As their name indicates, liquid crystals simultaneously exhibit some characteristics common to both ordinary isotropic liquids and solid crystals. This ambivalence is also found in the effects of surfaces on these systems which lead to a great diversity of phenomena. These phenomena are reviewed focusing on nematic liquid crystals which have the simplest structure among the many existing types and which have been the most extensively studied. Three main kinds of effects can be distinguished. The first concerns the perturbation of the liquid crystalline structure close to the surface. Beyond this transition region, the bulk liquid crystalline structure is recovered with an orientation which is fixed by the surface: this phenomenon of orientation of liquid crystals by surfaces is the so-called anchoring. Finally, close to bulk phase transitions, critical adsorption or wetting can occur at surfaces as is also seen in isotropic systems.

https://iopscience.iop.org/article/10.1088/0034-4885/54/3/002/pdf

Surface effects and anchoring in liquid crystals

If the potential for a boom in the global hydrogen economy is realized, there will be an increase in the need for accurate hydrogen thermodynamic property standards. Based on current and anticipated needs, new fundamental equations of state for parahydrogen, normal hydrogen, and orthohydrogen were developed to replace the existing property models. To accurately predict thermophysical properties near the critical region and in liquid states, the quantum law of corresponding states was applied to improve the normal hydrogen and orthohydrogen formulations in the absence of available experimental data. All three equations of state have the same maximum pressure of 2000MPa and upper temperature limit of 1000K. Uncertainty estimates in this paper can be considered to be estimates of a combined expanded uncertainty with a coverage factor of 2 for primary data sets. The uncertainty in density is 0.04% in the region between 250 and 450K and at pressures up to 300MPa. The uncertainties of vapor pressures and saturated liquid densities vary from 0.1% to 0.2%. Heat capacities are generally estimated to be accurate to within 1%, while speed-of-sound values are accurate to within 0.5% below 100MPa.

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Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen

Developments in the foundations of statistical mechanics during the past ten years or so. The author discusses how statistical concepts enter the treatment of deterministic mechanical systems, with particular reference to trajectory instabilities and to the KAM theorem. Then he deals with large systems: the thermodynamic limit and the theory of infinite systems. Non-equilibrium statistical mechanics is covered but LC relativistic statistical mechanics is not.

https://iopscience.iop.org/article/10.1088/0034-4885/42/12/002/pdf

Foundations of statistical mechanics

Phase transitions in liquid crystals

Landau theory of the nematic-isotropic phase transition

Sound velocity measurements in liquid methane as a function of pressure

Experimental investigation of thermomagnetic torques in dilute nitrogen

A high precision rotating ellipsometer was used to perform a systematic study of the pretransitional orientational order induced by the free surface of n-alkylcyanobiphenyl liquid crystals (n=5-12) in the isotropic phase. All the compounds of this series show a complete wetting behaviour at the free surface. The temperature dependence of the surface order parameter was determined via calculations based on the Landau-de Gennes theory and the results show an even-odd behaviour. Moreover, we used a neural network recognition algorithm to reconstruct the order parameter profile S (z) near the surface. The results of this model-independent analysis are compared with the model based calculations.

W. Van Dael

Papers

Sound velocity measurements in liquid methane as a function of pressure

Experimental investigation of thermomagnetic torques in dilute nitrogen

Systematic study of pretransitional orientational order at the free surface of ncb liquid crystals (n=5-12) in the isotropic phase

Low temperature adsorption of normal and equilibrium hydrogen and deuterium on silver and graphite

Ultrasonic velocity in liquid carbon dioxide