Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 9.447
Filtrar
1.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2662-2666, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018554

RESUMO

Left ventricular assist devices (LVADs) have increasingly been used clinically to treat heart failure patients. However, hemolysis, pump thrombosis, infection and bleeding still persist as major limitations of LVAD technology. Assessing LVAD hemocompatibility using a blood shear stress device (BSSD) has clear advantages, as the BSSD could provide a better experimental platform to develop reliable, quantifiable blood trauma assays to perform iterative testing of LVAD designs. In this study, a BSSD was proposed with short blood exposure time and no seals or contact bearings to reduce blood trauma caused by the test platform. Enlarged air-gap drive motor in BSSD is essential to avoid high shear stress; however, it would significantly reduce the motor torque, which may result in inadequate force to drive the entire system. In order to evaluate and optimize the drive motor air-gap to ensure adequate motor torque as well as acceptable range for blood exposure time and shear stress, a numerical brushless DC (BLDC) motor model was established using finite element method (FEM) in numerical simulation software COMSOL. The model was first validated by the experimental results. Then numerical model with different air-gap was evaluated on the torque and speed constant changes. In the end, two equations were generated based on the curves derived from the torque and speed constant calculations. Determining these relationships between motor performance and motor air-gap will facilitate the development of an appropriate BLDC motor size for the BSSD, considering the design limitations in our future work.


Assuntos
Insuficiência Cardíaca , Coração Auxiliar , Animais , Hemólise , Humanos , Estresse Mecânico , Torque
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3501-3504, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018758

RESUMO

The scope and relevance of wearable robotics spans across a number of research fields with a variety of applications. A challenge across these research areas is improving user-interface control. One established approach is using neural control interfaces derived from surface electromyography (sEMG). Although there has been some success with sEMG controlled prosthetics, the coarse nature of traditional sEMG processing has limited the development of fully functional prosthetics and wearable robotics. To solve this problem, blind source separation (BSS) techniques have been implemented to extract the user's movement intent from high-density sEMG (HDsEMG) measurements; however, current methods have only been well validated during static, low-level muscle contractions, and it is unclear how they will perform during movement. In this paper we present a neural drive based method for predicting output torque during a constant force, concentric contraction. This was achieved by modifying an existing HDsEMG decomposition algorithm to decompose 1 sec. overlapping windows. The neural drive profile was computed using both rate coding and kernel smoothing. Neither rate coding nor kernel smoothing performed as well as HDsEMG amplitude estimation, indicating that there are still significant limitations in adapting current methods to decompose dynamic contractions, and that sEMG amplitude estimation methods still remain highly reliable estimators.


Assuntos
Movimento , Contração Muscular , Algoritmos , Eletromiografia , Torque
3.
Stud Health Technol Inform ; 273: 91-96, 2020 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-33087596

RESUMO

A lower-extremity exoskeleton can facilitate the lower limbs' rehabilitation by providing additional structural support and strength. This article discusses the design and implementation of a functional prototype of lower extremity brace actuation and its wireless communication control system. The design provides supportive torque and increases the range of motion after complications reducing muscular strength. The control system prototype facilitates elevating a leg, gradually followed by standing and slow walking. The main control modalities are based on an Artificial Neural Network (ANN). The prototype's functionality was tested by time-angle graphs. The final prototype demonstrates the potential application of the ANN in the control system of exoskeletons for joint impairment therapy.


Assuntos
Exoesqueleto Energizado , Extremidade Inferior , Redes Neurais de Computação , Torque , Caminhada
4.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3807-3810, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018830

RESUMO

Completing motor tasks that require contact is dependent on an ability to regulate the relationship between limb motions and interaction forces with the environment. This can be achieved by exploiting the mechanical properties of a limb or through active regulation of joint torques through changes in muscle activation. Leveraging the mechanical properties of a joint might simplify neural control when they are matched to the functional requirements of a task. The purpose of this study was to determine if humans change their control strategy, relying on limb mechanics rather than regulated muscle activation, when feasible. This was accomplished by measuring ankle impedance and muscle activation strategies in three tasks requiring joint torques to: oppose movement, assist movement, or remain constant during movement. We found that subjects produced more torque due to impedance and less torque due to muscle activation in the torque-oppose task, the only task that could feasibly be completed through impedance modulation. These results demonstrate that people do leverage the mechanical properties of a joint to complete certain task, lessening the need for precisely timed muscle contractions.


Assuntos
Movimento , Fenômenos Fisiológicos do Sistema Nervoso , Articulação do Tornozelo , Humanos , Contração Muscular , Torque
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3965-3968, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018868

RESUMO

Recognizing human intentions from the human counterpart is very important in human-robot interaction applications. Surface electromyography(sEMG) has been considered as a potential source for motion intention because the signal represents the on-set timing and amplitude of muscle activation. It is also reported that sEMG has the advantage of knowing body movements ahead of actual movement. However, sEMG based applications suffer from electrode location variation because sEMG shows different characteristics whenever the skin condition is different. They need to recreate the estimation model if electrodes are attached to different locations or conditions. In this paper, we developed a sEMG torque estimation model for electrode location variation. A decomposition model of sEMG signals was developed to discriminate the muscle source signals for electrode location variation, and we verified this model without making a new torque estimation model. Torque estimation accuracy using the proposed method was increased by 24.8% and torque prediction accuracy was increased by 47.7% for the electrode location variation in comparison with the method without decomposition. Therefore, the proposed sEMG decomposition method showed an enhancement in torque estimation for electrode location variation.


Assuntos
Movimento , Músculo Esquelético , Eletrodos , Eletromiografia , Humanos , Torque
6.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 4775-4778, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019058

RESUMO

The performance and safety of human robot interaction (HRI) can be improved by using subject-specific movement prediction. Typical models include biomechanical (parametric) or black-box (non-parametric) models. The current work aims to investigate the benefits and drawbacks of these approaches by comparing elbow-joint torque predictions based on electromyography signals of the elbow flexors and extensors. To this end, a parameterized biomechanical model is compared to a non-parametric (Gaussian-process) approach. Both models showed adequate results in predicting the elbow-joint torques. While the non-parametric model requires minimal modeling effort, the parameterized biomechanical model can lead to deeper insight of the underlying subject specific musculoskeletal system.


Assuntos
Articulação do Cotovelo , Movimento , Cotovelo , Eletromiografia , Humanos , Torque
7.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 4854-4857, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019077

RESUMO

A method for ankle torque prediction ahead of the current time is proposed in this paper. The mean average value of EMG signals from four muscles, alongside the joint angle and angular velocity of the right ankle, were used as input parameters to train a time-delayed artificial neural network. Data collected from five healthy subjects were used to generate the dataset to train and test the model. The model predicted ankle torque for five different future times from zero to 2 seconds. Model predictions were compared to torque calculated from inverse dynamics for each subject. The model predicted ankle torque up to 1 second ahead of time with normalized root mean squared error of less than 15 percent while the coefficient of determination was over 0.85.Clinical Relevance- the potential of the model for predicting joint torque ahead of time is helpful to establish an intuitive interaction between human and assistive robots. This model has application to assist patients with neurological disorders.


Assuntos
Tornozelo , Músculo Esquelético , Articulação do Tornozelo , Humanos , Redes Neurais de Computação , Torque
8.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 4913-4916, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019090

RESUMO

In this study, we present a new design of a shoulder perturbation robot that can characterise the dynamics of the shoulder in two degrees of freedom. It uses two linear electric motors to perturb the shoulder joint in internal/external rotation and abduction/adduction, and force and position sensors to measure the corresponding torque and angular displacement about the joint. System identification techniques are used to estimate the dynamics of the muscles around the joint. The advantage our apparatus offers over the existing ones is that it can efficiently transfer torque to the joint and measure its dynamics separately with minimal interference from soft tissues. We verified that the apparatus can accurately estimate joint dynamics by conducting tests on a phantom of known properties. In addition, experiments were conducted on a human participant. It has been demonstrated that the measured dynamics of participant's arm are repeatable. The potential impact of our apparatus is to be used in clinic as a diagnostic tool for rotator cuff injuries.


Assuntos
Articulação do Ombro , Humanos , Amplitude de Movimento Articular , Manguito Rotador , Ombro , Torque
9.
PLoS One ; 15(10): e0238785, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33052931

RESUMO

A human cadaveric specimen-specific knee model with appropriate soft tissue constraints was developed to appropriately simulate the biomechanical environment in the human knee, in order to pre-clinically evaluate the biomechanical and tribological performance of soft tissue interventions. Four human cadaveric knees were studied in a natural knee simulator under force control conditions in the anterior posterior (AP) and tibial rotation (TR) axes, using virtual springs to replicate the function of soft tissues. The most appropriate spring constraints for each knee were determined by comparing the kinematic outputs in terms of AP displacement and TR angle of the human knee with all the soft tissues intact, to the same knee with all the soft tissues resected and replaced with virtual spring constraints (spring rate and free length/degree). The virtual spring conditions that showed the least difference in the AP displacement and TR angle outputs compared to the intact knee were considered to be the most appropriate spring conditions for each knee. The resulting AP displacement and TR angle profiles under the appropriate virtual spring conditions all showed similar shapes to the individual intact knee for each donor. This indicated that the application of the combination of virtual AP and TR springs with appropriate free lengths/degrees was successful in simulating the natural human knee soft tissue function. Each human knee joint had different kinematics as a result of variations in anatomy and soft tissue laxity. The most appropriate AP spring rate for the four human knees varied from 20 to 55 N/mm and the TR spring rate varied from 0.3 to 1.0 Nm/°. Consequently, the most appropriate spring condition for each knee was unique and required specific combinations of spring rate and free length/degree in each of the two axes.


Assuntos
Joelho/fisiologia , Modelos Biológicos , Idoso , Fenômenos Biomecânicos , Cadáver , Simulação por Computador , Tecido Conjuntivo/anatomia & histologia , Tecido Conjuntivo/fisiologia , Feminino , Humanos , Joelho/anatomia & histologia , Articulação do Joelho/anatomia & histologia , Articulação do Joelho/fisiologia , Masculino , Pessoa de Meia-Idade , Amplitude de Movimento Articular , Rotação , Tíbia/anatomia & histologia , Tíbia/fisiologia , Torque
10.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3122-3125, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018666

RESUMO

Previous works have shown that whitening improves the processed electromyogram (EMG) signal for use in end applications such as EMG to torque modelling. Traditional whitening methods fit each subject from calibration contractions, which is a hindrance to their widespread use. To eliminate this cumbersome calibration, a universal whitening filter was developed using the whitening filters from a pre-existing data set (64 subjects, 8 electrodes/subject). Since the shape of each subject-specific whitening filter was observed to be relatively consistent across subjects, the universal whitening filter was formed as their ensemble average. The processed EMG was then used to model surface EMG to torque about the elbow. Traditional and universal whitening provided the same EMG-torque benefit, each improving statistically over unwhitened processing by ~14% during dynamic contractions. We further studied the use of root difference of squares (RDS) post-processing to attenuate additive measurement noise in EMG channels. With and without whitening, RDS processing (vs. no RDS processing) better attenuated additive noise, reducing it from 2-4% (on average) of the processed EMG from a 50% contraction down to < 1%. The combined use of universal whitening filters and RDS processing should be a particular benefit in real-time applications such as prosthesis control.


Assuntos
Articulação do Cotovelo , Processamento de Sinais Assistido por Computador , Cotovelo , Eletromiografia , Humanos , Torque
13.
PLoS One ; 15(8): e0237842, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866205

RESUMO

Isokinetic dynamometry is the gold standard for testing maximal strength in elite sport and rehabilitation settings. To be clinically useful, such tests should be valid and reliable. Despite some evidence regarding the relative test vs retest reliability of knee dynamometry, there is still a paucity of research regarding the absolute reliability parameters. The purpose of this study was to assess the absolute and relative intra-device reproducibility of isokinetic knee flexion and extension using the novel SMM iMoment dynamometer. A total of 19 participants (13 males and 6 females, aged 24 (2) years, height 178 (9) cm and weight 76 (11) kg) performed two identical knee isokinetic tests with at least a week of rest between measurements. Peak torque of knee extension and flexion were determined at 60°/s. Moderate (0.892) to excellent (0.988) relative reliability using the intraclass correlation coefficient (ICC) was obtained for peak knee torque. Absolute reliability assessed with a standard error of measurement (SEM %) was low, ranging from 2.54% to 6.93%, whereas the smallest real difference (SRD %) was moderate, ranging from 7.04% to 19.22%. Furthermore, there were no significant correlations between means and differences of two measurements, and Bland-Altman plots also showed no signs of heteroscedasticity. Our measurement protocol established the moderate to excellent reliability of the novel SMM iMoment isokinetic dynamometer. Therefore, this dynamometer can be applied in sport rehabilitation settings to measure maximal knee strength.


Assuntos
Joelho/fisiologia , Dinamômetro de Força Muscular , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Músculo Esquelético/fisiologia , Amplitude de Movimento Articular , Reprodutibilidade dos Testes , Torque , Adulto Jovem
14.
J Sports Med Phys Fitness ; 60(8): 1148-1158, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32955841

RESUMO

BACKGROUND: There is paucity of data examining the effectiveness of long-term Hatha yoga-based (HY) programs focused on the health-related fitness (H-RF) of asymptomatic, sedentary women. The purpose of this study was to examine the effects of a 6-month HY-based training program on H-RF components in sedentary middle-aged women. METHODS: Eighty sedentary women were randomly assigned into either the HY group (HYG) (N.=42) or the control group (CG) (N.=38). The 6-month HYG program involved a progressive series of Vinyasa Flow poses performed 3 times/week for 60 minutes (40 minutes within the exercise zone of 60-75% HRmax). The CG participants did not undergo any physical training or education. Health-related fitness parameters included measures of pre- and post-training: body composition, muscular strength and maximal voluntary isometric torques of elbow flexors and knee extensors, cardio-respiratory fitness, lower back and hamstring flexibility and a static-dynamic balance. RESULTS: Two-way mixed design ANOVA revealed significant main effects for all the indicators of H-RF. Tukey post-hoc tests confirmed that the HYG demonstrated significant improvements in every variable tested. Examples of the benefits achieved include (all P<.001): an average loss of 1.03 kg and a 4.82% decrease in body fat, 14.6% and 13.1% gains in isometric strength of the knee extensors and elbow flexors respectively, an increase in relative VO2max of 6.1% (33.12±5.30 to 35.14±4.82 mL/kg/min), a 4-cm or 10.4% increase in their MSAR, and an average improved Balance Index of 5.6 mm/s. Reversely, the CG showed non-significant changes in H-RF variables (all P>0.05; percent range from -1.4% to 1.1%). CONCLUSIONS: By participating in a moderate-intensity 6-month HY-based training program, middle-aged women can significantly improve their HR-F status. The application of progressive target heart rate goals facilitated greater than expected improvements in cardio-respiratory fitness and improvements in body composition.


Assuntos
Aptidão Física/fisiologia , Comportamento Sedentário , Ioga , Adulto , Composição Corporal , Aptidão Cardiorrespiratória , Cotovelo/fisiologia , Feminino , Frequência Cardíaca , Humanos , Contração Isométrica/fisiologia , Joelho/fisiologia , Estudos Longitudinais , Pessoa de Meia-Idade , Força Muscular/fisiologia , Equilíbrio Postural/fisiologia , Torque
15.
Proc Natl Acad Sci U S A ; 117(38): 23519-23526, 2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32900941

RESUMO

The structure of the dimeric ATP synthase from bovine mitochondria determined in three rotational states by electron cryo-microscopy provides evidence that the proton uptake from the mitochondrial matrix via the proton inlet half channel proceeds via a Grotthus mechanism, and a similar mechanism may operate in the exit half channel. The structure has given information about the architecture and mechanical constitution and properties of the peripheral stalk, part of the membrane extrinsic region of the stator, and how the action of the peripheral stalk damps the side-to-side rocking motions that occur in the enzyme complex during the catalytic cycle. It also describes wedge structures in the membrane domains of each monomer, where the skeleton of each wedge is provided by three α-helices in the membrane domains of the b-subunit to which the supernumerary subunits e, f, and g and the membrane domain of subunit A6L are bound. Protein voids in the wedge are filled by three specifically bound cardiolipin molecules and two other phospholipids. The external surfaces of the wedges link the monomeric complexes together into the dimeric structures and provide a pivot to allow the monomer-monomer interfaces to change during catalysis and to accommodate other changes not related directly to catalysis in the monomer-monomer interface that occur in mitochondrial cristae. The structure of the bovine dimer also demonstrates that the structures of dimeric ATP synthases in a tetrameric porcine enzyme have been seriously misinterpreted in the membrane domains.


Assuntos
Mitocôndrias/enzimologia , ATPases Mitocondriais Próton-Translocadoras , Animais , Bovinos , Membranas Mitocondriais/química , Membranas Mitocondriais/enzimologia , ATPases Mitocondriais Próton-Translocadoras/química , ATPases Mitocondriais Próton-Translocadoras/metabolismo , ATPases Mitocondriais Próton-Translocadoras/ultraestrutura , Modelos Moleculares , Conformação Proteica , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Prótons , Torque
16.
Prog Orthod ; 21(1): 32, 2020 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-32924097

RESUMO

BACKGROUND: The loss of third-order information in pre-adjusted brackets due to torsional play is a problem in clinical orthodontics. The aim of this study was to evaluate the impact of slot height, archwire height, width and edge bevel's radius on the torsional play for three brackets/archwire systems. METHODS: Ninety brackets with a 0.022 × 0.028 in. slot with McLaughlin-Bennett-Trevisi prescription from three different manufacturers were selected, and the slot's height and depth were measured using a profile projector. Sixty stainless-steel rectangular archwires from three different manufacturers were sectioned and observed with a SEM to measure their height, width, and radius of edge bevel. The recorded data were used to calculate the theoretical torsional play between different slot-archwire combinations. One-way ANOVA was used to compare the measurements within different bracket types and among different manufacturers. RESULTS: Slot height was usually oversized. Archwire's height was usually undersized, but oversized wires were also observed. The radius edge bevel was the most variable parameter. A certain degree of torsional play is always present that differs from one bracket type to another of the same producer and that can even be doubled from one manufacturer to another. CONCLUSIONS: Due to production tolerance, differences between the nominal values and the real dimensions of any components of a slot/archwire system are common. This results in a torsional play that limits torque expression. The archwire's edge bevel plays an important role in torque expression, and clearer information should be provided by the manufacturers regarding this aspect.


Assuntos
Braquetes Ortodônticos , Fios Ortodônticos , Desenho de Aparelho Ortodôntico , Aço Inoxidável , Torque
17.
PLoS Comput Biol ; 16(8): e1008081, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32750070

RESUMO

We rarely experience difficulty picking up objects, yet of all potential contact points on the surface, only a small proportion yield effective grasps. Here, we present extensive behavioral data alongside a normative model that correctly predicts human precision grasping of unfamiliar 3D objects. We tracked participants' forefinger and thumb as they picked up objects of 10 wood and brass cubes configured to tease apart effects of shape, weight, orientation, and mass distribution. Grasps were highly systematic and consistent across repetitions and participants. We employed these data to construct a model which combines five cost functions related to force closure, torque, natural grasp axis, grasp aperture, and visibility. Even without free parameters, the model predicts individual grasps almost as well as different individuals predict one another's, but fitting weights reveals the relative importance of the different constraints. The model also accurately predicts human grasps on novel 3D-printed objects with more naturalistic geometries and is robust to perturbations in its key parameters. Together, the findings provide a unified account of how we successfully grasp objects of different 3D shape, orientation, mass, and mass distribution.


Assuntos
Força da Mão/fisiologia , Modelos Biológicos , Desempenho Psicomotor/fisiologia , Adulto , Biologia Computacional , Feminino , Mãos/fisiologia , Humanos , Masculino , Torque , Adulto Jovem
18.
PLoS One ; 15(8): e0237768, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32813742

RESUMO

INTRODUCTION: In cycling, the utilization of the drops position (i.e. the lowest handlebar position relative to the ground) allows for reduced frontal area, likely improved aerodynamics and thus performance compared to the tops (i.e. the position producing the most upright trunk). The reduced trunk angle during seated submaximal cycling has been shown to influence cardiorespiratory factors but the effects on pedalling forces and joint specific power are unclear. The purpose of this study was to investigate the effect of changing handgrip position on joint specific power and cycling kinematics at different external work rates in recreational and professional cyclists. METHOD: Nine professional and nine recreational cyclists performed cycling bouts using three different handgrip positions and three external work rates (i.e. 100W, 200W and external work rate corresponding to the lactate threshold (WRlt)). Joint specific power was calculated from kinematic measurements and pedal forces using 2D inverse dynamics. RESULTS: We found increased hip joint power, decreased knee joint power and increased peak crank torque for the professional cyclist compared to the recreational cyclists, but only at WRlt where the professional cyclists were working at a higher external work rate. There was no main effect of changing handgrip position on any joint, but there was a small interaction effect of external work rate and handgrip position on hip joint power contribution (Generalized eta squared (ηg2) = 0.012). At 100W, changing handgrip position from the tops to the drops decreased the hip joint contribution (-2.0 ± 3.9 percentage points (pct)) and at the WRlt, changing handgrip position increased the hip joint power (1.6 ± 3.1 pct). There was a small effect of handgrip position with the drops leading to increased peak crank torque (ηg2 = 0.02), increased mean dorsiflexion (ηg2 = 0.05) and increased hip flexion (ηg2 = 0.31) compared to the tops. DISCUSSION: The present study demonstrates that there is no main effect of changing handgrip position on joint power. Although there seems to be a small effect on hip joint power when comparing across large ranges in external work rate, any potential negative performance effect would be outweighed by the aerodynamic benefit of the drops position.


Assuntos
Atletas , Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Postura/fisiologia , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Mãos/fisiologia , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Masculino , Torque , Adulto Jovem
19.
Int J Oral Maxillofac Implants ; 35(4): 700-706, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32724921

RESUMO

PURPOSE: This study was designed to evaluate the effects of four different surgical techniques on the primary stability of short implants in two sizes (4-mm and 6-mm length) through resonance frequency analysis and insertion torque measurement in vitro. MATERIALS AND METHODS: Forty implant site preparations and implant insertions were performed in pig ribs. Guided surgery, bone condensing, conventional drilling, and undersized preparation surgical techniques were used five times in each bone block to prepare 4-mm/6-mm-length implant beds. The maximum insertion torque and implant stability quotient (ISQ) values were recorded for each implant. RESULTS: Both the ISQ and torque differed significantly for various surgical techniques (P = .009 and P < .001). The conventional technique had higher ISQ (79.00), whereas the condenser technique had higher torque (48.00 Ncm) than did the other techniques. The mean torque was significantly higher in all surgical techniques other than the guided surgery group regardless of implant length (P < .01 for all). Implant lengths were not significantly different in terms of ISQ and torque in all surgical techniques. CONCLUSION: There are significant correlations between the implant bed preparation technique and primary implant stability when using short implants. Conventional surgery and the bone condensing technique are favorable alternatives with higher primary stability and torque values in short implants.


Assuntos
Implantação Dentária Endo-Óssea , Implantes Dentários , Animais , Retenção em Prótese Dentária , Análise de Frequência de Ressonância , Costelas/cirurgia , Suínos , Torque
20.
PLoS Biol ; 18(7): e3000740, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32649659

RESUMO

The carnivorous Venus flytrap catches prey by an ingenious snapping mechanism. Based on work over nearly 200 years, it has become generally accepted that two touches of the trap's sensory hairs within 30 s, each one generating an action potential, are required to trigger closure of the trap. We developed an electromechanical model, which, however, suggests that under certain circumstances one touch is sufficient to generate two action potentials. Using a force-sensing microrobotic system, we precisely quantified the sensory-hair deflection parameters necessary to trigger trap closure and correlated them with the elicited action potentials in vivo. Our results confirm the model's predictions, suggesting that the Venus flytrap may be adapted to a wider range of prey movements than previously assumed.


Assuntos
Droseraceae/fisiologia , Percepção do Tato/fisiologia , Potenciais de Ação/fisiologia , Fenômenos Biomecânicos , Eletricidade , Modelos Biológicos , Estimulação Física , Torque
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA