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[Display omitted] Noncovalent interactions are ubiquitous, endowing high feasibility on assembly and disassembly of gel network structure. Loading anticancer drugs in low molecular weight gelator (LMWG)-based gel through a noncovalently co-assembly process shows advantages of high efficacy, thixotropy, and controllable release. Drug-loaded fluorenylmethyloxycarbonyl-phenylalanine (Fmoc-F)/DMSO/H 2 O-doxorubicin (DOX) gels were fabricated by an effective solvent-triggering method dominated by solvated Fmoc-F with DMSO. Density Functional Theory (DFT) calculation results show that the noncovalent interactions between Fmoc-F and DOX drive the co-assembly of the gel. DOX can assemble with Fmoc-F and realize its co-assembly loading through the H-bonding and π-π stacking, similar to the way that gel networks form. Depending on a network dis-assembly process, sustained release of DOX was achieved along with carrier decomposition through a repetitive diffusion-surface erosion process. DOX loading and release prove the non-covalent interactions and the mechanism for controlling the assembly process. By such tailoring co-assembled loading, the administration of DOX is hoped to be optimized to improve the clinical application. [ABSTRACT FROM AUTHOR]

[Display omitted] In the current study we demonstrate a method of preparation of low-density polydimethylsiloxane (PDMS) foams from emulsions by using water-based thixotropic fluids as porogens. Aqueous dispersions of synthetic hectorite clay and nanocellulose were used as thixotropic fluids, enabling the preparation of fine emulsions in bulk form with the droplet size down to few tens of microns by simple hand mixing. Contrary to conventional emulsion templating where stabilization of emulsion is required, a strategy was developed for obtaining foams by using controlled destabilization of an emulsion, induced during the curing of the PDMS matrix phase by adding a carefully selected surfactant in optimized concentration. This strategy enables the preparation of bulk PDMS foams with interconnected porosity in a range of density values, fast and deformation-free drying and uniform porous structure with a range of mechanical properties. Clay microplatelet with clearly defined shape and with mass in the nanogram range is retained in spherical pores as the porogen is removed by evaporation. Foams with density down to 0.353 g/cm3 and thermal conductivity of 0.0745 W/m * K were prepared. Elastic modulus of the prepared foams ranged from 0.156 to 0.379 MPa, a reduction of 94.3–86.3% as compared to pure nonporous PDMS. [ABSTRACT FROM AUTHOR]

Purpose: The presence of organic matter in cohesive sediment results in the formation of clay-organic flocs, which eventually impart complex rheological behavior including shear-thinning, viscoelasticity, thixotropy and two-step yielding to mud. In this study, the influence of microbial degradation of sediment organic matter on the rheological properties of mud samples, having similar densities, was examined. Materials and methods: Mud samples were collected from three different locations in the Port of Hamburg, Germany, displaying varying organic matter content. The rheological analysis of fresh and degraded mud samples was performed with the help of several tests including stress ramp-up tests, amplitude sweep tests, frequency sweep tests, time-dependent tests, and structural recovery tests. Results and discussion: The results showed a significant decrease in rheological properties including yield stresses, complex modulus, etc. for degraded mud samples as compared to the fresh mud samples. The slopes of the line, correlating the change (degraded − fresh) in the above-mentioned rheological properties as a function of the same rheological property of the fresh mud, varied within the range of −0.28 to −0.49. The structural recovery tests displayed a better recovery (i.e., stronger system) in mud after the pre-shearing step for the degraded mud samples as compared to the fresh mud samples. The effect of degradation time on the rheological properties of mud samples showed two critical time periods (3 days and 150 days) after which a significant change in rheological properties of mud samples was observed. Conclusions: This study provided a useful understanding about the influence of organic matter degradation on the rheological properties of mud, which can be used to optimize sediment management strategies in ports and waterways. [ABSTRACT FROM AUTHOR]

Introduction. The article examines the quality indicators of low-fat ice cream with a different ratio between sugar and hydrolyzed and non-hydrolyzed concentrates of demineralized whey. Materials and methods. The degree of lactose hydrolysis was determined by iodometric and refractometric methods, the water activity in the mixtures was determined using the water activity analyzer, the rheological characteristics were determined using a rotary viscometer, the foam overrun and foam stability of the ice cream mixtures and the melting rate of ice cream were determined using modified methods, sensory indicators were determined using the descriptive-integral method. The mass fraction of protein, dry matter, overrun, resistance to melting in ice cream were determined using well-known methods. Results and discussion. Based on the calculation of the degree of sweetness of whey concentrates, taking into account the mass fraction of total solids, the degree of lactose hydrolysis and the known values of the relative sweetness of sugar, lactose, glucose and galactose, a concentrate with a solids content 40% was chosen for use in the ice cream formulation. According to the results of the study of the quality indicators of ice cream mixtures, it was found that the hydrolyzed concentrate of demineralized whey with a mass fraction of solids 40% could replace up to 42% of sugar in the composition of ice cream, while maintaining the degree of sweetness determined for this type of ice cream in the range from 0.8 to 0.9. According to the viscosity-speed characteristics, the mixture of low-fat ice cream with a concentrate of hydrolyzed demineralized whey is classified as a system with a pronounced coagulation structure with the detection of thixotropic properties. Ice cream based on hydrolyzed whey concentrate contains 3.3% of whey proteins, which corresponds to the standard chemical composition of ice cream. The high content of lactose hydrolysis products in ice cream increases overrun, but reduces the resistance to melting of ice cream, which must be taken into account during the technological process and when choosing a consumer container. Conclusions. The feasibility of using a hydrolyzed whey concentrate with a mass fraction of solids 40% as a sweetening and protein-containing ingredient in low-fat ice cream has been proven. [ABSTRACT FROM AUTHOR]

Nanogel is a promising drug delivery approach to improve the pharmacokinetics and pharmacodynamic prospect of phytopharmaceuticals. In the present review, phytopharmaceuticals with astonishing therapeutic utilities are being explored. However, their in vivo delivery is challenging, owing to poor biopharmaceutical attributes that impact their drug release profile, skin penetration, and the reach of optimal therapeutic concentrations to the target site. Nanogel and its advanced version in the form of nanoemulgel (oil-in-water nanoemulsion integrated gel matrix) offer better therapeutic prospects than other conventional counterparts for improving the biopharmaceutical attributes and thus therapeutic efficacy of phytopharmaceuticals. Nanoemulgel-loaded phytopharmaceuticals could substantially improve permeation behavior across skin barriers, subsequently enhancing the delivery and therapeutic effectiveness of the bioactive compound. Furthermore, the thixotropic characteristics of polymeric hydrogel utilized in the fabrication of nanogel/nanoemulgel-based drug delivery systems have also imparted improvements in the biopharmaceutical attributes of loaded phytopharmaceuticals. This formulation approach is about to be rife in the coming decades. Thus, the current review throws light on the recent studies demonstrating the role of nanogels in enhancing the delivery of bioactive compounds for treating various disease conditions and the challenges faced in their clinical translation. [ABSTRACT FROM AUTHOR]

Copyright of Silicone Material is the property of Silicone Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We formulate a nonlinear Maxwell-type constitutive equation for shear deformation of polymers in flow state or polymer viscoelastic melts and solutions which takes into account interaction of deformation process and structure evolution, namely, influence of the kinetics formation and breakage of chain cross-links, agglomerations of molecules and crystallites on viscosity and shear modulus and deformation influence on the kinetics. The constitutive equation is governed by an increasing material function and six positive parameters. We reduce it to the set of two nonlinear autonomous differential equations for two unknown functions (namely, stress and relative cross-links density) and prove existence and uniqueness of its equilibrium point and that its coordinates depend monotonically on every material parameter and on shear rate. We derive general equations for model flow curve and viscosity curve and prove that the first one increases and the second one decreases while the shear rate grows. Thus, the model describes basic phenomena observed for simple shear flow of shear thinning fluids. [ABSTRACT FROM AUTHOR]

Geopolymer composites can be used as a proper substitute for ordinary Portland cement, which can reduce carbon dioxide (CO2) emissions and make rational use of industrial waste. In this study, an investigation of the workability and compressive strength of geopolymer composites was carried out through a series of experiments, such as slump flow test, consistency meter test and compressive strength test, to clarify the interaction mechanism among superplasticizer (SP), polyvinyl alcohol (PVA) fiber, Nano-SiO2 (NS) and geopolymer composites, thereby improving the properties of engineered composites. The results showed that with the increase in PVA fiber content, the flowability of geopolymer composites decreased, while the thixotropy increased. With the increase in the NS content, the flowability of geopolymer composites first increased and then decreased, reaching its best at 1.0%, while the thixotropy was the opposite. With the increase in the SP content, the flowability of geopolymer composites increased, while the thixotropy decreased. A significant correlation between thixotropy and flowability of geopolymer composites was found (R2 > 0.85). In addition, the incorporation of single PVA fiber or NS significantly improved the compressive strength of geopolymer composites. Specifically, the compressive strength of geopolymer composites with 0.8% content PVA fiber (60.3 MPa) was 33.4% higher than that without PVA fiber (45.2 MPa), and the compressive strength of geopolymer composites with 1.5% content NS (52.6 MPa) was 16.4% higher than that without NS (45.2 MPa). Considering the synergistic effect, it is found that the compressive strength of geopolymer composites (58.5–63.3 MPa) was significantly higher than that without PVA fiber (45.2–52.6 MPa). However, the flowability and compressive strength of geopolymer composites were only slightly improved compared to that without NS. With the increase in the SP content, the compressive strength of geopolymer composites showed a trend of a slight decrease on the whole. Consequently, the results of this study may be useful for further research in the field of repair and prevention of the delamination of composite structures. [ABSTRACT FROM AUTHOR]

Hydroxypropyl trimethyl ammonium chloride chitosan (HACC) was synthesized by reacting chitosan with glycidyl trimethylammonium chloride. Atomic force microscopy showed that HACC exhibited disorderly coils in dilute solution and formed a three-dimensional network. Flow, thixotropy, and dynamic viscoelasticity tests were conducted using an MCR301 rheometer. The HACC solution was a non-Newtonian pseudoplastic fluid, and the shear behavior of different concentrations (2–6 %, w/v) was evaluated by the Williamson model fitting. Furthermore, the thixotropy was highly dependent on concentration changes: the high-concentration solution structure was difficult to recover in a short time. The dynamic viscoelasticity test indicated that the viscoelasticity of the HACC solution not only exhibited a viscous behavior similar to that of a fluid, but also exhibited elastic properties of weak gel. HACC exhibited high-strength solid-like gel characteristics at high temperature. [ABSTRACT FROM AUTHOR]

We report a detailed experimental study of peculiar thixotropic dynamics of carbon black (CB, Vulcan XC-72) suspensions in mineral oil, specifically the observation of sequential stress increase then decrease at a fixed shear rate in a step-down test. We verify that such dynamics, though peculiar, come from a true material response rather than experimental artifacts. We also reveal how this long-time stress decay is associated with antithixotropic structural change rather than viscoelastic stress relaxation by using orthogonal superposition (OSP) rheometry to probe viscoelastic moduli during the step-down tests. The orthogonal storage and loss moduli are present, showing this two-timescale recovery then decay response, which demonstrates that this response is antithixotropic, and it involves shear-induced structuring. We further show a mechanical anisotropy in the CB suspension under shear using OSP. Based on the rheological results, a microstructural schematic is proposed, considering qualitatively thixotropic structure build-up, antithixotropic densification, and anisotropic structure evolution. Our observation for these CB suspensions is outside the standard paradigm of thixotropic structure-parameter models, and the elastic response provides us with new insight into the transient dynamics of CB suspensions. [ABSTRACT FROM AUTHOR]

There is no universal model for thixotropy, and comparing thixotropic effects between different fluids is a subtle yet challenging problem. We introduce a generalized (model-insensitive) framework for comparing thixotropic properties based on thixotropic spectra. A superposition of exponential stress modes distributed over thixotropic time scales is used to quantify buildup and breakdown times and mode strengths in response to step-change input. This mathematical framework is tested with several experimental step-shear rate data on colloidal suspensions. Low-dimensional metrics based on moments of the distribution reveal characteristic average thixotropic properties, which are visualized on Ashby-style diagrams. This method outlines a framework for describing thixotropy across a diverse range of microstructures, supporting scientific studies as well as material selection for engineering design applications. [ABSTRACT FROM AUTHOR]

The concept of a Deborah number is widely used in the study of viscoelastic materials to represent the ratio of a material relaxation time to the time scale of observation and to demarcate transitions between predominantly viscous or elastic material responses. However, this construct does not help quantify the importance of long transients and nonmonotonic stress jumps that are often observed in more complex time-varying systems. Many of these nonintuitive effects are lumped collectively under the term thixotropy; however, no proper nouns are associated with the key phenomena observed in such materials. Thixotropy arises from the ability of a complex structured fluid to remember its prior deformation history, so it is natural to name the dimensionless group representing such behavior with respect to the ability to remember. In Greek mythology, Mnemosyne was the mother of the nine Muses and the goddess of memory. We, thus, propose the definition of a Mnemosyne number as the dimensionless product of the thixotropic time scale and the imposed rate of deformation. The Mnemosyne number is, thus, a measure of the flow strength compared to the thixotropic time scale. Since long transient responses are endemic to thixotropic materials, one also needs to consider the duration of flow. The relevant dimensionless measure of this duration can be represented in terms of a mutation number, which compares the time scale of experiment/observation to the thixotropic time scale. Collating the mutation number and the Mnemosyne number, we can construct a general two-dimensional map that helps understand thixotropic behavior. We quantify these ideas using several of the simplest canonical thixotropic models available in the literature. [ABSTRACT FROM AUTHOR]

Semisolid metal processing is a well-known technology that can be used to enhance manufacturing product quality in broad industries. The technology controls the thixotropic properties of alloys within their solidus and liquidus temperature ranges. In general, most known alloys can generate semisolid slurries at high solid fractions, and the remaining can form slurries at low solid fractions. This has provided opportunities for many metals and alloys to be processed as semisolid slurries in today's casting industry. However, only a few researchers studied this technology potentially for a new metal-based additive manufacturing or 3D printing process. This article reviewed literature and findings from thixotropy rheology and semisolid metal processing methods, finally to thixotropic metal 3D printing. The survey shows that more future work is needed, including the investigation of thixotropic metal flow mechanics, the modelling and simulation of semisolid metal extrusion and further development of a fully thixotropic 3D printing system. [ABSTRACT FROM AUTHOR]

Surfactin is a kind of lipopeptide biosurfactant with good performance. In order to solve the difficulty of surfactin thickening, this study investigated the new viscoelastic micellar system composed of surfactin and octadecyl trimethyl ammonium chloride (OTAC) and its rheological properties. The influences of mass ratio, pH, and temperature on the rheological properties of the system were studied. Under optimized mass ratio and pH, the maximum viscosity of surfactin/OTAC (4.5/7.5 w/w, pH = 5.34) is obtained as 13,904 mPa s. The flow curves of surfactin/OTAC micelle system can be described by Cross constitutive equation. The rheological properties of surfactin/OTAC viscoelastic micelle systems are obtained, including thixotropy, viscoelasticity, and viscosity‐temperature properties. The research on the new surfactin/OTAC system expanded the viscoelastic micelle systems of microbial surfactant series, which was expected to provide the rheological basis for the research of the surfactin micellar systems and be applied to the development and production of daily chemical industry, oil recovery, and other fields. [ABSTRACT FROM AUTHOR]

In this paper, the behavior of Kaolinite suspensions is explored in the presence of two ionic surfactants, namely, cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). The steady-shear behavior of these suspensions is explored above and below the critical micelle concentration. The yield stress was found to increase monotonically with CTAB concentration, which can be explained by improved network strength. On the other hand, the yield stress was initially decreased with an increase in SDS concentration up to 10 mM with subsequent relatively small increase at higher concentrations. Both kaolinite and kaolinite-CTAB systems were found to exhibit thixotropic and anti-thixotropic behavior at short and long timescales, respectively. [ABSTRACT FROM AUTHOR]

Formwork lateral pressures are critical with respect to engineering safety, and laboratory tests are often limited by time, height, etc. Formwork lateral pressures are related to early concrete fluid behavior (e.g., thixotropy). In this paper, we propose the use of ultra-deep underground diaphragm walls instead of formwork for conventional lateral pressure testing. During the construction process, three measurement points were set up in an ultra-deep diaphragm wall at −40 m, −80 m and −100 m. The concrete was divided into 22 casts, and the development of lateral pressure and the effect of time on lateral pressure were observed under each of the casts. We found that the characteristic height of all three measurement points was approximately 21 m. The average casting speed for this test was 16.846 m/h, with the fastest speed of 32.148 m/h. A time-dependent phenomenon of rapid rise and fall in lateral pressure with each casting was observed. This method provides a new way to conceptualize formwork lateral pressure, with the advantages of long testing time, high casting height and multiple tests, not only for formwork lateral pressure but also for early age thixotropy measurement of concrete. [ABSTRACT FROM AUTHOR]

Thixotropy is a fascinating feature present in many gel systems that has garnered a lot of attention in the medical field in recent decades. When shear stress is applied, the gel transforms into sol and immediately returns to its original state when resting. The thixotropic nature of the hydrogel has inspired scientists to entrap and release enzymes, therapeutics, and other substances inside the human body, where the gel acts as a drug reservoir and can sustainably release therapeutics. Furthermore, thixotropic hydrogels have been widely used in various therapeutic applications, including drug delivery, cornea regeneration and osteogenesis, to name a few. Because of their inherent biocompatibility and structural diversity, peptides are at the forefront of cutting-edge research in this context. This review will discuss the rational design and self-assembly of peptide-based thixotropic hydrogels with some representative examples, followed by their biomedical applications. [ABSTRACT FROM AUTHOR]

In this work, the rheological behavior of passion fruit peel extract was determined at different temperatures (5–40 °C) and peel content in the extract (40–55% w/w). The extract was obtained after blanching the passion fruit peels at 95 °C for 5 min, then they were crushed to reduce their size, water was added, and finally, they were subjected to liquefaction and subsequent filtration. Rheological measurements were made using a rheometer with a plate and plate geometry. Extract samples were adequately described by the power-law model exhibiting pseudoplastic behavior, without the presence of thixotropy. The temperature did not influence the flow behavior index, but the consistency coefficient did. The dynamic study (the temperature sweep test) showed that passion fruit peel extract exhibits a more elastic than viscous behavior, typical of a gel. [ABSTRACT FROM AUTHOR]

Hydrogels have emerged as promising candidates for biomedical applications, such as replacing natural articular cartilage, owing to their unique viscoelastic properties. However, sufficient mechanical properties, self-healing ability, and adhesive nature are some issues limiting its application window. Here, a facile one-pot synthesis of dual cross-linked zinc-coordinated copolymer hydrogels is presented. The network structure of the copolymer hydrogels is strategically developed via dynamic and reversible physical cross-linking by Zn 2+ ions and simultaneous covalent cross-linking through a covalent cross-linker viz methylene bisacrylamide. Fourier-transform infrared (FTIR), X-ray diffraction (XRD) scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis have thoroughly characterized the structure of the synthesized hydrogels. The introduction of Zn 2+ offers dynamic and reversible complexation, leading to excellent mechanical properties and self-healing features. Moreover, the percentage of the equilibrium water content of zinc-coordinated copolymer hydrogel samples is comparable with that of natural articular cartilage. The Shear sliding study shows the dominant adhesive behavior of HGel-Zn(NO 3 ) 2 sample compared to the parent HGel sample. This facile dual cross-linked hydrogel, HGel-Zn(NO 3 ) 2, with a combination of good mechanical properties, efficient self-recovery, adequate water content, and favorable adhesive nature, seems very promising to mimic the articular cartilage., (© 2024 Wiley‐VCH GmbH.)

A comparative evaluation of the brand-name drug Mycospor and six generic drugs (IWAKI, Bifonol, F, YD, Sawai, and TEVA), all comprising a cream formulation containing the antifungal drug bifonazole, was performed based on physicochemical measurements. The pH of the various formulations was significantly higher for the generics Bifonol (pH 7.1), Sawai (pH 6.7), and TEVA (pH 7.3) and significantly lower for YD (pH 4.3) than for the brand-name drug Mycospor (pH 5.5). The viscosity of the various formulations was significantly higher for TEVA (25,011 mPa·s) versus Mycospor (22,376 mPa·s) and significantly lower for IWAKI, Bifonol, F, YD, and Sawai, with Bifonol (8,572 mPa·s) being particularly low. Considering the hysteresis loop area obtained for the shear rate vs. shear stress, which represents the thixotropic properties, and using the value of Mycospor as the reference for 100%, YD (179%), Sawai (557%), and TEVA (201%) showed significantly higher values. Furthermore, the membrane permeability of bifonazole at 24 hours was significantly higher for Bifonol (309 μg/mL) and F (182 μg/mL) and significantly lower for Sawai (124 μg/mL) and TEVA (92 μg/mL) than for Mycospor (153 μg/mL). Finally, optical micrographs showed that the dispersion of particles was similar in the various formulations, but the particles of F and TEVA were uniformly dispersed with a smaller particle size than the other formulations. Overall, significant differences were observed in the formulation characteristics between the brand-name drug and generic drugs, which were attributed to differences in the manufacturing process and the types of additives.

The thixotropic behavior of mechanically disk refined cellulose nanofibril (CNF) aqueous suspensions with 100% fines content at 1 and 3 wt% concentrations was investigated through creep, shear-recovery, multiple-step oscillation, startup, and flow loop experiments. The CNF suspensions exhibited the key thixotropic characteristics such as reduction in viscosity over time and structure recovery after cessation of flow. The results of shear recovery and multiple-step oscillation experiments suggested that regardless of the CNF concentration, lower extents of deformation impede the ability of the suspension to recover its structure at rest and higher levels of shear rates and strain amplitudes facilitate the structure recovery. Furthermore, the results of the startup experiments indicate that CNF suspensions form structures at two different levels where the flocs erode each other during flow. The different types of loops found in the flow loop experiments performed at different shear rates and time intervals were categorized and analyzed in terms of the effects of erosion of flocs and fiber rearrangement during flow., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Emphasizing the viscoelasticity of ophthalmic gels is crucial for understanding the residence time, structure, and stability of hydrogels. This study primarily aimed to propose an innovative rheology analysis method for ophthalmic gels, considering complex eye movements. This method was applied to select ophthalmic gels with favorable rheological characteristics. Additionally, the physical characteristics and in vitro release of the selected Panax notoginseng total saponins (PNS) gel were demonstrated. The selected PNS gel significantly increased the activities of SOD and decreased intracellular levels of MDA, TNF-α, and IL-1β in H 2 O 2 -treated ARPE-19 cells. Finally, the optimal formulation was selected as a suitable platform for ophthalmic delivery and was shown to significantly rescue ARPE-19 cells from oxidative cellular damage.

The rheological behavior and printing characteristics of the screen-printing slurry for Nd-Fe-B grain boundary diffusion are key factors that determine the quality of printing and magnetic performance. However, few studies have focused on the organic medium, a crucial material for slurry. In this paper, the rheology, thixotropy, and thermal decomposition behavior of the organic vehicle in Nd-Fe-B screen printing slurry were studied. The results show that the organic vehicle formed by terpineol and polyvinyl butyral (PVB) exhibits typical non-Newtonian fluid characteristics, with excellent rheology and thixotropy, ensuring that the slurry prepared from it has excellent static stability and printing consistency. Additionally, the carbon residue of the organic vehicle formed by terpineol and PVB is less than 0.1% at 900 °C, avoiding excessive carbon entering the magnet during the diffusion process. Moreover, studying the rheology and thixotropy of the organic vehicle through a rheometer can quickly screen the slurry system. This work provides valuable guidance for designing an organic vehicle for screen-printing slurry for Nd-Fe-B grain boundary diffusion in future research.

The flow of a thixotropic Bingham material past a rotating cylinder is studied under a wide range of Reynolds and Bingham numbers, thixotropic parameters, and rotational speeds. A microstructure transition of the material involving breakdown and recovery processes is modeled using a kinetic equation, and the BinghamPapanastasiou model is employed to represent shear stress-strain rate relations. Results show that the material’s structural state at equilibrium depends greatly on the rotational speed and the thixotropic parameters. A layer around the cylinder resembling a Newtonian fluid is observed, in which the microstructure is almost completely broken, the yield stress is negligibly small, and the apparent viscosity approximates that of the Newtonian fluid. The thickness of this Newtonian-like layer varies with the rotational speed and the Reynolds number, but more significantly with the former than with the latter. In addition, the lift and moment coefficients increase with the rotational speed. These values are found to be close to those of the Newtonian fluid as well as of an equivalent non-thixotropic Bingham fluid. Many other aspects of the flow such as the flow pattern, the unyielded zones, and strain rate distribution are presented and discussed.

Self-healing, thermoresponsive hydrogels with a triple network (TN) were obtained by copolymerizing N-isopropyl acryl amide (NiPAAm) with polyvinyl alkohol (PVA) functionalized with methacrylic acid and N,N′-methylene bis(acryl amide) crosslinker in the presence of low amounts (

The aim of this study was to assess the gelling potential of chiral oxalamide derivatives in vegetable oils. Special emphasis was given to the potential applications of the examined oil gels as sustained delivery systems and as fat substitutes in food products. The applicability of oil gelators is envisaged in food, cosmetics, and the pharmaceutical industry. The regulations requiring the elimination of saturated fats and rising concerns among consumers health motivated us to investigate small organic molecules capable of efficiently transforming from liquid oil to a gel state. The oxalamide organogelators showed remarkable gelation efficiency in vegetable oils, thermal and mechanical stability, self-healing properties, and a long period of stability. The physical properties of the gels were analysed by TEM microscopy, DSC calorimetry, and oscillatory rheology. The controlled release properties of acetylsalicylic acid, ibuprofen, and hydrocortisone were analysed by the LC–MS method. The influence of the oil type (sunflower, soybean, and olive oil) on gelation efficiency of diverse oxalamide derivatives was examined by oscillatory rheology. The oxalamide gelators showed thermoreversible and thixotropic properties in vegetable oils with a minimum gelation concentration of just 0.025 wt%. The substitution of palm fats with gelled sunflower oil applied in cocoa and milk spreads at gelator concentrations lower than 0.2 wt% have shown promising viscoelastic properties compared to that of the original food products.

Thixotropy is a very important and unique property of soft clay in engineering, which has been drawing more and more attention in recent years. This study investigated the thixotropic strength recovery of representative marine clays in different sites of offshore China. The microstructure changes of clay during thixotropy were observed using scanning electron microscopy, and then related microscopic characteristics were analyzed. Probability entropy, Ep , is proposed as a new indicator based on the statistics of the alteration of diameter and orientation of particles or aggregates. The results show that thixotropy had significant effect on the strength increase for all the offshore Chinese clays that were tested, but their strength regain with time varied between the different sites. Some good correlations were developed between the thixotropy strength ratio and index parameters, particularly for water content, plasticity index, liquidity index, and sensitivity. The microstructural evolution of the clay tested during thixotropy was characterized by the change in both the diameter and the arrangement of particles or aggregates. The probability entropy was proved to quantitatively describe and analyze the microstructural evolution during thixotropy of clay, and its value increases with time. This new indicator could help to provide deeper insight into the thixotropic mechanism of clay. [ABSTRACT FROM AUTHOR]

Pumping of concrete is an efficient placement technique. When the concrete is pumped in a pipe, the lubrication layer (LL) forms and its rheological properties predominantly dictate the flow and govern the resumption operations. The primary purpose of this study was to investigate the effects of a new admixture, limestone calcined clay (LC2) at variable replacements (0%, 5%, 10%, and 20% by weight) on rheological properties of cementitious suspensions (equivalent to lubricating layer). An increase in yield stress, plastic viscosity, structuration rate, and decreased percolation time were observed with increments in the proportion of LC2 in cementitious suspensions. However, at the optimal dosage of superplasticizer, yield stress and plastic viscosity were decreased by 78% and 82%, respectively, even for the maximum replacement (20%) of LC2. Similarly, the percolation time increased by 15% and the structuration rate decreased by 39%, allowing additional time to deal with any pumping operational delays. From the results, it is also evident that higher deformation ratio of the lubrication layer is beneficial for concretes at rest due to pumping interruption. This study contributes to the fundamental understanding of viscoelastic properties of LC2-based cementitious suspensions, which will improve understanding of lubrication layer behavior for pumping operations. [ABSTRACT FROM AUTHOR]

Little is known regarding the effectiveness of biopolymers in soil improvement, especially considering interactions among different clay minerals, porewater cations, and biopolymer polarities. This paper presents an experimental investigation of the effects and effectiveness of four biopolymers of varying polarity and structure (xanthan gum, guar gum, carrageenan, and dextran), on the liquid limit, undrained strength, and thixotropic hardening of soft clays consisting of predominantly kaolinite with lesser montmorillonite. The liquid limits were measured using the standard Casagrande cup method. Fall cone penetration was adapted to determine the development of undrained shear strengths of the samples with time and after remolding. Clay samples were amended by the four biopolymers with a range of concentrations as well as varying NaCl in the pore fluid. Results show different biopolymers affect the consistency and strength behavior of different clays to varying extents; such changes are dominated by the constituent clay minerals’ surface charges as well as the biopolymers’ polarity and structure. Addition of biopolymers to clays results in an immediate gain in undrained shear strength that stabilizes, and some biopolymers exhibit a concentration saturation. Moreover, the neutral biopolymers (guar gum and carrageenan) behave fundamentally differently from anionic xanthan gum and cationic dextran. Advantages and limitations of potential applications of biopolymers in terms of effectiveness, costs, and ease of application are discussed. This research can aid the decision-making processes for coastal geotechnical engineers to determine which of the tested biopolymers presents a safe, cost-effective soil improvement additive for reducing erosion of coastal cohesive soils. [ABSTRACT FROM AUTHOR]

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The rapid advancement of 3D concrete printing (3DCP) and the development of relevant cementitious material compositions can be seen in the last few decades. The commonly used 3DCP method is to build the structure layer by layer after extruding the material through a nozzle. Initially, the pumping and extrusion of the material should be done with considerable fluidity and workability. The extruded layers should retain their shape immediately after extruding and depositing. While constructing the structure in a layerwise manner, the bottom layers should have enough early age strength to support the layers at the top. Therefore, at different processes in 3DCP, the rheological requirement is contradictory. As the rheology of the material is the deterministic factor which decides the fluidity or workability of the mix, proper rheological characterization should be completed accurately. In some instances, due to the higher stiffness, and higher time and rate-dependent material behavior (thixotropic behavior) compared to the conventional concrete, standard rheology measurement techniques have many limitations when used for 3DCP material. Therefore, non-conventional and novel techniques can be implemented with suitable material models to characterize the rheology of 3DCP material. In this study, a comprehensive review was conducted on conventional and non-conventional methods used for characterizing the rheological parameters for 3DCP material. The previously conducted studies were highlighted with the targeted 3DCP processes in the study (if applicable), and rheological parameters achieved from the test (i.e., yield stress, viscosity, and thixotropy). In addition, some experimental studies were conducted to compare several selected testing methods. The rheological parameters achieved from different test methods were compared to identify the similarities, dissimilarities, pros, and cons between the test methods. Furthermore, the extrudability and buildability studies were conducted for the mixes to demonstrate the usage of the mixes in 3DCP applications and to correlate the achieved rheological parameters with these processes. [ABSTRACT FROM AUTHOR]

Gel fuel potentially combines the advantages of solid fuel and liquid fuel due to its special rheological properties, which have essential impacts on the application of gel fuel in propulsion systems. In this paper, we study the rheological property of organic kerosene gel through a series of measurements on its viscosity as a function of the shear rate, temperature, and shear history. The measured datasets are then fitted with constitutive relationships between the viscosity and shear rate at three different levels: the power law shear-thinning model, the power law dependency on both the temperature and shear rate, and the thixotropic property. It is found that intense pre-shear could exhaust thixotropy and reduce viscosity of the kerosene gel. For the power law shear-thinning model, the consistency index increases with the gellant mass fraction, whereas the power law exponent remains constant. The dependence of viscosity on temperature could be well approximated by an empirical power law relationship. As for the thixotropic property of the kerosene gel, the fitted second-order kinetic model corresponds accurately to the viscosity at different shear rates and shear times. The constitutive models fitted in this work at different levels are consistent with each other and provide useful tools for further applications of organic kerosene gel fuel. [ABSTRACT FROM AUTHOR]

DNA hydrogels have attracted increasing attention owing to their excellent permeability and high mechanical strength, together with thixotropy, versatile programmability and good biocompatibility. However, the moderate biostability and immune stimulation of DNA have arisen as big concerns for future potential clinical applications. Herein, we report the self‐assembly of a novel l‐DNA hydrogel, which inherited the extraordinary physical properties of a d‐DNA hydrogel. With the mirror‐isomer deoxyribose, this hydrogel exhibited improved biostability, withstanding fetal bovine serum (FBS) for at least 1 month without evident decay of its mechanical properties. The low inflammatory response of the l‐DNA hydrogel has been verified both in vitro and in vivo. Hence, this l‐DNA hydrogel with outstanding biostability and biocompatibility can be anticipated to serve as an ideal 3D cell‐culture matrix and implanted bio‐scaffold for long‐term biomedical applications. [ABSTRACT FROM AUTHOR]

In this article, the rheological and thixotropic properties of fresh cement pastes (fcps) with nonionic polyacrylamide (PAM) are investigated through the coaxial rotary method. The B-HB model is resorted to fit the shear stress versus shear rate diagram, from which the slurry plastic viscosity is particularly discussed. The results show that with the development of PAM, the plastic viscosity increases first, then decreases, and then increases again, exhibiting the "up-down-up" trend, which is consistent with the fcps fluidity. The adsorption, lubrication, and entanglement mechanisms of PAM are successfully used to interpret this phenomenon. Combined with the suspension density, the relationship among plastic viscosity, flowability, and density is successfully established follower via a multivariate linear regression method. The Durbin-Watson coefficient, variance inflation factor, μ significance, ρ significance, and R 2 are 2.122, 1.024, 0.014, 0.004, and 0.776, respectively, demonstrating the feasibility of fitting formula. Besides that, the PAM containing slurry which exhibits the explicit thixotropy is also found according to the appeared hysteresis curve during one shearing cycle. With the increase of PAM dosage, the thixotropic indexes including Th1 and Th2 decreased, until the PAM exceeded 0.5%-0.6% dosage, both of them yielded negative values. The phenomenon that the fcps final shear stress exceeds its initial value occurs. [ABSTRACT FROM AUTHOR]

In this paper, the deformation of an isolated single two-dimensional droplet under simple shear flow is studied regarding the thixotropic behavior. In doing so, a modified consistent weakly compressible smoothed particle hydrodynamics method is employed. It is assumed that the thixotropic fluid obeys the Moore model, and the surface tension is modeled by the continuum surface tension (CST) method. After verifying the utilized paradigm, it is applied to novel cases in which one of the fluids exhibits thixotropic behavior. The effects of Moore's model constants are examined through several numerical simulations. It is shown that the drop deformation is dramatically affected by thixotropic behavior. Generally speaking, the deformation of the Newtonian droplet is decreased by increasing the destruction-to-rebuild ratio of the surrounding thixotropic liquid. The same trend is found when the thixotropic droplet is exposed to the shear flow of a Newtonian fluid. Also, it is demonstrated that the presence of another droplet in the vicinity of the first droplet could dramatically change the flow domain. To the best of the author's knowledge, the effect of thixotropy is investigated on droplet deformation for the first time. • The effects of thixotropy are investigated on droplet deformation in the simple shear flow by a consistent WC-SPH. • Two distinguishable cases are considered: Newtonian drop in thixotropic shear flow and vice versa. • The deformation is decreased by increasing b/a for both cases. The effects are more pronounced in the first case. • The threshold values of b/a for thixotropic behavior are about 0.01 and 0.1 for the first and second cases, respectively. • The presence of the second droplet could dramatically affect the flow field, especially in the intermediate times. [ABSTRACT FROM AUTHOR]