529 research outputs found
Tightening the Penrose Inequality
The Penrose inequality estimates the lower bound of the mass of a black hole
in terms of the area of its horizon. This bound is not very ``tight'' for
extremal or near extremal black holes. We propose a new Penrose-like inequality
for static black holes involving the mass, the area of black hole event horizon
and the temperature. Our inequality includes the Penrose inequality as its
corollary and it is saturated by both the Schwarzschild black hole and
Reissner-Nordstr\"om (RN) black hole. In the spherically-symmetric case, we
prove this new inequality by assuming both the null and trace energy
conditions.Comment: latex, 19 page
Physical origin of color changes in lutetium hydride under pressure
Recently, near-ambient superconductivity was claimed in nitrogen-doped
lutetium hydride (LuHN) . Unfortunately, all
follow-up research still cannot find superconductivity signs in successfully
synthesized lutetium dihydride (LuH) and N-doped LuHN.
However, a similar intriguing observation was the pressure-induced color
changes (from blue to pink and subsequent red). The physical understanding of
its origin and the correlation between the color, crystal structure, and
chemical composition of Lu-H-N is still lacking. In this work, we theoretically
study the optical properties of LuH, LuH, and some potential N-doped
compounds using the first-principles calculations by considering both interband
and intraband contributions. Our results show that LuH has an optical
reflectivity peak around blue light up to 10 GPa. Under higher pressure, the
reflectivity of red light gradually becomes dominant. This evolution is driven
by changes in the direct band gap and the Fermi velocity of free electrons
under pressure. In contrast, LuH exhibits gray and no color change up to 50
GPa. Furthermore, we considered different types of N-doped LuH and LuH.
We find that N-doped LuH with the substitution of a hydrogen atom at the
tetrahedral position maintains the color change when the N-doping concentration
is low. As the doping level increases, this trend becomes less obvious. While
other N-doped structures do not show significant color change. Our results can
clarify the origin of the experimental observed blue-to-red color change in
lutetium hydride and also provide a further understanding of the potential
N-doped lutetium dihydride
Universal bounds on the size of a black hole
For static black holes in Einstein gravity, if matter fields satisfy a few
general conditions, we conjecture that three characteristic parameters about
the spatial size of black holes, namely the outermost photon sphere area
, the corresponding shadow area and the
horizon area satisfy a series of universal inequalities , where is the ADM
mass. We present a complete proof in the spherically symmetric case and some
pieces of evidence to support it in general static cases. We also discuss the
properties of the photon spheres in general static spacetimes and show that,
similar to horizon, photon spheres are also conformal invariant structures of
the spacetimes.Comment: latex, 8 pages, 5 figures, typos and errors corrected, references
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Erratum
'Beibinghong': A new grape cultivar for brewing ice red wineVitis 53 (2), 85-89 (2014
hCLP46 Increases Smad3 Protein Stability Via Inhibiting its Ubiquitin-Proteasomal Degradation
hCLP46 (human CAP10-like protein 46 kDa) was initially isolated and identified from human acute myeloid leukemia transformed from myelodysplastic syndrome (MDS-AML) CD34+ cells (Teng et al., 2006) and we demonstrated previously that hCLP46 is abnormally expressed in many hematopoietic malignancies (Wang et al., 2010). Studies fromits Drosophila homolog, Rumi, suggested that Notch is a potential target of hCLP46 (Acar et al., 2008). We also found that overexpression of hCLP46 enhances Notch activation and regulates cell proliferation in a cell type-dependent manner (Ma et al., 2011; Chu et al., 2013). However, hCLP46−/− embryos show more severe phenotypes compared to those displayed by other global regulators of canonical Notch signaling, suggesting that hCLP46 is likely to have additional important targets during mammalian development (Fernandez- Valdivia et al., 2011). Based on the crosstalk between Notch and the transforming growth factor-β (TGF-β) signaling, we proposed that hCLP46 might be involved in TGF-β signal regulation, but the detail mechanism remains unclear
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