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At least 1,369 records · Page 76Linked to original sources
PubMed1997

[Asymmetrical body tilt induced by vibration of the Achilles tendon in patients with unilateral vestibular hypofunction].

Unilateral vestibular lesion results in postural balance deficits, which progressively vanish with time compensation. This functional recovery is caused due to the reorganization of the CNS structures and afferent inputs, mainly of the proprioceptive afferentation. Our aim was to determine the postural effect of leg proprioceptive input induced by the Achilles tendon (AT) vibration in standing patients with unilateral vestibular hypofunction. The examined patients (9 patients unilateral vestibular neuritis and 3 patients with Meniere's disease) had unilaterally decreased caloric responses. The control were 20 healthy volunteers with intact vestibular and motor functions. The postural responses evoked by AT vibration were evaluated by the symmetry of centre of pressure (COP) of the subject. The postural responses induced by the AT vibration in the healthy were bilaterally symmetrical. In the patients the body lean evoked by vibration on the side of intact vestibular apparatus was significantly decreased. The AT vibration on the lesioned side evoked practically identical response to the response of healthy subjects. In the repeated examination after 6 months the asymmetry disappeared which was in accordance with the recovered clinical state. The findings of asymmetry of postural COP displacement in patients with acute unilateral vestibular hypofunction documented transitory asymmetry of influence from leg proprioceptive inputs. The direction of decreased postural response to the proprioceptive stimuli was the same as pathological body lean of patient to the side of lesioned vestibular apparatus. This fact allows us to hypothesize that the postural responses evoked by leg proprioceptive inputs, directionally identical with the pathological body lean induced by asymmetry of vestibular afferentation are inhibited. (Fig. 3, Ref. 15.)

Achilles Tendon↗
PubMed1997

Morphology and vibration pattern of the vocal cord after intracordal Teflon injection: long-term results.

BACKGROUND: Intracordal Teflon injection has been the mainstream management for unilateral vocal cord palsy over the past three decades. In recent years, some investigators concerned about its possible adverse effects on the vibration of the injected vocal cords. It is therefore necessary to clarify the clinical significance of these concerns if Teflon injection will stay as a viable treatment. METHODS: Twenty-one patients with unilateral vocal cord palsy, who had received Teflon injection for more than one year, were evaluated by flexible laryngovideostroboscopy, basic voice function evaluations and the patient self-assessment. RESULTS: The morphological and vibratory patterns of the post-injection vocal cords were categorized into seven types according to the videostroboscopic findings. Type I and type II cases had relatively normal morphology and vibration (assorted as group I). Type III through type VII cases showed various kinds of morphological and vibratory abnormalities (assorted as group II). Group I and group II were significantly different in the results of basic voice function evaluations and the patient self-assessment. Group I cases who showed relatively normal morphology and vibration had mean values closer to the normal ranges. For all the patients recruited, their voices were quite stable after injection. None with initial improvement of the voice suffered deterioration. CONCLUSIONS: The results showed that some patients had nearly normal vibration of the vocal cords years after Teflon injection. True (delayed onset, not due to improper injection) and voice-disturbing Teflon granuloma was not seen in the present study. The majority of cases with disturbed vibration were due to either improper location or an improper amount of injected Teflon. The problems were mostly induced by technical difficulties, not by Teflon-related foreign body reaction. Efforts should be made to avoid these technical errors to increase the predictability of the outcome.

Adult↗
PubMed1998

[The role of the working conditions in shaping the specific and nonspecific body reactions of miners in vibration-hazardous jobs].

An analysis was carried out of bodily functional status in miners engaged in basic mining occupations with known vibration-related health hazards (coal hewers, drifters), presenting with different stages of vibration pathology. Patterns were ascertained of chief components of both specific and unspecific bodily systemic reactions to a combined action of physical industrial factors (vibration, noise, dust, heating, microclimate). Important for those subjects engaged in occupations with vibration-related health threats are parameters characterizing labour conditions, such as, in the first place, integral-and-service duration-related exposure doses of industrial factors which are believed to be probabilistic risk factors for vibration pathology.

Coal Mining↗
PubMedDate not supplied

[Chrono-thermometry in the diagnosis of Raynaud-like vasculopathies caused by prolonged use of vibrating tools].

Raynaud's phenomenon may be secondary to several different pathological conditions. In some cases it is favoured by occupational exposure to vibration of the upper arms. The diagnosis of Raynaud's phenomenon requires clinical information together with specific technical investigations. This report presents the results of 232 chrono-thermometric tests performed on 157 workers exposed to vibrations during the use of different kinds of tools. Seventy-five subjects not exposed to vibrations of the upper arms but with suspected Raynaud's syndrome were also tested. Chrono-thermometry enabled us to distinguish between three different subgroups of subjects exposed to vibrations: 61 workers with "normal" chrono-thermometry, 33 subjects with "pathological" vascular reactivity to cold in some fingers and 63 workers with such reactivity in all fingers. Similarly the 75 patients not exposed to vibration could also be divided into three groups. No statistical difference was found between the chrono-thermometric results obtained from the exposed and non-exposed subjects when divided into the three subgroups. The overall analysis of the combined results of the different kinds of tests (capillaroscopy plus a vascular reactivity test) is discussed.

Adolescent↗
PubMed1999

Vibrational directionality in the southern green stink bug, Nezara viridula (L.), is mediated by female song.

We tested the hypothesis that male southern green stink bugs, Nezara viridula (L.), use substrate-borne songs to locate females. We recorded the responses of bugs on plants to the vibrations caused by a prerecorded female song and by an artificial sound. The female song caused males to walk, to respond with the calling and courtship songs and to approach the source of the song with characteristic search behaviour at junctions between branches on the plants. At a junction, a searching male stopped, stretched his legs and antennae and compared the vibratory signals on the two branches, with different combinations of legs and antennae. The males then left the junction and approached the source of the vibration. Males located the loudspeaker significantly more frequently in the presence than in the absence of vibratory stimuli on cyperus, Cyperus alternifolius L., and beans, Phaseolus vulgaris L. Vibrational directionality was also elicited by artificial pure tones whose spectral and temporal parameters were similar to those of natural female song. Females showed no reaction to vibratory stimulation and no vibrational directionality. We discuss possible mechanisms underlying vibrational directionality in the light of expected signal changes during transmission through plants. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1997

Vibrational Dynamics of H5 + and Its Deuterated Isotopomers

The vibrational dynamics of the H5 + complex and its deuterated isotopomers H4 D+ , H3 D2 + , H2 D3 + , HD4 + , and D5 + are investigated using a model Hamiltonian which is based on the assumption that on the potential energy hypersurface the barriers for the internal rotation motions are infinitely high except for the practically free propeller-like motion. According to our previous studies on H5 + , the propeller-like rotation essentially does not interact with the remaining vibrations and is therefore neglected in the present calculations. Within the framework of the adiabatic approximation the resulting eight-dimensional vibrational problem is separated into two smaller subproblems which are solved numerically applying the same scheme as previously. The calculations are performed using a new extended potential energy function which also provides a reliable description of the interactions between the degenerate stretching motions and the remaining vibrations. As in our previous calculations, the high-frequency fundamentals obtained for H5 + are in good agreement with their experimental counterparts, whereas the reliability of the present results for the low-frequency motions is considerably improved as a result of the appropriate description of the relevant interactions. Predictions of the vibrational energies of the other deuterated isotopomers are made on the same accuracy level. The zero-point energies derived from the present calculations are believed to be accurate enough for a quantitative determination of the binding energies of the different isotopomers.

Journal Article↗
PubMed1997

The Spectrum of Hot Water: Rotational Transitions and Difference Bands in the (020), (100), and (001) Vibrational States

Analysis of the hot H2 16O spectrum, presented by Polyansky et al. (1996, J. Mol. Spectrosc. 176, 305-315), is extended to higher vibrational states. Three hundred thirty mainly strong lines are assigned to pure rotational transitions in the (100), (001), and (020) vibrational states. These lines, which involve significantly higher rotational energy levels than were known previously, are assigned using high-accuracy variational calculations. Transitions in (020) are assigned up to Ka = 18, compared with the maximum Ka of 10 known previously. Crossings of vibration-rotation energy levels result in the observation of extra intensity-stealing transitions. In particular, this leads to the assignment of (020)-(100) and (100)-(020) rotational difference band transitions in addition to the conventional pure rotational lines in (020) and (100) states. These extra lines increase the number of transitions and they are likely to complicate the pure rotational water spectrum in higher excited vibrational states to an even greater extent. A few lines from our previous work on the pure rotational spectrum of hot water in the (000) and (010) vibrational states are also reassigned and some further assignments are made. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1998

Fourier Transform Infrared Spectroscopy and Vibrational Coupling in the OH-Bending Band of 13CH3OH.

We present in this work a high-resolution Fourier transform infrared study of the OH-bending vibrational band of 13CH3OH. We have investigated the 1070-1400 cm-1 spectral region at 0.002 cm-1 resolution using the modified Bomem DA3.002 Fourier transform spectrometer at the Steacie Institute for Molecular Sciences at the National Research Council of Canada in Ottawa. This study has led to (i) determination of excited-state J(J + 1) subband expansion coefficients and (ii) characterization of a variety of interactions coupling the different vibrational modes, notably a strong Fermi resonance between the OH bend and the torsionally excited CH3-rocking mode. The OH-bending band is widely spread with Q subbranches grouped in two peaks at about 1312 and 1338 cm-1. The lower levels for all assigned subbands were confirmed using closed loops of IR and FIR transitions. The subbands have been fitted to J(J + 1) power-series expansions in order to obtain the subband origins and the state-specific energy expansion coefficients for both the OH-bending and excited torsional CH3-rocking states. The strong interaction between the OH-bending state and the first excited torsional CH3-rocking state gives rise to several "extra" forbidden subbands due to intensity borrowing. The asymmetry splitting of the (ntauK) v = (122)OH A OH-bending doublet was found to be anomalously small, and the splitting of the (122)rA CH3-rocking doublet is observed to be enhanced. We have identified a network of intermode interactions causing this unusual behavior, but a quantitative analysis of the vibrational coupling is restricted by limited knowledge of the unperturbed positions of the interacting levels. All these interactions provide relaxation channels for intramolecular vibrational redistribution among the lower vibrational modes in 13CH3OH. Another important finding is that the torsion-K-rotation energy curves in the OH-bending state display an inverted pattern compared to the ground state. Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

Theoretical and Experimental (400-10 000 cm-1) Study of the Vibrational Spectrum of Pentachlorophenol.

Geometric and vibrational spectroscopic data (bond distances and angles, vibrational frequencies, infrared intensities) of pentachlorophenol-OH (PCP-OH) and pentachlorophenol-OD (PCP-OD) are calculated by density functional theory (B3LYP) using the 6-311G(d, p) basis set. Except for the vibrations involving the OH bond, the agreement between the experimental and calculated fundamental frequencies between 3600 and 400 cm-1 is very good. The theoretical method failed, however, to reproduce quantitatively the experimental intensities. The infrared spectra between 3600 and 10 000 cm-1 are studied, and the overtones or combination bands are assigned by comparing the spectra of PCP-OH and PCP-OD. The difference between the experimental and theoretical frequencies of the nu(OH) and nu(OD) frequencies can be mainly accounted for by the neglect of the anharmonicities of these vibrations in calculations. The binary or ternary combinations characterized by the highest coupling constants and the highest intensities are those involving the nu(OH), delta(OH), gamma(OH), and nu(C-O) vibrations. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Vibration-Internal Rotation-Overall Rotation Interactions in CH(2)DOH and CHD(2)OH.

The zeroth-order kinetic energy is developed for the vibrating-rotating-internally rotating CH(2)DOH and CHD(2)OH molecules using the general theory of Guan and Quade for the vibration-rotation-large amplitude internal motion interactions in molecules. A T transformation is applied to obtain the necessary (G(-1))(0) vibrational matrix elements in the kinetic energy for the R transformation that separates the internal rotation from the 3N-7 other vibrations. Then, a second T transformation is used to separate rotation from the 3N-7 other vibrations in zeroth order in the kinetic energy. The overall rotation and internal rotation remain coupled in zeroth order. All zeroth-order kinetic energy coefficients are calculated from the molecular structure and masses for the methyl alcohol molecules. The physical significance of the transformations is discussed in detail. This paper reports the results of the first segment of the three segments that are necessary in the calculation of the full solution to the problem. Copyright 1999 Academic Press.

Journal Article↗
PubMed2000

Experimental Characterization of the Higher Vibrationally Excited States of HCO(+): Determination of omega(2), x(22), g(22), and B(030).

Analyses of high Rydberg series of HCO converging to the (030) vibrational state of the cation establish rovibrational state-detailed thresholds for HCO(+). UV-visible laser double resonance isolates series for assignment. Strongly vertical Rydberg-Rydberg transitions from photoselected N' = 0 and N' = 2 rotational levels of the Sigma(-) Renner-Teller vibronic component of the 3ppi (2)Pi (030) complex define individual series converging to rotational levels, N(+) = 1 through 5 and 3 through 5 of the HCO(+) vibrational states (03(1)0) and (03(3)0), respectively. Extrapolation of autoionizing series locates the positions of these rovibrational states to within +/-0.01 cm(-1). The use of this information combined with precise ionization limits for lower vibrational states determined from earlier Rydberg extrapolations and spectroscopic information available from infrared absorption measurements enables an estimate of the force-field parameters for HCO(+) bending. These parameters include the harmonic bending frequency, omega(2) = 842.57 cm(-1), the vibrational angular momentum splitting constant, g(22) = 3.26 cm(-1), and the diagonal bending anharmonicity, x(22) = -2.53 cm(-1), separated from the off-diagonal contribution, x(12), by reference to ab initio calculations. Results of experiment on the higher vibrationally excited states of HCO(+) are compared with recent theoretical predictions. Copyright 2000 Academic Press.

Journal Article↗
PubMed2001

Torsional Splittings in Small-Amplitude Vibrational Fundamental States of Methanol-Type Molecules.

Group-theoretical methods are used to show that inverted torsional splittings in fundamental levels of small-amplitude vibrations of methanol-like molecules can be parameterized and understood in terms of the energy level patterns induced when a pair of high-barrier torsionally split components of given v(t) and (t)A+(t)E symmetry species in the molecular symmetry group G(6) is allowed to interact with small-amplitude vibrational modes of symmetry (v)E. Such doubly degenerate (v)E vibrational modes arise rather naturally in G(6) (isomorphic with the point-group C(3v)) for those methyl-group vibrations in point-group-C(s) asymmetric tops such as CH(3)-CHO that are analogs of the degenerate methyl-group stretch, bend, and rocking vibrations in point-group-C(3v) symmetric tops such as CH(3)-C identical withC-H. The present group-theoretical treatment is somewhat different from, but (as a comparison of model parameters shows) still fundamentally similar to, the recent local mode explanation of inverted torsional splittings in the C-H stretching fundamental region in methanol. Copyright 2001 Academic Press.

Journal Article↗
PubMed1977

Development of a simulator for use in the measurement of chain saw vibration.

The measurement of vibration production of light, hand held power tools is important in the assessment of the potential for elicitation of vibration injury to the operators of these tools. The manner in which these measurements are made can greatly affect the results. The measured vibration production of the tool becomes a function of the operator holding the saw during the measurement and his physical characteristics. The objective of the work reported here was to develop a simulator of the operator which might be used in the vibration production analysis of chain saws. The operator was modelled in terms of the driving point mechanical impedance characteristics of humans for input to the hands. A simulator was developed based on the driving point impedance characterization of the operator and evaluated with chain saw vibration measurements.

Journal Article↗
PubMed1978

The evaluation of vehicle vibration and seats.

Measurements of vibration in a variety of road vehicles in common use are compared with the guidance provided in ISO 2631-2974 (E) (Guide for the evaluation of human exposure to vibration). For typical journey durations many of the vibration levels are in excess of the levels corresponding to the 'reduced comfort boundaries' and 'fatigue decreased proficiency boundaries' defined in the ISO Standard. Some of the problems inherent in comparing the measured vibration levels with the Standard are outlined and the need for a revised format for the Standard is discussed. A method of summarising the vibration attenuation of vehicle seats is defined and it is shown that the isolation provided by many of the seats of the 16 vehicles used in the study is poor.

Journal Article↗
PubMed1996

Epidemiological and aetiological aspects of low back pain in vibration environments - an update.

The article reviews the substantial body of epidemiological evidence linking vibration exposure and low back pain. Drivers appear to be at particular risk if exposures exceed those recommended by the ISO exposure limit. Various aetiological factors associated with vehicular vibration, flattening of the lumbar lordosis, increased motion segment flexibility, disc pressure and mechanical softening are discussed. Vibration studies of functional spinal units are also discussed, as are in vivo whole-body vibration experiments. Animal models have shown that vibration leads to compromised nutrition, higher disc pressures, release of neuropeptides, increased creep and histological changes.

Journal Article↗
PubMed2004

Ab initio studies of solvent effect on molecular conformation and vibrational spectra of diacetamide.

The conformational equilibria and vibrational spectra of diacetamide have been investigated by ab initio molecular orbital studies using the basis sets 6-31g(d,p) and 6-31++g(d,p) at Hartree-Fock and MP2 levels. The vibrational spectra of diacetamide have been satisfactorily interpreted taking into consideration the agreement between the calculated harmonic vibrational frequencies, infrared and Raman band intensities and shifts in deuterated molecules with those observed. The solvent effects were investigated by the self-consistent reaction field (SCRF) theory. The effect of solvent on the conformational equilibria and vibrational spectra is discussed. The calculated changes in the geometry and vibrational spectra on going from the gas phase to the solvent medium are in accord with the increasing weight of the dipolar resonance structure of the amide group in more polar solvents.

Acetamides↗
PubMed2005

Ab initio and DFT studies on vibrational spectra of some mixed carbonyl-halide complexes of ruthenium(II).

The vibrational spectra of Ru(CO)6(2+) and some of its mixed carbonyl-halide complexes, cis-Ru(CO)2X4(2-), fac-Ru(CO)3X3- and Ru(CO)5X+ (X = F, Cl, Br and I), have been systematically investigated by ab initio RHF and density functional B3LYP methods with LanL2DZ and SDD basis sets. The calculated vibrational frequencies of complexes Ru(CO)6(2+), cis-Ru(CO)2X4(2-) and fac-Ru(CO)3X3- are evaluated via comparison with the experimental values. In the infrared frequency region, the C-O stretching vibrational frequencies calculated at B3LYP level with two basis sets are in good agreement with the observed values with deviations less than 5%. In the far-infrared region, the B3LYP/SDD method achieved the best results with deviations less than 8% for Ru-X stretching and less than 2% for Ru-C stretching vibrational frequencies. The vibrational frequencies for Ru(CO)5X+ that have not been experimentally reported were predicted.

Carbon↗
PubMed2005

Vibrational analysis of 1,4-diaminoanthraquinone and 1,5-dichloroanthraquinone. A joint FTIR, FT-Raman and scaled quantum mechanical study.

This work deals with the vibrational spectroscopy of 1,4-diaminoanthraquinone (1,4-DAAQ) and 1,5-dichloroanthraquinone (1,5-DCAQ). The mid and far FTIR and FT-Raman spectra were measured in the condensed state. The fundamental vibrational frequencies and intensity of the vibrational bands were evaluated using density functional theory (DFT) with the B3LYP functional and 6-31G* basis set. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The infrared and Raman spectra were also predicted from the calculated intensities. Unambiguous vibrational assignment of all the fundamentals were made using the potential energy distribution (PED).

Anthraquinones↗