Physical Sciences and Mathematics Commons^™

Model-Independent Plotting Of The Cosmological Scale Factor As A Function Of Lookback Time, H. I. Ringermacher, L. R. Mead

Faculty Publications

In this work we describe a model-independent method of developing a plot of scale factor a(t) versus lookback time t_L from the usual Hubble diagram of modulus data against redshift. This is the first plot of this type. We follow the model-independent methodology of Daly & Djorgovski used for their radio-galaxy data. Once the a(t)data plot is completed, any model can be applied and will display as described in the standard literature. We then compile an extensive data set to z = 1.8 by combining Type Ia supernovae (SNe Ia) data from SNLS3 …

Casimir Energies In Spherically Symmetric Background Potentials Revisited, Matthew Beauregard, Michael Bordag, Klaus Kirsten

Faculty Publications

In this paper we reconsider the formulation for the computation of the Casimir energy in spherically symmetric background potentials. Compared to the previous analysis, the technicalities are much easier to handle and final answers are surprisingly simple.

Measurement Of Quasiparticle Transport In Aluminum Films Using Tungsten Transition-Edge Sensors, Jeffrey Yen, Benjamin Shank, Betty Young, Blas Cabrera, Paul Brink, Matthew Cherry, John Mark Kreikebaum, Robert Moffatt, Peter Redl, Astrid Tomada, Ted Tortorici

Faculty Publications

We report on experimental studies of phonon sensors which utilize quasiparticle diusion in thin aluminum films connected to tungsten transition-edge-sensors (TESs) operated at 35 mK. We show that basic TES physics and a simple physical model of the overlap region between the W and Al lms in our devices enables us to accurately reproduce the experimentally observed pulse shapes from x-rays absorbed in the Al films. We further estimate quasiparticle loss in Al lms using a simple diusion equation approach. These studies allow the design of phonon sensors with improved performance.

Seqassist: A Novel Toolkit For Preliminary Analysis Of Next-Generation Sequencing Data, Yan Peng, Andrew S. Maxwell, Natalie D. Barker, Jennifer G. Laird, Alan J. Kennedy, Nan Wang, Chaoyang Zhang, Ping Gong

Faculty Publications

Background: While next-generation sequencing (NGS) technologies are rapidly advancing, an area that lags behind is the development of efficient and user-friendly tools for preliminary analysis of massive NGS data. As an effort to fill this gap to keep up with the fast pace of technological advancement and to accelerate data-to-results turnaround, we developed a novel software package named SeqAssist ("Sequencing Assistant" or SA).

Results: SeqAssist takes NGS-generated FASTQ files as the input, employs the BWA-MEM aligner for sequence alignment, and aims to provide a quick overview and basic statistics of NGS data. It consists of three separate workflows: …

Beyond Sustainability: A New Conceptual Model, Molly Kerby, Gayle Mallinger

Faculty Publications

Over the last few decades, the notion of sustainability has become an interdisciplinary buzz word. Sustainability has been an integrative concept that includes three constructs or pillars: a) social; b) economic; and c) ecological. Until recently, theoretical approaches based on the three pillars approach have operated in silos rather than exploring the interconnectedness of the constructs. Few models have moved beyond the idea that logical relations exist among the constructs (social, economic, and ecological) to consider factors external to communities, nor have they examined the internal socio-economic factors that influence positive outcomes. While this conceptualization has raised awareness about the …

Machine Learning Nuclear Detonation Features, Daniel T. Schmitt, Gilbert L. Peterson

Faculty Publications

Nuclear explosion yield estimation equations based on a 3D model of the explosion volume will have a lower uncertainty than radius based estimation. To accurately collect data for a volume model of atmospheric explosions requires building a 3D representation from 2D images. The majority of 3D reconstruction algorithms use the SIFT (scale-invariant feature transform) feature detection algorithm which works best on feature-rich objects with continuous angular collections. These assumptions are different from the archive of nuclear explosions that have only 3 points of view. This paper reduces 300 dimensions derived from an image based on Fourier analysis and five edge …

Timing Mark Detection On Nuclear Detonation Video, Daniel T. Schmitt, Gilbert L. Peterson

Faculty Publications

During the 1950s and 1960s the United States conducted and filmed over 200 atmospheric nuclear tests establishing the foundations of atmospheric nuclear detonation behavior. Each explosion was documented with about 20 videos from three or four points of view. Synthesizing the videos into a 3D video will improve yield estimates and reduce error factors. The videos were captured at a nominal 2500 frames per second, but range from 2300-3100 frames per second during operation. In order to combine them into one 3D video, individual video frames need to be correlated in time with each other. When the videos were captured …

First All-Sky Search For Continuous Gravitational Waves From Unknown Sources In Binary Systems, Tiffany Summerscales, Ligo Scientific Collaboration And Virgo Collaboration

Faculty Publications

We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ∼2,254  h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of …

Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar

Faculty Publications

We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV4O9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to the Néel phase. …

Observation Of Heavy- And Light-Hole Split Direct Bandgap Photoluminescence From Tensile-Strained Gesn (0.03% Sn), Thomas R. Harris, Yung Kee Yeo, Mee-Yi Ryu, Richard T. Beeler, John Kouvetakis

Faculty Publications

Temperature- (T-) and laser power-dependent photoluminescence (PL) measurements have been made for the tensile-strained, undoped GeSn (0.03% Sn) film grown on Si substrate. The PL results show not only clear strain-split direct bandgap transitions to the light-hole (LH) and heavy-hole (HH) bands at energies of 0.827 and 0.851 eV at 10 K, respectively, but also clearly show both strong direct and indirect bandgap related PL emissions at almost all temperatures, which are rarely observed. This split of PL emissions can be directly observed only at low T and moderate laser power, and the two PL peaks merge into one broad …

Epaminondas: Exploring Combat Tactics, David W. King, Gilbert L. Peterson

Faculty Publications

Epaminondas is a two-person, zero-sum strategy game that combines long-term strategic play with highly tactical move sequences. The game has two unique features that make it stand out from other games. The first feature is the creation of phalanxes, which are groups of pieces that can move as a whole unit. As the number of pieces in a phalanx increases, the mobility and capturing power of the phalanx also increases. The second feature differs from many other strategy games: when a player makes a crossing, a winning move in the game, the second player has an opportunity to respond. This …

Low-Lying Neutron Unbound States In Be-12, J. K. Smith, T. Baumann, D. Bazin, J. Brown, S. Casarotto, Paul A. De Young, N. Frank, J. Hinnefeld, M. Hoffman, M. D. Jones, Z. Kohley, B. Luther, B. Marks, N. Smith, J. Snyder, A. Spyrou, S. L. Stephenson, M. Thoennessen, N. Viscariello, S. J. Williams

Faculty Publications

The neutron decay of an unbound resonance in Be-12 has been measured at 1243 +/- 21 keV decay energy with a width of 634 +/- 60 keV. This state was populated with a one-proton removal reaction from a 71 MeV/u B-13 beam incident upon a beryllium target. The invariant mass reconstruction of the resonance was achieved by measuring the daughter fragment in coincidence with neutrons. Despite being above the 2n separation energy, the state decays predominantly by the emission of one neutron to Be-11, setting an upper limit on the branching ratio for the two-neutron decay channel to Be-10 of …

Living At The Friendship House: Findings From Thetransition Planning Inventory, Jane E. Finn, Vicky-Lynn Holmes, Rebecca Johnson

Faculty Publications

A residential initiative, named the Friendship House, was created through advocates focused on helping people with intellectual disabilities live independently in affordable and safe housing on a university campus. The Friendship House is a small residence hall where individuals with intellectual disabilities live side-by-side with similarly aged and same gendered university students. Qualitative finding as in resident reports and observational data provides support that the Friendship House experience has been successful. However, to better equip these residents with intellectual disabilities, it is important to assess the program in terms of post school transition acquisition skills. This study focuses on whether …

Antimagic-Type Labelings, Sogol Jahanbekam

Faculty Publications

No abstract provided.

Near- And Sub-Barrier Fusion Of The Be7+ Ni58 System, E. Martinez-Quiroz, E. F. Aguilera, D. Lizcano, P Amador-Valenzuela, H. Garcia-Martinez, J. J. Kolata, A. Roberts, L. O. Lamm, G. Rogachev, V. Guimaraes, F. D. Becchetti, A. Villano, M. Ojaruega, M. Febbraro, Y. Chen, H. Jiang, Paul A. De Young, Graham F. Peaslee

Faculty Publications

Evaporation proton yields were measured for the fusion of the radioactive proton-rich nucleus Be-7 onto a Ni-58 target at six near-barrier energies. Total fusion cross sections were deduced by using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential, even for energies above the Coulomb barrier. Inelastic couplings can account for the enhancement at the highest energy. Total fusion channels nearly saturate the total reaction cross section in the measured energy region. Comparison with previous results scaled appropriately for Be-7 + (Al-27, U-238) shows good agreement.

Integrating Microbial Physiology And Physio-Chemical Principles In Soils With The Microbial-Mineral Carbon Stabilization (Mimics) Model, William R. Wieder, A. Stuart Grandy, Cynthia M. Kallenbach, Gordon B. Bonan

Faculty Publications

A growing body of literature documents the pressing need to develop soil biogeochemistry models that more accurately reflect contemporary understanding of soil processes and better capture soil carbon (C) responses to environmental perturbations. Models that explicitly represent microbial activity offer inroads to improve representations of soil biogeochemical processes, but have yet to consider relationships between litter quality, functional differences in microbial physiology, and the physical protection of microbial byproducts in forming stable soil organic matter (SOM). To address these limitations, we introduce the MIcrobial-MIneral Carbon Stabilization (MIMICS) model, and evaluate it by comparing site-level soil C projections with observations from …

Land-Use Legacies Regulate Decomposition Dynamics Following Bioenergy Crop Conversion, Cynthia M. Kallenbach, A. Stuart Grandy

Faculty Publications

Land-use conversion into bioenergy crop production can alter litter decomposition processes tightly coupled to soil carbon and nutrient dynamics. Yet, litter decomposition has been poorly described in bioenergy production systems, especially following land-use conversion. Predicting decomposition dynamics in postconversion bioenergy production systems is challenging because of the combined influence of land-use legacies with current management and litter quality. To evaluate how land-use legacies interact with current bioenergy crop management to influence litter decomposition in different litter types, we conducted a landscape-scale litterbag decomposition experiment. We proposed land-use legacies regulate decomposition, but their effects are weakened under higher quality litter and …

Statistical Comparison Of Results Of Redox Titrations Using K-2 Cr-2o-7 And Kio-3 In The Undergraduate Analytical Chemistry Lab, David W. Randall, Luis K. Garibay

Faculty Publications

Reducing the quantity of hazardous substances used and hazardous waste generated by under- graduate laboratory experiments is important. However, simply replacing hazardous compounds with less hazardous reagents may not retain the pedagogical (or analytical) goal of the experiment if the chemistry does not fundamentally work. We evaluated several literature-based replacement oxidants for K2Cr2O7 (potassium dichromate) and identified KIO3 (potassium iodate) as the only che- mically viable alternative for thiosulfate standardizations, consistent with use of iodate by others. Using ANOVA analysis, two years of student results where K2Cr2O7 was used as the oxidant were compared with two years of student results …

Search For Gravitational Waves Associated With Γ-Ray Bursts Detected By The Interplanetary Network, Tiffany Summerscales, Ligo Scientific Collaboration, Virgo Collaboration, And Ipn Collaboration

Faculty Publications

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005–2010 during LIGO’s fifth and sixth science runs and Virgo’s first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search …

Mineralogical Transformation And Electrochemical Nature Of Magnesium-Rich Primers During Natural Weathering, Shashi S. Pathak, Michael D. Blanton, Sharathkumar K. Mendon, James W. Rawlins

Faculty Publications

Magnesium-rich primers (MgRP) have generated great interest as a promising alternative to chromium-based primers for the protection of aluminum substrates but their performance during exterior exposure has not been well documented. This paper focuses on the evaluation of MgRP during natural weathering to gain insight into its mineralogical phase transformation and electrochemical nature. Control studies were conducted on Mg and AA2024-T3 coupons. The results indicate that Mg particles in MgRP transform into a variety of hydroxide, carbonate, and hydroxy carbonates. During natural weathering, CO₂ inhibited the dissolution of both Mg and AA2024-T3 as a result of protective carbonate layer …

Querie: Collaborative Database Exploration, Magdalini Eirinaki, Suju Abraham, Neoklis Polyzotis, Naushin Shaikh

Faculty Publications

No abstract provided.

Perturbative Unitarity Constraints On A Supersymmetric Higgs Portal, Kassahun Betre, Sonia Hedri, Devin Walker

Faculty Publications

We place perturbative unitarity constraints on both the dimensionful and dimensionless couplings in the Next-to-Minimal Supersymmetric Standard Model Higgs Sector. These constraints, plus the requirement that the singlino and/or Higgsino constitutes at least part of the observed dark matter relic abundance, generate upper bounds on the Higgs and neutralino/chargino mass spectrum. We obtain an upper bound of 12 TeV for the charginos and neutralinos and 20 TeV for the heavy Higgses outside defined fine-tuned regions. By using the NMSSM as a template, we describe a method which replaces naturalness arguments with more rigorous perturbative unitarity arguments to get a better …

Investigating Access To And Attitudes Toward Programming In A Physics Camp, Gina Quan, Ayush Gupta

Faculty Publications

Computer programming has become a critical skill in much of physics research and undergraduate physics coursework. Our aim is to understand students' complex relationships (epistemological and affective associations) to coding and design, and in particular, how they experience and perceive access to programming in physics contexts. We piloted a project-based instructional module using Arduino Rovers (Arduino-integrated programmable robot-tanks) in a summer camp for high school students hosted by University of Maryland Physics Department. Throughout the program, participants worked through several open-ended design tasks before designing and completing a final project. In interviews, we asked students to reflect on their experiences …

Narratives As A Fundamental Component Of Consciousness, Sandra L. Vaughan, Robert F. Mills, Michael R. Grimaila, Gilbert L. Peterson, Steven K. Rogers

Faculty Publications

In this paper, we propose a conceptual architecture that models human (spatially-temporally-modally) cohesive narrative development using a computer representation of quale properties. Qualia are proposed to be the fundamental "cognitive" components humans use to generate cohesive narratives. The engineering approach is based on cognitively inspired technologies and incorporates the novel concept of quale representation for computation of primitive cognitive components of narrative. The ultimate objective of this research is to develop an architecture that emulates the human ability to generate cohesive narratives with incomplete or perturbated information.

Methods And Results Of A Search For Gravitational Waves Associated With Gamma-Ray Bursts Using The Geo 600, Ligo, And Virgo Detectors, Tiffany Summerscales, Ligo Scientific Collaboration And Virgo Collaboration

Faculty Publications

In this paper we report on a search for short-duration gravitational wave bursts in the frequency range 64 Hz–1792 Hz associated with gamma-ray bursts (GRBs), using data from GEO 600 and one of the LIGO or Virgo detectors. We introduce the method of a linear search grid to analyze GRB events with large sky localization uncertainties, for example the localizations provided by the Fermi Gamma-ray Burst Monitor (GBM). Coherent searches for gravitational waves (GWs) can be computationally intensive when the GRB sky position is not well localized, due to the corrections required for the difference in arrival time between detectors. …

Effect Of Z1/2, Eh5, And Ci1 Deep Defects On The Performance Of N-Type 4h-Sic Epitaxial Layers Schottky Detectors: Alpha Spectroscopy And Deep Level Transient Spectroscopy Studies, M. A. Mannan, S. K. Chaudhuri, K. V. Nguyen, K. C. Mandal

Faculty Publications

No abstract provided.

Search For Gravitational Radiation From Intermediate Mass Black Hole Binaries In Data From The Second Ligo-Virgo Joint Science Run, Tiffany Summerscales, Ligo Scientific Collaboration And Virgo Collaboration

Faculty Publications

This paper reports on an unmodeled, all-sky search for gravitational waves from merging intermediate mass black hole binaries (IMBHB). The search was performed on data from the second joint science run of the LIGO and Virgo detectors (July 2009–October 2010) and was sensitive to IMBHBs with a range up to ∼200  Mpc, averaged over the possible sky positions and inclinations of the binaries with respect to the line of sight. No significant candidate was found. Upper limits on the coalescence-rate density of nonspinning IMBHBs with total masses between 100 and 450  M⊙ and mass ratios between 0.25 and 1 were …

P‐Nexfs Analysis Of Aerosol Phosphorus Delivered To The Mediterranean Sea, Amelia F. Longo, Ellery D. Ingall, Julia M. Diaz, Michelle Oakes, Laura E. King, Athanasios Nenes, Nikolaos Mihalopoulos, Kaliopi Violaki, Anna Avila, Claudia R. Benitez-Nelson, Jay Brandes, Ian Mcnulty, David J. Vine

Faculty Publications

Biological productivity in many ocean regions is controlled by the availability of the nutrient phosphorus. In the Mediterranean Sea, aerosol deposition is a key source of phosphorus and understanding its composition is critical for determining its potential bioavailability. Aerosol phosphorus was investigated in European and North African air masses using phosphorus near‐edge X‐ray fluorescence spectroscopy (P‐NEXFS). These air masses are the main source of aerosol deposition to the Mediterranean Sea. We show that European aerosols are a significant source of soluble phosphorus to the Mediterranean Sea. European aerosols deliver on average 3.5 times more soluble phosphorus than North African aerosols …

Linked-Cluster Expansion For The Green's Function Of The Infinite-U Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry

Faculty Publications

We implement a highly efficient strong-coupling expansion for the Green's function of the Hubbard model. In the limit of extreme correlations, where the onsite interaction is infinite, the evaluation of diagrams simplifies dramatically enabling us to carry out the expansion to the eighth order in powers of the hopping amplitude. We compute the finite-temperature Green's function analytically in the momentum and Matsubara frequency space as a function of the electron density. Employing Padé approximations, we study the equation of state, Kelvin thermopower, momentum distribution function, quasiparticle fraction, and quasiparticle lifetime of the system at temperatures lower than, or of the …

Investr: An R Package For Inverse Estimation, Brandon M. Greenwell, Christine M. Schubert Kabban

Faculty Publications

Inverse estimation is a classical and well-known problem in regression. In simple terms, it involves the use of an observed value of the response to make inference on the corresponding unknown value of the explanatory variable. To our knowledge, however, statistical software is somewhat lacking the capabilities for analyzing these types of problems. In this paper, we introduce investr (which stands for inverse estimation in R), a package for solving inverse estimation problems in both linear and nonlinear regression models.