Chiral and herringbone symmetry breaking in water-surface monolayers

We report the observation from monolayers of eicosanoic acid in the L′2 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 L2d−L2h

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 Thigh—An 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