Vibrational characteristics of Balinese gamelan metallophones

A study of the eight metallophone pairs from a Balinese gamelan semara dana has been conducted. Acoustical recordings of metallophone bars being struck were used to examine ratios of overtone frequencies to the fundamental. Results showed large variability in the number and ratios of overtones present. Scanning laser Doppler vibrometry measurements made on several bars also revealed great variability in mode shapes present. The distribution of prominent overtones and their modal shapes do not appear to match those of Western metallophones. Notably, the overall gamelan metallophone characteristics are quite dissimilar to the glockenspiel, which disagrees with previous studies.     

Vibrational characteristics of rotating soft cylinders

Rotating structural components are omnipresent in engineering structures and natural world. This work investigates the effects of the centrifugal and Coriolis forces on the free vibrational characteristics of soft cylinders rotating with respect to the axis of symmetry based on the nonlinear elasticity and linear incremental theories. The formulations indicate that the biasing deformation, instantaneous elastic moduli, and incremental equations of motion strongly depend on the rotating speed. The characteristic equation for the natural frequency is derived using the state-space method and approximate laminate technique.The numerical examples included in this work demonstrate that the centrifugal and Coriolis forces might have significant effects on the vibrational characteristics of the cylinder. Results of this work will benefit the design and control of novel engineering systems with rotating soft cylinders or shafts.     

Vibrational characteristics of the niobium dichalcogenide. Bulk samples and nanofilms

A model of the niobium diselenide crystal lattice has been proposed. This model sufficiently describes the vibrational characteristics of both bulk samples and nanofilms with a thickness beyond one three-layered structural element. Calculation of the local Green functions and mean-squared atom amplitudes have been performed using the Jacobi-matrix method.Phonon density of states features stipulated by acoustic branches and low-frequency low-dispersion optical modes cross-over have been analyzed.     

Ultrasonic non-destructive measurements of cortical bone thickness in human cadaver femur

The knowledge of the cortical bone thickness profile in human bone has a two-fold clinical significance: to study the stress occurring in a loaded bone structure to optimize the design of prostheses; and to predict the onset of advanced bone disease such as osteoporosis. In this study, the cortical bone thickness in three embalmed human cadaver femora were measured non-destructively using an ultrasonic technique. These thickness measurements were also made using a computed tomographic (CT) scanning method. Subsequently bones were sectioned and the actual bone thicknesses in the same regions were measured using a micrometer. The correlation coefficient between the actual thickness and the ultrasonically measured thickness was 0.95 and with the CT was 0.62. Thus, these results show that, under present experimental conditions, ultrasonic thickness measurements compare well with the micrometer actual thickness results. This technique, when fully developed, can be used as a non-destructive tool for quantitative cortical bone thickness measurements. Moreover, the ultrasonic technique does not use ionizing radiation.     

Vibrational spectra of the tetramethylpnikogenonium ions

The tetramethylpnikogenonium ions (CH₃)₄X⁺ (X = N, P, As, Sb) have been studied by infrared and Raman spectroscopy. Additionally, their structures and vibrational frequencies were ab initio calculated at the HF/6-31+G* and for (CH₃)₄Sb⁺ at the HF/6-31+G*/LANL2DZ level of theory. For the tetrahedral cations an assignment of the vibrational frequencies is discussed on the basis of a comparison of calculated and measured frequencies.     

Vibrational spectroscopy of the seselin crystal

Seselin, C₁₄H₁₂O₃, is a coumarin which crystallizes in a monoclinic structure P2₁/b(C_2h⁵) with four molecules per unit cell. In a Fourier‐transform Raman spectroscopic study performed at room temperature, several normal modes were observed. Vibrational wavenumber and wave vector calculations using density functional theory were compared with experiment, which allowed the assignment of a number of normal modes of the crystal. Temperature‐dependent Raman spectra were recorded between 10 and 300 K. No anomalies were observed in the phonon spectra, indicating that the monoclinic structure remains stable. Copyright © 2007 John Wiley & Sons, Ltd.     

酚醌类化合物振动基频的计算,归属和讨论

本文对４,５－二羟基１,２－苯醌和２,５－二羟基－１,４－苯醌 的振动基频进行了量化计算和实验测定,应用Ｇａｕｓｓｉａｎ９４和ＭＯＰＡＣ计算相结合的方法,取长补短,归属了其振动光谱,并对两者的差异做了讨论。     

Vibrational modes of the stibine molecule

In this paper, we use the algebraic approach to describe the vibrational modes of stibine molecule (of C_3v molecular symmetry group) up to 21 quanta. As the stibine molecule exhibits stretch-bend resonances, we build an algebraic pyramidal coupling operator between stretching modes and bending modes adapted to this molecule. The standard deviation associated to the fit of the vibrational levels is 1.75 cm⁻¹.     

Vibrational resonance in the Morse oscillator

The occurrence of vibrational resonance is investigated in both classical and quantum mechanical Morse oscillators driven by a biharmonic force. The biharmonic force consists of two forces of widely different frequencies ω and Ω with Ω???ω. In the damped and biharmonically driven classical Morse oscillator, by applying a theoretical approach, an analytical expression is obtained for the response amplitude at the low-frequency ω. Conditions are identified on the parameters for the occurrence of resonance. The system shows only one resonance and moreover at resonance the response amplitude is 1/dω where d is the coefficient of linear damping. When the amplitude of the high-frequency force is varied after resonance the response amplitude does not decay to zero but approaches a nonzero limiting value. It is observed that vibrational resonance occurs when the sinusoidal force is replaced by a square-wave force. The occurrence of resonance and antiresonance of transition probability of quantum mechanical Morse oscillator is also reported in the presence of the biharmonic external field.     

Vibrational enhancement of the effective donor-acceptor coupling

This letter deals with a simple three-site model for charge transfer phenomena in a one-dimensional donor (D)-bridge (B)-acceptor (A) system coupled with vibrational dynamics of the B site. It is found that, in a certain range of parameters, the vibrational coupling leads to an enhancement of the effective donor-acceptor electronic coupling as a result of the formation of the polaron on the B site. This enhancement of the charge transfer efficiency is maximum at the resonance, where the effective energy of the fluctuating B site coincides with the donor (acceptor) energy.     

Vibrational spectroscopic and electrochemical characteristics of poly (propylene glycol)-silver triflate polymer electrolyte system

Fourier transform infrared spectroscopic and electrochemical complex impedance studies have been carried out on a series of complexes containing poly(propylene glycol) of molecular weight 4,000 and silver triflate (AgCF₃SO₃) salt corresponding to the ether oxygen to metal cation ratios (O : M) in the range 16:1 to 12:1. The formation of ion pairs and aggregates noticed in the case of specimens having high salt concentrations as well as the complete coordination of the cation with the ether oxygen at low salt concentrations within the PPG4000-AgCF₃SO₃ polymer electrolyte system have been confirmed. The appearance of two weak triflate bands at 1,032 and 1,272 cm⁻¹ in the absorption spectra in respect of low salt concentrations is indicative of the fact that triflate ions are free within the polymer matrix. The room temperature (298 K) electrical conductivity is found to increase with increasing ether oxygen content while exhibiting the maximum value of 7.1 × 10⁻⁵ Scm⁻¹ possibly due to silver ionic transport in the case of the typical composition having an O : M ratio of 16:1.     

Vibrational Spectrum of Tribromoethanol

Abstract

The molecular structure of tribromoethanol has been studied by Ab Initio theoretical calculations. The IR spectrum has been recorded in the range 4000—200 cm^?1. Whereas, the Raman spectrum has been determined by means of a SPEX 1403 spectrometer using the 5145Å exciting line of a Spectra—Physics 164 Ar ion laser. Depolarization ratios were also measured. The fundamental vibrations of CBr₃CH₂OH as well as some overtones, combinations and difference bands were assigned.     

Vibrational Spectrum of Bromal

Abstract

The molecular structure of tribromoacetaldehyde, Bromal, has been studied by Ab Initio theoretical calculations. The IR spectrum has been recorded in the range 4000–200 cm^?1. The Raman spectrum has been studied with a SPEX 1403 spectrometer using the 5145Å exciting line of a Spectra-Physics 164 Ar ion laser. Depolarization ratios were also measured. The fundamental vibrations of Br₃ CCOH and also some overtones, combinations and difference bands were assigned.     

Vibrational spectrum of perfluoroethane

We have obtained IR absorption spectra of a C₂F₆ gas and a C₂F₆ cryosolution in Xe (T = 163 K) in the fundamental and overtone ranges. We have interpreted 28 bands of ¹²C¹²CF₆ and three bands of ¹³C¹²CF₆. In the spectral ranges that correspond to vibrations that are combinations with ν₁, ν₇, and ν₅, we observe multiplets, which we attribute to interactions of the type of Fermi resonances between the states ν₁(A _1g ) ∼ ν₆(A _1g ), ν₇(E _g ) ∼ ν₆ + ν₁₁(E _g ) ∼ 2ν₈(E _g ), ν₅(A _2u ) ∼ ν₈ + ν ₁₁(A _2u ). We reveal an anomalous intensity distribution in the spectrum of an asymmetric isotopologue. For the basic and isotopic configurations of perfluoroethane, we calculate the coefficients of shapes of vibrations and the intensities of absorption bands. We reveal that the behavior of the groups ¹²CF₃ and ¹³CF₃ is indifferent to the excitation of doubly degenerate stretching vibrations ν₇(E _g ) and ν₁₀(Eu).     

Experimental analysis of the vibrational characteristics of the human skull

Analytical models of the human skull structure have generally been constructed so as to characterize the gross geometric features and material properties; however, a model should also have accurate frequency response characteristics since these are essential for collision and head injury analyses. An experimental investigation was conducted to identify the dynamic characteristics of freely vibrating human skulls. Resonant frequencies and associated mode shapes in the frequency band from 20 Hz to 5000 Hz were delineated for two dry human skulls. Osteometrically, one skull corresponds to a 50th percentile male (skull 1) and the second is representative of a 5th percentile female skull (skull 2). Digital Fourier analysis techniques were used to identify the resonant frequencies and corresponding mode shapes of each skull. Eleven resonant frequencies were identified for skull 1, with the lowest being 1385 Hz. In contrast, skull 2 exhibited only 6 resonant frequencies with the first being 1641 Hz. Nine mode shapes were identified for skull 1, but only 5 modes were recognized for skull 2. The vibrational pattern of the human skull, as indicated by its mode shapes in this limited study, seems to be a unique property of a particular skull. Skull satures did not appear to influence the modal pattern.     

Vibrational entropy and the structural organization of proteins

In this paper we analyze the vibrational spectra of a large ensemble of non-homologous protein structures by means of a novel tool, that we coin Hierarchical Network Model (HNM). Our coarse-grained scheme accounts for the intrinsic heterogeneity of force constants displayed by protein arrangements and also incorporates side chain degrees of freedom. Our analysis shows that vibrational entropy per unit residue correlates with the content of secondary structure. Furthermore, we assess the individual contribution to vibrational entropy of the novel features of our scheme as compared with the predictions of state-of-the-art network models. This analysis highlights the importance of properly accounting for the intrinsic hierarchy in force strengths typical of the different atomic bonds that build up and stabilize protein scaffolds. Finally, we discuss possible implications of our findings in the context of protein aggregation phenomena.