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Torus
Kinds of Torus Selected AbstractsThe Use of Mandibular Tori as a Donor Site for Autogenous Bone GraftJOURNAL OF PROSTHODONTICS, Issue 3 2000Periklis Proussaefs DDS [source] Observation of Mode like Coherent Structures in Curved Magnetic Fields of a Simple Magnetized TorusCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4 2004F. Greiner Abstract The spatio-temporal dynamics of large-scale structures in curved magnetic field of simple magnetized torus (SMT) are presented. The experiments are performed in the SMT BLAAMANN and employ the techniques of conditional averaging (CA) and cross-correlation (CCF) of Langmuir probe data. By means of a detailed comparison of radio-frequency and thermionic discharges, it is shown that general features of the observed large-scale structures are independent of the discharge mechanism. Further, the observed large scale structures have a pronounced spatio-temporal periodicity, which suggests a description as mode-like. The conjectured relationship between the observed coherent structures and the inverse energy cascade is therefore questioned again. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Heterotic strings on homogeneous spaces,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 9 2005D. Israël Abstract We construct heterotic string backgrounds corresponding to families of homogeneous spaces as exact conformal field theories. They contain left cosets of compact groups by their maximal tori supported by NS-NS 2-forms and gauge field fluxes. We give the general formalism and modular-invariant partition functions, then we consider some examples such as SU (2)/U (1) ~ S2 (already described in a previous paper) and the SU (3)/U(1)2 flag space. As an application we construct new supersymmetric string vacua with magnetic fluxes and a linear dilaton. [source] Fourier methods for quasi-periodic oscillationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2006Frank Schilder Abstract Quasi-periodic oscillations and invariant tori play an important role in the study of forced or coupled oscillators. This paper presents two new numerical methods for the investigation of quasi-periodic oscillations. Both algorithms can be regarded as generalizations of the averaging and the harmonic (spectral) balance methods. The algorithms are easy to implement and require only minimal a priori knowledge of the system. Most importantly, the methods do not depend on an a priori co-ordinate transformation. The methods are applied to a number of illustrative examples from non-linear electrical engineering and the results show that the methods are efficient and reliable. In addition, these examples show that the presented algorithms can also continue through regions of sub-harmonic (phase-locked) resonance even though they are designed only for the quasi-periodic case. Copyright © 2006 John Wiley & Sons, Ltd. [source] Oropharyngeal Skeletal Disease Accompanying High Bone Mass and Novel LRP5 Mutation,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2005Michael R Rickels Abstract Gain-of-function mutation in the gene encoding LRP5 causes high bone mass. A 59-year-old woman carrying a novel LRP5 missense mutation, Arg154Met, manifested skeletal disease affecting her oropharynx as well as dense bones, showing that exuberant LRP5 effects are not always benign. Introduction: Gain-of-function mutation (Gly171Val) of LDL receptor-related protein 5 (LRP5) was discovered in 2002 in two American kindreds with high bone mass and benign phenotypes. In 2003, however, skeletal disease was reported for individuals from the Americas and Europe carrying any of six novel LRP5 missense mutations affecting the same LRP5 protein domain. Furthermore, in 2004, we described a patient with neurologic complications from dense bones and extensive oropharyngeal exostoses caused by the Gly171Val defect. Materials and Methods: A 59-year-old woman was referred for dense bones. Three years before, mandibular buccal and lingual exostoses (osseous "tori") were removed because of infections from food trapping between the teeth and exostoses. Maxillary buccal and palatal exostoses were asymptomatic. Radiographic skeletal survey showed marked thickening of the skull base and diaphyses of long bones (endosteal hyperostosis). BMD Z scores assessed by DXA were +8.5 and +8.7 in the total hip and L1 -L4 spine (both ,195% average control), respectively. LRP5 mutation analysis was carried out for the LRP5 domain known to cause high bone mass. Results: Biochemical evaluation excluded most secondary causes of dense bones, and male-to-male transmission in her family indicated autosomal dominant inheritance. PCR amplification and sequencing of LRP5 exons 2-4 and adjacent splice sites revealed heterozygosity for a new LRP5 missense mutation, Arg154Met. Conclusions: LRP5 Arg154Met is a novel defect that changes the same first ",-propeller" module as the eight previously reported LRP5 gain-of-function missense mutations. Arg154Met alters a region important for LRP5 antagonism by dickkopf (Dkk). Therefore, our patient's extensive oropharyngeal exostoses and endosteal hyperostosis likely reflect increased Wnt signaling and show that exuberant LRP5 effects are not always benign. [source] A laboratory model of splash-form tektitesMETEORITICS & PLANETARY SCIENCE, Issue 9 2003Linda T. ELKINS-TANTON However, no detailed fluid dynamical investigation of their form and stability has yet been undertaken. Here, we review the dynamics and stability of spinning, translating fluid drops with a view to making inferences concerning the dynamic history of tektites. We conclude that, unless the differential speed between the molten tektite and ambient is substantially less than the terminal velocity, molten tektites can exist as equilibrium bodies of revolution only up to sizes of 3 mm. Larger tektites are necessarily non-equilibrium forms and so indicate the importance of cooling and solidification during flight. An examination of the shapes of rotating, translating drops indicates that rotating silicate drops in air will assume the shapes of bodies of rotation if their rotational speed is 1% or more of their translational speed. This requirement of only a very small rotational component explains why most splash-form tektites correspond to bodies of revolution. A laboratory model that consists of rolling or tumbling molten metallic drops reproduces all of the known forms of splashform tektites, including spheres, oblate ellipsoids, dumbbells, teardrops, and tori. The laboratory also highlights important differences between rolling drops and tumbling drops in flight. For example, toroidal drops are much more stable in the former than in the latter situation. [source] Dynamics of oscillating relativistic tori around Kerr black holesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2005Olindo Zanotti ABSTRACT We present a comprehensive numerical study of the dynamics of relativistic axisymmetric accretion tori with a power-law distribution of specific angular momentum orbiting in the background space,time of a Kerr black hole. By combining general relativistic hydrodynamics simulations with a linear perturbative approach we investigate the main dynamical properties of these objects over a large parameter space. The astrophysical implications of our results extend and improve two interesting results that have been recently reported in the literature. First, the induced quasi-periodic variation of the mass quadrupole moment makes relativistic tori of nuclear matter densities, as those formed during the last stages of binary neutron star mergers, promising sources of gravitational radiation, potentially detectable by interferometric instruments. Secondly, p-mode oscillations in relativistic tori of low rest-mass densities could be used to explain high-frequency quasi-periodic oscillations observed in X-ray binaries containing a black hole candidate under conditions more generic than those considered so far. [source] Spectropolarimetry of a complete infrared-selected sample of Seyfert 2 galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001S.L. Lumsden We report the results of a spectropolarimetric survey of a complete far-infrared-selected sample of Seyfert 2 galaxies. We have found polarized broad H, emission in one new source, NGC 5995. In the sample as a whole, there is a clear tendency for galaxies in which we have detected broad H, in polarized light to have warm mid,far-infrared colours in agreement with our previous results. However, a comparison of the optical, radio and hard X-ray properties of these systems leads us to conclude that this is a secondary consequence of the true mechanism governing our ability to see scattered light from the broad-line region. We find a strong trend for galaxies showing such emission to lie above a critical value of the relative luminosity of the active core to the host galaxy (as measured from the [O iii] 5007-Å equivalent width) which varies as a function of the obscuring column density as measured from hard X-ray observations. The warmth of the infrared colours is then largely due to a combination of the luminosity of the active core, the obscuring column and the relative importance of the host galaxy in powering the far-infrared emission, and not solely orientation as we inferred in our previous paper. Our data may also provide an explanation as to why the most highly polarized galaxies, which appear to have tori that are largely edge-on, are also the most luminous and have the most easily detectable scattered broad H,. [source] Vertex disjoint routings of cycles over toriNETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2007Jean-Claude Bermond Abstract We study the problem of designing a survivable WDM network based on covering the communication requests with subnetworks that are protected independently from each other. We consider here the case when the physical network is T(n), a torus of size n by n, the subnetworks are cycles and the communication scheme is all-to-all or total exchange (where all pairs of vertices communicate). We will represent the communication requests by a logical graph: a complete graph for the scheme of all-to-all. This problem can be modeled as follows: find a cycle partition or covering of the request edges of K, such that for each cycle in the partition, its request edges can be routed in the physical network T(n) by a set of vertex disjoint paths (equivalently, the routings with the request cycle form an elementary cycle in T(n)). Let the load of an edge of the WDM network be the number of paths associated with the requests using the edge. The cost of the network depends on the total load (the cost of transmission) and the maximum load (the cost of equipment). To minimize these costs, we will search for an optimal (or quasi optimal) routing satisfying the following two conditions: (a) each request edge is routed by a shortest path over T(n), and (b) the load of each physical edge resulting from the routing of all cycles of S is uniform or quasi uniform. In this article, we find a covering or partition of the request edges of K into cycles with an associated optimal or quasi optimal routing such that either (1) the number of cycles of the covering is minimum, or (2) the cycles have size 3 or 4. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 49(3), 217,225 2007 [source] The role of breathers in the anomalous decay of luminescencePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006Eva Mihóková Abstract Luminescence of alkali halides doped by heavy ns2 ions exhibits an anomaly in the slow component emission decay. The anomaly is explained by the formation of a discrete breather in the immediate neighborhood of the impurity. We study properties of these breathers, their phase space structure, robustness, and propensity for formation. Under a wide range of parameters and interionic potentials they form 2-dimensional Kolmogorov-Arnold-Moser tori (less than generic) in phase space. We show strobed views of these tori, useful in quantization. All features support the thesis of breather formation as the explanation for the luminescence decay anomaly that first motivated our breather proposal. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Dynamical modeling of chaos single-screw extruder and its three-dimensional numerical analysisPOLYMER ENGINEERING & SCIENCE, Issue 3 2000W. R. Hwang The Chaos Screw (CS) nonlinear dynamical model is proposed to describe the development of chaos in a single-screw extrusion process and the model is verified by three-dimensional numerical simulations. The only-barrier channel is the unperturbed Hamiltonian system, which consists of two homoclinic orbits and nested elliptic tori of nonlinear oscillation in periodic (extended) state space. A periodically inserted no-barrier zone represents a perturbation. For small perturbations, homoclinic tangle leads to the Cantor set near the homoclinic fixed point and elliptic rotations are changed into the resonance bands or KAM tori, depending on the commensurability of frequency ratio of the corresponding orbits. A finite element method of multivariant Q,1+PO elements is applied to solve the velocity fields and a 4th order Runge-Kutta method is used for the particle tracing. The resulting Poincaré section verifies the proposed dynamical model, showing the resonance band corresponding to rotation number 1/3 under small perturbations. As the strength of perturbation increases, the Poincaré sections indicate wider stochastic regions in which random particle motions take place. [source] The Granada workshop on High Redshift Radio Galaxies: An overviewASTRONOMISCHE NACHRICHTEN, Issue 2-3 2006H. J. A. Röttgering Abstract The Granada workshop on High Redshift Radio Galaxies (HzRGs) gave an excellent overview of the progress that has been made in this field during the last 3 years. Here we briefly review some of the results, with an emphasis on what studies of HzRGs can teach us about the formation and evolution of massive galaxies, clusters and active galactic nuclei (AGN). Of great relevance for this workshop are scenarios that describe certain aspects of the evolution of radio galaxies, including (i) the sequence of events after merging of galaxies that ultimately lead to extended powerful radio sources and (ii) the mass assembly and virialization of the hosting massive galaxies and their associated (proto-)clusters. Furthermore, I briefly discuss two projects that are important for a further understanding of AGN and high redshift radio galaxies. First, using the MIDI instrument mounted on the VLT Interferometer, the dusty tori of nearby AGN can be studied in the range of 8,13 micron at high angular resolution. The first result on the nearby AGN NGC 1068 as presented by Jaffe et al. (2004) indicated the presence of a hot (T > 800 K), compact (,1 pc) component, possible identified with the base of the jet and a warm (270 K), well-resolved (3 × 4 pc) component associated with the alleged torus. Second, LOFAR is a new low frequency radio telescope that is currently being build in the Netherlands and is expected to be operational in 2008. With 50 stations spread over an area of 100 km in diameter, its resolution and sensitivity will be unprecedented in the frequency range 10,240 MHz. LOFAR will be a unique instrument that will impact a broad range of astrophysical topics varying from the epoch of reionisation, to gamma ray bursts and cosmic rays. Surveys with LOFAR will be of paramount importance for studies of HzRGs: It will enable (i) defining samples of radio galaxies with redshifts higher than 6, (ii) observations of starbursting galaxies in proto-clusters, and (iii) mapping out the low-frequency radio emission of virtually all northern radio-loud AGN in revolutionary detail. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Radio galaxies and type-2 quasars in the Spitzer Extragalactic First Look SurveyASTRONOMISCHE NACHRICHTEN, Issue 2-3 2006M. Lacy Abstract We use mid-infrared colour-colour plots made with data from the Spitzer First Look Survey to explore the emission mechanisms of faint radio sources in that field. Using mid-infrared colours alone, we are able to see the transition from a starburst-dominated radio source population at sub-mJy levels to the radiogalaxy/quasar population at mJy levels. Both FR I and some FR II galaxies show little or no mid-infrared excess, suggesting they either lack dusty tori, or a strong continuum source to heat them, or both. Objects with hot, dusty tori, most likely radio-intermediate and radio-quiet AGN, make up a significant fraction of the faint radio source population. We also discuss the use of mid-infrared colour-colour plots to select radio quiet obscured AGN. Early results from imaging the host galaxies of these type-2 quasars at high spatial resolution with adaptive optics indicates that they, like type-1 quasars and radio galaxies, are often found to be hosted by giant elliptical galaxies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Towards a more realistic comparative analysis of multicomputer networksCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2004H. Sarbazi-Azad Abstract Several studies have examined the relative performance merits of the torus and hypercube taking into account the channel bandwidth constraints imposed by implementation technology. While the torus has been shown to outperform the hypercube under the constant wiring density constraint, the opposite conclusion has been reached when the constant pin-out constraint is considered. However, these studies have assumed a pure uniform traffic pattern and deterministic routing. The ,uniform traffic' assumption is not always justifiable in practice as there are many real-world parallel applications that exhibit non-uniform traffic patterns, which can create unbalanced traffic such as hotspots in the network. This paper re-examines the performance merits of the torus and hypercube in the presence of hotspot traffic. The comparative analysis is based on fully adaptive routing as this has been gaining popularity in recent practical multicomputers. Moreover, it uses a new cost model that takes into account the implementation cost of the network and its routers. The results reveal that for moderate and large system sizes, lower dimensional k -ary n -cubes (e.g. 2D torus) always outperform their higher dimensional counterparts even under the pin-out constraint. Copyright © 2004 John Wiley & Sons, Ltd. [source] Configuration Studies on the Heliotron Fusion Energy Reactor with Split-Type Helical CoilsCONTRIBUTIONS TO PLASMA PHYSICS, Issue 6-7 2010N. Yanagi Abstract Configuration optimization is examined for the heliotron fusion energy reactor FFHR in order to find sufficient clearances between the ergodic region outside the nested magnetic surfaces and blankets at the inboard side of the torus. The standard configuration of FFHR, which is similar to that of LHD, has a relatively large major radius of the helical coils in order to satisfy this requirement. It has been found, as an alternative design, that equivalent clearances are obtained with a shorter major radius both by employing a lower helical pitch parameter and splitting the helical coils in the poloidal cross-section at the outboard side. Splitting the helical coils also provides another configuration that ensures magnetic well formation in the fairly large nested magnetic surfaces with outward shifted configurations. Optimization is being carried out for these configurations by adjusting the pitch modulation parameter to improve the particle confinement (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Observation of Mode like Coherent Structures in Curved Magnetic Fields of a Simple Magnetized TorusCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4 2004F. Greiner Abstract The spatio-temporal dynamics of large-scale structures in curved magnetic field of simple magnetized torus (SMT) are presented. The experiments are performed in the SMT BLAAMANN and employ the techniques of conditional averaging (CA) and cross-correlation (CCF) of Langmuir probe data. By means of a detailed comparison of radio-frequency and thermionic discharges, it is shown that general features of the observed large-scale structures are independent of the discharge mechanism. Further, the observed large scale structures have a pronounced spatio-temporal periodicity, which suggests a description as mode-like. The conjectured relationship between the observed coherent structures and the inverse energy cascade is therefore questioned again. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Developmental changes in cell proliferation in the auditory midbrain of the bullfrog, Rana catesbeianaDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2006Andrea Megela Simmons Abstract We examined patterns of cell proliferation in the auditory midbrain (torus semicircularis) of the bullfrog, Rana catesbeiana, over larval and early postmetamorphic development, by visualizing incorporation of 5-bromo-2,-deoxyuridine (BrdU) in cycling cells. At all developmental stages, BrdU-labeled cells were concentrated around the optic ventricle. BrdU-labeled cells also appeared within the torus semicircularis itself, in a stage-specific manner. The mitotic index, quantified as the percent of BrdU-positive cells outside the ventricular zone per total cells available for label, varied over larval development. Mitotic index was low in hatchling, early larval, and late larval stages, and increased significantly in deaf period, metamorphic climax, and froglet stages. Cell proliferation was higher in metamorphic climax than at other stages, suggesting increased cell proliferation in preparation for the transition from an aquatic to an amphibious existence. The change in mitotic index over development did not parallel the change in the total numbers of cells available for label. BrdU incorporation was additionally quantified by dot-blot assay, showing that BrdU is available for label up to 72 h postinjection. The pattern of change in cell proliferation in the torus semicircularis differs from that in the auditory medulla (dorsal medullary nucleus and superior olivary nucleus), suggesting that cell proliferation in these distinct auditory nuclei is mediated by different underlying mechanisms. © 2006 Wiley Periodicals, Inc. J Neurobiol 66: 1212,1224, 2006 [source] M-theory and gauged supergravities,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2 2005D. Roest Abstract We present a pedagogical discussion of the emergence of gauged supergravities from M-theory. First, a review of maximal supergravity and its global symmetries and supersymmetric solutions is given. Next, different procedures of dimensional reduction are explained: reductions over a torus, a group manifold and a coset manifold and reductions with a twist. Emphasis is placed on the consistency of the truncations, the resulting gaugings and the possibility to generate field equations without an action. Using these techniques, we construct a number of gauged maximal supergravities in diverse dimensions with a string or M-theory origin. One class consists of the CSO gaugings, which comprise the analytic continuations and group contractions of SO(n) gaugings. We construct the corresponding half-supersymmetric domain walls and discuss their uplift to D- and M-brane distributions. Furthermore, a number of gauged maximal supergravities are constructed that do not have an action. [source] Grünbaum colorings of toroidal triangulationsJOURNAL OF GRAPH THEORY, Issue 1 2010Michael O. Albertson Abstract We prove that if G is a triangulation of the torus and ,(G),5, then there is a 3-coloring of the edges of G so that the edges bounding every face are assigned three different colors. © 2009 Wiley Periodicals, Inc. J Graph Theory 63: 68,81, 2010 [source] Multi-periodic eigensolutions to the Dirac operator and applications to the generalized Helmholtz equation on flat cylinders and on the n -torusMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 16 2009Denis Constales Abstract In this paper, we study the solutions to the generalized Helmholtz equation with complex parameter on some conformally flat cylinders and on the n -torus. Using the Clifford algebra calculus, the solutions can be expressed as multi-periodic eigensolutions to the Dirac operator associated with a complex parameter ,,,. Physically, these can be interpreted as the solutions to the time-harmonic Maxwell equations on these manifolds. We study their fundamental properties and give an explicit representation theorem of all these solutions and develop some integral representation formulas. In particular, we set up Green-type formulas for the cylindrical and toroidal Helmholtz operator. As a concrete application, we explicitly solve the Dirichlet problem for the cylindrical Helmholtz operator on the half cylinder. Finally, we introduce hypercomplex integral operators on these manifolds, which allow us to represent the solutions to the inhomogeneous Helmholtz equation with given boundary data on cylinders and on the n -torus. Copyright © 2009 John Wiley & Sons, Ltd. [source] On the global existence and small dispersion limit for a class of complex Ginzburg,Landau equationsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2009Hongjun Gao Abstract In this paper we consider a class of complex Ginzburg,Landau equations. We obtain sufficient conditions for the existence and uniqueness of global solutions for the initial-value problem in d -dimensional torus ,,d, and that solutions are initially approximated by solutions of the corresponding small dispersion limit equation for a period of time that goes to infinity as dispersive coefficient goes to zero. Copyright © 2008 John Wiley & Sons, Ltd. [source] Delayed X-ray emission from fallback in compact-object mergersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2009Elena M. Rossi ABSTRACT When double neutron star or neutron star,black hole binaries merge, the final remnant may comprise a central solar-mass black hole surrounded by a ,0.01,0.1 M, torus. The subsequent evolution of this disc may be responsible for short ,-ray bursts (SGRBs). A comparable amount of mass is ejected into eccentric orbits and will eventually fallback to the merger site after ,0.01 s. In this paper, we investigate analytically the fate of the fallback matter, which may provide a luminous signal long after the disc is exhausted. We find that matter in the eccentric tail returns at a super-Eddington rate and eventually (,0.1 s) is unable to cool via neutrino emission and accrete all the way to the black hole. Therefore, contrary to previous claims, our analysis suggests that fallback matter is not an efficient source of late-time accretion power and unlikely to cause the late-flaring activity observed in SGRB afterglows. The fallback matter rather forms a radiation-driven wind or a bound atmosphere. In both the cases, the emitting plasma is very opaque and photons are released with a degraded energy in the X-ray band. We therefore suggest that compact binary mergers could be followed by an ,X-ray renaissance', as late as several days to weeks after the merger. This might be observed by the next generation of X-ray detectors. [source] Shock heating in the group atmosphere of the radio galaxy B2 0838+32AMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008Nazirah N. Jetha ABSTRACT We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C 32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number 2.4+1.0,0.5 into the interstellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the active galactic nuclei (AGN) spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a type that has been associated with the presence of a radiatively inefficient accretion flow that could be controlled by an AGN heating and subsequent cooling of the hot, X-ray emitting gas. If correct, this means that B2 0838+32A is the first source in which we can directly see entropy-increasing processes (shocks) driven by accretion from the hot phase of the interstellar medium. [source] Radio imaging of the Subaru/XMM,Newton Deep Field , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008The 37 brightest radio sources ABSTRACT We study the 37 brightest radio sources in the Subaru/XMM,Newton Deep Field. We have spectroscopic redshifts for 24 of 37 objects and photometric redshifts for the remainder, yielding a median redshift zmed for the whole sample of zmed, 1.1 and a median radio luminosity close to the ,Fanaroff,Riley type I/type II (FR I/FR II)' luminosity divide. Using mid-infrared (mid-IR) (Spitzer MIPS 24 ,m) data we expect to trace nuclear accretion activity, even if it is obscured at optical wavelengths, unless the obscuring column is extreme. Our results suggest that above the FR I/FR II radio luminosity break most of the radio sources are associated with objects that have excess mid-IR emission, only some of which are broad-line objects, although there is one clear low-accretion-rate object with an FR I radio structure. For extended steep-spectrum radio sources, the fraction of objects with mid-IR excess drops dramatically below the FR I/FR II luminosity break, although there exists at least one high-accretion-rate ,radio-quiet' QSO. We have therefore shown that the strong link between radio luminosity (or radio structure) and accretion properties, well known at z, 0.1, persists to z, 1. Investigation of mid-IR and blue excesses shows that they are correlated as predicted by a model in which, when significant accretion exists, a torus of dust absorbs ,30 per cent of the light, and the dust above and below the torus scatters ,1 per cent of the light. [source] OH megamasers, starburst and AGN activity in Markarian 231MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005A. M. S. Richards ABSTRACT We present Multi-Element Radio-Linked Interferometer Network (MERLIN) observations of OH maser and radio continuum emission within a few hundred pc of the core of the ultraluminous infrared galaxy (ULIRG) Markarian 231. This is the only known OH megamaser galaxy classed as a Seyfert 1. Maser emission is identified with the 1665- and 1667-MHz transitions over a velocity extent of 720 km s,1. Both lines show a similar position,velocity structure including a gradient of 1.7 km s,1 pc,1 from NW to SE along the 420-pc major axis. The (unresolved) inner few tens of pc possess a much steeper velocity gradient. The maser distribution is modelled as a torus rotating about an axis inclined at ,45° to the plane of the sky. We estimate the enclosed mass density to be 320 ± 90 M, pc,3 in a flattened distribution. This includes a central unresolved mass of ,8 × 106 M,. All the maser emission is projected against a region with a radio continuum brightness temperature ,105 K, giving a maser gain of ,2.2. The 1667:1665 MHz line ratio is close to 1.8 (the value predicted for thermal emission) consistent with radiatively pumped, unsaturated masers. This behaviour and the kinematics of the torus suggest that the size of individual masing regions is in the range 0.25,4 pc with a covering factor close to unity. There are no very bright compact masers, in contrast to galaxies such as the Seyfert 2 Markarian 273, where the masing torus is viewed nearer edge-on. The comparatively modest maser amplification seen from Markarian 231 is consistent with its classification in the unification scheme for Seyfert galaxies. Most of the radio continuum emission on 50,500 pc scales is probably of starburst origin but the compact peak is 0.4 per cent polarized by a magnetic field running north,south, similar to the jet direction on these scales. There is no close correlation between maser and continuum intensity, suggesting that much of the radio continuum must originate in the foreground and indeed the relative continuum brightness is slightly greater in the direction of the approaching jet. Comparisons with other data show that the jet changes direction close the nucleus and suggest that the sub-kpc disc hosting the masers and starburst activity is severely warped. [source] The luminosity dependence of the type 1 active galactic nucleus fractionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005Chris Simpson ABSTRACT Using a complete, magnitude-limited sample of active galaxies from the Sloan Digital Sky Survey, we show that the fraction of broad-line (type 1) active galactic nuclei (AGNs) increases with luminosity of the isotropically emitted [O iii] narrow emission line. Our results are quantitatively in agreement with, and far less uncertain than, similar trends found from studies of X-ray and radio-selected active galaxies. While the correlation between broad-line fraction and luminosity is qualitatively consistent with the receding torus model, its slope is shallower and we therefore propose a modification to this model where the height of the torus increases slowly with AGN luminosity. We demonstrate that the faint-end slope of the AGN luminosity function steepens significantly when a correction for ,missing' type 2 objects is made, and that this can substantially affect the overall AGN luminosity density extrapolated from samples of more luminous objects. [source] XMM,Newton observations of warm absorbers in PG quasarsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2004C. E. Ashton ABSTRACT We present XMM,Newton European Photon Imaging Camera observations of warm absorbers in the quasars PG 1114+445 and PG 1309+355, both of which exhibit evidence for absorption by warm material in the line of sight. We find the absorption in PG 1114+445 to be in two phases, a ,hot' phase with a log ionization parameter, ,, of 2.57, and a ,cooler' phase with log ,= 0.83; an unresolved transition array (UTA) of M-shell iron is observed in the cooler phase. The absorption in this quasar is similar to that observed in the Seyfert 1 NGC 3783. The absorption in PG 1309+355 consists of a single phase, with log ,= 1.87. The absorbing gas lies at distances of 1018,1022 cm from the continuum radiation sources in these active galactic nuclei (AGN), which suggests that it could originate in a wind emanating from a molecular torus. We derive distances assuming that these X-ray warm absorbers have the same velocity as the ultraviolet warm absorbers observed in these quasars. The distances to the warm absorbers from the central continuum source scale approximately with the square root of the AGN ionizing luminosity, a result consistent with the warm absorber originating as a torus wind. The kinetic luminosities of these outflowing absorbers represent insignificant fractions (<10,3) of the energy budgets of the AGN. [source] On the anomalous silicate absorption feature of the prototypical Seyfert 2 galaxy NGC 1068MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2010M. Köhler ABSTRACT The first detection of the silicate absorption feature in Active Galactic Nuclei (AGNs) was made at 9.7 ,m for the prototypical Seyfert 2 galaxy NGC 1068 35 yr ago, indicating the presence of a large column of silicate dust in the line of sight to the nucleus. It is now well recognized that type 2 AGNs exhibit prominent silicate absorption bands, while the silicate bands of type 1 AGNs appear in emission. More recently, using the Mid-Infrared Interferometric Instrument on the Very Large Telescope Interferometer, Jaffe et al. for the first time spatially resolved the parsec-sized dust torus around NGC 1068 and found that the 10 ,m silicate absorption feature of the innermost hot component exhibits an anomalous profile differing from that of the interstellar medium and that of common olivine-type silicate dust. While they ascribed the anomalous absorption profile to gehlenite (Ca2Al2SiO7, a calcium aluminium silicate species), we propose a physical dust model and argue that, although the presence of gehlenite is not ruled out, the anomalous absorption feature mainly arises from silicon carbide. [source] A model for the infrared emission of FSC 10214+4724MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006Andreas Efstathiou ABSTRACT A model for the infrared emission of the high-redshift ultraluminous infrared galaxy FSC 10214+4724 is presented. The model assumes three components of emission: a dusty torus viewed edge-on, clouds that are associated with the narrow-line region and a highly obscured starburst. It is demonstrated that the presence of clouds in the narrow-line region, with a covering factor of 17 per cent, can explain why the mid-infrared spectrum of FSC 10214+4724 shows a silicate feature in emission despite the fact that its torus is viewed edge-on. It is also shown that the same model, but with the torus viewed face-on, predicts a spectrum with silicate emission features that is characteristic of the spectra of quasars recently observed with Spitzer. [source] Vertex disjoint routings of cycles over toriNETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2007Jean-Claude Bermond Abstract We study the problem of designing a survivable WDM network based on covering the communication requests with subnetworks that are protected independently from each other. We consider here the case when the physical network is T(n), a torus of size n by n, the subnetworks are cycles and the communication scheme is all-to-all or total exchange (where all pairs of vertices communicate). We will represent the communication requests by a logical graph: a complete graph for the scheme of all-to-all. This problem can be modeled as follows: find a cycle partition or covering of the request edges of K, such that for each cycle in the partition, its request edges can be routed in the physical network T(n) by a set of vertex disjoint paths (equivalently, the routings with the request cycle form an elementary cycle in T(n)). Let the load of an edge of the WDM network be the number of paths associated with the requests using the edge. The cost of the network depends on the total load (the cost of transmission) and the maximum load (the cost of equipment). To minimize these costs, we will search for an optimal (or quasi optimal) routing satisfying the following two conditions: (a) each request edge is routed by a shortest path over T(n), and (b) the load of each physical edge resulting from the routing of all cycles of S is uniform or quasi uniform. In this article, we find a covering or partition of the request edges of K into cycles with an associated optimal or quasi optimal routing such that either (1) the number of cycles of the covering is minimum, or (2) the cycles have size 3 or 4. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 49(3), 217,225 2007 [source] | ||||||||||||||||||||||||||||||||||