96 research outputs found
A finite-difference method for the one-dimensional time-dependent schrödinger equation on unbounded domain
AbstractA finite-difference scheme is proposed for the one-dimensional time-dependent Schrödinger equation. We introduce an artificial boundary condition to reduce the original problem into an initial-boundary value problem in a finite-computational domain, and then construct a finite-difference scheme by the method of reduction of order to solve this reduced problem. This scheme has been proved to be uniquely solvable, unconditionally stable, and convergent. Some numerical examples are given to show the effectiveness of the scheme
Floquet Chern Insulators of Light
Achieving topologically-protected robust transport in optical systems has
recently been of great interest. Most topological photonic structures can be
understood by solving the eigenvalue problem of Maxwell's equations for a
static linear system. Here, we extend topological phases into dynamically
driven nonlinear systems and achieve a Floquet Chern insulator of light in
nonlinear photonic crystals (PhCs). Specifically, we start by presenting the
Floquet eigenvalue problem in driven two-dimensional PhCs and show it is
necessarily non-Hermitian. We then define topological invariants associated
with Floquet bands using non-Hermitian topological band theory, and show that
topological band gaps with non-zero Chern number can be opened by breaking
time-reversal symmetry through the driving field. Furthermore, we show that
topological phase transitions between Floquet Chern insulators and normal
insulators occur at synthetic Weyl points in a three-dimensional parameter
space consisting of two momenta and the driving frequency. Finally, we
numerically demonstrate the existence of chiral edge states at the interfaces
between a Floquet Chern insulator and normal insulators, where the transport is
non-reciprocal and uni-directional. Our work paves the way to further exploring
topological phases in driven nonlinear optical systems and their optoelectronic
applications, and our method of inducing Floquet topological phases is also
applicable to other wave systems, such as phonons, excitons, and polaritons
Geometric similarities and topological phases in surface magnon polaritons
Highly spatially-squeezed polaritons, with propagation momentum significantly
larger than free-space modes at the same frequency, enable varied and extreme
control over light-matter interaction. Compared to other polaritons, surface
magnon polaritons, the magnetic counterpart of surface phonon polaritons, have
received relatively little attention. Here, we investigate the dispersion and
properties of surface-magnon polaritons, highlighting the impact of geometric
similarities and applying them to various surface-magnon polariton devices in
both conventional and topological settings. Our theory predicts a method for
strongly localizing and significantly enhancing magnetic fields in the
microwave range and developing compact and lossless connectors capable of
interconnecting waveguides with vastly different input and output impedances.
Our work opens new avenues for manipulating magnetic fields in the microwave
regime and for exploring topological phases in polariton platforms
Topological electromagnetic waves in dispersive and lossy plasma crystals
Topological photonic crystals, which offer topologically protected and
back-scattering-immune transport channels, have recently gained significant
attention for both scientific and practical reasons. Although most current
studies focus on dielectric materials with weak dispersions, this study focuses
on topological phases in dispersive materials and presents a numerical study of
Chern insulators in gaseous-phase plasma cylinder cells. We develop a numerical
framework to address the complex material dispersion arising from the plasma
medium and external magnetic fields and identify Chern insulator phases that
are experimentally achievable. Using this numerical tool, we also explain the
flat bands commonly observed in periodic plasmonic structures, via local
resonances, and how edge states change as the edge termination is periodically
modified. This work opens up opportunities for exploring band topology in new
materials with non-trivial dispersions and has potential RF applications,
ranging from plasma-based lighting to plasma propulsion engines.Comment: 10 pages, 4 figure
Observation of Floquet Chern insulators of light
The field of topological photonics studies unique and robust photonic systems
that are immune to defects and disorders due to the protection of their
underlying topological phases. Mostly implemented in static systems, the
studied topological phases are often defined in linear photonic band
structures. In this study, we experimentally demonstrate Floquet Chern
insulators in periodically driven nonlinear photonic crystals, where the
topological phase is controlled by the polarization and the frequency of the
driving field. Mediated by strong material nonlinearity, our system enters what
we call the 'strong Floquet coupling regime', where the photonic Floquet bands
cross and open new energy gaps with non-trivial topology as observed in our
transient sum-frequency generation measurements. Our work offers new
opportunities to explore the role of classical optical nonlinearity in
topological phases and their applications in nonlinear optoelectronics.Comment: 24 pages, 5 figure
Endoplasmic Reticulum Stress is Involved in DFMO Attenuating Isoproterenol-Induced Cardiac Hypertrophy in Rats
Metagenomic Sequencing From Mosquitoes in China Reveals a Variety of Insect and Human Viruses
We collected 8,700 mosquitoes in three sites in China, which belonged to seven species. Their viromes were tested using metagenomic sequencing and bioinformatic analysis. The abundant viral sequences were detected and annotated belonging to more than 50 viral taxonomic families. The results were verified by PCR, followed by phylogenetic analysis. In the present study, we identified partial viral genes of dengue virus (DENV), a novel circovirus (CCV), densovirus (DNV), Japanese encephalitis virus (JEV), and Wuhan mosquito virus (WMV) in mosquitoes. Metagenomic analysis and PCR amplification revealed three DENV sequences, which were as homologous to the NS3 gene of DENV from Singapore isolated in 2005, with at least 91% nucleotide (nt) identity. Seven fragments of JEV encoding structural proteins were identified belonging to genotype I. They all shared high homology with structural protein genes of JEV isolated from Laos in 2009. The production of infectious virus particles of the newly isolated virus YunnanJEV2017-4 increased after passage from the BHK-21 cell line to the Vero cell line. Novel circovirus-related genes were identified and as being related to an unnamed gene of a mosquito circovirus (MCCV) sequence from the USA isolated in 2011, with at least 41% nt identity: this distant relationship suggests that the parent virus might belong to a novel circovirus genus. Additionally, numerous known viruses and some unknown viruses were also detected in mosquitoes from Yunnan province, China, which will be tested for propagation
Metagenomic Analysis of Flaviviridae in Mosquito Viromes Isolated From Yunnan Province in China Reveals Genes From Dengue and Zika Viruses
More than 6,000 mosquitoes of six species from six sites were collected and tested for their virome using metagenomics sequencing and bioinformatic analysis. The identified viral sequences belonged to more than 50 viral families. The results were verified by PCR of selected viruses in all mosquitoes, followed by phylogenetic analysis. In the present study, we identified the partial dengue virus (DENV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV) sequences in mosquitoes. Metagenomic analysis and the PCR amplification revealed three DENV sequences, one of which encodes a partial envelope protein. Two ZIKV sequences both encoding partial nonstructural protein 3 and one JEV sequence encoding the complete envelope protein were identified. There was variability in the viral titers of the newly isolated virus JEV-China/YN2016-1 of different passage viruses. The newly identified Zika virus gene from ZIKV-China/YN2016-1 was an Asian genotype and shared the highest nucleotide sequence identity (97.1%) with a ZIKV sequence from Thailand isolated in 2004. Phylogenetic analysis of ZIKV-China/YN2016-1 and ZIKV-China/YN2016-2 with known Flavivirus genes indicated that ZIKV has propagated in Yunnan province, China
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