Shear Rate Conditions Research Articles

Low shear-induced fibrillar fibronectin: comparative analyses of morphologies and cellular effects on bovine aortic endothelial cell adhesion and proliferation

Wall shear stress (WSS) is a critical factor in vascular biology, and both high and low WSS are implicated in atherosclerosis. Fibronectin (FN) is a key extracellular matrix protein that plays an important role in cell activities. Under high shear stress, plasma FN undergoes fibrillogenesis; however, its behavior under low shear stress remains unclear. This study aimed to investigate the formation ofin vitrocell-free fibrillar FN (FFN) under low shear rate conditions and its effect on bovine aortic endothelial cell behavior. FN (500µg ml-1) was perfused through slide chambers at three flow rates (0.16 ml h-1, 0.25 ml h-1, and 0.48 ml h-1), corresponding to low shear rates of 0.35 s-1, 0.55 s-1, and 1.05 s-1, respectively, for 4 h at room temperature. The formed FN matrices were observed using fluorescence microscopy and scanning electron microscopy. Under low shear rates, distinct FN matrix structures were observed. FFN0.48 formed immense fibrils with smooth surfaces, FFN0.25 formed a matrix with a rough surface, and FFN16 exhibited nodular structures. FFN0.25 supported cell activities to a greater extent than native FN and other FFN surfaces. Our study suggests that abnormally low shear conditions impact FN structure and function and enhance the understanding of FN fibrillogenesis in vascular biology, particularly in atherosclerosis.

The Contrasting Effects of Bothrops lanceolatus and Bothrops atrox Venom on Procoagulant Activity and Thrombus Stability under Blood Flow Conditions.

Consumption coagulopathy and hemorrhagic syndrome are the typical features of Bothrops sp. snake envenoming. In contrast, B. lanceolatus envenoming can induce thrombotic complications. Our aim was to test whether crude B. lanceolatus and B. atrox venoms would display procoagulant activity and induce thrombus formation under flow conditions. Fibrin formation in human plasma was observed for B. lanceolatus venom at 250-1000 ng/mL concentrations, which also induced clot formation in purified human fibrinogen, indicating thrombin-like activity. The degradation of fibrinogen confirmed the fibrinogenolytic activity of B. lanceolatus venom. B. lanceolatus venom displayed consistent thrombin-like and kallikrein-like activity increases in plasma conditions. The well-known procoagulant B. atrox venom activated plasmatic coagulation factors in vitro and induced firm thrombus formation under high shear rate conditions. In contrast, B. lanceolatus venom induced the formation of fragile thrombi that could not resist shear stress. Our results suggest that crude B. lanceolatus venom displays amidolytic activity and can activate the coagulation cascade, leading to prothrombin activation. B. lanceolatus venom induces the formation of an unstable thrombus under flow conditions, which can be prevented by the specific monovalent antivenom Bothrofav®.

Rheology of polyborazanes with various molecular structures and dynamic transformation process

AbstractThe molecular structure of polymer precursors significantly affects their rheological properties, thermal stability, and ceramic conversion rates. For the first time, we revealed the effects of polyborazane molecular structure on rheology and molecular configuration dynamic transformation process. The systems studied are polyborazane precursors with rigid six‐membered ring structures. We synthesized precursors with different molecular structures, including polyborazanes with varying degrees of branching and molecular chain flexibility, and investigated how molecular structure affects viscosity under different conditions of temperature, time, and shear rates. The results indicate that decreasing the branching degree enhances thermal stability and reduces both zero‐shear viscosity and infinite‐shear viscosity. Increasing the flexibility of molecular chains notably reduces infinite‐shear viscosity, while having minimal impact on zero‐shear viscosity and thermal stability. In conclusion, the ideal molecular structure should aim to increase the flexibility of the molecular chains while maintaining a certain degree of branching, such as a dendritic molecular configuration. By correlating viscosity data with molecular structure, we constructed a dynamic transition process of molecular chain entanglement, disentanglement, and crosslinking. This research is essential for understanding polymer rheology and its applications in industry, particularly in designing and synthesizing precursor structures for producing various ceramic fibers through Polymer‐Derived Ceramics.

Effect of Acute Isometric Handgrip Exercise on Vascular Function in Children and Emerging Adults with Congenital Heart Disease

Endothelial dysfunction is common in congenital heart disease (CHD). Isometric handgrip (IHG) exercise may improve endothelial function; however, whether this applies to patients with CHD is unknown. We investigated brachial artery flow-mediated dilation (FMD) pre- and post- acute IHG exercise using duplex ultrasound in CHD and healthy controls (CTL; n=19 (7 F) vs. 21 (9 F), age: 13±4 vs. 13±4 y). Whereas IHG improved mean FMD in controls, it had no effect on the mean FMD response in patients with CHD. Subsequently, participants within each group were categorized based on ΔFMD response (post-pre IHG FMD), in which those that experienced a decrease were classified as non-responders (NRESP) and those that experienced an increase were classified as responders (RESP). Among NRESP, ΔFMD was lower in CHD vs. controls ( p=0.0224). Among RESP, ΔFMD was lower in CHD vs. controls ( p=0.0543). Data during pre-occlusion in NRESP from pre- to post-IHG exercise showed improved antegrade shear rate (condition effect, p=0.0078), retrograde shear rate (interaction effect, p=0.0410), and oscillatory shear index (interaction effect, p=0.049) in CHD compared to controls. Potentially, IHG exercise enhanced vascular sensitivity to shear, resulting in an increase in baseline diameter and reduced FMD in CHD NRESP. Thus, reduced FMD after acute IHG exercise is influenced by improvements in resting shear rate parameters in patients with CHD. Saskatchewan Health Research Foundation, Heart and Stroke Foundation of Canada. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Investigation of Zinc on hemorheological parameters in a rat model of diabetes

Diabetes mellitus (DM) is a complex, chronic metabolic disorder characterized by impaired regulation of blood glucose levels. Zinc (Zn) is an essential trace elements that plays a role in various physiological processes within the body, including those related to diabetes. The current study was investigated the effect of Zn supplementation on hemorheological parameters in a rat model of DM. After induction of DM, 32 male Wistar albino rats were divided into four groups: control, Zn, DM, and Zn+DM. Whole blood viscosity (WBV) was determined by using digital cone and plate viscometer and plasma viscosity (PV) was determined by a Coulter Harkness capillary viscometer. The rats in the DM Group showed a decrease in both Zn levels and body weight, as well as an increase in glucose levels when compared to the control group. Diabetic rats supplemented with Zn displayed lower blood glucose levels and higher concentrations of Zn compared to the DM Group. The higher PV and lower hematocrit level were measured in DM Group than control group and lower PV, higher hematocrit level were measured in Zn+DM group than DM Group. The WBV was measured at four different shear rates (57.6–115.2 - 172.8–230.4 s −1). A statistically significant increase was observed in the DM group compared to the control group. Additionally, a statistically significant decrease was observed in the Zn+DM Group compared to the DM Group at a shear rate of 230.4 s−1. Erythrocyte rigidity index (Tk) and oxygen delivery index (ODI) were computed under conditions of high shear rate. The rats in the DM group exhibited a reduction in ODI and an elevation in Tk in comparison to the control group. Conversely, the diabetic rats supplemented with Zn exhibited decreased Tk and increased ODI compared to the DM Group. Zn supplementation seems to have a potential beneficial effect for protecting adverse affect of diabetes on hemorheogical parameters and for maintaining vascular health.

Material removal model for magnetorheological polishing considering shear thinning and experimental verification

To establish a more accurate magnetorheological polishing material removal model, the shear thinning effect of magnetorheological polishing solution under high shear rate conditions was analyzed based on magnetic dipole theory, and the two-particle chain junction model was used to analyze the force of magnetic particles in magnetorheological polishing solution, and the shear yield stress of magnetic chain under tilted condition was obtained, and the magnetorheological polishing material removal model considering shear thinning was established by combining the modified Preston equation. The effect of shear thinning on the magnetorheological polishing material removal model was analyzed. The calculated results of the model are compared with the experimental data of magnetorheological polishing material removal, and the results show that the material removal model considering shear thinning can accurately predict the material removal rate of magnetorheological polishing, especially the trend of decreasing material removal rate of magnetorheological polishing at high shear rate is effectively predicted.

An Experimental Study of Polymer Flooding to Enhance Oil Recovery

Experimental investigation of the impact of a synthetic polymer used to enhance oil recovery in an Egyptian oilfield was the goal of the current study. According to the findings of the current study, polymer solutions display non-Newtonian flow behavior under a variety of temperature, salinity, and shear rate conditions. The shear rate, salt level, temperature, and solution concentration all affect the apparent viscosities of polymer solutions. Studying how salinity and temperature affect how polymer solutions of various concentrations flow through porous media revealed that, up to a certain point, the mobility of the solutions increases with the flow rate, after which the mobility decreases with the flow rate. The mobility as a function of water saturation showed that during the tertiary recovery stage as compared to that during the secondary recovery stage, both the water mobility and the total mobility greatly reduced, and the oil mobility somewhat rose. The mobility analysis suggested that motion might be important in understanding how these processes increase oil recovery.

EFFECTIVE VISCOSITY AND GLASS TRANSITION TEMPERATURE OF Cs<sub>2</sub>O–B<sub>2</sub>O<sub>3</sub> MELTS

Effective viscosity (viscoelasticity) of cesium and boron oxides melts was measured at temperatures 900–1600 K and concentrations 0 ≤ x ≤16 mol % Cs2O by vibration viscosimetry. It was shown that vibration leads to non-Newtonian flow of melts. This means that not only configuration activation energy, the switching energy of bridging oxygen bonds but also the elastic energy of structural units of melts associated with activation energy of viscous flow. Using parameters under conditions of Newtonian and non-Newtonian flow of melts, shear viscosity η', elastic modulus G' and stored viscosity η'' were calculated. It was shown that cesium boron melts in conditions of high shear rates can be considered as liquids with viscous and elastic properties. Glass transition temperature (Tg, K) was measured by DSC, its dependence of content of cesium oxide was plotted and explained.

Design of Dispersant in Cathode of Li-Ion Batteries for Cathode Slurry with High Solid Content and High Battery Performance

Generally, cathode of Li-ion batteries was fabricated through the process that cathode slurry composed of active material, conductive agent, binder and N-Methyl-2-pyrrolidone (NMP) as organic solvent was coated on the aluminum foil, dried and pressed. In recent years, decreasing an amount of NMP has been required in terms of low environmental impact and due to cost reduction regarding material, shipping and machining price. However, the decreasing is possible to raise the viscosity of the cathode slurry and cause the defect of manufacturing process such as mixing, carrying and coating. One of the means of the resolving is addition of dispersant to cathode slurry. The dispersant can make an effect to reduce the slurry viscosity with low amount of solvent because it spreads the distance between each particle and also keep the condition of particle distribution. However, the dispersant may have the potential to be the resistance of the battery reaction because the material is polymer. In this study, we have designed dispersants that have the low viscosity of the cathode slurry with low amount of NMP, and hardly block the battery reaction by means of clarifying the function of dispersants and optimizing the component. The cathode slurry was prepared by the following steps: firstly, acetylene black (AB) as conductive agent, polyvinylidene difluoride (PVdF) as binder and dispersants were mixed with NMP. This paste is commonly called ‘AB paste’. Secondly as active material was added to the AB paste and mixed. The weight ratio of each material is as follows, active material:AB:PVdF:dispersant=89.8:8:1.5:0, 0.16, 0.20. Three solid content concentrations were considered as 48, 56 and 62.5 wt.% by adjusting the amount of NMP. Two dispersant materials were considered as a polyvinyl alcohol (PVA) with the role adsorbing to AB, and an acrylate copolymer including amid groups (ACA) with the role adsorbing to not only AB and but also active materials. They were composed of polymers not to be resistant according to previous study. And three samples were evaluated such as PVA only, PVA/ACA mix (weight ratio; PVA:ACA=85:15) and dispersant free. Cathode was prepared through the process coated the slurry on aluminum foil, dried and pressed. The test cells were assembled with the prepared cathode, anode composed of graphite, separator, and electrolyte including LiPF6. The viscosity of cathode slurry was evaluated under 1S-1 shear rate condition by using Dynamic viscoelasticity measuring device (DMA). And the discharge resistance was evaluated under -30℃, 1C as battery performance. Fig.1 shows the results of cathode slurry viscosity with various solid content concentrations. The tendency that the viscosity increases with increasing solid content concentration is observed. Especially at the 62.5 wt.%, the viscosity with added dispersant had much lower than dispersant-free. Furthermore, the effect to decrease the viscosity with PVA/ACA mix was higher than that with PVA only and the viscosity with PVA/ACA mix is less than 10000 mPas-1 as the target with no defect in the mass production process. These results imply the repulsive force with not only AB but also active material is required at 62.5 wt.% due to the distance between each particle is shorter under higher solid content concentration. Fig.2 shows the discharge resistances with various weight ratios of dispersant / AB used by cathode slurry at 62.5 wt.%. The tendency that the discharge resistance with PVA/ACA mix is slightly higher than PVA only is observed. These results imply that ACA with the role adsorbing to active material may affect to the reaction at the surface of active material. However, the resistance with added dispersant at dispersant / AB = 2 php is close to that with dispersant free is appeared. These results may be mainly depended on the effect of dispersant components not to be resistant and less dispersion performance with dispersant free. More detailed and integrated analysis about the dispersant components will be presented and discussed in this work. Figure 1

Development of a Novel Surfactant-Based Viscoelastic Fluid System as an Alternative Nonpolymeric Fracturing Fluid and Comparative Analysis with Traditional Guar Gum Gel Fluid.

Surfactant-based viscoelastic (SBVE) fluids have recently gained interest from many oil industry researchers due to their polymer-like viscoelastic behaviour and ability to mitigate problems of polymeric fluids by replacing them during various operations. This study investigates an alternative SBVE fluid system for hydraulic fracturing with comparable rheological characteristics to conventional polymeric guar gum fluid. In this study, low and high surfactant concentration SBVE fluid and nanofluid systems were synthesized, optimized, and compared. Cetyltrimethylammonium bromide and counterion inorganic sodium nitrate salt, with and without 1 wt% ZnO nano-dispersion additives, were used; these are entangled wormlike micellar solutions of cationic surfactant. The fluids were divided into the categories of type 1, type 2, type 3, and type 4, and were optimized by comparing the rheological characteristics of different concentration fluids in each category at 25 °C. The authors have reported recently that ZnO NPs can improve the rheological characteristics of fluids with a low surfactant concentration of 0.1 M cetyltrimethylammonium bromide by proposing fluids and nanofluids of type 1 and type 2. In addition, conventional polymeric guar gum gel fluid is prepared in this study and analyzed for its rheological characteristics. The rheology of all SBVE fluids and the guar gum fluid was analyzed using a rotational rheometer at varying shear rate conditions from 0.1 to 500 s-1 under 25 °C, 35 °C, 45 °C, 55 °C, 65 °C, and 75 °C temperature conditions. The comparative analysis section compares the rheology of the optimal SBVE fluids and nanofluids in each category to the rheology of polymeric guar gum fluid for the entire range of shear rates and temperature conditions. The type 3 optimum fluid with high surfactant concentration of 0.2 M cetyltrimethylammonium bromide and 1.2 M sodium nitrate was the best of all the optimum fluids and nanofluids. This fluid shows comparative rheology to guar gum fluid even at elevated shear rate and temperature conditions. The comparison of average viscosity values under a different group of shear rate conditions suggests that the overall optimum SBVE fluid prepared in this study is a potential nonpolymeric viscoelastic fluid candidate for hydraulic fracturing operation that could replace polymeric guar gum fluids.

Toward a theranostic device for gliomas

BackgroundIn the surgical management of glioblastoma, a highly aggressive and incurable type of brain cancer, identification and treatment of residual tissue is the most common site of disease recurrence. Monitoring and localized treatment are achieved with engineered microbubbles (MBs) by combining ultrasound and fluorescence imaging with actively targeted temozolomide (TMZ) delivery. MethodsThe MBs were conjugated with a near-infrared fluorescence probe CF790, cyclic pentapeptide bearing the RGD sequence and a carboxyl-temozolomide, TMZA. The efficiency of adhesion to HUVEC cells was assessed in vitro in realistic physiological conditions of shear rate and vascular dimensions. Cytotoxicity of TMZA-loaded MBs on U87 MG cells and IC50 were assessed by MTT tests. ResultsWe report on the design of injectable poly(vinyl alcohol) echogenic MBs designed as a platform with active targeting ability to tumor tissues, by tethering on the surface a ligand having the tripeptide sequence, RGD. The biorecognition of RGD-MBs onto HUVEC cells is quantitatively proved. Efficient NIR emission from the CF790-decorated MBs was successfully detected. The conjugation on the MBs surface of a specific drug as TMZ is achieved. The pharmacological activity of the coupled-to-surface drug is preserved by controlling the reaction conditions. ConclusionsWe present an improved formulation of PVA-MBs to achieve a multifunctional device with adhesion ability, cytotoxicity on glioblastoma cells and supporting imaging.

Analyzing and Predicting the Viscosity of Polymer Nanocomposites in the Conditions of Temperature, Shear Rate, and Nanoparticle Loading with Molecular Dynamics Simulations and Machine Learning

Predicting the viscosity (η) of polymer nanocomposites (PNCs) is of critical importance as it governs a dominant role in PNCs' processing and application. Machine-learning (ML) algorithms, enabled by pre-existing experimental and computational data, have emerged as robust tools for the prediction of quantitative relationships between feature parameters and various physical properties of materials. In this work, we employed nonequilibrium molecular dynamics (NEMD) simulation with ML models to systematically investigate the η of PNCs over a wide range of nanoparticle (NP) loadings (φ), shear rates (γ̇), and temperatures (T). With the increase in γ̇, shear thinning takes place as the value of η decreases on the orders of magnitude. In addition, the φ dependence and T dependence reduce to the extent that it is not visible at high γ̇. The value of η for PNCs is proportional to φ and inversely proportional to T below the intermediate γ̇. Using the obtained NEMD results, four machine-learning models were trained to provide effective predictions for the η. The extreme gradient boosting (XGBoost) model yields the best accuracy in η prediction under complex conditions and is further used to evaluate feature importance. This quantitative structure-property relationship (QSPR) model used physical views to investigate the effect of process parameters, such as T, φ, and γ̇, on the η of PNCs and paves the path for theoretically proposing reasonable parameters for successful processing.

Contrast analysis in ultrafast ultrasound blood flow imaging of jugular vein

PurposeThe contrasts of flowing blood in in vitro experiments using porcine blood and in vivo measurements of human jugular veins were analyzed to demonstrate that the hemorheological property was dependent on the shear rate.MethodsBlood samples (45% hematocrit) suspended in saline or plasma were compared with examine the difference in viscoelasticity. Ultrafast plane-wave imaging at an ultrasonic center frequency of 7.5 MHz was performed on different steady flows in a graphite-agar phantom. Also, in vivo measurement was performed in young, healthy subjects and patients with diabetes. A spatiotemporal matrix of beamformed radio-frequency data was used for the singular value decomposition (SVD) clutter filter. The clutter-filtered B-mode image was calculated as the amplitude envelope normalized at the first frame in the diastolic phase to evaluate contrast. The shear rate was estimated as the velocity gradient perpendicular to the lateral axis.ResultsAlthough nonaggregated erythrocytes at a high shear rate exhibited a low echogenicity, the echogenicity in the plasma sample overall increased due to erythrocyte aggregation at a low shear rate. In addition, the frequency of detection of specular components, defined as components beyond twice the standard deviation of a contrast map obtained from a clutter-filtered B-mode image, increased in the porcine blood at a high shear rate and the venous blood in healthy subjects versus patients with diabetes.ConclusionThe possibility of characterizing hemorheological properties dependent on the shear rate and diabetes condition was indicated using ultrafast plane-wave imaging with an SVD-based clutter filter.

A New Rheological Model for Phosphate Slurry Flows

In this paper, a new rheological model for the flow of phosphate-water suspensions is proposed. The model’s ability to replicate the rheological characteristics of phosphate-water suspensions under different shear rate conditions is evaluated using rheometric tests, and it is found to be in good agreement with experimental data. A comprehensive methodology for obtaining the model parameters is presented. The proposed model is then incorporated into the OpenFoam numerical code. The results demonstrate that the model is capable of reproducing the rheological behavior of phosphate suspensions at both low and high concentrations by comparing it with suitable models for modeling the rheological behavior of phosphate suspensions. The proposed model can be applied to simulate and monitor phosphate slurry flows in industrial applications.

Application of desulfurization gypsum as activator for modified magnesium slag-fly ash cemented paste backfill material

Recycling industrial solid waste for mine backfill is one of the best ways to achieve green production in multiple industries. In this paper, the desulfurization gypsum (DG) as an activator is combined with the modified magnesium slag-fly ash cementitious paste backfill (MFPB) technology for the co-disposal of solid waste and goaf treatment, and the influence of DG on the performance of MFPB was comprehensively analyzed through rheological properties, mechanical properties, durability, microscopic analysis and environmental characteristics experiments. The results show that the fresh MFPB mortar conforms to the Herschel-Bulkley model at different maximum shear rate (γ̇max) conditions. When the γ̇max is 100 s−1, the mortar exhibits shear-thickening properties. The apparent viscosity, yield stress and static yield stress of mortar decreased first and then increased with the increase of DG content, and all had the minimum value when DG was 2.5 %. The thixotropy of the mortar was significantly increased with the addition of DG, and the change in thixotropy was significantly correlated with the difference between the two yield stresses. Both the rheological and mini-slump results demonstrate that DG can improve the flowability of MFPB mortars. In addition, the UCS of D0 under steam curing and standard water curing conditions for 28 d were 4.342 MPa and 2.827 MPa, and the sample containing DG were 6.109–8.241 MPa and 6.669–9.492 MPa, respectively. The addition of DG not only improves the strength of MFPB, but also improves the durability of MFPB. Microscopic analysis (XRD, SEM, and TG-DTG) indicated that this was mainly because DG promoted the hydration reaction of the MMS-FA system and accelerated the generation of C-S(A)-H and AFt. Finally, in the results of in situ leaching based on durability and leaching based on standard HJ 557, all the indexes of MFPB meet the standard of class III groundwater in GB/T 14848-2017, and it has an effective stabilization/solidification effect on heavy metals (As, Cu, Ni, Ba, Zn and Mo, etc.). To sum up, the collaboration of DG and MFPB technology can not only efficiently clean and utilize a variety of solid wastes (MMS, FA and DG), but also greatly improve the performance of MFPB to promote its application.

Influence of Normal Stiffness and Shear Rate on the Shear Behaviors and Acoustic Emissions Characteristics of Artificial Rock Joints

Understanding the asperity damage behaviors of joints during shearing is critical for evaluating the stability of deep underground engineering structures. In this paper, we prepared plaster joints and used them for direct shear tests under different normal stiffness (0–7 MPa/mm) and various shear rate (0.5–20 mm/min) conditions. The effects of normal stiffness and shear rate on mechanical behavior and AE characteristics were studied. With the increase of normal stiffness, the damaged area of the surface of the joint and the weight of the damaged, rough body basically show a linear increase. With the increase of the shear rate, the peak shear stress and the final shear stress of the joint are non-linearly decreased (the decrease rate at the shear rate of 0.5–5 mm/min is much larger than that at the shear rate of 5–20 mm/min), more local cracks appear on the surface of the joint, and the dilatancy of the joint slightly decreases. More than 60% of the acoustic emission signals in the shearing process of the joint are concentrated in the post-peak phase. With the increase of normal stiffness, the cumulative number of acoustic emission impacts and cumulative energy both increase. With the increase in shear rate, the accumulated acoustic emission impact number decreases, and the accumulated AE energy tends to increase when the shear rate is 0.5–5 mm/min and decreases when the shear rate increases to 5–20 mm/min.

Rheological properties of hyaluronic acid-based fillers for facial cosmetic aesthetics

Hyaluronic acid-based dermal fillers are the most used materials in cosmiatry, and their clinical implications are linked to their viscoelastic properties. This study aimed to determine the rheological behavior of HA products used in Brazil by changing specific physicochemical characteristics under different test frequencies. Laboratory analyses of 0.9 mL of samples were performed in a TA-Instruments AR-1500ex Rheometer at 25 °C, at oscillation frequencies of 100, 10, 1, and 0.1 radians/second, considering the measurements of G′, G′′, and Tan δ. The value of G' increased as the oscillation frequencies were increased. In parallel, the changes in G" were the ones that varied the most for frequencies 0.1 and 1 radian/second. The maximum G' was observed with Hialurox Ultra Lift® 26 mg/g (793.45; 554.06; 423.44 Pa, 100, 10 and 1 rad/s, respectively). While the lowest G' values were obtained with Rennova Ultra Deep® (43.01; 19.75; 10.75 and 10.42 Pa at 100, 10, 1, 0.1 rad/sec, respectively). The changes that occurred in the investigated properties indicated that hyaluronic acid-based fillers vary when subjected to different conditions of shear rate, which should be considered in their clinical indication for choosing the most appropriate material according to the region to be treated.

A Novel ZnO Nanoparticles Enhanced Surfactant Based Viscoelastic Fluid Systems for Fracturing under High Temperature and High Shear Rate Conditions: Synthesis, Rheometric Analysis, and Fluid Model Derivation.

Surfactant-based viscoelastic (SBVE) fluids are innovative nonpolymeric non-newtonian fluid compositions that have recently gained much attention from the oil industry. SBVE can replace traditional polymeric fracturing fluid composition by mitigating problems arising during and after hydraulic fracturing operations are performed. In this study, SBVE fluid systems which are entangled with worm-like micellar solutions of cationic surfactant: cetrimonium bromide or CTAB and counterion inorganic sodium nitrate salt are synthesized. The salt reagent concentration is optimized by comparing the rheological characteristics of different concentration fluids at 25 °C. The study aims to mitigate the primary issue concerning these SBVE fluids: significant drop in viscosity at high temperature and high shear rate (HTHS) conditions. Hence, the authors synthesized a modified viscoelastic fluid system using ZnO nanoparticle (NPs) additives with a hypothesis of getting fluids with improved rheology. The rheology of optimum fluids of both categories: with (0.6 M NaNO3 concentration fluid) and without (0.8 M NaNO3 concentration fluid) ZnO NPs additives were compared for a range of shear rates from 1 to 500 Sec−1 at different temperatures from 25 °C to 75 °C to visualize modifications in viscosity values after the addition of NPs additives. The rheology in terms of viscosity was higher for the fluid with 1% dispersed ZnO NPs additives at all temperatures for the entire range of shear rate values. Additionally, rheological correlation function models were derived for the synthesized fluids using statistical analysis methods. Subsequently, Herschel–Bulkley models were developed for optimum fluids depending on rheological correlation models. In the last section of the study, the pressure-drop estimation method is described using given group equations for laminar flow in a pipe depending on Herschel–Bulkley-model parameters have been identified for optimum fluids are consistency, flow index and yield stress values.

Visualization of platelet deposition in a flow chamber

Abstract The formation of thrombi is still a challenge when it comes to ventricular assist devices (VADs). This can be caused by the subsequent deposition of proteins and platelets on foreign surfaces. In VADs, the blood contacting components are mainly made of titanium alloys due to hemocompatible properties and corrosion resistance. However, surfaces where mechanical contact of the rotor and the stator occur like bearing areas of axial VADs require high wear resistance due to the greater potential of scratches. Therefore, an in vitro test bench to optically investigate the deposition of fluorescent labelled platelets on the protein layer of different surfaces is hereby presented, aiming to investigate the potential for thrombi formation of five different inorganic hard material coatings on titanium. The coating materials included Titanium Nitride (TiN), Titanium Niobium Nitride (TiNbN), Diamond-Like Carbon (Ionbond-Medthin-43 (DLCI) and Oerlikon Balimed A (DLCO)) and Wolfram Carbid Oerlikon Balimed C (WC). Uncoated titanium (Ti) was investigated as reference. Heparinized human whole blood was incubated with Mepacrine (fluorescent dye) and then pumped through a flow chamber with defined shear rate conditions over the samples. The adhered platelets were visualized via inverted fluorescence microscopy. The analyzation of the green values and the binary image of the generated fluorescent picture offers conclusions about the platelet accumulation and the percentage of the covered surface area, respectively. Statistical analysis showed a significant lower potential for platelet deposition for TiN compared to Ti and no significant differences for the rest. It can be concluded that none of these coatings have a higher potential for platelet deposition than Ti and therefore point towards suitability for blood contacting components.

Structural Characterization, Rheological Properties and Protection of Oxidative Damage of an Exopolysaccharide from Leuconostoc citreum 1.2461 Fermented in Soybean Whey.

Soybean whey is a kind of agricultural by-product enriched with nutritional value but with low utilization. The extracellular polysaccharides secreted by lactic acid bacteria during the fermentation possess a variety of structural characteristics and beneficial properties. In this study, an exopolysaccharide (EPS) was isolated from Leuconostoc citreum 1.2461 after fermentation in optimized soybean whey-enriched 10% sucrose at 37 °C for 24 h. The water-soluble EPS-1 was obtained by DEAE-52 anion exchange chromatography, and the structural characterization of EPS-1 was investigated. The EPS-1 was homogeneous with an average molecular weight of 4.712 × 106 Da and consisted mainly of glucose. Nuclear magnetic resonance (NMR) spectrum and flourier transform infrared (FT-IR) spectrum indicated that the EPS-1 contained →3)-α-D-Glcp-(1→ and →6)-α-D-Glcp-(1→ residues. The rheological properties of EPS-1 under the conditions of changing shear rate, concentration, temperature and coexisting ions showed its pseudoplastic fluid behaviors. In addition, the EPS-1 exhibited certain scavenging activity on the ABTS radical and chelating activity on metal ions at relatively high concentrations. Furthermore, EPS-1 with a certain concentration was confirmed to have significant protective effects on yeast cell injury induced by hydrogen peroxide. This study reported the structural characteristics of exopolysaccharide from Lc. citreum 1.2461 and provides a basis for its potential application in the field of functional foods.