Second Sound Research Articles

Second sound seen

Second sound seen

Stability of Laminated Beams with Second Sound

Stability of Laminated Beams with Second Sound

Clinical features and prognostic factors in children with idiopathic pulmonary arterial hypertension

Objective To investigate the clinical features and prognostic factors in children with idiopathic pulmonary arterial hypertension(IPAH). Methods The data of children with IPAH diagnosed in Beijing Children's Hospital from January 2006 to December 2015 were collected.The cases were divided into survival group and death group according to the prognosis.The risk factors influencing prognosis in children with IPAH were identified by Logistic regression analysis. Results Total 26 patients were enrolled in this study, and 17 of them survived and 9 of them were dead.IPAH was found to be more common in school-age children.The average age of the patients was(6.6±3.6)years and the male to female ratio was 1.17∶1.All of the children had the symptoms with decreased activity tolerance and fatigue.The incidence of syncope and dyspnea and edema of lower extremity were 34.6%, 23.1%.Accentuated pulmonic second sound(P2) was detected in 92.3% of patients during physical examination, which was also the most common sign.About 50.0% patients were functional class Ⅲ-Ⅳ.Echocardiography showed that all childrens' mean pulmonary artery systolic pressure(PASP) was(79.0±20.3) mmHg(1 mmHg=0.133 kPa) and 16 of them with right ventricular dilatation.Electrocardiogram with ST-T changes and right ventricular high voltage were common.The average plasma level of brain natriuretic peptide(BNP) in all cases was(870.4±720.9) pg/ml.The single factor analysis illustrated that syncope(OR=26.25, 95%CI 3.04-226.60, P=0.003), heart functional class Ⅲ-Ⅳ(OR=19.199, 95%CI 1.88-196.53, P=0.0128), PASP≥70 mmHg(OR=9.936, 95%CI 1.81-∞, P=0.005), BNP≥850 pg/ml(OR=59.991, 95%CI 4.69-767.62, P=0.002) indicated the worse outcome. Conclusion IPAH in children is rare and the prognosis is poor.Syncope, cardiac function grade, PASP and the levels of BNP are the main important factors affecting the prognosis of children with IPAH.BNP has important clinical significance for the evaluation of IPAH and the prognosis of the disease. Key words: Idiopathic pulmonary arterial hypertension; Clinical features; Prognosis; Children

BLOW UP OF SOLUTIONS TO THE SECOND SOUND EQUATION IN ONE SPACE DIMENSION

BLOW UP OF SOLUTIONS TO THE SECOND SOUND EQUATION IN ONE SPACE DIMENSION

Prevalence of Heart Disease in School Children of Islamabad

Material and Methods: Islamabad is the new capital of Pakistan and is about 18 years old with the population of 150,000. It is situated 330 36’N, 72-50’S and 73°-24’ East of Greenwhich at the foot of Margala Hills at the altitude of 503-610 meters. The temperature varies from a maximum of 42°C in Summer to a minimum average of 3.4°C in Winter. Aortic systolic murmur was deemed signif icant if it was graded 3 or above and was conducted to the neck and the aortic component of the second sound was relatively soft. Results: A Total number of 15,100 children were examined out of’ which 8,607 (57%) children were male and 6,943 (43%) children were female. The age distribution of the cases is given as below:— Age 05—-07 08—- 10 11 - 13 14—15 Total Number of cases 12 14 17 7 50 2% complained of undue dyspnoca on exertion. 60% children belonged to the families with monthly income of less than Rs. 625/-. 17.2% of the Throat Swab Cultures were positive for Beta Hemolytic group A Streptococci and A.S.O. Titre were 200 units and above in 29% of the cases. Discussion: Our figures for rheumatic heart disease(1 . 52) per thousand are comparable to those of Abbasi et al., from Karachi, Miller et al., from USA and Stuckey et al., from Australia. Otherreports from Pakistan, India, Iran, Morocco, Egypt 23 show a very high prevalence rate which may be due to selection of slums and overcrowded areas in the survey. Acknowledgements: This paper was previewed by Dr. T. Strasser of W.1-1.O. Geneva for which we are most grateful. We wish to acknowledge our thanks National Science Foundation Islamabad which provided us the funds to carry out this study.

Rayleigh-Bѐnard Convection in a Second-Order Fluid with Maxwell-Cattaneo Law

The objective of the paper is to study the Rayleigh-Bѐnard convection in second order fluid by replacing the classical Fourier heat law by non-classical Maxwell-Cattaneo law using Galerkin technique. The eigen value of the problem is obtained using the general boundary conditions on velocity and third type of boundary conditions on temperature. A linear stability analysis is performed. The influence of various parameters on the onset of convection has been analyzed. The classical Fourier flux law over predicts the critical Rayleigh number compared to that predicted by the non-classical law. The present non-classical Maxwell-Cattaneo heat flux law involves a wave type heat transport (SECOND SOUND) and does not suffer from the physically unacceptable drawback of infinite heat propagation speed. It is found that the results are noteworthy at short times and the critical eigen values are less than the classical ones. Over stability is the preferred mode of convection.

A Second Second Sound?

A Second Second Sound?

Study of Rayleigh-Bénard Magneto Convection in a Micropolar Fluid with Maxwell-Cattaneo Law

The effects of result from the substitution of the classical Fourier law by the non-classical Maxwell-Cattaneo law on the Rayleigh-Benard Magneto-convection in an electrically conducting micropolar fluid is studied using the Galerkin technique. The eigenvalue is obtained for free-free, rigid-free and rigid-rigid velocity boundary combinations with isothermal or adiabatic temperature on the spin-vanishing boundaries. The influences of various micropolar fluid parameters are analyzed on the onset of convection. The classical approach predicts an infinite speed for the propagation of heat. The present non-classical theory involves a wave type heat transport (SECOND SOUND) and does not suffer from the physically unacceptable drawback of infinite heat propagation speed. It is found that the results are noteworthy at short times and the critical eigenvalues are less than the classical ones.

Absence of Slow Sound Modes in Supersolid 4He

Torsional oscillator experiments on solid 4He have been interpreted as showing mass decoupling similar to what one observes in a superfluid. Within the context of a two-component model for the supersolid one would expect the appearance of a second, slow acoustic mode. We have searched for this mode using an acoustic resonance technique. We have used porous membranes in bulk solid 4He analogous to a second sound experiment in the superfluid. We also investigated solid helium in Vycor using piezoelectrically driven titanium diaphragms (analogous to a fourth sound experiment in the liquid). Our measurements have shown no indication of an additional sound mode in the kHz range.

Effect of Second Sound on the Onset of Rayleigh-Benard Convection in a Coleman - Noll Fluid

This paper deals with linear stability analysis of the effects resulting from the substitution of the classical Fourier law by the non-classical Maxwell - Cattaneo law in Rayleigh - Benard convection in second order fluid is studies. Coleman-Noll constitutive equaion is used to give a viscoelastic correction. The eigenvalue is obtained for free - free isothernal boundary combination. The classical approach predicts an infinite speed for the propagation of heat. The present non-classical theory involves a wave type heat transport (SECOND SOUND) and does not suffer from the physically unacceptable drawback of infinite heat propagation speed. It is found that the results are noteworthy at short times and the critical eigenvalues are less than the classical ones.

Effect of Second Sound on the Onset of Rayleigh- Benard Convection in a Micropolar Fluid

The effects resulting from the substitution of the classical Fourier law by the non-classical Maxwell-Cattaneo law in Rayleigh-Benard convention in micropolar fluid is studied. The classical approach predicts an infinite speed for the propagation of heat. The present non-classical theory involves a wave type heat transport (SECOND SOUND) and does not suffer from the physically unacceptable drawback of infinite heat propagation speed. It is found that the results are noteworthy at short times and the critical sign values are less than the classical ones.

Boomless hearing/speaking configuration for sound receiving means

A hearing/speaking configuration (1) having a housing (2), having sound-reproducing means (20) accommodated in the housing (2), and having sound-receiving means (19) designed without a boom, wherein the sound-receiving means (19) is accommodated in the housing (2), as is the sound-reproducing means (20), wherein a first sound passage opening (16) and a second sound passage opening (25) are provided in the housing (2) and the sound-receiving means (19) has a directional characteristic with a main direction (28) and an extinction direction (30), and wherein the extinction direction (30) extends from the sound-receiving means (19) to the sound-reproducing means (20).

Fiber bolometer and emitter with negligible reflection for second sound measurements near the λ-point

Superconducting Pb–Au thin film bolometers for second sound (SS) measurements near the λ-point have been made on 8 μm diameter glass fibers. The small diameter of the fibers provides negligible cross-section to SS waves as close as ∼10 −5 K to the λ-point (for f=10 kHz), thus eliminating reflections that may unduly complicate the wave distribution in the experimental cell. The bolometers have isotropic sensitivity to SS waves in the plane perpendicular to the fiber. The operating temperature of the bolometers can be adjusted by changing an external magnetic field and/or by varying the bias current, while still maintaining a figure of merit of ∼30. A SS emitter producing planar waves was made using the same fibers.

Parametric generation of second sound in superfluid helium: Linear stability and nonlinear dynamics

We report experimental studies of parametric excitation of second sound (SS) by first sound (FS) in superfluid helium in a resonance cavity. The results on several topics in this system are presented: (i) The linear properties of the instability, namely, the threshold, its temperature and geometrical dependencies, and the spectra of SS just above the onset were measured. They were found to be in good quantitative agreement with the theory. (ii) It was shown that the mechanism of SS amplitude saturation is due to the nonlinear attenuation of SS via three wave interactions between the SS waves. Strong low-frequency amplitude fluctuations of SS above the threshold were observed. The spectra of these fluctuations had a universal shape with exponentially decaying tails. Furthermore, the spectral width grew continuously with the FS amplitude. The role of three and four wave interactions are discussed with respect to the nonlinear SS behavior. The first evidence of Gaussian statistics of the wave amplitudes for the parametrically generated wave ensemble was obtained. (iii) The experiments on simultaneous pumping of the FS and independent SS waves revealed several effects. Below the instability threshold, the SS phase conjugation as a result of three wave interactions between the FS and SS waves was observed. Above the threshold two interesting effects were found: a giant amplification of the SS wave intensity and strong resonance oscillations of the SS wave amplitude as a function of the FS amplitude. Qualitative explanations of these effects are suggested.

Second sound

Second sound

Second sound

Second sound

Acoustic Phase Conjugation in Superfluid Helium

We present the first experimental observation of phase conjugate (PC) second sound (SS) waves in superfluid helium. The main feature of a PC wave is that its phase is complex conjugate to the incident wave phase. It is generated and amplified as a result of nonlinear interaction between an incident SS wave and a first sound (FS) pumping wave. At FS amplitudes larger than the threshold value, a parametric instability, i.e., spontaneous decay of a FS wave into two SS waves, takes place. Three main, theoretically predicted, features of phase conjugate waves were verified experimentally.

Hyperbolic framework for thermoelastic materials

A THERMODYNAMIC framework of a deformable continuum is developed in which the conservative state variable vector is enlarged by adding the spatial gradient of a scalar thermal internal state variable responsible for the description of thermal history effects. The theory leads to a modified model of thermoelasticity with internal state variables and with a wave-type heat conduction governed by a system of quasi-linear hyperbolic equations. In a general non-deformable case, the observed material properties such as specific heat, quasi-equilibrium thermal conductivity and speed of thermal (the so-called second sound) waves, all regarded as functions of , lead to a particular specification of all material functions and the evolution equation for the scalar internal state variable. The short review of the heat pulse experiment is made. Main assumptions of the present approach are formulated and some arguments referred to the rate-type description are presented. A set of remarks and comparisons with another modification of the Fourier law characterizes the model. An analysis of hyperbolicity of thermoelasticity by propagation conditions of weak discontinuity waves is performed.

Parametric generation of second sound by first sound in superfluid helium.

We report the first experimental observation of parametric generation of second sound (SS) by first sound (FS) in superfluid helium in a narrow temperature range in the vicinity of $T_\lambda $. The temperature dependence of the threshold FS amplitude is found to be in a good quantitative agreement with the theory suggested long time ago and corrected for a finite geometry. Strong amplitude fluctuations and two types of the SS spectra are observed above the bifurcation. The latter effect is quantitatively explained by the discreteness of the wave vector space and the strong temperature dependence of the SS dissipation length.

Stimulated light scattering in smectic A liquid crystals

Abstract The non-linear interaction of arbitrary polarized light with smectic layer deformations in smectic A liquids (SA) is considered. It is shown that the combined effect of anisotropy, fluidity and a characteristic kind of deformation cause a number of specific non-linear optical phenomena. Two-wave mixing in SA transforms into a partly degenerate four-wave mixing (FWM) when the polarization and the direction of propagation of the coupled electromagnetic (EM) waves are arbitrary. The interference of the EM waves gives rise to a dynamic grating of layer deformations without a change of mass density of SA. In the resonant case a propagating mode of a second sound (SS) is excited. The non-linear phenomena are analysed by solving the self-consistent system of the Maxwell equations for the non-linear anisotropic inhomogeneous medium and the hydrodynamic equations of SA in the external EM field. The explicit expressions of the EM and SS waves amplitudes are obtained. It is shown that the coupled fundamenta...