Poster Session

Colour code: Purple

Modeling the Role of Collective Cell Migration in Wound Healing.

Alexandra Brown, Jonathan Dawson, Michael Czajkowski, Mahesh Gandikota, M. Lisa Manning (research supervisor)

We employ a simple self-propelled particle model in a wound healing geometry to model the role of collective cell migration in wound healing. We first study a non-interacting version of the model, verified using the mean-squared displacement (MSD). We then study an interacting version of the model in a strip geometry with upper and lower bounding walls, which we analyze quantitatively using the MSD, and discuss additional metrics we might use to compare the model to experiment.

Partitioning of Space to Minimize Free Energy in Block Copolymer Spheres.

Michael Buckley, Ishan Prasad, Gregory Grason

Block copolymers that have phase separated into spherical cells in close-packed arrangement can assemble into periodic structures. We have used computational methods based on free energy minimization to try and identify which structure is most likely to form. We have considered a group of structures most often associated with this problem. The simulation was run in two ways: one where the volumes of the cells in each structure were static and equal, and one in which they were dynamic and not necessarily equal. We  found that the A15 structure is most likely to form in the first case, whereas the H structure is most likely to form in the second case. This raises questions as to what makes these structures preferable, as well as what other structures must also be considered.

Stability and flow fields of falling toroidal objects through a viscous fluid.

Hannahmariam Mekbib, Alexandros A. Fragkopoulos, Perry W. Ellis, Alberto Fernandez-Nieves

The relation between the geometry and the stability of an object will affect its behavior when immersed in a fluid. In this research project, we investigate the orientation and stability of falling tori using large field experiments and measure the flow fields caused by the falling tori using Particle Image Velocimetry (PIV).

A Transcranial Ultrasound Device to Detect Intracranial Hemorrhages.

Anjelica Molnar-Fenton, Bella Patel and Jason White

Blunt force trauma to the head can cause intracranial hemorrhages that require rapid detection and treatment. Currently, x-ray computed tomography (CT) is the standard method for detection, but has the associated disadvantages of size, cost, and the use of ionizing radiation. Based on existing evidence that coagulated blood is detectable with pulse-echo ultrasound, we propose the use of transcranial ultrasound as a portable, efficient, and safer alternative to CT for identifying the presence of intracranial bleeds. Our previous work has identified a method for transmitting ultrasound effectively through the skull bone to detect hyperechoic intracranial structures. This method, when optimized for detecting intracranial blood, will provide crucial indication for triage during emergency response.

Exploring Biophysical Mechanisms of Site Specific DNA Cleavage with Single Molecule Sensitivity.

Sadie Piatt, Raquel Ferreira, Allen Price (supervisor)

We have developed an assay for measuring site specific dsDNA cleavage with single molecule sensitivity. In our technique, micron sized beads are tethered with single DNAs in a microfluidic flow cell and imaged using video microscopy. The exact time of cleavage of each DNA is recorded as the time of disappearance of its tethered bead. We are using our assay to study facilitated diffusion and the role of divalent cations in restriction endonuclease (RE) mechanism. The theory of facilitated diffusion predicts RE cleavage rates should show a peak as salt concentration is varied as the one dimensional sliding length depends strongly on salt. We show that NdeI exhibits a peak in cleavage rates near 80 mM NaCl. We are currently designing experiments to verify that this effect is due to DNA sliding. In order to isolate the role of Mg2+ in the mechanism, we must eliminate the effects of diffusion to the cleavage site. We are doing this by designing an assay in which REs are pre-bound to DNA in the absence of Mg2+. Cleavage is then activated by introducing Mg2+ to the prebound enzyme-DNA complex. We report our current efforts to validate this new technique.

PatF and Cloud Chamber Workshop

Jacqueline Van Slycke, Dr. Matt Bellis, Madeline Hagen

Over the past summer, I along with help of Madeline Hagen and our advisor, Dr. Matt Bellis, improved upon the design and consistency of a student created cloud chamber from previous summers. Our version utilizes peltier thermocoolers and a CPU cooler instead of dry ice. At the end of our research we held a 4-day conference for high school physics teachers, teaching them how to construct their own cloud chambers, in addition to `new physics` lectures on incorporating modern research into their curriculum.   

The role of viscous coupling in determining subduction style within numerical models of mantle convection.

Molly James, Dave Stegman, UCSD; Robert Petersen, UCSD

Earth recycles its lithosphere through convective single-sided subduction, while other bodies such as Mercury and Mars, exhibit stagnant lithospheres. Using a numerical model of mantle convection, StagYY, we investigate how this spectrum of behavior from 1-sided, to 2-sided, to stagnant lid may arise due to a combination of viscous coupling in the system. A 2D reference model includes a 80 km plate with maximum viscosity 1E25 Pa-s and 8 km of “weak crust”, a viscous 1E20 Pa-s 660 km upper mantle of 1600 K, and 5E21 Pa-s 600 km lower mantle. The internal heated Rayleigh number remains constant at 1.8E8. The boundary conditions are free slip everywhere and the top has a pseudo-free surface with 100 km of sticky air. The weak crust has a lower viscosity than the mantle with values ranging between 0.001 and 1 times the mantle viscosity. The weak crust has different yield parameters than the mantle with values of cohesion ranging between 1 and 80 MPa (mantle value 150 MPa) and no depth dependence (mantle value 0.1). The weak crust converts back into mantle at a specified depth which is taken to be 150 km. Conversion depths less than 150 km result in stagnant lids due to a greatly increased viscous coupling at the plate interface. Similarly, this viscous coupling is sensitive to the minimum viscosity allowed (varied between 1E18 and 1E19 Pa-s). The system is more sensitive to crustal cohesion than the viscosity contrast which can alter the subduction style. These parameters control the viscous coupling between the plate interface and within the mantle wedge. Within the parameter space, a window of 1-sided subduction appears for intermediate values of cohesion and viscosity contrast. Low values of cohesion lead to 2-sided subduction and high values lead to stagnant lid. This is a nonlinear system due to the feedback between the stresses generated by viscous coupling and the amount of yielding in the weak crust both on the upper plate and on the subducting plate.

A Lagrangian Study on the Physical Components of Current in the Biddeford Pool

Kristen Falcinelli, Charles Tilburg, Ph.D, Markus Frederich, Ph.D

Understanding the current pathways of water flowing in and out of the Biddeford Pool is important in order to understand the effects of physical water properties on the transport of the larvae of the invasive crab, Carcinus maenas. This invasive species has proved to disrupt ecosystems along the east coast of North America. In the Prince Edward Island region of Canada, the C. maenas preys on species of clam that are preyed on by native crab species and mussel species that are not typically consumed by native species (Miron et al. 2005). Further studies show that the C. maenas is capable of outcompeting native species, such as the economically important Callinectes sapidus, for food (MacDonald et al. 2007). In commercial clam flats in New England, Mya arenaria populations have decreased in areas where C. maenas is common (Glude 2011). Patterns of decreasing M. arenaria populations and overall ecosystem imbalance may be observed in the Biddeford Pool, where C. maenas has been found. In order to study the movement of Carcinus maenas larvae and other particles in the Biddeford Pool, data will be collected by constructing and releasing global positioning system (GPS) drifters in the Biddeford Pool during different phases of the tidal cycle. It is important to recognize that there are multiple physical factors to take into consideration when analyzing current pathways from drifter data, including time in the tidal cycle, wind and other weather. Research has been conducted to observe the pathways drifters take when entering the Biddeford Pool during a flood tide, and when exiting on an ebb tide. MatLab and Google Earth were used in the analysis of data. Further work will be conducted to improve the drifters and to determine what major patterns are responsible for currents in the Biddeford Pool.

Colour code: Blue

Undergraduate ALFALFA Team: Analysis of Spatially-Resolved Star-Formation in Nearby Galaxy Groups and Clusters.

Natasha Collova, Sandy Spicer, Dr. Rose Finn

As part of the Undergraduate ALFALFA Team, we are conducting a survey of the gas and star-formation properties of galaxies in 36 groups and clusters in the local universe. The galaxies in our sample span a large range of galactic environments, from the centers of galaxy groups and clusters to the surrounding infall regions. One goal of the project is to map the spatial distribution of star-formation; the relative extent of the star-forming and stellar disks provides important information about the internal and external processes that deplete gas and thus drive galaxy evolution. We obtained wide-field H-alpha observations with the WIYN 0.9m telescope at Kitt Peak National Observatory for galaxies in the vicinity of the MKW11 and NRGb004 galaxy groups and the Abell 1367 cluster. We present a preliminary analysis of the relative size of the star-forming and stellar disks as a function of galaxy morphology and local galaxy density, and we calculate gas depletion times using star-formation rates and HI gas mass. We will combine these results with those from other UAT members to determine if and how environmentally-driven gas depletion varies with the mass and X-ray properties of the host group or cluster. This work has supported by NSF grants AST-0847430, AST-1211005 and AST-1637339. 

Spectroscopy of Planetary Nebulae at the Bright End of the Luminosity Function.

Anneliese Rilinger, Karen Kwitter, Bruce Balick, R. L. M. Corradi, Rebeca Galera Rosillo, George Jacoby, Richard Shaw

We have obtained spectra of 8 luminous planetary nebulae (PNe) in M31 and 4 in the Large Magellanic Cloud with the goal of understanding their properties and those of their progenitor stars. These PNe are at or near the M* region (the most luminous PNe) in their respective galaxies. M31 PNe were observed at the Gran Telescopio Canarias using the OSIRIS spectrograph; LMC PNe were observed with the FORS2 spectrograph at the Very Large Telescope. Line intensities were measured in IRAF. Using our n-level atom program, ELSA (Johnson,, 2006, Planetary Nebulae in our Galaxy and Beyond, 234, 439), we determined temperature, density, and elemental abundances for each nebula. We then modeled the nebulae and central stars with Cloudy (Ferland, et al. 1998, PASP, 110, 761). We plan to use these models of the central stars to estimate the masses and ages of the progenitor stars. We hope to discover whether the progenitor stars of M* PNe exhibit consistently different characteristics from those of other PNe progenitors.

Undergraduate ALFALFA Team: Analysis of Spatially-Resolved Star-Formation in Nearby Galaxy Groups and Clusters.

Sandy Spicer, Natasha Collova and Dr. Rose Finn

As part of the Undergraduate ALFALFA Team, we are conducting a survey of the gas and star-formation properties of galaxies in 36 groups and clusters in the local universe. The galaxies in our sample span a large range of galactic environments, from the centers of galaxy groups and clusters to the surrounding infall regions. One goal of the project is to map the spatial distribution of star-formation; the relative extent of the star-forming and stellar disks provides important information about the internal and external processes that deplete gas and thus drive galaxy evolution. We obtained wide-field H-alpha observations with the WIYN 0.9m telescope at Kitt Peak National Observatory for galaxies in the vicinity of the MKW11 and NRGb004 galaxy groups and the Abell 1367 cluster. We present a preliminary analysis of the relative size of the star-forming and stellar disks as a function of galaxy morphology and local galaxy density, and we calculate gas depletion times using star-formation rates and HI gas mass. We will combine these results with those from other UAT members to determine if and how environmentally-driven gas depletion varies with the mass and X-ray properties of the host group or cluster. This work has been supported by NSF grants AST-0847430, AST-1211005 and AST-1637339. 

Zonal Wind Profiles of the Jovian Planets.

Kathryn Waychoff, Dr. Amy A. Simon, Professor Robyn M. Millan

The proximity and massive scale of Jupiter has made it a uniquely observable case study in planetary atmospheric dynamics, resulting in a wealth of data from several missions. Jupiter’s characteristically striated atmosphere makes it a prime candidate for zonal wind profiles. These plots of longitudinally-averaged wind velocities given with respect to latitude give insight to a key component of the east-west motion of the Jovian atmosphere. Zonal winds have been studied in detail from previous Hubble (1990s–2010s), Cassini (2000–2001), and Voyager (1979) imaging. We now add on additional Hubble data points from 2015 and 2016, and contrast current behavior with past behavior. Images from Hubble are pieced together into single-rotation maps and contrast is significantly enhanced. Subsequent rotations are cross-correlated in pairs. By plotting longitudinally-averaged winds from -50º to 50º versus latitude, we create zonal wind profiles from each data set. We use red wavelengths (631 nm and 658 nm) as a baseline with supplemental data ranging from 275 nm to 889 nm. We find that Jupiter’s zonal winds have remained relatively constant over the past 40 years with minor fluctuations on a sub-seasonal time scale. By comparing images in di↵erent wavelengths we discover similar velocity structures at different altitudes, but higher variability in wavelengths both significantly longer and shorter than the baseline reds. Additionally we show that the same processes that have been applied to analyze Jupiter’s zonal wind velocities can be applied to Neptune and Uranus, with some difficulty.

MISE: A Search for Organics on Europa

Kelly Whalen, Jonathan Lunine; Diana Blaney

NASA’s planned Europa Flyby Mission will try to assess the habitability of Jupiter’s moon, Europa. One of the selected instruments on the mission is the Mapping Imaging Spectrometer for Europa (MISE). MISE is a near-infrared imaging spectrometer that takes spectra in the 0.8-5 micron range, and it will be capable of mapping Europa’s surface chemical composition. A primary goal of the MISE instrument is to determine if Europa is capable of supporting life by searching for amino acid signatures in the infrared spectra. We present spectra of pure amino acid at MISE’s resolution, and we analyze the effect of chirality on these spectra. Lastly, we present model spectra for diluted/mixed amino acids to simulate more realistic concentrations. We show MISE can distinguish between different types of amino acids, such as isoleucine, leucine, and their enantiomers.

Mapping the Full-Extent of Dust in Molecular Clouds.

Jaqueline Erazo, Timothy Paglione

Massive and dense clouds of gas and dust support the birth of stars and solar systems. An outstanding difficulty is accurately and sensitively quantifying the mass and structure of the cloud. A dust cloud between an observer and a star not only scatters the starlight and makes it fainter, but it also reddens the starlight. This effect is known as extinction. Extinction is wavelength dependent; shorter wavelengths are more preferentially scattered. Therefore, infrared bands (long wavelength colors) are used because we are able to “look through” the dense areas of dust clouds and detect stars despite the extinction. However, infrared studies are only able to probe relatively high extinctions. To measure very low extinction regions, shorter wavelengths are preferred. We compare both a test field and a control field via stellar infrared and optical colors in order to find an optimal method that combines all available bands in detecting and quantifying extinction.

Dramatic X-ray Variability in AGNs: New Insights into Black Hole Fueling.

Aylin Garcia Soto, Edward Moran

Recently, archival data have revealed dramatic X-ray and optical variability in a handful of radio-quiet quasars over a span of 10 years. In some cases, this variability has been accompanied by changes in spectral characteristics in the optical band, which may provide clues regarding how massive black holes are fueled. To explore this issue further, we have used X-ray data obtained with the Einstein and ROSAT observatories to identify objects that dimmed or brightened tremendously over the 10-year span between these missions. Some of the objects we have found were observed multiple times with ROSAT; thus, we have measured long-term X-ray light curves for these sources to confirm their extreme variability. From a sample of 40 such objects, we have focused on two quasars, 1RXS J1801+6624 and 1RXS J1732+6748, which dimmed by factors of 10 to 40 between 1980 and 1990. New optical data from the MDM observatory in Arizona confirm that the both are still emission-line AGNs that have not totally "turned off" despite the dramatic decrease in their accretion luminosity. Other objects in our sample could potentially reveal a population whose mass-accretion rates have declined, providing insight into the origin and duration of black-hole fueling mechanisms.

Design Considerations for the Installation of an Iodine (I2) Cell onto TRES.

Juliana Garcia-Mejia, John Johnson, Jason Eastman, Andrew Szentgyorgyi 

The radial velocity (RV) method utilizes the reflex motion of a target star to predict the presence of one or multiple exoplanets. However, the disparity in mass between planet and host star often results in RV oscillations below the precision of most modern spectrographs. Such is the case of TRES, the Tillinghast Reflector Echelle Spectrograph located in the Fred Lawrence Whipple Observatory in Mt. Hopkins, Arizona, with a radial velocity (RV) precision of ~ 20 m s-1, dominated by instrumental effects. Since 1992, the iodine cell technique, presented in Butler et al.(1992) has become widely used for the reduction of RV measurement errors. Here, we describe the beginning stages in the installation of one such cell onto TRES. After traveling to the telescope site to perform the first fitting of the iodine stage, I designed, built and fitted the first prototype of an improved thermal insulation system for the front end of the spectrograph, where the cell will be mounted. Here I present such a design, as well as a detailed description of the current state of the project. We expect the iodine cell to be fully functional in approximately 1 year. Once the cell is installed, we expect errors in radial velocity measurements to decrease by an order of magnitude from the aforementioned 20 m s-1. This increase in precision will come with an increase in stability of radial velocity measurements, allowing TRES to perform in-house spectroscopy of more nearby bright targets and high-cadence exoplanet follow-up.

Observation and  Color-Magnitude Analysis of NGC 7789.

Abigail Culp, LT James Toomey, USCG; Dr. David Harris; 4/c Darden Purrington, USCG

Using the Coast Guard Academy’s Stonington Observatory 20-inch reflecting telescope, Non-Globular Cluster 7789 was observed through B, V, and R filters, for a total exposure time of 30 minutes. The datasets were calibrated and compared analytically to produce color-magnitude diagrams of the stars in the cluster. From these preliminary comparisons, a basic Hertzsprung-Russell diagram can be derived. The project included applications of IDL programming to determine stellar members of the cluster from the initial image. Though similar to previous research in astrophysics, this project validated the functionality of the Coast Guard Academy`s observational equipment in preparation for future cadet and faculty research.

Spectrographs and Large Telescopes: A Study of Instrumentation.

Haley Fica, Jeffrey Crane; Alan Uomoto; Tyson Hare

It is a truth universally acknowledged, that a telescope in possession of a large aperture, must be in want of a high resolution spectrograph. Subsystems of these instruments require testing and upgrading to ensure that they can continue to be scientifically productive and usher in a new era of astronomical research. The Planet Finder Spectrograph (PFS) and Magellan Inamori Kyocera Echelle (MIKE), both on the Magellan II Clay telescope at Las Campanas Observatory, and the Giant Magellan Telescope (GMT) Consortium Large Earth Finder (G-CLEF) are examples of such instruments. Bluer flat field lamps were designed for PFS and MIKE to replace lamps no longer available in order to ensure continued, efficient functionality. These newly designed lamps will result in better flat fielding and calibration of data, and thus result in increased reduction of instrument noise. When it is built and installed in 2022, G-CLEF will be be fed by a tertiary mirror on the GMT. Stepper motors attached to the back of this mirror will be used to correct misalignments in the optical relay system. These motors were characterized to ensure that they function as expected to an accuracy of a few microns. These projects incorporate several key aspects of astronomical instrumentation: designing, building, and testing.

Shooting Through the Sun.

Amalia Gjerloev, W. Dean Pesnell

Heliophysics is a branch of science that is devoted to studying the Sun and its’ effects on surrounding celestial objects. Most of what is known about the Sun comes from measurements taken by satellites that orbit either the Sun or the Earth. In this project, we imagine a satellite’s orbital path at perihelion is inside the Sun in order to understand more about the behavior of a satellite that skims the Sun’s surface. Two problems arise: what is the magnitude of the normal force acting on the satellite if the path is a brachistochrone curve and what path would the satellite follow if the path was quasi-Keplerian. We assume the mass density inside the Sun can be described by solutions to the Lane-Emden equation. The first path was designed as a brachistochrone tunnel and only the normal force exerted by the walls of the tunnel was considered. The magnitude of these accelerations were found to be relatively large, approximately 500 g’s at 99% of the Sun’s outer radius, and would render a person unconscious at even 99.8% of the Sun’s radius. The quasi-keplerian paths would require the orbiting object to travel inside the Sun, ignoring heat and drag forces, but allowing for a changing gravitational potential energy of the object. Objects moving along Keplerian orbits experience no body forces and therefore they would seem to provide an “easier” trajectory for the satellite to travel along in comparison to the brachistochrone tunnels. We show that this change leads to prograde and retrograde precession of the orbits as the object travels in, through, and back out of the Sun. These paths resemble those of WIMPS in the Sun or stars in globular clusters.

Spinning, Viscoelastic Kuiper Belt objects using Rebound.

Andrea Kueter-Young, Dr. Alice Quillen

New Horizon`s was able to shed light with visual imagery on Kuiper Belt objects that were rather mysterious to astronomers, one of them being Haumea. Haumea is the fourth largest Dwarf Planet in the Kuiper Belt, with an extremely oblate shape and fastest rotating object in the solar system which is spinning near its rotational disruption rate and we do not know why it has this shape or rotational rate. To address these questions we developed a simple computational model which represents Haumea as a mass spring model in order to test different theories as to how it got these characteristics. We ran collision models, tidal interactions, and different ice concentrations at different locations to compare with our observations.

Distribution-dependent total exoplanet yield for a large aperture space telescope.

Evan Morris, David Schiminovich

Abstract: A major scientific goal for future large aperture space telescopes is the discovery and characterization of habitable earth-like planets around FGK+M stars out to 10-20 pc. Using the design and observing plan for such a mission, we calculated the total exoplanet yield of a direct imaging survey, with detections including but not limited to potential earth analogs. In light of uncertainty of exoplanet occurrence rates, we used several of the best available exoplanetary distribution functions and assumed architectures to produce a Monte Carlo simulation of nearby planetary systems and observational parameters, and assessed detectability across the sample. Our calculations show a range of yields depending on the assumed distribution functions. We also compare our predictions to those of other detection methods in order to identify areas of parameter space (e.g. radius, period) uniquely constrained by direct imaging. In general, our calculations suggest that a higher completeness can be achieved with direct imaging, which will allow for calculation of a more accurate occurrence rate in local space.

Investigating the Initial Mass Function with Increased Redshift.

Danielle Rowland, Prof. Steve Finkelstein, Intae Jung, Matt Stevans, Isaiah Tristan

The stellar initial mass function (IMF) is generally assumed to be universal but there are several factors that could alter it; one being that lower metallicities at higher redshift could lead to an increased production of higher mass stars. Understanding the IMF is crucial because inferred stellar population properties of galaxies from integrated photometry is heavily dependent on the assumed IMF. We present the initial findings of an investigation using the 3D-HST survey catalog to search for variations of the IMF for galaxies with redshift 0.7 < z < 1.5.  We calculate the ratio of H-alpha luminosity to the UV luminosity, which probes the ratio of ionizing to non-ionizing UV light, which is dependent on the slope of the upper mass portion of the IMF.  While the majority of our galaxies are consistent with having stars distributed according to a Saltpeter IMF (albeit with a range of star-formation histories resulting in significant scatter in the H-alpha/UV luminosity ratio), we do find eight galaxies with a luminosity ratio that is significantly higher than that expected for a Salpeter IMF. This increase in the expected amount of ionized photons could be caused by several factors that we will address, including but not limited to, Active Galactic Nuclei, varying star formation histories, or an increased production of high mass stars.

Timing will Tell: Constraining Pulsar Timing Errors in the Search for Gravitational Waves.

Ellianna Schwab, Scott Ransom

Millisecond pulsars provide extremely precise, clock-like electromagnetic radiation pulses. Theoretically, noise in the arrival times (TOAs) of these individual pulses could be used to measure nanohertz-frequency gravitational waves. However, variability in the individual pulse shapes and TOAs due to intrinsic effects of the pulsar, known as pulsar jitter, can mask the noise caused by gravitational waves. We examine the effects of both brightness and time resolution on jitter in a sample of 10 millisecond pulsars observed by the NANOGrav collaboration regularly over an 11-year observation span. We find that several pulsars show quantifiable jitter on their brightest days while others do not, and that jitter grows more pronounced both in pulsars with a high signal-to-noise ratio and as the observer approaches the time resolution of a single millisecond pulse. We provide two methods of quantifying jitter to allow for comparison, both between observations of different pulsars and between observations of the same pulsar on different days.

Comparing the Evolution of ELMs Formed from Supernova Remnant Accretion and from Mass Loss Caused by Roche-Lobe Overflow

Aimee Schechter, Alec Gordon, Jamie Sullivan, and Mike Montgomery (Research supervisor)

Extremely Low-Mass White Dwarfs (ELMs) are White Dwarfs that have a mass too low to be formed by traditional stellar evolution, as the star would not have had time to reach the White Dwarf stage. A large proportion of ELMs have neutron star companions, hinting that the binary system is responsible for the formation of the white dwarf. The current theory is that ELMs lose mass to a binary companion. We compared ELMs formed this way to ELMs that formed from the accumulation of the remnants of a supernova. We think that ELMs may be created from the remnants of a supernova because of the ELM and neutron star binaries. We used MESA to analyze the differences in the cooling process between these two types of ELMs. The ELMs from supernova accretion had a faster cooling track than the ELMs with binary companions. Adding Hydrogen to the ELMs accreted by supernovae remnants delayed the cooling process. The next step would be to run more models at different masses and with a higher isotope reaction network and compare those cooling tracks with each other and see if they fit with observational data.

Colour code: Green

Neutron Production Rates in Dark Matter Detector Materials.

Tia Martineau, Dr. Alan E. Robinson (Fermilab)

One of the sources of background radiation for direct detection dark matter experiments is neutrons produced by (α,n) nuclear reactions in the detector materials. Using the programming language Python, an open-source calculator is being developed to calculate the anisotropic reaction rates from the (α,n) reaction process as well as the angles and energies of the outgoing neutrons produced. With these computations, it will be possible to minimize the amount of background radiation present in direct detection dark matter experiments like PICO-2L and SuperCDMS. A stopping power calculation for any given detector material and a differential cross section portion of the code have been written and are used in the energy spectrum and reaction rate calculation. This last portion of the code will determine the final reaction rates, angles and energies of the neutron yields. Further developments of the code will enable a user to work with detector materials containing more than one element and with a greater number of target isotopes.

Assembling and Preliminary Testing of the CMS GE1/1 chambers.

Jessica Allan, Archana Sharma (CERN), Michele Bianco (CERN)

The CMS (Compact Muon Solenoid) detector is one of two general-purpose detectors currently collecting data at the LHC (Large Hadron Collider). It uses many layers of detecting material to record the products of proton-proton collisions, which are essential to building up the picture of what happened at the heart of the collision.  This means the detectors are constantly evolving and being upgraded with the latest technology, in order to collect the largest amount of data most efficiently. My project involved the testing of specially designed foils that will be installed into the Endcap of the CMS detector. Each foil will be combined into a chamber of three foils to produce a GEM (Gas Electron Multiplier) detector. I used a high voltage power supply, controlled by LabVIEW code I wrote, to test 8 foils simultaneously and ensure they were ready for assembly into GEM chambers, and for eventual installation during the second long shutdown in 2019. The test was conducted in a climate-controlled box, whose temperature and humidity I also monitored using data loggers. In the event of a failure, the foils would be taken back to their assembly site at CERN and modified in an attempt to fix the problem, though failure rate of foils was relatively low. I was able to test 120 foils, and they will continue to be tested until the 216 needed are deemed to be suitable.

Designing a Single Top Control Region for a One Lepton SUSY Search.

Katherine Fraser, Masahiro Morii, Stefano Zambito

Searches at the LHC need accurate background estimates to prevent small signals from being washed out in background uncertainty. In the one lepton SUSY search I worked on, the most common backgrounds are W + jets, ttbar, and single top. Both W + jets and ttbar background are currently well estimated, but single top background estimates have a large uncertainty. My goal has been to find a more precise estimate of this background. Backgrounds are estimated starting with Monte Carlo simulation, which is normalized to actual data in specified control regions of phase space. Currently there exist control regions for ttbar and W + jets, but not for single top. I studied the effect of subdividing the ttbar control region to create a single top control region with a high single top purity (which is the fraction of background events that are single top). I analyzed the control regions of two signal regions with non-negligible single top background, known as the GG 4J high-x and GG 6J bulk regions. For the GG 4J high-x region, making a hard cut on the variable topness achieved a single top purity of 40% while retaining 15 single top events. In this region, actually performing fits would be a useful next step. For the GG 6J bulk region I was unable to obtain a single top region with both a large enough number of events and high enough purity because even prior to subdividing there were only 23 single top events with 8% purity. 

Development of an electronic testing framework and procedures for protoDUNE

Amanda Depoian, Elizabeth Worcester, Matthew Worcester

The Deep Underground Neutrino Experiment (DUNE) at Fermi National Accelerator Laboratory (FNAL) in Illinois will send neutrinos underground 800 miles to the Sanford Underground Research facility (SURF) in South Dakota to measure the parameters governing neutrino oscillations and to search for differences between the oscillations of neutrinos and antineutrinos.  The experiment is building a prototype detector (protoDUNE) at the European Organization for Nuclear Research (CERN).  Front-end electronics containing Analog to Digital Converter (ADC) application-specific integrated circuits (ASICs) are used inside the detectors to digitize and read out the signals from particle interactions.  These 16-channel ADC ASICs need to be tested to make sure they are working correctly at room and cryogenic temperatures. My project was to help develop an automated testing procedure for these ASICs and create a new graphical user interface (GUI) to run it.  The goal of the GUI is to validate these ASICs quickly without needing to execute a complicated series of tests by hand.  I used Python with PyGTK and PyROOT to create the GUI.  One GUI shows either the digitized waveform or the Fast Fourier Transform (FFT) of the waveform from a single channel of the ADC in real time.  The second GUI automates the ADC ASIC validation process by collecting data over a range of DC input voltage, analyzing the data for all 16 channels, and reporting the outcome of the test in  simple format.  Once the scripts are done, the GUI reports back to the user if the ASIC passed or failed the predetermined cuts. 

Static Characteristics of Prototype Silicon Sensors

Blanca Nino, Dr. Matthew Rudolph

The LHCb (Large Hadron Collider, Beauty) experiment analyzes b mesons, heavy particles containing a bottom quark, that occur as a result of colliding two protons at 13TeV energies. The Upstream Tracker (UT) is an upgrade to LHCb, which will be able to operate at higher luminosity. The UT is comprised of four planes of micro strip detectors. Each plane reads the position of incoming particles, allowing us to recreate their trajectory paths. UT’s primary objective is to maintain a high efficiency, and reduce the number of ghost tracks, or misread particle decay paths. This poster presents results of two major research and development tests into the static properties of these prototype sensors. The total sensor leakage current test analyzes leakage current resulting from high reverse bias voltage. The single strip leakage current test analyzes how this total current is distributed to individual strips. Our preliminary results will be followed up with additional investigation. Certain areas of the sensor read higher than expected average current to individual strips, while another reads lower. These results could be due to offset meter calibration, as there may be a systematic uncertainty of 1nAmp. Mainly, further work would be required to see better precision at the 100pAmp level. Our next step is testing the resistor in between strips, which could be too small to prevent currents from flowing to neighboring strips.

Colour Code: Orange

Metastable States in Terminal Orientation of Symmetric Bodies in a Flow

Doralia Castillo, A. Vaidya, K.Soriano, H.Su, B.Chung

Symmetric bodies such as cylinders and spheroidal bodies, in their stable terminal state, are long known to have their axis align itself perpendicular to the direction of the flow. This property has been verified theoretically, experimentally, and numerically and the transition to a terminal stable state is believed to coincide with the onset of significant inertial effects in the flow. However the threshold at which this transition occurs is yet to be determined. We conduct an experimental study to examine the nature of the transition of prolate spheroids and cylinders of various aspect ratios, from initial to their terminal stable equilibrium. Specifically, our experiments reveal the presence of intermediate metastable states which are sensitive to the flow Reynolds number and gradually lead to the stable state. A phase diagram of Reynolds number versus non-dimensional inertia clearly demarcates the metastable, stable, and oscillatory states that the bodies undergo in current and past studies.

Optical Characteristics of Thin TaS​2 ​Flakes

Christa Harper

The development of smaller technological devices, such as transistors or batteries, could utilize the newly discovered physical properties of thin TaS2 and other transition metal dichalcogenides. Interestingly, atomically thin TaS2, between 1-7 layers thick, has a higher superconducting critical temperature than bulk TaS2. However, it still requires atomic force microscopy (AFM) and Raman Spectroscopy to verify flake thickness, because less data about thin TaS2 has been collected and examined by researchers. The purpose of this study is to gather optical contrast and flake thickness data, then graph the relationship between them, allowing researchers to use only optical contrast observations to identify thin TaS2 flakes. The concept of using optical contrast vs. flake thickness to characterize thin materials is similar to what researchers already do to quickly identify graphene. The thinnest TaS2 layer found in this study was ∼1.3nm, corresponding to one unit cell. The most useful data was found for TaS2 flakes exfoliated onto a 285 nm SiO2/Si substrate, as opposed to the thinner 90 nm SiO2/Si substrate. Knowing reliable, time-saving lab procedures for using thin TaS2 might facilitate more research on superconductivity in thin TaS2.

Many-body localization and Quantum Simulation with Tensor Networks.

Carolyn Zhang, Frank Pollmann, S. L. Sondhi, Roderich Moessner

We generalize the recently introduced Density-Matrix Renormalization Group (DMRG-X) [Khemani et al, PRL 2016] algorithm to obtain Floquet eigenstates of one-dimensional, periodically driven many-body localized systems. This generalization is made possible by the fact that the time-evolution operator for a period can be efficiently represented using a matrix-product operator. We first benchmark the method by comparing to exact diagonalization for small systems. We then obtain Floquet eigenstates for larger systems and show unambiguously that the characteristic area-law scaling remains robust. To translate for a more general audience: Consider a completely isolated quantum system, without coupling to any external reservoir. One may then ask, “How does it thermalize?” The Eigenstate Thermalization Hypothesis (ETH) developed by Deutsch notes that the rest of the system can act as a bath for a subsystem, to give subsystems thermal distributions. However, Anderson had shown in 1958 that in non-interacting systems, any finite disorder would cause a failure of thermalization. This suggests a dichotomy between thermalization, in which the system can act as its own bath, and localization, in which the system fails to do so. Recently, bolstered by advances in numerical tools as well as quantum simulation with ultracold atoms, the interacting case has become an area of intense research. Many-body localization (MBL) occurs in systems with a critical level of random disorder, and opens a new field of non-equilibrium statistical mechanics, challenging our current understanding of phase transitions and thermalization. Since many-body Hamitonians grow exponentially in system size, I used a numerical method involving tensor networks to find a way to accurately and efficiently simulate MBL systems with periodic (Floquet) driving. We use this method to study larger systems to give insight into the dynamical phase transition.