Informing the management of multiple stressors on estuarine ecosystems using an expert-based Bayesian Network model.

The approach of applying stressor load limits or thresholds to aid estuarine management is being explored in many global case studies. However, there is growing concern regarding the influence of multiple stressors and their cumulative effects on the functioning of estuarine ecosystems due to the considerable uncertainty around stressor interactions. Recognising that empirical data limitations hinder parameterisation of detailed models of estuarine ecosystem responses to multiple stressors (suspended sediment, sediment mud and metal content, and nitrogen inputs), an expert driven Bayesian network (BN) was developed and validated. Overall, trends in estuarine condition predicted by the BN model were well supported by field observations, including results that were markedly higher than random (71-84% concordance), providing confidence in the overall model dynamics. The general BN framework was then applied to a case study estuary to demonstrate the model's utility for informing management decisions. Results indicated that reductions in suspended sediment loading were likely to result in improvements in estuarine condition, which was further improved by reductions in sediment mud and metal content, with an increased likelihood of high abundance of ecological communities relative to baseline conditions. Notably, reductions in suspended sediment were also associated with an increased probability of high nuisance macroalgae and phytoplankton if nutrient loading was not also reduced (associated with increased water column light penetration). Our results highlight that if stressor limit setting is to be implemented, limits must incorporate ecosystem responses to cumulative stressors, consider the present and desired future condition of the estuary of interest, and account for the likelihood of unexpected ecological outcomes regardless of whether the experts (or empirical data) suggest a threshold has or has not been triggered.

Increasing the magnetic helicity content of a plasma by pulsing a magnetized source.

By operating a magnetized coaxial gun in a pulsed mode it is possible to produce large voltage pulses of duration approximately 500 mus while reaching a few kV, giving a discrete input of helicity into a spheromak. In the sustained spheromak physics experiment (SSPX), it is observed that pulsing serves to nearly double the stored magnetic energy and double the temperature. We discuss these results by comparison with 3D MHD simulations of the same phenomenon.

New mode of operating a magnetized coaxial plasma gun for injecting magnetic helicity into a spheromak.

By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (approximately 1 kV) are produced, giving the highest sustained voltage approximately 500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B/B>/=2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments.

Suppression of MHD fluctuations leading to improved confinement in a gun-driven spheromak.

Magnetic fluctuations have been reduced to approximately 1% during discharges on the Sustained Spheromak Physics Experiment by shaping the spatial distribution of the bias magnetic flux in the device. In the resulting quiescent regime, the safety factor profile is nearly flat in the plasma and the dominant ideal and resistive MHD modes are greatly reduced. During this period, the temperature profile is peaked at the magnetic axis and maps onto magnetic flux contours. Energy confinement time is improved over previous reports in a driven spheromak.

Cord blood lymphocyte subpopulations and mitogenic activity in whole blood microculture.

Comparative studies on cord and adult blood showed that cord blood contained at least twice as many lymphocytes as adult blood. Relatively, the percentage of T cells (E-RFC) was significantly lower in cord blood lymphocytes. The percentage of B cells (EAC-RFC and SmIg bearing cells), as well as the total number of T and B cells (mm(-3)), was significantly higher in cord blood. In vitro mitogen transformation of cord and adult lymphocytes in while blood, cultured for different times and diluted to contain equivalent numbers of lymphocytes per culture, showed significant qualitative and quantitative differences. Responses to the T cell mitogens phytohaemagglutinin (PHA) and concanavalin A (Con A) were examined from 3 to 6 days in culture. Cord blood lymphocytes were significantly more responsive when cultured for 3 to 4 days, similar to adult cells after 5 days, but significantly less responsive after 6 days in culture. The optimal levels of T cell mitogen responsiveness in cord cells (Day 4) were similar to adut cells (Day 6). Spontaneous transformation of unstimulated lymphocytes and B cell mitogen transformation with pokeweed mitogen (PWM) and staphylococcal protein A (SpA) were all significantly higher in cord blood than in adult whole blood cultured for 5 days.

T- and B-lymphocyte subpopulations following radiotherapy for invasive squamous cell carcinoma of the uterine cervix.

Lymphocyte subpopulations in patients with cervical carcinoma were studied before and after radiotherapy. T lymphocytes were recognized by their ability to form spontaneous rosettes with sheep erythrocytes (E rosettes). Two surface marker characteristics were used to detect B lymphocytes: receptors for activated complement responsible for erythrocyte--antibody--complement (EAC) rosette formation, and surface membrane immunoglobulin (SmIg), readily stainable by immunofluorescence. We have demonstrated a significant depression of total lymphocytes after radiotherapy which persists for more than 5 years. This reduction in lymphocytes is due to a loss of E rosette-forming T cells, SmIg-bearing B cells and null cells. Absolute numbers of EAC rosette-forming B cells are not altered by treatment, and there is a rise in this cell type when the results are expressed as percentages of the total lymphocyte count. The possible functional immunological significance of these changes is discussed.

T- and B-lymphocyte subpopulations in pre-invasive and invasive carcinoma of the cervix.

Lymphocyte subpopulations in patients with pre-invasive and invasive cervical carcinoma, other gynaecological malignancies and controls were studied. T lymphocytes were recognized by their ability to form spontaneous rosettes with sheep red blood cells (E rosettes). Two surface marker characteristics were used to detect B lymphocytes: the receptors for activated complement responsible for erythrocyte-antibody-complement (EAC) rosette formation, and surface membrane immunoglobulin (SMIg), which is readily stainable by immunofluorescence. There was a significant depression in T cells in association with invasive but not pre-invasive cervical carcinoma. The results for B cells varied according to the method used for their detection. EAC rosette-forming (EAC-RFC) were significantly raised in patients with invasive cancers but not in patients with pre-invasive cancer. SMIg-bearing cells were not significantly altered by the presence of malignant disease. The changes in E-RFC and EAC-RFC numbers were more marked in patients with extensive cancers. Possible functional implications of these findings are discussed.

Depletion of circulating T lymphocytes in pregnancy.

Changes were assessed in lymphocyte sub-populations in various stages of human pregnancy. The percentage and absolute number of E-RFC decreased during pregnancy. There was a concomitant rise in the percentages of EAC-RFC and cells bearing SmIg with little change in their absolute numbers. EAC-RFC continued to rise post-natally.