1,697 research outputs found
Energetic electron transport in the presence of magnetic perturbations in magnetically confined plasmas
The transport of energetic electrons is sensitive to magnetic perturbations.
By using 3D numerical simulation of test particle drift orbits we show that the
transport of untrapped electrons through an open region with magnetic
perturbations cannot be described by a diffusive process. Based on our test
particle simulations, we propose a model that leads to an exponential loss of
particles.Comment: Accepted for publication in Journal of Plasma Physics (Energetic
Electrons special issue
On the validity of the 5-dimensional Birkhoff theorem: The tale of an exceptional case
The 5-dimensional (5d) Birkhoff theorem gives the class of 5d vacuum
space-times containing spatial hypersurfaces with cosmological symmetries. This
theorem is violated by the 5d vacuum Gergely-Maartens (GM) space-time, which is
not a representant of the above class, but contains the static Einstein brane
as embedded hypersurface. We prove that the 5d Birkhoff theorem is still
satisfied in a weaker sense: the GM space-time is related to the degenerated
horizon metric of certain black-hole space-times of the allowed class. This
result resembles the connection between the Bertotti-Robinson space-time and
the horizon region of the extremal Reissner-Nordstrom space-time in general
relativity.Comment: 13 pages; v2: title amended, to be published in Classical and Quantum
Gravit
SU(3) Anderson impurity model: A numerical renormalization group approach exploiting non-Abelian symmetries
We show how the density-matrix numerical renormalization group (DM-NRG)
method can be used in combination with non-Abelian symmetries such as SU(N),
where the decomposition of the direct product of two irreducible
representations requires the use of a so-called outer multiplicity label. We
apply this scheme to the SU(3) symmetrical Anderson model, for which we analyze
the finite size spectrum, determine local fermionic, spin, superconducting, and
trion spectral functions, and also compute the temperature dependence of the
conductance. Our calculations reveal a rich Fermi liquid structure.Comment: 18 pages, 9 figure
Kerr-Schild metrics revisited I. The ground state
The Kerr-Schild pencil of metrics g_{ab}+\La l_al_b is investigated in the
generic case when it maps an arbitrary vacuum space-time with metric
to a vacuum space-time. The theorem is proved that this generic case, with the
field shearing, does not contain the shear-free subclass as a smooth limit.
It is shown that one of the K\'ota-Perj\'es metrics is a solution in the
shearing class.Comment: 16 page
Staurosporine induces necroptotic cell death under caspase-compromised conditions in U937 cells
For a long time necrosis was thought to be an uncontrolled process but evidences recently have revealed that necrosis can also occur in a regulated manner. Necroptosis, a type of programmed necrosis is defined as a death receptor-initiated process under caspase-compromised conditions. The process requires the kinase activity of receptor-interacting protein kinase 1 and 3 (RIPK1 and RIPK3) and mixed lineage kinase domain-like protein (MLKL), as a substrate of RIPK3. The further downstream events remain elusive. We applied known inhibitors to characterize the contributing enzymes in necroptosis and their effect on cell viability and different cellular functions were detected mainly by flow cytometry. Here we report that staurosporine, the classical inducer of intrinsic apoptotic pathway can induce necroptosis under caspase-compromised conditions in U937 cell line. This process could be hampered at least partially by the RIPK1 inhibitor necrotstin-1 and by the heat shock protein 90 kDa inhibitor geldanamycin. Moreover both the staurosporine-triggered and the classical death ligand-induced necroptotic pathway can be effectively arrested by a lysosomal enzyme inhibitor CA-074-OMe and the recently discovered MLKL inhibitor necrosulfonamide. We also confirmed that the enzymatic role of poly(ADP-ribose)polymerase (PARP) is dispensable in necroptosis but it contributes to membrane disruption in secondary necrosis. In conclusion, we identified a novel way of necroptosis induction that can facilitate our understanding of the molecular mechanisms of necroptosis. Our results shed light on alternative application of staurosporine, as a possible anticancer therapeutic agent. Furthermore, we showed that the CA-074-OMe has a target in the signaling pathway leading to necroptosis. Finally, we could differentiate necroptotic and secondary necrotic processes based on participation of PARP enzyme
Active Galactic Nuclei with Starbursts: Sources for Ultra High Energy Cosmic Rays
Ultra high energy cosmic ray events presently show a spectrum, which we
interpret here as galactic cosmic rays due to a starburst in the radio galaxy
Cen A pushed up in energy by the shock of a relativistic jet. The knee feature
and the particles with energy immediately higher in galactic cosmic rays then
turn into the bulk of ultra high energy cosmic rays. This entails that all
ultra high energy cosmic rays are heavy nuclei. This picture is viable if the
majority of the observed ultra high energy events come from the radio galaxy
Cen A, and are scattered by intergalactic magnetic fields across most of the
sky.Comment: 4 pages, 1 figure, proceedings of "High-Energy Gamma-rays and
Neutrinos from Extra-Galactic Sources", Heidelber
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