Research Group to prepare and study water-sensitive films comprised of nanofibers. Using a state-of-the art electrospinning apparatus, films will be prepared and then examined with light and electron microscopy. Further, water-induced shrinkage of the films will be quantified by water-immersion and time-sampling of dimensions. Finally, and for the bulk of the project, the STEM scholar will explore water-induced folding of the films.
Our preliminary observations have shown a remarkable effect, for certain compositions, wherein drawing a line of water with a fine paintbrush leads to sharp folding of the thin films with a crease along the line drawn. Explorations surrounding this exciting observation will reveal the extent to which this phenomena can be expanded to the creation of origami structures assembled by paintbrush strokes with water. Knowledge about polymer science, chemical engineering, nanoscience, and manufacturing will be acquired by the student, as will the principle that creativity is a highly valued attribute of successful scientists and engineers. || Learn more about Professor Mather, Dean of the College of Engineering.
"How Chromosomes Communicate with One Another Over a Distance"
The Paliulis group studies the key differences between metaphase and anaphase chromosomes, and one project concerns how chromosomes communicate with one another over a distance. A number of organisms have chromosomes that do not pair and stick together in meiosis I but almost always separate correctly from one another. Somehow the position of one chromosome is "communicated" to its partner chromosome.
We have been studying this phenomenon in spiders (black widow and yellow sac), showing that partner chromosomes only complete meiosis I when they are correctly positioned relative to one another. We are currently examining Mesostoma ehrenbergii, a flatworm with multiple chromosomes that display distance interactions. || Learn more about Professor Paliulis.
"The Physics of Chaotic Mixing, Propagating Reaction Fronts and Bacterial Swimmers"
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 currently testing theories of "burning invariant manifolds" (BIMs) that predict barriers impeding the motion of fronts in simple two- and three-dimensional flows. We are also studying BIM-like barriers that impede the motion of bacteria swimming in fluid 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 or culturing the 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. || Learn more about Professor Solomon.
"An Analysis of Nitrogen Fixing Cyanobacteria Found in the West Branch of the Susquehanna River
Cyanobacteria are bacteria that obtain their primary source of energy through the process of photosynthesis, which involves using light to convert water and carbon dioxide into sugars and oxygen. In addition to their photosynthetic capabilities, cyanobacteria have many additional metabolisms important to the function of the ecosystems they inhabit; many cyanobacteria are nitrogen fixers. Previous research has produced a picture of the cyanobacterial community in the river that could contain nitrogen-fixing species. However, none of the organisms actually isolated from the river have the genes indicating they are capable of nitrogen fixation. Moreover, SR411 fails to survive when exogenous nitrogen is not supplied in the media. An additional strain of cyanobacteria has been isolated from the river and its nitrogen fixing ability will be studied.
Given the conserved nature of the genes involved in nitrogen fixation, we can use degenerate primers to amplify genes in metagenomic DNA samples to identify the prevalence of this metabolism in the river environment. Gene amplification and PCR will be used to examine the genes of particular strains and determine the nitrogen fixation capabilities. We will be able to compare the metabolism specific analysis of the river community to the community analysis conducted previously. The analysis last summer looked only at “who” was in the community and not at their metabolic capabilities. This project will give a glimpse into specific metabolisms that contribute to the productivity of the river community. || Learn more about Professor Stowe.
"Imaging Forces and Jammed Granular Materials"
Our lab focuses on experimental studies of granular materials and multiphase flows, such as particle-fluid suspensions. In these "complex systems," relatively simple building blocks interact through nonlinear forces such that complicated behavior emerges. For instance, a large number of solid grains interacting simply through friction and collisions can produce the sudden avalanching of a hillside or the spontaneous plugging of supply lines in industry. This striking phenomenon, known as the jamming transition, depends on factors such as the local geometry of particles and stresses in the system, which are carried through a complex network of force chains. We study simplified lab-scale experimental models of these granular/fluid systems to characterize jamming and flow.
Specific goals for this summer include using photoelastic grains, which are made of a material that light up when stressed between polarizing filters, to image the complex network of force chains. While we have completed a number of 2D experiments, the goal is to extend the method to image static 3D systems. This project will involve constructing an experimental apparatus, analyzing video data through computer-aided image analysis, and extracting quantitative and statistical information about the force networks. || Learn more about Professor Utter.
"Bottom-up Cracks in Expansive Soils"
Expansive soils are being increasingly used as structural soil in foundations and embankments. Desiccation cracks, extending down from the soil surface are very common in expansive soils. But, even in some structurally engineered expansive soils under loading, crack are being noted that seem to extend from the bottom and extend upwards, as bottom-up cracks, These cracks are more prevalent in dynamic loading conditions (vehicular traffic for example). Internal stress distribution plays an important role in the initiation and propagation of desiccation cracks, but it is generally suggested that bottom-up cracks are due to external loading. Similar to desiccation cracks, this research postulates that the initiation of bottom-up cracks are not due to external loading, but are due to the internal stress distribution, but the propagation of these cracks are then due to external loading after crack initiation.
A STEM Scholar involved with this research would work on state-of-art-equipment. This research involves the use of triaxial equipment that allows the application of both air and water phases on soil. This research may also involve the use of a micro computed tomography or micro CT scanner which would help in analyzing movement of water within the soil's void-spaces and the connectivity of the void spaces to help characterize crack initiation in compacted expansive soils. || Learn more about Professor Walton-McCauley.
"Analysis of Cyclical Fatigue Performance of Parts Fabricated by Additive Manufacturing"
Additive manufacturing (AM) methods (such as 3D printing) are capable of fabricating components having complex geometrical shapes in a single step process. Although traditionally used for rapid prototyping, AM methods are evolving into manufacturing processes intended to produce functional components for end use in marketable products. This advancement requires that a thorough understanding of the mechanical properties and behavior of AM parts exists.
This project is an extension of ongoing research focused on the cyclical fatigue performance of AM components. A STEM scholar who joins this effort will be working together with another undergraduate researcher involved in the design, fabrication, residual strength testing, and performance analysis of AM specimens made by fused deposition modeling and subjected to cyclical loading. || Learn more about Professor Constance Ziemian.
"Computational Analysis of the Stability of Structures"
This project is an extension of ongoing research that has established guidelines for the implementation of a novel computational method for the stability design of steel structures. In contrast with previous practices, this methodology explicitly includes all significant factors (directly affecting structural stability) within the analysis model. This computational method was recently specified by the governing body for the design of steel structures, the American Institute of Steel Construction. Current research is focused on developing, performing, and analyzing related validation studies. A STEM scholar who joins this effort should be interested in studying one or more of the interdisciplinary aspects of this project, including the implementation of computational analysis methods using MATLAB, the development of the graphical user interface needed to perform the analyses, and/or the mechanics-based analysis of structural systems. || Learn more about Professor Ronald Ziemian.
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