The acoustic impedance of liquid helium-3

1965 ◽  
Vol 284 (1396) ◽  
pp. 125-136 ◽  
Keyword(s):  
Acoustic Impedance ◽  
Fermi Liquid ◽  
Quartz Crystal ◽  
Zero Sound ◽  
Saturated Vapour Pressure ◽  
Saturated Vapour ◽  
A Value ◽  
Reflexion Coefficient ◽  
Helium 3 ◽  
Good Agreement

Measurements have been made of the acoustic impedance ( Z ) of liquid 3 He under its saturated vapour pressure in the temperature range 0·035 to 0·6°K. A 1000 Mc/s sound wave is propagated along the axis of an X -cut quartz crystal, and undergoes many reflexions from each end of the crystal. Values are obtained for the reflexion coefficient at an interface between quartz and liquid 3 He by comparing the rate at which the signal decays in the crystal, with and without liquid 3 He present on the ends. These values then lead directly to the acoustic impedance ( Z ) of the liquid. Usually, Z / ρ (where ρ is the density) should be equal to the velocity of sound, and above 0·1°K this is found to be so. However, at about 0·1°K the value of Z / ρ increases abruptly, and at lower temperatures has a value about 10% greater. This result is in good agreement with Landau’s theory of a Fermi liquid, which relates the change in impedance with the propagation of a new mode of sound, the so-called 'zero-sound’.

The viscosity and acoustic impedance of liquid helium-3

1965 ◽  
Vol 289 (1416) ◽  
pp. 34-45 ◽  
Keyword(s):  
Acoustic Impedance ◽  
Low Temperatures ◽  
Fermi Liquid ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Sound Waves ◽  
Zero Sound ◽  
Saturated Vapour Pressure ◽  
Saturated Vapour ◽  
Thermal Relaxation Times

Previous experiments have shown that at low temperatures the acoustic impedance of liquid 3 He under the saturated vapour pressure rises by about 10% below about 0.092 °K. This rise is predicted by Landau’s theory of a Fermi liquid. It comes about because, at sufficiently low temperatures, sound waves in liquid 3 He are propagated as a new mode, the so-called zero sound. The present experiments study the dependence on pressure of the temperature and magnitude of the transition in the impedance. The transition temperature is shifted from 0.092 to about 0.07 °K on subjecting the liquid to a pressure of 12.5 atm, and the magnitude of the change considerably reduced. To interpret these results, measurements have also been made of the viscosity as a function of pressure. (These give information about the thermal relaxation times in the liquid.) All the results are in accord with the theory of zero sound in a Fermi liquid.

scholarly journals The accommodation coefficient and the evaporation coefficient of water

1935 ◽  
Vol 149 (866) ◽  
pp. 104-116 ◽  
Keyword(s):  
Liquid Surface ◽  
Pure Water ◽  
Direct Calculation ◽  
Accommodation Coefficient ◽  
Evaporation Coefficient ◽  
Saturated Vapour Pressure ◽  
Saturated Vapour ◽  
A Value ◽  
Temperature Equilibrium ◽  
Rate Of Evaporation

Previous experiments have already indicated that the maximum rate of evaporation of water into a vacuum is not so great as would be expected theoretically. The ratio of the experimental to the theoretical rate is defined as the evaporation coefficient f and has been found to have a value of about 0⋅04 for pure water at temperatures about 0º C. This result would indicate that, of the vapour molecules striking the liquid surface, about 96% must return to the vapour without entering the liquid. It is therefore of interest to enquire whether these vapour molecules attain temperature equilibrium with the surface or rebound at once before this equilibrium can be established. In the present paper experiments are described in which vapour molecules are incident on a liquid surface which is at a temperature lower than that of the vapour itself and the itself and the energy transferred to the surface by the vapour molecules is measured. If α, the accommodation coefficient, is defined as usual as the ratio of the energy actually transferred to the maximum possible transfer, it is found that for water at 10º C— α= 1⋅0 f = 0⋅036 so that, while only a very small fraction of the vapour molecules enter the liquid, all of them reach temperature equilibrium with the surface before re-evaporating into the vapour. Method If a drop of water is allowed to form on a glass tip in a vessel maintained at a pressure ( p ) which is lower than the saturated vapour pressure corresponding to the temperature of the drop, steady evaporation takes place from the surface of the latter throughout the period of its formation. This evaporation cools the surface. When the drop is fully formed it falls from the tip and may be collected and the drop weight determined. The surface tension can be deduced therefrom and hence the surface temperature may be obtained. This data makes possible the direct calculation of f as follows.

Standardisation of von Willebrand Factor in Therapeutic Concentrates: Calibration of the 1st International Standard for von Willebrand Factor Concentrate (00/514)

2002 ◽  
Vol 88 (09) ◽  
pp. 380-386 ◽  
Author(s):  
Dawn Sands ◽  
Andrew Chang ◽  
Claudine Mazurier ◽  
Anthony Hubbard
Keyword(s):  
Von Willebrand Factor ◽  
International Study ◽  
Expert Committee ◽  
International Standard ◽  
A Value ◽  
Significant Difference ◽  
Factor Concentrate ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Good Agreement

SummaryAn international study involving 26 laboratories assayed two candidate von Willebrand Factor (VWF) concentrates (B and C) for VWF:Antigen (VWF:Ag), VWF:Ristocetin Cofactor (VWF:RCo) and VWF:Collagen binding (VWF:CB) relative to the 4th International Standard Factor VIII/VWF Plasma (4th IS Plasma) (97/586). Estimates of VWF:Ag showed good agreement between different methods, for both candidates, and the overall combined means were 11.01 IU/ml with inter-laboratory variability (GCV) of 10.9% for candidate B and 14.01 IU/ml (GCV 11.8%) for candidate C. Estimates of VWF:RCo showed no significant difference between methods for both candidates and gave overall means of 9.38 IU/ml (GCV 23.7%) for candidate B and 10.19 IU/ml (GCV 24.4%) for candidate C. Prior to the calibration of the candidates for VWF:CB it was necessary to calibrate the 4th IS Plasma relative to local frozen normal plasma pools; there was good agreement between different collagen reagents and an overall mean of 0.83 IU per ampoule (GCV 11.8%) was assigned. In contrast, estimates of VWF:CB in both candidates showed large differences between collagen reagents with inter-laboratory GCV’s of 40%. Candidate B (00/514) was established as the 1st International Standard von Willebrand Factor Concentrate by the WHO Expert Committee on Biological Standardisation in November 2001 with assigned values for VWF:Ag (11.0 IU/ampoule) and VWF:RCo (9.4 IU/ampoule). Large inter-laboratory variability of estimates precluded the assignment of a value for VWF:CB.

scholarly journals Propagation of shear stress in strongly interacting metallic Fermi liquids enhances transmission of terahertz radiation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
D. Valentinis ◽  
J. Zaanen ◽  
D. van der Marel
Keyword(s):  
Shear Stress ◽  
Terahertz Radiation ◽  
Fermi Liquid ◽  
Zero Sound ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
Collisionless Regime ◽  
Propagating Shear ◽  
Mass Enhancement

AbstractA highlight of Fermi-liquid phenomenology, as explored in neutral $$^3$$ 3 He, is the observation that in the collisionless regime shear stress propagates as if one is dealing with the transverse phonon of a solid. The existence of this “transverse zero sound” requires that the quasiparticle mass enhancement exceeds a critical value. Could such a propagating shear stress also exist in strongly correlated electron systems? Despite some noticeable differences with the neutral case in the Galilean continuum, we arrive at the verdict that transverse zero sound should be generic for mass enhancement higher than 3. We present an experimental setup that should be exquisitely sensitive in this regard: the transmission of terahertz radiation through a thin slab of heavy-fermion material will be strongly enhanced at low temperature and accompanied by giant oscillations, which reflect the interference between light itself and the “material photon” being the actual manifestation of transverse zero sound in the charged Fermi liquid.

Heat-flow experiments in liquid 4He with a variable cylindrical geometry

1987 ◽  
Vol 174 ◽  
pp. 209-231 ◽  
Author(s):  
H. Gao ◽  
G. Metcalfe ◽  
T. Jung ◽  
R. P. Behringer
Keyword(s):  
Cylindrical Geometry ◽  
Small Scale ◽  
Onset Of Convection ◽  
Aspect Ratios ◽  
A Value ◽  
Prandtl Numbers ◽  
Convection Rolls ◽  
Flow Experiments ◽  
Increasing Function ◽  
Good Agreement

This paper first describes an apparatus for measuring the Nusselt number N versus the Rayleigh number R of convecting normal liquid 4He layers. The most important feature of the apparatus is its ability to provide layers of different heights d, and hence different aspect ratios [Gcy ]. The horizontal cross-section of each layer is circular, and [Gcy ] is defined by [Gcy ] = D/2d where D is the diameter of the layer. We report results for 2.4 [les ] [Gcy ] [les ] 16 and for Prandtl numbers Pr spanning 0.5 [lsim ] Pr [lsim ] 0.9 These results are presented in terms of the slope N1 = RcdN/dR evaluated just above the onset of convection at Rc. We find that N1 is only a slowly increasing function of [Gcy ] in the range 6 [lsim ] [Gcy ] [lsim ] 16, and that it has a value there which is quite close to 0.72. This value of N1 is in good agreement with variational calcuations by Ahlers et al. (1981) pertinent to parallel convection rolls in cylindrical geometry. Particularly for [Gcy ] [lsim ] 6, we find additional small-scale structure in N1 associated with changes in the number of convection rolls with changing [Gcy ]. An additional test of the linearzied hydrodynamics is given by measurements of Rc. We find good agreement between theory and our data for Rc.

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