Gular pouch diversity in the Chamaeleonidae

Numerous chameleon species possess an out-pocketing of the trachea known as the gular pouch. After surveying more than 250 specimens, representing nine genera and 44 species, we describe two different morphs of the gular pouch. Species of the genera Bradypodion and Chamaeleo, as well as Trioceros goetzei, all possess a single gular pouch (morph one) formed from ventral expansion of soft tissue where the larynx and trachea meet. Furcifer oustaleti and Furcifer verrucosus possess from one to four gular pouches (morph two) formed by the expansion of soft tissue between sequential hyaline cartilage rings of the trachea. In Trioceros melleri, examples of both morphs of the gular pouch were observed. Morphometric data are presented for 100 animals representing eight species previously known to possess a gular pouch and two additional species, Bradypodion thamnobates and Bradypodion transvaalense. In the species with the absolutely and relatively largest gular pouch, Chamaeleo calyptratus, a significant difference was found between sexes in its width and volume, but not its length. In C. calyptratus, we show that an inflated gular pouch is in contact with numerous hyoid muscles and the tongue. Coupled with the knowledge that C. calyptratus generates vibrations from the throat region, we posit that the tongue (M. accelerator linguae and M. hyoglossus) and supporting hyoid muscles (i.e., Mm. sternohyoideus profundus et superficialis and Mm. mandibulohyoideus) are involved in the production of vibrations to produce biotremors that are amplified by the inflated gular pouch and used in substrate-borne communication.     

Vibration-induced muscle fatigue,a possible contribution to musculoskeletal injury

Localized muscle fatigue resulting from 30-min sustained and intermittent grip exertions of 5% maximal voluntary contraction (MVC) with and without hand-vibration exposure (10 Hz, 7 mm displacement amplitude) was investigated. Muscle fatigue was quantified by the magnitude of the twitch force elicited in the right flexor digitorum superficialis muscle of the long finger using the low-frequency fatigue (LFF) method. The influence of vibration in the sustained grip exertion condition exacerbates fatigue as seen with the reduction in twitch force 30–60 min post-work task. Intermittent low grip force exertion conditions with and without vibration exposure show negligible fatigue, suggesting the benefit of rest in the work cycle. Perception of muscle fatigue was dissociated from the objective measure of twitch force, suggesting that LFF was not perceived. The presence of LFF and the lack of perception of LFF may increase the risk for the development of musculoskeletal disorders. The findings of this study may apply to the design of the work cycles and tasks that require the use of vibratory tools. Electronic Publication     

下肢外骨骼的新型足部机构舒适性优化

为减小在高负重的情况下穿戴下肢外骨骼时足部与地面接触产生的冲击,本文设计了一种用于提高足部舒适性的外骨骼足部机构,并对其影响舒适性的关键指标进行了优化。首先,本文基于步态周期的足底受力特点建立了足部机构物理模型,进而抽象出振动数学模型,并用有限元分析软件ANSYS仿真验证了模型的正确性。然后,本文基于振动数学模型分析了振动参数对绝对传递率的影响,并用数学计算软件MATLAB遗传算法工具箱优化振动参数。最后,本文以白噪声模拟路面高程作为振动输入,利用MATLAB中的可视化仿真工具Simulink并结合振动方程构建加速度仿真模型,进而计算足部的振动加权均方根加速度值。研究结果表明,该足部舒适性机构能够满足减振性与足底压力的舒适性指标。本文为外骨骼足部机构的设计提供了一套较为完整的设计方法,对于其他外骨骼的足部设计以及踝关节康复机构的设计具有借鉴意义。     

Hand tremor suppression device for patients suffering from Parkinson’s disease

Abstract

In this study, a wearable device is developed as a mechanical treatment to suppress hand tremors in people with Parkinson's disease (PwPD). The biodynamic modelling of the human hand was done by considering the hand as a primary mass-spring-damper system. Dual passive vibration absorbers have been designed to match the frequencies of tremors. The performance assessment of the device was performed using the temporal response of hand tremors. The results showed that the device reduced the amplitude of the angular movement of the wrist by 57.25%. The device fabricated in the form of a bracelet was easy to wear by PwPD when needed.     

低幅高频振动对骨质疏松性骨折合并闭合性动脉损伤的作用

目的利用卵巢切除大鼠建立骨质疏松骨折模型,研究低幅高频振动对骨质疏松性骨折愈合及患肢远端血供的作用。方法 32只6月龄雌性SD大鼠行卵巢切除术,3个月后构建右侧股骨干闭合性横行骨折合并股动脉损伤模型,术后随机平均分为振动组与对照组。每周摄股骨侧位X片以监测外骨痂尺寸及骨折愈合情况。第2、4、8周,应用脉冲多普勒超声测量患肢远端血流速度及阻力指数。Micro-CT扫描重建骨折部位,并作定性定量分析。结果超声检测发现,第2、4周振动组患肢股动脉远端收缩期峰值血流速度较对照组明显增高(P<0.05),阻力指数降低。X片及Micro-CT分析显示,振动组在愈合过程中,骨痂形成、矿化程度、重塑效果、桥接愈合率均显著优于对照组。结论低幅高频振动可有效改善患肢远端血供,促进骨质疏松性骨折愈合。     

Memory for fingertip forces: passive hand muscle vibration interferes with predictive grip force scaling

When subjects repetitively lift an object, the grip force they select is influenced by the mechanical object properties of the preceding lift. Similar effects on grip force scaling are observed whether the subsequent lift is performed with the same hand or the hand contralateral to the preceding lift. Here we demonstrate that passive vibration of the hand muscles involved in the generation of grip force in the interval between two blocks of lifting trials interferes with predictive grip force scaling. Following ten trials in which subjects lifted an object with constant mechanical properties with the dominant hand, muscle vibration was given to the first interosseus and adductor pollicis muscles of the dominant hand during a 10-min rest period. Compared with the last lift preceding vibration, peak rates of grip force increase and peak grip forces were scaled too high during the first lift following vibration whether the lift was made with the dominant or non-dominant hand. Subjects scaled grip force accurately to the object properties within three lifts following vibration. If subjects rested for 10 min after the first ten trials and received no vibration, then there was no significant difference in the peak grip force or its rate of increase between the last lift preceding rest and the first lift following it. We suggest that vibration impairs the memory processes responsible for predictive grip force scaling. Our data are consistent with the recent suggestion that these memory processes are neither specific for a certain motor action nor do they reflect internal representations of mechanical object properties.     

Correlation between acceleration magnitude and ocular vestibular-evoked myogenic potential

This study combined bone-conducted vibration (BCV) stimulation with triaxial accelerometry to correlate the acceleration magnitudes of BCV stimuli with ocular vestibular-evoked myogenic potential (oVEMP) test results. Fourteen healthy volunteers underwent oVEMP test using BCV stimuli with simultaneous monitoring the triaxial acceleration. All (100%) subjects exhibited clear oVEMPs in response to BCV stimuli from a vibrator. The lowest acceleration magnitudes for eliciting oVEMPs along the x-, y- and z-axes were 0.05±0.01 g, 0.16±0.08 g, and 0.04±0.01 g, respectively, exhibiting significantly higher acceleration magnitude along the y-axis than those along the x- and z-axes. In addition, significantly positive correlations were noted between the acceleration magnitude along each axis and the oVEMP amplitude. In conclusion, measuring the acceleration magnitude throughout oVEMP testing revealed a significant correlation between linear acceleration and oVEMP responses. Restated, increasing acceleration magnitude may have more synchronization of firing of vestibular afferents, resulting in more synchronized evoked potentials and greater oVEMP amplitude.     

Finite-Element Modelling of the Response of the Gerbil Middle Ear to Sound

We present a finite-element model of the gerbil middle ear that, using a set of baseline parameters based primarily on a priori estimates from the literature, generates responses that are comparable with responses we measured in vivo using multi-point vibrometry and with those measured by other groups. We investigated the similarity of numerous features (umbo, pars-flaccida and pars-tensa displacement magnitudes, the resonance frequency and break-up frequency, etc.) in the experimental responses with corresponding ones in the model responses, as opposed to simply computing frequency-by-frequency differences between experimental and model responses. The umbo response of the model is within the range of variability seen in the experimental data in terms of the low-frequency (i.e., well below the middle-ear resonance) magnitude and phase, the main resonance frequency and magnitude, and the roll-off slope and irregularities in the response above the resonance frequency, but is somewhat high for frequencies above the resonance frequency. At low frequencies, the ossicular axis of rotation of the model appears to correspond to the anatomical axis but the behaviour is more complex at high frequencies (i.e., above the pars-tensa break-up). The behaviour of the pars tensa in the model is similar to what is observed experimentally in terms of magnitudes, phases, the break-up frequency of the spatial vibration pattern, and the bandwidths of the high-frequency response features. A sensitivity analysis showed that the parameters that have the strongest effects on the model results are the Young’s modulus, thickness and density of the pars tensa; the Young’s modulus of the stapedial annular ligament; and the Young’s modulus and density of the malleus. Displacements of the tympanic membrane and manubrium and the low-frequency displacement of the stapes did not show large changes when the material properties of the incus, stapes, incudomallear joint, incudostapedial joint, and posterior incudal ligament were changed by ±10 % from their values in the baseline parameter set.     

Deleterious effects of whole‐body vibration on the spine: A review of in vivo,ex vivo,and in vitro models

Occupational exposure to whole‐body vibration is associated with the development of musculoskeletal, neurological, and other ailments. Low back pain and other spine disorders are prevalent among those exposed to whole‐body vibration in occupational and military settings. Although standards for limiting exposure to whole‐body vibration have been in place for decades, there is a lack of understanding of whole‐body vibration‐associated risks among safety and healthcare professionals. Consequently, disorders associated with whole‐body vibration exposure remain prevalent in the workforce and military. The relationship between whole‐body vibration and low back pain in humans has been established largely through cohort studies, for which vibration inputs that lead to symptoms are rarely, if ever, quantified. This gap in knowledge highlights the need for the development of relevant in vivo, ex vivo, and in vitro models to study such pathologies. The parameters of vibrational stimuli (eg, frequency and direction) play critical roles in such pathologies, but the specific cause‐and‐effect relationships between whole‐body vibration and spinal pathologies remain mostly unknown. This paper provides a summary of whole‐body vibration parameters; reviews in vivo, ex vivo, and in vitro models for spinal pathologies resulting from whole‐body vibration; and offers suggestions to address the gaps in translating injury biomechanics data to inform clinical practice.     

100 Hz正弦波振动对悬吊大鼠比目鱼肌肌梭传入放电的影响

目的探讨100 Hz正弦波振动对尾部悬吊大鼠比目鱼肌肌梭传入放电的影响.方法采用尾部悬吊大鼠模型模拟失重,用振动仪实施100 Hz正弦波刺激,利用从背根分离神经细束并记录比目鱼肌肌梭传入放电的方法,7 d后观察大鼠比目鱼肌肌梭传入放电的变化.结果 1)吊尾7 d后,大鼠比目鱼肌肌梭的传入放电与对照组相比明显减低(P<0.05).2)吊尾加100 Hz正弦波振动7 d后,与单纯吊尾组相比肌梭的传入放电明显增多(P<0.05). 结论 100 Hz正弦波振动可选择性兴奋肌梭,使悬吊大鼠比目鱼肌肌梭的传入放电明显增多.