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Mitsumasa Iwamoto - One of the best experts on this subject based on the ideXlab platform.
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dipolar electrostatic energy effect on relaxation process of Monolayers at air water interface analysis of thermodynamics and kinetics
Journal of Chemical Physics, 2009Co-Authors: Wei Ouyang, Takaaki Manaka, Martin Weis, Mitsumasa IwamotoAbstract:In order to understand the effect of electrostatic energy on phase transition from Monolayer to multilayer, isobaric relaxation process of Langmuir Monolayers composed of stearic acid or ferroelectric polyvinylidene fluoride and trifluoroethylene copolymer with various vinylidene fluoride (VDF) ratios is investigated in terms of thermodynamic and kinetic analysis. A monotonous decreasing tendency of material loss with respect to temperature is observed for stearic acid Monolayer, which is due to thermal activation effect on phase transition from Monolayer to multilayer. In contrast, for the ferroelectric Monolayer it presents a nonmonotonous behavior of losing materials with a peak position near the Curie temperature, which is not only owing to thermal activation but also dipole moment change. This observation is confirmed for the copolymer Monolayers with other VDF content ratios. Amazingly, for the ferroelectric Monolayers a good correspondence is found for critical temperatures evaluated from several i...
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dipolar electrostatic energy effect on relaxation process of Monolayers at air water interface analysis of thermodynamics and kinetics
Journal of Chemical Physics, 2009Co-Authors: Wei Ouyang, Takaaki Manaka, Martin Weis, Keanchuan Lee, Mitsumasa IwamotoAbstract:In order to understand the effect of electrostatic energy on phase transition from Monolayer to multilayer, isobaric relaxation process of Langmuir Monolayers composed of stearic acid or ferroelectric polyvinylidene fluoride and trifluoroethylene copolymer with various vinylidene fluoride (VDF) ratios is investigated in terms of thermodynamic and kinetic analysis. A monotonous decreasing tendency of material loss with respect to temperature is observed for stearic acid Monolayer, which is due to thermal activation effect on phase transition from Monolayer to multilayer. In contrast, for the ferroelectric Monolayer it presents a nonmonotonous behavior of losing materials with a peak position near the Curie temperature, which is not only owing to thermal activation but also dipole moment change. This observation is confirmed for the copolymer Monolayers with other VDF content ratios. Amazingly, for the ferroelectric Monolayers a good correspondence is found for critical temperatures evaluated from several independent methods including the analysis on slow collapse. This finding again tells the fact that the relaxation process, namely phase transition from Monolayer to multilayer, is greatly influenced by dipolar electrostatic energy. Moreover, the study of time dependent relaxation process reveals a diffusionlike behavior of multilayer structure formation, which cannot be interpreted by classical models. Hence a new model based on diffusion-driven material transfer is proposed and diffusivity of the copolymer molecules is estimated with a value of 0.4x10(-5) cm(2)/s. As a whole, this research reflects the importance of dipolar electrostatic energy for phase transition of Monolayers at air-water interface.
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a study on the dielectric relaxation time of arachidic acid Monolayers by mdc measurement
Molecular Crystals and Liquid Crystals, 2000Co-Authors: Jinwon Song, Youngil Choi, Mitsumasa IwamotoAbstract:Abstract Maxwell displacement current (MDC) measurement has been employed to study the dielectric property of Langmuir-films. A method for determining the dielectric relaxation time of floating Monolayers on the water surface is presented. MDC flowing across the Monolayers is analyzed using a rod-like molecular model. It is revealed that the dielectric relaxation time of Monolayer in the isotropic polar orientational phase is determined using a linear relationship between the Monolayer compression speed and the molecular area Am . Compression speed α- was about 30, 40, 50mm/min.
Wei Ouyang - One of the best experts on this subject based on the ideXlab platform.
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dipolar electrostatic energy effect on relaxation process of Monolayers at air water interface analysis of thermodynamics and kinetics
Journal of Chemical Physics, 2009Co-Authors: Wei Ouyang, Takaaki Manaka, Martin Weis, Mitsumasa IwamotoAbstract:In order to understand the effect of electrostatic energy on phase transition from Monolayer to multilayer, isobaric relaxation process of Langmuir Monolayers composed of stearic acid or ferroelectric polyvinylidene fluoride and trifluoroethylene copolymer with various vinylidene fluoride (VDF) ratios is investigated in terms of thermodynamic and kinetic analysis. A monotonous decreasing tendency of material loss with respect to temperature is observed for stearic acid Monolayer, which is due to thermal activation effect on phase transition from Monolayer to multilayer. In contrast, for the ferroelectric Monolayer it presents a nonmonotonous behavior of losing materials with a peak position near the Curie temperature, which is not only owing to thermal activation but also dipole moment change. This observation is confirmed for the copolymer Monolayers with other VDF content ratios. Amazingly, for the ferroelectric Monolayers a good correspondence is found for critical temperatures evaluated from several i...
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dipolar electrostatic energy effect on relaxation process of Monolayers at air water interface analysis of thermodynamics and kinetics
Journal of Chemical Physics, 2009Co-Authors: Wei Ouyang, Takaaki Manaka, Martin Weis, Keanchuan Lee, Mitsumasa IwamotoAbstract:In order to understand the effect of electrostatic energy on phase transition from Monolayer to multilayer, isobaric relaxation process of Langmuir Monolayers composed of stearic acid or ferroelectric polyvinylidene fluoride and trifluoroethylene copolymer with various vinylidene fluoride (VDF) ratios is investigated in terms of thermodynamic and kinetic analysis. A monotonous decreasing tendency of material loss with respect to temperature is observed for stearic acid Monolayer, which is due to thermal activation effect on phase transition from Monolayer to multilayer. In contrast, for the ferroelectric Monolayer it presents a nonmonotonous behavior of losing materials with a peak position near the Curie temperature, which is not only owing to thermal activation but also dipole moment change. This observation is confirmed for the copolymer Monolayers with other VDF content ratios. Amazingly, for the ferroelectric Monolayers a good correspondence is found for critical temperatures evaluated from several independent methods including the analysis on slow collapse. This finding again tells the fact that the relaxation process, namely phase transition from Monolayer to multilayer, is greatly influenced by dipolar electrostatic energy. Moreover, the study of time dependent relaxation process reveals a diffusionlike behavior of multilayer structure formation, which cannot be interpreted by classical models. Hence a new model based on diffusion-driven material transfer is proposed and diffusivity of the copolymer molecules is estimated with a value of 0.4x10(-5) cm(2)/s. As a whole, this research reflects the importance of dipolar electrostatic energy for phase transition of Monolayers at air-water interface.
Fumio Mizutani - One of the best experts on this subject based on the ideXlab platform.
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in situ stm imaging of individual molecules in two component self assembled Monolayers of 3 mercaptopropionic acid and 1 decanethiol on au 111
Journal of Electroanalytical Chemistry, 2001Co-Authors: Takahiro Sawaguchi, Yukari Sato, Fumio MizutaniAbstract:Two-component self-assembled Monolayers composed of 3-mercaptopropionic acid (MPA) and 1-decanethiol (CH3(HC2)9SH:C10SH) on Au(111) were investigated with in situ scanning tunneling microscopy (STM) and cyclic voltammetry, where the Monolayers I and II were prepared in 0.1 mM ethanol+water solutions with the ratios of MPA:C10SH=95:5 and 90:10, respectively. In situ STM images revealed that both Monolayer I and II consisted of phase-separated domains with molecularly ordered structures, each of which was predominantly formed by one of the constituent molecules. Based on the STM images, the surface fractions of constituent molecules were evaluated as MPA:C10SH=0.61:0.28 for Monolayer I, and MPA:C10SH=0.34:0.57 for Monolayer II. Cyclic voltammograms of the reductive desorption of the thiols provided the surface fractions of MPA:C10SH=0.69:0.31 for Monolayer I, and MPA:C10SH=0.41 and 0.59 for Monolayer II, which were in good agreement with the results obtained from STM images. Molecular resolution imaging allowed us to visualize the individual MPA and C10SH molecules and to determine the interfacial structures in the molecularly ordered domains of the phase-separated Monolayer. The C10SH domains in the Monolayer exhibited ordered phases with densely packed (√3×√3)R30° and p(3×2√3R−30°) structures, which are well-characterized structures for alkanethiol Monolayers. On the other hand, a completely different molecular arrangement of MPA defined as a (3×3) structure was consistently observed in the MPA domains, where the molecular arrangement is almost the same as that of (√3×√3)R30° but intermolecular hydrogen bonding is thought to exist in the three neighboring MPA molecules located around the corner of the (3×3) unit cell. It was demonstrated that individual molecules of the Monolayer constituents were successfully imaged in the two-component, phase-separated Monolayer in solution.
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ordered structures of self assembled Monolayers of 3 mercaptopropionic acid on au 111 in situ scanning tunneling microscopy study
Physical Chemistry Chemical Physics, 2001Co-Authors: Takahiro Sawaguchi, Yukari Sato, Fumio MizutaniAbstract:In situ scanning tunneling microscopy (STM) and cyclic voltammetry were employed to investigate self-assembled Monolayers of 3-mercaptopropionic acid (MPA) on Au(111) in perchloric acid solutions. In situ STM revealed that the MPA Monolayer was composed of translationally and rotationally ordered MPA domains, and some disordered portions also coexisted on the surface, particularly near the etch pits. The ordered Monolayer exhibited a molecularly ordered (3 × 3) structure, where three MPA molecules in triangular positions stand fairly close together due to intermolecular hydrogen bonding. Two distinctly different phase boundaries were found between the ordered (3 × 3) domains, and high-resolution STM images disclosed the molecular arrangement of the MPA Monolayers. The MPA Monolayer desorbed at negative potentials, causing transformation of the surface into the Au(111)-(√3 × 23) reconstruction. The in situ STM successfully elucidated the interfacial structure and phase boundary of the MPA Monolayers on Au(111) under electrochemical conditions.
Ka Yee C. Lee - One of the best experts on this subject based on the ideXlab platform.
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protegrin interaction with lipid Monolayers grazing incidence x ray diffraction and x ray reflectivity study
Soft Matter, 2008Co-Authors: Frances Neville, Alan J. Waring, Ka Yee C. Lee, Oleg Konovalov, Yuji Ishitsuka, Chris S Hodges, Robert I Lehrer, David GidalevitzAbstract:Interactions of the antimicrobial peptide protegrin-1 (PG-1) with phospholipid Monolayers have been investigated by using grazing incidence X-ray diffraction (GIXD) and specular X-ray reflectivity (XR). The structure of a PG-1 film at the air–aqueous interface was also investigated by XR for the first time. Dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylglycerol (DPPG) and lipid A Monolayers were formed at the air–aqueous interface to mimic the surface of human erythrocytes, Gram-positive bacterial cell membranes and Gram-negative bacterial outer membranes, respectively. Experiments were carried out under constant area conditions where the pressure changes upon insertion of peptide into the Monolayer. GIXD data suggest that the greatest Monolayer disruption produced by PG-1 is seen with the DPPG system at 20 mN m−1 since the Bragg peaks completely disappear after introduction of PG-1 to the system. PG-1 shows greater insertion into the lipid A system compared to the DPPC system when both films are held at the same initial surface pressure of 20 mN m−1. The degree of insertion lessens at 30 mN m−1 with both DPPC and DPPG Monolayer systems. XR data further reveal that PG-1 inserts primarily in the head group region of lipid Monolayers. However, only the XR data of the anionic lipids suggest the existence of an additional adsorbed peptide layer below the head group of the Monolayer. Overall, the data show that the extent of peptide–lipid interaction and lipid Monolayer disruption depends not only on the lipid composition of the Monolayer, but the packing density of the lipids in the Monolayer prior to the introduction of peptide to the subphase.
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Lateral stress relaxation and collapse in lipid Monolayers
Soft matter, 2008Co-Authors: Luka Pocivavsek, Shelli L. Frey, Kapilanjan Krishan, Kseniya Gavrilov, Piotr Ruchala, Alan J. Waring, Frans J. Walther, Michael Dennin, Thomas A. Witten, Ka Yee C. LeeAbstract:Surfactants at air/water interfaces are often subjected to mechanical stresses as the interfaces they occupy are reduced in area. The most well characterized forms of stress relaxation in these systems are first order phase transitions from lower density to higher density phases. Here we study stress relaxation in lipid Monolayers that occurs once chemical phase transitions have been exhausted. At these highly compressed states, the Monolayer undergoes global mechanical relaxations termed collapse. By studying four different types of Monolayers, we determine that collapse modes are most closely linked to in-plane rigidity. We characterize the rigidity of the Monolayer by analyzing in-plane morphology on numerous length scales. More rigid Monolayers collapse out-of-plane via a hard elastic mode similar to an elastic membrane, while softer Monolayers relax in-plane by shearing.
Nargess Khalilgharibi - One of the best experts on this subject based on the ideXlab platform.
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stress relaxation in epithelial Monolayers is controlled by the actomyosin cortex
Nature Physics, 2019Co-Authors: Nargess Khalilgharibi, Jonathan Fouchard, Nina Asadipour, Ricardo Barrientos, Maria Duda, Alessandra Bonfanti, Amina Yonis, Andrew R HarrisAbstract:Epithelial Monolayers are one-cell-thick tissue sheets that line most of the body surfaces, separating internal and external environments. As part of their function, they must withstand extrinsic mechanical stresses applied at high strain rates. However, little is known about how Monolayers respond to mechanical deformations. Here, by subjecting suspended epithelial Monolayers to stretch, we find that they dissipate stresses on a minute timescale and that relaxation can be described by a power law with an exponential cut-off at timescales larger than about 10 s. This process involves an increase in Monolayer length, pointing to active remodelling of cellular biopolymers at the molecular scale during relaxation. Strikingly, Monolayers consisting of tens of thousands of cells relax stress with similar dynamics to single rounded cells, and both respond similarly to perturbations of the actomyosin cytoskeleton. By contrast, cell–cell junctional complexes and intermediate filaments do not relax tissue stress, but form stable connections between cells, allowing Monolayers to behave rheologically as single cells. Taken together, our data show that actomyosin dynamics governs the rheological properties of epithelial Monolayers, dissipating applied stresses and enabling changes in Monolayer length.
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generating suspended cell Monolayers for mechanobiological studies
Nature Protocols, 2013Co-Authors: Andrew R Harris, Julien Bellis, Nargess Khalilgharibi, Tom P J Wyatt, Buzz Baum, Alexandre Kabla, Guillaume CharrasAbstract:Cell Monolayers line most of the surfaces and cavities in the human body. During development and normal physiology, Monolayers sustain, detect and generate mechanical stresses, yet little is known about their mechanical properties. We describe a cell culture and mechanical testing protocol for generating freely suspended cell Monolayers and examining their mechanical and biological response to uniaxial stretch. Cells are cultured on temporary collagen scaffolds polymerized between two parallel glass capillaries. Once cells form a Monolayer covering the collagen and the capillaries, the scaffold is removed with collagenase, leaving the Monolayer suspended between the test rods. The suspended Monolayers are subjected to stretching by prying the capillaries apart with a micromanipulator. The applied force can be measured for the characterization of Monolayer mechanics. Monolayers can be imaged with standard optical microscopy to examine changes in cell morphology and subcellular organization concomitant with stretch. The entire preparation and testing protocol requires 3-4 d.
