. S. Dans-le-cas-d-'un-cholestérique-compenséako01-]-r, R. B. Akopyan, E. A. Alaverdian, Y. S. Santrosian, and . Chilingarian, le groupe ponctuel de symétrie est seulement D ? car le milieu n'est invariant par aucune réflexion ? il est chiral. 17. Notons au passage que la structure en hélice d'un cholestérique est une conséquence macroscopique des interactions à l'échelle microscopique entre les molécules chirales, Thermomechanical effects in the nematic liquid crystals, pp.3371-3376, 2001.

]. R. Ako04, B. Y. Akopyan, E. H. Zeldovich, and . Seferyan, Thermomechanical coupling in a cylindrical hybrid-aligned nematic liquid crystal, Journal of Experimental and Theoretical Physics, vol.99, issue.8, pp.1039-1043, 2004.

]. R. Ako84, B. Y. Akopyan, and . Zeldovich, Thermomechanical effects in deformed nematics, Zhurnal Eksperimentalnoi I Teoreticheskoi Fiziki, vol.87, issue.8, pp.1660-1669, 1984.

J. Baudry, M. Brazovskaia, L. Lejcek, P. Oswald, and E. S. Pirkl, Arch-texture in cholesteric liquid crystals, Liquid Crystals, vol.1, issue.6, pp.893-901, 1996.
DOI : 10.1080/00268948208074481

J. Baudry, S. Pirkl, and E. P. Oswald, Effect of the electric conductivity on the drift velocity of the cholesteric fingers of the second type in confined geometry, Physical Review E, vol.60, issue.3, pp.2990-2993, 1992.
DOI : 10.1103/PhysRevE.60.2990

]. H. Bra97, H. Brand, and . Pleiner, Flexoelectric effects in cholesteric liquid crystals. Molecular Crystals and Liquid Crystals Science and Technology Section A -Molecular Crystals and Liquid Crystals Influence of flexoelectricity above the nematic Freedericksz transition, Physical Review E, vol.292, issue.68, pp.141-146, 1997.

]. A. Deq07a, P. Dequidt, ]. Oswalddeq07b, P. Dequidt, ]. A. Oswalddeq08 et al., Lehmann effect in compensated cholesteric liquid crystals Lehmann effect in a compensated cholesteric liquid crystal: Experimental evidence with fixed and gliding boundary conditions Planar degenerated anchoring of liquid crystals obtained by surface memory passivation Éber et I. Jánossy. Thermomechanical coupling in compensated cholesterics Macroscopic description of compensated cholesterics and chiral smectic liquid crystals, Does the electric Lehmann effect exist in cholesteric liquid crystals ? European Physical Journal EEbe82] N. Éber et I. Jánossy. An experiment on the thermomechanical coupling in cholestericsEbe88] N. Éber et I. Jánossy. Note onFri93] T. Frisch, L. Gil, et J. M. Gilli. Two-dimensional Landaude Gennes dynamical model for the unwinding transition of a cholesteric liquid crystal, pp.157-166, 1982.

P. De-gennes, J. Prost, R. M. Pelcovitsgil94-]-j, L. Gilli, . Gilgil97-]-l et al., The physics of liquid crystals Static and dynamic textures obtained under an electric-field in the neighborhood of the winding transition of a strongly confined cholesteric Is the electromechanical coupling the driving force for the perpendicular drift of first class cholesteric finger ? Molecular chirality and chiral parameters, Physics Today Liquid Crystals Journal De Physique II Reviews of Modern Physics, vol.48, issue.71 3, pp.70-98, 1994.

H. P. Hinov and E. Kukleva, A Novel Polar Electro-Optic Effect in Thin Large-Pitch Cholesteric Films, Molecular Crystals and Liquid Crystals, vol.16, issue.2-4, pp.203-224, 1984.
DOI : 10.1080/00268948408078707

]. I. Jan81 and . Jánossy, Diffuso-mechanical coupling in cholesteric liquid crystals, Journal De Physique Lettres, vol.42, pp.41-43, 1981.

H. Kneppe, F. Schneider, and N. K. Sharma, Rotational viscosity gamma_1 of nematic liquid crystals Lavrentovich et V. Sergan. Parity-breaking phase transition in tangentially anchored nematic drops, The Journal of Chemical Physics Il Nuovo Cimento D, vol.77, issue.12, pp.3203-3208, 1982.

]. O. Leh00 and . Lehmann, Struktur, System und magnetisches Verhalten flüssiger Krystalle und deren Mischbarkeit mit festen, Annalen der Physik, vol.307, issue.5 6, pp.649-705, 1900.

O. Lehmann, Flüssige Krystalle und ihr scheinbares Leben, 1921.

]. F. Les68 and . Leslie, Some thermal effects in cholesteric liquid crystals, Proceedings of the Royal Society of London Series A-Mathematical and Physical Sciences, vol.307, issue.3, pp.359-372, 1968.

K. C. Lim and J. T. Ho, Apparatus for High-Resolution Birefringence Measurement in Liquid Crystals, Molecular Crystals and Liquid Crystals, vol.271, issue.3-4, pp.173-177, 1978.
DOI : 10.1063/1.89751

]. N. Mad87, R. Madhusudana, and . Pratibha, Electromechanical coupling in cholesteric liquid crystals, Molecular Crystals and Liquid Crystals Letters, vol.5, issue.10, pp.43-51, 1987.

]. N. Mad89, R. Madhusudana, and . Pratibha, An experimental investigation of electromechanical coupling in cholesteric liquidcrystals, Liquid Crystals, vol.5, issue.11, pp.1827-1840, 1989.

]. N. Mad91, R. Madhusudana, H. P. Pratibha, and . Padmini, Electromechanical effect in cholesteric liquid-crystals with fixed boundary-conditions, Molecular Crystals and Liquid Crystals, vol.202, issue.12, pp.35-49, 1991.

R. B. Meyer, Piezoelectric Effects in Liquid Crystals, Physical Review Letters, vol.22, issue.18, pp.918-921, 1969.
DOI : 10.1103/PhysRevLett.22.918

]. S. Mor86, P. Morris, D. A. Palffymuhoray, and . Balzarini, Measurements of the bend and splay elastic-constants of octylcyanobiphenyl, Molecular Crystals and Liquid Crystals, vol.139, pp.263-280, 1986.

P. R. Murthy, V. A. Raghunathan, and N. V. Madhusudana, Experimental determination of the flexoelectric coefficients of some nematic liquid crystals, Liquid Crystals, vol.46, issue.2, pp.483-496, 1993.
DOI : 10.1063/1.1681578

J. Nehring, A. R. Kmetz, and T. J. Scheffer, Analysis of weak-boundary-coupling effects in liquid-crystal displays, Journal of Applied Physics, vol.47, issue.3, pp.850-857, 1976.
DOI : 10.1063/1.322718

M. Nespoulous, C. Blanc, and E. M. Nobili, Ultraweak azimuthal anchoring of a nematic liquid crystal on a planar orienting photopolymer, Journal of Applied Physics, vol.102, issue.7, pp.73519-73526, 2007.
DOI : 10.1063/1.2784974
URL : https://hal.archives-ouvertes.fr/hal-01208084

C. W. Oseen, The theory of liquid crystals, Transactions of the Faraday Society, vol.29, issue.140, pp.883-899, 1933.
DOI : 10.1039/tf9332900883

P. Oswald and P. Pieranski, Les cristaux liquides, pp.69-107, 2000.

]. P. Osw08a, A. Oswald, and . Dequidt, Direct measurement of the thermomechanical Lehmann coefficient in a compensated cholesteric liquid crystal, Europhysics Letters, vol.83, pp.16005-100, 2008.

]. P. Osw08b, A. Oswald, and . Dequidt, Measurement of the continuous Lehmann rotation of cholesteric droplets subjected to a temperature gradient, Osw08c] P. Oswald et A. Dequidt. Thermomechanically driven spirals in a cholesteric liquid crystal, pp.217802-217806, 2008.

]. P. Osw08d, A. Oswald, A. Dequidt, and . Zywocí-nski, Sliding planar anchoring and viscous surface torque in a cholesteric liquid crystal, Physical Review E, vol.77, pp.61703-61712, 2008.

H. P. Padmini, N. V. Madhusudanapir93, ]. S. Pirkl, P. Ribière, P. Oswaldpir96-]-s et al., Forming process and stability of bubble domains in dielectrically positive cholesteric liquid crystals From bubble domains to spirals in cholesteric liquid crystals Macroscopic description of compensated cholesterics and chiral smectic liquid crystals, Ple88] H. Pleiner et H. R. Brand. Thermomechanical coupling in compensated cholesteric and chiral smectic liquid crystals. Molecular Crystals and Liquid Crystals Letters, pp.497-511, 1987.

Y. Pomeau, Ph??nom??nes de transport pour des molecules optiquement actives, Physics Letters A, vol.34, issue.3, pp.143-144, 1971.
DOI : 10.1016/0375-9601(71)90794-8

E. P. Raynes, P. Ribière, P. Oswald, S. Pirklsar00, ]. Sarmansve06 et al., The theory of supertwist transitions Crawling and spiraling of cholesteric fingers in electric-field Molecular dynamics simulation of thermomechanical coupling in cholesteric liquid crystals Transport properties of cholesteric liquid crystals studied by molecular dynamics simulation Phase winding in chiral liquid crystalline monolayers due to Lehmann effects Coherent collective precession of molecular rotors with chiral propellers, Molecular Crystals and Liquid CrystalsSar99] S. Sarman. Molecular theory of thermomechanical coupling in cholesteric liquid crystals, pp.1-8, 1986.

O. S. Tarasov, Structural transitions and dynamics of liquid crystals under flows and electric fields, Thèse de doctorat, p.14, 2003.

]. O. Tar03b, A. P. Tarasov, E. L. Krekhov, and . Kramer, Dynamics of cholesteric structures in an electric field, Physical Review E, vol.68, issue.14, pp.31708-31725, 2003.

]. O. Tar03c, A. P. Tarasov, E. L. Krekhov, and . Kramer, Rotation of cholesteric drops under dc electric field. preprint http ://www.anrb.ru Probabilities, data reduction and error analysis in the physical sciences. Les éditions de physique, 1988. 88 [Zyw03] A. ? Zywocí nski. Spinodal temperatures at the nematic to isotropic phase transition from precise volumetric measurements, Journal of Physical Chemistry B, vol.14, issue.87, pp.49-9491, 2003.