scholarly journals Residence Time Effects on Molybdenum Adsorption on Soils: Elucidation by Multi-Reaction Modeling and XANES Analysis

Soil Systems ◽  
2019 ◽  
Vol 3 (3) ◽  
pp. 55
Author(s):  
Wenguang Sun ◽  
Amitava Roy ◽  
H. Magdi Selim
Keyword(s):  
Sequential Extraction ◽  
Residence Time ◽  
Goodness Of Fit ◽  
Reaction Model ◽  
Retention Data ◽  
Edge Structure ◽  
Batch Type ◽  
Important Host ◽  
Xanes Analysis

To investigate the influence of residence time on molybdenum [Mo(VI)] adsorption behavior in soil environments, kinetic batch experiments coupled with X-ray near-edge structure (XANES) spectroscopy were performed for a neutral-pH soil (Webster loam) and two acidic soils (Mahan sand and Windsor sand) at different time scales (1 day–1 year). Batch-type experiments indicated that retention of Mo(VI) was rate limited and typical biphasic for soils. Initial rapid retention was followed by a continued slow retention with increasing aging time for Mahan and Windsor soils. In contrast, the reaction for Webster soil was nearly complete after 8 h, reflecting difference in soil properties. XANES analysis for Webster soil confirmed that most of Mo was bound to montmorillonite during long-term reaction time, whereas kaolinite constitutes a very important host phase for Mahan and Windsor soils. Sequential extraction results indicated that the percentages of Fe/Al oxide and residual fractions increased at the advanced time periods for Mahan and Windsor soils. The goodness-of-fit of numerical modeling results indicated that a simple version of multi-reaction model (MRM) with equilibrium and kinetic sorption sites was capable of describing Mo(VI) retention data for Webster loam. However, for Windsor and Mahan soils, an additional irreversible sorption site was required to simulate Mo(VI) retention over time. Although each site from MRM model cannot be unequivocally clarified from each other by either XANES analysis or sequential extraction results, their finding provided evidence of surface irreversible reactions at long residence times.

scholarly journals Microscale Heterogeneous Distribution and Speciation of Phosphorus in Soils Amended with Mineral Fertilizer and Cattle Manure Compost

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 121
Author(s):  
Noriko Yamaguchi ◽  
Toshiaki Ohkura ◽  
Atsuko Hikono ◽  
Yohey Hashimoto ◽  
Aomi Suda ◽  
...  
Keyword(s):  
Hot Spots ◽  
Mineral Fertilizer ◽  
Chemical Extraction ◽  
Heterogeneous Distribution ◽  
Edge Structure ◽  
Soil P ◽  
Macro Scale ◽  
Cattle Manure Compost ◽  
High Degree

Global concerns for the sustainability of agriculture have emphasized the need to reduce the use of mineral fertilizer. Although phosphorus (P) is accumulated in farmland soils due to the long-term application of fertilizer, most soil P is not readily available to plants. The chemical speciation of P in soils, which comprise heterogeneous microenvironments, cannot be evaluated with a high degree of specificity using only macroscopic analyses. In this study, we investigated the distribution and speciation of P accumulated in soils by using both macro- and microscopic techniques including chemical extraction, solution and solid-state 31P NMR, bulk- and micro- P K-edge X-ray absorption near edge structure (XANES), and electron probe microanalysis (EPMA). Soil samples were collected from a field in which cabbage was cultivated under three amendment treatments: i) mineral fertilizer (NPK), ii) mineral fertilizer and compost (NPK + compost), and iii) mineral fertilizer plus compost but without nitrogen fertilizer (PK + compost). Macro-scale analyses suggested that accumulated P was predominantly inorganic P and associated with Al-bearing minerals. The repeated application of compost to the soils increased the proportion of P associated with Ca which accounted for 17% in the NPK + compost plot and 40% in the PK + compost plot. At the microscale, hot spots of P were heterogeneously distributed, and P was associated with Fe and Ca in hot spots of the NPK + compost (pH 6) and PK + compost (pH 7) treated samples, respectively. Our results indicate that application of compost contributed to creating diverse microenvironments hosting P in these soils.

137 Recovery Dynamics in a Biomathematical Model of Fatigue

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A56-A56
Author(s):  
Mark McCauley ◽  
Peter McCauley ◽  
Hans Van Dongen
Keyword(s):  
Sleep Deprivation ◽  
Goodness Of Fit ◽  
Sleep Loss ◽  
Sleep Restriction ◽  
Commercial Aviation ◽  
Circadian Misalignment ◽  
Total Sleep Deprivation ◽  
Homeostatic Process ◽  
Recovery Sleep

Abstract Introduction In commercial aviation and other operational settings where biomathematical models of fatigue are used for fatigue risk management, accurate prediction of recovery during rest periods following duty periods with sleep loss and/or circadian misalignment is critical. The recuperative potential of recovery sleep is influenced by a variety of factors, including long-term, allostatic effects of prior sleep/wake history. For example, recovery tends to be slower after sustained sleep restriction versus acute total sleep deprivation. Capturing such dynamics has proven to be challenging. Methods Here we focus on the dynamic biomathematical model of McCauley et al. (2013). In addition to a circadian process, this model features differential equations for sleep/wake regulation including a short-term sleep homeostatic process capturing change in the order of hours/days and a long-term allostatic process capturing change in the order of days/weeks. The allostatic process modulates the dynamics of the homeostatic process by shifting its equilibrium setpoint, which addresses recently observed phenomena such as reduced vulnerability to sleep loss after banking sleep. It also differentiates the build-up and recovery rates of fatigue under conditions of chronic sleep restriction versus acute total sleep deprivation; nonetheless, it does not accurately predict the disproportionately rapid recovery seen after total sleep deprivation. To improve the model, we hypothesized that the homeostatic process may also modulate the allostatic process, with the magnitude of this effect scaling as a function of time awake. Results To test our hypothesis, we added a parameter to the model to capture modulation by the homeostatic process of the allostatic process build-up during wakefulness and dissipation during sleep. Parameter estimation using previously published laboratory datasets of fatigue showed this parameter as significantly different from zero (p<0.05) and yielding a 10%–20% improvement in goodness-of-fit for recovery without adversely affecting goodness-of-fit for pre-recovery days. Conclusion Inclusion of a modulation effect of the allostatic process by the homeostatic process improved prediction accuracy in a variety of sleep loss and circadian misalignment scenarios. In addition to operational relevance for duty/rest scheduling, this finding has implications for understanding mechanisms underlying the homeostatic and allostatic processes of sleep/wake regulation. Support (if any) Federal Express Corporation

Mathematical modeling of fluid movement inside the eyeball during intravitreal injection

2021 ◽  
pp. 106-109
Author(s):  
D.V. Lipatov ◽  
◽  
S.A. Skladchikov ◽  
N.P. Savenkova ◽  
V.V. Novoderezkin ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Residence Time ◽  
Complex Structure ◽  
Posterior Vitreous Detachment ◽  
Vitreous Body ◽  
Complete Removal ◽  
Intravitreal Injections ◽  
The World

Background. The avalanche-like growth of intravitreal injections in the world has significantly increased interest in the hemodynamics of the processes that occur in the eye when a drug is injected into the vitreous cavity. Every year, the number of intravitreally used drugs and promising areas in which they can be used is growing. This also applies to the creation of new combined medicines and the development of drugs with a long-term therapeutic effect. Aims. Create mathematical model of eyeball to evaluate the movement of the drug substance in it; to estimate the time of the drug's presence in the eye cavity before its complete removal, to characterize the ways of its removal from the eye cavity; to assess the significance of posterior vitreous detachment during the time when the drug is present in the eye cavity; to evaluate the effect on the hydrodynamics of the depth of drug administration. Results. When the drug is administered closer to the center of the eyeball, its residence time increases in comparison with the parietal administration. With a complete posterior detachment of the vitreous body, the time of finding the drug in the eye is prolonged compared to its absence. The obtained results of mathematical modeling of the movement of the drug administered intravitreally cannot be mechanically transferred to the human eye, due to the more complex structure of the latter. Key words: intravitreal injections, vitreous body, mathematic computing.

Detection and residence time of bisphosphonates in bone of horses

2021 ◽  
Vol 34 (1) ◽  
pp. 23-27
Author(s):  
Heather K. Knych ◽  
Jennifer Janes ◽  
Laura Kennedy ◽  
Daniel S. McKemie ◽  
Rick M. Arthur ◽  
...  
Keyword(s):  
Synovial Fluid ◽  
Residence Time ◽  
Bone Fractures ◽  
Limited Information ◽  
Long Term Effects ◽  
Normal Bone ◽  
Postmortem Blood ◽  
Affect Bone Healing ◽  
Postmortem Sample

Bisphosphonates are potent anti-resorptive agents that have the potential to adversely affect bone healing in equine athletes, and normal bone adaption in young racehorses. A concern exists that bisphosphonate inhibition of normal bone metabolism could lead to increased bone fractures during high-intensity exercise. We found only a single report describing concentrations of tiludronate in the bone of horses, and no studies describing clodronate. Knowledge of the residence time in bone could allow for a better understanding of the long-term effects of these compounds. Our objectives were to develop a method for detection of bisphosphonates in bone and add to the limited information available regarding the disposition of these drugs in the bone of horses. Two horses received clodronate and 2 tiludronate disodium. Postmortem collection of bones and teeth occurred either 4 or 30 d post drug administration. Additionally, postmortem blood, synovial fluid, aqueous humor, and bone samples from racehorses with various histories of bisphosphonate administration were collected, and concentrations determined using the developed LC-MS/MS method. Bisphosphonates were detected in bones and teeth tested at 4 and 30 d. In a postmortem sample, clodronate was detected in bone from a horse with reported administration 18 mo prior; clodronate was not detected in other sample types collected from this horse. Bisphosphonates reside in bone for extended periods of time, which could lead to potential long-term effects, increasing the potential for bone fractures in young and/or athletic horses.

scholarly journals Long-term experience with an ultrapure individual dialysis fluid with a batch type machine

1998 ◽  
Vol 13 (12) ◽  
pp. 3118-3125 ◽  
Author(s):  
W. Kleophas ◽  
B. Haatert ◽  
G. Backus ◽  
P. Hilgers ◽  
A. Westhoff ◽  
...  
Keyword(s):  
Dialysis Fluid ◽  
Batch Type ◽  
Type Machine ◽  
Long Term Experience

scholarly journals Predicting the cumulative medical load of COVID-19 outbreaks after the peak in daily fatalities

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0247272
Author(s):  
Claudius Gros ◽  
Roser Valenti ◽  
Lukas Schneider ◽  
Benedikt Gutsche ◽  
Dimitrije Marković
Keyword(s):  
Phase Space ◽  
Sir Model ◽  
Reaction Model ◽  
Space Representation ◽  
Cumulative Number ◽  
Short Term ◽  
Before And After ◽  
The Status ◽  
Short And Long Term

The distinct ways the COVID-19 pandemic has been unfolding in different countries and regions suggest that local societal and governmental structures play an important role not only for the baseline infection rate, but also for short and long-term reactions to the outbreak. We propose to investigate the question of how societies as a whole, and governments in particular, modulate the dynamics of a novel epidemic using a generalization of the SIR model, the reactive SIR (short-term and long-term reaction) model. We posit that containment measures are equivalent to a feedback between the status of the outbreak and the reproduction factor. Short-term reaction to an outbreak corresponds in this framework to the reaction of governments and individuals to daily cases and fatalities. The reaction to the cumulative number of cases or deaths, and not to daily numbers, is captured in contrast by long-term reaction. We present the exact phase space solution of the controlled SIR model and use it to quantify containment policies for a large number of countries in terms of short and long-term control parameters. We find increased contributions of long-term control for countries and regions in which the outbreak was suppressed substantially together with a strong correlation between the strength of societal and governmental policies and the time needed to contain COVID-19 outbreaks. Furthermore, for numerous countries and regions we identified a predictive relation between the number of fatalities within a fixed period before and after the peak of daily fatality counts, which allows to gauge the cumulative medical load of COVID-19 outbreaks that should be expected after the peak. These results suggest that the proposed model is applicable not only for understanding the outbreak dynamics, but also for predicting future cases and fatalities once the effectiveness of outbreak suppression policies is established with sufficient certainty. Finally, we provide a web app (https://itp.uni-frankfurt.de/covid-19/) with tools for visualising the phase space representation of real-world COVID-19 data and for exporting the preprocessed data for further analysis.

scholarly journals Influence of Customer Attrition on Diffusion of Business Education Services

2017 ◽  
Vol 2 (2) ◽  
pp. 125-134
Author(s):  
Nitin Sachdeva
Keyword(s):  
Goodness Of Fit ◽  
New Product ◽  
Mean Value ◽  
Diffusion Models ◽  
Primary Data ◽  
Type I ◽  
Modeling Framework ◽  
Customer Attrition ◽  
The Impact

Innovation diffusion models have been developed by many researchers during the past few decades based on the famous Bass (1969) model. Several such diffusion models have been developed in consideration of price, marketing efforts etc., however, it is hardly seen that customer attrition (disadoption) can play a significant role in long term growth process of any new product or service. This paper defines two types of disadoption process, Type I disadoption and Type II disadoption process, representing disadopters from innovators and imitators, respectively. We illustrate that there is an increase in the market size along with the adoption of new product and this increase is addressed in this paper. The explicit mean value function for the two types of disadoption processes is derived in this paper. The thrust of the research is on studying the management educational services in the Delhi/NCR region of India and the impact of disadoption on the long term growth of such services. In order to validate the proposed modeling framework, we make use of different goodness-of-fit criteria on primary data collected from an institute in Delhi/NCR.

scholarly journals Kinetic Modeling and Mechanisms of Manganese Removal from Alkaline Mine Water Using a Pilot Scale Column Reactor

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 99
Author(s):  
Shigeshi Fuchida ◽  
Shota Tajima ◽  
Takuro Nishimura ◽  
Chiharu Tokoro
Keyword(s):  
Kinetic Modeling ◽  
Mine Water ◽  
Pilot Scale ◽  
Silica Sand ◽  
Edge Structure ◽  
Column Reactor ◽  
Molar Ratios ◽  
Manganese Removal ◽  
Water Ph ◽  
Xanes Analysis

Manganese (Mn) is a major element in various aqueous and soil environments that is sometimes highly concentrated in mine water and other mineral processing wastewater. In this study, we investigated Mn removal from alkaline mine water (pH > 9) with an Mn-coated silica sand packed into a pilot-scale column reactor and examined the specific reaction mechanism using X-ray absorption near-edge structure (XANES) analysis and geochemical kinetic modeling. The kinetic effect of dissolved Mn(II) removal by birnessite (δ-Mn(IV)O2) at pH 6 and 8 was evaluated at different Mn(II)/Mn(IV) molar ratios of 0.1–10. Our results confirmed the positive effect of the presence of δ-MnO2 on the short-term removal (60 min) of dissolved Mn. XANES analysis results revealed that δ-MnO2 was more abundant than Mn(III)OOH in the reactor, which may have accumulated during a long-term reaction (4 months) after the reactor was turned on. A gradual decrease in dissolved Mn(II) concentration with depth was observed in the reactor, and comparison with the kinetic modeling result confirmed that δ-MnO2 interaction was the dominant Mn removal mechanism. Our results show that δ-MnO2 contents could play a significant role in controlling Mn removability from mine water in the reactor.

scholarly journals Using the RISK-PCI Score in the Long-Term Prediction of Major Adverse Cardiovascular Events and Mortality after Primary Percutaneous Coronary Intervention

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Lidija Savic ◽  
Igor Mrdovic ◽  
Milika Asanin ◽  
Sanja Stankovic ◽  
Gordana Krljanac ◽  
...  
Keyword(s):  
Cardiovascular Events ◽  
Goodness Of Fit ◽  
Coronary Intervention ◽  
Major Adverse Cardiovascular Events ◽  
C Statistic ◽  
Percutaneous Coronary ◽  
Long Term Follow Up ◽  
One Year

Background/Aim. The RISK-PCI is a simple score for the prediction of 30-day major adverse cardiovascular events (MACE) and mortality in patients treated with primary PCI (pPCI). The aim of the present study is to evaluate the prognostic performance of the RISK-PCI score in predicting MACE and mortality in the long-term follow-up of STEMI patients treated with pPCI. Method. The present study enrolled 2,096 STEMI patients treated with pPCI included in the RISK-PCI trial. Patients presenting with cardiogenic shock were excluded. The composite end-point MACE comprising cardiovascular mortality, nonfatal reinfarction and stroke. Patients were followed up at 6 years after enrollment. Results. One-year and 6-year MACE occurred in 229 (10.9%) and 285 (13.6%) patients, respectively; and 1-year and 6-year mortality occurred in 128 (6.2%) and 151 (7.2%) patients, respectively. The RISK-PCI score was an independent predictor for 1-year MACE (HR 1.24, 95% CI 1, 18–1.31, p<0.001), 6-year MACE (HR 1.22, 95% CI 1.16–1.28, p<0.001), 1-year mortality (HR 1.21, 95% CI 1.13–1.29, p<0.001), and 6-year mortality (HR 1.23, 95% CI 1.15–1.31, p<0.001). The discrimination of the RISK-PCI score to predict 1-year and 6-year MACE and mortality was good: for 1-year MACE c-statistic 0.78, for 6-year MACE c-statistic 0.75, for 1-year mortality c-statistic 0.87, and for 6-year mortality c-statistic 0.83. The nonsignificant Hosmer–Lemeshow goodness-of-fit estimates for 1-year MACE (p=0.619), 6-year MACE (p=0.319), 1-year mortality (p=0.258), and 6-year mortality (p=0.540) indicated a good calibration of the model. Conclusion. The RISK-PCI score demonstrates good characteristics in the assessment of the risk for the occurrence of MACE and mortality during long-term follow-up after pPCI.

scholarly journals Variables Affecting Peri-Implant Radiographic Bone Loss-8-23 Years Follow-Up

2020 ◽  
Vol 10 (23) ◽  
pp. 8591
Author(s):  
Michael Saminsky ◽  
Anat Ben Dor ◽  
Jacob Horwitz
Keyword(s):  
Bone Loss ◽  
Goodness Of Fit ◽  
Operating Characteristic ◽  
Characteristic Curve ◽  
Area Under The Curve ◽  
Factors Associated ◽  
Implant Placement ◽  
Dental Records

The aim of this study is to evaluate factors associated with long-term peri-implant bone-loss and to create a statistical model explaining bone-loss. The dental records in a private periodontal practice were screened for implant-patients with a minimal follow-up period of 8 years with periapical radiographs at implant-placement (T0) and last follow-up (Tf). Collected data included demographics, general health, medications, periodontal parameters, implant parameters, bone augmentation procedures, restoration and antagonist data, number of supportive periodontal appointments (SPT), and radiographic bone-loss between T0 and Tf. Bivariate and Mixed Logistic Regression analyses were performed. “Goodness-of-fit” of the model was elaborated with Receiver Operating Characteristic Curve (ROC) analyses. Thirty-seven patients receiving 142 implants were included. Mean clinical follow-up period was 11.7 ± 3.7 years (range 8–23). Most implants 64.4% were SPT-maintained more than twice a year. Patients with osteoporosis and smokers were prone to increased radiographic peri-implant bone-loss. External-hex implants placed without guided bone regeneration (GBR) and implants 10–12 mm long and diameter of 3.7–4 mm showed less peri-implant bone-loss. The model’s Area Under the Curve (AUC) was 76.9% (Standard Error 4.6%, CI 67.8%–86%).

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