Large effects of tiny structural changes on the cluster formation process in model colloidal fluids: an integral equation study

AbstractWe studied the formation process of star clusters using high-resolutionN-body/smoothed particle hydrodynamics simulations of colliding galaxies. The total number of particles is 1.2×108for our high resolution run. The gravitational softening is 5 pc and we allow gas to cool down to ~10 K. During the first encounter of the collision, a giant filament consists of cold and dense gas found between the progenitors by shock compression. A vigorous starburst took place in the filament, resulting in the formation of star clusters. The mass of these star clusters ranges from 105−8M⊙. These star clusters formed hierarchically: at first small star clusters formed, and then they merged via gravity, resulting in larger star clusters.

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Influence of the Para-Substituent in Lanthanoid Complexes of Bistetrazole Substituted Calix[4]arenes

10.26434/chemrxiv.9255209 ◽

2019 ◽

Author(s):

Rene Z.H. Phe ◽

Brian Skelton ◽

Massimiliano Massi ◽

Mark Ogden

Keyword(s):

Structural Changes ◽

Cluster Formation ◽

Ammonium Cation ◽

Ammonium Salts ◽

X Ray Diffraction ◽

One Dimensional ◽

X Ray ◽

Mononuclear Complexes ◽

Scattering Measurements ◽

The Impact

5,11,17,23-Tetra-tert-butyl-25,27-dihydroxy-26,28-bis(tetrazole-5-ylmethoxy)calix[4]arene has been reported to form remarkable Ln19 and Ln12 elongated clusters, upon addition of aqueous ammonium carboxylates. The impact of the para substituent on lanthanoid cluster formation has been studied by synthesising two new bis-tetrazole calixarenes, with p-H, and p-allyl substituents. Solution phase dynamic light scattering measurements of the reaction mixtures indicated that clusters are not formed with the p-H and p-allyl derivatives, in contrast with the behaviour of the t-butyl analogue. Lanthanoid complexes of the p-H and p-allyl calixarenes were characterised by single crystal X-ray diffraction, and were found to form mononuclear complexes, linked to form a one-dimensional coordination polymer for the p-allyl system. All of the complexes were isolated as ammonium salts, with ammonium cation included in the calixarene cavity in most cases. It is concluded that the nature of the para substituent has a profound impact on the lanthanoid cluster formation process, and derivatives with more subtle structural changes will be required to determine if additional lanthanoid “bottlebrush” clusters can be isolated.

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CS Lines and Dust Continuum Observations of the OMC2 Infrared Cluster

International Astronomical Union Colloquium ◽

10.1017/s025292110001962x ◽

1994 ◽

Vol 140 ◽

pp. 245-246

Author(s):

T. Umemoto ◽

N. Ohashi ◽

Y. Murata ◽

K. Tatematsu ◽

M. Suzuki

Keyword(s):

Formation Process ◽

Molecular Clouds ◽

Large Scale ◽

Near Infrared ◽

Infrared Imaging ◽

Cluster Formation ◽

Young Stars ◽

Ir Sources ◽

Near Ir ◽

Molecular Core

It is known that stars in GMCs are often born as clusters. Recently, near infrared imaging has enabled us to study the young stars within molecular clouds (e.g., Lada & Lada 1991). Orion Molecular Cloud 2 (OMC2) is located 12' north of the Trapezium cluster in the Orion A cloud, and contains a cluster of about 20 near-IR sources and several FIR sources distributed within a diameter of 0.2 pc (Rayner et al... 1989; Johnson et al. 1990; Mezger, Wink, & Zylka 1990). By large scale mapping observations using the NRO 45 m telescope, this infrared cluster is found to be associated with a dense molecular core (Tatematsu et al. 1993, Umemoto et al. 1993). The region was observed using the Nobeyama Millimeter Array (NMA) to elucidate the structure and cluster formation process within a core.

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Direct observation of oxygen-vacancy formation and structural changes in Bi2WO6 nanoflakes induced by electron irradiation

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.10.141 ◽

2019 ◽

Vol 10 ◽

pp. 1434-1442 ◽

Cited By ~ 1

Author(s):

Hong-long Shi ◽

Bin Zou ◽

Zi-an Li ◽

Min-ting Luo ◽

Wen-zhong Wang

Keyword(s):

Electron Irradiation ◽

Oxygen Vacancies ◽

Structural Changes ◽

Cluster Formation ◽

Energetic Electron ◽

Structural Evolution ◽

Formation Mechanisms ◽

Tungsten Oxides ◽

Transmission Electron ◽

Oxygen Vacancy Formation

The prominent role of oxygen vacancies in the photocatalytic performance of bismuth tungsten oxides is well recognized, while the underlying formation mechanisms remain poorly understood. Here, we use the transmission electron microscopy to investigate the formation of oxygen vacancies and the structural evolution of Bi2WO6 under in situ electron irradiation. Our experimental results reveal that under 200 keV electron irradiation, the breaking of relatively weak Bi–O bonds leads to the formation of oxygen vacancies in Bi2WO6. With prolonged electron irradiation, the reduced Bi cations tend to form Bi clusters on the nanoflake surfaces, and the oxygen atoms are released from the nanoflakes, while the W–O networks reconstruct to form WO3. A possible mechanism that accounts for the observed processes of Bi cluster formation and oxygen release under energetic electron irradiation is also discussed.

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Formation Process and Structural Changes of Iron rust

Zairyo-to-Kankyo ◽

10.3323/jcorr.57.66 ◽

2008 ◽

Vol 57 (2) ◽

pp. 66-69 ◽

Cited By ~ 3

Author(s):

Shigeru Suzuki

Keyword(s):

Formation Process ◽

Structural Changes

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Agonist-evoked inositol trisphosphate receptor (IP3R) clustering is not dependent on changes in the structure of the endoplasmic reticulum

Biochemical Journal ◽

10.1042/bj20051130 ◽

2006 ◽

Vol 394 (1) ◽

pp. 57-66 ◽

Cited By ~ 32

Author(s):

Mark Chalmers ◽

Michael J. Schell ◽

Peter Thorn

Keyword(s):

Endoplasmic Reticulum ◽

Protein Interactions ◽

Cell Activation ◽

Structural Changes ◽

Fluorescent Protein ◽

Cluster Formation ◽

Yellow Fluorescent Protein ◽

Resting Cells ◽

Trisphosphate Receptor ◽

Er Membrane

The size and number of IP3R (inositol 1,4,5-trisphosphate receptor) clusters located on the surface of the ER (endoplasmic reticulum) is hypothesized to regulate the propagation of Ca2+ waves in cells, but the mechanisms by which the receptors cluster are not understood. Using immunocytochemistry, live-cell imaging and heterologous expression of ER membrane proteins we have investigated IP3R clustering in the basophilic cell line RBL-2H3 following the activation of native cell-surface antigen receptors. IP3R clusters are present in resting cells, and upon receptor stimulation, form larger aggregates. Cluster formation and maintenance required the presence of extracellular Ca2+ in both resting and stimulated cells. Using transfection with a marker of the ER, we found that the ER itself also showed structural changes, leading to an increased number of ‘hotspots’, following antigen stimulation. Surprisingly, however, when we compared the ER hotspots and IP3R clusters, we found them to be distinct. Imaging of YFP (yellow fluorescent protein)–IP3R transfected in to living cells confirmed that IP3R clustering increased upon stimulation. Photobleaching experiments showed that the IP3R occupied a single contiguous ER compartment both before and after stimulation, suggesting a dynamic exchange of IP3R molecules between the clusters and the surrounding ER membrane. It also showed a decrease in the mobile fraction after cell activation, consistent with receptor anchoring within clusters. We conclude that IP3R clustering in RBL-2H3 cells is not simply a reflection of bulk-changes in ER structure, but rather is due to the receptor undergoing homotypic or heterotypic protein–protein interactions in response to agonist stimulation.

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