Accreting matter around clusters of galaxies: One-dimensional considerations

During the formation of large-scale structure in the Universe, matter accretes on to high-density peaks. Accreting collisionless dark matter (DM) forms caustics around them, while accreting collisional baryonic matter (BM) forms accretion shocks. The properties of the accreting matter depend upon the power spectrum of the initial perturbations on a given scale as well as the background expansion in a given cosmological model. In this paper, we have calculated the accretion of DM particles in one-dimensional spherical geometry under various cosmological models including the Einstein-de Sitter universe, the open universe with Omega(0) < 1, and the flat universe with Omega(A) = 1 - Omega(0). A density parameter in the range 0.1 less than or equal to Omega(0) less than or equal to 1 has been considered. The initial perturbation characterized by a point mass at the origin has been considered. Since the accretion shock of BM is expected to form close to the first caustic of DM, the properties of the accreting BM are common with those of the DM. Hence, the accretion calculations with DM particles have been used to find the position and velocity of the accretion shock and the cluster mass inside it. The average temperature of BM has been estimated by adopting simplifying assumptions. The velocity of the accreting BM around clusters of a given temperature is lower in a universe with lower Omega(0), but only by up to similar to 24 per cent in the models with 0.1 less than or equal to Omega(0) less than or equal to 1. Thus, it would be difficult to use that quantity to discriminate among the cosmological models. However, the accretion velocity around clusters of a given mass or a given radius depends more sensitively on the cosmological models. It is lower in a universe with lower Omega(0) by up to similar to 41 and similar to 65 per cent, respectively. So, it can provide a better signature of the background expansion for different cosmological models. Although the existence of the caustics and the accretion shocks may not be confirmed by direct X-ray observations, the infalling warm gas of 10(4)-10(5) K upstream of the shocks may be observed as the absorption systems of quasar emission lines. According to this study, the suggestion made by Kang, Ryu & Jones that the large-scale accretion shocks around clusters of galaxies can serve as possible acceleration sites of ultrahigh-energy cosmic rays above 10(18) eV remains plausible in all viable cosmological modelsopen131

Cosmic magnetic fields in large scale filaments and sheets

We consider the possibility that cosmic magnetic field, instead of being uniformly distributed, is strongly correlated with the large scale structure of the universe. Then, the observed rotational measure of extra-galactic radio sources would be caused mostly by the clumpy magnetic field in cosmological filaments/sheets rather than by a uniform magnetic field, which was often assumed in previous studies. As a model for the inhomogeneity of the cosmological magnetic field, we adopt a cosmological hydrodynamic simulation, where the field is passively included, and can approximately represent the real field distribution with an arbitrary normalization for the field strength. Then, we derive an upper limit of the magnetic field strength by comparing the observed limit of rotational measure with the rotational measure expected from the magnetic field geometry in the simulated model universe. The resulting upper limit to the magnetic field in filaments and sheets is (B) over bar(fs) less than or similar to 1 mu G which is similar to 10(3) times higher than the previously quoted values. This value is close to, but larger than, the equipartition magnetic field strength in filaments and sheets. The amplification mechanism of the magnetic field to the above strength is uncertain. The implications of such a strength of the cosmic magnetic field are discussedopen15012

First report of Perkinsus honshuensis in the variegated carpet shell clam Ruditapes variegatus in Korea

The recent discovery of Perkinsus honshuensis, a new Perkinsus species infecting Manila clams Ruditapes philippinarum (Sowerby, 1852), in Japan, suggested that, based on proximity, P. honshuensis could also be in Korean waters, where to date, P. olseni was believed to be the only Perkinsus species present. Perkinsus sp. infections consistently occurred among Ruditapes variegatus clams on a pebble beach on Jeju Island, off the south coast of Korea. The typical \u27signet ring\u27 morphology of the parasite was observed in the connective tissue of the digestive gland, and infection intensity was comparatively low (3.3 x 10(3) +/- 1.2 x 10(4) to 1.3 x 10(4) +/- 6.1 x 10(4) cells g(-1) gill weight). Further DNA analyses of internal transcribed spacer (ITS-1, 5.8S and ITS-2) and non-transcribed spacer (NTS) regions of the parasite showed 98.9-99.8 and 98.5-99.5% similarity to those of P. honshuensis from Japan, respectively. Phylogenetic analyses using ITS and NTS sequences indicated that Perkinsus sp. from Jeju formed a highly supported clade with P. honshuensis. This is the first report of P. honshuensis infections in clams in Korean waters and the first report of R. variegatus as a host for that parasite

Effect of liquid spreading due to nano/microstructures on the critical heat flux during pool boiling

It is well known that nanoparticles deposited on a heating surface during nanofluid boiling can change the characteristics of the heating surface and increase the critical heat flux (CHF) dramatically. We considered a new approach to investigate the nanoparticle surface effect on CHF enhancement using surfaces modified with artificial micro/nanostructures similar to deposited nanoparticle structures. We examined the effect of the surface wettability and liquid spreading ability on the CHF. The results demonstrated that the CHF enhancement on the modified surfaces was a consequence of both the improved surface wettability and the liquid spreading ability of the artificial micro/nanostructures. © 2011 American Institute of Physics.open11102116Nsciescopu

Multiscale architectured materials with composition and grain size gradients manufactured using high-pressure torsion

The concept of multiscale architectured materials is established using composition and grain size gradients. Composition-gradient nanostructured materials are produced from coarse grained interstitial free steels via carburization and high-pressure torsion. Quantitative analyses of the dislocation density using X-ray diffraction and microstructural studies clearly demonstrate the gradients of the dislocation density and grain size. The mechanical properties of the gradient materials are compared with homogeneous nanostructured carbon steel without a composition gradient in an effort to investigate the gradient effect. Based on the above observations, the potential of multiscale architecturing to open a new material property is discussed.111010Ysciescopu

Comparison of Stemness and Gene Expression between Gingiva and Dental Follicles in Children

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Variation of structural, electrical, and optical properties of Zn <inf>1-x</inf>Mg <inf>x</inf>O thin films

Zn 1-xMg xO thin films on (001) sapphire substrates were deposited using pulsed laser deposition. As the substrate temperature increased, the Mg content in the Zn 1-xMg xO thin films increased and the photoluminescence (PL) peak position of the Zn 1-xMg xO thin films shifted from 370 to 356 nm, indicating a band gap expansion. Variations of the structural, electrical, and optical properties of Zn 1-xMgO thin films have been observed and analyzed by x-ray diffraction, Hall measurements, and PL measurements. © 2006 American Institute of Physics

Physiological Functions of the COPI Complex in Higher Plants

COPI vesicles are essential to the retrograde transport of proteins in the early secretory pathway. The COPI coatomer complex consists of seven subunits, termed alpha-, beta-, beta&apos;-, gamma-, delta-, epsilon-, and zeta-COP, in yeast and mammals. Plant genomes have homologs of these subunits, but the essentiality of their cellular functions has hampered the functional characterization of the subunit genes in plants. Here we have employed virus-induced gene silencing (VIGS) and dexamethasone (DEX)-inducible RNAI of the COPI subunit genes to study the in vivo functions of the COPI coatomer complex in plants. The beta&apos;-, gamma-, and delta-COP subunits localized to the Golgi as GFP-fusion proteins and interacted with each other in the Golgi. Silencing of beta&apos;-, gamma-, and delta-COP by VIGS resulted in growth arrest and acute plant death in Nicotiana benthamiana, with the affected leaf cells exhibiting morphological markers of programmed cell death. Depletion of the COPI subunits resulted in disruption of the Golgi structure and accumulation of autolysosome-like structures in earlier stages of gene silencing. In tobacco BY-2 cells, DEX-inducible RNAi of beta&apos;-COP caused aberrant cell plate formation during cytokinesis. Collectively, these results suggest that COPI vesicles are essential to plant growth and survival by maintaining the Golgi apparatus and modulating cell plate formation.1196Ysciescopu

Separation of a benzene and nitric oxide mixture by a molecule prism

A study was performed on the separation of nitric oxide and benzene mixture by a molecule prism. The energy conservation and wave properties of molecules were used to obtain the molecule-optical index of refraction for a nonresonant infrared laser pulse. A chromatographic resolution of 0.62 for the spatial separation of a mixture was obtained using the focused Nd:YAG laser pulse as a molecule prism.open273

Genetic Comparison of Stemness of Human Umbilical Cord and Dental Pulp

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