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Sample records for circumbinary molecular ring

  1. Molecular emission from GG Car's circumbinary disk

    CERN Document Server

    Kraus, Michaela; Nickeler, Dieter; Muratore, Florencia; Fernandes, Marcelo Borges; Aret, Anna; Cidale, Lydia; de Wit, Willem-Jan

    2012-01-01

    The appearance of the B[e] phenomenon in evolved massive stars such as B[e] supergiants is still a mystery. While these stars are generally found to have disks that are cool and dense enough for efficient molecule and dust condensation, the origin of the disk material is still unclear. We aim at studying the kinematics and origin of the disk in the eccentric binary system GG Car, whose primary component is proposed to be a B[e] supergiant. Based on medium- and high-resolution near-infrared spectra we analyzed the CO-band emission detected from GG Car. The complete CO-band structure delivers information on the density and temperature of the emitting region, and the detectable 13CO bands allow us to constrain the evolutionary phase. In addition, the kinematics of the CO gas can be extracted from the shape of the first 12CO band head. We find that the CO gas is located in a ring surrounding the eccentric binary system, and its kinematics agrees with Keplerian rotation with a velocity, projected to the line of si...

  2. CIRCUMBINARY GAS ACCRETION ONTO A CENTRAL BINARY: INFRARED MOLECULAR HYDROGEN EMISSION FROM GG Tau A

    International Nuclear Information System (INIS)

    We present high spatial resolution maps of ro-vibrational molecular hydrogen emission from the environment of the GG Tau A binary component in the GG Tau quadruple system. The H2 v = 1-0 S(1) emission is spatially resolved and encompasses the inner binary, with emission detected at locations that should be dynamically cleared on several hundred year timescales. Extensions of H2 gas emission are seen to ∼100 AU distances from the central stars. The v = 2-1 S(1) emission at 2.24 μm is also detected at ∼30 AU from the central stars, with a line ratio of 0.05 ± 0.01 with respect to the v = 1-0 S(1) emission. Assuming gas in LTE, this ratio corresponds to an emission environment at ∼1700 K. We estimate that this temperature is too high for quiescent gas heated by X-ray or UV emission from the central stars. Surprisingly, we find that the brightest region of H2 emission arises from a spatial location that is exactly coincident with a recently revealed dust 'streamer' which seems to be transferring material from the outer circumbinary ring around GG Tau A into the inner region. As a result, we identify a new excitation mechanism for ro-vibrational H2 stimulation in the environment of young stars. The H2 in the GG Tau A system appears to be stimulated by mass accretion infall as material in the circumbinary ring accretes onto the system to replenish the inner circumstellar disks. We postulate that H2 stimulated by accretion infall could be present in other systems, particularly binaries and 'transition disk' systems which have dust-cleared gaps in their circumstellar environments.

  3. Near-infrared imaging polarimetry of the GG $\\tau$ circumbinary ring

    CERN Document Server

    Silber, J; Duchêne, G; Ménard, F; Silber, Joel; Gledhill, Tim; Duchene, Gaspard; Menard, Franccois

    2000-01-01

    We present 1 micron Hubble Space Telescope/NICMOS resolved imaging polarimetry of the GG Tau circumbinary ring. We find that the ring displays east-west asymmetries in surface brightness as well as several pronounced irregularities, but is smoother than suggested by ground-based adaptive optics observations. The data are consistent with a 37 deg system inclination and a projected rotational axis at a position angle of 7 deg east of north, determined from millimeter imaging. The ring is strongly polarized, up to 50%, which is indicative of Rayleigh-like scattering from sub-micron dust grains. Although the polarization pattern is broadly centrosymmetric and clearly results from illumination of the ring by the central stars, departures from true centrosymmetry and the irregular flux suggest that binary illumination, scattering through unresolved circumstellar disks, and shading by these disks, may all be factors influencing the observed morphology. We confirm a 0.25 arcsec shift between the inner edges of the NI...

  4. A multi-wavelength scattered light analysis of the dust grain population in the GG Tau circumbinary ring

    Energy Technology Data Exchange (ETDEWEB)

    Duchene, G; McCabe, C; Ghez, A; Macintosh, B

    2004-02-04

    We present the first 3.8 {micro}m image of the dusty ring surrounding the young binary system GG Tau, obtained with the W. M. Keck II 10m telescope's adaptive optics system. THis is the longest wavelength at which the ring has been detected in scattered light so far, allowing a multi-wavelength analysis of the scattering proiperties of the dust grains present in this protoplanetary disk in combination with previous, shorter wavelengths, HST images. We find that the scattering phase function of the dust grains in the disk is only weakly dependent on the wavelength. This is inconsistent with dust models inferred from observations of the interstellar medium or dense molecular clouds. In particular, the strongly forward-throwing scattering phase function observed at 3.8 {micro}m implies a significant increase in the population of large ({approx}> 1 {micro}m) grains, which provides direct evidence for grain growth in the ring. However, the grain size distribution required to match the 3.8 {micro}m image of the ring is incompatible with its published 1 {micro}m polarization map, implying that the dust population is not uniform throughout the ring. We also show that our 3.8 {micro}m image of the ring is incompatible with its published 1 {micro}m polarization map, implying that the dust population is not uniform throughout the ring. We also show that our 3.8 {micro}m scattered light image probes a deeper layer of the ring than previous shorter wavelength images, as demonstrated by a shift in the location of the inner edge of the disk's scattered light distribution between 1 and 3.8 {micro}m. We therefore propose a stratified structure for the ring in which the surface layers, located {approx} 50 AU above the ring midplane, contain dust grains that are very similar to those found in dense molecular clouds, while the region of the ring located {approx} 25 AU from the midplane contains significantly larger grains. This stratified structure is likely the result of

  5. Molecular content of polar ring galaxies

    CERN Document Server

    Combes, Francoise; Reshetnikov, Vladimir

    2013-01-01

    We have searched for CO lines in a sample of 21 new morphologically determined polar ring galaxies (of which 9 are kinematically confirmed), obtained from a wide search in the Galaxy Zoo project by Moiseev and collaborators. Polar ring galaxies (PRG) are a unique class of objects, tracing special episodes in the galaxy mass assembly: they could be formed through galaxy interaction, merging, but also through accretion from cosmic filaments. Beside, they enable the study of dark matter haloes in 3 dimensions. The polar ring itself is a sub-system rich in gas, where molecular gas is expected, and new stars are formed. Among the sample of 21 PRG, we have detected five CO-rich systems, that can now be followed up with higher spatial resolution. Their average molecular mass is 9.4 10**9 Mo, and their average gas fraction is 27% of their baryonic mass, with a range from 15 to 43%, implying that they just accreted a large amount of gas. The position of the detected objects in the velocity-magnitude diagram is offset ...

  6. Circumbinary Habitability Niches

    CERN Document Server

    Mason, Paul A; Cuartas-Restrepo, Pablo A; Clark, Joni M

    2014-01-01

    Binaries could provide the best niches for life in the galaxy. Though counterintuitive, this assertion follows directly from stellar tidal interaction theory and the evolution of lower mass stars. There is strong evidence that chromospheric activity of rapidly rotating young stars may be high enough to cause mass loss from atmospheres of potentially habitable planets. The removal of atmospheric water is most critical. Tidal breaking in binaries could help reduce magnetic dynamo action and thereby chromospheric activity in favor of life. We call this the Binary Habitability Mechanism (BHM), that we suggest allows for water retention at levels comparable to or better than Earth. We discuss novel advantages that life may exploit, in these cases, and suggest that life may even thrive on some circumbinary planets. We find that while many binaries do not benefit from BHM, high quality niches do exist for various combinations of stars between 0.55 and 1.0 solar masses. For a given pair of stellar masses, BHM operate...

  7. Molecular Model of the Contractile Ring

    CERN Document Server

    Biron, D; Tlusty, Tsvi; Moses, Elisha; 10.1103/PhysRevLett.95.098102

    2010-01-01

    We present a model for the actin contractile ring of adherent animal cells. The model suggests that the actin concentration within the ring and consequently the power that the ring exerts both increase during contraction. We demonstrate the crucial role of actin polymerization and depolymerization throughout cytokinesis, and the dominance of viscous dissipation in the dynamics. The physical origin of two phases in cytokinesis dynamics ("biphasic cytokinesis") follows from a limitation on the actin density. The model is consistent with a wide range of measurements of the midzone of dividing animal cells.

  8. The Abundance of Circumbinary Exoplanets

    Science.gov (United States)

    Armstrong, David J.

    2015-12-01

    Circumbinary planets, planets orbiting around binary stars, represent a new angle of information on planet formation theories, showing us how the different processes that form a planet react to the torque of a central host binary. I will present recently published observational constraints on the occurrence rates and orbital element distributions of circumbinary planets. This work utilises the Kepler dataset of ~2000 eclipsing binaries, along with an independently developed tailored search algorithm, to debias the dataset and find the underlying frequency of these planets. We discover that circumbinary planets have a similar occurrence rate to planets around single stars, but only if they are preferentially coplanar with their host binary. If they are more misaligned, they must be significantly more common. This effect is strong enough that following a reductio ad absurdum argument, we confirm the coplanar preference for these planets. Along with these results, we confirm the previously noted tendency for circumbinary planets to not be found around the closest (P(binary) < ~7 days) host binaries. This last result may be a marker of the binary star formation process.

  9. Laser pulse induced multiple exciton kinetics in molecular ring structures

    Science.gov (United States)

    Hou, Xiao; Wang, Luxia

    2016-11-01

    Multiple excitons can be formed upon strong optical excitation of molecular aggregates and complexes. Based on a theoretical approach on exciton-exciton annihilation dynamics in supramolecular systems (May et al., 2014), exciton interaction kinetics in ring aggregates of two-level molecules are investigated. Excited by the sub-picosecond laser pulse, multiple excitons keep stable in the molecular ring shaped as a regular polygon. If the symmetry is destroyed by changing the dipole of a single molecule, the excitation of different molecules becomes not identical, and the changed dipole-dipole interaction initiates subsequent energy redistribution. Depending on the molecular distance and the dipole configuration, the kinetics undergo different types of processes, but all get stable within some hundreds of femtoseconds. The study of exciton kinetics will be helpful for further investigations of the efficiency of optical devices based on molecular aggregates.

  10. AROUND THE RING WE GO: THE COLD, DENSE RING OF MOLECULAR GAS IN NGC 1614

    International Nuclear Information System (INIS)

    We present high-resolution archival Atacama Large Millimeter/submillimeter Array (ALMA) 12CO J = 3-2 and J = 6-5 and HCO+ J = 4-3 observations and new CARMA 12CO and 13CO J = 1-0 observations of the luminous infrared galaxy NGC 1614. The high-resolution maps show the previously identified ring-like structure while the 12CO J = 3-2 map shows extended emission that traces the extended dusty features. We combined these new observations with previously published Submillimeter Array 12CO and 13CO J = 2-1 observations to constrain the physical conditions of the molecular gas at a resolution of 230 pc using a radiative transfer code and a Bayesian likelihood analysis. At several positions around the central ring-like structure, the molecular gas is cold (20-40 K) and dense (>103.0 cm–3). The only region that shows evidence of a second molecular gas component is the ''hole'' in the ring. The 12CO-to-13CO abundance ratio is found to be greater than 130, more than twice the local interstellar medium value. We also measure the CO-to-H2 conversion factor, αCO, to range from 0.9 to 1.5 M ☉ (K km s–1 pc2)–1

  11. Molecular Split-Ring Resonators Based on Metal String Complexes

    CERN Document Server

    Shen, Yao; Ai, Qing; Peng, Shie-Ming; Jin, Bih-Yaw

    2014-01-01

    Metal string complexes or extended metal atom chains (EMACs) belong to a family of molecules that consist of a linear chain of directly bonded metal atoms embraced helically by four multidentate organic ligands. These four organic ligands are usually made up of repeating pyridyl units, single-nitrogen-substituted heterocyclic annulenes, bridged by independent amido groups. Here, in this paper, we show that these heterocyclic annulenes are actually nanoscale molecular split-ring resonators (SRRs) that can exhibit simultaneous negative electric permittivity and magnetic permeability in the UV-Vis region. Moreover, a monolayer of self-assembled EMACs is a periodic array of molecular SRRs which can be considered as a negative refractive index material. In the molecular scale, where the quantum-size effect is significant, we apply the tight-binding method to obtain the frequency-dependent permittivity and permeability of these molecular SRRs with their tensorial properties carefully considered.

  12. On the Abundance of Circumbinary Planets

    CERN Document Server

    Armstrong, D J; Brown, D; Faedi, F; Chew, Y Gómez Maqueo; Martin, D; Pollacco, D; Udry, S

    2014-01-01

    Circumbinary planets have been the subject of much recent work, providing both simulations and new discoveries. We present the first observationally based determination of the rate of occurrence of these planets. This is derived from the publicly available Kepler data, using an automated search algorithm and debiasing process to produce occurrence rates implied by the seven systems already known. These rates depend critically on the planetary inclination distribution: if circumbinary planets are preferentially coplanar with their host binaries, as has been suggested, then the rate of occurrence of planets with $R_p>6R_\\oplus$ orbiting with $P_p}10R_\\oplus$) are significantly less common in circumbinary orbits than their smaller siblings, and confirm that the proposed shortfall of circumbinary planets orbiting the shorter period binaries in the Kepler sample is a real effect.

  13. Secular and tidal evolution of circumbinary systems

    CERN Document Server

    Correia, Alexandre C M; Laskar, Jacques

    2016-01-01

    We investigate the secular dynamics of three-body circumbinary systems under the effect of tides. We use the octupolar non-restricted approximation for the orbital interactions, general relativity corrections, the quadrupolar approximation for the spins, and the viscous linear model for tides. We derive the averaged equations of motion in a simplified vectorial formalism, which is suitable to model the long-term evolution of a wide variety of circumbinary systems in very eccentric and inclined orbits. In particular, this vectorial approach can be used to derive constraints for tidal migration, capture in Cassini states, and stellar spin-orbit misalignment. We show that circumbinary planets with initial arbitrary orbital inclination can become coplanar through a secular resonance between the precession of the orbit and the precession of the spin of one of the stars. We also show that circumbinary systems for which the pericenter of the inner orbit is initially in libration present chaotic motion for the spins ...

  14. The excited state antiaromatic benzene ring: a molecular Mr Hyde?

    Science.gov (United States)

    Papadakis, Raffaello; Ottosson, Henrik

    2015-09-21

    The antiaromatic character of benzene in its first ππ* excited triplet state (T1) was deduced more than four decades ago by Baird using perturbation molecular orbital (PMO) theory [J. Am. Chem. Soc. 1972, 94, 4941], and since then it has been confirmed through a range of high-level quantum chemical calculations. With focus on benzene we now first review theoretical and computational studies that examine and confirm Baird's rule on reversal in the electron count for aromaticity and antiaromaticity of annulenes in their lowest triplet states as compared to Hückel's rule for the ground state (S0). We also note that the rule according to quantum chemical calculations can be extended to the lowest singlet excited state (S1) of benzene. Importantly, Baird, as well as Aihara [Bull. Chem. Soc. Jpn. 1978, 51, 1788], early put forth that the destabilization and excited state antiaromaticity of the benzene ring should be reflected in its photochemical reactivity, yet, today these conclusions are often overlooked. Thus, in the second part of the article we review photochemical reactions of a series of benzene derivatives that to various extents should stem from the excited state antiaromatic character of the benzene ring. We argue that benzene can be viewed as a molecular "Dr Jekyll and Mr Hyde" with its largely unknown excited state antiaromaticity representing its "Mr Hyde" character. The recognition of the "Jekyll and Hyde" split personality feature of the benzene ring can likely be useful in a range of different areas. PMID:25960203

  15. Warped circumbinary disks in active galactic nuclei

    International Nuclear Information System (INIS)

    We study a warping instability of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on a circular orbit. Such a circumbinary disk is subject to not only tidal torques due to the binary gravitational potential but also radiative torques due to radiation emitted from an accretion disk around each black hole. We find that a circumbinary disk initially aligned with the binary orbital plane is unstable to radiation-driven warping beyond the marginally stable warping radius, which is sensitive to both the ratio of vertical to horizontal shear viscosities and the mass-to-energy conversion efficiency. As expected, the tidal torques give no contribution to the growth of warping modes but tend to align the circumbinary disk with the orbital plane. Since the tidal torques can suppress the warping modes in the inner part of circumbinary disk, the circumbinary disk starts to be warped at radii larger than the marginally stable warping radius. If the warping radius is of the order of 0.1 pc, a resultant semi-major axis is estimated to be of the order of 10–2 pc to 10–4 pc for 107 M☉ black hole. We also discuss the possibility that the central objects of observed warped maser disks in active galactic nuclei are binary supermassive black holes with a triple disk: two accretion disks around the individual black holes and one circumbinary disk surrounding them.

  16. RPMDrate: Bimolecular chemical reaction rates from ring polymer molecular dynamics

    KAUST Repository

    Suleimanov, Yu.V.

    2013-03-01

    We present RPMDrate, a computer program for the calculation of gas phase bimolecular reaction rate coefficients using the ring polymer molecular dynamics (RPMD) method. The RPMD rate coefficient is calculated using the Bennett-Chandler method as a product of a static (centroid density quantum transition state theory (QTST) rate) and a dynamic (ring polymer transmission coefficient) factor. The computational procedure is general and can be used to treat bimolecular polyatomic reactions of any complexity in their full dimensionality. The program has been tested for the H+H2, H+CH 4, OH+CH4 and H+C2H6 reactions. © 2012 Elsevier B.V. All rights reserved.

  17. AROUND THE RING WE GO: THE COLD, DENSE RING OF MOLECULAR GAS IN NGC 1614

    Energy Technology Data Exchange (ETDEWEB)

    Sliwa, Kazimierz; Wilson, Christine D. [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Iono, Daisuke [National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Peck, Alison [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Matsushita, Satoki, E-mail: sliwak@mcmaster.ca, E-mail: wilson@physics.mcmaster.ca, E-mail: d.iono@nao.ac.jp, E-mail: apeck@alma.cl, E-mail: satoki@asiaa.sinica.edu.tw [Academia Sinica Institute of Astronomy and Astrophysics, PO Box 23-141, Taipei 10617, Taiwan (China)

    2014-11-20

    We present high-resolution archival Atacama Large Millimeter/submillimeter Array (ALMA) {sup 12}CO J = 3-2 and J = 6-5 and HCO{sup +} J = 4-3 observations and new CARMA {sup 12}CO and {sup 13}CO J = 1-0 observations of the luminous infrared galaxy NGC 1614. The high-resolution maps show the previously identified ring-like structure while the {sup 12}CO J = 3-2 map shows extended emission that traces the extended dusty features. We combined these new observations with previously published Submillimeter Array {sup 12}CO and {sup 13}CO J = 2-1 observations to constrain the physical conditions of the molecular gas at a resolution of 230 pc using a radiative transfer code and a Bayesian likelihood analysis. At several positions around the central ring-like structure, the molecular gas is cold (20-40 K) and dense (>10{sup 3.0} cm{sup –3}). The only region that shows evidence of a second molecular gas component is the ''hole'' in the ring. The {sup 12}CO-to-{sup 13}CO abundance ratio is found to be greater than 130, more than twice the local interstellar medium value. We also measure the CO-to-H{sub 2} conversion factor, α{sub CO}, to range from 0.9 to 1.5 M {sub ☉} (K km s{sup –1} pc{sup 2}){sup –1}.

  18. A Formulation of the Ring Polymer Molecular Dynamics

    CERN Document Server

    Horikoshi, Atsushi

    2014-01-01

    The exact formulation of the path integral centroid dynamics is extended to include composites of the position and momentum operators. We present the generalized centroid dynamics (GCD), which provides a basis to calculate Kubo-transformed correlation functions by means of classical averages. We define various types of approximate GCD, one of which is equivalent to the ring polymer molecular dynamics (RPMD). The RPMD and another approximate GCD are tested in one-dimensional harmonic system, and it is shown that the RPMD works better in the short time region.

  19. Warping and tearing of misaligned circumbinary disks around eccentric SMBH binaries

    OpenAIRE

    Hayasaki, Kimitake; Sohn, Bong Won; Okazaki, Atsuo T.; Jung, TaeHyun; Zhao, Guangyao; Naito, Tsuguya

    2015-01-01

    We study the warping and tearing of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on an eccentric orbit. The circumbinary disk is significantly misaligned with the binary orbital plane, and is subject to the time-dependent tidal torques. In principle, such a disk is warped and precesses, and is torn into mutually misaligned rings in the region, where the tidal precession torques are stronger than the local viscous torques. We derive the tidal-warp...

  20. Birth Locations of the Kepler Circumbinary Planets

    CERN Document Server

    Silsbee, Kedron

    2015-01-01

    The Kepler mission has discovered about a dozen circumbinary planetary systems, all containing planets on ~ 1 AU orbits. We place bounds on the locations in the circumbinary protoplanetary disk, where these planets could have formed through collisional agglomeration starting from small (km-sized or less) planetesimals. We first present a model of secular planetesimal dynamics that accounts for the (1) perturbation due to the eccentric precessing binary, as well as the (2) gravity and (3) gas drag from a precessing eccentric disk. Their simultaneous action leads to rich dynamics, with (multiple) secular resonances emerging in the disk. We derive analytic results for size-dependent planetesimal eccentricity, and demonstrate the key role of the disk gravity for circumbinary dynamics. We then combine these results with a simple model for collisional outcomes and find that in systems like Kepler 16, planetesimal growth starting with 10-100 m planetesimals is possible outside a few AU. The exact location exterior t...

  1. Energetic disorder and exciton states of individual molecular rings

    International Nuclear Information System (INIS)

    Exciton states in molecular rings (resembling, e.g. the B850 ring from LH2 complexes of purple bacterium Rhodopseudomonas acidophila) with strong intermolecular interaction are still a question of interest [V. Sundstrom, T. Pullerits, R. van Grondelle, J. Phys. Chem. B 103 (1999) 2327]. In our theoretical model we use the ring of two-level systems, simulating, e.g., the bacteriochlorophylls B850. The dynamical aspects in ensemble of rings are reflected in optical line shapes of electronic transitions. The observed linewidths reflect the combined influence of different types of static and dynamic disorder. To avoid the broadening of lines due to ensemble averaging one uses the single-molecule spectroscopy technique to obtain a fluorescence-excitation spectrum. For zero disorder the exciton manifold features two non-degenerate and eight pairwise degenerate states. In the presence of energetic disorder the degeneracy of the exciton states is lifted and oscillator strength is redistributed among the exciton states. A satisfactory understanding of the nature of static disorder in light-harvesting systems has not been reached [S. Jang, S.F. Dempster, R.J. Silbey, J. Phys. Chem. B 105 (2001) 6655]. In the local site basis, there can be present static disorder in both diagonal and off-diagonal Hamiltonian matrix elements. Silbey et al. [J. Phys. Chem. B 105 (2001) 6655] pointed out several questions: is former enough or the latter should be included as well? If both are considered, then there remains a question about whether they are independent or correlated. The distribution of the energetic separation E(k=+/-1) and relative orientation of the transition-dipole moments has been recently investigated [S. Jang, et al., J. Phys. Chem. B 105 (2001) 6655; C. Hofmann, T.J. Aartsma, J. Koehler, Chem. Phys. Lett. 395 (2004) 373]. In our present contribution we have extended such a type of investigation to four models of noncorrelated static disorder: (A) Gaussian disorder in the

  2. Angular momentum exchange by gravitational torques and infall in the circumbinary disk of the protostellar system L1551 NE

    International Nuclear Information System (INIS)

    We report an ALMA observation of the Class I binary protostellar system L1551 NE in the 0.9 mm continuum, C18O (3-2), and 13CO (3-2) lines at a ∼1.6 times higher resolution and a ∼6 times higher sensitivity than those of our previous SubMillimeter Array (SMA) observations, which revealed a r ∼ 300 AU scale circumbinary disk in Keplerian rotation. The 0.9 mm continuum shows two opposing U-shaped brightenings in the circumbinary disk and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the systemic velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust features coincide with locations where gravitational torques from the central binary system are predicted to impart angular momentum to the circumbinary disk, producing shocks and hence density enhancements seen as a pair of spiral arms. The observed inward gas motion coincides with locations where angular momentum is predicted to be lowered by the gravitational torques. The good agreement between our observation and model indicates that gravitational torques from the binary stars constitute the primary driver for exchanging angular momentum so as to permit infall through the circumbinary disk of L1551 NE.

  3. Angular momentum exchange by gravitational torques and infall in the circumbinary disk of the protostellar system L1551 NE

    Energy Technology Data Exchange (ETDEWEB)

    Takakuwa, Shigehisa; Ho, Paul T. P. [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Saito, Masao [Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago (Chile); Saigo, Kazuya [ALMA Project Office, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Matsumoto, Tomoaki [Faculty of Humanity and Environment, Hosei University, Chiyoda-ku, Tokyo 102-8160 (Japan); Lim, Jeremy [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Hanawa, Tomoyuki, E-mail: takakuwa@asiaa.sinica.edu.tw [Center for Frontier Science, Chiba University, Inage-ku, Chiba 263-8522 (Japan)

    2014-11-20

    We report an ALMA observation of the Class I binary protostellar system L1551 NE in the 0.9 mm continuum, C{sup 18}O (3-2), and {sup 13}CO (3-2) lines at a ∼1.6 times higher resolution and a ∼6 times higher sensitivity than those of our previous SubMillimeter Array (SMA) observations, which revealed a r ∼ 300 AU scale circumbinary disk in Keplerian rotation. The 0.9 mm continuum shows two opposing U-shaped brightenings in the circumbinary disk and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the systemic velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust features coincide with locations where gravitational torques from the central binary system are predicted to impart angular momentum to the circumbinary disk, producing shocks and hence density enhancements seen as a pair of spiral arms. The observed inward gas motion coincides with locations where angular momentum is predicted to be lowered by the gravitational torques. The good agreement between our observation and model indicates that gravitational torques from the binary stars constitute the primary driver for exchanging angular momentum so as to permit infall through the circumbinary disk of L1551 NE.

  4. Detection of Sharp Symmetric Features in the Circumbinary Disk Around AK Sco

    CERN Document Server

    Janson, Markus; Boccaletti, Anthony; Maire, Anne-Lise; Zurlo, Alice; Marzari, Francesco; Meyer, Michael R; Carson, Joseph C; Augereau, Jean-Charles; Garufi, Antonio; Henning, Thomas; Desidera, Silvano; Asensio-Torres, Ruben; Polh, Adriana

    2015-01-01

    The Search for Planets Orbiting Two Stars (SPOTS) survey aims to study the formation and distribution of planets in binary systems by detecting and characterizing circumbinary planets and their formation environments through direct imaging. With the SPHERE Extreme Adaptive Optics instrument, a good contrast can be achieved even at small (<300 mas) separations from bright stars, which enables studies of planets and disks in a separation range that was previously inaccessible. Here, we report the discovery of resolved scattered light emission from the circumbinary disk around the well-studied young double star AK Sco, at projected separations in the ~13--40 AU range. The sharp morphology of the imaged feature is surprising, given the smooth appearance of the disk in its spectral energy distribution. We show that the observed morphology can be represented either as a highly eccentric ring around AK Sco, or as two separate spiral arms in the disk, wound in opposite directions. The relative merits of these inte...

  5. Molecular dynamics simulations of ring inversion in RDX

    Science.gov (United States)

    Wallis, Eric P.; Thompson, Donald L.

    1993-08-01

    Molecular dynamics simulations, using the finite volume method of Murrell and co-workers [J. Chem. Phys. 94, 3908 (1991)], have been carried out to study conformational changes in hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in isolation and in dense Xe gas. The configurational distributions for RDX in a Xe bath and in the gas-phase are markedly different. The results show that as the solvent concentration increases, the concentration of RDX molecules in the boat conformation increases by a factor of about 4. The rate constant for the chair→boat ring inversion was calculated as a function of the xenon concentration [Xe]. The rate constant obeys Lindemann behavior at low concentrations, i.e., it increases with increasing solvent density. At [Xe]˜6.2 mol dm-3, the rate constant reaches a maximum (Kramer's turnover) and becomes a decreasing function of the solvent concentration. For [Xe] above 16.2 mol dm-3, the rate constant again increases as a function of the solvent density.

  6. Angular Momentum Exchange by Gravitational Torques and Infall in the Circumbinary Disk of the Protostellar System L1551 NE

    CERN Document Server

    Takakuwa, Shigehisa; Saigo, Kazuya; Matsumoto, Tomoaki; Lim, Jeremy; Hanawa, Tomoyuki; Ho, Paul T P

    2014-01-01

    We report the ALMA observation of the Class I binary protostellar system L1551 NE in the 0.9-mm continuum, C18O (3-2), and 13CO (3-2) lines at a ~1.6 times higher resolution and a ~6 times higher sensitivity than those of our previous SMA observations, which revealed a r ~300 AU-scale circumbinary disk in Keplerian rotation. The 0.9-mm continuum shows two opposing U-shaped brightenings in the circumbinary disk, and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the systemic velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly-observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust featur...

  7. Reflected eclipses on circumbinary planets

    Directory of Open Access Journals (Sweden)

    Deeg H.J.

    2011-02-01

    Full Text Available A photometric method to detect planets orbiting around shortperiodic binary stars is presented. It is based on the detection of eclipse-signatures in the reflected light of circumbinary planets. Amplitudes of such ’reflected eclipses’ will depend on the orbital configurations of binary and planet relative to the observer. Reflected eclipses will occur with a period that is distinct from the binary eclipses, and their timing will also be modified by variations in the light-travel time of the eclipse signal. For the sample of eclipsing binaries found by the Kepler mission, reflected eclipses from close circumbinary planets may be detectable around at least several dozen binaries. A thorough detection effort of such reflected eclipses may then detect the inner planets present, or give solid limits to their abundance.

  8. Recent Kepler Results On Circumbinary Planets

    OpenAIRE

    Welsh, William F.; Orosz, Jerome A.; Carter, Joshua A.; Fabrycky, Daniel C.

    2013-01-01

    Ranked near the top of the long list of exciting discoveries made with NASA's Kepler photometer is the detection of transiting circumbinary planets. In just over a year the number of such planets went from zero to seven, including a multi-planet system with one of the planets in the habitable zone (Kepler-47). We are quickly learning to better detect and characterize these planets, including the recognition of their transit timing and duration variation "smoking gun" signature. Even with only...

  9. Stability of habitable exomoons of circumbinary planets

    Science.gov (United States)

    Satyal, Suman; Haghighipour, Nader; Quarles, Billy

    2015-12-01

    Among the currently known Kepler circumbinary planets, three, namely Kepler-453b, Kepler-16b, and Kepler-47c are in the binary habitable zone (HZ). Given the large sizes of these planets, it is unlikely that they would be habitable. However, similar to the giant planets in our solar system, these planets may have large moons, which orbit their host planets while in the HZ. These exomoons, if exist, present viable candidates for habitability. As a condition for habitability, the planet-moon system has to maintain its orbital stability for long time. Usually, the empirical formula by Holeman & Wiegert (1999) is used as a measure of orbital stability in circumbinary systems. However, this formula was obtained by assuming planets to be test particles and therefore does not include possible perturbation of the planet on the binary. In this work, we present results of more realistic calculations of stability of circumbinary planets where the interactions between planets and their central binaries are taken into account. We map the region of stability, which in this case will be specific to each system, and determine the range of the orbital parameters of the moons for which their orbits will be long-term stable.

  10. DETECTION OF SHARP SYMMETRIC FEATURES IN THE CIRCUMBINARY DISK AROUND AK Sco

    Energy Technology Data Exchange (ETDEWEB)

    Janson, Markus; Asensio-Torres, Ruben [Department of Astronomy, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Thalmann, Christian; Meyer, Michael R.; Garufi, Antonio [Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Boccaletti, Anthony [LESIA, Observatoire de Paris—Meudon, CNRS, Université Pierre et Marie Curie, Université Paris Didierot, 5 Place Jules Janssen, F-92195 Meudon (France); Maire, Anne-Lise; Henning, Thomas; Pohl, Adriana [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Zurlo, Alice [Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago (Chile); Marzari, Francesco [Dipartimento di Fisica, University of Padova, Via Marzolo 8, I-35131 Padova (Italy); Carson, Joseph C. [Department of Physics and Astronomy, College of Charleston, 66 George Street, Charleston, SC 29424 (United States); Augereau, Jean-Charles [Université Grenoble Alpes, IPAG, F-38000 Grenoble (France); Desidera, Silvano [INAF—Osservatorio Astromonico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova (Italy)

    2016-01-01

    The Search for Planets Orbiting Two Stars survey aims to study the formation and distribution of planets in binary systems by detecting and characterizing circumbinary planets and their formation environments through direct imaging. With the SPHERE Extreme Adaptive Optics instrument, a good contrast can be achieved even at small (<300 mas) separations from bright stars, which enables studies of planets and disks in a separation range that was previously inaccessible. Here, we report the discovery of resolved scattered light emission from the circumbinary disk around the well-studied young double star AK Sco, at projected separations in the ∼13–40 AU range. The sharp morphology of the imaged feature is surprising, given the smooth appearance of the disk in its spectral energy distribution. We show that the observed morphology can be represented either as a highly eccentric ring around AK Sco, or as two separate spiral arms in the disk, wound in opposite directions. The relative merits of these interpretations are discussed, as well as whether these features may have been caused by one or several circumbinary planets interacting with the disk.

  11. Testing dust trapping in the circumbinary disk around GG Tau A

    CERN Document Server

    Cazzoletti, P; Birnstiel, T; Lodato, G

    2016-01-01

    The protoplanetary disk around the GGTau A binary system is so far one of the most studied young circumbinary disk. Observations of the dust continuum emission at sub-mm/mm wavelengths detected a dust ring located between 200AU and 300AU from the center of mass of the system. If the disk and the binary orbit are coplanar, given the observed projected separation of the stars in the binary system, the classical theory of tidal interaction between a binary system and its circumbinary disk predicts a truncation radius which is significantly smaller than the measured inner radius of the mm-sized dust ring. We investigate the origin of this dust ring structure in the GG Tau A disk, test whether the interaction between the binary and the disk can produce a dust trap at the location of the observed ring, and discuss an alternative scenario which invokes a misalignment between the disk and the stellar orbital planes. We run a set of hydrodynamical simulations for an orbit consistent with the astrometric solutions for ...

  12. Examining Tatooine: Atmospheric Models of Neptune-Like Circumbinary Planets

    CERN Document Server

    May, E M

    2016-01-01

    Circumbinary planets experience a time varying irradiation pattern as they orbit their two host stars. In this work, we present the first detailed study of the atmospheric effects of this irradiation pattern on known and hypothetical gaseous circumbinary planets. Using both a one-dimensional Energy Balance Model and a three-dimensional General Circulation Model, we look at the temperature differences between circumbinary planets and their equivalent single-star cases in order to determine the nature of the atmospheres of these planets. We find that for circumbinary planets on stable orbits around their host stars, temperature differences are on average no more than 1.0% in the most extreme cases. Based on detailed modeling with the General Circulation Model, we find that these temperature differences are not large enough to excite circulation differences between the two cases. We conclude that gaseous circumbinary planets can be treated as their equivalent single-star case in future atmospheric modeling effor...

  13. Examining Tatooine: Atmospheric Models of Neptune-like Circumbinary Planets

    Science.gov (United States)

    May, E. M.; Rauscher, E.

    2016-08-01

    Circumbinary planets experience a time-varying irradiation pattern as they orbit their two host stars. In this work, we present the first detailed study of the atmospheric effects of this irradiation pattern on known and hypothetical gaseous circumbinary planets. Using both a one-dimensional energy balance model (EBM) and a three-dimensional general circulation model (GCM), we look at the temperature differences between circumbinary planets and their equivalent single-star cases in order to determine the nature of the atmospheres of these planets. We find that for circumbinary planets on stable orbits around their host stars, temperature differences are on average no more than 1.0% in the most extreme cases. Based on detailed modeling with the GCM, we find that these temperature differences are not large enough to excite circulation differences between the two cases. We conclude that gaseous circumbinary planets can be treated as their equivalent single-star case in future atmospheric modeling efforts.

  14. Circumbinary planets II - when transits come and go

    CERN Document Server

    Martin, David V

    2016-01-01

    Circumbinary planets are generally more likely to transit than equivalent single-star planets, but practically the geometry and orbital dynamics of circumbinary planets make the chance of observing a transit inherently time-dependent. In this follow-up paper to Martin & Triaud (2015), the time-dependence is probed deeper by analytically calculating when and for how long the binary and planet orbits overlap, allowing for transits to occur. The derived equations are applied to the known transiting circumbinary planets found by Kepler to predict when future transits will occur, and whether they will be observable by upcoming space telescopes TESS, CHEOPS and PLATO. The majority of these planets spend less than 50% of their time in a transiting configuration, some less than 20%. From this it is calculated that the known Kepler eclipsing binaries likely host an additional ~ 17 - 30 circumbinary planets that are similar to the ten published discoveries, and they will ultimately transit some day, potentially dur...

  15. Where Are The Circumbinary Planets of Contact Binaries?

    CERN Document Server

    Demircan, O

    2014-01-01

    Up to present date, no circumbinary planet around contact binaries were discovered neither by transit method nor by the minima times variation, although they are known having third component stars around. We thus ask: where are the circumbinary planets of contact binaries? By considering the physical and geometrical parameters we simulated the light curves of contact binaries with possible transiting circumbinary jovian planets. It seems either the circumbinary jovian planets are not formed around contact binaries, probably due to dynamical effects of the binary and third component stars, or they are present but the discovery of such planets were not possible so far due to larger distortions then expected in the photometric data and in the minima times.

  16. Kepler-16: A Transiting Circumbinary Planet

    CERN Document Server

    Doyle, Laurance R; Fabrycky, Daniel C; Slawson, Robert W; Howell, Steve B; Winn, Joshua N; Orosz, Jerome A; Prsa, Andrej; Welsh, William F; Quinn, Samuel N; Latham, David; Torres, Guillermo; Buchhave, Lars A; Marcy, Geoffrey W; Fortney, Jonathan J; Shporer, Avi; Ford, Eric B; Lissauer, Jack J; Ragozzine, Darin; Rucker, Michael; Batalha, Natalie; Jenkins, Jon M; Borucki, William J; Koch, David; Middour, Christopher K; Hall, Jennifer R; McCauliff, Sean; Fanelli, Michael N; Quintana, Elisa V; Holman, Matthew J; Caldwell, Douglas A; Still, Martin; Stefanik, Robert P; Brown, Warren R; Esquerdo, Gilbert A; Tang, Sumin; Furesz, Gabor; Geary, John C; Berlind, Perry; Calkins, Michael L; Short, Donald R; Steffen, Jason H; Sasselov, Dimitar; Dunham, Edward W; Cochran, William D; Boss, Alan; Haas, Michael R; Buzasi, Derek; Fischer, Debra

    2011-01-01

    We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size, and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20% and 69% as massive as the sun, and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5 degree of a single plane, suggesting that the planet formed within a circumbinary disk.

  17. Effects of molecular structure parameters on ring-openingreaction of benzoxazines

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A colorless monoclinic crystal of dichloro-benzoxazine was obtained and examined bysingle crystal X-ray diffraction analysis. At the same time, molecular modeling analysis of ninebenzoxazine compounds with different substituting groups was performed. Both single crystalX-ray diffraction analysis and molecular modeling analysis provide a detailed picture of molecularstructure on molecular level and show good consistence with each other. On the basis of structuralanalysis, the effects of molecular structure parameters on ring-opening polymerization of ben-zoxazines have been explored.

  18. How to remove the spurious resonances from ring polymer molecular dynamics

    CERN Document Server

    Rossi, Mariana; Manolopoulos, David E

    2014-01-01

    Two of the most successful methods that are presently available for simulating the quantum dynamics of condensed phase systems are centroid molecular dynamics (CMD) and ring polymer molecular dynamics (RPMD). Despite their conceptual differences, practical implementations of these methods differ in just two respects: the choice of the Parrinello-Rahman mass matrix and whether or not a thermostat is applied to the internal modes of the ring polymer during the dynamics. Here we explore a method which is halfway between the two approximations: we keep the path integral bead masses equal to the physical particle masses but attach a Langevin thermostat to the internal modes of the ring polymer during the dynamics. We justify this by showing analytically that the inclusion of an internal mode thermostat does not affect any of the desirable features of RPMD: thermostatted RPMD (TRPMD) is equally valid with respect to everything that has actually been proven about the method as RPMD itself. In particular, because of ...

  19. Molecular buffer using a PANDA ring resonator for drug delivery use

    Directory of Open Access Journals (Sweden)

    N Suwanpayak

    2011-03-01

    Full Text Available N Suwanpayak1, MA Jalil2, MS Aziz3, J Ali3, PP Yupapin11Nanoscale Science and Engineering Research Alliance (N’SERA, Advanced Research Center for Photonics, Faculty of Science, King Mongkut’s Institute of Technology, Ladkrabang, Bangkok, Thailand; 2Ibnu Sina Institute of Fundamental Science Studies (IIS, 3Institute of Advanced Photonics Science, Nanotechnology Research Alliance, Universitiy Teknologi Malaysia, Johor Bahru, MalaysiaAbstract: A novel design of molecular buffer for molecule storage and delivery using a PANDA ring resonator is proposed. The optical vortices can be generated and controlled to form the trapping tools in the same way as the optical tweezers. In theory, the trapping force is formed by the combination between the gradient field and scattering photons, which is reviewed. By using the intense optical vortices generated within the PANDA ring resonator, the required molecules can be trapped and moved (transported dynamically within the wavelength router or network, ie, a molecular buffer. This can be performed within the wavelength router before reaching the required destination. The advantage of the proposed system is that a transmitter and receiver can be formed within the same system, which is available for molecule storage and transportation.Keywords: molecular buffer, molecular memory, molecular transceiver, molecular repeater, PANDA ring resonator 

  20. Circumbinary disks around T Tauri stars HST/NICMOS near-infrared images and polarimetric maps

    CERN Document Server

    Duchêne, G; Ménard, F; Gledhill, T M

    2000-01-01

    We have obtained new near-infrared images of both GG Tau and UY Aur circumbinary disks with the polarimetric modes of NICMOS aboard the Hubble Space Telescope. The 1 micron intensity map of GG Tau reveals a more complete elliptical shape than in previous ground-based images. Its eastern and western sides are definitely asymmetric. Our image strongly supports the ring geometry proposed by Guilloteau, Dutrey & Simon (1999) on the basis of their millimetre interferometry images: a geometrically thick and sharply edged ring surrounding an empty gap around the binary. Around UY Aur, we identify structures that are in excellent agreement with the optical images of M\\'enard et al. (1999), which confirms that the inclination of the system to the line-of-sight is about 60 degrees. We also find tentative new structures closer to the stars.

  1. Warping and tearing of misaligned circumbinary disks around eccentric SMBH binaries

    CERN Document Server

    Hayasaki, Kimitake; Okazaki, Atsuo T; Jung, Taehyun; Zhao, Guangyao; Naito, Tsuguya

    2015-01-01

    We study the warping and tearing of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on an eccentric orbit. The circumbinary disk is significantly misaligned with the binary orbital plane, and is subject to the time-dependent tidal torques. In principle, such a disk is warped and precesses, and is torn into mutually misaligned rings in the region, where the tidal precession torques are stronger than the local viscous torques. We derive the tidal-warp and tearing radii of the misaligned circumbinary disks around eccentric SMBH binaries. We find that in disks with the viscosity parameter, alpha, larger than a critical value depending on the disk aspect ratio, the disk warping appears outside the tearing radius. This condition is expressed as alpha > sqrt{H/3r} for H/r ~<0.1, where H is the disk scale height. If alpha < sqrt{H/3r}, only the disk tearing occurs because the tidal warp radius is inside the tearing radius, where most of disk material is likely to rapi...

  2. Caustic Structures and Detectability of Circumbinary Planets in Microlensing

    Science.gov (United States)

    Luhn, Jacob K.; Penny, Matthew T.; Gaudi, B. Scott

    2016-08-01

    Recent discoveries of circumbinary planets in Kepler data show that there is a viable channel of planet formation around binary main-sequence stars. Motivated by these discoveries, we have investigated the caustic structures and detectability of circumbinary planets in microlensing events. We have produced a suite of animations of caustics as a function of the projected separation and angle of the binary host to efficiently explore caustic structures over the entire circumbinary parameter space. Aided by these animations, we have derived a semi-empirical analytic expression for the location of planetary caustics, which are displaced in circumbinary lenses relative to those of planets with a single host. We have used this expression to show that the dominant source of caustic motion will be due to the planet’s orbital motion and not that of the binary star. Finally, we estimate the fraction of circumbinary microlensing events that are recognizable as such to be significant (5%–50%) for binary projected separations in the range 0.1–0.5 in units of Einstein radii.

  3. An analysis of nonadiabatic ring-polymer molecular dynamics and its application to vibronic spectra

    CERN Document Server

    Richardson, Jeremy O; Pleinert, Marc-Oliver; Thoss, Michael

    2016-01-01

    Nonadiabatic ring-polymer molecular dynamics employs the mapping approach to describe nonadiabatic effects within the ring-polymer ansatz. In this paper, it is generalized to allow for the nuclear and electronic degrees of freedom to be described by different numbers of ring-polymer beads. Analysis of the resulting method shows that as the number of electronic mapping variables increases, certain problems associated with the approach are removed, such as the non-unique choice of the mapping Hamiltonian and negative populations leading to inverted potential-energy surfaces. Explicit integration over cyclic variables reduces the sign problem for the initial distribution in the general case. A new application for the simulation of vibronic spectra is described and promising results are presented for a model system.

  4. Physical Properties and Galactic Distribution of Molecular Clouds Identified in the Galactic Ring Survey

    Science.gov (United States)

    Roman-Duval, Julia; Jackson, James M.; Heyer, Mark; Rathborne, Jill; Simon, Robert

    2010-11-01

    We derive the physical properties of 580 molecular clouds based on their 12CO and 13CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys. We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the interstellar medium is around 2.36. This relation, M = (228 ± 18) R 2.36 ± 0.04, allows us to derive masses for an additional 170 Galactic Ring Survey (GRS) molecular clouds not covered by the UMSB survey. We derive the Galactic surface mass density of molecular gas and examine its spatial variations throughout the Galaxy. We find that the azimuthally averaged Galactic surface density of molecular gas peaks between Galactocentric radii of 4 and 5 kpc. Although the Perseus arm is not detected in molecular gas, the Galactic surface density of molecular gas is enhanced along the positions of the Scutum-Crux and Sagittarius arms. This may indicate that molecular clouds form in spiral arms and are disrupted in the inter-arm space. Finally, we find that the CO excitation temperature of molecular clouds decreases away from the Galactic center, suggesting a possible decline in the star formation rate with Galactocentric radius. There is a marginally significant enhancement in the CO excitation temperature of molecular clouds at a Galactocentric radius of about 6 kpc, which in the longitude range of the GRS corresponds to the Sagittarius arm. This temperature increase could be associated with massive star formation in the Sagittarius spiral arm.

  5. Molecular cytogenetic and phenotypic characterization of ring chromosome 13 in three unrelated patients

    Science.gov (United States)

    Abdallah-Bouhjar, Inesse B.; Mougou-Zerelli, Soumaya; Hannachi, Hanene; Gmidène, Abir; Labalme, Audrey; Soyah, Najla; Sanlaville, Damien; Saad, Ali; Elghezal, Hatem

    2013-01-01

    We report on the cytogenetic and molecular investigations of constitutional de-novo ring chromosome 13s in three unrelated patients for better understanding and delineation of the phenotypic variability characterizing this genomic rearrangement. The patient’s karyotypes were as follows: 46,XY,r(13)(p11q34) dn for patients 1 and 2 and 46,XY,r(13)(p11q14) dn for patient 3, as a result of the deletion in the telomeric regions of chromosome 13. The patients were, therefore, monosomic for the segment 13q34 → 13qter; in addition, for patient 3, the deletion was larger, encompassing the segment 13q14 → 13qter. Fluorescence in situ hybridization confirmed these rearrangement and array CGH technique showed the loss of at least 2.9 Mb on the short arm and 4.7 Mb on the long arm of the chromosome 13 in patient 2. Ring chromosome 13 (r(13)) is associated with several phenotypic features like intellectual disability, marked short stature, brain and heart defects, microcephaly and genital malformations in males, including undescended testes and hypospadias. However, the hearing loss and speech delay that were found in our three patients have rarely been reported with ring chromosome 13. Although little is known about its etiology, there is interesting evidence for a genetic cause for the ring chromosome 13. We thus performed a genotype-phenotype correlation analysis to ascertain the contribution of ring chromosome 13 to the clinical features of our three cases.

  6. A transiting circumbinary planet in KIC 10753734

    Science.gov (United States)

    Orosz, Jerome A.; Welsh, William F.; Short, Donald R.; Endl, Michael; Cochran, William D.; Johnson, Marshall C.; Mills, Sean; Fabrycky, Daniel; Haghighipour, Nader; Windmiller, Gur

    2016-06-01

    KIC 10753734 is an eclipsing binary discovered by NASA's Kepler mission. The binary period is about 19.4 days with a moderately large eccentricity of e=0.52. Spectroscopic observations from McDonald Observatory show the system is double-lined, which allow us to derive masses for the primary and secondary stars, both of which are roughly solar-like. Two weak transit-like events separated by 6.5 days appear in the Kepler light curve near the end of the nominal mission. A careful examination of the light curve at earlier times reveals two weak transit events (separated by about 7 days) that occurred about 250 days earlier. We show that the two pairs of events represent transits of both stars at successive conjunctions of a circumbinary planet with a period of about 260 days and a radius of about 6 Earth radii. The lack of large eclipse timing variations limit the third body to be sub-stellar in mass, i.e. a planet. Despite the deep primary and secondary eclipses, the analysis is hampered by spots on both stars. We present a progress report on the modelling effort to date, and present preliminary characteristics of the planet.

  7. Analytic orbit propagation for transiting circumbinary planets

    CERN Document Server

    Georgakarakos, Nikolaos

    2015-01-01

    The herein presented analytical framework fully describes the motion of coplanar systems consisting of a stellar binary and a planet orbiting both stars on orbital as well as secular timescales. Perturbations of the Runge-Lenz vector are used to derive short period evolution of the system, while octupole secular theory is applied to describe its long term behaviour. A post Newtonian correction on the stellar orbit is included. The planetary orbit is initially circular and the theory developed here assumes that the planetary eccentricity remains relatively small (e_2<0.2). Our model is tested against results from numerical integrations of the full equations of motion and is then applied to investigate the dynamical history of some of the circumbinary planetary systems discovered by NASA's Kepler satellite. Our results suggest that the formation history of the systems Kepler-34 and Kepler-413 has most likely been different from the one of Kepler-16, Kepler-35, Kepler-38 and Kepler-64, since the observed plan...

  8. Effects of XUV radiation on circumbinary planets

    CERN Document Server

    Sanz-Forcada, J; Micela, G

    2014-01-01

    Several circumbinary planets have recently been discovered. The orbit of a planet around a binary stellar system poses several dynamic constraints. The effects that radiation from the host stars may have on the planet atmospheres must be considered. Because of the configuration of a close binary system, these stars have a high rotation rate, which causes a permanent state of high stellar activity and copious XUV radiation. The accumulated effects are stronger than for exoplanets around single stars, and cause a faster evaporation of their atmospheres. We evaluate the effects that stellar radiation has on the evaporation of exoplanets around binary systems and on the survival of these planets. We considered the XUV spectral range to account for the photons that are easily absorbed by a planet atmosphere that is mainly composed of hydrogen. A more complex atmospheric composition is expected to absorb this radiation more efficiently. We used direct X-ray observations to evaluate the energy in the X-rays range an...

  9. How bright are the gaps in circumbinary disk systems?

    CERN Document Server

    Shi, Ji-Ming

    2016-01-01

    When a circumbinary disk surrounds a binary whose secondary's mass is at least $\\sim 10^{-2}\\times$ the primary's mass, a nearly empty cavity with radius a few times the binary separation is carved out of the disk. Narrow streams of material pass from the inner edge of the circumbinary disk into the domain of the binary itself, where they eventually join onto the small disks orbiting the members of the binary. Using data from 3-d MHD simulations of this process, we determine the luminosity of these streams; it is mostly due to weak laminar shocks, and is in general only a few percent of the luminosity of adjacent regions of either the circumbinary disk or the "mini-disks". This luminosity therefore hardly affects the deficit in the thermal continuum predicted on the basis of a perfectly dark gap region.

  10. Well-defined polyethylene molecular brushes by polyhomologation and ring opening metathesis polymerization

    KAUST Repository

    Zhang, Hefeng

    2014-01-01

    A novel strategy using polyhomologation and ring opening metathesis polymerization (ROMP) has been developed for the synthesis of well-defined polyethylene (PE) molecular brushes. Polyhomologation was used to afford an OH-terminated PE, which after transformation to the norbornyl PE macromonomer was subjected to ROMP. Kinetics of ROMP of the PE macromonomer was studied by in situ1H NMR monitoring. The brush structure was proved from HT-GPC, 1H NMR and DSC results.

  11. Role of aromatic rings in the molecular recognition of aminoglycoside antibiotics: implications for drug design.

    Science.gov (United States)

    Vacas, Tatiana; Corzana, Francisco; Jiménez-Osés, Gonzalo; González, Carlos; Gómez, Ana M; Bastida, Agatha; Revuelta, Julia; Asensio, Juan Luis

    2010-09-01

    Aminoglycoside antibiotics participate in a large variety of binding processes involving both RNA and proteins. The description, in recent years, of several clinically relevant aminoglycoside/receptor complexes has greatly stimulated the structural-based design of new bioactive derivatives. Unfortunately, design efforts have frequently met with limited success, reflecting our incomplete understanding of the molecular determinants for the antibiotic recognition. Intriguingly, aromatic rings of the protein/RNA receptors seem to be key actors in this process. Indeed, close inspection of the structural information available reveals that they are frequently involved in CH/pi stacking interactions with sugar/aminocyclitol rings of the antibiotic. While the interaction between neutral carbohydrates and aromatic rings has been studied in detail during past decade, little is known about these contacts when they involve densely charged glycosides. Herein we report a detailed experimental and theoretical analysis of the role played by CH/pi stacking interactions in the molecular recognition of aminoglycosides. Our study aims to determine the influence that the antibiotic polycationic character has on the stability, preferred geometry, and dynamics of these particular contacts. With this purpose, different aminoglycoside/aromatic complexes have been selected as model systems. They varied from simple bimolecular interactions to the more stable intramolecular CH/pi contacts present in designed derivatives. The obtained results highlight the key role played by electrostatic forces and the desolvation of charged groups in the molecular recognition of polycationic glycosides and have clear implications for the design of improved antibiotics.

  12. Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey

    OpenAIRE

    Roman-Duval, Julia; Jackson, James M.; Heyer, Mark; Rathborne, Jill; Simon, Robert

    2010-01-01

    We derive the physical properties of 580 molecular clouds based on their 12CO and 13CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys. We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the ISM is around 2.36. This relation, M = (228 +/- 18) R^{2.36+/-0.04}, allows us to derive masses for an additional 170 G...

  13. Detecting circumbinary planets: A new quasi-periodic search algorithm

    Directory of Open Access Journals (Sweden)

    Pollacco D.

    2013-04-01

    Full Text Available We present a search method based around the grouping of data residuals, suitable for the detection of many quasi-periodic signals. Combined with an efficient and easily implemented method to predict the maximum transit timing variations of a transiting circumbinary exoplanet, we form a fast search algorithm for such planets. We here target the Kepler dataset in particular, where all the transiting examples of circumbinary planets have been found to date. The method is presented and demonstrated on two known systems in the Kepler data.

  14. Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey

    CERN Document Server

    Roman-Duval, Julia; Heyer, Mark; Rathborne, Jill; Simon, Robert

    2010-01-01

    We derive the physical properties of 580 molecular clouds based on their 12CO and 13CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys. We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the ISM is around 2.36. This relation, M = (228 +/- 18) R^{2.36+/-0.04}, allows us to derive masses for an additional 170 GRS molecular clouds not covered by the UMSB survey. We derive the Galactic surface mass density of molecular gas and examine its spatial variations throughout the Galaxy. We find that the azimuthally averaged Galactic surface density of molecular gas peaks between Galactocentric radii of 4 and 5 kpc. Although the Perseus arm is not detected in molecular gas, the Galactic surface density of molecular gas is enhanced along the positions of the Scutum-Crux and Sagittarius arms. This may indicate that molecular clouds form in...

  15. The NGC 1614 Interacting Galaxy: Molecular Gas Feeding a "Ring of Fire"

    CERN Document Server

    König, S; Muller, S; Beswick, R J; Gallagher, J S

    2013-01-01

    Minor mergers frequently occur between giant and gas-rich low mass galaxies and can provide significant amounts of interstellar matter to refuel star formation and power AGN in the giant systems. Major starbursts and/or AGN result when fresh gas is transported and compressed in the central regions of the giant galaxy. This is the situation in NGC1614, whose molecular medium we explore at half arcsecond angular resolution through our observations of 12CO(2-1) emission using the SMA. We compare our maps with optical and Pa alpha, HST and high angular resolution radio continuum images to study the relationships between dense molecular gas and the starburst region. The most intense CO emission occurs in a partial ring with ~230pc radius around the center, with an extension to the north-west into the dust lane that contains diffuse molecular gas. We resolve 10 GMAs in the ring which has an integrated molecular mass of ~8x10^8M_sun. Our observations filter out a large part of the CO(1-0) emission mapped at shorter ...

  16. Should thermostatted ring polymer molecular dynamics be used to calculate thermal reaction rates?

    International Nuclear Information System (INIS)

    We apply Thermostatted Ring Polymer Molecular Dynamics (TRPMD), a recently proposed approximate quantum dynamics method, to the computation of thermal reaction rates. Its short-time transition-state theory limit is identical to rigorous quantum transition-state theory, and we find that its long-time limit is independent of the location of the dividing surface. TRPMD rate theory is then applied to one-dimensional model systems, the atom-diatom bimolecular reactions H + H2, D + MuH, and F + H2, and the prototypical polyatomic reaction H + CH4. Above the crossover temperature, the TRPMD rate is virtually invariant to the strength of the friction applied to the internal ring-polymer normal modes, and beneath the crossover temperature the TRPMD rate generally decreases with increasing friction, in agreement with the predictions of Kramers theory. We therefore find that TRPMD is approximately equal to, or less accurate than, ring polymer molecular dynamics for symmetric reactions, and for certain asymmetric systems and friction parameters closer to the quantum result, providing a basis for further assessment of the accuracy of this method

  17. Should Thermostatted Ring Polymer Molecular Dynamics be used to calculate reaction rates?

    CERN Document Server

    Hele, Timothy J H

    2015-01-01

    We apply Thermostatted Ring Polymer Molecular Dynamics (TRPMD), a recently-proposed approximate quantum dynamics method, to the computation of thermal reaction rates. Its short-time Transition-State Theory (TST) limit is identical to rigorous Quantum Transition-State Theory, and we find that its long-time limit is independent of the location of the dividing surface. TRPMD rate theory is then applied to one-dimensional model systems, the atom-diatom bimolecular reactions H+H$_2$, D+MuH and F+H$_2$, and the prototypical polyatomic reaction H+CH$_4$. Above the crossover temperature, the TRPMD rate is virtually invariant to the strength of the friction applied to the internal ring-polymer normal modes, and beneath the crossover temperature the TRPMD rate generally decreases with increasing friction, in agreement with the predictions of Kramers theory. We therefore find that TRPMD is less accurate than Ring Polymer Molecular Dynamics (RPMD) for symmetric reactions, and in certain asymmetric systems closer to the q...

  18. Analytical Formulas of Molecular Ion Abundances and N2H+ Ring in Protoplanetary Disks

    CERN Document Server

    Aikawa, Yuri; Nomura, Hideko; Qi, Chunhua

    2015-01-01

    We investigate the chemistry of ion molecules in protoplanetary disks, motivated by the detection of N$_2$H$^+$ ring around TW Hya. While the ring inner radius coincides with the CO snow line, it is not apparent why N$_2$H$^+$ is abundant outside the CO snow line in spite of the similar sublimation temperatures of CO and N$_2$. Using the full gas-grain network model, we reproduced the N$_2$H$^+$ ring in a disk model with millimeter grains. The chemical conversion of CO and N$_2$ to less volatile species (sink effect hereinafter) is found to affect the N$_2$H$^+$ distribution. Since the efficiency of the sink depends on various parameters such as activation barriers of grain surface reactions, which are not well constrained, we also constructed the no-sink model; the total (gas and ice) CO and N$_2$ abundances are set constant, and their gaseous abundances are given by the balance between adsorption and desorption. Abundances of molecular ions in the no-sink model are calculated by analytical formulas, which a...

  19. Static and dynamic properties of polymer brush with topological ring structures: Molecular dynamic simulation

    Science.gov (United States)

    Wan, Wu-Bing; Lv, Hong-Hong; Merlitz, Holger; Wu, Chen-Xu

    2016-10-01

    By defining a topological constraint value (rn), the static and dynamic properties of a polymer brush composed of moderate or short chains with different topological ring structures are studied using molecular dynamics simulation, and a comparison with those of linear polymer brush is also made. For the center-of-mass height of the ring polymer brush scaled by chain length h ˜ N ν , there is no significant difference of exponent from that of a linear brush in the small topological constraint regime. However, as the topological constraint becomes stronger, one obtains a smaller exponent. It is found that there exists a master scaling power law of the total stretching energy scaled by chain length N for moderate chain length regime, F ene ˜ Nρ ν , for ring polymer brushes, but with a larger exponent ν than 5/6, indicating an influence of topological constraint to the dynamic properties of the system. A topological invariant of free energy scaled by 5/4 is found. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374243 and 11574256).

  20. High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Adelnia, Fatemeh; Lascialfari, Alessandro [Dipartimento di Fisica, Università degli Studi di Milano and INSTM, Milano (Italy); Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, Pavia (Italy); Mariani, Manuel [Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna (Italy); Ammannato, Luca; Caneschi, Andrea; Rovai, Donella [Dipartimento di Chimica, Università degli Studi di Firenze and INSTM, Firenze (Italy); Winpenny, Richard; Timco, Grigore [School of Chemistry, The University of Manchester, Manchester (United Kingdom); Corti, Maurizio, E-mail: maurizio.corti@unipv.it; Borsa, Ferdinando [Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, Pavia (Italy)

    2015-05-07

    We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac){sub 3}NITEt and the magnetically frustrated Gd(hfac){sub 3}NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr{sub 8} closed ring and in Cr{sub 7}Cd and Cr{sub 8}Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime.

  1. Polymorphic Ring-Shaped Molecular Clusters Made of Shape-Variable Building Blocks

    Directory of Open Access Journals (Sweden)

    Keitel Cervantes-Salguero

    2015-02-01

    Full Text Available Self-assembling molecular building blocks able to dynamically change their shapes, is a concept that would offer a route to reconfigurable systems. Although simulation studies predict novel properties useful for applications in diverse fields, such kinds of building blocks, have not been implemented thus far with molecules. Here, we report shape-variable building blocks fabricated by DNA self-assembly. Blocks are movable enough to undergo shape transitions along geometrical ranges. Blocks connect to each other and assemble into polymorphic ring-shaped clusters via the stacking of DNA blunt-ends. Reconfiguration of the polymorphic clusters is achieved by the surface diffusion on mica substrate in response to a monovalent salt concentration. This work could inspire novel reconfigurable self-assembling systems for applications in molecular robotics.

  2. Accelerating ring-polymer molecular dynamics with parallel-replica dynamics.

    Science.gov (United States)

    Lu, Chun-Yaung; Perez, Danny; Voter, Arthur F

    2016-06-28

    Nuclear quantum effects are important for systems containing light elements, and the effects are more prominent in the low temperature regime where the dynamics also becomes sluggish. We show that parallel replica (ParRep) dynamics, an accelerated molecular dynamics approach for infrequent-event systems, can be effectively combined with ring-polymer molecular dynamics, a semiclassical trajectory approach that gives a good approximation to zero-point and tunneling effects in activated escape processes. The resulting RP-ParRep method is a powerful tool for reaching long time scales in complex infrequent-event systems where quantum dynamics are important. Two illustrative examples, symmetric Eckart barrier crossing and interstitial helium diffusion in Fe and Fe-Cr alloy, are presented to demonstrate the accuracy and long-time scale capability of this approach. PMID:27369499

  3. Accelerating ring-polymer molecular dynamics with parallel-replica dynamics

    Science.gov (United States)

    Lu, Chun-Yaung; Perez, Danny; Voter, Arthur F.

    2016-06-01

    Nuclear quantum effects are important for systems containing light elements, and the effects are more prominent in the low temperature regime where the dynamics also becomes sluggish. We show that parallel replica (ParRep) dynamics, an accelerated molecular dynamics approach for infrequent-event systems, can be effectively combined with ring-polymer molecular dynamics, a semiclassical trajectory approach that gives a good approximation to zero-point and tunneling effects in activated escape processes. The resulting RP-ParRep method is a powerful tool for reaching long time scales in complex infrequent-event systems where quantum dynamics are important. Two illustrative examples, symmetric Eckart barrier crossing and interstitial helium diffusion in Fe and Fe-Cr alloy, are presented to demonstrate the accuracy and long-time scale capability of this approach.

  4. How to remove the spurious resonances from ring polymer molecular dynamics.

    Science.gov (United States)

    Rossi, Mariana; Ceriotti, Michele; Manolopoulos, David E

    2014-06-21

    Two of the most successful methods that are presently available for simulating the quantum dynamics of condensed phase systems are centroid molecular dynamics (CMD) and ring polymer molecular dynamics (RPMD). Despite their conceptual differences, practical implementations of these methods differ in just two respects: the choice of the Parrinello-Rahman mass matrix and whether or not a thermostat is applied to the internal modes of the ring polymer during the dynamics. Here, we explore a method which is halfway between the two approximations: we keep the path integral bead masses equal to the physical particle masses but attach a Langevin thermostat to the internal modes of the ring polymer during the dynamics. We justify this by showing analytically that the inclusion of an internal mode thermostat does not affect any of the established features of RPMD: thermostatted RPMD is equally valid with respect to everything that has actually been proven about the method as RPMD itself. In particular, because of the choice of bead masses, the resulting method is still optimum in the short-time limit, and the transition state approximation to its reaction rate theory remains closely related to the semiclassical instanton approximation in the deep quantum tunneling regime. In effect, there is a continuous family of methods with these properties, parameterised by the strength of the Langevin friction. Here, we explore numerically how the approximation to quantum dynamics depends on this friction, with a particular emphasis on vibrational spectroscopy. We find that a broad range of frictions approaching optimal damping give similar results, and that these results are immune to both the resonance problem of RPMD and the curvature problem of CMD. PMID:24952532

  5. A search for circumbinary planets in CoRoT eclipsing binary light curves

    Directory of Open Access Journals (Sweden)

    Klagyivik Peter

    2015-01-01

    Full Text Available Several transiting circumbinary planets have been found in data of the Kepler mission [1–5]. Both CoRoT and Kepler have surveyed similar numbers of stars, and the photometric precision of CoRoT is sufficient that it could detect most of the known circumbinary planets; the main draw-back by CoRoT is the much shorter coverage. Still, there is a high chance that some circumbinary planets may be found in its sample of eclipsing binaries (hereafter EBs. Here we report on an ongoing search for circumbinary planets in the full CoRoT data set.

  6. Warping and tearing of misaligned circumbinary disks around eccentric supermassive black hole binaries

    Science.gov (United States)

    Hayasaki, K.; Sohn, B. W.; Okazaki, A. T.; Jung, T.; Zhao, G.; Naito, T.

    2015-07-01

    We study the warping and tearing of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on an eccentric orbit. The circumbinary disk is significantly misaligned with the binary orbital plane, and is subject to the time-dependent tidal torques. In principle, such a disk is warped and precesses, and is torn into mutually misaligned rings in the region, where the tidal precession torques are stronger than the local viscous torques. We derive the tidal-warp and tearing radii of the misaligned circumbinary disks around eccentric SMBH binaries. We find that in disks with the viscosity parameter α larger than a critical value depending on the disk aspect ratio, the disk warping appears outside the tearing radius. This condition is expressed for small amplitude warps as α > √H/(3r) for H/rlesssim0.1, where H is the disk scale height. If α warp radius is inside the tearing radius, where most of disk material is likely to rapidly accrete onto SMBHs. In warped and torn disks, both the tidal-warp and the tearing radii most strongly depend on the binary semi-major axis, although they also mildly depend on the other orbital and disk parameters. This strong dependence enables us to estimate the semi-major axis, once the tidal warp or tearing radius is determined observationally: for the tidal warp radius of 0.1 pc, the semi-major axis is estimated to be ~10-2 pc for 107 Msolar black hole with typical orbital and disk parameters. We also briefly discuss the possibility that central objects of observed warped maser disks in active galactic nuclei are supermassive black hole binaries.

  7. First Detections of Molecular Gas Associated with the Wolf-Rayet Ring Nebula NGC 3199

    Science.gov (United States)

    Marston, A. P.

    2001-12-01

    This paper presents the first observations of molecular gas associated with the Wolf-Rayet ring nebula NGC 3199 around the WR star WR 18. This includes first observations of the molecules HCN, HCO+, CN, and HNC seen in any Wolf-Rayet ring nebula. Our observations immediately suggest the presence of high-density molecular gas (>104 cm-3) in the nebula with significant amounts of associated molecular gas, which is in the form of clumpy ejecta and/or interstellar material. Molecular CO gas was mapped across the optically bright portion of the nebula and out into the diffuse ionized component using the 12CO J=1-->0 line. CO gas is not seen within the optically bright rim of NGC 3199 but adjacent to it. The optical emission rim therefore appears to mark regions of photodissociation. Velocity components in the CO data are consistent with those seen in high-resolution optical spectra of the Hα line but extend beyond the visible emission. A prior suggestion of the formation of the nebula via a bow shock appears unlikely since Hipparcos measurements show the proper motion of WR 18 is almost at right angles to the direction required for the bow shock model. Instead, line splitting toward the north of the nebula suggests that a possible blowout of the Wolf-Rayet wind through surrounding ejecta may be responsible for some of the velocity features observed. Preliminary estimates of molecular abundances in the nebula seen toward the central star are significantly higher than for the interstellar medium and are similar to those in planetary nebulae, although CN is distinctly underabundant in comparison to the very high values found in many planetary nebulae. The abundances found are consistent with the idea that at least a portion of the molecular material is associated with ejecta from the central star. Based on observations collected at the Swedish-ESO Submillimetre Telescope (SEST) at the European Southern Observatory, La Silla, Chile. The Swedish-ESO Submillimetre Telescope

  8. Assessing Circumbinary Habitable Zones using Latitudinal Energy Balance Modelling

    CERN Document Server

    Forgan, Duncan

    2013-01-01

    Previous attempts to describe circumbinary habitable zones have been concerned with the spatial extent of the zone, calculated analytically according to the combined radiation field of both stars. By contrast to these "spatial HZs", we present a numerical analysis of the "orbital HZ", a habitable zone defined as a function of planet orbital elements. This orbital HZ is better equipped to handle (for example) eccentric planet orbits, and is more directly connected to the data returned by exoplanet observations. Producing an orbital HZ requires a large number of climate simulations to be run to investigate the parameter space - we achieve this using Latitudinal Energy Balance Models (LEBMs), which handle the insolation of the planet by both stars (including mutual eclipses), as well as the planetary atmosphere's ability to absorb, transfer and lose heat. We present orbital HZs for several known circumbinary planetary systems: Kepler-16, Kepler-34, Kepler-35, Kepler-47 and PH-1. Generally, the orbital HZs at zer...

  9. Planet Formation in Circumbinary Configurations: Turbulence Inhibits Planetesimal Accretion

    Science.gov (United States)

    Meschiari, Stefano

    2012-12-01

    The existence of planets born in environments highly perturbed by a stellar companion represents a major challenge to the paradigm of planet formation. In numerical simulations, the presence of a close binary companion stirs up the relative velocity between planetesimals, which is fundamental in determining the balance between accretion and erosion. However, the recent discovery of circumbinary planets by Kepler establishes that planet formation in binary systems is clearly viable. We perform N-body simulations of planetesimals embedded in a protoplanetary disk, where planetesimal phasing is frustrated by the presence of stochastic torques, modeling the expected perturbations of turbulence driven by the magnetorotational instability. We examine perturbation amplitudes relevant to dead zones in the midplane (conducive to planet formation in single stars), and find that planetesimal accretion can be inhibited even in the outer disk (4-10 AU) far from the central binary, a location previously thought to be a plausible starting point for the formation of circumbinary planets.

  10. Uncovering Circumbinary Planetary Architectural Properties from Selection Biases

    CERN Document Server

    Li, Gongjie; Tao, Molei

    2016-01-01

    The new discoveries of circumbinary planetary systems shed light on the understanding of planetary system formation. Learning the architectural properties of these systems is essential for constraining the different formation mechanisms. We first revisit the stability limit of circumbinary planets. Next, we focus on eclipsing stellar binaries and obtain an analytical expression for the transit probability in a realistic setting, where finite observation period and planetary orbital precession are included. Then, understanding of the architectural properties of the currently observed transiting systems is refined, based on Bayesian analysis and a series of hypothesis tests. We find 1) it is not a selection bias that the innermost planets reside near the stability limit for eight of the nine observed systems, and this is consistent with a log uniform distribution of the planetary semi-major axis; 2) it is not a selection bias that the planetary and stellar orbits are nearly coplanar ($\\lesssim 3^\\circ$), and th...

  11. More on the circumbinary disk of SS 433

    CERN Document Server

    Bowler, M G

    2010-01-01

    Certain lines in spectra of the Galactic microquasar SS 433, in particular the brilliant H alpha line, have been interpreted as emission from a circumbinary disk. In this interpretation the orbital speed of the glowing material is in excess of 200 km/s and the mass of the binary system in excess of 40 solar masses. A very simple model of excitation of disk material is in remarkable agreement with the observations, yet it seems that the very existence of a circumbinary disk is regarded as controversial. Published spectra, taken almost nightly over two orbital periods of the binary system, show H alpha and He I lines; these were analysed as superpositions of Gaussian components. A model in which the excitation of any given patch of putative circumbinary material is proportional to the inverse square of its instantaneous distance from the compact object was constructed and compared with observations. The new model provides an excellent description of the observations. The variation of the H alpha and He I spectr...

  12. Interpretation of observations of the circumbinary disk of SS 433

    CERN Document Server

    Bowler, M G

    2010-01-01

    Context. The Galactic microquasar SS 433 is possessed of a circumbinary disk most clearly seen in the brilliant Balmer H alpha emission line. The orbital speed of the glowing material is an important determinant of the mass of the binary system. The circumbinary disk may be fed through the L2 point and in turn may feed a very extended radio feature known as the ruff. Aims. To present an analysis of spectroscopic optical data from H alpha and He I spectral lines which reveal the circumbinary disk. To use comparisons of the rather different signals to better understand the disk and improve estimates of the rotational speed of the inner rim. To present a simple model which naturally explains some apparently bizarre spectral variations with orbital phase. Methods. Published spectra, taken almost nightly over two orbital periods of the binary system, are analysed. H alpha and He I lines are analysed as superpositions of Gaussian components and a simple model constructed. Results. The data are understood in terms o...

  13. Modelling Circumbinary Gas Flows in Close T Tauri Binaries

    CERN Document Server

    de Val-Borro, M; Stempels, H C; Pepliński, A

    2011-01-01

    Young close binaries open central gaps in the surrounding circumbinary accretion disc, but the stellar components may still gain mass from gas crossing through the gap. It is not well understood how this process operates and how the stellar components are affected by such inflows. Our main goal is to investigate how gas accretion takes place and evolves in close T Tauri binary systems. In particular, we model the accretion flows around two close T Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission lines, although their orbital characteristics are very different. In order to derive the density and velocity maps of the circumbinary material, we employ two-dimensional hydrodynamic simulations with a locally isothermal equation of state. The flow patterns become quasi-stable after a few orbits in the frame co-rotating with the system. Gas flows across the circumbinary gap through the co-rotating Lagrangian points, and local circumstellar discs develop around both components. Spiral de...

  14. Transits of Planets with Small Intervals in Circumbinary Systems

    CERN Document Server

    Liu, Hui-Gen; Zhang, Hui; Zhou, Ji-Lin

    2014-01-01

    Transit times around single stars can be described well by a linear ephemeris. However, transit times in circumbinary systems are influenced both by the gravitational perturbations and the orbital phase variations of the central binary star. Adopting a coplanar analog of Kepler-16 as an example, we find that circumbinary planets can transit the same star more than once during a single planetary orbit, a phenomenon we call "tight transits". In certain geometric, the projected orbital velocity of the planet and the secondary star can approach zero and change sign, resulting in very long transits and/or 2-3 transits during a single binary orbit. Whether tight transits are possible for a particular system depends primarily on the binary mass ratio and the orbital architecture of both the binary and the planet. We derive a time-dependent criterion to judge when tight transits are possible for any circumbinary system. These results are verified with full dynamical integrations that also reveal other tight transit c...

  15. Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

    CERN Document Server

    Kraus, M; Arias, M L; Maravelias, G; Nickeler, D H; Torres, A F; Fernandes, M Borges; Aret, A; Cure, M; Vallverdu, R; Barba, R H

    2016-01-01

    We aim to improve our knowledge on the structure and dynamics of the circumstellar disk of the LMC B[e] supergiant LHA 120-S 73. High-resolution optical and near-IR spectroscopic data were obtained over a period of 16 and 7 years, respectively. The spectra cover the diagnostic emission lines from [CaII] and [OI], as well as the CO bands. These features trace the disk at different distances from the star. We analyzed the kinematics of the individual emission regions by modeling their emission profiles. A low-resolution mid-infrared spectrum was obtained as well, which provides information on the composition of the dusty disk. All diagnostic emission features display double-peaked line profiles, which we interpret as due to Keplerian rotation. We find that LHA 120-S 73 is surrounded by at least four individual rings of material with alternating densities (or by a disk with strongly non-monotonic radial density distribution). Moreover, we find that the molecular ring must have gaps or at least strong density inh...

  16. Miniature Chemical Sensor combining Molecular Recognition with Evanescent Wave Cavity Ring-Down Spectroscopy

    International Nuclear Information System (INIS)

    To address the chemical sensing needs of DOE, a new class of chemical sensors is being developed that enables qualitative and quantitative, remote, real-time, optical diagnostics of chemical species in hazardous gas, liquid, and semi-solid phases by employing evanescent wave cavity ring-down spectroscopy (EW-CRDS). The feasibility and sensitivity of EW-CRDS was demonstrated previously under Project No.60231. The objective of this project is to enhance the selectivity and domain of application of EW-CRDS. Selectivity is enhanced by using molecular recognition (MR) chemistry and polarized ''fingerprint'' near-IR spectroscopy, while the domain of application is expanded by combining EW-CRDS with the unique optical properties of nanoparticles and by extending the technique to liquids

  17. Chemical Reaction Rates from Ring Polymer Molecular Dynamics: Theory and Practical Applications

    CERN Document Server

    Suleimanov, Yury V; Guo, Hua

    2016-01-01

    This Feature Article presents an overview of the current status of Ring Polymer Molecular Dynamics (RPMD) rate theory. We first analyze theory and its connection to quantum transition state theory. We then focus on its practical application to prototypical chemical reactions in the gas phase, which demonstrate how accurate and reliable RPMD is for calculating thermal chemical reaction rates in multifarious cases. This review serves as an important checkpoint in RPMD rate theory development, which shows that RPMD is shifting from being just one of recent novel ideas to a well-established and validated alternative to conventional techniques for calculating thermal chemical rates. We also hope it will motivate further applications of RPMD to various chemical reactions.

  18. Molecular modelling studies of side-chain rotation in substituted triazine rings

    Science.gov (United States)

    Birkett, Helen E.; Cherryman, Julian C.; Margaret Chippendale, A.; Hazendonk, Paul; Harris, Robin K.

    2002-01-01

    Molecular modelling computation using the GAUSSIAN 94 package of programs was carried out to estimate four different barriers to internal rotation about amine nitrogen to sp 2 carbon bonds for two compounds with triazine rings. Whereas two of the processes appear to retain a planar side-chain nitrogen environment throughout the internal rotation, the other two involve pyramidalisation. In the latter two cases, after the barrier is passed, the process may or may not include a transient inversion at nitrogen. The internal rotation for cyclotriazine systems is discussed in relation to those for aniline and formamide. The four barrier magnitudes calculated for the triazines are in the same order as (though somewhat larger than) those measured by variable-temperature NMR bandshape analysis for a relevant compound.

  19. Mouse Aortic Ring Assay: A New Approach of the Molecular Genetics of Angiogenesis

    Directory of Open Access Journals (Sweden)

    Masson Véronique

    2002-01-01

    Full Text Available Angiogenesis, a key step in many physiological and pathological processes, involves proteolysis of the extracellular matrix. To study the role of two enzymatic families, serine-proteases and matrix metalloproteases in angiogenesis, we have adapted to the mouse, the aortic ring assay initially developed in the rat. The use of deficient mice allowed us to demonstrate that PAI-1 is essential for angiogenesis while the absence of an MMP, MMP-11, did not affect vessel sprouting. We report here that this model is attractive to elucidate the cellular and molecular mechanisms of angiogenesis, to identify, characterise or screen "pro- or anti-angiogenic agents that could be used for the treatment of angiogenesis-dependent diseases. Approaches include using recombinant proteins, synthetic molecules and adenovirus-mediated gene transfer.

  20. A Step Forward in Molecular Diagnostics of Lyssaviruses – Results of a Ring Trial among European Laboratories

    DEFF Research Database (Denmark)

    Fischer, Melina; Wernike, Kerstin; Freuling, Conrad M.;

    2013-01-01

    Rabies is a lethal and notifiable zoonotic disease for which diagnostics have to meet the highest standards. In recent years, an evolution was especially seen in molecular diagnostics with a wide variety of different detection methods published. Therefore, a first international ring trial specifi...

  1. A Step Forward in Molecular Diagnostics of Lyssaviruses – Results of a Ring Trial among European Laboratories

    NARCIS (Netherlands)

    Fischer, M.; Wernike, K.; Freuling, C.M.; Müller, T.; Aylan, O.; Brochier, B.; Cliquet, F.; Vázquez-Morón, S.; Hostnik, P.; Huovilainen, A.; Isaksson, M.; Kooi, E.A.

    2013-01-01

    Rabies is a lethal and notifiable zoonotic disease for which diagnostics have to meet the highest standards. In recent years, an evolution was especially seen in molecular diagnostics with a wide variety of different detection methods published. Therefore, a first international ring trial specifical

  2. Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

    Science.gov (United States)

    Kraus, M.; Cidale, L. S.; Arias, M. L.; Maravelias, G.; Nickeler, D. H.; Torres, A. F.; Borges Fernandes, M.; Aret, A.; Curé, M.; Vallverdú, R.; Barbá, R. H.

    2016-10-01

    Context. B[e] supergiants are evolved massive stars, enshrouded in a dense wind and surrounded by a molecular and dusty disk. The mechanisms that drive phases of enhanced mass loss and mass ejections, responsible for the shaping of the circumstellar material of these objects, are still unclear. Aims: We aim to improve our knowledge on the structure and dynamics of the circumstellar disk of the Large Magellanic Cloud B[e] supergiant LHA 120-S 73. Methods: High-resolution optical and near-infrared spectroscopic data were obtained over a period of 16 and 7 yr, respectively. The spectra cover the diagnostic emission lines from [Ca ii] and [O i], as well as the CO bands. These features trace the disk at different distances from the star. We analyzed the kinematics of the individual emission regions by modeling their emission profiles. A low-resolution mid-infrared spectrum was obtained as well, which provides information on the composition of the dusty disk. Results: All diagnostic emission features display double-peaked line profiles, which we interpret as due to Keplerian rotation. We find that the profile of each forbidden line contains contributions from two spatially clearly distinct rings. In total, we find that LHA 120-S 73 is surrounded by at least four individual rings of material with alternating densities (or by a disk with strongly non-monotonic radial density distribution). Moreover, we find that the molecular ring must have gaps or at least strong density inhomogeneities, or in other words, a clumpy structure. The optical spectra additionally display a broad emission feature at 6160-6180 Å, which we interpret as molecular emission from TiO. The mid-infrared spectrum displays features of oxygen- and carbon-rich grain species, which indicates a long-lived, stable dusty disk. We cannot confirm the previously reported high value for the stellar rotation velocity. He i λ 5876 is the only clearly detectable pure atmospheric absorption line in our data. Its

  3. On the RZ Draconis substellar circumbinary companions. Stability study of the proposed substellar circumbinary system

    Science.gov (United States)

    Hinse, Tobias C.; Horner, Jonathan; Lee, Jae Woo; Wittenmyer, Robert A.; Lee, Chung-Uk; Park, Jang-Ho; Marshall, Jonathan P.

    2014-05-01

    Context. Recently, using the light-travel time effect, planets and substellar companions have been proposed to orbit around binary star systems (also known as circumbinary companions) as a result of variations in timing of the observed eclipses. For the majority of these systems the proposed orbital architecture features a crossing of the orbital configurations as a result of high eccentricities for one or both of the companions. For such systems, strong mutual gravitational interactions are expected, resulting in catastrophic orbital instabilities, or collisions between the proposed components, on very short timescales. Aims: We re-examine the primary and secondary eclipse timings of the short-period and semi-detached binary RZ Draconis (RZ Dra). The proposed companions were reported to have masses of around ≃0.07 and ≃0.18 M⊙ with the inner companion on an orbit with moderate eccentricity (0.46), whose apocenter distance crosses the orbit of the outer companion. We show that the companions proposed previously follow highly unstable orbits. In an attempt to find a stable system we searched the underlying χ2 parameter space for a best-fit model and carried out an orbit-stability study to test possible best-fit models. If the binary period changes are truly due to additional massive companions in a hierarchical configuration, they must follow stable orbits. Methods: For numerical orbital stability calculations we used well established orbit integration routines. Computations were carried out using a large-scale multi-CPU computing environment. Our data analysis of times of primary and secondary eclipse is based on the Levenberg-Marquardt least-squares minimization algorithm using the two-body Keplerian light-travel time effect model. Results: Despite the wide variety of potential models tested for the RZ Dra system in this work, we found very few models that were stable for even one million years, with the vast majority of systems tested falling apart on

  4. On the RZ Draconis Sub-stellar Circumbinary Companions Stability Study of the Proposed Sub-stellar Circumbinary System

    CERN Document Server

    Hinse, Tobias C; Lee, Jae Woo; Wittenmyer, Robert A; Lee, Chung-Uk; Marshall, Jang-Ho Park Jonathan P

    2014-01-01

    In this work we revisit the proposed multi-circumbinary system RZ Dra. We find the proposed system to be highly unstable. We attempt to find a best-fit light-travel time model rendering the orbits to follow stable orbits. We found a best-fit solution, but the resulting orbits also exhibit short-term orbital instabilities. We therefore conclude that the observed timing variation must be due to other astrophysical effects causing a change in the binary orbital period. Follow-up observations of this system is encouraged.

  5. Molecular Analysis of Ring Y Chromosome in a 10-Year-Old Boy with Mixed Gonadal Dysgenesis and Growth Hormone Deficiency

    OpenAIRE

    Milenkovic, T; Guc-Scekic, M; Zdravkovic, D; Topic, V; Liehr, T.; Joksic, G; Radivojevic, D; Lakic, N

    2011-01-01

    Ring Y chromosome is a very rare chromosomal aberration. The published mixed gonadal dysgenesis (MGD) patients with a ring Y chromosome are short in stature, but are not growth hormone (GH) deficient. We present the molecular cytogenetic and molecular characterization of ring Y chromosome mosaicism in a 10-year-old boy with MGD whose short stature could be explained by the high percentage of cells monosomic for the X-chromosome, but also by the presence of severe GH deficiency. The ring Y chr...

  6. AN ANALYTIC THEORY FOR THE ORBITS OF CIRCUMBINARY PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Leung, Gene C. K.; Lee, Man Hoi [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong)

    2013-02-15

    Three transiting circumbinary planets (Kepler-16 b, Kepler-34 b, and Kepler-35 b) have recently been discovered from photometric data taken by the Kepler spacecraft. Their orbits are significantly non-Keplerian because of the large secondary-to-primary mass ratio and orbital eccentricity of the binaries, as well as the proximity of the planets to the binaries. We present an analytic theory, with the planet treated as a test particle, which shows that the planetary motion can be represented by the superposition of the circular motion of a guiding center, the forced oscillations due to the non-axisymmetric components of the binary's potential, the epicyclic motion, and the vertical motion. In this analytic theory, the periapse and ascending node of the planet precess at nearly equal rates in opposite directions. The largest forced oscillation term corresponds to a forced eccentricity (which is an explicit function of the parameters of the binary and of the guiding center radius of the planet), and the amplitude of the epicyclic motion (which is a free parameter of the theory) is the free eccentricity. Comparisons with direct numerical orbit integrations show that this analytic theory gives an accurate description of the planetary motion for all three Kepler systems. We find that all three Kepler circumbinary planets have nonzero free eccentricities.

  7. Predicting a third planet in the Kepler-47 circumbinary system

    CERN Document Server

    Hinse, Tobias C; Kostov, Veselin B; Goździewski, Krzysztof

    2014-01-01

    We have explored the possibility of a third circumbinary planet having a dynamically stable orbit in the Kepler-47 system and producing the single, unexplained transit event (not associated with either the binary star or the two known circumbinary planets) reported in the discovery paper (Orosz et al. 2012). We applied the dynamical mapping MEGNO technique to identify regions in the phase space of the system where this third planet can maintain stable, quasi-periodic orbits. The long-term, Lagrangian stability of the entire 5-body configuration (eclipsing binary + three planets) is confirmed by direct numerical integrations for 10 Myr. We identified several long-term stable regions between the two confirmed planets, and also an extended region beyond the orbit of the outer planet Kepler-47c. To further constrain the orbit of the hypothetical third planet, we compared the synthetic single transit duration it produces from the ensemble of stable orbits to the measured duration of the unexplained transit event (...

  8. Ab initio molecular dynamics with nuclear quantum effects at classical cost: ring polymer contraction for density functional theory

    CERN Document Server

    Marsalek, Ondrej

    2015-01-01

    Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ab initio ring polymer contraction (AI-RPC) scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive pro...

  9. Co-conformational Exchange Triggered by Molecular Recognition in a Di(acylamino)pyridine-Based Molecular Shuttle Containing Two Pyridine Rings at the Macrocycle.

    Science.gov (United States)

    Martinez-Cuezva, Alberto; Carro-Guillen, Fernando; Pastor, Aurelia; Marin-Luna, Marta; Orenes, Raul-Angel; Alajarin, Mateo; Berna, Jose

    2016-06-17

    We describe the incorporation of endo-pyridine units into the tetralactam ring of di(acylamino)pyridine-based rotaxanes. This macrocycle strongly associates with the linear interlocked component as confirmed by X-ray diffraction studies of rotaxane 2 b. Dynamic NMR studies of 2 b in solution revealed a rotational energy barrier that was higher than that of the related rotaxane 2 a, which lacks of pyridine rings in the macrocycle. The macrocycle distribution of the molecular shuttle 4 b, containing two endo-pyridine rings, shows that the major co-conformer is that with the cyclic component sitting over the di(acylamino)pyridine station. DFT calculations also support the marked preference of the ring for occupying the heterocyclic binding site. The association of N-hexylthymine with the di(acylamino)pyridine binding site of 4 b led to the formation of a rare 'S'-shaped co-conformer in which the tetralactam ring interacts simultaneously with both stations of the thread. PMID:26698891

  10. Motions of Kepler circumbinary planets in restricted three-body problem under radiating primaries

    Energy Technology Data Exchange (ETDEWEB)

    Dermawan, B., E-mail: budider@as.itb.ac.id; Hidayat, T., E-mail: taufiq@as.itb.ac.id [Astronomy Research Division, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132 (Indonesia); Huda, I. N., E-mail: ibnu.nurul@students.itb.ac.id; Mandey, D., E-mail: mandey.de@gmail.com; Utama, J. A., E-mail: judhistira@yahoo.com; Tampubolon, I., E-mail: ihsan.tampubolon@gmail.com [Department of Astronomy, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132 (Indonesia); Wibowo, R. W., E-mail: ridlo.w.wibowo@gmail.com [Department of Computational Science, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132 (Indonesia)

    2015-09-30

    By observing continuously a single field of view in the sky, Kepler mission reveals outstanding results on discoveries of exoplanets. One of its recent progress is the discoveries of circumbinary planets. A circumbinary planet is an exoplanet that moves around a binary system. In this study we investigate motions of Kepler circumbinary planets belong to six binary systems, namely Kepler-16, -34, -35, -38, -47, and -413. The motions are considered to follow the Restricted Three-Body Problem (RTBP). Because the primaries (central massive objects) are stars, they are both radiatives, while the planet is an infinitesimal object. The primaries move in nearly circular and elliptic orbits with respect to their center of masses. We describe, in general, motions of the circumbinary planets in RTBP under radiating primaries. With respect to the averaged zero velocity curves, we show that motions of the exoplanets are stable, in accordance with their Hill stabilities.

  11. A New Method for Detecting Transiting Circumbinary Planets in Kepler Data

    Science.gov (United States)

    Welsh, William F.; Orosz, Jerome A.; Windmiller, Gur; Short, Donald R.

    2016-06-01

    The discovery of Kepler-16 started a new branch of exoplanet research: observations of transiting circumbinary planets. To date, eleven transiting circumbinary planets have been discovered. The detection of a circumbinary planet is much more difficult than the detection of a planet around a single star because the transit times are not strictly periodic, the transit widths and depths can change dramatically, and the deep binary star eclipses overwhelm the much smaller planetary transits. Because of these complications, most of the known circumbinary planets were discovered via visual inspection of the Kepler light curves. This requires that the transits be easily detectable by eye, which translates to large-radii planets. Here we present a new method for visual dectection of circumbinary planets, based on the idea of phase-folding the light curve into a "trailed eclipsogram" image. While this method works well for deep transits (and hence will work for new, large circumbinary planets to be found by TESS), in principle it can also be extended to much smaller planets below the threshold for visual detection using image pattern recognition tools.

  12. Diagrams of stability of circumbinary planetary systems (Abstract)

    Science.gov (United States)

    Popova, E.

    2015-08-01

    The stability diagrams in the "pericentric distance - eccentricity" plane of initial data are built and analysed for Kepler-38, Kepler-47, and PH1. This completes a survey of stability of the known up to now circumbinary planetary systems, initiated by Popova and Shevchenko (ApJ, 769, 152, 2013), where the analysis was performed for Kepler-16, 34, and 35. In the diagrams, the planets appear to be "embedded" in the fractal chaos border; however, I make an attempt to measure the "distance" to the chaos border in a physically consistent way. The obtained distances are compared to those given by the widely used numerical-experimental criterion by Holman and Wiegert (1999), who employed smooth polynomial approximations to describe the border. I identify the resonance cells, hosting the planets. Results of this study will appear in Proceedings of IAU Symposium 310 "Complex planetary systems".

  13. Planet Formation in Circumbinary Configurations: Turbulence Inhibits Planetesimal Accretion

    CERN Document Server

    Meschiari, Stefano

    2012-01-01

    The existence of planets born in environments highly perturbed by a stellar companion represents a major challenge to the paradigm of planet formation. In numerical simulations, the presence of a close binary companion stirs up the relative velocity between planetesimals, which is fundamental in determining the balance between accretion and erosion. However, the recent discovery of circumbinary planets by Kepler establishes that planet formation in binary systems is clearly viable. We perform N-body simulations of planetesimals embedded in a protoplanetary disk, where planetesimal phasing is frustrated by the presence of stochastic torques, modeling the expected perturbations of turbulence driven by the magnetorotational instability (MRI). We examine perturbation amplitudes relevant to dead zones in the midplane (conducive to planet formation in single stars), and find that planetesimal accretion can be inhibited even in the outer disk (4-10 AU) far from the central binary, a location previously thought to be...

  14. Forming Circumbinary Planets: N-body Simulations of Kepler-34

    CERN Document Server

    Lines, Stefan; Paardekooper, Sijme-Jan; Baruteau, Clement; Thebault, Philippe

    2014-01-01

    Observations of circumbinary planets orbiting very close to the central stars have shown that planet formation may occur in a very hostile environment, where the gravitational pull from the binary should be very strong on the primordial protoplanetary disk. Elevated impact velocities and orbit crossings from eccentricity oscillations are the primary contributors towards high energy, potentially destructive collisions that inhibit the growth of aspiring planets. In this work, we conduct high resolution, inter-particle gravity enabled N-body simulations to investigate the feasibility of planetesimal growth in the Kepler-34 system. We improve upon previous work by including planetesimal disk self-gravity and an extensive collision model to accurately handle inter-planetesimal interactions. We find that super-catastrophic erosion events are the dominant mechanism up to and including the orbital radius of Kepler-34(AB)b, making in-situ growth unlikely. It is more plausible that Kepler-34(AB)b migrated from a regio...

  15. The Complex Circumstellar and Circumbinary Environment of V356 Sgr

    CERN Document Server

    Lomax, Jamie R; Malatesta, Michael A; Babler, Brian; Bednarski, Daniel; Berdis, Jodi R; Bjorkman, Karen S; Bjorkman, Jon E; Carciofi, Alex C; Davidson, James W; Keil, Marcus; Meade, Marilyn R; Nordsieck, Kenneth; Scheffler, Matt; Hoffman, Jennifer L; Wisniewski, John P

    2016-01-01

    We analyze 45 spectropolarimetric observations of the eclipsing, interacting binary star V356 Sgr, obtained over a period of 21 years, to characterize the geometry of the system's circumstellar material. After removing interstellar polarization from these data, we find the system exhibits a large intrinsic polarization signature arising from electron scattering. In addition, the lack of repeatable eclipses in the polarization phase curves indicates the presence of a substantial pool of scatterers not occulted by either star. We suggest that these scatterers form either a circumbinary disk coplanar with the gainer's accretion disk or an elongated structure perpendicular to the orbital plane of V356 Sgr, possibly formed by bipolar outflows. We also observe small-scale, cycle-to-cycle variations in the magnitude of intrinsic polarization at individual phases, which we interpret as evidence of variability in the amount of scattering material present within and around the system. This may indicate a mass transfer ...

  16. THE NEPTUNE-SIZED CIRCUMBINARY PLANET KEPLER-38b

    Energy Technology Data Exchange (ETDEWEB)

    Orosz, Jerome A.; Welsh, William F.; Short, Donald R.; Windmiller, Gur [Department of Astronomy, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182 (United States); Carter, Joshua A.; Torres, Guillermo; Geary, John C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Brugamyer, Erik; Cochran, William D.; Endl, Michael; MacQueen, Phillip [McDonald Observatory, University of Texas at Austin, Austin, TX 78712-0259 (United States); Buchhave, Lars A. [Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, DK-2100 Copenhagen (Denmark); Ford, Eric B. [Astronomy Department, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL 32611 (United States); Agol, Eric [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Barclay, Thomas; Caldwell, Douglas A.; Clarke, Bruce D. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Doyle, Laurance R. [SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Fabrycky, Daniel C. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States); Haghighipour, Nader [Institute for Astronomy and NASA Astrobiology Institute University of Hawaii-Manoa, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States); and others

    2012-10-20

    We discuss the discovery and characterization of the circumbinary planet Kepler-38b. The stellar binary is single-lined, with a period of 18.8 days, and consists of a moderately evolved main-sequence star (M{sub A} = 0.949 {+-} 0.059 M {sub Sun} and R{sub A} = 1.757 {+-} 0.034 R {sub Sun }) paired with a low-mass star (M{sub B} = 0.249 {+-} 0.010 M {sub Sun} and R{sub B} = 0.2724 {+-} 0.0053 R {sub Sun }) in a mildly eccentric (e = 0.103) orbit. A total of eight transits due to a circumbinary planet crossing the primary star were identified in the Kepler light curve (using Kepler Quarters 1-11), from which a planetary period of 105.595 {+-} 0.053 days can be established. A photometric dynamical model fit to the radial velocity curve and Kepler light curve yields a planetary radius of 4.35 {+-} 0.11 R {sub Circled-Plus }, or equivalently 1.12 {+-} 0.03 R {sub Nep}. Since the planet is not sufficiently massive to observably alter the orbit of the binary from Keplerian motion, we can only place an upper limit on the mass of the planet of 122 M {sub Circled-Plus} (7.11 M {sub Nep} or equivalently 0.384 M {sub Jup}) at 95% confidence. This upper limit should decrease as more Kepler data become available.

  17. Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory.

    Science.gov (United States)

    Marsalek, Ondrej; Markland, Thomas E

    2016-02-01

    Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost. PMID:26851913

  18. Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory

    International Nuclear Information System (INIS)

    Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost

  19. Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Marsalek, Ondrej; Markland, Thomas E., E-mail: tmarkland@stanford.edu [Department of Chemistry, Stanford University, Stanford, California 94305 (United States)

    2016-02-07

    Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost.

  20. How to obtain thermostatted ring polymer molecular dynamics from exact quantum dynamics and when to use it

    CERN Document Server

    Hele, Timothy J H

    2015-01-01

    We obtain thermostatted ring polymer molecular dynamics (TRPMD) from exact quantum dynamics via Matsubara dynamics, a recently-derived form of linearization which conserves the quantum Boltzmann distribution. Performing a contour integral in the complex quantum Boltzmann distribution of Matsubara dynamics, replacement of the imaginary Liouvillian which results with a Fokker-Planck term gives TRPMD. We thereby provide error terms between TRPMD and quantum dynamics and predict the systems in which they are likely to be small. Using a harmonic analysis we show that careful addition of friction causes the correct oscillation frequency of the higher ring-polymer normal modes in a harmonic well, which we illustrate with calculation of the position-squared autocorrelation function. However, no physical friction parameter will produce the correct fluctuation dynamics for a parabolic barrier. The results in this paper are consistent with previous numerical studies and advise the use of TRPMD for the computation of spe...

  1. EVIDENCE FOR INFALLING GAS OF LOW ANGULAR MOMENTUM TOWARD THE L1551 NE KEPLERIAN CIRCUMBINARY DISK

    International Nuclear Information System (INIS)

    We report follow-up C18O(3-2) line observations of the Class I binary protostellar system L1551 NE with the Submillimeter Array in its compact and subcompact configurations. Our previous observations at a higher angular resolution in the extended configuration revealed a circumbinary disk exhibiting Keplerian motion. The combined data, with more extensive spatial coverage (∼140-2000 AU), verify the presence of a Keplerian circumbinary disk and reveal for the first time a distinct low-velocity (∼–1 from the systemic velocity) component that displays a velocity gradient along the minor axis of the circumbinary disk. Our simple model that reproduces the main features seen in the position-velocity diagrams comprises a circumbinary disk exhibiting Keplerian motion out to a radius of ∼300 AU, beyond which the gas exhibits pure infall at a constant velocity of ∼0.6 km s–1. This velocity is significantly smaller than the expected free-fall velocity of ∼2.2 km s–1 onto the L1551 NE protostellar mass of ∼0.8 M☉ at ∼300 AU, suggesting that the infalling gas is decelerated as it moves into regions of high gas pressure in the circumbinary disk. The discontinuity in angular momenta between the outer infalling gas and the inner Keplerian circumbinary disk implies an abrupt transition in the effectiveness at which magnetic braking is able to transfer angular momentum outward, a result perhaps of the different plasma β values and the ionization fractions between the outer and inner regions of the circumbinary disk

  2. Three-dimensional ordering of cold ion beams in a storage ring: A molecular-dynamics simulation study

    International Nuclear Information System (INIS)

    Three-dimensional (3D) ordering of a charged-particle beams circulating in a storage ring is systematically studied with a molecular-dynamics simulation code. An ion beam can exhibit a 3D ordered configuration at ultralow temperature as a result of powerful 3D laser cooling. Various unique characteristics of the ordered beams, different from those of crystalline beams, are revealed in detail, such as the single-particle motion in the transverse and longitudinal directions, and the dependence of the tune depression and the Coulomb coupling constant on the operating points

  3. Three-dimensional ordering of cold ion beams in a storage ring: A molecular-dynamics simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Yuri, Yosuke, E-mail: yuri.yosuke@jaea.go.jp [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-machi Takasaki, Gunma 370-1292 Japan (Japan)

    2015-06-29

    Three-dimensional (3D) ordering of a charged-particle beams circulating in a storage ring is systematically studied with a molecular-dynamics simulation code. An ion beam can exhibit a 3D ordered configuration at ultralow temperature as a result of powerful 3D laser cooling. Various unique characteristics of the ordered beams, different from those of crystalline beams, are revealed in detail, such as the single-particle motion in the transverse and longitudinal directions, and the dependence of the tune depression and the Coulomb coupling constant on the operating points.

  4. Molecular cloning and characterization of a gene encoding RING zinc finger ankyrin protein from drought-tolerant Artemisia desertorum

    Indian Academy of Sciences (India)

    Xiuhong Yang; Chao Sun; Yuanlei Hun; Zhongping Lin

    2008-03-01

    A RING zinc finger ankyrin protein gene, designated AdZFP1, was isolated from drought-tolerant Artemisia desertorum Spreng by mRNA differential display and RACE. Its cDNA was 1723 bp and encoded a putative protein of 445 amino acids with a predicted molecular mass of 47.9 kDa and an isoelectric point (pI) of 7.49. A typical C3HC4-type RING finger domain was found at the C-terminal region of the AdZFP1 protein, and several groups of ankyrin repeats were found at the N-terminal region. Alignments of amino acid sequence showed that AdZFP1 was 66% identical to the Arabidopsis thaliana putative RING zinc finger ankyrin protein AAN31869. Transcriptional analysis showed that AdZFP1 was inducible under drought stress in root, stem and leaf of the plant. Semi-quantitative reverse-transcriptase-polymerase chain reaction (RT-PCR) analysis showed that the transcript of AdZFP1 was strongly induced by exogenous abscisic acid (ABA) and also by salinity, cold and heat to some extent. Overexpression of the AdZFP1 gene in transgenic tobacco enhanced their tolerance to drought stress.

  5. Application of ring-opening metathesis polymerization in study of polymer molecular weight-mediated catalytic properties of immobilized lipase

    Institute of Scientific and Technical Information of China (English)

    DU Chuang; ZHANG Guo; WANG Zhi; LI Lei; TANG Jun; WANG Lei

    2009-01-01

    Recently, significant efforts have been devoted into the study of the effect of hydrophobic supports on the catalytic properties of immobilized lipases. It seems that immobilization lipases on hydrophobic supports is a simple and efficient method to improve the catalytic activity of lipases. In this study, the hydrophobic poly(N-propyl-norbornene-exo-2,3-dicarboximide)s with well-controlled molecular weight were synthesized by the living ring-opening metathesis polymerization, and the lipases from Pseudo-monas sp. were then immobilized on these hydrophobic polymer supports through the physical ad-sorption. The immobilized lipases exhibited higher activity and enantioselectivity for the transesterifi-cation of 2-octanol than those of free lipases. Furthermore, we investigated the polymer molecular weight-mediated catalytic properties of immobilized lipases. It was found that the catalytic activity and E value of the immobilized lipases increased with the increase of the polymer molecular weight. At the polymeric molecular weight of about 40kDa, the highest E value (58 at 54.2% of conversion, enanti-omeric excess = 99%) was reached. After the molecular weight of polymers getting higher than 40 kDa, catalytic activity end E value of the immobilized lipase decreased.

  6. On possible circumbinary configurations of the planetary systems of α Centauri and EZ Aquarii

    Science.gov (United States)

    Popova, E. A.; Shevchenko, I. I.

    2016-04-01

    Possible configurations of the planetary systems of the binary stars α Cen A-BandEZAqr A-C are analyzed. The P-type orbits—circumbinary ones, i.e., the orbits around both stars of the binary, are studied. The choice of these systems is dictated by the fact that α Cen is closest to us in the Galaxy, while EZ Aqr is the closest system whose circumbinary planets, as it turns out, may reside in the "habitability zone." The analysis has been performed within the framework of the planar restricted three-body problem. The stability diagrams of circumbinary motion have been constructed: on representative sets of initial data (in the pericentric distance-eccentricity plane), we have computed the Lyapunov spectra of planetary motion and identified the domains of regular and chaotic motion through their statistical analysis. Based on present views of the dynamics and architecture of circumbinary planetary systems, we have determined the most probable planetary orbits to be at the centers of the main resonance cells, at the boundary of the dynamical chaos domain around the parent binary star, which allows the semimajor axes of the orbits to be predicted. In the case of EZ Aqr, the orbit of the circumbinary planet is near the habitability zone and, given that the boundary of this zone is uncertain, may belong to it.

  7. The Role of Disc Self-Gravity in Circumbinary Planet Systems: I. Disc Structure and Evolution

    CERN Document Server

    Mutter, Matthew M; Nelson, Richard P

    2016-01-01

    We present the results of 2-dimensional hydrodynamic simulations of self-gravitating circumbinary discs around binaries whose parameters match those of the circumbinary planet-hosting systems Kepler-16, -34 and -35. Previous work has shown that non-self-gravitating discs in these systems form an eccentric precessing inner cavity due to tidal truncation by the binary, and planets which form at large radii migrate until stalling at this cavity. While this scenario appears to provide a natural explanation for the observed orbital locations of the circumbinary planets, previous simulations have failed to match the observed planet orbital parameters. The aim of this work is to examine the role of self-gravity in modifying circumbinary disc structure as a function of disc mass, prior to considering the evolution of embedded circumbinary planets. In agreement with previous work, we find that for disc masses between 1--5 times the minimum mass solar nebula (MMSN), disc self-gravity affects modest changes in the struc...

  8. Dethreading of a Photoactive Azobenzene-Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation.

    Science.gov (United States)

    Tabacchi, Gloria; Silvi, Serena; Venturi, Margherita; Credi, Alberto; Fois, Ettore

    2016-06-17

    Pseudorotaxanes formed by a dibenzo[24]crown-8 ring (R) and a dialkylammonium axle bearing either two E- or two Z-azobenzene units (EE-A or ZZ-A) revealed useful for the construction of light-powered molecular machines and motors, as they provide the opportunity of photocontrolling self-assembly/disassembly processes. The potential energies profiles for the dethreading of these complexes have been investigated by adopting a combination of first-principles molecular dynamics, metadynamics and quantum-chemical geometry optimization approaches. While the dethreading of the EE-A axle is associated with a monotonic energy increase, for that of the ZZ-A axle a transition state and an intermediate structure, in which the components are still threaded together, are found. The rate determining step for the dethreading of the ZZ axle has a higher energy barrier than that of the EE axle, in agreement with the experimental kinetic data. Moreover, the results suggest that the elliptic shape of the ring cavity is important for discriminating between the E and Z terminal azobenzene during dethreading.

  9. Searching for circumbinary planets with CB-BLS

    Science.gov (United States)

    Ofir, Aviv

    2015-08-01

    Transiting circumbinary planets (CBP) produce transit signals that are neither periodic not constant in duration or depth. These complications contribute to the low number of detected transiting CBP (nine in total so far), and limited detection to systems that exhibit transits that are relatively deep, i.e. individually-significant transit events. Planets around single stars taught us that small planets far outnumber larger ones, consequently the ability to detect small CBP is of the essence in order to correctly describe CBP demographics. Unfortunately, all currently known transiting CBP were detected either by eye or by some ad-hoc technique that has nothing to do with the 3-body dynamics of CBP (e.g. QATS, Carter & Agol 2013) -- limiting their detection power. CB-BLS (Ofir 2008) is an algorithm for the detection of transiting CBP that was proposed well before the first transiting CBP was detected (Doyle et al 2011). CB-BLS is tailored for CBP dynamics and is optimally sensitive and general. Here we present further evolution and the Matlab source code of CB-BLS that allows it to detect all currently known transiting CBP, including in eccentric and/or inclined orbits. We then describe our preliminary results on searching for transiting CBP in a small subset of the Kepler eclipsing binaries.

  10. Imaging the dust sublimation front of a circumbinary disk

    CERN Document Server

    Hillen, M; Bouquin, J -B Le; Van Winckel, H; Berger, J -P; Kamath, D; Bujarrabal, V

    2016-01-01

    We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust. A very rich interferometric data set in six spectral channels was acquired of IRAS08544-4431 with the new RAPID camera on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the \\textit{H} band was reconstructed by combining the data of all spectral channels using the SPARCO method. We spatially separate all the building blocks of the IRAS08544-4431 system in our milliarcsecond-resolution image. Our dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an unexpected flux signal of $\\sim$4\\% from the secondary star. The energy output from this companion indicates the presence of a compact circum-companion accretion disk, which is likely the origin of the fast outflow detected in H$\\alpha$. Our image provides the most detailed view into the heart of a dusty circums...

  11. Imaging the dust sublimation front of a circumbinary disk

    Science.gov (United States)

    Hillen, M.; Kluska, J.; Le Bouquin, J.-B.; Van Winckel, H.; Berger, J.-P.; Kamath, D.; Bujarrabal, V.

    2016-04-01

    Aims: We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust. Methods: A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed by combining the data of all spectral channels using the SPARCO method. Results: We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an unexpected flux signal of ~4% from the secondary star. The energy output from this companion indicates the presence of a compact circum-companion accretion disk, which is likely the origin of the fast outflow detected in Hα. Conclusions: Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program ID 094.D-0865.

  12. Constraining the Radiation and Plasma Environment of the Kepler Circumbinary Habitable Zone Planets

    CERN Document Server

    Zuluaga, Jorge I; Cuartas, Pablo A

    2015-01-01

    The remarkable discovery of many planets and candidates using the Kepler telescope even includes ten planets orbiting eight binaries. Three out of the eight, Kepler 16, Kepler 47, and KIC 9632895, have at least one planet in the circumbinary habitable zone (BHZ). In previous work (Mason et al. 2013), we investigated the potential habitability of Earth-like circumbinary planets. In particular, we highlighted the role of mutual stellar tidal interaction and the resulting impact on terrestrial planet habitability. The Kepler binaries with planets in the BHZ are studied in order to constrain the high energy radiation and plasma environment of potentially habitable circumbinary planets. The limits of the BHZ in these binaries as a function of time are estimated and the habitability lifetime is calculated. A self-consistent model of the evolution of stellar rotation including the effect of tidal interaction is key to establishing the plasma and radiation environment. A comprehensive model of the evolution of stella...

  13. Miniature chemical sensor combining molecular recognition with evanescent wave cavity ring-down spectroscopy

    International Nuclear Information System (INIS)

    A new chemical detection technology has been realized that addresses DOE environmental management needs. The new technology is based on a variant of the sensitive optical absorption technique, cavity ring-down spectroscopy (CRDS). Termed evanescent-wave cavity ring-down spectroscopy (EW-CRDS), the technology employs a miniature solid-state optical resonator having an extremely high Q-factor as the sensing element, where the high-Q is achieved by using ultra-low-attenuation optical materials, ultra-smooth surfaces, and ultra-high reflectivity coatings, as well as low-diffraction-loss designs. At least one total-internal reflection (TIR) mirror is integral to the resonator permitting the concomitant evanescent wave to probe the ambient environment. Several prototypes have been designed, fabricated, characterized, and applied to chemical detection. Moreover, extensions of the sensing concept have been explored to enhance selectivity, sensitivity, and range of application. Operating primarily in the visible and near IR regions, the technology inherently enables remote detection by optical fiber. Producing 11 archival publications, 5 patents, 19 invited talks, 4 conference proceedings, a CRADA, and a patent-license agreement, the project has realized a new chemical detection technology providing >100 times more sensitivity than comparable technologies, while also providing practical advantages

  14. A Molecular Einstein Ring Imaging a Starburst Disk Surrounding a Quasi-Stellar Object

    CERN Document Server

    Carilli, C L; Djorgovski, S G; Mahabal, A A; Cox, P; Bertoldi, F; Omont, A

    2003-01-01

    Images of the CO 2-1 line emission, and the radio continuum emission, from the redshift 4.12 gravitationally lensed quasi-stellar object (QSO) PSS J2322+1944 reveal an Einstein ring with a diameter of 1.5". These observations are modeled as a star forming disk surrounding the QSO nucleus with a radius of 2 kpc. The implied massive star formation rate is 900 M_sun/year. At this rate a substantial fraction of the stars in a large elliptical galaxy could form on a dynamical time scale of 10^8 years. The observation of active star formation in the host galaxy of a high-redshift QSO supports the hypothesis of coeval formation of supermassive black holes and stars in spheroidal galaxies.

  15. Thermal Rate Coefficients for the Astrochemical Process C + CH$^+$ $\\to$ C$_2^+$ + H by Ring Polymer Molecular Dynamics

    CERN Document Server

    Rampino, Sergio

    2016-01-01

    Thermal rate coefficients for the astrochemical reaction C + CH$^+$ $\\to$ C$_2^+$ + H were computed in the temperature range 20-300 K by using novel rate theory based on ring polymer molecular dynamics (RPMD) on a recently published bond-order based potential energy surface and compared with previous Langevin capture model (LCM) and quasi-classical trajectory (QCT) calculations. Results show that there is a significant discrepancy between the RPMD rate coefficients and the previous theoretical results which can lead to overestimation of the rate coefficients for the title reaction by several orders of magnitude at very low temperatures. We argue that this can be attributed to a very challenging energy profile along the reaction coordinate for the title reaction, not taken into account in extenso by either the LCM or QCT approximation. In the absence of any rigorous quantum mechanical or experimental results, the computed RPMD rate coefficients represent state-of-the-art estimates to be included in astrochemic...

  16. Modelling circumbinary protoplanetary disks II. Gas disk feedback on planetesimal dynamical and collisional evolution in the circumbinary systems Kepler-16 and 34

    CERN Document Server

    Lines, S; Baruteau, C; Paardekooper, S -J; Carter, P J

    2016-01-01

    Aims. We investigate the feasibility of planetesimal growth in circumbinary protoplanetary disks around the observed systems Kepler- 16 and Kepler-34 under the gravitational influence of a precessing eccentric gas disk. Methods. We embed the results of our previous hydrodynamical simulations of protoplanetary disks around binaries into an N-body code to perform 3D, high-resolution, inter-particle gravity-enabled simulations of planetesimal growth and dynamics that include the gravitational force imparted by the gas. Results. Including the full, precessing asymmetric gas disk generates high eccentricity orbits for planetesimals orbiting at the edge of the circumbinary cavity, where the gas surface density and eccentricity have their largest values. The gas disk is able to efficiently align planetesimal pericenters in some regions leading to phased, non-interacting orbits. Outside of these areas eccentric planetesimal orbits become misaligned and overlap leading to crossing orbits and high relative velocities d...

  17. Conformational analysis of six- and twelve-membered ring compounds by molecular dynamics

    DEFF Research Database (Denmark)

    Christensen, I T; Jørgensen, Flemming Steen

    1997-01-01

    A molecular dynamics (MD)-based conformational analysis has been performed on a number of cycloalkanes in order to demonstrate the reliability and generality of MD as a tool for conformational analysis. MD simulations on cyclohexane and a series of methyl-substituted cyclohexanes were performed a...... provided 19 out of the 20 most stable conformations found in the MM2 force field. Finally, the general performance of the MD method for conformational analysis is discussed.......A molecular dynamics (MD)-based conformational analysis has been performed on a number of cycloalkanes in order to demonstrate the reliability and generality of MD as a tool for conformational analysis. MD simulations on cyclohexane and a series of methyl-substituted cyclohexanes were performed...

  18. Aspects on the Dynamics and Detection of Additional Circumbinary Extrasolar Planets

    Science.gov (United States)

    Hinse, Tobias C.; Haghighipour, Nader; Goździewski, Krzysztof

    2014-04-01

    The presence of additional bodies orbiting a binary star system can be detected by monitoring the binary's eclipse timing. These so-called circumbinary objects will reveal themselves by i) either introducing a reflex motion of the binary system about the total system's barycenter creating a geometric light-travel time effect (LITE), ii) by gravitational perturbations on the binary orbit, or iii) a combination of the two effects resulting in eclipse timing (ETV) and transit timing (TTV) variations. Motivated by the four recently detected circumbinary planets by the Kepler space telescope (Kepler-16b, Kepler-34b, Kepler-35b and Kepler-38b) we have begun to study their dynamics in the presence of an additional massive perturber. In particular we used Kepler-16b as a test bed case. We are aiming to study the detectability of non-transiting and inclined circumbinary planets using the ETV effect along with the fast indicator MEGNO to quantitatively map the chaotic/quasi-periodic regions of the orbital parameter-space and to determine where the orbit of a circumbinary planet will be stable. We have calculated the amplitudes of TTV and ETV signals for different values of the mass and orbital elements of the planet and binary.

  19. The First Circumbinary Planet Found by Microlensing: OGLE-2007-BLG-349L(AB)c

    CERN Document Server

    Bennett, D P; Udalski, A; Gould, A; Tsapras, Y; Kubas, D; Bond, I A; Greenhill, J; Cassan, A; Rattenbury, N J; Boyajian, T S; Luhn, J; Penny, M T; Anderson, J; Abe, F; Bhattacharya, A; Botzler, C S; Donachie, M; Freeman, M; Fukui, A; Hirao, Y; Itow, Y; Koshimoto, N; Li, M C A; Ling, C H; Masuda, K; Matsubara, Y; Muraki, Y; Nagakane, M; Ohnishi, K; Oyokawa, H; Perrott, Y C; Saito, To; Sharan, A; Sullivan, D J; Sumi, T; Suzuki, D; Tristram, P J; Yonehara, A; Yock, P C M; Szymanski, M K; Soszynski, I; Ulaczyk, K; Wyrzykowski, L; Allen, W; DePoy, D; Gal-Yam, A; Gaudi, B S; Han, C; Monard, I A G; Ofek, E; Pogge, R W; Street, R A; Bramich, D M; Dominik, M; Horne, K; Snodgrass, C; Steele, I A; Albrow, M D; Bachelet, E; Batista, V; Beaulieu, J -P; Brillant, S; Caldwell, J A R; Cole, A; Coutures, C; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouque, P; Hundertmark, M; Jorgensen, U G; Kains, N; Kane, S R; Marquette, J -B; Menzies, J; Pollard, K R; Ranc, C; Sahu, K C; Wambsganss, J; Williams, A; Zub, M

    2016-01-01

    We present the analysis of the first circumbinary planet microlensing event, OGLE-2007-BLG-349. This event has a strong planetary signal that is best fit with a mass ratio of $q \\approx 3.4\\times 10^{-4}$, but there is an additional signal due to an additional lens mass, either another planet or another star. We find acceptable light curve fits with two classes of models: 2-planet models (with a single host star) and circumbinary planet models. The light curve also reveals a significant microlensing parallax effect, which constraints the mass of the lens system to be $M_L \\approx 0.7 M_\\odot$. Hubble Space Telescope images resolve the lens and source stars from their neighbors, and indicate excess flux due to the star(s) in the lens system. This is consistent with the predicted flux from the circumbinary models, where the lens mass is shared between two stars, but there is not enough flux to be consistent with the 2-planet, 1-star models. So, only the circumbinary models are consistent with the HST data. They...

  20. The evolved circumbinary disk of AC Herculis: a radiative transfer, interferometric, and mineralogical study

    NARCIS (Netherlands)

    M. Hillen; B.L. de Vries; J. Menu; H. van Winckel; M. Min; G.D. Mulders

    2015-01-01

    Context. Many post-asymptotic giant branch (post-AGB) stars in binary systems have an infrared (IR) excess arising from a dusty circumbinary disk. The disk formation, current structure, and further evolution are, however, poorly understood. Aims. We aim to constrain the structure of the circumstella

  1. Radiation-driven warping of circumbinary disks around eccentric young star binaries

    International Nuclear Information System (INIS)

    We study a warping instability of a geometrically thin, non-self-gravitating, circumbinary disk around young binary stars on an eccentric orbit. Such a disk is subject to both the tidal torques due to a time-dependent binary potential and the radiative torques due to radiation emitted from each star. The tilt angle between the circumbinary disk plane and the binary orbital plane is assumed to be very small. We find that there is a radius within/beyond which the circumbinary disk is unstable to radiation-driven warping, depending on the disk density and temperature gradient indices. This marginally stable warping radius is very sensitive to viscosity parameters, a fiducial disk radius and the temperature measured there, the stellar luminosity, and the disk surface density at a radius where the disk changes from optically thick to thin for the irradiation from the central stars. On the other hand, it is insensitive to the orbital eccentricity and binary irradiation parameter, which is a function of the binary mass ratio and luminosity of each star. Since the tidal torques can suppress the warping in the inner part of the circumbinary disk, the disk starts to be warped in the outer part. While the circumbinary disks are most likely to be subject to the radiation-driven warping on an AU to kilo-AU scale for binaries with young massive stars more luminous than 104 L ☉, the radiation-driven warping does not work for those around young binaries with the luminosity comparable to the solar luminosity.

  2. A Molecular Einstein Ring at z=4.12: Imaging the Dynamics of a Quasar Host Galaxy Through a Cosmic Lens

    CERN Document Server

    Riechers, Dominik A; Brewer, Brendon J; Carilli, Christopher L; Lewis, Geraint F; Bertoldi, Frank; Cox, Pierre

    2008-01-01

    We present high-resolution (0.3") Very Large Array (VLA) imaging of the molecular gas in the host galaxy of the high redshift quasar PSS J2322+1944 (z=4.12). These observations confirm that the molecular gas (CO) in the host galaxy of this quasar is lensed into a full Einstein ring, and reveal the internal dynamics of the molecular gas in this system. The ring has a diameter of ~1.5", and thus is sampled over ~20 resolution elements by our observations. Through a model-based lens inversion, we recover the velocity gradient of the molecular reservoir in the quasar host galaxy of PSS J2322+1944. The Einstein ring lens configuration enables us to zoom in on the emission and to resolve scales down to ~1 kpc. From the model-reconstructed source, we find that the molecular gas is distributed on a scale of 5 kpc, and has a total mass of M(H2)=1.7 x 10^10 M_sun. A basic estimate of the dynamical mass gives M_dyn = 4.4 x 10^10 (sin i)^-2 M_sun, that is, only ~2.5 times the molecular gas mass, and ~30 times the black h...

  3. Low temperature magnetic properties and spin dynamics in single crystals of Cr{sub 8}Zn antiferromagnetic molecular rings

    Energy Technology Data Exchange (ETDEWEB)

    Adelnia, Fatemeh [Dipartimento di Fisica, Università degli Studi di Milano and INSTM, I-20133 Milano (Italy); Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, I-27100 Pavia (Italy); Chiesa, Alessandro; Bordignon, Sara; Carretta, Stefano [Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, I-43124 Parma (Italy); Ghirri, Alberto; Candini, Andrea [CNR Institute Nanosciences S3, I- 41125 Modena (Italy); Cervetti, Christian [Dipartimento di Scienze Fisiche, Informatiche, Matematiche, Università di Modena e Reggio Emilia, I-41125 Modena (Italy); Evangelisti, Marco [CNR Institute Nanosciences S3, I- 41125 Modena (Italy); Dipartimento di Scienze Fisiche, Informatiche, Matematiche, Università di Modena e Reggio Emilia, I-41125 Modena (Italy); Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Affronte, Marco [CNR Institute Nanosciences S3, I- 41125 Modena (Italy); Dipartimento di Scienze Fisiche, Informatiche, Matematiche, Università di Modena e Reggio Emilia, I-41125 Modena (Italy); Sheikin, Ilya [Grenoble High Magnetic Field Laboratory, CNRS-LNCMI, 25, B.P. 166, 38042 Grenoble Cedex 9 (France); Winpenny, Richard; Timco, Grigore [The Lewis Magnetism Laboratory, The University of Manchester, M13 9PL Manchester (United Kingdom); Borsa, Ferdinando [Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, I-27100 Pavia (Italy); and others

    2015-12-28

    A detailed experimental investigation of the effects giving rise to the magnetic energy level structure in the vicinity of the level crossing (LC) at low temperature is reported for the open antiferromagnetic molecular ring Cr{sub 8}Zn. The study is conducted by means of thermodynamic techniques (torque magnetometry, magnetization and specific heat measurements) and microscopic techniques (nuclear magnetic resonance line width, nuclear spin lattice, and spin-spin relaxation measurements). The experimental results are shown to be in excellent agreement with theoretical calculations based on a minimal spin model Hamiltonian, which includes a Dzyaloshinskii-Moriya interaction. The first ground state level crossing at μ{sub 0}H{sub c1} = 2.15 T is found to be an almost true LC while the second LC at μ{sub 0}H{sub c2} = 6.95 T has an anti-crossing gap of Δ{sub 12} = 0.19 K. In addition, both NMR and specific heat measurements show the presence of a level anti-crossing between excited states at μ{sub 0}H = 4.5 T as predicted by the theory. In all cases, the fit of the experimental data is improved by introducing a distribution of the isotropic exchange couplings (J), i.e., using a J strain model. The peaks at the first and second LCs in the nuclear spin-lattice relaxation rate are dominated by inelastic scattering and a value of Γ ∼ 10{sup 10} rad/s is inferred for the life time broadening of the excited state of the open ring, due to spin phonon interaction. A loss of NMR signal (wipe-out effect) is observed for the first time at LC and is explained by the enhancement of the spin-spin relaxation rate due to the inelastic scattering.

  4. Retrograde binaries of massive black holes in circumbinary accretion discs

    Science.gov (United States)

    Amaro-Seoane, Pau; Maureira-Fredes, Cristián; Dotti, Massimo; Colpi, Monica

    2016-06-01

    Context. We explore the hardening of a massive black hole binary embedded in a circumbinary gas disc under a specific circumstance: when the binary and the gas are coplanar and the gas is counter-rotating. The binary has unequal mass and the interaction of the gas with the lighter secondary black hole is the main cause of the braking torque on the binary that shrinks with time. The secondary black hole, revolving in the direction opposite to the gas, experiences a drag from gas-dynamical friction and from direct accretion of part of it. Aims: In this paper, using two-dimensional (2D) hydrodynamical grid simulations we investigate the effect of changing the accretion prescriptions on the dynamics of the secondary black hole, which in turn affect the binary hardening and eccentricity evolution. Methods: We find that realistic accretion prescriptions lead to results that differ from those inferred assuming accretion of all the gas within the Roche Lobe of the secondary black hole. Results: When considering gas accretion within the gravitational influence radius of the secondary black hole (which is smaller than the Roche Lobe radius) to better describe gas inflows, the shrinking of the binary is slower. In addition, in this case, a smaller amount of accreted mass is required to reduce the binary separation by the same amount. Different accretion prescriptions result in different discs' surface densities, which alter the black hole's dynamics back. Full 3D Smoothed-particle hydrodynamics realizations of a number of representative cases, run over a shorter interval of time, validate the general trends observed in the less computationally demanding 2D simulations. Conclusions: Initially circular black hole binaries increase their eccentricity only slightly, which then oscillates around small values (<0.1) while they harden. By contrast, initially eccentric binaries become more and more eccentric. A semi-analytical model describing the black hole's dynamics under

  5. THE ECLIPSING SYSTEM EP ANDROMEDAE AND ITS CIRCUMBINARY COMPANIONS

    International Nuclear Information System (INIS)

    We present new long-term CCD photometry for EP And acquired during the period 2007-2012. The light curves display total eclipses at primary minima and season-to-season light variability. Our synthesis for all available light curves indicates that the eclipsing pair is a W-type overcontact binary with parameters of q = 2.578, i = 83.°3, ΔT = 27 K, f = 28%, and l3 = 2%-3%. The asymmetric light curves in 2007 were satisfactorily modeled by a cool spot on either of the eclipsing components from a magnetic dynamo. Including our 95 timing measurements, a total of 414 times of minimum light spanning about 82 yr was used for a period study. A detailed analysis of the eclipse timing diagram revealed that the orbital period of EP And has varied as a combination of an upward-opening parabola and two periodic variations, with cycle lengths of P3 = 44.6 yr and P4 = 1.834 yr and semi-amplitudes of K3 = 0.0100 days and K4 = 0.0039 days, respectively. The observed period increase at a fractional rate of +1.39 × 10–10 is in excellent agreement with that calculated from the W-D code and can be plausibly explained by some combination of mass transfer from the primary to the secondary star and angular momentum loss due to magnetic braking. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of a third and fourth component with projected masses of M3 = 0.25 M☉ and M4 = 0.90 M☉. The more massive companion could be revealed using high-resolution spectroscopic data extending over the course of a few years and could also be a binary itself. It is possible that the circumbinary objects may have played an important role in the formation and evolution of the eclipsing pair, which would cause it to have a short initial orbital period and thus evolve into an overcontact configuration by angular momentum loss.

  6. The Eclipsing System EP Andromedae and Its Circumbinary Companions

    Science.gov (United States)

    Lee, Jae Woo; Hinse, Tobias Cornelius; Park, Jang-Ho

    2013-04-01

    We present new long-term CCD photometry for EP And acquired during the period 2007-2012. The light curves display total eclipses at primary minima and season-to-season light variability. Our synthesis for all available light curves indicates that the eclipsing pair is a W-type overcontact binary with parameters of q = 2.578, i = 83.°3, ΔT = 27 K, f = 28%, and l 3 = 2%-3%. The asymmetric light curves in 2007 were satisfactorily modeled by a cool spot on either of the eclipsing components from a magnetic dynamo. Including our 95 timing measurements, a total of 414 times of minimum light spanning about 82 yr was used for a period study. A detailed analysis of the eclipse timing diagram revealed that the orbital period of EP And has varied as a combination of an upward-opening parabola and two periodic variations, with cycle lengths of P 3 = 44.6 yr and P 4 = 1.834 yr and semi-amplitudes of K 3 = 0.0100 days and K 4 = 0.0039 days, respectively. The observed period increase at a fractional rate of +1.39 × 10-10 is in excellent agreement with that calculated from the W-D code and can be plausibly explained by some combination of mass transfer from the primary to the secondary star and angular momentum loss due to magnetic braking. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of a third and fourth component with projected masses of M 3 = 0.25 M ⊙ and M 4 = 0.90 M ⊙. The more massive companion could be revealed using high-resolution spectroscopic data extending over the course of a few years and could also be a binary itself. It is possible that the circumbinary objects may have played an important role in the formation and evolution of the eclipsing pair, which would cause it to have a short initial orbital period and thus evolve into an overcontact configuration by angular momentum loss.

  7. Diverse developmental disorders from The One Ring: distinct molecular pathways underlie the cohesinopathies

    Directory of Open Access Journals (Sweden)

    Julia eHorsfield

    2012-09-01

    Full Text Available The multi-subunit protein complex, cohesin, is responsible for sister chromatid cohesion during cell division. The interaction of cohesin with DNA is controlled by a number of additional regulatory proteins. Mutations in cohesin, or its regulators, cause a spectrum of human developmental syndromes known as the ‘cohesinopathies’. Cohesinopathy disorders include Cornelia de Lange Syndrome and Roberts Syndrome. The discovery of novel roles for chromatid cohesion proteins in regulating gene expression led to the idea that cohesinopathies are caused by dysregulation of multiple genes downstream of mutations in cohesion proteins. Consistent with this idea, Drosophila, mouse and zebrafish cohesinopathy models all show altered expression of developmental genes. However, there appears to be incomplete overlap among dysregulated genes downstream of mutations in different components of the cohesion apparatus. This is surprising because mutations in all cohesion proteins would be predicted to affect cohesin’s roles in cell division and gene expression in similar ways. Here we review the differences and similarities between genetic pathways downstream of components of the cohesion apparatus, and discuss how such differences might arise, and contribute to the spectrum of cohesinopathy disorders. We propose that mutations in different elements of the cohesion apparatus have distinct developmental outcomes that can be explained by sometimes subtly different molecular effects.

  8. Ring Theory

    CERN Document Server

    Jara, Pascual; Torrecillas, Blas

    1988-01-01

    The papers in this proceedings volume are selected research papers in different areas of ring theory, including graded rings, differential operator rings, K-theory of noetherian rings, torsion theory, regular rings, cohomology of algebras, local cohomology of noncommutative rings. The book will be important for mathematicians active in research in ring theory.

  9. Spin-orbit coupling and chaotic rotation for circumbinary bodies. Application to the small satellites of the Pluto-Charon system

    CERN Document Server

    Correia, Alexandre C M; Robutel, Philippe

    2015-01-01

    Circumbinary bodies are objects that orbit around a more massive binary system. Here we show that, contrarily to the classical two-body problem, circumbinary bodies in planar quasi-circular orbits can present stable non-synchronous rotation. Denoting $n_b$ and $n$ the orbital mean motion of the binary and of the circumbinary body, respectively, there is an entirely new family of spin-orbit resonances at the frequencies $n\\pm k\

  10. (Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units.

    Science.gov (United States)

    Grucela-Zajac, Marzena; Bijak, Katarzyna; Kula, Slawomir; Filapek, Michal; Wiacek, Malgorzata; Janeczek, Henryk; Skorka, Lukasz; Gasiorowski, Jacek; Hingerl, Kurt; Sariciftci, Niyazi Serdar; Nosidlak, Natalia; Lewinska, Gabriela; Sanetra, Jerzy; Schab-Balcerzak, Ewa

    2014-06-19

    New symmetrical arylene bisimide derivatives formed by using electron-donating-electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N'-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2'-bithiophene-5,5'-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (E g) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and E g were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm(2) were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of V oc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69-0.90%. PMID:24966893

  11. Physics of quantum rings

    CERN Document Server

    Fomin, Vladimir M

    2013-01-01

    This book deals with a new class of materials, quantum rings. Innovative recent advances in experimental and theoretical physics of quantum rings are based on the most advanced state-of-the-art fabrication and characterization techniques as well as theoretical methods. The experimental efforts allow to obtain a new class of semiconductor quantum rings formed by capping self-organized quantum dots grown by molecular beam epitaxy. Novel optical and magnetic properties of quantum rings are associated with non-trivial topologies at the nanoscale. An adequate characterization of quantum rings is po

  12. Disruption of Planetary Orbits Through Evection Resonance with an External Companion: Circumbinary Planets and Multiplanet Systems

    CERN Document Server

    Xu, Wenrui

    2016-01-01

    Planets around binary stars and those in multiplanet systems may experience resonant eccentricity excitation and disruption due to perturbations from a distant stellar companion. This "evection resonance" occurs when the apsidal precession frequency of the planet, driven by the quadrupole associated with the inner binary or the other planets, matches the orbital frequency of the external companion. We develop an analytic theory to study the effects of evection resonance on circumbinary planets and multiplanet systems. We derive the general conditions for effective eccentricity excitation or resonance capture of the planet as the system undergoes long-term evolution. Applying to circumbinary planets, we show that inward planet migration may lead to eccentricity growth due to evection resonance with an external perturber, and planets around shrinking binaries may not survive the resonant eccentricity growth. On the other hand, significant eccentricity excitation in multiplanet systems occurs in limited paramete...

  13. Disruption of planetary orbits through evection resonance with an external companion: circumbinary planets and multiplanet systems

    Science.gov (United States)

    Xu, Wenrui; Lai, Dong

    2016-07-01

    Planets around binary stars and those in multiplanet systems may experience resonant eccentricity excitation and disruption due to perturbations from a distant stellar companion. This `evection resonance' occurs when the apsidal precession frequency of the planet, driven by the quadrupole associated with the inner binary or the other planets, matches the orbital frequency of the external companion. We develop an analytic theory to study the effects of evection resonance on circumbinary planets and multiplanet systems. We derive the general conditions for effective eccentricity excitation or resonance capture of the planet as the system undergoes long-term evolution. Applying to circumbinary planets, we show that inward planet migration may lead to eccentricity growth due to evection resonance with an external perturber, and planets around shrinking binaries may not survive the resonant eccentricity growth. On the other hand, significant eccentricity excitation in multiplanet systems occurs in limited parameter space of planet and binary semimajor axes, and requires the planetary migration to be sufficiently slow.

  14. How to build Tatooine: reducing secular excitation in Kepler circumbinary planet formation

    CERN Document Server

    Rafikov, Roman R

    2012-01-01

    Circumbinary planetary systems recently discovered by Kepler represent an important testbed for planet formation theories. Planetesimal growth in disks around binaries has been expected to be inhibited interior to ~10 AU by secular excitation of high relative velocities between planetesimals, leading to their collisional destruction (rather than agglomeration). Here we show that gravity of the gaseous circumbinary disk in which planets form drives fast precession of both the planetesimal and binary orbits, resulting in strong suppression of planetesimal eccentricities beyond 2-3 AU and making possible growth of 1-100 km objects in this region. The precise location of the boundary of accretion-friendly region depends on the size of the inner disk cavity cleared by the binary torques and on the disk mass (even 0.01 M_Sun disk strongly suppresses planetesimal excitation), among other things. Precession of the orbit of the central binary, enhanced by the mass concentration naturally present at the inner edge of a...

  15. Circumbinary Planet Formation in the Kepler-16 system. I. N-body Simulations

    CERN Document Server

    Meschiari, Stefano

    2012-01-01

    The recently discovered circumbinary planets (Kepler-16 b, Kepler-34 b, Kepler-35 b) represent the first direct evidence of the viability of planet formation in circumbinary orbits. We report on the results of N-body simulations investigating planetesimal accretion in the Kepler-16 b system, focusing on the range of impact velocities under the influence of both stars' gravitational perturbation and friction from a putative protoplanetary disk. Our results show that planet formation might be effectively inhibited for a large range in semi-major axis (1.75 < a_P < 4 AU), suggesting that the planetary core must have either migrated from outside 4 AU, or formed in situ very close to its current location.

  16. Rotational Synchronization May Enhance Habitability for Circumbinary Planets: Kepler Binary Case Studies

    CERN Document Server

    Mason, Paul A; Clark, Joni; Cuartas, Pablo A

    2013-01-01

    We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression towards planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of XUV radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in some cases improved environments, if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass c...

  17. Limits to the presence of transiting circumbinary planets in CoRoT data

    CERN Document Server

    Klagyivik, P; Cabrera, J; Csizmadia, Sz; Almenara, J M

    2016-01-01

    The CoRoT mission during its flight-phase 2007-2012 delivered the light-curves for over 2000 eclipsing binaries. Data from the Kepler mission have proven the existence of several transiting circumbinary planets. Albeit light-curves from CoRoT have typically lower precision and shorter coverage, CoRoT's number of targets is similar to Kepler, and some of the known circumbinary planets could potentially be detected in CoRoT data as well. The aim of this work has been a revision of the entire CoRoT data-set for the presence of circumbinary planets, and the derivation of limits to the abundances of such planets. We developed a code which removes the light curve of the eclipsing binaries and searches for quasi-periodic transit-like features in a light curve after removal of binary eclipses and instrumental features. The code needs little information on the sample systems and can be used for other space missions as well, like Kepler, K2, TESS and PLATO. The code is broad in the requirements leading to detections, b...

  18. The Solaris project. A timing survey for circumbinary planets around eclipsing binary stars.

    Science.gov (United States)

    Konacki, M.

    2014-03-01

    The SOLARIS project aims to detect from the ground circumbinary planets with the timing of eclipses of eclipsing binary stars. For the SOLARIS project, we were granted 2.5 million Euro to establish a network of four robotic 0.5-m telescopes on three continents (Australia, Africa and South America) to carry out high cadence, high precision photometry of a sample of eclipsing binary stars. Three of the telescopes are already installed and the fourth one will become operational in early 2014. The project's web site is www.projectsolaris.eu/. This effort is accompanied by our radial velocity (RV) survey for circumbinary planets which employs our novel iodine cell based technique tailored to provide very high precision RVs of double-lined binaries. Altogether these two efforts, targeting about 300 eclipsing binary stars, constitute the biggest ground based survey for circumbinary planets. Moreover, we expect that both these efforts will have a significant impact on the observational stellar astronomy. In particular for at least half of our sample we expect to deliver masses of the stars with an accuracy 10-1000 times better than the current state of the art.

  19. A circumbinary planet in orbit around the short-period white dwarf eclipsing binary RR Cae

    Science.gov (United States)

    Qian, S.-B.; Liu, L.; Zhu, L.-Y.; Dai, Z.-B.; Fernández Lajús, E.; Baume, G. L.

    2012-05-01

    By using six newly determined mid-eclipse times together with those collected from the literature, we have found that the observed minus calculated (O-C) curve of RR Cae shows a cyclic change with a period of 11.9 yr and an amplitude of 14.3 s while it undergoes an upward parabolic variation [revealing a long-term period increase at a rate of ?]. The cyclic change was analysed for the light-travel-time effect that arises from the gravitational influence of a third companion. The mass of the third body was determined to be M3sin i'= 4.2(± 0.4) MJup, suggesting that it is a circumbinary giant planet when its orbital inclination is larger than 17?6. The orbital separation of the circumbinary planet from the central eclipsing binary is about 5.3(± 0.6) au. The period increase is opposite to the changes caused by angular momentum loss via magnetic braking or/and gravitational radiation; and it cannot be explained by the mass transfer between both components because of its detached configuration. These indicate that the observed upward parabolic change is only a part of a long-period (longer than 26.3 yr) cyclic variation, which may reveal the presence of another giant circumbinary planet in a wide orbit.

  20. Viscous Hydrodynamics Simulations of Circumbinary Accretion Discs: Variability, Quasi-Steady State, and Angular Momentum Transfer

    CERN Document Server

    Miranda, Ryan; Lai, Dong

    2016-01-01

    Circumbinary discs are found in a variety of astrophysical contexts, including around young stellar binaries and supermassive black hole binaries. We carry out a suite of numerical simulations of circumbinary discs, solving the viscous hydrodynamics equations on a polar grid covering an extended disc outside the binary co-orbital region. We use carefully controlled outer boundary conditions and long-term integrations to ensure that the disc reaches a quasi-steady state, in which the time-averaged mass accretion rate onto the binary, $\\langle\\dot{M}\\rangle$, matches the mass supply rate at the outer disc. We focus on binaries with comparable masses, but with a wide range of eccentricities ($e_\\mathrm{B}$). For $e_\\mathrm{B} \\lesssim 0.05$, the mass accretion rate of the binary is modulated with a period of about $5$ times the binary period; otherwise it is modulated at the binary period. The inner part of the circumbinary disc generally becomes coherently eccentric. For low and high $e_\\mathrm{B}$, the disc li...

  1. Surface Flux Patterns on Planets in Circumbinary Systems, and Potential for Photosynthesis

    CERN Document Server

    Forgan, Duncan H; Cockell, Charles S; Raven, John A

    2014-01-01

    Recently, the Kepler Space Telescope has detected several planets in orbit around a close binary star system. These so-called circumbinary planets will experience non-trivial spatial and temporal distributions of radiative flux on their surfaces, with features not seen in their single-star orbiting counterparts. Earthlike circumbinary planets inhabited by photosynthetic organisms will be forced to adapt to these unusual flux patterns. We map the flux received by putative Earthlike planets (as a function of surface latitude/longitude and time) orbiting the binary star systems Kepler-16 and Kepler-47, two star systems which already boast circumbinary exoplanet detections. The longitudinal and latitudinal distribution of flux is sensitive to the centre of mass motion of the binary, and the relative orbital phases of the binary and planet. Total eclipses of the secondary by the primary, as well as partial eclipses of the primary by the secondary add an extra forcing term to the system. We also find that the patte...

  2. Quantum ring-polymer contraction method: Including nuclear quantum effects at no additional computational cost in comparison to ab initio molecular dynamics

    Science.gov (United States)

    John, Christopher; Spura, Thomas; Habershon, Scott; Kühne, Thomas D.

    2016-04-01

    We present a simple and accurate computational method which facilitates ab initio path-integral molecular dynamics simulations, where the quantum-mechanical nature of the nuclei is explicitly taken into account, at essentially no additional computational cost in comparison to the corresponding calculation using classical nuclei. The predictive power of the proposed quantum ring-polymer contraction method is demonstrated by computing various static and dynamic properties of liquid water at ambient conditions using density functional theory. This development will enable routine inclusion of nuclear quantum effects in ab initio molecular dynamics simulations of condensed-phase systems.

  3. Quantum Ring-Polymer Contraction Method: Including nuclear quantum effects at no additional computational cost in comparison to ab-initio molecular dynamics

    CERN Document Server

    John, Chris; Habershon, Scott; Kühne, Thomas D

    2015-01-01

    We present a simple and accurate computational method, which facilitates ab-initio path-integral molecular dynamics simulations, where the quantum mechanical nature of the nuclei is explicitly taken into account, at essentially no additional computational cost in comparison to the corresponding calculation using classical nuclei. The predictive power of the proposed quantum ring-polymer contraction method is demonstrated by computing various static and dynamic properties of liquid water at ambient conditions. This development permits to routinely include nuclear quantum effects in ab-initio molecular dynamics simulations.

  4. Quantum ring-polymer contraction method: Including nuclear quantum effects at no additional computational cost in comparison to ab initio molecular dynamics.

    Science.gov (United States)

    John, Christopher; Spura, Thomas; Habershon, Scott; Kühne, Thomas D

    2016-04-01

    We present a simple and accurate computational method which facilitates ab initio path-integral molecular dynamics simulations, where the quantum-mechanical nature of the nuclei is explicitly taken into account, at essentially no additional computational cost in comparison to the corresponding calculation using classical nuclei. The predictive power of the proposed quantum ring-polymer contraction method is demonstrated by computing various static and dynamic properties of liquid water at ambient conditions using density functional theory. This development will enable routine inclusion of nuclear quantum effects in ab initio molecular dynamics simulations of condensed-phase systems. PMID:27176426

  5. Effects of X-ray and extreme UV radiation on circumbinary planets

    Science.gov (United States)

    Sanz-Forcada, J.; Desidera, S.; Micela, G.

    2014-10-01

    Context. Several circumbinary planets have recently been discovered. The orbit of a planet around a binary stellar system poses several dynamic constraints. In addition to these constraints, the effects that radiation from the host stars may have on the planet atmospheres must be considered. We here evaluate these effects. Because of the configuration of a close binary system, these stars have a high rotation rate, even for old stars. The fast rotation of close, tidally locked binaries causes a permanent state of high stellar activity and copious XUV radiation. The accumulated effects are stronger than for normal exoplanets around single stars and cause a faster evaporation of their atmospheres. Aims: We evaluate the effects that stellar radiation has on the evaporation of exoplanets around binary systems and on the survival of these planets. Methods: We considered the X-ray and EUV spectral ranges (XUV, 1-912 Å) to account for the photons that are easily absorbed by a planet atmosphere that is mainly composed of hydrogen. A more complex atmospheric composition is expected to absorb this radiation more efficiently. We used direct X-ray observations to evaluate the energy in the X-rays range and coronal models to calculate the (nondetectable) EUV part of the spectrum. Results: We considered in this problem different configurations of stellar masses, and a resonance of 4:1 and 3:1. The simulations show that exoplanets orbiting close binary systems in a close orbit will suffer strong photoevaporation that may cause a total loss of atmosphere in a short time. We also applied our models to the best real example, Kepler-47 b, to estimate the current mass-loss rates in circumbinary planets and the accumulated effects over the time. Conclusions: A binary system of two solar-like stars will be highly efficient in evaporating the atmosphere of the planet (less than 6 Gyr in our case). These systems will be difficult to find, even if they are dynamically stable. Still

  6. Pathobiological behavior and molecular mechanism of signet ring cell carcinoma and mucinous adenocarcinoma of the stomach:A comparative study

    Institute of Scientific and Technical Information of China (English)

    Xue-Fei Yang; Lin Yang; Xiao-Yun Mao; Dong-Ying Wu; Su-Min Zhang; Yan Xin

    2004-01-01

    AIM: To elucidate the distinctive pathobiological behavior between signet ring cell carcinoma (SRC) and mucinous adenocarcinoma of the stomach.METHODS: Based on the histological growth patterns and cell-functional differentiation classifications of stomach carcinoma, we conducted a series of comparative studies.All paraffin-embedded and frozen blocks were collected from the files of Cancer Institute of China Medical University. On the basis of histopathological observation, we applied enzymatic and mucous histochemistry, immunohistochemistry,flow cytometry (FCM) and molecular biology to compare these two categories of gastric cancers in terms of the DNA ploidy, proliferative kinetics, the expression of gastric carcinoma associated gene product and instabilities of mitochondrial DNA (mtDNA).RESULTS: Gastric SRC was commonly seen in females below 45 years, mostly presenting diffuse growth and ovary or uterine cervix metastasis. The majority of SRC were absorptive and mucus-producing functional differentiation type (AMlPFDT), which growth relied on estrogen. Meanwhile,stomach mucinous adenocarcinomas were mostly observed in males over 50 years, prone to massive growth or nest growth and extensive peritoneal infiltration, showing two categories of cell-functional differentiation types: AMPFDT and mucus-secreting functional differentiation type (MSFDT).Expressions of ER, enzyme c-PDE and 67kDaLN-R in SRC were evidently higher than that in mucinous adenocarcinoma,while expressions of LN, CN-IV, CD44v6, and PTEN protein were obviously lower in SRC than that in mucinous adenocarcinoma (P<0.05). There was no statistic significance in VEGF, ECD and instabilities of mtDNA (P>0.05) between the above two gastric carcinomas.CONCLUSION: Though SRC and mucinous adenocarcinoma were both characterized by abundant mucus-secretion, they were quite different in morphology, ultrastructure, cellfunctional differentiation and protein expression, indicating different mechanisms of

  7. Obscuration of Supersoft X-ray Sources by Circumbinary Material - A Way to Hide Type Ia Supernova Progenitors?

    DEFF Research Database (Denmark)

    Nielsen, Mikkel; Dominik, Carsten; Nelemans, Gijs;

    2012-01-01

    single degenerate binary system. In case of obscured systems we wish to determine their general observational characteristics. We examine the emergent X-ray emission from a canonical SSS system surrounded by a spherically symmetric configuration of material, assuming a black body spectrum with T_BB=50 e......V and L=10^38 erg/s. The circumbinary material is assumed to be of solar chemical abundances, and we leave the mechanism behind the mass loss into the circumbinary region unspecified. If steadily accreting, nuclear burning WDs are canonical SSS our analysis suggests that they can be obscured by relatively...... modest circumbinary mass loss rates. This may explain the discrepancy of SSS compared to the SN Ia rate inferred from observations if the SD progenitor scenario contributes significantly to the SN Ia rate. Recycled emissions from obscured systems may be visible in other wavebands than X-rays. It may also...

  8. Cytogenetic and molecular analysis of a ring (21) in a patient with partial trisomy 21 and megakaryocytic leukemia

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, C.G.; Blouin, J.L.; Bull, M.J. [Indiana Univ. School of Medicine, Indianapolis, IN (United States)]|[Univ. of Geneva Medical School, Geneva (Switzerland)] [and others

    1995-07-17

    We describe a patient with an asymmetric double ring 21 in mosaic form, 45,XX,-21/46,X,-21,+r(21), who has limited manifestations of Down syndrome and who developed acute myelofibrosis and megakaryocytic leukemia (AMKL), FAB M7, a hematologic disorder particularly common in Down syndrome patients. In situ hybridization studies, gene dosage, and DNA polymorphism analysis showed that the ring chromosome carries a duplicated region which extends from D21S406 on the centromeric side and includes marker D21S3 on the telomeric side. FISH studies indicate two sizes of ring 21 in the patient. The origin of the supernumerary chromosome 21 in the proband was paternal; furthermore, the r(21) probably was formed postzygotically. Included in the duplicated segment are the candidate genes for leukemia AML-1, ETS, and ERG. The potential significance of disomic homozygosity of loci on 21q in M7 megakaryocytic leukemia is discussed. 35 refs., 6 figs., 6 tabs.

  9. Wave-like warp propagation in circumbinary discs I. Analytic theory and numerical simulations

    OpenAIRE

    Facchini, Stefano; Lodato, Giuseppe; Price, Daniel J.

    2013-01-01

    In this paper we analyse the propagation of warps in protostellar circumbinary discs. We use these systems as a test environment in which to study warp propagation in the bending-wave regime, with the addition of an external torque due to the binary gravitational potential. In particular, we want to test the linear regime, for which an analytic theory has been developed. In order to do so, we first compute analytically the steady state shape of an inviscid disc subject to the binary torques. ...

  10. The Eccentric Response of Kepler's Circumbinary Planets to Common-Envelope Evolution

    Science.gov (United States)

    Moore, Keavin; Veselin B. Kostov, Daniel Tamayo, Ray Jayawardhana, Stephen A. Rinehart

    2016-10-01

    Inspired by the recent Kepler discoveries of circumbinary planets orbiting close binary stars, we explore the fate of the former as the latter evolve off the main sequence. By combining binary stellar evolutionary models and dynamical simulations using numerical integration, we study the orbital evolution of these planets as a result of the common-envelope stages of their host binaries. Half of the Kepler systems experiences at least one common-envelope stage using their default physical parameters. During the common-envelope stage, the binary stars either shrink to very short orbits or coalesce; one system may trigger a double-degenerate supernova explosion. As the common-envelope stage is a complex and still-uncertain process, we test multiple efficiency parameters for each system. Much of the uncertainty in circumbinary systems is believed to be a result of tidal effects, and so we also vary the tides within our simulations. We find that, for common-envelope mass-loss rates of 1 solar mass per year, their planets predominantly remain gravitationally bound to the system at the end of this stage, migrate to larger orbits, and gain significant eccentricity. This orbital expansion can be up to an order of magnitude, and occurs over the course of a single planetary orbit. Some systems retain their planets even in the runaway regime of instantaneous mass loss. For slower mass loss rates of 0.1 solar masses per year, our results indicate an adiabatic orbital expansion for all except Kepler-1647, where this mass loss corresponds to the transition regime. Interestingly, the planets can experience both adiabatic and non-adiabatic orbital expansion if the host binaries experience multiple common-envelope stages (i.e. Kepler-1647); multiplanet circumbinary systems like Kepler-47 can experience both modes simultaneously during the same common-envelope stage. Our results show that, unlike Mercury, a circumbinary planet with the same semi-major axis can survive the common

  11. Kepler-413b: a slightly misaligned, Neptune-size transiting circumbinary planet

    OpenAIRE

    Kostov, V. B.; McCullough, P. R.; Carter, J. A; Deleuil, M.; R. F. D\\xfdaz; Fabrycky, D. C.; G. H\\xfdbrard; Hinse, T. C.; Mazeh, T.; Orosz, J. A.; Tsvetanov, Z. I.; Welsh, W. F.

    2014-01-01

    We report the discovery of a transiting, Rp = 4.347+/-0.099REarth, circumbinary planet (CBP) orbiting the Kepler K+M Eclipsing Binary (EB) system KIC 12351927 (Kepler-413) every ~66 days on an eccentric orbit with ap = 0.355+/-0.002AU, ep = 0.118+/-0.002. The two stars, with MA = 0.820+/-0.015MSun, RA = 0.776+/-0.009RSun and MB = 0.542+/-0.008MSun, RB = 0.484+/-0.024RSun respectively revolve around each other every 10.11615+/-0.00001 days on a nearly circular (eEB = 0.037+/-0.002) orbit. The ...

  12. Cytogenetic and molecular analysis of a ring (21) in a patient with partial trisomy 21 and megakaryocytic leukemia

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, C.G.; Bull, M.; Breitfeld, P. [Indiana Univ., Indianapolis, IN (United States)] [and others

    1994-09-01

    We describe a patient with an asymmetrical double ring 21 in mosaic form, 45,XX, -21/46,XX, -21, +r(21) (q22.11{yields}p11.2::q11.1{yields}q22.3), who has limited manifestations of Down`s syndrome and who developed acute myelofibrosis and megakaryocytic leukemia (AMKL), M7, a hematologic disorder particularly common in Down`s syndrome patients. In situ hybridization studies (gene dosage and DNA polymorphism analysis) show that the ring chromosome carries a duplicated region which extends from D21S258 on the centromeric side and includes marker D21S1245 on the telomeric side, but does not include the region from PFKL and ITGB2 through the telomere. FISH studies indicate two sizes of ring 21 in the patient. The origin of the supernumerary chromosome 21 in the proband was paternal; furthermore, the r(21) was probably formed post-zygotically. Included in the duplicated segment are the candidate genes for leukemia AML-1, ETS2 and ERG. If disomic homozygosity is important in the development of AMKL in the proband, the gene responsible maps either between the centromere and D21S11 or between D21S1239 and D21S1245.

  13. On the energy dissipation rate at the inner edge of circumbinary discs

    CERN Document Server

    Terquem, Caroline

    2016-01-01

    We study, by means of numerical simulations and analysis, the details of the accretion process from a disc onto a binary system. We show that energy is dissipated at the edge of a circumbinary disc and this is associated with the tidal torque that maintains the cavity: angular momentum is transferred from the binary to the disc through the action of compressional shocks and viscous friction. These shocks can be viewed as being produced by fluid elements which drift into the cavity and, before being accreted, are accelerated onto trajectories that send them back to impact the disc. The rate of energy dissipation is approximately equal to the product of potential energy per unit mass at the disc's inner edge and the accretion rate, estimated from the disc parameters just beyond the cavity edge, that would occur without the binary. For very thin discs, the actual accretion rate onto the binary may be significantly less. We calculate the energy emitted by a circumbinary disc taking into account energy dissipation...

  14. On the energy dissipation rate at the inner edge of circumbinary discs

    Science.gov (United States)

    Terquem, Caroline; Papaloizou, John C. B.

    2016-10-01

    We study, by means of numerical simulations and analysis, the details of the accretion process from a disc onto a binary system. We show that energy is dissipated at the edge of a circumbinary disc and this is associated with the tidal torque that maintains the cavity: angular momentum is transferred from the binary to the disc through the action of compressional shocks and viscous friction. These shocks can be viewed as being produced by fluid elements which drift into the cavity and, before being accreted, are accelerated onto trajectories that send them back to impact the disc. The rate of energy dissipation is approximately equal to the product of potential energy per unit mass at the disc's inner edge and the accretion rate, estimated from the disc parameters just beyond the cavity edge, that would occur without the binary. For very thin discs, the actual accretion rate onto the binary may be significantly less. We calculate the energy emitted by a circumbinary disc taking into account energy dissipation at the inner edge and also irradiation arising there from reprocessing of light from the stars. We find that, for tight PMS binaries, the SED is dominated by emission from the inner edge at wavelengths between 1-4 and 10 μm. This may apply to systems like CoRoT 223992193 and V1481 Ori.

  15. A dynamical stability study of Kepler Circumbinary Planetary systems with one planet

    CERN Document Server

    Chavez, C E; Prodan, S; Reyes-Ruiz, M; Aceves, H

    2014-01-01

    To date, 17 circumbinary planets have been discovered. In this paper, we focus our attention on the stability of the Kepler circumbinary planetary systems with only one planet, i.e. Kepler-16, Kepler-34, Kepler-35, Kepler-38, Kepler-64 and Kepler-413. In addition to their intrinsic interest, the study of such systems is an opportunity to test our understanding of planetary system formation and evolution around binaries. The investigation is done by means of numerical simulations. We perform numerical integrations of the full equations of motion of each system with the aim of checking the stability of the planetary orbit. The investigation of the stability of the above systems consists of three numerical experiments. In the first one we perform a long term (1Gyr) numerical integration of the nominal solution of the six Kepler systems under investigation. In the second experiment, we look for the critical semimajor axis of the six planetary orbits, and finally, in the third experiment, we construct two dimensio...

  16. IRAS 19135+3937: An SRd variable as interacting binary surrounded by a circumbinary disc

    CERN Document Server

    Gorlova, N; Ikonnikova, N P; Burlak, M A; Komissarova, G V; Jorissen, A; Gielen, C; Debosscher, J; Degroote, P

    2015-01-01

    Semi-regular (SR) variables are not a homogeneous class and their variability is often explained due to pulsations and/or binarity. This study focuses on IRAS 19135+3937, an SRd variable with an infra-red excess indicative of a dusty disc. A time-series of high-resolution spectra, UBV photometry as well as a very accurate light curve obtained by the Kepler satellite, allowed us to study the object in unprecedented detail. We discovered it to be a binary with a period of 127 days. The primary has a low surface gravity and an atmosphere depleted in refractory elements. This combination of properties unambiguously places IRAS 19135+3937 in the subclass of post-Asymptotic Giant Branch stars with dusty discs. We show that the light variations in this object can not be due to pulsations, but are likely caused by the obscuration of the primary by the circumbinary disc during orbital motion. Furthermore, we argue that the double-peaked Fe emission lines provide evidence for the existence of a gaseous circumbinary Kep...

  17. The Response of a Circumbinary Disk to a Black Hole Merger

    Science.gov (United States)

    Haiman, Zoltan

    Finding electromagnetic counterparts of future gravitational wave sources would bring rich scientific benefits. A promising possibility, in the case of the coalescence of a super- massive black hole binary, is that prompt emission will be detectable from merger- induced disturbances in a circumbinary disk. Motivated by this possibility, we propose a major effort, to investigate the dynamical response of a circumbinary disk to the SMBH merger, and to compute the expected light-curve and spectrum of the emerging radiation. Our work will consist of several stages of increasing complexity: starting from semi- analytical orbital calculations for a collisionless disk of massless test particles, and culminating in three-dimensional simulations, with an approximate treatment of radiative transfer. The proposed collaboration is built on previous work of the PI and the Co-I, and will lead to an understanding of the physics of how the disturbed disks light up, as well as the nature of the disk emission. Our results will significantly enhance the science return from the LISA satellite, in which NASA is invested, and will directly support NASA's Strategic Plan, Sub-Goal 3D: ``Discover the origin, structure, evolution and destiny of the universe''.

  18. No circumbinary planets transiting the tightest Kepler binaries - a fingerprint of a third star

    CERN Document Server

    Martin, David V; Fabrycky, Daniel C

    2015-01-01

    The Kepler mission has yielded the discovery of eight eclipsing binaries, within period range of 7 - 40 d, hosting circumbinary planets. This is longer than the typical eclipsing binary period found by Kepler, and hence there is a dearth of planets around the closest binaries. In this paper we demonstrate how this dearth may be explained by the presence of a distant stellar tertiary companion, which shrunk the inner binary orbit by the process of Kozai cycles and tidal friction, a mechanism that has been implicated for producing most binaries with periods below 7 d. We show that the geometry and orbital dynamics of these evolving triple-star systems are highly restrictive for a circumbinary planet, which is subject itself to Kozai modulation, on one hand, and can shield the two inner stars from their Kozai cycle and subsequent shrinking, on the other hand. Only small planets on wide and inclined orbits may form, survive and allow for the inner binary shrinkage. Those are difficult to detect.

  19. ROTATIONAL SYNCHRONIZATION MAY ENHANCE HABITABILITY FOR CIRCUMBINARY PLANETS: KEPLER BINARY CASE STUDIES

    Energy Technology Data Exchange (ETDEWEB)

    Mason, Paul A. [Department of Physics, University of Texas at El Paso, El Paso, TX 79968 (United States); Zuluaga, Jorge I.; Cuartas-Restrepo, Pablo A. [FACom-Instituto de Fisica-FCEN, Universidad de Antioquia, Calle 70 No. 52-21, Medellin (Colombia); Clark, Joni M. [Department of Mathematics and Physical Sciences, New Mexico State University-DACC, Las Cruces, NM 88003 (United States)

    2013-09-10

    We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression toward planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of X-ray and ultraviolet (XUV) radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in some cases improved environments if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass companions, like Kepler 47, allow for protected planets over a wide range of secondary masses and binary periods. Kepler 38 and related binaries are marginal cases. Kepler 64 and analogs have dramatically reduced stellar aggression due to synchronization of the primary, but are limited by the short lifetime. Kepler 16 appears to be inhospitable to planets due to extreme XUV flux. These results have important implications for estimates of the number of stellar systems containing habitable planets in the Galaxy and allow for the selection of binaries suitable for follow-up searches for habitable planets.

  20. Ring theory

    CERN Document Server

    Rowen, Louis H

    1991-01-01

    This is an abridged edition of the author's previous two-volume work, Ring Theory, which concentrates on essential material for a general ring theory course while ommitting much of the material intended for ring theory specialists. It has been praised by reviewers:**""As a textbook for graduate students, Ring Theory joins the best....The experts will find several attractive and pleasant features in Ring Theory. The most noteworthy is the inclusion, usually in supplements and appendices, of many useful constructions which are hard to locate outside of the original sources....The audience of non

  1. Why Are Ring Galaxies Interesting?

    CERN Document Server

    Higdon, James L

    2010-01-01

    Compared with ordinary spirals, the ISM in ring galaxies experiences markedly different physical conditions and evolution. As a result, ring galaxies provide interesting perspectives on the triggering/quenching of large scale star formation and the destructive effects of massive stars on molecular cloud complexes. We use high resolution radio, sub-millimeter, infrared, and optical data to investigate the role of gravitational stability in star formation regulation, factors influencing the ISM's molecular fraction, and evidence of peculiar star formation laws and efficiencies in two highly evolved ring galaxies: Cartwheel and the Lindsay-Shapley ring.

  2. cis-Nitenpyram Analogues Bearing Acyloxy Segments Anchored on the Tetrahydropyrimidine Ring: Synthesis,Insecticidal Activities and Molecular Docking Studies

    Institute of Scientific and Technical Information of China (English)

    SUN Chuan-wen; WU Ying; CHEN Yan-xia; NAN Shi-bin; ZHANG Wang-geng

    2013-01-01

    A series of novel cis-nitenpyram analogues bearing acyloxy segments anchored on the tetrahydropyrimidine ring was designed and synthesized.Preliminary bioassays indicate that all the nitenpyram analogues 3a—3n exhibit good insecticidal activities against Nilaparvata lugens and Aphis medicaginis at 100 mg/L,while analogue 3k affords the best activity in vitro and the lethal concentration 50(LC50) values(0.187,0.214 mg/L) are close to that of nitenpyram.The structure activity relationships(SARs) suggest that their insecticidal potency is influenced by the species of acyloxy segments.The docking results reveal that analogue 3k forms stronger hydrogen-bonding with the nAChR,which explain the structure activity relationships(SARs) observed in vitro and imply that the strategies of our designed nitenpyram analogues are feasible.

  3. Communication: Rate coefficients of the H + CH4 → H2 + CH3 reaction from ring polymer molecular dynamics on a highly accurate potential energy surface

    International Nuclear Information System (INIS)

    The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ≤ T ≤ 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures

  4. Communication: Rate coefficients of the H + CH4 → H2 + CH3 reaction from ring polymer molecular dynamics on a highly accurate potential energy surface

    Science.gov (United States)

    Meng, Qingyong; Chen, Jun; Zhang, Dong H.

    2015-09-01

    The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ≤ T ≤ 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures.

  5. Circumbinary disk, an efficient medium extracting orbital angular momentum in close binaries

    Institute of Scientific and Technical Information of China (English)

    CHEN WenCong; ZENG QingGuo

    2009-01-01

    The loss of orbital angular momentum plays an important role in the mass transfer and orbital evolution of close binaries. The traditional mechanisms of orbital angular momentum loss consist of gravitational wave radiation, mass loss and magnetic braking. However, a small fraction of the mass outflow may form a thin circumbinary disk (CB disk) located in the orbital plane of the binary during mass exchange. The tide torques caused by the gravitational interaction between a CB disk and a binary system brake binary effectively, and extract the orbital angular momentum from the binary system. In this study, numerical calculations for the evolution of the white dwarf binary show that a CB disk is an efficient medium extracting orbital angular momentum even if the mass loss is very small. Finally, some theo-retical research and observational progress on CB disks are presented.

  6. Planetary Rings

    CERN Document Server

    Tiscareno, Matthew S

    2011-01-01

    Planetary rings are the only nearby astrophysical disks, and the only disks that have been investigated by spacecraft. Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 1e-7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close-range and in real-time in planetary rings. We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The main rings of Saturn comprise our system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty...

  7. Planetary Rings

    Science.gov (United States)

    Gordon, M. K.; Araki, S.; Black, G. J.; Bosh, A. S.; Brahic, A.; Brooks, S. M.; Charnoz, S.; Colwell, J. E.; Cuzzi, J. N.; Dones, L.; Durisen, R. H.; Esposito, L. W.; Ferrari, C.; Festou, M.; French, R. G.; Giuliatti-Winter, S. M.; Graps, A. L.; Hamilton, D. P.; Horanyi, M.; Karjalainen, R. M.; Krivov, A. V.; Krueger, H.; Larson, S. M.; Levison, H. F.; Lewis, M. C.; Lissauer, J. J.; Murray, C. D.; Namouni, F.; Nicholson, P. D.; Olkin, C. B.; Poulet, F.; Rappaport, N. J.; Salo, H. J.; Schmidt, J.; Showalter, M. R.; Spahn, F.; Spilker, L. J.; Srama, R.; Stewart, G. R.; Yanamandra-Fisher, P.

    2002-08-01

    The past two decades have witnessed dramatic changes in our view and understanding of planetary rings. We now know that each of the giant planets in the Solar System possesses a complex and unique ring system. Recent studies have identified complex gravitational interactions between the rings and their retinues of attendant satellites. Among the four known ring systems, we see elegant examples of Lindblad and corotation resonances (first invoked in the context of galactic disks), electromagnetic resonances, spiral density waves and bending waves, narrow ringlets which exhibit internal modes due to collective instabilities, sharp-edged gaps maintained via tidal torques from embedded moonlets, and tenuous dust belts created by meteoroid impact onto, or collisions between, parent bodies. Yet, as far as we have come, our understanding is far from complete. The fundamental questions confronting ring scientists at the beginning of the twenty-first century are those regarding the origin, age and evolution of the various ring systems, in the broadest context. Understanding the origin and age requires us to know the current ring properties, and to understand the dominant evolutionary processes and how they influence ring properties. Here we discuss a prioritized list of the key questions, the answers to which would provide the greatest improvement in our understanding of planetary rings. We then outline the initiatives, missions, and other supporting activities needed to address those questions, and recommend priorities for the coming decade in planetary ring science.

  8. Kepler-47 Circumbinary Planets obey Quantization of Angular Momentum per Unit Mass predicted by Quantum Celestial Mechanics (QCM

    Directory of Open Access Journals (Sweden)

    Potter F.

    2014-01-01

    Full Text Available The Kepler-47 circumbinary system has three known planets orbiting its binary star barycenter and therefore can provide a precision test of the Quantum Celestial Mechan- ics (QCM prediction of the quantization of angular momentum per unit mass in all gravitationally bound systems. Two of the planets are in the Habitable Zone (HZ, so system stability can be a primary concern. QCM may be a major contributor to the stability of this system.

  9. SUPRAMITRAL RING

    Directory of Open Access Journals (Sweden)

    Rajesh G

    2011-11-01

    Full Text Available Supra mitral ring is a rare cause for congenital mitral valve obstr uction. The reported incidence of supramitral ring is 0.2-0.4% in general population and 8% in patients with congenital mitral valve disease. The condition is characterized by an abnormal ridge of connective tissue often circumferential in shape ,on the atrial side of the mitral valve encroaching on the orifice of the mitral valve. It may adhere to the leaflets of the valve and restrict their movements. Although a supramitral ring may be rarely nonobstructive, it often results in mitral valve inflow obstruction.

  10. CIRCUMBINARY CHAOS: USING PLUTO'S NEWEST MOON TO CONSTRAIN THE MASSES OF NIX AND HYDRA

    International Nuclear Information System (INIS)

    The Pluto system provides a unique local laboratory for the study of binaries with multiple low-mass companions. In this paper, we study the orbital stability of P4, the most recently discovered moon in the Pluto system. This newfound companion orbits near the plane of the Pluto-Charon (PC) binary, roughly halfway between the two minor moons Nix and Hydra. We use a suite of few body integrations to constrain the masses of Nix and Hydra, and the orbital parameters of P4. For the system to remain stable over the age of the solar system, the masses of Nix and Hydra likely do not exceed 5 × 1016 kg and 9 × 1016 kg, respectively. These upper limits assume a fixed mass ratio between Nix and Hydra at the value implied by their median optical brightness. Our study finds that stability is more sensitive to their total mass and that a downward revision of Charon's eccentricity (from our adopted value of 0.0035) is unlikely to significantly affect our conclusions. Our upper limits are an order of magnitude below existing astrometric limits on the masses of Nix and Hydra. For a density at least that of ice, the albedos of Nix and Hydra would exceed 0.3. This constraint implies they are icy, as predicted by giant impact models. Even with these low masses, P4 only remains stable if its eccentricity e ∼< 0.02. The 5:1 commensurability with Charon is particularly unstable, combining stability constraints with the observed mean motion places the preferred orbit for P4 just exterior to the 5:1 resonance. These predictions will be tested when the New Horizons satellite visits Pluto. Based on the results for the PC system, we expect that circumbinary, multi-planet systems will be more widely spaced than their singleton counterparts. Further, circumbinary exoplanets close to the three-body stability boundary, such as those found by Kepler, are less likely to have other companions nearby.

  11. Dynamic Kerr effect study on six-membered-ring molecular liquids: benzene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, cyclohexene, and cyclohexane.

    Science.gov (United States)

    Kakinuma, Shohei; Shirota, Hideaki

    2015-04-01

    The intermolecular dynamics of five six-membered-ring molecular liquids having different aromaticities-benzene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, cyclohexene, and cyclohexane-measured by femtosecond Raman-induced Kerr effect spectroscopy have been compared in this study. The line shapes of the Fourier transform low-frequency spectra, which arise from the intermolecular vibrational dynamics, are trapezoidal for benzene and 1,3-cyclohexadiene, triangular for 1,4-cyclohexadiene and cyclohexene, and monomodal for cyclohexane. The trapezoidal shapes of the low-frequency spectra of benzene and 1,3-cyclohexadiene are due to the librational motions of their aromatic planar structures, which cause damped nuclear response features. The time integrals of the nuclear responses of the five liquids correlate to the squares of the polarizability anisotropies of the molecules calculated on the basis of density functional theory. The first moments of the low-frequency spectra roughly linearly correlate to the bulk parameters of the square roots of the surface tensions divided by the densities and the square roots of the surface tensions divided by the molecular weights, but the plots for cyclohexene deviate slightly from the correlations. The picosecond overdamped transients of the liquids are well fitted by a biexponential function. The fast time constants of all of the liquids are approximately 1.1-1.4 ps, and they do not obey the Stokes-Einstein-Debye hydrodynamic model. On the other hand, the slow time constants are roughly linearly proportional to the products of the shear viscosities and the molar volumes. The observed intramolecular vibrational modes at less than 700 cm(-1) for all of the liquids are also assigned on the basis of quantum chemistry calculations. PMID:25741755

  12. Determinantal rings

    CERN Document Server

    Bruns, Winfried

    1988-01-01

    Determinantal rings and varieties have been a central topic of commutative algebra and algebraic geometry. Their study has attracted many prominent researchers and has motivated the creation of theories which may now be considered part of general commutative ring theory. The book gives a first coherent treatment of the structure of determinantal rings. The main approach is via the theory of algebras with straightening law. This approach suggest (and is simplified by) the simultaneous treatment of the Schubert subvarieties of Grassmannian. Other methods have not been neglected, however. Principal radical systems are discussed in detail, and one section is devoted to each of invariant and representation theory. While the book is primarily a research monograph, it serves also as a reference source and the reader requires only the basics of commutative algebra together with some supplementary material found in the appendix. The text may be useful for seminars following a course in commutative ring theory since a ...

  13. Conformations of some lower-size large-ring cyclodextrins derived from conformational search with molecular dynamics and principal component analysis

    Science.gov (United States)

    Ivanov, Petko

    2012-02-01

    Computational studies were conducted on the conformations of some lower-size large-ring cyclodextrins, CDn (n = 11, 12, 13, 15, 16, 17). Principal component analysis (PCA) was applied for post-processing of trajectories from conformational search based on 100.0 ns molecular dynamics (MD) simulations. The dominant PCA modes for concerted motions of the macroring atoms were monitored in a lower-dimensions subspace. The first six lowest indexed principal components contribute more than 90% of the total atomic motions in all cases, with about 70% (CD12) to 90% (CD17) contribution coming from the three highest-eigenvalue principal components. Representative average geometries of the cyclodextrin macrorings were also obtained for the whole simulation and for the ten 10.0 ns time intervals of the simulation. We concluded that the whole set of structures could be sorted into two clearly distinguished groups, separated by the figure-eight conformation of CD14: (i) open bent boat-like macrorings (CD11 to CD13), and (ii) two winded single helical strands (an anti-parallel double helix with foldbacks at each end), CD15 to CD17, shaped as number eight for the odd-number-residues cases, CD15 and CD17. CD13 and CD14 mark the borderline between lower and higher flexibilities of the lower-size LR-CDs macrorings.

  14. Ring polymer molecular dynamics fast computation of rate coefficients on accurate potential energy surfaces in local configuration space: Application to the abstraction of hydrogen from methane

    Science.gov (United States)

    Meng, Qingyong; Chen, Jun; Zhang, Dong H.

    2016-04-01

    To fast and accurately compute rate coefficients of the H/D + CH4 → H2/HD + CH3 reactions, we propose a segmented strategy for fitting suitable potential energy surface (PES), on which ring-polymer molecular dynamics (RPMD) simulations are performed. On the basis of recently developed permutation invariant polynomial neural-network approach [J. Li et al., J. Chem. Phys. 142, 204302 (2015)], PESs in local configuration spaces are constructed. In this strategy, global PES is divided into three parts, including asymptotic, intermediate, and interaction parts, along the reaction coordinate. Since less fitting parameters are involved in the local PESs, the computational efficiency for operating the PES routine is largely enhanced by a factor of ˜20, comparing with that for global PES. On interaction part, the RPMD computational time for the transmission coefficient can be further efficiently reduced by cutting off the redundant part of the child trajectories. For H + CH4, good agreements among the present RPMD rates and those from previous simulations as well as experimental results are found. For D + CH4, on the other hand, qualitative agreement between present RPMD and experimental results is predicted.

  15. Kepler-1647b: The Largest and Longest-period Kepler Transiting Circumbinary Planet

    Science.gov (United States)

    Kostov, Veselin B.; Orosz, Jerome A.; Welsh, William F.; Doyle, Laurance R.; Fabrycky, Daniel C.; Haghighipour, Nader; Quarles, Billy; Short, Donald R.; Cochran, William D.; Endl, Michael; Ford, Eric B.; Gregorio, Joao; Hinse, Tobias C.; Isaacson, Howard; Jenkins, Jon M.; Jensen, Eric L. N.; Kane, Stephen; Kull, Ilya; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Mazeh, Tsevi; Müller, Tobias W. A.; Pepper, Joshua; Quinn, Samuel N.; Ragozzine, Darin; Shporer, Avi; Steffen, Jason H.; Torres, Guillermo; Windmiller, Gur; Borucki, William J.

    2016-08-01

    We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the still-small family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around the eclipsing binary system Kepler-1647 has a very long orbital period (˜1100 days) and was at conjunction only twice during the Kepler mission lifetime. Due to the singular configuration of the system, Kepler-1647b is not only the longest-period transiting CBP at the time of writing, but also one of the longest-period transiting planets. With a radius of 1.06 ± 0.01 R Jup, it is also the largest CBP to date. The planet produced three transits in the light curve of Kepler-1647 (one of them during an eclipse, creating a syzygy) and measurably perturbed the times of the stellar eclipses, allowing us to measure its mass, 1.52 ± 0.65 M Jup. The planet revolves around an 11-day period eclipsing binary consisting of two solar-mass stars on a slightly inclined, mildly eccentric (e bin = 0.16), spin-synchronized orbit. Despite having an orbital period three times longer than Earth’s, Kepler-1647b is in the conservative habitable zone of the binary star throughout its orbit.

  16. Resolving the relative influence of strong field spacetime dynamics and MHD on circumbinary disk physics

    CERN Document Server

    Zilhão, Miguel; Campanelli, Manuela; Zlochower, Yosef

    2014-01-01

    In this paper we evolve magnetized and unmagnetized circumbinary accretion disks around supermassive black hole binaries in the relativistic regime. We use a post-Newtonian expansion to construct an analytical spacetime and determine how the order of the post-Newtonian (PN) expansion affects the dynamics of the gas. We find very small differences in the late-time bulk dynamics of non-magnetized hydrodynamic evolutions between the two spacetimes down to separations of approximately $40GM/c^2$ where $M$ is the total mass of the binary. For smaller separations, the differences due to PN-order become comparable to differences caused by using initial data further from equilibrium. For magnetized gas, MHD dynamics, which drives the accretion dynamics, tends to mask all higher order PN effects even at separations of $20GM/c^2$, leading to essentially the same observed electromagnetic luminosity. This implies that our calculations of the EM signal may be robust down to small binary separations. Our investigation is t...

  17. Circumbinary Planets Orbiting the Rapidly Pulsating Subdwarf B-type binary NY Vir

    CERN Document Server

    Qian, S -B; Dai, Z -B; Lajús, E Fernández; Xiang, F -Y; He, J -J

    2011-01-01

    We report here the tentative discovery of a Jovian planet in orbit around the rapidly pulsating subdwarf B-type (sdB-type) eclipsing binary NY Vir. By using new determined eclipse times together with those collected from the literature, we detect that the observed-calculated (O-C) curve of NY Vir shows a small-amplitude cyclic variation with a period of 7.9\\,years and a semiamplitude of 6.1\\,s, while it undergoes a downward parabolic change (revealing a period decrease at a rate of $\\dot{P}=-9.2\\times{10^{-12}}$). The periodic variation was analyzed for the light-travel time effect via the presence of a third body. The mass of the tertiary companion was determined to be $M_3\\sin{i^{\\prime}}=2.3(\\pm0.3)$\\,$M_{Jupiter}$ when a total mass of 0.60\\,$M_{\\odot}$ for NY Vir is adopted. This suggests that it is most probably a giant circumbinary planet orbiting NY Vir at a distance of about 3.3 astronomical units (AU). Since the rate of period decrease can not be explained by true angular momentum loss caused by grav...

  18. CIRCUMBINARY PLANETS ORBITING THE RAPIDLY PULSATING SUBDWARF B-TYPE BINARY NY Vir

    International Nuclear Information System (INIS)

    We report here the tentative discovery of a Jovian planet in orbit around the rapidly pulsating subdwarf B-type (sdB-type) eclipsing binary NY Vir. By using newly determined eclipse times together with those collected from the literature, we detect that the observed-calculated (O – C) curve of NY Vir shows a small-amplitude cyclic variation with a period of 7.9 yr and a semiamplitude of 6.1 s, while it undergoes a downward parabolic change (revealing a period decrease at a rate of P-dot = -9.2 x 10-12). The periodic variation was analyzed for the light-travel-time effect via the presence of a third body. The mass of the tertiary companion was determined to be M3sin i' = 2.3(± 0.3)MJupiter when a total mass of 0.60 M☉ for NY Vir is adopted. This suggests that it is most probably a giant circumbinary planet orbiting NY Vir at a distance of about 3.3 astronomical units (AU). Since the rate of period decrease cannot be explained by true angular momentum loss caused by gravitational radiation or/and magnetic braking, the observed downward parabolic change in the O – C diagram may be only a part of a long-period (longer than 15 years) cyclic variation, which may reveal the presence of another Jovian planet (∼2.5 MJupiter) in the system.

  19. Response of a circumbinary accretion disc to black hole mass loss

    CERN Document Server

    Rosotti, Giovanni P; Price, Daniel J

    2012-01-01

    We investigate the evolution of the surface density of a circumbinary accretion disc after the mass loss induced by the merger of two supermassive black holes. We first introduce an ana- lytical model, under the assumption of a disc composed of test particles, to derive the surface density evolution of the disc following the mass loss. The model predicts the formation of sharp density peaks in the disc; the model also allows us to compute the typical timescale for the formation of these peaks. To test and validate the model, we run numerical simulations of the process using the Smoothed Particle Hydrodynamics (SPH) code PHANTOM, taking fluid effects into account. We find good agreement in the shape and position of the peaks between the model and the simulations. In a fluid disc, however, the epicyclic oscillations induced by the mass loss can dissipate, and only some of the predicted peaks form in the simulation. To quantify how fast this dissipation proceeds, we introduce an appropriate parameter, and we sho...

  20. Planet Hunters: A Transiting Circumbinary Planet in a Quadruple Star System

    CERN Document Server

    Schwamb, Megan E; Carter, Joshua A; Welsh, William F; Fischer, Debra A; Torres, Guillermo; Howard, Andrew W; Crepp, Justin R; Keel, William C; Lintott, Chris J; Kaib, Nathan A; Terrell, Dirk; Gagliano, Robert; Jek, Kian J; Parrish, Michael; Smith, Arfon M; Lynn, Stuart; Simpson, Robert J; Giguere, Matthew J; Schawinski, Kevin

    2012-01-01

    We report the discovery and confirmation of a transiting circumbinary planet (PH1) around KIC 4862625, an eclipsing binary in the Kepler field. The planet was discovered by volunteers searching the first six Quarters of publicly available Kepler data as part of the Planet Hunters citizen science project. Transits of the planet across the larger and brighter of the eclipsing stars are detectable by visual inspection every ~137 days, with seven transits identified in Quarters 1-11. The physical and orbital parameters of both the host stars and planet were obtained via a photometric-dynamical model, simultaneously fitting both the measured radial velocities and the Kepler light curve of KIC 4862625.The 6.18 $\\pm$ 0.17 Earth radii planet orbits outside the 20-day orbit of an eclipsing binary consisting of an F dwarf (1.734 +/- 0.044 Solar radii, 1.528 +/- 0.087 Solar masses) and M dwarf (0.378 +/0 0.023 Solar radii, 0.408 +/- 0.024 solar masses). For the planet, we find an upper mass limit of 169 Earth masses(0.5...

  1. Wave-like warp propagation in circumbinary discs I. Analytic theory and numerical simulations

    CERN Document Server

    Facchini, Stefano; Price, Daniel J

    2013-01-01

    In this paper we analyse the propagation of warps in protostellar circumbinary discs. We use these systems as a test environment in which to study warp propagation in the bending-wave regime, with the addition of an external torque due to the binary gravitational potential. In particular, we want to test the linear regime, for which an analytic theory has been developed. In order to do so, we first compute analytically the steady state shape of an inviscid disc subject to the binary torques. The steady state tilt is a monotonically increasing function of radius. In the absence of viscosity, the disc does not present any twist. Then, we compare the time-dependent evolution of the warped disc calculated via the known linearised equations both with the analytic solutions and with full 3D numerical simulations, which have been performed with the PHANTOM SPH code using 2 million particles. We find a good agreement both in the tilt and in the phase evolution for small inclinations, even at very low viscosities. Mor...

  2. Retrograde binaries of massive black holes in circum-binary accretion discs

    CERN Document Server

    Amaro-Seoane, Pau; Dotti, Massimo; Colpi, Monica

    2016-01-01

    We explore the hardening of a massive black hole binary embedded in a circum-binary gas disc when the binary and the gas are coplanar and the gas is counter-rotating. The secondary black hole, revolving in the direction opposite to the gas, experiences a drag from gas-dynamical friction and from direct accretion of part of it. Using two-dimensional (2D) hydrodynamical grid simulations we investigate the effect of changing the accretion prescriptions on the dynamics of the secondary black hole which in turn affect the binary hardening and eccentricity evolution. We find that realistic accretion prescriptions lead to results that differ from those inferred assuming accretion of all the gas within the Roche Lobe of the secondary black hole. Different accretion prescriptions result in different disc's surface densities which alter the black hole's dynamics back. Full 3D SPH realizations of a number of representative cases, run over a shorter interval of time, validate the general trends observed in the less compu...

  3. The evolved circumbinary disk of AC Her: a radiative transfer, interferometric and mineralogical study

    CERN Document Server

    Hillen, M; Menu, J; Van Winckel, H; Min, M; Mulders, G D

    2015-01-01

    We aim to constrain the structure of the circumstellar material around the post-AGB binary and RV Tauri pulsator AC Her. We want to constrain the spatial distribution of the amorphous as well as of the crystalline dust. We present very high-quality mid-IR interferometric data that were obtained with MIDI/VLTI. We analyse the MIDI data and the full SED, using the MCMax radiative transfer code, to find a good structure model of AC Her's circumbinary disk. We include a grain size distribution and midplane settling of dust self-consistently. The spatial distribution of crystalline forsterite in the disk is investigated with the mid-IR features, the 69~$\\mu$m band and the 11.3~$\\mu$m signatures in the interferometric data. All the data are well fitted. The inclination and position angle of the disk are well determined at i=50+-8 and PA=305+-10. We firmly establish that the inner disk radius is about an order of magnitude larger than the dust sublimation radius. Significant grain growth has occurred, with mm-sized ...

  4. Kepler-413b: a slightly misaligned, Neptune-size transiting circumbinary planet

    CERN Document Server

    Kostov, Veselin B; Carter, Joshua A; Deleuil, Magali; Diaz, Rodrigo F; Fabrycky, Daniel C; Hebrard, Guillaume; Hinse, Tobias C; Mazeh, Tsevi; Orosz, Jerome A; Tsvetanov, Zlatan I; Welsh, William F

    2014-01-01

    We report the discovery of a transiting, Rp = 4.347+/-0.099REarth, circumbinary planet (CBP) orbiting the Kepler K+M Eclipsing Binary (EB) system KIC 12351927 (Kepler-413) every ~66 days on an eccentric orbit with ap = 0.355+/-0.002AU, ep = 0.118+/-0.002. The two stars, with MA = 0.820+/-0.015MSun, RA = 0.776+/-0.009RSun and MB = 0.542+/-0.008MSun, RB = 0.484+/-0.024RSun respectively revolve around each other every 10.11615+/-0.00001 days on a nearly circular (eEB = 0.037+/-0.002) orbit. The orbital plane of the EB is slightly inclined to the line of sight (iEB = 87.33+/-0.06 degrees) while that of the planet is inclined by ~2.5 degrees to the binary plane at the reference epoch. Orbital precession with a period of ~11 years causes the inclination of the latter to the sky plane to continuously change. As a result, the planet often fails to transit the primary star at inferior conjunction, causing stretches of hundreds of days with no transits (corresponding to multiple planetary orbital periods). We predict t...

  5. The Hot Companion and Circumbinary Disk of the Be Star HR 2142

    CERN Document Server

    Peters, Geraldine J; Gies, Douglas R; Grundstrom, Erika D

    2016-01-01

    We present a spectroscopic investigation of the Be+sdO binary system HR 2142 that is based upon large sets of ultraviolet observations from the International Ultraviolet Explorer and ground-based H-alpha observations. We measured radial velocities for the Be star component from these spectra, and computed a revised orbit. In order to search for the spectral signature of the hot subdwarf, we cross-correlated the short wavelength end of each IUE spectrum with a model hot star spectrum, and then we used the predicted Doppler shifts of the subdwarf to shift-and-add all the cross-correlation functions to the frame of the subdwarf. This merged function shows the weak signal from the spectral lines of the hot star, and a best fit is obtained with a mass ratio M_2/M_1 = 0.07 +/- 0.02, companion temperature T_{eff} > 43 +/- 5 kK, projected rotational velocity V sin i 0.009 +/- 0.001. This hot subdwarf creates a one-armed spiral, tidal wake in the disk of the Be star, and we present a circumbinary disk model that can ...

  6. KOI-2939b: the largest and longest-period Kepler transiting circumbinary planet

    CERN Document Server

    Kostov, Veselin B; Welsh, William F; Doyle, Laurance R; Fabrycky, Daniel C; Haghighipour, Nader; Quarles, Billy; Short, Donald R; Cochran, William D; Endl, Michael; Ford, Eric B; Gregorio, Joao; Hinse, Tobias C; Isaacson, Howard; Jenkins, Jon M; Jensen, Eric L N; Kull, Ilya; Latham, David W; Lissauer, Jack J; Marcy, Geoffrey W; Mazeh, Tsevi; Muller, Tobias W A; Pepper, Joshua; Quinn, Samuel N; Ragozzine, Darin; Shporer, Avi; Steffen, Jason H; Torres, Guillermo; Windmiller, Gur; Borucki, William J

    2015-01-01

    We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the still-small family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around the eclipsing binary system KOI-2939 has a very long orbital period (~1100 days) and was at conjunction only twice during the Kepler mission lifetime. Due to the singular configuration of the system, KOI-2939b is not only the longest-period transiting CBP at the time of writing, but also one of the longest-period transiting planets. With a radius of 1.06+/-0.01 RJup it is also the largest CBP to date. The planet produced three transits in the light-curve of KOI-2939 (one of them during an eclipse, creating a syzygy) and measurably perturbed the times of the stellar eclipses, allowing us to measure its mass to be 1.52+/-0.65 MJup. The planet revolves around an 11-day period eclipsing binary consisting of two Solar-m...

  7. Spin-Orbit Alignment for the Circumbinary Planet Host Kepler-16A

    CERN Document Server

    Winn, Joshua N; Johnson, John Asher; Torres, Guillermo; Cochran, William D; Marcy, Geoffrey W; Howard, Andrew; Isaacson, Howard; Fischer, Debra; Doyle, Laurance; Welsh, William; Carter, Joshua A; Fabrycky, Daniel C; Ragozzine, Darin; Quinn, Samuel N; Shporer, Avi; Howell, Steve B; Latham, David W; Orosz, Jerome; Prsa, Andrej; Slawson, Robert W; Borucki, William J; Koch, David; Barclay, Thomas; Boss, Alan P; Christensen-Dalsgaard, Jorgen; Girouard, Forrest R; Jenkins, Jon; Klaus, Todd C; Meibom, Soren; Morris, Robert L; Sasselov, Dimitar; Still, Martin; Van Cleve, Jeffrey

    2011-01-01

    Kepler-16 is an eccentric low-mass eclipsing binary with a circumbinary transiting planet. Here we investigate the angular momentum of the primary star, based on Kepler photometry and Keck spectroscopy. The primary star's rotation period is 35.1 +/- 1.0 days, and its projected obliquity with respect to the stellar binary orbit is 1.6 +/- 2.4 degrees. Therefore the three largest sources of angular momentum---the stellar orbit, the planetary orbit, and the primary's rotation---are all closely aligned. This finding supports a formation scenario involving accretion from a single disk. Alternatively, tides may have realigned the stars despite their relatively wide separation (0.2 AU), a hypothesis that is supported by the agreement between the measured rotation period and the "pseudosynchronous" period of tidal evolution theory. The rotation period, chromospheric activity level, and fractional light variations suggest a main-sequence age of 2-4 Gyr. Evolutionary models of low-mass stars can reproduce the observed ...

  8. XMM-NEWTON MONITORING OF THE CLOSE PRE-MAIN-SEQUENCE BINARY AK SCO. EVIDENCE OF TIDE-DRIVEN FILLING OF THE INNER GAP IN THE CIRCUMBINARY DISK

    Energy Technology Data Exchange (ETDEWEB)

    Gomez de Castro, Ana Ines [S. D. Astronomia y Geodesia and Instituto de Matematica Interdisciplinar, Fac. de CC Matematicas, Universidad Complutense, E-28040 Madrid (Spain); Lopez-Santiago, Javier [Departamento de Astrofisica, Fac de CC Fisicas, Universidad Complutense, E-28040 Madrid (Spain); Talavera, Antonio [European Space Astronomy Center, Villanueva de la Canada, E-28691, Madrid (Spain); Sytov, A. Yu.; Bisikalo, D. [Institute of Astronomy of the Russian Academy of Sciences, Pyatnitskaya St. 48, 109017 Moscow (Russian Federation)

    2013-03-20

    AK Sco stands out among pre-main-sequence binaries because of its prominent ultraviolet excess, the high eccentricity of its orbit, and the strong tides driven by it. AK Sco consists of two F5-type stars that get as close as 11 R{sub *} at periastron passage. The presence of a dense (n{sub e} {approx} 10{sup 11} cm{sup -3}) extended envelope has been unveiled recently. In this article, we report the results from an XMM-Newton-based monitoring of the system. We show that at periastron, X-ray and UV fluxes are enhanced by a factor of {approx}3 with respect to the apastron values. The X-ray radiation is produced in an optically thin plasma with T {approx} 6.4 Multiplication-Sign 10{sup 6} K and it is found that the N{sub H} column density rises from 0.35 Multiplication-Sign 10{sup 21} cm{sup -2} at periastron to 1.11 Multiplication-Sign 10{sup 21} cm{sup -2} at apastron, in good agreement with previous polarimetric observations. The UV emission detected in the Optical Monitor band seems to be caused by the reprocessing of the high-energy magnetospheric radiation on the circumstellar material. Further evidence of the strong magnetospheric disturbances is provided by the detection of line broadening of 278.7 km s{sup -1} in the N V line with Hubble Space Telescope/Space Telescope Imaging Spectrograph. Numerical simulations of the mass flow from the circumbinary disk to the components have been carried out. They provide a consistent scenario with which to interpret AK Sco observations. We show that the eccentric orbit acts like a gravitational piston. At apastron, matter is dragged efficiently from the inner disk border, filling the inner gap and producing accretion streams that end as ring-like structures around each component of the system. At periastron, the ring-like structures come into contact, leading to angular momentum loss, and thus producing an accretion outburst.

  9. Topological rings

    CERN Document Server

    Warner, S

    1993-01-01

    This text brings the reader to the frontiers of current research in topological rings. The exercises illustrate many results and theorems while a comprehensive bibliography is also included. The book is aimed at those readers acquainted with some very basic point-set topology and algebra, as normally presented in semester courses at the beginning graduate level or even at the advanced undergraduate level. Familiarity with Hausdorff, metric, compact and locally compact spaces and basic properties of continuous functions, also with groups, rings, fields, vector spaces and modules, and with Zorn''s Lemma, is also expected.

  10. Ring interferometry

    CERN Document Server

    Malykin, Grigorii B; Zhurov, Alexei

    2013-01-01

    This monograph is devoted to the creation of a comprehensive formalism for quantitative description of polarized modes' linear interaction in modern single-mode optic fibers. The theory of random connections between polarized modes, developed in the monograph, allows calculations of the zero shift deviations for a fiber ring interferometer. The monograph addresses also the

  11. Constraining the Radiation and Plasma Environment of the Kepler Circumbinary Habitable-zone Planets

    Science.gov (United States)

    Zuluaga, Jorge I.; Mason, Paul A.; Cuartas-Restrepo, Pablo A.

    2016-02-01

    The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation properties as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net.

  12. CIRCUMBINARY PLANETS ORBITING THE RAPIDLY PULSATING SUBDWARF B-TYPE BINARY NY Vir

    Energy Technology Data Exchange (ETDEWEB)

    Qian, S.-B.; Zhu, L.-Y.; Dai, Z.-B.; He, J.-J. [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China); Fernandez-Lajus, E. [Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires (Argentina); Xiang, F.-Y., E-mail: qsb@ynao.ac.cn [Physics Department, Xiangtan University, 411105 Xiangtan, Funan Province (China)

    2012-02-15

    We report here the tentative discovery of a Jovian planet in orbit around the rapidly pulsating subdwarf B-type (sdB-type) eclipsing binary NY Vir. By using newly determined eclipse times together with those collected from the literature, we detect that the observed-calculated (O - C) curve of NY Vir shows a small-amplitude cyclic variation with a period of 7.9 yr and a semiamplitude of 6.1 s, while it undergoes a downward parabolic change (revealing a period decrease at a rate of P-dot = -9.2 x 10{sup -12}). The periodic variation was analyzed for the light-travel-time effect via the presence of a third body. The mass of the tertiary companion was determined to be M{sub 3}sin i' = 2.3({+-} 0.3)M{sub Jupiter} when a total mass of 0.60 M{sub Sun} for NY Vir is adopted. This suggests that it is most probably a giant circumbinary planet orbiting NY Vir at a distance of about 3.3 astronomical units (AU). Since the rate of period decrease cannot be explained by true angular momentum loss caused by gravitational radiation or/and magnetic braking, the observed downward parabolic change in the O - C diagram may be only a part of a long-period (longer than 15 years) cyclic variation, which may reveal the presence of another Jovian planet ({approx}2.5 M{sub Jupiter}) in the system.

  13. CONSTRAINING THE RADIATION AND PLASMA ENVIRONMENT OF THE KEPLER CIRCUMBINARY HABITABLE-ZONE PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Zuluaga, Jorge I. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Mason, Paul A. [New Mexico State University—DACC, Las Cruces, NM 88003 (United States); Cuartas-Restrepo, Pablo A. [FACom—Instituto de Física—FCEN, Universidad de Antioquia, Calle 70 No. 52-21, Medellín (Colombia)

    2016-02-20

    The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation properties as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net.

  14. Friction between Ring Polymer Brushes

    OpenAIRE

    2015-01-01

    Friction between ring-polymer brushes at melt densities sliding past each other are studied using extensive course-grained molecular dynamics simulations and scaling arguments, and the results are compared to the friction between linear-polymer brushes. We show that for a velocity range spanning over three decades, the frictional forces measured for ring-polymer brushes are half the corresponding friction in case of linear brushes. In the linear-force regime, the weak inter-digitation of two ...

  15. Tatooine's Future: The Eccentric Response of Kepler's Circumbinary Planets to Common-Envelope Evolution of their Host Stars

    CERN Document Server

    Kostov, Veselin B; Tamayo, Daniel; Jayawardhana, Ray; Rinehart, Stephen A

    2016-01-01

    Inspired by the recent Kepler discoveries of circumbinary planets orbiting nine close binary stars, we explore the fate of the former as the latter evolve off the main sequence. We combine binary star evolution models with dynamical simulations to study the orbital evolution of these planets as their hosts undergo common-envelope stages, losing in the process a tremendous amount of mass on dynamical timescales. Five of the systems experience at least one Roche-lobe overflow and common-envelope stages (Kepler-1647 experiences three), and the binary stars either shrink to very short orbits or coalesce; two systems trigger a double-degenerate supernova explosion. Kepler's circumbinary planets predominantly remain gravitationally bound at the end of the common-envelope phase, migrate to larger orbits, and may gain significant eccentricity; their orbital expansion can be more than an order of magnitude and can occur over the course of a single planetary orbit. The orbits these planets can reach are qualitatively c...

  16. A Circumbinary Planet in Orbit Around the Short-Period White-Dwarf Eclipsing Binary RR Cae

    CERN Document Server

    Qian, S -B; Zhu, L -Y; Dai, Z -B; Lajus, E Fernandez; Baume, G L

    2012-01-01

    By using six new determined mid-eclipse times together with those collected from the literature, we found that the Observed-Calculated (O-C) curve of RR Cae shows a cyclic change with a period of 11.9 years and an amplitude of 14.3s, while it undergoes an upward parabolic variation (revealing a long-term period increase at a rate of dP/dt =+4.18(+-0.20)x10^(-12). The cyclic change was analyzed for the light-travel time effect that arises from the gravitational influence of a third companion. The mass of the third body was determined to be M_3*sin i' = 4.2(+-0.4) M_{Jup} suggesting that it is a circumbinary giant planet when its orbital inclination is larger than 17.6 degree. The orbital separation of the circumbinary planet from the central eclipsing binary is about 5.3(+-0.6)AU. The period increase is opposite to the changes caused by angular momentum loss via magnetic braking or/and gravitational radiation, nor can it be explained by the mass transfer between both components because of its detached configur...

  17. Gas Absorption in the KH 15D System: Further Evidence for Dust Settling in the Circumbinary Disk

    CERN Document Server

    Lawler, S M; Redfield, S; Hamilton, C M; Johns-Krull, C M; Winn, J N; Johnson, J A; Mundt, R

    2010-01-01

    Na I D lines in the spectrum of the young binary KH 15D have been analyzed in detail. We find an excess absorption component that may be attributed to foreground interstellar absorption, and to gas possibly associated with the solids in the circumbinary disk. The derived column density is log N_NaI = 12.5 cm^-2, centered on a radial velocity that is consistent with the systemic velocity. Subtracting the likely contribution of the ISM leaves log N_NaI ~ 12.3 cm^-2. There is no detectable change in the gas column density across the "knife edge" formed by the opaque grain disk, indicating that the gas and solids have very different scale heights, with the solids being highly settled. Our data support a picture of this circumbinary disk as being composed of a very thin particulate grain layer composed of millimeter-sized or larger objects that are settled within whatever remaining gas may be present. This phase of disk evolution has been hypothesized to exist as a prelude to the formation of planetesimals through...

  18. GAS ABSORPTION IN THE KH 15D SYSTEM: FURTHER EVIDENCE FOR DUST SETTLING IN THE CIRCUMBINARY DISK

    International Nuclear Information System (INIS)

    Na I D lines in the spectrum of the young binary KH 15D have been analyzed in detail. We find an excess absorption component that may be attributed to foreground interstellar absorption, and to gas possibly associated with the solids in the circumbinary disk. The derived column density is log NNaI = 12.5 cm-2, centered on a radial velocity that is consistent with the systemic velocity. Subtracting the likely contribution of the interstellar medium leaves log NNaI∼ 12.3 cm-2. There is no detectable change in the gas column density across the 'knife edge' formed by the opaque grain disk, indicating that the gas and solids have very different scale heights, with the solids being highly settled. Our data support a picture of this circumbinary disk as being composed of a very thin particulate grain layer composed of millimeter-sized or larger objects that are settled within whatever remaining gas may be present. This phase of disk evolution has been hypothesized to exist as a prelude to the formation of planetesimals through gravitational fragmentation, and is expected to be short-lived if much gas were still present in such a disk. Our analysis also reveals the presence of excess Na I emission relative to the comparison spectrum at the radial velocity of the currently visible star that plausibly arises within the magnetosphere of this still-accreting young star.

  19. Prospects of the Detection of Circumbinary Planets With Kepler and CoRoT Using the Variations of Eclipse Timing

    CERN Document Server

    Schwarz, R; Eggl, S; Pilat-Lohinger, E; Funk, B

    2011-01-01

    In close eclipsing binaries, measurements of the variations in binary's eclipse timing may be used to infer information about the existence of circumbinary objects. To determine the possibility of the detection of such variations with CoRoT and Kepler space telescopes, we have carried out an extensive study of the dynamics of a binary star system with a circumbinary planet, and calculated its eclipse timing variations (ETV) for different values of the mass-ratio and orbital elements of the binary and the perturbing body. Here, we present the results of our study and assess the detectability of the planet by comparing the resulting values of ETVs with the temporal sensitivity of CoRoT and Kepler. Results point to extended regions in the parameter-space where the perturbation of a planet may become large enough to create measurable variations in the eclipse timing of the secondary star. Many of these variations point to potentially detectable ETVs and the possible existence of Jovian-type planets.

  20. Molecular cloning and characterization of a novel RING zinc-finger protein gene up-regulated under in vitro salt stress in cassava.

    Science.gov (United States)

    dos Reis, Sávio Pinho; Tavares, Liliane de Souza Conceição; Costa, Carinne de Nazaré Monteiro; Brígida, Aílton Borges Santa; de Souza, Cláudia Regina Batista

    2012-06-01

    Cassava (Manihot esculenta Crantz) is one of the world's most important food crops. It is cultivated mainly in developing countries of tropics, since its root is a major source of calories for low-income people due to its high productivity and resistance to many abiotic and biotic factors. A previous study has identified a partial cDNA sequence coding for a putative RING zinc finger in cassava storage root. The RING zinc finger protein is a specialized type of zinc finger protein found in many organisms. Here, we isolated the full-length cDNA sequence coding for M. esculenta RZF (MeRZF) protein by a combination of 5' and 3' RACE assays. BLAST analysis showed that its deduced amino acid sequence has a high level of similarity to plant proteins of RZF family. MeRZF protein contains a signature sequence motif for a RING zinc finger at its C-terminal region. In addition, this protein showed a histidine residue at the fifth coordination site, likely belonging to the RING-H2 subgroup, as confirmed by our phylogenetic analysis. There is also a transmembrane domain in its N-terminal region. Finally, semi-quantitative RT-PCR assays showed that MeRZF expression is increased in detached leaves treated with sodium chloride. Here, we report the first evidence of a RING zinc finger gene of cassava showing potential role in response to salt stress.

  1. Wave-like warp propagation in circumbinary discs - I. Analytic theory and numerical simulations

    Science.gov (United States)

    Facchini, Stefano; Lodato, Giuseppe; Price, Daniel J.

    2013-08-01

    In this paper we analyse the propagation of warps in protostellar circumbinary discs. We use these systems as a test environment in which to study warp propagation in the bending-wave regime, with the addition of an external torque due to the binary gravitational potential. In particular, we want to test the linear regime, for which an analytic theory has been developed. In order to do so, we first compute analytically the steady-state shape of an inviscid disc subject to the binary torques. The steady-state tilt is a monotonically increasing function of radius, but misalignment is found at the disc inner edge. In the absence of viscosity, the disc does not present any twist. Then, we compare the time-dependent evolution of the warped disc calculated via the known linearized equations both with the analytic solutions and with full 3D numerical simulations. The simulations have been performed with the PHANTOM smoothed particle hydrodynamics (SPH) code using two million particles. We find a good agreement both in the tilt and in the phase evolution for small inclinations, even at very low viscosities. Moreover, we have verified that the linearized equations are able to reproduce the diffusive behaviour when α > H/R, where α is the disc viscosity parameter. Finally, we have used the 3D simulations to explore the non-linear regime. We observe a strongly non-linear behaviour, which leads to the breaking of the disc. Then, the inner disc starts precessing with its own precessional frequency. This behaviour has already been observed with numerical simulations in accretion discs around spinning black holes. The evolution of circumstellar accretion discs strongly depends on the warp evolution. Therefore, the issue explored in this paper could be of fundamental importance in order to understand the evolution of accretion discs in crowded environments, when the gravitational interaction with other stars is highly likely, and in multiple systems. Moreover, the evolution of

  2. Kepler-413B: A slightly misaligned, Neptune-size transiting circumbinary planet

    Energy Technology Data Exchange (ETDEWEB)

    Kostov, V. B.; McCullough, P. R.; Tsvetanov, Z. I. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Carter, J. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Deleuil, M.; Díaz, R. F. [Laboratoire d' Astrophysique de Marseille, 38 rue Frédéric Joliot-Curie, F-13388 Marseille cedex 13 (France); Fabrycky, D. C. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Hébrard, G. [Institut d' Astrophysique de Paris, UMR 7095 CNRS, Université Pierre and Marie Curie, 98 bis boulevard Arago, F-75014 Paris (France); Hinse, T. C. [Korea Astronomy and Space Science Institute (KASI), Advanced Astronomy and Space Science Division, Daejeon 305-348 (Korea, Republic of); Mazeh, T. [Department of Astronomy and Astrophysics, Tel Aviv University, 69978 Tel Aviv (Israel); Orosz, J. A.; Welsh, W. F., E-mail: vkostov@pha.jhu.edu [Department of Astronomy, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182 (United States)

    2014-03-20

    We report the discovery of a transiting, R{sub p} = 4.347 ± 0.099R {sub ⊕}, circumbinary planet (CBP) orbiting the Kepler K+M eclipsing binary (EB) system KIC 12351927 (Kepler-413) every ∼66 days on an eccentric orbit with a{sub p} = 0.355 ± 0.002 AU, e{sub p} = 0.118 ± 0.002. The two stars, with M{sub A} = 0.820 ± 0.015 M {sub ☉}, R{sub A} = 0.776 ± 0.009 R {sub ☉} and M{sub B} = 0.542 ± 0.008 M {sub ☉}, R{sub B} = 0.484 ± 0.024 R {sub ☉}, respectively, revolve around each other every 10.11615 ± 0.00001 days on a nearly circular (e {sub EB} = 0.037 ± 0.002) orbit. The orbital plane of the EB is slightly inclined to the line of sight (i {sub EB} = 87.°33 ± 0.°06), while that of the planet is inclined by ∼2.°5 to the binary plane at the reference epoch. Orbital precession with a period of ∼11 yr causes the inclination of the latter to the sky plane to continuously change. As a result, the planet often fails to transit the primary star at inferior conjunction, causing stretches of hundreds of days with no transits (corresponding to multiple planetary orbital periods). We predict that the next transit will not occur until 2020. The orbital configuration of the system places the planet slightly closer to its host stars than the inner edge of the extended habitable zone. Additionally, the orbital configuration of the system is such that the CBP may experience Cassini State dynamics under the influence of the EB, in which the planet's obliquity precesses with a rate comparable to its orbital precession. Depending on the angular precession frequency of the CBP, it could potentially undergo obliquity fluctuations of dozens of degrees (and complex seasonal cycles) on precession timescales.

  3. Spitzer IRAC observations of IR excess in Holmberg IX X-1: A circumbinary disk or a variable jet?

    CERN Document Server

    Dudik, R P; Roberts, T P; Grise, F; Singh, A; Pagano, R; Winter, L M

    2016-01-01

    We present Spitzer Infrared Array Camera (IRAC) photometric observations of the Ultra-luminous X-ray Source (ULX, X-1) in Holmberg IX. We construct a spectral energy distribution (SED) for Holmberg IX X-1 based on published optical, UV and X-ray data combined with the IR data from this analysis. We modeled the X-ray and optical data with disk and stellar models, however we find a clear IR excess in the ULX SED that cannot be explained by fits or extrapolations of any of these models. Instead, further analysis suggests that the IR excess results either from dust emission, possibly from a circumbinary disk or from a variable jet.

  4. 2D mapping of young stars in the inner 180 pc of NGC 1068: correlation with molecular gas ring and stellar kinematics

    CERN Document Server

    Storchi-Bergmann, Thaisa; Riffel, Rogerio; Diniz, Marlon R; Vale, Tiberio Borges; McGregor, Peter J

    2012-01-01

    We report the first two-dimensional mapping of the stellar population and non-stellar continua within the inner 180 pc (radius) of NGC 1068 at a spatial resolution of 8 pc, using integral field spectroscopy in the near-infrared. We have applied the technique of spectral synthesis to data obtained with the instrument NIFS and the adaptive optics module ALTAIR at the Gemini North Telescope. Two episodes of recent star formation are found to dominate the stellar population contribution: the first occurred 300 Myr ago, extending over most of the nuclear region; the second occurred just 30 Myr ago, in a ring-like structure at ~100 pc from the nucleus, where it is coincident with an expanding ring of H2 emission. Inside the ring, where a decrease in the stellar velocity dispersion is observed, the stellar population is dominated by the 300 Myr age component. In the inner 35 pc, the oldest age component (age > 2Gyr) dominates the mass, while the flux is dominated by black-body components with temperatures in the ran...

  5. Prime rings with PI rings of constants

    CERN Document Server

    Kharchenko, V K; Rodríguez-Romo, S

    1996-01-01

    It is shown that if the ring of constants of a restricted differential Lie algebra with a quasi-Frobenius inner part satisfies a polynomial identity (PI) then the original prime ring has a generalized polynomial identitiy (GPI). If additionally the ring of constants is semiprime then the original ring is PI. The case of a non-quasi-Frobenius inner part is also considered.

  6. Weakly Dual Rings

    Institute of Scientific and Technical Information of China (English)

    魏俊潮; 孙建华

    2004-01-01

    In This paper, the concept of weakly dual ring is introduced, which is a proper generalization of the dual ring. If R is a right weakly dual ring, then (1)Z(RR) = J(R); (2) If R is also a zero-division power ring, then R is a right AP-injective ring. In addition, some properties of weakly dual rings are given.

  7. Radical theory of rings

    CERN Document Server

    Gardner, JW

    2003-01-01

    Radical Theory of Rings distills the most noteworthy present-day theoretical topics, gives a unified account of the classical structure theorems for rings, and deepens understanding of key aspects of ring theory via ring and radical constructions. Assimilating radical theory's evolution in the decades since the last major work on rings and radicals was published, the authors deal with some distinctive features of the radical theory of nonassociative rings, associative rings with involution, and near-rings. Written in clear algebraic terms by globally acknowledged authorities, the presentation

  8. Alternative loop rings

    CERN Document Server

    Goodaire, EG; Polcino Milies, C

    1996-01-01

    For the past ten years, alternative loop rings have intrigued mathematicians from a wide cross-section of modern algebra. As a consequence, the theory of alternative loop rings has grown tremendously. One of the main developments is the complete characterization of loops which have an alternative but not associative, loop ring. Furthermore, there is a very close relationship between the algebraic structures of loop rings and of group rings over 2-groups. Another major topic of research is the study of the unit loop of the integral loop ring. Here the interaction between loop rings and group ri

  9. Communication: Rate coefficients of the H + CH{sub 4} → H{sub 2} + CH{sub 3} reaction from ring polymer molecular dynamics on a highly accurate potential energy surface

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Qingyong, E-mail: mengqingyong@dicp.ac.cn; Chen, Jun, E-mail: chenjun@dicp.ac.cn; Zhang, Dong H., E-mail: zhangdh@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, 116023 Dalian (China)

    2015-09-14

    The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ≤ T ≤ 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures.

  10. The Structure of the Evolved Circumbinary Disk around V4046 Sgr

    CERN Document Server

    Rosenfeld, Katherine A; Wilner, David J; Kastner, J H; McClure, M K

    2013-01-01

    We present sensitive, sub-arcsecond resolution Submillimeter Array observations of the protoplanetary disk around the nearby, pre-main sequence spectroscopic binary V4046 Sgr. We report for the first time a large inner hole (r=29 AU) spatially resolved in the 1.3 mm continuum emission and study the structure of this disk using radiative transfer calculations to model the spectral energy distribution (SED), continuum visibilities, and spectral line emission of CO and its main isotopologues. Our modeling scheme demonstrates that the majority of the dust mass is distributed in a narrow ring (centered at 37 AU with a FWHM of 16 AU) that is ~5 times more compact than the gas disk. This structure implies that the dust-to-gas mass ratio has a strong spatial variation, ranging from a value much larger than typical of the interstellar medium (ISM) at the ring to much smaller than that of the ISM at larger disk radii. We suggest that these basic structural features are potentially observational signatures of the accumu...

  11. A Combined Spitzer and Herschel Infrared Study of Gas and Dust in the Circumbinary Disk Orbiting V4046 Sgr

    CERN Document Server

    Rapson, Valerie A; Sacco, G Germano; Kastner, Joel H; Wilner, David; Rosenfeld, Katherine; Andrews, Sean; Herczeg, Gregory; van der Marel, Nienke

    2015-01-01

    We present results from a spectroscopic Spitzer and Herschel mid-to-far-infrared study of the circumbinary disk orbiting the evolved (age ~12-23 Myr) close binary T Tauri system V4046 Sgr. Spitzer IRS spectra show emission lines of [Ne II], H_2 S(1), CO_2 and HCN, while Herschel PACS and SPIRE spectra reveal emission from [O I], OH, and tentative detections of H_2O and high-J transitions of CO. We measure [Ne III]/[Ne II] < 0.13, which is comparable to other X-ray/EUV luminous T Tauri stars that lack jets. We use the H_2 S(1) line luminosity to estimate the gas mass in the relatively warm surface layers of the inner disk. The presence of [O I] emission suggests that CO, H_2O, and/or OH is being photodissociated, and the lack of [C I] emission suggests any excess C may be locked up in HCN, CN and other organic molecules. Modeling of silicate dust grain emission features in the mid-infrared indicates that the inner disk is composed mainly of large (r~5 um) amorphous pyroxene and olivine grains (~86% by mass)...

  12. An interferometric study of the post-AGB binary 89 Herculis. II Radiative transfer models of the circumbinary disk

    CERN Document Server

    Hillen, M; Van Winckel, H; Min, M; Gielen, C; Wevers, T; Mulders, G D; Regibo, S; Verhoelst, T

    2014-01-01

    The presence of disks and outflows is widespread among post-AGB binaries. In the first paper of this series, a surprisingly large fraction of optical light was found to be resolved in the 89 Her post-AGB system. The data showed this flux to arise from close to the central binary. Scattering off the inner rim of the circumbinary disk, or in a dusty outflow were suggested as two possible origins. With detailed dust radiative transfer models of the disk we aim to discriminate between these two configurations. By including Herschel/SPIRE photometry, we extend the SED such that it now fully covers UV to sub-mm wavelengths. The MCMax radiative transfer code is used to create a large grid of disk models. Our models include a self-consistent treatment of dust settling as well as of scattering. A Si-rich composition with two additional opacity sources, metallic Fe or amorphous C, are tested. The SED is fit together with mid-IR (MIDI) visibilities as well as the optical and near-IR visibilities of Paper I, to constrain...

  13. On JB-Rings

    Institute of Scientific and Technical Information of China (English)

    Huanyin CHEN

    2007-01-01

    A ring R is a QB-ring provided that aR + bR = R with a, b ∈ R implies that there exists a y ∈ R such that a+by ∈ R-1q. It is said that a ring R is a JB-ring provided that R/J(R) is a QB-ring, where J(R) is the Jacobson radical of R. In this paper, various necessary and sufficient conditions, under which a ring is a JB-ring, are established. It is proved that JB-rings can be characterized by pseudo-similarity. Furthermore, the author proves that R is a J B-ring iff so is R/J(R)2.

  14. Tube Dynamics Works for Randomly Entangled Rings.

    Science.gov (United States)

    Qin, Jian; Milner, Scott T

    2016-02-12

    The tube model is the cornerstone of molecular theory for polymer rheology. We test its microscopic assumptions by simulating topologically equilibrated ring polymers, whose dynamics is free from end segment relaxation. We show that a closed-form expression derived from the tube model adapted to ring polymers quantitatively predicts the segmental mean squared displacements over the entire range of time scales from local motion to complete equilibration, with a time-independent local friction factor.

  15. New dust belts of Uranus: one ring, two ring, red ring, blue ring.

    Science.gov (United States)

    de Pater, Imke; Hammel, Heidi B; Gibbard, Seran G; Showalter, Mark R

    2006-04-01

    We compared near-infrared observations of the recently discovered outer rings of Uranus with Hubble Space Telescope results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced by impacts into the embedded moon Mab, which apparently orbits at a location where nongravitational perturbations favor the survival and spreading of submicron-sized dust. R/2003 U 2 more closely resembles Saturn's G ring, which is red, a typical color for dusty rings. PMID:16601188

  16. Cloning and Molecular Characterization of a RING Zinc-Finger Gene of Hevea brasiliensis%巴西橡胶树环锌指蛋白基因克隆及其分子特性

    Institute of Scientific and Technical Information of China (English)

    朱家红; 李辉亮; 屠发志; 田维敏; 彭世清

    2006-01-01

    Using the information about the sequence from a differentially expressed clone (designated as HbSSH10)encodes a protein specifying a cysteine-rich sequence containing a putative "RING finger" or "C3HC4" consensus motif that was cloned recently by the subtractive hybridization between latex and leaves from rubber tree (Hevea brasiliensis). A full-length cDNA encoding C3HC4 type zinc-finger protein was isolated and characterized from rubber tree. Sequence analysis revealed that the ORFs of HbRZF encode 156 amino acid residues with a total predicted molecular mass of 17.2 kD,HbRZF protein having a putative "RING finger" segment (amino acid residues 100-144). The deduced amino acid sequences of HbRZF showed high identities of 48%,52% and 50% to those of the ring zinc protein from Poncirus trifoliata, Arabidopsis thaliana, Thellungiella halophila. The result of Northern blot analysis indicated that the transcripts of the HbRZF were expressed more in the latex than in the leaves, whereas little expression was detected in roots and flowers. The transcription of HbRZF was induced by jasmonic acid, whereas ethylene had little effect.%在先前的研究中通过抑制缩减杂交获得了一个在巴西橡胶树胶乳中特异表达的片段(HbSSH10),该片段含有"RING finger"或"C3HC4"保守序列.根据HbSSH10的序列信息设计引物并通过3'-RACE和5'-RACE的方法,获得了一个全长的cDNA(HbRZF).该cDNA含有589个核苷酸,含有完整的阅读框架,编码156个氨基酸.从它推导出的氨基酸序列中含有"RING finger"或"C3HC4"保守区(氨基酸100~144).该氨基酸序列与Poncirus trifoliata、Arabidopsis thaliana和Thellungiella halophila的环锌指蛋白的同源性分别为48%、52%和50%.Northern杂交分析表明HbRZF在胶乳中大量表达,在叶片中微量表达,而在根和花中几乎没有表达.茉莉酸处理可以诱导胶乳中HbRZF的表达,而乙烯对胶乳中HbRZF的表达基本上没有影响.

  17. Groups, rings, modules

    CERN Document Server

    Auslander, Maurice

    2014-01-01

    This classic monograph is geared toward advanced undergraduates and graduate students. The treatment presupposes some familiarity with sets, groups, rings, and vector spaces. The four-part approach begins with examinations of sets and maps, monoids and groups, categories, and rings. The second part explores unique factorization domains, general module theory, semisimple rings and modules, and Artinian rings. Part three's topics include localization and tensor products, principal ideal domains, and applications of fundamental theorem. The fourth and final part covers algebraic field extensions

  18. Muon storage ring

    CERN Multimedia

    1974-01-01

    The muon storage ring where the g-2 of the muon is being measured with extremely high accuracy. The ring is 14-m in diameter and has very precise magnetic bending and electric focussing fields so that the muons orbit the ring under well-defined conditions.

  19. Rings Around Uranus

    Science.gov (United States)

    Maran, Stephen P.

    1977-01-01

    Events leading up to the discovery of the rings of Uranus are described. The methods used and the logic behind the methods are explained. Data collected to prove the existence of the rings are outlined and theories concerning the presence of planetary rings are presented. (AJ)

  20. Seeing Through the Ring: Near-Infrared Photometry of V582 Mon (KH 15D)

    CERN Document Server

    Arulanantham, Nicole A; Cody, Ann Marie; Stauffer, John R; Rebull, Luisa M; Agol, Eric; Windemuth, Diana; Marengo, Massimo; Winn, Joshua N; Hamilton, Catrina M; Mundt, Reinhard; Johns-Krull, Christopher M; Gutermuth, Robert A

    2016-01-01

    We examine the light and color evolution of the T Tauri binary KH 15D through photometry obtained at wavelengths between 0.55 and 8.0 $\\mu$m. The data were collected with ANDICAM on the 1.3 m SMARTS telescope at Cerro-Tololo Inter-American Observatory and with IRAC on the Spitzer Space Telescope. We show that the system's circumbinary ring, which acts as a screen that covers and uncovers different portions of the binary orbit as the ring precesses, has reached an orientation where the brighter component (star B) fully or nearly fully emerges during each orbital cycle. The fainter component (star A) remains fully occulted by the screen at all phases. The leading and trailing edges of the screen move across the sky at the same rate of $\\sim$15 meters per second, consistent with expectation for a ring with a radius and width of $\\sim$4 AU and a precession period of $\\sim$6500 years. Light and color variations continue to indicate that the screen is sharp edged and opaque at \\emph{VRIJH} wavelengths. However, we ...

  1. SEEING THROUGH THE RING: NEAR-INFRARED PHOTOMETRY OF V582 MON (KH 15D)

    Energy Technology Data Exchange (ETDEWEB)

    Arulanantham, Nicole A.; Herbst, William [Astronomy Department, Wesleyan University, Middletown, CT 06459 (United States); Cody, Ann Marie [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Stauffer, John R.; Rebull, Luisa M. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Agol, Eric; Windemuth, Diana [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Marengo, Massimo [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Winn, Joshua N. [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Hamilton, Catrina M. [Physics and Astronomy Department, Dickinson College, Carlisle, PA 17013 (United States); Mundt, Reinhard [Max Planck Institute for Astronomy, D-69117 Heidelberg (Germany); Johns-Krull, Christopher M. [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States); Gutermuth, Robert A. [Department of Astronomy, University of Massachusetts, Amherst, MA 01002 (United States)

    2016-04-15

    We examine the light and color evolution of the T Tauri binary KH 15D through photometry obtained at wavelengths between 0.55 and 8.0 μm. The data were collected with A Novel Dual Imaging CAMera (ANDICAM) on the 1.3 m SMARTS telescope at Cerro-Tololo Inter-American Observatory and with InfraRed Array Camera on the Spitzer Space Telescope. We show that the system’s circumbinary ring, which acts as a screen that covers and uncovers different portions of the binary orbit as the ring precesses, has reached an orientation where the brighter component (star B) fully or nearly fully emerges during each orbital cycle. The fainter component (star A) remains fully occulted by the screen at all phases. The leading and trailing edges of the screen move across the sky at the same rate of ∼15 m s{sup −1}, consistent with expectation for a ring with a radius and width of ∼4 au and a precession period of ∼6500 years. Light and color variations continue to indicate that the screen is sharp edged and opaque at VRIJH wavelengths. However, we find an increasing transparency of the ring edge at 2.2, 3.6, and 4.5 μm. Reddening seen at the beginning of the eclipse that occurred during the CSI 2264 campaign particularly suggests selective extinction by a population of large dust grains. Meanwhile, the gradual bluing observed while star B is setting is indicative of forward scattering effects at the edge of the ring. The spectral energy distribution of the system at its bright phase shows no evidence of infrared excess emission that can be attributed to radiation from the ring or other dust component out to 8 μm.

  2. Seeing Through the Ring: Near-infrared Photometry of V582 Mon (KH 15D)

    Science.gov (United States)

    Arulanantham, Nicole A.; Herbst, William; Cody, Ann Marie; Stauffer, John R.; Rebull, Luisa M.; Agol, Eric; Windemuth, Diana; Marengo, Massimo; Winn, Joshua N.; Hamilton, Catrina M.; Mundt, Reinhard; Johns-Krull, Christopher M.; Gutermuth, Robert A.

    2016-04-01

    We examine the light and color evolution of the T Tauri binary KH 15D through photometry obtained at wavelengths between 0.55 and 8.0 μm. The data were collected with A Novel Dual Imaging CAMera (ANDICAM) on the 1.3 m SMARTS telescope at Cerro-Tololo Inter-American Observatory and with InfraRed Array Camera on the Spitzer Space Telescope. We show that the system’s circumbinary ring, which acts as a screen that covers and uncovers different portions of the binary orbit as the ring precesses, has reached an orientation where the brighter component (star B) fully or nearly fully emerges during each orbital cycle. The fainter component (star A) remains fully occulted by the screen at all phases. The leading and trailing edges of the screen move across the sky at the same rate of ˜15 m s-1, consistent with expectation for a ring with a radius and width of ˜4 au and a precession period of ˜6500 years. Light and color variations continue to indicate that the screen is sharp edged and opaque at VRIJH wavelengths. However, we find an increasing transparency of the ring edge at 2.2, 3.6, and 4.5 μm. Reddening seen at the beginning of the eclipse that occurred during the CSI 2264 campaign particularly suggests selective extinction by a population of large dust grains. Meanwhile, the gradual bluing observed while star B is setting is indicative of forward scattering effects at the edge of the ring. The spectral energy distribution of the system at its bright phase shows no evidence of infrared excess emission that can be attributed to radiation from the ring or other dust component out to 8 μm.

  3. Skew polynomial rings over abelian and idempotent reflexive rings

    OpenAIRE

    Louzari, Mohamed

    2015-01-01

    Let $R$ be a ring and $\\sigma$ an endomorphism of $R$. In this note, we study skew polynomial rings and skew power series rings over idempotent reflexive rings and abelian rings. Also, we introduce the concept of right (resp., left) $\\sigma$-idempotent reflexive rings which generalizes right (resp., left) idempotent reflexive rings and $\\sigma$-abelian rings. Certain results are obtained as corollaries from our results.

  4. Envelopes of Commutative Rings

    Institute of Scientific and Technical Information of China (English)

    Rafael PARRA; Manuel SAOR(I)N

    2012-01-01

    Given a significative class F of commutative rings,we study the precise conditions under which a commutative ring R has an F-envelope.A full answer is obtained when.F is the class of fields,semisimple commutative rings or integral domains.When F is the class of Noetherian rings,we give a full answer when the Krull dimension of R is zero and when the envelope is required to be epimorphic.The general problem is reduced to identifying the class of non-Noetherian rings having a monomorphic Noetherian envelope,which we conjecture is the empty class.

  5. New Dust Belts of Uranus: One Ring, Two Ring, Red Ring, Blue Ring

    Energy Technology Data Exchange (ETDEWEB)

    de Pater, I; Hammel, H B; Gibbard, S G; Showalter, M R

    2006-02-02

    We compare near-infrared observations of the recently discovered outer rings of Uranus with HST results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced via impacts into the embedded moon Mab, which apparently orbits at a location where non-gravitational perturbations favor the survival and spreading of sub-micron sized dust. R/2003 U 2 more closely resembles Saturn's G ring.

  6. On Exchange QB∞-Rings

    Institute of Scientific and Technical Information of China (English)

    Huanyin Chen

    2007-01-01

    In this paper, we introduce a new class of rings, the QB∞-rings. We investigate necessary and sufficient conditions under which an exchange ring is a QB∞-ring. The modules over an exchange QB∞-ring are studied. Also, we prove that every regular square matrix over an exchange QB∞-ring admits a diagonal reduction by pseudo-invertible matrices.

  7. Token Ring Project

    Directory of Open Access Journals (Sweden)

    Adela Ionescu

    2007-01-01

    Full Text Available Ring topology is a simple configuration used to connect processes that communicate among themselves. A number of network standards such as token ring, token bus, and FDDI are based on the ring connectivity. This article will develop an implementation of a ring of processes that communicate among themselves via pipe links. The processes are nodes in the ring. Each process reads from its standard input and writes in its standard output. N-1 process redirects the its standard output to a standard input of the process through a pipe. When the ring-structure is designed, the project can be extended to simulate networks or to implement algorithms for mutual exclusion

  8. Token ring technology report

    CERN Document Server

    2013-01-01

    Please note this is a Short Discount publication. This report provides an overview of the IBM Token-Ring technology and products built by IBM and compatible vendors. It consists of two sections: 1. A summary of the design trade-offs for the IBM Token-Ring. 2. A summary of the products of the major token-ring compatible vendors broken down by adapters and components, wiring systems, testing, and new chip technology.

  9. On -Coherent Endomorphism Rings

    Indian Academy of Sciences (India)

    Li-Xin Mao

    2008-11-01

    A ring is called right -coherent if every principal right ideal is finitely presented. Let $M_R$ be a right -module. We study the -coherence of the endomorphism ring of $M_R$. It is shown that is a right -coherent ring if and only if every endomorphism of $M_R$ has a pseudokernel in add $M_R; S$ is a left -coherent ring if and only if every endomorphism of $M_R$ has a pseudocokernel in add $M_R$. Some applications are given.

  10. A Beautiful Ring

    Institute of Scientific and Technical Information of China (English)

    王对成

    2000-01-01

    Helen bought a very nice ring(戒指)and she wore it to the office the next day. Nobody saw her ring. She moved her hand this way and that, but still nobbdy in the offiee saw the ring on her finger. At tea time when they were sitting'round,she suddenly (突然地) stood up. “it is very hot here,”she said. “I think I'll take off my ring.”

  11. Homorooty in Rings

    Directory of Open Access Journals (Sweden)

    M. H. Hooshmand

    2010-03-01

    Full Text Available The topic of ”Homorooty” (for integer numbers has been introduced and studied in [2]. There are some applications of the homorooty in studying and solving some Diophantine equations and systems, as an interesting and useful elementary method. As a continuation of the Homorooty, we consider it for arbitrary rings and will study its properties in different rings, especially UFD and homorooty rings (which will be introduced. At last we shall state some applications of homorooty in studying some equations over homorooty rings

  12. Ring Around a Galaxy

    Science.gov (United States)

    1999-01-01

    Space Telescope Science Institute astronomers are giving the public chances to decide where to aim NASA's Hubble Space Telescope. Guided by 8,000 Internet voters, Hubble has already been used to take a close-up, multi-color picture of the most popular object from a list of candidates, the extraordinary 'polar-ring' galaxy NGC 4650A. Located about 130 million light-years away, NGC 4650A is one of only 100 known polar-ring galaxies. Their unusual disk-ring structure is not yet understood fully. One possibility is that polar rings are the remnants of colossal collisions between two galaxies sometime in the distant past, probably at least 1 billion years ago. What is left of one galaxy has become the rotating inner disk of old red stars in the center. Meanwhile, another smaller galaxy which ventured too close was probably severely damaged or destroyed. The bright bluish clumps, which are especially prominent in the outer parts of the ring, are regions containing luminous young stars, examples of stellar rebirth from the remnants of an ancient galactic disaster. The polar ring appears to be highly distorted. No regular spiral pattern stands out in the main part of the ring, and the presence of young stars below the main ring on one side and above on the other shows that the ring is warped and does not lie in one plane. Determining the typical ages of the stars in the polar ring is an initial goal of our Polar Ring Science Team that can provide a clue to the evolution of this unusual galaxy. The HST exposures were acquired by the Hubble Heritage Team, consisting of Keith Noll, Howard Bond, Carol Christian, Jayanne English, Lisa Frattare, Forrest Hamilton, Anne Kinney and Zolt Levay, and guest collaborators Jay Gallagher (University of Wisconsin-Madison), Lynn Matthews (National Radio Astronomy Observatory-Charlottesville), and Linda Sparke (University of Wisconsin-Madison).

  13. Revocable Ring Signature

    Institute of Scientific and Technical Information of China (English)

    Dennis Y. W. Liu; Joseph K. Liu; Yi Mu; Willy Susilo; Duncan S. Wong

    2007-01-01

    Group signature allows the anonymity of a real signer in a group to be revoked by a trusted party called group manager. It also gives the group manager the absolute power of controlling the formation of the group. Ring signature, on the other hand, does not allow anyone to revoke the signer anonymity, while allowing the real signer to forma group (also known as a ring) arbitrarily without being controlled by any other party. In this paper, we propose a new variant for ring signature, called Revocable Ring Signature. The signature allows a real signer to form a ring arbitrarily while allowing a set of authorities to revoke the anonymity of the real signer. This new variant inherits the desirable properties from both group signature and ring signature in such a way that the real signer will be responsible for what it has signed as the anonymity is revocable by authorities while the real signer still has the freedom on ring formation. We provide a formal security model for revocable ring signature and propose an efficient construction which is proven secure under our security model.

  14. EBT ring physics

    International Nuclear Information System (INIS)

    This workshop attempted to evaluate the status of the current experimental and theoretical understanding of hot electron ring properties. The dominant physical processes that influence ring formation, scaling, and their optimal behavior are also studied. Separate abstracts were prepared for each of the 27 included papers

  15. Jupiter's Rings: Sharpest View

    Science.gov (United States)

    2007-01-01

    The New Horizons spacecraft took the best images of Jupiter's charcoal-black rings as it approached and then looked back at Jupiter. The top image was taken on approach, showing three well-defined lanes of gravel- to boulder-sized material composing the bulk of the rings, as well as lesser amounts of material between the rings. New Horizons snapped the lower image after it had passed Jupiter on February 28, 2007, and looked back in a direction toward the sun. The image is sharply focused, though it appears fuzzy due to the cloud of dust-sized particles enveloping the rings. The dust is brightly illuminated in the same way the dust on a dirty windshield lights up when you drive toward a 'low' sun. The narrow rings are confined in their orbits by small 'shepherding' moons.

  16. The cryogenic storage ring CSR

    Science.gov (United States)

    von Hahn, R.; Becker, A.; Berg, F.; Blaum, K.; Breitenfeldt, C.; Fadil, H.; Fellenberger, F.; Froese, M.; George, S.; Göck, J.; Grieser, M.; Grussie, F.; Guerin, E. A.; Heber, O.; Herwig, P.; Karthein, J.; Krantz, C.; Kreckel, H.; Lange, M.; Laux, F.; Lohmann, S.; Menk, S.; Meyer, C.; Mishra, P. M.; Novotný, O.; O'Connor, A. P.; Orlov, D. A.; Rappaport, M. L.; Repnow, R.; Saurabh, S.; Schippers, S.; Schröter, C. D.; Schwalm, D.; Schweikhard, L.; Sieber, T.; Shornikov, A.; Spruck, K.; Sunil Kumar, S.; Ullrich, J.; Urbain, X.; Vogel, S.; Wilhelm, P.; Wolf, A.; Zajfman, D.

    2016-06-01

    An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm-3 is derived, equivalent to a room-temperature pressure below 10-14 mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

  17. The cryogenic storage ring CSR.

    Science.gov (United States)

    von Hahn, R; Becker, A; Berg, F; Blaum, K; Breitenfeldt, C; Fadil, H; Fellenberger, F; Froese, M; George, S; Göck, J; Grieser, M; Grussie, F; Guerin, E A; Heber, O; Herwig, P; Karthein, J; Krantz, C; Kreckel, H; Lange, M; Laux, F; Lohmann, S; Menk, S; Meyer, C; Mishra, P M; Novotný, O; O'Connor, A P; Orlov, D A; Rappaport, M L; Repnow, R; Saurabh, S; Schippers, S; Schröter, C D; Schwalm, D; Schweikhard, L; Sieber, T; Shornikov, A; Spruck, K; Sunil Kumar, S; Ullrich, J; Urbain, X; Vogel, S; Wilhelm, P; Wolf, A; Zajfman, D

    2016-06-01

    An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm(-3) is derived, equivalent to a room-temperature pressure below 10(-14) mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams. PMID:27370434

  18. 丙交酯开环聚合法合成高分子量聚乳酸%Synthesis of High Molecular Weight Poly Lactic Acid by Lactide Ring-opening Polymerization

    Institute of Scientific and Technical Information of China (English)

    刘辉; 王肖杰; 张留学

    2015-01-01

    以80%的L-乳酸为原料,辛酸亚锡为催化剂,丙交酯开环聚合得到了粘均分子量为5.1×105的聚乳酸。考察了脱水时间、反应温度、催化剂用量对丙交酯合成的影响,得到了合成丙交酯的最佳工艺条件,其收率最高达到76.7%;研究了合成高分子量聚乳酸的最佳工艺条件。红外光谱表征并对比分析了合成的丙交酯和聚乳酸。用DSC-TG分析了不同提纯次数的丙交酯的纯度,表明提纯三次后的丙交酯纯度较高,同时也分析了在不同温度下合成的聚乳酸,表明在130℃下合成的聚乳酸热稳定性好。%Using 80% L-lactic acid as raw materials , stannous caprylate as the catalyst , sticky molecular weight 5.1×105 of poly lactic acid (PLA) was synthesized by the lactide ring-opening polymerization.The influence factors of lactide synthesis such as reaction time , temperature and catalyst dosage were studied , obtained the optimum technological conditions for synthesis of lactide , its yield was up to 76.7%.Aynthetic optimum process conditions for the synthesis of high molecular weight poly lactic acid , fourier transforms infrared spectrum characterization and analysis of the synthesis of lactide and poly lactic acid were researched.Analyzed by DSC and TG in different times for the purification of the purity of lactide , the results showed that the purity was higher after the three times for the purification of lactide.Synthesis of poly lactic acid under the different synthesis temperature was analyzed too.It was suggested that heat stability of synthetic poly lactic acid was good in 130 ℃.

  19. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance.

    Science.gov (United States)

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R; Junge, Wolfgang; Khan, Shahid

    2015-09-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings. The residue coevolution reflects the physiological importance of the dynamics that may

  20. The Enceladus Ring

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] The Enceladus Ring (labeled) This excellent view of the faint E ring -- a ring feature now known to be created by Enceladus -- also shows two of Saturn's small moons that orbit within the ring, among a field of stars in the background. The E ring extends from three to eight Saturn radii -- about 180,000 kilometers (118,000 miles) to 482,000 kilometers (300,000 miles). Its full extent is not visible in this view. Calypso (22 kilometers, or 14 miles across) and Helene (32 kilometers, or 20 miles across) orbit within the E ring's expanse. Helene skirts the outer parts of the E ring, but here it is projected in front of a region deeper within the ring. Calypso and Helene are trojan satellites, or moons that orbit 60 degrees in front or behind a larger moon. Calypso is a Tethys trojan and Helene is a trojan of Dione. An interesting feature of note in this image is the double-banded appearance of the E-ring, which is created because the ring is somewhat fainter in the ringplane than it is 500-1,000 kilometers (300-600 miles) above and below the ringplane. This appearance implies that the particles in this part of the ring have nonzero inclinations (a similar affect is seen in Jupiter's gossamer ring). An object with a nonzero inclination does not orbit exactly at Saturn's ringplane. Instead, its orbit takes it above and below the ringplane. Scientists are not entirely sure why the particles should have such inclinations, but they are fairly certain that the reason involves Enceladus. One possible explanation is that all the E ring particles come from the plume of icy material that is shooting due south out of the moon's pole. This means all of the particles are created with a certain velocity out of the ringplane, and then they orbit above and below that plane. Another possible explanation is that Enceladus produces particles with a range of speeds, but the moon gravitationally scatters any particles that lie very close to

  1. Phase behaviour of polyethylene knotted ring chains

    Institute of Scientific and Technical Information of China (English)

    Wen Xiao-Hui; Zhang Lin-Xi; Xia A-Gen; Chen Hong-Ping

    2011-01-01

    The phase behaviour of polyethylene knotted ring chains is investigated by using molecular dynamics simulations.In this paper, we focus on the collapse of the polyethylene knotted ring chain, and also present the results of linear and ring chains for comparison. At high temperatures, a fully extensive knot structure is observed. The mean-square radius of gyration per bond〈S2〉/(Nb2)and the shape factor(δ*)depend on not only the chain length but also the knot type.With temperature decreasing, chain collapse is observed, and the collapse temperature decreases with the chain length increasing. The actual collapse transition can be determined by the specific heat capacity Cv, and the knotted ring chain undergoes gas-liquid-solid-like transition directly. The phase transition of a knotted ring chain is only one-stage collapse, which is different from the polyethylene linear and ring chains. This investigation can provide some insights into the statistical properties of knotted polymer chains.

  2. Ring species as demonstrations of the continuum of species formation

    DEFF Research Database (Denmark)

    Pereira, Ricardo José Do Nascimento; Wake, David B.

    2015-01-01

    in this issue of Molecular Ecology by Fuchs et al. (2015), focused on the entire genealogy of a bulbul (Alophoixus) species complex, offers key insights into the evolutionary processes underlying diversification of this Indo-Malayan bird. Their findings fulfil most of the criteria that can be expected for ring...... species (Fig. ): an ancestor has colonized the mainland from Sundaland, expanded along the forested habitat wrapping around Thailand's lowlands, adjacent taxa intergrade around the ring distribution, and terminal taxa overlap at the ring closure. Although it remains unclear whether ring divergence has...

  3. Dynamics of the Uranian Rings

    Science.gov (United States)

    Dermott, S. F.

    1984-01-01

    Some of the problems of the shepherding satellite model of Goldreich ant tremaine are discussed. The following topics are studied: (1) optical depths of the all the observed narrow rings; (2) satellite and ring separation timescales; (3) ring edge sharpness; (4) shock formation in narrow rings; (5) the existence of small satellites near the Uranian rings; and (6) the apse and node alignments of the eccentric and inclined rings.

  4. Ring chromosome 13

    DEFF Research Database (Denmark)

    Brandt, C A; Hertz, Jens Michael; Petersen, M B;

    1992-01-01

    A stillborn male child with anencephaly and multiple malformations was found to have the karyotype 46,XY,r(13) (p11q21.1). The breakpoint at 13q21.1, determined by high resolution banding, is the most proximal breakpoint ever reported in patients with ring chromosome 13. In situ hybridisation...... with the probe L1.26 confirmed the derivation from chromosome 13 and DNA polymorphism analysis showed maternal origin of the ring chromosome. Our results, together with a review of previous reports of cases with ring chromosome 13 with identified breakpoints, could neither support the theory of distinct clinical...

  5. Group ring cryptography

    CERN Document Server

    Hurley, Barry

    2011-01-01

    Cryptographic systems are derived using units in group rings. Combinations of types of units in group rings give units not of any particular type. This includes cases of taking powers of units and products of such powers and adds the complexity of the {\\em discrete logarithm} problem to the system. The method enables encryption and (error-correcting) coding to be combined within one system. These group ring cryptographic systems may be combined in a neat way with existing cryptographic systems, such as RSA, and a combination has the combined strength of both systems. Examples are given.

  6. Saturn's Rings are Fractal

    OpenAIRE

    Li, Jun; Ostoja-Starzewski, Martin

    2012-01-01

    Over the past few decades, various conjectures were advanced that Saturn's rings are Cantor-like sets, although no convincing fractal analysis of actual images has ever appeared. We focus on the images sent by the Cassini spacecraft mission: slide #42 "Mapping Clumps in Saturn's Rings" and slide #54 "Scattered Sunshine". Using the box-counting method, we determine the fractal dimension of rings seen here (and in several other images from the same source) to be consistently about 1.6~1.7. This...

  7. A new storage-ring light source

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Alex [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-06-01

    A recently proposed technique in storage ring accelerators is applied to provide potential high-power sources of photon radiation. The technique is based on the steady-state microbunching (SSMB) mechanism. As examples of this application, one may consider a high-power DUV photon source for research in atomic and molecular physics or a high-power EUV radiation source for industrial lithography. A less challenging proof-of-principle test to produce IR radiation using an existing storage ring is also considered.

  8. Ringed Seal Distribution Map

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains GIS layers that depict the known spatial distributions (i.e., ranges) of the five subspecies of ringed seals (Phoca hispida). It was produced...

  9. Remotely operated locking ring

    International Nuclear Information System (INIS)

    A ring for fastening tubes with conical ends with only one manipulator is described. It is opened by compression of a spring with the manipulator grip, placed on the tubes to fasten, closed by releasing the pressure and locked

  10. The g-2 ring

    CERN Multimedia

    1974-01-01

    The precise measurement of "g-2", the anomalous magnetic moment of the muon, required a special muon storage ring with electrostatic focussing and very accurate knowledge of the magnetic bending field. For more details see under photo 7405430.

  11. Storage Ring EDM Experiments

    Science.gov (United States)

    Semertzidis, Yannis K.

    2016-04-01

    Dedicated storage ring electric dipole moment (EDM) methods show great promise advancing the sensitivity level by a couple orders of magnitude over currently planned hadronic EDM experiments. We describe the present status and recent updates of the field.

  12. Child sex rings.

    OpenAIRE

    Wild, N J; Wynne, J M

    1986-01-01

    Details of 11 child sex rings identified in one working class community were obtained by interviewing investigating police officers and examining health and social services records. The rings contained 14 adult male perpetrators and 175 children aged 6-15 years. Most perpetrators used child ringleaders to recruit victims; others became a "family friend" or obtained a position of authority over children. Secrecy was encouraged and bribery, threats, and peer pressure used to induce participatio...

  13. The Cryogenic Storage Ring CSR

    CERN Document Server

    von Hahn, Robert; Berg, Felix; Blaum, Klaus; Breitenfeldt, Christian; Fadil, Hisham; Fellenberger, Florian; Froese, Michael; George, Sebastian; Göck, Jürgen; Grieser, Manfred; Grussie, Florian; Guerin, Elisabeth A; Heber, Oded; Herwig, Philipp; Karthein, Jonas; Krantz, Claude; Kreckel, Holger; Lange, Michael; Laux, Felix; Lohmann, Svenja; Menk, Sebastian; Meyer, Christian; Mishra, Preeti M; Novotný, Oldřich; Connor, Aodh P O; Orlov, Dmitry A; Rappaport, Michael L; Repnow, Roland; Saurabh, Sunny; Schippers, Stefan; Schröter, Claus Dieter; Schwalm, Dirk; Schweikhard, Lutz; Sieber, Thomas; Shornikov, Andrey; Spruck, Kaija; Kumar, Sudhakaran Sunil; Ullrich, Joachim; Urbain, Xavier; Vogel, Stephen; Wilhelm, Patrick; Wolf, Andreas; Zajfman, Daniel

    2016-01-01

    An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 $\\pm$ 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion) and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas den...

  14. Ringed accretion disks: equilibrium configurations

    CERN Document Server

    Pugliese, D

    2015-01-01

    We investigate a model of ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the General Relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can be then determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We pr...

  15. Saturn's Other Ring Current

    Science.gov (United States)

    Crary, F. J.

    2014-04-01

    Saturn's main rings orbit the planet within an atmosphere and ionosphere of water, oxygen and hydrogen, produced by meteoritic impacts on and ultraviolet photodesorbtion of the ring particles [Johnson et al., 2006; Luhmann et al., 2006; Tseng et al., 2010]. The neutral atmosphere itself has only been tentatively detected through ultraviolet fluorescents of OH [Hall et al., 1996] while the ionosphere was observed in situ by the Cassini spacecraft shortly after orbital insertion [Coates et al.,2005; Tokar et al. 2005, Waite et al. 2005]. Although the plasma flow velocity of this ionosphere is not well-constrained, but the close association with the rings suggests that its speed would be couppled to the keplarian velocity of the rings themselves. As a result, the motion of the plasma through Saturn's magnetic field would produce an induced voltage, oriented away from the planet outside synchronous orbit and towards the planet inside synchronous orbit. Such a potential could result in currents flowing across the ring plane and closeing along magnetic field lines and through Saturn's ionosphere at latitudes between 36o and 48o. Cassini observations of whistler-mode plasma wave emissions [Xin et al.,2006] centered on synchronous orbit (1.76 Rs, mapping to 41o latitude) have been interpreted as a product of field-aligned electron beams associated with such a current. This presentation will investigate the magnitude of these currents and the resulting Joule heating of the ionosphere. An important constraint is that no auroral ultraviolet emissions have been observed at the relevant latitudes. In contrast, Joule heating could affect infrared emissions from H3+. Variations in H3+ emission associated with Saturn's rings have been reported by O'Donoghue et al., 2013, and interpreted as a result of ring "rain", i.e. precipitating water group species from the rings which alter ionosphereic chemistry and H3+ densities. As noted by O'Donoghue et al., this interpretation may be

  16. Electronic Aromaticity Index for Large Rings

    CERN Document Server

    Matito, Eduard

    2015-01-01

    We introduce a new electronic aromaticity index, AV1245, consisting in the average of the 4-center MCI values along the ring that keep a positional relationship of 1,2,4,5. AV1245 measures the extent of transferability of the delocalized electrons between bonds 1-2 and 4-5, which is expected to be large in conjugated circuits and, therefore, in aromatic molecules. A new algorithm for the calculation of MCI for large rings is also introduced and used to produce the data for the calibration of the new aromaticity index. AV1245 does not rely on reference values, does not suffer from large numerical precision errors, and it does not present any limitation on the nature of atoms, the molecular geometry or the level of calculation. It is a size-extensive measure with a small computational cost that grows linearly with the number of ring members. Therefore, it is specially suitable to study the aromaticity of large molecular rings as those occurring in belt-shaped M\\"obius structures or porphyrins.

  17. Physics of planetary rings

    Science.gov (United States)

    Gorkavyi, N.

    2007-08-01

    It is difficult to enumerate all the surprises presented by the planetary rings. The Saturnian rings are stratified into thousands of ringlets and the Uranian rings are compressed into narrow streams, which for some reason or other differ from circular orbits like the wheel of an old bicycle. The edge of the rings is jagged and the rings themselves are pegged down under the gravitational pressure of the satellites, bending like a ship's wake. There are spiral waves, elliptical rings, strange interlacing of narrow ringlets, and to cap it all one has observed in the Neptunian ring system three dense, bright arcs - like bunches of sausages on a transparent string. For celestial mechanics this is a spectacle as unnatural as a bear's tooth in the necklace of the English queen. In the dynamics of planetary rings the physics of collective interaction was supplemented by taking collisions between particles into account. One was led to study a kinetic equation with a rather complex collision integral - because the collisions are inelastic - which later on made it possible, both by using the Chapman-Enskog method and by using the solution of the kinetic equation for a plasma in a magnetic field, to reduce it to a closed set of (hydrodynamical) moment equations [1]. The hydrodynamical instabilities lead to the growth of short-wavelength waves and large-scale structures of the Saturnian rings [1]. We have shown that the formation of the existing dense Uranian rings is connected with the capture of positively drifting ring particles in inner Lindblad resonances which arrest this drift [1]. After the formation of dense rings at the positions of satellite resonances the collective interaction between resonant particles is amplified and the rings can leave the resonance and drift away from the planet and the parent resonance. We can expect in the C ring an appreciable positive ballistic particle drift caused by the erosion of the B ring by micrometeorites. It is therefore natural

  18. Spontaneous actin dynamics in contractile rings

    Science.gov (United States)

    Kruse, Karsten; Wollrab, Viktoria; Thiagarajan, Raghavan; Wald, Anne; Riveline, Daniel

    Networks of polymerizing actin filaments are known to be capable to self-organize into a variety of structures. For example, spontaneous actin polymerization waves have been observed in living cells in a number of circumstances, notably, in crawling neutrophils and slime molds. During later stages of cell division, they can also spontaneously form a contractile ring that will eventually cleave the cell into two daughter cells. We present a framework for describing networks of polymerizing actin filaments, where assembly is regulated by various proteins. It can also include the effects of molecular motors. We show that the molecular processes driven by these proteins can generate various structures that have been observed in contractile rings of fission yeast and mammalian cells. We discuss a possible functional role of each of these patterns. The work was supported by Agence Nationale de la Recherche, France, (ANR-10-LABX-0030-INRT) and by Deutsche Forschungsgemeinschaft through SFB1027.

  19. Rings dominate western Gulf

    Science.gov (United States)

    Vidal L., Francisco V.; Vidal L., Victor M. V.; Molero, José María Pérez

    Surface and deep circulation of the central and western Gulf of Mexico is controlled by interactions of rings of water pinched from the gulf's Loop Current. The discovery was made by Mexican oceanographers who are preparing a full-color, 8-volume oceanographic atlas of the gulf.Anticyclonic warm-core rings pinch off the Loop Current at a rate of about one to two per year, the scientists of the Grupo de Estudios Oceanográficos of the Instituto de Investigaciones Eléctricas (GEO-IIE) found. The rings migrate west until they collide with the continental shelf break of the western gulf, almost always between 22° and 23°N latitude. On their westward travel they transfer angular momentum and vorticity to the surrounding water, generating cyclonic circulations and vortex pairs that completely dominate the entire surface and deep circulation of the central and western gulf.

  20. Oligomeric ferrocene rings

    Science.gov (United States)

    Inkpen, Michael S.; Scheerer, Stefan; Linseis, Michael; White, Andrew J. P.; Winter, Rainer F.; Albrecht, Tim; Long, Nicholas J.

    2016-09-01

    Cyclic oligomers comprising strongly interacting redox-active monomer units represent an unknown, yet highly desirable class of nanoscale materials. Here we describe the synthesis and properties of the first family of molecules belonging to this compound category—differently sized rings comprising only 1,1‧-disubstituted ferrocene units (cyclo[n], n = 5–7, 9). Due to the close proximity and connectivity of centres (covalent Cp–Cp linkages; Cp = cyclopentadienyl) solution voltammograms exhibit well-resolved, separated 1e– waves. Theoretical interrogations into correlations based on ring size and charge state are facilitated using values of the equilibrium potentials of these transitions, as well as their relative spacing. As the interaction free energies between the redox centres scale linearly with overall ring charge and in conjunction with fast intramolecular electron transfer (∼107 s‑1), these molecules can be considered as uniformly charged nanorings (diameter ∼1–2 nm).

  1. Decay ring design

    CERN Document Server

    Chancé, A; Bouquerel, E; Hancock, S; Jensen, E

    The study of the neutrino oscillation between its different flavours needs pureand very intense fluxes of high energy, well collimated neutrinos with a welldetermined energy spectrum. A dedicated machine seems to be necessarynowadays to reach the required flux. A new concept based on the β-decayof radioactive ions which were accelerated in an accelerator chain was thenproposed. After ion production, stripping, bunching and acceleration, the unstableions are then stored in a racetrack-shaped superconducting decay ring.Finally, the ions are accumulated in the decay ring until being lost. The incomingbeam is merged to the stored beam by using a specific RF system, whichwill be presented here.We propose here to study some aspects of the decay ring, such as its opticalproperties, its RF system or the management of the losses which occur in thering (mainly by decay or by collimation).

  2. On Simple Noetherian Rings

    Institute of Scientific and Technical Information of China (English)

    Somyot Plubtieng

    2003-01-01

    A module M is called a CS-module (or extending module [5]) if every submodule of M is essential in a direct summand of M. It is shown that (i) a simple ring R is right noetherian if and only if every cyclic singular right R-module is either a CS-module or a noetherian module; (ii) for a prime ring R, if every proper cyclic right R-module is a direct sum of a quasi-injective module and a finitely cogenerated module, then R is either semisimple artinian or a right Ore domain; and (iii) a prime ring R is right noetherian if and only if every cyclic right R-module is a direct sum of a quasi-injective module and a noetherian module.

  3. Tunneling Through Black Rings

    Institute of Scientific and Technical Information of China (English)

    ZHAO Liu

    2007-01-01

    Hawking radiation of black ring solutions to 5-dimensional Einstein-Maxwell-dilaton theory is analyzed by use of the Parikh-Wilczek tunneling method. To get the correct tunneling amplitude and emission rate, we adopt and develop the Angheben-Nadalini-Vanzo-Zerbini covariant approach to cover the effects of rotation and electronic discharge all at once, and the effect of back reaction is also taken into account. This constitutes a unified approach to the tunneling problem. Provided the first law of thermodynamics for black rings holds, the emission rate is proportional to the exponential of the change of Bekenstein-Hawking entropy. Explicit calculation for black ring temperatures agrees exactly with the results obtained via the classical surface gravity method and the quasi-local formalism.

  4. Autocatalytic chemical smoke rings

    CERN Document Server

    Rogers, M C; Rogers, Michael C.; Morris, Stephen W.

    2005-01-01

    Buoyant plumes, evolving free of boundary constraints, may develop well-defined mushroom shaped heads. In normal plumes, overturning flow in the head entrains less buoyant fluid from the surroundings as the head rises, robbing the plume of its driving force. We consider here a new type of plume in which the source of buoyancy is an autocatalytic chemical reaction. The reaction occurs at a sharp front which separates reactants from less dense products. In this type of plume, entrainment assists the reaction, producing new buoyancy which fuels an accelerating plume head. When the head has grown to a critical size, it detaches from the upwelling conduit, forming an accelerating, buoyant vortex ring. This vortex is analogous to a rising smoke ring. A second-generation head then develops at the point of detachment.Multiple generations of chemical vortex rings can detach from a single triggering event.

  5. Almost ring theory

    CERN Document Server

    2003-01-01

    This book develops thorough and complete foundations for the method of almost etale extensions, which is at the basis of Faltings' approach to p-adic Hodge theory. The central notion is that of an "almost ring". Almost rings are the commutative unitary monoids in a tensor category obtained as a quotient V-Mod/S of the category V-Mod of modules over a fixed ring V; the subcategory S consists of all modules annihilated by a fixed ideal m of V, satisfying certain natural conditions. The reader is assumed to be familiar with general categorical notions, some basic commutative algebra and some advanced homological algebra (derived categories, simplicial methods). Apart from these general prerequisites, the text is as self-contained as possible. One novel feature of the book - compared with Faltings' earlier treatment - is the systematic exploitation of the cotangent complex, especially for the study of deformations of almost algebras.

  6. Den mindst ringe verdensorden

    DEFF Research Database (Denmark)

    Hansen, Birthe

    2015-01-01

    I 25 år har USA's styrkeposition og politik forsynet os med en 'verdensorden', der i et historisk perspektiv fremstår som den mindst ringe: fravær af store krige, mere demokrati, økonomisk fremgang - men dog også sammenbrudte stater og terrorisme.......I 25 år har USA's styrkeposition og politik forsynet os med en 'verdensorden', der i et historisk perspektiv fremstår som den mindst ringe: fravær af store krige, mere demokrati, økonomisk fremgang - men dog også sammenbrudte stater og terrorisme....

  7. On toric face rings

    OpenAIRE

    Ichim, Bogdan; Roemer, Tim

    2006-01-01

    Following a construction of Stanley we consider toric face rings associated to rational pointed fans. This class of rings is a common generalization of the concepts of Stanley--Reisner and affine monoid algebras. The main goal of this article is to unify parts of the theories of Stanley--Reisner- and affine monoid algebras. We consider (non-pure) shellable fan's and the Cohen--Macaulay property. Moreover, we study the local cohomology, the canonical module and the Gorenstein property of a tor...

  8. Ringed accretion disks: instabilities

    CERN Document Server

    Pugliese, D

    2016-01-01

    We analyze the possibility that several instability points may be formed, due to the Paczy\\'nski mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider recently proposed model of ringed accretion disk, made up by several tori (rings) which can be corotating or counterrotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

  9. Unidirectional ring lasers

    Science.gov (United States)

    Hohimer, J.P.; Craft, D.C.

    1994-09-20

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity is disclosed. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction. 21 figs.

  10. The covariant chiral ring

    Science.gov (United States)

    Bourget, Antoine; Troost, Jan

    2016-03-01

    We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N = (4 , 4) supersymmetry in two dimensions. For seed target spaces K3 and T 4, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.

  11. The Covariant Chiral Ring

    CERN Document Server

    Bourget, Antoine

    2015-01-01

    We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N=(4,4) supersymmetry in two dimensions. For seed target spaces K3 and T4, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.

  12. Electrothermal Ring Burn

    OpenAIRE

    Yakup Çil; Hamza Yıldız; Özlem Karabudak Abuaf

    2012-01-01

    Low-voltage fountainheads such as car, tractor or motorcycle batteries are predisposed to produce large currents. Any metal object that comes into contact with these batteries may result in short-circuit. This may result in rapid and excessive heating of metal object and an electrothermal burn. Herein we presented a motorcycle driver who was 28-year-old man with electrothermal ring burn which was caused by metal chain that was used as a ring. (Turk J Dermatol 2012; 6: 106-7)

  13. Electrothermal Ring Burn

    Directory of Open Access Journals (Sweden)

    Yakup Çil

    2012-09-01

    Full Text Available Low-voltage fountainheads such as car, tractor or motorcycle batteries are predisposed to produce large currents. Any metal object that comes into contact with these batteries may result in short-circuit. This may result in rapid and excessive heating of metal object and an electrothermal burn. Herein we presented a motorcycle driver who was 28-year-old man with electrothermal ring burn which was caused by metal chain that was used as a ring. (Turk J Dermatol 2012; 6: 106-7

  14. Flushing Ring for EDM

    Science.gov (United States)

    Earwood, L.

    1985-01-01

    Removing debris more quickly lowers cutting time. Operation, cutting oil and pressurized air supplied to ring placed around workpiece. Air forces oil through small holes and agitates oil as it flows over workpiece. High flow rate and agitation dislodge and remove debris. Electrical discharge removes material from workpiece faster.

  15. A dissected ring current model for assessing magnetic aromaticity: a general approach for both organic and inorganic rings.

    Science.gov (United States)

    Foroutan-Nejad, Cina; Shahbazian, Shant; Feixas, Ferran; Rashidi-Ranjbar, Parviz; Solà, Miquel

    2011-08-01

    A model based on classical electrodynamics is used to measure the strength of ring currents of different molecular orbitals, i.e., σ- and π-orbitals, and characteristics of ring current loops, i.e., ring current radii and height of current loops above/below the ring planes, among a number of organic as well as inorganic molecules. For the π-current, the present model represents an improvement of previous approaches to determine ring current intensity. It is proven that the present model is more precise than previous models as they could not explain presence of the minimum in the plot of NICS(πzz) versus distance close to the ring plane. Variations in the charge of molecules and the types of constituent atoms of each species affect the ring current radii of both σ- and π-current loops as well as the height of π-current loops above/below the ring plane. It is suggested that variation in the distribution of the one-electron density in different systems is the main source of differences of the ring current characteristics. PMID:21598277

  16. Fusion Rings for Quantum Groups

    DEFF Research Database (Denmark)

    Andersen, Henning Haahr; Stroppel, Catharina

    2012-01-01

    We study the fusion rings of tilting modules for a quantum group at a root of unity modulo the tensor ideal of negligible tilting modules. We identify them in type A with the combinatorial rings from [12] and give a similar description of the sp2n-fusion ring in terms of noncommutative symmetric...... functions. Moreover we give a presentation of all fusion rings in classical types as quotients of polynomial rings. Finally we also compute the fu- sion rings for type G2....

  17. Fusion rings and fusion ideals

    DEFF Research Database (Denmark)

    Andersen, Troels Bak

    This dissertation investigates fusion rings, which are Grothendieck groups of rigid, monoidal, semisimple, abelian categories. Special interest is in rational fusion rings, i.e., fusion rings which admit a finite basis, for as commutative rings they may be presented as quotients of polynomial rings...... by the so-called fusion ideals. The fusion rings of Wess-Zumino-Witten models have been widely studied and are well understood in terms of precise combinatorial descriptions and explicit generating sets of the fusion ideals. They also appear in another, more general, setting via tilting modules for quantum...

  18. Rings from Close Encounters

    Science.gov (United States)

    Kohler, Susanna

    2016-09-01

    Weve recently discovered narrow sets of rings around two minor planets orbiting in our solar system. How did these rings form? A new study shows that they could be a result of close encounters between the minor planets and giants like Jupiter or Neptune.Unexpected Ring SystemsPositions of the centaurs in our solar system (green). Giant planets (red), Jupiter trojans (grey), scattered disk objects (tan) and Kuiper belt objects (blue) are also shown. [WilyD]Centaurs are minor planets in our solar system that orbit between Jupiter and Neptune. These bodies of which there are roughly 44,000 with diameters larger than 1 km have dynamically unstable orbits that cross paths with those of one or more giant planets.Recent occultation observations of two centaurs, 10199 Chariklo and 2060 Chiron, revealed that these bodies both host narrow ring systems. Besides our four giant planets, Chariklo and Chiron are the only other bodies in the solar system known to have rings. But how did these rings form?Scientists have proposed several models, implicating collisions, disruption of a primordial satellite, or dusty outgassing. But a team of scientists led by Ryuki Hyodo (Paris Institute of Earth Physics, Kobe University) has recently proposed an alternative scenario: what if the rings were formed from partial disruption of the centaur itself, after it crossed just a little too close to a giant planet?Tidal Forces from a GiantHyodo and collaborators first used past studies of centaur orbits to estimate that roughly 10% of centaurs experience close encounters (passing within a distance of ~2x the planetary radius) with a giant planet during their million-year lifetime. The team then performed a series of simulations of close encounters between a giant planet and a differentiated centaur a body in which the rocky material has sunk to form a dense silicate core, surrounded by an icy mantle.Some snapshots of simulation outcomes (click for a closer look!) for different initial states of

  19. e-læring

    DEFF Research Database (Denmark)

    Helms, Niels Henrik

    e-læring kan defineres på ganske mange måder. Ordet e-læring består jo tydeligt nok af to elementer. E + læring ligesom e-handel eller e-banking, og umiddelbart vil de fleste nok sige, at det så handler om læring vha. internettet. I bidraget advokeres for en læringsmæssig frem for normativ tilgang....

  20. The Black Ring is Unstable

    CERN Document Server

    Santos, Jorge E

    2015-01-01

    We study non-axisymmetric linearised gravitational perturbations of the Emparan-Reall black ring using numerical methods. We find an unstable mode whose onset lies within the "fat" branch of the black ring and continues into the "thin" branch. Together with previous results using Penrose inequalities that fat black rings are unstable, this provides numerical evidence that the entire black ring family is unstable.

  1. RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

    2015-12-15

    We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

  2. DC-Powered Jumping Ring

    Science.gov (United States)

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  3. Fusion Rings for Quantum Groups

    DEFF Research Database (Denmark)

    Andersen, Henning Haahr; Stroppel, Catharina

    2014-01-01

    We study the fusion rings of tilting modules for a quantum group at a root of unity modulo the tensor ideal of negligible tilting modules. We identify them in type A with the combinatorial rings from Korff, C., Stroppel, C.: The sl(ˆn)k-WZNW fusion ring: a combinato-rial construction and a realis...

  4. Torsion units in group rings

    OpenAIRE

    Bist, Vikas

    1992-01-01

    Let U(RG) be the unit group of the group ring RG. In this paper we study group rings RG whose support elements of every torsion unit are torsion, where R is either the ring of integers Z or a field K.

  5. Hexagonal graphene onion rings.

    Science.gov (United States)

    Yan, Zheng; Liu, Yuanyue; Lin, Jian; Peng, Zhiwei; Wang, Gunuk; Pembroke, Elvira; Zhou, Haiqing; Xiang, Changsheng; Raji, Abdul-Rahman O; Samuel, Errol L G; Yu, Ting; Yakobson, Boris I; Tour, James M

    2013-07-24

    Precise spatial control of materials is the key capability of engineering their optical, electronic, and mechanical properties. However, growth of graphene on Cu was revealed to be seed-induced two-dimensional (2D) growth, limiting the synthesis of complex graphene spatial structures. In this research, we report the growth of onion ring like three-dimensional (3D) graphene structures, which are comprised of concentric one-dimensional hexagonal graphene ribbon rings grown under 2D single-crystal monolayer graphene domains. The ring formation arises from the hydrogenation-induced edge nucleation and 3D growth of a new graphene layer on the edge and under the previous one, as supported by first principles calculations. This work reveals a new graphene-nucleation mechanism and could also offer impetus for the design of new 3D spatial structures of graphene or other 2D layered materials. Additionally, in this research, two special features of this new 3D graphene structure were demonstrated, including nanoribbon fabrication and potential use in lithium storage upon scaling. PMID:23815279

  6. Uranus rings and two moons

    Science.gov (United States)

    1986-01-01

    Voyager 2 has discovered two 'shepherd' satellites associated with the rings of Uranus. The two moons -- designated 1986U7 and 1986U8 -- are seen here on either side of the bright epsilon ring; all nine of the known Uranian rings are visible. The image was taken Jan. 21, 1986, at a distance of 4.1 million kilometers (2.5 million miles) and resolution of about 36 km (22 mi). The image was processed to enhance narrow features. The epsilon ring appears surrounded by a dark halo as a result of this processing; occasional blips seen on the ring are also artifacts. Lying inward from the epsilon ring are the delta, gamma and eta rings; then the beta and alpha rings; and finally the barely visible 4, 5 and 6 rings. The rings have been studied since their discovery in 1977, through observations of how they diminish the light of stars they pass in front of. This image is the first direct observation of all nine rings in reflected sunlight. They range in width from about 100 km (60 mi) at the widest part of the epsilon ring to only a few kilometers for most of the others. The discovery of the two ring moons 1986U7 and 1986U8 is a major advance in our understanding of the structure of the Uranian rings and is in good agreement with theoretical predictions of how these narrow rings are kept from spreading out. Based on likely surface brightness properties, the moons are of roughly 2O- and 3O-km diameter, respectively. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.

  7. Self-replication of DNA rings

    Science.gov (United States)

    Kim, Junghoon; Lee, Junwye; Hamada, Shogo; Murata, Satoshi; Ha Park, Sung

    2015-06-01

    Biology provides numerous examples of self-replicating machines, but artificially engineering such complex systems remains a formidable challenge. In particular, although simple artificial self-replicating systems including wooden blocks, magnetic systems, modular robots and synthetic molecular systems have been devised, such kinematic self-replicators are rare compared with examples of theoretical cellular self-replication. One of the principal reasons for this is the amount of complexity that arises when you try to incorporate self-replication into a physical medium. In this regard, DNA is a prime candidate material for constructing self-replicating systems due to its ability to self-assemble through molecular recognition. Here, we show that DNA T-motifs, which self-assemble into ring structures, can be designed to self-replicate through toehold-mediated strand displacement reactions. The inherent design of these rings allows the population dynamics of the systems to be controlled. We also analyse the replication scheme within a universal framework of self-replication and derive a quantitative metric of the self-replicability of the rings.

  8. Magnetic fields in ring galaxies

    CERN Document Server

    Moss, D; Silchenko, O; Sokoloff, D; Horellou, C; Beck, R

    2016-01-01

    Many galaxies contain magnetic fields supported by galactic dynamo action. However, nothing definitive is known about magnetic fields in ring galaxies. Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. We use tested methods for modelling $\\alpha-\\Omega$ galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513 where th...

  9. The Rings Characterized by Minimal Left Ideals

    Institute of Scientific and Technical Information of China (English)

    Jun Chao WEI

    2005-01-01

    We study these rings with every minimal left ideal being a projective, direct summand and a p-injective module, respectively. Some characterizations of these rings are given, and the relations among them are obtained. With these rings, we characterize semisimple rings. Finally, we introduce MC2 rings, and give some characterizations of MC2 rings.

  10. Continuous ring furnaces

    Energy Technology Data Exchange (ETDEWEB)

    De Stefani, G.; Genevois, J.L.; Paolo, P.

    1981-01-06

    A smoke conducting apparatus for use particularly with continuous ring furnaces (e.g., Hoffman furnaces) wherein each furnace chamber is connected to the smoke channel, the latter being a metal pipe inclined slightly from horizontal and provided with one or more traps along the length of its bottom surface, each trap containing a removable receptacle, and heating means being disposed along the bottom of the channel to fluidize tarry deposits of combustion products so that such deposits will flow by gravity into the removable receptacle.

  11. The Structure of Saturn's Rings

    Science.gov (United States)

    Colwell, J. E.; Nicholson, P. D.; Tiscareno, M. S.; Murray, C. D.; French, R. G.; Marouf, E. A.

    Our understanding of the structure of Saturn's rings has evolved steadily since their discovery by Galileo Galilei in 1610. With each advance in observations of the rings over the last four centuries, new structure has been revealed, starting with the recognition that the rings are a disk by Huygens in 1656 through discoveries of the broad organization of the main rings and their constituent gaps and ringlets to Cassini observations that indirectly reveal individual clumps of particles tens of meters in size. The variety of structure is as broad as the range in scales. The main rings have distinct characteristics on a spatial scale of 104 km that suggest dramatically different evolution and perhaps even different origins. On smaller scales, the A and C ring and Cassini Division are punctuated by gaps from tens to hundreds of kilometer across, while the B ring is littered with unexplained variations in optical depth on similar scales. Moons are intimately involved with much of the structure in the rings. The outer edges of the A and B rings are shepherded and sculpted by resonances with the Janus—Epimetheus coorbitals and Mimas, respectively. Density waves at the locations of orbital resonances with nearby and embedded moons make up the majority of large-scale features in the A ring. Moons orbiting within the Encke and Keeler gaps in the A ring create those gaps and produce wakes in the nearby ring. Other gaps and wave-like features await explanation. The largest ring particles, while not massive enough to clear a gap, produce localized propeller-shaped disturbances hundreds of meters long. Particles throughout the A and B rings cluster into strands or self-gravity wakes tens of meters across that are in equilibrium between gravitational accretion and Keplerian shear. In the peaks of strong density waves particles pile together in a cosmic traffic jam that results in kilometer-long strands that may be larger versions of self-gravity wakes. The F ring is a showcase

  12. Viscosity of ring polymer melts

    KAUST Repository

    Pasquino, Rossana

    2013-10-15

    We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

  13. Chromosomal breakpoints characterization of two supernumerary ring chromosomes 20.

    Science.gov (United States)

    Guediche, N; Brisset, S; Benichou, J-J; Guérin, N; Mabboux, P; Maurin, M-L; Bas, C; Laroudie, M; Picone, O; Goldszmidt, D; Prévot, S; Labrune, P; Tachdjian, G

    2010-02-01

    The occurrence of an additional ring chromosome 20 is a rare chromosome abnormality, and no common phenotype has been yet described. We report on two new patients presenting with a supernumerary ring chromosome 20 both prenatally diagnosed. The first presented with intrauterine growth retardation and some craniofacial dysmorphism, and the second case had a normal phenotype except for obesity. Conventional cytogenetic studies showed for each patient a small supernumerary marker chromosome (SMC). Using fluorescence in situ hybridization, these SMCs corresponded to ring chromosomes 20 including a part of short and long arms of chromosome 20. Detailed molecular cytogenetic characterization showed different breakpoints (20p11.23 and 20q11.23 for Patient 1 and 20p11.21 and 20q11.21 for Patient 2) and sizes of the two ring chromosomes 20 (13.6 Mb for case 1 and 4.8 Mb for case 2). Review of the 13 case reports of an extra r(20) ascertained postnatally (8 cases) and prenatally (5 cases) showed varying degrees of phenotypic abnormalities. We document a detailed molecular cytogenetic chromosomal breakpoints characterization of two cases of supernumerary ring chromosomes 20. These results emphasize the need to characterize precisely chromosomal breakpoints of supernumerary ring chromosomes 20 in order to establish genotype-phenotype correlation. This report may be helpful for prediction of natural history and outcome, particularly in prenatal diagnosis.

  14. The cryogenic storage ring project

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Robert von; Blaum, Klaus; Becker, Arno; Fellenberger, Florian; George, Sebastian; Grieser, Manfred; Grussie, Florian; Herwig, Philipp; Krantz, Claude; Kreckel, Holger; Lange, Michael; Menk, Sebastian; Repnow, Roland; Vogel, Stephen; Wolf, Andreas [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Spruck, Kaija [Justus-Liebig-Universitaet, Giessen (Germany)

    2014-07-01

    At MPIK the electrostatic cryogenic storage ring CSR is nearing completion. At beam energies of 20 to 300 keV per charge unit and 35 m circumference the CSR will allow experiments in a cryogenic environment providing conditions of extremely low vacuum and heat radiation. By using liquid helium at 2 K for cryopumping, the projected vacuum (confirmed at a prototype) lies at 1E-13 mbar or below, ensuring long storage times for slow singly charged and highly charged ions, molecules and clusters. Moreover, phase space cooling by electrons will be implemented. The internal quantum states of molecular and cluster ions can be cooled to low temperature, yielding well defined vibrational and for smaller systems also rotational structures. In the CSR construction, the cryogenic ion beam vacuum system has been set up. Extensive tests confirming the criteria on heat flow, alignment and high-voltage stability were successfully completed on the first quadrant. In addition beam diagnostic units for electric pickup signals and spatial profiles, detectors for neutral and charged fragments, the injection beam line, and an electron cooling device are under construction.

  15. Shock accelerated vortex ring

    CERN Document Server

    Haehn, N; Oakley, J; Anderson, M; Rothamer, D; Bonazza, R

    2009-01-01

    The interaction of a shock wave with a spherical density inhomogeneity leads to the development of a vortex ring through the impulsive deposition of baroclinic vorticity. The present fluid dynamics videos display this phenomenon and were experimentally investigated at the Wisconsin Shock Tube Laboratory's (WiSTL) 9.2 m, downward firing shock tube. The tube has a square internal cross-section (0.25 m x 0.25 m) with multiple fused silica windows for optical access. The spherical soap bubble is generated by means of a pneumatically retracted injector and released into free-fall 200 ms prior to initial shock acceleration. The downward moving, M = 2.07 shock wave impulsively accelerates the bubble and reflects off the tube end wall. The reflected shock wave re-accelerates the bubble (reshock), which has now developed into a vortex ring, depositing additional vorticity. In the absence of any flow disturbances, the flow behind the reflected shock wave is stationary. As a result, any observed motion of the vortex rin...

  16. Ring Image Analyzer

    Science.gov (United States)

    Strekalov, Dmitry V.

    2012-01-01

    Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

  17. Buoyant Norbury's vortex rings

    Science.gov (United States)

    Blyth, Mark; Rodriguez-Rodriguez, Javier; Salman, Hayder

    2014-11-01

    Norbury's vortices are a one-parameter family of axisymmetric vortex rings that are exact solutions to the Euler equations. Due to their relative simplicity, they are extensively used to model the behavior of real vortex rings found in experiments and in Nature. In this work, we extend the original formulation of the problem to include buoyancy effects for the case where the fluid that lies within the vortex has a different density to that of the ambient. In this modified formulation, buoyancy effects enter the problem through the baroclinic term of the vorticity equation. This permits an efficient numerical solution of the governing equation of motion in terms of a vortex contour method that tracks the evolution of the boundary of the vortex. Finally, we compare our numerical results with the theoretical analysis of the short-time evolution of a buoyant vortex. Funded by the Spanish Ministry of Economy and Competitiveness through grant DPI2011-28356-C03-02 and by the London Mathematical Society.

  18. n-X-Coherent Rings

    CERN Document Server

    Bennis, Driss

    2010-01-01

    This paper unifies several generalizations of coherent rings in one notion. Namely, we introduce $n$-$\\mathscr{X}$-coherent rings, where $\\mathscr{X}$ is a class of modules and $n$ is a positive integer, as those rings for which the subclass $\\mathscr{X}_n$ of $n$-presented modules of $\\mathscr{X}$ is not empty, and every module in $\\mathscr{X}_n$ is $n+1$-presented. Then, for each particular class $\\mathscr{X}$ of modules, we find correspondent relative coherent rings. Our main aim is to show that the well-known Chase's, Cheatham and Stone's, Enochs', and Stenstrom's characterizations of coherent rings hold true for any $n$-$\\mathscr{X}$-coherent rings.

  19. On thickness of Saturn rings

    International Nuclear Information System (INIS)

    Electronographic plates of Saturn were taken during the transit of the Earth through the ring plane. Observing conditions were more favorable than those prevailing in 1966. Thanks to the quality of the detectors and the telescopes, it has been possible to make a more precise photometric determination of the brightness of the ring seen edge on and to measure the brightness variation with respect to the distance to the center of the planet. Extrapolating to the case where the elevation of the Earth above the ring plane is strictly zero, we deduce an apparent photometric ring thickness equal to 1.5+-0.3 km. For an homogeneous layer of small particles colliding inelastically, theory predicts a thickness of the order of a few particles radii, i.e. a few tens of meters. The observed brightness could be explained by the E ring, the brightness of large chunks, condensations and warping of the ring

  20. Burnside Rings of Fusion Systems

    DEFF Research Database (Denmark)

    Reeh, Sune Precht

    , and we produce a basis for the Burnside ring that shares properties with the transitive sets for a finite group. We construct a transfer map from the p-local Burnside ring of the underlying p-group S to the p-local Burnside ring of F. Using such transfer maps, we give a new explicit construction...... of Burnside rings given by multiplication with the characteristic idempotent, and we show that this map is the transfer map previously constructed. Applying these results, we show that for every saturated fusion system the ring generated by all (non-idempotent) characteristic elements in the p-local double...... of the characteristic idempotent of F { the unique idempotent in the p-local double Burnside ring of S satisfying properties of Linckelmann and Webb. We describe this idempotent both in terms of fixed points and as a linear combination of transitive bisets. Additionally, using fixed points we determine the map...

  1. SPOTS: The Search for Planets Orbiting Two Stars. II. First constraints on the frequency of sub-stellar companions on wide circumbinary orbits

    Science.gov (United States)

    Bonavita, M.; Desidera, S.; Thalmann, C.; Janson, M.; Vigan, A.; Chauvin, G.; Lannier, J.

    2016-09-01

    A large number of direct imaging surveys for exoplanets have been performed in recent years, yielding the first directly imaged planets and providing constraints on the prevalence and distribution of wide planetary systems. However, like most of the radial velocity ones, these generally focus on single stars, hence binaries and higher-order multiples have not been studied to the same level of scrutiny. This motivated the Search for Planets Orbiting Two Stars (SPOTS) survey, which is an ongoing direct imaging study of a large sample of close binaries, started with VLT/NACO and now continuing with VLT/SPHERE. To complement this survey, we have identified the close binary targets in 24 published direct imaging surveys. Here we present our statistical analysis of this combined body of data. We analysed a sample of 117 tight binary systems, using a combined Monte Carlo and Bayesian approach to derive the expected values of the frequency of companions, for different values of the companion's semi-major axis. Our analysis suggest that the frequency of sub-stellar companions in wide orbit is moderately low (≲ 13% with a best value of 6% at 95% confidence level) and not significantly different between single stars and tight binaries. One implication of this result is that the very high frequency of circumbinary planets in wide orbits around post-common envelope binaries, implied by eclipse timing, cannot be uniquely due to planets formed before the common-envelope phase (first generation planets), supporting instead the second generation planet formation or a non-Keplerian origin of the timing variations.

  2. Sensitivity limits of continuous wave cavity ring-down spectroscopy.

    Science.gov (United States)

    Huang, Haifeng; Lehmann, Kevin K

    2013-12-19

    An optimized nonlinear least-squares fit algorithm for data processing in cavity ring-down spectroscopy (CRDS) is discussed, which improves the calculation efficiency substantially over using a general purpose fitting package. Theoretical absorption sensitivity limits for both the detector noise and the shot noise limited situations are derived and compared with experimental results. The effect of limiting the bandwidth of detection system on ring-down signal is discussed and compared with real ring-down data. The optimal trigger level and fitting interval are obtained for continuous wave cavity ring-down spectroscopy (cw-CRDS) in both the detector noise and shot noise limits, with the resulting sensitivity in units of cm(-1) per (Hz(1/2)) derived. Interestingly, it is found that the optimized shot noise limited sensitivity in cw-CRDS method is, in principle, comparable with the ultimate sensitivity of noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS). PMID:23978273

  3. Filtration on a Ring Make a Quasi Valuation or Valuation Ring

    OpenAIRE

    Mohammad Hassan Anjom SHoa

    2014-01-01

    In this paper we show that if R is a filtered ring then we can define a quasi valuation ring. And there exists a valuation ring if R is some kind of filtered ring. Then we prove some properties and relations between filtered ring and quasi valuation ring and valuation ring.

  4. Filtration on a Ring Make a Quasi Valuation or Valuation Ring

    OpenAIRE

    SHoa, Mohammad Hassan Anjom

    2014-01-01

    In this paper we show that if R is a filtered ring then we can define a quasi valuation ring. And there exists a valuation ring if R is some kind of filtered ring. Then we prove some properties and relations between filtered ring and quasi valuation ring and valuation ring

  5. Platinum-catalysed intravaginal rings

    OpenAIRE

    Malcolm, Karl; Woolfson, David; Romano, Joseph

    2012-01-01

    The present invention provides improved intravaginal drug delivery devices, i.e., intravaginal rings, useful for the prophylactic administration of an antimicrobial compound, e.g., Dapivirine, to a human. The intravaginal rings of the invention address previous stability issues by utilizing a platinum catalyst (e.g., in the form of a platinum-siloxane complex) for the cross-linking reaction. The vaginal rings surprisingly achieve relatively high and steady release rates in vivo with a matrix ...

  6. On g-Semisymmetric Rings

    OpenAIRE

    Farahat S. Aly; Al Mestady, Mohammed O.

    2012-01-01

    We introduce right (left) g-semisymmetric ring as a new concept to generalize the well-known concept: symmetric ring. Examples are given to show that these classes of rings are distinct. They coincide under some conditions. It is shown that R is bounded right g-semisymmetric with boundary 1 from right if and only if R is symmetric, whenever R is regular. It is shown that a ring R is strongly regular if and only if R is regular and bounded right g-semisymmetric with boundary 1 from right. For ...

  7. Topics in commutative ring theory

    CERN Document Server

    Watkins, John J

    2009-01-01

    Topics in Commutative Ring Theory is a textbook for advanced undergraduate students as well as graduate students and mathematicians seeking an accessible introduction to this fascinating area of abstract algebra. Commutative ring theory arose more than a century ago to address questions in geometry and number theory. A commutative ring is a set-such as the integers, complex numbers, or polynomials with real coefficients--with two operations, addition and multiplication. Starting from this simple definition, John Watkins guides readers from basic concepts to Noetherian rings-one of

  8. On Weakly P.P. Rings

    Institute of Scientific and Technical Information of China (English)

    Xiang Yue-ming; Ouyang Lun-qun; Wang Shu-gui

    2015-01-01

    We introduce, in this paper, the right weakly p.p. rings as the generaliza-tion of right p.p. rings. It is shown that many properties of the right p.p. rings can be extended onto the right weakly p.p. rings. Relative examples are constructed. As applications, we also characterize the regular rings and the semisimple rings in terms of the right weakly p.p. rings.

  9. The eRHIC Ring-Ring Collider Design

    CERN Document Server

    Wang, Fuhua; Beebe-Wang, Joanne; Deshpande, Abhay A; Farkhondeh, Manouchehr; Franklin, Wilbur; Graves, William; Litvinenko, Vladimir N; MacKay, William W; Milner, Richard; Montag, Christoph; Ozaki, Satoshi; Parker, Brett; Peggs, Steve; Ptitsyn, Vadim; Roser, Thomas; Tepikian, Steven; Trbojevic, Dejan; Tschalär, C; Wang, Dong; Zolfaghari, Abbasali; Zwart, Townsend; van der Laan, Jan

    2005-01-01

    The eRHIC ring-ring collider is the main design option of the future lepton-ion collider at Brookhaven National Laboratory. We report the revisions of the ring-ring collider design features to the baseline design presented in the eRHIC Zeroth Design Report (ZDR). These revisions have been made during the past year. They include changes of the interaction region which are required from the modifications in the design of the main detector. They also include changes in the lepton storage ring for high current operations as a result of better understandings of beam-beam interaction effects. The updated collider luminosity and beam parameters also take into account a more accurate picture of current and future operational aspects of RHIC.

  10. Magnetic fields in ring galaxies

    Science.gov (United States)

    Moss, D.; Mikhailov, E.; Silchenko, O.; Sokoloff, D.; Horellou, C.; Beck, R.

    2016-07-01

    Context. Many galaxies contain magnetic fields supported by galactic dynamo action. The investigation of these magnetic fields can be helpful for understanding galactic evolution; however, nothing definitive is known about magnetic fields in ring galaxies. Aims: Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. Methods: We use tested methods for modelling α-Ω galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Results: Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513, where the ring counter-rotates with respect to the disc. Strong shear in the region between the disc and the ring is associated with unusually strong dynamo drivers in such counter-rotators. The effect of the strong drivers is found to be unexpectedly moderate. With counter-rotation in the disc, a generic model shows that a steady mixed parity magnetic configuration that is unknown for classical spiral galaxies, may be excited, although we do not specifically model NGC 4513. Conclusions: We deduce that ring galaxies constitute a morphological class of galaxies in which identification of large-scale magnetic fields from observations of polarized radio emission, as well as dynamo modelling, may be possible. Such studies have the potential to throw additional light on the physical nature of rings, their lifetimes, and evolution.

  11. Optical line shapes of dynamically disordered ring aggregates

    NARCIS (Netherlands)

    Bakalis, LD; Coca, M; Knoester, J

    1999-01-01

    We study the absorption line shape caused by Frenkel excitons in one-dimensional ring-shaped molecular aggregates, such as circular light-harvesting systems, subjected to dynamic disorder with a finite correlation time. We focus on dichotomic noise and show that for arbitrary orientations of the mol

  12. A GAS GIANT CIRCUMBINARY PLANET TRANSITING THE F STAR PRIMARY OF THE ECLIPSING BINARY STAR KIC 4862625 AND THE INDEPENDENT DISCOVERY AND CHARACTERIZATION OF THE TWO TRANSITING PLANETS IN THE KEPLER-47 SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Kostov, V. B.; Tsvetanov, Z. I. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); McCullough, P. R.; Valenti, J. A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Hinse, T. C. [Korea Astronomy and Space Science Institute (KASI), Advanced Astronomy and Space Science Division, Daejeon 305-348 (Korea, Republic of); Hebrard, G. [Institut d' Astrophysique de Paris, UMR 7095 CNRS, Universite Pierre and Marie Curie, 98bis boulevard Arago, F-75014 Paris (France); Diaz, R. F.; Deleuil, M., E-mail: vkostov@pha.jhu.edu [Laboratoire d' Astrophysique de Marseille, 38 rue Frederic Joliot-Curie, F-13388 Marseille cedex 13 (France)

    2013-06-10

    We report the discovery of a transiting, gas giant circumbinary planet orbiting the eclipsing binary KIC 4862625 and describe our independent discovery of the two transiting planets orbiting Kepler-47. We describe a simple and semi-automated procedure for identifying individual transits in light curves and present our follow-up measurements of the two circumbinary systems. For the KIC 4862625 system, the 0.52 {+-} 0.018 R{sub Jupiter} radius planet revolves every {approx}138 days and occults the 1.47 {+-} 0.08 M{sub Sun }, 1.7 {+-} 0.06 R{sub Sun} F8 IV primary star producing aperiodic transits of variable durations commensurate with the configuration of the eclipsing binary star. Our best-fit model indicates the orbit has a semi-major axis of 0.64 AU and is slightly eccentric, e = 0.1. For the Kepler-47 system, we confirm the results of Orosz et al. Modulations in the radial velocity of KIC 4862625A are measured both spectroscopically and photometrically, i.e., via Doppler boosting, and produce similar results.

  13. Clean Elements in Abelian Rings

    Indian Academy of Sciences (India)

    Angelina Y M Chin

    2009-04-01

    Let be a ring with identity. An element in is said to be clean if it is the sum of a unit and an idempotent. is said to be clean if all of its elements are clean. If every idempotent in is central, then is said to be abelian. In this paper we obtain some conditions equivalent to being clean in an abelian ring.

  14. DELPHI's Ring Imaging Cherenkov Chamber

    CERN Multimedia

    1989-01-01

    The hundreds of mirrors around this Ring Imaging Cherenkov Chamber reflect cones of light created by fast moving particles to a detector. The velocity of a particle can be measured by the size of the ring produced on the detector. DELPHI, which ran from 1989 to 2000 on the LEP accelerator, was primarily concerned with particle identification.

  15. Reversible Seeding in Storage Rings

    Energy Technology Data Exchange (ETDEWEB)

    Ratner, Daniel; Chao, Alex; /SLAC

    2011-12-14

    We propose to generate steady-state microbunching in a storage ring with a reversible seeding scheme. High gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG) are two promising methods for microbunching linac electron beams. Because both schemes increase the energy spread of the seeded beam, they cannot drive a coherent radiator turn-by-turn in a storage ring. However, reversing the seeding process following the radiator minimizes the impact on the electron beam and may allow coherent radiation at or near the storage ring repetition rate. In this paper we describe the general idea and outline a proof-of-principle experiment. Electron storage rings can drive high average power light sources, and free-electron lasers (FELs) are now producing coherent light sources of unprecedented peak brightness While there is active research towards high repetition rate FELs (for example, using energy recovery linacs), at present there are still no convenient accelerator-based sources of high repetition rate, coherent radiation. As an alternative avenue, we recently proposed to establish steady-state microbunching (SSMB) in a storage ring. By maintaining steady-state coherent microbunching at one point in the storage ring, the beam generates coherent radiation at or close to the repetition rate of the storage ring. In this paper, we propose a method of generating a microbunched beam in a storage ring by using reversible versions of linac seeding schemes.

  16. Almost ring theory - sixth release

    OpenAIRE

    Gabber, Ofer; Ramero, Lorenzo

    2002-01-01

    We develop almost ring theory, which is a domain of mathematics somewhere halfway between ring theory and category theory (whence the difficulty of finding appropriate MSC-class numbers). We apply this theory to valuation theory and to p-adic analytic geometry. You should really have a look at the introductions (each chapter has one).

  17. Constructions over localizations of rings

    Directory of Open Access Journals (Sweden)

    Alessandro Logar

    1987-11-01

    Full Text Available In this paper we construct a category of effective noetherian rings in which linear equations can be “solved”. This category is closed with respect to some important constructions like trascendental extensions, quotientations, finite products and localizations with respect to a large class of multiplicatively closed systems. Hence it gives a definition of “constructive” rings.

  18. A Note on Clean Rings

    Institute of Scientific and Technical Information of China (English)

    Zhou Wang; Jianlong Chen

    2007-01-01

    Let R be a ring and g(x) a polynomial in C[x],where C=C(R) denotes the center of R.Camillo and Sim6n called the ring g(x)-clean if every element of R can be written as the sum of a unit and a root of g(x).In this paper,we prove that for a,b (E) C,the ring R is clean and b - a is invertible in R if and only if R is g1(x)-clean,where gl(x) = (x - a)(x - b).This implies that in some sense the notion of g(x)-clean rings in the Nicholson-Zhou Theorem and in the Camillo-Sim6n Theorem is indeed equivalent to the notion of clean rings.

  19. Black Hole Ringing, Quasinormal Modes, and Light Rings

    CERN Document Server

    Khanna, Gaurav

    2016-01-01

    Modelling of gravitational waves from binary black hole inspiral has played an important role in the recent observations of such signals. The late-stage ringdown phase of the gravitational waveform is often associated with the null particle orbit (\\light ring") of the black hole spacetime. With simple models we show that this link between the light ring and spacetime ringing is based more on the history of applications than on an actual constraining relationship. We also show, in particular, that a better understanding of the disassociation between the two, may be relevant to the astrophysically interesting case of rotating (Kerr) black holes.

  20. Supported Catalysts Useful in Ring-Closing Metathesis, Cross Metathesis, and Ring-Opening Metathesis Polymerization

    Directory of Open Access Journals (Sweden)

    Jakkrit Suriboot

    2016-04-01

    Full Text Available Ruthenium and molybdenum catalysts are widely used in synthesis of both small molecules and macromolecules. While major developments have led to new increasingly active catalysts that have high functional group compatibility and stereoselectivity, catalyst/product separation, catalyst recycling, and/or catalyst residue/product separation remain an issue in some applications of these catalysts. This review highlights some of the history of efforts to address these problems, first discussing the problem in the context of reactions like ring-closing metathesis and cross metathesis catalysis used in the synthesis of low molecular weight compounds. It then discusses in more detail progress in dealing with these issues in ring opening metathesis polymerization chemistry. Such approaches depend on a biphasic solid/liquid or liquid separation and can use either always biphasic or sometimes biphasic systems and approaches to this problem using insoluble inorganic supports, insoluble crosslinked polymeric organic supports, soluble polymeric supports, ionic liquids and fluorous phases are discussed.

  1. Is the bell ringing?

    CERN Multimedia

    Francesco Poppi

    2010-01-01

    During the Nobel prize-winning UA1 experiment, scientists in the control room used to ring a bell if a particularly interesting event had occurred. Today, the “CMS Exotica hotline” routine produces a daily report that lists the exotic events that were recorded the day before.   Display of an event selected by the Exotica routine. Take just a very small fraction of the available data (max. 5%); define the events that you want to keep and set the parameters accordingly; run the Exotica routine and only look at the very few images that the system has selected for you. This is the recipe that a small team of CMS researchers has developed to identify the signals coming from possible new physics processes. “This approach does not replace the accurate data analysis on the whole set of data. However, it is a very fast and effective way to focus on just a few events that are potentially very interesting”, explains Maurizio Pierini (CERN), who developed the...

  2. JAERI storage ring JSR

    International Nuclear Information System (INIS)

    A design study for a next generation 8 GeV synchrotron radiation facility is in progress in Japan, and the Japan Atomic Energy Research Institute (JAERI) and Institute of Physical and Chemical Research (RIKEN) have join forces in this project. A compact electron storage ring JSR has been under construction in the linac building in the Tokai Research Establishment of JAERI to serve for studies of various kind of accelerator technologies, examination of insertion devices and beam monitors, and training of young researchers. This paper describes the lattice design, injection system, magnets, vacuum system, RF system, control system and beam monitors and presents some operation results regarding the electron beam injection and storage. The JSR is presently in good condition concerning it's fundamental functions such as injection, storage at around 150 MeV and 300 MeV, and acceleration from 150 MeV and 300 MeV. Photon induced gas desorption is still large because the vacuum chamber has not been aged heavily by synchrotron radiation. (N.K.)

  3. Atomic cranks and levers control sugar ring conformations

    International Nuclear Information System (INIS)

    In this paper we review the conformational analysis of sugar rings placed under tension during mechanical manipulations of single polysaccharide molecules with the atomic force microscope and during steered molecular dynamics simulations. We examine the role of various chemical bonds and linkages between sugar rings in inhibiting or promoting their conformational transitions by means of external forces. Small differences in the orientation of one chemical bond on the sugar ring can produce significantly different mechanical properties at the polymer level as exemplified by two polysaccharides: cellulose, composed of β-1→4-linked D-glucose, and amylose, composed of α-1→4-linked D-glucose. In contrast to β-glucose rings, which are mechanically stable and produce simple entropic elasticity of the chain, α-glucose rings flip under tension from their chair to a boat-like structure and these transitions produce deviations of amylose elasticity from the freely jointed chain model. We also examine the deformation of two mechanically complementary 1→6-linked polysaccharides: pustulan, a β-1→6-linked glucan, and dextran, a α-1→6-linked glucan. Forced rotations about the C5-C6 bonds govern the elasticity of pustulan, and complex conformational transitions that involve simultaneous C5-C6 rotations and chair-boat transitions govern the elasticity of dextran. Finally, we discuss the likelihood of various conformational transitions in sugar rings in biological settings and speculate on their significance

  4. Ion Rings for Magnetic Fusion

    Energy Technology Data Exchange (ETDEWEB)

    Greenly, John, B.

    2005-07-31

    This Final Technical Report presents the results of the program, Ion Rings for Magnetic Fusion, which was carried out under Department of Energy funding during the period August, 1993 to January, 2005. The central objective of the program was to study the properties of field-reversed configurations formed by ion rings. In order to reach this objective, our experimental program, called the Field-reversed Ion Ring Experiment, FIREX, undertook to develop an efficient, economical technology for the production of field-reversed ion rings. A field-reversed configuration (FRC) in which the azimuthal (field-reversing) current is carried by ions with gyro-radius comparable to the magnetic separatrix radius is called a field-reversed ion ring. A background plasma is required for charge neutralization of the ring, and this plasma will be confined within the ring's closed magnetic flux. Ion rings have long been of interest as the basis of compact magnetic fusion reactors, as the basis for a high-power accelerator for an inertial fusion driver, and for other applications of high power ion beams or plasmas of high energy density. Specifically, the FIREX program was intended to address the longstanding question of the contribution of large-orbit ions to the observed stability of experimental FRCs to the MHD tilt mode. Typical experimental FRCs with s {approx} 2-4, where s is the ratio of separatrix radius to ion gyro-radius, have been stable to tilting, but desired values for a fusion reactor, s > 20, should be unstable. The FIREX ring would consist of a plasma with large s for the background ions, but with s {approx} 1 for the ring ions. By varying the proportions of these two populations, the minimum proportion of large-orbit ions necessary for stability could be determined. The incorporation of large-orbit ions, perhaps by neutral-beam injection, into an FRC has been advanced for the purpose of stabilizing, heating, controlling angular momentum, and aiding the formation

  5. Moving ring reactor 'Karin-1'

    International Nuclear Information System (INIS)

    The conceptual design of a moving ring reactor ''Karin-1'' has been carried out to advance fusion system design, to clarify the research and development problems, and to decide their priority. In order to attain these objectives, a D-T reactor with tritium breeding blanket is designed, a commercial reactor with net power output of 500 MWe is designed, the compatibility of plasma physics with fusion engineering is demonstrated, and some other guideline is indicated. A moving ring reactor is composed mainly of three parts. In the first formation section, a plasma ring is formed and heated up to ignition temperature. The plasma ring of compact torus is transported from the formation section through the next burning section to generate fusion power. Then the plasma ring moves into the last recovery section, and the energy and particles of the plasma ring are recovered. The outline of a moving ring reactor ''Karin-1'' is described. As a candidate material for the first wall, SiC was adopted to reduce the MHD effect and to minimize the interaction with neutrons and charged particles. The thin metal lining was applied to the SiC surface to solve the problem of the compatibility with lithium blanket. Plasma physics, the engineering aspect and the items of research and development are described. (Kako, I.)

  6. Generalized PP and Zip Subrings of Matrix Rings

    Institute of Scientific and Technical Information of China (English)

    LIU ZHONG-KUI; QIAO HU-SHENG

    2010-01-01

    Let R be an abelian ring. We consider a special subring An, relative to the ring An is a generalized right PP-ring (right zip ring) if and only if the ring R is a generalized right PP-ring (right zip ring). Our results yield more examples of generalized right PP-rings and right zip rings.

  7. Velocity peaks and caustic rings

    International Nuclear Information System (INIS)

    The late infall of cold dark matter onto an isolated galaxy produces flows with definite velocity vectors at any physical point in the galactic halo. It also produces caustic rings, which are places in space where the dark matter density is very large. The self-similar model of galactic halo formation predicts that the caustic ring radii an follow the approximate law an ≅ 1/n. Bumps in the rotation curves of NGC 3198 and of our own galaxy are interpreted as due to caustic rings of dark matter

  8. Molecular elimination of Br{sub 2} in photodissociation of CH{sub 2}BrC(O)Br at 248 nm using cavity ring-down absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fan He; Tsai, Po-Yu; Lin, King-Chuen [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China); Lin, Cheng-Wei; Yan, Chi-Yu; Yang, Shu-Wei; Chang, A. H. H. [Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan (China)

    2012-12-07

    The primary elimination channel of bromine molecule in one-photon dissociation of CH{sub 2}BrC(O)Br at 248 nm is investigated using cavity ring-down absorption spectroscopy. By means of spectral simulation, the ratio of nascent vibrational population in v = 0, 1, and 2 levels is evaluated to be 1:(0.5 {+-} 0.1):(0.2 {+-} 0.1), corresponding to a Boltzmann vibrational temperature of 581 {+-} 45 K. The quantum yield of the ground state Br{sub 2} elimination reaction is determined to be 0.24 {+-} 0.08. With the aid of ab initio potential energy calculations, the obtained Br{sub 2} fragments are anticipated to dissociate on the electronic ground state, yielding vibrationally hot Br{sub 2} products. The temperature-dependence measurements support the proposed pathway via internal conversion. For comparison, the Br{sub 2} yields are obtained analogously from CH{sub 3}CHBrC(O)Br and (CH{sub 3}){sub 2}CBrC(O)Br to be 0.03 and 0.06, respectively. The trend of Br{sub 2} yields among the three compounds is consistent with the branching ratio evaluation by Rice-Ramsperger-Kassel-Marcus method. However, the latter result for each molecule is smaller by an order of magnitude than the yield findings. A non-statistical pathway so-called roaming process might be an alternative to the Br{sub 2} production, and its contribution might account for the underestimate of the branching ratio calculations.

  9. Commissioning of the Cryogenic Plant for the Cryogenic Storage Ring (CSR) at Heidelberg

    CERN Document Server

    von Hahn, R; Grieser, M; Haberstroh, C; Kaiser, D; Lange, M; Laux, F; Menk, S; Orlov, D A; Repnow, R; Sieber, T; Quack, H; Varju, J; Wolf A

    2009-01-01

    At the Max-Planck-Institute for Nuclear Physics in Heidelberg a next generation electrostatic storage ring for low velocity atomic and molecular ion beams is under construction. In contrast to existing electrostatic storage rings, the Cryogenic Storage Ring CSR will be cooled down to temperatures below 2 K. Thus acting as a large cryopump it will provide long storage times and, in addition, open a new field of quantum state controlled molecular physics due to a low heat radiation background from space-like environment. A concept for cooling the storage ring has been developed and is presently tested by means of a linear trap as a prototype with a length of 1/10 of the planned ring. A commercial refrigerator with 21 W at 2 K has been successfully commissioned and was connected to the prototype. This paper presents the status of the cryogenic plant after the commissioning and one year of operation.

  10. Vibration insensitive optical ring cavity

    Institute of Scientific and Technical Information of China (English)

    Miao Jin; Jiang Yan-Yi; Fang Su; Bi Zhi-Yi; Ma Long-Sheng

    2009-01-01

    The mounting configuration of an optical ring cavity is optimized for vibration insensitivity by finite element analysis. A minimum response to vertical accelerations is found by simulations made for different supporting positions.

  11. Prototype moving-ring reactor

    International Nuclear Information System (INIS)

    We have completed a design of the Prototype Moving-Ring Reactor. The fusion fuel is confined in current-carrying rings of magnetically-field-reversed plasma (Compact Toroids). The plasma rings, formed by a coaxial plasma gun, undergo adiabatic magnetic compression to ignition temperature while they are being injected into the reactor's burner section. The cylindrical burner chamber is divided into three burn stations. Separator coils and a slight axial guide field gradient are used to shuttle the ignited toroids rapidly from one burn station to the next, pausing for 1/3 of the total burn time at each station. D-T-3He ice pellets refuel the rings at a rate which maintains constant radiated power

  12. Perturbations of vortex ring pairs

    CERN Document Server

    Gubser, Steven S; Parikh, Sarthak

    2015-01-01

    We study pairs of co-axial vortex rings starting from the action for a classical bosonic string in a three-form background. We complete earlier work on the phase diagram of classical orbits by explicitly considering the case where the circulations of the two vortex rings are equal and opposite. We then go on to study perturbations, focusing on cases where the relevant four-dimensional transfer matrix splits into two-dimensional blocks. When the circulations of the rings have the same sign, instabilities are mostly limited to wavelengths smaller than a dynamically generated length scale at which single-ring instabilities occur. When the circulations have the opposite sign, larger wavelength instabilities can occur.

  13. Ring Model for Pneumatic Tires

    Institute of Scientific and Technical Information of China (English)

    危银涛; 范成建; 管迪华

    2002-01-01

    This paper reviews the state-of-the-art of the ring modeling method for tires, emphasizing the differences among the various tire ring models. A general tire ring model was then developed including all the nonlinear terms in the ring strain and the initial stresses induced by the internal pressure and rotation. The general equations of motion were derived from the Hamilton principle whth the geometric parameters for the model directly obtained from the tire design. The physical parameters were calculated from experimental mode parameters. A numerical example is given for a 195/70 R14-type tire. The analysis shows that the predicted natural frequencies and the tire mode shape agree well with experimental results.

  14. Autumn study on storage rings

    CERN Multimedia

    1974-01-01

    The first two weeks of October have seen storage ring people from accelerator Laboratories throughout the world at CERN to study the fundamental problems of very high energy protonproton colliding beam machines.

  15. Perturbations of vortex ring pairs

    Science.gov (United States)

    Gubser, Steven S.; Horn, Bart; Parikh, Sarthak

    2016-02-01

    We study pairs of coaxial vortex rings starting from the action for a classical bosonic string in a three-form background. We complete earlier work on the phase diagram of classical orbits by explicitly considering the case where the circulations of the two vortex rings are equal and opposite. We then go on to study perturbations, focusing on cases where the relevant four-dimensional transfer matrix splits into two-dimensional blocks. When the circulations of the rings have the same sign, instabilities are mostly limited to wavelengths smaller than a dynamically generated length scale at which single-ring instabilities occur. When the circulations have the opposite sign, larger wavelength instabilities can occur.

  16. Concise synthesis of the A/BCD-ring fragment of gambieric acid A

    Science.gov (United States)

    Fuwa, Haruhiko; Fukazawa, Ryo; Sasaki, Makoto

    2014-01-01

    Gambieric acid A (GAA) and its congeners belong to the family of marine polycyclic ether natural products. Their highly complex molecular architecture and unique biological activities have been of intense interest within the synthetic community. We have previously reported the first total synthesis, stereochemical reassignment, and preliminary structure–activity relationships of GAA. Here we disclose a concise synthesis of the A/BCD-ring fragment of GAA. The synthesis started from our previously reported synthetic intermediate that represents the A/B-ring. The C-ring was synthesized via an oxiranyl anion coupling and a 6-endo cyclization, and the D-ring was forged by means of an oxidative lactonization and subsequent palladium-catalyzed functionalization of the lactone ring. In this manner, the number of linear synthetic steps required for the construction of the C- and D-rings was reduced from 22 to 11. PMID:25629027

  17. Missing rings in Pinus halepensis

    OpenAIRE

    Novak, Klemen; De Luis, Martin; Saz, Miguel Angel; Longares, Luis Alberto; Serrano-Notivoli, Roberto; Raventós, Josep; Čufar, Katarina; Gričar, Jožica; Di Filippo, Alfredo; Piovesan, Gianluca; Rathgeber, Cyrille; Papadopoulos, Andreas; Kevin T. Smith

    2016-01-01

    Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean cli...

  18. Collector ring project at FAIR

    Science.gov (United States)

    Dolinskii, A.; Berkaev, D.; Blell, U.; Dimopoulou, C.; Gorda, O.; Leibrock, H.; Litvinov, S.; Laier, U.; Koop, I.; Schurig, I.; Starostenko, A.; Shatunov, P.; Weinrich, U.

    2015-11-01

    The collector ring is a dedicated ring for fast cooling of ions coming from separators at the FAIR project. To accommodate optimal technical solutions, a structure of a magnet lattice was recently reviewed and modified. Consequently, more appropriate technical solutions for the main magnets could be adopted. A general layout and design of the present machine is shown. The demanding extraction schemes have been detailed and open design issues were completed.

  19. ring og forandring

    DEFF Research Database (Denmark)

    I de sidste ti år har læring været på dagsordenen som aldrig før. Inden for uddannelsesverdenen og den pædagogiske debat har man kunnet se et markant skift, hvor læringsbegrebet er blevet tematiseret langt stærkere på bekostning af undervisningsbegrebet. Samtidig er læring blevet sat på dagsorden...

  20. Rings Whose Modules Have Grade Zero

    Institute of Scientific and Technical Information of China (English)

    Zhi Xiang WU

    2005-01-01

    In this paper, we prove that R is a two-sided Artinian ring and J is a right annihilator ideal if and only if (i) for any nonzero right module, there is a nonzero linear map from it to a projective module; (ii) every submodule of RR is not a radical module for some right coherent rings. We call a ring a right X ring if HomR(M, R) = 0 for any right module M implies that M = 0. We can prove some left Goldie and right X rings are right Artinian rings. Moreover we characterize semisimple rings by using X rings. A famous Faith's conjecture is whether a semipimary PF ring is a QF ring. Similarly we study the relationship between X rings and QF and get many interesting results.

  1. Collar nut and thrust ring

    Science.gov (United States)

    Lowery, Guy B.

    1991-01-01

    A collar nut comprises a hollow cylinder having fine interior threads at one end for threadably engaging a pump mechanical seal assembly and an inwardly depending flange at the other end. The flange has an enlarged portion with a groove for receiving an O-ring for sealing against the intrusion of pumpage from the exterior. The enlarged portion engages a thrust ring about the pump shaft for crushing a hard O-ring, such as a graphite O-ring. The hard O-ring seals the interior of the mechanical seal assembly and pump housing against the loss of lubricants or leakage of pumpage. The fine threads of the hollow cylinder provide the mechanical advantage for crushing the hard O-ring evenly and easily with a hand tool from the side of the collar nut rather than by tightening a plurality of bolts from the end and streamlines the exterior surface of the mechanical seal. The collar nut avoids the spatial requirements of bolt heads at the end of a seal and associated bolt head turbulence.

  2. A Rational Approach to Ring Flexibility in Internal Coordinate Dynamics

    CERN Document Server

    Mazur, A K

    1998-01-01

    Internal coordinate molecular dynamics (ICMD) is an efficient method for studying biopolymers, but it is readily applicable only to molecules with tree topologies, that is with no internal flexible rings. Common examples violating this condition are prolines and loops closed by S-S bridges in proteins. The most important such case, however, is nucleic acids because the flexibility of the furanose rings always plays an essential role in conformational transitions both in DNA and RNA. There are a few long-known theoretical approaches to this problem, but, in practice, rings with fixed bond lengths are closed by adding appropriate harmonic distance restraints, which is not always acceptable especially in dynamics. This paper tries to overcome this handicap of ICMD and proposes a rational strategy which results in practical numerical algorithms. It gives a unified analytical treatment which shows that this problem is very close to the difficulties encountered by the method of constraints in Cartesian coordinate d...

  3. Perylenetetracarboxylic anhydride as a precursor of fluorescent carbon nanoonion rings

    Science.gov (United States)

    Baldoví, Herme G.; Herance, José Raul; Manuel Víctor, Víctor; Alvaro, Mercedes; Garcia, Hermenegildo

    2015-07-01

    Thermal annealing at 400 °C of perylenetetracarboxylic anhydride in low molecular mass PEG gives rise to the formation of well defined nanoobjects of 2.5 nm height and size distribution from 10 to 65 nm (average 40 nm) after purification of the raw mixture with silicagel chromatography. TEM reveals that the flat nanoobjects are constituted of concentric graphenic rings (0.34 nm interlayer distance). The morphology of the nanoparticles resembles onion rings of nanometric dimensions (nanoonion rings C-NOR). C-NOR particles have an excitation dependent emission with λem from 430 to 570 nm and a maximum emission quantum yield of 0.49. C-NOR particles can be internalized into Hep3B human hepatoma cells as determined by confocal fluorescence microscopy and are remarkably biocompatible affecting slightly cell viability according to the MTT test.

  4. Conducting liquid conveyer of plasma rings

    International Nuclear Information System (INIS)

    Current-carrying plasma rings can be conveyed in a cylindrical channel with a conducting liquid flow to which outer poloidal fields of the rings freeze. Fast tilting motion of the ring is stabilized when the liquid surface is set close to the ring within a critical distance. Effects of a resistive tube duct installed for the liquid are also examined. (author)

  5. Concentric ring flywheel without expansion separators

    Science.gov (United States)

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion.

  6. EXTRACELLULAR POLYSACCHARIDES OF POTATO RING ROT PATHOGEN

    Directory of Open Access Journals (Sweden)

    Shafikova Т.N.

    2006-03-01

    Full Text Available Many bacteria, including phytopathogenic ones produce extracellular polysaccharides or exopolysaccharides which are universal molecules. Causal agent of potato ring rot, Clavibacter michiganensis subspecies sepedonicus, secretes exopolysaccharides which role in pathogenesis is poorly investigated. The aim of our research is to ascertain the composition and structure of Clavibacter michiganensis subspecies sepedonicus exopolysaccharides. Exopolysaccharides of Clavibacter michiganensis subspecies sepedonicus are determined to consist of 4-6 anionic and neutral components which have molecular weights from 700 kDa. Glucose is a major monomer of polysaccharides and arabinose, rhamnose and mannose are minor monomers. Glucose is present in α-Dglucopyranose and β-D-glucopyranose configurations. Calcium is determined to be a component of exopolysaccharides. Components of exopolysaccharides of potato ring rot pathogen are probably capableto associate via calcium ions and other ionic interactions that may result in a change of their physiological activity. Further studies of Clavibacter michiganensis subspecies sepedonicus exopolysaccharides composition and structure can serve a base for the synthesis of their chemical analogues with elicitor action.

  7. Ring wormholes via duality rotations

    Science.gov (United States)

    Gibbons, Gary W.; Volkov, Mikhail S.

    2016-09-01

    We apply duality rotations and complex transformations to the Schwarzschild metric to obtain wormhole geometries with two asymptotically flat regions connected by a throat. In the simplest case these are the well-known wormholes supported by phantom scalar field. Further duality rotations remove the scalar field to yield less well known vacuum metrics of the oblate Zipoy-Voorhees-Weyl class, which describe ring wormholes. The ring encircles the wormhole throat and can have any radius, whereas its tension is always negative and should be less than -c4 / 4 G. If the tension reaches the maximal value, the geometry becomes exactly flat, but the topology remains non-trivial and corresponds to two copies of Minkowski space glued together along the disk encircled by the ring. The geodesics are straight lines, and those which traverse the ring get to the other universe. The ring therefore literally produces a hole in space. Such wormholes could perhaps be created by negative energies concentrated in toroidal volumes, for example by vacuum fluctuations.

  8. Ring wormholes via duality rotations

    CERN Document Server

    Gibbons, Gary W

    2016-01-01

    We apply duality rotations and complex transformations to the Schwarzschild metric to obtain wormhole geometries with two asymptotically flat regions connected by a throat. In the simplest case these are the well-known wormholes supported by phantom scalar field. Further duality rotations remove the scalar field to yield less well known vacuum metrics of the oblate Zipoy-Voorhees-Weyl class, which describe ring wormholes. The ring encircles the wormhole throat and can have any radius, whereas its tension is always negative and should be less than $-c^4/4G$. If the tension reaches the maximal value, the geometry becomes exactly flat, but the topology remains non-trivial and corresponds to two copies of Minkowski space glued together along the disk encircled by the ring. The geodesics are straight lines, and those which traverse the ring get to the other universe. The ring therefore literally produces a whole in space. Such wormholes could perhaps be created by negative energies concentrated in toroidal volumes...

  9. Ring polymers in confined geometries

    CERN Document Server

    Usatenko, Z; Kuterba, P

    2016-01-01

    The investigation of a dilute solution of phantom ideal ring polymers and ring polymers with excluded volume interactions (EVI) in a good solvent confined in a slit geometry of two parallel repulsive walls and in a solution of colloidal particles of big size were performed. Taking into account the correspondence between the field theoretical $\\phi^4$ $O(n)$-vector model in the limit $n\\to 0$ and the behavior of long-flexible polymer chains in a good solvent the correspondent depletion interaction potentials, depletion forces and the forces which exert phantom ideal ring and ring polymer chains with EVI on the walls were obtained in the framework of the massive field theory approach at fixed space dimensions d=3 up to one-loop order. Additionally, the investigation of a dilute solution of phantom ideal ring polymers in a slit geometry of two inert walls and mixed walls with one repulsive and other one inert wall were performed and correspondent depletion interaction potentials and the depletion forces were cal...

  10. CYCLIC CODES OVER FORMAL POWER SERIES RINGS

    Institute of Scientific and Technical Information of China (English)

    Dougherty Steven T.; Liu Hongwei

    2011-01-01

    In this article, cyclic codes and negacyclic codes over formal power series rings are studied. The structure of cyclic codes over this class of rings is given, and the relationship between these codes and cyclic codes over finite chain rings is obtained. Using an isomorphism between cyclic and negacyclic codes over formal power series rings, the structure of negacyclic codes over the formal power series rings is obtained.

  11. On Ideals of Regular Rings

    Institute of Scientific and Technical Information of China (English)

    CHEN Huan Yin; LI Fu An

    2002-01-01

    In this paper, we investigate ideals of regular rings and give several characterizations for an ideal to satisfy the comparability. In addition, it is shown that, if Ⅰ is a minimal two-sided ideal of a regular ring R, then Ⅰ satisfies the comparability if and only if Ⅰ is separative. Furthermore, we prove that, for ideals with stable range one, Roth's problem has an affirmative solution. These extend the corresponding results on unit-regularity and one-sided unit-regularity.

  12. Nanoscale nonlinear PANDA ring resonator

    CERN Document Server

    Yupapin, Preecha

    2012-01-01

    Microring/nanoring resonator is an interesting device that has been widely studied and investigated by researchers from a variety of specializations. This book begins with the basic background of linear and nonlinear ring resonators. A novel design of nano device known as a PANDA ring resonator is proposed. The use of the device in the form of a PANDA in applications such as nanoelectronics, measurement, communication, sensors, optical and quantum computing, drug delivery, hybrid transistor and a new concept of electron-hole pair is discussed in detail.

  13. On Simple-Injective Rings

    Institute of Scientific and Technical Information of China (English)

    W.K. Nicholson; Jae Keol Park; M.F. Yousif

    2002-01-01

    A ring R is called right simple-injective if every R-linear map from a right ideal of R to R with simple image can be extended to R. It is shown that a right simple-injective ring R is quasi-Frobenius if R is right Goldie with essential right socle, or R is left perfect and the right annihilator of k ∈ R is finitely generated whenever kR or Rk is simple. This extends a result of Bjork.

  14. Modelling the formation of the circumnuclear ring in the Galactic centre

    CERN Document Server

    Mapelli, Michela

    2016-01-01

    Several thousand solar masses of molecular, atomic and ionized gas lie in the innermost ~10 pc of our Galaxy. The most relevant structure of molecular gas is the circumnuclear ring (CNR), a dense and clumpy ring surrounding the supermassive black hole (SMBH), with a radius of ~2 pc. We propose that the CNR formed through the tidal disruption of a molecular cloud, and we investigate this scenario by means of N-body smoothed-particle hydrodynamics simulations. We ran a grid of simulations with different cloud mass (4X10^4, 1.3X10^5 solar masses), different initial orbital velocity (v_in=0.2-0.5 v_esc, where v_esc is the escape velocity from the SMBH), and different impact parameter (b=8, 26 pc). The disruption of the molecular cloud leads to the formation of very dense and clumpy gas rings, containing most of the initial cloud mass. If the initial orbital velocity of the cloud is sufficiently low (v_in0.5 v_esc), at least two rings form around the SMBH: an inner ring (with radius ~0.4 pc) and an outer ring (wit...

  15. A Experimental Study of Viscous Vortex Rings.

    Science.gov (United States)

    Dziedzic, Mauricio

    Motivated by the role played by vortex rings in the process of turbulent mixing, the work is focused on the problem of stability and viscous decay of a single vortex ring. A new classification is proposed for vortex rings which is based on extensive hot-wire measurements of velocity in the ring core and wake and flow visualization. Vortex rings can be classified as laminar, wavy, turbulence-producing, and turbulent. Prediction of vortex ring type is shown to be possible based on the vortex ring Reynolds number. Linear growth rates of ring diameter with time are observed for all types of vortex rings, with different growth rates occurring for laminar and turbulent vortex rings. Data on the viscous decay of vortex rings are used to provide experimental confirmation of the accuracy of Saffman's equation for the velocity of propagation of a vortex ring. Experimental data indicate that instability of the vortex ring strongly depends on the mode of generation and can be delayed by properly adjusting the generation parameters. A systematic review of the literature on vortex-ring interactions is presented in the form of an appendix, which helps identify areas in which further research may be fruitful.

  16. SELF-DUAL PERMUTATION CODES OVER FORMAL POWER SERIES RINGS AND FINITE PRINCIPAL IDEAL RINGS

    Institute of Scientific and Technical Information of China (English)

    张光辉; 刘宏伟

    2013-01-01

    In this paper, we study self-dual permutation codes over formal power series rings and finite principal ideal rings. We first give some results on the torsion codes associated with the linear codes over formal power series rings. These results allow for obtaining some conditions for non-existence of self-dual permutation codes over formal power series rings. Finally, we describe self-dual permutation codes over finite principal ideal rings by examining permutation codes over their component chain rings.

  17. Characteristic of Rings. Prime Fields

    Directory of Open Access Journals (Sweden)

    Schwarzweller Christoph

    2015-12-01

    Full Text Available The notion of the characteristic of rings and its basic properties are formalized [14], [39], [20]. Classification of prime fields in terms of isomorphisms with appropriate fields (ℚ or ℤ/p are presented. To facilitate reasonings within the field of rational numbers, values of numerators and denominators of basic operations over rationals are computed.

  18. E-læring

    DEFF Research Database (Denmark)

    Heilesen, Simon

    2001-01-01

    E-læring er et modeord og et mantra. Undervisning bliver ikke automatisk bedre af, at der sættes et ”e-” foran. Forbedring og fornyelse af undervisningen er betinget af, at vi forstår computermediets muligheder og skaber forandring ved at tilpasse det til de undervisningsformer, vi ønsker....

  19. Singularities of ordinary deformation rings

    CERN Document Server

    Snowden, Andrew

    2011-01-01

    Let R^univ be the universal deformation ring of a residual representation of a local Galois group. Kisin showed that many loci in MaxSpec(R^univ[1/p]) of interest are Zariski closed, and gave a way to study the generic fiber of the corresponding quotient of R^univ. However, his method gives little information about the quotient ring before inverting p. We give a method for studying this quotient in certain cases, and carry it out in the simplest non-trivial case. Precisely, suppose that V_0 is the trivial two dimensional representation and let R be the unique Z_p-flat and reduced quotient of R^univ such that MaxSpec(R[1/p]) consists of ordinary representations with Hodge--Tate weights 0 and 1. We describe the functor of points of (a slightly modified version of) R and show that the irreducile components of Spec(R) are normal, Cohen--Macaulay and not Gorenstein. This has two well-known applications to global deformation rings: first, a global deformation ring employing these local conditions is torsion-free; a...

  20. Ringing phenomenon in silica microspheres

    Institute of Scientific and Technical Information of China (English)

    Chunhua Dong; Changling Zou; Jinming Cui; Yong Yang; Zhengfu Han; Guangcan Guo

    2009-01-01

    Whispering gallery modes in silica microspheres are excited by a tunable continuous-wave laser through the fiber taper. Ringing phenomenon can be observed with high frequency sweeping speed. The thermal nonlinearity in the microsphere can enhance this phenomenon. Our measurement results agree very well with the theoretical predictions by the dynamic equation.

  1. The Lord of the Rings

    Institute of Scientific and Technical Information of China (English)

    潘金梅

    2002-01-01

    Peter Jackson's first film in The Lord of the Rings trilogy (三步曲) has just grabbed (夺得) four Oscars-awards for the best make-up, best cinematography (摄影), best visual effects and best original score.Chinese audience had a chance to watch the fihn from late April.

  2. Generalized Double Ring Network Structures

    DEFF Research Database (Denmark)

    Pedersen, Jens Myrup; Patel, A.; Knudsen, Thomas Phillip;

    2004-01-01

    This paper describes and studies generalizations of the well-known double ring network structures. Two classes of structures are studied, the N2R(p; q) and N2R(p; q; r) structures, of which the former is a special case of the well known Generalized Petersen Graphs. Basic properties of these struc...

  3. Cascaded uncoupled dual-ring modulator

    CERN Document Server

    Gu, Tingyi; Wong, Chee Wei; Dong, Po

    2014-01-01

    We demonstrate that by coherent driving two uncoupled rings in same direction, the effective photon circulating time in the dual ring modulator is reduced, with increased modulation quality. The inter-ring detuning dependent photon dynamics, Q-factor, extinction ratio and optical modulation amplitude of two cascaded silicon ring resonators are studied and compared with that of a single ring modulator. Experimentally measured eye diagrams, together with coupled mode theory simulations, demonstrate the enhancement of dual ring configuration at 20 Gbps with a Q ~ 20,000.

  4. High-Speed Ring Bus

    Science.gov (United States)

    Wysocky, Terry; Kopf, Edward, Jr.; Katanyoutananti, Sunant; Steiner, Carl; Balian, Harry

    2010-01-01

    The high-speed ring bus at the Jet Propulsion Laboratory (JPL) allows for future growth trends in spacecraft seen with future scientific missions. This innovation constitutes an enhancement of the 1393 bus as documented in the Institute of Electrical and Electronics Engineers (IEEE) 1393-1999 standard for a spaceborne fiber-optic data bus. It allows for high-bandwidth and time synchronization of all nodes on the ring. The JPL ring bus allows for interconnection of active units with autonomous operation and increased fault handling at high bandwidths. It minimizes the flight software interface with an intelligent physical layer design that has few states to manage as well as simplified testability. The design will soon be documented in the AS-1393 standard (Serial Hi-Rel Ring Network for Aerospace Applications). The framework is designed for "Class A" spacecraft operation and provides redundant data paths. It is based on "fault containment regions" and "redundant functional regions (RFR)" and has a method for allocating cables that completely supports the redundancy in spacecraft design, allowing for a complete RFR to fail. This design reduces the mass of the bus by incorporating both the Control Unit and the Data Unit in the same hardware. The standard uses ATM (asynchronous transfer mode) packets, standardized by ITU-T, ANSI, ETSI, and the ATM Forum. The IEEE-1393 standard uses the UNI form of the packet and provides no protection for the data portion of the cell. The JPL design adds optional formatting to this data portion. This design extends fault protection beyond that of the interconnect. This includes adding protection to the data portion that is contained within the Bus Interface Units (BIUs) and by adding to the signal interface between the Data Host and the JPL 1393 Ring Bus. Data transfer on the ring bus does not involve a master or initiator. Following bus protocol, any BIU may transmit data on the ring whenever it has data received from its host. There

  5. Interactions between ring polymers in dilute solution studied by Monte Carlo simulation

    Science.gov (United States)

    Suzuki, Jiro; Takano, Atsushi; Matsushita, Yushu

    2015-01-01

    The second virial coefficient, A2, for trivial-ring polymers in dilute condition was estimated from a Metropolis Monte Carlo (MC) simulation, and the temperature dependence of A2 has been discussed with their Flory's scaling exponent, ν, in Rg ∝ Nν, where Rg is radius of gyration of a polymer molecule. A limited but not too small number of polymer molecules were employed in the simulation, and the A2 values at various temperatures were calculated from the molecular density fluctuation in the solution. In the simulation, the topology of ring polymers was kept, since chain crossing was prohibited. The excluded volume effects can be screened by the attractive force between segments, which depends on the temperature, Tα, defined in the Metropolis MC method. Linear and trivial-ring polymers have the ν value of 1/2 at Tα = 10.605 and 10.504. At Tα = 10.504, the excluded volume effects are screened by the attractive force generated between segments in a ring polymer, but the A2 value for ring polymers is positive. Thus, the temperature at A2 = 0 for a ring polymer is lower than that at ν = 1/2, and this fact can be explained with the following two reasons. (a) Rg value for a ring polymer is much smaller than that for a linear polymer at the same temperature and molecular weight, where interpenetration of a ring polymer chain into neighboring chains is apparently less than a linear chain. (b) The conformation of trivial rings can be statistically described as a closed random walk at ν = 1/2, but their topologies are kept, being produced topological constraints, which strongly relate not only to the long-distance interaction between segments in a molecule but also the inter-molecular interaction.

  6. The Canarias Einstein ring: a newly discovered optical Einstein ring

    Science.gov (United States)

    Bettinelli, M.; Simioni, M.; Aparicio, A.; Hidalgo, S. L.; Cassisi, S.; Walker, A. R.; Piotto, G.; Valdes, F.

    2016-09-01

    We report the discovery of an optical Einstein ring in the Sculptor constellation, IAC J010127-334319, in the vicinity of the Sculptor dwarf spheroidal galaxy. It is an almost complete ring (˜300°) with a diameter of ˜4.5 arcsec. The discovery was made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging data. Confirmation of the object nature has been obtained by deriving spectroscopic redshifts for both components, lens and source, from observations at the 10.4 m Gran Telescopio CANARIAS (GTC) with the spectrograph OSIRIS. The lens, a massive early-type galaxy, has a redshift of z = 0.581, while the source is a starburst galaxy with redshift of z = 1.165. The total enclosed mass that produces the lensing effect has been estimated to be Mtot = (1.86 ± 0.23) × 1012 M⊙.

  7. B环不同羟基取代影响黄酮苷元透膜能力的分子动力学模拟研究%Molecular dynamic simulation on membrane permeability of flavonoid aglycones substituted with different hydroxyl positions on B ring

    Institute of Scientific and Technical Information of China (English)

    卜晓斐; 郝本前; 徐为人; 刘鹏; 段桂运; 孟凡翠; 汤立达

    2012-01-01

    目的 利用分子动力学模拟方法研究黄酮苷元B环不同羟基取代对透膜能力的影响规律,并考察理论方法与实验结果的相关性.方法 利用GROMACS程序包,通过附加加速度的分子动力学模拟方法得到5种黄酮苷元在双层脂质膜9个不同位置的轨迹,分析分子透膜过程中的能垒、方向性、氢键、相互作用等参数.结果 分子动力学模拟数据与文献报道人结肠腺癌Caco-2细胞实验数据具有良好的相关性(r=-0.7862),分子透过磷脂酰胆碱(DPPC)膜的能垒越小,越有利于药物分子透过生物膜.黄酮苷元透膜难易受静电的影响大于范德华作用的影响,分子在膜内形成氢键能力越强,滞留时间就越长.2′位取代可以增加分子各羟基形成氢键的能力,3′或5′位存在羟基时,与极性层适当的静电排斥作用有利于分子透过极性层.结论 B环不同位置取代对黄酮苷元透膜过程中的氢键形成能力、方向、静电相互作用和能垒都有明显的影响,理论模拟的能垒可以作为预测黄酮类化合物透膜吸收的一个重要指标.%Objective To understand the mechanism on membrane permeability of flavonoid aglycones substituted with different hydroxyl positions and numbers on B ring, and to observe the correlation between molecular dynamic (MD) simulation and experimental results. Methods MD simulation was performed with GROMACS software package. Using accelerated MD simulation, the transmembrane behaviors of five flavonoid aglycones were simulated from nine different initial positions of bilayer lipid. The energy barrier, orientation, hydrogen bonding, and interaction during the transmembrane process were calculated from recorded trajectories. Results The results of MD simulation had a good correlation with the reported experimental data of Caco-2 (r = -0.786 2). According to our results, the lower energy barrier was for molecules to penetrate the membrane of dipalmitoyl

  8. Planetary science: Shepherds of Saturn's ring

    Science.gov (United States)

    Crida, Aurélien

    2015-09-01

    Saturn's F ring is chaperoned on both sides by the tiny moons Prometheus and Pandora. Numerical simulations show that this celestial ballet can result from the collision of two aggregates that evolved out of Saturn's main rings.

  9. Traumatic corneal endothelial rings from homemade explosives.

    Science.gov (United States)

    Ng, Soo Khai; Rudkin, Adam K; Galanopoulos, Anna

    2013-08-01

    Traumatic corneal endothelial rings are remarkably rare ocular findings that may result from blast injury. We present a unique case of bilateral traumatic corneal endothelial rings secondary to blast injury from homemade explosives. PMID:23474743

  10. The Structure of gr-simple Rings

    Institute of Scientific and Technical Information of China (English)

    朱彬

    2003-01-01

    A characterization of gr-simple rings is given by using the notion of componentwise-dense subrings of a full matrix ring over a division ring. As a conse-quence, any G-graded full matrix ring over a division ring is isomorphic to a dense subring of a full matrix ring with a good G-grading. Some conditions for a grading of a full matrix ring to be isomorphic to a good one are given, which generalize some results in: Dáscáscu, S., Lon, B., Niǎstǎsescu, C. and Montes, J. R., Group gradingson full matrix rings, J. Algebra, 220(1999), 709-728.

  11. International Tree Ring Data Bank (ITRDB)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Tree ring data from the International Tree Ring Data Bank and World Data Center for Paleoclimatology archives. Data include raw treering measurements (most are...

  12. Optical fiber having wave-guiding rings

    Science.gov (United States)

    Messerly, Michael J.; Dawson, Jay W.; Beach, Raymond J.; Barty, Christopher P. J.

    2011-03-15

    A waveguide includes a cladding region that has a refractive index that is substantially uniform and surrounds a wave-guiding region that has an average index that is close to the index of the cladding. The wave-guiding region also contains a thin ring or series of rings that have an index or indices that differ significantly from the index of the cladding. The ring or rings enable the structure to guide light.

  13. Hidden Beauty in Twisted Viking Neck Rings

    OpenAIRE

    Olsen, Kasper; Bohr, Jakob

    2010-01-01

    Many hoards found in Ireland, Scotland, Orkney Islands, and Scandinavia demonstrate the vikings ability to fabricate beautiful arm and neck rings of twisted silver and gold rods. Characteristic for such rings is the uniform appearance of the twisted pattern along the length of the arm ring, as well as from one arm ring to another, also when found at distant geographical locations. How can the appearance of the twisted wires be so perfectly repetitive? We demonstrate that the answer is that th...

  14. Nonlinear analysis of ring oscillator circuits

    KAUST Repository

    Ge, Xiaoqing

    2010-06-01

    Using nonlinear systems techniques, we analyze the stability properties and synchronization conditions for ring oscillator circuits, which are essential building blocks in digital systems. By making use of its cyclic structure, we investigate local and global stability properties of an n-stage ring oscillator. We present a sufficient condition for global asymptotic stability of the origin and obtain necessity if the ring oscillator consists of identical inverter elements. We then give a synchronization condition for identical interconnected ring oscillators.

  15. Dysphagia due to Multiple Esophageal Rings

    Directory of Open Access Journals (Sweden)

    Stephen N Sullivan

    1995-01-01

    Full Text Available A 27-year-old Saudi man with dysphagia due to multiple esophageal rings is reported and the literature reviewed. Dysphagia due to multiple esophageal rings is very rare. Only 15 cases have been reported. The patient is usually male and has had dysphagia for many years when presenting. The cause of the rings is unknown. Theories to explain dysphagia are that the rings are either congenital or an unusual manifestation of gastroesophageal reflux.

  16. RRF Rings which are not LRF

    Indian Academy of Sciences (India)

    K Varadarajan

    2000-05-01

    Define a ring to be RRF (respectively LRF) if every right (respectively left) -module is residually finite. We determine the necessary and sufficient conditions for a formal triangular matrix ring $$T=\\begin{pmatrix}A & 0\\\\ M & B\\end{pmatrix}$$ to be RRF (respectively LRF). Using this we give examples of RRF rings which are not LRF.

  17. On the intersection ring of graph manifolds

    OpenAIRE

    Doig, Margaret I.; Horn, Peter D.

    2014-01-01

    We calculate the intersection ring of three-dimensional graph manifolds with rational coefficients and give an algebraic characterization of these rings when the manifold's underlying graph is a tree. We are able to use this characterization to show that the intersection ring obstructs arbitrary three-manifolds from being homology cobordant to certain graph manifolds.

  18. Familial transmission of a ring chromosome 21

    DEFF Research Database (Denmark)

    Hertz, Jens Michael

    1987-01-01

    A ring chromosome 21 was found in a phenotypically normal mother and her son. The clinical findings in the son were bilateral retention of the testes and a slightly delayed puberty onset. Consequences of a ring formation of a chromosome 21 in phenotypically normal patients are presented...... and discussed, and the previously reported cases of familially transmitted G-group ring chromosomes are reviewed....

  19. The Phase Shift in the Jumping Ring

    Science.gov (United States)

    Jeffery, Rondo N.; Amiri, Farhang

    2008-01-01

    The popular physics demonstration experiment known as Thomson's Jumping Ring (JR) has been variously explained as a simple example of Lenz's law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenz's law explanation is shown by the time the ring takes to jump and by levitation.…

  20. Interactions between unidirectional quantized vortex rings

    Science.gov (United States)

    Zhu, T.; Evans, M. L.; Brown, R. A.; Walmsley, P. M.; Golov, A. I.

    2016-08-01

    We have used the vortex filament method to numerically investigate the interactions between pairs of quantized vortex rings that are initially traveling in the same direction but with their axes offset by a variable impact parameter. The interaction of two circular rings of comparable radii produces outcomes that can be categorized into four regimes, dependent only on the impact parameter; the two rings can either miss each other on the inside or outside or reconnect leading to final states consisting of either one or two deformed rings. The fraction of energy that went into ring deformations and the transverse component of velocity of the rings are analyzed for each regime. We find that rings of very similar radius only reconnect for a very narrow range of the impact parameter, much smaller than would be expected from the geometrical cross-section alone. In contrast, when the radii of the rings are very different, the range of impact parameters producing a reconnection is close to the geometrical value. A second type of interaction considered is the collision of circular rings with a highly deformed ring. This type of interaction appears to be a productive mechanism for creating small vortex rings. The simulations are discussed in the context of experiments on colliding vortex rings and quantum turbulence in superfluid helium in the zero-temperature limit.

  1. Type Ⅱ codes over finite rings

    Institute of Scientific and Technical Information of China (English)

    DOUGHERTY; Steven; T

    2010-01-01

    In this paper,we generalize the concept of Type Ⅱ codes to arbitrary finite rings. We focus on Type Ⅱ codes over finite chain rings and use the Chinese Remainder Theorem on these codes to study Type Ⅱ codes over principal ideal rings.

  2. Self-gravitation in Saturn's rings

    International Nuclear Information System (INIS)

    In a ring-shaped collisional system self-gravitation reduces the equilibrium values of the geometric and optical thickness. In Saturn's rings both effects are appreciable. The previously found discrepancy between the calculated profile and the observed profile of the rings is chiefly caused by the omission of self-gravitation. (Auth.)

  3. Investigation of supramolecular architectures of bent-shaped pyridine derivatives: from a three-ring crystalline compound towards five-ring mesogens

    CERN Document Server

    Trišović, Nemanja; Rogan, Jelena; Poleti, Dejan; Tóth-Katona, Tibor; Salamonczyk, Miroslaw; Jákli, Antal; Fodor-Csorba, Katalin

    2016-01-01

    In searching for novel photoactive liquid crystals, we have synthesized a series of five-ring pyridine-based bent-core compounds bearing different substituents at the peripheral phenyl rings (CH3O, Cl and NO2). Their mesomorphic behaviour has been investigated by polarizing optical microscopy, differential scanning calorimetry and X-ray scattering, and then compared with the unsubstituted parent compound. The introduction of the methoxy groups at the peripheral phenyl rings of the bent core results in a non-mesomorphic compound, whereas the chloro- and nitro-substituted compounds form enantiotropic B1-like phases. Significant changes of the textures and transition temperatures of the mesophase have been observed under UV light. The presented investigation of the mesomorphic properties of the synthesized compounds, coupled with analysis of the molecular packing of the related three-ring compounds, will help to design self-organized molecules suitable for UV indicators.

  4. E-læring

    DEFF Research Database (Denmark)

    Hansbøl, Mikala

    2010-01-01

    Når der etableres forbindelser mellem uddannelse og it, så sker der forandringer af, hvad det vil sige at tale om uddannelse. Uddannelsen har måske ikke en fysisk campus. Det er heller ikke sikkert, at man behøver at gå i formel skole eller tage musiktimer hos en musiklærer ansigt-til-ansigt for ...... lære at spille guitar. E-læring eller på engelsk e-learning vil sige, at undervisningen og dermed din læring sker med it - noget som man er nødt til at tage bestik af....

  5. Drag of buoyant vortex rings.

    Science.gov (United States)

    Vasel-Be-Hagh, Ahmadreza; Carriveau, Rupp; Ting, David S-K; Turner, John Stewart

    2015-10-01

    Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015)], a perturbation analysis is performed to modify Turner's radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turner's radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers. PMID:26565349

  6. APS storage ring vacuum system

    International Nuclear Information System (INIS)

    The Advanced Photon Source synchrotron radiation facility, under construction at the Argonne National Laboratory, incorporates a large ring for the storage of 7 GeV positrons for the generation of photon beams for the facility's experimental program. The Storage Ring's 1104 m circumference is divided into 40 functional sectors. The sectors include vacuum, beam transport, control, acceleration and insertion device components. The vacuum system, which is designed to operate at a pressure of 1 n Torr, consists of 240 connected sections, the majority of which are fabricated from an aluminum alloy extrusion. The sections are equipped with distributed NeG pumping, photon absorbers with lumped pumping, beam position monitors, vacuum diagnostics and valving. The details of the vacuum system design, selected results of the development program and general construction plans are presented. 11 refs., 6 figs., 3 tabs

  7. Drag of buoyant vortex rings

    Science.gov (United States)

    Vasel-Be-Hagh, Ahmadreza; Carriveau, Rupp; Ting, David S.-K.; Turner, John Stewart

    2015-10-01

    Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015), 10.1017/jfm.2015.126], a perturbation analysis is performed to modify Turner's radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turner's radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers.

  8. On co-semihereditary rings

    Institute of Scientific and Technical Information of China (English)

    薛卫民

    1997-01-01

    A ring R is left co-semihereditary (strongly left co-semihereditary) if every finitely cogenerated factor of a finitely cogenerated (arbitrary) injective left R-module is injective.A left co-semihereditary ring,which is not strongly left co-semihereditary,is given to answer a question of Miller and Tumidge in the negative.If RUS defines a Morita duality,R is proved to be left co-semihereditary (left semihereditary) if and only if S is right semihereditary (right co-semihereditary).Assuming that S≥R is an almost excellent extension,S is shown to be (strongly) right co-semihereditary if and only if R is (strongly) right co-semihereditary.

  9. ring og it

    DEFF Research Database (Denmark)

      Antologien er et bidrag til didaktiske diskussioner om brug af f.eks. programpakker til sprogundervisning, præsentationsprogrammel og konferencesystemer på de videregående uddannelser. Antologien diskuterer ideen om, at multimediale medier og internettet kan understøtte læring, undervisning og ...... samarbejde ud fra konkrete eksempler på it-anvendelser, hvor fokus er på potentialer, barrierer og faldgruber....

  10. Selvreguleret læring

    DEFF Research Database (Denmark)

    Pedersen, Kirsten Hyldahl

    2012-01-01

    forudsætninger. For mange lærere er differentieret undervisning dog et diffust begreb, der kan være vanskeligt at forholde sig til i praksis. I denne artikel vil jeg derfor forsøge at svare på, om der kan findes en undervisningsstrategi, der vægter selvreguleret læring som værktøj, til at differentiere...

  11. Clic ring to main Linac

    CERN Document Server

    Stulle, F; Snuverink, J; Latina, A; Molloy, S

    2010-01-01

    The low emittance transport had been identified as one of the feasibility issues for CLIC. We discuss beam dynamics challenges occurring in the beam lines connecting the damping rings and the main linac. And we outline how these motivate design choices for the general RTML layout as well as its integration into the overall CLIC layout. Constraints originating from longitudinal dynamics and stabilization requirements of beam energy and phase at the main linac entrance are emphasized.

  12. Two Superconducting Storage Rings: ISABELLE

    Energy Technology Data Exchange (ETDEWEB)

    Sanford, J. R.

    1978-01-01

    The general features of the design and the status of the ISABELLE storage ring project at the present time are reported. It brings up to date the results reported at the National Particle Accelerator Conference in March 1977. The most significant change since that time has been an upgrading of the energy of the overall facility, and acceptance of the project by the Department of Energy.

  13. ring mellem elever

    DEFF Research Database (Denmark)

    Georgsen, Marianne; Davidsen, Jacob

    2010-01-01

    I denne rapport præsenteres resultater fra følgeforskningen til projektet Læring gennem Bevægelse, som er gennemført på Søndervangskolen i Hammel i perioden august 2009 - maj 2010. Projektet er gennemført i samspil mellem lærere, it-vejleder, elever og skolens ledelse. Projektets overordnede formål...

  14. ring mellem elever

    DEFF Research Database (Denmark)

    Davidsen, Jacob; Georgsen, Marianne

    I denne rapport tilbyder vi et indblik i det gennemførte projekt, og forfatterne har valgt nogle forhold ud, som belyses og diskuteres, mens andre ikke berøres eller diskuteres nævneværdigt i denne rapport. Det skyldes blandt andet projektets mange facetter, som dækker både læring, teknologi, pæd...

  15. Fluctuation-induced forces between rings threaded around a polymer chain under tension

    CERN Document Server

    Gilles, F M; Pastorino, C

    2016-01-01

    We characterize the fluctuation properties of a polymer chain under external tension and the fluctuation-induced forces between two ring molecules threaded around the chain. The problem is relevant in the context of fluctuation-induced forces in soft matter systems, features of liquid interfaces and to describe properties of polyrotaxanes and slide-ring materials. We perform molecular dynamics simulations of the Kremer-Grest bead-spring model for the polymer and a simple ring-molecule model, in the canonical ensemble. We study transverse fluctuations of the stretched chain, as a function of chain stretching and in the presence of ring-shaped threaded molecules. The fluctuation spectra of the chains are analyzed in equilibrium at constant temperature and the differences in presence of two ring molecules are compared. For the rings located at fixed distances, we find an attractive fluctuation-induced force between the rings, proportional to the temperature and decaying with the ring distance. We characterize th...

  16. THE RELATION BETWEEN QUASI VALUATION AND VALUATION RING AND FILTERED RING

    OpenAIRE

    Mohammad Hassan Anjom SHoa

    2014-01-01

    In this paper we show the relation between filtered ring and quasi valuation and valuation ring . We show if R is a filtered ring then we can define a quasi valuation. And if R is some kind of filtered ring then we can define a valuation. Then we prove some properties and relations for R.

  17. THE RELATION BETWEEN QUASI VALUATION AND VALUATION RING AND FILTERED RING

    OpenAIRE

    SHoa, Mohammad Hassan Anjom

    2014-01-01

    In this paper we show the relation between filtered ring and quasi valuation and valuation ring . We show if is a filtered ring then we can define a quasi valuation. And if is some kind of filtered ring then we can define a valuation. Then we prove some properties and relations for

  18. RVB1/RVB2: running rings around molecular biology

    OpenAIRE

    Jha, Sudhakar; Dutta, Anindya

    2009-01-01

    RVB1/RVB2 are two highly conserved members of the AAA+ family that are present in different protein and nucleoprotein complexes. Recent studies implicate that RVB-containing complexes play a role in variable cellular processes such as transcription, DNA damage response, snoRNP assembly, cellular transformation and cancer metastasis. In this review we discuss recent advances in the understanding of RVB-containing complexes and the functions of RVBs in these pathways.

  19. Anisotropic Effects on Magnetoelastic Transition in Magnetic Molecular Rings

    Institute of Scientific and Technical Information of China (English)

    LI Peng-Fei; CHEN Yu-Guang; CHEN Hong

    2006-01-01

    @@ We numerically study the anisotropic effects on the magnetoelastic transition in an S = 1/2 XXZ model with a finite lattice number. It is found that the order of the magnetoelastic transition is strongly affected by the anisotropy parameter A and there may exist a critical λc dividing the first-order transition and the continuous transition.

  20. Molecular Carbon Chains and Rings in TMC-1

    OpenAIRE

    Cernicharo, José; Fosse, David; Gerin, M.; Cox, Pierre

    2000-01-01

    We present mapping results in several rotational transitions of HC3N, C6H, both cyclic and linear C3H2 and C3H, towards the cyanopolyyne peak of the filamentary dense cloud TMC-1 using the IRAM 30m and MPIfR 100m telescopes. The spatial distribution of the cumulene carbon chain propadienylidene H2C3 (hereafter l-C3H2) is found to deviate significantly from the distributions of the cyclic isomer c-C3H2, HC3N, and C6H which in turn look very similar. The cyclic over linear abundance ratio of C3...

  1. Molecular Carbon Chains and Rings in TMC-1

    CERN Document Server

    Fosse, D; Gerin, M; Cox, P; Fosse, David; Cernicharo, Jose; Gerin, Maryvonne; Cox, Pierre

    2000-01-01

    We present mapping results in several rotational transitions of HC3N, C6H, both cyclic and linear C3H2 and C3H, towards the cyanopolyyne peak of the filamentary dense cloud TMC-1 using the IRAM 30m and MPIfR 100m telescopes. The spatial distribution of the cumulene carbon chain propadienylidene H2C3 (hereafter l-C3H2) is found to deviate significantly from the distributions of the cyclic isomer c-C3H2, HC3N, and C6H which in turn look very similar. The cyclic over linear abundance ratio of C3H2 increases by a factor of 3 across the filament, with a value of 28 at the cyanopolyyne peak. This abundance ratio is an order of magnitude larger than the range (3 to 5) we observed in the diffuse interstellar medium. The cyclic over linear abundance ratio of C3H also varies by ~2.5 in TMC-1, reaching a maximum value (13) close to the cyanopolyyne peak. These behaviors might be related to competitive processes between ion-neutral and neutral-neutral reactions for cyclic and linear species.

  2. Contraceptive vaginal ring (NuvaRing)-a novel, convenient and effective contraceptive option

    Institute of Scientific and Technical Information of China (English)

    Chen Wei-lin; Fan Guang-sheng

    2011-01-01

    Contraceptive vaginal ring (NuvaRing) is a new combined hormonal contraceptive method.Each ring contains 2.7mg ethinyl estradiol (EE) and 11.7mg etonogestrel.The ring is characteristic with its ease of use,lower EE systemic exposure and excellent cycle control.Studies have demonstrated that the efficacy and safety of the ring are equivalent to combined oral contraceptive (COC).The side effects of the ring are fewer and the biocompatibility is good.Recent studies have proved that the NuvaRing is a new,effective hormonal contraceptive option for women.

  3. Beam Measurements in Storage Rings

    Science.gov (United States)

    Hofmann, Albert

    1996-05-01

    Beam measurements in storage rings are made to diagnose performance limitations and to gain knowledge of the beam behavior in view of improvements and to the benefit for other machines. In beam optics the measurement of the orbit or the trajectory with beam position monitors distributed around the ring reveals deflection errors. The overall focusing is checked by measuring the betatron frequency (tune) using a pulse or continuous excitation of the oscillation. Observing this oscillation with all the beam position monitors around the ring the beta function and the betatron phase advance are obtained. This measurement done for different momenta, i.e. RF-frequencies, gives the local chromaticity and its correction. The tune dependence on quadrupole strength gives the value of the local beta function. Synchrotron radiation is a powerful diagnostics tool and can give the beam cross section. Beam instabilities are investigated with similar methods. The growth or damping rates and frequencies of betatron and synchrotron oscillations, observed as a function of intensity, give a convolution of the resistive and reactive part of the transverse and longitudinal impedance with the spectrum of the oscillation mode. Coupled bunch instabilities are caused by narrow band impedances at particular frequencies while single traversal effects, including energy loss and bunch lengthening, are due to a broad band impedance. A model of the impedance can be constructed from such measurements done with different bunch lengths, tunes and other parameters. In some cases the element causing an instability can be identified. The dependence of the orbit and phase advance around the ring on intensity can give the location of impedances. To probe the impedance at very high frequencies the effects on very short bunches or the energy loss of a continuous beam due to its Schottky noise are measured. The beam energy, usually known from magnetic measurements, can be obtained directly with high

  4. Generalized fuzzy ideals of near-rings

    Institute of Scientific and Technical Information of China (English)

    ZHAN Jian-ming; Dawaz B.

    2009-01-01

    The concept of ((∈),(∈)V (q))-fuzzy subnear-rings (ideals) of a near-ring is introduced and some of its related properties are investigated. In particular, the relationships among ordinary fuzzy subnear-rings (ideals), (∈,∈V q)-fuzzy subnear-rings (ideals) and ((∈),(∈)V (q))-fuzzy subnearrings (ideals) of near-rings are described. Finally, some characterization of [μ]t is given by means of (∈,∈V q)-fuzzy ideals.

  5. K stability and stability of chiral ring

    CERN Document Server

    Collins, Tristan C; Yau, Shing-Tung

    2016-01-01

    We define a notion of stability for chiral ring of four dimensional N=1 theory by introducing test chiral rings and generalized a maximization. We conjecture that a chiral ring is the chiral ring of a superconformal field theory if and only if it is stable. We then study N=1 field theory derived from D3 branes probing a three-fold singularity X, and show that the K stability which implies the existence of Ricci-flat conic metric on X is equivalent to the stability of chiral ring of the corresponding field theory.

  6. DYNAMICAL BALANCE STUDY OF RING REDUCER

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The basic structure of epicyclical gear transmission with inner teeth of single-ring, double-ring, three-ring and four-ring reducer are analyzed. The force analysis model of ring reducer is built. Following this, it is concluded that the present ring reducers have the problem that the inertia force or the inertia moment is lopsided. On the base of analysis and calculation the balanced ring reducer which can realize the balance of inertia force and inertia moment is brought forward, and so is its concrete realizing step. The specimen of the balanced ring reducer is designed and manufactured; the experiment is carried out on the gear transmission test bench. Compared with other ring reducer of the same power, the balanced ring reducer has many advantages, such as low vibration noise, low cost and less production difficulty and less heat. It is the substitute of other ring reducer of the same kind. Therefore, it has important theoretic significance and highly practical engineering value.

  7. Persistent current in a magnetized Rashba ring

    Institute of Scientific and Technical Information of China (English)

    Zhang Lin; Wang Jun

    2011-01-01

    We theoretically study the persistent currents flowing in a Rashba quantum ring subjected to the Rashba spinorbit interaction.By introducing uniform or nonuniform magnetization into the ring,we find that a nonzero persistent charge current circulates in the ring,which stems from the original equilibrium spin current due to the Rashba spinorbit interaction.Because of broken time reversal symmetry,the two oppositely flowing spin-up and spin-down charge currents of the equilibrium spin current are no longer equal,and so a net persistent charge current can flow in the system.It is also found that the persistent current can be modulated by the Fermi energy,the Rashba spin-orbit interaction strength and the magnetization in the ring.Moreover,the magnetization perpendicular to the ring plane can optimize the current.The persistent current flowing in the ring is a manifestation of the nonzero equilibrium spin current existing in the ring.

  8. Feasibility of a ring FEL at low emittance storage rings

    Energy Technology Data Exchange (ETDEWEB)

    Agapov, I., E-mail: ilya.agapov@xfel.eu

    2015-09-01

    A scheme for generating coherent radiation at latest generation low emittance storage rings such as PETRA III at DESY (Balewski et al., 2004 [1]) is proposed. The scheme is based on focusing and subsequent defocusing of the electron beam in the longitudinal phase space at the undulator location. The expected performance characteristics are estimated for radiation in the wavelength range of 500–1500 eV. It is shown that the average brightness is increased by several orders of magnitude compared to spontaneous undulator radiation, which can open new perspectives for photon-hungry soft X-ray spectroscopy techniques.

  9. Rings with each right ideal automorphism-invariant

    OpenAIRE

    KOŞAN, M. Tamer; Quynh, Truong Cong; Srivastava, Ashish K.

    2015-01-01

    In this paper, we study rings having the property that every right ideal is automorphism-invariant. Such rings are called right $a$-rings. It is shown that (1) a right $a$-ring is a direct sum of a square-full semisimple artinian ring and a right square-free ring, (2) a ring $R$ is semisimple artinian if and only if the matrix ring $\\mathbb{M}_n(R)$ for some $n>1$ is a right $a$-ring, (3) every right $a$-ring is stably-finite, (4) a right $a$-ring is von Neumann regular if and only if it is s...

  10. Rings in random environments: sensing disorder through topology.

    Science.gov (United States)

    Michieletto, Davide; Baiesi, Marco; Orlandini, Enzo; Turner, Matthew S

    2015-02-14

    In this paper we study the role of topology in DNA gel electrophoresis experiments via molecular dynamics simulations. The gel is modelled as a 3D array of obstacles from which half edges are removed at random with probability p, thereby generating a disordered environment. Changes in the microscopic structure of the gel are captured by measuring the electrophoretic mobility of ring polymers moving through the medium, while their linear counterparts provide a control system as we show they are insensitive to these changes. We show that ring polymers provide a novel, non-invasive way of exploiting topology to sense microscopic disorder. Finally, we compare the results from the simulations with an analytical model for the non-equilibrium differential mobility, and find a striking agreement between simulation and theory.

  11. Aromatic rings in chemical and biological recognition: energetics and structures.

    Science.gov (United States)

    Salonen, Laura M; Ellermann, Manuel; Diederich, François

    2011-05-16

    This review describes a multidimensional treatment of molecular recognition phenomena involving aromatic rings in chemical and biological systems. It summarizes new results reported since the appearance of an earlier review in 2003 in host-guest chemistry, biological affinity assays and biostructural analysis, data base mining in the Cambridge Structural Database (CSD) and the Protein Data Bank (PDB), and advanced computational studies. Topics addressed are arene-arene, perfluoroarene-arene, S⋅⋅⋅aromatic, cation-π, and anion-π interactions, as well as hydrogen bonding to π systems. The generated knowledge benefits, in particular, structure-based hit-to-lead development and lead optimization both in the pharmaceutical and in the crop protection industry. It equally facilitates the development of new advanced materials and supramolecular systems, and should inspire further utilization of interactions with aromatic rings to control the stereochemical outcome of synthetic transformations. PMID:21538733

  12. Einstein Ring in Distant Universe

    Science.gov (United States)

    2005-06-01

    Using ESO's Very Large Telescope, Rémi Cabanac and his European colleagues have discovered an amazing cosmic mirage, known to scientists as an Einstein Ring. This cosmic mirage, dubbed FOR J0332-3557, is seen towards the southern constellation Fornax (the Furnace), and is remarkable on at least two counts. First, it is a bright, almost complete Einstein ring. Second, it is the farthest ever found. ESO PR Photo 20a/05 ESO PR Photo 20a/05 Deep Image of a Region in Fornax (FORS/VLT) [Preview - JPEG: 400 x 434 pix - 60k] [Normal - JPEG: 800 x 867 pix - 276k] [Full Res - JPEG: 1859 x 2015 pix - 3.8M] ESO PR Photo 20b/05 ESO PR Photo 20b/05 Zoom-in on the Newly Found Einstein Ring (FORS/VLT) [Preview - JPEG: 400 x 575 pix - 168k] [Normal - JPEG: 630 x 906 pix - 880k] Caption: ESO PR Photo 20a/05 is a composite image taken in two bands (B and R) with VLT/FORS1 of a small portion of the sky (field-of-view 7x7' or 1/15th of the area of the full moon). The faintest object seen in the image has a magnitude 26, that is, it is 100 million times fainter than what can be observed with the unaided eye. The bright elliptical galaxy on the lower-left quadrant is a dwarf galaxy part of a large nearby cluster in the Fornax constellation. As for all deep images of the sky, this field shows a variety of objects, the brightest ponctual sources being stars from our Galaxy. By far the field is dominated by thousands of faint background galaxies the colours of which are related to the age of their dominant stellar population, their dust content and their distance. The newly found Einstein ring is visible in the top right part of the image. ESO PR Photo 20b/05 zooms-in on the position of the newly found cosmic mirage. ESO PR Photo 20c/05 ESO PR Photo 20c/05 Einstein Ring in Distant Universe (FORS/VLT) [Preview - JPEG: 400 x 584 pix - 104k] [Normal - JPEG: 800 x 1168 pix - 292k] [Full Res - JPEG: 1502 x 2192 pix - 684k] Caption of ESO PR Photo 20c/05: The left image is magnified and centred

  13. Triazatriangulene as binding group for molecular electronics

    DEFF Research Database (Denmark)

    Wei, Zhongming; Wang, Xintai; Borges, Anders;

    2014-01-01

    The triazatriangulene (TATA) ring system was investigated as a binding group for tunnel junctions of molecular wires on gold surfaces. Self-assembled monolayers (SAMs) of TATA platforms with three different lengths of phenylene wires were fabricated, and their electrical conductance was recorded ...... with its high stability and directionality make this binding group very attractive for molecular electronic measurements and devices. (Figure Presented)....

  14. The SABS finger ring service

    International Nuclear Information System (INIS)

    All radiation workers are required by law to wear personal dosimeters to measure the radiation dose they receive in the course of their work. However, there was a need to measure the radiation dose received by the fingers and hands, because they are much closer to the source of radiation than the rest of the body. In April 1982 a finger ring service was instituted on a routine basis. A thermoluminescent dosimeter (TLD) is used, which is suitable for both X-rays and gamma rays. Materials that are used for thermoluminescent dosimeters includes LiF:Mg, CaF2:Dy and CaSO4:Dy

  15. Viden og Læring

    DEFF Research Database (Denmark)

    Bordum, Anders

    2005-01-01

    Jeg vil i denne sammenhæng præsentere en fortolkning af hvordan Jürgen Habermas i forhold til klassisk epistemologi forstår viden og læring. Jeg vil argumentere for at vi i videnssamfundet har brug for den realistiske diskursbaserede model for videnstestning og vidensdannelse Habermas repræsenterer....... Endvidere vil jeg ved at rekonstruere Habermas' position med overbevisningen og propositionen som omdrejningspunkt vise at Habermas teori direkte kan omsættes som analysegrundlag og forståelsesramme for en hvilken som helst tematiseret praksis. Alt hvad der er virkeligt kan udtrykkes propositionelt. Den...

  16. Interface-læring

    DEFF Research Database (Denmark)

    Thorhauge, Sally

    2015-01-01

    Interface-læring er den læringsoplevelse, der kan opstå i grænsefladen mellem to væsensforskellige læringsmiljøer, når de mødes og griber ind i hinanden. Et gymnasium og et museum er eksempler på to sådanne læringsmiljøer. Artiklen præsenterer nogle af de væsentligste resultater fra min ph.d. afh.......d. afhandling Interface Learning - New goals for museum and upper secondary school collaboration (2014)....

  17. Nanofiber-segment ring resonator

    CERN Document Server

    Jones, D E; Franson, J D; Pittman, T B

    2016-01-01

    We describe a fiber ring resonator comprised of a relatively long loop of standard single-mode fiber with a short nanofiber segment. The evanescent mode of the nanofiber segment allows the cavity-enhanced field to interact with atoms in close proximity to the nanofiber surface. We report on an experiment using a warm atomic vapor and low-finesse cavity, and briefly discuss the potential for reaching the strong coupling regime of cavity QED by using trapped atoms and a high-finesse cavity of this kind.

  18. Nanofiber-segment ring resonator

    Science.gov (United States)

    Jones, D. E.; Hickman, G. T.; Franson, J. D.; Pittman, T. B.

    2016-08-01

    We describe a fiber ring resonator comprised of a relatively long loop of standard single-mode fiber with a short nanofiber segment. The evanescent mode of the nanofiber segment allows the cavity-enhanced field to interact with atoms in close proximity to the nanofiber surface. We report on an experiment using a warm atomic vapor and low-finesse cavity, and briefly discuss the potential for reaching the strong coupling regime of cavity QED by using trapped atoms and a high-finesse cavity of this kind.

  19. Storage ring proton EDM experiment

    CERN Document Server

    CERN. Geneva

    2015-01-01

    sensitivity of 10^-29 e-cm.  The strength of the method originates from the fact that there are high intensity polarized proton beams available and the fact that the so-called geometric phase systematic error background cancels with clock-wise and counter-clock-wise storage possible in electric rings. The ultimate sensitivity of the method is 10^-30 e-cm. At this level it will either detect a non-zero EDM or it will eliminate electro-weak baryogenesis.

  20. Interaction of ring dark solitons with ring impurities in Bose-Einstein condensates

    International Nuclear Information System (INIS)

    The interaction of ring dark solitons/vortexes with the ring-shaped repulsive and attractive impurities in two-dimensional Bose-Einstein condensates is investigated numerically. Very rich interaction phenomena are obtained, i.e., not only the interaction between the ring soliton and the impurity, but also the interaction between vortexes and the impurity. The interaction characters, i.e., snaking of ring soliton, quasitrapping or reflection of ring soliton and vortexes by the impurity, strongly depend on initial ring soliton velocity, impurity strength, initial position of ring soliton and impurity. The numerical results also reveal that ring dark solitons/vortexes can be trapped and dragged by an adiabatically moving attractive ring impurity

  1. Hermitian Groups over Local Rings

    Institute of Scientific and Technical Information of China (English)

    Guoping Tang

    2001-01-01

    The general hermitian group GH2n(R,a1,... ,ar) of rank n and its elementary subgroup EH2n(R,a1,... ,ar) were introduced by Bak [1] and Tang [4], respectively. It is known that EH2n(R, a1,... , ar) is perfect whenever n ≥ r+ 3 and the stable elementary hermitian group EH(R,a1,... ,ar) is the commutator subgroup of the stable general hermitian group GH(R, a1,... , ar).In this paper, we prove that, when R is a local ring, EH2n(R, a1,... , ar) is a normal subgroup of GH2n (R, a1,... , ar) if n ≥ r+2, and is the commutator subgroup of GH2n(R, a1,... , ar) if n ≥ r + 3. In the special case that R is a division ring,we show that the quotient group of GH2n(R, a1,... , ar) by EH2n(R, a1,... , ar)is independent of the choice of a1,... , ar.

  2. SLC positron damping ring optics design

    International Nuclear Information System (INIS)

    The basic SLAC Linear Collider operation scheme assumes the use of two damping rings, one for the e-, one for the e+, in order to reduce the colliding beam normalized emittances to 30 π μradm hence raising the corresponding luminosity by a factor 170. The e- damping ring optics, designed by H. Wiedemann, has been extensively studied and modelled since it's completion at the end of 1982. The e+ damping ring being built will be based on the same design except for some modifications resulting from the studies on the e- damping ring which clearly pointed out two major weak points as far as the optics is concerned. The present paper describes the basic modifications of the ring lattice and main equipment positions in order to improve the situation in the Positron Damping Ring. 16 refs., 2 figs., 1 tab

  3. A first course in noncommutative rings

    CERN Document Server

    Lam, T Y

    2001-01-01

    A First Course in Noncommutative Rings, an outgrowth of the author's lectures at the University of California at Berkeley, is intended as a textbook for a one-semester course in basic ring theory. The material covered includes the Wedderburn-Artin theory of semisimple rings, Jacobson's theory of the radical, representation theory of groups and algebras, prime and semiprime rings, local and semilocal rings, perfect and semiperfect rings, etc. By aiming the level of writing at the novice rather than the connoisseur and by stressing th the role of examples and motivation, the author has produced a text that is suitable not only for use in a graduate course, but also for self- study in the subject by interested graduate students. More than 400 exercises testing the understanding of the general theory in the text are included in this new edition.

  4. Threshold Ring Signature Scheme Based on TPM

    Institute of Scientific and Technical Information of China (English)

    Gong Bei; Jiang Wei; Lin Li; Li Yu; Zhang Xing

    2012-01-01

    The conventional ring signature schemes cannot address the scenario where the rank of members of the ring needs to be distinguished, for example, in electronically commerce application. To solve this problem, we presented a Trusted Platform Module (TPM)-based threshold ring signature schen. Employing a reliable secret Share Distribution Center (SDC), the proposed approach can authenticate the TPM-based identity rank of members of the ring but not track a specific member's identity. A subset including t members with the same identity rank is built. With the signing cooperation of t members of the subset, the ring signature based on Chinese remainder theorem is generated. We proved the anonymity and unforgeability of the proposed scheme and compared it with the threshold ring signature based on Lagrange interpolation polynomial. Our scheme is relatively simpler to calculate.

  5. Stable Bound Orbits around Black Rings

    Energy Technology Data Exchange (ETDEWEB)

    Igata, Takahisa; Ishihara, Hideki; Takamori, Yohsuke, E-mail: igata@sci.osaka-cu.ac.jp [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan)

    2011-09-22

    We study stable bound orbits of a free particle around a black ring. Unlike the higher-dimensional black hole case, we find that there exist stable bound orbits in toroidal spiral shape near the ring axis and stable circular orbits on the axis. In addition, radii of stable bound orbits can be infinitely large if the ring thickness is less than a critical value.

  6. Inductive Rings and Systems of Diophantine Equations

    Institute of Scientific and Technical Information of China (English)

    Rong Fang BIE; Shi Qiang WANG

    2006-01-01

    In this paper, by using model-theoretic methods, it is shown that some systems of unsolved cubic diophantine equations in number theory can have solutions in certain inductive extension rings of the ring I of rational integers. These inductive rings are not fields, and every element of them is a sum of 4 cubes and a sum of 3 squares. Also some of them satisfy the Goldbach conjecture and some others don't.

  7. Good Gradings of Generalized Incidence Rings

    CERN Document Server

    Price, Kenneth L

    2011-01-01

    This inquiry is based on both the construction of generalized incidence rings due to Gene Abrams and the construction of good group gradings of incidence algebras due to Molli Jones. We provide conditions for a generalized incidence ring to be graded isomorphic to a subring of an incidence ring over a preorder. We also extend Jones's construction to good group gradings for incidence algebras over preorders with crosscuts of length one or two.

  8. Weakly and Strongly Regular Near-rings

    Institute of Scientific and Technical Information of China (English)

    N.Argac; N.J.Groenewald

    2005-01-01

    In this paper, we prove some basic properties of left weakly regular near-rings.We give an affirmative answer to the question whether a left weakly regular near-ring with left unity and satisfying the IFP is also right weakly regular. In the last section, we use among others left 0-prime and left completely prime ideals to characterize strongly regular near-rings.

  9. Braided rings a scattering billiard model

    CERN Document Server

    Bénet, L

    1999-01-01

    We introduce a billiard scattering model consisting of two non-overlapping rotating discs in the context of the formation and structural properties of planetary rings. We show that due to the arrangement of the symmetric periodic orbits, stable orbits are found which in the configuration space lead to the appearance of patterns qualitatively similar to planetary rings. Rings associated with different stability regions are naturally braided; different braids may overlap displaying features similar to clumps. Erosion mechanisms within the model are discussed.

  10. Saturn Ring Data Analysis and Thermal Modeling

    Science.gov (United States)

    Dobson, Coleman

    2011-01-01

    CIRS, VIMS, UVIS, and ISS (Cassini's Composite Infrared Specrtometer, Visual and Infrared Mapping Spectrometer, Ultra Violet Imaging Spectrometer and Imaging Science Subsystem, respectively), have each operated in a multidimensional observation space and have acquired scans of the lit and unlit rings at multiple phase angles. To better understand physical and dynamical ring particle parametric dependence, we co-registered profiles from these three instruments, taken at a wide range of wavelengths, from ultraviolet through the thermal infrared, to associate changes in ring particle temperature with changes in observed brightness, specifically with albedos inferred by ISS, UVIS and VIMS. We work in a parameter space where the solar elevation range is constrained to 12 deg - 14 deg and the chosen radial region is the B3 region of the B ring; this region is the most optically thick region in Saturn's rings. From this compilation of multiple wavelength data, we construct and fit phase curves and color ratios using independent dynamical thermal models for ring structure and overplot Saturn, Saturn ring, and Solar spectra. Analysis of phase curve construction and color ratios reveals thermal emission to fall within the extrema of the ISS bandwidth and a geometrical dependence of reddening on phase angle, respectively. Analysis of spectra reveals Cassini CIRS Saturn spectra dominate Cassini CIRS B3 Ring Spectra from 19 to 1000 microns, while Earth-based B Ring Spectrum dominates Earth-based Saturn Spectrum from 0.4 to 4 microns. From our fits we test out dynamical thermal models; from the phase curves we derive ring albedos and non-lambertian properties of the ring particle surfaces; and from the color ratios we examine multiple scattering within the regolith of ring particles.

  11. Report of the eRHIC Ring-Ring Working Group

    Energy Technology Data Exchange (ETDEWEB)

    Aschenauer, E. C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Berg, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brennan, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fedotov, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fischer, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Litvinenko, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Montag, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Palmer, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Parker, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Peggs, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ptitsyn, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ranjbar, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tepikian, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Trbojevic, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Willeke, F. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-10-13

    This report evaluates the ring-ring option for eRHIC as a lower risk alternative to the linac-ring option. The reduced risk goes along with a reduced initial luminosity performance. However, a luminosity upgrade path is kept open. This upgrade path consists of two branches, with the ultimate upgrade being either a ring-ring or a linac-ring scheme. The linac-ring upgrade could be almost identical to the proposed linac-ring scheme, which is based on an ERL in the RHIC tunnel. This linac-ring version has been studied in great detail over the past ten years, and its significant risks are known. On the other hand, no detailed work on an ultimate performance ring-ring scenario has been performed yet, other than the development of a consistent parameter set. Pursuing the ring-ring upgrade path introduces high risks and requires significant design work that is beyond the scope of this report.

  12. Natural occupation numbers in two-electron quantum rings.

    Science.gov (United States)

    Tognetti, Vincent; Loos, Pierre-François

    2016-02-01

    Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.

  13. RING OPENING POLYMERIZATION OF TETRAHYDROFURAN CATALYSED BY MAGHNITE-H+

    Institute of Scientific and Technical Information of China (English)

    Khadidja Benkenfoud; Amine Harrane; Mohammed Belbachir

    2012-01-01

    The cationic ring-opening polymerization of tetrahydrofuran using maghnite-H- is reported.Maghnite-H+,is a non-toxic solid catalyst issued from proton exchanged montmorillonite clay.Polytetrahydrofuran,also called "poly(butandiol) ether",with acetate and hydroxyl end groups was successfully synthesized.Effects of reaction temperature,weight ratio of initiator/monomer and reaction time on the conversion of monomer and on the molecular weight are investigated.A cationic mechanism of the reaction was proposed.This chemistry can be considered as a suitable route for preparing poly(THF) as a soft segment for thermoplastic elastomers.

  14. Natural occupation numbers in two-electron quantum rings.

    Science.gov (United States)

    Tognetti, Vincent; Loos, Pierre-François

    2016-02-01

    Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems. PMID:26851909

  15. Natural occupation numbers in two-electron quantum rings

    Energy Technology Data Exchange (ETDEWEB)

    Tognetti, Vincent, E-mail: vincent.tognetti@univ-rouen.fr [Normandy Univ., COBRA UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, 1 rue Tesniére, 76821 Mont Saint Aignan, Cedex (France); Loos, Pierre-François [Research School of Chemistry, Australian National University, Canberra ACT 2601 (Australia)

    2016-02-07

    Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.

  16. Simulation of Rings about Ellipsoidal Bodies

    Science.gov (United States)

    Gupta, Akash; Nadkarni-Ghosh, Sharvari; Sharma, Ishan

    2016-10-01

    Recent discovery of rings around Chariklo, a centaur orbiting the Sun (F. Braga-Ribas et al., 2014) and speculations of rings around minor planet, Chiron (Ortiz et al., 2015), Saturn's satellites, Rhea (Jones et al., 2008; Schenk et al., 2011), Iapetus (Ip, 2006) or exoplanets, suggest that rings about non-spherical bodies is perhaps a more general phenomenon than anticipated. As a first step towards understanding such systems, we examine the dynamical behavior of rings around similar bodies using N-body simulations. Our code employs the `local simulation method' (Wisdom & Tremaine, 1988; Salo, 1995) and accounts for particle interactions via collisions using Discrete Element Method (Cundall & Strack, 1978; Bhateja et al., 2016) and mutual gravitation. The central body has been modeled as an axisymmetric ellipsoid characterized by its axis ratio, or defined via characteristic frequencies (circular, vertical and epicyclic frequency) representing the gravitational field of an axisymmetric body. We vary the central body's characterizing parameter and observe the change in various ring properties like the granular temperature, impact frequency, radial width and vertical thickness. We also look into the effect on ring properties upon variation in the size of the central body-ring system. Further, we investigate the role of characteristic frequencies in dictating the ring dynamics, and how this could help in qualitatively estimating the ring dynamics about any arbitrary central body with symmetry about the equatorial plane and the axis normal to it.

  17. Role of Friction in Cold Ring Rolling

    Institute of Scientific and Technical Information of China (English)

    He YANG; Lianggang GUO; Mei ZHAN

    2005-01-01

    Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming process parameters and friction, etc. Among these factors,friction between rolls and ring blank plays animportant role in keeping the stable forming of cold ring rolling. An analytical method was firstly presented for proximately determining the critical friction coefficient of stable forming and then a method was proposed to determine thecritical friction coefficient by combining analytical method with numerical simulation. And the influence of friction coefficient on the quality of end-plane and side spread of ring,rolling force, rolling moment and metal flow characteristic in the cold ring rolling process have been explored using the three dimensional (3D) numerical simulation based on the elastic-plastic dynamic finite element method (FEM)under the ABAQUS software environment, and the results show that increasing the friction on the contact surfaces between rolls and ring blank is useful not only for improving the stability of cold ring rolling but also for improving the geometry and dimension precision of deformed ring.

  18. What Perturbs the ggrdgr Rings of Uranus?

    Science.gov (United States)

    French, R G; Kangas, J A; Elliot, J L

    1986-01-31

    The gamma and delta rings have by far the largest radial perturbations of any of the nine known Uranian rings. These two rings deviate from Keplerian orbits, having typical root-mean-square residuals of about 3 kilometers (compared to a few hundred meters for the other seven known rings). Possible causes for the perturbations include nearby shepherd satellites and Lindblad resonances. If shepherd satellites are responsible, they could be as large as several tens of kilometers in diameter. The perturbation patterns of the gamma and delta rings have been examined for evidence of Lindblad resonances of azimuthal wave number m = 0, 1, 2, 3, and 4. The beta ring radial residuals are well matched by a 2:1 Lindblad resonance. If this represents a real physical phenomenon and is not an artifact of undersampling, then the most plausible interpretation is that there is an undiscovered satellite orbiting 76,522 +/- 8 kilometers from Uranus, with an orbital period of 15.3595 +/- 0.0001 hours and a radius of 75 to 100 kilometers. Such a satellite would be easily detected by the Voyager spacecraft when it encounters Uranus. The 2:1 resonance location is 41 +/- 9 kilometers inside the delta ring, which makes it unlikely that the resonance is due to a viscous instability within the ring. In contrast, no low-order Lindblad resonance matches the gamma ring perturbations, which are probably caused by one or more shepherd satellites large enough to be clearly visible in Voyager images. PMID:17776019

  19. Programmable DNA Nanosystem for Molecular Interrogation

    Science.gov (United States)

    Mathur, Divita; Henderson, Eric R.

    2016-06-01

    We describe a self-assembling DNA-based nanosystem for interrogating molecular interactions. The nanosystem contains a rigid supporting dumbbell-shaped frame, a cylindrical central core, and a mobile ring that is coaxial with the core. Motion of the ring is influenced by several control elements whose force-generating capability is based on the transition of single-stranded DNA to double-stranded DNA. These forces can be directed to act in opposition to adhesive forces between the ring and the frame thereby providing a mechanism for molecular detection and interrogation at the ring-frame interface. As proof of principle we use this system to evaluate base stacking adhesion and demonstrate detection of a soluble nucleic acid viral genome mimic.

  20. Anomalous ring-opening reaction of 4-styrylcoumarin dimer with amines; 4-suchirirukumarin niryotai no amin ni yoru ijo kaikan hanno

    Energy Technology Data Exchange (ETDEWEB)

    Miura, H.; Tanaka, K.; Saito, K.; Takata, T.; Hasegawa, M. [Toin University of Yokohama, Kanagawa (Japan). Department of Functional Chemistry and Technology

    2000-01-10

    Coumarin dimers generally show high reactivity in ring-opening polyaddition reaction with diamine to give a high-molecular-weight polyamide. However, the reaction of anti head-to-tail 4-styrylcoumarin dimer with hexamethylenediamine gave no polyamide at all. It was found that after the first ring-opening reaction by amine, styryl group on cyclobutane ring unexpectedly decreased electrophilicity of carbonyl group and disturbed the second ring opening reaction. After the first ring-opening, IR peaks of carbonyl group in the lactone ring and olefin group in the styryl group, remarkably shifted to the lower wavenumber. Based on the observed IR spectral shifts, unusual stabilization of the second lactone ring was shown. (author)

  1. THREE-DIMENSIONAL DUST MAPPING REVEALS THAT ORION FORMS PART OF A LARGE RING OF DUST

    Energy Technology Data Exchange (ETDEWEB)

    Schlafly, E. F.; Rix, H.-W.; Martin, N. F. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Green, G.; Finkbeiner, D. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Burgett, W. S.; Chambers, K. C.; Kaiser, N.; Morgan, J. S.; Tonry, J. L.; Wainscoat, R. J.; Waters, C. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 (United States); Draper, P. W.; Metcalfe, N. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Price, P. A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2015-02-01

    The Orion Molecular Complex is the nearest site of ongoing high-mass star formation, making it one of the most extensively studied molecular complexes in the Galaxy. We have developed a new technique for mapping the three-dimensional distribution of dust in the Galaxy using Pan-STARRS1 photometry. We isolate the dust at the distance to Orion using this technique, revealing a large (100 pc, 14° diameter), previously unrecognized ring of dust, which we term the ''Orion dust ring''. The ring includes Orion A and B, and is not coincident with current Hα features. The circular morphology suggests formation as an ancient bubble in the interstellar medium, though we have not been able to conclusively identify the source of the bubble. This hint at the history of Orion may have important consequences for models of high-mass star formation and triggered star formation.

  2. Concentric ring flywheel with hooked ring carbon fiber separator/torque coupler

    Science.gov (United States)

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel with expandable separators, which function as torque couplers, between the rings to take up the gap formed between adjacent rings due to differential expansion between different radius rings during rotation of the flywheel. The expandable separators or torque couplers include a hook-like section at an upper end which is positioned over an inner ring and a shelf-like or flange section at a lower end onto which the next adjacent outer ring is positioned. As the concentric rings are rotated the gap formed by the differential expansion there between is partially taken up by the expandable separators or torque couplers to maintain torque and centering attachment of the concentric rings.

  3. Control of ring lasers by means of coupled cavities

    DEFF Research Database (Denmark)

    Buchhave, Preben; Abitan, Haim; Tidemand-Lichtenberg, Peter

    2000-01-01

    Variable phase coupling to an external ring is used to control a unidirectional ring laser. The observed behavior of the coupled rings is explained theoretically. We have found experimentally that by quickly changing the phase of the feedback from the external ring it is possible to Q-switch the...... ring laser. Also, at certain values of the phase of the feedback in the external ring, instabilities in the total system occur and oscillations arise in the ring laser....

  4. Mechanical support of a ceramic gas turbine vane ring

    Science.gov (United States)

    Shi, Jun; Green, Kevin E.; Mosher, Daniel A.; Holowczak, John E.; Reinhardt, Gregory E.

    2010-07-27

    An assembly for mounting a ceramic turbine vane ring onto a turbine support casing comprises a first metal clamping ring and a second metal clamping ring. The first metal clamping ring is configured to engage with a first side of a tab member of the ceramic turbine vane ring. The second metal clamping ring is configured to engage with a second side of the tab member such that the tab member is disposed between the first and second metal clamping rings.

  5. Low-emittance Storage Rings

    CERN Document Server

    Wolski, A

    2014-01-01

    The effects of synchrotron radiation on particle motion in storage rings are discussed. In the absence of radiation, particle motion is symplectic, and the beam emittances are conserved. The inclusion of radiation effects in a classical approximation leads to emittance damping: expressions for the damping times are derived. Then, it is shown that quantum radiation effects lead to excitation of the beam emittances. General expressions for the equilibrium longitudinal and horizontal (natural) emittances are derived. The impact of lattice design on the natural emittance is discussed, with particular attention to the special cases of FODO-, achromat- and theoretical-minimum-emittance-style lattices. Finally, the effects of betatron coupling and vertical dispersion (generated by magnet alignment and lattice tuning errors) on the vertical emittance are considered.

  6. Relations in the tautological ring

    CERN Document Server

    Pandharipande, R

    2011-01-01

    These notes cover our series of three lectures at Humboldt University in Berlin for the October 2010 conference "Intersection theory on moduli space" (organized by G. Farkas). The topic concerns relations among the kappa classes in the tautological ring of the moduli space of genus g curves. After a discussion of classical constructions in Wick form, we derive an explicit set of relations obtained from the virtual geometry of the moduli space of stable quotients. In a series of steps, the stable quotient relations are transformed to simpler and simpler forms. Our final result establishes a previously conjectural set of tautological relations proposed a decade ago by Faber-Zagier. The Faber-Zagier relations are defined using g and a single series in one variable with coefficients (6i)!/(3i)!(2i)!. Whether these relations span the complete set of relations among the kappa classes on the moduli space of genus g curves is an interesting question.

  7. On PMM Rings%关于PMM环

    Institute of Scientific and Technical Information of China (English)

    李忠华; 宋光天; 储诚浩

    2005-01-01

    The PMM rings are defined and studied in this paper.A ring R is called a PMM ring if for any ring S which is Morita similar to R,Mm(S) is isomorphic to Mn(R) for some n,m∈N. The following results are proved in this paper.A ring R is a PMM ring if and only if whenever given a progenerator P over R, there exist m,n∈N and some Picard progenerator Q over R such that Pm is isomorphic to Qn. PMM rings with VBN property are just T2-rings;and with IBN property are T1-rings.If R is a commutative PMM ring,then R is indecomposable and the Picard group of R is power divisible.In particular,a Dedekind domain R is a PMM ring if and only if the Picard group of R is power divisible.%定义了PMM环.环R称为PMM环,若对任何Morita相似于R的环S,存在m,n∈N,使得Mm(S)同构于Mn(R).证明了如下结果:环R是PMM环当且仅当任给R的投射生成元P,存在m,n∈N以及R上的Picard投射生成元Q,使得Pm同构于Qn.具有VBN性质的PMM环是T2-环;具有IBN性质的PM环是T1-环.若交换环R是PMM环,则R是不可分解的且R的Picard群是幂可除的.特别地,Dedekind整环R是PMM环当且仅当R的Picard群是幂可除的.

  8. Photo-driven Molecular Wankel Engine B$_{13}^+$

    CERN Document Server

    Zhang, Jin; Sparta, Manuel; Alexandrova, Anastassia N

    2012-01-01

    We report a molecular Wankel motor, the dual-ring structure B13+, driven by circularly-polarized infrared electromagnetic radiation, under which a guided uni-directional rotation of the outer ring is achieved with rotational frequency of the order of 300 MHz.

  9. Enzyme-catalyzed ring-opening polymerization of unsubstituted beta-lactam

    NARCIS (Netherlands)

    Schwab, Leendert W.; Kroon, Renee; Schouten, Arend Jan; Loos, Katja

    2008-01-01

    The synthesis of poly(beta-alanine) by Candida antarctica lipase B immobilized as novozyme 435 catalyzed ring-opening of 2-azetidinone is reported. After removal of cyclic side products and low molecular weight species pure linear poly(beta-alanine) is obtained. The formation of the polymer is confi

  10. Evanescent-wave cavity ring-down detection of cytochrome c on surface-modified prisms

    NARCIS (Netherlands)

    Sneppen, van der L.; Gooijer, C.; Ubachs, W.M.G.; Ariese, F.

    2009-01-01

    Adsorption kinetics and molecular interactions on different Surface interfaces are studied by means of evanescent-wave cavity ring-down spectroscopy, using total internal reflection surfaces Onto Which different self-assembled monolayers are covalently attached. The adsorption of cytochrome c (a pos

  11. Influence of ring growth rate on damage development in hot ring rolling

    NARCIS (Netherlands)

    Wang, C.; Geijselaers, H.J.M.; Omerspahic, E.; Recina, V.; Boogaard, van den A.H.

    2016-01-01

    As an incremental forming process of bulk metal, ring rolling provides a cost effective process route to manufacture seamless rings. In the production of hot rolled rings, defects such as porosity can sometimes be found in high alloyed steel, manufactured from ingots having macro-segregation. For th

  12. VUV optical ring resonator for Duke storage ring free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Park, S.H.; Litvinenko, V.N.; Madey, J.M.J. [Duke Univ., Durham, NC (United States)] [and others

    1995-12-31

    The conceptual design of the multifaceted-mirror ring resonator for Duke storage ring VUV FEL is presented. The expected performance of the OK-4 FEL with ring resonator is described. We discuss in this paper our plans to study reflectivity of VUV mirrors and their resistivity to soft X-ray spontaneous radiation from OK-4 undulator.

  13. The combined contraceptive vaginal ring (NuvaRing) and endometrial histology.

    NARCIS (Netherlands)

    Bulten, J.; Grefte, J.M.M.; Siebers, A.G.; Dieben, T.

    2005-01-01

    We investigated the effects of NuvaRing on endometrial histology in a 2-year open-label, multicenter trial in 103 premenopausal women aged 18-35 years. Subjects received 26 cycles of treatment, each comprising 3 weeks of ring use followed by a 1-week ring-free period. Endometrial biopsies were taken

  14. Photo- and electro-chromism of diarylethene modified ITO electrodes - towards molecular based read-write-erase information storage

    NARCIS (Netherlands)

    Areephong, J.; Browne, W.R.; Katsonis, N.; Feringa, B.L.

    2006-01-01

    Molecular memory devices based on dithienylethene switch modified ITO electrodes undergo reversible ring opening/closing both photo- and electro-chemically with non-destructive electrochemical readout.

  15. Vortex Ring Interaction with Multiple Permeable Screens

    Science.gov (United States)

    Musta, Mustafa N.; Krueger, Paul S.

    2008-11-01

    Previous experiments on the interaction of a vortex ring impinging on single thin permeable screen demonstrated the formation of secondary vortices and a transmitted vortex ring. The present work concerns experimental investigation of the interaction of a vortex ring with multiple permeable screens. Vortex rings are formed by piston-cylinder type vortex ring generator and impinge on an array of parallel, transparent screens. The screens have an open ratio of 84% and the spacing between screens is variable. The vortex rings were formed with an approximate jet Reynolds number of 1300 and a piston stroke-to-jet diameter ratio (L/D) of approximately 4. Dye visualization of the vortex rings shows that they break into multiple vortices after impinging on first screen The vortices subsequently disintegrate, but the total distance required for disintegration is relatively unaffected by the number of screens through with the vortices pass due to the regular structure of the screens. It is also observed that the location of the initial vortex ring axis relative to the screen rods has a significant effect on the vortex breakup and disintegration process.

  16. Pulsed magnetic field distribution near conducting rings

    International Nuclear Information System (INIS)

    Measurements and calculations of the magnetic field distribution in the vicinity of stainless steel rings immersed in a pulsed magnetic field are compared. The computer code TRIDIF is found to produce results in good agreement with the measurements. The perturbations in magnetic field due to the rings are found to be considerably less than one would expect from one-dimensional skin depth considerations

  17. On the nonlinear modeling of ring oscillators

    KAUST Repository

    Elwakil, Ahmed S.

    2009-06-01

    We develop higher-order nonlinear models of three-stage and five-stage ring oscillators based on a novel inverter model. The oscillation condition and oscillation frequency are derived and compared to classical linear model analysis. Two important special cases for five-stage ring oscillators are also studied. Numerical simulations are shown. © 2009 World Scientific Publishing Company.

  18. Rank 2 fusion rings are complete intersections

    DEFF Research Database (Denmark)

    Andersen, Troels Bak

    We give a non-constructive proof that fusion rings attached to a simple complex Lie algebra of rank 2 are complete intersections.......We give a non-constructive proof that fusion rings attached to a simple complex Lie algebra of rank 2 are complete intersections....

  19. On Polynomial Functions over Finite Commutative Rings

    Institute of Scientific and Technical Information of China (English)

    Jian Jun JIANG; Guo Hua PENG; Qi SUN; Qi Fan ZHANG

    2006-01-01

    Let R be an arbitrary finite commutative local ring. In this paper, we obtain a necessary and sufficient condition for a function over R to be a polynomial function. Before this paper, necessary and sufficient conditions for a function to be a polynomial function over some special finite commutative local rings were obtained.

  20. Ideals in Polynomial Near-rings

    Institute of Scientific and Technical Information of China (English)

    Mark Farag

    2002-01-01

    In this paper, we further explore the relationship between the ideals of N and those of N[x], where N is a zero-symmetric right near-ring with identity and N[x] is the polynomial near-ring introduced by Bagley in 1993.

  1. Local Duality for 2-Dimensional Local Ring

    Indian Academy of Sciences (India)

    Belgacem Draouil

    2008-11-01

    We prove a local duality for some schemes associated to a 2-dimensional complete local ring whose residue field is an -dimensional local field in the sense of Kato–Parshin. Our results generalize the Saito works in the case =0 and are applied to study the Bloch–Ogus complex for such rings in various cases.

  2. C and C* among intermediate rings

    NARCIS (Netherlands)

    J. Sack; S. Watson

    2013-01-01

    Given a completely regular Hausdorff space X, an intermediate ring A(X) is a ring of real valued continuous functions between C*(X) and C(X). We discuss two correspondences between ideals in A(X) and z-filters on X, both reviewing old results and introducing new results. One correspondence, ZA, exte

  3. On Hochschild cohomology rings of Fibonacci algebras

    Institute of Scientific and Technical Information of China (English)

    FAN Jinmei; XU Yunge

    2006-01-01

    Let A be a Fibonacci algebra over a field k.The multiplication of Hochschild cohomology ring of A induced by the Yoneda product is described explicitly.As a consequence,the multiplicative structure of Hochschild cohomology ring of A is proved to be trivial.

  4. Dieudonn\\'e theory over semiperfect rings

    OpenAIRE

    Lau, Eike

    2016-01-01

    The Dieudonn\\'e crystal of a p-divisible group over a semiperfect ring R can be endowed with a window structure. If R satisfies a boundedness condition, this construction gives an equivalence of categories. As an application one obtains a classification of p-divisible groups over arbitrary perfectoid rings by Breuil-Kisin modules.

  5. Let Freedom Ring! Bulletin, 1937, No. 32

    Science.gov (United States)

    Calhoun, Harold G.; Calhoun, Dorothy; Hatch, Roy W.; Cohen, Philip H.; Schramm, Rudolf

    1937-01-01

    This volume of "Let Freedom Ring!" contains the scripts of the 13 national broadcasts of the radio series of that name presented in the spring of 1937 over the national network of the Columbia Broadcast System. In "Let Freedom Ring!" you will find the courage, the struggle, the triumph of men and women who fought to win and safeguard liberties…

  6. Fuzzy Rough Ring and Its Prop erties

    Institute of Scientific and Technical Information of China (English)

    REN Bi-jun; FU Yan-ling

    2013-01-01

    This paper is devoted to the theories of fuzzy rough ring and its properties. The fuzzy approximation space generated by fuzzy ideals and the fuzzy rough approximation operators were proposed in the frame of fuzzy rough set model. The basic properties of fuzzy rough approximation operators were analyzed and the consistency between approximation operators and the binary operation of ring was discussed.

  7. Giant Rings in the CMB Sky

    CERN Document Server

    Kovetz, Ely D; Itzhaki, Nissan

    2010-01-01

    We find a unique direction in the CMB sky around which giant rings have an anomalous mean temperature profile. This direction is in very close alignment with the afore measured anomalously large bulk flow direction. We argue that a cosmic defect seeded by a pre-inflationary particle could explain the giant rings, the large bulk flow and their alignment.

  8. Prometheus Induced Vorticity In Saturns F Ring

    CERN Document Server

    Sutton, Phil J

    2016-01-01

    Saturns rings are known to show remarkable real time variability in their structure. Many of which can be associated to interactions with nearby moons and moonlets. Possibly the most interesting and dynamic place in the rings, probably in the whole Solar System, is the F ring. A highly disrupted ring with large asymmetries both radially and azimuthally. Numerically non zero components to the curl of the velocity vector field (vorticity) in the perturbed area of the F ring post encounter are witnessed, significantly above the background vorticity. Within the perturbed area rich distributions of local rotations is seen located in and around the channel edges. The gravitational scattering of ring particles during the encounter causes a significant elevated curl of the vector field above the background F ring vorticity for the first 1-3 orbital periods post encounter. After 3 orbital periods vorticity reverts quite quickly to near background levels. This new found dynamical vortex life of the ring will be of grea...

  9. A ring burn--electric or contact?

    Science.gov (United States)

    Attalla, M F; el-Ekiabi, S; Al-Baker, A

    1990-02-01

    A circumferential band of deep burn affecting the ring finger sustained by a car electrician is presented. Although it was caused by short circuiting the car battery by a metal spanner and the ring he was wearing, the injury was purely a contact burn. PMID:2322399

  10. Highest Weight Categories For Number Rings

    CERN Document Server

    Pilkington, Annette

    2011-01-01

    This paper examines the concept of a stratified exact category in the context of number rings and corresponding Galois groups. BGG reciprocity and duality are proven for these categories making them highest weight categories. The strong connections between the structure of the category and ramification in the ring are explored.

  11. New Horizons Imaging of Jupiter's Main Ring

    Science.gov (United States)

    Throop, Henry B.; Showalter, Mark Robert; Dones, Henry C. Luke; Hamilton, D. P.; Weaver, Harold A.; Cheng, Andrew F.; Stern, S. Alan; Young, Leslie; Olkin, Catherine B.; New Horizons Science Team

    2016-10-01

    New Horizons took roughly 520 visible-light images of Jupiter's ring system during its 2007 flyby, using the spacecraft's Long-Range Reconnaissance Imager (LORRI). These observations were taken over nine days surrounding Jupiter close-approach. They span a range in distance of 30 - 100 RJ, and a phase angle range of 20 - 174 degrees. The highest resolution images -- more than 200 frames -- were taken at a resolution approaching 20 km/pix.We will present an analysis of this dataset, much of which has not been studied in detail before. Our results include New Horizons' first quantitative measurements of the ring's intrinsic brightness and variability. We will also present results on the ring's azimuthal and radial structure. Our measurements of the ring's phase curve will be used to infer properties of the ring's dust grains.Our results build on the only previous analysis of the New Horizons Jupiter ring data set, presented in Showalter et al (2007, Science 318, 232-234), which detected ring clumps and placed a lower limit on the population of undetected ring-moons.This work was supported by NASA's OPR program.

  12. Flexible Twin Open Ring Metro WDM Network

    Institute of Scientific and Technical Information of China (English)

    Susumu Kinoshita; Cechan Tian; Satoru Ohdate; Koji Takeguchi; Yasuhiko Aoki

    2003-01-01

    We have demonstrated a flexible twin open ring WDM network for metro applications. A pair of optical switches in the network keeps the fiber rings open to prevent signal circulation. Traffics are broadcast to every node and selected at the receiving side. Superior transmission and protection switching are proved.

  13. Interactions between unidirectional quantized vortex rings

    CERN Document Server

    Zhu, T; Brown, R A; Walmsley, P M; Golov, A I

    2016-01-01

    We have used the vortex filament method to numerically investigate the interactions between pairs of quantized vortex rings that are initially traveling in the same direction but with their axes offset by a variable impact parameter. The interaction of two circular rings of comparable radii produce outcomes that can be categorized into four regimes, dependent only on the impact parameter; the two rings can either miss each other on the inside or outside, or they can reconnect leading to final states consisting of either one or two deformed rings. The fraction of of energy went into ring deformations and the transverse component of velocity of the rings are analyzed for each regime. We find that rings of very similar radius only reconnect for a very narrow range of the impact parameter, much smaller than would be expected from geometrical cross-section alone. In contrast, when the radii of the rings are very different, the range of impact parameters producing a reconnection is close to the geometrical value. A...

  14. Ethinyl Estradiol and Etonogestrel Vaginal Ring

    Science.gov (United States)

    ... cervix (opening of the uterus) to prevent sperm (male reproductive cells) from entering. The contraceptive ring is a very effective method of birth ... will help you choose a method, such as male condoms and/or spermicides. You ... not use a diaphragm when a contraceptive ring is in place.You do not need ...

  15. Non-commutative Modal Rings and Internalized Equality

    Institute of Scientific and Technical Information of China (English)

    D. Fearnley-Sander; A.V. Kelarev; T. Stokes

    2002-01-01

    We generalize the notion of modal Boolean rings to rings in general. The connection between Boolean rings with equality and modal Boolean rings provides a cue for the definition. The main motivation lies in the existence of examples such as matrix and polynomial rings over modal Boolean rings and Cartesian products of associative rings with identity, along with the desire that the class of "modal rings" be closed under formation of not only the usual homomorphic image, subalgebra and direct product constructions, but also the ring-theoretic constructions of forming matrices and polynomials.

  16. ATOMIC FORCE MICROSCOPY STUDIES OF POLYCAPROLACTONE RINGED SPHERULITES

    Institute of Scientific and Technical Information of China (English)

    Jian-bin Zhang; De-zhu Ma; Hua Zhong; Xiao-lie Luo

    2000-01-01

    The surface morphology of free-surface PCL ringed spherulites was investigated by using atomic force microscopy. The spherulites were obtained by crystallization of PCL/PVC blends of different compositions. It was found that the ringed spherulite exhibited regularly fluctuating rings on its surface. Compared with the bright-dark ring pattern of the spherulite under a polarizing microscope, it was proved that the optical characteristics of the ringed spherulite under polarizing microscope coincided with its surface characteristics. The bright rings in polarizing micrographs of the spherulite coincided with the convex rings on its surface, while the dark rings coincided with the concave rings.

  17. Process Design by FEM Simulation for Shape Ring Rolling of Large-Sized Ring

    Science.gov (United States)

    Lee, Y. S.; Lee, M. W.; Park, S. S.; Lee, I.; Moon, Y. H.

    2010-06-01

    Ring rolling process is usually used to fabricate large-sized ring, such as, tower flange for wind power electric generator. Many kinds of seamless ring are used in wind power electric generator and manufactured by ring rolling process. In general, final part is machined after forming with shape of plain square section. Since interests for near net shaping of seamless ring have been increased gradually because of green energy, it is necessary to develop the technology for shape ring rolling with respect to the market demands and cost. Therefore, we studied the process and die design for shape ring rolling of large sized ring over 3,500 mm out diameter by experiment and FEM simulation. Ring rolling process is very difficult to solve by FEM method because of equilibrium state and size effect, etc. Moreover, shape ring rolling is more difficult to solve the problem that two plastic deformation zones are different each other, that is main roll and conical roll. Also since conical roll has a shape, deformation velocity field is very much complex and the deformed section passed axial roll is different section and velocity field. The FE simulations are performed to analyze process variables affected in forming of profiled ring. Therefore, the main features of used FE model are: (1) it adopts a transient or unsteady state full ring mesh to model the deformation processes and shape development; (2) the mandrel and conical rolls are modeled using coupled heat-transfer elements; (3) the model involves the full process from blank through perform to final profiled ring. From these calculated results, we have proposed the mechanisms of various tools, such as mandrel and conical roll. The calculated results are compared experimental results. Calculated results can predict the tilting of profiled ring and then process variables to form large sized ring.

  18. Radiation from structured-ring resonators

    CERN Document Server

    Maling, B; Craster, R V

    2016-01-01

    We investigate the scalar-wave resonances of systems composed of identical Neumann-type inclusions arranged periodically around a circular ring. Drawing on natural similarities with the undamped Rayleigh-Bloch waves supported by infinite linear arrays, we deduce asymptotically the exponentially small radiative damping in the limit where the ring radius is large relative to the periodicity. In our asymptotic approach, locally linear Rayleigh-Bloch waves that attenuate exponentially away from the ring are matched to a ring-scale WKB-type wave field. The latter provides a descriptive physical picture of how the mode energy is transferred via tunnelling to a circular evanescent-to-propagating transition region a finite distance away from the ring, from where radiative grazing rays emanate to the far field. Excluding the zeroth-order standing-wave modes, the position of the transition circle bifurcates with respect to clockwise and anti-clockwise contributions, resulting in striking spiral wavefronts.

  19. Hidden Beauty in Twisted Viking Neck Rings

    CERN Document Server

    Olsen, Kasper

    2010-01-01

    Many hoards found in Ireland, Scotland, Orkney Islands, and Scandinavia demonstrate the vikings ability to fabricate beautiful arm and neck rings of twisted silver and gold rods. Characteristic for such rings is the uniform appearance of the twisted pattern along the length of the arm ring, as well as from one arm ring to another, also when found at distant geographical locations. How can the appearance of the twisted wires be so perfectly repetitive? We demonstrate that the answer is that the vikings utilized a self-forming motif: The pattern arises from a twisting of the wires to a maximally rotated configuration. That is why the twist patterns in these arm and neck rings are beautiful, repetitive, and universal.

  20. The rings of Uranus - Nature and origin

    Science.gov (United States)

    Dermott, S. F.; Gold, T.; Sinclair, A. T.

    1979-01-01

    Effects of a resonance between a set of ring particles and individual satellites are considered. It is suggested that the resonances are 1:1 for the rings of Uranus and that each ring must contain an as-yet unseen satellite. A model is proposed in which the rings of Uranus were caused by small satellites that entered the Roche zone due to tidal drag. According to this model, the satellites gradually lost material from their surfaces in this zone, the particles left a satellite with relatively low speeds and must have entered orbits similar to that of the satellite, and the gravitational force of the satellite compelled these particles to remain in a narrow sharply defined ring.

  1. A topologically driven glass in ring polymers

    Science.gov (United States)

    Michieletto, Davide

    2016-05-01

    The static and dynamic properties of ring polymers in concentrated solutions remains one of the last deep unsolved questions in polymer physics. At the same time, the nature of the glass transition in polymeric systems is also not well understood. In this work, we study a novel glass transition in systems made of circular polymers by exploiting the topological constraints that are conjectured to populate concentrated solutions of rings. We show that such rings strongly interpenetrate through one another, generating an extensive network of topological interactions that dramatically affects their dynamics. We show that a kinetically arrested state can be induced by randomly pinning a small fraction of the rings. This occurs well above the classical glass transition temperature at which microscopic mobility is lost. Our work both demonstrates the existence of long-lived inter-ring penetrations and realizes a novel, topologically induced, glass transition.

  2. Interdigitated ring electrodes: Theory and experiment

    CERN Document Server

    Barnes, Edward O; Pozo-Ayuso, Diego F; Castaño-Alvarez, Mario; Lewis, Grace E M; Dale, Sara E C; Marken, Frank; Compton, Richard G

    2013-01-01

    The oxidation of potassium ferrocyanide, K_4Fe(CN)_6, in aqueous solution under fully supported conditions is carried out at interdigitated band and ring electrode arrays, and compared to theoretical models developed to simulate the processes. Simulated data is found to fit well with experimental results using literature values of diffusion coefficients for Fe(CN)_6^(4-) and Fe(CN)_6^(3-). The theoretical models are used to compare responses from interdigitated band and ring arrays, and the size of ring array required to approximate the response to a linear band array is investigated. An equation is developed for the radius of ring required for a pair of electrodes in a ring array to give a result with 5% of a pair of electrodes in a band array. This equation is found to be independent of the scan rate used over six orders of magnitude.

  3. 46 CFR 117.70 - Ring life buoys.

    Science.gov (United States)

    2010-10-01

    ... the body of the ring life buoy. (3) Each floating waterlight installed after March 11, 1997, on a... 46 Shipping 4 2010-10-01 2010-10-01 false Ring life buoys. 117.70 Section 117.70 Shipping COAST... Ring Life Buoys and Life Jackets § 117.70 Ring life buoys. (a) A vessel must have one or more ring...

  4. Tandem Ring-Opening-Ring-Closing Metathesis for Functional Metathesis Catalysts.

    Science.gov (United States)

    Nagarkar, Amit A; Yasir, Mohammad; Crochet, Aurelien; Fromm, Katharina M; Kilbinger, Andreas F M

    2016-09-26

    Use of a tandem ring-opening-ring-closing metathesis (RORCM) strategy for the synthesis of functional metathesis catalysts is reported. Ring opening of 7-substituted norbornenes and subsequent ring-closing metathesis forming a thermodynamically stable 6-membered ring lead to a very efficient synthesis of new catalysts from commercially available Grubbs' catalysts. Hydroxy functionalized Grubbs' first- as well as third-generation catalysts have been synthesized. Mechanistic studies have been performed to elucidate the order of attack of the olefinic bonds. This strategy was also used to synthesize the ruthenium methylidene complex. PMID:27592840

  5. Tandem Ring-Opening-Ring-Closing Metathesis for Functional Metathesis Catalysts.

    Science.gov (United States)

    Nagarkar, Amit A; Yasir, Mohammad; Crochet, Aurelien; Fromm, Katharina M; Kilbinger, Andreas F M

    2016-09-26

    Use of a tandem ring-opening-ring-closing metathesis (RORCM) strategy for the synthesis of functional metathesis catalysts is reported. Ring opening of 7-substituted norbornenes and subsequent ring-closing metathesis forming a thermodynamically stable 6-membered ring lead to a very efficient synthesis of new catalysts from commercially available Grubbs' catalysts. Hydroxy functionalized Grubbs' first- as well as third-generation catalysts have been synthesized. Mechanistic studies have been performed to elucidate the order of attack of the olefinic bonds. This strategy was also used to synthesize the ruthenium methylidene complex.

  6. Semi-algebraic function rings and reflectors of partially ordered rings

    CERN Document Server

    Schwartz, Niels

    1999-01-01

    The book lays algebraic foundations for real geometry through a systematic investigation of partially ordered rings of semi-algebraic functions. Real spectra serve as primary geometric objects, the maps between them are determined by rings of functions associated with the spectra. The many different possible choices for these rings of functions are studied via reflections of partially ordered rings. Readers should feel comfortable using basic algebraic and categorical concepts. As motivational background some familiarity with real geometry will be helpful. The book aims at researchers and graduate students with an interest in real algebra and geometry, ordered algebraic structures, topology and rings of continuous functions.

  7. Nuclear Star-Forming Ring of the Milky Way: Simulations

    CERN Document Server

    Kim, Sungsoo S; Jeon, Myoungwon; Figer, Donald F; Merritt, David; Wada, Keiichi

    2011-01-01

    We present hydrodynamic simulations of gas clouds in the central kpc region of the Milky Way that is modeled with a three-dimensional bar potential. Our simulations consider realistic gas cooling and heating, star formation, and supernova feedback. A ring of dense gas clouds forms as a result of X1-X2 orbit transfer, and our potential model results in a ring radius of ~200 pc, which coincides with the extraordinary reservoir of dense molecular clouds in the inner bulge, the Central Molecular Zone (CMZ). The gas clouds accumulated in the CMZ can reach high enough densities to form stars, and with an appropriate choice of simulation parameters, we successfully reproduce the observed gas mass and the star formation rate (SFR) in the CMZ, ~2x10^7 Msun and ~0.1 Msun/yr. Star formation in our simulations takes place mostly in the outermost X2 orbits, and the SFR per unit surface area outside the CMZ is much lower. These facts suggest that the inner Galactic bulge may harbor a mild version of the nuclear star-formin...

  8. Size filtering effect in vertical stacks of In(Ga)As/GaAs self-assembled quantum rings

    International Nuclear Information System (INIS)

    We present a systematic study of closely In(Ga)As/InAs quantum rings (QRs) grown by molecular beam epitaxy (MBE). Photoluminescence (PL) experiments show a strong filtering effect in the ring being stacked and simultaneous linewidth narrowing for the appropriate layer thickness (thinner thickness). If the spacer thickness is further reduced, a strong coupling between the nanostructures is produced and the signal shifts to low energy

  9. Wheels of Fire IV. Star Formation and the Neutral Interstellar Medium in the Ring Galaxy AM0644-741

    CERN Document Server

    Higdon, James L; Rand, Richard J

    2011-01-01

    We combine data from the ATNF and SEST to investigate the neutral ISM in AM0644-741, a large robustly star forming ring galaxy. The galaxy's ISM is concentrated in the 42-kpc diameter ring and appears dominated by HI, with a global molecular fraction of only 6.2%. Outside the starburst peak, the gas ring appears gravitationally stable (Q_gas = 3-11). Including the stellar component lowers Q overall, but not enough to make Q100 Myr confinement time in the starburst ring, which amplifies the effects of embedded massive stars and SNe. The ring's molecular ISM becomes dominated by small clouds, causing H2 to be significantly underestimated by 12CO line fluxes: in effect X_CO >> X_Gal despite the ring's >solar metallicity. The observed HI is primarily a low density photo-dissociation product, i.e., a tracer rather than a precursor of star formation. Such an "over-cooked" ISM may be a general characteristic of evolved ring galaxies.

  10. ring av erfaring?

    DEFF Research Database (Denmark)

    Ramvi, Ellen

    Hva skal til for å lære av erfaring? Denne avhandlingen er en empirisk baseret undersøkelse av ungdosmskolelæreres muligheter og betingelser for å "lære av erfaring" i den særlige betydning av begrepet  W. Bion gir i sin psykoanalytiske teori. Undersøgelsen baserer seg på et feltarbeid som strekker...... seg over ett skoleår. Datamaterialet ble samlet inn via observerasjoner og mer eller mindre strukturerte samtaler med lærere ved to forskellige norske ungdsomsskoler. Analysen av materialet foregår i to trinn: først en fenomenologisk analyse, tett på lærernes egne beskrivelser og refleksjoner av...... lærerarbeidet, dets udfordringer og vanskeligheter, og deretter en psykoanalytisk perspektivering av de fenomenologiske analyseresultatene. Analysen viser en almindelig lærerhverdag og en skoleorganisation, hvor lærernes "læring av erfaring" i stor utstrekning blokkeres i et vekselspill mellem lærernes flukt...

  11. Molecular physics

    CERN Document Server

    Williams, Dudley

    2013-01-01

    Methods of Experimental Physics, Volume 3: Molecular Physics focuses on molecular theory, spectroscopy, resonance, molecular beams, and electric and thermodynamic properties. The manuscript first considers the origins of molecular theory, molecular physics, and molecular spectroscopy, as well as microwave spectroscopy, electronic spectra, and Raman effect. The text then ponders on diffraction methods of molecular structure determination and resonance studies. Topics include techniques of electron, neutron, and x-ray diffraction and nuclear magnetic, nuclear quadropole, and electron spin reson

  12. Low Temperature Photoluminescence Kinetics of Double-Ring Structured GaAs Quantum Dots.

    Science.gov (United States)

    Myoung, Soung; Mun, Ok Mi; Yim, Sang-Youp; Kim, Jong Su

    2015-11-01

    This work is focused on spectroscopically characterizing kinetic properties of concentric quantum-ring complexes of GaAs quantum dots. Quantum-ring (or double-ring) GaAs quantum dots, embedded in an Al0.3Ga0.7As barrier layer, were grown by a droplet epitaxy method during molecular beam epitaxy on a GaAs (001) substrate. Emission peaks of photoluminescence spectra with different excitation power, were measured as 702 nm at 0.17 mW and 690 nm at 400 mW, were blue-shifted as the excitation power increased. In addition, excitation laser power dependence of time-resolved photoluminescence of double-ring GaAs quantum dots at 10 K under 400 nm excitation wavelength was performed, revealing that photoluminescence lifetime slowly decreased in comparison to that of single disc-like quantum dots as excitation power increased, implying that carrier transfer between inner ring and outer ring could slow down the decay process. The luminescence lifetime at 10 K increased from 245 to 409 ps in the range from 0.17 to 400 mW of excitation power. PMID:26726575

  13. Commissioning of the DESIREE storage rings – a new facility for cold ion-ion collisions

    International Nuclear Information System (INIS)

    We report on the ongoing commissioning of the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. Beams of atomic carbon anions (C−) and smaller carbon anion molecules (C−2, C−3, C−4 etc.) have been produced in a sputter ion source, accelerated to 10 keV or 20 keV, and stored successfully in the two electrostatic rings. The rings are enclosed in a common vacuum chamber cooled to below 13 Kelvin. The DESIREE facility allows for studies of internally relaxed single isolated atomic, molecular and cluster ions and for collision experiments between cat- and anions down to very low center-of-mass collision energies (meV scale). The total thermal load of the vacuum chamber at this temperature is measured to be 32 W. The decay rates of stored ion beams have two components: a non-exponential component caused by the space charge of the beam itself which dominates at early times and an exponential term from the neutralization of the beam in collisions with residual gas at later times. The residual gas limited storage lifetime of carbon anions in the symmetric ring is over seven minutes while the 1/e lifetime in the asymmetric ring is measured to be about 30 seconds. Although we aim to improve the storage in the second ring, the number of stored ions are now sufficient for many merged beams experiments with positive and negative ions requiring milliseconds to seconds ion storage

  14. Estimating the mass of Saturn's B ring

    Science.gov (United States)

    Hedman, Matthew M.; Nicholson, Philip D.

    2016-10-01

    The B ring is the brightest and most opaque of Saturn's rings, but it is also amongst the least well understood because basic parameters like its surface mass density have been poorly constrained. Elsewhere in the rings, spiral density waves driven by resonances with Saturn's various moons provide precise and robust mass density estimates, but for most the B ring extremely high opacities and strong stochastic optical depth variations obscure the signal from these wave patterns. We have developed a new wavelet-based technique that combines data from multiple stellar occultations (observed by the Visual and Infrared Mapping Spectrometer instrument onboard the Cassini spacecraft) that has allowed us to identify signals that appear to be due to waves generated by the strongest resonances in the central and outer B ring. These wave signatures yield new estimates of the B-ring's mass density and indicate that the B-ring's total mass could be quite low, between 1/3 and 2/3 the mass of Saturn's moon Mimas.

  15. Magnetization reversal in arrays of Co rings

    Science.gov (United States)

    Welp, U.; Vlasko-Vlasov, V. K.; Hiller, J. M.; Zaluzec, N. J.; Metlushko, V.; Ilic, B.

    2003-08-01

    The magnetization behavior of arrays of individual and coupled Co rings has been studied using superconducting quantum interference device magnetometry, magneto-optical imaging, and Lorentz transmission and scanning transmission electron microscopy. The transition from the polarized into the vortex state of isolated rings is shown to occur through the motion and annihilation of head-to-head domain boundaries. The chirality of the vortex state is fixed on subsequent magnetization cycles, indicating that it is predetermined by structural imperfections of the rings. The effect of interactions between the rings has been investigated in arrays of chains of touching rings. For fields applied parallel to the chains rings in extended sections of the chains are found to switch simultaneously. Neighboring rings in these sections can display alternating chirality as well as the same chirality accompanied by a 180° boundary on the nodes. For fields perpendicular to the chain direction the switching occurs pairwise. This coupling introduces a broad distribution of switching fields and correspondingly a magnetization curve that is significantly broader than that for the parallel orientation.

  16. Microstructural heterogeneity of forged rolled rings

    Directory of Open Access Journals (Sweden)

    J. Herian

    2007-04-01

    Full Text Available Purpose: The paper presents the processes which condition the quality of steel cast strands and properties of rolled products. It touches upon the technology of small-size rings manufacture from the 42CrMo4 steel used for the production of rolling bearings and toothed rings.Design/methodology/approach: Investigations were made on the 42CrMo4 steel based process of small-size rings manufacture of weight not exceeding 100 kg and the internal diameter up to 600 mm.Findings: Microstructure heterogeneity has been proven on the cross section of rods and rings under hot rolling and thermal treatment. Non-uniformity in hardness distribution was found on the hot rolled rings’ face surface and cross section. Final products made from rings with heterogeneous properties characterize: difficulties with machining, cracking during surface hardening and decrease of life time. After the process modification, the rings’ microstructure homogeneity and advantageous hardness distribution were obtained.Practical implications: A good quality of final rings after heat treatment is obtained in the case of charge characterized by a uniform pearlitic/ferritic microstructure. After the process technology modification, the rings’ microstructure homogeneity and advantageous hardness distribution were obtained.Originality/value: The minimum processing degree in the rolling of rod products should guarantee obtaining a homogeneous microstructure on the rings cross section and properties which would ensure a good quality and the required functional properties of the final products.

  17. Vortex Ring Interaction with a Heated Screen

    Science.gov (United States)

    Smith, Jason; Krueger, Paul S.

    2008-11-01

    Previous examinations of vortex rings impinging on porous screens has shown the reformation of the vortex ring with a lower velocity after passing through the screen, the creation of secondary vortices, and mixing. A heated screen could, in principle, alter the vortex-screen interaction by changing the local liquid viscosity and density. In the present investigation, a mechanical piston-cylinder vortex ring generator was used to create vortex rings in an aqueous sucrose solution. The rings impinged on a screen of horizontal wires that were heated using electrical current. The flow was visualized with food color and video imaging. Tests with and without heat were conducted at a piston stroke-to-jet diameter ratio of 4 and a jet Reynolds number (Re) of 1000. The vortex rings slowed after passing through the screen, but in tests with heat, they maintained a higher fraction of their before-screen velocity due to reduction in fluid viscosity near the wires. In addition, small ``fingers'' that developed on the front of the vortex rings as they passed through the screen exhibited positive buoyancy effects in the heated case.

  18. Radically enhanced molecular recognition

    KAUST Repository

    Trabolsi, Ali

    2009-12-17

    The tendency for viologen radical cations to dimerize has been harnessed to establish a recognition motif based on their ability to form extremely strong inclusion complexes with cyclobis(paraquat-p-phenylene) in its diradical dicationic redox state. This previously unreported complex involving three bipyridinium cation radicals increases the versatility of host-guest chemistry, extending its practice beyond the traditional reliance on neutral and charged guests and hosts. In particular, transporting the concept of radical dimerization into the field of mechanically interlocked molecules introduces a higher level of control within molecular switches and machines. Herein, we report that bistable and tristable [2]rotaxanes can be switched by altering electrochemical potentials. In a tristable [2]rotaxane composed of a cyclobis(paraquat-p-phenylene) ring and a dumbbell with tetrathiafulvalene, dioxynaphthalene and bipyridinium recognition sites, the position of the ring can be switched. On oxidation, it moves from the tetrathiafulvalene to the dioxynaphthalene, and on reduction, to the bipyridinium radical cation, provided the ring is also reduced simultaneously to the diradical dication. © 2010 Macmillan Publishers Limited. All rights reserved.

  19. Weakly Dual Rings%弱对偶环

    Institute of Scientific and Technical Information of China (English)

    WEI Jun-chao; SUN Jian-hua

    2004-01-01

    In This paper, the concept of weakly dual ring is introduced, which is a proper generalization of the dual ring. IfR is a right weakly dual ring, then (1) Z(RR) = J(R); (2) If R is also a zero-division power ring, then R is a right Apinjective ring. In addition, some properties of weakly dual rings are given.

  20. A census of Gulf Stream rings, spring 1975

    Science.gov (United States)

    Richardson, P. L.; Worthington, L. V.; Cheney, R. E.

    1978-01-01

    During 1975 several shipboard expendable bathythermograph surveys plus satellite infrared imagery provided a nearly synoptic view of the distribution and number of Gulf Stream rings in the western North Atlantic. Twelve rings were identified; nine were cyclonic (cold core) rings and three were anticyclonic (warm core) rings. This is the largest number of rings ever observed during a short period of time (4 months). Evidence suggests that the mean movement of these rings was southwestward.