The Evolution of Complex DNAPL Releases: Rates of Migration and Dissolution

A series of local and bench scale laboratory experiments and bench and field scale numerical simulations were conducted to develop a better understanding of the interrelationship between nonwetting phase (NWP) source zones and downgradient aqueous phase concentrations in saturated porous media contaminated by immiscible organic liquids. Specific emphasis was placed on the factors governing the rate of NWP source zone evolution and the factors governing the rate of mass transfer from the NWP to the aqueous phase. Hysteretic NWP relative permeability-saturation (krN-SW) relationships were measured at the local scale for six sands to examine the relationship between krN-SW functions and porous media type. Parameterization of the measured constitutive relationships revealed a strong correlation between mean grain diameter and the maximum value of NWP relative permeability. The measured krN-SW relationships, were validated through a bench scale experiment involving the infiltration, redistribution, and immobilisation of NWP in an initially water saturated heterogeneous porous medium. This match of simulation to experiment represents the first validation of a multiphase flow model for transient, fixed volume NWP releases. Multiphase flow simulations of the bench scale experiment were only able to reproduce the experimental observations, in both time and space, when the measured krN-SW relationships were employed. Two-dimensional field scale simulations of a fixed volume NWP release into a heterogeneous aquifer demonstrate the influence of spatially variable krN-S relationships correlated to porous media type. Both the volume of the NWP invaded porous media, and the length of time during which NWP is migrating, will be under predicted if variable (correlated) kr,N is not accounted for in the numerical model iv formulation. This under prediction is exacerbated as the mean intrinsic permeability of the release location decreases. A new, thermodynamically-based interfacial area (IFA) model was developed for use in the single-boundary layer expression of mass transfer as an alternative to existing empirical correlation expressions. The IFA model considers consistency and continuity of constitutive relationships, energy losses, effective specific interfacial area for mass transfer, and dissolution of residual NWP. A bench scale experiment involving the release and dissolution of a transient NWP source zone in heterogeneous porous media was conducted to evaluate the appropriateness of the developed IFA model when utilised to predict NWP dissolution rates. Comparison of measured downgradient dissolved phase concentrations and source zone NWP saturations in time and space with those from numerical simulations of the experiment reveal that the proposed IFA model is superior to both a local equilibrium assumption and existing empirical correlation expressions. This represents the first mass transfer model validated for the dissolution of a complex NWP source zone. Twodimensional simulations at the field scale of multiphase flow and dissolution suggest that employing existing mass transfer expressions instead of the IFA model lead to incorrect predictions of the life spans of NWP source zones, downgradient dissolved phase concentrations, and the rate of mass flux through a downgradient boundary. The practical implication of this research is that accurate numerical predictions of the evolution of a transient NWP source in porous media require consideration of krN-S relationships and NWP / aqueous phase IFA, as these factors dictate the rates of the key subsurface contaminant processes of migration and dissolution, respectively

ENV-654: NUMERICAL MODELLING OF SMOULDERING COMBUSTION TO OPTIMIZE EX SITU SOIL TREATMENT SYSTEM DESIGN

There is widespread soil contamination at thousands of cites in Canada resulting from the historical improper storage and disposal of industrial liquids (Story et al., 2014). Large financial resources are allocated to remediation efforts due to the human and environmental health risks associated with exposure to such contamination, with over $582 million CAN spent on remediation in 2014-15 by the Canadian government alone (Treasury Board of Canada, 2016). Our scientific understanding of site remediation has evolved greatly over the past decades and it is now widely accepted that remediation of the contaminant source zone is necessary to achieve a high level of long-term remediation (Kueper et al., 2014). Non-aqueous phase liquids, or NAPLS, are one of the most prevalent contaminants at contaminated sites and are challenging to remediate due to their highly recalcitrant nature (Kueper et al., 2003). Although many remediation technologies have been developed over the past decades, the challenge in source zone remediation of NAPLs persists. The application of smouldering combustion to treat NAPL contaminated soils has been proven as an effective technology with both the laboratory experiments and applied in situ at a field site (Switzer et al., 2009, Pironi et al., 2011, Switzer et al, 2014, Salman et al., 2015, Scholes et al., 2015). This technology, titled “Self-sustaining treatment for active remediation”, or STAR, utilizes the high calorific value of NAPLs to ignite and sustain a smouldering oxidation reaction, effectively destroying the contaminant in the process. A phenomenological model developed by MacPhee et al. (2012) uniquely combined a multiphase flow model, perimeter expansion model, and analytical expression for the forward smouldering front velocity. This model is able to predict the propagation of the reaction front in response to the interplay between a heterogeneous distribution of permeability and the time-dependent distribution of air flux. After subsequent calibration by Hasan et al. (2014), the model was shown to correctly predict the ultimate extent and time of remediation during treatment for 2D lab scale experiments

ENV-601: A NEW METHOD FOR CONVERTING SEWAGE TO ENERGY USING SELF-SUSTAINING SMOULDERING

A major challenge in designing resilient infrastructure is to meet the needs of sustainable development (Kennedy & Corfee-Morlot, 2013). Sustainable development requires a high degree of energy efficiency. Municipal wastewater treatment plants (WWTPs), in particular, have the potential to be much more sustainable. In the U.S., 3 – 4% of the total energy consumed is dedicated to WWTPs and drinking water services, accounting for 30 – 40% of energy consumed by municipalities (U.S. EPA, 2014). In Canada, 25% of the $123 billion municipal deficit in 2006 was tied to water supply systems (i.e., drinking water, wastewater, and storm water) (Mirza, 2006). This problem becomes further complicated as much of North America’s WWTP infrastructure approaches the end of its design life. An estimated$298 billion and $39 billion is required in the U.S. and Canada, respectively, to satisfactorily refurbish WWTP infrastructure (ASCE, 2013; Félio et al., 2012). Within WWTPs, around 50% of the operating and capital costs are dedicated to managing the solid by-product, biosolids, making it the most expensive system component (Khiari et al., 2004). In Canada, 90% of biosolids are either incinerated or land applied for agricultural purposes (Apedaile, 2001). These methods are expensive, requiring high energy inputs in various forms (e.g., fuel, labour, transportation) (Wang et al., 2008). Land application is also subject to limitations and uncertain risks due to the potential for introducing synthetic contaminants into the environment (Hale et al., 2001; U.S. EPA, 1995). In general, managing biosolids persists as a major energy intensive challenge within WWTPs and there is a strong need to provide novel solutions (Tyagi & Lo, 2013). Self-sustaining smouldering combustion of organic wastes was originally developed as a chemical waste management and soil-clean up technology (Pironi et al., 2011; Scholes et al., 2015; Switzer et al., 2009). Smouldering is a flameless form of combustion for solid and liquid fuels, where a common example is glowing red charcoal in a traditional barbeque (Ohlemiller, 1985). The fuel (e.g. oil sludge) is mixed with sand to form a fixed-bed; this increases the surface area for reaction, provides porosity for the oxidant (air), and efficiently transfers, stores, and recycles the released reaction energy (Switzer et al., 2009). The smouldering reaction typically reaches temperatures between 500-800°C for many minutes in one location resulting in upwards of 99% conversion of organic waste to heat (Pironi et al., 2011). Smouldering in this configuration is unique as it supports an extremely energy efficient, self-sustaining reaction; therefore, following ignition, no external energy is required to sustain the reaction indefinitely. As a result, the process can smoulder fuels containing little energy or significant water contents that would otherwise not burn (e.g., via incineration) (Switzer et al., 2009; Yermán et al., 2015). Proof-of-concept experiments demonstrated for the first time that biosolids, obtained from Greenway Pollution Control Centre (London, ON) could be successfully destroyed via self-sustained smouldering. Thirty experiments in 40 cm tall, 15 cm diameter fixed-bed columns mapped the parameter space of self-sustained smouldering as a function of sand dilution, biosolids water content, and injected air flow rate. The results demonstrate that a self-sustaining reaction was achieved using biosolids with water contents as high as 80% (1.6 MJ/kg, effective calorific value). With little input of energy, the biosolids were converted to heat, steam, and emissions dominated by carbon dioxide. These ENV-601-2 results suggest that smouldering presents strong potential as a cost and energy effective waste management alternative for WWTP biosolids, achieving on-site destruction with minimal energy input and limited preliminary processing (Rashwan et al., 2016). This underscores the beneficial application of smouldering as a novel waste management technique that may be useful in designing resilient infrastructure

Advanced power sources for space missions

Approaches to satisfying the power requirements of space-based Strategic Defense Initiative (SDI) missions are studied. The power requirements for non-SDI military space missions and for civil space missions of the National Aeronautics and Space Administration (NASA) are also considered. The more demanding SDI power requirements appear to encompass many, if not all, of the power requirements for those missions. Study results indicate that practical fulfillment of SDI requirements will necessitate substantial advances in the state of the art of power technology. SDI goals include the capability to operate space-based beam weapons, sometimes referred to as directed-energy weapons. Such weapons pose unprecedented power requirements, both during preparation for battle and during battle conditions. The power regimes for these two sets of applications are referred to as alert mode and burst mode, respectively. Alert-mode power requirements are presently stated to range from about 100 kW to a few megawatts for cumulative durations of about a year or more. Burst-mode power requirements are roughly estimated to range from tens to hundreds of megawatts for durations of a few hundred to a few thousand seconds. There are two likely energy sources, chemical and nuclear, for powering SDI directed-energy weapons during the alert and burst modes. The choice between chemical and nuclear space power systems depends in large part on the total duration during which power must be provided. Complete study findings, conclusions, and eight recommendations are reported

Epidemiology of time-loss injuries in English community-level rugby union

OBJECTIVES: Using a prospective cohort study design, to establish the incidence and nature of time-loss injuries in English community rugby and to assess the differences between different playing levels. SETTING: English community rugby clubs. PARTICIPANTS: Injury information for 4635 matches was collected during seasons 2009/2010 (46 clubs), 2010/2011(67 clubs) and 2011/2012 (76 clubs). Clubs were subdivided into groups A (semiprofessional), B (amateur) and C (recreational) for analysis. PRIMARY AND SECONDARY OUTCOME MEASURES: Any injury resulting in 8 days or greater absence from match play was reported by injury management staff at the clubs. The primary outcome measure was injury incidence (per 1000 player match-hours) and the secondary outcome measure was severity (ie, days absence). RESULTS: Overall match injury incidence was 16.9 injuries per 1000 player match-hours. Incidence was higher for group A (21.7; 95% CI 19.8 to 23.6) compared with group B (16.6; 95% CI 15.2 to 17.9) and C (14.2; 95% CI 13.0 to 15.5, both p<0.001). The mean time-loss was 7.6 weeks absence, with knee and shoulder injuries the most severe with mean absences of 11.6 and 9.3 weeks, respectively. Half of all injuries occurred to the lower limb, with knee and ankle joint/ligament injuries the most common diagnoses. Shoulder joint/ligament injuries were the most common and severe upper limb injuries. Contact events accounted for 80% of all injuries and tackles accounted for 50%. Running was the most common non-contact injury event, of which 56% were hamstring injuries. CONCLUSIONS: More time-loss injuries occur at higher levels of community rugby. Injury prevention strategies should focus on good technique in the tackle and conditioning exercises for the knee, ankle, hamstrings and shoulder

Radiation dose reduction and image enhancement in biological imaging through equally-sloped tomography

Electron tomography is currently the highest resolution imaging modality available to study the 3D structures of pleomorphic macromolecular assemblies, viruses, organelles and cells. Unfortunately, the resolution is currently limited to 3–5 nm by several factors including the dose tolerance of biological specimens and the inaccessibility of certain tilt angles. Here we report the first experimental demonstration of equally-sloped tomography (EST) to alleviate these problems. As a proof of principle, we applied EST to reconstructing frozen-hydrated keyhole limpet hemocyanin molecules from a tilt-series taken with constant slope increments. In comparison with weighted back-projection (WBP), the algebraic reconstruction technique (ART) and the simultaneous algebraic reconstruction technique (SART), EST reconstructions exhibited higher contrast, less peripheral noise, more easily detectable molecular boundaries and reduced missing wedge effects. More importantly, EST reconstructions including only two-thirds the original images appeared to have the same resolution as full WBP reconstructions, suggesting that EST can either reduce the dose required to reach a given resolution or allow higher resolutions to be achieved with a given dose. EST was also applied to reconstructing a frozen-hydrated bacterial cell from a tilt-series taken with constant angular increments. The results confirmed similar benefits when standard tilts are utilized

MCL-CAw: A refinement of MCL for detecting yeast complexes from weighted PPI networks by incorporating core-attachment structure

Abstract Background The reconstruction of protein complexes from the physical interactome of organisms serves as a building block towards understanding the higher level organization of the cell. Over the past few years, several independent high-throughput experiments have helped to catalogue enormous amount of physical protein interaction data from organisms such as yeast. However, these individual datasets show lack of correlation with each other and also contain substantial number of false positives (noise). Over these years, several affinity scoring schemes have also been devised to improve the qualities of these datasets. Therefore, the challenge now is to detect meaningful as well as novel complexes from protein interaction (PPI) networks derived by combining datasets from multiple sources and by making use of these affinity scoring schemes. In the attempt towards tackling this challenge, the Markov Clustering algorithm (MCL) has proved to be a popular and reasonably successful method, mainly due to its scalability, robustness, and ability to work on scored (weighted) networks. However, MCL produces many noisy clusters, which either do not match known complexes or have additional proteins that reduce the accuracies of correctly predicted complexes. Results Inspired by recent experimental observations by Gavin and colleagues on the modularity structure in yeast complexes and the distinctive properties of "core" and "attachment" proteins, we develop a core-attachment based refinement method coupled to MCL for reconstruction of yeast complexes from scored (weighted) PPI networks. We combine physical interactions from two recent "pull-down" experiments to generate an unscored PPI network. We then score this network using available affinity scoring schemes to generate multiple scored PPI networks. The evaluation of our method (called MCL-CAw) on these networks shows that: (i) MCL-CAw derives larger number of yeast complexes and with better accuracies than MCL, particularly in the presence of natural noise; (ii) Affinity scoring can effectively reduce the impact of noise on MCL-CAw and thereby improve the quality (precision and recall) of its predicted complexes; (iii) MCL-CAw responds well to most available scoring schemes. We discuss several instances where MCL-CAw was successful in deriving meaningful complexes, and where it missed a few proteins or whole complexes due to affinity scoring of the networks. We compare MCL-CAw with several recent complex detection algorithms on unscored and scored networks, and assess the relative performance of the algorithms on these networks. Further, we study the impact of augmenting physical datasets with computationally inferred interactions for complex detection. Finally, we analyse the essentiality of proteins within predicted complexes to understand a possible correlation between protein essentiality and their ability to form complexes. Conclusions We demonstrate that core-attachment based refinement in MCL-CAw improves the predictions of MCL on yeast PPI networks. We show that affinity scoring improves the performance of MCL-CAw.http://deepblue.lib.umich.edu/bitstream/2027.42/78256/1/1471-2105-11-504.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78256/2/1471-2105-11-504-S1.PDFhttp://deepblue.lib.umich.edu/bitstream/2027.42/78256/3/1471-2105-11-504-S2.ZIPhttp://deepblue.lib.umich.edu/bitstream/2027.42/78256/4/1471-2105-11-504.pdfPeer Reviewe

Tuberculosis control in South African gold mines: mathematical modeling of a trial of community-wide isoniazid preventive therapy.

A recent major cluster randomized trial of screening, active disease treatment, and mass isoniazid preventive therapy for 9 months during 2006-2011 among South African gold miners showed reduced individual-level tuberculosis incidence but no detectable population-level impact. We fitted a dynamic mathematical model to trial data and explored 1) factors contributing to the lack of population-level impact, 2) the best-achievable impact if all implementation characteristics were increased to the highest level achieved during the trial ("optimized intervention"), and 3) how tuberculosis might be better controlled with additional interventions (improving diagnostics, reducing treatment delay, providing isoniazid preventive therapy continuously to human immunodeficiency virus-positive people, or scaling up antiretroviral treatment coverage) individually and in combination. We found the following: 1) The model suggests that a small proportion of latent infections among human immunodeficiency virus-positive people were cured, which could have been a key factor explaining the lack of detectable population-level impact. 2) The optimized implementation increased impact by only 10%. 3) Implementing additional interventions individually and in combination led to up to 30% and 75% reductions, respectively, in tuberculosis incidence after 10 years. Tuberculosis control requires a combination prevention approach, including health systems strengthening to minimize treatment delay, improving diagnostics, increased antiretroviral treatment coverage, and effective preventive treatment regimens

Second primary cancers in patients with skin cancer: a population-based study in Northern Ireland

Among all 14 500 incident cases of basal cell carcinoma (BCC), 6405 squamous cell carcinomas (SCC) and 1839 melanomas reported to the Northern Ireland Cancer Registry between 1993 and 2002, compared with the general population, risk of new primaries after BCC or SCC was increased by 9 and 57%, respectively. The subsequent risk of cancer, overall, was more than double after melanoma