Dislocation and disclination loops in the virtual-defect method

A method of virtual circular defect loops is developed for determining the elastic fields produced by defects in a bounded medium in the case of an axially symmetric geometry. In this method, continuously distributed virtual circular Volterra and Somigliana dislocation loops are adjusted in such a way as to satisfy the boundary conditions imposed at free surfaces and interfaces. Original calculations of the elastic fields of circular defect loops of different types are carried out. The elastic fields are found for the case of straight dislocations and disclinations in a plate that are perpendicular to the plate plane and for the case of circular disclination loops parallel to the plate plane or to an interface.     

CHAOS AND MULTIPLE PERIODS IN AN UNSYMMETRICAL SPRING AND DAMPING SYSTEM WITH CLEARANCE

Chaos and multiple periods are presented for the harmonically excited unsymmetrical spring and damping system with clearance. This paper demonstrates the non-linear behaviour of the motion through simulation and experiment. Intensive care and caution are taken in the experiments to observe the chaos and the multiple periods properly. The focus in this paper is mainly on the change of the bilinear spring stiffness ratio as a prime factor by which chaotic motions occur from quasi-periodic motion. Other investigations and effects on motion are also discussed for the changing of the extent of clearance. The investigations are based on frequency response curves. To understand the dynamics of the non-linearity of this model, all possible data processing and displaying techniques are taken into account. To observe the overall phenomena of this bilinear system, the resonance curves and the bifurcation diagrams are taken thoroughly for a wide frequency region.     

Microwave absorption studies of MgB2 superconductor

Microwave absorption studies have been carried out on MgB₂ superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime.     

Structure of electroactive coatings based on fullerene and its derivatives

The structures and properties of electroactive coatings based on fullerene and pyridyl-substituted fullerenopyrrolidines were studied using cyclic voltammetry, optical spectroscopy, atomic force microscopy, and other methods. The surface of the electrode of the ITO conducting glass (alloy of indium and tin oxides) was modified by direct casting or the introduction of an electroactive substance into a tetra(n-octyl)ammonium bromide matrix. Changes in the absorption spectra of the coatings agree with the presence of an electronic interaction between adjacent fullerene molecules. Tetra(n-octyl)ammonium bromide is involved in the organization of the fullerene-containing coatings with retention of the layered structure. According to the data of atomic force microscopy, the coating surface depends on both the composition of the solution and preparation method and the nature of addends in a C₆₀ molecule. The dispersion of fullerene in the tetra(n-octyl)ammonium bromide matrix and its interaction with the alkyl groups of the latter provide the hydrophobic microenvironment necessary for reversible electrochemical processes in an aqueous solution to occur. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 308–315, February, 2008.     

Complexation of amine free radicals during the radiation-induced chain oxidation reaction of <Emphasis Type="Italic">N,N,N′,N′</Emphasis>-tetramethyl-4,4′-diaminodiphenylmethane

Complexation of free radicals derived from the amine in the chain redox reaction in γ-irradiated solid PVC films doped with N,N,N′-N′-tetramethyl-4,4′-diaminodiphenylmethane (Am) and CBr₄ was studied by means of the ESR and luminescence techniques. The effect of concentration of the additives Am and CBr₄ on the quenching of fluorescence of Am^· radicals was examined. The data were rationalized in terms of the Stern-Volmer formalism for static quenching, which results from the formation of nonfluorescing ground-state charge-transfer complexes between the radical Am^·, as well as its dimeric form Am ₂ ^· , and CBr₄. The association constants of the complexes were determined. The mechanism of radiation-induced chain oxidation of Am involving these complexes is discussed.     

Analysis of Voice and Quantitative Measurement of Glottal Gap After Thyroplasty Type I in the Treatment of Unilateral Vocal Paralysis

Thyroplasty type I is one of several surgical treatments in which improving the voice of unilateral vocal fold paralysis is the ultimate objective. The goal of the surgery is the medialization of the paralyzed vocal fold. The purpose of this study is to evaluate the effectiveness of thyroplasty type I through acoustical analysis, aerodynamic measures, and quantitative videostroboscopic measurements. We report on 20 patients with unilateral vocal cord paralysis who underwent thyroplasty type I. We performed preoperative and postoperative video image analysis (normalized glottal gap area) and computer-assisted voice analysis (fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, mean phonation time, mean flow rate, mean subglottic pressure) in all patients. The glottal gap was significantly reduced after thyroplasty type I. Postoperative voice quality was characterized by an improved pitch and amplitude pertubation (jitter and shimmer), phonation time (mean phonation time), and subglottic pressure (mean subglottic pressure). Thyroplasty type I is an effective method for regaining glottal closure and vocal function.     

Laryngeal Gestures During Stop Production Using High-Speed Digital Images

On acoustic and fiberscopic studies of stop consonants, voice onset time and glottal width have been shown to be greatest in heavily aspirated stops, next greater for slightly aspirated stops, and least for unaspirated stops. Integrated activity of the thyroarytenoid and posterior cricoarytenoid muscles has been reported to be involved in differentiating aspirate characteristics of the stops. However, the fine movement of mucosal edges of vocal folds during the production of stops has not been well documented. In recent years, a new method for high-speed digital recording of laryngeal dynamics has made this possible. In the current study, the movements of vocal fold edges were documented during the period of stop production using a fiberscopic system of high-speed digital images. By observing the glottal width and the visual vibratory movements of vocal folds before voice onset, the heavily aspirated stop was characterized as being more prominent and dynamic than the slightly aspirated and unaspirated stops.     

Hyaluronic Acid: Its Role in Voice

The extracellular matrix (ECM), once regarded simply as a structural scaffold, is now recognized as an important modulator of cellular behavior and function. One component that plays a prominent role in this process is hyaluronic acid (HA)--a molecule found in many different tissues. Research into the roles of HA indicates that it plays a key role in tissue viscosity, shock absorption, and space filling. Specifically, research into the role of HA in laryngology indicates that it has profound effects on the structure and viscosity of vocal folds. This article provides an introduction to the structure and biological functions of HA and its importance in voice. In addition, an overview of the pharmaceutical applications of HA is discussed.     

Vocal Nodules and Laryngeal Morphology

Our purpose was to study the occurrence of vocal fold nodules under conditions of habitual vocal abuse associated with increased laryngeal muscle tension, to identify the existence of a relationship between vocal nodules and laryngeal morphology. We studied one group of 30 subjects with vocal nodules, 18 to 50 years old, who were compared with two control groups, one of females and one of males, consisting of 30 subjects each. The parameters evaluated were: type of vocal folds coaptation, glottic proportion (GP) and abduction angle (AA), obtained by videotelelaryngoscopy. In the nodules group, the larynges presented a mean value of GP similar to that of the female group, both of which were lower than the mean GP value of the male group. On the other hand, the mean AA was lower than the one in the female group, and closer to the one in the male group. We concluded that vocal nodules were present only in larynges with a predominantly young female morphology, with functional limitations of abduction.     

Synthesis and properties of oxide ion conductor Pr2Mo2O9 with La2Mo2O9 structure

Polycrystalline Pr₂Mo₂O₉ samples have been prepared by solid-state synthesis and single crystals of this compound have been grown. Pr₂Mo₂O₉ is unstable in the temperature range 700–900°C and partially decomposes with the formation of Pr₂Mo₃O₁₂ at these temperatures, but upon further heating to 1000–1050°C, Pr₂Mo₂O₉ is recovered. At room temperature, the structure, polymorphism, and physical properties of Pr₂Mo₂O₉ are similar to those of the known oxide ion conductor La₂Mo₂O₉. Pr₂Mo₂O₉ exhibits a reversible first-order phase transition to the cubic phase in the temperature range 520–540°C. The electric conductivity of Pr₂Mo₂O₉ is close to that of La₂Mo₂O₉ and amounts to 3.5 × 10⁻² S/cm at 700°C. The conductivity of Pr₂Mo₂O₉ is described by the Arrhenius law in the low-temperature phase and by the Vogel-Fulcher-Tammann equation in the high-temperature phase.