Search Results (121)

Rheum cordatum Losinsk is a plant species distributed in Kazakhstan but remains relatively understudied despite its promising biological potential. The present study aimed to explore leaf extracts of R. cordatum by utilizing advanced green extraction technologies including supercritical CO₂ (ScCO₂), subcritical ethanol (Sc) and ultrasound-assisted extraction (UAE) to characterize their phytochemical composition and evaluate their antioxidant and antimicrobial activities. A total of 53 phytochemical compounds were identified, with gallic acid (30.71 µg/mg UAE-EtOH-4h), rutin (21.93 µg/mg ScCO₂-150) and hesperidin (14.98 µg/mg ScCO₂-150) being notably abundant. Among the tested extracts, ScCO₂ extraction at 150 bar (ScCO₂-150) demonstrated the highest antioxidant activity, exhibiting IC₅₀ values of 0.0132 mg/mL (DPPH) and 0.0462 mg/mL (ABTS), coupled with the highest total phenolic content (140 mg GAE/g). Moreover, the ScCO₂-150 extract showed pronounced antimicrobial efficacy, particularly against Bacillus subtilis Pseudomonas aeruginosa and Staphylococcus aureus, with minimum inhibitory concentrations (MIC) ranging from 125 to 250 µg/mL. These findings highlight the considerable potential of R. cordatum leaves as a valuable, abundant and sustainable source of natural antioxidants and antimicrobial agents, with supercritical CO₂ extraction presenting substantial advantages in selectively obtaining bioactive phytochemicals. Full article

Let ${\left(Z_n\right)}_{n\ge 0}$ be a supercritical branching process with offspring distribution $p_r=\mathbb{P}(Z_1=r),r\ge 0,$ such that $p_0=p_1=\dots =p_{k_0-1}=0$ and $p_{k_0}>0$, where $k_0\ge 2$. The Lotka–Nagaev estimator $Z_{n+1}/Z_n$ is an important estimator for the offspring mean $m={\sum }_{i=k_0}^{\infty }i{p}_i$. In this paper, we establish a self-normalized large deviation result and self-normalized Cramér type moderate deviations for the Lotka–Nagaev estimator. An application to constructing confidence intervals for m is also discussed. Full article

Abnormalities in plasma lipoproteins observed in patients with diabetes promote atherosclerosis. However, the association between various lipid species and classes and atherosclerosis remains unclear. Here, we aimed to identify the plasma lipid characteristics associated with atherosclerosis progression in patients with diabetes. We performed semi-targeted lipidomic analysis of fasting plasma samples using supercritical fluid chromatography coupled with mass spectrometry in two independent patient groups with type 2 diabetes (n = 223 and 31) and evaluated cross-sectional associations between plasma lipids and carotid intima-media thickness (CIMT). Ten plasma lipid species, including eight diacylglycerols (DGs), and total DG levels were significantly associated with CIMT in both groups. Patients of the former group were partly observed for 5 years, and we investigated associations between DGs and CIMT progression in these patients (n = 101). As a result, 22 DGs among the 26 identified DGs and total DG (β = 0.398, p < 0.001) were significantly associated with the annual change in CIMT. Furthermore, plasma DG levels improved the predictive ability for CIMT progression, with an adjusted R-squared increase of 0.105 [95% confidence interval: 0.010, 0.232] in the models. Plasma DGs are associated with CIMT progression in patients with type 2 diabetes. Measurement of total plasma DG levels may be beneficial in assessing the risk of atherosclerosis progression. Full article

Understanding mineral–fluid interactions in shale under supercritical CO₂ (scCO₂) conditions is relevant for assessing long-term geochemical containment. This study characterizes mineralogical transformations and elemental redistribution in five Caney Shale samples serving as proxies for reservoir (R1, R2, R3) and caprock (D1, D2) facies, subjected to 30-day static exposure to pure scCO₂ at 60 °C and 17.23 MPa (2500 psi), with no brine or impurities introduced. SEM-EDS analyses were conducted before and after exposure, with mineral phases classified into silicates, carbonates, sulfides, and organic matter. Initial compositions were dominated by quartz (38–47 wt.%), illite (16–23 wt.%), carbonates (12–18 wt.%), and organic matter (8–11 wt.%). Post-exposure, carbonate loss ranged from 15 to 40% in reservoir samples and up to 20% in caprock samples. Illite and K-feldspar showed depletion of Fe²⁺, Mg²⁺, and K⁺ at grain edges and cleavages, while pyrite underwent oxidation with Fe redistribution. Organic matter exhibited scCO₂-induced surface alteration and apparent sorption effects, most pronounced in R2 and R3. Elemental mapping revealed Ca²⁺, Mg²⁺, Fe²⁺, and Si⁴⁺ mobilization near reactive interfaces, though no secondary mineral precipitates formed. Reservoir samples developed localized porosity, whereas caprock samples retained more structural clay integrity. The results advance understanding of mineral reactivity and elemental fluxes in shale-based CO₂ sequestration. Full article

This paper investigates the existence and uniqueness of local and global solutions to the incompressible three-dimensional Navier–Stokes equations within the framework of homogeneous Lei–Lin–Gevrey spaces ${\mathcal{X}}_{a,\gamma }^{\rho }({\mathbb{R}}^3)$, where $\rho \in [-1,0),a>0$, and $\gamma \in (0,1)$. These function spaces combine the critical scaling structure of the Lei–Lin spaces with the exponential regularity of Gevrey classes, thereby enabling a refined treatment of analytic regularity and frequency localization. The main results are obtained under the assumption of small initial data in the critical Lei–Lin space ${\mathcal{X}}^{\rho }({\mathbb{R}}^3)$, extending previous works and improving regularity thresholds. In particular, we establish that for suitable initial data, the Navier–Stokes system admits unique solutions globally in time. The influence of the Gevrey parameter $\gamma$ on the high-frequency behavior of solutions is also discussed. This work contributes to a deeper understanding of regularity and decay properties in critical and supercritical regimes. Full article

This study explores novel alginate–konjac glucomannan core–shell aerogel particles for drug delivery systems fabricated via air-assisted coaxial prilling. A systematic approach is needed for the optimization of this method due to the numerous processing variables involved. This study investigated the influence of six variables: alginate and konjac glucomannan concentrations, compressed airflow, liquid pump pressures, and nozzle configuration. A hybrid software using Artificial Neural Networks and genetic algorithms was used to model and optimize the hydrogel formation, achieving a 100% desirable solution. The optimal formulation identified resulted in particles displaying a log-normal size distribution (R² = 0.967) with an average diameter of 1.57 mm. Supercritical CO₂ drying yielded aerogels with macropores and mesopores and a high specific surface area (201 ± 10 m²/g). The loading of vancomycin hydrochloride (Van) or a dexamethasone base (DX) into the aerogel cores during the process was tested. The aerogels exhibited appropriate structural characteristics, and both drugs showed burst release profiles with ca. 80% release within 10 min for DX and medium-dependent release for Van. This study demonstrates the feasibility of producing konjac aerogel particles for delivery systems and the high potential of AI-driven optimization methods, highlighting the need for coating modifications to achieve the desired release profiles. Full article

This study investigated the use of supercritical carbon dioxide (CO₂) to extract bioactive compounds from Thai fingerroot (Boesenbergia rotunda), focusing on the effects of pressure, temperature, CO₂ flow rate, and ethanol co-solvent concentration. A central composite design within a response surface methodology framework was employed to optimize the total extraction yield, total phenolic content (TPC), and total flavonoid content (TFC). Conventional ethanol maceration was used as a benchmark. High-performance liquid chromatography identified the major compounds in the extracts, such as pinostrobin and pinocembrin. The results showed that the yield, TPC, and TFC increased with higher pressure, CO₂ flow rate, and co-solvent levels, whereas higher temperatures had a negative effect (p ≤ 0.05). Interactions between pressure and temperature favored the yield and TPC but not TFC. The optimal conditions—250 bar, 45 °C, 3 L/min CO₂ flow rate, and 100% ethanol—produced a yield of 28.67%, TPC of 354.578 mg GAE/g, and TFC of 273.479 mg QE/g. These values exceeded those obtained using conventional extraction (9.91% yield, 332.86 mg GAE/g TPC, and 77.57 mg QE/g TFC at 60 min). The regression models showed strong predictive accuracy (R² > 0.9). Pinostrobin and pinocembrin were the dominant phenolic compounds. These findings demonstrate the superior efficiency of supercritical CO₂ extraction for isolating phenolic compounds from B. rotunda. Full article

Hydrodynamic journal bearings play a vital role in high-speed, heavy-load machinery. Their performance directly affects system efficiency and reliability. Supercritical carbon dioxide (S-CO₂), with its favorable thermophysical properties, is a promising lubricant. This study focused on a four-oil-cavity hydrodynamic journal bearing using S-CO₂ as the working fluid. A numerical model was established in ANSYS Workbench 2024 R1 using a fluid–structure interaction (FSI) method. The model was validated through comparison with literature data. Parametric studies were conducted by varying radial clearance, eccentricity, inlet diameter, and oil cavity size. Results showed that reducing the oil cavity wrap angle enhanced load capacity. Larger inlet diameters improved lubrication but could increase deformation. An appropriate combination of inlet diameter and eccentricity effectively reduced shell deformation. These findings offer design guidance for S-CO₂-lubricated bearings in high-speed applications. Full article

Background: Particulate matter (PM) is a major environmental pollutant that induces oxidative stress, inflammation, and extracellular matrix (ECM) degradation, leading to skin damage and accelerated aging. Xanthorrhizol (XAN), a bioactive compound derived from Curcuma xanthorrhiza Roxb., exhibits anti-inflammatory and antioxidative properties, making it a promising candidate for protecting against PM-induced skin damage. This study investigated the protective effects of XAN and C. xanthorrhiza supercritical extract (CXSE) on PM-exposed skin cells. Methods: A 3D-reconstructed skin model and HaCaT human keratinocytes were exposed to PM (100 µg/mL) with or without CXSE or XAN. Histological analysis, enzyme-linked immunosorbent assay (ELISA), Western blot, reverse transcription-polymerase chain reaction (RT-PCR), and reporter gene assays were performed to assess the ECM integrity, inflammatory cytokine production, aryl hydrocarbon receptor (AhR) activation, and oxidative stress responses. Results: PM exposure activates AhR and mitogen-activated protein kinases (MAPK) signaling, increases reactive oxygen species (ROS) levels, and upregulates matrix metalloproteinases (MMPs) and inflammatory cytokines. CXSE and XAN suppresses AhR-mediated transcriptional activity and downregulates the expression of AhR target genes. Additionally, CXSE and XAN reduces ROS production by upregulating antioxidant enzyme-related genes. Conclusions: CXSE and XAN protect against PM-induced skin damage by inhibiting oxidative stress, inflammation, and ECM degradation, highlighting their potential as natural anti-pollution skincare ingredients. Full article

Ruta graveolens L. has been described as possessing antifungal and nematicidal activity. Among the bioactive compounds present in this plant, alkaloids and furanocoumarins have attracted considerable attention. The aim of this study was to evaluate the in vitro biological activity of extracts from rue enriched in bioactive compounds against Fusarium oxysporum, F. circinatum, and Meloidogyne incognita, and to correlate the chemical profile of the extracts with their biological activities. Six extracts with contrasting chemical profiles, obtained by pressurized liquid extraction and supercritical fluid extraction using green solvents, were selected for biological evaluation. The highest F. oxysporum growth inhibition was achieved with the extracts enriched in fatty acids and furanocoumarins at concentrations of 4, 8, and 16 mg/mL, while for F. circinatum, the highest growth inhibition was obtained using the extract enriched in terpenes at 16 mg/mL; moreover, the six extracts evaluated caused mortality in M. incognita. Therefore, enriched extracts of R. graveolens might be considered as an alternative for pathogen control on economically important crops such as potatoes, tomatoes, and onions, among others. Correlations between biological activities and chemical compositions suggest the importance of fatty acids against F. oxysporum, fatty acids and terpenes against F. circinatum, and alkaloids, coumarins, and furanocoumarins for M. incognita. Full article

The combined cooling, heating, and power system is based on the principle of energy cascade utilization, which is conducive to reducing fossil energy consumption and improving the comprehensive utilization efficiency of energy. With the characteristics of a lower expansion ratio and larger recuperation of a supercritical carbon dioxide (SCO₂) power cycle, a combined cooling, heating, and power (CCHP) system is proposed. The system is based on a SCO₂ cycle and is driven by solar energy. The system is located in Qingdao and simulated by MATLAB/Simulink software (R2022b). Firstly, the thermodynamic performance of the CCHP system at the design condition is analyzed. The energy utilization efficiency of the CCHP system is 79.75%, and the exergy efficiency is 58.63%. Then, the thermodynamic, environmental, and economic performance analyses of the system under variable conditions are carried out. Finally, the solar multiple is optimized. The results show that the minimum levelized cost of electricity is 10.4 ¢/(kW·h), while the solar multiple is 4.8. The annual primary energy saving rate of the CCHP system is 85.04%, and the pollutant emission reduction rate is 86.05%, compared with the reference system. Therefore, an effective way to reduce environmental pollution and improve the utilization efficiency of solar energy is provided. Full article

Accurately measuring the discharge in partially full pipe flow is both difficult and demanding. In this regard, a new meter sensor using microwave technology has been evaluated for determining partially full pipe discharge across a range of flow depths. A range of experiments with smooth PVC pipes of two different pipe diameters (101.6 and 152.4 mm) at two different pipe slopes (1° and 2°) were carried out under turbulent (Reynolds numbers = (0.27–3.25) × 10⁵) and supercritical flows with Froude numbers F_r in the range of 1.5 ≤ F_r ≤ 3.6. Our results showed that when combining the microwave sensor readings with either the Chezy equation or Manning’s law, reliable discharge predictions were found compared to the measured discharge across all experiments. The range of R² values obtained from the plots of predicted versus measured discharge were all greater than 97%, indicating an accuracy allowing the meter to be used in commercial applications. Full article

In this paper, we have investigated the existence of normalized solutions for a class of fractional Kirchhoff equations involving nonlinearity and critical nonlinearity. The nonlinearity satisfies $L^2$-supercritical conditions. We transform the problem into an extremal problem within the framework of Lagrange multipliers by utilizing the energy functional of the equation in the fractional Sobolev space and applying the mass constraint condition (i.e., for given $m>0,$${\int }_{{\mathbb{R}}^N}{|u|}^{2}dx=m^2$). We introduced a new set and proved that it is a natural constraint. The proof is based on a constrained minimization method and some characterizations of the mountain pass levels are given in order to prove the existence of ground state normalized solutions. Full article

Gravel coverage on slopes influences overland flow and soil erosion. However, the effect of different gravel sizes on the soil erosion process remains underexplored. In this study, a runoff scour test was performed to examine the effects of gravel coverage on the hydrodynamic characteristics of slope runoff and sediment transport capacity (T_c). The slope gradient varied from 18% to 84%, the unit flow discharge ranged from 0.27 × 10⁻³ to 1.11 × 10⁻³ m² s⁻¹, and gravel coverage was adjusted from 0% to 90%. The results reveal that water depth, shear stress, and stream power increased with gravel coverage. However, once coverage exceeded 20%, flow velocity and unit stream power decreased and stabilized. As gravel coverage increased, the hydraulic regimes transitioned from laminar to turbulent flow and shifted from supercritical to subcritical. Consequently, T_c first increased and then decreased with the increase in gravel coverage, reaching a peak at 20% coverage (1.66 kg m⁻¹ s⁻¹). Moreover, the degree of coverage indirectly influenced T_c through grain shear stress. The new equations, based on the Box–Lucas function, incorporated slope, grain shear stress, and flow velocity, thereby effectively simulating T_c for runoff on gravel-covered slopes (R² = 0.94, NSE = 0.94). These findings provide a basis for modeling soil erosion on gravel-covered slopes. Full article

Nuclear magnetic resonance (NMR) and high-pressure mercury injection (HPMI) have been widely used as common characterization methods of pore-throat. It is generally believed that there is a power function relationship between transverse relaxation time (T₂) and pore-throat radius (r), but the segmentation process of the pore-throat interval is subjective, which affects the conversion accuracy. In this paper, ordered clustering is used to improve the existing segmentation method of the pore-throat interval, eliminate the subjectivity in the segmentation process, and obtain a more accurate distribution curve of the pore-throat. For the three kinds of cores with ordinary-low permeability (K > 1 mD), ultra-low permeability (0.1 mD < K < 1 mD), and super-low permeability (K < 0.1 mD), the pore-throat distribution curves of the cores were obtained by using the improved T₂ conversion method. Then, the oil and gas two-phase displacement experiment was carried out to investigate the degree of recovery and cumulative gas–oil ratio changes during the displacement process. Finally, the converted T₂ spectrum was used to quantify the utilization of different pore sizes. The improved T₂ conversion method not only has better accuracy but also is not limited by the pore-throat distribution types (such as unimodal, bimodal, and multi-modal, etc.) and is suitable for any core with measured HPMI pore-throat distribution and an NMR T₂ spectrum. Combined with the results of core displacement and the degree of pore-throat utilization, it is found that the potential of miscible flooding to improve the recovery degree is in the order of ordinary-low permeability core (18–22%), ultra-low permeability core (25–29%), and super-low permeability core (8–12%). The utilization degree of immiscible flooding to the <10 nm pore-throat is low (up to 35%), while miscible flooding can effectively use the <3.7 nm pore-throat (up to 73%). The development effect of supercritical CO₂ flooding on K < 0.1 mD reservoirs is not good, the seepage resistance of CO₂ is large, the miscible flooding makes it difficult to improve the recovery degree, and the utilization effect of pore-throat is poor. Full article