MBE growth, fabrication, and electrical characterisation of terahertz frequency quantum cascade lasers

The terahertz (THz) range in the electromagnetic radiation spectrum lies between the high-frequency edge of the microwave band and the long-wavelength edge of the far-infrared band. THz technology is important for both scientific and commercial applications so the production of coherent, high power sources operating at room temperature is of great interest. Quantum cascade lasers (QCLs) are unipolar emitters operating from THz to infrared range. Molecular beam epitaxy (MBE) is the main technique for the growth of THz QCLs, offering precise control of layer thickness and composition under ultra-high vacuum conditions. The output power, maximum operating temperature, threshold and dynamic range are essential parameters in THz QCL performances. Since high power in THz QCLs is a desirable performance in particular to areas such as imaging and remote sensing. The threshold and dynamic ranges are influenced by the injector doping levels determining the losses. Moreover, the interface roughness affects the electrical and optical properties of semiconductor devices, which can be improved by misorientation of (100) GaAs substrates. This thesis reviews the development of THz QCLs, investigates MBE growth, fabrication and electrical characterisation process, and the enhancement of THz QCL performances. Chapter 1 summarizes the development and application of THz technology, different THz sources, as well as the development of THz QCLs. Chapter 2 outlines the MBE system, and investigates the calibration methods, the growth process, and growth reproducibility. Chapter 3 explains the fabrication techniques, electrical characterisation of THz QCLs, and the factors that influence the device performance. Chapter 4 investigates the enhancement in THz QCL power performance; whilst Chapter 5 probes the injector doping effects and background impurity level influences on BTC and hybrid THz QCL performance. In Chapter 6, the effects and possible significance of misorientation on THz QCLs are discussed. Chapter 7 concludes the thesis and suggests future directions

Decentralized Multi-Armed Bandit Can Outperform Classic Upper Confidence Bound

This paper studies a decentralized multi-armed bandit problem in a multi-agent network. The problem is simultaneously solved by N agents assuming they face a common set of M arms and share the same mean of each arm's reward. Each agent can receive information only from its neighbors, where the neighbor relations among the agents are described by a directed graph whose vertices represent agents and whose directed edges depict neighbor relations. A fully decentralized multi-armed bandit algorithm is proposed for each agent, which twists the classic consensus algorithm and upper confidence bound (UCB) algorithm. It is shown that the algorithm guarantees each agent to achieve a better logarithmic asymptotic regret than the classic UCB provided the neighbor graph is strongly connected. The regret can be further improved if the neighbor graph is undirected

Passive Integrated Sensing and Communication Scheme based on RF Fingerprint Information Extraction for Cell-Free RAN

This paper investigates how to achieve integrated sensing and communication (ISAC) based on a cell-free radio access network (CF-RAN) architecture with a minimum footprint of communication resources. We propose a new passive sensing scheme. The scheme is based on the radio frequency (RF) fingerprint learning of the RF radio unit (RRU) to build an RF fingerprint library of RRUs. The source RRU is identified by comparing the RF fingerprints carried by the signal at the receiver side. The receiver extracts the channel parameters from the signal and estimates the channel environment, thus locating the reflectors in the environment. The proposed scheme can effectively solve the problem of interference between signals in the same time-frequency domain but in different spatial domains when multiple RRUs jointly serve users in CF-RAN architecture. Simulation results show that the proposed passive ISAC scheme can effectively detect reflector location information in the environment without degrading the communication performance.Comment: 11 pages, 6 figures, submitted on 28-Feb-2023, China Communication, Accepted on 14-Sep-202

Macrophage‐derived apoptotic bodies promote the proliferation of the recipient cells via shuttling microRNA‐221/222

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141103/1/jlb1349.pd

Quality of life and its contributors among adults with late-onset Pompe disease in China.

BACKGROUND: Pompe disease (PD) is a rare inherited disorder caused by the deficiency of acid-α glucosidase, which leads to the impairment of organ and tissue functions and causes disabilities. As the first national survey on patients with late-onset PD (LOPD) in China, this study investigated the quality of life (QOL) of adult patients with LOPD in China and explored its contributors. METHODS: Data were derived from a nation-based, cross-sectional, self-response survey on rare diseases (RDs) in early 2018. Answers from 68 adult Chinese patients with LOPD were used for data analysis. QOL was measured using the World Health Organization Quality of Life: Brief Version. Covariates included age, gender, education, employment, reliance on assistive devices, medication history, social support, and disease economic burden. Data were analyzed using linear regression in R. RESULTS: For adult patients with LOPD, the average scores and standard deviations (SD) of the four dimensions of QOL were physical health = 33.77 (SD = 18.28), psychological health = 43.81 (SD = 21.70), environmental health = 39.43 (SD = 16.93), and social relationship = 46.20 (SD = 19.76); the scoring for each dimension was evaluated on a scale of 0 to 100. At the significance level of p < 0.05, with increasing age, the patients experienced a significant decrease in physical health QOL (β = - 0.75) and environmental health QOL (β = - 0.79). Those who relied heavily on assistive devices had lower perceived physical health (β = - 17.8), psychological health (β = - 22.76), environmental health (β = - 17.8), and social relationships (β = - 22.12) than those who did not. A one-unit increase in the amount of social support, as a form of social interaction, led to a significant increase in physical health (β = 0.28), psychological health (β = 0.71), environmental health (β = 0.72), and social relationships (β = 0.70). CONCLUSION: Adult Chinese patients with LOPD had a lower physical health and QOL compared to their counterparts with other RDs. Being employed was found to affect the QOL of adult Chinese patients with LOPD in almost all dimensions. Encouraging adult Chinese patients with LOPD to be socially active and help them become more involved in social life might improve their QOL