Extension Force Research Articles

Conformational Diversity in Partially Fluorinated N‐Alkyl Pipecolic Acid Amide Derivatives

AbstractThe molecular and crystal structures of 19 N‐alkyl‐substituted pipecolamide derivatives with partial fluorination of N‐propyl and N‐butyl groups are presented. Fluorination patterns include one F‐atom at internal or terminal locations, two F‐atoms in geminal or vicinal arrangements at various positions, as well as terminal trifluoromethylation. Due to the presence of the carboxamide side chain in pipecolamide derivatives, enantiomeric fluorination patterns in the N‐alkyl group result in diastereomeric compounds, which exhibit dramatically different crystal and molecular structures. An extraordinary conformational diversity is diagnosed for the various N‐alkylpiperidine units. Structural comparisons and theoretical assessments based on extensive force field calculations provide insight into consistent conformational patterns that point to intramolecular factors as well as intermolecular modulations due to crystal packing effects.

Rotation manipulation of single-molecule magnetic trapping and gene transcription regulation dynamics

Gene transcription regulation is a key step for gene expression in all organisms and responsible for the transmission of genetic information and genome integrity. As one of the most important mechanisms in gene transcription, an RNA polymerase (RNAP) specifically interacts with and unwinds genome DNA to form a transcription bubble where a nascent RNA transcript is polymerized, taking one of the unwound DNA strands as its template. The RNAP translocates along the DNA to transcribe the whole gene by carrying the transcription bubble. In such a way, an RNAP completes its biological task of gene expression by physically acting as a molecular machinery. Thus, an RNAP molecule can be considered as a research object for physicists who are willing to uncover the mechanisms of life processes in a physical view. To achieve this, single-molecule method has been invented and used widely. As one of these methods, single-molecule magnetic trapping manipulates biological molecules by applying extension force or torque to the magnetic beads tethered through biological molecule to pre-coated glass surfaces by manipulating the position or rotation of a pair of magnets. A linear DNA molecule can be manipulated in such a way to generate plectonemes, i.e. DNA supercoils, under an extension force of 0.3 pN (1 pN = 10<sup>–12</sup> N), possessing the feature that the number of unwound base pairs of a supercoiled DNA can be observed by the changes in the number of supercoils reflected by the DNA extension changes. Thus, the DNA unwound by RNAP, i.e. the transcription bubble, during transcription can be observed in this way. By monitoring the kinetics of the transcription bubble in real time, this method thus allows single-molecule detection with single-base resolution and a high-throughput data collection fashion in the kinetic studies of transcription. Owing to the advantages of the manipulation of DNA supercoils with single-molecule magnetic trapping, one can mimic the mechanistic feature of DNAs in vivo and characterize the kinetics of transcription under such conditions. This method can also be combined with single-molecule fluorescence method which can be applied to studying the mechanism of transcription regulation while monitoring the behaviors of fluorescently labeled biological molecules that interact with functional RNAP molecules, providing examples for studying the mechanisms of transcription regulations in more complex systems.

Comparison of contraction intensity and perceived intensity between dominant and non-dominant leg in sedentary adults

IntroductionAccurate measurement of isometric contraction intensity is a prerequisite for establishing an exercise program and developing a rehabilitation plan. Despite numerous studies performed previously, there is no research on sedentary populations susceptible to injury during exercise. Additionally, although dominant and non-dominant legs showed differences in muscle properties, the legs were not separately investigated. The purposes of this study were to compare the contraction intensity with target intensity and with perceived intensity across 3 different target intensities in sedentary adults and examine the difference between the dominant and non-dominant leg.MethodsVoluntary isometric contractions were performed with resistance provided by a sling rope and measured with a strain gauge during hip extension. First, maximum voluntary contraction (MVC) was executed; subsequently, submaximal contractions at target intensities (75%, 50%, and 25% of MVC) were randomly performed. Perceived intensity was measured at each target intensity.ResultsHip extension forces were significantly different across the 3 intensities (<i>p</i> < 0.001), with no significant difference between target intensity and contraction intensity or between perceived intensity and contraction intensity. There was no significant difference between the dominant and non-dominant leg. Bland-Altman analysis of the agreement between perceived and contraction intensities revealed a proportional bias for the values within each target intensity (mean bias: –1.15%, standard deviation of bias: 20.96).ConclusionsSedentary subjects were able to distinguish 3 different contraction intensities. Perceived intensity could statistically significantly predict contraction intensity. However, clinicians should note that under- or overestimation can occur regardless of the level of target intensity.

Setting Up a Bio-AFM to Study Protein Misfolding in Neurodegenerative Diseases.

The clinical pathology of neurodegenerative diseases suggests that earlier onset and progression are related to the accumulation of protein aggregates due to misfolding. A prominent way to extract useful information regarding single-molecule studies of protein misfolding at the nanoscale is by capturing the unbinding molecular forces through forced mechanical tension generated and monitored by an atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS). This AFM-driven process results in an amount of data in the form of force versus molecular extension plots (force-distance curves), the statistical analysis of which can provide insights into the underlying energy landscape and assess a number of characteristic elastic and kinetic molecular parameters of the investigated sample. This chapter outlines the setup of a bio-AFM-based SMFS technique for single-molecule probing. The infrastructure used as a reference for this presentation is the Bruker ForceRobot300.

Biomechanical gait analysis for a hip disarticulation prosthesis: power source for the swing phase of a hip disarticulation prosthetic limb.

[Purpose] This study aimed to clarify the power source for the swing phase of a hip disarticulation prosthetic limb using biomechanical gait analysis. [Participants and Methods] In this cross-sectional study, six participants who underwent hip disarticulation and seven healthy adults were recruited. Their gaits were assessed using the three-dimensional motion analysis and four force plates. [Results] From pre-swing to initial swing, the angle of the lumbar spine's angle changed by 9° from the flexion to extension positions. However, the power of the lumbar spine was <0.003 W/kg for the entire gait cycle. The peak value of joint moment and hip joint power on the unaffected side were 1 nm/kg and 0.7 W/kg, respectively. From pre-swing to initial swing, the prosthetic limb is pushed forward by extension of the hip joint on the intact side, while the spine returns to the flexion direction. [Conclusion] The hip extension force on the unaffected side was the main force responsible for swinging out the prosthesis, not the lumbar vertebrae's force.

PS-C25-12: CORRELATION OF RENAL FUNCTION AND MUSCLE MASS IN YOUNG ATHLETES

Objective: Renal function is closely associated with the development of hypertension. Creatinine is often used as a serum marker of renal function. Since creatinine is a metabolite of muscle, its concentration in serum is affected by muscle mass. Therefore, serum creatinine levels are high in individuals with high muscle mass, and renal function is underestimated. On the other hand, in elderly people with low muscle mass, serum creatinine concentration tends to be low, and there is a risk that renal function is estimated better than it actually is. Since another renal function marker, cystatin C, is produced in every cell of humans, it is considered to be unaffected by skeletal muscle mass. Therefore, cystatin C is often used as a renal function marker that is less dependent on muscle mass than creatinine. In this study, we analyzed the correlation between muscle mass and renal function in young athletes with high muscle mass. Design and Methods: The subjects are 250 first-year male students at the National Institute of Fitness and Sports in Kanoya. The impedance method was used to measure muscle mass. Serum creatinine and cystatin C levels were measured by a clinical laboratory. Grip strength was measured with a Smedley-type hand dynamometer, and isometric measurement was performed to measure the leg extension force. Results: Muscle mass showed a significant correlation with left and right grip strength and right leg extension force. These results show that the muscle mass of the whole body measured in this study reveals the skeletal muscle mass, from which serum creatinine is derived. Muscle mass showed a significant correlation with serum creatinine levels. It also showed a significant correlation with the glomerular filtration rate estimated from creatinine concentration, age, and gender. Muscle mass also showed a significant correlation with serum cystatin C levels. It also showed a significant correlation with the glomerular filtration rate estimated from cystatin C, age, and gender. Conclusion: In general, serum creatinine concentration is a renal function marker that is affected by muscle mass, and cystatin C is a renal function marker that is less affected by muscle mass. The results in this study show that muscle mass should be taken into consideration for the evaluation of renal function based on serum cystatin C level in young athletes.

Deconstructing body axis morphogenesis in zebrafish embryos using robot-assisted tissue micromanipulation

Classic microsurgical techniques, such as those used in the early 1900s by Mangold and Spemann, have been instrumental in advancing our understanding of embryonic development. However, these techniques are highly specialized, leading to issues of inter-operator variability. Here we introduce a user-friendly robotic microsurgery platform that allows precise mechanical manipulation of soft tissues in zebrafish embryos. Using our platform, we reproducibly targeted precise regions of tail explants, and quantified the response in real-time by following notochord and presomitic mesoderm (PSM) morphogenesis and segmentation clock dynamics during vertebrate anteroposterior axis elongation. We find an extension force generated through the posterior notochord that is strong enough to buckle the structure. Our data suggest that this force generates a unidirectional notochord extension towards the tailbud because PSM tissue around the posterior notochord does not let it slide anteriorly. These results complement existing biomechanical models of axis elongation, revealing a critical coupling between the posterior notochord, the tailbud, and the PSM, and show that somite patterning is robust against structural perturbations.

Feasibility and early effects of bed-cycling eccentric training: Potential clinical applications.

This study aimed to evaluate feasibility and early effects of moderate intensity bed-cycling eccentric training on healthy individuals, and establish whether this training modality could be implemented into bedridden patients'routine care. Longitudinal study with prepost exercise intervention measurements. The development of a bed-adapted eccentric ergometer allowed to conduct five training sessions during 3 weeks at increasing intensity on 11 healthy individuals. Force-speed relationship, maximal voluntary knee extension force and neural activation of subjects were evaluated before and after the programme. Five training sessions were sufficient to decrease the rate of perceived exertion whereas eccentric power output increased (+40%). After training, maximal voluntary isometric contraction force measured during knee extension had significantly improved in all subjects, with a mean increase of 17%. Maximal cycling power was also significantly higher (+7%) after the training programme. Taken together, these results show that moderate load eccentric bed cycling (i) was feasible and efficient, (ii) did not generate excessive individual perception of effort during exercise nor develop major muscular or joint pain after training and (iii) allowed early force and power gains in healthy subjects.

Muscle mass, quality, and strength; physical function and activity; and metabolic status in cachectic patients with head and neck cancer

Cancer cachexia is commonly associated with poor prognosis in patients with head and neck cancer (HNC). However, its pathophysiology and treatment are not well established. The current study aimed to assess the muscle mass/quality/strength, physical function and activity, resting energy expenditure (REE), and respiratory quotient (RQ) in cachectic patients with HNC. This prospective cross-sectional study analyzed 64 patients with HNC. Body composition was measured via direct segmental multifrequency bioelectrical impedance analysis, and muscle quality was assessed using echo intensity on ultrasonography images. Muscle strength was investigated utilizing handgrip strength and isometric knee extension force (IKEF). Physical function was evaluated using the 10-m walking speed test and the five times sit-to-stand (5-STS) test. Physical activity was examined using a wearable triaxial accelerometer. REE and RQ were measured via indirect calorimetry. These parameters were compared between the cachectic and noncachectic groups. In total, 23 (36%) patients were diagnosed with cachexia. The cachectic group had a significantly lower muscle mass than the noncachectic group. Nevertheless, there was no significant difference in terms of fat between the two groups. The cachectic group had a higher quadriceps echo intensity and a lower handgrip strength and IKEF than the noncachectic group. Moreover, they had a significantly slower normal and maximum walking speed and 5-STS speed. The number of steps, total activity time, and time of activity (<3 Mets) did not significantly differ between the two groups. The cachectic group had a shorter time of activity (≥3 Mets) than the noncachectic group. Furthermore, the cachectic group had a significantly higher REE/body weight and REE/fat free mass and a significantly lower RQ than the noncachectic group. The cachectic group had a lower muscle mass/quality/strength and physical function and activity and a higher REE than the noncachectic group. Thus, REE and physical activity should be evaluated to determine energy requirements. The RQ was lower in the cachectic group than that in the noncachectic group, indicating changes in energy substrate. Further studies must be conducted to examine effective nutritional and exercise interventions for patients with cancer cachexia.

Thermal fatigue crack growth behavior of Ni60 coating and bonding area on 20CrNiMo alloy strengthened by laser shock processing

After the laser cladding repair of the brake disc surface in high-speed trains, thermal fatigue cracks in the cladding layer and bonding area are easily observed during the service process. With the aim of solving this problem and decreasing hidden risks, effects of laser shock processing (LSP) on the thermal fatigue life and crack growth behavior of the coating and bonding area of the brake disc were investigated. The results indicate that LSP can refine the columnar grain structures of the cladding layer and bonding area while simultaneously converting residual tensile stress into compressive stress; as a result, the thermal fatigue performance of the brake disc repaired by laser cladding is enhanced. After strengthening by LSP, on the one hand, grain refinement made the structure more uniform and generated more grain boundaries; on the other hand, a pre-set compressive stress field in the cladding layer and bonding area existed. Both aspects were beneficial to dissipate the alternating stress generated by the thermal fatigue process, dissipating the driving force of crack extension and promoting the transformation of thermal fatigue cracks from lateral growth along the interface between the cladding layer and bonding area to the growth into the substrate.

Pitch controls the flexibility of helical ribbons

Helical objects are often implemented in electronic or mechanical micro-systems, requiring a precise understanding of their mechanical properties. While helices formed by cylindrical filaments have been intensely investigated, little is known about the role of the cross-section of the filament at the basis of the helical shape. We study experimentally the force–extension response of micro-helices fabricated from ultra-thin PMMA ribbons. Leveraging newly achieved control on the helix geometry, the influence of the helical pitch is quantified and a significant stiffening of the helical ribbons with increasing pitch is highlighted. Two phenomena are identified: a mechanical transition from a regime dominated by twisting of the ribbon at small pitch to a bending-dominated regime at high pitch and a purely geometrical effect, specific to helical ribbons. Excellent agreement is found with a previously established analytical model of inextensible elastic strips.

Preliminary study of elastic-tension digital neoprene orthoses for proximal interphalangeal joint flexion contracture

Flexion contracture of the proximal interphalangeal joint (PIPJ) is one of the most frequent complications in finger trauma. Orthoses are the most widely used method to optimize total end-range time (TERT). No previous studies showed that an elastic tension orthosis could be applied for longer than 12 h. We aimed to demonstrate that the elastic-tension digital neoprene orthosis (ETDNO) can achieve higher TERT and therefore better range of motion than other elastic-tension orthoses (ETO) described in the literature. A prospective study of treatment of PIPJ flexion contracture included 10 PIP joints in 8 patients who met the selection criteria. They were instructed to use the ETDNO for around 23 h per day as far as possible, during a period of 3 weeks. Patients reported a mean TERT of 20.6 h a day. PIPJ contracture improved by a mean Torque Range of Motion (TROM) of 23.5° at 500 g and 22.9° at 800 g of passive extension force during the 3-week treatment. Based on the results of this study, the ETDNO appears to offer a highly effective approach for improving PIPJ flexion contracture, increasing range of motion in extension. ETDNO’s efficacy probably lies in the significantly improved comfort and low-profile design, enabling excellent compliance and thus optimizing TERT. Level of evidenceLevel III.

Impact of muscle echo intensity on post-exercise blood pressure response in older normotensive and hypertensive females: Pilot study.

Exaggerated post-exercise blood pressure (BP) is considered a risk factor for the development of cardiovascular disease in older females. Muscle echo intensity (EI) using ultrasound can be used to evaluate intramuscular fat, one of the risk factors for cardiovascular disease. This study aimed to determine whether intramuscular fat assessed by muscle echo intensity is associated with the post-exercise BP response in older females. Ten older normotensive (SBP <130 mmHg, 71 ± 4 years), eight systolic BP-controlled (78 ± 4 years), and 17 hypertensive (SBP ≥130 mmHg, 74 ± 6 years) females were studied. After obtaining ultrasound images to assess the EI, participants performed ramp-up exercise until 50% maximal voluntary contraction (MVC: ~30-s; 3% MVC/s gradually increased knee extension force from 0% to 50% MVC followed by sustaining the force at 50% MVC for 10-s) and then five MVCs (~50 s; 10-s rest between each contraction). BP was measured before and immediately after exercise. Mean arterial pressure (MAP) pre- and post-exercise were significantly lower in normotensive and SBP-controlled, than in -uncontrolled hypertensive females (PRE: 85 ± 5 and 87 ± 7 vs. 106 ± 9; POST: 92 ± 8 and 94 ± 9 vs. 103 ± 11 mmHg, respectively, p < 0.05). EI was negatively correlated with ∆diastolic BP (∆DBP) but not ∆SBP and ∆MAP in normotensive females only (∆SBP, r=-0.21, p=0.56; ∆DBP, R=-0.73, p=0.02; ∆MAP, R=-0.49, p=0.15). Greater intramuscular fat as indicated by higher EI is associated with less BP elevation immediately after exercise in older normotensive females. Greater intramuscular fat may lead to lower intramuscular pressure, resulting in less post-exercise BP elevation.

Ensemble inequivalence and negative extensibility in a strongly stretched wormlike chain with fluctuating bending stiffness.

Many semiflexible polymers exhibit fluctuations in the local bending stiffness along their contour. This may be due to intrinsic conformational changes (e.g., denaturation bubble formation in double stranded DNA or helix-coil transition in polypeptides) or the reversible adsorption and desorption of molecules from the polymer's environment (e.g., DNA-protein interactions or hybridization of oligonucleotides). In this article, we analyze the tensile elasticity of a strongly stretched wormlike chain, which consists of N concatenated segments, where each segment can be in one of two states, A or B, which differ in bending stiffness. We call this model the reversible wormlike chain (rWLC) model. In the Gibbs (fixed-force, isotensional) ensemble, we obtain analytic expressions for the force-extension relation and the mean fraction of B segments. We show that, under certain conditions, there is a tension-induced crossover from a mostly A to a mostly B rWLC. In the Helmholtz (fixed-extension, isometric) ensemble, we obtain analytic expressions up to a summation. We show that, for finite N, there is marked ensemble inequivalence. Remarkably, in the Helmholtz ensemble, the rWLC can exhibit negative extensibility and multiple peaks.

Oral Presentation No. 121 Aortic stiffness descriptors by cardiac magnetic resonance are correlated with mechanical testing of ex-vivo aortic aneurysms specimens

Abstract Background Aortic stiffness independently predicts mayor adverse cardiovascular events and mortality in the general population. Cardiovascular magnetic resonance (CMR) permits the assessment of a number of parameters theoretically linked to aortic stiffness, such as distensibility (AD), pulse wave velocity (PWV) and proximal aorta longitudinal strain. However, no previous study validates these parameters as descriptors of aortic wall stiffness against ex-vivo mechanical testing. Materials and methods Ascending aorta (AAo) specimens were collected from 20 patients undergoing AAo replacement for aneurysms. Patients underwent a CMR protocol in the days leading to the surgery, including 4D flow CMR. Two 15×5 mm specimens (one oriented in the circumferential and the other in the longitudinal aortic direction) were extracted during surgery, and later tested controlling for extension force. Elongation was measured by laser video extensometer and the tangent of the stress-strain curve at diastolic pressure was extracted. AAo PWV and the Eh product (E being Young modulus and h wall thickness) were measured from 4D flow CMR while AD and AAo longitudinal were quantified from cine images. Results and conclusions Marked correlations were found between circumferential elastic modulus and AAo AD (R = −0.502), PWV(R = 0.652) and Eh (R = 0.602). Similarly, strong correlation was identified between AAo longitudinal strain and longitudinal elastic modulus(R = −0.513). In conclusion, PWV and the Eh product are positively related to aortic wall stiffness while aortic distensibility and strain show negative relationships. Thus, these biomarkers are a reliable expression of aortic wall stiffness. Funding PI17/00381,SEC/FEC-INV-CLI20/015,LCF/BQ/PR22/11920008.

The physiological, perceptual and neuromuscular responses of team sport athletes to a running and cycling high intensity interval training session

PurposeThe acute physiological, perceptual and neuromuscular responses to volume-matched running and cycling high intensity interval training (HIIT) were studied in team sport athletes.MethodsIn a randomized cross-over design, 11 male team sport players completed 3 × 6 min (with 5 min between sets) repeated efforts of 15 s exercising at 120% speed (sdot{text{V}}O2max) or power (pdot{text{V}}O2max) at dot{text{V}}O2max followed by 15 s passive recovery on a treadmill or cycle ergometer, respectively.ResultsAbsolute mean dot{text{V}}O2 (ES [95% CI] = 1.46 [0.47–2.34], p < 0.001) and heart rate (ES [95% CI] = 1.53 [0.53–2.41], p = 0.001) were higher in running than cycling HIIT. Total time at > 90% dot{text{V}}O2max during the HIIT was higher for running compared to cycling (ES [95% CI] = 1.21 [0.26–2.07], p = 0.015). Overall differential RPE (dRPE) (ES [95% CI] = 0.55 [− 0.32–1.38], p = 0.094) and legs dRPE (ES [95% CI] = − 0.65 [− 1.48–0.23], p = 0.111) were similar, whereas breathing dRPE (ES [95% CI] = 1.01 [0.08–1.85], p = 0.012) was higher for running. Maximal isometric knee extension force was unchanged after running (ES [95% CI] = − 0.04 [− 0.80–0.8], p = 0.726) compared to a moderate reduction after cycling (ES [95% CI] = − 1.17 [− 2.02–0.22], p = 0.001).ConclusionCycling HIIT in team sport athletes is unlikely to meet the requirements for improving run-specific metabolic adaptation but might offer a greater lower limb neuromuscular load.

Correlation Between Muscle Strength Asymmetry and Its Impact on Functional Scores after Ankle Sprain Rehabilitation

Category: Sports; Ankle Introduction/Purpose: Ankle sprain is one of the most common sports-related injuries. Treatment of these lesions can be performed conservatively with satisfactory results in up to 80% of cases. The main goals of rehabilitation are the recovery of mobility, strength and balance; but there is no consensus on decision make criteria to return to sport. It is known that the time elapsed from trauma may be insufficient reference and may induce early return, while the individual still does not have symmetric parameters of mobility, strength and proprioception. Purpose: To assess the proportionality of muscle strength between the healthy and rehabilitated sides 16 weeks after ankle sprain related to physical activity and to correlate with its impact on function scores. Methods: 131 individuals, from 18 to 64 years old, were evaluated after rehabilitation of simple sprain. Physical examination was performed with anterior drawer test, measurement of leg circumference by perimetry and by the method of figure in '8'; determination of active and passive range of motion using goniometer; muscle strength conference with hand held dynamometer and finally with the application of function scores. Equality test between two proportions, T-student test, Chi-square test and Pearson correlation were used to determine the significance between the values and correlations found. Results: We identified an average age of 36.1 (+- 2.5) years, 56 (42.70%) women and 75 (57.30%) men. 19.8% of sprains were severe. Limb volume and range of motion evaluations did not show significant differences. The anterior drawer remained positive in 19.1% of the individuals with the highest proportion in severe sprains (36.6%). Force asymmetry for flexion (52.7%), extension (50.4%), eversion (46.6%) and inversion (56.5%) movements above the 10% limit were observed. Impact on function scores showed a moderate correlation (0.59) with the proportionality of ankle extension forces. Conclusion: Individuals adequately rehabilitated after an ankle sprain and considered able to return to sports may present changes anterior drawer test and asymmetries in lower limb muscle strength impacting performance on function scores.

Challenging the mechanism of distal biceps tendon rupture using a video analysis study.

The conventionally described mechanism of distal biceps tendon rupture (DBTR) is of a 'considerable extension force suddenly applied to a resisting, actively flexed forearm'. This has been commonly paraphrased as an 'eccentric contracture to a flexed elbow'. Both definitions have been frequently used in the literature with little objective analysis or citation. The aim of the present study was to use video footage of real time distal biceps ruptures to revisit and objectively define the mechanism of injury. An online search identified 61 videos reporting a DBTR. Videos were independently reviewed by three surgeons to assess forearm rotation, elbow flexion, shoulder position, and type of muscle contraction being exerted at the time of rupture. Prospective data on mechanism of injury and arm position was also collected concurrently for 22 consecutive patients diagnosed with an acute DBTR in order to corroborate the video analysis. Four videos were excluded, leaving 57 for final analysis. Mechanisms of injury included deadlift, bicep curls, calisthenics, arm wrestling, heavy lifting, and boxing. In all, 98% of ruptures occurred with the arm in supination and 89% occurred at 0° to 10° of elbow flexion. Regarding muscle activity, 88% occurred during isometric contraction, 7% during eccentric contraction, and 5% during concentric contraction. Interobserver correlation scores were calculated as 0.66 to 0.89 using the free-marginal Fleiss Kappa tool. The prospectively collected patient data was consistent with the video analysis, with 82% of injuries occurring in supination and 95% in relative elbow extension. Contrary to the classically described injury mechanism, in this study the usual arm position during DBTR was forearm supination and elbow extension, and the muscle contraction was typically isometric. This was demonstrated for both video analysis and 'real' patients across a range of activities leading to rupture.Cite this article: Bone Jt Open2022;3(10):826-831.

Systematic Variation of Friction of Rods

Abstract The mechanical response of a knot tied in elastic rods strongly depends on the frictional force due to rod–rod contact. The behavior of a knot can be qualitatively different based on the frictional coefficient of the elastic rod. Systematic variation of friction during rod–rod contact is a crucial component of any experimental design to uncover the underlying ingredients behind the mechanics of knots. In this paper, we demonstrate a novel process of controlling the friction of a continuous rod by adhering non-spherical inorganic micro-particles. Polymeric binder is used to deliver the particles as asperities over the rod substrate and by controlling their size and distribution the coefficient of friction of the rod is determined. In parallel, numerical simulations with the discrete elastic rods algorithm are used to reproduce the experimental observations. Tabletop experiments are performed where overhand knots with a variety of unknotting numbers are pulled tight. The force–extension curve of these experiments shows that the proposed process can successfully tune the friction between rods.

Influence of brine compositions on wetting preference of montmorillonite in rock/brine/oil system: An in silico study

In this paper, we investigated dependency of thin brine film stability confined between rock and hydrocarbon layer on brine solution properties in terms of salinity and anionic components. Molecular Dynamics simulation was used to investigate behavior of the system at rock/brine and brine/oil interfaces to characterize thin brine film. Here, montmorillonite, a thin water film containing different salinities (low salinity water, 5,000 ppm, and high salinity water, 70,000 ppm) of NaCl and Na2SO4, and organic components constituting 3:1 M mixture of decane and sodium decanoate were considered to represent rock, brine, and oil, respectively. High salinity brine makes the thin film more stable. Extensive repulsive electrostatic forces between Cl− anions distributed in brine film and carboxylate functional groups at the brine/oil interface impede penetration of oil components into the brine film and then their adsorption onto the clay surface. Low salinity Na2SO4 showed the most stable brine film, in which distribution of anions at the brine/oil interface prevents intrusion of oil components into the brine film. However, high salinity Na2SO4 showed strong potential in forming ionic aggregations comprising Na+ cations and anions. These ionic aggregations act as bridging agents to adhere oil constituents onto the clay slab.