scholarly journals Seyfert Activity in Ring Galaxies Due to Galactic Interactions

1999 ◽  
Vol 194 ◽  
pp. 424-425
Author(s):  
Tapan K. Chatterjee

Observations indicate that ring galaxies are more active than spirals (e.g., Ghigo et al., 1983 Appleton and Struck-Marcell, 1987). However, Seyfert activity is noted in only a few ring galaxies, e.g. NGC 985 (de Vaucouleurs & de Vaucouleurs 1975), NGC 1144 = Arp 118 (Huchra et al. 1982), ring galaxy in Sextans-optical counterpart of the IRAS source 09595-0755 (Wakamatus & Nishida). This is indicative of the fact that this type of activity requires favorable circumstances. In this context a previous work on the stellar episode of ring formation, Chatterjee (1984), is extended, including gas and studying the evolution of the ring structure, due to rebounds of the compact elliptical about the plane of the disk.

Author(s):  
Omkar Bait ◽  
Sushma Kurapati ◽  
Pierre-Alain Duc ◽  
Jean-Charles Cuillandre ◽  
Yogesh Wadadekar ◽  
...  

Abstract Here we report the discovery with the Giant Metrewave Radio Telescope of an extremely large (∼115 kpc in diameter) H i ring, located around a massive quenched galaxy, AGC 203001, but off-centered, with respect to it. This ring does not have any bright extended optical counterpart unlike several other known ring galaxies. Our deep g, r, and i optical imaging of the H i ring, using the MegaCam instrument on the Canada-France-Hawaii Telescope, shows however several regions with faint optical emission at a surface brightness level of ∼28 mag/arcsec2. Such an extended H i structure is very rare with only one other case known so far – the Leo ring. Conventionally, off-centered rings have been explained by a collision with an “intruder” galaxy leading to expanding density waves of gas and stars in the form of a ring. However, in such a scenario the impact also leads to large amounts of star formation in the ring which is not observed in the ring presented in this paper. We discuss possible scenarios for the formation of such H i dominated rings.


Author(s):  
J. Silcox ◽  
R. H. Wade

Recent work has drawn attention to the possibilities that small angle electron scattering offers as a source of information about the micro-structure of vacuum condensed films. In particular, this serves as a good detector of discontinuities within the films. A review of a kinematical theory describing the small angle scattering from a thin film composed of discrete particles packed close together will be presented. Such a model could be represented by a set of cylinders packed side by side in a two dimensional fluid-like array, the axis of the cylinders being normal to the film and the length of the cylinders becoming the thickness of the film. The Fourier transform of such an array can be regarded as a ring structure around the central beam in the plane of the film with the usual thickness transform in a direction normal to the film. The intensity profile across the ring structure is related to the radial distribution function of the spacing between cylinders.


Author(s):  
Chi-Ming Wei ◽  
Margaret Hukee ◽  
Christopher G.A. McGregor ◽  
John C. Burnett

C-type natriuretic peptide (CNP) is a newly identified peptide that is structurally related to atrial (ANP) and brain natriuretic peptide (BNP). CNP exists as a 22-amino acid peptide and like ANP and BNP has a 17-amino acid ring formed by a disulfide bond. Unlike these two previously identified cardiac peptides, CNP lacks the COOH-terminal amino acid extension from the ring structure. ANP, BNP and CNP decrease cardiac preload, but unlike ANP and BNP, CNP is not natriuretic. While ANP and BNP have been localized to the heart, recent investigations have failed to detect CNP mRNA in the myocardium although small concentrations of CNP are detectable in the porcine myocardium. While originally localized to the brain, recent investigations have localized CNP to endothelial cells consistent with a paracrine role for CNP in the control of vascular tone. While CNP has been detected in cardiac tissue by radioimmunoassay, no studies have demonstrated CNP localization in normal human heart by immunoelectron microscopy.


Planta Medica ◽  
2007 ◽  
Vol 73 (09) ◽  
Author(s):  
RM Pádua ◽  
R Waibel ◽  
SP Kuate ◽  
PK Riedl ◽  
P Gmeiner ◽  
...  
Keyword(s):  

Author(s):  
Claire Voisin

This book provides an introduction to algebraic cycles on complex algebraic varieties, to the major conjectures relating them to cohomology, and even more precisely to Hodge structures on cohomology. The book is intended for both students and researchers, and not only presents a survey of the geometric methods developed in the last thirty years to understand the famous Bloch-Beilinson conjectures, but also examines recent work by the author. It focuses on two central objects: the diagonal of a variety—and the partial Bloch-Srinivas type decompositions it may have depending on the size of Chow groups—as well as its small diagonal, which is the right object to consider in order to understand the ring structure on Chow groups and cohomology. An exploration of a sampling of recent works by the author looks at the relation, conjectured in general by Bloch and Beilinson, between the coniveau of general complete intersections and their Chow groups and a very particular property satisfied by the Chow ring of K3 surfaces and conjecturally by hyper-Kähler manifolds. In particular, the book delves into arguments originating in Nori's work that have been further developed by others.


Author(s):  
Tian Lu ◽  
Qinxue Chen ◽  
Zeyu Liu

Although cyclo[18]carbon has been theoretically and experimentally investigated since long time ago, only very recently it was prepared and directly observed by means of STM/AFM in condensed phase (Kaiser et al., <i>Science</i>, <b>365</b>, 1299 (2019)). The unique ring structure and dual 18-center π delocalization feature bring a variety of unusual characteristics and properties to the cyclo[18]carbon, which are quite worth to be explored. In this work, we present an extremely comprehensive and detailed investigation on almost all aspects of the cyclo[18]carbon, including (1) Geometric characteristics (2) Bonding nature (3) Electron delocalization and aromaticity (4) Intermolecular interaction (5) Reactivity (6) Electronic excitation and UV/Vis spectrum (7) Molecular vibration and IR/Raman spectrum (8) Molecular dynamics (9) Response to external field (10) Electron ionization, affinity and accompanied process (11) Various molecular properties. We believe that our full characterization of the cyclo[18]carbon will greatly deepen researchers' understanding of this system, and thereby help them to utilize it in practice and design its various valuable derivatives.


Author(s):  
Tian Lu ◽  
Qinxue Chen ◽  
Zeyu Liu

Although cyclo[18]carbon has been theoretically and experimentally investigated since long time ago, only very recently it was prepared and directly observed by means of STM/AFM in condensed phase (Kaiser et al., <i>Science</i>, <b>365</b>, 1299 (2019)). The unique ring structure and dual 18-center π delocalization feature bring a variety of unusual characteristics and properties to the cyclo[18]carbon, which are quite worth to be explored. In this work, we present an extremely comprehensive and detailed investigation on almost all aspects of the cyclo[18]carbon, including (1) Geometric characteristics (2) Bonding nature (3) Electron delocalization and aromaticity (4) Intermolecular interaction (5) Reactivity (6) Electronic excitation and UV/Vis spectrum (7) Molecular vibration and IR/Raman spectrum (8) Molecular dynamics (9) Response to external field (10) Electron ionization, affinity and accompanied process (11) Various molecular properties. We believe that our full characterization of the cyclo[18]carbon will greatly deepen researchers' understanding of this system, and thereby help them to utilize it in practice and design its various valuable derivatives.


2018 ◽  
Vol 9 (1) ◽  
pp. 26-45
Author(s):  
Ruth Henderson

The enigmatic wisdom poem of Job 28:1–28 stands apart from the rest of the book of Job in style and structure. Most read this poem in linear progression as three strophes (vv. 1–11; 15–19; 23–28) with an intervening refrain (vv. 12–14; 20–22). In this study, it is suggested that the poem has been presented in the form of a concentric or compositional ring structure, which juxtaposes arguments rather than presenting them in a linear fashion. According to this structure there are five compositional units, the centre of which holds the main point of the text (A, B, C, B1, A1). A central section (C vv. 15–19), maintains the traditional view of the supreme value of wisdom. The central unit is surrounded by two inner parallel sections each beginning with a rhetorical question concerning the location of wisdom (Sections B vv. 12–14 and B1 vv. 20–22), and two outer sections (A vv. 1–11 and A1 vv. 23–28) in which two contrasting ways of acquiring wisdom are presented: by independent human effort presented in the form of a mining metaphor (A vv. 1–11); or by contemplation of God’s omnipotent creative power and reverence for Him resulting in right behaviour (A1). Each of the major units also follows a concentric pattern.


2018 ◽  
Vol 481 (2) ◽  
pp. 174-178
Author(s):  
V. Levitskiy ◽  
◽  
I. Levitskiy ◽  
L. Pavlova ◽  
V. Solodilova ◽  
...  

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