Moderate Force Research Articles

Current amplification through deformable arch-shaped film based direct-current triboelectric nanogenerator for harvesting wind energy

Triboelectric nanogenerators (TENGs) are one of energy harvesting technologies in spotlight that can produce electrical output from various mechanical movements such as vertical vibration, sliding motion, and rotation through different designs. Despite this potential, frictional damage is inevitable since TENG utilizes contact electrification that require repeated contact and separation on the surfaces of two materials. To decrease the frictional wear, flexible materials of designs with soft contact can be applied, but the efficiency of generating electrical output will be lowered. In this study, the deformable arch-shaped film TENG (DAS-TENG) is developed to decrease an unnecessary friction force by applying moderate normal force and increase the contact area with dielectric materials. By additional metal-to-metal contact between the fixed and moving electrodes, it can generate RMS output power of 633.44 mW and direct-current output by a wind input and charge the 100 µF capacitor to 1.74 V for 200 s even without rectifying circuit. We believe that DAS-TENG can be further developed to be primary power source for existing electronics.

Performance Evaluation of Vertical Discs and Disc Coulters for Conservation Tillage in an Intensive Rice–Wheat Rotation System

As an advanced agricultural production technology, conservation tillage has been developed rapidly and adopted widely for many crops all over the world, but challenges remain with regard to dealing with excessive residues, especially for intensive rice–wheat rotation systems. Most studies to date have been based on a single type of tool and the indoor bin test to explore its performance. Accurate field test data on the tillage performance of different types of tools for conservation tillage are lacking in this area. In this study, five tillage tools were tested in a paddy field with plenty of crop residues to compare their performance. They were three vertical discs with plain disc (PD), notched disc (ND), and rippled disc (RD) and two disc coulters with plain disc coulter (PDC) and notched disc coulter (NDC). All five tools were tested using a specific field test rig at two different working depths of 70 and 100 mm. Tillage forces, straw cutting efficiency, soil disturbance width, and soil cutting depth were measured. The results showed that tool geometry and working depth had a significant impact on tillage performance. The vertical disc performed a higher average straw cutting efficiency, as well as lower tillage forces and lower soil disturbance width than the disc coulter. For straw handling and furrowing operations, RD had the highest straw cutting efficiency, moderate tillage force, and appropriate soil disturbance width among the five tools. For all five tools, the 100 mm working depth results in 40% higher draught force, 39% greater vertical force, and 18% higher straw cutting efficiency on average. For no-tillage seeding in the intensive rice–wheat rotation system, the RD would be a more suitable rotary tool for conservation tillage practice.

Experimental study on PSPC beam – Concrete encased CFST column frame installed with novel steel panel dampers

A concrete-filled steel tubular (CFST) column has a bearing capacity with a relatively small cross section. From the perspective of the assembly, a partially steel-reinforced precast concrete (PSPC) beam can combine the merits of both the reinforced concrete beam and steel beam. However, strong earthquake action puts forwards a dramatic seismic requirement for the high-rise frame. In this study, to improve the seismic performance of the structure in an economical way, the duplex assembled I-shaped steel panel damper (DAISPD) was introduced to the PSPC beam-concrete encased CFST column frame through the eccentric brace. A half-scaled two-storey two-bay substructure specimen was tested under cyclic loading. A series of seismic properties was then analysed, including the failure modes, hysteretic performance, and energy dissipation capacity. To further investigate the contribution of the damper, groups of numerical analyses were conducted on the key design parameters of the DAISPD. The introduction of the damper provides an adequate lateral stiffness and energy absorption to the frame, especially when the interstorey drift is within the elastic and plastic drift limits. The damage of the damper and the beam hinge mechanism occurs sequentially, which results in a two-stage failure mode. Considering the predamage contribution and the postdamage influence of the damper, it is recommended to design with a moderate yield force and a small height.

Sex Differences in Pain: Spinal Cord Injury in Female and Male Mice Elicits Behaviors Related to Neuropathic Pain.

Spinal cord injury (SCI) in humans frequently causes intractable chronic pain. Females are susceptible to worse pain than males, and females may show higher pain prevalence after SCI. Despite this difference in the clinical prevalence of SCI pain, few pre-clinical studies have systematically studied sex differences in SCI-elicited pain-related behaviors in rodents. Here, we leverage data from a large cohort of mice to test whether contusion SCI consistently causes pain symptoms in mice, and to establish whether female (vs. male) mice display heightened hypersensitivity after SCI. Mechanical and heat sensory thresholds were assessed using the von Frey and Hargreaves tests, respectively. In an initial experiment, female mice receiving moderate 60 kDyn SCI or moderate-to-severe 75 kDyn SCI at T9 both exhibited mechanical and heat pain symptoms compared with sham controls. A 75 kDyn SCI caused excess motor deficits that confounded defining pain sensitivity at acute times; therefore, the moderate SCI force was used for subsequent experiments. Next, adult female and male C57BL6/J mice received sham surgery or T9 moderate contusion SCI. Comparing female to male mice after SCI, we reveal that mice of both sexes displayed mechanical and heat hypersensitivity compared with sham controls, from acute-to-chronic post-injury times. Females had amplified SCI-elicited hypersensitivity compared with males. Our data suggest that thoracic contusion SCI elicits consistent and persistent pain-associated symptoms, which are more intense in female than in male mice. These results have important implications for uncovering sex-specific mechanisms and therapeutic targets to ameliorate neuropathic pain after SCI.

Is there a u-shaped relationship between load levels and fatigue and recovery? An examination of possible mechanisms

In a previous study, an unexpected u-shaped relationship was observed between load level and fatigue/recovery responses. Moderate load levels resulted in lower perceived discomfort, pain, and fatigue, and shorter recovery times compared to either low or high load levels. This phenomenon has been reported in other studies, but no article has examined the possible mechanisms that might explain this u-shaped relationship. In this paper, we re-examined the previously published data and found that the phenomenon does not appear to be due to the experimental artefact; the u-shape may be due to unexpectedly lower fatigue effects at moderate loads, and higher fatigue effects at lower loads. We then conducted a literature review and identified several possible physiological, perceptual, and biomechanical explanatory mechanisms. No single mechanism explains the entirety of the phenomenon. Further research is needed on the relationship between work exposures, fatigue, and recovery, and the mechanisms related to the u-shaped relationship. Practitioner summary: We examine a previously observed u-shaped relationship between load level and fatigue/recovery, where moderate force resulted in lower perceived fatigue and shorter recovery times. A u-shaped fatigue response suggests that simply minimising load levels might not be an optimal approach to reduce the risk of workplace injuries.

Aging-induced alterations in EEG spectral power associated with graded force motor tasks.

It has been demonstrated that in young and healthy individuals, there is a strong association between the amplitude of EEG-derived motor activity-related cortical potential or EEG spectral power (ESP) and voluntary muscle force. This association suggests that the motor-related ESP may serve as an index of central nervous system function in controlling voluntary muscle activation Therefore, it may potentially be used as an objective marker to track changes in functional neuroplasticity due to neurological disorders, aging, and following rehabilitation therapies. To this end, the relationship between the band-specific ESP-combined spectral power of EEG oscillatory and aperiodic (noise) components-and voluntary elbow flexion (EF) force has been analyzed in elder and young individuals. 20 young (22.6 ± 0.87year) and 28 elderly (74.79 ± 1.37year) participants performed EF contractions at 20%, 50%, and 80% of maximum voluntary contraction (MVC) while high-density EEG signals were recorded. Both the absolute and relative ESPs were computed for the EEG frequency bands of interest. The MVC force generated by the elderly was foreseeably lower than that of the young participants. Compared to young, the elderly cohort's (1) total ESP was significantly lower for the high (80% MVC) force task; (2) relative ESP in beta band was significantly elevated for the low and moderate (20% MVC and 50% MVC) force tasks; (3) absolute ESP failed to have a positive trend with force for EEG frequency bands of interest; and (4) beta-band relative ESP did not exhibit a significant decrease with increasing force levels. As opposed to young subjects, the beta-band relative ESP in elderly did not significantly decrease with increasing EF force values. This observation suggests the use of beta-band relative ESP as a potential biomarker for age-related motor control degeneration.

Measuring the Diameter of Single-Wall Carbon Nanotubes Using AFM.

In this work, we identify two issues that can significantly affect the accuracy of AFM measurements of the diameter of single-wall carbon nanotubes (SWCNTs) and propose a protocol that reduces errors associated with these issues. Measurements of the nanotube height under different applied forces demonstrate that even moderate forces significantly compress several different types of SWCNTs, leading to errors in measured diameters that must be minimized and/or corrected. Substrate and nanotube roughness also make major contributions to the uncertainty associated with the extraction of diameters from measured images. An analysis method has been developed that reduces the uncertainties associated with this extraction to <0.1 nm. This method is then applied to measure the diameter distribution of individual highly semiconducting enriched nanotubes in networks prepared from polyfluorene/SWCNT dispersions. Good agreement is obtained between diameter distributions for the same sample measured with two different commercial AFM instruments, indicating the reproducibility of the method. The reduced uncertainty in diameter measurements based on this method facilitates: (1) determination of the thickness of the polymer layer wrapping the nanotubes and (2) measurement of nanotube compression at tube-tube junctions within the network.

Biochemical and Physiological Responses of Arabidopsis thaliana Leaves to Moderate Mechanical Stimulation

Mechanical stimulation of plants can be caused by various abiotic and biotic environmental factors. Apart from the negative consequences, it can also cause positive changes, such as acclimatization of plants to stress conditions. Therefore, it is necessary to study the physiological and biochemical mechanisms underlying the response of plants to mechanical stimulation. Our aim was to evaluate the response of model plant Arabidopsis thaliana to a moderate force of 5 N (newton) for 20 s, which could be compared with the pressure caused by animal movement and weather conditions such as heavy rain. Mechanically stimulated leaves were sampled 1 h after exposure and after a recovery period of 20 h. To study a possible systemic response, unstimulated leaves of treated plants were collected 20 h after exposure alongside the stimulated leaves from the same plants. The effect of stimulation was assessed by measuring oxidative stress parameters, antioxidant enzymes activity, total phenolics, and photosynthetic performance. Stimulated leaves showed increased lipid peroxidation 1 h after treatment and increased superoxide dismutase activity and phenolic oxidation rate after a 20-h recovery period. Considering photosynthetic performance after the 20-h recovery period, the effective quantum yield of the photosystem II was lower in the stimulated leaves, whereas photochemical quenching was lower in the unstimulated leaves of the treated plants. Nonphotochemical quenching was lower in the stimulated leaves 1 h after treatment. Our study suggested that plants sensed moderate force, but it did not induce pronounced change in metabolism or photosynthetic performance. Principal component analysis distinguished three groups–leaves of untreated plants, leaves analysed 1 h after stimulation, while stimulated and unstimulated leaves of treated plants analysed 20 h after treatment formed together the third group. Observed grouping of stimulated and unstimulated leaves of treated plants could indicate signal transduction from the stimulated to distant leaves, that is, a systemic response to a local application of mechanical stimuli.

The Republic of Moldova on its way to Europe

The author figures out statehood formation processes in Moldova. He pays attention to a controversial legacy that Moldova gained after collapse of the USSR and declaration of independence. Due to industrialisation in the second half of the XX-th century Moldova turned from agrarian into an industrial-agrarian country of the average development. At the same time, Moldovans then as a titular nation experienced significant russification and assimilation. Together with one million of the Russian population’s transfer to Moldova and more than half a million Moldovans’ removal to other republics of the USSR Moldova became then a multinational state. By the end of the XX-th century, Russian-speaking population made up 35% of the republic’s inhabitants, this share in Transdniestria was two thirds then. Russian newcomers and Russian language began to take over socio-political, administrative-economic and cultural-educational life of the country. The author pays attention to the fact that in course of gaining independence of Moldova national-liberational, patriotic and nationalist forces were strengthened to a huge degree. Latin script spelling of Moldovan was resumed and it was given a status of a common state language on the territory of Moldova and its identity with Romanian was accepted. The ideology of unionism and unification with Romania matured. The former dominant Russian was assigned the role of the language of international communication. Unitary form with autonomous rights for national minorities in one country became a model of the state. Russian society and russified Ukrainian community that was the largest in number in Moldova, stood up against state- and nation-building processes in the country. Transdniestria became their struggle. Separatists began to demand provision of the status of the second state language to Russian on the whole territory of Moldova, formation of federal order, according to which Transdniestria would get federation subject status with the right of veto over the decisions of Chisinau in case Tiraspol would disagree with them, and rejection of unification plans with Romania. Moldovan authorities rejected. In response, separatist leaders declared establishment of Transdniestrian Moldovan Republic, its independence and uniting with Russian Federation, preserving Russian armed forces in the area for its defence. Attempts in March-July 1992 to eliminate rebels in Transdniestria and to restore there the power of Chisinau were conquered by Russian armed forces. The author underlines that independence of Transdniestria, declared in 1991, hasn’t been accepted by a single state in the world, even by Russia, and for the last 30 years no plans, projects, memoranda or other international formats have helped solving Transdniestrian conflict. The reason is the passive role of international organisations, which Russia is treacherously making use of. The author stresses that in conditions of the frozen conflict every side that takes part in it suffers great losses. With time, unionist ideas of the society of Republic of Moldova have lost their actuality; moderate forces have taken the upper hand. The state is constantly following the course of neutrality and keeping its sovereignty. There are two currents in RM that for the latest 15 years have displayed their political maturity targeting at EU and Russia. A constructive use of the both international factors has begun dominating in RM. Moldovan course on euro-integration is a priority, nevertheless much attention is also being paid to a constructive collaboration with RF on mutual beneficial terms. Such position stays principal for RM, and declares constant sovereignty is the best confirmation to this. Although, RF and TDR continue to sabotage Chisinau’s initiatives. They believe disintegration of Transdniestria is a serious obstacle for euro-integration of Moldova, Ukraine and Georgia, of spreading of EU and NATO to the East. The author stresses that international community is unique in its longing to preserve sovereignty and territorial integrity of RM, but it has no consensus in the national idea realisation that is based on unitary principles and preventing federalisation of the republic. Many countries consider it appropriate to ensure autonomy for Russian-speaking population or even introduce a federal system in the country. RM continues the course of development of mono-centric state, where national communities have to gain autonomy like in Gagauzia. In spite of this, TDR supported by RF, continues to follow its own independent course. Ukraine is interested in acceleration of Transdniestrian conflict settlement, taking hard efforts for reaching success in the issue that creates real danger for Ukraine. The author also underlines that Ukraine is the only neighbouring country of TDR and a reliable strategic partner that supports its interests steadfastly. It is marked in the article as well that present Moldovan leadership exercise is especially active in European and Russian directions, which contribute to the development of acceptable conditions for both parts of the Republic for advancement of the “common state”.

A classification of the plantar intrinsic foot muscles based on the physiological cross-sectional area and muscle fiber length in healthy young adult males

BackgroundPlantar intrinsic foot muscles (PIFMs) are composed of 10 muscles and play an essential role in achieving functional diversity in the foot. Previous studies have identified that the morphological profiles of PIFMs vary between individuals. The morphological profiles of a muscle theoretically reflect its output potentials: the physiological cross-sectional area (PCSA) of a muscle is proportional to its maximum force generation, and the muscle fiber length (FL) is its shortening velocity. This implies that the PCSA and FL may be useful variables for characterizing the functional diversity of the individual PIFM. The purpose of this study was to examine how individual PIFMs can be classified based on their PCSA and FL.MethodsIn 26 healthy young adult males, the muscle volume and muscle length of seven PIFMs (abductor hallucis, ABDH; abductor digiti minimi, ABDM; adductor hallucis oblique head, ADDH-OH; ADDH transverse head, ADDH-TH; flexor digitorum brevis, FDB; flexor hallucis brevis, FHB; quadratus plantae, QP) were measured using magnetic resonance imaging. The PCSA and FL of each of the seven PIFMs were then estimated by combining the data measured from the participants and those of muscle architectural parameters documented from cadavers in previous studies. A total of 182 data samples (26 participants × 7 muscles) were classified into clusters using k-means cluster analysis. The optimal number of clusters was evaluated using the elbow method.ResultsThe data samples of PIFMs were assigned to four clusters with different morphological profiles: ADDH-OH and FHB, characterised by large PCSA and short FL (high force generation and slow shortening velocity potentials); ABDM and FDB, moderate PCSA and moderate FL (moderate force generation and moderate shortening velocity potentials); QP, moderate PCSA and long FL (moderate force generation and rapid shortening velocity potentials); ADDH-TH, small PCSA and moderate FL (low force generation and moderate shortening velocity potentials). ABDH components were assigned equivalently to the first and second clusters.ConclusionsThe approach adopted in this study may provide a novel perspective for interpreting the PIFMs’ function based on their maximal force generation and shortening velocity potentials.

Роль Конгресса США в разработке и осуществлении политики “стратегической неопределенности” в Тайваньском проливе

The article considers the evolution of the U.S. political strategy in relation to the Taiwan problem. For several decades, the American approach has been marked by “strategic ambiguity”, but recently there have been signs of more unequivocal support for Taiwan. The question of whether the era of “strategic ambiguity” can be considered to be over is resolved by the author using an analysis of changes in the American foreign policy mechanism. It is noted that the U.S. Congress, starting from the period of D. Trump’s presidency, not only performs its traditional functions of defending democratic Taiwan from encroachments by the PRC, but also neutralizes the most radical initiatives of the executive branch aimed at the transition to “strategic clarity” in relations with China and Taiwan. This indicates the desire of some legislators to delay the elimination of “strategic ambiguity” that is beneficial for the United States, but the steps already taken by the U.S. government make abandoning it almost inevitable. Political polarization in the United States is an additional and increasingly significant factor influencing the development of a strategy towards Taiwan. The desire of congressmen and senators to attract the sympathy of more radical voters is leading to a revision of the approaches that have developed over the decades since 1979. Maintaining the status quo in the Taiwan Strait is no longer considered unconditionally good, because, according to the new bipartisan consensus in the U.S., that status quo has already disrupted due to China’s rising military power and political ambitions. In such an environment, even American politicians who were previously not prone to provocative behavior, including those representing the Democratic Party, are starting to aggravate the game, while the influence of moderate forces is weakening: the U.S. executive and legislative branches of government are literally racing to demonstrate their readiness to give a tough rebuff to China in the Taiwan Strait. Thus, the internal political split in the United States contributes to further deterioration of the American-Chinese relations, therefore, the mechanism for balancing the U.S. relations with China and Taiwan that has developed over decades can no longer work with the same efficiency.

Interaction between Micro-Amplitude Vibration and Thrust Force in Ultrasonic-Vibration-Assisted Drilling of Glass-Fiber-Reinforced Plastics

This research intends to investigate the effect and potential of the ultrasonic vibration of tools for drilling glass-fiber-reinforced plastics (GFRPs), especially with the aim of minimizing the thrust force. As an important parameter to characterize the vibration intensity, the vibration amplitude has a significant effect on the thrust force in the ultrasonic-vibration-assisted drilling (UVD) of GFRPs. It has been observed that the thrust force also influences the vibration amplitude, which may eventually result in a failure of the vibration. In this study, a method for the in-process measurement of the vibration amplitude was introduced to enable the investigation of the interaction between the thrust force and vibration amplitude in UVD. It was investigated how variations of the thrust force and vibration amplitude influence each other from holistic and individual perspectives. The critical condition was identified to ensure a sufficient ultrasonic vibration effect during drilling. Additionally, UVD experiments with different vibration amplitudes were carried out. The interaction between thrust force and vibration amplitude in UVD was revealed. It can be concluded that the combination of a moderate thrust force, low vibration amplitude reduction ratio, and high vibration amplitude increases the thrust force reduction ratio and secondly that an excessive thrust force undermines the effect of ultrasonic vibration. This provides an in-depth understanding of the interaction between vibration and thrust force in UVD, and helps to further improve the effect of ultrasonic vibration.

Lula ha vinto, Bolsonaro non è sconfitto

The electoral victory of Lula Inácio da Silva in Brazil consolidates the affirmation of a new progressive wave in the Latin American region. However, left-wing governments will have to face serious constraints, between the need to find agreements with the more moderate parliamentary forces and the aggressiveness of the neo-conservative right, starting with Bolsonarism.

THE ROLE OF THE TUNISIAN ARMED FORCES DURING THE ‘ARAB SPRING’ AND IN THE PROCESS OF THE FORMATION OF THE NEW AUTOCRACY

Tunisia was the birthplace of “the Arab Spring” and the first country were the Islamists won the elections, which led to the activation of moderate, radical or extremist Islamist forces in the Middle East, both in politics and beyond it, following the example of Syria. That is why, in addition to other factors, special attention is paid to the role of the Tunisian armed forces at the first stages of the "Arab uprising" and in the political processes in post-revolutionary Tunisia, the motivations that led to changes in their positions in the political arena and the differences between the interests of the Tunisian, Egyptian and Syrian armed forces are also the main focus of the article.

Vom drohenden Bürgerkrieg zum demokratischen Gewaltmonopol (1918–1924).

Struggle and crisis characterized post-WWI Germany between 1918 and 1924. Coup attempts, acts of terrorism and right- and left-wing uprisings made the survival of the new republic seem problematic. Rampant inflation, the occupation of the Rhineland by French and Belgian troops and political assassinations by Feme terrorists also challenged the authority and viability of the government. This collection of essays effectively charts the major developments during that tumultuous time by considering how the Weimar Republic survived and moved toward relative stability in spite of these multiple crises. The essays consider numerous themes including the roles of the Reichswehr (the regular army), various militia groups, police, universities and the press in the early life of the republic. The writers analyse the political groupings on the Left and Right and their challenges to the more moderate centrist forces that came to dominate the republic during the period of stability in the mid twenties. Serious though these threats were, the general sense of these historians is that no group really had the power to seize the government by force. The essays follow the difficult path trodden by the republic’s leaders as they struggled to obtain a monopoly on the use of force necessary for a stable government.

Anchorage effects of ligation and direct occlusion in orthodontics: A finite element analysis

Background and objectiveDuring orthodontic treatment, the figure-of-eight ligature and the physiological occlusion play an important role in providing anchorage effects. However, their effects on reaction forces of tooth and stress state in periodontal ligament (PDL) have not been quantitatively evaluated yet. In this study, we presented a finite element analysis process for simulating posterior molar ligature and direct occlusion during orthodontics in order to quantitatively assess their anchorage effects. MethodsA high precision 3D biomechanical model containing upper and lower teeth, PDL, brackets and archwire was generated from the images of computed tomographic scan and sophisticated modelling procedures. The orthodontic treatment of closing the extraction gap was simulated via the finite element method to evaluate the biomechanical response of the molars under the conditions with or without ligation. The simulations were divided into experimental and control groups. In the experimental group, orthodontic force of 1 N was first applied, then direct occlusal forces of 3 and 10 N were applied on each opposite tooth. While in the control group, occlusal forces were applied without orthodontic treatment. The tooth displacement, the stress state in the PDL and the directions of the resultant forces on each tooth were evaluated. ResultsIn the case of molars ligated, the maximum hydrostatic stress in the molars’ PDL decreases by 60%. When an initial tooth displacement of several microns occurs in response to an orthodontic force, the direction of the occlusal force changes simultaneously. Even a moderate occlusal force (3 N per tooth) can almost completely offset the mesial forces on the maxillary teeth, thus to provide effective anchorage effect for the orthodontics. ConclusionsThe proposed method is effective for simulating ligation and direct occlusion. Figure-of-eight ligature can effectively disperse orthodontic forces on the posterior teeth, while a good original occlusal relationship provides considerable anchorage effects in orthodontics.

Hydrogen-Induced Aggregation of Au@Pd Nanoparticles for Eye-Readable Plasmonic Hydrogen Sensors.

Plasmonic materials provide a promising platform for optical hydrogen detection, but their sensitivities remain limited. Herein, a new type of eye-readable H2 sensor based on Au@Pd core-shell nanoparticle arrays (NAs) is reported. After exposed to 2% H2, Au@Pd (16/2) NAs demonstrate a dramatic decrease in the optical extinction intensity, along with an obvious color change from turquoise to gray. Experimental results and theoretical calculations prove that the huge optical change resulted from the H2-induced aggregation of Au@Pd nanoparticles (NPs), which remarkably alters the plasmon coupling effect between NPs. Moreover, we optimize the sensing behavior from two aspects. The first is selecting appropriate substrates (either rigid glass substrate or flexible polyethylene terephthalate substrate) to offer moderate adhesion force to NAs, ensuring an efficient aggregation of Au@Pd NPs upon H2 exposure. The second is adjusting the Pd shell thickness to control the extent of NP aggregation and thus the detection range of the as-prepared sensors. This work highlights the advantage of designing eye-readable plasmonic H2 sensors from the aspect of tuning the interparticle plasmonic coupling in NP assemblies. Au@Pd NAs presented here have several advantages in terms of simple fabrication method, eye-readability in air background at room temperature, tunable detection range, and high cost-effectiveness.

The effects of wrist position and radioulnar wrist compression on median nerve longitudinal mobility

BackgroundCarpal tunnel syndrome is an entrapment neuropathy at the wrist characterized by compromised median nerve mobility. The purpose of this study was to investigate the effect of wrist position on median nerve longitudinal mobility in healthy subjects and the effect of radioulnar wrist compression on the median nerve mobility under non-neutral wrist positions. MethodsDynamic B mode ultrasound images captured longitudinal median nerve motion in the carpal tunnel in 10 healthy subjects at wrist neutral position, 30-degree flexion, and 30-degree extension. In each position, RWC of 0, 5, 10, and 15 N were applied. One-way repeated measure analysis of variance (ANOVA), Post-hoc Tukey's tests, and the Friedman Test were used to show the significant differences of median nerve longitudinal mobility at different wrist positions and force conditions. FindingsMedian nerve longitudinal mobility was found to be significantly influenced by wrist position (P < 0.05). The mobility under wrist neutral position was 3.02 mm/s, 38% higher than under wrist flexion (2.18 ± 0.60 mm/s), and 32% higher than under wrist extension (2.29 ± 0.43 mm/s). The impaired median nerve mobility was significantly restored under 10 N radioulnar wrist compression (P < 0.05), by 34.4% under wrist flexion (3.03 ± 0.85 mm/s), and 38.9% under wrist extension (3.07 ± 0.79 mm/s). InterpretationNon-neutral wrist positions compromise median nerve longitudinal mobility, but moderate radioulnar compressive forces are beneficial in the recovery of median nerve longitudinal mobility, and may help to prevent symptoms associated with carpal tunnel syndrome.

Myosin II Adjusts Motility Properties and Regulates Force Production Based on Motor Environment.

Myosin II has been investigated with optical trapping, but single motor-filament assay arrangements are not reflective of the complex cellular environment. To understand how myosin interactions propagate up in scale to accomplish system force generation, we devised a novel actomyosin ensemble optical trapping assay that reflects the hierarchy and compliancy of a physiological environment and is modular for interrogating force effectors. Hierarchical actomyosin bundles were formed in vitro. Fluorescent template and cargo actin filaments (AF) were assembled in a flow cell and bundled by myosin. Beads were added in the presence of ATP to bind the cargo AF and activate myosin force generation to be measured by optical tweezers. Three force profiles resulted across a range of myosin concentrations: high force with a ramp-plateau, moderate force with sawtooth movement, and baseline. The three force profiles, as well as high force output, were recovered even at low solution concentration, suggesting that myosins self-optimize within AFs. Individual myosin steps were detected in the ensemble traces, indicating motors are taking one step at a time while others remain engaged in order to sustain productive force generation. Motor communication and system compliancy are significant contributors to force output. Environmental conditions, motors taking individual steps to sustain force, the ability to backslip, and non-linear concentration dependence of force indicate that the actomyosin system contains a force-feedback mechanism that senses the local cytoskeletal environment and communicates to the individual motors whether to be in a high or low duty ratio mode. The online version contains supplementary material available at 10.1007/s12195-022-00731-1.

How Strong Can We Pull? Critical Thresholds for Traction Forces on the Aortic Annulus: Measurements on Fresh Porcine Hearts.

Background and Objectives: Friable or infected tissue remains a challenge in surgical aortic valve replacement. We recently described the “Caput medusae” method, in which circumferential tourniquets temporarily secure the prosthesis and are then gently knotted. Tourniquets have been shown to develop significantly less force than knots. The current study investigates the critical threshold forces for tissue damage to the aortic annulus. Materials and Methods: In 14 fresh porcine hearts, the aortic valve leaflets were removed and several pledgeted sutures were placed along the annulus at defined locations. The hearts were mounted in a self-constructed device. Incremental traction force was applied to every suture and continuously recorded. The movement of each Teflon pledget was filmed with a high-speed camera. Forces at the moment of pledget “cut-in” as well as complete “tear-out” were determined from the recordings. Results: The average threshold force was determined 9.31 ± 6.04 N for cut-in and 20.41 ± 10.02 N for tear-out. Detailed analysis showed that the right coronary region had lower threshold forces than the other regions (4.77 ± 3.28 N (range, 1.67–12.75 N) vs. 10.67 ± 6.04 N (1.62–26.00 N) for cut-in and 10.67 ± 4.04 N (5.40–18.64 N) vs. 23.33 ± 9.42 N (9.22–51.23 N) for tear-out). The findings are discussed in conjunction with the knot and tourniquet forces from our previous study. Conclusions: Even in healthy tissue, moderate forces can reach a critical level at which a Teflon pledget will cut into the annulus, while a complete tear-out is unlikely. The right coronary portion is more susceptible to damage than the remaining regions. When compared to previous data, forces during manual knotting may exceed the critical cut-in level, while rubber tourniquets may provide a higher safety margin against tissue rupture.