Priority Based Buffering over Multiple Lossy Links Using TCP Aware Layer Buffering

Wireless military information systems require high reliability, which is difficult to achieve in adverse conditions. To provide high reliability, one must overcome packet loss across multiple wireless hops. Buffering packets in a lossy environment is well explored; however, the ability to selectively buffer TCP traffic across multiple lossy links is a new area of research. This document seeks to explore the delivery of high priority traffic in a lossy environment and conclude that prioritized buffing can increase the probability that a high priority download will finish, where others will fail. It is shown that buffering provides six times the throughput in a network with each link experiencing 25% loss. Prioritizing TCP packet flows provides a varied outcome, as it cannot overcome the TCP mechanisms, when the packet loss recovery time is greater than the retransmission timeout event. However, the future work in chapter 6 may provide roadmap to gaining control authority of the challenged network

Some features of the upwelling off Oman

Hydrographic and ADCP data were collected in the coastal waters of Oman during the 1987 summer monsoon. The minimum surface temperatures, up to 5°C below ambient offshore values, were found close to the coast and in the vicinity of the Kuria Muria Islands. Strong surface gradients were observed near Ras al Hadd at the entrance to the Gulf of Oman where the geostrophic surface flow exceeded 1.0 m/s. The alongshore flux in the top 300 m of a region extending 100 km from the coast was estimated to be 10 × 106 m3/s. Evidence for an offshore filament of cool water was found in both current and temperature data

The influence of water motion on the growth rate of the kelp Laminaria digitata

The work described in this paper was produced as part of SuperGen Marine Energy Research Consortium II, which was funded by the UK Engineering and Physical Science Research Council (grant number EP/E040136/1).The shallow water kelp Laminaria digitata, abundant in coastal zones of the North Atlantic, is exposed to a range of hydrodynamic environments that makes it ideal for assessing the role of water motion on their growth rate. Here we quantify the growth of L. digitata, as a factor of blade and stipe elongation, at sites adjacent to Strangford Lough, Northern Ireland under different hydrodynamic conditions over a one year period. A modelling approach was used to numerically determine both the temporal and spatial variability of the hydrodynamic environment. Ambient seawater nutrient concentrations, temperature and irradiance were measured as well as the internal nutrient status of the L. digitata populations. Kelp populations growing in the greatest and lowest water motion showed the lowest growth rates. Differences observed in growth rate could not be attributed to seawater nutrient availability, temperature or light. The internal nutrient status also suggested no influence on the observed differences in growth rate. Therefore if there are minimal differences in light, temperature and nutrients between sites, then populations of L. digitata exposed to different water motions are likely to exhibit different growth rates. It is suggested that the growth rate differences observed were a function of water motion with the possibility that, in response to the hydrodynamic forces experienced by the algal cells, L. digitata kelps in the high energy environments were putting more energy into strengthening cell walls rather than blade elongation.Publisher PDFPeer reviewe

Anatomy of a Langmuir supercell event

Langmuir supercells (LS), which are Langmuir circulations (LC) extending over full water column depth during storms and revealed by high water column backscatter from surface-origin microbubbles and bottom-origin sediment, were discovered in 2003 during several months of measurements in 15 m of water near the coast of New Jersey. Both the structures themselves and the specific forcing conditions under which they occur have been documented elsewhere. This paper provides an account of the broader oceanographic setting of supercell events, focusing on conditions at the start and end. The start of events is associated with the presence of surface waves of intermediate type that “feel bottom” with amplitudes sufficiently large to resuspend sediment and achievement of three conditions for full-depth LC: an unstratified water column, La \u3c ∼0.3 and |Ra| \u3c 105, where Ra and La are dimensionless parameters derived from scaling of the wave-averaged momentum equation. Event cessation is associated with failure of one of the latter two conditions or the reappearance of stratification. There is no fixed order in which conditions necessary for full-depth LC are met or fail. Comparison with data from a deeper site off Georgia suggests that coherent full-depth Langmuir circulations will not generally be observed in unstratified water columns much deeper than 25–30 m, a depth determined primarily by the wavelength of surface waves generated by typical storms. We also document two features of LC acting in the surface layer of the stratified water column that existed prior to onset of the prototype LS event. First, LC confined to the surface layer generated first mode internal waves with frequency that of the stratified interior. Secondly, active surface layer LC did not act efficiently as direct agents of mixed layer deepening, which occurred primarily in two separate episodes of Richardson number lowered by increased shear. Instead, as a result of quasi-organized structure and enhanced vertical penetration relative to stress-driven turbulence, the primary role of LC may be to increase efficiency of momentum transfer to the surface layer, enhancing surface layer acceleration and contributing to onset of the shear instability that does deepen the surface layer

Reproductive Biology of the Brown Tree Snake, Boiga irregularis (Reptilia: Colubridae), during Colonization of Guam and Comparison with That in Their Native Range.

v. ill. 23 cm.QuarterlySince their introduction to Guam shortly after World War II, brown tree snakes, Boiga irregularis (Merrem), have seriously impacted the biota and human population of the island. Understanding the biology of this exotic species will likely be important to the success of control programs. We compared the reproductive biology of 782 B. irregularis caught on Guam during the 1980s with results from published studies of native-range populations. Average and maximum sizes of mature snakes on Guam were larger than those from Australian populations. The majority of female brown tree snakes matured at snoutvent lengths (SVLs) of 910–1,025 mm, and most males matured at SVLs of 940–1,030 mm on Guam. Based on growth rates from the early 1990s on Guam, sexual maturity is estimated to occur during a snake’s third or fourth year. Only one female (0.3%) in our data set had oviductal eggs. Clutch size was estimated at 4.3 (SD ¼ 2:2), based on large vitellogenic ovarian follicle (b30 mm in length) and oviductal egg counts. Unlike their Australian counterparts, the Guam population reproduced year-round. Our data offer insights into the likely reproductive patterns of brown tree snakes should they infest other islands in the Pacific region

Development of a Methodology for the Quantitative Assessment of Ireland’s Inshore Kelp Resource

Lead Partner: Queen’s University, Belfast. Project Partners: University College Cork and Envision Mapping Ltd.The main aim of the project was to develop and demonstrate an acoustic methodology for the estimation of kelp biomass based on a low-cost commercial marine acoustic system and modification of the standard software. The approach will be of significant value to regulatory authorities for the monitoring of healthy kelp beds and their associated fauna and flora. It will also provide a scientific basis for future kelp harvesting trials, be instrumental in developing appropriate management plans for such practices and will aid in the evaluation of the recovery in harvested areas.This project (Grant-Aid Agreement No. PBA/SW/07/002(01)) was carried out under the Sea Change strategy with the support of the Marine Institute and the Marine Research Sub-Programme of the National Development Plan 2007–2013.Funder: Marine Institut

Increased S-nitrosylation and proteasomal degradation of caspase-3 during infection contribute to the persistence of adherent invasive escherichia coli (AIEC) in immune cells

Adherent invasive Escherichia coli (AIEC) have been implicated as a causative agent of Crohn's disease (CD) due to their isolation from the intestines of CD sufferers and their ability to persist in macrophages inducing granulomas. The rapid intracellular multiplication of AIEC sets it apart from other enteric pathogens such as Salmonella Typhimurium which after limited replication induce programmed cell death (PCD). Understanding the response of infected cells to the increased AIEC bacterial load and associated metabolic stress may offer insights into AIEC pathogenesis and its association with CD. Here we show that AIEC persistence within macrophages and dendritic cells is facilitated by increased proteasomal degradation of caspase-3. In addition S-nitrosylation of pro- and active forms of caspase-3, which can inhibit the enzymes activity, is increased in AIEC infected macrophages. This S-nitrosylated caspase-3 was seen to accumulate upon inhibition of the proteasome indicating an additional role for S-nitrosylation in inducing caspase-3 degradation in a manner independent of ubiquitination. In addition to the autophagic genetic defects that are linked to CD, this delay in apoptosis mediated in AIEC infected cells through increased degradation of caspase-3, may be an essential factor in its prolonged persistence in CD patients