Low Tension Research Articles

Effects of different tennis racket string tension on forehand stroke effect and racket dynamic impact.

This study investigates the effect of varying tennis racket string tension on stroke effect and the dynamic response of the racket. Using the YSV dynamic acceleration signal acquisition system and a portable radar speed gun collect data on racket acceleration, stress-strain signals, and ball speed from 15 male athletes. Stroke accuracy and depth were assessed according to the International Tennis Number. The recorded stroke speeds were 108.87±13.57 km/h, 111.83±16.34 km/h, and 107.76±12.53 km/h for the low, medium, and high tension, respectively. A significantly higher ball speed was observed at 54lbs compared to both 48lbs and 60lbs (P <0.05). Control scores were 4.90±0.61,5.46±0.84, and 4.64±0.69 for the respective tensions. The control at 54lbs was significantly higher than at 60lbs (P<0.05). Deformation measurements were 18.53±4.90με, 16.31±4.42με, and 20.90±3.53με, with significantly lower deformation at 54lbs compared to 60lbs (P<0.05). The impact forces recorded were 381.81±48.51m/s2, 380.53±50.47m/s2, and 380.04±53.70m/s2, with no significant effect of string tension on impact force. Racket vibration frequencies were 44.14±0.48Hz, 44.08±0.35Hz, and 44.14±0.25Hz, with no significant difference among three string tensions. Rackets with three string tensions showed significantly higher vibration frequencies during the collision phase compared to before or after (P<0.01). In conclusion, string tension affect the stroke effect, racket strung at medium tension can optimize stroke effect while got milder dynamic impact, suggesting that racket strung at medium tension is recommended for tennis enthusiasts to enhance stroke performance and to decrease the risk of resonance damage in the forearm soft tissues.

A Pore-Scale Investigation of Oil Contaminant Remediation in Soil: A Comparative Study of Surfactant- and Polymer-Enhanced Flushing Agents

Pore-scale remediation investigation of oil-contaminated soil is important in several environmental and industrial applications, such as quick responses to sudden accidents. This work aims to investigate the oil pollutant removal process and optimize the oil-contaminated soil remediation performance at the pore scale to find the underlying mechanisms for oil removal from soil. The conservative forms of the phase-field model and the non-Newtonian power-law fluid model are employed to track the moving interface between two immiscible phases, and oil pollutant flushing removal process from soil pores is investigated. The effects of viscosity, interfacial tension, wettability, and flushing velocity on pore-scale oil pollutant removal regularity are explored. Then, the oil pollutant removal effects of two flushing agents (surfactant system and surfactant–polymer system) are compared using an oil content prediction curve based on UV-Visible transmittance. The results show that the optimal removal efficiency is obtained for a weak water-wetting system with a contact angle of 60° due to the stronger two-phase fluid interaction, deeper penetration, and more effective entrainment flow. On the basis of the dimensionless analysis, a relatively larger flushing velocity, resulting in a higher capillary number (Ca) in a certain range, can achieve rapid and efficient oil removal. In addition, an appropriately low interfacial tension, rather than ultra-low interfacial intension, contributes to strengthening the oil removal behavior. A reasonably high viscosity ratio (M) with a weak water-wetting state plays synergetic roles in the process of oil removal from the contaminated soil. In addition, the flushing agent combined with a surfactant and polymer can remarkably enhance the oil removal efficiency compared to the sole use of the surfactant, achieving a 2.5-fold increase in oil removal efficiency. This work provides new insights into the often-overlooked roles of the pore scale in fluid dynamics behind the remediation of oil-contaminated soil via flushing agent injection, which is of fundamental importance to the development of effective response strategies for soil contamination.

Moderating effects of chord progressions on the emotional experience of major and minor chords.

Numerous studies have shown the major chords express positive emotions, while minor chords convey negative emotions. However, several research suggest that the association between major/minor chords and emotional valence may vary due to certain musical contextual factors. This study investigates whether the emotional experience associated with major and minor chords is influenced by chord progressions. Employing subjective evaluations, participants were asked to evaluate the emotional valence, stability, and tension of individual chords (Experiment 1) and the final chords in chord sequences (Experiment 2). Results indicate that the pleasantness ratings of major chords are significantly higher than those of minor chords, while tension ratings are significantly lower. However, stability ratings between major and minor chords did not significantly differ. Notably, when major chords served as the final chords in stable termination progressions, their ratings in pleasantness and stability will be significantly higher compared to those of minor chords, and at the same time, they will also elicit lower tension ratings. While unstable terminations show no significant differences in ratings between major and minor chords across the dimensions of pleasantness, stability, and tension. Thus, this study reveals that chord progressions, as a musical context, influence the emotional valence of major and minor chords through variations in their stability and tension.

Drug Delivery Applications of Hydrophobic Deep Eutectic Solvent-in-Water Nanoemulsions: A Comparative Analysis of Ultrasound Emulsification and Membrane-Assisted Nanoemulsification.

The emergence of green chemistry and engineering principles to enforce sustainability aspects has ensured the prevalence of green solvents and green processes. Our study addresses this quest by exploring drug delivery applications of hydrophobic deep eutectic solvents (DESs) which are alternative green solvents. Initially, this work showcases the hydrophobic drug solubilization capabilities of a natural hydrophobic DES, menthol, and decanoic acid. To consider biomedical applications wherein polar media are encountered, this work further demonstrates the potential drug delivery application of these systems by encapsulating the anti-inflammatory local anesthetic lidocaine in hydrophobic DES-in-water nanoemulsions. NMR studies confirm the high solubility of the hydrophobic drug in hydrophobic DES comprising menthol and decanoic acid (1:2 molar ratio). Ultrasound emulsification and energy-efficient membrane emulsification techniques were employed to disperse 4% (v/v) DES into a 2% (w/w) Tween 20 surfactant aqueous solution. An isoporous microengineered membrane (nominal pore size ∼ 9 μm) was used to produce lidocaine-loaded DES-based nanoemulsions. Such membrane-assisted nanoemulsification was possible because the hydrophobic DES exhibits relatively low interfacial tension with the continuous phase and acts as a cosurfactant. Moreover, increased concentrations of lidocaine within the DES resulted in a further decrease in the interfacial tension and a lower melting point. Among the kinetic models analyzed to evaluate the release of lidocaine encapsulated in hydrophobic DES-in-water nanoemulsions, the Korsmeyer-Peppas kinetic model provided the best fit. The release constant "n" of <0.5 indicates that the drug release mechanism is predominantly governed by diffusion. Additionally, cytotoxicity against various human cell lines demonstrated the nanoemulsion's potential for anti-inflammatory drug delivery applications. Consequently, the nanoemulsion of DES presents a promising solution for the effective loading and delivery of poorly soluble drugs. This innovative approach enhances drug solubility and bioavailability, providing a versatile platform for controlled drug release. By leveraging the advantages of nanoemulsion technology, our study underscores the potential of DES-based formulations to promote drug delivery systems across a variety of therapeutic applications.

Tannic acid coordination assembly enhances the interfacial properties of salted egg white gel particles.

Tannic acid (TA) has attracted the attention of researchers as a promising organic ligand capable of forming metal-organic coordination networks with various metal ions at interfaces to impact surface properties. In this study, we innovatively reported a self-assembly method for surface decoration by depositing TA/Fe3+ coatings on the surface of desalted duck egg white nanoparticles (DEWN), further studying the oil/water interfacial properties of the modified particles. The results showed that the ratio and concentration of TA to Fe3+ could modulate interfacial properties. The modified DEWN has low interfacial tension, with TFe2 having near-neutral wettability (θo/w ~ 90°) and stabilizing emulsions for over 60 days. Moreover, the emulsions stabilized by TFe1 and TFe2 formed stronger gel structures with better thixotropic recovery (98.82 % and 89.26 %). After further increasing the oil phase ratio, the increased layer assembly concentration improved the stability of the oil phase and formed a dense gel mesh structure. The effects of temperature and salt ion concentration on the emulsion were investigated under optimum conditions, both of which showed good stability. Overall, our research not only highlighted straightforward strategies for preparing emulsions with higher stability using green and sustainable raw materials, but also broadened the range of applications for metal-phenol decoration.

Simple Metric Measurement To Choose A keystone Flap Design On Extremities: A Cadaveric Study

Background: Closing defect on extremities can be challenging because of limited donor area in order to obtain similar quality, color, texture, and adequate size with the defect. The keystone flap has gained popularity as a tool for local reconstruction because of its simple design, short operative time, good aesthetic outcome, and cost-effective wound closure. The aim of this study is to introduce a method in choosing a keystone flap design based on simple metric measurement resulting in lower tension.. Methods: Four circular defects were created on 4 different regions of a fresh cadaver’s upper limbs. Diameters were 5 cm for upper arms and 3 cm for lower arms. Two options of keystone flaps designs were introduced. The keystone could be advanced in longitudinal manner or in transversal manner according to limb’s axis. We then calculated the percentage of the skin required to stretch, in order to close the defects. The less percentage of skin required to stretch between the two manners indicated the lower tension of the keystone flap. Results: Measurements in all of 4 regions of upper limbs showed that the percentage of skin stretch in closing the defects was lower in longitudinal advancement keystone flap compared to transversal advancement (19.88% versus 27.8% for upper arms and 15.71% versus 21.67% for lower arms) Conclusion: Simple metric measurements in choosing a keystone flap can be applied to defects on extremities. With less tension when raising the keystone flap, acceptable scar is expected and the occurrence of contracture and flap necrosis can be reduced.

Microscopic Mechanism for Precise Control of the Sizes of Molybdenum Blue Nanorings.

Molybdenum blue (MB) nanorings with monodispersed, well-defined structures can be feasibly prepared via treatment of molybdate solutions with reducing agents at acidic conditions. However, the hidden constraints that control their ring sizes have been unknown for decades. Herein, the formation of 3.4 and 4.1 nm nanorings, {Mo154} and {Mo176}, is monitored using small-angle X-ray scattering (SAXS) with systematically varied synthetic conditions. Results suggest that {Mo154} forms quickly in solution and then undergoes slow transformation into {Mo176} when reducing agents are used, while {Mo176} can form directly with MoCl5 supplied as reduced MoV. These are attributed to {Mo154} being the kinetic product catalyzed by the template-effect while {Mo176} is the thermodynamic product due to its low ring tension. Our findings unravel one of the long-standing mysteries in MB and point out effective routes for the precise synthesis of nanorings.

Properties of Pickering Stabilized Associative Water‐In‐Water Emulsions Based on Ultra‐High Molecular Weight Polyacrylamides

AbstractCompletely water‐based multicompartment systems have attracted a broad interest in recent years, mainly due to their versatile features such as permeability. Here, the associative formation of water‐in‐water (w/w) emulsions based on ultra‐high molecular weight poly(N,N‐dimethylacrylamide) (PDMA) and poly(4‐acryloylmorpholine) (PAM) is studied. The system is investigated using a combination of fluorescence microscopy and spectroscopy techniques. The system phase‐separates into aqueous droplets at very low polymer concentrations and exhibits intriguing physical properties. The formed emulsion droplets are extremely fluid (5–10 mPa.s), enable fast (5 µm2 s−1), nearly complete (mobile fraction ≈0.8) and unhindered diffusion within and across compartments, which is a hallmark of fluids. Furthermore, the very low interfacial tension (0.18–0.40 mN m−1) enables droplet coalescence leading to equilibrium formation of various emulsion structures. These properties show similarities to cell cytoplasm and coacervates and hence this type of w/w emulsion formed via associative non‐ionic interactions is a new direction in the field of synthetic cells and synthetic biology.

Non‐Ionic Fluorosurfactants for Droplet‐Based in vivo Applications

AbstractFluorocarbon oils are uniquely suited for many biomedical applications due to their inert, bioorthogonal properties. In order to interface fluorocarbon oils with biological systems, non‐ionic fluorosurfactants are necessary. However, there is a paucity of non‐ionic fluorosurfactants with low interfacial tension (IFT) to stabilize fluorocarbon phases in aqueous environments (such as oil‐in‐water emulsions). We developed non‐ionic fluorosurfactants composed of a polyethylene glycol (PEG) segment covalently bonded to a flexible perfluoropolyether (PFPE) segment that confer low IFTs between a fluorocarbon oil (HFE‐7700) and water. The synthesis of a panel of surfactants spanning a molecular weight range of 0.64–66 kDa with various hydrophilic‐lipophilic balances allowed for identification of minimal IFTs, ranging from 1.4 to 17.8 mN m−1. The majority of these custom fluorosurfactants display poor solubility in water, allowing their co‐introduction with fluorocarbon oils and minimal leaching. We applied the PEG5PFPE1 surfactant for mechanical force measurements in zebrafish, enabling exceptional sensitivity.

Effect of CO2-assisted surfactant/polymer flooding on enhanced oil recovery and its mechanism

D oilfield is a typical heavy oil reservoir affected by bottom water and has the characteristics of high porosity, high permeability, and strong heterogeneity. However, water flooding leaves oil behind due to unfavorable mobility ratios and capillary forces. The layer (well section) with poor or no liquid entry ability originally has been improved in the process of surfactant/polymer flood. However, fluid entry distribution interlayers were not improved obviously in the middle and late stages. To further improve the recovery efficiency of surfactant/polymer flooding on bottom water reservoirs, the CO2-assisted surfactant/polymer flooding development method had been proposed. The optimal composition of the surfactant/polymer system was selected by evaluating the oil-water interfacial tension and viscosity. Three-dimensional cores with bottom water were used in CO2-assisted surfactant/polymer flooding experiments to improve oil recovery. On this foundation, the screening of oil displacement agents, optimization of oil production well location, and injection pressure were carried out. Based on the comprehensive analysis of the produced liquid, the CO2 assisted surfactant/polymer flooding to enhanced oil recovery mechanism was analyzed. The results showed that the surfactant named BS had a low oil-water interfacial tension of 3.79 × 10-3 mN/m. In addition, salinity decreases the viscosity of the surfactant/polymer solution. It was found that conducting CO2 huff and puff after chemical flooding can improve oil recovery. Among the four chemical agents, CO2-assisted the anionic nonionic surfactant and the salt-resistant polymer system flooding had the highest recovery. Moreover, the location of the oil production well, that is, the distance between it and the bottom water layer, has an impact on the recovery. During the experiment, 2.5 cm was the farthest distance between the oil production well and the bottom water layer, at which point the recovery was highest at 70.9%, and the bottom water breakthrough rate was 2.4%. These results provide theoretical and technical support for the development of CO2-assisted surfactant/polymer flooding and its application in wells.

Nonlinear diffusion mechanism of porous media and countercurrent imbibition distance of fracturing fluids

Fracturing fluids countercurrent imbibition is a significant method to enhance recovery during hydraulic fracturing and soaking in shale reservoirs. Most investigations have primarily focused on the fracturing fluids imbibition recovery. In this work, an on-line computed tomography device was employed for the first time to conduct experiments on the imbibition distance of fracturing fluids, quantifying the imbibition distance of fracturing fluids, establishing the model of fracturing fluids imbibition, and clarifying the mechanism of countercurrent imbibition for fracturing fluids. The findings demonstrated that the imbibition distance was 2.625 cm for high mass fraction fracturing fluid and 2.375 cm for low mass fraction fluid. For formation water with viscoelastic fracturing fluids, the imbibition distances were 1.125 and 0.875 cm. Compared to the permeability of 0.082 × 10−3 μm2, the imbibition distance increased by 2.625 times at 0.217 × 10−3μm2 and by 3.25 times at 0.760 × 10−3μm2. At injection pressures of 20 and 15 MPa, the imbibition distance increased by 1.7 and 1.61 times, compared to 5 MPa. Parameter sensitivity analysis demonstrated that crude oil and fracturing fluids viscosity were negatively correlated with imbibition distance. Low interfacial tension boosts imbibition power, extending the imbibition distance. High interfacial tension raises flow resistance, shortening the imbibition distance. Reducing the contact angle improves hydrophilicity and capillary force, extending the imbibition distance. When the permeability is below 1 × 10−3μm2, the imbibition distance increases significantly with rising permeability. When the permeability exceeds 1 × 10−3μm2, the rate of increase diminishes. The investigation in this paper provides guidance for the efficient development of shale oil.

Examining the safe-haven and hedge capabilities of gold and cryptocurrencies: A GARCH and regression quantiles approach in geopolitical and market extremes

This paper examines gold and cryptocurrencies' hedge and safe-haven capabilities against various downturns, including the COVID-19 pandemic and Geopolitical Risks (GPR), across different market conditions. The study covers a sample period from 2013 to 2021 at a daily frequency, employing the GARCH model and quantile regression with binary variables.The empirical results indicate that neither gold nor cryptocurrencies can act as strong hedges against infectious disease pandemics. However, gold, Bitcoin, and Ethereum exhibit weak safe-haven abilities during geopolitical risks.Using regression quantiles, the study finds that gold demonstrates a strong safe-haven against low and high Infectious Disease Epidemic Market Volatility (IDEMV) during extremely bearish and bullish markets. In contrast, Bitcoin and Ethereum act as strong safe havens only against low IDEMV during extreme bearish markets. Gold also shows a strong hedge propriety against extreme geopolitical events, while cryptocurrencies provide a weak hedge.Overall, gold exhibits strong safe-haven properties against low and high Geopolitical tensions, while cryptocurrencies' hedging and safe-haven abilities vary across markets. These findings convey insights for investors and guidance to supervisors on the evolution of gold, Bitcoin, and Ethereum as safe-haven and hedge instruments during both bearish and bullish markets.

Effect of salt ions (Na+, Ca2+ and Mg2+) and EOR anionic and nonionic surfactants on the dispersion stability of cellulose nanocrystals

The application of cellulose nanocrystals (CNCs) in enhanced oil recovery (EOR) is a developing hotspot. To improve the stability of CNCs in salt environments, the effects of sodium dodecylbenzene sulfonate (SDBS) and polyoxyethylene sorbitan monooleate (Tween 80) on the stability of CNCs in the presence of sodium (Na+), calcium (Ca2+) and magnesium (Mg2+) were investigated. The range of salt ions and the stability mechanism for improving the CNCs stability in the presence of SDBS and Tween 80 were pointed out. SDBS improved the stability of CNCs in the presence of 30–100 mM Na+, 1–2 mM Ca2+ and 2 mM Mg2+, respectively. Tween 80 improved the stability of CNCs in the presence of Na+ ≤ 300 mM, Ca2+ ≤ 10 mM and Mg2+ ≤ 10 mM, respectively. The mechanism was explained by the bridging effect of salt ions, electrostatic effect and spatial stability effect. The combined systems of surfactants (SDBS and Tween 80) with CNCs exhibited strong emulsifying properties, low interfacial tension (0.023 mN/m and 1.85 mN/m), and the ability to alter the wettability of oil wet rocks. This made the combined systems have better oil displacement performance.

High precision acoustofluidic synthesis of stable, biocompatible water-in-water emulsions

Water-in-water (w/w) emulsions, comprising aqueous droplets within another continuous aqueous phase, rely on a low interfacial tension for stability. Thus far, it has been challenging to control their size and stability without the use of stabilizers. In this study, we introduce a microfluidic technique that addresses these challenges, producing stable w/w emulsions with precisely controlled size and uniformity. Results shows that using an acoustically actuated microfluidic mixer, PEG, Dextran, and alginate solutions (84.66 mPa.s viscosity difference) were homogenized rapidly, forming uniformly distributed w/w emulsions stabilized in alginate gels.The emulsion size, uniformity, and shear sensitivity can be tuned by modifying the alginate concentration. Biocompatibility was evaluated by monitoring the viability of kidney cells in the presence of emulsions and gels. In conclusion, this study not only showed emulsion formation with a high mixing efficiency exceeding 90 % for all viscosities, actuated at an optimized frequency of 1.064 MHz, but also demonstrated that an aqueous, solvent, and emulsifier-free composition exhibited remarkable biocompatibility, holding promise for precise drug delivery, cosmetics, and food applications.

Fission of double-membrane tubes under tension

The division of a cellular compartment culminates with the scission of a highly constricted membrane neck. Scission requires lipid rearrangements, topology changes, and transient formation of nonbilayer intermediate structures driven by curvature stress. Often, a side effect of this stress is pore-formation, which may lead to content leakage and thus breaching of the membrane barrier function. In single-membrane systems, leakage is avoided through the formation of a hemifusion (HF) intermediate, whose structure is still a subject of debate. The consequences of curvature stress have not been explored in double-membrane systems, such as the mitochondrion. Here, we combine experimental and theoretical approaches to study neck constriction and scission driven by tension in biomimetic lipid systems, namely single- and double-membrane nanotubes (sNTs and dNTs), respectively. In sNTs, constriction by high tension gives rise to a metastable HF intermediate (seen as stalk or worm-like micelle), whereas poration is universally slower in a simple neck. In dNTs, high membrane tension causes sequential rupture of each membrane. In contrast, low tension leads to the HF of both membranes, which may lead to a leaky fusion pathway, or may progress to further fusion of the two membranes along a number of transformation pathways. These findings provide a new mechanistic basis for fundamental cellular processes.

Tensions on the actin cytoskeleton and apical cell junctions in the C. elegans spermatheca are influenced by spermathecal anatomy, ovulation state and activation of myosin.

Cells generate mechanical forces mainly through myosin motor activity on the actin cytoskeleton. In C. elegans, actomyosin stress fibers drive contractility of the smooth muscle-like cells of the spermatheca, a distensible, tube-shaped tissue in the hermaphrodite reproductive system and the site of oocyte fertilization. Stretching of the spermathecal cells by oocyte entry triggers activation of the small GTPase Rho. In this study, we asked how forces are distributed in vivo, and explored how spermathecal tissue responds to alterations in myosin activity. In animals expressing GFP labeled actin or apical membrane complexes, we severed these structures using femtosecond laser ablation and quantified retractions. RNA interference was used to deplete key contractility regulators. We show that the basal actomyosin fibers are under tension in the occupied spermatheca. Reducing actomyosin contractility by depletion of the phospholipase C-ε/PLC-1 or non-muscle myosin II/NMY-1, leads to distended spermathecae occupied by one or more embryos, but does not alter tension on the basal actomyosin fibers. However, activating myosin through depletion of the Rho GAP SPV-1 increases tension on the actomyosin fibers, consistent with earlier studies showing Rho drives spermathecal contractility. On the inner surface of the spermathecal tube, tension on the apical junctions is decreased by depletion of PLC-1 and NMY-1. Surprisingly, when basal contractility is increased through SPV-1 depletion, the tension on apical junctions also decreases, with the most significant effect on the junctions aligned in perpendicular to the axis of the spermatheca. Our results suggest that much of the tension on the basal actin fibers in the occupied spermatheca is due to the presence of the embryo. Additionally, increased tension on the outer basal surface may compress the apical side, leading to lower tensions apically. The three dimensional shape of the spermatheca plays a role in force distribution and contractility during ovulation.

Influence of Gamma irradiation on shape memory polymer nano-composite for satellite deployment mechanism

This research investigates the impact of gamma irradiation on epoxy-MWCNT nanocomposites for satellite deployment mechanisms. Nanocomposites, enhanced with surfactants, were meticulously prepared and subjected to controlled gamma irradiation (250–1000 kGy) utilizing the Cobalt-60 facility Industrial Mega Gamma-1 at NCRRT in Egypt. Surface tension measurements explored surfactant effects on epoxy-MWCNT composites in acetone. Acetone reduced tension from 26.7 to be 24.2 (mN/m). Surfactants (Tween 80, SDS) effectively lowered tension (24.4 mN/m), while surfactant-free systems had higher tension (25.1 mN/m). Cationic surfactant (CTAB) slightly increased tension (25.4 mN/m) but aided MWCNT dispersion. Nonionic and anionic surfactants showed superior dispersing power, aligning with MWCNTs and enhancing dispersion. Thermogravimetric analysis (TGA) unveiled alterations in the thermal stability of epoxy-MWCNT nanocomposites induced by radiation, particularly evident at elevated doses (500 and 1000 kGy). Notably, surfactant-modified specimens exhibited discernible effects on various thermal stability parameters. DMA analysis revealed radiation-induced changes in viscoelastic properties. Unirradiated epoxy exhibited a Tg of 58 °C, while 250 kGy irradiation enhanced crosslinking (Tg: 64 °C). Higher doses (500 kGy, 1000 kGy) caused marginal Tg changes. Surfactant-modified samples showed varied effects, with Tween 80 emphasizing its role in phase separation. Results highlighted radiation’s influence on stiffness and energy dissipation. Shape memory behavior indicated increased recovery time with higher doses, except at 250 kGy. Epoxy-MWCNT exhibited a stable recovery time, suggesting a MWCNT stabilizing effect. Fixation rates consistently reached 100%, indicating improved shape recovery influenced by MWCNTs and surfactants. This study provides insights into optimizing nanocomposites for satellite deployment applications.

Stick-slip unfolding favors self-association of expanded HTT mRNA

In Huntington’s Disease (HD) and related disorders, expansion of CAG trinucleotide repeats produces a toxic gain of function in affected neurons. Expanded huntingtin (expHTT) mRNA forms aggregates that sequester essential RNA binding proteins, dysregulating mRNA processing and translation. The physical basis of RNA aggregation has been difficult to disentangle owing to the heterogeneous structure of the CAG repeats. Here, we probe the folding and unfolding pathways of expHTT mRNA using single-molecule force spectroscopy. Whereas normal HTT mRNAs unfold reversibly and cooperatively, expHTT mRNAs with 20 or 40 CAG repeats slip and unravel non-cooperatively at low tension. Slippage of CAG base pairs is punctuated by concerted rearrangement of adjacent CCG trinucleotides, trapping partially folded structures that readily base pair with another RNA strand. We suggest that the conformational entropy of the CAG repeats, combined with stable CCG base pairs, creates a stick-slip behavior that explains the aggregation propensity of expHTT mRNA.

HEART RATE VARIABILITY IN FOOTBALL PLAYERS AND TRACK AND FIELD ATHLETES

Objective of the study: To investigate the state of the autonomic nervous system in athletes based on heart rate variability indicators. Materials and methods: The study was conducted on 142 male athletes (67 football players and 75 track and field athletes) aged 17-20 years, with an average age of 18.5±1.5 years. Depending on the type of higher nervous activity, athletes were divided into 4 groups: sanguine (41.55%), choleric (28.87%), phlegmatic (19.01%), and melancholic (10.56%). Heart rate variability (HRV) was studied using the "BioMouse" system. A t-test for independent samples (Welch's t-test) was used to analyze the significance of differences between the groups. Results of the study: It was found that the highest adaptive capabilities were observed in phlegmatic athletes, who demonstrated high SDNN and HF values, as well as a low tension index (IN). Their calm temperament allows for better adaptation to physical exertion and maintaining a balance between sympathetic and parasympathetic activity. The lowest adaptive capabilities were observed in melancholics, who showed high IN and LF values, as well as low SDNN and HF, indicating an imbalance in the autonomic nervous system and lower resilience to physical stress. Overall, beginner athletes tended to have slightly higher heart rates and lower HRV indicators (SDNN), LF, and HF compared to more experienced athletes of the 2nd-3rd ranks. This is due to the fact that first-year athletes have not yet fully adapted to physical loads, leading to more pronounced dominance of the sympathetic nervous system and less parasympathetic activity. KEYWORDS: variability, heart rate, athletes, football players, track and field athletes, autonomic nervous system, physical exertion

Non-thermal recovery of a viscous oil with a surfactant-polymer process

The goal of this work is to improve recovery of a viscous oil reservoir at 70 °C using a non-thermal process. Polymer floods can improve sweep efficiency, but leave behind a residual oil saturation. A surfactant-polymer flood has the potential to improve both the sweep as well as the displacement efficiency. Phase behavior experiments with the viscous oil, water and surfactants were conducted to identify surfactants. 1D and 2D sandpack displacements were conducted to evaluate the efficacy of the process. Phase behavior experiments showed Winsor type I behavior with a low interfacial tension using a single surfactant, but not ultralow tension. Water flood recovered about 50% OOIP and reduced the oil saturation to about 45% in 1D floods. The subsequent SP flood increased the cumulative oil recovery to 99% in sandpacks when the viscosity of chemical slugs exceeded the oil viscosity. When the permeability decreased (as in a Bentheimer core), the oil recovery decreased to about 86%. Secondary SP floods also recovered most of the oil and faster than tertiary floods. Reduction of polymer concentration (and viscosity to about 1/4th of the oil viscosity) reduced the oil recovery, especially in 2D sandpack floods. Decrease in interfacial tension increased the requirement of polymer concentration to maintain flood front stability. This flood demonstrates the effectiveness of Winsor type I SP formulation for viscous oil, high permeability reservoirs. Such a SP process would reduce the carbon footprint of viscous oil recovery compared to that of thermal processes.