8,218 research outputs found
The substructure and halo population of the Double Cluster and Persei
In order to study the stellar population and possible substructures in the
outskirts of Double Cluster and Persei, we investigate using the
GAIA DR2 data a sky area of about 7.5 degrees in radius around the Double
Cluster cores. We identify member stars using various criteria, including their
kinematics (viz, proper motion), individual parallaxes, as well as photometric
properties. A total of 2186 member stars in the parameter space were identified
as members. Based on the spatial distribution of the member stars, we find an
extended halo structure of and Persei, about 6 - 8 times larger than
their core radii. We report the discovery of filamentary substructures
extending to about 200 pc away from the Double Cluster. The tangential
velocities of these distant substructures suggest that they are more likely to
be the remnants of primordial structures, instead of a tidally disrupted stream
from the cluster cores. Moreover, the internal kinematic analysis indicates
that halo stars seems to be experiencing a dynamic stretching in the RA
direction, while the impact of the core components is relatively negligible.
This work also suggests that the physical scale and internal motions of young
massive star clusters may be more complex than previously thought.Comment: 9 pagges, 9 figures, Accecpted to A&
The Ability of a Tetrel Bond to Transition a Neutral Amino Acid into a Zwitterion
The interaction between glycine and F2CO/F2SiO occurs through the formation of a π-tetrel bond between the C/Si atom and a carboxyl O atom. The interaction energy is some 20 kJ/mol for the C···O tetrel bond, but exceeds 300 kJ/mol for Si···O. As part of the latter complexation process, the proton engaged in the intramolecular OH··N H-bond is transferred across to the N, forming a zwitterion. This Si···O tetrel bond is more effective at inducing this proton transfer than is placement of the glycine in an aqueous medium, complexation with an anionic BH4-, or adding an electron to the glycine
Stability Analysis of Fractional Order Systems with Time Delay
In this paper, we mainly study the stability of linear and interval linear fractional systems with time delay.
By applying the characteristic equations, a necessary and sufficient stability condition is obtained firstly,
and then some sufficient conditions are deserved. In addition, according to the equivalent relationship of fractional order systems with order
and with order , one may get more relevant theorems. Finally, two examples are provided to demonstrate the effectiveness
of our results
Stability Analysis of Fractional Order Systems with Time Delay
In this paper, we mainly study the stability of linear and interval linear fractional systems with time delay.
By applying the characteristic equations, a necessary and sufficient stability condition is obtained firstly,
and then some sufficient conditions are deserved. In addition, according to the equivalent relationship of fractional order systems with order
and with order , one may get more relevant theorems. Finally, two examples are provided to demonstrate the effectiveness
of our results
(1R,3S)-Methyl 3-[(S)-2-(hydroxydiphenylmethyl)pyrrolidin-1-ylmethyl]-2,2-dimethylcyclopropanecarboxylate
The asymmetric unit of the title compound, C25H31NO3, prepared from (−)-1R-cis-caronaldehyde, contains three independent molecules with similar conformations. The hydroxy groups are involved in intramolecular O—H⋯N hydrogen bonds. The crystal packing exhibits weak intermolecular O—H⋯O and C—H⋯O hydrogen bonds
- …