Physical Sciences and Mathematics Commons^™

Herschel/Pacs Observations Of Young Sources In Taurus: The Far-Infrared Counterpart Of Optical Jets, L Podio, I Kamp, D Flower, C Howard, G Sandell, A Mora, G Aresu, Sean D. Brittain, W.R.F. Dent, C Pinte, G J. White

Publications

Context. Observations of the atomic and molecular line emission associated with jets and outflows emitted by young stellar objects provide sensitive diagnostics of the excitation conditions, and can be used to trace the various evolutionary stages they pass through as they evolve to become main sequence stars. Aims. To understand the relevance of atomic and molecular cooling in shocks, and how accretion and ejection efficiency evolves with the evolutionary state of the sources, we will study the far-infrared counterparts of bright optical jets associated with Class I and II sources in Taurus (T Tau, DG Tau A, DG Tau B, …

Observed Seasonal Variations In Exospheric Effective Temperatures, E. J. Mierkiewicz, F. L. Roesler, S. M. Nossal

Publications

High spectral resolution line profile observations indicate a reproducible semi-annual variation in the geocoronal hydrogen Balmer α effective temperature. These observations were made between 08 January 2000 and 21 November 2001 from Pine Bluff Observatory (WI) with a second generation double etalon Fabry-Perot annular summing spectrometer operating at a resolving power of 80,000. This data set spans sixty-four nights of observations (1404 spectra in total) over 20 dark-moon periods. A two cluster Gaussian model fitting procedure is used to determine Doppler line widths, accounting for fine structure contributions to the line, including those due to cascade; cascade contributions at Balmer …

Ionospheric Plasma Transport And Loss In Auroral Downward Current Regions, M. Zettergren, J. L. Semeter

Publications

A detailed study of the effects of auroral current systems on thermal ionospheric plasma transport and loss is conducted using a new ionospheric model. The mathematical formulation of the model is a variation on the 5‐moment approximation which describes the temporal evolution of density, drift, and temperature for five different ion species in two spatial dimensions. The fluid system is closed through a 2‐D electrostatic treatment of the auroral currents. This model is used to examine the interplay between ion heating, perpendicular transport, molecular ion generation, and type‐1 ion upflows in a self‐consistent way for the first time. Simulations confirm …

Topological Thermoelectric Effects In Spin-Orbit Coupled Electron- And Hole-Doped Semiconductors, E Dumitrescu, Chuanwei Zhang, D C. Marinescu, Sumanta Tewari

Publications

We compute the intrinsic contributions to the Berry-phase mediated anomalous Hall and Nernst effects in electron- and hole-doped semiconductors in the presence of an in-plane magnetic field as well as Rashba and Dresselhaus spin-orbit couplings. For both systems we find that the regime of chemical potential which supports the topological superconducting state in the presence of the superconducting proximity effect can be characterized by plateaus in the topological Hall and Nernst coefficients flanked by well-defined peaks marking the emergence of the topological regime. The plateaus arise from a clear momentum space separation between the region where the Berry curvature is …

Predicting Nonspecific Ion Binding Using Delphi, Marharyta Petukh, Maxim Zhenirovskyy, Chuan Li, Lin Li, Lin Wang, Emil Alexov

Publications

Ions are an important component of the cell and affect the corresponding biological macromolecules either via direct binding or as a screening ion cloud. Although some ion binding is highly specific and frequently associated with the function of the macromolecule, other ions bind to the protein surface nonspecifically, presumably because the electrostatic attraction is strong enough to immobilize them. Here, we test such a scenario and demonstrate that experimentally identified surface-bound ions are located at a potential that facilitates binding, which indicates that the major driving force is the electrostatics. Without taking into consideration geometrical factors and structural fluctuations, we …

Observations Of Herbig Ae/Be Stars With Herschel/Pacs. The Atomic And Molecular Contents Of Their Protoplanetary Discs, G Meeus, B Montesinos, I Mendigutia, I Kamp, W F. Thi, C Eiroa, C A. Grady, G Mathews, G Sandell, C. Martin-Zaidi, Sean D. Brittain, W.R.F. Dent, C Howard, F Menard, C Pinte, A Roberge, B Vandenbussche, J P. Williams

Publications

We observed a sample of 20 representative Herbig Ae/Be stars and 5 A-type debris discs with PACS onboard Herschel, as part of the GAS in Protoplanetary Systems (GASPS) project. The observations were done in spectroscopic mode, and cover the far-infrared lines of [O i], [C ii], CO, CH+, H2O, and OH. We have a [Oi] 63 μm detection rate of 100% for the Herbig Ae/Be and 0% for the debris discs. The [Oi] 145 μm line is only detected in 25% and CO J = 18–17 in 45% (and fewer cases for higher J transitions) of the Herbig Ae/Be stars, …

Topology And Geometry Of Mixing Of Fluids, Andrei Ludu, S.C. Mancas, Ionutz Ionescu, Audrey Gbagaudi, Matthew Schumacher

Publications

We present an enhancement of diffusive mixing on a compact Riemannian manifold by a fast incompressible flow.

We describe the class of flows that make the deviation of the solution from its average arbitrarily small in an arbitrarily short time, provided that the flow amplitude is large enough.

The necessary and sufficient condition on such flows is expressed naturally in terms of the spectral properties of the dynamical system associated with the flow.

Further studies are needed for non-compact manifolds, or compact manifolds with Dirichlet BC. The optimal shape of the fixed obstacles in the mixing device could be obtained …

2d Novel Structures Along An Opitcal Fiber, Charles-Julien Vandamme, S.C. Mancas

Publications

By using spectral methods, we present seven classes of stable and unstable structures that occur in a dissipative media. By varying parameters and initial conditions we find ranges of existence of stable structures (spinning elliptic, pulsating, stationary, organized exploding), and unstable structures (filament, disorganized exploding, creeping). By varying initial conditions, vorticity, and parameters of the equation, we find a reacher behavior of solutions in the form of creeping-vortex (propellers), spinning rings and spinning “bean-shape” solitons. Each class differentiates from the other by distinctive features of their shape and energy evolution, as well as domain of existence.

Gravity Wave Propagation In A Diffusively Separated Gas: Effects On The Total Gas, Michael P. Hickey Ph.D., R. L. Walterscheid

Publications

We present a full-wave model that simulates acoustic-gravity wave propagation in a binary-gas mixture of atomic oxygen and molecular nitrogen, including molecular viscosity and thermal conductivity appropriately partitioned between the two gases. Compositional effects include the collisional transfer of heat and momentum by mutual diffusion between the two gases. An important result of compositional effects is that the velocity and temperature summed over species can be significantly different from the results of one-gas models with the same height dependent mean molecular weight (M(z)). We compare the results of our binary-gas model to two one-gas full-wave models: one where M is …

Delphi: A Comprehensive Suite For Delphi Software And Associated Resources, Lin Li, Chuan Li, Subhra Sarkar, Jie Zhang, Shawn Witham, Zhe Zhang, Lin Wang, Nicholas Smith, Marharyta Petukh, Emil Alexov

Publications

Background

Accurate modeling of electrostatic potential and corresponding energies becomes increasingly important for understanding properties of biological macromolecules and their complexes. However, this is not an easy task due to the irregular shape of biological entities and the presence of water and mobile ions.

Results

Here we report a comprehensive suite for the well-known Poisson-Boltzmann solver, DelPhi, enriched with additional features to facilitate DelPhi usage. The suite allows for easy download of both DelPhi executable files and source code along with a makefile for local installations. The users can obtain the DelPhi manual and parameter files required for the corresponding …

Book Review: Astronomy At The Frontiers Of Science, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Astronomy at the Frontiers of Science, edited by Jean-Pierre Lasota, Springer, 2011. 357p, 9789400716575 $179.00.

Asteroid Retrieval Feasibility Study, John Brophy, Fred Culick, Louis Friedman, Pedro Llanos, Et Al.

Publications

This report describes the results of a study sponsored by the Keck Institute for Space Studies (KISS) to investigate the feasibility of identifying, robotically capturing, and returning an entire Near-Earth Asteroid (NEA) to the vicinity of the Earth by the middle of the next decade. The KISS study was performed by people from Ames Research Center, Glenn Research Center, Goddard Space Flight Center, Jet Propulsion Laboratory, Johnson Space Center, Langley Research Center, the California Institute of Technology, Carnegie Mellon, Harvard University, the Naval Postgraduate School, University of California at Los Angeles, University of California at Santa Cruz, University of Southern …

Synoptic-Scale Analysis Of Freezing Rain Events In Montreal, Quebec, Canada, Gina M. Ressler, Shawn M. Milrad, Eyad H. Atallah, John R. Gyakum

Publications

Freezing rain is a major environmental hazard that is especially common along the St. Lawrence River valley (SLRV) in southern Quebec, Canada. For large cities such as Montreal, severe events can have a devastating effect on people, property, and commerce. In this study, a composite analysis of 46 long-duration events for the period 1979–2008 is presented to identify key synoptic-scale structures and precursors of Montreal freezing rain events. Based on the observed structures of the 500-hPa heights, these events are manually partitioned into three types—west, central, and east—depending on the location and tilt of the 500-hPa trough axis. West events …

Observed And Modeled Solar Cycle Variation In Geocoronal Hydrogen Using Nrlmsise-00 Thermosphere Conditions And The Bishop Analytic Exosphere Model, S. M. Nossal, E. J. Mierkiewicz, F. L. Roesler

Publications

High precision observations during Solar Cycle 23 using the Wisconsin H‐alpha Mapper (WHAM) Fabry‐Perot quantify a factor of 1.5 ± 0.15 higher Balmer α column emission intensity during near‐solar‐maximum than during solar minimum conditions. An unresolved question is how does the observed solar cycle variation in the hydrogen column emission compare with that calculated from the hydrogen distribution in atmospheric models? We have compared WHAM solar minimum and near‐solar‐maximum column intensity observations with calculations using the thermospheric hydrogen density profile and background thermospheric conditions from the Mass Spectrometer Incoherent Scatter (NRLMSISE‐00) empirical model extended to exospheric altitudes using the analytic …

Energetic Feedback And 26al From Massive Stars And Their Supernovae In The Carina Region, R. Voss, P. Martin, R. Diehl, J. S. Vink, Dieter H. Hartmann, T. Preibisch

Publications

We study the populations of massive stars in the Carina region and their energetic feedback and ejection of 26Al. Methods. We did a census of the stellar populations in young stellar clusters within a few degrees of the Carina nebula. For each star we estimated the mass, based on the spectral type and the host cluster age. We used population synthesis to calculate the energetic feedback and ejection of 26Al from the winds of the massive stars and their supernova explosions. We used 7 years of INTEGRAL observations to measure the 26Al signal from the region. Results. The INTEGRAL 26Al …

Synoptic-Scale Environments Conducive To Orographic Impacts On Cold-Season Surface Wind Regimes At Montreal, Quebec, Alissa Razy, Shawn M. Milrad, Eyad H, Atallah, John R. Gyakum

Publications

Orographic wind channeling, defined as dynamically and thermally induced processes that force wind to blow along the axis of a valley, is a common occurrence along the St. Lawrence River Valley (SLRV) in Quebec, Canada, and produces substantial observed weather impacts at stations along the valley, including Montreal (CYUL). Cold-season observed north-northeast (n = 55) and south-southeast (n = 16) surface wind events at CYUL are identified from 1979 to 2002. The authors partition the north-northeast wind events into four groups using manual synoptic typing. Types A and D (“inland cyclone” and “northwestern cyclone”) are associated with strong lower-tropospheric geostrophic …

Weak Localization In A Lateral Superlattice With Rashba And Dresselhaus Spin-Orbit Interaction, D C. Marinescu, Andrei Manolescu

Publications

We calculate the weak localization (WL) correction to the conductivity of a lateral superlattice (LSL) with Rashba (R)-Dresselhaus (D) spin-orbit interaction (SOI). The superlattice is modeled as a sequence of parallel wires that support tunneling between adjacent sites, leading to the formation of extended Bloch states along its axis and a miniband in the energy spectrum. Our results, obtained by calculating the eigenvalues of the Cooperon operator in the diffusion approximation, indicate that the electron dephasing rate that determines the antilocalization correction is enhanced by a term proportional with the LSL potential and the bandwidth. Within the same formalism, the …

Gravity-Wave-Induced Variations In Exothermic Heating In The Low-Latitude, Equinox Mesophere And Lower Thermosphere Region, Michael P. Hickey Ph.D., Tai-Yin Huang

Publications

We investigate gravity-wave-induced variations in exothermic heating in the OH nightglow region at a latitude of 18° in the Northern and Southern Hemispheres during March. An OH nightglow chemistry model with gravity wavefields from a spectral full-wave model is used for the investigation. Our simulation results show that the wave packet induces a large secular increase in the number densities of the minor species involved in the OH chemistry, a 50% increase in O3, 42% in O, and 29% in OH (v= 8), and the ultimate driver for these increases is the wave-driven downward transport of O. We find that …

Observational Constraints On The Degenerate Mass-Radius Relation, J. B. Holberg, Terry D. Oswalt, M. A. Barstow

Publications

The white dwarf mass–radius relationship is fundamental to modern astrophysics. It is central to routine estimation of DA white dwarf masses derived from spectroscopic temperatures and gravities. It is also the basis for observational determinations of the white dwarf initial–final-mass relation. Nevertheless, definitive and detailed observational confirmations of the mass–radius relation (MRR) remain elusive owing to a lack of sufficiently accurate white dwarf masses and radii. Current best estimates of masses and radii allow only broad conclusions about the expected inverse relation between masses and radii in degenerate stars. In this paper, we examine a restricted set of 12 DA …

Analyzing Effects Of Naturally Occurring Missense Mutations, Zhe Zhang, Maria A. Miteva, Lin Wang, Emil Alexov

Publications

Single-point mutation in genome, for example, single-nucleotide polymorphism (SNP) or rare genetic mutation, is the change of a single nucleotide for another in the genome sequence. Some of them will produce an amino acid substitution in the corresponding protein sequence (missense mutations); others will not. This paper focuses on genetic mutations resulting in a change in the amino acid sequence of the corresponding protein and how to assess their effects on protein wild-type characteristics. The existing methods and approaches for predicting the effects of mutation on protein stability, structure, and dynamics are outlined and discussed with respect to their underlying …

Bl Lacertae Objects Beyond Redshift 1.3 - Uv-To-Nir Photometry And Photometric Redshift For Fermi/Lat Blazars, A. Rau, P. Schady, J. Greiner, M. Salvato, M. Ajello, E. Bottacini, N. Gehrels, P.M. J. Afonso, J. Elliott, R Filgas, D A. Kann, S Klose, T Krühler, M Nardini, A Nicuesa Guelbenzu, F Olivares E., A Rossi, V Sudilovsky, A C. Updike, Dieter H. Hartmann

Publications

Context.Observations of the γ -ray sky with Fermi led to significant advances towards understanding blazars, the most extreme classof Active Galactic Nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whosesample has always suff ered from a severe redshift incompleteness due to the quasi-featureless optical spectra.Aims.Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LACFermi/LAT cataloge.Methods.For 103 Fermi/LAT blazars, photometric redshifts using spectral energy distribution fitting have been obtained. The pho-tometry includes 13 broad-band filters from the far ultraviolet …

Cxom31 J004253.1+411422: The First Ultraluminous X-Ray Transient In M 31, A. Kaur, M. Henze, F. Haberl, W. Pietsch, J. Greiner, A. Rau, Dieter H. Hartmann, G. Sala, M. Hernanz

Publications

Context. We seek clarification of the nature of X-ray sources detected in M 31. Here we focus on CXOM31 J004253.1+411422, the brightness of which suggests that it belongs to the class of ultraluminous X-ray sources. Aims. We determine the X-ray properties of sources detected in the XMM-Newton/Chandra monitoring program. We investigate spectral properties and search for periodic or quasi-periodic oscillations. Methods. A multicomponent model was applied to the spectra obtained from XMM-Newton data to evaluate the relative contributions from thermal and nonthermal emission. The time dependence of this ratio was evaluated over a period of forty days. We simultaneously fit …

Nested Canalyzing Depth And Network Stability, Lori Layne, Elena Dimitrova, Matthew Macauley

Publications

We introduce the nested canalyzing depth of a function, which measures the extent to which it retains a nested canalyzing structure. We characterize the structure of functions with a given depth and compute the expected activities and sensitivities of the variables. This analysis quantifies how canalyzation leads to higher stability in Boolean networks. It generalizes the notion of nested canalyzing functions (NCFs), which are precisely the functions with maximum depth. NCFs have been proposed as gene regulatory network models, but their structure is frequently too restrictive and they are extremely sparse. We find that functions become decreasingly sensitive to input …

3-D Mesoscale Mhd Simulations Of Magnetospheric Cusp-Like Configurations: Cusp Diamagnetic Cavities And Boundary Structure, E. Adamson, A. Otto, K. Nykyri

Publications

We present results from mesoscale simulations of the magnetospheric cusp region for both strongly northward and strongly southward interplanetary magnetic field (IMF). Simulation results indicate an extended region of depressed magnetic field and strongly enhanced plasma B which exhibits a strong dependence on IMF orientation. These structures correspond to the Cusp Diamagnetic Cavities (CDC’s). The typical features of these CDC’s are generally well reproduced by the simulation. The inner boundaries between the CDC and the magnetosphere are gradual transitions which form a clear funnel shape, regardless of IMF orientation. The outer CDC/magnetosheath boundary exhibits a clear indentation in both the …

On The Stability Of A Microstructure Model, Mihhail Berezovski, Arkadi Berezovski

Publications

Abstract

The asymptotic stability of solutions of the Mindlin-type microstructure model for solids is analyzed in the paper. It is shown that short waves are asymptotically stable even in the case of a weakly non-convex free energy dependence on microdeformation.

Research highlights

The Mindlin-type microstructure model cannot describe properly short wave propagation in laminates. A modified Mindlin-type microstructure model with weakly non-convex free energy resolves this discrepancy. It is shown that the improved model with weakly non-convex free energy is asymptotically stable for short waves.

The Initial–Final Mass Relation Among White Dwarfs In Wide Binaries, J. K. Zhao, T. D. Oswalt, L. A. Willson, Q. Wang, G. Zhao

Publications

We present the initial–final mass relation derived from 10 white dwarfs in wide binaries that consist of a main-sequence star and a white dwarf. The temperature and gravity of each white dwarf were measured by fitting theoretical model atmospheres to the observed spectrum using a χ² fitting algorithm. The cooling time and mass were obtained using theoretical cooling tracks. The total age of each binary was estimated from the chromospheric activity of its main-sequence component to an uncertainty of about 0.17 dex in log t. The difference between the total age and white dwarf cooling time is taken …

Web Supported Emplotment: Using Object And Event Descriptions To Facilitate Storytelling Online And In Galleries, Trevor Collins, Paul Mulholland, Annika Wolff

Publications

The process of emplotment refers to the selection of significant events in a story and the identification of pertinent relations between them, in order to produce a plot providing an interpretation of those events. We are investigating how models of emplotment can be applied to develop web-based tools for creating and interpreting narratives. In particular, we are focusing on the process undertaken by art gallery professionals to design and present exhibitions. This paper presents a set of plot relations developed in collaboration with museum professionals from two national galleries in Ireland, and shows how theories of narrative and digital cultural …

Loft: The Observatory For X-Ray Timing, M. Feroci, J. W. Den Herder, E. Bozzo, D. Barret, S. Brandt, M. Hernanz, M. Van Der Klis, M. Pohl, A. Santangelo, L Stella, A Watts, J Wilms, S Zane

Publications

The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor …

Measuring The Stellar Accretion Rates Of Herbig Ae/Be Stars, Brian Donehew, Sean D. Brittain

Publications

The accretion rate of young stars is a fundamental characteristic of these systems.While accretion onto T Tauri stars has been studied extensively, little work has been done on measuring the accretion rate of their intermediate-mass analogs, the Herbig Ae/Be stars. Measuring the stellar accretion rate of Herbig Ae/Bes is not straightforward both because of the dearth of metal absorption lines available for veiling measurements and the intrinsic brightness of Herbig Ae/Be stars at ultraviolet wavelengths where the brightness of the accretion shock peaks. Alternative approaches to measuring the accretion rate of young stars by measuring the luminosity of proxies such …

Curate And Storyspace: An Ontology And Web-Based Environment For Describing Curatorial Narratives, Paul Mulholland, Annika Wolff, Trevolr Collins

Publications

focus on describing the heritage objects that the museum holds in its collection. These are used to manage and describe individual heritage objects according to properties such as artist, date and preservation requirements. Curatorial narratives, such as physical or online exhibitions tell a story that spans across heritage objects and have a meaning that does not necessarily reside in the individual heritage objects themselves. Here we present curate, an ontology for describing curatorial narratives. This draws on structuralist accounts that distinguish the narrative from the story and plot, and also a detailed analysis of two museum exhibitions and the curatorial …