Shear Frequency Research Articles

Modifying Anti-Compression Property and Water-Soluble Ability of Polyglycolic Acid via Melt Blending with Polyvinyl Alcohol.

Biodegradable polymeric materials have become the most attractive research interest in recent years and are gradually widely used in various fields in the case of environmental pollution. In this paper, binary blends, mainly including varying contents of polyglycolic acid (PGA) and poly(vinyl alcohol) (PVA), were prepared via a melt compounding strategy. The ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) was employed as the compatibilizer to improve the compatibility between the PGA and PVA and the polyolefin elastomer (POE) was used as toughening agent. The anti-compression property and water-soluble ability of the blends were particularly studied to explore their potential application in an oil/gas exploitation field. Special attentions were paid to the evolution of the water-soluble ability of PGAX with the PVA concentration. Furthermore, isothermal shear measurement and thermogravimetric analysis were performed to evaluate the thermal stability of PGA and PGA blends (PGAX) during melt processing. The results showed that the incompatibility between PGA and PVA largely deteriorated the mechanical property, i.e., anti-compression strength, leading to fragile characteristics under a lower compressive load for the PGAX samples with varied contents of PVA. The presence of PVA and EMA-GMA greatly enhanced the viscoelasticity of the PGA melt, showing an increased storage modulus and viscosity at a low shear frequency; however, the thermal instability of PGAX was intensified owing to the greater ease of thermal degradation of PVA than that of PGA. Meanwhile, the water-soluble ability of PGAX was improved due to the high water dissolution of PVA, which played the role as a sacrificial material. The purpose of this work is to pursue an effective modification for PGA processing and application via melt blending.

Relative Effects of the Greenhouse Gases and Stratospheric Ozone Increases on Temperature and Circulation in the Stratosphere over the Arctic

Using a stratosphere-resolving general circulation model, the relative effects of stratospheric ozone and greenhouse gases (GHGs) increase on the temperature and circulation in the Arctic stratosphere are examined. Results show that stratospheric ozone or GHGs increase alone could result in a cooling and strengthening extratropical stratosphere during February, March and April. However, the contribution of stratospheric ozone increases alone on the cooling and strengthening Arctic stratosphere is approximately 2 fold that of the GHGs increase alone. Model simulations suggested that the larger responses of the Arctic stratosphere to the ozone increase alone are closely related to the wave fluxes in the stratosphere, rather than the wave activity in the stratosphere. In response to the ozone increase, the vertical propagation of planetary waves from the troposphere into the mid-latitude stratosphere weakens, mainly contributed by its wavenumber-1 component. The impeded planetary waves tend to result from the larger zonal wind shear and vertical gradient of the buoyancy frequency. The magnitudes of anomalies in the zonal wind shear and buoyancy frequency in response to GHGs increase alone are smaller than in response to the ozone increase, which is in accordance with the larger contribution of stratospheric ozone to the temperature and circulation in the Arctic stratosphere.

Investigation on rheological characteristics of magnetorheological shear thickening fluids mixed with micro CBN abrasive particles

The novel magnetorheological shear thickening polishing fluids (MRSTPFs) were developed by mixing micro cubic boron nitride (CBN) abrasive particles into traditional magnetorheological shear thickening fluids. MRSTPFs were constructed by uniformly fumed silica and polyethylene glycol as shear thickening fluids, carbonyl iron particles (CIPs) as ferromagnetic phase and CBN particles as abrasive phase. In this work, various MRSTPFs were prepared to explore their rheological characteristics. Sweeps of steady shear rate and dynamic shear frequency were conducted under different magnetic flux densities, respectively. A mathematical model was presented to explain shear rate variation with shear stress. The magnetorheological shear thickening mechanism was well described. The rheological experiment results have revealed that shear thickening effect was still existing in magnetic flux density. However, the increased magnetic flux density played a negative role on the shear thickening effect. Particle size optimization of CIPs was thus essential to maximize the shear thickening effect. On the other hand, with increased shear frequency, the viscoelastic feature of MRSTPFs was converted from linear to non-linear. It was found that the shear yield stress of the MRSTPFs was magnified with the stronger magnetic flux density and larger CIPs size. The investigation of rheological characteristics demonstrated that MRSTPFs could enhance polishing performance, which contributed to developing a high-efficiency and ultra-precision polishing process.

Effects of different combinations of probiotics on rheology, microstructure, and moisture distribution of soy materials-based yogurt.

The effects of different probiotics on the texture, rheological properties, microstructure, and water distribution of yogurt fermented with soy powder, soy isolate protein powder, soy umbilical powder, and soy whey as the main raw materials were studied. The soy materials-based yogurt fermented by Danisco mixed probiotic reached the end of fermentation after 4 h, which significantly shortened the fermentation time compared with other probiotic combinations. The fermentation with Danisco mixed probiotic and Kefir mixed probiotic respectively resulted in good texture and a denser and more homogeneous microstructure, which was consistent with the sensory evaluation results. Both fermentations had a high water holding capacity of 90.92% and 78.30%, respectively, in agreement with the results of moisture distribution tests. However, the elastic and viscous behaviors were weaker at certain shear frequency. This study achieved a high value-added utilization of soy whey and the development of a new soy materials-based yogurt that met the consumption needs of people with lactose intolerance and high cholesterol. PRACTICAL APPLICATION: In this study, high value-added utilization of soy whey was realized, which solved the problems of resource waste and environmental pollution. Meanwhile, the research and development of soy materials-based yogurt provided another nutritional and healthy consumption demand for lactose intolerant people.

Comparative Study of Linear Static and Linear Dynamic Method of Seismic Analysis of RCC Multistoried Building Using ETABS

Abstract: As the modern buildings have been getting taller and narrower than before, the structural engineers have to perform both static and dynamic analysis for seismic loads that may affect on structures in order to make sure of the safety verifications and the optimal design requirements. Reinforced concrete (RC) building frames are the most common types of constructions in urban India. Throughout their lifetime, these are subjected to various types of forces such as static forces due to dead loads, live loads and dynamic forces due to earthquakes. In the present study, one tall RCC building of 10 stories is assumed to be situated in seismic zone 4 is analyzed using two different methods i.e., Equivalent static method (static) and response spectrum method (dynamic), using ETABS software. From analysis, the parameters like storey displacement, storey drift, base shear and time period and frequency are determined and also comparative study is done for both the methods Keywords: {RCC Buildings, Equivalent static method, response spectrum method, storey displacement, storey drift, Base shear, time period.}

Property transitions of neat and styrene–butadiene-styrene (SBS)-modified asphalt binders from small, medium to large-amplitude oscillatory shears

ABSTRACT Tests on asphalt binder are typically performed in its linear viscoelastic (LVE) range. In this research, the rheological properties of neat and styrene–butadiene-styrene (SBS)-modified asphalt binders were examined from 0.01% to 1000% at a high usage temperature, and focus was placed on their non-linear viscoelastic (NLVE) behaviours. Experimental variations and binder property changes in small, medium and large-amplitude oscillatory shears were revealed. Besides strain amplitude, the effects of polymer content, short-term aging and test frequency on NLVE behaviours were also analysed based on three quantitative methods. Additionally, polymers in asphalt binders were examined by using confocal fluorescence microscopy. The NLVE behaviours were found to be affected by shear strain amplitude, polymer content, shear frequency, and the interactions of such factors, but to a less extent by short-term aging. Besides polymer content, the size and morphology of polymer phase likely affect the property variations of modified asphalt binders. Large amplitude oscillatory shear (LAOS) test and morphology analysis help identify the threshold polymer content in producing high-quality polymer-modified asphalt binders.

Enabling thermally enhanced vibration attenuation via biomimetic Zr–fumarate MOF-based shear thickening fluid

This work reported a biomimetic shear thickening fluid (STF) with thermally enhanced shear thickening effect for smart vibration attenuation system. It was developed by introducing Zr–fumarate metal-organic framework (MOF) crystals into a solvent mixture comprised of polyethylene glycol, polyacrylic acid and Ca2+, which endowed it with the cooperative effect of electrostatic and hydrophobic interactions. As the temperature raised from 25 to 35 °C, the STF containing 55 vol% MOF (STF-55) yielded a favorable shear thickening reinforcement with a notable viscosity growth of 1760-7953 Pa s. Besides, its storage modulus increased from 14 to 3036 Pa at 25–55 °C under a 0.1 Hz shear frequency, revealing a significant improvement in mechanical performance, as also demonstrated by transient shear rheological experiments. STF was incorporated into sandwich structures to improve the damping performance, with the natural frequency and damping ratio investigated at various ambient temperatures. Since the thermal enhanced viscosity could promote energy dissipation, the damping ratio of STF-55 filled sandwich structure obtained a substantial improvement from 0.85% to 1.93% at 25–55 °C. Thus, STF-55 based turbine blade and building damping pile were fabricated, which not only reduced the external vibration stimuli with average responsive accelerations of 7.3 and 0.8 m2s-1, but also presented attenuated levels of 6.9 and 0.6 m2s-1 at increasing temperatures, respectively. In conclusion, this work provided guiding approach for highly adaptive vibration attenuation at high-temperature environment.

Intra- and Inter-sample Variation in Wool Cortisol Concentrations of Australian Merino Lambs Between Twice or Single Shorn Ewes

Stress in Merino sheep can cause a reduction in the quantity and quality of fine wool production. Furthermore, it has been found that environmental stress during pregnancy can negatively affect the wool follicles of the developing fetus. This study was part of a larger field investigation on the effects maternal shearing frequency on sheep reproductive and productivity outcomes. For this study, we investigated the intra- and inter- sample variation in wool cortisol levels of weaner lambs. We conducted two experiments, the first was to determine the intra- and inter- sample variation in wool samples taken from the topknot of weaned lambs, and the other aim was to determine any difference between maternal shearing treatment (single or twice shearing) on absolute wool cortisol levels of weaned lambs. In the first experiment, topknot wool was collected from 10 lambs, and each sample was further divided into four subsamples, leading to a total of 40 wool subsamples. For the second experiment, we collected the topknot from the 23 lambs produced by the shearing frequency treatment ewes (once or twice shorn). The samples were then extracted and analyzed using a commercially available cortisol enzyme-immunoassay in order to determine the concentration of cortisol in each of the samples. Statistical analysis for the first experiment showed that there was no significant difference between the subsamples of each topknot wool sample taken from each lamb (p = 0.39), but there was a statistical difference between samples (p < 0.001), which was to be expected. In the second experiment, there was a significant difference between the lambs born to the one shearing and two shearing treatments (p = 0.033), with the lambs of the twice sheared ewes having higher average wool cortisol levels [2.304 ± 0.497 ng/g (SE); n = 14] than the ones born to once shorn ewes [1.188 ± 0.114 ng/g (SE), n = 8]. This study confirms that the topknot wool sampling can be a reliable method adapted by researchers for wool hormonal studies in lambs. Second, ewes shorn mid-pregnancy gave birth to lambs with higher cortisol concentrations than ewes that remained unshorn during pregnancy. This result warrants further investigation in a controlled study to determine if maternal access to nutrition (feed and water) may impact on the HPA-axis of lambs.

Perpendicular heating of ions by low-frequency polarized Alfvén waves

The expression for the perpendicular saturation temperature of ions heated by a low-frequency shear Alfvén wave due to nonresonant interaction in low-β plasmas has been derived. This expression is closely related to the frequency, polarization, and amplitude of the low-frequency shear Alfvén wave. The derived expression has been verified by performing simulations. Because of the Doppler effect, the saturation temperature is different for different polarized waves. The saturation value of the perpendicular ion temperature has a lower limit for the left-handed polarized Alfvén wave and a higher limit for the right-handed polarized Alfvén wave. The results might be helpful to explain the heating of ions in the solar wind.

Predicting Dielectric and Shear-Rheology Properties of Glass-Forming Pharmaceutical Liquids from Each Other: Applications and Limitations.

Acetaminophen, nicotine, and lidocaine hydrochloride were investigated in their deeply supercooled liquid states using oscillatory shear rheology. The mechanical spectra of these drugs are presented in modulus, compliance, as well as fluidity formats. Their frequency profiles can be described via models adapted from the field of charge transport. Inspired by the success of this approach, the Barton-Nakajima-Namikawa relation, best known from the same field, was also tested. When adapted to rheology, this approach interrelates static and dynamic characteristics of viscous flow and was found to work excellently. The temperature dependence of the characteristic shear frequencies was checked against the shoving model, which relates them to the temperature-dependent instantaneous shear modulus and acceptable agreement was found. Combined with shear mechanical literature data on ibuprofen and indomethacin, a modified version of the phenomenological model by Gemant, DiMarzio, and Bishop (GDB) was employed to successfully predict the shape and amplitude of the dielectric spectra for all studied liquids, except for lidocaine hydrochloride. For the latter, the modified GDB model is suggested to aid in mapping out the reorientational part of the dielectric response, while the experimental results are strongly superimposed by ionic conduction phenomena. The reverse transformation, the calculation of rheological spectra based on dielectric ones, is also successfully demonstrated. For the example of acetyl salicylic acid, it is shown how dielectric spectra can be used to even predict rheological ones. The limits of the central parameter governing these mutual transformations, the electroviscoelastic material constant, and indications for its correlation with the dielectric relaxation strength are discussed. For pharmaceuticals characterized by a strong dynamical decoupling of the electrical from the mechanical degrees of freedom, the modified GDB model is not expected to be applicable.

Interplay Between Stress and Reproduction: Novel Epigenetic Markers in Response to Shearing Patterns in Australian Merino Sheep (Ovis aries).

In this study, we determined the effect(s) of early shearing on Australian Merino ewes (Ovis aries) and their lambs. To test this research question, we used a suite of field and laboratory methods including GPS collars, wool cortisol, and epigenetic change between ewes and lambs identified using Illumina NovaSeq RRBS. Once shorn ewes (n = 24) were kept on their full fleece throughout the entire gestation period, whereas twice (early) shorn ewes (n = 24) had their wool shorn pre-joining. Top-knot wool sample was taken from ewes during pre-joining, day 50 (mid-gestation), and day 90 (late gestation) for laboratory analysis. Ewes were pregnancy scanned at mid-gestation to determine whether they were early or late parturition (this confirmation is provided by the pregnancy scanner based on fetus size). Top-knot wool sample was also taken from the lambs at weaning for hormone and wool quality testing. Ear tissue was taken from ewes at day 50 (mid-gestation) and from lambs at lamb marking for DNA analysis. Results showed that twice or early shorn ewes grazed 10% higher and maintained stronger body condition than once shorn ewes. Wool cortisol levels were also significantly lower in the early shorn ewes between mid- and late gestation. Lambs bred from twice shorn ewes had on average better visual wool quality parameters in terms of micron, spin finesses, and curvature. For the DNA methylation results, when comparing a group of once sheared with twice sheared ewes, we have discovered one locus (Chr20:50404014) that was significantly differentially methylated [False Discovery Rate (FDR) = 0.005]. This locus is upstream of a protein-coding gene (ENSOARG00000002778.1), which shows similarities to the forkhead box C1 (FOXC1) mRNA using BLAST searches. To further our understanding of the potential interaction between pregnancy status and shearing frequency of the ewes, we performed further differential methylation analysis using a combination of shearing treatment and pregnancy scanning status. The comparisons (1) late pregnancy vs. early pregnancy for ewes with one shearing treatment and (2) late pregnancy vs. early pregnancy for sheep with two shearing treatments were carried out to identify associations between loci and pregnancy duration for sheep with either one or two shearing events. We discovered that 36 gene loci were significantly modulated either between different shearing treatments or late vs. early pregnancy status of ewes. This result suggests that maternal pregnancy and nutritional status during gestation influence DNA methylation. We further investigated DNA methylation in lambs and identified 16 annotated gene loci that showed epigenetic modulation as a result of being born from an early or late stage pregnancy. From the genomics data, we pointed out that ewes go through epigenetic modifications during gestation, and there is a degree of intra-individual variation in the reproductive performance of ewes, which could be due to combination of intrinsic (genetic and physiological) and extrinsic (management and climatic) factors. Collectively, this research provides novel dataset combining physiological, molecular epigenetics, and digital tracking indices that advances our understanding of how Merino ewes respond to shearing frequency, and this information could guide further research on Merino sheep breeding and welfare.

Self-healing and printable elastomer with excellent shear stiffening and magnetorheological properties

This work reports a novel kind of hybrid magnetorheological elastomer (HMRE) that possesses multi-functions including excellent shear stiffening and magnetorheological (MR) effects, as well as self-healing and printable abilities. The HMRE materials are prepared by embedding carbonyl iron particles (CIPs) into a blend of silicon rubber (SR) and low cross-linking gel-like polyurethane (PU). The relative shear stiffening effect of HMRE-3:1 (the mass ratio of PU and SR is 3:1, and 50 wt% CIPs) is 6095% as the shear frequency increases from 0.1 Hz to 100 Hz, which is about 150 times that of SR based magnetorheological elastomer (MRE). With the magnetic flux density from 0 to 1T, MR effect of isotropic HMRE-3:1 is as high as 266%, which is 3.5 times that of SR based MRE. Notably, HMRE obtains extraordinary mechanical and electrical healing capabilities. HMRE with a destructive cut-through injury can sustain an extensibility of 425% (the initial extensibility ≈ 650%) after healing. Meanwhile, possible mechanisms are proposed to explain the shear stiffening properties, MR effect, and self-healing performance of HMRE. Moreover, the extruded modeling 3D printing of flexible HMRE actuators can be achieved due to the plasticine property of pre-polymerized HMRE, which bestows HMRE with magnetic particle distribution programmability and shape designability. This work may provide a new way for the next-generation multifunctional materials with exceptional shear stiffening behavior, magnetically mechanical properties, self-healabilities, and printable performance.

Thermal Shear Waves Induced in Mesoscopic Liquids at Low Frequency Mechanical Deformation

Abstract We show that a confined viscous liquid emits a dynamic thermal response upon applying a low frequency (∼1 Hz) shear excitation. Hot and cold thermal waves are observed in situ at atmospheric pressure and room temperature, in a viscous liquid (polypropylene glycol) at various thicknesses ranging from 100 µm up to 340 µm, upon applying a mechanical oscillatory shear strain. The observed thermal effects, synchronous with the mechanical excitation, are inconsistent with a viscous behaviour. It indicates that mesoscopic liquids are able to (partly) convert mechanical shear energy in non-equilibrium thermodynamic states. This effect called thermo-elasticity is well known in solid materials. The observation of a thermal coupling to the mechanical shear deformation reinforces the assumption of elastically correlated liquid molecules. The amplitude of the thermo-elastic waves increases linearly by increasing the shear strain amplitude up to a transition to a non-linear thermal behavior, similar to a transition from an elastic to plastic regime. The thermo-elastic effects do not give rise to any change in stress measurements and thus the dynamic thermal analysis provides unique information about dynamic liquid properties.

Effect of shear stiffening gel rheology on its Kevlar fabric reinforced composite under low-velocity impact

Shear stiffening gel (SSG) with significant shear stiffening effect overcomes the problems of fluid volatilization and particle deposition, and exhibits a wide range of application prospects in intelligent protection. In this work, SSG with different rheological properties were manufactured by mechanical blending and crosslinking and coated on Kevlar fabric. The dynamic rheological properties of SSG and the low-velocity impact resistance of Kevlar/SSG composites were investigated, and the coupling mechanism between SSG and Kevlar fabric was analyzed. The results reveal that the storage modulus of SSG increases by 3–6 orders of magnitude when shear frequency ranges from 0.1 to 100 Hz, and the highest storage modulus reached 2.53 MPa. The impact deformation of the composite is reduced after SSG stiffening, and the infiltration of SSG inside the fabric also prevents fibers pull-out during the impact process. By synergizing the performance of SSG and Kevlar fabric, the optimal single-layer T280 composite can absorb up to 70.21% of the impact energy, reaching the energy absorption efficiency of 0.5 J/g. The process optimization and rheological design provide a theoretical foundation to further enhance the impact resistance performance.

Advanced MXene/shear stiffening composite-based sensor with high-performance electromagnetic interference shielding and anti-impacting Bi-protection properties for smart wearable device

Smart wearable devices with mechanical anti-impact property and electromagnetic interference shielding performance are highly required for providing comprehensive and effective protection for human beings under special conditions. Herein, a multifunctional SSE/MXene-NWF/SSE (SMS) sandwich composite with multiple sensing properties, electromagnetic interference shielding performance and anti-impacting ability was developed. By decorating conductive MXene onto the middle non-woven fabric (NWF), the as-fabricated SMS composite protects human from the harmful electromagnetic radiation with the shielding effectiveness up to 58 dB. The shear stiffening elastomer (SSE) whose storage modulus increases with the shear frequency displays typical shear stiffening effect, and thus confers SMS sandwich composite outstanding anti-impacting and safe-guarding properties which can dissipate nearly 97% impact energy. In addition, this SMS sandwich composite also meets the development needs of smart wearable devices, which can be comfortably attached onto human parts to monitor different human motions. Moreover, the intelligent alarm system and mechanical manipulator based on SMS sensor shows the promising application in wireless transmission and human–machine interaction. Finally, the designed SMS-based sensor array further displays its multi-perceptive characteristic under various stimuli as well as double-safeguarding abilities under impact and electromagnetic radiation. This work opens a new perspective for the development of multifunctional composite as smart wearable devices with anti-impacting and electromagnetic interference shielding properties for the comprehensive safeguarding of human beings.

Water tank Seismic Analysis Noting Effect on time Period

In the case of an earthquake, an elevated water tank is a crucial building component. In order to store water at a constant level, an elevated water tank is built and height for water distribution system pressurization. Uplifted water tanks, as was learned the hard way, suffered significant damage or collapsed during earthquakes. As a result of the raised water tanks' extreme sensitivity to earthquake parameters including peak ground acceleration, frequency contents, and duration records. The purpose of this study is to gain insight into the dynamic behavior of an elevated water tank fitted with a UG sump subjected to various recorded ground vibrations from earthquakes. An RCC square water tank with 14-, 17-, and 20-meter staging heights was subjected to a Time History Analysis using StaadPro software to simulate the effects of five distinct seismic ground movements. Roof displacement, velocity, acceleration, base shear, drift, and natural frequency were measured and compared for three different tank fill levels: empty, halfway, and full. Bhuj earthquake ground motion was the strongest, whereas Kobe earthquake ground motion was the weakest.

Caracterização reológica de ovos rhea (Rhea americana) submetidos a diferentes períodos de armazenamento

Abstract Eggs are used as food industry ingredients due to their functional properties. Eggs from different bird species are used in industrial processing; therefore, rheological experiments were carried out at steady state to obtain the flow curves and also at a dynamic state to study the rheological properties of greater rhea eggs. The viscoelastic behavior of the fluids as a function of the coagulation temperatures for albumen and yolk and of the oscillatory shear frequency was studied. Fifteen rhea eggs stored for up to 28 days at 10 °C were analyzed at 1, 7, 14, 21, and 28 days. The albumen and yolk fractions showed pseudoplastic rheological behavior with small initial flow shear and dependence on shear time, with albumen demonstrating thixotropy and the yolk showing rheopexy. In low shear rheological tests, thermal gelation of albumen was observed, presenting a first change in the elastic modulus around 56 °C, and a second from 78 °C. In the yolk, a change was observed from 66 °C, with more structural variations in the development of the gel at higher temperatures. For rhea eggs, the gel structuring (gelation) temperature of albumen (80 °C) and egg yolk (69 °C) did not undergo variations during the storage periods. Compared to commercial eggs, the higher viscosity and gelation temperatures presented by the rhea eggs can help determine the size of the industrial processing system as they can be submitted to higher temperatures without modifying protein structures and hindering the process.

Dynamic study of tip-link tension and stereocilia motion in cochlea

Explanation of cochlear active acoustic amplification mechanism has been an unsolved medical problem. This mechanism is closely related to the motion of the stereocilia at the top of the outer hair cells in the cochlea. The motion of stereocilia is regulated by the tip-link tension and the fluid force of the lymph fluid. Therefore, studying the tip-link tension during the motion of stereocilia is an important part of the explanation of the cochlea's active sensory sound amplification mechanism. Most of previous studies regarded the stereocilia as rigid bodies, and ignored the influence of shaft bending when studying the mechanical properties of hair bundle. Most of the researches on elastic stereocilia used the finite element simulation, or simplified the model by ignoring the fluid-solid coupling with lymph fluid, or considered only static loading. Based on the Poiseuille flow combined with the distributed parameter model, the analytical solution of the elastic motion of stereocilia is derived in this work. The dynamic response of the stereocilia under the shear force of the tectorial membrane and the change law of tip-link tension are studied. The shaft bending produces a nonlinear accumulation of displacement at the height of the stereocilia. The higher the stereocilia, the more obvious the accumulation effect is. Under the action of dynamic load, the shaft bending contributes most to the displacement response in the tall stereocilium, and this contribution is easily affected by frequency change. Under low frequency load, the displacement response of tall stereocilium comes mainly from the root deflection. At high frequency, the shaft bending increases significantly, and the displacement response is produced by the combination of shaft bending and root deflection. The change of F-actin content in the cochlea exposed to noise would affect the stereocilia stiffness. In this paper, it is found that the decrease of stereociliary Young's modulus will increase the peak value of normalized tension and reduce its peak frequency, and the amplitude of normalized tension will increase under the low frequency shear load. Since the tip-link is connected to an ion channel, the change of normalized tension will affect the probability of ion channels opening, change the ability of cochlea to perceive the sound of corresponding frequency, and then affect the frequency selectivity of hair bundle. Therefore, previous studies of stereocilia regarded as rigid bodies underestimated the response of the cochlea to low-frequency acoustic signals. This model accurately describes the law of tip-link tension and provides a corresponding theoretical explanation for hearing impairment caused by noise environment. Previous experiments have shown that the lymphatic viscous resistance has little effect on the deflection of stereocilia. In this paper, when the viscous resistance is ignored, the tip-link tension changes very little, and when the pressure between the stereocilia is ignored, the tip-link tension changes significantly and the resonance peak of <inline-formula><tex-math id="M4">\begin{document}$ {f_2} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20211105_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20211105_M4.png"/></alternatives></inline-formula> disappears. Therefore, lymphatic fluid regulates the resonance properties of the tip-link tension by creating the pressure between the stereocilia. The presence of lymphatics is essential for generating the frequency characteristics of the hair bundle. In the low frequency domain, the motion of stereocilia is regulated mainly by tip-link, and in the high frequency domain, it is regulated mainly by lymphatic pressure.

Synthesis of a hydrophobic association polymer with an inner salt structure for fracture fluid with ultra-high-salinity water

This study used a compound initiation free radical polymerization process to synthesize a hydrophobic association polymer (PDMA1) with good salt resistance for use in ultra-high salinity reservoirs. The critical association and entanglement concentrations of PDMA1 in deionized (DI) water were 1596 and 2799 mg/L, respectively. The properties of the polymer in simulated formation (SF) water were investigated using viscosity change and conductivity tests, and the apparent viscosity of the PDMA1 solution was investigated using apparent viscosity, viscoelasticity, and thixotropy experiments. To a certain extent, the apparent viscosity of the solution was found to be influenced by metal ions. Under total dissolved solids (TDS) concentrations of up to 239,500 ppm, when the polymer concentration exceeded the critical entanglement concentration, the apparent viscosity of the polymer remained close to that of DI water. Additionally, the viscosity of the PDMA1 solution was affected by different types of metal ions, and the polymer solution thickened owing to divalent cations. PDMA1 is resistant to salt owing to hydrophobic interaction, electrostatic shielding, and double-layer compression. The results of the thixotropy and viscoelasticity tests revealed the thixotropy loop area of the PDMA1 solution in SF water to be greater than that in DI water. Under these conditions, PDMA1 is mostly viscous at low shear frequencies and mostly elastic at high shear frequencies. The PDMA1 inner-salt hydrophobic association polymer can be utilized as a chemical agent for tertiary recovery and fracturing, processes in high-salinity reservoirs, particularly for aggravating fracturing fluid.

Cross flow frequency determines the physical structure and cohesion of membrane biofilms developed during gravity-driven membrane ultrafiltration of river water: Implication for hydraulic resistance

We evaluated how intermittent shear influences the physical structure, material properties and hydraulic resistance of membrane biofilms developed during gravity-driven ultrafiltration of river water, with the ultimate goal of increasing the filtration performances. Our results indicate intermittent shear helps slowing-down the flux decline but does not help to increase the level of stabilisation of the permeate flux. After several weeks, the biofilms exposed to different shear regimes were indeed characterised by similar hydraulic resistance. But the characteristic time to achieve a stable flux increased from 7 d to 25d when increasing the shear frequency. Also, most of the hydraulic resistance (up to 95%) was governed by the base layer that remained attached after erosion tests. With increasing exposure to shear conditions, the biofilms became more cohesive and more elastic, thus resisting better to cross flow conditions. Overall, our results demonstrate that engineering membrane biofilms with a desired permeability is not feasible using intermittent shear due to significant adaptability of the biofilms to their hydraulic environment.