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5 - Irregularities In Young Stellar Models: Are Starspots To Blame?, Jessica Hamilton 2018 University of North Georgia

5 - Irregularities In Young Stellar Models: Are Starspots To Blame?, Jessica Hamilton

Georgia Undergraduate Research Conference (GURC)

Starspots are dark areas on a star’s surface formed by intense magnetic fields that actively suppress the flow of energy, causing the area to become cooler and darker than its surroundings. Starspots threaten a star’s equilibrium because they prevent energy from leaving the star, causing a buildup of pressure. The prevailing assumption is that increased pressure will cause the star to inflate, producing a cooler and larger star. For this reason, starspots have been proposed to explain why some stars appear cooler and larger than we expect. This requires energy blocked by a spot to be trapped deep ...


4 - A Flexible Model For Investigating The Properties Of Starspots: Comparison Of Model Predictions To Observed Data, Amanda Ash 2018 University of North Georgia

4 - A Flexible Model For Investigating The Properties Of Starspots: Comparison Of Model Predictions To Observed Data, Amanda Ash

Georgia Undergraduate Research Conference (GURC)

Accurate age estimates provide a wealth of information about the mechanisms of different astrophysical phenomenon. However, current methods of applying stellar evolution models to obtain these estimates has proven to be flawed, with models having little consistency. It has been speculated the source of this inconsistency may arise from deviations in stellar properties due to the presence of dark blemishes, starspots, present on young cool stars (Feiden, 2016). Using predictions of expected properties from the flexible starspot model to observed properties of various open clusters, we aim to define what starspot properties bring model predictions into agreement with observed data ...


The Periglacial Landscape Of Mars: Insight Into The 'Decameter-Scale Rimmed Depressions' In Utopia Planitia, Arya Bina 2018 The University of Western Ontario

The Periglacial Landscape Of Mars: Insight Into The 'Decameter-Scale Rimmed Depressions' In Utopia Planitia, Arya Bina

Electronic Thesis and Dissertation Repository

Currently, Mars appears to be in a ‘frozen’ and ‘dry’ state, with the clear majority of the planet’s surface maintaining year-round sub-zero temperatures. However, the discovery of features consistent with landforms found in periglacial environments on Earth, suggests a climate history for Mars that may have involved freeze and thaw cycles. Such landforms include hummocky, polygonised, scalloped, and pitted terrains, as well as ice-rich deposits and gullies, along the mid- to high-latitude bands, typically with no lower than 20o N/S. The detection of near-surface and surface ice via the Phoenix lander, excavation of ice via recent impact cratering ...


Astromimetics: The Dawn Of A New Era For (Bio)Materials Science?, Vuk Uskoković, Victoria M. Wu 2018 Chapman University

Astromimetics: The Dawn Of A New Era For (Bio)Materials Science?, Vuk Uskoković, Victoria M. Wu

Pharmacy Faculty Articles and Research

Composite, multifunctional fine particles are likely to be at the frontier of materials science in the foreseeable future. Here we present a submicron composite particle that mimics the stratified structure of the Earth by having a zero-valent iron core, a silicate/silicide mantle, and a thin carbonaceous crust resembling the biosphere and its biotic deposits. Particles were formulated in a stable colloidal form and made to interact with various types of healthy and cancer cells in vitro. A selective anticancer activity was observed, promising from the point of view of the intended use of the particles for tumor targeting across ...


Strong Evidence For The Density-Wave Theory Of Spiral Structure From A Multi-Wavelength Study Of Disk Galaxies, Hamed Pour-Imani 2018 University of Arkansas, Fayetteville

Strong Evidence For The Density-Wave Theory Of Spiral Structure From A Multi-Wavelength Study Of Disk Galaxies, Hamed Pour-Imani

Theses and Dissertations

The density-wave theory of spiral structure, though first proposed as long ago as the mid-1960s by C.C. Lin and F. Shu (Lin & Shu, 1964; Bertin & Lin, 1996; Shu, 2016), continues to be challenged by rival theories, such as the manifold theory. One test of these theories which has been proposed is that the pitch angle of spiral arms for galaxies should vary with the wavelength of the image in the density-wave theory, but not in the manifold theory. The reason is that stars are born in the density wave but move out of it as they age. In this dissertation, I combined large ...


Impact Melt Emplacement On Mercury, Jeffrey Daniels 2018 The University of Western Ontario

Impact Melt Emplacement On Mercury, Jeffrey Daniels

Electronic Thesis and Dissertation Repository

Impact cratering is an abrupt, spectacular process that occurs on any world with a solid surface. On Earth, these craters are easily eroded or destroyed through endogenic processes. The Moon and Mercury, however, lack a significant atmosphere, meaning craters on these worlds remain intact longer, geologically. In this thesis, remote-sensing techniques were used to investigate impact melt emplacement about Mercury’s fresh, complex craters. For complex lunar craters, impact melt is preferentially ejected from the lowest rim elevation, implying topographic control. On Venus, impact melt is preferentially ejected downrange from the impact site, implying impactor-direction control. Mercury, despite its heavily-cratered ...


Education, Support, And Results For Wyoming Participants In The Citizen Cate (Continental-America Telescopic Eclipse) Experiment, Gabriel Miller 2018 University of Wyoming

Education, Support, And Results For Wyoming Participants In The Citizen Cate (Continental-America Telescopic Eclipse) Experiment, Gabriel Miller

Honors Theses AY 17/18

Throughout the spring and summer of 2017, the Citizen CATE (Continental- America Telescopic Eclipse) Experiment was active in Wyoming and across the contiguous United States, with the goal of achieving an unbroken line of citizen- operated telescopes and cameras along the path of totality for the August eclipse. Eleven sites were active in Wyoming, composed of teachers, students, amateur and professional astronomers, and interested members of the community. In two large educational sessions, as well as several localized practice events, these groups were trained to use the telescopes and cameras provided for them. Working closely with the National Solar Observatory ...


An Investigation Into The Suitability Of Sulfate-Reducing Bacteria As Models For Martian Forward Contamination, Maxwell M. W. Silver 2018 University of Arkansas, Fayetteville

An Investigation Into The Suitability Of Sulfate-Reducing Bacteria As Models For Martian Forward Contamination, Maxwell M. W. Silver

Theses and Dissertations

The NASA Planetary Protection policy requires interplanetary space missions do not compromise the target body for a current or future scientific investigation and do not pose an unacceptable risk to Earth, including biologic materials. Robotic missions to Mars pose a risk to planetary protection in the forms of forward and reverse contamination. To reduce these risks, a firm understanding of microbial response to Mars conditions is required. Sulfate-reducing bacteria are prime candidates for potential forward contamination on Mars. Understanding the potential for forward-contamination of sulfate-reducers on Mars calls for the characterization of sulfate-reducers under Mars atmosphere, temperature, and sulfate-brines. This ...


Magnetic Field Design To Reduce Systematic Effects In Neutron Electric Dipole Moment Measurements, James Ryan Dadisman 2018 University of Kentucky

Magnetic Field Design To Reduce Systematic Effects In Neutron Electric Dipole Moment Measurements, James Ryan Dadisman

Theses and Dissertations--Physics and Astronomy

Charge-Conjugation (C) and Charge-Conjugation-Parity (CP) Violation is one of the three Sakharov conditions to explain via baryogenesis the observed baryon asymmetry of the universe (BAU). The Standard Model of particle physics (SM) contains sources of CP violation, but cannot explain the BAU. This motivates searches for new physics beyond the standard model (BSM) which address the Sakharov criteria, including high-precision searches for new sources of CPV in systems for which the SM contribution is small, but larger effects may be present in BSM theories. A promising example is the search for the electric dipole moment of the neutron (nEDM), which ...


Detection Of Extragalactic Magnetic Fields Through Analysis Of Photon Arrival Directions, Omkar H. Ramachandran 2018 University of Colorado, Boulder

Detection Of Extragalactic Magnetic Fields Through Analysis Of Photon Arrival Directions, Omkar H. Ramachandran

Undergraduate Honors Theses

The existence of large-scale extragalactic magnetic fields (EGMFs) has been a subject of some debate over the last few decades. Recent work done on the analysis of cascade photons from high energy sources like Blazars (Tashiro and Vachaspati, 2013; Chen et al., 2015; Tashiro and Vachaspati, 2015) offer an exciting possibility of definitively proving the existence of such fields. In this thesis, the existing analysis of magnetic field measurements via cascade photon correlators will be extended to the most recent repository of data from the Fermi Large Area Telescope. In addition, a new Monte-Carlo routine to account for noise from ...


Observations Of Ion Density And Temperature Around The International Space Station During Two Geomagnetic Storms, Alex M. Wright 2018 University of New Hampshire, Durham

Observations Of Ion Density And Temperature Around The International Space Station During Two Geomagnetic Storms, Alex M. Wright

Honors Theses and Capstones

The International Space Station (ISS) is a low Earth orbit research facility and host to an international crew. Geomagnetic storms cause changes in the Earth’s magnetic field and affect the ion density and temperature in the ionosphere which could pose a hazard to ISS crew. This hazard is measured by the Floating Potential Measurement Unit (FPMU) which measures ion density, ion temperature, and the charge differential of the ISS relative to its surrounding environment. I analyzed data collected by Narrow Sweep Langmuir Probe for two storms in 2015. Ion density and temperature were affected by geomagnetic storms, but the ...


Relationship Between Interplanetary Conditions And Changes In The Geomagnetic Field To Understand The Causes Of Geomagnetically Induced Currents, Cameron P. Maillet 2018 University of New Hampshire, Durham

Relationship Between Interplanetary Conditions And Changes In The Geomagnetic Field To Understand The Causes Of Geomagnetically Induced Currents, Cameron P. Maillet

Honors Theses and Capstones

Geomagnetically Induced Currents (GICs) are electrical currents induced in ground-level conductive networks, like power lines and pipelines, which can cause costly damage to infrastructure. GICs are induced in response to fast changes in the geomagnetic field (GMF) according to Faraday’s Law of Electromagnetic Induction. The purpose of this study was to identify the parameters of the solar wind and interplanetary shocks which are most strongly correlated with large, fast changes in the magnitude of the GMF. GMF data is 1-min averaged time series of mid- and high-latitude magnetometer measurements in the Sym/H and AL indices, respectively. For solar ...


The Coincident Coherence Of Extreme Doppler Velocity Events With P-Mode Patches In The Solar Photosphere, Rachel Mcclure 2018 University of Colorado, Boulder

The Coincident Coherence Of Extreme Doppler Velocity Events With P-Mode Patches In The Solar Photosphere, Rachel Mcclure

Undergraduate Honors Theses

Observations of the solar photosphere show many spatially compact Doppler velocity events with short life spans and extreme values. In the IMaX spectropolarimetric inversion data of the first flight of the SUNRISE balloon in 2009 these striking flashes in the intergranule lanes and complementary outstanding values in the centers of granules have line of sight Doppler velocity values in excess of 4σ from the mean. We conclude that values outside 4σ are a result from the superposition of the granulation flows and the p-modes.

To determine how granulation and p-modes contribute to these outstanding Doppler events, I separate the two ...


Scalar Field Vacuum Expectation Value Induced By Gravitational Wave Background, Preston Jones, Patrick McDougall, Michael Ragsdale, Douglas Singleton 2018 Embry-Riddle Aeronautical University

Scalar Field Vacuum Expectation Value Induced By Gravitational Wave Background, Preston Jones, Patrick Mcdougall, Michael Ragsdale, Douglas Singleton

Publications

We show that a massless scalar field in a gravitational wave background can develop a non-zero vacuum expectation value. We draw comparisons to the generation of a non-zero vacuum expectation value for a scalar field in the Higgs mechanism and with the dynamical Casimir vacuum. We propose that this vacuum expectation value, generated by a gravitational wave, can be connected with particle production from gravitational waves and may have consequences for the early Universe where scalar fields are thought to play an important role.


Correlation Between Emission Lines And Radio Luminosities Of Active Galactic Nuclei, Jessica Short-Long 2018 University of Kentucky

Correlation Between Emission Lines And Radio Luminosities Of Active Galactic Nuclei, Jessica Short-Long

Theses and Dissertations--Physics and Astronomy

Radio-loud active galactic nuclei (AGN) are one class of objects associated with accretion activity onto supermassive black holes in centers of massive galaxies. They are believed to be in a radiatively-inefficient accretion mode with low accretion rate. To understand this accretion mode, it is important to measure its radiative output at high energies (> 13.6eV), which can be traced through optical emission lines. However, little is known about their true radiative output. This is because no correlation between optical emission-line and radio luminosity has been found for the majority of low-luminosity radio AGN, which are often classified as low-excitation radio ...


Energy From Active Galactic Nuclei And The Effects On Host Spiral Galaxies, Amanda Schilling 2017 University of Arkansas, Fayetteville

Energy From Active Galactic Nuclei And The Effects On Host Spiral Galaxies, Amanda Schilling

Theses and Dissertations

I have investigated the energy output of active galactic nuclei (AGN) in order to understand how these objects evolve and the impact they may have on host galaxies. First, I looked at a sample of 96 AGN at redshifts $z \sim 2, 3,$ and $4$ which have imaging and thus luminosity measurements in the $griz$ and $JHK$ observed wavebands. For these galaxies, I have co-epochal data across those bands which accounted for variability in AGN luminosity. I used the luminosity measurements in the five bands to construct spectral energy distributions (SED) in the emitted optical-UV bands for each AGN. I ...


Ion-Scale Wave Properties And Enhanced Ion Heating Across The Low-Latitude Boundary Layer During Kelvin-Helmholtz Instability, T. W. Moore, K. Nykyri, A. P. Dimmock 2017 Embry-Riddle Aeronautical University

Ion-Scale Wave Properties And Enhanced Ion Heating Across The Low-Latitude Boundary Layer During Kelvin-Helmholtz Instability, T. W. Moore, K. Nykyri, A. P. Dimmock

Publications

In the Earth's magnetosphere, the magnetotail plasma sheet ions are much hotter than in the shocked solar wind. On the dawn sector, the cold-component ions are more abundant and hotter by 30–40% when compared to the dusk sector. Recent statistical studies of the flank magnetopause and magnetosheath have shown that the level of temperature asymmetry of the magnetosheath is unable to account for this, so additional physical mechanisms must be at play, either at the magnetopause or plasma sheet that contributes to this asymmetry. In this study, we perform a statistical analysis on the ion-scale wave properties in ...


Physoon - Radiation Detection In Various High Altitude Environments, Christopher Helmerich 2017 DePaul University

Physoon - Radiation Detection In Various High Altitude Environments, Christopher Helmerich

2017 Academic High Altitude Conference

Physoon is a high altitude ballooning payload designed and built by members of the Space Hardware Club for the purpose of comparing cosmic and terrestrial radiation from a variety of environmental conditions, including clear days, night times, solar events (eclipses, solar flares, coronal mass ejections), and thunderstorms. Over three design iterations, Physoon has flown eleven times with various combinations of Geiger counters sensors: a low energy Alpha-Beta-Gamma detector, an unshielded high-energy Beta-Gamma detector, and a shielded high-energy Beta-Gamma detector. One of these iterations successfully recovered data from high altitude during totality of the Great American Solar Eclipse. Another iteration was ...


On The Dawn-Dusk Asymmetry Of The Kelvin-Helmholtz Instability Between 2007 And 2013, Z. W. Henry, K. Nykyri, T. W. Moore, A. P. Dimmock, X. Ma 2017 Embry-Riddle Aeronautical University

On The Dawn-Dusk Asymmetry Of The Kelvin-Helmholtz Instability Between 2007 And 2013, Z. W. Henry, K. Nykyri, T. W. Moore, A. P. Dimmock, X. Ma

Publications

Using data from Time History of Events and Macroscale Interactions during Substorms (THEMIS), a statistical study was performed to determine whether a dawn-dusk asymmetry exists in the occurrence rates of the Kelvin-Helmholtz (KH) instability during Parker-Spiral (PS) and Ortho-Parker-Spiral (OPS) orientations of the interplanetary magnetic field (IMF). It is determined from the data that there is a strong preference toward the dawn side during PS orientation, and although a preference to the dusk side during OPS is suggested, this requires further study for an unambiguous confirmation. The uncertainty in the OPS result is due to a low number of events ...


Martian Cave Air-Movement Via Helmholtz Resonance, Kaj E. Williams, Timothy N. Titus, Chris H. Okubo, Glen E. Cushing 2017 U.S. Geological Survey

Martian Cave Air-Movement Via Helmholtz Resonance, Kaj E. Williams, Timothy N. Titus, Chris H. Okubo, Glen E. Cushing

International Journal of Speleology

Infrasonic resonance has previously been measured in terrestrial caves by other researchers, where Helmholtz resonance has been suggested as the plausible mechanism resulting in periodic wind reversals within cave entrances. We extend this reasoning to possible Martian caves, where we examine the characteristics of four atypical pit craters (APCs) on Tharsis, suggested as candidate cave entrance locations. The results show that, for several possible cave air movement periods, we are able to infer the approximate cave volumes. The utility of inferring cave volumes for planetary cave exploration is discussed.


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