Physical Sciences and Mathematics Commons^™

On The Absence Of Non-Thermal X-Ray Emission Around Runaway O Stars, Jesus A. Toalá, Lidia M. Oskinova, Richard Ignace

Richard Ignace

Theoretical models predict that the compressed interstellar medium around runaway O stars can produce high-energy non-thermal diffuse emission, in particular, non-thermal X-ray and γ-ray emission. So far, detection of non-thermal X-ray emission was claimed for only one runaway star, AE Aur. We present a search for non-thermal diffuse X-ray emission from bow shocks using archived XMM-Newton observations for a clean sample of six well-determined runaway O stars. We find that none of these objects present diffuse X-ray emission associated with their bow shocks, similarly to previous X-ray studies toward ζ Oph and BD+43°3654. We carefully investigated multi-wavelength observations of …

An X-Ray Study Of Two B+B Binaries: Ah Cep And Cw Cep, Richard Ignace, K. T. Hole, Lidia M. Oskinova, J. P. Rotter

Richard Ignace

AH Cep and CW Cep are both early B-type binaries with short orbital periods of 1.8 days and 2.7 days, respectively. All four components are B0.5V types. The binaries are also double-lined spectroscopic and eclipsing. Consequently, solutions for orbital and stellar parameters make the pair of binaries ideal targets for a study of the colliding winds between two B stars. Chandra ACIS-I observations were obtained to determine X-ray luminosities. AH Cep was detected with an unabsorbed X-ray luminosity at a 90% confidence interval of erg s−1, or , relative to the combined Bolometric luminosities of the two components. While formally …

Limb Darkening And Planetary Transits: Testing Center-To-Limb Intensity Variations And Limb-Darkening Directly From Model Stellar Atmospheres, Hilding R. Neilson, Joseph T. Mcneil, Richard Ignace, John B. Lester

Richard Ignace

The transit method, employed by Microvariability and Oscillation of Stars (MOST), Kepler, and various ground-based surveys has enabled the characterization of extrasolar planets to unprecedented precision. These results are precise enough to begin to measure planet atmosphere composition, planetary oblateness, starspots, and other phenomena at the level of a few hundred parts per million. However, these results depend on our understanding of stellar limb darkening, that is, the intensity distribution across the stellar disk that is sequentially blocked as the planet transits. Typically, stellar limb darkening is assumed to be a simple parameterization with two coefficients that are derived …

A Math Research Project Inspired By Twin Motherhood, Tiffany N. Kolba

Tiffany N Kolba

The phenomenon of twins, triplets, quadruplets, and other higher order multiples has fascinated humans for centuries and has even captured the attention of mathematicians who have sought to model the probabilities of multiple births. However, there has not been extensive research into the phenomenon of polyovulation, which is one of the biological mechanisms that produces multiple births. In this paper, I describe how my own experience becoming a mother to twins led me on a quest to better understand the scientific processes going on inside my own body and motivated me to conduct research on polyovulation frequencies. An overview of …

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sarana idr

Semi-Transparent Energy-Harvesting Solar Concentrator Windows Employing Infrared Transmission-Enhanced Glass And Large-Area Microstructured Diffractive Elements, Mikhail Vasiliev, Kamal Alameh, Mohsin Ali Badshah, Seok-Min Kim, Mohammad Nur-E-Alam

Mikhail Vasiliev

Jual Hammer Of Thor Asli Cod Di Surabaya 081234944066, Herbal Shop

herbal shop

Mathchat: Computational Mathematics Via A Social Machine, Manfred Minimair

Manfred Minimair

Magnetic Properties Of A Sediment Core From Andvord Drift, Emily Youcha, Stefanie A. Brachfeld

Stefanie Brachfeld

No abstract provided.

Magnetic Granulometry Of Igneous And Metasedimentary Rocks From Northern Graham Land, Antarctic Peninsula, Stefanie A. Brachfeld, Anne Grunow, Emily Youcha

Stefanie Brachfeld

No abstract provided.

Rock-Magnetic Analysis Of Sediments From Andvord Bay, Stefanie A. Brachfeld

Stefanie Brachfeld

No abstract provided.

Lzamoras18.Pdf, Lilliann Zamora

Lilliann Yvette Zamora

Knowledge Extraction From Metacognitive Reading Strategies Data Using Induction Trees, Christopher Taylor, Arun D. Kulkarni, Kouider Mokhtari

Kouider Mokhtari

The assessment of students’ metacognitive knowledge and skills about reading is critical in determining their ability to read academic texts and do so with comprehension. In this paper, we used induction trees to extract metacognitive knowledge about reading from a reading strategies dataset obtained from a group of 1636 undergraduate college students. Using a C4.5 algorithm, we constructed decision trees, which helped us classify participants into three groups based on their metacognitive strategy awareness levels consisting of global, problem-solving and support reading strategies. We extracted rules from these decision trees, and in order to evaluate accuracy of the extracted rules, …

Assessing Metacognitive Skills Using Adaptive Neural Networks, Anderson Justin, Kouider Mokhtari, Arun Kulkarni

Kouider Mokhtari

The assessment of student's levels of metacognitive knowledge and skills is critical in determining their ability to effectively perform complex cognitive tasks such as solving mathematics or reading comprehension problems. In this paper, we use an adaptive multiplayer perceptron model to categorize participants based on their metacognitive awareness and perceived use of reading strategies while reading. Eight hundred and sixty-five middle school students participated in the study. All participants completed a 30-item instrument- the Metacognitive Awareness-of-Reading Strategies Inventory (MARSI). We used adaptive multi-layer perceptron models to classify participants into three groups based on their metacognitive strategy awareness levels using thirteen …

Synthesis, Characterization, And Crystal Structure Of The (Η5-C5ph5)Cr(Co)3 Radical, Ray J. Hoobler, Marc A. Hutton, Mills M. Dillard, Michael Castellani, Arnold L. Rheingold, Anne L. Rieger, Philip H. Rieger, Thomas C. Richards, William E. Geiger

Michael P. Castellani

The reaction between Cr(CO)₆ and Na(C₅Ph₅ ) in refluxing diglyme yields [Na(diglyme)_3/2][(C₅Ph₅)Cr(CO)₃], 1. Metathesis of 1 with [Ph₃P=N=PPh₃ ]Cl in CH₂Cl₂ yields [Ph₃P=N=PPh₃][(C₅Ph₅)Cr(CO)₃], 2. Oxidation of 1 by AgBF4 in cold THF under an argon atmosphere produces (C₅Ph₅)Cr(CO)₃, 3. Complexes 2 and 3 form a redox pair connected by a quasireversible one-electron process, E⁰ = -0.69 V vs ferrocene in CH₂Cl₂, …

Synthesis And X-Ray Crystal Structure Of [(C5ph5)Crcl(Μ-Cl)2tl]2: An Example Of The Rare M-X-Tli Linkage (X = Halide), K. Brian Davis, T. David Harris, Michael Castellani, James A. Golen, Arnold L. Rheingold

Michael P. Castellani

Reaction of solid TlCl with [(C5Ph5)CrCl(m-Cl)]2 in CH2Cl2 solvent yields the monomeric complex (C5Ph5)CrCl(m-Cl)2Tl in 80% isolated yield. The C5H5 and C5Me5 analogues do not react with TlCl suggesting a steric basis for the reaction of the C5Ph5 material. An X-ray crystal structure of [(C5Ph5)CrCl(m-Cl)2Tl]2•2CH2Cl2 was obtained.

Substitution Reactions Of (C5ph5)Cr(Co)3: Structural, Electrochemical, And Spectroscopic Characterization Of (C5ph5)Cr(Co)2l, L = Pme3, Pme2ph, P(Ome)3, D. John Hammack, Mills M. Dillard, Michael Castellani, Arnold L. Rheingold, Anne L. Rieger, Philip H. Rieger

Michael P. Castellani

The radical complex (C₅Ph₅)Cr(CO)₃ reacts with small, neutral, monodentate Lewis bases (PMe₃, PMe₂Ph, P(OMe)₃) in THF at −78 °C (PMe₂Ph reacts at ambient temperature) to yield the monomeric substitution products (C₅Ph₅)Cr(CO)₂L·THF as thermally stable solids. Electrochemical and spectroscopic data are provided. An X-ray crystal structure of the hemisolvate (C₅Ph₅)Cr(CO)₂PMe₃·0.5THF was obtained. Frozen-solution ESR spectra of (C₅Ph₅)Cr(CO)₂L in toluene are comparable to those of other low-spin d^{5 …}

Multicomponent Cubic Oxide Exsolution In Synthetic Basalts: Temperature Dependence And Implications For Magnetic Properties, Julie A. Bowles, Lisa Tatsumi-Petrochilos, Julie E. Hammer, Stefanie A. Brachfeld

Stefanie Brachfeld

Although the compositional unmixing of cubic-structured iron oxides has profound effects on the magnetic properties of rocks that contain them, a basic understanding of the kinetics and thermodynamics of this process has not been achieved in experimental studies due to sluggish reaction rates in binary oxide phases. Exploiting the fact that many natural Fe-oxides contain multiple additional cations, including Ti, Mg and Al, we perform novel “forward” laboratory experiments in which cubic-cubic phase exsolution proceeds from initially homogeneous multicomponent oxides. A variety of Fe-Ti-Mg-Al cubic iron oxides were nucleated and grown in synthetic, multicomponent basalt under different ƒO2 environments, and …

Magnetic And Petrologic Characterization Of Synthetic Martian Basalts And Implications For The Surface Magnetization Of Mars, Julie A. Bowles, Julie E. Hammer, Stefanie A. Brachfeld

Stefanie Brachfeld

A suite of synthetic Martian basalts is generated with the objective of providing fundamental material properties data for use in modeling and interpretation of mission data. We systematically evaluate the effects of major element composition, oxygen fugacity (ƒO₂), and cooling rate on phase chemistry and magnetic mineralogy, grain size, and intensity of remanent magnetization. The range of experimental compositions and ƒO2 are chosen to bracket the range expected in the Martian crust; our results should therefore span the range of possible mineralogies, textures, and magnetic properties in rapidly cooled Mars crustal materials. Two starting compositions are used for …

Contribution Of Multidomain Titanomagnetite To The Intensity And Stability Of Mars Crustal Magnetic Anomalies, Stefanie A. Brachfeld, David Cuomo, Lisa Tatsumi-Petrochilos, Julie A. Bowles, Deepa Shah, Julie E. Hammer

Stefanie Brachfeld

Two basalts with compositions relevant to the crusts of Mars and Earth were synthesized at igneous temperatures and held at 650°C for 21 to 257 days under quartz-fayalite-magnetite ƒO₂ buffer conditions. The run products are germane to slowly cooled igneous intrusions, which might be a significant volumetric fraction of the Martian crust and carriers of magnetic anomalies in the Southern Highlands. Both basalts acquired intense thermoremanent magnetizations and intense but easily demagnetized anhysteretic remanent magnetizations carried by homogeneous multidomain titanomagnetite. Hypothetical intrusions on Mars composed of these materials would be capable of acquiring intense remanences sufficient to generate the …

The Late Quaternary Flow Through The Bering Strait Has Been Forced By The Southern Ocean Winds, Joseph D. Ortiz, Doron Nof, Leonid Polyak, Guillame St-Onge, Agatha Lisé-Pronovost, Sathy Naidu, Dennis Darby, Stefanie Brachfeld

Stefanie Brachfeld

Because North and South America are surrounded by water, they constitute together a gigantic island whose peripheral sea level is controlled by the winds east of the island, winds along the western boundary of the island, the freshwater flux, and the meridional overturning cell. This idea has been expressed in several articles where a series of analytical models show that the Bering Strait (BS) flow is controlled by the interplay of the Southern Winds (sometimes referred to as the “Subantarctic Westerlies”), and the North Hemisphere freshwater flux. Here, the authors report a paleoceanographic analysis of proxies in the BS as …

1,1´-Diethyl-2,2´,3,3´,4,4´,5,5´-Octamethylferrocenium Tetracyanoethylenide, [Fe(C5etme4)2]+[Tcne]–, A Charge-Transfer Salt Magnetic Solid With A Novel Structural Motif, T. David Harris, Michael Castellani, Arnold L. Rheingold, William M. Reiff, Gordon T. Yee

Michael P. Castellani

1,1′-Diethyl-2,2′,3,3′,4,4′,5,5′-octamethylferrocene has been utilized as a one-electron donor in the synthesis of a tetracyanoethylene charge-transfer salt, [Fe(C₅EtMe₄)₂]⁺[TCNE]⁻. Structural characterization shows that it adopts an arrangement of anions and cations completely different from the usual π stacking seen in analogous decamethylferrocenium compounds. The TCNE radical sits along side of the ferrocene, nearly perpendicular to the planes of the C₅ rings. The nearly square geometry of the TCNE anion creates disorder over two orientations. [Fe(C₅EtMe₄)₂]⁺[TCNE]⁻ is a simple paramagnet exhibiting neither long-range …

Synthesis, Characterization, And Molecular Structure Of Bis(Tetraphenylcyclopentdienyl)Rhodium(Ii)⊗, James E. Collins, Michael Castellani, Arnold L. Rheingold, Edward J. Miller, William E. Geiger, Anne L. Rieger, Philip H. Rieger

Michael P. Castellani

A 5 day diglyme reflux of Rh(acac)3 and K(C5HPh4), followed by treatment with aqueous HPF6, produces orange-yellow [(C5HPh4)2Rh]PF66 in 40 - 50% yield. Reduction of [(C5HPh4)2Rh]PF6 with sodium amalgam in THF yields olive green (C5HPh4)2Rh in 70% yield. (C5HPh4)2Rh crystallizes in the triclinic [Error : unloaded OLE object or mail attachment]space group with unit-cell parameters of a = 8.622 (3) Å, b = 10.778 (4) Å, c = 12.894 (5) Å, a = 65.58 (3)°, b = 72.66 (3)°, g = 83.52 (3)°, and Z = 1. The least squares data refined to RF = 7.63% and …

Halogen Oxidation Reactions Of (C5ph5)Cr(Co)3 And Lewis Base Addition To [(C5ph5)Cr(Μ-X)X]2: Electrochemical, Magnetic, And Raman Spectroscopic Characterization Of [(C5ph5)Crx2]2 And (C5ph5)Crx2(Thf) (X = Cl, Br, I). X-Ray Crystal Structure Of [(C5ph5)Cr(Μ-Cl)Cl]2, Marc A. Hutton, James C. Durham, Robert W. Grady, Brett E. Harris, Carter S. Jarrell, J. Matthew Mooney, Michael Castellani, Arnold L. Rheingold, Ulrich Kölle, Brenda J. Korte, Roger D. Sommer, Gordon T. Yee, J. Matthew Boggess, Roman S. Czernuszewicz

Michael P. Castellani

The 17-electron complex (C5Ph5)Cr(CO)3 reacts with halogens (C6H5I•Cl2, Br2, and I2) in C6H6 to yield the dimeric oxidation products [(C5Ph5)Cr(m-X)X]2 as thermally stable solids. Reactions with other chlorinating agents similarly yield [(C5Ph5)CrCl2]2. An X-ray crystal structure of [(C5Ph5)Cr(m-Cl)Cl]2 was obtained. The magnetic properties of the Cl₂ bridged dimer have been determined and modeled using the usual isotropic hamiltonian which yields J/k = –30 K. Low-temperature (77 K) Raman spectra of solid [(C5Ph5)CrX2]2 (X = Cl, I) allow assignments to be made for the metal-ring and metal halogen stretching modes in the low frequency region (< 600 cm-1). Tetrahydrofuran (THF) cleaves these dimers to yield complexes of the form (C5Ph5)CrX2(THF).

Temperaments And Learning Styles Vs. Academic Performance Of First-Semester Physics Students, Shel Randall

Shel Randall

Tiered Approaches In Analyzing Rice Field Pesticide Fate And Transport For Ecological Risk Assessment, Ruoyu Wang

Ruoyu Wang

No abstract provided.

Excess Versions Of The Minkowski And Hölder Inequalities, Iosif Pinelis

Iosif Pinelis

No abstract provided.

Robustness And Mode Selectivity In Parity-Time (Pt) Symmetric Lasers, M. H. Teimourpour, M. Khajavikhan, Demetrios N. Christodoulides, Ramy El-Ganainy

Ramy El-Ganainy

We investigate two important aspects of PT symmetric photonic molecule lasers, namely the robustness of their single longitudinal mode operation against instabilities triggered by spectral hole burning effects, and the possibility of more versatile mode selectivity. Our results, supported by numerically integrating the nonlinear rate equations and performing linear stability analysis, reveals the following: (1) In principle a second threshold exists after which single mode operation becomes unstable, signaling multimode oscillatory dynamics, (2) For a wide range of design parameters, single mode operation of PT lasers having relatively large free spectral range (FSR) can be robust even at higher gain …

Non-Hermitian Matter-Wave Mixing In Bose-Einstein Condensates: Dissipation-Induced Amplification, S. Wuster, Ramy El-Ganainy

Ramy El-Ganainy

We investigate the nonlinear scattering dynamics in interacting atomic Bose-Einstein condensates under non-Hermitian dissipative conditions. We show that, by carefully engineering a momentum-dependent atomic loss profile, one can achieve matter-wave amplification through four-wave mixing in a quasi-one-dimensional nearly-free-space setup—a process that is forbidden in the counterpart Hermitian systems due to energy mismatch. Additionally, we show that similar effects lead to rich nonlinear dynamics in higher dimensions. Finally, we propose a physical realization for selectively tailoring the momentum-dependent atomic dissipation. Our strategy is based on a two-step process: (i) exciting atoms to narrow Rydberg or metastable excited states, and (ii) introducing …

Sequence Stratigraphy Of The Andrill And-2a Drillcore, Antarctica: A Long-Term, Ice-Proximal Record Of Early To Mid-Miocene Climate, Sea-Level And Glacial Dynamism, Christopher R. Fielding, Greg H. Browne, Brad Field, F. Florindo, D. M. Harwood, L. A. Krissek, Richard Levy, K. Panter, Sandra Passchier, Stephen F. Pekar

Sandra Passchier

Present understanding of Antarctic climate change during the Early to Mid-Miocene, including major cycles of glacial expansion and contraction, relies in large part on stable isotope proxies from deep sea core drilling. Here, we summarize the lithostratigraphy of the ANDRILL Southern McMurdo Sound Project drillcore AND-2A. This core offers a hitherto unavailable ice-proximal stratigraphic archive from a high-accommodation continental margin setting, and provides clear evidence of repeated fluctuations in climate, ice expansion/contraction and attendant sea-level change over the period c. 20.2–14.2 Ma, with a more fragmentary record of Late Miocene and Pliocene time. The core is divided into seventy-four high-frequency …