26 research outputs found
Chiral and herringbone symmetry breaking in water-surface monolayers
We report the observation from monolayers of eicosanoic acid in the LâČ2 phase of three distinct out-of-plane first-order diffraction peaks, indicating molecular tilt in a nonsymmetry direction and hence the absence of mirror symmetry. At lower pressures the molecules tilt in the direction of their nearest neighbors. In this region we find a structural transition, which we tentatively identify as the rotator-herringbone transition L2dâL2h
Stabilization of tilt order by chain flexibility in Langmuir monolayers
Langmuir monolayers are modeled as systems of short chains, which are
confined to a planar surface at one end, but free to move within the plane. The
phase behavior is calculated in a mean field approximation, which combines the
self consistent field method with elements of classical density functional
theory. It is shown that phases with tilt order are unstable in systems of
stiff chains, but can be stabilized by chain conformational entropy in systems
of sufficiently flexible chains. The chain entropy is also responsible for the
appearance of an additional untilted phase, the liquid expanded phase. The
region of stability of the different phases is discussed, and their microscopic
structure is analyzed in some detail.Comment: to appear in Phys. Rev.
Unilocular Cystic Lymphangioma of ThighâAn Extremely Rare Clinical Entity
Majority of cystic lymphangiomas are multilocular and occur in neck and axilla. The cystic lymphangioma is also known as cystic hygroma. Unilocular cystic hygroma of neck and breast have been reported in literature and have been termed hydrocele of neck and breast respectively. However unilocular cystic hygroma of thigh is probably being reported for the first time
A grazing-incidence X-ray diffraction study of octadecanol monolayers at high surface pressures
The structure of water-surface monolayers of octadecanol is studied using grazing incidence diffraction at three distinct temperatures near room temperature and in the region of high surface pressures in the vicinity of the tilting transition and of the transition reported by Lawrie and Barnes (J. Colloid Interface Sci. 1994, 162, 36). The data mere obtained in independent experiments by different groups at two different synchrotrons. The tilting transition between a low-pressure phase in which the molecules are inclined to the substrate normal and a high-pressure upright phase was observed at surface conditions reported by other authors. We conclude that the grazing incidence technique is not sensitive to the transition of Lawrie and Barnes