Vibrational Symmetry Research Articles

L-glutamine: Dynamical properties investigation by means of INS, IR, RAMAN, 1H NMR and DFT techniques

Vibrational spectra of L-glutamine in the solid state were studied using the inelastic neutron scattering (INS), infrared (IR), Raman and 1H NMR spectroscopy techniques. DFT calculation using CASTEP code with the periodic boundary conditions was used to determine and describe the normal modes in the vibrational spectra of pure L-glutamine. An excellent agreement between the calculated and experimental INS, IR and Raman data has been found. Bands assigned to the stretching vibrations of the NH3+ group in hydrogen bonds are observed at 2400, 2618 and 2619cm−1, while the NH3+ torsion vibration mode is observed at 441cm−1. The band at 2041cm−1 is assigned to combinations of the NH3+ bending symmetry vibration and the CO2- rocking vibration and can be used as an “indicator band” for the identification of the NH3+ groups in amino acid. For the L-glutamine an activation energy needed for the NH3+ group reorientation was obtained as 7.4kcal/mol. It was found, that the combination three spectroscopic methods (INS, IR and Raman) with calculations for the crystal state proved to be an effective tool to investigate dynamical properties of amino acid crystals.

Enhanced ultra-low-frequency interlayer shear modes in folded graphene layers.

Few-layer graphene has attracted tremendous attention owing to its exceptional electronic properties inherited from single-layer graphene and new features led by introducing extra freedoms such as interlayer stacking sequences or rotations. Effectively probing interlayer shear modes are critical for unravelling mechanical and electrical properties of few-layer graphene and further developing its practical potential. Unfortunately, shear modes are extremely weak and almost fully blocked by a Rayleigh rejecter in Raman measurements. This greatly hinders investigations of shear modes in few-layer graphene. Here, we demonstrate enhancing of shear modes by properly folding few-layer graphene. As a direct benefit of the strong signal, enhancement mechanism, vibrational symmetry, anharmonicity and electron-phonon coupling of the shear modes are uncovered through studies of Raman mapping, polarization- and temperature-dependent Raman spectroscopy. This work complements Raman studies of graphene layers, and paves an efficient way to exploit low-frequency shear modes of few-layer graphene and other two-dimensional layered materials.

Vibrational modes and symmetry in a hexagonal-cross-section nanowire

We theoretically study acoustic phonon modes in hexagonal-cross-section nanowires with a wurtzite structure. As numerical examples, we examine the dispersion relations of solid and hollow GaN nanowires. The calculated dispersion curves are classified into six modes: A1, A2, B1, B2, E1, and E2 modes. It is found that the eigenfrequencies of the E2, B1, and B2 modes are particularly sensitive to the ratio of the inner side to outer side lengths of the hexagonal hollow nanowire.

Vibrational Activation of Methane Chemisorption: The Role of Symmetry.

Quantum state-resolved reactivity measurements probe the role of vibrational symmetry on the vibrational activation of the dissociative chemisorption of CH4 on Pt(111). IR-IR double resonance excitation in a molecular beam is used to prepare CH4 in all three different vibrational symmetry components A1, E, and F2 of the 2ν3 antisymmetric stretch overtone vibration. Methyl dissociation products chemisorbed on the cold Pt(111) surface are detected via reflection absorption infrared spectroscopy (RAIRS). We observe similar reactivity for CH4 prepared in the A1 and F2 sublevels but up to a factor of 2 lower reactivity for excitation of the E sublevel. It is suggested that differences in the localization of the C-H stretch amplitudes for the three states at the transition state leads to the observed difference in reactivity rather than state-specific vibrational energy transfer to electronic excitation of the metal.

Improvement of Vocal Pathologies Diagnosis Using High-Speed Videolaryngoscopy

Introduction The study of the dynamic properties of vocal fold vibration is important for understanding the vocal production mechanism and the impact of organic and functional changes. The advent of high-speed videolaryngoscopy (HSV) has provided the possibility of seeing the real cycle of vocal fold vibration in detail through high sampling rate of successive frames and adequate spatial resolution. Objective To describe the technique, advantages, and limitations of using HSV and digital videokymography in the diagnosis of vocal pathologies. Methods We used HSV and digital videokymography to evaluate one normophonic individual and four patients with vocal fold pathologies (nodules, unilateral paralysis of the left vocal fold, intracordal cyst, and adductor spasmodic dysphonia). The vocal fold vibration parameters (glottic closure, vibrational symmetry, periodicity, mucosal wave, amplitude, and glottal cycle phases) were assessed. Results Differences in the vocal vibration parameters were observed and correlated with the pathophysiology. Conclusion HSV is the latest diagnostic tool in visual examination of vocal behavior and has considerable potential to refine our knowledge regarding the vocal fold vibration and voice production, as well as regarding the impact of pathologic conditions have on the mechanism of phonation.

Emergence of colour symmetry in free-vibration acoustic resonance of a nonlinear hyperelastic material

We investigated free-vibration acoustic resonance (FVAR) of two-dimensional St Venant-Kirchhoff-type hyperelastic materials and revealed the existence and structure of colour symmetry embedded therein. The hyperelastic material is isotropic and frame indifferent and includes geometrical nonlinearity in its constitutive equation. The FVAR state is formulated using the principle of stationary action with a subsidiary condition. Numerical analysis based on the Ritz method revealed the existence of four types of nonlinear FVAR modes associated with the irreducible representations of a linearized system. Projection operation revealed that the FVAR modes can be classified on the basis of a single colour (black or white) and three types of bicolour (black and white) magnetic point groups: [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. These results demonstrate that colour symmetry naturally arises in the finite amplitude nonlinear FVAR modes, and its vibrational symmetries are explained in terms of magnetic point groups rather than the irreducible representations that have been used for linearized systems. We also predicted a grey colour nonlinear FVAR mode which cannot be derived from a linearized system.

Correlation Between the Basic Video Laryngostroboscopic Parameters and Multidimensional Voice Measurements

The aim of this study is to evaluate the correlations among the basic video laryngostroboscopic (VLS) parameters and vocal function assessed using a multidimensional set of perceptive, acoustic, aerodynamic, and subjective measurements. Digital VLS recordings and multidimensional voice assessment were performed for 108 individuals, namely 26 healthy and 82 patients with mass lesions of vocal folds and paralysis. The VLS variables (glottal closure, regularity, mucosal wave on the affected/healthy side, symmetry of vibration, and symmetry of image) were rated and quantified on a visual analog scale. Correlations among the VLS parameters and results of acoustic voice analysis and voice range profile (VRP), data of subjective (voice handicap index [VHI] and glottal function index [GFI]), perceptual (G-grade, R-roughness, B-breathiness, A-asthenic scale), and dysphonia severity index (DSI) measurements were tested using Pearson's correlation coefficient. The intercorrelations of VLS parameters in vocal performance were moderate to strong and statistically significant for the entire functional measurements obtained through different modalities. The definitive correlations between VLS and VRP parameters were as follows: r=0.69-0.79 for normal profile coverage, r=0.67-0.76 for dynamic intensity, and r=0.67-0.74 for maximum intensity. All VLS parameters correlated moderately with VHI, GFI, and DSI (r=0.5-0.65, r=0.4-0.57, and r=0.61-0.69, respectively). The strongest correlations were found between VLS parameters and G factor of the GRBA scale (r=0.68-0.88). Correlation analysis of the vibratory pattern of the vocal folds obtained via VLS provides more comprehensive insight into the pathophysiology of phonation and suggests the documented and measurable evidence of complex mechanisms of vocal outcome.

Recovery of vibratory function after vocal fold microflap in a rabbit model

The purpose of this study was to evaluate the return of vibratory function and restoration of vibration amplitude and symmetry after vocal fold microflap surgery. Prospective in vivo animal model. Microflap surgery was performed on 30 New Zealand white breeder rabbits. The left vocal fold received a 3-mm epithelial incision and mucosal elevation, while the contralateral vocal fold was left intact to serve as an internal control. Quantitative analysis of amplitude ratio and lateral phase difference were measured using high-speed laryngeal imaging at a frame rate of 10,000 frames per second from animals undergoing evoked phonation on postoperative days 0, 1, 3, 5, and 7. Quantitative measures revealed a significantly reduced amplitude ratio and lateral phase difference on day 0 after microflap. These impairments of vibratory function on day 0 were associated with separation of the vocal fold's body-cover layer. Amplitude ratio increased significantly by day 3 after microflap, with further increases in vibration amplitude on days 5 and 7. While the amplitude ratio improved significantly on day 3, lateral phase difference decreased significantly on day 3, and returned to normal on days 5 and 7. High-speed laryngeal imaging was used to investigate the natural time course of postmicroflap recovery of vibratory function. Results revealed the restoration of vibration amplitude and lateral phase difference by days 3 to 7 after microflap. The time period of improved vibratory function observed in this study coincides with the end of the well-documented inflammatory phase of vocal fold wound repair. N/A.

Effectiveness of Laryngostroboscopy for Monitoring the Evolution of Functional Dysphonia after Rehabilitator Treatment

The aim of this study is to evaluate the effectiveness of the laryngostroboscopy for monitoring the evolution of patients with functional dysphonia before and after the logopedic vocal treatment. We performed a prospective observational study of 65 dysphonic patients diagnosed of functional dysphonia, where we analyzed four stroboscopic parameters (glottal closure, vocal fold vibration, mucosal wave and phase symmetry) by a protocol based on systematic subjective evaluation of the stroboscopic images before and after the rehabilitator treatment; and the results were stratified according to the clinical course. All patients, before the treatment, had some abnormality in at least one of the four analyzed aspects. After the vocal treatment, we found improvement of the four parameters in different degrees, and we just found a statistically significant relationship between the evolution of the glottal closure and the clinical course. We believe that the laryngostroboscopy, systematized through a protocol, is a useful technique for the diagnosis of functional abnormalities in patients with functional dysphonia but it is not a very useful technique for evaluating the results after the rehabilitator treatment, as there is not a statistically significant relationship between clinical course and the change in the most stroboscopic parameters, so it shouldn't be the only technique used for these proposes.

Quantitative Evaluation of Video Laryngostroboscopy: Reliability of the Basic Parameters

The purpose of this study was to evaluate quantitatively the basic parameters of the video laryngostroboscopy (VLS) and determine the sensitivity and specificity of these parameters discriminating healthy and pathological voice classes. Digital VLS recordings were performed for 159 individuals: 26 healthy and 133 patients. VLS variables (glottal closure, regularity, mucosal wave on the affected/healthy side, symmetry of vibration, and symmetry of image) were rated two times with the time interval of 1 year by three laryngologists. To evaluate interrater and test-retest reliability, intraclass correlation coefficients (ICCs) were calculated. To evaluate sensitivity and specificity of the VLS parameters, discriminant analysis was used. Moderate to almost perfect levels (ICC 0.46-0.90) of interrater reliability were revealed for most of the basic VLS parameters. The ICC of the interrater reliability was highest for symmetry of glottal image; the most problematic VLS parameter for rating was mucosal wave on the healthy side. ICC of the test-retest reliability were 0.71-0.95, P<0.001. An optimum system of VLS parameters discriminating normal and pathological voice subgroups with sensitivity 96.3% and specificity 100% included glottal closure and mucosal wave on the affected side. The quantitative evaluation of the VLS using basic parameters showed to be reliable in clinical settings and demonstrated high sensitivity and specificity distinguishing healthy and pathological voice patient groups.

Lattice dynamics of Ti-based pnictide superconductors Ba1−xNaxTi2Sb2O

The lattice dynamics of layered Ba${}_{1\ensuremath{-}x}$Na${}_{x}$Ti${}_{2}$Sb${}_{2}$O pnictides ($0\ensuremath{\le}x\ensuremath{\le}0.3$) is studied experimentally by means of Raman scattering and theoretically within the density functional theory. Both symmetry allowed Raman-active modes are observed in the spectra and assigned to the lattice eigenmodes: $z$-axis motion of Sb ions ($A$${}_{1g}$-symmetry mode) and in-$xy$-plane displacement of Sb ($E$${}_{g}$-symmetry vibration). Calculated and experimental frequencies of these modes are found to be in good agreement. The $E$${}_{g}$ mode exhibits a nonmonotonous dependence of its frequency upon doping, which is found to correlate with the variation of Sb-Ti distances and strength of the interaction between Ti${}_{2}$Sb${}_{2}$O slabs.

2P1-10 Vibrational modes and symmetry in a hexagonal cross-section nanowire(Poster Session)

2P1-10 Vibrational modes and symmetry in a hexagonal cross-section nanowire(Poster Session)

Vibronic coupling in asymmetric bichromophores: Theory and application to diphenylmethane

The theory for modeling vibronic interactions in bichromophores was introduced in sixties by Witkowski and Moffitt [J. Chem. Phys. 33, 872 (1960)] and extended by Fulton and Gouterman [J. Chem. Phys. 35, 1059 (1961)]. The present work describes extension of this vibronic model to describe bichromophores with broken vibrational symmetry such as partly deuterated molecules. Additionally, the model is extended to include inter-chromophore vibrational modes. The model can treat multiple vibrational modes by employing Lanczos diagonalization procedure of sparse matrices. The developed vibronic model is applied to simulation of vibronic spectra of flexible bichromophore diphenylmethane and compared to high-resolution experimental spectra [J. A. Stearns, N. R. Pillsbury, K. O. Douglass, C. W. Müller, T. S. Zwier, and D. F. Plusquellic, J. Chem. Phys. 129, 224305 (2008)].

Preliminary modeling of CH3D from 4000 to 4550 cm−1

A new study of 12CH3D line positions and intensities was performed for the upper portion of the Enneadecad polyad between 4000 and 4550cm−1. For this, FTIR spectra were recorded with D-enriched methane samples (at 80K with a Bruker 125 IFS at 0.005cm−1 resolution and at 291K with the McMath-Pierce FTS at 0.011cm−1 resolution, respectively). Line positions and intensities were retrieved by least square curve-fitting procedures and analyzed using the effective Hamiltonian and the effective dipole moment expressed in terms of irreducible tensor operators adapted to symmetric top molecules. Initially, only the cold spectrum was used to identify quantum assignments and predict 12CH3D relative intensities in this region. To assign higher quanta up to J equal 14, additional line positions and intensities were obtained from two room temperature spectra. In the final stage, measured intensities from both the cold and the room temperature data were normalized to corresponding values at 296K and then averaged. Combining the two temperature datasets confirmed the assumed quantum assignments and also demonstrated the relative accuracies to be better than ±0.0002cm−1 for line positions and at least ±6% for intensities so that ∼1160 features were selected. Including additional assignments from the room temperature spectra alone permitted 1362 line intensities of 11 bands (involving 23 vibrational symmetry components) to be reproduced with an RMS of 9%. Over 4085 selected positions for 12 bands were modeled to 0.008cm−1. Nevertheless a number of known assignments could not be modeled to within our experimental precisions. More work is needed to obtain a complete characterization of this complex polyad.

Effectiveness of laryngostroboscopy for monitoring the evolution of vocal nodules after rehabilitator treatment

The aim of this study is to evaluate the effectiveness of the laryngostroboscopy for monitoring the evolution of patients with vocal nodules before and after the logopedic vocal treatment. We performed a prospective observational study of 97 dysphonic patients diagnosed of vocal nodules, where we analyzed four stroboscopic parameters (glottal closure, vocal fold vibration, mucosal wave and phase symmetry) by a protocol based on systematic subjective evaluation of the stroboscopic images before and after the rehabilitator vocal treatment; and the results were stratified according to the clinical course. All patients, before the treatment, had some abnormality in at least one of the four analyzed aspects. After the vocal treatment, we found improvement of the four parameters in different degrees. Also, we found a statistically significant relationship between the evolution of each parameter and the clinical course. We believe that the laryngostroboscopy, systematized through a protocol, is a useful technique for the diagnosis of structural abnormalities in patients with vocal nodules and is a useful technique for evaluating the results after the rehabilitator treatment, as there is a statistically significant relationship between clinical course and the change in the stroboscopic findings. However it should not be the only technique used for these proposes.

Formation and Infrared Emissivity of Microarc Oxidation Coatings on Mg-7Li Alloy

Ceramic coatings were successfully fabricated on Mg-7Li alloy in Na2SiO3 electrolyte by microarc oxidation (MAO). The phase composition, formation mechanism and infrared emissivity of the coatings were investigated. Results show that the surface of MAO coating exists some micropores with a diameter of 2-6μm due to electric breakdown. The MAO coating with 13μm thickness is mainly composed of MgO, Li2O2 and Mg2SiO4. The infrared emissivity of the MAO coating is higher than that of bare Mg-7Li alloy, mainly because the coating consisting of ionic crystals has lower lattice vibration symmetry and larger dipole moment.

Vocal Fold Vibratory Behavior Changes following Surgical Treatment of Polyps Investigated with High-Speed Videoendoscopy and Phonovibrography

The goal of this study was to objectively quantify the changes in vocal fold vibratory characteristics before and after surgery with high-speed videoendoscopy and the image analysis tool phonovibrography. High-speed videoendoscopic data, audio recordings, and Voice Handicap Index scores were collected from 8 subjects with a diagnosis of unilateral vocal fold polyps, before operation and at 1 week and 1 to 3 months after operation. We then analyzed the objective phonovibrographic patterns and parameters describing the vocal fold vibratory behavior. On phonovibrography, the visual representations of the vocal fold vibratory characteristics, from both the individual and the group data, demonstrated very different patterns before surgery and both 1 week and 1 to 3 months after surgery. The individual phonovibrograms obtained from the left and right true vocal folds clearly demonstrated the lesion site and its effects on the vocal fold vibratory characteristics for each subject. The improvements in amplitude and symmetry (relative vibratory amplitude and vibration amplitude symmetry) of vocal fold vibration were quantified; the difference was greatest between data from before surgery and data from 1 week after surgery. The visual phonovibrographic patterns and quantitative data revealed marked changes in vocal fold vibratory patterns after operation and continued improvement at 1 to 3 months.

Ionic Structures of Nanobased FeCl3/[C4mim]Cl Ionic Liquids

We synthesized a series of FeCl(3)/[C(4)mim]Cl (iron(III) chloride with 1-butyl-3-methylimidazolium chloride) ionic liquids. The temperature dependence of the Raman spectra of the FeCl(3)/[C(4)mim]Cl ionic liquids was measured for the first time to analyze their ionic species. In addition, the infrared spectra, thermodynamic properties, and freeze-fracture transmission electron microscopy were combined together with the Raman spectra to reveal the microscopic information of the FeCl(3)/[C(4)mim]Cl ionic liquids. When the mole ratio of FeCl(3)/[C(4)mim]Cl is less than 1, the Raman scattering identifies the presence of [FeCl(4)](-) in the ionic liquid. When FeCl(3) is in excess, [Fe(2)Cl(7)](-) begins to appear. Besides, we found that the relative intensity of the two symmetry vibrations of [Fe(2)Cl(7)](-) is changing as the temperature is varied. The strength of the interionic interactions in FeCl(3)/[C(4)mim]Cl ionic liquids follows the order 1/1.5 > 1.5/1 > 1/1 due to the formation of [FeCl(4)](-) and [Fe(2)Cl(7)](-). The nanostructures in FeCl(3)/[C(4)mim]Cl ionic liquids were observed for the first time by using biological imaging. The sizes of the local domains are found to be tens of nanometers.

A symmetry adapted approach to the dynamic Jahn‐Teller problem: Application to mixed‐valence polyoxometalate clusters with keggin structure

AbstractIn this article, we present a symmetry‐adapted approach aimed to the accurate solution of the dynamic vibronic problem in large scale Jahn‐Teller (JT) systems. The algorithm for the solution of the eigen‐problem takes full advantage of the point symmetry arguments. The system under consideration is supposed to consist of a set of electronic levels mixed by the active JT and pseudo JT vibrational modes. Applying the successive coupling of the bosonic creation operators, we introduce the irreducible tensors that are called multivibronic operators. Action of the irreducible multivibronic operators on the vacuum state creates the vibrational symmetry adapted basis that is subjected to the Gram‐Schmidt orthogonalization at each step of evaluation. Finally, the generated vibrational basis is coupled to the electronic one to get the symmetry adapted electron‐vibrational (vibronic) basis within which the full matrix of the JT Hamiltonian is blocked according to the irreducible representations (irreps) of the point group. The proposed approach is a part of our study of the nanosized mixed valence (MV) clusters with large number of delocalized electrons that are at the border line between quantum and classical objects. Here, we illustrate in detail the developed technique by the application to the 2e‐reduced MV dodecanuclear Keggin anion in which the electronic pair is delocalized over 12 sites (overall symmetry Td) giving rise to the (1T2+1E+1A1)⊗(e+t2) (3T1+3T2)⊗(e+t2) combined JT/pseudo JT problems for the spin‐singlet and spin‐triplet states. © 2012 Wiley Periodicals, Inc.

Chondrocytes suspended in modified fibrin glue for vocal fold augmentation: An in vitro study in a porcine larynx model

Injection laryngoplasty is an option for treatment of dysphonia following vocal fold paralysis. Modified fibrin glue with suspended chondrocytes might be a favorable cell-based material for permanent vocal fold medialization. We compared fibrin glue with suspended chondrocytes to collagen and hyaluronic acid gels concerning alteration of vocal fold vibration and correct intralaryngeal placement after intralaryngeal injection into porcine larynges. Viscoelastic properties of the materials were analyzed by means of a parallel plate rheometer. Fibrin glue with cells was comparable to collagen and hyaluronic acid with respect to amplitudes, symmetry, and periodicity of vocal fold vibration. Application and positioning of fibrin glue with suspended chondrocytes were technically undemanding and comparable with controls. Complex stress modulus of fibrin glue with suspended cells was comparable to that of collagen gel. Fibrin glue with suspended chondrocytes seems suitable for the indication of injection laryngoplasty and holds promise for permanent vocal fold medialization.