Edwardsiella ictaluri causes enteric septicemia of catfish (ESC), which is one of the most important bacterial diseases causing significant economic losses in the US catfish industry. Understanding the virulence mechanisms of E. ictaluri plays a vital role to develop preventives, such as vaccines for the disease. Therefore, further research is necessary to discover the new virulence mechanisms of this pathogen. The long-term goal of our group is to determine the mechanism of E. ictaluri pathogenesis and to develop effective live attenuated vaccines against ESC. The overall goal of this project is to understand the role of Type 6 secretion system (T6SS) in E. ictaluri virulence and determine the safety and efficacy of T6SS mutants in the catfish host. The central hypothesis is that T6SS in E. ictaluri provide an ability to invade the host cells and survive inside of the channel catfish neutrophils and macrophages, and mutation of T6SS genes will cause attenuation of the bacterial virulence. The rationale for the proposed research is that characterization of the T6SS in E. ictaluri will enlighten its role in E. ictaluri virulence, and T6SS genes can be targeted to develop live attenuated vaccines. In this study, we first constructed mutants of individual T6SS genes and a double mutant. The persistence, virulence, and vaccine efficacy of T6SS mutants were determined in the catfish fingerlings and fry infection model. The T6SS mutants Ei?evpC, Ei?evpC?hcp2, Ei?evpD, Ei?evpE, Ei?evpG, Ei?evpJ, and Ei?evpK were significantly attenuated and provided better protection against E. ictaluri 93-146 in channel catfish fingerlings. The role of T6SS mutants in adhesion and invasion of in vitro catfish epithelial indicated that Ei?evpN, Ei?evpO, and Ei?evpP significantly were less adherent and invasive. The survival and replication of T6SS mutants in in vitro catfish peritoneal macrophages cell line showed that T6SS mutants could survive up to 6 hours after phagocyted by catfish macrophages. The survival and resistance of T6SS mutants to stress conditions present in macrophages phagosome showed that hydrogen peroxide could limit the growth of T6SS mutants in BHI and minimal medium. Ei?evpA, Ei?evpH, Ei?evpM, Ei?evpN, and Ei?evpO exhibited a significant growth decrease.

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Yes / An assessment of the performance of OFDM transmissions over the wideband mobile radio channel is reported. The simulation in MATLAB /Simulink is based on the CODIT channel model. The results show that BER deteriorates significantly as the mobile velocities increase from 0 to 30 m/s. Significant variability in the BER for a given channel type is quantified. For a given instance of the channel the standard deviation of the estimated BER is 20%, but when averaged over many separate instances of the same channel type, a standard deviation of 47% is found.

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<p> Wireless optical communication systems have the potential of establishing secure high data rate communication links. In order to realize the ultimate promise of these links, channel modeling and communication algorithms must be developed. This thesis addresses free-space optical (FSO) system design and provides novel contributions in four major areas: 1) channel modeling, 2) channel capacity and optimal signal design, 3) signaling algorithms, and 4) formal methods to jointly design code rate and beamwidth for FSO systems.</p> <p> A novel statistical channel model taking into account atmospheric and misalignment fading is developed that generalizes the existing models and accounts for transmitter beamwidth. The channel capacity is analyzed under average and peak optical power constraints and a new class of non-uniform discrete input distributions are developed with mutual information that closely approaches the channel capacity. Algorithms to realize the proposed non-uniform signaling and achieve the promising rates are also presented. Numerical simulations are conducted with finite length low density parity check codes showing significant improvement in system performance. Finally, the developed signaling is applied to FSO channels considering the above impairments. Beamwidth optimization is considered to maximize the channel capacity subject to outage. It is shown that a rate gain of 80% can be achieved with beamwidth optimization.</p> / Thesis / Doctor of Philosophy (PhD)

<p> This thesis deals with the analytical and experimental study of buckling strength, of thin walled channel struts, of different geometrical dimensions. The influence of the dimensions of the columns on the buckling strength has been studied.</p> <p> The experimental work consisted of testing different channels of thin sheeting to failure. Comparison has been made with the previous work done and a comparison is made between the theoretical predicted values and the experimental results. The Appendix includes detailed mathematical procedure and matrices formulations.</p> / Thesis / Master of Engineering (MEngr)

The prevalence of side-channel attacks exploiting hardware vulnerabilities leads to the exfil- tration of secretive data such as secret keys, which poses a significant threat to the security of modern processors. The RISC-V BOOM core is an open-source modern processor design widely utilized in research and industry. It enables experimentation with microarchitec- tures and memory hierarchies for optimized performance in various workloads. The RISC-V BOOM core finds application in the IoT and Embedded systems sector, where addressing side-channel attacks becomes crucial due to the significant emphasis on security. While prior studies on BOOM mainly focus on the side channel in the memory hierarchy such as caches or physical attacks such as power side channel. Recently, the front-end of microprocessors, which is responsible for fetching and decoding instructions, is found to be another potential source of side-channel attacks on Intel Processors. In this study, I present four timing-based side-channel attacks that leverage components in the front-end of BOOM. I tested the effectiveness of the attacks using a simulator and Xilinx VCU118 FPGA board. Finally, I provided possible mitigation techniques for these types of attacks to improve the overall security of modern processors. Our findings underscore the importance of identifying and addressing vulnerabilities in the front-end of modern pro- cessors, such as the BOOM core, to mitigate the risk of side-channel attacks and enhance system security. / Master of Science / In today's digital landscape, the security of modern processors is threatened by the increasing prevalence of side-channel attacks that exploit hardware vulnerabilities. These attacks are a type of security threat that allows attackers to extract sensitive information from computer systems by analyzing the physical behavior. The risk of such attacks is further amplified when multiple users or applications share the same hardware resources. Attackers can ex- ploit the interactions and dependencies among shared resources to gather information and compromise the integrity and confidentiality of critical data. The RISC-V BOOM core, a widely utilized modern processor design, is not immune to these side-channel attacks. This issue demands urgent attention, especially considering its deploy- ment in data-sensitive domains such as IoT and embedded systems. Previous studies have focused on side-channel vulnerabilities in other areas of BOOM, ne- glecting the front-end. However, the front-end, responsible for processing initial information, has recently emerged as another potential target for side-channel attacks. To address this, I conducted a study on the vulnerability of the RISC-V BOOM core's front-end. By conduct- ing tests using both a software-based simulator and a physical board, I uncovered potential security threats and discussed potential techniques to mitigate these risks, thereby enhanc- ing the overall security of modern processors. These findings underscore the significance of addressing vulnerabilities in the front-end of processors to prevent side-channel attacks and safeguard against potential malicious activities.

Bakgrund: Med digital utveckling ökar användandet av digitala kanaler för att köpa produkter. Utvecklingen sätter ökad press på handeln att utveckla sitt digitala erbjudande. Problemformulering: Förutsättningarna att driva handel skiljer sig åt online jämfört med offline, sett både ur perspektiv från återförsäljare och köpare. Begränsad yta i en fysisk butik i närområdet jämfört med stort centralt lager för e-handel ger olika förutsättningar för vilka produkter som kan erbjudas. Konsumenten med tillgång till näst intill oändligt antal affärer digitalt med enkel jämförelse av pris och produkter. Syfte: Syftet med denna uppsats är att undersöka hur försäljningskoncentrationen av produkter i dagligvaruhandeln i Sverige skiljer sig mellan e-handel och fysisk butik. Forskningsfrågor: Hur fördelas försäljningen av produkter online jämfört med fysisk butik?  Är försäljningen i fysisk butik mer koncentrerad till färre produkter jämfört med online handel? Teori: Både longtail-fenomenet och paretoprincipen existerar praktiskt och litterärt, men det beror på vilken typ av produkt, period och marknad det gäller om begreppen är sanna eller inte. Metod: Kvantitativ metod med primärdata från dagligvaruhandeln där 2 585 produkters försäljning online och offline analyserats med en kombination av RStudio och Microsoft Excel. Slutsatser: Försäljningen är mer koncentrerad till ett lägre antal produkter online jämfört med offline. Det finns dock variationer mellan produktkategorier. Nyckelord: Longtail, pareto, superstars, dagligvaror, e-handel, omni-channel, multi-channel, försäljningskoncentration. / Background: Digital development has increased the use of digital channels to buy products. This development puts increased pressure on the retail sector to enhance its digital offerings. Problem statement: The conditions for buying and selling products differ online compared to offline for both the buyer and seller. Limited space in a physical store in the local area compared to a large central warehouse for e-commerce. Consumers have access to nearly an infinite number of digital stores with easy comparisons of prices and products. Purpose: The purpose of this thesis is to examine how the sales concentration of products in the grocery retail sector in Sweden differs between e-commerce and physical stores. Research questions: How does the distribution of product sales differ online compared to physical stores? Is the sales concentration in physical stores more focused to fewer products compared to e-commerce? Theory: Both the longtail phenomenon and the Pareto principle exist practically and literarily, but their validity depends on the type of product, period, and market in question. Method: Quantitative method using primary data from the grocery retail sector, where the sales of 2 585 products online and offline have been analyzed using a combination of RStudio and Microsoft Excel. Conclusions: Sales are more concentrated to fewer products online compared to offline, there are however variations between product categories. Keywords: Long tail, Pareto, superstars, grocery, e-commerce, omni-channel, multi-channel, sales concentration.

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No description available.