Anticonical anchoring and surface transitions in a nematic liquid crystal.

Recent works reported planar and conical azimuthally degenerated nematic anchorings. Here we predict an additional "anticonical" degenerated anchoring. Its energy presents two minima, parallel and perpendicular to the substrate plane, separated by a conical energy barrier.

Zenithal gliding of the easy axis of a nematic liquid crystal.

We present experimental evidence of zenithal gliding of the nematic easy axis on a polyimide surface. The reorientation dynamics of the easy axis under external torque, and its relaxation, are extremely slow processes which cannot be described by a single exponential time. They show similarities with aging phenomena previously encountered in glassy systems.

Biaxial melting of the nematic order under a strong electric field.

We study the action of a strong electric field on a nematic, topologically stabilized with director n perpendicular to E. Above a threshold field the nematic order on the cell midplane is "melted" and rapidly reconstructed with n axially E. In a Landau-de Gennes model, we show that the observed transient "melted" state is a biaxial nematic and not an isotropic liquid.

Anchoring screening of defects interaction in a nematic liquid crystal.

The relaxation dynamic of a dipole of +1/2 and -1/2 parallel disclination lines in a confined geometry is measured. The confinement and the planar anchoring conditions force the disclinations to be normal to the glass plates. In a first asymptotic regime, the direct elastic interaction between disclination is completely screened out by the anchoring energy.

Memory-free conic anchoring of liquid crystals on a solid substrate.

We show that the anchoring memory of liquid crystals on solid substrates can be completely removed by grafting highly mobile polymer chains. Using grafted polystyrene, we obtain uniform, stable, and reproducible memory-free and conically degenerated anchoring of the nematic 5CB. The symmetry of the conic anchoring enables two different zenithal anchoring breakings, towards homeotropic and planar states.

Respiratory cross-sectional area-flux measurements of the human chest wall.

A new device that utilizes the voltages induced in separate coils encircling the rib cage and abdomen by a magnetic field is described for measurement of cross-sectional areas of the human chest wall (rib cage and abdomen) and their variation during breathing. A uniform magnetic field (1.4 X 10(-7) Tesla at 100 kHz) is produced by generating an alternating current at 100 kHz in two square coils, 1.

What does inductance plethysmography really measure?

Inasmuch as it has been claimed that inductance plethysmography can measure cross-sectional area changes, we tested this assumption. We present experimental and computed relationships between self-inductance (L) of coils and areas (A) included inside for a coil with a well-defined side wavy pattern (triangular or sinusoidal) and for a real belt (Respitrace) placed on elliptical or rectangular configurations. The results are applied to the physiological field using measurements obtained from a computed tomography experiment.