Non-Abelian statistics of vortices with non-Abelian Dirac fermions

We extend our previous analysis on the exchange statistics of vortices having a single Dirac fermion trapped in each core, to the case where vortices trap two Dirac fermions with U(2) symmetry. Such a system of vortices with non-Abelian Dirac fermions appears in color superconductors at extremely high densities, and in supersymmetric QCD. We show that the exchange of two vortices having doublet Dirac fermions in each core is expressed by non-Abelian representations of a braid group, which is explicitly verified in the matrix representation of the exchange operators when the number of vortices is up to four. We find that the result contains the matrices previously obtained for the vortices with a single Dirac fermion in each core as a special case. The whole braid group does not immediately imply non-Abelian statistics of identical particles because it also contains exchanges between vortices with different numbers of Dirac fermions. However, we find that it does contain, as its subgroup, a genuine non-Abelian statistics for the exchange of the identical particles, that is, vortices with the same number of Dirac fermions. This result is surprising compared with conventional understanding because all Dirac fermions are defined locally at each vortex, unlike the case of Majorana fermions for which Dirac fermions are defined non-locally by Majorana fermions located at two spatially separated vortices.Comment: 32 pages, no figures, v3: published versio

Little-Parks oscillations with half-quantum fluxoid features in Sr2RuO4 micro rings

In a micro ring of a superconductor with a spin-triplet equal-spin pairing state, a fluxoid, a combined object of magnetic flux and circulating supercurrent, can penetrate as half-integer multiples of the flux quantum. A candidate material to investigate such half-quantum fluxoids is Sr$_\mathsf{2}$RuO$_\mathsf{4}$. We fabricated Sr$_\mathsf{2}$RuO$_\mathsf{4}$ micro rings using single crystals and measured their resistance behavior under magnetic fields controlled with a three-axes vector magnet. Proper Little-Parks oscillations in the magnetovoltage as a function of an axially applied field, associated with fluxoid quantization are clearly observed, for the first time using bulk single crystalline superconductors. We then performed magnetovoltage measurements with additional in-plane magnetic fields. By carefully analyzing both the voltages $V_+$ ($V_-$) measured at positive (negative) current, we find that, above an in-plane threshold field of about 10 mT, the magnetovoltage maxima convert to minima. We interpret this behavior as the peak splitting expected for the half-quantum fluxoid states.Comment: 16 pages, 15 figure

Deep Adversarial Reinforcement Learning With Noise Compensation by Autoencoder

We present a new adversarial learning method for deep reinforcement learning (DRL). Based on this method, robust internal representation in a deep Q-network (DQN) was introduced by applying adversarial noise to disturb the DQN policy; however, it was compensated for by the autoencoder network. In particular, we proposed the use of a new type of adversarial noise: it encourages the policy to choose the worst action leading to the worst outcome at each state. When the proposed method, called deep Q-W-network regularized with an autoencoder (DQWAE), was applied to seven different games in an Atari 2600, the results were convincing. DQWAE exhibited greater robustness against the random/adversarial noise added to the input and accelerated the learning process more than the baseline DQN. When applied to a realistic automatic driving simulation, the proposed DRL method was found to be effective at rendering the acquired policy robust against random/adversarial noise

Covalently bound flavin in the NqrB and NqrC subunits of Na+-translocating NADH-quinone reductase from Vibrio alginolyticus

AbstractNa+-translocating NADH-quinone reductase (NQR) from the marine bacterium Vibrio alginolyticus is composed of six subunits (NqrA to NqrF). On SDS–PAGE of the purified complex, NqrB and NqrC subunits were found to give yellow–green fluorescent bands under UV illumination. Both the NqrB and NqrC, electroeluted from the gel, had an absorption maximum at 448 nm, and the fluorescence excitation maxima at 365 and 448 nm and the emission maximum at 514 nm. The electroeluted NqrB and NqrC, respectively, were identified from their N-terminal amino acid sequences. These results clearly indicated that the NqrB and NqrC subunits have covalently bound flavins. The two subunits were digested by protease and then the fluorescent peptide fragments were separated by a reversed-phase high performance liquid chromatography. N-Terminal amino acid sequence analyses of the fluorescent peptides revealed that the flavin is linked to Thr-235 in the NqrB and Thr-223 in the NqrC subunits. This is the first example that the flavin is linked to a threonine residue. The amino acid sequence around the flavin-linked threonine was well conserved between NqrB and NqrC. Identification of the flavin group is in progress

甲状腺癌細胞におけるSNAIL誘導上皮間葉移行とALDH陰性分画における癌幹細胞様特性

Background: Epithelial-to-mesenchymal transition (EMT) is thought to play a critical role in the invasion and metastasis of cancer and to be associated with cancer stem cell (CSC) properties. It is not clear if there is a link between EMT and CSCs in thyroid cancers. We therefore investigated the CSC properties of thyroid cancers that underwent EMT. Method: To induce EMT (spindle-like cell morphology, loss and acquisition of expression of an epithelial marker E-cadherin and a mesenchymal marker vimentin respectively) in an epithelial-type thyroid cancer cell line ACT-1, we used transforming growth factor-β (TGF-β), BRAFV600E, and/or Snail homolog 1 (SNAI1, also known as SNAIL). CSC properties were analyzed with assays for cell proliferation, chemosensitivity, in vitro and in vivo tumor formation ability, cell surface antigens, and intracellular aldehyde dehydrogenase (ALDH; a known CSC marker) activities. Results: EMT was induced most efficiently by SNAIL (ACT-SNAIL cells), whereas TGF-β and BRAFV600E were less efficient. ACT-SNAIL cells showed slightly but significantly enhanced tumor formation ability in an in vitro sphere assay (approximately 3-fold) but not an in vivo subcutaneous tumor growth assay, and showed comparable chemosensitivity compared with the parental ACT-1 cells. However, of interest, although the in vitro sphere-formation ability of ALDH+ cells was almost unchanged after SNAIL induction, SNAIL overexpression induced much higher (approximately 14-fold) spheres in ALDH- cells. Thus, ALDH was no longer a CSC marker in ACT-SNAIL cells. Conclusions: All these data indicate that EMT confers CSC properties in ALDH- cells and appears to influence the ability of ALDH to enrich CSCs.長崎大学学位論文 学位記番号:博(医歯薬)甲第714号 学位授与年月日:平成26年9月19日Author: Kazuaki Yasui, Mika Shimamura, Norisato Mitsutake, Yuji NagayamaCitation: Thyroid, 23(8), pp.989-996; 2013Nagasaki University (長崎大学)課程博