An interconnected single-star bridge-cell topology for grid support

FG Sagittae is one of the most important key objects of post-AGB stellar evolutionary studies. As a consequence of a final helium shell flash, this unique variable has shown real evolutionary changes on human time scales during this century. The observational history was reviewed in comparison with predictions from evolutionary models. The central star of the old planetary nebula (Hel-5) evolved from left to right in the HR diagram, going in just hundred years from the hot region of exciting sources of planetary nebulae to the cool red supergiant domain just before our eyes becoming a newly-born post-AGB star. The effective temperature of the star was around 50,000 K at the beginning of this century, and the last estimates in the late 1980s give 5,000-6,500 K. Recent spectroscopic observations obtained by Ingemar Lundström show definite changes in the nebular line intensities. This fact undoubtedly rules out the possibility that, instead of FG Sge, a hidden hot object would be the true central star of the nebula. Consequently, the observed evolutionary changes are connected with the evolution of a single star.

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The effects of surface fossil magnetic fields on massive star evolution: III. The case of τ Sco

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab893 ◽

2021 ◽

Author(s):

Z Keszthelyi ◽

G Meynet ◽

F Martins ◽

A de Koter ◽

A David-Uraz

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Massive Star ◽

Slow Rotation ◽

Single Star ◽

Surface Magnetic Field ◽

Fundamental Parameters ◽

Chemical Enrichment ◽

Star Models ◽

Nitrogen Excess

Abstract τ Sco, a well-studied magnetic B-type star in the Uτer Sco association, has a number of surprising characteristics. It rotates very slowly and shows nitrogen excess. Its surface magnetic field is much more complex than a purely dipolar configuration which is unusual for a magnetic massive star. We employ the cmfgen radiative transfer code to determine the fundamental parameters and surface CNO and helium abundances. Then, we employ mesa and genec stellar evolution models accounting for the effects of surface magnetic fields. To reconcile τ Sco’s properties with single-star models, an increase is necessary in the efficiency of rotational mixing by a factor of 3 to 10 and in the efficiency of magnetic braking by a factor of 10. The spin down could be explained by assuming a magnetic field decay scenario. However, the simultaneous chemical enrichment challenges the single-star scenario. Previous works indeed suggested a stellar merger origin for τ Sco. However, the merger scenario also faces similar challenges as our magnetic single-star models to explain τ Sco’s simultaneous slow rotation and nitrogen excess. In conclusion, the single-star channel seems less likely and versatile to explain these discrepancies, while the merger scenario and other potential binary-evolution channels still require further assessment as to whether they may self-consistently explain the observables of τ Sco.

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THE EFFECTS OF DIFFERENT PERTURBATIONS ON THE DYNAMICS OF THE ACCRETION DISK AROUND THE BLACK HOLE

International Journal of Modern Physics A ◽

10.1142/s0217751x07036166 ◽

2007 ◽

Vol 22 (10) ◽

pp. 1875-1898 ◽

Cited By ~ 1

Author(s):

ORHAN DÖNMEZ

Keyword(s):

Shock Wave ◽

Black Hole ◽

Shock Waves ◽

Accretion Disk ◽

Periodic Oscillation ◽

Single Star ◽

Special Cases ◽

Galactic Black Hole ◽

General Relativistic ◽

Armed Spiral

We investigate the special cases of the formation of shocks in the accretion disks around the nonrotating (Schwarzschild) black holes in cases where one or few stars perturb the disk. We model the structure of disk with a 2D fully general relativistic hydrodynamic code and investigate a variety of cases in which the stars interacting with the disk are captured at various locations. We have found the following results: (1) if the stars perturb the disk at nonsymmetric locations, a moving one-armed spiral shock wave is produced and it destroys the disk eventually; (2) if the disk is perturbed by a single star located close to the black hole, a standing shock wave is produced while the disk becomes an accretion tori; (3) if the disk is perturbed by stars at symmetric locations, moving two-armed spiral shock waves are produced while the disk reaches a steady state; (4) continuous injection of matter into the stable disk produces a standing shock wave behind the black hole. Our outcomes reinforce the view that different perturbations on the stable accretion disk carry out different types of shock waves which produce Quasi-Periodic Oscillation (QPO) phenomena in galactic black hole candidates and it is observed as a X-ray.

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Spectroscopic and microscopic comparisons of cell topology and chemistry analysis of mouse embryonic stem cell, somatic cell and cancer cell

Acta Histochemica ◽

10.1016/j.acthis.2021.151763 ◽

2021 ◽

Vol 123 (6) ◽

pp. 151763

Author(s):

Berrin Ozdil ◽

Duygu Calik-Kocaturk ◽

Cisem Altunayar-Unsalan ◽

Eda Acikgoz ◽

Volkan Gorgulu ◽

...

Keyword(s):

Stem Cell ◽

Embryonic Stem Cell ◽

Somatic Cell ◽

Cancer Cell ◽

Embryonic Stem ◽

Mouse Embryonic Stem Cell ◽

Cell Topology

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Nanotomography of Cell Surfaces with Evanescent Fields

Advances in Optical Technologies ◽

10.1155/2008/254317 ◽

2008 ◽

Vol 2008 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Michael Wagner ◽

Petra Weber ◽

Wolfgang S. L. Strauss ◽

Henri-Pierre Lassalle ◽

Herbert Schneckenburger

Keyword(s):

Total Internal Reflection ◽

3D Imaging ◽

Cell Swelling ◽

Cholesterol Depletion ◽

In Vitro Diagnostics ◽

Axial Resolution ◽

Cell Surfaces ◽

Cell Substrate ◽

Cell Topology

The technique of variable-angle total internal reflection fluorescence microscopy (TIRFM) and its application to nanotomography of cell surfaces are described. Present applications include (1) 3D imaging of chromosomes in their metaphase to demonstrate axial resolution in the nanometre range, (2) measurements of cell-substrate topology, which upon cholesterol depletion shows some loosening of cell-substrate contacts, and (3) measurements of cell topology upon photodynamic therapy (PDT), which demonstrate cell swelling and maintenance of focal contacts. The potential of the method for in vitro diagnostics, but also some requirements and limitations are discussed.

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Starlight-inertial integrated navigation based on single star vector

Optics and Precision Engineering ◽

10.37188/ope.20212903.0503 ◽

2021 ◽

Vol 29 (3) ◽

pp. 503-512

Author(s):

Chuan QIAO ◽

◽

Xiao LI ◽

Shao-long PANG ◽

Peng-bo YAN ◽

...

Keyword(s):

Integrated Navigation ◽

Single Star

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Single star count ups odds of aliens

The New Scientist ◽

10.1016/s0262-4079(10)61715-0 ◽

2010 ◽

Vol 207 (2769) ◽

pp. 14

Keyword(s):

Single Star ◽

Star Count

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The geometric formulas of the Lewis’s law and Aboav-Weaire’s law in two dimensions based on ellipse packing

10.7287/peerj.preprints.27797 ◽

2019 ◽

Author(s):

Kai Xu

Keyword(s):

Two Dimensions ◽

Empirical Formulas ◽

Von Neumann ◽

Upper Limit ◽

Edge Distribution ◽

Cell Topology ◽

Neighbor Relationship ◽

New Formula ◽

Geometric Formula ◽

Ellipse Packing

The two-dimensional (2D) Lewis’s law and Aboav-Weaire’s law are two simple formulas derived from empirical observations. Numerous attempts have been made to improve the empirical formulas. In this study, we simulated a series of Voronoi diagrams by randomly disordered the seed locations of a regular hexagonal 2D Voronoi diagram, and analyzed the cell topology based on ellipse packing. Then, we derived and verified the improved formulas for Lewis’s law and Aboav-Weaire’s law. Specifically, we found that the upper limit of the second moment of edge number is 3. In addition, we derived the geometric formula of the von Neumann-Mullins’s law based on the new formula of the Aboav-Weaire’s law. Our results suggested that the cell area, local neighbor relationship, and cell growth rate are closely linked to each other, and mainly shaped by the effect of deformation from circle to ellipse and less influenced by the global edge distribution.

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