Search results for " vibration"
showing 10 items of 296 documents
Hypothesis of whiplike motion as a possible traumatizing mechanism in vocal fold vibration.
2003
The mucosal waves on the vibrating vocal folds may move in anterior-posterior, mediolateral and in caudal-cranial direction. This article discusses the possible significance of the vertical movement from the point of view of mechanical stress in phonation and the formation of vocal fold traumas. It is hypothesized that in certain conditions the vocal folds may behave in cranial direction like a quasi-free end of a long lash producing very rapid vibratory waves (e.g. the waves in a whiplash). This could be detrimental to the tissue structure. The role of phonation type in enhancing/diminishing this effect will also be discussed.
DOSE–RESPONSE RELATIONSHIPS BETWEEN WHOLE-BODY VIBRATION AND LUMBAR DISK DISEASE—A FIELD STUDY ON 388 DRIVERS OF DIFFERENT VEHICLES
1998
Abstract In a longitudinal study, the dose–response relationships between long term occupational exposure to whole-body vibration and degenerative processes in the lumbar spine caused by the lumbar disks were examined. From 1990 to 1992, 388 vibration-exposed workers from different driving jobs were examined medically and by lumbar X-ray. For each individual, a history of all exposure conditions was recorded, and a cumulative vibration dose was calculated allowing comparisons between groups of low, middle, and high intensity of exposure. 310 subjects were selected for a follow-up four years later, of whom 90·6% (n=281) agreed to participate. In comparing the exposure groups, the results ind…
Long-term effects on motor cortical excitability induced by repeated muscle vibration during contraction in healthy subjects
2008
article i nfo Objective: The effects of a novel repeated muscle vibration intervention (rMV; 100 Hz, 90 min over 3 consecutive days) on corticomotor excitability were studied in healthy subjects. Methods: rMV was applied over the flexor carpi radialis (FCR) during voluntary contraction (experiment 1), during relaxation and during contraction without vibration (experiment 2). Focal transcranial magnetic stimulation (TMS) was applied before rMV and one hour, and one, two and three weeks after the last muscle vibration intervention. At each of these time points, we assessed the motor map area and volume in the FCR, extensor digitorum communis (EDC) and abductor digiti minimi (ADM). Short-inter…
Structural factors controlling ligand binding to myoglobin: a kinetic hole-burning study.
1998
Using temperature-derivative spectroscopy in the temperature range below 100 K, we have studied the dependence of the Soret band on the recombination barrier in sperm whale carbonmonoxy myoglobin (MbCO) after photodissociation at 12 K. The spectra were separated into contributions from the photodissociated species, Mb*CO, and CO-bound myoglobin. The line shapes of the Soret bands of both photolyzed and liganded myoglobin were analyzed with a model that takes into account the homogeneous bandwidth, coupling of the electronic transition to vibrational modes, and static conformational heterogeneity. The analysis yields correlations between the activation enthalpy for rebinding and the model p…
Effect of segmental muscle vibration on upper extremity functional ability poststroke: A randomized controlled trial.
2019
Abstract Background: Upper extremity functional impairments are common consequences of stroke. Therefore, continuous investigation of effective interventions for upper extremity functions after stroke is a necessity. Segmental muscle vibration (SMV) is one of the interventions that incorporate sensory stimulation to improve motor cortical excitability. The aim of this study was to investigate the influence of 5-minute SMV application along with supervised physical therapy (SPT) on improving activities of daily living and motor recovery on the hemiparetic upper extremity in patients with stroke. Methods: A sample of 37 patients poststroke (29 males) was randomly allocated to either SPT contr…
Effect of segmental muscle vibration on upper extremity functional ability poststroke
2019
Abstract Background: Upper extremity functional impairments are common consequences of stroke. Therefore, continuous investigation of effective interventions for upper extremity functions after stroke is a necessity. Segmental muscle vibration (SMV) is one of the interventions that incorporate sensory stimulation to improve motor cortical excitability. The aim of this study was to investigate the influence of 5-minute SMV application along with supervised physical therapy (SPT) on improving activities of daily living and motor recovery on the hemiparetic upper extremity in patients with stroke. Methods: A sample of 37 patients poststroke (29 males) was randomly allocated to either SPT contr…
First principles calculations of the vibrational properties of single and dimer F-type centers in corundum crystals
2020
The present paper investigates the F-type centers in α-Al2O3 through their electronic and vibrational properties from first principle calculations using a periodic supercell approach, a hybrid functional, and all-electron Gaussian basis sets as implemented in the CRYSTAL17 code. Single F-type and dimer F2-type centers related to oxygen vacancies in various charge states were considered. The defect-induced vibrational modes were identified and found to appear mainly in the low (up to 300 cm-1) and high (above 700 cm-1) frequency regions, depending on the defect charge. The perturbation introduced by the defects to the thermal nuclear motion in the crystal lattice is discussed in terms of ato…
XRD and micro Raman characterization of epitaxial Bi-2201, Bi-2212 and Bi-2223 thin films
1997
Copyright (c) 1997 Elsevier Science B.V. All rights reserved. Micro Raman characterization is performed on high quality thin films of Bi 2 Sr 2 CuO 6+x (2201), Bi 2 Sr 2 CaCu 2 O 8+x (2212), Bi 2 Sr 2 Ca 2 Cu 3 O 10+x (2223) made by dc-sputtering. Single crystal X-ray measurements reveal the full epitaxy of the films, which allows for polarized Raman spectra to be obtained.
Phonon Dispersion of Wurtzite CdSe: The Bond Charge Model
2000
The phonon dispersion of wurtzite CdSe is presented along the main directions of the Brillouin zone. The study has been performed by using a bond charge model for wurtzite-type semiconductors with only six adjustable parameters. The results are compared against neutron scattering data and ab initio calculations. The phonon eigenvectors corresponding to the vibrational modes at the Γ-point are in very good agreement with the ab initio calculations.
Structural disorder and silanol groups content in amorphousSiO2
2009
We present a study on the features of the Urbach edge in amorphous silicon dioxide $(a{\text{-SiO}}_{2})$. The effects of temperature on the absorption edge in the range from 4 to 300 K were studied in both materials having negligible (dry, $l{10}^{17}\text{ }{\text{cm}}^{\ensuremath{-}3}$) and significant (wet, $g{10}^{19}\text{ }{\text{cm}}^{\ensuremath{-}3}$) silanol groups contents. Remarkable differences in the values and in the temperature dependence of the Urbach energy in the dry and wet samples were observed. These differences are interpreted as a consequence of a drastic reduction in the degree of disorder in wet materials, which turn out to be characterized by an electronic struc…