Search Results (5,321)

Background: Removal of large uraemic toxins is still a challenge. Haemodiafiltration (HDF) has produced some results, although large convective volume, optimal vascular access to increase the blood flow rate and strict water quality management are required. Medium cut-off, high-retention-onset membranes have been recently developed, introducing the concept therapy called expanded haemodialysis (HDx). Furthermore, vitamin E-coated membrane has potential beneficial effects on inflammation and oxidative stress. Methods: A prospective longitudinal multicentre study was conducted for 3 months among 24 chronic haemodialysis patients. Patients were randomly assigned into either HDF with high-flux membrane or HDx with Theranova or ViE-X membrane. The primary goal was to assess albumin loss among the three types of dialyzers. Secondary goals included assessment of depurative efficacy for uraemic toxins and clinical outcomes. Results: Mean albumin loss was significantly higher in patients undergoing HDx with Theranova membrane, without any difference in serum albumin concentration among the three groups. Instantaneous clearance of small and middle molecules was significantly higher in patients undergoing HDF, but we did not find differences in removal ratio and Kt/V. Reduction in the erythropoietin resistance index was observed in patients treated with ViE-X membrane due to their lower dialysis vintage. Conclusions: The higher albumin loss during HDx has no effects on pre-dialysis serum albumin. HDx with Theranova in the presence of lower session length, lower Qb, lower convective dose, and lower instantaneous clearance reached the same dialysis efficacy compared to HDF. Full article

An experimental study was carried out on the ignition and combustion processes of particles (100–200 µm in size) of coals of different degrees of metamorphism and biomass, as well as mixtures based on them, under conditions of conductive and convective heating, which correspond to the conditions of fuel ignition in boiler furnaces at grates and flaring combustion. The biomass contents in the composition of the coal-based fuel mixtures were 10, 20, and 30 wt.%. Under the conductive (at 700–1000 °C) and convective (at 500–800 °C) heating of fuel particles, ignition delay times were determined using a hardware–software complex for the high-speed video registration of fast processes. The ignition delay times were found to vary from 1 to 12.2 s for conductive heating and from 0.01 to 0.19 s for convective heating. The addition of 10–30 wt.% biomass to coals reduced the ignition delay times of fuel mixtures by up to 70%. An analysis of the flue gas composition during the combustion of solid fuels allowed us to establish the concentrations of the main anthropogenic emissions. The use of biomass as an additive (from 10 to 230 wt.%) to coal reduced NO_x and SO_x emissions by 19–42% and 24–39%, respectively. The propensity of fuels to cause slagging depending on their component composition was established. The use of up to 30 wt.% of biomass in the mixture composition did not affect the increase in the tendency to cause slagging on heating surfaces in the boiler furnace and did not pose a threat to the layer agglomeration during the layer combustion of the mixtures. Full article

Using Gaia DR3 we derive new distances and luminosities for a sample of Galactic B supergiants which were thought to be post main-sequence (MS) objects from their HR diagram location beyond the terminal-age MS (TAMS). When applying the newer Gaia distances in addition to enhanced amounts of core-boundary mixing, aka convective overshooting, we show that these Galactic B supergiants are likely enclosed within the MS band, indicating an evolutionary stage of steady core hydrogen burning. We discuss the importance of considering enhanced overshooting and how vectors in the mass-luminosity plane (ML-plane) can be used to disentangle the effects of wind mass loss from interior mixing. We finish with the key message that any proposed solution to the BSG problem should consider not only an explanation for the sheer number of B supergiants inside the Hertzsprung gap, but should at the same time also account for the steep drop in rotation rates identified at spectral type B1—corresponding to an effective temperature of ∼21 kK, and for which two distinct families of solutions have been proposed. Full article

With varying tangential winds and combinations of stratiform and convective clouds, tropical cyclones (TCs) can be difficult to accurately portray when mosaicking data from ground-based radars. This study utilizes the Dual-frequency Precipitation Radar (DPR) from the Global Precipitation Measurement Mission (GPM) satellite to evaluate reflectivity obtained using four sampling methods of Weather Surveillance Radar 1988-Doppler data, including ground radars (GRs) in the GPM ground validation network and three mosaics, specifically the Multi-Radar/Multi-Sensor System plus two we created by retaining the maximum value in each grid cell (MAX) and using a distance-weighted function (DW). We analyzed Hurricane Laura (2020), with a strong gradient in tangential winds, and Tropical Storm Isaias (2020), where more stratiform precipitation was present. Differences between DPR and GR reflectivity were larger compared to previous studies that did not focus on TCs. Retaining the maximum value produced higher values than other sampling methods, and these values were closest to DPR. However, some MAX values were too high when DPR time offsets were greater than 120 s. The MAX method produces a more consistent match to DPR than the other mosaics when reflectivity is <35 dBZ. However, even MAX values are 3–4 dBZ lower than DPR in higher-reflectivity regions where gradients are stronger and features change quickly. The DW and MRMS mosaics produced values that were similar to one another but lower than DPR and MAX values. Full article

Solar supergranulation is a large-scale convective structure on the solar surface, whose formation mechanism and dynamical properties are closely related to key physical processes such as solar magnetic field evolution, coronal heating, and solar wind acceleration. This paper reviews recent research progress on solar supergranulation, focusing on the latest achievements in high-resolution observations, theoretical models, and numerical simulations. By analyzing the flow field structure, magnetic field distribution, and their relationship with the solar activity cycle, the crucial role of supergranulation in solar physics is revealed. Studies indicate that supergranulation is not only a crucial component of the solar convection zone but also drives coronal heating and solar wind acceleration through mechanisms such as magnetic reconnection and Alfvén wave propagation. Furthermore, the interaction between supergranulation and larger-scale convective patterns (e.g., giant cells) provides new insights into the dynamics of the solar interior. Despite significant progress in recent years, the formation mechanism and dynamical nature of supergranulation remain unresolved. Future research should combine high-resolution observations, theoretical modeling, and numerical simulations to further elucidate the complex dynamical processes and the central role of supergranulation in solar physics. Full article

In this study, our aim is to diagnose how two quasi-linear convective systems (QLCS) are organized so one can determine the possible role of the city of Chicago, IL, USA, in modifying convective precipitation systems. In this Part I of a two-part study, we employ large-scale analyses, radiosonde soundings, surface observations, and Doppler radar data to diagnose the precursor atmospheric circulations that organize the evolution of two mesoscale convective systems and compare those circulations to radar and precipitation. Several multi-scale processes are found that organize and modify convection over the Chicago metroplex. Two sequential quasi-linear convective systems (QLCS #1 and #2) were organized that propagated over Chicago, IL, USA, during an eight-hour period on 5–6 July 2018. The first squall line (QLCS #1) built from the southwest to the northeast while strengthening as it propagated over the city, and the second (QLCS #2) propagated southeastwards and weakened as it passed over the city in association with a polar cold front. The weak upper-level divergence associated with a diffluent flow poleward of an expansive ridge built over and strengthened a low-level trough and confluence zone, triggering QLCS #1. Convective downdrafts from QLCS #1 produced a cold pool that interacted with multiple confluent low-level jets surrounding and focused on the metroplex urban heat island, thus advecting the convection poleward over the metroplex. The heaviest precipitation occurred just south-southeast of Midway Airport, Chicago. Subsequently, a polar cold front propagated into the metroplex, which triggered QLCS #2. However, the descending air above it under the polar jet and residual cold pool from QLCS #1 rapidly dissipated the cold frontal convection. This represents a case study where very active convection built over the metroplex and was likely modified by it, as evidenced in numerical simulations to be described in Part II. Full article

This study aimed to optimize the ultrasound-assisted extraction (UAE) of polysaccharides from fermented Astragalus membranaceus (FAPS) and to investigate the physicochemical properties and antioxidant activities of the extracted polysaccharides. Using a combination of single-factor experiments and response surface methodology based on a Box–Behnken design, we improved the extraction of crude FAPS without deproteinization. Under optimal conditions (50 °C, 60 min, 8 mL/g, 480 W), the yield of crude FAPS obtained by UAE (7.35% ± 0.08) exceeded the yield from convectional hot water extraction (6.95% ± 0.24). After protein removal, the FAPS was subjected to comprehensive chemical analyses, including HPLC, HPGPC, FT-IR, UV spectroscopy, and a Congo red assay. The results showed that FAPS had a significantly higher carbohydrate content compared to the non-fermented group (95.38% ± 6.20% vs. 90.938% ± 3.80%), while the protein content was significantly lower than that of the non-fermented Astragalus polysaccharides (APS) group (1.26% ± 0.34% vs. 6.76% ± 0.87%). In addition, FAPS had a higher average molecular weight and a lower Mw/Mn ratio compared to APS. The primary monosaccharides in FAPS were identified as Glc, Ara, Gal and GalA, with a molar ratio of 379.72:13.26:7.75:6.78, and FAPS lacked a triple helix structure. In vitro, antioxidant assays showed that FAPS possessed superior antioxidant properties compared to APS. These results emphasize the significant potential of FAPS as an antioxidant, possibly superior to that of APS. The results of this study suggest that fermentation and UAE offer promising applications for the development and utilization of Astragalus membranaceus for human and animal health. Full article

Accurate prediction of the temperature and pressure fields in carbon dioxide (CO₂) injection wells is critical for enhancing oil recovery efficiency and ensuring safe carbon sequestration. At present, the prediction model generally assumes that CO₂ is pure and does not consider the influence of impurities in CO₂ components. This study takes into account the common impurities, such as air and various alkanes in CO₂, and uses Refprop 9.0 software to calculate the physical parameters of the mixture. A comprehensive coupling model was developed to account for axial heat conduction, convective heat transfer, frictional heat generation, the soup coke effect, pressure work, and gas composition. The model was solved iteratively using numerical methods. We validated the accuracy of the calculated results by comparing our model with the Ramey model using measured injection well data. Compared with the measured bottom hole temperature and pressure data, the error percentage of our model to predict the bottom hole temperature and pressure is less than 1%, while the error percentage of Ramey model to predict the bottom hole temperature and pressure is 5.15% and 1.33%, respectively. Our model has higher bottom hole temperature and pressure prediction accuracy than the Ramey model. In addition, we use the model to simulate the influence of different injection parameters on wellbore temperature and pressure and consider the influence of different gas components. Each injection parameter uses three components. Based on the temperature and pressure data calculated by the model simulation, the phase state of CO₂ was analyzed. The results show that the impurities in CO₂ have a great influence on the predicted wellbore pressure, critical temperature, and critical pressure. In the process of CO₂ injection, increasing the injection pressure can significantly increase the bottom hole pressure, and changing the injection rate can adjust the bottom hole temperature. The research provides valuable insights for CO₂ sequestration and enhanced oil recovery (EOR). Full article

Between 11 and 14 August 2017, the southern belt of the central Himalaya experienced extreme precipitation, with some stations recording more than 500 mm of accumulated rainfall, which resulted in widespread, devastating flooding. Precipitation was concentrated over the sub-Himalaya, and the established forecasting systems failed to predict the event. In this study, we evaluate the performance of six cloud microphysics schemes in the Weather Research and Forecasting (WRF) model forced with the advanced ERA5 dataset. We also examine the importance of the cumulus scheme in WRF at 3 km horizontal grid spacing in highly convective events like this. Six WRF simulations, each with one of the six different microphysics schemes with the Kain–Fritsch cumulus scheme turned off, all fail to reproduce the spatial variability of accumulated precipitation during this devastating flood-producing precipitation event. In contrast, the simulations exhibit greatly improved performance with the cumulus scheme turned on. In this study, the cumulus scheme helps to initiate convection, after which grid-scale precipitation becomes dominant. Amongst the different simulations, the WRF simulation using the Morrison microphysics scheme with the cumulus turned on displayed the best performance, with the smallest normalized root mean square error (NRMSE) of 0.25 and percentage bias (PBIAS) of −6.99%. The analysis of cloud microphysics using the two best-performing simulations reveals that the event is strongly convective, and it is essential to keep the cumulus scheme on for such convective events and capture all the precipitation characteristics showing that in regions of extreme topography, the cumulus scheme is still necessary even down to the grid spacing of at least 3 km. Full article

With the continuous increase in the thermal power of electronic devices, air cooling is becoming increasingly challenging in terms of meeting heat dissipation requirements. Liquid cooling media have a higher specific heat capacity and better heat dissipation effect, making it a more efficient cooling method. In order to improve the heat dissipation effect of liquid cooling, a TPMS structure with a larger specific surface area, which implicit function parameters can control, can be arranged in a shape manner and it is easy to expand the structural design. It has excellent potential for application in the field of heat dissipation. At present, research is still in its initial stage and lacks comparative studies on liquid cooled convective heat transfer of TPMS structures G (Gyroid), D (Diamond), and P (Primitive). This paper investigates the heat transfer performance and pressure drop characteristics of a sheet-like microstructure composed of classic TPMS structures, G (Gyroid), D (Diamond), and P (Primitive), with a single crystal cell length of 2π (mm), a cell number of 1 × 1 × 5, and a microstructure size of 2π (mm) × 2π (mm) × 22π (mm) using a constant temperature surface model. By analyzing the outlet temperature $t_{out}$, structural pressure $p$, average convective heat transfer coefficient $h_0$, Nusselt number $Nu$, and average wall friction factor $f$ of the microstructure within the speed range of 0.01–0.11 m/s and constant temperature surface temperature is 100 °C, the heat transfer capacity D > G > P and pressure drop D > G > P were obtained (the difference in pressure drop between G and P is very small, less than 20 Pa, which can be considered consistent). When flow velocity is 0.01 m/s, the maximum temperature difference at the outlet of the four structures reached 17.14 °C, and the maximum difference in wall friction factor $f$ reached 103.264, with a relative change of 646%. When flow velocity is 0.11 m/s, the maximum pressure difference among the four structures reached 8461.84 Pa, and the maximum difference in $h_0$ reached 7513 W/(m²·K), with a relative change of 63.36%; the maximum difference between Nu reached 76.32, with a relative change of 62.09%. This paper explains the reasons for the above conclusions by analyzing the proportion of solid area on the constant temperature surface of the structure, the porosity of the structure, and the characteristics of streamlines in the microstructure. Full article

Hyperthermia is a promising medical treatment that uses controlled heat to target and destroy cancer cells while minimizing damage to the surrounding healthy tissue. Unlike conventional methods, it offers reduced risks of infection and shorter recovery periods. This study focuses on the integration of carbon nanotubes (CNTs) within the blood to enable precise heat transfer to tumors. The central idea is that by adjusting the concentration, shape, and size of CNTs, as well as the strength of an external magnetic field, heat transfer can be controlled for targeted treatment. A theoretical model is developed to analyze laminar natural convection within a simplified rectangular porous enclosure resembling a tumor, considering the composition of blood, and the geometric characteristics of CNTs, including the interfacial nanolayer thickness. Using an asymptotic expansion method, ordinary differential equations for mass, momentum, and energy balances are derived and solved. Results show that increasing CNT concentration decelerates fluid flow and reduces heat transfer efficiency, while elongated CNTs and thicker nanolayers enhance conduction over convection, to the detriment of heat transfer. Finally, increased tissue permeability—characteristic of cancerous tumors—significantly impacts heat transfer. In conclusion, although the model simplifies real tumor geometries and treatment conditions, it provides valuable theoretical insights into hyperthermia and nanofluid applications for cancer therapy. Full article

Longitudinal dispersion coefficient is a key parameter governing solute transport in porous media, with significant implications for various industrial processes. However, the impact of microfractures on the longitudinal dispersion coefficient remains insufficiently understood. In this study, pore-scale direct numerical simulations are performed to analyze solute transport in microfractured porous media during unstable miscible displacement. Spatiotemporal concentration profiles were fitted to the analytical solution of the convection–dispersion equation to quantify the longitudinal dispersion coefficient across different microfracture configurations. The results indicate that the longitudinal dispersion coefficient is highly sensitive to microfracture characteristics. Specifically, an increased projection length of microfractures in the flow direction and a reduced lateral projection length enhance longitudinal dispersion at the outlet. When Peclet number ≥1, the longitudinal dispersion coefficient follows a three-stage variation pattern along the flow direction, with microfracture connectivity and orientation dominating its scale sensitivity. Furthermore, both diffusion-dominated and mixed advective-diffusion regimes are observed. In diffusion-dominated regimes, significant channeling alters the applicability of traditional scaling laws, with the relationship between longitudinal dispersion coefficient and porosity holding only when the Peclet number is below 0.07. These results provide a comprehensive scale-up framework for CO₂ miscible flooding in unconventional reservoirs and CO₂ storage in saline aquifers, offering valuable insights for the numerical modeling of heterogeneous reservoir development. Full article

Thermal management at a high heat flux is crucial for electronic devices, and jet impingement cooling is a promising solution. The heat transfer properties of a rectangular-finned heat sink are investigated under angled and multi-impingement jet configurations in this study. Experiments were conducted with three different nozzle diameters, three different heat sink angles, three dimensionless nozzle-to-heat sink distance ratios, and five different velocity values. As a result, the obtained data are presented as Nu-Re graphs, and the impacts of the parameters on heat transfer (HT) are analyzed. It is concluded that the Nusselt number increases with the increasing nozzle diameter and Reynolds number, whereas it decreases with increasing distance between the nozzle and the heat sink. When comparing the angle values under an identical flow velocity, nozzle diameter, and dimensionless h/d distance experimental conditions, it was found that the Nusselt numbers were very close to each other. Under constant heat flux and for all investigated angles, the highest Nusselt number for the rectangular-finned inclined heat sink was observed at a 10° heat sink inclination, a nozzle diameter of D = 40 mm, a dimensionless distance of h/d = 6, and a flow velocity of 9 m/s. This study deepens the understanding of the heat transfer mechanism of impinging jets and provides an efficient method framework for practical applications. Full article

The two-dimensional semiconductor material MoS₂, grown via chemical vapor deposition, has shown significant potential to surpass silicon in advanced electronic technologies. However, the mass transfer and chemical reaction processes critical to the nucleation and growth of MoS₂ grains remain poorly understood. In this study, we conducted an in-depth investigation into the mass transfer and chemical reaction processes during the chemical vapor deposition of MoS₂, employing a novel multi-physics coupling model that integrates flow fields, temperature fields, mass transfer, and chemical reactions. Our findings reveal that the intermediate product Mo₃O₉S₄ not only fails to participate directly in MoS₂ film growth but also hinders the diffusion of MoS₆, limiting the growth process. We demonstrate that increasing the growth temperature accelerates the diffusion rate of MoS₆, mitigates the adverse effects of Mo₃O₉S₄, and promotes the layered growth of MoS₂ films. Additionally, lowering the growth pressure enhances the convective diffusion of reactants, accelerating grain growth. This research significantly advances our understanding of the mass transport and reaction processes in MoS₂ film growth and provides critical insights for optimizing chemical vapor deposition systems. Full article

In the Himalayan regions of complex terrains, such as Himachal Pradesh, the occurrence of extreme rainfall events (EREs) has been increasing, triggering landslides and flash floods. Investigating the dynamics and precipitation characteristics and improving the prediction of such events are crucial and could play a vital role in contributing to sustainable development in the region. This study employs a high-resolution numerical weather prediction framework, the weather research and forecasting (WRF) model, to deeply investigate an ERE which occurred between 8 July and 13 July 2023. This ERE caused catastrophic floods in the Mandi and Kullu districts of Himachal Pradesh. The WRF model was configured with nested domains of 12 km and 4 km horizontal grid resolutions, and the results were compared with global high-resolution precipitation products and the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis dataset. The selected case study was amplified by the synoptic scale features associated with the position and intensity of the monsoon trough, including mesoscale processes like orographic lifting. The presence of a western disturbance and the heavy moisture transported from the Arabian Sea and the Bay of Bengal both intensified this event. The model has effectively captured the spatial distribution and large-scale dynamics of the phenomenon, demonstrating the importance of high-resolution numerical modeling in accurately simulating localized EREs. Statistical evaluation revealed that the WRF model overestimated extreme rainfall intensity, with the root mean square error reaching 17.33 mm, particularly during the convective peak phase. The findings shed light on the value of high-resolution modeling in capturing localized EREs and offer suggestions for enhancing disaster management and flood forecasting. Full article