Increasing Shear Rate Research Articles

Development of kiwi fruit leather incorporated with hydrocolloids and betacyanin microcapsules: Rheological behaviour and release kinetics of betacyanin

The kiwi fruit leather incorporated with betacyanin microcapsules was prepared using three hydrocolloids namely xanthan gum, gellan gum, and guar gum. The four-kiwi fruit puree prepared for the study were kiwi fruit puree without hydrocolloid (CP), with xanthan gum (XE), with gellan gum (EP), and with guar gum (UP). The influence of various hydrocolloids and temperatures on rheological properties of kiwi fruit puree was investigated using the Cross, Carreau, and modified Powell model. The apparent viscosity was decreased with increase in shear rate and rise of temperature. The incorporation of hydrocolloid also increased viscosity of prepared puree. Cross model (R2>0.989) found to fit the apparent viscosity with respect to shear rate. The flow behaviour index of four kiwi fruit puree samples was found to be less than one depicting pseudoplastic fluid with shear thinning behaviour. For dynamic rheology study in the frequency range of 1–60 rad/s, the storage modulus was higher than loss modulus at specific frequency that implies, elastic properties of puree were dominant over the viscous ones suggesting the weak gel-like network of kiwi fruit puree. The glass transition temperature of prepared kiwi fruit leathers ranged from 59-64°C. The in vitro betacyanin release from the leather sample was studied and Peppas-Sahlin model was observed to be one of the ideal model when compared with the other kinetic models. The development of kiwi fruit leather with hydrocolloids and betacyanin microcapsules represented a successful strategy to create a functional snack that combines health benefits with consumer-desirable sensory attributes.

Rheo-impedance behavior of cellulose nanofibers produced by mechanical processing

AbstractCNFs are one of the renewable and the sustainable resources with low environmental impact and have various characteristics such as increased strength and weight reduction when added to resins. Since CNFs are one of the new materials that can fulfill the goals of the Sustainable Development Goals (hereafter abbreviated as SDGs), many researchers have been studying the nano-fibrillation of wood fibers. From the viewpoint of SDGs, it is necessary to avoid using a large amount of chemical agents and consuming a large amount of energy for the production of CNFs. To realize these requirements, it is important to find a way to industrially utilize CNFs containing insufficiently nanosized fibers, and for these purposes, it is essential to evaluate the physical properties of these CNFs from multiple perspectives. Cellulose fibers are intrinsically insulating materials, but how their electrochemical properties are changed by nano-fibrillization has been little studied. Therefore, we decided to clarify the relationship between the size of CNFs and the electrochemical impedance properties of the CNF suspensions containing un-fibrillated fibers, which were prepared by a wet refinement system. The fiber diameter remained constant as the number of mechanical treatments (hereafter referred to as the “number of collisions”) increased. On the other hand, the cumulative medium volume diameter, D50, defined as the apparent fiber length (hereafter referred to as the “fiber length”, in microns), significantly decreases with the increasing number of collisions. The rheo-impedance |Z| of the CNF suspension remained nearly constant in the intermediate frequency range of 103–106 Hz, even if the internal structure of the system was deformed by the increasing shear rate. This means that the electrochemical properties of the CNFs are independent of the changes in the macroscopic aggregation structure. Furthermore, the internal resistance R1 calculated from the impedance |Z| characteristics (Nyquist plot) became decreased with the increasing number of collisions, indicating a proportional relationship between the resistance R1 and the CNF fiber length, D50. This suggests that R1 related to the resistance caused by the electrolyte in the suspensions or the protons dissociated by the hydration of the hydroxyl groups of the cellulose molecule as they move across the gaps between the microfibrils. Based on these results, it appears that the electrochemical properties of the CNF suspensions are independent of the changes in the macroscopic aggregation structure and simply depend on the fiber length, in other words, the electrochemical properties are a useful method for indirectly evaluating the fiber length of the CNFs.

Shear-Sensing by C-Reactive Protein: Linking Aortic Stenosis and Inflammation.

CRP (C-reactive protein) is a prototypical acute phase reactant. Upon dissociation of the pentameric isoform (pCRP [pentameric CRP]) into its monomeric subunits (mCRP [monomeric CRP]), it exhibits prothrombotic and proinflammatory activity. Pathophysiological shear rates as observed in aortic valve stenosis (AS) can influence protein conformation and function as observed with vWF (von Willebrand factor). Given the proinflammatory function of dissociated CRP and the important role of inflammation in the pathogenesis of AS, we investigated whether shear stress can modify CRP conformation and induce inflammatory effects relevant to AS. To determine the effects of pathological shear rates on the function of human CRP, pCRP was subjected to pathophysiologically relevant shear rates and analyzed using biophysical and biochemical methods. To investigate the effect of shear on CRP conformation in vivo, we used a mouse model of arterial stenosis. Levels of mCRP and pCRP were measured in patients with severe AS pre- and post-transcatheter aortic valve implantation, and the presence of CRP was investigated on excised valves from patients undergoing aortic valve replacement surgery for severe AS. Microfluidic models of AS were then used to recapitulate the shear rates of patients with AS and to investigate this shear-dependent dissociation of pCRP and its inflammatory function. Exposed to high shear rates, pCRP dissociates into its proinflammatory monomers (mCRP) and aggregates into large particles. Our in vitro findings were further confirmed in a mouse carotid artery stenosis model, where the administration of human pCRP led to the deposition of mCRP poststenosis. Patients undergoing transcatheter aortic valve implantation demonstrated significantly higher mCRP bound to circulating microvesicles pre-transcatheter aortic valve implantation compared with post-transcatheter aortic valve implantation. Excised human stenotic aortic valves display mCRP deposition. pCRP dissociated in a microfluidic model of AS and induces endothelial cell activation as measured by increased ICAM-1 and P-selectin expression. mCRP also induces platelet activation and TGF-β (transforming growth factor beta) expression on platelets. We identify a novel mechanism of shear-induced pCRP dissociation, which results in the activation of cells central to the development of AS. This novel mechanosensing mechanism of pCRP dissociation to mCRP is likely also relevant to other pathologies involving increased shear rates, such as in atherosclerotic and injured arteries.

Influence of the rigidity of the backbone and arms on the dynamical and conformational properties of the comb polymer in shear flow.

The dynamical and conformational properties of the comb polymer with various rigidities of the backbone and arms in steady shear flow are studied by using a hybrid mesoscale simulation approach that combines multiparticle collision dynamics with standard molecular dynamics. First, during the process of the comb polymer undergoing periodic tumbling motion, we find that the rigidity of the arms always promotes the tumbling motion of the comb polymer, but the rigidity of the backbone shifts from hindering to promoting it with increasing the rigidity of the arms. In addition, the comb polymer transitions from vorticity tumbling to gradient tumbling with the increase in shear rate. Second, the range of variation of the end-to-end distance of the backbone and the average end-to-end distance of the arms increases with the increase in the rigidity of the arms and backbone, respectively, and the range of both changes grows with the increase in shear rate. Furthermore, as the rigidity increases, the moldability of the comb polymer decreases and the orientation angle of the comb polymer increases.

Reverse Nonequilibrium Molecular Dynamics Simulations of a Melt of Kremer-Grest Type Model under Fast Shear.

Although the reverse nonequilibrium molecular dynamics (RNEMD) simulation method has been widely employed, the range of applicability is yet to be discussed. In this study, for the first time, we systematically examine the method against an unentangled melt of the Kremer-Grest type chain. The simulation results indicate that as the shear rate increases, the temperature and density become inhomogeneous. However, the average viscosity remains consistent with the results obtained using the SLLOD method under homogeneous temperature and density. We also confirm that the temperature-density inhomogeneity does not significantly affect polymer conformation.

Rheological behavior of deep eutectic solvent promoted methane hydrate formation

Natural gas hydrates are recognized as a crucial and sustainable energy resource. The formation, dissociation, and flow properties of CH4 hydrate from deep eutectic solvents (DESs) are investigated using a high-pressure rheometer. In this work, rheological experiments are performed using two DESs namely, tetrabutylammonium bromide + ethylene Glycol (TBAB + EG, DES1) and methyltriphenylphosphonium bromide + ethylene Glycol (MTPB + EG, DES2) at 1 wt% concentration, 274 K temperature and 8 MPa pressure. The hydrate formation starts around 1.7 h for DES1 and around 4 h for DES2. Pressure and viscosity of the slurry are analyzed while methane hydrate forms and dissociates. The pressure drop experienced during hydrate formation is roughly 1.4 MPa for DES1 and 1.7 MPa for DES2. Further, viscosity profiles are analyzed for both DESs with varying shear rate. The viscosity gradually decreases as the shear rate increases. At equilibrium conditions of pure CH4, a spike is observed during dissociation. The rheological data is further analyzed with Cross model to validate the shear-thinning behavior of methane hydrate.

Wax crystal dynamics and viscosity abnormal reduction in asphaltene-containing waxy oil at low temperatures

A micro-rheological integration experiment was conducted on model oils without asphaltene and with 0.05 wt% asphaltene. The study examined the viscosity-temperature characteristics of both model oils under different cooling rates and shear rates. Significant changes were observed in the viscosity-temperature curve of the asphaltene-containing model oil. At low shear rates, a distinct wavelet peak was identified in the temperature range of 37-30 °C, where viscosity initially increased, then decreased, and subsequently increased again. This wavelet peak diminished with the increasing shear rate, eventually forming a “buffer platform”. The underlying mechanism was attributed to asphaltene altering the wax crystal behavior from “uniform precipitation network structure formation” to “formation of unstable large aggregates - dissociation into multiple small stable aggregates - growth into larger stable aggregates.” In addition, the wax precipitation rate remained constant in the model oil without asphaltene, while in the asphaltene-containing model oil, the rate significantly accelerated between 34.5 °C and 32.5 °C. And the asphaltenes promoted the formation of small wax crystal particles but inhibited the growth of wax crystal particles.

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.

Constructing stable emulsion gel from gelatin and sodium alginate as pork fat substitute: Emphasis on lipid digestion in vitro

This study aimed to develop a gelatin-sodium alginate (G-SA) emulsion gel that can efficiently hold corn oil, as a substitute for pork fat while controlling the digestive behaviors of lipids in vitro. UV, fluorescence, and circular dichroism spectra and surface hydrophobicity measurements of the G-SA mixtures indicated that gelatin and sodium alginate primarily form aggregates through hydrogen bonds and hydrophobic interactions, and the optimum gelatin-to-sodium alginate w/w ratio was identified as 1.9. The final emulsion gel contained 3.15% gelatin and 1.65% sodium alginate (w/w) with a corn oil content of 40% (w/w). G-SA emulsion gel had a higher proportion of polyunsaturated fatty acids (PUFAs, 53.95 g/100 g) than pork fat (15.17 g/100 g). In addition, the G-SA emulsion gel exhibited stable viscoelastic properties without storage and loss moduli changes at increasing shear rates. The G-SA emulsion gel had a higher melting temperature (42.63 °C) than pork fat (35.07 °C). In vitro digestion studies showed that corn oil had a higher free fatty acid release (40.32%) compared to the G-SA emulsion gel (12.66%) and pork fat (8.53%) (P<0.05), indicating that the digestibility of corn oil was reduced in the G-SA emulsion gel. Calcein release experiments revealed that G-SA emulsion gel released the least amount of calcein (P<0.05) during digestion at a slow rate. The G-SA emulsion gel, similar to pork fat, contained evenly distributed digestive particles encapsulating corn oil after in vitro gastric digestion, with the smallest particle size among the treatments. After the in vitro small intestinal digestion phase, the G-SA emulsion gel maintained small droplet sizes with bridging flocculation. The in vitro digesta of the G-SA emulsion gel contained a significantly higher proportion of PUFAs compared to pork fat (P<0.05). Consequently, the G-SA emulsion gel can be a potential substitute for pork fat, offering higher proportions of PUFAs, lower fat content, and controlled lipid digestion with reduced lipid digestibility.

Investigation of cellulose nanocrystals fabricated via sulfuric acid combined with deep eutectic solvent route

To make full use of tobacco waste in cigarette production and enhance resource utilization efficiency, cellulose nanocrystals (CNCs) were prepared by a method of sulfuric acid combined with a deep eutectic solvent. This method was compared with conventional methods, and the CNCs were thoroughly characterized. The results indicated that the yield of CNCs prepared by the sulfuric acid combined with a deep eutectic solvent method exceeded 26 %, with the highest yield reaching 29.5 %, surpassing the yields from two other methods of 12.5 %, 17.2 %, corresponding to sulfuric acid and sulfuric acid-oxalic acid, respectively. Scanning electron microscopy revealed a laminar morphology of CNCs, in which the CNCs maintained a cellulose type I structure with well-preserved crystallinity. In addition, CNCs prepared by the sulfuric acid combined with a deep eutectic solvent method exhibited good thermal stability, with maximum mass loss at temperature of 342.8 °C during third pyrolysis stage, higher than that of sulfuric acid at 316.7 °C and sulfuric acid-oxalic acid at 335.9 °C. Steady-state rheological testing revealed that the viscosity of the CNCs suspension decreased with an increasing shear rate, which is characteristic of pseudoplastic fluid shear thinning behavior. CNCs prepared by the sulfuric acid combined with DES method reduced the amount of sulfuric acid, and the yield was much higher than that of the other two methods. Moreover, the method using sulfuric acid combined with DES method was simple and safe, and the obtained CNCs had high thermal stability and viscosity, which expands the application prospects in biocomposite material fields.

Dynamic conformational response of von Willebrand factor to varying shear stress: A hybrid computational approach

This computational study examines the mechanobiological responses of von Willebrand Factor (vWF) to different shear stress levels, emphasizing the unique structural dynamics of its various domains. We introduce a novel coarse-grained model, representing each cluster of six amino acids as a bead, to synthesize the Lattice Boltzmann method with Brownian dynamics. This approach captures the vWF molecule’s conformational adaptability across a spectrum of shear rates, ranging from 5 to 5e + 7s−1, encompassing normal physiological flows to those resembling the high-shear environment of arterial stenosis.Our results reveal domain-specific responses of vWF, particularly in the A2 and A3 domains, which demonstrate significant elongation under elevated shear—reflecting their pivotal roles in clotting processes. Moreover, the study underscores the critical influence of random thermal forces on the molecule’s conformation, with simulations including these forces showing substantially greater conformational variability compared to those without.As shear rates increase, we observe a notable reorganization in the spatial arrangement of vWF domains. This reconfiguration is most evident in the increased separation between the A1 and D’D3 domains under high shear conditions, potentially enhancing the accessibility of platelets to key binding sites on vWF. These findings are paramount for a deeper understanding of vWF’s mechanical behavior in blood clotting and thrombosis, particularly the delicate balance between facilitating platelet adhesion and avoiding excessive stretching that could lead to thrombosis.Our work provides a foundation for future studies investigating vWF behavior in complex flow geometries and its interactions with other blood components. Such insights pave the way for more informed therapeutic strategies targeting vWF function in vascular health and disease, potentially leading to improved treatments for thrombotic disorders.

POLYMER BIOCOMPOSITES IN THE FORM OF HYDROGEL USED FOR THE TREATMENT OF PRESSURE SORES

This paper presents research related to the development of hydrogel polymer biocomposites (chitosan and alginate) with an analgesic medication (lidocaine hydrochloride). The pharmaceutical availability of lidocaine hydrochloride from the hydrogel preparations was evaluated for transdermal systems in accordance with the Polish Pharmacopoeia, XI Edition. The rheological tests showed that these preparations had the characteristics of non-Newtonian, pseudoplastic liquids, for which the viscosity decreases as the shear rate increases. The developed hydrogel preparations showed bacteriostatic and bactericidal effects against both Escherichia coli and Staphylococcus aureus. The release of lidocaine hydrochloride from the tested hydrogel was a complex process that followed first-order kinetics. The rate of release could be influenced by appropriate selection of the composition of the biocomposite.

Effect of Ozonation on Physicochemical Properties of Olive Oil Based Sunscreen Product

ABSTRACT Ozone serves as a potent oxidizing agent and a universal antiseptic, extensively employed in industries such as food, pharmaceuticals, and cosmetics due to its ability to dissolve in water and decompose into oxygen. This study aimed to treat virgin olive oil (VOO) with the ozonation process prior to its incorporation into a sunscreen product, and to discover any new potentially useful properties by comparing it with a sunscreen containing non-ozonated olive oil. The comparison was based on physicochemical properties, physical appearance, and sun protection factor (SPF) value. VOO treated with 0.017 mole/L ozone was tested for various physicochemical properties such as color, viscosity, refractive index, acid value, iodine value, peroxide value, saponification value, and oxidative stability. The composition was analyzed using gas chromatography (GC) and gas chromatography – mass spectrometry (GC-MS). The properties of ozonated olive oil (OOO) differed from VOO in terms of viscosity and flow behavior. An increase in shear rate significantly reduced the viscosity of OOO, while VOO maintained a constant viscosity and exhibited Newtonian flow behavior. When OOO was incorporated into sunscreen products, it enhanced the spreadability of the product on the skin, resulting in a significantly higher SPF value. The ability of a sunscreen to spread evenly on the skin and form a continuous thin film is crucial for effective protection against the sun’s rays. These findings highlight the potential of OOO in enhancing the photoprotection efficacy of sunscreen products by providing valuable data for its incorporation into formulations aiming to improve sun protection. Future research could focus on long-term stability and potential side effects of OOO in cosmetic formulations.

Large-scale molecular dynamics simulation and aggregate behavior research on asphalt

In this comprehensive study, a molecular dynamics (MD) model consisting of approximately 150,000 atoms was developed within the Strategic Highway Research Program (SHRP) framework to investigate the behavior of AAA asphalt, focusing on asphaltene aggregate dynamics behavior over a simulation time span of 0.282 microseconds. The findings reveal that the model achieves a stable state in terms of both energy and microstructure without significant changes or the formation of densely clustered molecules, despite the extensive simulation period. Notably, the patterns of asphaltene aggregation were found to significantly influence the MD system energy, with variations ranging from loosely organized structures due to dispersed asphaltenes to more structured, energy-efficient clusters formed by encapsulated asphaltene pentamers. The size of asphaltene aggregates emerged as a pivotal factor, affecting their encapsulation and leading to distinct formation patterns. Furthermore, the research highlighted that increasing shear rates prompt the depolymerization of asphaltene aggregates, shifting from large-scale structures to smaller ones and adapting dynamically to the flow conditions by aligning parallel to the shear direction. This study underscores the critical impact of asphaltene aggregate behavior and shear rates on the structural integrity and distribution within the asphalt model, offering profound insights into the MD of asphalt materials.

Foam Properties Evaluation under Harsh Conditions: Implications for Enhanced Eco-Friendly Underbalanced Drilling Practices

Summary Foam drilling offers advantages such as reduced formation damage and faster drilling in underbalanced drilling (UBD) operations. The efficacy of foam drilling is influenced by factors including pressure, temperature, salt content, foam quality, and pH levels. However, a gap exists in the evaluation of foam properties under rigorous conditions, particularly those involving high pH and mixed salt environments common in drilling scenarios, highlighting the need for further research. In this study, a high-pressure, high-temperature (HPHT) foam analyzer and rheometer were employed to examine the stability and rheological behavior of ammonium alchohol ether sulfate (AAES) foam under simulated alkaline drilling conditions. The foaming solution, designed to replicate such conditions, consisted of synthetic seawater (SW) with a salt mixture totaling approximately 67.70 g/L and a 0.5 wt.% foaming agent adjusted to a pH of 9.5. This approach differs from the individual salt studies prevalent in existing literature and provides a unique perspective on foam stability and behavior. Driven by environmental sustainability considerations, the effects of eco-friendly surfactant AAES and various drilling fluid additives: polyanionic cellulose (PAC), carboxymethyl cellulose sodium (CMC), and xanthan gum (XG), were investigated for foam formulation. The apparent viscosity of the AAES foam was evaluated at different pressures and temperatures across varying shear rates. A consistent decrease in foam viscosity with increasing shear rates was observed, irrespective of pressure and temperature. An increase in foam viscosity was also noted with higher pressures (from 14.7 psi to 3,000 psi) at low shear rates, with values rising from 8.04 cp to 14.74 cp, and from 3.71 cp to 5.79 cp at high shear rates of 1,000 s⁻¹. Increasing foam quality from 65% to 85% resulted in significant improvements in viscosity, approximately 37% at low shear rates and about 79% at high shear rates. The introduction of additives to AAES foam at 1,000 psi and 90°C led to a substantial increase in viscosity, with PAC showing the most significant enhancement: 33.28 cp at low shear rates and 18.15 cp at high shear rates. Conversely, the viscosity of both base AAES foam and additive-enhanced foams decreased with rising temperatures, although PAC exhibited the greatest resistance to viscosity variations due to temperature changes. The addition of PAC also resulted in a notable increase in foam yield stress, potentially leading to more efficient cuttings transport and hole cleaning. Furthermore, foam stability was significantly improved by the additives, with XG and CMC doubling stability to 48 minutes, and PAC resulting in a threefold increase in half-life to 65 minutes. This study presents AAES and the tested additives as viable components for eco-friendly foam formulations, promoting enhanced properties suitable for UBD applications.

Influence of physical properties and shear rate on static liquefaction of saturated loess

Flow sliding instability of saturated loess slopes is a common geological hazard in loess areas of China. Previous studies have found that the occurrence of flow-slip loess landslides is closely related to static liquefaction and is controlled by physical characteristics and load conditions. In this work, we comprehensively study these influences of physical properties (i.e. initial pore structure, gradation, dry density) and shear rate on the static liquefaction of saturated loess through a series of consolidated undrained triaxial tests, and the effect mechanism of these related factors on the static liquefaction of saturated loess are also discussed. The results present that: (1) The peak deviator stress and the maximum pore pressure of the undisturbed loess are much greater than these of the remodeled one under each level of confining pressure (except 450 kPa). Further, the calculated liquefaction potential index (LPI) of undisturbed loess is much greater, indicating that undisturbed loess is more prone to static liquefaction due to the initial pore structure. (2) The lower the relative clay/silt content ratio of the saturated remodeled loess, the stronger the potential liquefaction ability. With the increase of the relative content of clay from 0.125 to 0.698, the stress-strain curve gradually transitions from strain softening to hardening. (3) The remodeled loess show the steady-state strength tends to continuously increase with the increase of dry density from 1.38 g/cm3 to 1.56 g/cm3, while the LPI increases first and then decreases, and the largest value appears when the dry density reaches to 1.44 g/cm3. The reason is that the value of 1.44 g/cm3 is the normal consolidated condition, which essentially reflects the potential liquefaction change during the transformation from under consolidated to over consolidated state.(4) The effect of shear rate on the stress-strain curve of remolded loess is not significant, but the peak strength and ultimate pore pressure show a trend of increasing and then decreasing with the increase of shear rate. There exists a “critical shear rate “of 0.1 mm/min reflecting the liquefaction of loess is more likely to occur when reaches to this critical value. (5) Based on the comparison of static liquefaction tests, the influencing factors of static liquefaction of saturated loess are: initial pore structure> gradation > dry density > shear rate. This study can provide a systematic evaluation for understanding the influencing factors of static liquefaction capacity of saturated loess (especially remolded one), and also has a reference for explaining the loess flow-sliding failure mechanism under disturbance conditions.

Heterogeneous solvent dissipation coupled with particle rearrangement in shear-thinning non-Brownian suspensions.

Dense non-Brownian suspensions exhibit significant shear thinning, although a comprehensive understanding of the full scope of this phenomenon remains elusive. This study numerically reveals intimate heterogenous coupled dynamics between many-body particle motions and solvent hydrodynamics in shear-thinning non-Brownian suspensions. In our simulation systems, we do not account for frictional contact forces, reflecting experimental conditions under low shear rates where shear thinning occurs, while hydrodynamic interactions are directly incorporated using the Smoothed Profile Method. We demonstrate the spatially correlated viscous dissipation and particle motions; they share the same characteristic length, which decreases with increasing shear rate. We further show that, at lower shear rates, significant particle density changes are induced against the incompressibility of the solvent, suggesting the cooperative creation and annihilation of gaps and flow channels. We discuss that hydrodynamic interactions may substantially restrict particle rearrangements even in highly dense suspensions, influencing the quantitative aspects of macroscopic rheology.

Rheology, stability, and physicochemical properties of NaOH-tannic acid solvent for β-chitin dissolution

The applicability of chitin in food systems is limited by its poor solubility in ordinary solvents. This study explores a novel solvent system composed of sodium hydroxide and tannic acid (NaOH/TA) in combination with a repeated freeze-thaw process for dissolving chitin. The highest chitin solubility in 8% NaOH/0.3% TA and 10% NaOH/0.3% TA was 2.1% and 2.3% (w/v), respectively. The lower NaOH and excessive tannic acid content may lead to reduction of chitin solubility. We also observed a unique rheological property of the chitin/NaOH/TA system. A higher concentration of TA reduced the chitin solution's shear viscosity, storage modulus, loss modulus, and gelling temperature. Its shear viscosity decreases with increasing shear rate, showing a shear thinning behavior. When the chitin/NaOH/TA solution system was stored at 30oC, the crystalline degree of chitin decreased, and the diffraction peak shifted, suggesting the formation of different intermolecular forces. The TA contents show no significant effect on the crystallinity of chitin. With increased storage time, the molecular weight of chitin decreased, and the degree of deacetylation (DD) increased. These results underscore the potential applications of the chitin/NaOH/TA system in the food industry.

High-Strength Controllable Resin Plugging Agent and Its Performance Evaluation for Fractured Formation.

Lost circulation is a common and complicated situation in drilling engineering. Serious lost circulation may lead to pressure drop in the well, affect normal drilling operations, and even cause wellbore instability, formation fluid flooding into the wellbore, and blowout. Therefore, appropriate preventive and treatment measures need to be taken to ensure the safe and smooth operation of drilling operations. So, it is necessary to conduct in-depth research on the development and performance of the plugging materials. In this study, urea formaldehyde resin with high temperature resistance and strength was used as the main raw material, and the curing conditions were optimized and adjusted by adding a variety of additives. The curing time, compressive strength, temperature resistance, and other key performance indexes of the resin plugging agent were studied, and a resin plugging agent system with excellent plugging performance was prepared. The formula is as follows: 25% urea formaldehyde resin +1% betaine +1% silane coupling agent KH-570 + 3% ammonium chloride +1% hexamethylenetetramine +1% sodium carboxymethyl cellulose. The optimal curing temperature is between 60 and 80 °C, with a controllable curing time of 1-3 h. Experimental studies examined the rheological and curing properties of the resin plugging agent system. The results showed that the viscosity of the high-strength curable resin system before curing remained stable with increasing shear rates. Additionally, the storage modulus and loss modulus of the resin solutions increased with shear stress, with the loss modulus being greater than the storage modulus, indicating a viscous fluid. The study also investigated the effect of different salt ion concentrations on the curing effect of the resin plugging system. The results showed that formation water containing Na+ at concentrations between 500 mg/L and 10,000 mg/L increased the resin's curing strength and reduced curing time. However, excessively high concentrations at lower temperatures reduced the curing strength. Formation water containing Ca2+ increased the curing time of the resin plugging system and significantly impacted the curing strength, reducing it to some extent. Moreover, the high-strength curable resin plugging agent system can effectively stay in various fracture types (parallel, wedge-shaped) and different fracture sizes, forming a high-strength consolidation under certain temperature conditions for effective plugging. In wedge-shaped fractures with a width of 10 mm, the breakthrough pressure of the high-strength curable resin plugging agent system reached 8.1 MPa. As the fracture width decreases, the breakthrough pressure increases, reaching 9.98 MPa in wedge-shaped fractures with an outlet fracture width of 3 mm, forming a high-strength plugging layer. This research provides new ideas and methods for solving drilling fluid loss in fractured loss zones and has certain application and promotion value.

Acute neuromuscular, cardiovascular, and muscle oxygenation responses to low-intensity aerobic interval exercises with blood flow restriction.

We investigated the influence of short- and long-interval cycling exercise with blood flow restriction (BFR) on neuromuscular fatigue, shear stress and muscle oxygenation, potent stimuli to BFR-training adaptations. During separate sessions, eight individuals performed short- (24×60s/30s; SI) or long-interval (12×120s/60s; LI) trials on a cycle ergometer, matched for total work. One leg exercised with (BFR-leg) and the other without (CTRL-leg) BFR. Quadriceps fatigue was quantified using pre- to post-interval changes in maximal voluntary contraction (MVC), potentiated twitch force (QT) and voluntary activation (VA). Shear rate was measured by Doppler ultrasound at cuff release post-intervals. Vastus lateralis tissue oxygenation was measured by near-infrared spectroscopy during exercise. Following the initial interval, significant (P<0.05) declines in MVC and QT were found in both SI and LI, which were more pronounced in the BFR-leg, and accounted for approximately two-thirds of the total reduction at exercise termination. In the BFR-leg, reductions in MVC (-28±15%), QT (-42±17%), and VA (-15±17%) were maximal at exercise termination and persisted up to 8min post-exercise. Exercise-induced muscle deoxygenation was greater (P<0.001) in the BFR-leg than CTRL-leg and perceived pain was more in LI than SI (P<0.014). Cuff release triggered a significant (P<0.001) shear rate increase which was consistent across trials. Exercise-induced neuromuscular fatigue in the BFR-leg exceeded that in the CTRL-leg and was predominantly of peripheral origin. BFR also resulted in diminished muscle oxygenation and elevated shear stress. Finally, short-interval trials resulted in comparable neuromuscular and haemodynamic responses with reduced perceived pain compared to long-intervals.