Virtual histology study of atherosclerotic plaque composition in patients with stable angina and acute phase of acute coronary syndromes without ST segment elevation

Introduction Rupture of vulnerable atherosclerotic plaques is the cause of most acute coronary syndromes (ACS). Postmortem studies which compared stable coronary lesions and atherosclerotic plaques in patients who have died because of ACS indicated high lipid-core content as one of the major determinants of plaque vulnerability. Objective Our primary goal was to assess the potential relations of plaque composition determined by IVUS-VH (Intravascular Ultrasound - Virtual Histology) in patients with stable angina and subjects in acute phase of ACS without ST segment elevation. Methods The study comprised of 40 patients who underwent preintervention IVUS examination. Tissue maps were reconstructed from radio frequency data using IVUS-VH software. Results We analyzed 53 lesions in 40 patients. Stable angina was diagnosed in 24 patients (29 lesions), while acute phase of ACS without ST elevation was diagnosed in 16 patients (24 lesions). In the patients in acute phase of ACS without ST segment elevation IVUS-VH examination showed a significantly larger area of the necrotic core at the site of minimal lumen area and a larger mean of the necrotic core volume in the entire lesion comparing to stable angina subjects (1.84±0.90 mm2 vs. 0.96±0.69 mm2; p3 vs. 11.54±14.15 mm3; p<0.05 respectively). Conclusion IVUS-VH detected that the necrotic core was significantly larger in atherosclerotic lesions in patients in acute phase of ACS without ST elevation comparing to the stable angina subjects and that it could be considered as a marker of plaque vulnerability

The Acoustic Pressure Radiated by a Vibrating Circular Plate within the Fraunhofer Zone of the Three-Wall Corner Region

The Neumann boundary value problem has been solved for the region bounded by the three perfect rigid infinite baffles arranged perpendicularly to one another. The harmonically vibrating clamped circular plate embedded in one of the baffles is the sound source. It has been assumed that the amplitude of the plate's transverse vibrations is small to use the linear Kelvin-Voigt theory. The Green function has been applied to obtain the asymptotic formulae describing the distribution of the acoustic pressure within the Fraunhofer zone. The analysis of sound radiation has been performed for some selected surface excitations and for some different plate's locations. The acoustic pressure distribution has been examined including the acoustic attenuation and the internal attenuation of the plate's material

The acoustic power radiated by a circular membrane excited for vibration both by means of the edge and by external surface load

In this paper the acoustic power of the circular membrane, excited both by the edge and external exciting forces uniformly distributed over the whole surface, is examined. Some different amplitudes of exciting factors and some differences between the phases of excitations were considered. It has been assumed that the source of a sound is located in a flat, rigid and infinite baffle and is sourrounded by a lossless and homogeneous fluid medium. The vibrations are axisymmetric and time-harmonic. Employing the Cauchy's theorem of residues and asymptotic formulae for the Bessel functions, the asymptotes for active and reactive power consisting of elementary functions are obtained. The acoustic power radiated by the membrane was shown graphically in terms of the parameters describing both kinds of excitations

Asymptotic Formulae of the Modal Acoustic Impedance for the Asymmetric Vibrations of a Clamped Circular Plate

The asymptotic and approximate formulae for the asymmetric modal acoustic self- and mutual-impedance have been presented for a clamped circular plate embedded into a flat rigid baffle. The formulae have been obtained for the wide frequency band covering the low frequencies, the high frequencies and the middle frequencies. The high frequency asymptotics have been achieved using the method of contour integral and the method of stationary phase. The products of the Bessel and Neumann functions have been expressed as the asymptotic expansions. Further, the approximate formulae valid within the low and middle frequencies have been obtained from the high frequency asymptotics using some mathematical manipulations. The formulae presented are valid for both the axisymmetric vibrations and the asymmetric vibrations

The Acoustic Pressure Radiated by a Vibrating Circular Plate within the Fraunhofer Zone of the Three-Wall Corner Region

The Neumann boundary value problem has been solved for the region bounded by the three perfect rigid infinite baffles arranged perpendicularly to one another. The harmonically vibrating clamped circular plate embedded in one of the baffles is the sound source. It has been assumed that the amplitude of the plate's transverse vibrations is small to use the linear Kelvin-Voigt theory. The Green function has been applied to obtain the asymptotic formulae describing the distribution of the acoustic pressure within the Fraunhofer zone. The analysis of sound radiation has been performed for some selected surface excitations and for some different plate's locations. The acoustic pressure distribution has been examined including the acoustic attenuation and the internal attenuation of the plate's material

Acoustic Power Radiated by a System of Two Vibrating Circular Membranes Located at the Boundary of Three-Wall Corner Spatial Region

Two vibrating circular membranes radiate acoustic waves into the region bounded by three infinite baffles arranged perpendicularly to one another. The Neumann boundary value problem has been inves- tigated in the case when both sources are embedded in the same baffle. The analyzed processes are time harmonic. The membranes vibrate asymmetrically. External excitations of different surface distributions and different phases have been applied to the sound sources’ surfaces. The influence of the radiated acoustic waves on the membranes’ vibrations has been included. The acoustic power of the sound sources system has been calculated by using a complete eigenfunctions system

The acoustic radiation impedance of a circular membrane vibrating near the three-wall corner

A flat circular membrane is located near the three- wall corner, limited by the three rigid baffles arranged perpendicularly to each other. The problem of sound radiation has been solved using the spectral form of the Green function for this Neumann boundary value problem together with the complete eigenfunction system of the axisymmetric and asymmetric modes of the membrane is excited by a surface vibrating harmonically with respect to time within the vacuum. The membrane is excited by a surface force. The acoustic attenuation 3399effect has been taken into account as well as the influence of the corner baffles. The resultant sound pressure and the resultant acoustic impedance have been presented as their eigenfunction series. The modal, self and mutual, radiation resistance has been presented in the form of the approximation valid within the low frequency vibration range. The low frequency approximation for the modal radiation reactance has been obtained on the basis of the radiation resistance using the Hilbert transform

The Low Frequency Approximation of the Sound Radiation Power of Two Vibrating Circular Pistons Embedded in Two Dierent Rigid Planes of a Three-wall Corner

The problem of sound radiation by a system consisting of two vibrating circular pistons embedded in two of three dierent planes perpendicular to one another forming a three-wall corner is considered. The earlier published results dealing with the sound radiation by sources vibrating in a three-wall corner are the basis of analysis. According to the earlier studies, the exact formulae for acoustic power of radiation of two circular pistons are used. The formulae are expressed as double Fourier integrals. The active and reactive, self and mutual, components are separated from them as well as the corresponding expressions of the acoustic power of mirror images of the piston sources. The acoustic power of the two sources are expressed in the form of the Rayleigh formulae whereas, in the case of the mirror images, it is expressed in the form of the single series expansion containing spherical Bessel and Neumann functions. In the case of the mutual acoustic power of the sources, approximate formulae are presented for low frequencies. On the basis of the results obtained, the corresponding formulae valid for a two-wall corner are presented as the limiting transitions. All the results presented can be useful, e.g. in designing the room acoustics and outdoor system everywhere the free eld conditions are disturbed by the acoustic waves reected at rigid vertical walls for the wavelengths being considerably shorter than the geometric sizes of the walls

The Modal Low Frequency Noise of an Elastically Supported Circular Plate

The modal low frequency noise generated by a vibrating elastically supported circular plate embedded into a flat infinite baffle has been examined. The main aim of this study is the analysis of the radiation efficiency. Low frequency approximated formulas have been presented. They are valid for all the limiting boundary conditions of the plate with its edge clamped, guided, simply supported or free as well as for all the intermediate axisymmetric boundary configurations. The formulas are expressed in the elementary form, useful for numerical computations. They are a generalization of some earlier published results. First, they are valid for axisymmetric and asymmetric modes since both kinds of modes play an important role in the low frequency range. Second, a single formula for the radiation efficiency, valid for all the axisymmetric boundary configurations, has been proposed. A numerical example for the sound power radiation has been given for some hatchway covers mounted on a ship deck