197 research outputs found
Observation of valley Landau-Zener-Bloch oscillations and pseudospin imbalance in photonic graphene
We demonstrate inter-valley Bloch oscillation (BO) and Landau-Zener tunneling
(LZT) in an optically-induced honeycomb lattice with a refractive index
gradient. Unlike previously observed BO in a gapped square lattice, we show
non-adiabatic beam dynamics that are highly sensitive to the direction of the
index gradient and the choice of the Dirac cones. In particular, a
symmetry-preserving potential leads to nearly perfect LZT and coherent BO
between the inequivalent valleys, whereas a symmetry-breaking potential
generates asymmetric scattering, imperfect LZT, and valley-sensitive generation
of vortices mediated by a pseudospin imbalance. This clearly indicates that,
near the Dirac points, the transverse gradient does not always act as a simple
scalar force as commonly assumed, and the LZT probability is strongly affected
by the sublattice symmetry as analyzed from an effective Landau-Zener
Hamiltonian. Our results illustrate the anisotropic response of an otherwise
isotropic Dirac platform to real-space potentials acting as strong driving
fields, which may be useful for manipulation of pseudospin and valley degrees
of freedom in graphene-like systems
Dynamic Furnace Temperature Setting Research on Combustion System of Rolling Mill Reheating Furnace
AbstractThe setting of furnace temperature in combustion system of reheating furnace at rolling mill is an important parameter in the production process. Variety of some factors such as furnace heating capacity, steel thermal stress, production rhythm etc. directly affects the setting of furnace temperature, it is an industry problem. This article analysis about how the above mentioned factors affect the furnace temperature setting, and mainly focus on dynamic setting strategy of furnace temperature so as to fit fluctuation of production rhythm through theoretical analysis on the energy balance of billet heat transfer in the furnace. This strategy has been verified by production and experiment, and matches with the related data
Valley vortex states and degeneracy lifting via photonic higher-band excitation
We demonstrate valley-dependent vortex generation in a photonic graphene.
Without breaking the inversion symmetry, excitation of two equivalent valleys
leads to formation of an optical vortex upon Bragg-reflection to the third
valley, with its chirality determined by the valley degree of freedom.
Vortex-antivortex pairs with valley-dependent topological charge flipping are
also observed and corroborated by numerical simulations. Furthermore, we
develop a three-band effective Hamiltonian model to describe the dynamics of
the coupled valleys, and find that the commonly used two-band model is not
sufficient to explain the observed vortex degeneracy lifting. Such
valley-polarized vortex states arise from high-band excitation without
inversion symmetry breaking or synthetic-field-induced gap opening. Our results
from a photonic setting may provide insight for the study of valley contrasting
and Berry-phase mediated topological phenomena in other systems
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
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
Persistent homology analysis of a generalized Aubry-Andr\'{e}-Harper model
Observing critical phases in lattice models is challenging due to the need to
analyze the finite time or size scaling of observables. We study how the
computational topology technique of persistent homology can be used to
characterize phases of a generalized Aubry-Andr\'{e}-Harper model. The
persistent entropy and mean squared lifetime of features obtained using
persistent homology behave similarly to conventional measures (Shannon entropy
and inverse participation ratio) and can distinguish localized, extended, and
crticial phases. However, we find that the persistent entropy also clearly
distinguishes ordered from disordered regimes of the model. The persistent
homology approach can be applied to both the energy eigenstates and the
wavepacket propagation dynamics.Comment: Published version. 8 pages, 9 figure
Multiple flat bands and localized states in photonic super-Kagome lattices
We demonstrate multiple flat bands and compact localized states (CLSs) in a
photonic super-Kagome lattice (SKL) that exhibits coexistence of singular and
nonsingular flat bands within its unique band structure. Specifically, we find
that the upper two flat bands of an SKL are singular - characterized by
singularities due to band touching with their neighboring dispersive bands at
the Brillouin zone center. Conversely, the lower three degenerate flat bands
are nonsingular, and remain spectrally isolated from other dispersive bands.
The existence of such two distinct types of flat bands is experimentally
demonstrated by observing stable evolution of the CLSs with various geometrical
shapes in a laser-written SKL. We also discuss the classification of the flat
bands in momentum space, using band-touching singularities of the Bloch wave
functions. Furthermore, we validate this classification in real space based on
unit cell occupancy of the CLSs in a single SKL plaquette. These results may
provide insights for the study of flatband transport, dynamics, and nontrivial
topological phenomena in other relevant systems.Comment: 5 pages,4 figure
Cancer impacts microRNA expression, release and function in cardiac and skeletal muscle
Circulating microRNAs are emerging as important biomarkers of various diseases including cancer. Intriguingly, circulating levels of several microRNAs are lower in cancer patients compared with healthy individuals. In this study, we tested the hypothesis that a circulating microRNA might serve as a surrogate of the effects of cancer on microRNA expression or release in distant organs. Here we report that circulating levels of the muscle-enriched miR-486 is lower in breast cancer patients compared with healthy individuals, and that this difference is replicated faithfully in MMTV-PyMT and MMTV-Her2 transgenic mouse models of breast cancer. In tumor-bearing mice, levels of miR-486 were relatively reduced in muscle, where there was elevated expression of the miR-486 target genes PTEN and FOXO1A and dampened signaling through the PI3K/AKT pathway. Skeletal muscle expressed lower levels of the transcription factor MyoD which controls miR-486 expression. Conditioned media (CM) obtained from MMTV-PyMT and MMTV-Her2/Neu tumor cells cultured in vitro was sufficient to elicit reduced levels of miR-486 and increased PTEN and FOXO1A expression in C2C12 murine myoblasts. Cytokine analysis implicated TNFα and four additional cytokines as mediators of miR-486 expression in CM-treated cells. Since miR-486 is a potent modulator of PI3K/AKT signaling and the muscle-enriched transcription factor network in cardiac/skeletal muscle, our findings implicated TNFα-dependent miRNA circuitry in muscle differentiation and survival pathways in cancer
Histone H3 Lysine 9 Methyltransferase DIM5 Is Required for the Development and Virulence of Botrytis cinerea
Histone methylation is widely present in animals, plants and fungi, and the methylation modification of histone H3 has important biological functions. Methylation of Lys9 of histone H3 (H3K9) has been proven to regulate chromatin structure, gene silencing, transcriptional activation, plant metabolism and other processes. In this work, we investigated the functions of a H3K9 methyltransferase gene BcDIM5 in Botrytis cinerea, which contains a PreSET domain, a SET domain and a PostSET domain. Characterization of BcDIM5 knockout transformants showed that the hyphal growth rate and production of conidiophores and sclerotia were significantly reduced, while complementary transformation of BcDIM5 could restore the phenotypes to the levels of wild type. Pathogenicity assays revealed that BcDIM5 was essential for full virulence of B. cinerea. BcDIM5 knockout transformants exhibited decreased virulence, down-regulated expression of some pathogenic genes and drastically decreased H3K9 trimethylation level. However, knockout transformants of other two genes heterochromatin protein 1 (HP1) BcHP1 and DNA methyltransferase (DIM2) BcDIM2 did not exhibit significant change in the growth phenotype and virulence compared with the wild type. Our results indicate that H3K9 methyltransferase BcDIM5 is required for H3K9 trimethylation to regulate the development and virulence of B. cinerea
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