Physics

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Browsing Physics by Author "Khain, Evgeniy"

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    Neuromorphic Computing with Antiferromagnetic Artificial Neurons
    (2024-01-01) Bradley, Hannah D; Tyberkevych, Vasyl; Tyberkevych, Vasyl; Slavin, Andrei; Khain, Evgeniy; Bozhko, Dmytro
    The increasing focus on Artificial Intelligence (AI) presents notable challenges, especially in the power requirements essential for training AI models. Consequently, there is a growing emphasis on neuromorphic computing, which aims to construct Artificial Neural Networks (ANNs) from artificial neurons to replicate the speed and efficiency of the human brain. With their significantly lower power consumption, spintronic devices acting as artificial neurons offer the potential for ANNs that rival conventional components. This innovative approach not only tackles the energy efficiency challenges but also paves the way for advancements in neuromorphic computing by integrating magnetic materials and spin-dependent effects. Antiferromagnetic (AFM) materials, characterized by their inherent THz frequencies, provide a unique opportunity for spintronic devices with ultra-fast dynamics. There's a proposal to utilize AFM materials to craft ultra-fast spin-Hall oscillators. These oscillators emit spiking signals resembling those of biological neurons, indicating their potential as artificial neurons. AFM oscillators exhibit exceptionally fast characteristics, including picosecond-scale spike widths and unique features absent in conventional artificial neuron models. This research examines the utilization of AFM oscillators as artificial neurons and their significance in the realm of neuromorphic computing. This dissertation begins with a comprehensive overview of relevant topics, covering the principles of spintronics, AFM materials, and neuromorphic computing. It examines the unique dynamics of AFM neurons, such as response latency and refraction time, which arise from an effective internal inertia. Then, it explores innovative AFM neuron circuits that exhibit functionalities unattainable by conventional artificial neurons, such as non-monotonic inhibition. Additionally, conventional learning algorithms like backpropagation are use to train AFM ANNs for pattern recognition. Finally, it leverages the similarities between AFM and biological neurons to model the biological neural network responsible for the withdrawal reflex. With their simplistic design and high speeds, AFM neurons exhibit energy efficiencies several orders of magnitude higher than traditional artificial neurons and even other spintronic designs. This suggests that AFM ANNs will excel at training AI models while addressing the energy crisis impeding technological progress. As a result, AFM neurons drive forward the progress of spintronic neuromorphic computing, providing a promising alternative for future technological development
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    Structural Characteristics of Articular Cartilage in the Early Detection of Post-Traumatic Osteoarthritis by Microscopic Imaging Techniques
    (2023-01-01) Mantebea, Hannah; Xia, Yang; Roth, Bradley j; Khain, Evgeniy; Surdutovic, Eugene; Quan, Jiang
    Cartilage is a specialized form of connective tissue that provides support and cushioning to adjacent tissues in the body. Cartilage is of three types: Hyaline, fibrocartilage, and elastic. The articular cartilage is a hyaline type and is the most found throughout the animal and human bodies. Articular cartilage is composed of a dense extracellular matrix (ECM) with specialized cells, and chondrocytes, which are sparsely distributed. The ECM is primarily made up of collagen, proteoglycan, water, non-collagenous proteins, and glycoproteins. The components of the ECM are subject to change in the disease state, especially in osteoarthritis. As a result of the complex and unique nature of the articular cartilage, early detection, treatment, and repair pose a challenge in clinic. Imaging techniques such as magnetic resonance imaging (MRI) has been used in the noninvasive evaluation of the cartilage structure, and polarized light microscopy (PLM) allows the examination of the molecular organization at optical resolution.The first project in this dissertation aimed to study the structural characteristics of the articular cartilage in the patella and the fibrocartilage of the suprapatella in the knee joint. This was achieved quantitatively using µMRI and PLM at both low and high resolutions. The second project in this dissertation aimed to compare the structures between the immature and mature articular cartilage of the femur and humerus qualitatively and quantitatively using µMRI and PLM. The third project in this dissertation was aimed at the structural characteristics of the articular cartilage in the disease state. Specifically qualitative and quantitative characteristics from traumatized joints (post-traumatic osteoarthritis) were studied using µMRI and PLM at high resolutions. These studies confirmed the ability of µMRI and PLM to examine the cartilage structure quantitatively and qualitatively in a healthy state and in a diseased state. The ability to study the microscopic anatomy of cartilage and pathology (osteoarthritis) in the early stage will contribute to the treatment and early diagnosis of arthritis.