Concentration Gradient Research Articles

Integrating proteomics and metabolomics to elucidate the regulatory mechanisms of pimpled egg production in chickens: Multi-omics analysis of the mechanism of pimpled egg formation.

Eggshells not only protect the contents of the egg from external damage but are also a key factor influencing consumer choice, second only to price. In the later stages of egg production, the incidence of pimpled eggs significantly increases, severely affecting the hatchability and food safety of the eggs. This study compares the differences in the uterine proteomes and metabolomes of hens producing pimpled eggs and those producing normal eggs, aiming to identify the proteins and metabolites that may play a crucial role in the formation of pimpled eggs. A total of 242 differentially expressed proteins (DEPs) were identified in uterine tissue, of which 116 were upregulated and 126 were downregulated. Enrichment analysis revealed that the DEPs were enriched in pathways related to ion transport, energy metabolism, and immune responses. The study found that in the normal eggs (NE) group, HCO₃⁻ was predominantly transported via SLC4A1, although other transport pathways may also play a role. In contrast, in the pimpled eggs (PE) group, bicarbonate ions (HCO₃⁻) was primarily transported through SLC4A4. Additionally, a total of 44 differentially metabolites (DMs) were identified in the uterus, with 5'-Adenylic acid (ATP) being significantly downregulated in the PE group. The ions and matrix proteins required for eggshell formation are transported from uterine cells to the uterine fluid against a concentration gradient, a process that consumes a substantial amount of energy. The decrease in ATP concentration in the PE group may be a significant factor influencing the formation of pimpled eggs. Subsequently, we found that the DEPs and DMs were jointly enriched in several signaling pathways, including the FoxO signaling pathway related to energy metabolism, nicotinate and nicotinamide metabolism, and tryptophan metabolism associated with immune response. Notably, the DMs involved in these signaling pathways were all downregulated in the PE group. Our research findings indicate that SLC4A1, SLC4A2, and ATP2B4 (DEPs), along with 5'-adenylic acid and trigonelline (DMs), influence the formation of eggshells through mechanisms related to energy metabolism, ion transport, and immune response. These DEPs and DMs may serve as potential biomarkers for the genetic improvement of eggshell quality.

Solutal Marangoni effect influencing bubble dynamics with varied electrolyte compositions

In the photoelectrochemical (PEC) water splitting system, the intricate interplay between bubble evolution and charge transfer at the electrode-electrolyte interface underscores the paramount importance of studying electrolyte properties. In this paper, the bubble dynamics and gas-liquid interface mass transfer on TiO2 nanorod and nanotube film electrodes are investigated by changing the cation types (K+, Na+, Li+) and concentrations (0.1 M-1.5 M) in alkaline electrolytes. The results indicate that the photocurrent and gas production follow the order of K+ > Na+ > Li+ under the same concentration, which is affected by the solvation of metal cations in aqueous solution and the adsorption on the photoanode surface. Compared with the nanotube electrode, the nanorod electrode enables the bubble to detach at a smaller size and faster rate. The trend of bubble detachment diameter variation with concentration in different cation electrolytes is the same, and follows the order of K+ > Na+ > Li+, which indicates that the force caused by Marangoni effect shows similar rules. The results reveal that the surface tension variation rate induced by ion concentration gradient varies significantly under different cation concentrations, while the variation rate driven by temperature gradient remains notably stable. This confirms that the bubble growth and detachment depend on the solutal Marangoni effect caused by the surface tension variation rate of different alkaline electrolytes with concentration. Therefore, the suitable choice of electrolyte composition is pivotal for regulating the bubble evolution at the electrode-electrolyte interface and improving the PEC system efficiency.

Numerical study on the effects of obstacle shape and thickness on deflagration-to-detonation transition in hydrogen–air mixtures with a transverse concentration gradient

Numerical study on the effects of obstacle shape and thickness on deflagration-to-detonation transition in hydrogen–air mixtures with a transverse concentration gradient

An Integrating Microfluidic System for Concentration Gradient Generation of Exosomes and Exosome-Assisted Single-Cell-Derived Tumor-Sphere Formation.

To enhance exploration on tumor stem-like cells (TSCs) without altering their cellular biological characteristics, researchers advocate for application of single-cell-derived tumor-spheres (STSs). TSCs are regulated by their surrounding microenvironment, making it crucial to simulate a tumor microenvironment to facilitate STS formation. Recently, exosomes that originated from the tumor microenvironment have emerged as a promising approach for mimicking the tumor microenvironment. In the tumor microenvironment, various associated cells (such as fibroblasts, endothelial cells, and immune cells) play crucial roles. Utilizing exosomes derived from these cells enabled us to simulate the tumor microenvironment and promote STS formation. Herein, we have developed an integrated microfluidic platform to generate serial concentration gradients and evaluate the effects of multiple exosomes on STS formation. To demonstrate the feasibility of our approach, we generated serial concentration gradients of exosomes derived from two different cell types (HUVEC and NIH/3T3 cells) and assessed their effects on STS formation. Subsequently, we investigated the drug resistance of STSs treated with free doxorubicin and doxorubicin-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles. Our findings revealed that the serial concentration gradients of mixed exosomes could be successfully generated, leading to an enhanced formation rate and size of STSs. Compared to exosomes derived from one cell type, the mixed exosomes exhibited superior promotion of STS formation. Additionally, nanomedicines demonstrated a reduction in the drug resistance of TSCs compared to free drug treatment, particularly in smaller and/or more deformable TSCs. This platform provides an innovative approach for STS formation enhancement and tumor microenvironment simulation.

Modified Solution–Diffusion Model Incorporating Rotational Kinetic Energy in Pressure Retarded Osmosis

Pressure-retarded osmosis (PRO) is a process that allows the production of mechanical energy from the chemical potential difference between two solutions of different concentrations separated by a semi-permeable membrane. One of the main obstacles for this technology to be commercially competitive is the difference between the theoretical power density and the experimental power density due to negative factors like ICP. Analytical models facilitate the analysis of the relationships between system parameters and thus facilitate the optimization of components. In general, PRO has traditionally been explained through the solution–diffusion model, where the flow of water through the membrane depends on a diffusivity factor, the concentration gradient, and the hydraulic pressure gradient. This paper focuses on developing a modified solution–diffusion model that includes means to control the ICP through rotational kinetic energy. An energy balance method for obtaining a solution diffusion-based model is explained, and an analytical model is obtained. Finally, said model is verified through simulations with parameters reported in the literature to obtain insight on the required dimensions for a prototype. It was found that a turning radius of 0.5 m and an angular speed of less than 3000 rev/min could generate enough kinetic energy to compensate for ICP losses in a PRO scenario. Also, the results suggest that bigger concentration differences could benefit more of this technology, as they require almost the same energy as smaller concentration differences but allow for more energy extraction.

Fully automated in vivo screening system for multi-organ imaging and pharmaceutical evaluation

Advancements in screening technologies employing small organisms have enabled deep profiling of compounds in vivo. However, current strategies for phenotyping of behaving animals, such as zebrafish, typically involve tedious manipulations. Here, we develop and validate a fully automated in vivo screening system (AISS) that integrates microfluidic technology and computer-vision-based control methods to enable rapid evaluation of biological responses of non-anesthetized zebrafish to molecular gradients. Via precise fluidic control, the AISS allows automatic loading, encapsulation, transportation and immobilization of single-larva in droplets for multi-organ imaging and chemical gradients generation inaccessible in previous systems. Using this platform, we examine the cardiac sensitivity of an antipsychotic drug with multiple concentration gradients, and reveal dramatic diversity and complexity in the accurate chemical regulation of cardiac functions in vivo. This proposed system expands the arsenal of tools available for in vivo screening and facilitates comprehensive profiling of pharmaceuticals.

Specificity and tunability of efflux pumps: A new role for the proton gradient?

Efflux pumps that transport antibacterial drugs out of bacterial cells have broad specificity, commonly leading to broad spectrum resistance and limiting treatment strategies for infections. It remains unclear how efflux pumps can maintain this broad spectrum specificity to diverse drug molecules while limiting the efflux of other cytoplasmic content. We have investigated the origins of this broad specificity using theoretical models informed by the experimentally determined structural and kinetic properties of efflux pumps. We developed a set of mathematical models describing operation of efflux pumps as a discrete cyclic stochastic process across a network of states characterizing pump conformations and the presence/absence of bound ligands and protons. These include a minimal three-state model that lends itself to clear analytic calculations as well as a five-state model that relaxes some of the simpler model's most strict assumptions. We found that the pump specificity is determined not solely by the drug affinity to the pump-as is commonly assumed-but it is also directly affected by the periplasmic pH and the transmembrane potential. Therefore, changes to the proton concentration gradient and voltage drop across the membrane can influence how effective the pump is at extruding a particular drug molecule. Furthermore, we found that while both the proton concentration gradient across the membrane and the transmembrane potential contribute to the thermodynamic force driving the pump, their effects on the efflux enter not strictly in a combined proton motive force. Rather, they have two distinguishable effects on the overall throughput. These results highlight the unexpected effects of thermodynamic driving forces out of equilibrium and illustrate how efflux pump structure and function are conducive to the emergence of multidrug resistance.

Transcardiac gradients of pro-cholecystokinin, cholecystokinin, and gastrin in patients with and without heart failure with reduced ejection fraction.

Cholecystokinin (CCK) is secreted from the intestines in response to food intake. We previously reported that the CCK gene is also expressed in the mammalian heart, and it has been hypothesized that proCCK could be a novel cardiac biomarker. However, it is not known whether cardiac gene expression leads to secretion in humans. To investigate myocardial secretion of proCCK in patients with heart failure with reduced ejection fraction (HFrEF) or arrythmias. A total of 115 patients undergoing invasive cardiac procedures were included: 55 with HFrEF (67 years [interquartile range (IQR) 60-76], 72% male, LVEF 30% [IQR 20-35]), and 60 without HFrEF (26 with Wolff-Parkinson-White syndrome (WPW) (30 years [IQR 26-39], 61.5% male), and 34 with atrial fibrillation (AFIB) (66 years [IQR 60-71], 61.8% male)). Blood was collected from the coronary sinus (CS) as well as the left atrium or femoral artery (A) to determine the transcardiac concentration gradient (TCproCCK) (CS proCCK concentration - A proCCK concentration). Radioimmunoassays were used for measurements of plasma hormones. TCproCCK across failing hearts was 0.05 pmol/l (IQR: -1.49 to 2.67) (p = 0.365). In non-failing hearts, TCproCCK was 0.35 pmol/l (IQR: -1.57 to 1.29) (p = 0.778) for WPW and 0.68 pmol/l (IQR: -1.58 to 3.28) (p = 0.133) for AFIB. Transcardiac gradients for N-terminal pro B-type natriuretic peptide (NT-proBNP) were observed in all groups. No evidence of net myocardial secretion of proCCK was found in either failing or structurally normal hearts, questioning its proposed role as a cardiac biomarker.

A Dive Into Yeast's Sugar Diet-Comparing the Metabolic Response of Glucose, Fructose, Sucrose, and Maltose Under Dynamic Feast/Famine Conditions.

Microbes experience dynamic conditions in natural habitats as well as in engineered environments, such as large-scale bioreactors, which exhibit increased mixing times and inhomogeneities. While single perturbations have been studied for several organisms and substrates, the impact of recurring short-term perturbations remains largely unknown. In this study, we investigated the response of Saccharomyces cerevisiae to repetitive gradients of four different sugars: glucose, fructose, sucrose, and maltose. Due to different transport mechanisms and metabolic routes, nonglucose sugars lead to varied intracellular responses. To characterize the impact of the carbon sources and the dynamic substrate gradients, we applied both steady-state and dynamic cultivation conditions, comparing the physiology, intracellular metabolome, and proteome. For maltose, the repeated concentration gradients led to a significant decrease in biomass yield. Under glucose, fructose, and sucrose conditions, S. cerevisiae maintained the biomass yield observed under steady-state conditions. Although the physiology was very similar across the different sugars, the intracellular metabolome and proteome were clearly differentiated. Notably, the concentration of upper glycolytic enzymes decreased for glucose and maltose (up to -60% and -40%, respectively), while an increase was observed for sucrose and fructose when exposed to gradients. Nevertheless, for all sugar gradient conditions, a stable energy charge was maintained, ranging between 0.78 and 0.89. This response to maltose is particularly distinct compared to previous single-substrate pulse experiments or limitation to excess shifts, which led to maltose-accelerated death in earlier studies. At the same time, enzymes of lower glycolysis were elevated. Interestingly, common stress-related proteins (GO term: cellular response to oxidative stress) decreased during dynamic conditions.

Enhancing Photodynamic Therapy Efficacy via Photo-Triggered Calcium Overload and Oxygen Delivery in Tumor Hypoxia Management.

Background: Photodynamic therapy (PDT) has emerged as a promising treatment for cancer, primarily due to its ability to generate reactive oxygen species (ROS) that directly induce tumor cell death. However, the hypoxic microenvironment commonly found within tumors poses a significant challenge by inhibiting ROS production. This study aims to investigate the effect of improving tumor hypoxia on enhancing PDT. Result: We employed polylactic-co-glycolic acid (PLGA) as a delivery vector for the encapsulation of indocyanine green (ICG), a photosensitizer, and perfluorohexane (PFH), with surface labeling mannose to facilitate targeted delivery. A potential therapeutic nanoplatform was fabricated, designated as Man-PFH-ICG@PLGA. These nanospheres are capable of localizing at tumor sites and can be tracked using photoacoustic (PA) imaging. Upon laser irradiation, the ROS generated by PDT activated the transient receptor potential cation channel subfamily A member 1 (TRPA1) located on the cell membrane. This activation led to an influx of extracellular Ca2+ and subsequently resulted in calcium overload. The excessive Ca2+ selectively accumulated in mitochondria, disrupting the function of enzymes involved in the mitochondrial respiratory chain. This disruption inhibits cellular respiration and decreases oxygen consumption in tumor cells, ultimately contributing to the alleviation of the hypoxic microenvironment within tumors. Simultaneously, PFH exhibited a high affinity for oxygen and can deliver exogenous oxygen directly to the tumor site through simple diffusion along the concentration gradient. Both the direct and indirect mechanisms synergistically contribute to ameliorating the hypoxic conditions within tumors, thereby augmenting the efficacy of PDT. Conclusions: The synergistic effect of photocontrolled calcium overload from endogenous sources and the oxygen-carrying nanoplatform alleviates tumor hypoxia, thereby enhancing the efficacy of PDT. This approach provides a new perspective on PDT.

Shape-Directed Dynamic Assembly of Active Colloidal Metamachines.

Modularly organizing active micromachines into high-grade metamachines makes a great leap for operating the microscopic world in a biomimetic way. However, modulating the nonreciprocal interactions among different colloidal motors through chemical reactions to achieve the controllable construction of active colloidal metamachines with specific dynamic properties remains challenging. Here, we report the phototactic active colloidal metamachines constructed by shape-directed dynamic self-assembly of chemically driven peanut-shaped TiO2 colloidal motors and Janus spherical Pt/SiO2 colloidal motors. The long-range diffusiophoretic attraction generated by the photocatalytic reaction dominates the sensing and collision of peanut TiO2 motors with Janus Pt/SiO2 motors. The coupling of local chemical concentration gradient fields between the two types of motors generates short-range site-selective interactions, promoting the shape-directed assembly toward active colloidal metamachines with well-defined spatial configurations. Metamachines, made of colloidal motors, exhibit configuration-dependent kinematics. The colloidal metamachines can be reversibly reconstructed by adjusting lighting conditions and can move phototactically along a predetermined path under the structured light field. Such chemically driven colloidal metamachines that integrate multiple active agents provide a significant avenue for fabricating active soft matter materials and intelligent robotic systems with advanced applications.

Characterizing safety, toxicity, and breast cancer risk reduction using a long-term fulvestrant eluting implant

For individuals at high risk of developing breast cancer, interventions to mitigate this risk include surgical removal of their breasts and ovaries or five years treatment with the anti-estrogen tamoxifen or aromatase inhibitors. We hypothesized that a silicone based anti-estrogen-eluting implant placed within the breast would provide the risk reduction benefit of hormonal therapy, but without the adverse effects that limit compliance. To this end, we demonstrate that when placed adjacent to mammary tissue in the 7,12-dimethylbenz[a]anthracene-induced rat breast cancer model a fulvestrant-eluting implant delays breast cancer with minimal systemic exposure. Using adult female sheep, surgical placement of fulvestrant-eluting implants was safe and did not elicit significant breast tissue pathology when placed at the base of the udder for directed elution into the mammary tissue. At 30 days of elution, fulvestrant was found to penetrate mammary tissue forming a concentration gradient beyond 15 mm from the implant. Consistent with the small animal rat study, minimal systemic fulvestrant biodistribution was found. Together, these studies provide the proof of principle that a breast indwelling fulvestrant-eluting implant can reduce the risk of breast cancer and limit systemic exposure, while penetrating and distributing through breast tissue.

Exploring potential targets and mechanisms of renal tissue damage caused by N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) through network toxicology and animal experiments: A case of chronic kidney disease.

6-PPDQ is a new type of environmental contaminant contained in tire rubber. No studies have been reported on the potential targets and mechanisms of action of 6-PPDQ on renal tissue damage. In the present study, we used CKD as an example to explore the potential targets and biological mechanisms of renal injury caused by 6-PPDQ using Network toxicology and animal experiments. A total of 1361 6-PPDQ-related target genes were obtained from the CTD database. 17,296 CKD-related target genes were obtained through the GeneCards database. After intersecting the two, a total of 908 intersecting genes were obtained. Next, we constructed a PPI protein interaction network. Using different algorithms in Cytoscape software and "Logistic regression analysis", five key target genes were finally identified as NOTCH1, TP53, TNF, IL1B and IL6. We constructed a diagnostic model using five key target genes, and the ROC curves, calibration curves and DCA curves proved that the model has good diagnostic value. Molecular docking demonstrated high affinity between 6-PPDQ and five key target gene proteins. In animal experiments, repeated intraperitoneal injections of 6-PPDQ using different concentration gradients for 28days revealed that the expression levels of five key target genes in renal tissues increased progressively with the increase of the concentration, and the damage to renal tissues was also aggravated. ssGSEA and animal experiments revealed a key role for activation of the MAPK signaling pathway. Finally, we also identified a significant correlation between five key target genes and the level of infiltration of multiple immune cells. In conclusion, these findings suggest that 6-PPDQ can cause damage to renal tissue and that the level of damage progressively increases with increasing concentration. Among them, NOTCH1, TP53, TNF, IL1B and IL6 may be its potential targets of action. Activation of the MAPK signaling pathway is a potential mechanism of action.

Gradient Design with Low-tortuosity Overcoming Kinetic Limitations in High-Loading Solid-State Cathodes.

The extensive commercialization of practical solid-state batteries (SSBs) necessitates the development of high-loading solid-state cathodes with fast charging capability. However, electrochemical kinetics are severely delayed in thick cathodes due to tortuous ion transport pathways and slow solid-solid ion diffusion, which limit the achievable capacity of SSBs at high current densities. In this work, we propose a conductivity gradient cathode with low-tortuosity to enable facile ion transport and counterbalance ion concentration gradient, thereby overcoming the kinetic limitations and achieving fast charging capabilities in thick cathodes. The LiNi0.8Co0.1Mn0.1O2 cathodes deliver a room-temperature (RT) capacities of 147 and 110 mAh g-1 at 5 C and 10 C, respectively, and meanwhile achieve a RT areal capacity of 3.3 mAh cm-² at 3 C, enabling SSBs simultaneously high energy and power densities. The universality of this strategy is demonstrated in LiFePO4 cathodes, providing a novel solution for fast charging and large-scale application of high-loading SSBs.

Flow environment affects nutrient transport in soft plant roots.

This work estimates Michaelis-Menten kinetics parameters for nutrient transport under varying flow rates in the soft roots of Indian mustard (Brassica juncea) using a plant fluidic device. To find the metallic components within the roots, inductively coupled plasma mass spectrometry (ICP-MS) analysis was performed. The flow rate-dependent metabolic changes were examined using Raman spectral analysis. In addition, three-dimensional numerical simulations were conducted to assess mechanical stresses resulting from the concentration difference that enhances osmotic pressure and flow loading at the root-liquid interface. Convection, the primary mode of nutrient transport in flowing media, was observed to reduce nutrient uptake at higher flow rates. In contrast, diffusion became more prevalent in areas where the complex root structure restricted the flow field. The concentration gradient between the upstream and downstream regions of the root caused nutrient diffusion from downstream to upstream. As seen, an increase in flow rate resulted in a decrease in root length due to the reduction of advantageous metabolites, which led to lower average mechanical stress and osmotic pressure loading. Additionally, osmotic pressure at the root-liquid interface was found to increase over time. Numerical simulations revealed that the average internal mechanical stress was substantially greater when osmotic pressure was considered. This emphasizes the importance of accounting for osmotic pressure when assessing mechanical stress in roots. This study uses a fluidic device that replicates hydroponic conditions for the first time in order to evaluate the convection-dependent Michaelis-Menten kinetics of nutrient uptake in plant roots.

Inorganic nitrogen and organic matter jointly regulate ectomycorrhizal fungi-mediated iron acquisition.

Ectomycorrhizal fungi (EMF) play a crucial role in facilitating plant nutrient uptake from the soil although inorganic nitrogen (N) can potentially diminish this role. However, the effect of inorganic N availability and organic matter on shaping EMF-mediated plant iron (Fe) uptake remains unclear. To explore this, we performed a microcosm study on Pinus taeda roots inoculated with Suillus cothurnatus treated with +/-Fe-coated sand, +/-organic matter, and a gradient of NH4NO3 concentrations. Mycorrhiza formation was most favorable under conditions with organic matter, without inorganic N. Synchrotron X-ray microfluorescence imaging on ectomycorrhizal cross-sections suggested that the effect of inorganic N on mycorrhizal Fe acquisition largely depended on organic matter supply. With organic matter, mycorrhizal Fe concentration was significantly decreased as inorganic N levels increased. Conversely, an opposite trend was observed when organic matter was absent. Spatial distribution analysis showed that Fe, zinc, calcium, and copper predominantly accumulated in the fungal mantle across all conditions, highlighting the mantle's critical role in nutrient accumulation and regulation of nutrient transfer to internal compartments. Our work illustrated that the liberation of soil mineral Fe and the EMF-mediated plant Fe acquisition are jointly regulated by inorganic N and organic matter in the soil.

Study on improving yield and antioxidant enzyme activities in millet by rationing molybdenum and nitrogen

The application of appropriate nitrogen and molybdenum fertilizer can improve the growth and development of plants, increase photosynthetic efficiency, regulate active oxygen metabolism in vivo, maintain the oxidation balance required for normal cell growth, enhance the activity of crop antioxidant enzymes and dry matter accumulation, so as to increase crop yield. In order to investigate the effect mechanism of nitrogen fertilizer combined with foliar molybdenum fertilizer on millet yield and antioxidant enzyme activity, two nitrogen application gradients (N0 (0 kg/hm2) and N1 (75 kg/hm2) were set with millet variety Changnong 47 as material. Leaf molybdenum fertilizer Mo0 (0 %), Mo1 (0.1 %), Mo2 (0.2 %), Mo3 (0.3 %) and Mo4 (0.4 %) were sprayed at the joining stage. Photosynthetic parameters, chlorophyll content, antioxidant enzyme activity, dry matter accumulation and yield at the complete ripening stage were measured. After the analysis of significant difference, the results showed that the combined application of molybdenum nitrogen significantly increased the yield of millet, and the maximum yield under the Mo3 treatment was 5869.04 kg/hm2 under the N1 condition, which was 13% higher than that under the no fertilization treatment. The total dry matter accumulation was 36.96 g/ plant, which was 31% higher than that without fertilization. The net photosynthetic rate (Pn) and stomatal conductivity (gs) increased first and then decreased with the increase of molybdenum fertilizer concentration gradient, and reached the maximum values under N1Mo3 condition, which were 24.77 μmol•m-2•s-1 and 391.33 mol•m-2•s-1, respectively. Application of molybdenum fertilizer can improve the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the test samples. In conclusion, under N1 condition, Mo3 (0.3%) treatment can effectively improve millet yield, photosynthetic characteristics and antioxidant enzyme activity. The results of this study provided theoretical basis and data support for the application of nitrogen and molybdenum fertilizer in millet production.

On-Chip Stimulated Raman Scattering Imaging and Quantification of Molecular Diffusion in Aqueous Microfluidics.

Numerous chemical reactions and most life processes occur in aqueous solutions, where the physical diffusion of small molecules plays a vital role, including solvent water molecules, solute biomolecules, and ions. Conventional methods of measuring diffusion coefficients are often limited by technical complexity, large sample consumption, or significant time cost. Here, we present an optical imaging method to study molecular diffusion by combining stimulated Raman scattering (SRS) microscopy with microfluidics: a "Y"-shaped microfluidic channel forming two laminar flows with a stable concentration gradient across the interface. SRS imaging of a specific molecule allows us to obtain a high-resolution chemical profile of the diffusion region at varying inspection locations and flow rates, which enables the extraction of diffusion coefficients using the convection-diffusion model. As a proof of concept, we measured diffusion coefficients of molecules including water, protein, and multiple ions, with a sample volume of less than 1 mL and a time cost of less than 10 min. Moreover, we demonstrated a high-resolution three-dimensional (3D) reconstruction of the diffusion patterns in the microfluidic channel. The high-speed microfluidic SRS platform holds the potential for quantitative measurements of molecular diffusion, chemical reaction, and fluidic dynamics at the liquid-liquid interfaces.

Mapping Spatiotemporal Solvent Velocity from Measured Concentration Gradients in a Polarized Electrolyte

Abstract The electric-field induced motion of neutral species impedes the efficacy of electrochemical devices. By combining operando X-ray transmission measurements with continuum mechanics, we have developed a methodology for determining the velocity of neutral solvent molecules under an applied field. The X-ray transmission experiments were used to determine ion concentration profiles as a function of space and time in a polymer electrolyte. The unsteady state solvent mass balance equation was solved numerically with experimental concentration profiles to map spatiotemporal solvent velocities. We compare our experimentally derived results with predictions made with concentrated solution theory. We use the cation transference number as the only adjustable parameter to match experimental measurements of both concentration and solvent velocity. Our approach may be used to determine solvent velocity with any operando technique used to measure time-dependent ion concentration profiles.

Diffusion Characteristics of Dissolved Gases in Oil Under Different Oil Flow Circulations

The prediction of dissolved gas concentrations in oil can provide crucial data for the assessment of power transformer conditions and early fault diagnosis. Current simulations mainly focus on the generation and accumulation of characteristic gases, lacking a global perspective on gas diffusion and dissolution. This study simulates the characteristic gases produced by typical faults at different flow rates. Using ANSYS 2022 R1 simulation software, a gas–liquid two-phase model is established to simulate the flow and diffusion of characteristic gases under fault conditions. Additionally, a fault-simulation gas production test platform was built based on a ±400 kV actual converter transformer. The experimental data show good consistency with the simulation trends. The results indicate that the diffusion of dissolved gases in oil is significantly affected by the oil flow velocity. At higher flow rates, the characteristic gases primarily move within the oil tank along with the oil circulation, leading to a faster rate of gas dissolution in oil and a shorter time to reach equilibrium within the tank. At lower flow rates, the diffusion of characteristic gases depends not only on oil flow circulation but also on self-diffusion driven by concentration gradients, resulting in a nonlinear change in gas concentration across various monitoring points.