scholarly journals Sensitivity Analyses for Modeling Evolving Reactivity of Granular Iron for the Treatment of Trichloroethylene

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1878
Author(s):  
Sung-Wook Jeen
Keyword(s):  
Numerical Model ◽  
Permeable Reactive Barrier ◽  
Sensitivity Analyses ◽  
Base Case ◽  
Model Parameters ◽  
Iron Corrosion ◽  
Predictive Tool ◽  
Previous Modeling Study ◽  
Granular Iron

To better predict long-term performance of a remediation system, parameters of a numerical model should be constrained with care by calibrating with reliable experimental data. This study conducted sensitivity analyses for model parameters, which were shown to represent reasonably well the observed geochemical behaviors for the column experiments that evaluated evolving reactivity of granular iron for the treatment of trichloroethylene (TCE) resulting from precipitation of secondary minerals. The particular model parameters tested include iron corrosion rate, aragonite and Fe2(OH)2CO3 precipitation rates, and proportionality constants for each mineral. For sensitivity analyses, a specific parameter was systematically changed, while other parameters were fixed at the values for the base case. The ranges of parameters tested were determined based on the previous modeling study. The results showed that the most important and sensitive model parameters were secondary mineral precipitation rates. Also, not only absolute precipitation rate for each mineral but also relative precipitation rates among different minerals were important for system performance. With help of sensitivity analysis, the numerical model can be used as a predictive tool for designing an iron permeable reactive barrier (PRB) and can provide implications for the long-term changes in reactivity and permeability of the system.

Evaluation of permeable reactive barrier (PRB) integrity using electrical imaging methods

Geophysics ◽  
2003 ◽  
Vol 68 (3) ◽  
pp. 911-921 ◽  
Author(s):  
Lee Slater ◽  
Andrew Binley
Keyword(s):  
Geophysical Methods ◽  
Permeable Reactive Barrier ◽  
Electrical Measurements ◽  
Cross Sectional ◽  
Imaging Methods ◽  
Reactive Barrier ◽  
Electrical Imaging ◽  
Granular Iron

The permeable reactive barrier (PRB) is a promising in‐situ technology for treatment of hydrocarbon‐contaminated groundwater. A PRB is typically composed of granular iron which degrades chlorinated organics into potentially nontoxic dehalogenated organic compounds and inorganic chloride. Geophysical methods may assist assessment of in‐situ barrier integrity and evaluation of long‐term barrier performance. The highly conductive granular iron makes the PRB an excellent target for conductivity imaging methods. In addition, electrochemical storage of charge at the iron–solution interface generates an impedance that decreases with frequency. The PRB is thus a potential induced polarization (IP) target. Surface and cross‐borehole electrical imaging (conductivity and IP) was conducted at a PRB installed at the U.S. Department of Energy's Kansas City plant. Poor signal strength (25% of measurements exceeding 8% reciprocal error) and insensitivity at depth, which results from current channeling in the highly conductive iron, limited surface imaging. Crosshole 2D and 3D electrical measurements were highly effective at defining an accurate, approximately 0.3‐m resolution, cross‐sectional image of the barrier in‐situ. Both the conductivity and IP images reveal the barrier geometry. Crosshole images obtained for seven panels along the barrier suggest variability in iron emplacement along the installation. On five panels the PRB structure is imaged as a conductive feature exceeding 1 S/m. However, on two panels the conductivity in the assumed vicinity of the PRB is less than 1 S/m. The images also suggest variability in the integrity of the contact between the PRB and bedrock. This noninvasive, in‐situ evaluation of barrier geometry using conductivity/IP has broad implications for the long‐term monitoring of PRB performance as a method of hydrocarbon removal.

scholarly journals Cost-effectiveness of physical activity interventions in adolescents: model development and illustration using two exemplar interventions

BMJ Open ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. e027566 ◽  
Author(s):  
Vijay S Gc ◽  
Marc Suhrcke ◽  
Andrew J Atkin ◽  
Esther van Sluijs ◽  
David Turner
Keyword(s):  
Physical Activity ◽  
Cost Effectiveness ◽  
Complex Interventions ◽  
School Intervention ◽  
Sensitivity Analyses ◽  
Secondary Outcome ◽  
Model Parameters ◽  
Lifetime Horizon ◽  
Physical Activity Interventions

ObjectiveTo develop a model to assess the long-term costs and health outcomes of physical activity interventions targeting adolescents.DesignA Markov cohort simulation model was constructed with the intention of being capable of estimating long-term costs and health impacts of changes in activity levels during adolescence. The model parameters were informed by published literature and the analysis took a National Health Service perspective over a lifetime horizon. Univariate and probabilistic sensitivity analyses were undertaken.SettingSchool and community.ParticipantsA hypothetical cohort of adolescents aged 16 years at baseline.InterventionsTwo exemplar school-based: a comparatively simple, after-school intervention and a more complex multicomponent intervention compared with usual care.Primary and secondary outcome measuresIncremental cost-effectiveness ratio as measured by cost per quality-adjusted life year gained.ResultsThe model gave plausible estimates of the long-term effect of changes in physical activity. The use of two exemplar interventions suggests that the model could potentially be used to evaluate a number of different physical activity interventions in adolescents. The key model driver was the degree to which intervention effects were maintained over time.ConclusionsThe model developed here has the potential to assess long-term value for money of physical activity interventions in adolescents. The two applications of the model indicate that complex interventions may not necessarily be the ones considered the most cost-effective when longer-term costs and consequences are taken into account.

Abstract 15622: Cost-Effectiveness of Pediatric Heart Transplantation Across a Positive Crossmatch

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Brian Feingold ◽  
Steven A Webber ◽  
Cindy L Bryce ◽  
Heather E Tomko ◽  
Seo Y Park ◽  
...  
Keyword(s):  
Cost Effectiveness ◽  
Heart Transplantation ◽  
Cost Effective ◽  
Sensitivity Analyses ◽  
Lower Probability ◽  
Base Case ◽  
Model Parameters ◽  
Risk Of Death ◽  
Life Years ◽  
Pediatric Heart Transplantation

Introduction: Allosensitized children listed with a requirement for a negative prospective crossmatch (XM) have a high risk of death awaiting heart transplantation (HTx). Previously we found that acceptance of the first suitable organ offer for these patients, regardless of the possibility of a +XM, results in a survival benefit at all times after listing, including post-HTx. The cost-effectiveness of this strategy is unknown. Methods: We used a Markov-state transition model with a 10 yr time horizon to compare survival, costs, and utility (i.e. quality of life) for 2 waitlist strategies for sensitized candidates: requiring a negative prospective XM (WAIT) vs. accepting the first suitable organ offer (TAKE). Model data were derived from OPTN status 1A pediatric HTx listings from 1999-2009, the PHTS and HCUP KIDS databases, and other published sources. We assumed no possibility of a +XM in the wait strategy and that the probability of a +XM in the take strategy was equal to the pre-transplant PRA. Results: At base case, TAKE was dominant; it cost less ($122,856) and gained more (1.04) quality-adjusted life-years (QALYs) than WAIT. In sensitivity analyses varying all model parameters individually over clinically plausible ranges, TAKE remained dominant or favored (using a $100,000/QALY cost-effectiveness threshold) except when the probability of HTx for TAKE was <55% over 2 years (base case value 67%). After adjustment of the model so that waitlist probabilities of death and delisting were equal in both strategies (while maintaining the lower probability of HTx associated with WAIT), TAKE remained dominant. WAIT was no longer dominated if mortality after HTx across a +XM was >30%/year (equivalent to median post-HTx survival of <3 yrs); yet even at the extreme assumption of 100% 1-year mortality after HTx across a +XM for TAKE, the wait strategy was not cost effective ($350,097/QALY). CONCLUSIONS: Among sensitized status 1A pediatric HTx candidates, we found that taking the first suitable organ offer is less costly and results in greater survival than awaiting HTx across a negative prospective XM. This suggests that HTx should not be denied based on sensitization status alone.

scholarly journals Predicting the Impact of Typhoid Conjugate Vaccines on Antimicrobial Resistance

2019 ◽  
Vol 68 (Supplement_2) ◽  
pp. S96-S104 ◽  
Author(s):  
Samantha Kaufhold ◽  
Reza Yaesoubi ◽  
Virginia E Pitzer
Keyword(s):  
Vaccination Coverage ◽  
Selective Pressure ◽  
Sensitivity Analyses ◽  
Relative Fitness ◽  
Base Case ◽  
Model Parameters ◽  
Case Scenario ◽  
Conjugate Vaccines ◽  
Model Predictions ◽  
The Impact

Abstract Background Empiric prescribing of antimicrobials in typhoid-endemic settings has increased selective pressure on the development of antimicrobial-resistant Salmonella enterica serovar Typhi. The introduction of typhoid conjugate vaccines (TCVs) in these settings may relieve this selective pressure, thereby reducing resistant infections and improving health outcomes. Methods A deterministic transmission dynamic model was developed to simulate the impact of TCVs on the number and proportion of antimicrobial-resistant typhoid infections and chronic carriers. One-way sensitivity analyses were performed to ascertain particularly impactful model parameters influencing the proportion of antimicrobial-resistant infections and the proportion of cases averted over 10 years. Results The model simulations suggested that increasing vaccination coverage would decrease the total number of antimicrobial-resistant typhoid infections but not affect the proportion of cases that were antimicrobial resistant. In the base-case scenario with 80% vaccination coverage, 35% of all typhoid infections were antimicrobial resistant, and 44% of the total cases were averted over 10 years by vaccination. Vaccination also decreased both the total number and proportion of chronic carriers of antimicrobial-resistant infections. The prevalence of chronic carriers, recovery rates from infection, and relative fitness of resistant strains were identified as crucially important parameters. Conclusions Model predictions for the proportion of antimicrobial resistant infections and number of cases averted depended strongly on the relative fitness of the resistant strain(s), prevalence of chronic carriers, and rates of recovery without treatment. Further elucidation of these parameter values in real-world typhoid-endemic settings will improve model predictions and assist in targeting future vaccination campaigns and treatment strategies.

Economic evaluation of enhanced staff contact for the promotion of breastfeeding for low birth weight infants

2010 ◽  
Vol 26 (2) ◽  
pp. 133-140 ◽  
Author(s):  
Stephen J. C. Rice ◽  
Dawn Craig ◽  
Felicia McCormick ◽  
Mary J. Renfrew ◽  
Anthony F. Williams
Keyword(s):  
Economic Evaluation ◽  
Birth Weight ◽  
Cost Effectiveness ◽  
Sensitivity Analyses ◽  
Future Research ◽  
Base Case ◽  
Tree Model ◽  
Low Birth Weight Infants ◽  
Life Years

Objectives: There is evidence that breastmilk feeding reduces mortality and short and long-term morbidity among infants born too soon or too small. The aim of this study was to evaluate the cost-effectiveness of enhanced staff contact for mothers with infants in a neonatal unit with a birth weight of 500–2,500 g from the perspective of the UK National Health Service.Methods: A decision-tree model linked clinical outcomes with long-term health outcomes. The study population was divided into three weight bands: 500–999 g, 1000–1,749 g, and 1,750–2,500 g. Clinical and resource use data were obtained from literature reviews. The measure of benefit was quality-adjusted life-years. Uncertainty was evaluated using cost-effectiveness acceptability curves and sensitivity analyses.Results: The intervention was less costly and more effective than the comparator in the base–case analysis for each birth weight group. The results were quite robust to the sensitivity analyses performed.Conclusions: This is the first economic evaluation in this complex field and offers a model to be developed in future research. The results provide preliminary indications that enhanced staff contact may be cost-effective. However, the limited evidence available, and the limited UK data in particular, suggest that further research is required to provide results with confidence.

scholarly journals Economic Impact of Changes in Neonatal Intensive Care Unit Ventilation Strategies with the Advent of New Noninvasive Ventilation Techniques: A Review and Proposed Assessment Framework for High Flow Therapy as a Routine Respiratory Support Paradigm

10.36469/9840 ◽  
2015 ◽  
Vol 3 (1) ◽  
pp. 34-42
Author(s):  
Jan B. Pietzsch ◽  
Abigail M. Garner ◽  
Michael McQueen
Keyword(s):  
Intensive Care ◽  
Economic Impact ◽  
Neonatal Intensive Care ◽  
High Flow ◽  
Respiratory Support ◽  
Sensitivity Analyses ◽  
Base Case ◽  
Model Parameters ◽  
Current Standard ◽  
Term Infants

Background: High flow therapy (HFT) has been demonstrated to be a safe and effective noninvasive respiratory support technique for the treatment of pre-term infants in neonatal intensive care. Objectives: Our objective was to develop a quantitative framework based on available evidence to estimate the economic impact of adoption of a HFT respiratory support strategy compared to current standard of care. Methods: Model parameters were derived from a recent study comparing respiratory modality utilization between five US-based neonatal intensive care units (NICUs) adopting a HFT strategy and a larger pool of NICUs in the Vermont-Oxford Network (VON), and from single center experience. We computed the total cost difference between the respiratory support strategies based on published cost data. Parameter uncertainty was tested in sensitivity analyses. Results: The constructed model projected expected cost savings of $2,317 for the HFT strategy for the base case. Results were sensitive to length of HFT use, length of CMV, cost of HFT, and length of nCPAP support. Conclusions: Adoption of a HFT strategy appears to be associated with meaningful savings in total NICU episode of care costs, primarily because of reductions in the time of conventional mechanical ventilation. Further research is warranted to substantiate these findings.

Deferasirox for myelodysplastic syndrome patients with transfusional iron overload: A budget impact analysis

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 17019-17019 ◽  
Author(s):  
N. Mody-Patel ◽  
S. L. Goldberg ◽  
V. Barghout
Keyword(s):  
Iron Overload ◽  
Incremental Cost ◽  
Budget Impact ◽  
Chelation Therapy ◽  
Cost Driver ◽  
Sensitivity Analyses ◽  
Care Plan ◽  
Base Case ◽  
Model Parameters ◽  
Medication Costs

17019 Background: Myelodysplastic syndromes (MDS) affect 12–20,000 in the US yearly. Blood transfusions, a mainstay of treatment, place MDS patients (pts) at risk for complications of transfusional iron overload (IO). Although recent data suggests iron accumulation significantly reduces survival in low and intermediate -1 risk MDS, incremental cost of adding chelators to health plan formularies are unknown. The economic impact of treating transfusional IO in MDS with two commercially available chelating agents were estimated from a health care plan (hcp) perspective. Methods: An Excel based model was developed to ascertain the incremental cost per treated MDS pt associated with oral deferasirox (DSX) relative to subcutaneous (sq) deferoxamine (DFO). Annual Per Member Per Month (PMPM) cost was calculated by dividing differences in annual expenditures for DSX and DFO by total plan membership. Data from published literature and pivotal clinical trials were used to estimate MDS prevalence and chelation eligibility. Costs associated with infusing sq DFO were based on medical claims analysis from 2001 to 2004. Medication costs were based on wholesale acquisition costs assuming 100% compliance. Sensitivity analyses were performed by varying model parameters. Results: A hcp of one million pts is estimated to have 119 pts with MDS, of which 22% are eligible for iron chelation therapy. The base-case model resulted in an incremental annual saving of $389.48 per treated MDS pt and an incremental budget impact of $0.0 PMPM of the hcp (function of relatively few MDS pts spread over million in hcp) associated with the use of DSX. Overall, 34.2% of DSX cost was offset by the absence of infusion costs, the key cost driver. Sensitivity analyses of varying pt weight and infusion costs showed the model results were robust. Conclusions: The annual budget impact of switching MDS patients with IO to DSX from DFO will potentially result in cost-savings for US health plans. These results should be considered in the selection of chelation therapy. No significant financial relationships to disclose.

Abstract WP330: Unreliable Long-term Cost Data Introduces Substantial Uncertainty Into Stroke Cost-Effectiveness Models

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
Michelle Leppert ◽  
James Burke ◽  
Jennifer Simpson ◽  
Jonathan Campbell
Keyword(s):  
Cost Effectiveness ◽  
Cost Effective ◽  
Sensitivity Analyses ◽  
Tissue Type ◽  
Base Case ◽  
Decision Analytic Model ◽  
Term Care ◽  
Cost Estimates ◽  
The Cost

Background: Cost effectiveness analysis (CEA) models evaluate the value of stroke care methods. Estimates of long-term costs of stroke, a key input, vary substantially. We explored the effect of long-term cost variation on the interpretation of stroke CEA models. Methods: We estimated the lifetime costs and outcomes associated with intravenous tissue-type plasminogen treatment in acute ischemic stroke within the 0-3 hr and 3-4.5 hr windows. Decision analytic model inputs were from previously published literature, and clinical trials. We varied annual long term care costs, using cost groupings (i.e. cost per year at a given level of function) from published CEA models. Low estimates were from the Stroke Treatment Economic Model based on cost in the United Kingdom. High estimates were from the Rochester Stroke Registry from 1987 to1989. Split estimate took cost of minor disability from the low estimate and cost of major disability from the high estimate. We estimated incremental cost effectiveness ratio (ICER) for the base-case and conducted probabilistic sensitivity analyses. Results: The split estimate resulted in the lowest ICERs and was the dominant strategy (improved efficacy, cost savings) in all three conditions (0-3hr, 3-4.5hr, ECASS III) with ICERS -$67,530, -$223,294, and -$39,517 respectively. The low estimate, while still cost effective, increased ICERS substantially to $809, $144, and $18,549 respectively. When low cost estimates were substituted for split cost estimates, the percentage of dominant stimulations dropped by more than half (figure 1). Conclusion: Varying cost estimates led to considerably different conclusions regarding the cost effectiveness of tPA . For a highly cost-effective therapy, these differences do not affect the overall judgement of cost-effectiveness. However, this uncertainty could alter the cost effectiveness of more marginally effective or costly treatments. More reliable long term stroke cost estimates are needed.

EXPRESS: Drip-and-Ship versus Mothership for Endovascular Treatment of Acute Stroke: A Comparative Effectiveness Analysis

2021 ◽  
pp. 174749302110087
Author(s):  
Xiao Wu ◽  
Charles Wira ◽  
Charles Matouk ◽  
Howard Forman ◽  
Dheeraj Gandhi ◽  
...  
Keyword(s):  
Acute Stroke ◽  
Health Benefit ◽  
Sensitivity Analyses ◽  
Base Case ◽  
Decision Analytic Model ◽  
Model Parameters ◽  
Stroke Patients ◽  
Case Scenario ◽  
Life Years ◽  
Stroke Center

Background Triage for suspected acute stroke has two main options (1) transport to the closest primary stroke center (PSC) and then to the nearest comprehensive stroke center (CSC) (Drip-and-Ship) or (2) transport the patient to the nearest CSC, bypassing a closer PSC (mothership). The purpose was to evaluate the effectiveness of drip-and-ship versus mothership models for acute stroke patients. Methods A Markov decision-analytic model was constructed. All model parameters were derived from recent medical literature. Our target population is adult patient with sudden onset of acute stroke over a one-year horizon. The primary outcome is quantified in term of quality-adjusted-life-years (QALYs). Results The base-case scenario shows the Drip-and-Ship strategy has a slightly higher expected health benefit, 0.591 QALY, as compared to 0.586 QALY in the Mothership strategy when the time to PSC is 30 minutes and to CSC is 65 minutes, although the difference in health benefit becomes minimal as the time to PSC increases towards 60 min. Multiple sensitivity analyses show that when both PSC and CSC are far from place of onset (>1.5 hours away), Drip-and-Ship becomes the better strategy. Mothership strategy is favored by smaller difference between distances to PSC and CSC, shorter transfer time from PSC to CSC, and longer delay in reperfusion in CSC for transferred patients. Drip-and-Ship is favored by the reverse. Conclusion Drip-and-ship has a slightly higher utility than mothership. This study assesses the complex issue of prehospital triage of acute stroke patients, and can provide a framework for real-world data input.

Modelling heavy metal mobilisation in solid waste deposits - a predictive tool for environmental risk assessment

1999 ◽  
Vol 39 (10-11) ◽  
pp. 193-196
Author(s):  
J. Petersen ◽  
J. G. Petrie
Keyword(s):  
Heavy Metal ◽  
Solid Waste ◽  
Environmental Risk ◽  
Mechanistic Model ◽  
Small Sample ◽  
Waste Material ◽  
Metal Species ◽  
Model Parameters ◽  
Assessment Methodology ◽  
Predictive Tool

The release of heavy metal species from deposits of solid waste materials originating from minerals processing operations poses a serious environmental risk should such species migrate beyond the boundaries of the deposit into the surrounding environment. Legislation increasingly places the liability for wastes with the operators of the process that generates them. The costs for long-term monitoring and clean-up following a potential critical leakage have to be factored in the overall project plan from the outset. Thus assessment of the potential for a particular waste material to generate a harmful leachate is directly relevant for estimating the environmental risk associated with the planned disposal operation. A rigorous mechanistic model is proposed, which allows prediction of the time-dependent generation of a leachate from a solid mineral waste deposit. Model parameters are obtained from a suitably designed laboratory waste assessment methodology on a relatively small sample of the prospective waste material. The parameters are not specific to the laboratory environment in which they were obtained but are valid also for full-scale heap modelling. In this way the model, combined with the assessment methodology, becomes a powerful tool for meaningful assessment of the risks associated with solid waste disposal strategies.

Sign in / Sign up

Export Citation Format

Share Document