613 research outputs found
High Chern number quantum anomalous Hall phases in graphene ribbons with Haldane orbital coupling
We investigate possible phase transitions among the different quantum
anomalous Hall (QAH) phases in a zigzag graphene ribbon under the influence of
the exchange field. The effective tight-binding Hamiltonian for graphene is
made up of the hopping term, the Kane-Mele and Rashba spin-orbit couplings as
well as the Haldane orbital term. We find that the variation of the exchange
field results in bulk gap-closing phenomena and phase transitions occur in the
graphene system. If the Haldane orbital coupling is absent, the phase
transition between the chiral (anti-chiral) edge state () and
the pseudo-quantum spin Hall state () takes place. Surprisingly, when
the Haldane orbital coupling is taken into account, an intermediate QSH phase
with two additional edge modes appears in between phases and .
This intermediate phase is therefore either the hyper-chiral edge state of high
Chern number or anti-hyper-chiral edge state of when the
direction of exchange field is reversed. We present the band structures, edge
state wave functions and current distributions of the different QAH phases in
the system. We also report the critical exchange field values for the QAH phase
transitions.Comment: 4 figure
Influence of unsymmetrical periodicity on extraordinary transmission through periodic arrays of subwavelength holes
Quadrate hole array is explored to study the influence of unsymmetrical
periodicity on extraordinary optical transmission through periodic arrays of
subwavelength holes. It is found that the transmission efficiency of light and
the ratio between transmission efficiencies of horizontal and vertical
polarized light can be continuously tuned by rotating the quadrate hole array.
We can calculate out the transmission spectra (including the heights and
locations of peaks) for any rotation angle with a simple theoretical
model.Comment: 6 pages, 5 figure
Inhibition of class II histone deacetylases in the spinal cord attenuates inflammatory hyperalgesia
<p>Abstract</p> <p>Background</p> <p>Several classes of histone deacetylases (HDACs) are expressed in the spinal cord that is a critical structure of the nociceptive pathway. HDAC-regulated histone acetylation is an important component of chromatin remodeling leading to epigenetic regulation of gene transcription. To understand the role of histone acetylation in epigenetic regulation of pathological pain, we have studied the impact of different classes of HDACs in the spinal cord on inflammatory hyperalgesia induced by complete Freund's adjuvant (CFA).</p> <p>Results</p> <p>We intrathecally applied inhibitors specific to different classes of HDACs and evaluated their impact on inflammatory hyperalgesia. Pre-injected inhibitors targeting class I as well as II (SAHA, TSA, LAQ824) or IIa (VPA, 4-PB) HDACs significantly delayed the thermal hyperalgesia induced by unilateral CFA injection in the hindpaw. Existing hyperalgesia induced by CFA was also attenuated by the HDAC inhibitors (HDACIs). In contrast, these inhibitors did not interfere with the thermal response either in naïve animals, or on the contralateral side of inflamed animals. Interestingly, MS-275 that specifically inhibits class I HDACs failed to alter the hyperalgesia although it increased histone 3 acetylation in the spinal cord as SAHA did. Using immunoblot analysis, we further found that the levels of class IIa HDAC members (HDAC4, 5, 7, 9) in the spinal dorsal horn were upregulated following CFA injection while those of class I HDAC members (HDAC1, 2, 3) remained stable or were slightly reduced.</p> <p>Conclusions</p> <p>Our data suggest that activity of class II HDACs in the spinal cord is critical to the induction and maintenance of inflammatory hyperalgesia induced by CFA, while activity of class I HDACs may be unnecessary. Comparison of the effects of HDACIs specific to class II and IIa as well as the expression pattern of different HDACs in the spinal cord in response to CFA suggests that the members of class IIa HDACs may be potential targets for attenuating persistent inflammatory pain.</p
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