151
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Abstract
We have connected the dynamic fragility, namely, the steepness of the relaxation-time variation upon temperature reduction, to the excess entropy and heat capacity of a large number of glass-forming polymers. The connection was obtained in a natural way from the Adam-Gibbs equation, relating the structural relaxation time to the configurational entropy. We find a clear correlation for a group of polymers. For another group of polymers, for which this correlation does not work, we emphasize the role of relaxation processes unrelated to the alpha process in affecting macroscopic thermodynamic properties. Once the residual excess entropy at the Vogel temperature is removed from the total excess entropy, the correlation between dynamic fragility and thermodynamic properties is reestablished.
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Affiliation(s)
- D Cangialosi
- Fundacion Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain.
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152
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Pérez Aparicio R, Arbe A, Colmenero J, Frick B, Willner L, Richter D, Fetters LJ. Quasielastic Neutron Scattering Study on the Effect of Blending on the Dynamics of Head-to-Head Poly(propylene) and Poly(ethylene−propylene). Macromolecules 2006. [DOI: 10.1021/ma052006k] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. Pérez Aparicio
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France; Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; and School of Chemical and Biomolecular Engineering, Cornell University, Ithaca,
| | - A. Arbe
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France; Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; and School of Chemical and Biomolecular Engineering, Cornell University, Ithaca,
| | - J. Colmenero
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France; Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; and School of Chemical and Biomolecular Engineering, Cornell University, Ithaca,
| | - B. Frick
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France; Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; and School of Chemical and Biomolecular Engineering, Cornell University, Ithaca,
| | - L. Willner
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France; Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; and School of Chemical and Biomolecular Engineering, Cornell University, Ithaca,
| | - D. Richter
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France; Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; and School of Chemical and Biomolecular Engineering, Cornell University, Ithaca,
| | - L. J. Fetters
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France; Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; and School of Chemical and Biomolecular Engineering, Cornell University, Ithaca,
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153
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Narros A, Arbe A, Alvarez F, Colmenero J, Zorn R, Schweika W, Richter D. Partial Structure Factors in 1,4-Polybutadiene. A Combined Neutron Scattering and Molecular Dynamics Simulations Study. Macromolecules 2005. [DOI: 10.1021/ma051466a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. Narros
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastian, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - A. Arbe
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastian, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - F. Alvarez
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastian, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - J. Colmenero
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastian, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - R. Zorn
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastian, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - W. Schweika
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastian, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - D. Richter
- Departamento de Física de Materiales, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain; Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastian, Spain; Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain; and Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
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154
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Cangialosi D, Schwartz GA, Alegría A, Colmenero J. Combining configurational entropy and self-concentration to describe the component dynamics in miscible polymer blends. J Chem Phys 2005; 123:144908. [PMID: 16238425 DOI: 10.1063/1.2052592] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We provide a new approach to describe the component segmental dynamics of miscible polymer blends combining the concept of chain connectivity, expressed in terms of the self-concentration, and the Adam-Gibbs model. The results show an excellent agreement between the prediction of our approach and the experimental data. The self-concentrations obtained yield length scales between 1 and 3.2 nm depending on the temperature, the flexibility of the polymer, expressed in terms of the Kuhn segment, and its concentration in the blends, at temperatures above the glass transition range of the blend.
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Affiliation(s)
- D Cangialosi
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain.
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155
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Genix AC, Arbe A, Alvarez F, Colmenero J, Willner L, Richter D. Dynamics of poly(ethylene oxide) in a blend with poly(methyl methacrylate): a quasielastic neutron scattering and molecular dynamics simulations study. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 72:031808. [PMID: 16241474 DOI: 10.1103/physreve.72.031808] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 06/20/2005] [Indexed: 05/05/2023]
Abstract
In this paper, we have addressed the question of the dynamic miscibility in a blend characterized by very different glass-transition temperatures, Tg, for the components: poly(ethylene oxide) and poly(methyl methacrylate) (PEO/PMMA). The combination of quasielastic neutron scattering with isotopic labeling and fully atomistic molecular dynamics simulations has allowed us to selectively investigate the dynamics of the two components in the picosecond-10 nanoseconds scale at temperatures close and above the Tg of the blend. The main focus was on the PEO component, i.e., that of the lowest Tg, but first we have characterized the dynamics of the other component in the blend and of the pure PEO homopolymer as reference. In the region investigated, the dynamics of PMMA in the blend is strongly affected by the alpha-methyl rotation; an additional process detected in the experimental window 65 K above the blend-Tg can be identified as the merged alphabeta process of this component that shows strong deviations from Gaussian behavior. On the other hand, pure PEO displays entropy driven dynamics up to very large momentum transfers. Such kind of motion seems to freeze when the PEO chains are in the blend. There, we have directly observed a very heterogeneous and moreover confined dynamics for the PEO component. The presence of the hardly moving PMMA matrix leads to the creation of little pockets of mobility where PEO can move. The characteristic size of such confined islands of mobility might be estimated to be of approximately 1 nm. These findings are corroborated by the simulation study, which has been an essential support and guide in our data analysis procedure.
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Affiliation(s)
- A-C Genix
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain
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156
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Sancho-Bru P, Bataller R, Gasull X, Colmenero J, Khurdayan V, Gual A, Nicolás JM, Arroyo V, Ginès P. Genomic and functional characterization of stellate cells isolated from human cirrhotic livers. J Hepatol 2005; 43:272-82. [PMID: 15964095 DOI: 10.1016/j.jhep.2005.02.035] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2004] [Revised: 01/17/2005] [Accepted: 02/23/2005] [Indexed: 02/06/2023]
Abstract
BACKGROUND/AIMS Hepatic stellate cells (HSCs) are believed to participate in liver fibrogenesis and portal hypertension. Knowledge on human HSCs is based on studies using HSCs isolated from normal livers. We investigated the phenotypic, genomic and functional characteristics of HSCs from human cirrhotic livers. METHODS HSC were obtained from normal and cirrhotic human livers. Cells were characterized by immunocytochemistry and gene microarray analysis. Cell proliferation, Ca(2+) changes and cell contraction were assessed by 3H-thymidine incorporation and by using an epifluorescence microscope. RESULTS HSCs freshly isolated from human cirrhotic livers showed phenotypical features of myofibroblasts. These features were absent in HSCs freshly isolated from normal human livers and become prominent after prolonged culture. HSCs from cirrhotic human livers markedly express genes involved in fibrogensis, inflammation and apoptosis. HSCs from normal livers after prolonged culture preferntially expressed genes related to fibrogenesis and contractility. Agonists induced proliferation, Ca(2+) increase and cell contraction in HSCs isolated from human cirrhotic livers. Response to agonists was more marked in culture-activated HSCs and was not observed in HSCs freshly isolated from normal livers. CONCLUSIONS HSCs from human cirrhotic livers show fibrogenic and contractile features. However, the current model of HSCs activated in culture does not exactly reproduce the activated phenotype found in cirrhotic human livers.
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Affiliation(s)
- Pau Sancho-Bru
- Liver Unit, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Catalonia, Spain
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157
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Cerveny S, Colmenero J, Alegría A. Dielectric Investigation of the Low-Temperature Water Dynamics in the Poly(vinyl methyl ether)/H2O System. Macromolecules 2005. [DOI: 10.1021/ma050811t] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- S. Cerveny
- Unidad de Física de Materiales, Centro Mixto CSIC-UPV/EHU, and Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU), Facultad de Química, Apartado 1072, 20018, San Sebastián, Spain, and Donostia Internacional Physics Center, Paseo Manuel de Lardizabal 4, 20018, San Sebastián, Spain
| | - J. Colmenero
- Unidad de Física de Materiales, Centro Mixto CSIC-UPV/EHU, and Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU), Facultad de Química, Apartado 1072, 20018, San Sebastián, Spain, and Donostia Internacional Physics Center, Paseo Manuel de Lardizabal 4, 20018, San Sebastián, Spain
| | - A. Alegría
- Unidad de Física de Materiales, Centro Mixto CSIC-UPV/EHU, and Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU), Facultad de Química, Apartado 1072, 20018, San Sebastián, Spain, and Donostia Internacional Physics Center, Paseo Manuel de Lardizabal 4, 20018, San Sebastián, Spain
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158
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Arrese-Igor S, Arbe A, Alegría A, Colmenero J, Frick B. Sub-Tg dynamics in polycarbonate by neutron scattering and its relation with secondary γ relaxation. J Chem Phys 2005; 123:014907. [PMID: 16035869 DOI: 10.1063/1.1948372] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have investigated the dynamics of phenylene rings in glassy bisphenol-A (BPA) polycarbonate (PC) by means of quasielastic neutron scattering. Taking advantage of selective deuteration of the samples, we have studied the incoherent scattering of hydrogens in phenylene rings on the one hand, and on the other hand the coherent quasielastic scattering of all the atoms in the sample. Two different types of neutron spectrometers, time of flight and backscattering, were used in order to cover a wide dynamic range, which extends from microscopic (approximately 10(-13) s) to mesoscopic (approximately 10(-9) s) times. Moreover, neutron-diffraction experiments with polarization analysis were carried out in order to characterize the structural features, and the relative coherent and incoherent contributions of the samples investigated. In contrast with previous studies of phenylene ring dynamics in BPA polysulfone performed by us also by neutron scattering, phenylene rings in BPA PC exhibit an "extra" motion in addition to those found for BPA polysulfone's phenylene rings. This extra motion of the rings in PC perfectly correlates with the main carbonate group motion followed by dielectric spectroscopy and allows us to (i) consistently interpret the PC's gamma relaxation in terms of two different motions; and (ii) experimentally confirm the relation between the motion of phenylene rings and carbonate groups within BPA PC formerly predicted by computational methods.
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Affiliation(s)
- S Arrese-Igor
- Departamento de Física de Materiales, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain.
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159
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Affiliation(s)
- I. Quintana
- Departamento de Física de Materiales UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain, Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Apartado 1072, 20080 San Sebastián, Spain, and Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
| | - A. Arbe
- Departamento de Física de Materiales UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain, Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Apartado 1072, 20080 San Sebastián, Spain, and Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
| | - J. Colmenero
- Departamento de Física de Materiales UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain, Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Apartado 1072, 20080 San Sebastián, Spain, and Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
| | - B. Frick
- Departamento de Física de Materiales UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain, Unidad Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Apartado 1072, 20080 San Sebastián, Spain, and Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
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160
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Arrese-Igor S, Arbe A, Alegrı́a A, Colmenero J, Frick B. Erratum: “Phenylene ring dynamics in bisphenol-A-polysulfone by neutron scattering” [J. Chem. Phys. 120, 423 (2004)]. J Chem Phys 2005. [DOI: 10.1063/1.1839573] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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161
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Lorthioir C, Alegría A, Colmenero J, Deloche B. Heterogeneity of the Segmental Dynamics of Poly(dimethylsiloxane) in a Diblock Lamellar Mesophase: Dielectric Relaxation Investigations. Macromolecules 2004. [DOI: 10.1021/ma049011t] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- C. Lorthioir
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales Centro Mixto (CSIC-UPV/EHU), Facultad de Química, Apartado 1072, 20080 San Sebastián, Spain; Fundación Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; and Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, 91405 Orsay, France
| | - A. Alegría
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales Centro Mixto (CSIC-UPV/EHU), Facultad de Química, Apartado 1072, 20080 San Sebastián, Spain; Fundación Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; and Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, 91405 Orsay, France
| | - J. Colmenero
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales Centro Mixto (CSIC-UPV/EHU), Facultad de Química, Apartado 1072, 20080 San Sebastián, Spain; Fundación Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; and Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, 91405 Orsay, France
| | - B. Deloche
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales Centro Mixto (CSIC-UPV/EHU), Facultad de Química, Apartado 1072, 20080 San Sebastián, Spain; Fundación Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain; and Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, 91405 Orsay, France
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162
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Macho E, Alegría A, Colmenero J. Determining viscosity temperature behavior of four amorphous thermoplastics using a parallel plate technique. POLYM ENG SCI 2004. [DOI: 10.1002/pen.760271107] [Citation(s) in RCA: 9] [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] [Indexed: 11/08/2022]
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163
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Narros A, Alvarez F, Arbe A, Colmenero J, Richter D, Farago B. Hydrogen motions in the α-relaxation regime of poly(vinyl ethylene): A molecular dynamics simulation and neutron scattering study. J Chem Phys 2004; 121:3282-94. [PMID: 15291640 DOI: 10.1063/1.1772761] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydrogen motion in poly(vinyl ethylene) (1,2-polybutadiene) in the alpha-relaxation regime has been studied by combining neutron spin echo (NSE) measurements on a fully protonated sample and fully atomistic molecular dynamics simulations. The almost perfect agreement between experiment and simulation results validates the simulated cell. A crossover from Gaussian to non-Gaussian behavior is observed for the intermediate scattering function obtained from both NSE measurements and simulations. This crossover takes place at unusually low Q values, well below the first maximum of the static structure factor. Such anomalous deviation from Gaussian behavior can be explained by the intrinsic dynamic heterogeneity arising from the differences in the dynamics of the different protons in this system. Side group hydrogens show a markedly higher mobility than main chain protons. Taking advantage of the simulations we have investigated the dynamic features of all different types of hydrogens in the sample. Considering each kind of proton in an isolated way, deviations from Gaussian behavior are also found. These can be rationalized in the framework of a simple picture based on the existence of a distribution of discrete jumps underlying the atomic motions in the alpha process.
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Affiliation(s)
- A Narros
- Departamento de Física de Materiales UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain
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164
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Carrión JA, Bellot P, Colmenero J, Garcia Pagan JC. Large spontaneous splenorenal shunt as a cause of chronic hepatic encephalopathy. J Hepatol 2004; 40:868. [PMID: 15094238 DOI: 10.1016/j.jhep.2003.12.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2003] [Revised: 12/18/2003] [Accepted: 12/23/2003] [Indexed: 12/17/2022]
Affiliation(s)
- José A Carrión
- Liver Unit, Hospital Clínic, Villarroel 170, 08036 Barcelona, Spain
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165
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Arrese-Igor S, Arbe A, Alegría A, Colmenero J, Frick B. Phenylene ring dynamics in bisphenol-A-polysulfone by neutron scattering. J Chem Phys 2004; 120:423-36. [PMID: 15267305 DOI: 10.1063/1.1630013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have investigated the dynamics of phenylene rings in a glassy polysulfone (bisphenol-A-polysulfone) by means of quasielastic neutron scattering. Nowadays it is well known that these molecular motions are directly connected with the mechanical properties of engineering thermoplastics in general. The particular system investigated by us has the advantage that by selective deuteration of the methyl groups, the neutron scattering measured is dominated by the incoherent contribution from the protons in the phenylene rings. In this way, the dynamics of such molecular groups can be experimentally isolated. Two different types of neutron spectrometers: time of flight and backscattering, were used in order to cover a wide dynamic range, which extends from microscopic (10(-13) s) to mesoscopic (10(-9) s) times. Moreover, neutron diffraction experiments with polarization analysis were also carried out in order to characterize the structural features of the sample investigated. Fast oscillations of increasing amplitude with temperature and pi-flips are identified for phenylene rings motions. Due to the structural disorder characteristic of the amorphous state, both molecular motions display a broad distribution of relaxation times, which spreads over several orders of magnitude. Based on the results obtained, we propose a model for phenylene rings dynamics, which combines the two kinds of molecular motions identified. This model nicely describes the neutron scattering results in the whole dynamic range investigated.
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Affiliation(s)
- S Arrese-Igor
- Departamento de Física de Materiales UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain
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166
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Lorthioir C, Alegría A, Colmenero J. Self-confined polymer dynamics in miscible binary blends. Eur Phys J E Soft Matter 2003; 12 Suppl 1:S127-S130. [PMID: 15011031 DOI: 10.1140/epjed/e2003-01-029-9] [Citation(s) in RCA: 7] [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: 12/20/2002] [Indexed: 05/24/2023]
Abstract
The segmental dynamics of PVME within the single-phase state of poly(styrene)/poly(vinyl methyl ether) blends (PS/PVME) was examined by dielectric spectroscopy. A particular attention has been given to the high PS concentration regime. In this latter, rather localized, weakly cooperative motions of the PVME segments are detected at low temperatures, in addition of the secondary relaxation processes. This feature is attributed to confinement effects induced by the PS chains on the PVME.
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Affiliation(s)
- C Lorthioir
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain
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167
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Moreno AJ, Colmenero J, Alegría A, Alba-Simionesco C, Dosseh G, Morineau D, Frick B. Methyl group dynamics in a confined glass. Eur Phys J E Soft Matter 2003; 12 Suppl 1:S43-S46. [PMID: 15011013 DOI: 10.1140/epjed/e2003-01-011-7] [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: 01/01/2003] [Indexed: 05/24/2023]
Abstract
We present a neutron scattering investigation on methyl group dynamics in glassy toluene confined in mesoporous silicates of different pore sizes. The experimental results have been analysed in terms of a barrier distribution model, such a distribution following from the structural disorder in the glassy state. Confinement results in a strong decreasing of the average rotational barrier in comparison to the bulk state. We have roughly separated the distribution for the confined state in a bulk-like and a surface-like contribution, corresponding to rotors at a distance from the pore wall respectively larger and smaller than the spatial range of the interactions which contribute to the rotational potential for the methyl groups. We have estimated a distance of 7 A as a lower limit of the interaction range, beyond the typical nearest-neighbour distance between centers-of-mass (4.7 A).
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Affiliation(s)
- A J Moreno
- Laboratoire des Verres, CNRS-UMR 5587, Université de Montpellier II, Bâtiment 13, 34095 Montpellier, France.
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168
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Lorthioir C, Deloche B, Alegría A, Colmenero J, Auroy P, Gallot Y. Segmental order and dynamics of polymer chains confined in block copolymer lamellar mesophases: NMR and dielectric relaxation studies. Eur Phys J E Soft Matter 2003; 12 Suppl 1:S121-S125. [PMID: 15011030 DOI: 10.1140/epjed/e2003-01-028-x] [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: 12/20/2002] [Indexed: 05/24/2023]
Abstract
The PDMS lamellar sublayers of a poly(styrene)-poly(dimethylsiloxane) diblock (PS-PDMS) and PS-PDMS-PS triblocks are investigated by NMR and dielectric spectroscopy. Some segments of the confined PDMS chains display anisotropic orientational fluctuations along the interfaces with the PS glassy blocks, whereas the others display fluctuations rather parallel to the lamellae normal. This coexistence results from a competitive ordering effect induced by the glassy interfaces and the chain-end anchoring junctions. The distribution of PDMS relaxation times within the sublayers is also examined: in particular, a slowing down of the segmental motions, together with a broadening of this distribution, are detected.
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Affiliation(s)
- C Lorthioir
- Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, 91405 Orsay, France
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169
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Affiliation(s)
- Vicente Arroyo
- Liver Unit, Institute of Digestive Diseases, Hospital Clínic, Villarroel, 170, University of Barcelona, 08036 Barcelona, Spain.
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170
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Abstract
The use of intravenous albumin in cirrhosis has been reactivated during the last two decades. During this period several investigations have shown that albumin (1) prevents circulatory dysfunction in patients with massive ascites treated by paracentesis, (2) prevents circulatory dysfunction and type-1 HRS and increases survival in patients with SBP, and (3) in association with vasoconstrictors normalizes circulatory function and serum creatinine and increases survival in patients with type-1 HRS. Indications 2 and 3 are clear. There is discussion, however, regarding indication number 1. Although no significant differences in survival have been observed in trials comparing patients treated by paracentesis with and without albumin, in none of these studies was survival an end-point of the trial. In contrast, there is evidence that paracentesis-induced circulatory dysfunction is associated with a bad outcome. In consequence, although further studies on this indication are clearly required, with the current data it is advisable to use albumin as a plasma expander in patients with massive ascites treated by paracentesis.
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Affiliation(s)
- V Arroyo
- Liver Unit, Institut de Malalties Digestives, Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain.
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171
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Arrese-Igor S, Arbe A, Alegrı́a A, Colmenero J, Frick B. Short-time dynamics of phenylene-rings in bisphenol based engineering thermoplastics. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00023-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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172
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Bataller R, Sancho-Bru P, Ginès P, Lora JM, Al-Garawi A, Solé M, Colmenero J, Nicolás JM, Jiménez W, Weich N, Gutiérrez-Ramos JC, Arroyo V, Rodés J. Activated human hepatic stellate cells express the renin-angiotensin system and synthesize angiotensin II. Gastroenterology 2003; 125:117-25. [PMID: 12851877 DOI: 10.1016/s0016-5085(03)00695-4] [Citation(s) in RCA: 268] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND & AIMS The renin-angiotensin system plays an important role in hepatic fibrogenesis. In other organs, myofibroblasts accumulated in damaged tissues generate angiotensin II, which promotes inflammation and extracellular matrix synthesis. It is unknown whether myofibroblastic hepatic stellate cells, the main hepatic fibrogenic cell type, express the renin-angiotensin system and synthesize angiotensin II. The aim of this study was to investigate whether quiescent and activated human hepatic stellate cells contain the components of the renin-angiotensin system and synthesize angiotensin II. METHODS Hepatic stellate cells were freshly isolated from normal human livers (quiescent hepatic stellate cells) and from human cirrhotic livers (in vivo activated hepatic stellate cells). Culture-activated hepatic stellate cells were used after a second passage of quiescent hepatic stellate cells. Angiotensinogen, renin, and angiotensin-converting enzyme were assessed by quantitative polymerase chain reaction. Angiotensin II production was assessed by enzyme-linked immunosorbent assay and immunohistochemistry. RESULTS Quiescent hepatic stellate cells barely express the renin-angiotensin system components--angiotensinogen, renin, and angiotensin-converting enzyme--and do not secrete angiotensin II. In contrast, both in vivo activated hepatic stellate cells and culture-activated hepatic stellate cells highly express active renin and angiotensin-converting enzyme and secrete angiotensin II to the culture media. Mature angiotensin II protein is also detected in the cytoplasm of in vivo activated and culture-activated hepatic stellate cells. Growth factors (platelet-derived growth factor and epidermal growth factor) and vasoconstrictor substances (endothelin-1 and thrombin) stimulate angiotensin II synthesis, whereas transforming growth factor-beta and proinflammatory cytokines have no effect. Vasodilator substances markedly attenuate the effect of endothelin-1. CONCLUSIONS After activation, human hepatic stellate cells express the components of the renin-angiotensin system and synthesize angiotensin II. These results suggest that locally generated angiotensin II could participate in tissue remodeling in the human liver.
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Affiliation(s)
- Ramón Bataller
- Department of Medicine, Hospital Clínic, Institut d'Investigacions Biomédiques August Pi y Sunyer, University of Brescia School of Medicine, Barcelona, Catalonia, Spain
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173
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Arbe A, Colmenero J, Alvarez F, Monkenbusch M, Richter D, Farago B, Frick B. Experimental evidence by neutron scattering of a crossover from Gaussian to non-Gaussian behavior in the alpha relaxation of polyisoprene. Phys Rev E Stat Nonlin Soft Matter Phys 2003; 67:051802. [PMID: 12786170 DOI: 10.1103/physreve.67.051802] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2002] [Indexed: 05/24/2023]
Abstract
We report incoherent quasielastic neutron scattering experiments exploring the alpha-relaxation range in polyisoprene over an unprecedented range in momentum transfer Q. The data corroborate and validate earlier molecular dynamics simulations and reveal the existence of a crossover from Gaussian to non-Gaussian character of the main chain protons self-correlation function in the alpha-relaxation regime. The real challenge of the experiment was to push the neutron techniques to cover a Q range as wide as possible. By combining two neutron spin echo spectrometers and a backscattering instrument, we have been able to study the dynamics in a Q range of 0.1 < or = Q < or = 4.7 A(-1). In the low-Q regime the shape of the relaxation function was found to be related to the dispersion of the relaxation times as predicted by the Gaussian assumption. At short distances or large Q, this relationship is strongly violated indicating a non-Gaussian regime. We have performed a detailed comparison between the experiments and simulations at different temperatures and found, apart from a temperature shift, complete agreement. Combining experiments and simulations led to a consistent interpretation in terms of a distribution of jumps underlying the diffusive motion of protons in the alpha process. This model leads to a time-dependent non-Gaussianity parameter that agrees nearly quantitatively with the simulations and exhibits all features resolved so far from various simulations.
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Affiliation(s)
- A Arbe
- Unidad Física de Materiales, CSIC-UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain
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174
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Arbe A, Colmenero J, Alvarez F, Monkenbusch M, Richter D, Farago B, Frick B. Non-Gaussian nature of the alpha relaxation of glass-forming polyisoprene. Phys Rev Lett 2002; 89:245701. [PMID: 12484957 DOI: 10.1103/physrevlett.89.245701] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2002] [Indexed: 05/24/2023]
Abstract
We report quasielastic neutron scattering experiments exploring the alpha relaxation in polyisoprene over an unprecedented range in momentum transfer. Corroborating and validating earlier molecular dynamics simulations, the measurements reveal a crossover from a Gaussian regime of sublinear diffusion to a strongly non-Gaussian regime at short distances. We show that a consistent interpretation in terms of a distribution of finite jumps underlying the alpha process is possible. This model leads to a time-dependent non-Gaussian parameter exhibiting all features revealed so far from various simulations.
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Affiliation(s)
- A Arbe
- Unidad de Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain
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175
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Alvarez F, Colmenero J, Zorn R, Willner L, Richter D. Partial Structure Factors of Polyisoprene: Neutron Scattering and Molecular Dynamics Simulation. Macromolecules 2002. [DOI: 10.1021/ma021397p] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- F. Alvarez
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain, and Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425, Jülich, Germany
| | - J. Colmenero
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain, and Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425, Jülich, Germany
| | - R. Zorn
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain, and Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425, Jülich, Germany
| | - L. Willner
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain, and Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425, Jülich, Germany
| | - D. Richter
- Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU) y Unidad de Física de Materiales (CSIC−UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain, Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastián, Spain, and Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425, Jülich, Germany
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176
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Arbe A, Moral A, Alegrı́a A, Colmenero J, Pyckhout-Hintzen W, Richter D, Farago B, Frick B. Heterogeneous structure of poly(vinyl chloride) as the origin of anomalous dynamical behavior. J Chem Phys 2002. [DOI: 10.1063/1.1485283] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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177
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Farago B, Arbe A, Colmenero J, Faust R, Buchenau U, Richter D. Intermediate length scale dynamics of polyisobutylene. Phys Rev E Stat Nonlin Soft Matter Phys 2002; 65:051803. [PMID: 12059584 DOI: 10.1103/physreve.65.051803] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2001] [Indexed: 05/23/2023]
Abstract
We report on a neutron spin echo investigation of the intermediate scale dynamics of polyisobutylene studying both the self-motion and the collective motion. The momentum transfer (Q) dependences of the self-correlation times are found to follow a Q(-2/beta) law in agreement with the picture of Gaussian dynamics. In the full Q range of observation, their temperature dependence is weaker than the rheological shift factor. The same is true for the stress relaxation time as seen in sound wave absorption. The collective times show both temperature dependences; at the structure factor peak, they follow the temperature dependence of the viscosity, but below the peak, one finds the stress relaxation behavior.
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Affiliation(s)
- B Farago
- Institut Laue-Langevin, 156X, 38042 Grenoble Cedex, France
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178
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179
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Alegria A, Colmenero J, Ngai KL, Roland CM. Observation of the Component Dynamics in a Miscible Polymer Blend by Dielectric and Mechanical Spectroscopies. Macromolecules 2002. [DOI: 10.1021/ma00094a009] [Citation(s) in RCA: 181] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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180
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Colmenero J, Alegria A, Santangelo PG, Ngai KL, Roland CM. Detailed correspondences between dielectric and mechanical relaxations in poly(vinylethylene). Macromolecules 2002. [DOI: 10.1021/ma00080a013] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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181
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Alegria A, Elizetxea C, Cendoya I, Colmenero J. Anomalous Dynamical Homogeneity of the Dielectric α-Relaxation in Miscible Polymer Blends of Poly(epichlorohydrin) and Poly(vinyl methyl ether). Macromolecules 2002. [DOI: 10.1021/ma00130a014] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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182
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Alvarez F, Colmenero J, Wang CH, Xia JL, Fytas G. Segmental Dynamics in Bulk Poly(isobornyl methacrylate) and Its Random Copolymer with Poly(methyl methacrylate) near Tg. Macromolecules 2002. [DOI: 10.1021/ma00123a015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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183
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Alegria A, Macho E, Colmenero J. Dynamic mechanical study of four amorphous polymers around and above the glass transition: breakdown of the time-temperature superposition principle in the frame of the coupling model. Macromolecules 2002. [DOI: 10.1021/ma00018a026] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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184
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Alegria A, Guerrica-Echevarria E, Goitiandia L, Telleria I, Colmenero J. .alpha.-Relaxation in the Glass Transition Range of Amorphous Polymers. 1. Temperature Behavior across the Glass transition. Macromolecules 2002. [DOI: 10.1021/ma00109a025] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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185
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Ngai KL, Colmenero J, Alegria A, Arbe A. Interpretation of anomalous momentum transfer dependences of local chain motion of polymers observed by quasielastic incoherent neutron scattering experiments. Macromolecules 2002. [DOI: 10.1021/ma00050a056] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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186
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Colmenero J, Alvarez F, Arbe A. Self-motion and the alpha relaxation in a simulated glass-forming polymer: crossover from Gaussian to non-Gaussian dynamic behavior. Phys Rev E Stat Nonlin Soft Matter Phys 2002; 65:041804. [PMID: 12005863 DOI: 10.1103/physreve.65.041804] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2001] [Revised: 12/10/2001] [Indexed: 05/23/2023]
Abstract
We present fully atomistic molecular dynamics simulations for a realistic model of a glass-forming polymer: polyisoprene. The simulations are carried out at 363 K and extend until 20 ns. We calculate the self-part of the Van Hove correlation function G(s)(r,t), the mean-squared displacement <r(2)(t)>, the second-order non-Gaussian parameter alpha(2)(t), and the incoherent intermediate scattering function F(s)(Q,t) for the main chain protons. In addition, we also calculate the density-density correlation function F(Q,t)/F(Q,0) and the second-order autocorrelation function M2(t) for different C-H bonds of the main chain. alpha(2)(t) shows a broad maximum centered at a time t(*) approximately 4 ps, which corresponds to the intermediate region of <r(2)(t)> between microscopic dynamics and sublinear diffusion. The analysis of F(s)(Q,t), F(Q,t)/F(Q,0), and M2(t) focuses on the second slow step which is associated to the alpha relaxation. Following the usual experimental procedure this decay is described in terms of a Kohlrausch-Williams-Watts (KWW) function: A exp[-(t/tau)(beta)]. In the Q range below Q(max), where Q(max) is the value at which the static structure factor shows its first maximum, the Q dependence of the KWW relaxation time of F(s)(Q,t) follows a law tau approximately Q(-2/beta). This kind of Q dependence corresponds to a Gaussian behavior of G(s)(r,t) and F(s)(Q,t). This law has been experimentally found in this Q range for different polymers. In the higher Q range-not easily accessible experimentally-strong deviations from the Gaussian behavior manifest. This crossover from Gaussian to non-Gaussian behavior can be understood in the framework of the mode coupling theory as well as in terms of a crossover from homogeneous to heterogeneous dynamics. This last interpretation opens a possible way of rationalizing the apparent contradiction between the neutron scattering and relaxation techniques results concerning dynamical heterogeneity of the alpha relaxation.
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Affiliation(s)
- J Colmenero
- Departamento de Física de Materiales, Universidad del País Vasco UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain.
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187
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Affiliation(s)
- A. Alegría
- Departamento de Física de Materiales UPV/EHU y Unidad de Fısica de Materiales CSIC-UPV/EHU, Facultad de Química, Apartado 1072, 20080 San Sebastián, Spain
| | - D. Gómez
- Departamento de Física de Materiales UPV/EHU y Unidad de Fısica de Materiales CSIC-UPV/EHU, Facultad de Química, Apartado 1072, 20080 San Sebastián, Spain
| | - J. Colmenero
- Departamento de Física de Materiales UPV/EHU y Unidad de Fısica de Materiales CSIC-UPV/EHU, Facultad de Química, Apartado 1072, 20080 San Sebastián, Spain
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188
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Fernández J, Navasa M, Gómez J, Colmenero J, Vila J, Arroyo V, Rodés J. Bacterial infections in cirrhosis: epidemiological changes with invasive procedures and norfloxacin prophylaxis. Hepatology 2002; 35:140-8. [PMID: 11786970 DOI: 10.1053/jhep.2002.30082] [Citation(s) in RCA: 596] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The extensive use of invasive procedures and of long-term norfloxacin prophylaxis in the management of cirrhotic patients may have influenced the epidemiology of bacterial infections in cirrhosis. We conducted a prospective evaluation of all bacterial infections diagnosed in patients with cirrhosis in a Liver Unit between April 1998 and April 2000. A total of 405 patients presented 572 bacterial infections in 507 admissions. Spontaneous bacterial peritonitis was the most frequent infection (138 cases). Gram-positive cocci were responsible for 53% of total bacterial infections in the study, being the main bacteria isolated in nosocomial infections (59%). Patients requiring treatment in an intensive care unit and those submitted to invasive procedures presented a higher rate of infections caused by gram-positive cocci (77% vs. 48%, P <.001 and 58% vs. 40%, P <.02, respectively). Fifty percent of culture-positive spontaneous bacterial peritonitis in patients on long-term norfloxacin administration (n = 93) and 16% in patients not receiving this therapy (n = 414) were caused by quinolone-resistant gram-negative bacilli, P =.01. The rate of culture-positive spontaneous bacterial peritonitis caused by trimethoprim-sulfamethoxazole-resistant gram-negative bacilli was also very high in patients on long-term norfloxacin administration (44% vs. 18%, P =.09). In conclusion, infections caused by gram-positive cocci have markedly increased in cirrhosis. This phenomenon may be related to the current high degree of instrumentation of cirrhotic patients. Quinolone-resistant spontaneous bacterial peritonitis constitutes an emergent problem in patients on long-term norfloxacin prophylaxis, with trimethoprim-sulfamethoxazole not being a valid alternative.
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Affiliation(s)
- Javier Fernández
- Liver Unit, IMD, and Department of Microbiology and IDIBAPS, Hospital Clinic, University of Barcelona, Barcelona, Spain
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189
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Moreno AJ, Alegrı́a A, Colmenero J, Prager M, Grimm H, Frick B. Methyl group dynamics in glassy toluene: A neutron scattering study. J Chem Phys 2001. [DOI: 10.1063/1.1413742] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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190
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Moreno AJ, Alegría A, Colmenero J, Frick B. Methyl Group Dynamics in Poly(methyl methacrylate): From Quantum Tunneling to Classical Hopping. Macromolecules 2001. [DOI: 10.1021/ma0100854] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. J. Moreno
- Departamento de Física de Materiales y Centro Mixto CSIC-UPV/EHU, Universidad del País Vasco (UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain
| | - A. Alegría
- Departamento de Física de Materiales y Centro Mixto CSIC-UPV/EHU, Universidad del País Vasco (UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain
| | - J. Colmenero
- Departamento de Física de Materiales y Centro Mixto CSIC-UPV/EHU, Universidad del País Vasco (UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain
| | - B. Frick
- Institute Laue Langevin, BP 156X, F-38042 Grenoble, France
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191
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Affiliation(s)
- D. Gómez
- Departamento de Física de Materiales Universidad del País Vasco, and Unidad de Física de Materiales {CSIC-UPV/EHU), Apdo. 1072, 20080 San Sebastián, Spain
| | - A. Alegría
- Departamento de Física de Materiales Universidad del País Vasco, and Unidad de Física de Materiales {CSIC-UPV/EHU), Apdo. 1072, 20080 San Sebastián, Spain
| | - A. Arbe
- Departamento de Física de Materiales Universidad del País Vasco, and Unidad de Física de Materiales {CSIC-UPV/EHU), Apdo. 1072, 20080 San Sebastián, Spain
| | - J. Colmenero
- Departamento de Física de Materiales Universidad del País Vasco, and Unidad de Física de Materiales {CSIC-UPV/EHU), Apdo. 1072, 20080 San Sebastián, Spain
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Alvarez F, Arbe A, Colmenero J. Methyl group dynamics above the glass transition temperature: a molecular dynamics simulation in polyisoprene. Chem Phys 2000. [DOI: 10.1016/s0301-0104(00)00225-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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193
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Alvarez F, Alegría A, Colmenero J, Nicholson TM, Davies GR. Origin of the Distribution of Potential Barriers for Methyl Group Dynamics in Glassy Polymers: A Molecular Dynamics Simulation in Polyisoprene. Macromolecules 2000. [DOI: 10.1021/ma9919256] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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194
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Hoffmann S, Willner L, Richter D, Arbe A, Colmenero J, Farago B. Origin of dynamic heterogeneities in miscible polymer blends: A quasielastic neutron scattering study. Phys Rev Lett 2000; 85:772-775. [PMID: 10991395 DOI: 10.1103/physrevlett.85.772] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/1999] [Indexed: 05/23/2023]
Abstract
In order to investigate the origin of the often invoked nanoheterogeneities in miscible polymer blends, we have performed quasielastic neutron scattering experiments on the component dynamics within the miscible polymer blend polyisoprene/polyvinyl ether including the pure components as a reference. We find that the apparent local heterogeneities observed by spectroscopic techniques originate from the chain specific crossover properties between entropy driven and local chain dynamics and are, thus, a purely dynamical phenomenon.
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Affiliation(s)
- S Hoffmann
- Institut fur Festkorperforschung, Forschungszentrum Julich, 52425 Julich, Germany and Institut Laue-Langevin, 156X, 38042 Grenoble CEDEX, France
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195
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196
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Arbe A, Alegría A, Colmenero J, Hoffmann S, Willner L, Richter D. Segmental Dynamics in Poly(vinylethylene)/Polyisoprene Miscible Blends Revisited. A Neutron Scattering and Broad-Band Dielectric Spectroscopy Investigation. Macromolecules 1999. [DOI: 10.1021/ma990402v] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | - S. Hoffmann
- Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany, and Institut Laue-Langevin, 156X, 38042 Grenoble Cedex, France
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197
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Richter D, Monkenbusch M, Allgeier J, Arbe A, Colmenero J, Farago B, Cheol Bae Y, Faust R. From Rouse dynamics to local relaxation: A neutron spin echo study on polyisobutylene melts. J Chem Phys 1999. [DOI: 10.1063/1.479907] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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198
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Jiménez W, Ros J, Morales-Ruiz M, Navasa M, Solé M, Colmenero J, Sort P, Rivera F, Arroyo V, Rodés J. Nitric oxide production and inducible nitric oxide synthase expression in peritoneal macrophages of cirrhotic patients. Hepatology 1999; 30:670-6. [PMID: 10462373 DOI: 10.1002/hep.510300310] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The present study assessed whether peritoneal macrophages isolated from cirrhotic patients produce nitric oxide (NO) and express NO synthase type II (NOS II) mRNA and protein. Patients with cirrhosis and ascites without peritonitis or with unresolved or resolved spontaneous bacterial peritonitis (SBP) were studied. Following paracentesis, ascites NO(2)(-) + NO(3)(-) content (NOx) was measured. Peritoneal macrophages from ascites were seeded on well plates, and NO(2)(-) in the medium was determined. NOx was higher in patients with unresolved or resolved SBP than in cirrhotic patients without peritonitis. Macrophages of patients with SBP or resolved SBP produced NO(2)(-) after 30 hours in culture, but those obtained from patients without peritonitis did not. Reverse-transcription polymerase chain reaction (RT-PCR) and immunocytochemical analysis revealed the presence of a clear signal for NOS II mRNA and protein in macrophages of SBP patients, regardless of whether or not the infection subsided. Therefore, peritoneal macrophages isolated from cirrhotic patients with unresolved or resolved SBP produce NO and express the NOS II mRNA and protein, suggesting that NOS II may contribute to the control of SBP, or to its associated pathology, in human cirrhosis.
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Affiliation(s)
- W Jiménez
- Hormonal Laboratory, Hospital Clínic Universitari and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain.
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199
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Alegría A, Colmenero J, Mari PO, Campbell IA. Dielectric investigation of the temperature dependence of the nonexponentiality of the dynamics of polymer melts. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 59:6888-95. [PMID: 11969676 DOI: 10.1103/physreve.59.6888] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/1998] [Revised: 12/24/1998] [Indexed: 11/07/2022]
Abstract
Using broad band dielectric spectroscopy (10(-5)-10(9) Hz), combining time domain and frequency domain techniques, we study the temperature dependence of the non-Debye character of the alpha relaxation of polymer melts in the glass transition temperature T(g) range. The alpha relaxation process is described in terms of the Kohlrausch-Williams-Watts relaxation function which has a single parameter beta to characterize the nonexponentiality of the relaxation. At high temperatures, beta remains nearly insensitive to temperature changes, whereas in the vicinity of T(g) a nearly linear increasing of beta with temperature is found. The temperature range where the change of the beta(T) behavior occurs is located for all the polymers investigated around 1.2T(g). Moreover, our results indicate a common value of beta approximately equal to 1/3 at the temperature where the relaxation time diverges. The beta(T) behavior near T(g) is discussed in terms of a "rugged landscape" phase space which allows us to rationalize both the beta(T) behavior observed as well as the similarities of our findings near T(g) with the results reported in simulations on Ising spin glasses and other model systems.
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Affiliation(s)
- A Alegría
- Departamento de Física de Materiales y Centro Mixto CSIC-UPV/EHU, Facultad de Química, UPV/EHU, Apartado 1072, 20080 San Sebastián, Spain
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200
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Cendoya I, Alegría A, Alberdi JM, Colmenero J, Grimm H, Richter D, Frick B. Effect of Blending on the PVME Dynamics. A Dielectric, NMR, and QENS Investigation. Macromolecules 1999. [DOI: 10.1021/ma9819539] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | | | | | | | | | - B. Frick
- Institut Laue-Langevin, BP. 156, F-38042 Grenoble, France
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