The hydrogeology of bromate contamination in the Hertfordshire Chalk: incorporating karst in predictive models

Point source contamination of groundwater by bromate (BrO3^-) in the Hertfordshire Chalk Aquifer forced the closure in 2000, of a major public supply ground- water abstraction and presents a continuing threat to regional water resources. Solute transport in the Chalk is dominantly dual porosity in character but in the bromate-aected region of Hertfordshire, karst development along the feather edge of overlying Palaeocene sands and gravels complicates groundwater ow and transport. Tracer tests conducted in the early 20th century indicated rapid (1-3km/day) flow paths of 8-15km in length but a lack of quantitative data has meant that the karst system has not been adequately incorporated into existing models of bromate transport. A new suite of quantitative tracer tests was conducted to investigate the spatial relationship between karst flows and distribution of the bromate contamination, and to establish hydrodynamic transport parameters. Bacteriophage were introduced into the aquifer at 3 locations and their appearance was monitored downgradient. Results indicate that karstication is more widespread than previously indicated. Multiple flow pathways are indicated and evidence of karst penetrating into regions not previously considered karstic. The interpretation has contributed to the development of a new conceptual understanding of the function, geometry and evolution of the Hertfordshire Chalk karst and its influence upon the bromate contamination. Tracer breakthrough analysis suggests a `dual porosity' exchange between karst conduits and the Chalk matrix, and/or micro-fractures. The analysis enabled determination of transport parameters for incorporation within a regional groundwater flow and transport model.The new conceptual understanding has been incorporated into a spatially distributed groundwater ow and transport model which has been able to reproduce the main features of the karst and transport of the bacteriophage tracers. The model has been applied to simulate bromate transport towards points of interest in the catchment incorporating possible bromate source histories and stresses

Atypical eye contact in autism: Models, mechanisms and development

An atypical pattern of eye contact behaviour is one of the most significant symptoms of Autism Spectrum Disorder (ASD). Recent empirical advances have revealed the developmental, cognitive and neural basis of atypical eye contact behaviour in ASD. We review different models and advance a new ‘fast-track modulator model’. Specifically, we propose that atypical eye contact processing in ASD originates in the lack of influence from a subcortical face and eye contact detection route, which is hypothesized to modulate eye contact processing and guide its emergent specialization during development

A benefit–cost analysis of different response scenarios to COVID ‐19: A case study

Background This paper compares the direct benefits to the State of Western Australia from employing a “suppression” policy response to the COVID-19 pandemic rather than a “herd immunity” approach. Methods An S-I-R (susceptible-infectious-resolved) model is used to estimate the likely benefits of a suppression COVID-19 response compared to a herd immunity alternative. Direct impacts of the virus are calculated on the basis of sick leave, hospitalizations, and fatalities, while indirect impacts related to response actions are excluded. Results Preliminary modeling indicates that approximately 1700 vulnerable person deaths are likely to have been prevented over 1 year from adopting a suppression response rather than a herd immunity response, and approximately 4500 hospitalizations. These benefits are valued at around AUD4.7 billion. If a do nothing policy had been adopted, the number of people in need of hospitalization is likely to have overwhelmed the hospital system within 50 days of the virus being introduced. Maximum hospital capacity is unlikely to be reached in either a suppression policy or a herd immunity policy. Conclusion Using early international estimates to represent the negative impact each type of policy response is likely to have on gross state product, results suggest the benefit–cost ratio for the suppression policy is slightly higher than that of the herd immunity policy, but both benefit–cost ratios are less than one

Validation of Observed Bedload Transport Pathways Using Morphodynamic Modeling

Phenomena related to braiding, including local scour and fill, channel bar development, migration and avulsion, make numerical morphodynamic modeling of braided rivers challenging. This paper investigates the performance of a Delft3D model, in a 2D depth-averaged formulation, to simulate the morphodynamics of an anabranch of the Rees River (New Zealand). Model performance is evaluated using data from field surveys collected on the falling limb of a major high flow, and using several sediment transport formulas. Initial model results suggest that there is generally good agreement between observed and modeled bed levels. However, some discrepancies in the bed level estimations were noticed, leading to bed level, water depth and water velocity estimation errors

SCC: A Service Centered Calculus

We seek for a small set of primitives that might serve as a basis for formalising and programming service oriented applications over global computers. As an outcome of this study we introduce here SCC, a process calculus that features explicit notions of service definition, service invocation and session handling. Our proposal has been influenced by Orc, a programming model for structured orchestration of services, but the SCC’s session handling mechanism allows for the definition of structured interaction protocols, more complex than the basic request-response provided by Orc. We present syntax and operational semantics of SCC and a number of simple but nontrivial programming examples that demonstrate flexibility of the chosen set of primitives. A few encodings are also provided to relate our proposal with existing ones

Preparing Priests to Lead Parish Schools: Concerns and Recommendations

Canon law recognizes the pastor as the chief educational officer (CEO) of the parish school. However, recent studies demonstrate that seminaries do not prepare seminarians for work in or leadership of Catholic schools, and recent scholarship also demonstrates that an increasing number of seminarians lack the desire to lead a parish school. Our research study examined the post-seminary preparation of priests for leadership of parish schools. We also explored alternative governance models for Catholic schools. We conducted structured interviews with 10 national leaders to explore these two areas of interest. Our findings demonstrate that preparation of newly ordained and veteran priests for parish school leadership is woefully inadequate. Interviewees suggested that the pastor/principal relationship and school finance are two important topics that should be addressed in best practice preparation programs for school leaders. All 10 interviewees had difficulty imagining alternative governance models for schools in which the pastor would not serve as the CEO, but at the same time, some of the participants could see potential benefits of alternative governance models. Based on the findings of our study, we recommend that: (1) seminary programs include an initial introduction to the importance of Catholic schools for evangelization; (2) a new national model for preparing young and veteran priests for school leadership be developed and implemented; (3) existing best practices for alternative governance models be collated and promulgated; and (4) church leaders and stakeholders determine the best governance models for their schools and then prepare the appropriate people for leadership roles accordingly

The hydrology of glacier-bed overdeepenings : sediment transport mechanics, drainage system morphology, and geomorphological implications

Evacuation of basal sediment by subglacial drainage is an important mediator of rates of glacial erosion and glacier flow. Glacial erosion patterns can produce closed basins (i.e., overdeepenings) in glacier beds, thereby introducing adverse bed gradients that are hypothesised to reduce drainage system efficiency and thus favour basal sediment accumulation. To establish how the presence of a terminal overdeepening might mediate seasonal drainage system evolution and glacial sediment export, we measured suspended sediment transport from Findelengletscher, Switzerland during late August and early September 2016. Analyses of these data demonstrate poor hydraulic efficiency of drainage pathways in the terminus region but high sediment availability. Specifically, the rate of increase of sediment concentration with discharge was found to be significantly lower than that anticipated if channelised flow paths were present. Sediment availability to these flow paths was also higher than would be anticipated for discrete bedrock-floored subglacial channels. Our findings indicate that subglacial drainage in the terminal region of Findelengletscher is dominated by distributed flow where entrainment capacity increases only marginally with discharge, but flow has extensive access to an abundant sediment store. This high availability maintains sediment connectivity between the glacial and proglacial realm and means daily sediment yield is unusually high relative to yields exhibited by similar Alpine glaciers. We present a conceptual model illustrating the potential influence of ice-bed morphology on subglacial drainage evolution and sediment evacuation mechanics, patterns and yields, and recommend that bed morphology should be an explicit consideration when monitoring and evaluating glaciated basin sediment export rates

Heavy mineral analysis by ICP-AES a tool to aid sediment provenancing

Correlation and provenancing of sediments/sedimentary rocks can be achieved by several techniques; a common approach is through the identification and quantification of heavy minerals using a petrological microscope. This can be time consuming, the analysis of heavy minerals by inductively coupled plasma atomic emission spectroscopy offers a faster alternative, by determining key elements associated with specific heavy minerals. Here we outline a method for determining heavy mineral species though ICP-AES using high temperature fusion with a lithium metaborate flux to ensure complete dissolution of resistate minerals. The method was tested in a provenance study of desert sands from the United Arab Emirates. The results are compared with those derived from traditional optical microscopy. These show good agreement for minerals with specific geochemical signatures, whilst the overall geochemistry of the heavy mineral concentrate was diagnostic of potential sediment sources. This geochemical approach is capable of processing large numbers of samples rapidly and is advocated as a screening technique. A combination of geochemical and mineralogical data produced by these techniques provides a powerful diagnostic tool for studies of heavy mineral signatures in sediments frequently used in mineral reconnaissance, paleogeographic reconstruction and reservoir characterisation in the petroleum industry

Energy landscape of relaxed amorphous silicon

We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40,000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model and that the activation energy is limited by the cost of breaking one bond, independently of the complexity of the mechanism. The overall shape of the activation-energy-barrier distribution is also insensitive to the exact details of the configuration, indicating that well-relaxed configurations see essentially the same environment. These results underscore the localized nature of relaxation in this material.Comment: 8 pages, 12 figure