A Novel Tactile Sensing System Utilizing Magnetorheological Structures for Dynamic Contraction and Relaxation Motions.

It is well known that the rheological properties of magnetorheological (MR) material change under a magnetic field. So far, most works on MR materials have been oriented toward actuating characteristics instead of sensing functions. In this work, to realize dynamic tactile motion, a spherical MR structure was designed as a sensor, incorporating a magnetic circuit core to provide maximum dynamic motion. After manufacturing a prototype (sample), a sinusoidal magnetic field of varying exciting frequency and magnitude was applied to the sample, and the dynamic contraction and relaxation motion depending on the exciting magnetic field was observed. Among the test results, when 10% deformation occurred, the instantaneous force generated was from 2.8 N to 8.8 N, and the force when relaxed was from 1.2 N to 3.5 N. It is also shown that the repulsive force within this range can be implemented using an acceptable input current. The special tactile sensing structure proposed in this work can be used as a sensor to measure the field-dependent viscoelastic properties of human tissues such as stomach, liver, and overall body. In addition, it could be usefully applied to robot surgery, because it can mimic the dynamic motions of various human organs under various surgical conditions.

Half-Bridge Silicon Strain Gauges with Arc-Shaped Piezoresistors.

Half-bridge silicon strain gauges are widely used in the fabrication of diaphragm-type high-pressure sensors, but in some applications, they suffer from low output sensitivity because of mounting position constraints. Through a special design and fabrication approach, a new half-bridge silicon strain gauge comprising one arc gauge responding to tangential strain and another linear gauge measuring radial strain was developed using Silicon-on-Glass (SiOG) substrate technology. The tangential gauge consists of grid patterns, such as the reciprocating arc of silicon piezoresistors on a thin glass substrate. When two half-bridges are connected to form a full bridge with arc-shaped gauges that respond to tangential strain, they have the advantage of providing much higher output sensitivity than a conventional half-bridge. Pressure sensors tested under pressure ranging from 0 to 50 bar at five different temperatures indicate a linear output with a typical sensitivity of approximately 16 mV/V/bar, a maximum zero shift of 0.05% FS, and a span shift of 0.03% FS. The higher output level of pressure sensing gauges will provide greater signal strength, thus maintaining a better signal-to-noise ratio than conventional pressure sensors. The offset and span shift curves are quite linear across the operating temperature range, giving the end user the advantage of using very simple algorithms for temperature compensation of offset and span shift.

Contact line friction and dynamic contact angles of a capillary bridge between superhydrophobic nanostructured surfaces.

The Cassie-Baxter state of wetting explains a large equilibrium contact angle and the slippery dynamics of a water droplet on a superhydrophobic rough surface. It also causes a contact angle hysteresis (CAH) that cannot be fully described by dynamic wetting theories including the molecular kinetic theory (MKT). We analyze the contact line dynamics on a superhydrophobic surface in the framework of the MKT. Multi-body dissipative particle dynamics simulations of a capillary bridge confined between two rough surfaces under steady shear are performed. We find that, in addition to the contact line friction force from the MKT, an additional friction force contribution is needed on rough surfaces. It can be obtained by subtracting from the total friction force the force solely caused by the actual liquid-solid contact area. We find that the additional force is almost constant at all contact line velocities. Thus, it is directly related to the CAH. The CAH originates not only from contact line pinning but also from the shear flow due to the strong friction in the central region of the liquid-solid interface away from the contact line. The analysis of the particle flow inside the capillary bridge shows that liquid particles trapped in the grooves of the surface texture actually move with the same velocity as the surface and exert strong additional friction to other liquid particles. This work extends the MKT to rough surfaces, as well as to elucidate the origin of the CAH of a capillary bridge. The finding would help to better understand other situations of dynamic wetting on superhydrophobic surfaces.

A Cylindrical Grip Type of Tactile Device Using Magneto-Responsive Materials Integrated with Surgical Robot Console: Design and Analysis.

This paper proposes a cylindrical grip type of tactile device that is effectively integrated to a surgical robot console so that a surgeon can easily touch and feel the same stiffness as the operating organs. This is possible since the yield stress (or stiffness) of magnetic-responsive materials can be tuned or controlled by the magnetic field intensity. The proposed tactile device consists of two main parts: a magnetorheological elastomer (MRE) layer and a magnetorheological fluid (MRF) core. The grip shape of the device to be positioned on the handle part of the master of the surgical robot is configured and its operating principle is discussed. Then, a couple of equations to calculate the stiffness from the gripping force and the field-dependent yield stress of MRF are derived and integrated using the finite element analysis (FEA) model. After simulating the stiffness of the proposed tactile device as a function of the magnetic field intensity (or current), the stiffnesses of various human organs, including the liver and heart, are calculated from known data of an elastic modulus. It is demonstrated from comparative data between calculated stiffness from human tissues and simulated stiffness from FEA that the proposed tactile device can generate sufficient stiffness with a low current level to recognize various human organs which are significantly required in the surgical robot system.

Does Exercise Affect Telomere Length? A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background and objectives: Telomere length is an indicator of biological aging, and it shortens during cell division. A short telomere length is associated with various age-related diseases and mortality. It is suggested that physical activity has a positive effect on the rate of telomere length shortening. Materials and Methods: Related studies, published in electronic databases, were searched with keywords, including exercise, telomere length, and randomized controlled trial. The data were weighted and pooled through a fixed-effect model. Results: Of the total 49 studies searched, 7 studies with 939 participants were considered suitable, and were analyzed qualitatively and quantitatively. Exercise is beneficial to telomere length. Aerobic exercise was effective as the type of exercise (MD, -0.03; 95% CI, -0.04 to -0.01). In addition, exercise for more than 6 months, with a change in lifestyle, is beneficial for telomere length (MD, -0.02; 95% CI, -0.04 to -0.01). Conclusions: The type and duration of exercise for positive improvement in telomere length is aerobic exercise for more than 6 months.

Suppressing the rebound of impacting droplets from solvophobic surfaces by polymer additives: polymer adsorption and molecular mechanisms.

A liquid droplet impacting on a solvophobic surface normally rebounds. The rebound is suppressed by a small amount of dissolved polymer. In this work, using multi-body dissipative particle dynamics simulations, two anti-rebound mechanisms, the slow-retraction and the slow-hopping mechanisms, are identified. Which of them dominates depends on the polymer-surface attraction strength. However, these two mechanisms do not exclude each other but may coexist. During the droplet rebound, the surface-adsorbed polymer acts in two ways: the adsorbed beads mediate the solvent-surface interactions, and the highly stretching unadsorbed polymer segment exerts a retraction force on the liquid. Both actions increase the friction against retraction and the resistance against hopping. We also investigate the effects of the molecular weight and the concentration of the polymer additive, the droplet size, and the impact velocity on the rebound tendency. As the first work to provide a microscopic explanation of the anti-rebound mechanism by polymer additives, this study allows better understanding of wetting behavior by polymer-solution droplets.

Power-dependent photophysical pathways of upconversion in BaTiO3:Er3.

Lanthanide incorporated perovskite is one of the most promising systems for efficient energy conversion or light-emitting materials in terms of upconversion (UC). Investigation of the photophysical mechanism of UC in the lanthanide-doped system is here continued. However, research on the 4I13/2 energy state in Er3+ is rare and more is still needed. In our work, BaTiO3:Er3+ (E-BT) was irradiated by a 1532 nm laser which is a resonance to the energy between 4I13/2 and the ground 4I15/2 state in Er3+. Bright 1532 nm-pumped UC was generated, and the UC color changed from red to yellow under increasing laser power. In addition, pump-power-dependent UC contained interesting clues about the photophysical pathway of UC. By analyzing photon numbers for each UC (green: 2H11/2/4S3/2 → 4I15/2, red: 4F9/2 → 4I15/2, infrared: 4I9/2 → 4I15/2), we found that changes in photon number with pump-power increase contain three different phases (P). P1 is a red UC phase with a small cross-relaxation between Er3+ ions. However, in P2, there is a rapid decrease in the photon number with green UC generation, which is due to the enhancement of 4I13/2-populating cross-relaxation. Finally, in P3, a saturated 4I13/2 state causes little increase of photon number (compared with P2), with different mechanistic cross-relaxation enhancement. With these three different phases under 1532 nm pumping, photophysical mechanisms in E-BT are interpreted.

Impact of Cervical Sensory Feedback for Forward Head Posture on Headache Severity and Physiological Factors in Patients with Tension-type Headache: A Randomized, Single-Blind, Controlled Trial.

BACKGROUND Tension-type headache (TTH) decreases the ability to concentrate and function during daily activities in affected patients. As most patients with TTH exhibit forward head posture (FHP). Various interventions have been proposed to resolve TTH. However, research regarding the efficacy of these interventions remains lacking. The present study aimed to investigate the association between FHP and TTH, and to evaluate the efficacy of various intervention methods on headache symptoms and other clinical variables in patients with TTH induced by FHP. MATERIAL AND METHODS Participants were randomly allocated to 3 groups: biofeedback (BF, n1=21), manual therapy (MT, n2=20) and, stretching (ST, n3=21). Interventions were conducted 3 times per week for 4 weeks. Craniovertebral angle (CVA), electroencephalographic findings for attention, stress, and pressure-pain threshold (PPT), headache on activities of daily living (Henry Ford Headache Disability Inventory, HDI), and quality of life (QoL) assessments were obtained pre-intervention, post-intervention, and at the 2-week follow-up. RESULTS The correlation between CVA and HDI after intervention (R²=0.324, P<0.001), and at 2-week follow-up (R²=0.115, P<0.01) are significant. BF was associated with significant improvements in CVA (F2,59=3.393, P<0.001, η^2/P=0.130), attention (F2,59=5.186, P<0.01, η^2/P=0.150), stress [skin temperature (F2,59=6.005, P<0.001, η^2/P=0.169) and skin conductance (F2,59=4.900, P<0.01, η^2/P=0.142)], PPT (F2,59=5.050, P<0.01, η^2/P=0.146), HDI (F2,59=3.303, P<0.01, η^2/P=0.101), and QoL (F2,59=3.409, P<0.05, η^2/P=0.104). CONCLUSIONS Our findings indicate that BF was more effective than MT and ST in the treatment of TTH due to FHP. Such findings highlight the need to develop and promote a controlled exercise program to facilitate a return to normal daily activities in patients with TTH due to FHP.

Short-Foot Exercise Promotes Quantitative Somatosensory Function in Ankle Instability: A Randomized Controlled Trial.

BACKGROUND Ankle sprain reduces capacity for neurosensory information processing, and these patients commonly progress to chronic ankle instability (CAI). To address this problem, the short-foot exercise (SFE) may be used. However, there has been no previous research on the neurosensory impact of SFE. Therefore, the aim of this study was to assess improvement of quantitative neurosensory indicators after SFE and to determine the effect of proprioceptive sensory exercise (PSE) in patients with CAI. MATERIAL AND METHODS The present study included 30 adults (age range: 19-29 years; 50% female). Selection criteria for CAI (Cumberland Ankle Instability Tool £24) were implemented, and participants were randomly allocated to 2 groups: SFE (n1=15) and PSE (n2=15). Exercises were conducted 3 times per week for 8 weeks. Measurements of quantitative somatosensory of joint position sense and vibration sensory thresholds, dynamic balance, and ankle instability assessment were evaluated before and after completion of each intervention. Data were analyzed using a repeated- measures analysis of variance. RESULTS In a time-by-group comparison, the SFE group showed a more significant improvement with regards to eversion joint position sense (F1,28=4.543, p<0.05). For vibration sensory threshold, the SFE group showed a more significant improvement (F1,28=8.280, p<0.01). Balance index according to anterio-posterior, mediolateral, and overall index the SFE group a more significant improvement (F1,28=6.666, 4.585, 5.207, p<0.05). And ankle instability SFE group showed a more significant improvement (F1,28=6.890, p<0.05). CONCLUSIONS SFE is more effective than PSE for treating ankle sprain patients. There is a need to develop and promote an effective and controlled exercise program to facilitate the return of ankle sprain patients to normal daily life.

Thermodynamics of single polyethylene and polybutylene glycols with hydrogen-bonding ends: A transition from looped to open conformations.

A variety of linear polymer precursors with hydrogen bonding motifs at both ends enable us to design supramolecular polymer systems with tailored macroscopic properties including self-healing. In this study, we investigate thermodynamic properties of single polyethylene and polybutylene glycols with hydrogen bonding motifs. In this context, we first build a coarse-grained model of building blocks of the supramolecular polymer system based on all-atom molecular structures. The density of states of the single precursor is obtained using the stochastic approximation Monte Carlo method. Constructing canonical partition functions from the density of states, we find the transition from looped to open conformations at transition temperatures which are non-monotonously changing with an increasing degree of polymerization due to the competition between chain stiffness and loop-forming entropy penalty. In the complete range of chain length under investigation, a coexistence of the looped and open morphologies at the transition temperature is shown regardless of whether the transition is first-order-like or continuous. Polyethylene and polybutylene glycols show similar behavior in all the thermodynamic properties but the transition temperature of the more flexible polybutylene glycol is shown to change more gradually.

Distinct mechanisms for the upconversion of NaYF4:Yb3+,Er3+ nanoparticles revealed by stimulated emission depletion.

Upconversion nanoparticles (UCNPs) have attracted enormous interest over the past few years because of their unique optical properties and potential for use in various applications such as bioimaging probes, biosensors, and light-harvesting materials for photovoltaics. The improvement of imaging resolution is one of the most important goals for UCNPs used in biological applications. Super-resolution imaging techniques that overcome the fundamental diffraction limit of light rely on the photochemistry of organic dyes or fluorescent proteins. Here we report our progress toward super-resolution microscopy with UCNPs. We found that the red emission (655 nm) of core/shell UCNPs with the structure NaYF4:Yb3+,Er3+/NaYF4 could be modulated by emission depletion (ED) of the intermediate state that interacts resonantly with an infrared beam (1540 nm). In contrast, the green emission bands (525 and 545 nm) of the UCNPs were less affected by irradiation with the infrared beam. The origin of such distinct behaviors between the green and red emissions was attributed to their different photophysical pathways.

Upper thoracic spine mobilization and mobility exercise versus upper cervical spine mobilization and stabilization exercise in individuals with forward head posture: a randomized clinical trial.

BACKGROUND: Although upper cervical and upper thoracic spine mobilization plus therapeutic exercises are common interventions for the management of forward head posture (FHP), no study has directly compared the effectiveness of cervical spine mobilization and stabilization exercise with that of thoracic spine mobilization and mobility exercise in individuals with FHP. METHODS: Thirty-two participants with FHP were randomized into the cervical group or the thoracic group. The treatment period was 4 weeks, with follow-up assessment at 4 and 6 weeks after the initial examination. Outcome measures including the craniovertebral angle (CVA), cervical range of motion, numeric pain rating scale (NPRS), pressure pain threshold, neck disability index (NDI), and global rating of change (GRC) were collected. Data were examined with a two-way repeated-measures analysis of variance (group × time). RESULTS: Participants in the thoracic group demonstrated significant improvements (p < .05) in CVA, cervical extension, NPRS, and NDI at the 6-week follow-up compared with those in the cervical group. In addition, 11 of 15 (68.8%) participants in the thoracic group compared with 8 of 16 participants (50%) in the cervical group showed a GRC score of +4 or higher at the 4-week follow-up. CONCLUSIONS: The combination of upper thoracic spine mobilization and mobility exercise demonstrated better overall short-term outcomes in CVA (standing position), cervical extension, NPRS, NDI, and GRC compared with upper cervical spine mobilization and stabilization exercise in individuals with FHP. TRIAL REGISTRATION: KCT0002307 , April 11, 2017 (retrospectively registered).

Segregated structures of ring polymer melts near the surface: a molecular dynamics simulation study.

We study structural properties of a ring polymeric melt confined in a film in comparison to a linear counterpart using molecular dynamics simulations. Local structure orderings of ring and linear polymers in the vicinity of the surface are similar to each other because the length scale of surface-monomer excluded volume interactions is smaller than the size of an ideal blob of the ring. In a long length scale, while the Silberberg hypothesis can be used to provide the physical origin of the confined linear polymer results, it no longer holds for the ring polymer case. We also present different structural properties of ring and linear polymers in a melt, including the size of polymers, the adsorbed amount, and the coordination number of a polymer. Our observation reveals that a confined ring in a melt adopts a highly segregated conformation due to a topological excluded volume repulsion, which may provide a new perspective to understand the nature of biological processes, such as territorial segregation of chromosomes in eukaryotic nuclei.

Slowing down of ring polymer diffusion caused by inter-ring threading.

Diffusion of long ring polymers in a melt is much slower than the reorganization of their internal structures. While direct evidence for entanglements has not been observed in the long ring polymers unlike linear polymer melts, threading between the rings is suspected to be the main reason for slowing down of ring polymer diffusion. It is, however, difficult to define the threading configuration between two rings because the rings have no chain end. In this work, evidence for threading dynamics of ring polymers is presented by using molecular dynamics simulation and applying a novel analysis method. The simulation results are analyzed in terms of the statistics of persistence and exchange times that have proved useful in studying heterogeneous dynamics of glassy systems. It is found that the threading time of ring polymer melts increases more rapidly with the degree of polymerization than that of linear polymer melts. This indicates that threaded ring polymers cannot diffuse until an unthreading event occurs, which results in the slowing down of ring polymer diffusion.

Utilization of Mirror Visual Feedback for Upper Limb Function in Poststroke Patients: A Systematic Review and Meta-Analysis.

Mirror visual feedback (MVF), a noninvasive treatment method, is attracting attention as a possibility to promote the recovery of upper limb function in stroke patients. However, the cognitive effects of this therapy have received limited attention in the existing literature. To address this gap, we conducted a systematic review and meta-analysis to investigate the relationship between upper limb function and cognition in stroke patients and to evaluate the effect of MVF on improving upper limb function. A comprehensive search was performed on the Embase, MEDLINE, and PubMed databases to identify original articles and clinical studies published between 2013 and 2022. Qualitative analysis was performed using the Cochrane Risk of Bias tool, and in the quantitative analysis, a random-effects model was used as the effect model, and standard mean difference (SMD) was used as the effect measure. Eight studies that met the inclusion criteria were entered in the analysis. Data extraction included an assessment tool for upper extremity function. Results of the quantitative analysis demonstrate that MVF was effective in improving upper extremity function in stroke patients (SMD = 0.94, 95% CI 0.69 to 1.20). In conclusion, this systematic review and meta-analysis provides evidence supporting the effectiveness of MVF in improving upper limb function in stroke patients. However, further studies are needed to investigate the cognitive effects of MVF and elucidate the underlying mechanisms.

Rebound Suppression of a Droplet Impacting on a Supersolvophobic Surface by a Small Amount of Polymer Additives.

A small amount of polymer dissolved in a droplet suppresses droplet rebound when it impinges on a supersolvophobic surface. This work investigates impacting dynamics of a droplet of dilute polymer solution depending on the molecular weight and the concentration of the polymer by using multibody dissipative particle dynamics simulations. Either the long polymer or the high polymer concentration suppresses rebound of a droplet although its shear viscosity and the liquid-vapor surface tension are not different from those of a pure solvent droplet. We found a new mechanism of the anti-rebound in which the resistance is applied against the hopping motion, while behavior of the non-rebounding droplet at the earlier spreading and retraction stages is the same as for the rebounding droplets. Two polymer contributions to reducing the rebound tendency are quantitatively analyzed: the alteration of the substrate wettability by the polymer adsorption and the polymer elongation force.

Morphology and thermodynamics of polymers with monofunctional hydrogen bonding ends in dilute and semidilute concentration.

Rheological properties of supramolecular polymers (SMPs) depend on their equilibrium structure including the size, the number, and the topology of aggregates. A polymer with a hydrogen bonding (H-bonding) motif at both ends is one widely used precursor to build SMPs. Due to the complex interplay between chain stiffness, H-bonding interaction, polarity along a chain, and polymer conformational entropy, it is difficult to theoretically predict the structure of SMPs. In this work we investigate thermodynamics of SMPs with H-bonding ends in a wide range of densities. A replica exchange stochastic approximation Monte Carlo method with coarse-grained models for polyethylene and polybuthylene glycols is used. Our simulation shows that SMPs have two morphological transition lines with increasing temperature, a ring-linear transition, and a linear-free chain transition. The latter is a thermodynamic transition and turns out to be continuous. Comparing the two different spacers, we find that ring-linear transition temperatures differ from each other at the constant volume fraction due to different looping probabilities, which can be calculated from the average polymer size by mean field. However, the linear-free chain transition temperatures are similar because the entropic penalty to form a hydrogen bond mainly depends on the probability of finding H-bonding groups in a system, which is the same for both systems at a given volume fraction.

Slow Dynamics of Ring Polymer Melts by Asymmetric Interaction of Threading Configuration: Monte Carlo Study of a Dynamically Constrained Lattice Model.

Abnormally slower diffusional processes than its internal structure relaxation have been observed in ring polymeric melt systems recently. A key structural feature in ring polymer melts is topological constraints which allow rings to assume a threading configuration in the melt phase. In this work, we constructed a lattice model under the assumption of asymmetric diffusivity between two threading rings, and investigated a link between the structural correlation and its dynamic behavior via Monte Carlo simulations. We discovered that the hierarchical threading configurations render the whole system to exhibit abnormally slow dynamics. By analyzing statistical distributions of timescales of threading configurations, we found that the decoupling between internal structure relaxation and diffusion is crucial to understand the threading effects on the dynamics of a ring melt. In particular, in the limit of small but threaded rings, scaling exponents of the diffusion coefficient D and timescale τ diff with respect to the degree of polymerization N agree well with that of the annealed tree model as well as our mean-field analysis. As N increases, however, the ring diffusion abruptly slows down to the glassy behavior, which is supported by a breakdown of the Stokes⁻Einstein relation.

Upper cervical and upper thoracic spine mobilization versus deep cervical flexors exercise in individuals with forward head posture: A randomized clinical trial investigating their effectiveness.

BACKGROUND: Although commonly utilized treatments, no study has directly compared the effectiveness of joint mobilization and stabilization exercise in individuals with forward head posture (FHP). OBJECTIVE: This study aimed to investigate the effects of upper cervical and upper thoracic spine mobilization versus deep cervical flexors exercise (DCFE) in individuals with FHP. METHODS: Thirty-one participants with FHP were randomized into the mobilization (n= 15) or exercise (n= 16) group. The treatment period was 4 weeks with follow-up assessment at 4 weeks and 6 weeks after the initial examination. Outcomes assessed included the craniovertebral angle (CVA), numeric pain rating scale (NPRS), respiratory function, and the global rating of change (GRC). RESULTS: Participants in the mobilization group demonstrated significant improvements (p< 0.05) in CVA, NPRS, and respiratory function, as compared to those in the exercise group. In addition, 9 of 15 (60%) participants in the mobilization group, as compared to 4 of 16 participants (25%) in the exercise group, had a GRC score of +4 or higher. CONCLUSIONS: The combination of upper cervical and upper thoracic spine mobilization indicated better overall short-term outcomes in CVA, NPRS, respiratory function, and GRC compared with DCFE in individuals with FHP.

Effectiveness of mid-thoracic spine mobilization versus therapeutic exercise in patients with subacute stroke: A randomized clinical trial.

BACKGROUND: Although commonly used in clinical settings, evidence regarding the beneficial effectiveness of joint mobilization and therapeutic exercise in patients with stroke is still lacking. OBJECTIVE: This study aimed to investigate the effects of mid-thoracic spine mobilization and therapeutic exercise on dynamic balance and inspiratory function in patients with subacute stroke. METHODS: The participants included 33 patients with subacute stroke. Participants were randomly allocated to 1 of 2 groups: (1) a group that received segmental mobilization (T4-8), and (2) a group that received foam roller exercises (T4-8). Outcome measure included the limits of stability (LOS), inspiratory function, and global rating of change (GRC). RESULTS: The improvement in inspiratory function was statistically significant at 4 and 6 weeks after the initiation of the intervention and changes in the LOS were statistically significant at 6 weeks in the mobilization group (p< 0.05). In addition, 15 of 17 (88.2%) participants in the mobilization group, compared to 9 of 16 participants (56.2%) in the exercise group, indicated a GRC score of +4 or higher at the 4-week follow-up. CONCLUSIONS: This study demonstrates that patients with subacute stroke who receive mid-thoracic spine mobilization demonstrate effective short-term improvements in LOS and GRC.