1,869 research outputs found
Differing alterations of sodium currents in small dorsal root ganglion neurons after ganglion compression and peripheral nerve injury
Voltage-gated sodium channels play important roles in modulating dorsal root ganglion (DRG) neuron hyperexcitability and hyperalgesia after peripheral nerve injury or inflammation. We report that chronic compression of DRG (CCD) produces profound effect on tetrodotoxin-resistant (TTX-R) and tetrodotoxin-sensitive (TTX-S) sodium currents, which are different from that by chronic constriction injury (CCI) of the sciatic nerve in small DRG neurons. Whole cell patch-clamp recordings were obtained in vitro from L4 and/or L5 dissociated, small DRG neurons following in vivo DRG compression or nerve injury. The small DRG neurons were classified into slow and fast subtype neurons based on expression of the slow-inactivating TTX-R and fast-inactivating TTX-S Na+ currents. CCD treatment significantly reduced TTX-R and TTX-S current densities in the slow and fast neurons, but CCI selectively reduced the TTX-R and TTX-S current densities in the slow neurons. Changes in half-maximal potential (V1/2) and curve slope (k) of steady-state inactivation of Na+ currents were different in the slow and fast neurons after CCD and CCI treatment. The window current of TTX-R and TTX-S currents in fast neurons were enlarged by CCD and CCI, while only that of TTX-S currents in slow neurons was increased by CCI. The decay rate of TTX-S and both TTX-R and TTX-S currents in fast neurons were reduced by CCD and CCI, respectively. These findings provide a possible sodium channel mechanism underlying CCD-induced DRG neuron hyperexcitability and hyperalgesia and demonstrate a differential effect in the Na+ currents of small DRG neurons after somata compression and peripheral nerve injury. This study also points to a complexity of hyperexcitability mechanisms contributing to CCD and CCI hyperexcitability in small DRG neurons
Are gravitational wave ringdown echoes always equal-interval ?
Gravitational wave (GW) ringdown waveforms may contain "echoes" that encode
new physics in the strong gravity regime. It is commonly assumed that the new
physics gives rise to the GW echoes whose intervals are constant. We point out
that this assumption is not always applicable. In particular, if the
post-merger object is initially a wormhole, which slowly pinches off and
eventually collapses into a black hole, the late-time ringdown waveform exhibit
a series of echoes whose intervals are increasing with time. We also assess how
this affects the ability of Advanced LIGO/Virgo to detect these new signals.Comment: 10 pages,5 figure
Symmetric non-Hermitian skin effect with emergent nonlocal correspondence
The non-Hermitian skin effect (NHSE) refers to that an extensive number of
eigenstates of a non-Hermitian system are localized in open boundaries. Here we
predict a universal phenomenon that with local particle-hole(-like) symmetry
(PHS) the skin modes must be equally distributed on different boundaries,
manifesting a novel nonlocalization of the local PHS, which is unique to
non-Hermitian systems. We develop a generic theory for the emergent nonlocal
symmetry-protected NHSE by connecting the non-Hermitian system to an extended
Hermitian Hamiltonian in a quadruplicate Hilbert space, which maps the skin
modes to the topological zero modes and the PHS to an emergent nonlocal
symmetry in the perspective of many body physics. The predicted NHSE is robust
against perturbations. We propose optical Raman lattice models to observe the
predicted phenomena in all physical dimensions, which are accessible with
cold-atom experiments.Comment: 5+9 pages, 3+4 figure
An evolutionary algorithm with double-level archives for multiobjective optimization
Existing multiobjective evolutionary algorithms (MOEAs) tackle a multiobjective problem either as a whole or as several decomposed single-objective sub-problems. Though the problem decomposition approach generally converges faster through optimizing all the sub-problems simultaneously, there are two issues not fully addressed, i.e., distribution of solutions often depends on a priori problem decomposition, and the lack of population diversity among sub-problems. In this paper, a MOEA with double-level archives is developed. The algorithm takes advantages of both the multiobjective-problemlevel and the sub-problem-level approaches by introducing two types of archives, i.e., the global archive and the sub-archive. In each generation, self-reproduction with the global archive and cross-reproduction between the global archive and sub-archives both breed new individuals. The global archive and sub-archives communicate through cross-reproduction, and are updated using the reproduced individuals. Such a framework thus retains fast convergence, and at the same time handles solution distribution along Pareto front (PF) with scalability. To test the performance of the proposed algorithm, experiments are conducted on both the widely used benchmarks and a set of truly disconnected problems. The results verify that, compared with state-of-the-art MOEAs, the proposed algorithm offers competitive advantages in distance to the PF, solution coverage, and search speed
Origin of giant valley splitting in silicon quantum wells induced by superlattice barriers
Enhancing valley splitting in SiGe heterostructures is a crucial task for
developing silicon spin qubits. Complex SiGe heterostructures, sharing a common
feature of four-monolayer (4ML) Ge layer next to the silicon quantum well (QW),
have been computationally designed to have giant valley splitting approaching 9
meV. However, none of them has been fabricated may due to their complexity.
Here, we remarkably simplify the original designed complex SiGe
heterostructures by laying out the Si QW directly on the Ge substrate followed
by capping a (Ge4Si4)n superlattice(SL) barrier with a small sacrifice on VS as
it is reduced from a maximum of 8.7 meV to 5.2 meV. Even the smallest number of
periods (n = 1) will also give a sizable VS of 1.6 meV, which is large enough
for developing stable spin qubits. We also develop an effective Hamiltonian
model to reveal the underlying microscopic physics of enhanced valley splitting
by (Ge4Si4)n SL barriers. We find that the presence of the SL barrier will
reduce the VS instead of enhancing it. Only the (Ge4Si4)n SL barriers with an
extremely strong coupling with Si QW valley states provide a remarkable
enhancement in VS. These findings lay a solid theoretical foundation for the
realization of sufficiently large VS for Si qubits
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