Stable suspensions of tunicate cellulose microfibrils were prepared by acid hydrolysis of the cellulosic mantles of tunicin. They formed a chiral nematic phase above a critical concentration. External magnetic fields were applied to the chiral nematic phase in two different manners to control its phase structure. (i) Static magnetic fields ranging 1-28 T were used to align the chiral nematic axis (helical axis) in the field direction. (ii) A rotating magnetic field (5 T, 10 rpm) was applied to unwind the helices and to form a nematic phase. These phenomena were interpreted in terms of the anisotropic diamagnetic susceptibility of the cellulose microfibril. The diamagnetic susceptibility of the microfibril is smaller in the direction parallel (chi( parallel)) to the fiber axis than in the direction perpendicular (chi( perpendicular)) to the fiber axis, that is, chi( parallel) < chi( perpendicular) < 0. Because the helical axis coincides with the direction normal ( perpendicular) to the fiber axis, the helical axis aligned parallel to the applied field. On the other hand, the rotating magnetic field induced the uniaxial alignment of the smallest susceptibility axis, that is, chi( parallel) in the present case, and brought about unwinding of the helices.

Background-In the treatment of type B acute aortic dissection without complications, better results are obtained if surgery is performed before enlargement of the aorta in patients who are predicted to show aortic enlargement and if drug-based treatment is continued for patients who are predicted to show no enlargement. The purpose of this study was to predict the acute-phase factors that may affect chronic-phase aortic enlargement by studying chronic-phase enlargement of dissections in patients without complications during the acute phase. Methods and Results-In 101 patients with type B acute dissection who had no complications, univariate and multivariate factor analyses were performed to determine the predictors for chronic-phase enlargement (Ն60 mm) of the dissected aorta. The independent predominant predictors for aortic enlargement in the chronic phase were a maximum aortic diameter of Ն40 mm and a patent false lumen during the acute phase. The values of actuarial freedom from aortic enlargement for the patients with a maximum aortic diameter of 40 mm and a patent false lumen at 1, 5, and 10 years were 43%, 33%, and 22%, respectively, whereas in patients with a maximum aortic diameter of Ͻ40 mm and a closed false lumen, the values were 97%, 94%, and 84%, respectively. Conclusions-These results suggest that patients with type B acute aortic dissection who show a maximum aortic diameter of Ն40 mm and a patent false lumen should undergo surgery earlier during the chronic phase before enlargement of aorta, whereas patients with a maximum aortic diameter of Ͻ40 mm and a closed false lumen should continue to receive hypotensive therapy.

Fourier transform infrared (FTIR)-attenuated total reflection (ATR) spectra have been recorded of Langmuir-Blodgett (LB) films of stearic acid deposited on a germanium plate with 1, 2, 3, 5, and 9 monolayers. Examination of the CH2 scissoring band suggests that the hydrocarbon chain of stearic acid in the first monolayer is in a hexagonal or pseudohexagonal subcell packing where each hydrocarbon chain is freely rotated around its axis oriented approximately perpendicular to the surface. In the LB films thicker than 2 monolayers, on the other hand, the molecules in the upper monolayers other than the first monolayer crystallize with the monoclinic form where the hydrocarbon chains are packed alternately and are inclined at an angle of about 30°with respect to the surface normal, showing a tendency to align their a crystal axes parallel to the direction of the withdrawal of the germanium plate in the film preparation. It is also concluded from frequencies and intensities of the progression bands due to the CH2 wagging vibrations that stearic acid occurs as the cis configuration for the C=0 and Ca-€ß bonds in the 1-monolayer film but the trans configuration starts to appear in the 3-monolayer film. A striking feature in this study is the absence of the C-O stretching band of stearic acid in the first monolayer on the germanium plate. This phenomenon may be interpreted by the short-range image field model for its oscillating dipole parallel to the germanium surface.