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  • 1
    Digitale Medien
    Digitale Medien
    Dead time correction of photon correlation functions (1986)
    Springer
    Applied physics 41 (1986), S. 95-102 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.65.Eh ; 82.80.Di ; 85.10.Pe
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamic range of single photon counting measurements in quasi elastic light scattering is restricted by detector and counter dead time effects. While distortions of single interval statistics have been treated at great length, only lowest order corrections or very special cases of dead time effects on temporal correlation functions were computed in the past. Dead times result in a direct distortion of correlograms on time scales comparable to the dead time. This effect exists even at low count-rates. It is independent of the count rate for paralyzable systems. Nonparalyzable systems show a count rate dependence with increasing correlation times at high count rates. Furthermore, counting saturation produces additional distortions extending to all lag times. These distortions are computed for the rather general case of Γ-distributed intensities with arbitrary shape of the photon correlation function. Such signals are commonly found in multiparticle homodyne experiments with a finite size detector, i.e. arbitrary value of the intercept or contrast of the correlogram. Exact results are provided for the paralyzable system including the effect of fluctuating dead times. The latter case is then used to compute a useful approximation for nonparalyzable systems as well.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00702660
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  • 2
    Digitale Medien
    Digitale Medien
    Scaling in colloidal crystallization (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1149-1157 
    Details
    ISSN: 0392-6737
    Schlagwort(e): Physics of crystal growth ; Colloids ; Conference proceedings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary The process of colloidal crystallization has already been separately investigated by light scattering mearurements of the crystalline order (Bragg peaks) and of long-ranged density fluctuations (small-angle scattering). We present the firstsimultaneous small- and large-angle light scattering experiment. Our measurements have been performed on hard-sphere colloids of different particle densities. We show results for the temporal evolution of crystallization and find two distinct regimes: homogeneous nucleation and diffusion- or reaction-limited growth at early times, followed by ripening of the Lifshitz-Slyozov or Lifshitz-Allen-Cahn type. To our preliminary experience, we can already state that the results are always consistent in both partial experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02458795
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  • 3
    Digitale Medien
    Digitale Medien
    Correlation techniques in dynamic light scattering (1987)
    Springer
    Applied physics 42 (1987), S. 193-213 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 05.40.+6 ; 47.80.+v ; 06.50.Dc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The motion of small scatterers in a laser beam results in Doppler shifts of the scattered light. Various homodyne or heterodyne experiments may be used to measure such shifts. The stochastic nature of spatial particle arrangements and of the photon-detection process leads to statistic data processing schemes like temporal correlation or the computation of structure functions. Photon correlation is one of these schemes and has found numerous applications in velocimetry and Brownian motion studies. Topics of current interest are dead-time corrections, the use of photon structure functions, and multiple tau measurements, which access large ranges of time constants in a single run. More recent data processing techniques are recurrence rate correlation for the immediate determination of velocity correlation functions in seeded fluid flows and the measurement of amplitude-weighted phase structure functions, which is able to resolve very small particle displacements otherwise completely obscured by random Brownian motion. Rate correlation found applications in hydrodynamic studies of the route to turbulence, while the major use of phase structure function processing is a very significant increase in the sensitivity of electrophoretic mobility measurements by light scattering.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00693937
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  • 4
    Digitale Medien
    Digitale Medien
    Signal preprocessing for digital correlators (1980)
    Springer
    Applied physics 22 (1980), S. 251-256 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 06.50 ; 07.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The input format of fast digital correlators, such as used in photon correlation or recurrence rate correlation, is often exceeded by input signals, if high count rates coincide with sample times of the order of several hundred nanoseconds or more. Clipping, random clipping, and scaling are well known methods to reduce such signals appropriately. We discuss these procedures with special attention to noise performance possible errors introduced into the correlogram. Generalizations from single to multi-bit correlators are presented with a thorough discussion of random preset scaling, a new process suitable for multi-bit correlation of signals with arbitrary statistics. Furthermore we describe a new additional preprocessor which offers significant decrease of quantization noise, if constant background contributions are present in the signal. Though demonstrated on optical measurements, the methods treated in this paper generally apply, whenever the format of digital data has to be reduced prior to correlation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886016
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  • 5
    Digitale Medien
    Digitale Medien
    Untersuchungen über das Vorkommen von Coli-Bakterien in der molkereimäßig pasteurisierten Milch und überlegungen über die Deutung der Befunde (1953)
    Springer
    Medical microbiology and immunology 137 (1953), S. 284-292 
    Details
    ISSN: 1432-1831
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Zusammenfassung Es wird berichtet über die Ergebnisse bakteriologischer Untersuchungen an Molkerei- und Handelsmilch, bei denen wir dieselbe Milchcharge vom Kühler der Molkerei bis zur Ausgabe an den Verbraucher stufenförmig kontrollierten. Es werden besonders die Colibefunde dargestellt und ihre Bewertung erörtert. Im Gegensatz zur Wasserhygiene dürfen die Colibakterien in der Milchhygiene nicht als Indicator für fäkale Verunreinigungen betrachtet werden, sondern sie haben eine wichtige andersartige Bedeutung als bakteriologischer Indicator für die wirksame Pasteurisierung, für die ausreichende Kühlung und für die saubere Arbeit in den Molkereien. Eine laufende bakteriologische Eigenkontrolle der Betriebe ist anzustreben. Es wird bei einem Vergleich der Coligesamtwerte mit den Ergebnissen des Colititers im Gährröhrchen und denjenigen der Indolprobe gezeigt, daß die Kombination der beiden letzteren Methoden die Auszählung ersetzen kann und festgestellt, daß diese beiden Methoden, kombiniert miteinander, in der Eigenkontrolle der Molkereien verwendet werden können.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02149988
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  • 6
    Digitale Medien
    Digitale Medien
    Laser light scattering and correlation techniques for characterization of colloidal suspensions (1987)
    Springer
    The European physical journal 68 (1987), S. 229-232 
    Details
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Particle motion in colloidal suspensions causes Doppler shifts in scattered laser light. For pure diffusion, the resulting spectral broadening may be measured by intensity interferometry and photon correlation techniques. Measured line widths or decay times yield particle size information. Electrophoretic mobilities may be determined, if an electric field is applied to the suspension. However, resulting line shifts can be extremely small and real-time optical phase processing may be required to resolve it. Finally, information about particle interactions may be obtained by studying angular cross sections or by photon correlation measurements on a small number of particles, i.e. using a very small scattering volume.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01304230
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