Viscosity Loss Research Articles

Research on the Mechanism and Prediction Model of Pressure Drive Recovery in Low-Permeability Oil Reservoirs

China boasts significant reserves of low-permeability oil reservoirs, and the economic and efficient development of these reservoirs plays a crucial role in enhancing oil and gas production. However, the “difficult injection and difficult recovery” issue in low-permeability oil reservoirs is a major challenge. To address this, research is conducted on the mechanism of pressure drive based on the mathematical model of oil-water seepage in low-permeability reservoirs and the model of fracture permeability. The study finds that pressure drive technology, by directly delivering the pressure drive agent deep into the low-permeability reservoir, effectively prevents viscosity loss and adhesion retention of the agent in the near-wellbore area. This technology expands the swept volume, improves oil washing efficiency, replenishes formation energy, and facilitates the gathering and production of scattered remaining oil. For reservoirs with higher permeability, pressure drive yields quick results, and high-pressure water injection can be directly adopted for pressure drive to reduce costs. On the other hand, reservoirs with lower permeability have difficulty in water absorption, and the use of surfactant-based pressure drive can effectively reduce the seepage resistance of the reservoir, enhancing its water absorption capacity and improving development outcomes. Based on the mechanism of pressure drive development, further research is conducted on the production characteristics of pressure drive mines. Addressing the variability in pressure drive effects, big data analysis tools such as SHAP analysis and correlation analysis are employed to evaluate the main controlling factors of pressure drive in both new and old areas. Additionally, non-time series and time series pressure drive production forecasting models are established based on pressure drive data.

Pasting, structural properties, and in vitro digestibility of water chestnut (Eleocharis dulcis Burm. f., Cyperaceae) starch co-gelatinized with different hydrocolloids

Hydrocolloids have been widely used to modulate the processing properties of native starch, this study aimed to investigate the effects of carrageenan (KC), tamarind seed polysaccharide (TSP), and xanthan gum (XG) on the pasting, rheology, structural properties, and in vitro digestibility of water chestnut starch (WCS). The pasting results showed that XG increased the peak viscosity (PV), trough viscosity (TV), final viscosity (FV) and breakdown viscosity (BD) of WCS gel, but decreased the setback (SB), TSP significantly increased SB. The rheological data found that KC, TSP and XG increased the apparent viscosity and storage modulus (G') and loss modulus (G'') of WCS, which gradually increased by the concentration gradient of hydrocolloids. The hardness of starch with KC increased from 171.52g to 323.36g, and the addition of 0.3% KC and 0.5% KC enhanced the thermal stability. Furthermore, XG significantly increased the resistant starch (RS) content and decreased the hydrolysis rate of starch. These results will provide theoretical references for expanding the application range of WCS.

Lubrication flow law and cooling mechanism considering cavitation in mechanical seals with Rayleigh step pattern

The purpose of this research is to obtain the cavitation cooling characteristics and flow law in mechanical seals with Rayleigh step pattern. A new cooling approach has been proposed, which is of great significance to preventing liquid film vaporization and limiting thermal deformation of sealing face. Based on the previous literatures focused only on cavitation or viscous heat, the thermohydrodynamic lubrication (THD) and hydrodynamic lubrication (HD) numerical models with cavitation in mechanical seals are developed to obtain the cavitation cooling characteristics and flow mechanism by FLUENT software. The results show that the liquid film cavitation occurs severely in the reverse Rayleigh step and generates a remarkable local cooling effect to the fluid film and sealing faces, which leads to a temperature rise reduction of up to 39.2% and a leakage rate reduction of up to 72.7%. Meanwhile, the high-temperature zone at downstream side migrates upstream, especially, forming temperature valley and peak zones at liquid film rupture and reformation boundaries. The cooling level is controlled by the intensity and area of cavitation. Moreover, the vapor phase block of cavitation, the pressure flow and the shear flow collectively generate a vortex flow behind the cavitation zone in the reverse Rayleigh step. The center and intensity of vortices are closely related to the cavitation area, viscous heat, shear flow and pressure flow. Under THD conditions, the vortex is enhanced due to the viscosity loss and the small cavitation area. The cavitation, viscous heat and vortex flow have important effects on the sealing performance.

Study on the Shear Degradation Law of Polymer Drag Reducing Agents

Abstract The use of drag reducing agents in oil pipeline transportation can reduce driving energy consumption and has certain energy-saving benefits. However, irreversible degradation occurs when polymer drag reducing agents are sheared through pumping. In order to study the viscosity loss of polymer drag reducing agents caused by mechanical shear during the pumping process, the combination of methods such as a rotational rheometer and an indoor drag reducing loop testing system was used to test and analyze the rheological and drag reducing properties of the drag reducing agent solution, and to study the shear degradation law of polymer drag reducing agent solution under different conditions. The results showed that the shear stress of the polymer drag reducing agent solution increased with the increase in shear rate, and the viscosity increased with the increase of shear stress, showing shear thickening. When the polymer drag reducing agent solution is not sheared, the drag reduction rate increases and then decreases with the increase of concentration, and reaches the maximum value at 20 mg·L−1. However, after shear, the drag reduction performance decreases rapidly, but the high concentration still maintains a good drag reduction rate. The research results provide a theoretical basis for improving the performance of polymer drag reducing agents under different operating conditions and play a guiding role in further improving and perfecting the polymer drag reducing technology.

Enhancing the mouthfeel of non-alcoholic beers: The influence of dextrin and arabinoxylan on perceived viscosity and body

Carbohydrates in beer are recognized for enhancing viscosity. Increasing their levels during the production of non-alcoholic beers (NABs) may serve as a valuable strategy to compensate for the loss in viscosity and palate fullness due to dealcoholization. This study assessed the effectiveness of dextrin and arabinoxylan (AX) in this respect, within their content range and with the structural characteristics found in commercial beers. The addition of purified dextrin and AX isolates to water, pilsner beer, and NAB revealed that 30 g/L dextrin or 1.5 g/L high-molecular-weight AX (HMW AX) was required to compensate for the dealcoholization-induced viscosity loss. Evaluating the effect of both components on perceived palate fullness and mouthfeel involved producing eight NABs with varying dextrin and HMW AX levels and assessing them by a trained sensory panel (n = 12). Dextrin and HMW AX combined significantly increased palate fullness (p < 0.10), while solely increasing either was insufficient to achieve this effect. Increasing beer viscosity by itself could not fully compensate for palate fullness loss due to dealcoholization. Thus, adjusting NAB production to elevate HMW AX and dextrin levels simultaneously emerges as a viable strategy for improving palate fullness, offering valuable insights for brewers towards enhanced NAB quality.

Innovation in Idli batter preservation through betel leaf essential oil-based nanoemulsion: Evaluating fermentation kinetics and physicochemical analysis

Extending shelf life while maintaining quality of traditional fermented foods is a major challenge. This study aimed to investigate betel leaf essential oil nanoemulsions (BLEONE) as a clean-label preservative for fermented Idli batter. BLEONE (1–10 %) was incorporated into Idli batter and evaluated for physicochemical properties, sensory quality, and shelf life during ambient (30 °C) and refrigerated (4 °C) storage. Kinetic modeling and analysis of variance (ANOVA) were used to quantify BLEONE's effects on fermentation dynamics and assess statistical significance. At 5 % concentration, BLEONE significantly (p < 0.05) maintained pH (4.5 vs 3.8 in control), restricted acidity increases (1.2 % vs 1.8 % in control), and limited viscosity loss (15 % vs 40 % in control) during fermentation compared to untreated and sodium benzoate-treated samples. Sensory analysis showed acceptable attributes up to 5 % BLEONE. Optimally fermented Idli batter with 5 % BLEONE extended shelf-life to 7 days at 30 °C and 25 days at 4 °C storage. The nanoemulsion's enhanced antimicrobial efficacy and controlled release of active compounds significantly improved safety and quality preservation during storage. This research demonstrates the potential of essential oil nanoemulsions as effective clean-label preservatives for traditional fermented foods, offering a promising solution to extend shelf life while maintaining product quality.

Effect of ionic liquids on the polymerization behavior of acrylamide‐based copolymers

AbstractTo explore the influence of reaction medium on the copolymerization behavior of acrylamide‐based copolymers, three types of copolymers (P(AM‐St)(ILs), P(AM‐MMA)(ILs), and P(AM‐AMPS)(ILs)) were synthesized by combining insoluble, slightly soluble, and easily soluble monomers with acrylamide in the 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM]BF4) reaction medium. The reactivity ratio, Fourier transform infrared spectroscopy, 1H NMR spectroscopy, elemental analysis, and scanning electron microscopy were employed to characterize the copolymers' properties. The results indicated that in [BMIM]BF4 copolymerization, the reactivity ratio of AM and St in P(AM‐St)(ILs) decreased, the reactivity ratio of AM in P(AM‐MMA)(ILs) will increase. While the reactivity ratio of MMA will decrease. The reactivity ratio of AM in P(AM‐AMPS)(ILs) will increase and the reactivity ratio of AMPS will decrease. The distribution of AM and St segments in P(AM‐St)(ILs) molecular chains is more uniform and compact. When AM polymerizes with hydrophobic monomers (St) in [BMIM]BF4, its copolymer solution exhibits lower viscosity loss rates in temperature, shear, and salt resistance tests. Therefore, ionic liquids are more suitable as reaction media for the synthesis of hydrophobic‐modified polyacrylamides, which facilitate a more uniform distribution of hydrophobic monomers within the copolymer chains and exhibit enhanced resistance to temperature, salt, and shear stresses.

A systematic study of the effect of nano-additives on the functional characteristics of hydraulic fracturing gels

Currently, the main technique for the development of low-permeability reservoirs is hydraulic fracturing technology. To further enhance its efficiency and reduce costs, it is necessary to improve the formulations and properties of liquids used for hydraulic fracturing. The use of nanoparticles for these purposes may become one of the promising directions. In this paper, for the first time, the effect of concentration, size, material and form of nano-additives on colloidal stability, viscosity, wetting characteristics and filtration losses of cross-linked gels for hydraulic fracturing were studied systematically. In the preparation of cross-linked gels, a guar gum biopolymer was used as a typical gel-forming agent and sodium tetraborate in glycerin was applied as a cross-linker. Spherical nanoparticles of silicon oxide and aluminum oxide, single-walled carbon nanotubes, and aluminum oxide nanofibers were employed as nano-additives. The average size of the nanoparticles varied from 11 to 216 nm. The concentration of nano-additives in the gels ranged from 0.01 to 0.8 wt%. The temperature was changed from 25 to 70 °C. The research has shown that the dependences of the functional characteristics of nano-modified gels on the concentration and size of nano-additives are non-monotonic in nature. The optimal concentration of nanoparticles to control the properties of the gel is in the range of 0.05–0.2 wt%, and the optimal average size is 70–80 nm. With these parameters, nanomaterial additives can radically change the properties of hydraulic fracturing gels (increase the effective viscosity several times, reduce filtration losses tenfold and significantly change the hydrophobicity).

Production and Evaluation of Hydroxypropyl Starch as a Viscosifying Agent for Enhanced Oil Recovery

AbstractIn this study, starch was obtained from rice wastes and the maximum extraction yield was 90.95 %. Chemical modification reactions were carried out by hydroxypropylation to obtain a modified starch extract, named 005A, soluble in synthetic injection brine. Extract 005A had a modified starch concentration of 1.24 %, with a pseudoplastic rheological profile and viscosities of 325.54 cP and 121.03 cP at temperatures of 25 and 60 °C, respectively. The application of extract 005A was evaluated by injectivity/filterability tests, which indicated a good filtration rate and viscosity loss of 3.81 % when passing the fluid through the filtering membrane. Stability tests indicated that the 005A extract had a viscosity loss of 21.35 %, at the temperature of 60 °C, after 60 days. The application of this extract enabled additional mineral oil recovery of 12.19 % in simulated core flooding tests. Therefore, the extract of hydroxypropyl starch is a promising viscosifying agent for Enhanced Oil Recovery (EOR) fluids.

Achilles tendon enthesis behavior under cyclic compressive loading: Consequences of unloading and early remobilization

The Achilles tendon enthesis (ATE) anchors the Achilles tendon into the calcaneus through fibrocartilaginous tissue. The latter is enriched in type II collagen and proteoglycans (PGs), both of which give the enthesis its capacity to withstand compressive stress. Because unloading and reloading induce remodeling of the ATE fibrocartilage (Camy et al., 2022), chronic changes in the mechanical load could modify the mechanical response under compressive stress. Therefore, we investigated the ATE fatigue behavior in mice, under cyclic compressive loading, after 14 days of hindlimb suspension and 6 days of reloading. In addition, we performed a qualitative histological study of PGs in ATE fibrocartilage. The mechanical behavior of ATE was impaired in unloaded mice. A significant loss of 27 % in Δd (difference between the maximum and minimum displacements) was observed at the end of the test. In addition, the hysteresis area decreased by approximately 27 % and the stiffness increased by over 45 %. The increased stiffness and loss of viscosity were thrice and almost twice those of the control, respectively. In the reloaded entheses, where the loss of Δd was not significant, we found a significant 28 % decrease in the hysteresis area and a 26 % increase in stiffness, both of which were higher regarding the control condition. These load-dependent changes in the mechanical response seem partly related to changes in PGs in the uncalficied part of the ATE. These findings highlight the importance of managing compressive loading on ATE when performing prophylactic and rehabilitation exercises.

Helium screw compressor for 5tpd large-scale hydrogen liquefier

Liquid hydrogen has promising applications in various industries. As an important heart role, compressors are essential for efficient hydrogen liquefaction. This study introduced a novel profile screw compressor employed in large-scale hydrogen liquefaction processes. The development addressed the challenges associated with large-scale rotors, high pressure differences, and demanding capacity or torque requirements. By utilizing a 5/7-lobe combination of male to female rotors, this technology effectively tackled issues related to rotor dynamics, such as heavy-load rotor stiffness and dynamic balance. The profile design followed hydrodynamics principles, reducing viscosity loss and oil–gas flow loss at high speeds, large flow rates, and significant pressure differences. The profile curve’s curvature and geometric configuration were tailored to the specific pressure state during compression. In high-pressure areas, the profile remained relatively flat to maintain machining accuracy. While in low-pressure areas, the curvature was increased, and the meshing clearance was reduced to minimize helium leakage. Experimental tests conducted under conditions similar to actual hydrogen liquefaction processes have successfully validated the theoretical profile design and the newly developed multi-point oil injection cooling technologies. These advancements have led to an impressive isothermal efficiency of 58.1 % for the entire screw set. Furthermore, the stability and reliability of the compressor were verified through noise and vibration signal testing. The results demonstrated that the compressor operated with noise levels below 96 dB (A) and vibration levels below 7 mm/s, further ensured its suitability for large-scale cryogenic applications. These compressors have successfully run stably on the 5.17 tpd (ton per day) hydrogen liquefier. Overall, this research would significantly contribute to the advancement of screw compressors and large-scale cryogenic technology.

Viscosity reduction of xanthan gum through free radical mechanisms mediated by ascorbic acid

Xanthan gum (XG) is a widely used thickener known for its high viscosity and excellent stability. However, the presence of ascorbic acid (AA) leads to a clear decrease in its viscosity, thereby affecting the application of xanthan gum in food products containing AA. Therefore, the aim of this study was to uncover the mechanism by which AA reduces the viscosity of xanthan gum. Ascorbic acid (0.1 mmol/L) caused a viscosity loss reaching up to 96% for xanthan gum solutions (2 g/L). The reaction was further enhanced by heating at 60 °C for 1 h without stirring, a weakly acidic system at pH 5.4, and the addition of hydrogen peroxide or metal ions (Fe2+ and Cu2+). Interestingly, AA induction produces free radicals and changes in their content correlate with a decrease in XG viscosity. Moreover, removing dissolved oxygen by heating and nitrogen purging treatment effectively reduced AA-derived free radical levels and prevented the decrease in XG viscosity. The decrease in viscosity of XG caused by AA involved its free radicals generated through an oxygen-dependent pathway.

Effect of Chemical Composition of Metal-Organic Crosslinker on the Properties of Fracturing Fluid in High-Temperature Reservoir.

To investigate the effect of the chemical composition of a metal-organic crosslinker on the performances of fracturing fluid in high-temperature conditions, four zirconium (Zr) crosslinkers and one aluminum-zirconium (Al-Zr) crosslinker with a polyacrylamide were used. The crosslinkers possessed the same Zr concentration, but they differed in component amounts and the order of the addition of the crosslinker components, leading to different chemical compositions in the crosslinkers. The fracturing fluids prepared by different tested crosslinkers were compared in terms of properties of rheological behavior, sand-carrying ability, microstructure, and gel breaking characteristics. The results showed that the fracturing fluids prepared by zirconium lactic acid, ethanediamine, and sorbitol crosslinkers offered the slowest viscosity development and highest final viscosity compared to the zirconium lactic acid crosslinker and the zirconium lactic acid and ethanediamine crosslinker. The zirconium sorbitol, lactic acid, and ethanediamine crosslinker exhibited a faster crosslinking rate and a higher final viscosity than the zirconium lactic acid, ethanediamine, and sorbitol crosslinker; the crosslinker showed crosslinking density and crosslinking reactivity, resulting in more crosslinking sites and a higher strength in the fracturing fluid. The Al-Zr-based crosslinker possessed better properties in temperature and shear resistance, viscoelasticity, shear recovery, and sand-carrying ability than the Zr-based crosslinker due to the synergistic crosslinking effect of aluminum and zirconium ions. The tertiary release gelation mechanism of the Al-Zr-based fracturing fluid achieved a temperature resistance performance in the form of continuous crosslinking, avoiding the excessive crosslinking dehydration and reducing viscosity loss caused by early shear damage. These results indicated that the chemical compositions of metal-organic crosslinkers were important factors in determining the properties of fracturing fluids. Therefore, the appropriate type of crosslinker could save costs without adding the additional components required for high-temperature reservoirs.

Pore-scale flooding experiments reveal the thermally regulated flow fields of the curdlan solution

Polymers can enhance oil recovery depending on viscoelasticity. In a field, during polymer flow through porous strata, continuous shear forces result in severe viscosity loss. However, polymers with great shear resistance result in limited migration distance. One solution to the above dilemma is to regulate viscosity, which enables a polymer to migrate long distances through pores with low viscosity and subsequently maintain high viscosity in deep reservoirs. The viscosity of curdlan can be regulated by changing temperature. By curdlan, we mean a biopolymer that shows applications in food industry. However, regarding oil reservoirs, it is unclear whether curdlan viscosity can be effectively regulated in pores. To reveal the feasibility of curdlan viscosity regulation to enhance oil recovery, flooding experiments combined with micro-particle image velocimetry were conducted in a two-dimensional pore network to investigate flow fields of curdlan solutions (0.25%, 0.5%, 1%, and 2%, w/v) at different temperatures (40, 65, and 85 °C). As a result, at 40 °C, curdlan solution (0.25%) easily migrated with low viscosity loss and low adsorption [88.3% original throat diameter (OTD)], and the mobility of curdlan was higher than hydrolyzed polyacrylamide. After heating (65 °C), the viscoelasticity, adsorption (55.1% OTD), and flow resistance (injection pressure, 2.2–8.8 kPa) of curdlan increased, and the greater adsorption capacity of curdlan than xanthan gum led to a more homogeneous flow field [average velocity ratio (Rm), from 2.6 to 1.1]. Since a homogeneous flow field indicated better sweep efficiency, curdlan regulated by temperature could achieve both long-distance migration and improved sweep efficiency in deep strata. These results suggested that viscosity regulation by curdlan could potentially improve oil recovery in water-flooded reservoirs.

Rheological properties of magnesium bentonite and sepiolite suspensions after dynamic ageing at high temperatures

Abstract The rheological properties of three Na-activated, trioctahedral Mg-bentonites (hectorite clay from the CMS Source Clay Project repository, saponite clay from Spain and stevensite clay from Rhassoul, Morocco) and a sepiolite clay from Greece were examined after dynamic ageing at temperatures up to 230°C. The 5% w/v suspensions were prepared by dispersing the clay mineral samples in distilled water. The suspensions underwent dynamic, thermal ageing for 16 h before determination of the viscosity, filtration loss, filter cake thickness and pH and the concentration of dissolved Na+ and Mg2+. Thermal ageing contributed to the dispersion of clay particles, with a direct effect on plastic and apparent viscosity, introducing pseudoplastic behaviour. With the exception of the stevensite clay at 230°C that displayed limited dissolution at 230°C and partial conversion to kerolite, the clays were stable at high temperatures. The Na-activation of all clays except for stevensite was not adversely affected by thermal ageing. Thermal ageing of stevensite at 230°C facilitated Na exchange and yielded suspension with high viscosity and low filtrate loss. Only the suspensions of hectorite and those of stevensite aged at 230°C met with American Petroleum Institute specifications. The thermal behaviour and rheological properties of the clays might be interpreted according to the intrinsic properties of the clay minerals, such as layer charge and charge distribution.

Understanding Plugging Agent Emplacement Depth with Polymer Shear Thinning: Insights from Experiments and Numerical Modeling

Polymer-plugging agents are widely employed in profile control and water-plugging measures, serving as a crucial component for efficient reservoir development. However, quantitatively monitoring the emplacement depth of polymer-plugging agents in low-permeability and high-permeability layers remains a challenging bottleneck. Presently, insufficient attention on shear thinning, a critical rheological property for water shut-off and profile control, has limited our understanding of polymer distribution laws. In this study, polymer shear-thinning experiments are firstly conducted to explore polymer variations with flow rate. The novelty of the research is that varying polymer viscosity is implemented instead of the fixed-fluid viscosity that is conventionally used. The fitted correlation is then integrated into the 2D and 3D heterogeneous numerical models for simulations, and a multivariate nonlinear regression analysis is performed based on the simulation results. The results show that lower polymer emplacement depth ratios corresponded to higher viscosity loss rates under the same flow rate. An increase in the initial permeability ratio corresponds to a decrease in the emplacement ratio, along with a reduction in the fraction of the plugging agent penetrating the low permeability formations. The model was applied to the Kunan Oilfield and demonstrated a polymer reduction of approximately 3000 tons compared to traditional methods. Despite the slightly complex nature of the multivariate nonlinear mathematical model, it presents clear advantages in controlling plugging agent distribution and estimating dosage, laying good theoretical ground for the effective and efficient recovery of subsurface resources.

Evaluation of nanoparticle effect on heavy and light wellbore cement slurries

Cementing around the casing in oil and gas wellbores provides multiple benefits such as proper zonal isolation, casing support, and prevention of fluid migration. Wellbore cement is an important part of the completion and abandonment process. However, wellbore cement has some drawbacks such as micro-annuli formation or loss of zonal isolation. Nanoparticles (NPs) have been shown to improve the characteristics of wellbore drilling fluids but have not been used extensively in cement. The objective of this paper is to show the effect of NPs’ concentration on wellbore cement characteristics such as thickening time, viscosity, and fluid loss properties. Nanoparticle barite and magnetite were added to heavy cement and bentonite was added to light cement in intervals of 1, 3, and 5 % by weight of cement to test the resulting cement characteristics. The results showed that the thickening time increased for all concentrations of nanoparticles, except for the 5 % magnetite. The resulting yield stress of both cement mixtures increased for all concentrations of nanoparticles. The viscosity for all concentrations of nanoparticles in the heavy cement was greater than the control case, while no change in viscosity was seen with the light cement. Fluid loss generally decreased by increasing nanoparticle concentrations for both heavy and light cement. The results of this work in combination with results from the literature show that the addition of barite, magnetite, or bentonite nanoparticles can enhance wellbore cement without diminishing the pumpability and curing time.

Evaluation of the Thermal, Chemical, Mechanical, and Microbial Stability of New Nanohybrids Based on Carboxymethyl-Scleroglucan and Silica Nanoparticles for EOR Applications.

Scleroglucan (SG) is resistant to harsh reservoir conditions such as high temperature, high shear stresses, and the presence of chemical substances. However, it is susceptible to biological degradation because bacteria use SG as a source of energy and carbon. All degradation effects lead to viscosity loss of the SG solutions, affecting their performance as an enhanced oil recovery (EOR) polymer. Recent studies have shown that nanoparticles (NPs) can mitigate these degradative effects. For this reason, the EOR performance of two new nanohybrids (NH-A and NH-B) based on carboxymethyl-scleroglucan and amino-functionalized silica nanoparticles was studied. The susceptibility of these products to chemical, mechanical, and thermal degradation was evaluated following standard procedures (API RP 63), and the microbial degradation was assessed under reservoir-relevant conditions (1311 ppm and 100 °C) using a bottle test system. The results showed that the chemical reactions for the nanohybrids obtained modified the SG triple helix configuration, impacting its viscosifying power. However, the nanohybrid solutions retained their viscosity during thermal, mechanical, and chemical degradation experiments due to the formation of a tridimensional network between the nanoparticles (NPs) and the SG. Also, NH-A and NH-B solutions exhibited bacterial control because of steric hindrances caused by nanoparticle modifications to SG. This prevents extracellular glucanases from recognizing the site of catalysis, limiting free glucose availability and generating cell death due to substrate depletion. This study provides insights into the performance of these nanohybrids and promotes their application in reservoirs with harsh conditions.

Microbubble-enhanced transcranial MR-guided focused ultrasound brain hyperthermia: heating mechanism investigation using finite element method

Recently, our group developed a synergistic brain drug delivery method to achieve simultaneous transcranial hyperthermia and localized blood–brain barrier opening via MR-guided focused ultrasound (MRgFUS). In a rodent model, we demonstrated that the ultrasound power required for transcranial MRgFUS hyperthermia was significantly reduced by injecting microbubbles (MBs). However, the specific mechanisms underlying the power reduction caused by MBs remain unclear. The present study aims to elucidate the mechanisms of MB-enhanced transcranial MRgFUS hyperthermia through numerical studies using the finite element method. The microbubble acoustic emission (MAE) and the viscous dissipation (VD) were hypothesized to be the specific mechanisms. Acoustic wave propagation was used to model the FUS propagation in the brain tissue, and a bubble dynamics equation for describing the dynamics of MBs with small shell thickness was used to model the MB oscillation under FUS exposures. A modified bioheat transfer equation was used to model the temperature in the rodent brain with different heat sources. A theoretical model was used to estimate the bubble shell’s surface tension, elasticity, and viscosity losses. The simulation reveals that MAE and VD caused a 40.5% and 52.3% additional temperature rise, respectively. Compared with FUS only, MBs caused a 64.0% temperature increase, which is consistent with our previous animal experiments. Our investigation showed that MAE and VD are the main mechanisms of MB-enhanced transcranial MRgFUS hyperthermia.

Characterizing interregional differences in the rheological properties and composition of rat small intestinal mucus.

The mucus layer in the small intestine is generally regarded as a barrier to drug absorption. However, the mucus layer is a complex system, and presently, only a few studies have been conducted to elucidate its physicochemical properties. The current study hypothesizes that the mucus layer contains solubility-enhancing surfactants and thus might aid the oral absorption of poorly water-soluble drugs.Mucus was sampled from sections of the small intestine of fasted rats to analyze the rheological properties and determine the mucus pH and concentrations of proteins and endogenous surfactants, i.e., bile salts, polar lipids, and neutral lipids.The mucus layer in the two proximal sections of the small intestine exhibited different rheological properties such as higher zero-shear viscosity and lower loss tangent and higher protein concentrations compared to all subsequent sections of the small intestine. The pH of the mucus layer was stable at ~ 6.5 throughout most of the small intestine, but increased to 7.5 in the ileum.The bile salt concentrations increased from the duodenum (16.0 ± 2.2mM) until the mid jejunum (55.1 ± 9.5mM), whereas the concentrations of polar lipids and neutral lipids decreased from the duodenum (17.4 ± 2.2mM and 37.8 ± 1.6mM, respectively) until the ileum (4.8 ± 0.4mM and 10.7 ± 1.1mM, respectively).In conclusion, the mucus layer of the rat small intestine contains endogenous surfactants at levels that might benefit solubilization and absorption of orally administered poorly water-soluble drugs.