881 research outputs found

    Novel Magnetic and Thermodynamic Properties of Thiospinel Compound CuCrZrS4_{4}

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    We have carried out dc magnetic susceptibility, magnetization and specific heat measurements on thiospinel CuCrZrS4_{4}. Below TC∗=T_{\rm C}^{*} = 58 K, dc magnetic susceptibility and magnetization data show ferromagnetic behavior with a small spontaneous magnetization 0.27 μB/\mu_{\rm B}/f. u.. In dc magnetic susceptibility, large and weak irreversibilities are observed below Tf=T_{\rm f} = 6 K and in the range Tf<T<TC∗T_{\rm f}< T < T_{\rm C}^{*} respectively. We found that there is no anomaly as a peak or step in the specific heat at TC∗T_{\rm C}^{*}.Comment: 11 pages, 4 figure

    Lyman Alpha Emitters in the Hierarchically Clustering Galaxy Formation

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    We present a new theoretical model for the luminosity functions (LFs) of Lyman alpha (Lya) emitting galaxies in the framework of hierarchical galaxy formation. We extend a semi-analytic model of galaxy formation that reproduces a number of observations for local and high-z galaxies, without changing the original model parameters but introducing a physically-motivated modelling to describe the escape fraction of Lya photons from host galaxies (f_esc). Though a previous study using a hierarchical clustering model simply assumed a constant and universal value of f_esc, we incorporate two new effects on f_esc: extinction by interstellar dust and galaxy-scale outflow induced as a star formation feedback. It is found that the new model nicely reproduces all the observed Lya LFs of the Lya emitters (LAEs) at different redshifts in z ~ 3-6. Especially, the rather surprisingly small evolution of the observed LAE Lya LFs compared with the dark halo mass function is naturally reproduced. Our model predicts that galaxies with strong outflows and f_esc ~ 1 are dominant in the observed LFs. This is also consistent with available observations, while the simple universal f_esc model requires f_esc << 1 not to overproduce the brightest LAEs. On the other hand, we found that our model significantly overpredicts LAEs at z > 6, and absorption of Lya photons by neutral hydrogen in intergalactic medium (IGM) is a reasonable interpretation for the discrepancy. This indicates that the IGM neutral fraction x_HI rapidly evolves from x_HI << 1 at z < 6 to a value of order unity at z ~ 6-7, which is broadly consistent with other observational constraints on the reionization history.Comment: 14 pages, 7 figures, 1 table; accepted to ApJ; the html abstract is replaced to match the accepted version, the .ps and .pdf files are strictly identical between the 2nd and the 3rd version

    Heparin inhibits endothelin-1 production in cultured rat mesangial cells

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    Heparin inhibits endothelin-1 production in cultured rat mesangial cells. The present study was designed to examine whether heparin inhibits basal or stimulated endothelin-1 production by arginine vasopressin (AVP) and platelet-derived growth factor (PDGF) in cultured rat mesangial cells. In addition, the reversibility of the heparin effect on mesangial cell endothelin-1 production was examined. AVP and PDGF stimulated endothelin-1 secretion in a concentration-dependent manner in these cells. Heparin (10 to 100 U/ml) exhibited concentration-related inhibition of AVP- and PDGF-stimulated endothelin-1 secretion. Heparin also had weak but significant inhibitory effects on basal endothelin-1 secretion in these cells. The protein kinase (PKC)-activating phorbor ester, phorbor myristate acetate (PMA), stimulated endothelin-1 secretion and heparin inhibited PMA-stimulated endothelin-1 secretion. In addition, the inhibitory effect of heparin was completely abolished in PKC-depleted mesangial cells. Mesangial cells which were exposed to a high concentration (100 U/ml) of heparin for 24 hours were capable of producing endothelin-1 after a short lag period of removal of heparin from the culture medium. These mesangial cells also showed recovery of responses to AVP and PDGF by secreting a significantly greater amount of endothelin-1 than the non-stimulated level. These results indicate that heparin potently inhibits mesangial cell endothelin-1 production, especially when stimulated by AVP or PDGF. This inhibitory effect of heparin is probably PKC dependent, and reversible
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