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At least 1,171 records · Page 65Linked to original sources
PubMed1988

Bone conduction threshold levels for different bone vibrator types.

This study determined if bone conduction (BC) thresholds were influenced by vibrator type. BC thresholds were obtained for 100 subjects using mastoid placement of Radioear B-71 and B-72 and Pracitronic KH 70 bone vibrators. The nontest ear was masked (30 dB EL) and the ear ipsilateral to the vibrator was open except when testing at 3000 and 4000 Hz when the ear canal was occluded with an earplug to guard against acoustic radiation. BC thresholds at 250 Hz obtained with the B-72 and KH 70 were significantly (p less than .05) higher by 10.5 dB and at 500 Hz were significantly (p less than .05) lower by 5.5 dB than for the B-71. BC thresholds at other frequencies (1000, 2000, 3000, and 4000 Hz) were not significantly different among vibrator types. The findings indicated that reference equivalent threshold force levels (RETFLs) for BC audiometry should be specified by bone vibrator type.

Adult↗
PubMed2001

Maintenance of condylar position using an occlusal splint after mechanical vibrating-traction of the TMJ.

Although adequate relief of excess mechanical loading to the joint has been accepted as one of the important treatment concepts in the orthopaedic field, a treatment method for the temporomandibular joint (TMJ) to relieve excess mechanical loading has not yet been established. This study aimed to clarify the effect of an occlusal splint on the maintenance of the distracted condylar position achieved by vibrating-traction method. Vibrating dynamic traction force was applied for 5 min to the right TMJ using vibrating-traction apparatus. A flat stabilization splint was adjusted to keep the mandibular position and the condylar displacement was evaluated for 6 h after the dynamic traction procedure. Mean vertical displacement of the mandibular right first molar immediately after the vibrating-traction for the six subjects was 156 microm (ranging from 141 to 179 microm). The calculated mean condylar displacement immediately after the traction was 480 mum and could be kept to be 381 mum even after 6 h by wearing the flat stabilization splint. From the results of this study, it was revealed that the mechanically tracted condylar position could be maintained by a flat occlusal splint. It was suggested that the vibrating-traction method followed by the provision of occlusal support might have a possibility to work as a mechanical relieving procedure for the TMJ.

Adult↗
PubMed2002

Clinical versus quantitative vibration assessment: improving clinical performance.

In 3 large cohorts (total of 787 patients), clinical vibration impairment (CVI) of the great toe using a tuning fork was compared with quantitative vibration threshold (QVT). Using a stepwise multivariate analysis, we assessed demographic and anthropomorphic patient characteristics associated with the difference between CVI and QVT for the various cohorts and the chosen QVT ranges of percentile abnormality. We also compared CVI or QVT abnormality with a composite score of nerve conduction abnormality to confirm that QVT is a valid measure of severity of neuropathy. Highly significant associations between CVI and QVT were found in all 3 cohorts studied, regardless of the chosen QVT percentile level of abnormality. However, in the 2 cohorts evaluated by many different physicians, CVI overestimated QVT much more often than underestimated it. The discordance between CVI and QVT in all QVT abnormality percentile levels was associated with age, height and body surface area (BSA) in 1 cohort, with age and BSA in another cohort, and with age in the third cohort. In the third cohort, the correlation between QVT and the composite score of nerve conduction abnormality was significantly higher than the correlation between CVI and the composite score. Using a tuning fork, neuromuscular physicians overestimate vibration sensation loss more often than when QVT testing is done, which employs quantitative stimuli, a broad range of stimulus magnitudes, null stimuli, validated algorithms of testing and validated reference values. To improve assessment of vibration sensation, physicians should take into account age, height and weight (or body surface area) when judging vibration abnormalities. Applying some useful approaches to quantitative sensory testing might improve the accuracy of clinical sensory testing.

Adult↗
PubMed2002

Hand-arm-vibration syndrome (HAVS): is there a central nervous component? An fMRI study.

Hand-held vibrating tools may result in neuromuscular dysfunction and vasospastic problems of the hand. Sensory and motor dysfunction can be explained by injury to peripheral structures, but could also be due to changes in cortical somatotopic mapping of the hand in the brain. The purpose of the present study was to use functional magnetic resonance imaging (fMRI) to assess the somatotopic cortical representation of the hands of workers subjected to occupational vibration. The study included six men with severe vibration exposures who were suffering from hand-arm-vibration syndrome (HAVS) and six controls. The analysis focused on the pattern and degree of activation of contra- and ipsilateral hemispheres of the brain with tactile stimulation and motor activation of the hand. These stimulations resulted in well-defined activation of the contralateral, and to a lesser extent the ipsilateral hemisphere. Statistical analysis of this limited patient material did not indicate any significant somatotopic cortical changes following long-term exposure to vibrating hand-held tools, although there was a tendency to a shift of activation towards the more cranial parts of the cortex in the patient group.

Adult↗
PubMed2004

Fifth-order contributions to ultrafast spectrally resolved vibrational echoes: heme-CO proteins.

The fifth order contributions to the signals of ultrafast infrared spectrally resolved stimulated vibrational echoes at high intensities have been investigated in carbonmonoxy heme proteins. High intensities are often required to obtain good data. Intensity dependent measurements are presented on hemoglobin-CO (Hb-CO) and a mutant of myoglobin, H64V-CO. The spectrally resolved vibrational echoes demonstrate that fifth order effects arise at both the 1-0 and the 2-1 emission frequencies of the stretching mode of the CO chromophore bound at the active site of heme proteins. Unlike one-dimensional experiments, in which the signal is integrated over all emission frequencies, spectrally resolving the signal shows that the fifth order contributions have a much more pronounced influence on the 2-1 transition than on the 1-0 transition. By spectrally isolating the 1-0 transition, the influence of fifth order contributions to vibrational echo data can be substantially reduced. Analysis of fifth order Feynman diagrams that contribute in the vibrational echo phase-matched direction demonstrates the reason for the greater influence of fifth order processes on the 1-2 transition, and that the fifth order contributions are heterodyne amplified by the third order signal. Finally, it is shown that the anharmonic oscillations in vibrational echo data of Hb-CO that previous work had attributed strictly to fifth order effects arise even without fifth order contributions.

Carbon Monoxide↗
PubMed2006

Vibrational dynamics of DNA. II. Deuterium exchange effects and simulated IR absorption spectra.

In Paper I, we studied vibrational properties of normal bases, base derivatives, Watson-Crick base pairs, and multiple layer base pair stacks in the frequency range of 1400-1800 cm(-1). However, typical IR absorption spectra of single- and double-stranded DNA have been measured in D(2)O solution. Consequently, the more relevant bases and base pairs are those with deuterium atoms in replacement with labile amino hydrogen atoms. Thus, we have carried out density functional theory vibrational analyses of properly deuterated bases, base pairs, and stacked base pair systems. In the frequency range of interest, both aromatic ring deformation modes and carbonyl stretching modes appear to be strongly IR active. Basis mode frequencies and vibrational coupling constants are newly determined and used to numerically simulate IR absorption spectra. It turns out that the hydration effects on vibrational spectra are important. The numerically simulated vibrational spectra are directly compared with experiments. Also, the (18)O-isotope exchange effect on the poly(dG):poly(dC) spectrum is quantitatively described. The present calculation results will be used to further simulate two-dimensional IR photon echo spectra of DNA oligomers in the companion Paper III.

Base Pairing↗
PubMed2004

Coherent vibrational climbing in carboxyhemoglobin.

We demonstrate vibrational climbing in the CO stretch of carboxyhemoglobin pumped by midinfrared chirped ultrashort pulses. By use of spectrally resolved pump-probe measurements, we directly observed the induced absorption lines caused by excited vibrational populations up to v = 6. In some cases, we also observed stimulated emission, providing direct evidence of vibrational population inversion. This study provides important spectroscopic parameters on the CO stretch in the strong-field regime, such as transition frequencies and dephasing times up to the v = 6 to v = 7 vibrational transition. We measured equally spaced vibrational transitions, in agreement with the energy levels of a Morse potential up to v = 6. It is interesting that the integral of the differential absorption spectra was observed to deviate far from zero, in contrast to what one would expect from a simple one-dimensional Morse model assuming a linear dependence of dipole moment with bond length.

Carboxyhemoglobin↗
PubMedDate not supplied

Current perception thresholds in vibration-induced neuropathy.

The authors evaluated the usefulness of current perception threshold testing for the assessment of vibration-induced neuropathy. The study population comprised 20 male controls and 59 males with hand-arm vibration syndrome. Current perception threshold at three test frequencies (i.e., 5 Hz, 250 Hz, and 2,000 Hz) was determined on the distal phalanges of the index and little fingers. Large myelinated fibers, small myelinated fibers, and unmyelinated fibers were evaluated selectively at 2,000-Hz, 250-Hz, and 5-Hz frequencies, respectively. The vibration-induced neuropathy groups had significantly increased current perception thresholds in both the index and little fingers. There was a significant increase in current perception threshold for the myelinated fibers, but not the unmyelinated fibers. The diagnostic sensitivity for vibration-induced neuropathy was relatively high. It appeared that current perception threshold evaluation was useful for the assessment of vibration-induced neuropathy.

Aged↗
PubMed1993

Vibration on poultry transporters.

1. This research established the magnitudes and frequencies of vibration acceleration on two typical broiler bird transporters, one with leaf and the other with air suspension. 2. Vibration measurements were made using triaxial accelerometers mounted on the chassis and in the bird containers, with vehicles both loaded and unloaded. 3. In the vertical axis the fundamental vehicle frequency is between 1 and 2 Hz with a secondary peak at 10 Hz. 4. In the lateral axis with air suspension, the maximum level of vibration on the chassis occurred at 12 to 18 Hz; this was less evident with leaf suspension. 5. The magnitudes of vibration acceleration occurring in the bird containers would be fairly uncomfortable for the seated human. Frequency weightings and response to different axes and magnitudes of vibration must be established before the response of birds can be predicted.

Animals↗
PubMed2003

In-vehicle vibration study of child safety seats.

This paper reports experimental measurements of the in-vehicle vibrational behaviour of stage 0&1 child safety seats. Road tests were performed for eight combinations of child, child seat and automobile. Four accelerometers were installed in the vehicles and orientated to measure as closely as possible in the vertical direction; two were attached to the floor and two located at the human interfaces. An SAE pad was placed under the ischial tuberosities of the driver at the seat cushion and a child pad, designed for the purpose of this study, was placed under the child. Four test runs were made over a pave' (cobblestone) surface for the driver's seat and four for the child seat at both 20 km h(-1) and 40 km h(-1). Power spectral densities were determined for all measurement points and acceleration transmissibility functions (ATFs) were estimated from the floor of the vehicle to the human interfaces. The system composed of automobile seat, child seat and child was found to transmit greater vibration than the system composed of automobile seat and driver. The ensemble mean transmissibility in the frequency range from 1 to 60 Hz was found to be 77% for the child seats systems as opposed to 61% for the driver's seats. The acceleration transmissibility for the child seat system was found to be higher than that of the driver's seat at most frequencies above 10 Hz for all eight systems tested. The measured ATFs suggest that the principal whole-body vibration resonance of the children occurred at a mean frequency of 8.5, rather than the 3.5 to 5.0 Hz typically found in the case of seated adults. It can be concluded that current belt-fastened child seats are less effective than the vehicle primary seating systems in attenuating vibrational disturbances. The results also suggest the potential inability of evaluating child comfort by means of existing whole-body vibration standards.

Acceleration↗
PubMed1990

Back pain and exposure to whole body vibration in helicopter pilots.

In a questionnaire survey the prevalence of back pain in 163 helicopter pilots was compared to that in a control group of 297 non-flying air force officers who underwent the same pre-employment medical examination. Since pilots document their hours of flight in a personal flight log, an accurate estimate of the duration of exposure could be made. In addition, vibration levels of the helicopters were measured and an accumulative vibration dose was calculated for each pilot. 'Transient' back pain of a short duration was more frequent amongst the pilots compared to the control group, and the prevalence of 'chronic' back pain of a persistent nature was also higher amongst the helicopter pilots. Transient back pain seemed to be most strongly related to the average hours of flight per day, whereas chronic back pain was more closely related to total hours of flight or the accumulative vibration dose. A significant higher prevalence of this chronic back pain was observed only after 2000 hours of flight or a vibration dose of 400 m2h/s4. The observed health effects may be due to vibration or constrained posture but are most likely due to concomitant exposure to both factors.

Adult↗
PubMed1995

Mechanisms of vibration-induced interference with manual control performance.

An experiment is described in which eight subjects performed three simple tasks (A, B and C) in static conditions and during exposure to whole-body vertical (z-axis) vibration at 0.5 and 4.0 Hz, at an acceleration magnitude of 2.1 ms-2 r.m.s. All subjects performed all conditions with and without an arm support. The objective was to explore the mechanisms that may cause disruption of manual control performance during vibration exposure. With task A subjects simply held a control with no visual feedback of activity at the control. With task B, subjects used the control to hold a controlled element stationary on a display. Task C was the same as task B, except that subjects had improved visual feedback of movement of the controlled element. Results showed that both 0.5 and 4.0 Hz vibration caused significant increases in control activity at frequencies of up to about 1 Hz compared with the condition without vibration. With visual feedback in task C, subjects were able to detect drifting of the controlled element on the display and introduced compensatory control activity at frequencies above about 0.2 Hz. The arm support reduced the magnitude of vibration transmitted to the control at 4.0 Hz, but did not otherwise change the results.

Aircraft↗
PubMed1978

Myocardial depressant effect of vibrations in the isolated rabbit heart.

A working rabbit heart preparation was developed in which vibrations could be induced in the left ventricular outflow tract. The vibrations were produced by a special vibrator from which a metal pin was connected to a thin metal plate sutured onto the left ventricle. Vibrations of 0.3, 0.6 and 1.2 mm amplitude and frequencies of 50, 80 and 100 Hz were used. Increasing amplitudes or frequencies resulted in more pronounced reduction of cardiac output, aortic flow and left ventricular peak systolic pressure. The left ventricular end diastolic pressure increased at higher amplitudes or frequencies. The coronary flow was not significantly changed. It is suggested that vibrations of the ventricular wall might be a myocardial depressant factor of importance in valvular heart disease.

Animals↗
PubMed2007

Whole-body vibration can reduce calciuria induced by high protein intakes and may counteract bone resorption: A preliminary study.

Excess protein intake can adversely affect the bone via an increase in calcium excretion, while suitable mechanical loading promotes osteogenesis. We therefore investigated whether vibration exposure could alleviate the bone mineral losses associated with a metabolic acidosis. Ten healthy individuals aged 22 - 29 years (median = 25) underwent three 5-day study periods while monitoring their dietary intake. The study consisted of recording the participants' usual dietary intake for 5 consecutive days. Participants were then randomly divided into two groups, one of which received a protein supplement (2 g x kg(-1) body mass x day(-1); n = 5) and the other whole-body low-magnitude (3.5 g), low-frequency (30 Hz) mechanical vibration (WBV) delivered through a specially designed vibrating plate for 10 min each day (n = 5). Finally, for the third treatment period, all participants consumed the protein supplement added to their normal diet and were exposed to WBV exercise for 10 min per day. Daily urine samples were collected throughout the experimental periods to determine the excretion of calcium, phosphate, titratable acid, urea, and C-telopeptide. As expected, when the participants underwent the high protein intake, there was an increase in urinary excretion rates of calcium (P < 0.001), phosphate (P < 0.003), urea (P < 0.001), titratable acid (P < 0.001), and C-telopeptide (P < 0.05) compared with baseline values. However, high protein intake coupled with vibration stimulation resulted in a significant reduction in urinary calcium (P = 0.006), phosphate excretion (P = 0.021), and C-telopeptide (P < 0.05) compared with protein intake alone, but did not affect titratable acid and urea output. The participants showed no effect of WBV exercise alone on urinary excretion of calcium, phosphate, urea, titratable acid, or C-telopeptide. The results indicate that vibration stimulation can moderate the increase in bone resorption and reduction in bone formation caused by a metabolic acidosis.

Acidosis↗
PubMed1990

Vibration thresholds as a function of age and diagnosis of carpal tunnel syndrome: a preliminary report.

To determine if vibration thresholds vary independently with age and carpal tunnel syndrome (CTS), 61 subjects, including 27 diagnosed with carpal tunnel-induced neuropathy, and 34 non-CTS controls, ranging in age from 20 to 65 years, were tested using the Optacon, a device used to assess vibration thresholds. No statistically significant interaction was found between the age and diagnosis factors. Results did confirm the findings of previous studies that vibration thresholds increased with age and that thresholds were elevated within the CTS group, compared to the controls. These results indicate that age-adjusted norms for vibration threshold data need to be developed. Without age-adjusted norms, screening programs for CTS that rely on vibration threshold data are likely to generate high levels of false positives, particularly for workers over 40 years of age.

Adult↗
PubMed2003

The vibrations of texture.

The Pacinian channel has been implicated in the perception of fine textures (Hollins et al., Somatosens Mot Res 18: 253-262, 2001a). In the present study, we investigate candidate codes for Pacinian-mediated roughness perception. We use a Hall effect transducer to record the vibrations elicited in the skin when a set of textured surfaces is passively presented to the index finger. The peak frequency of the vibrations is found to decrease systematically as spatial period increases. The power of the vibrations--weighted according to the spectral sensitivity of the Pacinian system--increases with spatial period for all but the coarsest surfaces. By varying the scanning velocity, we manipulate the temporal and intensive characteristics of the texture-induced vibrations and assess the effect of the manipulation on perceived roughness. We find that doubling the scanning velocity does not result in the substantial decrease in roughness predicted by a frequency theory of vibrotactile roughness perception. On the other hand, the effects of speed on roughness match those of speed on power. We propose that the roughness of a fine surface (spatial period<200 microm) is a function of the Pacinian-weighted power of the vibrations it elicits.

Adult↗
PubMed2004

Vibration as a possible explanation for putative electromagnetic field effects: a case study on marine diatoms.

PURPOSE: We examined the conjecture that mechanical vibration, being an uncontrolled and variable factor from one trial to another, might explain the inconsistency of results from investigations of the influence of extremely low frequency electromagnetic fields on the Ca-dependent motility of marine diatoms (Amphora coffeaeformis, strain #2038). MATERIALS AND METHODS: Owing to slight differences in culture of diatoms in previous studies, culture techniques are described in detail here. Diatoms showed maximal motility in logarithmic growth and motility was dependent on external [Ca], reducing at <.25 mM added Ca. Ninety-six different vertical vibration treatments were applied to the petri dishes containing the agar on which the diatoms were placed. The envelope of amplitudes varied from 50-500 pmicro at 10Hz to 100 nm-l1mmicro at 500 Hz. RESULTS: No significant effect of the mechanical vibrations on the motility response of diatoms was observed. We were unable to impose deliberate vibrations in a horizontal direction though some component of horizontal movement was probably present in our tests. CONCLUSIONS: The results imply that the variability of earlier experiments with extremely low frequency electromagnetic fields is unlikely to be ascribable to mechanical vibration.

Animals↗
PubMed2003

Short daily exposure to hand-arm vibrations in Swedish car mechanics.

The aim of the study was to examine the daily exposure times to hand-arm vibrations in Swedish car mechanics, to test a method for estimating the exposure time without observing the workers for whole days, and to use the results for predicting the prevalence of vibration-induced white fingers (VWF) by the ISO 5349-model. Six garages were surveyed. In each garage, 5-10 car mechanics were observed in random order every 30 seconds throughout working days. The daily exposure time for each mechanic was estimated from the fraction of the observations that the mechanic was exposed. A total of 51 mechanics were observed, most of them on two different working days, yielding estimates for 95 days. The median effective exposure time was 10 minutes per day (95% confidence interval 5-15 minutes, arithmetic mean 14 minutes, maximum 80 minutes), and most of the exposure time was attributable to fastening and loosening nuts. The within-worker and between-worker variability was high (total sigma2 0.99, geometric standard deviation of 2.7). Using the observed exposure time and data on vibration levels of the main tools in Swedish car mechanics (average weighted acceleration level of 3.5 m/s2), the model in ISO-standard 5349 would predict that only three percent of the car mechanics will suffer from VWF after 20 years of exposure. In contrast, a recent survey of VWF showed the prevalence to be 25 percent. The precision of the observation method was estimated and was found to be good for the group daily mean. On the individual level the precision was only acceptable if the daily exposure time was > or = 40 minutes. In conclusion, the daily exposure time was short and the vibration level was limited. Nevertheless, hand-arm vibrations cause VWF in a significant number of car mechanics. The method of observing workers intermittently seemed to work well.

Arm↗