Unconventional Flatband Line States in Photonic Lieb Lattices

Flatband systems typically host "compact localized states"(CLS) due to destructive interference and macroscopic degeneracy of Bloch wave functions associated with a dispersionless energy band. Using a photonic Lieb lattice(LL), we show that conventional localized flatband states are inherently incomplete, with the missing modes manifested as extended line states which form non-contractible loops winding around the entire lattice. Experimentally, we develop a continuous-wave laser writing technique to establish a finite-sized photonic LL with specially-tailored boundaries, thereby directly observe the unusually extended flatband line states.Such unconventional line states cannot be expressed as a linear combination of the previously observed CLS but rather arise from the nontrivial real-space topology.The robustness of the line states to imperfect excitation conditions is discussed, and their potential applications are illustrated

Photonic realization of a generic type of graphene edge states exhibiting topological flat band

Cutting a honeycomb lattice (HCL) can end up with three types of edges (zigzag, bearded and armchair), as is well known in the study of graphene edge states. Here we theoretically investigate and experimentally demonstrate a class of graphene edges, namely, the twig-shaped edges, using a photonic platform, thereby observing edge states distinctive from those observed before. Our main findings are: (i) the twig edge is a generic type of HCL edges complementary to the armchair edge, formed by choosing the right primitive cell rather than simple lattice cutting or Klein edge modification; (ii) the twig edge states form a complete flat band across the Brillouin zone with zero-energy degeneracy, characterized by nontrivial topological winding of the lattice Hamiltonian; (iii) the twig edge states can be elongated or compactly localized along the boundary, manifesting both flat band and topological features. Such new edge states are realized in a laser-written photonic graphene and well corroborated by numerical simulations. Our results may broaden the understanding of graphene edge states, bringing about new possibilities for wave localization in artificial Dirac-like materials.Comment: 13 pages, 4 figure

Subcellular localization and function study of a secreted phospholipase C from Nocardia seriolae

Fish nocardiosis is a chronic systemic granulomatous disease, andNocardia seriolaeis the main pathogen that causes this disease. But the pathogenesis and virulence factors ofN. seriolaeare not fully understood. A phospholipase C (PLC), which was likely to be a secreted protein targeting host cell mitochondria, was found by the bioinformatics analysis on the whole genome sequence ofN. seriolae. In order to determine the subcellular localization and study the preliminary function of PLC fromN. seriolae(NsPLC), the gene cloning, secreted protein identification, subcellular localization in host cells and apoptosis detection of NsPLC were carried out in this study. The results showed that NsPLC was a secreted protein by mass spectrometry analysis of extracellular products fromN. seriolae. Subcellular localization of NsPLC-GFP fusion protein in FHM cells revealed that the green fluorescence exhibited a punctate distribution near the nucleus and did not co-localize with mitochondria. In addition, apoptosis assay suggested that apoptosis was induced in FHM cells by the overexpression of NsPLC. This study may lay the foundation for further study on the function of NsPLC and promote the understanding of the virulence factors and pathogenic mechanism ofN. seriolae

Flatband Line States in Photonic Super-Honeycomb Lattices

We establish experimentally a photonic super-honeycomb lattice (sHCL) by use of a cw-laser writing technique, and thereby demonstrate two distinct flatband line states that manifest as noncontractible-loop-states in an infinite flatband lattice. These localized states (straight and zigzag lines) observed in the sHCL with tailored boundaries cannot be obtained by superposition of conventional compact localized states because they represent a new topological entity in flatband systems. In fact, the zigzag-line states, unique to the sHCL, are in contradistinction with those previously observed in the Kagome and Lieb lattices. Their momentum-space spectrum emerges in the high-order Brillouin zone where the flat band touches the dispersive bands, revealing the characteristic of topologically protected bandcrossing. Our experimental results are corroborated by numerical simulations based on the coupled mode theory. This work may provide insight to Dirac like 2D materials beyond graphene

Non-linear ICA Analysis of Resting-State fMRI in Mild Cognitive Impairment

Compared to linear independent component analysis (ICA), non-linear ICA is more suitable for the decomposition of mixed components. Existing studies of functional magnetic resonance imaging (fMRI) data by using linear ICA assume that the brain's mixed signals, which are caused by the activity of brain, are formed through the linear combination of source signals. But the application of the non-linear combination of source signals is more suitable for the mixed signals of brain. For this reason, we investigated statistical differences in resting state networks (RSNs) on 32 healthy controls (HC) and 38 mild cognitive impairment (MCI) patients using post-nonlinear ICA. Post-nonlinear ICA is one of the non-linear ICA methods. Firstly, the fMRI data of all subjects was preprocessed. The second step was to extract independent components (ICs) of fMRI data of all subjects. In the third step, we calculated the correlation coefficient between ICs and RSN templates, and selected ICs of the largest spatial correlation coefficient. The ICs represent the corresponding RSNs. After finding out the eight RSNs of MCI group and HC group, one sample t-tests were performed. Finally, in order to compare the differences of RSNs between MCI and HC groups, the two-sample t-tests were carried out. We found that the functional connectivity (FC) of RSNs in MCI patients was abnormal. Compared with HC, MCI patients showed the increased and decreased FC in default mode network (DMN), central executive network (CEN), dorsal attention network (DAN), somato-motor network (SMN), visual network(VN), MCI patients displayed the specifically decreased FC in auditory network (AN), self-referential network (SRN). The FC of core network (CN) did not reveal significant group difference. The results indicate that the abnormal FC in RSNs is selective in MCI patients

Universal momentum-to-real-space mapping of topological singularities

Topological properties of materials, as manifested in the intriguing phenomena of quantum Hall effect and topological insulators, have attracted overwhelming transdisciplinary interest in recent years. Topological edge states, for instance, have been realized in versatile systems including electromagnetic-waves. Typically, topological properties are revealed in momentum space, using concepts such as Chern number and Berry phase. Here, we demonstrate a universal mapping of the topology of Dirac-like cones from momentum space to real space. We evince the mapping by exciting the cones in photonic honeycomb (pseudospin-1/2) and Lieb (pseudospin-1) lattices with vortex beams of topological charge l, optimally aligned for a chosen pseudospin state s, leading to direct observation of topological charge conversion that follows the rule of l to l+2s. The mapping is theoretically accounted for all initial excitation conditions with the pseudospin-orbit interaction and nontrivial Berry phases. Surprisingly, such a mapping exists even in a deformed lattice where the total angular momentum is not conserved, unveiling its topological origin. The universality of the mapping extends beyond the photonic platform and 2D lattices: equivalent topological conversion occurs for 3D Dirac-Weyl synthetic magnetic monopoles, which could be realized in ultracold atomic gases and responsible for mechanism behind the vortex creation in electron beams traversing a magnetic monopole field

Realization of robust boundary modes and non-contractible loop states in photonic Kagome lattices

Corbino-geometry has well-known applications in physics, as in the design of graphene heterostructures for detecting fractional quantum Hall states or superconducting waveguides for illustrating circuit quantum electrodynamics. Here, we propose and demonstrate a photonic Kagome lattice in the Corbino-geometry that leads to direct observation of non-contractible loop states protected by real-space topology. Such states represent the "missing" flat-band eigenmodes, manifested as one-dimensional loops winding around a torus, or lines infinitely extending to the entire flat-band lattice. In finite (truncated) Kagome lattices, however, line states cannot preserve as they are no longer the eigenmodes, in sharp contrast to the case of Lieb lattices. Using a continuous-wave laser writing technique, we experimentally establish finite Kagome lattices with desired cutting edges, as well as in the Corbino-geometry to eliminate edge effects. We thereby observe, for the first time to our knowledge, the robust boundary modes exhibiting self-healing properties, and the localized modes along toroidal direction as a direct manifestation of the non-contractible loop states

DNSN-1 recruits GINS for CMG helicase assembly during DNA replication initiation in <i>Caenorhabditis elegans</i>

Assembly of the CMG (CDC-45-MCM-2-7-GINS) helicase is the key regulated step during eukaryotic DNA replication initiation. Until now, it was unclear whether metazoa require additional factors that are not present in yeast. In this work, we show that Caenorhabditis elegans DNSN-1, the ortholog of human DONSON, functions during helicase assembly in a complex with MUS-101/TOPBP1. DNSN-1 is required to recruit the GINS complex to chromatin, and a cryo-electron microscopy structure indicates that DNSN-1 positions GINS on the MCM-2-7 helicase motor (comprising the six MCM-2 to MCM-7 proteins), by direct binding of DNSN-1 to GINS and MCM-3, using interfaces that we show are important for initiation and essential for viability. These findings identify DNSN-1 as a missing link in our understanding of DNA replication initiation, suggesting that initiation defects underlie the human disease syndrome that results from DONSON mutations.</p