Biomedical subjects

M Sprung

Publications and source records attributed to M Sprung.

16 recordsLinked to original sources

PubMed2004

Surface roughness of supercooled polymer melts.

We report on in situ x-ray reflectivity measurements of the surface roughness of supercooled glass forming polymers in a temperature range from 190 to 330 K. The experimentally determined rms roughness has been found to obey the capillary wave model of a single liquid/vapor interface over the entire temperature range. An expression for the surface roughness below the bulk glass transition (T(G) approximately equal to 200 K) is deduced from the viscoelastic theory of surface fluctuations; however, no indication of a frozen-in surface roughness has been observed in the experiment. Additionally, it is shown that precise values of the surface tension of highly viscous liquids in the supercooled state can be determined by x-ray reflectivity.

Journal Article↗

PubMed2004

Capillary waves at the transition from propagating to overdamped behavior.

We measure the dispersion relation of capillary waves on a liquid surface by heterodyne x-ray photon correlation spectroscopy near the transition from propagating to overdamped dynamic behavior. A strong deviation of the propagation frequency from the small-damping result omega(p) proportional, variant k(3/2) is observed long before the actual transition where ( partial differential omega(p)/ partial differential k)<0 and omega(p) tends to zero. This behavior is successfully described by expressions derived within linear response theory.

Journal Article↗

PubMed2003

Observation of heterodyne mixing in surface x-ray photon correlation spectroscopy experiments.

We report measurements of propagating capillary waves on a liquid water surface at T=5 degrees C with x-ray photon correlation spectroscopy. The experiment has been performed under grazing incidence conditions with an incoming x-ray beam below the critical angle of total external reflection. In the q region investigated the measured intensity-intensity autocorrelation functions of the liquid water surface were found to be heterodyne signals, i.e., a combination of first- and second-order correlation functions g(1)(tau) and g(2)(tau).

Journal Article↗

PubMed1985