Stable isotope analysis of benthic-pelagic coupling in North East Atlantic fishes

PhD ThesisIn continental-shelf ecosystems, consumers may be sustained by benthic and/or pelagic pathways, the linkages between them contributing to benthic-pelagic coupling. The relative flux from each pathway can influence the productivity and stability of the food web, yet few studies have investigated this form of benthicpelagic coupling and its influence on resilience of species at ecosystem scale. This PhD investigated the extent to which shelf-sea fish species are affiliated with benthic and pelagic pathways across four UK seas (North, Celtic, Irish Sea and English Channel), what influences this and how this relates to fluctuations in fish abundance. Studied drivers of benthic-pelagic coupling included consumer body mass and trophic level, and water depth, temperature and salinity. Factors influencing variability in species’ abundances including benthic-pelagic coupling, life history characteristics and variability in fishing pressure, were also examined. Stable isotope analysis was used to reveal time-integrated species affiliations to the pathways. Isoscapes were created using queen scallops (sedentary bivalve) and predictor variables to correct for baseline spatial variation in sampled fish species’ isotopic values. δ13C and δ34S were used to assess the relative contribution of the pathways to fish consumer production. Use of both δ13C and δ34S isotopes as opposed to just δ13C reduced uncertainty in modal use estimates. Across UK seas most species relied to some extent on both pathways, suggesting strong benthic-pelagic coupling, potentially improving community resilience to perturbations. Trophic level most influenced species’ affiliations, with an increase in trophic level causing a marked increase in benthic affiliation and a decrease in pelagic affiliation. A positive but weaker relationship between benthic affiliation and mass was also present, whilst the environmental variables had small and inconsistent effects. A significant positive relationship between variability in species’ abundance and benthic-pelagic coupling was found, whilst weaker non-significant relationships existed with the other factors. These results may aid understanding of ecosystem resilience to climatic and anthropogenic perturbations.NERC (NE/L008718/1) and the UK Department of Environment, Food and Rural Affairs (project MF1225 Integration of environmental and fisheries management

Exploring the feasibility of multi-site flow cytometric processing of gut associated lymphoid tissue with centralized data analysis for multi-site clinical trials

The purpose of this study was to determine whether the development of a standardized approach to the collection of intestinal tissue from healthy volunteers, isolation of gut associated lymphoid tissue mucosal mononuclear cells (MMC), and characterization of mucosal T cell phenotypes by flow cytometry was sufficient to minimize differences in the normative ranges of flow parameters generated at two trial sites. Forty healthy male study participants were enrolled in Pittsburgh and Los Angeles. MMC were isolated from rectal biopsies using the same biopsy acquisition and enzymatic digestion protocols. As an additional comparator, peripheral blood mononuclear cells (PBMC) were collected from the study participants. For quality control, cryopreserved PBMC from a single donor were supplied to both sites from a central repository (qPBMC). Using a jointly optimized standard operating procedure, cells were isolated from tissue and blood and stained with monoclonal antibodies targeted to T cell phenotypic markers. Site-specific flow data were analyzed by an independent center which analyzed all data from both sites. Ranges for frequencies for overall CD4+ and CD8+ T cells, derived from the qPBMC samples, were equivalent at both UCLA and MWRI. However, there were significant differences across sites for the majority of T cell activation and memory subsets in qPBMC as well as PBMC and MMC. Standardized protocols to collect, stain, and analyze MMC and PBMC, including centralized analysis, can reduce but not exclude variability in reporting flow data within multi-site studies. Based on these data, centralized processing, flow cytometry, and analysis of samples may provide more robust data across multi-site studies. Centralized processing requires either shipping of fresh samples or cryopreservation and the decision to perform centralized versus site processing needs to take into account the drawbacks and restrictions associated with each method

Systematic investigation on the use of cylindrical tools for the production of 3D complex shapes on CNC EDM machines

The need for better utilization of Electro Discharge Machining (EDM) machines with a minimum cost has forced researchers and machine tool builders to carry out a great deal of development to provide optimum conditions for the EDM process. In this respect, the application of Computer Numeric Control (CNC) to EDM has added a new dimension to the ways in which the electrode and workpiece can be moved relative to each other. It has also increased the efficiency and productivity of the process. However, the CNC system, introduced on ram-type EDM machines, offers more than just the capability for positioning the electrodes and process control. It also facilitates more sophisticated tool motions and the ability to generate complex shapes with simply shaped electrodes. This paper investigates the machining characteristics of 3D form and cylindrical tools and shows the most beneficial results when selecting one of these machining methods. Finally, the paper introduces the economical comparison between these machining methods based upon EDM machining and hand finishing times. © 1994