Splenectomy in Egyptian splenomegaly

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Characteristics of Small Social Networks

Two dozen networks are analyzed using three parameters that attempt to capture important properties of social networks: leadership L, member bonding B, and diversity of expertise D. The first two of these parameters have antecedents, the third is new. A key part of the analysis is to examine networks at multiple scales by dissecting the entire network into its n subgraphs of a given radius of two edge steps about each of the n nodes. This scale-based analysis reveals constraints on what we have dubbed "cognitive" networks, as contrasted with biological or physical networks. Specifically, "cognitive" networks appear to maximize bonding and diversity over a range of leadership dominance. Asymptotic relations between the bonding and diversity measures are also found when small, nearly complete subgraphs are aggregated to form larger networks. This aggregation probably underlies changes in a regularity among the LBD parameters; this regularity is a U-shaped function of networks size, n, which is minimal for networks around 80 or so nodes

Factors affecting nitrate distribution in shallow groundwater under a beef farm in South Eastern Ireland

peer-reviewedGroundwater contamination was characterised using a methodology which combines shallow groundwater geochemistry data from 17 piezometers over a 2 yr period in a statistical framework and hydrogeological techniques. Nitrate–N (NO3-N) contaminant mass flux was calculated across three control planes (rows of piezometers) in six isolated plots. Results showed natural attenuation occurs on site although the method does not directly differentiate between dilution and denitrification. It was further investigated whether NO3-N concentration in shallow groundwater (<5 m below ground level) generated from an agricultural point source on a 4.2 ha site on a beef farm in SE Ireland could be predicted from saturated hydraulic conductivity (Ksat) measurements, ground elevation (m Above Ordnance Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and distance from a dirty water point pollution source. Tobit regression, using a background concentration threshold of 2.6 mg NO3-N L−1 showed, when assessed individually in a step wise procedure, Ksat was significantly related to groundwater NO3-N concentration. Distance of the point dirty water pollution source becomes significant when included with Ksat in the model. The model relationships show areas with higher Ksat values have less time for denitrification to occur, whereas lower Ksat values allow denitrification to occur. Areas with higher permeability transport greater NO3-N fluxes to ground and surface waters. When the distribution of Cl− was examined by the model, Ksat and ground elevation had the most explanatory power but Ksat was not significant pointing to dilution having an effect. Areas with low NO3 concentration and unaffected Cl− concentration points to denitrification, low NO3 concentration and low Cl− chloride concentration points to dilution and combining these findings allows areas of denitrification and dilution to be inferred. The effect of denitrification is further supported as mean groundwater NO3-N was significantly (P < 0.05) related to groundwater N2/Ar ratio, redox potential (Eh), dissolved O2 and N2 and was close to being significant with N2O (P = 0.08). Calculating contaminant mass flux across more than one control plane is a useful tool to monitor natural attenuation. This tool allows the identification of hot spot areas where intervention other than natural attenuation may be needed to protect receptors.Research Stimulus Fund, Department of Agriculture Fisheries and Food (Ireland

Effect of Agricultural Practices on Nitrate Leaching

Teagasc wishes to acknowledge with gratitude funding from the 2000-2006 EPA RTDI programme in financing this research project.End of project reportA farm-scale study, carried out at Teagasc, Moorepark (Curtin’s farm), examined the effect of four managements (treatments) on nitrate-nitrogen (NO3-N) leaching over the period 2001-`05. Leaching was measured in these treatments: (T1) plots receiving dirty water and N fertilizer which were grazed; (T2) 2-cut silage and grazing plots receiving slurry and fertilizer N; (T3) grazed plots receiving fertilizer N and (T4) 1-cut silage and grazing plots receiving slurry and fertilizer N. The soil is a free-draining sandy loam overlying Karstic fissured limestone. The mean direct N inputs (kg/ha) for T1-T4 in 2001-`04 were 311, 309, 326, 331, respectively, with stocking rates (LU/ha) of 2.12 - ~2.47. Eight ceramic cups per plot, in 3 replicate plots of each treatment, were used to collect water, on a weekly basis, from 1.0 m deep using 50 kPa suction. There were 33, 37, 26 and 24 sampling dates in the 4 years, respectively. The NO3-N and NH4-N concentrations (mg/l) were determined in the water samples. The annual average and weekly concentration of these parameters was statistically analysed for all years, using a repeated measures analysis. The aggregated data were not normally distributed. There was an interaction between treatment and year (p<0.001). Significant differences (p=0.05) in NO3-N concentrations showed between the treatments in years 1, 2, 4 but not in year 3. For the NH4-N data there was no interaction between treatment and year, p=0.12, or main effect of treatment, p=0.54 but there were differences between years, p=0.01. Mean weekly concentrations were analysed separately for each year. For NO3-N, in years 1, 2 and 4 there was an interaction between treatment and week (p<0.001). With NH4-N, there was an interaction between treatment and week in all 4 years. Dirty water was significantly higher than grazed and 1 cut silage in NO3-N concentrations in year 1; in year 2, dirty water and 2 cut silage were significantly higher than the other treatments while in year 4, dirty water and grazed were significantly higher than the other two treatments. The overall four-year weighted mean NO3-N and NH4-N concentrations were 8.2 and 0.297 mg/l. The NCYCLE (UK) model was adapted for Irish conditions as NCYCLE_IRL. The NCYCLE empirical approach proved to be suitable to predict N fluxes from Irish grassland systems in most situations. Experimental data appeared to agree quite well, in most cases, with the outputs from NCYCLE_IRL. The model was not capable of predicting data from some of the leaching experiments, which suggests that the observed leaching phenomena in these experiments could be governed by non-average conditions or other parameters not accounted for in NCYCLE_IRL. An approach that took into account denitrification, leaching and herbage yield would probably explain the differences found. NCYCLE_IRL proved to be a useful tool to analyse N leaching from grazed and cut grassland systems in Ireland.Environmental Protection Agenc

VLA 1.4GHz observations of the GOODS-North Field: Data Reduction and Analysis

We describe deep, new, wide-field radio continuum observations of the Great Observatories Origins Deep Survey -- North (GOODS-N) field. The resulting map has a synthesized beamsize of ~1.7" and an r.m.s. noise level of ~3.9uJy/bm near its center and ~8uJy/bm at 15', from phase center. We have cataloged 1,230 discrete radio emitters, within a 40' x 40' region, above a 5-sigma detection threshold of ~20uJy at the field center. New techniques, pioneered by Owen & Morrison (2008), have enabled us to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources. We compare the 1.4-GHz (20-cm) source counts with those from other published radio surveys. Our differential counts are nearly Euclidean below 100uJy with a median source diameter of ~1.2". This adds to the evidence presented by Owen & Morrison (2008) that the natural confusion limit may lie near ~1uJy. If the Euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of our log N - log S, this indicates that the cutoff must be fairly sharp below 1uJy else the cosmic microwave background temperature would increase above 2.7K at 1.4 GHz.Comment: Accepted for publication in ApJS. 16 pages, 19 figures. Radio data and source list can be found at http://www.ifa.hawaii.edu/~morrison/GOODSN

Carbon and nitrogen dynamics: Greenhouse gases in groundwater beneath a constructed wetland treating municipal wastewater

Conference oral presentationConstructed wetlands (CW) act as nitrogen (N) sinks and reactors facilitating a number of physical, chemical and biological processes. The N removal efficiency of through-flowing water in such systems when used to treat municipal wastewater is variable. Their overall removal efficiencies do not specifically explain which N species have been removed by physical attenuation, and by biological assimilation or transformation to other forms. A wider understanding of how N removal occurs would help elucidate how losses of N and associated gases from CW impact on water and air quality. The objective of this study is to investigate the C and N cycling processes in the porewater of soils immediately adjacent, up-gradient and down- gradient to helophyte —vegetated CW cells

Exploring the relationship between groundwater geochemical factors and denitrification potentials on a dairy farm in southeast Ireland

NOTICE: this is the author’s version of a work that was accepted for publication in the journal Ecological Engineering. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Ecological Engineering, volume 37, issue 9, September 2011, 1304-1313. DOI: 10.1016/j.ecoleng.2011.03.025peer-reviewedNitrate (NO3−) loss from agriculture to shallow groundwater and transferral to sensitive aquatic ecosystems is of global concern. Denitrifying bioreactor technology, where a solid carbon (C) reactive media intercepts contaminated groundwater, has been successfully used to convert NO3− to di-nitrogen (N2) gas. One of the challenges of groundwater remediation research is how to track denitrification potential spatially and temporally within reactive media and subsoil. First, using δ15N/δ18O isotopes, eight wells were divided into indicative transformational processes of ‘nitrification’ or ‘denitrification’ wells. Then, using N2/argon (Ar) ratios these wells were divided into ‘low denitrification potential’ or high denitrification potential’ categories. Secondly, using falling head tests, the saturated hydraulic conductivity (Ksat) in each well was estimated, creating two groups of ‘slow’ (0.06 m day−1) and ‘fast’ (0.13 m day−1) wells, respectively. Thirdly, two ‘low denitrification potential’ wells (one fast and one slow) with high NO3− concentration were amended with woodchip to enhance denitrification. Water samples were retrieved from all wells using a low flow syringe to avoid de-gassing and analysed for N2/Ar ratio using membrane inlet mass spectrometry. Results showed that there was good agreement between isotope and chemical (N2/Ar ratio and dissolved organic C (DOC)) and physio-chemical (dissolved oxygen, temperature, conductivity and pH) parameters. To explain the spatial and temporal distribution of NO3− and other parameters on site, the development of predictive models using the available datasets for this field site was examined for NO3−, Cl−, N2/Ar and DOC. Initial statistical analysis was directed towards the testing of the effect of woodchip amendment. The analysis was formulated as a repeated measures analysis of the factorial structure for treatment and time. Nitrate concentrations were related to Ksat and water level (p < 0.0001 and p = 0.02, respectively), but did not respond to woodchip addition (p = 0.09). This non-destructive technique allows elucidation of denitrification potential over time and could be used in denitrifying bioreactor technology to assess denitrification hotspots in reactive media, while developing a NO3− spatial and temporal predictive model for bioreactor site specific conditions

Technical Note: Field experiences using UV/VIS sensors for high-resolution monitoring of nitrate in groundwater

peer-reviewedTwo different in situ spectrophotometers are compared that were used in the field to determine nitrate-nitrogen (NO3-N) concentrations at two distinct spring discharge sites. One sensor was a double wavelength spectrophotometer (DWS) and the other a multiple wavelength spectrophotometer (MWS). The objective of the study was to review the hardware options, determine ease of calibration, accuracy, influence of additional substances and to assess positive and negative aspects of the two sensors as well as troubleshooting and trade-offs. Both sensors are sufficient to monitor highly time-resolved NO3-N concentrations in emergent groundwater. However, the chosen path length of the sensors had a significant influence on the sensitivity and the range of detectable NO3-N. The accuracy of the calculated NO3-N concentrations of the sensors can be affected if the content of additional substances such as turbidity, organic matter, nitrite or hydrogen carbonate significantly varies after the sensors have been calibrated to a particular water matrix. The MWS offers more possibilities for calibration and error detection but requires more expertise compared with the DWS.The authors would like to acknowledge the Teagasc Walsh Fellowship scheme for funding the study in Ireland, and the German federal Ministry of Education and Research (BMBF) for sponsoring the SMART-project (grant no. 02WM1079-1086, 02WM1211-1212) for the study in Jordan.Teagasc Walsh Fellowship Programm

Mobilisation or dilution? Nitrate response of karst springs to high rainfall events

peer-reviewedNitrate (NO3−) contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate can discharge to surface waters unabated. However, such systems also react quickest to agricultural management changes that aim to improve water quality. In response to storm events, nitrate concentrations can alter significantly, i.e. rapidly decreasing or increasing concentrations. The current study examines the response of a specific karst spring situated on a grassland farm in South Ireland to rainfall events utilising high-resolution nitrate and discharge data together with on-farm borehole groundwater fluctuation data. Specifically, the objectives of the study are to formulate a scientific hypothesis of possible scenarios relating to nitrate responses during storm events, and to verify this hypothesis using additional case studies from the literature. This elucidates the controlling key factors that lead to mobilisation and/or dilution of nitrate concentrations during storm events. These were land use, hydrological condition and karstification, which in combination can lead to differential responses of mobilised and/or diluted nitrate concentrations. Furthermore, the results indicate that nitrate response in karst is strongly dependent on nutrient source, whether mobilisation and/or dilution occur and on the pathway taken. This will have consequences for the delivery of nitrate to a surface water receptor. The current study improves our understanding of nitrate responses in karst systems and therefore can guide environmental modellers, policy makers and drinking water managers with respect to the regulations of the European Union (EU) Water Framework Directive (WFD). In future, more research should focus on the high-resolution monitoring of karst aquifers to capture the high variability of hydrochemical processes, which occur at time intervals of hours to days.Teagasc Walsh Fellowship Programm