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  • 1
    Electronic Resource
    Electronic Resource
    MOLECULAR ORBITAL CALCULATIONS FOR CYCLOÖCTATETRAENE1 (1961)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 65 (1961), S. 2102-2103 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100828a501
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  • 2
    Electronic Resource
    Electronic Resource
    Recent Developments in Rayleigh-Benard Convection (2000)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 32 (2000), S. 709-778 
    Details
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This review summarizes results for Rayleigh-Benard convection that have been obtained over the past decade or so. It concentrates on convection in compressed gases and gas mixtures with Prandtl numbers near one and smaller. In addition to the classical problem of a horizontal stationary fluid layer heated from below, it also briefly covers convection in such a layer with rotation about a vertical axis, with inclination, and with modulation of the vertical acceleration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fluid.32.1.709
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  • 3
    Electronic Resource
    Electronic Resource
    Apparatus for the study of Rayleigh–Bénard convection in gases under pressure (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 2043-2067 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We review the history of experimental work on Rayleigh–Bénard convection in gases, and then describe a modern apparatus that has been used in our experiments on gas convection. This system allows for the study of patterns in a cell with an aspect ratio (cell radius/fluid layer depth) as large as 100, with the cell thickness uniform to a fraction of a μm, and with the pressure controlled at the level of one part in 105. This level of control can yield a stability of the critical temperature difference for the convective onset of better than one part in 104. The convection patterns are visualized and the temperature field can be inferred using the shadowgraph technique. We describe the flow visualization and image processing necessary for this. Some interesting results obtained with the system are briefly summarized. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147511
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental test of the perturbation expansion for the Taylor instability at various wavenumbers (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 250-255 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the Fourier components of the axial variation of the velocity component w in a Taylor–Couette apparatus containing ten pairs of vortices at various average wavenumbers q, as a function of ε≡R/Rc−1, are reported. For all values of q studied, excellent agreement with the perturbation expansion of Davey [J. Fluid Mech. 14, 336 (1962)] for the amplitudes of the Fourier components was obtained, provided the power law dependence on ε was taken as a function of ε˜≡ε−εm(q). Here εm(q) is the marginal stability curve, below which the laminar flow state is stable against perturbations of wavenumber q. The wavenumber dependence of the leading coefficients in the expansions for the fundamental and first harmonic was also measured, and it was found that while the coefficient for the fundamental was independent of q, the coefficient for the first harmonic monotonically decreased with increasing q, over the range studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866855
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of "Kalliroscope'' flow visualization particles on rotating Couette–Taylor flow (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1204-1206 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results are presented which show that Taylor vortex flow in a vertically mounted rotating Couette system, visualized with a "Kalliroscope'' suspension evolves to a spatially nonperiodic flow which is also nonperiodically time dependent. These effects are most noticeable in systems of large aspect ratio and depend on the concentration of the suspension. Experimental evidence is presented that suggests that these phenomena are caused by the evolution of a periodic variation of the Kalliroscope particle concentration along the cylinder axis and parallel to the gravitational field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.864997
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  • 6
    Electronic Resource
    Electronic Resource
    Critical heat flow in a thick He II film near the superfluid transition (1969)
    Springer
    Journal of low temperature physics 1 (1969), S. 159-172 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of critical heat flow in a thick He II film near the onset temperatureT 0are presented. Estimates of the film thickness were made by comparison with the critical velocity for bulk helium in pores, and from the onset temperature for superfluidity. These comparisons yield a thickness of 2.5×10−5 and 2×10−5 cm, respectively. The observed critical heat flow, in conjunction with reasonable estimates of the superfluid density, yields a critical velocityv sc * that has the same temperature dependence as the critical velocityv scobtained by Clow and Reppy from gyroscopic measurements. The present results are consistent with the idea that there is a region nearT 0wherev sc * =vsc∝ ρ s and it is independent of geometry, and a geometry-dependent region well belowT 0wherev sc * =vsc≅ constant. Available data on the depression of the onset temperature are examined. Although they are consistent with recent phenomenological calculations, they are not sufficiently accurate to provide conclusive evidence in favor of these theories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00628405
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  • 7
    Electronic Resource
    Electronic Resource
    4He very nearT λ heated from above (1996)
    Springer
    Journal of low temperature physics 105 (1996), S. 255-266 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the feasibility and likely results of measurements of the thermal conductivity λ(Q,t) of4He very nearT λ ≡T λ(Q = 0) as a function of the heat currentQ and the reduced temperature t ≡[T —Tλ]/T λ by heating a sample from above and cooling it from below. Although the expansion coefficient is negative, the experiment should be possible without inducing convection in the HeI layer provided the sample length does not significantly exceed one cm. Fort ≲ 10−7(Q ≳ 0.2 erg/s cm2), a state of self-organized criticality can be attained. For these conditions, the thermal gradient cancels the gradient inT λ induced by gravity, thus permitting measurements extremely close to the transition even in an Earthbound laboratory. However, the data will be only for a unique path in the Q—t plane. For 0.2 ≲Q ≲ 0.5 erg/s cm2 (10−7≳t≳ 10−8) they will be in the range of linear response and give λ(0,t); for Q between about 0.5 and 10 erg/s cm2 and over a temperature range of about 20 nK, the experimental path samples the regime where the conductivity is expected to be influenced by nonlinear finite-current effects. The small currents and narrow temperature range of the experiment imply that ultra-high resolution thermometry as well as very careful control of stray heat currents will be required. ForQ ≳ 10 erg/s cm2 and up to very largeQ, the method can be used to determine the onset temperatureT c (Q) of thermal resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00754636
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  • 8
    Electronic Resource
    Electronic Resource
    Superfluid fraction of4He from 1.5 K toT λ(P) and from vapor pressure to the melting curve (1987)
    Springer
    Journal of low temperature physics 66 (1987), S. 173-190 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New measurements of the first-, second-, and fourth-sound velocities are reported and used to obtain the superfluid fraction ρ s /ρ at pressures from vapor pressure to the melting curve and from 1.5 K to within 1% of the superfluid transition temperatureT λ(P). Close toT λ, the new results agree very well with previous measurements by Greywall and Ahlers. At low temperatures they agree well with the tabulations by Maynard; but in the range within 10% or so ofT λ(P) and at the higher pressures they differ from Maynard's values by several percent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681820
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  • 9
    Electronic Resource
    Electronic Resource
    Critical properties of4He in aerogel near the λ-line (1992)
    Springer
    Journal of low temperature physics 89 (1992), S. 79-89 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We measured the superfluid fraction ρs/ρ and the isobaric thermal expansion coefficient βP of4He confined in an aerogel. Data were obtained near the λ-line along several isobars. Powerlaw fits to the results for ρs/ρ as a function of t≡T/Tc−1 (Tc is the transition temperature) give a pressure—independent exponent ς=0.755 when a confluent singular term is included. Fits to the βP data of power laws yield the specific-heat exponents α≅−0.6 and α′≅−1.0≠α above and below Tc respectively. When an analytic background term a×t is included in the fit, the pressure-independent value α=α′≅−0.59 is permitted, but the amplitude ratio A′/A is found to be near zero and the coefficient of the analytic term is large. The measured values for ς and α′ or α are inconsistent with hyperscaling in three dimensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692580
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  • 10
    Electronic Resource
    Electronic Resource
    Second sound very near Tλ (1993)
    Springer
    Journal of low temperature physics 93 (1993), S. 131-182 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of an experimental investigation of the evolution of planar, non-linear, second-sound pulses in superfluid4He, to within 650 nK of the λ-transition, are presented. A new method for extracting the second-sound velocity and damping is demonstrated. As predicted from two-fluid hydrodynamics, the pulses are well modeled by the solutions of Burgers' equation. The second-sound velocity (u 20) and damping (D 2) are extracted from fits of the model to the data. Damping data are obtained in this fashion to 3×10−7 in reduced temperature at saturated vapor pressure; nearly two decades closer to Tλ then any previous measurements. The superfluid density is extracted from theu 20 measurements and the critical exponent, ζ, is determined. A study of very large amplitude pulses near Tλ is also presented. These pulses extend well beyond the range of validity of Burgers' equation. The amplitude of the shock that forms at the trailing edge of the pulse is observed to saturate as a function of heater power and then decrease suddenly, as has been previously observed away from Tλ. However, the pulse shapes are quite different from any previously observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682285
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