99 research outputs found
Three dimensional photonic Dirac points in metamaterials
Topological semimetals, representing a new topological phase that lacks a
full bandgap in bulk states and exhibiting nontrivial topological orders,
recently have been extended to photonic systems, predominantly in photonic
crystals and to a lesser extent, metamaterials. Photonic crystal realizations
of Dirac degeneracies are protected by various space symmetries, where Bloch
modes span the spin and orbital subspaces. Here, we theoretically show that
Dirac points can also be realized in effective media through the intrinsic
degrees of freedom in electromagnetism under electromagnetic duality. A pair of
spin polarized Fermi arc like surface states is observed at the interface
between air and the Dirac metamaterials. These surface states show linear
k-space dispersion relation, resulting in nearly diffraction-less propagation.
Furthermore, eigen reflection fields show the decomposition from a Dirac point
to two Weyl points. We also find the topological correlation between a Dirac
point and vortex/vector beams in classic photonics. The theoretical proposal of
photonic Dirac point lays foundation for unveiling the connection between
intrinsic physics and global topology in electromagnetism.Comment: 15 pages, 5 figure
Analysis of the imaging and clinical features of subsolid pulmonary nodules in stage IA non-small cell lung cancer
The subsolid pulmonary nodules (SSPNs) in the imaging diagnosis of stage IA non-small cell lung cancer (NSCLC) is very important since they are closely related to early lung cancer. The CT imaging and pathology data of 230 patients with solitary pulmonary nodules (SPNs) who underwent thoracoscopic treatment at Guizhou Provincial People’s Hospital between July 2021 and June 2022 were collected. Based on postoperative pathology, the patients were divided into a benign group and a stage IA NSCLC group. The imaging and clinical features of SPNs in stage IA NSCLC were analysed. A total of 230 patients with SPNs were enrolled. There were 146 cases of SSPNs (including 34 cases of pure ground-glass opacities (pGGOs) and 112 cases of mixed GGOs (mGGOs)), and the incidence rate was significantly higher in the stage IA NSCLC group than in the benign group [96.7% (146/151) vs. 74.7% (59/79), P<0.05]. The overall malignancy rate of subsolid nodules was 71.2% (146/205); the malignancy rate of mGGO lesions was higher (75.2%) than that of pGGO lesions (60.7%) and solid nodules (20%). Malignant subsolid nodules mostly occurred in middle-aged women, mostly in the upper lobe of the lungs, with unclear edges and lobular signs, and accompanied by spur signs and pleural indentation signs (P<0.05). SSPNs are an important sign of lung cancer, and mGGO lesions have the highest malignant tendency. CT imaging findings such as unclear lesion edges, lobular signs, and pleural indentation signs are important for determining benign and malignant SSPNs. CT imaging manifestations are helpful for correctly assessing the nature of early SSPNs so that patients can receive timely and effective treatment
Phenomenological modeling of Geometric Metasurfaces
Metasurfaces, with their superior capability in manipulating the optical
wavefront at the subwavelength scale and low manufacturing complexity, have
shown great potential for planar photonics and novel optical devices. However,
vector field simulation of metasurfaces is so far limited to
periodic-structured metasurfaces containing a small number of meta-atoms in the
unit cell by using full-wave numerical methods. Here, we propose a general
phenomenological method to analytically model metasurfaces made up of
arbitrarily distributed meta-atoms based on the assumption that the meta-atoms
possess localized resonances with Lorentz-Drude forms, whose exact form can be
retrieved from the full wave simulation of a single element. Applied to phase
modulated geometric metasurfaces, our analytical results show good agreement
with full-wave numerical simulations. The proposed theory provides an efficient
method to model and design optical devices based on metasurfaces.Comment: 16 pages, 8 figure
Heisenberg-limited spin squeezing in coupled spin systems
Spin squeezing plays a crucial role in quantum metrology and quantum
information science. Its generation is the prerequisite for further
applications but still faces an enormous challenge since the existing physical
systems rarely contain the required squeezing interactions. Here we propose a
universal scheme to generate spin squeezing in coupled spin models with
collective spin-spin interactions, which commonly exist in various systems. Our
scheme can transform the coupled spin interactions into squeezing interactions,
and reach the extreme squeezing with Heisenberg-limited measurement precision
scaling as for particles. Only constant and continuous driving fields
are required, which is accessible to a series of current realistic experiments.
This work greatly enriches the variety of systems that can generate the
Heisenberg-limited spin squeezing, with broad applications in quantum precision
measurement
Recovering lossless propagation of polaritons with synthesized complex frequency excitation
Surface plasmon polaritons and phonon polaritons offer a means of surpassing
the diffraction limit of conventional optics and facilitate efficient energy
storage, local field enhancement, high sensitivities, benefitting from their
subwavelength confinement of light. Unfortunately, losses severely limit the
propagation decay length, thus restricting the practical use of polaritons.
While optimizing the fabrication technique can help circumvent the scattering
loss of imperfect structures, the intrinsic absorption channel leading to heat
production cannot be eliminated. Here, we utilize synthetic optical excitation
of complex frequency with virtual gain, synthesized by combining the
measurements taken at multiple real frequencies, to restore the lossless
propagations of phonon polaritons with significantly reduced intrinsic losses.
The concept of synthetic complex frequency excitation represents a viable
solution to compensate for loss and would benefit applications including
photonic circuits, waveguiding and plasmonic/phononic structured illumination
microscopy.Comment: 20 pages, 4 figure
Silencing SARS-CoV Spike protein expression in cultured cells by RNA interference
AbstractThe severe acute respiratory syndrome (SARS) has been one of the most epidemic diseases threatening human health all over the world. Based on clinical studies, SARS-CoV (the SARS-associated coronavirus), a novel coronavirus, is reported as the pathogen responsible for the disease. To date, no effective and specific therapeutic method can be used to treat patients suffering from SARS-CoV infection. RNA interference (RNAi) is a process by which the introduced small interfering RNA (siRNA) could cause the degradation of mRNA with identical sequence specificity. The RNAi methodology has been used as a tool to silence genes in cultured cells and in animals. Recently, this technique was employed in anti-virus infections in human immunodeficiency virus and hepatitis C/B virus. In this study, RNAi technology has been applied to explore the possibility for prevention of SARS-CoV infection. We constructed specific siRNAs targeting the S gene in SARS-CoV. We demonstrated that the siRNAs could effectively and specifically inhibit gene expression of Spike protein in SARS-CoV-infected cells. Our study provided evidence that RNAi could be a tool for inhibition of SARS-CoV
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