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We demonstrate supramolecular polymerization and formation of 1D nanofiber of azobenzene based organogelator (AZO‐4) in cyclic hydrocarbon solvents (toluene and methylcyclohexane). The AZO‐4 exhibits J‐ and H‐type aggregates in toluene: MCH (9 : 1) and MCH: toluene (9 : 1) respectively. The type of aggregate was governed by the geometry of the solvents used in the self‐assembly process. The J‐type aggregates with high thermal stability in toluene is due to the enhanced interaction of AZO‐4 π‐ surface with the toluene π‐surface, whereas H‐aggregate with moderate thermal stability in MCH was due to the interruption of the cyclic hydrocarbon in van der Waals interactions of peripheral chains of AZO‐4 molecule. The light induced reversible photoisomerization is observed for both J‐ and H‐aggregates. The macroscopic property revealed spontaneous and strong gelation in toluene preferably due to the strong interactions of the AZO‐4 nanofibers with the toluene solvent molecules compared to the MCH. The rheological measurements revealed thixotropic nature of the gels by step‐strain experiments at room temperature. The thermodynamic parameter (ΔHm) of gel‐to‐sol transition was determined for all the gels to get more insight into the gelation property. Furthermore, the phase selective gelation property was extended to the oil spill recovery application using diesel/water and petrol/water mixture. [ABSTRACT FROM AUTHOR]

Allantoin possesses numerous beneficial properties for the skin, like anti-irritant effects, wound healing, skin hydration, and epithelization. In this paper, we investigated a suitable preparation method for an allantoin hydrogel using the Semi-Solid Control Diagram (SSCD) method and characterized its rheological and consistency behavior. To accomplish this, xanthan gum (XG) was selected as a model gelling agent. Briefly, four hydrogels were prepared, two without allantoin (coded M01 and M02) and two with allantoin (M1 and M2). Similarly, the formulations were either prepared through magnetic stirring (M01 and M1) or homogenization in a mortar (M02 and M2). The prepared hydrogels were evaluated using the SSCD for specific parameters and indexes. The Good Quality Index (GQI) shows a higher value for the formulation, M1 = 6.27, compared to M2 = 5.45. This result is also underlined by the value of M01 = 6.45, which is higher than M02 = 6.38. Considering the consistency, the formulation M01 possessed the highest spreadability, followed by M02 and then the allantoin hydrogels M1 and M2. The rheological behavior had a thixotropic pseudoplastic flow for all the formulations. The use of SSCD pictographs outlined the rheological properties that need improvement, the method that is suitable to prepare the allantoin hydrogels, and the influence of the allantoin suspended in the XG hydrogel. [ABSTRACT FROM AUTHOR]

Cracks in coal goaf provide air leakage pathways and therefore increase the likelihood of coal spontaneous combustion, thus strongly affecting the safety of mining operations. Herein, an inorganic thixotropic gel (ITG) was proposed for inhibiting coal spontaneous combustion by blocking this leakage. The orthogonal experiments were designed to examine the effects of gel composition on gelation time and rheological/thixotropic properties. The three interval thixotropy test of the optimal-composition gel (4 wt% sodium bentonite, 3 wt% laponite, and 0.46 wt% silicate cement) revealed its good thixotropic recovery. The viscoelasticity test indicated that this gel retained elasticity-dominated behavior before being completely transformed into a sol and was not easy to break into pieces under pressure. By testing the characteristics of the ITG, it was proven that the ITG had an excellent water retention capacity, and high-temperature resistance and the apparent effects on blocking air leakage and extinguishing coal fire. By the thermogravimetric test, the influence of ITG on coal activation energy was calculated based on the ignition activation energy theory. FTIR was also introduced to analyze the effect of ITG on active groups of coal. In addition, structural characterization showed that ITG featured a tight surface and a stable overall structure, which further agreed with its prominent ability to block air leakage. [ABSTRACT FROM AUTHOR]

Oil-based drilling fluids are widely used in challenging wells such as those with large displacements, deepwater and ultra-deepwater wells, deep wells, and ultra-deep wells due to their excellent temperature resistance, inhibition properties, and lubrication. However, there is a challenging issue of rheological deterioration of drilling fluids under high-temperature conditions. In this study, a dual-amphiphilic segmented high-temperature-resistant gelling agent (HTR-GA) was synthesized using poly fatty acids and polyether amines as raw materials. Experimental results showed that the initial decomposition temperature of HTR-GA was 374 °C, indicating good thermal stability. After adding HTR-GA, the emulsion coalescence voltage increased for emulsions with different oil-to-water ratios. HTR-GA could construct a weak gel structure in oil-based drilling fluids, significantly enhancing the shear-thinning and thixotropic properties of oil-based drilling fluids under high-temperature conditions. Using HTR-GA as the core, a set of oil-based drilling fluid systems with good rheological properties, a density of 2.2 g/cm3, and temperature resistance up to 220 °C were constructed. After aging for 24 h at 220 °C, the dynamic shear force exceeded 10 Pa, and G′ exceeded 7 Pa, while after aging for 96 h at 220 °C, the dynamic shear force exceeded 4 Pa, and G″ reached 7 Pa. The synthesized compound HTR-GA has been empirically validated to significantly augment the rheological properties of oil-based drilling fluids, particularly under high-temperature conditions, showcasing impressive thermal stability with a resistance threshold of up to 220 °C. This notable enhancement provides critical technical reinforcement for progressive exploration endeavors in deep and ultra-deep well formations, specifically employing oil-based drilling fluids. [ABSTRACT FROM AUTHOR]

The corrosion of steel in post-tensioned tendons has been associated with deficient grout materials containing high free sulfate ion concentrations. In a Florida bridge in 2011, tendon corrosion failures occurred for a prepackaged thixotropic grout that had developed material segregation. However, the available grout and corrosion testing prescribed in material specifications, such as grout bleed water testing, was not able to identify the propensity or modality for the grout deficiencies and the associated steel corrosion that was observed in the field. It was of interest to identify corrosion testing methods that could prescribe grout resistance to segregation-related deficiencies that can form by aberrations in construction. The objectives of the work presented here included (1) characterizing the development of physical and chemical grout deficiencies due to excess mix water and water volume displacement, (2) developing small scale test methodologies that identify deficient grout, and (3) developing test methodologies to identify steel corrosion in deficient grout. The inverted-tee test (INT) and a modified incline-tube (MIT) test were assessed and both were shown to be useful to identify the robustness of grout materials to adverse mixing conditions (such as overwatering and pre-hydration) by parameters such as sulfate content, moisture content, electrical resistance, and steel corrosion behavior. It was shown that the different grout products have widely different propensities for segregation and accumulation of sulfate ions but adverse grout mixing practices promoted the development of grout deficiencies, including the accumulation of sulfate ions. Corrosion potentials of steel < −300 mVCSE developed in the deficient grout with higher sulfate concentrations. Likewise, the corrosion current density showed generally high values of >0.1 μA/cm2 in the deficient grouts. The values produced from the test program here were consistent with historical data from earlier research that indicated corrosion conditions of steel in deficient grout with >0.7 mg/g sulfate, further verifying the adverse effects of elevated sulfate ion concentrations in the segregated grout. [ABSTRACT FROM AUTHOR]

Organic‐inorganic hybrid materials are highly important for designing and engineering bioinspired structures and functions. Herein, we have demonstrated the synthesis and metallogelation of triazole‐appended phenylalanine and resulting stiffness enhancement. The 2,5‐diphenyl‐2H‐[1,2,3]triazole‐4‐carboxylic acid was synthesized by sequential C−N bond formation and electro‐oxidative N−N coupling under metal‐free conditions and coupled with L‐Phe to develop the gelator. Starting with basic (pH 11) solutions (5 mg/mL) of gelator, we show that significant stiffness enhancement is achieved upon adding Ca2+. From rheology, the storage modulus exhibits 8‐fold increase by the calcium‐induced gelation. The calcium‐induced gels are thixotropic in nature. The calcium ion bivalency leads to "cross‐links" and promote assembly of gelators, which not only influences the gel microstructure but also manipulates subsequent mechanical properties of the metallogels. [ABSTRACT FROM AUTHOR]

Molecular oleogels have the potential to be used as materials in healthcare applications. However, their design and synthesis are complex, thus requiring simple and effective methods for their preparation. This paper reports on alkylanilides that are low molecular-weight organogelators, which when appropriately mixed with different alkyl chain lengths could result in the formation of mixed molecular gels that exhibit excellent gel-forming ability and mechanical properties. In addition, the single and mixed molecular organogel systems were found to be applicable as single and mixed molecular oleogel systems capable of gelling oils such as olive oil and squalane. This has been found to be true, especially in molecular oleogel systems consisting of squalane, which is used as solvents in healthcare. The mixed squalene-molecular oleogel systems showed an increase in the critical (minimum) gelation concentration from 1.0 to 0.1 wt.% in the single system and an improvement in the thixotropic behavior recovery time. The thixotropic behavior of the molecular oleogels in the mixed system was quantitatively evaluated through dynamic viscoelasticity measurements; however, it was not observed for the single-system molecular oleogels. Scanning electron microscopy of the xerogels suggested that this behavior is related to the qualitative improvement of the network owing to the refinement of the mesh structure. These mixed molecular oleogels, composed of alkylanilides displaying such thixotropic behavior, could be used as candidates for ointment-base materials in the healthcare field. [ABSTRACT FROM AUTHOR]

A gelation solvent containing a diamide‐based thixotropic additive with two hydrocarbons and organo‐modified nanodiamonds was prepared and evaluated herein as a coating film. Nanodiamonds were introduced into a solvent containing diamide‐based thixotropic additive molecules with 12‐hydroxystearyl chains which were uniformly dispersed due to organic chain modification on the outermost layer surface. In addition to common solvents including toluene, ethyl cetyl hexanoate, a cosmetic emollient, forms nanodiamond‐containing gels. The helical nanofibers formed by the diamide‐based thixotropic additive molecule with two hydrocarbons in the gel showed affinity for the organo‐modified nanodiamonds, and the contact morphology between the nanofibers and nanodiamond particles was confirmed. Nanodiamonds exhibited a denaturation effect on biomolecules adsorbed on their surfaces. Overall, nanodiamond‐containing emollient gels are expected to exhibit antibacterial properties against viruses and malodorous bacteria on skin as part of thixotropic immobilization films for cosmetic powders. [ABSTRACT FROM AUTHOR]

This article discusses the issue of poor platelet counts in platelet-rich plasma (PRP) kits that use a thixotropic gel separator. The authors conducted a study to understand the cause of this problem and found that a large portion of platelets were getting trapped in the gel separator during the PRP preparation process. They compared the traditional inversion method with a patented agitation method and found that the agitation method resulted in higher platelet counts and platelet capture efficiency. The authors suggest that using the agitation method can increase the yield of platelets in PRP preparation and potentially enhance the regenerative properties of PRP in dermatologic applications. [Extracted from the article]

Chitosan‐based hydrogels are prepared via the formation of polypseudorotaxanes (PPR), by selectively threading α‐cyclodextrin (α‐CD) macrocycles onto polymeric chains, which, through the formation of microcrystalline domains, act as junction points for the network. Specifically, host–guest inclusion complexes are formed between α‐CD and PEGylated chitosan (PEG‐Ch), resulting in the formation of supramolecular gels. PEG‐grafted chitosan is obtained with a reaction yield of 79.8%, a high degree of grafting (50.9% GW) and water solubility (≈16 mg mL−1), as assessed by turbidimetry. A range of compositions for mixtures of PEG‐Ch solutions (0.2–0.8% w/w) and α‐CD solutions (2−12% w/w, or 0.04–0.2% mol) are studied. Regardless of PEG content, gels are not formed at low α‐CD concentrations (<4%). Dynamic rheology measurements reveal stiff gels (G' above 15k) and a narrow linear viscoelastic region, reflecting their brittleness. The highest elastic modulus is obtained for a hydrogel composition of 0.4% PEG‐Ch and 6% α‐CD. Steady‐state measurements, cycling between low and high shear rates, confirm the thixotropic nature of the gels, demonstrating their capacity to fully recover their mechanical properties after being exposed to high stress, making them good candidates to use as in‐situ gel‐forming materials for drug delivery to topical or parenteral sites. [ABSTRACT FROM AUTHOR]

Composite films containing >0.5% polymer could be produced from mixed aqueous solutions of poly(vinyl alcohol) (PVA), simple amino acids (glycine and L-cysteine), and silver nitrate by casting in Petri dishes followed by drying at 30ºC. The viscosity characteristics of the mixed solutions and the mechanical properties of films produced from these solutions were studied as a function of the PVA concentration. A supramolecular gel with thixotropic properties formed with a low PVA content (≤0.1%) in the solution while the thixotropic properties disappeared and the ability to produce films appeared for concentrations ≥0.5%. The higher the polymer content in the solution and film was, the higher their viscous and stress-strain properties were. The structures and properties of the mixed solutions and hydrogels and films prepared from aqueous solutions of glycine, PVA, and silver nitrate were studied using viscometry, UV spectroscopy, dynamic light scattering, scanning electron microscopy, and elemental analysis. The presence of glycine in the solution and gel was observed to reduce the viscosity because it weakened the H-bonding between polymer macromolecules. Films that were very light sensitive with respect to formation of silver nanoparticles could be produced at PVA solution concentrations of 5% and greater, like for films based on L-cysteine and silver nitrate. [ABSTRACT FROM AUTHOR]

The rheological behavior of gel propellants is crucial for their practical applications, especially in the rocket engine and ramjet fields. The thixotropic characteristics of gel propellants are an important component of their rheological properties and have a notable impact on their flow and injection process. However, most gel propellants contain rich, dynamic cross-linked network structures, which impart complex non-Newtonian fluid properties, and it is difficult to establish a unified mathematical model. In view of this, this study addresses the thixotropy of a prepared RP-3 kerosene gel and determines the mathematical model and model parameters describing its thixotropy. Experiments show that the kerosene gel exhibits shear-thinning properties as well as thixotropy. To describe the microstructural changes in the gel, three thixotropic constitutive models are introduced to analyze the rheological data, and the constitutive equation parameters are optimized. The three models are all structural dynamic models, which can be used to describe microstructural changes within the material. In addition, the fitting of the constitutive equation is a multiparameter optimization problem, and an appropriate optimization method must be used for parameter fitting. Therefore, the Bayesian optimization method combined with Gaussian process regression and the upper confidence bound (UCB) acquisition function is used in the multiparameter fitting of the constitutive models. Both experiments and numerical results show that the thixotropic model, which introduces a pre-factor with shear strain and assumes that the breakdown of the gel structure is related to energy dissipation rather than the shear rate, has a better fitting effect and prediction ability with regard to the gel. Combined with transient experiments at different shear rates, the model parameters of the constitutive law can be determined quickly by applying the Bayesian optimization method. [ABSTRACT FROM AUTHOR]

The present work provides characterization of rheological properties of a new bentonite-based thixotropic gel emulsion nasal spray (AM-301), its nasal residence time, distribution, safety and tolerability. The nasal epithelium is a portal of entry for allergens and primary infection by airborne pathogens. Non-pharmacological interventions, which enhance physical and biological barriers, protect against allergens and pathogens without drug-related side effects. AM-301 has shown promising efficacy and safety in the nasal epithelium against viruses (in vitro) and pollen (clinical). Technical part (i) spray characterization was performed with a validated droplet size distribution method; evaluation of the rheological properties of the formulation was performed by a validated amplitude sweep method and a validated oscillation, rotation, oscillation; Clinical part (ii) nasal and oropharyngeal endoscopy were used to provide a semi-quantitative evaluation of distribution and residence time of fluorescein-labelled AM-301 in the nose and oropharynx of healthy volunteers; (iii) tolerability and safety. (i) The non-Newtonian rheological properties of the formulation allow AM-301 to be sprayed and then to revert to a gel to prevent run-off from the nasal cavity; (ii) the formulation remains on the inferior turbinate, septum and oropharynx of volunteers for up to 210 min and on the middle turbinate for up to 60 min; two nasal sprays provide no substantial benefit over a single application with regards to coverage or retention; (iii) the spray is well tolerated Single dose spray delivery of AM-301 provides extended coverage of the nasal mucosa up to the inferior turbinates. [ABSTRACT FROM AUTHOR]

Zinc oxide nanoparticles (ZnO NPs) modified by oxopyrymidine alcohol, also known as xymedone (Xym), were obtained and studied using FTIR, UV-vis, and fluorescent spectroscopy, and SEM, BET, powder XRD, and DLS analysis. A formulation of thixotropic hydrophilic gels containing Carbopol-based Xym and ZnO NPs was developed. A vertical Franz cell with a cellulose acetate membrane was used as a model to investigate the passive diffusion of the gel components by AAS. The gel components—Xym and ZnO NPs—were shown to penetrate through acetyl cellulose membrane within 5–7 h depending on an initial amount, and its values were in the range of 56–77%. The penetration of modified ZnO NPs by Xym was more effective in contrast to ZnO NPs without modification. The burn wound healing activity of ZnO NPs–Xym gel was demonstrated on a thermal burn wound model on rats. SOD and GR activity was increased by 30–35% during ZnO NPs–Xym gel treatment, the burn area on 10 postburn day decreased by 10% in contrast to a positive control, Methyluracyl®® ointment. [ABSTRACT FROM AUTHOR]

The author reported molecular organogels using N-alkylhydantoins as new low-molecular-weight gelators for the first time, and thixotropic mixed molecular organogels using a set of N-alkylhydantoin gelators with different alkyl chain lengths. These homologous compounds with different alkyl chains are found to form macroscopic crystals or solution states in polar solvents, but form homogeneous organogels in non-polar solvents, such as n-octane and squalane. Although there is no significant increase in the minimum gelation concentration of the mixed molecular gels using squalane as a solvent, these mixed molecular organogels show improved mechanical properties, especially in their thixotropic behavior, which is not observed in the single N-alkylhydantoin gels. Furthermore, they exhibit reversible thixotropic behavior with quick recovery of the gel state in a minute by quantitatively measuring dynamic viscoelasticity measurements of rheometry of mixed molecular gels. Based on the morphological observations of the xerogels, the self-assembling fibers of the gelators become finer, indicating an increase in the density of the mesh structure inside the gel, which could explain its thixotropic behavior. These thixotropic mixed molecular gels may be applicable to ointment base materials, because they are gelled with squalane oil. [ABSTRACT FROM AUTHOR]

• The thixotropic gel YSL synthesized by AM, SMA, TA, KA and LAP showed good shear thinning behavior, thixotropic behavior, viscoelasticity and adhesion performance. • The shear thixotropic mechanism of gel YSL depends on the physical cross-linking of hydrophobic monomers and clay particles in the gel: hydrogen bonding, hydrophobic association and electrostatic interaction. • TA in the gel improves its adhesion ability in the leakage channels (TA and the rock surface will produce non-covalent bonding: metal coordination and cation-π). • Gel YSL can be used as a lost circulation material in the drilling field, plugging mechanism of gel YSL was explained. Gel-based plugging materials have become commonplace in addressing lost circulation wells. However, traditional gels are associated with challenges such as difficulties in injection, irreversible structural damage under high shear stress, poor retention capacity within leakage channels, resulting in diminished pressure-bearing capabilities, subpar sealing efficacy, and prolonged non-production periods. In this study, a plugging gel, denoted as YSL, was synthesized via free-radical aqueous solution polymerization using AM, hydrophobic monomer SMA, and TA as raw materials, with KA and LAP as inorganic additives. The physicochemical properties were characterized using FT-IR, TGA, and SEM. Additionally, the rheological properties, thixotropic behavior, viscoelasticity, adhesion performance, and plugging performance of the YSL gel were systematically investigated. The results indicate that increasing the hydrophobic monomer and inorganic clay particles can enhance the viscosity, thixotropic ability, and storage modulus of the gel, although excessive non-covalent interactions diminish the adhesion capability of TA in the gel. Compared to commercial polymer gels and bridging plugging materials, YSL exhibits superior pressure-bearing plugging capability. Additionally, plugging mechanism of the gel in leakage channels was analyzed. The findings suggest significant potential applications of YSL in drilling leakage prevention and plugging in the oil and gas industry. [ABSTRACT FROM AUTHOR]

Low‐molecular‐weight hydrogelators containing stearoyl, glycine, and D‐glucamine moieties with or without methyl groups were synthesized to prepare chemically tuned molecular hydrogels. To evaluate the role of hydrogen bonding of hydrogelators in molecular hydrogel formation, the author has newly synthesized hydrogelators with or without methyl groups at their N−H in amide groups, contributing to the hydrogen bond formation in fiber in molecular hydrogels. The obtained hydrogels exhibited improved thixotropic performance with tunable softness, exhibiting pseudo‐reversible thixotropic cycles that depended on the methyl substitution positions in the hydrogelators. To change the hydrogen bonds′ positions by chemical modification has made it possible to tune the mechanical properties of molecular gels. [ABSTRACT FROM AUTHOR]

This work compared thermally reversible emulsion gels and high internal phase emulsions (HIPEs) based on pea protein for 3D printing at different oil volume fraction (ϕ) ranging from 0.2 to 0.8. Thermally reversible emulsion gels were obtained with ϕ from 0.2 to 0.65, which melt into liquid emulsion as temperature increased, and recovered into emulsion gels upon cooling as reflected by consistent rheological measurements. The Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the transition between intermolecular β-sheet at 1630 cm−1 and intramolecular β-sheet at 1618 cm−1 through reversible H-bonds upon changes in temperature, which was responsible for the repeated thermo-reversibility. With ϕ increased to 0.74–0.8, HIPEs were confirmed by Scanning Electron Microscope (SEM) and Confocal Laser Scanning Microscope (CLSM), yet the thermo-reversibility was not maintained. In addition, the thermally reversible emulsion gels exhibited strong shear-thinning and thixotropic recovery through the untangling and reformation of the H-bonded gel network. Whereas deformation and restructuring of the close packed droplets were responsible for such behaviors in HIPEs. 3D printing test has further demonstrated excellent performance of thermally reversible emulsion-filled gel with ϕ 0.4, comparable to HIPE with ϕ 0.74 b y enabling printed objects with high shape fidelity (printability index (Pr) of 0.95–1.08) and shape stability (prints height maintenance (Hm) of 82.2%–87.8%). This research opens up thermally reversible emulsion gels solely from sustainable protein source for 3D printing, with low oil content and no synthetic ingredients needed. [Display omitted] • Emulsion-filled pea protein gels reversibly melt and recover with temperature change. • The above thermo-reversibility allowed excellent 3D printability comparable to HIPEs. • FTIR revealed that the reversible H-bonds contributed to the thermo-reversibility. • HIPEs lost thermo-reversibility at higher oil volumes yet showed great heat stability. • 3D printable low-fat emulsion-filled gels can be prepared solely by pea protein. [ABSTRACT FROM AUTHOR]

The wide spread of antimicrobial resistance (AMR) is a crisis caused by the misuse of antibiotics. Despite the development of rapid antimicrobial susceptibility testing (AST) methods, there is an urgent need for an alternative rapid AST method that does not rely on testing equipment especially in resource-limited settings. In this work, a bacterial proliferation sensor based on naked-eye detection for rapid AST was developed. The sensor included the macroscopic bacterial culture chambers and bacterial growth detection microchannels for naked eye observation. After incubation at different antibiotic concentrations for 3–5 h, a one-step centrifugation effectively concentrated the suspended bacterial cells into visually observable microbars with length proportional to the number of cells, enabling to directly compare the bacterial accumulation under different drug concentrations. As a proof of concept, the sensor was able to determine the sensitivity of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) to drugs using the naked eye within 3–5 h. Furthermore, by combining with the thixotropic gel centrifugation method for bacteria separated from positive blood cultures (PBCs), we proposed a rapid and low-cost AST method for complex samples and evaluated the feasibility using clinical samples from cerebrospinal fluid-positive, blood-positive, ascites-positive and bile-positive culture bottles. The results were highly consistent with that from the clinical standard methods. The proposed sensor could achieve a rapid, low-cost, naked-eye detectable AST method for complex clinical samples, which would be applicable to the resource-limited areas. [Display omitted] • A rapid naked-eye detection bacterial proliferation sensor for antimicrobial susceptibility testing (AST) was developed. • Combined with thixotropic gel centrifugation, a rapid and low-cost AST method for complex samples was proposed. • The AST method was successfully applied to the diagnosis of clinical samples with reliable and fast results. [ABSTRACT FROM AUTHOR]

This manuscript developed a novel DLC–supramolecular gel (HTG) composite lubrication system to achieve long-life outstanding lubrication under extreme contact stress while avoiding sealing challenges relying on the unique thixotropic properties of the gel. DLC–HTG exhibited ultra-low wear and excellent friction reduction performance under a maximum contact stress of 2.24 GPa. DLC films with designed double transition layers possess high interfacial bond strength and mechanical properties, providing the basis for high wear resistance. The establishment of a robust tribofilm and the confinment effect of HTG on wear debris dominate the achievement of ultra-low wear. This ultra-low wear sliding extends the service life of the lubrication system with the broad implications for mechanical engineering, transportation, and wind power generation. [Display omitted] [ABSTRACT FROM AUTHOR]

Ultra Violet radiations induced skin damage and associated skin disorders are a widespread concern. The consequences of sun exposure include a plethora of dermal conditions like aging, solar urticaria, albinism and cancer. Sunscreens provide effective protection to skin from these damages. Besides FDA approved physical and chemical UV filters, phytoconstituents with their multi functionalities are emerging as frontrunners in Therapy of skin disorders. Objective of this study was to develop novel phyto-dermal gel (PDG) with dual action of sun protection and antioxidant potential using polymeric mixed micelles (PMMs) are nanocarriers. PMMs of Pluronic F127 and Pluronic F68 loaded with curcumin and quercetin were optimized by 32 factorial designs. Responses studied were vesicle size, SPF, entrapment efficiency of curcumin and quercetin and antioxidant activity. Droplet size ranged from 300 to 500 nm with PDI in between 0.248 and 0.584. Combination of curcumin and quercetin showed enhanced sun protection and antioxidant activity. Pluronics played a significant positive role in various parameters. In present studies vesicle size of factorial batches was found to be between 387 and 527 nm, and SPF was found to be between 18.86 and 28.32. Transmission electron microscopy revealed spherical morphology of micelles. Optimized micelles were incorporated into Carbopol 940. Optimized PDG was evaluated for pH, drug content, spreadability, rheology, syneresis, ex vivo permeation, and skin retention. Hysteresis loop in the rheogram suggested thixotropy of PDG. Syneresis for gels from day 0–30 days was found to be between 0% and 12.46% w/w. SPF of optimized PDG was 27±0.5. Optimized PDG showed no signs of erythema and edema on Wistar rats. PMMs thus effectively enhanced antioxidant and skin protective effect of curcumin and quercetin. [Display omitted] • Curcumin and quercetin loaded in mixed polymeric micelles. • Factorial design to study relationship between independent and dependent variables. • Phytoconstituents loaded micelles incorporated into thixotropic gel. • Gel exhibits enhanced antioxidant activity and sun protection factor. [ABSTRACT FROM AUTHOR]

Zinc oxide nanoparticles (ZnO NPs) modified by oxopyrymidine alcohol, also known as xymedone (Xym), were obtained and studied using FTIR, UV-vis, and fluorescent spectroscopy, and SEM, BET, powder XRD, and DLS analysis. A formulation of thixotropic hydrophilic gels containing Carbopol-based Xym and ZnO NPs was developed. A vertical Franz cell with a cellulose acetate membrane was used as a model to investigate the passive diffusion of the gel components by AAS. The gel components—Xym and ZnO NPs—were shown to penetrate through acetyl cellulose membrane within 5–7 h depending on an initial amount, and its values were in the range of 56–77%. The penetration of modified ZnO NPs by Xym was more effective in contrast to ZnO NPs without modification. The burn wound healing activity of ZnO NPs–Xym gel was demonstrated on a thermal burn wound model on rats. SOD and GR activity was increased by 30–35% during ZnO NPs–Xym gel treatment, the burn area on 10 postburn day decreased by 10% in contrast to a positive control, Methyluracyl®® ointment.

In this paper, the impact of different substitution levels of cress seed gum (CSG, 0, 5, 10, and 15%) and sucrose (SUC, 0, 5, and 10%) on the rheological properties, textural attributes, syneresis, FTIR and microstructure of native wheat starch (NWS, 4%) gel was investigated. According to the rheological tests, the NWS-CSG and NWS-CSG-SUC gels showed thixotropic behavior and all the samples exhibited shear-thinning flow behavior. Increasing the CSG substitution level up to 15% elevated the apparent viscosity, consistency coefficient whereas the SUC substitution with NWS reduced these values. The higher apparent viscosity, consistency coefficient, and stronger pseudoplastic behavior were obtained for NWS-CSG-SUC gel than NWS gel. The addition of CSG greatly decreased hardness and consistency from 140 to 55.5 g and from 6.9 to 3.0 mJ, respectively during storage at 4 °C for 14 days; while in the presence of SUC these values slightly decreased. After storage, syneresis of NWS and NWS-10%SUC gels increased by 46.78% and 32.11%, respectively; whereas it decreased 19.88% for NWS-15%CSG gel. The SEM images showed that the mixed gels had a denser structure with a smaller pore size. The results indicated that CSG had positive effect in modifying the properties of NWS-SUC mixed gels. • Wheat starch (NWS)-sugar-gum ternary system was characterized in the present study. • Cress seed gum (CSG) improved the sugar-starch gel properties in the ternary system. • CSG reduced the syneresis of NWS-sucrose (SUC) gel after storage for 14 days. • SUC and CSG retarded retrogradation of NWS gel during storage. • CSG caused a significant decrease in the hardness and consistency during storage. [ABSTRACT FROM AUTHOR]

A variable focus optical lens using a thixotropic gel and ultrasonic vibration is discussed. The surface profile of the gel could be deformed via acoustic radiation force generated by ultrasound. A thixotropic gel in which the viscosity was changed by shear stress was employed as a transparent lens material. The thixotropic gel allowed the lens to maintain shape deformation in the absence of continuous ultrasound excitation. The lens had a simple structure with no mechanical moving parts and included an annular piezoelectric transducer, a glass disk, and the thixotropic gel film. The axisymmetric concentric flexural vibration mode was generated on the lens at 71 kHz, which resulted in static surface deformation of the gel via the acoustic radiation force. The preservation rate was investigated after switching off the ultrasonic excitation. There was a trade-off between the preservation rate of the lens deformation and the response time for focusing. The focal length could be controlled via the input voltage to the lens, and a variable-focus convex lens could be realized; the change in the focal length with 4.0 Vpp was 0.54 mm. The optical transmittance of the lens was measured and the transmittance ranged 70%–80% in the visible spectral region. [ABSTRACT FROM AUTHOR]

The article is devoted to influence of the clay thixotropic solutions on the strength of resistance to movement of the earthmoving machines' working elements. The forces of resistance to the movement of a flat plate, a smooth cylinder and real working bodies in a clay solution for various modes of solution flow (bingamian, pseudo-laminar and turbulent) are established. Mathematical models of movement of the earthmoving machines working elements in clay solution are developed and investigated. Dynamics of the working element of an earthmoving machine movement in a clay solution is studied. Dependence of the feed force, torque and dynamic coefficient on the resistance forces, acting on the working body from the clay solution, is established. [ABSTRACT FROM AUTHOR]

The present article aims to decipher the effect of preheating a segment of the pipe on the pressure propagation mechanisms and flow restart operation in a gelled pipeline. During the restart operation, shear-thinning thixotropic rheology governs the gel properties, where the viscosity is a function of shear strain and thermal history. A finite volume method is employed to solve the governing equations for a weakly compressible gel. Rheology of the initial gel incorporates the effect of temperature distribution from the preheating stage. Flow restart in the thixotropic gel involves three different timescales: namely, the compressive diffusion timescale (acoustic wave propagation timescale), the viscous timescale, and the gel degradation timescale. In an isothermal case, the flow restart occurs at the gel degradation timescale, whereas flow restart in the preheated gel takes place at the viscous timescale. Time evolution of nonlinear axial pressure profile and residual viscosity provides a theoretical understanding of the gel degradation process in the thermal diffusion-controlled and advection-controlled flow regimes, defined in terms of Peclet number (Pe). The results indicate that the gel degradation process is affected by thermal-induced melting in addition to shear melting. Partial preheating tends to dislodge the gel into plugs, and this is more significant at low Pe and high pristine gel strength. The local Nusselt number (Nu) at the heated portion of the wall during flow restart suggests that the wall-heat transfer is prominent when the pressure wavefront has not reached the outlet. [ABSTRACT FROM AUTHOR]

Production of whipped confectionery (marshmallows, pressed fruit paste, sweets with light-textured centres) is a complex process difficult to control. To expand and modernise their production, it is necessary to find simpler technologies, both resource-and energy-saving, to increase the stability of the heterogeneous dispersed system, and to improve the quality of finished products. In this respect, applying food additives of the nanometer range in technology looks very promising due to their unique physicochemical parameters and their many functional and technological properties. In the paper, it is suggested to solve the problem of stabilising the polyphase structure of whipped confectionery products and to form their quality by using the food additive Magnetofood based on ferrous and ferric oxides (FeO.Fe2O3). Magnetofood is ultrafine powder with a particle size of ~80 nm. It has a high functional and technological potential: large specific surface and a set of useful properties (the additive is surface-active, with complex-forming, sorption, and stabilising properties). This allows us to recommend Magnetofood as an additive with a complex action to improve the quality and extend the shelf life of sugar confections like fruit paste and fruit jelly products, in particular, white and pink marshmallows. It has been found that addition of Magnetofood in the form of an aqueous suspension at the stage of swelling and dissolution of the gelling agent improves the shape and consistency, reduces the density of the foam structure by 1.12–1.15 times, reduces the amount of gelling agent by 10–12% for agar and by 7–9% for pectin, increases the mechanical strength of marshmallows by 11.5–12.6% for agar and by 8.2-9.1% for pectin. Besides, the foaming ability of egg white increases by 1.14-1.4 times (with constant foam stability (99±1)% due to the stabilising effect of Magnetofood nanoparticles), and the thixotropic property of the gel structure becomes 1.4–1.5 times as much. [ABSTRACT FROM AUTHOR]

Background: Drug-free viscous nasal applications have been shown to reduce nasal symptoms in individuals with seasonal allergic rhinitis (SAR). Nascum®-Plus (NP), a commercially available thixotropic gel, has been designed to reduce dryness and soreness of the nasal mucosa and prevent the absorption of small particles. Objectives: The aim of this study was to assess the efficacy of single-dose NP in treating nasal symptoms and secretion during challenge in an allergen challenge chamber (ACC). Furthermore, the effect of this treatment on biomarkers and immune cells of the allergic cascade were measured. Methods: This open-label, cross-over, sequence-randomized, monocentric trial randomized 18 adults with SAR and a positive skin prick test reaction to Dactylis glomerata pollen to receive NP or no treatment during two 4-h ACC sessions 3 weeks apart. On Day 1, 9 subjects were challenged for 4 h with treatment, the other 9 without treatment, and vice versa on Day 22. Nasal lavage fluid and nasal filter eluate samples were obtained pre, 2, and 18 h post challenge in the ACC. Results: NP significantly reduced nasal symptoms, assessed by total nasal symptom score (p < 0.001), and minimized nasal secretion (p = 0.047), while no significant effect on biomarkers and immune cells in the nasal fluid was observed. The treatment was safe and well-tolerated. Conclusions: The physical barrier built by NP nasal gel can be safely applied in patients with allergic rhinitis. It reduces allergic nasal symptoms and secretion, but application of a single dose does not affect local inflammatory biomarkers. [ABSTRACT FROM AUTHOR]

• A facile method was proposed to prepare thixotropic emulsion gels. • Ca2+ incorporation could greatly enhance the stackability of the emulsion gels. • Freeze-thawing treatment slightly increased the stiffness of the emulsion gel. • Emulsified oil droplets in the gel matrix served as inactive fillers. In this study, a series of emulsion gels were prepared by dispersing emulsified oil droplets into alginate (Alg) gel matrix, and the final emulsion gels contained 2% Alg (w/v), 0.5% Tween 80 (v/v) and gradient concentrations of oil phase fractions (5–30%, v/v). Subsequently, the effects of Ca2+ addition, heating, and freeze thawing treatments on the emulsion gels were also investigated by a combination of rheological tests, confocal and scanning electron microscopy techniques. It was found that within the range of 0–30% of oil phase fraction, 0–0.15% of CaCl 2 addition (w/v), all the emulsion gels could achieve significant thixotropy and good emulsion stability, without discernible oil droplet coalescence observed after heating and/or freeze thawing treatments. The yield stress value and gel stiffness increased with increasing oil phase fraction and Ca2+ addition, which is attributed to the strengthened gel network cross-links in the emulsion gels, as confirmed by SEM results. Interestingly, after freeze thawing treatment, the gel stiffness was slightly improved, which may be due to the intermolecular self-association of Alg during freezing stage. Overall, these results show the potential application of Alg-stabilized emulsion gels in preparation of low-fat mayonnaise products and other similar emulsion foods. [ABSTRACT FROM AUTHOR]

The viscosity and the surface profile of a thixotropic gel were controlled via ultrasound vibrations. The ultrasound device consisted of two piezoelectric lead zirconate titanate transducers glued to each end of a 60-mm-long rectangular glass substrate. It generated a 71-kHz flexural standing wave along the length. A 0.9-mm-thick thixotropic gel film made from silicone oil and hydrophobic fumed silica was formed on the glass substrate. The ultrasound vibration decreased the film viscosity, and its surface profile could be changed by the acoustic radiation force acting from the gel to the surrounding air, generated by the flexural vibration of the substrate. The transient response of the surface profile was observed by switching the ultrasound excitation ON and OFF. When the excitation was switched OFF, the gel displacement gradually decreased, but the surface profile did not return to that of the initial steady state, indicating that the viscosity recovered in time to preserve the surface profile. When a pulsed megahertz (MHz) signal was used to control the gel deformation, the surface profile rapidly approached the initial steady-state profile after the excitation. [ABSTRACT FROM AUTHOR]

Therapeutic levels of lactulose were used with commercial starters (Yoflex 801, Yoflex 901 and Yomix 486) in yoghurt. In fact, Yoflex 801 was supplemented with 1.5% lactulose resulting in minor yoghurt quality alterations. This co-culture was retained to study the influence of lactulose levels (0, 4, 6, and 8 %) on yoghurt quality for 28 days at 4°C. Kinetic parameters, syneresis, proteolysis degree, and sensory characteristics were improved by increasing lactulose dose; thus, thixotropic and pseudoplastic gel was shown. Accordingly, functional yoghurt fermented with Yoflex 801, containing 4 to 6 % of lactulose, proved to be the most adequate choice. [ABSTRACT FROM AUTHOR]

The self-association equilibria of doxorubicin hydrochloride (DX), at high drug and NaCl concentrations, are studied by temperature scan fluorescence spectroscopy, with the support of molecular dynamics (MD) calculations. Even though all anthracyclines show dimerization equilibria, DX only can further associate into long polymeric chains according to DX mon ⇄ DX dim ⇄ DX pol. This is reflected not only in the mechanical properties of DX pol solutions (behaving as thixotropic gels) but also in their spectroscopic behaviour. Fluorescence, in particular, is the technique of election to study this complex set of equilibria. Upon increasing the temperature, DX pol melts into DX dim , which in turn is in equilibrium with DX mon. Since DX dim is non fluorescent, with a fluorescence temperature scan experiment the DX pol ⇄ DX mon equilibrium is probed. However, also information on the DX dimerization equilibrium can be derived together with the relevant thermodynamic parameters ruling the dimerization process (Δ H d i m ° = - 56 k J m o l - 1 ; Δ S d i m ° = - 97 J m o l - 1 K - 1). The residence time of DX molecules in the dimer (74.7 μs), as well as the monomers mutual orientation in the dimer, are characterized by means of theoretical and computational modelling. [ABSTRACT FROM AUTHOR]

Herein, we present the synthesis of surface-oxidized cellulose nanofiber (CNF) hydrogel and characterization with various physicochemical analyses and spectroscopic tools as well as its suitability for cellular encapsulation and delivery. The structure-property relationship as shear thinning, thixotropy, creep-recovery and stimuli responsiveness are explored. The CNF hydrogel is capable to inject possessing shear thinning behavior at shear rate (~10 s−1) range in the normal injecting process. In time-dependent thixotropy, the hydrogel showed rapid transform from flowable fluid back to structured hydrogel fully recovering in less than 60 s. The presence of cell-culture media did not alter shear thinning behavior of CNF hydrogel and showed increased thixotropicity with respect to the control gel. The CNF hydrogel forms 3D structures, without any crosslinker, with a wide range of tunable moduli (~36–1000 Pa) based on concentration and external stimuli. The biological characteristics of the thixotropic gels are studied for human breast cancer cells and mouse embryonic stem cells and indicated high cell viability, long-term survival, and spherical morphology. [ABSTRACT FROM AUTHOR]

Oleogel with tailored viscoelasticity is a great interest for food structuring, while its potential benefits for edible film performance are not clear. In this study, β‐sitosterol (0, 5, 10, 15, and 20 wt%)‐corn oil oleogel was developed and used in the formation of gelatin‐based films. Importantly, adding oleogel significantly decreased water vapor permeability of the gelatin films, however, it had little negative influence on film strength. In addition, the results of this study demonstrated that increasing the sitosterol in oleogels led to an increasing number of ordered crystals formed in the oleogel, which contributed to compact and smooth surface of the film. Moreover, the incorporation of oleogel also caused some changes in molecule conformation and film barrier property. Therefore, the superior mechanical performance and moisture resistance properties of the film were obtained when 15% β‐sitosterol was used to prepare oleogel. Practical Application: Corn oil oleogels β‐sitosterol was incorporated with gelatin to prepare the gelatin film aiming to improve the water resistance of the films for its variety of practical production. The enhanced vapor permeability and accepted strength of the emulsion film indicated the potential application of it with a variety of edible packaging forms, such as films, pouch and sachet in medium and high humid condition. [ABSTRACT FROM AUTHOR]

A novel shortening was developed based on oleogels structured by ethylcellulose (EC) polymers. The texture and oil retention ability of EC oleogels were characterized against the level of viscosity of different grades of EC, as well as the rheological properties in relation to the polymer structure in the gel network. EC100, which has an average viscosity of 100 cP, was selected as the most suitable organogelator at 4% (w/w) in combination with base oil (30% degree of saturation by mixing palm stearin and soybean oil) to form the shortening. Triglyceryl monostearate (TMS) was found to be the most effective emulsifier as evidenced by its ability to strengthen air‐incorporation ability of the shortening while creating evenly distributed fine crystals in the system. The EC100 shortening was able to create breads with excellent specific volume, indicating its ability to incorporate air bubbles during dough development and to serve as an antifirming agent to create bread with stable soft texture. Practical Application: In the present study, we attempted to create a novel shortening by employing oleogels structured by ethylcellulose (EC), the most promising gelation agent to develop gel network capable of replacing solid fat without health concerns. EC oleogels in shortening with detailed characterization of the shortening microstructure in relation to its functional properties was elucidated. The optimal formulation in relation to preservation of gel structure and consistency with enhanced moisture and air retention were also identified. [ABSTRACT FROM AUTHOR]

BACKGROUND Phytosterols, in particular a mixture of pure γ‐oryzanol and β‐sitosterol, develop a tubular system that is able to structure oil. In this study, different concentrations of a combination of γ‐oryzanol and a commercial phytosterol mixture, Vitaesterol®, were used for the development of edible oil oleogels. RESULTS: Small‐angle X‐ray scattering (SAXS) and X‐ray diffraction (XRD) were used to characterize at nano and molecular scale the aforementioned oleogels and confirm the formation of sterols‐based hollow tubule structures. Increased hardness was observed with the increase of gelator content used in oleogel manufacturing. The produced oleogels showed promising features such as tailored mechanical strength and low opacity, which are important features when considering their incorporation into food products. CONCLUSION: Despite differences in gel strength, oleogels exhibited textural characteristics that make these structures suitable for incorporation in food products. The oil migration profile associated with these oleogels can provide a solution for the controlled release of lipophilic compounds as well as for the retention of oil in cooked food products. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract A thixotropic polyvinyl alcohol (PVA) hydrogel, containing a hydrophilic poly-vinyl pyrrolidone (PVP) core, was obtained in order to develop a preformed 3D network able to maintain injectability. PVA was mixed with PVP in two different molar ratios (1:1 and 1:3) and chemically cross-linked using trisodium trimetaphosphate (STMP), which is able to react only with PVA component. A combination of Time of Flight- Secondary Ion Mass Spectrometry (ToF-SIMS), elemental analysis and UV spectroscopy permitted to determine both the cross-linking arm length and the crosslinking degree. Hydrogels were characterized in terms of swelling pressurization, rheological and mechanical behaviour. In particular, the viscoelastic behaviour of the hydrogel was analysed in shear and compression stress under dynamic conditions and compared with the performance of healthy human nucleus pulposus. In conclusion, the study demonstrated that the scaffold obtained mixing PVA and PVP in a molar ratio 1:1 can be considered a promising material to be utilised in the replacement of nucleus pulposus. [ABSTRACT FROM AUTHOR]

Graphical abstract A thixotropic cysteine linked silver clusters hydrogel was prepared via photoreduction and was successfully applied as a drug delivery system. Highlights • A cysteine linked silver clusters (CLSC) hydrogel was prepared by photoreduction. • The CLSC hydrogel presented pH-stimuli behavior under acidic conditions. • The thixotropic property ensures direct injection and drug delivery to cancer cells. • The DOX@CLSC hydrogel shows remarkable inhibition efficacy on tumor growth. Abstract A biocompatible thixotropic hydrogel via photoreduction and self-assembly of silver clusters is described. This reaction avoids use of hydrogelators, crosslinkers or any exogenous toxic reducing agents, making it a facile and green method. Moreover, the formed 'smart' thixotropic hydrogel is pH-responsive and can encapsulate the hydrophobic anticancer drug doxorubicin hydrochloride (DOX). The thixotropic property allows it to be sol state, which can be injected directly into the site of breast tumors in mice; after removal of the shear stress, the sol reverts back to hydrogel, where it remains for delivery of DOX into cancerous cells. The DOX-loaded hydrogel presents remarkable inhibition efficacy towards tumor growth, in addition to reducing the organ toxicity. [ABSTRACT FROM AUTHOR]

Abstract An experimental study of the flow of yield stress materials was conducted. The main goal was to understand the relationship between the minimum axial pressure gradient required for the onset of motion and the rheological properties. The sought-for application is the startup flow of waxy crude oils in subsea pipelines. We examined two types of yield stress materials, namely a non-thixotropic acrylic polymer solution and a layered silicate suspension which presents thixotropic properties. We observed that for both materials the measured minimum axial pressure gradient was in good agreement with the prediction of a simple force balance. On the other hand, a puzzling fact is observed in the oil industry, namely that the just mentioned force balance result grossly overestimates the minimum axial pressure gradient for the case of gelled waxy crude oils. One often evoked explanation is the thixotropic behavior of the gelled crude, but the present results serve to falsify it. [ABSTRACT FROM AUTHOR]

Abstract We have designed an aqueous gel electrolyte containing fumed silica as the thixotropic gelling agent and poly(ethylene glycol) (MW = 300 g·mol−1) as the non-thixotropic gelling agent. Poly(ethylene glycol) is also the dendrite suppressor and the corrosion inhibitor. Both PEG300 and fumed silica can inhibit dendrite formation, shown by chronoamperometry results and ex-situ scanning electron microscopy images. Furthermore, the corrosion current density on the Zn anode in the 4 wt%FS-1 wt%PEG300 gel electrolyte is 27% less than that of the Zn in the reference aqueous electrolyte. Secondary Zn/LiMn 2 O 4 batteries using the 4 wt%FS-1 wt%PEG300 gel electrolyte exhibit higher cyclability (12% and 39% higher capacity retention, after 300 and 1000 cycles, in Swagelok and large cells, respectively) than those using the reference aqueous electrolyte. The vast improvements in cycling performance, reliability, and higher resistance to premature failure makes the PEG-FS gel a much better alternative to liquid electrolytes for maintenance-free energy storage applications. Graphical abstract Unlabelled Image Highlights • 27% decrease in the corrosion current density of the zinc electrode in gel vs. aqueous electrolyte. • 75% reduction in the chronoamperometric current density of the zinc electrode - indicating improved dendrite inhibition. • 39% improvement in the capacity retention after 1000 cycles compared to the control in our bespoke large battery system. [ABSTRACT FROM AUTHOR]

Abstract Increased interest in aesthetic, natural nail coatings has encouraged more in-depth studies, and particularly of ultraviolet curable coatings, their formation, processing, characteristics, and removal. This study investigated the impact of various thixotropic agents (organically modified hectorite and bentonite clays) on water-based oligomer system rheology. Ingredients were evaluated to determine their influence on unreacted composite characteristics (viscosity and pigment suspension stability) and reacted film characteristics (modulus of elasticity, elongation at break, and film adhesion force). It is concluded that clay-based thixotropic agents are suitable for use as a suspension agent in nail polish formulations and, depending on the concentration, can decrease the risk of pigment sedimentation and syneresis. [ABSTRACT FROM AUTHOR]

Highlights • CFD simulations of particle trajectories in shear flows of shear-thinning fluids. • Particle-induced shear accounted for by shear rate vector magnitude concept. • Various drag law concepts (Newtonian, shear-thinning, viscoelastic) investigated. • Trajectory analysis and validation with exp. findings of Khatibi et al. (2016). • Mismatch between CFD and exp. trajectories at lower channel wall. Abstract For improving CFD models of particle transport in wellbore flows, i.e. cuttings transport , we have extended the Lagrangian Discrete-Particle-Model model of the commercial code ANSYS Fluent 17.2 to describe the motion of a particle settling in an orthogonal shear flow of a shear-thinning, mildly viscoelastic fluid. Essentially, the fluid strain rate as the magnitude of the fluid deformation rate tensor is corrected by a particle-induced shear rate. This corrected strain rate is used to compute an apparent viscosity. The fluid is treated as a Generalized Newtonian Fluid using Cross and Carreau material functions. Different drag laws are investigated, including one which accounts for the fluids viscoelastic wake structure behavior via a correction term. We validate the model with eight different particle trajectories representing different combinations of particle diameters, fluid flow rates and rheological properties (water and polymeric solutions) provided by Khatibi et al. [1]. In general, the experimental trajectories are satisfactorily replicated by the CFD model. However, for small particles a trajectory mismatch is observed close to the lower channel wall. We find this mismatch to be a consequence of unexpectedly high particle x -velocities in the experimental data. Various possible causes are identified and discussed. More detailed experimental near-wall data of both particle and fluid velocities as well as more sophisticated modeling of the fluids rheology, including the rheology effect on the forces acting on the particles, may be required to minimize the mismatch. In addition, we further conclude that in case of the polymeric solutions particle drag is the dominant particle force, that the viscoelastic wake of the particle is not significantly affecting the trajectories, and that a Newtonian drag law may be used as long as the particle-induced shear rate is estimated with ‖ v r ‖/ d p and a material function accounting for the limiting zero-shear Newtonian viscosity is applied. [ABSTRACT FROM AUTHOR]

An analysis is introduced to investigate the salient features of nonlinear convective flow of thixotropic fluid in the version of Cattaneo-Christov heat flux theory. The stagnation point flow is present. The flow phenomenon is by an impermeable stretching sheet. The energy expression is modeled through the theory of Cattaneo-Christov heat flux. Characteristics of heat transfer phenomenon are described within the frame of variable thermal conductivity. Suitable variables reduced to the nonlinear partial differential expressions to the ordinary differential expressions. Series solutions of resulting systems are acquired within the frame of homotopy theory. Convergence analysis is achieved and suitable values are determined by capturing the so-called ℏ−curves. Graphical results for velocity and temperature are displayed and argued for sundry physical variables. Expression of skin friction coefficient is calculated through numerical values. Higher values of mixed convection parameter, Prandtl number, and thermal relaxation time lead to decay the temperature and layer thickness. [ABSTRACT FROM AUTHOR]

Redox‐active G‐quadruplex hydrogels were prepared by dynamic boronate ester formation between ferroceneboronic acid and guanosine. Dynamic boronate esters imparted thixotropic and 3D‐printability to the hydrogel. Initially, the ferrocene moiety was oxidised to produce a weaker ferrocenium‐based green hydrogel. However, the less stable ferrocenium converted into more stable ferrocene to produce a hydrophobic, water‐stable and robust hydrogel. Printable hydrogels: Redox‐active G‐quadruplex hydrogels were prepared by dynamic boronate ester formation between ferroceneboronic acid and guanosine. Dynamic boronate esters imparted thixotropic and 3D‐printability to the hydrogel. Initially, the ferrocene moiety was oxidised to produce a weaker ferrocenium‐based green hydrogel. However, the less stable ferrocenium converted into more stable ferrocene to produce a hydrophobic, water‐stable and robust hydrogel. [ABSTRACT FROM AUTHOR]