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The dynamics of digits: calculating Pi with Galperin's billiards
No full textMathematics, Volume 8, Issue 4, 1 April 2020, Article number 509.In Galperin billiards, two balls colliding with a hard wall form an analog calculator for the digits of the number π. This classical, one-dimensional three-body system (counting the hard wall) calculates the digits of π in a base determined by the ratio of the masses of the two particles. This base can be any integer, but it can also be an irrational number, or even the base can be π itself. This article reviews previous results for Galperin billiards and then pushes these results farther. We provide a complete explicit solution for the balls' positions and velocities as a function of the collision number and time. We demonstrate that Galperin billiard can be mapped onto a two-particle Calogero-type model. We identify a second dynamical invariant for any mass ratio that provides integrability for the system, and for a sequence of specific mass ratios we identify a third dynamical invariant that establishes superintegrability. Integrability allows us to derive some new exact results for trajectories, and we apply these solutions to analyze the systematic errors that occur in calculating the digits of π with Galperin billiards, including curious cases with irrational number bases
Ecological costs of discrimination: racism, red cedar and resilience in farm bill conservation policy in Oklahoma
No full textRenewable Agriculture and Food Systems, Volume 35, Issue 4, 1 August 2020, Pages 420-434.This article makes the case that the legacy of institutional racism by the United States Department of Agriculture (USDA) is connected to the encroachment of the invasive species Juniperus virginiana (eastern red cedar) on farming land. Red cedar's encroachment impacts Black farmers disproportionately in Oklahoma, even as it undermines broader USDA conservation goals and ability to adapt to climate change. As such, this case study illustrates the shortcomings of Farm Bill Conservation Title programs to address ecological issues across the landscape—shortcomings that hinder farmers' ability to carry out long-term adaptation and mitigate risks. Conversely, we show how the work of Oklahoma Black Historical Research Project, Inc. and the Rural Coalition has been vital allies in Black farmers inter-related struggles against racial injustice and red cedar. Thus, we argue community-based organizations have a pivotal, but under-supported, role to play in the shaping and application of farm bill programs and funds
Neighbors Dry Cleaning
No full textSigns on the door of Neighbors Dry Cleaning on E and 11th Streets SE. The large green sign displays the business' temporary hours due to Coronavirus; another sign highlights the power of dry cleaning to kill viruses; a third sign advertises masks for sale for $7.00
Hopeful note posted on a bus schedule sign
No full textA pink note is posted to a G* bus schedule sign. Handwritten on the note in red marker is the phrase 'EVERYTHING WILL BE ALRIGHT
The effect of economy type on heroin and saccharin essential value
No full textAuthor manuscript. Final version published in: Experimental and Clinical Psychopharmacology, Volume 27, Issue 6, December 2019, Pages 598-608.According to behavioral economics, reinforcer value should be lower in an open economy than in a closed economy. An animal model was used to determine how economy type affected the value of heroin and saccharin. In a first phase, separate groups of rats worked for heroin or saccharin. The price of these reinforcers increased over sessions. For rats in the open heroin or open saccharin economies, the work period of each session was followed by a postwork period where a cheaper source of heroin or saccharin was available for three hours. For rats in the closed economies, the work period was their only opportunity to obtain the reinforcer. Rats in the open saccharin economy worked less hard to defend consumption of saccharin as price increased than rats in the closed saccharin economy. That is, opening the saccharin economy reduced its essential value. In contrast, economy type had no effect on heroin's essential value. In a second phase, rats were allowed to choose between heroin and saccharin. The majority of rats strongly preferred saccharin over heroin regardless of economy type. The finding that economy type changed the essential value of saccharin, but not heroin, adds to previous findings suggesting that the value of drug reinforcers is unaffected by future drug availability. The difference in effect of economy type on drug versus nondrug reinforcers could be relevant to addiction
Altered local cerebellar and brainstem development in preterm infants
No full textNeuroImage, Volume 213, June 2020, Article number 116702.Background: Premature birth is associated with high prevalence of neurodevelopmental impairments in surviving infants. The putative role of cerebellar and brainstem dysfunction remains poorly understood, particularly in the absence of overt structural injury. Method: We compared in-utero versus ex-utero global, regional and local cerebellar and brainstem development in healthy fetuses (n = 38) and prematurely born infants without evidence of structural brain injury on conventional MRI studies (n = 74) that were performed at two time points: the first corresponding to the third trimester, either in utero or ex utero in the early postnatal period following preterm birth (30–40 weeks of gestation; 38 control fetuses; 52 premature infants) and the second at term equivalent age (37–46 weeks; 38 control infants; 58 premature infants). We compared 1) volumetric growth of 7 regions in the cerebellum (left and right hemispheres, left and right dentate nuclei, and the anterior, neo, and posterior vermis); 2) volumetric growth of 3 brainstem regions (midbrain, pons, and medulla); and 3) shape development in the cerebellum and brainstem using spherical harmonic description between the two groups. Results: Both premature and control groups showed regional cerebellar differences in growth rates, with the left and right cerebellar hemispheres showing faster growth compared to the vermis. In the brainstem, the pons grew faster than the midbrain and medulla in both prematurely born infants and controls. Using shape analyses, premature infants had smaller left and right cerebellar hemispheres but larger regional vermis and paravermis compared to in-utero control fetuses. For the brainstem, premature infants showed impaired growth of the superior surface of the midbrain, anterior surface of the pons, and inferior aspects of the medulla compared to the control fetuses. At term-equivalent age, premature infants had smaller cerebellar hemispheres bilaterally, extending to the superior aspect of the left cerebellar hemisphere, and larger anterior vermis and posteroinferior cerebellar lobes than healthy newborns. For the brainstem, large differences between premature infants and healthy newborns were found in the anterior surface of the pons. Conclusion: This study analyzed both volumetric growth and shape development of the cerebellum and brainstem in premature infants compared to healthy fetuses using longitudinal MRI measurements. The findings in the present study suggested that preterm birth may alter global, regional and local development of the cerebellum and brainstem even in the absence of structural brain injury evident on conventional MRI
EXAMINATION OF WATER QUALITY IN THE ANACOSTIA WATERSHED: COMPARATIVE ANALYSIS OF FLUORANTHENE, NAPHTHALENE, PYRENE, DECAMETHYLCYCLOPENTASILOXANE (D5), AND 2, 4, 6, 8-TETRAMETHYLCYCLOTETRASILOXANE (2468) IN URBAN AND SUBURBAN LOCATIONS
No full textThe Anacostia River is a major waterway located in Washington, D.C. It is also one of the nation’s 10 most contaminated rivers, containing sewage, metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs), and has been cited by the EPA as a "major area of concern" for the Chesapeake region. The following research aimed to determine the concentrations of five contaminants – fluoranthene, naphthalene, pyrene, decamethylcyclopentasilolxane (D5) and 2,4,6,8-Tetramethylcyclotetrasiloxane (2468) – at five sites within the Anacostia watershed to determine whether there was a correlation between land use patterns and contaminant concentrations. There were no statistically significant differences in contaminant concentrations between urban and suburban sites except for D5, in which urban sites had higher concentrations. There was no statistically significant difference when comparing seasonality to fluoranthene concentrations. There was no predictive relationship at all between population density, precipitation, discharge rates and the concentrations observed. Although 2468 was not identified in any of the samples, these results provided concentrations for fluoranthene, naphthalene, pyrene, and D5 amongst the five chosen sample sites. The average sediment concentrations for fluoranthene (2.70 x 10^1 ± 2.18 x 10^1 µM/g), naphthalene (1.37 x 10^2 ± 1.58 x 10^-2 µM/g), and pyrene (2.01 x 10^2 ± 3.66 x 10^1 µM/g) have increased in comparison to studies published in the early 2000s.Environmental scienceGeochemistryGeographic information science and geodesyAnacostia Watershed, Geochemistry, Geographic Information Science, Land Use, Polycyclic Aromatic Hydrocarbons, SiloxanesEnvironmental ScienceDegree Awarded: M.S. Environmental Science. American Universit
Observations of Jupiter family comet 252P/LINEAR during a close approach to Earth reveal large abundances of Methanol and Ethane
No full textThe Astronomical Journal, Volume 158, Number 3.We observed short-period comet 252P/LINEAR post-perihelion during its 2016 passage, which presented a favorable opportunity to survey its chemical composition at a close Earth approach (~0.14 au). We characterized the comet's chemical composition on four dates (UT 2016 April 12, 19, 26, and 29) using spectroscopic measurements with the Near-infrared Spectrograph (NIRSPEC) at the Keck Observatory on Maunakea, HI. Our high-resolution infrared spectra yielded production rates for four species (H2O, CH3OH, C2H6, and HCN) and upper limits for five species (NH3, H2CO, C2H2, CO, and CH4). We measured water at an average production rate of 4.9 ± 0.1 × 1027 molec s−1. The chemical properties of 252P suggest a rather typical composition, yet somewhat enriched in methanol and ethane but low in formaldehyde (upper limit) compared to other short-period comets surveyed at infrared wavelengths. Analysis of the ortho/para ratio in water indicates a nuclear spin temperature larger than ~38 K, consistent with statistical equilibrium (2σ). Spatial distributions of gases, which are representative of possible heterogeneity in the nucleus and/or gas dynamics upon sublimation, showed rather symmetric profiles, with subtle enhancements of the more volatile species C2H6 and HCN toward the sunward hemisphere, while water showed spatial distributions that were extended toward the anti-sunward hemisphere. The continuum was characterized by a narrow distribution. We place our infrared results in the context of observations with the Discovery Channel Telescope, the James Clerk Maxwell submillimeter Telescope, and the Hubble Space Telescope
View of Magic Fingers Hair Designer, Inc. on H Street NE
No full textView of the Magic Fingers Hair Designer, Inc. storefront located on H Street NE. A message to customers about closing is posted on the door
Optimizing waste collection routes in Howard County using Mathematical Modeling tools
No full textA presentation that was delivered in the Fifth University Research Day at the Catholic University of America in 2020.This research was collaborated with Sarthak Regm