Increased Residence Time Research Articles

Modeling and Optimization of a Suspension Crystallization Separation Process for para-Xylene Purification

The morphology and DSC methods were used for measuring the crystallization kinetics of para-xylene. Solubility data from DSC experiments were fitted using the activity coefficient model and classical solid–liquid phase equilibrium theory, while the rates of nucleation, growth, aggregation, and breakage (functions of supersaturation) were built from morphological experiments. The particle size distribution was modeled via a population balance equation and validated by experimental data on a suspension crystallization separation process. The effects of the crystallizer operating temperature and residence time on product yield were also investigated; although the rates of nucleation, growth, breakage, and aggregation increase with decreasing temperature and increasing residence time, the breakage and aggregation are dominant at low temperatures and long residence times. Therefore, the crystallization process should be operated at an optimal temperature and residence time. The models built for this work can be used further in additional process design and optimization.

Experimental and simulation-based investigation of the interplay between factor gradients following pulsed electric field treatments triggering whey protein aggregation

Novel pulsed electric field (PEF) applications to modify the techno-functionality of biomacromolecules have recently emerged. Insights into the involved interplay of factor domains (electrical, flow, concentration, temperature) with respect to the treatment chamber locations, and into the scalability are lacking. Therefore, a parallel plate batch (0.8 mL) and a scaled up parallel plate continuous (50 mL, 0.83 mL s −1 ) setup were built and simulated to investigate these domains and resulting gradient interactions using liquid whey protein solutions (0.5% w/w). In both setups, protein agglomerations and aggregations were observed below 60 °C at the electrode boundary layers for pulses in the range of 2–2.5 kV cm −1 , 10 μs, 40–350 Hz. The boundary layer is characterized by higher protein concentrations due to temperature- and pH-dependent migration trajectories, increased electrochemical reactivity (e.g., pH), and increased residence times due to the laminar flow or no flow conditions. Characterizing the domain interconnectivity led to effective scaling-up approaches of protein aggregations and insights into involved mechanisms. • Pulsed electric fields trigger whey protein migration and aggregations below 60 °C. • Identified regimes might provide a new process window to alter techno-functionalities. • Migration direction and aggregation location are pH-dependent. • Translation of observations from a batch to a scaled up continuous system. • Reactive boundary layer is characterized by overlaying factor domains and gradients.

Experimental investigation on the degradation of polymer-containing oily sludge in sub-/supercritical water

ABSTRACT Polymer-containing oily sludge (PCOS) has caused tremendous hazards with the broad application of polymer flooding technology. Traditional methods cannot meet the treatment demand due to the high-water content of PCOS. In this work, the degradation of PCOS in sub-/supercritical water is studied to explore an appropriate treatment method. The influence of residence time (15–90 min), temperature (340–700°C), catalysts (sulfates, carbonates, and alkalis), and co-solvents (methanol-water and ethanol-water) on the distribution of end products is studied in details. Results show that PCOS is hardly gasified under the subcritical conditions and the increase in residence time and temperature has positive effects on the phase conversion. The conversion rate reaches 81.77% at 60 min, 340°C, compared to 67.09% at 15 min. Supercritical water shows a great solubility for PCOS, and no solid residues are detected at supercritical conditions (400–700°C, 23 MPa). Organic matter in liquid phase is classified into nine types, and the increase in temperature greatly changes its composition. The relative proportion of ketones reaches more than 50% of the organic matter in liquid at 400°C. Ketones are proven to be the main source of CO2 and disappear at above 500°C. Moreover, the migration of elements (carbon and nitrogen) is comprehensively studied.

Reaction pathway and kinetics study on supercritical water gasification of oily sludge

Supercritical water gasification of oily sludge is a clean technology for waste disposal and energy recovery. In this work, gaseous productions from supercritical water gasification (SCWG) of oily sludge in a batch reactor under different temperatures (550–650 °C) and residence times (1–40 min) was studied. Then, a quantitative kinetic model was employed to study the reaction mechanism and optimize the H2 and CH4 productions. The H2 yield was promoted with the increase in temperature and residence time. The CH4 yield and carbon gasification efficiency (CE) increased with the prolongation of residence time, but reached the maximum when the temperature was 600 °C. The liquid products were mainly composed of alkene, acetone, benzene, toluene, ethylbenzene and xylene, phenolic substances and polycyclic aromatic hydrocarbons (PAHs). Higher temperatures promoted the formation of phenol and PAHs in liquid products, which were hard for gasification. The results of kinetic model indicated that higher temperatures accelerated the reaction rate and intermediates formation, but the effect on gas formation was limited. Reaction rate analysis at 650 °C indicated that H2 was mainly produced from pyrolysis rather than steam reforming. CH4 was produced mostly from pyrolysis and methanation reaction can be neglected.

Anodic Reaction in Syngas-Fueled Proton-Conducting Solid Oxide Fuel Cells

Anode-supported proton-conducting solid oxide fuel cells (PC-SOFCs) fabricated with two representative proton-conducting oxides, BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) and BaZr0.8Y0.2O3-δ (BZY), were compared to obtain the insight into the electrochemical performances when fueled with syngas at 700°C and the correlation between the anode thickness (0.4, 0.8, and 1.6 mm) and operational stability. We have demonstrated that, in stability tests, the BCZYYb cells exhibited significantly higher maximum power density (MPD) than the BZY cells when operating on H2, 1.22 and 0.48 W/cm2 for the BCZYYb and BZY cells, but the BCZYYb cells degraded more rapidly than the BZY cells when operating on syngas. In addition, decreasing the anode thickness significantly enhanced the stability of BCZYYb cells operating on syngas, a reduction of 81, 76, and 71% in MPD for 1.6, 0.8, and 0.4 mm anode after 30 min. The electrochemical impedance spectra and X-ray diffraction patterns indicated that the rapid degradation of cerate-based cells with syngas could be mainly attributed to the considerable increase in polarization resistance due to the phase decomposition of the electrolyte powder in the anode. Heterogeneous catalysis was performed to study the catalytic reaction of the H2–CO mixture over anode powders prepared with the two proton-conducting oxides (Ni-BCZYYb and Ni-BZY) in a fixed bed reactor, and the CO conversion and selectivity to CO2 and CH4 were determined. For all anode powders, continuous CO2 production was initially observed with CH4 formation, and no significant difference in catalytic activity trends was observed between both anode powders. An increased residence time substantially decreased the normalized CO2 yield, which was associated with the potential secondary reaction of CO2 with H2, CH4, or perovskite oxide. Based on the results of heterogeneous catalysis with both anode powders, the observed cell degradation on both cells during operation with syngas may be primarily attributed to carbon coking due to CO disproportionation; however, more than 4 times rapid degradation of the cerate-based cell when operating with syngas was clearly demonstrated to be attributed to the decomposition of the electrolyte powder in anode by the resulting CO2 from the catalytic reaction of the H2–CO mixture.

Mapping groundwater discharge seeps by thermal UAS imaging on a wetland restoration site

One of the key metrics for the effectiveness of wetland restoration is whether a restored wetland behaves hydrologically like a natural wetland. Restoration is designed to increase the water residence time on the surface of the site in order to capture and process nutrients, mitigate the impact of local flooding and drought, and provide a habitat for wetland species abundance and biodiversity. Quantifying the change in groundwater presence at the wetland’s surface will inform future freshwater wetland restorations across New England. The ability to produce a comprehensive map of the locations of groundwater discharge over a large area has the potential to provide insight into restoration practice, its success, and its effects on individual seeps over time. Identification, mapping, and measurement of groundwater discharge sites have long been a challenge, but new methodologies are developing with the advances in unmanned aerial systems (UAS). This study uses a UAS-mounted thermal infrared camera to map groundwater seeps on a 25-ha (62-acre) site in Plymouth, Massachusetts, before and after it underwent restoration to a freshwater wetland. Using the thermal map, we located and quantified the spatial extent that of groundwater seeps pre-restoration and the changes after restoration. The location and size of these seeps show that existing groundwater seeps remained immobile through restoration, but their surface expression grew, indicating that restoration removed barriers to surface expression and successfully increased residence time. This analysis using a thermal camera-enabled UAS allows for a temporal comparison over large spatial scales and provides insight into restoration impacts to groundwater expression on the surface of post-agricultural wetland sites.

On the hydrothermal depolymerisation of kraft lignin using glycerol as a capping agent

Abstract Depolymerisation of kraft lignin under hydrothermal conditions was investigated at short residence times (1–12 min) with glycerol being used as a capping agent. The weight average molecular weight (M w) of the products decreased within the first minute of residence time, with the inter-unit ether linkages breaking accordingly. Furthermore, the M w of the product fractions decreased at increasing residence times, while the char yield increased. Short residence times thus appear to be beneficial for mitigating the formation of char. Also, addition of NaOH reduced the yield of char. Although the addition of glycerol caused a decrease in the M w of the products, it seemed to increase the yield of char and therefore might not be a suitable capping agent for kraft lignin depolymerisation.

Seagrass macrobenthic biodiversity does not vary in conformity with a leaky-lagoonal confinement gradient

Coastal lagoon ecology often changes on progression from the open, well-flushed mouth region to the depositional zone furthest from the open sea. This is generally considered consequent on increasing ‘confinement’ and associated features, rather than on the often co-occurringly decreasing salinity. The 12 km Rainbow Channel connecting part of Moreton Bay, a microtidal leaky lagoon, to the adjacent Pacific provides a gradient of increasing confinement without any significant salinity change, i.e. a tenfold increase in water residence time for a salinity decrease of <1. Macrobenthic faunal assemblages characterising intertidal Zostera seagrass at strategic points along its length were compared to test whether their nature changed in conformity with confinement models. Results suggest that it does not; faunal abundance, species richness, evenness and composition remaining effectively unchanged along the gradient. Seagrass systems may constitute a special case because they decouple renewal times of the overlying water and local organic enrichment/decomposition; as may leaky lagoons because of their high tidal velocities.

Effect of preheat temperature, pressure, and residence time on methanation performance

The present work studies the effect of reagent preheat temperature on methanation while maintaining the initial temperature of the catalytic bed constant. An adiabatic packed bed reactor was used with 193 g of commercial 10% Ni/Al2O3 catalyst. The tested preheat temperatures were 25 °C, 100 °C, 180 °C, and 280 °C, while the initial catalytic bed temperature was 280 °C. Two tests were performed in which the effect of preheat temperature was evaluated: the first comparing gas hourly space velocities (GHSVs) of 935 h−1 and 1559 h−1, and the second comparing gauge pressures of 0 bar, 1 bar, and 4 bar. Similar behavior was observed for the temperature inside the reactor and final CO2 conversion for preheating temperatures of 100 °C, 180 °C, and 280 °C at a gauge pressure of 0 bar. However, at this pressure, conversion was considerably reduced for the preheat temperature of 25 °C, due to a large part of the catalytic bed serving to preheat the reactants to the minimum reaction temperature. This effect can be partially attenuated by decreasing the GHSV, due to the increased residence time. Finally, increased pressure significantly improved the final CO2 conversion for all preheating temperatures (Tin), and attenuates the effect of Tin. These results show that certain operating conditions do not require as high a reactant preheat temperature for methanation, which offers energy savings in certain processes such as power-to-gas (P2G), where the hydrogen is produced from electrolysis and can leave the process at a lower temperature than that required for methanation.

Microwave Devulcanization of Ground Tire Rubber and Its Improved Utilization in Natural Rubber Compounds

We devulcanized ground tire rubber (GTR) with microwaves at different temperatures (140–200 °C) and heating rates (2–18 °C/min). We measured the soluble content and the cross-link density of the samples, and then evaluated them by Horikx’s analysis and determined the specific microwave energy during devulcanization and the selectivity parameter of the treatments. We also introduced the K·D number that can be calculated as the product of the selectivity parameter (K) and the relative decrease in the cross-link density (D). The results showed that GTR devulcanized at lower temperatures, selectivity was very high, and the degree of devulcanization was adequate. At higher temperatures (180–200 °C), the degree of devulcanization reached 85%, but the selectivity parameter was low, which indicates severe degradation at this temperature range. At lower temperatures (140–160 °C) and decreasing heating rate, i.e., increasing residence time, the degree of devulcanization showed an increase, but at higher temperatures, the heating rate had no significant effect on the degree of devulcanization. We introduced different devulcanized GTRs (dGTRs) to natural rubber-based mixtures and produced samples with two different mixing methods: conventional mixing and so-called two-step mixing. In the latter one, in the first mixing step, we added vulcanizing agents to the dGTR, and in the second mixing step, we added this mixture to the reference mixture. Two-step mixing helped recover mechanical properties, especially tear strength. Scanning electron microscopy–energy-dispersive spectroscopy and atomic force microscopy showed that microwave devulcanization and the vulcanizing agents mixed with dGTR acted in the cross-section of dGTR.

Index-Based Spatiotemporal Assesment Of Water Quality In Tarbela Reservoir, Pakistan (1990−2020)

Anthropogenic activities can greatly influence the lake ecosystems across the globe. Within these ecosystems, the impacts of human activities are most evident on sedimentation, light and nutrient availability, and disturbance frequency. There have been times of natural environmental healing of reservoirs and the present research aims to explore the variations in the water quality of Tarbela reservoir, Pakistan the largest rock-filled dam of the world, from 1990 to 2020. Landsat imagery (Landsat 4-5, 5, 7 and 8) was used to monitor Land Use Land Cover (LULC), Normalized Difference Chlorophyll Index (NDCI), Normalized Difference Turbidity Index (NDTI) and Normalized Difference Water Index (NDWI) in Tarbela reservoir, and its surrounding area from 1990−2020, on decadal interval. The results indicated a significant increase in built-up area, of about 630 km2 , in the western and eastern parts of the reservoir, whereas turbidity level, revealed a substantial decline with 4% decrease observed in the last decade, 2010-2020 thus confirming improved water quality. The study also presented expanse in the spatial coverage of chlorophyll index and water index, indicating increase in residence time of the water. It is concluded that the water quality continued to deteriorate with time, however, 2020 was a year of environmental healing and there was an overall water quality improvement of the reservoir observed. The study recommends policies to be formulated for sediment flushing and turbidity reduction for longer time duration to enhance the life of this mega reservoir.

Computational investigation of non-premixed hydrogen-air laminar flames

Laminar diffusion hydrogen/air flames are numerically investigated. Detailed and global mechanisms are compared. NO formation is modelled by full nitrogen chemistry and the extended Zeldovich mechanism. A satisfactory agreement between the present predictions and the experiments of other authors is observed. Significance of different ingredients of mathematical modelling is analyzed. Minor roles of thermal diffusion and radiation, but a significant role of buoyancy is observed. It is observed that the full and quasi multi-component diffusion deliver the same results, whereas assuming Le = 1 to a remarkable difference. NO emissions logarithmically increase with increasing residence time. NO is the dominating nitrogen oxide. Its share increases with residence time, whereby NO2 and N2O show a reverse trend. It is observed that the NNH route plays a remarkable role in NO formation, where the share of the Zeldovich mechanism increases with residence time from about 20% to 85%, within the considered range.

Mixing-layer depth-based backwards trajectory analysis of the sources of high O3 concentrations at the Wutaishan station, North China

In the present study, we investigate the formation, characteristics and sources of high O3 concentrations at the high-altitude Wutaishan station (WTS, 2209.9 m a. s. l.) from 2017 to 2020 using a novel and simple approach based on the mixing layer depth of a backwards trajectory. This new approach can roughly distinguish between high concentrations of O3 caused by human activities and those transported from the upper troposphere. The diurnal variation in O3 concentration shows a distinctly different pattern between the warm and cold seasons, with day and night averages of 58.6 ppb and 62.1 ppb for warm seasons and 40.2 ppb and 38.8 ppb for cold seasons, respectively. The study shows that photochemical reactions are not the main factor causing the increase in O3 concentration; instead, the transport process significantly influences the high O3 concentrations at the Wutaishan station. The O3 concentration is closely related to the residence time of the airflow in the mixing layer during the transport process. The trajectory residence time in the mixing layer during the warm seasons is positively correlated with the O3 concentration at the Wutaishan station; the correlation coefficient is higher during the day than during the night due to the fierce photochemical reaction and more significant O3 transport processes from below the mixing layer. During the cold seasons, the average concentration of O3 increases during the day and decreased during the night in response to the increased residence time in the mixing layer; this phenomenon indicates the apparent effect of free tropospheric airflows on increasing O3 concentrations.

Investigation of macromolecular transport through tunable collagen hyaluronic acid matrices

Therapeutic macromolecules possess properties such as size and electrostatic charge that will dictate their transport through subcutaneous (SC) tissue and ultimate bioavailability and efficacy. To improve therapeutic design, platforms that systematically measure the transport of macromolecules as a function of both drug and tissue properties are needed. We utilize a Transwell chamber with tunable collagen-hyaluronic acid (ColHA) hydrogels as an in vitro model to determine mass transport of macromolecules using non-invasive UV spectroscopy. Increasing hyaluronic acid (HA) concentration from 0 to 2 mg/mL within collagen gels decreases the mass transport of five macromolecules independent of size and charge and results in a maximum decrease in recovery of 23.3% in the case of bovine immunoglobulin G (IgG). However, in a pure 10 mg/mL HA solution, negatively-charged macromolecules bovine serum albumin (BSA), β-lactoglobulin (BLg), dextran (Dex), and IgG had drastically increased recovery by 20–40% compared to their performance in ColHA matrices. This result was different from the positively-charged macromolecule Lysozyme (Lys), which, despite its small size, showed reduced recovery by 3% in pure HA. These results demonstrate two distinct regimes of mass transport within our tissue model. In the presence of both collagen and HA, increasing HA concentrations decrease mass transport; however, in the absence of collagen, the high negative charge of HA sequesters and increases residence time of positively-charged macromolecules and decreases residence time of negatively-charged macromolecules. Through our approach, ColHA hydrogels serve as a platform for the systematic evaluation of therapeutic macromolecule transport as a function of molecular characteristics.

How many microplastics do we ingest when using disposable drink cups?

Microplastics in food are receiving increasing attention because they are directly ingested by humans and pose a health threat. However, little attention has been paid to the microplastics resulting from the disposable drink cups. Here, we analyzed the microplastic contamination in beverages in three commonly used plastic cups (PP, PET, and PE cups). Effects of the cup materials, the residence time of the drink in the cup, shaking, and water temperatures on the microplastic release were systematically investigated. The results showed that the microplastic abundance in water reached 723–1,489 particles cup -1 after 5 min exposure and increased significantly with increasing residence time. The size of released microplastics was mainly in the range of <50 μm. The shaking applied during transport promoted the release of microplastics from plastic cups. Besides, the results showed that cups released more microplastics when serving hot drinks than serving cold drinks. Based on the results, we estimated that people may unconsciously ingest 37,613–89,294 microplastics a year due to the use of one plastic cup every 4–5 days. Considering the potential harm of microplastics, the contamination of microplastics resulting from the use of plastic cups for drinks needs to be taken seriously. • Microplastics were released from different types of disposable drink cups. • Violent shaking could cause the plastic cups to release more microplastics. • Washing plastic cups before use reduced the risks of microplastic release. • People may ingest 37,613–89,294 microplastics through plastic cups a year.

Refugees’ occupational future time perspective: Implications for their integration in receiving countries

While refugees’ occupational integration is of interest for many receiving countries, refugees face multiple barriers in this process. The current research addresses psychological processes within refugees in response to their situation. Specifically, we proposed that experienced migration forcedness, as a key characteristic of refugee vs. non-refugee migration, restricts migrants’ perception of their occupational future time perspective (OFTP) in the receiving country. In turn, a limited OFTP should impair migrants’ occupational integration efforts. Moreover, we assumed that residence time in the receiving country moderates the relation between forcedness and OFTP, such that the relation is stronger in the beginning and weaker with increasing residence time. Preregistered hypotheses were tested in a cross-sectional study with online and paper-pencil surveys answered by N = 258 migrants in Germany. Contrary to expectations, results indicated no overall relation between migration forcedness and OFTP. However, the results confirmed the expected moderation by residence time. Moreover, results confirmed the expected relation between migrants’ OFTP and their occupational integration efforts, i.e., development of career-relevant skills and coworker relationships, work engagement, organizational commitment, and avoidance of underemployment. Finally, moderated mediation analyses confirmed migrants’ OFTP as a moderated mediator between migration forcedness and migrants’ occupational integration efforts. These results demonstrate that OFTP is a central process that affects the integration of refugees into receiving countries.

Chemical synthesis mono- and diacylglycerol from palm stearin-olein blend using continuous high shear stirred tank reactor

This research aimed to evaluate the effect of flow rate and processing time on the synthesis of high mono- and diacylglycerol (MDAG) from palm stearin-olein blend using high shear continuous stirred tank reactor (HS-CSTR). Glycerolysis-interesterification was performed at 120 ºC and flow rates of 6, 10, 14, 18, and 22 mL/min. Glycerol:oil ratio, stearin:olein ratio, NaOH concentration, and agitation rate were 1:5 (mol/mol), 60:40 (w/w), 3%, and 2000 rpm, respectively. The result showed that flow rate significantly affected MDAG concentration and the product's physical characteristics. The highest MDAG was obtained at a flow rate of 6 mL/min. MDAG concentration, slip melting point (SMP), melting point (MP), hardness, emulsion capacity, and stability were 60.36 ± 1.61%, 42.3 ± 0.01 ºC, 43.3 ± 0.06 ºC, 6.04 ± 0.32 N, 87.6 ± 1.75 % and 91.8 ± 2.99 % respectively. An increase in residence time, which means flow rate decreased, increased MDAG, SMP, MP, hardness, emulsion capacity, and stability of the product. Processing time did not significantly affect MDAG concentration and the product's physical properties. It means that acylglycerol concentrations and physical properties of the product did not fluctuate significantly during the process. Thus, it confirmed that the continuous process was stable and reached a steady state throughout the process.

Ash characterisation formed under different oxy-fuel circulating fluidized bed conditions

The CO2-intensive oil shale power industry accounts for more than 70% of the Estonian energy sector, producing large amounts of ash that are mainly landfilled. Adopting oxy-fuel technology in the Estonian energy sector, in conjunction with CO2 storage, can be a critical tool for reducing carbon footprint. Nevertheless, several differences in ash formation under oxy-fuel conditions can be expected, which can lead to additional ash handling/utilization and related environmental concerns. In this context, the composition of oil shale ash was obtained from a series of combustion experiments in a 60 kWth circulating fluidized bed (CFB) test unit under both air and oxy-fuel combustion regimes studied by means of physical, chemical analysis as quantitative X-ray diffraction and element analysis for ashes from different separation ports. During the experimental work, special attention was given to understanding the impacts of the boiler temperature, recycled flue gas (RFG), and elevated oxygen concentration. As a result, the primary goal of this research is to characterise the ash produced by oxy-fuel combustion of oil shale in order to gain a better understanding of its chemical and mineral compositions, including Ca-Mg silicates and clay minerals, as well as to investigate the behaviour of the formation of free lime and anhydrite, which are the major compounds influencing potential ash utilisation routes. The results show that although the decomposition of calcium carbonates was limited during oxy-fuel combustion because of the high CO2 partial pressure, the contents of secondary silicates and anhydrite were slightly higher. The increased particle temperature and the higher SO2 partial pressure (with RFG) can explain this. The particle size distributions (PSDs) were wider under oxy combustion, and the specific surface area (SSA) in Filter ashes were much higher under elevated inlet O2% atmosphere. Oxy-fuel combustion had no significant impact on the concentration of elements in the ash. Overall, the mineralogy of the ashes formed in air and oxy-fuel combustion environments is similar, yet slight differences exist in the formation of clay minerals in the case of increased oxygen concentrations and with the application of RFG as a result of the increased residence time of the particles.

Patient-specific fluid simulation of transcatheter mitral valve replacement in mitral annulus calcification.

Transcatheter mitral valve replacement is a promising alternative to open-heart surgery in elderly patients. Patients with severe mitral annulus calcification (MAC) are a particularly high-risk population, where postprocedural complications can have catastrophic effects. Amongst these, obstruction of the left ventricular outflow tract can lead to ventricular hypertrophic remodeling and subsequent heart failure, while subclinical valve thrombosis can result in early bioprosthetic valve failure. To elucidate the mechanisms of left ventricular outflow tract obstruction and valve thrombosis following valve-in-MAC procedures, we used image processing and Computational Fluid Dynamics (CFD) software to generate patient- and device-specific models based on preprocedural CT data. Personalized computer simulations were performed to predict the left ventricular haemodynamics after implantation in three patients with severe MAC. The simulations have successfully captured the increased pressure gradient in the left ventricular outflow tract as a result of the partial obstruction due to the implanted valve. Regions of wall shear stress above the threshold value for platelet activation were also observed on the bioprosthetic frame as a result of the reduced outflow tract area, which led to increases in flow resistance and blood residence time inside the ventricle. Consistent with these findings, areas of slow recirculating flow and blood stasis formed near the valve frame, creating potential pro-thrombotic conditions. This study provides insight into the relationship between size and shape of the outflow tract post-implantation, pressure gradients and pro-thrombotic flow metrics such as wall shear stress and blood residence time. Results show the potential of CFD modeling to bring key functional metrics into preprocedural assessment for a comprehensive evaluation of post-procedural risks beyond anatomical factors. Following further validation and extension to the atrial chamber, this approach can provide an in-depth analysis of the likelihood of valvular thrombosis.

Superporous acrylic acid and HPMC hydrogels of mefenamic acid: Formulation, characterization and optimization by central composite design.

The purpose of the study was to devise the superporous hydrogels (SPHs) of mefenamic acid (MA) to acquire the sustained action of the MA in the body. The superporous hydrogels of mefenamic acid were formulated by employing the gas blowing method. The central composite rotatable design (CCRD) was applied to optimize the effect of independent formulation factors like acrylic acid (AC), HPMC and glycerol (GLY) over dependent variables like porosity, viscosity, drug content and swelling ratio of superporous hydrogels in water, phosphate buffer (pH 6.8) and in 0.1N HCl (pH 1.2). A number of characteristics such as void fraction, surface morphology by Scanning electron microscopy (SEM) and in vitro drug release study were governed along with physico-chemical analysis by Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC) and appraised statistically by employing the ANOVA. The comparative analgesic activity of optimized superporous hydrogel formulation SPH17 was also analyzed by using tail flick method. The Fourier transform infrared spectroscopy and Differential scanning calorimetry studies approved the physical compatibility between the polymers and the drug. The Scanning electron microscopy study specified micrographic insight about the structure of formed formulations comprising presence of pores, fibers and drug-hole aggregates. The superporous hydrogels were detected to be low dense as they expressed density lower than 0.75g/cc. The decrease in concentration of the polymers and cross linker contributed towards the increase in the void fraction of the superporous hydrogel formulations. The optimized formulation SPH 17 exhibited a highly sustained release of MA for up to 10h in the both 0.1N HCl and phosphate buffer (66.6%) media. The non-fickian release of drug revealed the coupling of the diffusion and polymer relaxation mechanism of the drug release from the formulations. The obtained outcomes suggested that analgesic effect of SPH 17 was significantly (p < 0.05) higher than that of simple suspension of mefenamic acid and total analgesic effect duration for superporous hydrogel was also doubled as compared to the duration of analgesic effect produced by drug suspension. The successfully formulated SPH with HPMC K100M as a gelling agent had sustained the action of the mefenamic acid (MF) by improving its poor solubility and permeability. The introduction of inter-penetrating polymeric network (acrylic acid) using glycerol as a cross linker impart increased residence time to superporous hydrogels which ultimately enhanced the feasibility of using superporous hydrogel as oral sustained release devices particularly for gastric retention.