scholarly journals Formation of the young compact cluster GM 24 triggered by a cloud–cloud collision

2018 ◽  
Vol 70 (SP2) ◽  
Author(s):  
Yasuo Fukui ◽  
Mikito Kohno ◽  
Keiko Yokoyama ◽  
Atsushi Nishimura ◽  
Kazufumi Torii ◽  
...  
Keyword(s):  
Compact Cluster

scholarly journals Refining the true parameters of the open cluster NGC 4852

2009 ◽  
Vol 5 (S266) ◽  
pp. 539-539
Author(s):  
Gladys Solivella ◽  
Edgard Giorg ◽  
Rubén Vázquez ◽  
Giovanni Carraro
Keyword(s):  
Emission Line ◽  
Open Cluster ◽  
Open Clusters ◽  
Occurrence Rate ◽  
Hot Stars ◽  
Cluster Area ◽  
Young Object ◽  
Cluster Distance ◽  
Be Star ◽  
Compact Cluster

AbstractNGC 4852 is a moderately compact cluster centered at α2000 = 13 : 00 : 09; δ = −59 : 36 : 48, located near the center of an Hα superring. This cluster forms part of an extended region including young stellar aggregates inside a circle with a radius of 3 degrees, where many show an abundance of emission line stars. In the field of this cluster, two stars of known type exist: Wray 15–1039 (emission-line object) and CD −58:4845 (emission-line star). We do not yet know whether the Be phase is transient or whether it is just what randomly happens in some hot stars. It appears that Be star may be found even in clusters as old as 70 Myr with a high occurrence rate in clusters of 25–27 Myr old. A recent photometric survey in NGC 4852 down to V = 22 – 23 mag established that NGC 4852 is about 200 – 250 Myr old, located at 1.1 kpc from the Sun and with a mean E(B − V) = 0.45 mag. Since the presence of potential Be-type stars in the cluster area suggests it may be a very young object instead of moderately old, we decided to carry out spectroscopy for 33 selected stars and CCD UBVI photometry for the bright objects in the cluster area. This way, we attempt to clarify their evolutionary state and include them in the framework of emission-line stars and open clusters. From our analysis, we agree with the cluster distance and reddening determined by earlier studies, but we derive that the age of NGC 4852 is younger than 40 Myr.

Zoospore ultrastructure in the genus Rhizophydium (Chytridiales)

1978 ◽  
Vol 56 (19) ◽  
pp. 2380-2404 ◽  
Author(s):  
D. J. S. Barr ◽  
V. E. Hadland-Hartmann
Keyword(s):  
Membrane System ◽  
Double Membrane ◽  
Lipid Globule ◽  
Lateral Posterior ◽  
Membrane Bound ◽  
Relationship Of ◽  
The Relationship ◽  
Posterior Position ◽  
Compact Cluster ◽  
Peripheral Cytoplasm

The zoospore ultrastructure of 12 species of Rhizophydium is described. Species include the following: R. chlorogonii (Serbinow) Jaczewski; R. constantineani Saccardo; R. haynaldii (Schaarschmidt) Fischer; R. capillaceum Barr; two morphologically and cytologically different species, each previously identified as R. sphaerotheca Zopf; R. patellarium Scholz; R. biporosum (Couch) Barr; R. subangulosum (Braun) Rabenhorst; R. laterale (Braun) Rabenhorst; R. sphaerocarpum (Zopf) Fischer var. spirogyrae Barr; and two isolates of R. pollinis-pini (Braun) Zopf. The Rhizophydium zoospore is basically similar to the Chytridium zoospore having (1) the nucleus, a compact cluster of ribosomes, one or more mitochondria, and a microbody – lipid globule complex compartmentalized into the core of the zoospore by a double membrane system and (2) two to five microtubules connecting one side of the kinetosome to the rumposome on the lipid globule surface and thus anchoring the lipid globule in a lateral–posterior position in the zoospore. Rhizophydium patellarium does not have kinetosome-associated microtubules or a rumposome but does have the membrane-bound core area. In all species, a microbody and mitochondrion are associated with the lipid globule. The number of mitochondria varies from 1 in some species to several or to over 30 in other species. In one isolate of R. pollinis-pini, there is 1 large mitochondrion and in the other there were 30–35 small mitochondria. The peripheral cytoplasm of all species contains clusters of vesicles or endoplasmic reticulum which bud from the double membrane system, vesicles of moderate electron density, and vacuoles of various sizes; R. capillaceum, R. patellarium, and R. subangulosum have in addition vesicles which contain very electron-dense material. Rhizophydium capillaceum and R. sphaerocarpum zoospores have virus-like particles and the R. biporosum zoospore contains a paracrystalline body. The taxonomic significance of the observations and the relationship of Rhizophydium to other chytrids are stressed in the Discussion.

scholarly journals Multiscale Modeling of EEG/MEG Response of a Compact Cluster of Tightly Spaced Pyramidal Neocortical Neurons

2020 ◽  
pp. 195-211
Author(s):  
Sergey N. Makarov ◽  
Jyrki Ahveninen ◽  
Matti Hämäläinen ◽  
Yoshio Okada ◽  
Gregory M. Noetscher ◽  
...  
Keyword(s):  
High Resolution ◽  
Boundary Element ◽  
Multiscale Modeling ◽  
Cluster Size ◽  
Fast Multipole Method ◽  
Head Model ◽  
Current Dipole ◽  
Neocortical Neurons ◽  
Dipole Sources ◽  
Compact Cluster

AbstractIn this study, the boundary element fast multipole method or BEM-FMM is applied to model compact clusters of tightly spaced pyramidal neocortical neurons firing simultaneously and coupled with a high-resolution macroscopic head model. The algorithm is capable of processing a very large number of surface-based unknowns along with a virtually unlimited number of elementary microscopic current dipole sources distributed within the neuronal arbor.The realistic cluster size may be as large as 10,000 individual neurons, while the overall computation times do not exceed several minutes on a standard server. Using this approach, we attempt to establish how well the conventional lumped-dipole model used in electroencephalography/magnetoencephalography (EEG/MEG) analysis approximates a compact cluster of realistic neurons situated either in a gyrus (EEG response dominance) or in a sulcus (MEG response dominance).

scholarly journals An experimental study of the dynamics of ascent of the bubble system in the presence of a surfactant

2018 ◽  
Vol 194 ◽  
pp. 01002
Author(s):  
Alexandra Antonnikova ◽  
Sergey Basalaev ◽  
Anna Usanina ◽  
Eugene Maslov
Keyword(s):  
Experimental Study ◽  
Reynolds Numbers ◽  
Experimental Setup ◽  
Bubble Cluster ◽  
Bubble System ◽  
Wide Range ◽  
Compact Cluster ◽  
Glycerol Medium

This paper presents investigations on the new experimental setup for obtaining a compact cluster of monodisperse bubbles of a given diameter is presented. Also we provided the results of experimental study of the bubble cluster floating-up in the presence of a surfactant in a wide range of Reynolds numbers. There was held a comparison of the dynamics of the floating-up of a monodisperse bubble cluster in a glycerol medium and in the medium glycerin supplemented with a surfactant.

Human type I cytokeratin genes are a compact cluster

1997 ◽  
Vol 77 (3-4) ◽  
pp. 169-174 ◽  
Author(s):  
N. Ceratto ◽  
C. Dobkin ◽  
M. Carter ◽  
E. Jenkins ◽  
X.-L. Yao ◽  
...  
Keyword(s):  
Type I ◽  
Human Type ◽  
Compact Cluster

Pi ZW 1305.4 + 2941 at Z = 0.24 - Another rich, red, compact cluster

1988 ◽  
Vol 333 ◽  
pp. 586 ◽  
Author(s):  
David C. Koo ◽  
Richard G. Kron ◽  
D. Nanni ◽  
A. Vignato ◽  
D. Treverse
Keyword(s):  
Compact Cluster

Inertial effects on clusters of spheres falling in a viscous fluid

1964 ◽  
Vol 20 (3) ◽  
pp. 401-410 ◽  
Author(s):  
F. P. Bretherton
Keyword(s):  
Viscous Fluid ◽  
Viscous Liquid ◽  
Inertial Effects ◽  
Small Perturbations ◽  
Clusters Of Spheres ◽  
Compact Cluster

A compact cluster of 3 to 6 rigid equal spheres is falling under gravity in a viscous liquid. The small effects of intertia on a horizontal regular polygonal configuration are that the polygon expands as it falls and small perturbations from this configuration die out, although when the polygon is large enough it becomes weakly unstable. This is an extension of the analysis of Hocking (1964, which was applied to the experiments of Jayaweera, Mason & Slack (1964).

Development of compact cluster ion sources using metal cluster complexes

2004 ◽  
Vol 231-232 ◽  
pp. 945-948 ◽  
Author(s):  
T. Mizota ◽  
H. Nonaka ◽  
T. Fujimoto ◽  
A. Kurokawa ◽  
S. Ichimura
Keyword(s):  
Metal Cluster ◽  
Ion Sources ◽  
Cluster Complexes ◽  
Cluster Ion ◽  
Compact Cluster

scholarly journals Dynamics of Galactic Nuclei Containing Massive Remnant Stars

1996 ◽  
Vol 174 ◽  
pp. 293-302
Author(s):  
H. M. Lee
Keyword(s):  
Stellar System ◽  
Dynamical Evolution ◽  
Galactic Nuclei ◽  
Low Mass Stars ◽  
Stellar Component ◽  
Long Time ◽  
Low Mass ◽  
Relaxation Time Scale ◽  
Three Body ◽  
Compact Cluster

We have examined the dynamical evolution of stellar system containing massive remnant stellar component. If individual mass of remnant stars is much heavier than that of normal stars which comprise most of the mass in the cluster, remnant stars quickly form a subsystem within the core of cluster of ordinary stars. The subsystem evolves on its own relaxation time scale which is very short. However, the post collapse expansion driven by the three-body binary heating becomes very slow because the expansion energy of the compact subcluster can be easily absorbed by surrounding cluster. The gravitational radiation can lead to the merger of binaries when binaries become very hard. A central seed black hole might form if repeated merger becomes very efficient. Otherwise, relatively stable two-component phase of central compact cluster of remnant stars surrounded by larger cluster of low mass stars would last for a long time.

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