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Articles 181 - 210 of 587

Full-Text Articles in Physical Sciences and Mathematics

Early Dark Energy Can Resolve The Hubble Tension, V. Poulin, Tristan L. Smith, T. Karwal, M. Kamionkowski Jun 2019

Early Dark Energy Can Resolve The Hubble Tension, V. Poulin, Tristan L. Smith, T. Karwal, M. Kamionkowski

Physics & Astronomy Faculty Works

Early dark energy (EDE) that behaves like a cosmological constant at early times (redshifts z≳3000) and then dilutes away like radiation or faster at later times can solve the Hubble tension. In these models, the sound horizon at decoupling is reduced resulting in a larger value of the Hubble parameter H0 inferred from the cosmic microwave background (CMB). We consider two physical models for this EDE, one involving an oscillating scalar field and another a slowly rolling field. We perform a detailed calculation of the evolution of perturbations in these models. A Markov Chain Monte Carlo search of the parameter …

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Magnetothermodynamics: An Experimental Study Of The Equations Of State Applicable To A Magnetized Plasma, M. Kaur, Michael R. Brown, A. D. Light May 2019

Magnetothermodynamics: An Experimental Study Of The Equations Of State Applicable To A Magnetized Plasma, M. Kaur, Michael R. Brown, A. D. Light

Physics & Astronomy Faculty Works

Measuring the equations of state of a compressed magnetized plasma is important for both advancing fusion experiments and understanding natural systems such as stellar winds. In this paper, we present results from our experiments on the thermodynamics of compressed magnetized plasmas; we call these studies “magnetothermodynamics.” In these experiments, we generate parcels of relaxed, magnetized plasma at one end of the linear Swarthmore Spheromak eXperimental device and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. Instances of ion heating during compression are identified by constructing a pressure-volume diagram using …

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G-Quadruplex Dynamics Contribute To Regulation Of Mitochondrial Gene Expression, M. Falabella, J. E. Kolesar, C. Wallace, D. De Jesus, L. Sun, Y. V. Taguichi, C. Wang, T. Wang, Irene M. Xiang , '18, J. K. Alder, R. Maheshan, W. Horne, Joshua R. Turek-Herman , '16, P. J. Pagano, C. M. St. Croix, N. Sondheimer, Liliya A. Yatsunyk, F. B. Johnson, B. A. Kaufman Apr 2019

G-Quadruplex Dynamics Contribute To Regulation Of Mitochondrial Gene Expression, M. Falabella, J. E. Kolesar, C. Wallace, D. De Jesus, L. Sun, Y. V. Taguichi, C. Wang, T. Wang, Irene M. Xiang , '18, J. K. Alder, R. Maheshan, W. Horne, Joshua R. Turek-Herman , '16, P. J. Pagano, C. M. St. Croix, N. Sondheimer, Liliya A. Yatsunyk, F. B. Johnson, B. A. Kaufman

Chemistry & Biochemistry Faculty Works

Single-stranded DNA or RNA sequences rich in guanine (G) can adopt non-canonical structures known as G-quadruplexes (G4). Mitochondrial DNA (mtDNA) sequences that are predicted to form G4 are enriched on the heavy-strand and have been associated with formation of deletion breakpoints. Increasing evidence supports the ability of mtDNA to form G4 in cancer cells; however, the functional roles of G4 structures in regulating mitochondrial nucleic acid homeostasis in non-cancerous cells remain unclear. Here, we demonstrate by live cell imaging that the G4-ligand RHPS4 localizes primarily to mitochondria at low doses. We find that low doses of RHPS4 do not induce …

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Lab Practicum For Bias In Algorithms, Ameet Soni, Krista Karbowski Thomason Apr 2019

Lab Practicum For Bias In Algorithms, Ameet Soni, Krista Karbowski Thomason

Digital Humanities Curricular Development

This is a course assignment to demonstrate potential biases encoded in algorithms (this can be linked more specifically to natural language processing, machine learning, or artificial intelligence) using the Word Embedding Association Test. In lab, students will work with programs that demonstrate the usefulness of word embedding algorithms in finding relationships between words. Then, students will use an implementation of the algorithm in "Semantics derived automatically from language corpora contain human-like biases" by Caliskan et al. to detect gender and racial bias encoded in word embeddings. The assignment has students design and run an experiment using the WEAT algorithm to …

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Fys: Ethics And Technology (Phil 07/Cpsc 15) Syllabus, Ameet Soni, Krista Karbowski Thomason Apr 2019

Fys: Ethics And Technology (Phil 07/Cpsc 15) Syllabus, Ameet Soni, Krista Karbowski Thomason

Digital Humanities Curricular Development

There has been an accelerated shift in the influence of computing technology and the use of algorithms in our daily lives. With this technology comes serious ethical questions. Philosophers are often well-equipped to wrestle with ethical questions, but less well-equipped to wrestle with questions of technology itself. Computer scientists are well-equipped to deal with the problems and challenges of technology, but less well-equipped to deal with the ethical problems and challenges that technology can pose. In this co-taught course, we bring together the two fields to address ethical questions involving social media, data mining, self-driving cars, artificial intelligence, and other …

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Soma-Axon Coupling Configurations That Enhance Neuronal Coincidence Detection, Joshua H. Goldwyn, M. W. H. Remme, J. Rinzel Mar 2019

Soma-Axon Coupling Configurations That Enhance Neuronal Coincidence Detection, Joshua H. Goldwyn, M. W. H. Remme, J. Rinzel

Mathematics & Statistics Faculty Works

Coincidence detector neurons transmit timing information by responding preferentially to concurrent synaptic inputs. Principal cells of the medial superior olive (MSO) in the mammalian auditory brainstem are superb coincidence detectors. They encode sound source location with high temporal precision, distinguishing submillisecond timing differences among inputs. We investigate computationally how dynamic coupling between the input region (soma and dendrite) and the spike-generating output region (axon and axon initial segment) can enhance coincidence detection in MSO neurons. To do this, we formulate a two-compartment neuron model and characterize extensively coincidence detection sensitivity throughout a parameter space of coupling configurations. We focus on …

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Resolved Young Binary Systems And Their Disks, R. L. Akeson, Eric L.N. Jensen, J. Carpenter, L. Ricci, S. Laos, N. F. Nogueira, Emma M. Suen-Lewis , '18 Feb 2019

Resolved Young Binary Systems And Their Disks, R. L. Akeson, Eric L.N. Jensen, J. Carpenter, L. Ricci, S. Laos, N. F. Nogueira, Emma M. Suen-Lewis , '18

Physics & Astronomy Faculty Works

We have conducted a survey of young single and multiple systems in the Taurus–Auriga star-forming region with the Atacama Large Millimeter Array (ALMA), substantially improving both the spatial resolution and sensitivity with which individual protoplanetary disks in these systems have been observed. These ALMA observations can resolve binary separations as small as 25–30 au and have an average 3σ detection level of 0.35 mJy, equivalent to a disk mass of 4 × 10−5 M ⊙ for an M3 star. Our sample was constructed from stars that have an infrared excess and/or signs of accretion and have been classified as Class …

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Probing Spatial Variation Of The Fine-Structure Constant Using The Cmb, Tristan L. Smith, D. Grin, David B. Robinson , '19, Davy Qi , '19 Feb 2019

Probing Spatial Variation Of The Fine-Structure Constant Using The Cmb, Tristan L. Smith, D. Grin, David B. Robinson , '19, Davy Qi , '19

Physics & Astronomy Faculty Works

The fine-structure constant, α, controls the strength of the electromagnetic interaction. There are extensions of the standard model in which α is dynamical on cosmological length and time scales. The physics of the cosmic microwave background (CMB) depends on the value of α. The effects of spatial variation in α on the CMB are similar to those produced by weak lensing: smoothing of the power spectrum, and generation of non-Gaussian features. These would induce a bias to estimates of the weak-lensing potential power spectrum of the CMB. Using this effect, Planck measurements of the temperature and polarization power spectrum, as …

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Ring Expansion Of Alkylidenecarbenes Derived From Lactams, Lactones, And Thiolactones Into Strained Heterocyclic Alkynes: A Theoretical Study, N. N. Thu Le, J. Just, J. M. Pankauski, Paul R. Rablen, D. M. Thamattoor Feb 2019

Ring Expansion Of Alkylidenecarbenes Derived From Lactams, Lactones, And Thiolactones Into Strained Heterocyclic Alkynes: A Theoretical Study, N. N. Thu Le, J. Just, J. M. Pankauski, Paul R. Rablen, D. M. Thamattoor

Chemistry & Biochemistry Faculty Works

Strained cycloalkynes are of considerable interest to theoreticians and experimentalists, and possess much synthetic value as well. Herein, a series of cyclic alkylidenecarbenes—formally obtained by replacing the carbonyl oxygen of four-, five-, and six-membered lactams, lactones, and thiolactones with a divalent carbon—were modeled at the CCSD(T)/cc-pVTZ//B3LYP/6-311+G** and CCSD(T)/cc-pVTZ//CCSD/6-311+G** levels of theory. The singlet carbenes were found to be more stable than the triplets. The strained heterocyclic alkynes formed by ring expansion of these singlet carbenes were also modeled. Interestingly, the C≡C bonds in the five-membered heterocycles, obtained from the rearrangement of β-lactam- and β-lactone-derived alkylidenecarbenes, displayed lengths intermediate between formal …

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Extreme Resonance Line Profile Variations In The Ultraviolet Spectra Of Ngc 1624-2: Probing The Giant Magnetosphere Of The Most Strongly Magnetized Known O-Type Star, A. David-Uraz, C. Erba, V. Petit, A. W. Fullerton, F. Martins, N. R. Walborn, R. Macinnis, R. H. Barbá, David H. Cohen, J. Maíz Apellániz, Y. Nazé, S. P. Owocki, J. O. Sundqvist, A Ud-Doula, G. A. Wade Feb 2019

Extreme Resonance Line Profile Variations In The Ultraviolet Spectra Of Ngc 1624-2: Probing The Giant Magnetosphere Of The Most Strongly Magnetized Known O-Type Star, A. David-Uraz, C. Erba, V. Petit, A. W. Fullerton, F. Martins, N. R. Walborn, R. Macinnis, R. H. Barbá, David H. Cohen, J. Maíz Apellániz, Y. Nazé, S. P. Owocki, J. O. Sundqvist, A Ud-Doula, G. A. Wade

Physics & Astronomy Faculty Works

In this paper, we present high-resolution HST/COS observations of the extreme magnetic O star NGC 1624-2. These represent the first ultraviolet spectra of this archetypal object. We examine the variability of its wind-sensitive resonance lines, comparing it to that of other known magnetic O stars. In particular, the observed variations in the profiles of the C  iv and Si  iv doublets between low state and high state are the largest observed in any magnetic O-type star, consistent with the expected properties of NGC 1624-2’s magnetosphere. We also observe a redshifted absorption component in the low state, a feature not seen …

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Tess Discovery Of An Ultra-Short-Period Planet Around The Nearby M Dwarf Lhs 3844, R. Vanderspek, C. X. Huang, A. Vanderburg, G. R. Ricker, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins, J. Burt, J. Dittmann, E. Newton, S. N. Quinn, A. Shporer, D. Charbonneau, J. Irwin, K. Ment, J. G. Winters, K. A. Collins, P. Evans, T. Gan, R. Hart, Eric L.N. Jensen, J. Kielkopf, S. Mao, W. Waalkes, F. Bouchy, M. Marmier, L. D. Nielsen, G. Ottoni, F. Pepe, D. Ségransan, S. Udry, T. Henry, L. A. Paredes, H.-S. James, R. H. Hinojosa, M. L. Silverstein, E. Palle, Z. Berta-Thompson, I. Crossfield, M. D. Davies, D. Dragomir, M. Fausnaugh, A. Glidden, J. Pepper, E. H. Morgan, M. Rose, J. D. Twicken, J. N. S. Villaseñor, L. Yu, G. Bakos, J. Bean, L. A. Buchhave, J. Christensen-Dalsgaard, J. L. Christiansen, D. R. Ciardi, M. Clampin, N. De Lee, D. Deming, J. Doty, J. G. Jernigan, L. Kaltenegger, J. J. Lissauer, P. R. Mccullough, N. Narita, M. Paegert, A. Pal, S. Rinehart, D. Sasselov, B. Sato, A. Sozzetti, K. G. Stassun, G. Torres Feb 2019

Tess Discovery Of An Ultra-Short-Period Planet Around The Nearby M Dwarf Lhs 3844, R. Vanderspek, C. X. Huang, A. Vanderburg, G. R. Ricker, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins, J. Burt, J. Dittmann, E. Newton, S. N. Quinn, A. Shporer, D. Charbonneau, J. Irwin, K. Ment, J. G. Winters, K. A. Collins, P. Evans, T. Gan, R. Hart, Eric L.N. Jensen, J. Kielkopf, S. Mao, W. Waalkes, F. Bouchy, M. Marmier, L. D. Nielsen, G. Ottoni, F. Pepe, D. Ségransan, S. Udry, T. Henry, L. A. Paredes, H.-S. James, R. H. Hinojosa, M. L. Silverstein, E. Palle, Z. Berta-Thompson, I. Crossfield, M. D. Davies, D. Dragomir, M. Fausnaugh, A. Glidden, J. Pepper, E. H. Morgan, M. Rose, J. D. Twicken, J. N. S. Villaseñor, L. Yu, G. Bakos, J. Bean, L. A. Buchhave, J. Christensen-Dalsgaard, J. L. Christiansen, D. R. Ciardi, M. Clampin, N. De Lee, D. Deming, J. Doty, J. G. Jernigan, L. Kaltenegger, J. J. Lissauer, P. R. Mccullough, N. Narita, M. Paegert, A. Pal, S. Rinehart, D. Sasselov, B. Sato, A. Sozzetti, K. G. Stassun, G. Torres

Physics & Astronomy Faculty Works

Data from the newly commissioned Transiting Exoplanet Survey Satellite has revealed a "hot Earth" around LHS 3844, an M dwarf located 15 pc away. The planet has a radius of 1.303 ± 0.022 R⊕ and orbits the star every 11 hr. Although the existence of an atmosphere around such a strongly irradiated planet is questionable, the star is bright enough (I = 11.9, K = 9.1) for this possibility to be investigated with transit and occultation spectroscopy. The star's brightness and the planet's short period will also facilitate the measurement of the planet's mass through Doppler spectroscopy.

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Diagnosing The Clumpy Protoplanetary Disk Of The Uxor Type Young Star Gm Cephei, P. C. Huang, W. P. Chen, M. Mugrauer, R. Bischoff, J. Budaj, O. Burkhonov, S. Ehgamberdiev, R. Errmann, Z. Garai, H. Y. Hsiao, C. L. Hu, R. Janulis, Eric L.N. Jensen, S. Kiyota, K. Kuramoto, C. S. Lin, H. C. Lin, J. Z. Liu, O. Lux, H. Naito, R. Neuhäuser, J. Ohlert, E. Pakštienė, T. Pribulla, J. K. T. Qvam, S. Raetz, S. Sato, M. Schwartz, E. Semkov, S. Takagi, D. Wagner, M. Watanabe, Y. Zhang Feb 2019

Diagnosing The Clumpy Protoplanetary Disk Of The Uxor Type Young Star Gm Cephei, P. C. Huang, W. P. Chen, M. Mugrauer, R. Bischoff, J. Budaj, O. Burkhonov, S. Ehgamberdiev, R. Errmann, Z. Garai, H. Y. Hsiao, C. L. Hu, R. Janulis, Eric L.N. Jensen, S. Kiyota, K. Kuramoto, C. S. Lin, H. C. Lin, J. Z. Liu, O. Lux, H. Naito, R. Neuhäuser, J. Ohlert, E. Pakštienė, T. Pribulla, J. K. T. Qvam, S. Raetz, S. Sato, M. Schwartz, E. Semkov, S. Takagi, D. Wagner, M. Watanabe, Y. Zhang

Physics & Astronomy Faculty Works

UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM Cephei is such a UXor in the young (∼4 Myr) open cluster Trumpler 37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008–2018) detects (1) an ∼3.43 day period, likely arising from rotational modulation by surface starspots, (2) sporadic brightening on timescales of days due to accretion, (3) irregular minor flux drops due to circumstellar dust extinction, and (4) major flux drops, each lasting for a couple of months with a recurrence time, though not …

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Optimal Separation And Strong Direct Sum For Randomized Query Complexity, E. Blais, Joshua Brody Jan 2019

Optimal Separation And Strong Direct Sum For Randomized Query Complexity, E. Blais, Joshua Brody

Computer Science Faculty Works

We establish two results regarding the query complexity of bounded-error randomized algorithms. Bounded-error separation theorem. There exists a total function f : {0,1}^n -> {0,1} whose epsilon-error randomized query complexity satisfies overline{R}_epsilon(f) = Omega(R(f) * log 1/epsilon). Strong direct sum theorem. For every function f and every k >= 2, the randomized query complexity of computing k instances of f simultaneously satisfies overline{R}_epsilon(f^k) = Theta(k * overline{R}_{epsilon/k}(f)). As a consequence of our two main results, we obtain an optimal superlinear direct-sum-type theorem for randomized query complexity: there exists a function f for which R(f^k) = Theta(k log k * R(f)). …

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Optimal Separation And Strong Direct Sum For Randomized Query Complexity, E. Blais, Joshua Brody Jan 2019

Optimal Separation And Strong Direct Sum For Randomized Query Complexity, E. Blais, Joshua Brody

Computer Science Faculty Works

We establish two results regarding the query complexity of bounded-error randomized algorithms. Bounded-error separation theorem. There exists a total function f : {0,1}^n -> {0,1} whose epsilon-error randomized query complexity satisfies overline{R}_epsilon(f) = Omega(R(f) * log 1/epsilon). Strong direct sum theorem. For every function f and every k >= 2, the randomized query complexity of computing k instances of f simultaneously satisfies overline{R}_epsilon(f^k) = Theta(k * overline{R}_{epsilon/k}(f)). As a consequence of our two main results, we obtain an optimal superlinear direct-sum-type theorem for randomized query complexity: there exists a function f for which R(f^k) = Theta(k log k * R(f)). …

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N-Methyl Mesoporphyrin Ix As A Highly Selective Light-Up Probe For G-Quadruplex Dna, Ariana Yett , '21, Linda Yingqi Lin , '20, Dana Beseiso , '21, Joanne Miao , '22, Liliya A. Yatsunyk Jan 2019

N-Methyl Mesoporphyrin Ix As A Highly Selective Light-Up Probe For G-Quadruplex Dna, Ariana Yett , '21, Linda Yingqi Lin , '20, Dana Beseiso , '21, Joanne Miao , '22, Liliya A. Yatsunyk

Chemistry & Biochemistry Faculty Works

N-methyl mesoporphyrin IX (NMM) is a water-soluble, non-symmetric porphyrin with excellent optical properties and unparalleled selectivity for G-quadruplex (GQ) DNA. G-quadruplexes are non-canonical DNA structures formed by guanine-rich sequences. They are implicated in genomic stability, longevity, and cancer. The ability of NMM to selectively recognize GQ structures makes it a valuable scaffold for designing novel GQ binders. In this review, we survey the literature describing the GQ-binding properties of NMM as well as its wide utility in chemistry and biology. We start with the discovery of the GQ-binding properties of NMM and the development of NMM-binding aptamers. We then discuss …

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Schur's Lemma For Coupled Reducibility And Coupled Normality, D. Lahat, C. Jutten, Helene Shapiro Jan 2019

Schur's Lemma For Coupled Reducibility And Coupled Normality, D. Lahat, C. Jutten, Helene Shapiro

Mathematics & Statistics Faculty Works

Let $\mathcal A = \{A_{ij} \}_{i, j \in \mathcal I}$, where $\mathcal I$ is an index set, be a doubly indexed family of matrices, where $A_{ij}$ is $n_i \times n_j$. For each $i \in \mathcal I$, let $\mathcal V_i$ be an $n_i$-dimensional vector space. We say $\mathcal A$ is reducible in the coupled sense if there exist subspaces, $\mathcal U_i \subseteq \mathcal V_i$, with $\mathcal U_i \neq \{0\}$ for at least one $i \in \mathcal I$, and $\mathcal U_i \neq \mathcal V_i$ for at least one $i$, such that $A_{ij} (\mathcal U_j) \subseteq \mathcal U_i$ for all $i, j$. Let …

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Kelt-22ab: A Massive, Short-Period Hot Jupiter Transiting A Near-Solar Twin, J. Labadie-Bartz, J. E. Rodriguez, K. G. Stassun, D. R. Ciardi, K. Penev, M. C. Johnson, B. S. Gaudi, K. D. Colón, A. Bieryla, D. W. Latham, J. Pepper, K. A. Collins, P. Evans, H. Relles, R. J. Siverd, J. Bento, X. Yao, C. Stockdale, T.-G. Tan, G. Zhou, J. D. Eastman, M. D. Albrow, D. Bayliss, T. G. Beatty, P. Berlind, V. Bozza, M. L. Calkins, David H. Cohen, I. A. Curtis, G. A. Esquerdo, D. Feliz, B. J. Fulton, J. Gregorio, D. James, Eric L.N. Jensen, J. A. Johnson, S. A. Johnson, M. D. Joner, D. Kasper, J. F. Kielkopf, R. B. Kuhn, M. B. Lund, A. Malpas, M. Manner, N. Mccrady, K. K. Mcleod, T. E. Oberst, M. T. Penny, P. A. Reed, D. H. Sliski, D. C. Stephens, D. J. Stevens, S. Villanueva Jr., R. A. Wittenmyer, J. T. Wright, R. Zambelli Jan 2019

Kelt-22ab: A Massive, Short-Period Hot Jupiter Transiting A Near-Solar Twin, J. Labadie-Bartz, J. E. Rodriguez, K. G. Stassun, D. R. Ciardi, K. Penev, M. C. Johnson, B. S. Gaudi, K. D. Colón, A. Bieryla, D. W. Latham, J. Pepper, K. A. Collins, P. Evans, H. Relles, R. J. Siverd, J. Bento, X. Yao, C. Stockdale, T.-G. Tan, G. Zhou, J. D. Eastman, M. D. Albrow, D. Bayliss, T. G. Beatty, P. Berlind, V. Bozza, M. L. Calkins, David H. Cohen, I. A. Curtis, G. A. Esquerdo, D. Feliz, B. J. Fulton, J. Gregorio, D. James, Eric L.N. Jensen, J. A. Johnson, S. A. Johnson, M. D. Joner, D. Kasper, J. F. Kielkopf, R. B. Kuhn, M. B. Lund, A. Malpas, M. Manner, N. Mccrady, K. K. Mcleod, T. E. Oberst, M. T. Penny, P. A. Reed, D. H. Sliski, D. C. Stephens, D. J. Stevens, S. Villanueva Jr., R. A. Wittenmyer, J. T. Wright, R. Zambelli

Physics & Astronomy Faculty Works

We present the discovery of KELT-22Ab, a hot Jupiter from the KELT-South survey. KELT-22Ab transits the moderately bright (V ~ 11.1) Sun-like G2V star TYC 7518-468-1. The planet has an orbital period of P = 1.3866529 ± 0.0000027 days, a radius of RP = 1.285 ((+0.12)/(=0.071)) RJ, and a relatively large mass of MP = 3.47 ((+0.15)/(=0.14)) MJ. The star has R★ = 1.099 ((+0.079)/(=0.046)) R⊙, M★ = 1.092 ((+0.045)/(-0.041) M⊙, Teff = 5767 ((+50)/(-49) K, log g★ = 4.393 ((+0.039)/(-0.060)) (cgs), and [m/H] = …

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Equivalence Between Uniform L²⋆(Ω) A-Priori Bounds And Uniform L∞(Ω) A-Priori Bounds For Subcritical Elliptic Equations, A. Castro, Nsoki Mavinga, R. Pardo Jan 2019

Equivalence Between Uniform L²⋆(Ω) A-Priori Bounds And Uniform L∞(Ω) A-Priori Bounds For Subcritical Elliptic Equations, A. Castro, Nsoki Mavinga, R. Pardo

Mathematics & Statistics Faculty Works

We provide sufficient conditions for a uniform L²⋆(Ω) bound to imply a uniform L∞(Ω) bound for positive classical solutions to a class of subcritical elliptic problems in bounded C² domains in Rᴺ. We also establish an equivalent result for sequences of boundary value problems.

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Decision-Making In Forensic Identification Tasks, Amanda Luby Jan 2019

Decision-Making In Forensic Identification Tasks, Amanda Luby

Mathematics & Statistics Faculty Works

No abstract provided.

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Magnetothermodynamics In Ssx: Measuring The Equations Of State Of A Compressible Magnetized Plasma, Michael R. Brown, M. Kaur Jan 2019

Magnetothermodynamics In Ssx: Measuring The Equations Of State Of A Compressible Magnetized Plasma, Michael R. Brown, M. Kaur

Physics & Astronomy Faculty Works

Magnetothermodynamics is the study of compression and expansion of magnetized plasma with an eye toward identifying equations of state (EOSs) for magneto-inertial fusion experiments. We present recent results from Swarthmore Spheromak Experiment (SSX) experiments on the thermodynamics of compressed magnetized plasmas called Taylor states. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a 1.5-m-long copper flux conserver and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion heating during compression are identified by constructing a pressure-volume diagram …

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Mechanism For Copper(Ii)-Mediated Disaggregation Of A Porphyrin J-Aggregate, M. Trapani, I. G. Occhiuto, R. Zagami, G. De Luca, M. A. Castriciano, A. Romeo, L. M. Scolaro, Robert F. Pasternack Dec 2018

Mechanism For Copper(Ii)-Mediated Disaggregation Of A Porphyrin J-Aggregate, M. Trapani, I. G. Occhiuto, R. Zagami, G. De Luca, M. A. Castriciano, A. Romeo, L. M. Scolaro, Robert F. Pasternack

Chemistry & Biochemistry Faculty Works

J-aggregates of anionic meso-tetrakis(4-sulfonatophenyl)porphyrin form at intermediate pH (2.3–3.1) in the presence of NiSO₄ or ZnSO₄ (ionic strength, I.S. = 3.2 M). These aggregates convert to monomeric porphyrin units via metallation with copper(II) ions. The kinetics for the disassembly process, as monitored by UV/vis spectroscopy, exhibits zeroth-order behavior. The observed zeroth-order rate constants show a two-term dependence on copper(II) ion concentrations: linear and second order. Also observed is an inverse dependence on hydrogen ion concentration. Activation parameters have been determined for the disassembly process leading to ΔH^≠ = (+163 ± 15) kJ·mol⁻¹ and ΔS^≠ = (+136 ± 11) J·K⁻¹. A …

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Optimization Of Detergent-Mediated Reconstitution Of Influenza A M2 Protein Into Proteoliposomes, Catherine Hirshfeld Crouch, Margaret H. Bost , '17, Tae H. Kim , '14, Bryan M. Green , '16, Douglas Stuart Arbuckle , '17, Carl H. Grossman, Kathleen P. Howard Dec 2018

Optimization Of Detergent-Mediated Reconstitution Of Influenza A M2 Protein Into Proteoliposomes, Catherine Hirshfeld Crouch, Margaret H. Bost , '17, Tae H. Kim , '14, Bryan M. Green , '16, Douglas Stuart Arbuckle , '17, Carl H. Grossman, Kathleen P. Howard

Physics & Astronomy Faculty Works

We report the optimization of detergent-mediated reconstitution of an integral membrane-bound protein, full-length influenza M2 protein, by direct insertion into detergent-saturated liposomes. Detergent-mediated reconstitution is an important method for preparing proteoliposomes for studying membrane proteins, and must be optimized for each combination of protein and membrane constituents used. The purpose of the reconstitution was to prepare samples for site-directed spin-labeling electron paramagnetic resonance (SDSL-EPR) studies. Our goals in optimizing the protocol were to minimize the amount of detergent used, reduce overall proteoliposome preparation time, and confirm the removal of all detergent. The liposomes were comprised of (1-palmitoyl-2-oleyl-sn-glycero-phosphocholine (POPC) and 1-palmitoyl-2-oleyl-sn-glycero-3-[phospho-rac-(1-glycerol)] …

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Interactions Between Spermine-Derivatized Tentacle Porphyrins And The Human Telomeric Dna G-Quadruplex, Navin C. Sabharwal , '14, Jessica Chen , '17, Joo Hyun Lee , '17, C. M. A. Gangemi, A. D'Urso, Liliya A. Yatsunyk Nov 2018

Interactions Between Spermine-Derivatized Tentacle Porphyrins And The Human Telomeric Dna G-Quadruplex, Navin C. Sabharwal , '14, Jessica Chen , '17, Joo Hyun Lee , '17, C. M. A. Gangemi, A. D'Urso, Liliya A. Yatsunyk

Chemistry & Biochemistry Faculty Works

G-rich DNA sequences have the potential to fold into non-canonical G-Quadruplex (GQ) structures implicated in aging and human diseases, notably cancers. Because stabilization of GQs at telomeres and oncogene promoters may prevent cancer, there is an interest in developing small molecules that selectively target GQs. Herein, we investigate the interactions of meso-tetrakis-(4-carboxysperminephenyl)porphyrin (TCPPSpm4) and its Zn(II) derivative (ZnTCPPSpm4) with human telomeric DNA (Tel22) via UV-Vis, circular dichroism (CD), and fluorescence spectroscopies, resonance light scattering (RLS), and fluorescence resonance energy transfer (FRET) assays. UV-Vis titrations reveal binding constants of 4.7 × 10⁶ and 1.4 × 10⁷ M⁻¹ and binding stoichiometry of …

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The Kelt Follow-Up Network And Transit False-Positive Catalog: Pre-Vetted False Positives For Tess, K. A. Collins, K. I. Collins, J. Pepper, J. Labadie-Bartz, K. G. Stassun, B. S. Gaudi, D. Bayliss, J. Bento, K. D. Colón, D. Feliz, D. James, M. C. Johnson, R. B. Kuhn, M. B. Lund, M. T. Penny, J. E. Rodriguez, R. J. Siverd, D. J. Stevens, X. Yao, G. Zhou, M. Akshay, G. F. Aldi, C. Ashcraft, S. Awiphan, Ö. Baştürk, D. Baker, T. G. Beatty, P. Benni, P. Berlind, G. B. Berriman, Z. Berta-Thompson, A. Bieryla, V. Bozza, S. C. Novati, M. L. Calkins, J. M. Cann, D. R. Ciardi, W. D. Cochran, David H. Cohen, D. Conti, J. R. Crepp, I. A. Curtis, G. D'Ago, K. A. Diazeguigure, C. D. Dressing, F. Dubois, E. Ellington, T. G. Ellis, G. A. Esquerdo, P. Evans, A. Friedli, A. Fukui, B. J. Fulton, E. J. Gonzales, J. C. Good, J. Gregorio, T. Gumusayak, D. A. Hancock, C. K. Harada, R. Hart, E. G. Hintz, H. Jang-Condell, E. J. Jeffery, Eric L.N. Jensen, E. Jofré, M. D. Joner, A. Kar, D. H. Kasper, B. Keten, J. F. Kielkopf, S. Komonjinda, C. Kotnik, D. W. Latham, J. Leuquire, T. R. Lewis, L. Logie, S. J. Lowther, P. J. Macqueen, T. J. Martin, D. Mawet, K. K. Mcleod, G. Murawski, N. Narita, J. Nordhausen, T. E. Oberst, C. Odden, P. A. Panka, R. Petrucci, P. Plavchan, S. N. Quinn, S. Rau, P. A. Reed, H. Relles, J. P. Renaud, G. Scarpetta, R. L. Sorber, A. D. Spencer, M. Spencer, D. C. Stephens, C. Stockdale, T.-G. Tan, M. Trueblood, P. Trueblood, S. Vanaverbeke, S. Villanueva Jr., E. M. Warner, M. L. West, S. Yalçınkaya, R. Yeigh, R. Zambelli Nov 2018

The Kelt Follow-Up Network And Transit False-Positive Catalog: Pre-Vetted False Positives For Tess, K. A. Collins, K. I. Collins, J. Pepper, J. Labadie-Bartz, K. G. Stassun, B. S. Gaudi, D. Bayliss, J. Bento, K. D. Colón, D. Feliz, D. James, M. C. Johnson, R. B. Kuhn, M. B. Lund, M. T. Penny, J. E. Rodriguez, R. J. Siverd, D. J. Stevens, X. Yao, G. Zhou, M. Akshay, G. F. Aldi, C. Ashcraft, S. Awiphan, Ö. Baştürk, D. Baker, T. G. Beatty, P. Benni, P. Berlind, G. B. Berriman, Z. Berta-Thompson, A. Bieryla, V. Bozza, S. C. Novati, M. L. Calkins, J. M. Cann, D. R. Ciardi, W. D. Cochran, David H. Cohen, D. Conti, J. R. Crepp, I. A. Curtis, G. D'Ago, K. A. Diazeguigure, C. D. Dressing, F. Dubois, E. Ellington, T. G. Ellis, G. A. Esquerdo, P. Evans, A. Friedli, A. Fukui, B. J. Fulton, E. J. Gonzales, J. C. Good, J. Gregorio, T. Gumusayak, D. A. Hancock, C. K. Harada, R. Hart, E. G. Hintz, H. Jang-Condell, E. J. Jeffery, Eric L.N. Jensen, E. Jofré, M. D. Joner, A. Kar, D. H. Kasper, B. Keten, J. F. Kielkopf, S. Komonjinda, C. Kotnik, D. W. Latham, J. Leuquire, T. R. Lewis, L. Logie, S. J. Lowther, P. J. Macqueen, T. J. Martin, D. Mawet, K. K. Mcleod, G. Murawski, N. Narita, J. Nordhausen, T. E. Oberst, C. Odden, P. A. Panka, R. Petrucci, P. Plavchan, S. N. Quinn, S. Rau, P. A. Reed, H. Relles, J. P. Renaud, G. Scarpetta, R. L. Sorber, A. D. Spencer, M. Spencer, D. C. Stephens, C. Stockdale, T.-G. Tan, M. Trueblood, P. Trueblood, S. Vanaverbeke, S. Villanueva Jr., E. M. Warner, M. L. West, S. Yalçınkaya, R. Yeigh, R. Zambelli

Physics & Astronomy Faculty Works

The Kilodegree Extremely Little Telescope (KELT) project has been conducting a photometric survey of transiting planets orbiting bright stars for over 10 years. The KELT images have a pixel scale of ~23'' pixel⁻¹—very similar to that of NASA's Transiting Exoplanet Survey Satellite (TESS)—as well as a large point-spread function, and the KELT reduction pipeline uses a weighted photometric aperture with radius 3'. At this angular scale, multiple stars are typically blended in the photometric apertures. In order to identify false positives and confirm transiting exoplanets, we have assembled a follow-up network (KELT-FUN) to conduct imaging with spatial resolution, cadence, and …

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Cosmological Implications Of Ultralight Axionlike Fields, V. Poulin, Tristan L. Smith, D. Grin, R. Karwal, M. Kamionkowski Oct 2018

Cosmological Implications Of Ultralight Axionlike Fields, V. Poulin, Tristan L. Smith, D. Grin, R. Karwal, M. Kamionkowski

Physics & Astronomy Faculty Works

Cosmological observations are used to test for imprints of an ultralight axionlike field (ULA), with a range of potentials V(ϕ)∝[1−cos(ϕ/f)]ⁿ set by the axion-field value ϕ and decay constant f. Scalar field dynamics dictate that the field is initially frozen and then begins to oscillate around its minimum when the Hubble parameter drops below some critical value. For n=1, once dynamical, the axion energy density dilutes as matter; for n=2 it dilutes as radiation and for n=3 it dilutes faster than radiation. Both the homogeneous evolution of the ULA and the dynamics of its linear perturbations are included, using an …

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A Computational Study Of The Role Of Spatial Receptive Field Structure In Processing Natural And Non-Natural Scenes, Victor J. Barranca, G. Zhu Oct 2018

A Computational Study Of The Role Of Spatial Receptive Field Structure In Processing Natural And Non-Natural Scenes, Victor J. Barranca, G. Zhu

Mathematics & Statistics Faculty Works

The center-surround receptive field structure, ubiquitous in the visual system, is hypothesized to be evolutionarily advantageous in image processing tasks. We address the potential functional benefits and shortcomings of spatial localization and center-surround antagonism in the context of an integrate-and-fire neuronal network model with image-based forcing. Utilizing the sparsity of natural scenes, we derive a compressive-sensing framework for input image reconstruction utilizing evoked neuronal firing rates. We investigate how the accuracy of input encoding depends on the receptive field architecture, and demonstrate that spatial localization in visual stimulus sampling facilitates marked improvements in natural scene processing beyond uniformly-random excitatory connectivity. …

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Brownian Dynamics Of Particles “Dressed” By Chiral Director Configurations In Lyotropic Chromonic Liquid Crystals, A. Martinez, Peter J. Collings, A. G. Yodh Oct 2018

Brownian Dynamics Of Particles “Dressed” By Chiral Director Configurations In Lyotropic Chromonic Liquid Crystals, A. Martinez, Peter J. Collings, A. G. Yodh

Physics & Astronomy Faculty Works

We study Brownian dynamics of colloidal spheres, with planar anchoring conditions, suspended in the nematic phase of the lyotropic chromonic liquid crystal disodium chromoglycate (DSCG). Unlike typical liquid crystals, the unusually small twist elastic modulus of DSCG permits two energetically distinct helical distortions (twisted tails) of the nematic director to “dress” the suspended spheres. Video microscopy is used to characterize the helical distortions versus particle size and to measure particle mean-square displacements. Diffusion coefficients parallel and perpendicular to the far-field director, and their anisotropy ratio, are different for the two twisted tail configurations. Moreover, the crossover from subdiffusive to diffusive …

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Gain Control With A-Type Potassium Current: Ia As A Switch Between Divisive And Subtractive Inhibition, Joshua H. Goldwyn, B. R. Slabe, J. B. Travers, D. Terman Jul 2018

Gain Control With A-Type Potassium Current: Ia As A Switch Between Divisive And Subtractive Inhibition, Joshua H. Goldwyn, B. R. Slabe, J. B. Travers, D. Terman

Mathematics & Statistics Faculty Works

Neurons process and convey information by transforming barrages of synaptic inputs into spiking activity. Synaptic inhibition typically suppresses the output firing activity of a neuron, and is commonly classified as having a subtractive or divisive effect on a neuron’s output firing activity. Subtractive inhibition can narrow the range of inputs that evoke spiking activity by eliminating responses to non-preferred inputs. Divisive inhibition is a form of gain control: it modifies firing rates while preserving the range of inputs that evoke firing activity. Since these two “modes” of inhibition have distinct impacts on neural coding, it is important to understand the …

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Multiple Stellar Flybys Sculpting The Circumstellar Architecture In Rw Aurigae, J. E. Rodriguez, R. Loomis, S. Cabrit, T. H. Haworth, S. Facchini, C. Dougados, R. A. Booth, Eric L.N. Jensen, C. J. Clarke, K. G. Stassun, W. R. F. Dent, J. Pety Jun 2018

Multiple Stellar Flybys Sculpting The Circumstellar Architecture In Rw Aurigae, J. E. Rodriguez, R. Loomis, S. Cabrit, T. H. Haworth, S. Facchini, C. Dougados, R. A. Booth, Eric L.N. Jensen, C. J. Clarke, K. G. Stassun, W. R. F. Dent, J. Pety

Physics & Astronomy Faculty Works

We present high-resolution ALMA Band 6 and 7 observations of the tidally disrupted protoplanetary disks of the RW Aurigae binary. Our observations reveal tidal streams in addition to the previously observed tidal arm around RW Aur A. The observed configuration of tidal streams surrounding RW Aur A and B is incompatible with a single star–disk tidal encounter, suggesting that the RW Aurigae system has undergone multiple flyby interactions. We also resolve the circumstellar disks around RW Aur A and B, with CO radii of 58 au and 38 au consistent with tidal truncation, and 2.5 times smaller dust emission radii. …

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Quadruplexes In ‘Dicty’: Crystal Structure Of A Four-Quartet G-Quadruplex Formed By G-Rich Motif Found In The Dictyostelium Discoideum Genome, A. Guédin, Linda Yingqi Lin , '20, S. Armane, L. Lacroix, J.-L. Mergny, S. Thore, Liliya A. Yatsunyk Jun 2018

Quadruplexes In ‘Dicty’: Crystal Structure Of A Four-Quartet G-Quadruplex Formed By G-Rich Motif Found In The Dictyostelium Discoideum Genome, A. Guédin, Linda Yingqi Lin , '20, S. Armane, L. Lacroix, J.-L. Mergny, S. Thore, Liliya A. Yatsunyk

Chemistry & Biochemistry Faculty Works

Guanine-rich DNA has the potential to fold into non-canonical G-quadruplex (G4) structures. Analysis of the genome of the social amoeba Dictyostelium discoideum indicates a low number of sequences with G4-forming potential (249–1055). Therefore, D. discoideum is a perfect model organism to investigate the relationship between the presence of G4s and their biological functions. As a first step in this investigation, we crystallized the dGGGGGAGGGGTACAGGGGTACAGGGG sequence from the putative promoter region of two divergent genes in D. discoideum. According to the crystal structure, this sequence folds into a four-quartet intramolecular antiparallel G4 with two lateral and one diagonal loops. The G-quadruplex …

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