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This study studied the optimum nitrogen (N) and phosphorus (P) concentrations for biomass and astaxanthin production in Spirogyra sp. Spirogyra sp. was cultivated in Blue Green (BG) medium with N/P concentrations adjusted to 1.1/0.01; 1.1/0.03; 1.1/06; 1.1/0.09; 2.2/0.01; 2.2/0.03; 2.2/0.06; 2.2/0.09; 4.4/0.01; 4.4/0.03; 4.4/0.06; 4.4/0.09, 6.6/0.01; 6.6/0.03; 6.6/0.06 and 6.6/0.09 mM. The results showed an increase in biomass accumulation for lower concen‐ trations of N and N:P ratio with the highest accumulation at N/P 1.1/0.03 mM, i.e. 485 mgdryweight and a growth rate of 0.22 d‐1. Astaxanthin accumulation was also found to increase, with the highest at N/P 1.1/0.01 mM, i.e. 0.269 mg/gdryweight, on the 12th day of cultivation. Based on biomass and astaxanthin accumulation, the highest astaxanthin productivity was 0.07 μg/cm2/d at N/P concentration 1.1/0.09 mM. Kinetic models were developed using the Haldane and Luedeking–Piret equations. The growth and astaxanthin production parameters obtained were μmax 0.18±0.02 d‐1, kN 68.2 ± 24.2 mg/L, ki 301.8 ± 78.5 mg/L, YN 0.93 ± 0.68 gbiomass/nitrate, α 0.36 ± 0.69, β ‐0.01 ± 0.02, and kA 0.04 ± 0.03, thus indicating that a lower N concentration is suitable for the cultivation of Spirogyra sp. In conclusion, Spirogyra sp. should be cultivated under nitrogen deficiency for continuous astaxanthin production.

Orevactaene yellow pigment was produced by solid-state fermentation of broken rice using Epicoccum nigrum. The pigment was extracted using water as a solvent and subjected to stability studies at different temperatures (30, 40, 60, and 80°C), pH (4, 6, and 8), sterilization, and sunlight exposure treatment. The observed data were fitted in the first-order kinetic model. Yellow pigment stability was found to vary at different temperatures studied. At 30°C, only a 4% decrease in color intensity was observed after 2 h; at 40°C, an 8% decrease was observed, and at 80°C and pH 6.0, 17% of color intensity was lost. These results showed that the orevactaene pigment produced by E. nigrum is heat-sensitive and changes in color intensity should be expected in heat-processed products. After 180 min at 80°C, yellow pigments maintained 82 and 76% of the initial color at pH 6 and 8, while a 65% decrease in color intensity was observed at 80°C, pH 4. Autoclaving resulted in 69% decay and exposure of pigment to sunlight for 2 h showed 1% decay. The half-life period of the pigment at different temperatures varied from 82.5 to 5.25 h. The decimal reduction time decreased from 275 to 17.5 h with an increase in the temperature. Thermodynamic parameters for pigment decay at pH 6.0 were represented in terms of enthalpy ∆H, activation energy E a, free energy ∆G, and entropy ∆S. The values observed were 44.52–44.93, 48.48, 96.60–105.18 kJ/mol, and −170.50 to −171.85 J/mol/K, respectively. All these parameters help in predicting the quality changes in terms of appearance during thermal processing and optimizing the process.

Abstract Background The glymphatic system actively exchanges cerebrospinal fluid (CSF) and interstitial fluid (ISF) to eliminate toxic interstitial waste solutes from the brain parenchyma. Impairment of the glymphatic system has been linked to several neurological conditions. Glioblastoma, also known as Glioblastoma multiforme (GBM) is a highly aggressive form of malignant brain cancer within the glioma category. However, the impact of GBM on the functioning of the glymphatic system has not been investigated. Using dynamic contrast-enhanced magnetic resonance imaging (CE-MRI) and advanced kinetic modeling, we examined the changes in the glymphatic system in rats with GBM. Methods Dynamic 3D contrast-enhanced T1-weighted imaging (T1WI) with intra-cisterna magna (ICM) infusion of paramagnetic Gd-DTPA contrast agent was used for MRI glymphatic measurements in both GBM-induced and control rats. Glymphatic flow in the whole brain and the olfactory bulb was analyzed using model-derived parameters of arrival time, infusion rate, clearance rate, and residual that describe the dynamics of CSF tracer over time. Results 3D dynamic T1WI data identified reduced glymphatic influx and clearance, indicating an impaired glymphatic system due to GBM. Kinetic modeling and quantitative analyses consistently indicated significantly reduced infusion rate, clearance rate, and increased residual of CSF tracer in GBM rats compared to control rats, suggesting restricted glymphatic flow in the brain with GBM. In addition, our results identified compromised perineural pathway along the optic nerves in GBM rats. Conclusions Our study demonstrates the presence of GBM-impaired glymphatic response in the rat brain and impaired perineural pathway along the optic nerves. Reduced glymphatic waste clearance may lead to the accumulation of toxic waste solutes and pro-inflammatory signaling molecules which may affect the progression of the GBM.

This study investigated the adsorption of an azo dye called Congo red from aqueous solution. Ash prepared from sunflower seed waste was used as the adsorbent. Brunauer–Emmett–Teller (BET), Scanning electron microscopy (SEM), and Fourier-Transform Infrared spectroscopy (FT-IR) analyses were performed to characterize the prepared adsorbent. Based on the results of BET, the specific active surface area was about 102 m2/g, and the results of SEM indicated that the adsorbent surface had a very fine porosity that could be attributed to the presence of cellulosic materials in the adsorbent structure. In this study, the effect of the initial concentration of Congo red dye (10-50 mg/L), the concentration of adsorbent (1-5 g/L), and the processing time (10-240 min) on the rate of Congo red dye removal was investigated. The results showed that the highest percentage of dye removal, i.e., 92%, was achieved at a dye concentration of 50 mg/L, an adsorbent concentration of 3 g/L, and a processing time of 180 min. Under these conditions, the amount of adsorbed dye per gram of the adsorbent was 15.5 mg/g. In addition, pseudo-first order and pseudo-second order kinetic models were also used for modeling. The modeling results indicated that the pseudo-second order model had a higher level of accuracy. Finally, washing adsorbent with different solvents (one molar sodium hydroxide, double distilled water, and ethanol) was investigated, the results indicated that the adsorbent washed with one molar sodium hydroxide had a proper performance after five times of reuse.

The uEXPLORER total-body PET/CT system provides a very high level of detection sensitivity and simultaneous coverage of the entire body for dynamic imaging for quantification of tracer kinetics. This article describes the fundamentals and potential benefits of total-body kinetic modeling and parametric imaging focusing on the noninvasive derivation of blood input function, multiparametric imaging, and high-temporal resolution kinetic modeling. Along with its attractive properties, total-body kinetic modeling also brings significant challenges, such as the large scale of total-body dynamic PET data, the need for organ and tissue appropriate input functions and kinetic models, and total-body motion correction. These challenges, and the opportunities using deep learning, are discussed.

A telescoped, two-step synthesis was investigated by applying Quality by Design principles. A kinetic model consisting of 12 individual reactions was successfully established to describe the synthesis and side reactions. The resulting model predicts the effects of changes in process parameters on total yield and quality. Contour plots were created by varying process parameters and displaying the model predicted process response. The areas in which the process response fulfils predetermined quality requirements are called design spaces. New ranges for process parameters were explored within these design spaces. New conditions were found that increased the robustness of the process and allowed for a considerable reduction of the used amounts of a reagent. Further optimizations, based on the newly generated knowledge, are expected. Improvements can either be direct process improvements or enhancements to control strategies. The developed strategies can also be applied to other processes, enhancing upcoming and preexisting research and development efforts.

Immuno-positron emission tomography (immunoPET) enables imaging of specific targets that play a role in targeted therapy and immunotherapy, such as antigens on cell membranes, targets in the disease microenvironment, or immune cells. The most common immunoPET applications use a monoclonal antibody labeled with a relatively long-lived positron emitter such as 89Zr (T1/2 = 78.4 h), but smaller antibody-based constructs labeled with various other positron emitting radionuclides are also being investigated. This molecular imaging technique can thus guide the development of new drugs and may have a pivotal role in selecting patients for a particular therapy. In early phase immunoPET trials, multiple imaging time points are used to examine the time-dependent biodistribution and to determine the optimal imaging time point, which may be several days after tracer injection due to the slow kinetics of larger molecules. Once this has been established, usually only one static scan is performed and semi-quantitative values are reported. However, total PET uptake of a tracer is the sum of specific and nonspecific uptake. In addition, uptake may be affected by other factors such as perfusion, pre-/co-administration of the unlabeled molecule, and the treatment schedule. This article reviews imaging methodologies used in immunoPET studies and is divided into two parts. The first part summarizes the vast majority of clinical immunoPET studies applying semi-quantitative methodologies. The second part focuses on a handful of studies applying pharmacokinetic models and includes preclinical and simulation studies. Finally, the potential and challenges of immunoPET quantification methodologies are discussed within the context of the recent technological advancements provided by long axial field of view PET/CT scanners.

Purpose: The main objective was to characterize the tracer uptake kinetics of [18F]fluoromethylcholine ([18F]F-CHO) in high-grade gliomas (HGG) through a full PET kinetic modeling approach. Secondarily, we aimed to explore the relationship between the PET uptake measures and the HGG molecular features. Materials and methods: Twenty-four patients with a suspected diagnosis of HGG were prospectively included. They underwent a dynamic brain [18F]F-CHO-PET/CT, from which a tumoral time-activity curve was extracted. The plasma input function was obtained through arterial blood sampling with metabolite correction. These data were fitted to 1- and 2-tissue-compartment models, the best of which was selected through the Akaike information criterion. We assessed the correlation between the kinetic parameters and the conventional static PET metrics (SUVmax, SUVmean and tumor-to-background ratio TBR). We explored the association between the [18F]F-CHO-PET quantitative parameters and relevant molecular biomarkers in HGG. Results: Tumoral time-activity curves in all patients showed a rapid rise of [18F]F-CHO uptake followed by a plateau-like shape. Best fits were obtained with near-irreversible 2-tissue-compartment models. The perfusion-transport constant K1 and the net influx rate Ki showed strong correlation with SUVmax (r = 0.808–0.861), SUVmean (r = 0.794–0.851) and TBR (r = 0.643–0.784), p

The present work study the acidic pug leaching technique for U-extraction in addition to some associated valuable metals from a collected technological sample of ferruginous shale from Wadi Um Hamed, Um Bogma Formation, Abu Thor locality, southwestern Sinai, Egypt. A representative sample of the ore material was found to assay 9000, 700 and 4000 ppm of REEs, U and Cu, respectively, in addition to some major and minor oxides. Numerous steps were performed upon the studied sample to process parametric studies such as sulphuric acid concentration (50–150 kg/ton), curing time (0.5–5.0 h) and curing temperature (50–150°C) in order to find the optimum condition. Under the optimal conditions (150 kg/ton sulphuric acid for 4.0 h at 150°C), the first step involved Fe-removal as hydroxide from the pregnant leaching solution using pH adjustment method followed by U-recovery through sorption/desorption and precipitation steps with the help of Amberlite IRA-400-Cl (strongly basic anion exchange resin) via column method. In the third step, REEs- recovery from U-free effluent was investigated using oxalic acid precipitation process while Cu-recovery by precipitation as hydroxide with ammonia solution took place. Energy dispersive X-ray analysis performed on the different obtained precipitates showed successive recovery of all above mentioned elements. Finally, U-uptake data were subjected to kinetic modelling. The kinetics of leaching reaction followed shrinking core model with chemical reaction as controlling mechanism based on activation energy value. [ABSTRACT FROM AUTHOR]

Chromium [Cr] contamination in groundwater is one of the serious environmental concerns due to the carcinogenicity of its water-soluble and mobile hexavalent [Cr(VI)] form. In spite of the existence of multiple precipitation and adsorption-based Cr(VI) remediation technologies, the usage of sulfidated nano zerovalent iron (S-nZVI) has recently attracted researchers due to its high selectivity. Although S-nZVI effectively immobilized Cr(VI), its long-term performance in multiple shifted equilibrium has not been explored. In this contribution, influences of S-nZVI dosage, initial concentration of Cr(VI), pH, ionic strength, total hardness, sulfate, carbonate, and silicate were probed in ultrapure water. Further experiments were performed in synthetic groundwater to investigate the effects of initial concentration of Cr(VI) in the pH range of 4–8 for 1 g L−1 S-nZVI dosage. Cr(VI) removal rate was quantified in groundwater without pH fixation. Finally, a comparative study between conventional nano zerovalent iron (nZVI) and S-nZVI was conducted in sequential batch reactors to investigate their respective efficiencies during repeated usage. Mechanistic interpretation of the processes governing the immobilization of Cr(VI) was done by integrating the results of these experiments with the metadata. While aggregation due to magnetic properties and rapid oxidation of Fe decreased the efficiency of nZVI with repeated usage, sulfidation minimized the passivation and favored an extended reducing environment because of continuous electron transfer from iron and sulfur components. [ABSTRACT FROM AUTHOR]

The near-threshold dissociation of ionized and neutral methyl chloroformate (CH3COOCl, MCF) was explored with imaging photoelectron photoion coincidence spectroscopy. The threshold photoelectron spectrum (TPES) for MCF was acquired for the first time; the large geometry changes upon ionization of MCF result in a broad, poorly defined TPES. Franck–Condon simulations are consistent with an adiabatic ionization energy (IE) of 10.90 ± 0.05 eV. Ionized MCF dissociates by chlorine atom loss at a measured 0 K appearance energy (AE) of 11.30 ± 0.01 eV. Together with the above IE, this AE suggests a reaction barrier of 0.40 ± 0.05 eV, consistent with the SVECV-f12 computational result of 0.41 eV. At higher internal energies, the loss of CH3O• becomes competitive due to its lower entropy of activation. Pyrolysis of neutral MCF formed the anticipated major products CH3Cl + CO2 (R1) and the minor products HCl + CO + CH2O (R2). The thermal decomposition products were identified by their photoion mass-selected threshold photoelectron spectrum (ms-TPES). Possible reaction pathways were explored computationally to confirm the dominant ones: R1 proceeds by a concerted Cl atom migration via a four-membered transition state in agreement with the mechanism proposed in the literature. R2 is a two-step reaction first yielding 2-oxiranone by HCl loss, which then decomposes to CH2O and CO. Kinetic modeling of the neutral decomposition could simulate the observed reactions only if the vibrational temperature of the MCF was assumed not to cool in the expansion. [ABSTRACT FROM AUTHOR]

The influence of the formation of microheterogeneous soot particles on the gas-phase conversion of rich mixtures of methane with oxygen into synthesis gas in a temperature range from 1500 to 1800 K under the conditions of an adiabatic reactor was studied by kinetic modeling. The effect of CO2 and H2O additives on this process was studied. The appearance of soot particles was observed in rich mixtures, starting from the fuel excess factor ϕ = 3.33. At relatively low temperatures of ~1500 K, a small amount of microheterogeneous soot particles was formed, which did not significantly affect other components of the reacting system. A noticeable effect of soot particles at this temperature was observed at a higher value of ϕ = 8.0. This was most clearly manifested in the temperature profile of the process, in which two maximums were observed at times of about 0.01 and 0.1 s upon the addition of water to the reacting mixture. In the case of CO2 additions, the second maximum in the temperature profile was almost not pronounced. A complex temperature profile led to the appearance of the second concentration maximum of hydroxyl radicals OH at times of ~0.1 s. The addition of H2O and CO2 made it possible to vary the H2/CO ratio in the synthesis gas over a wide range, which is necessary for the synthesis of various products. Because the added CO2 under these conditions was actually involved in the chemical process of obtaining synthesis gas, its partial recirculation from the conversion products made it possible to reduce its emission in the production of synthesis gas. [ABSTRACT FROM AUTHOR]

The paper reports the results of a kinetic and thermodynamic analysis of non-catalytic partial oxidation of methane and C2–C4 hydrocarbon/hydrogen mixtures (C/H = 1 : 4) at 1400–1700 K. The hydrocarbon conversion sequence and the time periods of the major process stages were identified for isothermal conditions. The initial stage of the oxidative conversion of C2+ hydrocarbons consists of their pyrolysis, primarily into ethylene and propylene, followed by oxidation of the pyrolysis products. In this respect, the kinetics of C2+ hydrocarbon oxidative conversion are different from those of methane conversion, marked by the almost simultaneous and significantly slower occurrence of pyrolysis and oxidation. The subsequent stages involve steam and dry reforming of the oxidation products, namely acetylene and methane; these stages continue until the main products (H2, CO, CO2, and H2O) reach an equilibrium distribution for the given temperature. The study findings are important for the optimization of various techniques for high-temperature syngas production via partial oxidation of C2+ hydrocarbons, as well as Moderate or Intense Low-Oxygen Dilution (MILD) combustion processes. [ABSTRACT FROM AUTHOR]

The present study focuses on the synthesis of the natural product 4-methyl-umbelliferone (4-MU, hymecromone), the preparation, characterization, and biological activity evaluation of 4-MU inclusion complexes with β-cyclodextrin (β-CD), as well as their incorporation into pharmaceutical tablets. The inclusion complexes (ICs) were characterized using DLS, SEM, TGA as well as FT-IR, UV-vis, and NMR spectroscopies. The release profile of 4-MU from the β-CD-4-MU ICs was studied in three different pH: 1.2 (aqueous hydrochloric acid), 7.4, and 6.8 (phosphate-buffered solutions), to simulate the stomach, physiological, and intestine pH, respectively. The ICs were incorporated in pharmaceutical tablets which were prepared by direct compression and were characterized for their mechanical properties. The optimal composition of 4-MU as the active pharmaceutical ingredient (API) and excipients was determined using design of experiment (DoE), and the dissolution studies were performed at pH 1.2 at 37 ± 0.5 °C. The sustained release profile of the pharmaceutical tablets showed a delayed burst release effect at 20 min (20% drug release) compared to that of the ICs at the same time interval (70%). The results indicated that the kinetic model describing the release profile of 4-MU from the ICs and tablets is the Higuchi model, while the release mechanism is swelling and diffusion, as was indicated by the Korsmeyer–Peppas kinetic model. The optimization analysis revealed that the optimum composition contains x1 = 150.95 mg of β-CD-4-MU ICs, x2 = 82.65 mg of microcrystalline cellulose, and x3 = 12.40 mg of calcium phosphate. [ABSTRACT FROM AUTHOR]

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Recently, the main polymers present in the health‐care waste (HCW) of a Brazilian university hospital were identified, revealing a composition of polypropylene (85%), high‐density polyethylene (6%), polystyrene (5%), and cellulose (4%). Recognizing the potential for these materials to generate energy through pyrolysis, this study aimed to assess the thermal degradation of the HCW polymers and their respective polymer mixture using thermogravimetric analysis. Thermalgravimetric analysis encompassed three heating rates (5, 10, and 20°C min−1). The kinetic parameters of thermal degradation were estimated using the first‐order reaction model. Friedman differential isoconversional method, as well as Ozawa, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose integral isoconversional methods, were applied to obtain the kinetic parameters, which can predict the thermal degradation kinetics of the polymers in thermal conversion process. Through statistical evaluation of the parameter estimation, it was demonstrated that the proposed methodology yielded fitted models for the experimental data on HCW. These models may be implemented in designing pyrolysis reactors that convert these polymers into energy, thereby mitigating environmental pollution. [ABSTRACT FROM AUTHOR]

Recent studies suggest that, despite its aurora‐like appearance, the picket fence may not be driven by magnetospheric particle precipitation but instead by local electric fields parallel to Earth's magnetic field. Here, we evaluate the parallel electric fields hypothesis by quantitatively comparing picket fence spectra with the emissions generated in a kinetic model driven by local parallel electric fields energizing ambient electrons in a realistic neutral atmosphere. We find that, at a typical picket fence altitude of 110 km, parallel electric fields between 40 and 70 Td (∼80–150 mV/m at 110 km) energize ambient electrons sufficiently so that, when they collide with neutrals, they reproduce the observed ratio of N2 first positive to atomic oxygen green line emissions, without producing N2+ ${\mathrm{N}}_{2}^{+}$ first negative emissions. These findings establish a quantitative connection between ionospheric electrodynamics and observable picket fence emissions, offering verifiable targets for future models and experiments. Plain Language Summary: The "picket fence" is a captivating visual phenomenon featuring vibrant green streaks often observed with and at lower altitudes than the rare purpleish‐white arc called STEVE (Strong Thermal Emission Velocity Enhancement). It occurs in the subauroral sky, at lower latitudes than the auroral oval, raising questions about whether it is a type of aurora or a separate phenomenon. A recent hypothesis proposes that electric fields aligned with Earth's magnetic field in the dense part of the atmosphere where the picket fence forms might energize local electrons, which collide with the neutral atmosphere to create picket fence emissions. This distinguishes the picket fence from traditional auroras caused by energetic particles accelerated higher up in space which stream down and collide with the upper atmosphere. In this study, we compare optical observations of the picket fence to a detailed calculation of the emissions produced by ambient electrons energized by parallel electric fields in the upper atmosphere. The results show that large parallel electric fields can indeed replicate the observed picket fence phenomenon. These findings offer important targets for future picket fence models and experiments. This research demonstrates that the picket fence serves as a valuable testing ground for understanding the chemistry and electrodynamics of Earth's upper atmosphere. Key Points: Observations of picket fence spectra differ quantitatively from green aurora spectral observations, suggesting different originsKinetic modeling driven by local parallel electric fields replicates picket fence spectra without requiring particle precipitationAt 110 km, parallel electric fields between 40 and 70 Townsend (∼80–150 mV/m at 110 km) reproduce observed picket fence spectra [ABSTRACT FROM AUTHOR]

Atmospheric heavy metal pollution presents a severe threat to public health and environmental stability. Transition metal catalysts have emerged as a potent solution for the selective capture and removal of these pollutants. This review provides a comprehensive summary of current advancements in the field, emphasizing the efficiency and specificity of nanostructured transition metals, including manganese, iron, cobalt, nickel, copper, and zinc. Looking forward, we delve into the prospective trajectory of catalyst development, underscoring the need for materials with enhanced stability, regenerability, and environmental compatibility. We project that advancements in computational materials science, nanotechnology, and green chemistry will be pivotal in discovering innovative catalysts that are economically and environmentally sustainable. The integration of smart technologies for real-time monitoring and adaptive control is anticipated to revolutionize heavy metal remediation, ensuring efficient and responsive pollution abatement strategies in the face of evolving industrial scenarios and regulatory landscapes. [ABSTRACT FROM AUTHOR]

Quick liquid absorption is one of baby biscuits' most important quality criteria. A practical procedure based on liquid absorption kinetics was developed for the quality assessment of baby biscuits in this study. Biscuits made of plain flour, wholewheat flour, and vegetable puree were immersed in water, milk, and fruit juices to determine their liquid absorption rates. The data were analyzed by means of Peleg and modified Weibull models. The parameters describing physical properties such as specific volume, texture, and pore size distribution of biscuits were calculated from the model fits. High values of the scale parameter (α) of the modified Weibull model and the Peleg rate constant (k1) indicated a high rate of absorption. The initial absorption rate was related to the average pore size and followed the order: plain (395 µm) > wholewheat (334 µm) > vegetable puree biscuits (208 µm). Equilibrium absorption value was related to the total porosity of biscuits, and it was the highest for wholewheat biscuits. Liquid transfer mechanism was diffusion according to shape parameter values. The absorption behavior of biscuits in liquids was similar and explained by both models. [ABSTRACT FROM AUTHOR]

Metabolic connectivity (MC) has been previously proposed as the covariation of static [18F]FDG PET images across participants, i.e., across-individual MC (ai-MC). In few cases, MC has been inferred from dynamic [18F]FDG signals, i.e., within-individual MC (wi-MC), as for resting-state fMRI functional connectivity (FC). The validity and interpretability of both approaches is an important open issue. Here we reassess this topic, aiming to 1) develop a novel wi-MC methodology; 2) compare ai-MC maps from standardized uptake value ratio (SUVR) vs. [18F]FDG kinetic parameters fully describing the tracer behavior (i.e., K i, K 1, k 3); 3) assess MC interpretability in comparison to structural connectivity and FC. We developed a new approach based on Euclidean distance to calculate wi-MC from PET time-activity curves. The across-individual correlation of SUVR, K i, K 1, k 3 produced different networks depending on the chosen [18F]FDG parameter (k 3 MC vs. SUVR MC, r = 0.44). We found that wi-MC and ai-MC matrices are dissimilar (maximum r = 0.37), and that the match with FC is higher for wi-MC (Dice similarity: 0.47–0.63) than for ai-MC (0.24–0.39). Our analyses demonstrate that calculating individual-level MC from dynamic PET is feasible and yields interpretable matrices that bear similarity to fMRI FC measures. [ABSTRACT FROM AUTHOR]

Superparamagnetic iron oxide nanoparticles (SPIONs) have gathered tremendous scientific interest, especially in the biomedical field, for multiple applications, including bioseparation, drug delivery, etc. Nevertheless, their manipulation and separation with magnetic fields are challenging due to their small size. We recently reported the coupling of cooperative magnetophoresis and sedimentation using quadrupole magnets as a promising strategy to successfully promote SPION recovery from media. However, previous studies involved SPIONs dispersed in organic solvents (non-biocompatible) at high concentrations, which is detrimental to the process economy. In this work, we investigate, for the first time, the magnetic separation of 20 nm and 30 nm SPIONs dispersed in an aqueous medium at relatively low concentrations (as low as 0.5 g·L−1) using our custom, permanent magnet-based quadrupole magnetic sorter (QMS). By monitoring the SPION concentrations along the vessel within the QMS, we estimated the influence of several variables in the separation and analyzed the kinetics of the process. The results obtained can be used to shed light on the dynamics and interplay of variables that govern the fast separation of SPIONs using inexpensive permanent magnets. [ABSTRACT FROM AUTHOR]

Dimethyl ether (DME) is an environmentally friendly fuel and economical compound that can be synthesized through methanol (MeOH) dehydration or direct synthesis from syngas via the water-gas shift reaction. Catalysts such as Cu/ZnO/Al2O3 (CZA) for syngas conversion to MeOH and ferrierite (FER), a group of zeolites, or γ-Al2O3 for MeOH dehydration are necessary for these reactions. A hybrid catalyst, CZA/FER, can be used to directly convert syngas into DME via MeOH. While previous studies have developed kinetic models for these catalytic reaction systems using lumped or microkinetic models, differences in describing elementary reactions have led to variations in detail. In this study, we developed a microkinetic model for DME synthesis from syngas via MeOH over a CZA/FER hybrid bifunctional catalyst. We considered detailed reaction rates and site fractions to determine the dominance of DME synthesis path between the associative and dissociative paths. The model is based on a two-site fraction model for each catalyst, with 28 reactions over CZA and nine reactions over FER. Reaction parameters were determined using transition state theory (TST) and the UBI-QEP method for CZA and the second-order Møller-Plesset perturbation theory (MP2) for FER The pre-exponential factors of Arrhenius rate constants were estimated with experimental data at 250 °C which supported the model's accuracy. Our results show that the associative pathway is dominant for DME synthesis over a CZA/FER hybrid catalyst, which differs from our previous research on microkinetic modeling for MeOH dehydration to DME over an FER zeolite. We also suggest an operating condition range for converting CO2 in the feed. We compared the relative reaction rates of elementary reactions and site fractions in each catalyst to enhance the understanding of the catalytic reaction system. [ABSTRACT FROM AUTHOR]

Purpose: Arterial spin labeling (ASL) acquisitions at multiple post‐labeling delays may provide more accurate quantification of cerebral blood flow (CBF), by fitting appropriate kinetic models and simultaneously estimating relevant parameters such as the arterial transit time (ATT) and arterial cerebral blood volume (aCBV). We evaluate the effects of denoising strategies on model fitting and parameter estimation when accounting for the dispersion of the label bolus through the vasculature in cerebrovascular disease. Methods: We analyzed multi‐delay ASL data from 17 cerebral small vessel disease patients (50 ± 9 y) and 13 healthy controls (52 ± 8 y), by fitting an extended kinetic model with or without bolus dispersion. We considered two denoising strategies: removal of structured noise sources by independent component analysis (ICA) of the control‐label image timeseries; and averaging the repetitions of the control‐label images prior to model fitting. Results: Modeling bolus dispersion improved estimation precision and impacted parameter values, but these effects strongly depended on whether repetitions were averaged before model fitting. In general, repetition averaging improved model fitting but adversely affected parameter values, particularly CBF and aCBV near arterial locations in patients. This suggests that using all repetitions allows better noise estimation at the earlier delays. In contrast, ICA denoising improved model fitting and estimation precision while leaving parameter values unaffected. Conclusion: Our results support the use of ICA denoising to improve model fitting to multi‐delay ASL and suggest that using all control‐label repetitions improves the estimation of macrovascular signal contributions and hence perfusion quantification near arterial locations. This is important when modeling flow dispersion in cerebrovascular pathology. [ABSTRACT FROM AUTHOR]

Pyrolysis and combustion experiments were performed on two facemasks (hereafter named Tissue and Surgical) commonly used in the Russian Federation, first in a thermobalance and under four low-temperature ramps (5, 10, 15, and 20 °C/min). The pyrolysis mass rate curves present a unique devolatilization peak. The combustion mass rate curves present a unique devolatilization peak followed by a shoulder or a small further peak on its right-hand side. Both processes mainly occur between 200 and 500 °C. Simulations of these pyrolysis and combustion processes are performed with good agreement using the extended independent parallel reaction (EIPR) model. The gas chromatography technique was used to analyze the by-products of pyrolysis experiments performed under isothermal temperatures of 300, 400, and 500 °C. Combustion experiments were finally performed in a horizontal oven under a temperature ramp approximately equal to 5 °C/min to measure the main gaseous emissions: CO2 emissions are the main emissions of the Tissue mask, while total hydrocarbons are the main emissions of the Surgical mask. Significant differences are observed between the results obtained for the two masks because of the fibers they are built with (natural or synthetic). [ABSTRACT FROM AUTHOR]

The effect of hyperbaric storage (HS) on polyphenoloxidase activity (PPO) was studied in model solutions and apple juice. Model solutions containing increasing amounts of mushroom (Agaricus bisporus) PPO (up to 26 U) were stored at room temperature at pressure up to 200 MPa. During HS, samples were assessed for residual PPO activity. The enzyme was completely inactivated according to a first-order kinetic model that was used to calculate PPO decimal reduction time (Dp) and pressure sensitivity (zp = 140.8 MPa) in diluted model solutions (2 U PPO). The increase in enzyme concentration (6–26 U) nullified the effect of HS, probably due to protein structure stabilization by self-crowding. The application of HS at 100 and 200 MPa to apple juice promoted a decrease in total bacteria, lactic acid bacteria, yeasts, and molds. These changes occurred in concomitance with the inactivation of PPO (zp = 227.3 MPa). At 200 MPa, PPO inactivation followed a biphasic first-order kinetic, suggesting the presence of PPO isozymes with different pressure sensitivity. The inactivation of PPO was observed to occur more rapidly with increasing storage pressure and led to the maintenance of the original bright juice color. This study proves the capability of HS to control enzyme-related quality decay in fruit juices and, potentially, in many other food matrices suffering enzymatic alteration. [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NOx), which result from the decomposition of nitrocellulose (NC)-based solid propellants, promote the degradation of this later and alter its long-term stability. Thus, to avoid such situation and ensure a better stability, conventional stabilizers such as aromatic amines or urea compounds are usually added to the NC-based formulations. However, these latter may generate carcinogenic and toxic species that may negatively affect both human health and environment. Herein, based on its selective adsorption capacity of NOx, the stability potential of a porous inorganic compound, namely, mordenite (MOR), on nitrocellulose was assessed. Three NC-based samples (S1–S3) were prepared through the incorporation of 3 wt.% of stabilizing agents, i.e., S1: pure NC, S2: NC + DPA, and S3: NC + MOR. The effect on the stability of this inorganic compound with regard to pure NC has been highlighted utilizing stability tests and kinetic modeling. Beforehand, the compatibility of mordenite with nitrocellulose was initially checked by means of DSC and FTIR. Furthermore, the obtained results via Vacuum Stability Test (VST) and Bergmann–Junk (B&J) test demonstrated that S3 displayed a better stability than S1 and comparable behavior to S2. The determination of the kinetic triplet by isoconversional methods confirmed the effectiveness of MOR as a stabilizing agent. These findings claim that such inorganic compound may be used efficiently as a stabilizer for NC-based energetic formulations. [ABSTRACT FROM AUTHOR]

In this study, the degradability of the antibiotic Ceftriaxone was investigated with the help of genetically engineered Pseudomonas putida, in which the gene producing the enzyme catechol 2 and 3 dioxygenase was designed and then inserted into the pUC18 plasmid and replicated by E. coli. It was purified and extracted and transformed into Pseudomonas putida. Finally, the degradation rate of Ceftriaxone by this bacterium in spiked soil was evaluated using the HPLC measurement technique. Finally, the kinetics of Ceftriaxone degradation by genetically engineered Pseudomonas putida was investigated using zero, first, and second -order kinetic models for all factors. The results of HPLC measurement showed that the biodegradation of ceftriaxone in spiked soil was significant by genetically engineered P. putida compared to autoclaved soil inoculated by wild P. putida and normal soil with normal microbial flora (p<0.001) and this bacterium was able to degrade ceftriaxone by 69.53% and kinetic modeling showed that the rate of removal by genetically engineered Pseudomonas putida follows the zero-degree reaction model. These findings indicate that Pseudomonas putida, which produces Catechol 2,3-dioxygenase, can be useful and practical in the biological treatment of environment from cephalosporins. [ABSTRACT FROM AUTHOR]

Deep insights into the combustion kinetics of ammonia (NH 3) can facilitate its application as a promising carbon-free fuel. Due to the low reactivity of NH 3 , experimental data of NH 3 combustion can only be obtained within a limited range. In this work, nitrous oxide (N 2 O) and hydrogen (H 2) were used as additives to investigate NH 3 auto-ignition in a rapid compression machine (RCM). Ignition delay times for NH 3 , NH 3 /N 2 O blends, and NH 3 /H 2 blends were measured at 30 bar, temperatures from 950 to 1437 K. The addition of N 2 O and H 2 ranged from 0 to 50% and 0 to 25% of NH 3 mole fraction, respectively. Time-resolved species profiles were recorded during the auto-ignition process using a fast sampling system combined with a gas chromatograph (GC). An NH 3 combustion model was developed, in which the rate constants of key reactions were constrained by current experimental data. The addition of N 2 O affected the ignition of NH 3 primarily through the decomposition of N 2 O (N 2 O (+M) = N 2 + O (+M), R1) and direct reaction between N 2 O and NH 2 (N 2 H 2 + NO = NH 2 + N 2 O, R2). The rate constant of R2 was constrained effectively by experimental data of NH 3 /N 2 O mixtures. Two-stage ignition behaviors were observed for NH 3 /H 2 mixtures, and the corresponding first-stage ignition delay times were reported for the first time. Experimental species profiles suggested the first-stage ignition resulted from the consumption of H 2. The oxidation of H 2 provided extra HO 2 radicals, which promoted the production of OH radicals and initiated first-stage ignition. Reactions between HO 2 radicals and NH 3 /NH 2 dominated the first-ignition delay times of NH 3 /H 2 mixtures. Moreover, the first-stage ignition led to the fast production of NO 2 , which acted as a key intermediate and affected the following total ignition. Consequently, the reaction NH 2 + NO 2 = H 2 NO + NO (R3) was constrained by total ignition delay times. [ABSTRACT FROM AUTHOR]

Ammonia is a promising alternative clean fuel due to its carbon-free character and high hydrogen density. However, the low reactivity of ammonia and the potential high NO x emissions hinder its applications. Blending methane into ammonia can effectively improve the reactivity of pure NH 3. In addition, lean combustion, as a high-efficiency and low-pollution combustion technology, is an effective measure to control the potential increase in NO x emissions. In the present work, the ignition delay times (IDTs) of NH 3 /CH 4 mixtures highly diluted in Ar (98%) with CH 4 mole fractions of 0%, 10%, and 50% were measured in a shock tube at an equivalence ratio of 0.5, pressures of 1.75 and 10 bar and a temperature range of 1421 K - 2149 K. A newly comprehensive kinetic model (named as HUST-NH 3 model) for the NH 3 /CH 4 mixtures oxidation was developed based on our previous work. Four kinetic models, the HUST-NH 3 model, Glarborg model [19] , Okafor model [7] , and CEU model [10] , were evaluated against the ignition delay times, laminar flame speeds, and species profiles of pure ammonia and ammonia/methane mixtures from the present work and literature. The simulation results indicated that the HUST-NH 3 model shows the best performance among the above four models. Kinetic analysis results indicated that the absence of NH 3 + M = NH 2 + H + M (R819) and N 2 H 2 + M = H + NNH + M (R902) in the CEU model and Okafor model cause the deviations between the experimental and simulation results. The overestimation of the rate constants of NH 2 + NO = NNH + OH (R838) in the Glarborg model is the main reason for the overprediction of the NH 3 laminar flame speeds. [ABSTRACT FROM AUTHOR]

The present study investigates the chemical kinetics of low-temperature oxidation of propane activated by nanosecond pulsed dielectric barrier discharge in a flow reactor. Molecular beam mass spectrometry with tunable synchrotron vacuum ultraviolet photoionization (SVUV-PIMS) is employed for components identification and quantification. A series of hydrocarbons and oxygenated intermediates are observed, including fuel-specific species reported for the first time in this system like propyl hydroperoxide (C 3 H 7 OOH), acrolein (C 3 H 4 O 2), oxetane (-CH 2 CH 2 CH 2 O-), methyloxirane (-CH(CH 3)CH 2 O-), and propanol (n -/ i -C 3 H 7 OH), which provide original kinetic information in the plasma-assisted low-temperature oxidation of propane. The detection of alkyl hydroperoxide (ROOH) demonstrates the existence of alkyl peroxy (RO 2) formed through oxygen addition to alkyl (R) and the detection of cyclic ethers provides evidence for the presence of hydroperoxyl alkyl (QOOH). A kinetic model incorporating plasma chemistry and combustion chemistry is developed for plasma-assisted oxidation of propane. Path fluxes of fuel consumption and oxygenated intermediates formation are provided based on model analysis. Besides H abstractions by the OH radical, reactions activated by plasma involving electron impact dissociation, O(1D)/Ar* quenching dissociation, and ionization contribute much to fuel consumption. The formed propyl (n -/ i -C 3 H 7) are exclusively consumed through oxygen addition producing propyl peroxy (n -/ i -C 3 H 7 O 2). Propyl peroxy can participate in self- and cross-reactions yielding various oxygenated intermediates such as aldehydes, ketones, alcohols, and propoxy (n -/ i -C 3 H 7 O). Discrepancies between simulations and experiments suggest that further kinetic studies on low-temperature mechanisms, including propyl peroxy related reactions for plasma-assisted combustion modeling, are still desired. [ABSTRACT FROM AUTHOR]

The chemical kinetics of plasma-assisted low-temperature oxidation of ethylene (C 2 H 4) is explored by molecular beam mass spectrometry and kinetic modeling. In the experiments, a dielectric barrier discharge (DBD) flow reactor coupled with photoionization and electron ionization molecular beam mass spectrometry (PI-MBMS/EI-MBMS) is employed to provide detailed speciation information, including ions, radicals, and molecules in C 2 H 4 /O 2 /Ar systems (∼340 K, 30 Torr). A series of hydrocarbons and oxygenated intermediates including ethenol, methyl hydroperoxide, ethyl hydroperoxide, diacetylene, vinylacetylene, and hydroxyacetaldehyde is detected for the first time in this system. A kinetic mechanism that contains both combustion and plasma reaction networks is developed. The path fluxes of fuel consumption and oxygenates formation are obtained based on the rate of production analysis. Based on our experimental observations and modeling analysis, new insights into the kinetics of C 2 H 4 /O 2 /Ar plasmas are provided. The fuel is mainly consumed through OH addition, dissociation after e/Ar* collision, reactions with O/O(1D), and dissociative ionization. H abstraction reactions that are favored in alkane plasmas contribute little to the fuel consumption of ethylene. Formation pathways of C1 oxygenates are mainly initiated by CH 3 produced by O/O(1D) reactions with fuel, and the subsequent pathways of OH/H addition to the fuel are responsible for the formation of most C2 oxygenates. Oxygen addition-elimination reactions of C 2 H 4 OH isomers are the sources of ethenol formation. The concentration profiles for some of the species under different oxygen mole fractions are measured. The two distinct patterns of species mole fraction profiles with increasing oxygen concentrations indicate the different dominating formation pathways, namely oxidation pathways and non-oxidation pathways. And the competition between oxidation effects and plasma effects is displayed by the non-monotonic mole fractions profiles of oxidation products. [ABSTRACT FROM AUTHOR]

After improving the cycle algorithm, the parameters of a single-event kinetic model, which is composed of elementary steps catalogued by carbenium ions type, are estimated through data of ethylene oligomerization and aromatization with HZSM-5 catalyst. By introducing adsorption descriptors into the model, the results obtained indicate that the physisorption heat and chemisorption heat are related to the stability of carbenium ions, and the physisorption heat and chemisorption heat released by tertiary carbenium ions are the most, and those released by primary carbenium ions are the least. The influence of the hydrocarbon precursor with different carbon number for coking deactivation on the elemental steps in the reaction network was investigated by adding deactivation parameters φ to the kinetic model, and it was found that the formation of carbon deposition precursors maximally hinders ali-β scission, endo-β scission and cyclization. The kinetic model with the adsorption descriptors was extended to the dehydrogenation of alkanes. It was confirmed that the single-event kinetic parameters did not change with the feedstock, and it was found that the ethane dehydrogenation step in ethane dehydroaromatization with Zn/ZSM-5 catalyst reached thermodynamic equilibrium state, but the butane dehydrogenation step in the propane dehydroaromatization reaction with HZSM-5 catalyst did not reach thermodynamic equilibrium state. [ABSTRACT FROM AUTHOR]

Kinetic modeling is essential in understanding and controlling the process of cellulose hydrolysis for producing value-added cellulose derivatives. This study aims to adopt a set of dominate kinetic ordinary differential equations of cornstalk cellulose hydrolysis in supercritical water for mechanism-based prediction of the production of cellulose, glucose, fructose, glyceraldehyde, erythrose, 5-hydroxymethyl furfural, glycolaldehyde, threose, aldose, and other cellulose derivatives from cornstalks under processing conditions with a pressure of 89 MPa and a temperature of 378 °C, as considered in a recent experimental study in the literature. The yield rates of several cellulose derivatives, e.g., glucose, fructose, 5-HMF, and erythrose as predicted by the present model, are close to those of experimental measurements. The model is further used to predict the yield rates of a few new cellulose derivatives, e.g., glycolaldehyde, threose, and aldose, that are potentially generated in cornstalk cellulose hydrolysis in supercritical water. The present model and computational simulations can be utilized as a rational tool to predict, control, and optimize the derivative yields in cellulose hydrolysis in supercritical water via tuning the process parameters, and, therefore, are useful for the optimal production of targeted bio-based fuels and chemicals from cornstalks and other agricultural and municipal wastes. [ABSTRACT FROM AUTHOR]

This study investigated the adsorption of an azo dye called Congo red from aqueous solution. Ash prepared from sunflower seed waste was used as the adsorbent. Brunauer–Emmett–Teller (BET), Scanning electron microscopy (SEM), and Fourier-Transform Infrared spectroscopy (FT-IR) analyses were performed to characterize the prepared adsorbent. Based on the results of BET, the specific active surface area was about 102 m² /g, and the results of SEM indicated that the adsorbent surface had a very fine porosity that could be attributed to the presence of cellulosic materials in the adsorbent structure. In this study, the effect of the initial concentration of Congo red dye (10-50 mg/L), the concentration of adsorbent (1-5 g/L), and the processing time (10- 240 min) on the rate of Congo red dye removal was investigated. The results showed that the highest percentage of dye removal, i.e., 92%, was achieved at a dye concentration of 50 mg/L, an adsorbent concentration of 3 g/L, and a processing time of 180 min. Under these conditions, the amount of adsorbed dye per gram of the adsorbent was 15.5 mg/g. In addition, pseudo-first order and pseudo-second order kinetic models were also used for modeling. The modeling results indicated that the pseudo-second order model had a higher level of accuracy. Finally, washing adsorbent with different solvents (one molar sodium hydroxide, double distilled water, and ethanol) was investigated, the results indicated that the adsorbent washed with one molar sodium hydroxide had a proper performance after five times of reuse. [ABSTRACT FROM AUTHOR]

More and more attention has been paid to the important roles of external fields in controlled radical polymerization (CRP). However, their essential roles have not been studied thoroughly yet, which hinders the in‐depth understanding of the mechanism and kinetics. Herein, a strategy combining quantum chemical calculations (QCC) and kinetic modeling was adopted to identify the essential roles of light and ultrasonication in the dual‐stimuli regulated bulk atom transfer radical polymerization (ATRP). At the molecular level, the impact of light on Cu‐catalyzed ATRP was investigated. The CuIIBr/Me6TREN has high absorbance at an experimental wavelength of 365 nm (main excitation S0 → D7 accounts for 84.93%). Electron transfer reactions involving Me6TREN are more favorable paths for photochemical reactions, and the mechanism of the copper activation/deactivation pathway is inner sphere electron transfer. At the micro‐scale, a kinetic model based on the method of moment was established with a "series" encounter pair model to consider the influence of ultrasound on diffusional limitation. Simulation results show that the changes of the reaction rate coefficients ka, kda, and kt at high conversion reflect the degree of diffusional limitation by ultrasound. The multiscale modeling strategy applied in this study identifies the essential roles of photo and ultrasonication in dual‐stimuli regulated model systems, which can be extended to other external‐field regulated CRP to improve the mechanistic understanding. [ABSTRACT FROM AUTHOR]

IntroductionQuantitative positron emission tomography (PET) studies of neurodegenerative diseases typically require the measurement of arterial input functions (AIF), an invasive and risky procedure. This study aims to assess the reproducibility of [11C]DPA-713 PET kinetic analysis using population-based input function (PBIF). The final goal is to possibly eliminate the need for AIF.Materials and methodsEighteen subjects including six healthy volunteers (HV) and twelve Parkinson disease (PD) subjects from two [11C]-DPA-713 PET studies were included. Each subject underwent 90 min of dynamic PET imaging. Five healthy volunteers underwent a test-retest scan within the same day to assess the repeatability of the kinetic parameters. Kinetic modeling was carried out using the Logan total volume of distribution (VT) model. For each data set, kinetic analysis was performed using a patient-specific AIF (PSAIF, ground-truth standard) and then repeated using the PBIF. PBIF was generated using the leave-one-out method for each subject from the remaining 17 subjects and after normalizing the PSAIFs by 3 techniques: (a) Weightsubject×DoseInjected, (b) area under AIF curve (AUC), and (c) Weightsubject×AUC. The variability in the VT measured with PSAIF, in the test-retest study, was determined for selected brain regions (white matter, cerebellum, thalamus, caudate, putamen, pallidum, brainstem, hippocampus, and amygdala) using the Bland-Altman analysis and for each of the 3 normalization techniques. Similarly, for all subjects, the variabilities due to the use of PBIF were assessed.ResultsBland-Altman analysis showed systematic bias between test and retest studies. The corresponding mean bias and 95% limits of agreement (LOA) for the studied brain regions were 30% and ± 70%. Comparing PBIF- and PSAIF-based VT estimate for all subjects and all brain regions, a significant difference between the results generated by the three normalization techniques existed for all brain structures except for the brainstem (P-value = 0.095). The mean % difference and 95% LOA is -10% and ±45% for Weightsubject×DoseInjected; +8% and ±50% for AUC; and +2% and ± 38% for Weightsubject×AUC. In all cases, normalizing by Weightsubject×AUC yielded the smallest % bias and variability (% bias = ±2%; LOA = ±38% for all brain regions). Estimating the reproducibility of PBIF-kinetics to PSAIF based on disease groups (HV/PD) and genotype (MAB/HAB), the average VT values for all regions obtained from PBIF is insignificantly higher than PSAIF (%difference = 4.53%, P-value = 0.73 for HAB; and %difference = 0.73%, P-value = 0.96 for MAB). PBIF also tends to overestimate the difference between PD and HV for HAB (% difference = 32.33% versus 13.28%) and underestimate it in MAB (%difference = 6.84% versus 20.92%).ConclusionsPSAIF kinetic results are reproducible with PBIF, with variability in VT within that obtained for the test-retest studies. Therefore, VT assessed using PBIF-based kinetic modeling is clinically feasible and can be an alternative to PSAIF.

Abstract Background Despite recent attention, pathways and mechanisms of fluid transposition in the brain are still a matter of intense discussion and driving forces underlying waste clearance in the brain remain elusive. Consensus exists that net solute transport is a prerequisite for efficient clearance. The individual impact of neuronal activity and cerebrospinal fluid (CSF) formation, which both vary with brain state and anesthesia, remain unclear. Methods To separate conditions with high and low neuronal activity and high and low CSF formation, different anesthetic regimens in naive rat were established, using Isoflurane (ISO), Medetomidine (MED), acetazolamide or combinations thereof. With dynamic contrast-enhanced MRI, after application of low molecular weight contrast agent (CA) Gadobutrol to cisterna magna, tracer distribution was monitored as surrogate for solute clearance. Simultaneous fiber-based Ca2+-recordings informed about the state of neuronal activity under different anesthetic regimen. T2-weighted MRI and diffusion-weighted MRI (DWI) provided size of subarachnoidal space and aqueductal flow as surrogates for CSF formation. Finally, a pathway and mechanism-independent two-compartment model was introduced to provide a measure of efficiency for solute clearance from the brain. Results Anatomical imaging, DWI and Ca2+-recordings confirmed that conditions with distinct levels of neuronal activity and CSF formation were achieved. A sleep-resembling condition, with reduced neuronal activity and enhanced CSF formation was achieved using ISO+MED and an awake-like condition with high neuronal activity using MED alone. CA distribution in the brain correlated with the rate of CSF formation. The cortical brain state had major influence on tracer diffusion. Under conditions with low neuronal activity, higher diffusivity suggested enlargement of extracellular space, facilitating a deeper permeation of solutes into brain parenchyma. Under conditions with high neuronal activity, diffusion of solutes into parenchyma was hindered and clearance along paravascular pathways facilitated. Exclusively based on the measured time signal curves, the two-compartment model provided net exchange ratios, which were significantly larger for the sleep-resembling condition than for the awake-like condition. Conclusions Efficiency of solute clearance in brain changes with alterations in both state of neuronal activity and CSF formation. Our clearance pathway and mechanism agnostic kinetic model informs about net solute transport, solely based on the measured time signal curves. This rather simplifying approach largely accords with preclinical and clinical findings.

Designing antiviral therapeutics is of great concern per current pandemics caused by novel coronavirus or SARS-CoV-2. The core polymerase enzyme in the viral replication/transcription machinery is generally conserved and serves well for drug target. In this work we briefly review structural biology and computational clues on representative single-subunit viral polymerases that are more or less connected with SARS-CoV-2 RNA dependent RNA polymerase (RdRp), in particular, to elucidate how nucleotide substrates and potential drug analogs are selected in the viral genome synthesis. To do that, we first survey two well studied RdRps from Polio virus and hepatitis C virus in regard to structural motifs and key residues that have been identified for the nucleotide selectivity. Then we focus on related structural and biochemical characteristics discovered for the SARS-CoV-2 RdRp. To further compare, we summarize what we have learned computationally from phage T7 RNA polymerase (RNAP) on its stepwise nucleotide selectivity, and extend discussion to a structurally similar human mitochondria RNAP, which deserves special attention as it cannot be adversely affected by antiviral treatments. We also include viral phi29 DNA polymerase for comparison, which has both helicase and proofreading activities on top of nucleotide selectivity for replication fidelity control. The helicase and proofreading functions are achieved by protein components in addition to RdRp in the coronavirus replication-transcription machine, with the proofreading strategy important for the fidelity control in synthesizing a comparatively large viral genome.

The objective of this work was to gain insight into the operating conditions that affect the efficiency of ultrasound-assisted extraction (UAE) parameters to achieve the best recovery of bioactive compounds from broccoli leaf and floret byproducts. Therefore, total phenolic content (TPC) and the main sulfur bioactive compounds (sulforaphane (SFN) and glucosinolates (GLSs)) were assayed. Distilled water was used as solvent. For each byproduct type, solid/liquid ratio (1:25 and 2:25 g/mL), temperature (25, 40, and 55 °C), and extraction time (2.5, 5, 7.5, 10, 15, and 20 min) were the studied variables to optimize the UAE process by using a kinetic and a cubic regression model. TPC was 12.5-fold higher in broccoli leaves than in florets, while SFN was from 2.5- to 4.5-fold higher in florets regarding the leaf’s extracts obtained from the same plants, their precursors (GLS) being in similar amounts for both plant tissues. The most efficient extraction conditions were at 25 °C, ratio 2:25, and during 15 or 20 min according to the target phytochemical to extract. In conclusion, the type of plant tissue and used ratio significantly influenced the extraction of bioactive compounds, the most efficient UAE parameters being those with lower energy consumption.

This study focuses on optimizing the ultrasound-assisted extraction (UAE) of bioactive compounds from purple-fleshed sweet potatoes (PFSP) for potential use as natural colorants. Factors such as time, temperature, and solid-to-liquid ratio were varied using a Box–Behnken Design. The optimal conditions were determined as 75 min, 70 °C, and a 1:15 m/v solid-to-liquid ratio, resulting in 18.372 mg/100 g total anthocyanin (TA) and 151.160 mg GAE/100 g total phenolic content (TPC). The validation yielded 18.822 mg/100 g for total anthocyanin and 162.174 mg GAE/100 g for total phenolic content, showing a 7% difference from predictions. UAE significantly increased TA extraction by 81% and TPC by 93% compared with the conventional method, with a notable reduction in process time from 24 h to 75 min. Additionally, three kinetic models were tested to compare extraction mechanisms, confirming the efficiency of UAE for PFSP bioactive compound recovery. This study proposes the UAE technique as a highly effective means of extracting bioactive compounds from PFSP, offering promising applications across multiple industries.

The release of industrial wastewater containing textile organic dyes without treatment affects human health and the environment. In this study, a two-step process to treat water contaminated with cellulose-reactive anionic dye is presented. First, the dye was adsorbed onto an inexpensive water hyacinth root powder (WHRP) bioadsorbent. Then, the dye-loaded WHRP was treated with Fenton reagents, allowing for in situ heterogeneous oxidation of the dye. The adsorption was performed from a solution containing between 100 and 300 mg dye/L, consistent with the effluent from textile processing plants. The corresponding loading on the WHRP was between 16.40 and 41.80 mg dye/g adsorbent. A short treatment time (less than 25 min) was achieved, which is more practical than previous reports that took several hours. To fully characterize the process, we studied the conditions affecting the in situ oxidation of adsorbed dye and developed a kinetic model for the reaction to find the optimal operating conditions necessary to achieve a high dye degradation percentage in a short timeframe. A first-order dependence between the reaction rate and the dye concentration was found, coupled with catalyst deactivation at a constant rate. However, increasing either the catalyst or the oxidant concentration above a certain threshold resulted in the inhibition of the dye degradation reaction. In this study, optimal dye degradation could be achieved using up to 31.60 mg dye/g adsorbent, with 0.9 M H2O2 and 3.6 mM Fe2+ at pH 3, resulting in more than 99 % dye degradation and nearly complete mineralization in less than 20 min. Thus, a relatively simple in situ dye oxidation process, well-suited for scale-up and continuous operation, was achieved.

Abstract Recent studies suggest that, despite its aurora‐like appearance, the picket fence may not be driven by magnetospheric particle precipitation but instead by local electric fields parallel to Earth's magnetic field. Here, we evaluate the parallel electric fields hypothesis by quantitatively comparing picket fence spectra with the emissions generated in a kinetic model driven by local parallel electric fields energizing ambient electrons in a realistic neutral atmosphere. We find that, at a typical picket fence altitude of 110 km, parallel electric fields between 40 and 70 Td (∼80–150 mV/m at 110 km) energize ambient electrons sufficiently so that, when they collide with neutrals, they reproduce the observed ratio of N2 first positive to atomic oxygen green line emissions, without producing N2+ first negative emissions. These findings establish a quantitative connection between ionospheric electrodynamics and observable picket fence emissions, offering verifiable targets for future models and experiments.