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Search Results: 1 - 10 of 6870 matches for " atomic force microscopy "
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In Situ Atomic Force Microscopy Observation of Octacalcium Phosphate (100) Face Dissolution in Weak Acidic Solutions  [PDF]
Kazuo Onuma, Mayumi Iijima
Journal of Crystallization Process and Technology (JCPT) , 2015, DOI: 10.4236/jcpt.2015.51001
Abstract: Dissolution of the (100) face of octacalcium phosphate (OCP) single crystal in weak acidic solutions (pH = 6.5; 25°;C) was observed in situ using atomic force microscopy. Monomolecular steps (2.0 nm high) were observed; they originated from etch pits or crystal edges. Advancement of the dissolution process led to precipitation of nanoparticles as small as ~10 nm even though the solution was undersaturated with respect to OCP. This precipitation of nanoparticles was accompanied by a drastic decrease in the dissolution rate; however, the substrate OCP continued to dissolve, indicating that dissolution and growth occurred simultaneously on the same surface. The precipitated nanoparticles coalesced and eventually covered the entire surface without changing the surface morphology of the substrate crystal. The step height after complete coverage was ~2.0 nm, the same as that observed on the dissolving OCP surface. These findings indicate that the precipitated phase was a pseudomorph of OCP crystal.
Interaction Energy between an Atomic Force Microscope Tip and a Charged Particle in Electrolyte  [PDF]
Wai-Ting Lam, Fredy R. Zypman
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.411199
Abstract: A variational principle to the nonlinear Poisson-Boltzmann equation (PB) in three dimensions is used to first obtain solutions to the electrostatic potential surrounding a pair of spherical colloidal particles, one of them modeling the tip of an Atomic Force Microscope. Specifically, we consider the PB action integral for the electrostatic potential produced by charged colloidal particles and propose an analytical ansatz solution. This solution introduces the density and its corresponding electrostatic potential parametrically. The PB action is then minimized with respect to the parameter. Polynomial-exponential approximations for the parameters as functions of tip-particle separation and boundary electrostatic potential are obtained. With that information, tip-particle energy-separation curves are computed as well. Finally, based on the shape of the energy-separation curves, we study the stability properties predicted by this theory.
Joint Operation of Atomic Force Microscope and Advanced Laser Confocal Microscope for Observing Surface Processes in a Protein Crystal  [PDF]
Shin-ichiro Yanagiya, Nobuo Goto
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2012, DOI: 10.4236/jsemat.2012.223032
Abstract: We demonstrated the insitu observation of a moving atomic force microscope (AFM) cantilever using a laser confocal microscope combined with a differential interference microscope (LCM-DIM). The AFM cantilever scanned or indented the {110} surface of a hen egg-white lysozyme crystal in a supersaturated solution. Using a soft cantilever, we could observe the step growth with high time resolution by LCM-DIM and perform quantitative measurements of the step height by AFM simultaneously. In addition, a hard cantilever was used with LCM-DIM to observe the dynamics of crystal surface scratching and indentation. In the supersaturated solution, the small steps generated from the scratched line aggregated to macro steps, and subsequently flattened the surface.
The Use of Light Diffracted from Grating Etched onto the Backside Surface of an Atomic Force Microscope Cantilever Increases the Force Sensitivity  [PDF]
Sergey K. Sekatskii, Mounir Mensi, Andrey G. Mikhaylov, Giovanni Dietler
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2013, DOI: 10.4236/jsemat.2013.34A1004

A reflecting diffraction grating has been etched onto the backside of a standard cantilever for atomic force microscopy, and the diffracted light has been used to monitor the angular position of the cantilever. It is shown experimentally that for small angles of incidence and for large reflection angles, the force sensitivity can be improved by few times when an appropriate detection scheme based on the position sensitive (duolateral) detector is used. The first demonstration was performed with a one micron period amplitude diffraction grating onto the backside of an Al-coated cantilever etched by a focused ion beam milling for the experiments in air and an analogous 600 nm-period grating for the experiments in air and in water.

Advanced atomic force microscopy techniques
Thilo Glatzel,Hendrik H?lscher,Thomas Schimmel,Mehmet Z. Baykara
Beilstein Journal of Nanotechnology , 2012, DOI: 10.3762/bjnano.3.99
Dynamic force microscopy for imaging of viruses under physiological conditions
Kienberger Ferry,Zhu Rong,Moser Rosita,Rankl Christian
Biological Procedures Online , 2004, DOI: 10.1251/bpo80
Abstract: Dynamic force microscopy (DFM) allows imaging of the structure and the assessment of the function of biological specimens in their physiological environment. In DFM, the cantilever is oscillated at a given frequency and touches the sample only at the end of its downward movement. Accordingly, the problem of lateral forces displacing or even destroying bio-molecules is virtually inexistent as the contact time and friction forces are reduced. Here, we describe the use of DFM in studies of human rhinovirus serotype 2 (HRV2) weakly adhering to mica surfaces. The capsid of HRV2 was reproducibly imaged without any displacement of the virus. Release of the genomic RNA from the virions was initiated by exposure to low pH buffer and snapshots of the extrusion process were obtained. In the following, the technical details of previous DFM investigations of HRV2 are summarized.
Soluble Structure of CLIC and S100 Proteins Investigated by Atomic Force Microscopy  [PDF]
Stella M. Valenzuela, Mark Berkahn, Alexander Porkovich, Thuan Huynh, Jesse Goyette, Donald K. Martin, Carolyn L. Geczy
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.21002
Abstract: The ability to visualise proteins in their native environment and discern information regarding stoichiometry is of critical importance when studying protein interactions and function. We have used liquid cell atomic force microscopy (AFM) to visualise proteins in their native state in buffer and have determined their molecular volumes. The human proteins S100A8, S100A9, S100A12 and CLIC1 were used in this investigation. The effect of oxidation on the protein structure of CLIC1 was also investigated and we found that CLIC1 multimerisation could be discerned by AFM, which supports similar findings by other methods. We have found good correlation between the molecular volumes measured by AFM and the calculated volumes of the individual proteins. This method allows for the study of single soluble proteins under physiological conditions and could potentially be extended to study the structure of these proteins when located within a membrane environment.
New Organic Thin-Film Encapsulation for Organic Light Emitting Diodes  [PDF]
Rakhi Grover, Ritu Srivastava, Omwati Rana, D. S. Mehta, M. N. Kamalasanan
Journal of Encapsulation and Adsorption Sciences (JEAS) , 2011, DOI: 10.4236/jeas.2011.12003
Abstract: Organic Light-Emitting diodes (OLEDs) are extremely sensitive to water vapour and oxygen, which causes rapid degradation. Epoxy and cover glass with large amount of desiccant are commonly applied to encapsulate bottom emitting OLEDs which is not a viable option for flexible as well as top emitting OLEDs. This paper reports a completely organic encapsulating layer consisting of four periods of alternate stacks of two organic materials with different morphologies deposited by simple vacuum thermal evaporation technique. Standard green OLED structures with and without encapsulation were fabricated and investigated using structural, optical and electrical studies. Moreover, the encapsulation presented being organic is safe for underlying organic layers in OLEDs and is ultrathin, transparent and without any cover glass and desiccant, ensuring its application in flexible and top emitting OLEDs.
AFM Height Measurements of Molecular Layers of a Carbocyanine Dye  [PDF]
Valery V. Prokhorov, Sergey I. Pozin, Dmitry A. Lypenko, Olga M. Perelygina, Eugene I. Mal’tsev, Anatoly V. Vannikov
World Journal of Nano Science and Engineering (WJNSE) , 2011, DOI: 10.4236/wjnse.2011.13010
Abstract: Atomic force microscopy (AFM) was used for the morphological characterization and precise height meas-urements of two-dimensional molecular layers of carbocyanine dye 3,3’-di(r-sulfopropyl)-4,4’,5,5’-dibenzo-9-ethylthiacarbocyanine betaine pyridinium salt. The AFM measurements reveal three morphological types of molecular aggregates: leaves, stripes and spots. The leaves are stripes have same monolayer height ~1.4 nm and different crystal shapes: the leaves are monoloyers with the lens shape and the stripes are bilay-ers with the shape of extended rectangles. The monolayer height ~1.4 nm was interpreted as indicating the symmetrical packing arrangement of dye molecules. In the symmetrical monolayer, the sulfopropyl groups of all-trans monomer units are located on both monolayer sides whereas the adjacent stacked dye molecules have a lateral slippage providing the J-aggregate optical properties. The lower height of spots ~1 nm was explained by the model of an asymmetric monolayer with sulfopropyl groups of all-trans monomers occupy-ing the same position with respect to the monolayer plane. The packing arrangement of all-trans monomers in the asymmetric monolayer corresponds to H-aggregate. The alternative models of the packing arrange-ment in monolayers with mono-cis1 monomer configuration are discussed.
Elasticity Mapping Analysis of Apical Cell Periphery Actin Structures of Normal Fibroblasts and Cervical Cancer Cells  [PDF]
Takanori Kihara, Takuji Yoshida, Seyed M. Ali Haghparast, Jun Miyake
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2013, DOI: 10.4236/jasmi.2013.32015

The cell mechanical features are largely regulated by actin cytokeleton. By analyzing the mechanical features, it is possible to evaluate the characteristics of the complicated actin cytoskeleton in diverse cell types. In this study, we examined the sub-membrane mechanical structures of normal fibroblasts TIG-1 cells, and cervical cancer Hela cells using local elasticity mapping method of atomic force microscope. Especially we aimed at clarifying the regulatory mechanisms of sub-membrane actin structures in these cells by activation of actomyosin formation using calyculin A. This technique revealed that TIG-1 and Hela cells bore clearly different sub-membrane mechanical structures. TIG-1 cells had aligned stiff filamentous structures, whereas Hela cells had crooked and relatively soft filaments. The surface stiffness of TIG-1 cells increased slightly by actomyosin formation due to stiffness increase of the aligned filamentous structures. On the other hand, the surface stiffness of Hela cells increased by actomyosin formation due to upregulation of the apical actin filaments. Therefore, the structural and regulatory differences of the apical actin filaments could be demonstrated by atomic force microscopy elasticity mapping analysis.

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