Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • critical phenomena  (3)
  • thermal diffusivity  (2)
  • Food  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The process of heat and mass transport at the critical point of pure fluids (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1051-1058 
    Details
    ISSN: 1572-9567
    Keywords: critical phenomena ; D2 Mission ; density relaxation ; microgravity ; SF6 ; temperature relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effects of fast isentropic temperature propagation, called the “piston effect,” or “critical speeding up,” and slow mass diffusion, called “critical slowing down,” are investigated. A temperature propagation experiment in a spherical cell filled with pure SF6 at critical density was performed during the Second German Spacelab Mission D2 in 1993. The results evidently confirm the presence of the piston effect both in the one-phase region and in the two-phase region. The numerical simulations are in remarkable good quantitative agreement with the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02081274
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Isochoric specific heat of sulfur hexafluoride at the critical point: Laboratory results and outline of a spacelab experiment for the d1-mission in 1985 (1986)
    Springer
    International journal of thermophysics 7 (1986), S. 343-356 
    Details
    ISSN: 1572-9567
    Keywords: critical phenomena ; critical exponents ; isochoric specific heat ; scanning ratio calorimeter ; microgravity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The specific heat at constant volume cv shows a weak singularity at the critical point. Renormalization group techniques have been applied, predicting a universal critical behavior which has to be experimentally confirmed for different systems. In this paper an experiment is presented to measure the specific heat of SF6 along the critical isochore (ρc=0.737 g·cm−3), applying a continuous heating method. The results cover a temperature span of −1.5×10−2〈 τ〈1.70×10−2 [τ=(T−T c)/T c] and were strongly affected by gravity effects that emerge in the sample of 1-mm hydrostatic height near the critical point. Using regression analysis, data were fitted with functions of the form c v/R=A × ¦τ¦−α + B for the one-phase state and c v/R=A″ × ¦τ¦−α″ + B″ for the twophase state. Within their error bounds the critical values (α=α″=0.098, A″/A=1.83) represent the measurements for the temperature span 3.5×10−5〈 ¦τ¦〈2.0×10 −3, in good agreement with theoretical predictions. In order to exclude density profiles in the specimen, which are unavoidable in terrestrial experiments due to the high compressibility of fluids at the critical point and the gravity force, a space-qualified scanning ratio calorimeter has been constructed, which will permit long-term cv measurements under microgravity (μ-g) conditions. The experiment will be part of the German Spacelab mission in October 1985. The significant features of the apparatus are briefly sketched.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500160
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Experimental apparatus for measuring the thermal diffusivity of pure fluids at high temperatures (1988)
    Springer
    International journal of thermophysics 9 (1988), S. 911-921 
    Details
    ISSN: 1572-9567
    Keywords: critical region ; light scattering ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Dynamic light scattering represents a suitable method for measuring the thermal diffusivity of optically transparent fluids. The classic application of the method is the immediate vicinity around the critical point due to its dependence upon the intensity of scattered light and its high sensitivity to undesired light scattering. By means of subsequent modifications of the experimental setup, we have been able to expand this region of applicability over the last 12 years and could systematically investigate numerous substances and their binary mixtures within a temperature range of 280 K〈T〈350 K. Our planned investigation of fluids suitable for ORC-HP-technology necessitates performing measurements at higher temperatures and pressures. The experimental apparatus newly designed for this purpose is capable of sustaining a relatively high temperature constance at temperatures up to 700 K. Factors restricting the measurable range of state and their influence on the design of the sample cell are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133259
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Measurements of the isochoric heatc v at the critical point of SF6 under microgravity: Results of the German Spacelab Mission D2 (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 1033-1049 
    Details
    ISSN: 1572-9567
    Keywords: critical phenomena ; isochoric heat capacity ; microgravity ; sulfur hexafluoride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During the Second German Spacelab Mission D2 (April 26 to May 6, 1993) the isochoric specific heatc v of SF6 was measured along the critical isochore under microgravity conditions with a newly developed scanning radiation calorimeter. This calorimeter provided the possibility to perform comparable heating and cooling runs with variable ramp rates since the spherical sample cell was heated and cooled only by radiation. During the experimental time of 220 h, 11 heating and cooling runs with different ramp rates were performed in a temperature range ofT–T c=±6 K. ApproachingT c by cooling from the homogeneous one-phase region avoided significant temperature and density gradients in the fluid, which would have distorted the integral measurement ofc v. The inhomogenities introduced by a finite ramp rate were greatly reduced by the fast dynamic temperature propagation (“critical speeding up”). Thec v data achieved with slow cooling runs are in remarkably good agreement with the theoretical prediction more than one order of magnitude closer to the critical point than anyc v measurements done so far. The preliminary value for the critical exponentα is 0.107±0.02, and for the amplitude ratio we obtainedA −/A +=1.94±0.07. In contrast to the cooling runs, the heating runs showed a strong hysteresis ofc v. A comparison to 1g measurements is provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02081273
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Thermal diffusivity of fluids in a broad region around the critical point (1987)
    Springer
    International journal of thermophysics 8 (1987), S. 165-180 
    Details
    ISSN: 1572-9567
    Keywords: dynamic light scattering ; ethane ; gas-liquid critical point ; nitrous oxide ; sulfur hexafluoride ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Dynamic light scattering is a suitable method for the investigation of transport properties such as the thermal diffusivity of optically transparent fluids. The main advantages of the method are its quickness, the fact of the thermodynamic state of equilibrium of the sample (gradients are not required), and the relatively simple evaluation of data without the necessity of calibration. However, an insufficient production of intensity of scattered light may be a limiting effect. For that reason the vicinity of the gas-liquid critical point represents the classical range of application. In this paper, it is shown that by means of an appropriate choice of experimental apparatus, measurements are also feasible in an extended range of states. Broad regions around critical points of three pure fluids (sulfur hexafluoride, SF6; ethane, C2H6; nitrous oxide, N2O) over temperature ranges ¦T-T c¦ of 0.02 to 50 K and density ranges (ρ/ρc) of 0.2 to 2 were investigated. In this region the thermal diffusivity shows great variations with temperature and density and cannot be described by means of ideal-gas behavior or relations for liquids. The measurements were carried out along the coexistence curve for both phases, along the critical isochore and along some isotherms with T≶T c. The measured or calculated density, pressure, and thermal diffusivity data as well as some correlations are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00515200
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Development and application of a heterologous internal standard for polymerase-chain-reaction-based detection of Campylobacter jejuni and Campylobacter coli in foods (1999)
    Springer
    European food research and technology 209 (1999), S. 180-184 
    Details
    ISSN: 1438-2385
    Keywords: Key words Polymerase chain reaction ; Campylobacter ; Internal standard ; Food ; False negatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A heterologous internal standard, termed "mimic", was developed for the polymerase chain reaction (PCR)-based detection of Campylobacter jejuni and Campylobacter coli in food. Mimic was designed to contain a heterologous DNA fragment of plasmid pUC18, flanked by a primer binding site, identical to the bacterial target DNA. Application of mimic in the PCR permitted its co-amplification together with the bacterial DNA with similar efficiency. As the length of the amplified products differed, they were easily detectable by agarose gel electrophoresis. The presence or absence of the mimic PCR product was indicative of the efficacy of the PCR. The use of approximately 60 mimic molecules per reaction was optimal for determining the reliability of the diagnostic PCR assays without decreasing the detection limit. This system for the detection of the two species of Campylobacter was successfully applied in routine food surveillance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002170050476
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...