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At least 811 records · Page 45Linked to original sources
PubMed1993

Abdominal vibration alters sleep state in fetal sheep.

Many pregnant women are exposed to low frequency sounds and vibrations while at work or play. How the fetus is affected by these physical stimuli is not clearly documented. We recorded behavioral state and intrauterine sound pressure levels in eight fetal sheep previously instrumented with electrocortical, electroocular and neck electromyographic leads, and with a miniature hydrophone. Data were collected before, during and after 30 min of abdominal vibration using a belt vibrator commonly used by humans in weight reduction programs. A sudden shift in behavioral state occurred at the onset of vibration. There was a decrease in non-rapid eye movement sleep (P < 0.02) and an increase in time during which the sleep state could not be determined (P < 0.03). A 63% increase in number of epochs spent in this indeterminate period was evident during vibration. During the post-stimulus period, percentage of time spent in rapid eye movement sleep decreased as compared to the pre-stimulus period (P < 0.04), and non-rapid eye movement sleep increased as compared to the stimulus period (P < 0.01). Vibration-induced intrauterine sound pressures ranged from 131-142 dB at the fundamental frequency of 19 Hz and were 20-40 dB lower at the overtones which appeared in the spectrum between 35-200 Hz. Results indicated that environmental vibration can disrupt fetal behavioral state, induce abnormal state changes, and alter distribution of sleep states.

Acoustic Stimulation↗
PubMed1993

Effect of vibrations on the organism--possibilities for development of non-specific diseases and their prognostication.

Changes in the lipid metabolism, electrolytes, trace elements, acid-base balance in experimental animals and in workers exposed to vibrations, as well in patients suffering from vibration disease were investigated. The role of vibrations as a modifier of chemically induced cancerogenesis, and in implanted tumour cells was studied under laboratory conditions. A study was carried out on the morbidity with temporal work incapacity and total morbidity according to the turnover of the investigated groups (workers and patients suffering from vibration disease) in industrial branches with exposure to vibrations. Using statistical and mathematical methods of dispersion, correlation, factor and discriminant analysis, we detected interrelations between the investigated non-specific and specific indices of vibration exposure on the one hand, and possibilities for the development and the prognostication of cardiovascular, osteo-arthritic and other diseases and pathologic states, non-specific for vibration exposure, on the other hand.

Acid-Base Equilibrium↗
PubMed1977

[Vibrations as an experimental factor affecting intestinal resorption].

The authors treated white rats daily at one and the same time for a period of one hour with vibrations. One of the groups of animals were treated with vibrations and examined after that, but the other two groups were treated respectively for 45 and 90 days. Examination was carried out during vibration, immediately after that and three hours after the vibrations. They used the method of the turned bags of Wilson and Waisman, by means of which they checked the resorption of glucose through the intestinal wall in vitro, it was established that during continuous vibration action the values of the resorption glucose were statistically lower than those of the control group. There were statistically significant differences in the values of the resorbed glucose in the subgroups examined during the vibration immediately and there hours after that. The authors discuss the obtained results in the light of the current concepts for the action of vibrations as a stress factor and their influence on intestinal resorption.

Animals↗
PubMed1996

Reduction of the vibration of the hand-arm system by optimization of rotary hammer drills.

When operating a hand-held vibrating power tool, for example impact drills and rotary hammers, high vibration loads are introduced into the hand-arm system of the operator. In the long run these mechanical vibrations can lead to health problems of the hand-arm system. Hammer drilling tools for treatment of mineral materials are offered with many different designs of the cutting edge in the diameter range between 16 mm and 50 mm. In this research project the influences of the cutting edge design of drilling tools on the vibration characteristics of rotary hammers are investigated. The vibration exposure of the hand-arm system due to the tool and the volume of chip production are regarded. The gauge being a combination of the weighted acceleration and the drilling capacity. Based on the current spectrum of drillings tools neutral test have been developed to examine geometrical parameters. Both sets of drilling tools have been subjected to the same test programme. The analysis of the results led to the definition of the characteristics of an optimized rotary hammer drilling tool. Lists of criterions have been developed for the different groups of tools. Using these it is possible to create drilling tools optimized for vibration exposure. This was demonstrated by prototype drilling tools. The comparison of the results showed, that the averaged volume of chip production could be significantly improved by modifying the design of the drilling tools retaining the weighted acceleration. The comparison also showed that the total vibration severity parameter decreased.

Arm↗
PubMed1996

Hand-arm vibration hazard and prevention in China.

The status of the hand-arm vibration exposure and action for reducing vibration risk in China is outlined. The survey indicated that more than three million workers are exposed to hand-arm vibration. The vibration syndrome has been reported in sixteen provinces; over ten industries and twenty types of job. The measurement and assessment were conducted on twenty-four types of vibrating tools under normal working condition. The investigation of preventive measures is described, which includes the development of anti-vibration tools, improvement of technological processes, personal protection. A series of standards and regulations involving local vibration drawn up and published since 1980s is reviewed.

Arm↗
PubMedDate not supplied

Limitation of small-solute exchange across the visceral peritoneum: effects of vibration.

OBJECTIVE: To evaluate the importance of the peritoneal membrane diffusion resistances to small solutes prevailing outside the capillaries in the visceral versus the parietal peritoneum during acute peritoneal dialysis (PD). DESIGN: Experimental study in anesthetized Wistar rats undergoing PD in a single exchange (120 min) using 1.36% Dianeal as dialysis fluid. Vibration, using a standard laboratory shaker at 10 Hz, was used to induce dialysate mixing and reduce the impact of "unstirred layers" in intact and eviscerated rats. Nonvibrated rats served as controls. MEASUREMENTS: The mass transfer area coefficient (PS) for chromium 51-ethylenediamine tetraacetic acid (51 Cr-EDTA), continuously infused intravenously, the plasma-to-peritoneal clearance (Cl-->D) of radioiodinated (125I) serum albumin (human)(RISA), as well as the total clearance out of the peritoneal cavity (Cl) of Evans blue labeled albumin, given as an intraperitoneal volume marker, and the portion of this Cl reaching the plasma per unit time (Cl-->P) were assessed. RESULTS: In intact rats there was a marked increase in PS for 51 Cr-EDTA, from 0.297 +/- 0.036 mL/min to 0.642 +/- 0.122 mL/min (n = 7, p < 0.01), and a moderate increase in Cl and Cl-->D, from 37.6 +/- 1.3 microL/min to 63.3 +/- 9.0 microL/min and from 6.04 +/- 0.51 microL/min to 9.54 +/- 0.93 microL/min (n = 7, p < 0.05), respectively, upon vibration. However, the plasma absorption clearance of albumin (Cl-->P) was unchanged after vibration. Furthermore, in eviscerated rats, vibration caused no significant changes in either of the exchange parameters measured. CONCLUSION: In conclusion, the visceral peritoneal transport of small solutes is normally limited by the presence of diffusion resistance outside the capillaries, which may be markedly reduced by "stirring" of the dialysate by vibration. Normally, the parietal, rather than the visceral, peritoneum is the major site for small-solute mass transfer in stationary animals. However, the visceral peritoneum apparently becomes increasingly important after stirring. The moderate increases in transperitoneal clearances of macromolecules occurring upon vibration, which were quite unexpected, indicate that vibration may also increase the dialysate/peritoneal membrane contact and/or cause some recruitment of capillaries.

Animals↗
PubMed1995

Involvement of endothelin in peripheral circulatory change induced by hand-arm vibration.

Physiologic mechanisms involving local vasoregulating factor, endothelium-derived relaxing factor (EDRF) and endothelium-derived constricting factors (EDCF) have been postulated to play a role in VWF. Recent evidence that endothelin is a potent vasoconstrictor peptide indicates that it may play a role in vasoregulation during vibration exposure through the local actions of EDRF or EDCF. Therefore, we examined the effects of grasping (50 N) and hand-arm vibration with an unweighted acceleration of 50 m/s2 rms at a frequency of 120 Hz in the direction of X-axis on digital blood flow (DBF) and on the level of plasma endothelin in 7 healthy male office workers. DBF was measured by an apparatus based on the thermal diffusion method where the thermal diffusion flow probe was incorporated in the Peltier's stack. In the grasping test, DBF decreased by about 40% from resting level within 1 minute after the grasping was begun, and was maintained at almost the same level during grasping, but increased immediately after cessation of grasping. In the vibration exposure test, initial decrease in DBF due to grasping was the same as that observed in the grasping test, but DBF gradually increased when exposure to vibration was performed simultaneously. No significant change in plasma endothelin level was induced by grasping. Endothelin was significantly lower after exposure to vibration than at rest and after grasping. The grasping-induced decrease in DBF seemed to be due to mechanical compression of the vessels. The negative correlation between DBF and endothelin during vibration exposure suggests that a reduction in release of endothelin from smooth muscle into the vessel cavity during vibration leads to vasodilatation, possibly attributable to the local axon reflex.

Blood Flow Velocity↗
PubMed1995

Assessment of heat pain perception in relation to vibration exposure.

The effect of vibration on thin unmyelinated sensory fibers was studied by perception threshold measurement of heat pain. The investigation was a cross-sectional study of 98 vibration-exposed and 53 non-vibration-exposed workers. Pain perception was determined by using the "Marstock" method. The perception threshold of contact heat induced pain was assessed by the method of limits. Quantified personal energy-equivalent vibration exposure was assessed for all subjects on a group basis. The cumulated lifetime equivalent frequency-weighted vibration exposure was estimated based on measurements according to ISO 5349. The mean heat perception threshold was 46.2 degrees C (SD 2.6 degrees C) for the right hand and 46.0 degrees C (SD 2.7 degrees C) for the left. The results showed no mean difference (left = 0.1 degree C, right = 0.6 degree C) in heat pain perception between vibration-exposed and non-exposed subjects. There was a high correlation between the right and left hand measurements (r = 0.81). The risk (rate ratio) for impairment was 1.02 (95% CI 0.81-1.30) for the right hand and 1.00 (95% CI 0.79-1.26) for the left. The results of the study did not indicate any impairment as assessed by an increased perception threshold for heat pain. The lack of an increased heat pain threshold among the vibration-exposed workers in our study cannot exclude a possible lesional somatosensory influence from the exposure, as the lesional effect may also be a lowering of the threshold. The multiple and unrelated percepts of thermal sensations imply that it is not legitimate to draw conclusions about the total status of the small calibre afferents when testing only the heat pain perception.

Adult↗
PubMed1995

Screening of vibration-induced disorders in the building industry using digital tactilometry. Results of a field study.

As occupational physicians in the building industry, we observed among these workers a high frequency of vibration exposure, during different tasks. We intended to study vibration exposure effects on vibration perception thresholds measured by digital tactilometry in this population of construction workers. A cross-sectional field study was made, 405 subjects were examined; each of them answered a questionnaire, underwent a medical examination and performed a test measuring his vibration perception thresholds, 150 subjects constituted the reference group. A close relationship between age and thresholds among the non-exposed group was observed. A threshold normalization of age of study the 204 exposed subjects was applied. Two exposure indices allowing time dependency vibration exposure analysis were defined the present daily exposure and cumulated exposure. In the examined population, thresholds rise with the present daily exposure in hours per day for 125 Hertz, while no significant influence of cumulated exposure is apparent. It was also pointed out that subjects exposed more than one and a half hour per day have higher thresholds than reference subjects, even if they do not have any clinical neurological complaints. This results seems to indicate the infraclinical feature of the test. These results suggest that screening of hand-arm vibration exposed population should be developed using this method. As occupational physicians in the construction industry, practising in Paris and surrounding areas, the authors studied the relationship between neurological disorders measured by vibrotactile perception thresholds, and hand-arm vibration exposure, among workers. They present the results of a field study they led within their institute, in collaboration with the tested workers' firms, and with the financial participation of the French Ministry of Labour.

Adult↗
PubMed1995

Determination of "vibration emission values" for fastener driving tools (nailers).

Hand-held fastener driving tools (nailers, staplers, pinners) differ considerably from other vibrating tools in terms of mode of vibration. For satisfying the requirements of the Machinery Directive 89/392/EEC, including also the compulsory declaration of a characteristic vibration value, appropriate measuring methods had to be developed. The measuring method elaborated by the BIA and standardised under ISO 8662-11 takes into account existing regulations and, in particular, specifications applying to the standardised vibration measuring instrument. Apart from aspects related to measuring and working conditions, a particular problem consisted of excluding vibrations which are recorded although not generated by the tool. In addition, the use of vibration measuring instruments according to ISO 8041 was required, too. For these reasons a release cycle time was defined which is both a representative measure for the daily vibration dose and a compromise in terms of measuring accuracy. The paper presents first results obtained on the basis of the standard. It also gives an overview of the state of the art by indicating the load range as a function of the fastener size.

Acceleration↗
PubMed1995

Consideration of grip and push forces for the assessment of vibration exposure.

There is much influence of the coupling forces between hand and grip of the vibrating tool on the measuring results as well as on the vibration effects on the hand-arm system. In a research project the effects of grip and push forces on acute responses of the hand-arm system under vibration conditions have been studied. Using these results of the biodynamic response, vibration perception threshold and subjective vibration sensation a bonus/malus system for a correction of the measured frequency-weighted r.m.s. acceleration was drafted, to assess the hand-arm vibration at the workplace: Since there is no difference between the acute effects of grip force and push force, so the forces have to be added and defined as coupling force Fcf. On the basis of this coupling force Fcf a correcting factor cF may be calculated. The factor amounts to 0.6 at Fcf = 20 N, 1.0 at Fcf = 120 N and 1.1 at Fcf = 200 N. To correct the measured weighted r.m.s. acceleration ahwz (Fcf) depending on coupling forces the r.m.s. acceleration has to be multiplied with the correcting factor cF. The drafted procedure enables to assess vibration exposure depending on coupling forces in a standardized way.

Acceleration↗
PubMed1992

Technical characteristics of overhead cranes influencing the vibration exposure of the operators.

The study was undertaken to determine the technical factors responsible for the generation of vibration and shocks in overhead cranes and therefore responsible for complaints by the workers. Vibration measurements were made on the floor and on the seat of the cabin on 21 cranes. Vibration levels were correlated with the characteristics of the cranes. The study showed that vibration accelerations increased with the span of the crane and were very dependent upon the state of the runway. The type of speed regulation and the position of the cabin also play a significant role. The suspension systems of the cabin and the seat are clearly inadequate to give significant reduction of the vibration. In several cases, it was even shown to amplify the vibration in the most critical frequency range. These results should be taken into account by designers as well as maintenance services in order to prevent the development of vibration at the source.

Journal Article↗
PubMed1994

Effects of horizontal whole-body vibration on reading.

Text from a newspaper was read by seated subjects (8 male, 8 female) during exposure to fore-and-aft and lateral whole-body vibration. With narrow-band random vibration at frequencies between 0.5 Hz and 10 Hz and with vibration magnitudes between 0.63 m s(-2) rms and 1.25 m s(-2) rms, reading speed was measured and subject ratings of reading speed were obtained. During exposure to fore-and-aft vibration, the subjects' ratings suggested that reading speed was significantly reduced at frequencies between 1.25 Hz and 6.3 Hz, with greater impairment at higher magnitudes of vibration. Maximum interference with reading was reported at 4 Hz. Measures of reading speed showed that subjects consistently overestimated their reduction in reading speed. Lateral vibration produced similar results, but the effect was less than that with fore-and-aft vibration.

Journal Article↗
PubMed1997

Substrate vibrations elicit defensive behaviour in leafminer pupae.

Late instar larvae and pupae of the spotted tentiform leafminer Phyllonorycter malella (Ger.) (Lepidoptera: Gracillariidae) react with defensive behaviour when attacked by one of their parasitoids, the eulophid wasp Sympiesis sericeicornis Nees (Hymenoptera: Eulophidae). Vibrations produced during the insertion of the ovipositor into the mine are known to be important cues by which larvae detect the presence of their enemies. The aim of this study was to investigate which frequency components elicit defensive reactions in leafminer pupae using synthetic vibrations. Sine vibrations and bandlimited noise stimuli were offered to both free pupae and pupae concealed in their leafmines. Using Laser vibrometry we measured the vibrations experienced by pupae inside their mines and assessed the influence of the mine. Pupae were shown to react to substrate vibrations, and do so over a broad range of frequencies. Behavioural reactions to noise stimuli were stronger than to pure sine stimuli. Mine tissue attenuated vibration amplitudes of the input signal from 5.1 to 22.6dB. However, as response thresholds of concealed pupae were only twice as high as thresholds of free pupae (which is adequate to 3dB) pupae inside their mine were more sensitive than expected. This discrepancy is discussed both in terms of the conditions of pupae and in terms of mine structure. The results indicate that broadbandedness of vibrations produced by hunting parasitoids during ovipositor insertion into the mine may be a major criterion used by leafminers to perceive parasitoid presence and to escape ovipositor stings.

Journal Article↗
PubMed2001

Zero-point vibrational effects on proton shieldings: functional-group contributions from ab initio calculations.

We investigate the effects of zero-point vibrational motion on the nuclear magnetic shielding constants of a large number of organic molecules. The vibrational corrections include anharmonic contributions from the potential energy surface and harmonic contributions from the curvature of the property surface. Particular attention is paid to vibrational corrections to hydrogen shielding constants where we show that vibrational corrections may be substantial, ranging from about +0.50 to -0.70 ppm, and thus demonstrating that ignoring these effects may give errors in the chemical shifts by more than 1 ppm in certain extreme cases. These effects can therefore not be neglected when comparing calculated results with experiment, not even for the chemical shifts. However, we also demonstrate that the vibrational corrections to the hydrogen shieldings are to a large extent transferable from one molecule to another. We have tabulated functional vibrational corrections to the hydrogen shieldings, based on results for more than 35 molecules. Unfortunately, no similar transferability has been observed for the vibrational corrections to shielding constants of other nuclei such as carbon, nitrogen, or oxygen.

Journal Article↗
PubMed2005

New scale factors for harmonic vibrational frequencies using the B3LYP density functional method with the triple-zeta basis set 6-311+G(d,p).

We have calculated optimal frequency scaling factors for the B3LYP/ 6-311+G(d,p) method for fundamental vibrational frequencies on the basis of a set of 125 molecules. Using the new scaling factor, the vibrational frequencies calculated with the triple-zeta basis set 6-311+G(d,p) give significantly better accuracy than those calculated with the double-zeta 6-31G(d) basis set. Scale factors were also determined for low-frequency vibrations using the molecular set of 125 molecules and for zero-point energies using a smaller set of 40 molecules. We have studied the effect on the calculated vibrational frequencies for various combinations of diffuse and polarization functions added to the triple-zeta 6-311G basis set. The 6-311+G(d,p) basis set is found to give almost converged frequencies for most molecules, and we conclude that our optimum scaling factors are valid for the basis sets 6-311G(d,p) to 6-311++G(3df,3pd). The new scale factors are 0.9679 for vibrational frequencies, 1.0100 for low-frequency vibrations, and 0.9877 for zero-point vibrational energies.

Journal Article↗
PubMed2005

Ultrafast dynamics of myoglobin without the distal histidine: stimulated vibrational echo experiments and molecular dynamics simulations.

Ultrafast protein dynamics of the CO adduct of a myoglobin mutant with the polar distal histidine replaced by a nonpolar valine (H64V) have been investigated by spectrally resolved infrared stimulated vibrational echo experiments and molecular dynamics (MD) simulations. In aqueous solution at room temperature, the vibrational dephasing rate of CO in the mutant is reduced by approximately 50% relative to the native protein. This finding confirms that the dephasing of the CO vibration in the native protein is sensitive to the interaction between the ligand and the distal histidine. The stimulated vibrational echo observable is calculated from MD simulations of H64V within a model in which vibrational dephasing is driven by electrostatic forces. In agreement with experiment, calculated vibrational echoes show slower dephasing for the mutant than for the native protein. However, vibrational echoes calculated for H64V do not show the quantitative agreement with measurements demonstrated previously for the native protein.

Histidine↗
PubMed2006

Intramolecular vibrational energy redistribution involving the torsion in CF3CH3: a molecular dynamics study.

Classical trajectory calculations on intramolecular vibrational energy redistribution (IVR) involving the torsion in 1,1,1-trifluoroethane (TFE) are reported. Two potential energy functions (PEFs) are used to describe the potential energy surface. The "full" PEF gives excellent agreement with the experimental vibrational frequencies. The "simple" PEF omits nondiagonal interaction terms, but still gives very good agreement with the experimental frequencies. The "simple" PEF is intended to minimize mode-mode coupling. Neither PEF includes the HF elimination reaction. Calculations are carried out both with nominal microcanonical selection of initial coordinates and momenta, and with a modified selection method that places controlled amounts of energy in the torsion. Total (classical) vibrational energies from 0.005 to 140 kcal mol(-1) are investigated. The calculated time constants describing energy flow out of the torsional mode are <10 ps for classical vibrational energies near the classical reaction threshold energy (approximately 75 kcal mol(-1)) and greater. It is found that the rate of decay from the torsion largely depends on the amount of energy in the other vibrational modes. Analysis using power spectra shows that the torsional mode in TFE is strongly coupled to the other vibrational modes. These results strongly suggest that vibrational energy in TFE will not be sequestered in the torsion for time periods greater than a few tens of picoseconds when the molecule has enough energy to react via HF elimination.

Journal Article↗