Total Annual Cost Research Articles

Optimal 4E design and innovative R-curve approach for a gas-solar- biological waste polygeneration system for power, freshwater, and methanol production

BackgroundCogeneration power plants traditionally rely on fossil fuels to produce stable power and heat. However, increasing energy demand and population growth have intensified the emission of biological pollutants due to fossil fuel use. The Global Alliance on Health and Pollution advocates for integrating renewable energy sources to mitigate these issues. ObjectivesThis study aims to evaluate the integration of a solar-biomass polygeneration system with a hybrid solar-waste-fossil fuel cogeneration system. The goal is to analyze the system from technical, economic, and environmental perspectives, focusing on optimizing energy demand and minimizing environmental impact. MethodsTo assess energy demand and supply, the R-curve methodology was applied to the hybrid cogeneration system, with a specific focus on solar and biomass renewable energies. Various scenarios were analyzed, including total annual costs, pollutant emissions, water footprint, and overall environmental impact based on life cycle assessment. The study examined and compared the performance of three types of biomass waste (Municipal solid waste, mixed paper waste, and date palm waste). Multi-objective optimization was performed using artificial intelligence and machine learning techniques, employing four meta-heuristic algorithms. The conditions generated by each algorithm were analyzed and compared. ResultsMunicipal solid waste, being the most readily available fuel, provided the most favorable economic conditions for the system. Environmentally, municipal solid waste ranked in the middle compared to other fuels. Among the optimization algorithms, the Salps swarm algorithm proved to be the most efficient in terms of calculation time and system efficiency improvements. The optimization improved net power generation by 5.25 %, overall energy efficiency by 16.27 %, total cost rate by 10.19 %, and total environmental impact rate by 14.02 %. ConclusionThe integrated system's performance was analyzed across different climatic change throughout the year. The multi-objective Salps swarm algorithm optimization demonstrated significant benefits in enhancing system efficiency and reducing costs and environmental impacts.

The Economic Burden of Type 2 Diabetes Mellitus in Pakistan: A Cost of Illness Study.

Type 2 Diabetes Mellitus (T2DM) is a highly prevalent disease with a chronic nature and poses a significant health burden worldwide, with no exception in Pakistan. Hence, this study aimed to explore the financial burden of T2DM in Pakistan through cost of illness analysis. A prevalence-based, cross-sectional study was conducted using a structured data collection tool from the patient's perspective. Through structured interviews by trained data collectors, the data regarding direct medical costs, direct non-medical costs, and indirect costs were collected and further verified through prescriptions and bills. After testing the normality of data, mean and median with interquartile range were used to present cost data, while non-parametric tests, i.e., the Mann-Whitney U test and the Kruskal-Wallis test, were used to assess factors associated with costs, as cost data were not normally distributed. The study included 522 participants, with a majority being female (54%) and aged between 41 and 60 years (64%). The mean annual total cost per patient was USD 235.1 (median = USD 162.8), comprising direct medical costs, 93.2% (mean = USD 219.2; median = USD 150.0), direct non-medical costs, 5.3% (mean = USD 12.4; median = USD 7.1), and indirect costs, 1.5% (mean = USD 3.5; median = USD 1.9). Costs were significantly higher for patients with advanced age, high literacy, higher household incomes, duration of diabetes, more than one complication, and using combination therapy. The economic burden of T2DM in Pakistan is substantial, with medication costs being the largest component. Effective management strategies and policy interventions are crucial to mitigate this burden and improve the economic and health outcomes for diabetic patients.

Dimethyl carbonate/methanol separation by azeotropic distillation with water: An alternative process driven by low-pressure steam

This study reported a conceptual design of dimethyl carbonate/methanol (DMC/MET) separation via an azeotropic distillation (AD) process with water as the entrainer. Water can form a minimum azeotrope with DMC, stripping DMC from MET via a distillation column. Meanwhile, the liquid–liquid equilibrium can lift the DMC fraction from the azeotropic composition to a much higher level with a decanter. It enables the subsequent distillation column to produce pure DMC. The techno-economic analysis after process optimization demonstrated that the total annualized cost (TAC) of the AD process is 13.8 % lower than the conventional extractive distillation (ED) process. Subsequently, heat integration and double-effect distillation were introduced to further increase the energy efficiency. The improved AD process is also superior to the improved ED process (31.7 % energy cost and 4.1 % TAC saved). Moreover, the moderate temperature of the reboilers of the AD process with water as the entrainer further elevates its superiority since industrial waste heat can be applied in this case.

Budget Impact Analysis of Dapagliflozin in Treating Patients With Heart Failure With Reduced Ejection Fraction From the Perspective of Malaysian Public Healthcare System

PurposeThis is a budget impact analysis that compared the scenario of treating heart failure with reduced ejection fraction (HFrEF) using dapagliflozin plus standard of care (SoC) versus a scenario without dapagliflozin, from the perspective of Ministry of Health (MOH) Malaysia over a 5-year time horizon. MethodsA Microsoft Excel-based cost calculator was developed for such comparison. The estimated size of eligible population, uptake rates for dapagliflozin, as well as costs related to drugs, clinical events, and adverse events were based on published data, official tariffs, and databases, and expert opinion. Clinical data from the DAPA-HF trial were used to inform efficacy and safety inputs (i.e., hospitalization for heart failure (hHF), cardiovascular death, and adverse events). Results were reported as total annual and cumulative costs (in 2023 Malaysian Ringgits [RM], United States Dollars [USD], and European Union Euros, [EUR]; with exchange rates of 1 USD = RM 4.40 and 1 EUR = RM 4.90]), as well as the number of clinical events. Sensitivity and scenario analyses were also conducted. FindingsThe base-case analysis estimated that over a five-year period, the adoption of dapagliflozin for HFrEF treatment would result in a cumulative cost-saving of RM 2.6 million (USD 0.6 million/EUR 0.5 million), representing a 0.3% reduction in costs, driven primarily by reduced expenditure on hHF. Moreover, dapagliflozin treatment would lead to 731 fewer hHF and 366 fewer cardiovascular deaths. Sensitivity and scenario analyses revealed that the results were most sensitive to assumptions regarding loop diuretic requirements and the cost of dapagliflozin. Although cost savings or a net-zero balance were projected for the first four years, an anticipated 2.5% annual increase in dapagliflozin uptake in the longer term would lead to additional costs for the MOH, starting from the fifth year. ImplicationsIncorporating dapagliflozin into the SoC can improve health outcomes for HFrEF patients and may generate cost savings, potentially easing the economic strain of HFrEF management on Malaysia's public healthcare system in the short term. Nonetheless, a modest increase in budget should be anticipated as more patients gain access to the treatment over time.

Safety-driven design of carbon capture utilization and storage (CCUS) supply chains: A multi-objective optimization approach

Carbon capture, utilization, and storage supply chains (CCUS) play a pivotal role in achieving sustainability targets but necessitate meticulous risk identification and mitigation measures. Traditional safety assessments often occur post-design, constraining proactive risk management efforts. Hence, there is a pressing need to optimize safety performance during the design stages. To address this challenge, a framework for evaluating and optimizing CCUS supply chain safety performance using inherent safety index system (ISI) is introduced. Recognizing the trade-offs between total cost, environmental impact reduction, and risk mitigation, our approach considers multi-objective optimization to concurrently address these sustainability objectives and generate a Pareto set of solutions. Utilizing the augmented ε-constraint method, we applied this framework to optimize CCUS networks and develop sustainable designs across three key objectives. The method was applied to a CCUS system that includes various CO2 utilization pathways to minimize the total annual cost, CO2 emissions, and safety risks. The resulting Pareto surface illustrates unique network configurations, each representing a distinct trade-off scenario. Through a case study, we optimized a CCUS network to achieve economic, environmental, and safety objectives. The most economically viable design, with a total annual cost of $97 million and a 40 % net carbon reduction, prioritizes CO2 utilization for value-added products, while limiting CO2 sequestration. Conversely, safety-focused designs shift utilization towards safer routes, including CO2 sequestration and algae production. The proposed framework offers a systematic approach to developing sustainable CCUS supply chain designs, balancing economic viability, environmental sustainability, and safety.

Cost-effectiveness analysis of continuous positive airway pressure treatment for obstructive sleep apnea in Singapore from a health system perspective.

This study assessed the cost-effectiveness of continuous positive airway pressure treatment for obstructive sleep apnea in Singapore from a health system perspective. The analysis evaluated a 5-year care pathway using a Markov model, considering per-patient costs of treatment, health system cost savings of obstructive sleep apnea and attributed conditions, the effectiveness measured in disability-adjusted life years with a discount rate of 3% and a weighted 5-year continuous positive airway pressure adherence of 74.1% from Singapore studies. Per-patient costs of treatment were from a large public hospital in Singapore. Efficacy of continuous positive airway pressure treatment, health system costs and disability-adjusted life years were obtained from literature; costs are in US dollars. We conducted probabilistic sensitivity analysis, one-way sensitivity analysis and what-if analysis. Based on a willingness-to-pay threshold of US $50,000 per disability-adjusted life year in USA, continuous positive airway pressure therapy was highly cost-effective, with an incremental cost-effectiveness ratio of $13,822 per disability-adjusted life year averted. Compared with the annual total costs of $856 for patients with continuous positive airway pressure treatment diagnosed by an inpatient sleep study, the total costs for those diagnosed by a home sleep test were $625, resulting in a remarkable 27% reduction per patient per year. One-way sensitivity analysis indicated that costs of treatment, effectiveness of continuous positive airway pressure treatment and adherence had a higher impact on the cost-effectiveness of continuous positive airway pressure therapy. The what-if analysis suggested that for continuous positive airway pressure treatment to be cost-effective, adherence rate should be at least 16.1%. These findings provide valuable insights for policymakers in making informed decisions on funding diagnosis and continuous positive airway pressure therapy within Singapore's healthcare system.

Kinetic insights into energy-saving and low-carbon reactive distillation processes for the transesterification to dimethyl carbonate

The transesterification of propylene carbonate (PC) or ethylene carbonate (EC) to dimethyl carbonate (DMC) by using catalytic reactive distillation (RD) is a promising approach for carbon dioxide utilization. However, there is still scarcity of comprehensive comparison between the two RD processes. Hence, using the UNIQUAC model and kinetics calibrated by literature and our experiments, we conduct an extensive comparison of the two RD processes. Based on the kinetic insights, laboratory RD processes for both reactions are modeled, analyzed, and experimentally validated. Consequently, two RD processes designed to produce 60 ktpy of DMC are optimized and compared. The interplay and control factors between reaction and separation are elucidated and clarified via investigating variations of the actual chemical equilibrium constant profile compared with theoretical values along the reactive section at various pressures, liquid holdups, etc. The results reveal that the optimized EC RD process achieves almost 50 % reductions in both total annual cost and carbon dioxide emission compared to the PC RD process. This work facilitates the carbon neutrality and provides an essential guide for quantitatively assessing the two routes.

Economy and energy flexibility optimization of the photovoltaic heat pump system with thermal energy storage

Photovoltaic systems have been widely applied in building energy systems. However, with the sharp increase in demand of electricity in buildings during heating and cooling seasons, the uncertainty of photovoltaic generation further exacerbates the peak-valley difference in electricity use. To improve the economy and energy flexibility of buildings in hot summer and cold winter zones of China, a rule-based operation strategy was proposed for the photovoltaic heat pump with thermal energy storage system to optimize the size of the thermal energy storage system and system operation, with aims of minimizing the total annual cost of the system and maximizing the self-consumption rate of the photovoltaic generation. The effects of grid export power limits, grid import power limits, feed-in tariffs, and PV generation on the system operation optimization results were also investigated. The results indicated that by integrating the thermal energy storage system into the photovoltaic heat pump system, the self-consumption rate of the photovoltaic generation was reduced by 2.39 %, the total annual cost of the system was decreased by 6.61 %, and the payback period of the thermal energy storage system was 1.31 years. The optimum size of the thermal energy storage system and the self-consumption rate of the photovoltaic generation decreased with the increasing grid export power limits and grid import power limits. In contrast, higher grid export power limits, grid import power limits, feed-in tariffs, and PV generation all resulted in a lower total annual cost. This study provided a systematic design and operation optimization method for building energy systems.

Biologics and Biosimilars in Albania; Consumption and Costs

Biological therapies use proteins that have been produced with biological technology to generate targeted effects within the body, impact the body's immune system, and reduce inflammation at various stages. Biologics are used in the treatment of conditions such as rheumatoid arthritis, systemic lupus, ankylosing spondylitis, arthropathic psoriasis, and psoriatic arthritis. The aim of the study is to conduct a comprehensive review and analyze the market dynamics related to the use of these treatments in Albania. Methods: This is a retrospective and observational study based on FDSKSH’s data for 2023. Results: The total annual reimbursement cost for 2023 was ALL 188,208,780 (1 ALL = 0.01 USD). The average reimbursement cost per patient was ALL 209820.2679. The use of biologics and biosimilars represents 0.028% of all prescriptions and accounts for 1.56% of the total reimbursement costs for drugs. In 2023, the reimbursement cost covered by FDSKSH was 7.14% lower than in 2022. 87.17% of the patients were treated with Tumor Necrosis Factor (TNF) Inhibitors. Etanercept 25 mg (biosimilar) had the highest price reduction of 32.83% in 2024. The most expensive drug in 2023 was Secukinumab 150 mg. Biologics account for 61% of the total annual reimbursement cost, while biosimilars account for 39%. Conclusions: The prescription of biologics is lower compared to biosimilars, but they are associated with significant costs that impact the overall reimbursement costs. The prices of biologics and biosimilars were lower than those in Kosovo, Italy, Greece and will decrease in 2024. Costeconomic evaluations of the most expensive biologics and biosimilars are important for the management of financial resources.

Mechanism analysis and performance comparison of extractive distillation with different extractants for separating methyl tert-butyl ether/methanol mixture

Methyl tert-butyl ether (MTBE) is an important chemical raw material and fuel additive commonly used in the chemical industry and can form minimum boiling azeotrope with methanol (MeOH). In this article, extractive distillation processes with common-extractant (diethylene glycol, DG), counter-extractant (chlorobenzene, CB) and ionic liquid ([MIM][HSO4]) for the separation of MTBE and MeOH binary azeotrope are investigated simultaneously for the first time. Moreover, five quantum chemical calculation methods of σ-profiles, electrostatic potential, interaction energy, Hirshfeld surface and weak interaction are used simultaneously for the first time to reveal the extractive distillation mechanism of different extractants in detail. Finally, three extractive distillation processes (CED-IL, CED-DG, CED-CB) are established and optimized with total annual costs (TAC) and CO2 emissions as objectives. Their performances are comprehensively compared from the aspects of economy, environment, energy, exergy and inherent safety under the optimal conditions. The results demonstrate that, in comparison to the CED-DG process, the CED-IL process reduces TAC by 31.0%, total energy consumption (TEC) and gas emissions by 27.7%, process route index (PRI) by 36.4% and increase thermodynamic efficiency by 46.4%, while the CED-CB process increases TAC by 29.1%, TEC and gas emissions by 23.2%, PRI by 22.1% and reduce thermodynamic efficiency by 11.4%.

Ionic liquid-ethanol mixed solvent design for the post-combustion carbon capture

Global warming driven by CO2 emissions is a critical global issue, with a significant portion of post-combustion emissions. Effective capture and recovery of CO2 from flue gas are essential for mitigating the greenhouse effect and advancing a low-carbon economy. This study proposes an ionic liquid (IL)-ethanol mixed solvent for post-combustion carbon capture. The [C1Py][CF3COO]-ethanol mixed solvent is tailored by solving a computer-aided ionic liquid design (CAILD)-based MINLP optimization problem. The performance of this mixed solvent was thoroughly evaluated through rigorous process simulations. Additionally, a standard oil-based measurement is introduced to assess the quality of energy consumption. The results indicate that the post-combustion carbon capture process using the [C1Py][CF3COO]-ethanol mixed solvent reduces carbon emissions, energy consumption, and total annual cost by 62.33%-75.51%, 64.71%-72.7%, and 53.6%-61.7%, respectively, compared to the MEA/MDEA processes. These findings suggest that the IL-ethanol mixed solvent process is a highly feasible and promising solution for environmental protection, energy efficiency, and economic viability in post-combustion carbon capture applications.

Optimal allocation of autonomous PV-powered fast charging stations for electrified transportation considering traffic dynamics

In response to the imperative to reduce greenhouse gas emissions, global efforts are focusing on electrifying transportation and adopting renewable energy sources. This necessitates establishing reliable fast-charging stations (FCSs) for the widespread integration of electric vehicles (EVs). Indeed, the arbitrary distribution of FCSs can detrimentally affect the efficiency of traffic movement. Thus, this paper presents a planning methodology aimed at optimizing the allocation of FCSs within large-scale transportation networks. The energy system proposed includes an autonomous photovoltaic (PV)-powered FCS based on a DC microgrid, supplemented by a stationary battery energy storage system for backup power. The behavior of EVs within the traffic flow is modeled using a realistic traffic simulation software called Dynamic Network Assignment Simulation for Advanced Road Telematics (DYNASMAT). The conflicting objectives of minimizing total annual costs and EV average waiting time at stations are addressed through multi-objective optimization. To solve this optimization problem, the GAMS software is employed. A transportation network with 92 nodes and 284 links is utilized to test the proposed approach. The proposed autonomous PV-powered FCS is compared with Natural Gas-fired Distributed Generators (NGDG)-powered FCS. The simulation results show that while the NGDG-powered FCS exhibits higher emissions, the autonomous PV-powered equivalent operates emission-free. However, the annual cost of the autonomous PV-powered FCS is higher than that of the NGDG-powered FCS.

Enhancing exergy efficiency and environmental sustainability in pressure swing azeotropic distillation

This study explores the economic, energetic, exergy efficiency, and environmental benefits of energy integration in pressure-swing distillation, focusing on the separation of tetrahydrofuran/water and acetone/chloroform azeotropes. Heat integration and heat pump techniques are applied to reduce energy consumption. Three energy-efficient configurations are examined, comparing total annual cost (TAC), total energy consumption (TEC), CO2 emissions, and second-law efficiency. In the tetrahydrofuran/water system, heat integration and heat pump technologies outperform conventional processes, achieving up to 50.2% TAC reduction, 59.6% TEC reduction, 82.8% CO2 emission reduction, and thermodynamic efficiencies up to 23.5%. In the acetone/chloroform system, similar improvements are observed, with up to 70.9% TAC reduction, 87.2% CO2 emission reduction, and thermodynamic efficiencies up to 17.6%. These findings demonstrate the effectiveness of energy-saving strategies, endorsing process intensification for environmentally sustainable azeotropic mixture separations.

Direct and indirect costs of paediatric asthma in the UK: a cost analysis

ObjectiveTo estimate the cost of paediatric asthma from a UK National Health Service (NHS) and societal perspective and explore determinants of these costs.DesignCost analysis based on data from a large...

Estimated economic costs of dental implants among older South Korean adults, 2015-2018.

Dental implants are a considerable financial burden for elderly people and their caregivers. This study aimed to calculate the estimated economic costs of dental implants on the Korean older population. The economic costs of dental implants for adults aged 75 years and older were estimated from a societal perspective, considering both direct and indirect expenditures. We used data from the Korean National Health Insurance Service for the period 2015-2018 to estimate the medical costs. Noninsured medical costs were estimated from research on medical expenses by the National Health Insurance Review and Assessment Service. Indirect costs related to transportation fees and time loss were obtained. The Cochran Armitage trend test was performed to examine the trend of the economic burden of dental implants. The estimated economic costs showed from 2015 to 2018 (total costs: $26.54-55.66 million, total costs after discount: $17.11-39.56 million). Direct costs, including insured and noninsured medical costs, represented from $25.81 to $47.03 million. Indirect costs, including transportation and time costs, ranged from $0.73 to $1.63 million. The impact of the total dental implant costs was 0.0018%-0.0034% of the Korean annual gross domestic product and 1.03%-1.59% of the annual total costs of dental care benefits. The estimated economic burden of dental implants significantly increased from 2015 to 2018 in older South Korean adults. These results will provide a foundation and guidance for further health economic studies on the burden of dental implants in the elderly population.

A modified multi-objective particle swarm optimization (M-MOPSO) for optimal sizing of a solar–wind–battery hybrid renewable energy system

This study proposes and utilizes a modified multi-objective particle swarm optimization (M-MOPSO) algorithm for the optimal sizing of a solar-wind-battery hybrid renewable energy system for a rural community in Rivers State, Nigeria. Unlike previous studies that primarily focused on minimizing total economic cost (TEC) and total annual cost (TAC), this research emphasizes minimizing the loss of power supply probability (LPSP) and levelized cost of energy (LCOE). The M-MOPSO algorithm introduces a dynamic inertia weight, a unique repository update mechanism, and a dominance-based personal best update strategy, which collectively enhance its performance. Comparative analysis with PSO, NSGA-II, MOPSO and hybrid GA-PSO demonstrates that M-MOPSO consistently achieves a lower LPSP, although its LCOE remains higher. The M-MOPSO optimal configuration when simulated under various climatic scenarios was able to meet the energy needs of the community irrespective of ambient condition.

Bus fleet decarbonization under macroeconomic and technological uncertainties: A real options approach to support decision-making

Fleet owners deal with various and critical uncertainties while planning bus fleet replacement, encompassing macroeconomic and technological factors, such as fuel and electricity prices, energy consumption, purchasing costs of electric batteries and powertrains, and bus salvage value upon resale. This paper proposes a Real Option-based framework to evaluate investment choices in different bus technologies over time (diesel, hybrid electric, compressed natural gas, and full-electric), where the proposed options usually involve replacing existing diesel fleets with alternatively powered buses. In particular, we provide a multi-option least squares Monte Carlo simulation to help fleet owners in making cost-effective investment decisions, resulting in potential cost savings of up to 10% of the annual total cost of ownership. By applying the proposed approach to different bus route types (inner-city, urban, suburban, commuter), the results show how the optimal investment choices for fleet replacement change over time. Initially, diesel buses or, at most, compressed natural gas buses are more cost-effective compared to electric technology. However, as electric technology becomes increasingly competitive, internal combustion buses are phased out. Inner-city and urban routes are better suited for the electric transition, whereas the transition may progress more slowly on other route types.Finally, we show that, under technological and macroeconomic uncertainties, the duration of contracts can strongly affect the investment decisions, in absence of specific guarantees on the new fleet.

A Comparative Study on the Corrosion Performance of A7, A36 and A588 Alloys at Different NaCl Concentration Exposure

Corrosion can significantly impact the performance of structures, and corrosion-related maintenance is a primary contribution to annual transportation infrastructure costs. The current NBI data reports that the poor condition of the bridges around US have increased by 10%, and 50% of the bridges in Connecticut are either in poor or fair condition. Bridges in the US share approximately 37% of the total annual cost due to corrosion. Bridges are primarily constructed of A7, A36, A588, and A242 steel. ASTM A7 steel was used in bridge construction until 1967. Major limitations of A7 steel include poor corrosion resistance and mechanical properties, which ultimately led to the replacement of A7 steel by A36 steel after 1967. Though A36 steel shows better mechanical properties, it does not possess improved corrosion performance compared to A7. A588 and A242, which are also called weathering steels, display significantly higher corrosion resistance paired with desired mechanical properties, but the cost of these so-called weathering steels is also higher. The present study aims at characterizing the corrosion performance of bridge steels A7, A36 and A588 under a wide range of chloride-rich environments so that we may improve our predictions for bridge longevity.A major portion of the existing literature on steel corrosion mechanisms considers the study of plain carbon steel. Plain carbon steels form corrosion products such as Goethite, Akageneite, Lepidocrocite, and Magnetite, having the chemical formulas α-FeOOH, β-FeOOH and γ-FeOOH and Fe3O4 respectively. γ-FeOOH forms during the initial stages of corrosion formation where Magnetite being the final product. β-FeOOH is an intermediate product but is detrimental for the performance of the bridge since the oxide formed is not protective.The addition of specific alloying elements in the bridge steel grades (including Cu) can heavily influence the corrosion mechanisms at work and subsequently the corrosion rates. Further, the exposure to various environmental conditions such as rain, snow, hail, wind, and thermal cycles will lead to successive wetting and drying conditions. Bridges in colder climates are exposed to de-icing salts that can accumulate on horizontal surfaces or within the corrosion products that form. Each of these factors makes accurate prediction of corrosion rates on specific bridge components difficult.The current study compares the corrosion performance of A7, A36 and A588 alloys at different NaCl concentration exposure (1 wt.%, 2 wt.%, 3.5 wt.% and 5 wt.%) for difference steel surface conditions (oxidized and polished). Corrosion studies on these alloys were performed using wet-dry cyclic exposure to obtain corrosion at an accelerated pace. Each wet-dry cycle consisted of 15 minutes of wetting and 1 hour drying period. Test coupons were in the size of 50 mm×25 mm×4.76 mm. A total of 400 wet/dry cycles were performed to determine the effect of longer exposure to salt environments. Batches of samples of each alloy were collected at 25, 50,75, 100, 150, 200, 250, 300, 350, 400 cycles to observe corrosion trends with increase in cycles. Further, the samples were photographed, and the surfaces were compared. Corrosion samples retrieved from bridges in Connecticut were compared to the lab-tested coupons. The phases present in the corrosion products were characterized using XRD and SEM. The results showed lower magnetite compared to the field samples, and the presence of detrimental β – FeO(OH,Cl) was significantly higher at the higher [Cl-] concentrations. Mass gain studies were performed by measuring the weight of each test coupon at regular intervals throughout the wet-dry cyclic testing. The mass gain per unit surface area of the sample was calculated for the different conditions. Cross-sections of the corroded samples were examined using optical light microscopy and SEM-EDS. These results will be used to build and validate a prediction tool for field evaluation of bridge corrosion.

Prediction and Prevention of Bridge Performance Degradation Due to Corrosion, Material Loss, and Microstructural Changes

Corrosion can significantly impact the performance of structures, and corrosion-related maintenance is a primary contribution to annual transportation infrastructure costs. The current NBI data reports that the poor condition of the bridges around US have increased by 10%, and 50% of the bridges in Connecticut are either in poor or fair condition. Bridges in the US share approximately 37% of the total annual cost due to corrosion. Bridges are primarily constructed of A7, A36, A588, and A242 steel. ASTM A7 steel was used in bridge construction until 1967. Major limitations of A7 steel include poor corrosion resistance and mechanical properties, which ultimately led to the replacement of A7 steel by A36 steel after 1967. Though A36 steel shows better mechanical properties, it does not possess improved corrosion performance compared to A7. A588 and A242, which are also called weathering steels, display significantly higher corrosion resistance paired with desired mechanical properties, but the cost of these so-called weathering steels is also higher. The present study aims at characterizing the corrosion performance of bridge steels A7, A36 and A588 under a wide range of chloride-rich environments so that we may improve our predictions for bridge longevity.A major portion of the existing literature on steel corrosion mechanisms considers the study of plain carbon steel. Plain carbon steels form corrosion products such as Goethite, Akageneite, Lepidocrocite, and Magnetite, having the chemical formulas α-FeOOH, β-FeOOH and γ-FeOOH and Fe3O4 respectively. γ-FeOOH forms during the initial stages of corrosion formation where Magnetite being the final product. β-FeOOH is an intermediate product but is detrimental for the performance of the bridge since the oxide formed is not protective.The addition of specific alloying elements in the bridge steel grades (including Cu) can heavily influence the corrosion mechanisms at work and subsequently the corrosion rates. Further, the exposure to various environmental conditions such as rain, snow, hail, wind, and thermal cycles will lead to successive wetting and drying conditions. Bridges in colder climates are exposed to de-icing salts that can accumulate on horizontal surfaces or within the corrosion products that form. Each of these factors makes accurate prediction of corrosion rates on specific bridge components difficult.The current study compares the corrosion performance of A7, A36 and A588 alloys at different NaCl concentration exposure (1 wt.%, 2 wt.%, 3.5 wt.% and 5 wt.%) for difference steel surface conditions (oxidized and polished). Corrosion studies on these alloys were performed using wet-dry cyclic exposure to obtain corrosion at an accelerated pace. Each wet-dry cycle consisted of 15 minutes of wetting and 1 hour drying period. Test coupons were in the size of 50 mm×25 mm×4.76 mm. A total of 400 wet/dry cycles were performed to determine the effect of longer exposure to salt environments. Batches of samples of each alloy were collected at 25, 50,75, 100, 150, 200, 250, 300, 350, 400 cycles to observe corrosion trends with increase in cycles. Further, the samples were photographed, and the surfaces were compared. Corrosion samples retrieved from bridges in Connecticut were compared to the lab-tested coupons. The phases present in the corrosion products were characterized using XRD and SEM. The results showed lower magnetite compared to the field samples, and the presence of detrimental β – FeO(OH,Cl) was significantly higher at the higher [Cl-] concentrations. Mass gain studies were performed by measuring the weight of each test coupon at regular intervals throughout the wet-dry cyclic testing. The mass gain per unit surface area of the sample was calculated for the different conditions. Cross-sections of the corroded samples were examined using optical light microscopy and SEM-EDS. These results will be used to build and validate a prediction tool for field evaluation of bridge corrosion.

Economic burden of recurrent hyperkalemia in patients with chronic kidney disease.

Hyperkalemia is a common complication of chronic kidney disease (CKD) and can become recurrent in half of cases. However, the incremental economic burden associated with recurrent hyperkalemia is unknown. To evaluate all-cause health care resource utilization (HRU) and medical costs in patients with stage 3/4 CKD with recurrent hyperkalemia vs normokalaemia and vs nonrecurrent hyperkalemia. Data were from Optum's de-identified Market Clarity Data (January 1, 2016, to August 1, 2022). This retrospective observational cohort study compared patients with stage 3/4 CKD with recurrent hyperkalemia (≥2 hyperkalemia events within 1 year [hyperkalemia event: hyperkalemia diagnosis or potassium [K+]>5 mmol/l]; index was the first hyperkalemia event) with an exact- and propensity score-matched cohort of patients with normokalemia (K+ ≥3.5 to ≤5 mmol/l; random K+ as index) and separately with a matched cohort of patients with nonrecurrent hyperkalemia (1 hyperkalemia event within 1 year; index was hyperkalemia event). Patient characteristics, medication use, HRU, and medical costs were compared between cohorts using standardized mean differences during the 12-month baseline period. All-cause HRU and medical costs during the 12-month follow-up were compared using Wilcoxon rank sum tests for continuous variables and McNemar tests for categorical variables. Substudies of recurrent hyperkalemia vs normokalemia were conducted for patients with Medicare coverage and renin-angiotensin-aldosterone system inhibitor (RAASi) use. The recurrent hyperkalemia vs normokalemia sample comprised 4,549 matched pairs (Medicare substudy: 3,151; RAASi substudy: 3,535) and the recurrent hyperkalemia vs nonrecurrent hyperkalemia sample comprised 1,599 matched pairs. Baseline characteristics, HRU, and medical costs of the cohorts were similar after matching. During follow-up, patients with recurrent hyperkalemia had a mean of 11.2 more health care encounters (0.5 more inpatient admissions, 0.3 more emergency department visits, and 7.2 more outpatient visits) than patients with normokalemia. Patients with recurrent hyperkalemia also had double the total annual medical costs vs normokalemia ($34,163 vs $15,175; P < 0.001), mainly driven by inpatient costs ($21,250 vs $7,392), which accounted for 62.2% and 48.7% of total costs, respectively. Results were similar in the RAASi and Medicare substudies. Recurrent hyperkalemia was associated with a mean 4.3 more all-cause health care encounters and $14,057 higher medical costs (both P < 0.001) than nonrecurrent hyperkalemia. Recurrent hyperkalemia in patients with stage 3/4 CKD was associated with higher all-cause HRU and medical costs compared with normokalemia (including in patients with Medicare coverage and RAASi use) and nonrecurrent hyperkalemia. Research is needed to understand if long-term treatment strategies aimed at preventing hyperkalemia recurrence may alleviate this economic burden.