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Sökning: WFRF:(Beltran S)

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61.
  • Jimenez, Jose Beltran, et al. (författare)
  • Modified Gravity with Vector Distortion and Cosmological Applications
  • 2017
  • Ingår i: Universe. - : MDPI AG. - 2218-1997. ; 3:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We briefly review the basics of Weyl geometry and its natural extension by a general linear "distortion" of the metric connection by a vector field. A special class of the connections has torsion but retains the Weyl's semi-metricity condition. We present ghost-free gravitational theories in this geometrical setup and highlight their possible cosmological applications, such as new self-tuning solutions and new bouncing solutions found in the quadratic-curvature theories. The vector distortion can mimic the cosmological effects of dark matter.
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62.
  • Jimenez, Jose Beltran, et al. (författare)
  • Spacetimes with vector distortion : Inflation from generalised Weyl geometry
  • 2016
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 756, s. 400-404
  • Tidskriftsartikel (refereegranskat)abstract
    • Spacetime with general linear vector distortion is introduced. Thus, the torsion and the nonmetricity of the affine connection are assumed to be proportional to a vector field (and not its derivatives). The resulting two-parameter family of non-Riemannian geometries generalises the conformal Weyl geometry and some other interesting special cases. Taking into account the leading nonlinear correction to the Einstein-Hilbert action results uniquely in the one-parameter extension of the Starobinsky inflation known as the alpha-attractor. The most general quadratic curvature action introduces, in addition to the canonical vector kinetic term, novel ghost-free vector-tensor interactions.
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63.
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67.
  • Palasz, A.T., et al. (författare)
  • Effects of hyaluronan, BSA, and serum on bovine embryo in vitro development, ultrastructure, and gene expression patterns
  • 2006
  • Ingår i: Molecular Reproduction and Development. - : Wiley-Blackwell. - 1040-452X .- 1098-2795. ; 73:12, s. 1503-1511
  • Tidskriftsartikel (refereegranskat)abstract
    • Effects of hyaluronan (HA), BSA, and FCS on in vitro development, ultrastructure, and mRNA transcription of four developmentally important genes: apoptosis (Bax), oxidative stress (SOX), growth factor (IGF-II), and cell-to-cell adhesion (Ecad) were examined. Two biological origin HA, Hylartil and Hyonate and one produced by fermentation (f-HA) MAP-5 were tested. Embryos were cultured in SOF medium with 0.4% BSA or with 0.4% BSA and 10% FCS. HA was added 96 hr post insemination (pi) to half of the embryos from each culture group. Embryo development was not affected by either HA preparation, however, hatching rates were higher in Hyalartil and MAP-5 than in control and Hyonate (P less than 0.05). There was no effect of HA on number of blastocysts developed in SOF + BSA. However, more blastocysts developed in SOF + BSA + f-HA than in SOF + BSA + FCS or with BSA + FCS + f-HA. HA added to SOF + BSA, increased level of expression of epidermal growth factor (EGF)-II and decreased the levels of expression of BAX, SOX, and Ecad (P less than 0.05). Presence of FCS increased the levels of SOX and decreased the level of IGF-II (P less than 0.05) and the addition of f-HA to SOF containing FCS showed no effect on the level of transcription of any analyzed genes. The fine structure of embryos cultured with f-HA irrespective of protein sources used was clearly improved. In summary, f-HA added 96 hr pi to SOF supplemented with BSA but not FCS improved development, molecular composition and fine structure of bovine embryos.
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69.
  • Pälike, Heiko, et al. (författare)
  • A Cenozoic record of the equatorial Pacific carbonate compensation depth
  • 2012
  • Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 488:7413, s. 609-614
  • Tidskriftsartikel (refereegranskat)abstract
    • Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
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  • Resultat 61-70 av 71
  • Föregående 1...23456[7]8Nästa

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