In this paper, a cooperative underwater multi-channel MAC (CUMAC) protocol has been proposed with both delay mapping and channel allocation assessment in order to improve network performance and handle triple hidden terminal (THT) problems in underwater sensor networks. A novel channel allocation matrix (CAM) was developed for estimating propagation delay and increasing utilization of channel. In the proposed scheme, every node maintains a database for delay mapping, based on which the sender runs a scheduling algorithm prior to transmitting any data. This delay mapping database assists a node in predicting packet collision probability. The overall objectives are—first, to increase the rate of successful transmission through mitigation of THT problems in multi-channel underwater sensor networks; and second, to increase channel utilization leveraging the database of delay mapping and channel allocation assessment. Results from performance evaluation demonstrate the efficiency of the proposed CUMAC-CAM protocol in terms of packet delivery ratio, energy consumption, end-to-end delay, network throughput, collision probability, packet loss ratio and fairness index compared to the contemporary CUMAC protocol and RTS/CTS based multi-channel MAC protocols.

The tremendous spreading of multimedia via Internet motivates the watermarking as a new promising technology for copyright protection. This work is concerned with the design and development of novel algorithms in the spatial and transform domains for robust and secure watermarking of coloured images. These algorithms are adaptive, content-dependent and compatible with the Human Visual System (HVS). The host channels have the ability to host a large information payload. Furthermore, it has enough capacity to accept multiple watermarks. Abstract This work achieves several contributions in the area of coloured images watermarking. The most challenging problem is to get a robust algorithm that can overcome geometric attacks, which is solved in this work. Also, the search for a very secure algorithm has been achieved via using double secret keys. In addition, the problem of multiple claims of ownership is solved here using an unusual approach. Furthermore, this work differentiates between terms, which are usually confusing the researchers and lead to misunderstanding in most of the previous algorithms. One of the drawbacks in most of the previous algorithms is that the watermark consists of a small numbers of bits without strict meaning. This work overcomes this weakness III in using meaningful images and text with large amounts of data. Contrary to what is found in literature, this work shows that the green-channel is better than the blue-channel to host the watermarks. A more general and comprehensive test bed besides a broad band of performance evaluation is used to fairly judge the algorithms.

Since being first reported in the late 1980ies, the Enterobacterium Edwardsiella ictaluri has rose in prevalence to become one of the two most damaging pathogens affecting the channel catfish industry. Despite this significance of the pathogen, understanding of the development of the disease, especially its route of entry into the host and the earlier stages of the infection, is still incomplete. A series of challenges were conducted using bioluminescent E. ictaluri either by infecting fish through immersion or topical application of the bacteria directly on the intact or abraded epithelium. This showed that abraded fish developed septicemia and died faster than non-abraded ones. Furthermore, results from a co-habitation challenge suggested that the bacterium induced septicemia through the skin instead of becoming water-borne. Finally, a histological technique was developed allowing the determination that the bacteria radiated from the initial skin infection site and penetrated deeper into the tissue as the challenge progressed. These results all suggest that site of abrasion on the skin can act as a route of entrance for the pathogen into the fish, a fact never previously reported. Transposon mutagenesis was also performed to construct a library of 1728 mutants. Screening of this library allowed us to identify 16 genes which inactivation lead to a decrease in the bacterium ability to colonize the epithelium or cause mortality. Sequencing of these genes allowed the identification of RstA/B, a regulator of invasion genes in Salmonella enterica Typhimurium, a putative ribonuclease, similar to a Shigella protein regulating the expression of adhesin and a protein that constitutes the second member of a newly discovered adhesin family. Finally, to investigate the development of the infection, fish were infected by bioluminescent E. ictaluri and sampled at various time points. At each time point, nine organs (gills, muscles, intestine, spleen, liver, stomach, heart, head kidney and trunk kidney) were sampled, and their bioluminescence was measured and half of these organs were homogenized, serial diluted, and plate counts determined. This allowed confirmation of a complex disease pathogenesis during ESC involving a period of intense reproduction in the spleen, anterior and posterior kidneys followed by a sharp increase in the levels of bacteria in the blood.

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