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1.
J Exp Biol ; 227(10)2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38699818

RESUMO

Little is known regarding the precise muscle, bone and joint actions resulting from individual and simultaneous muscle activation(s) of the lower limb. An in situ experimental approach is described herein to control the muscles of the rabbit lower hindlimb, including the medial and lateral gastrocnemius, soleus, plantaris and tibialis anterior. The muscles were stimulated using nerve-cuff electrodes placed around the innervating nerves of each muscle. Animals were fixed in a stereotactic frame with the ankle angle set at 90 deg. To demonstrate the efficacy of the experimental technique, isometric plantarflexion torque was measured at the 90 deg ankle joint angle at a stimulation frequency of 100, 60 and 30 Hz. Individual muscle torque and the torque produced during simultaneous activation of all plantarflexor muscles are presented for four animals. These results demonstrate that the experimental approach was reliable, with insignificant variation in torque between repeated contractions. The experimental approach described herein provides the potential for measuring a diverse array of muscle properties, which is important to improve our understanding of musculoskeletal biomechanics.


Assuntos
Membro Posterior , Músculo Esquelético , Torque , Animais , Coelhos , Músculo Esquelético/fisiologia , Músculo Esquelético/inervação , Membro Posterior/fisiologia , Fenômenos Biomecânicos , Estimulação Elétrica , Masculino
2.
J Mol Model ; 30(6): 173, 2024 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-38767734

RESUMO

CONTEXT: Ubiquitin-like with PHD and RING finger domain containing protein 1 (UHRF1) is responsible for preserving the stability of genomic methylation through the recruitment of DNA methyltransferase 1 (DNMT1). However, the interaction between Developmental pluripotency associated 3 (DPPA3) and the pre-PHD-PHD (PPHD) domain of UHRF1 hinders the nuclear localization of UHRF1. This disruption has implications for potential cancer treatment strategies. Drugs that mimic the binding pattern between DPPA3 and PPHD could offer a promising approach to cancer treatment. Our study reveals that DPPA3 undergoes dissociation from the C-terminal through three different modes of helix unfolding. Furthermore, we have identified key residue pairs involved in this dissociation process and potential drug-targeting residues. These findings offer valuable insights into the dissociation mechanism of DPPA3 from PPHD and have the potential to inform the design of novel drugs targeting UHRF1 for cancer therapy. METHODS: To comprehend the dissociation process and binding patterns of PPHD-DPPA3, we employed enhanced sampling techniques, including steered molecular dynamics (SMD) and conventional molecular dynamics (cMD). Additionally, we utilized self-organizing maps (SOM) and time-resolved force distribution analysis (TRFDA) methodologies. The Gromacs software was used for performing molecular dynamics simulations, and the AMBER FF14SB force field was applied to the protein.


Assuntos
Proteínas Estimuladoras de Ligação a CCAAT , Simulação de Dinâmica Molecular , Ligação Proteica , Ubiquitina-Proteína Ligases , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/metabolismo , Proteínas Estimuladoras de Ligação a CCAAT/química , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Humanos , Sítios de Ligação
3.
J Oral Implantol ; 50(4): 421-425, 2024 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-38699942

RESUMO

The aim is to compare the resistance to torsion between 2 implant systems with internal hexagon connection: one using screw-retained abutments (Titanium Fix) and the other using cementable abutments (ITEC) under a tangential load. An in vitro experimental study was carried out. Fourteen implants, 7 implants from each system, were included in this study. The implants were placed at a 45° angle into metal blocks to simulate their position in the maxilla. Then, implants were subjected to a resistance test on a CMT5L universal testing machine, and the maximum load was applied to each sample. The maximum force with which the torsion was achieved in each sample was analyzed. The data were tested using the Shapiro-Wilk test and showed normal distribution. Student t test was used to examine statistical significance between the two groups, and the P value was set at P < .05. There was a statistically significant difference between the two groups (P = .001). ITEC implants with a cementable abutment showed greater flexural strength compared to the Titanium Fix with a screwed abutment implant system. The cemented abutment showed more resistance to torsion against a tangential load compared with the screwed abutment.


Assuntos
Dente Suporte , Análise do Estresse Dentário , Projetos Piloto , Projeto do Implante Dentário-Pivô , Titânio/química , Torção Mecânica , Cimentos Dentários , Humanos , Teste de Materiais , Técnicas In Vitro , Parafusos Ósseos
4.
Bioengineering (Basel) ; 11(4)2024 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-38671815

RESUMO

The efficacy of retainers is a pivotal concern in orthodontic care. This study examined the biomechanical behaviour of retainers, particularly the influence of retainer stiffness and tooth resilience on force transmission and stress distribution. To do this, a finite element model was created of the lower jaw from the left to the right canine with a retainer attached on the oral side. Three levels of tooth resilience and variable retainer bending stiffness (influenced by retainer type, retainer diameter, and retainer material) were simulated. Applying axial or oblique (45° tilt) loads on a central incisor, the force transmission increased from 2% to 65% with increasing tooth resilience and retainer stiffness. Additionally, a smaller retainer diameter reduced the uniformity of the stress distribution in the bonding interfaces, causing concentrated stress peaks within a small field of the bonding area. An increase in retainer stiffness and in tooth resilience as well as a more oblique load direction all lead to higher overall stress in the adhesive bonding area associated with a higher risk of retainer bonding failure. Therefore, it might be recommended to avoid the use of retainers that are excessively stiff, especially in cases with high tooth resilience.

5.
Stud Health Technol Inform ; 310: 1430-1431, 2024 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-38269681

RESUMO

In this paper we designed a household cognitive level assessment system based on finger force distribution. The system evaluates the user's current cognitive level according to the degree of matching between the characteristics of user's grip force and finger force distribution data and the characteristics in the database. The system based on finger force distribution will greatly reduce the space and economic cost of household cognitive level assessment.


Assuntos
Cognição , Extremidade Superior , Bases de Dados Factuais
6.
BMC Oral Health ; 23(1): 888, 2023 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-37986159

RESUMO

BACKGROUND: The aim of orthodontic treatment, apart from esthetic and functional corrections, is uniform force distribution. Hence Occlusal analysis using a T scan gives scope for a precisely targeted treatment plan. The T-scan evaluation of occlusal force, time, and location of contacts from initial occlusal contact to maximum intercuspation enables the orthodontist to sequentially balance the occlusal forces on the right and left sides through specific treatment plan options. OBJECTIVE: The current study aimed to determine the force distribution in the different individuals by using a T-Scan as well as the net discrepancies of forces generated at a maximum intercuspation position in the first molar region between the left and right sides of the mouth. METHODS: This is a descriptive-correlational study that was carried out in Ras Al Khaimah College of Dental Sciences clinics and Ajman University clinics from January 2020 to September 2022 by using the convenience sampling technique. The T-scan III Novus was employed in this investigation to record multi-bite scans for several patients. T-scan was utilised to examine various malocclusions. RESULTS: The present study consisted of 158 participants. Analysis of Variance (ANOVA) showed that there is a statistically significant difference in the percentage of force between the three types of malocclusions (I, II, and III) on the right molar side (B-16 and B-46) (p < 0.05). Moreover, the overall discrepancy showed a statistically significant difference in the three types of malocclusion classifications (p < 0.05). On the other hand, there was no statistically significant difference in the percentage of force between B-26 and B-36 (p > 0.05). Post hoc analysis showed a statistically significant difference in the percentage of force between malocclusion classes I and III on the right molar, with a mean difference of 4.11190 (p < 0.05). Similarly, there was a statistically significant difference in B-46 between Malocclusion Classes I and II, 4.01806 (p < 0.05). Additionally, post hoc analysis showed a statistically significant difference between malocclusion classes I and III, with a mean difference of -4.79841 (p < 0.05) on the right molar. CONCLUSION: The T-Scan is a useful tool for assessing occlusal discrepancies and can be helpful during treatment planning and follow-up, especially for orthognathic surgery patients. A T-scan could be used in orthodontic therapy in a simple and efficient way. Also, it turned out to be a useful tool for diagnosing problems and gave us new information about how therapies work. In this study, T-Scan showed that it can measure occlusal forces in timing in an objective, accurate, and repeated manner. The current study found that T-Scan was better able to report the difference in the percentage of force on the right molar side than on the left side.


Assuntos
Força de Mordida , Má Oclusão , Humanos , Oclusão Dentária , Estudos Transversais , Má Oclusão/diagnóstico , Má Oclusão/terapia , Dente Molar/diagnóstico por imagem
7.
Front Bioeng Biotechnol ; 11: 1254661, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37731759

RESUMO

Introduction: Knee OA progression is related to medial knee contact forces, which can be altered by anatomical parameters of tibiofemoral alignment and contact point locations. There is limited and controversial literature on medial-lateral force distribution and the effect of anatomical parameters, especially in motor activities different from walking. We analyzed the effect of tibiofemoral alignment and contact point locations on knee contact forces, and the medial-lateral force distribution in knee OA subjects with varus malalignment during walking, stair ascending and stair descending. Methods: Fifty-one knee OA subjects with varus malalignment underwent weight-bearing radiographs and motion capture during walking, stair ascending and stair descending. We created a set of four musculoskeletal models per subject with increasing level of personalization, and calculated medial and lateral knee contact forces. To analyze the effect of the anatomical parameters, statistically-significant differences in knee contact forces among models were evaluated. Then, to analyze the force distribution, the medial-to-total contact force ratios were calculated from the fully-informed models. In addition, a multiple regression analysis was performed to evaluate correlations between forces and anatomical parameters. Results: The anatomical parameters significantly affected the knee contact forces. However, the contact points decreased medial forces and increased lateral forces and led to more marked variations compared to tibiofemoral alignment, which produced an opposite effect. The forces were less medially-distributed during stair negotiation, with medial-to-total ratios below 50% at force peaks. The anatomical parameters explained 30%-67% of the variability in the knee forces, where the medial contact points were the best predictors of medial contact forces. Discussion: Including personalized locations of contact points is crucial when analyzing knee contact forces in subjects with varus malalignment, and especially the medial contact points have a major effect on the forces rather than tibiofemoral alignment. Remarkably, the medial-lateral force distribution depends on the motor activity, where stair ascending and descending show increased lateral forces that lead to less medially-distributed loads compared to walking.

8.
J Neurophysiol ; 130(3): 608-618, 2023 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-37529847

RESUMO

Large bilateral asymmetry and task deficits are typically observed during bimanual actions of stroke survivors. Do these abnormalities originate from unilateral impairments affecting their more-impaired limb, such as weakness and abnormal synergy, or from bilateral impairments such as incoordination of two limbs? To answer this question, 23 subjects including 10 chronic stroke survivors and 13 neurologically intact subjects participated in an experiment where they produced bimanual forces at different hand locations. The force magnitude and directional deviation of the more-impaired arm were measured for unilateral impairments and bimanual coordination across locations for bilateral impairments. Force asymmetry and task error were used to define task performance. Significant unilateral impairments were observed in subjects with stroke; the maximal force capacity of their more-impaired arm was significantly lower than that of their less-impaired arm, with a higher degree of force deviation. However, its force contribution during submaximal tasks was greater than its relative force capacity. Significant bilateral impairments were also observed, as stroke survivors modulated two forces to a larger degree across hand locations but in a less coordinated manner than control subjects did. But only unilateral, not bilateral, impairments explained a significant amount of between-subject variability in force asymmetry across subjects with stroke. Task error, in contrast, was correlated with neither unilateral nor bilateral impairments. Our results suggest that unilateral impairments of the more-impaired arm of stroke survivors mainly contribute to its reduced recruitment, but that the degree of its participation in bimanual task may be greater than their capacity as they attempt to achieve symmetry.NEW & NOTEWORTHY We studied how unilateral and bilateral impairments in stroke survivors affect their bimanual task performance. Unilateral impairments of the more-impaired limb, both weakness and loss of directional control, mainly contribute to bimanual asymmetry, but stroke survivors generally produce higher force with their more-impaired limb than their relative capacity. Bilateral force coordination was significantly impaired in stroke survivors, but its degree of impairment was not related to their unilateral impairments.


Assuntos
Reabilitação do Acidente Vascular Cerebral , Acidente Vascular Cerebral , Humanos , Lateralidade Funcional , Acidente Vascular Cerebral/complicações , Extremidade Superior , Mãos , Reabilitação do Acidente Vascular Cerebral/métodos
9.
Polymers (Basel) ; 15(13)2023 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-37447554

RESUMO

Micro- and nanofabrication on polymer substrate is integral to the development of flexible electronic devices, including touch screens, transparent conductive electrodes, organic photovoltaics, batteries, and wearable devices. The demand for flexible and wearable devices has spurred interest in large-area, high-throughput production methods. Roll-to-roll (R2R) nanoimprint lithography (NIL) is a promising technique for producing nano-scale patterns rapidly and continuously. However, bending in a large-scale R2R system can result in non-uniform force distribution during the imprinting process, which reduces pattern quality. This study investigates the effects of R2R imprinting module geometry parameters on force distribution via simulation, using grey relational analysis to identify optimal parameter levels and ANOVA to determine the percentage of each parameter contribution. The study also investigates the length and force ratio on a backup roller used for bending compensation. The simulation results and the artificial neural network (ANN) model enable the prediction of nip pressure and force distribution non-uniformity along the roller, allowing the selection of the optimal roller geometry and force ratio for minimal non-uniformity on a specific R2R system. An experiment was conducted to validate the simulation results and ANN model.

10.
Front Bioeng Biotechnol ; 11: 1170768, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37324425

RESUMO

Introduction: In this paper we introduce an adult-sized FE full-body HBM for seating comfort assessments and present its validation in different static seating conditions in terms of pressure distribution and contact forces. Methods: We morphed the PIPER Child model into a male adult-sized model with the help of different target sources including his body surface scans, and spinal and pelvic bone surfaces and an open sourced full body skeleton. We also introduced soft tissue sliding under the ischial tuberosities (ITs). The initial model was adapted for seating applications with low modulus soft tissue material property and mesh refinements for buttock regions, etc. We compared the contact forces and pressure-related parameters simulated using the adult HBM with those obtained experimentally from the person whose data was used for the model development. Four seat configurations, with the seat pan angle varying from 0° to 15° and seat-to-back angle fixed at 100°, were tested. Results: The adult HBM could correctly simulate the contact forces on the backrest, seat pan, and foot support with an average error of less than 22.3 N and 15.5 N in the horizontal and vertical directions, which is small considering the body weight (785 N). In terms of contact area, peak, and mean pressure, the simulation matched well with the experiment for the seat pan. With soft tissue sliding, higher soft tissue compression was obtained in agreement with the observations from recent MRI studies. Discussion: The present adult model could be used as a reference using a morphing tool as proposed in PIPER. The model will be published openly online as part of the PIPER open-source project (www.PIPER-project.org) to facilitate its reuse and improvement as well as its specific adaptation for different applications.

11.
Angew Chem Int Ed Engl ; 62(2): e202213980, 2023 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-36394518

RESUMO

Block copolymers (BCPs) are used in numerous applications in modern materials science. Yet, like homopolymers, BCPs can undergo covalent bond scission when mechanically stressed (mechanochemistry), which could lead to unexpected consequences in such applications. BCPs' heterogeneity may affect force transduction, perhaps changing force distribution and localization. To verify this, a gem-dichlorocyclopropane (gDCC) embedded linear chain is prepared and extended with a poly(methyl methacrylate) block. When stressed in solution, the mechanochemical ring-opening of gDCC is accelerated compared to homopolymers, even though the mechanophores are at the chain ends. Moreover, a higher mechanophore activation selectivity is obtained. These results indicate that mechanochemical response outside, and even far from the chain center is quite prominent in BCPs, and that forces along the polymer chain can efficiently activate multi-mechanophores regions, even when far from the polymer midchain.

12.
Sensors (Basel) ; 22(21)2022 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-36366054

RESUMO

In the study of braking force distribution of trucks, the accurate estimation of the state parameters of the vehicle is very critical. However, during the braking process, the state parameters of the vehicle present a highly nonlinear relationship that is difficult to estimate accurately and that seriously affects the accuracy of the braking force distribution strategy. To solve this problem, this paper proposes a machine-learning-based state-parameter estimation method to provide a solid data base for the braking force distribution strategy of the vehicle. Firstly, the actual collected complete vehicle information is processed for data; secondly, random forest is applied for the feature screening of data to reduce the data dimensionality; subsequently, the generalized regression neural network (GRNN) model is trained offline, and the vehicle state parameters are estimated online; the estimated parameters are used to implement the four-wheel braking force distribution strategy; finally, the effectiveness of the method is verified by joint simulation using MATLAB/Simulink and TruckSim.


Assuntos
Veículos Automotores , Simulação por Computador
13.
Cranio ; : 1-11, 2022 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-36101939

RESUMO

OBJECTIVE: To evaluate the effect of body posture on occlusal contact. METHODS: A total of 30 healthy subjects were evaluated. T-Scan™ III was used to analyze the center of occlusal force (COF) and occlusal force distribution while subjects remained supine (SP), upright sitting with the head fixed (UP-HFI), upright sitting with the head free (UP-HFR), and natural standing (NS). RESULTS: The total trajectory length of COF was significantly longer in NS than in SP, UP-HFI, and UP-HFR. The COF area was significantly larger in UP-HFR than in SP and UP-HFI and also significantly larger in NS than in SP, UP-HFI, and UP-HFR. The anteroposterior occlusal force distribution (AOD) in NS shifted significantly forward, compared to SP, UP-HFI, and UP-HFR. AOD in UP-HFI and UP-HFR shifted significantly forward, compared to the SP position. CONCLUSION: Changes in body posture affect the stability and anteroposterior balance of occlusal contacts.

14.
Soft Robot ; 9(5): 861-870, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-34619070

RESUMO

Artificial tactile sensing for robots is a counterpart to the human sense of touch, serving as a feedback interface for sensing and interacting with the environment. A vision-based tactile sensor has emerged as a novel and advantageous branch of artificial tactile sensors. Compared with conventional tactile sensors, vision-based tactile sensors possess stronger potential thanks to acquiring multimodal contact information in much higher spatial resolution, although they typically suffer from bulky size and fabrication challenges. In this article, we report a thin vision-based tactile sensor that draws inspiration from natural compound eye structures and demonstrate its capability of sensing three-dimensional (3D) force. The sensor is composed of an array of vision units, an elastic touching interface, and a supporting structure with illumination. Experiments validated the sensor's advantages, including competitive spatial resolution of deformation as high as 1016 dpi on a 5 × 8 mm2 sensing area, superior accuracy of 3D force measurement at levels of 0.018 N for tangential force and 0.213 N (0.108 N at the center region) for normal force, and real-time processing at 30 Hz, while achieving a thin size of 5 mm. We further demonstrate the sensor capability in sensing 3D force and slip occurrence in real grasping experiments. This device paves the way for robotic applications that require rich tactile information with miniaturized sensor structure.


Assuntos
Robótica , Percepção do Tato , Humanos , Tato , Força da Mão , Fenômenos Mecânicos
15.
Bioengineering (Basel) ; 8(9)2021 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-34562951

RESUMO

Hand prostheses partially restore hand appearance and functionalities. In particular, 3D printers have provided great opportunities by simplifying the manufacturing process and reducing costs. The "Federica" hand is 3D-printed and equipped with a single servomotor, which synergically actuates its five fingers by inextensible tendons; no springs are used for hand opening. A differential mechanical system simultaneously distributes the motor force on each finger in predefined portions. The proportional control of hand closure/opening is achieved by monitoring muscle contraction by means of a thin force sensor, as an alternative to EMG. The electrical current of the servomotor is monitored to provide sensory feedback of the grip force, through a small vibration motor. A simple Arduino board was adopted as the processing unit. A closed-chain, differential mechanism guarantees efficient transfer of mechanical energy and a secure grasp of any object, regardless of its shape and deformability. The force sensor offers some advantages over the EMG: it does not require any electrical contact or signal processing to monitor muscle contraction intensity. The activation speed (about half a second) is high enough to allow the user to grab objects on the fly. The cost of the device is less then 100 USD. The "Federica" hand has proved to be a lightweight, low-cost and extremely efficient prosthesis. It is now available as an open-source project (CAD files and software can be downloaded from a public repository), thus allowing everyone to use the "Federica" hand and customize or improve it.

16.
Sensors (Basel) ; 21(10)2021 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-34066273

RESUMO

A mandibular advancement device (MAD) is a commonly used treatment modality for patients with mild-to-moderate obstructive sleep apnea. Although MADs have excellent therapeutic efficacy, dental side effects were observed with long-term use of MADs. The aim of this study was to analyze the force distribution on the entire dentition according to the materials and design of the MADs. Three types of MADs were applied: model 1 (single layer of polyethylene terephthalate glycol (PETG)), model 2 (double layer of PETG + thermoplastic polyurethane (TPU)), and model 3 (core-reinforced multilayer). In the maxilla, regardless of the model, the incisors showed the lowest force distribution. In most tooth positions, the force distribution was lower in models 2 and 3 than in model 1. In the mandible, the mandibular second molar showed a significantly lower force in all models. The mandibular incisors, canines, and molars showed the highest force values in model 1 and the lowest values in model 3. Depending on the material and design of the device, the biomechanical effect on the dentition varies, and the core-reinforced multilayered MAD can reduce the force delivered to the dentition more effectively than the conventional single- or double-layer devices.


Assuntos
Avanço Mandibular , Apneia Obstrutiva do Sono , Humanos , Placas Oclusais , Resultado do Tratamento
17.
Front Vet Sci ; 8: 633509, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33898542

RESUMO

The purpose of this study was to quantitatively assess the vertical force distribution (VFD) of subject-specific healthy blue sheep while walking on different slopes using a pressure-sensing walkway. The blue sheep was trained to walk over the pressure-sensing walkway by choosing a comfortable walking speed, and the slope angle increased from 0° to 25°. The sheep's hooves were divided into four quadrants, namely, the cranio-lateral, cranio-medial, caudo-lateral, and caudo-medial quadrants, to investigate the VFD of the peak vertical force (PVF), vertical impulse (VI) and occurrence time of the PVF during the stance phase (TPVF). This study demonstrates that the main stressed quadrant of the front hoof changes from the caudo-medial quadrant to the cranio-medial quadrant with increasing slope. The main stressed quadrant of the rear hoof is the cranio-medial quadrant and does not change with the increasing slope. For all the slopes, the vertical force shifted from the lateral quadrant to the medial quadrant and from the caudal quadrant to the cranial quadrant. All the results obtained in the study suggest the feasibility of detecting gait changes in blue sheep, which has potential for the diagnosis of lower limb musculoskeletal diseases in quadrupeds.

18.
Sensors (Basel) ; 21(5)2021 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-33803481

RESUMO

This work describes the development of a vision-based tactile sensor system that utilizes the image-based information of the tactile sensor in conjunction with input loads at various motions to train the neural network for the estimation of tactile contact position, area, and force distribution. The current study also addresses pragmatic aspects, such as choice of the thickness and materials for the tactile fingertips and surface tendency, etc. The overall vision-based tactile sensor equipment interacts with an actuating motion controller, force gauge, and control PC (personal computer) with a LabVIEW software on it. The image acquisition was carried out using a compact stereo camera setup mounted inside the elastic body to observe and measure the amount of deformation by the motion and input load. The vision-based tactile sensor test bench was employed to collect the output contact position, angle, and force distribution caused by various randomly considered input loads for motion in X, Y, Z directions and RxRy rotational motion. The retrieved image information, contact position, area, and force distribution from different input loads with specified 3D position and angle are utilized for deep learning. A convolutional neural network VGG-16 classification modelhas been modified to a regression network model and transfer learning was applied to suit the regression task of estimating contact position and force distribution. Several experiments were carried out using thick and thin sized tactile sensors with various shapes, such as circle, square, hexagon, for better validation of the predicted contact position, contact area, and force distribution.

19.
J Shoulder Elbow Surg ; 30(2): e60-e68, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32540315

RESUMO

BACKGROUND: The rotator cuff (RC) and the deltoid muscle are 2 synergistic units that enable the functionally demanding movements of the shoulder. A number of biomechanical studies assume similar force contribution of the force couple (RC and deltoid) over the whole range of motion, whereas others propose position-dependent force distribution. There is a lack of in vivo data regarding the deltoid's contribution to shoulder flexion and abduction strength. This study aimed to create reliable in vivo data quantifying the deltoid's contribution to shoulder flexion and abduction strength throughout the range of motion. METHODS: Active range of motion and isometric muscle strength of shoulder abduction and flexion in 0°, 30°, 60°, 90°, and 120° of abduction/flexion as well as internal and external rotation in 0° and 90° of abduction were obtained in 12 healthy volunteers on the dominant arm before and after an ultrasound-guided isolated axillary nerve block. Needle electromyography was performed before and after the block to confirm deltoid paralysis. Radiographs of the shoulder and an ultrasonographic examination were used to exclude relevant shoulder pathologies. RESULTS: Active range of motion showed a minimal to moderate reduction to 94% and 88% of the preintervention value for abduction and flexion. Internal and external rotation amplitude was not impaired. The abduction strength was significantly reduced to 76% at 0° (P = .002) and to 25% at 120° (P < .001) of abduction. The flexion strength was significantly reduced to 64% at 30° (P < .001) and to 30% at 120° (P < .001) of flexion. The strength reduction was linear, depending on the flexion/abduction angle. The maximal external rotation strength showed a significant decrease to 53% in 90° (P < .001) of abduction, whereas in adduction no strength loss was observed (P = .09). The internal rotation strength remained unaffected in 0° and 90° of abduction (P = .28; P = .13). CONCLUSION: The deltoid shows a linear contribution to maximal shoulder strength depending on the abduction or flexion angle, ranging from 24% in 0° to 75% in 120° of abduction and from 11% in 0° to 70% in 120° of flexion, respectively. The overall contribution to abduction strength is higher than to flexion strength. The combination of deltoid muscle and teres minor contributes about 50% to external rotation strength in 90° of abduction. The internal rotation strength is not influenced by a deltoid paralysis. This study highlights the position-dependent contribution of the shoulder muscles to strength development and thereby provides an empirical approach to better understand human shoulder kinematics.


Assuntos
Articulação do Ombro , Ombro , Fenômenos Biomecânicos , Músculo Deltoide , Humanos , Amplitude de Movimento Articular , Rotação , Manguito Rotador , Articulação do Ombro/diagnóstico por imagem
20.
Eur Biophys J ; 50(2): 181-186, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33355710

RESUMO

The mechanosensitive TREK-2 potassium channel, a member of the K2P family, has essential physiological roles and is, therefore, a pharmaceutical target. A combination of experimental and computational studies have established that of the two known conformations, "up" and "down", membrane tension directly favors the "up" state, which displays a higher conductance. However, these studies did not reveal the exact mechanism by which the membrane affects the channel conformation. In this work, we show that changes in protein-lipid interaction patterns suffice in predicting this conformational change, and pinpoint potentially important residues involved in this phenomenon.


Assuntos
Ativação do Canal Iônico , Metabolismo dos Lipídeos , Mecanotransdução Celular , Proteínas de Membrana/metabolismo
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