Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “VIBRATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed2004

Six-dimensional vibrational analysis of coupled intermolecular vibrations in a binary cluster.

We report on full- (six-) dimensional calculations of the intermolecular vibrations of a binary aromatic-solvent cluster. An exact Hamiltonian for this kind of interaction is modified in a general manner in order to perform calculations of molecules without symmetry. The binary cluster phenol(H2O)1 is used as a test case since its intermolecular vibrations are anharmonic and highly coupled. The formulation of the Schrodinger equation leads to a complex-valued eigenvalue problem with a dimension larger than two million, which is solved by filter diagonalization to obtain both eigenvalues and eigenvectors. With the knowledge of the eigenvectors, an interpretation of all eigenvalues is possible by a characterization with pseudoquantum numbers that are related to the widely used nomenclature of intermolecular normal motions in aromatic(solvent) clusters.

Journal Article↗
PubMed2006

Vibrational and rotational energy transfers involving the CH B 2Sigma(-) v=1 vibrational level in collisions with Ar, CO, and N2O.

With photolysis-probe technique, we have studied vibrational and rotational energy transfers of CH involving the B (2)Sigma(-) (v=1, 0 F(1) transitions are larger than the reverse F(1)-->F(2) transitions in DeltaN=0 for the Ar and CO collisions. The trend of fine-structure conservation is along the order of N(2)O<CO approximately Ar. For the CH-Ar collisions, the fine-structure conservation is less pronounced as compared with the v=0 level reported previously. In general, the propensity rules obeyed in the v=0 collision with Ar are valid in v=1, but the latter case shows a weaker tendency. It might be caused by the anisotropy difference of interaction potential when vibrational excitation is considered. For the polyatomic collider, the strong long-range dipole-dipole interaction may have the chance to vary the rotational orientation to increase the fine-structure-changing transitions.

Journal Article↗
PubMed2006

Converged vibrational energy levels and quantum mechanical vibrational partition function of ethane.

The vibrational partition function of ethane is calculated in the temperature range of 200-600 K using well-converged energy levels that were calculated by vibrational configuration interaction, and the results are compared to the harmonic oscillator partition function. This provides the first test of the harmonic oscillator approximation for a molecule with more than five atoms. The absolute free energies computed by the harmonic oscillator approximation are in error by 0.59-0.62 kcal/mol over the 200-600 K temperature range.

Journal Article↗
PubMed2006

The bending vibrational levels of the acetylene cation: a case study of the Renner-Teller effect in a molecule with two degenerate bending vibrations.

Forty three vibronic levels of C2H2+, X 2Pi u, with upsilon4 = 0-6, upsilon5 = 0-3, and K = 0-4, lying at energies of 0-3520 cm(-1) above the zero-point level, have been recorded at rotational resolution. These levels were observed by double resonance, using 1+1' two-color pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy. The intermediate states were single rovibrational levels chosen from the A1Au, 4nu3 (K = 1-2), 5nu3 (K = 1), nu2+4nu3 (K = 0), and 47,206 cm(-1) (K = 1) levels of C2H2. Seven of the trans-bending levels of C2H2+ (upsilon4 = 0-3, K = 0-2) had been reported previously by Pratt et al. [J. Chem. Phys. 99, 6233 (1993)]; our results for these levels agree well with theirs. A full analysis has been carried out, including the Renner-Teller effect and the vibrational anharmonicity for both the trans- and cis-bending vibrations. The rotational structure of the lowest 16 vibronic levels (consisting of the complete set of levels with upsilon4 + upsilon5 < or = 2, except for the unobserved upper (2Pi u component of the 2nu4 overtone) could be fitted by least squares using 16 parameters to give an rms deviation of 0.21 cm(-1). The vibronic coupling parameter epsilon5 (about whose magnitude there has been controversy) was determined to be -0.0273(7). For the higher vibronic levels, an additional parameter, r45, was needed to allow for the Darling-Dennison resonance between the two bending manifolds. Almost all the observed levels of the upsilon4 + upsilon5 = 3 and 4 polyads (about half of the predicted number) could then be assigned. In a final fit to 39 vibronic levels with upsilon4 + upsilon5 < or = 5, an rms deviation of 0.34 cm(-1) was obtained using 20 parameters. An interesting finding is that Hund's spin-coupling cases (a) and (b) both occur in the Sigmau components of the nu4 + 2nu5 combination level. The ionization potential of C2H2 (from the lowest rotational level of the ground state to the lowest rotational level of the cation) is found to be 91,953.77 +/- 0.09 cm(-1) (3sigma).

Journal Article↗
PubMed2006

Torsion-vibration coupling in methanol: the adiabatic approximation and intramolecular vibrational redistribution scaling.

The four-dimensional model Hamiltonian of Wang and Perry [J. Chem. Phys. 109, 10795 (1998)] is used to compare the approximate adiabatic separation of the torsion and CH stretches in methanol to an exact solution of the same Hamiltonian. The adiabatic approximation accounts for the pattern of the energy levels in the lowest torsional states, including the inverted tunneling splittings, but does not account for the pattern of systematic two- and four-fold near degeneracies at high torsional excitation. In the adiabatic basis, the nonadiabatic couplings mix the torsional and vibrational degrees of freedom and hence are a source for intramolecular vibrational redistribution (IVR). These IVR matrix elements are found to decrease by only a factor of 2 or 3 with each higher coupling order, in agreement with the results of Pearman and Gruebele [Z. Phys. Chem. Munich 214, 1439 (2000)]. This gentle scaling behavior, which contrasts with a steeper falloff with coupling order in more rigid molecules, points to a more important role for direct high-order couplings in torsional molecules. In this model, the scaling behavior derives from a single coupling term that is low order in the torsional angular momentum in combination with one-dimensional torsional functions that include contributions from many torsional angular momenta.

Journal Article↗
PubMed2006

Near-resonant vibration-to-vibration energy transfer in the NO+-N2 collisions.

First principles model calculations of the vibration-to-vibration (VV) energy transfer (ET) processes NO(+)(nu=1)+N(2)(nu=n-1)-->NO(+)(nu=0)+N(2)(nu=n)+(28.64n-14.67) cm(-1) and NO(+)(nu=n)+N(2)(nu=0)-->NO(+)(nu=n-1)+N(2)(nu=1)+(32.52(n-1)+13.97) cm(-1) for n=1-3 in the 300-1000 K temperature range are performed. The VV ET probability is computed for three mechanisms: (1) The charge on NO(+) acting on the average polarizability of N(2) induces a dipole moment in N(2) which then interacts with the permanent dipole moment of NO(+) to mediate the energy transfer. (2) The charge on NO(+) acting on the anisotropic polarizability of N(2) induces a dipole moment in N(2) which then interacts with the permanent dipole moment of NO(+) to mediate the energy transfer. (3) The dipole moment of NO(+) interacts with the quadrupole moment of N(2) to mediate the energy transfer. Because the probability amplitudes of the second and third mechanisms add coherently the ET probability for these two mechanisms is given as a single number. The probability of energy transfer per collision is in the 5 x 10(-3) range. The results of this calculation are compared with the available experimental data. This calculation should help quantify the role of NO(+) in the energy budget of the upper atmosphere.

Journal Article↗
PubMed2007

Theoretical investigation of highly excited vibrational states in DFCO: calculation of the out-of-plane bending states and simulation of the intramolecular vibrational energy redistribution.

A previously developed modified Davidson scheme [C. Iung and F. Ribeiro, J. Chem. Phys. 121, 174105 (2005)] is applied to compute and analyze highly excited (nu2,nu6) eigenstates in DFCO. The present paper is also devoted to the simulations of the intramolecular vibrational energy redistribution (IVR) initiated by an excitation of the out-of-plane bending vibration (nnu6, n=2,4,6, . . . ,18, and 20). The multiconfiguration time-dependent Hartree method is exploited to propagate the corresponding six-dimensional wave packets. A comprehensive comparison with experimental data as well as with previous simulations of IVR in HFCO [G. Pasin et al. J. Chem. Phys. 124, 194304 (2006)] is presented.

Journal Article↗
PubMed1986

Effect of middle ear modification on umbo vibration. Human temporal bone experiments with a new vibration measuring system.

The effects of aditus blockage, decrease of tympanic cavity volume, and resection of the tensor tympani muscle on umbo displacement were studied in human temporal bones using a new non-contacting video measuring system. This system, combined with stroboscopic illumination, allowed measurement of umbo vibration down to 0.3 micron in the 0.1- to 4.5-kHz frequency range for a constant 124-dB sound pressure level at the tympanic membrane. Aditus blockage caused a mean increase of 5.4 dB with a peak at 2.8 kHz and a mean decrease of 3.4 dB below 1.6 kHz. Decrease of the tympanic cavity volume by 30% to 42% showed an improvement of 2.2 dB in the 1.4- to 3-kHz range and a similar loss below 1 kHz. Resection of the tensor tympani muscle produced a slight improvement of 1.7 dB at 1.8 kHz.

Bone Conduction↗
PubMed1987

Difference in electromyographic response of finger flexion muscles between tonic vibration reflex and finger flexion reflex induced by finger tip vibration.

Vibratory stimulus applied to the skin of the finger tip induced flexion reflex in that finger. By using the cross-correlation function, characteristics of this reflex were compared to those of tonic vibration reflex (TVR). In the cross-correlogram between unitary electromyogram (EMG) activity in the muscle flexor digitorum superficialis and vibratory stimulus with random frequency, one mode was seen in TVR, and two modes in finger flexion reflex. The secondary mode was significantly wider than the primary mode. Thus it may originate from skin mechanoreceptors and manifest via a reflex center involving a long loop.

Adult↗
PubMed2005

Vibrational and surface-enhanced vibrational spectra of 6-nitrochrysene.

The infrared and Raman spectra of solids and thin solid films of 6-nitrochrysene, its electronic spectra, and resonance Raman scattering (RRS) obtained with UV-laser excitation at 325 nm are reported. The vibrational assignment is supported by ab initio computations at the B3LYP/6-311G(d, p) level of theory. The molecular organization in nanometric films evaporated onto smooth metal surfaces of silver and copper was probed using reflection-absorption infrared spectroscopy (RAIRS). The results of the surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) obtained from nanometric films evaporated onto silver island films are also discussed. It was found that the molecule efficiently interacts with silver island film surfaces, and that the interaction leads to extensive photochemical reaction at the metal surface under laser illumination.

Chrysenes↗
PubMed1986

Vibrational analysis of the structure of gramicidin A. II. Vibrational spectra.

Raman and infrared spectra have been obtained of gramicidin A (GA) in the crystalline state both in the native form and complexed with CsSCN and KSCN, in solution in dioxane, and incorporated into lipid vesicles. Based on predictions from normal mode calculations of a number of relevant single- and double-stranded beta-helix conformations (Naik and Krimm, 1986), it has been possible to assign the structures of GA that are present under the above conditions. In the crystalline state, native GA has a double-stranded increases decreases beta 5.6 structure, whereas complexes with CsSCN or KSCN adopt a increases decreases beta 7.2 structure. In dioxane solution, the increases decreases beta 5.6 structure predominates. In lipid vesicles, the single-stranded beta 6.3-helix is found, which converts to a double-stranded helix on drying the sample. These results support our previous studies in showing that normal mode analysis can be a powerful technique in obtaining three-dimensional structural information from vibrational spectra.

Gramicidin↗
PubMed1989

Interpretation of DNA vibration modes: IV--A single-helical approach to assign the phosphate-backbone contribution to the vibrational spectra in A and B conformations.

A calculated approach based on the Higgs method for assigning the vibration modes of an infinite helicoidal polymeric chain has been performed on the basis of a reliable valence force field. The calculated results allowed the phosphate-backbone marker modes of the A and B forms, to be interpreted. In the dynamic models used, the bases have been omitted and no interchain interaction was considered. The calculation can also interprete quite satisfactorily the characteristic Raman peaks and infrared bands in the 1250-700 cm-1 spectral region arising from the sugar or sugar-phosphate association and reproduce their evolution upon the B----A DNA conformational transition. They clearly show that the phosphate-backbone modes in the above mentioned spectral region constitute the optical branches of the phonon dispersion curves with no detectable variation in the first Brillouin-zone.

Animals↗
PubMed1978

Vibration-induced hyperresponsiveness of arterial smooth muscle to noradrenaline with special reference to Raynaud's phenomenon in vibration disease.

Effects of in vitro and in vivo vibratory stimulations were studied on dose-response relationships of noradrenaline in excised femoral arteries of dogs and rats. The responsiveness of these arteries were enhanced after the application of the stimulation. The degree of the hyperresponsiveness was dependent upon frequency, amplitude, and duration of the stimulation. Based on the experimental results, a possible explanation was offered for Raynaud's phenomenon in vibration disease.

Animals↗
PubMed1985

Comparative study of vibration disease among operators of vibrating tools by factor analysis.

Principal component analysis was carried out to determine the interrelationships between subjective symptoms experienced by workers using various types of vibrating tools (brush saws (41), rock drills (39), chipping hammers (42) and chain saws (49)) and control groups (clerks (44), farmers (42)). The characteristics of the patterns of common factors extracted from these symptoms and the frequency distribution of the factor score of the main principal components were compared among the groups. From a wide variety of symptoms, a principal component related to peripheral nerves, muscles, and joints and a component related to peripheral circulation were extracted specifically and separately. The complaints of rock drillers reflected peripheral circulatory factor and those of chain saw users presented a complex factor of nerve muscle, and joints.

Adult↗
PubMed1997

Comparison of a neurothesiometer and vibration in measuring vibration perception thresholds and relationship to nerve conduction studies.

OBJECTIVE: To compare vibration perception thresholds (VPTs) obtained with two different instruments, a neurothesiometer and a vibratron, and to characterize variability of repeat measures and correlation with sural nerve conduction parameters. RESEARCH DESIGN AND METHODS: A total of 152 patients with diabetic peripheral neuropathy received electrodiagnostic evaluation and quantitative VPT testing with the Vibratron II and the Horwell Neurothesiometer. Of the patients, 42 returned for repeat nerve conduction studies and VPT testing with both types of equipment on three separate occasions. RESULTS: The variability of repeat testing for the vibratron was 34 and 31% in the right and left first toes, respectively. Variability for neurothesiometer was 8 and 6% for the right and left toes. This variability compares with that of sural nerve conduction velocity of 2% and that of sural nerve amplitude of 8% in this series of patients. CONCLUSIONS: We conclude that VPT determined with the neurothesiometer is less variable than with the vibratron and more reflective of peripheral nerve function. Our results indicate that the neurothesiometer can be used reliably in clinical research trials.

Diabetes Complications↗
PubMed1992

[Current aspects of the etiology, pathogenesis, clinical picture and prevention of vibration disease from local vibration].

Vibratory pathology goes on occupying the leading position in the pattern of occupational diseases. As to the industrial sources of local vibration, a hand power tool is most dangerous. The authors review differences in approaches to the estimation of vibratory disorders in the USSR and abroad, provide the main classifications of the vibratory syndrome and vibratory disease. Show that the pathogenesis of vibratory disease rests on a complex mechanism of neuroreflex and neurohumoral disorders leading to the development of congestive excitation followed by stable changes both in the receptor apparatus and different parts of the nervous system. The clinical symptomatology may include neurovascular disorders, lesions of the neuromuscular system, impairment of the bones and joints, alterations in metabolism, and so forth. In elaborating current measures aimed at vibratory disease prevention, use was made of the data of the prognosis of vibratory pathology risk. Measures for primary and secondary medical prophylaxis, new methods of early diagnosis, pathogenetic therapy with the use of stimulants of non-specific body resistance are described in detail.

Humans↗