Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
1.
ACS Appl Mater Interfaces ; 15(37): 43732-43744, 2023 Sep 20.
Artículo en Inglés | MEDLINE | ID: mdl-37673786

RESUMEN

Massive carbon dioxide (CO2) emission from recent human industrialization has affected the global ecosystem and raised great concern for environmental sustainability. The solid oxide electrolysis cell (SOEC) is a promising energy conversion device capable of efficiently converting CO2 into valuable chemicals using renewable energy sources. However, Sr-containing cathode materials face the challenge of Sr carbonation during CO2 electrolysis, which greatly affects the energy conversion efficiency and long-term stability. Thus, A-site Ca-doped La1-xCaxCo0.2Fe0.8O3-δ (0.2 ≤ x ≤ 0.6) oxides are developed for direct CO2 conversion to carbon monoxide (CO) in an intermediate-temperature SOEC (IT-SOEC). With a polarization resistance as low as 0.18 Ω cm2 in pure CO2 atmosphere, a remarkable current density of 2.24 A cm-2 was achieved at 1.5 V with La0.6Ca0.4Co0.2Fe0.8O3-δ (LCCF64) as the cathode in La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) electrolyte (300 µm) supported electrolysis cells using La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) as the air electrode at 800 °C. Furthermore, symmetrical cells with LCCF64 as the electrodes also show promising electrolysis performance of 1.78 A cm-2 at 1.5 V at 800 °C. In addition, stable cell performance has been achieved on direct CO2 electrolysis at an applied constant current of 0.5 A cm-2 at 800 °C. The easily removable carbonate intermediate produced during direct CO2 electrolysis makes LCCF64 a promising regenerable cathode. The outstanding electrocatalytic performance of the LCCF64 cathode is ascribed to the highly active and stable metal/perovskite interfaces that resulted from the in situ exsolved Co/CoFe nanoparticles and the additional oxygen vacancies originated from the Ca2Fe2O5 phase synergistically providing active sites for CO2 adsorption and electrolysis. This study offers a novel approach to design catalysts with high performance for direct CO2 electrolysis.

2.
Nutrients ; 15(3)2023 Jan 17.
Artículo en Inglés | MEDLINE | ID: mdl-36771185

RESUMEN

The COVID-19 pandemic is worsening the disparities in food access in the United States. As consumers have been increasingly using grocery online ordering services to limit their exposure to the COVID-19 virus, participants of federal nutrition assistance programs lack the online benefit redemption option. With the support of the US Department of Agriculture (USDA), retailers are pilot-testing online food benefit ordering in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). By combining the Oklahoma WIC administrative data, the online ordering data from a grocery store chain in Oklahoma, and the COVID-19 data in Oklahoma, this study examines how WIC participants responded to the online food benefit ordering option and how their adoption of online ordering was associated with the COVID-19 incidence. Results show that from July to December 2020, 15,171 WIC households redeemed WIC benefits at an Oklahoma chain store, but only 819 of them adopted online ordering. They together completed 102,227 online orders, which accounted for 2.7% of the store visits and 2.6% of the monetary value of WIC redemptions at these stores. There was no significant relationship between WIC online ordering adoption and COVID-19 incidence in Oklahoma.


Asunto(s)
COVID-19 , Asistencia Alimentaria , Lactante , Niño , Humanos , Estados Unidos , Femenino , Supermercados , Oklahoma/epidemiología , Pandemias , Abastecimiento de Alimentos , COVID-19/epidemiología , Pobreza
3.
Artículo en Inglés | MEDLINE | ID: mdl-36294052

RESUMEN

BACKGROUND: Occupational studies on N-N-dimethylformamide (DMF) exposure among migrant workers in Korea are scarce. We determined the urine concentration of N-methylformamide (NMF) among migrant workers with DMF exposure and compared the data with those of native workers. METHODS: Data were collected from Workers' Special Health Examination and Work Environment Monitoring databases during 2014-2019. Workers aged ≥20 years were eligible to participate in the special health examination for DMF exposure. Urine concentrations of NMF were determined and compared between migrant and native workers. We also evaluated the factors affecting the difference in the urine concentration of NMF between the migrant and native workers. Multiple logistic regression was performed by adding confounders step by step. RESULTS: Among 9259 subjects, 504 (5.2%) were migrant workers. The mean urinary concentration of NMF was 6.73 mg/L in migrant workers, which was significantly higher than that in native workers (2.06 mg/L, p < 0.001). The odds of a urine concentration of NMF > 30 mg/L were significantly higher in migrant workers than in native workers after adjusting for sex and age (odds ratio [OR] = 7.31, 95% confidence interval [CI] = 4.66-11.45). However, the odds between the native and migrant workers were not significantly different when fully adjusted for confounders (OR = 1.12, 95% CI = 0.65-1.94). CONCLUSIONS: The excessive exposure to DMF among migrant workers was attributed not to differences in biological characteristics but to their work environment. Workers must have awareness of the use of protective equipment and knowledge of hazardous chemicals that they may be exposed to, especially at the workplace.


Asunto(s)
Exposición Profesional , Migrantes , Humanos , Dimetilformamida , Exposición Profesional/análisis , Industria Manufacturera , República de Corea , Sustancias Peligrosas
4.
MethodsX ; 9: 101857, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36176333

RESUMEN

In this study, a discrete element method (DEM) that can simulate particle plastic deformation, sintering, and electrode compaction of all-solid-state batteries was developed. The model can simulate elastic, plastic, and viscoelastic deformations that occur particularly in mold compaction processes. When the stress exceeds the yield strength of the material, inelastic deformation occurs, which can be described by either a plastic or viscoelastic response. We applied this model to simulate mold compaction of an All-Solid-State Battery (ASSB) electrode. This study implements the following novel features:•The model was derived from the Maxwell viscoelastic model and enabled the simulation of the elastic, plastic, and viscoelastic deformation of particles in a mold.•Particle deformation and sintering are modelled by the rate expression of the equilibrium overlap.•The area and spring factors are introduced to account for numerical issues when the porosity approaches zero.

5.
Korean J Intern Med ; 37(2): 468-477, 2022 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-35176208

RESUMEN

BACKGROUND/AIMS: Drugs with anticholinergic properties (DAPs) are associated with adverse health outcomes in older patients. The objective of this study was to evaluate the factors that determine the prescribing of more DAPs in long-term care hospitals (LTCHs) in Korea. In addition, the current patterns of DAP prescription were explored using a novel platform, which can collect data from LTCHs. METHODS: This was a Health-RESPECT (integrated caRE Systems for elderly PatiEnts using iCT) sub-study, which is a pragmatic, cluster-randomized, controlled trial. The Health-RESPECT platform was used to collect prescribed medication data of 466 patients (aged ≥ 65 years) from seven LTCHs. DAPs were identified using the Korean Anticholinergic Burden Scale (KABS). Physical frailty, cognitive function, functional status, and quality of life were evaluated. RESULTS: Among 466 LTCH patients, 88.8% (n = 414) were prescribed DAPs, and the prevalence of high KABS (≥ 3) was 70.4% (n = 328). The drugs that contributed most to the total KABS were quetiapine (20.7%), chlorpheniramine (19.5%), tramadol (9.8%), cimetidine (5.8%), and furosemide (3.6%). Polypharmacy, higher body mass index, less dependence, better communication and cognitive functions, and poorer quality of life were associated with high KABS. CONCLUSION: Although the patients with a high burden of DAPs were less dependent and had better cognitive and communication functions, they had poorer quality of life. DAP use in LTCH patients should be monitored carefully, and the risk/ benefit relationship for their use should be considered.


Asunto(s)
Antagonistas Colinérgicos , Cuidados a Largo Plazo , Anciano , Antagonistas Colinérgicos/efectos adversos , Hospitales , Humanos , Polifarmacia , Calidad de Vida , República de Corea/epidemiología
6.
Artículo en Inglés | MEDLINE | ID: mdl-35162828

RESUMEN

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) is a nutrition assistance program in the United States (U.S.). Participants in the program redeem their prescribed food benefits in WIC-authorized grocery stores. Online ordering is an innovative method being pilot-tested in some stores to facilitate WIC participants' food benefit redemption, which has become especially important in the COVID-19 pandemic. The present research aimed to examine the online ordering (OO) behaviors among 726 WIC households who adopted WIC OO in a grocery chain, XYZ (anonymous) store, in Oklahoma (OK). These households represented approximately 5% of WIC households who redeemed WIC benefits in XYZ stores during the study period, which was 1 July to 31 December 2020. This period was during the COVID-19 pandemic but after the temporary lockdown in Oklahoma had been lifted. Descriptive statistics were estimated for WIC OO households' adoption behaviors and their orders. The Cox proportional hazard model and zero-truncated negative binomial regression were applied to examine the relationship between participants' socio-demographics and the length of time between 1 July 2020, and their first OO, as well as the number of WIC online orders. About 80% of these online orders were picked up without any changes. Minority households had a significantly longer time before adopting their first OO (hazard ratio (HR) < 1, p < 0.001), while households with a child or a woman participant, or more participants, had a shorter time before adopting OO (HR > 1, p < 0.05). Non-Hispanic black households had a fewer number of OOs than non-Hispanic white households (B = -0.374, p = 0.007). OO adoption varied across socio-demographics. More efforts are needed to ensure equal access and adoption of WIC OO.


Asunto(s)
COVID-19 , Asistencia Alimentaria , Niño , Control de Enfermedades Transmisibles , Estudios Transversales , Femenino , Humanos , Lactante , Oklahoma , Pandemias , Pobreza , SARS-CoV-2 , Estados Unidos
7.
Biom J ; 64(3): 617-634, 2022 03.
Artículo en Inglés | MEDLINE | ID: mdl-34873728

RESUMEN

With improvements to cancer diagnoses and treatments, incidences and mortality rates have changed. However, the most commonly used analysis methods do not account for such distributional changes. In survival analysis, change point problems can concern a shift in a distribution for a set of time-ordered observations, potentially under censoring or truncation. We propose a sequential testing approach for detecting multiple change points in the Weibull accelerated failure time model, since this is sufficiently flexible to accommodate increasing, decreasing, or constant hazard rates and is also the only continuous distribution for which the accelerated failure time model can be reparameterized as a proportional hazards model. Our sequential testing procedure does not require the number of change points to be known; this information is instead inferred from the data. We conduct a simulation study to show that the method accurately detects change points and estimates the model. The numerical results along with real data applications demonstrate that our proposed method can detect change points in the hazard rate.


Asunto(s)
Modelos de Riesgos Proporcionales , Simulación por Computador , Distribuciones Estadísticas , Análisis de Supervivencia
8.
Stat Methods Med Res ; 31(1): 62-75, 2022 01.
Artículo en Inglés | MEDLINE | ID: mdl-34784808

RESUMEN

In general, the change point problem considers inference of a change in distribution for a set of time-ordered observations. This has applications in a large variety of fields, and can also apply to survival data. In survival analysis, most existing methods compare two treatment groups for the entirety of the study period. Some treatments may take a length of time to show effects in subjects. This has been called the time-lag effect in the literature, and in cases where time-lag effect is considerable, such methods may not be appropriate to detect significant differences between two groups. In this paper, we propose a novel non-parametric approach for estimating the point of treatment time-lag effect by using an empirical divergence measure. Theoretical properties of the estimator are studied. The results from the simulated data and the applications to real data examples support our proposed method.


Asunto(s)
Análisis de Supervivencia , Humanos
9.
Am J Health Promot ; 36(2): 310-313, 2022 02.
Artículo en Inglés | MEDLINE | ID: mdl-34789011

RESUMEN

PURPOSE: This study aims to examine the relationship between cash value benefit (CVB) redemption outcomes in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) across food processing types and socio-demographics. DESIGN: Cross-sectional and panel analyses. SETTING: Virginia. SUBJECTS: 98,067 Virginia WIC households. MEASURES: CVB redemption rate. RESULTS: The predominant share of CVB redemption was for fresh produce (77.3%). Non-Hispanic whites and blacks redeemed a smaller share of fresh produce than Hispanic participants (P < .001). Non-Hispanic black WIC households have a significantly lower CVB redemption rate than non-Hispanic white WIC households (ß = -.008, P < .001). Households with a child participant tend to have a higher redemption rate (ß = .01, P < .001). The redemption rates of fruits and of vegetables were positively correlated with household size. CONCLUSIONS: Minority status and household size were significantly related to CVB redemptions among Virginia WIC participants.


Asunto(s)
Asistencia Alimentaria , Niño , Electrónica , Composición Familiar , Femenino , Frutas , Humanos , Lactante , Verduras
10.
Toxicol Rep ; 8: 1839-1845, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34815948

RESUMEN

1-Propanol is a colorless volatile liquid at room temperature and is an important industrial alcohol. Workers are potentially exposed to it through inhalation during industrial activities, including manufacturing, sampling, filling, and mixing processes, as well as during cleaning, maintenance, and repair. Consequently, further information and/or testing for inhalation-related toxicological data is required to assess occupational risk. In this study, 80 (40 male and 40 female) F344 rats were exposed to 1-propanol vapors for 13 weeks (6 h a day, 5 days per week) at target concentrations of 0, 500, 1,600, and 5200 ppm in a whole-body inhalation chamber system. Clinical signs, mean body weight changes, food consumption, hematology, blood biochemistry, necropsy, organ weight, and histopathological findings were observed. The exposure concentrations in chambers were 501.30 ± 9.54 ppm, 1605.43 ± 66.55 ppm, and 5202.19 ± 102.74 ppm for the low, middle, and high dose groups, respectively. No changes related to 1-propanol were observed, including histopathological findings, except for mean body weight changes. The significant decrease in mean body weight at a high dose was not considered to be an adverse effect. Based on these results, the no observed adverse effect concentration of 1-propanol was estimated to be 5202.19 ppm.

11.
J Nutr Educ Behav ; 53(9): 779-786, 2021 09.
Artículo en Inglés | MEDLINE | ID: mdl-34175218

RESUMEN

OBJECTIVE: To examine the relationship between WICShopper application (app) usage and full redemption of Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) food benefits. DESIGN: A cross-sectional study. SETTING: West Virginia WIC program. PARTICIPANTS: A total of 23,050 West Virginia WIC households in 2019. MAIN OUTCOME MEASURES: Full redemptions were defined as the redemption rate of ≥ 90% for a given food benefit. ANALYSIS: App/non-app users were defined as households with someone using/not using the WICShopper app. Multivariate logistic regressions were applied. To address the potential self-selection bias in app usage, the propensity score (PS) of app usage was estimated. The regressions were rerun with the balanced sample by matching the PS. RESULTS: With PS matching, the prevalence of full redemption at the household level was 7.2% for app users vs 4.7% for nonapp users (odds ratio, 1.64; 95% confidence interval, 1.40-1.92; P < 0.001). App users had a higher prevalence of full redemption in most food categories, even with PS matching. CONCLUSIONS AND IMPLICATIONS: Use of the WICShopper app was associated with a higher prevalence of full redemptions in most food benefits after controlling the self-selection bias.


Asunto(s)
Asistencia Alimentaria , Aplicaciones Móviles , Niño , Estudios Transversales , Composición Familiar , Femenino , Humanos , Lactante , Puntaje de Propensión
12.
Food Policy ; 1012021 May.
Artículo en Inglés | MEDLINE | ID: mdl-34054198

RESUMEN

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provides breastfeeding support and free formula to low-income participating infants in the U.S. Literature has consistently documented worse breastfeeding outcomes in WIC infants and children than in non-participants, although self-selection bias poses a challenge in examining the relationship between WIC participation and breastfeeding in low-income mother-child dyads. The WIC program adopted a comprehensive food package revision in 2009, the first one in four decades. Since that time, few national studies have examined the relationship between WIC participation and breastfeeding while controlling for the endogeneity of WIC participation with the propensity score method. This paper applied an instrumental variable (IV) approach on a large, nationally representative survey sample of children, the National Immunization Surveys (NIS), to examine the relationship between WIC participation and breastfeeding among children born between 2005 and 2014. We identified state Supplemental Nutrition Assistance Program (SNAP) enrollment rates and SNAP Policy Indices as valid IVs to address WIC participation endogeneity. Without the IVs, WIC participation had a significantly negative relationship with breastfeeding. After addressing endogeneity using the IVs, the relationship became insignificant in the whole sample and in the subpopulations across race/ethnicity and child gender. The neutrality of WIC participation on breastfeeding is important for policy makers to understand in seeking to improve breastfeeding among WIC participants.

13.
Toxicol Res ; 36(4): 285-292, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-33005587

RESUMEN

1-Propanol is used as a solvent for waxes, vegetable oils, resins, cellulose esters, and ethers, and is not considered harmful to humans by food and non-occupational exposures. However, workers are potentially exposed to 1-propanol by inhalation when it is used in the workplace. Thus, inhalation toxicity data are needed to assess the hazard of 1-propanol for workers safety. Five male and five female F344 rats were exposed to 1-propanol vapor for 4-weeks (6 h/day, 5 days/week) at concentrations of 0, 100, 400, and 1600 ppm in a whole-body inhalation chamber system. The actual exposure concentrations were 100.11 ± 5.10, 403.19 ± 12.31, and 1598.08 ± 139.58 ppm for the low, middle, and high dose groups, respectively. No clinical signs, significant mean body weight changes, significant changes of hematology or blood biochemistry results, or histopathological abnormalities were seen related to exposure to the test substance. Under the conditions of this study, the no-observed-adverse-effect level of 1-propanol was over 1600 ppm.

14.
J Toxicol ; 2020: 9172569, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33029140

RESUMEN

We evaluated the toxicity of 1-propanol exposure following repeated inhalation over 28- and 90-day periods in male and female B6C3F1 mice to confirm the potential target organs and to determine the no-observable-adverse-effect levels (NOAELs). Five mice of each sex were exposed to 1-propanol at concentrations of 0, 100, 400, or 1600 ppm for 28 days and showed no consequent toxicity. Following this, ten mice of each sex were exposed at concentrations of 0, 500, 1600, or 5200 ppm for 90 days. We observed no effects on food consumption, body weight, organ weight, clinical signs, hematology and biochemistry parameters, or gross or histological features even at the maximum concentration. Therefore, the NOAEL of inhaled 1-propanol was defined as 5200 ppm (12.8 mg/L) for male and female mice under study conditions.

16.
JMIR Mhealth Uhealth ; 8(10): e20720, 2020 10 14.
Artículo en Inglés | MEDLINE | ID: mdl-33052133

RESUMEN

BACKGROUND: The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) is one of the most important food assistance programs in the United States, serving 6.4 million low-income, eligible women, infants, and children under 5 years of age in 2019. In the program, participants are prescribed a list of food benefits, which can be redeemed in WIC-authorized stores. However, there are multiple behavioral barriers in the program and the stores that prevent participants from redeeming the benefits fully. OBJECTIVE: This study aims to examine the relationship between the use of a widely used mobile phone app, WICShopper, and the redemption of the prescribed food packages. METHODS: WIC administrative data were obtained from West Virginia for the period January 2019 to January 2020 and included 30,440 WIC households that had received food benefits in that period. The redemption rates of 18 WIC food benefits were compared between app users and nonapp users, that is, those who never used the app in the study period. The use behaviors were defined for the app users, including the number of active use benefit cycles, active benefit cycle rates, number of active use days in the cycle, and proportion rates of daytime use. Panel linear regressions were applied to examine how the redemption rates were related to these behaviors over time. RESULTS: App users consistently had higher average redemption rates than nonapp users; the difference ranged from 3.6% (4.8% relative) for infant formula to 14.3% (40.7% relative) for fish. After controlling for sociodemographics, the coefficients of app use were significantly positive for all benefit categories except for WIC-eligible nutritionals. More active cycles and active days in the cycle were significantly related to redemption rates for all categories, except for frozen juice (coefficient=-0.002, P=.09). Daytime app access was positively associated with redemption rates for most food benefits except only a few, such as infant formula (coefficient=-0.03, P<.001). CONCLUSIONS: Use of the WIC app was significantly related to higher redemption rates across food benefits, although the association varied across benefit categories. More active days were positively related to benefit redemptions across food categories, and the app's daytime use was positively associated with the redemption of most benefit categories. These findings suggest that the WIC app can be an important tool for the promotion of benefit redemption among WIC participants.


Asunto(s)
Asistencia Alimentaria , Aplicaciones Móviles , Niño , Preescolar , Estudios Transversales , Femenino , Humanos , Lactante , Pobreza , Estados Unidos/epidemiología
17.
BMC Geriatr ; 19(1): 289, 2019 10 26.
Artículo en Inglés | MEDLINE | ID: mdl-31655551

RESUMEN

BACKGROUND: Postoperative delirium (POD) is a common clinical syndrome with significant negative outcomes. Thus, we aimed to evaluate the feasibility and effectiveness of a delirium screening tool and multidisciplinary delirium prevention project. METHODS: A retrospective cohort study was conducted at a single teaching center in Korea. A cohort of patients who underwent a delirium prevention program using a simple delirium screening tool from December 2018 to February 2019 (intervention group, N = 275) was compared with the cohort from the year before implementation of the delirium prevention program (December 2017 to February 2018) (control group, N = 274). Patients aged ≥65 years who were admitted to orthopedic wards and underwent surgery were included. The incidence rates of delirium before and after implementation of the delirium prevention program, effectiveness of the delirium screening tool, change in the knowledge score of nurses, and length of hospital stay were assessed. RESULTS: The sensitivity and specificity of the screening tool for the incidence of POD were 94.1 and 72.7%, respectively. The incidence rates of POD were 10.2% (control group) and 6.2% (intervention group). The odds ratio for the risk reduction effect of the project related to the incidence of POD was 0.316 (95% confidence interval: 0.125-0.800, p = 0.015) after adjustment for possible confounders. The delirium knowledge test score increased from 40.52 to 43.24 out of 49 total points (p < 0.001). The median length of hospital stay in the intervention and control groups was 6.0 (interquartile range, 4-9) and 7.0 (interquartile range, 4-10) days, respectively (p = 0.062). CONCLUSION: The screening tool successfully identified patients at a high risk of POD at admission. The POD prevention project was feasible to implement, effective in preventing delirium, and improved knowledge regarding delirium among the medical staff. TRIAL REGISTRATION: None.


Asunto(s)
Delirio/epidemiología , Delirio/prevención & control , Hospitalización/tendencias , Procedimientos Ortopédicos/tendencias , Complicaciones Posoperatorias/epidemiología , Complicaciones Posoperatorias/prevención & control , Anciano , Estudios de Cohortes , Delirio/diagnóstico , Femenino , Humanos , Tiempo de Internación/tendencias , Masculino , Procedimientos Ortopédicos/efectos adversos , Complicaciones Posoperatorias/diagnóstico , República de Corea/epidemiología , Estudios Retrospectivos
18.
ACS Appl Mater Interfaces ; 11(1): 457-468, 2019 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-30525425

RESUMEN

To develop reliable and durable protonic ceramic fuel cells (PCFCs), the impacts of the operation protocols of PCFCs on the cell durability are investigated through analyses of the main degradation mechanisms. We herein propose three appropriately designed control protocols, including cathode air depletion, shunt current, and fuel cell/electrolysis cycling, to fully circumvent the operating-induced degradation of PCFCs. For this purpose, anode-supported cells, comprised of a NiO-BaCe0.7Zr0.1Y0.1Yb0.1O3-δ anode, BaCe0.7Zr0.1Y0.1Yb0.1O3-δ electrolyte, and NdBa0.5Sr0.5Co1.5Fe0.5O5+δ-Nd0.1Ce0.9O2-δ composite cathode, are prepared, and their long-term performances are evaluated under a galvanostatic condition of 0.5 A·cm-2 at 650 °C. The cell voltages of the protected cells using the operation protocols to prevent performance degradation are stably maintained under the applied current density for more than 1200 h without any noticeable degradation, whereas the performance of the unprotected cell gradually decreased with time, and the decay ratio was 14.9% over 850 h. The significant performance decay of the unprotected cell is strongly associated with the cathode degradation phenomenon, which was caused by the water vapor continuously produced during the electrochemical reactions. Hence, the performance recovery of the PCFCs with the operation protocols is achieved by incrementally decreasing the cathode potential (close to a value of zero) to minimize the effect of high PH2O and PO2 during the PCFC operations.

19.
Lifetime Data Anal ; 24(2): 310-327, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-28132157

RESUMEN

Medical treatments often take a period of time to reveal their impact on subjects, which is the so-called time-lag effect in the literature. In the survival data analysis literature, most existing methods compare two treatments in the entire study period. In cases when there is a substantial time-lag effect, these methods would not be effective in detecting the difference between the two treatments, because the similarity between the treatments during the time-lag period would diminish their effectiveness. In this paper, we develop a novel modeling approach for estimating the time-lag period and for comparing the two treatments properly after the time-lag effect is accommodated. Theoretical arguments and numerical examples show that it is effective in practice.


Asunto(s)
Análisis de Supervivencia , Tiempo de Tratamiento , Algoritmos , Interpretación Estadística de Datos , Humanos , Modelos de Riesgos Proporcionales
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...