Stress Analysis of a Sheared Athermal System with Pins

Numerous studies have investigated the jamming transition in granular media. Recent research has indicated that quenched disorder in the form of fixed pins provide additional stabilizing forces to the system, which causes the jamming threshold to decrease and therefore provides a fourth degree of freedom in the jamming transition. Using molecular dynamics simulations, we study a two-dimensional, granular system subjected to a wall-driven flow in the vicinity of jamming in order to understand how pins affect the dynamics of the system. We implement a shear by freezing the top and bottom of the binary mixture, and move the walls at a constant shear rate. The system is a 50:50 binary mixture with purely repulsive harmonic interactions of size ratio 0.004:1:1.4 of pins:small:large particles. Pins are located on a square lattice. We will present results concerning shear stress and pressure as a function of packing fraction and strain rate. We will also show preliminary results for the statistics of the shear stress as function of time.

Continue reading Michael Bolish »

An Analysis of the Transportation of Metals and Trace Metals in an Abandoned Mine Drainage Treatment Site
Abandoned mine drainage (AMD) is a contaminant problem that watersheds across the United States face. AMD is the result of water traveling through abandoned mines, dissolving harmful metals into the water, which is then brought out into streams and rivers. These toxic metals can cause harm to aquatic life, and can affect recreational activities. The treatment site known as scarlift site 15 works to remove iron from the contaminated water and lower the pH. The main goal of this research was to analyze the travel and transportation of these toxic metals in scarlift site 15, a passive mine drainage treatment site located in Ranshaw, PA.
Water samples from the treatment center were collected, filtered, and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography (IC). These results were used to observe the patterns of where the metals precipitated in the system. These patterns were used in conjunction with the size of the particles in order to see if they were traveling attached or with another metal.
Cobalt, nickel, and zinc all follow the trend of precipitation out of the water that aluminum has. Iron primarily comes out without other trace metals, implying that the trace metals were finding another way out of the water. In the system, the iron was not coming out from the treatment within the system, but rather it was precipitating out of the water from sitting in the pools of the treatment site.

Continue reading Hannah Schultheis »

Solanum acanthophisum: a new dioecious bush tomato species from the Australian Monsoon Tropics
Estimates suggest that over 70% of the Australian flora and fauna has yet to be scientifically described. Numerous new plant species are still being described each year from across the continent. Here, we investigate a potential new species represented by just a few herbarium collections made in the remote Deaf Adder Gorge of Kakadu National Park, a biodiversity hotspot and UNESCO World Heritage Site. The new taxon was previously suggested as a possible localized variant of the functionally dioecious Kakadu endemic Solanum asymmetriphyllum and close relative of its sister species S. sejunctum. Using seeds removed from a herbarium sheet, a single ex situ plant was grown and used to assess more than 30 morphological characters to document the differences among S. asymmetriphyllum, S. sejunctum, and the putative new species. Morphometric analyses provide evidence that the three taxa are distinct from one another and support the segregation of the Deaf Adder Gorge variant as Solanum acanthophisum sp. nov. The specific epithet, “acanthophisum” is derived from the generic name of the sympatric death/deaf adder snake, Acanthophis praelongus. Solanum acanthophisum is now one of three recognized Solanum species occurring in Kakadu that exhibit functional dioecy, a sexual system in which morphologically bisexual flowers produce non-functional inaperturate pollen.

Continue reading Claire Marino »

Investigations into the compressive behavior of a Miura-ori folded structure

Structural origami is an emerging field that combines the Japanese art of paper folding known as origami with structural engineering in order to assess the structures that can be created and their enhanced properties, such as compressive capacity and deformation pattern. Using an origami fold known as Miura-ori, a series of geometrical models were created representing three different angles along with two different thicknesses of the thin walls. The specimens were printed using plastic material called Polylactic Acid (PLA). A testing jig was designed and fabricated for the origami specimens to model a boundary condition with no translation during testing. The resulting deformation from compression testing appeared to follow a relatively consistent pattern of buckling, with some cracking and splitting happening on one edge. The specimens with a shallower angle could withstand less load. This correlates with elastic buckling theory as the height and width of the plates in these specimens are greater, and larger plates will buckle at a lower load. Further testing is needed to ensure the repeatability of these results. In addition, future research is needed to consider the deformation behavior of the individual plates to confirm whether the failure mode is buckling or a combination of crushing and buckling.

Continue reading Iona Pitkin »

Segregation of the Univalent X Chromosome in the Two-striped Planthopper Acanalonia bivittata

Correct segregation in meiosis I depends on homologous chromosomes pairing to form bivalents. To achieve a successful reduction in ploidy, bivalents align on the metaphase plate and then homologues segregate during anaphase I. While bivalent formation is generally required for correct segregation in meiosis I, many organisms pose an exception to this requirement. Our objective was to study one such exception, the two-striped planthopper Acanalonia bivittata (Hemiptera, Auchenorrhyncha), which has a univalent X chromosome. A. bivittata were collected and their identification was confirmed through DNA barcoding. Chromosome number was found to be consistent with previously published karyotypes for the species. To observe the behavior of unpaired chromosomes in male primary spermatocytes, live-cell and confocal imaging of stained cells was conducted. The univalent X chromosomes were found to be characterized by independent and delayed segregation that occurred after autosomal segregation during early anaphase I. Delayed segregation of the univalent chromosome was associated with the loss of microtubule connections to one spindle pole, leaving the chromosome aligned on the metaphase plate, often in a position outside the main spindle body. This study characterized the behavior of an unpaired chromosome in an alteration to the traditional meiotic program. This work has translational implications in organisms in which a chromosomal pairing partner is lost, such as the diminution and potential loss of a Y chromosome in mammals.

Continue reading Ashley Borseth »

Segregation of the Univalent X Chromosome in the Two-striped Planthopper Acanalonia bivittata

Correct segregation in meiosis I depends on homologous chromosomes pairing to form bivalents. To achieve a successful reduction in ploidy, bivalents align on the metaphase plate and then homologues segregate during anaphase I. While bivalent formation is generally required for correct segregation in meiosis I, many organisms pose an exception to this requirement. Our objective was to study one such exception, the two-striped planthopper Acanalonia bivittata (Hemiptera, Auchenorrhyncha), which has a univalent X chromosome. A. bivittata were collected and their identification was confirmed through DNA barcoding. Chromosome number was found to be consistent with previously published karyotypes for the species. To observe the behavior of unpaired chromosomes in male primary spermatocytes, live-cell and confocal imaging of stained cells was conducted. The univalent X chromosomes were found to be characterized by independent and delayed segregation that occurred after autosomal segregation during early anaphase I. Delayed segregation of the univalent chromosome was associated with the loss of microtubule connections to one spindle pole, leaving the chromosome aligned on the metaphase plate, often in a position outside the main spindle body. This study characterized the behavior of an unpaired chromosome in an alteration to the traditional meiotic program. This work has translational implications in organisms in which a chromosomal pairing partner is lost, such as the diminution and potential loss of a Y chromosome in mammals.

Continue reading Ashley Borseth »

Developing an Assistive Technology to Support Effective Note-Taking Skills

Many students utilized note-taking strategies to record information for classes. Studies have shown effective note-taking techniques are critical for all students’ academic performance. The purpose of this research study is to investigate note-taking support for college students with Learning Disabilities (LDs) and English Language Learners (ELLs) by answering these three research questions: (1) What types of note-taking support are available for college students with LDs and ELLs? (2) What are the strengths and limitations of currently available note-taking support? (3) How can currently available note-taking support be improved for college students with LDs and ELLs? This study employed qualitative and quantitative methods. Surveys and interviews were conducted to find out the strengths and weaknesses of current note-taking support at various institutions.

Continue reading Bangyan Li »