Impact of the capillary pressure-saturation pore-size distribution parameter on geological carbon sequestration estimates

Cost estimates for geologic carbon sequestration (GCS) are vital for policy and decision makers evaluating carbon capture and storage strategies. Numerical models are often used in feasibility studies for the different stages of carbon injection and redistribution. Knowledge of the capillary pressure-saturation function for a selected storage rock unit is essential in applications used for simulating multiphase fluid flow and transport. However, the parameters describing these functions (e.g. the van Genuchten m pore size distribution parameter) are often not measured or neglected compared to other physical properties such as porosity and intrinsic permeability. In addition, the use of average instead of point estimates of m for numerical simulations of flow and transport can result in significant errors, especially in the case of coarse-grained sediments and fractured rocks. Such erroneous predictions can pose great risks and challenges to decision-making. We present a comparison of numerical simulation results based on average and point estimates of the van Genuchten m parameter for different porous media. Forward numerical simulations using the STOMP code were employed to illustrate the magnitudes of the differences in carbon sequestration predictions resulting from the use of height-averaged instead of point parameters. The model predictions were converted into cost estimates and the results indicate that varying m values in GCS modeling can cause cost differences of up to hundreds of millions dollars

Solute and Bacterial Transport through Partially-Saturated Intact Soil Blocks

Steady-state transport of water, chloride and bacteria was measured through intact blocks of Maury and Cecil soils, under partially saturated conditions. Major objectives were to determine if transport occurs uniformly or via preferential flow paths, and if soil physical properties could be used to predict breakthrough. The blocks were instrumented with TDR probes and mounted on a vacuum chamber containing 100 cells that collected eflluent. After each experiment the blocks were sampled for soil physical properties. The fluxes showed no spatial autocorrelation and the eflluent variance was not statistically different between soils. Less than 3% of the influent bacteria appeared in the effluent. Maximum bacterial breakthrough occurred after 0.25 water-filled pore volumes had been leached, and was greater for Cecil soil than for Maury soil. The chloride breakthrough curves were fitted to the convection dispersion equation. The best predictor of dispersivity was volumetric water content (R2 = 0.28, P \u3c 0.01), with dispersivity increasing with decreasing water content. Lower water contents lead to more tortuous flow paths and thus, a broadening of the velocity distribution. Soil structural controls on solute dispersion under partially saturated conditions are likely to be indirect, and related to differences in water content at given flux produced by differences in pore-size distribution

First Reported Case of Cryptococcus gattii in the Southeastern USA: Implications for Travel-Associated Acquisition of an Emerging Pathogen

In 2007, the first confirmed case of Cryptococcus gattii was reported in the state of North Carolina, USA. An otherwise healthy HIV negative male patient presented with a large upper thigh cryptococcoma in February, which was surgically removed and the patient was started on long-term high-dose fluconazole treatment. In May of 2007, the patient presented to the Duke University hospital emergency room with seizures. Magnetic resonance imaging revealed two large CNS lesions found to be cryptococcomas based on brain biopsy. Prior chest CT imaging had revealed small lung nodules indicating that C. gattii spores or desiccated yeast were likely inhaled into the lungs and dissemination occurred to both the leg and CNS. The patient's travel history included a visit throughout the San Francisco, CA region in September through October of 2006, consistent with acquisition during this time period. Cultures from both the leg and brain biopsies were subjected to analysis. Based on phenotypic and molecular methods, both isolates were C. gattii, VGI molecular type, and distinct from the Vancouver Island outbreak isolates. Based on multilocus sequence typing of coding and noncoding regions and virulence in a heterologous host model, the leg and brain isolates are identical, but the two differed in mating fertility. Two clinical isolates, one from a transplant recipient in San Francisco and the other from Australia, were identical to the North Carolina clinical isolate at all markers tested. Closely related isolates that differ at only one or a few noncoding markers are present in the Australian environment. Taken together, these findings support a model in which C. gattii VGI was transferred from Australia to California, possibly though an association with its common host plant E. camaldulensis, and the patient was exposed in San Francisco and returned to present with disease in North Carolina

Development of Occupant-Preferred Landing Profiles for Personal Aerial Vehicles

With recent increased interest in autonomous vehicles and the associated technology, the prospect of realizing a personal aerial vehicle (PAV) seems closer than ever. However, there is likely to be a continued requirement for any occupant of an air vehicle to be comfortable with both the automated portions of the flight and their ability to take manual control as and when required. This paper, using the approach to landing as an example maneuver, examines what a comfortable trajectory for PAV occupants might look like. Based upon simulated flight data, a ‘natural’ flight trajectory was designed and then compared to constant deceleration and constant optic flow descent profiles. It was found that PAV occupants with limited flight training and no artificial guidance followed the same longitudinal trajectory as had been found for professionally trained helicopter pilots. Further, the final stages of the approach to hover could be well described using Tau Theory. For automatic flight, PAV occupants preferred a constant deceleration profile. For approaches flown manually, the newly designed natural profile was preferred

Virulence Factors Identified by Cryptococcus neoformans Mutant Screen Differentially Modulate Lung Immune Responses and Brain Dissemination

Deletions of cryptococcal PIK1, RUB1, and ENA1 genes independently rendered defects in yeast survival in human CSF and within macrophages. We evaluated virulence potential of these genes by comparing wild-type Cryptococcus neoformans strain H99 with deletant and complement strains in a BALB/c mouse model of pulmonary infection. Survival of infected mice; pulmonary cryptococcal growth and pathology; immunological parameters; dissemination kinetics; and CNS pathology were examined. Deletion of each PIK1, RUB1, and ENA1 differentially reduced pulmonary growth and dissemination rates of C. neoformans and extended mice survival. Furthermore, pik1Δ induced similar pathologies to H99, however, with significantly delayed onset; rub1Δ was more efficiently contained within pulmonary macrophages and was further delayed in causing CNS dissemination/pathology; whereas ena1Δ was progressively eliminated from the lungs and did not induce pathological lesions or disseminate into the CNS. The diminished virulence of mutant strains was associated with differential modulation of pulmonary immune responses, including changes in leukocyte subsets, cytokine responses, and macrophage activation status. Compared to H99 infection, mutants induced more hallmarks of a protective Th1 immune response, rather than Th2, and more classical, rather than alternative, macrophage activation. The magnitude of immunological effects precisely corresponded to the level of virulence displayed by each strain. Thus, cryptococcal PIK1, RUB1, and ENA1 differentially contribute to cryptococcal virulence, in correlation with their differential capacity to modulate immune responses

"Black holes in the fabric of the nation": Refugees in Mohsin Hamid’s "Exit West".

This article explores the representation of refugees in Mohsin Hamid’s Exit West (2017), a novel which marks an early and particularly prominent literary response to the ‘international refugee crisis’. In a distinct echo of Salman Rushdie’s claim, a quarter of a century ago, that it ‘may be argued that the past is a country from which we have all emigrated’, Hamid’s novel similarly claims that ‘we are all migrants through time.’ Moreover, like Rushdie’s fiction, Hamid’s novel incorporates elements of magical realism and fable. Its protagonists, Nadia and Saeed, escape their unnamed war-torn city through a ‘door’ that instantaneously transports them to Mykonos; they subsequently travel through other such ‘doors’ to London and San Francisco. Their story is interspersed with a series of vignettes in which other refugees also find themselves magically transported to ‘first-world’ nations. As well as considering the ways in which Hamid’s novel seeks to humanize refugees, this article considers the novel’s evocation of a world in which human beings have – like capital, images, and (mis)information – gained access to largely ungovernable networks of instantaneous travel across vast distances. It argues that Hamid’s novel is not just ‘about’ refugees but also constitutes a reflection on how they, and their journeys, are represented and mediated by actually-existing technologies

Approaches to Antifungal Therapies and Their Effectiveness among Patients with Cryptococcosis

ABSTRACT The goal of this study was to determine the degree to which the persistence of cryptococcosis, overall 1-year mortality, and 1-year mortality due to cryptococcosis were influenced by initial antifungal treatment regimen in a cohort of adults with cryptococcosis treated at a tertiary care medical center. Risk factors, underlying conditions, treatment, and mortality information were obtained for 204 adults with cryptococcosis from Duke University Medical Center (DUMC) from 1996 to 2009. Adjusted risk ratios (RR) for persistence and hazard ratios (HR) for mortality were estimated for each exposure. The all-cause mortality rate among patients with nonsevere disease (20%) was similar to that in the group with disease (26%). However, the rate of cryptococcosis-attributable mortality with nonsevere disease (5%) was much lower than with severe disease (20%). Flucytosine exposure was associated with a lower overall mortality rate (HR, 0.4; 95% confidence interval [CI], 0.2 to 0.9) and attributable mortality rate (HR, 0.5; 95% CI, 0.2 to 1.2). Receiving a nonrecommended antifungal regimen was associated with a higher relative risk of persistent infection at 4 weeks (RR, 1.9; 95% CI, 0.9 to 4.3), and the rate of attributable mortality among those not receiving the recommended dose of initial therapy was higher than that of those receiving recommended dosing (HR, 2.3; 95% CI, 1.0 to 5.0). Thus, the 2010 Infectious Diseases Society of America (IDSA) guidelines are supported by this retrospective review as a best-practice protocol for cryptococcal management. Future investigations should consider highlighting the distinction between all-cause mortality and attributable mortality so as not to overestimate the true effect of cryptococcosis on patient death

Comparison and Temporal Trends of Three Groups with Cryptococcosis: HIV-Infected, Solid Organ Transplant, and HIV-Negative/Non-Transplant

BackgroundThe Infectious Disease Society of America (IDSA) 2010 Clinical Practice Guidelines for the management of cryptococcosis outlined three key populations at risk of disease: (1) HIV-infected, (2) transplant recipient, and (3) HIV-negative/non-transplant. However, direct comparisons of management, severity and outcomes of these groups have not been conducted.Methodology/Principal FindingsAnnual changes in frequency of cryptococcosis diagnoses, cryptococcosis-attributable mortality and mortality were captured. Differences examined between severe and non-severe disease within the context of the three groups included: demographics, symptoms, microbiology, clinical management and treatment. An average of nearly 15 patients per year presented at Duke University Medical Center (DUMC) with cryptococcosis. Out of 207 study patients, 86 (42%) were HIV-positive, 42 (20%) were transplant recipients, and 79 (38%) were HIV-negative/non-transplant. HIV-infected individuals had profound CD4 lymphocytopenia and a majority had elevated intracranial pressure. Transplant recipients commonly (38%) had renal dysfunction. Nearly one-quarter (24%) had their immunosuppressive regimens stopped or changed. The HIV-negative/non-transplant population reported longer duration of symptoms than HIV-positive or transplant recipients and 28% (22/79) had liver insufficiency or underlying hematological malignancies. HIV-positive and HIV-negative/non-transplant patients accounted for 89% of severe disease cryptococcosis-attributable deaths and 86% of all-cause mortality.Conclusions/SignificanceIn this single-center study, the frequency of cryptococcosis did not change in the last two decades, although the underlying case mix shifted (fewer HIV-positive cases, stable transplant cases, more cases with neither). Cryptococcosis had a relatively uniform and informed treatment strategy, but disease-attributable mortality was still common