Torus Structure Research Articles

Photocentric variability of quasars caused by variations in their inner structure: consequences forGaiameasurements

We study the photocenter position variability due to variations in the quasar inner structure. We consider variability in the accretion disk emissivity and torus structure variability due to different illumination by the central source. We discuss possible detection of these effects by Gaia. Observations of the photocenter variability in two AGNs, SDSS J121855+020002 and SDSS J162011+1724327 have been reported and discussed. With investigation of the variations in the quasar inner structure we explore how much this effect can affect the position determination and whether it can be (or not) detected with Gaia mission. We used (a) a model of a relativistic disk, including the perturbation that can increase brightness of a part of the disk, and consequently offset the photocenter position, and (b) a model of a dusty torus which absorbs and re-emits the incoming radiation from accretion disk. We estimated the value of the photocenter offset due to these two effects. We found that perturbations in the inner structure can significantly offset the photocenter. It depends on the characteristics of perturbation and accretion disk and structure of the torus. In the case of two considered QSOs the observed photocenter offsets cannot be explained by variations in the accretion disk and other effects should be considered. We discussed possibility of exploding stars very close to the AGN source, and also possibility that there are two variable sources in the center of these two AGNs that may indicate a binary super-massive black hole system on a kpc (pc) scale. The Gaia mission seems to be very perspective, not only for astrometry, but also for exploring the inner structure of AGNs. We conclude that variations in the quasar inner structure can affect the observed photocenter (up to several mas). There is a chance to observe such effect in the case of bright and low-redshifted QSOs.

Astrometry of 6.7 GHz Methanol Maser toward W 3(OH) with Japanese VLBI Network

Abstract We present the results of multiepoch VLBI observations for a 6.7 GHz methanol maser toward the UC H II region of W 3(OH) with Japanese VLBI Network (JVN). Based on phase-referencing VLBI astrometry, we derived the trigonometric annual parallax to be 0.598$\ \pm\ $0.067 mas, corresponding to a distance of 1.67$^{+0.21}_{-0.17}$ kpc. This is the first detection of parallax for a 6.7 GHz methanol maser with JVN, and demonstrates that JVN/VERA is capable of conducting VLBI astrometry for 6.7 GHz methanol maser sources within few kpc from the Sun. Based on in-beam mapping of the W 3(OH) methanol maser, we also measured the internal proper motions of its 6.7 GHz methanol maser for the first time. The internal proper motions basically show north–south expansion with a velocity of few km s$^{-1}$, being similar to OH masers. The spatial distribution and the internal proper motions of 6.7 GHz methanol masers suggest a rotating and expanding torus structure surrounding the UC H II region.

The Mid-Infrared luminosity function of galaxies using the AKARI mid-infrared All-Sky Survey Catalogue

AbstractWe present the first determination of the 18 μm luminosity function (LF) of galaxies at 0.006 < z < 0.7 (the average redshift is ~ 0.04) using the AKARI mid-infrared All-Sky Survey catalogue. We have selected a 18 μm flux-limited sample of 243 galaxies from the catalogue in the SDSS spectroscopic region. We then classified the sample into four types; Seyfert 1 galaxies (including QSOs), Seyfert 2 galaxies, LINERs and Star-Forming galaxies using mainly [OIII]/Hβ vs. [NII]/Hα line ratios obtained from the SDSS.As a result of constructing Seyfert 1 and Seyfert 2 LFs, we found the following results; (i) the number density ratio of Seyfert 2s to Seyfert 1s is 3.98 ± 0.41 obtained from Sy1 and Sy2 LFs; this value is larger than the results obtained from optical LFs. (ii) the fraction of Sy2s in the entire AGNs may be anti-correlated with 18 μm luminosity. These results suggest that the torus structure probably depends on the mid-infrared luminosity of AGNs and most of the AGNs in the local Universe are obscured by dust.

Monodisperse red blood cell-like particles via consolidation of charged droplets

Recently, researchers have tried to produce non-spherical and anisotropic particles to be used in the next generation of multi-functional materials. Of key interest is the red blood cell-like particle. The torus structure was produced under the relatively fast consolidation of monodisperse droplets, and its parameters were found to be tunable by temperature as well as solvent type and concentration. The observation of consolidation demonstrated that the polymers were accumulated and solidified in the torus structure, naturally, whereas there was the critical droplet size to induce the asymmetry diffusivities. The torus structures could be simply tuned by the flow rate and concentration. The coaxial nozzle system produced the core/shell torus particles. These results state that the consolidation mechanism can hold important clues to enhance the range of tuning capabilities.

Torus-Bifurcation Mechanisms in a DC/DC Converter With Pulsewidth-Modulated Control

Pulse-modulated converter systems play an important role in modern power electronics. However, by virtue of the complex interplay between ordinary (smooth) and so-called border-collision bifurcations generated by the switching dynamics, the changes in behavior that can occur in multilevel converter systems under varying operational conditions still remain to be explored in full. Considering the dynamics of a three-level dc/dc-converter, we demonstrate a number of new scenarios for the birth or destruction of resonant and ergodic tori. One scenario involves the formation of a doubled-layered torus structure around a stable focus point through three subsequent border-collision fold bifurcations. Another scenario replaces one of the fold bifurcations by a global bifurcation. In both of these scenarios, the basic mode of the converter remains stable while other modes grow up and bifurcate around it. We also illustrate the subcritical birth of both an ergodic and a resonance torus from the basic operational mode.

Fe-K LINE PROBING OF MATERIAL AROUND THE ACTIVE GALACTIC NUCLEUS CENTRAL ENGINE WITHSUZAKU

We systematically analyzed the high-quality Suzaku data of 88 Seyfert galaxies. We obtained a clear relation between the absorption column density and the equivalent width of the 6.4 keV line above 10$^{23}$ cm$^{-2}$, suggesting a wide-ranging column density of $10^{23-24.5}$ cm$^{-2}$ with a similar solid and a Fe abundance of 0.7--1.3 solar for Seyfert 2 galaxies. The EW of the 6.4 keV line for Seyfert 1 galaxies are typically 40--120 eV, suggesting the existence of Compton-thick matter like the torus with a column density of $>10^{23}$ cm$^{-2}$ and a solid angle of $(0.15-0.4)*4pi$, and no difference of neutral matter is visible between Seyfert 1 and 2 galaxies. An absorber with a lower column density of $10^{21-23}$ cm$^{-2}$ for Compton-thin Seyfert 2 galaxies is suggested to be not a torus but an interstellar medium. These constraints can be understood by the fact that the 6.4 keV line intensity ratio against the 10--50 keV flux is almost identical within a range of 2--3 in many Seyfert galaxies. Interestingly, objects exist with a low EW, 10--30 eV, of the 6.4 keV line, suggesting that those torus subtends only a small solid angle of $<0.2*4pi$. Ionized Fe-K$\alpha$ emission or absorption lines are detected from several percents of AGNs. Considering the ionization state and equivalent width, emitters and absorbers of ionized Fe-K lines can be explained by the same origin, and highly ionized matter is located at the broad line region. The rapid increase in EW of the ionized Fe-K emission lines at $N_{H}>10^{23}$ cm$^{-2}$ is found, like that of the cold material. It is found that these features seem to change for brighter objects with more than several $10^{44}$ erg/s such that the Fe-K line features become weak. We discuss this feature, together with the torus structure.

CHANDRAVIEW OF PULSAR WIND NEBULA TORI

The results from a systematic study of eleven pulsar wind nebulae with a torus structure observed with the Chandra X-ray observatory are presented. A significant observational correlation is found between the radius of the tori, r, and the spin-down luminosity of the pulsars, Edot. A logarithmic linear fit between the two parameters yields log r = (0.57 +- 0.22) log Edot -22.3 +- 8.0 with a correlation coefficient of 0.82, where the units of r and Edot are pc and ergs s^-1, respectively. The value obtained for the Edot dependency of r is consistent with a square root law, which is theoretically expected. This is the first observational evidence of this dependency, and provides a useful tool to estimate the spin-down energies of pulsars without direct detections of pulsation. Applications of this dependency to some other samples are also shown.

RTTM: New interconnection network structure with hierarchical twist Torus

Because of low utilization rate and uneven load value of rectangular Torus,this paper presented a new hierarchical twist Torus structure named Rectangular Twisted Torus Meshes (RTTM). At the lowest level of RTTM network,the level-1 sub-network,also called a basic module,consisted of a mesh connection of 2m×2m nodes. Successively higher level networks were built by recursively interconnecting a×2a next lower level sub-networks in the form of a rectangular twisted Torus. RTTM network has smaller diameter and average distance,which implies a minimization of the network communication delays. The simulation results by OPNET,consistent with theoretical analysis,show that the network is of high utilization rate,small end-to-end delay and larger capacity.

Observations of ‘wisps’ in magnetohydrodynamic simulations of the Crab Nebula

In this paper, we describe results of new high-resolution axisymmetric relativistic magnetohydrodynamic (MHD) simulations of pulsar wind nebulae. The simulations reveal strong breakdown of the equatorial symmetry and highly variable structure of the pulsar wind-termination shock. The synthetic synchrotron maps, constructed using a new more accurate approach, show striking similarity with the well-known images of the Crab Nebula obtained by Chandra and the Hubble Space Telescope. In addition to the jet–torus structure, these maps reproduce the Crab's famous moving wisps whose speed and rate of production agree with the observations. The variability is then analysed using various statistical methods, including the method of structure function and wavelet transform. The results point towards the quasi-periodic behaviour with the periods of 1.5–3 years and MHD turbulence on scales below 1 year. The full account of this study will be presented in a follow-up paper.

Fat H-Tree: A Cost-Efficient Tree-Based On-Chip Network

The topological explorations of on-chip networks are important for efficiently using their enormous wire resources for low-latency and high-throughput communications using a modest silicon budget. In this paper, we propose a novel tree-based interconnection network called Fat H-Tree that meets these requirements. A Fat H-Tree provides a torus structure by combining two folded H-Tree networks and is an attractive alternative to tree-based networks such as the Fat Trees in a microarchitecture domain. We introduce its chip layout schemes based on a folding technique for 2D and 3D ICs. Three deadlock-free routing schemes are proposed for Fat H-Tree. We evaluate the performance of Fat H-Tree and other tree-based networks using real application traces. In addition, the network logic area, wire resource, and energy consumption of Fat H-Tree are compared with other topologies, based on a typical implementation of on-chip routers synthesized with a 90-nm standard cell library. The results show that (1) a Fat H-Tree outperforms a Fat Tree with two upward and four downward connections in terms of the throughput and average hop count, (2) a Fat H-Tree requires 19.8 percent-27.8 percent smaller network logic area than the Fat Tree, (3) a Fat H-Tree consumes slightly less energy than the Fat Tree does, and (4) a Fat H-Tree uses slightly more wire resources than the Fat Tree, but the current process technology can provide sufficient wire resources for implementing Fat-H-Tree-based on-chip networks.

Design and simulation of a Torus topology for network on chip

Aiming at the applications of NOC (network on chip) technology in rising scale and complexity on chipsystems, a Torus structure and corresponding route algorithm for NOC is proposed. This Torus structure improvestraditional Torus topology and redefines the denotations of the routers. Through redefining the router denotationsand changing the original router locations, the Torus structure for NOC application is reconstructed. On the basisof this structure, a dead-lock and live-lock free route algorithm is designed according to dimension increase. SystemC is used to implement this structure and the route algorithm is simulated. In the four different traffic patterns, average, hotspot 13%, hotspot 67% and transpose, the average delay and normalization throughput of this Torusstructure are evaluated. Then, the performance of delay and throughput between this Torus and Mesh structure iscompared. The results indicate that this Torus structure is more suitable for NOC applications.

Structure of the Thiazole Biosynthetic Enzyme THI1 from Arabidopsis thaliana

Thiamin pyrophosphate is an essential coenzyme in all organisms that depend on fermentation, respiration or photosynthesis to produce ATP. It is synthesized through two independent biosynthetic routes: one for the synthesis of 2-methyl-4-amino-5-hydroxymethylpyrimidine pyrophosphate (pyrimidine moiety) and another for the synthesis of 4-methyl-5-(beta-hydroxyethyl) thiazole phosphate (thiazole moiety). Herein, we will describe the three-dimensional structure of THI1 protein from Arabidopsis thaliana determined by single wavelength anomalous diffraction to 1.6A resolution. The protein was produced using heterologous expression in bacteria, unexpectedly bound to 2-carboxylate-4-methyl-5-beta-(ethyl adenosine 5-diphosphate) thiazole, a potential intermediate of the thiazole biosynthesis in Eukaryotes. THI1 has a topology similar to dinucleotide binding domains and although details concerning its function are unknown, this work provides new clues about the thiazole biosynthesis in Eukaryotes.

Dipole–vortex structure of the obscuring tori in active galactic nuclei

AbstractA “matrjoshka” scheme for obscuring vortex torus structure is proposed, which could help to explain the AGN radiation flares, variability and evolution.

Dynamic Testing of an Inflatable, Self-Supporting, Unpressurized Thin-Film Torus

Dynamic testing of an inflatable thin-film torus structure with regular formed convex dome surface features has been performed to evaluate structural natural frequencies, mode shapes, and modal damping ratios. The structure presented two unique challenges with respect to modal testing. First, it is extremely lightweight, flexible, and highly damped. Second, the thin film that provides the integrity to the structure is not smooth and flat, but has a pattern of hexagonal dome structures formed into it that increases the local stiffness of the thin film to the point that the structure is self-supporting in the gravity environment of Earth when the internal pressure is released. The dynamic testing was performed in this self-supporting state. In the modal test a loudspeaker provided acoustic excitation, and a laser displacement sensor was used to measure the vibration response at various points on the torus surface. The acoustic excitation and the laser displacement measuring technique were chosen because they are all noncontact methods that avoid mass loading of the structure as would happen if accelerometers and a shaker were used. Three in-plane and three out-of-plane modes were extracted using this approach. The experimental results indicate that the noncontact modal data-acquisition approach for extremely lightweight structures is suitable and effective. The modal identification procedure found modes that are analogous to elastic ring modes as well as widely spaced repeated modes.

Temporal and Spatial Evolution of a Laser Spark in Air

Experiments were conducted to quantify the temperature and electron number density of a laser spark formed in air. The laser spark was created by focusing a 180-mJ beam from the second harmonic (wavelength of 532 nm) of a pulsed Nd:YAG laser with a 100-mm focal length lens. For early times, between 50 ns and 1 μs, images of the spark emission have been obtained to characterize the geometry. Also the temperature and electron number density were measured from the emission spectra between 490 and 520 nm where 46 N II lines are observed. The methodology of fitting the experimental data to the modeled spectra to deduce the temperature and electron number density is described. For the initial temporal range, the temperature peaks at approximately 50,000 K and decays over the first 1 μs. The electron number density peaks at approximately 10 19 cm -3 , decaying only slightly slower than t -1 . For the longer temporal evolution, from 20 to 1000 μs, planar temperature measurements were achieved using filtered Rayleigh scattering. The peak temperature starts at approximately 4100 K at 20 μs and decays to 580 K by 1 ms. The planar temperature images show a center jet propagating in the opposite direction as the initiating laser beam, which induces a vortex ring (or torus) propagating in the direction of the beam. The evolution of the position and radius of the torus structure is described and fit with a power law utilized by previous investigators. The temperature of the plasma created by laser-induced optical breakdown appears to fit quite well using a triple exponential over the four orders of magnitude of temporal range where measurements were conducted.

The HST view of the nuclear emission line region in low luminosity radio-galaxies

We study the properties of the emission line regions in two samples of low luminosity radio-galaxies, while focusing on the Compact Emission Line Region (CELR) revealed to be a characteristic feature of these objects by HST narrow-band imaging. We find a strong correlation between line and optical continuum nuclear emission, which suggests that the optical cores (most likely of non-thermal origin) can be directly associated to the source of ionizing photons, i.e. that we are seeing a jet-ionized narrow line region. A photon budget argument indicates that the optical nuclear sources produce sufficient photon flux provided that the covering factor of the circum-nuclear gas is rather large, on average ∼0.3. Analysis of HST images and spectra suggests that the CELR may take the form of a pc-scale, high filling factor structure, possibly an optically thin torus. Estimates of the CELR mass lead to values as small as 10−10 3 M� , and photon counting sets a limit to the Broad Line Region mass of MBLR < 10 −2 M� . When considered together with the low accretion rate and the tenuous torus structure, a general paucity of gas in the innermost regions of low luminosity radio-galaxies emerges as the main characterizing difference from more powerful Active Galactic Nuclei.

On the formation of Io’s inner torus

In December 1995 and November 2002, the Galileo spacecraft traversed the inner Io plasma torus on the J0 and A34 passes, respectively. Observations of electron density showed a steep drop off at the inner boundary located between 4.5 R J and 5 R J on the two passes, and a much more gradual decrease in the outer torus. The [Wang, Y.-L., Russell, C.T., Raeder, J. The Io mass loading disk: model calculations. Journal of Geophysical Research 106, 26243–26260, 2001] model of torus formation considers multiple ionization and neutralization stages for the pickup ions, and predicts an inner torus boundary location which depends on the local plasma velocity at Io. For an inner torus boundary at ∼4.7 R J, ions are picked up into a plasma flowing at ∼37 km/s (74 km/s is the corotation velocity at 5.9 R J). The steepness of the boundary and the double peaked density structure seen on the two Galileo passes is not reproduced by the [Wang, Y.-L., Russell, C.T., Raeder, J. The Io mass loading disk: model calculations. Journal of Geophysical Research 106, 26243–26260, 2001] model, which considers the source of mass loading at Io to be uniformly distributed around the moon and does not include outward radial convection. Adding this convection to the model, as would be required to maintain a steady state magnetodisk, steepens the inner torus boundary, but does so over very long timescales. The different inner torus density structure observed on the J0 and A34 passes is not reproduced by either the [Wang, Y.-L., Russell, C.T., Raeder, J. The Io mass loading disk: model calculations. Journal of Geophysical Research 106, 26243–26260, 2001] or outward radial convection models and indicates the possible occurrence of a large mass loading event in the 7 years between the passes or longitudinal asymmetry in the torus structure.

Disks, tori, and cocoons: emission and absorption diagnostics of AGN environments

One of the most important problems in the study of active galaxies is understanding the detailed geometry, physics, and evolution of the central engines and their environments. The leading models involve an accretion disk and torus structure around a central dense object, thought to be a supermassive black hole. Gas found in the environment of active galactic nuclei (AGN) is associated with different structures: molecular accretion disks, larger scale atomic tori, ionized and neutral “cocoons” in which the nuclear regions can be embedded. All of them can be studied at radio wavelengths by various means. Here, we summarize the work that has been done to date in the radio band to characterize these structures. Much has been learned about the central few parsecs of AGN in the last few decades with contemporary instruments but the picture remains incomplete. In order to be able to define a more accurate model of this region, significant advances in sensitivity, spectral and angular resolution, and bandpass stability are required. The necessary advances will only be provided by the Square Kilometer Array and we discuss the possibilities that these dramatic improvements will open for the study of the gas in the central region of AGN.

Coxeter and Dynkin Diagrams and Their Associated Twisted Partition Functions for the Virasoro Minimal Models

To a pair (G′, G″) of ADE Dynkin diagrams one can associate five types of sesquilinear forms on the space of Virasoro characters. These forms can be interpreted, in terms of minimal models, as twisted partition functions. Our classification rests on the possibility of twisting the “torus structures” of the two diagrams G′ and G″. For the torus structure of a given diagram, one can introduce a single twist, two twists, or no twist at all. We describe the general situation and study an example pertaining to the case of the Virasoro minimal models.

Giant single-molecule magnets: a [Mn84] torus and its supramolecular nanotubes.

The discovery a decade ago that individual molecules can function as magnetizable magnets provided a new, 'bottom-up' approach to nanoscale magnetic materials, and such molecules have since been called single-molecule magnets (SMMs). Each molecule functions as a nanoscale, single-domain magnetic particle that, below its blocking temperature (TB), exhibits the classical macroscale property of a magnet, namely magnetization hysteresis. In addition, they straddle the classical/quantum interface in also displaying quantum tunnelling of magnetization (QTM) and quantum phase interference, the properties of the atomic or microscale. SMMs have a number of potential applications, including very high density information storage, where each bit would be stored as the magnetization orientation of an individual molecule, and as quantum bits for quantum computing, taking advantage of the quantum superposition of states provided by the QTM. To facilitate development of techniques for addressing individual SMMs for such applications, and other reasons, it has been of interest to us to explore whether very large examples (by molecular standards) could be synthesized. In effect, can the molecular (or 'bottom-up') approach reach the size regime of the classical (or 'top-down') approach to nanoscale magnetic materials? Indeed, here we sure that a giant Mn84 SMM can be prepared with a torus structure of 4 nm dimensions, that it displays both magnetization hysteresis and QTM, and that it crystallizes as highly ordered, supramolecular nanotubes.