Nodal Spin Density Wave and band topology of the FeAs based materials

The recently discovered FeAs-based materials exhibit a $(\pi,0)$ Spin Density Wave (SDW) in the undoped state, which gives way to superconductivity upon doping. Here we show that due to an interesting topological feature of the band structure, the SDW state cannot acquire a full gap. This is demonstrated within the SDW mean-field theory of both a simplified two band model and a more realistic 5-band model. The positions of the nodes are different in the two models and can be used to detected the validity of each model.Comment: rewritten for clarit

Nearly flat band with Chern number C=2 on the dice lattice

We point out the possibility of nearly flat band with Chern number C=2 on the dice lattice in a simple nearest-neighbor tightbinding model. This lattice can be naturally formed by three adjacent $(111)$ layers of cubic lattice, which may be realized in certain thin films or artificial heterostructures, such as SrTiO$_3$/SrIrO$_3$/SrTiO$_3$ trilayer heterostructure grown along $(111)$ direction. The flatness of two bands is protected by the bipartite nature of the lattice. Including the Rashba spin-orbit coupling on nearest-neighbor bonds separate the flat bands with others but maintains their flatness. Repulsive interaction will drive spontaneous ferromagnetism on the Kramer pair of flat bands and split them into two nearly flat bands with Chern number $C=\pm 2$. We thus propose that this may be a route to quantum anomalous Hall effect and further conjecture that partial filling of the C=2 band may realize exotic fractional quantum Hall effects.Comment: updated references, 5 pages, 4 figures, RevTex

A Numerical Renormalization Group Study of the Superconducting and Spin Density Wave Instabilities in MFeAsO1−x_{1-x}Fx_x Compounds

We apply the fermion renormalization group method, implemented numerically by Honerkamp et.al., to a two-band model of FeAs-based materials. At half filling we find the $(\pi,0)$ or $(0,\pi)$ spin density wave order and a sub-dominant superconducting pairing tendency. Due to a topological reason, the spin density wave gap has nodes on the fermi surfaces. Away from half filling we find an unconventional s-wave and a sub-dominant $d_{x^2-y^2}$ pairing instability. The former has $s$ symmetry around the hole fermi surface but exhibits $s+d_{x^2-y^2}$ symmetry around the electron pockets where the 90 degree rotation is broken. The pairing mechanism is inter-pocket pair hopping. Interestingly, the same interaction also drives the antiferromagnetism.Comment: 5 pages, 4 figures, RevTex4. Since the two-band model is insufficient to describe the iron pnictides, this paper will not be submitted for publication. Please see arXiv: 0807.0498 for improved work for five-band mode

The mPEG-PCL Copolymer for Selective Fermentation of Staphylococcus lugdunensis Against Candida parapsilosis in the Human Microbiome.

Many human skin diseases, such as seborrheic dermatitis, potentially occur due to the over-growth of fungi. It remains a challenge to develop fungicides with a lower risk of generating resistant fungi and non-specifically killing commensal microbes. Our probiotic approaches using a selective fermentation initiator of skin commensal bacteria, fermentation metabolites or their derivatives provide novel therapeutics to rein in the over-growth of fungi. Staphylococcus lugdunensis (S. lugdunensis) bacteria and Candida parapsilosis (C. parapsilosis) fungi coexist in the scalp microbiome. S. lugdunensis interfered with the growth of C. parapsilosis via fermentation. A methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-PCL) copolymer functioned as a selective fermentation initiator of S. lugdunensis, selectively triggering the S. lugdunensis fermentation to produce acetic and isovaleric acids. The acetic acid and its pro-drug diethyleneglycol diacetate (Ac-DEG-Ac) effectively suppressed the growth of C. parapsilosis in vitro and impeded the fungal expansion in the human dandruff. We demonstrate for the first time that S. lugdunensis is a skin probiotic bacterium that can exploit mPEG-PCL to yield fungicidal short-chain fatty acids (SCFAs). The concept of bacterial fermentation as a part of skin immunity to re-balance the dysbiotic microbiome warrants a novel avenue for studying the probiotic function of the skin microbiome in promoting health

HCCS1-armed, quadruple-regulated oncolytic adenovirus specific for liver cancer as a cancer targeting gene-viro-therapy strategy

<p>Abstract</p> <p>Background</p> <p>In previously published studies, oncolytic adenovirus-mediated gene therapy has produced good results in targeting cancer cells. However, safety and efficacy, the two most important aspects in cancer therapy, remain serious challenges. The specific expression or deletion of replication related genes in an adenovirus has been frequently utilized to regulate the cancer cell specificity of a virus. Accordingly, in this study, we deleted 24 bp in E1A (bp924-bp947) and the entirety of E1B, including those genes encoding E1B 55kDa and E1B19kDa. We used the survivin promoter (SP) to control E1A in order to construct a new adenovirus vector named Ad.SP.E1A(Δ24).ΔE1B (briefly Ad.SPDD). HCCS1 (hepatocellular carcinoma suppressor 1) is a novel tumor suppressor gene that is able to specifically induce apoptosis in cancer cells. The expression cassette AFP-HCCS1-WPRE-SV40 was inserted into Ad.SPDD to form Ad.SPDD-HCCS1, enabling us to improve the safety and efficacy of oncolytic-mediated gene therapy for liver cancer.</p> <p>Results</p> <p>Ad.SPDD showed a decreased viral yield and less toxicity in normal cells but enhanced toxicity in liver cancer cells, compared with the cancer-specific adenovirus ZD55 (E1B55K deletion). Ad.SPDD-HCCS1 exhibited a potent anti-liver-cancer ability and decreased toxicity in vitro. Ad.SPDD-HCCS1 also showed a measurable capacity to inhibit Huh-7 xenograft tumor growth on nude mice. The underlying mechanism of Ad.SPDD-HCCS1-induced liver cancer cell death was found to be via the mitochondrial apoptosis pathway.</p> <p>Conclusions</p> <p>These results demonstrate that Ad.SPDD-HCCS1 was able to elicit reduced toxicity and enhanced efficacy both in vitro and in vivo compared to a previously constructed oncolytic adenovirus. Ad.SPDD-HCCS1 could be a promising candidate for liver cancer therapy.</p

Quantum magnetism and criticality

Magnetic insulators have proved to be fertile ground for studying new types of quantum many body states, and I survey recent experimental and theoretical examples. The insights and methods transfer also to novel superconducting and metallic states. Of particular interest are critical quantum states, sometimes found at quantum phase transitions, which have gapless excitations with no particle- or wave-like interpretation, and control a significant portion of the finite temperature phase diagram. Remarkably, their theory is connected to holographic descriptions of Hawking radiation from black holes.Comment: 39 pages, 10 figures, review article for non-specialists; (v2) added clarifications and references; (v3) minor corrections; (v4) added footnote on hydrodynamic long-time tail