Search Results (239)

Introduction: Although the incidence of mechanical complications of myocardial infarction is decreasing, the associated mortality rate remains high. Such complications require an early diagnosis and multidisciplinary management. In most cases, surgery is the only definitive treatment, despite it being associated with high peri-operative mortality and morbidity. An intra-aortic balloon pump (IABP) or Extracorporeal Membrane Oxygenation (ECMO) may also be required for unstable patients. After the employment of mechanical assistance, ultrasound and chemical parameters are associated with successful weaning, indicating adequate cardiac function, perfusion, and oxygen delivery. Case presentation: The aim of this case report is to describe the weaning from the extracorporeal support in a case of post-myocardial-infarction ventricular septal defect (VSD) and Left ventricle (LV) apical aneurysm. The patient underwent surgery for VSD closure and aneurysm exclusion. After the emergency surgery, the patient developed a severe post-cardiotomy cardiogenic shock, which required veno-arterial femoral–femoral extracorporeal membrane oxygenation (VA-ff-ECMO), IABP, and maximal pharmacologic support. During the ICU stay, we weaned the patient from the ECMO support based on transesophageal echocardiography (TEE) imaging and pulmonary artery catheter (PAC) monitoring and quantified the shunt fraction. On the fifth post-operative day, we started the weaning trial. Hemodynamic and ultrasound monitoring showed an adequate cardiac function, and the shunt fraction calculated with both the ultrasound parameters and Fick’s law was acceptable. We removed the ECMO the day after, and the weaning was successful. Discussion: Data deriving from the Swan–Ganz catheter has been found to be important in guiding the process of weaning a patient from extracorporeal support. Nevertheless, the TEE played a pivotal role in the decision-making process and in clinical management. We reduced the ECMO blood flow following a real-time echocardiographic cardiac function assessment. Conclusions: Following the fundamental guides for both PAC monitoring and TEE imaging, we successfully removed the extracorporeal support, with a positive outcome. Full article

Experimental and theoretical techniques have been developed to quantify foamy oil behaviour of solvent-heavy oil systems at bubble level during a gas exsolution process. During constant composition expansion (CCE) tests, we artificially induced foamy oil dynamics for solvent-heavy oil systems by gradually reducing pressure and recorded the changed pressures and volumes in an isolated PVT setup at a given temperature. By discretizing gas bubbles on the basis of the classical nucleation theory, we theoretically integrated the population balance equation (PBE), Fick’s law, and the Peng–Robinson equation of state (PR EOS) to reproduce the experimental measurements. Pseudo-bubblepoint pressure for a given solvent-heavy oil system can be increased with either a lower pressure depletion rate or a higher temperature, during which gas bubble growth is facilitated with a reduction in viscosity and/or an increase in solvent concentration, but gas bubble nucleation and mitigation is hindered with an increase in solvent concentration. Compared to CO₂, CH₄ is found to yield stronger and more stable foamy oil, indicating that foamy oil is more stable with a larger amount of dispersed gas bubbles at lower temperatures. Using the PR EOS together with the modified alpha functions at T_r = 0.7 and T_r = 0.6, the absolute average relative deviation (AARD) is reduced from 4.58% to 2.24% with respect to the predicted pseudo-bubblepoint pressures. Full article

The accurate analysis of the sealing performance of underground lined cavern hydrogen storage is critical for enhancing the stability and economic viability of storage facilities. This study conducts an innovative investigation into hydrogen leakage behavior by developing a multiphysical coupled model for a composite system of support structures and surrounding rock in the operation process. By integrating Fick’s first law with the steady-state gas permeation equation, the gas leakage rates of stainless steel and polymer sealing layers are quantified, respectively. The Arrhenius equation is employed to characterize the effects of temperature on hydrogen permeability and the evolution of gas permeability. Thermalmechanical coupled effects across different materials within the storage system are further considered to accurately capture the hydrogen leakage process. The reliability of the established model is validated against analytical solutions and operational data from a real underground compressed air storage facility. The applicability of four materials—stainless steel, epoxy resin (EP), ethylene–vinyl alcohol copolymer (EVOH), and polyimide (PI)—as sealing layers in underground hydrogen storage caverns is evaluated, and the influences of four operational parameters (initial temperature, initial pressure, hydrogen injection temperature, and injection–production rate) on sealing layer performance are also systematically investigated. The results indicate that all four materials satisfy the required sealing performance standards, with stainless steel and EP demonstrating superior sealing performance. The initial temperature of the storage and the injection temperature of hydrogen significantly affect the circumferential stress in the sealing layer—a 10 K increase in initial temperature leads to an 11% rise in circumferential stress, while a 10 K increase in injection temperature results in a 10% increase. In addition, the initial storage pressure and the hydrogen injection rate exhibit a considerable influence on airtightness—a 1 MPa increase in initial pressure raises the leakage rate by 11%, and a 20 kg/s increase in injection rate leads to a 12% increase in leakage. This study provides a theoretical foundation for sealing material selection and parameter optimization in practical engineering applications of underground lined caverns for hydrogen storage. Full article

Presently, numerous non-conventional power resources have been applied in power system networks. However, these resources are very effective in islanded microgrid (IMG) scenarios for addressing numerous operational challenges. Additionally, it is observed that the power output of most of these resources is environment-dependent and intermittent in nature. This intermittency causes a power imbalance between the overall generated power and the load demand, which results in an undesired frequency oscillation. In order to address this unwanted frequency fluctuation, this research work proposes power–frequency synchronisation considering an islanded microgrid scenario under numerous non-conventional power resources. The major contribution of this work includes implementing a suitable and optimised control scheme that effectively controls diverse power system disturbances and various uncertainties. A Fick’s law optimisation-based proportional–integral–derivative–acceleration controller (PIDA) is implemented under this proposed power scenario. Additionally, an extensive performance assessment is conducted considering different simulation test cases in order to verify the performance of the proposed control topology. Further, the effectiveness of the suggested power network is tested on a 33-bus radial distribution network. Finally, simulation results are shown to show the effectiveness of the proposed control scheme for the efficient operation of the microgrid in achieving the desired performance under the diverse operating conditions. Full article

Graft copolymers of polysaccharides with side chains of carbon-chain monomers have significant potential for a variety of practical applications. In this work, the effect of the N,N-methylenebisacrylamide (MBA) introduction stage and acrylamide concentration in microwave-assisted radical copolymerization with xanthan gum on the structure and sorption properties of the cross-linked graft copolymer was studied. It has been found that the spatial network density and average molecular weight of interstitial fragments can be controlled by varying these factors. Moderate crystallinity (<50%) and a highly developed surface of our synthesized samples were revealed using XRD and SEM. The graft copolymer exhibits the Schroeder effect; its liquid water sorption obeys Fick’s law and increases with MBA introduction at later stages and with increasing grafting degree, reaching 17.2 g/g. Studying the methylene blue sorption kinetics using pseudo-first/pseudo-second order models, a combined model and an average pseudo-order model have shown that the lower the monomer concentration in the reaction mixture and the earlier (from the onset of the reaction) the cross-linking agent is introduced, the higher the equilibrium sorption. The observed “equilibrium degree of sorption on xanthan gum vs. pseudo-order” relationship, which passes through a minimum, is explained by chemisorption and the sorbate consumption effect. An assumption is made about the prospects of using our synthesized copolymers for designing selective sorbents and ion-exchange membranes. Full article

This study examined the diffusion of nutrients (NH₄⁺, NO₃⁻, and PO₄³⁻) in the pore water of intertidal sediments in Lake Komuke (located in the northeastern part of Hokkaido on the coast of Okhotsk Sea) across nine stations, at 0 cm to 40 cm depths, from 19 May to 23 August 2015. A comparison was made between the traditional version of Fick’s first law and a modified version to understand nutrient diffusion in the intertidal flat. The novelty of this study lies in establishing a flux correction factor as a function of the activity coefficient in intertidal sediments. The outcomes of the standard and modified versions of Fick’s law exhibited observable physical differences between stations for all nutrients. However, the statistical analysis demonstrated significant differences only for NO₃⁻ and PO₄³⁻ at stations D, E, and F, suggesting that there is no statistically meaningful difference in NH₄⁺ flux. A statistical comparison of 27 pairs of fluxes obtained by the classical and modified versions of Fick’s first law indicated that 88.9% of the differences were not statistically significant between the two methods, and 11.1% were statistically significant. This shows the consistency of the modified method, firstly in reproducing the classical version of Fick’s law, and secondly in improving upon it, in a porous medium. These findings indicate that the modified version of Fick’s first law is an accurate methodology for evaluating nutrient diffusion dynamics in intertidal environments, and is potentially applicable to coastal salt marshes, with practical implications for environmental management and conservation efforts. Full article

Schinus molle L. is a tree commonly found in agricultural fields, deserts, and semi-arid areas of central Mexico. Its distinctive aroma makes it a source of essential oil, extracted mainly from the bark and fruits. The leaves contain phenolic compounds, and their extracts have demonstrated antimicrobial activity. Obtaining these extracts requires a prior drying process. This study aimed to evaluate the effect of convective drying on phenolic compounds in pirul leaves and determine the thermodynamic properties of the process, including the effective diffusivity of water vapor (D) and activation energy (Ea). Drying kinetics were conducted at different air-drying temperatures (30, 40, and 50 °C) at a constant rate of 1 ms⁻¹, and the results were fitted to the second Fick’s law and semi-empirical models. After drying, a decrease in total flavonoid content was observed as the drying temperature increased, with losses of 37%, 49%, and 62% at 30, 40, and 50 °C, respectively. The final values ranged from 37.96 to 21.02 mg QE/100 g of dry leaf. The D varied between 1.32 × 10⁻¹² and 6.71 × 10⁻¹² m² s⁻¹, with an Ea of 66.06 kJ mol⁻¹. The fitting criteria (R², RMSE, AIC/BIC) indicated that the Logarithmic model best described the kinetics at 30–40 °C, while Page was adequate at 50 °C. These findings suggest an inverse relationship between drying temperature and flavonoid content, while higher temperatures accelerate water vapor diffusivity, reducing the processing time, as observed in plant matrices. Full article

This study establishes an efficient and eco-friendly ultrasound-assisted extraction (UAE) method for total flavonoids present in Cercis chinensis seeds using natural deep eutectic solvents (NADES). Among nine NADES formulations screened, choline chloride–levulinic acid (ChCl–Lev, 1:2) demonstrated optimal performance, yielding 112.1 mg/g total flavonoids. Through Response Surface Methodology (RSM), the ultrasound-assisted extraction (UAE) parameters were explored. Under the optimized conditions (water content of 30%, time of 28 min, temperature of 60 °C, and solvent-to-solid ratio of 1:25 g/mL), the total flavonoid yield reached 128.5 mg/g, representing a 195% improvement compared to conventional ethanol extraction. The recyclability of NADES was successfully achieved via AB-8 macroporous resin, retaining 80.89% efficiency after three cycles. Extraction kinetics, modeled using Fick’s second law, confirmed that the rate constant (k) increased with temperature, highlighting temperature-dependent diffusivity as a key driver of efficiency. The extracted flavonoids exhibited potent antioxidant activity, with IC₅₀ values of 0.86 mg/mL (ABTS•⁺) and 0.69 mg/mL (PTIO•). This work presents a sustainable NADES-UAE platform for flavonoid recovery and offers comprehensive mechanistic and practical insights for green extraction of plant bioactives. Full article

To quantitatively analyze the macroscopic diffusion process of chloride ions in existing concrete members, the Peridynamic Differential Operator (PDDO) was introduced to formulate a discrete format for Fick’s second law, and a simulation model was established and validated. Subsequently, the influence of specific or randomly distributed defects in the concrete is reflected by adjusting the coefficients in the model’s global matrix. Moreover, the complex geometry of concrete members is captured by employing a point set-based spatial discretization approach. The model also accommodates for the complex corrosion conditions encountered in practice by imposing different boundary conditions. These features allowed for the simulation and validation of chloride ion diffusion experiments on concrete under natural environmental conditions. The study further analyzed how factors such as defects, diffusion coefficients, boundary conditions, and the geometric shape of members influence the macroscopic diffusion process. The findings indicate that the numerical model based on the PDDO can effectively quantify the macroscopic diffusion of chloride ions in existing concrete members. It provides fundamental data for the durability maintenance of concrete infrastructures and potentially reduces their carbon footprint by preventing unnecessary rehabilitation or reconstruction. Full article

This study investigates the extraction kinetics of luteolin, a bioactive flavonoid with recognized antioxidant and health-promoting properties, from the aerial parts of Reseda luteola (dyer’s weld), with emphasis on its industrial potential. A comparative analysis with peanut shells (Arachis hypogea) identified R. luteola as a superior source, containing 14 ± 3 mg of LUT/g of material, approximately eight times higher than the amount in peanut shells. Luteolin occurred predominantly as luteolin-7-O-glycoside (57%) and the aglycone (35%). Methanolic semi-batch extraction at 25 °C yielded 9.6 mg LUT/g (70%) within 60 min at a solid-to-liquid ratio of 1:9, demonstrating significantly greater solvent efficiency than conventional Soxhlet or maceration techniques. Kinetic modeling, based on Fick’s second law, revealed a biphasic process with a low rate constant ratio (3:1) between the two stages, indicating the need for process optimization. These results establish R. luteola as a cost-effective and sustainable source of luteolin for dietary supplements and functional foods, while indicating the need to explore alternative solvents and advanced extraction methods to further optimize yield and efficiency. Full article

With the increasing number of existing buildings, the implementation of durability-preserving repair procedures is becoming increasingly important. The chemical re-alkalization (CRA) enables the protection of reinforced concrete structures exposed to carbonation by maintaining or restoring the alkalinity in the concrete through the application of an alkaline mortar, such as hybrid alkali-activated binders (HAABs). However, the process of CRA is still insufficiently understood, which means that the requirements for the repair mortars can only be roughly formulated. This paper therefore investigates the process of CRA using laser-induced breakdown spectroscopy (LIBS). Based on the quantitative results of potassium transport in the composite system, a time-dependent attenuation factor can be determined that allows for the adaptation of Fick’s second law of diffusion previously used to predict CRA. The attenuation factor provides further insight into the course of potassium transport, which, based on the results, never follows an ideal diffusion process. Adjusting the diffusion law allows for an improved prediction of the maximum achievable re-alkalization depth depending on the repair mortar, where a potassium content of, e.g., 2.3 wt% leads to a complete re-alkalization of 16 mm. The present study demonstrates the potential of LIBS to quantitatively represent CRA for the first time thus providing new insights into potassium transport and the dynamics of the process. Full article

Global warming is attributed to anthropogenic emissions of CO₂ and the contribution from the transport sector is significant. Estimating on-road vehicle CO₂ emission factors is essential for guiding carbon-reduction efforts in transportation. In order to accurately calculate carbon emission factors from vehicles, this study built a multi-scenario model for open, semi-enclosed, and enclosed road environments based on Fick’s second law and the law of conservation of mass. During the model optimization phase, it was found that the model’s applicability domain effectively encompassed most urban roadway scenarios, making it suitable for estimating urban traffic CO₂ emissions. The spatiotemporal heterogeneity analysis of field measurements indicated that this method can effectively distinguish variations in CO₂ emission factors across different road types and time periods. The method proposed in this study offers an effective solution for the real-time monitoring of large-scale on-road vehicle carbon emissions. Full article

Viscosity is an inherent frictional characteristic of fluids that enables them to resist flow or deformation, thereby reflecting their flow resistance. It is significantly affected by concentration, but traditional viscosity measurements are limited to discrete concentrations, and multiple experiments are required for different concentrations, so the process is time-consuming. To overcome this limitation, this study presents a “viscosity–diffusion coupling” measurement system using a liquid-core cylindrical lens (LCL) as both the diffusion chamber and imaging element. It captures concentration profiles via focal plane imaging and solves Fick’s second law and Stokes–Einstein relation numerically to determine the viscosity at varying concentrations. Experiments on the viscosity of glycerol solutions (0–50% mass fraction) at three temperatures were conducted and showed strong agreement with literature values. The method enables continuous viscosity measurement across varying concentrations within a single experiment, demonstrating reliability, accuracy, and stability in the rapid assessment of concentration-dependent viscosity. Full article

Tartary buckwheat hulls, a phenolic-rich by-product of buckwheat processing, offer great potential for resource utilization. In this study, ultrasound-assisted enzymatic extraction with two temperatures (40 °C and 50 °C) was employed to obtain phenolics from Tartary buckwheat hulls. Compared with the traditional extraction method (207 mg/100 g), ultrasound-assisted enzymatic extraction increased the total phenolic yield by 91.3% at 50 °C. Numerical simulations based on Fick’s law indicated that enzyme pretreatment concentration positively correlated with the effective diffusion coefficient ($D_e$), which increased from 9.15 × 10⁻⁷ to 2.00 × 10⁻⁶ m²/s at 40 °C. Meanwhile, the neuro-fuzzy inference system (ANFIS) successfully predicted the extraction yield under various ultrasonic conditions (R² > 0.98). Regarding quantitative analysis of phenolic compounds in extracts, the results revealed that catechins and epicatechins were the most abundant in Tartary buckwheat hull. Additionally, phenolic acids rapidly diffused at higher temperatures (50 °C), and flavonoids were highly sensitive to temperature and enzyme synergy. Phenolic extracts exhibit significant potential for value-added applications in food processing, particularly in improving antioxidative stability, prolonging shelf life. This study provides a theoretical basis for green, efficient phenolic extraction from plant residues. Full article

This paper addresses the issue of reduced lifespan of coastal concrete piles due to chloride ion corrosion. A combination of concrete mix optimization and pile geometry improvement measures is proposed. Based on the diffusion coefficient optimization of Fick’s second law, the service life prediction of concrete piles in corrosive environments is completed. The results show that, compared to single slag incorporation and the “slag-fly ash” dual-component mix, the “slag-fly ash-corrosion inhibitor” triple-component concrete achieves a 28-day compressive strength of 67.4 MPa, and the chloride ion diffusion coefficient is reduced to 1.14 × 10⁻¹² m²/s, significantly improving overall performance. Finite element simulations reveal that, compared to ordinary square piles, cut-corner square piles can effectively alleviate stress concentration at the pile tip and reduce settlement. The maximum stress is 3.94 MPa, and the settlement is 22.64 mm, representing reductions of about 16.3% and 15.5%, respectively, compared to ordinary square piles. Concrete service life prediction confirms that the concrete with corrosion inhibitors has a predicted service life of 31.5 years, extending 7.4 years and 13.3 years longer than the single slag and the “slag-fly ash” dual-component groups, respectively. The “material-structure” optimization theory proposed in this study provides a theoretical basis and technical path for the long-life design of coastal engineering pile foundations. Full article