Nanoscale structures for tunable and low-loss resonators

Light manipulation at the nanoscale, which is known as nanophotonics, has attracted enormous attention. Particularly, metallic nano-resonators, which support localized surface plasmons, have been under intense study. The potential applications of metallic nano-resonators include surface-enhanced spectroscopy, plasmon-enhanced solar energy harvesting, ultra-thin optical components, etc. However, two issues that hinder their applications in real life have long been identified. On the one hand, the optical response lacks tunability once the nano-resonators are fabricated. On the other hand, the large Ohmic losses inherent in noble metals severely limit their performance. In this thesis, these two issues are investigated through both numerical and experimental studies. In the first part, phase-change material Ge2Sb2Te5 (GST) is introduced to add tunability to the nano-resonators. GST has a large refractive index contrast between its amorphous and crystalline phases. In this research, it is used as a tunable dielectric environment for the resonators, achieving significant shifts of the resonances. Practical applications, such as hotspot manipulation and phase-front engineering, are studied in detail. In the second part, nano-resonators made of polar crystals (4H-SiC and hexagonal-BN) that support phonon polaritons are investigated. Due to the absence of free charge carriers, Ohmic losses are greatly reduced in these materials. The field enhancements and quality factors of the corresponding resonators are therefore found to be much larger than their plasmonic counterparts. Further analyses of the near-field distributions reveal the natures of the resonances, providing fundamental knowledge for future nanophotonic designs based on phonon polaritons.Open Acces

NANOSCALE STRUCTURES FOR TUNABLE AND LOW-LOSS RESONATORS

Ph.DNUS-ICL JOINT PH.D. (FoE

Integrated prediction of green bond return under the dual risks of climate change and energy crisis

Prediction of bond return is a classic problem in financial area, providing an important basis for portfolio construction and risk management. The sustainable investment attribute of green bonds has been favored by investors, so that green bonds have become an important component for major asset allocation. However, due to the specific investment focus of green bonds, investors’ return expectations are influenced not only by traditional corporate bond factors, but also by related factors such as climate change and energy transition. Against the backdrop of increasingly severe climate risks and the global energy crisis, this paper analyses the volatility characteristics of China’s green bonds at multiple time scales, and introduces exogenous variables such as returns of the alternative financial assets, climate risks and returns of energy markets for prediction. Based on the LSTM model, the volatility of green bond yield at different time scales is separately predicted using optimal exogenous variable before integration. It is found that the new integrated prediction model can significantly improve the forecasting performance compared to traditional single LSTM models and simple decomposition-integrated models. Further, both climate risks and energy markets variables have a significant improvement effect on predicting green bond in low-frequency item, while energy markets variables also have a better predictive effect on trend items. Building on the use of only LSTM model, it could be further enhanced by integrating more algorithms to select the best single model for each component, further improve the prediction accuracy and provide a more effective quantitative tool for investment decision-making and risk management in related fields

Effect of electronic stimulation at Neiguan (PC 6) acupoint on gene expression of adenosine triphosphate-sensitive potassium channel and protein kinases in rats with myocardial ischemia

AbstractObjectiveTo investigate the effects of electronic stimulation at acupoints Neiguan (PC 6) and Lieque (LU 7) on the gene expression of the adenosine triphosphate (ATP)-Sensitive potassium channel (KATP: Kir6.1, Kir6.2, SUR2A, and SUR2B) and protein kinases (PKA, PKG, and PKCβ2) in myocardial cells of rats with myocardial ischemia (MI) induced by isoproterenol (ISO).MethodsRats were randomly divided into a control, model, Neiguan (PC 6), Lieque (LU 7), and non-acupoint groups. The MI model was established by injecting rats with ISO. Electro-acupuncture treatment was given to the acupuncture groups, once a day for 7 days. Gene expression was analyzed with real-time PCR.ResultsThe gene expression of KATP and protein kinases in the model group was higher than those in the control group (P < 0.05). After acupuncture treatment, the KATP and protein kinase expression levels were significantly lower in the Neiguan (PC 6) and Lieque (LU 7) groups compared with the model group (P < 0.05). The Neiguan (PC 6) group lowered these levels significantly more than that of the Lieque (LU 7) group (P < 0.05). No significant differences were observed between the model and non-acupoint groups (P > 0.05).ConclusionOur findings suggest that electronic needling of Neiguan (PC 6) can both reduce the gene expression of KATP and protein kinases in rats with ISO-induced MI

Resonant enhancement of second harmonic generation in the mid-infrared using localized surface phonon polaritons in sub-diffractional nanostructures

We report on strong enhancement of mid-infrared second harmonic generation (SHG) from SiC nanopillars due to the resonant excitation of localized surface phonon-polaritons within the Reststrahlen band. The magnitude of the SHG peak at the monopole mode experiences a strong dependence on the resonant frequency beyond that described by the field localization degree and the dispersion of linear and nonlinear-optical SiC properties. Comparing the results for the identical nanostructures made of 4H and 6H SiC polytypes, we demonstrate the interplay of localized surface phonon polaritons with zone-folded weak phonon modes of the anisotropic crystal. Tuning the monopole mode in and out of the region where the zone-folded phonon is excited in 6H-SiC, we observe a prominent increase of the already monopole-enhanced SHG output when the two modes are coupled. Envisioning this interplay as one of the showcase features of mid-infrared nonlinear nanophononics, we discuss its prospects for the effective engineering of nonlinear-optical materials with desired properties in the infrared spectral range.Comment: 16 pages, 3 figure

CO2 emissions converge in China and G7 countries? Further evidence from Fourier quantile unit root test

G7 countries and China are considered not only the biggest energy producers globally but also the largest CO2 emission groups of countries among the world. In this study, we apply the Fourier quantile unit root test to investigate whether CO2 emissions converge in China and G7 countries using per capita CO2 emissions data over 1950–2013. While traditional unit root test results indicate that per capita CO2 emissions do not converge among these G7 countries and China, empirical results from the Fourier quantile unit root test point out that the CO2 emissions did converge in Germany, Italy, and the United Kingdom. Although the results of this study do not find strong CO2 emission convergence in the other five countries (i.e., Canada, France, Japan, the United States, and China), the CO2 emissions did converge in certain quantiles for these five countries. Our empirical results have important policy implications for the governments of G7 countries and China to implement the effective energy policy to reduce the CO2 emissions.MOE (Ministry of Education in China) Youth Foundation Project of Humanities and Social Sciences and by HSTSPC (Hubei Science and Technology Support Program in China) Soft Science.https://journals.sagepub.com/home/eaehj2020Economic

Better synoptic and subseasonal sea ice thickness predictions are urgently required: a lesson learned from the YOPP data validation

In the context of global warming, Arctic sea ice has declined substantially during the satellite era (Kwok 2018). The retreating and thinning of Arctic sea ice provide opportunities for human activities in the Arctic, such as tourism, fisheries, shipping, natural resource exploitation, and wildlife management; however, new risks emerge. To ensure the safety and emergency management of human activities in the Arctic, reliable Arctic sea ice prediction is essential

Circular RNA circNOL10 Inhibits Lung Cancer Development by Promoting SCLM1-Mediated Transcriptional Regulation of the Humanin Polypeptide Family

circNOL10 is a circular RNA expressed at low levels in lung cancer, though its functions in lung cancer remain unknown. Here, the function and molecular mechanism of circNOL10 in lung cancer development are investigated using in vitro and in vivo studies, and it is shown that circNOL10 significantly inhibits the development of lung cancer and that circNOL10 expression is co‐regulated by methylation of its parental gene Pre‐NOL10 and by splicing factor epithelial splicing regulatory protein 1 (ESRP1). circNOL10 promotes the expression of transcription factor sex comb on midleg‐like 1 (SCML1) by inhibiting transcription factor ubiquitination and thus also affects regulation of the humanin (HN) polypeptide family by SCML1. circNOL10 also affects mitochondrial function through regulating the humanin polypeptide family and affecting multiple signaling pathways, ultimately inhibiting cell proliferation and cell cycle progression, and promoting the apoptosis of lung cancer cells, thereby inhibiting lung cancer development. This study investigates the functions and molecular mechanisms of circNOL10 in the development of lung cancer and reveals its involvement in the transcriptional regulation of the HN polypeptide family by SCML1. The results also demonstrate the inhibitory effect of HN on lung cancer cells growth. These findings may identify novel targets for the molecular therapy of lung cancer

Mobile Flowering Locus T RNA – Biological Relevance and Biotechnological Potential

Many systemically mobile mRNAs have been revealed in phloem. However, very few of them have been found to be of clear signaling functions. One of such rare examples is the mobile Flowering locus T (FT) mRNA despite the continuous debate about its mobility and biological relevance to the control of flowering time in plants. Nevertheless, accumulating evidence supports the notion of the long-distance movement of FT mRNA from leaf to shoot apex meristem and its role in flowering. In this review, we discuss the discovery of florigenic FT, the initial debate on long-distance movement of FT mRNA, emerging evidence to prove its mobility, and the use of mobile FT mRNA to generate heritable transgenerational gene editing in plants. We elaborate on evidence from virus-based RNA mobility assay, plant grafting, RNA with fluorescent protein labeling, and CRISPR/Cas9 gene-editing technology, to demonstrate that the FT mRNA besides the FT protein can move systemically and function as an integral component of the florigenic signal in flowering. We also propose a model to prompt further research on the molecular mechanism underlying the long-distance movement of this important mobile signaling RNA in plants