Asymmetric Bar Research Articles

Formation of asymmetric arms in barred galaxies

ABSTRACTWe establish a dynamical mechanism to explain the origin of the asymmetry between the arms observed in some barred disc galaxies, where one of the two arms emanating from the bar ends is very well defined, while the second one displays a ragged structure, extending between its ridge and the bar. To this purpose, we study the invariant manifolds associated with the Lyapunov periodic orbits around the unstable equilibrium points at the ends of the bar. Matter from the galaxy centre is transported along these manifolds to the periphery, forming this way the spiral arms that emanate from the bar ends. If the mass distribution in the galaxy centre is not homogeneous, because of an asymmetric bar with one side stronger than the other, or because of a non-centred bulge, the dynamics about the two unstable Lagrange points at the ends of the bar will not be symmetric as well. One of their invariant manifolds becomes more extended than the other, enclosing a smaller section and the escaping orbits on it are fewer and dispersed in a wider region. The result is a weaker arm and more ragged than the one at the other end of the bar.

Strong gravitational lens image of the M87 black hole with a simple accreting matter model

ABSTRACT We study simulated images generated from an accretion disc surrounding the supermassive black hole hosted in the nearby galaxy M87. We approach the problem employing very simple accreting models inspired from magnetohydrodynamical simulations and introducing a new recipe for dealing with the combined integration of the geodesic and geodesic deviation equations in Kerr space–time, which allows for a convenient and efficient way to manage the system of equations. The geometry of the basic emission model is given by a two-temperature thin disc in the equatorial plane of the black hole supplemented by an asymmetric bar structure. We show that this configuration permits to generate the most salient features appearing in the EHT Collaboration images of M87 with impressive fidelity.

Operation of a traction machine’s wheel mover with a locked asymmetrical balance bar

The problems of determining the parameters of a traction machine’s wheel mover with a locked asymmetrical balance bar operation, taking into account the kinematic mismatch arising from the redistribution of the vertical reactions at the driving wheels due to off-center pushing force, have been considered. An algorithm for calculating traction and braking forces, as well as drive wheels’ slippage and skid of an asymmetric balance bar based on their traction balance and the condition of equal actual speeds under a variable vertical load, have been presented. As a result of research it has been found that the greatest additional loads in the drive and tire wear of the wheel mover with a locked asymmetric balance bar will occur when it moves in transport mode on a support surface with high traction properties.

Asymmetric Bar Winding for High-Speed Traction Electric Machines

A new asymmetric bar winding concept along with the analysis and benefits for high-speed traction electric machines is presented. The objective is to reduce the ac losses, especially at high speeds, utilizing optimized and asymmetric conductor heights within a slot for bar-wound stators. Detailed winding diagram, height optimization, ac loss analysis, and thermal performance are presented for both symmetric, i.e., conventional, and asymmetric bar windings. The proposed idea is validated using the closed-form analytical equation and 2-D time-stepped finite-element analysis (FEA). A substantial reduction of ac losses and improvement in continuous power over the wide operation range is achieved as demonstrated for a 12-pole, 100-kW high-speed (15 000 r/min) PM traction machine. Thermal performance analysis using forced liquid cooling is also included. The design and analysis methodology is presented to support high-speed traction electric machine designers meet the ever-increasing demand on efficiency and performance with bar-type windings.

HIGH-END PECTUS SURGERY: TOTAL CHEST WALL REMODELING FOR PECTUS EXCAVATUM, CARINATUM, AND MIXED DEFORMITIES

SESSION TITLE: Cardiothoracic Surgery SESSION TYPE: Original Investigation Posters PRESENTED ON: 10/10/2018 01:00 PM - 02:00 PM PURPOSE: Pectus anomaly contains always two components together, excavatum and carinatum portions, in a given deformity. For example, excavatum with lower costal flaring or carinatum with portions of depression. To treat all these components of pectus deformity in best quality, our approach has been “total remodeling” to treat all excavations and focal protuberances in pectus excavatum, carinatum, and all varieties of mixed forms. The purpose of this study is to illustrate the individual techniques for each specific component of the deformity, and to appraise the results. METHODS: We retrospectively analyzed the data of the total chest wall remodeling approach using pectus bars, which included 1153 patients with pectus excavatum and carinatum or mixed deformities between 2011 and 2016. Total remodeling approach represents all the components in a given deformity are treated in a single operative setting. The surgical techniques for the depressed chest wall was lifted with symmetric or asymmetric pectus bars in the fashions of single, parallel, or cross bars. The protruded part(s) of chest wall was compressed with the sandwich technique using the pectus bars or strings (flare-buster, magic string). RESULTS: The mean age of the patients was 10.1 years (3–55 years). The techniques used for the repair of excavatum portions were symmetric bar 779(67.6%), asymmetric bar 354(30.7%), single bar 679(58.9%), parallel bar 421(36.5%), cross-bar 33(2.9%), claw fixator 828(71.8%), hinge plate 395(34.3%), bridge connection 274(23.8%). The techniques used for the repair of carinatum portions were sandwich technique 20(1.7%), asymmetric bar 20(1.7%), bridge connection 20(1.7%), flare-buster 481(41.7%), magic string 51(4.4%). The major complication rates were: pneumothorax, 15 (1.3%); bar displacement, 6 (0.52%); pleural effusion, 27 (2.3%). There was no mortality. Reoperation was required in 10 patients (0.87%). The CT index changed after repair: Depression Index, 1.74 ± 0.67 to 1.00 ±0.00 (p<0.001), Asymmetry Index, 1.05 ± 0.22 to 0.97 ± 0.21 (p<0.001), Eccentricity Index, 1.45 ± 0.69 to 1.01 ±0.01 (p<0.001), and Unbalance Index, 1.13 ±0.27 to 1.02 ±0.01 (p<0.001). CONCLUSIONS: The total remodeling of the chest wall in repair of pectus deformity seemed to be effective in solving the morphological variations including pectus excavatum/carinatum complex and lower costal flare. With this concept, we achieved decent cosmetic outcomes in a single setting of surgery without residual deformities. CLINICAL IMPLICATIONS: Total chest wall remodeling strategy can be applied to treat the excavatum, carinatum, or mixed deformity with the combination of various repair techniques to fulfill a single-step comprehensive repair of the deformity. DISCLOSURES: No relevant relationships by Hyung Park, source=Web Response

Vibration isolation of a symmetric and asymmetric rigid bar using struts subject to axial static and dynamic excitation

Many developed modern machineries such as compressors, engines, and presses represent a serious source of undesirable, uncomfortable, and uncontrollable vibrations leading to harmful failure and loss of machine availability. Therefore, research of mechanical engineers in maintenance sections in the industry has been devoted to the control, isolation, and minimi-zation of harmful effects of such vibrations. The objective of the present paper is to study the influence of using a specific type of vibration isolator based on using post-buckled elastic clamped—clamped struts as an effective solution tool to relieve vibrating machines from these harmful effects. A model that consists of post-buckled struts acting as vibration isolators used to support symmetric and asymmetric rigid bars is introduced. The proposed clamped—clamped struts are subject to axial harmonic excitation at the base. The isolated bar is allowed to displace laterally. Displacement transmissibility is selected as the governing optimization variable of the isolator's effectiveness with the main objective to minimize vibrations transmitted from the base to the rigid bar. The transmissibility is calculated over a wide range of frequencies and plotted in the form of design charts to determine its effect on the vibration behaviour of struts. The lateral motion of the bar is considered. These plots are used to recognize the range of frequencies, for which full isolation is maintained. The frequencies at which resonance occurs in the system can then be depicted from the design graphs. The study reveals that at resonance frequencies, the most effective transmissibility is well below unity. Vibration characteristics are determined at specific frequencies, such that the physical performance of the vibrating system can be studied. All variables used in the analysis are normalized, such that the results are not dependent on any geometric of material property, such as the modulus of elasticity of the material, the section modulus of the profile used, or the length of the strut. In this way, the obtained results can be applied over a wide range of elastic materials, regardless of the type of material or section properties.

Extreme eccentric canal type pectus excavatum: morphological study and repair techniques

Extreme eccentric canal type pectus excavatum (Grand Canyon type, GC, Type 2A3), is a distinct morphological variation, characterized by an eccentric longitudinal canal. Due to the extent of depression and asymmetry, repair is often challenging with the minimally invasive technique. Following, we present its morphologic characteristics and evaluate repair techniques according to morphology type. Extreme eccentric canal type pectus excavatum is an eccentric, long canal-like chest wall depression from the infra-clavicle to lower chest. Among 851 patients who underwent pectus excavatum repair from 1999 to 2007, 112 patients (13.2%) had the eccentric canal type. Morphologic type and repair techniques were evaluated; results were assessed by pectus indices (depression index (DI), asymmetry index (AI), and eccentricity index (EI)). Of the asymmetric cases, 31% (112/361) were the eccentric canal type. Female proportion (male to female ratio=2.3) was higher than in general pectus excavatum (4.1, p<0.05). Young female adults were more frequently affected (8/17, 47%, p<0.05). Repair techniques included asymmetric bar (n=97, 86.6%), seagull bar (n=53, 47.3%), crest compression (n=13, 11.6%), and parallel bar (n=79, 70.5 %) techniques. Pectus indices changes were: DI (pre 2.89 to post 1, p<0.01), AI (pre 1.11 to post 1.03, p<0.01), and EI (pre 1.69 to post 1, p<0.01). AI change represented asymmetric to symmetric correction. Extreme eccentric canal type pectus excavatum represents a distinctive morphology and requires special techniques for repair. Post-repair symmetry can be achieved by an asymmetric bar technique. Upper chest wall depression can be corrected by a parallel bar technique. Protruding ridge was relieved by a seagull bar or crest compression technique.

The impact of feedback using video display and image frames on some biomechanics of backwards flip and landing using the uneven bars (asymmetric bar ) events for students of physical education

The impact of feedback using video display and image frames on some biomechanics of backwards flip and landing using the uneven bars (asymmetric bar ) events for students of physical education

Technical Innovations in the Minimally Invasive Approach for Treating Pectus Excavatum: A Paradigm Shift through Six Years’ Experience with 630 Patients

: The multiple-momentum (MM) based multitarget (MT) approach has been developed through a single surgeon's experience to overcome the limits of the conventional Nuss procedure, which is the single target-single momentum approach that corrects only symmetric pectus excavatum (PE). The new techniques that have been devised on a morphologic basis, according to the Terrain Contour Matching (TERCOM) system, have made this approach a comprehensive one that can cover all types of pectus deformity. The aim of this study was to elucidate the difference between the conventional technique and the new approach. : The data of 630 PE patients who received the modified Nuss procedure, based on the MM-MT-TERCOM approach, between 1999 and 2005, were retrospectively studied. The conceptual differences between the new approach and the conventional one were determined. The techniques according to a new paradigm, for treating asymmetry, adults, and complex morphology, as well as the bar fixation technique, were analyzed. The results of the repair were assessed with a new CT index, the Asymmetry Index (AI). : According to the morphologic classification, 269 patients were asymmetric (42.7%): 138 were eccentric (53 Grand Canyon type), 88 were unbalanced, and 36 were combined. On the basis of the MM-MT-TERCOM concept for repairing complex morphology, multiple targets were selected in 224 patients (35.6%). To correct targets simultaneously, positive momentum (630 patients, 100%) and negative momentum (124 patients, 19.7%) were applied as appropriate. The techniques used were an asymmetric bar (250 patients, 39.7%), a seagull bar (107 patients, 17%), a complex bar via TERCOM (126 patients, 20%), the crest compression technique (59 patients, 9.4%), and a compound bar (84 patients, 13.3%). The postoperative changes of the AI were from 1.03 ± 0.06 to 1.02 ± 0.13 (P = 0.117) in the symmetric group and they were from 1.1 ± 0.05 to 1.02 ± 0.02 (P < 0.001) in the asymmetric group. : Refinement of techniques in accordance with the morphology and cause-effect basis of the bar action provided reproducible results for achieving postrepair symmetry for treating complex PE. Therefore, the new approach with techniques that use multiple momentums (MM-MT-TERCOM) supports the new paradigm of the Nuss procedure is effective in repair of all morphologic types of PE.

The Active Merging System ESO 202-G23 (Carafe Nebula)

We present the results of observations both in imaging and spectroscopy of the nearby active galaxy ESO 202-G23 (Carafe Nebula). The main result of this investigation is that the peculiar morphology of the galaxy, formerly attributed to the presence of an asymmetric bar, is produced by the merging of two galaxies both hosting an active nucleus. Our deep R image reveals unexpectedly the presence of a knot (G2), not visible in the B image, at 3.5 kpc on the northern of the nucleus (G1), classified in the literature as a Seyfert 2. A long-slit spectrum provides evidence that G1 is a Seyfert 1.5 nucleus and that G2 is also a nucleus, showing features typical of a LINER heavily reddened by dust. The presence of tails and plumes in the outermost parts of the galaxy and the double U shape of the rotation curve of the gas around G1 and G2 strongly support the hypothesis of a merger that occurred 106–109 years ago, as suggested by the comparison of the current (14 M⊙ yr-1) and the recent (24 M⊙ yr-1) star formation rates. The system ESO 202-G23 is an infrared bright source (LFIR/L⊙ = 2.18 × 1010) and the IRAS flux ratios suggest a predominantly thermal origin of the infrared emission. The analysis of the IRAS data allows us to obtain some important properties concerning both the gas and the dust: Td(warm) ~ 36 K; Md(warm) = 4.1 × 106 M⊙; Td(cold) ~ 21 K; Md(cold) = (6.9–8.3) × 107 M⊙; MH I = 8.6 × 109 M⊙; MH II = (2.3–4.3) × 109 M⊙; Mgas = (1.1–1.3) × 1010 M⊙. The derived mass-to-light ratio MH I/LB = 2.23 and the value of the parameter K = vmax/rmax, K(G1) = 201, K(G2) = 179, indicate that the precursor is not later than Sbc.