Transport Processes Research Articles

Static magnetic field-modulated mesenchymal stem cell-derived mitochondria-containing microvesicles for enhanced intervertebral disc degeneration therapy

Intervertebral disc degeneration (IVDD) is characterized by the senescence and declining vitality of nucleus pulposus cells (NPCs), often driven by mitochondrial dysfunction. This study elucidates that mesenchymal stem cells (MSCs) play a crucial role in attenuating NPC senescence by secreting mitochondria-containing microvesicles (mitoMVs). Moreover, it demonstrates that static magnetic fields (SMF) enhance the secretion of mitoMVs by MSCs. By distinguishing mitoMV generation from exosomes, this study shifts focus to understanding the molecular mechanisms of SMF intervention, emphasizing cargo transport and plasma membrane budding processes, with RNA sequencing indicating the potential involvement of the microtubule-based transport protein Kif5b. The study further confirms the interaction between Rab22a and Kif5b, revealing Rab22a’s role in sorting mitoMVs into microvesicles (MVs) and potentially mediating subsequent plasma membrane budding. Subsequent construction of a gelatin methacrylate (GelMA) hydrogel delivery system further addresses the challenges of in vivo application and verifies the substantial potential of mitoMVs in delaying IVDD. This research not only sheds light on the molecular intricacies of SMF-enhanced mitoMV secretion but also provides innovative perspectives for future IVDD therapeutic strategies.

Development of the adjoint of the unified tropospheric–stratospheric chemistry extension (UCX) in GEOS-Chem adjoint v36

Abstract. Atmospheric sensitivities (gradients), quantifying the atmospheric response to emissions or other perturbations, can provide meaningful insights on the underlying atmospheric chemistry or transport processes. Atmospheric adjoint modeling enables the calculation of receptor-oriented sensitivities of model outputs of interest to input parameters (e.g., emissions), overcoming the numerical cost of conventional (forward) modeling. The adjoint of the GEOS-Chem atmospheric chemistry-transport model is a widely used such model, but prior to v36 it lacked extensive stratospheric capabilities. Here, we present the development and evaluation of the discrete adjoint of the global chemistry-transport model (CTM) GEOS-Chem unified chemistry extension (UCX) for stratospheric applications, which extends the existing capabilities of the GEOS-Chem adjoint to enable the calculation of sensitivities that include stratospheric chemistry and interactions. This development adds 37 new tracers, 273 kinetic and photolysis reactions, an updated photolysis scheme, treatment of stratospheric aerosols, and all other features described in the original UCX paper. With this development the GEOS-Chem adjoint model is able to capture the spatial, temporal, and speciated variability in stratospheric ozone depletion processes, among other processes. We demonstrate its use by calculating 2-week sensitivities of stratospheric ozone to precursor species and show that the adjoint captures the Antarctic ozone depletion potential of active halogen species, including the chlorine activation and deactivation process. The spatial variations in the sensitivity of stratospheric ozone to NOx emissions are also described. This development expands the scope of research questions that can be addressed by allowing stratospheric interactions and feedbacks to be considered in the tropospheric sensitivity and inversion applications.

Flow analysis of water conveying nanomaterials over a rotating surface with thermal radiation

PurposeThe present findings aim to investigate the thermal behavior of water-based nanofluid flow over a rotating surface, focusing on understanding the effects of different types of nanoparticles on thermal efficiency, considering thermal radiation and variable viscosity effects. By considering four distinct nanoparticles – silicon dioxide titanium dioxide, aluminum oxide and molybdenum disulfide – the study aims to provide insights into how nanoparticle addition influences heat production, thermal boundary layer thickness and overall thermal performance.Design/methodology/approachThe study employs computational methods, utilizing the BVP mid-rich algorithm for the solution procedure. The computational approach allows for a detailed investigation of the thermal behavior of nanofluid flows across a rotating surface under varying conditions.FindingsThe study concludes that adding nanoparticles in the base liquid increases heat production in the system, resulting in enhanced thermal boundary layer thickness. The comparative analysis shows that different nanoparticle types exhibit varying effects on thermal efficiency, suggesting that careful selection of nanoparticles can optimize heat transport and thermal management processes. Moreover, there's a noteworthy uptrend in the radial velocity profile concerning the stretching parameter, whereas a converse trend is observed in the thermal profile.Originality/valueThis study contributes original insights by comprehensively investigating the thermal behavior of water-based hybrid nanofluid flow over a rotating surface.

A generalized van Genuchten model for unsaturated soil hydraulic conductivity

AbstractThe hydrodynamics of variably saturated soils or porous media in general are described via nonlinear functions of water retention and hydraulic conductivity, which facilitate the simulation of various mass and energy transport processes (e.g., water, heat, contaminants, colloids) within the porous medium. We set out to derive improved functions for more accurate estimations of soil hydraulic functions to advance the simulation of porous medium hydrodynamics. A new model is proposed for estimating the unsaturated hydraulic conductivity (UHC) from a soil water retention (SWR) function that is parameterized via nonlinear regression of measured data. The function can be viewed as a generalized van Genuchten (1980) model (GVG). We tested the new SWR and UHC expressions for numerous data sets from literature that cover a wide range of soil textures. Our comparisons reveal more accurate estimations using the GVG model by comparison with the original van Genuchten model.

Systematic Assessment of Mechanisms, Developments, Innovative Solutions, and Future Perspectives of Microplastics and Ecotoxicity – A Review

AbstractAs plastics become more ubiquitous, their impact on the environment and on human health cannot be overlooked. Once generated, micro‐ and nano‐plastics end‐up in the environment, causing widespread health and environmental risks. This is a significant environmental problem given the minuscule sizes of microplastics, and therefore warrants further investigation. This study presents a comprehensive review of the ecotoxicology of microplastics and methods for their degradation and decomposition besides discussing the fate and transport processes, recent progress, emerging strategies, challenges and potential future directions. The authors carefully evaluate the processes through which microplastics cause harm, from molecular interactions in species, to ecological impacts, and end with advances in microplastic biodegradation. Different kinds of microplastics found in the environment include polyethylene, polystyrene, polypropylene, polyvinyl chloride, polycarbonate, polyurethane, polypropylene, and polyethylene terephthalate. Analysis of microbial and enzymatic decomposition provides several swelling mitigation strategies designed to reduce environmental threats. In‐depth investigations of microplastic ecotoxicity and biodegradation are being facilitated by interdisciplinary proposals in the areas of nanotechnology, new analytical methods, and synthetic biology. The extensive study helps understand microplastics comprehensively which in‐turn ensures informed actions to mitigate the challenge of the environmental impact of microplastics for sustainable future.

Analyzing resilience influencing factors in the prefabricated building supply chain based on SEM-SD methodology

The supply chain for prefabricated buildings (PB) currently grapples with pressing challenges. In order to ensure the safe and stable development of the prefabricated building supply chains (PBSC), this study aims to identify the key factors and internal mechanisms affecting the PBSC, and propose a supply chain resilience enhancement mechanism, so as to promote the sustainable development of the PB industry. The study combined a literature review and survey data to identify key resilience factors in PBSC. A Structural Equation Model (SEM) was used to explore the relationships between these factors. System dynamics were applied to create a simulation model, assessing the resilience impact level and conducting sensitivity analysis. The results show that the transportation and procurement processes are the most significant factors influencing supply chain resilience. The external environmental factors wielded a more pronounced impact on the overall evaluation of supply chain resilience than the delivery and use processes, but delivery and use processes are more sensitive. The study uses the Pressure-State-Response (PSR) model to suggest strategies for enhancing supply chain resilience. This study contributes to more sustainable and efficient construction practices by offering an innovative theoretical framework to analyze the factors influencing PBSC resilience and proposing enhancement strategies.

SNW YOLOv8: improving the YOLOv8 network for real-time monitoring of lump coal

Abstract Due to the large size of the coal and the high mining output, lump coal is one of the hidden risks of mining conveyor damage. Typically, lump coal can cause jamming and even damage to the conveyor belt during the coal mining and transportation process. This study proposes a novel real-time detection method for lump coal on a conveyor belt. The Space-to-Depth Conv (SPD-Conv) module is introduced into the feature extraction network to extract the features of the mine's low-resolution lump coal. To enhance the feature extraction capability of the model, the Normalization-based Attention Module (NAM) is combined to adjust weight sparsity. After loss function optimization using the Wise-IoU v3 (WIoU v3) module, the SPD-Conv-NAM-WIoU v3 YOLOv8 (SNW YOLO v8) model is proposed. The experimental results show that the SNW YOLOv8 model outperforms the widely used model (YOLOv8) in terms of precision and recall by 15.82% and 11.71%, respectively. Significantly, the real-time detection speed of the SNW YOLOv8 model is increased to 192.93 f/s. Compared to normal models, the SNW YOLO v8 model overcomes the disadvantages of normal models, such as being overweight, and the parameters of SNW YOLO v8 are reduced to only 6.04 million with a small model volume of 12.3 MB. Meanwhile, the floating point of SNW YOLOv8 is significantly reduced. Consequently, it demonstrates excellent lump coal detection performance, which may open up a new window for coal mining optimization.

Energetic particles transport in constants of motion space due to collisions in tokamak plasmas

The spatio-temporal evolution of the energetic particles in the transport time scale in tokamak plasmas is a key issue of the plasmas confinement, especially in burning plasmas. In order to include sources and sinks and collisional slowing down processes, a new solver, ATEP-3D was implemented to simulate the evolution of the energetic particle (EP) distribution in the three-dimensional constants of motion (CoM) space. The Fokker–Planck collision operator represented in the CoM space is derived and numerically calculated. The collision coefficients are averaged over the unperturbed orbits to capture the fundamental properties of EPs. ATEP-3D is fully embedded in ITER IMAS framework and combined with the LIGKA/HAGIS codes. The finite volume method and the implicit Crank-Nicholson scheme are adopted due to their optimal numerical properties for transport time scale studies. ATEP-3D allows the analysis of the particle and power balance with the source and sink during the transport process to evaluate the EP confinement properties.

The effect of pore morphology on thermal insulation properties of thermal barrier coatings

The inhomogeneous-geometry microstructures caused by pores make thermal barrier coatings (TBCs) to have excellent thermal insulation properties, thus ensuring that the superalloy matrix is stable in its service at higher temperatures. Consequently, significant attention has been paid to understand the relationship between pore morphology and thermal conductivity. However, unclear the influence mechanisms of pore morphology-thermal insulation properties leads to a poor guide to the structural tailoring for better thermal insulation for TBC. In this study, a finite element method was used to simulate the thermal transport behavior of porous structures, and the influence mechanism of pore morphology on the thermal transport behavior of coatings was clarified. It indicated that thermal conductivity has a significant dependence on the pore aspect ratio, orientation angle, and porosity. The thermal insulation properties would be enhanced when large aspect ratio prolate spheroids are inserted with a pillar at the center. Further, the results shed light on the heat transport process across highly porous structures and provide a guide to design the coating with high thermal insulation properties.

Correction: Influence of Street Trees on Turbulent Fluctuations and Transport Processes in an Urban Canyon: A Wind Tunnel Study

Correction: Influence of Street Trees on Turbulent Fluctuations and Transport Processes in an Urban Canyon: A Wind Tunnel Study

Hybrid and coupled modeling for the design of fixed and suspended biomass reactors treating sanitary landfill leachates

This paper deals with an approach for hybrid and coupled modeling of the design of fixed and suspended biomass reactors for organic matter removal from sanitary landfill leachates. Five bioreactors, comprising Rotating Biological Contactors, Trickling Filter, Upflow Anaerobic Sludge Blanket, Upflow Anaerobic Filter in Two Separated Stages (UAF-2SS) and Upflow Anaerobic Filter in Three Separated Stages (UAF-3SS) were evaluated by treating the organic matter contained in the leachates produced in two sanitary landfills. With respect to the hybrid and coupled models, the best performance in the approximation of the measured values in the Se/Si ratio to the predicted results of models were the equations for UAF-2SS and UAF-3SS reactors. Hybrid models were made up of a combination of mass conservation law and equations for estimating transformation process. Coupled models consisted of a combination of transport process models and transformation models based on the substrate utilization rate by the microorganisms.

The Normal/Umklapp/Intervally/Intravally transport property of 2D SnSe

Based on the Boltzmann transport equation, both the electrical and thermal transport properties of 2D SnSe have been accurately calculated. The mobility of n-type SnSe is higher than that of p type due to the greater average velocity and smaller electron-phonon coupling matrix. For both n-type and p-type electron-phonon scattering, the LA phonon mode primarily governs the total, Normal, Umklapp, Intervally, and Intravally scattering processes. As the temperature increases from 300K to 800K, the LA phonon remains the dominant scattering mode. Compared to the Umklapp and Intervally scattering process, both Normal and Intravally scattering processes mainly govern electrical transport. In terms of phonon-electron scattering, the Normal/Intravalley processes dominate initially, followed by the Umklapp/Intervalley processes governing thermal transport as the temperature increases, governing thermal transport. The critical carrier concentration changes from 1018 cm−3 to 1019 cm−3, as the temperature rises from 300K to 800K, indicating a shift in the competitive relationship between Normal/Intravalley and Umklapp/Intervalley processes with temperature. Using the iteration method, the optimal power factor for n type@300K, p type@300K, n type@800K, p type@800K are 1.63 μW/cmK, 5.62 μW/cmK, 2.30 μW/cmK, 4.04 μW/cmK, respectively. After considering phonon-electron scattering, the lattice thermal conductivity of n type (p type) is 0.70 W/mK (0.64 W/mK) at 300K and 0.31 W/mK (0.30 W/mK) at 800K. The optimal ZT of n type is 1.17 at 800K, originating from the Normal scattering process, while the optimal ZT of p type is 0.86, stemming from the Intravally scattering process. Our results provide a deeper understanding of the transport processes in SnSe and offer insights for tuning the thermoelectric properties of two-dimensional materials through electron-phonon and phonon-electron scattering processes.

Transport coefficient approach for characterizing nonequilibrium dynamics in soft matter

Nonequilibrium states in soft condensed matter require a systematic approach to characterize and model materials, enhancing predictability and applications. Among the tools, X-ray photon correlation spectroscopy (XPCS) provides exceptional temporal and spatial resolution to extract dynamic insight into the properties of the material. However, existing models might overlook intricate details. We introduce an approach for extracting the transport coefficient, denoted as [Formula: see text], from the XPCS studies. This coefficient is a fundamental parameter in nonequilibrium statistical mechanics and is crucial for characterizing transport processes within a system. Our method unifies the Green-Kubo formulas associated with various transport coefficients, including gradient flows, particle-particle interactions, friction matrices, and continuous noise. We achieve this by integrating the collective influence of random and systematic forces acting on the particles within the framework of a Markov chain. We initially validated this method using molecular dynamics simulations of a system subjected to changes in temperatures over time. Subsequently, we conducted further verification using experimental systems reported in the literature and known for their complex nonequilibrium characteristics. The results, including the derived [Formula: see text] and other relevant physical parameters, align with the previous observations and reveal detailed dynamical information in nonequilibrium states. This approach represents an advancement in XPCS analysis, addressing the growing demand to extract intricate nonequilibrium dynamics. Further, the methods presented are agnostic to the nature of the material system and can be potentially expanded to hard condensed matter systems.

Thermal conductance of interfaces between titanium nitride and group IV semiconductors at high temperatures

Measuring the temperature dependence of material properties is a standard method for better understanding the microscopic origins for that property. Surprisingly, only a few experimental studies of thermal boundary conductance at high temperatures exist. This lack of high temperature data makes it difficult to evaluate competing theories for how inelastic processes contribute to thermal conductance. To address this, we report time domain thermoreflectance measurements of the thermal boundary conductance for TiN on diamond, silicon-carbide, silicon, and germanium between 120 and 1000 K. In all systems, the interface conductance increases monotonically without stagnating at higher temperatures. For TiN/SiC interfaces, G ranges from 330 to 1000 MW/m2-K, with a room temperature conductance of 750 MW/m2-K. The interface conductance for TiN/diamond ranges from 140 to 950 MW/m2-K. Notably, for all four interfacial systems, the conductance continues to increase with temperature even after all phonon modes in the vibrationally soft material are thermally excited. This observation suggests that inelastic processes are significant contributors to the thermal conductance in all four interfacial systems, regardless of whether the materials forming the interface are vibrationally similar or dissimilar. Our study fills a notable gap in the literature for how interfacial conductance evolves at high temperatures and tests burgeoning theories for the role of inelastic processes in interfacial thermal transport.

Multicomponent and Surface Charge Effects on PFOS Sorption and Transport in Goethite-Coated Porous Media under Variable Hydrochemical Conditions.

Perfluorooctanesulfonate (PFOS), a toxic anionic perfluorinated surfactant, exhibits variable electrostatic adsorption mechanisms on charge-regulated minerals depending on solution hydrochemistry. This work explores the interplay of multicomponent interactions and surface charge effects on PFOS adsorption to goethite surfaces under flow-through conditions. We conducted a series of column experiments in saturated goethite-coated porous media subjected to dynamic hydrochemical conditions triggered by step changes in the electrolyte concentration of the injected solutions. Measurements of pH and PFOS breakthrough curves at the outlet allowed tracking the propagation of multicomponent reactive fronts. We performed process-based reactive transport simulations incorporating a mechanistic network of surface complexation reactions to quantitatively interpret the geochemical processes. The experimental and modeling outcomes reveal that the coupled spatio-temporal evolution of pH and electrolyte fronts, driven by the electrostatic properties of the mineral, exerts a key control on PFOS mobility by determining its adsorption and speciation reactions on goethite surfaces. These results illuminate the important influence of multicomponent transport processes and surface charge effects on PFOS mobility, emphasizing the need for mechanistic adsorption models in reactive transport simulations of ionizable PFAS compounds to determine their environmental fate and to perform accurate risk assessment.

Allogenic and autologous nondiluted serum eye drops-validation strategy compliant with good manufacturing practice.

Serum eye drops alleviate ocular symptoms of diseases such as sicca syndrome, or chronic graft-versus-host disease. This study was designed for good manufacturing practice validation of our standard manufacturing, storage and transport processes for both autologous and allogenic SEDs. Specifications of quality parameters are lacking and were aimed to be defined. Using sterile collected, coagulated whole blood, serum was separated by centrifugation and filled into single-use eye drop applicator vials. Quality control tests included visual inspection, sterility, leukocyte concentration, pH, vitamin A, TGF-ß and VEGF-A. Samples were collected after manufacture and after 24 h and 6 months of frozen storage (-20°C). Sterility testing was performed after opening the SED applicators at specified intervals. For transport validation, SEDs were packed in insulated transport bags and stored at 20-24°C and 30-32°C for 8 h. Vitamin A, TGF-ß and VEGF-A assays showed no difference in concentration between fresh and 24 h frozen serum. All specifications for pH (aim 7.4) and cellular contamination were met and microbiological contamination tests were negative. Shelf-life was defined as 6 months at -20°C. Once opened, the product must be used within 24 h to avoid bacterial outgrowth. Transporting frozen SEDs from the manufacturer via a local pharmacy to the patient within a maximum of 4 h was demonstrated. The GMP compliance of our production, storage and transport processes for autologous and allogenic SEDs was successfully validated. 100% serum eye drops in single-use applicators can be safely used for up to 24 h after opening.

Influence of sand particle size on the erosion-corrosion resistance of Ni2FeCrMo0.2 HEA in seawater: Particle-surface-electrochemistry interaction

The erosion-corrosion mechanism in rotary flowing seawater is hugely complicated due to the multiscale coupling processes of particle-surface impact, ion mass transfer, and interface electrochemistry. Therefore, developing erosion-corrosion resistant material and exploring the synergistic mechanism between sand erosion and electrochemical corrosion is vital. This study conducted the erosion-corrosion test on Ni2FeCrMo0.2 high-entropy alloy under the particle-seawater flow. Based on a coupled analysis of multi-component weight loss, electrochemical behavior, and microscopic damage morphology, the multiscale coupling processes of sand transportation, particle-surface impact, ion mass transfer, and interface electrochemistry were revealed. The present study found that with the increase of sand size, the energy carried by the particles promoted impact erosion. Additionally, particle movement enhanced ion mass transfer through turbulent effects, and the impact behavior disrupted the passivation film to promote electrochemical processes by reducing the thickness of the passivation film, leading to an increase in the erosion-corrosion rate. However, when the particle size continued to increase to a certain extent, the impact frequency decreased, reducing the erosion-corrosion rate. As the sand size grew, the dominant damage mechanism transitioned from pure corrosion (100 μm) to synergistic effects (200 μm, 400 μm) and then to pure erosion (800 μm). This study provides an in-depth understanding of the erosion-corrosion mechanism in seawater from the perspective of particle-ion-fluid-surface interaction by multi-element characterization.

Photosynthetic performance of the red algae Gracilariopsis lemaneiformis under high seawater pH: Excess reactive oxygen production due to carbon limitation.

The red algae Gracilariopsis lemaneiformis is extensively cultivated at high densities, leading to significant increases in regional seawater pH due to its photosynthetic removal of inorganic carbon. We conducted a study on G. lemaneiformis cultured under various pH conditions (normal pH, pH 9.3, and pH 9.6) and light levels (dark and 100 μmol photons m-2 s-1) to investigate how high pH seawater environments affect the metabolic processes of G. lemaneiformis. The high pH did not directly damage the photosynthetic light reactions or the Calvin cycle. Instead, the observed reduction in photosynthetic rates was primarily due to CO2 limitation. However, under illuminated conditions, a high pH environment leads to a decrease in electron transport efficiency (ETo/RC) and reaction center density (RC/CSo), while simultaneously increasing the levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), and the activity of antioxidant enzymes. Under illuminated conditions, the limitation of inhibit the photosynthetic electron transport process, leading to energy imbalance and excessive production of reactive oxygen species, which in turn resulted in lipid peroxidation of the cell membrane. This might be one of the inducing factors responsible for the bleaching in sea-farmed G. lemaneiformis plants.

Modelling gravity-driven aqueous humour flow and drug delivery in Descemet’s membrane detachment

Topical medications are common initial treatments for Descemet’s membrane detachment (DMD). It is crucial to understand the aqueous humour (AH) flow and drug transport to facilitate the DMD treatment. This paper presents a mathematical model to analyse AH flow and drug transport in the anterior of the human eye considering gravity orientation effects. Utilizing the finite element method, the model couples AH flow dynamics, temperature-induced buoyancy, and drug transport by convection-diffusion. COMSOL Multiphysics is used to simulate the spatial-temporal distribution of AH and drugs delivery. The findings indicate that the eye positioning influences the directional flow of AH, due to temperature differences, and impacts the delivery of drug concentrations. It is also discovered that eye drops diffuse faster due to tear turnover in the eye yet more eye ointment is delivered as it has a longer contact time in the cornea. By understanding the AH flow and transport process, this proposed model may offer appropriate guidelines for optimizing DMD treatment under various forms of topical drugs and eye positions.

Modeling Alternative Conformational States of Pseudo-Symmetric Solute Carrier Transporters using Methods from Machine Learning.

The Solute Carrier (SLC) superfamily of integral membrane proteins function to transport a wide array of solutes across the plasma and organelle membranes. SLC proteins also function as important drug transporters and as viral receptors. Despite being classified as a single superfamily, SLC proteins do not share a single common fold classification; however, most belong to multi-pass transmembrane helical protein fold families. SLC proteins populate different conformational states during the solute transport process, including outward open, intermediate (occluded), and inward open conformational states. For some SLC fold families this structural "flipping" corresponds to swapping between conformations of their N-terminal and C-terminal symmetry-related sub-structures. Conventional AlphaFold2 or Evolutionary Scale Modeling methods typically generate models for only one of these multiple conformational states of SLC proteins. Here we describe a fast and simple approach for modeling multiple conformational states of SLC proteins using a combined ESM - AF2 process. The resulting multi-state models are validated by comparison with sequence-based evolutionary co-variance data (ECs) that encode information about contacts present in the various conformational states adopted by the protein. We also explored the impact of mutations on conformational distributions of SLC proteins modeled by AlphaFold2 using both conventional and enhanced sampling methods. This approach for modeling conformational landscapes of pseudo-symmetric SLC proteins is demonstrated for several integral membrane protein transporters, including SLC35F2 the receptor of a feline leukemia virus envelope protein required for viral entry into eukaryotic cells.