1
|
Duhamel P, Baus A, Bich C, Duhoux A, Brachet M, Ponsin P, Leclerc T, Verdaguer C, Rogez D, Annette S, Colas M, Lantiéri L, Bey E. Enjeux et perspectives des allotransplantations de tissus composites en chirurgie reconstructrice pour les très grands brûlés. Bulletin de l'Académie Nationale de Médecine 2022. [DOI: 10.1016/j.banm.2022.06.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
2
|
Baus A, Bich CS, Grosset A, de Rousiers A, Duhoux A, Brachet M, Duhamel P, Thomas M, Rogez D, Mathieu L, Bey E. Medical and surgical management of lower extremity war-related injuries. Experience of the French Military Health Service (FMHS). ANN CHIR PLAST ESTH 2020; 65:447-478. [DOI: 10.1016/j.anplas.2020.05.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 05/13/2020] [Indexed: 01/27/2023]
|
3
|
Rogez D, Krause S, Martinoty P. Main-chain liquid-crystal elastomers versus side-chain liquid-crystal elastomers: similarities and differences in their mechanical properties. Soft Matter 2018; 14:6449-6462. [PMID: 30035290 DOI: 10.1039/c8sm00936h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
After a general introduction on the main aspects of the mechanical properties of main-chain liquid-crystal elastomers (MCLCEs) and side-chain liquid-crystal elastomers (SCLCEs), new results will be presented dealing with several MCLCEs with a cross-linker density C = 8%, 6% and 4% and with a SCLCE with C = 10%, all prepared by the two-step cross-linking process. A non-SCLCE with bulky side-groups similar in shape to the mesogens was also synthesized for comparison with the SCLCE. Most of the experiments were performed with a piezorheometer allowing the determination of the shear anisotropy of the samples by applying shear in a direction parallel or perpendicular to the director, and with a thermo-elastic device for the E measurements. The main results concern: (a) the influence of the supercritical nature of SCLCE and the subcritical nature of MCLCEs on the mechanical properties of these elastomers, as well as that of SmC domains present in MCLCEs; (b) the relationship between the degrees of elongation and of anisotropy deduced from the variations of and during the poly-domain to mono-domain transition of the 10% SCLCE and the 8% MCLCE; (c) the determination of the Poisson's ratio showing that it is isotropic for the non-SCLCE, with a crossover between 0.5 (classical value for rubbers) for small strains and 0.38 for high strains, and anisotropic for the 10% SCLCE and 8% MCLCE, with values <0.5. The particular behaviors of the Poisson's ratios can be explained by confinement effects occurring when stretching increases.
Collapse
Affiliation(s)
- D Rogez
- Institut Charles Sadron, UPR 22, CNRS, 23 rue du Loess, 67034 Strasbourg Cedex 2, France.
| | | | | |
Collapse
|
4
|
Truffaut S, Thomas-Pohl M, Borrini L, Rogez D, Facione J, Lapeyre E. Rehabilitation through adapted sports: The French military way. Ann Phys Rehabil Med 2018. [DOI: 10.1016/j.rehab.2018.05.164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
5
|
De Brier G, Rogez D, Nguyen A, Lapeyre E. Returning to walk for a two arms and one leg amputated man. Ann Phys Rehabil Med 2014. [DOI: 10.1016/j.rehab.2014.03.455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
6
|
De Brier G, Rogez D, Nguyen A, Lapeyre E. Reprise de la marche chez un patient amputé des deux membres supérieurs et d’un membre inférieur. Ann Phys Rehabil Med 2014. [DOI: 10.1016/j.rehab.2014.03.488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
7
|
Thomas-Pohl M, Truffaut-Laude S, Compere S, Azoulay MD, Borrini L, Bisseriex H, Pohl JB, Rogez D, Lapeyre E. From lower limb injuries to bionic prosthesis: Experience of three combat amputees. Ann Phys Rehabil Med 2013. [DOI: 10.1016/j.rehab.2013.07.079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
8
|
Truffaut-Laude S, Rogez D, Borrini L, Thomas-Pohl M, Lapeyre E. War-related “deck-slap” injuries: Conservative strategy or secondary amputation? The French experience at Percy military hospital. Ann Phys Rehabil Med 2013. [DOI: 10.1016/j.rehab.2013.07.077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
9
|
Facione J, Rogez D, Stephan A, Lapeyre E. The military Physical Medicine and Rehabilitation and the socio-medical action: Building multidisciplinary an integrative approach in favor of war wounded soldiers. Ann Phys Rehabil Med 2013. [DOI: 10.1016/j.rehab.2013.07.076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
10
|
Facione J, Rogez D, Stephan A, Lapeyre E. Médecine physique et de réadaptation et action médico-sociale : construction d’une approche multidisciplinaire et intégrative au profit des blessés de guerre. Ann Phys Rehabil Med 2013. [DOI: 10.1016/j.rehab.2013.07.069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
11
|
Thomas-Pohl M, Truffaut-Laude S, Compere S, Azoulay MD, Borrini L, Bisseriex H, Pohl JB, Rogez D, Lapeyre E. De l’amputation fémorale à la prothèse bionique : expérience de trois militaires français. Ann Phys Rehabil Med 2013. [DOI: 10.1016/j.rehab.2013.07.072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
12
|
Thomas-Pohl M, Rogez D, Gelbert F, Nioche C, Pillet H, Genet F, Lapeyre E. Analyse couplée en IRM fonctionnelle et analyse de marche chez l’amputé : à propos d’un cas de plasticité cérébrale dans l’acquisition tardive de la marche chez une patiente agénésique. Ann Phys Rehabil Med 2013. [DOI: 10.1016/j.rehab.2013.07.177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
13
|
Truffaut-Laude S, Rogez D, Borrini L, Thomas-Pohl M, Lapeyre E. Blessures de guerre par « pied de pont » : stratégie conservatrice ou amputation secondaire ? L’expérience française à l’hôpital d’instruction des armées Percy. Ann Phys Rehabil Med 2013. [DOI: 10.1016/j.rehab.2013.07.070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
14
|
Mistral A, Josse M, Corvee C, Rogez D, Lapeyre E, Dochez F. Proposal of an analytical cognitive skills grid for adults with acquired brain injury during a game group in occupational therapy. Ann Phys Rehabil Med 2012. [DOI: 10.1016/j.rehab.2012.07.337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
15
|
Truffaut-Laude S, Thomas-Pohl M, Bisseriex H, Dochez F, Compere S, Mercier H, Rogez D, Lapeyre E. Pied de mine : chirurgie versus traitement conservateur. Discussion à partir d’un cas. Ann Phys Rehabil Med 2012. [DOI: 10.1016/j.rehab.2012.07.230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
16
|
Bisseriex H, Rogez D, Compere S, Mercier H, Dochez F, Lapeyre E. The heterotopic ossifications in the traumatic limb amputation by war wounds: Case report. Ann Phys Rehabil Med 2012. [DOI: 10.1016/j.rehab.2012.07.451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
17
|
Bisseriex H, Thefenne L, Compere S, Rogez D, Dochez F, Mercier H, Lapeyre E. The treatment of the hyperhidrosis of the residual limb, the contribution of the botulinum toxin: About a series of case at the military hospital Percy. Ann Phys Rehabil Med 2012. [DOI: 10.1016/j.rehab.2012.07.218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
18
|
Bisseriex H, Rogez D, Thomas M, Truffaut S, Compere S, Mercier H, Dochez F, Lapeyre E, Thefenne L. [Amputation in low-income countries: particularities in epidmiological features and management practices]. Med Trop (Mars) 2011; 71:565-571. [PMID: 22393622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The epidemiological features and management practices associated with amputation in low-income countries, generally synonymous with the tropics, are different from those observed in Western countries. Unlike developed countries, amputation most frequently involves traumatic injury in young active people. However, Westernization of the lifestyle is leading to an increasing number of cases involving diabetes and atherosclerotic disease. In the developing world, leprosy and Buruli ulcer are still significant etiologic factors for amputation. In war-torn countries, use of antipersonnel landmines is another major cause of amputation with characteristic features. Management of amputees in the developing world is hindered by the lack of facilities for rehabilitation and prosthetic fitting. Many international organizations are supporting national programs to develop such facilities. In addition to being affordable, prosthetics and orthotics must be adapted to the living conditions of a mostly rural amputee population, i.e., heat, humidity, and farm work. The rehabilitation process must be part of a global handicap policy aimed at changing attitudes about disability and reintegrating amputees both socially and professionally.
Collapse
Affiliation(s)
- H Bisseriex
- Hôpital d'Instruction des Armées Percy, Clamart.
| | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Thomas-Pohl M, Rogez D, Calcina P, Pillet H, Lapeyre E. Plasticité cérébrale et acquisition tardive de la marche appareillée : données d’IRM fonctionnelle et d’analyse de marche chez une patiente agénésique. Résultats préliminaires. Ann Phys Rehabil Med 2011. [DOI: 10.1016/j.rehab.2011.07.597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
20
|
Rogez D, Martinoty P. Mechanical properties of monodomain nematic side-chain liquid-crystalline elastomers with homeotropic and in-plane orientation of the director. Eur Phys J E Soft Matter 2011; 34:69. [PMID: 21755436 DOI: 10.1140/epje/i2011-11069-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 04/02/2011] [Accepted: 06/22/2011] [Indexed: 05/31/2023]
Abstract
We present the first study of the shear mechanical properties of monodomain nematic side-chain liquid-crystal elastomers (SCLCEs) prepared by cross-linking with UV irradiation a nematic side-chain liquid-crystal polymer oriented with an electric or a magnetic field. Their elastic behavior was studied in the dry, swollen and stretched states, in order to check the various theoretical descriptions of these systems. The shear measurements taken on the dry samples show that the shear anisotropy is much smaller than that of the usual twice cross-linked samples oriented by a mechanical stretching of the network formed after the first cross-linking step, demonstrating that the elasticity of the networks strongly depends on the preparation procedure used. The shear experiments performed on the swollen state of these two different types of elastomers reveal that the elasticity of the network is Gaussian for the elastomers oriented with the electric or the magnetic field, and non-Gaussian for the elastomers oriented with the usual stretching procedure. The analysis of the stress-strain curves of both types of elastomers with the neoclassical model based on Gaussian rubber elasticity confirms the Gaussian and non-Gaussian nature of their elasticity. The shear experiments performed as a function of the elongation of the homeotropically oriented elastomer when the shear is applied in a direction parallel to the elongation, do not show the decrease of the associated shear modulus, which is theoretically expected when the strain approaches the threshold value marking the beginning of the elastic plateau. However, the observation of this effect could be prevented by possible small misalignments of the director, as suggested by a calculation presented in one of the theories describing this effect.
Collapse
Affiliation(s)
- D Rogez
- UPR 22, CNRS/UDS, Institut Charles Sadron, 23 rue du Loess, 67034 Strasbourg, France
| | | |
Collapse
|
21
|
Thefenne L, Dubecq C, Zing E, Rogez D, Soula M, Escobar E, Defuentes G, Lapeyre E, Berets O. A rare case of paraplegia complicating a lumbar epidural infiltration. Ann Phys Rehabil Med 2010; 53:575-83. [PMID: 20870478 DOI: 10.1016/j.rehab.2010.08.029] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Accepted: 08/20/2010] [Indexed: 11/26/2022]
Abstract
OBJECTIVE We report the case of a patient who developed paraplegia following a low lumbar epidural steroid injection. Alternative approaches to (or alternative means of) performing transforaminal injections should be considered, in order to avoid devastating neurological complications. CASE REPORT A 54-year-old man (who had undergone surgery 14 years earlier to cure an L5-S1 slipped disc with right S1 radiculopathy) presented with low back pain (which had begun 6 weeks previously) and left S1 radiculopathy. During a second infiltration of prednisolone acetate, the patient reported feeling a heat sensation in his legs and concomitantly developed facial flushing. Immediately after the injection, the patient developed complete, flaccid T7 ASIA A motor and sensory paraplegia. Three days later, T2 magnetic resonance imaging (MRI) of the spine revealed a spontaneous hypersignal in the conus medullaris and from T6 to T9, suggesting medullary ischemia. Recovery has been slow; after 4 months of treatment in a physical and rehabilitation medicine department, urinary and sensory disorders are still present (T7 ASIA D paraplegia). The patient can walk 200 m unaided. Three months later, the MRI data had not changed. DISCUSSION This is a rare case report of paraplegia following low lumbar epidural infiltration via an interlaminar route. The mechanism is not clear. Most of authors suggest that the pathophysiological basis of this type of complication is ischemia caused by accidental interruption of the medullary blood supply. Direct damage to a medullary artery, arterial spasm or corticosteroid-induced occlusion due to undetected intra-arterial injection could result in medullary infarction. This serious incident should prompt us to consider how to avoid further problems in the future. It also raises the issue of providing patients with information on the risks inherent in this type of procedure. CONCLUSION Despite the rarity of this complication, patients should be made aware of its potential occurrence. In the case reported here, the functional prognosis is uncertain.
Collapse
Affiliation(s)
- L Thefenne
- Service de médecine physique et réadaptation, hôpital d'instruction des armées Laveran, Marseille cedex 13, France.
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Pozo O, Collin D, Finkelmann H, Rogez D, Martinoty P. Gel-like elasticity in glass-forming side-chain liquid-crystal polymers. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:031801. [PMID: 19905137 DOI: 10.1103/physreve.80.031801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Indexed: 05/28/2023]
Abstract
We study the complex shear modulus G of two side-chain liquid-crystal polymers (SCLCPs), a methoxy-phenylbenzoate substituted polyacrylate (thereafter called PAOCH3 ), and a cyanobiphenyl substituted polyacrylate supplied by Merck (thereafter called LCP105) using a piezoelectric rheometer. Two methods of filling the cell are used: (a) a capillary method, which can be used only at high temperature because of the low value of the viscosity, and (b) the classical one, thereafter called compression method, which consists in placing the sample between the two slides of the cell and to bring them closer. By filling the cell at high temperature either with the compression or the capillary method, we show that the response of both compounds is liquidlike ( G' approximately f2 and G'' approximately f , where f is the frequency) for temperatures higher than a certain temperature T0 and gel-like (G' approximately const, G'' approximately f) below T0. This change in behavior from the conventional flow response to a gel-like response, when approaching the glass transition, is observed for nonsliding conditions and for very weak-imposed shear strains. It can be explained by a percolation-type mechanism of preglassy elastic clusters, which correspond to long-range and long-lived density fluctuations that are frozen at the time scale of the experiment. The sample response is therefore the sum of two contributions: one is due to the flow response of the polymer melt and the other to the elastic response of the network formed by the preglassy elastic clusters. By filling the cell below T0 with the compression method, both compounds exhibit a gel-type behavior by gently bringing closer the slides of the cell and an anomalous low-frequency behavior characterized by G'=const and G''=const by increasing the pressure used to bring closer the slides of the cell. A compression-assisted aggregation of the preglassy elastic clusters can explain both the increase in the low-frequency elastic plateau when the sample thickness is decreased and the anomalous low-frequency behavior. Further evidence for the existence of these elastic clusters is provided by the following results: (a) the nonlinear response of the samples as a function of the strain amplitude, which can be explained by the Payne effect, and (b) the aggregation effects, which can be mimicked by a polydimethylsiloxane melt filled with silica particles, the silica particles playing the role of the preglassy elastic clusters. All these observations show that PAOCH3 is not a macroscopically solidlike material with an unconventional type of elasticity, as claimed by Mendil [Phys. Rev. Lett. 96, 077801 (2006)]. The gel-type behavior observed here on two SCLCPs ( PAOCH3 and LCP105) and previously on some conventional flexible polymers (atactic polystyrene, poly-n-butylacrylate) seems to be a generic effect of the glass transition. The presence of the preglassy elastic clusters questions the widely accepted hypothesis of ergodicity in the supercooled state.
Collapse
Affiliation(s)
- O Pozo
- Institut Charles Sadron, UPR 22, 67034 Strasbourg Cedex 2, France
| | | | | | | | | |
Collapse
|
23
|
Cremades S, Rogez D, Couppey N, Cremades A, Lechevalier D. Une tumeur spinale rare: le lymphome épidural primitif. Rev Med Interne 2006. [DOI: 10.1016/j.revmed.2006.10.228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
24
|
Rogez D, Francius G, Finkelmann H, Martinoty P. Shear mechanical anisotropy of side chain liquid-crystal elastomers: influence of sample preparation. Eur Phys J E Soft Matter 2006; 20:369-78. [PMID: 16896566 DOI: 10.1140/epje/i2005-10132-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2005] [Accepted: 07/18/2006] [Indexed: 05/11/2023]
Abstract
We study the mechanical anisotropy of a series of uniaxial side chain nematic elastomers prepared with the same chemical composition but with different preparation protocols. For all the compounds, the experiments performed as a function of temperature show no discontinuity in both G' (//) and G' ( perpendicular) (the labels // and perpendicular stand for the director parallel, respectively perpendicular to the shear displacement) around the nematic-isotropic (N-I) phase transition temperature determined by DSC. They also all show a small decrease in G' (//) starting at temperatures well above this temperature (from approximately 4( degrees ) C to approximately 20( degrees ) C depending on the compound studied) and leading to a small hydrodynamic value of the G' ( perpendicular)/G' (//) ratio. The measurements taken as a function of frequency show that the second plateau in G' (//) and the associated dip in G (//)" expected from dynamic semi-soft elasticity are not observed. These results can be described by the de Gennes model, which predicts small elastic anisotropy in the hydrodynamic and linear regimes. They correspond to the behavior expected for compounds beyond the mechanical critical point, which is consistent with the NMR and specific heat measurements taken on similar compounds. We also show that a reduction in the cross-linking density does not change the non-soft character of the mechanical response. From the measurements taken as a function of frequency at several temperatures we deduce that the time-temperature superposition method does not apply. From these measurements, we also determine the temperature dependence of the longest relaxation time tau(E) of the network for the situations where the director is either parallel or perpendicular to the shear velocity. Finally, we discuss the influence on the measurements of the mechanical constraint associated with the fact that the samples cannot change their shape around the pseudo phase transition, because of their strong adherence on the sample-bearing glass slides.
Collapse
Affiliation(s)
- D Rogez
- Institut de Mécanique des Fluides et des Solides, UMR 7507, CNRS-ULP, 67000, Strasbourg, France
| | | | | | | |
Collapse
|
25
|
Rogez D, Benguigui LG, Martinoty P. Behavior of the layer compression elastic modulus near, above, and below a smectic C-hexatic I critical point in binary mixtures. Eur Phys J E Soft Matter 2005; 16:193-198. [PMID: 15729510 DOI: 10.1140/epje/e2005-00020-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Indexed: 05/24/2023]
Abstract
We present the first study of the layer compression modulus B carried out near, above and below the Smectic C-Hexatic I critical point in racemic mixtures of methylbutyl phenyl octylbiphenyl-carboxylate (8SI) and the octyloxy biphenyl analog (8OSI), at frequencies ranging from 0.2 Hz to 2 x 10(3) Hz. The behavior of B as a function of temperature shows a progressive evolution from a first order transition in 8SI to a continuous supercritical behavior in 8OSI. The latter is characterized by an increase in B, which appears above the transition, and which is followed by a leveling off when the temperature is decreased towards the transition. It is proposed that this behavior stems from the relaxation of the hexatic domains which are frozen in the frequency range studied. For the supercritical and near-critical compounds, B exhibits a small dip near the transition temperature, which is visible in the low frequency range only, indicating that the dynamics associated with the critical point is very slow. We also report measurements in the Crystal-J phase of the pure compounds, and show that 8SI behaves mechanically as a hexatic phase and 8OSI as a soft crystal phase.
Collapse
Affiliation(s)
- D Rogez
- Laboratoire de Dynamique des Fluides Complexes, UMR n 7506, ULP-CNRS, Université Louis Pasteur 4, rue Blaise Pascal, 67070 Strasbourg Cedex, France
| | | | | |
Collapse
|
26
|
Rogez D, Collin D, Martinoty P. Behavior of the layer compression modulus as a function of frequency near the nematic-smectic-A and re-entrant nematic-smectic-A phase transitions. Eur Phys J E Soft Matter 2004; 14:43-47. [PMID: 15221589 DOI: 10.1140/epje/i2004-10004-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Indexed: 05/24/2023]
Abstract
A progressive cross-over of the layer compression modulus B from a simple power law behavior to a saturation behavior when the frequency is increased from 1 Hz to 2 x 10(3) Hz is observed for the first time near the nematic-smectic-A and the re-entrant nematic-smectic-A phase transitions of a mixture of 4-cyano-4'-( n-hexyloxy)biphenyl and 4-cyano-4'-( n-octyloxy)biphenyl (6OCB-8OCB). This result shows that the saturation of B determined by second sound near the nematic-smectic-A phase transition of a similar mixture is dynamic in nature, and cannot be associated with the static saturation effect predicted by the dislocation loop model, as proposed previously.
Collapse
Affiliation(s)
- D Rogez
- Laboratoire de Dynamique des Fluides Complexes, UMR no. 7506, ULP-CNRS, Université Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg Cedex, France
| | | | | |
Collapse
|
27
|
Krüger JK, Grammes C, Jiménez R, Schreiber J, Bohn K, Baller J, Fischer C, Rogez D, Schorr C, Alnot P. Second-order elasticity of liquid crystals within their nematic state at high frequencies. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1995; 51:2115-2128. [PMID: 9962872 DOI: 10.1103/physreve.51.2115] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
|
28
|
Grammes C, Krüger JK, Bohn K, Baller J, Fischer C, Schorr C, Rogez D, Alnot P. Universal relaxation behavior of classical liquid crystals at hypersonic frequencies. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1995; 51:430-440. [PMID: 9962661 DOI: 10.1103/physreve.51.430] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
|
29
|
Cerf R, Salehi ST, Rogez D. Ultrasonic Cole-Cole diagram for solutions and application to alpha-chymotrypsin. Biophys J 1989; 55:649-54. [PMID: 2720063 PMCID: PMC1330547 DOI: 10.1016/s0006-3495(89)82862-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Deconvolution of ultrasonic data into single relaxations is rarely feasible when only the absorption or the velocity of the waves is measured. Here we use both series of data to construct a Cole-Cole diagram for a solution. When applied to alpha-chymotrypsin, this method shows two relaxations that are well separated on the time scale, a result that will help simplify analyses of the ultrasonic data for this enzyme.
Collapse
Affiliation(s)
- R Cerf
- Laboratoire de Spectrométrie et d'Imagerie Ultrasonores, Université Louis Pasteur, Strasbourg, France
| | | | | |
Collapse
|
30
|
Rogez D, Cerf R, Andrianjara R, Salehi ST, Fouladgar H. Ultrasonic studies of proton-transfer reactions at the catalytic site of alpha-chymotrypsin. FEBS Lett 1987; 219:22-6. [PMID: 3036598 DOI: 10.1016/0014-5793(87)81183-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Ultrasonic relaxation measurements for alpha-chymotrypsin in phosphate, sulfite and arsenate buffers exhibit a high peak of absorption at neutral pH. The analysis is based on: comparison of the relaxation measurements for the enzyme and for the zymogen and inhibited enzyme; X-ray and neutron diffraction data, and high-resolution NMR data. The ultrasonic relaxation is shown to result mainly from a proton-transfer reaction that involves the histidine at the catalytic site (His-57). The question is raised of whether the enhanced ultrasonic effect observed in the enzyme is indicative of a property that plays a part in the catalytic activity.
Collapse
|
31
|
|