The gamma-variate in contrast-enhanced imaging: a unified view and method from computed to electrical impedance tomography.

Objective.Modern medical imaging plays a vital role in clinical practice, enabling non-invasive visualization of anatomical structures. Dynamic contrast enhancement (DCE) imaging is a technique that uses contrast agents to visualize blood flow dynamics in a time-resolved manner. It can be applied to different modalities, such as computed tomography (CT) and electrical impedance tomography (EIT). This study aims to develop a common theoretical and practical hemodynamic extraction basis for DCE modelling across modalities, based on the gamma-variate function.Approach.The study introduces a framework to generate time-intensity curves for multiple DCE imaging modalities from user-defined hemodynamic parameters. Thus, extensive datasets were simulated for both DCE-CT and EIT, representing different hemodynamic scenarios. Additionally, gamma-variate extensions to account for several physiological effects were detailed in a modality-agnostic manner, and three corresponding fitting strategies, namely nonlinear, linear, and a novel hybrid approach, were implemented and compared on the basis of accuracy of parameter estimation, first pass reconstruction, speed of computation, and failure rate.Main results.As a result, we found the linear method to be the most modality-dependent, exhibiting the greatest bias, variance and failure rates, although remaining the fastest alternative. The hybrid method at least matches the state-of-the-art nonlinear method's accuracy, while improving its robustness and speed by 10 times.Significance.Our research suggests that the hybrid method may bring noteworthy accuracy and efficiency improvements in handling the high-dimensionality of DCE imaging in general, being a step towards real-time processing. Moreover, our generative model presents a potential asset to produce benchmarking and data augmentation datasets across modalities.

Fe-Ni/MWCNTs Nano-Composites for Hexavalent Chromium Reduction in Aqueous Environment.

A novel Cr (VI) removal material was designed and produced comprising multi-walled carbon nanotubes (MWCNTs) as a support with a high specific surface area and the loaded Fe-Ni bimetallic particles as catalytic reducing agents. Such a design permits the composite particle to perform the adsorption, reduction, and immobilisation of Cr (VI) quickly and efficiently. Due to MWCNTs' physical adsorption, Cr (VI) in solution aggregates in the vicinity of the composite, and Fe rapidly reduces Cr (VI) to Cr (III) catalysed by Ni. The results demonstrated that the Fe-Ni/MWCNTs exhibits an adsorption capacity of 207 mg/g at pH = 6.4 for Cr (VI) and 256 mg/g at pH 4.8, which is about twice those reported for other materials under similar conditions. The formed Cr (III) is solidified to the surface by MWCNTs and remains stable for several months without secondary contamination. The reusability of the composites was proven by retaining at least 90% of the adsorption capacity for five instances of reutilization. Considering the facile synthesis process, low cost of raw material, and reusability of the formed Fe-Ni/MWCNTs, this work shows great potential for industrialisation.

Triamcinolone acetonide release modelling from novel bilayer mucoadhesive films: an in vitro study.

OBJECTIVES: Recurrent aphthous stomatitis (RAS) is a painful disorder that commonly appears as ulcers on the oral mucosa, lasting ∼two weeks (minor) to months (major and herpetiform). Current treatment often necessitates the use of topical steroids in the form of pastes, mouthwashes, or gels, but these forms are often ineffective due to inadequate drug contact time with the ulcers. In this study, the performance of novel bilayer mucoadhesive buccal films loaded with triamcinolone acetonide (TA) has been evaluated for targeted drug delivery. METHODS: Experimental mucoadhesive films of hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol (PVA), and polyvinyl pyrrolidone (PVP) were prepared by the solvent casting method, and ethyl cellulose (EC) was applied as the backing layer. The films were characterized for their physical properties, including swelling index (SI), folding endurance, adhesion force with porcine buccal mucosa, residence time and in-vitro drug release. RESULTS: The data showed that the films were flexible with folding endurance> 300 times. With porcine buccal mucosa i) suitable adhesion forces were obtained (between 2.72 and 4.03 N), ii) residence times of> 24 h, and iii) surface pH between 6.8 and 7.1 indicating they would be non-irritant. All films released 100% TA over 6 h, but with varying profiles. The release of TA (over 6 h) from PVP-free films followed Fickian diffusion kinetics (diffusion-controlled release of drug), whereas the mechanism of release from PVP-containing films was found to be a superposition of diffusion-controlled and erosion-controlled release (anomalous). SIGNIFICANCE: The developed films hold great promise for potentially treating RAS and other oral conditions.

Carbonate treated coffee powder (CTCP) for selective sorption of Pu4+ over Am3+, Np4+, NpO22+, and PuO22+ from aqueous acidic solution: Investigation on mechanism, kinetics, thermodynamics, stripping and radiolytic stability.

An attempt was made for understanding the sorption behaviour of different actinide ions Pu4+, PuO22+, Am3+, Np4+, and NpO22+ on carbonate treated exhausted coffee powder (CTCP). Very efficient sorption of Pu4+ over other actinide ions from aqueous acidic medium was observed. Almost 4 h were required for achieving equilibrium. Experimental results for Pu+4 were fitted into different sorption isotherm model: Langmuir isotherm, Freundlich isotherm, D.R, isotherm and Temkin isotherm. Based on the linear regression, it was found that, Freundlich isotherm was predominantly operative. Pseudo 2nd order kinetics was found to be effective for the sorption of Pu+4. More than 80 % of loaded Pu4+ was found to desorb by 0.25 M oxalic acid solution. CTCP exhibited relatively good radiation stability. Sorption of Pu+4 on CTCP was exothermic, and spontaneous in nature. The sorption process was simple, cost effective and environmentally benign, as it did not involve any sophisticated, multi-step, sorbent synthesis.

Kinetics of combined hydrothermal pretreatment and anaerobic digestion of lignocellulosic biomass (pepper plant and eggplant).

A large quantity of lignocellulosic biomass is generated annually across the world which leads to environmental pollution and requires valorization. This study investigated the effect of hydrothermal pretreatment on the anaerobic digestion and co-digestion of the residual pepper plant and eggplant with a focus on kinetics. Two thermal hydrolysis rates were observed, with the optimal conditions for the hydrothermal pretreatment of lignocellulosic biomass being 120°C for 40 min. Subsequently, single and combined biomethanization was successfully carried out in laboratory-scale completely stirred tank reactors at mesophilic temperature (35°C). A high increase in methane production was observed after the pretreatment of the pepper plant and eggplant. The pretreated and co-digested wastes led to an optimal methane yield of 79 ± 23 mL CH4/g VS. The modified Gompertz model was used to fit the cumulative methane production of the pretreated lignocellulosic substrates. The kinetic model adequately reproduced the experimental results and might be considered a useful tool to simulate the biomethanization behaviour of complex organic substrates.

Understanding the volatile flavour changes during accelerated shelf-life testing of oats using chemometrics and kinetic modelling.

This study investigated volatile flavour changes during accelerated shelf-life testing (ASLT) of oats using chemometrics and kinetic modelling. Oat samples were stored at 15, 25, 35 and 45 °C for up to 42 weeks. Headspace fingerprinting enabled the detection of a wide range of volatiles. Chemometrics was applied to explore the volatile changes and related reaction pathways and identify discriminant compounds. Most volatiles significantly increased as a function of time and could be linked to lipid oxidation and the Maillard reaction. Volatiles, such as hexanal, could be selected as potential ASLT markers for processed oat products. The volatile changes were adequately modelled using an empirical logistic model to estimate reaction rate constant and temperature dependency. Based on the estimated kinetic parameters, the selective ASLT markers could be used as a reference to track volatile changes, control off-flavour generation and improve oat product storage stability.

Monopersulfate in water treatment: Kinetics.

The kinetics of monopersulfate based systems in the elimination of potential harmful contaminants has been assessed from a theoretical point of view. A detailed reaction mechanism sustained in the generation of radicals (mainly hydroxyl and sulfate), propagation and termination stages has been proposed. The system of first order differential equations derived has numerically been solved. The effect of main influencing parameters such as contaminant and peroxymonosulfate initial concentrations, intermediate generation, presence of organic matter, role played by anions, has been theoretically obtained. Discussion of simulated results has been accomplished by comparison with experimental data found in the literature. At the sight of the theoretical and empirical data, use of simplistic pseudo first order kinetics is discouraged. Despite considering a significant number of elemental reactions, modelling of the system reveals that a high fraction of them can be neglected due to their insignificant role played in the mechanism. The entire mechanism has been tested when peroxymonosulfate has been activated by UV radiation, although results can be fairly extrapolated to other activation strategies. Finally, a generic model capable of accounting for the effect of a diversity of parameters is proposed. No theoretical background is behind the model, however the generic model clearly improves the results obtained by simple first order kinetics.

Evaluating the efficiency of enzyme accelerated CO2 capture: chemical kinetics modelling for interpreting measurement results.

In this paper, the efficiency of the carbonic anhydrase (CA) enzyme in accelerating the hydration of CO2 is evaluated using a measurement system which consists of a vessel in which a gaseous flow of mixtures of nitrogen and CO2 is bubbled into water or water solutions containing a known quantity of CA enzyme. The pH value of the solution and the CO2 concentration at the measurement system gas exhaust are continuously monitored. The measured CO2 level allows for assessing the quantity of CO2, which, subtracted from the gaseous phase, is dissolved into the liquid phase and/or hydrated to bicarbonate. The measurement procedure consists of inducing a transient and observing and modelling the different kinetics involved in the steady-state recovery with and without CA. The main contribution of this work is exploiting dynamical system theory and chemical kinetics modelling for interpreting measurement results for characterising the activity of CA enzymes. The data for model fitting are obtained from a standard bioreactor, in principle equal to standard two-phase bioreactors described in the literature, in which two different techniques can be used to move the process itself away from the steady-state, inducing transients.

Stability assessment of extracts obtained from Arbutus unedo L. fruits in powder and solution systems using machine-learning methodologies.

Arbutus unedo L. (strawberry tree) has showed considerable content in phenolic compounds, especially flavan-3-ols (catechin, gallocatechin, among others). The interest of flavan-3-ols has increased due their bioactive actions, namely antioxidant and antimicrobial activities, and by association of their consumption to diverse health benefits including the prevention of obesity, cardiovascular diseases or cancer. These compounds, mainly catechin, have been showed potential for use as natural preservative in foodstuffs; however, their degradation is increased by pH and temperature of processing and storage, which can limit their use by food industry. To model the degradation kinetics of these compounds under different conditions of storage, three kinds of machine learning models were developed: i) random forest, ii) support vector machine and iii) artificial neural network. The selected models can be used to track the kinetics of the different compounds and properties under study without the prior knowledge requirement of the reaction system.

New insights on mercury abatement and modeling in a full-scale municipal solid waste incineration flue gas treatment unit.

Modeling approaches are generally used to describe mercury transformations in a single step of flue gas treatment processes. However, less attention has been given to the interactions between the different process stages. Accordingly, the mercury removal performance of a full-scale solid waste incineration plant, equipped with a dry flue gas treatment line was investigated using two complementary modeling strategies: a thermochemical equilibrium approach to study the mercury transformation mechanisms and speciation in the flue gas, and a kinetic approach to describe the mercury adsorption process. The modeling observations were then compared to real-operation full-scale data. Considering the typical flue gas composition of waste incineration facilities (high concentrations of HCl compared to Hg), it was found that a process temperature decrease results in better mercury removal efficiencies, associated with a higher oxidation extent of Hg in HgCl2, and the enhancement of the sorbent capacity. Improvements can also be attained by increasing the sorbent injection rate to the process, or the solid/gas separation cycles. An empirical correlation to predict the mercury removal efficiency from the main operating parameters of dry flue gas treatment units was proposed, representing a useful tool for waste incineration facilities. The presented modeling approach proved to be suitable to evaluate the behavior of full-scale gas treatment units, and properly select the most adequate adjustments in operating parameters, in order to respect the increasingly constraining mercury emissions regulations.

Phosphoric Acid Activated Carbon from Melia azedarach Waste Sawdust for Adsorptive Removal of Reactive Orange 16: Equilibrium Modelling and Thermodynamic Analysis.

Waste wood biomass as precursor for manufacturing activated carbon (AC) can provide a solution to ever increasing global water quality concerns. In our current work, Melia azedarach derived phosphoric acid-treated AC (MA-AC400) was manufactured at a laboratory scale. This novel MA-AC400 was tested for RO16 dye removal performance as a function of contact time, adsorbent dosage, pH, temperature and initial dye concentration in a batch scale arrangement. MA-AC400 was characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering (DLS) and fluorescence spectroscopy. MA-AC400 is characterized as mesoporous with BET surface area of 293.13 m2 g-1 and average pore width of 20.33 Å. pHPZC and Boehm titration confirm the acidic surface charges with dominance of phenolic functional groups. The average DLS particle size of MA-AC400 was found in the narrow range of 0.12 to 0.30 µm and this polydispersity was confirmed with multiple excitation fluorescence wavelengths. MA-AC400 showed equilibrium adsorption efficiency of 97.8% for RO16 dye at its initial concentration of 30 mg L-1 and adsorbent dose of 1 g L-1. Thermodynamic study endorsed the spontaneous, favorable, irreversible and exothermic process for RO16 adsorption onto MA-AC400. Equilibrium adsorption data was better explained by Langmuir with high goodness of fit (R2, 0.9964) and this fitness was endorsed with lower error functions. The kinetics data was found well fitted to pseudo-second order (PSO), and intra-particle diffusion kinetic models. Increasing diffusion constant values confirm the intraparticle diffusion at higher RO16 initial concentration and reverse was true for PSO chemisorption kinetics. MA-AC400 exhibited low desorption with studied eluents and its cost was calculated to be $8.36/kg.

Pyrolysis and combustion kinetics of Sida cordifolia L. using thermogravimetric analysis.

Sida cordifolia L. (Sida) is an annual invasive plant that remains underutilized in Niger. The goal of this study was to characterize the thermal decomposition of Sida for its valorisation as a source of energy through thermogravimetric analysis (TGA). TGA was carried out under nitrogen and air atmospheres. Thus, five different heating rates were used as 10, 20, 30, 40, 50 °C min-1. Kinetic and thermodynamic parameters were determined by isoconversional models of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The results showed that the average activation energy (Ea) of Sida calculated by KAS and FWO in pyrolysis was found to be 74.74 and 80.74 kJ mol-1 respectively, while it was 51.08 and 58.91 kJ mol-1 in combustion respectively. Kinetic and thermodynamic parameters such as Ea, ΔH, ΔS, and ΔG obtained by KAS and FWO show that Sida is a remarkable feedstock for bioenergy.

Drying of a single droplet of dextrin: Drying kinetics modeling and particle formation.

Powder production by spray drying is achieved through the dehydration of droplets. The physical properties of the dried powder often influence its application. The drying kinetics of a single droplet of dextrin solution into the solid phase were monitored during the drying process. An acoustic levitator was used to suspend the droplet in the acoustic field. Such experiments are essential for achieving a fundamental understanding of the drying process. Droplets with different initial solid content (dextrin aqueous solution of 10% and 30%) were investigated at different gas drying temperatures. The drying curves were compared to the Reaction Engineering Approach (REA) model. A good agreement between the model prediction and the experimental results was demonstrated, with an absolute relative error of about 2% between the initial droplet mass and the droplet mass that the REA model predicted. The final particle diameter was estimated theoretically and compared to the experimental data. Single droplet simulations have enormous potential for drying step characterization of expensive compounds and highly potent drugs, due to the low amounts that the experiments require.

Modelling geochemical and kinetic processes involved in lead (Pb) remobilization during resuspension events of contaminated sediments.

The objective of this paper is to present a model simulating and predicting the exchange kinetics of lead (Pb) between contaminated sediments and water during resuspension events potentially occurring in reservoirs. We developed an innovative model that combines thermodynamic speciation of particulate surfaces (oxides and Particulate Organic Carbon (POC)), thermodynamic Pb speciation in water, and kinetic modelling of exchanges between free Pb and particulate sites (i.e., dissolution of a carbonate carrier phase, adsorption/coprecipitation and desorption/dissolution to/from oxides, and adsorption and desorption/degradation to/from particulate organic particles). We used results from laboratory resuspension experiments performed on sediments from three contaminated dam reservoirs to calibrate a new chemical speciation model. Uptake and release processes to/from sediments were found to be controlled by at least two successive reactions that are associated with two particulate pools (here oxides and POC). Kinetic adsorption and desorption rates were calibrated for seven experimental conditions. Variability in kinetic rates allowed evaluation of the effect of the solid-to-liquid ratio and sediment origin on exchange kinetics at the water-particle interface. The kinetic release of dissolved Pb by desorption or dissolution from the oxides was reproduced almost identically between the experiments, regardless of the solid-to-liquid ratio or sediment origin. Long-term readsorption on POC sites is more variable, even if ranges of variation in the adsorption and desorption kinetic rates related to POC remain limited, considering that tested sediments vary significantly. CAPSULE: A kinetic model simulating the dynamics of lead (Pb) during sediment resuspension was developed and calibrated to laboratory experiments performed on three contaminated sediments.

Ensiling fermentation reveals pre-treatment effects for anaerobic digestion of sugarcane biomass: An assessment of ensiling additives on methane potential.

Ensiling of sugarcane trash (SCT) and sugarcane stalks (SCS) was studied to assess the effects of molasses (MOL) and lactic acid bacteria (LAB) inoculant on methane potential. The experiment was run for 70 days and monitoring parameters were analyzed at days 0, 5, 15 and 70. Biochemical methane potential (BMP) tests performed with fresh and ensiled material at day 70 showed an increase in methane potential by 24.0%, 23.4%, 1.7% and 71.1% for SCSctr, SCTctr, SCTmol and SCTmol + lab, respectively. Such improved performance is explained by the formation of organic acids (mostly acetate and lactate) which were able to decrease the pH of the silages from 5.7-5.9 to 3.8-4.2 for all SCT treatments and from 5.9 up to 3.4 for SCS treatment. Thus, the ensiling process provided similar effects to a pre-treatment at low acid concentrations, which in turn improved the digestibility of the cellulosic biomass for methane production.

Thermal Degradation Kinetics of Sugarcane Bagasse and Soft Wood Cellulose.

The properties of untreated sugar cane bagasse (SCB) and soft wood (SW) and their respective celluloses were investigated. The celluloses indicated improved crystallinity index values and decreased concentration of lignin and hemicellulose compared to their untreated counterparts. Three degradation models, Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (OFW), and Kissinger (KGR) methods were employed to determine apparent activation energy values. Generally, the thermal degradation processes of both sugarcane bagasse and soft wood included dehydration, degradation of hemicellulose and cellulose, whereas the lignin degraded from the degradation temperature of hemicellulose to the end of the cellulose. The apparent activation energy values obtained from the OFW and KAS models vary with the degree of conversion, and showed similar trends. The activation energies obtained by KGR were relatively lower than those obtained from the KAS and OFW methods.

Application of a Predictive Growth Model of Pseudomonas spp. for Estimating Shelf Life of Fresh Agaricus bisporus.

For prediction of the shelf life of the mushroom Agaricus bisporus, the growth curve of the main spoilage microorganisms was studied under isothermal conditions at 2 to 22°C with a modified Gompertz model. The effect of temperature on the growth parameters for the main spoilage microorganisms was quantified and modeled using the square root model. Pseudomonas spp. were the main microorganisms causing A. bisporus decay, and the modified Gompertz model was useful for modelling the growth curve of Pseudomonas spp. All the bias factors values of the model were close to 1. By combining the modified Gompertz model with the square root model, a prediction model to estimate the shelf life of A. bisporus as a function of storage temperature was developed. The model was validated for A. bisporus stored at 6, 12, and 18°C, and adequate agreement was found between the experimental and predicted data.

Thermal stability of the functional ingredients, glucosylated benzophenones and xanthones of honeybush (Cyclopia genistoides), in an aqueous model solution.

Thermal stability of the benzophenones, 3-ß-d-glucopyranosyl-4-ß-d-glucopyranosyloxyiriflophenone (1), 3-ß-d-glucopyranosylmaclurin (2) and 3-ß-d-glucopyranosyliriflophenone (3), and the xanthones, mangiferin (4) and isomangiferin (5), was assessed separately in an aqueous model solution (pH 5) to delineate their major degradation products and mechanism(s). Degradation followed first-order reaction kinetics and the temperature-dependence of the respective reaction rate constants complied with the Arrhenius equation. The stability of the compounds increased in the order 2>4>3>5>1. 4-O-Glucosylation significantly stabilised 1 against degradation compared to 3, enediol B-ring functionality of 2 decreased stability compared to 3 and position of glucosylation affected the stability of the xanthones with 5 being more stable than 4. The xanthone nucleus (C-ring) conferred higher stability to 4 and 5 compared to their benzophenone analogue 2. Cyclisation of 2 to 4 and 5 would underestimate their degradation in mixtures. Other reactions were isomerisation, dimerisation, acetylation and hydrolysis.

Characterization, enhancement and modelling of mannosylerythritol lipid production by fungal endophyte Ceriporia lacerate CHZJU.

The glycolipid biosurfactants mannosylerythritol lipids (MELs) attract great attention for their biodegradability, super emulsifying properties and versatile bioactivities. In this study, the MEL deriving from Ceriporia lacerate CHZJU was identified as MEL-A, and its critical micelle concentration and emulsifying activities were assessed. To examine the production of MELs from Ceriporia lacerate, a Plackett-Burman design and response surface methodology were used to optimize the culture nutrients. The optimal medium contains 1g/L yeast extract, 1.5g/L (NH4)2SO4, 0.5g/L KH2PO4, 0.04g/L CaCl2, 119.6mL/L soybean oil and 0.297g/L MnSO4. Subsequent verification revealed that the yield of MELs was 129.64±5.67g/L. Furthermore, an unstructured kinetic model was developed for mycelial growth, MEL production and substrate utilization. This work provides insight into Ceriporia lacerate CHZJU, a predominant fungus producing MEL-A. Optimization using response surface methodology enhanced the mannosylerythritol lipid recovery. Importantly, we developed fermentation kinetic modelling for mannosylerythritol lipid production.