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J Klier

Publications and source records attributed to J Klier.

8 recordsLinked to original sources
PubMed2002

Triple-point wetting on rough substrates.

The influence of substrate roughness on the wetting scenario of adsorbed van der Waals films is investigated by theory and experiment. Calculating the bending free energy penalty of a solid sheet picking up the substrate roughness, we show that a finite roughness always leads to triple-point wetting reducing the widths of the adsorbed solid films considerably as compared to that of smooth substrates. Testing the theory against our experimental data for molecular hydrogen adsorbed on gold, we find quantitative agreement.

Journal Article↗
PubMed2000

Model for the extreme wetting hysteresis of liquid helium on cesium

Although the liquid- 4He-cesium system is a nearly ideal one for studying wetting phenomena, it can show extreme hysteresis which is profoundly nonideal in behavior. It is suggested that this is due to the roughness of these Cs surfaces. We show that stable micropuddles of liquid 4He can form in shallow cavities on a Cs surface. It is the potential to form micropuddles, as the liquid tries to recede, which pins the contact line due to the large energy needed to create the surface of a micropuddle. This model also accounts for the memory that these surfaces have of being in contact with liquid 4He.

Journal Article↗
PubMed1998

Equilibrium swelling of poly(methacrylic acid-g-ethylene glycol) hydrogels. Effect of swelling medium and synthesis conditions.

Responsive hydrogel networks comprising of poly(methacrylic acid) (PMAA) backbone and oligomeric ethylene glycol (PEG) grafts were synthesized by free-radical solution polymerization and their equilibrium swelling properties were characterized in aqueous solutions of a homologous series of alcohols. These hydrogels are known to exhibit swelling transitions in response to external stimuli which lead to formation or disruption of hydrogen-bonded complexes between the backbone and the grafts. Swelling studies performed in aqueous mixtures of methanol, ethanol and propanol revealed that the effectiveness of an alcohol in breaking the PMAA/PEG complexes increased as the aliphatic segment length of the alcohol was increased. These results confirm the importance of hydrophobic interactions for stabilizing the complexes. Studies performed to determine the effect of the synthesis conditions on the equilibrium swelling properties revealed that the equilibrium degree of swelling increased as the solvent fraction during synthesis was increased. Finally, molecular stimulations revealed that it is sterically possible to form complexes with a 1:1 stoichiometry between chains of poly(methacrylic acid) and poly(ethylene glycol) with essentially no additional bond strain.

Alcohols↗
PubMed1986

Oxygen limitation on L-serine production in a hollow-fiber bioreactor.

Pseudomonas AM1 utilizes glycine and methanol to produce L-serine aerobically. The consumption of methanol in this bioconversion is stoichiometrically in excess of L-serine production. Consequently, the oxygen requirement associated with L-serine production is higher than expected for the conversion from glycine. One method of L-serine production investigated was a technique utilizing a hollow-fiber ultrafiltration cartridge as a bioreactor. Oxygen diffusion limitations appear to impede the consumption of methanol and, consequently, the production of L-serine in such a reactor. Methanol consumption data agree with predictions based on a hollow-fiber diffusion model.

Glycine↗