Study of acoustic waves in stressed muscle

The spectral characteristics of mechanical vibrations generated by stressed human biceps, referred to as "muscle sounds", were studied. Attempts were made to establish a relationship between these vibrations and conformational rearrangements of muscle proteins during contraction. It was found experimentally that the steepness of the spectral amplitudes of vibrations varies with muscle load. The method proposed made it possible to quantitatively study vibrations of frequencies up to 1 kHz.     

Control Model for Dampening Hand Vibrations Using Information of Internal and External Coordinates

In the present study, we investigate a control mechanism that dampens hand vibrations. Here, we propose a control method with two components to suppress hand vibrations. The first is a passive suppression method that lowers the joint stiffness to passively dampen the hand vibrations. The second is an active suppression method that adjusts an equilibrium point based on skyhook control to actively dampen the hand vibrations. In a simulation experiment, we applied these two methods to dampen hand vibrations during the shoulder’s horizontal oscillation. We also conducted a measurement experiment wherein a subject’s shoulder was sinusoidally oscillated by a platform that generated horizontal oscillations. The results of the measurement experiments showed that the jerk of each part of the arm in a task using a cup filled with water was smaller than the shoulder jerk and that in a task with a cup filled with stones was larger than the shoulder jerk. Moreover, the amplitude of the hand trajectory in both horizontal and vertical directions was smaller in a task using a cup filled with water than in a task using a cup filled with stones. The results of the measurement experiments were accurately reproduced by the active suppression method based on skyhook control. These results suggest that humans dampen hand vibrations by controlling the equilibrium point through the information of the external workspace and the internal body state rather than by lowering joint stiffness only by using internal information.     

Electrochemical engineering approach to the irrigation of tooth canals under the influence of a vibrating file

Doubt exists concerning the irrigation of secondary tooth canals when the vibration of a file introduced into the main root canal is superimposed on flow-through irrigation of the main canal. Depending on the type of commercial equipment used, the vibrations of the file are sonic or ultrasonic. We use the methodology of an electrochemical engineering approach in a study of the intensity of the irrigation of the secondary canals under the influence of sonic and ultrasonic vibrations of a file located at various heights in the main canal. The tooth canals are simulated by small electrochemical cells containing electrodes located at the end of cavities simulating the secondary canals. An electrochemical method is used to measure the mass transfer coefficients at these electrodes, a classical method in electrochemical engineering laboratories. The values of the mass transfer coefficients are representative of the importance of the irrigation of the electrodes. Thus they give a quantitative idea of the vibrations on the irrigation of secondary tooth canals. The work demonstrates the usefulness of the electrochemical engineering approach in contributing to the solution of a biomedical problem.     

Bending vibrations of the femur and the oscillatory behavior of a cemented femoral hip endoprosthesis

The paper presents a novel method for recording amplitude and phase of 6D-vibrations of a spatial pendulum over a wide frequency range (10 Hz up to 20 kHz). The six degrees of freedom of the pendulum mass were monitored by three electrodynamic stereo pickups. At rest, the tips of the needles and the pendulum's center of mass defined the reference system with respect to which the oscillations of the mass were recorded in terms of their amplitudes and phases. Its small dimensions, constant transfer characteristics, linearity, high dynamics, and virtual lack of reaction onto the moving system over the entire frequency range provided the advantages of the measuring system. This method was used to analyze the spatial 6D-vibrations of the head of a cemented femoral hip endoprosthesis when the femur was stimulated to bending vibrations. The head of the prosthesis carried out axial rotational vibrations at every frequency used to stimulate the femur. The amplitudes of the axial rotations of the cortical bone were small in comparison to the ones of the prosthesis head, indicating that axial rotational vibrations following femur bending vibrations mainly stressed the spongiosa and the cement layer. This was observed over the entire frequency range, including at the low frequencies relevant for gait. Over the low-frequency range, as well as at some of the higher resonance frequencies, stationary instantaneous helical axes characterized the vibrations. The measurements suggest the mechanism that the interface "implant-bone" may already be stressed by axial torsional loads when the femur is loaded by bending impacts that are known to occur during walking.     

A technique for the measurement of cadence using walkway vibrations

A new method has been developed to measure cadence while walking. The method uses instrumentation to detect the vibrations transmitted in the walkway surface. These vibrations are produced when a subject's foot makes initial contact with the walking surface. The method was tested against heel switches and was found to measure stride duration with RMS errors of around 1%. The vibration method requires no instrumentation to be attached to the subject, can be used with bare feet or any other footwear, is simple to use and is very robust and reliable.     

Quantification of the input signal for soft tissue vibration during running

Soft tissue compartment vibrations are initiated at heel-strike in heel-toe running. The concept of muscle tuning suggests that the body tries to minimize these vibrations with a muscle adaptation that changes the mechanical properties of the soft tissue compartment. A muscle tuning adaptation can be quantified by determining the biodynamic response, of the soft tissue compartment for different experimental conditions. To determine the biodynamic response a measure of both the input signal and the soft tissue compartment vibrations are required. The input signal for the vibrations is the rapid deceleration of the leg after initial ground contact. The aim of this study was to evaluate three non-invasive methods to quantify the input signal for the triceps surae soft tissue vibrations. Data from a force platform, a shoe mounted accelerometer and a video analysis of a reflective skin marker were used to quantify leg deceleration. Both the shoe mounted accelerometer and skin marker method provided a satisfactory evaluation of the input signal and could be used to determine the biodynamic response of the soft tissue compartment. The impact portion of the ground reaction force is primarily due to the deceleration of the leg at landing. However, due to the influence of the effective body mass on the impact magnitude, the force plate data was not appropriate for quantifying a muscle tuning response.     

Assassin bug uses aggressive mimicry to lure spider prey

Assassin bugs (Stenolemus bituberus) hunt web-building spiders by invading the web and plucking the silk to generate vibrations that lure the resident spider into striking range. To test whether vibrations generated by bugs aggressively mimic the vibrations generated by insect prey, we compared the responses of spiders to bugs with how they responded to prey, courting male spiders and leaves falling into the web. We also analysed the associated vibrations. Similar spider orientation and approach behaviours were observed in response to vibrations from bugs and prey, whereas different behaviours were observed in response to vibrations from male spiders and leaves. Peak frequency and duration of vibrations generated by bugs were similar to those generated by prey and courting males. Further, vibrations from bugs had a temporal structure and amplitude that were similar to vibrations generated by leg and body movements of prey and distinctly different to vibrations from courting males or leaves, or prey beating their wings. To be an effective predator, bugs do not need to mimic the full range of prey vibrations. Instead bugs are general mimics of a subset of prey vibrations that fall within the range of vibrations classified by spiders as 'prey'.     

Parasitoid vibrations as potential releasing stimulus of evasive behaviour in a leafminer

Abstract. The aim of this study was to characterize the vibratory signals produced by the parasitoid Sympiesis sericeicornis Nees (Hymenoptera: Eulophidae) while foraging on apple leaves infested by one of its hosts, the spotted tentiform leafminer Phyllonorycter malella (Ger.) (Lepidoptera: Gracillariidae).This leafminer changes its behaviour as a function of the parasitoid's behaviour to escape parasitization.We propose that the leafminer uses vibrations triggered by the parasitoid to detect the presence of its enemy.We measured vibrations produced by a foraging parasitoid on a mine with a laser vibrometer.By recording concurrently the behaviour of the parasitoid on video, vibrations could be assigned to particular behaviours.Subsequently, vibrations were characterized by their dominant frequencies and intensities.The behaviours Landing and Take-off both produced strong impact-like vibrations characterized by an initial irregular phase during which frequencies up to 25 kHz occurred followed by a slow decaying regular phase.Vibrations elicited by Moving, Standing and Probing showed no clear temporal pattern.During Probing , dominant frequencies of up to 5.6 kHz were observed frequently at intensities well above the background noise (>10 dB).During Moving and Standing , vibrations were more scarce and of lower frequencies and intensities.Due to their impact-like nature, vibrations produced by Landing and Take-off are probably not specific to the parasitoid.Vibrations produced by Moving and Standing are difficult to detect and not reliable because of their non-specificity.Therefore, only Probing provides a reliable and detectable source of information for the host.The vibrations elicited during Probing could account for the evasive behaviour that is observed in this and other leafminers.     

Sound production and chorusing behaviour in larvae of Icosium tomentosum

Substrate-borne vibrations produced by the larvae of non-lamiinae longicorn Icosium tomentosum Lucas, 1854 (Cerambycidae: Cerambycinae) are also emitted as loud sounds audible to humans. The vibrations consists of a long sequence of regularly repeated pulses at a rate of 8 pulses per second. The duration of the pulses are 0.061±0.009 s and the interpulse intervals are 0.065±0.015 s. The mechanism of vibration generation is the scraping by strongly sclerotised mandibles against the bark. Chorusing behaviour previously unknown in Cerambycidae larvae have been observed when the larvae feeding in the same or nearby branches starting to produce the audible vibrations in reaction to the vibrations of another larva.     

Remote photonic sensing of cerebral hemodynamic changes via temporal spatial analysis of acoustic vibrations

A novel photonic method for remote monitoring of task‐related hemodynamic changes in human brain activation is presented. Physiological processes associated with neural activity, such as nano‐vibrations due to blood flow and tissue oxygenation in the brain, are detected by remote sensing of nano‐acoustic vibrations using temporal spatial analysis of defocused self‐interference random patterns. Temporal nanometric changes of the speckle pattern due to visual task‐induced hemodynamic responses were tracked by this method. Reversing visual checkerboard stimulation alternated with rest epochs, and responsive signals were identified in occipital lobe using near‐infrared spectroscopy. Temporal vibrations associated with these hemodynamic response functions were observed using three different approaches: (a) single spot illumination at active and control areas simultaneously, (b) subspots cross‐correlation‐based analysis, and (c) multiwavelength measurement using a magnitude‐squared wavelet coherence function. Findings show remote sensing of task‐specific neural activity in the human brain.     

Stridulation in Aphodius Dung Beetles: Behavioral Context and Intraspecific Variability of Song Patterns in Aphodius ater (Scarabaeidae)

Aphodius dung beetles produce substrate vibrations by means of an abdomino-alary stridulatory organ. Applying a method that allows the recording of Aphodius vibrations under natural conditions in a small amount of dung, the stridulatory behavior of Aphodius ater was investigated. Male A. ater are acoustically active, while females rarely stridulate. Males have a complex song, which consists of a series of different patterns that are displayed in a specific order over a considerable time when a female is encountered in the dung. Different populations show the same stridulatory patterns but individual variability is high and males display songs with differing complexity. It is hypothesized that females use the information within the song in the context of mate choice.     

Proposal for a method of non-restrictive measurement of resting heart rate in a lying position

Daily monitoring of heart rates is important in health management. Many researchers have analysed heart rate variability by using the resting heart rate because such an analysis can facilitate the early discovery of a variety of illnesses and health conditions. Some problems that arise in measuring heart rate are the feeling of confinement. Therefore, we required a system that could measure the resting heart rate in a static position in such a way that the subject is completely unaware that the measurement is being recorded. We propose a non-restrictive measurement method that uses only an acceleration sensor placed inside a down quilt. This method is easy for home use. The acceleration sensor was placed inside the quilt such that it was positioned opposite to the left-hand side of the subject's chest. Six healthy subjects were requested to lie in the supine position and were covered with the quilt equipped with the acceleration sensor. Mechanical vibrations that resulted from heart activity were carried through the quilt to the acceleration sensor. As a result, periodic vibrations were measured successfully, and in the six subjects, these vibrations were proved to be highly correlated with the R wave of electrocardiograms. The same results were obtained even when the subjects were lying in the left lateral position. The results indicated that our new method, which used an acceleration sensor placed inside a down quilt, was simple and could be used to measure the resting heart rate in a lying position.     

Vibration detection and discrimination in the masked birch caterpillar (Drepana arcuata)

Leaf-borne vibrations are potentially important to caterpillars for communication and risk assessment. Yet, little is known about the vibratory environment of caterpillars, or how they detect and discriminate between vibrations from relevant and non-relevant sources. We measured the vibratory ‘landscape’ of the territorial masked birch caterpillar Drepana arcuata (Drepanidae), and assessed its ability to detect and respond to vibrations generated by conspecific and predatory intruders, wind and rain. Residents of leaf shelters were shown to respond to low amplitude vibrations generated by a crawling conspecific intruder, since removal of the vibrations through leaf incision prevented the resident’s response. Residents did not respond to large amplitude, low frequency disturbances caused by wind and rain alone, but did respond to approaching conspecifics under windy conditions, indicating an ability to discriminate between these sources. Residents also responded differently in the presence of vibrations generated by approaching predators (Podisus) and conspecifics. An analysis of vibration characteristics suggests that despite significant overlap between vibrations from different sources, there are differences in frequency and amplitude characteristics that caterpillars may use to discriminate between sources. Caterpillars live in a vibration-rich environment that we argue forms a prominent part of the sensory world of substrate bound holometabolous larvae.     

Grunting for worms: seismic vibrations cause Diplocardia earthworms to emerge from the soil

Harvesting earthworms by a practice called 'worm grunting' is a widespread and profitable business in the southeastern USA. Although a variety of techniques are used, most involve rhythmically scraping a wooden stake driven into the ground, with a flat metal object. A common assumption is that vibrations cause the worms to surface, but this phenomenon has not been studied experimentally. We demonstrate that Diplocardia earthworms emerge from the soil within minutes following the onset of grunting. Broadband low frequency (below 500 Hz) pulsed vibrations were present in the soil throughout the area where worms were harvested, and the number of worms emerging decreased as the seismic signal decayed over distance. The findings are discussed in relation to two hypotheses: that worms are escaping vibrations caused by digging foragers and that worms are surfacing in response to vibrations caused by falling rain.     

Terahertz optical measurements of correlated motions with possible allosteric function

A suggested mechanism for allosteric response is the distortion of the energy landscape with agonist binding changing the protein structure’s access to functional configurations. Intramolecular vibrations are indicative of the energy landscape and may have trajectories that enable functional conformational change. Here, we discuss the development of an optical method to measure the intramolecular vibrations in proteins, namely, crystal anisotropy terahertz microscopy, and the various approaches which can be used to identify the spectral data with specific structural motions.     

Collective vibrations of an alpha-helix. A molecular dynamics study.

The internal dynamics of a 20-residue polyalanine helix was investigated by molecular dynamics simulations. Special attention was paid to the collective vibrations of the helix backbone. The stretch and bend vibrations could be assigned unambiguously to oscillations with periods of 1.4 and 4.3 ps, respectively. The influence of the environment on the dynamics of the collective vibrations was studied by coupling the helix to a heat bath and by adding water molecules. In the presence of water, the stretch vibration becomes more strongly dampened, but still exists as a vibration , while the bend vibration becomes overdamped and degenerates into a relaxation process. The results are compared with available experimental data.     

Effects of low frequency vibrations on the human spine

There is a general agreement in literature about effects of low frequency vibrations on spine in tractor drivers. Tractor drivers are exposed to noxious vibrations transmitted mostly by the seat. Spine generally presents a picture of degenerative lesions with higher incidence than in control groups. A statistical relation to the precocity of tractor driving can be shown.     

Vibratory stimuli in host location by parasitic wasps

Parasitic wasps use a broad spectrum of different stimuli for host location and host acceptance. Here we review the published evidence for the use of mechanical stimuli, i.e. substrate born vibrations which are invariably regarded as vibrotaxis. We propose a set of criteria to class behavioural reactions as vibrotaxis or vibrokinesis and characterize 14 studies reporting the use of host-associated vibrations by parasitoids. The studies are compared concerning (i) experimental design; (ii) characterisation of vibrational signals; and (iii) progress of the parasitoid towards the host.The recent experimental development based on new measurement techniques shows the growing body of evidence that host-associated vibrations are exploited by parasitic wasps. Nevertheless a definite proof for vibrotaxis is still lacking. To assess the exact mechanisms by which parasitoids use vibrations bioassays comparing reactions to natural and artificially generated signals are needed. Vibrotaxis as well as vibrokinesis are both helpful host location strategies for parasitoids foraging in a multimodal environment. At the community level they may lead to niche differentiation.     

A fluid-structure interaction problem in biomechanics: prestressed vibrations of the eye by the finite element method.

The object of this work has been to develop a mechanical and numerical model of the eye submitted to vibrations, and in particular, to calculate the influence of intraocular pressure (IOP) on the eye resonance frequencies. Our mechanical model of the eye relies upon the theory of the mechanics of continuous media. The numerical model results from a model analysis of the vibrations of the eye using a finite element method (FEM) for discretization. The eye can be schematically represented as a prestressed shell, filled by an inviscid barotropic compressible fluid, which leads us to formulate and solve a problem of vibrations of a coupled fluid-structure system. The corneoscleral shell has been modeled as a thin and thick shell, taking into account material nonlinearities in the thick case. Numerical results obtained for the attached eye demonstrate a fair sensitivity of the resonance frequencies to the variations of the IOP; thus, founding the interest of the surveillance of the resonance frequency of the eye.     

Soft-tissue vibrations in the quadriceps measured with skin mounted transducers

The purpose of this study was to develop a method to characterize the frequency and damping of vibrations in the soft tissues of the leg. Vibrations were measured from a surface-mounted accelerometer attached to the skin overlying the quadriceps muscles. The free vibrations in this soft tissue were recorded after impact whilst the muscle was performing isometric contractions at 0, 50, and 100% maximum voluntary force and with the knee held at 20, 40, and 60 degrees angles of flexion. The acceleration signals indicated that the soft tissue oscillated as under-damped vibrations. The frequency and damping coefficients for these vibrations were estimated from a model of sinusoidal oscillations with an exponential decay. This technique resolved the vibration coefficients to 2 and 7% of the mean values for frequency and damping, respectively.