Iskanje po katalogu digitalne knjižnice

Opis: This dissertation introduces a novel off-chain channel model aimed at enhancing existing solutions to address scalability challenges in blockchain technology. It begins with an overview of the problem statement, research objectives, methodology, and potential limitations before establishing a thesis and hypotheses. A comprehensive theoretical background on blockchain technology, scalability solutions, and the off-chain channel approach ensures a common understanding of the topic. To provide a thorough overview of existing off-chain channel solutions and identify and categorize their limitations, we conducted a systematic literature review, identifying 65 relevant studies. Through detailed analysis, six categories of solutions and six implemented off-chain channel solutions were identified. Five primary categories of limitations were also identified: routing, flexibility, privacy, network properties, and online assumptions, some with sub-limitations. To address these limitations, a new off-chain channel model, named ”Off-chain Channel as a Service,” is proposed, featuring four core design decisions: eliminating the need for an off-chain channel network, assuming blockchain properties by design, introducing a trustworthy service, and enabling flexibility by design. Validation and evaluation of the proposed model employ case-study and experiment research methods to confirm compliance with off-chain channel principles, validate it against identified limitations of existing solutions, analyze its impact on blockchain scalability, and assess its applicability across blockchain platforms. For this purpose, two off-chain payment channel prototype solutions have been implemented, each using a different underlying blockchain platform, namely Ethereum and Solana. Moreover, the proposed model’s security evaluation using risk-analysis methodology is also provided. Qualitative and quantitative analysis demonstrates that the proposed off-chain channel model adheres to off-chain channel principles, improves most identified limitations of existing solutions, positively impacts blockchain scalability, and can be applied to different blockchain platforms supported by smart contracts.
Ključne besede: blockchain, distributed ledger technology, smart contracts, scalability, off-chain channel, payment channel
Objavljeno v DKUM: 01.10.2024; Ogledov: 0; Prenosov: 26
Celotno besedilo (3,87 MB)

Opis: Ultra-wideband is becoming a key technological element in the consumer industry, providing a safe and reliable way to enable more precise location services as well as secure access to a multitude of systems. Ultra-wideband radar is a subset of that technology, providing not only device-free localization techniques but also complementing expensive medical-level devices or providing means to measure vital signs in a more accessible way. Ultra-wideband radars embedded in smart devices like smartphones can be used for presence detection, gesture recognition, and vital sign monitoring (i.e., breathing detection and heart rate monitoring). Ultra-wideband radar is still in development, and during that process it needs to be well-tested to match the customers’ expectations and standards that apply to the technology. In this master’s thesis, we start by providing a brief overview of ultra-wideband technology. Then we propose and develop an automated measurement system for UWB radar that tests the radio frequency functionality of a radar device, its compliance with standards, frequency regulations, and use-case testing. Performing measurements to test the aforementioned radar devices is a time-consuming and cumbersome task that can be replaced by our developed automated measurement system. We demonstrate the advantages in terms of reduced measurement time and improved test reproducibility, resulting in a well-tested ultra-wideband radar device during the development cycle.
Ključne besede: automated system, channel impulse response, IR-UWB, radar
Objavljeno v DKUM: 17.02.2022; Ogledov: 1094; Prenosov: 5
Celotno besedilo (4,50 MB)

Opis: The hERG potassium channel is essential for repolarization of the cardiac action potential. Due to this vital function, absence of unintended and potentially life-threatening interactions with hERG is required for approval of new drugs. The structure of hERG is therefore one of the most sought-after. To provide purified hERG for structural studies and new hERG biomimetic platforms for detection of undesirable interactions, we have developed a hERG expression platform generating unprecedented amounts of purified and functional hERG channels. Full-length hERG, with or without a C-terminally fused green fluorescent protein (GFP) His 8-tag was produced from a codon-optimized hERG cDNA in Saccharomyces cerevisiae. Both constructs complemented the high potassium requirement of a knock-out Saccharomyces cerevisiae strain, indicating correct tetramer assembly in vivo. Functionality was further demonstrated by Astemizole binding to membrane embedded hERG-GFP-His 8 with a stoichiometry corresponding to tetramer assembly. The 156 kDa hERG-GFP protein accumulated to a membrane density of 1.6%. Fluorescence size exclusion chromatography of hERG-GFP-His 8 solubilized in Fos-Choline-12 supplemented with cholesteryl-hemisuccinate and Astemizole resulted in a monodisperse elution profile demonstrating a high quality of the hERG channels. hERG-GFP-His 8 purified by Ni-affinity chromatography maintained the ability to bind Astemizole with the correct stoichiometry indicating that the native, tetrameric structure was preserved. To our knowledge this is the first reported high-yield production and purification of full length, tetrameric and functional hERG. This significant breakthrough will be paramount in obtaining hERG crystal structures, and in establishment of new high-throughput hERG drug safety screening assays.
Ključne besede: potassium channel, membrane protein production, functional expression, cardiac action potential
Objavljeno v DKUM: 29.06.2017; Ogledov: 1508; Prenosov: 348
Celotno besedilo (2,85 MB)
Gradivo ima več datotek! Več...

Opis: We investigated the changes in muscle fiber conduction velocity, recruitment and derecruitment thresholds, and discharge rate of low-threshold motor units during a series of ramp contractions. The aim was to compare the adjustments in motor unit activity relative to the duration that each motor unit was active during the task. Multichannel surface electromyographic (EMG) signals were recorded from the abductor pollicis brevis muscle of eight healthy men during 12-s contractions (n = 25) in which the force increased and decreased linearly from 0 to 10% of the maximum. The maximal force exhibited a modest decline (8.5 +- 9.3%; P < 0.05) at the end of the task. The discharge times of 73 motor units that were active for 16-98% of the time during the first five contractions were identified throughout the task by decomposition of the EMG signals. Action potential conduction velocity decreased during the task by a greater amount for motor units that were initially active for >70% of the time compared with that of less active motor units. Moreover, recruitment and derecruitment thresholds increased for these most active motor units, whereas the thresholds decreased for the less active motor units. Another 18 motor units were recruited at an average of 171 +- 32 s after the beginning of the task. The recruitment and derecruitment thresholds of these units decreased during the task, but muscle fiber conduction velocity did not change. These results indicate that low-threshold motor units exhibit individual adjustments in muscle fiber conduction velocity and motor neuron activation that depended on the relative duration of activity during intermittent contractions.
Ključne besede: electromyography, surface electromyography, multi-channel EMG, motor units, decompostion, recruitment treshold, derecruitment treshold_
Objavljeno v DKUM: 01.06.2012; Ogledov: 1982; Prenosov: 283
Povezava na celotno besedilo