12,438 research outputs found
Azimuthal asymmetry in cosmic-ray boosted dark matter flux
Light halo dark matter (DM) particles up-scattered by high-energy cosmic rays
(referred to as CRDM) can be energetic and become detectable at conventional DM
and neutrino experiments. We show that the CRDM flux has a novel and detectable
morphological feature. Unlike most of the recently proposed boosted DM (BDM)
models which predict azimuthally symmetric DM fluxes around the Galactic
Center, the CRDM flux breaks the azimuthal symmetry significantly. Using
cosmic-ray electron distribution in the whole Galaxy and optimized search
region in the sky according to the morphology of the CRDM flux, we derive so
far the most stringent constraints on the DM-electron scattering cross section
from the Super-Kamiokande (SK) IV data, which improves the previous constraints
from the SK-IV full-sky data by more than an order of magnitude. Based on the
improved constraints, we predict that the azimuthal symmetry-breaking effect
can be observed in the future Hyper-Kamiokande experiment at
level.Comment: 5 pages, 4 figures + appendix. We comment that the BBN cosntraints on
CR-boostded DM are always model dependent, and cannot be naively applied to
light sub-MeV DM. Version accepted by Phys. Rev.
Entropy dissipative higher order accurate positivity preserving time-implicit discretizations for nonlinear degenerate parabolic equations
We develop entropy dissipative higher order accurate local discontinuous Galerkin (LDG) discretizations coupled with Diagonally Implicit Runge–Kutta (DIRK) methods for nonlinear degenerate parabolic equations with a gradient flow structure. Using the simple alternating numerical flux, we construct DIRK-LDG discretizations that combine the advantages of higher order accuracy, entropy dissipation and proper long-time behavior. We theoretically prove the entropy dissipation of the implicit Euler-LDG discretization without any time-step restrictions when no positivity constraint is imposed. Next, in order to ensure the positivity of the numerical solution, we use the Karush–Kuhn–Tucker (KKT) limiter, which achieves a positive solution by coupling the positivity preserving KKT conditions with higher order accurate DIRK-LDG discretizations using Lagrange multipliers. In addition, mass conservation of the positivity-limited solution is ensured by imposing a mass conservation equality constraint to the KKT equations. Under a time step restriction, the unique solvability and entropy dissipation for implicit first order accurate in time, but higher order accurate in space, positivity-preserving LDG discretizations with periodic boundary conditions are proved, which provide a first theoretical analysis of the KKT limiter. Finally, numerical results demonstrate the higher order accuracy and entropy dissipation of the positivity-preserving DIRK-LDG discretizations for problems requiring a positivity limiter. In addition, we can observe from the numerical results that the implicit time-discrete methods alleviate the time-step restrictions needed for the stability of the numerical discretizations, which improves computational efficiency.</p
Indole-thiophene conjugate inhibits proliferation of human cervical cancer cell lines through DNA damage
Purpose: To investigate the inhibitory effect of indole-thiophene conjugate (ITC) against cervical cancer cells.
Methods: The effect of ITC on the proliferation of cervical cells was determined using 3 (4,5 dimethylthiazol 2 yl) 2,5 diphenyltetrazolium bromide (MTT) assay. The apoptosis-inducing effect of ITC was analysed with flow cytometry, while its effect on cell invasion was assessed using Transwell assay.
Results: ITC inhibited proliferation of HeLa and Caski cancer cell lines, but it had no cytotoxicity against HCvEpC normal epithelial cells. Exposure to ITC at a dose of 12 μmol/L reduced the viability of HeLa and Caski cells to 22.56 and 24.78 %, respectively (p < 0.05). ITC treatment of HeLa cells enhanced the proportion of apoptotic cells. Exposure to ITC at a dose of 12 μmol/L led to near-complete inhibition of the invasive potential of HeLa cells. Moreover, exposure of HeLa cells to ITC downregulated the protein expressions of MMP-2 and MMP-9 (p < 0.05). The expressions of Bcl-2, p-ERK1/2 and p-Akt were markedly decreased in HeLa cells by ITC exposure. In addition, ITC increased Bax expression, and decreased Bcl-2/Bax ratio (p < 0.05).
Conclusion: ICT inhibits the proliferation and invasion of cervical cancer cells, and induces their apoptosis. It exhibits these effects via the suppression of Akt and ERK phosphorylation, thereby downregulating the PI3K and MAPK pathways. Therefore, ITC may be beneficial for the treatment of cervical cancer
Constraining light dark matter upscattered by ultrahigh-energy cosmic rays
Light halo dark matter (DM) particles upscattered by high-energy cosmic rays
(CRs) can be energetic, and become detectable by conventional direct detection
experiments. The current constraints derived from space-based direct CR
measurements can reach for a constant
DM-nucleon scattering cross section. We show that if the CR energy spectrum
follows a power law of type , the derived constraints on the
scattering cross section will be highly insensitive to DM particle mass. This
suggests that ultrahigh-energy CRs (UHECRs) indirectly measured by ground-based
detectors can be used to place constraints on ultralight DM particles, as
is a very good approximation of the UHECR energy spectrum up to energy
. Using the recent UHECR flux data, we show that the
current constraints derived from space-based CR measurements can in principle
be extended to ultralight DM particles far below eV scale.Comment: 25 pages, 6 figures, match the publsied versio
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