Photonic Crystal Millimetre Wave and Terahertz Waveguides and Functional Components

This work discusses both the theoretical and experimental guidance of low-loss single-mode millimetre-wave (mmW) and terahertz (THz) waves within microstructured photonic crystal fibre or waveguides, as well as functional components which can be built upon them. The aim of this work is to provide good interconnects for mmW and THz system. The interconnects are desired to be low loss, single mode, low dispersion, as well as easy to fabricate and integrate. In this work, photonic crystal structures, which can easily manipulate the wave-behaving photons by artificially changing its geometrical and material properties, are used in the proposed mmW and THz waveguides. The proposed photonic crystal waveguides includes cylindrical Bragg fibres and flat hollow photonic crystal integrated waveguides. The geometrical differences between Bragg fibres and photonic crystal integrated waveguides make them work better for different challenges. The former are promising for long distance guidance of signals due to its ultra-low loss, while the latter are strong candidates for compact and multilayer packaging applications since its flatness and other exceptional properties. The thesis has three primary themes. The first them is about the design principles, analysis, and fabrication and measurement of low-loss asymptotically single-mode THz Bragg fibres. A design principle for manipulating the photonic bandgap of Bragg fibres, which is called as the generalized half-wavelength condition, is proposed. Based on the design principle, an ultra-low loss THz Bragg fibre with single mode and low dispersion is proposed, verified by the simulation. Considering practical fabrication challenges, a sub-THz Bragg fibre is fabricated using 3D printing technology and characterized to be one of the lowest loss waveguide at around 300 GHz. The mode transition and filtering in the fabricated sub-THz Bragg fibre is investigated, disclosing the mechanisms of asymptotically single-mode operation pattern of Bragg fibres. The second theme is about the design, fabrication and measurement of single-mode mmW flat and hollow photonic crystal integrated waveguides with low loss and zero group velocity dispersion. The hollow photonic crystal integrated waveguides comprise of air-core line-defect photonic crystal structures sandwiched by a pair of metallic parallel plates. Two different types of photonic crystals are used in the designs, namely hexagonal lattice array of air holes in dielectric slab and Bragg reflectors that consist of periodic arrangement of dielectric layers and air layers. Therefore, two types of hollow photonic crystal integrated waveguides are designed. The designs are fabricated and verified at Ka-band by measurements. The hollow photonic crystal integrated waveguides possess the merits of both substrate integrated waveguide and photonic crystal waveguide, but eliminates their drawbacks, making them strong candidates for compact and multilayer mmW and THz system-in-package applications. The third theme is about the design and simulation of mmW and THz functional components built upon the previously designed microstructured photonic crystal fibres and flat waveguides. The functional components that have been designed include waveguide bends, power splitters or combiners, cavity, h-plane horn antenna, and circular Bragg fibre horn antenna. This theme aims to demonstrate the expansibility and flexibility of the proposed microstructured photonic crystal fibres and flat waveguides as promising platforms for designing mmW and THz functional components. Though each theme discusses the theoretical analysis and/or experimental measurements of distinct phenomena, they are deeply related within the overall theme of engineering low-loss single-mode fibres or waveguides and their integration into mmW or THz systems

Kerker-Type Positional Disorder Immune Metasurfaces

Metasurfaces that can work without the rigorous periodic arrangement of meta-atoms are highly desired by practical optical micro-nano devices. In this work, we proposed two kinds of Kerker-type metasurfaces possessing positional disorder immunity. The metasurfaces are composed of two different core-shell cylinders satisfying the first and second Kerker conditions, respectively. Even with large positional disorder perturbation of the meta-atoms, the metasurfaces can still maintain the same excellent performances as periodic ones, such as the total transmission and magnetic mirror responses. This disorder immunity is due to the unidirectional forward and backward scatterings of a single core-shell cylinder leading to very weak lateral couplings between neighboring cylinders thus rarely affecting the multiple scatterings in the forward or backward direction. In contrast, the dominant response of the disordered non-Kerker-type metasurface decreases significantly. Our findings provide a new idea for designing robust metasurfaces and extend the scope of metasurface applications in sensing and communication under complex practical circumstances.Comment: 18 pages, 9 figure

Substrate Integrated Bragg Waveguide: an Octave-bandwidth Single-mode Functional Transmission-Line for Millimeter-Wave and Terahertz Applications

We demonstrate an air-core single-mode hollow waveguide that uses Bragg reflector structures in place of the vertical metal walls of the standard rectangular waveguide or via holes of the so-called substrate integrated waveguide. The high-order modes in the waveguide are substantially suppressed by a modal-filtering effect, making the waveguide operate in the fundamental mode over more than one octave. Numerical simulations show that the propagation loss of the proposed waveguide can be lower than that of classic hollow metallic rectangular waveguides at terahertz frequencies, benefiting from a significant reduction in Ohmic loss. To facilitate fabrication and characterization, a proof-of-concept 20 to 45 GHz waveguide is demonstrated, which verifies the properties and advantages of the proposed waveguide. A zero group-velocity dispersion point is observed at near the middle of the operating band. This work offers a step towards a novel hybrid transmission-line medium that can be used in a variety of functional components for broadband millimeter-wave and terahertz applications.Comment: 11 pages, 9 figures, journal articl

Cryo-electron tomography of Kaposi\u27s sarcoma-associated herpesvirus capsids reveals dynamic scaffolding structures essential to capsid assembly and maturation.

Kaposi\u27s sarcoma-associated herpesvirus (KSHV) is a recently discovered DNA tumor virus that belongs to the gamma-herpesvirus subfamily. Though numerous studies on KSHV and other herpesviruses, in general, have revealed much about their multilayered organization and capsid structure, the herpesvirus capsid assembly and maturation pathway remains poorly understood. Structural variability or irregularity of the capsid internal scaffolding core and the lack of adequate tools to study such structures have presented major hurdles to earlier investigations employing more traditional cryo-electron microscopy (cryoEM) single particle reconstruction. In this study, we used cryo-electron tomography (cryoET) to obtain 3D reconstructions of individual KSHV capsids, allowing direct visualization of the capsid internal structures and systematic comparison of the scaffolding cores for the first time. We show that B-capsids are not a structurally homogenous group; rather, they represent an ensemble of B-capsid-like particles whose inner scaffolding is highly variable, possibly representing different intermediates existing during the KSHV capsid assembly and maturation. This information, taken together with previous observations, has allowed us to propose a detailed pathway of herpesvirus capsid assembly and maturation

Feasibility of Oil Slick Detection Using BeiDou-R Coastal Simulation

Oil spills, which can cause severe immediate and long-term harm to marine ecological environments for decades after the initial accident, require rapid and accurate monitoring. Currently, optical and radar satellite images are used to monitor oil spills; however, remote sensing generally needs a long revisit period. Global Navigation Satellite System reflected signals (GNSS-R) can provide all-weather and all-day ocean monitoring and is therefore more suitable for oil spill monitoring. To assess the feasibility of the BeiDou Navigation Satellite System reflected signals (BeiDou-R) in detecting oil slicks, a BeiDou-R coastal simulated experiment is performed in this study on the oil slick distribution of an oil pipeline explosion accident. We set up an observation point and selected observation satellites, and a delay-Doppler map (DDM) of an oil-slicked sea surface under coastal scenarios was created by combining the mean-square slope (MSS) model for oil-slicked/clean surfaces and the Zavorotny–Voronovich (Z–V) scattering model. DDM simulation of the coastal scenarios effectively represents the scattering coefficient distribution of the presence of an oil slick. Theoretical analysis revealed that oil slicks can be detected within a radius of less than 5 km around the specular reflection point (SP) for BeiDou-R coastal simulation

Bacoside-A exerts protective effect against Parkinson’s disease-induced functional damage in mice via inhibition of apoptosis and oxidative response

Purpose: To determine the effect of bacoside-A on Parkinson's disease (PD) in a rat model, and elucidate its mechanism of action.Methods: A rat model of PD was established by administration of 5 µL of 6-hydroxydopamine in ascorbic acid (0.1 %). Measurement of serum levels of inflammatory factors was carried out using enzyme-linked immunosorbent assay (ELISA) kits. Western blotting was used to assay Bax, cytochrome c and Bcl-2 in rat hippocampus.Results: Bacoside-A treatment significantly reduced PD-induced high turning values in rats (p < 0.05). Treatment with bacoside-A reversed PD-mediated suppression of serum activities of CAT and glutathione peroxidase (GPx). In bacoside-A-treated PD rats, dose-dependent suppression of acetylcholinesterase (AChE) and inducible nitric oxide synthase (iNOS) activities were observed (p < 0.05). Bacoside-A-treated PD rats significantly (p < 0.018) reduced interleukin (IL)-1β and IL-6 levels. Treatment of PD rats with bacoside-A effectively reduced levels of tumor necrosis factor (TNF)-α, NF-κB p65, (COX)-2 and p53 protein, and also reversed up-regulations of Bax, cytochrome C, caspase-3 and caspase-9.Conclusion: Bacoside-A exhibits a protective effect against Parkinson disease-induced oxidative damage and neuronal degeneration in rats through downregulation of iNOS, AChE, inflammatory cytokines and pro-apoptotic proteins. Therefore, bacoside-A has potentials for use in the management of Parkinson disease. Keywords: Parkinson disease, Neuroprotective, Pro-apoptotic, Cytokines, Neurotoxicit

Collapse and reappearance of magnetic orderings in spin frustrated TbMnO3 induced by Fe substitution

We studied the temperature dependent magnetic phase evolution in spin frustrated TbMnO3 affected by Fe doping via powder neutron diffraction. With the introduction of Fe (10% and 20%), the long range incommensurate magnetic orderings collapse. When the Fe content is increased to 30%, a long-range antiferromagnetic ordering develops, while a spin reorientation transition is found near 35 K from a canted G-type antiferromagnetic ordering to a collinear G-type antiferromagnetic ordering. This work demonstrates the complex magnetic interactions existing in transition metal oxides, which helps to understand the frustrated spin states in other similar systems and design magnetic materials as well

Experience and Lessons Learned in the Treatment of Transforming Small Cell Neuroendocrine Carcinoma of the Prostate: A Case Report and Literature Review

Introduction: Small cell neuroendocrine carcinoma of the prostate (SCNECP) is a rare and highly malignant tumor that commonly transforms into conventional prostate adenocarcinoma (CPAC). Most of SCNECP cases cannot be detected and diagnosed early, and SCNECP is often diagnosed when there is liver and lung metastasis. Therefore, the early detection of the process from CPAC to SCNECP is crucial. Case Report: We present a case of a 73-year-old man who was initially admitted to our hospital with metastatic CPAC. He was administered goserelin acetate 3.6 mg combined with bicalutamide tablets (50 mg) once daily for endocrine therapy and docetaxel (100 mg) combined with prednisone (5 mg) twice a day. After treatment, the prostate-specific antigen (PSA) level decreased significantly, but the CEA, CA199, and CA125 levels began to increase progressively after a short decline. However, no solid tumor recurrence was observed in multiple reexaminations. It was not until 9 months after the elevation of tumor markers that multiple metastatic lesions appeared in the liver, which finally confirmed the diagnosis of metastatic SCNECP. After chemotherapy with etoposide 360 mg combined with carboplatin 200 mg, the tumor size was significantly reduced, and tumor markers decreased. However, the remission time was only 3 months. The patient’s liver metastases continued to grow, and CEA, CA199, and CA125 levels continued to increase. Conclusion: During CPAC treatment, PSA levels continued to decrease, whereas CEA, CA199, and CA125 levels continued to increase. This suggests the possibility of the transformation of CPAC into SCNECP