2,043 research outputs found
E1-Like Activating Enzyme Atg7 Is Preferentially Sequestered into p62 Aggregates via Its Interaction with LC3-I
p62 is constitutively degraded by autophagy via its interaction with LC3. However, the interaction of p62 with LC3 species in the context of the LC3 lipidation process is not specified. Further, the p62-mediated protein aggregation's effect on autophagy is unclear. We systemically analyzed the interactions of p62 with all known Atg proteins involved in LC3 lipidation. We find that p62 does not interact with LC3 at the stages when it is being processed by Atg4B or when it is complexed or conjugated with Atg3. p62 does interact with LC3-I and LC3-I:Atg7 complex and is preferentially recruited by LC3-II species under autophagic stimulation. Given that Atg4B, Atg3 and LC3-Atg3 are indispensable for LC3-II conversion, our study reveals a protective mechanism for Atg4B, Atg3 and LC3-Atg3 conjugate from being inappropriately sequestered into p62 aggregates. Our findings imply that p62 could potentially impair autophagy by negatively affecting LC3 lipidation and contribute to the development of protein aggregate diseases. © 2013 Gao et al
Vortex structure in spinor F=2 Bose-Einstein condensates
Extended Gross-Pitaevskii equations for the rotating F=2 condensate in a
harmonic trap are solved both numerically and variationally using trial
functions for each component of the wave function. Axially-symmetric vortex
solutions are analyzed and energies of polar and cyclic states are calculated.
The equilibrium transitions between different phases with changing of the
magnetization are studied. We show that at high magnetization the ground state
of the system is determined by interaction in "density" channel, and at low
magnetization spin interactions play a dominant role. Although there are five
hyperfine states, all the particles are always condensed in one, two or three
states. Two novel types of vortex structures are also discussed.Comment: 6 pages, 3 figure
Larkin-Ovchinnikov-Fulde-Ferrell phase in the superconductor (TMTSF)2ClO4: Theory versus experiment
We consider a formation of the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase
in a quasi-one-dimensional (Q1D) conductor in a magnetic field, parallel to its
conducting chains, where we take into account both the paramagnetic
spin-splitting and orbital destructive effects against superconductivity. We
show that, due to a relative weakness of the orbital effects in a Q1D case, the
LOFF phase appears in (TMTSF)ClO superconductor for real values of its
Q1D band parameters. We compare our theoretical calculations with the recent
experimental data by Y. Maeno's group [S. Yonezawa et al., Phys. Rev. Lett.
\textbf{100}, 117002 (2008)] and show that there is a good qualitative and
quantitative agreement between the theory and experimental data.Comment: 4 pages, 1 figur
Effect of Quadratic Zeeman Energy on the Vortex of Spinor Bose-Einstein Condensates
The spinor Bose-Einstein condensate of atomic gases has been experimentally
realized by a number of groups. Further, theoretical proposals of the possible
vortex states have been sugessted. This paper studies the effects of the
quadratic Zeeman energy on the vortex states. This energy was ignored in
previous theoretical studies, although it exists in experimental systems. We
present phase diagrams of various vortex states taking into account the
quadratic Zeeman energy. The vortex states are calculated by the
Gross-Pitaevskii equations. Several new kinds of vortex states are found. It is
also found that the quadratic Zeeman energy affects the direction of total
magnetization and causes a significant change in the phase diagrams.Comment: 6 pages, 5 figures. Published in J. Phys. Soc. Jp
Analytic Representation of The Dirac Equation
In this paper we construct an analytical separation (diagonalization) of the
full (minimal coupling) Dirac equation into particle and antiparticle
components. The diagonalization is analytic in that it is achieved without
transforming the wave functions, as is done by the Foldy-Wouthuysen method, and
reveals the nonlocal time behavior of the particle-antiparticle relationship.
We interpret the zitterbewegung and the result that a velocity measurement (of
a Dirac particle) at any instant in time is, as reflections of the fact that
the Dirac equation makes a spatially extended particle appear as a point in the
present by forcing it to oscillate between the past and future at speed c. From
this we infer that, although the form of the Dirac equation serves to make
space and time appear on an equal footing mathematically, it is clear that they
are still not on an equal footing from a physical point of view. On the other
hand, the Foldy-Wouthuysen transformation, which connects the Dirac and square
root operator, is unitary. Reflection on these results suggests that a more
refined notion (than that of unitary equivalence) may be required for physical
systems
On the feasibility of cooling and trapping metastable alkaline-earth atoms
Metastability and long-range interactions of Mg, Ca, and Sr in the
lowest-energy metastable state are investigated. The calculated
lifetimes are 38 minutes for Mg*, 118 minutes for Ca*, and 17 minutes for Sr*,
supporting feasibility of cooling and trapping experiments. The
quadrupole-quadrupole long-range interactions of two metastable atoms are
evaluated for various molecular symmetries. Hund's case (c) 4_g potential
possesses a large 100-1000 K potential barrier. Therefore magnetic trap losses
can possibly be reduced using cold metastable atoms in a stretched M=2 state.
Calculations were performed in the framework of ab initio relativistic
configuration interaction method coupled with the random-phase approximation.Comment: 8 pages, 2 figures; to appear in PR
Majorana edge modes of superfluid 3He A-phase in a slab
Motivated by a recent experiment on the superfluid 3He A-phase with a chiral
p-wave pairing confined in a thin slab, we propose designing a concrete
experimental setup for observing the Majorana edge modes that appear around the
circumference edge region. We solve the quasi-classical Eilenberger equation,
which is quantitatively reliable, to evaluate several observables. To derive
the property inherent to the Majorana edge state, the full quantum mechanical
Bogoliubov-de Gennes equation is solved in this setting. On the basis of the
results obtained, we perform decisive experiments to check the Majorana nature.Comment: 5 pages, 5 figure
Superexchange in Dilute Magnetic Dielectrics: Application to (Ti,Co)O_2
We extend the model of ferromagnetic superexchange in dilute magnetic
semiconductors to the ferromagnetically ordered highly insulating compounds
(dilute magnetic dielectrics). The intrinsic ferromagnetism without free
carriers is observed in oxygen-deficient films of anatase TiO_2 doped with
transition metal impurities in cation sublattice. We suppose that ferromagnetic
order arises due to superexchange between complexes [oxygen vacancies +
magnetic impurities], which are stabilized by charge transfer from vacancies to
impurities. The Hund rule controls the superexchange via empty vacancy related
levels so that it becomes possible only for the parallel orientation of
impurity magnetic moments. The percolation threshold for magnetic ordering is
determined by the radius of vacancy levels, but the exchange mechanism does not
require free carriers. The crucial role of the non-stoichiometry in formation
of the ferromagnetism makes the Curie temperatures extremely sensitive to the
methods of sample preparation.Comment: 18 pages, 2 figure
Production of the Smallest QED Atom: True Muonium (mu^+ mu^-)
The "true muonium" (mu^+ mu-) and "true tauonium" (tau^+ tau^-) bound states
are not only the heaviest, but also the most compact pure QED systems. The
rapid weak decay of the tau makes the observation of true tauonium difficult.
However, as we show, the production and study of true muonium is possible at
modern electron-positron colliders.Comment: 4 pages, ReVTeX, 4 eps figures; minor wording changes and reordering
of a reference. Version accepted by Phys. Rev. Let
Homogeneous Fermion Superfluid with Unequal Spin Populations
For decades, the conventional view is that an s-wave BCS superfluid can not
support uniform spin polarization due to a gap in the quasiparticle
excitation spectrum. We show that this is an artifact of the dismissal of
quasiparticle interactions in the conventional approach at the
outset. Such interactions can cause triplet fluctuations in the ground state
and hence non-zero spin polarization at "magnetic field" . The
resulting ground state is a pairing state of quasiparticles on the ``BCS
vacuum". For sufficiently large , the spin polarization of at unitarity
has the simple form . Our study is motivated by the recent
experiments at Rice which found evidence of a homogenous superfluid state with
uniform spin polarization.Comment: 4 pages, 3 figure
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