Hearing aids aim to process and modify sounds into the most desirable forms for hearing impaired people to receive. However, due to multiple reasons including inconvenience and limited quality, only 20 percent of the people in the US who could benefit from a hearing aid wear one. This figure is likely to be much lower in other less developed countries.
Recently, smartphones with powerful computation capability and great mobility have emerged as a possible alternative for this problem. We have developed a preliminary iOS application with certain sound processing functionalities. It is able to collect all the sounds in the vicinity and amplify custom frequencies depending on the prescriptions of a specific user. In addition, the application can also produce different output on either the left or the right headphone piece. We have taken initial steps to make the system operate wirelessly with a Bluetooth earpiece; however, due to time and resources constraints, the application has not yet able to divide two distinct output like what it does on the normal iPhone earpiece. Also, a method for shifting sounds to lower frequency has not yet been implemented. We also have not yet tested the program to its fullest potential due to the sole access to only built-in iPhone’s microphone. A special microphone with many features such as noises canceling, separate streaming, and high sampling rate will enables us fully customize and prepare the application for future technologies. Our future system is expected to address these challenges.
In this experiment, we examine the non-linear dynamics of a mechanical system consisting of an inverted pendulum with one free-turning rotational degree-of-freedom attached to a computer-controlled cart with one linear degree-of-freedom. Using a Quanser Linear Servo Base Unit with Inverted Pendulum and paired software package, we used first principles to develop the non-linear control system needed to move the pendulum from stable equilibrium to unstable equilibrium and maintain unstable equilibrium. This combines the self-erecting inverted pendulum experiment and the classic pendulum experiment. Through the paired software package, we were able to derive the dynamic equations to develop the transfer function and proportional-velocity feedback system that describe the linear motion of the cart, successfully creating the non-linear control system for both phases of the experiment.
This report examines the function, accuracy, and ease of use of an XBOX Kinect™ as a 3D surface scanner. The purpose of this experiment is to demonstrate the utility of a Kinect™ for XBOX 360 (Microsoft®) paired with Skanect (Occipital) and MeshLab software packages as a low cost solution to surface scanning and processing. My conclusion is that the Kinect™ is able to accurately model the recorded point cloud as a continuous 3D surface that matches the contour and scale of the test subject surface. Both Skanect and MeshLab effectively interpolated the smoothing of the 3D surfaces and provided higher resolution imaging than an unaltered image. The resultant resolution of the contoured surface is higher than the resolution of the 3D printers used in this experiment, demonstrating an effective digital duplication of a physical surface.
For this project, a digital grip gauge was designed for Lockheed Martin to measure the grip length of the aircraft skin of the F-35. The objective of the electrical group is to ensure that the gauge will be capable of recognizing when the measurement has stabilized. When stabilized, a light will turn on, which allows the operator to know the measurement is ready for reading. We developed three prototypes that each complete this objective. The first prototype uses two force sensitive resistors (FSR) powered by Arduino. The Arduino code is programmed to turn on a light when the forces on the sensors are equal for a certain range within different zones. The second prototype consists of a comparator circuit with two FSRs connected to a NAND gate. When both FSRs measure the same force, within a range, a light will turn on. The third prototype utilizes two small push buttons that complete a circuit. When both buttons are pressed, the circuit is completed and a light will turn on, indicating to the operator that the part is flush with the aircraft skin and the measurement is stabilized. While each of these prototypes satisfies the objective, the third prototype was ultimately selected due to size constraints of the gauge design.
Compressive line sensing is a process of acquiring data and reconstructing images. The objective of this study is to explore the impact of the two parameters that are used in the image reconstruction algorithm on the quality of the reconstructed image. These two parameters are the compression ratio and the line group. The compression ratio is the ratio of the number of measurements taken at each line vs. the resolution of each line. The line group is the number of lines that are grouped together and solved jointly when reconstructing the image. A higher compression ratio results in degraded image quality because less measurement data is used to reconstruct the image. The larger the line group, the better the quality of the image at a cost of longer computation time. The key is to find a balance between the compression ratio and line group choices so that the image is reconstructed with as little data as possible while still maintaining a high image quality. We will present images reconstructed with different compression ratio and line group based on the data obtained in air and in water.
The objective of our work is to design and build a depth gauge that efficiently and accurately measures the depth of a narrow hole, and give feedback via an electronic screen on the device. This design is being made for Lockheed Martin and will allow their employees to measure a large amount of rivet holes both quicker and more accurately than their current solution. Speeding up the measuring process while retaining accuracy will cut down on production time significantly. Our design was founded on the idea of a small hole gage, we modified the gage to be set up as a probe and anchor onto the back side of the hole. The probe has been coined as a “split-ball” due to its inner shaft splitting the outer shaft that contains a ball type end effecter. Our prototype has been through many iterations utilizing the on campus Fab Lab to 3D print most of our parts. Our mechanical team has been in close work with our electrical team to ensure that the mechanics and electronics function together seamlessly.
The objective of our work is to design and build a depth gauge that efficiently and accurately measures the depth of a narrow hole, and give feedback via an electronic screen on the device. This design is being made for Lockheed and Martin and will allow their employees to measure a large amount of rivet holes both quicker and more accurately than their current solution. Speeding up the measuring process while retaining accuracy will cut down on production time significantly. Our design is small enough to be held in one hand and contains a wire probe that is plunged into the hole and latches onto the other side. The probe is “Tweezer-like” in design, with two wires that collapse and expand with the use of a button. Many parts of our design are made using a 3D printer for convenience and repeatability. Our design is able to communicate with electronics stored within the gauge that measures the depth and displays to an LCD screen.
Klein Tools is a major hand tools manufacturer in US focused on electrical and utility applications for professionals. One of Klein Tools products is called a fish rod that is used by professional electricians to pull wiring through walls, conduit, and plenums to route wire from one place to another. The current fish rod assembly process at Klein Tools involves manual dispensing of glue into the metal connectors before affixing them to fiberglass rods. The objective of this Klein Tools-sponsored project is to improve the throughput of assembly system and increase the accuracy and the consistency of the amount of glue dispensed to reduce product failures and adhesive waste.
The overall system in development consists of an automated metal connector orientation system, conveyor belt assembly, a glue dispensing system and a control system. Through the application of vibratory hopper feeders, pneumatic rotary tables and grippers, sensing cameras, break line sensors, and a conveyor belt, the system will orient the metal connectors glue side up, and present the connectors with adhesive to the operator for final assembly of the fish rods.
In this research project, the aim was to create a small, self-operated robot car to transport items. In addition, the robot-car can generate a distance when traveling through unknown places, and self-locate them in the next travels. The student authors hope that this robot car can be used to physically communicate and send medical supplies between severe patients and doctors in hospitals.
The Barby Formation makes up part of the Konkiep Terrane, which is a major Mesoproterozoic arc complex along the Kalahari craton margin in southwest Namibia. Previous mapping indicates that the Barby Formation contains a laterally and vertically complex series of basaltic to rhyolitic lavas, rhyolitic ignimbrites, and associated hypabyssal intrusions. Our new work shows that significant basaltic to andesitic pyroclastic successions are also present within the unit and record a wide variation in eruption styles.
Detailed mapping reveals the presence of Hawaiian, Strombolian and phreatomagmatic pyroclastic deposits forming successions up to X m thick emplaced close to source vents and intercalated with fine-grained lacustrine strata in an area ~20 km2. The most abundant deposits consist of basaltic to andesitic spatter accumulations formed from vigorous lava fountains during Hawaiian-style eruptions. These sequences show random vertical transitions on the scale of a few meters from moderately agglutinated to densely welded spatter, which reflect variations in pyroclast accumulation rates. Individual spatter pieces are up to x cm long. The densely welded spatter forms lava-like units, but we see no evidence of clastogenic lava flows. Sequences of basaltic lapillistone with dispersed ribbon and fusiform bombs up to 50 cm across record Strombolian eruptions during episodes of lower magma flux without involvement of external water. The spatter accumulations typically grade upward into phreatomagmatic deposits containing minor amounts of spatter and cauliflower bombs mixed with poorly vesicular lapilli tuff, in which particle shapes are controlled mostly by fracture surfaces rather than broken bubble walls; up to 30% lacustrine sediment is intermixed with juvenile lapilli and ash in these deposits. We infer that changes in eruptive style in this part of the arc sequence were controlled at least partly by variations in magma ascent rates at shallow depths, as documented in numerous other volcanic provinces. Transitions from Hawaiian to phreatomagmatic eruptions may at least partly reflect a decrease in magma flux in the presence of external water, lowering the magma-to-water mass ratio so that hydrovolcanic explosions became possible.
Northwestern South America is highly deformed due to the transpressive boundary with complex interactions among the Caribbean plate, the South American plate, the Nazca plate and the Panama arc. Previous studies suggest that the Cenozoic uplifting of the Mérida Andes and Eastern Cordillera of Colombia affected sediment dispersal patterns in the region, shifting from a Paleocene foreland basin configuration with an axial major fluvial system, to the modern configuration of isolated basins with distinctive sediment dispersal patterns. Well-exposed Cretaceous to Pliocene strata in the Táchira saddle between the Easter Cordillera and Merida Andes provide a unique opportunity to test proposed sediment dispersal patterns in the region. U-Pb detrital zircon geochronology and supplementary XRD heavy mineral identification were used together to document provenance of Cretaceous to Pliocene clastic rocks collected from the area of La Alquitrana. Results from the U-Pb detrital zircon geochronology show that there are six age groups recorded in this samples. Two groups related with Precambrian Guyana shield Terranes and Putumayo basement in the Eastern Cordillera, and four groups related to different magmatic episodes during the Andean Orogenic process. Three major paleogeography changes were also recorded in these detrital signatures, including a transition between the Cretaceous passive margin and the Paleocene foreland basin, the initial uplifting of the Eastern Cordillera with the isolation the Llanos Basin and Táchira Saddle from the Central Cordillera and the Magdalena Valley in the Early Oligocene, and the uplifting of the Mérida Andes by the Early Miocene. The outcomes of this study emphasize the importance of the Mérida Andes and Eastern Cordillera Uplift in controlling the evolution of the sediment dispersal patterns in northern South America and represent a contribution in the understanding of the paleogeographic evolution in the region.
Fluvio-lacustrine systems are prone to experiencing significant flood events separated by longer low energy periods. During low flow, sediment is stored upstream of the lake as mid-channel and side-attached bars. During high-discharge events, water level rises above the topographically low delta front levees, the turbulent jet of the river is positioned upstream of the levee terminus where levees are less confining, and the previously stored sediment is flushed from the channel into the lake basin laterally as sheets. This process forms a laterally extensive, well sorted wedge shaped deposit of fine grained sand called a blowout wing (after Tomanka, 2013). These wings are documented in the ancient within the Kayenta Formation, UT, where the sand wings demonstrated a significant increase in connectivity between statistically clustered fluvio-lacustrine channel belts. In this research, we document two examples of blowout wings forming in the modern. The first example is a lake sourced by a mud dominated river (Denton Creek, Lake Grapevine, TX), and the second is a lake sourced by a sandy, bedload dominated river (Red River, Lake Texoma, TX). Wings are composed of fine to medium grained, well sorted, and clean sand. The deposits are thin and laterally continuous, with measured thicknesses of 5-10 cm that thin away from channel axis. Wings have an aerial extent up several hundred meters, scaling to 4-6 times the channel width. The Red River at Lake Texoma has a channel width of 125m and deposits wings with an aerial extent of 250-350m long along the levee of the delta channel and 300-500m laterally. As the Red River has prograded into the basin, 5-6 individual blowout wings form a wing complex 1500m long and 500-600m laterally from the channel. Denton Creek at Lake Grapevine has a channel width of 25m and deposits wings on the order of 50-125m along the levee of the delta channel and 60-150m laterally. Three wings at Lake Grapevine form a wing complex 300m long and 100-150m laterally. The amalgamation and statistical clustering of fluvio-deltaic channel belts is increased by the presence of blowout wings, resulting in higher total reservoir size and connectivity. Blowout wings should be, and are, found in modern systems and subsequently the rock record recording fluvio-lacustrine environments of deposition.
Thin sand sheets presumed to be terminal splay bodies have potential to serve as hydrocarbon reservoirs. The few studies of terminal splays managed from arid systems has provided insight, but ground study of the humid equivalent is lacking. Deposited in the distal zone of a distributary fluvial system (DFS), the splay bodies are formed as rivers terminate from loss of slope into unconfined dispersive flow and deposit bed load as splays and advect mud to more distal floodplains. The splay sheets and floodplain together provide potential for both reservoir and seal. We examined terminal splay deposits in a modern humid terminal splay system, Andean foreland of northern Argentina, and in ancient foreland deposits, Paleocene Raton Formation of the Colorado Raton Basin. I am going to compare the two locations in terms of grain-size, sedimentary structures, geometry, and scale and see how they relate. I hypothesize that the two are going to have similar grain sizes, and that the sedimentary structures and geometries will also be analogous but expect them to be scaled down in the Raton Basin.
The modern splay in Argentina is nearly 1.3 km wide and 1.9 km long and was deposited during a single large flood in 2012. Cross sections generated by hand augers show a maximum thickness of 0.8 m, an average of 0.5 m, and a consistently very fine-grained to lower medium-grained sand texture throughout. Total sand deposited in the flood event is ~ 1.2 million cubic meters (~2.0 million cubic meter maximum), and accumulates over earlier splay deposits separated by weakly developed soils that are locally removed by splay incision. Subsequent dissection of the splay permits examination of sedimentary structures, which are dominantly climbing ripples, planar laminations, and cross sets, but climbing antidunes are locally found near the splay apex. Ancient terminal splays of the Raton Formation are made of thinner sand sheets (~0.25 m) and tend to have thicker muddy floodplain deposits between. Grain-size distribution, sheet geometry, and sedimentary structures however are consistent between the modern and ancient examples. Both the Argentina and Raton examples reflect the distal end of a humid Distributive Fluvial System, however, the Raton system appears to have been of smaller scale. This is consistent with the comparatively smaller scale of the Raton vs. Andean tectonic system.
The Late Paleozoic Ouachita fold-and-thrust belt extends from the southern terminus of the Appalachian thrust belt in eastern Mississippi up through central Arkansas, southeastern Oklahoma, and Texas terminating in northeastern Mexico. A series of Carboniferous foreland basins were formed sequentially to the thrust front. The interaction between the Laurentian craton and the Appalachian-Ouachita orogenic belts controlled sedimentation in the southern midcontinent region throughout the Paleozoic. In contrast to the Appalachian orogenic belt to the east, the Ouachita orogenic belt and associated sediments remain poorly documented and less constrained.
In this study, seven Ordovician to Mississippian aged clastic units from the Ouachita Mountain in central Arkansas were sampled and tested using U-Pb detrital zircon geochronology. Three major age peaks are prominent, including the Grenville Province (~0.95-1.2 Ga), the Granite-Rhyolite Province (~1.3-1.5 Ga), and the Superior Province (>~2.5 Ga) in Ordovician to Silurian aged rocks. A change in this signature becomes clear at the beginning of the Carboniferous from Early Mississippian Stanley Group samples showing the additional Paleozoic age peak (~490-520 Ma) potentially derived from the Appalachian orogenic belt to the east, and/or from peri-Gondwanan terranes accreted to Laurentia just before the collision with Gondwana. This stratigraphic variation of detrital zircon age signature suggests that the transition from a passive to an active margin in the Ouachita trough started, at the latest, in early Mississippian times. Results of this study is the first systematic study of the U-Pb detrital zircon signature of the Ouachita orogenic belt and have important implications in sediment dispersal, provenance interpretations, and paleogeography reconstructions in North America, especially in the southern mid-continent and surrounding areas.
This study involved the examination of core samples from the Lower Cretaceous aged Kiamichi Formation of the East Texas Basin in order to interpret its organic and elemental geochemistry using various techniques. The Kiamichi Formation may have the potential to be a source rock for hydrocarbons, and may be a plausible target for oil and gas companies to produce using unconventional techniques. Since this formation has yet to be thoroughly analyzed, this project has lead to further understanding of its potential by using techniques such as handheld x-ray ﬂuorescence tool to estimate for the abundance of rare earth elements and trace metals, as well as a CHNS analyzer to determine the amount of organic carbon of the formation. Upon completion of the sample analysis, this geochemical information about the Kiamichi Formation provides beneficial information for further research on the overall Kiamichi Seaway.
The Eagle Ford Shale in south Texas is one of the most prolific unconventional hydrocarbon plays in the world (Breyer, 2016). In 2015, natural gas and oil from this field hit peak production numbers at 5,539 MMcf (million cubic feet) and 1,118,648 Bbl (barrels) per day, respectively (Texas RRC, 2016). In order for this low-permeability formation to produce, companies are using hydraulic fracturing, a stimulation treatment used in low-permeability rock whereby fluids are pumped at high pressures into reservoirs, causing new fractures to form and possibly reactivating existing fractures (Schlumberger, 2016). The aim of this study is to identify any geomechanical and geochemical properties that optimize fracture connectivity within the Boquillas Formation, the West Texas Eagle Ford equivalent. Energy-dispersive x-ray fluorescence (ED-XRF) and strength/hardness data from this study suggests that fracture frequency and length are affected by the clay and calcium carbonate content, and, by inference, the strength of the rock.
Author(s): Nick Baroni Interdisciplinary Micah Eimerbrink Psychology Kelsey Paulhus Biology Julia Peterman Psychology Morgan Thompson Biology Jordon White Psychology
Advisor(s): Gary Boehm Psychology
Influence of Isolation Stress on Aβ Production and Cognitive Function in 5xFAD mice Baroni, N. J.,1 Peterman, J. L.1, White, J. D.1, Eimerbrink, M. J.1, Paulhus, K. C.2, Thompson, M. A.2, Chumley, M. J.2 & Boehm G. W.1,
1Department of Psychology, Texas Christian University
2Department of Biology, Texas Christian University
Alzheimer's Disease (AD) is a devastating neurodegenerative disease that affects nearly 44 million people worldwide, and is increasing exponentially in prevalence. Thus, research into its causes and prevention is crucial. Transgenic mouse models of Alzheimer's disease are often used to better study AD pathology. These mice have genetic mutations that result in heightened production of amyloid beta (Aβ), a pathological hallmark of AD. It has been well established that stress can influence AD pathology. This study investigates how isolation stress influences the production of amyloid beta in 5xFAD transgenic mice. In addition, we investigated whether isolation stress impacts cognition in the contextual fear conditioning (CFC) paradigm. The mice were group-housed or isolated for both 2 and 3 months, followed by cognitive testing and tissue collection. Specifically, we utilized histochemistry to examine Aβ plaque counts and an ELISA to examine soluble Aβ production. We found that isolated 5xFAD+ mice had significantly more amyloid beta plaques than group-housed animals. 5xFAD+ mice isolated for 3 months also displayed a cognitive deficit in contextual fear conditioning. All together, our results support the research that isolation stress influences Aβ production and cognitive function, and extends that to the 5xFAD transgenic mice.
Author(s): Alexa Calcagno Psychology Philip Crain Psychology Micah Eimerbrink Psychology Amy Hardy Biology Kelsey Paulhus Biology Julia Peterman Psychology Morgan Thompson Biology Jordon White Psychology
Advisor(s): Gary Boehm Psychology Michael Chumley Biology
Alzheimer’s Disease (AD) is a neurodegenerative disease currently affecting about 5.5 million Americans, and the number of people affected may rise as high as 16 million by 2050. Characteristic AD pathology of deteriorating cognitive function is correlated with neurofibrillary tangles of tau protein and Amyloid-beta (Aβ) plaques. Aβ is a peptide resulting from cleavage of the Amyloid Precursor Protein (APP) primarily present within neuronal cell membranes. The Aβ peptide can be cleaved at different lengths, but Aβ1-42 is the most neurotoxic. Aβ1-42 primarily aggregates in the hippocampus, where it further stimulates the release of cytokine proteins initiating an inflammatory response. Previous studies in our lab have shown that short-term inflammation induced by injection of lipopolysaccharide (LPS) leads to an inflammatory response that stimulates production of Aβ1-42 peptides. The goal of this project was to determine whether this effect could be exacerbated through a second injection series of LPS after a fourteen-day recovery interval, thus modeling multiple, independent, bacterial infections, like that seen in humans. The animals were given 7 days of 250 mg/kg LPS or saline injections, a two-week break, and another 7 days of LPS or saline. Contrary to what was predicted, Aβ levels were not potentiated. This effect was found to be related to decreased inflammatory response upon secondary administration of LPS, as IL-1β mRNA was significantly lower in the group that got two rounds of LPS. Current studies of our lab are evaluating whether these results are related to the presence of antibodies to LPS or a specific tolerance mechanism.
The challenge of taking care of aged patients who lost control of their bladders and bowel movements is to respond to the patients’ needs in a timely manner, which often requires a caretaker (e.g. a family member or a hired assistant) to stay on watch 24/7. In light of advance in cloud computing, we present a real-time low-cost monitoring and notification system that can continuously monitor the patients bedding condition, detect the conditions that help is needed and notify the care-takers. The system consists of TI SensorTags, Raspberry Pis, and IBM Bluemix. The TI SensorTag is a sensing device, while Raspberry Pi acts as a messenger receiving data collected by TI SensorTags via Bluetooth technology and transmitting the data to Bluemix, a cloud-based platform developed by IBM, via WiFi.
The system frequently senses bedding conditions of patients. Data is uploaded to a server residing on IBM Cloud, which processes data and sends appropriate notifications. The availability of cloud technology and small signal processing units, as well as advance in sensor technologies, allow us to build a low-cost system that can help caregivers address the patients’ needs effectively. As a result, the quality of care for patients is improved.
The winding number of a continuous function on the unit circle counts how many times a graph of the function loops around the origin. It is homotopy invariant and has applications to several areas of Mathematics.
Toeplitz operators with continuous symbol are bounded linear operators on the Hardy Space involving multiplication by a continuous function. The index of such a Toeplitz operator is closely connected to the winding number of its symbol.
This connection is examined and then extended for Toeplitz operators with crossed product symbols.
Personality psychologists often apply clustering techniques on questionnaire data to model personality structure. Inspired by this work, we apply techniques from topological data analysis (TDA) to understand the structure of this data. The data comes from Cattell’s Sixteen Personality Factor Questionnaire (collected by Bell, Rose, & Damon in 1972). Subjects were 969 adult male volunteers divided into three age groups: 25 to 34, 35 to 54, and 55 to 82. We use persistent homology (a TDA tool) to cluster the data and identify that personality structure is slightly different between the age groups. It is also curious to note that data from the youngest age group appears to have a topological “hole”, which raises questions of the psychological significance. This work suggests that additional research, including applying TDA tools to other questionnaire data sets can provide insights to the study of personality.
An algebraic integer is a complex number that is a root of a monic polynomial with integer coefficients. It is well-known that there is not always a single algebraic integer that can generate the ring of algebraic integers contained in a field extension of the rational numbers. The index of an algebraic integer is a natural number that measures how far a ring of integers is from having such a "primitive element." We investigate these indices in cubic fields and determine which natural numbers occur as indices in given families.
Background: There have been many food waste studies done in elementary schools around the country. Several studies have determined that main entrées contribute significantly to plate waste in elementary school food programs, but studies relating the use of condiments and their influence on food waste need further exploration.
Objectives: Determine the correlation between the addition of condiments and the amount of plate waste from a chicken entrée.
Methods: In Phase I, data was collected in an elementary afterschool meal program. Researchers evaluated plate waste for the chicken entrée once a week for a total of four weeks. Chicken entrée plate waste was evaluated by weight and visual assessment. The waste weight was compared to the weight of one serving of the chicken entrée. A photograph of the total plate waste was taken each week for visual comparison. Researchers compared the total number of servings prepared to the number of servings leftover. In Phase II of the study a condiment (ketchup) was added to the menu when the chicken entrée was served. A marketing campaign was implemented with flyers to advertise the addition of the condiment. For the remaining four weeks, plate waste was documented using the same methods utilized during Phase I.
Results: In Phase I, an average of 26.7% of chicken entrées was wasted. In Phase II, an average of 20.8% of chicken entrées was wasted. No statistically significant difference was found in the percentage of food leftover between Phase I and Phase II (p<0.06). After adjusting for differences in initial portion size, there was still no statistically significant difference in weight of entrée left over (p<0.3).
Conclusion: Though there was no significant difference, the amount of waste is large enough to draw attention to the problem of waste in school foodservice. More research is necessary to determine what factors are leading to food waste.
Located inside the Large Magellanic Cloud, fierce explosions called supernovae have thrown out massive amounts of gas in every direction. A portion of this gas is aimed toward the Milky Way and is on a crash course with our galaxy. We are observing this gas with the Wisconsin H-Alpha Mapper, which provides a window into how the gas is distributed. These observations show two periods of supernovae explosions that created two distinct gas winds. One of these winds is currently active while the other was produced roughly 300 Million years old. Studying these gas clouds will provide information on how massive these winds are and the rate at which they are produced. The ejected gas is headed toward the Milky Way could supply our galaxy with additional gas to form stars in the future.
Author(s): Md Tanvir Hasan Physics & Astronomy Roberto Gonzalez-Rodriguez Chemistry & Biochemistry Anton Naumov Physics & Astronomy Conor Ryan Physics & Astronomy Brian Senger Physics & Astronomy
Advisor(s): Anton Naumov Physics & Astronomy
(Presentation is private)
Graphene oxide (GO) inherits high transparency, substantial conductivity, high tensile strength from its parent materials graphene. Apart from these properties, it emits fluorescence which makes it a potential material to use in optoelectronics and bio-sensing applications. In this work, we have utilized systematic ozone treatment to alter the optical band gap of single-layered graphene oxide in aqueous suspensions. Due to controlled ozonation, additional functionalization takes place in GO graphitic sheet which changes GO electronic structure. This is confirmed by the increase in vibrational transitions of a number of oxygen-containing functional groups with treatment and the appearance of the prominent carboxylic group feature at c.a. 1700 1/cm. Albeit, timed ozone induction introduces only slight change in color and absorption spectra of GO samples, the emission spectra show a gradual increase in intensity with a significant blue shift up to 100 nm from deep red to green. This large blue shift suggests an increase in optical band gap with additional functionalization introduced by ozone treatment. We utilize a semi-empirical theoretical approach to describe the effects of functionalization-induced changes. This model attributes the origins of fluorescence emission to the quantum confined sp² carbon islands in GO encircled by the functional groups. As we decrease the graphitic carbon cluster size on the GO sheet, the optical bandgap calculated via HyperChem molecular modeling increases, which supports the experimentally observed blue shifts in emission. This theoretical result is further supported by the TEM measurement of ozone-treated samples, which shows a decreasing trend of average ordered graphitic carbon cluster size on GO sheets with treatment time. Theoretical modeling, as well as the experimental results, indicate that the optical bandgap and emission intensity of GO are alterable with controlled ozone treatment, which allows tailoring the optical properties of GO for specific applications in optoelectronics and bio-sensing.