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PubMed1988

The transmission of translational seat vibration to the head--I. Vertical seat vibration.

Vibration in the three translational (fore-and-aft, lateral and vertical) and the three rotational (roll, pitch and yaw) axes of the head has been measured during exposure to whole-body random vibration. Using an instrumented bar gripped between the teeth, the influence of variations in bite grip and bite-bar mass on movements of the head were found to be small up to a mass of 375 g. The repeatability of measures of seat-to-head transmissibility within a single subject and the variability in transmissibility across a group of twelve subjects have been determined with two seating conditions: a rigid seat with a backrest and the same seat with no backrest. Seat-to-head transmissibilities associated with vertical seat vibration are presented at frequencies up to 25 Hz for all six axes of head vibration both with and without a backrest. Head motion occurred principally in the fore-and-aft, vertical and pitch axes of the head. The backrest increased the magnitude of head vibration in most cases. Intra-subject variability was generally small compared to inter-subject variability.

Adult↗
PubMed1988

The transmission of translational seat vibration to the head--II. Horizontal seat vibration.

The second part of this study of the six axes of head motion caused by translational seat vibration is concerned with the effect of fore-and-aft (x-axis) and lateral (y-axis) seat vibration. Seat-to-head transmissibilities have been determined at frequencies up to 16 Hz for each of the three translational and three rotational axes of the head during exposure to random vibration of the seat. Repeatability measures within a single subject and studies of the variability across a group of twelve subjects have been conducted with two seating conditions: a rigid seat with a backrest, and the same seat with no backrest. Fore-and-aft seat motion mainly resulted in head motion within the mid-sagittal plane (x-z plane). Without the backrest, transmissibilities for the fore-and-aft, vertical and pitch axes of the head were greatest at about 2 Hz. The backrest greatly increased head vibration at frequencies above 4 Hz and caused a second peak in the transmissibility curves at about 6 to 8 Hz. Lateral seat motion mainly caused lateral head motion with a maximum transmissibility at about 2 Hz. The backrest had little effect on the transmission of lateral vibration to the head. For both axes of excitation inter-subject variability was much greater than intra-subject variability.

Head↗
PubMed2002

Ab initio vibration and ro-vibrational spectrum of the 1A1 state of He2Si2+.

The low-lying ro-vibrational states for the ground electronic state (1A1) of HeSi2+ have been calculated using an ab initio variational solution of the nuclear Schrödinger equation. A 96 point CCSD(T)/cc-pCVQZ potential energy surface (PES) has been calculated and a Ogilvie-Padé (3,6) potential energy function has been generated. This force field was embedded in the Eckart-Watson Hamiltonian from which the vibrational and ro-vibrational eigenfunctions and eigenenergies have been variationally calculated. A 70 point QCISD/aug-cc-pCVTZ discrete dipole moment surface (DMS) was calculated and a 5th order power series expansion (in terms of the two bond lengths and the included bond angle) has been generated. Absolute line intensities have been calculated and are presented for some of the most intense transitions between the vibrational ground state and the low-lying ro-vibrational states of this ion.

Algorithms↗
PubMed2002

Oxygen uptake in whole-body vibration exercise: influence of vibration frequency, amplitude, and external load.

Vibration exercise (VbX) is a new type of physical training to increase muscle power. The present study was designed to assess the influence of whole-body VbX on metabolic power. Specific oxygen uptake (sVO(2)) was assessed, testing the hypotheses that sVO(2) increases with the frequency of vibration (tested in 10 males) and with the amplitude (tested in 8 males), and that the VbX-related increase in sVO(2) is enhanced by increased muscle force (tested in 8 males). With a vibration amplitude of 5 mm, a linear increase in sVO(2) was found from frequencies 18 to 34 Hz (p < 0.01). Each vibration cycle evoked an oxygen consumption of approximately 2.5 micro l x kg(-1). At a vibration frequency of 26 Hz, sVO(2) increased more than proportionally with amplitudes from 2.5 to 7.5 mm. With an additional load of 40 % of the lean body mass attached to the waist, sVO(2) likewise increased significantly. A further increase was observed when the load was applied to the shoulders. The present findings indicate that metabolic power in whole-body VbX can be parametrically controlled by frequency and amplitude, and by application of additional loads. These results further substantiate the view that VbX enhances muscular metabolic power, and thus muscle activity.

Adult↗
PubMed2006

Vibrational dynamics of DNA. I. Vibrational basis modes and couplings.

Carrying out density functional theory calculations of four DNA bases, base derivatives, Watson-Crick (WC) base pairs, and multiple-layer base pair stacks, we studied vibrational dynamics of delocalized modes with frequency ranging from 1400 to 1800 cm(-1). These modes have been found to be highly sensitive to structure fluctuation and base pair conformation of DNA. By identifying eight fundamental basis modes, it is shown that the normal modes of base pairs and multilayer base pair stacks can be described by linear combinations of these vibrational basis modes. By using the Hessian matrix reconstruction method, vibrational coupling constants between the basis modes are determined for WC base pairs and multilayer systems and are found to be most strongly affected by the hydrogen bonding interaction between bases. It is also found that the propeller twist and buckle motions do not strongly affect vibrational couplings and basis mode frequencies. Numerically simulated IR spectra of guanine-cytosine and adenine-thymine bases pairs as well as of multilayer base pair stacks are presented and described in terms of coupled basis modes. It turns out that, due to the small interlayer base-base vibrational interactions, the IR absorption spectrum of multilayer base pair system does not strongly depend on the number of base pairs.

Base Pairing↗
PubMed2006

Vibrational dynamics of DNA. III. Molecular dynamics simulations of DNA in water and theoretical calculations of the two-dimensional vibrational spectra.

A theoretical description of the vibrational excitons in DNA is presented by using the vibrational basis mode theory developed in Papers I and II. The parameters obtained from the density functional theory calculations, such as vibrational coupling constants and basis mode frequencies, are used to numerically simulate two-dimensional (2D) IR spectra of dG(n):dC(n) and dA(n):dT(n) double helices with n varying from 1 to 10. From the molecular dynamics simulations of dG(5)C(5) and dA(5)T(5) double helices in D(2)O solution, it is found that the thermally driven internal motions of these systems in an aqueous solution do not induce strong fluctuations of basis mode frequencies nor vibrational couplings. In order to construct the two-exciton Hamiltonian, the vibrational anharmonicities of eight basis modes are obtained by carrying out B3LYP6-31G(*) calculations for the nine basis modes. The simulated 2D IR spectra of dG(n):dC(n) double helix in D(2)O solution are directly compared with closely related experimental results. The 2D IR spectra of dG(n):dC(n) and dA(n):dT(n) are found to be weakly dependent on the number of base pairs. The present work demonstrates that the computational procedure combining quantum chemistry calculation and molecular dynamics simulation methods can be of use to predict 2D IR spectra of nucleic acids in solutions.

Base Pairing↗
PubMed1993

The vibration characteristics of chain saws and their influence on vibration white finger disease.

The vibration from chain saws can cause vibration-induced white finger disease (VWFD). Measurements of vibration levels on the front and rear handles of different chain saw-types, and on the operator's middle finger were collected at three logging camps on Vancouver Island. Factors effecting the vibration levels on the finger and handles were investigated. The acceleration at the firing frequency was found to be the dominant factor effecting handle and finger vibration. Other factors which were investigated were: grip force; the presence of handle covers; and chain sharpening procedure. Weighted acceleration levels are calculated and this information is used to assess the latency period for fallers to develop VWF disease.

Equipment Design↗
PubMed1985

Relation of haemostatic function, neurovascular impairment, and vibration exposure in workers with different stages of vibration induced white finger.

Haemostatic function and neurovascular symptoms were investigated in 67 workers exposed to vibration and 46 comparable referents. Of these 65.6% of vibration workers complained of neurological disturbances (stages 0T, 0N of Taylor's classification for vibration induced white finger (VWF) and 20.9% suffered from Raynaud's phenomenon (stages 1-2-3). The severity of the staging symptoms showed a close relation with an index of vibration dose computed on the basis of vibration measurement and individual exposure time. Indices of platelet aggregation, both in vitro and in vivo, antithrombin III, fibrinogen and fibrinopeptide A levels were not different in the exposed workers compared with the referents. No relation was found between haemostatic parameters and the severity of VWF. Exposed workers responded to a cooling procedure with a more pronounced vasoconstriction in the digital vessels than the referents, as indicated by delayed recovery time of finger skin temperature after the cold test. These findings suggest that both in the early stages (0T, 0N) and in more severe stages of VWF (stages 1-2) cold induced hyperreactivity in the digital vessels and Raynaud's syndrome are vascular disorders of functional origin occurring without any prethrombotic alterations.

Adult↗
PubMed2007

Lateral vibration of a water drop and its motion on a vibrating surface.

The resonant modes of sessile water drops on a hydrophobic substrate subjected to a small-amplitude lateral vibration are investigated using computational fluid dynamic (CFD) modeling. As the substrate is vibrated laterally, its momentum diffuses within the Stokes layer of the drop. Above the Stokes layer, the competition between the inertial and Laplace forces causes the formation of capillary waves on the surface of the drop. In the first part of this paper, the resonant states of water drops are illustrated by investigating the velocity profile and the hydrostatic force using a 3d simulation of the Navier-Stokes equation. The simulation also allows an estimation of the contact angle variation on both sides of the drop. In the second part of the paper, we investigate the effect of vibration on a water drop in contact with a vertical plate. Here, as the plate vibrates parallel to gravity, the contact line oscillates. Each oscillation is, however, rectified by hysteresis, thus inducing a ratcheting motion to the water droplet vertically downward. Maximum rectification occurs at the resonant states of the drop. A comparison between the frequency-dependent motion of these drops and the variation of contact angles on their both sides is made. The paper ends with a discussion on the movements of the drops on a horizontal hydrophobic surface subjected to an asymmetric vibration.

Computer Simulation↗
PubMed1989

Human left ventricular wall vibration responded to precordial minute vibration.

We examined, noninvasively, the response of the left ventricular (LV) wall to precordially applied vibration in seven normal subjects. The LV posterobasal wall vibration was detected by an esophageal vibration sensor. Even though the amplitude of input vibration was maintained at a constant level, a sharp change in amplitude of the LV wall vibration was observed during the cardiac cycle, especially when 1) the subject was lying in a 45 degree left anterior oblique supine position, 2) the sensor was positioned at approx. 40 cm from the incisor teeth and 3) breath was at expiration. The pattern of this amplitude modulation changed with the input frequency. We concluded that the change in amplitude of output signal must have resulted from LV contraction and relaxation.

Adult↗
PubMed1997

[Effect of vibrational factors on the evaluation of whole-body vibrational intensity].

The aim of this study is to obtain basic data useful to evaluate the riding comfort of railway vehicles. The apparatus used in the present experiment made it possible to simulate various vibrations of railway vehicles. Twenty-two adult subjects participated in this experiment. They were exposed to lateral vibration with varying peak and root mean square (rms) accelerations and frequencies. The types and ranges of vibrations used in this experiment approximated to the typical vibrations of railway vehicles. The subjects were asked to rate the intensity of each vibration given to them successively, using the 7-step rating scale. Results indicated that both peak and rms accelerations significantly affected for the evaluation, although the effect of frequency was not significant. As for interactions, it was found that there were significant interacting effects between frequency and peak acceleration, between frequency and rms acceleration, and between peak and rms accelerations. It was also found that the relationship between the rms acceleration and the evaluated score changed with varying peak accelerations.

Adult↗
PubMed1990

[Pathogenesis of motor disorders in patients with vibration disease caused by local vibration (clinico-electroneuromyographic study].

The author provides the data on clinical, neurophysiological examinations of 195 patients suffering from vibration disease, stages I and II, due to local vibration. Three types of axonal injuries were established: axonal degeneration, demyelinization of the distal part of axon and demyelinization of its proximal part. All the three types of neural disorders were attended by synaptic alterations with a decrement of the M-response and the syndrome of "working in". The initial manifestations of neurophysiological pathology were axonal degenerative disorders with changes in neuromuscular transmission; on longer exposure to vibration there appeared the signs of demyelination. The length of service with vibrating tools is given fr the occupational groups with above-indicated neural disorders. The patterns of motor disorders did not depend on the type of vibrating tools, whereas the localization of the pathological alterations was related to the characteristic features of an industry.

Adult↗
PubMed1985

[Isotope capillary test in the diagnosis of a vascular form of vibration syndrome caused by local mechanical vibration].

The authors have compared evaluations of the rate of hand skin capillary flow at rest with the results of other studies used in the clinical diagnosis of the vibration syndrome resulting from the hand-transmitted vibrations. Multispecialist medical and auxiliary examinations including the radioisotopic capillary test, have been carried out in 78 patients referred to the Clinic because of suspected vibration syndrome. The values of flow at rest have been taken into account. In 34 patients the flow was slowed down. The lack of correlation between the slowed capillary flow at rest and clinical evaluation of pathological changes indicates a limited usefulness of the isotopic capillary test in the diagnosis of the vascular form of the vibration syndrome due to local vibrations.

Adult↗
PubMedDate not supplied

Studies on the transmission of vibrations in human organism exposed to low-frequency whole-body vibration.

Investigations were carried out in a group of 20 males with a definite morpho-physiological type, at two selected ranges of acceleration values chosen according to ISO criteria in the range of 2-20 Hz. In the subjects exposed to vibration the values of vibration acceleration were measured in different points along the spine at the levels of S3, L3, Th7, C3 and at the vertex. The investigations demonstrated that the frequency is the parameter of crucial significance for the propagation of vibrations in the human organism. Vibration within the frequency range up to 12 Hz affects the whole human organism, while the vibrations above 12 Hz have only a local effect.

Adult↗
PubMed2004

Labeling vibrations by light: ultrafast transient 2D-IR spectroscopy tracks vibrational modes during photoinduced charge transfer.

We report on a novel ultrafast two-dimensional infrared laser experiment that correlates vibrational bands of reactant and product of a photoreaction. The possibilities of this technique are demonstrated for the metal-to-ligand charge transfer (MLCT) in [Re(CO)3Cl(dmbpy)] (dmbpy = 4,4'-dimethyl-2,2'bipyridine) where we correlated the CO vibrational modes of the ground state and the MLCT state. A distinct vibrational mode is excited in the electronic ground state by an infrared laser pulse. This vibrational label survives the subsequent electronic excitation and can be followed in the excited electronic state. It is shown that the order of the vibrational energy levels is not preserved when exciting the molecule as was commonly assumed in the literature.

Journal Article↗
PubMed2004

Nonperturbative vibrational energy relaxation effects on vibrational line shapes.

A general formulation of nonperturbative quantum dynamics of solutes in a condensed phase is proposed to calculate linear and nonlinear vibrational line shapes. In the weak solute-solvent interaction limit, the temporal absorption profile can be approximately factorized into the population relaxation profile from the off-diagonal coupling and the pure-dephasing profile from the diagonal coupling. The strength of dissipation and the anharmonicity-induced dephasing rate are derived in Appendix A. The vibrational energy relaxation (VER) rate is negligible for slow solvent fluctuations, yet it does not justify the Markovian treatment of off-diagonal contributions to vibrational line shapes. Non-Markovian VER effects are manifested as asymmetric envelops in the temporal absorption profile, or equivalently as side bands in the frequency domain absorption spectrum. The side bands are solvent-induced multiple-photon effects which are absent in the Markovian VER treatment. Exact path integral calculations yield non-Lorentzian central peaks in absorption spectrum resulting from couplings between population relaxations of different vibrational states. These predictions cannot be reproduced by the perturbative or the Markovian approximations. For anharmonic potentials, the absorption spectrum shows asymmetric central peaks and the asymmetry increases with anharmonicity. At large anharmonicities, all the approximation schemes break down and a full nonperturbative path integral calculation that explicitly accounts for the exact VER effects is needed. A numerical analysis of the O-H stretch of HOD in D(2)O solvent reveals that the non-Markovian VER effects generate a small recurrence of the echo peak shift around 200 fs, which cannot be reproduced with a Markovian VER rate. In general, the nonperturbative and non-Markovian VER contributions have a stronger effect on nonlinear vibrational line shapes than on linear absorption.

Journal Article↗
PubMed2004

Real-time detection of doorway states in the intramolecular vibrational energy redistribution of the OH/OD stretch vibration of phenol.

A picosecond time-resolved IR-UV pump-probe spectroscopic study was carried out for the intramolecular vibrational energy redistribution of the OH/OD stretching vibration of isolated phenol and its isotopomers in supersonic beams. The time evolution due to IVR showed a significant isotope effect; the OH stretch vibration showed a single exponential decay and its lifetime is greatly lengthened upon the deuterium substitution of the CH group. The OD stretch vibration exhibited prominent quantum beats. Especially, in phenol-d1 (C6H5OD), the electronic transitions from the doorway states were clearly observed. They exhibited an out-of-phase quantum beat with respect to that of the OD stretch level and disappeared due to further IVR to the dense bath states. The transient spectra as well as the time evolution clearly evidenced the tier-model of the description of intramolecular vibrational energy redistribution.

Journal Article↗
PubMed2005

Picosecond IR-UV pump-probe spectroscopic study on the intramolecular vibrational energy redistribution of NH2 and CH stretching vibrations of jet-cooled aniline.

Intramolecular vibrational energy redistribution (IVR) of the NH2 symmetric and asymmetric stretching vibrations of jet-cooled aniline has been investigated by picosecond time-resolved IR-UV pump-probe spectroscopy. A picosecond IR laser pulse excited the NH2 symmetric or asymmetric stretching vibration of aniline in the electronic ground state and the subsequent time evolutions of the excited level as well as redistributed levels were observed by a picosecond UV pulse. The IVR lifetimes for symmetric and asymmetric stretches were obtained to be 18 and 34 ps, respectively. In addition, we obtained the direct evidence that IVR proceeds via two-step bath states; that is, the NH2 stretch energy first flows into the doorway state and the energy is further dissipated into dense bath states. The rate constants of the second step were estimated to be comparable to or slower than those of the first step IVR. The relaxation behavior was compared with that of IVR of the OH stretching vibration of phenol [Y. Yamada, T. Ebata, M. Kayano, and M. Mikami J. Chem. Phys. 120, 7400 (2004)]. We found that the second step IVR process of aniline is much slower than that of phenol, suggesting a large difference of the "doorway state increasing the dense bath states" anharmonic coupling strength between the two molecules. We also observed IVR of the CH stretching vibrations, which showed much faster IVR behavior than that of the NH2 stretches. The fast relaxation is described by the interference effect, which is caused by the coherent excitation of the quasistationary states.

Journal Article↗